Lack of enhanced photocatalytic formation of iodine on particulate semiconductor mixtures.

PubMed

Karunakaran, C; Anilkumar, P; Vinayagamoorthy, P

2012-12-01

Under UV-A light illumination, formation of iodine from iodide ion on the surfaces of anatase TiO(2), ZnO, Fe(2)O(3), CeO(2), MoO(3), Bi(2)O(3), and Nb(2)O(5) increases with the concentration of iodide ion, airflow rate and light intensity and conform to the Langmuir-Hinshelwood kinetic model. Measurement of the particle size of the semiconductor oxides by light scattering method and deduction of the same from the determined specific surface area show that the oxide particles agglomerate in suspension. However, mixtures of any two listed particulate semiconductors do not show enhanced photocatalytic formation of iodine indicating absence of interparticle charge transfer. The results are rationalized. Copyright © 2012 Elsevier B.V. All rights reserved.

An evaluation of the efficacy of various coal combustion models for predicting char burnout

DOE Office of Scientific and Technical Information (OSTI.GOV)

McConnell, Josh; Goshayeshi, Babak; Sutherland, James C.

Coal combustion is comprised of several subprocesses including devolatilization and heterogeneous reactions of the coal char with O 2, CO 2, H 2O and potentially several other species. Much effort has been put forth to develop models for these processes which vary widely in both complexity and computational cost. This work investigates the efficacy of models for devolatilization and char reactions at either end of the complexity and cost spectrums for a range of particle sizes and furnace temperatures and across coal types. The overlap of simulated devolatilization and char consumption is also examined. In the gas phase, a detailedmore » kinetics model based on a reduced version of the GRI 3.0 mechanism is used. The Char Conversion Kinetics and an n th-order Langmuir-Hinshelwood models are considered for char oxidation. The Chemical Percolation and Devolatilization and a two-step model are considered for devolatilization. Results indicate that high-fidelity models perform better at representing particle temperature and mass data across a wide range of O 2 concentrations as well as coal types. A significant overlap in devolatilization and char consumption is observed for both char chemistry and devolatilization models.« less

An evaluation of the efficacy of various coal combustion models for predicting char burnout

DOE PAGES

McConnell, Josh; Goshayeshi, Babak; Sutherland, James C.

2016-11-22

Coal combustion is comprised of several subprocesses including devolatilization and heterogeneous reactions of the coal char with O 2, CO 2, H 2O and potentially several other species. Much effort has been put forth to develop models for these processes which vary widely in both complexity and computational cost. This work investigates the efficacy of models for devolatilization and char reactions at either end of the complexity and cost spectrums for a range of particle sizes and furnace temperatures and across coal types. The overlap of simulated devolatilization and char consumption is also examined. In the gas phase, a detailedmore » kinetics model based on a reduced version of the GRI 3.0 mechanism is used. The Char Conversion Kinetics and an n th-order Langmuir-Hinshelwood models are considered for char oxidation. The Chemical Percolation and Devolatilization and a two-step model are considered for devolatilization. Results indicate that high-fidelity models perform better at representing particle temperature and mass data across a wide range of O 2 concentrations as well as coal types. A significant overlap in devolatilization and char consumption is observed for both char chemistry and devolatilization models.« less

Hydrodesulfurization of dibenzothiophene (DBT) catalyzed by sulfided CoO-MoO/sub 3//. gamma. -Al/sub 2/O/sub 3/: the reaction kinetics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Broderick, D.H.; Gates, B.C.

1980-01-01

Rates of the two competing conversion routes of DBT, a model compound for components of heavy oils and coal liquids, i.e., aromatic ring hydrogenation followed by hydrodesulfurization of the tetra- and hexahydro-DBT intermediates to cyclohexylbenzene (the hydrogenation route) and direct DBT hydrodesulfurization to biphenyl (the hydrogenolysis route) were measured independently at 548/sup 0/, 573/sup 0/, and 598/sup 0/K and 178 atm over an in-situ desulfurized commercial CoO-MoO/sub 3//..gamma..-Al/sub 2/O/sub 3/ catalyst. The rate data were fitted to Langmuir-Hinshelwood equations derived by nonlinear least-squares regression analysis, and all the kinetic parameters were accurately estimated. The selectivity for the hydrogenolysis route canmore » be increased, and hence hydrogen consumption minimized, by increasing temperature, reducing hydrogen sulfide concentration in the system through recycle gas scrubbing, or by adding quinoline which acts as inhibitor of the hydrogenation route preferentially.« less

Kinetic study of gold nanoparticle mediated photocatalytic degradation of Victoria blue.

PubMed

Jishma, P; Roshmi, Thomas; Snigdha, S; Radhakrishnan, E K

2018-02-01

In the study, biogenic gold nanoparticles (AuNPs) were used for the photocatalytic degradation of triphenylmethane dyes Victoria blue B (VBB) and R (VBR). The process was found to result in an approximate degradation of 65 and 52%, respectively, for VBB and VBR within a period of 8 h. The relative rate of photocatalytic degradation of VBB and VBR was identified to be 0.0195 ± 0.0031/min and 0.0295 ± 0.0025/min, respectively, by using the Langmuir-Hinshelwood model. By using the Vigna unguiculata model system, the degradation products were demonstrated to have non-toxic effect. Moreover, the less toxic nature of AuNPs used for dye removal highlights its feasibility for large-scale application. Hence, the AuNPs-based photocatalytic dye degradation as described in the study is cost-effective, rapid and environment-friendly.

Photochemical degradation of an anionic surfactant by TiO2 nanoparticle doped with C, N in aqueous solution

NASA Astrophysics Data System (ADS)

Zamiri, M.; Giahi, M.

2016-12-01

Novel C,N-doped TiO2 nanoparticles were prepared by a solid phase reaction. The catalyst was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). The results showed that crystallite size of synthesized C,N-doped TiO2 particles were in nanoscale. UV light photocatalytic studies were carried out using sodium naphthalenesulfonate formaldehyde condensate (SNF) as a model pollutant. The effects of initial concentration of surfactant, catalyst amount, pH, addition of oxidant on the reaction rate were ascertained and optimum conditions for maximum degradation was determined. The results indicated that for a solution of 20 mg/L of SNF, almost 98.7% of the substance were removed at pH 4.0 and 0.44 g/L photocatalyst load, with addition of 1 mM K2S2O8 and irradiation time of 90 min. The kinetics of the process was studied, and the photodegradation rate of SNF was found to obey pseudo-first-order kinetics equation represented by the Langmuir-Hinshelwood model.

A potential photocatalytic, antimicrobial and anticancer activity of chitosan-copper nanocomposite.

PubMed

Arjunan, Nithya; Singaravelu, Chandra Mohan; Kulanthaivel, Jeganathan; Kandasamy, Jothivenkatachalam

2017-11-01

In this study, chitosan-copper (CS-Cu) nanocomposite was synthesized without the aid of any external chemical reducing agents. The optical, structural, spectral, thermal and morphological analyses were carried out by several techniques. The prepared nanocomposite acts as a photocatalyst for the removal of Rhodamine B (RhB) and Conge red (CR) dyes under visible light irradiation. The pseudo first order kinetics was derived according to Langmuir-Hinshelwood (L-H) model. The nanocomposite also proved to be an excellent antimicrobial agent against Gram-positive and Gram-negative bacteria; and also show activity against fungus. The advanced material was used for the major research areas which include photocatalytic materials for waste water treatment; biological applications in the development of drug resistant antimicrobials and anticancer agents. Copyright © 2017 Elsevier B.V. All rights reserved.

Time resolved study of hydroxyl radical oxidation of oleic acid at the air-water interface

NASA Astrophysics Data System (ADS)

Zhang, Xinxing; Barraza, Kevin M.; Upton, Kathleen T.; Beauchamp, J. L.

2017-09-01

The ubiquity of oleic acid (OA) renders it a poster child for laboratory investigations of environmental oxidation chemistry. In the current study, mechanistic details of the oxidation of OA by hydroxyl radicals at the air-water interface are investigated using field-induced droplet ionization mass spectrometry (FIDI-MS). Products from OH oxidation of both unsaturated and saturated carbon atoms are identified, and mechanisms for both types of oxidation processes are proposed. Uptake of oxygen in the interfacial layer increases linearly with time, consistent with Langmuir-Hinshelwood reaction kinetics. These results provide fundamental knowledge relating to OH initiated degradation of fatty acids in atmospheric aerosols.

Removal of toxic Cr(VI) ions from tannery industrial wastewater using a newly designed three-phase three-dimensional electrode reactor

NASA Astrophysics Data System (ADS)

Grace Pavithra, K.; Senthil Kumar, P.; Carolin Christopher, Femina; Saravanan, A.

2017-11-01

In this research, the wastewater samples were collected from leather tanning industry at different time intervals. The parameters like pH, electrical conductivity, temperature, turbidity, chromium and chemical oxygen demand (COD) of the samples were analyzed. A three-phase three-dimensional fluidized type electrode reactor (FTER) was newly designed for the effective removal of toxic pollutants from wastewater. The influencing parameters were optimized for the maximum removal of toxic pollutants from wastewater. The optimum condition for the present system was calculated as: contact time of 30 min, applied voltage of 3 V and the particle electrodes of 15 g. The particle electrode was characterized by using FT-IR analysis. Langmuir-Hinshelwood and pseudo-second order kinetic models were fits well with the experimental data. The results showed that the FTER can be successfully employed for the treatment of industrial wastewater.

Enhanced removal of nitrate from water using nZVI@MWCNTs composite: synthesis, kinetics and mechanism of reduction.

PubMed

Babaei, Ali Akbar; Azari, Ali; Kalantary, Roshanak Rezaei; Kakavandi, Babak

2015-01-01

Herein, multi-wall carbon nanotubes (MWCNTs) were used as the carrier of nano-zero valent iron (nZVI) particles to fabricate a composite known as nZVI@MWCNTs. The composite was then characterized and applied in the nitrate removal process in a batch system under anoxic conditions. The influential parameters such as pH, various concentrations of nitrate and composite were investigated within 240 min of the reaction. The mechanism, kinetics and end-products of nitrate reduction were also evaluated. Results revealed that the removal nitrate percentage for nZVI@MWCNTs composite was higher than that of nZVI and MWCNTs alone. Experimental data from nitrate reduction were fitted to the Langmuir-Hinshelwood kinetic model. The values of observed rate constant (kobs) decreased with increasing the initial concentration of nitrate. Our experiments proved that the nitrate removal efficiency was favorable once both high amounts of nZVI@MWCNTs and low concentrations of nitrate were applied. The predominant end-products of the nitrate reduction were ammonium (84%) and nitrogen gas (15%). Our findings also revealed that ZVI@MWCNTs is potentially a good composite for removal/reduction of nitrate from aqueous solutions.

Comparative study of the degradation of carbamazepine in water by advanced oxidation processes.

PubMed

Dai, Chao-Meng; Zhou, Xue-Fei; Zhang, Ya-Lei; Duan, Yan-Ping; Qiang, Zhi-Min; Zhang, Tian C

2012-06-01

Degradation of carbamazepine (CBZ) using ultraviolet (UV), UV/H2O2, Fenton, UV/Fenton and photocatalytic oxidation with TiO2 (UV/TiO2) was studied in deionized water. The five different oxidation processes were compared for the removal kinetics of CBZ. The results showed that all the processes followed pseudo-first-order kinetics. The direct photolysis (UV alone) was found to be less effective than UV/H2O2 oxidation for the degradation of CBZ. An approximate 20% increase in the CBZ removal efficiency occurred with the UV/Fenton reaction as compared with the Fenton oxidation. In the UV/TiO2 system, the kinetics of CBZ degradation in the presence of different concentrations of TiO2 followed the pseudo-first order degradation, which was consistent with the Langmuir-Hinshelwood (L-H) model. On a time basis, the degradation efficiencies ofCBZ were in the following order: UV/Fenton (86.9% +/- 1.7%) > UV/TiO2 (70.4% +/- 4.2%) > Fenton (67.8% +/- 2.6%) > UV/H2O2 (40.65 +/- 5.1%) > UV (12.2% +/- 1.4%). However, the lowest cost was obtained with the Fenton process.

Solar photocatalytic degradation of isoproturon over TiO2/H-MOR composite systems.

PubMed

Sharma, Mangalampalli V Phanikrishna; Durgakumari, Valluri; Subrahmanyam, Machiraju

2008-12-30

The photocatalytic degradation and mineralization of isoproturon herbicide was investigated in aqueous solution containing TiO2 over H-mordenite (H-MOR) photocatalysts under solar light. The catalysts are characterized by X-ray diffraction (XRD), UV-Vis diffused reflectance spectra (UV-Vis DRS), Fourier transform-infra red spectra (FT-IR) and scanning electron microscopy (SEM) techniques. The effect of TiO2, H-MOR support and different wt% of TiO2 over the support on the photocatalytic degradation and influence of parameters such as TiO2 loading, catalyst amount, pH and initial concentration of isoproturon on degradation are evaluated. 15wt% TiO2/H-MOR composite is found to be optimum. The degradation reaction follows pseudo-first order kinetics and is discussed in terms of Langmuir-Hinshelwood (L-H) kinetic model. The extent of isoproturon mineralization studied with chemical oxygen demand (COD) and total organic carbon (TOC) measurements and approximately 80% mineralization occurred in 5h. A plausible mechanism is proposed based on the intermediates identified by liquid chromatography-mass spectroscopy (LC-MS).

Application of nano filter for organic pollutant degradation

NASA Astrophysics Data System (ADS)

Qandalee, Mohammad; Hatami, Mehdi; Majedi, Ali; Bateni, Mohsen; Vahdat, Seyed Mohammad

2012-12-01

In this study, the possibility of using a novel nanocomposite structure based on nanoscale titanium dioxide as a filter toward elimination of organic pollutant was investigated. Methyl Orange (MO) was selected as a typical organic pollutant and effect of lamp intensity, addition of hydrogen peroxide and MO concentration were investigated. The photocatalytic degradation of MO was modeled using Langmuir-Hinshelwood equation and the removal rates were simulated.

Novel Solar Photocatalytic Reactor for Wastewater Treatment

NASA Astrophysics Data System (ADS)

Sutisna; Rokhmat, M.; Wibowo, E.; Murniati, R.; Khairurrijal; Abdullah, M.

2017-07-01

A new solar photocatalytic reactor (photoreactor) using TiO2 nanoparticles coated onto plastic granules has been designed. Catalyst granules are placed into the cavity of a reactor panel made of glass. A pump is used to circulate wastewater in the photoreactor. Methylene blue (MB) dissolved in water was chosen as the wastewater model. The performance of the photoreactor was evaluated based on changes in MB concentration with respect to time. The photoreactor showed a good performance by degrading 10 L of MB solution up to 96.54% after 48 h of solar irradiation. The photoreactor was scaled up by enlarging the panel area to twice its original size. The increase in the surface area of the reactor panel and therefore of the mass of catalyst granules and reactor volume led to a three-fold increase of the photodegradation rate. In addition, the MB degradation kinetics were also studied. Data analysis confirmed the applicability of the pseudo-first-order Langmuir-Hinshelwood model. The proposed photoreactor has great potential for use in large-scale wastewater treatment.

A Kinetic Model for GaAs Growth by Hydride Vapor Phase Epitaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schulte, Kevin L.; Simon, John; Jain, Nikhil

2016-11-21

Precise control of the growth of III-V materials by hydride vapor phase epitaxy (HVPE) is complicated by the fact that the growth rate depends on the concentrations of nearly all inputs to the reactor and also the reaction temperature. This behavior is in contrast to metalorganic vapor phase epitaxy (MOVPE), which in common practice operates in a mass transport limited regime where growth rate and alloy composition are controlled almost exclusively by flow of the Group III precursor. In HVPE, the growth rate and alloy compositions are very sensitive to temperature and reactant concentrations, which are strong functions of themore » reactor geometry. HVPE growth, particularly the growth of large area materials and devices, will benefit from the development of a growth model that can eventually be coupled with a computational fluid dynamics (CFD) model of a specific reactor geometry. In this work, we develop a growth rate law using a Langmuir-Hinshelwood (L-H) analysis, fitting unknown parameters to growth rate data from the literature that captures the relevant kinetic and thermodynamic phenomena of the HVPE process. We compare the L-H rate law to growth rate data from our custom HVPE reactor, and develop quantitative insight into reactor performance, demonstrating the utility of the growth model.« less

Predicting heavy metals' adsorption edges and adsorption isotherms on MnO2 with the parameters determined from Langmuir kinetics.

PubMed

Hu, Qinghai; Xiao, Zhongjin; Xiong, Xinmei; Zhou, Gongming; Guan, Xiaohong

2015-01-01

Although surface complexation models have been widely used to describe the adsorption of heavy metals, few studies have verified the feasibility of modeling the adsorption kinetics, edge, and isotherm data with one pH-independent parameter. A close inspection of the derivation process of Langmuir isotherm revealed that the equilibrium constant derived from the Langmuir kinetic model, KS-kinetic, is theoretically equivalent to the adsorption constant in Langmuir isotherm, KS-Langmuir. The modified Langmuir kinetic model (MLK model) and modified Langmuir isotherm model (MLI model) incorporating pH factor were developed. The MLK model was employed to simulate the adsorption kinetics of Cu(II), Co(II), Cd(II), Zn(II) and Ni(II) on MnO2 at pH3.2 or 3.3 to get the values of KS-kinetic. The adsorption edges of heavy metals could be modeled with the modified metal partitioning model (MMP model), and the values of KS-Langmuir were obtained. The values of KS-kinetic and KS-Langmuir are very close to each other, validating that the constants obtained by these two methods are basically the same. The MMP model with KS-kinetic constants could predict the adsorption edges of heavy metals on MnO2 very well at different adsorbent/adsorbate concentrations. Moreover, the adsorption isotherms of heavy metals on MnO2 at various pH levels could be predicted reasonably well by the MLI model with the KS-kinetic constants. Copyright © 2014. Published by Elsevier B.V.

Supporting technology for the development of Controlled Ecological Life Support Systems (CELSS)

NASA Technical Reports Server (NTRS)

Li, Ku-Yen; Yaws, Carl L.; Simon, William E.; Mei, Harry T.

1995-01-01

To support the development of Controlled Ecological Life Support Systems (CELSS) in the space program, a metabolic simulator has been selected for use in a closed chamber to test functions of the CELSS. This metabolic simulator is a catalytic reactor which oxidizes the methyl acetate to produce carbon dioxide and water vapor. In this project, kinetic studies of catalytic oxidation of methyl acetate were conducted using monolithic and pellet catalysts with 0.5% (by weight) platinum (Pt) on aluminum oxide (Al2O3). The reaction was studied at a pressure of one atmosphere and at temperatures varying from 160 C to 420 C. By-products were identified at the exit of the preheater and reactor. For the kinetic study with the monolithic catalyst, a linear regression method was used to correlate the kinetic data with zero-order, first-order and Langmuir-Hinshelwood models. Results indicate that the first-order model represents the data adequately at low concentrations of methyl acetate. For higher concentrations of methyl acetate, the Langmuir-Hinshelwood model best represents the kinetic data. Both rate constant and adsorption equilibrium constants were estimated from the regression. A Taguchi orthogonal array (L(sub 9)) was used to investigate the effects of temperature, flow rate, and concentration on the catalytic oxidation of methyl acetate. For the monolithic catalyst, temperature exerts the most significant effect, followed by concentration of methyl acetate. For the pellet catalyst, reaction temperature is the most significant factor, followed by gas flow rate and methyl acetate concentration. Concentrations of either carbon dioxide or oxygen were seen to have insignificant effect on the methyl acetate conversion process. Experimental results indicate that the preheater with glass beads can accomplish thermal cracking and catalytic reaction of methyl acetate to produce acetic acid, methanol, methyl formate, and 1-propanol. The concentration of all by-products was measured in ppmv (parts per million by volume). At higher temperatures, greater amounts of these products are produced, as expected. In all cases, methanol was the predominant concentration detected, followed by methyl formate. At temperatures lower than 320 C for the P-type monolithic catalyst, methanol, acetic acid, and acetone were detected, whereas, for the E-type monolithic catalyst, only methanol was detected at 160 C. Both P and E types of the monolithic catalyst were specified with the same substrates (ceramic), washcoat (Al2O3), and promoter (Pt). However, the manufacturing and treatment procedures were quite different. It was therefore concluded that the performance of the E-type monolithic catalyst is superior to that of the P-type for oxidation of methyl acetate. At higher reaction temperatures, e.g., above 420 C, all reactants and byproducts were completely oxidized using these two types of monolithic catalyst to produce carbon dioxide and water vapor. A complex heterogenous catalytic reaction mechanism was proposed to explain the formation of the byproducts (methanol, acetic acid, and methyl formate) as the methyl acetate traveled through the preheater packed with glass beads. The by-product, 1-propanol, may be formed only through a homogeneous reaction, since it is difficult to develop a reasonable sequence of heterogeneous reaction steps to explain its formation. The homogeneous thermal decomposition of methyl acetate to form free radicals was proposed to explain the formation of 1-propanol, and also methanol, in the preheater. A dual-site catalytic reaction mechanism was proposed for the oxidation of methyl acetate over Pt/Al2O3 monolithic catalyst. The dual-site mechanism describes the chemisorption of oxygen molecules as well as a physical adsorption of methyl acetate on the active sites. On the active sites, methyl acetate is oxidized rapidly to form carbon dioxide and water vapor. A rate equation derived from this mechanism gives the Langmuir-Hinshelwood rate formula which has been observed from the experimental data obtained in this project for high methyl acetate concentration (greater than 1000 ppmv) over a monolithic catalyst. If the oxygen concentration is very high and methyl acetate concentration is very low, the reaction rate equation is then reduced to a first-order with respect to methyl acetate concentration. The first-order model has also been observed from the experimental data obtained in this project for low methyl acetate concentration (less than 1000 ppmv).

Kinetics of Chronic Oxidation of NBG-17 Nuclear Graphite by Water Vapor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Contescu, Cristian I; Burchell, Timothy D; Mee, Robert

2015-05-01

This report presents the results of kinetic measurements during accelerated oxidation tests of NBG-17 nuclear graphite by low concentration of water vapor and hydrogen in ultra-high purity helium. The objective is to determine the parameters in the Langmuir-Hinshelwood (L-H) equation describing the oxidation kinetics of nuclear graphite in the helium coolant of high temperature gas-cooled reactors (HTGR). Although the helium coolant chemistry is strictly controlled during normal operating conditions, trace amounts of moisture (predictably < 0.2 ppm) cannot be avoided. Prolonged exposure of graphite components to water vapor at high temperature will cause very slow (chronic) oxidation over the lifetimemore » of graphite components. This behavior must be understood and predicted for the design and safe operation of gas-cooled nuclear reactors. The results reported here show that, in general, oxidation by water of graphite NBG-17 obeys the L-H mechanism, previously documented for other graphite grades. However, the characteristic kinetic parameters that best describe oxidation rates measured for graphite NBG-17 are different than those reported previously for grades H-451 (General Atomics, 1978) and PCEA (ORNL, 2013). In some specific conditions, certain deviations from the generally accepted L-H model were observed for graphite NBG-17. This graphite is manufactured in Germany by SGL Carbon Group and is a possible candidate for the fuel elements and reflector blocks of HTGR.« less

Dechlorination of trichloroethylene formed from 1,1,2,2-tetrachloroethane by dehydrochlorination in Portland cement slurry including Fe(II).

PubMed

Jung, Bahngmi; Batchelor, Bill

2008-03-01

Transformation of 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA) by Fe(II) in 10% cement slurries was characterized using a batch reactor system. 1,1,2,2-TeCA was completely converted to trichloroethylene (TCE) within 1h in all experiments, even in controls with cement that did not include Fe(II). Therefore, complete degradation of 1,1,2,2-TeCA depends on the behavior of TCE. The half-life of TCE was observed to be 15d when concentrations of Fe(II) and 1,1,2,2-TeCA were 98mM and 0.245mM, respectively. The kinetics of TCE removal was observed to be dependent on Fe(II) dose, pH and initial substrate concentration. Pseudo-first-order rate constants linearly increased with Fe(II) dose up to 198mM when initial target concentration was 0.245mM. Pseudo-first-order kinetics generally described the degradation reactions of TCE at a specific initial concentration, but a modified Langmuir-Hinshelwood model was necessary to describe the degradation kinetics of TCE over a wide range of initial concentrations. A surface reaction of TCE on active solids, which were formed from Fe(II) and products of cement hydration appears to control observed TCE degradation kinetics.

Beyond the classical kinetic model for chronic graphite oxidation by moisture in high temperature gas-cooled reactors

DOE PAGES

Contescu, Cristian I.; Mee, Robert W.; Lee, Yoonjo; ...

2017-11-03

Four grades of nuclear graphite with various microstructures were subjected to accelerated oxidation tests in helium with traces of moisture and hydrogen in order to evaluate the effects of chronic oxidation on graphite components in high temperature gas cooled reactors. Kinetic analysis showed that the Langmuir-Hinshelwood (LH) model cannot consistently reproduce all results. In particular, at high temperatures and water partial pressures oxidation was always faster than the LH model predicts, with stronger deviations for superfine grain graphite than for medium grain grades. It was also found empirically that the apparent reaction order for water has a sigmoid-type variation withmore » temperature which follows the integral Boltzmann distribution function. This suggests that the apparent activation with temperature of graphite reactive sites that causes deviations from the LH model is rooted in specific structural and electronic properties of surface sites on graphite. A semi-global kinetic model was proposed, whereby the classical LH model was modified with a temperature-dependent reaction order for water. The new Boltzmann-enhanced model (BLH) was shown to consistently predict experimental oxidation rates over large ranges of temperature (800-1100 oC) and partial pressures of water (3-1200 Pa) and hydrogen (0-300 Pa), not only for the four grades of graphite but also for the historic grade H-451. The BLH model offers as more reliable input for modeling the chemical environment effects during the life-time operation of new grades of graphite in advanced nuclear reactors operating at high and very high temperatures.« less

Beyond the classical kinetic model for chronic graphite oxidation by moisture in high temperature gas-cooled reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Contescu, Cristian I.; Mee, Robert W.; Lee, Yoonjo

Four grades of nuclear graphite with various microstructures were subjected to accelerated oxidation tests in helium with traces of moisture and hydrogen in order to evaluate the effects of chronic oxidation on graphite components in high temperature gas cooled reactors. Kinetic analysis showed that the Langmuir-Hinshelwood (LH) model cannot consistently reproduce all results. In particular, at high temperatures and water partial pressures oxidation was always faster than the LH model predicts, with stronger deviations for superfine grain graphite than for medium grain grades. It was also found empirically that the apparent reaction order for water has a sigmoid-type variation withmore » temperature which follows the integral Boltzmann distribution function. This suggests that the apparent activation with temperature of graphite reactive sites that causes deviations from the LH model is rooted in specific structural and electronic properties of surface sites on graphite. A semi-global kinetic model was proposed, whereby the classical LH model was modified with a temperature-dependent reaction order for water. The new Boltzmann-enhanced model (BLH) was shown to consistently predict experimental oxidation rates over large ranges of temperature (800-1100 oC) and partial pressures of water (3-1200 Pa) and hydrogen (0-300 Pa), not only for the four grades of graphite but also for the historic grade H-451. The BLH model offers as more reliable input for modeling the chemical environment effects during the life-time operation of new grades of graphite in advanced nuclear reactors operating at high and very high temperatures.« less

Catalytic methods using molecular oxygen for treatment of PMMS and ECLSS waste streams, volume 2

NASA Technical Reports Server (NTRS)

Akse, James R.

1992-01-01

Catalytic oxidation has proven to be an effective addition to the baseline sorption, ion exchange water reclamation technology which will be used on Space Station Freedom (SSF). Low molecular weight, polar organics such as alcohols, aldehydes, ketones, amides, and thiocarbamides which are poorly removed by the baseline multifiltration (MF) technology can be oxidized to carbon dioxide at low temperature (121 C). The catalytic oxidation process by itself can reduce the Total Organic Carbon (TOC) to below 500 ppb for solutions designed to model these waste waters. Individual challenges by selected contaminants have shown only moderate selectivity towards particular organic species. The combined technology is applicable to the more complex waste water generated in the Process Materials Management System (PMMS) and Environmental Control and Life Support System (ECLSS) aboard SSF. During the phase 3 Core Module Integrated Facility (CMIF) water recovery tests at NASA MSFC, real hygiene waste water and humidity condensate were processed to meet potable specifications by the combined technology. A kinetic study of catalytic oxidation demonstrates that the Langmuir-Hinshelwood rate equation for heterogeneous catalysts accurately represent the kinetic behavior. From this relationship, activation energy and rate constants for acetone were determined.

Solar photocatalytic degradation of mono azo methyl orange and diazo reactive green 19 in single and binary dye solutions: adsorbability vs photodegradation rate.

PubMed

Ong, Soon-An; Min, Ohm-Mar; Ho, Li-Ngee; Wong, Yee-Shian

2013-05-01

The objective of this study was to examine the effects of adsorbability and number of sulfonate group on solar photocatalytic degradation of mono azo methyl orange (MO) and diazo Reactive Green 19 (RG19) in single and binary dye solutions. The adsorption capacity of MO and RG19 onto the TiO₂ was 16.9 and 26.8 mg/g, respectively, in single dye solution, and reduced to 5.0 and 23.1 mg/g, respectively, in the binary dye solution. The data obtained for photocatalytic degradation of MO and RG19 in single and binary dye solution were well fitted with the Langmuir-Hinshelwood kinetic model. The pseudo-first-order rate constants of diazo RG19 were significant higher than the mono azo MO either in single or binary dye solutions. The higher number of sulfonate group in RG19 contributed to better adsorption capacity onto the surface of TiO₂ than MO indicating greater photocatalytic degradation rate.

Effect of deposition of Ag on TiO2 nanoparticles on the photodegradation of Reactive Yellow-17.

PubMed

Rupa, A Valentine; Manikandan, D; Divakar, D; Sivakumar, T

2007-08-25

Nanoparticles of TiO(2) were synthesized by sol-gel technique and the photodeposition of about 1% Ag on TiO(2) particles was carried out. Ag-deposited TiO(2) catalyst was characterised by XRD, TEM and UV-vis spectroscopy. The Ag-TiO(2) catalyst was evaluated for their photocatalytic activity towards the degradation of Reactive Yellow-17 (RY-17) under UV and visible light irradiations. Then the results were compared with synthesized nano-TiO(2) sol and P-25 Degussa and the enhanced degradation was obtained with Ag-deposited TiO(2). This enhanced activity of Ag-TiO(2) may be attributed to the trapping of conduction band electrons. The effect of initial dye concentration, pH and electron acceptors such as H(2)O(2), K(2)S(2)O(8) on the photocatalytic activity were studied and the results obtained were fitted with Langmuir-Hinshelwood model to study the degradation kinetics and discussed in detail.

[TiO2-Induced Photodegradation of Levofloxacin by Visible Light and Its Mechanism].

PubMed

Guo, Hong-sheng; Liu, Ya-nan; Qiao, Qi; Wei, Hong; Dong, Cheng-xing; Xue, Jie; Li, Ke-bin

2015-05-01

Levofloxacin is an emerging pollutant. Single levofloxacin and TiO2 have no visible-light activity. However, photodegradation of levofloxacin dramatically enhanced in the presence of TiO2 under visible light irradiation. Considering this finding, he photodegradation of levofloxacin over TiO2 was investigated under visible light irradiation. Effects of TiO2 dosage, levofloxacin concentration, and solution pH on levofloxacin photodegradation were examined by monitoring its concentration decay with time. The results showed that levofloxacin photodegradation fitted the Langmuir-Hinshelwood kinetic model. Solution pH, TiO2 dose, and levofloxacin concentration had significant effects on the photodegradation rates. In addition, batch adsorption experiments revealed that adsorption of levofloxacin on TiO2 conformed to the pseudo-second-order kinetics and the Langmuir isotherm. DRS spectrum of levofloxacin-adsorbed TiO2 suggested that a surface complex was formed between levofloxacin and TiO2. Addition of radical scavengers and N2-degassing affecting levofloxacin photodegradation indicated that the superoxide ion radical was mainly active species. UV-Vis spectra of a deaerated TiO2 and levofloxacin suspensions further confirmed that the electron injection into TiO2 conduction band took place under visible light irradiation. Based on these results, a charge-transfer mechanism initiated by photoexcitation of TiO2/ levofloxacin surface complex was proposed for levofloxacin photocatalytic degradation over TiO2 under visible light. This study indicates that the charge-transfer-complex-mediated photocatalytic technique has promising applications in the removal of colorless organic pollutants.

Photocatalytic degradation of carbofuran by TiO2-coated activated carbon: Model for kinetic, electrical energy per order and economic analysis.

PubMed

Vishnuganth, M A; Remya, Neelancherry; Kumar, Mathava; Selvaraju, N

2016-10-01

The photocatalytic removal of carbofuran (CBF) from aqueous solution in the presence of granular activated carbon supported TiO2 (GAC-TiO2) catalyst was investigated under batch-mode experiments. The presence of GAC enhanced the photocatalytic efficiency of the TiO2 catalyst. Experiments were conducted at different concentrations of CBF to clarify the dependence of apparent rate constant (kapp) in the pseudo first-order kinetics on CBF photodegradation. The general relationship between the adsorption equilibrium constant (K) and reaction rate constant (kr) were explained by using the modified Langmuir-Hinshelwood (L-H) model. From the observed kinetics, it was observed that the surface reaction was the rate limiting step in the GAC-TiO2 catalyzed photodegradation of CBF. The values of K and kr for this pseudo first-order reaction were found to be 0.1942 L  mg(-1) and 1.51 mg L(-1) min(-1), respectively. In addition, the dependence of kapp on the half-life time was determined by calculating the electrical energy per order experimentally (EEO experimental) and also by modeling (EEO model). The batch-mode experimental outcomes revealed the possibility of 100% CBF removal (under optimized conditions and at an initial concentration of 50 mg L(-1) and 100 mg L(-1)) at a contact time of 90 min and 120 min, respectively. Both L-H kinetic model and EEO model fitted well with the batch-mode experimental data and also elucidated successfully the phenomena of photocatalytic degradation in the presence of GAC-TiO2 catalyst. Copyright © 2016 Elsevier Ltd. All rights reserved.

Adsorption and photocatalytic degradation of 2-CP in wastewater onto CS/CoFe₂O ₄ nanocomposite synthesized using gamma radiation.

PubMed

Taleb, Manal F Abou

2014-12-19

Photocatalytic degradation of 2-chlorophenol (2-CP) was studied using the photocatalyst chitosane/CoFe2O4 nanocomposite (CS/CF) under visible light. CS/CF nanocomposites were synthesized via gamma irradiation cross-linking method with the aid of sonication. Physical characteristics of CS/CF were studied using infrared spectrophotometer (IR), scanning electron microscopy (SEM), transmission electron microscope (TEM) and ultraviolet-visible (UV-vis) spectroscopy. Their photocatalytic activity was tested for the degradation of 2-CP in aqueous medium using sunlight. The effect of different parameters such as catalyst concentration, 2-CP concentration and reaction pH on degradation was also examined. It was verified that the 2-CP degradation rate fits a pseudo-first-order kinetics for initial 2-CP concentrations between 25 and 100mg/l, at 30°C. The degradation kinetics fit well Langmuir-Hinshelwood rate law. The degradation of (2-CP) follows pseudo-first-order kinetics. Results showed that after the catalyst had been used 5 times repeatedly, the degradation rate was still above 80%. Copyright © 2014 Elsevier Ltd. All rights reserved.

Extracting surface diffusion coefficients from batch adsorption measurement data: application of the classic Langmuir kinetics model.

PubMed

Chu, Khim Hoong

2017-11-09

Surface diffusion coefficients may be estimated by fitting solutions of a diffusion model to batch kinetic data. For non-linear systems, a numerical solution of the diffusion model's governing equations is generally required. We report here the application of the classic Langmuir kinetics model to extract surface diffusion coefficients from batch kinetic data. The use of the Langmuir kinetics model in lieu of the conventional surface diffusion model allows derivation of an analytical expression. The parameter estimation procedure requires determining the Langmuir rate coefficient from which the pertinent surface diffusion coefficient is calculated. Surface diffusion coefficients within the 10 -9 to 10 -6  cm 2 /s range obtained by fitting the Langmuir kinetics model to experimental kinetic data taken from the literature are found to be consistent with the corresponding values obtained from the traditional surface diffusion model. The virtue of this simplified parameter estimation method is that it reduces the computational complexity as the analytical expression involves only an algebraic equation in closed form which is easily evaluated by spreadsheet computation.

Modeling and 3D-simulation of hydrogen production via methanol steam reforming in copper-coated channels of a mini reformer

NASA Astrophysics Data System (ADS)

Sari, Ataallah; Sabziani, Javad

2017-06-01

Modeling and CFD simulation of a three-dimensional microreactor includes thirteen structured parallel channels is performed to study the hydrogen production via methanol steam reforming reaction over a Cu/ZnO/Al2O3 catalyst. The well-known Langmuir-Hinshelwood macro kinetic rate expressions reported by Peppley and coworkers [49] are considered to model the methanol steam reforming reactions. The effects of inlet steam to methanol ratio, pre-heat temperature, channels geometry and size, and the level of external heat flux on the hydrogen quality and quantity (i.e., hydrogen flow rate and CO concentration) are investigated. Moreover, the possibility of reducing the CO concentration by passing the reactor effluent through a water gas shift channel placed in series with the methanol reformer is studied. Afterwards, the simulation results are compared with the experimental data reported in the literature considering two different approaches of mixture-averaged and Maxwell-Stefan formulations to evaluate the diffusive flux of mass. The results indicate that the predictions of the Maxwell-Stefan model is in better agreement with experimental data than mixture-averaged one, especially at the lower feed flow rates.

Photocatalytic degradation kinetics of naphthenic acids in oil sands process-affected water: Multifactorial determination of significant factors.

PubMed

Leshuk, Tim; de Oliveira Livera, Diogo; Peru, Kerry M; Headley, John V; Vijayaraghavan, Sucharita; Wong, Timothy; Gu, Frank

2016-12-01

Oil sands process-affected water (OSPW) is generated as a byproduct of bitumen extraction in Canada's oil sands. Due to the water's toxicity, associated with dissolved acid extractable organics (AEO), especially naphthenic acids (NAs), along with base-neutral organics, OSPW may require treatment to enable safe discharge to the environment. Heterogeneous photocatalysis is a promising advanced oxidation process (AOP) for OSPW remediation, however, predicting treatment efficacy can be challenging due to the unique water chemistry of OSPW from different tailings ponds. The objective of this work was to study various factors affecting the kinetics of photocatalytic AEO degradation in OSPW. The rate of photocatalytic treatment varied significantly in two different OSPW sources, which could not be accounted for by differences in AEO composition, as studied by high resolution mass spectrometry (HRMS). The effects of inorganic water constituents were investigated using factorial and response surface experiments, which revealed that hydroxyl (HO) radical scavenging by iron (Fe 3+ ) and bicarbonate (HCO 3 - ) inhibited the NA degradation rate. The effects of NA concentration and temperature on the treatment kinetics were also evaluated in terms of Langmuir-Hinshelwood and Arrhenius models; pH and temperature were identified as weak factors, while dissolved oxygen (DO) was critical to the photo-oxidation reaction. Accounting for all of these variables, a general empirical kinetic expression is proposed, enabling prediction of photocatalytic treatment performance in diverse sources of OSPW. Copyright © 2016 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polster, C. S.; Zhang, R.; Cyb, M. T.

CO and H{sub 2} oxidation were studied over a series of Pt/CeO{sub 2} catalysts with differing Pt loadings and dispersions. Kinetic rate analysis confirms the presence of dual Langmuir-Hinshelwood (L-H) and Mars and van Krevelen (M-vK) pathways and is used to explain the loss in CO oxidation selectivity at low CO concentrations. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) shows the strong CO coverage dependence on both CO and O{sub 2} concentrations and explains the transition from L-H to M-vK reaction character. Redox site measurements are performed on Pt/CeO{sub 2} catalysts by anaerobic titrations under conditions where themore » M-vK pathway dominates the reaction rate. Similar redox site densities per interfacial Pt atom suggest that interfacial Pt-O-Ce sites are responsible for M-vK redox activity.« less

Solar photocatalytic degradation of chlorophenols mixture (4-CP and 2,4-DCP): Mechanism and kinetic modelling.

PubMed

Abeish, Abdulbasit M; Ang, Ha Ming; Znad, Hussein

2015-01-01

The solar-photocatalytic degradation mechanisms and kinetics of 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) using TiO2 have been investigated both individually and combined. The individual solar-photocatalytic degradation of both phenolic compounds showed that the reaction rates follow pseudo-first-order reaction. During the individual photocatalytic degradation of both 4-CP and 2,4-DCP under the same condition of TiO2 (0.5 g L(-1)) and light intensities (1000 mW cm(-2)) different intermediates were detected, three compounds associated with 4-CP (hydroquinone (HQ), phenol (Ph) and 4-chlorocatechol (4-cCat)) and two compounds associated with 2,4-DCP (4-CP and Ph). The photocatalytic degradation of the combined mixture (4-CP and 2,4-DCP) was also investigated at the same conditions and different 2,4-DCP initial concentrations. The results showed that the degradation rate of 4-CP decreases when the 2,4-DCP concentration increases. Furthermore, the intermediates detected were similar to that found in the individual degradation but with high Ph concentration. Therefore, a possible reaction mechanism for degradation of this combined mixture was proposed. Moreover, a modified Langmuir-Hinshelwood (L-H) kinetic model considering all detected intermediates was developed. A good agreement between experimental and estimated results was achieved. This model can be useful for scaling-up purposes more accurately as its considering the intermediates formed, which has a significant effect on degrading the main pollutants (4-CP and 2,4-DCP).

Preparation of photocatalytic ZnO nanoparticles and application in photochemical degradation of betamethasone sodium phosphate using taguchi approach

NASA Astrophysics Data System (ADS)

Giahi, M.; Farajpour, G.; Taghavi, H.; Shokri, S.

2014-07-01

In this study, ZnO nanoparticles were prepared by a sol-gel method for the first time. Taguchi method was used to identify the several factors that may affect degradation percentage of betamethasone sodium phosphate in wastewater in UV/K2S2O8/nano-ZnO system. Our experimental design consisted of testing five factors, i.e., dosage of K2S2O8, concentration of betamethasone sodium phosphate, amount of ZnO, irradiation time and initial pH. With four levels of each factor tested. It was found that, optimum parameters are irradiation time, 180 min; pH 9.0; betamethasone sodium phosphate, 30 mg/L; amount of ZnO, 13 mg; K2S2O8, 1 mM. The percentage contribution of each factor was determined by the analysis of variance (ANOVA). The results showed that irradiation time; pH; amount of ZnO; drug concentration and dosage of K2S2O8 contributed by 46.73, 28.56, 11.56, 6.70, and 6.44%, respectively. Finally, the kinetics process was studied and the photodegradation rate of betamethasone sodium phosphate was found to obey pseudo-first-order kinetics equation represented by the Langmuir-Hinshelwood model.

Kinetic and catalytic analysis of mesoporous Co3O4 on the oxidation of morin

NASA Astrophysics Data System (ADS)

Xaba, Morena. S.; Meijboom, Reinout

2017-11-01

Herein we report on the synthesis, characterization and catalytic evaluation of mesoporous cobalt oxides on the oxidation of morin. These mesoporous cobalt oxides were synthesized using an inverse surfactant micelle method, they are connected, well-defined with intra-particle voids. These materials were calcined to different final heating temperatures of 150, 250, 350, 450 and 550 °C, and each mesoporous cobalt oxide catalyst showed unique physical properties and catalytic behavior. Morin oxidation was used as a model reaction in the presence of hydrogen peroxide to evaluate the kinetic and catalytic activity of calcined mesoporous cobalt oxides. The adsorption-desorption equilibrium rate constants of morin and hydrogen peroxide were found to be inversely proportional to the crystallite size of the mesoporous cobalt oxide, and the characteristic path length in which the mass transfer takes place was found to be directly proportional to the crystallite size. The materials were characterized using powder X-Ray Diffraction (p-XRD), N2-sorption isotherms (BET), hydrogen temperature programmed reduction (H2-TPR) and High Resolution-Transmission Electron Microscopy (HR-TEM). UV-vis spectrophotometry was used to monitor the time-resolved absorbance of morin at λmax = 410 nm. The surface reaction in this system is described in terms of the well-established Langmuir-Hinshelwood model. The thermodynamic parameters, EA, ΔH#, ΔS# and ΔG# were calculated and catalyst recycling and reusability is demonstrated.

Efficient photo-catalytic degradation of malachite green using nickel tungstate material as photo-catalyst.

PubMed

Helaïli, N; Boudjamaa, A; Kebir, M; Bachari, K

2017-03-01

The present study focused on the evaluation of photo-catalytic and photo-electrochemical properties of the photo-catalyst based on nickel tungstate material prepared by a nitrate method through the degradation of malachite green (MG) dye's. The effect of catalyst loading and dye concentration was examined. Physico-chemical, optical, electrical, electrochemical, and photo-electrochemical properties of the prepared material were analyzed by X-ray diffraction (XRD), fourier transform-infrared spectroscopy (FTIR), BET analysis, optical reflectance diffuse (DR), scanning electron microscopy (SEM/EDX), electrical conductivity, cyclic voltammetry (CV), current intensity, mott-shottky, and nyquist. XRD revealed the formation of monoclinic structure with a small particle size. BET surface area of the sample was around 10 m 2 /g. The results show that the degradation of MG was more than 80%, achieved after 3 h of irradiation at pH 4.6 and with a catalyst loading of 75 mg. Also, it was found that the dye photo-degradation obeyed the pseudo-first order kinetic via Langmuir Hinshelwood model.

Investigation of optimum conditions and costs estimation for degradation of phenol by solar photo-Fenton process

NASA Astrophysics Data System (ADS)

Gar Alalm, Mohamed; Tawfik, Ahmed; Ookawara, Shinichi

2017-03-01

In this study, solar photo-Fenton reaction using compound parabolic collectors reactor was assessed for removal of phenol from aqueous solution. The effect of irradiation time, initial concentration, initial pH, and dosage of Fenton reagent were investigated. H2O2 and aromatic intermediates (catechol, benzoquinone, and hydroquinone) were quantified during the reaction to study the pathways of the oxidation process. Complete degradation of phenol was achieved after 45 min of irradiation when the initial concentration was 100 mg/L. However, increasing the initial concentration up to 500 mg/L inhibited the degradation efficiency. The dosage of H2O2 and Fe+2 significantly affected the degradation efficiency of phenol. The observed optimum pH for the reaction was 3.1. Phenol degradation at different concentration was fitted to the pseudo-first order kinetic according to Langmuir-Hinshelwood model. Costs estimation for a large scale reactor based was performed. The total costs of the best economic condition with maximum degradation of phenol are 2.54 €/m3.

Preparation and application of nanoglued binary titania-silica aerogel.

PubMed

Luo, Liang; Cooper, Adrienne T; Fan, Maohong

2009-01-15

Nanoglued binary titania (TiO2)-silica (SiO2) aerogel, as a novel type of photocatalyst, has been synthesized on glass substrates. Using an about-to-gel SiO2 sol as nanoglue, anatase TiO2 aerogel was immobilized into a three-dimensional mesoporous network of the SiO2. Factorial designs were employed to optimize both TiO2 aerogel and binary TiO2-SiO2 aerogel synthesis. Characterization of the as-prepared TiO2 and binary samples by surface area, porosity, and surface chemical composition showed that the photocatalysts were high-surface-area nanoporous materials, with a Ti4+ valency. The binary aerogel exhibited high photocatalytic activity for the degradation of methylene blue (MB) under simulated solar light; the reaction followed the pseudo first-order Langmuir-Hinshelwood (L-H) kinetic model. Fluorescence spectroscopy revealed that the hydroxyl (*OH) radical was formed during the illumination of the binary TiO2-SiO2 aerogel in a solution of probe molecules, which corroborates the probable mechanism of hydroxyl radical oxidation of contaminants in photocatalytic reactions.

Molecular Hydrogen Formation : Effect of Dust Grain Temperature Fluctuations

NASA Astrophysics Data System (ADS)

Bron, Emeric; Le Bourlot, Jacques; Le Petit, Franck

2013-06-01

H_{2} formation is a hot topic in astrochemistry. Thanks to Copernicus and FUSE satellites, its formation rate on dust grains in diffuse interstellar gas has been inferred (Jura 1974, Gry et al. 2002). Nevertheless, detection of H_2 emission in PDRs by ISO and Spitzer (Habart et al., 2004, 2005, 2011 ) showed that its formation mechanism can be efficient on warm grains (warmer than 30K), whereas experimental studies showed that Langmuir-Hinshelwood mechanism is only efficient in a narrow window of grain temperatures (typically between 10-20 K). The Eley-Rideal mechanism, in which H atoms are chemically bound to grains surfaces could explain such a formation rate in PDRs (Le Bourlot et al. 2012 ). Usual dust size distributions (e.g. Mathis et al. 1977 ) favor smaller grains in a way that makes most of the available grain surface belong to small grains. As small grains are subject to large temperature fluctuations due to UV-photons absorption, calculations at a fixed temperature give incorrect results under strong UV-fields. Here, we present a comprehensive study of the influence of this stochastic effect on H_2 formation by Langmuir-Hinshelwood and Eley-Rideal mechanisms. We use a master equation approach to calculate the statistics of coupled fluctuations of the temperature and adsorbed H population of a grain. Doing so, we are able to calculate the formation rate on a grain under a given radiation field and given gas conditions. We find that the Eley-Rideal mechanism remains an efficient mechanism in PDRs, and that the Langmuir-Hinshelwood mechanism is more efficient than expected on warm grains. This procedure is then coupled to full cloud simulations with the Meudon PDR code. We compare the new results with more classical evaluations of the formation rate, and present the differences in terms of chemical structure of the cloud and observable line intensities. We will also highlight the influence of some microphysical parameters on the results.

Photocatalytic degradation of E. coliform in water.

PubMed

Sun, Darren Delai; Tay, Joo Hwa; Tan, Koh Min

2003-08-01

This study aims to further investigate the total mineralization of the bacteria to the extent of death and cell-mass inactivation using a TiO2-Fe2O3 membrane photocatalytic oxidation reactor. Experimental results clearly indicated that dissolved oxygen (DO), hydraulic retention time (HRT) and concentration of the model bacteria (Escherichia coliform) affected the removal efficiency. It was found that the ultimate removal efficiency was 99% at DO level of 21.34 mg/l, HRT at 60s and high concentration of E. coli at 10(9)CFU/ml. The morphologic studies also showed that E. coliform could be further mineralized into CO2 and H2O. Dissolved organic carbon, pH and gas chromatograph analysis had justified most importantly the evolution of CO2. Experimental results revealed that the photomineralization rate of E. coliform followed pseudo-first-order kinetics by the role of DO. The derived empirical models were found consistent with the proposed reaction pathways of a combined UV breakdown on mass cell and a dual-site Langmuir-Hinshelwood mechanism where the rate-controlling step is the surface interaction between the adsorbed cleavage bacterial cells and hydroxyl radicals.

Photocatalytic characteristic and photodegradation kinetics of toluene using N-doped TiO2 modified by radio frequency plasma.

PubMed

Shie, Je-Lueng; Lee, Chiu-Hsuan; Chiou, Chyow-San; Chen, Yi-Hung; Chang, Ching-Yuan

2014-01-01

This study investigates the feasibility of applications of the plasma surface modification of photocatalysts and the removal of toluene from indoor environments. N-doped TiO2 is prepared by precipitation methods and calcined using a muffle furnace (MF) and modified by radio frequency plasma (RF) at different temperatures with light sources from a visible light lamp (VLL), a white light-emitting diode (WLED) and an ultraviolet light-emitting diode (UVLED). The operation parameters and influential factors are addressed and prepared for characteristic analysis and photo-decomposition examination. Furthermore, related kinetic models are established and used to simulate the experimental data. The characteristic analysis results show that the RF plasma-calcination method enhanced the Brunauer Emmett Teller surface area of the modified photocatalysts effectively. For the elemental analysis, the mass percentages of N for the RF-modified photocatalyst are larger than those of MF by six times. The aerodynamic diameters of the RF-modifiedphotocatalyst are all smaller than those of MF. Photocatalytic decompositions of toluene are elucidated according to the Langmuir-Hinshelwood model. Decomposition efficiencies (eta) of toluene for RF-calcined methods are all higher than those of commercial TiO2 (P25). Reaction kinetics ofphoto-decomposition reactions using RF-calcined methods with WLED are proposed. A comparison of the simulation results with experimental data is also made and indicates good agreement. All the results provide useful information and design specifications. Thus, this study shows the feasibility and potential use of plasma modification via LED in photocatalysis.

The effect of water presence on the photocatalytic oxidation of benzene, toluene, ethylbenzene and m-xylene in the gas-phase

NASA Astrophysics Data System (ADS)

Korologos, Christos A.; Philippopoulos, Constantine J.; Poulopoulos, Stavros G.

2011-12-01

In the present work, the gas-solid heterogeneous photocatalytic oxidation of benzene, toluene, ethylbenzene and m-xylene (BTEX) over UV-irradiated titanium dioxide was studied in an annular reactor operated in the CSTR (continuous stirred-tank reactor) mode. GC-FID and GC-MS were used for analysing reactor inlet and outlet streams. Initial BTEX concentrations were in the low parts per million (ppmv) range, whereas the water concentration was in the range of 0-35,230 ppmv and the residence time varied from 50 to 210 s. The effect of water addition on the photocatalytic process showed strong dependence on the type of the BTEX and the water vapour concentration. The increase in residence time resulted in a considerable increase in the conversion achieved for all compounds and experimental conditions. There was a clear interaction between residence time and water presence regarding the effect on conversions achieved. It was established that conversions over 95% could be achieved by adjusting appropriately the experimental conditions and especially the water concentration in the reactor. In all cases, no by-products were detected above the detection limit and carbon dioxide was the only compound detected. Finally, various Langmuir-Hinshelwood kinetic models have been tested in the analysis of the experimental data obtained. The kinetic data obtained confirmed that water had an active participation in the photocatalytic reactions of benzene, toluene, ethylbenzene and m-xylene since the model involving reaction of BTEX and water adsorbed on different active sites yielded the most successful fitting to the experimental results for the first three compounds, whereas the kinetic model based on the assumption that reaction between VOC and water dissociatively adsorbed on the photocatalyst takes place was the most appropriate in the case of m-xylene.

A kinetic model for the synthesis of high-molecular-weight alcohols over a sulfided Co-K-Mo/C catalyst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gunturu, A.K.; Kugler, E.L.; Cropley, J.B.

A statistically designed set of experiments was run in a recycle reactor to evaluate the kinetics of the formation of higher-molecular-weight alcohols (higher alcohols) and total hydrocarbon byproducts from synthesis gas (hydrogen and carbon monoxide) in a range of experimental conditions that mirrors the limits of commercial production. The alkali-promoted, C-supported Co-Mo sulfide catalyst that was employed in this study is well known for its sulfur resistance. The reaction was carried out in a gradientless Berty-type recycle reactor. A two-level fractional-factorial set consisting of 16 experiments was performed. Five independent variables were selected for this study, namely, temperature, partial pressuremore » of carbon monoxide, partial pressure of hydrogen, partial pressure of inerts, and methanol concentration in the feed. The major oxygenated products were linear alcohols up to n-butanol, but alcohols of higher carbon number were also detected, and analysis of the liquid product revealed the presence of trace amounts of ethers also. Yields of hydrocarbons were non-negligible. The alcohol product followed an Anderson-Schultz-Flory distribution. From the results of the factorial experiments, a preliminary power-law model was developed, and the statistically significant variables in the rate expression for the production of each alcohol were found. Based on the results of the power-law models, rate expressions of the Langmuir-Hinshelwood type were fitted. The observed kinetics are consistent with the rate-limiting step for the production of each higher alcohol being a surface reaction of the alcohol of next-lower carbon number. All other steps, including CO-insertion, H{sub 2}-cleavage, and hydrogenation steps, do not appear to affect the rate correlations.« less

Dissolution of Nickel Ferrite in Aqueous Solutions Containing Oxalic Acid and Ferrous Salts.

PubMed

Figueroa, Carlos A.; Sileo, Elsa E.; Morando, Pedro J.; Blesa, Miguel A.

2000-05-15

The dissolution of nickel ferrite in oxalic acid and in ferrous oxalate-oxalic acid aqueous solution was studied. Nickel ferrite was synthesized by thermal decomposition of a mixed tartrate; the particles were shown to be coated with a thin ferric oxide layer. Dissolution takes place in two stages, the first one corresponding to the dissolution of the ferric oxide outer layer and the second one being the dissolution of Ni(1.06)Fe(1.96)O(4). The kinetics of dissolution during this first stage is typical of ferric oxides: in oxalic acid, both a ligand-assisted and a redox mechanism operates, whereas in the presence of ferrous ions, redox catalysis leads to a faster dissolution. The rate dependence on both oxalic acid and on ferrous ion is described by the Langmuir-Hinshelwood equation; the best fitting corresponds to K(1)(ads)=25.6 mol(-1) dm(-3) and k(1)(max)=9.17x10(-7) mol m(-2) s(-1) and K(2)(ads)=37.1x10(3) mol(-1) dm(-3) and k(2)(max)=62.3x10(-7) mol m(-2) s(-1), respectively. In the second stage, Langmuir-Hinshelwood kinetics also describes the dissolution of iron and nickel from nickel ferrite, with K(1)(ads)=20.8 mol(-1) dm(3) and K(2)(ads)=1.16x10(5) mol(-1) dm(3). For iron, k(1)(max)=1.02x10(-7) mol of Fe m(-2) s(-1) and k(2)(max)=2.38x10(-7) mol of Fe m(-2) s(-1); for nickel, the rate constants k(1)(max) and k(2)(max) are 2.4 and 1.79 times smaller, respectively. The factor 1.79 agrees nicely with the stoichiometric ratio, whereas the factor 2.4 implies the accumulation of some nickel in the residual particles. The rate of nickel dissolution in oxalic acid is higher than that in bunsenite by a factor of 8, whereas hematite is more reactive by a factor of 9 (in the absence of Fe(II)) and 27 (in the presence of Fe (II)). It may be concluded that oxalic acid operates to dissolve iron, and the ensuing disruption of the solid framework accelerates the release of nickel. Copyright 2000 Academic Press.

Scattering, Adsorption, and Langmuir-Hinshelwood Desorption Models for Physisorptive and Chemisorptive Gas-Surface Systems

DTIC Science & Technology

2013-09-01

respectively, and ΦQw is the reflected flux of Q at complete accommodation. Typical properties of Q are tangential momentum mct , normal mo- mentum mcn, and...that σt ≡ mct −mc′t mct −mcw = ct − c′t ct , (9) 23 where c′t is the post-collisional tangential speed, and cw is the speed of the wall, which in this...was measured within an experimental error of ±0.02, and the coverage θ noise level was about 0.01 ML. 35 MKS simulations are compared with data in

Photodegradation of bisphenol-A in a batch TiO2 suspension reactor.

PubMed

Tsai, Wen-Tien; Lee, Mei-Kuei; Su, Ting-Yi; Chang, Yuan-Ming

2009-08-30

In this work, the photocatalytic behaviors of bisphenol-A (BPA), which has been listed as one of endocrine disrupting chemicals, were carried out in a batch TiO(2) suspension reactor. The photodegradation efficiency has been investigated under the controlled process parameters including initial BPA concentration (i.e., 1-50 mg L(-1)), TiO(2) dosage (i.e., 5-600 mg/200 cm(3)), initial pH (i.e., 3-11), and temperature (i.e., 10-70 degrees C). It was found that the optimal conditions in the photoreaction process could be coped with at initial BPA concentration=20 mg L(-1), TiO(2) dosage=0.5 g L(-1) (100mg/200 cm(3)), initial pH=7.0, and temperature=25 degrees C. According to the Langmuir-Hinshelwood model, the results showed that the photodegradation kinetics for the destruction of BPA in water also followed the first-order model well. The apparent first-order reaction constants (k(obs)), thus obtained from the fittings of the model, were in line with the destruction-removal efficiencies of BPA in all the photocatalytic experiments. Based on the intermediate products identified in the study, the possible mechanisms for the photodegradation of BPA in water were also proposed in the present study.

Photocatalytic removal of doxycycline from aqueous solution using ZnO nano-particles: a comparison between UV-C and visible light.

PubMed

Pourmoslemi, Shabnam; Mohammadi, Ali; Kobarfard, Farzad; Amini, Mohsen

2016-10-01

Zinc oxide nano-particles were synthesized, characterized and used for photocatalytic degradation of doxycycline using UV-C and visible light. Effects of several operational factors including initial pH of antibiotic solution, initial antibiotic concentration and ZnO nano-particles loading amount were investigated. Comparing photocatalytic degradation and mineralization of doxycycline under UV-C and visible light showed successful application of the method under both light sources. However, reaction rate was higher under UV-C irradiation, which degraded doxycycline almost completely in 5 hours, and 68% mineralization was achieved. Synthesized ZnO nano-particles were successfully applied for photocatalytic degradation of doxycycline in a pharmaceutical wastewater sample. The process was fitted to the pseudo first order kinetic model with rate constants in the range of 6-22(×10 -3 ) mg L -1 min -1 with respect to initial concentration of doxycycline under UV-C irradiation. The Langmuir-Hinshelwood model was also employed for describing the photocatalytic reaction with surface reaction kinetic constant k c and equilibrium adsorption constant K LH values calculated as 0.12 mg L -1 min -1 and 2.2 L mg -1 , respectively. Degradation of doxycycline was followed by UV-visible spectroscopy and a validated stability indicating high-performance liquid chromatography method that was developed using stressed samples of doxycycline and could selectively determine doxycycline in the presence of its degradation products. Mass spectrometry was used for determining final degradation products.

Fabrication of TiO2/MoS2@zeolite photocatalyst and its photocatalytic activity for degradation of methyl orange under visible light

NASA Astrophysics Data System (ADS)

Zhang, Weiping; Xiao, Xinyan; Zheng, Lili; Wan, Caixia

2015-12-01

TiO2/MoS2@zeolite composite photocatalysts with visible-light activity were fabricated via a simple ultrasonic-hydrothermal synthesis method, using TiCl4 as Ti source, MoS2 as a direct sensitizer, glycerol water solution with certain dispersion agent as hydrolytic agent, and zeolite as carrier. The structure, morphology, composition, optical properties, and specific surface area of the as-prepared photocatalysts were characterized by using XRD, FTIR, SEM-EDS, TEM, XPS, UV-vis, PL and BET analyzer, respectively. And the photocatalytic degradation of methyl orange (MO) in aqueous suspension has been employed to evaluate the photocatalytic activity and degradation kinetics of as-prepared photocatalysts with xenon lamp as irradiation source. The results indicate that: (1) TiO2/MoS2@zeolite composite photocatalysts exhibit enhanced photocatalytic activities for methyl orange (MO) degradation compared to Degussa P25; (2) photocatalytic degradation of MO obeys Langmuir-Hinshelwood kinetic model (pseudo-first order reaction), and its degradation rate constant (kapp) (2.304 h-1) is higher than that of Degussa P25 (0.768 h-1); (3) the heterostructure consisted of zeolite, MoS2 and TiO2 nanostructure could provide synergistic effect for degradation of MO due to the efficient electron transfer process and better absorption property of TiO2/MoS2@zeolite composite photocatalyst.

Comparative study on the process behavior and reaction kinetics in sonocatalytic degradation of organic dyes by powder and nanotubes TiO2.

PubMed

Pang, Yean Ling; Abdullah, Ahmad Zuhairi

2012-05-01

Sonocatalytic degradation of various organic dyes (Congo Red, Reactive Blue 4, Methyl Orange, Rhodamine B and Methylene Blue) catalyzed by powder and nanotubes TiO(2) was studied. Both catalysts were characterized using transmission electron microscope (TEM), surface analyzer, Raman spectroscope and thermal gravimetric analyzer (TGA). Sonocatalytic activity of powder and nanotubes TiO(2) was elucidated based on the degradation of various organic dyes. The former catalyst was favorable for treatment of anionic dyes, while the latter was more beneficial for cationic dyes. Sonocatalytic activity of TiO(2) nanotubes could be up to four times as compared to TiO(2) powder under an ultrasonic power of 100 W and a frequency of 42 kHz. This was associated with the higher surface area and the electrostatic attraction between dye molecules and TiO(2) nanotubes. Fourier transform-infrared spectrometer (FT-IR) was used to identify changes that occurred on the functional group in Rhodamine B molecules and TiO(2) nanotubes after the reaction. Sonocatalytic degradation of Rhodamine B by TiO(2) nanotubes apparently followed the Langmuir-Hinshelwood adsorption kinetic model with surface reaction rate of 1.75 mg/L min. TiO(2) nanotubes were proven for their high potential to be applied in sonocatalytic degradation of organic dyes. Copyright © 2011 Elsevier B.V. All rights reserved.

Synthesis, characterization and activity of an immobilized photocatalyst: natural porous diatomite supported titania nanoparticles.

PubMed

Wang, Bin; de Godoi, Fernanda Condi; Sun, Zhiming; Zeng, Qingcong; Zheng, Shuilin; Frost, Ray L

2015-01-15

Diatomite, a porous non-metal mineral, was used as support to prepare TiO2/diatomite composites by a modified sol-gel method. The as-prepared composites were calcined at temperatures ranging from 450 to 950 °C. The characterization tests included X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with an energy-dispersive X-ray spectrometer (EDS), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption/desorption measurements. The XRD analysis indicated that the binary mixtures of anatase and rutile exist in the composites. The morphology analysis confirmed the TiO2 particles were uniformly immobilized on the surface of diatom with a strong interfacial anchoring strength, which leads to few drain of photocatalytic components during practical applications. In further XPS studies of hybrid catalyst, we found the evidence of the presence of Ti-O-Si bond and increased percentage of surface hydroxyl. In addition, the adsorption capacity and photocatalytic activity of synthesized TiO2/diatomite composites were evaluated by studying the degradation kinetics of aqueous Rhodamine B under UV-light irradiation. The photocatalytic degradation was found to follow pseudo-first order kinetics according to the Langmuir-Hinshelwood model. The preferable removal efficiency was observed in composites by 750 °C calcination, which is attributed to a relatively appropriate anatase/rutile mixing ratio of 90/10. Copyright © 2014 Elsevier Inc. All rights reserved.

Development of solar-driven electrochemical and photocatalytic water treatment system using a boron-doped diamond electrode and TiO2 photocatalyst.

PubMed

Ochiai, Tsuyoshi; Nakata, Kazuya; Murakami, Taketoshi; Fujishima, Akira; Yao, Yanyan; Tryk, Donald A; Kubota, Yoshinobu

2010-02-01

A high-performance, environmentally friendly water treatment system was developed. The system consists mainly of an electrochemical and a photocatalytic oxidation unit, with a boron-doped diamond (BDD) electrode and TiO(2) photocatalyst, respectively. All electric power for the mechanical systems and the electrolysis was able to be provided by photovoltaic cells. Thus, this system is totally driven by solar energy. The treatment ability of the electrolysis and photocatalysis units was investigated by phenol degradation kinetics. An observed rate constant of 5.1 x 10(-3)dm(3)cm(-2)h(-1) was calculated by pseudo-first-order kinetic analysis for the electrolysis, and a Langmuir-Hinshelwood rate constant of 5.6 microM(-1)min(-1) was calculated by kinetic analysis of the photocatalysis. According to previous reports, these values are sufficient for the mineralization of phenol. In a treatment test of river water samples, large amounts of chemical and biological contaminants were totally wet-incinerated by the system. This system could provide 12L/day of drinking water from the Tama River using only solar energy. Therefore, this system may be useful for supplying drinking water during a disaster. (c) 2009 Elsevier Ltd. All rights reserved.

Kinetic model for microbial growth and desulphurisation with Enterobacter sp.

PubMed

Liu, Long; Guo, Zhiguo; Lu, Jianjiang; Xu, Xiaolin

2015-02-01

Biodesulphurisation was investigated by using Enterobacter sp. D4, which can selectively desulphurise and convert dibenzothiophene into 2-hydroxybiphenyl (2-HBP). The experimental values of growth, substrate consumption and product generation were obtained at 95 % confidence level of the fitted values using three models: Hinshelwood equation, Luedeking-Piret and Luedeking-Piret-like equations. The average error values between experimental values and fitted values were less than 10 %. These kinetic models describe all the experimental data with good statistical parameters. The production of 2-HBP in Enterobacter sp. was by "coupled growth".

Efficiency of barium removal from radioactive waste water using the combination of maghemite and titania nanoparticles in PVA and alginate beads.

PubMed

Majidnia, Zohreh; Idris, Ani; Majid, MuhdZaimiAbd; Zin, RosliMohamad; Ponraj, Mohanadoss

2015-11-01

In this paper, both maghemite (γ-Fe2O3) and titanium oxide (TiO2) nanoparticles were synthesized and mixed in various ratios and embedded in PVA and alginate beads. Batch sorption experiments were applied for removal of barium ions from aqueous solution under sunlight using the beads. The process has been investigated as a function of pH, contact time, temperature, initial barium ion concentration and TiO2:γ-Fe2O3 ratios (1:10, 1:60 and 1). The recycling attributes of these beads were also considered. Furthermore, the results revealed that 99% of the Ba(II) was eliminated in 150min at pH 8 under sunlight. Also, the maghemite and titania PVA-alginate beads can be readily isolated from the aqueous solution after the process and reused for at least 7 times without significant losses of their initial properties. The reduction of Ba(II) with maghemite and titania PVA-alginate beads fitted the pseudo first order and second order Langmuir-Hinshelwood (L-H) kinetic model. Copyright © 2015. Published by Elsevier Ltd.

Improved WO3 photocatalytic efficiency using ZrO2 and Ru for the degradation of carbofuran and ampicillin.

PubMed

Gar Alalm, Mohamed; Ookawara, Shinichi; Fukushi, Daisuke; Sato, Akira; Tawfik, Ahmed

2016-01-25

The photocatalytic degradation of carbofuran (pesticide) and ampicillin (pharmaceutical) using synthesized WO3/ZrO2 nanoparticles under simulated solar light was investigated. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectra analyses were used to characterize the prepared catalysts. The optimum ratio of WO3 to ZrO2 was determined to be 1:1 for the degradation of both contaminants. The degradation of carbofuran and ampicillin by WO3/ZrO2 after 240 min of irradiation was 100% and 96%, respectively. Ruthenium (Ru) was employed as an additive to WO3/ZrO2 to enhance the photocatalytic degradation rate. Ru/WO3/ZrO2 exhibited faster degradation rates than WO3/ZrO2. Furthermore, 100% and 97% degradation of carbofuran and ampicillin, respectively, was achieved using Ru/WO3/ZrO2 after 180 min of irradiation. The durability of the catalyst was investigated by reusing the same suspended catalyst, which achieved 92% of its initial efficiency. The photocatalytic degradation of ampicillin and carbofuran followed pseudo-first order kinetics according to the Langmuir-Hinshelwood model. Copyright © 2015 Elsevier B.V. All rights reserved.

Synthesis and photocatalytic activity of ytterbium-doped titania/diatomite composite photocatalysts

NASA Astrophysics Data System (ADS)

Tang, Wenjian; Qiu, Kehui; Zhang, Peicong; Yuan, Xiqiang

2016-01-01

Ytterbium-doped titanium dioxide (Yb-TiO2)/diatomite composite materials with different Yb concentrations were prepared by sol-gel method. The phase structure, morphology, and chemical composition of the as-prepared composites were well characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), and ultraviolet-visible (UV-vis) diffuse reflection spectroscopy. The XRD and Raman spectroscopy analysis indicated that the TiO2 existed in the form of pure anatase in the composites. The SEM images exhibited the well deposition and dispersion of TiO2 nanoparticles with little agglomeration on the surfaces of diatoms. The UV-vis diffuse reflection spectra showed that the band gap of TiO2 could be narrowed by the introduction of Yb species, which was further affected by doping concentration of Yb. The photocatalytic activity of synthesized samples was investigated by the degradation of methylene blue (MB) under UV light irradiation. It was observed that the photocatalytic degradation followed a pseudo-first-order kinetics according to the Langmuir-Hinshelwood model. Compared to TiO2 and TiO2/diatomite, the Yb-TiO2/diatomite composites exhibited higher photocatalytic activity toward degradation of MB using UV light irradiation.

Ultrasonic degradation of aqueous phenolsulfonphthalein (PSP) in the presence of nano-Fe/H2O2.

PubMed

Ayanda, Olushola S; Nelana, Simphiwe M; Naidoo, Eliazer B

2018-10-01

In this study, nano iron (nano-Fe) was successfully synthesized by sodium borohydride reduction of ferric chloride solution to enhance the ultrasonic degradation of phenolsulfonphthalein (PSP). The nano-Fe was characterized by scanning electron microscopy - energy dispersive spectroscopy (SEM-EDX), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), attenuated total reflection - Fourier transform infrared spectroscopy (ATR-FTIR), and Brunauer, Emmett and Teller (BET) surface area determination. Experimental results demonstrated that a combined ultrasonic/nano-Fe/H 2 O 2 system was more effective for PSP removal in combination than they were individually and there was a significant difference between the combined and single processes. The ultrasonic/nano-Fe/H 2 O 2 degradation follows the Langmuir-Hinshelwood (L-H) kinetic model. The addition of nano-Fe and H 2 O 2 to the ultrasonic reactor greatly accelerated the degradation of PSP (25 mg/L) from 12.5% up to 96.5%. These findings indicated that ultrasonic degradation in the presence of nano-Fe and H 2 O 2 is a promising and efficient technique for the elimination of emerging micropollutants from aqueous solution. Copyright © 2018 Elsevier B.V. All rights reserved.

Development and understanding of La0.85Sr0.15Cr1-xNixO3-δ anodes for La5.6WO11.4-δ-based Proton Conducting Solid Oxide Fuel Cells

NASA Astrophysics Data System (ADS)

Solís, Cecilia; Navarrete, Laura; Balaguer, María; Serra, José M.

2014-07-01

Porous electrodes based on the system La0.85Sr0.15Cr1-xNixO3-δ (x = 0.1 and 0.2) have been investigated as anodes for proton conducting solid oxide fuel cells based on the La5.6WO11.4-δ (LWO) electrolyte material. The microstructure of the anodes was optimized by varying both the starting powder morphology and the final anode sintering temperature. Two different electrode thicknesses were studied, i.e. 15 and 30 μm. The importance of the catalytic role of Ni was also studied by using different concentrations of Ni (10% and 20%) in the chromite and by tuning the Ni particle sizes through the control of the reduction temperature. Additionally, a ceramic-ceramic (cer-cer) composite electrode comprising a physical mixture of the optimized chromite and LWO phase was also considered. Finally, a kinetics study and modeling based on Langmuir-Hinshelwood mechanism was carried out in order to quantitatively describe the rate of dissociative adsorption of H2 on the Ni particles spread on the chromite surface.

Preparation and Characterization of Cu and Ni on Alumina Supports and Their Use in the Synthesis of Low-Temperature Metal-Phthalocyanine Using a Parallel-Plate Reactor.

PubMed

Sánchez-De la Torre, Fernando; De la Rosa, Javier Rivera; Kharisov, Boris I; Lucio-Ortiz, Carlos J

2013-09-30

Ni- and Cu/alumina powders were prepared and characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), and N₂ physisorption isotherms were also determined. The Ni/Al₂O₃ sample reveled agglomerated (1 μm) of nanoparticles of Ni (30-80 nm) however, NiO particles were also identified, probably for the low temperature during the H 2 reduction treatment (350 °C), the Cu/Al₂O₃ sample presented agglomerates (1-1.5 μm) of nanoparticles (70-150 nm), but only of pure copper. Both surface morphologies were different, but resulted in mesoporous material, with a higher specificity for the Ni sample. The surfaces were used in a new proposal for producing copper and nickel phthalocyanines using a parallel-plate reactor. Phthalonitrile was used and metallic particles were deposited on alumina in ethanol solution with CH₃ONa at low temperatures; ≤60 °C. The mass-transfer was evaluated in reaction testing with a recent three-resistance model. The kinetics were studied with a Langmuir-Hinshelwood model. The activation energy and Thiele modulus revealed a slow surface reaction. The nickel sample was the most active, influenced by the NiO morphology and phthalonitrile adsorption.

Surface retention and photochemical reactivity of the diphenylether herbicide oxyfluorfen.

PubMed

Scrano, Laura; Bufo, Sabino A; Cataldi, Tommaso R I; Albanis, Triantafyllos A

2004-01-01

The photochemical behavior of oxyfluorfen [2-chloro-1-(3-etoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene] on two Greek soils was investigated. Soils were sampled from Nea Malgara and Preveza regions, characterized by a different organic matter content. Soils were spiked with the diphenyl-ether herbicide and irradiation experiments were performed either in the laboratory with a solar simulator (xenon lamp) or outside, under natural sunlight irradiation; other soil samples were kept in the dark to control the retention reaction. Kinetic parameters of both retention and photochemical reactions were calculated using zero-, first- and second- (Langmuir-Hinshelwood) order equations, and best fit was checked through statistical analysis. The soil behaviors were qualitatively similar but quantitatively different, with the soil sampled from the Nea Malgara region much more sorbent as compared with Preveza soil. All studied reactions followed second-order kinetics and photochemical reactions were influenced by retaining capability of the soils. The contributions of the photochemical processes to the global dissipation rates were also calculated. Two main metabolites were identified as 2-chloro-1-(3-ethoxy-4-hydroxyphenoxy)-4-(trifluoromethyl)benzene and 2-chloro-1- (3-hydroxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene.

In situ photoelectrochemical/photocatalytic study of a dye discoloration in a microreactor system using TiO2 thin films.

PubMed

Montero-Ocampo, C; Gago, A; Abadias, G; Gombert, B; Alonso-Vante, N

2012-11-01

In this work, we report in situ studies of UV photoelectrocatalytic discoloration of a dye (indigo carmine) by a TiO(2) thin film in a microreactor to demonstrate the driving force of the applied electrode potential and the dye flow rate toward dye discoloration kinetics. TiO(2) 65-nm-thick thin films were deposited by PVD magnetron sputtering technique on a conducting glass substrate of fluorinated tin oxide. A microreactor to measure the discoloration rate, the electrode potential, and the photocurrent in situ, was developed. The dye solutions, before and after measurements in the microreactor, were analyzed by Raman spectroscopy. The annealed TiO(2) thin films had anatase structure with preferential orientation (101). The discoloration rate of the dye increased with the applied potential to TiO(2) electrode. Further, acceleration of the photocatalytic reaction was achieved by utilizing dye flow recirculation to the microreactor. In both cases the photoelectrochemical/photocatalytic discoloration kinetics of the dye follows the Langmuir-Hinshelwood model, with first-order kinetics. The feasibility of dye discoloration on TiO(2) thin film electrodes, prepared by magnetron sputtering using a flow microreactor system, has been clearly demonstrated. The discoloration rate is enhanced by applying a positive potential (E (AP)) and/or increasing the flow rate. The fastest discoloration and shortest irradiation time (50 min) produced 80% discoloration with an external anodic potential of 0.931 V and a flow rate of 12.2 mL min(-1).

Kinetic Study of Methyl Acetate Oxidation in a Pt/Al2O3 Fixed-Bed Reactor

NASA Technical Reports Server (NTRS)

Hoy, Michael; Li, K. Y.; Li, Jeffrey S.; Chen, S. M.; Yaws, C. L.; Chu, H. W.; Simon, W. E.

1994-01-01

To support technology development for future long-term missions, a metabolic simulator will be used in a closed chamber to test the functions of a Controlled Ecological Life Support System (CELSS). Methyl acetate (MA) was selected as the fuel because its metabolic respiratory quotient is near that of humans. A kinetic study of the catalytic oxidation of MA over Pt/Al203 was then conducted to support the design and operation of the simulator. Kinetic data were obtained as a conversion percentage of MA versus retention time. The reaction was studied at one atmosphere and temperatures from 220 to 340 deg. C. The inlet MA concentration was varied from 100 to 2000 ppm with retention times from 0.01 to 10 sec. A first-order rate law and a Langmuir-Hinshelwood rate equation were tested by nonlinear regression of the kinetic data to estimate rate constants in the rate law. Regression results of the L-H equation explain the kinetic data better than the results of the first-order rate law. A Taguchi experimental design was used to study the effects of temperature, retention time, and concentrations of MA, CO2, and O2 on the conversion of MA. Results indicate that temperature has greatest effect, followed by retention time, and finally MA concentration. It was further determined that the effects of CO2 and O2 concentrations, and the cross effects, are negligible.

Adsorption of aromatic hydrocarbons and ozone at environmental aqueous surfaces.

PubMed

Vácha, Robert; Cwiklik, Lukasz; Rezác, Jan; Hobza, Pavel; Jungwirth, Pavel; Valsaraj, Kalliat; Bahr, Stephan; Kempter, Volker

2008-06-05

Adsorption of environmentally important aromatic molecules on a water surface is studied by means of classical and ab initio molecular dynamics simulations and by reflection-absorption infrared spectroscopy. Both techniques show strong activity and orientational preference of these molecules at the surface. Benzene and naphthalene, which bind weakly to water surface with a significant contribution of dispersion interactions, prefer to lie flat on water but retain a large degree of orientational flexibility. Pyridine is more rigid at the surface. It is tilted with the nitrogen end having strong hydrogen bonding interactions with water molecules. The degree of adsorption and orientation of aromatic molecules on aqueous droplets has atmospheric implications for heterogeneous ozonolysis, for which the Langmuir-Hinshelwood kinetics mechanism is discussed. At higher coverages of aromatic molecules the incoming ozone almost does not come into contact with the underlying aqueous phase. This may rationalize the experimental insensitivity of the ozonolysis on the chemical nature of the substrate on which the aromatic molecules adsorb.

NO—CO—O2 Reaction on a Metal Catalytic Surface using Eley—Rideal Mechanism

NASA Astrophysics Data System (ADS)

Waqar, Ahmad

2008-10-01

Interactions among the reacting species NO, CO and O2 on metal catalytic surfaces are studied by means of Monte Carlo simulation using the Eley-Rideal (ER) mechanism. The study of this three-component system is important for understanding of the reaction kinetics by varying the relative ratios of the reactants. It is found that contrary to the conventional Langmuir-Hinshelwood (LH) thermal mechanism in which two irreversible phase transitions are obtained between active states and poisoned states, a single phase transition is observed when the ER mechanism is combined with the LH mechanism. The phase diagrams of the surface coverage and the steady state production of CO2, N2 and N2 O are evaluated as a function of the partial pressures of the reactants in the gas phase. The continuous production of CO2 starts as soon as the CO pressure is switched on and the second order phase transition at the first critical point is eliminated, which is in agreement with the experimental findings.

Rate acceleration of the heterogeneous reaction of ozone with a model alkene at the air-ice interface at low temperatures.

PubMed

Ray, Debajyoti; Malongwe, Joseph K'Ekuboni; Klán, Petr

2013-07-02

The kinetics of the ozonation reaction of 1,1-diphenylethylene (DPE) on the surface of ice grains (also called "artificial snow"), produced by shock-freezing of DPE aqueous solutions or DPE vapor-deposition on pure ice grains, was studied in the temperature range of 268 to 188 K. A remarkable and unexpected increase in the apparent ozonation rates with decreasing temperature was evaluated using the Langmuir-Hinshelwood and Eley-Rideal kinetic models, and by estimating the apparent specific surface area of the ice grains. We suggest that an increase of the number of surface reactive sites, and possibly higher ozone uptake coefficients are responsible for the apparent rate acceleration of DPE ozonation at the air-ice interface at lower temperatures. The increasing number of reactive sites is probably related to the fact that organic molecules are displaced more to the top of a disordered interface (or quasi-liquid) layer on the ice surface, which makes them more accessible to the gas-phase reactants. The effect of NaCl as a cocontaminant on ozonation rates was also investigated. The environmental implications of this phenomenon for natural ice/snow are discussed. DPE was selected as an example of environmentally relevant species which can react with ozone. For typical atmospheric ozone concentrations in polar areas (20 ppbv), we estimated that its half-life on the ice surface would decrease from ∼5 days at 258 K to ∼13 h at 188 K at submonolayer DPE loadings.

Effect of cold plasma pre-treatment on photocatalytic activity of 3D fabric loaded with nano-photocatalysts: Response surface methodology

NASA Astrophysics Data System (ADS)

Ghoreishian, Seyed Majid; Badii, Khashayar; Norouzi, Mohammad; Malek, Kaveh

2016-03-01

In this study, the physico-chemical effects occasioned by the cold plasma discharge (CPD) on the photo-decolorization of Reactive Orange 16 (RO16) by 3D fabrics (spacer fabrics) loaded with ZnO:TiO2 nano-photocatalysts (nphs) were optimized via response surface methodology (RSM). CPD was employed to improve the surface characteristics of the spacer fabrics for nphs loading. Surface morphology and color variation were studied utilizing scanning electron microscopy (SEM) and CIE-Lab system, respectively. The effect of CPD on the wetting ability of the spacer fabrics was examined using dynamic adsorption measurement (DAM). Also, X-ray fluorescence (XRF) was utilized to investigate the durability of the nphs on the spacer fabrics. All the experiments were implemented in a Box-Behnken design (BBD) with three independent variables (CPD treatment time, dye concentration and irradiation time) in order to optimize the decolorization of RO16. The anticipated values of the decolorization efficiency were found to be in excellent agreement with the experimental values (R2 = 0.9996, Adjusted R2 = 0.9992). The kinetic analysis demonstrated that the photocatalytic decolorization followed the Langmuir-Hinshelwood kinetic model. In conclusion, this heterogeneous photocatalytic process is capable of decolorizing and mineralizing azoic reactive dye in textile wastewater. Moreover, the results confirmed that RSM based on the BBD was a suitable method to optimize the operating conditions of RO16 degradation.

Investigation of Ag-TiO2 nanostructures photocatalytic properties prepared by modified dip coating method

NASA Astrophysics Data System (ADS)

AlArfaj, Esam

2016-05-01

In this article, titanium dioxide and silver nanostructures were deposited on glass substrates using modified sol-gel methods and dip-coating technique. The films were characterised chemically and physically using different techniques (TLC, UV-Vis and XRD) and tested for environmental applications regarding degradation of aromatic hydrocarbons. The photocatalytic activity of the TiO2 nanostructures is tested with different small concentrations of phenol in water and reaction mechanisms discussed. Considerable enhancement is observed in the photodegradation activity of Ag-modified (3 wt.%) TiO2 compared to unmodified TiO2 nanostructures for phenol concentrations within the pseudo-first-order Langmuir-Hinshelwood (LH) model for reaction kinetics. The pseudo-first-order global degradation rate constant increased from <0.005 min-1 for TiO2 to 0.013 min-1 for 3 mol% Ag-modified TiO2. The enhancement is attributed to the incorporation of Ag which promotes the generation of reactive oxygen species and increases the carrier recombination life-time. In addition, Ag has been observed to extend the absorption to the visible region by its surface plasmon resonances and to suppress the anatase-rutile phase transformation. Moreover, TiO2 grain size prepared was found to be 10 nm which maximises the active surface area. For phenol initial concentrations as low as 0.0002 M, saturation trend in the degradation process occurred at 0.00014 M and the reaction rate can be fitted with half-order LH kinetics.

Photocatalytic degradation of humic acid in saline waters. Part 1. Artificial seawater: influence of TiO2, temperature, pH, and air-flow.

PubMed

Al-Rasheed, Radwan; Cardin, David J

2003-06-01

We report the first systematic study on the photocatalytic oxidation of humic acid (HA) in artificial seawater (ASW). TiO(2) (Degussa P25) dispersions were used as the catalyst with irradiation from a medium-pressure mercury lamp. The optimum quantity of catalyst was found to be between 2 and 2.5 gl(-1); while the decomposition was fastest at low pH values (pH 4.5 in the range examined), and the optimum air-flow, using an immersion well reactor with a capacity of 400 ml, was 850 ml min(-1). Reactivity increased with air-flow up to this figure, above which foaming prevented operation of the reactor. Using pure oxygen, an optimal flow rate was observed at 300 ml min(-1), above which reactivity remains essentially constant. Following treatment for 1 h, low-salinity water (2700 mg l(-1)) was completely mineralised, whereas ASW (46000 mg l(-1)) had traces of HA remaining. These effects are interpreted and kinetic data presented. To avoid problems of precipitation due to change of ionic strength humic substances were prepared directly in ASW, and the effects of ASW on catalyst suspension and precipitation have been taken into account. The Langmuir-Hinshelwood kinetic model has been shown to be followed only approximately for the catalytic oxidation of HA in ASW. The activation energy for the reaction derived from an Arrhenius treatment was 17 (+/-0.6) kJ mol(-1).

New insight of hybrid membrane to degrade Congo red and Reactive yellow under sunlight.

PubMed

Rajeswari, A; Jackcina Stobel Christy, E; Pius, Anitha

2018-02-01

A study was carried out to investigate the degradation of organic contaminants (Congo red and Reactive yellow - 105) using cellulose acetate - polystyrene (CA-PS) membrane with and without ZnO impregnation. Scanning electron microscope (SEM), electron dispersive analysis of X-rays (EDAX), Fourier transform infrared spectrometer (FTIR), atomic force microscope (AFM) and thermogravimeric analysis (TG-DTA) analysis were carried out to characterize bare and ZnO impregnated CA-PS membranes. Membrane efficiency was also tested for pure water flux and antifouling performance. The modified membrane showed almost 85% water flux recovery. Blending of ZnO nanoparticles to CA-PS matrix could decrease membrane fouling and increase permeation quality of the membrane with above 90% of photocatalytic degradation efficiency for dyes. The rate of degradation of dyes was observed using UV-Vis spectrometer. Reusability of CA-PS-ZnO membrane was studied and no significant change was noted in the degradation efficiency until fourth cycle. Langmuir-Hinshelwood kinetic model well describes the photo degradation capacity and the degradation of dyes CR and RY - 105 exhibited pseudo-first order kinetics. The regression coefficient (R) of CR and RY - 105 found to be 0.99. The novelty of the prepared CA-PS-ZnO membrane is that it has better efficiency and high thermal stability than our previously reported material. Therefore, ZnO impregnated CA-PS membrane had proved to be an innovative alternative for the degradation of CR and RY - 105 dyes. Copyright © 2017 Elsevier B.V. All rights reserved.

Photocatalytic degradation of model textile dyes in wastewater using ZnO as semiconductor catalyst.

PubMed

Chakrabarti, Sampa; Dutta, Binay K

2004-08-30

Semiconductor photocatalysis often leads to partial or complete mineralization of organic pollutants. Upon irradiation with UV/visible light, semiconductors catalyze redox reactions in presence of air/O2 and water. Here, the potential of a common semiconductor, ZnO, has been explored as an effective catalyst for the photodegradation of two model dyes: Methylene Blue and Eosin Y. A 16 W lamp was the source of UV-radiation in a batch reactor. The effects of process parameters like, catalyst loading, initial dye concentration, airflow rate, UV-radiation intensity, and pH on the extent of photo degradation have been investigated. Substantial reduction of COD, besides removal of colour, was also achieved. A rate equation for the degradation based on Langmuir-Hinshelwood model has been proposed.

Light-induced protein nitration and degradation with HONO emission

NASA Astrophysics Data System (ADS)

Meusel, Hannah; Elshorbany, Yasin; Kuhn, Uwe; Bartels-Rausch, Thorsten; Reinmuth-Selzle, Kathrin; Kampf, Christopher J.; Li, Guo; Wang, Xiaoxiang; Lelieveld, Jos; Pöschl, Ulrich; Hoffmann, Thorsten; Su, Hang; Ammann, Markus; Cheng, Yafang

2017-10-01

Proteins can be nitrated by air pollutants (NO2), enhancing their allergenic potential. This work provides insight into protein nitration and subsequent decomposition in the presence of solar radiation. We also investigated light-induced formation of nitrous acid (HONO) from protein surfaces that were nitrated either online with instantaneous gas-phase exposure to NO2 or offline by an efficient nitration agent (tetranitromethane, TNM). Bovine serum albumin (BSA) and ovalbumin (OVA) were used as model substances for proteins. Nitration degrees of about 1 % were derived applying NO2 concentrations of 100 ppb under VIS/UV illuminated conditions, while simultaneous decomposition of (nitrated) proteins was also found during long-term (20 h) irradiation exposure. Measurements of gas exchange on TNM-nitrated proteins revealed that HONO can be formed and released even without contribution of instantaneous heterogeneous NO2 conversion. NO2 exposure was found to increase HONO emissions substantially. In particular, a strong dependence of HONO emissions on light intensity, relative humidity, NO2 concentrations and the applied coating thickness was found. The 20 h long-term studies revealed sustained HONO formation, even when concentrations of the intact (nitrated) proteins were too low to be detected after the gas exchange measurements. A reaction mechanism for the NO2 conversion based on the Langmuir-Hinshelwood kinetics is proposed.

Solar photodegradation of a textile azo dye using synthesized ZnO/Bentonite.

PubMed

Boutra, B; Trari, M

2017-03-01

The present work is devoted to the synthesis of a new photocatalyst ZnO (7.5%)/Bentonite prepared by impregnation method and its successful application for the degradation of Solophenyl Red 3BL (SR 3BL) under solar light (∼660 W/m 2 ). The X-ray diffraction (XRD) indicates mixed phases of the nanocomposite catalyst (ZnO/Bentonite), characterized by scanning electron microscopy, X-ray fluorescence and attenuated total reflection. The optical properties confirm the presence of the Wurtzite ZnO phase with an optical gap of 3.27 eV. The catalyst dose (0.25-1 gL -1 ), pH solution (2.5-11) and initial dye concentration (5-75 mg/L) are optimized. The optimal pH (∼6.7) is close to the natural environment. The photodegradation yield increases with decreasing the SR 3BL concentration. The equilibrium is reached within 160 min and the data are well fitted by the Langmuir-Hinshelwood model; the SR 3BL disappearance obeys to a first-order kinetic with an apparent rate constant of 10 - 2 mn - 1 . The best yield of SR 3BL photodegradation (92%) is achieved for a concentration of 5 mg/L and a catalyst dose of 0.75 gL -1 at free pH.

Photocatalytic removal of polychlorinated biphenyls (PCBs) using carbon-modified titanium oxide nanoparticles

NASA Astrophysics Data System (ADS)

Shaban, Yasser A.; El Sayed, Mohamed A.; El Maradny, Amr A.; Al Farawati, Radwan Kh.; Al Zobidi, Mosa I.; Khan, Shahed U. M.

2016-03-01

In this work, the sonicated sol-gel method was used for synthesizing carbon-modified titanium oxide nanoparticles. Carbon incorporation was achieved by using titanium (IV) isopropoxide as a titanium and carbon-containing precursor. The photocatalytic efficiency of the synthesized photocatalyst was assessed by examining the photocatalytic removal of polychlorinated biphenyls (PCBs) from aqueous solution. For comparison, unmodified (regular) titanium dioxide (n-TiO2) was used as a reference catalyst. To confirm the carbon incorporation in CM-n-TiO2 nanoparticles, energy dispersive spectroscopy (EDS) analysis was used. Significantly, the bandgap energy was found to be reduced from 2.99 eV for n-TiO2 to 1.8 eV for CM-n-TiO2, which in turn improved the performance of CM-n-TiO2 toward the photocatalytic removal of PCBs. The effects of CM-n-TiO2 loading, PCBs concentration, and pH of the solution on the photodegradation rate of PCBs were investigated. The highest removal rate was found to be at pH 5 and CM-n-TiO2 loading of 0.5 g L-1. According to Langmuir-Hinshelwood model, the photodegradation of PCBs using CM-n-TiO2 followed a pseudo-first order reaction kinetics.

Preparation and Characterization of Cu and Ni on Alumina Supports and Their Use in the Synthesis of Low-Temperature Metal-Phthalocyanine Using a Parallel-Plate Reactor

PubMed Central

Sánchez-De la Torre, Fernando; De la Rosa, Javier Rivera; Kharisov, Boris I.; Lucio-Ortiz, Carlos J.

2013-01-01

Ni- and Cu/alumina powders were prepared and characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), and N2 physisorption isotherms were also determined. The Ni/Al2O3 sample reveled agglomerated (1 μm) of nanoparticles of Ni (30–80 nm) however, NiO particles were also identified, probably for the low temperature during the H2 reduction treatment (350 °C), the Cu/Al2O3 sample presented agglomerates (1–1.5 μm) of nanoparticles (70–150 nm), but only of pure copper. Both surface morphologies were different, but resulted in mesoporous material, with a higher specificity for the Ni sample. The surfaces were used in a new proposal for producing copper and nickel phthalocyanines using a parallel-plate reactor. Phthalonitrile was used and metallic particles were deposited on alumina in ethanol solution with CH3ONa at low temperatures; ≤60 °C. The mass-transfer was evaluated in reaction testing with a recent three-resistance model. The kinetics were studied with a Langmuir-Hinshelwood model. The activation energy and Thiele modulus revealed a slow surface reaction. The nickel sample was the most active, influenced by the NiO morphology and phthalonitrile adsorption. PMID:28788334

A comparative approach of methylparaben photocatalytic degradation assisted by UV-C, UV-A and Vis radiations.

PubMed

Doná, Giovanna; Dagostin, João Luiz Andreoti; Takashina, Thiago Atsushi; de Castilhos, Fernanda; Igarashi-Mafra, Luciana

2018-05-01

Due to the widespread use of methylparaben (MEP) and its high chemical stability, it can be found in wastewater treatment plants and can act as an endocrine disrupting compound. In this study, the photocatalytic degradation and mineralization of MEP solutions were evaluated under UV-A, UV-C and Vis radiations in the presence of the photocatalyst TiO 2 . In this sense, the effects of the catalyst load, pH and MEP initial concentration were studied. Remarkably higher reaction rates and total photodegradation were achieved in systems assisted by UV-C radiation. The complete degradation was achieved after 60 min of reaction using the MEP concentration of 30 mg L -1 at pH 9 and 500 mg L -1 TiO 2 . The experimental data apparently followed a Langmuir-Hinshelwood kinetic model, which could predict 88-98% of the reaction behavior. For the best photodegradation condition, the model predicted an apparent reaction rate constant (k app ) equal to 0.0505 min -1 and an initial reaction rate of 1.5641 mg (L min) -1 . Mineralization analyses showed high removal for MEP and derived compounds from the initial solution when using UV-C after 90 min of reaction. The lower toxicity was also confirmed by in vivo tests using MEP solutions previously treated by photocatalysis.

Ozonation of isoproturon adsorbed on silica particles under atmospheric conditions

NASA Astrophysics Data System (ADS)

Pflieger, Maryline; Grgić, Irena; Kitanovski, Zoran

2012-12-01

The results on heterogeneous ozonation of a phenylurea pesticide, isoproturon, under atmospheric conditions are presented for the first time in the present study. The study was carried out using an experimental device previously adopted and validated for the heterogeneous reactivity of organics toward ozone (Pflieger et al., 2011). Isoproturon was adsorbed on silica particles via a liquid-to-solid equilibrium with a load far below a monolayer (0.02% by weight/surface coverage of 0.5%). The rate constants were estimated by measuring the consumption of the organic (dark, T = 26 °C, RH < 1%). The experimental data were fitted by both the modified Langmuir-Hinshelwood and the Eley-Rideal patterns, resulting in atmospheric lifetimes of heterogeneous ozonation of 4 and 6 days, respectively (for 40 ppb of O3). Parameters, such as the number and the quantity of pesticides adsorbed on the solid support, which can significantly influence the heterogeneous kinetics, were investigated as well. The results obtained suggest that the organic compound is adsorbed in multilayer aggregates on the aerosol even though submonolayer coverage is assumed. The presence of a second herbicide, trifluralin, together with isoproturon on the aerosol surface does not affect the kinetics of ozonation, indicating that both compounds are adsorbed on different surface sites of silica particles.

The surface reactivity of acrylonitrile with oxygen atoms on an analogue of interstellar dust grains

NASA Astrophysics Data System (ADS)

Kimber, Helen J.; Toscano, Jutta; Price, Stephen D.

2018-06-01

Experiments designed to reveal the low-temperature reactivity on the surfaces of interstellar dust grains are used to probe the heterogeneous reaction between oxygen atoms and acrylonitrile (C2H3CN, H2C=CH-CN). The reaction is studied at a series of fixed surface temperatures between 14 and 100 K. After dosing the reactants on to the surface, temperature-programmed desorption, coupled with time-of-flight mass spectrometry, reveals the formation of a product with the molecular formula C3H3NO. This product results from the addition of a single oxygen atom to the acrylonitrile reactant. The oxygen atom attack appears to occur exclusively at the C=C double bond, rather than involving the cyano(-CN) group. The absence of reactivity at the cyano site hints that full saturation of organic molecules on dust grains may not always occur in the interstellar medium. Modelling the experimental data provides a reaction probability of 0.007 ± 0.003 for a Langmuir-Hinshelwood style (diffusive) reaction mechanism. Desorption energies for acrylonitrile, oxygen atoms, and molecular oxygen, from the multilayer mixed ice their deposition forms, are also extracted from the kinetic model and are 22.7 ± 1.0 kJ mol-1 (2730 ± 120 K), 14.2 ± 1.0 kJ mol-1 (1710 ± 120 K), and 8.5 ± 0.8 kJ mol-1 (1020 ± 100 K), respectively. The kinetic parameters we extract from our experiments indicate that the reaction between atomic oxygen and acrylonitrile could occur on interstellar dust grains on an astrophysical time-scale.

Uranium biosorption by Padina sp. algae biomass: kinetics and thermodynamics.

PubMed

Khani, Mohammad Hassan

2011-11-01

Kinetic, thermodynamic, and equilibrium isotherms of the biosorption of uranium ions onto Padina sp., a brown algae biomass, in a batch system have been studied. The kinetic data were found to follow the pseudo-second-order model. Intraparticle diffusion is not the sole rate-controlling factor. The equilibrium experimental results were analyzed in terms of Langmuir isotherm depending with temperature. Equilibrium data fitted very well to the Langmuir model. The maximum uptakes estimated by using the Langmuir model were 434.8, 416.7, 400.0, and 370.4 mg/g at 10°C, 20°C, 30°C, and 40°C, respectively. Gibbs free energy was spontaneous for all interactions, and the adsorption process exhibited exothermic enthalpy values. Padina sp. algae were shown to be a favorable biosorbent for uranium removal from aqueous solutions.

A chimeric α-amylase engineered from Bacillus acidicola and Geobacillus thermoleovorans with improved thermostability and catalytic efficiency.

PubMed

Parashar, Deepak; Satyanarayana, T

2016-04-01

The α-amylase (Ba-amy) of Bacillus acidicola was fused with DNA fragments encoding partial N- and C-terminal region of thermostable α-amylase gene of Geobacillus thermoleovorans (Gt-amy). The chimeric enzyme (Ba-Gt-amy) expressed in Escherichia coli displays marked increase in catalytic efficiency [K cat: 4 × 10(4) s(-1) and K cat/K m: 5 × 10(4) mL(-1) mg(-1) s(-1)] and higher thermostability than Ba-amy. The melting temperature (T m) of Ba-Gt-amy (73.8 °C) is also higher than Ba-amy (62 °C), and the CD spectrum analysis revealed the stability of the former, despite minor alteration in secondary structure. Langmuir-Hinshelwood kinetic analysis suggests that the adsorption of Ba-Gt-amy onto raw starch is more favourable than Ba-amy. Ba-Gt-amy is thus a suitable biocatalyst for raw starch saccharification at sub-gelatinization temperatures because of its acid stability, thermostability and Ca(2+) independence, and better than the other known bacterial acidic α-amylases.

The role of N1 domain on the activity, stability, substrate specificity and raw starch binding of amylopullulanase of the extreme thermophile Geobacillus thermoleovorans.

PubMed

Nisha, M; Satyanarayana, T

2015-07-01

In order to understand the role of N1 domain (1-257 aa) in the amylopullulanase (gt-apu) of the extremely thermophilic bacterium Geobacillus thermoleovorans NP33, N1 deletion construct (gt-apuΔN) has been generated and expressed in Escherichia coli. The truncated amylopullulanase (gt-apuΔN) exhibits similar pH and temperature optima like gt-apu, but enhanced thermostability. The gt-apuΔN has greater hydrolytic action and specific activity on pullulan than gt-apu. The k cat (starch and pullulan) and K m (starch) values of gt-apuΔN increased, while K m (pullulan) decreased. The enzyme upon N1 deletion hydrolyzed maltotetraose as the smallest substrate in contrast to maltopentaose of gt-apu. The role of N1 domain of gt-apu in raw starch binding has been confirmed, for the first time, based on deletion and Langmuir-Hinshelwood kinetics. Furthermore, N1 domain appears to exert a negative influence on the thermostability of gt-apu because N1 truncation significantly improves thermostability.

Preparation and Characterization of Ni-Doped TiO2 Materials for Photocurrent and Photocatalytic Applications

PubMed Central

Ganesh, Ibram; Gupta, A. K.; Kumar, P. P.; Sekhar, P. S. C.; Radha, K.; Padmanabham, G.; Sundararajan, G.

2012-01-01

Different amounts of Ni-doped TiO2 (Ni = 0.1 to 10%) powders and thin films were prepared by following a conventional coprecipitation and sol-gel dip coating techniques, respectively, at 400 to 800°C, and were thoroughly characterized by means of XRD, FT-IR, FT-Raman, DRS, UV-visible, BET surface area, zeta potential, flat band potential, and photocurrent measurement techniques. Photocatalytic abilities of Ni-doped TiO2 powders were evaluated by means of methylene blue (MB) degradation reaction under simulated solar light. Characterization results suggest that as a dopant, Ni stabilizes TiO2 in the form of anatase phase, reduces its bandgap energy, and adjusts its flat band potentials such that this material can be employed for photoelectrochemical (PEC) oxidation of water reaction. The photocatalytic activity and photocurrent ability of TiO2 have been enhanced by doping of Ni in TiO2. The kinetic studies revealed that the MB degradation reaction follows the Langmuir-Hinshelwood first-order reaction relationship. PMID:22619580

Kinetic study of acetaminophen degradation by visible light photocatalysis.

PubMed

Gotostos, Mary Jane N; Su, Chia-Chi; De Luna, Mark Daniel G; Lu, Ming-Chun

2014-01-01

In this work, a novel photocatalyst K3[Fe(CN)6]/TiO2 synthesized via a simple sol-gel method was utilized to degrade acetaminophen (ACT) under visible light with the use of blue and green LED lights. Parameters (medium pH, initial concentration of reactant, catalyst concentration, temperature, and number of blue LED lights) affecting photocatalytic degradation of ACT were also investigated. The experimental result showed that compared to commercially available Degussa P-25 (DP-25) photocatalyst, K3[Fe(CN)6]/TiO2 gave higher degradation efficiency and rate constant (kapp) of ACT. The degradation efficiency or kapp decreased with increasing initial ACT concentration and temperature, but increased with increased number of blue LED lamps. Additionally, kapp increased as initial pH was increased from 5.6 to 6.9, but decreased at a high alkaline condition (pH 8.3). Furthermore, the degradation efficiency and kapp of ACT increased as K3[Fe(CN)6]/TiO2 loading was increased to 1 g L(-1) but decreased and eventually leveled off at photocatalyst loading above this value. Photocatalytic degradation of ACT in K3[Fe(CN)6]/TiO2 catalyst system follows a pseudo-first-order kinetics. The Langmuir-Hinshelwood equation was also satisfactorily used to model the degradation of ACT in K3[Fe(CN)6]/TiO2 catalyst system indicated by a satisfactory linear correlation between 1/kapp and Co, with kini = 6.54 × 10(-4) mM/min and KACT = 17.27 mM(-1).

Reduction of chromium (VI) on the hetero-system CuBi2O4/TiO2 under solar light

NASA Astrophysics Data System (ADS)

Lahmar, H.; Benamira, M.; Akika, F. Z.; Trari, M.

2017-11-01

The CuBi2O4/TiO2 heterojunction was tested with success for the photo-catalytic reduction of chromate ions under sunlight. CuBi2O4, prepared by nitrate process, was characterised photo-electrochemically. The oxide is stable against photo corrosion by consumption of holes in presence of oxalic acid. The light absorption promotes electrons in the conduction band of the sensitizer (CuBi2O4) with a very negative potential (-1.74 VSCE) to participate in the exchange of the electron with HCrO4-. The enhanced activity is due to electron injection of activated CuBi2O4 into TiO2-CB (-0.97 VSCE). The band gap of the semiconductor CuBi2O4 is 1.50 eV with a direct optical transition. This compound is a p-type semiconductor with a flat band potential of -0.39 VSCE and activation energy of 0.18 eV. The electrochemical impedance spectroscopy was undertaken to study the semiconductor/electrolyte interfacial phenomena. The photoactivity on the heterojunction is strongly enhanced. A remarkable performance is obtained in less than 4 h for a concentration of 30 mg in (Cr (VI)) at pH ∼ 4 and a dose of 1 mg/mL; a 98% reduction has been obtained. The kinetic of chromate photoreduction is well described by the Langmuir-Hinshelwood model. The chromate elimination obeys to a pseudo-first order kinetic with an apparent rate constant of 0.014 min-1.

Tunneling Rate Constants for H2CO+H on Amorphous Solid Water Surfaces

NASA Astrophysics Data System (ADS)

Song, Lei; Kästner, Johannes

2017-12-01

Formaldehyde (H2CO) is one of the most abundant molecules observed in the icy mantle covering interstellar grains. Studying its evolution can contribute to our understanding of the formation of complex organic molecules in various interstellar environments. In this work, we investigated the hydrogenation reactions of H2CO yielding CH3O, CH2OH, and the hydrogen abstraction resulting in H2+HCO on an amorphous solid water (ASW) surface using a quantum mechanics/molecular mechanics (QM/MM) model. The binding energies of H2CO on the ASW surface vary broadly, from 1000 to 9370 K. No correlation was found between binding energies and activation energies of hydrogenation reactions. Combining instanton theory with QM/MM modeling, we calculated rate constants for the Langmuir-Hinshelwood and the Eley-Rideal mechanisms for the three product channels of H+H2CO surface reactions down to 59 K. We found that the channel producing CH2OH can be ignored, owing to its high activation barrier leading to significantly lower rates than the other two channels. The ASW surface influences the reactivity in favor of formation of CH3O (branching ratio ˜80%) and hinders the H2CO dissociation into H2+HCO. In addition, kinetic isotope effects are strong in all reaction channels and vary strongly between the channels. Finally, we provide fits of the rate constants to be used in astrochemical models.

Characterization and photocatalytic performance evaluation of various metal ion-doped microstructured TiO2 under UV and visible light.

PubMed

Sahoo, Chittaranjan; Gupta, Ashok K

2015-01-01

Commercially available microcrystalline TiO2 was doped with silver, ferrous and ferric ion (1.0 mol %) using silver nitrate, ferrous sulfate and ferric nitrate solutions following the liquid impregnation technology. The catalysts prepared were characterised by FESEM, XRD, FTIR, DRS, particle size and micropore analysis. The photocatalytic activity of the prepared catalysts was tested on the degradation of two model dyes, methylene blue (3,7-bis (Dimethylamino)-phenothiazin-5-ium chloride, a cationic thiazine dye) and methyl blue (disodium;4-[4-[[4-(4-sulfonatoanilino)phenyl]-[4-(4-sulfonatophenyl)azaniumylidenecyclohexa-2,5-dien-1-ylidene]methyl]anilino]benzene sulfonate, an anionic triphenyl methane dye) under irradiation by UV and visible light in a batch reactor. The efficiency of the photocatalysts under UV and visible light was compared to ascertain the light range for effective utilization. The catalysts were found to have the anatase crystalline structure and their particle size is in a range of 140-250 nm. In the case of Fe(2+) doped TiO2 and Fe(3+) doped TiO2, there was a greater shift in the optical absorption towards the visible range. Under UV light, Ag(+) doped TiO2 was the most efficient catalyst and the corresponding decolorization was more than 99% for both the dyes. Under visible light, Fe(3+) doped TiO2 was the most efficient photocatalyst with more than 96% and 90% decolorization for methylene blue and methyl blue, respectively. The kinetics of the reaction under both UV and visible light was investigated using the Langmuir-Hinshelwood pseudo-first-order kinetic model. Kinetic measurements confirmed that, Ag(+) doped TiO2 was most efficient in the UV range, while Fe(3+) doped TiO2 was most efficient in the visible range.

Catalytic wet oxidation: mathematical modeling of multicompound destruction.

PubMed

Yang, J; Hand, D W; Hokanson, D R; Crittenden, J C; Oman, E J

2003-01-01

A mathematical model of a three-phase catalytic reactor, CatReac, was developed for analysis and optimization of a catalytic oxidation reactor that is used in the International Space Station potable water processor. The packed-bed catalytic reactor, known as the volatile reactor assembly (VRA), is operated as a three-phase reactor and contains a proprietary catalyst, a pure-oxygen gas phase, and the contaminated water. The contaminated water being fed to the VRA primarily consists of acetic acid, acetone, ethanol, 1-propanol, 2-propanol, and propionic acid ranging in concentration from 1 to 10 mg/L. The Langmuir-Hinshelwood Hougen-Watson (L-H) (Hougen, 1943) expression was used to describe the surface reaction rate for these compounds. Single and multicompound short-column experiments were used to determine the L-H rate parameters and calibrate the model. The model was able to predict steady-state multicomponent effluent profiles for short and full-scale reactor experiments.

Biosorption of lead (II) ions by NaOH-activated apple (Malus domestica) juice residue

NASA Astrophysics Data System (ADS)

Arimurti, Devita Dwi; Heraldy, Eddy; Lestari, Witri Wahyu

2016-02-01

This research studied the removal of Pb(II) ions from aqueous solutions using NaOH-activated apple (Malus domestica) juice residue. Biosorbent was characterized with Fourier Transform Infrared Spectrophotometer (FTIR), and Surface Area Analyzer (SAA). The effects of biosorbent dosage, pH, contact time and initial metal ion concentration had been investigated in batch-adsorption method. The biosorption kinetic data were analyzed by pseudo-first-order and pseudo-second-order kinetics model. Freundlich and Langmuir's isotherm were used to describe the biosorption process. The optimum conditions of Pb(II) adsorption was observed at 60 min of contact time, pH 4, and 0.1 g biosorbent dosage in 25 ml solution. The biosorption kinetics followed the pseudo-second-order kinetic model, resulted biosorption constant rate of 0.184 g.mg-1.min-1. The Langmuir isotherm model exhibited the best fit to experimental data. The maximum biosorption capacity of Pb(II) determined according to the Langmuir model was 90.90 mg.g-1 at 302 K, with the adsorption energy of 26.429 kJ.mol-1.

VUV-Photocatalytic Degradation of Bezafibrate by Hydrothermally Synthesized Enhanced {001} Facets TiO2/Ti Film.

PubMed

Sayed, Murtaza; Fu, Pingfeng; Shah, Luqman Ali; Khan, Hasan M; Nisar, Jan; Ismail, M; Zhang, Pengyi

2016-01-14

In the present study, a novel TiO2/Ti film with enhanced {001} facets was synthesized by the hydrothermal technique followed by calcination for studying the removal of bezafibrate (BZF), from an aqueous environment. The synthesized photocatalyst was characterized by FE-SEM, XRD, HR-TEM, and PL-technique. The second-order rate constant of (•)OH with BZF was found to be 5.66 × 10(9) M(-1) s(-1). The steady state [(•)OH] was measured as 1.16 × 10(-11) M, on the basis of oxidation of terephthalic acid. The photocatalytic degradation of BZF followed pseudo-first-order kinetics according to the Langmuir-Hinshelwood model (k1 = 2.617 mg L(-1) min(-1) and k2 = 0.0796 (mg L(-1))(-1)). The effects of concentration and the nature of various additives including inorganic anions (NO3(-), NO2(-), HCO3(-), CO3(2-), Cl(-)) and organic species (fulvic acid) and initial solution pHs (2, 4, 6, 9) on photocatalytic degradation of BZF were investigated. It was found that the nature and concentration of studied additives significantly affected the photocatalytic degradation of BZF. The efficiency of the photocatalytic degradation process in terms of electrical energy per order was estimated. Degradation schemes were proposed on the basis of the identified degradation byproducts by ultraperformance liquid chromatography.

Photocatalytic removal of SO2 using natural zeolite modified by TiO2 and polyoxypropylene surfactant.

PubMed

Amini, Nasibeh; Soleimani, Mohsen; Mirghaffari, Nourollah

2018-01-25

Air pollution due to emission of various hazardous gases such as SO 2 into the atmosphere and its control is an important environmental issue. Application of photocatalysts is considered as a suitable process to control the gaseous pollutants. In this study, the efficiency of clinoptilolite as a natural zeolite (Ze) modified by TiO 2 (Ze-Ti) and a polymeric surfactant polyoxypropylene (Ze-Ti-POP) for removal of SO 2 was investigated. The nanocomposites were characterized by SEM, EDX, and BET analyses. The photocatalytic oxidation experiments of SO 2 by the nanocomposites and natural zeolite were done under UV irradiation with initial SO 2 concentration of 500 ppm in a photoreactor. The effects of different factors including reaction time, catalyst dose, UV irradiation intensity, humidity content, and calcination temperature and dose of TiO 2 were studied. The modification of clinoptilolite by TiO 2 and POP increased considerably the BET specific surface area of the nanocomposites. The results showed that maximum removal efficiencies of SO 2 by Ze-Ti and Ze-Ti-POP under the optimum experimental conditions were 82.1 and 87.4%, respectively. Adsorption kinetics data well fitted with the Langmuir-Hinshelwood model. Moreover, reusing of nanocomposites after three regeneration cycles indicated that application of Ze-Ti and Ze-Ti-POP nanocomposites could be a promising approach for SO 2 removal. Graphical abstract ᅟ.

Zinc oxide-mediated photocatalytic decolorization of Ponceau S in aqueous suspension by visible light

NASA Astrophysics Data System (ADS)

Muslim, Muhammad; Habib, Md Ahsan; Mahmood, Abu Jafar; Islam, Tajmeri Selima Akhter; Ismail, Iqbal Mohmmad Ibrahim

2012-10-01

ZnO, comprising nanosize particles (approximately 40 nm) has been prepared by heating (300°C) ZnCO3, which was obtained as precipitate by mixing ZnSO4 and (NH4)2CO3 solutions. The prepared ZnO was characterized by X-ray diffraction, scanning electron microscopy (SEM), laser-induced breakdown spectroscopy, and adsorption studies. It has been used to catalyze the decolorization of Ponceau S (PS), a model diazo dye, in an aqueous suspension under visible light ( I ≈ 1.8 × 10-4 W cm-2). This ZnO was found to be more efficient as a photocatalyst compared to pristine ZnO. ZnO samples with higher temperatures (500°C and 700°C) show less catalytic activity. SEM images show that the particle size of ZnO increases with the increase in calcined temperature of ZnO through agglomeration, resulting in a decrease in surface area. Photodecolorization of PS is affected by its and ZnO concentrations, but unaffected by the initial pH of the solutions in the range of 4 to 7. Illumination for a sufficiently long time completely mineralizes the dye, but no Zn2+ can be detected in the clear solution. Photodegradation kinetics in the ZnO suspension obeys the Langmuir-Hinshelwood equation, and some activation of the ZnO surface by light is indicated.

Removal of 2-ClBP from soil-water system using activated carbon supported nanoscale zerovalent iron.

PubMed

Zhang, Wei; Yu, Tian; Han, Xiaolin; Ying, Weichi

2016-09-01

We explored the feasibility and removal mechanism of removing 2-chlorobiphenyl (2-ClBP) from soil-water system using granular activated carbon (GAC) impregnated with nanoscale zerovalent iron (reactive activated carbon or RAC). The RAC samples were successfully synthesized by the liquid precipitation method. The mesoporous GAC based RAC with low iron content (1.32%) exhibited higher 2-ClBP removal efficiency (54.6%) in the water phase. The result of Langmuir-Hinshelwood kinetic model implied that the different molecular structures between 2-ClBP and trichloroethylene (TCE) resulted in more difference in dechlorination reaction rates on RAC than adsorption capacities. Compared to removing 2-ClBP in the water phase, RAC removed the 2-ClBP more slowly in the soil phase due to the significant external mass transfer resistance. However, in the soil phase, a better removal capacity of RAC was observed than its base GAC because the chemical dechlorination played a more important role in total removal process for 2-ClBP. This important result verified the effectiveness of RAC for removing 2-ClBP in the soil phase. Although reducing the total RAC removal rate of 2-ClBP, soil organic matter (SOM), especially the soft carbon, also served as an electron transfer medium to promote the dechlorination of 2-ClBP in the long term. Copyright © 2016. Published by Elsevier B.V.

High-informative version of nonlinear transformation of Langmuir waves to electromagnetic waves

NASA Astrophysics Data System (ADS)

Erofeev, Vasily I.; Erofeev

2014-04-01

The concept of informativeness of nonlinear plasma physical scenario is discussed. Basic principles for heightening the informativeness of plasma kinetic models are explained. Former high-informative correlation analysis of plasma kinetics (Erofeev, V. 2011 High-Informative Plasma Theory, Saarbrücken: LAP) is generalized for studies of weakly turbulent plasmas that contain fields of solenoidal plasma waves apart from former potential ones. Respective machinery of plasma kinetic modeling is applied to an analysis of fusion of Langmuir waves with transformation to electromagnetic waves. It is shown that the customary version of this phenomenon (Terashima, Y. and Yajima, N. 1963 Prog. Theor. Phys. 30, 443; Akhiezer, I. A., Danelia, I. A. and Tsintsadze, N. L. 1964 Sov. Phys. JETP 19, 208; Al'tshul', L. M. and Karpman, V. I. 1965 Sov. Phys. JETP 20, 1043) substantially distorts the picture of merging of Langmuir waves with long wavelengths (λ >~ c/ωpe ).

Solar Fenton and solar TiO2 catalytic treatment of ofloxacin in secondary treated effluents: evaluation of operational and kinetic parameters.

PubMed

Michael, I; Hapeshi, E; Michael, C; Fatta-Kassinos, D

2010-10-01

Two different technical approaches based on advanced oxidation processes (AOPs), solar Fenton homogeneous photocatalysis (hv/Fe(2+)/H(2)O(2)) and heterogeneous photocatalysis with titanium dioxide (TiO(2)) suspensions were studied for the chemical degradation of the fluoroquinolone ofloxacin in secondary treated effluents. A bench-scale solar simulator in combination with an appropriate photochemical batch reactor was used to evaluate and select the optimal oxidation conditions of ofloxacin spiked in secondary treated domestic effluents. The concentration profile of the examined substrate during degradation was determined by UV/Vis spectrophotometry. Mineralization was monitored by measuring the dissolved organic carbon (DOC). The concentrations of Fe(2+) and H(2)O(2) were the key factors for the solar Fenton process, while the most important parameter of the heterogeneous photocatalysis was proved to be the catalyst loading. Kinetic analyses indicated that the photodegradation of ofloxacin can be described by a pseudo-first-order reaction. The rate constant (k) for the solar Fenton process was determined at different Fe(2+) and H(2)O(2) concentrations whereas the Langmuir-Hinshelwood (LH) kinetic expression was used to assess the kinetics of the heterogeneous photocatalytic process. The conversion of ofloxacin depends on several parameters based on the various experimental conditions, which were investigated. A Daphnia magna bioassay was used to evaluate the potential toxicity of the parent compound and its photo-oxidation by-products in different stages of oxidation. In the present study solar Fenton has been demonstrated to be more effective than the solar TiO(2) process, yielding complete degradation of the examined substrate and DOC reduction of about 50% in 30 min of the photocatalytic treatment. Copyright © 2010 Elsevier Ltd. All rights reserved.

The Utility of the Lambert Function W[a exp(a - bt)] in Chemical Kinetics

ERIC Educational Resources Information Center

Williams, Brian Wesley

2010-01-01

The mathematical Lambert function W[a exp(a - bt)] is used to find integrated rate laws for several examples, including simple enzyme and Lindemann-Christiansen-Hinshelwood (LCH) unimolecular decay kinetics. The results derived here for the well-known LCH mechanism as well as for a dimer-monomer reaction mechanism appear to be novel. A nonlinear…

Pseudo second order kinetics and pseudo isotherms for malachite green onto activated carbon: comparison of linear and non-linear regression methods.

PubMed

Kumar, K Vasanth; Sivanesan, S

2006-08-25

Pseudo second order kinetic expressions of Ho, Sobkowsk and Czerwinski, Blanachard et al. and Ritchie were fitted to the experimental kinetic data of malachite green onto activated carbon by non-linear and linear method. Non-linear method was found to be a better way of obtaining the parameters involved in the second order rate kinetic expressions. Both linear and non-linear regression showed that the Sobkowsk and Czerwinski and Ritchie's pseudo second order model were the same. Non-linear regression analysis showed that both Blanachard et al. and Ho have similar ideas on the pseudo second order model but with different assumptions. The best fit of experimental data in Ho's pseudo second order expression by linear and non-linear regression method showed that Ho pseudo second order model was a better kinetic expression when compared to other pseudo second order kinetic expressions. The amount of dye adsorbed at equilibrium, q(e), was predicted from Ho pseudo second order expression and were fitted to the Langmuir, Freundlich and Redlich Peterson expressions by both linear and non-linear method to obtain the pseudo isotherms. The best fitting pseudo isotherm was found to be the Langmuir and Redlich Peterson isotherm. Redlich Peterson is a special case of Langmuir when the constant g equals unity.

Modeling aerosol surface chemistry and gas-particle interaction kinetics with K2-SURF: PAH oxidation

NASA Astrophysics Data System (ADS)

Shiraiwa, M.; Garland, R.; Pöschl, U.

2009-04-01

Atmospheric aerosols are ubiquitous in the atmosphere. They have the ability to impact cloud properties, radiative balance and provide surfaces for heterogeneous reactions. The uptake of gaseous species on aerosol surfaces impacts both the aerosol particles and the atmospheric budget of trace gases. These subsequent changes to the aerosol can in turn impact the aerosol chemical and physical properties. However, this uptake, as well as the impact on the aerosol, is not fully understood. This uncertainty is due not only to limited measurement data, but also a dearth of comprehensive and applicable modeling formalizations used for the analysis, interpretation and description of these heterogeneous processes. Without a common model framework, comparing and extrapolating experimental data is difficult. In this study, a novel kinetic surface model (K2-SURF) [Ammann & Pöschl, 2007; Pöschl et al., 2007] was used to describe the oxidation of a variety of polycyclic aromatic hydrocarbons (PAHs). Integrated into this consistent and universally applicable kinetic and thermodynamic process model are the concepts, terminologies and mathematical formalizations essential to the description of atmospherically relevant physicochemical processes involving organic and mixed organic-inorganic aerosols. Within this process model framework, a detailed master mechanism, simplified mechanism and parameterizations of atmospheric aerosol chemistry are being developed and integrated in analogy to existing mechanisms and parameterizations of atmospheric gas-phase chemistry. One of the key aspects to this model is the defining of a clear distinction between various layers of the particle and surrounding gas phase. The processes occurring at each layer can be fully described using known fluxes and kinetic parameters. Using this system there is a clear separation of gas phase, gas-surface and surface bulk transport and reactions. The partitioning of compounds can be calculated using the flux values between the layers. By describing these layers unambiguously, the interactions of all species in the system can be appropriately modeled. In describing the oxidation of PAHs, the focus was on the interactions between the sorption layer and quasi-static surface layer. The results from a variety of published experimental studies [Pöschl et al., 2001; Kahan et al., 2006; Kwamena et al., 2004, 2006, 2007; Mmereki and Donaldson, 2003; Mmereki et al., 2004; Dubowski et al., 2004; Donaldson et al., 2005; Segal-Rosenheimer and Dubowski, 2007] were analyzed and compared utilizing K2-SURF. The heterogeneous reaction of PAH and O3 are found to follow a Langmuir-Hinshelwood mechanism, in which ozone first absorbs to the surface and then reacts with PAH. The Langmuir equilibrium constants and second-order-rate coefficients of surface reaction were estimated. In PAH/O3/solid substrate system, they showed similar reaction rate (×10), but large difference (×1000) in adsorption. The mean residence time and adsorption enthalpy were estimated for O3 at the surface of substrates, suggesting the chemisorption of O3 molecules or O atoms, respectively. Initial uptake coefficients of O3 under different conditions were also investigated. The observed dependence on gas-phase O3 concentration was well explained with K2-SURF model in five-order range. In addition, competitive adsorption of other gas phase species (NO2, H2O) was well described by the model. Possible mechanism of PAH degradation system and atmospheric implications are discussed.

Modeling the photocatalytic mineralization in water of commercial formulation of estrogens 17-β estradiol (E2) and nomegestrol acetate in contraceptive pills in a solar powered compound parabolic collector.

PubMed

Colina-Márquez, José; Machuca-Martínez, Fiderman; Li Puma, Gianluca

2015-07-22

Endocrine disruptors in water are contaminants of emerging concern due to the potential risks they pose to the environment and to the aquatic ecosystems. In this study, a solar photocatalytic treatment process in a pilot-scale compound parabolic collector (CPC) was used to remove commercial estradiol formulations (17-β estradiol and nomegestrol acetate) from water. Photolysis alone degraded up to 50% of estradiol and removed 11% of the total organic carbon (TOC). In contrast, solar photocatalysis degraded up to 57% of estrogens and the TOC removal was 31%, with 0.6 g/L of catalyst load (TiO2 Aeroxide P-25) and 213.6 ppm of TOC as initial concentration of the commercial estradiols formulation. The adsorption of estrogens over the catalyst was insignificant and was modeled by the Langmuir isotherm. The TOC removal via photocatalysis in the photoreactor was modeled considering the reactor fluid-dynamics, the radiation field, the estrogens mass balance, and a modified Langmuir-Hinshelwood rate law, that was expressed in terms of the rate of photon adsorption. The optimum removal of the estrogens and TOC was achieved at a catalyst concentration of 0.4 g/L in 29 mm diameter tubular CPC reactors which approached the optimum catalyst concentration and optical thickness determined from the modeling of the absorption of solar radiation in the CPC, by the six-flux absorption-scattering model (SFM).

The surface characteristics of hyperbranched polyamide modified corncob and its adsorption property for Cr(VI)

NASA Astrophysics Data System (ADS)

Lin, Hai; Han, Shaoke; Dong, Yingbo; He, Yinhai

2017-08-01

A low-cost anion adsorbent for Cr(VI) effectively removing was synthesized by hyperbranched polyamide modified corncob (HPMC). Samples were characterized by Brunauer-Emmett-Teller (BET) surface area analysis, field-emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray spectroscopy, Fourier transform infrared (FTIR) and zeta potential analysis. Kinetics, isotherms and thermodynamics studies of HPMC for Cr(VI) adsorption were investigated in batch static experiments, in the temperature range of 25-45 °C, pH = 2.0. Results showed that the adsorption was rapid and stable, with the uptake capacity higher than 80% after 30 min. Adsorption behavior and rate-controlling mechanisms were analyzed using three kinetic models (pseudo-first order, pseudo-second order, intra-particle kinetic model). Kinetic studies showed that the adsorption of HPMC to Cr(VI) relied the pseudo-second-order model, and controlled both by the intra-particle diffusion and film diffusion. Equilibrium data was tested by Langmuir and Freundlich adsorption isotherm models. Langmuir model was more suitable to indicate a homogeneous distribution of active sites on HPMC and monolayer adsorption. The maximum adsorption capacity from the Langmuir model, qmax, was 131.6 mg/g at pH 2.0 and 45 °C for HPMC. Thermodynamic parameters revealed spontaneous and endothermic nature of the Cr(VI) adsorption onto HPMC.

Development of a Detailed Surface Chemistry Framework in DSMC

NASA Technical Reports Server (NTRS)

Swaminathan-Gopalan, K.; Borner, A.; Stephani, K. A.

2017-01-01

Many of the current direct simulation Monte Carlo (DSMC) codes still employ only simple surface catalysis models. These include only basic mechanisms such as dissociation, recombination, and exchange reactions, without any provision for adsorption and finite rate kinetics. Incorporating finite rate chemistry at the surface is increasingly becoming a necessity for various applications such as high speed re-entry flows over thermal protection systems (TPS), micro-electro-mechanical systems (MEMS), surface catalysis, etc. In the recent years, relatively few works have examined finite-rate surface reaction modeling using the DSMC method.In this work, a generalized finite-rate surface chemistry framework incorporating a comprehensive list of reaction mechanisms is developed and implemented into the DSMC solver SPARTA. The various mechanisms include adsorption, desorption, Langmuir-Hinshelwood (LH), Eley-Rideal (ER), Collision Induced (CI), condensation, sublimation, etc. The approach is to stochastically model the various competing reactions occurring on a set of active sites. Both gas-surface (e.g., ER, CI) and pure-surface (e.g., LH, desorption) reaction mechanisms are incorporated. The reaction mechanisms could also be catalytic or surface altering based on the participation of the bulk-phase species (e.g., bulk carbon atoms). Marschall and MacLean developed a general formulation in which multiple phases and surface sites are used and we adopt a similar convention in the current work. Microscopic parameters of reaction probabilities (for gas-surface reactions) and frequencies (for pure-surface reactions) that are require for DSMC are computed from the surface properties and macroscopic parameters such as rate constants, sticking coefficients, etc. The energy and angular distributions of the products are decided based on the reaction type and input parameters. Thus, the user has the capability to model various surface reactions via user-specified reaction rate constants, surface properties and parameters.

Adsorption of malachite green from aqueous solution by using novel chitosan ionic liquid beads.

PubMed

Naseeruteen, Faizah; Hamid, Nur Shahirah Abdul; Suah, Faiz Bukhari Mohd; Ngah, Wan Saime Wan; Mehamod, Faizatul Shimal

2018-02-01

Chitosan ionic liquid beads were prepared from chitosan and 1-butyl-3-methylimidazolium based ionic liquids to remove Malachite Green (MG) from aqueous solutions. Batch adsorption experiments were carried out as a function of initial pH, adsorbent dosage, agitation time and initial MG concentration. The optimum conditions were obtained at pH 4.0, 0.008g of adsorbent dosage and 20min of agitation time were utilized in the kinetic and isotherm studies. Three kinetic models were applied to analyze the kinetic data and pseudo-second order was found to be the best fitted model with R 2 >0.999. In order to determine the adsorption capacity, the sorption data were analyzed using the linear form of Langmuir, Freundlich and Temkin equations. The isotherm was best fitted by Langmuir isotherm model. The maximum adsorption capacity (q max ) obtained from Langmuir isotherm for two chitosan beads 1-butyl-3-methylimidazolium acetate A and 1-butyl-3-methylimidazolium B are 8.07mgg -1 and 0.24mgg -1 respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

Adsorption of anionic and cationic dyes on activated carbon from aqueous solutions: equilibrium and kinetics.

PubMed

Rodríguez, Araceli; García, Juan; Ovejero, Gabriel; Mestanza, María

2009-12-30

Activated carbon was utilized as adsorbent to remove anionic dye, Orange II (OII), and cationic dye, Methylene blue (MB), from aqueous solutions by adsorption. Batch experiments were conducted to study the effects of temperature (30-65 degrees C), initial concentration of adsorbate (300-500 mg L(-1)) and pH (3.0-9.0) on dyes adsorption. Equilibrium adsorption isotherms and kinetics were investigated. The equilibrium experimental data were analyzed by the Langmuir, Freundlich, Toth and Redlich-Peterson models. The kinetic data obtained with different carbon mass were analyzed using a pseudo-first order, pseudo-second order, intraparticle diffusion, Bangham and Chien-Clayton equations. The best results were achieved with the Langmuir isotherm equilibrium model and with the pseudo-second order kinetic model. The activated carbon was found to be very effective as adsorbent for MB and OII from aqueous solutions.

Enhanced hydrogen release by catalyzed hydrolysis of sodium borohydride-ammonia borane mixtures: a solution-state 11B NMR study.

PubMed

Hannauer, J; Demirci, U B; Geantet, C; Herrmann, J M; Miele, P

2011-03-07

Hydrolysis of mixtures consisting of sodium borohydride NaBH(4) (SB) and ammonia borane NH(3)BH(3) (AB) was studied in the absence/presence of a Co catalyst. The kinetics of the H(2) evolutions was measured. The reactions were followed in situ by solution-state (11)B NMR and the hydrolysis by-products characterized by NMR, XRD and IR. It is demonstrated that the combination of the two compounds gives a synergetic effect. SB rapidly reduces the Co catalyst precursor and the NH(4)(+) ions from AB contribute in the dispersion of the in situ formed Co nanoparticles. As a result, the kinetics of H(2) evolution is greatly improved. For instance, a hydrogen generation rate of 29.6 L min(-1) g(-1)(Co) was found for a mixture consisting of 81 wt% NH(3)BH(3), 9 wt% NaBH(4) and 10 wt% CoCl(2). By (11)B NMR, it was showed that the reaction mechanisms are quite trivial. As soon as the Co catalyst forms in situ, SB, rather than AB, hydrolyzes until it is totally converted. Then, the overall hydrolysis continues with that of AB. Both reactions follow a bimolecular Langmuir-Hinshelwood mechanism; no reaction intermediates were observed during the process. In fact, SB and AB convert directly into B(OH)(4)(-), which comes in equilibrium with a polyborate compound identified as B(3)O(3)(OH)(4)(-). All of these results are discussed herein.

Catalytic hydrodeoxygenation of methyl-substituted phenols: correlations of kinetic parameters with molecular properties.

PubMed

Massoth, F E; Politzer, P; Concha, M C; Murray, J S; Jakowski, J; Simons, Jack

2006-07-27

The hydrodeoxygenation of methyl-substituted phenols was carried out in a flow microreactor at 300 degrees C and 2.85 MPa hydrogen pressure over a sulfided CoMo/Al(2)O(3) catalyst. The primary reaction products were methyl-substituted benzene, cyclohexene, cyclohexane, and H(2)O. Analysis of the results suggests that two independent reaction paths are operative, one leading to aromatics and the other to partially or completely hydrogenated cyclohexanes. The reaction data were analyzed using Langmuir-Hinshelwood kinetics to extract the values of the reactant-to-catalyst adsorption constant and of the rate constants characterizing the two reaction paths. The adsorption constant was found to be the same for both reactions, suggesting that a single catalytic site center is operative in both reactions. Ab initio electronic structure calculations were used to evaluate the electrostatic potentials and valence orbital ionization potentials for all of the substituted phenol reactants. Correlations were observed between (a) the adsorption constant and the two reaction rate constants measured for various methyl-substitutions and (b) certain moments of the electrostatic potentials and certain orbitals' ionization potentials of the isolated phenol molecules. On the basis of these correlations to intrinsic reactant-molecule properties, a reaction mechanism is proposed for each pathway, and it is suggested that the dependencies of adsorption and reaction rates upon methyl-group substitution are a result of the substituents' effects on the electrostatic potential and orbitals rather than geometric (steric) effects.

Efficient degradation of Methylene Blue dye over highly reactive Cu doped strontium titanate (SrTiO3) nanoparticles photocatalyst under visible light.

PubMed

Rahman, Qazi Inamur; Ahmad, Musheer; Misra, Sunil Kumar; Lohani, Minaxi

2012-09-01

Visible light induced photocatalysts of Cu doped SrTiO3 (Cu/SrTiO3) nanoparticles with the size -60-75 nm were prepared via facile sol-gel method. The morphological, optical, crystalline properties and compositions of synthesized Cu/SrTiO3 nanoparticles were thoroughly characterized by field emission scanning electron microscopy (FE-SEM), powder X-ray diffraction (XRD), ultra violet-visible spectroscopy (UV-Vis) and energy dispersive X-ray (EDX). A significant red shift in the UV-diffused reflectance spectrum was observed and the absorption edge shifted to visible region by the Cu doping. Surprisingly, the band gap of SrTiO3 was changed from 3.2 eV drop to 2.96 eV. The photocatalytic activity of the synthesized Cu/SrTiO3 nanoparticles was demonstrated for the degradation of Methylene Blue dye under visible light irradiation. The formation of new acceptor region in Cu/SrTiO3 was responsible for high photocatalytic activity of Cu/SrTiO3 nanoparticles. The results showed that the Methylene Blue dye was degraded by -66% within time span of 2 h over the Cu/SrTiO3 nanoparticles. This dye degradation reaction followed the Langmuir-Hinshelwood kinetics and also exhibited first order reaction rate. The calculated rate constant for the degradation reaction following first order kinetics was k = 0.0016 min(-1).

Photoelectrocatalytic degradation of methylene blue using F doped TiO2 photoelectrode under visible light irradiation.

PubMed

Liu, Dong; Tian, Renwen; Wang, Jianqiao; Nie, Er; Piao, Xianqing; Li, Xin; Sun, Zhuo

2017-10-01

Photoelectrocatalysis (PEC) has attracted great interest due to cost effectiveness and high efficiency in water treatment. In this study, F doped TiO 2 (F-TiO 2 ) photoelectrodes with honeycomb like morphology were prepared, and the PEC performance was investigated. F-TiO 2 particles that showed enhanced absorption of visible light were synthesized via a sol-gel method. F-TiO 2 particles were anchored onto the surface of F-doped SnO 2 glass by a screen-printing method to prepare the F-TiO 2 photoelectrodes. The PEC performance of the F-TiO 2 photoelectrodes was investigated via the degradation of methylene blue (MB) under visible light irradiation. The results show that the F-TiO 2 photoelectrodes exhibited an excellent PEC performance that was affected by the F doping content, applied bias and solution pH. A maximum decolorization percentage of 97.8% was achieved by the FT-15 photoelectrode, with a 1.4 V bias at pH 9.94 after 4.0 h of visible light irradiation. The high PEC performance of the F-TiO 2 photoelectrodes is mainly ascribed to the efficient separation of electron-hole (e - -h + ) pairs and the creation of active radicals such as hydroxyl radicals (OH). The PEC decolorization kinetic data were analyzed using the first-order kinetic model and the Langmuir-Hinshelwood (L-H) model. The data indicates that the PEC degradation of MB molecules mainly occurred on the surface of the F-TiO 2 photoelectrodes, and the MB molecules were discolored mainly by h + (41.5%) and OH (46.5%). In addition, 8.2% of the MB molecules were discolored by other oxidative species, and 3.8% of the MB molecules were discolored by self-sensitized oxidation. Copyright © 2017 Elsevier Ltd. All rights reserved.

The novel kinetics expression of Cadmium (II) removal using green adsorbent horse dung humic acid (Hd-Ha)

NASA Astrophysics Data System (ADS)

Basuki, Rahmat; Santosa, Sri Juari; Rusdiarso, Bambang

2017-03-01

Humic acid from dry horse dung powder has been prepared and this horse dung humic acid (HD-HA) was then applied as a sorbent to adsorb Cadmium(II) from a solution. Characterization of HD-HA was conducted by detection of its functional group, UV-Vis spectra, ash level, and total acidity. Result of the work showed that HD-HA had similar character compared with peat soil humic acid (PS-HA) and previous researchers. The adsorption study of this work was investigated by batch experiment in pH 5. The thermodynamics parameters in this work were determined by the Langmuir isotherm model for monolayer sorption and Freundlich isotherm model multilayer sorption. Monolayer sorption capacity (b) for HD-HA was 1.329 × 10-3 mol g-1, equilibrium constant (K) was 5.651 (mol/L)-1, and multilayer sorption capacity was 2.646 × 10-2 mol g-1. The kinetics parameters investigated in this work were determined by the novel kinetics expression resulted from the mathematical derivation the availability of binding sites of sorbent. Adsorption rate constant (ka) from this novel expression was 43.178 min-1 (mol/L)-1 and desorption rate constant (kd) was 1.250 × 10-2 min-1. Application of the kinetics model on sorption Cd(II) onto HD-HA showed the nearly all of models gave a good linearity. However, only this proposed kinetics expression has good relation with Langmuir model. The novel kinetics expression proposed in this paper seems to be more realistic and reasonable and close to the experimental real condition because the value of ka/kd (3452 (mol/L)-1) was fairly close with K from Langmuir isotherm model (5651 (mol/L)-1). Comparison of this novel kinetics expression with well-known Lagergren pseudo-first order kinetics and Ho pseudo-second order kinetics was also critically discussed in this paper.

Kinetic and catalytic analysis of mesoporous metal oxides on the oxidation of Rhodamine B

NASA Astrophysics Data System (ADS)

Xaba, Morena S.; Noh, Ji-Hyang; Mokgadi, Keabetswe; Meijboom, Reinout

2018-05-01

In this study, we demonstrate the synthesis and catalytic activity of different mesoporous transition metal oxides, silica (SiO2), copper oxide (CuO), chromium oxide (Cr2O3), iron oxide (Fe2O3) cobalt oxide (Co3O4), cerium oxide (CeO2) and nickel oxide (NiO), on the oxidation of a pollutant dye, Rhodamine B (RhB). These metal oxides were synthesized by inverse micelle formation method and characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), adsorption-desorption isotherms (BET) and H2-temperature programmed reduction (TPR). UV-vis spectrophotometry was used to monitor the time-resolved absorbance of RhB at λmax = 554 nm. Mesoporous copper oxide was calcined at different final heating temperatures of 250, 350, 450 and 550 °C, and each mesoporous copper oxide catalyst showed unique physical properties and catalytic behavior. Mesoporous CuO-550 with the smallest characteristic path length δ, proved to be the catalyst of choice for the oxidation of RhB in aqueous media. We observed that the oxidation of RhB in aqueous media is dependent on the crystallite size and characteristic path length of the mesoporous metal oxide. The Langmuir-Hinshelwood model was used to fit the experimental data and to prove that the reaction occurs on the surface of the mesoporous CuO. The thermodynamic parameters, EA, ΔH#, ΔS# and ΔG# were calculated and catalyst recycling and reusability were demonstrated.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vargas, Ronald; Nunez, Oswaldo

Photodegradation/mineralization (TiO{sub 2}/UV Light) of the hydrocarbons: p-nitrophenol (PNP), naphthalene (NP) and dibenzothiophene (DBT) at three different reactors: batch bench reactor (BBR), tubular bench reactor (TBR) and tubular pilot-plant (TPP) were kinetically monitored at pH = 3, 6 and 10, and the results compared using normalized UV light exposition times. The results fit the Langmuir-Hinshelwood (LH) model; therefore, LH adsorption equilibrium constants (K) and apparent rate constants (k) are reported as well as the apparent pseudo-first-order rate constants, k{sub obs}{sup '} = kK/(1 + Kc{sub r}). The batch bench reactor is the most selective reactor toward compound and pH changesmore » in which the reactivity order is: NP > DBT > PNP, however, the catalyst adsorption (K) order is: DBT > NP > PNP at the three pH used but NP has the highest k values. The tubular pilot-plant (TPP) is the most efficient of the three reactors tested. Compound and pH photodegradation/mineralization selectivity is partially lost at the pilot plant where DBT and NP reaches ca. 90% mineralization at the pH used, meanwhile, PNP reaches only 40%. The real time, in which these mineralization occur are: 180 min for PNP and 60 min for NP and DBT. The mineralization results at the TPP indicate that for the three compounds, the rate limiting step is the same as the degradation one. So that, there is not any stable intermediate that may accumulate during the photocatalytic treatment. (author)« less

Comparative evaluation of adsorption kinetics of diclofenac and isoproturon by activated carbon.

PubMed

Torrellas, Silvia A; Rodriguez, Araceli R; Escudero, Gabriel O; Martín, José María G; Rodriguez, Juan G

2015-01-01

Adsorption mechanism of diclofenac and isoproturon onto activated carbon has been proposed using Langmuir and Freundlich isotherms. Adsorption capacity and optimum adsorption isotherms were predicted by nonlinear regression method. Different kinetic equations, pseudo-first-order, pseudo-second-order, intraparticle diffusion model and Bangham kinetic model, were applied to study the adsorption kinetics of emerging contaminants on activated carbon in two aqueous matrices.

Sorption isotherm and kinetic modeling of aniline on Cr-bentonite.

PubMed

Zheng, Hong; Liu, Donghong; Zheng, Yan; Liang, Shuping; Liu, Zhe

2009-08-15

In this paper, the sorption characteristics of aniline on Cr-bentonite prepared using synthetic wastewater containing chromium was investigated in a batch system at 30 degrees C. The effects of relevant parameters, such as pH value of solution, adsorbent dosage and initial aniline concentration were examined. The experimental data were analyzed by the Langmuir and Freundlich, and Temkin models of sorption. The sorption isotherm data were fitted well to Langmuir isotherm and the monolayer sorption capacity was found to be 21.60 mg/g at 30 degrees C. Dubinin-Redushkevich (D-R) isotherm was applied to describe the nature of aniline uptake and it was found that it occurred chemically. The kinetic data obtained at different concentrations were analyzed using a pseudo first-order, pseudo second-order kinetic equation and intraparticle diffusion model. The experimental data fitted very well the pseudo second-order kinetic model. Intraparticle diffusion affects aniline uptake. The results indicate that there is significant potential for Cr-bentonite as an adsorbent material for aniline removal from aqueous solutions.

An introduction to photocatalysis through methylene blue photodegradation

NASA Astrophysics Data System (ADS)

Petit, Matthieu; Michez, Lisa; Raimundo, Jean-Manuel; Malinowski, Tuhiti; Dumas, Philippe

2016-11-01

We described a simple experimental set-up for lab work on the photocatalytic degradation of methylene blue by TiO2 nanoparticles. The photocatalysis process can be used for many applications. Treatments for diluted wastewater industries, air purifying in underground car parks, and preventing fouling on glass surfaces, are some of the potential applications of this phenomenon. The described experiment is easy to perform and the interpretation can be easily adapted to different levels of students, from high school students demonstrating their interest in sustainable development, to students obtaining a Masters in science departments who want to propose a full explanation for all phenomena of the photocatalytic process. Starting with a description of the experimental set-up, we analysed the photocatalyst nanoparticles and applied the Langmuir-Hinshelwood model to our experimental data. Finally we briefly discussed the respective energetic levels of the photocatalyst semiconductor and methylene blue.

Remarkable NO oxidation on single supported platinum atoms

DOE PAGES

Narula, Chaitanya K.; Allard, Lawrence F.; Stocks, G. M.; ...

2014-11-28

Our first-principles density functional theoretical modeling suggests that NO oxidation is feasible on fully oxidized single θ-alumina-supported platinum atoms via a modified Langmuir-Hinshelwood pathway. This is in contrast to the known decrease in NO oxidation activity of supported platinum with decreasing Pt particle size believed to be due to increased platinum oxidation. In order to validate our theoretical study, we evaluated single θ-Al 2O 3-supported platinum atoms and found them to exhibit remarkable NO oxidation activity. A comparison of turnover frequencies (TOF) of single supported Pt atoms with those of platinum particles for NO oxidation shows that single supported Ptmore » atoms are as active as fully formed platinum particles. The overall picture of NO oxidation on supported Pt is that NO oxidation activity decreases with decreasing Pt particle size but accelerates when Pt is present only as single atoms.« less

Equilibrium and kinetics study on hexavalent chromium adsorption onto diethylene triamine grafted glycidyl methacrylate based copolymers.

PubMed

Maksin, Danijela D; Nastasović, Aleksandra B; Milutinović-Nikolić, Aleksandra D; Suručić, Ljiljana T; Sandić, Zvjezdana P; Hercigonja, Radmila V; Onjia, Antonije E

2012-03-30

Two porous and one non-porous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [abbreviated PGME] were prepared by suspension copolymerization and functionalized with diethylene triamine [abbreviated PGME-deta]. Samples were characterized by elemental analysis, mercury porosimetry, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Kinetics of Cr(VI) sorption by PGME-deta were investigated in batch static experiments, in the temperature range 25-70°C. Sorption was rapid, with the uptake capacity higher than 80% after 30 min. Sorption behavior and rate-controlling mechanisms were analyzed using five kinetic models (pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion and Bangham model). Kinetic studies showed that Cr(VI) adsorption adhered to the pseudo-second-order model, with definite influence of pore diffusion. Equilibrium data was tested with Langmuir, Freundlich and Tempkin adsorption isotherm models. Langmuir model was the most suitable indicating homogeneous distribution of active sites on PGME-deta and monolayer sorption. The maximum adsorption capacity from the Langmuir model, Q(max), at pH 1.8 and 25°C was 143 mg g(-1) for PGME2-deta (sample with the highest amino group concentration) while at 70°C Q(max) reached the high value of 198 mg g(-1). Thermodynamic parameters revealed spontaneous and endothermic nature of Cr(VI) adsorption onto PGME-deta. Copyright © 2012 Elsevier B.V. All rights reserved.

Adsorption Processes of Lead Ions on the Mixture Surface of Bentonite and Bottom Sediments.

PubMed

Hegedűsová, Alžbeta; Hegedűs, Ondrej; Tóth, Tomáš; Vollmannová, Alena; Andrejiová, Alena; Šlosár, Miroslav; Mezeyová, Ivana; Pernyeszi, Tímea

2016-12-01

The adsorption of contaminants plays an important role in the process of their elimination from a polluted environment. This work describes the issue of loading environment with lead Pb(II) and the resulting negative impact it has on plants and living organisms. It also focuses on bentonite as a natural adsorbent and on the adsorption process of Pb(II) ions on the mixture of bentonite and bottom sediment from the water reservoir in Kolíňany (SR). The equilibrium and kinetic experimental data were evaluated using Langmuir isotherm kinetic pseudo-first and pseudo-second-order rate equations the intraparticle and surface diffusion models. Langmuir isotherm model was successfully used to characterize the lead ions adsorption equilibrium on the mixture of bentonite and bottom sediment. The pseudo second-order model, the intraparticle and surface (film) diffusion models could be simultaneously fitted the experimental kinetic data.

Epoxide reduction with hydrazine on graphene: a first principles study.

PubMed

Kim, Min Chan; Hwang, Gyeong S; Ruoff, Rodney S

2009-08-14

Mechanisms for epoxide reduction with hydrazine on a single-layer graphene sheet are examined using quantum mechanical calculations within the framework of gradient-corrected spin-polarized density-functional theory. We find that the reduction reaction is mainly governed by epoxide ring opening which is initiated by H transfer from hydrazine or its derivatives. In addition, our calculations suggest that the epoxide reduction by hydrazine may predominantly follow a direct Eley-Rideal mechanism rather than a Langmuir-Hinshelwood mechanism. We also discuss the generation of various hydrazine derivatives during the reduction of graphene oxide with hydrazine and their potential contribution to lowering the barrier height of epoxide ring opening.

Kinetics and Equilibrium of Fe3+ Ions Adsorption on Carbon Nanofibers

NASA Astrophysics Data System (ADS)

Alimin; Agusu, La; Ahmad, L. O.; Kadidae, L. O.; Ramadhan, L.; Nurdin, M.; Isdayanti, N.; Asria; Aprilia M, P.; Hasrudin

2018-05-01

Generally, the interaction between metal ions and adsorbent is governed by many factors including; concentration of metal ions, interaction time and solution pH. In this work, we applied liquid phase adsorption for studying the interaction between Fe3+ ions and Carbon Nanofibers (CNFs) irradiated by ultrasonic waves. Kinetics and isotherms model of the Fe3+ ion adsorption was investigated by varying contact time and pH. We found that the Fe3+ ions were efficiently adsorbed on CNFs for 0.5 h in acidic pH of around 5. In order to obtain the best-fitted isotherms model, Langmuir and Freundlich’s isotherms were used in this work. The adsorption equilibrium Fe3+ metal ions on CNFs tend to follow Langmuir. Adsorption kinetics of Fe3+ ions on CNFs were investigated by using both pseudo-first and pseudo-second orders. The adsorption kinetics coincided well with the pseudo-second-order.

Intra-particle migration of mercury in granular polysulfide-rubber-coated activated carbon (PSR-AC)

PubMed Central

Kim, Eun-Ah; Masue-Slowey, Yoko; Fendorf, Scott; Luthy, Richard G.

2011-01-01

The depth profile of mercuric ion after the reaction with polysulfide-rubber-coated activated carbon (PSR-AC) was investigated using micro-x-ray fluorescence (μ-XRF) imaging techniques and mathematical modeling. The μ-XRF results revealed that mercury was concentrated at 0~100 μm from the exterior of the particle after three months of treatment with PSR-AC in 10 ppm HgCl2 aqueous solution. The μ-X-ray absorption near edge spectroscopic (μ-XANES) analyses indicated HgS as a major mercury species, and suggested that the intra-particle mercury transport involved a chemical reaction with PSR polymer. An intra-particle mass transfer model was developed based on either a Langmuir sorption isotherm with liquid phase diffusion (Langmuir model) or a kinetic sorption with surface diffusion (kinetic sorption model). The Langmuir model predicted the general trend of mercury diffusion, although at a slower rate than observed from the μ-XRF map. A kinetic sorption model suggested faster mercury transport, which overestimated the movement of mercuric ions through an exchange reaction between the fast and slow reaction sites. Both μ-XRF and mathematical modeling results suggest mercury removal occurs not only at the outer surface of the PSR-AC particle but also at some interior regions due to a large PSR surface area within an AC particle. PMID:22133913

Adsorption of 2,4-dichlorophenoxyacetic acid and 4-chloro-2-metylphenoxyacetic acid onto activated carbons derived from various lignocellulosic materials.

PubMed

Doczekalska, Beata; Kuśmierek, Krzysztof; Świątkowski, Andrzej; Bartkowiak, Monika

2018-05-04

Adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-metylphenoxyacetic acid (MCPA) from aqueous solution onto activated carbons derived from various lignocellulosic materials including willow, miscanthus, flax, and hemp shives was investigated. The adsorption kinetic data were analyzed using two kinetic models: the pseudo-first order and pseudo-second order equations. The adsorption kinetics of both herbicides was better represented by the pseudo-second order model. The adsorption isotherms of 2,4-D and MCPA on the activated carbons were analyzed using the Freundlich and Langmuir isotherm models. The equilibrium data followed the Langmuir isotherm. The effect of pH on the adsorption was also studied. The results showed that the activated carbons prepared from the lignocellulosic materials are efficient adsorbents for the removal of 2,4-D and MCPA from aqueous solutions.

A comparative examination of the adsorption mechanism of an anionic textile dye (RBY 3GL) onto the powdered activated carbon (PAC) using various the isotherm models and kinetics equations with linear and non-linear methods

NASA Astrophysics Data System (ADS)

Açıkyıldız, Metin; Gürses, Ahmet; Güneş, Kübra; Yalvaç, Duygu

2015-11-01

The present study was designed to compare the linear and non-linear methods used to check the compliance of the experimental data corresponding to the isotherm models (Langmuir, Freundlich, and Redlich-Peterson) and kinetics equations (pseudo-first order and pseudo-second order). In this context, adsorption experiments were carried out to remove an anionic dye, Remazol Brillant Yellow 3GL (RBY), from its aqueous solutions using a commercial activated carbon as a sorbent. The effects of contact time, initial RBY concentration, and temperature onto adsorbed amount were investigated. The amount of dye adsorbed increased with increased adsorption time and the adsorption equilibrium was attained after 240 min. The amount of dye adsorbed enhanced with increased temperature, suggesting that the adsorption process is endothermic. The experimental data was analyzed using the Langmuir, Freundlich, and Redlich-Peterson isotherm equations in order to predict adsorption isotherm. It was determined that the isotherm data were fitted to the Langmuir and Redlich-Peterson isotherms. The adsorption process was also found to follow a pseudo second-order kinetic model. According to the kinetic and isotherm data, it was found that the determination coefficients obtained from linear method were higher than those obtained from non-linear method.

Characterizations of strontium(II) and barium(II) adsorption from aqueous solutions using dolomite powder.

PubMed

Ghaemi, Ahad; Torab-Mostaedi, Meisam; Ghannadi-Maragheh, Mohammad

2011-06-15

In this research, adsorption technique was applied for strontium and barium removal from aqueous solution using dolomite powder. The process has been investigated as a function of pH, contact time, temperature and adsorbate concentration. The experimental data was analyzed using equilibrium isotherm, kinetic and thermodynamic models. The isotherm data was well described by Langmuir isotherm model. The maximum adsorption capacity was found to be 1.172 and 3.958 mg/g for Sr(II) and Ba(II) from the Langmuir isotherm model at 293 K, respectively. The kinetic data was tested using first and pseudo-second order models. The results indicated that adsorption fitted well with the pseudo-second order kinetic model. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were also determined using the equilibrium constant value obtained at different temperatures. The results showed that the adsorption for both ions was feasible and exothermic. Copyright © 2011 Elsevier B.V. All rights reserved.

Solar photocatalytic gas-phase degradation of n-decane--a comparative study using cellulose acetate monoliths coated with P25 or sol-gel TiO₂ films.

PubMed

Miranda, Sandra M; Lopes, Filipe V S; Rodrigues-Silva, Caio; Martins, Susana D S; Silva, Adrián M T; Faria, Joaquim L; Boaventura, Rui A R; Vilar, Vítor J P

2015-01-01

Cellulose acetate monoliths (CAM) were used as the substrate for the deposition of TiO2 films to produce honeycombed photoactive structures to fill a tubular photoreactor equipped with a compound parabolic collector. By using such a setup, an efficient single-pass gas-phase conversion was achieved in the degradation of n-decane, a model volatile organic compound. The CAM three-dimensional, gas-permeable transparent structure with a rugged surface enables a good adhesion of the catalytic coating. It also provides a rigid structure for packing the tubular photoreactor, and maximizing the illuminated catalyst surface. The efficiency of the photocatalytic oxidation (PCO) process on n-decane degradation was evaluated under different operating conditions, such as feeding concentration (73 and 146 ppm), gas stream flow rate (73, 150, and 300 mL min(-1)), relative humidity (3 and 25 %), and UV irradiance (18.9, 29.1, and 38.4 WUV m(-2)). The results show that n-decane degradation by neat photolysis is negligible, but mineralization efficiencies of 86 and 82 % were achieved with P25-CAM and SG-CAM, respectively, for parent pollutant conversions above 95 %, under steady-state conditions. A mass transfer model, considering the mass balance to the plug-flow packed photoreactor, and PCO reaction given by a Langmuir-Hinshelwood bimolecular non-competitive two types of sites equation, was able to predict well the PCO kinetics under steady-state conditions, considering all the operational parameters tested. Overall, the performance of P25-CAM was superior taking into account mineralization efficiency, cost of preparation, surface roughness, and robustness of the deposited film.

Atomic-Scale Design of Iron Fischer-Tropsch Catalysts; A Combined Computational Chemistry, Experimental, and Microkinetic Modeling Approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manos Mavrikakis; James Dumesic; Rahul Nabar

2008-09-29

This work focuses on (1) searching/summarizing published Fischer-Tropsch synthesis (FTS) mechanistic and kinetic studies of FTS reactions on iron catalysts; (2) preparation and characterization of unsupported iron catalysts with/without potassium/platinum promoters; (3) measurement of H{sub 2} and CO adsorption/dissociation kinetics on iron catalysts using transient methods; (3) analysis of the transient rate data to calculate kinetic parameters of early elementary steps in FTS; (4) construction of a microkinetic model of FTS on iron, and (5) validation of the model from collection of steady-state rate data for FTS on iron catalysts. Three unsupported iron catalysts and three alumina-supported iron catalysts weremore » prepared by non-aqueous-evaporative deposition (NED) or aqueous impregnation (AI) and characterized by chemisorption, BET, temperature-programmed reduction (TPR), extent-of-reduction, XRD, and TEM methods. These catalysts, covering a wide range of dispersions and metal loadings, are well-reduced and relatively thermally stable up to 500-600 C in H{sub 2} and thus ideal for kinetic and mechanistic studies. Kinetic parameters for CO adsorption, CO dissociation, and surface carbon hydrogenation on these catalysts were determined from temperature-programmed desorption (TPD) of CO and temperature programmed surface hydrogenation (TPSR), temperature-programmed hydrogenation (TPH), and isothermal, transient hydrogenation (ITH). A microkinetic model was constructed for the early steps in FTS on polycrystalline iron from the kinetic parameters of elementary steps determined experimentally in this work and from literature values. Steady-state rate data were collected in a Berty reactor and used for validation of the microkinetic model. These rate data were fitted to 'smart' Langmuir-Hinshelwood rate expressions derived from a sequence of elementary steps and using a combination of fitted steady-state parameters and parameters specified from the transient measurements. The results provide a platform for further development of microkinetic models of FTS on Fe and a basis for more precise modeling of FTS activity of Fe catalysts. Calculations using periodic, self-consistent Density Functional Theory (DFT) methods were performed on various realistic models of industrial, Fe-based FTS catalysts. Close-packed, most stable Fe(110) facet was analyzed and subsequently carbide formation was found to be facile leading to the choice of the FeC(110) model representing a Fe facet with a sub-surface C atom. The Pt adatom (Fe{sup Pt}(110)) was found to be the most stable model for our studies into Pt promotion and finally the role of steps was elucidated by recourse to the defected Fe(211) facet. Binding Energies(BEs), preferred adsorption sites and geometries for all FTS relevant stable species and intermediates were evaluated on each model catalyst facet. A mechanistic model (comprising of 32 elementary steps involving 19 species) was constructed and each elementary step therein was fully characterized with respect to its thermochemistry and kinetics. Kinetic calculations involved evaluation of the Minimum Energy Pathways (MEPs) and activation energies (barriers) for each step. Vibrational frequencies were evaluated for the preferred adsorption configuration of each species with the aim of evaluating entropy-changes, pre exponential factors and serving as a useful connection with experimental surface science techniques. Comparative analysis among these four facets revealed important trends in their relative behavior and roles in FTS catalysis. Overall the First Principles Calculations afforded us a new insight into FTS catalysis on Fe and modified-Fe catalysts.« less

Adsorptive Removal of Cadmium (II) from Aqueous Solution by Multi-Carboxylic-Functionalized Silica Gel: Equilibrium, Kinetics and Thermodynamics

NASA Astrophysics Data System (ADS)

Li, Min; Meng, Xiaojing; Yuan, Jinhai; Deng, Wenwen; Liang, Xiuke

2018-01-01

In the present study, the adsorption behavior of cadmium (II) ion from aqueous solution onto multi-carboxylic-functionalized silica gel (SG-MCF) has been investigated in detail by means of batch and column experiments. Batch experiments were performed to evaluate the effects of various experimental parameters such as pH value, contact time and initial concentration on adsorption capacity of cadmium (II) ion. The kinetic data were analyzed on the basis of the pseudo-first-order kinetic and the pseudo-second-order kinetic models and consequently, the pseudo-second-order kinetic can better describe the adsorption process than the pseudo-first-order kinetic model. Equilibrium isotherms for the adsorption of cadmium (II) ion were analyzed by Freundlich and Langmuir isotherm models, the results indicate that Langmuir isotherm model was found to be credible to express the data for cadmium (II) ion from aqueous solution onto the SG-MCF. Various thermodynamics parameters of the adsorption process, including free energy of adsorption (ΔG0 ), the enthalpy of adsorption (ΔH0 ) and standard entropy changes (ΔS0 ), were calculated to predict the nature of adsorption. The positive value of the enthalpy change and the negative value of free energy change indicate that the process is endothermic and spontaneous process.

Liquid-phase hydrogenation of citral over Pt/SiO{sub 2} catalysts. 1. Temperature effects on activity and selectivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, U.K.; Vannice, M.A.

2000-04-01

Liquid-phase hydrogenation of citral (3,7-dimethyl-2,6-octadienal) over Pt/SiO{sub 2} catalysts was studied in the temperature and pressure ranges 298--423 K and 7--21 atm, respectively. The reaction kinetics were shown to be free of artifacts arising from transport limitations and poisoning effects. The reaction rate in hexane at the solvent exhibited an activity minimum at 373 K. The initial turnover frequency for citral disappearance over 1.44% Pt/SiO{sub 2} catalyst at 20 atm H{sub 2} pressure decreased from 0.19 s{sup {minus}1} at 298 K to 0.02 s{sup {minus}1} at 373 K, but exhibited normal Arrhenius behavior between 373 and 423 K with anmore » activation energy of 7 kcal/mol. Reaction at 298 K produced substantial deactivation, with the rate decreasing by more than an order of magnitude during the first 4 h of reaction; however, reaction at temperatures greater than 373 K exhibited negligible deactivation and a constant rate up to citral conversions greater than 70%. These unusual temperature effects were modeled using Langmuir-Hinshelwood kinetics invoking dissociative adsorption of hydrogen, competitive adsorption between hydrogen and the organic compounds, and addition of the second hydrogen atom to each reactant as the rate-determining step. Decomposition of the unsaturated alcohol (either geraniol or nerol) was proposed to occur concurrently with the hydrogenation steps to yield adsorbed CO and carbonaceous species which cause the deactivation, but at higher temperatures these species could be removed from the Pt surface by desorption or rapid hydrogenation, respectively. The activity minimum observed in the present study is attributed to the relative rates of the alcohol decomposition reaction and CO desorption, with the decomposition reaction having an activation barrier lower than that for CO desorption.« less

Degradation kinetics and mechanism of RDX and HMX in TiO2 photocatalysis.

PubMed

Choi, J K; Son, H S; Kim, T S; Stenstrom, M K; Zoh, K D

2006-02-01

This study was undertaken to examine the photocatalytic degradation of explosives hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) with a circular photocatalytic reactor, using a UV lamp as a light source and TiO2 as a photocatalyst. The effects of various parameters, such as the RDX or HMX concentration, the amount of TiO, and the initial pH, on the photocatalytic degradation rates of explosives were examined. In the presence of both UV light and TiO2 RDX and HMX were more effectively degraded than with either UV or TiO2 alone. The degradation rates were found to obey pseudo-first-order kinetics represented by the Langmuir-Hinshelwood model. Increases in the RDX and HMX degradation rates were obtained with decreasing initial concentrations of the explosives. The RDX and HMX degradation rates were higher at pH 7 than at either pH 3 or pH 11. A dose of approximately 0.7 g l(-1) of TiO2 degraded HMX more rapidly than did higher or lower TiO2 doses. RDX (20 mg l(-1)) photocatalysis resulted in an approximately 20% decrease in TOC, and HMX (5 mg l(-1)) photocatalysis resulted in a 60%, decrease in TOC within 150 minutes. A trace amount of formate was produced as an intermediate that was further mineralized by RDX or HMX photocatalysis. The nitrogen byproducts from the photocatalysis of RDX and HMX were mainly NO3- with NO2-, and NH4+. The total nitrogen recovery was about 60% from RDX (20 mg l(-1)), and 70% from HMX (5 mg l(-1)), respectively. Finally, a mechanism for RDX/HMX photocatalysis was proposed, along with supporting qualitative and quantitative evidence.

Simultaneous production of oil enriched in ω-3 polyunsaturated fatty acids and biodiesel from fish wastes.

PubMed

Enascuta, Cristina Emanuela; Stepan, Emil; Bolocan, Ion; Bombos, Dorin; Calin, Catalina; Oprescu, Elena-Emilia; Lavric, Vasile

2018-05-01

The waste resulted from fish processing industries are discarded into the environment around the world, causing environmental pollution. The main problem of fish oil extracted from waste is the high content in free fatty acids (FFA) which decrease the yield in fatty acids esters during transesterification reactions. Therefore, to correct the fish-oil properties, a new environmentally friendly heterogeneous superacid catalyst (SO 4 2- /SnO 2 -ZrO 2 ) was tested in the esterification reaction of FFA with ethanol. The catalyst was characterized by different techniques (XRD, FT-IR, FT-IR of adsorbed pyridine, BET, SEM-EDX, TGA and acidity measurements). The reaction was found to follow a Langmuir-Hinshelwood (L-H) dual-site mechanism with the novelty that both Brönsted and Lewis acid centers participate equally in the esterification reaction. The pre-treated oil was subjected to transesterification reaction with ethanol over a heterogeneous base catalyst and then, the saturated and unsaturated fractions of fatty acid ethyl esters (FAEE) were separated using a vacuum rectification unit with falling film. The saturated content can be used as biofuel, while the unsaturated FAEE are further transesterified with glycerol in order to obtain oil with high content in polyunsaturated fatty acids (PUFA). A detailed study of the intrinsic kinetic process at the surface of the superacid catalyst and a thorough mathematical model of the fixed bed reactor were written and validated by an experimental program, designed according to the D-optimal methodology. Copyright © 2018 Elsevier Ltd. All rights reserved.

Removal of anionic surfactant sodium dodecyl benzene sulfonate (SDBS) from wastewaters by zero-valent iron (ZVI): predominant removal mechanism for effective SDBS removal.

PubMed

Takayanagi, Akari; Kobayashi, Maki; Kawase, Yoshinori

2017-03-01

Mechanisms for removal of anionic surfactant sodium dodecyl benzene sulfonate (SDBS) in wastewaters by zero-valent iron (ZVI) were systematically examined. The contributions of four removal mechanisms, i.e., reductive degradation, oxidative degradation, adsorption, and precipitation, changed significantly with solution pH were quantified and the effective removal of SDBS by ZVI was found to be attributed to the adsorption capability of iron oxides/hydroxides on ZVI surface at nearly neutral pH instead of the degradation at acidic condition. The fastest SDBS removal rate and the maximum TOC (total organic carbon) removal efficiency were obtained at pH 6.0. The maximum TOC removal at pH 6.0 was 77.8%, and the contributions of degradation, precipitation, and adsorption to TOC removal were 4.6, 14.9, and 58.3%, respectively. At pH 3.0, which is an optimal pH for oxidative degradation by the Fenton reaction, the TOC removal was only 9.8% and the contributions of degradation, precipitation, and adsorption to TOC removal were 2.3, 4.6, and 2.9%, respectively. The electrostatic attraction between dodecyl benzene sulfate anion and the iron oxide/hydroxide layer controlled the TOC removal of SDBS. The kinetic model based on the Langmuir-Hinshelwood/Eley-Rideal approach could successfully describe the experimental results for SDBS removal by ZVI with the averaged correlation coefficient of 0.994. ZVI was found to be an efficient material toward the removal of anionic surfactant at nearly neutral pH under the oxic condition.

Nonlinear isotherm and kinetics of adsorption of copper from aqueous solutions on bentonite

NASA Astrophysics Data System (ADS)

Sadeghalvad, Bahareh; Khosravi, Sara; Azadmehr, Amir Reza

2016-11-01

Bentonite is one of the most significant of clay minerals that has been studied extensively due to its potential applications in removal of various environmental pollutants. This ability is related to its high ionic exchange capacity and high specific surface area. Copper is one of the important elements of non-ferrous metals found in industrial waste waters. In the present work, the removal of copper from aqueous solutions with Iranian bentonite (from Birjand area, southeastern Iran) used without any chemical pretreatment, was studied. The experimental results were fitted by adsorption isotherms equations with two or three parameters, which include Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Redlich-Peterson, Khan, and Toth models. The best correlation coefficient ( r 2) is 0.9879 observed for Langmuir model, maximum adsorption capacity of bentonite was 55.71 mg/g. The first-order and pseudo-second-order kinetic equations were used to describe the kinetics of adsorption. The experimental data were well fitted by the pseudo-second-order kinetics.

Equilibrium and Kinetic Studies of Cd2+ Biosorption by the Brown Algae Sargassum fusiforme

PubMed Central

Zou, Hui-Xi; Li, Nan; Wang, Li-Hua; Yu, Ping; Yan, Xiu-Feng

2014-01-01

A fundamental investigation of the biosorption of Cd2+ from aqueous solution by the edible seaweed Sargassum fusiforme was performed under batch conditions. The influences of experimental parameters, such as the initial pH, sorption time, temperature, and initial Cd2+ concentration, on Cd2+ uptake by S. fusiforme were evaluated. The results indicated that the biosorption of Cd2+ depended on the initial Cd2+ concentration, as well as the pH. The uptake of Cd2+ could be described by the Langmuir isotherm model, and both the Langmuir biosorption equilibrium constant and the maximum biosorption capacity of the monolayer decreased with increasing temperature, thereby confirming the exothermic character of the sorption process. The biosorption kinetics follows the pseudo-second-order kinetic model, and intraparticle diffusion is the sole rate-limiting step for the entire biosorption period. These fundamental equilibrium and kinetic results can support further studies to the removal of cadmium from S. fusiforme harvested from cadmium-polluted waters. PMID:24736449

SUPRATHERMAL SOLAR WIND ELECTRONS AND LANGMUIR TURBULENCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Sunjung; Yoon, Peter H.; Choe, G. S.

2016-09-01

The steady-state model recently put forth for the solar wind electron velocity distribution function during quiet time conditions, was originally composed of three population electrons (core, halo, and superhalo) with the core remaining nonresonant with any plasma waves while the halo and superhalo separately maintained steady-state resonance with whistler- and Langmuir-frequency range fluctuations, respectively. However, a recent paper demonstrates that whistler-range fluctuations in fact have no significant contribution. The present paper represents a consummation of the model in that a self-consistent model of the suprathermal electron population, which encompasses both the halo and the superhalo, is constructed solely on themore » basis of the Langmuir fluctuation spectrum. Numerical solutions to steady-state particle and wave kinetic equations are obtained on the basis of an initial trial electron distribution and Langmuir wave spectrum. Such a finding offers a self-consistent explanation for the observed steady-state electron distribution in the solar wind.« less

Single Pd Atoms on θ-Al 2O 3 (010) Surface do not Catalyze NO Oxidation

DOE PAGES

Narula, Chaitanya K.; Allard, Lawrence F.; Moses-DeBusk, Melanie; ...

2017-04-03

New convenient wet chemistry synthetic routes have made it possible to explore catalytic activities of a variety of single supported atoms. The majority of single supported atoms have been synthesized on active supports which participate in oxidation reactions. The single supported atoms on inert substrates (e.g. alumina) are limited to Pt adatoms and Pd cations, and are generally active toward CO oxidation. In this manuscript, we show that single Pd atoms on -alumina show high CO oxidation activity; however, they exhibit no detectable NO oxidation under our experimental conditions. This led us to employ first principles modeling to explore multiplemore » Langmuir-Hinshelwood-type pathways to explain high CO oxidation activity but lack of NO oxidation activity. For completeness, we have also examined Eley-Riedel pathways. We find that a pathway that involves carbonate or nitrate as an intermediate can explain the experimental results of CO and NO oxidation on single alumina supported Pd cations.« less

Time-dependent Tonks-Langmuir model is unstable

NASA Astrophysics Data System (ADS)

Sheridan, T. E.; Baalrud, S. D.

2017-11-01

We investigate a time-dependent extension of the Tonks-Langmuir model for a one-dimensional plasma discharge with collisionless kinetic ions and Boltzmann electrons. Ions are created uniformly throughout the volume and flow from the center of the discharge to the boundary wall due to a self-consistent, zero-order electric field. Solving this model using a particle-in-cell simulation, we observe coherent low-frequency, long-wavelength unstable ion waves which move toward the boundary with a speed below both the ion acoustic speed and the average ion velocity. The maximum amplitude of the wave potential fluctuations peaks at ≈0.09 Te near the wall, where Te is the electron temperature in electron volts. Using linear kinetic theory, we identify this instability as slow ion-acoustic wave modes which are destabilized by the zero-order electric field.

Modified Fe3O4- hydroxyapatite nanocomposites as heterogeneous catalysts in three UV, Vis and Fenton like degradation systems

NASA Astrophysics Data System (ADS)

Valizadeh, S.; Rasoulifard, M. H.; Dorraji, M. S. Seyed

2014-11-01

The magnetite-hydroxyapatite (M-HAP) nanocomposites were prepared by a chemical co- precipitation procedure and characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and diffuse reflectance spectra (DRS). The ability of the synthesized catalyst for photocatalytic degradation of Acid Blue 25 (AB25), as an organic dye, under UV irradiation was studied. The catalyst was modified employing transition metals (Mn, Fe, Co, Ni, Cu and Zn) trying to improve the catalytic performance of HAP in absence of UV irradiation and in the presence of hydrogen peroxide i.e. a Fenton like reaction. The best results obtained for Cu and Co modified M-HAPs and the effect of operational parameters such pH, amount of catalyst and hydrogen peroxide concentration was studied. In order to investigate the performance of HAP based photocatalyst in visible light region, M-HAP was modified with silver ions. At the end, Langmuir-Hinshelwood kinetic expression used to evaluate and compare the catalytic systems. The strongest degradation activity was observed for Ag-M-HAP/Vis system because of Ag3PO4 formation. Apparent reaction rate constant (Kapp) by Ag-M-HAP/Vis was 63, 36 and 19 times faster than Cu-M-HAP(II)/H2O2, Co-M-HAP(II)/H2O2 and M-HAP (I)/UV systems, respectively.

Evaluation of water matrix effects, experimental parameters, and the degradation pathway during the TiO2 photocatalytical treatment of the antibiotic dicloxacillin.

PubMed

Villegas-Guzman, Paola; Silva-Agredo, Javier; González-Gómez, Duván; Giraldo-Aguirre, Ana L; Flórez-Acosta, Oscar; Torres-Palma, Ricardo A

2015-01-01

The photocalytic degradation of dicloxacillin (DXC) using TiO2 was studied in synthetic and natural waters. The degradation route and the effect of different experimental variables such as pH, applied power, and the initial concentrations of DXC and the catalyst were investigated. The best performances were achieved at a natural pH 5.8 and using 2.0 g L(-1) of TiO2 with 150 W of applied power. The photodegradation process followed Langmuir-Hinshelwood kinetics. The water matrix effect was evaluated in terms of degradation efficiency in the presence of organic compounds (oxalic acid, glucose), Fe(2+) ion and natural water. An increase in degradation was observed when ferrous ion was part of the solution, but the process was inhibited with all evaluated organic compounds. Similarly, inhibition was observed when natural water was used instead of distilled water. The extent of degradation of the process was evaluated following the evolution of chemical oxygen demand (COD), antimicrobial activity (AA), total organic carbon (TOC) and biochemical oxygen demand (BOD5). Total removal of DXC was achieved after 120 min of treatment and 95% mineralization was observed after 480 min of treatment. Additionally, the total removal of antimicrobial activity and a high level of biodegradability were observed after the photocalytical system had been operating for 240 min.

Anti-site defected MoS2 sheet for catalytic application

NASA Astrophysics Data System (ADS)

Sharma, Archana; Husain, Mushahid; Khan, Mohd. Shahid

2018-04-01

To prevent harmful and poisonous CO gas molecules, catalysts are needed for converting them into benign substances. Density functional theory (DFT) calculations have been used to investigate CO oxidation on the surface of MoS2 monolayer with Mo atom embedded at S-vacancy site (anti-site defect). The stronger interaction between Mo metal with O2 molecule as compared with CO molecule suggests high catalytic activity. The complete oxidation of CO is studied in a two-step procedure using Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) mechanisms with a low overall energy barrier of 0.35 eV. Creation of anti-site defect makes the surface of MoS2 nanosheet catalytically active for the CO oxidation to take place.

Synthesis of hierarchical Ni(OH)(2) and NiO nanosheets and their adsorption kinetics and isotherms to Congo red in water.

PubMed

Cheng, Bei; Le, Yao; Cai, Weiquan; Yu, Jiaguo

2011-01-30

Ni(OH)(2) and NiO nanosheets with hierarchical porous structures were synthesized by a simple chemical precipitation method using nickel chloride as precursors and urea as precipitating agent. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy and nitrogen adsorption-desorption isotherms. Adsorption of Congo red (CR) onto the as-prepared samples from aqueous solutions was investigated and discussed. The pore structure analyses indicate that Ni(OH)(2) and NiO nanosheets are composed of at least three levels of hierarchical porous organization: small mesopores (ca. 3-5 nm), large mesopores (ca. 10-50 nm) and macropores (100-500 nm). The equilibrium adsorption data of CR on the as-prepared samples were analyzed by Langmuir and Freundlich models, suggesting that the Langmuir model provides the better correlation of the experimental data. The adsorption capacities for removal of CR was determined using the Langmuir equation and found to be 82.9, 151.7 and 39.7 mg/g for Ni(OH)(2) nanosheets, NiO nanosheets and NiO nanoparticles, respectively. Adsorption data were modeled using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics equations. The results indicate that pseudo-second-order kinetic equation and intra-particle diffusion model can better describe the adsorption kinetics. The as-prepared Ni(OH)(2) and NiO nanosheets are found to be effective adsorbents for the removal of Congo red pollutant from wastewater as a result of their unique hierarchical porous structures and high specific surface areas. Copyright © 2010 Elsevier B.V. All rights reserved.

Atomic-Scale Design of Iron Fischer-Tropsch Catalysts: A Combined Computational Chemistry, Experimental, and Microkinetic Modeling Approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manos Mavrikakis; James A. Dumesic; Amit A. Gokhale

2006-03-03

Efforts during this second year focused on four areas: (1) continued searching and summarizing of published Fischer-Tropsch synthesis (FTS) mechanistic and kinetic studies of FTS reactions on iron catalysts; (2) investigation of CO adsorption/desorption and temperature programmed hydrogenation (TPH) of carbonaceous species after FTS on unsupported iron and alumina-supported iron catalysts; (3) activity tests of alumina-supported iron catalysts in a fixed bed reactor; (4) sequential design of experiments, for the collection of rate data in a Berty CSTR reactor, and nonlinear-regression analysis to obtain kinetic parameters. Literature sources describing mechanistic and kinetic studies of Fischer-Tropsch synthesis on iron catalysts weremore » compiled in a review. Temperature-programmed desorption/reaction methods (the latter using mass-spectrometry detection and also thermogravimetric analyzer (TGA)) were utilized to study CO adsorption/-desorption on supported and unsupported iron catalysts. Molecular and dissociative adsorptions of CO occur on iron catalysts at 25-150 C. The amounts adsorbed and bond strengths of adsorption are influenced by supports and promoters. That CO adsorbs dissociatively on polycrystalline Fe at temperatures well below those of FT reaction indicates that CO dissociation is facile and unlikely to be the rate-limiting step during FTS. Carbonaceous species formed after FT reaction for only 5 minutes at 200 C were initially hydrogenated under mild, isothermal condition (200 C and 1 atm), followed by TPH to 800 C. During the mild, isothermal hydrogenation, only about 0.1-0.2 mL of atomic carbon is apparently removed, while during TPH to 800 C multilayer equivalents of atomic, polymeric, carbidic, and graphitic carbons are removed. Rates of CO conversion on alumina-supported iron catalysts at 220-260 C and 20 atm are correlated well by a Langmuir-Hinshelwood expression, derived assuming carbon hydrogenation to CH and OH recombination to water to be rate-determining steps. In the coming year, studies will focus on quantitative determination of the rates of kinetically-relevant elementary steps on Fe catalysts with/without K and Pt promoters and at various levels of Al{sub 2}O{sub 3} support, providing a database for understanding (1) effects of promoter and support on elementary kinetic parameters and (2) for validation of computational models that incorporate effects of surface structure and promoters. Kinetic parameters will be incorporated into a microkinetics model, enabling prediction of rate without invoking assumptions, e.g. of a rate-determining step or a most-abundant surface intermediate. Calculations using periodic, self-consistent Density Functional Theory (DFT) methods were performed on two model surfaces: (1) Fe(110) with 1/4 ML subsurface carbon, and (2) Fe(110) with 1/4 ML Pt adatoms. Reaction networks for FTS on these systems were characterized in full detail by evaluating the thermodynamics and kinetics of each elementary step. We discovered that subsurface C stabilizes all the reactive intermediates, in contrast to Pt, which destabilizes most of them. A comparative study of the reactivities of the modified-Fe surfaces against pure Fe is expected to yield a more comprehensive understanding of promotion mechanisms for FTS on Fe.« less

STEADY-STATE MODEL OF SOLAR WIND ELECTRONS REVISITED

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoon, Peter H.; Kim, Sunjung; Choe, G. S., E-mail: yoonp@umd.edu

2015-10-20

In a recent paper, Kim et al. put forth a steady-state model for the solar wind electrons. The model assumed local equilibrium between the halo electrons, characterized by an intermediate energy range, and the whistler-range fluctuations. The basic wave–particle interaction is assumed to be the cyclotron resonance. Similarly, it was assumed that a dynamical steady state is established between the highly energetic superhalo electrons and high-frequency Langmuir fluctuations. Comparisons with the measured solar wind electron velocity distribution function (VDF) during quiet times were also made, and reasonable agreements were obtained. In such a model, however, only the steady-state solution for themore » Fokker–Planck type of electron particle kinetic equation was considered. The present paper complements the previous analysis by considering both the steady-state particle and wave kinetic equations. It is shown that the model halo and superhalo electron VDFs, as well as the assumed wave intensity spectra for the whistler and Langmuir fluctuations, approximately satisfy the quasi-linear wave kinetic equations in an approximate sense, thus further validating the local equilibrium model constructed in the paper by Kim et al.« less

Adsorption-photodegradation of humic acid in water by using ZnO coupled TiO2/bamboo charcoal under visible light irradiation.

PubMed

Wang, Xuejiang; Wu, Zhen; Wang, Yin; Wang, Wei; Wang, Xin; Bu, Yunjie; Zhao, Jianfu

2013-11-15

ZnO coupled TiO2/bamboo charcoal (ZnO-TiO2/BC) was prepared using the sol-gel method combined with microwave irradiation. The ZnO-TiO2/BC and TiO2/BC were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), N2 adsorption (BET), and UV-vis diffuse reflectance spectroscopy (UV-vis-DRS). The ZnO dopant promoted the transformation of anatase TiO2 to rutile phase, and a significant red shift of absorption edge was brought out due to the interfacial coupling effect between ZnO and TiO2 particles. The BET specific surface area and total pore volume decreased with ZnO doping, indicating that some micropores were blocked. SEM studies indicated that ZnO was almost uniformly deposited on the surface of the ZnO-TiO2/BC. The adsorption and photocatalytic degradation experiments showed that the photo-degrade efficiency for Zno-TiO2/BC was higher than that of TiO2/BC, and for both composites, the removal efficiency of HA increased as pH decreased from 10.0 to 2.0. The degradation of HA by ZnO-TiO2/BC and TiO2/BC fitted well with the Langmuir-Hinshelwood kinetics model, and HA degradation was achieved through a synergistic mechanism of adsorption and photocatalysis. ZnO-TiO2/BC could be used as an effective and alternative photocatalyst for the treatment of water contaminated by organic pollutants. Copyright © 2013 Elsevier B.V. All rights reserved.

Synthesis and characterization of titanate nanotube/single-walled carbon nanotube (TNT/SWCNT) porous nanocomposite and its photocatalytic activity on 4-chlorophenol degradation under UV and solar irradiation

NASA Astrophysics Data System (ADS)

Payan, A.; Fattahi, M.; Jorfi, S.; Roozbehani, B.; Payan, S.

2018-03-01

The titanate nanotube/single-wall carbon nanotube (TNT/SWCNT) nanocomposites from different titania precursors were prepared by a two-step hydrothermal process. These nanocomposites were characterized by XRD, BET, Raman, FESEM, TEM, EDX, EDS, EIS, UV-vis DRS and FTIR techniques. The FESEM and TEM images showed the high porous nanocomposites with two types of tubular structure relating to TNTs and SWCNTs which were interwoven together uniformly. The XRD and Raman analysis further corroborated the chemical interaction between the SWCNT and the TNT in the nanocomposites. The photocatalytic performance of the as-synthesized composites were examined by the photodegradation of 4-CP under solar and UV illumination. The results revealed an impressive enhancement in photocatalytic activity of the nanocomposites under both irradiation conditions comparison to bare TNPs and TNTs. Amongst the TNT/SWCNT nanocomposites, 10% loading of SWCNT under UV irradiation and 5% loading of SWCNT under solar irradiation exhibited the maximum photocatalytic performance while the photocatalytic degradation efficiency of nanocomposites were not affected considerably by the type of precursor. Moreover, the mechanism and role of SWCNT were investigated and the plausible degradation pathways of 4-CP was suggested. TOC analyses was performed for determination of 4-CP mineralization rate and results showed complete mineralization after 240 and 390 min under UV and solar irradiation, respectively. The trapping experiments corroborated the O2- and OH radicals as the main reactive species in 4-CP degradation process. Langmuir-Hinshelwood kinetic model was fittingly matched with the experimental data (R2: 0.9218 and 0.9703 for UV and solar irradiation). Additionally, the stability of the nanocomposites were investigated and revealed 8% decrease in degradation efficiency after four cycles.

Linkage of iron elution and dissolved oxygen consumption with removal of organic pollutants by nanoscale zero-valent iron: Effects of pH on iron dissolution and formation of iron oxide/hydroxide layer.

PubMed

Fujioka, Nanae; Suzuki, Moe; Kurosu, Shunji; Kawase, Yoshinori

2016-02-01

The iron elution and dissolved oxygen (DO) consumption in organic pollutant removal by nanoscale zero-valent iron (nZVI) was examined in the range of solution pH from 3.0 to 9.0. Their behaviors were linked with the removal of organic pollutant through the dissolution of iron and the formation of iron oxide/hydroxide layer affected strongly by solution pH and DO. As an example of organic pollutants, azo-dye Orange II was chosen in this study. The chemical composition analyses before and after reaction confirmed the corrosion of nZVI into ions, the formation of iron oxide/hydroxide layer on nZVI surface and the adsorption of the pollutant and its intermediates. The complete decolorization of Orange II with nZVI was accomplished very quickly. On the other hand, the total organic carbon (TOC) removal was considerably slow and the maximum TOC removal was around 40% obtained at pH 9.0. The reductive cleavage of azo-bond by emitted electrons more readily took place as compared with the cleavage of aromatic rings of Orange II leading to the degradation to smaller molecules and subsequently the mineralization. A reaction kinetic model based on the Langmuir-Hinshelwood/Eley-Rideal approach was developed to elucidate mechanisms for organic pollutant removal controlled by the formation of iron oxide/hydroxide layer, the progress of which could be characterized by considering the dynamic concentration changes in Fe(2+) and DO. The dynamic profiles of Orange II removal linked with Fe(2+) and DO could be reasonably simulated in the range of pH from 3.0 to 9.0. Copyright © 2015 Elsevier Ltd. All rights reserved.

Fabrication of novel ternary Au/CeO2@g-C3N4 nanocomposite: kinetics and mechanism investigation of 4-nitrophenol reduction, and benzyl alcohol oxidation

NASA Astrophysics Data System (ADS)

Kohantorabi, Mona; Gholami, Mohammad Reza

2018-06-01

Au nanoparticles supported on cerium oxide/graphitic carbon nitride (CeO2@g-C3N4) was synthesized and used as heterogeneous catalyst in redox reaction. The catalyst was characterized by different techniques such as FT-IR, XRD, FE-SEM, EDS, TEM, BET, TGA, and ICP. The as-prepared ternary nanocomposite was used as an effective catalyst for the reduction of toxic 4-nitrophenol to useful 4-aminophenol by NaBH4. The rate constant value of reduction reaction reached up to 0.106 s-1 by Au/CeO2@g-C3N4, which was 3.8, and 8.8 times higher than that of Au@CeO2 (0.028 s-1), and Au@g-C3N4 (0.012 s-1) nanocomposites, respectively. The superior catalytic performance of as-prepared catalyst in 4-NP reduction can be attributed to synergistic effect between Au nanoparticles and CeO2@g-C3N4 support, and efficient electron transfer. The reduction reaction was carried out at different temperatures, and the energy of activation ({Ea}), and thermodynamic parameters including, activation of entropy (Δ S^ ≠), enthalpy (Δ H^ ≠), and Gibbs free energy (Δ G^ ≠) were determined. Additionally, the mechanism of reaction was studied in details, and equilibrium constants of 4-NP ( K 4-NP), and {BH}4^{ - } ({K_{{BH}4^{{ - }} }}) were calculated using Langmuir-Hinshelwood model. Furthermore, this nanocomposite exhibited excellent catalytic activity in oxidation of benzyl alcohol by molecular oxygen as a green oxidant. This study revealed that the ternary Au/CeO2@g-C3N4 nanocomposite is an attractive candidate for catalytic applications.

Solar photocatalysis for treatment of Acid Yellow-17 (AY-17) dye contaminated water using Ag@TiO2 core-shell structured nanoparticles.

PubMed

Khanna, Ankita; Shetty K, Vidya

2013-08-01

Wastewater released from textile industries causes water pollution, and it needs to be treated before discharge to the environment by cost effective technologies. Solar photocatalysis is a promising technology for the treatment of dye wastewater. The Ag@TiO2 nanoparticles comprising of Ag core and TiO2 shell (Ag@TiO2) have unique photocatalytic property of inhibition of electron-hole recombination and visible light absorption, which makes it a promising photocatalyst for use in solar photocatalysis and with higher photocatalytic rate. Therefore, in the present work, the Ag@TiO2 nanoparticles synthesized by one pot method with postcalcination step has been used for the degradation of Acid Yellow-17 (AY-17) dye under solar light irradiation. The Ag@TiO2 nanoparticles were characterized using thermogravimetric-differential thermal analysis, X-ray diffraction, transmission electron microscopy, selected area electron diffraction, and energy dispersive X-ray analysis. The catalyst has been found to be very effective in solar photocatalysis of AY-17, as compared to other catalysts. The effects of pH, catalyst loading, initial dye concentration, and oxidants on photocatalysis were also studied. The optimized parameters for degradation of AY-17 using Ag@TiO2 were found to be pH 3, dye/catalyst ratio of 1:10 (g/g), and 2 g/L of (NH4)2S2O8 as oxidant. Efficient decolorization and mineralization of AY-17 was achieved. The kinetics of color, total organic carbon, and chemical oxygen demand removal followed the Langmuir-Hinshelwood model. Ag@TiO2 catalyst can be reused thrice without much decline in efficiency. The catalyst exhibited its potential as economic photocatalyst for treatment of dye wastewater.

Utilization of cross-linked chitosan/bentonite composite in the removal of methyl orange from aqueous solution.

PubMed

Huang, Ruihua; Liu, Qian; Zhang, Lujie; Yang, Bingchao

2015-01-01

A kind of biocomposite was prepared by the intercalation of chitosan in bentonite and the cross-linking reaction of chitosan with glutaraldehyde, which was referred to as cross-linked chitosan/bentonite (CCS/BT) composite. Adsorptive removal of methyl orange (MO) from aqueous solutions was investigated by batch method. The adsorption of MO onto CCS/BT composite was affected by the ratio of chitosan to BT and contact time. pH value had only a minor impact on MO adsorption in a wide pH range. Adsorption kinetics was mainly controlled by the pseudo-second-order kinetic model. The adsorption of MO onto CCS/BT composite followed the Langmuir isotherm model, and the maximum adsorption capacity of CCS/BT composite calculated by the Langmuir model was 224.8 mg/g. Experimental results indicated that this adsorbent had a potential for the removal of MO from aqueous solutions.

Copper removal by algae Gelidium, agar extraction algal waste and granulated algal waste: kinetics and equilibrium.

PubMed

Vilar, Vítor J P; Botelho, Cidália M S; Boaventura, Rui A R

2008-03-01

Biosorption of copper ions by an industrial algal waste, from agar extraction industry has been studied in a batch system. This biosorbent was compared with the algae Gelidium itself, which is the raw material for agar extraction, and the industrial waste immobilized with polyacrylonitrile (composite material). The effects of contact time, pH, ionic strength (IS) and temperature on the biosorption process have been studied. Equilibrium data follow both Langmuir and Langmuir-Freundlich models. The parameters of Langmuir equilibrium model were: q(max)=33.0mgg(-1), K(L)=0.015mgl(-1); q(max)=16.7mgg(-1), K(L)=0.028mgl(-1) and q(max)=10.3mgg(-1), K(L)=0.160mgl(-1) respectively for Gelidium, algal waste and composite material at pH=5.3, T=20 degrees C and IS=0.001M. Increasing the pH, the number of deprotonated active sites increases and so the uptake capacity of copper ions. In the case of high ionic strengths, the contribution of the electrostatic component to the overall binding decreases, and so the uptake capacity. The temperature has little influence on the uptake capacity principally for low equilibrium copper concentrations. Changes in standard enthalpy, Gibbs energy and entropy during biosorption were determined. Kinetic data at different solution pH (3, 4 and 5.3) were fitted to pseudo-first-order and pseudo-second-order models. The adsorptive behaviour of biosorbent particles was modelled using a batch reactor mass transfer kinetic model, which successfully predicts Cu(II) concentration profiles.

Adsorption of saturated fatty acid in urea complexation: Kinetics and equilibrium studies

NASA Astrophysics Data System (ADS)

Setyawardhani, Dwi Ardiana; Sulistyo, Hary; Sediawan, Wahyudi Budi; Fahrurrozi, Mohammad

2018-02-01

Urea complexation is fractionation process for concentrating poly-unsaturated fatty acids (PUFAs) from vegetable oil or animal fats. For process design and optimization in commercial industries, it is necessary to provide kinetics and equilibrium data. Urea inclusion compounds (UICs) as the product is a unique complex form which one molecule (guest) is enclosed within another molecule (host). In urea complexation, the guest-host bonding exists between saturated fatty acids (SFAs) and crystalline urea. This research studied the complexation is analogous to an adsorption process. The Batch adsorption process was developed to obtain the experimental data. The ethanolic urea solution was mixed with SFA in certain compositions and adsorption times. The mixture was heated until it formed homogenous and clear solution, then it cooled very slowly until the first numerous crystal appeared. Adsorption times for the kinetic data were determined since the crystal formed. The temperature was maintained constant at room temperature. Experimental sets of data were observed with adsorption kinetics and equilibrium models. High concentration of saturated fatty acid (SFA) was used to represent adsorption kinetics and equilibrium parameters. Kinetic data were examined with pseudo first-order, pseudo second-order and intra particle diffusion models. Linier, Freundlich and Langmuir isotherm were used to study the equilibrium model of this adsorption. The experimental data showed that SFA adsorption in urea crystal followed pseudo second-order model. The compatibility of the data with Langmuir isotherm showed that urea complexation was a monolayer adsorption.

OPAC (orange peel activated carbon) derived from waste orange peel for the adsorption of chlorophenoxyacetic acid herbicides from water: Adsorption isotherm, kinetic modelling and thermodynamic studies.

PubMed

Pandiarajan, Aarthi; Kamaraj, Ramakrishnan; Vasudevan, Sudharshan; Vasudevan, Subramanyan

2018-08-01

This study presents the orange peel activated carbon (OPAC), derived from biowaste precursor (orange peel) by single step pyrolysis method and its application for the adsorption of chlorophenoxyacetic acid herbicides from the water. The OPAC exhibited the surface area of 592.471 m 2  g -1 , pore volume and pore diameter of 0.242 cc g -1 and 1.301 nm respectively. The adsorption kinetics and thermodynamic equilibrium modelling for all chlorophenoxyacetic acid herbicides were investigated. The various parametric effects such as pH and temperature were evaluated. A pseudo-second-order kinetic model was well fitted for all the herbicides. The Langmuir isotherm was obeyed for all the herbicides and the maximum Langmuir capacity of 574.71 mg g -1 was achieved. The thermodynamic studies revealed that the adsorption increases with increase in temperature. The results shows that the orange peel derived carbon (OPAC) as effective and efficient adsorbent material for the removal of chlorophenoxyacid herbicides from the water. Copyright © 2018 Elsevier Ltd. All rights reserved.

Adsorption of an anionic dye on a novel low-cost mesoporous adsorbent: kinetic, thermodynamic and isotherm studies

NASA Astrophysics Data System (ADS)

Msaad, Asmaa; Belbahloul, Mounir; Zouhri, Abdeljalil

2018-05-01

Our activated carbon was prepared successfully using phosphoric acid as an activated agent. The activated carbon was characterized by Scanning Electron Micrograph (SEM), Brunauer-Emmett- Teller (BET), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The aim of our study is to evaluate the adsorption capacity of Methyl Orange (MO) on Ziziphus lotus activated carbon. Adsorption isotherms were studied according to Langmuir and Freundlich Model, and adsorption kinetics according to pseudo-first and second-order. Results show that the maximum adsorption was reached in the first 10min at ambient temperature with a yield of 96.31%. The Langmuir isotherm shows a correlation coefficient of 99.4 % higher than Freundlich model and the adsorption kinetic model follow a pseudo-second-order with a maximum adsorption capacity of 769.23 mg/g. FTIR and X-Ray spectroscopy indicate that our activated carbon has an amorphous structure with the presence of functional groups, where BET analysis revealed a high surface area of 553 mg/g, which facilitate the adsorption process

Utilization of oil palm biodiesel solid residue as renewable sources for preparation of granular activated carbon by microwave induced KOH activation.

PubMed

Foo, K Y; Hameed, B H

2013-02-01

In this work, preparation of granular activated carbon from oil palm biodiesel solid residue, oil palm shell (PSAC) by microwave assisted KOH activation has been attempted. The physical and chemical properties of PSAC were characterized using scanning electron microscopy, volumetric adsorption analyzer and elemental analysis. The adsorption behavior was examined by performing batch adsorption experiments using methylene blue as dye model compound. Equilibrium data were simulated using the Langmuir, Freundlich and Temkin isotherm models. Kinetic modeling was fitted to the pseudo-first-order, pseudo-second-order and Elovich kinetic models, while the adsorption mechanism was determined using the intraparticle diffusion and Boyd equations. The result was satisfactory fitted to the Langmuir isotherm model with a monolayer adsorption capacity of 343.94mg/g at 30°C. The findings support the potential of oil palm shell for preparation of high surface area activated carbon by microwave assisted KOH activation. Copyright © 2012 Elsevier Ltd. All rights reserved.

Kinetic sorption of contaminants of emerging concern by a palygorskite-montmorillonite filter medium.

PubMed

Berhane, Tedros M; Levy, Jonathan; Krekeler, Mark P S; Danielson, Neil D

2017-06-01

Kinetic sorption of bisphenol A (BPA), carbamazepine (CMZ) and ciprofloxacin (CIP) by three palygorskite-montmorillonite (Pal-Mt) granule sizes was studied. For BPA, CMZ and CIP, apparent sorption equilibrium was reached within about 3, 5 and 16 h, respectively. The highest and the lowest sorption capacities were by the small and the large granule sizes, respectively. Experimental results were compared to various sorption kinetics models to gain insights regarding the sorption processes and achieve a predictive capacity. The pseudo-second order (PSO) and the Elovich models performed the best while the pseudo-first order (PFO) model was only adequate for CMZ. The intraparticle-diffusion (IPD) model showed a two-step linear plot of BPA, CMZ and CIP sorption versus square root of time that was indicative of surface-sorption followed by IPD as a rate-limiting process before equilibrium was reached. Using the pseudo-first order (PFO) and the pseudo-second order (PSO) rate constants combined with previously-established Langmuir equilibrium sorption models, the kinetic sorption (k a ) and desorption (k d ) Langmuir kinetic rate constants were theoretically calculated for BPA and CIP. Kinetic sorption was then simulated using these theoretically calculated k a and k d values, and the simulations were compared to the observed behavior. The simulations fit the observed sorbed concentrations better during the early part of the experiments; the observed sorption during later times occurred more slowly than expected, supporting the hypothesis that IPD becomes a rate-limiting process during the course of the experiment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Equilibrium, kinetics and process design of acid yellow 132 adsorption onto red pine sawdust.

PubMed

Can, Mustafa

2015-01-01

Linear and non-linear regression procedures have been applied to the Langmuir, Freundlich, Tempkin, Dubinin-Radushkevich, and Redlich-Peterson isotherms for adsorption of acid yellow 132 (AY132) dye onto red pine (Pinus resinosa) sawdust. The effects of parameters such as particle size, stirring rate, contact time, dye concentration, adsorption dose, pH, and temperature were investigated, and interaction was characterized by Fourier transform infrared spectroscopy and field emission scanning electron microscope. The non-linear method of the Langmuir isotherm equation was found to be the best fitting model to the equilibrium data. The maximum monolayer adsorption capacity was found as 79.5 mg/g. The calculated thermodynamic results suggested that AY132 adsorption onto red pine sawdust was an exothermic, physisorption, and spontaneous process. Kinetics was analyzed by four different kinetic equations using non-linear regression analysis. The pseudo-second-order equation provides the best fit with experimental data.

Adsorption of methyl orange from aqueous solution by aminated pumpkin seed powder: Kinetics, isotherms, and thermodynamic studies.

PubMed

Subbaiah, Munagapati Venkata; Kim, Dong-Su

2016-06-01

Present research discussed the utilization of aminated pumpkin seed powder (APSP) as an adsorbent for methyl orange (MO) removal from aqueous solution. Batch sorption experiments were carried to evaluate the influence of pH, initial dye concentration, contact time, and temperature. The APSP was characterized by using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The experimental equilibrium adsorption data were fitted using two two-parameter models (Langmuir and Freundlich) and two three-parameter models (Sips and Toth). Langmuir and Sips isotherms provided the best model for MO adsorption data. The maximum monolayer sorption capacity was found to be 200.3mg/g based on the Langmuir isotherm model. The pseudo-first-order and pseudo-second-order model equations were used to analyze the kinetic data of the adsorption process and the data was fitted well with the pseudo-second-order kinetic model (R(2)>0.97). The calculated thermodynamic parameters such as ΔG(0), ΔH(0) and ΔS(0) from experimental data showed that the sorption of MO onto APSP was feasible, spontaneous and endothermic in the temperature range 298-318 K. The FTIR results revealed that amine and carboxyl functional groups present on the surface of APSP. The SEM results show that APSP has an irregular and porous surface which is adequate morphology for dye adsorption. Desorption experiments were carried to explore the feasibility of adsorbent regeneration and the adsorbed MO from APSP was desorbed using 0.1M NaOH with an efficiency of 93.5%. Findings of the present study indicated that APSP can be successfully used for removal of MO from aqueous solution. Copyright © 2016 Elsevier Inc. All rights reserved.

Sorption kinetics and isotherm studies of a cationic dye using agricultural waste: broad bean peels.

PubMed

Hameed, B H; El-Khaiary, M I

2008-06-15

In this paper, broad bean peels (BBP), an agricultural waste, was evaluated for its ability to remove cationic dye (methylene blue) from aqueous solutions. Batch mode experiments were conducted at 30 degrees C. Equilibrium sorption isotherms and kinetics were investigated. The kinetic data obtained at different concentrations have been analyzed using pseudo-first-order, pseudo-second-order and intraparticle diffusion equations. The experimental data fitted very well the pseudo-first-order kinetic model. Analysis of the temportal change of q indicates that at the beginning of the process the overall rate of adsorption is controlled by film-diffusion, then at later stage intraparticle-diffusion controls the rate. Diffusion coefficients and times of transition from film to pore-diffusion control were estimated by piecewise linear regression. The experimental data were analyzed by the Langmuir and Freundlich models. The sorption isotherm data fitted well to Langmuir isotherm and the monolayer adsorption capacity was found to be 192.7 mg/g and the equilibrium adsorption constant Ka is 0.07145 l/mg at 30 degrees C. The results revealed that BBP was a promising sorbent for the removal of methylene blue from aqueous solutions.

Adsorption of leather dye onto activated carbon prepared from bottle gourd: equilibrium, kinetic and mechanism studies.

PubMed

Foletto, Edson Luiz; Weber, Caroline Trevisan; Paz, Diego Silva; Mazutti, Marcio Antonio; Meili, Lucas; Bassaco, Mariana Moro; Collazzo, Gabriela Carvalho

2013-01-01

Activated carbon prepared from bottle gourd has been used as adsorbent for removal of leather dye (Direct Black 38) from aqueous solution. The activated carbon obtained showed a mesoporous texture, with surface area of 556.16 m(2) g(-1), and a surface free of organic functional groups. The initial dye concentration, contact time and pH significantly influenced the adsorption capacity. In the acid region (pH 2.5) the adsorption of dye was more favorable. The adsorption equilibrium was attained after 60 min. Equilibrium data were analyzed by the Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. The equilibrium data were best described by the Langmuir isotherm, with maximum adsorption capacity of 94.9 mg g(-1). Adsorption kinetic data were fitted using the pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models. The adsorption kinetic was best described by the second-order kinetic equation. The adsorption process was controlled by both external mass transfer and intraparticle diffusion. Activated carbon prepared from bottle gourd was shown to be a promising material for adsorption of Direct Black 38 from aqueous solution.

Equilibrium and kinetic modelling of Cd(II) biosorption by algae Gelidium and agar extraction algal waste.

PubMed

Vilar, Vítor J P; Botelho, Cidália M S; Boaventura, Rui A R

2006-01-01

In this study an industrial algal waste from agar extraction has been used as an inexpensive and effective biosorbent for cadmium (II) removal from aqueous solutions. This biosorbent was compared with the algae Gelidium itself, which is the raw material for agar extraction. Equilibrium data follow both Langmuir and Redlich-Peterson models. The parameters of Langmuir equilibrium model are q(max)=18.0 mgg(-1), b=0.19 mgl(-1) and q(max)=9.7 mgg(-1), b=0.16 mgl(-1), respectively for Gelidium and the algal waste. Kinetic experiments were conducted at initial Cd(II) concentrations in the range 6-91 mgl(-1). Data were fitted to pseudo-first- and second-order Lagergren models. For an initial Cd(II) concentration of 91 mgl(-1) the parameters of the pseudo-first-order Lagergren model are k(1,ads)=0.17 and 0.87 min(-1); q(eq)=16.3 and 8.7 mgg(-1), respectively, for Gelidium and algal waste. Kinetic constants vary with the initial metal concentration. The adsorptive behaviour of biosorbent particles was modelled using a batch reactor mass transfer kinetic model. The model successfully predicts Cd(II) concentration profiles and provides significant insights on the biosorbents performance. The homogeneous diffusivity, D(h), is in the range 0.5-2.2 x10(-8) and 2.1-10.4 x10(-8)cm(2)s(-1), respectively, for Gelidium and algal waste.

Syntheses, Characterization and Kinetics of Nickel-Tungsten Nitride Catalysts for Hydrotreating of Gas Oil

NASA Astrophysics Data System (ADS)

Botchwey, Christian

This thesis summarizes the methods and major findings of Ni-W(P)/gamma-Al 2O3 nitride catalyst synthesis, characterization, hydrotreating activity, kinetic analysis and correlation of the catalysts' activities to their synthesis parameters and properties. The range of parameters for catalyst synthesis were W (15-40 wt%), Ni (0-8 wt%), P (0-5 wt%) and nitriding temperature (TN) (500-900 °C). Characterization techniques used included: N2 sorption studies, chemisorption, elemental analysis, temperature programmed studies, x-ray diffraction, scanning electron microscopy, energy dispersive x-ray, infrared spectroscopy, transmission electron microscopy and x-ray absorption near edge structure. Hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and hydrodearomatization (HDA) were performed at: temperature (340-380 °C), pressure (6.2-9.0 MPa), liquid hourly space velocity (1-3 h-1) and hydrogen to oil ratio (600 ml/ml, STP). The predominant species on the catalyst surface were Ni3N, W2N and bimetallic Ni2W3N. The bimetallic Ni-W nitride species was more active than the individual activities of the Ni3N and W2N. P increased weak acid sites while nitriding temperature decreased amount of strong acid sites. Low nitriding temperature enhanced dispersion of metal particles. P interacted with Al 2O3 which increased the dispersion of metal nitrides on the catalyst surface. HDN activity increased with Ni and P loading but decreased with increase in nitriding temperature (optimum conversion; 60 wt%). HDS and HDA activities went through a maximum with increase in the synthesis parameters (optimum conversions; 88. wt% for HDS and 47 wt% for HDA). Increase in W loading led to increase in catalyst activity. The catalysts were stable to deactivation and had the nitride structure conserved during hydrotreating in the presence of hydrogen sulfide. The results showed good correlation between hydrotreating activities (HDS and HDN) and the catalyst nitrogen content, number of exposed active sites, catalyst particle size and BET surface area. HDS and HDN kinetic analyses, using Langmuir-Hinshelwood models, gave activation energies of 66 and 32 kJ/mol, respectively. There were no diffusion limitations in the reaction process. Two active sites were involved in HDS reaction while one site was used for HDN. HDS and HDN activities of the Ni-W(P)/gamma-Al 2O3 nitride catalysts were comparable to the corresponding sulfides.

Removal of ibuprofen, naproxen and carbamazepine in aqueous solution onto natural clay: equilibrium, kinetics, and thermodynamic study

NASA Astrophysics Data System (ADS)

Khazri, Hassen; Ghorbel-Abid, Ibtissem; Kalfat, Rafik; Trabelsi-Ayadi, Malika

2017-10-01

This study aimed to describe the adsorption of three pharmaceuticals compounds (ibuprofen, naproxen and carbamazepine) onto natural clay on the basis of equilibrium parameters such as a function of time, effect of pH, varying of the concentration and the temperature. Adsorption kinetic data were modeled using the Lagergren's first-order and the pseudo-second-order kinetic equations. The kinetic results of adsorption are described better using the pseudo-second order model. The isotherm results were tested in the Langmuir, Freundlich and Dubinin-Radushkevich models. The thermodynamic parameters obtained indicate that the adsorption of pharmaceuticals on the clay is a spontaneous and endothermic process.

Derived and thiourea-functionalized silica for cadmium removal: isotherm, kinetic and thermodynamic studies

NASA Astrophysics Data System (ADS)

Omotunde, Iyanu; Okoronkwo, Afamefuna; Oluwashina, Olugbenga

2018-03-01

The present study explored the feasibility of using derived and thiourea-functionalized silica as adsorbent for the removal of cadmium under different experimental conditions. Effects of various parameters such as function of point of zero charge (pHPZC), solution pH, sorbent-sorbate resident time and ratio, concentration and temperature were investigated. The sorption of cadmium followed the pseudo-second-order rate kinetics. Thermodynamic studies revealed that the sorption of cadmium was endothermic and spontaneous, with good affinity toward the sorbent. Various isotherm models, viz. Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Harkins-Jura, and Halsey isotherms were used to analyze the equilibrium data at different temperatures. The Freundlich, Halsey, Langmuir, and Temkin models were found to be in good agreement with the experimental data with high R 2, low RMSE, and low χ 2 values. The results show that the sorption capacity increases with an increase in solution temperature from 28 to 65 °C. The maximum sorption capacity calculated from Langmuir isotherm was 27.55 and 28.41 mg g-1 for derived and thiourea-functionalized silica, respectively, at optimum condition of pH 5 and contact time of 120 min.

Comparison of linear and non-linear models for the adsorption of fluoride onto geo-material: limonite.

PubMed

Sahin, Rubina; Tapadia, Kavita

2015-01-01

The three widely used isotherms Langmuir, Freundlich and Temkin were examined in an experiment using fluoride (F⁻) ion adsorption on a geo-material (limonite) at four different temperatures by linear and non-linear models. Comparison of linear and non-linear regression models were given in selecting the optimum isotherm for the experimental results. The coefficient of determination, r², was used to select the best theoretical isotherm. The four Langmuir linear equations (1, 2, 3, and 4) are discussed. Langmuir isotherm parameters obtained from the four Langmuir linear equations using the linear model differed but they were the same when using the nonlinear model. Langmuir-2 isotherm is one of the linear forms, and it had the highest coefficient of determination (r² = 0.99) compared to the other Langmuir linear equations (1, 3 and 4) in linear form, whereas, for non-linear, Langmuir-4 fitted best among all the isotherms because it had the highest coefficient of determination (r² = 0.99). The results showed that the non-linear model may be a better way to obtain the parameters. In the present work, the thermodynamic parameters show that the absorption of fluoride onto limonite is both spontaneous (ΔG < 0) and endothermic (ΔH > 0). Scanning electron microscope and X-ray diffraction images also confirm the adsorption of F⁻ ion onto limonite. The isotherm and kinetic study reveals that limonite can be used as an adsorbent for fluoride removal. In future we can develop new technology for fluoride removal in large scale by using limonite which is cost-effective, eco-friendly and is easily available in the study area.

Synthesis of activated carbon-based amino phosphonic acid chelating resin and its adsorption properties for Ce(III) removal.

PubMed

Chen, Tao; Yan, Chunjie; Wang, Yixia; Tang, Conghai; Zhou, Sen; Zhao, Yuan; Ma, Rui; Duan, Ping

2015-01-01

This work aims to investigate the adsorption of Ce(III) onto chelating resin based on activated carbon (CRAC). The CRAC adsorbent was prepared from activated carbon (AC) followed by oxidation, silane coupling, ammoniation and phosphorylation, and characterized by Fourier transform-infrared spectrometry, nitrogen adsorption measurements and scanning electron microscopy. The effects of solution pH, adsorbent dosage and contact time were studied by batch technique. Langmuir and Freundlich isotherms were used to describe the adsorption behaviour of Ce(III) by CRAC, and the results showed that the adsorption behaviour well fitted the Langmuir model. The maximum uptake capacity (qmax) calculated by using the Langmuir equation for cerium ions was found to be 94.34 mg/g. A comparison of the kinetic models and the overall experimental data was best fitted with the type 1 pseudo second-order kinetic model. The calculated thermodynamic parameters (ΔG°, ΔH° and ΔS°) showed that the adsorption for Ce(III) was feasible, spontaneous and exothermic at 25-45 °C. The CRAC showed an excellent adsorptive selectivity towards Ce(III). Moreover, more than 82% of Ce(III) adsorbed onto CRAC could be desorbed with HCl and could be used several times.

Hydrodynamic and kinetic study of a hybrid detoxification process with zero liquid discharge system in an industrial wastewater treatment.

PubMed

Abid, Mohammad Fadhil; Abdulrahman, Amir Aziz; Hamza, Noor Hussein

2014-01-01

This work focused on the degradation of toxic organic compounds such as methyl violet dye (MV) in water, using a combined photocatalysis/low pressure reverse osmosis (LPRO) system. The performance of the hybrid system was investigated in terms of the degradation efficiency of MV, COD and membrane separation of TiO2. The aim of the present study was to design a novel solar reactor and analyze its performance for removal of MV from water with titanium dioxide as the photocatalyst. Various operating parameters were studied to investigate the behavior of the designed reactor like initial dye concentration (C = 10-50 mg/L), loading of catalyst (CTiO2 = 200-800 mg/L), suspension flow rate (QL = 0.3-1.5 L/min), pH of suspension (5-10), and H2O2 concentration (CH2O2 = 200-1000 mg/L). The operating parameters were optimized to give higher efficiency to the reactor performance. Optimum parameters of the photocatalysis process were loading of catalyst (400 mg/L), suspension flow rate (0.5 L/min), H2O2 concentration (400 mg/L), and pH = 5. The designed reactor when operating at optimum conditions offered a degradation of MV up to 0.9527 within one hours of operation time, while a conversion of 0.9995 was obtained in three hours. The effluent from the photocatalytic reactor was fed to a LPRO separation system which produced permeate of turbidity value of 0.09 NTU which is closed to that of drinking water (i.e., 0.08 NTU). The product water was analyzed using UV-spectrophotometer and FTIR. The analysis results confirmed that the water from the Hybrid-System could be safely recycled and reuse. It was found that the kinetics of dye degradation was first order with respect to dye concentration and could be well described by Langmuir-Hinshelwood model. A power-law based empirical correlation was developed for the photocatalysis system, related the dye degradation (R) with studied operating conditions.

Production of pyrite nanoparticles using high energy planetary ball milling for sonocatalytic degradation of sulfasalazine.

PubMed

Khataee, Alireza; Fathinia, Siavash; Fathinia, Mehrangiz

2017-01-01

Sonocatalytic performance of pyrite nanoparticles was evaluated by the degradation of sulfasalazine (SSZ). Pyrite nanoparticles were produced via a high energy mechanical ball milling (MBM) in different processing time from 2h to 6h, in the constant milling speed of 320rpm. X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FT-IR) analysis and Brunauer-Emmett-Teller (BET) confirmed the production of pyrite nanoparticles during 6h of ball milling with the average size distribution of 20-80nm. The effects of various operational parameters including pH value, catalyst amount (mg/L), SSZ concentration (mg/L), ultrasonic frequency (kHz) and reaction time on the SSZ removal efficiency were examined. The obtained results showed that the maximum removal efficiency of 97.00% was obtained at pH value of 4, catalyst dosage of 0.5g/L, SSZ concentration of 10mg/L and reaction time of 30min. Experimental results demonstrated that the kinetic of the degradation process can be demonstrated using Langmuir-Hinshelwood (L-H) kinetic model. The effect of different inorganic ions such as Cl - , CO 3 2- and SO 4 2- was investigated on the L-H reaction rate (k r ) and adsorption (K s ) constants. Results showed that the presence of the mentioned ions significantly influenced the L-H constants. The impact of ethanol as a OH radical scavenger and some enhancers including H 2 O 2 and K 2 S 2 O 8 was investigated on the SSZ removal efficiency. Accordingly, the presence of ethanol suppressed SSZ degradation due to the quenching of OH radicals and the addition of K 2 S 2 O 8 and H 2 O 2 increased the SSZ removal efficiency, due to the formation of SO 4 - and additional OH radicals, respectively. Under the identical conditions of operating parameters, pyrite nanoparticles maintained their catalytic activity during four consecutive runs. Copyright © 2016 Elsevier B.V. All rights reserved.

Solar photocatalitycal treatment of carbofuran at lab and pilot scale: effect of classical parameters, evaluation of the toxicity and analysis of organic by-products.

PubMed

Lopez-Alvarez, Blady; Torres-Palma, Ricardo A; Peñuela, Gustavo

2011-07-15

In this work the TiO(2) solar-photocatalytical degradation of the pesticide carbofuran (CBF) in water, at lab and pilot scale, was studied. At lab scale the evaluation of CBF concentration (14-282 μmol L(-1)) showed that the system followed a Langmuir-Hinshelwood kinetics type. TiO(2) concentration (0.05-2 g L(-1)) and initial pH (3-9) were also evaluated and optimized using the surface response methodology and the Pareto diagram. In the range of variables studied, initial pH 7.60 and 1.43 g L(-1) of TiO(2) favoured the efficiency of the process. Under optimal conditions the evolution of substrate, chemical oxygen demand, dissolved organic carbon, toxicity and organics by-products were evaluated. In the pilot scale tests, using direct sunlight, 55 mg L(-1) of CBF in a commercial formulation was eliminated after 420 min; while after 900 min of treatment 80% of toxicity (1/E(50) on Vibrium Fischeri), 80% of chemical oxygen demand and 60% of dissolved organic carbon were removed. The analysis and evolution of five CBF by-products, as well the evaluation of the treatment in the presence of isopropanol or using acetonitrile as a solvent suggest that the degradation is mainly carried out by OH radical attack. Finally, a schema depicting the main degradation pathway is proposed. Copyright © 2011 Elsevier B.V. All rights reserved.

Photocatalytic oxidation of nitrogen oxides using TiO2 loading on woven glass fabric.

PubMed

Wang, Haiqiang; Wu, Zhongbiao; Zhao, Weirong; Guan, Baohong

2007-01-01

TiO2 loading on woven glass fabric is applied to treat nitrogen oxides (NOx) by photocatalytic oxidation (PCO). In this paper, the PCO behavior of NO at high concentrations was studied by PCO of NOx at source levels (20-168 ppm). The PCO efficiency reached 27% in this experiment, while the inlet NOx concentration was 168 ppm (147 ppm NO). The dependency of the reaction rate on several key influencing factors (relative humidity, space time, inlet concentration, oxygen percentage) was also studied. The results illustrate that the resulting hydroxyl radical and active oxide play an important role in the oxidation of NOx. The reactions are limited by the thermodynamic equilibrium after ca. 15s space time. A possible explanation for the catalyst deactivation is the accumulation of nitric acid and nitrous acid on the TiO2 surface during the PCO of NOx. However, the photocatalytic activity can be recovered with a simple heat treatment. The results from the study of the effect of the inlet concentration were described with the Langmuir-Hinshelwood model.

Photocatalytic activity of CdS and Ag2S quantum dots deposited on poly(amidoamine) functionalized carbon nanotubes

PubMed Central

Neelgund, Gururaj M.; Oki, Aderemi

2011-01-01

Two novel ternary nanocatalysts, f-MWCNTs-CdS and f-MWCNTs-Ag2S were successfully constructed by covalent grafting of fourth generation (G4) hyperbranched, crosslinked poly(amidoamine) (PAMAM) to carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) and subsequent deposition of CdS or Ag2S quantum dots (QDs). The structural transformation, surface potential, and morphology of functionalized MWCNTs (f-MWCNTs) and nanocatalysts were characterized by UV-vis spectrophotometer, Fourier transform infrared spectroscopy, powder X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy and energy dispersive spectroscopy. Transmission electron microscopy reveals the effective anchoring of QDs on f-MWCNTs. The catalytic activity of nanocatalysts was evaluated by photodegradation of methyl orange under illumination of UV light. The coupling of MWCNTs, PAMAM and CdS or Ag2S QDs significantly enhanced the catalytic efficiency of nanocatalysts. The rate constants for degradation of methyl orange in presence of nanocatalysts were calculated using the Langmuir-Hinshelwood model. Overall, the excellence in photodegradation was accomplished by hybridizing f-MWCNTs with CdS or Ag2S PMID:22267895

Thermocatalytic Destruction of Gas-Phase Perchloroethylene Using Propane as a Hydrogen Source

PubMed Central

Willinger, Marty; Rupp, Erik; Barbaris, Brian; Gao, Song; Arnolda, Robert; Betterton, Eric; Sáez, A. Eduardo

2009-01-01

The use of propane in combination with oxygen to promote the destruction of perchloroethylene (PCE) over a platinum (Pt)/rhodium (Rh) catalyst on a cerium/zirconium oxide washcoat supported on an alumina monolith was explored. Conversions of PCE were measured in a continuous flow reactor with residence times less than 0.5 s and temperatures ranging from 200 to 600°C. The presence of propane was shown to increase significantly the conversion of PCE over oxygen-only conditions. Conversions close to 100% were observed at temperatures lower than 450°C with 20% oxygen and 2% propane in the feed, which makes this process attractive from a practical standpoint. In the absence of oxygen, PCE conversion is even higher, but the catalyst suffers significant deactivation in less than an hour. Even though results show that oxygen competes with reactants for active sites on the catalyst, the long-term stability that oxygen confers to the catalyst makes the process an efficient alternative to PCE oxidation. A Langmuir-Hinshelwood competitive adsorption model is proposed to quantify PCE conversion. PMID:19217713

Kinetic and isotherm modeling of Cd (II) adsorption by L-cysteine functionalized multi-walled carbon nanotubes as adsorbent.

PubMed

Taghavi, Mahmoud; Zazouli, Mohammad Ali; Yousefi, Zabihollah; Akbari-adergani, Behrouz

2015-11-01

In this study, multi-walled carbon nanotubes were functionalized by L-cysteine to show the kinetic and isotherm modeling of Cd (II) ions onto L-cysteine functionalized multi-walled carbon nanotubes. The adsorption behavior of Cd (II) ion was studied by varying parameters including dose of L-MWCNTs, contact time, and cadmium concentration. Equilibrium adsorption isotherms and kinetics were also investigated based on Cd (II) adsorption tests. The results showed that an increase in contact time and adsorbent dosage resulted in increase of the adsorption rate. The optimum condition of the Cd (II) removal process was found at pH=7.0, 15 mg/L L-MWCNTs dosage, 6 mg/L cadmium concentration, and contact time of 60 min. The removal percent was equal to 89.56 at optimum condition. Langmuir and Freundlich models were employed to analyze the experimental data. The data showed well fitting with the Langmuir model (R2=0.994) with q max of 43.47 mg/g. Analyzing the kinetic data by the pseudo-first-order and pseudo-second-order equations revealed that the adsorption of cadmium using L-MWSNTs following the pseudo-second-order kinetic model with correlation coefficients (R2) equals to 0.998, 0.992, and 0.998 for 3, 6, and 9 mg/L Cd (II) concentrations, respectively. The experimental data fitted very well with the pseudo-second-order. Overall, treatment of polluted solution to Cd (II) by adsorption process using L-MWCNT can be considered as an effective technology.

Kinetics of alkali-based photocathode degradation

DOE PAGES

Pavlenko, Vitaly; Liu, Fangze; Hoffbauer, Mark A.; ...

2016-11-02

Here, we report on a kinetic model that describes the degradation of the quantum efficiency (QE) of Cs 3Sb and negative electron affinity (NEA) GaAs photocathodes under UHV conditions. Additionally, the generally accepted irreversible chemical change of a photocathode’s surface due to reactions with residual gases, such as O 2, CO 2, and H 2O, the model incorporates an intermediate reversible physisorption step, similar to Langmuir adsorption. Moreover, this intermediate step is needed to satisfactorily describe the strongly non-exponential QE degradation curves for two distinctly different classes of photocathodes –surface-activated and “bulk,” indicating that in both systems the QE degradationmore » results from surface damage. The recovery of the QE upon improvement of vacuum conditions is also accurately predicted by this model with three parameters (rates of gas adsorption, desorption, and irreversible chemical reaction with the surface) comprising metrics to better characterize the lifetime of the cathodes, instead of time-pressure exposure expressed in Langmuir units.« less

Effective adsorption of phenolic compound from aqueous solutions on activated semi coke

NASA Astrophysics Data System (ADS)

Gao, Xiaoming; Dai, Yuan; Zhang, Yu; Fu, Feng

2017-03-01

Activated Semi coke was prepared by KOH activation and employed as adsorbent to study adsorption function of phenolic compound from aqueous solutions. The adsorption result showed that the adsorption capacity of the activated semi coke for phenolic compound increased with contact time and adsorbent dosage, and slightly affected by temperature. The surface structure property of the activated semi coke was characterized by N2 adsorption, indicating that the activated semi coke was essentially macroporous, and the BET surface area was 347.39 m2 g-1. Scanning electron microscopy indicated that the surface of the activated semi coke had a high developed pore. The adsorption kinetics were investigated according to pseudofirst order, pseudosecond order and intraparticle diffusion, and the kinetics data were fitted by pseudosecond order model, and intraparticle diffusion was not the only rate-controlling step. Adsorption isotherm was studied by Langmuir, Freundlich, Temkin, Redlich-Peterson, Sips and Toth models. The result indicated that adsorption isotherm data could fit well with Langmuir, Redlich-Peterson, Sips and Toth models.

Turbulent Equilibria for Charged Particles in Space

NASA Astrophysics Data System (ADS)

Yoon, Peter

2017-04-01

The solar wind electron distribution function is apparently composed of several components including non-thermal tail population. The electron distribution that contains energetic tail feature is well fitted with the kappa distribution function. The solar wind protons also possess quasi power-law tail distribution function that is well fitted with an inverse power law model. The present paper discusses the latest theoretical development regarding the dynamical steady-state solution of electrons and Langmuir turbulence that are in turbulent equilibrium. According to such a theory, the Maxwellian and kappa distribution functions for the electrons emerge as the only two possible solution that satisfy the steady-state weak turbulence plasma kinetic equation. For the proton inverse power-law tail problem, a similar turbulent equilibrium solution can be conceived of, but instead of high-frequency Langmuir fluctuation, the theory involves low-frequency kinetic Alfvenic turbulence. The steady-state solution of the self-consistent proton kinetic equation and wave kinetic equation for Alfvenic waves can be found in order to obtain a self-consistent solution for the inverse power law tail distribution function.

Simulations of chemical vapor deposition diamond film growth using a kinetic Monte Carlo model and two-dimensional models of microwave plasma and hot filament chemical vapor deposition reactors

NASA Astrophysics Data System (ADS)

May, P. W.; Harvey, J. N.; Allan, N. L.; Richley, J. C.; Mankelevich, Yu. A.

2010-12-01

A one-dimensional kinetic Monte Carlo (KMC) model has been developed to simulate the chemical vapor deposition of a diamond (100) surface under conditions used to grow single-crystal diamond (SCD), microcrystalline diamond (MCD), nanocrystalline diamond (NCD), and ultrananocrystalline diamond (UNCD) films. The model considers adsorption, etching/desorption, lattice incorporation and surface migration but not defect formation or renucleation processes. Two methods have been devised for estimation of the gas phase concentrations of species at the growing diamond surface, and are used to determine adsorption rates for C1Hx hydrocarbons for the different conditions. The rate of migration of adsorbed carbon species is governed by the availability of neighboring radical sites, which, in turn, depend upon the rates of H abstraction and of surface-radical migration. The KMC model predicts growth rates and surface roughness for each of diamond types consistent with experiment. In the absence of defect formation and renucleation the average surface diffusion length, ℓ, is a key parameter controlling surface morphology. When ℓ <2, surface migration is limited by the lack of availability of surface radical sites, and the migrating surface species simply hop back and forth between two adjacent sites but do not travel far beyond their initial adsorption site. Thus, Eley-Rideal processes dominate the growth, leading to the rough surfaces seen in NCD and UNCD. The maximum or "intrinsic" surface roughness occurs for nominally zero-migration conditions (ℓ =0) with an rms value of approximately five carbon atoms. Conversely, when migration occurs over greater distances (ℓ >2), Langmuir-Hinshelwood processes dominate the growth producing the smoother surfaces of MCD and SCD. By extrapolation, we predict that atomically smooth surfaces over large areas should occur once migrating species can travel approximately five sites (ℓ ˜5). β-scission processes are found to be unimportant for MCD and SCD growth conditions, but can remove up to 5% of the adsorbing carbon for NCD and UNCD growth. C1Hx insertion reactions also contribute <1% to the growth for nearly all conditions, while C2Hx (x <2) insertion reactions are negligible due their very low concentrations at the surface. Finally, the predictions for growth rate and morphology for UNCD deposition in a microwave system were found to be anomalous compared to those for all the other growth conditions, suggesting that carbonaceous particulates created in these plasmas may significantly affect the gas chemistry.

Sorption of diclofenac and naproxen onto MWCNT in model wastewater treated by H2O2 and/or UV.

PubMed

Czech, Bożena; Oleszczuk, Patryk

2016-04-01

The application of oxidation processes such as UV and/or H2O2 will change the physicochemical properties of carbon nanotubes (CNT). It may affect the sorption affinity of CNT to different contaminants and then affect their fate in the environment. In the present study the adsorption of two very common used pharmaceuticals (diclofenac and naproxen) onto CNT treated by UV, H2O2 or UV/H2O2 was investigated. Four different adsorption models (Freundlich, Langmuir, Temkin, Dubinin-Radushkevich) were tested. The best fitting of experimental data was observed for Freundlich or Langmuir model. The significant relationships between Q calculated from Langmuir model with O% and dispersity were observed. Kinetics of diclofenac and naproxen followed mainly pseudo-second order indicating for chemisorption limiting step of adsorption. The data showed that the mechanism of sorption was physical or chemical depending on the type of CNT modification. Copyright © 2015 Elsevier Ltd. All rights reserved.

In situ DRIFTS investigation of NH3-SCR reaction over CeO2/zirconium phosphate catalyst

NASA Astrophysics Data System (ADS)

Zhang, Qiulin; Fan, Jie; Ning, Ping; Song, Zhongxian; Liu, Xin; Wang, Lanying; Wang, Jing; Wang, Huimin; Long, Kaixian

2018-03-01

A series of ceria modified zirconium phosphate catalysts were synthesized for selective catalytic reduction of NO with ammonia (NH3-SCR). Over 98% NOx conversion and 98% N2 selectivity were obtained by the CeO2/ZrP catalyst with 20 wt.% CeO2 loading at 250-425 °C. The interaction between CeO2 and zirconium phosphate enhanced the redox abilities and surface acidities of the catalysts, resulting in the improvement of NH3-SCR activity. The in situ DRIFTS results indicated that the NH3-SCR reaction over the catalysts followed both Eley-Rideal and Langmuir-Hinshelwood mechanisms. The amide (sbnd NH2) groups and the NH4+ bonded to Brønsted acid sites were the important intermediates of Eley-Rideal mechanism.

Preparation and characterization of poly(AA co PVP)/PGS composite and its application for methylene blue adsorption.

PubMed

Yang, Cai-xia; Lei, Lei; Zhou, Peng-xin; Zhang, Zhe; Lei, Zi-qiang

2015-04-01

Poly (AA co PVP)/PGS (PAPP) composite adsorbent was prepared by radical polymerization from Acrylic acid (AA), Polyvinylpyrrolidone (PVP) and Palygorskite (PGS), using N,N-methylenebisacrylamide (MBA) as cross-linker and potassium persulfate (KPS) as initiator. The PAPP was characterized with Fourier transform infrared (FT-IR), thermogravimetric analysis (TG), scanning electron microscope (SEM) and transmission electron microscopy (TEM). PAPP was used as adsorbent for the removal of methylene blue from aqueous solutions. The influences of pH, adsorption temperature and adsorption time on the adsorption properties of the composite to the dye were also investigated. Meanwhile, the adsorption rate data and adsorption equilibrium date were analyzed based on the pseudo-first-order and pseudo-second-order kinetic model, Langmuir and Freundlich isotherm models, respectively. The results indicating that the kinetic behavior better fit with the pseudo-second-order kinetic model. The maximum equilibrium adsorption capacity (q(m)) is 1815 mg/g at 289 K. The isotherm behavior can be explained by the Langmuir isotherm models. The activation energy was also evaluated for the removal of methylene blue onto PAPP. These results demonstrate that this composite material could be used as a good adsorbent for the removal of cationic dyes from wastewater. Copyright © 2014 Elsevier Inc. All rights reserved.

Ultrasonic-assisted synthesis of novel nanocomposite of poly(vinyl alcohol) and amino-modified MCM-41: A green adsorbent for Cd(II) removal.

PubMed

Soltani, Roozbeh; Dinari, Mohammad; Mohammadnezhad, Gholamhossein

2018-01-01

Amino-modified MCM-41/poly(vinyl alcohol) nanocomposite (M-MCM-41/PVOH NC) was developed for the adsorption of Cd(II) from aqueous media. M-MCM-41/PVOH NC was prepared through ultrasonic-assisted and simple blending procedure with economical and environmentally friendly polymer. The as-prepared adsorbent was characterized by FT-IR, TEM, FE-SEM and TGA. The contact time, solution pH and initial concentration of Cd(II) were found to affect the adsorption of Cd(II) from aqueous media. Kinetic studies were carried out and pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich, and intra-particle diffusion (IPD) reaction kinetic models were examined. The kinetic results revealed that the adsorption of Cd(II) onto M-MCM-41/PVOH NC followed PSO kinetic model and is a chemical adsorption. The equilibrium adsorption data were evaluated by different isotherms viz. Langmuir, Freundlich, and Dubinin Radushkevich (D-R) equations. The equilibrium data fitted better with the Langmuir isotherm and the maximum adsorption capacity of M-MCM-41/PVOH NC at 298K was calculated to be 46.73mgg -1 for Cd(II) on a typical saturated monomolecular layer with a fixed number of localized adsorption sites. Copyright © 2017 Elsevier B.V. All rights reserved.

Removal of tetracycline from wastewater using pumice stone: equilibrium, kinetic and thermodynamic studies

PubMed Central

2014-01-01

In this study, pumice stone was used for the removal of tetracyline (TC) from aqueous solutions. It was characterized by XRD, FT-IR, SEM and BET analyses. Cation exchange capacity of pumice stone was found to be 9.9 meq/100 g. Effect of various parameters such as solution pH (2–11), adsorbent dosage (0.5-10 g/L), contact time (2.5-120 min), initial TC concentration (5–300 mg/L) and temperature (20–50°C) on TC adsorption onto pumice was investigated. Also the adsorption of TC on pumice stone was studied as a function of Na+ and Cu2+ cations changing pH from 2 to 11 using batch experiments. The best removal efficiency performance was exhibited at adsorbent dosage 10 g/L, pH 3, contact time 120 min. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models were applied to the equilibrium data. The result has shown that the adsorption was favorable, physicochemical in nature and agrees well with Langmuir and Freundlich models. The maximum Langmuir adsorption capacity was found to be 20.02 mg/g. The adsorption behavior of TC on pumices stone was fitted well in the pseudo-second order kinetics model. Thermodynamic parameters calculated from the adsorption data at different temperature showed that the adsorption reaction was feasible, spontaneous and exothermic. PMID:24936305

Cadmium hydroxide nanowire loaded on activated carbon as efficient adsorbent for removal of Bromocresol Green

NASA Astrophysics Data System (ADS)

Ghaedi, Mehrorang; Khajesharifi, Habibollah; Hemmati Yadkuri, Amin; Roosta, Mostafa; Sahraei, Reza; Daneshfar, Ali

2012-02-01

In the present research, cadmium hydroxide nanowire loaded on activated carbon (Cd(OH) 2-NW-AC) was synthesized and characterized. This new adsorbent was applied for the removal of Bromocresol Green (BCG) molecules from aqueous solutions. The influence of effective variables such as solution pH, contact time, initial BCG concentration, amount of Cd(OH) 2-NW-AC and temperature on the adsorption efficiency of BCG in batch system was examined. During all experiments BCG contents were determined by UV-Vis spectrophotometer. Fitting the experimental data to different kinetic models including pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion kinetic models show the suitability of the pseudo-second-order kinetic model to interpret in the experimental data. Equilibrium isotherm studies were examined by application of different conventional models such as Langmuir, Freundlich and Tempkin models to explain the experimental data. Based on considering R2 value as criterion the adsorption data well fitted to Langmuir model with maximum adsorption capacity of 108.7 mg g -1. Thermodynamic parameters (Gibb's free energy, entropy and enthalpy) of adsorption were calculated according to general procedure to take some information about the on-going adsorption process. The high negative value of Gibb's free energy and positive value of enthalpy show the feasibility and endothermic nature of adsorption process.

Cadmium hydroxide nanowire loaded on activated carbon as efficient adsorbent for removal of Bromocresol Green.

PubMed

Ghaedi, Mehrorang; Khajesharifi, Habibollah; Hemmati Yadkuri, Amin; Roosta, Mostafa; Sahraei, Reza; Daneshfar, Ali

2012-02-01

In the present research, cadmium hydroxide nanowire loaded on activated carbon (Cd(OH)(2)-NW-AC) was synthesized and characterized. This new adsorbent was applied for the removal of Bromocresol Green (BCG) molecules from aqueous solutions. The influence of effective variables such as solution pH, contact time, initial BCG concentration, amount of Cd(OH)(2)-NW-AC and temperature on the adsorption efficiency of BCG in batch system was examined. During all experiments BCG contents were determined by UV-Vis spectrophotometer. Fitting the experimental data to different kinetic models including pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion kinetic models show the suitability of the pseudo-second-order kinetic model to interpret in the experimental data. Equilibrium isotherm studies were examined by application of different conventional models such as Langmuir, Freundlich and Tempkin models to explain the experimental data. Based on considering R(2) value as criterion the adsorption data well fitted to Langmuir model with maximum adsorption capacity of 108.7 mg g(-1). Thermodynamic parameters (Gibb's free energy, entropy and enthalpy) of adsorption were calculated according to general procedure to take some information about the on-going adsorption process. The high negative value of Gibb's free energy and positive value of enthalpy show the feasibility and endothermic nature of adsorption process. Copyright © 2011 Elsevier B.V. All rights reserved.

Preparation of a specific bamboo based activated carbon and its application for ciprofloxacin removal.

PubMed

Wang, Y X; Ngo, H H; Guo, W S

2015-11-15

The studied bamboo based activated carbon (BbAC) with high specific surface area (SSA) and high micro pore volume was prepared from bamboo scraps by the combined activation of H3PO4 and K2CO3. The BbAC was characterized based on the N2 adsorption isotherm at 77K. The results showed that the SSA and pore volume of BbAC increased with increasing impregnation ratio and reached maxima at the impregnation ratio of 3:1 at 750°C. Under these optimal conditions, the BbAC obtained could have a maximum SSA of 2237 m(2)/g and a maximum total pore volume of 1.23 cm(3)/g with the micro pore ratio of more than 90%. The adsorption performance of ciprofloxacin (CIP) on the BbAC was determined at 298 K. The Langmuir and Freundlich models were employed to describe the adsorption equilibrium and the kinetic data were fitted by pseudo first-order and pseudo second-order kinetic models. The results showed that the Langmuir model and the pseudo second-order kinetic model presented better fittings for the adsorption equilibrium and kinetics data, respectively. The maximum adsorption amount of CIP (613 mg/g) on the BbAC was much higher than the report in the literature. Conclusively, the BbAC could be a promising adsorption material for CIP removal from water. Copyright © 2015 Elsevier B.V. All rights reserved.

A deterministic mathematical model for bidirectional excluded flow with Langmuir kinetics.

PubMed

Zarai, Yoram; Margaliot, Michael; Tuller, Tamir

2017-01-01

In many important cellular processes, including mRNA translation, gene transcription, phosphotransfer, and intracellular transport, biological "particles" move along some kind of "tracks". The motion of these particles can be modeled as a one-dimensional movement along an ordered sequence of sites. The biological particles (e.g., ribosomes or RNAPs) have volume and cannot surpass one another. In some cases, there is a preferred direction of movement along the track, but in general the movement may be bidirectional, and furthermore the particles may attach or detach from various regions along the tracks. We derive a new deterministic mathematical model for such transport phenomena that may be interpreted as a dynamic mean-field approximation of an important model from mechanical statistics called the asymmetric simple exclusion process (ASEP) with Langmuir kinetics. Using tools from the theory of monotone dynamical systems and contraction theory we show that the model admits a unique steady-state, and that every solution converges to this steady-state. Furthermore, we show that the model entrains (or phase locks) to periodic excitations in any of its forward, backward, attachment, or detachment rates. We demonstrate an application of this phenomenological transport model for analyzing ribosome drop off in mRNA translation.

Removal of anionic dyes (Reactive Black 5 and Congo Red) from aqueous solutions using Banana Peel Powder as an adsorbent.

PubMed

Munagapati, Venkata Subbaiah; Yarramuthi, Vijaya; Kim, Yeji; Lee, Kwon Min; Kim, Dong-Su

2018-02-01

The adsorption characteristics of Reactive Black 5 (RB5) and Cong Red (CR) onto Banana Peel Powder (BPP) from aqueous solution were investigated as a function of pH, contact time, initial dye concentration and temperature. The BPP was characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) analysis. FTIR results revealed that hydroxyl (-OH), amine (-NH) and carboxyl (-C˭O) functional groups present on the surface of BPP. The SEM results show that BPP has an irregular and porous surface morphology which is adequate for dye adsorption. The equilibrium data were analyzed using Langmuir and Freundlich isotherm models. Experimental results were best represented by the Langmuir isotherm model. The adjustments of models were confirmed by the Chi-square (χ 2 ) test and the correlation coefficients (R 2 ). The maximum monolayer adsorption capacities of RB5 and CR on BPP calculated from Langmuir isotherm model were 49.2 and 164.6mg/g at pH 3.0 and 298K. Experimental data were also tested in terms of adsorption kinetics using pseudo-first-order and pseudo-second-order kinetic models. The results showed that the adsorption processes of both RB5 and CR followed well pseudo-second-order kinetic models. The calculated thermodynamic parameters ΔG°, ΔH° and ΔS° showed that the adsorption of RB5 and CR onto BPP was feasible, spontaneous and endothermic in the temperature range 298-318K. The RB5 and CR were desorbed from BPP using 0.1M NaOH. The recovery for both anionic dyes was found to be higher than 90%. Based on these it can be concluded that BPP can be used as an effective, low cost, and eco-friendly adsorbent for CR removal than RB5 from aqueous solution. Copyright © 2017 Elsevier Inc. All rights reserved.

Effect of Na+ impregnated activated carbon on the adsorption of NH4(+)-N from aqueous solution.

PubMed

Shi, Mo; Wang, Zhengfang; Zheng, Zheng

2013-08-01

Two kinds of activated carbons modified by Na+ impregnation after pre-treatments involving oxidation by nitric acid or acidification by hydrochloric acid (denoted as AC/N-Na and AC/HCl-Na, respectively), were used as adsorbents to remove NH4(+)-N. The surface features of samples were investigated by BET, SEM, XRD and FT-IR. The adsorption experiments were conducted in equilibrium and kinetic conditions. Influencing factors such as initial solution pH and initial concentration were investigated. A possible mechanism was proposed. Results showed that optimal NH4(+)-N removal efficiency was achieved at a neutral pH condition for the modified ACs. The Langmuir isotherm adsorption equation provided a better fit than other models for the equilibrium study. The adsorption kinetics followed both the pseudo second-order kinetics model and intra-particle kinetic model. Chemical surface analysis indicated that Na+ ions form ionic bonds with available surface functional groups created by pre-treatment, especially oxidation by nitric acid, thus increasing the removal efficiency of the modified ACs for NH4(+)-N. Na(+)-impregnated ACs had a higher removal capability in removing NH4(+)-N than unmodified AC, possibly resulting from higher numbers of surface functional groups and better intra-particle diffusion. The good fit of Langmuir isotherm adsorption to the data indicated the presence of monolayer NH4(+)-N adsorption on the active homogenous sites within the adsorbents. The applicability of pseudo second-order and intra-particle kinetic models revealed the complex nature of the adsorption mechanism. The intra-particle diffusion model revealed that the adsorption process consisted not only of surface adsorption but also intra-particle diffusion.

Poly(acrylic acid) modifying bentonite with in-situ polymerization for removing lead ions.

PubMed

He, Y F; Zhang, L; Yan, D Z; Liu, S L; Wang, H; Li, H R; Wang, R M

2012-01-01

In this paper, a new kind of poly(acrylic acid) modified clay adsorbent, the poly(acrylic acid)/bentonite composite (PAA/HB) was prepared by in-situ polymerization, and utilized to remove lead(II) ions from solutions. The maximum adsorption of adsorbent is at pH 5 for metal ions, whereas the adsorption starts at pH 2. The effects of contact time (5-60 min), initial concentration of metal ions (200-1,000 mg/L) and adsorbent dosage (0.04-0.12 g/100 mL) have been reported in this article. The experimental data were investigated by means of kinetic and equilibrium adsorption isotherms. The kinetic data were analyzed by the pseudo-first-order and pseudo-second-order equation. The experimental data fitted the pseudo-second-order kinetic model very well. Langmuir and Freundlich isotherms were tried for the system to better understand the adsorption isotherm process. The maximal adsorption capacity of the lead(II) ions on the PAA/HB, as calculated from the Langmuir model, was 769.2 mg/g. The results in this study indicated that PAA/HB was an attractive candidate for removing lead(II) (99%).

Cr(VI) sorption by free and immobilised chromate-reducing bacterial cells in PVA-alginate matrix: equilibrium isotherms and kinetic studies.

PubMed

Rawat, Monica; Rawat, A P; Giri, Krishna; Rai, J P N

2013-08-01

Chromate-resistant bacterial strain isolated from the soil of tannery was studied for Cr(VI) bioaccumulation in free and immobilised cells to evaluate its applicability in chromium removal from aqueous solution. Based on the comparative analysis of the 16S rRNA gene, and phenotypic and biochemical characterization, this strain was identified as Paenibacillus xylanilyticus MR12. Mechanism of Cr adsorption was also ascertained by chemical modifications of the bacterial biomass followed by Fourier transform infrared spectroscopy analysis of the cell wall constituents. The equilibrium biosorption analysed using isotherms (Langmuir, Freundlich and Dubinin-Redushkevich) and kinetics models (pseudo-first-order, second-order and Weber-Morris) revealed that the Langmuir model best correlated to experimental data, and Weber-Morris equation well described Cr(VI) biosorption kinetics. Polyvinyl alcohol alginate immobilised cells had the highest Cr(VI) removal efficiency than that of free cells and could also be reused four times for Cr(VI) removal. Complete reduction of chromate in simulated effluent containing Cu(2+), Mg(2+), Mn(2+) and Zn(2+) by immobilised cells, demonstrated potential applications of a novel immobilised bacterial strain MR12, as a vital bioresource in Cr(VI) bioremediation technology.

Adsorption kinetics, isotherm, and thermodynamics studies of acetyl-11-keto-β-boswellic acids (AKBA) from Boswellia serrata extract using macroporous resin.

PubMed

Niphadkar, Sonali S; Rathod, Virendra K

2017-09-14

An acetyl-11-keto-β-boswellic acid (AKBA) is potent anti-inflammatory agent found in Boswellia serrata oleogum resin. Adsorption characteristics of AKBA from B. serrata were studied using macroporous adsorbent resin to understand separation and adsorption mechanism of targeted molecules. Different macroporous resins were screened for adsorption and desorption of AKBA and Indion 830 was screened as it showed higher adsorption capacity. The kinetic equations were studied and results showed that the adsorption of AKBA on Indion 830 was well fitted to the pseudo first-order kinetic model. The influence of two parameters such as temperature (298, 303, and 308 K) and pH (5-8) on the adsorption process was also studied. The experimental data was further investigated using Langmuir, Freundlich, and Temkin isotherm models. It was observed that Langmuir isotherm model was found to be the best fit for AKBA adsorption by Indion 830 and highest adsorption capacity (50.34 mg/g) was obtained at temperature of 303 K. The values of thermodynamic parameters such as the change of Gibbs free energy (ΔG*), entropy (ΔS*), and enthalpy (ΔH*), indicated that the process of adsorption was spontaneous, favourable, and exothermic.

An eco-friendly dyeing of woolen yarn by Terminalia chebula extract with evaluations of kinetic and adsorption characteristics.

PubMed

Shabbir, Mohd; Rather, Luqman Jameel; Shahid-Ul-Islam; Bukhari, Mohd Nadeem; Shahid, Mohd; Ali Khan, Mohd; Mohammad, Faqeer

2016-05-01

In the present study Terminalia chebula was used as an eco-friendly natural colorant for sustainable textile coloration of woolen yarn with primary emphasis on thermodynamic and kinetic adsorption aspects of dyeing processes. Polyphenols and ellagitannins are the main coloring components of the dye extract. Assessment of the effect of pH on dye adsorption showed an increase in adsorption capacity with decreasing pH. Effect of temperature on dye adsorption showed 80 °C as optimum temperature for wool dyeing with T. chebula dye extract. Two kinetic equations, namely pseudo first-order and pseudo second-order equations, were employed to investigate the adsorption rates. Pseudo second-order model provided the best fit (R (2) = 0.9908) to the experimental data. The equilibrium adsorption data were fitted by Freundlich and Langmuir isotherm models. The adsorption behavior accorded well (R (2) = 0.9937) with Langmuir isotherm model. Variety of eco-friendly and sustainable shades were developed in combination with small amount of metallic mordants and assessed in terms of colorimetric (CIEL(∗) a (∗) b (∗) and K/S) properties measured using spectrophotometer under D65 illuminant (10° standard observer). The fastness properties of dyed woolen yarn against light, washing, dry and wet rubbing were also evaluated.

An eco-friendly dyeing of woolen yarn by Terminalia chebula extract with evaluations of kinetic and adsorption characteristics

PubMed Central

Shabbir, Mohd; Rather, Luqman Jameel; Shahid-ul-Islam; Bukhari, Mohd Nadeem; Shahid, Mohd; Ali Khan, Mohd; Mohammad, Faqeer

2016-01-01

In the present study Terminalia chebula was used as an eco-friendly natural colorant for sustainable textile coloration of woolen yarn with primary emphasis on thermodynamic and kinetic adsorption aspects of dyeing processes. Polyphenols and ellagitannins are the main coloring components of the dye extract. Assessment of the effect of pH on dye adsorption showed an increase in adsorption capacity with decreasing pH. Effect of temperature on dye adsorption showed 80 °C as optimum temperature for wool dyeing with T. chebula dye extract. Two kinetic equations, namely pseudo first-order and pseudo second-order equations, were employed to investigate the adsorption rates. Pseudo second-order model provided the best fit (R2 = 0.9908) to the experimental data. The equilibrium adsorption data were fitted by Freundlich and Langmuir isotherm models. The adsorption behavior accorded well (R2 = 0.9937) with Langmuir isotherm model. Variety of eco-friendly and sustainable shades were developed in combination with small amount of metallic mordants and assessed in terms of colorimetric (CIEL∗a∗b∗ and K/S) properties measured using spectrophotometer under D65 illuminant (10° standard observer). The fastness properties of dyed woolen yarn against light, washing, dry and wet rubbing were also evaluated. PMID:27222752

Removal Rate of Organic Matter Using Natural Cellulose via Adsorption Isotherm and Kinetic Studies.

PubMed

Din, Mohd Fadhil Md; Ponraj, Mohanadoss; Low, Wen-Pei; Fulazzaky, Mohamad Ali; Iwao, Kenzo; Songip, Ahmad Rahman; Chelliapan, Shreeshivadasan; Ismail, Zulhilmi; Jamal, Mohamad Hidayat

2016-02-01

In this study, the removal of natural organic matter (NOM) using coconut fiber (CF) and palm oil fiber (POF) was investigated. Preliminary analysis was performed using a jar test for the selection of optimal medium before the fabricated column model experiment. The equilibrium studies on isotherms and kinetic models for NOM adsorption were analyzed using linearized correlation coefficient. Results showed that the equilibrium data were fitted to Langmuir isotherm model for both CF and POF. The most suitable adsorption model was the pseudo-first-order kinetic model for POF and pseudo-second-order kinetic model for CF. The adsorption capacities achieved by the CF and POF were 15.67 and 30.8 mg/g respectively. Based on this investigation, it can be concluded that the POF is the most suitable material for the removal of NOM in semi polluted river water.

Optimization of the combined ultrasonic assisted/adsorption method for the removal of malachite green by gold nanoparticles loaded on activated carbon: Experimental design

NASA Astrophysics Data System (ADS)

Roosta, M.; Ghaedi, M.; Shokri, N.; Daneshfar, A.; Sahraei, R.; Asghari, A.

2014-01-01

The present study was aimed to experimental design optimization applied to removal of malachite green (MG) from aqueous solution by ultrasound-assisted removal onto the gold nanoparticles loaded on activated carbon (Au-NP-AC). This nanomaterial was characterized using different techniques such as FESEM, TEM, BET, and UV-vis measurements. The effects of variables such as pH, initial dye concentration, adsorbent dosage (g), temperature and sonication time on MG removal were studied using central composite design (CCD) and the optimum experimental conditions were found with desirability function (DF) combined response surface methodology (RSM). Fitting the experimental equilibrium data to various isotherm models such as Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich models show the suitability and applicability of the Langmuir model. Kinetic models such as pseudo -first order, pseudo-second order, Elovich and intraparticle diffusion models applicability was tested for experimental data and the second-order equation and intraparticle diffusion models control the kinetic of the adsorption process. The small amount of proposed adsorbent (0.015 g) is applicable for successful removal of MG (RE > 99%) in short time (4.4 min) with high adsorption capacity (140-172 mg g-1).

Adsorption-desorption of oxytetracycline on marine sediments: Kinetics and influencing factors.

PubMed

Li, Jia; Zhang, Hua

2016-12-01

To reveal the kinetics and mechanisms of antibiotic adsorption/desorption processes, batch and stirred flow chamber (SFC) experiments were carried out with oxytetracycline (OTC) on two marine sediments. The OTC adsorption capacities of the marine sediments were relatively weak and related to their organic carbon (OC) and contents of fine particles. Sorption isotherms of OTC on marine sediment can be well described by both the Langmuir and Freundlich models. Langmuir adsorption maxima (q max ) and Freundlich distribution coefficients (K f ) increased with the decrease of salinity and pH, which indicated the importance of variable charged sites on sediment surfaces. A second order kinetic model successfully described adsorption and desorption kinetics of OTC and well reproduced the concentration change during stop-flow. The adsorption kinetic rates (k a ) for OTC under different experimental conditions ranged from 2.00 × 10 -4 to 1.97 × 10 -3  L (mg min) -1 . Results of SFC experiments indicated that diffusive mass transfer was the dominant mechanism of the time-dependent adsorption of OTC and its release from marine sediment was mildly hysteretic. The high desorption percentage (43-75% for LZB and 58-75% for BHB) implied that binding strength of OTC on two marine sediments was weak. In conclusion, marine sediment characteristics and environmental factors such as salinity, pH, and flow rate are critical factors determine extent of OTC sorption on marine sediment and need to be incorporated in modeling fate and transport of OTC in marine environment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Comparison of cadmium hydroxide nanowires and silver nanoparticles loaded on activated carbon as new adsorbents for efficient removal of Sunset yellow: Kinetics and equilibrium study.

PubMed

Ghaedi, Mehrorang

2012-08-01

Adsorption of Sunset yellow (SY) onto cadmium hydroxide nanowires loaded on activated carbon (Cd(OH)(2)-NW-AC) and silver nanoparticles loaded on activated carbon (Ag-NP-AC) was investigated. The effects of pH, contact time, amount of adsorbents, initial dye concentration, agitation speed and temperature on Sunset yellow removal on both adsorbents were studied. Following the optimization of variables, the experimental data were fitted to different conventional isotherm models like Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich (D-R) based on linear regression coefficient R(2) the Langmuir isotherm was found to be the best fitting isotherm model and the maximum monolayer adsorption capacities calculated based on this model for Cd(OH)(2)-NW-AC and Ag-NP-AC were found to be 76.9 and 37.03mg g(-1) at room temperatures, respectively. The experimental fitting of time dependency of adsorption of SY onto both adsorbent shows the applicability of second order kinetic model for interpretation of kinetic data. The pseudo-second order model best fits the adsorption kinetics. Thermodynamic parameters such as enthalpy, entropy, activation energy, sticking probability, and Gibb's free energy changes were also calculated. It was found that the sorption of SY over (Cd(OH)(2)-NW-AC) and (Ag-NP-AC) was spontaneous and endothermic in nature. Efficiency of the adsorbent was also investigated using real effluents and more than 95% SY removal for both adsorbents was observed. Copyright © 2012 Elsevier B.V. All rights reserved.

Kinetic and isotherm analyses for thorium (IV) adsorptive removal from aqueous solutions by modified magnetite nanoparticle using response surface methodology (RSM)

NASA Astrophysics Data System (ADS)

Karimi, Mohammad; Milani, Saeid Alamdar; Abolgashemi, Hossein

2016-10-01

In this study, the ability and the adsorption capacity of magnetite/aminopropyltriethoxysilane/glutaraldehyde (Fe3O4/APTES/GA) adsorbent were evaluated for the adsorption of thorium (IV) ions from aqueous solutions. The influence of the several variables such as pH (1-5), Th (IV) initial concentration (50-300 mg L-1) and adsorbent concentration (1-5 g L-1) on the Th (IV) adsorption were investigated by response surface methodology (RSM). The results showed that the highest absorption capacity (q) was 107.23 mg g-1 with respect to pH = 4.5, initial concentration of 250 mg L-1 and adsorbent concentration of 1 g L-1 for 90 min. Modeling equilibrium sorption data with the Langmuir, Freundlich and Dubinin-Radushkevich models pointed out that the results were in good agreement with Langmuir model. The experimental kinetic data were well fitted to pseudo-second-order equation with R2 = 0.9739. Also thermodynamic parameters (ΔGo, ΔHo, ΔSo) declared that the Th (IV) adsorption was endothermic and spontaneous.

Simultaneous separation and purification of chlorogenic acid, epicatechin, hyperoside and phlorizin from thinned young Qinguan apples by successive use of polyethylene and polyamide resins.

PubMed

Sun, Lijun; Liu, Dongjie; Sun, Jiaojiao; Yang, Xingbin; Fu, Minghai; Guo, Yurong

2017-09-01

The method for separating and purifying chlorogenic acid (CA), epicatechin (EC), hyperoside (HY) and phlorizin (PH) simutaneously from young Qinguan apples by successive use of X-5 and polyamide resins has been developed in this study. The order of adsorption capacities of X-5 for the four phenolics was PH>HY>EC>CA, and the adsorption equilibriums of the four phenolics onto X-5 resin conformed to Langmuir isotherms preferentially. The adsorption kinetics of EC and CA onto X-5 conformed to the pseudo-first-order model, while that of HY and PH accorded with the pseudo-second-order model. Interestingly, the values of equilibrium adsorption capacities (Q e ) calculated in the preferential kinetics models were closer to that of theoretical maximum adsorption capacities (Q 0 ) calculated by Langmuir isotherms. Through dynamic adsorption and desorption using X-5 and polyamide resins with ethanol solution as strippant, CA, EC, HY and PH were obtained with purities of 96.21%, 95.34%, 95.36% and 97.36%, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

Biosorption of Pb(II) from aqueous solution by Solanum melongena leaf powder as a low-cost biosorbent prepared from agricultural waste.

PubMed

Yuvaraja, Gutha; Krishnaiah, Nettem; Subbaiah, Munagapati Venkata; Krishnaiah, Abburi

2014-02-01

Solanum melongena leaves are relatively galore and used as inexpensive material. This paper presents the characterization and evaluation of potential of S. melongena leaf powder (SMLP) for removal of Pb(II) from aqueous solution as a function of pH, biomass dosage, initial metal ion concentration, contact time and temperature. Experimental data were analyzed in terms of three kinetic models such as the pseudo-first-order, pseudo-second-order and intraparticle diffusion models and the results showed that the biosorption processes of Pb(II) followed well pseudo-second-order kinetics. Langmuir and Freundlich isotherm models were applied to describe the biosorption process. Langmuir isotherm described the equilibrium data very well, with a maximum monolayer sorption capacity of 71.42 mg/g for Pb(II) ions at 323 K. The biosorption process was spontaneous and endothermic in nature with negative ΔG° (-8.746, -8.509 and -7.983 kJ/mol) and positive value for ΔH° (3.698 kJ/mol). Copyright © 2013 Elsevier B.V. All rights reserved.

Removal of acid blue 062 on aqueous solution using calcinated colemanite ore waste.

PubMed

Atar, Necip; Olgun, Asim

2007-07-19

Colemanite ore waste (CW) has been employed as adsorbent for the removal of acid blue 062 anionic dye (AB 062) from aqueous solution. The adsorption of AB 062 onto CW was examined with respect to contact time, calcination temperature, particle size, pH, adsorbent dosage and temperature. The physical and chemical properties of the CW, such as particle sizes and calcinations temperature, play important roles in dye adsorption. The dye adsorption largely depends on the initial pH of the solution with maximum uptake occurring at pH 1. Three simplified kinetics models, namely, pseudo-first order, pseudo-second order, and intraparticle diffusion models were tested to investigate the adsorption mechanisms. The kinetic adsorption of AB 062 on CW follows a pseudo-second order equation. The adsorption data have been analyzed using Langmuir and Freundlich isotherms. The results indicate that the Langmuir model provides the best correlation of the experimental data. Isotherms have also been used to obtain the thermodynamic parameters such as free energy, enthalpy and entropy of the adsorption of dye onto CW.

Atomic-Scale Design of Iron Fischer-Tropsch Catalysts: A Combined Computational Chemistry, Experimental, and Microkinetic Modeling Approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manos Mavrikakis; James A. Dumesic; Rahul P. Nabar

2006-09-29

Work continued on the development of a microkinetic model of Fischer-Tropsch synthesis (FTS) on supported and unsupported Fe catalysts. The following aspects of the FT mechanism on unsupported iron catalysts were investigated on during this third year: (1) the collection of rate data in a Berty CSTR reactor based on sequential design of experiments; (2) CO adsorption and CO-TPD for obtaining the heat of adsorption of CO on polycrystalline iron; and (3) isothermal hydrogenation (IH) after Fischer Tropsch reaction to identify and quantify surface carbonaceous species. Rates of C{sub 2+} formation on unsupported iron catalysts at 220 C and 20more » atm correlated well to a Langmuir-Hinshelwood type expression, derived assuming carbon hydrogenation to CH and OH recombination to water to be rate-determining steps. From desorption of molecularly adsorbed CO at different temperatures the heat of adsorption of CO on polycrystalline iron was determined to be 100 kJ/mol. Amounts and types of carbonaceous species formed after FT reaction for 5-10 minutes at 150, 175, 200 and 285 C vary significantly with temperature. Mr. Brian Critchfield completed his M.S. thesis work on a statistically designed study of the kinetics of FTS on 20% Fe/alumina. Preparation of a paper describing this work is in progress. Results of these studies were reported at the Annual Meeting of the Western States Catalysis and at the San Francisco AIChE meeting. In the coming period, studies will focus on quantitative determination of the rates of kinetically-relevant elementary steps on unsupported Fe catalysts with/without K and Pt promoters by SSITKA method. This study will help us to (1) understand effects of promoter and support on elementary kinetic parameters and (2) build a microkinetics model for FTS on iron. Calculations using periodic, self-consistent Density Functional Theory (DFT) methods were performed on models of defected Fe surfaces, most significantly the stepped Fe(211) surface. Binding Energies (BE's), preferred adsorption sites and geometries of all the FTS relevant stable species and intermediates were evaluated. Each elementary step of our reaction model was fully characterized with respect to its thermochemistry and comparisons between the stepped Fe(211) facet and the most-stable Fe(110) facet were established. In most cases the BE's on Fe(211) reflected the trends observed earlier on Fe(110), yet there were significant variations imposed on the underlying trends. Vibrational frequencies were evaluated for the preferred adsorption configurations of each species with the aim of evaluating the entropy-changes and preexponential factors for each elementary step. Kinetic studies were performed for the early steps of FTS (up to CH{sub 4} formation) and CO dissociation. This involved evaluation of the Minimum Energy Pathway (MEP) and activation energy barrier for the steps involved. We concluded that Fe(211) would allow for far more facile CO dissociation in comparison to other Fe catalysts studied so far, but the other FTS steps studied remained mostly unchanged.« less

Simple size-controlled synthesis of Au nanoparticles and their size-dependent catalytic activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suchomel, Petr; Kvitek, Libor; Prucek, Robert

The controlled preparation of Au nanoparticles (NPs) in the size range of 6 to 22 nm is explored in this study. The Au NPs were prepared by the reduction of tetrachloroauric acid using maltose in the presence of nonionic surfactant Tween 80 at various concentrations to control the size of the resulting Au NPs. With increasing concentration of Tween 80 a decrease in the size of produced Au NPs was observed, along with a significant decrease in their size distribution. The size-dependent catalytic activity of the synthesized Au NPs was tested in the reduction of 4-nitrophenol with sodium borohydride, resultingmore » in increasing catalytic activity with decreasing size of the prepared nanoparticles. Eley-Rideal catalytic mechanism emerges as the more probable, in contrary to the Langmuir-Hinshelwood mechanism reported for other noble metal nanocatalysts.« less

Simple size-controlled synthesis of Au nanoparticles and their size-dependent catalytic activity

DOE PAGES

Suchomel, Petr; Kvitek, Libor; Prucek, Robert; ...

2018-03-15

The controlled preparation of Au nanoparticles (NPs) in the size range of 6 to 22 nm is explored in this study. The Au NPs were prepared by the reduction of tetrachloroauric acid using maltose in the presence of nonionic surfactant Tween 80 at various concentrations to control the size of the resulting Au NPs. With increasing concentration of Tween 80 a decrease in the size of produced Au NPs was observed, along with a significant decrease in their size distribution. The size-dependent catalytic activity of the synthesized Au NPs was tested in the reduction of 4-nitrophenol with sodium borohydride, resultingmore » in increasing catalytic activity with decreasing size of the prepared nanoparticles. Eley-Rideal catalytic mechanism emerges as the more probable, in contrary to the Langmuir-Hinshelwood mechanism reported for other noble metal nanocatalysts.« less

High-Performance Ru1 /CeO2 Single-Atom Catalyst for CO Oxidation: A Computational Exploration.

PubMed

Li, Fengyu; Li, Lei; Liu, Xinying; Zeng, Xiao Cheng; Chen, Zhongfang

2016-10-18

By means of density functional theory computations, we examine the stability and CO oxidation activity of single Ru on CeO 2 (111), TiO 2 (110) and Al 2 O 3 (001) surfaces. The heterogeneous system Ru 1 /CeO 2 has very high stability, as indicated by the strong binding energies and high diffusion barriers of a single Ru atom on the ceria support, while the Ru atom is rather mobile on TiO 2 (110) and Al 2 O 3 (001) surfaces and tends to form clusters, excluding these systems from having a high efficiency per Ru atom. The Ru 1 /CeO 2 exhibits good catalytic activity for CO oxidation via the Langmuir-Hinshelwood mechanism, thus is a promising single-atom catalyst. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Probing reaction pathways for oxidation of CO by O2 molecule over P-doped divacancy graphene: A DFT study

NASA Astrophysics Data System (ADS)

Esrafili, Mehdi D.; Mousavian, Parisasadat

2018-05-01

Using the dispersion-corrected density functional theory calculations, the catalytic performance of P-doped graphene with divacancy (P-GDV) is examined for the oxidation of CO by O2 molecule. According to our results, the first step of CO oxidation (CO + O2 → CO2 + O∗) proceeds via Langmuir-Hinshelwood mechanism with a small activation energy (0.28 eV). The remaining O atom (O∗) is then eliminated by another incoming CO molecule with an energy barrier of 0.59 eV. It is found that the orbital hybridization between the O2-2π and CO-2π∗ states in the coadsorbed structure plays an important role for the first step of the CO oxidation. Our result indicates that the low-cost P-GDV can be regarded as an active metal-free catalyst for CO oxidation at room temperature.

Observation of the adsorption and desorption of vibrationally excited molecules on a metal surface

NASA Astrophysics Data System (ADS)

Shirhatti, Pranav R.; Rahinov, Igor; Golibrzuch, Kai; Werdecker, Jörn; Geweke, Jan; Altschäffel, Jan; Kumar, Sumit; Auerbach, Daniel J.; Bartels, Christof; Wodtke, Alec M.

2018-06-01

The most common mechanism of catalytic surface chemistry is that of Langmuir and Hinshelwood (LH). In the LH mechanism, reactants adsorb, become thermalized with the surface, and subsequently react. The measured vibrational (relaxation) lifetimes of molecules adsorbed at metal surfaces are in the range of a few picoseconds. As a consequence, vibrational promotion of LH chemistry is rarely observed, with the exception of LH reactions occurring via a molecular physisorbed intermediate. Here, we directly detect adsorption and subsequent desorption of vibrationally excited CO molecules from a Au(111) surface. Our results show that CO (v = 1) survives on a Au(111) surface for 1 × 10-10 s. Such long vibrational lifetimes for adsorbates on metal surfaces are unexpected and pose an interesting challenge to the current understanding of vibrational energy dissipation on metal surfaces. They also suggest that vibrational promotion of surface chemistry might be more common than is generally believed.

The promise of a specially-designed graft copolymer of acrylic acid onto cellulose as selective sorbent for heavy metal ions.

PubMed

Essawy, Hisham A; Mohamed, Magdy F; Ammar, Nabila S; Ibrahim, Hanan S

2017-10-01

A specially-designed graft copolymer of acrylic acid onto in-situ formed cellulose-fulvate hybrid showed privileged tendency for uptake of Pb(II) during competitive removal from a mixture containing Cd(II) and Ni(II) within 5min at pH 5. This novel trend is attributed mainly to the crowded high content of coordinating centers within the designed graft copolymer along with the acquired superabsorbency. This provides an outstanding tool to separate some metal ions selectively from mixtures containing multiple ions on kinetic basis. Thus, the designed graft copolymer structure exhibited superior efficiency that reached ∼95% for sole removal of Pb(II). Kinetic modeling for Pb(II) individual removal showed excellent fitting with a pseudo second-order model. Intraparticle diffusion model on the other hand ensured governance of boundary layer effect over diffusion during the removal process due to the superabsorbency feature of the graft copolymer. The experimental findings were described with models such as Freundlich, Langmuir, and Dubinin-Radushkevich. The Langmuir and Freundlich models showed convenience with the adsorption isotherm of Pb(II) onto the developed graft copolymer. Copyright © 2017 Elsevier B.V. All rights reserved.

Efficient removal of cadmium using magnetic multiwalled carbon nanotube nanoadsorbents: equilibrium, kinetic, and thermodynamic study

NASA Astrophysics Data System (ADS)

Pashai Gatabi, Maliheh; Milani Moghaddam, Hossain; Ghorbani, Mohsen

2016-07-01

Adsorptive potential of maghemite decorated multiwalled carbon nanotubes (MWCNTs) for the removal of cadmium ions from aqueous solution was investigated. The magnetic nanoadsorbent was synthesized using a versatile and cost effective chemical route. Structural, magnetic and surface charge properties of the adsorbent were characterized using FTIR, XRD, TEM, VSM analysis and pHPZC determination. Batch adsorption experiments were performed under varied system parameters such as pH, contact time, initial cadmium concentration and temperature. Highest cadmium adsorption was obtained at pH 8.0 and contact time of 30 min. Adsorption behavior was kinetically studied using pseudo first-order, pseudo second-order, and Weber-Morris intra particle diffusion models among which data were mostly correlated to pseudo second-order model. Adsorbate-adsorbent interactions as a function of temperature was assessed by Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models from which Freundlich model had the highest consistency with the data. The adsorption capacity increased with increasing temperature and maximum Langmuir's adsorption capacity was found to be 78.81 mg g-1 at 298 K. Thermodynamic parameters and activation energy value suggest that the process of cadmium removal was spontaneous and physical in nature, which lead to fast kinetics and high regeneration capability of the nanoadsorbent. Results of this work are of great significance for environmental applications of magnetic MWCNTs as promising adsorbent for heavy metals removal from aqueous solutions.

Wide-range and accurate modeling of linear alkylbenzene sulfonate (LAS) adsorption/desorption on agricultural soil.

PubMed

Oliver-Rodríguez, B; Zafra-Gómez, A; Reis, M S; Duarte, B P M; Verge, C; de Ferrer, J A; Pérez-Pascual, M; Vílchez, J L

2015-11-01

In this paper, rigorous data and adequate models about linear alkylbenzene sulfonate (LAS) adsorption/desorption on agricultural soil are presented, contributing with a substantial improvement over available adsorption works. The kinetics of the adsorption/desorption phenomenon and the adsorption/desorption equilibrium isotherms were determined through batch studies for total LAS amount and also for each homologue series: C10, C11, C12 and C13. The proposed multiple pseudo-first order kinetic model provides the best fit to the kinetic data, indicating the presence of two adsorption/desorption processes in the general phenomenon. Equilibrium adsorption and desorption data have been properly fitted by a model consisting of a Langmuir plus quadratic term, which provides a good integrated description of the experimental data over a wide range of concentrations. At low concentrations, the Langmuir term explains the adsorption of LAS on soil sites which are highly selective of the n-alkyl groups and cover a very small fraction of the soil surface area, whereas the quadratic term describes adsorption on the much larger part of the soil surface and on LAS retained at moderate to high concentrations. Since adsorption/desorption phenomenon plays a major role in the LAS behavior in soils, relevant conclusions can be drawn from the obtained results. Copyright © 2015 Elsevier Ltd. All rights reserved.

Bimetallic core-based cuboctahedral core-shell nanoclusters for the formation of hydrogen peroxide (2e- reduction) over water (4e- reduction): role of core metals.

PubMed

Mahata, Arup; Pathak, Biswarup

2017-07-13

The design of an efficient and selective catalyst for hydrogen peroxide (H 2 O 2 ) formation is highly sought due to its industrial importance. As alternatives to a conventional Pd-Au alloy-based catalyst, three cuboctahedral core-shell nanoclusters (Au 19 @Pt 60 , Co 19 @Pt 60 and Au 10 Co 9 @Pt 60 NCs) have been investigated. Their catalytic activities toward H 2 O 2 formation have been compared with that of pure Pt cuboctahedral NC (Pt 79 ). Much attention has been devoted to thermodynamic and kinetic parameters to find out the feasibility of the two-electron (2e - ) over the four-electron (4e - ) oxygen reduction reaction (ORR) to improve the product selectivity (H 2 O vs. H 2 O 2 ). Elementary steps corresponding to H 2 O 2 formation are significantly improved over the Au 10 Co 9 @Pt 60 NC catalyst compared with the pure core-shell NCs and periodic surface based catalysts. Furthermore, the Au 10 Co 9 @Pt 60 NC favours H 2 O 2 formation via the much desired Langmuir-Hinshelwood mechanism. The potential-dependent study shows that the H 2 O 2 formation is thermodynamically favourable up to 0.43 V on the Au 10 Co 9 @Pt 60 NC and thus the overpotential for the 2e - ORR process is significantly lowered. Besides, the Au 10 Co 9 @Pt 60 NC is highly selective for H 2 O 2 formation over H 2 O formation.

Superiority of solar Fenton oxidation over TiO2 photocatalysis for the degradation of trimethoprim in secondary treated effluents.

PubMed

Michael, I; Hapeshi, E; Michael, C; Fatta-Kassinos, D

2013-01-01

The overall aim of this work was to examine the degradation of trimethoprim (TMP), which is an antibacterial agent, during the application of two advanced oxidation process (AOP) systems in secondary treated domestic effluents. The homogeneous solar Fenton process (hv/Fe(2+)/H2O2) and heterogeneous photocatalysis with titanium dioxide (TiO2) suspensions were tested. It was found that the degradation of TMP depends on several parameters such as the amount of iron salt and H2O2, concentration of TiO2, pH of solution, solar irradiation, temperature and initial substrate concentration. The optimum dosages of Fe(2+) and H2O2 for homogeneous ([Fe(2+)] = 5 mg L(-1), [H2O2] = 3.062 mmol L(-1)) and TiO2 ([TiO2] = 3 g L(-1)) for heterogeneous photocatalysis were established. The study indicated that the degradation of TMP during the solar Fenton process is described by a pseudo-first-order reaction and the substrate degradation during the heterogeneous photocatalysis by the Langmuir-Hinshelwood kinetics. The toxicity of the treated samples was evaluated using a Daphnia magna bioassay and was finally decreased by both processes. The results indicated that solar Fenton is more effective than the solar TiO2 process, yielding complete degradation of the examined substrate within 30 min of illumination and dissolved organic carbon (DOC) reduction of about 44% whereas the respective values for the TiO2 process were ∼70% degradation of TMP within 120 min of treatment and 13% DOC removal.

Removal of Rhodamine B from aqueous solution using magnetic NiFe nanoparticles.

PubMed

Liu, Yan; Liu, Kaige; Zhang, Lin; Zhang, Zhaowen

2015-01-01

Surface-modified magnetic nano alloy particles Ni2.33Fe were prepared using a hydrothermal method and they were utilized for removing Rhodamine B (RhB) from aqueous solution. The magnetic nanoparticles were characterized by X-ray diffraction, scanning electron microscopy, thermogravimetric analysis and Fourier transform infrared spectroscopy, which confirmed that the surface of the magnetic product with a face-centered cubic-type structure was successfully modified by sodium citrate. Kinetics studies were conducted. The pseudo-second-order kinetic model was used for fitting the kinetic data successfully. The Freundlich and Langmuir adsorption models were employed for the mathematical description of adsorption equilibrium. It was found that the adsorption isotherm can be very satisfactorily fitted by the Freundlich model.

Pecan nutshell as biosorbent to remove Cu(II), Mn(II) and Pb(II) from aqueous solutions.

PubMed

Vaghetti, Julio C P; Lima, Eder C; Royer, Betina; da Cunha, Bruna M; Cardoso, Natali F; Brasil, Jorge L; Dias, Silvio L P

2009-02-15

In the present study we reported for the first time the feasibility of pecan nutshell (PNS, Carya illinoensis) as an alternative biosorbent to remove Cu(II), Mn(II) and Pb(II) metallic ions from aqueous solutions. The ability of PNS to remove the metallic ions was investigated by using batch biosorption procedure. The effects such as, pH, biosorbent dosage on the adsorption capacities of PNS were studied. Four kinetic models were tested, being the adsorption kinetics better fitted to fractionary-order kinetic model. Besides that, the kinetic data were also fitted to intra-particle diffusion model, presenting three linear regions, indicating that the kinetics of adsorption should follow multiple sorption rates. The equilibrium data were fitted to Langmuir, Freundlich, Sips and Redlich-Peterson isotherm models. Taking into account a statistical error function, the data were best fitted to Sips isotherm model. The maximum biosorption capacities of PNS were 1.35, 1.78 and 0.946mmolg(-1) for Cu(II), Mn(II) and Pb(II), respectively.

Insights into the equilibrium, kinetic and thermodynamics of nickel removal by environmental friendly Lansium domesticum peel biosorbent.

PubMed

Lam, Yun Fung; Lee, Lai Yee; Chua, Song Jun; Lim, Siew Shee; Gan, Suyin

2016-05-01

Lansium domesticum peel (LDP), a waste material generated from the fruit consumption, was evaluated as a biosorbent for nickel removal from aqueous media. The effects of dosage, contact time, initial pH, initial concentration and temperature on the biosorption process were investigated in batch experiments. Equilibrium data were fitted by the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models using nonlinear regression method with the best-fit model evaluated based on coefficient of determination (R(2)) and Chi-square (χ(2)). The best-fit isotherm was found to be the Langmuir model exhibiting R(2) very close to unity (0.997-0.999), smallest χ(2) (0.0138-0.0562) and largest biosorption capacity (10.1mg/g) at 30°C. Kinetic studies showed that the initial nickel removal was rapid with the equilibrium state established within 30min. Pseudo-second-order model was the best-fit kinetic model indicating the chemisorption nature of the biosorption process. Further data analysis by the intraparticle diffusion model revealed the involvement of several rate-controlling steps such as boundary layer and intraparticle diffusion. Thermodynamically, the process was exothermic, spontaneous and feasible. Regeneration studies indicated that LDP biosorbent could be regenerated using hydrochloric acid solution with up to 85% efficiency. The present investigation proved that LDP having no economic value can be used as an alternative eco-friendly biosorbent for remediation of nickel contaminated water. Copyright © 2016 Elsevier Inc. All rights reserved.

Rapid recipe formulation for plasma etching of new materials

NASA Astrophysics Data System (ADS)

Chopra, Meghali; Zhang, Zizhuo; Ekerdt, John; Bonnecaze, Roger T.

2016-03-01

A fast and inexpensive scheme for etch rate prediction using flexible continuum models and Bayesian statistics is demonstrated. Bulk etch rates of MgO are predicted using a steady-state model with volume-averaged plasma parameters and classical Langmuir surface kinetics. Plasma particle and surface kinetics are modeled within a global plasma framework using single component Metropolis Hastings methods and limited data. The accuracy of these predictions is evaluated with synthetic and experimental etch rate data for magnesium oxide in an ICP-RIE system. This approach is compared and superior to factorial models generated from JMP, a software package frequently employed for recipe creation and optimization.

Biosorption of copper ions from dilute aqueous solutions on base treated rubber (Hevea brasiliensis) leaves powder: kinetics, isotherm, and biosorption mechanisms.

PubMed

Wan Ngah, W S; Hanafiah, M A K M

2008-01-01

The efficiency of sodium hydroxide treated rubber (Hevea brasiliensis) leaves powder (NHBL) for removing copper ions from aqueous solutions has been investigated. The effects of physicochemical parameters on biosorption capacities such as stirring speed, pH, biosorbent dose, initial concentrations of copper, and ionic strength were studied. The biosorption capacities of NHBL increased with increase in pH, stirring speed and copper concentration but decreased with increase in biosorbent dose and ionic strength. The isotherm study indicated that NHBL fitted well with Langmuir model compared to Freundlich and Dubinin-Radushkevich models. The maximum biosorption capacity determined from Langmuir isotherm was 14.97 mg/g at 27 degrees C. The kinetic study revealed that pseudosecond order model fitted well the kinetic data, while Boyd kinetic model indicated that film diffusion was the main rate determining step in biosorption process. Based on surface area analysis, NHBL has low surface area and categorized as macroporous. Fourier transform infrared (FT-IR) analyses revealed that hydroxyl, carboxyl, and amino are the main functional groups involved in the binding of copper ions. Complexation was one of the main mechanisms for the removal of copper ions as indicated by FT-IR spectra. Ion exchange was another possible mechanism since the ratio of adsorbed cations (Cu2+ and H+) to the released cations (Na+, Ca2+, and Mg2+) from NHBL was almost unity. Copper ions bound on NHBL were able to be desorbed at > 99% using 0.05 mol/L HCl, 0.01 mol/L HNO3, and 0.01 mol/L EDTA solutions.

Facile synthesis of palladium nanoparticle doped polyaniline nanowires in soft templates for catalytic applications

NASA Astrophysics Data System (ADS)

Kshirasagar, Krushna J.; Markad, Uddhav S.; Saha, Abhijit; Sharma, Kiran Kumar K.; Sharma, Geeta K.

2017-02-01

Palladium nanoparticles doped polyaniline (Pd-PANI) nanocomposite (NCs) is synthesized in surfactant based liquid crystalline mesophase by chemical oxidation followed by radiolysis. The confinement of the liquid crystalline mesophase facilitates polymerization of aniline monomers and their 1D growth into polyaniline (PANI) nanowires by using ammonium persulfate. The PANI nanowires have an average diameter of 30-40 nm. The in situ radiolytic reduction of palladium ions ensures uniform size distribution of the palladium (Pd) nanoparticles on the surface of the PANI nanowires. The synthesized Pd-PANI nanocomposites show wire like structures of PANI (diameter ~30-40 nm) on which Pd nanoparticles of the size 10 nm are decorated. The identical average diameter of the PANI nanowires before and post gamma irradiation suggest high stability of the PANI nanowires in liquid crystalline mesophase. Surface characterization of the NCs were carried out using BET and XPS. The catalytic activity of Pd-PANI NCs are investigated in the reduction of methylene blue (MB) and 4-nitro phenol (4-NP) by sodium borohydride (NaBH4). The kinetics of the Pd-PANI NCs catalysed reactions are analysed using the Langmuir-Hinshelwood model. The apparent rate constant (k app) for the MB and 4-NP reduction reactions is 29  ×  10-3 s-1 and 20  ×  10-3 s-1 respectively with an actual Pd catalyst loading of 2.665  ×  10-4 ppm. Further, the recyclability of the Pd-PANI NCs catalyst in both the reduction reactions shows the stability of the catalyst up to four reaction cycles tested in this investigation and the multifunctional nature of the catalyst. The study provides a new approach for the directional synthesis of conducting polymer-metal nanocomposites and their possible application as a nanocatalyst in environmental remediation.

UV-induced reaction kinetics of dilinoleoylphosphatidylethanolamine monolayers.

PubMed Central

Viitala, T; Peltonen, J

1999-01-01

The UV-induced reactivity of dilinoleoylphosphatidylethanolamine (DLiPE) Langmuir and Langmuir-Blodgett films has been studied by in situ measurements of the changes in the mean molecular area, UV-vis and Fourier transform infrared spectroscopy, and atomic force microscopy (AFM). Optimum orientation and packing density of the DLiPE molecules in the monolayer were achieved by adding uranyl acetate to the subphase. A first-order reaction kinetic model was successfully fitted to the experimental reaction kinetics data obtained at a surface pressure of 30 mN/m. Topographical studies of LB films by AFM were performed on bilayer structures as a function of subphase composition and UV irradiation time. The orientational effect of the uranyl ions on the monolayer molecules was observed as an enhanced homogeneity of the freshly prepared monomeric LB films. However, the long-term stability of these films proved to be bad; clear reorganization and loss of a true monolayer structure were evidenced by the AFM images. This instability was inhibited for the UV-irradiated films, indicating that the UV irradiation gave rise to a cross-linked structure. PMID:10233096

Measurement of Electron Density Using the Multipole Resonance Probe, Langmuir Probe and Optical Emission Spectroscopy in Low Pressure Plasmas with Different Electron Energy Distribution Functions

NASA Astrophysics Data System (ADS)

Oberberg, Moritz; Bibinov, Nikita; Ries, Stefan; Awakowicz, Peter; Institute of Electrical Engineering; Plasma Technology Team

2016-09-01

In recently publication, the young diagnostic tool Multipole Resonance Probe (MRP) for electron density measurements was introduced. It is based on active plasma resonance spectroscopy (APRS). The probe was simulated und evaluated for different devices. The geometrical and electrical symmetry simplifies the APRS model, so that the electron density can be easily calculated from the measured resonance. In this work, low pressure nitrogen mixture plasmas with different electron energy distribution functions (EEDF) are investigated. The results of the MRP measurement are compared with measurements of a Langmuir Probe (LP) and Optical Emission Spectroscopy (OES). Probes and OES measure in different regimes of kinetic electron energy. Both probes measure electrons with low kinetic energy (<10 eV), whereas the OES is influenced by electrons with high kinetic energy which are needed for transitions of molecule bands. By the determination of the absolute intensity of N2(C-B) and N2+(B-X)electron temperature and density can be calculated. In a non-maxwellian plasma, all plasma diagnostics need to be combined.

Adsorption of benzyldimethylhexadecylammonium chloride at the hydrophobic silica-water interface studied by total internal reflection Raman spectroscopy: effects of silica surface properties and metal salt addition.

PubMed

Grenoble, Zlata; Baldelli, Steven

2013-08-29

The adsorption of the cationic surfactant benzyldimethylhexadecylammonium (BDMHA(+)) chloride was studied at an octadecyltrichlorosilane (OTS)-monolayer-modified silica-water interface by Raman spectroscopy in total internal reflection (TIR) geometry. The present study demonstrates the capabilities of this spectroscopic technique to evaluate thermodynamic and kinetic BDMHA(+)Cl(-) adsorption properties at the hydrophobic silica surface. The surface coverage of BDMHA(+) decreased by 50% at the hydrophobic OTS-silica surface relative to the surface coverage on bare silica; the dominating driving mechanisms for surfactant adsorption were identified as hydrophobic effects and head group charge screening by the electrolyte counterions. Addition of magnesium metal salt (MgCl2) to the aqueous solution (∼ neutral pH) lowered the surface coverage and moderately increased the Langmuir adsorption constants relative to those of the pure surfactant. These trends were previously observed at the hydrophilic, negatively charged silica surface but with a smaller change in the Gibbs free energy of adsorption at the hydrophobic silica surface. The hydrophobic OTS-silica surface properties resulted in shorter times for the surfactant to reach steady-state adsorption conditions compared to the slow adsorption kinetics previously seen with the surfactant at the hydrophilic surface. Adsorption isotherms, based on Raman signal intensities from spectral analysis, were developed according to the Langmuir adsorption model for the pure surfactant at the OTS-silica-water interface; the modified Langmuir model was applied to the surfactant adsorption in the presence of 5, 10, 50, and 100 mM magnesium chloride. Spectral analysis of the Raman scattering intensities and geometric considerations suggests a hemimicelle-type surface aggregate as the most likely surfactant structure at the OTS-silica surface. The different kinetics observed at the hydrophilic versus the hydrophobic silica surface further indicate that the surface charge and potential influence the surfactant diffusion and kinetic rates of adsorption at the silica-water interface.

Application of zeolite-activated carbon macrocomposite for the adsorption of Acid Orange 7: isotherm, kinetic and thermodynamic studies.

PubMed

Lim, Chi Kim; Bay, Hui Han; Neoh, Chin Hong; Aris, Azmi; Abdul Majid, Zaiton; Ibrahim, Zaharah

2013-10-01

In this study, the adsorption behavior of azo dye Acid Orange 7 (AO7) from aqueous solution onto macrocomposite (MC) was investigated under various experimental conditions. The adsorbent, MC, which consists of a mixture of zeolite and activated carbon, was found to be effective in removing AO7. The MC were characterized by scanning electron microscopy (SEM), energy dispersive X-ray, point of zero charge, and Brunauer-Emmett-Teller surface area analysis. A series of experiments were performed via batch adsorption technique to examine the effect of the process variables, namely, contact time, initial dye concentration, and solution pH. The dye equilibrium adsorption was investigated, and the equilibrium data were fitted to Langmuir, Freundlich, and Tempkin isotherm models. The Langmuir isotherm model fits the equilibrium data better than the Freundlich isotherm model. For the kinetic study, pseudo-first-order, pseudo-second-order, and intraparticle diffusion model were used to fit the experimental data. The adsorption kinetic was found to be well described by the pseudo-second-order model. Thermodynamic analysis indicated that the adsorption process is a spontaneous and endothermic process. The SEM, Fourier transform infrared spectroscopy, ultraviolet-visible spectral and high performance liquid chromatography analysis were carried out before and after the adsorption process. For the phytotoxicity test, treated AO7 was found to be less toxic. Thus, the study indicated that MC has good potential use as an adsorbent for the removal of azo dye from aqueous solution.

Liquid-phase separation of reactive dye by wood-rotting fungus: a biotechnological approach.

PubMed

Binupriya, Arthur R; Sathishkumar, Muthuswamy; Dhamodaran, Kavitha; Jayabalan, Rasu; Swaminathan, Krishnaswamy; Yun, Sei Eok

2007-08-01

The live and pretreated mycelial pellets/biomass of Trametes versicolor was used for the biosorption of a textile dye, reactive blue MR (RBMR) from aqueous solution. The parameters that affect the biosorption of RBMR, such as contact time, concentration of dye and pH, on the extent of RBMR adsorption were investigated. To develop an effective and accurate design model for removal of dye, adsorption kinetics and equilibrium data are essential basic requirements. Lagergren first-order, second-order and Bangham's model were used to fit the experimental data. Results of the kinetic studies showed that the second order kinetic model fitted well for the present experimental data. The Langmuir, Freundlich and Temkin adsorption models were used for the mathematical description of the biosorption equilibrium. The biosorption equilibrium data obeyed well for Langmuir isotherm and the maximum adsorption capacities were found to be 49.8, 51.6, 47.4 and 46.7 mg/g for live, autoclaved, acid- and alkali-pretreated biomass. The dye uptake capacity order of the fungal biomass was found as autoclaved > live > acid-treated > alkali-pretreated. The Freundlich and Temkin models were also able to describe the biosorption equilibrium on RBMR on live and pretreated fungal biomass. Acidic pH was favorable for the adsorption of dye. Studies on pH effect and desorption show that chemisorption seems to play a major role in the adsorption process. On comparison with fixed bed adsorption, batch mode adsorption was more efficient in adsorption of RBMR.

Kinetics and equilibrium studies for the removal of heavy metals in both single and binary systems using hydroxyapatite

NASA Astrophysics Data System (ADS)

Ramesh, S. T.; Rameshbabu, N.; Gandhimathi, R.; Nidheesh, P. V.; Srikanth Kumar, M.

2012-09-01

Removal of heavy metals is very important with respect to environmental considerations. This study investigated the sorption of copper (Cu) and zinc (Zn) in single and binary aqueous systems onto laboratory prepared hydroxyapatite (HA) surfaces. Batch experiments were carried out using synthetic HA at 30 °C. Parameters that influence the adsorption such as contact time, adsorbent dosage and pH of solution were investigated. The maximum adsorption was found at contact time of 12 and 9 h, HA dosage of 0.4 and 0.7 g/l and pH of 6 and 8 for Cu and Zn, respectively, in single system. Adsorption kinetics data were analyzed using the pseudofirst-, pseudosecond-order and intraparticle diffusion models. The results indicated that the adsorption kinetic data were best described by pseudosecond-order model. Langmuir and Freundlich isotherm models were applied to analyze adsorption data, and Langmuir isotherm was found to be applicable to this adsorption system, in terms of relatively high regression values. The removal capacity of HA was found to be 125 mg of Cu/g, 30.3 mg of Zn/g in single system and 50 mg of Cu/g, 15.16 mg of Zn/g in binary system. The results indicated that the HA used in this work proved to be effective material for removing Cu and Zn from aqueous solutions.

Optimization of the combined ultrasonic assisted/adsorption method for the removal of malachite green by gold nanoparticles loaded on activated carbon: experimental design.

PubMed

Roosta, M; Ghaedi, M; Shokri, N; Daneshfar, A; Sahraei, R; Asghari, A

2014-01-24

The present study was aimed to experimental design optimization applied to removal of malachite green (MG) from aqueous solution by ultrasound-assisted removal onto the gold nanoparticles loaded on activated carbon (Au-NP-AC). This nanomaterial was characterized using different techniques such as FESEM, TEM, BET, and UV-vis measurements. The effects of variables such as pH, initial dye concentration, adsorbent dosage (g), temperature and sonication time on MG removal were studied using central composite design (CCD) and the optimum experimental conditions were found with desirability function (DF) combined response surface methodology (RSM). Fitting the experimental equilibrium data to various isotherm models such as Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich models show the suitability and applicability of the Langmuir model. Kinetic models such as pseudo -first order, pseudo-second order, Elovich and intraparticle diffusion models applicability was tested for experimental data and the second-order equation and intraparticle diffusion models control the kinetic of the adsorption process. The small amount of proposed adsorbent (0.015 g) is applicable for successful removal of MG (RE>99%) in short time (4.4 min) with high adsorption capacity (140-172 mg g(-1)). Copyright © 2013. Published by Elsevier B.V.

Biosorption of Fe(II) and Mn(II) Ions from Aqueous Solution by Rice Husk Ash

PubMed Central

Zhao, Jiaying; Jiang, Zhao; Shan, Dexin; Lu, Yan

2014-01-01

Rice husk ash (RHA), an agricultural waste, was used as biosorbent for the removal of Iron(II) and Manganese(II) ions from aqueous solutions. The structural and morphological characteristics of RHA and its elemental compositions before and after adsorption of Fe(II) and Mn(II) were determined by scanning electron microscopic (SEM) and X-ray fluorescence (XRF) analyses. Batch experiments were carried out to determine the influence of initial pH, contact time, adsorbent dosage, and initial concentration on the removal of Fe(II) and Mn(II) ions. Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) models were applied to describe the biosorption isotherm of the metal ions by RHA. The correlation coefficient (R 2) of Langmuir and Freundlich isotherm models equals 0.995 and 0.901 for Fe(II), 0.9862 and 0.8924 for Mn(II), respectively, so the Langmuir model fitted the equilibrium data better than the Freundlich isotherm model. The mean free energy values evaluated from the D-R model indicated that the biosorption of Fe(II) and Mn(II) onto RHA was physical in nature. Experimental data also showed that the biosorption processes of both metal ions complied with the pseudo-second-order kinetics. PMID:24982918

A maximally informative version of inelastic scattering of electromagnetic waves by Langmuir waves

NASA Astrophysics Data System (ADS)

Erofeev, V. I.

2015-09-01

The concept of informativeness of nonlinear plasma physics scenarios is explained. Natural ideas of developing highly informative models of plasma kinetics are spelled out. A maximally informative version of inelastic scattering of electromagnetic waves by Langmuir waves in a weakly turbulent inhomogeneous plasma is developed with consideration of possible changes in wave polarization. In addition, a new formula for wave drift in spatial positions and wave vectors is derived. New scenarios of the respective wave drift and inelastic scattering are compared with the previous visions. The results indicate the need for further revision of the traditional understanding of nonlinear plasma phenomena.

Biosorption of arsenic from groundwater using Vallisneria gigantea plants. Kinetics, equilibrium and photophysical considerations.

PubMed

Iriel, Analia; Lagorio, M Gabriela; Fernández Cirelli, Alicia

2015-11-01

Arsenic (V) uptake from groundwater by using Vallisneria gigantea plants was studied using batch experiments. Reflectance and fluorescence of intact plants were investigated and changes in photophysical properties following arsenic absorption were reported. Good correlations have been found between arsenic concentration in groundwater and parameters derived from reflectance and fluorescence measurements. This system reached its equilibrium after seven days when the removal quantities were strongly dependent on the initial arsenic concentration. Interestingly, Vallisneria plants were able to accumulate from 100 to 600 mg As kg(-1) in roots and fronds although the translocation factors were low (0.6-1.6). Kinetic data for biosorption process followed a first-order law. At low arsenic concentrations the uptake in plants was governed by diffusion aspects. Langmuir, Freundlich and Dubinin-Radushkevich models were applied and results demonstrated that arsenic uptake was better described by the Langmuir model. As a final remark we concluded that a plant of this species should be able to remove 1mg As per week. Copyright © 2015 Elsevier Ltd. All rights reserved.

Utilization of Waste Biomass (Kitchen Waste) Hydrolysis Residue as Adsorbent for Dye Removal: Kinetic, Equilibrium, and Thermodynamic Studies.

PubMed

Li, Panyu; Chen, Xi; Zeng, Xiaotong; Zeng, Yu; Xie, Yi; Li, Xiang; Wang, Yabo; Xie, Tonghui; Zhang, Yongkui

2018-02-02

Kitchen waste hydrolysis residue (KWHR), which is produced in the bioproduction process from kitchen waste (KW), is usually wasted with potential threats to the environment. Herein, experiments were carried out to evaluate the potential of KWHR as adsorbent for dye (methylene blue, MB) removal from aqueous solution. The adsorbent was characterized using FT-IR and SEM. Adsorption results showed that the operating variables had great effects on the removal efficiency of MB. Kinetic study indicated pseudo-second-order model was suitable to describe the adsorption process. Afterwards, the equilibrium data were well fitted by using Langmuir isotherm model, suggesting a monolayer adsorption. The Langmuir monolayer adsorption capacity was calculated to be 110.13 mg/g, a level comparable to some other low-cost adsorbents. It was found that the adsorption process of MB onto KWHR was spontaneous and exothermic through the estimation of thermodynamic parameters. Thus, KWHR was of great potential to be an alternative adsorbent material to improve the utilization efficiency of bioresource (KW) and lower the cost of adsorbent for color treatment.

Biosorption of toxic lead (II) ions using tomato waste (Solanum lycopersicum) activated by NaOH

NASA Astrophysics Data System (ADS)

Permatasari, Diah; Heraldy, Eddy; Lestari, Witri Wahyu

2016-02-01

This research present to uptake lead (II) ion from aqueous solutions by activated tomato waste. Biosorbent were characterized by applying Fourier Transform Infrared Spectroscopy (FTIR) and Surface Area Analyzer (SAA). The biosorption investigated with parameters including the concentration of NaOH, effects of solution pH, biosorbent dosage, contact time,and initial metal concentration. Experimental data were analyzed in terms of two kinetic model such us the pseudo-first order and pseudo-second order. Langmuir and Freundlich isotherm models were applied todescribe the biosorption process. According to the experiment, the optimum concentration of NaOH was achieved at 0.1 M. The maximum % lead (II) removal was achieved at pH 4 with 94.5%. Optimum biosorbentdosage were found as 0.1 g/25 mL solution while optimum contact time were found at 75 minutes. The results showed that the biosorption processes of Lead (II) followed pseudo-second order kinetics. Langmuir adsorption isotherm was found fit the adsorption data with amaximum capacity of 24.079 mg/g with anadsorption energy of 28.046 kJ/mol.

Shikimic Acid Ozonolysis is Influenced by its Physical State

NASA Astrophysics Data System (ADS)

Steimer, S.; Krieger, U. K.; Lampimäki, M.; Peter, T.; Ammann, M.

2013-12-01

Atmospheric aerosols play an important role in climate, air quality and human health. They undergo continuous transformation, changing their physical and chemical properties. Recent findings show that secondary organic aerosol (SOA) particles can form amorphous solids and semi-solids under atmospheric conditions [1]. Such physical states are highly viscous, leading to a decreased diffusivity within the bulk of the material. Inhibited mass transport could slow down chemical reactions, thereby increasing the lifetime of the organic compounds involved. First indications of such behavior were recently shown for the reaction of thin protein films with ozone [2] and formation of organonitrogen from ammonia uptake to α-pinene secondary organic material [3]. In this study, we investigated the influence of physical state on the ozonolysis of shikimic acid. This carboxylic acid is a constituent of biomass burning aerosols and used here as a proxy for oxygenated organic aerosol. The viscosity of the organic material was adjusted by varying the humidity of the system between 0% and 92% RH, assuming a correlation between the two parameters since water acts as a plasticizer. The system was probed with two complementary techniques: coated wall flow tube measurements, where the uptake of ozone is measured via loss from the gas phase and in situ X-ray microspectroscopy on single particles, where oxidation of the bulk can be observed. Additionally, data from electrodynamic balance measurements and kinetic modeling were used to facilitate data analysis. The dependence of the ozonolysis on relative humidity was clearly observed with both techniques. The coated wall flow tube measurements showed a long term, gradually changing ozone uptake over more than 15 hours, the magnitude of which varied over nearly two orders between driest and wettest conditions. It was possible to separate the uptake into two distinct kinetic regimes, the first of which displayed a Langmuir-Hinshelwood type behavior regarding the ozone gas phase concentration. Microspectroscopy showed that the speed at which the characteristic double bond peak of shikimic acid disappeared was humidity dependent. The measured humidity dependence supports the hypothesis that the uptake coefficient is highly dependent on the diffusion coefficients of ozone and/or shikimic acid in the organic film. [1] Nature, 2010, 467, 824-827. [2] Proc. Natl. Acad. Sci. U. S. A., 2011, 108, 11003-11008. [3] Proc. Natl. Acad. Sci. U. S. A., 2012, 109, 17354-17359.

Equilibrium and kinetic modelling of chromium(III) sorption by animal bones.

PubMed

Chojnacka, Katarzyna

2005-04-01

The paper discusses sorption of Cr(III) ions from aqueous solutions by animal bones. Animal bones were found to be an efficient sorbent with the maximum experimentally determined sorption capacity in the range 29-194 mg g(-1) that depended on pH and temperature. The maximum experimentally determined sorption capacity was obtained at 50 degrees C, pH 5. Batch kinetics and equilibrium experiments were performed in order to investigate the influence of contact time, initial concentration of sorbate and sorbent, temperature and pH. It was found that sorption capacity increased with increase of Cr(III) concentration, temperature and initial pH of metal solution. Mathematical models describing kinetics and statics of sorption were proposed. It was found that process kinetics followed the pseudo-second-order pattern. The influence of sorbent concentration was described with Langmuir-type equation and the influence of sorbate concentration was described with empirical dependence. The models were positively verified.

Treatment of wastewater containing toxic chromium using new activated carbon developed from date palm seed.

PubMed

El Nemr, Ahmed; Khaled, Azza; Abdelwahab, Ola; El-Sikaily, Amany

2008-03-21

The use of a new activated carbon developed from date palm seed wastes, generated in the jam industry, for removing toxic chromium from aqueous solution has been investigated. The activated carbon has been achieved from date palm seed by dehydrating methods using concentrated sulfuric acid. The batch experiments were conducted to determine the adsorption capacity of the biomass. The effect of initial metal concentration (25-125mgl(-1)), pH, contact time, and concentration of date palm seed carbon have been studied at room temperature. A strong dependence of the adsorption capacity on pH was observed, the capacity increase as pH value decrease and the optimum pH value is pH 1.0. Kinetics and adsorption equilibrium were studied at different sorbent doses. The adsorption process was fast and the equilibrium was reached within 180min. The maximum removal was 100% for 75mgl(-1) of Cr(+ concentration on 4gl(-1) carbon concentration and the maximum adsorption capacity was 120.48mgg(-1). The kinetic data were analyzed using various kinetic models - pseudo-first order equation, pseudo-second order equation, Elovich equation and intraparticle diffusion equation - and the equilibrium data were tested using several isotherm models, Langmuir, Freundlich, Koble-Corrigan, Redlich-Peterson, Tempkin, Dubinin-Radushkevich and Generalized isotherm equations. The Elovich equation and pseudo-second order equation provide the greatest accuracy for the kinetic data and Koble-Corrigan and Langmuir models the closest fit for the equilibrium data. Activation energy of sorption has also been evaluated as 0.115 and 0.229kJmol(-1).

Modeling biosorption of Cr(VI) onto Ulva compressa L. from aqueous solutions.

PubMed

Aid, Asma; Amokrane, Samira; Nibou, Djamel; Mekatel, Elhadj; Trari, Mohamed; Hulea, Vasile

2018-01-01

The marine biomass Ulva compressa L. (ECL) was used as a low-cost biosorbent for the removal of Cr(VI) from contaminated aqueous solutions. The operating variables were optimized: pH ∼ 2, initial concentration of 25 mg/L, solid/liquid ratio of 6 g/L and a temperature of 50 °C, leading to an uptake elimination of 96%. A full factorial experimental design technique enabled us to obtain a mathematical model describing the Cr(VI) biosorption and to study the main effects and interactions among operational parameters. The equilibrium isotherm was analyzed by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models; it has been found that the adsorption process follows well the Langmuir model. Kinetic studies showed that the pseudo-second order model describes suitably the experimental data. The thermodynamic parameters indicated an endothermic heat and a spontaneity of the Cr(VI) biosorption onto ECL.

Ultrasonically assisted solvothermal synthesis of novel Ni/Al layered double hydroxide for capturing of Cd(II) from contaminated water

NASA Astrophysics Data System (ADS)

Rahmanian, Omid; Maleki, Mohammad Hassan; Dinari, Mohammad

2017-11-01

A novel adsorbent of nickel aluminum layered double hydroxide (Ni/Al-LDH) was prepared through the precipitation of metal nitrates by ultrasonically assisted solvothermal method. The surface morphology, chemical structure and thermal properties of this compound were examined by X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) techniques. The XRD, TEM and FE-SEM results established that the synthesized LDH have a well-ordered layer structure with good crystalline nature. Then it was applied to remove excessive Cd(II) ions from water and the effects of contact time, pH and adsorbent dose were examined at initial Cd(II) concentration of 10 mg/L. Results show that the time required to reach equilibrium was fast (40 min) and working pH solution was neutral (pH 7). Langmuir and Freundlich model of adsorption isotherms were explored; the results show that the Freundlich model was better fitted than that Langmuir model. This results predicting a multilayer adsorption of Cd(II) on LDH. The equilibrium kinetic adsorption data were fixed to the pseudo-second order kinetic equation.

Investigation of adsorption of Rhodamine B onto a natural adsorbent Argemone mexicana.

PubMed

Khamparia, Shraddha; Jaspal, Dipika

2016-12-01

The present study aims at exploring the potential of the seeds of a tropical weed, Argemone mexicana (AM), for the removal of a toxic xanthene textile dye, Rhodamine B (RHB), from waste water. Impact of pH, adsorbent dosage, particle size, contact time and dye concentration have been assessed during adsorption. The weed has been well characterized by several latest techniques thereby providing an indepth information of the mechanism during adsorption. About 80% removal has been attained with 0.06 g of adsorbent over the studied system. Thermodynamic and kinetic studies, followed by second order kinetic model, directed towards the endothermic nature of adsorption. The results obtained from batch experiments were modelled using Langmuir and Freundlich isotherm and were analysed on the basis of R 2 and six error functions for selection of appropriate model. Langmuir isotherm was found to be best fitted to the experimental data with high values of R 2 and lower values of error functions. Adsorption study revealed the affinity of AM seeds for the dye ions present in waste water, introducing a novel adsorbent in field of waste water treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Removal of ammonium ion from water by Na-rich birnessite: Performance and mechanisms.

PubMed

Cheng, Ya; Huang, Tinglin; Shi, Xinxin; Wen, Gang; Sun, Yuankui

2017-07-01

Na-rich birnessite (NRB) was synthesized by a simple synthesis method and used as a high-efficiency adsorbent for the removal of ammonium ion (NH 4 + ) from aqueous solution. In order to demonstrate the adsorption performance of the synthesized material, the effects of contact time, pH, initial ammonium ion concentration, and temperature were investigated. Adsorption kinetics showed that the adsorption behavior followed the pseudo second-order kinetic model. The equilibrium adsorption data were fitted to Langmuir and Freundlich adsorption models and the model parameters were evaluated. The monolayer adsorption capacity of the adsorbent, as obtained from the Langmuir isotherm, was 22.61mg NH 4 + -N/g at 283K. Thermodynamic analyses showed that the adsorption was spontaneous and that it was also a physisorption process. Our data revealed that the higher NH 4 + adsorption capacity could be primarily attributed to the water absorption process and electrostatic interaction. Particularly, the high surface hydroxyl-content of NRB enables strong interactions with ammonium ion. The results obtained in this study illustrate that the NRB is expected to be an effective and economically viable adsorbent for ammonium ion removal from aqueous system. Copyright © 2016. Published by Elsevier B.V.

Trivalent chromium removal from wastewater using low cost activated carbon derived from agricultural waste material and activated carbon fabric cloth.

PubMed

Mohan, Dinesh; Singh, Kunwar P; Singh, Vinod K

2006-07-31

An efficient adsorption process is developed for the decontamination of trivalent chromium from tannery effluents. A low cost activated carbon (ATFAC) was prepared from coconut shell fibers (an agricultural waste), characterized and utilized for Cr(III) removal from water/wastewater. A commercially available activated carbon fabric cloth (ACF) was also studied for comparative evaluation. All the equilibrium and kinetic studies were conducted at different temperatures, particle size, pHs, and adsorbent doses in batch mode. The Langmuir and Freundlich isotherm models were applied. The Langmuir model best fit the equilibrium isotherm data. The maximum adsorption capacities of ATFAC and ACF at 25 degrees C are 12.2 and 39.56 mg/g, respectively. Cr(III) adsorption increased with an increase in temperature (10 degrees C: ATFAC--10.97 mg/g, ACF--36.05 mg/g; 40 degrees C: ATFAC--16.10 mg/g, ACF--40.29 mg/g). The kinetic studies were conducted to delineate the effect of temperature, initial adsorbate concentration, particle size of the adsorbent, and solid to liquid ratio. The adsorption of Cr(III) follows the pseudo-second-order rate kinetics. From kinetic studies various rate and thermodynamic parameters such as effective diffusion coefficient, activation energy and entropy of activation were evaluated. The sorption capacity of activated carbon (ATFAC) and activated carbon fabric cloth is comparable to many other adsorbents/carbons/biosorbents utilized for the removal of trivalent chromium from water/wastewater.

Amino-functionalized mesoporous MCM-41 silica as an efficient adsorbent for water treatment: batch and fixed-bed column adsorption of the nitrate anion

NASA Astrophysics Data System (ADS)

Ebrahimi-Gatkash, Mehdi; Younesi, Habibollah; Shahbazi, Afsaneh; Heidari, Ava

2017-07-01

In the present study, amino-functionalized Mobil Composite Material No. 41 (MCM-41) was used as an adsorbent to remove nitrate anions from aqueous solutions. Mono-, di- and tri-amino functioned silicas (N-MCM-41, NN-MCM-41 and NNN-MCM-41) were prepared by post-synthesis grafting method. The samples were characterized by means of X-ray powder diffraction, FTIR spectroscopy, thermogravimetric analysis, scanning electron microscopy and nitrogen adsorption-desorption. The effects of pH, initial concentration of anions, and adsorbent loading were examined in batch adsorption system. Results of adsorption experiments showed that the adsorption capacity increased with increasing adsorbent loading and initial anion concentration. It was found that the Langmuir mathematical model indicated better fit to the experimental data than the Freundlich. According to the constants of the Langmuir equation, the maximum adsorption capacity for nitrate anion by N-MCM-41, NN-MCM-41 and NNN-MCM-41 was found to be 31.68, 38.58 and 36.81 mg/g, respectively. The adsorption kinetics were investigated with pseudo-first-order and pseudo-second-order model. Adsorption followed the pseudo-second-order rate kinetics. The coefficients of determination for pseudo-second-order kinetic model are >0.99. For continuous adsorption experiments, NNN-MCM-41 adsorbent was used for the removal of nitrate anion from solutions. Breakthrough curves were investigated at different bed heights, flow rates and initial nitrate anion concentrations. The Thomas and Yan models were utilized to calculate the kinetic parameters and to predict the breakthrough curves of different bed height. Results from this study illustrated the potential utility of these adsorbents for nitrate removal from water solution.

Enhanced photocatalytic performance of mesoporous TiO{sub 2} coated SBA-15 nanocomposites fabricated through a novel approach: supercritical deposition aided by liquid-crystal template

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Chen; Lin, Xiao; Li, Youji, E-mail: bcclyj@163.com

2016-03-15

Highlights: • Highly uniform mesoporous TiO{sub 2} nanopartices were coated SBA-15. • MT showed smaller crystallite size, higher hydroxyl content and surface area. • MT/SBA-15 show enhanced photocatalytic activity and high reused activity. • The optimum MT loading rate and calcination temperature were obtained to be 15% and 400 °C, respectively. • Photocatalytic behaviors are discussed in terms of the Langmuir–Hinshelwood model. - Abstract: Mesoporous TiO2 coated SBA-15 (MT@S) nanocomposites were fabricated through supercritical CO{sub 2} deposition aided by liquid-crystal template. The as-prepared samples were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, diffuse reflectance spectroscopy and so on. Themore » results reveal that MT uniformly deposited onto silica with titania incorporated in SBA-15 channels, showed smaller crystallite size, higher hydroxyl content and surface area than nonporous TiO{sub 2} coated SBA-15 (NT@S) obtained by a similar route without template. With TiO{sub 2} loading ratio of 15 wt% and calcination temperature of 400 °C, 15%MT@S-400 showed the enhanced degradation efficiency for azo dyes (methylene blue, methyl orange, and rhodamine B) and phenol in comparsion with 15%NT@S-400, due to those improved textural and physicochemical properties. Meanwhile, the reused MT@S also showed high photoactivity. Additionally, the effects of MT content and calcination temperature have been examined as operational parameters. Photocatalytic reactions followed pseudo-first-order kinetics and are discussed in terms of the Langmuir–Hinshelwood model.« less

Single and multi-component adsorption of psychiatric pharmaceuticals onto alternative and commercial carbons.

PubMed

Calisto, Vânia; Jaria, Guilaine; Silva, Carla Patrícia; Ferreira, Catarina I A; Otero, Marta; Esteves, Valdemar I

2017-05-01

This work describes the adsorptive removal of three widely consumed psychiatric pharmaceuticals (carbamazepine, paroxetine and oxazepam) from ultrapure water. Two different adsorbents were used: a commercial activated carbon and a non-activated waste-based carbon (PS800-150-HCl), produced by pyrolysis of primary paper mill sludge. These adsorbents were used in single, binary and ternary batch experiments in order to determine the adsorption kinetics and equilibrium isotherms of the considered pharmaceuticals. For the three drugs and both carbons, the equilibrium was quickly attained (with maximum equilibrium times of 15 and 120 min for the waste-based and the commercial carbons, respectively) even in binary and ternary systems. Single component equilibrium data were adequately described by the Langmuir model, with the commercial carbon registering higher maximum adsorption capacities (between 272 ± 10 and 493 ± 12 μmol g -1 ) than PS800-150-HCl (between 64 ± 2 and 74 ± 1 μmol g -1 ). Multi-component equilibrium data were also best fitted by the single component Langmuir isotherm, followed by the Langmuir competitive model. Overall, competitive effects did not largely affect the performance of both adsorbents. Binary and ternary systems maintained fast kinetics, the individual maximum adsorption capacities were not lower than half of the single component systems and both carbons presented improved total adsorption capacities for multi-component solutions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Potential adsorption of methylene blue from aqueous solution using green macroalgaePosidonia oceanica.

NASA Astrophysics Data System (ADS)

Allouche, F.-N.; Yassaa, N.

2018-03-01

The use of inexpensive biological materials, such as marine algae for removing dyes from contaminated industrial effluents appears as a potential alternative method. The aim of this study is to investigate the aptitude of marine macroalgae Posidonia Oceanica local biomass abundant on the coasts of Algeria for selective sorption of methylene blue (MB) from an aqueous solution in batch experiments at 20 °C. A maximum percentage removal of Posidonia oceanica occurs at pH 5. Equilibrium isotherm data were analyzed using the Langmuir and the Freundlich isotherms. The adsorption equilibrium of methylene blue was best describe by Langmuir model than the Freundlich model. The maximum sorption capacity was 357 mgg-1at pH 5. The sorption data were very well described by the pseudo-second-order model. Keywords: Posidonia oceanica, Methylene blue (MB), Biosorption, Isotherm Equilibrium, Kinetics; Modelling.

Design of a new integrated chitosan-PAMAM dendrimer biosorbent for heavy metals removing and study of its adsorption kinetics and thermodynamics.

PubMed

Zarghami, Zabihullah; Akbari, Ahmad; Latifi, Ali Mohammad; Amani, Mohammad Ali

2016-04-01

In this research, different generations of PAMAM-grafted chitosan as integrated biosorbents were successfully synthesized via step by step divergent growth approach of dendrimer. The synthesized products were utilized as adsorbents for heavy metals (Pb(2+) in this study) removing from aqueous solution and their reactive Pb(2+) removal potential was evaluated. The results showed that as-synthesized products with higher generations of dendrimer, have more adsorption capacity compared to products with lower generations of dendrimer and sole chitosan. Adsorption capacity of as-prepared product with generation 3 of dendrimer is 18times more than sole chitosan. Thermodynamic and kinetic studies were performed for understanding equilibrium data of the uptake capacity and kinetic rate uptake, respectively. Thermodynamic and kinetic studies showed that Langmuir isotherm model and pseudo second order kinetic model are more compatible for describing equilibrium data of the uptake capacity and kinetic rate of the Pb(2+) uptake, respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.

Equilibrium, kinetic and thermodynamic studies on aluminum biosorption by a mycelial biomass (Streptomyces rimosus).

PubMed

Tassist, Amina; Lounici, Hakim; Abdi, Nadia; Mameri, Nabil

2010-11-15

This work focused on kinetic, equilibrium and thermodynamic studies on aluminum biosorption by Streptomyces rimosus biomass. Infrared spectroscopy analysis shows that S. rimosus present some groups: hydroxyl, methyl, carboxyl, amine, thiol and phosphate. The maximum biosorption capacity of S. rimosus biomass was found to be 11.76 mg g(-1) for the following optimum conditions: particle size, [250-560] μm, pH 4-4.25, biomass content of 25 g L(-1), agitation of 250 rpm and temperature of 25 °C. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models were applied to describe the biosorption isotherms at free pH (pH(i) 4) and fixed pH (pH(f) 4). Langmuir model is the most adequate. With fixed pH, the maximum biosorption capacity is enhanced from 6.62 mg g(-1) to 11.76 mg g(-1). The thermodynamic parameters (ΔG°, ΔH° and ΔS°) showed the feasibility, endothermic and spontaneous nature of the biosorption at 10-80 °C. The activation energy (Ea) was determined as 52.18 kJ mol(-1) using the Arrhenius equation and the rate constant of pseudo-second-order model (the most adequate kinetic model). The mean free energy was calculated as 12.91 kJ mol(-1) using the D-R isotherm model. The mechanism of Al(III) biosorption on S. rimosus could be a chemical ion exchange and carboxyl groups are mainly involved in this mechanism. Copyright © 2010 Elsevier B.V. All rights reserved.

Mechanistic understanding and performance of biosorption of metal ions by grapefruit peel using FTIR spectroscopy, kinetics and adsorption isotherms modeling, alkali and alkaline metal displacement and EDX analysis

USDA-ARS?s Scientific Manuscript database

The performance and mechanism of the sorptive removal of Ni2+ and Zn2+ from aqueous solution using grapefruit peel (GFP) as a new sorbent was investigated. The sorption process was fast, equilibrium was established in 60 min. The equilibrium process was described well by the Langmuir isotherm model,...

Interplay between the spin-selection rule and frontier orbital theory in O2 activation and CO oxidation by single-atom-sized catalysts on TiO2(110).

PubMed

Li, Shunfang; Zhao, Xingju; Shi, Jinlei; Jia, Yu; Guo, Zhengxiao; Cho, Jun-Hyung; Gao, Yanfei; Zhang, Zhenyu

2016-09-28

Exploration of the catalytic activity of low-dimensional transition metal (TM) or noble metal catalysts is a vital subject of modern materials science because of their instrumental role in numerous industrial applications. Recent experimental advances have demonstrated the utilization of single atoms on different substrates as effective catalysts, which exhibit amazing catalytic properties such as more efficient catalytic performance and higher selectivity in chemical reactions as compared to their nanostructured counterparts; however, the underlying microscopic mechanisms operative in these single atom catalysts still remain elusive. Based on first-principles calculations, herein, we present a comparative study of the key kinetic rate processes involved in CO oxidation using a monomer or dimer of two representative TMs (Pd and Ni) on defective TiO2(110) substrates (TMn@TiO2(110), n = 1, 2) to elucidate the underlying mechanism of single-atom catalysis. We reveal that the O2 activation rates of the single atom TM catalysts deposited on TiO2(110) are governed cooperatively by the classic spin-selection rule and the well-known frontier orbital theory (or generalized d-band picture) that emphasizes the energy gap between the frontier orbitals of the TM catalysts and O2 molecule. We further illuminate that the subsequent CO oxidation reactions proceed via the Langmuir-Hinshelwood mechanism with contrasting reaction barriers for the Pd monomer and dimer catalysts. These findings not only provide an explanation for existing observations of distinctly different catalytic activities of Pd@TiO2(110) and Pd2@TiO2(110) [Kaden et al., Science, 2009, 326, 826-829] but also shed new insights into future utilization and optimization of single-atom catalysis.

A potential low cost adsorbent for the removal of cationic dyes from aqueous solutions

NASA Astrophysics Data System (ADS)

Uddin, Md. Tamez; Rahman, Md. Arifur; Rukanuzzaman, Md.; Islam, Md. Akhtarul

2017-10-01

This study was aimed at using mango leaf powder (MLP) as a potential adsorbent for the removal of methylene blue (MB) from aqueous solutions. Characterization of the adsorbent was carried out with scanning electron microscopy, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption analysis. The pH at the point of zero charge of the adsorbent was determined by titration method and was found a value to be 5.6 ± 0.2. Batch studies were performed to evaluate the influence of various experimental parameters like initial solution pH, contact time, initial concentration of dye and adsorbent dosage on the removal of MB. An adsorption-desorption study was carried out resulting the mechanism of adsorption was carried out by electrostatic force of attraction. The adsorption equilibrium time required for the adsorption of MB on MLP was almost 2 h and 85 ± 5% of the total amount of dye uptake was found to occur in the first rapid phase (30 min). The Langmuir and Freundlich isotherm models were used for modeling the adsorption equilibrium. The experimental equilibrium data could be well interpreted by Langmuir isotherm with maximum adsorption capacity of 156 mg/g. To state the sorption kinetics, the fits of pseudo-first-order and pseudo-second-order kinetic models were investigated. It was obtained that the adsorption process followed the pseudo-second-order rate kinetics. The above findings suggest that MLP can be effectively used for decontamination of dye containing wastewater.

Photocatalytic degradation of C. I. Reactive Red 24 solution with K₆SiW₁₁O₃₉Sn(II.).

PubMed

Guo, Guixiang; Zhu, Xiuhua; Shi, Fuyou; Wang, Anning; Wang, Wei; Mu, Jun; Wan, Quanli; Zhang, Rong

2013-12-01

Environmental friendly materials, K6SiW11O39Sn (SiWSn), was synthesized. SiWSn photocatalytic decomposition of C. I. Reactive Red 24 (RR24) with the UV-lamp (253.7 nm, 20 W), Xenon lamp filtered less than 390 nm light (500 W) and sun light was investigated. The results showed that RR24 solution could be effectively decolorized with the SiWSn photocatalyst. The photocatalytic degradation efficiency of RR24 with SiWSn was affected by the initial concentration of RR2 solution, the amount of SiWSn and the photolysis time. It is demonstrated that the process of photodegradation of RR24 with SiWSn is a pesudo first-order reaction, which can be described by Langmuir-Hinshelwood equation. Hydroxyl radicals and holes are both the main oxidants in the photocatalytic reaction of RR24 with SiWSn. Copyright © 2013 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

DFT study of cyanide oxidation on surface of Ge-embedded carbon nanotube

NASA Astrophysics Data System (ADS)

Gao, Wei; Milad Abrishamifar, Seyyed; Ebrahimzadeh Rajaei, Gholamreza; Razavi, Razieh; Najafi, Meysam

2018-03-01

In recent years, the discovery of suitable catalyst to oxidation of the cyanide (CN) has high importance in the industry. In present study, in the first step, the carbon nanotube (CNT) with the Ge atom embedded and the surface of Ge-CNT via the O2 molecule activated. In second step, the oxidation of CN on surface of the Ge-CNT via the Langmuir Hinshelwood (LH) and the Eley Rideal (ER) mechanisms was investigated. Results show that O2-Ge-CNT oxidized the CN molecule via the Ge-CNT-O-O∗ + CN → Ge-CNT-O-O∗-CN → Ge-CNT-O∗ + OCN and the Ge-CNT-O∗ + CN → Ge-CNT + OCN reactions. Results show that oxidation of CN on surface of Ge-CNT via the LH mechanism has lower energy barrier than ER mechanism. Finally, calculated parameters reveal that Ge-CNT is acceptable catalyst with high performance for CN oxidation, form theoretical point of view.

CO oxidation on Alsbnd Au nano-composite systems

NASA Astrophysics Data System (ADS)

Rajesh, C.; Majumder, C.

2018-03-01

Using first principles method we report the CO oxidation behaviour of Alsbnd Au nano-composites in three different size ranges: Al6Au8, Al13Au42 and a periodic slab of Alsbnd Au(1 1 1) surface. The clusters prefer enclosed structures with alternating arrangement of Al and Au atoms, maximising Auδ-sbnd Alδ+ bonds. Charge distribution analysis suggests the charge transfer from Al to Au atoms, corroborated by the red shift in the density of states spectrum. Further, CO oxidation on these nano-composite systems was investigated through both Eley - Rideal and Langmuir Hinshelwood mechanism. While, these clusters interact with O2 non-dissociatively with an elongation of the Osbnd O bond, further interaction with CO led to formation of CO2 spontaneously. On contrary, the CO2 evolution by co-adsorption of O2 and CO molecules has a transition state barrier. On the basis of the results it is inferred that nano-composite material of Alsbnd Au shows significant promise toward effective oxidative catalysis.

Removal of the methyl violet 2B dye from aqueous solution using sustainable adsorbent Artocarpus odoratissimus stem axis

NASA Astrophysics Data System (ADS)

Kooh, Muhammad Raziq Rahimi; Dahri, Muhammad Khairud; Lim, Linda B. L.

2017-11-01

This study investigates the potential of the stem axis of Artocarpus odoratissimus fruit (TSA) as an adsorbent for the removal of methyl violet 2B (MV). The functional group analysis was carried out using Fourier-transform infrared spectroscopy. Investigation of the effects of pH and ionic strength provide insights on the involvement of electrostatic attraction and hydrophobic-hydrophobic attraction between the adsorbent and adsorbates. Kinetics models (pseudo-first-order, pseudo-second-order, Weber-Morris and Boyd) and isotherm models (Langmuir, Freundlich and Dubinin-Raduskevich) were used for characterising the adsorption process. The Langmuir model predicted a high q m of 263.7 mg g-1. Thermodynamics studies indicate the adsorption system is spontaneous, endothermic and physical sorption dominant. The spent adsorbent was successfully regenerated using water and obtained adsorption capacity close to the unused adsorbent even after fifth cycle of washing.

Landau damping of Langmuir twisted waves with kappa distributed electrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arshad, Kashif, E-mail: kashif.arshad.butt@gmail.com; Aman-ur-Rehman; Mahmood, Shahzad

2015-11-15

The kinetic theory of Landau damping of Langmuir twisted modes is investigated in the presence of orbital angular momentum of the helical (twisted) electric field in plasmas with kappa distributed electrons. The perturbed distribution function and helical electric field are considered to be decomposed by Laguerre-Gaussian mode function defined in cylindrical geometry. The Vlasov-Poisson equation is obtained and solved analytically to obtain the weak damping rates of the Langmuir twisted waves in a nonthermal plasma. The strong damping effects of the Langmuir twisted waves at wavelengths approaching Debye length are also obtained by using an exact numerical method and aremore » illustrated graphically. The damping rates of the planar Langmuir waves are found to be larger than the twisted Langmuir waves in plasmas which shows opposite behavior as depicted in Fig. 3 by J. T. Mendoça [Phys. Plasmas 19, 112113 (2012)].« less

Adsorptive removal of dissolved organic matter (DOM) in landfill leachate by iron oxide nanoparticles (FeONPs)

NASA Astrophysics Data System (ADS)

Ghani, Zaidi Ab; Yusoff, Mohd Suffian; Zaman, Nastaein Qamaruz; Andas, Jeyashelly; Aziz, Hamidi Abdul

2017-10-01

A study was conducted to investigate the efficiency of iron oxide nanoparticle (FeONPs) adsorption for removing of DOM in landfill leachate. FeONPs was directly prepared via sodium borohydride (KBH4) reduction method. Adsorption kinetics, isotherm and thermodynamic studies were developed to design the model for DOM removal. Pseudo first-order and pseudo second-order model have been studied to fit the experimental data. The regression results showed that the adsorption kinetics were more accurately represented by a pseudo second-order model. The Weber-Morris intraparticle diffusion model was used to analyze the adsorption kinetics data. The plot of qt versus t1/2 represents multi linearity, which showed that the adsorption processes occurred in more than one step. Adsorption isotherms were analyzed by Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich, isotherms model. Equilibrium data were well fitted to the Dubinin- Radushkevich isotherm model. Maximum monolayer adsorption based on Langmuir was calculated to be 21.74 mg/g. Thermodynamic parameters such as free energy changes (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were evaluated between temperatures of 25 °C and 40 °C. The ΔG° was noticed progressively decrease from -9.620 -9.820 -10.021, and -10.222 kJ/mol as the temperature increase. The ΔH° and ΔS° values were found to be 2.350 kJ/mol and 40.165 J/mol.K respectively. The results showed that the overall adsorption process was endothermic and spontaneous. The results from this study suggested that FeNPs could be a viable adsorbent in managing higher DOM problems associated with landfill leachate.

Adsorption of intrinsically disordered barnacle adhesive proteins on silica surface

NASA Astrophysics Data System (ADS)

Wang, Xiaoqiang; Wang, Chao; Xu, Baomei; Wei, Junting; Xiao, Yang; Huang, Fang

2018-01-01

The adsorption of recombinant barnacle proteins Bacp19k and Mrcp19k on hydrophilic silica surface was characterized by spectroscopic ellipsometry in artificial seawater (pH = 8.2). They are homologous adhesive proteins destined for underwater adhesion but bear opposite net charges in seawater. As assessed with their primary and secondary structures, both proteins are intrinsically disordered and thus distinct from globular proteins that have dominated research in the field. Different from Mrcp19k, higher initial rate and adsorbed amount were obtained via curve fitting for Bacp19k in kinetic studies, due to favorable charge interactions with silica surface. The good fitting with the same dynamic model also indicates the formation of monolayer coverage in both cases. The two adsorption isotherms of Bacp19k and Mrcp19k are different in the initial change and maximum adsorption level, indicating different protein-surface affinities and charge interactions. Each isotherm fits the Langmuir model well, which is commonly used to describe monolayer adsorption, thus consistent with the predication from kinetic fitting. To further examine the effect of electrostatic interaction on the adsorption, the isotherm of the 1:1 mixture of Bacp19k and Mrcp19k was also constructed, which showed a higher correlation fit for Jovanovic than for Langmuir model. The presence of electrostatic attraction between Bacp19k and Mrcp19k deviated from one of the required conditions for Langmuir behavior, which may also result in the highest coadsorption level but slowest initial change among the three isotherms. The surface state of the adhesive proteins and the change with adsorption time were also examined by atomic force microscopy. The results thus obtained are in good agreement with the corresponding ellipsometric measurement.

Biosorption of Food Green 3 by a novel green generation composite biosorbent from aqueous environment.

PubMed

Deniz, Fatih; Kepekci, Remziye Aysun

2017-06-03

A green type composite biosorbent composed of pine, oak, hornbeam, and fir sawdust biomasses modified with cetyltrimethylammonium bromide (CTAB) was first used for biosorption of an unsafe synthetic food dye, Food Green 3 from liquid medium in this study. Batch studies were carried by observing the effects of pH, dye concentration, biosorbent amount, and contact time. The equilibrium data were analyzed using Freundlich, Langmuir, and Dubinin-Radushkevich equations. Freundlich model gave a better conformity than other equations. The maximum dye removal potential of biosorbent was found to be 36.6 mg/g based on Langmuir isotherm. The pseudo-first-order, pseudo-second-order, Elovich, and intra-particle diffusion models were applied to clarify the process kinetics of biosorption. The mechanism studies suggested the biosorption process obeying Elovich kinetics and involving pore diffusion. The estimated values of biosorption free energy from Dubinin-Radushkevich isotherm (E value <8 kJ/mol) and thermodynamic studies (0 < ΔG° < -20 kJ/mol) implied a spontaneous, feasible, and physical process. Hence, this investigation suggested that the CTAB modified mix sawdust biomass could be a promising biosorbent for biosorption of such problematic dyes from impacted media.

Biosorption of hexavalent chromium from aqueous medium with Opuntia biomass.

PubMed

Fernández-López, José A; Angosto, José M; Avilés, María D

2014-01-01

The biosorption of hexavalent chromium from aqueous solutions by Opuntia cladodes and ectodermis from cactus fruits was investigated. Both types of biomass are considered low-cost, natural, and ecofriendly biosorbents. Batch experiments were carried out to determine Cr(VI) biosorption capacity and the efficiency of the biosorption process under different pH, initial Cr(VI) concentration, and sorbent dosage. The biosorption of Cr(VI) by Opuntia biomass was highly pH dependent, favoring higher metal uptake at low pH. The higher biosorption capacity was exhibited at pH 2. The optimal conditions were obtained at a sorbent dosage of 1 g L(-1) and initial metal concentration of 10 mg L(-1). Biosorption kinetic data were properly fitted with the pseudo-second-order kinetic model. The rate constant, the initial biosorption rate, and the equilibrium biosorption capacity were determined. The experimental equilibrium data obtained were analyzed using two-parameter isotherm models (Langmuir, Freundlich, and Temkin). The Langmuir maximum monolayer biosorption capacity (q max) was 18.5 mg g(-1) for cladodes and 16.4 mg g(-1) for ectodermis. The results suggest that Opuntia biomass could be considered a promising low-cost biosorbent for the ecofriendly removal of Cr(VI) from aqueous systems.

Comparative evaluation of sorption kinetics and isotherms of pyrene onto microplastics.

PubMed

Wang, Wenfeng; Wang, Jun

2018-02-01

Concerns regarding microplastics pollution and their potential to concentrate and transport organic contaminants in aquatic environments are growing in recent years. Sorption of organic chemicals by microplastics may affect the distribution and bioavailability of the chemicals. Here sorption process of pyrene (Pyr), a frequently encountered polycyclic aromatic hydrocarbon in aquatic environments, on three types of mass-produced plastic particles (high-density polyethylene (PE), polystyrene (PS) and polyvinylchloride (PVC)), was investigated by comparative analysis of different sorption kinetic and isotherm models. Optimum kinetic and isotherm models were predicted by the linear least-squares regression method. The pseudo-second-order kinetic model was more appropriate in describing the entire sorption process (R 2  > 0.99). Sorption rates of Pyr onto microplastics were mainly controlled by intraparticle diffusion. PE exhibited the highest affinity for Pyr, followed by PS and PVC. The sorption equilibrium data were best fitted to the Langmuir isotherm (R 2  > 0.99), indicating monolayer coverage of Pyr onto the microplastics. Copyright © 2017 Elsevier Ltd. All rights reserved.

Adsorption of hexavalent chromium onto sisal pulp/polypyrrole composites

NASA Astrophysics Data System (ADS)

Tan, Y. Y.; Wei, C.; Gong, Y. Y.; Du, L. L.

2017-02-01

Sisal pulp/polypyrrole composites(SP/PPy) utilized for the removal of hexavalent chromium [Cr(VI)] from wastewater, were prepared via in-situ chemical oxidation polymerization approach. The structure and morphology of the SP/PPy were analyzed by polarizing optical microscopy (POM), field-emission scanning electron microscopy (SEM)), Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), the results indicated SP could be efficient dispersion of PPy. The hexavalent chromium adsorption results indicate adsorption capacity of the SP/PPy were dependent on the initial pH, with an optimum pH of 2.0. The sorption kinetic data fitted well to the pseudo-second order model and isotherm data fitted well to the Langmuir isotherm model. The maximum adsorption capacity determined from the Langmuir isotherm is 336.70 mg/g at 25° C.

Eco-friendly polyvinyl alcohol/carboxymethyl cellulose hydrogels reinforced with graphene oxide and bentonite for enhanced adsorption of methylene blue.

PubMed

Dai, Hongjie; Huang, Yue; Huang, Huihua

2018-04-01

Eco-friendly polyvinyl alcohol/carboxymethyl cellulose (isolated from pineapple peel) hydrogels reinforced with graphene oxide and bentonite were prepared as efficient adsorbents for methylene blue (MB). The structure and morphology of the prepared hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), thermogravimetry (TG) and differential scanning calorimetry (DSC). Introducing graphene oxide and bentonite into the hydrogels evidently enhanced the thermal stability, swelling ability and MB adsorption capacity. The effects of initial concentration of MB, pH, contact time and temperature on MB adsorption capacity of the prepared hydrogels were investigated. Adsorption kinetics and equilibrium adsorption isotherm fitted pseudo-second-order kinetic model and Langmuir isotherm model well, respectively. After introducing graphene oxide and bentonite into the hydrogels, the maximum adsorption capacity calculated from the Langmuir isotherm model reached 172.14 mg/g at 30 °C, obviously higher than the hydrogels prepared without these additions (83.33 mg/g). Furthermore, all the prepared hydrogels also displayed good reusability for the efficient removal of MB. Consequently, the prepared hydrogels could be served as eco-friendly, stable, efficient and reusable adsorbents for anionic dyes in wastewater treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Kinetics and thermodynamics studies of silver ions adsorption onto coconut shell activated carbon.

PubMed

Silva-Medeiros, Flávia V; Consolin-Filho, Nelson; Xavier de Lima, Mateus; Bazzo, Fernando Previato; Barros, Maria Angélica S D; Bergamasco, Rosângela; Tavares, Célia R G

2016-12-01

The presence of silver in the natural water environment has been of great concern because of its toxicity, especially when it is in the free ion form (Ag(+)). This paper aims to study the adsorption kinetics of silver ions from an aqueous solution onto coconut shell activated carbon using batch methods. Batch kinetic data were fitted to the first-order model and the pseudo-second-order model, and this last equation fits correctly the experimental data. Equilibrium experiments were carried out at 30°C, 40°C, and 50°C. The adsorption isotherms were reasonably fit using Langmuir model, and the adsorption process was slightly influenced by changes in temperature. Thermodynamic parameters (ΔH°, ΔG°, and ΔS°) were determined. The adsorption process seems to be non-favorable, exothermic, and have an increase in the orderness.

Photoluminescence kinetics in CdS nanoclusters formed by the Langmuir-Blodgett technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zarubanov, A. A., E-mail: alexsundr@mail.ru; Zhuravlev, K. S.

2015-03-15

The photoluminescence kinetics in CdS nanocrystals produced by the Langmuir-Blodgett technique is studied at a temperature of 5 K. The photoluminescence kinetics is described by the sum of two exponential functions, with characteristic times of about 30 and 160 ns. It is found that the fast and slow decay times become longer, as the nanocrystal size increases. Analysis of the data shows that the fast decay time is controlled by trion recombination in nanocrystals with defects, whereas the slow decay time is controlled by the annihilation of optically inactive excitons in nanocrystals without defects. It is established that, as themore » nanocrystal size is decreased, the fraction of imperfect nanocrystals is reduced because of an increase in the energy of defect formation.« less

Carbonised jackfruit peel as an adsorbent for the removal of Cd(II) from aqueous solution.

PubMed

Inbaraj, B Stephen; Sulochana, N

2004-08-01

The fruit of the jack (Artocarpus heterophyllus) is one of the popular fruits in India, where the total area under this fruit is about 13,460 ha. A significant amount of peel (approximately 2,714-11,800 kg per tree per year) is discarded as agricultural waste, as apart from its use as a table fruit, it is popular in many culinary preparations. Treatment of jackfruit peel with sulphuric acid produced a carbonaceous product which was used to study its efficiency as an adsorbent for the removal of Cd(II) from aqueous solution. Batch experiments were performed as a function of process parameters; agitation time, initial metal concentration, adsorbent concentration and pH. Kinetic analyses made with Lagergren pseudo-first-order, Ritchie second-order and modified Ritchie second-order models showed better fits with modified Ritchie second-order model. The Langmuir-Freundlich (Sips equation) model best defined the experimental equilibrium data among the three isotherm models (Freundlich, Langmuir and Langmuir-Freundlich) tested. Taking a particular metal concentration, the optimum dose and pH required for the maximum metal removal was established. A complete recovery of the adsorbed metal ions from the spent adsorbent was achieved by using 0.01 M HCl.

Impacts of amount of impregnated iron in granular activated carbon on arsenate adsorption capacities and kinetics.

PubMed

Chang, Qigang; Lin, Wei; Ying, Wei-Chi

2012-06-01

Iron-impregnated granular activated carbons (Fe-GAC) can remove arsenic effectively from water. In this study, Fe-GACs with iron content of 1.64 to 28.90% were synthesized using a new multi-step procedure for the investigation of effects of iron amount on arsenic adsorption capacities and kinetics. Langmuir model satisfactorily fit arsenic adsorption on Fe-GACs. The maximum arsenic adsorption capacity (q(m)) increased significantly with iron impregnation and reached 1,867 to 1,912 microg/g with iron content of 9.96 to 13.59%. Further increase of iron content (> 13.59%) caused gradual decrease of q(m). It was found that the amount of impregnated iron showed little impact on the affinity for arsenate. Kinetic study showed that the amount of impregnated iron affected the arsenic intraparticle diffusion rate greatly. The pseudo-second-order kinetic model fit arsenic adsorption kinetics on Fe-GACs better than the pseudo-first-order model. The arsenic adsorption rate increased with increasing of iron content from 1.64% to 13.59%, and then decreased with more impregnated iron (13.59 to 28.90%).

APTES-modified mesoporous silicas as the carriers for poorly water-soluble drug. Modeling of diflunisal adsorption and release

NASA Astrophysics Data System (ADS)

Geszke-Moritz, Małgorzata; Moritz, Michał

2016-04-01

Four mesoporous siliceous materials such as SBA-16, SBA-15, PHTS and MCF functionalized with (3-aminopropyl)triethoxysilane were successfully prepared and applied as the carriers for poorly water-soluble drug diflunisal. Several techniques including nitrogen sorption analysis, XRD, TEM, FTIR and thermogravimetric analysis were employed to characterize mesoporous matrices. Adsorption isotherms were analyzed using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models. In order to find the best-fit isotherm for each model, both linear and nonlinear regressions were carried out. The equilibrium data were best fitted by the Langmuir isotherm model revealing maximum adsorption capacity of 217.4 mg/g for aminopropyl group-modified SBA-15. The negative values of Gibbs free energy change indicated that the adsorption of diflunisal is a spontaneous process. Weibull release model was employed to describe the dissolution profile of diflunisal. At pH 4.5 all prepared mesoporous matrices exhibited the improvement of drug dissolution kinetics as compared to the dissolution rate of pure diflunisal.

Synthesis and characterization of low-cost activated carbon prepared from Malawian baobab fruit shells by H3PO4 activation for removal of Cu(II) ions: equilibrium and kinetics studies

NASA Astrophysics Data System (ADS)

Vunain, Ephraim; Kenneth, Davie; Biswick, Timothy

2017-12-01

In this study, low-cost activated carbon (AC) prepared from baobab fruit shells by chemical activation using phosphoric acid was evaluated for the removal of Cu(II) ions from aqueous solution. The prepared activated carbon samples were characterized using N2-adsorption-desorption isotherms, SEM, FTIR, EDX and XRD analysis. The sample activated at 700 °C was chosen as our optimized sample because its physicochemical properties and BET results were similar to those of a commercial sample. The N2-adsorption-desorption results of the optimized sample revealed a BET surface area of 1089 m2/g, micropore volume of 0.3764 cm3/g, total pore volume of 0.4330 cm3/g and pore size of 1.45 nm. Operational parameters such as pH, initial copper concentration, contact time, adsorbent dosage and temperature were studied in a batch mode. Equilibrium data were obtained by testing the adsorption data using three different isotherm models: Langmuir, Freundlich and Dubinin-Radushkevish (D-R) models. It was found that the adsorption of copper correlated well with the Langmuir isotherm model with a maximum monolayer adsorption capacity of 3.0833 mg/g. The kinetics of the adsorption process was tested through pseudo-first-order and pseudo-second-order models. The pseudo-second-order kinetic model provided the best correlation for the experimental data studied. The adsorption followed chemisorption process. The study provided an effective use of baobab fruit shells as a valuable source of adsorbents for the removal of copper ions from aqueous solution. This study could add economic value to baobab fruit shells in Malawi, reduce disposal problems, and offer an economic source of AC to the AC users.

Removal of copper (II) ion from aqueous solution using zeolite Y synthesized from rice husk ash: Equilibrium and kinetic study

NASA Astrophysics Data System (ADS)

Tuyen, Nguyen Thi Kim; Nhan, Do Nguyen Thanh; Nhat, Trieu Thi; An, Ngo Thanh; Long, Nguyen Quang

2017-09-01

Zeolite Y was synthesized from silica of rice-husk ash using hydrothermal process. The crystalline structure FAU of zeolite Y was characterized by X-ray diffraction (XRD). Surface's area of the catalyst was determined by physic-adsorption method using BET model. The zeolite was examined for possibility of Cu2+ adsorbent by an ion-exchange mechanism. Various adsorption isotherm models, such as Langmuir, Freundlich and Dubinin-Radushkevich were tested for equilibrium study. The integration method was applied to find out the possible kinetic equation of the Cu2+ adsorption on the zeolite Y which obtained from cheap and locally available rice husk ash.

The effect of model fidelity on prediction of char burnout for single-particle coal combustion

DOE PAGES

McConnell, Josh; Sutherland, James C.

2016-07-09

In this study, practical simulation of industrial-scale coal combustion relies on the ability to accurately capture the dynamics of coal subprocesses while also ensuring the computational cost remains reasonable. The majority of the residence time occurs post-devolatilization, so it is of great importance that a balance between the computational efficiency and accuracy of char combustion models is carefully considered. In this work, we consider the importance of model fidelity during char combustion by comparing combinations of simple and complex gas and particle-phase chemistry models. Detailed kinetics based on the GRI 3.0 mechanism and infinitely-fast chemistry are considered in the gas-phase.more » The Char Conversion Kinetics model and nth-Order Langmuir–Hinshelwood model are considered for char consumption. For devolatilization, the Chemical Percolation and Devolatilization and Kobayashi-Sarofim models are employed. The relative importance of gasification versus oxidation reactions in air and oxyfuel environments is also examined for various coal types. Results are compared to previously published experimental data collected under laminar, single-particle conditions. Calculated particle temperature histories are strongly dependent on the choice of gas phase and char chemistry models, but only weakly dependent on the chosen devolatilization model. Particle mass calculations were found to be very sensitive to the choice of devolatilization model, but only somewhat sensitive to the choice of gas chemistry and char chemistry models. High-fidelity models for devolatilization generally resulted in particle temperature and mass calculations that were closer to experimentally observed values.« less

The effect of model fidelity on prediction of char burnout for single-particle coal combustion

DOE Office of Scientific and Technical Information (OSTI.GOV)

McConnell, Josh; Sutherland, James C.

In this study, practical simulation of industrial-scale coal combustion relies on the ability to accurately capture the dynamics of coal subprocesses while also ensuring the computational cost remains reasonable. The majority of the residence time occurs post-devolatilization, so it is of great importance that a balance between the computational efficiency and accuracy of char combustion models is carefully considered. In this work, we consider the importance of model fidelity during char combustion by comparing combinations of simple and complex gas and particle-phase chemistry models. Detailed kinetics based on the GRI 3.0 mechanism and infinitely-fast chemistry are considered in the gas-phase.more » The Char Conversion Kinetics model and nth-Order Langmuir–Hinshelwood model are considered for char consumption. For devolatilization, the Chemical Percolation and Devolatilization and Kobayashi-Sarofim models are employed. The relative importance of gasification versus oxidation reactions in air and oxyfuel environments is also examined for various coal types. Results are compared to previously published experimental data collected under laminar, single-particle conditions. Calculated particle temperature histories are strongly dependent on the choice of gas phase and char chemistry models, but only weakly dependent on the chosen devolatilization model. Particle mass calculations were found to be very sensitive to the choice of devolatilization model, but only somewhat sensitive to the choice of gas chemistry and char chemistry models. High-fidelity models for devolatilization generally resulted in particle temperature and mass calculations that were closer to experimentally observed values.« less

Biosorption of Cd(II) from aqueous solution using xanthated nano banana cellulose: equilibrium and kinetic studies.

PubMed

Pillai, Saumya S; Deepa, B; Abraham, Eldho; Girija, N; Geetha, P; Jacob, Laly; Koshy, Mathew

2013-12-01

Present study explored the biosorption capacity of xanthated nano banana cellulose (XNBC) for Cd(II) from aqueous solution. The biosorbent containing sulfur-bearing groups have a high affinity for heavy metals. Sulfur can be considered as a soft ligand group having strong affinity for cadmium. In the present study, the influence of various important parameters such as pH, time, biosorbent dose and initial Cd(II) concentration on the biosorption capacity were investigated. The maximum biosorption capacity of XNBC for Cd(II) was found to be 154.26 mg g⁻¹ at 298 K. The Cd(II) sorption of XNBC was confirmed by SEM-EDS and XRF analysis. The isotherms such as Langmuir, Freundlich, Redlich-Peterson and Tempkin were studied. The Langmuir and the Redlich-Peterson isotherms had been well fitted the biosorption of Cd(II) with xanthated nano banana cellulose. The kinetics of Cd(II) removal using XNBC was well explained by second-order kinetic model. The thermodynamic parameters were also evaluated from the biosorption measurements. Among the various desorbing agents tested, the desorbing efficiency was found to be maximum with 0.1 mol L⁻¹ HCl. It was found that XNBC is also suitable to be used under column operation. © 2013 Elsevier Inc. All rights reserved.

Individual and competitive adsorption of phenol and nickel onto multiwalled carbon nanotubes

PubMed Central

Abdel-Ghani, Nour T.; El-Chaghaby, Ghadir A.; Helal, Farag S.

2014-01-01

Individual and competitive adsorption studies were carried out to investigate the removal of phenol and nickel ions by adsorption onto multiwalled carbon nanotubes (MWCNTs). The carbon nanotubes were characterized by different techniques such as X-ray diffraction, scanning electron microscopy, thermal analysis and Fourier transformation infrared spectroscopy. The different experimental conditions affecting the adsorption process were investigated. Kinetics and equilibrium models were tested for fitting the adsorption experimental data. The characterization experimental results proved that the studied adsorbent possess different surface functional groups as well as typical morphological features. The batch experiments revealed that 300 min of contact time was enough to achieve equilibrium for the adsorption of both phenol and nickel at an initial adsorbate concentration of 25 mg/l, an adsorbent dosage of 5 g/l, and a solution pH of 7. The adsorption of phenol and nickel by MWCNTs followed the pseudo-second order kinetic model and the intraparticle diffusion model was quite good in describing the adsorption mechanism. The Langmuir equilibrium model fitted well the experimental data indicating the homogeneity of the adsorbent surface sites. The maximum Langmuir adsorption capacities were found to be 32.23 and 6.09 mg/g, for phenol and Ni ions, respectively. The removal efficiency of MWCNTs for nickel ions or phenol in real wastewater samples at the optimum conditions reached up to 60% and 70%, respectively. PMID:26257938

Ni(II) removal from aqueous solutions using cone biomass of Thuja orientalis.

PubMed

Malkoc, Emine

2006-09-21

The biomass of terrestrial-plant materials has high removal capacities for a number of heavy metal ions. The Ni(II) biosorption capacity of the cone biomass of Thuja orientalis was studied in the batch mode. The biosorption equilibrium level was determined as a function of contact time, pH, temperature, agitation speed at several initial metal ion and adsorbent concentrations. The removal of Ni(II) from aqueous solutions increased with adsorbent concentration, temperature and agitation speed of the solution were increased. The biosorption process was very fast; 90% of biosorption occurred within 3 min and equilibrium was reached at around 7 min. It is found that the biosorption of Ni(II) on the cone biomass was correlated well (R2 > 0.99) with the Langmuir equation as compared to Freundlich, BET Temkin and D-R isotherm equation under the concentration range studied. According to Langmuir isotherm, the monolayer saturation capacity (Q(o)) is 12.42 mg g(-1). The pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models were applied to test the experimental data for initial Ni(II) and cone biomass concentrations. The pseudo-second-order kinetic model provided the best correlation of the used experimental data compared to the pseudo-first-order and intraparticle diffusion kinetic models. The activation energy of biosorption (E(a)) was determined as 36.85 kJ mol(-1) using the Arrhenius equation. This study indicated that the cone biomass of T. orientalis can be used as an effective and environmentally friendly adsorbent for the treatment of Ni(II) containing aqueous solutions.

Fast removal of malachite green dye using novel superparamagnetic sodium alginate-coated Fe3O4 nanoparticles.

PubMed

Mohammadi, Abbas; Daemi, Hamed; Barikani, Mehdi

2014-08-01

In this study, superparamagnetic sodium alginate-coated Fe3O4 nanoparticles (Alg-Fe3O4) as a novel magnetic adsorbent were prepared by in situ coprecipitation method, in which Fe3O4 nanoparticles were precipitated from FeCl3 and FeCl2 under alkaline medium in the presence of sodium alginate. The Alg-Fe3O4 nanoparticles were used for removal of malachite green (MG) from aqueous solutions using batch adsorption technique. The characterization of synthesized nanoparticles was performed using XRD, FTIR, TEM, TGA and vibrating sample magnetometer (VSM) techniques. FTIR analysis of synthesized nanoparticles provided the evidence that sodium alginate was successfully coated on the surface of Fe3O4 nanoparticles. The FT-IR and TGA characterization showed that the Alg-Fe3O4 nanoparticles contained about 14% (w/w) of sodium alginate. Moreover, TEM analysis indicated that the average diameter of the Alg-Fe3O4 nanoparticles was about 12nm. The effects of adsorbent dosage, pH and temperature were investigated on the adsorption properties of MG onto Alg-Fe3O4 nanoparticles. The equilibrium adsorption data were modeled using the Langmuir and Freundlich isotherms. The maximum adsorption capacity obtained from Langmuir isotherm equation was 47.84mg/g. The kinetics of adsorption of MG onto Alg-Fe3O4 nanoparticles were investigated using the pseudo-first-order and pseudo-second-order kinetic models. The results showed that the adsorption of MG onto nanoparticles followed pseudo-second-order kinetic model. Copyright © 2014 Elsevier B.V. All rights reserved.

Adsorption of Pb(II) ions from aqueous environment using eco-friendly chitosan schiff's base@Fe3O4 (CSB@Fe3O4) as an adsorbent; kinetics, isotherm and thermodynamic studies.

PubMed

Weijiang, Zhang; Yace, Zhang; Yuvaraja, Gutha; Jiao, Xu

2017-12-01

Chitosan and its derivatives can be used to modify magnetic materials to promote the adsorption properties of the magnetic materials for the removal of meal ions. In this study a novel CSB@Fe 3 O 4 was prepared, characterized by XRD, FTIR, SEM, TEM, and VSM analysis and utilized as an adsorbent material for the removal of Pb(II) ions from aqueous solution. Batch studies were performed to evaluate the influences of various experimental parameters like pH, adsorbent dosage, contact time, initial concentration, and the effect of temperature. Optimum conditions for Pb(II) removal were found to be pH 5, adsorbent dosage 0.5g and equilibrium time of 105min. The pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to analyze kinetic data. The data fit well with the second-order kinetic model. The equilibrium data were analyzed using the Langmuir, and Freundlich isotherm models. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacity was found to be 83.33mg/g for CSB@Fe 3 O 4 . The calculated thermodynamic parameters ΔG°(-9.728, -9.034 and -7.883kJ/mol for 303, 313, and 323K), ΔH° (20.39kJ/mol) and ΔS° (0.0947J/molK) showed that the adsorption of Pb(II) ions were feasible, spontaneous and endothermic in nature. Copyright © 2017 Elsevier B.V. All rights reserved.

Modeling and Uncertainty Quantification of Vapor Sorption and Diffusion in Heterogeneous Polymers

DOE PAGES

Sun, Yunwei; Harley, Stephen J.; Glascoe, Elizabeth A.

2015-08-13

A high-fidelity model of kinetic and equilibrium sorption and diffusion is developed and exercised. The gas-diffusion model is coupled with a triple-sorption mechanism: Henry’s law absorption, Langmuir adsorption, and pooling or clustering of molecules at higher partial pressures. Sorption experiments are conducted and span a range of relative humidities (0-95%) and temperatures (30-60°C). Kinetic and equilibrium sorption properties and effective diffusivity are determined by minimizing the absolute difference between measured and modeled uptakes. Uncertainty quantification and sensitivity analysis methods are described and exercised herein to demonstrate the capability of this modeling approach. Water uptake in silica-filled and unfilled poly(dimethylsiloxane) networksmore » is investigated; however, the model is versatile enough to be used with a wide range of materials and vapors.« less

Novel biosynthesized silver nanoparticles from cobweb as adsorbent for Rhodamine B: equilibrium isotherm, kinetic and thermodynamic studies

NASA Astrophysics Data System (ADS)

Azeez, Luqmon; Lateef, Agbaje; Adebisi, Segun A.; Oyedeji, Abdulrasaq O.

2018-03-01

This study has investigated the adsorption of Rhodamine B (Rh-B) dye on novel biosynthesized silver nanoparticles (AgNPs) from cobweb. The effects of contact time, initial pH, initial dye concentration, adsorbent dosage and temperature were studied on the removal of Rh-B and they significantly affected its uptake. Adsorption isotherms were evaluated using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. The adsorption process was best described by Langmuir isotherm with R 2 of 0.9901, indicating monolayer adsorption. The maximum adsorption capacity ( q max) of 59.85 mg/g showed that it has relatively high performance, while adsorption intensity showed a favourable adsorption process. Pseudo-second-order kinetics fitted best the rate of adsorption and intra-particle diffusion revealed both surface adsorption and intra-particle diffusion-controlled adsorption process. Negative values of thermodynamic parameters (Δ H°, Δ S° and Δ G°) indicated an exothermic and spontaneous adsorption process. The mean sorption energy ( E) and activation energy ( E a) suggested the uptake of Rh-B onto AgNPs was chemical in nature (chemosorption).

Did Irving Langmuir Observe Langmuir Circulations?

NASA Astrophysics Data System (ADS)

D'Asaro, E. A.; Harcourt, R. R.; Shcherbina, A.; Thomson, J. M.; Fox-Kemper, B.

2012-12-01

Although surface waves are known to play an important role in mixing the upper ocean, the current generation of upper ocean boundary layer parameterizations does not include the explicit effects of surface waves. Detailed simulations using LES models which include the Craik-Leibovich wave-current interactions, now provide quantitative predictions of the enhancement of boundary layer mixing by waves. Here, using parallel experiments in Lake Washington and at Ocean Station Papa, we show a clear enhancement of vertical kinetic energy across the entire upper ocean boundary layer which can be attributed to surface wave effects. The magnitude of this effect is close to that predicted by LES models, but is not large, less than a factor of 2 on average, and increased by large Stokes drift and shallow mixed layers. Global estimates show the largest wave enhancements occur on the equatorial side of the westerlies in late Spring, due to the combination of large waves, shallow mixed layers and weak winds. In Lakes, however, the waves and the Craik-Leibovich interactions are weak, making it likely that the counter-rotating vortices famously observed by Irving Langmuir in Lake George were not driven by wave-current interactions.

Adsorption of tobacco-specific nitrosamine 4-(methylnitrosamino) -1- (3-pyridyl)-1-butanone from aqueous solution with graphene aerogel

NASA Astrophysics Data System (ADS)

Xu, T. G.; Shi, R.; Lu, N.; Zhang, J.; Bai, R. S.; Yang, Z. D.; Zhou, J.

2018-03-01

The adsorption behavior of graphene aerogel in the 4-(Methylnitrosamino)-1-(3-pryidyl)-1-butanone (NNK) aqueous solution was studied. The adsorption kinetics fitted pseudo-second-order model with the rate constant (k2) of 0.154 g/mg·h. The adsorption isotherm was investigated and fitted Langmuir and Freundlich models well, and the maximum adsorption capacity (qm) was 59.66 mg/g estimated from Langmuir isotherm. Thermodynamic result indicated that the process of adsorption of NNK onto graphene aerogel was spontaneous and exothermic. Higher pH solution was favorable for NNK adsorption on graphene aerogel. The adsorption for NNK on graphene aerogel arose from the π-π interaction between them, and the high adsorption efficiency was resulted from the -NO2 functional groups. The capability of graphene aerogel was maintained after repeated absorption-desorption cycles, which was benefit for convenient separating and recycling of graphene aerogel.

Study of the Kinetics and Equilibrium of the Adsorption of Oils onto Hydrophobic Jute Fiber Modified via the Sol-Gel Method.

PubMed

Lv, Na; Wang, Xiaoli; Peng, Shitao; Zhang, Huaqin; Luo, Lei

2018-05-12

A new kind of hydrophobic and oil sorbent based on jute fiber was successfully prepared by the integration of silica onto a fiber surface via the sol-gel method and subsequent hydrophobic modification with octadecyltrichlorosilane (OTS). Compared with the hydrophilic raw fiber, the modified fiber had a water contact angle (CA) of 136.2°, suggesting that the material has good hydrophobicity. Furthermore, the ability of oil in the oil/water system (taking diesel for example) to absorb was revealed by the kinetics, the isotherm equation, and the thermodynamic parameters. Adsorption behavior was kinetically investigated using pseudo first-order and pseudo second-order models. The data mostly correlated with the pseudo first-order model. The equilibrium adsorption at 298 K was assessed by using the Langmuir and Freundlich isotherm models. The Freundlich model had greater consistency with the experimental data. The obtained thermodynamic parameters demonstrate that the adsorption of diesel is spontaneous, favorable, and exothermic.

Photocatalytic degradation of p,p'-DDT under UV and visible light using interstitial N-doped TiO₂.

PubMed

Ananpattarachai, Jirapat; Kajitvichyanukul, Puangrat

2015-01-01

1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (or p,p'-DDT) is one of the most persistent pesticides. It is resistant to breakdown in nature and cause the water contamination problem. In this work, a major objective was to demonstrate the application of N-doped TiO2 in degradation and mineralization of the p,p'-DDT under UV and visible light in aqueous solution. The N-doped TiO2 nanopowders were prepared by a simple modified sol-gel procedure using diethanolamine (DEA) as a nitrogen source. The catalyst characteristics were investigated using XRD, SEM, TEM, and XPS. The adsorption and photocatalytic oxidation of p,p'-DDT using the synthesized N-doped TiO2 under UV and visible light were conducted in a batch photocatalytic experiment. The kinetics and p,p'-DDT degradation performance of the N-doped TiO2 were evaluated. Results show that the N-doped TiO2 can degrade p,p'-DDT effectively under both UV and visible lights. The rate constant of the p,p'-DDT degradation under UV light was only 0.0121 min(-1), whereas the rate constant of the p,p'-DDT degradation under visible light was 0.1282 min(-1). Under visible light, the 100% degradation of p,p'-DDT were obtained from N-doped TiO2 catalyst. The reaction rate of p,p'-DDT degradation using N-doped TiO2 under visible light was sixfold higher than that under UV light. According to Langmuir-Hinshelwood model, the adsorption equilibrium constant (K) for the N-doped TiO2 under visible light was 0.03078 L mg(-1), and the apparent reaction rate constant (k) was 1.3941 mg L(-1)-min. Major intermediates detected during the p,p'-DDT degradation were p,p'-DDE, o,p'-DDE, p,p'-DDD and p,p'-DDD. Results from this work can be applied further for the breakdown of p,p'-DDT molecule in the real contaminated water using this technology.

Adsorption Properties of Low-Cost Biomaterial Derived from Prunus amygdalus L. for Dye Removal from Water

PubMed Central

Deniz, Fatih

2013-01-01

The capability of Prunus amygdalus L. (almond) shell for dye removal from aqueous solutions was investigated and methyl orange was used as a model compound. The effects of operational parameters including pH, ionic strength, adsorbent concentration and mesh size, dye concentration, contact time, and temperature on the removal of dye were evaluated. The adsorption kinetics conformed to the pseudo-second-order kinetic model. The equilibrium data pointed out excellent fit to the Langmuir isotherm model with maximum monolayer adsorption capacity of 41.34 mg g−1 at 293 K. Thermodynamic analysis proved a spontaneous, favorable, and exothermic process. It can be concluded that almond shell might be a potential low-cost adsorbent for methyl orange removal from aqueous media. PMID:23935442

Removal of three nitrophenols from aqueous solutions by adsorption onto char ash: equilibrium and kinetic modeling

NASA Astrophysics Data System (ADS)

Magdy, Yehia M.; Altaher, Hossam; ElQada, E.

2018-03-01

In this research, the removal of 2,4 dinitrophenol, 2 nitrophenol and 4 nitrophenol from aqueous solution using char ash from animal bones was investigated using batch technique. Three 2-parameter isotherms (Freundlich, Langmuir, and Temkin) were applied to analyze the experimental data. Both linear and nonlinear regression analyses were performed for these models to estimate the isotherm parameters. Three 3-parameter isotherms (Redlich-Peterson, Sips, Toth) were also tested. Moreover, the kinetic data were tested using pseudo-first order, pseudo-second order, Elovich, Intraparticle diffusion and Boyd methods. Langmuir adsorption isotherm provided the best fit for the experimental data indicating monolayer adsorption. The maximum adsorption capacity was 8.624, 7.55, 7.384 mg/g for 2 nitrophenol, 2,4 dinitrophenol, and 4 nitrophenol, respectively. The experimental data fitted well to pseudo-second order model suggested a chemical nature of the adsorption process. The R 2 values for this model were 0.973 up to 0.999. This result with supported by the Temkin model indicating heat of adsorption to be greater than 10 kJ/mol. The rate controlling step was intraparticle diffusion for 2 nitrophenol, and a combination of intraparticle diffusion and film diffusion for the other two phenols. The pH and temperature of solution were found to have a considerable effect, and the temperature indicated the exothermic nature of the adsorption process. The highest adsorption capacity was obtained at pH 9 and 25 °C.

Efficacy of mangrove leaf powder for bioremediation of chromium (VI) from aqueous solutions: kinetic and thermodynamic evaluation

NASA Astrophysics Data System (ADS)

Sathish, Thadikamala; Vinithkumar, N. V.; Dharani, G.; Kirubagaran, R.

2015-06-01

Biosorption of heavy metals by bio-materials has been posited as a potential alternative to the existing physicochemical technologies for detoxification and recovery of toxic and valuable metals from wastewaters. In this context, the role of mangrove leaf powder (MLP) as biosorbent for chromium removal was investigated. In the present study, the effect of process parameters such as particle size, solution pH, initial concentration of Cr(VI) ion and adsorbent dose on chromium removal by MLP was investigated. The maximum sorption was observed at particle size 0.5 mm and pH 2.0. The adsorption data follow the pseudo second-order kinetics model. The isotherms denote that Langmuir model is the best fitted than Freundlich model. The maximum adsorption capacity ( Q 0) of 60.24 mg/g of Cr(VI) at 30 min on MLP was determined using the Langmuir model. The adsorption isotherm model indicates that the chromium is adsorbing as monolayer on the surface of MLP with heterogeneous energetic distribution of active sites. Various thermodynamic parameters, such as Gibb's free energy (∆ G °), enthalpy (∆ H °) and entropy (∆ S °) have been calculated. The thermodynamic data revealed that the adsorption of chromium ions onto MLP is endothermic in nature and a spontaneous process. The results of the present study suggest that MLP is an effective bioremediation measure for removal of high concentration of Cr(VI) in waste waters.

Biosorption of Cu(II) ions by cellulose of cabbage waste as biosorbent from agricultural waste

NASA Astrophysics Data System (ADS)

Heraldy, Eddy; Wireni, Lestari, Witri Wahyu

2016-02-01

Biosorption on lignocellulosic wastes has been identified as an appropriate alternative technology to remove heavy metal ions from wastewater. The purpose of this research was to study the ability of cabbage waste biosorbent prepared from agricultural waste on biosorption of Cu(II). Cabbage waste biosorbent was activated with sodium hydroxide at concentration 0.1 M. The biosorption optimum conditions were studied with initial pH (2-8), biosorbent dosage (0.2-1) g/L, contact time (15-90) minutes, and metal ion concentrations (10-100) mg/L by batch method. Experimental data were analyzed in terms of two kinetic models such as pseudo-first-order and pseudo-second-order models. Langmuir and Freundlich isotherm models were applied to describe the biosorption process. The results showed that cabbage biosorbent activated by 0.1 M sodium hydroxide enhanced the biosorption capacity from 9,801 mg/g to 12,26 mg/g. The FTIR spectra have shown a typical absorption of cellulose and typical absorption of lignin decrease after activation process. The kinetic biosorption was determined to be appropriate to the pseudo-second order model with constant rate of 0,091 g/mg.min, and the biosorption equilibrium was described well by the Langmuir isotherm model with maximum biosorption capacity of 37.04 mg/g for Cu(II) at pH 5, biosorption proses was spontaneous in nature with biosorption energy 25.86 kJ/mol at 302 K.

Synthesis, characterization and study of sorption parameters of multi-walled carbon nanotubes/chitosan nanocomposite for the removal of picric acid from aqueous solutions.

PubMed

Khakpour, Roghayeh; Tahermansouri, Hasan

2018-04-01

The modification of carboxylated multi-wall carbon nanotubes (MWCNT-COOH) with chitosan (Chi) has been investigated to prepare a nanocomposite material (MWCNT-Chi) for the removal of picric acid from aqueous solutions. Materials were characterized by FT-IR, TGA, DTG, FESEM, EDX, BET and zeta potential. Batch experiments such as solution pH, dosage of adsorbents, contact time, concentration of the picric acid and temperature were achieved to study sorption process. Kinetic studies were well described by pseudo-second-order kinetic model for both adsorbents. The six isotherm models: Langmuir (four linear forms), Freundlich, Tempkin, Halsey, Harkins-Jura and Dubinin-Radushkevich models were applied to determine the characteristic parameters of the adsorption process. Isotherm studies showed that the Langmuir isotherm for MWCNT-Chi and Freundlich and Halsey models for both adsorbents were found to best represent the measured sorption data. In addition, the results of Dubinin-Radushkevich model confirmed the physical adsorption. Negative ΔG° values for MWCNT-Chi and positive ones for MWCNT-COOH indicated the nature of spontaneous and unspontaneous, respectively for adsorption process in the range of the studied concentrations. In addition, picric acid molecules can be desorbed from MWCNT-Chi up to 90% at pH = 9 and that the consumed MWCNT-Chi could be reutilized up to 5th cycle of regeneration. Copyright © 2017 Elsevier B.V. All rights reserved.

Molecular features of nonionic detergents involved in the binding kinetics and solubilization efficiency, as studied in model (Langmuir films) and biological (Erythrocytes) membranes.

PubMed

Casadei, Bruna Renata; Domingues, Cleyton Crepaldi; Clop, Eduardo M; Couto, Verônica Muniz; Perillo, Maria Angelica; de Paula, Eneida

2018-06-01

The effect of the nonionic detergents Brij-98 and Brij-58 over human erythrocytes was studied through quantitative hemolysis and in Langmuir films. Hemolytic tests revealed that Brijs are stronger membrane solubilizers than Triton X-100 (TX-100), with effective detergent/lipid ratios of 0.18 and 0.37 for Brij-98 and Brij-58, respectively. Experiments with Langmuir films provided significant information on the kinetics and thermodynamics of detergent-membrane interaction. The adsorption (k a ) and desorption (k d ) rate constants of Brijs were lower than those of TX-100. In the case of k a , that is probably due to their larger hydrophilic head (with twice (20) the oxyethylene units of TX-100). As for the thermodynamic binding constant, the linear and longer hydrophobic acyl chains of Brijs favor their stabilization in-between the lipids, through London van der Waals forces. Consequently, K b,m values of Brij-98 (12,500 M -1 ) and Brij-58 (19,300 M -1 ) resulted higher than TX-100 (7500 M -1 ), in agreement with results from the hemolytic tests. Furthermore, Brij-58 binds with higher affinity than Brij-98 to bilayers and monolayers, despite its shorter (palmitic) hydrocarbon chain, showing that unsaturation restrains the detergent insertion into these environments. Our results provide significant information about the mechanism of interaction between Brijs and membranes, supporting their distinct solubilization effect. Copyright © 2018 Elsevier B.V. All rights reserved.

Application of activated carbon derived from scrap tires for adsorption of Rhodamine B.

PubMed

Li, Li; Liu, Shuangxi; Zhu, Tan

2010-01-01

Activated carbon derived from solid hazardous waste scrap tires was evaluated as a potential adsorbent for cationic dye removal. The adsorption process with respect to operating parameters was investigated to evaluate the adsorption characteristics of the activated pyrolytic tire char (APTC) for Rhodamine B (RhB). Systematic research including equilibrium, kinetics and thermodynamic studies was performed. The results showed that APTC was a potential adsorbent for RhB with a higher adsorption capacity than most adsorbents. Solution pH and temperature exert significant influence while ionic strength showed little effect on the adsorption process. The adsorption equilibrium data obey Langmuir isotherm and the kinetic data were well described by the pseudo second-order kinetic model. The adsorption process followed intra-particle diffusion model with more than one process affecting the adsorption process. Thermodynamic study confirmed that the adsorption was a physisorption process with spontaneous, endothermic and random characteristics.

Insight into biosorption equilibrium, kinetics and thermodynamics of crystal violet onto Ananas comosus (pineapple) leaf powder

NASA Astrophysics Data System (ADS)

Chakraborty, Sagnik; Chowdhury, Shamik; Saha, Papita Das

2012-06-01

Biosorption performance of pineapple leaf powder (PLP) for removal of crystal violet (CV) from its aqueous solutions was investigated. To this end, the influence of operational parameters such as pH, biosorbent dose, initial dye concentration and temperature were studied employing a batch experimental setup. The biosorption process followed the Langmuir isotherm model with high correlation coefficients ( R 2 > 0.99) at different temperatures. The maximum monolayer biosorption capacity was found to be 78.22 mg g-1 at 293 K. The kinetic data conformed to the pseudo-second-order kinetic model. The activation energy of the system was calculated as 58.96 kJ mol- 1 , indicating chemisorption nature of the ongoing biosorption process. A thermodynamic study showed spontaneous and exothermic nature of the biosorption process. Owing to its low cost and high dye uptake capacity, PLP has potential for application as biosorbent for removal of CV from aqueous solutions.

Ammonium Removal from Aqueous Solutions by Clinoptilolite: Determination of Isotherm and Thermodynamic Parameters and Comparison of Kinetics by the Double Exponential Model and Conventional Kinetic Models

PubMed Central

Tosun, İsmail

2012-01-01

The adsorption isotherm, the adsorption kinetics, and the thermodynamic parameters of ammonium removal from aqueous solution by using clinoptilolite in aqueous solution was investigated in this study. Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich (D-R)) and four three-parameter (Redlich-Peterson (R-P), Sips, Toth and Khan) isotherm models. D-R and R-P isotherms were the models that best fitted to experimental data over the other two- and three-parameter models applied. The adsorption energy (E) from the D-R isotherm was found to be approximately 7 kJ/mol for the ammonium-clinoptilolite system, thereby indicating that ammonium is adsorbed on clinoptilolite by physisorption. Kinetic parameters were determined by analyzing the nth-order kinetic model, the modified second-order model and the double exponential model, and each model resulted in a coefficient of determination (R2) of above 0.989 with an average relative error lower than 5%. A Double Exponential Model (DEM) showed that the adsorption process develops in two stages as rapid and slow phase. Changes in standard free energy (∆G°), enthalpy (∆H°) and entropy (∆S°) of ammonium-clinoptilolite system were estimated by using the thermodynamic equilibrium coefficients. PMID:22690177

Ammonium removal from aqueous solutions by clinoptilolite: determination of isotherm and thermodynamic parameters and comparison of kinetics by the double exponential model and conventional kinetic models.

PubMed

Tosun, Ismail

2012-03-01

The adsorption isotherm, the adsorption kinetics, and the thermodynamic parameters of ammonium removal from aqueous solution by using clinoptilolite in aqueous solution was investigated in this study. Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich (D-R)) and four three-parameter (Redlich-Peterson (R-P), Sips, Toth and Khan) isotherm models. D-R and R-P isotherms were the models that best fitted to experimental data over the other two- and three-parameter models applied. The adsorption energy (E) from the D-R isotherm was found to be approximately 7 kJ/mol for the ammonium-clinoptilolite system, thereby indicating that ammonium is adsorbed on clinoptilolite by physisorption. Kinetic parameters were determined by analyzing the nth-order kinetic model, the modified second-order model and the double exponential model, and each model resulted in a coefficient of determination (R(2)) of above 0.989 with an average relative error lower than 5%. A Double Exponential Model (DEM) showed that the adsorption process develops in two stages as rapid and slow phase. Changes in standard free energy (∆G°), enthalpy (∆H°) and entropy (∆S°) of ammonium-clinoptilolite system were estimated by using the thermodynamic equilibrium coefficients.

Cu (II) binded chitosan/Fe3O4 nanocomomposite as a new biosorbent for efficient and selective removal of phosphate.

PubMed

Zavareh, Siamak; Behrouzi, Zahra; Avanes, Armen

2017-08-01

The aim of this study was to develop a chitosan-based magnetic adsorbent for selective and effective removal of phosphate from aqueous solutions. For this purpose, Cu-chitosan/Fe 3 O 4 nanocomposite was prepared using a facile method and characterized. The prepared adsorbent exhibited more porous surface with higher specific area compared to neat chitosan based on SEM and BET studies. The FTIR and EDX studies indicated the presence of Cu(II) bonded to the adsorbent surface. Crystalline properties of the adsorbent were also studied using XRD. Experimental isotherm data were fitted to nonlinear forms of Langmuir and Freunlich models. The maximum capacity for the modified adsorbent was calculated to be 88mg P 2 O 5 /g, much higher than that for neat chitosan and chitosan/Fe 3 O 4 according to the Langmuir isotherm. The adsorption by the modified adsorbent had fast kinetics and obeyed pseudo-second-order kinetic model. Interestingly, the maximum removal efficiency for the modified adsorbent was observed in neutral pH values, pHs of natural waters. A high selectivity against natural waters common anions as well as good regeneration ability was obtained for the introduced adsorbent. Copyright © 2017 Elsevier B.V. All rights reserved.

Biosorption of Hexavalent Chromium from Aqueous Medium with Opuntia Biomass

PubMed Central

2014-01-01

The biosorption of hexavalent chromium from aqueous solutions by Opuntia cladodes and ectodermis from cactus fruits was investigated. Both types of biomass are considered low-cost, natural, and ecofriendly biosorbents. Batch experiments were carried out to determine Cr(VI) biosorption capacity and the efficiency of the biosorption process under different pH, initial Cr(VI) concentration, and sorbent dosage. The biosorption of Cr(VI) by Opuntia biomass was highly pH dependent, favoring higher metal uptake at low pH. The higher biosorption capacity was exhibited at pH 2. The optimal conditions were obtained at a sorbent dosage of 1 g L−1 and initial metal concentration of 10 mg L−1. Biosorption kinetic data were properly fitted with the pseudo-second-order kinetic model. The rate constant, the initial biosorption rate, and the equilibrium biosorption capacity were determined. The experimental equilibrium data obtained were analyzed using two-parameter isotherm models (Langmuir, Freundlich, and Temkin). The Langmuir maximum monolayer biosorption capacity (q max) was 18.5 mg g−1 for cladodes and 16.4 mg g−1 for ectodermis. The results suggest that Opuntia biomass could be considered a promising low-cost biosorbent for the ecofriendly removal of Cr(VI) from aqueous systems. PMID:24982975

Protein adsorption on electrospun zinc doped hydroxyapatite containing nylon 6 membrane: kinetics and isotherm.

PubMed

Esfahani, Hamid; Prabhakaran, Molamma P; Salahi, Esmaeil; Tayebifard, Ali; Keyanpour-Rad, Mansour; Rahimipour, Mohamad Reza; Ramakrishna, Seeram

2015-04-01

Surface modification of electrospun polymeric membrane surfaces is a critical step towards the separation process including protein adsorption. In this study, the electrospun Nylon fibers was incorporated with positively charged zinc doped hydroxyapatite (HAp) nanoparticles to study the adsorption of negatively charged proteins, namely bovine serum albumin (BSA). Effects of zinc amount within the atomic structure of HAp (nZH; n=0, 4, 8 At.%) was evaluated on produced scaffolds and consequently protein adsorption. The results showed that the ability of Nylon membrane to adsorb BSA increased with incorporation of nZH nanoparticles within the nylon structure. This phenomenon is appeared to be relate to different electrostatic charge and not to physical characteristic of scaffolds. The incorporated membrane (N-4ZH) by nanoparticles with highest zeta (ξ) potential adsorbed the maximum amount of protein. The adsorption of BSA was best fitted with pseudo-second order kinetic model. The experimental isotherm data were further analyzed by using Langmuir and Freundlich equations. By comparing the correlation coefficients obtained for each linear transformation of isotherm analysis, it was found that the Langmuir equation was the best fit equilibrium model that described the adsorption of BSA on these membranes. Copyright © 2014 Elsevier Inc. All rights reserved.

Low cost biosorbent "banana peel" for the removal of phenolic compounds from olive mill wastewater: kinetic and equilibrium studies.

PubMed

Achak, M; Hafidi, A; Ouazzani, N; Sayadi, S; Mandi, L

2009-07-15

The aim of this work is to determine the potential of application of banana peel as a biosorbent for removing phenolic compounds from olive mill wastewaters. The effect of adsorbent dosage, pH and contact time were investigated. The results showed that the increase in the banana peel dosage from 10 to 30 g/L significantly increased the phenolic compounds adsorption rates from 60 to 88%. Increase in the pH to above neutrality resulted in the increase in the phenolic compounds adsorption capacity. The adsorption process was fast, and it reached equilibrium in 3-h contact time. The Freundlich and Langmuir adsorption models were used for mathematical description of the adsorption equilibrium and it was found that experimental data fitted very well to both Freundlich and Langmuir models. Batch adsorption models, based on the assumption of the pseudo-first-order, pseudo-second-order and intraparticle diffusion mechanism, showed that kinetic data follow closely the pseudo-second-order than the pseudo-first-order and intraparticle diffusion. Desorption studies showed that low pH value was efficient for desorption of phenolic compounds. These results indicate clearly the efficiency of banana peel as a low-cost solution for olive mill wastewaters treatment and give some preliminary elements for the comprehension of the interactions between banana peel as a bioadsorbent and the very polluting compounds from the olive oil industry.

Synthesis, characterization and trivalent arsenic sorption potential of Ce-Al nanostructured mixed oxide

NASA Astrophysics Data System (ADS)

Bhattacharya, S.; Gupta, K.; Ghosh, U. C.

2017-04-01

Arsenic contamination in the ground water has serious health consequences in many parts of the world. The surface sorption method for arsenic mitigation has been widely investigated due to its simple method, inexpensive operation, highly efficient and low content of by-products. In the present study, nanostructured hydrated cerium aluminum oxide (NHCAO) was synthesized and characterized and its arsenic (III) sorption behavior from the aqueous solution was studied. The material was characterized in SEM, FE-SEM, TEM, AFM, XRD, and FT-IR. Batch method was used for the kinetics of As (III) sorption on nanoparticles at 303 (± 1.6) K and at pH 7.0 (± 0.2). The experiments on isotherm subject were performed individually at 288K, 303K, 318K temperatures at pH 7.0 (± 0.2) using the batch sorption method. In the kinetics study of arsenic (III) sorption, the sorption percentage was observed to remain nearly unchanged up to pH 9.0, thereafter only slight reduction in sorption percentage. The equilibrium sorption results were tested using the models of Langmuir and the Freundlich isotherm. The Langmuir model is the most fitted model for the sorption reaction. NHCAO was highly efficient in As(III) removal out of the water in the extensive range of pH and could be used for arsenic removal from contaminated water.

Abiotic uptake of gases by organic soils

NASA Astrophysics Data System (ADS)

Smagin, A. V.

2007-12-01

Methodological and experimental studies of the abiotic uptake of gaseous substances by organic soils were performed. The static adsorption method of closed vessels for assessing the interaction of gases with the solid and liquid soil phases and the dynamic method of determining the sorption isotherms of gases by soils were analyzed. The theoretical substantiation of the methods and their practical implementations on the basis of a PGA-7 portable gas analyzer (Russia) were considered. Good agreement between the equilibrium sorption isotherms of the gases and the Langmuir model was revealed; for the real ranges of natural gas concentrations, this model can be reduced to the linear Henry equation. The limit values of the gas sorption (Langmuir monolayer capacity) are typical for dry samples; they vary from 670 4000 g/m3 for methane and oxygen to 20 000 25 000 g/m3 for carbon dioxide. The linear distribution coefficients of gases between the solid and gas phases of organic soils (Henry constants) are 8 18 units for poorly sorbed gases (O2, CH4) and 40 60 units for CO2. The kinetics of the chemicophysical uptake of gases by the soil studied is linear in character and obeys the relaxation kinetic model of the first order with the corresponding relaxation constants, which vary from 1 h -1 in wet samples to 10 h -1 in dry samples.

Biosorption of neodymium on Chlorella vulgaris in aqueous solution obtained from hard disk drive magnets

PubMed Central

Kucuker, Mehmet Ali; Wieczorek, Nils; Kuchta, Kerstin; Copty, Nadim K.

2017-01-01

In recent years, biosorption is being considered as an environmental friendly technology for the recovery of rare earth metals (REE). This study investigates the optimal conditions for the biosorption of neodymium (Nd) from an aqueous solution derived from hard drive disk magnets using green microalgae (Chlorella vulgaris). The parameters considered include solution pH, temperature and biosorbent dosage. Best-fit equilibrium as well as kinetic biosorption models were also developed. At the optimal pH of 5, the maximum experimental Nd uptakes at 21, 35 and 50°C and an initial Nd concentration of 250 mg/L were 126.13, 157.40 and 77.10 mg/g, respectively. Analysis of the optimal equilibrium sorption data showed that the data fitted well (R2 = 0.98) to the Langmuir isotherm model, with maximum monolayer coverage capacity (qmax) of 188.68 mg/g, and Langmuir isotherm constant (KL) of 0.029 L/mg. The corresponding separation factor (RL) is 0.12 indicating that the equilibrium sorption was favorable. The sorption kinetics of Nd ion follows well a pseudo-second order model (R2>0.99), even at low initial concentrations. These results show that Chlorella vulgaris has greater biosorption affinity for Nd than activated carbon and other algae types such as: A. Gracilis, Sargassum sp. and A. Densus. PMID:28388641

Remediation of phosphate-contaminated water by electrocoagulation with aluminium, aluminium alloy and mild steel anodes.

PubMed

Vasudevan, Subramanyan; Lakshmi, Jothinathan; Jayaraj, Jeganathan; Sozhan, Ganapathy

2009-05-30

The present study provides an electrocoagulation process for the remediation of phosphate-contaminated water using aluminium, aluminium alloy and mild steel as the anodes and stainless steel as the cathode. The various parameters like effect of anode materials, effect of pH, concentration of phosphate, current density, temperature and co-existing ions, and so forth, and the adsorption capacity was evaluated using both Freundlich and Langmuir isotherm models. The adsorption of phosphate preferably fitting the Langmuir adsorption isotherm suggests monolayer coverage of adsorbed molecules. The results showed that the maximum removal efficiency of 99% was achieved with aluminium alloy anode at a current density of 0.2 A dm(-2), at a pH of 7.0. The adsorption process follows second-order kinetics.

Equilibrium and kinetic adsorption study of a cationic dye by a natural adsorbent--silkworm pupa.

PubMed

Noroozi, B; Sorial, G A; Bahrami, H; Arami, M

2007-01-02

In this work the use of silkworm pupa, which is the waste of silk spinning industries has been investigated as an adsorbent for the removal of C.I. Basic Blue 41. The amino acid nature of the pupa provided a reasonable capability for dye removal. Equilibrium adsorption isotherms and kinetics were investigated. The adsorption equilibrium data were analyzed by using various adsorption isotherm models and the results have shown that adsorption behavior of the dye could be described reasonably well by either Langmuir or Freundlich models. The characteristic parameters for each isotherm have been determined. The monolayer adsorption capacity was determined to be 555 mg/g. Kinetic studies indicated that the adsorption follows pseudo-second-order kinetics with a rate constant of 0.0434 and 0.0572 g/min mg for initial dye concentration of 200 mg/l at 20 and 40 degrees C, respectively. Kinetic studies showed that film diffusion and intra-particle diffusion were simultaneously operating during the adsorption process. The rate constant for intra-particle diffusion was estimated to be 1.985 mg/g min(0.5).

Modification of porous starch for the adsorption of heavy metal ions from aqueous solution.

PubMed

Ma, Xiaofei; Liu, Xueyuan; Anderson, Debbie P; Chang, Peter R

2015-08-15

Porous starch xanthate (PSX) and porous starch citrate (PSC) were prepared in anticipation of the attached xanthate and carboxylate groups respectively forming chelation and electrostatic interactions with heavy metal ions in the subsequent adsorption process. The lead(II) ion was selected as the model metal and its adsorption by PSX and PSC was characterized. The adsorption capacity was highly dependent on the carbon disulfide/starch and citric acid/starch mole ratios used during preparation. The adsorption behaviors of lead(II) ion on PSXs and PSCs fit both the pseudo-second-order kinetic model and the Langmuir isotherm model. The maximum adsorption capacity from the Langmuir isotherm equation reached 109.1 and 57.6 mg/g for PSX and PSC when preparation conditions were optimized, and the adsorption times were just 20 and 60 min, respectively. PSX and PSC may be used as effective adsorbents for removal of heavy metals from contaminated liquid. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Importance of tunneling in H-abstraction reactions by OH radicals. The case of CH4 + OH studied through isotope-substituted analogs

NASA Astrophysics Data System (ADS)

Lamberts, T.; Fedoseev, G.; Kästner, J.; Ioppolo, S.; Linnartz, H.

2017-03-01

We present a combined experimental and theoretical study focussing on the quantum tunneling of atoms in the reaction between CH4 and OH. The importance of this reaction pathway is derived by investigating isotope substituted analogs. Quantitative reaction rates needed for astrochemical models at low temperature are currently unavailable both in the solid state and in the gas phase. Here, we study tunneling effects upon hydrogen abstraction in CH4 + OH by focusing on two reactions: CH4 + OD → CH3 + HDO and CD4 + OH → CD3 + HDO. The experimental study shows that the solid-state reaction rate RCH4 + OD is higher than RCD4 + OH at 15 K. Experimental results are accompanied by calculations of the corresponding unimolecular and bimolecular reaction rate constants using instanton theory taking into account surface effects. For the work presented here, the unimolecular reactions are particularly interesting as these provide insight into reactions following a Langmuir-Hinshelwood process. The resulting ratio of the rate constants shows that the H abstraction (kCH4 + OD) is approximately ten times faster than D-abstraction (kCD4 + OH) at 65 K. We conclude that tunneling is involved at low temperatures in the abstraction reactions studied here. The unimolecular rate constants can be used by the modeling community as a first approach to describe OH-mediated abstraction reactions in the solid phase. For this reason we provide fits of our calculated rate constants that allow the inclusion of these reactions in models in a straightforward fashion.

Surface wave effects in the NEMO ocean model: Forced and coupled experiments

NASA Astrophysics Data System (ADS)

Breivik, Øyvind; Mogensen, Kristian; Bidlot, Jean-Raymond; Balmaseda, Magdalena Alonso; Janssen, Peter A. E. M.

2015-04-01

The NEMO general circulation ocean model is extended to incorporate three physical processes related to ocean surface waves, namely the surface stress (modified by growth and dissipation of the oceanic wavefield), the turbulent kinetic energy flux from breaking waves, and the Stokes-Coriolis force. Experiments are done with NEMO in ocean-only (forced) mode and coupled to the ECMWF atmospheric and wave models. Ocean-only integrations are forced with fields from the ERA-Interim reanalysis. All three effects are noticeable in the extratropics, but the sea-state-dependent turbulent kinetic energy flux yields by far the largest difference. This is partly because the control run has too vigorous deep mixing due to an empirical mixing term in NEMO. We investigate the relation between this ad hoc mixing and Langmuir turbulence and find that it is much more effective than the Langmuir parameterization used in NEMO. The biases in sea surface temperature as well as subsurface temperature are reduced, and the total ocean heat content exhibits a trend closer to that observed in a recent ocean reanalysis (ORAS4) when wave effects are included. Seasonal integrations of the coupled atmosphere-wave-ocean model consisting of NEMO, the wave model ECWAM, and the atmospheric model of ECMWF similarly show that the sea surface temperature biases are greatly reduced when the mixing is controlled by the sea state and properly weighted by the thickness of the uppermost level of the ocean model. These wave-related physical processes were recently implemented in the operational coupled ensemble forecast system of ECMWF.

Citric acid modified kenaf core fibres for removal of methylene blue from aqueous solution.

PubMed

Sajab, Mohd Shaiful; Chia, Chin Hua; Zakaria, Sarani; Jani, Saad Mohd; Ayob, Mohd Khan; Chee, Kah Leong; Khiew, Poi Sim; Chiu, Wee Siong

2011-08-01

Chemically modified kenaf core fibres were prepared via esterification in the presence of citric acid (CA). The adsorption kinetics and isotherm studies were carried out under different conditions to examine the adsorption efficiency of CA-treated kenaf core fibres towards methylene blue (MB). The adsorption capacity of the kenaf core fibres increased significantly after the citric acid treatment. The values of the correlation coefficients indicated that the Langmuir isotherm fitted the experimental data better than the Freundlich isotherm. The maximum adsorption capacity of the CA-treated kenaf core fibres was found to be 131.6mg/g at 60°C. Kinetic models, pseudo-first-order, pseudo-second-order and intraparticle diffusion, were employed to describe the adsorption mechanism. The kinetic data were found to fit pseudo-second-order model equation as compared to pseudo-first-order model. The adsorption of MB onto the CA-treated kenaf core fibres was spontaneous and endothermic. Copyright © 2011 Elsevier Ltd. All rights reserved.

Kinetics and equilibrium models for the sorption of tributyltin to nZnO, activated carbon and nZnO/activated carbon composite in artificial seawater.

PubMed

Ayanda, Olushola S; Fatoki, Olalekan S; Adekola, Folahan A; Ximba, Bhekumusa J

2013-07-15

The removal of tributyltin (TBT) from artificial seawater using nZnO, activated carbon and nZnO/activated carbon composite was systematically studied. The equilibrium and kinetics of adsorption were investigated in a batch adsorption system. Equilibrium adsorption data were analyzed using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) isotherm models. Pseudo first- and second-order, Elovich, fractional power and intraparticle diffusion models were applied to test the kinetic data. Thermodynamic parameters such as ΔG°, ΔS° and ΔH° were also calculated to understand the mechanisms of adsorption. Optimal conditions for the adsorption of TBT from artificial seawater were then applied to TBT removal from natural seawater. A higher removal efficiency of TBT (>99%) was obtained for the nZnO/activated carbon composite material and for activated carbon but not for nZnO. Copyright © 2013 Elsevier Ltd. All rights reserved.

Chlorinated phenol removal from aqueous media by tea (Camellia sinensis) leaf waste tailored activated carbon

NASA Astrophysics Data System (ADS)

Joseph, C. G.; Anisuzzaman, S. M.; Daud, W. M. A. W.; Krishnaiah, D.; Ng, K. A.

2017-06-01

In this study, activated carbons (ACs) wereprepared from tea leaves by using a two-stage self-generated atmosphere method. The process was done by semi-carbonizing the precursor at 300 °C for 1 h, followed by the impregnation of the resulting char at 85 °C for 4 h and finally activation at 500 °C for 2 h. The semi-carbonised samples were impregnated with different ratios of zinc chloride (ZnCl2) and their physicochemical effect was studied. The prepared ACs underwent several aspects of both, chemical and physical characterizations, such as the percentage of yield, moisture content, ash content, pH, porosity, adsorption capacity of 2,4-dichlorophenol (2,4-DCP), surface area, porosity, morphology and surface chemistry studies. It was found that sample AC2, with an impregnation ratio of 2:1 was the best AC produced in this study. The maximum Brunauer, Emmett and Teller surface area of AC2 was found to be 695 m2/g. Langmuir, Freundlich and Temkin isotherm models were used to examine the experimental isotherms while the kinetic data was analyzed using the pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. The 2,4-DCP adsorption isotherm results complied well to the Langmuir isotherm for the equilibrium data while the adsorption kinetic data fitted well to the pseudo-second order model, indicating that chemisorption by valency forces via the sharing (covalent bond) or exchanging of electrons between the AC and the 2,4-DCP molecules were mainly responsible for the adsorption process. From these findings, it is concluded that tea leaves can be used as a low cost precursor for the removal of 2,4-DCP in aqueous medium.

Conversion of waste FGD gypsum into hydroxyapatite for removal of Pb²⁺ and Cd²⁺ from wastewater.

PubMed

Yan, Yubo; Dong, Xiaoli; Sun, Xiaolei; Sun, Xiuyun; Li, Jiansheng; Shen, Jinyou; Han, Weiqing; Liu, Xiaodong; Wang, Lianjun

2014-09-01

Flue gas desulfurization (FGD) gypsum, a familiar waste generated from coal-fired power plants, was successfully transformed to hydroxyapatite (FGD-HAP) by hydrothermal method. The obtained FGD-HAP was characterized by XRD, FTIR, TEM and BET methods and investigated as adsorbent for removal of Pb(2+) and Cd(2+) from wastewater. Batch experiments were performed by varying the pH values, contact time and initial metal concentration. The result of pH impact showed that the adsorption of two ions was pH dependent process, and the pH 5.0-6.0 was found to be the optimum condition. The achieved experimental data were analyzed with various kinetic and isotherm models. The kinetic studies displayed that the pseudo-second order kinetic model could describe adsorption processes well with high correlation coefficient, and the Langmuir isotherm model provided the best fit to the equilibrium experimental data. The maximum adsorption capacities calculated from Langmuir equation were 277.8 and 43.10mg/g for Pb(2+) and Cd(2+), respectively, which can compete with other adsorbents. The thermodynamic parameters revealed the adsorption processes were endothermic and spontaneous in nature. In binary adsorption, the amount of Cd(2+) adsorbed on FGD-HAP decreased by 46.0% with increasing concentration of Pb(2+), which was higher than that of Pb(2+)(21.7%), demonstrating the stronger affinity between FGD-HAP and Pb(2+). The highest amount of Pb(2+) and Cd(2+) desorbed from saturated FGD-HAP by EDTA solution confirmed the FGD-HAP was a promising alternative adsorbent in treatment of toxic Pb(2+) and Cd(2+) wastewater. Copyright © 2014 Elsevier Inc. All rights reserved.

Photocatalysis of sub-ppm limonene over multiwalled carbon nanotubes/titania composite nanofiber under visible-light irradiation.

PubMed

Jo, Wan-Kuen; Kang, Hyun-Jung

2015-01-01

This study was conducted under visible-light exposure to investigate the photocatalytic characteristics of a multiwalled carbon nanotube/titania (TiO2) composite nanofiber (MTCN) using a continuous-flow tubular reactor. The MTCN was prepared by a sol-gel process, followed by an electrospinning technique. The photocatalytic decomposition efficiency for limonene on the MTCN was higher than those obtained from reference TiO2 nanofibers or P25 TiO2, and the experimental results agreed well with the Langmuir-Hinshelwood model. The CO concentrations generated during the photocatalysis did not reach levels toxic to humans. The mineralization efficiency for limonene on the MTCN was also higher than that for P25 TiO2. Moreover, the mineralization efficiency obtained using the MTCN increased steeply from 8.3 to 91.1% as the residence time increased from 7.8 to 78.0s, compared to the increase in the decomposition efficiencies for limonene from 90.1 to 99.9%. Three gas-phase intermediates (methacrolein, acetic acid, and limonene oxide) were quantitatively determined for the photocatalysis for limonene over the MTCN, whereas only two intermediates (acetic acid and limonene oxide) were quantitatively determined over P25 TiO2. Other provisional gas-phase intermediates included cyclopropyl methyl ketone and 2-ethylbutanal. Copyright © 2014 Elsevier B.V. All rights reserved.

Solid surface photochemistry of montmorillonite: mechanisms for the arsenite oxidation under UV-A irradiation.

PubMed

Yuan, Yanan; Wang, Yajie; Ding, Wei; Li, Jinjun; Wu, Feng

2016-01-01

Transformation of inorganic arsenic species has drawn great concern in recent decades because of worldwide and speciation-dependent pollution and the hazards that they pose to the environment and to human health. As(III) photooxidation in aquatic systems has received much attention, but little is known about photochemical transformation of arsenic species on top soil. As(III) photooxidation on natural montmorillonite under UV-A radiation was investigated by using a moisture- and temperature-controlled photochemical chamber with two black-light lamps. Initial As(III) concentration, pH, layer thickness, humic acid (HA) concentration, the presence of additional iron ions, and the contribution of reactive oxygen species (ROS) were examined. The results show that pH values of the clay layers greatly influenced As(III) photooxidation on montmorillonite. As(III) photooxidation followed the Langmuir-Hinshelwood model. HA and additional iron ions greatly promoted photooxidation, but excess Fe(II) competed with As(III) for oxidation by ROS. Scavenging experiments revealed that natural montmorillonite induced the conversion of As(III) to As(V) by generating ROS (mainly HO(•) and HO2(•)/O2(•-)) and that HO(•) radical was the predominant oxidant in this system. Our work demonstrates that photooxidation on the surface of natural clay minerals in top soil can be important to As(III) transformation. This allows understanding and predicting the speciation and behavior of arsenic on the soil surface.

Evaluation of the individuality of white rot macro fungus for the decolorization of synthetic dye.

PubMed

Pandey, Priyanka; Singh, Ram Praksh; Singh, Kailash Nath; Manisankar, Paramasivam

2013-01-01

A biosorbent was developed by simple dried Agaricus bisporus (SDAB) and effectively used for the biosorption of cationic dyes, Crystal Violet and Brilliant Green. For the evaluation of the biosorbent system, all the batch equilibrium parameters like pH, biomass dose, contact time, and temperature were optimized to determine the decolorization efficiency of the biosorbent. The maximum yields of dye removal were achieved at pH 4.0 for Crystal Violet (CV) and pH 5.0 for Brilliant Green (BG), which are closer to their natural pH also. Equilibrium was established at 60 and 40 min for CV and BG, respectively. Pseudo first-order, pseudo second-order, and intraparticle-diffusion kinetic models were studied at different temperatures. Isotherm models such as Freundlich, Langmuir, and Dubinin-Radushkevich were also studied. Biosorption processes were successfully described by Langmuir isotherm model and the pseudo second-order kinetic model. The biosorption capacity of A. bisporus over CV and BG were found as 21.74 and 12.16 mg gm(-1). Thermodynamic parameters indicated that the CV and BG dye adsorption onto A. bisporus is spontaneous and exothermic in the single and ternary systems. Scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy were used for the surface morphology, crystalline structure of biosorbent, and dye-biosorbent interaction, respectively. This analysis of the biosorption data confirmed that these biosorption processes are ecofriendly and economical. Thus, this biomass system may be useful for the removal of contaminating cationic dyes.

Single Pd Atoms on θ-Al2O3 (010) Surface do not Catalyze NO Oxidation.

PubMed

Narula, Chaitanya K; Allard, Lawrence F; Moses-DeBusk, Melanie; Stocks, G Malcom; Wu, Zili

2017-04-03

New convenient wet-chemistry synthetic routes have made it possible to explore catalytic activities of a variety of single supported atoms, however, the single supported atoms on inert substrates (e.g. alumina) are limited to adatoms and cations of Pt, Pd, and Ru. Previously, we have found that single supported Pt atoms are remarkable NO oxidation catalysts. In contrast, we report that Pd single atoms are completely inactive for NO oxidation. The diffuse reflectance infra-red spectroscopy (DRIFTS) results show the absence of nitrate formation on catalyst. To explain these results, we explored modified Langmuir-Hinshelwood type pathways that have been proposed for oxidation reactions on single supported atom. In the first pathway, we find that there is energy barrier for the release of NO 2 which prevent NO oxidation. In the second pathway, our results show that there is no driving force for the formation of O=N-O-O intermediate or nitrate on single supported Pd atoms. The decomposition of nitrate, if formed, is an endothermic event.

A review of carbon-based and non-carbon-based catalyst supports for the selective catalytic reduction of nitric oxide.

PubMed

Anthonysamy, Shahreen Binti Izwan; Afandi, Syahidah Binti; Khavarian, Mehrnoush; Mohamed, Abdul Rahman Bin

2018-01-01

Various types of carbon-based and non-carbon-based catalyst supports for nitric oxide (NO) removal through selective catalytic reduction (SCR) with ammonia are examined in this review. A number of carbon-based materials, such as carbon nanotubes (CNTs), activated carbon (AC), and graphene (GR) and non-carbon-based materials, such as Zeolite Socony Mobil-5 (ZSM-5), TiO 2 , and Al 2 O 3 supported materials, were identified as the most up-to-date and recently used catalysts for the removal of NO gas. The main focus of this review is the study of catalyst preparation methods, as this is highly correlated to the behaviour of NO removal. The general mechanisms involved in the system, the Langmuir-Hinshelwood or Eley-Riedeal mechanism, are also discussed. Characterisation analysis affecting the surface and chemical structure of the catalyst is also detailed in this work. Finally, a few major conclusions are drawn and future directions for work on the advancement of the SCR-NH 3 catalyst are suggested.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Xingchen; Salahub, Dennis R.

There is no doubt that a huge gap exists in understanding heterogeneous catalysis between a cluster model of a few atoms and a bulk model of periodic slabs. Nanoparticles, which are crucial in heterogeneous catalysis in industry, lie in the middle of the gap. We present here our work on the computational modelling of molybdenum carbide nanoparticles (MCNPs) as the catalysts for the upgrading of oil sands in the in-situ environment, using benzene hydrogenation as a model reaction. With a cluster model, efforts were first made to understand the mechanism of the reaction with a density functional theory (DFT) studymore » on the adsorption of benzene and its hydrogenation product – cyclohexane, as well as the cyclic hydrogenation reaction intermediates on the Mo{sub 2}C(0001) surface. From the thermodynamic data, along with literature information, it was found that the benzene hydrogenation reaction on molybdenum carbide happens most likely through a Langmuir-Hinshelwood mechanism with the gradual lifting up of the benzene molecule. The electron localization function (ELF) was then used to help understand the nature of the interactions between the MCNPs, identifying strong multi-center interactions between the adsorbates and the MCNPs. To enable the treatment of larger nanoparticles, a fast semi-empirical density functional tight-binding (DFTB) method was parameterized. With this method, the potential energy profiles of benzene hydrogenation reactions on different sizes of MCNPs are calculated. The study was then extended to consider a MCNP embedded in solvent (benzene), using a quantum mechanical (DFTB) / molecular mechanical approach. Calculations on the free energies profiles with the umbrella sampling method show that the entropy of the MCNPs and the solvent are essential in understanding the catalytic activity of the transition metal related nanoparticles for solid/liquid heterogeneous catalysis.« less

Adsorptive performance of MOF nanocomposite for methylene blue and malachite green dyes: Kinetics, isotherm and mechanism.

PubMed

Alqadami, Ayoub Abdullah; Naushad, Mu; Alothman, Z A; Ahamad, Tansir

2018-06-06

In the present study, Fe 3 O 4 @AMCA-MIL-53(Al) nanocomposite was utilized for the adsorptive removal of highly toxic MB and MG dyes from aqueous environment. The batch adsorption tests were performed at different contact time, pH, Fe 3 O 4 @AMCA-MIL-53(Al) dose, initial concentration of dyes and temperature. The maximum adsorption capacity of MB and MG dyes onto of Fe 3 O 4 @AMCA-MIL-53(Al) using Langmuir equation was 1.02 and 0.90 m mol/g, respectively. The isotherm and kinetic studies revealed that adsorption data were well fitted to Langmuir isotherm and pseudo-first-order kinetics models. Various thermodynamic parameters were also calculated and interpreted. The positive and negative values of ΔH° and ΔG° indicated that the adsorption was endothermic and spontaneous, respectively. The adsorptive binding of MB and MG on Fe 3 O 4 @AMCA-MIL53(Al) nanocomposite was directed by carboxylate and amide groups through electrostatic interaction, π-π interaction and hydrogen bonding. The desorption of both dyes from Fe 3 O 4 @AMCA-MIL-53(Al) was also performed using mixed solution of 0.01 M HCl/ethanol. Thus, we conclude that the Fe 3 O 4 @AMCA-MIL-53(Al) was an outstanding material for the removal of dyes from aqueous environment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Thermodynamic and kinetic studies of biosorption of iron and manganese from aqueous medium using rice husk ash

NASA Astrophysics Data System (ADS)

Adekola, F. A.; Hodonou, D. S. S.; Adegoke, H. I.

2016-11-01

The adsorption behavior of rice husk ash with respect to manganese and iron has been studied by batch methods to consider its application for water and waste water treatment. The optimum conditions of adsorption were determined by investigating the effect of initial metal ion concentration, contact time, adsorbent dose, pH value of aqueous solution and temperature. Adsorption equilibrium time was observed at 120 min. The adsorption efficiencies were found to be pH dependent. The equilibrium adsorption experimental data were found to fit the Langmuir, Freundlich and Temkin isotherms for iron, but fitted only Langmuir isotherm for manganese. The pseudo-second order kinetic model was found to describe the manganese and iron kinetics more effectively. The thermodynamic experiment revealed that the adsorption processes involving both metals were exothermic. The adsorbent was finally applied to typical raw water with initial manganese and iron concentrations of 3.38 mg/l for Fe and 6.28 mg/l, respectively, and the removal efficiency was 100 % for Mn and 70 % for Fe. The metal ions were desorbed from the adsorbent using 0.01 M HCl, it was found to quantitatively remove 67 and 86 % of Mn and Fe, respectively, within 2 h. The results revealed that manganese and iron are considerably adsorbed on the adsorbent and could be an economic method for the removal of these metals from aqueous solutions.

Kafirin adsorption on ion-exchange resins: isotherm and kinetic studies.

PubMed

Kumar, Prashant; Lau, Pei Wen; Kale, Sandeep; Johnson, Stuart; Pareek, Vishnu; Utikar, Ranjeet; Lali, Arvind

2014-08-22

Kafirin is a natural, hydrophobic and celiac safe prolamin protein obtained from sorghum seeds. Today kafirin is found to be useful in designing delayed delivery systems and coatings of pharmaceuticals and nutraceuticals where its purity is important and this can be obtained by adsorptive chromatography. This study is the first scientific insight into the isotherm and kinetic studies of kafirin adsorption on anion- and cation-exchange resins for practical applications in preparative scale chromatography. Adsorption isotherms of kafirin were determined for five anion- and two cation-exchange resins in batch systems. Isotherm parameters such as maximum binding capacity and dissociation constant were determined from Langmuir isotherm, and adsorptive capacity and affinity constant from Freundlich isotherm. Langmuir isotherm was found to fit the adsorption equilibrium data well. Batch uptake kinetics for kafirin adsorption on these resins was also carried out and critical parameters including the diffusion coefficient, film mass transfer coefficient, and Biot number for film-pore diffusion model were calculated. Both the isotherm and the kinetic parameters were considered for selection of appropriate resin for kafirin purification. UNOsphere Q (78.26 mg/ml) and Toyopearl SP-650M (57.4 mg/ml) were found to offer better kafirin binding capacities and interaction strength with excellent uptake kinetics under moderate operating conditions. With these adsorbents, film diffusion resistance was found to be major governing factor for adsorption (Bi<10 and δ<1). Based on designer objective function, UNOsphere Q was found be best adsorbent for binding of kafirin. The data presented is valuable for designing large scale preparative adsorptive chromatographic kafirin purification systems. Copyright © 2014 Elsevier B.V. All rights reserved.

Removal and recovery of vanadium from alkaline steel slag leachates with anion exchange resins.

PubMed

Gomes, Helena I; Jones, Ashley; Rogerson, Mike; Greenway, Gillian M; Lisbona, Diego Fernandez; Burke, Ian T; Mayes, William M

2017-02-01

Leachable vanadium (V) from steel production residues poses a potential environmental hazard due to its mobility and toxicity under the highly alkaline pH conditions that characterise these leachates. This work aims to test the efficiency of anion exchange resins for vanadium removal and recovery from steel slag leachates at a representative average pH of 11.5. Kinetic studies were performed to understand the vanadium sorption process. The sorption kinetics were consistent with a pseudo-first order kinetic model. The isotherm data cannot differentiate between the Langmuir and Freundlich models. The maximum adsorption capacity (Langmuir value q max ) was 27 mg V g -1 resin. In column anion exchange, breakthrough was only 14% of the influent concentration after passing 90 L of steel slag leachate with 2 mg L -1 V through the column. When eluting the column 57-72% of vanadium was recovered from the resin with 2 M NaOH. Trials on the reuse of the anion exchange resin showed it could be reused 20 times without loss of efficacy, and on average 69% of V was recovered during regeneration. The results document for the first time the use of anion exchange resins to remove vanadium from steel slag leachate. As an environmental contaminant, removal of V from leachates may be an obligation for long-term management requirements of steel slag repositories. Vanadium removal coupled with the recovery can potentially be used to offset long-term legacy treatment costs. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Competitive adsorption of textile dyes using peat: adsorption equilibrium and kinetic studies in monosolute and bisolute systems.

PubMed

Sepulveda, L; Troncoso, F; Contreras, E; Palma, C

2008-09-01

The purpose of this study is to investigate the adsorption by peat of four reactive textile dyes with the following commercial names: Yellow CIBA WR 200% (Y), Dark Blue CIBA WR (DB), Navy CIBA WB (N), and Red CIBA WB 150% (R), used in a cotton-polyester fabric finishing plant. The decolorization levels obtained varied between 5% and 30%, and the most significant variables were pH and ionic strength. Equilibrium studies were carried out at pH 2.8 and temperature of 25 degrees C. Maximum adsorption capacities were between 15 and 20 mg g(-1). Experimental data were fitted to the models of Langmuir. The equilibrium studies for bisolute systems were DB-R and Y-N mixtures. The Langmuir extended model indicated that there is competition for adsorption sites and without interaction between dyes. The results of the kinetic adsorption studies on monosolute and bisolute systems were fitted to the film-pore diffusion, variable diffusivity and quasi-stationary models. They showed that the diffusivity coefficients obtained varied between 2.0 x 10(-8) and 8.5 x 10(-8) cm2s(-1) when the variable diffusivity mass transfer model (VDM) was used and effective diffusion coefficient was fitted between 3.3 x 10(-7) and 56.0 x 10(-7) cm2s(-1) for the film-pore diffusion model (FPDM). The root of average of squares relative error obtained varied between 0.8% and 47.0% for the VDM and FPDM models, respectively.

One-step synthesized calcium phosphate-based material for the removal of alizarin S dye from aqueous solutions: isothermal, kinetics, and thermodynamics studies

NASA Astrophysics Data System (ADS)

Adeogun, Abideen Idowu; Babu, Ramesh Balakrishnan

2015-07-01

Calcium phosphate hydroxyapatite (Ca-Hap) synthesized from CaCO3 and H3PO5, it was characterized by scanning electron microscopy, Fourier transform infrared, and X-ray diffraction. The Ca-Hap was used for the removal of Alizarin Red S dye from its aqueous solution. The kinetics, equilibrium, and thermodynamic of the adsorption of the dye onto the Ca-Hap were investigated. The effects of contact time, initial dye concentration, pH as well as temperature on adsorption capacity of Ca-Hap were studied. Experimental data were analyzed using six model equations: Langmuir, Freudlinch, Redlich-Peterson, Temkin, Dubinin-Radushkevich, and Sips isotherms and it was found that the data fitted well with Sips and Dubinin-Radushkevich isotherm models. Pseudo-first-order, pseudo-second-order, Elovic, and Avrami kinetic models were used to test the experimental data in order to elucidate the kinetic adsorption process and it was found that pseudo-second-order model best fit the data. The calculated thermodynamics parameters (∆G°, ∆H° and ∆S°) indicated that the process is spontaneous and endothermic in nature.

Coalesced chitosan activated carbon composite for batch and fixed-bed adsorption of cationic and anionic dyes.

PubMed

Auta, M; Hameed, B H

2013-05-01

A renewable waste tea activated carbon (WTAC) was coalesced with chitosan to form composite adsorbent used for waste water treatment. Adsorptive capacities of crosslinked chitosan beads (CCB) and its composite (WTAC-CCB) for Methylene blue dye (MB) and Acid blue 29 (AB29) were evaluated through batch and fixed-bed studies. Langmuir, Freundlich and Temkin adsorption isotherms were tested for the adsorption process and the experimental data were best fitted by Langmuir model and least by Freundlich model; the suitability of fitness was adjudged by the Chi-square (χ(2)) and Marquadt's percent standard deviation error functions. Judging by the values of χ(2), pseudo-second-order reaction model best described the adsorption process than pseudo-first-order kinetic model for MB/AB29 on both adsorbents. After five cycles of adsorbents desorption test, more than 50% WTAC-CCB adsorption efficiency was retained while CCB had <20% adsorption efficiency. The results of this study revealed that WTAC-CCB composite is a promising adsorbent for treatment of anionic and cationic dyes in effluent wastewaters. Copyright © 2012 Elsevier B.V. All rights reserved.

Semi-aerobic stabilized landfill leachate treatment by ion exchange resin: isotherm and kinetic study

NASA Astrophysics Data System (ADS)

Zamri, Mohd Faiz Muaz Ahmad; Kamaruddin, Mohamad Anuar; Yusoff, Mohd Suffian; Aziz, Hamidi Abdul; Foo, Keng Yuen

2017-05-01

This study was carried out to investigate the treatability of ion exchange resin (Indion MB 6 SR) for the removal of chromium (VI), aluminium (III), zinc (II), copper (II), iron (II), and phosphate (PO4)3-, chemical oxygen demand (COD), ammonia nitrogen (NH3-N) and colour from semi-aerobic stabilized leachate by batch test. A range of ion exchange resin dosage was tested towards the removal efficiency of leachate parameters. It was observed that equilibrium data were best represented by the Langmuir model for metal ions and Freundlich was ideally fit for COD, NH3-N and colour. Intra particle diffusion model, pseudo first-order and pseudo second-order isotherm models were found ideally fit with correlation of the experimental data. The findings revealed that the models could describe the ion exchange kinetic behaviour efficiently, which further suggests comprehensive outlook for the future research in this field.

Microwave-assisted polyol synthesis and characterization of pvp-capped cds nanoparticles for the photocatalytic degradation of tartrazine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Darwish, Maher, E-mail: m-darwish@razi.tums.ac.ir; Mohammadi, Ali, E-mail: alimohammadi@tums.ac.ir; Nanotechnology Research Centre, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran

2016-02-15

Highlights: • PVP-stabilized CdS nanoparticles have been fabricated by a polyol-microwave method. • CdS nanoparticles were characterized and the size was approximately 48 ± 10 nm. • Catalytic activity of our nanoparticles was examined for tartrazine degradation. • Remarkable results were obtained under both UV and visible light irradiations. - Abstract: Polyvinylpyrrolidone capped cadmium sulfide nanoparticles have been successfully synthesized by a facile polyol method with ethylene glycol. Microwave irradiation and calcination were used to control the size and shape of nanoparticles. Characterization with scanning electron microscopy revealed a restricted nanoparticles growth comparing with the uncapped product, hexagonal phase andmore » 48 nm average particle size were confirmed by X-ray diffraction, and finally mechanism of passivation was suggested depending on Fourier transform infrared spectra. The efficiency of nanoparticles was evaluated by the photocatalytic degradation of tartrazine in aqueous solution under UVC and visible light irradiation. Complete degradation of the dye was observed after 90 min of UVC irradiation under optimized conditions. Kinetic of reaction fitted well to the pseudo-first-order kinetic and Langmuir–Hinshelwood models. Furthermore, 85% degradation of the dye in 9 h under visible light suggests that cadmium sulfide is a promising tool to work under visible light for environmental remediation.« less

Heavy metals binding properties of esterified lemon.

PubMed

Arslanoglu, Hasan; Altundogan, Hamdi Soner; Tumen, Fikret

2009-05-30

Sorption of Cd(2+), Cr(3+), Cu(2+), Ni(2+), Pb(2+) and Zn(2+) onto a carboxyl groups-rich material prepared from lemon was investigated in batch systems. The results revealed that the sorption is highly pH dependent. Sorption kinetic data indicated that the equilibrium was achieved in the range of 30-240 min for different metal ions and sorption kinetics followed the pseudo-second-order model for all metals studied. Relative sorption rate of various metal cations was found to be in the general order of Ni(2+)>Cd(2+)>Cu(2+)>Pb(2+)>Zn(2+)>Cr(3+). The binding characteristics of the sorbent for heavy metal ions were analyzed under various conditions and isotherm data was accurately fitted to the Langmuir equation. The metal binding capacity order calculated from Langmuir isotherm was Pb(2+)>Cu(2+)>Ni(2+)>Cd(2+)>Zn(2+)>Cr(3+). The mean free energy of metal sorption process calculated from Dubinin-Radushkevich parameter and the Polanyi potential was found to be in the range of 8-11 kJ mol(-1) for the metals studied showing that the main mechanism governing the sorption process seems to be ion exchange. The basic thermodynamic parameters of metals ion sorption process were calculated by using the Langmuir constants obtained from equilibration study. The DeltaG degrees and DeltaH degrees values for metals ion sorption on the lemon sorbent showed the process to be spontaneous and exothermic in nature. Relatively low DeltaH degrees values revealed that physical adsorption significantly contributed to the mechanism.

Adsorptive Removal of Toxic Chromium from Waste-Water Using Wheat Straw and Eupatorium adenophorum

PubMed Central

Song, Dagang; Pan, Kaiwen; Tariq, Akash; Azizullah, Azizullah; Sun, Feng; Li, Zilong; Xiong, Qinli

2016-01-01

Environmental pollution with heavy metals is a serious issue worldwide posing threats to humans, animals and plants and to the stability of overall ecosystem. Chromium (Cr) is one of most hazardous heavy metals with a high carcinogenic and recalcitrant nature. Aim of the present study was to select low-cost biosorbent using wheat straw and Eupatorium adenophorum through simple carbonization process, capable of removing Cr (VI) efficiently from wastewater. From studied plants a low cost adsorbent was prepared for removing Cr (VI) from aqueous solution following very simple carbonization method excluding activation process. Several factors such as pH, contact time, sorbent dosage and temperature were investigated for attaining ideal condition. For analysis of adsorption equilibrium isotherm data, Langmuir, Freundlich and Temkin models were used while pseudo-first-order, pseudo-second-order, external diffusion and intra-particle diffusion models were used for the analysis of kinetic data. The obtained results revealed that 99.9% of Cr (VI) removal was observed in the solution with a pH of 1.0. Among all the tested models Langmuir model fitted more closely according to the data obtained. Increase in adsorption capacity was observed with increasing temperature revealing endothermic nature of Cr (VI). The maximum Cr (VI) adsorption potential of E. adenophorum and wheat straw was 89.22 mg per 1 gram adsorbent at 308K. Kinetic data of absorption precisely followed pseudo-second-order model. Present study revealed highest potential of E. adenophorum and wheat straw for producing low cost adsorbent and to remove Cr (VI) from contaminated water. PMID:27911906

Adsorptive Removal of Toxic Chromium from Waste-Water Using Wheat Straw and Eupatorium adenophorum.

PubMed

Song, Dagang; Pan, Kaiwen; Tariq, Akash; Azizullah, Azizullah; Sun, Feng; Li, Zilong; Xiong, Qinli

2016-01-01

Environmental pollution with heavy metals is a serious issue worldwide posing threats to humans, animals and plants and to the stability of overall ecosystem. Chromium (Cr) is one of most hazardous heavy metals with a high carcinogenic and recalcitrant nature. Aim of the present study was to select low-cost biosorbent using wheat straw and Eupatorium adenophorum through simple carbonization process, capable of removing Cr (VI) efficiently from wastewater. From studied plants a low cost adsorbent was prepared for removing Cr (VI) from aqueous solution following very simple carbonization method excluding activation process. Several factors such as pH, contact time, sorbent dosage and temperature were investigated for attaining ideal condition. For analysis of adsorption equilibrium isotherm data, Langmuir, Freundlich and Temkin models were used while pseudo-first-order, pseudo-second-order, external diffusion and intra-particle diffusion models were used for the analysis of kinetic data. The obtained results revealed that 99.9% of Cr (VI) removal was observed in the solution with a pH of 1.0. Among all the tested models Langmuir model fitted more closely according to the data obtained. Increase in adsorption capacity was observed with increasing temperature revealing endothermic nature of Cr (VI). The maximum Cr (VI) adsorption potential of E. adenophorum and wheat straw was 89.22 mg per 1 gram adsorbent at 308K. Kinetic data of absorption precisely followed pseudo-second-order model. Present study revealed highest potential of E. adenophorum and wheat straw for producing low cost adsorbent and to remove Cr (VI) from contaminated water.

Influence of physical state on the ozonolysis of shikimic acid

NASA Astrophysics Data System (ADS)

Steimer, Sarah; Krieger, Ulrich; Lampimäki, Markus; Peter, Thomas; Ammann, Markus

2014-05-01

Atmospheric aerosols are an important focus of environmental research due to their effect on climate, air quality and human health. They undergo continuous transformation, changing their physical and chemical properties. Recent findings show that secondary organic aerosol (SOA) particles can form amorphous solids and semi-solids under atmospheric conditions [1]. Since such physical states are highly viscous, diffusivity within the bulk decreases. The decrease in mass transport could slow down chemical reactions, thereby increasing the lifetime of the organic compounds involved. First indications of such behavior were recently shown for reaction of thin protein films with ozone [2], formation of organonitrogen from ammonia uptake to α-pinene secondary organic material [3] and reaction of SOA-coated benzo[a]pyrene with ozone [4]. In this study, we investigated the influence of physical state on the ozonolysis of shikimic acid. Said carboxylic acid is a constituent of biomass burning aerosols and used here as a proxy for oxygenated organic material. Its viscosity was adjusted by varying the humidity of the system between 0% and 92% RH, assuming correlation between the two parameters since water acts as a plasticizer. The system was probed with three complementary techniques: an electrodynamic balance (EDB), measuring the response of single particles to changes in humidity, coated wall flow tube measurements, where uptake of ozone is measured via loss from the gas phase and in situ X-ray microspectroscopy on single particles, where oxidation of the bulk can be observed. Additionally, a kinetic model was used to facilitate data analysis. EDB measurements showed clear evidence of humidity dependent glass formation and correlation of water content and water diffusivity. The dependence of the ozonolysis on relative humidity was observed with both flow tube and microspectroscopy measurements. The coated wall flow tube experiments showed a long term, gradually changing ozone uptake over more than 15 hours, the magnitude of which varied over nearly two orders between lowest and highest humidity. It was possible to separate the uptake into two distinct kinetic regimes, the first of which displayed a Langmuir-Hinshelwood type behavior regarding the ozone gas phase concentration. Microspectroscopy showed that the speed at which the characteristic double bond peak of shikimic acid disappeared was humidity dependent. The measured dependence of the reaction kinetics on humidity supports the hypothesis that the uptake coefficient is highly dependent on the diffusion coefficients of ozone and/or shikimic acid in the organic film. [1] Virtanen, A., et al., An amorphous solid state of biogenic secondary organic aerosol particles. Nature, 2010. 467(7317): p. 824-827. [2] Shiraiwa, M., et al., Gas uptake and chemical aging of semisolid organic aerosol particles. Proceedings of the National Academy of Sciences of the United States of America, 2011. 108(27): p. 11003-11008. [3] Kuwata, M. and Martin, S. T., Phase of atmospheric secondary organic material affects its reactivity. Proceedings of the National Academy of Sciences of the United States of America, 109(43): p. 17354-17359. [4] Zhou, S., et al., Kinetic limitations in gas-particle reactions arising from slow diffusion in secondary organic aerosol. Faraday Discussions, 2013. 165: p. 391-406.

Kinetics, isothermal and thermodynamics studies of electrocoagulation removal of basic dye rhodamine B from aqueous solution using steel electrodes

NASA Astrophysics Data System (ADS)

Adeogun, Abideen Idowu; Balakrishnan, Ramesh Babu

2017-07-01

Electrocoagulation was used for the removal of basic dye rhodamine B from aqueous solution, and the process was carried out in a batch electrochemical cell with steel electrodes in monopolar connection. The effects of some important parameters such as current density, pH, temperature and initial dye concentration, on the process, were investigated. Equilibrium was attained after 10 min at 30 °C. Pseudo-first-order, pseudo-second-order, Elovich and Avrami kinetic models were used to test the experimental data in order to elucidate the kinetic adsorption process; pseudo-first-order and Avrami models best fitted the data. Experimental data were analysed using six model equations: Langmuir, Freudlinch, Redlich-Peterson, Temkin, Dubinin-Radushkevich and Sips isotherms and it was found that the data fitted well with Sips isotherm model. The study showed that the process depends on current density, temperature, pH and initial dye concentration. The calculated thermodynamics parameters (Δ G°, Δ H° and Δ S°) indicated that the process is spontaneous and endothermic in nature.

Simultaneous removal of potent cyanotoxins from water using magnetophoretic nanoparticle of polypyrrole: adsorption kinetic and isotherm study.

PubMed

Hena, S; Rozi, R; Tabassum, S; Huda, A

2016-08-01

Cyanotoxins, microcystins and cylindrospermopsin, are potent toxins produced by cyanobacteria in potable water supplies. This study investigated the removal of cyanotoxins from aqueous media by magnetophoretic nanoparticle of polypyrrole adsorbent. The adsorption process was pH dependent with maximum adsorption occurring at pH 7 for microcystin-LA, LR, and YR and at pH 9 for microcystin-RR and cylindrospermopsin (CYN). Kinetic studies and adsorption isotherms reflected better fit for pseudo-second-order rate and Langmuir isotherm model, respectively. Thermodynamic calculations showed that the cyanotoxin adsorption process is endothermic and spontaneous in nature. The regenerated adsorbent can be successfully reused without appreciable loss of its original capacity.

Synthesis of Magnesium Ferrites for the Adsorption of Congo Red from Aqueous Solution Using Batch Studies

NASA Astrophysics Data System (ADS)

Erdawati, E.; Darsef, D.

2018-04-01

A sol gel method with citric acid as an anionic surfactant was used to fabricate nano magnesium ferrites (MgFe2O4) under different calcination temperatures for 2h, respectively. The microstructure and surface morphology of magnesium ferrite powder were characterized by FTIR, XRD, SEM, and BET. The results of this study are useful for adsorption Congo red. The results showed that increasing solution pH and extending contact time are favorable for improving adsorption efficiency. with initial Congo red concentration of 50 mg/L and 100 mg/L. Adsorption data fits well with the Langmuir isotherm models with a maximum adsorption capacity (qm) and a Langmuir adsorption equilibrium constant (K) of 65.1 mg/g and 0.090 L/mg, respectively. The adsorption kinetic agrees well with pseudo second order model with the pseudo second rate constants (K2) of 0.0468 and0.00189 g/mg/min for solutions with initial congo red of 50 and 100 mg/L, respectively

Removal of Heavy Metals by Adsorption onto Activated Carbon Derived from Pine Cones of Pinus roxburghii.

PubMed

Saif, Muhammad Jawwad; Zia, Khalid Mahmood; Fazal-ur-Rehman; Usman, Muhammad; Hussain, Abdullah Ijaz; Chatha, Shahzad Ali Shahid

2015-04-01

Activated carbon derived from cones of Pinus roxburghii (Himalayan Pine) was used as an adsorbent for the removal of copper, nickel and chromium ions from waste water. Surface analysis was carried out to determine the specific surface area and pore size distribution of the pine cone derived activated carbon. Optimal parameters, effect of adsorbent quantity, pH, equilibrium time, agitation speed and temperature were studied. Equilibrium data were evaluated by Langmuir and Freundlich isotherm models. Langmuir isotherm afforded the best fit to the equilibrium data with a maximum adsorption capacity of 14.2, 31.4 and 29.6 mg/g for Cu(II), Ni(II) and Cr(VI) respectively. Maximum adsorption of Cu(II), Ni(II) was observed in the pH range 4.0 to 4.5, whereas the best adsorption of Cr(VI) was observed at pH 2.5. It was found that 180 minutes was sufficient to gain adsorption equilibrium. The adsorption process follows a pseudo-second-order kinetic model.

Chromium Biosorption from Cr(VI) Aqueous Solutions by Cupressus lusitanica Bark: Kinetics, Equilibrium and Thermodynamic Studies.

PubMed

Netzahuatl-Muñoz, Alma Rosa; Cristiani-Urbina, María del Carmen; Cristiani-Urbina, Eliseo

2015-01-01

The present study investigated the kinetics, equilibrium and thermodynamics of chromium (Cr) ion biosorption from Cr(VI) aqueous solutions by Cupressus lusitanica bark (CLB). CLB total Cr biosorption capacity strongly depended on operating variables such as initial Cr(VI) concentration and contact time: as these variables rose, total Cr biosorption capacity increased significantly. Total Cr biosorption rate also increased with rising solution temperature. The pseudo-second-order model described the total Cr biosorption kinetic data best. Langmuir´s model fitted the experimental equilibrium biosorption data of total Cr best and predicted a maximum total Cr biosorption capacity of 305.4 mg g(-1). Total Cr biosorption by CLB is an endothermic and non-spontaneous process as indicated by the thermodynamic parameters. Results from the present kinetic, equilibrium and thermodynamic studies suggest that CLB biosorbs Cr ions from Cr(VI) aqueous solutions predominantly by a chemical sorption phenomenon. Low cost, availability, renewable nature, and effective total Cr biosorption make CLB a highly attractive and efficient method to remediate Cr(VI)-contaminated water and wastewater.

Chromium Biosorption from Cr(VI) Aqueous Solutions by Cupressus lusitanica Bark: Kinetics, Equilibrium and Thermodynamic Studies

PubMed Central

Netzahuatl-Muñoz, Alma Rosa; Cristiani-Urbina, María del Carmen; Cristiani-Urbina, Eliseo

2015-01-01

The present study investigated the kinetics, equilibrium and thermodynamics of chromium (Cr) ion biosorption from Cr(VI) aqueous solutions by Cupressus lusitanica bark (CLB). CLB total Cr biosorption capacity strongly depended on operating variables such as initial Cr(VI) concentration and contact time: as these variables rose, total Cr biosorption capacity increased significantly. Total Cr biosorption rate also increased with rising solution temperature. The pseudo-second-order model described the total Cr biosorption kinetic data best. Langmuir´s model fitted the experimental equilibrium biosorption data of total Cr best and predicted a maximum total Cr biosorption capacity of 305.4 mg g-1. Total Cr biosorption by CLB is an endothermic and non-spontaneous process as indicated by the thermodynamic parameters. Results from the present kinetic, equilibrium and thermodynamic studies suggest that CLB biosorbs Cr ions from Cr(VI) aqueous solutions predominantly by a chemical sorption phenomenon. Low cost, availability, renewable nature, and effective total Cr biosorption make CLB a highly attractive and efficient method to remediate Cr(VI)-contaminated water and wastewater. PMID:26352933

Equilibrium isotherms, kinetics, and thermodynamics studies for congo red adsorption using calcium alginate beads impregnated with nano-goethite.

PubMed

Munagapati, Venkata Subbaiah; Kim, Dong-Su

2017-07-01

The present study is concerned with the batch adsorption of congo red (CR) from an aqueous solution using calcium alginate beads impregnated with nano-goethite (CABI nano-goethite) as an adsorbent. The optimum conditions for CR removal were determined by studying operational variables viz. pH, adsorbent dose, contact time, initial dye ion concentration and temperature. The CABI nano-goethite was characterized by Fourier transform infrared spectroscopy (FTIR), X- ray diffraction (XRD) and Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) analysis. The CR sorption data onto CABI nano-goethite were described using Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. The results show that the best fit was achieved with the Langmuir isotherm model. The maximum adsorption capacity (181.1mg/g) of CR was occurred at pH 3.0. Kinetic studies showed that the adsorption followed a pseudo-second-order model. Desorption experiments were carried out to explore the feasibility of regenerating the adsorbent and the adsorbed CR from CABI nano-goethite. The best desorbing agent was 0.1M NaOH with an efficiency of 94% recovery. The thermodynamic parameters ΔG°, ΔH°, and ΔS° for the CR adsorption were determined by using adsorption capacities at five different temperatures (293, 303, 313, 323 and 303K). Results show that the adsorption process was endothermic and favoured at high temperature. Copyright © 2017 Elsevier Inc. All rights reserved.

Biosorption of Cd+2 by green plant biomass, Araucaria heterophylla: characterization, kinetic, isotherm and thermodynamic studies

NASA Astrophysics Data System (ADS)

Sarada, B.; Krishna Prasad, M.; Kishore Kumar, K.; Murthy, Ch V. R.

2017-11-01

The present study attempted to analyze the biosorption behavior of novel biosorbent, Araucaria heterophylla (green plant) biomass, to remove Cd+2 from solutions against various parameters, i.e., initial metal ion concentration, pH, temperature, sorbent dosage and biomass particle size. The maximum biosorption was found to be 90.02% at pH 5.5 and biosorption capacity ( q e) of Cd+2 is 9.2506 mg g-1. The Langmuir and Freundlich equilibrium adsorption isotherms were studied and it was observed that Freundlich model is the best fit than the Langmuir model with correlation co-efficient of 0.999. Kinetic studies indicated that the biosorption process of Cd+2 well followed the pseudo-second-order model with R 2 0.999. Thermodynamic studies observed that the process is exothermic (Δ H ° negative). Free energy change (Δ G °) with negative sign reflected the feasibility and spontaneous nature of the process. The chemical functional -OH groups, CH2 stretching vibrations, C=O carbonyl group of alcohol, C=O carbonyl group of amide, P=O stretching vibrations and -CH groups were involved in the biosorption process. The XRD pattern of the A. heterophylla was found to be mostly amorphous in nature. The SEM studies showed Cd+2 biosorption on selective grains of the biosorbent. It was concluded that A. heterophylla leaf powder can be used as an effective, low-cost, and environmentally friendly biosorbent for the removal of Cd+2 from aqueous solution.

Adsorptive removal of malachite green from aqueous solutions by almond gum: Kinetic study and equilibrium isotherms.

PubMed

Bouaziz, Fatma; Koubaa, Mohamed; Kallel, Fatma; Ghorbel, Rhoudha Ellouz; Chaabouni, Semia Ellouz

2017-12-01

This work aimed at investigating the potential of almond gum as low cost adsorbent for the removal of the cationic dye; malachite green from aqueous solutions. Almond gum was first analyzed by scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR), and then the adsorption behavior was studied in batch system. The effects of the adsorption parameters (adsorbent dose, pH, contact time, particle size, initial dye concentration, temperature and agitation) on the dye removal have been studied. Adsorption equilibrium and isotherms were evaluated depending on temperature using the isotherms of Freundlich, Langmuir, and Tempkin. The obtained result showed that both Langmuir and Freundlich models were adapted to study the dye sorption. The maximum adsorption capacities were equal to 172.41mg/g, 181.81mg/g, and 196.07mg/g at 303.16K, 313.16K, and 323.16K, respectively. The kinetics of sorption were following the pseudo-second order model. The thermodynamic changes in enthalpy (ΔH), entropy (ΔS), and free energy (ΔG) indicated that the adsorption of malachite green at the surface of almond gum is endothermic and occurs spontaneously. Desorption experiments were conducted to regenerate almond gum, showing great desorption capacity when using HCl at pH 2. Copyright © 2017 Elsevier B.V. All rights reserved.

[Absorption of Uranium with Tea Oil Tree Sawdust Modified by Succinic Acid].

PubMed

Zhang, Xiao-feng; Chen, Di-yun; Peng, Yan; Liu, Yong-sheng; Xiong, Xue-ying

2015-05-01

In order to explore how the modification of succinic acid improves the adsorption of tea oil tree sawdust for uranium, the tea oil tree sawdust was modified by succinic acid, after the pretreatments of crushing, screening, alkalization and acidification. Infrared analysis indicated carboxylic acid groups and ester groups were added to the sawdust after modification, and scanning electron microscope demonstrated after modification the appearance of tea oil tree sawdust was transferred from the structure like compact and straight stripped into the structure like loose and wrinkled leaves, which meant modification increased its inner pores. By the static experiments, effects of reaction time between adsorbent and solvent, dosage of adsorbent, temperature, pH value and initial concentration of uranium were investigated. The results showed that after the modification by succinic acid, the absorption rate of tea oil tree sawdust for uranium increased significantly by about 20% in 12.5 mg · L(-1) initial concentration uranium solution. Adsorption equilibrium was achieved within 180 min, and the kinetic data can be well described by the pseudo-second-order kinetic model. The experimental adsorption isotherm followed the Langmuir and Freundlich models. In addition, the maximum adsorption amounts of tea oil tree sawdust after modification calculated from Langmuir equation raised from 21.413 3 to 31.545 7 mg · g(-1) at 35°C and pH 4.0.

Copper ions removal from water using functionalized carbon nanotubes–mullite composite as adsorbent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tofighy, Maryam Ahmadzadeh; Mohammadi, Toraj, E-mail: torajmohammadi@iust.ac.ir

Highlights: • CNTs–mullite composite was prepared via chemical vapor deposition (CVD) method. • The prepared composite was modified with concentrated nitric acid and chitosan. • The modified CNTs–mullite composites were used as novel adsorbents. • Copper ion removal from water by the prepared adsorbents was performed. • Langmuir and Freundlich isotherms and two kinetic models were applied to fit the experimental data. - Abstract: Carbon nanotubes–mullite composite was synthesized by direct growth of carbon nanotubes on mullite particles via chemical vapor deposition method using cyclohexanol and ferrocene as carbon precursor and catalyst, respectively. The carbon nanotubes–mullite composite was oxidized withmore » concentrated nitric acid and functionalized with chitosan and then used as a novel adsorbent for copper ions removal from water. The results demonstrated that modification with concentrated nitric acid and chitosan improves copper ions adsorption capacity of the prepared composite, significantly. Langmuir and Freundlich isotherms and two kinetic models were applied to fit the experimental data. The carbon nanotubes growth on mullite particles to form the carbon nanotubes–mullite composite with further modification is an inherently safe approach for many promising environmental applications to avoid some concerns regarding environment, health and safety. It was found that the modified carbon nanotubes–mullite composite can be considered as an excellent adsorbent for copper ions removal from water.« less

Biosorption of Cd(II) by live and dead cells of Bacillus cereus RC-1 isolated from cadmium-contaminated soil.

PubMed

Huang, Fei; Dang, Zhi; Guo, Chu-Ling; Lu, Gui-Ning; Gu, Roy R; Liu, Hong-Juan; Zhang, Hui

2013-07-01

The present study investigated the biosorption capacity of live and dead cells of Bacillus cereus RC-1 for Cd(II). The biosorption characteristics were investigated as a function of initial pH, contact time, and initial cadmium concentration. Equilibrium biosorption was modeled using Langmuir, Freundlich and Redlich-Peterson isotherm equations. It was found that the maximum biosorption capacities calculated from Langmuir isotherm were 31.95 mg/g and 24.01 mg/g for dead cells and live cells, respectively. The kinetics of the biosorption was better described by pseudo-second order kinetic model. Desorption efficiency of biosorbents was investigated at various pH values. These results indicated that dead cells have higher Cd(II) biosorption capacity than live cells. Furthermore, zeta potential, transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX), and Fourier transform infrared spectroscopy (FTIR) studies were carried out to understand the differences in the Cd(II) biosorption behavior for the both biosorbents. The bioaccumulation of Cd(II) by B. cereus RC-1 was found to depend largely on extracellular biosorption rather than intracellular accumulation. Based on the above studies, dead biomass appears to be a more efficient biosorbent for the removal of Cd(II) from aqueous solution. Copyright © 2013 Elsevier B.V. All rights reserved.

Photocatalytic degradation of Orange G dye under solar light using nanocrystalline semiconductor metal oxide.

PubMed

Thennarasu, G; Kavithaa, S; Sivasamy, A

2011-08-01

The photocatalytic degradation of Orange G (OG) dye has been investigated using synthesised nanocrystalline ZnO as a photocatalyst and sunlight as the irradiation source. The formation of ZnO prepared from its precursor was confirmed through FT-IR and powder X-ray diffraction analyses. Surface morphology was characterised by scanning electron microscope and transmission electron microscope analysis. Band gap energy of synthesised nanocrystalline ZnO was calculated using diffuse reflectance spectroscopy (DRS). Different experimental parameters such as effects of pH, dye concentrations and mass of catalyst were standardised in order to achieve complete degradation of the dye molecules under solar light irradiation. The kinetics of oxidation of OG was also studied. The complete degradation of OG was evident after 90 min of irradiation at an initial pH of 6.86. The degradation of OG was confirmed by UV-Visible spectrophotometer, high-pressure liquid chromatography, ESI-Mass and chemical oxygen demand analyses. The adsorption of dye onto catalytic surface was analysed employing model equations such as Langmuir and Freundlich isotherms, and it was found that the Langmuir isotherm model best fitted the adsorption data. The solar photodegradation of OG followed pseudo-first-order kinetics. HPLC and ESI-Mass analyses of the degraded samples suggested that the dye molecules were readily degraded under solar irradiation with nanocrystalline ZnO.

Measuring binding kinetics of aromatic thiolated molecules with nanoparticles via surface-enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Devetter, Brent M.; Mukherjee, Prabuddha; Murphy, Catherine J.; Bhargava, Rohit

2015-05-01

Colloidal plasmonic nanomaterials, consisting of metals such as gold and silver, are excellent candidates for advanced optical probes and devices, but precise control over surface chemistry is essential for realizing their full potential. Coupling thiolated (R-SH) molecules to nanoprobe surfaces is a convenient and established route to tailor surface properties. The ability to dynamically probe and monitor the surface chemistry of nanoparticles in solution is essential for rapidly manufacturing spectroscopically tunable nanoparticles. In this study, we report the development of surface-enhanced Raman spectroscopy (SERS) as a method to monitor the kinetics of gold-thiolate bond formation on colloidal gold nanoparticles. A theoretical model combining SERS enhancement with the Beer-Lambert law is proposed to explain ensemble scattering and absorption effects in colloids during chemisorption. In order to maximize biological relevance and signal reproducibility, experiments used to validate the model focused on maintaining nanoparticle stability after the addition of water-soluble aromatic thiolated molecules. Our results indicate that ligand exchange on gold nanoparticles follow a first-order Langmuir adsorption model with rate constants on the order of 0.01 min-1. This study demonstrates an experimental spectroscopic method and theoretical model for monitoring binding kinetics that may prove useful for designing novel probes.Colloidal plasmonic nanomaterials, consisting of metals such as gold and silver, are excellent candidates for advanced optical probes and devices, but precise control over surface chemistry is essential for realizing their full potential. Coupling thiolated (R-SH) molecules to nanoprobe surfaces is a convenient and established route to tailor surface properties. The ability to dynamically probe and monitor the surface chemistry of nanoparticles in solution is essential for rapidly manufacturing spectroscopically tunable nanoparticles. In this study, we report the development of surface-enhanced Raman spectroscopy (SERS) as a method to monitor the kinetics of gold-thiolate bond formation on colloidal gold nanoparticles. A theoretical model combining SERS enhancement with the Beer-Lambert law is proposed to explain ensemble scattering and absorption effects in colloids during chemisorption. In order to maximize biological relevance and signal reproducibility, experiments used to validate the model focused on maintaining nanoparticle stability after the addition of water-soluble aromatic thiolated molecules. Our results indicate that ligand exchange on gold nanoparticles follow a first-order Langmuir adsorption model with rate constants on the order of 0.01 min-1. This study demonstrates an experimental spectroscopic method and theoretical model for monitoring binding kinetics that may prove useful for designing novel probes. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01006c

Effects of Lewis acidity of metal oxide promoters on the activity and selectivity of Co-based Fischer–Tropsch synthesis catalysts

DOE PAGES

Johnson, Gregory R.; Bell, Alexis T.

2016-03-31

Metal oxides of Ce, Gd, La, Mn, and Zr were investigated as promoters for improving the activity and selectivity of Co-based FTS catalysts. The extent to which these promoters decrease the selectivity toward CH 4 and increase the selectivity toward C 5+ hydrocarbons was found to depend on both the loading and the composition of the oxide promoter. Elemental mapping by STEM-EDS revealed that the propensity for a given metal oxide to associate with Co affects the sensitivity of the product distribution to changes in promoter loading. For all promoters, a sufficiently high loading resulted in the product distributions becomingmore » insensitive to further increases in promoter loading, very likely due to the formation of a half monolayer of promoter oxide over the Co surface. Simulations suggest that the fraction of Co active sites that are adjacent to the promoter moieties approaches unity at this degree of coverage. The oxidation state of the promoter metal cation under reaction conditions, determined by in situ XANES measurements, was used to calculate relative Lewis acidity of the promoter metal cation. We found a strong positive correlation between the C 5+ product selectivity and the Lewis acidity of the promoter metal cations, suggesting that the promotional effects are a consequence of Lewis acid-base interactions between the reaction intermediates and the promoter metal cations. Rate data obtained at different pressures were used to estimate the apparent rate coefficient and the CO adsorption constant appearing in the Langmuir-Hinshelwood expression that describes the CO consumption kinetics for both unpromoted and the metal oxide-promoted catalysts. Both parameters exhibited positive correlations with the promoter Lewis acidity. Our results are consistent with the hypothesis that the metal cations of the promoter act as Lewis acids that interact with the O atom of adsorbed CO to facilitate CO adsorption and dissociation.« less

Role of ZrO 2 in Promoting the Activity and Selectivity of Co-Based Fischer–Tropsch Synthesis Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Gregory R.; Bell, Alexis T.

2015-11-17

The effects of Zr promotion on the structure and performance of Co-based Fischer-Tropsch synthesis (FTS) catalysts were investigated. Inclusion of Zr in the catalysts was found to increase the FTS turnover frequency and the selectivity to C 5+ hydrocarbons and to decrease the selectivity to methane under most operating conditions. These improvements to the catalytic performance are a function of Zr loading up to an atomic ratio of Zr/Co = 1.0, above which the product selectivity is insensitive to higher concentrations of the promoter. Characterization of the Co nanoparticles by different methods demonstrated that the optimal Zr loading corresponds tomore » half monolayer coverage of the Co surface by the promoter. Measurements of the rate of FTS at different pressures and temperatures established that the kinetics data for both the Zr-promoted and unpromoted catalysts are described by a two-parameter Langmuir-Hinshelwood expression. The parameters used to fit this rate law to the experimental data indicate that the apparent rate coefficient and the CO adsorption constant for the Zr-promoted catalysts are higher than those for the unpromoted catalyst. Elemental mapping by means of STEM-EDS provided evidence that Zr is highly dispersed over the catalyst surface and has limited preference for association with the Co nanoparticles. In situ X-ray absorption spectroscopy confirmed the absence of mixing between the Zr and Co in the nanoparticles. Here, these results suggest that Zr exists as a partial layer of ZrO 2 on the surface of the Co metal nanoparticles. Accordingly, it is proposed that Zr promotion effects originate from sites of enhanced activity at the interface between Co and ZrO 2. The possibility that ZrO 2 acts as a Lewis acid to assist in CO dissociation as well as to increase the ratio of CO to H adsorbed on the catalyst surface is discussed.« less

Chromium and zinc uptake by algae Gelidium and agar extraction algal waste: kinetics and equilibrium.

PubMed

Vilar, Vítor J P; Botelho, Cidália M S; Boaventura, Rui A R

2007-11-19

Biosorption of chromium and zinc ions by an industrial algal waste, from agar extraction industry has been studied in a batch system. This biosorbent was compared with the algae Gelidium itself, which is the raw material for agar extraction, and the industrial waste immobilized with polyacrylonitrile (composite material). Langmuir and Langmuir-Freundlich equilibrium models describe well the equilibrium data. The parameters of Langmuir equilibrium model at pH 5.3 and 20 degrees C were for the algae, q(L)=18 mg Cr(III)g(-1) and 13 mgZn(II)g(-1), K(L) = 0.021l mg(-1)Cr(III) and 0.026l mg(-1) Zn(II); for the algal waste, q(L)=12 mgCr(III)g(-1) and 7mgZn(II)g(-1), K(L)=0.033lmg(-1) Cr(III) and 0.042l mg(-1) Zn(II); for the composite material, q(L) = 9 mgCr(III)g(-1) and 6 mgZn(II)g(-1), K(L)=0.032l mg(-1)Cr(III) and 0.034l mg(-1)Zn(II). The biosorbents exhibited a higher preference for Cr(III) ions and algae Gelidium is the best one. The pseudo-first-order Lagergren and pseudo-second-order models fitted well the kinetic data for the two metal ions. Kinetic constants and equilibrium uptake concentrations given by the pseudo-second-order model for an initial Cr(III) and Zn(II) concentration of approximately 100 mgl(-1), at pH 5.3 and 20 degrees C were k(2,ads)=0.04 g mg(-1)Cr(III)min(-1) and 0.07 g mg(-1)Zn(II)min(-1), q(eq)=11.9 mgCr(III)g(-1) and 9.5 mgZn(II)g(-1) for algae; k(2,ads)=0.17 g mg(-1)Cr(III)min(-1) and 0.19 g mg(-1)Zn(II)min(-1), q(eq)=8.3 mgCr(III)g(-1) and 5.6 mgZn(II)g(-1) for algal waste; k(2,ads)=0.01 g mg(-1)Cr(III)min(-1) and 0.18 g mg(-1)Zn(II)min(-1), q(eq)=8.0 mgCr(III)g(-1) and 4.4 mgZn(II)g(-1) for composite material. Biosorption was modelled using a batch adsorber mass transfer kinetic model, which successfully predicts Cr(III) and Zn(II) concentration profiles. The calculated average homogeneous diffusivities, D(h), were 4.2 x 10(-8), 8.3 x 10(-8) and 1.4 x 10(-8)cm(2)s(-1) for Cr(III) and 4.8 x 10(-8), 9.7 x 10(-8) and 6.2 x 10(-8)cm(2)s(-1) for Zn(II), respectively, for Gelidium, algal waste and composite material. The algal waste has the lower intraparticle resistance.

Separation of aflatoxin B1 from synthetic physiological fluids using talc and diatomite: Kinetic and isotherm aspects.

PubMed

Sprynskyy, Myroslav; Krzemień-Konieczka, Iwona; Gadzała-Kopciuch, Renata; Buszewski, Bogusław

2018-01-01

The objective of the study was to examine adsorption of the aflatoxin B1 from synthetic gastric fluid and synthetic intestinal fluid by talc, raw and calcined diatomite. The kinetic and equilibrium adsorption processes were studied in the batch adsorption experiments applying high performance liquid chromatography for the aflatoxin B1 determination. The kinetic study showed a very fast adsorption of the aflatoxin B1 onto the selected adsorbents from the both physiological fluids with reaching equilibrium within 1-15min. The aflatoxin B1 was almost completely adsorbed in initial linear step of the kinetic process that can be described well by the zero-order kinetics model. The experimental data of the equilibrium adsorption were characterized using the Langmuir and Freundlich isotherm models. The high adsorption effectiveness was found in a range of 90%-100% and 60%-100% for the diatomite samples and the talc respectively at the initial concentrations of the aflatoxin B1 as 31-300ng/mL. The possible mechanisms of the aflatoxin adsorption onto the used mineral adsorbents are also discussed in the work. Copyright © 2017 Elsevier B.V. All rights reserved.

Equilibrium, kinetic and thermodynamic studies of uranium biosorption by calcium alginate beads.

PubMed

Bai, Jing; Fan, Fangli; Wu, Xiaolei; Tian, Wei; Zhao, Liang; Yin, Xiaojie; Fan, Fuyou; Li, Zhan; Tian, Longlong; Wang, Yang; Qin, Zhi; Guo, Junsheng

2013-12-01

Calcium alginate beads are potential biosorbent for radionuclides removal as they contain carboxyl groups. However, until now limited information is available concerning the uptake behavior of uranium by this polymer gel, especially when sorption equilibrium, kinetics and thermodynamics are concerned. In present work, batch experiments were carried out to study the equilibrium, kinetics and thermodynamics of uranium sorption by calcium alginate beads. The effects of initial solution pH, sorbent amount, initial uranium concentration and temperature on uranium sorption were also investigated. The determined optimal conditions were: initial solution pH of 3.0, added sorbent amount of 40 mg, and uranium sorption capacity increased with increasing initial uranium concentration and temperature. Equilibrium data obtained under different temperatures were fitted better with Langmuir model than Freundlich model, uranium sorption was dominated by a monolayer way. The kinetic data can be well depicted by the pseudo-second-order kinetic model. The activation energy derived from Arrhenius equation was 30.0 kJ/mol and the sorption process had a chemical nature. Thermodynamic constants such as ΔH(0), ΔS(0) and ΔG(0) were also evaluated, results of thermodynamic study showed that the sorption process was endothermic and spontaneous. Copyright © 2013 Elsevier Ltd. All rights reserved.

Optimization of the ultrasonic assisted removal of methylene blue by gold nanoparticles loaded on activated carbon using experimental design methodology.

PubMed

Roosta, M; Ghaedi, M; Daneshfar, A; Sahraei, R; Asghari, A

2014-01-01

The present study was focused on the removal of methylene blue (MB) from aqueous solution by ultrasound-assisted adsorption onto the gold nanoparticles loaded on activated carbon (Au-NP-AC). This nanomaterial was characterized using different techniques such as SEM, XRD, and BET. The effects of variables such as pH, initial dye concentration, adsorbent dosage (g), temperature and sonication time (min) on MB removal were studied and using central composite design (CCD) and the optimum experimental conditions were found with desirability function (DF) combined response surface methodology (RSM). Fitting the experimental equilibrium data to various isotherm models such as Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich models show the suitability and applicability of the Langmuir model. Analysis of experimental adsorption data to various kinetic models such as pseudo-first and second order, Elovich and intraparticle diffusion models show the applicability of the second-order equation model. The small amount of proposed adsorbent (0.01 g) is applicable for successful removal of MB (RE>95%) in short time (1.6 min) with high adsorption capacity (104-185 mg g(-1)). Copyright © 2013 Elsevier B.V. All rights reserved.

Genetic characterization, nickel tolerance, biosorption, kinetics, and uptake mechanism of a bacterium isolated from electroplating industrial effluent.

PubMed

Nagarajan, N; Gunasekaran, P; Rajendran, P

2015-04-01

Electroplating industries in Madurai city produce approximately 49,000 L of wastewater and 1200 L of sludge every day revealing 687-5569 ppm of nickel (Ni) with other contaminants. Seventeen Ni-tolerant bacterial strains were isolated from nutrient-enriched effluents. Among them one hyper Ni accumulating strain was scored and identified as Bacillus cereus VP17 on the basis of morphology, biochemical tests, 16S rDNA gene sequencing, and phylogenetic analysis. Equilibrium data of Ni(II) ions using the bacterium as sorbent at isothermal conditions (37 °C) and pH 6 were best adjusted by Langmuir (R(2) = 0.6268) and Freundlich models (R(2) = 0.9505). Experimental validation reveals Ni sorption takes place on a heterogeneous surface of the biosorbent, and predicted metal sorption capacity is 434 ppm. The pseudo-second-order kinetic model fitted the biosorption kinetic data better than the pseudo-first-order kinetic model (R(2) = 0.9963 and 0.3625). Scanning electron microscopy, energy dispersive X-ray, and Fourier transform infrared spectroscopy studies of the bacterial strain with and without Ni(II) ion reveals the biosorption mechanism. The results conclude possibilities of using B. cereus VP17 for Ni bioremediation.

Carbon composite lignin-based adsorbents for the adsorption of dyes.

PubMed

Wang, Xiaohong; Jiang, Chenglong; Hou, Bingxia; Wang, Yingying; Hao, Chen; Wu, Jingbo

2018-05-10

Carbon composite lignin-based adsorbent were prepared through hydrothermal method with glucose as carbon source, calcium lignosulfonate and triethylene tetramine as raw materials, respectively. The optimum synthesis conditions were determined by investigating the addition of carbon and triethylene tetramine. The adsorbent was used for the adsorption of azo dyes Congo red and Eriochrome blue black R, and the five factors affecting the adsorption were discussed, including pH of dyes, initial concentration, adsorption time, adsorption temperature and adsorbent dosage. The corresponding adsorption mechanism such as pseudo first order kinetics, pseudo second order kinetics, intraparticle diffusion, Langmuir adsorption isotherm, Freundlich isotherm, Temkin isotherm, Dubinin-Radushkevich adsorption isotherm, thermodynamics were also studied. When the dye concentration is 40 mg L -1 , Congo red and Eriochrome blue black R dye removal rates reach 99%. Moreover, the adsorption process of two kinds of dyes follow the pseudo second order kinetics and the Langmuir adsorption isotherm. Copyright © 2018 Elsevier Ltd. All rights reserved.

Kinetic and Isotherm Modelling of the Adsorption of
Phenolic Compounds from Olive Mill Wastewater onto Activated Carbon

PubMed Central

Casazza, Alessandro A.; Perego, Patrizia

2015-01-01

Summary The adsorption of phenolic compounds from olive oil wastewater by commercial activated carbon was studied as a function of adsorbent quantity and temperature. The sorption kinetics and the equilibrium isotherms were evaluated. Under optimum conditions (8 g of activated carbon per 100 mL), the maximum sorption capacity of activated carbon expressed as mg of caffeic acid equivalent per g of activated carbon was 35.8 at 10 °C, 35.4 at 25 °C and 36.1 at 40 °C. The pseudo-second-order model was considered as the most suitable for kinetic results, and Langmuir isotherm was chosen to better describe the sorption system. The results confirmed the efficiency of activated carbon to remove almost all phenolic compound fractions from olive mill effluent. The preliminary results obtained will be used in future studies. The carbohydrate fraction of this upgraded residue could be employed to produce bioethanol, and adsorbed phenolic compounds can be recovered and used in different industries. PMID:27904350

Preparation and characterization of erythromycin molecularly imprinted polymers based on distillation-precipitation polymerization.

PubMed

Liu, Jiang; Li, Le; Tang, Hui; Zhao, Feilang; Ye, Bang-Ce; Li, Yingchun; Yao, Jun

2015-09-01

Erythromycin-imprinted polymers with excellent recognition properties were prepared by an innovative strategy called distillation-precipitation polymerization. The interaction between erythromycin and methacrylic acid was studied by ultraviolet absorption spectroscopy, and the as-prepared materials were characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. Moreover, their binding performances were evaluated in detail by static, kinetic and selective sorption tests. It was found that the molecularly imprinted polymers afforded good morphology, monodispersity, and high adsorption capacity when the fraction of the monomers was 7 vol% in the whole reaction system, and the adsorption data for imprinted polymers correlated well with the Langmuir model. The maximum capacity of the imprinted and the non-imprinted polymers for adsorbing erythromycin is 44.03 and 19.95 mg/g, respectively. The kinetic studies revealed that the adsorption process fitted a pseudo-second-order kinetic model. Furthermore, the imprinted polymers display higher affinity toward erythromycin, compared with its analogue roxithromycin. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermodynamic and kinetic studies on CO2 capture with Poly[VBTMA][Arg

NASA Astrophysics Data System (ADS)

Raja Shahrom, Maisara Shahrom; Wilfred, Cecilia Devi; Chong, Fai Kait

2018-05-01

This paper discusses the technologies for capturing CO2 from the natural gas using poly[VBTMA][Arg], a type of poly(ionic liquids) with an amino acid as the anion. The results revealed that the CO2 uptake increased from 3.23 mmol/g to 7.91 mmol/g at 1-10 bar, 298 K due to both chemical absorption and physical adsorption increments. Four adsorption isotherm models were applied to study the interaction between adsorbate and adsorbent to study the physical adsorption i.e. Freundlich, Langmuir, Dubinin Raduschkevich and Temkin isotherms at 298 K, 313 K and 333 K. Promising results were obtained that suggested the Freundlich model and the pseudo-first order model are well fitted with the kinetic data at 298 K with a 0.9943 R2 value. This study has provided empirical evidence to the current body of knowledge pertaining to CO2 capture technologies.

Adsorption of 2,4-Dichlorophenoxyacetic Acid from an Aqueous Solution on Fly Ash.

PubMed

Kuśmierek, Krzysztof; Świątkowski, Andrzej

2016-03-01

The adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) on fly ash was studied. The effects of adsorbent dose, contact time, pH, ionic strength, and temperature on the adsorption were investigated. Adsorption kinetic data were analyzed using pseudo-first and pseudo-second order models, and results showed that adsorption kinetics were better represented by the pseudo-second order model. Adsorption isotherms of 2,4-D on fly ash were analyzed using the Freundlich and Langmuir models. Thermodynamic parameters (ΔG°, ΔH°, and ΔS°) indicated that the adsorption process was spontaneous and endothermic. The negative values of ΔG° and the positive value of ΔH° indicate the spontaneous nature of 2,4-D adsorption on fly ash, and that the adsorption process was endothermic. Results showed that fly ash is an efficient, low-cost adsorbent for removal of 2,4-D from water.

Effect of Fe3O4 addition on removal of ammonium by zeolite NaA.

PubMed

Liu, Haibo; Peng, Shuchuan; Shu, Lin; Chen, Tianhu; Bao, Teng; Frost, Ray L

2013-01-15

Magnetic zeolite NaA with different Fe(3)O(4) loadings was prepared by hydrothermal synthesis based on metakaolin and Fe(3)O(4). The effect of added Fe(3)O(4) on the removal of ammonium by zeolite NaA was investigated by varying the Fe(3)O(4) loading, pH, adsorption temperature, initial concentration, adsorption time. Langmuir, Freundlich, and pseudo-second-order modeling were used to describe the nature and mechanism of ammonium ion exchange using both zeolite and magnetic zeolite. Thermodynamic parameters such as change in Gibbs free energy, enthalpy and entropy were calculated. The results show that all the selected factors affect the ammonium ion exchange by zeolite and magnetic zeolite, however, the added Fe(3)O(4) apparently does not affect the ion exchange performance of zeolite to the ammonium ion. Freundlich model provides a better description of the adsorption process than Langmuir model. Moreover, kinetic analysis indicates the exchange of ammonium on the two materials follows a pseudo-second-order model. Thermodynamic analysis makes it clear that the adsorption process of ammonium is spontaneous and exothermic. Regardless of kinetic or thermodynamic analysis, all the results suggest that no considerable effect on the adsorption of the ammonium ion by zeolite is found after the addition of Fe(3)O(4). According to the results, magnetic zeolite NaA can be used for the removal of ammonium due to the good adsorption performance and easy separation method from aqueous solution. Copyright © 2012 Elsevier Inc. All rights reserved.

Modeling of ultrasonic degradation of non-volatile organic compounds by Langmuir-type kinetics.

PubMed

Chiha, Mahdi; Merouani, Slimane; Hamdaoui, Oualid; Baup, Stéphane; Gondrexon, Nicolas; Pétrier, Christian

2010-06-01

Sonochemical degradation of phenol (Ph), 4-isopropylphenol (4-IPP) and Rhodamine B (RhB) in aqueous solutions was investigated for a large range of initial concentrations in order to analyze the reaction kinetics. The initial rates of substrate degradation and H(2)O(2) formation as a function of initial concentrations were determined. The obtained results show that the degradation rate increases with increasing initial substrate concentration up to a plateau and that the sonolytic destruction occurs mainly through reactions with hydroxyl radicals in the interfacial region of cavitation bubbles. The rate of H(2)O(2) formation decreases with increasing substrate concentration and reaches a minimum, followed by almost constant production rate for higher substrate concentrations. Sonolytic degradation data were analyzed by the models of Okitsu et al. [K. Okitsu, K. Iwasaki, Y. Yobiko, H. Bandow, R. Nishimura, Y. Maeda, Sonochemical degradation of azo dyes in aqueous solution: a new heterogeneous kinetics model taking into account the local concentration OH radicals and azo dyes, Ultrason. Sonochem. 12 (2005) 255-262.] and Seprone et al. [N. Serpone, R. Terzian, H. Hidaka, E. Pelizzetti, Ultrasonic induced dehalogenation and oxidation of 2-, 3-, and 4-chlorophenol in air-equilibrated aqueous media. Similarities with irradiated semiconductor particulates, J. Phys. Chem. 98 (1994) 2634-2640.] developed on the basis of a Langmuir-type mechanism. The five linearized forms of the Okitsu et al.'s equation as well as the non-linear curve fitting analysis method were discussed. Results show that it is not appropriate to use the coefficient of determination of the linear regression method for comparing the best-fitting. Among the five linear expressions of the Okitsu et al.'s kinetic model, form-2 expression very well represent the degradation data for Ph and 4-IPP. Non-linear curve fitting analysis method was found to be the more appropriate method to determine the model parameters. An excellent representation of the experimental results of sonolytic destruction of RhB was obtained using the Serpone et al.'s model. The Serpone et al.'s model gives a worse fit for the sonolytic degradation data of Ph and 4-IPP. These results indicate that Ph and 4-IPP undergo degradation predominantly at the bubble/solution interface, whereas RhB undergoes degradation at both bubble/solution interface and in the bulk solution. (c) 2010 Elsevier B.V. All rights reserved.

Commercial Coffee Wastes as Materials for Adsorption of Heavy Metals from Aqueous Solutions

PubMed Central

Kyzas, George Z.

2012-01-01

This work aims to study the removal of Cu(II) and Cr(VI) from aqueous solutions with commercial coffee wastes. Materials with no further treatment such as coffee residues from café may act as adsorbents for the removal of Cu(II) and Cr(VI). Equilibrium data were successfully fitted to the Langmuir, Freundlich and Langmuir-Freundlich model (L-F). The maximum adsorption capacity of the coffee residues can reach 70 mg/g for the removal of Cu(II) and 45 mg/g for Cr(VI). The kinetic data were fitted to pseudo-first, -second and -third order equations. The equilibrium was achieved in 120 min. Also, the effect of pH on adsorption and desorption was studied, as well as the influence of agitation rate. Ten cycles of adsorption-desorption were carried out revealing the strong reuse potential of these low-cost adsorbents; the latter was confirmed from a brief economic approach.

Interaction of lactoferrin and lysozyme with casein micelles.

PubMed

Anema, Skelte G; de Kruif, C G Kees

2011-11-14

On addition of lactoferrin (LF) to skim milk, the turbidity decreases. The basic protein binds to the caseins in the casein micelles, which is then followed by a (partial) disintegration of the casein micelles. The amount of LF initially binding to casein micelles follows a Langmuir adsorption isotherm. The kinetics of the binding of LF could be described by first-order kinetics and similarly the disintegration kinetics. The disintegration was, however, about 10 times slower than the initial adsorption, which allowed investigating both phenomena. Kinetic data were also obtained from turbidity measurements, and all data could be described with one equation. The disintegration of the casein micelles was further characterized by an activation energy of 52 kJ/mol. The initial increase in hydrodynamic size of the casein micelles could be accounted for by assuming that it would go as the cube root of the mass using the adsorption and disintegration kinetics as determined from gel electrophoresis. The results show that LF binds to casein micelles and that subsequently the casein micelles partly disintegrate. All micelles behave in a similar manner as average particle size decreases. Lysozyme also bound to the casein micelles, and this binding followed a Langmuir adsorption isotherm. However, lysozyme did not cause the disintegration of the casein micelles.

Swift adsorptive removal of Congo red from aqueous solution by K1.33Mn8O16 nanowires.

PubMed

Wu, Junshu; Li, Hongyi; Wang, Jinshu; Li, Zhifei

2013-08-01

A swift and efficient approach to converting organic dye effluents into fresh water could be of substantial benefit. In this study, we presented facile hydrothermal synthesis of K1.33Mn8O16 nanowires in ammonium fluoride (NH4F) aqueous solution. The crystallization process of K1.33Mn8O16 nanowires was investigated. The as-obtained K1.33Mn8O16 nanowires were used for swift adsorptive removal of Congo red from aqueous solution without adjusting pH value at room temperature. Adsorption kinetic experimental data are well described by pseudo-second-order rate kinetic model, and the adsorption isotherm fits Langmuir isotherm model. The present investigation provides an efficient approach to designing and fabricating manganese-based nanomaterials for environmental remediation.

Selective adsorption of Pb(II), Cd(II), and Ni(II) ions from aqueous solution using chitosan-MAA nanoparticles.

PubMed

Heidari, Aghdas; Younesi, Habibollah; Mehraban, Zahra; Heikkinen, Harri

2013-10-01

Chitosan-MAA nanoparticles (CS-MAA) with an average size of 10-70 nm were prepared by polymerizing chitosan with methacrylic acid in aqueous solution. The physicochemical properties of nanoparticles were investigated using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS) and nuclear magnetic resonance (NMR). The adsorption of Pb(II), Cd(II) and Ni(II) from aqueous solution on CS-MAA was studied in a batch system. The effects of the solution pH, initial metal concentration, contact time, and dosage of the adsorbent on the adsorption process were examined. The experimental data were analyzed using the pseudo-second-order kinetic equations and the Langmuir, Freundlich and Redlish-Peterson isotherms. The maximum adsorption capacity was 11.30, 1.84, and 0.87 mg/g for Pb(II), Cd(II) and Ni(II) ions, respectively, obtained by the Langmuir isotherm. However, the adsorption isotherm was better explained by the Freundlich rather than by the Langmuir model, as the high correlation coefficients (R(2)>0.99) were obtained at a higher confidence level. Copyright © 2013 Elsevier B.V. All rights reserved.

Kinetics and thermodynamics of Pb(II) adsorption onto modified spent grain from aqueous solutions

NASA Astrophysics Data System (ADS)

Li, Qingzhu; Chai, Liyuan; Yang, Zhihui; Wang, Qingwei

2009-01-01

Spent grain, a main by-product of the brewing industry, is available in large quantities, but its main application has been limited to animal feeding. Nevertheless, in this study, spent grain modified with 1 M NaCl solution as a novel adsorbent has been used for the adsorption of Pb(II) in aqueous solutions. Isotherms, kinetics and thermodynamics of Pb(II) adsorption onto modified spent grain were studied. The equilibrium data were well fitted with Langmuir, Freundlich and Dubinin-Radushkevick (D-R) isotherm models. The kinetics of Pb(II) adsorption followed pseudo-second-order model, using the rate constants of pseudo-second-order model, the activation energy ( Ea) of Pb(II) adsorption was determined as 12.33 kJ mol -1 according to the Arrhenius equation. Various thermodynamic parameters such as Δ Gads, Δ Hads and Δ Sads were also calculated. Thermodynamic results indicate that Pb(II) adsorption onto modified spent grain is a spontaneous and endothermic process. Therefore, it can be concluded that modified spent grain as a new effective adsorbent has potential for Pb(II) removal from aqueous solutions.

Adsorption of Zinc(II) on diatomite and manganese-oxide-modified diatomite: a kinetic and equilibrium study.

PubMed

Caliskan, Necla; Kul, Ali Riza; Alkan, Salih; Sogut, Eda Gokirmak; Alacabey, Ihsan

2011-10-15

The removal of Zn(II) ions from aqueous solution was studied using natural and MnO(2) modified diatomite samples at different temperatures. The linear Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption equations were applied to describe the equilibrium isotherms. From the D-R model, the mean adsorption energy was calculated as >8 kJ mol(-1), indicating that the adsorption of Zn(II) onto diatomite and Mn-diatomite was physically carried out. In addition, the pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to determine the kinetic data. The experimental data were well fitted by the pseudo-second-order kinetic model. Thermodynamic parameters such as the enthalpy (ΔH(0)), Gibbs' free energy (ΔG(0)) and entropy (ΔS(0)) were calculated for natural and MnO(2) modified diatomite. These values showed that the adsorption of Zn(II) ions onto diatomite samples was controlled by a physical mechanism and occurred spontaneously. Copyright © 2011 Elsevier B.V. All rights reserved.

Thermodynamic, Kinetic, and Equilibrium Parameters for the Removal of Lead and Cadmium from Aqueous Solutions with Calcium Alginate Beads

PubMed Central

Alfaro-Cuevas-Villanueva, Ruth; Hidalgo-Vázquez, Aura Roxana; Cortés Penagos, Consuelo de Jesús; Cortés-Martínez, Raúl

2014-01-01

The sorption of cadmium (Cd) and lead (Pb) by calcium alginate beads (CAB) from aqueous solutions in batch systems was investigated. The kinetic and thermodynamic parameters, as well as the sorption capacities of CAB in each system at different temperatures, were evaluated. The rate of sorption for both metals was rapid in the first 10 minutes and reached a maximum in 50 minutes. Sorption kinetic data were fitted to Lagergren, pseudo-second-order and Elovich models and it was found that the second-order kinetic model describes these data for the two metals; comparing kinetic parameters for Cd and Pb sorption a higher kinetic rate (K 2) for Pb was observed, indicating that the interaction between lead cations and alginate beads was faster than for cadmium. Similarly, isotherm data were fitted to different models reported in literature and it was found that the Langmuir-Freundlich (L-F) and Dubinin-Radushkevich (D-R) models describe the isotherms in all cases. CAB sorption capacity for cadmium was 27.4 mg/g and 150.4 mg/g for lead, at 25°C. Sorption capacities of Cd and Pb increase as temperature rises. According to the thermodynamic parameters, the cadmium and lead adsorption process was spontaneous and endothermic. It was also found that pH has an important effect on the adsorption of these metals by CAB, as more were removed at pH values between 6 and 7. PMID:24587740

Adsorption capacity of Curcuma longa for the removal of basic green 1 dye--equilibrium, kinetics and thermodynamic study.

PubMed

Roopavathi, K V; Shanthakumar, S

2016-09-01

In the present study, Curcuma longa (turmeric plant) was used as an adsorbent to remove Basic Green 1 (BG) dye. Batch study was carried out to evaluate the adsorption potential of C. longa and influencing factors such as pH (4-10), adsorbent dose (0.2-5 g l-1), initial dye concentration (50-250 mg l-1) and temperature (30-50°C) on dye removal were analysed. The characterisation of adsorbent was carried out using fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and Brunauer, Emmett and Teller (BET) method. Isotherm models that included Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich, and kinetic models such as pseudo first order, pseudo second-order, Elovich and intraparticle diffusion models were studied. A maximum removal percentage (82.76%) of BG dye from aqueous solution was obtained with optimum conditions of pH 7, 1g l-1 adsorbent dose and 30°C temperature, for 100 mg l-1 initial dye concentration. The equilibrium and kinetic study revealed that the experimental data fitted suitably the Freundlich isotherm and Pseudo second order kinetic model. Thermodynamic analysis proved that adsorption system in this study was spontaneous, feasible and endothermic in nature.

Nonlinear Waves, Instabilities and Singularities in Plasma and Hydrodynamics

NASA Astrophysics Data System (ADS)

Silantyev, Denis Albertovich

Nonlinear effects are present in almost every area of science as soon as one tries to go beyond the first order approximation. In particular, nonlinear waves emerge in such areas as hydrodynamics, nonlinear optics, plasma physics, quantum physics, etc. The results of this work are related to nonlinear waves in two areas, plasma physics and hydrodynamics, united by concepts of instability, singularity and advanced numerical methods used for their investigation. The first part of this work concentrates on Langmuir wave filamentation instability in the kinetic regime of plasma. In Internal Confinement Fusion Experiments (ICF) at National Ignition Facility (NIF), where attempts are made to achieve fusion by compressing a small target by many powerful lasers to extremely high temperatures and pressures, plasma is created in the first moments of the laser reaching the target and undergoes complicated dynamics. Some of the most challenging difficulties arise from various plasma instabilities that occur due to interaction of the laser beam and a plasma surrounding the target. In this work we consider one of such instabilities that describes a decay of nonlinear plasma wave, initially excited due to interaction of the laser beam with the plasma, into many filaments in direction perpendicular to the laser beam, therefore named Langmuir filamentation instability. This instability occurs in the kinetic regime of plasma, klambda D > 0.2, where k is the wavenumber and lambda D is the Debye length. The filamentation of Langmuir waves in turn leads to the saturation of the stimulated Raman scattering (SRS) in laser-plasma interaction experiments which plays an essential role in ICF experiments. The challenging part of this work was that unlike in hydrodynamics we needed to use fully kinetic description of plasma to capture the physics in question properly, meaning that we needed to consider the distribution function of charged particles and its evolution in time not only with respect to spatial coordinates but with respect to velocities as well. To study Langmuir filamentation instability in its simplest form we performed 2D+2V numerical simulations. Taking into account that the distribution function in question was 4-dimensional function, making these simulation quite challenging, we developed an efficient numerical method making these simulations possible on modern desktop computers. Using the developed numerical method we studied how Langmuir wave filamentation instability depends on the parameters of the Langmuir wave such as wave length and amplitude that are relevant to ICF experiments. We considered several types of Langmuir waves, including nonlinear Langmuir waves exited by external electric field as well as an idealized approximation of such Langmuir waves by a particular family of Bernstein-Greene-Kruskal (BGK) modes that bifurcates from the linear Langmuir wave. The results of these simulations were compared to the theoretical predictions in our recent papers. An alternative approach to overcome computational difficulty of this problem was considered by our research group in Ref. It involves reducing the number of transverse direction in the model therefore lowering computational difficulty at a cost of lesser accuracy of the model. The second part of this work concentrates on 2D free surface hydrodynamics and in particular on computing Stokes waves with high-precision using conformal maps and spectral methods. Stokes waves are fully nonlinear periodic gravity waves propagating with the constant velocity on a free surface of two-dimensional potential flow of the ideal incompressible fluid of infinite depth. The increase of the scaled wave height H/lambda, where H is the wave height and lambda is the wavelength, from H/lambda = 0 to the critical value Hmax/lambda marks the transition from almost linear wave to a strongly nonlinear limiting Stokes wave. The Stokes wave of the greatest height H = Hmax has an angle of 120° at the crest. To obtain Stokes wave fully nonlinear Euler equations describing the flow can be reformulated in terms of conformal map of the fluid domain into the complex lower half-plane, with fluid free surface mapped into the real line. This description is convenient for analysis and numerical simulations since the whole problem is then reduced to a single nonlinear equation on the real line. Having computed solutions on the real line we extend them to the rest of the complex plane to analyze the singularities above real line. The distance vc from the closest singularity in the upper half-plane to the real line goes to zero as we approach the limiting Stokes wave with maximum hight Hmax/lambda, which is the reason for the widening of the solution's Fourier spectrum. (Abstract shortened by ProQuest.).

Development of an innovative validation strategy of gas-surface interaction modelling for re-entry applications

NASA Astrophysics Data System (ADS)

Joiner, N.; Esser, B.; Fertig, M.; Gülhan, A.; Herdrich, G.; Massuti-Ballester, B.

2016-12-01

This paper summarises the final synthesis of an ESA technology research programme entitled "Development of an Innovative Validation Strategy of Gas Surface Interaction Modelling for Re-entry Applications". The focus of the project was to demonstrate the correct pressure dependency of catalytic surface recombination, with an emphasis on Low Earth Orbit (LEO) re-entry conditions and thermal protection system materials. A physics-based model describing the prevalent recombination mechanisms was proposed for implementation into two CFD codes, TINA and TAU. A dedicated experimental campaign was performed to calibrate and validate the CFD model on TPS materials pertinent to the EXPERT space vehicle at a wide range of temperatures and pressures relevant to LEO. A new set of catalytic recombination data was produced that was able to improve the chosen model calibration for CVD-SiC and provide the first model calibration for the Nickel-Chromium super-alloy PM1000. The experimentally observed pressure dependency of catalytic recombination can only be reproduced by the Langmuir-Hinshelwood recombination mechanism. Due to decreasing degrees of (enthalpy and hence) dissociation with facility stagnation pressure, it was not possible to obtain catalytic recombination coefficients from the measurements at high experimental stagnation pressures. Therefore, the CFD model calibration has been improved by this activity based on the low pressure results. The results of the model calibration were applied to the existing EXPERT mission profile to examine the impact of the experimentally calibrated model at flight relevant conditions. The heat flux overshoot at the CVD-SiC/PM1000 junction on EXPERT is confirmed to produce radiative equilibrium temperatures in close proximity to the PM1000 melt temperature.This was anticipated within the margins of the vehicle design; however, due to the measurements made here for the first time at relevant temperatures for the junction, an increased confidence in this finding is placed on the computations.

Thermodynamic and kinetic modeling of grain boundary equilibrium segregation of P in α-Fe

DOE PAGES

Yang, Y.; Chen, S. -L.

2017-04-18

Phosphorus is a primary contributor to interface fracture and embrittlement in steels because of its strong segregation tendency at grain boundaries (GBs). The lack of consistency in literature data imposes great difficulties in performing segregation modeling that is compatible with both the Langmuir-Mclean segregation theory and the thermodynamic description of the Bcc(Fe,P) phase. Our work carefully evaluated experimental data for phosphorus segregation at GBs in -Fe and provided a new formula for converting the auger electron spectroscopy (AES) peak height ratio to GBs. Furthermore, based on newly assessed literature data, this work proposes that the major driving force for phosphorusmore » segregation is the formation of Fe 3P-type clusters at GBs, which is supported not only by the almost equivalent Gibbs energy of _Fe using the Bcc(Fe,P) substitutional model and the Bcc(Fe,Fe 3P, P) associate model, but also by the good agreement between thermodynamic/kinetic modeling results and experimental data.« less

Preparation of surface modified zinc oxide nanoparticle with high capacity dye removal ability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mahmoodi, Niyaz Mohammad, E-mail: nm_mahmoodi@yahoo.com; Najafi, Farhood

2012-07-15

Highlights: ► Amine-functionalized zinc oxide nanoparticle (AFZON) was synthesized. ► Isotherm and kinetics data followed Langmuir isotherm and pseudo-second order kinetic model, respectively. ► Q{sub 0} of ZON for AB25, DR23 and DR31 was 20, 12 and 15 mg/g, respectively. ► Q{sub 0} of AFZON for AB25, DR23 and DR31 was 1250, 1000 and 1429 mg/g, respectively. ► AFZON was regenerated at pH 12. -- Abstract: In this paper, the surface modification of zinc oxide nanoparticle (ZON) by amine functionalization was studied to prepare high capacity adsorbent. Dye removal ability of amine-functionalized zinc oxide nanoparticle (AFZON) and zinc oxide nanoparticlemore » (ZON) was also investigated. The physical characteristics of AFZON were studied using Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Acid Blue 25 (AB25), Direct Red 23 (DR23) and Direct Red 31 (DR31) were used as model compounds. The effect of operational parameters such as dye concentration, adsorbent dosage, pH and salt on dye removal was evaluated. The isotherm and kinetic of dye adsorption were studied. The maximum dye adsorption capacity (Q{sub 0}) was 20 mg/g AB25, 12 mg/g DR23 and 15 mg/g DR31 for ZON and 1250 mg/g AB25, 1000 mg/g DR23 and 1429 mg/g DR31 for AFZON. It was found that dye adsorption followed Langmuir isotherm. Adsorption kinetic of dyes was found to conform to pseudo-second order kinetics. Dye desorption tests (adsorbent regeneration) showed that the maximum dye release of 90% AB25, 86% for DR23 and 90% for DR31 were achieved in aqueous solution at pH 12. Based on the data of the present investigation, it can be concluded that the AFZON being an adsorbent with high dye adsorption capacity might be a suitable alternative to remove dyes from colored aqueous solutions.« less

The removal of uranium (VI) from aqueous solutions onto activated carbon developed from grinded used tire.

PubMed

Belgacem, Ahmed; Rebiai, Rachid; Hadoun, Hocine; Khemaissia, Sihem; Belmedani, Mohamed

2014-01-01

In this study, activated carbon was prepared from waste tire by KOH chemical activation. The pore properties including the BET surface area, pore volume, pore size distribution, and average pore diameter were characterized. BET surface area of the activated carbon was determined as 558 m(2)/g. The adsorption of uranium ions from the aqueous solution using this activated carbon has been investigated. Various physico-chemical parameters such as pH, initial metal ion concentration, and adsorbent dosage level and equilibrium contact time were studied by a batch method. The optimum pH for adsorption was found to be 3. The removal efficiency has also been determined for the adsorption system as a function of initial concentration. The experimental results were fitted to Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. A comparison of best-fitting was performed using the coefficient of correlation and the Langmuir isotherm was found to well represent the measured sorption data. According to the evaluation using the Langmuir equation, the saturated monolayer sorption capacity of uranium ions onto waste tire activated carbon was 158.73 mg/g. The thermodynamic equilibrium constant and the Gibbs free energy were determined and results indicated the spontaneous nature of the adsorption process. Kinetics data were best described by pseudo-second-order model.

Biosorption and desorption of Cd2+ from wastewater by dehydrated shreds of Cladophora fascicularis

NASA Astrophysics Data System (ADS)

Deng, Liping; Zhu, Xiaobin; Su, Yingying; Su, Hua; Wang, Xinting

2008-02-01

The adsorption and desorption of algae Cladophora fascicularis and their relation with initial Cd2+ concentration, initial pH, and co-existing ions were studied. Adsorption equilibrium and biosorption kinetics were established from batch experiments. The adsorption equilibrium was adequately described by the Langmuir isotherm, and biosorption kinetics was in pseudo-second order model. The experiment on co-existing ions showed that the biosorption capacity of biomass decreased with an increasing concentration of competing ions. Desorption experiments indicated that EDTA was efficient desorbent for recovery from Cd2+. With high capacities of metal biosorption and desorption, the biomass of Cladophora fascicularis is promising as a cost-effective biosorbent for the removal of Cd2+ from wastewater.

Adsorption of 2-propanol on ice probed by ambient pressure X-ray photoelectron spectroscopy

DOE PAGES

Newberg, John T.; Bluhm, Hendrik

2015-08-18

The interaction of 2-propanol with ice was examined via ambient pressure X-ray photoelectron spectroscopy (APXPS), a surface sensitive technique that probes the adsorbed 2-propanol directly with submonolayer resolution. Isothermal uptake experiments were performed on vapor deposited ice at 227 K in the presence of the equilibrium water vapor pressure of 0.05 Torr and 2-propanol partial pressures ranging from 5 × 10 -5 to 2 × 10 -3 Torr. The C 1s APXPS spectra of adsorbed 2-propanol showed two characteristic peaks associated with the C OH alcohol group and C Me methyl groups in a 1 : 2 ratio, respectively. Coveragemore » increased with 2-propanol partial pressure and followed first order Langmuir kinetics with a Langmuir constant of K = 6.3 × 10 3 Torr -1. The 1 : 2 ratio of C OH : C Me remained constant with increasing coverage, indicating there is no chemical reaction upon adsorption. The observed Langmuir kinetics using APXPS is consistent with previous observations of other small chain alcohols via indirect adsorption methods using, e.g., Knudsen cell and coated wall flow tube reactors.« less

In Situ μGISAXS: II. Thaumatin Crystal Growth Kinetic

PubMed Central

Gebhardt, Ronald; Pechkova, Eugenia; Riekel, Christian; Nicolini, Claudio

2010-01-01

The formation of thaumatin crystals by Langmuir-Blodgett (LB) film nanotemplates was studied by the hanging-drop technique in a flow-through cell by synchrotron radiation micrograzing-incidence small-angle x-ray scattering. The kinetics of crystallization was measured directly on the interface of the LB film crystallization nanotemplate. The evolution of the micrograzing-incidence small-angle x-ray scattering patterns suggests that the increase in intensity in the Yoneda region is due to protein incorporation into the LB film. The intensity variation suggests several steps, which were modeled by system dynamics based on first-order differential equations. The kinetic data can be described by two processes that take place on the LB film, a first, fast, process, attributed to the crystal growth and its detachment from the LB film, and a second, slower process, attributed to an unordered association and conversion of protein on the LB film. PMID:20713011

Evaluation of BTEX and phenol removal from aqueous solution by multi-solute adsorption onto smectite organoclay.

PubMed

Carvalho, M N; da Motta, M; Benachour, M; Sales, D C S; Abreu, C A M

2012-11-15

The removal process of BTEX and phenol was evaluated. The smectite organoclay for single-solute system reached removal was evaluated by adsorption on smectite organoclay adsorbent by kinetic and equilibrium efficiencies between 55 and 90% while was reached between 30 and 90% for multi-solute system at 297 K and pH 9. The Langmuir-Freundlich model was used to fit the experimental data with correlation coefficient between 0.98 and 0.99 providing kinetic and equilibrium parameter values. Phenol and ethylbenzene presented high maximum adsorbed amount, 8.28 and 6.67 mg/g, respectively, compared to the other compounds for single-solute. Toluene and p-xylene presented high values of adsorption constant which indicates a high adsorption affinity of compounds to organoclay surface and high binding energy of adsorption. Phenol presented low kinetic adsorption constant value indicating slow rate of adsorption. Copyright © 2012 Elsevier B.V. All rights reserved.

Adsorptive removal of an anionic dye Congo red by flower-like hierarchical magnesium oxide (MgO)-graphene oxide composite microspheres

NASA Astrophysics Data System (ADS)

Xu, Jing; Xu, Difa; Zhu, Bicheng; Cheng, Bei; Jiang, Chuanjia

2018-03-01

Flower-like magnesium oxide (MgO) microspheres and MgO-graphene oxide (GO) composites with an average diameter of 500 nm and hierarchical structure were synthesized through an ethylene glycol-mediated self-assembly process. The adsorption of Congo red (CR) by the prepared samples was evaluated in water under ambient conditions. The equilibrium adsorption isotherms of CR on the as-prepared samples could be described by the Langmuir model. The MgO-GO microspheres prepared with 0.5 wt% GO showed higher adsorption capacity (237.0 mg/g) than the MgO microspheres (227.7 mg/g). Adsorption kinetics results of CR indicated that pseudo-second-order kinetic equation could well explain the adsorption kinetics behaviors of CR. These findings indicate that the MgO-GO composite microspheres are potential adsorbents for effective removal of Congo red from wastewater.

Engineering-scale experiments of solar photocatalytic oxidation of trichloroethylene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pacheco, J.; Prairie, M.; Evans, L.

1990-01-01

A photocatalytic process is being developed to destroy organic contaminants in water. Tests with a common water pollutant, trichlorethylene (TCE), were conducted at the Solar Thermal Test Facility at Sandia with trough systems. Tests at this scale provide verification of laboratory studies and allow examination of design and operation issues that only arise in experiments on a realistic scale. The catalyst, titanium dioxide (TiO{sub 2}), is a harmless material found in paint, cosmetics and even toothpaste. We examined the effect of initial contaminant concentration and the effect of hydrogen peroxide on the photocatalytic decomposition of trichlorethylene (TCE). An aqueous solutionmore » of 5000 parts per billion (ppB) TCE with 0.1 weight {percent} suspended titanium dioxide catalyst required approximately 4.2 minutes of exposure to destroy the TCE to a detection limit of 5 ppB. For a 300 ppB TCE solution, the time required was only 2.5 minutes to reach the same level of destruction. Adding 250 parts per million (ppM) of hydrogen peroxide reduced the time required by about 1 minute. A two parameter Langmuir Hinshelwood model was able to describe the data. A simple flow apparatus was built to test four fixed catalyst supports and to measure their pressure drop and assess their ability to withstand flow conditions typical of a full-sized system. In this paper, we summarize the engineering-scale testing and results. 16 refs., 5 figs.« less

Kinetic and thermodynamic studies on the adsorption of heavy metals from aqueous solution by melanin nanopigment obtained from marine source: Pseudomonas stutzeri.

PubMed

Manirethan, Vishnu; Raval, Keyur; Rajan, Reju; Thaira, Harsha; Balakrishnan, Raj Mohan

2018-05-15

The difficulty in removal of heavy metals at concentrations below 10 mg/L has led to the exploration of efficient adsorbents for removal of heavy metals. The adsorption capacity of biosynthesized melanin for Mercury (Hg(II)), Chromium (Cr(VI)), Lead (Pb(II)) and Copper (Cu(II)) was investigated at different operating conditions like pH, time, initial concentration and temperature. The heavy metals adsorption process was well illustrated by the Lagergren's pseudo-second-order kinetic model and the equilibrium data fitted excellently to Langmuir isotherm. Maximum adsorption capacity obtained from Langmuir isotherm for Hg(II) was 82.4 mg/g, Cr(VI) was 126.9 mg/g, Pb(II) was 147.5 mg/g and Cu(II) was 167.8 mg/g. The thermodynamic parameters revealed that the adsorption of heavy metals on melanin is favorable, spontaneous and endothermic in nature. Binding of heavy metals on melanin surface was proved by Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). Contemplating the results, biosynthesized melanin can be a potential adsorbent for efficient removal of Hg(II), Cr(VI), Pb(II) and Cu(II) ions from aqueous solution. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effects of deposition temperature and ammonia flow on metal-organic chemical vapor deposition of hexagonal boron nitride

NASA Astrophysics Data System (ADS)

Rice, Anthony; Allerman, Andrew; Crawford, Mary; Beechem, Thomas; Ohta, Taisuke; Spataru, Catalin; Figiel, Jeffrey; Smith, Michael

2018-03-01

The use of metal-organic chemical vapor deposition at high temperature is investigated as a means to produce epitaxial hexagonal boron nitride (hBN) at the wafer scale. Several categories of hBN films were found to exist based upon precursor flows and deposition temperature. Low, intermediate, and high NH3 flow regimes were found to lead to fundamentally different deposition behaviors. The low NH3 flow regimes yielded discolored films of boron sub-nitride. The intermediate NH3 flow regime yielded stoichiometric films that could be deposited as thick films. The high NH3 flow regime yielded self-limited deposition with thicknesses limited to a few mono-layers. A Langmuir-Hinshelwood mechanism is proposed to explain the onset of self-limited behavior for the high NH3 flow regime. Photoluminescence characterization determined that the intermediate and high NH3 flow regimes could be further divided into low and high temperature behaviors with a boundary at 1500 °C. Films deposited with both high NH3 flow and high temperature exhibited room temperature free exciton emission at 210 nm and 215.9 nm.

Activation of CO and CO2 on homonuclear boron bonds of fullerene-like BN cages: first principles study

NASA Astrophysics Data System (ADS)

Sinthika, S.; Kumar, E. Mathan; Surya, V. J.; Kawazoe, Y.; Park, Noejung; Iyakutti, K.; Thapa, Ranjit

2015-12-01

Using density functional theory we investigate the electronic and atomic structure of fullerene-like boron nitride cage structures. The pentagonal ring leads to the formation of homonuclear bonds. The homonuclear bonds are also found in other BN structures having pentagon line defect. The calculated thermodynamics and vibrational spectra indicated that, among various stable configurations of BN-60 cages, the higher number of homonuclear N-N bonds and lower B:N ratio can result in the more stable structure. The homonuclear bonds bestow the system with salient catalytic properties that can be tuned by modifying the B atom bonding environment. We show that homonuclear B-B (B2) bonds can anchor both oxygen and CO molecules making the cage to be potential candidates as catalyst for CO oxidation via Langmuir-Hinshelwood (LH) mechanism. Moreover, the B-B-B (B3) bonds are reactive enough to capture, activate and hydrogenate CO2 molecules to formic acid. The observed trend in reactivity, viz B3 > B2 > B1 is explained in terms of the position of the boron defect state relative to the Fermi level.

Activation of CO and CO2 on homonuclear boron bonds of fullerene-like BN cages: first principles study.

PubMed

Sinthika, S; Kumar, E Mathan; Surya, V J; Kawazoe, Y; Park, Noejung; Iyakutti, K; Thapa, Ranjit

2015-12-02

Using density functional theory we investigate the electronic and atomic structure of fullerene-like boron nitride cage structures. The pentagonal ring leads to the formation of homonuclear bonds. The homonuclear bonds are also found in other BN structures having pentagon line defect. The calculated thermodynamics and vibrational spectra indicated that, among various stable configurations of BN-60 cages, the higher number of homonuclear N-N bonds and lower B:N ratio can result in the more stable structure. The homonuclear bonds bestow the system with salient catalytic properties that can be tuned by modifying the B atom bonding environment. We show that homonuclear B-B (B2) bonds can anchor both oxygen and CO molecules making the cage to be potential candidates as catalyst for CO oxidation via Langmuir-Hinshelwood (LH) mechanism. Moreover, the B-B-B (B3) bonds are reactive enough to capture, activate and hydrogenate CO2 molecules to formic acid. The observed trend in reactivity, viz B3 > B2 > B1 is explained in terms of the position of the boron defect state relative to the Fermi level.

Selective adsorption of Pt ions from chloride solutions obtained by leaching chlorinated spent automotive catalysts on ion exchange resin Diaion WA21J.

PubMed

Shen, Shaobo; Guishen, Liang; Pan, Tonglin; He, JunZhang; Guo, Zhanchen

2011-12-15

Thermodynamic and kinetics studies for adsorption of Pt ions complexes from the chloride solutions obtained by leaching chlorinated spent automotive catalysts on anionic exchange resin Diaion WA21J were carried out. It was found that only Si, Pt, Rh and Pd from the solution were selectively adsorbed on the resin Diaion WA21J more strongly. The adsorption equilibrium time for Pt ions was about 20 h. The isothermal adsorption of Pt ions was found to fit Langmuir, Freundlich and DKR models. The maximum monolayer adsorption capacities Q(max) and X(m) of Pt ions on the resin based on Langmuir and DKR model were 4.85, 5.36 and 5.69 mg/g as well as 5.01, 5.63 and 5.98 mg/g for temperatures 18°C, 28°C and 40°C, respectively. The apparent adsorption energy E(ad) based on DKR model were -11.79, -11.04 and -11.04 kJ/mol for the temperatures 18°C, 28°C and 40°C, respectively. Ion exchange was the mechanism involved in the adsorption process. The adsorption of Pt ions on the resin underwent pseudo-first-order kinetic process, and the apparent adsorption activation energy E(a,1) was 12.6 kJ/mol. The intraparticle diffusion of Pt ions was a main rate-controlling step in most of time of adsorption process. Copyright © 2011 Elsevier Inc. All rights reserved.

Cadmium telluride nanoparticles loaded on activated carbon as adsorbent for removal of sunset yellow

NASA Astrophysics Data System (ADS)

Ghaedi, M.; Hekmati Jah, A.; Khodadoust, S.; Sahraei, R.; Daneshfar, A.; Mihandoost, A.; Purkait, M. K.

2012-05-01

Adsorption is a promising technique for decolorization of effluents of textile dyeing industries but its application is limited due to requirement of high amounts of adsorbent required. The objective of this study was to assess the potential of cadmium telluride nanoparticles loaded onto activated carbon (CdTN-AC) for the removal of sunset yellow (SY) dye from aqueous solution. Adsorption studies were conducted in a batch mode varying solution pH, contact time, initial dye concentration, CdTN-AC dose, and temperature. In order to investigate the efficiency of SY adsorption on CdTN-AC, pseudo-first-order, pseudo-second-order, Elovich, and intra-particle diffusion kinetic models were studied. It was observed that the pseudo-second-order kinetic model fits better than other kinetic models with good correlation coefficient. Equilibrium data were fitted to the Langmuir model. Thermodynamic parameters such as enthalpy, entropy, activation energy, and sticking probability were also calculated. It was found that the sorption of SY onto CdTN-AC was spontaneous and endothermic in nature. The proposed adsorbent is applicable for SY removal from waste of real effluents including pea-shooter, orange drink and jelly banana with efficiency more than 97%.

The potential use of activated carbon prepared from Ziziphus species for removing dyes from waste waters

NASA Astrophysics Data System (ADS)

Regti, Abdelmajid; Laamari, My Rachid; Stiriba, Salah-Eddine; El Haddad, Mohammadine

2017-11-01

In this study, the adsorption potential of activated carbon prepared from Ziziphus mauritiana nuts for the removal of methylene blue (MB) from aqueous solution has been investigated using batch mode experiments. The effects of some operating parameters on the removal dye such as, initial pH (2-12), temperature (298-328 K), initial MB concentration (20-100 mg L-1), and contact time (5-70 min) were investigated. Adsorption kinetic showed that the rate adsorption followed the pseudo-second-order kinetic model. Four adsorption isotherms models were applied to experimental equilibrium data (Langmuir, Freundlich, Redlich-Peterson, and Fritz-Schlunder) and the different constants were calculated using non-linear equations models. Fritz-Schlunder model was found the best one to describe the adsorption process which suggests that the adsorption of MB onto activated carbon derived from Ziziphus mauritiana is heterogeneous with a multilayer. Thermodynamic adsorption showed that the process was endothermic and spontaneous in nature.

Adsorption of Rh(III) complexes from chloride solutions obtained by leaching chlorinated spent automotive catalysts on ion-exchange resin Diaion WA21J.

PubMed

Shen, Shaobo; Pan, Tonglin; Liu, Xinqiang; Yuan, Lei; Wang, Jinchao; Zhang, Yongjian; Guo, Zhanchen

2010-07-15

It was found that Rh, Pd and Pt contained in the spent ceramic automotive catalysts could be effectively extracted by dry chlorination with chlorine. In order to concentrate Rh(III) ions contained in the chloride solutions obtained, thermodynamic and kinetics studies for adsorption of Rh(III) complexes from the chloride solutions on an anionic exchange resin Diaion WA21J were carried out. Rh, Pd, Pt, Al, Fe, Si, Zn and Pb from the chloride solution could be adsorbed on the resin. The distribution coefficients (K(d)) of Rh(III) decreased with the increase in initial Rh(III) concentration or in adsorption temperature. The isothermal adsorption of Rh(III) was found to fit Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich models under the adsorption conditions. The maximum monolayer adsorption capacities Q(max) based on Langmuir adsorption isotherms were 6.39, 6.61 and 5.81 mg/g for temperatures 18, 28 and 40 degrees C, respectively. The apparent adsorption energy of Rh was about -7.6 kJ/mol and thus Rh(III) adsorption was a physical type. The experimental data obtained could be better simulated by pseudo-first-order kinetic model and the activation energy obtained was 6.54 J/mol. The adsorption rate of Rh(III) was controlled by intraparticle diffusion in most of time of adsorption process. 2010 Elsevier B.V. All rights reserved.

Novel Metal-Organic Framework (MOF) Based Composite Material for the Sequestration of U(VI) and Th(IV) Metal Ions from Aqueous Environment.

PubMed

Alqadami, Ayoub Abdullah; Naushad, Mu; Alothman, Zeid Abdullah; Ghfar, Ayman A

2017-10-18

The combination of magnetic nanoparticles and metal-organic frameworks (MOFs) has demonstrated their prospective for pollutant sequestration. In this work, a magnetic metal-organic framework nanocomposite (Fe 3 O 4 @AMCA-MIL53(Al) was prepared and used for the removal of U(VI) and Th(IV) metal ions from aqueous environment. Fe 3 O 4 @AMCA-MIL53(Al) nanocomposite was characterized by TGA, FTIR, SEM-EDX, XRD, HRTEM, BET, VSM (vibrating sample magnetometry), and XPS analyses. A batch technique was applied for the removal of the aforesaid metal ions using Fe 3 O 4 @AMCA-MIL53(Al) at different operating parameters. The isotherm and kinetic data were accurately described by the Langmuir and pseudo-second-order models. The adsorption capacity was calculated to be 227.3 and 285.7 mg/g for U(VI) and Th(IV), respectively, by fitting the equilibrium data to the Langmuir model. The kinetic studies demonstrated that the equilibrium time was 90 min for each metal ion. Various thermodynamic parameters were evaluated which indicated the endothermic and spontaneous nature of adsorption. The collected outcomes showed that Fe 3 O 4 @AMCA-MIL53(Al) was a good material for the exclusion of these metal ions from aqueous medium. The adsorbed metals were easily recovered by desorption in 0.01 M HCl. The excellent adsorption capacity and the response to the magnetic field made this novel material an auspicious candidate for environmental remediation technologies.

Exploring the interaction of silver nanoparticles with pepsin and its adsorption isotherms and kinetics.

PubMed

Li, Xiangrong; Wang, Kaiwei; Peng, Yanru

2018-04-25

The interaction of nanoparticles (NPs) with proteins is a topic of high relevance for the medical application of nanomaterials. In the study, a comprehensive investigation was performed for the binding properties of silver nanoparticles (AgNPs) to pepsin. The results indicate that the binding of AgNPs to pepsin may be a static quenching mechanism. Thermodynamic analysis reveals that AgNPs binds to pepsin is synergistically driven by enthalpy and entropy, and the major driving forces are hydrophobic and electrostatic interactions. Synchronous fluorescence spectroscopy shows that AgNPs may induce microenvironmental changes of pepsin. The hydrophobicity of Trp is increased while the hydrophility of Tyr is increased. The adsorption of pepsin on AgNPs was analyzed by Langmuir and Freundlich models, suggesting that the equilibrium adsorption data fit well with Freundlich model. The equilibrium adsorption data were modeled using the pseudo-first-order and pseudo-second-order kinetic equations. The results indicate that pseudo-second-order kinetic equation better describes the adsorption kinetics. The study provides an accurate and full basic data for clarifying the binding mechanism, adsorption isotherms and kinetic behaviors of AgNPs with pepsin. These fundamental works will provide some new insights into the safe and effective application of AgNPs in biological and medical areas. Copyright © 2018 Elsevier B.V. All rights reserved.

Removing polycyclic aromatic hydrocarbons from water using granular activated carbon: kinetic and equilibrium adsorption studies.

PubMed

Eeshwarasinghe, Dinushika; Loganathan, Paripurnanda; Kalaruban, Mahatheva; Sounthararajah, Danious Pratheep; Kandasamy, Jaya; Vigneswaran, Saravanamuthu

2018-05-01

Polycyclic aromatic hydrocarbons (PAHs) constitute a group of highly persistent, toxic and widespread environmental micropollutants that are increasingly found in water. A study was conducted in removing five PAHs, specifically naphthalene, acenaphthylene, acenaphthene, fluorene and phenanthrene, from water by adsorption onto granular activated carbon (GAC). The pseudo-first-order (PFO) model satisfactorily described the kinetics of adsorption of the PAHs. The Weber and Morris diffusion model's fit to the data showed that there were faster and slower rates of intra-particle diffusion probably into the mesopores and micropores of the GAC, respectively. These rates were negatively related to the molar volumes of the PAHs. Batch equilibrium adsorption data fitted well to the Langmuir, Freundlich and Dubinin-Radushkevich models, of which the Freundlich model exhibited the best fit. The adsorption affinities were related to the hydrophobicity of the PAHs as determined by the log K ow values. Free energies of adsorption calculated from the Dubinin-Radushkevich model and the satisfactory kinetic data fitting to the PFO model suggested physical adsorption of the PAHs. Adsorption of naphthalene, acenaphthylene and acenaphthene in fixed-bed columns containing a mixture of GAC (0.5 g) + sand (24.5 g) was satisfactorily simulated by the Thomas model.

Lateral interactions and non-equilibrium in surface kinetics

NASA Astrophysics Data System (ADS)

Menzel, Dietrich

2016-08-01

Work modelling reactions between surface species frequently use Langmuir kinetics, assuming that the layer is in internal equilibrium, and that the chemical potential of adsorbates corresponds to that of an ideal gas. Coverage dependences of reacting species and of site blocking are usually treated with simple power law coverage dependences (linear in the simplest case), neglecting that lateral interactions are strong in adsorbate and co-adsorbate layers which may influence kinetics considerably. My research group has in the past investigated many co-adsorbate systems and simple reactions in them. We have collected a number of examples where strong deviations from simple coverage dependences exist, in blocking, promoting, and selecting reactions. Interactions can range from those between next neighbors to larger distances, and can be quite complex. In addition, internal equilibrium in the layer as well as equilibrium distributions over product degrees of freedom can be violated. The latter effect leads to non-equipartition of energy over molecular degrees of freedom (for products) or non-equal response to those of reactants. While such behavior can usually be described by dynamic or kinetic models, the deeper reasons require detailed theoretical analysis. Here, a selection of such cases is reviewed to exemplify these points.

Graphene-a promising material for removal of perchlorate (ClO4-) from water.

PubMed

Lakshmi, Jothinathan; Vasudevan, Subramanyan

2013-08-01

A batch adsorption process was applied to investigate the removal of perchlorate (ClO4 (-)) from water by graphene. In doing so, the thermodynamic adsorption isotherm and kinetic studies were also carried out. Graphene was prepared by a facile liquid-phase exfoliation. Graphene was characterized by Raman spectroscopy, Fourier-transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscope, and zeta potential measurements. A systematic study of the adsorption process was performed by varying pH, ionic strength, and temperature. The adsorption efficiency of graphene was 99.2 %, suggesting that graphene is an excellent adsorbent for ClO4 (-) removal from water. The rate constants for all these kinetic models were calculated, and the results indicate that second-order kinetics model was well suitable to model the kinetic adsorption of ClO4 (-). Equilibrium data were well described by the typical Langmuir adsorption isotherm. The experimental results showed that graphene is an excellent perchlorate adsorbent with an adsorbent capacity of up to 0.024 mg/g at initial perchlorate concentration of 2 mg/L and temperature of 298 K. Thermodynamic studies revealed that the adsorption reaction was a spontaneous and endothermic process. Graphene removed the perchlorate present in the water and reduced it to a permissible level making it drinkable.

Liquid phase adsorptions of Rhodamine B dye onto raw and chitosan supported mesoporous adsorbents: isotherms and kinetics studies

NASA Astrophysics Data System (ADS)

Inyinbor, A. A.; Adekola, F. A.; Olatunji, G. A.

2017-09-01

Irvingia gabonensis endocarp waste was charred (DNc) and subsequently coated with chitosan (CCDNc). Physicochemical characteristics of the two adsorbents were established, while Fourier transform infrared (FTIR), Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface area methods were further employed for characterization. Efficiencies of the prepared adsorbents in the uptake of Rhodamine B (RhB) from aqueous effluent were investigated and adsorption data were tested using four isotherms and four kinetics models. The BET surface areas of the prepared adsorbent were 0.0092 and 4.99 m2/g for DNc and CCDNc, respectively, and maximum adsorption was recorded at pH between 3 and 4, respectively. While monolayer adsorption dominates the uptake of RhB onto DNc, uptake of RhB onto CCDNc was onto heterogeneous surface. The maximum monolayer adsorption capacities ( q max) obtained from the Langmuir equation are 52.90 and 217.39 mg/g for DNc and CCDNc, respectively. Pseudo second order and Elovich kinetic models well described the kinetics of the two adsorption processes. The mean sorption energy ( E) calculated from the D-R model and desorption efficiencies suggests that while the uptake of RhB onto DNc was physical in nature, for RhB-CCDNc system chemisorption dominates.

Amination of activated carbon for enhancing phenol adsorption: Effect of nitrogen-containing functional groups

NASA Astrophysics Data System (ADS)

Yang, Guo; Chen, Honglin; Qin, Hangdao; Feng, Yujun

2014-02-01

To study the contribution of different nitrogen-containing functional groups to enhancement of phenol adsorption, the aminated activated carbons (AC) were characterized by N2 adsorption/desorption, XPS, Boehm titration, and pH drift method and tested for adsorption behaviors of phenol. Adsorption isotherm fitting revealed that the Langmuir model was preferred for the aminated ACs. The adsorption capacity per unit surface area (qm/SSABET) was linearly correlated with the amount of pyridinic and pyrrolic N, which suggested that these two functional groups played a critical role in phenol adsorption. The enhancement of adsorption capacity was attributed to the strengthened π-π dispersion between phenol and basal plane of AC by pyridinic, pyrrolic N. The adsorption kinetics was found to follow the pseudo-second-order kinetic model, and intraparticle diffusion was one of the rate-controlling steps in the adsorption process.

Removal of fluoride from drinking water by cellulose@hydroxyapatite nanocomposites.

PubMed

Yu, Xiaolin; Tong, Shengrui; Ge, Maofa; Zuo, Junchao

2013-01-30

Cellulose@hydroxyapatite (HA) nanocomposites were prepared in NaOH/thiourea/urea/H(2)O solution via situ hybridization. The composite materials combine the advantage of cellulose and HA with the high specific surface area and the strong affinity toward fluoride. The composite materials were characterized by FTIR, SEM, XRD, TG and XPS, and the adsorption of fluoride was investigated. Adsorption kinetics indicated the adsorption equilibrium of fluoride was within 360 min and the adsorption process was well described by the pseudo-second-order kinetic model. The Langmuir and Freundlich isotherm models could fit the experimental data well. At the initial fluoride concentration of 10mg/L, the residual concentration using above 3g/L adsorbent dose could meet the drinking water standard of WHO norms. Furthermore, the coexisting anions had no significant effect on fluoride adsorption. Copyright © 2012 Elsevier Ltd. All rights reserved.

Sorption and desorption of lead (II) from wastewater by green algae Cladophora fascicularis.

PubMed

Deng, Liping; Su, Yingying; Su, Hua; Wang, Xinting; Zhu, Xiaobin

2007-05-08

Biosorption is an effective method to remove heavy metals from wastewater. In this work, adsorption features of Cladophora fascicularis were investigated as a function of time, initial pH, initial Pb(II) concentrations, temperature and co-existing ions. Kinetics and equilibria were obtained from batch experiments. The biosorption kinetics followed the pseudo-second order model. Adsorption equilibria were well described by the Langmuir and Freundlich isotherm models. The maximum adsorption capacity was 198.5 mg/g at 298K and pH 5.0. The adsorption processes were endothermic and the biosorption heat was 29.6 kJ/mol. Desorption experiments indicated that 0.01 mol/L Na(2)EDTA was an efficient desorbent for the recovery of Pb(II) from biomass. IR spectrum analysis suggested amido or hydroxy, CO and C-O could combine intensively with Pb(II).

Synthesis of graphene aerogel for adsorption of bisphenol A

NASA Astrophysics Data System (ADS)

Trinh, Truong Thi Phuong Nguyet Xuan; Long, Nguyen Huynh Bach Son; Quang, Dong Thanh; Hieu, Nguyen Huu

2018-04-01

In this research, graphene aerogel (GA) was synthesized by chemical reduction method using ethylene diamine as a reducing agent. The morphology and properties of GA were characterized by calculating apparent density, Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, and Brunauer-Emmett-Teller (BET) specific surface area. High-performance liquid chromatography (HPLC) was used to quantify the amount of the residual bisphenol A (BPA) concentration. The analysis results showed that GA exhibited low density ranging from 4-8 mg/cm3, hydrophobicity, high porosity, and specific surface area of 1883 m2/g according to BET. The obtained GA was used as an adsorbent for BPA. The effects of pH, contact time, and initial BPA concentration on the adsorption were investigated. The adsorption equilibrium time could be reached within 240 minutes. The adsorption data were well-fitted to pseudo-second-order kinetic equation and Langmuir isotherm model. The maximum adsorption capacity of GA for BPA calculated by the Langmuir model was 185.185 mg/g at pH 7. Accordingly, GA could be considered as promising adsorbents for BPA in water.

Design, characterization and evaluation of hydroxyethylcellulose based novel regenerable supersorbent for heavy metal ions uptake and competitive adsorption.

PubMed

Abbas, Azhar; Hussain, Muhammad Ajaz; Sher, Muhammad; Irfan, Muhammad Imran; Tahir, Muhammad Nawaz; Tremel, Wolfgang; Hussain, Syed Zajif; Hussain, Irshad

2017-09-01

Hydroxyethylcellulose succinate-Na (HEC-Suc-Na) was designed and evaluated for removal of some heavy metal ions from aqueous solution. Pristine sorbent HEC-Suc-Na was thoroughly characterized by FTIR and solid-state CP/MAS 13 C NMR spectroscopy, SEM-EDS and zero point charge analyses. Langmuir isotherm, pseudo second order kinetic and ion exchange models provided best fit to the experimental data of sorption of metal ions. Maximum sorption capacities of supersorbent HEC-Suc-Na for sorption of heavy metal ions from aqueous solution as calculated by Langmuir isotherm model were found to be 1000, 909.09, 666.6, 588 and 500mgg -1 for Pb(II), Cr(VI), Co(II), Cu(II) and Ni(II), respectively. Competitive sorption of these heavy metal ions was carried out from galvanic and nuclear waste water simulated environment. The negative values of ΔG° and ΔH° indicated spontaneity and exothermic nature of sorption. The sorbent was efficiently regenerated with no significant decrease in sorption capacity after five cycles. Copyright © 2017 Elsevier B.V. All rights reserved.

Removal of ammonium ions by laboratory-synthesized zeolite linde type A adsorption from water samples affected by mining activities in Ghana.

PubMed

Kwakye-Awuah, Bright; Labik, Linus Kweku; Nkrumah, Isaac; Williams, Craig

2014-03-01

Ammonium ion adsorption by laboratory-synthesized zeolite (linde type A; LTA) was investigated in batch kinetics experiments. Synthesized zeolite LTA was characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy and particle size analysis. Water samples were taken from the Nyam and Tano rivers in Ghana, and 0.8 g of zeolite was added to 100 ml portions of each sample. Portions of the samples were withdrawn every 30 min for 150 min and the concentration of ammonia in each sample was determined. The removal efficiency of zeolite LTA was evaluated by retrieving the zeolite from the water samples and adding to a fresh sample to repeat the process. Equilibrium data were fitted by Langmuir and Freundlich isotherms. Maximum adsorption capacities were 72.99 mg g(-1) for samples from the River Nyam and 72.87 mg g(-1) for samples from the River Tano. The equilibrium kinetic data were analysed using adsorption kinetic models: pseudo-first order and pseudo-second order kinetic models. Linear regression was used to estimate the adsorption and kinetic parameters. The results showed that the adsorption followed pseudo-second order kinetics and suggest that zeolite LTA is a good adsorbent for the removal of nitrogen ammonia from water.

Kinetics and equilibrium modelling of lead uptake by algae Gelidium and algal waste from agar extraction industry.

PubMed

Vilar, Vítor J P; Botelho, Cidália M S; Boaventura, Rui A R

2007-05-08

Pb(II) biosorption onto algae Gelidium, algal waste from agar extraction industry and a composite material was studied. Discrete and continuous site distribution models were used to describe the biosorption equilibrium at different pH (5.3, 4 and 3), considering competition among Pb(II) ions and protons. The affinity distribution function of Pb(II) on the active sites was calculated by the Sips distribution. The Langmuir equilibrium constant was compared with the apparent affinity calculated by the discrete model, showing higher affinity for lead ions at higher pH values. Kinetic experiments were conducted at initial Pb(II) concentrations of 29-104 mgl(-1) and data fitted to pseudo-first Lagergren and second-order models. The adsorptive behaviour of biosorbent particles was modelled using a batch mass transfer kinetic model, which successfully predicts Pb(II) concentration profiles at different initial lead concentration and pH, and provides significant insights on the biosorbents performance. Average values of homogeneous diffusivity, D(h), are 3.6 x 10(-8); 6.1 x 10(-8) and 2.4 x 10(-8)cm(2)s(-1), respectively, for Gelidium, algal waste and composite material. The concentration of lead inside biosorbent particles follows a parabolic profile that becomes linear near equilibrium.

Heavy Metal Adsorption onto Kappaphycus sp. from Aqueous Solutions: The Use of Error Functions for Validation of Isotherm and Kinetics Models

PubMed Central

Rahman, Md. Sayedur; Sathasivam, Kathiresan V.

2015-01-01

Biosorption process is a promising technology for the removal of heavy metals from industrial wastes and effluents using low-cost and effective biosorbents. In the present study, adsorption of Pb2+, Cu2+, Fe2+, and Zn2+ onto dried biomass of red seaweed Kappaphycus sp. was investigated as a function of pH, contact time, initial metal ion concentration, and temperature. The experimental data were evaluated by four isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and four kinetic models (pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models). The adsorption process was feasible, spontaneous, and endothermic in nature. Functional groups in the biomass involved in metal adsorption process were revealed as carboxylic and sulfonic acids and sulfonate by Fourier transform infrared analysis. A total of nine error functions were applied to validate the models. We strongly suggest the analysis of error functions for validating adsorption isotherm and kinetic models using linear methods. The present work shows that the red seaweed Kappaphycus sp. can be used as a potentially low-cost biosorbent for the removal of heavy metal ions from aqueous solutions. Further study is warranted to evaluate its feasibility for the removal of heavy metals from the real environment. PMID:26295032

Heavy Metal Adsorption onto Kappaphycus sp. from Aqueous Solutions: The Use of Error Functions for Validation of Isotherm and Kinetics Models.

PubMed

Rahman, Md Sayedur; Sathasivam, Kathiresan V

2015-01-01

Biosorption process is a promising technology for the removal of heavy metals from industrial wastes and effluents using low-cost and effective biosorbents. In the present study, adsorption of Pb(2+), Cu(2+), Fe(2+), and Zn(2+) onto dried biomass of red seaweed Kappaphycus sp. was investigated as a function of pH, contact time, initial metal ion concentration, and temperature. The experimental data were evaluated by four isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and four kinetic models (pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models). The adsorption process was feasible, spontaneous, and endothermic in nature. Functional groups in the biomass involved in metal adsorption process were revealed as carboxylic and sulfonic acids and sulfonate by Fourier transform infrared analysis. A total of nine error functions were applied to validate the models. We strongly suggest the analysis of error functions for validating adsorption isotherm and kinetic models using linear methods. The present work shows that the red seaweed Kappaphycus sp. can be used as a potentially low-cost biosorbent for the removal of heavy metal ions from aqueous solutions. Further study is warranted to evaluate its feasibility for the removal of heavy metals from the real environment.

Two dimensional kinetic analysis of electrostatic harmonic plasma waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fonseca-Pongutá, E. C.; Ziebell, L. F.; Gaelzer, R.

2016-06-15

Electrostatic harmonic Langmuir waves are virtual modes excited in weakly turbulent plasmas, first observed in early laboratory beam-plasma experiments as well as in rocket-borne active experiments in space. However, their unequivocal presence was confirmed through computer simulated experiments and subsequently theoretically explained. The peculiarity of harmonic Langmuir waves is that while their existence requires nonlinear response, their excitation mechanism and subsequent early time evolution are governed by essentially linear process. One of the unresolved theoretical issues regards the role of nonlinear wave-particle interaction process over longer evolution time period. Another outstanding issue is that existing theories for these modes aremore » limited to one-dimensional space. The present paper carries out two dimensional theoretical analysis of fundamental and (first) harmonic Langmuir waves for the first time. The result shows that harmonic Langmuir wave is essentially governed by (quasi)linear process and that nonlinear wave-particle interaction plays no significant role in the time evolution of the wave spectrum. The numerical solutions of the two-dimensional wave spectra for fundamental and harmonic Langmuir waves are also found to be consistent with those obtained by direct particle-in-cell simulation method reported in the literature.« less

Adsorption properties of kaolinite-based nanocomposites for Fe and Mn pollutants from aqueous solutions and raw ground water: kinetics and equilibrium studies.

PubMed

Shaban, Mohamed; Hassouna, Mohamed E M; Nasief, Fadya M; AbuKhadra, Mostafa R

2017-10-01

Raw kaolinite was used in the synthesis of metakaolinite/carbon nanotubes (K/CNTs) and kaolinite/starch (K/starch) nanocomposites. Raw kaolinite and the synthetic composites were characterized using XRD, SEM, and TEM techniques. The synthetic composites were used as adsorbents for Fe and Mn ions from aqueous solutions and natural underground water. The adsorption by the both composites is highly pH dependent and achieves high efficiency within the neutral pH range. The experimental adsorption data for the uptake of Fe and Mn ions by K/CNTs were found to be well represented by the pseudo-second-order kinetic model rather than the intra-particle diffusion model or Elovich model. For the adsorption using K/starch, the uptake results of Fe ions was well fitted by the second-order model, whereas the uptake of Mn ions fitted well to the Elovich model rather than pseudo-second-order and intra-particle diffusion models The equilibrium studies revealed the excellent fitting of the removal of Fe and Mn ions by K/CNTs and Fe using K/starch with the Langmuir isotherm model rather than with Freundlich and Temkin models. But the adsorption of Mn ions by K/starch is well fitted with Freundlich rather than Temkin and Langmuir isotherm models. The thermodynamic studies reflected the endothermic nature and the exothermic nature for the adsorption by K/CNTs and K/starch nanocomposites, respectively. Natural ground water contaminated by 0.4 mg/L Fe and 0.5 mg/L Mn was treated at the optimum conditions of pH 6 and 120 min contact time. Under these conditions, 92.5 and 72.5% Fe removal efficiencies were achieved using 20 mg of K/CNTs and K/starch nanocomposites, respectively. Also, K/CNTs nanocomposite shows higher efficiency in the removal of Mn ions as compared to K/starch nanocomposite.

Magnetic CuHCNPAN nano composite as an efficient adsorbent for strontium uptake

NASA Astrophysics Data System (ADS)

Mobtaker, Hossein Ghasemi; Pakzad, Seyed Mohammadreza; Yousefi, Taher

2018-06-01

An excellent composite was synthesized for sorption of strontium from solution. The composite (CuHCNPAN) components were copper hexacyanoferrate, magnetite and PAN. The XRD method confirmed the formation and presence of two crystalline phases of magnetite and copper hexacyanoferrate in composite. Particle sizes were determined by XRD and SEM methods. It was found that the particles were nano size. Some other methods such as FT IR, BET and TG methods were also used to determine the properties of the composite. The composite was used for sorption of strontium from solution. It was found that the kinetic of strontium sorption by the composite could be modeled by pseudo-second order. Among the isotherms applied to modeling the sorption in various concentrations, the Langmuir isotherm was founded to be more appropriate to fitting the experimental data. An excellent correlation coefficient was obtained (R2 > 0.98). The qmax for sorption of strontium ions which was calculated by Langmuir model was 80 mg/g. The thermodynamic parameters were calculated by determination of sorption in various temperatures and using the Vant Hoff plot. ΔG°, ΔH°, and ΔS° were calculated as -19.15, 2.28 and 0.071 kJ/mol respectively.

[Sorption mechanism of ofloxacin by carbon nanotubes].

PubMed

Zhao, Xing-Xing; Yu, Shui-Li; Wang, Zhe

2014-02-01

Sorption of ofloxacin (OFL) by carbon nanotubes is an effective method to control its fate in aquatic environment. The sorption process of OFL by mixed acid-treated and non-treated multi-walled carbon nanotubes was discussed. Sorption kinetics, sorption isotherm, desorption, sorption thermodynamics and effect of pH were investigated. The results indicated that the sorption kinetics followed the pseudo-second order kinetics model. The equilibrium sorption capacity of OFL on MWCNTs-O was higher. The sorption isotherm could be fitted by both the Langmuir and Freundlich models. The equilibrium sorption capacity dropped when the pH of aqueous solution was in the range of 6.0 to 10.0. Obvious desorption hysteresis was observed during the desorption experiments, especially on MWCNTs-O. Sorption thermodynamics analysis showed that the interactions between the OFL and sorbents were mainly between molecules. More oxygen-containing functional groups introduced on MWCNTs provided OFL molecules with more sorptive sites, which facilitated the generation of hydrogen bonds, a relatively strong interaction. The hydrogen bonds dominated the sorption process of OFL by MWCNTs/MWCNTs-O, explaining the experimental phenomena.

Adsorption isotherms and kinetics studies of malachite green on chitin hydrogels.

PubMed

Tang, Hu; Zhou, Weijie; Zhang, Lina

2012-03-30

A chitin hydrogel with concentration 3 wt% (CG3) was successfully prepared from chitin solution dissolved in 8 wt% NaOH/4 wt% urea aqueous system at low temperature by crosslinking with 5 wt% epichlorohydrin. The experimental results revealed that CG3 exhibited high efficiency to remove dye (malachite green) from aqueous solution, as a result of their microporous structure, large surface area and affinity on the dye. The equilibrium process was described well by the Langmuir isotherm model, showing a monolayer adsorption. From kinetic experiments, the adsorption process followed the pseudo-second-order kinetic model, indicating that the overall rate of dye uptake could be controlled by external mass transfer at the beginning of adsorption, while intraparticle diffusion controlled the overall rate of adsorption at a later stage. The activation energy calculated from Arrhenius equation and the result of SEM and FTIR indicated that the adsorption of malachite green on the CG3 was physical process. This work provided an attractive adsorbent for removing of the hazardous materials from wastewater. Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.

Synthesis of zeolite/nickel ferrite/sodium alginate bionanocomposite via a co-precipitation technique for efficient removal of water-soluble methylene blue dye.

PubMed

Bayat, Mahsa; Javanbakht, Vahid; Esmaili, Javad

2018-05-05

In this study, we sought to synthesize magnetic nanocomposite of zeolite/nickel ferrite through co-precipitation method and modify its surface by sodium alginate to enhance its methylene blue adsorption capacity and to prevent its oxidation. Nanocomposite characteristics were investigated by SEM, VSM, XRD and FTIR analyses. The results indicate that nanocomposite synthesis and modification has been completely successful. Adsorption thermodynamics, kinetics, and isotherms were examined and parameters were optimized by Minitab software using experimental design method, response surface methodology and Box-Behnken design. The highest capacity of methylene blue adsorption from the aqueous solution obtained at optimal pH of 5, the initial dye concentration of 10 mg/L and an adsorbent amount of 0.03 g was about 54.05 mg/g. Analyzing kinetic data of adsorption experiments confirmed that adsorption process complies with the pseudo-second-order kinetic model. Assessing equilibrium isotherm data at different temperatures showed that these data are in good agreement with Langmuir isotherm model. Copyright © 2018 Elsevier B.V. All rights reserved.

Applications of Brazilian pine-fruit shell in natural and carbonized forms as adsorbents to removal of methylene blue from aqueous solutions--kinetic and equilibrium study.

PubMed

Royer, Betina; Cardoso, Natali F; Lima, Eder C; Vaghetti, Julio C P; Simon, Nathalia M; Calvete, Tatiana; Veses, Renato Cataluña

2009-05-30

The Brazilian pine-fruit shell (Araucaria angustifolia) is a food residue, which was used in natural and carbonized forms, as low-cost adsorbents for the removal of methylene blue (MB) from aqueous solutions. Chemical treatment of Brazilian pine-fruit shell (PW), with sulfuric acid produced a non-activated carbonaceous material (C-PW). Both PW and C-PW were tested as low-cost adsorbents for the removal of MB from aqueous effluents. It was observed that C-PW leaded to a remarkable increase in the specific surface area, average porous volume, and average porous diameter of the adsorbent when compared to PW. The effects of shaking time, adsorbent dosage and pH on adsorption capacity were studied. In basic pH region (pH 8.5) the adsorption of MB was favorable. The contact time required to obtain the equilibrium was 6 and 4h at 25 degrees C, using PW and C-PW as adsorbents, respectively. Based on error function values (F(error)) the kinetic data were better fitted to fractionary-order kinetic model when compared to pseudo-first order, pseudo-second order, and chemisorption kinetic models. The equilibrium data were fitted to Langmuir, Freundlich, Sips and Redlich-Peterson isotherm models. For MB dye the equilibrium data were better fitted to the Sips isotherm model using PW and C-PW as adsorbents.

Adsorption of basic dyes on granular activated carbon and natural zeolite.

PubMed

Meshko, V; Markovska, L; Mincheva, M; Rodrigues, A E

2001-10-01

The adsorption of basic dyes from aqueous solution onto granular activated carbon and natural zeolite has been studied using an agitated batch adsorber. The influence of agitation, initial dye concentration and adsorbent mass has been studied. The parameters of Langmuir and Freundlich adsorption isotherms have been determined using the adsorption data. Homogeneous diffusion model (solid diffusion) combined with external mass transfer resistance is proposed for the kinetic investigation. The dependence of solid diffusion coefficient on initial concentration and mass adsorbent is represented by the simple empirical equations.

Studies on Thorium Adsorption Characteristics upon Activated Titanium Hydroxide Prepared from Rosetta Ilmenite Concentrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gado, M, E-mail: parq28@yahoo.com; Zaki, S

2016-01-01

The titanium hydroxide prepared from Rosetta ilmenite concentrate has been applied for Th (IV) adsorption from its acid aqueous solutions. The prepared hydroxide is first characterized by both Fourier transform infrared (FT-IR) spectrum and thermogravimetric analysis. The relevant factors affecting the adsorption process have been studied. The obtained equilibrium data fits well with the Langmuir isotherm rather than Freundlich isotherm, while the adsorption kinetic data follow the pseudo-second order model. The different thermodynamic parameters have also been calculated and indicate that the adsorption process is spontaneous.

Shape modeling with family of Pearson distributions: Langmuir waves

NASA Astrophysics Data System (ADS)

Vidojevic, Sonja

2014-10-01

Two major effects of Langmuir wave electric field influence on spectral line shapes are appearance of depressions shifted from unperturbed line and an additional dynamical line broadening. More realistic and accurate models of Langmuir waves are needed to study these effects with more confidence. In this article we present distribution shapes of a high-quality data set of Langmuir waves electric field observed by the WIND satellite. Using well developed numerical techniques, the distributions of the empirical measurements are modeled by family of Pearson distributions. The results suggest that the existing theoretical models of energy conversion between an electron beam and surrounding plasma is more complex. If the processes of the Langmuir wave generation are better understood, the influence of Langmuir waves on spectral line shapes could be modeled better.

Removal of trivalent chromium from water using low-cost natural diatomite.

PubMed

Gürü, Metin; Venedik, Duygu; Murathan, Ayşe

2008-12-30

Trivalent chromium was removed from the artificial wastewater using low-cost diatomite in batch and continuous systems. In batch system, four different sizes and five different amount of sorbent were used. The effect of the temperature on sorption was evaluated with using three different temperatures. As a result of the experiments, 85% of the trivalent chromium was removed from the wastewater in conditions of using 1.29mm grain material at 30 degrees C temperature for 60min in batch system but chromium removal was 82% at 30 degrees C temperature for 22min and 97% from the wastewater at 30 degrees C temperature for 80min in continuous system. Also, the equilibrium adsorption isotherms have been analyzed by Langmuir and Freundlich models. The Langmuir isotherms have the highest correlation coefficients. Langmuir adsorption isotherm constants corresponding to adsorption capacity, q0, were found to be 28.1, 26.5 and 21.8mg Cr3+/g diatomite at 15, 30 and 45 degrees C, respectively. Adsorption process was an exothermic process as a result of thermodynamic parameters calculations. The kinetic data of the sorption showed that the pseudo second-order equation was the more appropriate, which indicate that the intraparticle diffusion is the rate-limiting factor.

Adsorption studies of methylene blue and gentian violet on sugarcane bagasse modified with EDTA dianhydride (EDTAD) in aqueous solutions: kinetic and equilibrium aspects.

PubMed

Gusmão, Karla Aparecida Guimarães; Gurgel, Leandro Vinícius Alves; Melo, Tânia Márcia Sacramento; Gil, Laurent Frédéric

2013-03-30

In this study the adsorption of cationic dyes by modified sugarcane bagasse with EDTA dianhydride (EB) was examined using methylene blue (MB) and gentian violet (GV) as model compounds in aqueous single solutions. The synthesized adsorbent (EB) was characterized by FTIR, elemental analysis, and BET. The capacity of EB to adsorb dyes was evaluated at different contact times, pH values, and initial dye concentrations. According to the obtained results, the adsorption processes could be described by a pseudo-second-order kinetic model. The adsorption isotherms were well fitted by the Langmuir model. Maximum adsorption capacities for MB and GV on EB were found to be 202.43 and 327.83 mg/g, respectively. The free energy change during adsorption of MB and GV was found to be -22.50 and -24.21 kJ/mol, respectively, suggesting that chemisorption is the main mechanism controlling the adsorption process. Copyright © 2013 Elsevier Ltd. All rights reserved.

Charge transfer and adsorption-desorption kinetics in carbon nanotube and graphene gas sensing

NASA Astrophysics Data System (ADS)

Liang, Sang-Zi; Chen, Gugang; Harutyunyan, Avetik; Cole, Milton; Sofo, Jorge

2014-03-01

Detection of molecules in the gas phase by carbon nanotube and graphene has great application potentials due to the high sensitivity and surface-to-volume ratio. In chemiresistor, the conductance of the materials has been proposed to change as a result of charge transfer from the adsorbed molecules. Due to self-interaction errors, calculations using LDA or GGA density functionals have an innate disadvantage in dealing with charge transfer situations. A model which takes into consideration the dielectric interaction between the graphene surface and the molecule is employed to estimate the distance where charge transfer becomes favorable. Adsorption-desorption kinetics is studied with a modified Langmuir model, including sites from which the molecules do not desorb within the experimental time. Assuming a constant mobility, the model reproduces existing experimental conductance data. Its parameters provide information about the microscopic process during the detection and varying them allows optimization of aspects of sensor performance, including sensitivity, detection limit and response time. This work is supported by Honda Research Institute USA, Inc.

Cr(OH)3-NPs-CNC hybrid nanocomposite: a sorbent for adsorptive removal of methylene blue and malachite green from solutions.

PubMed

Nekouei, Farzin; Nekouei, Shahram; Keshtpour, Farzaneh; Noorizadeh, Hossein; Wang, Shaobin

2017-11-01

In this article, Cr(OH) 3 nanoparticle-modified cellulose nanocrystal (CNC) as a novel hybrid nanocomposite (Cr(OH) 3 -NPs-CNC) was prepared by a simple procedure and used as a sorbent for adsorptive removal of methylene blue (MB) and malachite green (MG) from aqueous solution. Different kinetic models were tested, and the pseudo-second-order kinetic model was found more suitable for the MB and MG adsorption processes. The BET and Langmuir models were more suitable for the adsorption processes of MB and MG. Thermodynamic studies suggested that the adsorption of MB and MG onto Cr(OH) 3 -NPs-CNC nanocomposite was a spontaneous and endothermic process. The maximum adsorption capacities for MB and MG were reached 106 and 104 mg/g, respectively, which were almost two times higher than unmodified CNC. The chemical stability and leaching tests of the Cr(OH) 3 -NPs-CNC hybrid nanocomposite showed that only small amounts of chromium were leached into the solution.

Activated bauxite waste as an adsorbent for removal of Acid Blue 92 from aqueous solutions.

PubMed

Norouzi, Sh; Badii, Kh; Doulati Ardejani, F

2010-01-01

Bauxite waste, known as red mud, is produced in some industrial processes, such as aluminum production process. In this process, the waste material is produced from leached bauxite as a by product. In this research, the removal of Acid Blue 92 (AB92) dye was investigated from aqueous solution onto the activated bauxite waste (red mud) in a batch equilibration system. Besides, the influences of pH, adsorbent dosage, contact time, initial concentration of dye and temperature have been considered. It was found that the OH group is an effective functional group for the adsorption process. The intensity of the peaks correspond to OH group has been significantly climbed after the activation process. The adsorption kinetics of AB92 can be well described by the pseudo-second-order reaction model. Based on the isotherm data obtained from the fittings of the adsorption kinetics, the Langmuir model appears to fit the adsorption process better than the Freundlich and Brunauer-Emmett-Teller (BET) models.

Removal of lead from aqueous solutions with a treated spent bleaching earth.

PubMed

Mana, Mohamed; Ouali, Mohand Said; Lindheimer, Marc; Menorval, Louis Charles de

2008-11-30

A spent bleaching earth from an edible oil refinery has been treated by impregnation with a normal sodium hydroxide solution followed by mild thermal treatment (100 degrees C). The obtained material (TSBE) was washed, dried and characterized by X-ray diffraction, FTIR, SEM, BET and thermal analysis. The clay structure was not apparently affected by the treatment and the impregnated organic matter was quantitatively removed. We have investigated the sorption of lead on this material, the spent bleaching earth (SBE) and the virgin bleaching earth (VBE). The kinetic results fit the pseudo second-order kinetic model and the Weber & Morris, intraparticle diffusion model. The pH had effect on the sorption efficiency. The sorption isotherms followed the Langmuir model for various sorbent concentrations with good values of determination coefficient. A comparison between the results obtained with this material and those of the literature highlighted a good removal capacity of the treated spent bleaching earth at low cost.

Phenol adsorption on surface-functionalized iron oxide nanoparticles: modeling of the kinetics, isotherm, and mechanism

NASA Astrophysics Data System (ADS)

Yoon, Soon Uk; Mahanty, Biswanath; Ha, Hun Moon; Kim, Chang Gyun

2016-06-01

Phenol adsorption from aqueous solution was carried out using uncoated and methyl acrylic acid (MAA)-coated iron oxide nanoparticles (NPs), having size <10 nm, as adsorbents. Batch adsorption studies revealed that the phenol removal efficiency of MAA-coated NPs (950 mg g-1) is significantly higher than that of uncoated NPs (550 mg g-1) under neutral to acidic conditions. However, this improvement disappears above pH 9. The adsorption data under optimized conditions (pH 7) were modeled with pseudo-first- and pseudo-second-order kinetics and subjected to Freundlich and Langmuir isotherms. The analysis determined that pseudo-second-order kinetics and the Freundlich model are appropriate for both uncoated and MAA-coated NPs (all R 2 > 0.98). X-ray photoelectron spectroscopy analysis of pristine and phenol-adsorbed NPs revealed core-level binding energy and charge for Fe(2 s) and O(1 s) on the NP surfaces. The calculations suggest that phenol adsorption onto MAA-coated NPs is a charge transfer process, where the adsorbate (phenol) acts as an electron donor and the NP surface (Fe, O) as an electron acceptor. However, a physisorption process appears to be the relevant mechanism for uncoated NPs.

Adsorption of Azo-Dye Orange II from Aqueous Solutions Using a Metal-Organic Framework Material: Iron- Benzenetricarboxylate

PubMed Central

Rojas García, Elizabeth; López Medina, Ricardo; May Lozano, Marcos; Hernández Pérez, Isaías; Valero, Maria J.; Maubert Franco, Ana M.

2014-01-01

A Metal-Organic Framework (MOF), iron-benzenetricarboxylate (Fe(BTC)), has been studied for the adsorptive removal of azo-dye Orange II from aqueous solutions, where the effect of various parameters was tested and isotherm and kinetic models were suggested. The adsorption capacities of Fe(BTC) were much higher than those of an activated carbon. The experimental data can be best described by the Langmuir isotherm model (R2 > 0.997) and revealed the ability of Fe(BTC) to adsorb 435 mg of Orange II per gram of adsorbent at the optimal conditions. The kinetics of Orange II adsorption followed a pseudo-second-order kinetic model, indicating the coexistence of physisorption and chemisorption, with intra-particle diffusion being the rate controlling step. The thermodynamic study revealed that the adsorption of Orange II was feasible, spontaneous and exothermic process (−25.53 kJ·mol−1). The high recovery of the dye showed that Fe(BTC) can be employed as an effective and reusable adsorbent for the removal of Orange II from aqueous solutions and showed the economic interest of this adsorbent material for environmental purposes. PMID:28788289

Adsorption of methylene blue onto activated carbon produced from tea (Camellia sinensis L.) seed shells: kinetics, equilibrium, and thermodynamics studies.

PubMed

Gao, Jun-Jie; Qin, Ye-Bo; Zhou, Tao; Cao, Dong-Dong; Xu, Ping; Hochstetter, Danielle; Wang, Yue-Fei

2013-07-01

Tea (Camellia sinensis L.) seed shells, the main byproduct of the manufacture of tea seed oil, were used as precursors for the preparation of tea activated carbon (TAC) in the present study. A high yield (44.1%) of TAC was obtained from tea seed shells via a one-step chemical method using ZnCl2 as an agent. The Brunauer-Emmett-Teller (BET) surface area and the total pore volumes of the obtained TAC were found to be 1530.67 mg(2)/g and 0.7826 cm(3)/g, respectively. The equilibrium adsorption results were complied with Langmuir isotherm model and its maximum monolayer adsorption capacity was 324.7 mg/g for methylene blue. Adsorption kinetics studies indicated that the pseudo-second-order model yielded the best fit for the kinetic data. An intraparticle diffusion model suggested that the intraparticle diffusion was not the only rate-controlling step. Thermodynamics studies revealed the spontaneous and exothermic nature of the sorption process. These results indicate that tea seed shells could be utilized as a renewable resource to develop activated carbon which is a potential adsorbent for methylene blue.

Adsorption of methylene blue onto activated carbon produced from tea (Camellia sinensis L.) seed shells: kinetics, equilibrium, and thermodynamics studies*

PubMed Central

Gao, Jun-jie; Qin, Ye-bo; Zhou, Tao; Cao, Dong-dong; Xu, Ping; Hochstetter, Danielle; Wang, Yue-fei

2013-01-01

Tea (Camellia sinensis L.) seed shells, the main byproduct of the manufacture of tea seed oil, were used as precursors for the preparation of tea activated carbon (TAC) in the present study. A high yield (44.1%) of TAC was obtained from tea seed shells via a one-step chemical method using ZnCl2 as an agent. The Brunauer-Emmett-Teller (BET) surface area and the total pore volumes of the obtained TAC were found to be 1 530.67 mg2/g and 0.782 6 cm3/g, respectively. The equilibrium adsorption results were complied with Langmuir isotherm model and its maximum monolayer adsorption capacity was 324.7 mg/g for methylene blue. Adsorption kinetics studies indicated that the pseudo-second-order model yielded the best fit for the kinetic data. An intraparticle diffusion model suggested that the intraparticle diffusion was not the only rate-controlling step. Thermodynamics studies revealed the spontaneous and exothermic nature of the sorption process. These results indicate that tea seed shells could be utilized as a renewable resource to develop activated carbon which is a potential adsorbent for methylene blue. PMID:23825151

Adsorption isotherm, kinetic and mechanism of expanded graphite for sulfadiazine antibiotics removal from aqueous solutions.

PubMed

Zhang, Ling; Wang, Yong; Jin, SuWan; Lu, QunZan; Ji, Jiang

2017-10-01

The adsorption of sulfadiazine from water by expanded graphite (EG), a low cost and environmental-friendly adsorbent, was investigated. Several adsorption parameters (including the initial sulfadiazine concentration, contact time, pH of solution, ionic strength and temperature) were studied. Results of equilibrium experiments indicated that adsorption of sulfadiazine onto EG were better described by the Langmuir and Tempkin models than by the Freundlich model. The maximum adsorption capacity is calculated to be 16.586 mg/g at 298 K. The kinetic data were analyzed by pseudo-first-order, pseudo-second-order and intraparticle models. The results indicated that the adsorption process followed pseudo-second-order kinetics and may be controlled by two steps. Moreover, the pH significantly influenced the adsorption process, with the relatively high adsorption capacity at pH 2-10. The electrostatic and hydrophobic interactions are manifested to be two main mechanisms for sulfadiazine adsorption of EG. Meanwhile, the ionic concentration of Cl - slightly impacted the removal of sulfadiazine. Results of thermodynamics analysis showed spontaneous and exothermic nature of sulfadiazine adsorption on EG. In addition, regeneration experiments imply that the saturated EG could be reused for sulfadiazine removal by immersing sodium hydroxide.

Titania-Coated Silica Alone and Modified by Sodium Alginate as Sorbents for Heavy Metal Ions

NASA Astrophysics Data System (ADS)

Kołodyńska, D.; Gęca, M.; Skwarek, E.; Goncharuk, O.

2018-04-01

The novel organic-inorganic biohybrid composite adsorbent was synthesized based on nanosized silica-titania modified with alginate within the development of effective adsorbent for heavy metal ions. Effects of metal species Cu(II), Zn(II), Cd(II), and Pb(II); concentrations; pH; temperature; and adsorption onto titania-coated silica (ST20) initial or modified by sodium alginate (ST20-ALG) were studied. The equilibrium and kinetic data of metal ions adsorption were analyzed using Langmuir and Freundlich adsorption models and kinetic models: pseudo first order, pseudo second order, intraparticle kinetic model, and Elovich. The maximum sorption capacities observed were higher for the ST20-ALG composite compared to the initial ST20 oxide for all studied metal ions, namely their values for ST20-ALG were 22.44 mg g- 1 for Cu(II) adsorption, 19.95 mg g- 1 for Zn(II), 18.85 mg g- 1 for Cd(II), and 32.49 mg g- 1 for Pb(II). Structure and properties of initial silica-titania ST20 and modified by sodium alginate ST20-ALG adsorbents were analyzed using nitrogen adsorption/desorption isotherms, ATR-FTIR, SEM-EDS, and pHpzc techniques.

Adsorption Isotherms and Surface Reaction Kinetics

ERIC Educational Resources Information Center

Lobo, L. S.; Bernardo, C. A.

1974-01-01

Explains an error that occurs in calculating the conditions for a maximum value of a rate expression for a bimolecular reaction. The rate expression is derived using the Langmuir adsorption isotherm to relate gas pressures and corresponding surface coverages. (GS)

A hemispherical Langmuir probe array detector for angular resolved measurements on droplet-based laser-produced plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gambino, Nadia, E-mail: gambinon@ethz.ch; Brandstätter, Markus; Rollinger, Bob

2014-09-15

In this work, a new diagnostic tool for laser-produced plasmas (LPPs) is presented. The detector is based on a multiple array of six motorized Langmuir probes. It allows to measure the dynamics of a LPP in terms of charged particles detection with particular attention to droplet-based LPP sources for EUV lithography. The system design permits to temporally resolve the angular and radial plasma charge distribution and to obtain a hemispherical mapping of the ions and electrons around the droplet plasma. The understanding of these dynamics is fundamental to improve the debris mitigation techniques for droplet-based LPP sources. The device hasmore » been developed, built, and employed at the Laboratory for Energy Conversion, ETH Zürich. The experimental results have been obtained on the droplet-based LPP source ALPS II. For the first time, 2D mappings of the ion kinetic energy distribution around the droplet plasma have been obtained with an array of multiple Langmuir probes. These measurements show an anisotropic expansion of the ions in terms of kinetic energy and amount of ion charge around the droplet target. First estimations of the plasma density and electron temperature were also obtained from the analysis of the probe current signals.« less

Dynamic Model of Basic Oxygen Steelmaking Process Based on Multizone Reaction Kinetics: Modeling of Decarburization

NASA Astrophysics Data System (ADS)

Rout, Bapin Kumar; Brooks, Geoffrey; Akbar Rhamdhani, M.; Li, Zushu; Schrama, Frank N. H.; Overbosch, Aart

2018-06-01

In a previous study by the authors (Rout et al. in Metall Mater Trans B 49:537-557, 2018), a dynamic model for the BOF, employing the concept of multizone kinetics was developed. In the current study, the kinetics of decarburization reaction is investigated. The jet impact and slag-metal emulsion zones were identified to be primary zones for carbon oxidation. The dynamic parameters in the rate equation of decarburization such as residence time of metal drops in the emulsion, interfacial area evolution, initial size, and the effects of surface-active oxides have been included in the kinetic rate equation of the metal droplet. A modified mass-transfer coefficient based on the ideal Langmuir adsorption equilibrium has been proposed to take into account the surface blockage effects of SiO2 and P2O5 in slag on the decarburization kinetics of a metal droplet in the emulsion. Further, a size distribution function has been included in the rate equation to evaluate the effect of droplet size on reaction kinetics. The mathematical simulation indicates that decarburization of the droplet in the emulsion is a strong function of the initial size and residence time. A modified droplet generation rate proposed previously by the authors has been used to estimate the total decarburization rate by slag-metal emulsion. The model's prediction shows that about 76 pct of total carbon is removed by reactions in the emulsion, and the remaining is removed by reactions at the jet impact zone. The predicted bath carbon by the model has been found to be in good agreement with the industrially measured data.

Dynamic Model of Basic Oxygen Steelmaking Process Based on Multizone Reaction Kinetics: Modeling of Decarburization

NASA Astrophysics Data System (ADS)

Rout, Bapin Kumar; Brooks, Geoffrey; Akbar Rhamdhani, M.; Li, Zushu; Schrama, Frank N. H.; Overbosch, Aart

2018-03-01

In a previous study by the authors (Rout et al. in Metall Mater Trans B 49:537-557, 2018), a dynamic model for the BOF, employing the concept of multizone kinetics was developed. In the current study, the kinetics of decarburization reaction is investigated. The jet impact and slag-metal emulsion zones were identified to be primary zones for carbon oxidation. The dynamic parameters in the rate equation of decarburization such as residence time of metal drops in the emulsion, interfacial area evolution, initial size, and the effects of surface-active oxides have been included in the kinetic rate equation of the metal droplet. A modified mass-transfer coefficient based on the ideal Langmuir adsorption equilibrium has been proposed to take into account the surface blockage effects of SiO2 and P2O5 in slag on the decarburization kinetics of a metal droplet in the emulsion. Further, a size distribution function has been included in the rate equation to evaluate the effect of droplet size on reaction kinetics. The mathematical simulation indicates that decarburization of the droplet in the emulsion is a strong function of the initial size and residence time. A modified droplet generation rate proposed previously by the authors has been used to estimate the total decarburization rate by slag-metal emulsion. The model's prediction shows that about 76 pct of total carbon is removed by reactions in the emulsion, and the remaining is removed by reactions at the jet impact zone. The predicted bath carbon by the model has been found to be in good agreement with the industrially measured data.

Comparison of ultrasonic with stirrer performance for removal of sunset yellow (SY) by activated carbon prepared from wood of orange tree: artificial neural network modeling.

PubMed

Ghaedi, A M; Ghaedi, M; Karami, P

2015-03-05

The present work focused on the removal of sunset yellow (SY) dye from aqueous solution by ultrasound-assisted adsorption and stirrer by activated carbon prepared from wood of an orange tree. Also, the artificial neural network (ANN) model was used for predicting removal (%) of SY dye based on experimental data. In this study a green approach was described for the synthesis of activated carbon prepared from wood of an orange tree and usability of it for the removal of sunset yellow. This material was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The impact of variables, including initial dye concentration (mg/L), pH, adsorbent dosage (g), sonication time (min) and temperature (°C) on SY removal were studied. Fitting the experimental equilibrium data of different isotherm models such as Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models display the suitability and applicability of the Langmuir model. Analysis of experimental adsorption data by different kinetic models including pseudo-first and second order, Elovich and intraparticle diffusion models indicate the applicability of the second-order equation model. The adsorbent (0.5g) is applicable for successful removal of SY (>98%) in short time (10min) under ultrasound condition. Copyright © 2014 Elsevier B.V. All rights reserved.

First-principles study of nitric oxide oxidation on Pt(111) versus Pt overlayer on 3d transition metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arevalo, Ryan Lacdao; Escaño, Mary Clare Sison; Kasai, Hideaki, E-mail: kasai@dyn.ap.eng.osaka-u.ac.jp

2015-03-15

Catalytic oxidation of NO to NO{sub 2} is a significant research interest for improving the quality of air through exhaust gas purification systems. In this paper, the authors studied this reaction on pure Pt and Pt overlayer on 3d transition metals using kinetic Monte Carlo simulations coupled with density functional theory based first principles calculations. The authors found that on the Pt(111) surface, NO oxidation proceeds via the Eley–Rideal mechanism, with O{sub 2} dissociative adsorption as the rate-determining step. The oxidation path via the Langmuir–Hinshelwood mechanism is very slow and does not significantly contribute to the overall reaction. However, inmore » the Pt overlayer systems, the oxidation of NO on the surface is more thermodynamically and kinetically favorable compared to pure Pt. These findings are attributed to the weaker binding of O and NO on the Pt overlayer systems and the binding configuration of NO{sub 2} that promotes easier N-O bond formation. These results present insights for designing affordable and efficient catalysts for NO oxidation.« less

Kinetics, equilibrium and thermodynamic studies on biosorption of Ag(I) from aqueous solution by macrofungus Pleurotus platypus.

PubMed

Das, Devlina; Das, Nilanjana; Mathew, Lazar

2010-12-15

Reports are available on silver binding capacity of some microorganisms. However, reports on the equilibrium studies on biosorption of silver by macrofungi are seldom known. The present study was carried out in a batch system using dead biomass of macrofungus Pleurotus platypus for the sorption of Ag(I). P. platypus exhibited the highest silver uptake of 46.7 mg g(-1) of biomass at pH 6.0 in the presence of 200 mg L(-1) Ag(I) at 20°C. Kinetic studies based on fractional power, zero order, first order, pseudo-first order, Elovich, second order and pseudo-second order rate expressions have been carried out. The results showed a very good compliance with the pseudo-first order model. The experimental data were analyzed using two parameter isotherms (Langmuir, Freundlich, Dubinin-Radushkevich, Temkin and Halsey), three parameter isotherms (Redlich-Peterson, Sips, Khan, Koble-Corrigan, Hill, Toth, Radke-Prausmitz, Jossens, Langmuir-Freundlich), four parameter isotherms (Weber-van Vliet, Fritz-Schlunder, Baudu) and five parameter isotherm (Fritz-Schlunder). Thermodynamic parameters of the biosorption (ΔG, ΔH and ΔS) were also determined. The present study confirmed that macrofungus P. platypus may be used as a cost effective efficient biosorbent for the removal of Ag(I) ions from aqueous solution. Copyright © 2010 Elsevier B.V. All rights reserved.

Study of 2,4-dichlorophenoxyacetic acid (2,4-D) removal by Cu-Fe-layered double hydroxide from aqueous solution

NASA Astrophysics Data System (ADS)

Nejati, Kamellia; Davary, Soheila; Saati, Marziye

2013-09-01

The hydrotalcite-like compound of Cu-Fe-layered double hydroxide was studied as a potential adsorbent of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). The nanoparticles of Cu-Fe layered double hydroxide were prepared by Cu/Fe molar ratio of 2:1 using a coprecipitation method at pH 8.5 and characterized by the X-ray powder diffraction (XRD), the Fourier transform infrared spectroscopy (FT-IR), the thermal gravimetric analysis (TGA) and the elemental analysis. The size and morphology of nanoparticles were examined by the transmission electron microscopy (TEM). The adsorption experiments on LDH, on the other hand, were conducted in three different procedures, namely, time-dependent, pH-dependent and temperature-dependent. Characterization of the adsorption products by the XRD method indicates that the intercalation of 2,4-D between the LDH layers has not occurred and the surface adsorption had taken place. The adsorption kinetic was tested for pseudo-first-order, pseudo-second-order, Elovich and Intra-particle diffusion kinetic models and the rate constants were calculated. The equilibrium adsorption data were described by Langmuir and Freundlich equations. It was observed that, the Langmuir isotherm slightly better fitted to the experimental data rather than that of Freundlich. In the adsorption experiments, the Gibbs free energy values, ΔG°, the enthalpy, ΔH°, and the entropy, ΔS° were also determined.

Effective adsorption of phosphate from wastewaters by big composite pellets made of reduced steel slag and iron ore concentrate.

PubMed

Wang, Hongjuan; Shen, Shaobo; Liu, Longhui; Ji, Yilong; Wang, Fuming

2015-01-01

In order to remove phosphate from wastewater, a large plastic adsorption column filled with big phosphate-adsorbing pellets with diameters of 10 mm, heated by electromagnetic induction coils, was conceived. It was found that the prepared big pellets, which were made of reduced steel slag and iron ore concentrate, contain magnetic Fe and Fe3O4. The thermodynamics and kinetics of adsorption of phosphate from synthetic wastewaters on the pellets were studied in this work. The phosphate adsorption on the pellets followed three models of Freundlich, Langmuir and Dubinin-Kaganer-Radushkevick. The maximum phosphate adsorption capacity Qmax of the pellets were 2.46, 2.74 and 2.77 mg/g for the three temperatures of 20°C, 30°C and 40°C, respectively, based on the Langmuir model. The apparent adsorption energies were -12.9 kJ/mol for the three temperatures. It implied that ion exchange was the main mechanism involved in the adsorption processes. The adsorbed phosphate existed on the pellet surface mainly in the form of Fe3(PO4)2. A reduction pre-treatment of the pellet precursor with H2 greatly enhanced pellet adsorption for phosphate. The adsorption kinetics is better represented by a pseudo-first-order model. The adsorbed phosphate amounts were similar for both real and synthetic wastewaters under similar adsorption conditions. The percentage of adsorbed phosphate for a real wastewater increased with increasing pellet concentration and reached 99.2% at a pellet concentration of 64 (g/L). Some specific phosphate adsorption mechanisms for the pellets were revealed and the pellets showed the potential to efficiently adsorb phosphate from a huge amount of real wastewaters in an industrial scale.

Experimental design based response surface methodology optimization of ultrasonic assisted adsorption of safaranin O by tin sulfide nanoparticle loaded on activated carbon

NASA Astrophysics Data System (ADS)

Roosta, M.; Ghaedi, M.; Daneshfar, A.; Sahraei, R.

2014-03-01

In this research, the adsorption rate of safranine O (SO) onto tin sulfide nanoparticle loaded on activated carbon (SnS-NPAC) was accelerated by the ultrasound. SnS-NP-AC was characterized by different techniques such as SEM, XRD and UV-Vis measurements. The present results confirm that the ultrasound assisted adsorption method has remarkable ability to improve the adsorption efficiency. The influence of parameters such as the sonication time, adsorbent dosage, pH and initial SO concentration was examined and evaluated by central composite design (CCD) combined with response surface methodology (RSM) and desirability function (DF). Conducting adsorption experiments at optimal conditions set as 4 min of sonication time, 0.024 g of adsorbent, pH 7 and 18 mg L-1 SO make admit to achieve high removal percentage (98%) and high adsorption capacity (50.25 mg g-1). A good agreement between experimental and predicted data in this study was observed. The experimental equilibrium data fitting to Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich models show that the Langmuir model is a good and suitable model for evaluation and the actual behavior of adsorption. Kinetic evaluation of experimental data showed that the adsorption processes followed well pseudo-second-order and intraparticle diffusion models.

Adsorption-desorption behavior of atrazine on agricultural soils in China.

PubMed

Yue, Lin; Ge, ChengJun; Feng, Dan; Yu, Huamei; Deng, Hui; Fu, Bomin

2017-07-01

Adsorption and desorption are important processes that affect atrazine transport, transformation, and bioavailability in soils. In this study, the adsorption-desorption characteristics of atrazine in three soils (laterite, paddy soil and alluvial soil) were evaluated using the batch equilibrium method. The results showed that the kinetics of atrazine in soils was completed in two steps: a "fast" adsorption and a "slow" adsorption and could be well described by pseudo-second-order model. In addition, the adsorption equilibrium isotherms were nonlinear and were well fitted by Freundlich and Langmuir models. It was found that the adsorption data on laterite, and paddy soil were better fitted by the Freundlich model; as for alluvial soil, the Langmuir model described it better. The maximum atrazine sorption capacities ranked as follows: paddy soil>alluvial soil>laterite. Results of thermodynamic calculations indicated that atrazine adsorption on three tested soils was spontaneous and endothermic. The desorption data showed that negative hysteresis occurred. Furthermore, lower solution pH value was conducive to the adsorption of atrazine in soils. The atrazine adsorption in these three tested soils was controlled by physical adsorption, including partition and surface adsorption. At lower equilibrium concentration, the atrazine adsorption process in soils was dominated by surface adsorption; while with the increase of equilibrium concentration, partition was predominant. Copyright © 2016. Published by Elsevier B.V.

Adsorption of methyl green dye onto multi-walled carbon nanotubes decorated with Ni nanoferrite

NASA Astrophysics Data System (ADS)

Bahgat, Mohamed; Farghali, Ahmed Ali; El Rouby, Waleed; Khedr, Mohamed; Mohassab-Ahmed, Mohassab Y.

2013-06-01

This research was carried out to evaluate the capability of multi-walled carbon nanotubes (CNTs) and NiFe2O4-decorated multi-walled carbon nanotubes (NiFe2O4-CNTs) toward waste water treatment relevant to organic dyes. CNTs were prepared via chemical vapor deposition method. NiFe2O4-CNTs were prepared by in-situ chemical precipitation of metal hydroxides followed by hydrothermal processing. The samples were characterized using XRD and TEM. The adsorption efficiency of CNTs and NiFe2O4-CNTs of methyl green dye at various temperatures was examined. The adsorbed amount increased with the CNTs and NiFe2O4-CNTs dosage. The linear correlation coefficients and standard deviations of Langmuir and Freundlich isotherms were determined. It was found that Langmuir isotherm fitted the experimental results well in both adsorption cases n of methyl green onto CNTs and NiFe2O4-CNTs. Kinetics analyses were conducted using pseudo first-order, second-order and the intraparticle diffusion models. The results showed that the adsorption kinetics was controlled by a pseudo second-order model for adsorption of methyl green onto CNTs and best controlled by pseudo first-order in case of NiFe2O4-CNTs. Changes in the free energy of adsorption (Δ G°), enthalpy (Δ H°), entropy (Δ S°), and the activation energy ( E a) were determined. The Δ H°, Δ G° and E a values indicated that the adsorption of methyl green onto MWCNTs and NiFe2O4-MWCNTs was physisorption.

Sequestration of dyes from artificially prepared textile effluent using RSM-CCD optimized hybrid backbone based adsorbent-kinetic and equilibrium studies.

PubMed

Sukriti; Sharma, Jitender; Chadha, Amritpal Singh; Pruthi, Vaishali; Anand, Prerna; Bhatia, Jaspreet; Kaith, B S

2017-04-01

Present work reports the synthesis of semi-Interpenetrating Network Polymer (semi-IPN) using Gelatin-Gum xanthan hybrid backbone and polyvinyl alcohol in presence of l-tartaric acid and ammonium persulphate as the crosslinker-initiator system. Reaction parameters were optimized with Response Surface Methodology (RSM) in order to maximize the percent gel fraction of the synthesized sample. Polyvinyl alcohol, l-Tartaric acid, ammonium persulphate, reaction temperature, time and pH of the reaction medium were found to make an impact on the percentage gel fraction obtained. Incorporation of polyvinyl alcohol chains onto hybrid backbone and crosslinking between the different polymer chains were confirmed through techniques like FTIR, SEM-EDX and XRD. Semi-IPN was found to be very efficient in the removal of cationic dyes rhodamine-B (70%) and auramine-O (63%) from a mixture with an adsorbent dose of 700 mg, initial concentration of rhodamine-B 6 mgL -1 and auramine-O 26 mgL -1 , at an time interval of 22-25 h and 30 °C temp. Further to determine the nature of adsorption Langmuir and Freundlich adsorption isotherm models were studied and it was found that Langmuir adsorption isotherm was the best fit model for the removal of mixture of dyes. Kinetic studies for the sorption of dyes favored the reaction mechanism to occur via a pseudo second order pathway with R 2 value about 0.99. Copyright © 2017 Elsevier Ltd. All rights reserved.

Biosorption of cationic basic dye and cadmium by the novel biosorbent Bacillus catenulatus JB-022 strain.

PubMed

Kim, Su Young; Jin, Mi Ra; Chung, Chang Ho; Yun, Yeoung-Sang; Jahng, Kwang Yeop; Yu, Kang-Yeol

2015-04-01

Biosorption of heavy metals and dyes is a promising technology that involves the removal of toxic metals from industrial wastes. The present study aims to screen the bacterial strains isolated from soils and polluted pond for their potential biosorption of both cationic dye and cadmium. Bacillus catenulatus JB-022 strain removed 58% and 66% of cationic basic blue 3 (BB3) and cadmium (Cd(II)) at the respective concentrations of 2000 mg/L and 150 mg/L. The biosorption equilibrium data were well fitted by the Langmuir adsorption isotherm, and the kinetic studies indicated that the biosorption followed the pseudo-second-order model. The biosorption kinetics showed that the equilibrium was reached within 10 min and 5 min for BB3 and Cd(II), respectively. According to the Langmuir model, the maximum uptakes of BB3 and Cd(II) by the JB-022 biomass were estimated to be 139.74 and 64.28 mg/g, respectively. To confirm the surface morphology and functional groups, field emission scanning electron microscope, energy-dispersive X-ray spectrometer, X-ray diffraction, and Fourier transform infrared spectroscopy analyses were carried out, and the results revealed that the biomass of JB-022 has carboxyl and phosphonate groups as potential surface functional groups capable of binding to cationic pollutants. In conclusion, B. catenulatus JB-022 is proposed as an excellent biosorbent with potentially important applications in removal of cationic pollutants from wastewaters. Copyright © 2014 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Synthesis and application of a new carboxylated cellulose derivative. Part III: Removal of auramine-O and safranin-T from mono- and bi-component spiked aqueous solutions.

PubMed

Teodoro, Filipe Simões; Elias, Megg Madonyk Cota; Ferreira, Gabriel Max Dias; Adarme, Oscar Fernando Herrera; Savedra, Ranylson Marcello Leal; Siqueira, Melissa Fabíola; da Silva, Luis Henrique Mendes; Gil, Laurent Frédéric; Gurgel, Leandro Vinícius Alves

2018-02-15

In the third part of this series of studies, the adsorption of the basic textile dyes auramine-O (AO) and safranin-T (ST) on a carboxylated cellulose derivative (CTA) were evaluated in mono- and bi-component spiked aqueous solutions. Adsorption studies were developed as a function of solution pH, contact time, and initial dye concentration. Adsorption kinetic data were modeled by monocomponent kinetic models of pseudo-first- (PFO), pseudo-second-order (PSO), intraparticle diffusion, and Boyd, while the competitive kinetic model of Corsel was used to model bicomponent kinetic data. Monocomponent adsorption equilibrium data were modeled by the Langmuir, Sips, Fowler-Guggenhein, Hill de-Boer, and Konda models, while the IAST and RAST models were used to model bicomponent equilibrium data. Monocomponent maximum adsorption capacities for AO and ST at pH 4.5 were 2.841 and 3.691 mmol g -1 , and at pH 7.0 were 5.443 and 4.074 mmol g -1 , respectively. Bicomponent maximum adsorption capacities for AO and ST at pH 7.0 were 1.230 and 3.728 mmol g -1 . Adsorption enthalpy changes (Δ ads H) were obtained using isothermal titration calorimetry. The values of Δ ads H ranged from -18.83 to -5.60 kJ mol -1 , suggesting that physisorption controlled the adsorption process. Desorption and re-adsorption of CTA was also evaluated. Copyright © 2017 Elsevier Inc. All rights reserved.

Adsorption of bentazon on CAT and CARBOPAL activated carbon: Experimental and computational study

NASA Astrophysics Data System (ADS)

Spaltro, Agustín; Simonetti, Sandra; Torrellas, Silvia Alvarez; Rodriguez, Juan Garcia; Ruiz, Danila; Juan, Alfredo; Allegretti, Patricia

2018-03-01

Removal of the bentazon by adsorption on two different types of activated carbon was investigated under various experimental conditions.Kinetics of adsorption is followed and the adsorption isotherms of the pesticide are determined. The effects of the changes in pH, ionic strength and temperature are analyzed. Computational simulation was employed to analyze the geometry and the energy of pesticide absorption on activated carbon. Concentration of bentazon decreases while increase all the variables, from the same initial concentration. Experimental data for equilibrium was analyzed by three models: Langmuir, Freundlich and Guggenheim-Anderson-de Boer isotherms. Pseudo-first and pseudo-second-order kinetics are tested with the experimental data, and pseudo-second-order kinetics was the best for the adsorption of bentazon by CAT and CARBOPAL with coefficients of correlation R2 = 0.9996 and R2 = 0.9993, respectively. The results indicated that both CAT and CARBOPAL are very effective for the adsorption of bentazon from aqueous solutions, but CAT carbon has the greater capacity.

Radioactive Cobalt(II) Removal from Aqueous Solutions Using a Reusable Nanocomposite: Kinetic, Isotherms, and Mechanistic Study

PubMed Central

Wang, Ximing; Chen, Zhangjing

2017-01-01

A lignocellulose/montmorillonite (LMT) nanocomposite was prepared as a reusable adsorbent for cobalt(II) ions, and characterized by nitrogen (N2) adsorption/desorption isotherm, X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), and Fourier Transform Infrared Spectroscopy (FTIR). LMT exhibited efficient adsorption of cobalt ions (Co(II)), and the adsorbed Co(II) was readily desorbed by nitric acid (HNO3). All parameters affecting the adsorption and/or desorption of Co(II), including initial Co(II) concentration, pH value, temperature, HNO3 concentration, and time, were optimized. The kinetic data analysis showed that the adsorption followed the pseudo-second-order kinetic model and fit well into the Langmuir isotherm equation. Notably, the nanocomposite can be used four times without significantly losing adsorbent capability. The Energy-Dispersive X-ray (EDX) and FTIR spectra analysis also revealed that the adsorption mechanism may be mainly a chemical adsorption dominated process. PMID:29186794

Enhancement of Cr(VI) Ion Removal Using Nanochitosan Coated on Bituminous Activated Carbon.

PubMed

Chooaksorn, Wanida; Nitisoravut, Rachnarin; Polprasert, Chongrak; Babel, Sandhya; Laohhasurayotin, Kritapas; Kangwansupamonkon, Wiyong

2016-11-01

  Bituminous activated carbon (AC) has been widely used as a sorbent for adsorption of non-polar species, but its performance for removal of ionic species such as heavy metals has not been as efficient. In this study, AC was modified with chitosan nanoparticles (CN) using facile methods of dip coating and wet impregnation. The CN-coated AC demonstrated an increase in Cr(VI) removal efficiency in both kinetics and adsorption capacity. The adsorption capacity of the CN-coated AC (mg/g) was more than twice that of the uncoated AC (36.36 mg/g), or pure chitosan (32.57 mg/g). The sizes of the synthesized CN (160-2,000 nm) can be controlled by varying the concentration of the chitosan/reagents used. The adsorption isotherms are better described using the Freundlich rather than the Langmuir model and are in agreement with the heterogeneity of the surfaces. Adsorption kinetics followed that of the pseudo-second-order kinetics, suggesting chemisorption as a rate limiting step.

The sorption of lead, cadmium, copper and zinc ions from aqueous solutions on a raw diatomite from Algeria.

PubMed

Safa, Messaouda; Larouci, Mohammed; Meddah, Boumediene; Valemens, Pierre

2012-01-01

The adsorption of Cu(2+), Zn(2+), Cd(2+) and Pb(2+) ions from aqueous solution by Algerian raw diatomite was studied. The influences of different sorption parameters such as contact pH solution, contact time and initial metal ions concentration were studied to optimize the reaction conditions. The metals ions adsorption was strictly pH dependent. The maximum adsorption capacities towards Cu(2+), Zn(2+), Cd(2+) and Pb(2+) were 0.319, 0.311, 0.18 and 0.096 mmol g(-1), respectively. The kinetic data were modelled using the pseudo-first-order and pseudo-second-order kinetic equations. Among the kinetic models studied, the pseudo-second-order equation was the best applicable model to describe the sorption process. Equilibrium isotherm data were analysed using the Langmuir and the Freundlich isotherms; the results showed that the adsorption equilibrium was well described by both model isotherms. The negative value of free energy change ΔG indicates feasible and spontaneous adsorption of four metal ions on raw diatomite. According to these results, the high exchange capacities of different metal ions at high and low concentration levels, and given the low cost of the investigated adsorbent in this work, Algerian diatomite was considered to be an excellent adsorbent.

Adsorption potential of a modified activated carbon for the removal of nitrogen containing compounds from model fuel

NASA Astrophysics Data System (ADS)

Anisuzzaman, S. M.; Krishnaiah, D.; Alfred, D.

2018-02-01

The purpose of this study is to find the effect of the modified activated carbon (MAC) on the adsorption activity for nitrogen containing compounds (NCC) removal from model fuel. Modification of commercial activated carbon (AC) involved impregnation with different ratios of sulfuric acid solution. Pseudo-first and pseudo-second order kinetic models were applied to study the adsorption kinetics, while the adsorption isotherms were used for the evaluation of equilibrium data. All of the experimental data were analyzed using ultraviolet-visible spectroscopy after adsorption experiment between different concentration dosage of adsorbent and model fuel. It has been found that adsorption of NCC by MAC was best fit is the Langmuir isotherm for quinoline (QUI) and Freundlich isotherm for indole (IND) with a maximum adsorption capacity of 0.13 mg/g and 0.16 mg/g respectively. Based on the experimental data, pseudo-first order exhibited the best fit for QUI with linear regression (R2) ranges from 0.0.9777 to 0.9935 and pseudo-second order exhibited the best fit for IND with linear regression (R2) ranges from 0.9701 to 0.9962. From the adsorption isotherm and kinetic studies result proven that commercial AC shows great potential in removing nitrogen.

Measuring binding kinetics of aromatic thiolated molecules with nanoparticles via surface-enhanced Raman spectroscopy.

PubMed

DeVetter, Brent M; Mukherjee, Prabuddha; Murphy, Catherine J; Bhargava, Rohit

2015-05-21

Colloidal plasmonic nanomaterials, consisting of metals such as gold and silver, are excellent candidates for advanced optical probes and devices, but precise control over surface chemistry is essential for realizing their full potential. Coupling thiolated (R-SH) molecules to nanoprobe surfaces is a convenient and established route to tailor surface properties. The ability to dynamically probe and monitor the surface chemistry of nanoparticles in solution is essential for rapidly manufacturing spectroscopically tunable nanoparticles. In this study, we report the development of surface-enhanced Raman spectroscopy (SERS) as a method to monitor the kinetics of gold-thiolate bond formation on colloidal gold nanoparticles. A theoretical model combining SERS enhancement with the Beer-Lambert law is proposed to explain ensemble scattering and absorption effects in colloids during chemisorption. In order to maximize biological relevance and signal reproducibility, experiments used to validate the model focused on maintaining nanoparticle stability after the addition of water-soluble aromatic thiolated molecules. Our results indicate that ligand exchange on gold nanoparticles follow a first-order Langmuir adsorption model with rate constants on the order of 0.01 min(-1). This study demonstrates an experimental spectroscopic method and theoretical model for monitoring binding kinetics that may prove useful for designing novel probes.

Measuring binding kinetics of aromatic thiolated molecules with nanoparticles via surface-enhanced Raman spectroscopy

PubMed Central

DeVetter, Brent M.; Mukherjee, Prabuddha; Murphy, Catherine J.; Bhargava, Rohit

2015-01-01

Colloidal plasmonic nanomaterials, consisting of metals such as gold and silver, are excellent candidates for advanced optical probes and devices, but precise control over surface chemistry is essential for realizing their full potential. Coupling thiolated (R-SH) molecules to nanoprobe surfaces is a convenient and established route to tailor surface properties. The ability to dynamically probe and monitor the surface chemistry of nanoparticles in solution is essential for rapidly manufacturing spectroscopically tunable nanoparticles. In this study, we report the development of surface-enhanced Raman spectroscopy (SERS) as a method to monitor the kinetics of gold-thiolate bond formation on colloidal gold nanoparticles. A theoretical model combining SERS enhancement with the Beer-Lambert law is proposed to explain ensemble scattering and absorption effects in colloids during chemisorption. In order to maximize biological relevance and signal reproducibility, experiments used to validate the model focused on maintaining nanoparticle stability after the addition of water-soluble aromatic thiolated molecules. Our results indicate that ligand exchange on gold nanoparticles follow a first-order Langmuir adsorption model with rate constants on the order of 0.01 min 1. This study demonstrates an experimental spectroscopic method and theoretical model for monitoring binding kinetics that may prove useful for designing novel probes. PMID:25905515

Defluoridation using biomimetically synthesized nano zirconium chitosan composite: kinetic and equilibrium studies.

PubMed

Prasad, Kumar Suranjit; Amin, Yesha; Selvaraj, Kaliaperumal

2014-07-15

The present study reports a novel approach for synthesis of Zr nanoparticles using aqueous extract of Aloe vera. Resulting nanoparticles were embedded into chitosan biopolymer and termed as CNZr composite. The composite was subjected to detailed adsorption studies for removal of fluoride from aqueous solution. The synthesized Zr nanoparticles showed UV-vis absorption peak at 420nm. TEM result showed the formation of polydispersed, nanoparticles ranging from 18nm to 42nm. SAED and XRD analysis suggested an fcc (face centered cubic) Zr crystallites. EDAX analysis suggested that Zr was an integral component of synthesized nanoparticles. FT-IR study indicated that functional group like NH, CO, CN and CC were involved in particle formation. The adsorption of fluoride on to CNZr composite worked well at pH 7.0, where ∼99% of fluoride was found to be adsorbed on adsorbent. Langmuir isotherm model best fitted the equilibrium data since it presented higher R(2) value than Freundlich model. In comparison to pseudo-first order kinetic model, the pseudo-second order model could explain adsorption kinetic behavior of F(-) onto CNZr composite satisfactorily with a good correlation coefficient. The present study revealed that CNZr composite may work as an effective tool for removal of fluoride from contaminated water. Copyright © 2014 Elsevier B.V. All rights reserved.

Investigating the Heavy Metal Adsorption of Mesoporous Silica Materials Prepared by Microwave Synthesis

NASA Astrophysics Data System (ADS)

Zhu, Wenjie; Wang, Jingxuan; Wu, Di; Li, Xitong; Luo, Yongming; Han, Caiyun; Ma, Wenhui; He, Sufang

2017-05-01

Mesoporous silica materials (MSMs) of the MCM-41 type were rapidly synthesized by microwave heating using silica fume as silica source and evaluated as adsorbents for the removal of Cu2+, Pb2+, and Cd2+ from aqueous solutions. The effects of microwave heating times on the pore structure of the resulting MSMs were investigated as well as the effects of different acids which were employed to adjust the solution pH during the synthesis. The obtained MCM-41 samples were characterized by nitrogen adsorption-desorption analyses, X-ray powder diffraction, and transmission electron microscopy. The results indicated that microwave heating method can significantly reduce the synthesis time of MCM-41 to 40 min. The MCM-41 prepared using citric acid (c-MCM-41(40)) possessed more ordered hexagonal mesostructure, higher pore volume, and pore diameter. We also explored the ability of c-MCM-41(40) for removing heavy metal ions (Cu2+, Pb2+, and Cd2+) from aqueous solution and evaluated the influence of pH on its adsorption capacity. In addition, the adsorption isotherms were fitted by Langmuir and Freundlich models, and the adsorption kinetics were assessed using pseudo-first-order and pseudo-second-order models. The intraparticle diffusion model was studied to understand the adsorption process and mechanism. The results confirmed that the as-synthesized adsorbent could efficiently remove the heavy metal ions from aqueous solution at pH range of 5-7. The adsorption isotherms obeyed the Langmuir model, and the maximum adsorption capacities of the adsorbent for Cu2+, Pb2+, and Cd2+ were 36.3, 58.5, and 32.3 mg/g, respectively. The kinetic data were well fitted to the pseudo-second-order model, and the results of intraparticle diffusion model showed complex chemical reaction might be involved during adsorption process.

Large-Amplitude High-Frequency Waves at Earth's Magnetopause

NASA Astrophysics Data System (ADS)

Graham, D. B.; Vaivads, A.; Khotyaintsev, Yu. V.; André, M.; Le Contel, O.; Malaspina, D. M.; Lindqvist, P.-A.; Wilder, F. D.; Ergun, R. E.; Gershman, D. J.; Giles, B. L.; Magnes, W.; Russell, C. T.; Burch, J. L.; Torbert, R. B.

2018-04-01

Large-amplitude waves near the electron plasma frequency are found by the Magnetospheric Multiscale (MMS) mission near Earth's magnetopause. The waves are identified as Langmuir and upper hybrid (UH) waves, with wave vectors either close to parallel or close to perpendicular to the background magnetic field. The waves are found all along the magnetopause equatorial plane, including both flanks and close to the subsolar point. The waves reach very large amplitudes, up to 1 V m-1, and are thus among the most intense electric fields observed at Earth's magnetopause. In the magnetosphere and on the magnetospheric side of the magnetopause the waves are predominantly UH waves although Langmuir waves are also found. When the plasma is very weakly magnetized only Langmuir waves are likely to be found. Both Langmuir and UH waves are shown to have electromagnetic components, which are consistent with predictions from kinetic wave theory. These results show that the magnetopause and magnetosphere are often unstable to intense wave activity near the electron plasma frequency. These waves provide a possible source of radio emission at the magnetopause.

Linear discrete systems with memory: a generalization of the Langmuir model

NASA Astrophysics Data System (ADS)

Băleanu, Dumitru; Nigmatullin, Raoul R.

2013-10-01

In this manuscript we analyzed a general solution of the linear nonlocal Langmuir model within time scale calculus. Several generalizations of the Langmuir model are presented together with their exact corresponding solutions. The physical meaning of the proposed models are investigated and their corresponding geometries are reported.

Using Weighted Least Squares Regression for Obtaining Langmuir Sorption Constants

USDA-ARS?s Scientific Manuscript database

One of the most commonly used models for describing phosphorus (P) sorption to soils is the Langmuir model. To obtain model parameters, the Langmuir model is fit to measured sorption data using least squares regression. Least squares regression is based on several assumptions including normally dist...

Removal of halogenated emerging contaminants from water by nitrogen-doped graphene decorated with palladium nanoparticles: Experimental investigation and theoretical analysis.

PubMed

Li, Lei; Gong, Li; Wang, Yi-Xuan; Liu, Qi; Zhang, Jie; Mu, Yang; Yu, Han-Qing

2016-07-01

The removal performance and mechanisms of halogenated emerging contaminants from water by palladium decorated nitrogen-doped graphene (Pd/NG) were investigated in this study. For comparison, three catalysts of Pd/NG, palladium decorated graphene (Pd/G) and commercial Pd/C were initially explored to degrade tetrabromobisphenol A (TBBPA). After that, the influence of various environmental parameters on TBBPA removal by the Pd/NG catalyst was evaluated. Moreover, both Langmuir-Hinshelwood model and density functional theory (DFT) were adopted to theoretically elucidate the adsorption and the activation of TBBPA on the catalyst. The results show that the apparent rate constant of TBBPA dehalogenation was increased by 26.7% and 39.0% in the presence of the Pd/NG catalyst compared to the Pd/G and Pd/C ones. Higher temperature, catalyst dosage and alkaline conditions resulted in the enhancement of TBBPA dehalogenation by the Pd/NG catalyst, while humic acid in the solution had a negatively effect on the transformation of TBBPA. The corresponding rate constant value exhibited a 2.1- and 1.8-fold increase with the rise of temperature from 298 to 328 K and initial pH from 6.5 to 9.0, respectively. On the contrary, the rate constant was decreased by 78.9% in the presence of 15 mg L(-1) humic acid. Theoretical analysis revealed that both adsorption and activation processes of TBBPA on the Pd/NG catalyst were enhanced through the N doping into graphene framework. Copyright © 2016 Elsevier Ltd. All rights reserved.

Use of carbonised beet pulp carbon for removal of Remazol Turquoise Blue-G 133 from aqueous solution.

PubMed

Dursun, Arzu Y; Tepe, Ozlem; Dursun, Gülbeyi

2013-01-01

Carbonised beet pulp (BPC) produced from agricultural solid waste by-product in sugar industry was used as adsorbent for the removal of Remazol Turquoise Blue-G 133 (RTB-G 133) dye in this study. The kinetics and equilibrium of sorption process were investigated with respect to pH, temperature and initial dye concentration. Adsorption studies with real textile wastewater were also performed. The results showed that adsorption was a strongly pH-dependent process, and optimum pH was determined as 1.0. The maximum dye adsorption capacity was obtained as 47.0 mg g(-1)at the temperature of 25 °C at this pH value. The Freundlich and Langmuir adsorption models were used for describing the adsorption equilibrium data of the dye, and isotherm constants were evaluated depending on sorption temperature. Equilibrium data of RTB-G 133 sorption fitted very well to the Freundlich isotherm. Mass transfer and kinetic models were applied to the experimental data to examine the mechanisms of adsorption and potential rate-controlling steps. It was found that both external mass transfer and intra-particle diffusion played an important role in the adsorption mechanisms of dye and adsorption kinetics followed the pseudo second-order type kinetic model. The thermodynamic analysis indicated that the sorption process was exothermic and spontaneous in nature.

Liquid Phase adsorption kinetics and equilibrium of toluene by novel modified-diatomite.

PubMed

Sheshdeh, Reza Khalighi; Abbasizadeh, Saeed; Nikou, Mohammad Reza Khosravi; Badii, Khashayar; Sharafi, Mohammad Sadegh

2014-01-01

The adsorption equilibria of toluene from aqueous solutions on natural and modified diatomite were examined at different operation parameters such as pH, contact time, initial toluene concentration was evaluated and optimum experimental conditions were identified. The surface area and morphology of the nanoparticles were characterized by SEM, BET, XRD, FTIR and EDX analysis. It was found that in order to obtain the highest possible removal of toluene, the experiments can be carried out at pH 6, temperature 25°C, an agitation speed of 200 rpm, an initial toluene concentration of 150 mg/L, a centrifugal rate of 4000 rpm, adsorbent dosage = 0.1 g and a process time of 90 min. The results of this work show that the maximum percentage removal of toluene from aqueous solution in the optimum conditions for NONMD was 96.91% (145.36 mg/g). Furthermore, under same conditions, the maximum adsorption of natural diatomite was 71.45% (107.18 mg/g). Both adsorption kinetic and isotherm experiments were carried out. The experimental data showed that the adsorption follows the Langmuir model and Freundlich model on natural and modified diatomite respectively. The kinetics results were found to conform well to pseudo-second order kinetics model with good correlation. Thus, this study demonstrated that the modified diatomite could be used as potential adsorbent for removal of toluene from aqueous solution.

Equilibrium and kinetic studies of sorption of 2.4-dichlorophenol onto 2 mixtures: bamboo biochar plus calcium sulphate (BC) and hydroxyapatite plus bamboo biochar plus calcium sulphate (HBC), in a fluidized bed circulation column

DOE PAGES

Alamin, Ahmed Hassan; Kaewsichan, Lupong

2016-06-30

Sorption studies were carried out to investigate removal of 2.4-dichlorophenol (2.4-DCP) from aqueous solution in a fluidized bed by two types of adsorbent mixtures: BC (Bamboo char plus Calcium sulphate), and HBC (Hydroxyapatite plus Bamboo char plus Calcium sulphate); both manufactured in ball shape. The main material bamboo char was characterized by FTIR, DTA and SEM. The adsorption experiments were conducted in a fluidized bed circulation column. Adsorption, isotherms and kinetic studies were established under 180 min operating process time, at different initial 2.4-DCP solution concentrations ranging from 5–10 mg/L, and at different flow rates ranging from 0.25–0.75 L/min. Themore » data obtained fitted well for both the Langmuir and Freundlich isotherm models; indicating favorable condition of monolayer adsorption. The kinetics of both adsorbents complies with the pseudo second-order kinetic model. BC was proven a new effective composite and low cost adsorbent which can be applied in the field of wastewater treatment, and it can also play an important role in industry water treatment« less

Equilibrium and kinetic studies of sorption of 2.4-dichlorophenol onto 2 mixtures: bamboo biochar plus calcium sulphate (BC) and hydroxyapatite plus bamboo biochar plus calcium sulphate (HBC), in a fluidized bed circulation column

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alamin, Ahmed Hassan; Kaewsichan, Lupong

Sorption studies were carried out to investigate removal of 2.4-dichlorophenol (2.4-DCP) from aqueous solution in a fluidized bed by two types of adsorbent mixtures: BC (Bamboo char plus Calcium sulphate), and HBC (Hydroxyapatite plus Bamboo char plus Calcium sulphate); both manufactured in ball shape. The main material bamboo char was characterized by FTIR, DTA and SEM. The adsorption experiments were conducted in a fluidized bed circulation column. Adsorption, isotherms and kinetic studies were established under 180 min operating process time, at different initial 2.4-DCP solution concentrations ranging from 5–10 mg/L, and at different flow rates ranging from 0.25–0.75 L/min. Themore » data obtained fitted well for both the Langmuir and Freundlich isotherm models; indicating favorable condition of monolayer adsorption. The kinetics of both adsorbents complies with the pseudo second-order kinetic model. BC was proven a new effective composite and low cost adsorbent which can be applied in the field of wastewater treatment, and it can also play an important role in industry water treatment« less

Investigation of kinetics and absorption isotherm models for hydroponic phytoremediation of waters contaminated with sulfate.

PubMed

Saber, Ali; Tafazzoli, Milad; Mortazavian, Soroosh; James, David E

2018-02-01

Two common wetland plants, Pampas Grass (Cortaderia selloana) and Lucky Bamboo (Dracaena sanderiana), were used in hydroponic cultivation systems for the treatment of simulated high-sulfate wastewaters. Plants in initial experiments at pH 7.0 removed sulfate more efficiently compared to the same experimental conditions at pH 6.0. Results at sulfate concentrations of 50, 200, 300, 600, 900, 1200, 1500 and 3000 mg/L during three consecutive 7-day treatment periods with 1-day rest intervals, showed decreasing trends of both removal efficiencies and uptake rates with increasing sulfate concentrations from the first to the second to the third 7-day treatment periods. Removed sulfate masses per unit dry plant mass, calculated after 23 days, showed highest removal capacity at 600 mg/L sulfate for both plants. A Langmuir-type isotherm best described sulfate uptake capacity of both plants. Kinetic studies showed that compared to pseudo first-order kinetics, pseudo-second order kinetic models slightly better described sulfate uptake rates by both plants. The Elovich kinetic model showed faster rates of attaining equilibrium at low sulfate concentrations for both plants. The dimensionless Elovich model showed that about 80% of sulfate uptake occurred during the first four days' contact time. Application of three 4-day contact times with 2-day rest intervals at high sulfate concentrations resulted in slightly higher uptakes compared to three 7-day contact times with 1-day rest intervals, indicating that pilot-plant scale treatment systems could be sized with shorter contact times and longer rest-intervals. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nanoscale Zero-Valent Iron (NZVI) supported on sineguelas waste for Pb(II) removal from aqueous solution: kinetics, thermodynamic and mechanism.

PubMed

Arshadi, M; Soleymanzadeh, M; Salvacion, J W L; SalimiVahid, F

2014-07-15

In this study, the synthesis and characterization of a new adsorbent containing nanoscale zerovalent iron particles (NZVI) decorated sineguelas waste (S-NaOH-NZVI) from agriculture biomass was investigated for the adsorption/reduction of inorganic pollution such as Pb(II) ions. The combination of ZVI particles on the surface of sineguelas waste can help to overcome the disadvantage of ultra-fine powders which may have strong tendency to agglomerate into larger particles, resulting in an adverse effect on both effective surface area and catalyst performance. The synthesized materials were characterized with different methods such as FT-IR, BET, XRD, TEM and pHPZC. Good dispersion of NZVI particles (ca. 10-70nm) on the sineguelas waste was observed. The effects of various parameters, such as contact time, pH, concentration, adsorbent dosage and temperature were studied. The adsorption of Pb(II) ions has been studied in terms of pseudo-first- and second-order kinetics, and the Freundlich, Langmuir and Langmuir-Freundlich isotherms models have also been used to the equilibrium adsorption data. The adsorption kinetics followed the mechanism of the pseudo-second-order equation. The thermodynamic parameters (ΔG, ΔH and ΔS) indicated that the adsorption of Pb(II) ions were feasible, spontaneous and endothermic at 25-80°C. XRD analysis indicated the presence of Pb(0) on the S-NaOH-NZVI surface. This study suggests that the modified sineguelas waste by NZVI particles can be prepared at low cost and the materials are environmentally benign for the removal of Pb(II) ions, and likely many other heavy metal ions, from water. Copyright © 2014 Elsevier Inc. All rights reserved.

Thermodynamic and kinetic studies of As(V) removal from water by zirconium oxide-coated marine sand.

PubMed

Khan, Tabrez Alam; Chaudhry, Saif Ali; Ali, Imran

2013-08-01

Arsenic contamination of groundwater is a major threat to human beings globally. Among various methods available for arsenic removal, adsorption is fast, inexpensive, selective, accurate, reproducible and eco-friendly in nature. The present paper describes removal of arsenate from water on zirconium oxide-coated sand (novel adsorbent). In the present work, zirconium oxide-coated sand was prepared and characterised by infrared and X-ray diffraction techniques. Batch experiments were performed to optimise different adsorption parameters such as initial arsenate concentration (100-1,000 μg/L), dose (1-8 g/L), pH of the solution (2-14), contact time (15-150 min.), and temperature (20, 30, 35 and 40 °C). The experimental data were analysed by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. Furthermore, thermodynamic and kinetic parameters were evaluated to know the mode of adsorption between ZrOCMS and As(V). The maximum removal of arsenic, 97 %, was achieved at initial arsenic concentration of 200 μg/L, after 75 min at dosage of 5.0 g/L, pH 7.0 and 27 ± 2 °C. For 600 μg/L concentration, the maximum Langmuir monolayer adsorption capacity was found to be 270 μg/g at 35 °C. Kinetic modelling data indicated that adsorption process followed pseudo-second-order kinetics. The mechanism is controlled by liquid film diffusion model. Thermodynamic parameter, ΔH°, was -57.782, while the values of ΔG° were -9.460, -12.183, -13.343 and -13.905 kJ/mol at 20, 30, 35 and 40 °C, respectively, suggesting exothermic and spontaneous nature of the process. The change in entropy, ΔS°= -0.23 kJ/mol indicated that the entropy decreased due to adsorption of arsenate ion onto the solid adsorbent. The results indicated that the reported zirconium oxide-coated marine sand (ZrOCMS) was good adsorbent with 97 % removal capacity at 200 μg/L concentration. It is interesting to note that the permissible limit of arsenic as per World Health Organization is 10 μg/L, and in real situation, this low concentration can be achieved through this adsorbent. Besides, the adsorption capacity showed that this adsorbent may be used for the removal of arsenic from any natural water resource.

Removal of phosphate from aqueous solution using magnesium-alginate/chitosan modified biochar microspheres derived from Thalia dealbata.

PubMed

Cui, Xiaoqiang; Dai, Xi; Khan, Kiran Yasmin; Li, Tingqiang; Yang, Xiaoe; He, Zhenli

2016-10-01

The objective of this study was to determine the feasibility of using magnesium-alginate/chitosan modified biochar microspheres to enhance removal of phosphate from aqueous solution. The introduction of MgCl2 substantially increased surface area of biochar (116.2m(2)g(-1)), and both granulation with alginate/chitosan and modification with magnesium improved phosphate sorption on the biochars. Phosphate sorption on the biochars could be well described by a simple Langmuir model, and the MgCl2-alginate modified biochar microspheres exhibited the highest phosphate sorption capacity (up to 46.56mgg(-1)). The pseudo second order kinetic model better fitted the kinetic data, and both the Yoon-Nelson and Thomas models were superior to other models in describing phosphate dynamic sorption. Precipitation with minerals and ligand exchange were the possible mechanisms of phosphate sorption on the modified biochars. These results imply that MgCl2-alginate modified biochar microspheres have potential as a green cost-effective sorbent for remediating P contaminated water environment. Copyright © 2016 Elsevier Ltd. All rights reserved.

2,4-Dinitrophenylhydrazine functionalized sodium dodecyl sulfate-coated magnetite nanoparticles for effective removal of Cd(II) and Ni(II) ions from water samples.

PubMed

Sobhanardakani, Soheil; Zandipak, Raziyeh

2015-07-01

2,4-Dinitrophenylhydrazine immobilized on sodium dodecyl sulfate (SDS)-coated magnetite and was used for removal of Cd(II) and Ni(II) ions from aqueous solution. The prepared product was characterized by X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The size of the nanoparticles according to SEM was obtained around 20-35 nm. In batch tests, the effects of pH, contact time, initial metal concentration, and temperature were studied. The kinetic and equilibrium data were modeled with recently developed models. The adsorption kinetics and isotherms were well fitted by the fractal-like pseudo-second-order model and Langmuir-Freundlich model, respectively. Maximum adsorption capacity by this adsorbent is 255.1 mg g(-1) for Cd(II) ion and 319.6 mg g(-1) for Ni(II) ion at pH 7.0 and 25 °C. The method was successfully applied to the removal of metal cations in real samples (tap water, river water, and petrochemical wastewater).

An experimental design approach for modeling As(V) adsorption from aqueous solution by activated carbon.

PubMed

Bakkal Gula, C; Bilgin Simsek, E; Duranoglu, D; Beker, U

2015-01-01

The present paper discusses response surface methodology as an efficient approach for predictive model building and optimization of As(V) adsorption on activated carbon derived from a food industry waste: peach stones. The objectives of the study are application of a three-factor 2³ full factorial and central composite design technique for maximizing As(V) removal by produced activated carbon, and examination of the interactive effects of three independent variables (i.e., solution pH, temperature, and initial concentration) on As(V) adsorption capacity. Adsorption equilibrium was investigated by using Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. First-order and second-order kinetic equations were used for modeling of adsorption kinetics. Thermodynamic parameters (ΔG °, ΔH °, and ΔS °) were calculated and used to explain the As(V) adsorption mechanism. The negative value of ΔH (-7.778 kJ mol⁻¹) supported the exothermic nature of the sorption process and the Gibbs free energy values (ΔG°) were found to be negative, which indicates that the As(V) adsorption is feasible and spontaneous.

Biosorption of Acid Black 172 and Congo Red from aqueous solution by nonviable Penicillium YW 01: kinetic study, equilibrium isotherm and artificial neural network modeling.

PubMed

Yang, Yuyi; Wang, Guan; Wang, Bing; Li, Zeli; Jia, Xiaoming; Zhou, Qifa; Zhao, Yuhua

2011-01-01

The main objective of this work was to investigate the biosorption performance of nonviable Penicillium YW 01 biomass for removal of Acid Black 172 metal-complex dye (AB) and Congo Red (CR) in solutions. Maximum biosorption capacities of 225.38 and 411.53 mg g(-1) under initial dye concentration of 800 mg L(-1), pH 3.0 and 40 °C conditions were observed for AB and CR, respectively. Biosorption data were successfully described with Langmuir isotherm and the pseudo-second-order kinetic model. The Weber-Morris model analysis indicated that intraparticle diffusion was the limiting step for biosorption of AB and CR onto biosorbent. Analysis based on the artificial neural network and genetic algorithms hybrid model indicated that initial dye concentration and temperature appeared to be the most influential parameters for biosorption process of AB and CR onto biosorbent, respectively. Characterization of the biosorbent and possible dye-biosorbent interaction were confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy. Copyright © 2010 Elsevier Ltd. All rights reserved.

Adsorption and bioadsorption of granular activated carbon (GAC) for dissolved organic carbon (DOC) removal in wastewater.

PubMed

Xing, W; Ngo, H H; Kim, S H; Guo, W S; Hagare, P

2008-12-01

In this study, the performances of GAC adsorption and GAC bioadsorption in terms of dissolved organic carbon (DOC) removal were investigated with synthetic biologically treated sewage effluent (BTSE), synthetic primary treated sewage effluent (PTSE), real BTSE and real PTSE. The main aims of this study are to verify and compare the efficiency of DOC removal by GAC (adsorption) and acclimatized GAC (bioadsorption). The results indicated that the performance of bioadsorption was significantly better than that of adsorption in all cases, showing the practical use of biological granular activated carbon (BGAC) in filtration process. The most significance was observed at a real PTSE with a GAC dose of 5g/L, having 54% and 96% of DOC removal by adsorption and bioadsorption, respectively. In addition, it was found that GAC adsorption equilibrium was successfully predicted by a hybrid Langmuir-Freundlich model whilst integrated linear driving force approximation (LDFA)+hybrid isotherm model could describe well the adsorption kinetics. Both adsorption isotherm and kinetic coefficients determined by these models will be useful to model the adsorption/bioadsorption process in DOC removal of BGAC filtration system.

Highly effective removal of basic fuchsin from aqueous solutions by anionic polyacrylamide/graphene oxide aerogels.

PubMed

Yang, Xiaoxia; Li, Yanhui; Du, Qiuju; Sun, Jiankun; Chen, Long; Hu, Song; Wang, Zonghua; Xia, Yanzhi; Xia, Linhua

2015-09-01

Novel anionic polyacrylamide/graphene oxide aerogels were prepared by a freeze drying method and used to remove basic fuchsin from aqueous solutions. These aerogels were sponge-like solid with lightweight, fluffy and porous structure. The batch adsorption experiments were carried out to study the effect of various parameters, such as the solution pH, adsorbent dose, contact time and temperature on adsorption properties of basic fuchsin onto anionic polyacrylamide/graphene oxide aerogels. The kinetics of adsorption corresponded to the pseudo-second-order kinetic model. The Langmuir adsorption isotherm was suitable to describe the equilibrium adsorption process. The maximum adsorption capacity was up to 1034.3 mg/g, which indicated that anionic polyacrylamide/graphene oxide aerogels were promising adsorbents for removing dyes pollutants from aqueous solution. Copyright © 2015 Elsevier Inc. All rights reserved.

The inhibition of calcium carbonate crystal growth by the cysteine-rich Mdm2 peptide.

PubMed

Dalas, E; Chalias, A; Gatos, D; Barlos, K

2006-08-15

The crystal growth of calcite, the most stable calcium carbonate polymorph, in the presence of the cysteine-rich Mdm2 peptide (containing 48 amino acids in the ring finger configuration), has been investigated by the constant composition technique. Crystallization took place exclusively on well-characterized calcite crystals in solutions supersaturated only with respect to this calcium carbonate salt. The kinetic results indicated a surface diffusion spiral growth mechanism. The presence of the Mdm2 peptide inhibited the crystal growth of calcite by 22-58% in the concentration range tested, through adsorption onto the active growth sites of the calcite crystal surface. The kinetic results favored a Langmuir-type adsorption model, and the value of the calculated affinity constant was k(aff)=147x10(4) dm(3)mol(-1), a(ads)=0.29.

Kinetic analysis on precursors for iturin A production from Bacillus amyloliquefaciens BPD1.

PubMed

Wu, Jiun-Yan; Liao, Jen-Hung; Shieh, Chwen-Jen; Hsieh, Feng-Chia; Liu, Yung-Chuan

2018-06-12

In this study, the precursor effect for iturin A production was quantitatively analyzed. A strain identified as Bacillus amyloliquefaciens BPD1 (Ba-BPD1) was selected due to its ability to produce iturin A. The enhancement of iturin A production in a submerged culture was tested using various additives, including palmitic acid, oils, and complex amino acids. Among these, complex amino acids triggered the highest yield at 559 mg/L. The respective amino acids that contribute to the structure of iturin A were used as precursors. In fact, it was found that the addition of l-proline, l-glutamine, l-asparagine and l-serine could improve iturin A yield in the defined medium. However, during the kinetic analysis, all the amino acids exhibited a lower saturation level than l-serine, which exhibited a high saturation level at 1.2% resulting in an iturin A yield of 914 mg/L. In contrast, a negative effect was observed following the addition of l-tyrosine. To analyze the kinetic behavior of l-serine, three kinetic models were adopted: the kinetic order equation, the Langmuir kinetic equation, and a modified logistic equation. The regression results showed that the modified logistic model was the best fit for the kinetic behavior of l-serine as the major precursor, which could be further referred to the biosynthesis pathway of iturin A. Among the proposed processes for iturin A production, this study achieved the highest iturin A levels as a result of the addition of precursors. Copyright © 2018 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Modeling cytoskeletal traffic: an interplay between passive diffusion and active transport.

PubMed

Neri, Izaak; Kern, Norbert; Parmeggiani, Andrea

2013-03-01

We introduce the totally asymmetric simple exclusion process with Langmuir kinetics on a network as a microscopic model for active motor protein transport on the cytoskeleton, immersed in the diffusive cytoplasm. We discuss how the interplay between active transport along a network and infinite diffusion in a bulk reservoir leads to a heterogeneous matter distribution on various scales: we find three regimes for steady state transport, corresponding to the scale of the network, of individual segments, or local to sites. At low exchange rates strong density heterogeneities develop between different segments in the network. In this regime one has to consider the topological complexity of the whole network to describe transport. In contrast, at moderate exchange rates the transport through the network decouples, and the physics is determined by single segments and the local topology. At last, for very high exchange rates the homogeneous Langmuir process dominates the stationary state. We introduce effective rate diagrams for the network to identify these different regimes. Based on this method we develop an intuitive but generic picture of how the stationary state of excluded volume processes on complex networks can be understood in terms of the single-segment phase diagram.

Fabrication and characterization of akaganeite/graphene oxide nanocomposite for arsenic removal from water

NASA Astrophysics Data System (ADS)

Trang, Nguyen Thi Thuy; Thy, Lu Thi Mong; Cuong, Pham Mai; Tu, Tran Hoang; Hieu, Nguyen Huu

2018-04-01

In this study, akageneite/graphene oxide (β-FeOOH/GO) nanocomposite was fabricated by in situ forced hydrolysis of iron (III) chloride. The structure and morphology of β-FeOOH/GO were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer-Emmett- Teller (BET) specific surface area. XRD, FTIR, and TEM results indicated that β-FeOOH nanoparticles were successfully decorated on the surface of GO nanosheets. The BET specific surface area of β-FeOOH/GO was observed of 97.94 m2/g. The nanocomposite was used as an adsorbent for removal of arsenic (As5+) from water. Adsorption experiments were carried out to investigate contact time, pH values, and As5+ initial concentrations. The adsorption equilibrium time was reached within 180 minutes. The adsorption was well-fitted by a pseudo-second-order kinetic and Langmuir isotherm model. The maximum adsorption capacity of β-FeOOH/GO for As5+ ions of 94.34 mg/g that was calculated from the Langmuir model at pH 3. Accordingly, the nanocomposite β-FeOOH/GO could be considered as a highly efficient adsorbent for removing arsenic from water.

Removal of aniline from air and water by polymers of intrinsic microporosity (PIM-1) electrospun ultrafine fibers.

PubMed

Satilmis, Bekir; Uyar, Tamer

2018-04-15

This research aims to investigate the possibility of electrospun fibers from Polymers of Intrinsic Microporosity (PIM-1) as an alternative adsorbent for aniline removal from both air and aqueous solution. Adsorption properties of electrospun PIM-1 fibers were compared with powder and film form of PIM-1. While electrospun PIM-1 nanofibrous mat can adsorb 871 mg g -1 aniline from air, it can also adsorb 78 ± 5.4 mg g -1 aniline from aqueous environment when 50 mg L -1 aniline solution is used. The experimental maximum adsorption capacity of electrospun PIM-1 fibers was found as (q e ) 138 mg g -1 . Langmuir and Freundlich isotherm models have been studied and Langmuir model found more appropriate for aniline adsorption on electrospun PIM-1 fibers. The study reveals that self-standing electrospun fibrous mat of PIM-1 has shown potential to be used as an efficient adsorbent material for the adsorption of VOCs from air and aqueous system thanks to its fast kinetic and high adsorption capacity. Copyright © 2018 Elsevier Inc. All rights reserved.

Graphene-poly(vinyl alcohol) composites: Fabrication, adsorption and electrochemical properties

NASA Astrophysics Data System (ADS)

Wang, Ning; Chang, Peter R.; Zheng, Pengwu; Ma, Xiaofei

2014-09-01

Porous composites of graphene oxide (GO)-poly(vinyl alcohol) (PVA) were fabricated using a process of aqueous suspension precursor freezing, solvent exchange, and ethanol drying. When frozen, ice crystals formed leaving a porous structure, composed of randomly oriented GO sheets consolidated by PVA. The yellow GO-PVA composite could be reduced with glucose to obtain a black porous RGO (PRGO). XRD revealed that PVA enlarged the GO interlay spacing in the GO-PVA composite, and that RGO sheets were highly disordered in single or several layers in PRGO. GO-PVA and PRGO exhibited ultralight densities of 10.52 and 11.42 mg/cm3, respectively. GO-PVA adsorbed greater quantities of water, ethanol, and soybean oil than PRGO. The methylene blue (MB) adsorption pattern for both materials was also investigated. The kinetic adsorption and isotherm data fit the pseudo second-order and the Langmuir models, respectively. The maximum adsorption capacity according to the Langmuir isotherm model was 571.4 mg/g for GO-PVA. The electrochemical properties of PRGO were estimated using cyclic voltammetry, electrochemical impedance spectrometry, and chronopotentiometry. The PRGO electrode exhibited large capacitance (82.8 F/g) and small internal resistance (0.52 Ω).

Potentiality of Neopestalotiopsis clavispora ASU1 in biosorption of cadmium and zinc.

PubMed

Hassan, Sedky H A; Koutb, Mostafa; Nafady, Nivien Allam; Hassan, Elhagag Ahmed

2018-07-01

In this study, a fungal isolate was isolated from avocado fruit collected from a market in Makkah city, Saudi Arabia, and identified as Neopestalotiopsis clavispora ASU1. The biomass of Neopestalotiopsis clavispora ASU1 was used as a natural bio-sorbent for removal of Cd(II) and Zn(II) from aqueous solutions. Characterization of fungal biomass was performed using Fourier transform infrared spectroscopy, X-ray Diffractometer, and BET surface area. Different factors on Cd(II) and Zn(II) biosorption were studied to evaluate the maximum conditions for metals biosorption. The (q max ) for Cd(II) and Zn (II) by N. clavispora ASU1 calculated from the Langmuir adsorption isotherm was 185.3 ± 0.25 and 153.8 ± 0.21 mg/g, respectively. Based on r 2 , the equilibrium biosorption isotherms fitted well with Langmuir model than Freundlich isotherm. The adsorption kinetics was studied, and the biosorption followed to the pseudo-second-order model. Thus, the current study indicated that the biomass of N. clavispora ASU1 is an effective adsorbent for the removal of heavy metals from aqueous solutions. Copyright © 2018 Elsevier Ltd. All rights reserved.

Adsorption of Pd(II) complexes from chloride solutions obtained by leaching chlorinated spent automotive catalysts on ion exchange resin Diaion WA21J.

PubMed

Shen, Shaobo; Pan, Tonglin; Liu, Xinqiang; Yuan, Lei; Zhang, Yongjian; Wang, Jinchao; Guo, Zhanchen

2010-05-01

It was found that Rh, Pd and Pt contained in the spent ceramic automotive catalysts could be effectively extracted by dry chlorination with chlorine. In order to concentrate Pd(II) contained in the chloride solution obtained from the dry chlorination process, thermodynamic and kinetics studies for adsorption of Pd(II) complexes from the chloride solutions on anionic exchange resin Diaion WA21J were carried out. It was found that Pd, Pt, Rh, Al, Fe, Si, Zn and Pb from the chloride solution could be adsorbed on the resin. The isothermal adsorption of Pd(II) was found to fit Freundlich, Langmuir and Dubinin-Kaganer-Radushkevich models under the adsorption conditions. The adsorption of Pd(II) on the resin was favorable according to the values of 1/n and R(L) from Freundlich and Langmuir adsorption isotherms, respectively. The maximum monolayer adsorption capacities Q(max) based on Langmuir adsorption isotherms were 5.70, 4.84 and 4.05 mg/g and the corresponding value X(m) based on Dubinin-Kaganer-Radushkevich were 5.55, 4.69 and 4.01 mg/g at temperatures 18 degrees C, 28 degrees C and 40 degrees C, respectively. The apparent adsorption energies (E(ad)) based on Dubinin-Kaganer-Radushkevich isotherm were -15.43, -16.22 and -23.57 kJ/mol for the temperatures 18 degrees C, 28 degrees C and 40 degrees C, respectively. Chemical adsorption was a main mechanism involved in the adsorption process. Pd(II) adsorption on the resin could be accelerated by increasing the adsorption temperature. The adsorption of Pd(II) from the chloride solution on the resin underwent pseudo-first order kinetic process and the apparent adsorption activation energy E(a) was 15.0 kJ/mol. The intra-particle diffusion was a main rate controlling step in the Pd(II) adsorption process under the adsorption conditions. Copyright 2010 Elsevier Inc. All rights reserved.

First Principles Study on the CO Oxidation on Mn-Embedded Divacancy Graphene

PubMed Central

Jiang, Quanguo; Zhang, Jianfeng; Ao, Zhimin; Huang, Huajie; He, Haiyan; Wu, Yuping

2018-01-01

The CO oxidation mechanism on graphene with divacancy (DG) embedded with transition metal from Sc to Zn has been studied by using first principles calculations. The results indicate that O2 molecule is preferentially adsorbed on Sc, Ti, V, Cr, Mn, and Fe-DG, which can avoid the CO poisoning problem that many catalysts facing and is beneficial to the CO oxidation progress. Further study indicates that Mn-DG shows the best catalytic properties for CO oxidation with consideration of both Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) oxidation mechanisms. Along the ER mechanism, the reaction energy barrier for the first step (CO free + O2 pre-adsorbed → OOCO) is 0.96 eV. Along the LH mechanism, the energy barrier for the rate limiting step (CO adsorbed + O2 adsorbed → OOCO) is only 0.41 eV, indicating that the CO oxidation on Mn-DG will occur along LH mechanism. The Hirshfeld charge distributions of O2 and CO molecules is tuned by the embedded Mn atom, and the charge transfer from the embedded Mn atom to the adsorbed molecules plays an important role for the CO oxidation. The result shows that the Mn-embedded divacancy graphene is a noble-metal free and efficient catalyst for CO oxidation at low temperature.

Single-step uncalcined N-TiO2 synthesis, characterizations and its applications on alachlor photocatalytic degradations

NASA Astrophysics Data System (ADS)

Suwannaruang, Totsaporn; Wantala, Kitirote

2016-09-01

The aims of this research were to synthesize nitrogen doped TiO2 (N-TiO2) photocatalysts produced by hydrothermal technique and to test the degradation performance of alachlor by photocatalytic process under UV irradiations in the effect of aging temperature and time in the preparation process. The characterizations of synthesized TiO2 such as specific surface area, particle size, phase structure and elements were analyzed by using the Brunauer-Emmett-Teller (BET) technique, Transmission Electron Microscopy (TEM), X-ray Diffractometer (XRD) and Energy Dispersive X-ray spectrometer (EDX), respectively. The Central Composite Design (CCD) was used to design the experiment to determine the optimal condition, main effects and their interactions by using specific surface area, percent alachlor removal and observed first-order rate constant as responses. The kinetic reactions of alachlor degradation were explained by using Langmuir-Hinshelwood expression to confirm the reaction took place on the surface of photocatalyst. The results showed that the effect of aging temperatures was significant on surface area, whereas aging time was insignificant. Additionally, the square term of aging temperature and interaction term were shown significant on the specific surface area as well. The highest specific surface area from response surface at aging temperature between 150-175 °C and aging time between 6-13 h was found in a range of 100-106 m2/g. The average particle size of TiO2 was similar to crystallite size. Therefore, it can be concluded that one particle has only one crystal. The element analysis has shown 10% of nitrogen in TiO2 structure that the energy band-gap about 2.95 eV was found. Although, the effects of aging temperature and time on percent alachlor removal and observed first-order rate constants were insignificant, both terms were significant in term of the square for alachlor photocatalytic degradation. The optimal condition of both responses was achieved at an aging temperature of 145 °C and aging time of 12 h.

Dye adsorption into transition metal-doped zinc oxide nanoparticles supported on natural zeolites to solve wastewater issue

NASA Astrophysics Data System (ADS)

Indra Pratiwi, Margaretha; Afifah, Nur; Saleh, Rosari

2017-03-01

In this work, Fe-doped zinc oxide/natural zeolite (Fe:ZnO/NZ) nanocomposites were prepared using the co-precipitation method with various NZ amounts. The nanocomposites were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis and thermogravimetric analysis (TGA). The nanocomposites were used to remove methylene blue (MB) dye from an aqueous solution. The effect of various NZ amounts and initial MB concentration were tested. The Pseudo-first-order and pseudo-second-order kinetic models were used to explain the adsorption mechanism. The Langmuir and the Freundlich isotherm models were used to fit the adsorption isotherms of the nanocomposites.

Enrichment and separation of chlorogenic acid from the extract of Eupatorium adenophorum Spreng by macroporous resin.

PubMed

Liu, Boyan; Dong, Beitao; Yuan, Xiaofan; Kuang, Qirong; Zhao, Qingsheng; Yang, Mei; Liu, Jie; Zhao, Bing

2016-01-01

A simple and efficient chromatographic method for separation of chlorogenic acid from Eupatorium adenophorum Spreng extract was developed. The adsorption properties of nine macroporous resins were evaluated. NKA-II resin showed much better adsorption/desorption properties. The adsorption of chlorogenic acid on NKA-II resin at 25°C was well fitted to Langmuir isotherm model and pseudo-second-order kinetic model. The dynamic adsorption and desorption experiments were carried out on columns packed with NKA-II resin to optimize the separation process. The content of chlorogenic acid in the product increased to 22.17%, with a recovery yield of 82.41%. Copyright © 2015 Elsevier B.V. All rights reserved.

Preparation of Magnetic Molecularly Imprinted Polymer for Chlorpyrifos Adsorption and Enrichment

NASA Astrophysics Data System (ADS)

Chen, M.; Ma, X.; Sheng, J.

2017-11-01

Magnetic molecularly imprinted polymer (MMIP) for chlorpyrifos was prepared and characterized. The adsorption performance of MMIP for chlorpyrifos was evaluated under various conditions. The results showed that the adsorption equilibrium was achieved within 1 h, the adsorption capacity was 16.8 mg/g, and the adsorption process could be well described by Langmuir isotherm model and pseudo-second-order kinetic model. The MMIP was used as the selective sorbent for solid-phase extraction of chlorpyrifos from environmental water and vegetable samples. Combined with gas chromatography-mass spectrometry, a LOD of 30 ng/L, spiked recovery of 89.6%-107.3% and RSD of 1.9%-3.8% for chlorpyrifos were obtained.

A study of the kinetics and isotherms for Cr(VI) adsorption in a binary mixture of Cr(VI)-Ni(II) using hierarchical porous carbon obtained from pig bone.

PubMed

Li, Chengxian; Huang, Zhe; Huang, Bicheng; Liu, Changfeng; Li, Chengming; Huang, Yaqin

2014-01-01

Cr(VI) adsorption in a binary mixture Cr(VI)-Ni(II) using the hierarchical porous carbon prepared from pig bone (HPC) was investigated. The various factors affecting adsorption of Cr(VI) ions from aqueous solutions such as initial concentration, pH, temperature and contact time were analyzed. The results showed excellent efficiency of Cr(VI) adsorption by HPC. The kinetics and isotherms for Cr(VI) adsorption from a binary mixture Cr(VI)-Ni(II) by HPC were studied. The adsorption equilibrium described by the Langmuir isotherm model is better than that described by the Freundlich isotherm model for the binary mixture in this study. The maximum adsorption capacity was reliably found to be as high as 192.68 mg/g in the binary mixture at pH 2. On fitting the experimental data to both pseudo-first- and second-order equations, the regression analysis of the second-order equation gave a better R² value.

The Efficient Removal of Heavy Metal Ions from Industry Effluents Using Waste Biomass as Low-Cost Adsorbent: Thermodynamic and Kinetic Models

NASA Astrophysics Data System (ADS)

Indhumathi, Ponnuswamy; Sathiyaraj, Subbaiyan; Koelmel, Jeremy P.; Shoba, Srinivasan U.; Jayabalakrishnan, Chinnasamy; Saravanabhavan, Munusamy

2018-05-01

The ability of green micro algae Chlorella vulgaris for biosorption of Cu(II) ions from an aqueous solution was studied. The biosorption process was affected by the solution pH, contact time, temperature and initial Cu(II) concentration. Experimental data were analyzed in terms of pseudo-first order, pseudo-second order and intra particle diffusion models. Results showed that the sorption process of Cu(II) ions followed pseudo-second order kinetics. The sorption data of Cu(II) ions are fitted to Langmuir, Freundlich, and Redlich-Peterson isotherms, and the Temkin isotherm. The thermodynamic study shows the Cu(II) biosorption was exothermic in nature. The Cu(II) ions were recovered effectively from Chlorella vulgaris biomass using 0.1 M H2SO4 with up to 90.3% recovery, allowing for recycling of the Cu. Green algae from freshwater bodies showed significant potential for Cu(II) removal and recovery from industrial wastewater.

Adsorption of Pb(II) ions onto biomass from Trifolium resupinatum: equilibrium and kinetic studies

NASA Astrophysics Data System (ADS)

Athar, Makshoof; Farooq, Umar; Aslam, Muhammad; Salman, M.

2013-09-01

The present study provides information about the binding of Pb(II) ions on an eco-friendly and easily available biodegradable biomass Trifolium resupinatum. The powdered biomass was characterized by FTIR, potentiometric titration and surface area analyses. The FTIR spectrum showed the presence of hydroxyl, carbonyl and amino functional groups and Pb(II) ions bound with the oxygen- and nitrogen-containing sites (hydroxyl and amino groups). The acidic groups were also confirmed by titrations. Effects of various environmental parameters (time, pH and concentration) have been studied. The biosorption process achieved equilibrium in a very short period of time (25 min). Non-linear approach for Langmuir and Freundlich models was used to study equilibrium process and root mean-square error was used as an indicator to decide the fitness of the mathematical model. The biosorption process was found to follow pseudo-second-order kinetics and was very fast. Thus, the biomass can be cost-effectively used for the binding of Pb(II) ions from aqueous solutions.

Iron oxide impregnated Morus alba L. fruit peel for biosorption of Co(II): biosorption properties and mechanism.

PubMed

Koduru, Janardhan Reddy; Chang, Yoon-Young; Yang, Jae-Kyu; Kim, Im-Soon

2013-01-01

Biosorption is an ecofriendly wastewater treatment technique with high efficiency and low operating cost involving simple process for the removal of heavy metal ions from aqueous solution. In the present investigation, Morus alba L. fruit peel powder (MAFP) and iron oxide impregnated Morus alba L. fruit peel powder (IO-MAFP) were prepared and used for treating Co(II) contaminated aqueous solutions. Further the materials were characterized by using FTIR and SEM-EDX analysis. From FT-IR analysis it was found that hydroxyl, methoxy, and carbonyl groups are responsible for Co(II) biosorption. The kinetic data obtained for both biosorbents was well fitted with pseudo-second-order kinetic model. The equilibrium data was in tune with the Langmuir and Freundlich isotherm models. The thermodynamic studies were also carried and it was observed that sorption process was endothermic at 298-328 K. These studies demonstrated that both biosorbents were promising, efficient, economic, and biodegradable sorbents.

Adsorption of Zn(II) and Cd(II) ions in batch system by using the Eichhornia crassipes.

PubMed

Módenes, A N; Espinoza-Quiñones, F R; Borba, C E; Trigueros, D E G; Lavarda, F L; Abugderah, M M; Kroumov, A D

2011-01-01

In this work, the displacement effects on the sorption capacities of zinc and cadmium ions of the Eichornia crassipes-type biosorbent in batch binary system has been studied. Preliminary single metal sorption experiments were carried out. An improvement on the Zn(II) and Cd(II) ions removal was achieved by working at 30 °C temperature and with non-uniform biosorbent grain sizes. A 60 min equilibrium time was achieved for both Zn(II) and Cd(II) ions. Furthermore, it was found that the overall kinetic data were best described by the pseudo second-order kinetic model. Classical multi-component adsorption isotherms have been tested as well as a modified extended Langmuir isotherm model, showing good agreement with the equilibrium binary data. Around 0.65 mequiv./g maximum metal uptake associated with the E. crassipes biosorbent was attained and the E. crassipes biosorbent has shown higher adsorption affinity for the zinc ions than for the cadmium ones in the binary system.

Heavy metal ion removal by thiol functionalized aluminum oxide hydroxide nanowhiskers

NASA Astrophysics Data System (ADS)

Xia, Zhiyong; Baird, Lance; Zimmerman, Natasha; Yeager, Matthew

2017-09-01

In this study, we developed a cost effective method of using thiol functionalized γ-aluminum oxide hydroxide (γ-AlOOH) filters for removing three key heavy metals from water: mercury, lead, and cadmium under non-concomitant conditions. Compared to non-thiol treated γ-AlOOH filters, the introduction of thiol functional groups greatly improved the heavy metal removal efficiency under both static and dynamic filtration conditions. The adsorption kinetics of thiol functionalized γ-AlOOH were investigated using the Lagergren first order and pseudo-second order kinetics models; whereas the isothermal adsorption behavior of these membranes was revealed through the Langmuir and Freundlich models. Heavy metal concentration was quantified by Inductively Coupled Plasma-Mass Spectroscopy, and the thiol level on γ-AlOOH surface was measured by a colorimetric assay using Ellman's reagent. X-ray photoelectron spectroscopy was used to further address the surface sulfur state on the membranes after heavy metal exposure. Mechanisms for heavy metal adsorption were also discussed.

Removal of Direct Red 12B by garlic peel as a cheap adsorbent: Kinetics, thermodynamic and equilibrium isotherms study of removal

NASA Astrophysics Data System (ADS)

Asfaram, A.; Fathi, M. R.; Khodadoust, S.; Naraki, M.

2014-06-01

The removal of dyes from industrial waste is very important from health and hygiene point of view and for environmental protection. In this work, efficiency and performance of garlic peel (GP) adsorbent for the removal of Direct Red 12B (DR12B) from wastewater was investigated. The influence of variables including pH, concentration of the dye and amount of adsorbent, particle size, contact time and temperature on the dye removal has been investigated. It was observed that the pseudo-second-order kinetic model fits better with good correlation coefficient and the equilibrium data fitted well with the Langmuir model. More than 99% removal efficiency was obtained within 25 min at adsorbent dose of 0.2 g per 50 ml for initial dye concentration of 50 mg L-1. Calculation of various thermodynamic parameters such as, Gibb's free energy, entropy and enthalpy of the on-going adsorption process indicate feasibility and endothermic nature of DR12B adsorption.

Effective adsorption of malachite green using magnetic barium phosphate composite from aqueous solution

NASA Astrophysics Data System (ADS)

Zhang, Fan; Wei, Zhong; Zhang, Wanning; Cui, Haiyan

2017-07-01

Magnetic Ba3(PO4)2/Fe3O4-nanoparticle (called BPFN) was prepared, characterized, and developed as a low-cost adsorbent for malachite green (MG) from aqueous solution. Factors such as adsorption temperature, pH of solution, dosage of adsorbent, adsorption kinetics and isotherms were investigated. The maximum adsorption capacity obtained in this work was 1639 mg g- 1 at 45 °C and pH 6. The adsorption process fitted the pseudo-first-order kinetic model and Langmuir isotherm model. Evidences from zeta potential, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) data revealed that the adsorption process was driven by electrostatic attraction, the interaction between Lewis base sbnd N(CH3)2 in MG and Lewis acid Ba sites of BPFN. In addition, the BPFN could be easily regenerated by a magnet and the adsorption capacity maintained at 70% after five cycles. The present study suggests that the BPFN had high potential of removing MG from wastewater.

Central composite design and genetic algorithm applied for the optimization of ultrasonic-assisted removal of malachite green by ZnO Nanorod-loaded activated carbon.

PubMed

Ghaedi, M; Azad, F Nasiri; Dashtian, K; Hajati, S; Goudarzi, A; Soylak, M

2016-10-05

Maximum malachite green (MG) adsorption onto ZnO Nanorod-loaded activated carbon (ZnO-NR-AC) was achieved following the optimization of conditions, while the mass transfer was accelerated by ultrasonic. The central composite design (CCD) and genetic algorithm (GA) were used to estimate the effect of individual variables and their mutual interactions on the MG adsorption as response and to optimize the adsorption process. The ZnO-NR-AC surface morphology and its properties were identified via FESEM, XRD and FTIR. The adsorption equilibrium isotherm and kinetic models investigation revealed the well fit of the experimental data to Langmuir isotherm and pseudo-second-order kinetic model, respectively. It was shown that a small amount of ZnO-NR-AC (with adsorption capacity of 20mgg(-1)) is sufficient for the rapid removal of high amount of MG dye in short time (3.99min). Copyright © 2016 Elsevier B.V. All rights reserved.

Central composite design and genetic algorithm applied for the optimization of ultrasonic-assisted removal of malachite green by ZnO Nanorod-loaded activated carbon

NASA Astrophysics Data System (ADS)

Ghaedi, M.; Azad, F. Nasiri; Dashtian, K.; Hajati, S.; Goudarzi, A.; Soylak, M.

2016-10-01

Maximum malachite green (MG) adsorption onto ZnO Nanorod-loaded activated carbon (ZnO-NR-AC) was achieved following the optimization of conditions, while the mass transfer was accelerated by ultrasonic. The central composite design (CCD) and genetic algorithm (GA) were used to estimate the effect of individual variables and their mutual interactions on the MG adsorption as response and to optimize the adsorption process. The ZnO-NR-AC surface morphology and its properties were identified via FESEM, XRD and FTIR. The adsorption equilibrium isotherm and kinetic models investigation revealed the well fit of the experimental data to Langmuir isotherm and pseudo-second-order kinetic model, respectively. It was shown that a small amount of ZnO-NR-AC (with adsorption capacity of 20 mg g- 1) is sufficient for the rapid removal of high amount of MG dye in short time (3.99 min).

Fluoride adsorption properties of three modified forms of activated alumina in drinking water.

PubMed

Duan, Ying; Wang, Chenchen; Li, Xuede; Xu, Wei

2014-12-01

The study describes the removal of fluoride from drinking water using activated alumina (AA). AA was modified with H2SO4, FeCl3 and a combination of the two to enhance fluoride adsorption. The AA adsorbents were characterized using Brunauer-Emmett-Teller surface area analysis and X-ray fluorescence. The maximum adsorption capacity of H2SO4- and FeCl3-modified AA adsorbents was 4.98 mg/g, which is 3.4 times higher compared with that of normal AA. The results showed that the surface area of AA increased when modified with H2SO4. AA modified with FeCl3 enhanced fluoride adsorption ability through ion-exchange between chlorine ions and fluoride ions. The fluoride adsorption properties of AA modified with both H2SO4 and FeCl3 were consistent with the Langmuir model. The fluoride adsorption kinetics of the adsorbents were well described by the pseudo-second-order kinetic model.

Biosorption of Pb(II) Ions by Klebsiella sp. 3S1 Isolated from a Wastewater Treatment Plant: Kinetics and Mechanisms Studies

PubMed Central

Muñoz, Antonio Jesús; Espínola, Francisco; Moya, Manuel; Ruiz, Encarnación

2015-01-01

Lead biosorption by Klebsiella sp. 3S1 isolated from a wastewater treatment plant was investigated through a Rotatable Central Composite Experimental Design. The optimisation study indicated the following optimal values of operating variables: 0.4 g/L of biosorbent dosage, pH 5, and 34°C. According to the results of the kinetic studies, the biosorption process can be described by a two-step process, one rapid, almost instantaneous, and one slower, both contributing significantly to the overall biosorption; the model that best fits the experimental results was pseudo-second order. The equilibrium studies showed a maximum lead uptake value of 140.19 mg/g according to the Langmuir model. The mechanism study revealed that lead ions were bioaccumulated into the cytoplasm and adsorbed on the cell surface. The bacterium  Klebsiella sp. 3S1 has a good potential in the bioremoval of lead in an inexpensive and effective process. PMID:26504824

Iron Oxide Impregnated Morus alba L. Fruit Peel for Biosorption of Co(II): Biosorption Properties and Mechanism

PubMed Central

Koduru, Janardhan Reddy; Chang, Yoon-Young; Yang, Jae-Kyu; Kim, Im-Soon

2013-01-01

Biosorption is an ecofriendly wastewater treatment technique with high efficiency and low operating cost involving simple process for the removal of heavy metal ions from aqueous solution. In the present investigation, Morus alba L. fruit peel powder (MAFP) and iron oxide impregnated Morus alba L. fruit peel powder (IO-MAFP) were prepared and used for treating Co(II) contaminated aqueous solutions. Further the materials were characterized by using FTIR and SEM-EDX analysis. From FT-IR analysis it was found that hydroxyl, methoxy, and carbonyl groups are responsible for Co(II) biosorption. The kinetic data obtained for both biosorbents was well fitted with pseudo-second-order kinetic model. The equilibrium data was in tune with the Langmuir and Freundlich isotherm models. The thermodynamic studies were also carried and it was observed that sorption process was endothermic at 298–328 K. These studies demonstrated that both biosorbents were promising, efficient, economic, and biodegradable sorbents. PMID:24324384

Synthesis and application of Amberlite xad-4 functionalized with alizarin red-s for preconcentration and adsorption of rhodium (III)

PubMed Central

2012-01-01

A new chelating resin was prepared by coupling Amberlite XAD-4 with alizarin red-s through an azo spacer, characterized by infra-red spectroscopy and thermal analysis and studied for Rh(III) preconcentration using inductively coupled plasma atomic emission spectroscopy (ICP-AES) for rhodium monitoring in the environment. The optimum pH for sorption of the metal ion was 6.5. The sorption capacity was found 2.1 mg/g of resin for Rh(III). A recovery of 88% was obtained for the metal ion with 1.5 M HCl as eluting agent. Kinetic adsorption data were analyzed by adsorption and desorption times of Rh(III) on modified resin. Scat chard analysis revealed that the homogeneous binding sites were formed in the polymers. The linear regression equation was Q/C = –1.3169Q + 27.222 (R2 = 0.9239), for Rh were formed in the SPE sorbent,Kd and Qmax for the affinity binding sites were calculated to be 0.76 μmol/mL and 20.67 μmol/g, respectively. The equilibrium data and parameters of Rh(III) adsorption on modified resin were analyzed by Langmuir, Freundlich, Temkin and Redlich–Peterson models. The experimental adsorption isotherm was in good concordance with Langmuir and Freundlich models (R2 > 0.998) and based on the Langmuir isotherm the maximum amount of adsorption (qmax) was 4.842 mg/g. The method was applied for rhodium ions determination in environmental samples. with high recovery (>80%). PMID:23369526

Synthesis and application of Amberlite xad-4 functionalized with alizarin red-s for preconcentration and adsorption of rhodium (III).

PubMed

Sid Kalal, Hossein; Panahi, Homayon Ahmad; Hoveidi, Hassan; Taghiof, Mohammad; Menderjani, Mahnaz Taheri

2012-09-18

A new chelating resin was prepared by coupling Amberlite XAD-4 with alizarin red-s through an azo spacer, characterized by infra-red spectroscopy and thermal analysis and studied for Rh(III) preconcentration using inductively coupled plasma atomic emission spectroscopy (ICP-AES) for rhodium monitoring in the environment. The optimum pH for sorption of the metal ion was 6.5. The sorption capacity was found 2.1 mg/g of resin for Rh(III). A recovery of 88% was obtained for the metal ion with 1.5 M HCl as eluting agent. Kinetic adsorption data were analyzed by adsorption and desorption times of Rh(III) on modified resin. Scat chard analysis revealed that the homogeneous binding sites were formed in the polymers. The linear regression equation was Q/C = -1.3169Q + 27.222 (R2 = 0.9239), for Rh were formed in the SPE sorbent,Kd and Qmax for the affinity binding sites were calculated to be 0.76 μmol/mL and 20.67 μmol/g, respectively. The equilibrium data and parameters of Rh(III) adsorption on modified resin were analyzed by Langmuir, Freundlich, Temkin and Redlich-Peterson models. The experimental adsorption isotherm was in good concordance with Langmuir and Freundlich models (R2 > 0.998) and based on the Langmuir isotherm the maximum amount of adsorption (qmax) was 4.842 mg/g. The method was applied for rhodium ions determination in environmental samples. with high recovery (>80%).

Biosorption of trivalent chromium by free and immobilized blue green algae: kinetics and equilibrium studies.

PubMed

Shashirekha, V; Sridharan, M R; Swamy, Mahadeswara

2008-03-01

The process of biosorption of trivalent chromium (Cr(3+)) by live culture of Spirulina platensis and the sorption potential by the dried biomass, in both free and immobilized states have been investigated for a simulated chrome liquor in the concentration range of 100-4500 ppm. Both live and dried biomass were very good biosorbents as they could remove high amounts of chromium from tannery wastewater. Polyurethane foam and sodium alginate were used as immobilizing agents and their performances compared. Biosorption kinetic data on Cr(3+) sorption onto dried biomass were analyzed using pseudo-first-and pseudo-second-order kinetic models in batch column experiments. The second-order equation was more appropriate to predict the rate of biosorption. Subsequently, the effects of height of packing & diameter of the column, concentration of blue-green algae (BGA) in varying amounts of sodium alginate, chromium concentration were studied. The results fit into both Langmuir & Freundlich isotherm models with very high regression coefficients. Furthermore, equilibrium studies using retan chrome liquor (RCL), with a chromium concentration of 1660 ppm, obtained from a tannery also showed promising results. In general, our studies indicate the efficacy of the algal species in removal of chromium from tannery wastewater.

Cadmium-109 Radioisotope Adsorption onto Polypyrrole Coated Sawdust of Dryobalanops aromatic: Kinetics and Adsorption Isotherms Modelling

PubMed Central

Olatunji, Michael Adekunle; Khandaker, Mayeen Uddin; Amin, Yusoff Mohd; Mahmud, Habibun Nabi Muhammad Ekramul

2016-01-01

A radiotracer study was conducted to investigate the removal characteristics of cadmium (109Cd) from aqueous solution by polypyrrole/ sawdust composite. Several factors such as solution pH, sorbent dosage, initial concentration, contact time, temperature and interfering metal ions were found to have influence on the adsorption process. The kinetics of adsorption was relatively fast, reaching equilibrium within 3 hours. A lowering of the solution pH reduced the removal efficiency from 99.3 to ~ 46.7% and an ambient temperature of 25°C was found to be optimum for maximum adsorption. The presence of sodium and potassium ions inhibited 109Cd removal from its aqueous solution. The experimental data for 109Cd adsorption showed a very good agreement with the Langmuir isotherm and a pseudo-first order kinetic model. The surface condition of the adsorbent before and after cadmium loading was investigated using BET, FESEM and FTIR. Considering the low cost of the precursor’s materials and the toxicity of 109Cd radioactive metal, polypyrrole synthesized on the sawdust of Dryobalanops aromatic could be used as an efficient adsorbent for the removal of 109Cd radioisotope from radionuclide-containing effluents. PMID:27706232

Comparative studies on adsorptive removal of heavy metal ions by biosorbent, bio-char and activated carbon obtained from low cost agro-residue.

PubMed

Kırbıyık, Çisem; Pütün, Ayşe Eren; Pütün, Ersan

2016-01-01

In this study, Fe(III) and Cr(III) metal ion adsorption processes were carried out with three adsorbents in batch experiments and their adsorption performance was compared. These adsorbents were sesame stalk without pretreatment, bio-char derived from thermal decomposition of biomass, and activated carbon which was obtained from chemical activation of biomass. Scanning electron microscopy and Fourier transform-infrared techniques were used for characterization of adsorbents. The optimum conditions for the adsorption process were obtained by observing the influences of solution pH, adsorbent dosage, initial solution concentration, contact time and temperature. The optimum adsorption efficiencies were determined at pH 2.8 and pH 4.0 for Fe(III) and Cr(III) metal ion solutions, respectively. The experimental data were modelled by different isotherm models and the equilibriums were well described by the Langmuir adsorption isotherm model. The pseudo-first-order, pseudo-second-order kinetic, intra-particle diffusion and Elovich models were applied to analyze the kinetic data and to evaluate rate constants. The pseudo-second-order kinetic model gave a better fit than the others. The thermodynamic parameters, such as Gibbs free energy change ΔG°, standard enthalpy change ΔH° and standard entropy change ΔS° were evaluated. The thermodynamic study showed the adsorption was a spontaneous endothermic process.