40 CFR 467.34 - New source performance standards.

Code of Federal Regulations, 2012 CFR

2012-07-01

... of 7.0 to 10.0 at all times. Subpart C Solution Heat Treatment Contact Cooling Water Pollutant or... the pH shall be within the range of 6.0 to 10.0 at all times. Subpart C Press Heat Treatment Contact...

40 CFR 467.34 - New source performance standards.

Code of Federal Regulations, 2014 CFR

2014-07-01

... of 7.0 to 10.0 at all times. Subpart C Solution Heat Treatment Contact Cooling Water Pollutant or... the pH shall be within the range of 6.0 to 10.0 at all times. Subpart C Press Heat Treatment Contact...

Reduction of the viscosity of solutions viscosified with xanthan gum polymers

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

Bridges, K.L.; Kalinski, K.L.

1991-10-08

This patent describes a process for reducing the viscosity of a drilling fluid containing Xanthan gum polymer solution. It comprises: contacting the drilling fluid with hydrogen peroxide and adjusting the pH of the solution to a level of at least about between 8 and 10.

Comparative study of antibacterial and antifungal effects of rigid gas permeable contact lens disinfecting solutions.

PubMed

Kuzman, Tomislav; Kutija, Marija Barisić; Kordić, Rajko; Popović-Sui, Smiljka; Jandroković, Sonja; Skegro, Ivan; Pokupec, Rajko

2013-04-01

The aim of this study was to compare antimicrobial efficacy of rigid contact lens disinfecting solutions. We tested five commercially available solutions: Unique pH (Alcon Laboratories), Boston Advance (Polymer Technology Corp.), Nitilens Conditioner GP (Avizor), Total Care (AMO), Boston Simplus (Bausch&Lomb). Their efficacy to disinfect saline solution experimentally contaminated with American Type Culture Collection (ATCC): Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), Candida albicans (ATCC 90028) and Staphylococcus epidermidis (isolated from our laboratory) was tested. All tested solutions reduced concentrations of bacteria and fungi below 1000 CFU/mL (Colony forming unit; reduction by 3 log and 1 log, respectively) after the 8 hours period. Overall, all contact lens care solutions showed good disinfecting activity against tested bacteria and fungi, with more variation in their antifungal than in antibacterial efficacy. Results of our study might be valuable when selecting appropriate solutions for non-compliant contact lens wearers.

Removal of inorganic mercury from aquatic environments by multi-walled carbon nanotubes.

PubMed

Yaghmaeian, Kamyar; Khosravi Mashizi, Reza; Nasseri, Simin; Mahvi, Amir Hossein; Alimohammadi, Mahmood; Nazmara, Shahrokh

2015-01-01

Mercury is considered as a toxic heavy metal in aquatic environments due to accumulation in bodies of living organisms. Exposure to mercury may lead to different toxic effects in humans including damages to kidneys and nervous system. Multi-walled carbon nanotubes (MWCNTs) were selected as sorbent to remove mercury from aqueous solution using batch technique. ICP instrument was used to determine the amount of mercury in solution. Moreover, pH, contact time and initial concentration of mercury were studied to determine the influence of these parameters on the adsorption conditions. Results indicate that the adsorption strongly depended on pH and the best pH for adsorption is about 7. The rate of adsorption process initially was rapid but it was gradually reduced with increasing of contact time and reached the equilibrium after 120 min. In addition, more than 85 % of initial concentration of 0.1 mg/l was removed at 0.5 g/l concentration of sorbent and contact time of 120 min. Meanwhile, the adsorption process followed the pseudo second-order model and the adsorption isotherms could be described by both the Freundlich and the Langmuir models. This study showed that MWCNTs can effectively remove inorganic mercury from aqueous solutions as adsorbent.

Leaching characteristics of selected South African fly ashes: Effect of pH on the release of major and trace species

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

Gitari, W.M.; Fatoba, O.O.; Petrik, L.F.

2009-07-01

Fly ash samples from two South African coal-fired power stations were subjected to different leaching tests under alkaline and acidic conditions in an attempt to assess the effect of pH on the leachability of species from the fly ashes and also assess the potential impact of the fly ashes disposal on groundwater and the receiving environment. To achieve this, German Standard leaching (DIN-S4) and Acid Neutralization Capacity (ANC) tests were employed. Ca, Mg, Na, K and SO{sub 4} were significantly leached into solution under the two leaching conditions with the total amounts in ANC leachates higher than that of DIN-S4.more » This indicates that a large fraction of the soluble salts in unweathered fly ash are easily leached. These species represents the fraction that can be flushed off initially from the surface of ash particles on contacting the ash with water. The amounts of toxic trace elements such as As, Se, Cd, Cr and Pb leached out of the fly ashes when in contact with de-mineralized water (DIN-S4 test) were low and below the Target Water Quality Range (TWQR) of South Africa. This is explained by their low concentrations in the fly ashes and their solubility dependence on the pH of the leaching solution. However the amounts of some minor elements such as B, Mn, Fe, As and Se leached out at lower pH ranging between 10 to 4 (ANC test) were slightly higher than the TWQR, an indication that the pH of the leaching solution plays a significant role on the leaching of species in fly ash. The high concentrations of the toxic elements released from the fly ashes at lower pH gives an indication that the disposal of the fly ash could have adverse effects on the receiving environment if the pH of the solution contacting the ashes is not properly monitored.« less

Efficiency Improvement of Some Agricultural Residue Modified Materials for Textile Dyes Absorption

NASA Astrophysics Data System (ADS)

Boonsong, P.; Paksamut, J.

2018-03-01

In this work, the adsorption efficiency was investigated of some agricultural residue modified materials as natural bio-adsorbents which were rice straw (Oryza sativa L.) and pineapple leaves (Ananas comosus (L.) Merr.) for the removal of textile dyes. Reactive dyes were used in this research. The improvement procedure of agricultural residue materials properties were alkali-acid modification with sodium hydroxide solution and hydrochloric acid solution. Adsorption performance has been investigated using batch experiments. Investigated adsorption factors consisted of adsorbent dose, contact time, adsorbent materials and pH of solution. The results were found that rice straw had higher adsorption capacity than pineapple leaves. The increasing of adsorption capacity depends on adsorbent dose and contact time. Moreover, the optimum pH for dye adsorption was acidic range because lowering pH increased the positively charges on the adsorbent surface which could be attacked by negatively charge of acid dyes. The agricultural residue modified materials had significant dye removal efficiency which these adsorbents could be used for the treatment of textile effluent in industries.

Effect of Gold on the Corrosion Behavior of an Electroless Nickel/Immersion Gold Surface Finish

NASA Astrophysics Data System (ADS)

Bui, Q. V.; Nam, N. D.; Yoon, J. W.; Choi, D. H.; Kar, A.; Kim, J. G.; Jung, S. B.

2011-09-01

The performance of surface finishes as a function of the pH of the utilized plating solution was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests in 3.5 wt.% NaCl solution. In addition, the surface finishes were examined by x-ray diffraction (XRD), and the contact angle of the liquid/solid interface was recorded. NiP films on copper substrates with gold coatings exhibited their highest coating performance at pH 5. This was attributed to the films having the highest protective efficiency and charge transfer resistance, lowest porosity value, and highest contact angle among those examined as a result of the strongly preferred Au(111) orientation and the improved surface wettability.

PROCESSES OF RECLAIMING URANIUM FROM SOLUTIONS

DOEpatents

Zumwalt, L.R.

1959-02-10

A process is described for reclaiming residual enriched uranium from calutron wash solutions containing Fe, Cr, Cu, Ni, and Mn as impurities. The solution is adjusted to a pH of between 2 and 4 and is contacted with a metallic reducing agent, such as iron or zinc, in order to reduce the copper to metal and thereby remove it from the solution. At the same time the uranium present is reduced to the uranous state The solution is then contacted with a precipitate of zinc hydroxide or barium carbonate in order to precipitate and carry uranium, iron, and chromium away from the nickel and manganese ions in the solution. The uranium is then recovered fronm this precipitate.

Kinetic, isotherm and thermodynamic studies of amaranth dye biosorption from aqueous solution onto water hyacinth leaves.

PubMed

Guerrero-Coronilla, Imelda; Morales-Barrera, Liliana; Cristiani-Urbina, Eliseo

2015-04-01

The present study explored the kinetics, equilibrium and thermodynamics of amaranth (acid red 27) anionic dye (AD) biosorption to water hyacinth leaves (LEC). The effect of LEC particle size, contact time, solution pH, initial AD concentration and temperature on AD biosorption was studied in batch experiments. AD biosorption increased with rising contact time and initial AD concentration, and with decreasing LEC particle size and solution pH. Pseudo-second-order chemical reaction kinetics provided the best correlation for the experimental data. Isotherm studies showed that the biosorption of AD onto LEC closely follows the Langmuir isotherm, with a maximum biosorption capacity of about 70 mg g(-1). The thermodynamic parameters confirm that AD biosorption by LEC is non-spontaneous and endothermic in nature. Results indicate that LEC is a strong biosorbent capable of effective detoxification of AD-laden wastewaters. Copyright © 2015 Elsevier Ltd. All rights reserved.

Adsorption of Crystal Violet Dye Using Zeolite A Synthesized From Coal Fly Ash

NASA Astrophysics Data System (ADS)

Jumaeri; Kusumastuti, E.; Santosa, S. J.; Sutarno

2017-02-01

Adsorption of Crystal Violet (CV) dye using zeolite A synthesized from coal fly ash (ZA) has been done. Effect of pH, contact time, and the initial concentration of dye adsorption was studied in this adsorption. Model experimental of adsorption isotherms and adsorption kinetics were also studied. The adsorption is done in a batch reactor at room temperature. A total of 0.01 g of zeolite A was added to the Erlenmeyer flask 50 mL containing 20 mL of the dye solution of Crystal Violet in a variety of conditions of pH, contact time and initial concentration. Furthermore, Erlenmeyer flask and its contents were shaken using an orbital shaker at a speed of 200 rpm. After a specified period of adsorption, the solution was centrifuged for 2 minutes so that the solids separated from the solution. The concentration of the dye after adsorption determined using Genesis-20 Spectrophotometer. The results showed that the Zeolite A synthesized from coal fly ash could be used as an effective adsorbent for Crystal Violet dye. The optimum adsorption occurs at pH 6, and contact time 45 minutes. At the initial concentration of 2 to 6 mg/L, adsorption is reduced from 79 to 62.8%. Crystal Violet dye adsorption in zeolite A fulfilled kinetic model of pseudo-order 2 and model of Freundlich adsorption isotherm.

Synthesis and Characterization of Hydrophobic Silica Thin Layer Derived from Methyltrimethoxysilane (MTMS)

NASA Astrophysics Data System (ADS)

Darmawan, Adi; Utari, Riyadini; Eka Saputra, Riza; Suhartana; Astuti, Yayuk

2018-01-01

This study investigated the synthesis and characterization of MTMS hydrophobic silica prepared by sol-gel method. In principle, silica xerogels and silica thin layer were obtained by reacting MTMS in ethanol solvent in some pH variations. The MTMS solution was used to modify the surface of the ceramic plate by dipcoating method to further be calcined at two different temperatures of 350°C and 500°C. The silica xerogels were analysed by FTIR, TGA-DSC and GSA to determine functional group characteristics, thermal properties and pore morphology respectively. Meanwhile, the silica thin layers were analysed their hydrophobic properties using water contact angle measurement and surface roughness determination using SEM. The results showed that the higher the pH used in the MTMS solution, the higher the resulting contact angle. The highest contact angle was obtained at pH 8.12 which reached 94.7° and 79.5° for silica thin layer calcined at 350°C and 500°C, respectively. The TGA results indicated that the methyl group survived up to 400°C and disappeared at 500°C which had implications on silica thin layer hydrophobic nature. GSA result exhibited that the silica xerogel had a close structure with a very low pore volume. While the SEM-EDX results displayed that the silica thin layer prepared at acidic pH had smoother surface morphology and became rough when prepared at an alkaline pH.

Fluorescent solute-partitioning characterization of layered soft contact lenses.

PubMed

Dursch, T J; Liu, D E; Oh, Y; Radke, C J

2015-03-01

Partitioning of aqueous packaging, wetting, and care-solution agents into and out of soft contact lenses (SCLs) is important for improving wear comfort and also for characterizing lens physico-chemical properties. We illustrate both features of partitioning by application of fluorescent-solute partitioning into DAILIES TOTAL1® (delefilcon A) water-gradient SCLs, which exhibit a layered structure of a silicone-hydrogel (SiHy) core sandwiched between thin surface-gel layers. Two-photon fluorescence confocal laser-scanning microscopy and attenuated total-reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) characterize the lens and assess uptake profiles of six prototypical fluorescent solutes. Comparison of solute uptake in a SiHy-core prototype lens (i.e., O2OPTIX(TM)) validates the core SiHy structure of DAILIESTOTAL1®. To establish surface-layer charge, partition coefficients and water contents are obtained for aqueous pH values of 4 and 7.4. Solute fluorescence-intensity profiles clearly confirm a layered structure for the DAILIES TOTAL1® lenses. In all cases, aqueous solute partition coefficients are greater in the surface layers than in the SiHy core, signifying higher water in the surface gels. ATR-FTIR confirms surface-layer mass water contents of 82±3%. Water uptake and hydrophilic-solute uptake at pH 4 compared with that at pH 7.4 reveal that the surface-gel layers are anionic at physiologic pH 7.4, whereas both the SiHy core and O2OPTIX™ (lotrafilcon B) are nonionic. We successfully confirm the layered structure of DAILIES TOTAL1®, consisting of an 80-μm-thick SiHy core surrounded by 10-μm-thick polyelectrolyte surface-gel layers of significantly greater water content and aqueous solute uptake compared with the core. Accordingly, fluorescent-solute partitioning in SCLs provides information on gel structure and composition, in addition to quantifying uptake and release amounts and rates. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Design and characterization of a plastic optical fiber pH sensor

NASA Astrophysics Data System (ADS)

Ferreira, Licínio; Simões, Pedro; Carvalho, Rui S.; Lopes, Paulo; Ferreira, Mário

2013-11-01

In this paper are present the design and characterization of a pH sensor using plastic optical fiber (POF) technology and a material produced by the sol-gel process with TEOS (tetraethyl orthosilicate) to immobilize universal indicator of pH (comprised of Thymol Blue, Methyl Red, Bromothymol Blue and Phenolphthalein) inside the silica matrix. This matrix is positioned between two extensions of plastic optical fiber tightly positioned at each side with both fibers aligned and sharing a common optical axis. This set will work as a pH sensor since the matrix embedded with indicator and in the presence of a solution (basic or acid solution) will change the optical transmittance properties. The optical source is a superluminescent white LED and the receiver is a photodiode having a good and linear responsivity in the visible spectrum. This pH sensitive matrix has large pores which allow the diffusion of the surrounding fluid molecules into the matrix and thus the close contact of these to the indicator molecules. This contact causes the change of color of the whole matrix allowing proper colorimetric detection by the photodiode. This variation of color associated with the detector wavelength linear response is the base of operation of the proposed device. This pH sensor presents many advantages over the standard and commercial pH meters namely, lightweight, portability and a low cost.

SEPARATION PROCESS FOR THORIUM SALTS

DOEpatents

Bridger, G.L.; Whatley, M.E.; Shaw, K.G.

1957-12-01

A process is described for the separation of uranium, thorium, and rare earths extracted from monazite by digesting with sulfuric acid. By carefully increasing the pH of the solution, stepwise, over the range 0.8 to 5.5, a series of selective precipitations will be achieved, with the thorium values coming out at lower pH, the rare earths at intermediate pH and the uranium last. Some mixed precipitates will be obtained, and these may be treated by dissolving in HNO/sub 3/ and contacting with dibutyl phosphate, whereby thorium or uranium are taken up by the organic phase while the rare earths preferentially remain in the aqueous solution.

Proton mediated control of biochemical reactions with bioelectronic pH modulation

NASA Astrophysics Data System (ADS)

Deng, Yingxin; Miyake, Takeo; Keene, Scott; Josberger, Erik E.; Rolandi, Marco

2016-04-01

In Nature, protons (H+) can mediate metabolic process through enzymatic reactions. Examples include glucose oxidation with glucose dehydrogenase to regulate blood glucose level, alcohol dissolution into carboxylic acid through alcohol dehydrogenase, and voltage-regulated H+ channels activating bioluminescence in firefly and jellyfish. Artificial devices that control H+ currents and H+ concentration (pH) are able to actively influence biochemical processes. Here, we demonstrate a biotransducer that monitors and actively regulates pH-responsive enzymatic reactions by monitoring and controlling the flow of H+ between PdHx contacts and solution. The present transducer records bistable pH modulation from an “enzymatic flip-flop” circuit that comprises glucose dehydrogenase and alcohol dehydrogenase. The transducer also controls bioluminescence from firefly luciferase by affecting solution pH.

Conversion of depleted uranium hexafluoride to a solid uranium compound

DOEpatents

Rothman, Alan B.; Graczyk, Donald G.; Essling, Alice M.; Horwitz, E. Philip

2001-01-01

A process for converting UF.sub.6 to a solid uranium compound such as UO.sub.2 and CaF. The UF.sub.6 vapor form is contacted with an aqueous solution of NH.sub.4 OH at a pH greater than 7 to precipitate at least some solid uranium values as a solid leaving an aqueous solution containing NH.sub.4 OH and NH.sub.4 F and remaining uranium values. The solid uranium values are separated from the aqueous solution of NH.sub.4 OH and NH.sub.4 F and remaining uranium values which is then diluted with additional water precipitating more uranium values as a solid leaving trace quantities of uranium in a dilute aqueous solution. The dilute aqueous solution is contacted with an ion-exchange resin to remove substantially all the uranium values from the dilute aqueous solution. The dilute solution being contacted with Ca(OH).sub.2 to precipitate CaF.sub.2 leaving dilute NH.sub.4 OH.

Removal of trivalent chromium from aqueous solution using aluminum oxide hydroxide.

PubMed

Bedemo, Agaje; Chandravanshi, Bhagwan Singh; Zewge, Feleke

2016-01-01

Water is second most essential for human being. Contamination of water makes it unsuitable for human consumption. Chromium ion is released to water bodies from various industries having high toxicity which affects the biota life in these waters. In this study aluminum oxide hydroxide was tested for its efficiency to remove trivalent chromium from aqueous solutions through batch mode experiments. Chromium concentrations in aqueous solutions and tannery waste water before and after adsorption experiments were determined using flame atomic absorption spectrometry. The effects of pH, contact time, initial concentration and adsorbent dosage on the adsorption of Cr(III) were studied. The study revealed that more than 99 % removal of Cr(III) was achieved over wide range of initial pH (3-10). The optimum conditions for the removal of Cr(III) were found to be at pH 4-6 with 40 g/L adsorbent dose at 60 min of contact time. The adsorption capacity was assessed using Langmuir and Freundlich isotherms. The equilibrium data at varying adsorbent dose obeyed the two isotherms. The adsorbent was found to be efficient for the removal of Cr(III) from tannery waste effluent.

From micelle supramolecular assemblies in selective solvents to isoporous membranes.

PubMed

Nunes, Suzana P; Karunakaran, Madhavan; Pradeep, Neelakanda; Behzad, Ali Reza; Hooghan, Bobby; Sougrat, Rachid; He, Haoze; Peinemann, Klaus-Viktor

2011-08-16

The supramolecular assembly of PS-b-P4VP copolymer micelles induced by selective solvent mixtures was used to manufacture isoporous membranes. Micelle order in solution was confirmed by cryo-scanning electron microscopy in casting solutions, leading to ordered pore morphology. When dioxane, a solvent that interacts poorly with the micelle corona, was added to the solution, polymer-polymer segment contact was preferential, increasing the intermicelle contact. Immersion in water gave rise to asymmetric porous membranes with exceptional pore uniformity and high porosity. The introduction of a small number of carbon nanotubes to the casting solution improved the membrane stability and the reversibility of the gate response in the presence of different pH values.

Boron removal from aqueous solution by direct contact membrane distillation.

PubMed

Hou, Deyin; Wang, Jun; Sun, Xiangcheng; Luan, Zhaokun; Zhao, Changwei; Ren, Xiaojing

2010-05-15

The removal of boron from aqueous solution by direct contact membrane distillation (DCMD) was studied with self-prepared polyvinylidene fluoride (PVDF) hollow fiber membranes in the present work. The effect of pH, boron concentration, temperature and salt concentration of the feed solution on the boron rejection was investigated. The experimental results indicated that boron rejection was less dependent on the feed pH and salt concentration. DCMD process had high boron removal efficiency (>99.8%) and the permeate boron was below the maximum permissible level even at feed concentration as high as 750 mg/L. Although the permeate flux was enhanced exponentially with the feed temperature increasing, the influence of feed temperature on the boron rejection could be neglected. Finally, the natural groundwater sample containing 12.7 mg/L of boron was treated by DCMD process. The permeate boron kept below 20 microg/L whether the feed was acidified or not, but pre-acidification was helpful to maintain the permeate flux stability. All the experimental results indicated that DCMD could be efficiently used for boron removal from aqueous solution. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Chromium(VI) Removal from Aqueous Solution by Magnetite Coated by a Polymeric Ionic Liquid-Based Adsorbent

PubMed Central

Ferreira, Thania Alexandra; Rodriguez, Jose Antonio; Paez-Hernandez, María Elena; Guevara-Lara, Alfredo; Barrado, Enrique; Hernandez, Prisciliano

2017-01-01

An evaluation of the chromium(VI) adsorption capacity of four magnetite sorbents coated with a polymer phase containing polymethacrylic acid or polyallyl-3-methylimidazolium is presented. Factors that influence the chromium(VI) removal such as solution pH and contact time were investigated in batch experiments and in stirred tank reactor mode. Affinity and rate constants increased with the molar ratio of the imidazolium. The highest adsorption was obtained at pH 2.0 due to the contribution of electrostatic interactions. PMID:28772865

RECOVERY OF URANIUM FROM CARBONATE LEACH LIQUORS

DOEpatents

Wilson, H.F.

1958-07-01

An improved process is described for the recovery of uranium from vanadifrous ores. In the prior art such ores have been digested with alkali carbonate solutions at a pH of less than 10 and then contacted with a strong base anion exchange resin to separate uranium from vanadium. It has been found that if the exchamge resin feed solution has its pH adjusted to the range 10.8 to 11.8, that vanadium adsorption on the resin is markedly decreased and the separation of uranium from the vanadium is thereby improved.

Adsorption of Cd(II) Metal Ion on Adsorbent beads from Biomass Saccharomycess cereviceae - Chitosan

NASA Astrophysics Data System (ADS)

Hasri; Mudasir

2018-01-01

The adsorbent beads that was preparation from Saccharomycess cereviceae culture strain FN CC 3012 and shrimp shells waste and its application for adsorption of Cd (II) metal ion has been studied. The study start with combination of Saccharomycess cereviceae biomass to chitosan (Sc-Chi), contact time, pH of solution and initial concentration of cations. Total Cd(II) metal ion adsorbed was calculated from the difference of metal ion concentration before and after adsorption by AAS. The results showed that optimum condition for adsorption of Cd(II) ions by Sc-Chi beads was achieved with solution pH of 4, contact time of 60 minutes and initial concentration adsorption 100mg/L. The hydroxyl (-OH) and amino (-NH2) functional groups were believed to be responsible for the adsorption of Cd(II) ions.

A study of Reactive Red 198 adsorption on iron filings from aqueous solutions.

PubMed

Azhdarpoor, Abooalfazl; Nikmanesh, Roya; Khademi, Fahime

2014-01-01

In recent years, reactive dyes have been widely used in textile industries with particular efficiency. They dyes are often toxic, carcinogenic and mutagenic. Improper treatment and non-scientific disposal of dyed wastewater from these industries into water sources has created many environmental problems and concerns around the world. The purpose of the present study is to investigate the efficiency of iron filings in adsorption of Reactive Red 198 from aqueous solutions. This study was conducted using an experimental method at the laboratory scale. In this study, the effects of operating parameters such as pH (1-11), initial dye concentration (40-400 mg/L), contact time (5-120 min) and iron dose (0.1-1 g) with a mesh of<100 were studied. Dye concentration was determined using a spectrophotometer at a wavelength of 520 nm. The results indicated that maximum adsorption capacity of the dye in question was obtained at pH 3, contact time of 60 min and adsorbent dose of 1 g. At initial dye concentration of 100 and 200 mg/L, by increasing the dose of waste iron from 0.1 to 1 g, the removal percentage increased from approximately 76.89% to 97.28% and from 22.64% to 68.03%, respectively. At pH 3, contact time of 5 min and constant waste iron dose of 0.8 g, the dye removal efficiency was 85.34%. By increasing the contact time to 120 min, the removal efficiency increased to 99.2%. Welding iron waste as an inexpensive and available adsorbent has an optimum ability for adsorption of Reactive Red 198 from aqueous solutions.

Removal of ammonium from aqueous solutions with volcanic tuff.

PubMed

Marañón, E; Ulmanu, M; Fernández, Y; Anger, I; Castrillón, L

2006-10-11

This paper presents kinetic and equilibrium data concerning ammonium ion uptake from aqueous solutions using Romanian volcanic tuff. The influence of contact time, pH, ammonium concentration, presence of other cations and anion species is discussed. Equilibrium isotherms adequately fit the Langmuir and Freundlich models. The results showed a contact time of 3h to be sufficient to reach equilibrium and pH of 7 to be the optimum value. Adsorption capacities of 19 mg NH(4)(+)/g were obtained in multicomponent solutions (containing NH(4)(+), Zn(2+), Cd(2+), Ca(2+), Na(2+)). The presence of Zn and Cd at low concentrations did not decrease the ammonium adsorption capacity. Comparison of Romanian volcanic tuff with synthetic zeolites used for ammonium removal (5A, 13X and ZSM-5) was carried out. The removal efficiciency of ammonium by volcanic tuff were similar to those of zeolites 5A and 13X at low initial ammonium concentration, and much higher than those of zeolite ZSM-5.

Statistical analysis and isotherm study of uranium biosorption by Padina sp. algae biomass.

PubMed

Khani, Mohammad Hassan

2011-06-01

The application of response surface methodology is presented for optimizing the removal of U ions from aqueous solutions using Padina sp., a brown marine algal biomass. Box-Wilson central composite design was employed to assess individual and interactive effects of the four main parameters (pH and initial uranium concentration in solutions, contact time and temperature) on uranium uptake. Response surface analysis showed that the data were adequately fitted to second-order polynomial model. Analysis of variance showed a high coefficient of determination value (R (2)=0.9746) and satisfactory second-order regression model was derived. The optimum pH and initial uranium concentration in solutions, contact time and temperature were found to be 4.07, 778.48 mg/l, 74.31 min, and 37.47°C, respectively. Maximized uranium uptake was predicted and experimentally validated. The equilibrium data for biosorption of U onto the Padina sp. were well represented by the Langmuir isotherm, giving maximum monolayer adsorption capacity as high as 376.73 mg/g.

Microwave-Assisted Synthesis of Goethite Nanoparticles Used for Removal of Cr(VI) from Aqueous Solution

PubMed Central

Kynicky, Jindrich; Adam, Vojtech

2017-01-01

The microwave-assisted synthesis of goethite nanoparticles has been studied. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential thermal analysis (DTA) and Brunauer–Emmett–Teller (BET) method. Goethite rod-like nanoparticles have been successfully synthesized in 10 min of microwave treating at 100 °C. Particle size is in the range from 30 to 60 nm in width and from 200 to 350 nm in length. BET analysis indicated that the surface area of the product is 158.31 m2g−1. The feasibility of Cr(VI) removal fromaqueous solution depends on the pH of the solution and contact time. The maximum adsorptionis reached at pH 4.0 and 540 min of contact time. The adsorption kinetics was analyzedby the pseudo-first- and second-order models and the results reveal that the adsorption process obeys the pseudo-second-order model. The adsorption data were fitted well with the Langmuir adsorption isotherm. PMID:28773142

SCM Paste Samples Exposed To Aggressive Solutions. Cementitious Barriers Partnership

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

Foster, T.

This report summarizes experimental work performed by SIMCO Technologies Inc. (SIMCO) as part of the Cementitious Barriers Partnership (CBP) project. The test series followed an experimental program dedicated to the study of ordinary Portland cement (OPC) hydrated cement pastes exposed to aggressive solutions. In the present study, the scope is extended to hydrated cement pastes incorporating supplementary cementitious materials (SCM) such as fly ash and ground granulated blast furnace slag (GGBFS). Also, the range of aggressive contact solutions was expanded. The experimental program aimed at testing aggressive contact solutions that more closely mimic the chemical composition of saltstone pore solution.more » Five different solutions, some of which incorporated high levels of carbonate and nitrate, were placed in contact with four different hydrated cement paste mixes. In all solutions, 150 mmol/L of SO 4 2– (14 400 ppm) were present. The solutions included different pH conditions and different sodium content. Two paste mixes were equivalent to Vault 1/4 and Vault 2 concrete mixes used at SRS in storage structures. Two additional paste mixes, cast at the same water-to-cement ratio and using the same cements but without SCMs, were also tested. The damage evolution in samples was monitored using ultrasonic pulse velocity (UPV) and mass measurements. After three and twelve months of exposure conditions, samples were taken out of solution containers and analyzed to perform migration tests and porosity measurements. Globally, results were in line with the previous study and confirmed that high pH may limit the formation of some deleterious phases like gypsum. In this case, ettringite may form but is not necessarily associated with damage. However, the high concentration of sodium may be associated with the formation of an AFm-like mineral called U-phase. The most significant evidences of damage were all associated with the Vault 2 paste analog. This material proved very sensitive to high pH. All measurement techniques used to monitor and evaluate damage to samples indicated significant alterations to this mix when immersed in contact solutions containing sodium hydroxide. It was hypothesized that the low cement content, combined with high silica content coming from silica fume, fly ash and GGBFS led to the presence unreacted silica. It is possible that the pozzolanic reaction of these SCMs could not be activated due to the low alkali content, a direct consequence of low cement content. In this scenario, the material end up having a lot of silica available to react upon contact with sodium hydroxide, possibly forming a gel that may be similar to the gel formed in alkali-silica reactions. This scenario needs further experimental confirmation, but it may well explain the poor behavior of mix PV2 in presence of NaOH.« less

Lead sorption by waste biomass of hazelnut and almond shell.

PubMed

Pehlivan, Erol; Altun, Türkan; Cetin, Serpil; Iqbal Bhanger, M

2009-08-15

The potential to remove Pb(2+) ion from aqueous solutions using the shells of hazelnut (HNS) (Corylus avellana) and almond (AS) (Prunus dulcis) through biosorption was investigated in batch experiments. The main parameters influencing Pb(2+) ion sorption on HNS and AS were: initial metal ion concentration, amount of adsorbent, contact time and pH value of solution. The influences of initial Pb(2+) ion concentration (0.1-1.0mM), pH (2-9), contact time (10-240 min) and adsorbent amount (0.1-1.0 g) have been investigated. Equilibrium isotherms have been measured and modelled. Adsorption of Pb(2+) ions was in all cases pH-dependent showing a maximum at equilibrium pH values between 6.0 and 7.0, depending on the biomaterial, that corresponded to equilibrium pH values of 6.0 for HNS and 7.0 for AS. The equilibrium sorption capacities of HNS and AS were 28.18 and 8.08 mg/g for lead, respectively after equilibrium time of 2h. The adsorption data fit well with the Langmuir isotherm model and the experimental result inferred that adsorption, chelation and ion exchange are major adsorption mechanisms for binding Pb(2+) ion to the sorbents.

SEPARATION OF PLUTONIUM VALUES FROM OTHER METAL VALUES IN AQUEOUS SOLUTIONS BY SELECTIVE COMPLEXING AND ADSORPTION

DOEpatents

Beaton, R.H.

1960-06-28

A process is given for separating tri- or tetravalent plutonium from fission products in an aqueous solution by complexing the fission products with oxalate, tannate, citrate, or tartrate anions at a pH value of at least 2.4 (preferably between 2.4 and 4), and contacting a cation exchange resin with the solution whereby the plutonium is adsorbed while the complexed fission products remain in solution.

Evolutions and equilibrium parameters of foam films from individual solutions of Bovine serum albumin, n-dodecyl-β-D-maltoside and from their mixed solutions

NASA Astrophysics Data System (ADS)

Gerasimova, Anelia Tsvetanova; Angarska, Jana Krumova; Tachev, Krasimir Dimov

2017-03-01

The evolutions of thinning of films from individual solutions of BSA, C12G2 and from their mixed solutions with molar ratios 1:1, 1:7.5, 1:50 and 1:100 with pH = 4.9 were recorded by modified (with video camera) interferometric method. Based on them the stages through which the film goes from its formation to the equilibrium state were distinguished. It was shown that: (i) the difference between the kinetic of drainage of films stabilized by high and low molecular surfactants is drastic; (ii) only the change of the pH solution under or above isoelectric point strongly retards the film drainage; (iii) the transition of the kinetic of thinning of films from mixed solutions from a kinetic typical for high molecular substances towards a kinetic for low substances depends on the molar ratio between the components in the solution. From the picture of film corresponding to its equilibrium state the type of film was determined. From the analysis of this picture the equilibrium thickness and contact angle were calculated. It was found that the criterion for Newtonium black films (based on the values of film thickness and contact angle) is not directly applicable for films from protein solutions or mixed solutions with the participation of proteins.

Copper, lead and zinc removal from metal-contaminated wastewater by adsorption onto agricultural wastes.

PubMed

Janyasuthiwong, Suthee; Phiri, Sheila M; Kijjanapanich, Pimluck; Rene, Eldon R; Esposito, Giovanni; Lens, Piet N L

2015-01-01

The use of agricultural wastes (groundnut shell, orange and banana peel, rice husk, coconut husk and Wawa tree saw dust) as potential cost-effective adsorbent for heavy metal removal from wastewater was evaluated. The effect of pH (2.0-6.0), adsorbent dosage (0.6-2.2 g), contact time (10-130 min) and initial concentration (Pb: 5-105 mg/L, Cu and Zn: 2.5-52.7 mg/L) on the metal removal efficiency and uptake capacity were investigated using response surface methodology to optimize the process conditions. Groundnut shell showed a high potential to remove Cu, Pb and Zn from synthetic wastewater. The highest removal efficiencies with groundnut as the adsorbent were 85% at pH 5.0 for Cu and 98% at pH 3.0 for Pb and Zn. The optimum conditions obtained were 2.5 g adsorbent with 40.7 mg/L Cu at pH 4.4 and 64 min contact time, 2.5 g adsorbent with 196.1 mg/L Pb at pH 5.6 and 60 min contact time and 3.1 g adsorbent with 70.2 mg/L Zn at pH 4.3 and 50 min contact time, for Cu, Pb and Zn, respectively. The regeneration of the groundnut shell was possible for a maximum of three cycles using 0.2 M HCl as the desorbing solution without any significant change in the adsorbing efficiency.

Predicting adsorptive removal of chlorophenol from aqueous solution using artificial intelligence based modeling approaches.

PubMed

Singh, Kunwar P; Gupta, Shikha; Ojha, Priyanka; Rai, Premanjali

2013-04-01

The research aims to develop artificial intelligence (AI)-based model to predict the adsorptive removal of 2-chlorophenol (CP) in aqueous solution by coconut shell carbon (CSC) using four operational variables (pH of solution, adsorbate concentration, temperature, and contact time), and to investigate their effects on the adsorption process. Accordingly, based on a factorial design, 640 batch experiments were conducted. Nonlinearities in experimental data were checked using Brock-Dechert-Scheimkman (BDS) statistics. Five nonlinear models were constructed to predict the adsorptive removal of CP in aqueous solution by CSC using four variables as input. Performances of the constructed models were evaluated and compared using statistical criteria. BDS statistics revealed strong nonlinearity in experimental data. Performance of all the models constructed here was satisfactory. Radial basis function network (RBFN) and multilayer perceptron network (MLPN) models performed better than generalized regression neural network, support vector machines, and gene expression programming models. Sensitivity analysis revealed that the contact time had highest effect on adsorption followed by the solution pH, temperature, and CP concentration. The study concluded that all the models constructed here were capable of capturing the nonlinearity in data. A better generalization and predictive performance of RBFN and MLPN models suggested that these can be used to predict the adsorption of CP in aqueous solution using CSC.

Polyethyleneimine-carbon nanotube polymeric nanocomposite adsorbents for the removal of Cr6+ from water

NASA Astrophysics Data System (ADS)

Sambaza, Shepherd S.; Masheane, Monaheng L.; Malinga, Soraya P.; Nxumalo, Edward N.; Mhlanga, Sabelo D.

2017-08-01

This work reports on the synthesis of multi-walled carbon nanotubes (MWCNTs) and their use in branched polyethyleneimine-multiwalled carbon nanotube (PEI-MWCNT) polymeric nanocomposite adsorbents for the removal of Cr6+ from contaminated water. The nanostructured materials were characterized using TEM, Raman, FTIR, BET surface area and zeta potential measurements. TEM confirmed the average diameter of the MWCNTs to be 25 nm. The point of zero-charge of PEI was at pH 8 and that of PEI-MWCNTs was at pH 7.7. FTIR analysis confirmed the formation of a new bond (-Cdbnd O at 1716 cm-1) between the functional groups on the MWCNTs and PEI. Batch adsorption and kinetic studies showed that the PEI-MWCNT nanocomposite materials were more efficient in the removal of Cr6+ solution from water samples. The optimum conditions for adsorption were pH ≤ 4, contact time of 60 min. When the PEI-MWCNT dosage was increased the adsorption capacity increased. The kinetic adsorption data obtained for Cr6+ solution followed pseudo-second order model. The adsorption of Cr6+ solution reached equilibrium within 60 min of contact time with a removal of 99%. The adsorbents were effective even after 5 cycles of use.

Controlled drug release from hydrogels for contact lenses: Drug partitioning and diffusion.

PubMed

Pimenta, A F R; Ascenso, J; Fernandes, J C S; Colaço, R; Serro, A P; Saramago, B

2016-12-30

Optimization of drug delivery from drug loaded contact lenses assumes understanding the drug transport mechanisms through hydrogels which relies on the knowledge of drug partition and diffusion coefficients. We chose, as model systems, two materials used in contact lens, a poly-hydroxyethylmethacrylate (pHEMA) based hydrogel and a silicone based hydrogel, and three drugs with different sizes and charges: chlorhexidine, levofloxacin and diclofenac. Equilibrium partition coefficients were determined at different ionic strength and pH, using water (pH 5.6) and PBS (pH 7.4). The measured partition coefficients were related with the polymer volume fraction in the hydrogel, through the introduction of an enhancement factor following the approach developed by the group of C. J. Radke (Kotsmar et al., 2012; Liu et al., 2013). This factor may be decomposed in the product of three other factors E HS , E el and E ad which account for, respectively, hard-sphere size exclusion, electrostatic interactions, and specific solute adsorption. While E HS and E el are close to 1, E ad >1 in all cases suggesting strong specific interactions between the drugs and the hydrogels. Adsorption was maximal for chlorhexidine on the silicone based hydrogel, in water, due to strong hydrogen bonding. The effective diffusion coefficients, D e , were determined from the drug release profiles. Estimations of diffusion coefficients of the non-adsorbed solutes D=D e ×E ad allowed comparison with theories for solute diffusion in the absence of specific interaction with the polymeric membrane. Copyright © 2016 Elsevier B.V. All rights reserved.

Removal of methylene blue from aqueous solution by wood millet carbon optimization using response surface methodology

NASA Astrophysics Data System (ADS)

Ghaedi, Mehrorang; Kokhdan, Syamak Nasiri

2015-02-01

The use of cheep, non-toxic, safe and easily available adsorbent are efficient and recommended material and alternative to the current expensive substance for pollutant removal from wastewater. The activated carbon prepared from wood waste of local tree (millet) extensively was applied for quantitative removal of methylene blue (MB), while simply. It was used to re-used after heating and washing with alkaline solution of ethanol. This new adsorbent was characterized by using BET surface area measurement, FT-IR, pH determination at zero point of charge (pHZPC) and Boehm titration method. Response surface methodology (RSM) by at least the number of experiments main and interaction of experimental conditions such as pH of solution, contact time, initial dye concentration and adsorbent dosage was optimized and set as pH 7, contact time 18 min, initial dye concentration 20 ppm and 0.2 g of adsorbent. It was found that variable such as pH and amount of adsorbent as solely or combination effects seriously affect the removal percentage. The fitting experimental data with conventional models reveal the applicability of isotherm models Langmuir model for their well presentation and description and Kinetic real rate of adsorption at most conditions efficiently can be represented pseudo-second order, and intra-particle diffusion. It novel material is good candidate for removal of huge amount of MB (20 ppm) in short time (18 min) by consumption of small amount (0.2 g).

Surface modification of melamine sponges for pH-responsive oil absorption and desorption

NASA Astrophysics Data System (ADS)

Lei, Zhiwen; Zhang, Guangzhao; Deng, Yonghong; Wang, Chaoyang

2017-09-01

Inspired by the development of smart oil/water separation materials, a pH responsive melamine sponge has been obtained by grafting poly (4-vinylpyridine) on the skeleton surface through atom transfer radical polymerization. Through scanning electron microscopy and x-ray photoelectron spectroscopy, the successful grafting of poly (4-vinylprridine) onto the melamine sponge has been confirmed. When contacting with different pH water droplets in air, the as-prepared product shows excellent switchable wettability between super-hydrophilicity (0°) and highly hydrophobicity (135°). Meanwhile, this responsive sponge also exhibits super-hydrophilic/oleophobic property underwater at pH = 1.0, and highly hydrophobic/super-oleophilic property in neutral solution at pH = 7.0. Furthermore, the excellent responsiveness is remained after five cycle water contact angle tests between two different pH stages at pH 1.0 and 7.0. The modified melamine sponges could not only absorb the oil from the oily water at pH = 7.0, but also quickly release the absorbed oil underwater at pH = 1.0 without leaving any residues and hurting the environment nearly, showing a good potential in controlled oil/water separation and oil recovery.

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.

Adsorption of Pb(II) using silica gel composite from rice husk ash modified 3-aminopropyltriethoxysilane (APTES)-activated carbon from coconut shell

NASA Astrophysics Data System (ADS)

Yusmaniar, Purwanto, Agung; Putri, Elfriyana Awalita; Rosyidah, Dzakiyyatur

2017-03-01

Silica gel modified by 3-aminopropyltriethoxysilane (APTES) was synthesized from rice husk ash combined with activated carbon from coconut shell yielded the composite adsorbent. The composite was characterized by Fourier Transform Infra Red spectroscopy (FT-IR), Electron Dispersive X-Ray (EDX), Surface Area Analyzer (SAA) and adsorption test by Atomic Absorption Spectrometry (AAS). This composite adsorbent has been used moderately for the removal of lead ions from metal solutions and compared with silica gel modified APTES and activated carbon. The adsorption experiments of Pb -ions by adsorbents were performed at different pH and contact time with the same metal solutions concentration, volume solution, and adsorbent dosage. The optimum pH for the adsorption was found to be 5.0 and the equilibrium was achieved for Pb with 20 min of contact time. Pb ions adsorption by composite silica gel modified APTES-activated carbon followed by Langmuir isotherm model with qmax value of 46.9483 mg/g that proved an adsorbent mechanism consistent to the mechanism of monolayer formation.

α-keratin/Alginate Biosorbent for Removal of Methylene Blue on Aqueous Solution in a Batch System

NASA Astrophysics Data System (ADS)

Fadillah, G.; Putri, E. N. K.; Febrianastuti, S.; Munawaroh, H.; Purnawan, C.; Wahyuningsih, S.

2018-03-01

Methylene Blue (MB) is a cationic dyes which is commonly used in textile industries for coloring agent. The precence of MB in water caused some negative effect on the environment and human health. Many common technologies such as membrane filtration, electrophoresis and adsorption have been widely empolyed for removal of MB in water, but the adsorption technique still has advantages than the others. In this study, removal of MB used a biosorbent α-keratin/alginate (KA). The biosorbent KA was prepared by using the encapsulation technique in CaCl2 2 % (w/v) solution. The biosorbent was characterized by Fourier Transform Infrared (FTIR) and Scanning Electron Microscope (SEM). The effect of composition of α-keratin and alginate, the pH of solution and contact time on the adsorption were investigated. The optimum adsorption of MB in aqueous solution was found at the composition of α-keratin and alginate of 1:2 (w/w), the pH at 5.0 and contact time at 4 hours. The adsorption of MB on KA biosorbent was comparatively higher than α-keratin and alginate only. Adsorption of MB dyes in aqueous solution followed the Langmuir adsorption isotherm, and the dynamic adsorption model could be described through a pseudo-second order kinetics.

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

Begg, James D.; Zavarin, Mavrik; Kersting, Annie B.

Desorption of plutonium (Pu) will likely control the extent to which it is transported by mineral colloids. In this article, we evaluated the adsorption/desorption behavior of Pu on SWy-1 montmorillonite colloids at pH 4, pH 6, and pH 8 using batch adsorption and flow cell desorption experiments. After 21 days adsorption, Pu(IV) affinity for montmorillonite displayed a pH dependency, with K d values highest at pH 4 and lowest at pH 8. The pH 8 experiment was further allowed to equilibrate for 6 months and showed an increase in K d, indicating that true sorption equilibrium was not achieved withinmore » the first 21 days. For the desorption experiments, aliquots of the sorption suspensions were placed in a flow cell, and Pu-free solutions were then pumped through the cell for a period of 12 days. Changes in influent solution flow rate were used to investigate the kinetics of Pu desorption and demonstrated that it was rate-limited over the experimental timescales. At the end of the 12-day flow cell experiments, the extent of desorption was again pH dependent, with pH 8 > pH 6 > pH 4. Further, at pH 8, less Pu was desorbed after an adsorption contact time of 6 months than after a contact time of 21 days, consistent with an aging of Pu on the clay surface. In addition, a conceptual model for Pu adsorption/desorption that incorporated known surface-mediated Pu redox reactions was used to fit the experimental data. The resulting rate constants indicated processes occurring on timescales of months and even years which may, in part, explain observations of clay colloid-facilitated Pu transport on decadal timescales. Importantly, however, our results also imply that migration of Pu adsorbed to montmorillonite colloids at long (50–100 year) timescales under oxic conditions may not be possible without considering additional phenomena, such as co-precipitation.« less

Desorption of plutonium from montmorillonite: An experimental and modeling study

DOE PAGES

Begg, James D.; Zavarin, Mavrik; Kersting, Annie B.

2017-01-15

Desorption of plutonium (Pu) will likely control the extent to which it is transported by mineral colloids. In this article, we evaluated the adsorption/desorption behavior of Pu on SWy-1 montmorillonite colloids at pH 4, pH 6, and pH 8 using batch adsorption and flow cell desorption experiments. After 21 days adsorption, Pu(IV) affinity for montmorillonite displayed a pH dependency, with K d values highest at pH 4 and lowest at pH 8. The pH 8 experiment was further allowed to equilibrate for 6 months and showed an increase in K d, indicating that true sorption equilibrium was not achieved withinmore » the first 21 days. For the desorption experiments, aliquots of the sorption suspensions were placed in a flow cell, and Pu-free solutions were then pumped through the cell for a period of 12 days. Changes in influent solution flow rate were used to investigate the kinetics of Pu desorption and demonstrated that it was rate-limited over the experimental timescales. At the end of the 12-day flow cell experiments, the extent of desorption was again pH dependent, with pH 8 > pH 6 > pH 4. Further, at pH 8, less Pu was desorbed after an adsorption contact time of 6 months than after a contact time of 21 days, consistent with an aging of Pu on the clay surface. In addition, a conceptual model for Pu adsorption/desorption that incorporated known surface-mediated Pu redox reactions was used to fit the experimental data. The resulting rate constants indicated processes occurring on timescales of months and even years which may, in part, explain observations of clay colloid-facilitated Pu transport on decadal timescales. Importantly, however, our results also imply that migration of Pu adsorbed to montmorillonite colloids at long (50–100 year) timescales under oxic conditions may not be possible without considering additional phenomena, such as co-precipitation.« less

Desorption of plutonium from montmorillonite: An experimental and modeling study

NASA Astrophysics Data System (ADS)

Begg, James D.; Zavarin, Mavrik; Kersting, Annie B.

2017-01-01

Desorption of plutonium (Pu) will likely control the extent to which it is transported by mineral colloids. We evaluated the adsorption/desorption behavior of Pu on SWy-1 montmorillonite colloids at pH 4, pH 6, and pH 8 using batch adsorption and flow cell desorption experiments. After 21 days adsorption, Pu(IV) affinity for montmorillonite displayed a pH dependency, with Kd values highest at pH 4 and lowest at pH 8. The pH 8 experiment was further allowed to equilibrate for 6 months and showed an increase in Kd, indicating that true sorption equilibrium was not achieved within the first 21 days. For the desorption experiments, aliquots of the sorption suspensions were placed in a flow cell, and Pu-free solutions were then pumped through the cell for a period of 12 days. Changes in influent solution flow rate were used to investigate the kinetics of Pu desorption and demonstrated that it was rate-limited over the experimental timescales. At the end of the 12-day flow cell experiments, the extent of desorption was again pH dependent, with pH 8 > pH 6 > pH 4. Further, at pH 8, less Pu was desorbed after an adsorption contact time of 6 months than after a contact time of 21 days, consistent with an aging of Pu on the clay surface. A conceptual model for Pu adsorption/desorption that incorporated known surface-mediated Pu redox reactions was used to fit the experimental data. The resulting rate constants indicated processes occurring on timescales of months and even years which may, in part, explain observations of clay colloid-facilitated Pu transport on decadal timescales. Importantly, however, our results also imply that migration of Pu adsorbed to montmorillonite colloids at long (50-100 year) timescales under oxic conditions may not be possible without considering additional phenomena, such as co-precipitation.

Anti-inflammatory activity of nanocrystalline silver-derived solutions in porcine contact dermatitis

PubMed Central

2010-01-01

Background Nanocrystalline silver dressings have anti-inflammatory activity, unlike solutions containing Ag+ only, which may be due to dissolution of multiple silver species. These dressings can only be used to treat surfaces. Thus, silver-containing solutions with nanocrystalline silver properties could be valuable for treating hard-to-dress surfaces and inflammatory conditions of the lungs and bowels. This study tested nanocrystalline silver-derived solutions for anti-inflammatory activity. Methods Inflammation was induced on porcine backs using dinitrochlorobenzene. Negative and positive controls were treated with distilled water. Experimental groups were treated with solutions generated by dissolving nanocrystalline silver in distilled water adjusted to starting pHs of 4 (using CO2), 5.6 (as is), 7, and 9 (using Ca(OH)2). Solution samples were analyzed for total silver. Daily imaging, biopsying, erythema and oedema scoring, and treatments were performed for three days. Biopsies were processed for histology, immunohistochemistry (for IL-4, IL-8, IL-10, TNF-α, EGF, KGF, KGF-2, and apoptotic cells), and zymography (MMP-2 and -9). One-way ANOVAs with Tukey-Kramer post tests were used for statistical analyses. Results Animals treated with pH 7 and 9 solutions showed clear visual improvements. pH 9 solutions resulted in the most significant reductions in erythema and oedema scores. pH 4 and 7 solutions also reduced oedema scores. Histologically, all treatment groups demonstrated enhanced re-epithelialisation, with decreased inflammation. At 24 h, pMMP-2 expression was significantly lowered with pH 5.6 and 9 treatments, as was aMMP-2 expression with pH 9 treatments. In general, treatment with silver-containing solutions resulted in decreased TNF-α and IL-8 expression, with increased IL-4, EGF, KGF, and KGF-2 expression. At 24 h, apoptotic cells were detected mostly in the dermis with pH 4 and 9 treatments, nowhere with pH 5.6, and in both the epidermis and dermis with pH 7. Solution anti-inflammatory activity did not correlate with total silver content, as pH 4 solutions contained significantly more silver than all others. Conclusions Nanocrystalline silver-derived solutions appear to have anti-inflammatory/pro-healing activity, particularly with a starting pH of 9. Solutions generated differently may have varying concentrations of different silver species, only some of which are anti-inflammatory. Nanocrystalline silver-derived solutions show promise for a variety of anti-inflammatory treatment applications. PMID:20170497

Factorial experimental design application in modification of volcanic ash as a natural adsorbent with Fenton process for arsenic removal.

PubMed

Jaafarzadeh, Neamat; Amiri, Hoda; Ahmadi, Mehdi

2012-01-01

This paper describes an experimental design technique for the modification of volcanic ash with Fenton reagent (FMVA) to be used as a natural adsorbent in the removal of As(III) and As(V) from aqueous solution. The influence of pH, contact time and Fe(2+)/H2O2 on arsenic removal by the modified volcanic ash was investigated. It was observed that the arsenic removal efficiency was influenced by two of these parameters. The Fe(2+)/H2O2 ratio is an important factor that affects both As(III) and As(V) adsorption (P = 0.000). The pH affects As(V) adsorption (P = 0.003) more significantly than As (III) adsorption (P = 0.02). It was observed that the maximum As(III) adsorption by the FMVA was obtained at pH 2, Fe(+2)/H2O2 = 0.06 and 30 min of contact time (39 microg As(III) per mg FMVA), whereas the maximum As(V) adsorption was obtained under the conditions of pH 5, Fe(+2)/H2O2 = 0.06 and 30 min of contact time (41 microg As(V) per mg FMVA).

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.

URANIUM RECOVERY PROCESS

DOEpatents

Hyman, H.H.; Dreher, J.L.

1959-07-01

The recovery of uranium from the acidic aqueous metal waste solutions resulting from the bismuth phosphate carrier precipitation of plutonium from solutions of neutron irradiated uranium is described. The waste solutions consist of phosphoric acid, sulfuric acid, and uranium as a uranyl salt, together with salts of the fission products normally associated with neutron irradiated uranium. Generally, the process of the invention involves the partial neutralization of the waste solution with sodium hydroxide, followed by conversion of the solution to a pH 11 by mixing therewith sufficient sodium carbonate. The resultant carbonate-complexed waste is contacted with a titanated silica gel and the adsorbent separated from the aqueous medium. The aqueous solution is then mixed with sufficient acetic acid to bring the pH of the aqueous medium to between 4 and 5, whereby sodium uranyl acetate is precipitated. The precipitate is dissolved in nitric acid and the resulting solution preferably provided with salting out agents. Uranyl nitrate is recovered from the solution by extraction with an ether such as diethyl ether.

Diffusion of water-soluble sorptive drugs in HEMA/MAA hydrogels.

PubMed

Liu, D E; Dursch, T J; Taylor, N O; Chan, S Y; Bregante, D T; Radke, C J

2016-10-10

We measure and, for the first time, theoretically predict four prototypical aqueous-drug diffusion coefficients in five soft-contact-lens material hydrogels where solute-specific adsorption is pronounced. Two-photon fluorescence confocal microscopy and UV/Vis-absorption spectrophotometry assess transient solute concentration profiles and concentration histories, respectively. Diffusion coefficients are obtained for acetazolamide, riboflavin, sodium fluorescein, and theophylline in 2-hydroxyethyl methacrylate/methacrylic acid (HEMA/MAA) copolymer hydrogels as functions of composition, equilibrium water content (30-90%), and aqueous pH (2 and 7.4). At pH2, MAA chains are nonionic, whereas at pH7.4, MAA chains are anionic (pKa≈5.2). All studied prototypical drugs specifically interact with HEMA and nonionic MAA (at pH2) moieties. Conversely, none of the prototypical drugs adsorb specifically to anionic MAA (at pH7.4) chains. As expected, diffusivities of adsorbing solutes are significantly diminished by specific interactions with hydrogel strands. Despite similar solute size, relative diffusion coefficients in the hydrogels span several orders of magnitude because of varying degrees of solute interactions with hydrogel-polymer chains. To provide a theoretical framework for the new diffusion data, we apply an effective-medium model extended for solute-specific interactions with hydrogel copolymer strands. Sorptive-diffusion kinetics is successfully described by local equilibrium and Henry's law. All necessary parameters are determined independently. Predicted diffusivities are in good agreement with experiment. Copyright © 2016 Elsevier B.V. All rights reserved.

SALICYLATE PROCESS FOR THORIUM SEPARATION FROM RARE EARTHS

DOEpatents

Cowan, G.A.

1959-08-25

The separation of thorium from rare earths is accomplished by forming an aqueous solution of salts of thorium and rare earths and sufficient acetate buffer to provide a pH of between 2 and 5, adding an ammonium salicylate to the aqueous buffered solution, contacting the resultant solution with a substantially water-immiscible organic solvent mixture of an ether and an ester, and separating the solvent extract phase containing thorium salicylate from the aqueous phase containing the rare earths.

Fabrication of pH sensitive nanovalves using smart surface coated nanopores

NASA Astrophysics Data System (ADS)

Nieto-Soto, A. M.; Diaz-Maldonado, D. K.; Rios Angarita, F. A.

2017-01-01

A pH sensitive nanovalve was fabricated using different smart surfaces covalently attached to an anodized aluminium oxide membrane (AAO). The smart surfaces were synthesized using a mixture of aliphatic and aminated silanes. Effect on the contact angle of the aliphatic silane chain length was evaluated. The smart surface, in conjunction with a nanoporous membrane, allowed the formation of a hydrophobic plug which controlled the transport of the molecule safranine depending on the pH of the solution. It was demonstrated that mixtures of butyl and methyl-trimethoxysilane with aminopropyl-trimethoxysilane were able to perform as effective nanovalves creating a plug that remained closed at pH>7 and opened up at pH<5.

Proton mediated control of biochemical reactions with bioelectronic pH modulation

DOE PAGES

Deng, Yingxin; Miyake, Takeo; Keene, Scott; ...

2016-04-07

In Nature, protons (H +) can mediate metabolic process through enzymatic reactions. Examples include glucose oxidation with glucose dehydrogenase to regulate blood glucose level, alcohol dissolution into carboxylic acid through alcohol dehydrogenase, and voltage-regulated H + channels activating bioluminescence in firefly and jellyfish. Artificial devices that control H + currents and H + concentration (pH) are able to actively influence biochemical processes. Here, we demonstrate a biotransducer that monitors and actively regulates pH-responsive enzymatic reactions by monitoring and controlling the flow of H + between PdH x contacts and solution. The present transducer records bistable pH modulation from an “enzymaticmore » flip-flop” circuit that comprises glucose dehydrogenase and alcohol dehydrogenase. Furthermore, the transducer also controls bioluminescence from firefly luciferase by affecting solution pH.« less

Proton mediated control of biochemical reactions with bioelectronic pH modulation

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

Deng, Yingxin; Miyake, Takeo; Keene, Scott

In Nature, protons (H +) can mediate metabolic process through enzymatic reactions. Examples include glucose oxidation with glucose dehydrogenase to regulate blood glucose level, alcohol dissolution into carboxylic acid through alcohol dehydrogenase, and voltage-regulated H + channels activating bioluminescence in firefly and jellyfish. Artificial devices that control H + currents and H + concentration (pH) are able to actively influence biochemical processes. Here, we demonstrate a biotransducer that monitors and actively regulates pH-responsive enzymatic reactions by monitoring and controlling the flow of H + between PdH x contacts and solution. The present transducer records bistable pH modulation from an “enzymaticmore » flip-flop” circuit that comprises glucose dehydrogenase and alcohol dehydrogenase. Furthermore, the transducer also controls bioluminescence from firefly luciferase by affecting solution pH.« less

Contact lens physical properties and lipid deposition in a novel characterized artificial tear solution

PubMed Central

Heynen, Miriam; Kay, Lise M.M.; Dominici, Claudia Yvette; Khan, Warda; Ng, Wendy W.S.; Jones, Lyndon

2011-01-01

Purpose To characterize various properties of a physiologically-relevant artificial tear solution (ATS) containing a range of tear film components within a complex salt solution, and to measure contact lens parameters and lipid deposition of a variety of contact lens materials after incubation in this ATS. Methods A complex ATS was developed that contains a range of salts, proteins, lipids, mucin, and other tear film constituents in tear-film relevant concentrations. This ATS was tested to confirm that its pH, osmolality, surface tension, and homogeneity are similar to human tears and remain so throughout the material incubation process, for up to 4 weeks. To confirm that silicone hydrogel and conventional hydrogel contact lens materials do not alter in physical characteristics beyond what is allowed by the International Organization for Standardization (ISO) 18369–2. The diameter, center thickness, and calculated base curve were measured for five different lens materials directly out of the blister pack, after a rinse in saline and then following a two week incubation in the modified ATS. To test the ATS and the effect of its composition on lipid deposition, two lens materials were incubated in the ATS and a modified version for several time points. Both ATS solutions contained trace amounts of carbon-14 cholesterol and phosphatidylcholine, such that deposition of these specific lipids could be quantified using standard methods. Results This ATS is a complex mixture that remains stable at physiologically relevant pH (7.3–7.6), osmolality (304–306 mmol/kg), surface tension (40–46 dynes/cm) and homogeneity over an incubation period of three weeks or more. The physical parameters of the lenses tested showed no changes beyond that allowed by the ISO guidelines. Incubations with the ATS found that balafilcon A lenses deposit significantly more cholesterol and phosphatidylcholine than omafilcon A lenses (p<0.05) and that removing lactoferrin and immunoglobulin G from the ATS can significantly decrease the mass of lipid deposited. Conclusions This paper describes a novel complex artificial tear solution specially designed for in-vial incubation of contact lens materials. This solution was stable and did not adversely affect the physical parameters of the soft contact lenses incubated within it and showed that lipid deposition was responsive to changes in ATS composition. PMID:22219635

Adsorption Effectivity Test of Andisols Clay-Zeolite (ACZ) Composite as Chromium Hexavalent (Cr(VI)) Ion Adsorbent

NASA Astrophysics Data System (ADS)

Pranoto; Masykur, A.; Nugroho, Y. A.

2018-03-01

Adsorption of chromium hexavalent (Cr(VI)) ion in aqueous solution was investigated. This research was purposed to study the influence of the composition of ACZ, temperature activation, and contact time against adsorption capacity of Cr(VI) ion in aqueous solution. Determination of adsorption effectivity using several parameter such as composition variation of ACZ, contact time, pH, activation temperature, and concentration. In this research, andisol clay and zeolite has been activated with NaOH 3 M and 1 M, respectively. Temperature variation used 100, 200, and 400°C. While composition variation ACZ used 0:100, 25:75, 50:50, 75:25, 100:0. The pH variation was used 2 – 6 and concentration variation using 2, 4, 6, 8, 10, and 12 ppm. Characterization in this research used such as UV-Vis, Surface Area Analyzer (SAA) and Acidity Analysis. Result of this research is known that optimum composition of ACZ was 50:50 with calcination temperature 100°C. Optimum adsorption of Cr(VI) at pH 4 with removal percentage 76.10 % with initial concentration 2 ppm and adsorption capacity is 0.16 mg/g. Adsorption isotherm following freundlich isotherm with value Kf = 0.17 mg/g and value n is 0.963. Based on results, ACZ composite can be used as Cr(VI) ion adsorbents in aqueous solutions.

Synthesis of walnut shell modified with titanium dioxide and zinc oxide nanoparticles for efficient removal of humic acid from aqueous solutions.

PubMed

Naghizadeh, Ali; Shahabi, Habibeh; Ghasemi, Fatemeh; Zarei, Ahmad

2016-12-01

The main aim of this research was to study the efficiency of modified walnut shell with titanium dioxide (TiO 2 ) and zinc oxide (ZnO) in the adsorption of humic acid from aqueous solutions. This experimental study was carried out in a batch condition to determine the effects of factors such as contact time, pH, humic acid concentration, dose of adsorbents (raw walnut shell, modified walnut shell with TiO 2 and ZnO) on the removal efficiency of humic acid. pH zpc of raw walnut shell, walnut shell modified with TiO 2 and walnut shell modified with ZnO were 7.6, 7.5, and 8, respectively. The maximum adsorption capacity of humic acid at concentration of 30 mg/L, contact time of 30 min at pH = 3 in an adsorbent dose of 0.02 g of walnut shell and ZnO and TiO 2 modified walnut shell were found to be 35.2, 37.9, and 40.2 mg/g, respectively. The results showed that the studied adsorbents tended to fit with the Langmuir model. Walnut shell, due to its availability, cost-effectiveness, and also its high adsorption efficiency, can be proposed as a promising natural adsorbent in the removal of humic acid from aqueous solutions.

Effect of pH on the adsorption of dodecylamine on montmorillonite: Insights from experiments and molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Peng, Chenliang; Min, Fanfei; Liu, Lingyun

2017-12-01

The hydrophobic aggregation in cationic surfactant suspension is an effective method to enhance the dewatering of clay-rich tailing. The solution pH can affect the adsorption behavior of cationic surfactant on clay mineral. The effect of pH on the adsorption of dodecylamine (DDA) on montmorillonite was investigated by the sedimentation test and the characterization of flocs images, contact angle, adsorption quantity, and fourier transform infrared (FTIR) spectroscopy, as well as molecular dynamics (MD) simulation. It was found that DDA ions were adsorbed on montmorillonite basal surfaces mainly by physical adsorption, including the electrostatic attraction and hydrogen bonding. A certain number of neutral DDA molecules can favor the adsorption of DDA. At pH around 8, the effect of hydrophobic modification was the best because DDA molecules and ions form compact and well-organized monolayer. The MD simulation results were in good agreement with that of contact angle, adsorption quantity and FTIR.

Effect of organic matter on cyanide removal by illuminated titanium dioxide or zinc oxide nanoparticles

PubMed Central

2013-01-01

Effect of different type of organic compounds (humic acid, oxalate, ethylenediaminetetraacetic acid, nitrilotriacetic acid, phenol) on the photocatalytic removal of cyanide with TiO2 or ZnO was studied in this work with variation of the solution pH, contact time, initial cyanide concentration and type of organic compounds. Photocatalytic oxidation efficiency of cyanide with TiO2 was greatly affected by the solution pH. It increased as the solution pH decreased. Also maximum removal of cyanide by ZnO was observed near at neutral pH because of the reduced photocatalytic activity of ZnO at exceedingly low and high pH values originated from either acidic/photochemical corrosion of the catalyst and/or surface passivation with Zn(OH)2. Removal efficiency of cyanide greatly decreased in the presence of humic acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid compared to that without presence of organic compound because of the competitive oxidation as well as surface blocking by relatively large organic compounds. The oxidation pattern of cyanide was better described by first-order kinetic model. Finally photocatalytic reaction with TiO2 or ZnO can be effectively applied to treat synthetic wastewater contaminated with cyanide. PMID:24499704

Process for the combined removal of SO.sub.2 and NO.sub.x from flue gas

DOEpatents

Chang, Shih-Ger; Liu, David K.; Griffiths, Elizabeth A.; Littlejohn, David

1988-01-01

The present invention in one aspect relates to a process for the simultaneous removal of NO.sub.x and SO.sub.2 from a fluid stream comprising mixtures thereof and in another aspect relates to the separation, use and/or regeneration of various chemicals contaminated or spent in the process and which includes the steps of: (A) contacting the fluid stream at a temperature of between about 105.degree. and 180.degree. C. with a liquid aqueous slurry or solution comprising an effective amount of an iron chelate of an amino acid moiety having at least one --SH group; (B) separating the fluid stream from the particulates formed in step (A) comprising the chelate of the amino acid moiety and fly ash; (C) washing and separating the particulates of step (B) with an aqueous solution having a pH value of between about 5 to 8; (D) subsequently washing and separating the particulates of step (C) with a strongly acidic aqueous solution having a pH value of between about 1 to 3; (E) washing and separating the particulates of step (D) with an basic aqueous solution having a pH value of between about 9 to 12; (F) optionally adding additional amino acid moiety, iron (II) and alkali to the aqueous liquid from step (D) to produce an aqueous solution or slurry similar to that in step (A) having a pH value of between about 4 to 12; and (G) recycling the aqueous slurry of step (F) to the contacting zone of step (A). Steps (D) and (E) can be carried out in the reverse sequence, however the preferred order is (D) and then (E). In another preferred embodiment the present invention provides a process for the removal of NO.sub.x, SO.sub.2 and particulates from a fluid stream which includes the steps of (A) injecting into a reaction zone an aqueous solution itself comprising (i) an amino acid moiety selected from those described above; (ii) iron (II) ion; and (iii) an alkali, wherein the aqueous solution has a pH of between about 4 and 11; followed by solids separation and washing as is described in steps (B), (C), (D) and (E) above. The overall process is useful to reduce acid rain components from combustion gas sources.

Adsorption of a textile dye "Indanthrene Blue RS (C.I. Vat Blue 4)" from aqueous solutions onto smectite-rich clayey rock.

PubMed

Chaari, Islem; Feki, Mongi; Medhioub, Mounir; Bouzid, Jalel; Fakhfakh, Emna; Jamoussi, Fakher

2009-12-30

The adsorption of a textile dye, namely, Indanthrene Blue RS (C.I. Vat Blue 4) onto smectite-rich clayey rock (AYD) and its sulphuric acid-activated products (AYDS) in aqueous solution was studied in a batch system with respect to contact time, pH, and temperature. The adsorbents employed were characterized by X-ray diffraction, infrared spectroscopy and specific surface area, cation exchange capacity and point of zero charge were also estimated. The effect of contact time on dye adsorption showed that the equilibrium was reached after a contact time of 40 min for the both adsorbents. The optimum pH for dye retention was found 6.0 for AYDS and 7.3 for AYD. The equilibrium adsorption data were analysed using the Langmuir and Freundlich isotherms. The adsorption capacities (Q(m)) for AYD and AYDS were found 13.92 mg/g and 17.85 mg/g, respectively. The effect of temperature on the adsorption was also investigated; adsorption of Indanthrene Blue RS is an endothermic process. This study demonstrates that all the considered adsorbents can be used as an alternative emerging technology for water treatment.

Crystallization of calcium oxalate dihydrate in a buffered calcium-containing glucose solution by irradiation with non-equilibrium atmospheric pressure plasma

NASA Astrophysics Data System (ADS)

Kurake, Naoyuki; Tanaka, Hiromasa; Ishikawa, Kenji; Nakamura, Kae; Kajiyama, Hiroaki; Kikkawa, Fumitaka; Mizuno, Masaaki; Ikehara, Yuzuru; Hori, Masaru

2017-10-01

Oxalate was synthesized in the glucose solution by irradiation with non-equilibrium atmospheric pressure plasma (NEAPP), in which the NEAPP plume contacted the solution surface, via the generation of several intermediate organic products such as gluconic acid. A thermodynamically unstable phase of calcium oxalate dihydrate crystallized rapidly during incubation of a NEAPP-irradiated glucose solution that contained calcium ions and was buffered at neutral pH. Longer irradiation times increased the growth rate and the number of seed crystals.

Papaya Seeds as A Low-Cost Sorbent for Removing Cr(VI) from The Aqueous Solution

NASA Astrophysics Data System (ADS)

Rahmawati, Atik; Marwoto, Putut; Karunia Z, Anita

2016-08-01

The presence of chromium (VI) contaminants and their toxicity in aqueous streams important environmental problems. Adsorption is one of the effective techniques that can be used for removing metal from wastewater. This research was initiated by preparing sorbent from papaya seeds and determining its functional group contents by using FT-IR. The adsorption process was carried out in a batch method. The study of adsorption aspects involved the pH, initial Cr (VI) concentration and contact time between Cr (VI) and sorbent. FT IR analysis results showed that the main functional groups are carbonyl, hydroxyl, and carboxylic. It was also found that the effective pH for Cr (VI) uptake is 2.0 and increasing contact time would increase the Cr (VI) uptake. In addition, the equilibrium was reached after 40 minutes interaction and the increase of initial chromium (VI) concentration would increase the sorbent uptake percentage. All these results indicated that papaya seed is a potential sorbent for removing Cr (VI) from aqueous solutions.

Synthesis and performance evaluation of Al/Fe oxide coated diatomaceous earth in groundwater defluoridation: Towards fluorosis mitigation.

PubMed

Izuagie, Anthony A; Gitari, Wilson M; Gumbo, Jabulani R

2016-08-23

The quest to reduce fluoride in groundwater to WHO acceptable limit of 1.5 mg/L to prevent diseases such as teeth mottling and skeletal fluorosis was the motivation for this study. Al/Fe oxide-modified diatomaceous earth was prepared and its defluoridation potential evaluated by batch method. The sorbent with pHpzc 6.0 ± 0.2 is very reactive. The maximum 82.3% fluoride removal attained in 50 min using a dosage of 0.3 g/100 mL in 10 mg/L fluoride was almost attained within 5 min contact time; 81.3% being the percent fluoride removal at 5 min contact time. The sorbent has a usage advantage of not requiring solution pH adjustment before it can exhibit its fluoride removal potential. A substantial amount of fluoride (93.1%) was removed from solution when a sorbent dosage of 0.6 g/100 mL was contacted with 10 mg/L fluoride solution for 50 min at a mixing rate of 200 rpm. The optimum adsorption capacity of the adsorbent was 7.633 mg/g using a solution containing initially 100 mg/L fluoride. The equilibrium pH of the suspensions ranged between 6.77 and 8.26 for 10 and 100 mg/L fluoride solutions respectively. Contacting the sorbent at a dosage of 0.6 g/100 mL with field water containing 5.53 mg/L at 200 rpm for 50 min reduced the fluoride content to 0.928 mg/L-a value below the upper limit of WHO guideline of 1.5 mg/L fluoride in drinking water. The sorption data fitted to both Langmuir and Freundlich isotherms but better with the former. The sorption data obeyed only the pseudo-second-order kinetic, which implies that fluoride was chemisorbed.

Porous silicon powder as an adsorbent of heavy metal (nickel)

NASA Astrophysics Data System (ADS)

Nabil, Marwa; Motaweh, Hussien A.

2018-04-01

New and inexpensive nanoporous silicon (NPS) powder was prepared by alkali chemical etching using sonication technique and was subsequently investigated as an adsorbent in batch systems for the adsorption Ni(II) ions in an aqueous solution. The optimum conditions for the Ni(II) ion adsorption capacity of the NPS powder were studied in detail by varying parameters such as the initial Ni(II) concentration, the solution pH value, the adsorption temperature and contact time. The results indicated that the maximum adsorption capacity and the maximum removal percent of Ni(II) reached 2665.33 mg/g and 82.6%, respectively, at an initial Ni(II) concentration of 100 mg/L, adsorption time of 30 min and no effect of the solution pH and adsorption temperature.

Removal of oxytetracycline from aqueous solutions by hydroxyapatite as a low-cost adsorbent

NASA Astrophysics Data System (ADS)

Harja, Maria; Ciobanu, Gabriela

2017-11-01

The present paper involved a study of the adsorption process of the oxytetracycline drug from aqueous medium by using the hydroxyapatite nanopowders as adsorbent materials. The batch adsorption experiments were performed by monitoring the solution pH, contact time, adsorbent dosage and drug solution concentration. At pH 8 and ambient temperature, high oxytetracycline removal rates of about 97.58% and 89.95% for the uncalcined and calcined nanohydroxyapatites, respectively, were obtained. The kinetic studies indicate that the oxytetracycline adsorption onto nanohydroxyapatite samples follows a pseudo-second order kinetic model. The maximum adsorption capacities of 291.32 mg/g and 278.27 mg/g for uncalcined and calcined nanohydroxyapatite samples, respectively, have been found. So, the conclusion can be drawn that the hydroxyapatite shows good adsorption ability towards oxytetracycline.

Removal of phosphate from aqueous solutions and sewage using natural and surface modified coir pith.

PubMed

Krishnan, K Anoop; Haridas, Ajit

2008-04-01

Iron impregnated coir pith (CP-Fe-I) can be effectively used for the removal of phosphate from aqueous streams and sewage. Iron impregnation on natural coir pith was carried out by drop by drop addition method. The effect of various factors such as pH, initial concentration of phosphate, contact time and adsorbent dose on phosphate adsorption was studied by batch technique. The pH at 3.0 favored the maximum adsorption of phosphate from aqueous solutions. The effect of pH on phosphate adsorption was explained by pH(zpc), phosphate speciation in solution and affinity of anions towards the adsorbent sites. A comparative study of the adsorption of phosphate using CP-Fe-I and CP (coir pith) was made and results show that the former one is five to six times more effective than the latter. Kinetic studies revealed that the adsorption process followed a pseudo-second order kinetic model. Adsorption followed Langmuir isotherm model. Column studies were conducted to examine the utility of the investigated adsorbent for the removal of phosphate from continuously flowing aqueous solutions.

Process for Nitrogen Oxide Waste Conversion to Fertilizer

NASA Technical Reports Server (NTRS)

Lueck, Dale E. (Inventor); Parrish, Clyde F. (Inventor)

2003-01-01

The present invention describes a process for converting vapor streams from sources containing at least one nitrogen-containing oxidizing agent therein to a liquid fertilizer composition comprising the steps of: a) directing a vapor stream containing at least one nitrogen-containing oxidizing agent to a first contact zone; b) contacting said vapor stream with water to form nitrogen oxide(s) from said at least one nitrogen-containing oxidizing agent; c) directing said acid(s) as a second stream to a second contact zone; d) exposing said second stream to hydrogen peroxide which is present within said second contact zone in a relative amount of at least 0.1% by weight of said second stream within said second contact zone to convert at least some of any nitrogen oxide species or ions other than in the nitrate form present within said second stream to nitrate ion; e) sampling said stream within said second contact zone to determine the relative amount of hydrogen peroxide within said second contact zone; f) adding hydrogen peroxide to said second contact zone when a level of hydrogen peroxide less than 0.1 % by weight in said second stream is determined by said sampling; g) adding a solution comprising potassium hydroxide to said second stream to maintain a pH between 6.0 and 11.0 within said second stream within said second contact zone to form a solution of potassium nitrate; and h) removing said solution of potassium nitrate from said second contact zone.

Process and Equipment for Nitrogen Oxide Waste Conversion to Fertilizer

NASA Technical Reports Server (NTRS)

Lueck, Dale E. (Inventor); Parrish, Clyde F. (Inventor)

2000-01-01

The present invention describes a process for converting vapor streams from sources containing at least one nitrogen-containing oxidizing agent therein to a liquid fertilizer composition comprising the steps of: (1) directing a vapor stream containing at least nitrogen-containing oxidizing agent to a first contact zone; (2) contacting said vapor stream with water to form nitrogen oxide(s) from said at least one nitrogen- containing oxidizing agent; (3) directing said acid(s) as a second stream to a second contact zone; (4) exposing said second stream to hydrogen peroxide which is present within said second contact zone in a relative amount of at least 0.1% by weight of said second stream within said second contact zone to convert at least some of any nitrogen oxide species or ions other than in the nitrite form present within said second stream to nitrate ion; (5) sampling said stream within said second contact zone to determine the relative amount of hydrogen peroxide within said second contact zone; (6) adding hydrogen peroxide to said second contact zone when a level on hydrogen peroxide less than 0.1% by weight in said second stream is determined by said sampling; (7) adding a solution comprising potassium hydroxide to said second stream to maintain a pH between 6.0 and 11.0 within said second stream within said second contact zone to form a solution of potassium nitrate; and (8) removing sais solution of potassium nitrate from said second contact zone.

Lead removal by Spirulina platensis biomass.

PubMed

Al-Homaidan, Ali A; Al-Abbad, Aljawharah F; Al-Hazzani, Amal A; Al-Ghanayem, Abdullah A; Alabdullatif, Jamila A

2016-01-01

In this investigation, we report on the biosorption of Pb (II) from aqueous solutions by the nonliving biomass of the micro-alga (cyanobacterium) Spirulina platensis. Propagation of the micro-alga was carried out in outside oblong raceway ponds. The biomass was cleaned, dried and used for the investigation. The effects of pH, adsorbent dose, temperature, initial concentration of Pb (II), and contact time on the adsorption of lead by the dry biomass were studied. The experiments were carried out in 250 ml conical flasks containing 100 ml of test solutions using an orbital incubator at 150 rpm. Concentrations of the metal before and after the experiments were measured using Atomic Absorption Spectrophotometer. Very high levels of Pb (II) removal (>91%) were obtained. The optimum conditions for maximal adsorption by S. platensis were found to be pH 3; 2 g of adsorbent dose; incubation at 26°C; 100 mg/l of lead initial concentration and 60 minutes of contact time. The experimental data fitted well with Freundlich isotherm equation with R(2) values greater than 0.97. Based on our results, we recommend the utilization of S. platensis biomass for heavy metal removal from aqueous solutions.

Removal of arsenic, vanadium, and/or nickel compounds from petroliferous liquids

DOEpatents

Fish, Richard H.

1986-01-01

Described is a process for removing arsenic, vanadium, and/or nickel from petroliferous derived liquids by contacting said liquid at an elevated temperature with a divinylbenzene-crosslinked polystyrene having catechol ligands anchored thereon. For vanadium and nickel removal an amine, preferably a diamine is included. Also, described is a process for regenerating spent catecholated polystyrene by removal of the arsenic, vanadium, and/or nickel bound to it from contacting petroliferous liquid as described above and involves: treating the spent polymer containing any vanadium and/or nickel with an aqueous acid to achieve an acid pH; and, separating the solids from the liquid; and then treating said spent catecholated polystyrene, at a temperature in the range of about 20.degree. to 100.degree. C. with an aqueous solution of at least one carbonate and/or bicarbonate of ammonium, alkali and alkaline earth metals, said solution having a pH between about 8 and 10; and, separating the solids and liquids from each other. Preferably the regeneration treatment of arsenic containing catecholated polymer is in two steps wherein the first step is carried out with an aqueous alcoholic carbonate solution containing lower alkyl alcohol, and, the steps are repeated using a bicarbonate.

Removal of arsenic, vanadium and/or nickel compounds from spent catecholated polymer

DOEpatents

Fish, R.H.

1987-04-21

Described is a process for removing arsenic, vanadium, and/or nickel from petroliferous derived liquids by contacting said liquid at an elevated temperature with a divinylbenzene-crosslinked polystyrene having catechol ligands anchored thereon. For vanadium and nickel removal an amine, preferably a diamine is included. Also, described is a process for regenerating spent catecholated polystyrene by removal of the arsenic, vanadium, and/or nickel bound to it from contacting petroliferous liquid as described above and involves: treating the spent polymer containing any vanadium and/or nickel with an aqueous acid to achieve an acid pH; and, separating the solids from the liquid; and then treating said spent catecholated polystyrene, at a temperature in the range of about 20 to 100 C with an aqueous solution of at least one carbonate and/or bicarbonate of ammonium, alkali and alkaline earth metals, said solution having a pH between about 8 and 10; and, separating the solids and liquids from each other. Preferably the regeneration treatment of arsenic containing catecholated polymer is in two steps wherein the first step is carried out with an aqueous alcoholic carbonate solution containing lower alkyl alcohol, and, the steps are repeated using a bicarbonate.

Removal of arsenic, vanadium and/or nickel compounds from spent catecholated polymer

DOEpatents

Fish, Richard H.

1987-01-01

Described is a process for removing arsenic, vanadium, and/or nickel from petroliferous derived liquids by contacting said liquid at an elevated temperature with a divinylbenzene-crosslinked polystyrene having catechol ligands anchored thereon. For vanadium and nickel removal an amine, preferably a diamine is included. Also, described is a process for regenerating spent catecholated polystyrene by removal of the arsenic, vanadium, and/or nickel bound to it from contacting petroliferous liquid as described above and involves: treating the spent polymer containing any vanadium and/or nickel with an aqueous acid to achieve an acid pH; and, separating the solids from the liquid; and then treating said spent catecholated polystyrene, at a temperature in the range of about 20.degree. to 100.degree. C. with an aqueous solution of at least one carbonate and/or bicarbonate of ammonium, alkali and alkaline earth metals, said solution having a pH between about 8 and 10; and, separating the solids and liquids from each other. Preferably the regeneration treatment of arsenic containing catecholated polymer is in two steps wherein the first step is carried out with an aqueous alcoholic carbonate solution containing lower alkyl alcohol, and, the steps are repeated using a bicarbonate.

The coordination chemistry of the neutral tris-2-pyridyl silicon ligand [PhSi(6-Me-2-py)3].

PubMed

Plajer, Alex J; Colebatch, Annie L; Enders, Markus; García-Romero, Álvaro; Bond, Andrew D; García-Rodríguez, Raúl; Wright, Dominic S

2018-05-22

Difficulties in the preparation of neutral ligands of the type [RSi(2-py)3] (where 2-py is an unfunctionalised 2-pyridyl ring unit) have thwarted efforts to expand the coordination chemistry of ligands of this type. However, simply switching the pyridyl substituents to 6-methyl-pyridyl groups (6-Me-2-py) in the current paper has allowed smooth, high-yielding access to the [PhSi(6-Me-2-py)3] ligand (1), and the first exploration of its coordination chemistry with transition metals. The synthesis, single-crystal X-ray structures and solution dynamics of the new complexes [{PhSi(6-Me-2-py)3}CuCH3CN][PF6], [{PhSi(6-Me-2-py)3}CuCH3CN][CuCl2], [{PhSi(6-Me-2-py)3}FeCl2], [{PhSi(6-Me-2-py)3}Mo(CO)3] and [{PhSi(6-Me-2-py)3}CoCl2] are reported. The paramagnetic Fe2+ and Co2+ complexes show strongly shifted NMR resonances for the coordinated pyridyl units due to large Fermi-contact shifts. However, magnetic anisotropy also leads to considerable pseudo-contact shifts so that both contributions have to be included in the paramagnetic NMR analysis.

A process for the preparation of cysteine from cystine

DOEpatents

Chang, Shih-Ger; Liu, David K.; Griffiths, Elizabeth A.; Littlejohn, David

1989-01-01

The present invention in one aspect relates to a process for the simultaneous removal of NO.sub.x and SO.sub.2 from a fluid stream comprising mixtures thereof and in another aspect relates to the separation, use and/or regeneration of various chemicals contaminated or spent in the process and which includes the steps of: (A) contacting the fluid stream at a temperature of between about 105.degree. and 180.degree. C. with a liquid aqueous slurry or solution comprising an effective amount of an iron chelate of an amino acid moiety having at least one --SH group; (B) separating the fluid stream from the particulates formed in step (A) comprising the chelate of the amino acid moiety and fly ash; (C) washing and separating the particulates of step (B) with an aqeous solution having a pH value of between about 5 to 8; (D) subsequently washing and separating the particulates of step (C) with a strongly acidic aqueous solution having a pH value of between about 1 to 3; (E) washing and separating the particulates of step (D) with an basic aqueous solution having a pH value of between about 9 to 12; (F) optionally adding additional amino acid moiety, iron (II) and alkali to the aqueous liquid from step (D) to produce an aqueous solution or slurry similar to that in step (A) having a pH value of between about 4 to 12; and (G) recycling the aqueous slurry of step (F) to the contacting zone of step (A). Steps (D) and (E) can be carried out in the reverse sequence, however the preferred order is (D) and then (E). In a preferred embodiment the present invention provides an improved process for the preparation (regeneration) of cysteine from cystine, which includes reacting an aqueous solution of cystine at a pH of between about 9 to 13 with a reducing agent selected from hydrogen sulfide or alkali metal sulfides, sulfur dioxide, an alkali metal sulfite or mixtures thereof for a time and at a temperature effective to cleave and reduce the cystine to cysteine with subsequent recovery of the cysteine. In another preferred embodiment the present invention provides a process for the removal of NO.sub.x, SO.sub.2 and particulates from a fluid stream which includes the steps of (A) injecting into a reaction zone an aqueous solution itself comprising (i) an amino acid moiety selected from those described above; (ii) iron (II) ion; and (iii) an alkali, wherein the aqueous solution has a pH of between about 4 and 11; followed by solids separation and washing as is described in steps (B), (C), (D) and (E) above. The overall process is useful to reduce acid rain components from combustion gas sources.

A Simple Method for Decreasing the Liquid Junction Potential in a Flow-through-Type Differential pH Sensor Probe Consisting of pH-FETs by Exerting Spatiotemporal Control of the Liquid Junction

PubMed Central

Yamada, Akira; Mohri, Satoshi; Nakamura, Michihiro; Naruse, Keiji

2015-01-01

The liquid junction potential (LJP), the phenomenon that occurs when two electrolyte solutions of different composition come into contact, prevents accurate measurements in potentiometry. The effect of the LJP is usually remarkable in measurements of diluted solutions with low buffering capacities or low ion concentrations. Our group has constructed a simple method to eliminate the LJP by exerting spatiotemporal control of a liquid junction (LJ) formed between two solutions, a sample solution and a baseline solution (BLS), in a flow-through-type differential pH sensor probe. The method was contrived based on microfluidics. The sensor probe is a differential measurement system composed of two ion-sensitive field-effect transistors (ISFETs) and one Ag/AgCl electrode. With our new method, the border region of the sample solution and BLS is vibrated in order to mix solutions and suppress the overshoot after the sample solution is suctioned into the sensor probe. Compared to the conventional method without vibration, our method shortened the settling time from over two min to 15 s and reduced the measurement error by 86% to within 0.060 pH. This new method will be useful for improving the response characteristics and decreasing the measurement error of many apparatuses that use LJs. PMID:25835300

Effect of aniline on cadmium adsorption by sulfanilic acid-grafted magnetic graphene oxide sheets.

PubMed

Hu, Xin-jiang; Liu, Yun-guo; Zeng, Guang-ming; Wang, Hui; Hu, Xi; Chen, An-wei; Wang, Ya-qin; Guo, Yi-Mming; Li, Ting-ting; Zhou, Lu; Liu, Shao-heng; Zeng, Xiao-xia

2014-07-15

Cd(II) has posed severe health risks worldwide. To remove this contaminant from aqueous solution, the sulfanilic acid-grafted magnetic graphene oxide sheets (MGOs/SA) were prepared and characterized. The mutual effects of Cd(II) and aniline adsorption on MGOs/SA were studied. The effects of operating parameters such as pH, ionic strength, contact time and temperature on the Cd(II) enrichment, as well as the adsorption kinetics and isotherm were also investigated. The results demonstrated that MGOs/SA could effectively remove Cd(II) and aniline from the aqueous solution and the two adsorption processes were strongly dependent on solution pH. The Cd(II) adsorption was reduced by the presence of aniline at pH<5.4 but was improved at pH>5.4. The presence of Cd(II) diminished the adsorption capacity for aniline at pH<7.8 but enhanced the aniline adsorption at pH>7.8. The decontamination of Cd(II) by MGOs/SA was influenced by ionic strength. Besides, the adsorption process could be well described by pseudo-second-order kinetic model. The intraparticle diffusion study revealed that the intraparticle diffusion was not the only rate-limiting step for the adsorption process. Moreover, the experimental data of isotherm followed the Freundlich isotherm model. Copyright © 2014 Elsevier Inc. All rights reserved.

Hexavalent chromium adsorption from aqueous solution using carbon nano-onions (CNOs).

PubMed

Sakulthaew, Chainarong; Chokejaroenrat, Chanat; Poapolathep, Amnart; Satapanajaru, Tunlawit; Poapolathep, Saranya

2017-10-01

The capacity of carbon nano-onions (CNOs) to remove hexavalent chromium (Cr(VI)) from aqueous solution was investigated. Batch experiments were performed to quantify the effects of the dosage rate, pH, counter ions, and temperature. The adsorption of Cr(VI) onto CNOs was best described by a pseudo-second order rate expression. The adsorption efficiency increased with increasing adsorbent dosage and contact time and reached equilibrium in 24 h. The equilibrium data showed better compliance with a Langmuir isotherm than a Freundlich isotherm. Effective removal of Cr(VI) was demonstrated at pH values ranging from 2 to 10. The adsorption capacity of Cr(VI) was found to be highest (82%) at pH 3.4 and greatly depended on the solution pH. We found that Cr(VI) adsorption decreased with increasing pH over the pH range of 3.4-10. The adsorption capacity increased dramatically when the temperature increased from 10 °C to 50 °C regardless of the amount of CNOs used. Cr(VI) removal decreased by ∼13% when Zn(II), Cu(II), and Pb(II) were present, while there were no significant changes observed when NO 3 - or SO 4 2- was present. The overall results support that CNOs can be used as an alternative adsorbent material to remove Cr(VI) in the water treatment industry. Copyright © 2017 Elsevier Ltd. All rights reserved.

The use of macroalgae (Gracilaria changii) as bio-adsorbent for Copper (II) removal

NASA Astrophysics Data System (ADS)

Lavania-Baloo; Idayu, Nordin; Umar Salihi, Ibrahim; Zainoddin, Jamari

2017-05-01

Biosorption of heavy metals using marine macroalgae biomass can be an effective process and alternative to conventional methods. Activated carbon was developed from macroalgae (Gracilaria changii) and used as adsorbents for the removal of copper (II) from wastewater. Gracilaria changii based activated carbon (GCBAC) was prepared using muffle furnace at a constant temperature of 300 °C for 1 hour. Batch adsorption experiments were conducted to investigate the effets of important parameters such as pH, contact time, initial metal concentration and adsorbent dosage on the removal of Cu (II) from synthetic aqueous solution. Batch adsorption study shows that removal of Cu (II) using GCBAC relied upon pH, contact time, initial metal concentration and GCBAC dosage. The optimum conditions parameters were found to be pH 6.0, time of 60 minutes and GCBAC dosage of 0.3 g, respectively. Adsorption data was described better by Freundlich isotherm model with R2 value of 0.7936. The maximum Cu (II) adsorption capacity of GCBAC was found to be 0.07 mg/g. The experimental adsorption data obtained fitted well into Pseudo-second-order kinetic model, with R2 value near unity. Thus, GCBAC can be used as an effective adsorbent for the removal of Cu (II) from aqueous solution.

Thermodynamic stability of CoOOH and its coprecipitation with manganese

USGS Publications Warehouse

Hem, J.D.; Roberson, C.E.; Lind, Carol J.

1985-01-01

A precipitate of cobalt oxyhydroxides formed by bubbling oxygen through a dilute solution of Co(NO3)2 held at pH 9.0 and 25??C was aged for 23 months in contact with the original solution, with access to atmospheric oxygen. Co3O4 and CoOOH were identified in the precipitate by X-ray diffraction. Chemical equilibria involving these solids were evaluated by measurements of solution pH and Co2+ activities and by redox potential measurements and gave a ??GcoOOH0 of -92.3 ?? 0.5 kcal/mole. This value and other thermodynamic data show relative feasibility of hypothetical reaction steps and changes in reaction paths during automated coprecipitation titrations and subsequent aging of a precipitate that finally contained ??MnOOH, MnO2 (birnessite) and CoOOH. ?? 1985.

Removal of Cr(VI) from Aqueous Environments Using Micelle-Clay Adsorption

PubMed Central

Qurie, Mohannad; Khamis, Mustafa; Manassra, Adnan; Ayyad, Ibrahim; Nir, Shlomo; Scrano, Laura; Bufo, Sabino A.; Karaman, Rafik

2013-01-01

Removal of Cr(VI) from aqueous solutions under different conditions was investigated using either clay (montmorillonite) or micelle-clay complex, the last obtained by adsorbing critical micelle concentration of octadecyltrimethylammonium ions onto montmorillonite. Batch experiments showed the effects of contact time, adsorbent dosage, and pH on the removal efficiency of Cr(VI) from aqueous solutions. Langmuir adsorption isotherm fitted the experimental data giving significant results. Filtration experiments using columns filled with micelle-clay complex mixed with sand were performed to assess Cr(VI) removal efficiency under continuous flow at different pH values. The micelle-clay complex used in this study was capable of removing Cr(VI) from aqueous solutions without any prior acidification of the sample. Results demonstrated that the removal effectiveness reached nearly 100% when using optimal conditions for both batch and continuous flow techniques. PMID:24222757

Removal of Arsenic (III, V) from aqueous solution by nanoscale zero-valent iron stabilized with starch and carboxymethyl cellulose

PubMed Central

2014-01-01

In this work, synthetic nanoscale zerovalent iron (NZVI) stabilized with two polymers, Starch and Carboxymethyl cellulose (CMC) were examined and compared for their ability in removing As (III) and As (V) from aqueous solutions as the most promising iron nanoparticles form for arsenic removal. Batch operations were conducted with different process parameters such as contact time, nanoparticles concentration, initial arsenic concentration and pH. Results revealed that starch stabilized particles (S-nZVI) presented an outstanding ability to remove both arsenate and arsenite and displayed ~ 36.5% greater removal for As (V) and 30% for As (III) in comparison with CMC-stabilized nanoparticles (C-nZVI). However, from the particle stabilization viewpoint, there is a clear trade off to choosing the best stabilized nanoparticles form. Removal efficiency was enhanced with increasing the contact time and iron loading but reduced with increasing initial As (III, V) concentrations and pH. Almost complete removal of arsenic (up to 500 μg/L) was achieved in just 5 min when the S-nZVI mass concentration was 0.3 g/L and initial solution pH of 7 ± 0.1. The maximum removal efficiency of both arsenic species was obtained at pH = 5 ± 0.1 and starched nanoparticles was effective in slightly acidic and natural pH values. The adsorption kinetics fitted well with pseudo-second-order model and the adsorption data obeyed the Langmuir equation with a maximum adsorption capacity of 14 mg/g for arsenic (V), and 12.2 mg/g for arsenic (III). It could be concluded that starch stabilized Fe0 nanoparticles showed remarkable potential for As (III, V) removal from aqueous solution e.g. contaminated water. PMID:24860660

Functional Layer-by-Layer Thin Films of Inducible Nitric Oxide (NO) Synthase Oxygenase and Polyethylenimine: Modulation of Enzyme Loading and NO-Release Activity.

PubMed

Gunasekera, Bhagya; Abou Diwan, Charbel; Altawallbeh, Ghaith; Kalil, Haitham; Maher, Shaimaa; Xu, Song; Bayachou, Mekki

2018-03-07

Nitric oxide (NO) release counteracts platelet aggregation and prevents the thrombosis cascade in the inner walls of blood vessels. NO-release coatings also prevent thrombus formation on the surface of blood-contacting medical devices. Our previous work has shown that inducible nitric oxide synthase (iNOS) films release NO fluxes upon enzymatic conversion of the substrate l-arginine. In this work, we report on the modulation of enzyme loading in layer-by-layer (LbL) thin films of inducible nitric oxide synthase oxygenase (iNOSoxy) on polyethylenimine (PEI). The layer of iNOSoxy is electrostatically adsorbed onto the PEI layer. The pH of the iNOSoxy solution affects the amount of enzyme adsorbed. The overall negative surface charge of iNOSoxy in solution depends on the pH and hence determines the density of adsorbed protein on the positively charged PEI layer. We used buffered iNOSoxy solutions adjusted to pHs 8.6 and 7.0, while saline PEI solution was used at pH 7.0. Atomic force microscopy imaging of the outermost layer shows higher protein adsorption with iNOSoxy at pH 8.6 than with a solution of iNOSoxy at pH 7.0. Graphite electrodes with PEI/iNOSoxy films show higher catalytic currents for nitric oxide reduction mediated by iNOSoxy. The higher enzyme loading translates into higher NO flux when the enzyme-modified surface is exposed to a solution containing the substrate and a source of electrons. Spectrophotometric assays showed higher NO fluxes with iNOSoxy/PEI films built at pH 8.6 than with films built at pH 7.0. Fourier transform infrared analysis of iNOSoxy adsorbed on PEI at pH 8.6 and 7.0 shows structural differences of iNOSoxy in films, which explains the observed changes in enzymatic activity. Our findings show that pH provides a strategy to optimize the NOS loading and enzyme activity in NOS-based LbL thin films, which enables improved NO release with minimum layers of PEI/NOS.

pH-dependent electron-transport properties of carbon nanotubes.

PubMed

Back, Ju Hee; Shim, Moonsub

2006-11-30

Carbon nanotube electrochemical transistors integrated with microfluidic channels are utilized to examine the effects of aqueous electrolyte solutions on the electron-transport properties of single isolated carbon nanotubes. In particular, pH and concentration of supporting inert electrolytes are examined. A systematic threshold voltage shift with pH is observed while the transconductance and subthreshold swing remain independent of pH and concentration. Decreasing pH leads to a negative shift of the threshold voltage, indicating that protonation does not lead to hole doping. Changing the type of contact metal does not alter the observed pH response. The pH-dependent charging of SiO2 substrate is ruled out as the origin based on measurements with suspended nanotube transistors. Increasing the ionic strength leads to reduced pH response. Contributions from possible surface chargeable chemical groups are considered.

Evaluation of calcium hydrogen carbonate mesoscopic crystals as a disinfectant for influenza A viruses

PubMed Central

NAKASHIMA, Ryuji; KAWAMOTO, Masaomi; MIYAZAKI, Shigeru; ONISHI, Rumiko; FURUSAKI, Koichi; OSAKI, Maho; KIRISAWA, Rikio; SAKUDO, Akikazu; ONODERA, Takashi

2017-01-01

In this study, the virucidal effect of a novel electrically charged disinfectant CAC-717 was investigated. CAC-717 is produced by applying an electric field to mineral water containing calcium hydrogen carbonate to generate mesoscopic crystals. Virus titration analysis showed a >3 log reduction of influenza A viruses after treatment with CAC-717 for 1 min in room temperature, while infectivity was undetectable after 15 min treatment. Adding bovine serum albumin to CAC-717 solution did not affect the disinfectant effect. Although CAC-717 is an alkaline solution (pH=12.39), upon contact with human tissue, its pH becomes almost physiological (pH 8.84) after accelerated electric discharge, which enables its use against influenza viruses. Therefore, CAC-717 may be used as a preventative measure against influenza A viruses and for biosecurity in the environment. PMID:28392537

pH triggered controlled drug delivery from contact lenses: Addressing the challenges of drug leaching during sterilization and storage.

PubMed

Maulvi, Furqan A; Choksi, Harsh H; Desai, Ankita R; Patel, Akanksha S; Ranch, Ketan M; Vyas, Bhavin A; Shah, Dinesh O

2017-09-01

In the present work a novel cyclosporine-loaded Eudragit S100 (pH-sensitive) nanoparticles-laden contact lenses were designed to provide sustained release of cyclosporine at therapeutic rates, without leaching of drug during sterilization and storage period (shelf life). The nanoparticles were prepared by Quasi-emulsion solvent diffusion technique using different weight ratios of cyclosporine to Eudragit S100. The contact lenses with direct drug entrapment were also fabricated (DL-50) for comparison. The percentage swelling and optical transparency of nanoparticles-laden contact lenses were improved in comparison to DL-50 lenses. The nanoparticles-laden contact lenses showed sustained drug release profiles, with inverse relationship to the amount of nanoparticles loaded in the contact lenses. It was interesting to note that nanoparticles form nanochannels/cavities after dissolution of Eudragit S 100 in tear fluid pH=7.4 (in vitro release study). This followed the precipitation of drug in hydrogel matrix of contact lenses. As the amount of nanoparticles loading increased, more number of cavities were formed, which caused the formation of large cavities in contact lens matrix. This in turn precipitated the drug. The nanoparticles-laden contact lenses with 1:1 (drug: Eudragit) weight ratio showed the most promising results of sustaining the drug release up to 156h, without affecting optical and physical properties of contact lenses. Packaging study confirmed that the drug was not leached in packaging solution (buffer, pH=6.5) from nanoparticles-laden lenses during shelf life period. In-vivo study in rabbit tear fluid showed sustained release up to 14days. The study revealed the application of pH-sensitive nanoparticles-laden contact lenses for controlled release of cyclosporine without altering the optical and physical properties of lens material. Copyright © 2017 Elsevier B.V. All rights reserved.

Removal of vertigo blue dyes from Batik textile wastewater by adsorption onto activated carbon and coal bottom ash

NASA Astrophysics Data System (ADS)

Kusmiyati, L., Puspita Adi; Deni, V.; Robi Indra, S.; Islamica, Dlia; Fuadi, M.

2016-04-01

Removal of vertigo blue dye from batik textile wastewater was studied by adsorptionprocess onto activated carbon (AC) and coal bottom ash (CBA).The influence of experimental conditions (pH solution, dye concentration, and contact time) were studied on the both adsorbents. At equilibrium conditions, the data were fitted to Langmuir and Freundlich adsorption models. The maximum adsorption capacity calculated from the Langmuir model for carbon active was 6.29mg/g at pH that found to be considerably higher than that obtained for coal bottom ash 3.72mg/g pH 9. From Freundlich model, the maximum adsorption capacity is less for coal bottom ash (pH 9) than that for carbon active (pH4).

Comparative uptake study of arsenic, boron, copper, manganese and zinc from water by different green microalgae.

PubMed

Saavedra, Ricardo; Muñoz, Raúl; Taboada, María Elisa; Vega, Marisol; Bolado, Silvia

2018-04-26

This work represents a comparative uptake study of the toxic elements arsenic, boron, copper, manganese and zinc in monometallic and multimetallic solutions by four green microalgae species (Chlamydomonas reinhardtii, Chlorella vulgaris, Scenedesmus almeriensis and an indigenous Chlorophyceae spp.), evaluating the effect of pH and contact time. Maximum removal efficiencies for each toxic element were 99.4% for Mn (C. vulgaris, pH 7.0, 3 h), 91.9% for Zn (Chlorophyceae spp., pH 5.5, 3 h), 88% for Cu (Chlorophyceae spp., pH 7.0, 10 min), 40.7% for As (S. almeriensis, pH 9.5, 3 h) and 38.6% for B (S. almeriensis, pH 5.5, 10 min). B removal efficiencies decreased remarkably in multimetallic solutions (down to 0.2% in C. reinhardtii), except for Chlorophyceae spp., the only species isolated from a polluted environment. FTIR spectra shown the highest interactions for As (1150-1300 cm -1 ) and Cu (3300, 1741, 1535, 1350-1400 cm -1 ). Results confirm microalgae biomass as a potential biosorbent for toxic elements. Copyright © 2018 Elsevier Ltd. All rights reserved.

pH and Protein Sensing with Functionalized Semiconducting Oxide Nanobelt FETs

NASA Astrophysics Data System (ADS)

Cheng, Yi; Yun, C. S.; Strouse, G. F.; Xiong, P.; Yang, R. S.; Wang, Z. L.

2008-03-01

We report solution pH sensing and selective protein detection with high-performance channel-limited field-effect transistors (FETs) based on single semiconducting oxide (ZnO and SnO2) nanobelts^1. The devices were integrated with PDMS microfluidic channels for analyte delivery and the source/drain contacts were passivated for in-solution sensing. pH sensing experiments were performed on FETs with functionalized and unmodified nanobelts. Functionalization of the nanobelts by APTES was found to greatly improve the pH sensitivity. The change in nanobelt conductance as functions of pH values at different gate voltages and ionic strengths showed high sensitivity and consistency. For the protein detection, we achieved highly selective biotinylation of the nanobelt channel with through APTES linkage. The specific binding of fluorescently-tagged streptavidin to the biotinylated nanobelt was verified by fluorescence microscopy; non-specific binding to the substrate was largely eliminated using PEG-silane passivation. The electrical responses of the biotinylated FETs to the streptavidin binding in PBS buffers of different pH values were systematically measured. The results will be presented and discussed. ^1Y. Cheng et al., Appl. Phys. Lett. 89, 093114 (2006). *Supported by NSF NIRT Grant ECS-0210332.

Mercury removal from aqueous solutions by zinc cementation.

PubMed

Ku, Young; Wu, Ming-Huan; Shen, Yung-Shen

2002-01-01

The main purpose of this research is to study the addition effect of the surfactant and other operating factors on the treatment of wastewater containing mercury ions in aqueous solution by cementation with sacrificing metal, zinc. The removal of mercury ions from aqueous solutions by cementation of zinc powder was found to be a function of solution pH and temperature, amount of zinc, concentration of mercury ion, contact time and the addition of several organic surfactants. Cementation of mercury was shown to be a feasible process to achieve a very high degree of mercury removal over a broad operational range within a fairly reasonable contact time. The reaction rate is approximately first order with respect to the concentration of mercury ion in aqueous solution. Among the surfactants used in this study, only the presence of SDS, an anionic surfactant, slightly enhanced the cementation rate of mercury. The presence of CTAB and Triton-X100 retarded the cementation of mercury by zinc.

Evidence for the contribution of multiple mechanisms in the feeding pattern of rats exposed to p-chloro-diphenyl diselenide-supplemented diets.

PubMed

Bortolatto, Cristiani F; Heck, Suélen O; Zborowski, Vanessa A; Gai, Bibiana M; Neto, José S S; Nogueira, Cristina W

2015-11-01

Preliminary findings suggest that food intake reduction induced by p-chloro-diphenyl diselenide [(p-ClPhSe)2] in rats is mediated by a satiating action; however, additional experiments are necessary to clarify its actions. The purpose of this study was to investigate the effects of diets supplemented with (p-ClPhSe)2 on feeding behavior of rats as well as the (p-ClPhSe)2 effectiveness in producing aversive reactions or specific flavor. The results demonstrated that behavioral satiety sequence (BSS) was preserved in animals exposed to (p-ClPhSe)2-supplemented diets (0.01 and 0.1%) and associated with a shift of the onset of resting to the left indicating a satiating action at the first contact. In addition, the frequency, the mean duration and the mean size of meals were decreased in rats exposed to a 0.1% (p-ClPhSe)2 diet. Alternatively, a second contact with a 0.01% (p-ClPhSe)2 diet caused disruption of BSS and pronounced changes in the meal pattern, suggesting that it produces aversiveness. In fact, rats developed a significant taste aversion to the saccharin solution after receiving the administration of (p-ClPhSe)2 (1 and 10mg/kg; i.p.). Lastly, a diet containing 0.1% of (p-ClPhSe)2 seems to alter the palatability of food given that rats had a preference for the control diet. The findings of the present study suggest that (p-ClPhSe)2 reduced the food intake of rats by inducing a satiating action at the first contact, but it also produced aversive reactions when rats were re-exposed to it. A specific flavor seems also to contribute to (p-ClPhSe)2 suppressant effects on feeding. Copyright © 2015 Elsevier Inc. All rights reserved.

Investigation of the erosive potential of sour novelty sweets.

PubMed

Aljawad, A; Morgan, M Z; Fairchild, R; Rees, J S

2017-04-21

Background The expansion of the novelty sweets market in the UK has major potential public health implications in children and young adults as they may cause dental erosion.Objective To investigate the erosive potential of the novelty sweets in term of their physiochemical properties and amount of enamel loss.Subjects and methods The pH of a variety of novelty sweets was tested in vitro using a pH meter and the neutralisable acidity was assessed by titrating the sweets against 0.1M NaOH. The viscosity of the novelty sweets was measured using a rotational viscometer. The wettability of enamel by each sweet was measured using dynamic contact angle analyser. Enamel loss was assessed using contact profilometry.Results The pH ranged from 1.8-3.2, the neutralisable acidity ranged from 9-201 ml of 0.1 NaOH. The viscosity of the novelty sweets that come in liquid form ranged from 2-594 mPa s. The surface enamel erosion ranged from 1.95-15.77 μm and from 2.5-17.6 μm with and without immersing in saliva for 1 hour before immersing in acidic solution respectively. The amount of subsurface enamel loss was ranged from 0.75 to 2.3 μm following ultrasonication at 0 min of acidic attack and from 0.23 to 0.85 μm at 60 minutes of acidic attack while immersed in saliva. The contact angle between enamel surface and four sweet was less than the angle formed between the orange juice and the enamel which caused more wettability of enamel.Conclusion The pH is lower than the critical value for enamel erosion (5.5), high neutralisable acidity and high sugar content strongly suggest that these sweets may cause significant amount of dental erosion clinically. In addition, the degree of wettability of enamel by solution is an important factor to consider in determining the enamel loss caused by acidic solution. Immediate tooth brushing would cause further enamel loss as a result of the mechanical removal of softened enamel. However, it has been suggested that postponing brushing after erosive attack should be reconsidered.

pH-Manipulated Underwater-Oil Adhesion Wettability Behavior on the Micro/Nanoscale Semicircular Structure and Related Thermodynamic Analysis.

PubMed

Tie, Lu; Guo, Zhiguang; Liu, Weimin

2015-05-20

Controlling oil of wettability behavior in response to the underwater out stimulation has shown promising applications in understanding and designing novel micro- or nanofluidic devices. In this article, the pH-manipulated underwater-oil adhesion wetting phenomenon and superoleophobicity on the micro- and nanotexture copper mesh films (CMF) were investigated. It should be noted that the surface exhibits underwater superoleophobicity under different pH values of the solution; however, the underwater-oil adhesion behavior on the surface is dramatically influenced by the pH value of the solution. On the basis of the thermodynamic analysis, a plausible mechanism to explain the pH-controllable underwater-oil adhesion and superoleophobic wetting behavior observed on a micro- and nanoscale semicircular structure has been revealed. Furthermore, variation of chemistry (intrinsic oil contact angle (OCA)) of the responsive surface that due to the carboxylic acid groups is protonated or deprotonated by the acidic or basic solution on free energy (FE) with its barrier (FEB) and equilibrium oil contact angle (EOCA) with it hysteresis (OCAH) are discussed. The result shows that a critical intrinsic OCA on the micro- and nano- semicircular texture is necessary for conversion from the oil Cassie impregnating to oil Cassie wetting state. In a water/oil/solid system, the mechanism reveals that the differences between the underwater OCA and oil adhesive force of the responsive copper mesh film under different pH values of solution are ascribed to the different oil wetting state that results from combining the changing intrinsic OCA and micro-/nanosemicircular structures. These results are well in agreement with the experiment.

Recovery of germanium-68 from irradiated targets

DOEpatents

Phillips, Dennis R.; Jamriska, Sr., David J.; Hamilton, Virginia T.

1993-01-01

A process for selective separation of germanium-68 from proton irradiated molybdenum targets is provided and includes dissolving the molybdenum target in a hydrogen peroxide solution to form a first ion-containing solution, contacting the first ion-containing solution with a cationic resin whereby ions selected from the group consisting of molybdenum, niobium, technetium, selenium, vanadium, arsenic, germanium, zirconium and rubidium remain in a second ion-containing solution while ions selected from the group consisting of rubidium, zinc, beryllium, cobalt, iron, manganese, chromium, strontium, yttrium and zirconium are selectively adsorbed by the first resin, adjusting the pH of the second ion-containing solution to within a range of from about 0.7 to about 3.0, adjusting the soluble metal halide concentration in the second ion-containing solution to a level adapted for subsequent separation of germanium, contacting the pH-adjusted, soluble metal halide-containing second ion-containing solution with a dextran-based material whereby germanium ions are separated by the dextran-based material, and recovering the germanium from the dextran-based material, preferably by distillation.

Directed spatial organization of zinc oxide nanostructures

DOEpatents

Hsu, Julia [Albuquerque, NM; Liu, Jun [Richland, WA

2009-02-17

A method for controllably forming zinc oxide nanostructures on a surface via an organic template, which is formed using a stamp prepared from pre-defined relief structures, inking the stamp with a solution comprising self-assembled monolayer (SAM) molecules, contacting the stamp to the surface, such as Ag sputtered on Si, and immersing the surface with the patterned SAM molecules with a zinc-containing solution with pH control to form zinc oxide nanostructures on the bare Ag surface.

Batch and continuous (fixed-bed column) biosorption of crystal violet by Artocarpus heterophyllus (jackfruit) leaf powder.

PubMed

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

2012-04-01

In this study, batch and fixed-bed column experiments were performed to investigate the biosorption potential of Artocarpus heterophyllus (jackfruit) leaf powder (JLP) to remove crystal violet (CV) from aqueous solutions. Batch biosorption studies were carried out as a function of solution pH, contact time, initial dye concentration and temperature. The biosorption equilibrium data showed excellent fit to the Langmuir isotherm model with maximum monolayer biosorption capacity of 43.39 mg g(-1) at pH 7.0, initial dye concentration=50 mg L(-1), temperature=293 K and contact time=120 min. According to Dubinin-Radushkevich (D-R) isotherm model, biosorption of CV by JLP was chemisorption. The biosorption kinetics followed the pseudo-second-order kinetic model. Thermodynamic analysis revealed that biosorption of CV from aqueous solution by JLP was a spontaneous and exothermic process. In order to ascertain the practical applicability of the biosorbent, fixed-bed column studies were also performed. The breakthrough time increased with increasing bed height and decreased with increasing flow rate. The Thomas model as well as the BDST model showed good agreement with the experimental results at all the process parameters studied. It can be concluded that JLP is a promising biosorbent for removal of CV from aqueous solutions. Copyright © 2011 Elsevier B.V. All rights reserved.

[Active carbon from Thalia dealbata residues: its preparation and adsorption performance to crystal violet].

PubMed

Chu, Shu-Yi; Yang, Min; Xiao, Ji-Bo; Zhang, Jun; Zhu, Yan-Ping; Yan, Xiang-Jun; Tian, Guang-Ming

2013-06-01

By using phosphoric acid as activation agent, active carbon was prepared from Thalia dealbata residues. The BET specific surface area of the active carbon was 1174.13 m2 x g(-1), micropore area was 426.99 m2 x g(-1), and average pore diameter was 3.23 nm. An investigation was made on the adsorption performances of the active carbon for crystal violet from aqueous solution under various conditions of pH, initial concentration of crystal violet, contact time, and contact temperature. It was shown that the adsorbed amount of crystal violet was less affected by solution pH, and the adsorption process could be divided into two stages, i. e., fast adsorption and slow adsorption, which followed the pseudo-second-order kinetics model. At the temperature 293, 303, and 313 K, the adsorption process was more accordance with Langmuir isotherm model, and the maximum adsorption capacity was 409.83, 425.53, and 438.59 mg x g(-1), respectively. In addition, the adsorption process was spontaneous and endothermic, and the randomness of crystal violet molecules increased.

Bioprospecting of gum kondagogu (Cochlospermum gossypium) for bioremediation of uranium (VI) from aqueous solution and synthetic nuclear power reactor effluents.

PubMed

Sashidhar, R B; Selvi, S Kalaignana; Vinod, V T P; Kosuri, Tanuja; Raju, D; Karuna, R

2015-10-01

An ecofriendly green chemistry method using a natural biopolymer, Gum Kondagogu (GK) for the removal of U (VI) from aqueous, simulated nuclear effluents was studied. The adsorption characteristic of GK towards U (VI) from aqueous solution was studied at varied pH, contact time, adsorbent dose, initial U (VI) concentration and temperature using UV-Visible spectroscopy and ICP-MS. Maximum adsorption was seen at pH 4, 0.1% GK with 60 min contact time at room temperature. The GK- U (VI) composite was characterized by FT-IR, zeta potential, TEM and SEM-EDAX. The Langmuir isotherm was found to be 487 mg of U (VI) g(-1) of GK. The adsorption capacity and (%) of U (VI) was found to be 490 ± 5.4 mg g(-1) and 98.5%. Moreover adsorption of U (VI) by GK was not influenced by other cations present in the simulated effluents. The adsorbed U (VI) was efficiently stripped from composite using 1 M HCl. Copyright © 2015 Elsevier Ltd. All rights reserved.

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.

Elastohydrodynamic lubrication of point contacts. Ph.D. Thesis - Leeds Univ.

NASA Technical Reports Server (NTRS)

Hamrock, B. J.

1976-01-01

A procedure for the numerical solution of the complete, isothermal, elastohydrodynamic lubrication problem for point contacts is given. This procedure calls for the simultaneous solution of the elasticity and Reynolds equations. By using this theory the influence of the ellipticity parameter and the dimensionless speed, load, and material parameters on the minimum and central film thicknesses was investigated. Thirty-four different cases were used in obtaining the fully flooded minimum- and central-film-thickness formulas. Lubricant starvation was also studied. From the results it was possible to express the minimum film thickness for a starved condition in terms of the minimum film thickness for a fully flooded condition, the speed parameter, and the inlet distance. Fifteen additional cases plus three fully flooded cases were used in obtaining this formula. Contour plots of pressure and film thickness in and around the contact have been presented for both fully flooded and starved lubrication conditions.

Use of UO 2 films for electrochemical studies

NASA Astrophysics Data System (ADS)

Miserque, F.; Gouder, T.; Wegen, D. H.; Bottomley, P. D. W.

2001-10-01

UO 2 films have been prepared by dc reactive sputtering of a uranium metal target in an Ar/O 2 atmosphere. We have used the films deposited on gold substrates as working electrodes for electrochemical investigations as simulating the surfaces of fuel pellets. Film composition was determined by photoelectron spectroscopy (XPS and UPS) and X-ray diffraction (XRD). The oxide stoichiometry as a function of deposition conditions was determined and the appropriate conditions for UO 2.0 formation established. AC impedance and cyclic voltammetry measurements were performed. A double RC electrical equivalent circuit was used to fit the data from impedance measurements, similar to those used in unirradiated UO 2 or spent fuel pellets. However due to the porosity or adhesion defects on the thin films that permitted a direct contact between the solution and the gold substrate, we were obliged to add a contribution simulating the water-gold system. Cyclic voltammetry measurements show the influence of pH on the dissolution mechanism. Alkaline solutions permit the formation of an oxidised layer (UO 2.33) which is not present in the acidic solutions. In both pH=2 and pH=6 solutions, a U VI species layer is formed.

Biotherapeutic formulation factors affecting metal leachables from stainless steel studied by design of experiments.

PubMed

Zhou, Shuxia; Evans, Brad; Schöneich, Christian; Singh, Satish K

2012-03-01

Trace amounts of metals are inevitably present in biotherapeutic products. They can arise from various sources. The impact of common formulation factors such as protein concentration, antioxidant, metal chelator concentration and type, surfactant, pH, and contact time with stainless steel on metal leachables was investigated by a design of experiments approach. Three major metal leachables, iron, chromium, and nickel were monitored by inductively coupled plasma-mass spectrometry. It was observed that among all the tested factors, contact time, metal chelator concentration, and protein concentration were statistically significant factors with higher temperature resulting in higher levels of leached metals. Within a pH range of 5.5-6.5, solution pH played a minor role for chromium leaching at 25°C. No statistically significant difference was observed due to type of chelator, presence of antioxidant, or surfactant. In order to optimize a biotherapeutic formulation to achieve a target drug product shelf life with acceptable quality, each formulation component must be evaluated for its impact.

Adsorption characteristics of sol gel-derived zirconia for cesium ions from aqueous solutions.

PubMed

Yakout, Sobhy M; Hassan, Hisham S

2014-07-01

Zirconia powder was synthesized via a sol gel method and placed in a batch reactor for cesium removal investigation. X-ray analysis and Fourier transform infrared spectroscopy were utilized for the evaluation of the developed adsorbent. The adsorption process has been investigated as a function of pH, contact time and temperature. The adsorption is strongly dependent on the pH of the medium whereby the removal efficiency increases as the pH turns to the alkaline range. The process was initially very fast and the maximum adsorption was attained within 60 min of contact. A pseudo-second-order model and homogeneous particle diffusion model (HPDM) were found to be the best to correlate the diffusion of cesium into the zirconia particles. Furthermore, adsorption thermodynamic parameters, namely the standard enthalpy, entropy, and Gibbs free energy, were calculated. The results indicate that cesium adsorption by zirconia is an endothermic (ΔH>0) process and good affinity of cesium ions towards the sorbent (ΔS>0) was observed.

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.

Heavy Metals Biosorption from Aqueous Solution by Endophytic Drechslera hawaiiensis of Morus alba L. Derived from Heavy Metals Habitats

PubMed Central

Hassanein, Naziha M.; Abd El-Hay Ibrahim, Hussein; Abd El-Baky, Doaa H.

2017-01-01

The ability of dead cells of endophytic Drechslera hawaiiensis of Morus alba L. grown in heavy metals habitats for bioremoval of cadmium (Cd2+), copper (Cu2+), and lead (Pb2+) in aqueous solution was evaluated under different conditions. Whereas the highest extent of Cd2+ and Cu2+ removal and uptake occurred at pH 8 as well as Pb2+ occurred at neutral pH (6–7) after equilibrium time 10 min. Initial concentration 30 mg/L of Cd2+ for 10 min contact time and 50 to 90 mg/L of Pb2+ and Cu2+ supported the highest biosorption after optimal contact time of 30 min achieved with biomass dose equal to 5 mg of dried died biomass of D. hawaiiensis. The maximum removal of Cd2+, Cu2+, and Pb2+ equal to 100%, 100%, and 99.6% with uptake capacity estimated to be 0.28, 2.33, and 9.63 mg/g from real industrial wastewater, respectively were achieved within 3 hr contact time at pH 7.0, 7.0, and 6.0, respectively by using the dead biomass of D. hawaiiensis compared to 94.7%, 98%, and 99.26% removal with uptake equal to 0.264, 2.3, and 9.58 mg/g of Cd2+, Cu2+, and Pb2+, respectively with the living cells of the strain under the same conditions. The biosorbent was analyzed by Fourier Transformer Infrared Spectroscopy (FT-IR) analysis to identify the various functional groups contributing in the sorption process. From FT-IR spectra analysis, hydroxyl and amides were the major functional groups contributed in biosorption process. It was concluded that endophytic D. hawaiiensis biomass can be used potentially as biosorbent for removing Cd2+, Cu2+, and Pb2+ in aqueous solutions. PMID:28781539

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.

Removal of arsenic, vanadium, and/or nickel compounds from petroliferous liquids

DOEpatents

Fish, R.H.

1985-05-17

Described is a process for removing arsenic, vanadium, and/or nickel from petroliferous derived liquids (shale oil, SRC, etc.) by contacting said liquid at an elevated temperature with a divinylbenzene-crosslinked polystyrene having catechol ligands anchored thereon. For vanadium and nickel removal an amine, preferably a diamine is included. Also, described is a process for regenerating spent catecholated polystyrene by removal of the arsenic, vanadium, and/or nickel bound to it from contacting petroliferous liquid as described above and involves: treating the spent polymer containing any vanadium and/or nickel with an aqueous acid to achieve an acid pH; and, separating the solids from the liquid; and then treating said spent catecholated polystyrene, at a temperature in the range of about 20/sup 0/ to 100/sup 0/C with an aqueous solution of at least one carbonate and/or bicarbonate of ammonium, alkali and alkaline earth metals, said solution having a pH between about 8 and 10; and, separating the solids and liquids from each other. Preferably the regeneration treatment of arsenic containing catecholated polymer is in two steps wherein the first step is carried out with an aqueous alcoholic carbonate solution containing lower alkyl alcohol, and, the steps are repeated using a bicarbonate.

Oil/water/rock wettability: Influencing factors and implications for low salinity water flooding in carbonate reservoirs

DOE PAGES

Chen, Yongqiang; Xie, Quan; Sari, Ahmad; ...

2017-11-21

Wettability of the oil/brine/rock system is an essential petro-physical parameter which governs subsurface multiphase flow behaviour and the distribution of fluids, thus directly affecting oil recovery. Recent studies [1–3] show that manipulation of injected brine composition can enhance oil recovery by shifting wettability from oil-wet to water-wet. However, what factor(s) control system wettability has not been completely elucidated due to incomplete understanding of the geochemical system. To isolate and identify the key factors at play we used in this paper SO 4 2—free solutions to examine the effect of salinity (formation brine/FB, 10 times diluted formation brine/10 dFB, and 100more » times diluted formation brine/100 dFB) on the contact angle of oil droplets at the surface of calcite. We then compared contact angle results with predictions of surface complexation by low salinity water using PHREEQC software. We demonstrate that the conventional dilution approach likely triggers an oil-wet system at low pH, which may explain why the low salinity water EOR-effect is not always observed by injecting low salinity water in carbonated reservoirs. pH plays a fundamental role in the surface chemistry of oil/brine interfaces, and wettability. Our contact angle results show that formation brine triggered a strong water-wet system (35°) at pH 2.55, yet 100 times diluted formation brine led to a strongly oil-wet system (contact angle = 175°) at pH 5.68. Surface complexation modelling correctly predicted the wettability trend with salinity; the bond product sum ([>CaOH 2 +][–COO -] + [>CO 3 -][–NH +] + [>CO 3 -][–COOCa +]) increased with decreasing salinity. Finally, at pH < 6 dilution likely makes the calcite surface oil-wet, particularly for crude oils with high base number. Yet, dilution probably causes water wetness at pH > 7 for crude oils with high acid number.« less

Oil/water/rock wettability: Influencing factors and implications for low salinity water flooding in carbonate reservoirs

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

Chen, Yongqiang; Xie, Quan; Sari, Ahmad

Wettability of the oil/brine/rock system is an essential petro-physical parameter which governs subsurface multiphase flow behaviour and the distribution of fluids, thus directly affecting oil recovery. Recent studies [1–3] show that manipulation of injected brine composition can enhance oil recovery by shifting wettability from oil-wet to water-wet. However, what factor(s) control system wettability has not been completely elucidated due to incomplete understanding of the geochemical system. To isolate and identify the key factors at play we used in this paper SO 4 2—free solutions to examine the effect of salinity (formation brine/FB, 10 times diluted formation brine/10 dFB, and 100more » times diluted formation brine/100 dFB) on the contact angle of oil droplets at the surface of calcite. We then compared contact angle results with predictions of surface complexation by low salinity water using PHREEQC software. We demonstrate that the conventional dilution approach likely triggers an oil-wet system at low pH, which may explain why the low salinity water EOR-effect is not always observed by injecting low salinity water in carbonated reservoirs. pH plays a fundamental role in the surface chemistry of oil/brine interfaces, and wettability. Our contact angle results show that formation brine triggered a strong water-wet system (35°) at pH 2.55, yet 100 times diluted formation brine led to a strongly oil-wet system (contact angle = 175°) at pH 5.68. Surface complexation modelling correctly predicted the wettability trend with salinity; the bond product sum ([>CaOH 2 +][–COO -] + [>CO 3 -][–NH +] + [>CO 3 -][–COOCa +]) increased with decreasing salinity. Finally, at pH < 6 dilution likely makes the calcite surface oil-wet, particularly for crude oils with high base number. Yet, dilution probably causes water wetness at pH > 7 for crude oils with high acid number.« less

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.

Removal of Cd (II) from water using the waste of jatropha fruit ( Jatropha curcas L.)

NASA Astrophysics Data System (ADS)

Nacke, Herbert; Gonçalves, Affonso Celso; Coelho, Gustavo Ferreira; Schwantes, Daniel; Campagnolo, Marcelo Angelo; Leismann, Eduardo Ariel Völz; Junior, Élio Conradi; Miola, Alisson Junior

2017-10-01

The aim of this work was to evaluate the removal of Cd (II) from water using three biosorbents originated from the biomass of jatropha (bark, endosperm, and endosperm + tegument). For that, batch tests were performed to verify the effect of solution pH, adsorbent mass, contact time, initial concentration of Cd (II), and the temperature of the process. The adsorption process was evaluated by the studies of kinetics, isotherms, and thermodynamics. The ideal conditions of solution pH were 5.5 and 8 g L-1 of adsorbent mass of biosorbents by solution volume, with an equilibrium time of 60 min. According to the Langmuir model, the maximum adsorption capacity for bark, endosperm, and bark + endosperm of jatropha was, respectively, 29.665, 19.562, and 34.674 mg g-1, predominating chemisorption in monolayers. The biosorbents presented potential for the remediation of waters contaminated with Cd (II).

Adsorptive removal of patulin from aqueous solution using thiourea modified chitosan resin.

PubMed

Liu, Bingjie; Peng, Xiaoning; Chen, Wei; Li, Yang; Meng, Xianghong; Wang, Dongfeng; Yu, Guangli

2015-09-01

In the present paper, thiourea modified chitosan resin (TMCR) was firstly prepared through converting hydroxyl groups of chitosan resin into thiol groups, using glutaraldehyde as cross-linking agent and thiourea as modification agent. TMCR was characterized by FTIR, EDXS, SEM, XRD and AFM technologies. Batch adsorption experiments were performed to study the adsorption capacity of TMCR for patulin at different pH, temperature, contact time and patulin concentration. The result showed that TMCR was effective in removal of patulin from aqueous solution. The adsorption capacity of TMCR for patulin was 1.0 mg/g at pH 4.0, 25 °C for 24 h. Adsorption process could be well described by pseudo-first order model, Freundlich isotherm model and intraparticle diffusion model. It indicated that TMCR is expected to be a new material for patulin adsorption from aqueous solutions. Copyright © 2015 Elsevier B.V. All rights reserved.

Influence of an americium solid phase on americium concentrations in solutions

NASA Astrophysics Data System (ADS)

Rai, Dhanpat; Strickert, R. G.; Moore, D. A.; Serne, R. J.

1981-11-01

Americium-241 concentrations in solutions contacting contaminated sediments for up to 2 yr were measured as a function of pH. Steady-state concentrations were reached within a few days. The solubility-limited Am concentration was found to decrease approximately 10-fold with one unit increase in pH. The log equilibrium constant for the solubility of Am (soil) solid [Am (soil) + H + ⇌ Am (aq complex)+] was found to be -4.12. The predictions based upon thermodynamic data suggest that Am (aq complex)+ is likely to be Am(OH) 2+. Although the chemical formula of Am (soil) was not determined, it does not appear to be Am(OH) 3(a). Published data on sorption coefficients of Am by different rocks, soils, and minerals were critically evaluated. Final Am solution concentrations calculated from the sorption coefficients of a variety of earth materials with several solutions agreed well with the concentrations predicted from the solubility of Am (soil) solid, indicating that the sorption coefficient data are controlled by Am precipitation.

Method of removing nitrogen monoxide from a nitrogen monoxide-containing gas using a water-soluble iron ion-dithiocarbamate, xanthate or thioxanthate

DOEpatents

Liu, D. Kwok-Keung; Chang, Shih-Ger

1987-08-25

The present invention relates to a method of removing of nitrogen monoxide from a nitrogen monoxide-containing gas which method comprises contacting a nitrogen oxide-containing gas with an aqueous solution of water soluble organic compound-iron ion chelate complex. The NO absorption efficiency of ferrous urea-dithiocarbamate and ferrous diethanolamine-xanthate as a function of time, oxygen content and solution ph is presented. 3 figs., 1 tab.

Removal of arsenic compounds from spent catecholated polymer

DOEpatents

Fish, Richard H.

1985-01-01

Described is a process for removing arsenic from petroliferous derived liquids by contacting said liquid at an elevated temperature with a divinylbenzene-crosslinked polystyrene having catechol ligands anchored thereon. Also, described is a process for regenerating spent catecholated polystyrene by removal of the arsenic bound to it from contacting petroliferous liquid as described above and involves: a. treating said spent catecholated polystyrene, at a temperature in the range of about 20.degree. to 100.degree. C. with an aqueous solution of at least one carbonate and/or bicarbonate of ammonium, alkali and alkaline earth metals, said solution having a pH between about 8 and 10 and, b. separating the solids and liquids from each other. Preferably the regeneration treatment is in two steps wherein step (a) is carried out with an aqueous alcoholic carbonate solution containing lower alkyl alcohol, and, steps (a) and (b) are repeated using a bicarbonate.

Removal of arsenic compounds from petroliferous liquids

DOEpatents

Fish, Richard H.

1985-01-01

Described is a process for removing arsenic from petroliferous derived liquids by contacting said liquid at an elevated temperature with a divinylbenzene-crosslinked polystyrene having catechol ligands anchored thereon. Also, described is a process for regenerating spent catecholated polystyrene by removal of the arsenic bound to it from contacting petroliferous liquid as described above and involves: a. treating said spent catecholated polystyrene, at a temperature in the range of about 20.degree. to 100.degree. C. with an aqueous solution of at least one carbonate and/or bicarbonate of ammonium, alkali and alkaline earth metals, said solution having a pH between about 8 and 10 and, b. separating the solids and liquids from each other. Preferably the regeneration treatment is in two steps wherein step (a) is carried out with an aqueous alcoholic carbonate solution containing lower alkyl alcohol, and, steps (a) and (b) are repeated using a bicarbonate.

Method of forming dynamic membrane on stainless steel support

NASA Technical Reports Server (NTRS)

Gaddis, Joseph L. (Inventor); Brandon, Craig A. (Inventor)

1988-01-01

A suitable member formed from sintered, powdered, stainless steel is contacted with a nitrate solution of a soluble alkali metal nitrate and a metal such as zirconium in a pH range and for a time sufficient to effect the formation of a membrane of zirconium oxide preferably including an organic polymeric material such as polyacrylic acid.

Macroion induced dehydration of weak polyelectrolyte brushes

NASA Astrophysics Data System (ADS)

Zheng, Zhongli; Zhu, Y. Elaine

2014-03-01

The interaction of macroions, including polyelectrolytes, DNAs, and proteins, with polymer and cellular surfaces is critically related to many biomolecular activities, such as protein adsorption and DNA hybridization at probe surfaces. In an experimental approach to examine the macroion electrostatic interaction with a polymer surface while minimizing the long-debated hydrophobic interaction, we study the interaction of molybdenum-based inorganic polyoxometalate (POM) nanoclusters carrying 42 negative charges as model hydrophilic macroions with surface-tethered poly-2-vinylpyridine (P2VP) brushes immersed in aqueous solutions. By AFM, QCM, and contact goniometer, we have observed the collapse of P2VP chains by adding POM macroions at a constant pH. Surprisingly, added POM macroions can cause the shift of swollen-to-collapse transition pH to a lower value, in contrast to the shift to high pH value by adding simple monovalent salts. At sufficiently high POM concentration, a stable POM-P2VP composite layer, showing little dependence on solution pH and additional salts, can be formed, suggesting a simple route to construct meso-porous polymer membranes.

Bias-stress characterization of solution-processed organic field-effect transistor based on highly ordered liquid crystals

NASA Astrophysics Data System (ADS)

Kunii, M.; Iino, H.; Hanna, J.

2017-06-01

Bias-stress effects in solution-processed, 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10) field effect transistors (FETs) are studied under negative and positive direct current bias. The bottom gate, bottom contact polycrystalline Ph-BTBT-10 FET with a hybrid gate dielectric of polystyrene and SiO2 shows high field effect mobility as well as a steep subthreshold slope when fabricated with a highly ordered smectic E liquid crystalline (SmE) film as a precursor. Negative gate bias-stress causes negative threshold voltage shift (ΔVth) for Ph-BTBT-10 FET in ambient air, but ΔVth rapidly decreases as the gate bias decreases and approaches to near zero when the gate bias goes down to 9 V in amplitude. In contrast, positive gate bias-stress causes negligible ΔVth even with a relatively high bias voltage. These results conclude that Ph-BTBT-10 FET has excellent bias-stress stability in ambient air in the range of low to moderate operating voltages.

Preparation of low cost activated carbon from Myrtus communis and pomegranate and their efficient application for removal of Congo red from aqueous solution

NASA Astrophysics Data System (ADS)

Ghaedi, Mehrorang; Tavallali, Hossein; Sharifi, Mahdi; Kokhdan, Syamak Nasiri; Asghari, Alireza

2012-02-01

In this research, the potential applicability of activated carbon prepared from Myrtus communis (AC-MC) and pomegranate (AC-PG) as useful adsorbents for the removal of Congo red (CR) from aqueous solutions in batch method was investigated. The effects of pH, contact time, agitation time and amount of adsorbents on removal percentage of Congo red on both adsorbents were examined. Increase in pH up to 6 for AC-MC and pH 7 for AC-PG increase the adsorption percentage (capacity) and reach equilibrium within 30 min of contact time. Fitting the experimental data to conventional isotherm models like Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich show that the experimental data fitted very well to the Freundlich isotherm for AC-MC and Langmuir isotherm for AC-PG. Fitting the experimental data to different kinetic models such as pseudo first-order, pseudo second-order, Elovich and intraparticle diffusion mechanism showed the applicability of a pseudo second-order with involvement of intraparticle diffusion model for interpretation of experimental data for both adsorbents. The adsorption capacity of AC-PG and AC-MC for the removal of CR was found to be 19.231 and 10 mg g -1. These results clearly indicate the efficiency of adsorbents as a low cost adsorbent for treatment of wastewater containing CR.

Preparation of low cost activated carbon from Myrtus communis and pomegranate and their efficient application for removal of Congo red from aqueous solution.

PubMed

Ghaedi, Mehrorang; Tavallali, Hossein; Sharifi, Mahdi; Kokhdan, Syamak Nasiri; Asghari, Alireza

2012-02-01

In this research, the potential applicability of activated carbon prepared from Myrtus communis (AC-MC) and pomegranate (AC-PG) as useful adsorbents for the removal of Congo red (CR) from aqueous solutions in batch method was investigated. The effects of pH, contact time, agitation time and amount of adsorbents on removal percentage of Congo red on both adsorbents were examined. Increase in pH up to 6 for AC-MC and pH 7 for AC-PG increase the adsorption percentage (capacity) and reach equilibrium within 30 min of contact time. Fitting the experimental data to conventional isotherm models like Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich show that the experimental data fitted very well to the Freundlich isotherm for AC-MC and Langmuir isotherm for AC-PG. Fitting the experimental data to different kinetic models such as pseudo first-order, pseudo second-order, Elovich and intraparticle diffusion mechanism showed the applicability of a pseudo second-order with involvement of intraparticle diffusion model for interpretation of experimental data for both adsorbents. The adsorption capacity of AC-PG and AC-MC for the removal of CR was found to be 19.231 and 10 mg g(-1). These results clearly indicate the efficiency of adsorbents as a low cost adsorbent for treatment of wastewater containing CR. Copyright © 2011 Elsevier B.V. All rights reserved.

Molecular layer deposition of APTES on silicon nanowire biosensors: Surface characterization, stability and pH response

NASA Astrophysics Data System (ADS)

Liang, Yuchen; Huang, Jie; Zang, Pengyuan; Kim, Jiyoung; Hu, Walter

2014-12-01

We report the use of molecular layer deposition (MLD) for depositing 3-aminopropyltriethoxysilane (APTES) on a silicon dioxide surface. The APTES monolayer was characterized using spectroscopic ellipsometry, contact angle goniometry, and atomic force microscopy. Effects of reaction time of repeating pulses and simultaneous feeding of water vapor with APTES were tested. The results indicate that the synergistic effects of water vapor and reaction time are significant for the formation of a stable monolayer. Additionally, increasing the number of repeating pulses improved the APTES surface coverage but led to saturation after 10 pulses. In comparing MLD with solution-phase deposition, the APTES surface coverage and the surface quality were nearly equivalent. The hydrolytic stability of the resulting films was also studied. The results confirmed that the hydrolysis process was necessary for MLD to obtain stable surface chemistry. Furthermore, we compared the pH sensing results of Si nanowire field effect transistors (Si NWFETs) modified by both the MLD and solution methods. The highly repeatable pH sensing results reflected the stability of APTES monolayers. The results also showed an improved pH response of the sensor prepared by MLD compared to the one prepared by the solution treatment, which indicated higher surface coverage of APTES.

Release behavior of uranium in uranium mill tailings under environmental conditions.

PubMed

Liu, Bo; Peng, Tongjiang; Sun, Hongjuan; Yue, Huanjuan

2017-05-01

Uranium contamination is observed in sedimentary geochemical environments, but the geochemical and mineralogical processes that control uranium release from sediment are not fully appreciated. Identification of how sediments and water influence the release and migration of uranium is critical to improve the prevention of uranium contamination in soil and groundwater. To understand the process of uranium release and migration from uranium mill tailings under water chemistry conditions, uranium mill tailing samples from northwest China were investigated with batch leaching experiments. Results showed that water played an important role in uranium release from the tailing minerals. The uranium release was clearly influenced by contact time, liquid-solid ratio, particle size, and pH under water chemistry conditions. Longer contact time, higher liquid content, and extreme pH were all not conducive to the stabilization of uranium and accelerated the uranium release from the tailing mineral to the solution. The values of pH were found to significantly influence the extent and mechanisms of uranium release from minerals to water. Uranium release was monitored by a number of interactive processes, including dissolution of uranium-bearing minerals, uranium desorption from mineral surfaces, and formation of aqueous uranium complexes. Considering the impact of contact time, liquid-solid ratio, particle size, and pH on uranium release from uranium mill tailings, reducing the water content, decreasing the porosity of tailing dumps and controlling the pH of tailings were the key factors for prevention and management of environmental pollution in areas near uranium mines. Copyright © 2017 Elsevier Ltd. All rights reserved.

METHOD OF RECOVERING URANIUM COMPOUNDS

DOEpatents

Poirier, R.H.

1957-10-29

S>The recovery of uranium compounds which have been adsorbed on anion exchange resins is discussed. The uranium and thorium-containing residues from monazite processed by alkali hydroxide are separated from solution, and leached with an alkali metal carbonate solution, whereby the uranium and thorium hydrorides are dissolved. The carbonate solution is then passed over an anion exchange resin causing the uranium to be adsorbed while the thorium remains in solution. The uranium may be recovered by contacting the uranium-holding resin with an aqueous ammonium carbonate solution whereby the uranium values are eluted from the resin and then heating the eluate whereby carbon dioxide and ammonia are given off, the pH value of the solution is lowered, and the uranium is precipitated.

Assessment of the Effects Exerted by Acid and Alkaline Solutions on Bone: Is Chemistry the Answer?

PubMed

Amadasi, Alberto; Camici, Arianna; Porta, Davide; Cucca, Lucia; Merli, Daniele; Milanese, Chiara; Profumo, Antonella; Rassifi, Nabila; Cattaneo, Cristina

2017-09-01

The treatment of corpses with extremely acid or basic liquids is sometimes performed in criminal contexts. A thorough characterization by chemical analysis may provide further help to macroscopic and microscopic analysis; 63 porcine bone samples were treated with solutions at different pH (1-14) for immersion periods up to 70 days, as well as in extremely acidic sulfuric acid solutions (9 M/18 M) and extremely basic sodium hydroxide. Inductively coupled optical emission spectrometry (ICP-OES)/plasma mass spectrometry (ICP-MS), Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray analysis (EDX), X-ray powder diffraction (XRPD), and scanning electron microscopy (SEM) showed that only the sulfuric acid solution 18 M was able to completely dissolve the sample. In addition, chemical analysis allowed to recognize the contact between bone and substances. Hydrated calcium sulfate arose from extreme pH. The possibility of detecting the presence of human material within the residual solution was demonstrated, especially with FT-IR, ICP-OES, and EDX. © 2017 American Academy of Forensic Sciences.

Uptake of Cr3+ from aqueous solution by lignite-based humic acids.

PubMed

Arslan, G; Pehlivan, E

2008-11-01

Humic acid (HA) produced from brown coal, a relatively abundant and inexpensive material is currently being investigated as an adsorbent to remove toxic metals from aqueous solution. The influence of five parameters (contact time, solution pH, initial metal concentration, temperature and amount of adsorbent) on the removal at 20+/-1 degrees C was studied. HAs were prepared from lignites by using alkaline extraction, sedimentation and acidic precipitation. Adsorption equilibrium was achieved in about 60 min for Cr3+ ion. The Langmuir adsorption isotherm was used to describe observed sorption phenomena. The maximum adsorption capacity of 0.17 mmol for Ilgin (HA1), 0.29 mmol for Beysehir (HA2) and 0.18 mmol Ermenek (HA3) and 0.17 mmol of Cr3+/g for activated carbon (AC) was achieved, respectively at pH of 4.1. More than 84% of Cr3+ was removed by HA2, 54% by HA3 and 51% by HA1 and 50% by AC from aqueous solution. The adsorption was strongly dependent on pH but independent of ionic strength and metal ions. The adsorption of Cr3+ was higher between pH 4.1 and 5.1 for all HAs and maximum sorption was observed at pH 4.1. The rise in temperature caused a slight decrease in the value of the equilibrium constant (Kc) for the sorption of Cr3+ ion. Complex mechanisms including ion exchange, complexation and adsorption and size exclusion are possible for sorption of Cr3+ ion on HAs.

Adsorption of sunset yellow FCF from aqueous solution by chitosan-modified diatomite.

PubMed

Zhang, Y Z; Li, J; Li, W J; Li, Y

2015-01-01

Sunset yellow (SY) FCF is a hazardous azo dye pollutant found in food processing effluent. This study investigates the use of diatomaceous earth with chitosan (DE@C) as a modified adsorbent for the removal of SY from wastewater. Fourier transform infrared spectroscopy results indicate the importance of functional groups during the adsorption of SY. The obtained N2 adsorption-desorption isotherm values accord well with IUPAC type II. Our calculations determined a surface area of 69.68 m2 g(-1) for DE@C and an average pore diameter of 4.85 nm. Using response surface methodology, optimized conditions of process variables for dye adsorption were achieved. For the adsorption of SY onto DE@C, this study establishes mathematical models for the optimization of pH, contact time and initial dye concentration. Contact time plays a greater role in the adsorption process than either pH or initial dye concentration. According to the adjusted correlation coefficient (adj-R2>0.97), the models used here are suitable for illustration of the adsorption process. Theoretical experimental conditions included a pH of 2.40, initial dye concentration of 113 mg L(-1) and 30.37 minutes of contact time. Experimental values for the adsorption rate (92.54%) were close to the values predicted by the models (95.29%).

Computation of adsorption parameters for the removal of dye from wastewater by microwave assisted sawdust: Theoretical and experimental analysis.

PubMed

S, Suganya; P, Senthil Kumar; A, Saravanan; P, Sundar Rajan; C, Ravikumar

2017-03-01

In this research, the microwave assistance has been employed for the preparation of novel material from agro/natural bio-waste i.e. sawdust, for the effective removal of methylene blue (MB) dye from aqueous solution. The characterization of the newly prepared microwave assisted sawdust (MASD) material was performed by using FTIR, SEM and XRD analyses. In order to obtain the maximum removal of MB dye from wastewater, the adsorption experimental parameters such as initial dye concentration, contact time, solution pH and adsorbent dosage were optimized by trial and error approach. The obtained experimental results were applied to the different theoretical models to predict the system behaviour. The optimum conditions for the maximum removal MB dye from aqueous solution for an initial MB dye concentration of 25mg/L was calculated as: adsorbent dose of 3g/L, contact time of 90min, solution pH of 7.0 and at the temperature of 30°C. Freundlich and pseudo-second order models was best obeyed with the studied experimental data. Langmuir maximum monolayer adsorption capacity of MASD for MB dye removal was calculated as 58.14mg of MB dye/g of MASD. Adsorption diffusion model stated that the present adsorption system was controlled by intraparticle diffusion model. The obtained results proposed that, novel MASD was considered to be an effective and low-cost adsorbent material for the removal of dye from wastewater. Copyright © 2017 Elsevier B.V. All rights reserved.

Atmospheric CO2 capture for the artificial photosynthetic system.

PubMed

Nogalska, Adrianna; Zukowska, Adrianna; Garcia-Valls, Ricard

2018-04-15

The aim of these studies is to evaluate the ambient CO 2 capture abilities of the membrane contactor system in the same conditions as leafs, such as ambient temperature, pressure and low CO 2 concentration, where the only driving force is the concentration gradient. The polysulfone membrane employed was made by a phase inversion process and characterized by ESEM micrographs which were used to determine the thickness, asymmetry and pore size. Besides, the porosity of the membrane was measured from the membrane and polysulfone density correlation and the hydrophobicity was analyzed by contact angle measurements. Moreover, the compatibility of membrane and absorbent was evaluated, in order to exclude wetting issues by meaning of swelling, dynamic contact angle and AFM analysis. The prepared membranes were introduced into a cross flow module and used as contactors between CO 2 and the absorbing media, a potassium hydroxide solution. The influence of the membrane thickness, absorbent stirring rate, solution pH and absorption time on CO 2 capture were evaluated. Absorbent solution stirring rate showed no statistically significant influence on absorption. We observed a non-linear correlation between the capture rate and the increase of absorbent solution pH as well as absorption time. The results showed that the efficiency of our CO 2 capture system is similar to stomatal carbon dioxide assimilation rate, achieving stable value of 20μmol/m 2 ·s after 1h of experiment. Copyright © 2017 Elsevier B.V. All rights reserved.

Influence of pH on wetting kinetics of a pine forest soil

NASA Astrophysics Data System (ADS)

Amer, Ahmad; Schaumann, Gabriele; Diehl, Dörte

2014-05-01

Water repellent properties of organic matter significantly alter soil water dynamics. Various environmental factors control appearance and breakup of repellency in soil. Beside water content and temperature also pH exerts an influence on soil water repellency although investigations achieved partly ambiguous results; some found increasing repellency with increasing pH (Terashima et al. 2004; Duval et al. 2005), other with decreasing pH (Karnok et al. 1993; Roper 2005) and some found repellency maxima at intermediate pH and an increase with decreasing and with increasing pH (Bayer and Schaumann 2007; Diehl et al. 2010). The breakup of repellency may be observed via the time dependent sessile drop contact angle (TISED). With water contact time, soil-water contact angle decreases until complete wetting is reached. Diehl and Schaumann (2007) calculated the activation energy of the wetting process from the rate of sessile drop wetting obtained at different temperatures and draw conclusions on chemical or physical nature of repellency. The present study aims at the influence of pH on the wetting kinetics of soil. Therefore, TISED of soil was determined as a function of pH and temperature. We used upper soil samples (0 - 10 cm) from a pine forest in the southwest of Germany (Rheinland-Pfalz). Samples were air-dried, sieved < 1.0 mm and pH was modified by NH3 and HCl gas (Diehl et al. 2010) and measured electrometrically in 0.01 M CaCl2 solution. TISED measurements (2007)were conducted at 10, 20 and 30 oC using OCA 15 Contact Angle Meter (Dataphysics, Germany) on three replications for each soil sample. Apparent work of adhesion was calculated, plotted vs. time and mathematically fitted using double exponential function. Rate constants of wetting were used to determine the activation energy by Arrhenius equation. First results indicated that despite comparable initial contact angles, pH alteration strongly changed the wetting rate suggesting maximum wetting resistance at the natural pH of 4.3 and decreasing wetting resistance at lower and at higher pH. The poster will present further current results of the ongoing study and discuss the activation energy of the wetting process in dependence of artificially altered soil pH. References: Bayer, J. V. and G. E. Schaumann (2007). Hydrol. Processes 21(17): 2266 - 2275. Diehl, D., J. V. Bayer, et al. (2010). Geoderma 158(3-4): 375-384. Diehl, D. and G. E. Schaumann (2007). Hydrol. Processes 21(17): 2255 - 2265. Duval, J. F. L., K. J. Wilkinson, et al. (2005). Environ Sci Technol 39(17): 6435-6445. Karnok, K. A., E. J. Rowland, et al. (1993). Agron J 85(5): 983-986. Roper, M. M. (2005). Aust J Soil Res 43: 803-810. Terashima, M., M. Fukushima, et al. (2004). Colloids and Surfaces, A: Physicochemical and Engineering Aspects 247(1-3): 77-83.

Stimuli Responsive Morphological Changes of Pnipa Polymer Brushes Synthesized on Silicon Substrate

NASA Astrophysics Data System (ADS)

Huda, Muhammad Nurul; Kabir, A. N. M. Hamidul

2013-08-01

High-density polymer brushes were grown from the silicon surface by atom transfer radical polymerization of Poly(N-isopropylacrylamide) (PNIPA) at different polymerization conditions. PNIPA brushes were prepared using Copper (I) Chloride/tris(2-(dimetylamino)ethyl)amine (Me6TREN) as a catalytic system in DMSO at 20°C. Free polymer formed during the brush formation was characterized by gel permeation chromatography. The grafting densities up to 0.52 chains/nm2 were obtained. The layer thickness of polymer brush increases with the increase of conversion of the monomer conversion as well as polymerization time. Atomic force microscopy and air bubble contact angle under pH solution were employed to study the surface morphology, reversible conformational changes of and stimulus-response behavior. PNIPA brushes exhibited a different nanomorphology after treatment with different pH solution. It also revealed a unique reversible wetting behavior with pH. The reversible properties of the PNIPA brushes can be used to regulate the adsorption of the sulfonated PS nanoparticles.

Adsorption of Ni(II) onto Chemically Modified Spent Grated Coconut (Cocos Nucifera)

NASA Astrophysics Data System (ADS)

Hamzah, F. I.; Khalid, K.; Hanafiah, M. A. K. M.

2017-06-01

A new adsorbent of plant waste origin from coconut processing food factory was explored for removing Ni(II) from aqueous solutions. Several parameters such as pH, dosage, concentration and contact time were studied to obtain optimum conditions for treatment of Ni(II) contaminated wastewater. Spent grated coconut (Cocos nucifera) treated with sulfuric acid (SSGC) showed good adsorption capacity for Ni(II) ion. The amount adsorbed was affected by solution pH with the highest value achieved at pH 5. Other optimum conditions found were; dosage of 0.02 g, and 60 min of equilibrium time. Ni(II) adsorption obeyed the pseudo-second order kinetic model which suggested that chemisorption mechanism occurred in the adsorption process. The equilibrium data presented a better fitting to the Langmuir isotherm model, an indication that monolayer adsorption occurred onto a homogeneous surface. The maximum adsorption capacity, qmax was 97.09 mg g-1, thus SSGC can be classified as good and comparable with other plant waste adsorbents.

Triple-Stimuli-Responsive Ferrocene-Containing PEGs in Water and on the Surface.

PubMed

Alkan, Arda; Steinmetz, Christian; Landfester, Katharina; Wurm, Frederik R

2015-12-02

Triple-stimuli-responsive PEG-based materials are prepared by living anionic ring-opening copolymerization of ethylene oxide and vinyl ferrocenyl glycidyl ether and subsequent thiol-ene postpolymerization modification with cysteamine. The hydrophilicity of these materials can be tuned by three stimuli: (i) temperature (depending on the comonomer ratio), (ii) oxidation state of iron centers in the ferrocene moieties, and (iii) pH-value (through amino groups), both in aqueous solution and at the interface after covalent attachment to a glass surface. In such materials, the cloud point temperatures are adjustable in solution by changing oxidation state and/or pH. On the surface, the contact angle increases with increasing pH and temperature and after oxidation, making these smart surfaces interesting for catalytic applications. Also, their redox response can be switched by temperature and pH, making this material useful for catalysis and electrochemistry applications. Exemplarily, the temperature-dependent catalysis of the chemiluminescence of luminol (a typical blood analysis tool in forensics) was investigated with these polymers.

Colloid formation in Hanford sediments reacted with simulated tank waste.

PubMed

Mashal, Kholoud; Harsh, James B; Flury, Markus; Felmy, Andrew R; Zhao, Hongting

2004-11-01

Solutions of high pH, ionic strength, and aluminum concentration have leaked into the subsurface from underground waste storage tanks atthe Hanford Reservation in Washington State. Here, we test the hypothesis that these waste solutions alter and dissolve the native minerals present in the sediments and that colloidal (diameter < 2 microm) feldspathoids form. We reacted Hanford sediments with simulated solutions representative of Hanford waste tanks. The solutions consisted of 1.4 or 2.8 mol/kg NaOH, 0.125 or 0.25 mol/kg NaAlO4, and 3.7 mol/kg NaNO3 and were contacted with the sediments for a period of 25 or 40 days at 50 degrees C. The colloidal size fraction was separated from the sediments and characterized in terms of mineralogy, morphology, chemical composition, and electrophoretic mobility. Upon reaction with tank waste solutions, native minerals released Si and other elements into the solution phase. This Si precipitated with the Al present in the waste solutions to form secondary minerals, identified as the feldspathoids cancrinite and sodalite. The solution phase was modeled with the chemical equilibrium model GMIN for solution speciation and saturation indices with respect to sodalite and cancrinite. The amount of colloidal material in the sediments increased upon reaction with waste solutions. At the natural pH found in Hanford sediments (pH 8) the newly formed minerals are negatively charged, similar to the unreacted colloidal material present in the sediments. The formation of colloidal material in Hanford sediments upon reaction with tank waste solutions is an important aspect to consider in the characterization of Hanford tank leaks and may affect the fate of hazardous radionuclides present in the tank waste.

A comparative study for adsorption of lysozyme from aqueous samples onto Fe3O4 magnetic nanoparticles using different ionic liquids as modifier.

PubMed

Kamran, Sedigheh; Absalan, Ghodratollah; Asadi, Mozaffar

2015-12-01

In this paper, nanoparticles of Fe3O4 as well as their modified forms with different ionic liquids (IL-Fe3O4) were prepared and used for adsorption of lysozyme. The mean size and the surface morphology of the nanoparticles were characterized by TEM, XRD and FTIR techniques. Adsorption studies of lysozyme were performed under different experimental conditions in batch system on different modified magnetic nanoparticles such as, lysozyme concentration, pH of the solution, and contact time. Experimental results were obtained under the optimum operational conditions of pH 9.0 and a contact time of 10 min when initial protein concentrations of 0.05-2.0 mg mL(-1) were used. The isotherm evaluations revealed that the Langmuir model attained better fits to the equilibrium data than the Freundlich model. The maximum obtained adsorption capacities were 370.4, 400.0 500.0 and 526.3 mg of lysozyme for adsorption onto Fe3O4 and modified magnetic nanoparticles by [C4MIM][Br], [C6MIM][Br] and [C8MIM][Br] per gram of adsorbent, respectively. The Langmuir adsorption constants were 0.004, 0.019, 0.024 and 0.012 L mg(-1) for adsorptions of lysozyme onto Fe3O4 and modified magnetic nanoparticles by [C4MIM][Br], [C6MIM][Br] and [C8MIM][Br], respectively. The adsorption capacity of lysozyme was found to be dependent on its chemical structure, pH of the solution, temperature and type of ionic liquid as modifier. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated. Furthermore, the thermodynamic parameters were calculated. Protein could desorb from IL-Fe3O4 nanoparticles by using NaCl solution at pH 9.5 and was reused.

Multi-responses optimization of simultaneous biosorption of cationic dyes by live yeast Yarrowia lipolytica 70562 from binary solution: Application of first order derivative spectrophotometry.

PubMed

Dil, Ebrahim Alipanahpour; Ghaedi, Mehrorang; Ghezelbash, Gholam Reza; Asfaram, Arash

2017-05-01

Present study is based on application of live yeast Yarrowia lipolytica 70562 as new biosorbent was investigated for the simultaneous biosorption of Crystal Violet (CV) and Brilliant Green (BG) from wastewater. The effect of operating parameters such as initial dye concentrations (6-14mgL -1 ), solution pH (4.0-8.0) and contact time (4-20h) was investigated by response surface methodology (RSM) for modeling and optimization of biosorption process and accordingly the best operational conditions was set as: initial CV and BG concentration of 8.0, and 10mgL -1 , pH of 7.0 and contact time of 16h. Above specified conditions lead to achievement of maximum biosorption of 98.823% and 99.927% for CV and BG dyes, respectively. The experimental equilibrium data well explained according to Langmuir isotherm model with maximum biosorption capacity of 65.359 and 56.497mgg -1 for BG and CV, respectively. The second order and intraparticle diffusion models as cooperative mechanism has high efficiency and performance for interpretation of real data. Copyright © 2017. Published by Elsevier Inc.

Facile synthesis of magnetic Fe3O4/graphene composites for enhanced U(VI) sorption

NASA Astrophysics Data System (ADS)

Zhao, Donglin; Zhu, Hongyu; Wu, Changnian; Feng, Shaojie; Alsaedi, Ahmed; Hayat, Tasawar; Chen, Changlun

2018-06-01

A novel magnetic Fe3O4/graphene composite (FGC) was fabricated by a facile one-step reaction route and shown to be effective for sorbing U(VI) from aqueous solution. The structure, properties and application of the prepared FGC composite were well evaluated. The high saturation magnetization (45.6 emu/g) made FGC easier to be separated from the media within several seconds under an external magnetic. Effects of different ambient conditions (i.e., pH and ionic strength, contact time, temperatures) on sorption behaviors of U(VI) on FGC were carried out by batch experiments. According to the calculation of Langmuir model, the maximum sorption capacity of U(VI) on the FGC at pH 5.5 and 298 K was 176.47 mg/g. The sorption was correlated with the effects of pH, contact time, and temperature. X-ray photoelectron spectroscopy analysis revealed that U(VI) was sorbed on FGC via oxygen-containing functional groups. This work demonstrated that FGC could be recycled and used as an effective recyclable sorbent for sorption of U(VI).

An integrated field-effect microdevice for monitoring membrane transport in Xenopus laevis oocytes via lateral proton diffusion.

PubMed

Schaffhauser, Daniel Felix; Patti, Monica; Goda, Tatsuro; Miyahara, Yuji; Forster, Ian Cameron; Dittrich, Petra Stephanie

2012-01-01

An integrated microdevice for measuring proton-dependent membrane activity at the surface of Xenopus laevis oocytes is presented. By establishing a stable contact between the oocyte vitelline membrane and an ion-sensitive field-effect (ISFET) sensor inside a microperfusion channel, changes in surface pH that are hypothesized to result from facilitated proton lateral diffusion along the membrane were detected. The solute diffusion barrier created between the sensor and the active membrane area allowed detection of surface proton concentration free from interference of solutes in bulk solution. The proposed sensor mechanism was verified by heterologously expressing membrane transport proteins and recording changes in surface pH during application of the specific substrates. Experiments conducted on two families of phosphate-sodium cotransporters (SLC20 & SLC34) demonstrated that it is possible to detect phosphate transport for both electrogenic and electroneutral isoforms and distinguish between transport of different phosphate species. Furthermore, the transport activity of the proton/amino acid cotransporter PAT1 assayed using conventional whole cell electrophysiology correlated well with changes in surface pH, confirming the ability of the system to detect activity proportional to expression level.

Adsorption of allura red dye by cross-linked chitosan from shrimp waste.

PubMed

Sánchez-Duarte, Reyna G; Sánchez-Machado, Dalia I; López-Cervantes, Jaime; Correa-Murrieta, Ma A

2012-01-01

The present study was designed to evaluate the chitosan, which has been obtained by deacetylation of chitin, as a biosorbent. The chitin was isolated from fermented shrimp waste by an important local industrial food biopolymer. The aim of this work was the characterization of chitosan and preparation of cross-linked chitosan- tripolyphosphate (chitosan-TPP) beads for the removal of allura red food dye from aqueous solutions. Conditions of batch adsorption such as pH, time and adsorbent dose were examined. The effectiveness of cross-linked chitosan beads for dye removal was found to be higher for pH 2 (98%, percentage of dye removal) and tends to decrease at pHs of 3 to 11 (up to 49%). The values of percentage removal show that the adsorption capacity increases with time of contact and dosage of chitosan-TPP, but red dye adsorption is mainly influenced by pH level. The cross-linked chitosan-TPP beads can significantly adsorb allura red monoazo dye from aqueous solutions even at acidic pHs unlike raw chitosan beads that tend to dissolve in acidic solutions. Consequently, this modified chitosan has characteristics that allow minimization of environmental pollution and widening the valorization of shrimp waste.

Complexing Agents and pH Influence on Chemical Durability of Type I Molded Glass Containers.

PubMed

Biavati, Alberto; Poncini, Michele; Ferrarini, Arianna; Favaro, Nicola; Scarpa, Martina; Vallotto, Marta

2017-01-01

Among the factors that affect the glass surface chemical durability, pH and complexing agents present in aqueous solution have the main role. Glass surface attack can be also related to the delamination issue causing glass particles' appearance in the pharmaceutical preparation. A few methods to check for glass containers delamination propensity and some control guidelines have been proposed. The present study emphasizes the possible synergy between a few complexing agents with pH on borosilicate glass chemical durability.Hydrolytic attack was performed in small-volume 23 mL type I glass containers autoclaved according to the European Pharmacopoeia or United States Pharmacopeia for 1 h at 121 °C, in order to enhance the chemical attack due to time, temperature, and the unfavorable surface/volume ratio. Solutions of 0.048 M or 0.024 M (M/L) of the acids citric, glutaric, acetic, EDTA (ethylenediaminetetraacetic acid), together with sodium phosphate with water for comparison, were used for the trials. The pH was adjusted ±0.05 units at fixed values 5.5, 6.6, 7, 7.4, 8, and 9 by LiOH diluted solution.Because silicon is the main glass network former, silicon release into the attack solutions was chosen as the main index of the glass surface attack and analysed by inductively coupled plasma atomic emission spectrophotometry. The work was completed by the analysis of the silicon release in the worst attack conditions of molded glass, soda lime type II glass, and tubing borosilicate glass vials to compare different glass compositions and forming technologies. Surface analysis by scanning electron microscopy was finally performed to check for the surface status after the worst chemical attack condition by citric acid. LAY ABSTRACT: Glass, like every packaging material, can have some usage limits, mainly in basic pH solutions. The issue of glass surface degradation particles that appear in vials (delamination) has forced a number of drug product recalls in recent years. To prevent such situations, pharmaceutical and biopharmaceutical manufacturers need to understand the reasons for accelerate surface glass corrosion mainly in the case of injectables.Some drugs can contain active components with known ability to corrode glass silica networks. Sometimes these ingredients are dissolved in an alkaline medium that dramatically increases the glass corrosion and potentially causes the issue. As this action is strongly affected by time and temperature, flaking may become visible only after a long storage time. The purpose of this investigation is to verify the borosilicate glass chemical durability during controlled conditions of time and temperature when in contact with testing solutions containing different complexing agents by varying the pH. Si concentration in the extract solution is taken as an index of glass dissolution during constant autoclaving conditions for 1 h at 121 °C, which simulates approximately five years of contact at room temperature.Acetate, citrate, ethylenediaminetetraacetic acid (EDTA), phosphate, and glutarate 0.048 M or 0.024 M solutions were used at increasing pH from 5.5 to 9.0. The chemical durability of two borosilicate tubing glass vials of different glass compositions were compared with the molded one in the worst attack conditions by citric acid. Even if no delamination issue has been experienced by this study in type I molded and tubing containers, the conclusions developed can provide pharmaceutical manufacturers with useful information to prevent glass delamination risk in their processes. © PDA, Inc. 2017.

Sensitive and selective determination of gallic acid in green tea samples based on an electrochemical platform of poly(melamine) film.

PubMed

Su, Ya-Ling; Cheng, Shu-Hua

2015-12-11

In this work, an electrochemical sensor coupled with an effective flow-injection amperometry (FIA) system is developed, targeting the determination of gallic acid (GA) in a mild neutral condition, in contrast to the existing electrochemical methods. The sensor is based on a thin electroactive poly(melamine) film immobilized on a pre-anodized screen-printed carbon electrode (SPCE*/PME). The characteristics of the sensing surface are well-characterized by field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and surface water contact angle experiments. The proposed assay exhibits a wide linear response to GA in both pH 3 and pH 7.0 phosphate buffer solutions (PBS) under the optimized flow-injection amperometry. The detection limit (S/N = 3) is 0.076 μM and 0.21 μM in the pH 3 and pH 7 solutions, respectively. A relative standard deviation (RSD) of 3.9% is obtained for 57 successive measurements of 50 μM GA in pH 7 solutions. Interference studies indicate that some inorganic salts, catechol, caffeine and ascorbic acid do not interfere with the GA assay. The interference effects from some orthodiphenolic compounds are also investigated. The proposed method and a conventional Folin-Ciocalteu method are applied to detect GA in green tea samples using the standard addition method, and satisfactory spiked recoveries are obtained. Copyright © 2015 Elsevier B.V. All rights reserved.

OPC Paste Samples Exposed To Aggressive Solutions. Cementitious Barriers Partnership

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

Langton, C.

2014-11-01

The study presented in this report focused on a low-activity wasteform containing a high-pH pore solution with a significant level of sulfate. The purpose of the study was to improve understanding of the complex concrete/wasteform reactive transport problem, in particular, the role of pH in sulfate attack. Paste samples prepared at three different water-to-cement ratios were tested. The mixtures were prepared with ASTM Type I cement, without additional admixtures. The samples were exposed to two different sodium sulfate contact solutions. The first solution was prepared at 0.15M Na 2SO 4. The second solution also incorporated 0.5M NaOH, to mimic themore » high pH conditions found in Saltstone. The data collected indicated that, in Na 2SO 4 solution, damage occurs to the pastes. In the case of the high-pH sulfate solution (Na 2SO 4 + NaOH), no signs of damage were observed on any of the paste mixtures. These results indicate that the high sulfate content found in the wasteform pore solution will not necessarily lead to severe damage to concrete. Good-quality mixtures could thus prove durable over the long term, and act as an effective barrier to prevent radionuclides from reaching the environment.« less

Protection of Tempered Aluminum Alloy in Contact with the Environment

NASA Astrophysics Data System (ADS)

Araoyinbo, A. O.; Salleh, M. A. A. Mohd; Rahmat, A.; Azmi, A. I.; Rahim, W. M. F. Wan Abd; Perju, M. C.; Jin, T. S.

2018-06-01

In many service applications an increasing temperature or inadequate protections often give rise to localized forms of corrosion in an initially free and unprotected system. This research understudy the corrosion chemistry, the effect of chromium as the inhibitor, Vickers hardness test, and weight loss on tempered aluminium alloy 7075 in corrosive mediums. The tempers of the aluminium alloy used are T6 and T73 where obtained by solution heat treatment at 470°C and quenched before immersion test in acidic (pH3), and slightly alkaline (pH7.5) solutions. The results obtained were characterized by conventional weight loss process and morphology observation with a microscope. The surface morphology shows exfoliation form of corrosion and the weight loss analysis shows the as received sample experience more weight loss when compared with the other heat treated samples.

Dosimeter and method for using the same

DOEpatents

Warner, Benjamin P.; Johns, Deidre M.

2003-06-24

A very sensitive dosimeter that detects ionizing radiation is described. The dosimeter includes a breakable sealed container. A solution of a reducing agent is inside the container. The dosimeter has an air-tight dosimeter body with a transparent portion and an opaque portion. The transparent portion includes a transparent chamber that holds the breakable container with the reducing agent. The opaque portion includes an opaque chamber that holds an emulsion of silver salt (AgX) selected from silver chloride, silver bromide, silver iodide, and combinations of them. A passageway in the dosimeter provides fluid communication between the transparent chamber and the opaque chamber. The dosimeter may also include a chemical pH indicator in the breakable container that provides a detectable color change to the solution for a pH of about 3-10. The invention also includes a method of detecting ionizing radiation that involves producing the dosimeter, breaking the breakable container, allowing the solution to flow through the passageway and contact the emulsion, detecting any color change in the solution and using the color change to determine a radiation dosage.

Preparation and Characterization of Biochars from Eichornia crassipes for Cadmium Removal in Aqueous Solutions.

PubMed

Li, Feng; Shen, Kaixuan; Long, Xiaolin; Wen, Jiasheng; Xie, Xiaojie; Zeng, Xiangyun; Liang, Yanyan; Wei, Yansha; Lin, Zefeng; Huang, Wenrou; Zhong, Ruida

2016-01-01

The study investigated the preparation and characterization of biochars from water hyacinth at 300°C to 700°C for cadmium (Cd) removal from aqueous solutions. The adsorption process was dominated by oxygen-containing functional groups with irregular surfaces via esterification reactions. Furthermore, the mineral components in the biochars also contributed to Cd absorption through precipitation. Parameters such as the effects of solution pH, contact time, and initial concentration were studied. The optimum pH value was observed at 5.0, in which nearly 90% of Cd was removed. The maximum Cd adsorption capacities based on the Langmuir isotherm were calculated at 49.837, 36.899, and 25.826 mg g(-1). The adsorption processes of the biochars followed the pseudo-second-order kinetics, with the equilibrium achieved around 5 h. The biochar from E. crassipes is a promising adsorbent for the treatment of wastewater, which can in turn convert one environmental problem to a new cleaning Technology.

Preparation and Characterization of Biochars from Eichornia crassipes for Cadmium Removal in Aqueous Solutions

PubMed Central

Li, Feng; Shen, Kaixuan; Long, Xiaolin; Wen, Jiasheng; Xie, Xiaojie; Zeng, Xiangyun; Liang, Yanyan; Wei, Yansha; Lin, Zefeng; Huang, Wenrou; Zhong, Ruida

2016-01-01

The study investigated the preparation and characterization of biochars from water hyacinth at 300°C to 700°C for cadmium (Cd) removal from aqueous solutions. The adsorption process was dominated by oxygen-containing functional groups with irregular surfaces via esterification reactions. Furthermore, the mineral components in the biochars also contributed to Cd absorption through precipitation. Parameters such as the effects of solution pH, contact time, and initial concentration were studied. The optimum pH value was observed at 5.0, in which nearly 90% of Cd was removed. The maximum Cd adsorption capacities based on the Langmuir isotherm were calculated at 49.837, 36.899, and 25.826 mg g−1. The adsorption processes of the biochars followed the pseudo-second-order kinetics, with the equilibrium achieved around 5 h. The biochar from E. crassipes is a promising adsorbent for the treatment of wastewater, which can in turn convert one environmental problem to a new cleaning Technology. PMID:26882239

Jute stick powder as a potential biomass for the removal of congo red and rhodamine B from their aqueous solution.

PubMed

Panda, Gopal C; Das, Sujoy K; Guha, Arun K

2009-05-15

Jute stick powder (JSP) has been found to be a promising material for adsorptive removal of congo red (C.I. 22120) and rhodamine B (C.I. 45170) from aqueous solutions. Physico-chemical parameters like dye concentration, solution pH, temperature and contact time have been varied to study the adsorption phenomenon. Favorable adsorption occurs at around pH 7.0 whereas temperature has no significant effect on adsorption of both the dyes. The maximum adsorption capacity has been calculated to be 35.7 and 87.7mg/g of the biomass for congo red and rhodamine B, respectively. The adsorption process is in conformity with Freundlich and Langmuir isotherms for rhodamine B whereas congo red adsorption fits well to Langmuir isotherm only. In both the cases, adsorption occurs very fast initially and attains equilibrium within 60min. Kinetic results suggest the intra-particle diffusion of dyes as rate limiting step.

Adsorptive removal of Congo red from aqueous solutions using crosslinked chitosan and crosslinked chitosan immobilized bentonite.

PubMed

Huang, Ruihua; Zhang, Lujie; Hu, Pan; Wang, Jing

2016-05-01

Batch experiments were executed to investigate the removal of Congo red (CR) from aqueous solutions using the crosslinked chitosan (CCS) and crosslinked chitosan immobilized bentonite (CCS/BT composite). The CCS and CCS/BT composite were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) techniques. The removal of CR was examined as a function of pH value of CR solution, contact time, and inorganic sodium salt and ionic strength. The equilibrium data of CCS and CCS/BT composite agreed well with the Langmuir model. The adsorption capacities of CCS and CCS/BT composite at 298K and natural pH value were 405 and 500 mg/g, respectively. The kinetic data correlated well with the pseudo-second-order model. The adsorption of CR onto the CCS was mainly controlled by chemisorption while the adsorption of CR onto the CCS/BT composite was controlled by chemisorption and the electrostatic attraction. Copyright © 2016 Elsevier B.V. All rights reserved.

Prediction of equilibrium parameters of adsorption of lead (II) ions onto diatomite

NASA Astrophysics Data System (ADS)

Salman, Taylan; Ardalı, Yüksel; Gamze Turan, N.

2013-04-01

Heavy metals from industrial wastewaters are one of the most important environmental issues to be solved today. Due to their toxicity and nonbiodegradable nature, heavy metals cause environmental and public health problems. Various techniques have been developed to remove heavy metals from aqueous solutions. These include chemical precipitation, reverse osmosis, ion Exchange and adsorption. Among them, adsorption is considered to be a particularly competitive and effective process for the removal of heavy metals from aqueous solutions. There is growing interest in using low cost, commercially available materials for the adsorption of heavy metals. Diatomite is a siliceous sedimentary rock having an amorphous form of silica (SiO2. nH2O) containing a small amount of microcrystalline material. It has unique combination of physical and chemical properties such as high porosity, high permeability, small particle size, large surface area, and low thermal conductivity. In addition, it is available in Turkey and in various locations around the world. Therefore, diatomite has been successfully used as adsorbent for the removal of heavy metals. The aim of the study is to investigate the adsorption properties of diatomite. The equilibrium adsorption data were applied to the Langmuir, Freundlich and Dubinin-Radushkevic (D-R) isotherm models. Adsorption experiments were performed under batch process, using Pb (II) initial concentration, pH of solution and contact time as variables. The results demonstrated that the adsorption of Pb (II) was strongly dependent on pH of solution. The effect of pH on adsorption of Pb(II) on diatomite was conducted by varying pH from 2 to 12 at 20 oC. In the pH range of 2.0-4.0, the adsorption percentage increases slightly as the pH increasing. At pH>4, the adsorption percentage decreases with increasing pH because hydrolysis product and the precipitation begin to play an important role in the sorption of Pb (II). At pH4, the maximum adsorption capacity of diatomite was found as 26.158 mg/g. The adsorption isotherms of Pb (II) on diatomite can be described well by the Freundlich model. The high adsorption capacity of diatomite makes it suitable low-cost material in the removal of Pb (II) from aqueous solutions.

Biosorption of cadmium and chromium in duckweed Wolffia globosa.

PubMed

Upatham, E Suchart; Boonyapookana, Benjaporn; Kruatrachue, Maleeya; Pokethitiyook, Prayad; Parkpoomkamol, Krisna

2002-01-01

The biosorption of cadmium (Cd) and chromium (Cr) by using dried Wolffia globosa biomass were investigated using batch technique. The effects of concentration and pH solution on the adsorption isotherm were measured by determining the adsorption isotherm at initial metal concentrations from 10 to 400 mg/L and pH 4 to 7 for Cd, and pH 1.5 to 6 for Cr. The adsorption equilibria were found to follow Langmuir models. The maximum adsorption capacity (Xm) at pH 7 in W. globosa-Cd system was estimated to be 80.7 mg/g, while the maximum removal achieved at pH 4, pH 5, and pH 6 were 35.1, 48.8, and 65.4 mg/g, respectively. The Xm at pH 1.5 in W. globosa--Cr system was estimated to be 73.5 mg/g, while the maximum removal achieved at pH 3, pH 5, and pH 6 were 47.4, 33.1, and 12.9 mg/g, respectively. The effects of contact times on Cd and Cr sorption indicated that they were absorbed rapidly and more efficiently at lower concentrations.

Regression model, artificial neural network, and cost estimation for biosorption of Ni(II)-ions from aqueous solutions by Potamogeton pectinatus.

PubMed

Fawzy, Manal; Nasr, Mahmoud; Adel, Samar; Helmi, Shacker

2018-03-21

This study investigated the application of Potamogeton pectinatus for Ni(II)-ions biosorption from aqueous solutions. FTIR spectra showed that the functional groups of -OH, C-H, -C = O, and -COO- could form an organometallic complex with Ni(II)-ions on the biomaterial surface. SEM/EDX analysis indicated that the voids on the biosorbent surface were blocked due to Ni(II)-ions uptake via an ion exchange mechanism. For Ni(II)-ions of 50 mg/L, the adsorption efficiency recorded 63.4% at pH: 5, biosorbent dosage: 10 g/L, and particle-diameter: 0.125-0.25 mm within 180 minutes. A quadratic model depicted that the plot of removal efficiency against pH or contact time caused quadratic-linear concave up curves, whereas the curve of initial Ni(II)-ions was quadratic-linear convex down. Artificial neural network with a structure of 5 - 6 - 1 was able to predict the adsorption efficiency (R 2 : 0.967). The relative importance of inputs was: initial Ni(II)-ions > pH > contact time > biosorbent dosage > particle-size. Freundlich isotherm described well the adsorption mechanism (R 2 : 0.974), which indicated a multilayer adsorption onto energetically heterogeneous surfaces. The net cost of using P. pectinatus for the removal of Ni(II)-ions (4.25 ± 1.26 mg/L) from real industrial effluents within 30 minutes was 3.4 $USD/m 3 .

Enhanced fluoride adsorption by nano crystalline γ-alumina: adsorption kinetics, isotherm modeling and thermodynamic studies

NASA Astrophysics Data System (ADS)

Chinnakoti, Prathibha; Chunduri, Avinash L. A.; Vankayala, Ranganayakulu K.; Patnaik, Sandeep; Kamisetti, Venkataramaniah

2017-09-01

Nano materials in particular nano oxides with enhanced surface area and an excellent catalytic surface serve as potential adsorbents for defluoridation of water. In the present study nano γ-alumina was synthesized through a simple and low cost, surfactant assisted solution combustion method. As synthesized material was characterized by XRD and FESEM for its phase, size and morphological characteristics. Surface properties have been investigated by BET method. Nano γ-alumina was further used for a detailed adsorption study to remove fluoride from water. Batches of experiments were performed at various experimental conditions such as solution pH, adsorbent dose, initial fluoride concentration and contact time to test the defluoridation ability of γ-alumina. Fluoride Adsorption by nano sized γ-alumina was rapid and reached equilibrium within two hours. The adsorption worked well at pH 4.0, where ˜96 % of fluoride was found to be adsorbed on adsorbent. It was possible to reduce fluoride levels to as low as 0.3 mg/L (within the safe limit of WHO: ≤1.5 mg/L) from an initial fluoride levels of 10 mg/L. This could be achieved using a very small quantity, 1 g/L of γ-alumina at pH 4 within 1 h of contact time. Defluoridation capacity of nano γ-alumina was further investigated by fitting the equilibrium data to various isotherm as well as kinetic models. The present study revealed that γ-alumina could be an efficient adsorbent for treating fluoride contaminated water.

Artificial neural network-genetic algorithm based optimization for the adsorption of methylene blue and brilliant green from aqueous solution by graphite oxide nanoparticle.

PubMed

Ghaedi, M; Zeinali, N; Ghaedi, A M; Teimuori, M; Tashkhourian, J

2014-05-05

In this study, graphite oxide (GO) nano according to Hummers method was synthesized and subsequently was used for the removal of methylene blue (MB) and brilliant green (BG). The detail information about the structure and physicochemical properties of GO are investigated by different techniques such as XRD and FTIR analysis. The influence of solution pH, initial dye concentration, contact time and adsorbent dosage was examined in batch mode and optimum conditions was set as pH=7.0, 2 mg of GO and 10 min contact time. Employment of equilibrium isotherm models for description of adsorption capacities of GO explore the good efficiency of Langmuir model for the best presentation of experimental data with maximum adsorption capacity of 476.19 and 416.67 for MB and BG dyes in single solution. The analysis of adsorption rate at various stirring times shows that both dyes adsorption followed a pseudo second-order kinetic model with cooperation with interparticle diffusion model. Subsequently, the adsorption data as new combination of artificial neural network was modeled to evaluate and obtain the real conditions for fast and efficient removal of dyes. A three-layer artificial neural network (ANN) model is applicable for accurate prediction of dyes removal percentage from aqueous solution by GO following conduction of 336 experimental data. The network was trained using the obtained experimental data at optimum pH with different GO amount (0.002-0.008 g) and 5-40 mg/L of both dyes over contact time of 0.5-30 min. The ANN model was able to predict the removal efficiency with Levenberg-Marquardt algorithm (LMA), a linear transfer function (purelin) at output layer and a tangent sigmoid transfer function (tansig) at hidden layer with 10 and 11 neurons for MB and BG dyes, respectively. The minimum mean squared error (MSE) of 0.0012 and coefficient of determination (R(2)) of 0.982 were found for prediction and modeling of MB removal, while the respective value for BG was the MSE and R(2) of 0.001 and 0.981, respectively. The ANN model results show good agreement with experimental data. Copyright © 2013 Elsevier B.V. All rights reserved.

Kinetics of protein adsorption/desorption mediated by pH-responsive polymer layer

NASA Astrophysics Data System (ADS)

Su, Xiao-Hang; Lei, Qun-Li; Ren, Chun-Lai

2015-11-01

We propose a new way of regulating protein adsorption by using a pH-responsive polymer. According to the theoretical results obtained from the molecular theory and kinetic approaches, both thermodynamics and kinetics of protein adsorption are verified to be well controlled by the solution pH. The kinetics and the amount of adsorbed proteins at equilibrium are greatly increased when the solution environment changes from acid to neutral. The reason is that the increased pH promotes the dissociation of the weak polyelectrolyte, resulting in more charged monomers and more stretched chains. Thus the steric repulsion within the polymer layer is weakened, which effectively lowers the barrier felt by the protein during the process of adsorption. Interestingly, we also find that the kinetics of protein desorption is almost unchanged with the variation of pH. It is because although the barrier formed by the polymer layer changes along with the change of pH, the potential at contact with the surface varies equally. Our results may provide useful insights into controllable protein adsorption/desorption in practical applications. Project supported by the National Natural Science Foundation of China (Grant Nos. 21274062, 11474155, and 91027040).

Effect of ordered mesoporous carbon contact layer on the sensing performance of sputtered RuO2 thin film pH sensor.

PubMed

Lonsdale, W; Maurya, D K; Wajrak, M; Alameh, K

2017-03-01

The effect of contact layer on the pH sensing performance of a sputtered RuO 2 thin film pH sensor is investigated. The response of pH sensors employing RuO 2 thin film electrodes on screen-printed Pt, carbon and ordered mesoporous carbon (OMC) contact layers are measured over a pH range from 4 to 10. Working electrodes with OMC contact layer are found to have Nernstian pH sensitivity (-58.4mV/pH), low short-term drift rate (5.0mV/h), low hysteresis values (1.13mV) and fast reaction times (30s), after only 1h of conditioning. A pH sensor constructed with OMC carbon contact layer displays improved sensing performance compared to Pt and carbon-based counterparts, making this electrode more attractive for applications requiring highly-accurate pH sensing with reduced conditioning time. Copyright © 2016 Elsevier B.V. All rights reserved.

Experimental studies of contact angle hysteresis phenomena on polymer surfaces – Toward the understanding and control of wettability for different applications.

PubMed

Grundke, K; Pöschel, K; Synytska, A; Frenzel, R; Drechsler, A; Nitschke, M; Cordeiro, A L; Uhlmann, P; Welzel, P B

2015-08-01

Contact angle hysteresis phenomena on polymer surfaces have been studied by contact angle measurements using sessile liquid droplets and captive air bubbles in conjunction with a drop shape method known as Axisymmetric Drop Shape Analysis - Profile (ADSA-P). In addition, commercially available sessile drop goniometer techniques were used. The polymer surfaces were characterized with respect to their surface structure (morphology, roughness, swelling) and surface chemistry (elemental surface composition, acid-base characteristics) by scanning electron microscopy (SEM), scanning force microscopy (SFM), ellipsometry, X-ray photoelectron spectroscopy (XPS) and streaming potential measurements. Heterogeneous polymer surfaces with controlled roughness and chemical composition were prepared by different routes using plasma etching and subsequent dip coating or grafting of polymer brushes, anodic oxidation of aluminium substrates coated with thin polymer films, deposition techniques to create regular patterned and rough fractal surfaces from core-shell particles, and block copolymers. To reveal the effects of swelling and reorientation at the solid/liquid interface contact angle hysteresis phenomena on polyimide surfaces, cellulose membranes, and thermo-responsive hydrogels have been studied. The effect of different solutes in the liquid (electrolytes, surfactants) and their impact on contact angle hysteresis were characterized for solid polymers without and with ionizable functional surface groups in aqueous electrolyte solutions of different ion concentrations and pH and for photoresist surfaces in cationic aqueous surfactant solutions. The work is an attempt toward the understanding of contact angle hysteresis phenomena on polymer surfaces aimed at the control of wettability for different applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Removal of lindane from an aqueous solution by using aminopropyl silica gel-immobilized calix[6]arene.

PubMed

Tor, Ali; Aydin, Mehmet Emin; Aydin, Senar; Tabakci, Mustafa; Beduk, Fatma

2013-11-15

An aminopropyl silica gel-immobilized calix[6]arene (C[6]APS) has been used for the removal of lindane from an aqueous solution in batch sorption technique. The C[6]APS was synthesized with p-tert-butylcalix[6]arene hexacarboxylate derivative and aminopropyl silica gel in the presence of N,N'-diisopropyl carbodiimide coupling reagent. The sorption study was carried out as functions of solution pH, contact time, initial lindane concentration, C[6]APS dosage and ionic strength of solution. The matrix effect of natural water samples on the sorption efficiency of C[6]APS was also investigated. Maximum lindane removal was obtained at a wide pH range of 2-8 and sorption equilibrium was achieved in 2h. The isotherm analysis indicated that the sorption data can be represented by both Langmuir and Freundlich isotherm models. Increasing ionic strength of the solutions increased the sorption efficiency and matrix of natural water samples had no effect on the sorption of lindane. By using multilinear regression model, regression equation was also developed to explain the effects of the experimental variables. Copyright © 2013 Elsevier B.V. All rights reserved.

Preparation and characterization of chitosan-clay nanocomposites for the removal of Cu(II) from aqueous solution.

PubMed

Azzam, Eid M S; Eshaq, Gh; Rabie, A M; Bakr, A A; Abd-Elaal, Ali A; El Metwally, A E; Tawfik, Salah M

2016-08-01

In the present study, chitosan assembled on gold and silver nanoparticles were prepared and characterized by UV-vis, TEM, EDX and DLS techniques. The nanocomposites chitosan (Ch)/clay, chitosan (Ch)/AgNPs/clay and chitosan (Ch)/AuNPs/clay were prepared by solution mixing method and characterized by FTIR, XRD, and SEM techniques. The adsorption of copper(II) ions onto the prepared hybrid composites from an aqueous solution using batch adsorption was examined. The results showed that benefiting from the surface property of clay, the abundant amino and hydroxyl functional groups of chitosan, the adsorbent provides adequate and versatile adsorption for the Cu(II) ions under investigation. The batch adsorption experiments showed that the adsorption of the Cu(II) is considerably dependent on pH of milieu, the amount of adsorbent, and contact time. Batch adsorption studies revealed that the adsorption capacity of Cu(II) increased with increase in initial concentration and contact time with optimum pH in the range around neutral. The maximum uptake of Cu(II) ions by (Ch)/AgNPs/clay composite was found to be 181.5mg/g. The adsorption efficiency of Cu(II) ions by prepared (Ch)/AgNPs/clay and (Ch)/AuNPs/clay is bigger than that the individual chitosan (Ch)/clay composite which clarifies the role of metal nanoparticles in enhancement the adsorption characters. The study suggests that the (Ch)/AgNPs/clay hybrid composite is a promising nano-adsorbent for the removal of Cu(II) ions from aqueous solution. Copyright © 2016 Elsevier B.V. All rights reserved.

Modification of Natural Zeolite with Fe(III) and Its Application as Adsorbent Chloride and Carbonate ions

NASA Astrophysics Data System (ADS)

Suhartana; Sukmasari, Emmanuella; Azmiyawati, Choiril

2018-04-01

The aim of the research is to natural zeolite with Fe(III) using anion exchange process to improve the anion exchange capacity. Natural zeolite was activated using HNO3 1 N and then mixed with FeCl3 solution and refluxed followed by oven and calcination at a temperature of 550°C. The influence of Fe(III) to zeolite was characterized by FTIR while presence of Fe in zeolite characterized by AAS. Zeolite and Zeolite-Fe adsorption capacity of chloride and carbonate anions were determined through adsorption test by variation of pH and contact time. In advanced, and then to determining the Fe adsorbed concentration at Zeolite using UV-Vis spectrophotometer. FTIR analysis result showed that the addition of Fe does not affect the zeolite’s structure but change the intensity of the zeolite spectra. The Fe concentration in Zeolite-Fe of 714 mg L-1, indicate that Fe was present in the zeolite. Both Zeolite and Zeolite-Fe adsorbtion results showed that optimum pH of Chloride anion is 2, with adsorption capacity 2,33 x 10-3 gg-1 and optimum contact time is 8 minutes. While Zeolite and Zeolite-Fe adsorbtion results showed that optimum pH of Carbonate anion is 5, with adsorption capacity 5,31 x 10-3 gg-1 and optimum contact time is 8 minutes.

Fe{sub 2}O{sub 3}-Bi{sub 2}O{sub 3}-B{sub 2}O{sub 3} glasses as lithium-free nonsilicate pH responsive glasses – Compatibility between pH responsivity and hydrophobicity

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

Hashimoto, Tadanori, E-mail: hasimoto@chem.mie-u.ac.jp; Hamajima, Mitsuaki; Ohta, Honami

Highlights: • Fe{sub 2}O{sub 3}-rich FeBiB glasses show high pH sensitivity and short pH response time. • Bi{sub 2}O{sub 3}-rich FeBiB glasses show relatively high contact angle for water. • FeBiB glasses are lithium-free nonsilicate pH responsive ones. • pH responsivity and hydrophobicity are obtained for optimum glass compositions. - Abstract: Lithium silicate-based glasses have widely been used as commercially available pH glass electrodes. It was revealed that Ti{sup 3+}-containing titanophosphate (TiO{sub 2}-P{sub 2}O{sub 5}, TP) glasses are pH responsive as lithium-free nonsilicate glasses for the first time. TP glasses with the compatibility between pH responsivity and self-cleaning property weremore » obtained by the sequential post-annealing (oxidation and reduction) of as-prepared glasses. Bi{sub 2}O{sub 3}-B{sub 2}O{sub 3} (BiB) glasses are relatively hydrophobic and are expected to show anti-fouling effect. They are unsuitable for pH responsive glasses, because they have high electrical resistivity. In the present study, xFe{sub 2}O{sub 3}·yBi{sub 2}O{sub 3}·(100 − x − y)B{sub 2}O{sub 3} glasses (xFeyBiB, x = 0–20 mol%, y = 20–80 mol%) glasses were selected as new pH responsive glasses with hydrophobicity, because Fe{sub 2}O{sub 3} is a representative component for causing hopping conduction to the glasses. BiB glass did not show pH responsivity, whereas xFeyBiB glasses showed good pH responsivity. xFeyBiB glasses are lithium-free nonsilicate pH responsive ones as well as TP glasses. The electrical resistivity and pH response time decreased with increasing Fe{sub 2}O{sub 3} content. The pH repeatability for standard solutions increased with increasing Bi{sub 2}O{sub 3} content. Silicate glass (20Fe70BiSi) showed better pH responsivity but lower contact angle than those of borate glass (20Fe70BiB). pH sensitivity increased in order of TP glasses (about 80%), xFeyBiB glasses (about 90%) and commercial pH responsive glass (about 100%). xFeyBiB glasses showed short pH response time compared to commercial pH responsive glass. The contact angle for water of xFeyBiB glasses was relatively high (about 90°) as well as BiB glasses, and increased slightly with increasing Bi{sub 2}O{sub 3} content regardless Fe{sub 2}O{sub 3} content. The high contact angle was related to low OH content determined by FT-IR measurement. Thus, 20Fe{sub 2}O{sub 3}·70Bi{sub 2}O{sub 3}·10B{sub 2}O{sub 3} glass was the most suitable one as pH responsive glasses with hydrophobicity. TP glasses are pH responsive ones with self-cleaning property, whereas xFeyBiB glasses are expected as pH responsive ones with anti-fouling property based on hydrophobicity.« less

Equilibrium, Kinetic, and Thermodynamic Studies on the Adsorption of Cadmium from Aqueous Solution by Modified Biomass Ash

PubMed Central

Zheng, Xuebo; Cui, Hongbiao; Zhu, Zhenqiu; Liang, Jiani

2017-01-01

Natural biomass ash of agricultural residuals was collected from a power plant and modified with hexagonal mesoporous silica and functionalized with 3-aminopropyltriethoxysilane. The physicochemical and morphological properties of the biomass ash were analyzed by ICP-OES, SEM, TEM-EDS, FTIR, and BET analysis. The adsorption behavior of the modified product for Cd2+ in aqueous solution was studied as a function of pH, initial metal concentration, equilibrium time, and temperature. Results showed that the specific surface area of the modified product was 9 times that of the natural biomass ash. The modified biomass ash exhibited high affinity for Cd2+ and its adsorption capacity increased sharply with increasing pH from 4.0 to 6.0. The maximum adsorption capacity was 23.95 mg/g in a pH 5 solution with an initial metal concentration of 50 mg/L and a contact time of 90 min. The adsorption of Cd2+ onto the modified biomass ash was well fitted to the Langmuir model and it followed pseudo-second-order kinetics. Thermodynamic analysis results showed that the adsorption of Cd2+ was spontaneous and endothermic in nature. The results suggest that the modified biomass ash is promising for use as an inexpensive and effective adsorbent for Cd2+ removal from aqueous solution. PMID:28348509

Synthesis and characterization of LTA nanozeolite using barley husk silica: Mercury removal from standard and real solutions

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

Azizi, Seyed Naser, E-mail: azizi@umz.ac.ir; Dehnavi, Ahmad Roozbehani, E-mail: Roozbehanisulfur@yahoo.com; Joorabdoozha, Amir

2013-05-15

Highlights: ► Silica extraction from barley husk with high purity for the synthesis of A nanozeolite. ► Free template A nanozeolite synthesized via new source of silica at low temperature. ► Optimization of SiO{sub 2}/Al{sub 2}O{sub 3}, Na{sub 2}O/SiO{sub 2} ratios, temperature and time of the synthesis. ► Utilizing of synthesized A nanozeolite for mercury removal from aqueous solutions. ► Mercury removal at optimized pH, contact time and adsorbent dose from real solution. - Abstract: In this study, synthesized Lined Type A (LTA) nanozeolite from barley husk silica (BHS) was used for mercury removal from standard and real aqueous solutions.more » The BHS in amorphous phase with 80% purity was extracted from barley husk ash (BHA), and used effectively as a new source of silica for the synthesis of NaA nanozeolite. The NaA nanocrystal in pure phase has been synthesized at low temperature, without adding any organic additives. The effects of heating time, reaction temperature, SiO{sub 2}/Al{sub 2}O{sub 3}, and Na{sub 2}O/SiO{sub 2} mole ratios on the crystallization of NaA nanozeolite were studied. The adsorption capacity of mercury (II) was studied as a function of pH, contact time, and amount of adsorbent. The crystallization of NaA nanozeolite from BHS was characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), Brunauer–Emmett–Teller (BET), and FTIR techniques. Moreover, concentration of Hg{sup 2+} ions in the aqueous solutions was analyzed by hydride generation atomic absorption spectroscopy method (HG-AAS). The standard and real samples analysis showed that NaA nanozeolite is capable of Hg{sup 2+} ions removal from the aqueous solutions. Efficiency of mercury (II) adsorption from real solutions onto the nano-sized NaA zeolite was 98%.« less

The potential use of a layer-by-layer strategy to develop LDPE antimicrobial films coated with silver nanoparticles for packaging applications.

PubMed

Azlin-Hasim, Shafrina; Cruz-Romero, Malco C; Cummins, Enda; Kerry, Joseph P; Morris, Michael A

2016-01-01

Commercial low-density polyethylene (LDPE) films were UV/ozone treated and coated using a layer-by-layer (LbL) technique by alternating the deposition of polyethyleneimine (PEI) and poly(acrylic acid) (PAA) polymer solutions and antimicrobial silver (Ag). The effects of the initial pH of the PEI/PAA polymer solutions alternating layers (pH 10.5/4 or 9/6.5) on the antimicrobial activity of the developed LbL coatings combined with Ag against Gram-negative and Gram-positive bacteria were investigated. The results from fourier transform infrared spectroscopy and toluidine blue O assay showed that LDPE LbL coated using PEI/PAA polymer solutions with initial pH of 10.5/4 significantly increased the presence of carboxylic acid groups and after Ag attachment the coating had higher antimicrobial activity against both Gram-negative and Gram-positive bacteria compared to the LDPE LbL coated using PEI/PAA polymer solutions with initial pH of 9/6.5. The LDPE LbL coated films using non-modified pH PEI/PAA polymer solutions decreased the water contact-angle indicating an increased hydrophilicity of the film, also increased the tensile strength and roughness of LDPE LbL coated films compared to uncoated LbL samples. The LDPE LbL coated films attached with Ag(+) were UV/ozone treated for 20 min to oxidise Ag(+) to Ag(0). The presence of Ag(0) (Ag nanoparticles (NPs)) on the LDPE LbL coated films was confirmed by XRD, UV-vis spectrophotometer and colour changes. The overall results demonstrated that the LbL technique has the potential to be used as a coating method containing antimicrobial Ag NPs and that the manufactured films could potentially be applied as antimicrobial packaging. Copyright © 2015 Elsevier Inc. All rights reserved.

Biosorption Behavior of Ciprofloxacin onto Enteromorpha prolifera: Isotherm and Kinetic Studies.

PubMed

Wu, Shaoling; Li, Yanhui; Zhao, Xindong; Du, Qiuju; Wang, Zonghua; Xia, Yanzhi; Xia, Linhua

2015-01-01

The studies aimed at the feasibility of using Enteromorpha prolifera for the removal of ciprofloxacin from aqueous solutions. Batch experiments were carried out for the biosorption of ciprofloxacin onto Enteromorpha prolifera. The factors affecting the biosorption process such as the initial concentration, dosage, pH and the contact time were studied. Enteromorpha prolifera exhibited a maximum biosorption capacity of 21.7 mg/g. The pseudo-second-order kinetic model described the ciprofloxacin biosorption process with a good fitting. The optimum pH of ciprofloxacin adsorbed by Enteromorpha prolifera was 10. Biosorption equilibrium studies demonstrated that the biosorption followed Freundlich isotherm model, which implied a heterogeneous biosorption phenomenon.

76 FR 63314 - Center for Scientific Review Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-12

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75 FR 38111 - Center for Scientific Review; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2010-07-01

..., (Virtual Meeting). Contact Person: Arnold Revzin, PhD, Scientific Review Officer, Center for Scientific..., (Virtual Meeting). Contact Person: Jerry L. Taylor, PhD, Scientific Review Officer, Center for Scientific... Rockledge Drive, Bethesda, MD 20892, (Virtual Meeting). Contact Person: Richard Ingraham, PhD, Scientific...

Electrically conductive PEDOT coating with self-healing superhydrophobicity.

PubMed

Zhu, Dandan; Lu, Xuemin; Lu, Qinghua

2014-04-29

A self-healing electrically conductive superhydrophobic poly(3,4-ethylenedioxythiophene) (PEDOT) coating has been prepared by chemical vapor deposition of a fluoroalkylsilane (POTS) onto a PEDOT film, which was obtained by electrochemical deposition. The coating not only maintained high conductivity with a low resistivity of 3.2 × 10(-4) Ω·m, but also displayed a water contact angle larger than 156° and a sliding angle smaller than 10°. After being etched with O2 plasma, the coating showed an excellent self-healing ability, spontaneously regaining its superhydrophobicity when left under ambient conditions for 20 h. This superhydrophobicity recovery process was found to be humidity-dependent, and could be accelerated and completed within 2 h under a high humidity of 84%. The coating also exhibited good superhydrophobicity recovering ability after being corroded by strong acid solution at pH 1 or strong base solution at pH 14 for 3 h.

Efficient Removal of Uranium from Aqueous Solution by Reduced Graphene Oxide-Zn0.5Ni0.5Fe2O4 Ferrite-Polyaniline Nanocomposite

NASA Astrophysics Data System (ADS)

Tran, Dat Quang; Pham, Hung Thanh; Do, Hung Quoc

2017-06-01

Reduced graphene oxide-Zn0.5Ni0.5Fe2O4 ferrite-polyaniline nanocomposite (RGO-ZNF-PANI) was synthesized by a three-step method. The prepared samples were characterized by x-ray diffraction, Raman spectroscopy, scanning electron microscopy and vibrating sample magnetometer. In particular, we found that this material is capable of effectively removing uranium from an aquatic environment. This is confirmed by our experimental results using the method of inductively coupled plasma mass spectrometry. Adsorptive behaviour of uranium from an aqueous solution on the RGO-ZNF-PANI nanocomposite was examined as a function of pH, contact time, and equilibrium. Uranium concentration was carried out by batch techniques. The adsorption isotherm agrees well with the Langmuir model, having a maximum sorption capacity of 1885 mg/g, at pH 5 and 25°C.

Apiaceae Family Plants as Low-Cost Adsorbents for the Removal of Lead Ion from Water Environment

NASA Astrophysics Data System (ADS)

Boontham, W.; Babel, S.

2017-06-01

Adsorbents prepared from the three selected plants from Apiaceae famaily commonly known as parsley, coriander and culantro were observed to remove lead from aqueous solutions. Batch experiments were conducted to study the effect of dosage, pH, contact time and agitation speed at 10 mg L-1 initial Pb(II) concentration. Results revealed that three selected plants showed high adsorption capacity for removal of lead from aqueous solutions. The maximum biosorption of Pb2+ was found to be more than 97% with 1.0 g/l dosage for all three adsorbents under optimum pH of 3-5. The adsorption equilibrium was established after about 1 hr. The equilibrium adsorption capacity of parsley and coriander were found to fit well with the Langmuir isotherm whereas the Freundlich isotherm was better fit for culantro. The studies showed that the adsorbents can be used for removing lead ions from contaminated waters.

Adsorption of Reactive Red M-2BE dye from water solutions by multi-walled carbon nanotubes and activated carbon.

PubMed

Machado, Fernando M; Bergmann, Carlos P; Fernandes, Thais H M; Lima, Eder C; Royer, Betina; Calvete, Tatiana; Fagan, Solange B

2011-09-15

Multi-walled carbon nanotubes and powdered activated carbon were used as adsorbents for the successful removal of Reactive Red M-2BE textile dye from aqueous solutions. The adsorbents were characterised by infrared spectroscopy, N(2) adsorption/desorption isotherms and scanning electron microscopy. The effects of pH, shaking time and temperature on adsorption capacity were studied. In the acidic pH region (pH 2.0), the adsorption of the dye was favourable using both adsorbents. The contact time to obtain equilibrium at 298K was fixed at 1h for both adsorbents. The activation energy of the adsorption process was evaluated from 298 to 323K for both adsorbents. The Avrami fractional-order kinetic model provided the best fit to the experimental data compared with pseudo-first-order or pseudo-second-order kinetic adsorption models. For Reactive Red M-2BE dye, the equilibrium data were best fitted to the Liu isotherm model. Simulated dyehouse effluents were used to check the applicability of the proposed adsorbents for effluent treatment. Copyright © 2011 Elsevier B.V. All rights reserved.

Acid Green 1 removal from wastewater by layered double hydroxides

NASA Astrophysics Data System (ADS)

Elkhattabi, El Hassan; Lakraimi, Mohamed; Berraho, Moha; Legrouri, Ahmed; Hammal, Radouan; El Gaini, Layla

2018-03-01

The paper presents the removal of Acid Green 1 (AG1) from aqueous solutions by [Zn-Al-Cl]-layered double hydroxides (LDHs). The LDH was prepared by coprecipitation at constant pH. The affinity of this material for AG1 was studied as a function of contact time, pH of the solution, LDH dose and AG1/LDH mass ratio. It was found that 32 h are enough to reach the equilibrium with a maximum retention at pH 8 for an LDH dose of 100 mg and with an AG1/LDH mass ratio higher than 2. The adsorption isotherm is of L-type, as described by the Langmuir model. The results demonstrate that AG1 retention on LDHs occurs by adsorption on external surface when AG1/LDH mass ratio is equal or lower than 2 and by both adsorption and interlayer ion exchange for ratios higher than 2. A mechanism for the AG1 removal has been confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric-differential thermal analyses and scanning electron microscopy.

Fluidized bed gasification of extracted coal

DOEpatents

Aquino, Dolores C.; DaPrato, Philip L.; Gouker, Toby R.; Knoer, Peter

1986-01-01

Coal or similar carbonaceous solids are extracted by contacting the solids in an extraction zone (12) with an aqueous solution having a pH above 12.0 at a temperature between 65.degree. C. and 110.degree. C. for a period of time sufficient to remove bitumens from the coal into said aqueous solution and the extracted solids are then gasified at an elevated pressure and temperature in a fluidized bed gasification zone (60) wherein the density of the fluidized bed is maintained at a value above 160 kg/m.sup.3. In a preferred embodiment of the invention, water is removed from the aqueous solution in order to redeposit the extracted bitumens onto the solids prior to the gasification step.

76 FR 38405 - Center for Scientific Review; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-30

..., 6701 Rockledge Drive, Bethesda, MD 20892 (Virtual Meeting). Contact Person: Michael H Chaitin, PhD... (Virtual Meeting). Contact Person: David L Williams, PhD, Scientific Review Officer, Center for Scientific... Health, 6701 Rockledge Drive, Bethesda, MD 20817 (Virtual Meeting). Contact Person: David L Williams, PhD...

76 FR 77544 - Center for Scientific Review; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-13

... 20892 (Virtual Meeting). Contact Person: John Firrell, Ph.D., Scientific Review Officer, Center for..., Bethesda, MD 20892 (Virtual Meeting). Contact Person: Aruna K Behera, Ph.D., Scientific Review Officer... Wharf, 2620 Jones Street, San Francisco, CA 94133. Contact Person: Joseph D Mosca, Ph.D., Scientific...

Molecular evidence of stereo-specific lactoferrin dimers in solution.

PubMed

Persson, Björn A; Lund, Mikael; Forsman, Jan; Chatterton, Dereck E W; Akesson, Torbjörn

2010-10-01

Gathering experimental evidence suggests that bovine as well as human lactoferrin self-associate in aqueous solution. Still, a molecular level explanation is unavailable. Using force field based molecular modeling of the protein-protein interaction free energy we demonstrate (1) that lactoferrin forms highly stereo-specific dimers at neutral pH and (2) that the self-association is driven by a high charge complementarity across the contact surface of the proteins. Our theoretical predictions of dimer formation are verified by electrophoretic mobility and N-terminal sequence analysis on bovine lactoferrin. 2010 Elsevier B.V. All rights reserved.

Immobilization of Candida antarctica lipase B by adsorption to green coconut fiber.

PubMed

Brígida, Ana I S; Pinheiro, Alvaro D T; Ferreira, Andrea L O; Gonçalves, Luciana R B

2008-03-01

An agroindustrial residue, green coconut fiber, was evaluated as support for immobilization of Candida antarctica type B (CALB) lipase by physical adsorption. The influence of several parameters, such as contact time, amount of enzyme offered to immobilization, and pH of lipase solution was analyzed to select a suitable immobilization protocol. Kinetic constants of soluble and immobilized lipases were assayed. Thermal and operational stability of the immobilized enzyme, obtained after 2 h of contact between coconut fiber and enzyme solution, containing 40 U/ml in 25 mM sodium phosphate buffer pH 7, were determined. CALB immobilization by adsorption on coconut fiber promoted an increase in thermal stability at 50 and 60 degrees C, as half-lives (t (1/2)) of the immobilized enzyme were, respectively, 2- and 92-fold higher than the ones for soluble enzyme. Furthermore, operational stabilities of methyl butyrate hydrolysis and butyl butyrate synthesis were evaluated. After the third cycle of methyl butyrate hydrolysis, it retained less than 50% of the initial activity, while Novozyme 435 retained more than 70% after the tenth cycle. However, in the synthesis of butyl butyrate, CALB immobilized on coconut fiber showed a good operational stability when compared to Novozyme 435, retaining 80% of its initial activity after the sixth cycle of reaction.

Removal of malachite green dye from aqueous solution using mesoporous silica synthesized from 1-octyl-3-methylimidazolium chloride ionic liquid

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

Ekka, Basanti; Nayak, Soumitra Ranjan; Dash, Priyabrat, E-mail: dashp@nitrkl.ac.in, E-mail: rkpatel@nitrkl.ac.in

2016-04-13

In this research, mesoporous silica was synthesized via a modified sol-gel route using 1-octyl-3-methylimidazolium chloride and was employed to remove malachite green (MG) dye from aqueous solution. Subsequently, this material was characterized and identified by different techniques such as Fourier transform infrared spectroscopy (FT-IR), N{sub 2} adsorption-desorption method, scanning electron microscopy (SEM), and thermosgravimetric analysis (TGA). Unique properties such as high surface area and pore diameter, in addition to highly reactive atoms and presence of various functional groups make the mesoporous silica possible for efficient removal of malachite green (MG). In batch experimental set-up, optimum conditions for quantitative removal ofmore » MG by mesoporous silica was attained by varying different variables such as adsorbent dosage, initial dye concentration, contact time, and pH. Optimum values were set as pH of 8.0, 0.5 g of adsorbent at contact time of 120 min. The adsorption of MG follows the pseudo-second-order rate equation. Equilibrium data fitted well with the Freundlich model at all amount of adsorbent, while maximum adsorption capacity was 5.981 mg g{sup −}1 for 0.5 g mesoporous silica synthesized in IL.« less

[Characteristics, stability and in vitro efficacy of cleaning products for contact lenses].

PubMed

Coiffard, L; Rivalland, P; De Roeck-Holtzhauer, Y

1995-01-01

We characterized some market products designed for cleaning contact lenses and we compared their properties to the main requirements of eye-washes. We performed several physicochemical controls including pH determination, viscosity with a Baume apparatus and the decreasing of the freezing point following the method described by the French Pharmacopea. In addition, we carried out certain analytical controls, concerning three active principles (thiomersal, chlorhexidin digluconate, hydrogen peroxide), at the opening of the different package and after accelerated aging. A microbiological control was performed when opening the product and after a simulation of a 5-day aging. We finally determined the efficacy of the products on four bacterial strains for tests and of deproteinizing products on artificial dust. The pH values obtained ranged from 4.0 (oxygenated water solutions) to 7.8. The viscosity was close to a water solution one. Contents in active substances were usually similar to those stated on the package. At opening, the bacteriological quality was excellent. But, the multidose package were highly contaminated when used. Finally decontaminating efficacy against some germs was very good for the products tested. The results obtained show that the rincing products best answer the eye-wash criteria taken as references. Their main disadvantage is their contamination in the case of multidose packaging.

[Determination of physicochemical characteristics and evaluation of decontaminating efficacy and in vitro safety of cleaning products for contact lenses].

PubMed

Simon, M; Coiffard, L J; Rivalland, P; De Roeck-Holtzhauer, Y

1996-01-01

This work aims to characterize products designed for cleaning contact lenses and particularly their physicochemical properties, their efficiency and their ocular irritancy potential compared to the main requirements of eye-washes. The physicochemical controls include pH determination, viscosity and freezing point depression. In addition, we carried out the hydrogen peroxide assay for products containing this active substance. A microbiological control was performed when opening the product and after simulation of a 21-day aging. We determined the decontaminating efficacy of the products on four bacterial strains and a fungal strain. Finally, we tested their ocular allowance by an in vitro test. The pH values obtained ranged from 3.2 (oxygenated water solutions) to 7.6. The viscosity was close to a water solution one (about 1 centipoise). The different assays showed hydrogen peroxide content similar to that stated on the package: rate averaged to 3% and was negligible after neutralization. At opening and after simulation the bacteriological quality was excellent. Finally, decontaminating efficiency against germs was very good for the products tested. The products were classified as non-irritant by the ocular irritancy test. The results obtained show that the products tested met the reference criteria, particularly eye-wash criteria.

Ab initio investigation of the surface properties of austenitic Fe-Ni-Cr alloys in aqueous environments

NASA Astrophysics Data System (ADS)

Rák, Zs.; Brenner, D. W.

2017-04-01

The surface energetics of two austenitic stainless steel alloys (Type 304 and 316) and three Ni-based alloys (Alloy 600, 690, and 800) are investigated using theoretical methods within the density functional theory. The relative stability of the low index surfaces display the same trend for all alloys; the most closely packed orientation and the most stable is the (111), followed by the (100) and the (110) surfaces. Calculations on the (111) surfaces using various surface chemical and magnetic configurations reveal that Ni has the tendency to segregate toward the surface and Cr has the tendency to segregate toward the bulk. The magnetic frustration present on the (111) surfaces plays an important role in the observed segregation tendencies of Ni and Cr. The stability of the (111) surfaces in contact with aqueous solution are evaluated as a function of temperature, pH, and concentration of aqueous species. The results indicate that the surface stability of the alloys decrease with temperature and pH, and increase slightly with concentration. Under conditions characteristic to an operating pressurized water reactor, the Ni-based alloy series appears to be of better quality than the stainless steel series with respect to corrosion resistance and release of aqueous species when in contact with aqueous solutions.

Immobilization of Candida antarctica Lipase B by Adsorption to Green Coconut Fiber

NASA Astrophysics Data System (ADS)

Brígida, Ana I. S.; Pinheiro, Álvaro D. T.; Ferreira, Andrea L. O.; Gonçalves, Luciana R. B.

An agroindustrial residue, green coconut fiber, was evaluated as support for immobilization of Candida antarctica type B (CALB) lipase by physical adsorption. The influence of several parameters, such as contact time, amount of enzyme offered to immobilization, and pH of lipase solution was analyzed to select a suitable immobilization protocol. Kinetic constants of soluble and immobilized lipases were assayed. Thermal and operational stability of the immobilized enzyme, obtained after 2 h of contact between coconut fiber and enzyme solution, containing 40 U/ml in 25 mM sodium phosphate buffer pH 7, were determined. CALB immobilization by adsorption on coconut fiber promoted an increase in thermal stability at 50 and 60 °C, as half-lives (t 1/2) of the immobilized enzyme were, respectively, 2- and 92-fold higher than the ones for soluble enzyme. Furthermore, operational stabilities of methyl butyrate hydrolysis and butyl butyrate synthesis were evaluated. After the third cycle of methyl butyrate hydrolysis, it retained less than 50% of the initial activity, while Novozyme 435 retained more than 70% after the tenth cycle. However, in the synthesis of butyl butyrate, CALB immobilized on coconut fiber showed a good operational stability when compared to Novozyme 435, retaining 80% of its initial activity after the sixth cycle of reaction.

A comprehensive adsorption study and modeling of antibiotics as a pharmaceutical waste by graphene oxide nanosheets.

PubMed

Rostamian, Rahele; Behnejad, Hassan

2018-01-01

The adsorption behavior of tetracycline (TCN), doxycycline (DCN) as the most common antibiotics in veterinary and ciprofloxacin (CPN) onto graphene oxide nanosheets (GOS) in aqueous solution was evaluated. The four factors influencing the adsorption of antibiotics (initial concentration, pH, temperature and contact time) were studied. The results showed that initial pH ∼ 6 to 7 and contact time ∼ 100 - 200min are optimum for each drug. The monolayer adsorption capacity was reduced with the increasing temperature from 25°C to 45°C. Non-linear regressions were carried out in order to define the best fit model for every system. To do this, eight error functions were applied to predict the optimum model. Among various models, Hill and Toth isotherm models represented the equilibrium adsorption data of antibiotics while the kinetic data were well fitted by pseudo second-order (PSO) kinetic model (DCN and TCN) and Elovich (CPN) models. The maximum adsorption capacity (q max ) is found to be in the following order: CPN > DCN > TCN, obtained from sips equation at the same temperature. The GOS shows highest adsorption capacity towards CPN up to 173.4mgg -1 . The study showed that GOS can be removed more efficiently from water solution. Copyright © 2017 Elsevier Inc. All rights reserved.

Potential immobilized Saccharomyces cerevisiae as heavy metal removal

NASA Astrophysics Data System (ADS)

Raffar, Nur Izzati Abdul; Rahman, Nadhratul Nur Ain Abdul; Alrozi, Rasyidah; Senusi, Faraziehan; Chang, Siu Hua

2015-05-01

Biosorption of copper ion using treated and untreated immobilized Saccharomyces cerevisiae from aqueous solution was investigate in this study. S.cerevisiae has been choosing as biosorbent due to low cost, easy and continuously available from various industries. In this study, the ability of treated and untreated immobilized S.cerevisiae in removing copper ion influence by the effect of pH solution, and initial concentration of copper ion with contact time. Besides, adsorption isotherm and kinetic model also studied. The result indicated that the copper ion uptake on treated and untreated immobilized S.cerevisiae was increased with increasing of contact time and initial concentration of copper ion. The optimum pH for copper ion uptake on untreated and treated immobilized S.cerevisiae at 4 and 6. From the data obtained of copper ion uptake, the adsorption isotherm was fitted well by Freundlich model for treated immobilized S.cerevisiae and Langmuir model for untreated immobilized S.cerevisiae according to high correlation coefficient. Meanwhile, the pseudo second order was described as suitable model present according to high correlation coefficient. Since the application of biosorption process has been received more attention from numerous researchers as a potential process to be applied in the industry, future study will be conducted to investigate the potential of immobilized S.cerevisiae in continuous process.

RECOVERY OF URANIUM AND THORIUM FROM AQUEOUS SOLUTIONS

DOEpatents

Calkins, G.D.

1958-06-10

>A process is described for the recovery of uranium and thorium from monazite sand, which is frequently processed by treating it with a hot sodium hydroxide solution whereby a precipitate forms consisting mainly of oxides or hydroxides of the rare earths, thorium and uranium. The precipitate is dissolved in mineral acid, and the acid solution is then neutralized to a pH value of between 5.2 and 6.2 whereby both the uranium and thorium precipitate as the hydroxides, while substantially all the rare earth metal values present remain in the solution. The uranium and thoriunn can then be separated by dissolving the precipitate in a solution containing a mixture of alkali carbonate and alkali bicarbonate: and contacting the carbonate solution with a strong-base anion exchange resin whereby the uranium values are adsorbed on the resin while the thorium remains in solution.

Removal of arsenic compounds from petroliferous liquids

DOEpatents

Fish, R.H.

1984-04-06

The present invention in one aspect comprises a process for removing arsenic from petroliferous-derived liquids by contacting said liquid with a divinylbenzene-crosslinked polystyrene polymer (i.e. PS-DVB) having catechol ligands anchored to said polymer, said contacting being at an elevated temperature. In another aspect, the invention is a process for regenerating spent catecholated polystyrene polymer by removal of the arsenic bound to it from contacting petroliferous liquid in accordance with the aspect described above which regenerating process comprises: (a) treating said spent catecholated polystyrene polymer with an aqueous solution of at least one member selected from the group consisting of carbonates and bicarbonates of ammonium, alkali metals, and alkaline earth metals, said solution having a pH between about 8 and 10, and said treating being at a temperature in the range of about 20/sup 0/ to 100/sup 0/C; (b) separating the solids and liquids from each other. In a preferred embodiment the regeneration treatment is in two steps wherein step: (a) is carried out with an aqueous alcoholic carbonate solution which includes at least one lower alkyl alcohol, and, steps (c) and (d) are added. Steps (c) and (d) comprise: (c) treating the solids with an aqueous alcoholic solution of at least one ammonium, alkali or alkaline earth metal bicarbonate at a temperature in the range of about 20 to 100/sup 0/C; and (d) separating the solids from the liquids.

Fabrication of a novel superhydrophobic and superoleophilic surface by one-step electrodeposition method for continuous oil/water separation

NASA Astrophysics Data System (ADS)

Xiang, Meisu; Jiang, Meihuizi; Zhang, Yanzong; Liu, Yan; Shen, Fei; Yang, Gang; He, Yan; Wang, Lilin; Zhang, Xiaohong; Deng, Shihuai

2018-03-01

A novel superhydrophobic and superoleophilic surface was fabricated by one-step electrodeposition on stainless steel meshes, and the durability and oil/water separation properties were assessed. Field emission scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), fourier transform infrared spectroscopy (FT-IR) and optical contact angle measurements were used to characterize surface morphologies, chemical compositions, and wettabilities, respectively. The results indicated that the as-prepared mesh preformed excellent superhydrophobicity and superoleophilicity with a high water contact angle (WCA) of 162 ± 1° and oil contact angle of (OCA) 0°. Meanwhile, the as-prepared mesh also exhibited continuous separation capacity of many kinds of oil/water mixtures, and the separation efficiency for lubrication oil/water mixture was about 98.6%. In addition, after 10 separation cycles, the as-prepared mesh possessed the WCAs of 155 ± 2°, the OCAs of 0° and the separation efficiency of 97.8% for lubrication oil/water mixtures. The as-prepared mesh also retained superhydrophobic and superoleophilic properties after abrading, immersing in salt solutions and different pH solutions.

Chemical Reaction between Boric Acid and Phosphine Indicates Boric Acid as an Antidote for Aluminium Phosphide Poisoning.

PubMed

Soltani, Motahareh; Shetab-Boushehri, Seyed F; Shetab-Boushehri, Seyed V

2016-08-01

Aluminium phosphide (AlP) is a fumigant pesticide which protects stored grains from insects and rodents. When it comes into contact with moisture, AlP releases phosphine (PH3), a highly toxic gas. No efficient antidote has been found for AlP poisoning so far and most people who are poisoned do not survive. Boric acid is a Lewis acid with an empty p orbital which accepts electrons. This study aimed to investigate the neutralisation of PH3 gas with boric acid. This study was carried out at the Baharlou Hospital, Tehran University of Medical Sciences, Tehran, Iran, between December 2013 and February 2014. The volume of released gas, rate of gas evolution and changes in pH were measured during reactions of AlP tablets with water, acidified water, saturated boric acid solution, acidified saturated boric acid solution, activated charcoal and acidified activated charcoal. Infrared spectroscopy was used to study the resulting probable adduct between PH3 and boric acid. Activated charcoal significantly reduced the volume of released gas (P <0.01). Although boric acid did not significantly reduce the volume of released gas, it significantly reduced the rate of gas evolution (P <0.01). A gaseous adduct was formed in the reaction between pure AlP and boric acid. These findings indicate that boric acid may be an efficient and non-toxic antidote for PH3 poisoning.

Preparation and biosorption evaluation of Bacillus subtilis/alginate–chitosan microcapsule

PubMed Central

Tong, Ke

2017-01-01

The aim of this study was to assess the effect of alginate–chitosan microcapsule on viability characteristics of Bacillus subtilis and the ability of B. subtilis/alginate–chitosan microcapsule to remove uranium ion from aqueous solution. The effects of particle size, chitosan molecular weight and inoculum density on viability characteristics were studied using alginate–chitosan microcapsule-immobilized B. subtilis experiments. In addition, the effects of pH, immobilized spherule dosage, temperature, initial uranium ion concentration and contact time on removal of uranium ion were studied using batch adsorption experiments. The results showed that alginate–chitosan microcapsule significantly improved the viability characteristics of B. subtilis and that B. subtilis/alginate–chitosan microcapsule strongly promoted uranium ion absorption. Moreover, the optimum values of pH was 6; immobilized spherule dosage was 3.5; temperature was 20°C; initial uranium ion concentration was 150 mg/L; contact time was 3 h of uranium ion absorption and the maximum adsorption capacity of uranium ion was 376.64 mg/g. PMID:28223783

Batch study of manganese removal from mine effluent using mixture of ferromanganese ore and humus

NASA Astrophysics Data System (ADS)

Kamal, Norinsafrina Mustaffa; Aziz, Hamidi Abdul; Sulaiman, Shamsul Kamal; Hussin, Hashim

2017-10-01

Environmental problem related to mining industry always associates with high heavy metal contents in mine effluent. Manganese is among the metals that need to be reduced before the mine effluent entering receiving waterways. In this batch study, mixture of ferromanganese ore and humus had been applied to remove manganese from mine effluent. Effect of particle size of ferromanganese ore, dosage, mix ratio, pH and contact time had been studied to examine the effectiveness of the mixture in removing manganese. Results from the study have shown that optimum manganese removal was 93.54% by using particle size of 0.25-0.5 mm of ferromanganese ore, 3g of dosage mixture, mix ratio of 20%;80%, solution pH of 7 and 210 minutes (3.5 hours) of contact time. Thus, it is proven that mixture of ferromanganese ore and humus has potential to be used for removal of manganese in mine effluent.

Native, acidic pre-treated and composite clay efficiency for the adsorption of dicationic dye in aqueous medium.

PubMed

Ehsan, Asma; Bhatti, Haq Nawaz; Iqbal, Munawar; Noreen, Saima

2017-02-01

Environmental applications of composites have attracted the interests of researchers due to their excellent adsorption efficiency for pollutants. Native, HCl pre-treated clay and MnFe 2 O 4 /clay composite were investigated as an adsorbent for removal of methyl green from aqueous solution. The adsorption behaviors of dye onto native, HCl pre-treated and composite clays were studied as a function of contact time, adsorbent dose, pH, initial dye concentration and temperature. Maximum dye adsorption of 44 mg/g was achieved at pH of 8, contact time 40 min, adsorbent dose 0.20 g/L and initial dye concentration of 125 mg/L using clay composite. The Langmuir isotherm and pseudo-second-order kinetic model best explained the methyl green dye adsorption onto clay adsorbents. Thermodynamic parameters revealed the endothermic and spontaneous adsorption nature of dye. From results, it is concluded that clay has potential for adsorbing methyl green and can be used for the removal of dyes from industrial effluents.

InGaN/GaN quantum dots as optical probes for the electric field at the GaN/electrolyte interface

NASA Astrophysics Data System (ADS)

Teubert, J.; Koslowski, S.; Lippert, S.; Schäfer, M.; Wallys, J.; Dimitrakopulos, G.; Kehagias, Th.; Komninou, Ph.; Das, A.; Monroy, E.; Eickhoff, M.

2013-08-01

We investigated the electric-field dependence of the photoluminescence-emission properties of InGaN/GaN quantum dot multilayers in contact with an electrolyte. Controlled variations of the surface potential were achieved by the application of external electric fields using the electrolytic Schottky contact and by variation of the solution's pH value. Prior to characterization, a selective electrochemical passivation process was required to suppress leakage currents. The quantum dot luminescence is strongly affected by surface potential variations, i.e., it increases exponentially with cathodic bias and acidic pH values. The results cannot be explained by a modification of intra-dot polarization induced electric fields via the quantum confined Stark effect but are attributed to the suppression/enhancement of non-radiative recombination processes, i.e., mainly hole transfer into the electrolyte. The results establish a link between the photoluminescence intensity and the magnitude of electric fields at the semiconductor/electrolyte interface.

Water-soluble drug partitioning and adsorption in HEMA/MAA hydrogels.

PubMed

Dursch, Thomas J; Taylor, Nicole O; Liu, David E; Wu, Rong Y; Prausnitz, John M; Radke, Clayton J

2014-01-01

Two-photon confocal microscopy and back extraction with UV/Vis-absorption spectrophotometry quantify equilibrium partition coefficients, k, for six prototypical drugs in five soft-contact-lens-material hydrogels over a range of water contents from 40 to 92%. Partition coefficients were obtained for acetazolamide, caffeine, hydrocortisone, Oregon Green 488, sodium fluorescein, and theophylline in 2-hydroxyethyl methacrylate/methacrylic acid (HEMA/MAA, pKa≈5.2) copolymer hydrogels as functions of composition, aqueous pH (2 and 7.4), and salinity. At pH 2, the hydrogels are nonionic, whereas at pH 7.4, hydrogels are anionic due to MAA ionization. Solute adsorption on and nonspecific electrostatic interaction with the polymer matrix are pronounced. To express deviation from ideal partitioning, we define an enhancement or exclusion factor, E ≡ k/φ1, where φ1 is hydrogel water volume fraction. All solutes exhibit E > 1 in 100 wt % HEMA hydrogels owing to strong specific adsorption to HEMA strands. For all solutes, E significantly decreases upon incorporation of anionic MAA into the hydrogel due to lack of adsorption onto charged MAA moieties. For dianionic sodium fluorescein and Oregon Green 488, and partially ionized monoanionic acetazolamide at pH 7.4, however, the decrease in E is more severe than that for similar-sized nonionic solutes. Conversely, at pH 2, E generally increases with addition of the nonionic MAA copolymer due to strong preferential adsorption to the uncharged carboxylic-acid group of MAA. For all cases, we quantitatively predict enhancement factors for the six drugs using only independently obtained parameters. In dilute solution for solute i, Ei is conveniently expressed as a product of individual enhancement factors for size exclusion (Ei(ex)), electrostatic interaction (Ei(el)), and specific adsorption (Ei(ad)):Ei≡Ei(ex)Ei(el)Ei(ad). To obtain the individual enhancement factors, we employ an extended Ogston mesh-size distribution for Ei(ex); Donnan equilibrium for Ei(el); and Henry's law characterizing specific adsorption to the polymer chains for Ei(ad). Predicted enhancement factors are in excellent agreement with experiment. Copyright © 2013 Elsevier Ltd. All rights reserved.

In vitro analysis of the physical properties of contact lens blister pack solutions.

PubMed

Menzies, Kara L; Jones, Lyndon

2011-04-01

Since the initial development of silicone hydrogels, many modifications to the bulk and surface properties of the lenses have been undertaken to improve the wettability and comfort of the lenses. Recently, manufacturers have incorporated various "wetting agents" or surface-active agents into the blister packaging solutions (BPSs) of the lenses to improve initial comfort of the lens on eye. The purpose of this study was to measure and compare the pH, surface tension (ST), viscosity, and osmolality of BPSs for a variety of silicone hydrogel and polyHEMA-based hydrogel lenses. In addition, two saline solutions were tested for comparison purposes. The pH, osmolality, ST, and viscosity were measured for the BPSs for lotrafilcon B and lotrafilcon A and lotrafilcon B with a "modified BPS" (m-lotrafilcon A, m-lotrafilcon B) (CIBA Vision, Duluth, GA); balafilcon A (Bausch & Lomb, Rochester, NY); galyfilcon A, senofilcon A, and narafilcon A (Johnson & Johnson, Jacksonville, FL); and comfilcon A and enfilcon A (CooperVision, Pleasanton, CA) and BPSs from two conventional polyHEMA-based materials-etafilcon A (Johnson & Johnson) and omafilcon A (CooperVision). The two saline solutions tested were Unisol (Alcon, Fort Worth, TX) and Softwear Saline (CIBA Vision). The pH results for the two saline solutions and all BPSs remained in the pH range of tears (6.6-7.8). The ST of the modified BPS was significantly lower (p < 0.01) than the original non-modified BPS. Viscosity measurements ranged between 0.90 and 1.00 cP for all BPSs and saline solutions, except for the modified BPS, which had significantly higher viscosities (p < 0.001). Osmolality measurements were not significantly different (p > 0.05) between BPSs made by the same manufacturer but were significantly different compared with BPSs made by different manufacturers (p < 0.05). The incorporation of wetting agents and surfactants into BPSs does alter the physical properties of the BPSs, which may have clinical implications regarding initial in-eye comfort.

PH Sensitive Polymers for Improving Reservoir Sweep and Conformance Control in Chemical Flooring

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

Mukul Sharma; Steven Bryant; Chun Huh

There is an increasing opportunity to recover bypassed oil from depleted, mature oilfields in the US. The recovery factor in many reservoirs is low due to inefficient displacement of the oil by injected fluids (typically water). The use of chemical flooding methods to increase recovery efficiencies is severely constrained by the inability of the injected chemicals to contact the bypassed oil. Low sweep efficiencies are the primary cause of low oil recoveries observed in the field in chemical flooding operations even when lab studies indicate high oil recovery efficiency. Any technology that increases the ability of chemical flooding agents tomore » better contact the remaining oil and reduce the amount of water produced in conjunction with the produced oil will have a significant impact on the cost of producing oil domestically in the US. This translates directly into additional economically recoverable reserves, which extends the economic lives of marginal and mature wells. The objective of this research project was to develop a low-cost, pH-triggered polymer for use in IOR processes to improve reservoir sweep efficiency and reservoir conformance in chemical flooding. Rheological measurements made on the polymer solution, clearly show that it has a low viscosity at low pH and exhibits a sudden increase in viscosity (by 2 orders of magnitude or more) at a pH of 3.5 to 4. This implies that the polymer would preferentially flow into zones containing water since the effective permeability to water is highest in these zones. As the pH of the zone increases due to the buffering capacity of the reservoir rock, the polymer solution undergoes a liquid to gel transition causing a sharp increase in the viscosity of the polymer solution in these zones. This allows operationally robust, in-depth conformance treatment of such water bearing zones and better mobility control. The rheological properties of HPAM solutions were measured. These include: steady-shear viscosity and viscoelastic behavior as functions of pH; shear rate; polymer concentration; salinity, including divalent ion effects; polymer molecular weight; and degree of hydrolysis. A comprehensive rheological model was developed for HPAM solution rheology in terms of: shear rate; pH; polymer concentration; and salinity, so that the spatial and temporal changes in viscosity during the polymer flow in the reservoir can be accurately modeled. A series of acid coreflood experiments were conducted to understand the geochemical reactions relevant for both the near-wellbore injection profile control and for conformance control applications. These experiments showed that the use hydrochloric acid as a pre-flush is not viable because of the high reaction rate with the rock. The use of citric acid as a pre-flush was found to be quite effective. This weak acid has a slow rate of reaction with the rock and can buffer the pH to below 3.5 for extended periods of time. With the citric acid pre-flush the polymer could be efficiently propagated through the core in a low pH environment i.e. at a low viscosity. The transport of various HPAM solutions was studied in sandstones, in terms of permeability reduction, mobility reduction, adsorption and inaccessible pore volume with different process variables: injection pH, polymer concentration, polymer molecular weight, salinity, degree of hydrolysis, and flow rate. Measurements of polymer effluent profiles and tracer tests show that the polymer retention increases at the lower pH. A new simulation capability to model the deep-penetrating mobility control or conformance control using pH-sensitive polymer was developed. The core flood acid injection experiments were history matched to estimate geochemical reaction rates. Preliminary scale-up simulations employing linear and radial geometry floods in 2-layer reservoir models were conducted. It is clearly shown that the injection rate of pH-sensitive polymer solutions can be significantly increased by injecting it at a pH below 3.5 (at a fixed bottom-hole pressure). This improvement in injectivity by a factor of 2 to 10 can have a significant impact on the economics of chemical flooding and conformance control applications. Simulation tools and experimental data presented in this report help to design and implement such polymer injection projects.« less

Effective removal of tetracycline from aqueous solution using activated carbon prepared from tomato (Lycopersicon esculentum Mill.) industrial processing waste.

PubMed

Sayğılı, Hasan; Güzel, Fuat

2016-09-01

Activated carbon (TAC) prepared under optimized conditions with ZnCl2 activation from a new precursor; tomato industrial processing waste (TW), was applied as an adsorbent to remove tetracycline (TC) from aqueous solution. The factors (TAC dosage, initial TC concentration, contact time, ionic strength and solution temperature) affecting the adsorption process were examined at natural pH (5.7) of TAC-TC system in aqueous solution. Kinetic data was found to be best complied by the pseudo-second order model. The isotherm analysis indicated that the equilibrium data could be represented by the Langmuir model. The maximum adsorption capacity was identified as 500.0mgg(-1) at 308K. Copyright © 2016 Elsevier Inc. All rights reserved.

[Adsorption behavior of copper ion and methylene blue on citric acid- esterified wheat straw].

PubMed

Sun, Jin; Zhong, Ke-Ding; Feng, Min; Liu, Xing-Yan; Gong, Ren-Min

2008-03-01

A cationic adsorbent with carboxyl groups derived from citric acid- esterified wheat straw (EWS) was prepared by the method of solid phase preparation, and a batch experiment was conducted to study the adsorption behaviors of Cu (II) and methylene blue (MB) in aqueous solution on the EWS under conditions of different initial pH, adsorbent dosage, adsorbate concentration, and contact time. The results showed that the maximum adsorption of Cu (II) and MB was obtained when the initial solution pH was > or = 4.0. 96% of Cu (II) in 100 mg x L(-1) Cu solution and 99% of MB in 250 mg x L(-1) dye solution could be removed by > or = 2.0 g x L(-1) of EWS. The adsorption of Cu (II) and MB fitted the Langmuir sorption isothermal model. The maximum removal capacity (Qm) of EWS was 79.37 mg x g(-1) for Cu (II) and 312.50 mg x g(-1) for MB, and the adsorption equilibrium of Cu (II) and MB was reached within 75 min and 5 h, respectively. The adsorption processes of Cu (II) and MB could be described by pseudo-first order and pseudo-second order kinetic functions, respectively.

High surface area mesoporous activated carbon-alginate beads for efficient removal of methylene blue.

PubMed

Nasrullah, Asma; Bhat, A H; Naeem, Abdul; Isa, Mohamed Hasnain; Danish, Mohammed

2018-02-01

High surface area mesoporous activated carbon-alginate (AC-alginate) beads were successfully synthesized by entrapping activated carbon powder derived from Mangosteen fruit peel into calcium-alginate beads for methylene blue (MB) removal from aqueous solution. The structure and surface characteristics of AC-alginate beads were analyzed using Fourier transform infra-red (FTIR) spectroscopy, scanning electron microscopy (SEM) and surface area analysis (S BET ), while thermal properties were tested using thermogravimetric analysis (TGA). The effect of AC-alginate dose, pH of solution, contact time, initial concentration of MB solution and temperature on MB removal was elucidated. The results showed that the maximum adsorption capacity of 230mg/g was achieved for 100mg/L of MB solution at pH 9.5 and temperature 25°C. Furthermore, the adsorption of MB on AC-alginate beads followed well pseudo-second order equation and equilibrium adsorption data were better fitted by the Freundlich isotherm model. The findings reveal the feasibility of AC-alginate beads composite to be used as a potential and low cost adsorbent for removal of cationic dyes. Copyright © 2017 Elsevier B.V. All rights reserved.

Surface functionalized composite nanofibers for efficient removal of arsenic from aqueous solutions.

PubMed

Mohamed, Alaa; Osman, T A; Toprak, M S; Muhammed, M; Uheida, A

2017-08-01

A novel composites nanofiber was synthesized based on PAN-CNT/TiO 2 -NH 2 nanofibers using electrospinning technique followed by chemical modification of TiO 2 NPs. PAN-CNT/TiO 2 -NH 2 nanofiber were characterized by XRD, FTIR, SEM, and TEM. The effects of various experimental parameters such as initial concentration, contact time, and solution pH on As removal were investigated. The maximum adsorption capacity at pH 2 for As(III) and As(V) is 251 mg/g and 249 mg/g, respectively, which is much higher than most of the reported adsorbents. The adsorption equilibrium reached within 20 and 60 min as the initial solution concentration increased from 10 to 100 mg/L, and the data fitted well using the linear and nonlinear pseudo first and second order model. Isotherm data fitted well to the linear and nonlinear Langmuir, Freundlich, and Redlich-Peterson isotherm adsorption model. Desorption results showed that the adsorption capacity can remain up to 70% after 5 times usage. This work provides a simple and an efficient method for removing arsenic from aqueous solution. Copyright © 2017 Elsevier Ltd. All rights reserved.

Evaluation of PAN-based manganese dioxide composite for the sorptive removal of cesium-137 from aqueous solutions.

PubMed

Nilchi, A; Saberi, R; Garmarodi, S Rasouli; Bagheri, A

2012-02-01

Hydrous manganese dioxide-polyacrylonitrile (MnO(2)-PAN) was chemically synthesized and evaluated, as an organic-inorganic composite material, for the removal of radio-contaminant cesium-137 from aqueous solutions. The physico-chemical characterization was carried out by Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), CHN elemental analysis, scanning electron microscopy (SEM), nitrogen adsorption-desorption studies and thermogravimetry-differential scanning calorimetry (TGA-DSC). Batch experiments were carried out as a function of contact time, interference of the coexisting ions and initial pH of adsorptive solution applying a radiotracer technique. The effect of temperature on the distribution coefficient of cesium has been utilized in order to evaluate the changes in the standard thermodynamic parameters. The results indicated that Cs(+) ions could be efficiently removed using MnO(2)-PAN composite in the pH range of 4-9 from aqueous solutions and the uptake of cesium is affected to varying degrees by the presence of some diverse co-ions. The equilibrium isotherms have been determined and the sorption data were successfully modeled using Freundlich model. Copyright © 2011 Elsevier Ltd. All rights reserved.

Nickel(II) biosorption from aqueous solutions by shrimp head biomass.

PubMed

Hernández-Estévez, Alejandro; Cristiani-Urbina, Eliseo

2014-11-01

The present study evaluates the capacity of shrimp (Farfantepenaeus aztecus) head to remove toxic Ni(II) ions from aqueous solutions. Relevant parameters that could affect the biosorption process, such as shrimp head pretreatment, solution pH level, contact time and initial Ni(II) concentration, were studied in batch systems. An increase in Ni(II) biosorption capacity and a reduction in the time required to reach Ni(II) biosorption equilibrium was manifested by shrimp head biomass pretreated by boiling in 0.5 N NaOH for 15 min; this biomass was thereafter denominated APSH. The optimum biosorption level of Ni(II) ions onto APSH was observed at pH 7.0. Biosorption increased significantly with rising initial Ni(II) concentration. In terms of biosorption dynamics, the pseudo-second-order kinetic model described Ni(II) biosorption onto APSH best. The equilibrium data adequately fitted the Langmuir isotherm model within the studied Ni(II) ion concentration range. According to this isotherm model, the maximum Ni(II) biosorption capacity of APSH was 104.22 mg/g. Results indicate that APSH could be used as a low-cost, environmentally friendly, and promising biosorbent with high biosorption capacity to remove Ni(II) from aqueous solutions.

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

Fabrication of the tea saponin functionalized reduced graphene oxide for fast adsorptive removal of Cd(II) from water

NASA Astrophysics Data System (ADS)

Li, Zhigang; Liu, Zhifeng; Wu, Zhibin; Zeng, Guangming; Shao, Binbin; Liu, Yujie; Jiang, Yilin; Zhong, Hua; Liu, Yang

2018-05-01

A novel graphene-based material of tea saponin functionalized reduced graphene oxide (TS-RGO) was synthesized via a facil thermal method, and it was characterized as the absorbent for Cd(II) removal from aqueous solutions. The factors on adsorption process including solution pH, contact time, initial concentration of Cd(II) and background electrolyte cations were studied to optimize the conditions for maximum adsorption at room temperature. The results indicated that Cd(II) adsorption was strongly dependent on pH and could be strongly affected by background electrolytes and ionic strength. The optimal pH and required equilibrium time was 6.0 and 10 min, respectively. The Cd(II) removal decreased with the presence of background electrolyte cations (Na+ < Ca2+ < Al3+). The adsorption kinetics of Cd(II) followed well with the pseudo-second-order model. The adsorption isotherm fitted well to the Langmuir model, indicating that the adsorption was a monolayer adsorption process occurred on the homogeneous surfaces of TS-RGO. The maximum monolayer adsorption capacity was 127 mg/g at 313 K and pH 6.0. Therefore, the TS-RGO was considered to be a cost-effective and promising material for the removal of Cd(II) from wastewater.

Evaluation of sprayed hypochlorous acid solutions for their virucidal activity against avian influenza virus through in vitro experiments.

PubMed

Hakim, Hakimullah; Thammakarn, Chanathip; Suguro, Atsushi; Ishida, Yuki; Kawamura, Akinobu; Tamura, Miho; Satoh, Keisuke; Tsujimura, Misato; Hasegawa, Tomomi; Takehara, Kazuaki

2015-02-01

Hypochlorous acid (HOCl) solutions were evaluated for their virucidal ability against a low pathogenic avian influenza virus (AIV), H7N1. HOCl solutions containing 50, 100 and 200 ppm chlorine (pH 6) or their sprayed solutions (harvested in dishes placed at 1 or 30 cm distance between the spray nozzle and dish) were mixed with the virus with or without organic materials (5% fetal bovine serum: FBS). Under plain diluent conditions (without FBS), harvested solutions of HOCl after spraying could decrease the AIV titer by more than 1,000 times, to an undetectable level (< 2.5 log10TCID50/ml) within 5 sec, with the exception of the 50 ppm solution harvested after spraying at the distance of 30 cm. Under the dirty conditions (in the presence of 5% FBS), they lost their virucidal activity. When HOCl solutions were sprayed directly on the virus on rayon sheets for 10 sec, the solutions of 100 and 200 ppm could inactivate AIV immediately after spraying, while 50 ppm solution required at least 3 min of contact time. In the indirect spray form, after 10 sec of spraying, the lids of the dishes were opened to expose the virus on rayon sheets to HOCl. In this form, the 200 ppm solution inactivated AIV within 10 min of contact, while 50 and 100 ppm could not inactivate it. These data suggest that HOCl can be used in spray form to inactivate AIV at the farm level.

Probing the interaction of U (VI) with phosphonate-functionalized mesoporous silica using solid-state NMR spectroscopy

DOE PAGES

Uribe, Eva C.; Mason, Harris E.; Shusterman, Jennifer A.; ...

2016-05-30

The fundamental interaction of U (VI) with diethylphosphatoethyl triethoxysilane functionalized SBA-15 mesoporous silica is studied by macroscopic batch experiments and solid-state NMR spectroscopy. DPTS-functionalized silica has been shown to extract U (VI) from nitric acid solutions at or above pH 3. Extraction is dependent on pH and ionic strength. Single-pulse 31P NMR on U (VI) contacted samples revealed that U (VI)only interacts with a fraction of the ligands present on the surface. At pH 4 the U (VI) extraction capacity of the material is limited to 27–37% of the theoretical capacity, based on ligand loading. We combined single pulse 31Pmore » NMR on U (VI)-contacted samples with batch studies to measure a ligand-to-metal ratio of approximately 2 : 1 at pH 3 and 4. Batch studies and cross-polarization NMR measurements reveal that U (VI) binds to deprotonated phosphonate and/or silanol sites. We use 31P– 31P DQ-DRENAR NMR studies to compare the average dipolar coupling between phosphorus spins for both U (VI)-complexed and non-complexed ligand environments. Furthermore, these measurements reveal that U (VI) extraction is not limited by inadequate surface distribution of ligands, but rather by low stability of the surface phosphonate complex.« less

Probing the interaction of U (VI) with phosphonate-functionalized mesoporous silica using solid-state NMR spectroscopy

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

Uribe, Eva C.; Mason, Harris E.; Shusterman, Jennifer A.

The fundamental interaction of U (VI) with diethylphosphatoethyl triethoxysilane functionalized SBA-15 mesoporous silica is studied by macroscopic batch experiments and solid-state NMR spectroscopy. DPTS-functionalized silica has been shown to extract U (VI) from nitric acid solutions at or above pH 3. Extraction is dependent on pH and ionic strength. Single-pulse 31P NMR on U (VI) contacted samples revealed that U (VI)only interacts with a fraction of the ligands present on the surface. At pH 4 the U (VI) extraction capacity of the material is limited to 27–37% of the theoretical capacity, based on ligand loading. We combined single pulse 31Pmore » NMR on U (VI)-contacted samples with batch studies to measure a ligand-to-metal ratio of approximately 2 : 1 at pH 3 and 4. Batch studies and cross-polarization NMR measurements reveal that U (VI) binds to deprotonated phosphonate and/or silanol sites. We use 31P– 31P DQ-DRENAR NMR studies to compare the average dipolar coupling between phosphorus spins for both U (VI)-complexed and non-complexed ligand environments. Furthermore, these measurements reveal that U (VI) extraction is not limited by inadequate surface distribution of ligands, but rather by low stability of the surface phosphonate complex.« less

Development of a graphene oxide/chitosan nanocomposite for the removal of picric acid from aqueous solutions: Study of sorption parameters.

PubMed

Mohseni Kafshgari, Mona; Tahermansouri, Hasan

2017-12-01

The functionalization of graphene oxide (GO) with chitosan (Chi) has been investigated to prepare a nanocomposite material (GO-Chi) for the removal of picric acid from aqueous solutions. Materials were characterized by FT-IR, TGA, DTG, FESEM, EDX, XRD and BET. Batch experiments such as solution pH, amount 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. Isotherm studies showed that the Langmuir isotherm for GO and Freundlich and Halsey models for GO-Chi were found to best represent the measured sorption data. Negative ΔG° values for GO-Chi and positive ones for GO indicated the nature of spontaneous and unspontaneous, respectively for adsorption process. In addition, picric acid molecules can be desorbed from GO-Chi up to 80% at pH=9 and that the consumed GO-Chi could be reutilized up to 5th cycle of regeneration. Copyright © 2017 Elsevier B.V. All rights reserved.

Study the adsorption of sulfates by high cross-linked polystyrene divinylbenzene anion-exchange resin

NASA Astrophysics Data System (ADS)

Fathy, Mahmoud; Moghny, Th. Abdel; Awadallah, Ahmed E.; El-Bellihi, Abdel-Hameed A.-A.

2017-03-01

In response to rising concerns about the effect of sulfate on water quality, human health, and agriculture, many jurisdictions around the world are imposing tighter regulations for sulfate discharge. This is driving the need for environmental compliance in industries like mining, metal processing, pulp and paper, sewage treatment, and chemical manufacturing. The sulfate removal from synthetic water by high cross-linked polystyrene divinylbenzene resin was studied at batch experiments in this study. The effect of pH, contact time, sulfates concentration, and adsorbent dose on the sulfate sequestration was investigated. The optimum conditions were studied on Saline water as a case study. The results showed that with increasing of the absorbent amount; contact time, and pH improve the efficiency of sulfate removal. The maximum sulfates uptake was obtained in pH and contact time 3.0 and 120 min, respectively. Also, with increasing initial concentration of sulfates in water, the efficiency of sulfate removal decreased. The obtained results in this study were matched with Freundlich isotherm and pseudo-second-order kinetic. The maximum adsorption capacity (Qm) and constant rate were found 0.318 (mg/g) and 0.21 (mg/g.min), respectively. This study also showed that in the optimum conditions, the sulfate removal efficiency from Saline water by 0.1 mg/L sulfates was 65.64 %. Eventually, high cross-linked polystyrene divinylbenzene resin is recommended as a suitable and low cost absorbent to sulfate removal from aqueous solutions.

Green Synthesis of Zinc Oxide Nanoparticles for Enhanced Adsorption of Lead Ions from Aqueous Solutions: Equilibrium, Kinetic and Thermodynamic Studies.

PubMed

Azizi, Susan; Mahdavi Shahri, Mahnaz; Mohamad, Rosfarizan

2017-06-08

In the present study, ZnO nanoparticles (NPs) were synthesized in zerumbone solution by a green approach and appraised for their ability to absorb Pb(II) ions from aqueous solution. The formation of as-synthesized NPs was established by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), and UV-visible studies. The XRD and TEM analyses revealed high purity and wurtzite hexagonal structure of ZnO NPs with a mean size of 10.01 ± 2.6 nm. Batch experiments were performed to investigate the impact of process parameters viz. Pb(II) concentration, pH of solution, adsorbent mass, solution temperature, and contact time variations on the removal efficiency of Pb(II). The adsorption isotherm data provided that the adsorption process was mainly monolayer on ZnO NPs. The adsorption process follows pseudo-second-order reaction kinetic. The maximum removal efficiencies were 93% at pH 5. Thermodynamic parameters such as enthalpy change (ΔH⁰), free energy change (ΔG⁰), and entropy change (ΔS⁰) were calculated; the adsorption process was spontaneous and endothermic. The good efficiency of the as-synthesized NPs makes them attractive for applications in water treatment, for removal of heavy metals from aqueous system.

Similar influence of stabilized alkaline and neutral sodium hypochlorite solutions on the fracture resistance of root canal-treated bovine teeth.

PubMed

Souza, Erick Miranda; Calixto, Amanda Martins; Lima, Camila Nara E; Pappen, Fernanda Geraldo; De-Deus, Gustavo

2014-10-01

Stabilizing sodium hypochlorite (NaOCl) at an alkaline pH is proposed to increase solution stability and tissue dissolution ability; however, a reduction on the flexural strength of dentin discs has been found to be a side effect. This study sought to determine whether a stabilized alkaline NaOCl reduces the fracture resistance of root canal-treated bovine teeth after root canal preparation compared with a neutral solution counterpart. The 4 anterior incisors were removed from 20 mandibular bovine jaws, and each 1 was randomly assigned to 1 of 4 groups (20 teeth each). Teeth were prepared with a sequence of 6 K-type files. The following experimental groups received a different irrigation regimen: G1: distilled water (negative control), G2: 5% NaOCl at a pH of 7.2, and G3: 5% NaOCl at a pH of 12.8; in the positive control group (G4), teeth remained untreated. The time of contact and volume of solution were carefully standardized. After bone and periodontal ligament simulation, teeth were subjected to a fracture resistance test. A significant difference was observed among the 4 groups tested (analysis of variance, P < .05). The 5% NaOCl groups (G2 and G3) presented significantly lower resistance to fracture than the control (G1 and G4) (Tukey test, P < .05). Both NaOCl solutions similarly reduced the fracture resistance at approximately 30% (Tukey test, P > .05). No differences were observed between positive and negative control groups (Tukey test, P > .05). Stabilized alkaline and neutral NaOCl solutions similarly reduced the fracture resistance of root canal-treated bovine teeth by about 30%. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Effect of experimental variables onto Co(2+) and Sr(2+) sorption behavior in red mud-water suspensions.

PubMed

Milenković, Aleksandra S; Smičiklas, Ivana D; Šljivić-Ivanović, Marija Z; Živković, Ljiljana S; Vukelić, Nikola S

2016-07-02

The prospects of rinsed red mud (alumina production residue) utilization for liquid radioactive waste treatment have been investigated, with Co(2+) and Sr(2+) as model cations of radioactive elements. To evaluate the sorption effectiveness and corresponding binding mechanisms, the process was analyzed in batch conditions, by varying experimental conditions (pH, Co(2+) and Sr(2+) concentrations in single solutions and binary mixtures, contact time, and the concentration of competing cations and ligands common in liquid radioactive waste). Comparison of the Co(2+) and Sr(2+) sorption pH edges with the red mud isoelectric point has revealed that Co(2+) removal took place at both positive and negative red mud surface, while Sr(2+) sorption abruptly increased when the surface became negatively charged. The increase of initial cation content and pH resulted in increased equilibrium times and sorption capacity and decreased rate constants. From single metal solutions and various binary mixtures, Co(2+) was sorbed more efficiently and selectively than Sr(2+). While Sr(2+) sorption was reduced by coexisting cations in the order Al(3+) ≥ Ca(2+) >Na(+) ≥Cs(+), removal of Co(2+) was affected by Al(3+) species and complexing agents (EDTA and citrate). Desorption of Co(2+) was negligible in Ca(2+) and Sr(2+) containing media and in solutions with initial pH 4-7. Sr(2+) desorption was generally more pronounced, especially at low pH and in the presence of Co(2+). Collected macroscopic data signify that Co(2+) sorption by red mud minerals occurred via strong chemical bonds, while Sr(2+) was retained mainly by weaker ion-exchange or electrostatic interactions. Results indicate that the rinsed red mud represent an efficient, low-cost sorbent for Co(2+) and Sr(2+) immobilization.

Abiotic transformation of high explosives by freshly precipitated iron minerals in aqueous Fe¹¹ solutions

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

Boparai, Hardiljeet K.; Comfort, Steve; Satapanajaru, Tunlawit

Zerovalent iron barriers have become a viable treatment for field-scale cleanup of various ground water contaminants. While contact with the iron surface is important for contaminant destruction, the interstitial pore water within and near the iron barrier will be laden with aqueous, adsorbed and precipitated FeII phases. These freshly precipitated iron minerals could play an important role in transforming high explosives (HE). Our objective was to determine the transformation of RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), and TNT (2,4,6-trinitrotoluene) by freshly precipitated iron FeII/FeIII minerals. This was accomplished by quantifying the effects of initial FeII concentration, pH, and the presence of aquifermore » solids (FeIII phases) on HE transformation rates. Results showed that at pH 8.2, freshly precipitated iron minerals transformed RDX, HMX, and TNT with reaction rates increasing with increasing FeII concentrations. RDX and HMX transformations in these solutions also increased with increasing pH (5.8-8.55). By contrast, TNT transformation was not influenced by pH (6.85-8.55) except at pH values <6.35. Transformations observed via LC/MS included a variety of nitroso products (RDX, HMX) and amino degradation products (TNT). XRD analysis identified green rust and magnetite as the dominant iron solid phases that precipitated from the aqueous FeII during HE treatment under anaerobic conditions. Geochemical modeling also predicted FeII activity would likely be controlled by green rust and magnetite. These results illustrate the important role freshly precipitated FeII/FeIII minerals in aqueous FeII solutions play in the transformation of high explosives.« less

Fluidized bed gasification of extracted coal

DOEpatents

Aquino, D.C.; DaPrato, P.L.; Gouker, T.R.; Knoer, P.

1984-07-06

Coal or similar carbonaceous solids are extracted by contacting the solids in an extraction zone with an aqueous solution having a pH above 12.0 at a temperature between 65/sup 0/C and 110/sup 0/C for a period of time sufficient to remove bitumens from the coal into said aqueous solution, and the extracted solids are then gasified at an elevated pressure and temperature in a fluidized bed gasification zone (60) wherein the density of the fluidized bed is maintained at a value above 160 kg/m/sup 3/. In a preferred embodiment of the invention, water is removed from the aqueous solution in order to redeposit the extracted bitumens onto the solids prior to the gasification step. 2 figs., 1 tab.

Removal of Reactofix Navy Blue 2 GFN from aqueous solutions using adsorption techniques.

PubMed

Gupta, Vinod Kumar; Jain, Rajeev; Varshney, Shaily; Saini, Vipin Kumar

2007-03-15

The wheat husk, an agricultural by-product, has been activated and used as an adsorbent for the adsorption of Reactofix Navy Blue 2 GFN from aqueous solution. In this work, adsorption of Reactofix Navy Blue 2 GFN on wheat husk and charcoal has been studied by using batch studies. The equilibrium adsorption level was determined to be a function of the solution pH, adsorbent dosage, dye concentration and contact time. The equilibrium adsorption capacities of wheat husk and charcoal for dye removal were obtained using Freundlich and Langmuir isotherms. Thermodynamic parameters such as the free energies, enthalpies and entropies of adsorption were also evaluated. Adsorption process is considered suitable for removing color, COD from waste water.

Potentiality of uranium biosorption from nitric acid solutions using shrimp shells.

PubMed

Ahmed, S H; El Sheikh, E M; Morsy, A M A

2014-08-01

Biosorption has gained important credibility during recent years because of its good performance and low cost. This work is concerned with studying the potentiality of the chitin component of the shrimp shells for uranium biosorption from nitric acid liquid solutions. The structural characteristics of the working chitin have been determined via Fourier Transform Infrared Spectroscopy (FTIR). The surface morphology was examined using Scanning Electron Microscopy (SEM). The adsorption capacity of biomass was investigated experimentally. The influence of contact time, pH, metal ion concentration, solution volume to mass ratio and temperature were evaluated and the results were fitted using adsorption isotherm models. The kinetic of uranium biosorption was also investigated as well as biosorption thermodynamic. Copyright © 2014 Elsevier Ltd. All rights reserved.

Fabrication of a novel NiFe2O4/Zn-Al layered double hydroxide intercalated with EDTA composite and its adsorption behavior for Cr(VI) from aqueous solution

NASA Astrophysics Data System (ADS)

Deng, Lin; Shi, Zhou; Wang, Li; Zhou, Shiqing

2017-05-01

A novel magnetic NiFe2O4/Zn-Al layered double hydroxide intercalated with EDTA composite (NiFe2O4/ZnAl-EDTA LDH) was prepared through modified coprecipitation method and employed for adsorptive removal of Cr(VI) from aqueous solution. The adsorbents were characterized using Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), and X-ray photoelectron spectroscopy (XPS). Factors affecting the Cr(VI) adsorption, such as initial solution pH, adsorbent dosage, contact time, initial Cr(VI) concentration, temperature and coexisting ions, were studied systematically. Experiments results show that the magnetic NiFe2O4/ZnAl-EDTA LDH exhibits high adsorption efficiency within a wide pH range of 3.0-7.0 (R>80% at Cr(VI) concentration 50 mg L-1, contact time 360 min, and adsorbent dosage 2 g/L) and quick separation property. The adsorption process is fitted well with the Langmuir isotherm and pseudo-second-order kinetic model. The maximum theoretical adsorption capacity is found to be 77.22 mg g-1 at pH 6.0 and 318 K. The positive ΔH value (2.907 kJ mol-1) and negative ΔG value (-4.722 kJ mol-1) at 298-318 K reveals that the adsorption process is feasible, spontaneous and endothermic. Coexisting anions (PO43-, SO42-, CO32-, HCO3-, Cl-, and NO3-) have no significant effect on Cr(VI) removal. The mechanism study indicates that the adsorption of Cr(VI) onto NiFe2O4/ZnAl-EDTA LDH mainly involves electrostatic attraction and ion exchange interaction. It is interesting to note that a proportion of Cr(VI) adsorbed on the adsorbent surface are reduced to Cr(III) during the adsorption process. Results from this study demonstrate the potential utility of the magnetic NiFe2O4/ZnAl-EDTA LDH that could be developed into a viable technology for efficient removal of Cr(VI) from aqueous solution.

The Influence of Glass Leachate on the Hydraulic, Physical, Mineralogical and Sorptive Properties of Hanford Sediment

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

Kaplan, Daniel I.; Serne, R. Jeffrey; Schaef, Herbert T.

2003-08-26

The Immobilized Low Activity Waste (ILAW) generated from the Hanford Site will be disposed of in a vitrified form. It is expected that leachate from the vitrified waste will have a high pH and high ionic strength. The objective of this study was to determine the influence of glass leachate on the hydraulic, physical, mineralogical, and sorptive properties of Hanford sediments. Our approach was to put solutions of NaOH, a simplified surrogate for glass leachate, in contact with quartz sand, a simplified surrogate for the Hanford subsurface sediment, and Warden soil, an actual Hanford sediment. Following contact with three differentmore » concentrations of sodium hydroxide solutions, changes in hydraulic conductivity, porosity, moisture retention, mineralogy, aqueous chemistry, and soil-radionuclide distribution coefficients were determined. Under chemical conditions approaching the most caustic glass leachate conditions predicted in the near-field of the ILAW disposal site, approximated by 0.3 M NaOH, significant changes in mineralogy were observed. The clay minerals of the Hanford sediment evidenced the greatest dissolution thereby increasing the relative proportions of the more resistant minerals, e.g., quartz, feldspar, and calcite, in the remaining mass. Some re-precipitation of solids (mostly amorphous gels) was observed after caustic contact with both solids; these precipitates increased the moisture retention in both sediments, likely because of water retained within the gel coatings. The hydraulic conductivities were slightly lower but, because of experimental artifacts, these reductions should not be considered significant. Thus, there does not seem to be large differences in the hydraulic properties of the quartz sand or Warden silt loam soil after 192 days of contact with caustic fluids similar to glass leachate. The long term projected impact of the increased moisture retention has not been evaluated but likely will not make past simplified performance projections invalid. Despite the fact that some clay minerals, smectites and kaolinite, almost totally dissolved within a year of contact with 3.0 M NaOH (and by inference after longer time frames for 0.3 M NaOH, a more realistic surrogate for ILAW glass leachate) other sorbing minerals such as illite and chlorite do not appreciably react. The net result on sorption of common and risk relevant mobile radionuclides is not expected to be significant. Specifically, little change in Cs-Kd values and a significant increase in Sr-Kd values were measured in the simulated glass leachates versus natural groundwater. The difference in the sorptive responses of the radionuclides was attributed to differences in sorption mechanisms (Cs sorbs strongly to high-energy sites, whereas Sr sorbs primarily by cation exchange but also is sensitive to pH mediated precipitation reactions). Caustic treated sediments contacted with NaOH solutions radiotraced with Sr exhibited high Kd’s likely because of precipitation with CaCO3. In caustic solutions there was no appreciable adsorption for the three anions I-, SeO42-, or TcO4-. In the “far field” vadose zone in past performance projections, some sorption has been allowed for selenate. Even if the caustic glass leachate completely dominates the entire vadose zone below the repository, such that there will be no sorption of selenate, the dilution and pH neutralization that will occur in the upper unconfined aquifer will allow selenate adsorption to occur onto the aquifer sediments. It is recommended that a future performance assessment sensitivity run be performed to address this point.« less

CONTINUOUS CHELATION-EXTRACTION PROCESS FOR THE SEPARATION AND PURIFICATION OF METALS

DOEpatents

Thomas, J.R.; Hicks, T.E.; Rubin, B.; Crandall, H.W.

1959-12-01

A continuous process is presented for separating metal values and groups of metal values from each other. A complex mixture. e.g., neutron-irradiated uranium, can be resolved into component parts. In the present process the values are dissolved in an acidic solution and adjusted to the proper oxidation state. Thenceforth the solution is contacted with an extractant phase comprising a fluorinated beta -diketone in an organic solvent under centain pH conditions whereupon plutonium and zirconium are extracted. Plutonium is extracted from the foregoing extract with reducing aqueous solutions or under specified acidic conditions and can be recovered from the aqueous solution. Zirconium is then removed with an oxalic acid aqueous phase. The uranium is recovered from the residual original solution using hexone and hexone-diketone extractants leaving residual fission products in the original solution. The uranium is extracted from the hexone solution with dilute nitric acid. Improved separations and purifications are achieved using recycled scrub solutions and the "self-salting" effect of uranyl ions.

Effective degradation of rhodamine B by electro-Fenton process, using ferromagnetic nanoparticles loaded on modified graphite felt electrode as reusable catalyst: in neutral pH condition and without external aeration.

PubMed

Tian, Jiangnan; Zhao, Jixiang; Olajuyin, Ayobami Matthew; Sharshar, Moustafa Mohamed; Mu, Tingzhen; Yang, Maohua; Xing, Jianmin

2016-08-01

Polytetrafluoroethylene/ferromagnetic nanoparticle/carbon black (PTFE/MNP/CB)-modified graphite felt (GF) was successfully applied as cathode for the mineralization of rhodamine B (RhB) in electro-Fenton (EF) process. The modified cathode showed high decolorization efficiency for RhB solution even in neutral pH condition and without external aeration, achieving nearly complete decolorization and 89.52 % total organic carbon (TOC) removal after 270-min oxidation with the MNP load 1.2 g at 50 A/m(2). Moreover, the operational parameters (current density, MNP load, initial pH, and airflow rate) were optimized. After that, adsorption isotherm was also conducted to compare the absorption quantity of CB and carbon nanotube (CNT). Then, the surface morphologies of MNPs were characterized by transmission electron microscope (TEM), energy-dispersive X-ray detector (EDX), and Fourier transform infrared spectroscopy (FTIR); and the modified cathode was characterized by SEM and contact angle. Finally, the stability and reusability of modified cathode were tested. Result uncovered that the PTFE/MNP/CB-modified cathode has the potential for industrial application and the solution after treatment was easily biodegradable.

Removal of some metal ions by activated carbon prepared from Phaseolus aureus hulls.

PubMed

Rao, M Madhava; Ramana, D K; Seshaiah, K; Wang, M C; Chien, S W Chang

2009-07-30

Removal of lead [Pb(II)], zinc [Zn(II)], copper [Cu(II)], and cadmium [Cd(II)] from aqueous solutions using activated carbon prepared from Phaseolus aureus hulls (ACPAH), an agricultural waste was studied. The influence of various parameters such as effect of pH, contact time, adsorbent dose, and initial concentration of metal ions on the removal was evaluated by batch method. The removal of metal ions by ACPAH was pH dependent and the optimum pH values were 7.0, 8.0, 7.0 and 6.0 for Cu(II), Cd(II), Zn(II), and Pb(II), respectively. The sorption isotherms were studied using Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Temkin isotherm models. The maximum adsorption capacity values of ACPAH for metal ions were 21.8 mg g(-1) for Pb(II), 21.2 mg g(-1) for Zn(II), 19.5 mg g(-1) for Cu(II), and 15.7 mg g(-1) for Cd(II). The experiments demonstrated that the removal of metal ions followed the pseudo-second-order kinetic model. Desorption experiments were carried out using HCl solution with a view to regenerate the spent adsorbent and to recover the adsorbed metal ions.

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.

Contact Lens Anterior Surface pH

DTIC Science & Technology

1991-02-01

greenhouse effect and contact lenses, in Trans- 4. Nom MS: Tear fluid pH in normals, contact lens wearers, actions of the British Contact Lens...Invest 3. Fullard R), Carney LG: Diurnal variation in human tear en- Op/hdanmol Vis Sci 1978;17:810-813. ymes. Exp Eye Res 1984;38:15-26. 20. Efron N: The

Removal of methylene blue from aqueous solution by Artist's Bracket fungi: kinetic and equilibrium studies.

PubMed

Naghipour, Daryush; Taghavi, Kamran; Moslemzadeh, Mehrdad

2016-01-01

In this study, adsorption of methylene blue (MB) dye onto Artist's Bracket (AB) fungi was investigated in aqueous solution. Fourier transform infrared and scanning electron microscopy were used to investigate surface characteristic of AB fungi. Influence of operational parameters such as pH, contact time, biosorbent dosage, dye concentration, inorganic salts and temperature was studied on dye removal efficiency. With the increase of pH from 3 to 9, removal efficiency increased from 74.0% to 90.4%. Also, it reduced from 99.8% to 81.8% with increasing initial MB concentration from 25 mg L(-1) to 100 mg L(-1), whereas it increased from 54.7% to 98.7% and from 98.5% to 99.9% with increasing biosorbent dosage from 0.5 g L(-1) to 2 g L(-1) and with increasing temperature from 25 °C to 50 °C, respectively. Isotherm studies have shown adsorption of MB dye over the AB fungi had a better coefficient of determination (R(2)) of 0.98 for Langmuir isotherm. In addition, the maximum monolayer adsorption capacity (qm) was 100 mg g(-1). Also, the MB dye adsorption process followed pseudo-second-order kinetic. In general, AB fungi particles can be favorable for removal of MB dye from dye aqueous solution with natural pH and high temperature.

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.

Accomplishing Equilibrium in ALSEP: Demonstrations of Modified Process Chemistry on 3-D Printed Enhanced Annular Centrifugal Contactors

DOE PAGES

Brown, M. Alex; Wardle, Kent E.; Lumetta, Gregg; ...

2016-12-01

Here, the major components of the modified ALSEP process have been demonstrated on a modified 2-cm annular centrifugal contactor with an enhanced mixing zone using stable fission products and radiotracers. The results show that by decreasing the pH of the minor actinide stripping solution, using HEDTA instead of DTPA, and increasing contact time, the process is very effective in separating americium from the lanthanides and the fission products.

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.

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

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.

A Comparative Study of the Adsorption of Methylene Blue onto Synthesized Nanoscale Zero-Valent Iron-Bamboo and Manganese-Bamboo Composites

PubMed Central

Shaibu, Solomon E.; Adekola, Folahan A.; Adegoke, Halimat I.; Ayanda, Olushola S.

2014-01-01

In this study, bamboo impregnated with nanoscale zero-valent iron (nZVI) and nanoscale manganese (nMn) were prepared by the aqueous phase borohydride reduction method and characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and PIXE analysis. The synthesized nMn-bamboo and nZVI-bamboo composites were subsequently applied to the sorption of methylene blue (MB) dye from aqueous solution. The adsorption of MB dye was investigated under various experimental conditions such as pH, contact time, initial concentration of MB dye and adsorbent dosage. The results showed that the synthesized nZVI-bamboo composite was more effective than nMn-bamboo composite in terms of higher MB dye adsorption capacity of 322.5 mg/g compared to 263.5 mg/g of nMn-bamboo composite. At a concentration of 140 mg/L MB dye, 0.02 g of nZVI-bamboo and nMn-bamboo composites resulted in 79.6% and 78.3% removal, respectively, at 165 rpm, contact time of 120 min and at a solution pH of 7.6. The equilibrium data was best represented by Freundlich isotherm model and the pseudo-second order kinetic model better explained the kinetic data for both nZVI-bamboo and nMn-bamboo composites. PMID:28788688

Investigations of Heavy Metal Ion Sorption Using Nanocomposites of Iron-Modified Biochar

NASA Astrophysics Data System (ADS)

Kołodyńska, D.; Bąk, J.; Kozioł, M.; Pylypchuk, L. V.

2017-06-01

Magnetic biochar nanocomposites were obtained by modification of biochar by zero-valent iron. The article provides information on the impact of contact time, initial Cd(II), Co(II), Zn(II), and Pb(II) ion concentrations, dose of the sorbents, solution pH and temperature on the adsorption capacity. On the basis of experiments, it was found that the optimum parameters for the sorption process are phase contact time 360 min (after this time, the equilibrium of all concentrations is reached), the dose of sorbent equal to 5 g/dm3, pH 5 and the temperature 295 K. The values of parameters calculated from the kinetic models and isotherms present the best match to the pseudo second order and Langmuir isotherm models. The calculated thermodynamic parameters ΔH 0, ΔS 0 and ΔG 0 indicate that the sorption of heavy metal ions is an exothermic and spontaneous process as well as favoured at lower temperatures, suggesting the physical character of sorption. The solution of nitric acid(V) at the concentration 0.1 mol/dm3 was the best acidic desorbing agent used for regeneration of metal-loaded magnetic sorbents. The physicochemical properties of synthesized composites were characterized by FTIR, SEM, XRD, XPS and TG analyses. The point characteristics of the double layer for biochar pHPZC and pHIEP were designated.

Textile dye removal from aqueous solutions by malt bagasse: Isotherm, kinetic and thermodynamic studies.

PubMed

Fontana, Klaiani B; Chaves, Eduardo S; Sanchez, Jefferson D S; Watanabe, Erica R L R; Pietrobelli, Juliana M T A; Lenzi, Giane G

2016-02-01

The biosorption of orange solimax TGL 182% (OS-TGL) textile dye onto new and low cost biossorbent (malt bagasse) in aqueous solutions was investigated. The malt bagasse was characterized by Fourier transform infrared spectroscopy and specific surface area (BET method).Batch biosorption experiments were conducted in order to determine the following parameters: particles size, pH, agitation speed, temperature, contact time, biomass dosage, influence of the ionic strength and, finally, the influence of other textile dye on the OS-TGL biosorption. The optimum conditions for OS-TGL removal were obtained at pH 1.5, agitation speed of 150rpm, contact time of 180min and biomass dosage 2, 8gL(-1). The results show that the kinetics of biosorption followed a pseudo-second-order model and by increasing the temperature from 293 up to 313K, the biosorption capacity was improved. The Langmuir model showed better fit and the estimated biosorption capacity was 23.2mgg(-1). The negative values of Gibbs free energy, ΔG°, and positive value of enthalpy, ΔH°, confirm the spontaneous nature and endothermic character of the biosorption process. The results of the ionic strength effect indicated that the biosorption process under study had a strong tolerance in high salt concentrations. The removal capacity (>95%) was not affected with the presence of other textile dyes. Copyright © 2015 Elsevier Inc. All rights reserved.

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.

Sorption properties of Th(IV) on the raw diatomite--effects of contact time, pH, ionic strength and temperature.

PubMed

Sheng, Guodong; Hu, Jun; Wang, Xiangke

2008-10-01

Diatomite has a number of unique physicochemical properties and has diversified industrial uses. Natural diatomite has been tested as a potential sorbent for the removal of Th(IV) from aqueous solutions. The results indicate that sorption of Th(IV) is strongly dependent on ionic strength at pH<3, and is independent of ionic strength at pH>3. Outer-sphere complexation or ion exchange may be the main sorption mechanism of Th(IV) to diatomite at low pH values, whereas the sorption of Th(IV) at pH>3 is mainly dominated by inner-sphere complexation or precipitation. The competition for Th(IV) between aqueous or surface adsorbed anions (e.g., herein ClO(4)(-), NO(3)(-) and Cl(-)) and surface functional groups of diatomite is important for Th(IV) sorption. The thermodynamic data (DeltaH(0), DeltaS(0), DeltaG(0)) are calculated from the temperature-dependent sorption isotherms. The results suggest that sorption process of Th(IV) on diatomite is spontaneous and endothermic.

Corrosion protection of galvanized steels by silane-based treatments

NASA Astrophysics Data System (ADS)

Yuan, Wei

The possibility of using silane coupling agents as replacements for chromate treatments was investigated on galvanized steel substrates. In order to understand the influence of deposition parameters on silane film formation, pure zinc substrates were first used as a model for galvanized steel to study the interaction between silane coupling agents and zinc surfaces. The silane films formed on pure zinc substrates from aqueous solutions were characterized by ellipsometry, contact angle measurements, reflection absorption infrared spectroscopy, x-ray photoelectron spectroscopy, and atomic force microscopy. The deposition parameters studied include solution concentration, solution dipping time and pH value of the applied solution. It appears that silane film formation involved a true equilibrium of hydrolysis and condensation reactions in aqueous solutions. It has been found that the silane film thickness obtained depends primarily on the solution concentration and is almost independent of the solution dipping time. The molecular orientation of applied silane films is determined by the pH value of applied silane solutions and the isoelectric point of metal substrates. The deposition window in terms of pH value for zinc substrates is between 6.0 and 9.0. The total surface energy of the silane-coated pure zinc substrates decreases with film aging time, the decrease rate, however, is determined by the nature of silane coupling agents. Selected silane coupling agents were applied as prepaint or passivation treatments onto galvanized steel substrates. The corrosion protection provided by these silane-based treatments were evaluated by salt spray test, cyclic corrosion test, electrochemical impedance spectroscopy, and stack test. The results showed that silane coupling agents can possibly be used to replace chromates for corrosion control of galvanized steel substrates. Silane coatings provided by these silane treatments serve mainly as physical barriers. Factors that affect the performance of a silane coupling agent in the application of corrosion control include chemical reactivity, hydrophobic character, siloxane crosslinker network, and film thickness. Good protections afforded by the silane treatments are a synergetic effect of all these factors.

Chemical Reaction between Boric Acid and Phosphine Indicates Boric Acid as an Antidote for Aluminium Phosphide Poisoning

PubMed Central

Soltani, Motahareh; Shetab-Boushehri, Seyed F.; Shetab-Boushehri, Seyed V.

2016-01-01

Objectives: Aluminium phosphide (AlP) is a fumigant pesticide which protects stored grains from insects and rodents. When it comes into contact with moisture, AlP releases phosphine (PH3), a highly toxic gas. No efficient antidote has been found for AlP poisoning so far and most people who are poisoned do not survive. Boric acid is a Lewis acid with an empty p orbital which accepts electrons. This study aimed to investigate the neutralisation of PH3 gas with boric acid. Methods: This study was carried out at the Baharlou Hospital, Tehran University of Medical Sciences, Tehran, Iran, between December 2013 and February 2014. The volume of released gas, rate of gas evolution and changes in pH were measured during reactions of AlP tablets with water, acidified water, saturated boric acid solution, acidified saturated boric acid solution, activated charcoal and acidified activated charcoal. Infrared spectroscopy was used to study the resulting probable adduct between PH3 and boric acid. Results: Activated charcoal significantly reduced the volume of released gas (P <0.01). Although boric acid did not significantly reduce the volume of released gas, it significantly reduced the rate of gas evolution (P <0.01). A gaseous adduct was formed in the reaction between pure AlP and boric acid. Conclusion: These findings indicate that boric acid may be an efficient and non-toxic antidote for PH3 poisoning. PMID:27606109

In vitro Characteristics of a Glass Ionomer Cement.

PubMed

Driscoll, C L; Green, J D; Beatty, C W; McCaffrey, T V; Marrs, C D

1998-01-01

Glass ionomer cements were first described by Wilson and Kent and have been used in dentistry since 1969. It has been recommended for bridging ossicular chain defects, fixation of ossicular chain prosthesis, anchoring of cochlear implants, mastoid obliteration, and repair of tegmen and posterior canal wall defects. The biocompatability and stability of this material over time is vital to its usefulness in neurotologic surgery. The purpose of this study was to assess the stability of a glass ionomer cement in the presence of bacteria and in different pH environments. We demonstrated that bacteria readily adhere to the surface and their presence is associated with accelerated loss of matrix. We found the cement to be susceptible to low pH and to release a visible cloud of debris upon contact with fluid. Calcium concentration in the solution was elevated at all pH levels. Although we are able to demonstrate these findings in vitro the clinical relevance is unclear. There have been several cases of aseptic meningitis possibly due to intracranial release of components of the cement. Until further studies are done use of the cement in contact with cerebral spinal fluid should be avoided. This cement, or a similar material, would be useful in neurotologic surgery but prior to widespread use further testing should be done to assess safety.

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.

Simulated Leaching (Migration) Study for a Model Container-Closure System Applicable to Parenteral and Ophthalmic Drug Products.

PubMed

Jenke, Dennis; Egert, Thomas; Hendricker, Alan; Castner, James; Feinberg, Tom; Houston, Christopher; Hunt, Desmond G; Lynch, Michael; Nicholas, Kumudini; Norwood, Daniel L; Paskiet, Diane; Ruberto, Michael; Smith, Edward J; Holcomb, Frank; Markovic, Ingrid

2017-01-01

A simulating leaching (migration) study was performed on a model container-closure system relevant to parenteral and ophthalmic drug products. This container-closure system consisted of a linear low-density polyethylene bottle (primary container), a polypropylene cap and an elastomeric cap liner (closure), an adhesive label (labeling), and a foil overpouch (secondary container). The bottles were filled with simulating solvents (aqueous salt/acid mixture at pH 2.5, aqueous buffer at pH 9.5, and 1/1 v/v isopropanol/water), a label was affixed to the filled and capped bottles, the filled bottles were placed into the foil overpouch, and the filled and pouched units were stored either upright or inverted for up to 6 months at 40 °C. After storage, the leaching solutions were tested for leached substances using multiple complementary analytical techniques to address volatile, semi-volatile, and non-volatile organic and inorganic extractables as potential leachables.The leaching data generated supported several conclusions, including that (1) the extractables (leachables) profile revealed by a simulating leaching study can qualitatively be correlated with compositional information for materials of construction, (2) the chemical nature of both the extracting medium and the individual extractables (leachables) can markedly affect the resulting profile, and (3) while direct contact between a drug product and a system's material of construction may exacerbate the leaching of substances from that material by the drug product, direct contact is not a prerequisite for migration and leaching to occur. LAY ABSTRACT: The migration of container-related extractables from a model pharmaceutical container-closure system and into simulated drug product solutions was studied, focusing on circumstances relevant to parenteral and ophthalmic drug products. The model system was constructed specifically to address the migration of extractables from labels applied to the outside of the primary container. The study demonstrated that (1) the extractables that do migrate can be correlated to the composition of the materials used to construct the container-closure systems, (2) the extent of migration is affected by the chemical nature of the simulating solutions and the extractables themselves, and (3) even though labels may not be in direct contact with a contained solution, label-related extractables can accumulate as leachables in those solutions. © PDA, Inc. 2017.

Coupling the Alkaline-Surfactant-Polymer Technology and the Gelation Technology to Maximize Oil Production

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

Malcolm Pitts; Jie Qi; Dan Wilson

2005-12-01

Gelation technologies have been developed to provide more efficient vertical sweep efficiencies for flooding naturally fractured oil reservoirs or reservoirs with different sand lenses with high permeability contrast. The field proven alkaline-surfactant-polymer technology economically recovers 15% to 25% OOIP more crude oil than waterflooding froin swept pore space of an oil reservoir. However, alkaline-surfactant-polymer technology is not amenable to naturally fractured reservoirs or reservoirs with high permeability contrast zones because much of injected solution bypasses target pore space containing oil. This work investigates whether combining these two technologies could broaden applicability of alkaline-surfactant-polymer flooding into these reservoirs. Fluid-fluid interaction withmore » different gel chemical compositions and alkaline-surfactant-polymer solution with pH values ranging from 9.2 to 12.9 have been tested. Aluminum-polyacrylamide gels are not stable to alkaline-surfactant-polymer solutions at any pH. Chromium-polyacrylamide gels with polymer to chromium ion ratios of 25 or greater were stable to alkaline-surfactant-polymer solutions if solution pH was 10.6 or less. When the polymer to chromium ion was 15 or less, chromium-polyacrylamide gels were stable to alkaline-surfactant-polymer solutions with pH values up to 12.9. Chromium-xanthan gum gels were stable to alkaline-surfactant-polymer solutions with pH values of 12.9 at the polymer to chromium ion ratios tested. Silicate-polyacrylamide, resorcinol-formaldehyde, and sulfomethylated resorcinol-formaldehyde gels were also stable to alkaline-surfactant-polymer solutions with pH values ranging from 9.2 to 12.9. Iron-polyacrylamide gels were immediately destroyed when contacted with any of the alkaline-surfactant-polymer solutions with pH values ranging from 9.2 to 12.9. Gel solutions under dynamic conditions of linear corefloods showed similar stability to alkaline-surfactant-polymer solutions as in the fluid-fluid analyses with the exception of the xanthan gum-chromium acetate gels. Aluminum-polyacrylamide flowing gels are not stable to alkaline-surfactant-polymer solutions of either pH 10.5 or 12.9, either in linear corefloods or in dual separate radial core, common manifold corefloods. Chromium acetate-polyacrylamide flowing and rigid tonguing gels are stable to subsequent alkaline-surfactant-polymer solution injection. Rigid tonguing chromium acetate-polyacrylamide gels maintained permeability reduction better than flowing chromium acetate-polyacrylamide gels. Chromium acetate gels were stable to injection of alkaline-surfactant-polymer solutions at 72 F, 125 F and 175 F in linear corefloods. Chromium acetate-polyacrylamide gels maintained diversion capability after injection of an alkaline-surfactant-polymer solution in stacked; radial coreflood with a common well bore. Chromium acetate-polyacrylamide gel used to seal fractured core maintain fracture closure if followed by an alkaline-surfactant-polymer solution. Chromium acetate-xanthan gum rigid gels are not stable to subsequent alkaline-surfactant-polymer solution injection at 72, 125, and 175 F. Silicate-polyacrylamide gels are not stable with subsequent injection of either a pH 10.5 or a 12.9 alkaline-surfactant-polymer solution. Resorcinol-formaldehyde gels were stable to subsequent alkaline-surfactant-polymer solution injection. When evaluated in a dual core configuration, injected fluid flows into the core with the greatest effective permeability to the injected fluid. The same gel stability trends to subsequent alkaline-surfactant-polymer injected solution were observed. Aluminum citrate-polyacrylamide, resorcinol-formaldehyde, and the silicate-polyacrylamide gel systems did not produce significant incremental oil in linear corefloods. Both flowing and rigid tonguing chromium acetate-polyacrylamide gels and the xanthan gum-chromium acetate gel system produced incremental oil with the rigid tonguing gel producing the greatest amount. Higher oil recovery could have been due to higher differential pressures across cores. Aluminum citrate-polyacrylamide gels, chromium acetate-polyacrylamide gels, silicate-polymer, and chromium-xanthan guin gels did not alter an alkaline-surfactant-polymer solution's ability to produce incremental oil. Incremental oil was reduced with the resorcinol-formaldehyde gel system. Total waterflood plus chemical flood oil recovery sequence recoveries were generally similar.« less

Evaluation of sprayed hypochlorous acid solutions for their virucidal activity against avian influenza virus through in vitro experiments

PubMed Central

HAKIM, Hakimullah; THAMMAKARN, Chanathip; SUGURO, Atsushi; ISHIDA, Yuki; KAWAMURA, Akinobu; TAMURA, Miho; SATOH, Keisuke; TSUJIMURA, Misato; HASEGAWA, Tomomi; TAKEHARA, Kazuaki

2014-01-01

Hypochlorous acid (HOCl) solutions were evaluated for their virucidal ability against a low pathogenic avian influenza virus (AIV), H7N1. HOCl solutions containing 50, 100 and 200 ppm chlorine (pH 6) or their sprayed solutions (harvested in dishes placed at 1 or 30 cm distance between the spray nozzle and dish) were mixed with the virus with or without organic materials (5% fetal bovine serum: FBS). Under plain diluent conditions (without FBS), harvested solutions of HOCl after spraying could decrease the AIV titer by more than 1,000 times, to an undetectable level (< 2.5 log10TCID50/ml) within 5 sec, with the exception of the 50 ppm solution harvested after spraying at the distance of 30 cm. Under the dirty conditions (in the presence of 5% FBS), they lost their virucidal activity. When HOCl solutions were sprayed directly on the virus on rayon sheets for 10 sec, the solutions of 100 and 200 ppm could inactivate AIV immediately after spraying, while 50 ppm solution required at least 3 min of contact time. In the indirect spray form, after 10 sec of spraying, the lids of the dishes were opened to expose the virus on rayon sheets to HOCl. In this form, the 200 ppm solution inactivated AIV within 10 min of contact, while 50 and 100 ppm could not inactivate it. These data suggest that HOCl can be used in spray form to inactivate AIV at the farm level. PMID:25421399

Highly Sensitive and Wide-Dynamic-Range Multichannel Optical-Fiber pH Sensor Based on PWM Technique.

PubMed

Khan, Md Rajibur Rahaman; Kang, Shin-Won

2016-11-09

In this study, we propose a highly sensitive multichannel pH sensor that is based on an optical-fiber pulse width modulation (PWM) technique. According to the optical-fiber PWM method, the received sensing signal's pulse width changes when the optical-fiber pH sensing-element of the array comes into contact with pH buffer solutions. The proposed optical-fiber PWM pH-sensing system offers a linear sensing response over a wide range of pH values from 2 to 12, with a high pH-sensing ability. The sensitivity of the proposed pH sensor is 0.46 µs/pH, and the correlation coefficient R² is approximately 0.997. Additional advantages of the proposed optical-fiber PWM pH sensor include a short/fast response-time of about 8 s, good reproducibility properties with a relative standard deviation (RSD) of about 0.019, easy fabrication, low cost, small size, reusability of the optical-fiber sensing-element, and the capability of remote sensing. Finally, the performance of the proposed PWM pH sensor was compared with that of potentiometric, optical-fiber modal interferometer, and optical-fiber Fabry-Perot interferometer pH sensors with respect to dynamic range width, linearity as well as response and recovery times. We observed that the proposed sensing systems have better sensing abilities than the above-mentioned pH sensors.

Highly Sensitive and Wide-Dynamic-Range Multichannel Optical-Fiber pH Sensor Based on PWM Technique

PubMed Central

Khan, Md. Rajibur Rahaman; Kang, Shin-Won

2016-01-01

In this study, we propose a highly sensitive multichannel pH sensor that is based on an optical-fiber pulse width modulation (PWM) technique. According to the optical-fiber PWM method, the received sensing signal’s pulse width changes when the optical-fiber pH sensing-element of the array comes into contact with pH buffer solutions. The proposed optical-fiber PWM pH-sensing system offers a linear sensing response over a wide range of pH values from 2 to 12, with a high pH-sensing ability. The sensitivity of the proposed pH sensor is 0.46 µs/pH, and the correlation coefficient R2 is approximately 0.997. Additional advantages of the proposed optical-fiber PWM pH sensor include a short/fast response-time of about 8 s, good reproducibility properties with a relative standard deviation (RSD) of about 0.019, easy fabrication, low cost, small size, reusability of the optical-fiber sensing-element, and the capability of remote sensing. Finally, the performance of the proposed PWM pH sensor was compared with that of potentiometric, optical-fiber modal interferometer, and optical-fiber Fabry–Perot interferometer pH sensors with respect to dynamic range width, linearity as well as response and recovery times. We observed that the proposed sensing systems have better sensing abilities than the above-mentioned pH sensors. PMID:27834865

Biologics formulation factors affecting metal leachables from stainless steel.

PubMed

Zhou, Shuxia; Schöneich, Christian; Singh, Satish K

2011-03-01

An area of increasing concern and scientific scrutiny is the potential contamination of drug products by leachables entering the product during manufacturing and storage. These contaminants may either have a direct safety impact on the patients or act indirectly through the alteration of the physicochemical properties of the product. In the case of biotherapeutics, trace amounts of metal contaminants can arise from various sources, but mainly from contact with stainless steel (ss). The effect of the various factors, buffer species, solution fill volume per unit contact surface area, metal chelators, and pH, on metal leachables from contact with ss over time were investigated individually. Three major metal leachables, iron, chromium, and nickel, were monitored by inductively coupled plasma-mass spectrometry because they are the major components of 316L ss. Iron was primarily used to evaluate the effect of each factor since it is the most abundant. It was observed that each studied factor exhibited its own effect on metal leachables from contact with ss. The effect of buffer species and pH exhibited temperature dependence over the studied temperature range. The metal leachables decreased with the increased fill volume (mL) per unit contact ss surface area (cm(2)) but a plateau was achieved at approximately 3 mL/cm(2). Metal chelators produced the strongest effect in facilitating metal leaching. In order to minimize the metal leachables and optimize biological product stability, each formulation factor must be evaluated for its impact, to balance its risk and benefit in achieving the target drug product shelf life. © 2011 American Association of Pharmaceutical Scientists

Removal of chromium (VI) from electroplating wastewater using an anion exchanger derived from rice straw.

PubMed

Cao, Wei; Dang, Zhi; Yia, Xiao-Yun; Yang, Chen; Lu, Gui-Ning; Liu, Yun-Feng; Huang, Se-Yan; Zheng, Liu-Chun

2013-01-01

An anion exchanger from rice straw was used to remove Cr (VI) from synthetic wastewater and electroplating effluent. The exchanger was characterized using Fourier transform infrared (FTIR) spectrum and scanning electron microscopy (SEM), and it was found that the quaternary amino group and hydroxyl group are the main functional groups on the fibrous surface of the exchanger. The effect of contact time, initial concentration and pH on the removal of Cr (VI), and adsorption isotherms at different temperature, was investigated. The results showed that the removal of Cr (VI) was very rapid and was significantly affected by the initial pH of the solution. Although acidic conditions (pH = 2-6) facilitated Cr (VI) adsorption, the exchanger was effective in neutral solution and even under weak base conditions. The equilibrium data fitted well with Langmuir adsorption model, and the maximum Cr (VI) adsorption capacities at pH 6.4 were 0.35, 0.36 and 0.38 mmol/g for 15, 25 and 35 degrees C, respectively. The exchanger was finally tested with real electroplating wastewater, and at sorbent dosage of 10 g/L, the removal efficiencies for Cr (VI) and total Cr were 99.4% and 97.8%, respectively. In addition, the positive relationship between adsorbed Cr (VI) and desorbed Cl- suggested that Cr (VI) was mainly removed by ion exchange with chlorine.

A New Chemical Pathway Yielding A-Type Vitisins in Red Wines

PubMed Central

Araújo, Paula; Fernandes, Ana; de Freitas, Victor; Oliveira, Joana

2017-01-01

A new chemical pathway yielding A-type vitisins in red wines is proposed herein from the reaction between anthocyanins and oxaloacetic acid (OAA). This new chemical path is thought to occur in the first stages of the wine production even during the fermentation process. This is due to the revealed high reactivity of OAA with anthocyanins compared with the already known precursor (pyruvic acid, PA). In model solutions at wine pH (3.5), when malvidin-3-O-glucoside (mv-3-glc) is in contact with OAA and PA a decrease in the OAA concentration is observed along with the formation of A-type vitisin. Moreover, part of the OAA is also chemically converted into PA in model solutions. The reaction yields were also determined for OAA and PA using different mv-3-glc:organic acid molar ratios (1:0.5, 1:1, 1:5, 1:10; 1:50, and 1:100) and these values were always higher for OAA when compared to PA, even at the lowest molar ratio (1:0.5). The reaction yields were higher at pH 2.6 in comparison to pH 1.5 and 3.5, being less affected at pH 3.5 for OAA. These results support the idea that OAA can be at the origin of A-type vitisins in the first stages of wine production and PA in the subsequent ageing process. PMID:28375190

A New Chemical Pathway Yielding A-Type Vitisins in Red Wines.

PubMed

Araújo, Paula; Fernandes, Ana; de Freitas, Victor; Oliveira, Joana

2017-04-04

A new chemical pathway yielding A-type vitisins in red wines is proposed herein from the reaction between anthocyanins and oxaloacetic acid (OAA). This new chemical path is thought to occur in the first stages of the wine production even during the fermentation process. This is due to the revealed high reactivity of OAA with anthocyanins compared with the already known precursor (pyruvic acid, PA). In model solutions at wine pH (3.5), when malvidin-3- O -glucoside (mv-3-glc) is in contact with OAA and PA a decrease in the OAA concentration is observed along with the formation of A-type vitisin. Moreover, part of the OAA is also chemically converted into PA in model solutions. The reaction yields were also determined for OAA and PA using different mv-3-glc:organic acid molar ratios (1:0.5, 1:1, 1:5, 1:10; 1:50, and 1:100) and these values were always higher for OAA when compared to PA, even at the lowest molar ratio (1:0.5). The reaction yields were higher at pH 2.6 in comparison to pH 1.5 and 3.5, being less affected at pH 3.5 for OAA. These results support the idea that OAA can be at the origin of A-type vitisins in the first stages of wine production and PA in the subsequent ageing process.

Eragrostis plana Nees as a novel eco-friendly adsorbent for removal of crystal violet from aqueous solutions.

PubMed

Filho, Augusto Cezar D; Mazzocato, Ana C; Dotto, Guilherme L; Thue, Pascal S; Pavan, Flávio A

2017-08-01

Eragrostis plana Nees (EPN) was used as new and eco-friendly adsorbent for the removal of crystal violet dye (CV) from aqueous solution. Specific surface area (BET), scanning electron microscopy (SEM), infrared spectroscopy (ATR-FTIR), point of zero charge (pH PZC ), and modified Boehm titration method were used to characterize the EPN material. The effects of initial pH of solution, adsorbent mass, contact time and initial dye concentration, and temperature were studied in batch adsorption mode. Kinetic data were evaluated by pseudo-first-order and pseudo-second-order models. The result exhibited that pseudo-second-order model well described the adsorption kinetics of CV onto EPN. Langmuir, Freundlich, and Sips isotherm models were used for analysis of the isothermal data. The equilibrium data of adsorption of CV onto EPN was better fitted with the Sips isotherm. Based on the Sips isotherm model, the maximum adsorption capacity was 76.20 ± 1.20 mg g -1 at 333 K. A high desorption of CV from EPN was obtained using 1.00 mol L -1 of CH 3 COOH as eluent. The thermodynamic data indicated that the adsorption was spontaneous, endothermic, and physical process. EPN can be used as alternative adsorbent to remove CV from aqueous solution.

Method of cross-linking polyvinyl alcohol and other water soluble resins

NASA Technical Reports Server (NTRS)

Phillipp, W. H.; May, C. E.; Hsu, L. C.; Sheibley, D. W. (Inventor)

1980-01-01

A self supporting sheet structure comprising a water soluble, noncrosslinked polymer such as polyvinyl alcohol which is capable of being crosslinked by reaction with hydrogen atom radicals and hydroxyl molecule radicals is contacted with an aqueous solution having a pH of less than 8 and containing a dissolved salt in an amount sufficient to prevent substantial dissolution of the noncrosslinked polymer in the aqueous solution. The aqueous solution is then irradiated with ionizing radiation to form hydrogen atom radicals and hydroxyl molecule radicals and the irradiation is continued for a time sufficient to effect crosslinking of the water soluble polymer to produce a water insoluble polymer sheet structure. The method has particular application in the production of battery separators and electrode envelopes for alkaline batteries.

Corneal epithelial and aqueous humor acidification during in vivo contact lens wear in rabbits.

PubMed

Giasson, C; Bonanno, J A

1994-03-01

Based on contact lens-induced stromal acidification of the cornea, it has been suggested that the corneal epithelial and endothelial cells also become acidotic during contact lens wear. This alleged acidification may have a role in altered cell appearance and metabolism during contact lens wear. This study investigated the effects of anoxia, carbon dioxide retention, and contact lens gas transmissibility on the epithelial and aqueous humor pH in living rabbits. Epithelial intracellular pH (pHi) and aqueous humor pH were fluorophotometrically measured with a pH sensitive-dye (BCECF) during contact lens wear or exposure to various gas mixtures. Polymethylmethacrylate (PMMA) lens wear acidified epithelial cells by preventing CO2 efflux and by inducing hypoxia. Increasing lens oxygen transmissibility decreased epithelial acidification. After initiation of rigid, gas-permeable (RGP) lens wear or CO2-air exposure, pHi dropped transiently and then recovered partially. This recovery of pHi was not observed during anoxia, whether induced by PMMA lens wear or exposure to 100% N2. The aqueous humor also acidified during PMMA lens wear, a phenomenon not observed during RGP lens wear. Changes in aqueous pH were smaller, slower, and delayed when compared to their epithelial counterparts. Hypoxic contact lens wear acidifies the corneal epithelium and aqueous humor. The aqueous humor pH change indicates a probable endothelial acidification during hypoxic contact lens wear; the pH changes are caused by two separate and additive effects, CO2 retention and hypoxic acidosis. Increases in the oxygen transmissibility of the lens decrease the cellular acidosis, which might minimize cellular complications arising from contact lens wear. We estimate that a lens with an oxygen transmissibility (Dk/L) of 300 x 10(-11) (cm/sec)(ml O2/ml x mm Hg) is needed to prevent epithelial pHi changes in the open eye. In contrast, lenses with Dk/L as low as 18 x 10(-9) (cm/sec)(ml O2/ml x mm Hg) can prevent aqueous humor pH changes.

77 FR 8266 - Center for Scientific Review; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-14

..., (Telephone Conference Call). Contact Person: Michael M. Sveda, Ph.D., Scientific Review Officer, Center for..., MD, Ph.D., Scientific Review Officer, Center for Scientific Review, National Institutes of Health...). Contact Person: Richard Panniers, Ph.D., Scientific Review Officer, Center for Scientific Review, National...

77 FR 74675 - Center for Scientific Review; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-17

... Rockledge Drive, Bethesda, MD 20892, (Telephone Conference Call). Contact Person: Rajiv Kumar, Ph.D., Chief... Chaudhari, Ph.D., Scientific Review Officer, Center for Scientific Review, National Institutes of Health... Conference Call). Contact Person: Syed M Quadri, Ph.D., Scientific Review Officer, Center for Scientific...

Use of natural clays as sorbent materials for rare earth ions: Materials characterization and set up of the operative parameters.

PubMed

Iannicelli-Zubiani, Elena Maria; Cristiani, Cinzia; Dotelli, Giovanni; Gallo Stampino, Paola; Pelosato, Renato; Mesto, Ernesto; Schingaro, Emanuela; Lacalamita, Maria

2015-12-01

Two mineral clays of the montmorillonite group were tested as sorbents for the removal of Rare Earths (REs) from liquid solutions. Lanthanum and neodymium model solutions were used to perform uptake tests in order to: (a) verify the clays sorption capability, (b) investigate the sorption mechanisms and (c) optimize the experimental parameters, such as contact time and pH. The desorption was also studied, in order to evaluate the feasibility of REs recovery from waters. The adsorption-desorption procedure with the optimized parameters was also tested on a leaching solution obtained by dissolution of a dismantled NdFeB magnet of a hard-disk. The clays were fully characterized after REs adsorption and desorption by means of X-ray powder diffraction (XRPD) and X-ray photoelectron spectroscopy (XPS); the liquid phase was characterized via Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) analyses. The experimental results show that both clays are able to capture and release La and Nd ions, with an ion exchange mechanism. The best total efficiency (capture ≈ 50%, release ≈ 70%) is obtained when the uptake and release processes are performed at pH=5 and pH=1 respectively; in real leached scrap solutions, the uptake is around 40% but release efficiency is strongly decreased passing from a mono-ion system to a real system (from 80% to 5%). Furthermore, a strong matrix effect is found, with the matrix largely affecting both the uptake and the release of neodymium. Copyright © 2015 Elsevier Ltd. All rights reserved.

Application of response surface methodology (RSM) for the removal of methylene blue dye from water by nano zero-valent iron (NZVI).

PubMed

Khosravi, Morteza; Arabi, Simin

In this study, iron zero-valent nanoparticles were synthesized, characterized and studied for removal of methylene blue dye in water solution. The reactions were mathematically described as the function of parameters such as nano zero-valent iron (NZVI) dose, pH, contact time and initial dye concentration, and were modeled by the use of response surface methodology. These experiments were carried out as a central composite design consisting of 30 experiments determined by the 2(4) full factorial designs with eight axial points and six center points. The results revealed that the optimal conditions for dye removal were NZVI dose 0.1-0.9 g/L, pH 3-11, contact time 20-100 s, and initial dye concentration 10-50 mg/L, respectively. Under these optimal values of process parameters, the dye removal efficiency of 92.87% was observed, which very close to the experimental value (92.21%) in batch experiment. In the optimization, R(2) and R(2)adj correlation coefficients for the model were evaluated as 0.96 and 0.93, respectively.

Simulations of the Viking Gas Exchange Experiment using palagonite and Fe-rich montmorillonite as terrestrial analogs: implications for the surface composition of Mars.

PubMed

Quinn, R; Orenberg, J

1993-10-01

Simulations of the Gas Exchange Experiment (GEX), one of the Viking Lander Biology Experiments, were run using palagonite and Fe-rich montmorillonite as terrestrial analogs of the Martian soil. These terrestrial analogs were exposed to a nutrient solution of the same composition as that of the Viking Landers under humid (no contact with nutrient) and wet (intimate contact) conditions. The headspace gases in the GEX sample cell were sampled and then analyzed by gas chromatography under both humid and wet conditions. Five gases were monitored: CO2, N2, O2, Ar, and Kr. It was determined that in order to simulate the CO2 gas changes of the Viking GEX experiment, the mixture of soil analog mineral plus nutrient medium must be slightly (pH = 7.4) to moderately basic (pH = 8.7). This conclusion suggests constraints upon the composition of terrestrial analogs to the Mars soil; acidic components may be present, but the overall mixture must be basic in order to simulate the Viking GEX results.

Simulations of the Viking gas exchange experiment using palagonite and Fe-rich montmorillonite as terrestrial analogs - Implications for the surface composition of Mars

NASA Astrophysics Data System (ADS)

Quinn, Richard; Orenberg, James

1993-10-01

Simulations of the Gas Exchange Experiment (GEX), one of the Viking Lander Biology Experiments, were run using palagonite and Fe-rich montmorillonite as terrestrial analogs of the Martian soil. These terrestrial analogs were exposed to a nutrient solution of the same composition as that of the Viking Landers under humid (no contact with nutrient) and wet (intimate contact) conditions. The headspace gases in the GEX sample cell were sampled and then analyzed by gas chromatography under both humid and wet conditions. Five gases were monitored: CO2, N2, O2, Ar, and Kr. It was determined that in order to simulate the CO2 gas changes of the Viking GEX experiment, the mixture of soil analog mineral plus nutrient medium must be slightly (pH = 7.4) to moderately basic (pH = 8.7). This conclusion suggests constraints upon the composition of terrestrial analogs of the Mars soil; acidic components may be present, but the overall mixture must be basic in order to simulate the Viking GEX results.

Theoretical study of the dissolution kinetics of galena and cerussite in an abandoned mining area (Zaida mine, Morocco)

NASA Astrophysics Data System (ADS)

El Alaoui, Lamiae; Dekayir, Abdelilah

2018-05-01

In the abandoned mine in Zaida, the pit lakes filled with water constitute significant water reserves. In these lakes, the waters are permanently in contact with ore deposit (cerussite and galena). The modelling of the interaction of waters with this mineralization shows that cerussite dissolves more rapidly than galena. This dissolution is controlled by the pH and dissolved oxygen concentration in solution. The lead concentrations recorded in these lakes come largely from the dissolution of cerussite.

76 FR 59707 - Center for Scientific Review; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-27

..., (Virtual Meeting). Contact Person: Rebecca Henry, PhD, Scientific Review Officer, Center for Scientific... Rockledge Drive, Bethesda, MD 20892, (Virtual Meeting). Contact Person: George M Barnas, PhD, Scientific... Institutes of Health, 6701 Rockledge Drive, Bethesda, MD 20892, (Virtual Meeting). Contact Person: George M...

Photocatalytic degradation of furfural in aqueous solution by N-doped titanium dioxide nanoparticles.

PubMed

Veisi, Farzaneh; Zazouli, Mohammad Ali; Ebrahimzadeh, Mohammad Ali; Charati, Jamshid Yazdani; Dezfoli, Amin Shiralizadeh

2016-11-01

The photocatalytic degradation of furfural in aqueous solution was investigated using N-doped titanium dioxide nanoparticles under sunlight and ultraviolet radiation (N-TiO 2 /Sun and N-TiO 2 /UV) in a lab-scale batch photoreactor. The N-TiO 2 nanoparticles prepared using a sol-gel method were characterized using XRD, X-ray photoelectron spectroscopy (XPS), and SEM analyses. Using HPLC to monitor the furfural concentration, the effect of catalyst dosage, contact time, initial solution pH, initial furfural concentration, and sunlight or ultraviolet radiation on the degradation efficiency was studied. The efficiency of furfural removal was found to increase with increased reaction time, nanoparticle loading, and pH for both processes, whereas the efficiency decreased with increased furfural concentration. The maximum removal efficiencies for the N-TiO 2 /UV and N-TiO 2 /Sun processes were 97 and 78 %, respectively, whereas the mean removal efficiencies were 80.71 ± 2.08 % and 62.85 ± 2.41 %, respectively. In general, the degradation and elimination rate of furfural using the N-TiO 2 /UV process was higher than that using the N-TiO 2 /Sun process.

CARBONATE METHOD OF SEPARATION OF TETRAVALENT PLUTONIUM FROM FISSION PRODUCT VALUES

DOEpatents

Duffield, R.B.; Stoughton, R.W.

1959-02-01

It has been found that plutonium forms an insoluble precipitate with carbonate ion when the carbonate ion is present in stoichiometric proportions, while an excess of the carbonate ion complexes plutonium and renders it soluble. A method for separating tetravalent plutonium from lanthanum-group rare earths has been based on this discovery, since these rare earths form insoluble carbonates in approximately neutral solutions. According to the process the pH is adjusted to between 5 and 7, and approximately stoichiometric amounts of carbonate ion are added to the solution causing the formation of a precipitate of plutonium carbonate and the lanthanum-group rare earth carbonates. The precipitate is then separated from the solution and contacted with a carbonate solution of a concentration between 1 M and 3 M to complex and redissolve the plutonium precipitate, and thus separate it from the insoluble rare earth precipitate.

PEROXIDE-INHIBITED DECONTAMINATION SOLUTIONS FOR CARBON STEEL AND OTHER METALS IN THE GAS-COOLED REACTOR PROGRAM. Progress Report, November 1959-July 1962

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

Meservey, A.B.

1963-01-01

A search for solutions suitable for dissolving uranium dioxide powder or lumps and yet noncorrosive enough to be used for decontaminating the carbon steel EGCR charge and service machines resulted in the development of buffered oxalate solutions of controlled temperature and pH, with hydrogen peroxide added to act as corrosion inhibitor, UO/sub 2/ oxidizer, and decontamination aid. Hydrogen peroxide acts either as a corrosion promoter or inhibitor, depending on factors such as its concentration, the ratio to other ingredients, acidity, temperature, the presence of complexing agents, and the ferric ion content of the solution. In general, oxalate-peroxide solutions for fissionmore » product decontamination from metal surfaces were superior to more conventional decontaminating solutions and had attractively low corrosion rates on carbon steel (less than 0.01 mil/hr), Solution instability, initially a serious drawback, was largely overcome. Of nearly a hundred formulations studied, the one having the best combination of long life, low corrosivity, high solvency for UO/sub 2/, decontamination power, safety, and ease of waste disposal was an aqueous solution of 0.4M oxalic acid, 0.18M ammonium citrate, and 0.34M H/sub 2/O/sub 2/, adjusted to pH 4.00 with ammonium hydroxide and used at 85 to 95 deg C. Similar solutions at lower pH, with increased H/sub 2/O/sub 2/ concentration to maintain noncorrosiveness, were successful decontaminants at 60 deg C when contact times were increased to several hours. Contaminated stainless steels heated to 500 deg C in helium resisted decontamination in noncorrosive reagents. Oxalate-peroxide soluttons are currently recommended as UO/sub 2/ solvents and as general decontaminants for mild steel and aluminum surfaces in the GCR program, and for stainless steels which were not strongly heated while contaminated. These solutions may also find application in the decontamination of metals used in the aqueous reprocessing of radioactive nuclear fuels. (auth)« less

Removal of reactive red-120 and 4-(2-pyridylazo) resorcinol from aqueous samples by Fe3O4 magnetic nanoparticles using ionic liquid as modifier.

PubMed

Absalan, Ghodratollah; Asadi, Mozaffar; Kamran, Sedigheh; Sheikhian, Leila; Goltz, Douglas M

2011-08-30

The nanoparticles of Fe(3)O(4) as well as the binary nanoparticles of ionic liquid and Fe(3)O(4) (IL-Fe(3)O(4)) were synthesized for removal of reactive red 120 (RR-120) and 4-(2-pyridylazo) resorcinol (PAR) as model azo dyes from aqueous solutions. The mean size and the surface morphology of the nanoparticles were characterized by TEM, DLS, XRD, FTIR and TGA techniques. Adsorption of RR-120 and PAR was studied in a batch reactor at different experimental conditions such as nanoparticle dosage, dye concentration, pH of the solution, ionic strength, and contact time. Experimental results indicated that the IL-Fe(3)O(4) nanoparticles had removed more than 98% of both dyes under the optimum operational conditions of a dosage of 60mg, a pH of 2.5, and a contact time of 2min when initial dyes concentrations of 10-200mg L(-1) were used. The maximum adsorption capacity of IL-Fe(3)O(4) was 166.67 and 49.26mg g(-1) for RR-120 and PAR, respectively. The isotherm experiments revealed that the Langmuir model attained better fits to the equilibrium data than the Freundlich model. The Langmuir adsorption constants were 5.99 and 3.62L mg(-1) for adsorptions of RR-120 and PAR, respectively. Both adsorption processes were endothermic and dyes could be desorbed from IL-Fe(3)O(4) by using a mixed NaCl-acetone solution and adsorbent was reusable. Copyright © 2011 Elsevier B.V. All rights reserved.

76 FR 54240 - National Institute of Allergy and Infectious Diseases; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-31

...: Robert G. Keefe, PhD, Scientific Review Officer, Scientific Review Program, DEA/NIAID/NIH/DHHS, Room 3256... Conference Call). Contact Person: Robert G. Keefe, PhD, Scientific Review Officer, Scientific Review Program... Drive, Bethesda, MD 20817 (Telephone Conference Call). Contact Person: Robert G. Keefe, PhD, Scientific...

Adsorption and removal of arsenic (V) using crystalline manganese (II,III) oxide: Kinetics, equilibrium, effect of pH and ionic strength.

PubMed

Babaeivelni, Kamel; Khodadoust, Amid P; Bogdan, Dorin

2014-01-01

Manganese (II,III) oxide (Mn3O4) crystalline powder was evaluated as a potential sorbent for removal of arsenic (V) from water. Adsorption isotherm experiments were carried out to determine the adsorption capacity using de-ionized (DI) water, a synthetic solution containing bicarbonate alkalinity, and two natual groundwater samples. Adsorption isotherm data followed the Langmuir and Freundlich equations, indicating favorable adsorption of arsenic (V) onto Mn3O4, while results from the Dubinin-Radushkevich equation were suggestive of chemisorption of arsenic (V). When normalized to the sorbent surface area, the maximum adsorption capacity of Mn3O4 for arsenic (V) was 101 μg m(-2), comparable to that of activated alumina. Arsenic (V) adsorption onto Mn3O4 followed pseudo-second-order kinetics. Adsorption of arsenic (V) was greatest at pH 2, while adsorption at pH 7-9 was within 91% of maximum adsorption, whereas adsorption decreased to 32% of maximum adsorption at pH 10. Surface charge analysis confirmed the adsorption of arsenic (V) onto the acidic surface of the Mn3O4 sorbent with a pHPZC of 7.32. The presence of coexisting ions bicarbonate and phosphate resulted in a decrease in arsenic (V) uptake. Comparable adsorption capacities were obtained for the synthetic solution and both groundwater samples. Overall, crystalline Mn3O4 was an effective and viable sorbent for removal of arsenic (V) from natural water, removing greater than 95% of arsenic (V) from a 1 mg L(-1) solution within 60 min of contact time.

An induced current method for measuring zeta potential of electrolyte solution-air interface.

PubMed

Song, Yongxin; Zhao, Kai; Wang, Junsheng; Wu, Xudong; Pan, Xinxiang; Sun, Yeqing; Li, Dongqing

2014-02-15

This paper reports a novel and very simple method for measuring the zeta potential of electrolyte solution-air interface. When a measuring electrode contacts the electrolyte solution-air interface, an electrical current will be generated due to the potential difference between the electrode-air surface and the electrolyte solution-air interface. The amplitude of the measured electric signal is linearly proportional to this potential difference; and depends only on the zeta potential at the electrolyte solution-air interface, regardless of the types and concentrations of the electrolyte. A correlation between the zeta potential and the measured voltage signal is obtained based on the experimental data. Using this equation, the zeta potential of any electrolyte solution-air interface can be evaluated quickly and easily by inserting an electrode through the electrolyte solution-air interface and measuring the electrical signal amplitude. This method was verified by comparing the obtained results of NaCl, MgCl2 and CaCl2 solutions of different pH values and concentrations with the zeta potential data reported in the published journal papers. Copyright © 2013 Elsevier Inc. All rights reserved.

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2010-03-17

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2013-02-01

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Contact Lens Solutions and Contact Lens Discomfort: Examining the Correlations Between Solution Components, Keratitis, and Contact Lens Discomfort.

PubMed

Kuc, Christopher J; Lebow, Kenneth A

2018-06-13

This article will examine the current literature, as it relates to contact lens discomfort (CLD) secondary to contact lens solutions. The reader will better understand the characteristics of contact lenses, as they uniquely interact with each type of contact lens solution and also gain a better comprehension of the components of contact lens solution such as preservatives, surfactants, and chelating agents, which may contribute to discomfort. By investigating corneal staining theory and the mechanisms that contribute to its presence, the reader will gain insight into this clinical finding, which relates to selection of contact lens solutions. The FDA standards for testing solutions and how this relates to contact lens keratitis will also be appraised in regards to current ISO recommendations. Finally, better selection of multipurpose contact lens solution (MPS) and hydrogen peroxide-based solutions for patients should be accessible to the clinician based on this review and preexisting clinical findings or diagnoses. A review of current published literature from peer reviewed journals and online journals was conducted to gain an understanding of contact lens solution's impact on contact lens discomfort. Many studies have been conducted comparing comfort between various types of contact lens solutions. It is challenging to decipher this information and apply it clinically when selecting solutions for patients. By comparing solution components, how contact lens solutions interact with different types of lenses, keratitis related to contact lenses, and preexisting ocular conditions, this review will improve a clinician's ability to eliminate CLD.

Artificial neural network (ANN) approach for modeling of Pb(II) adsorption from aqueous solution by Antep pistachio (Pistacia Vera L.) shells.

PubMed

Yetilmezsoy, Kaan; Demirel, Sevgi

2008-05-30

A three-layer artificial neural network (ANN) model was developed to predict the efficiency of Pb(II) ions removal from aqueous solution by Antep pistachio (Pistacia Vera L.) shells based on 66 experimental sets obtained in a laboratory batch study. The effect of operational parameters such as adsorbent dosage, initial concentration of Pb(II) ions, initial pH, operating temperature, and contact time were studied to optimise the conditions for maximum removal of Pb(II) ions. On the basis of batch test results, optimal operating conditions were determined to be an initial pH of 5.5, an adsorbent dosage of 1.0 g, an initial Pb(II) concentration of 30 ppm, and a temperature of 30 degrees C. Experimental results showed that a contact time of 45 min was generally sufficient to achieve equilibrium. After backpropagation (BP) training combined with principal component analysis (PCA), the ANN model was able to predict adsorption efficiency with a tangent sigmoid transfer function (tansig) at hidden layer with 11 neurons and a linear transfer function (purelin) at output layer. The Levenberg-Marquardt algorithm (LMA) was found as the best of 11 BP algorithms with a minimum mean squared error (MSE) of 0.000227875. The linear regression between the network outputs and the corresponding targets were proven to be satisfactory with a correlation coefficient of about 0.936 for five model variables used in this study.

Adsorption of Direct Blue 53 dye from aqueous solutions by multi-walled carbon nanotubes and activated carbon.

PubMed

Prola, Lizie D T; Machado, Fernando M; Bergmann, Carlos P; de Souza, Felipe E; Gally, Caline R; Lima, Eder C; Adebayo, Matthew A; Dias, Silvio L P; Calvete, Tatiana

2013-11-30

Multi-walled carbon nanotubes (MWCNT) and powder activated carbon (PAC) were used as adsorbents for adsorption of Direct Blue 53 dye (DB-53) from aqueous solutions. The adsorbents were characterised using Raman spectroscopy, N2 adsorption/desorption isotherms, and scanning and transmission electron microscopy. The effects of initial pH, contact time and temperature on adsorption capacity of the adsorbents were investigated. At pH 2.0, optimum adsorption of the dye was achieved by both adsorbents. Equilibrium contact times of 3 and 4 h were achieved by MWCNT and PAC adsorbents, respectively. The general order kinetic model provided the best fit of the experimental data compared to pseudo-first order and pseudo-second order kinetic adsorption models. For DB-53 dye, the equilibrium data (298-323 K) were best fitted to the Sips isotherm model. The maximum sorption capacity for adsorption of the dye occurred at 323 K, with the values of 409.4 and 135.2 mg g(-1) for MWCNT and PAC, respectively. Studies of adsorption/desorption were conducted and the results showed that DB-53 loaded MWCNT could be regenerated (97.85%) using a mixture 50% acetone + 50% of 3 mol L(-1) NaOH. Simulated dye house effluents were used to evaluate the application of the adsorbents for effluent treatment (removal of 99.87% and 97.00% for MWCNT and PAC, respectively, were recorded). Copyright © 2013 Elsevier Ltd. All rights reserved.

Magnetic-epichlorohydrin crosslinked chitosan schiff's base (m-ECCSB) as a novel adsorbent for the removal of Cu(II) ions from aqueous environment.

PubMed

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

2017-04-01

Metal ions cause a serious public health problem. It is a great challenge to find an effective and efficient adsorbent to remove heavy metals from wastewater. Chitosan-based adsorbents are potential and effective for heavy metal ion removal. Hence a novel m-ECCSB was synthesized, characterized and utilized as an adsorbent for the removal of Cu(II) ions from aqueous solution. Various factors affecting the uptake behavior such as pH, adsorbent dosage, contact time, initial concentration of Cu(II) and temperature effect were investigated. Maximum adsorption capability (123.10mg/g) was obtained at pH=6, adsorbent dose of=250mg, rotational speed=200rpm, contact time=60min, and temperature of 323K. The result of the kinetic study shows that the adsorption of Cu(II) could be described by the pseudo-second-order equation. Equilibrium data were analysed with the Langmuir, Freundlich and Dubinin-Radushkevich isotherms and Langmuir model was found to provide the best fit of the experimental data. The thermodynamic parameters showed that the adsorption of Cu(II) onto m-ECCSB was spontaneous (ΔG°=-8.990, -10.00 and -10.593kJ/mol), endothermic (ΔH°=15.674, 15.478 and 15.699kJ/mol) and ΔS° (0.0814J/molK) suggests an increased randomness at the solid/solution interface under the studied conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

Biosorption of Congo Red from aqueous solution onto burned root of Eichhornia crassipes biomass

NASA Astrophysics Data System (ADS)

Roy, Tapas Kumar; Mondal, Naba Kumar

2017-07-01

Biosorption is becoming a promising alternative to replace or supplement the present dye removal processes from dye containing waste water. In this work, adsorption of Congo Red (CR) from aqueous solution on burned root of Eichhornia crassipes ( BREC) biomass was investigated. A series of batch experiments were performed utilizing BREC biomass to remove CR dye from aqueous systems. Under optimized batch conditions, the BREC could remove up to 94.35 % of CR from waste water. The effects of operating parameters such as initial concentration, pH, adsorbent dose and contact time on the adsorption of CR were analyzed using response surface methodology. The proposed quadratic model for central composite design fitted very well to the experimental data. Response surface plots were used to determine the interaction effects of main factors and optimum conditions of the process. The optimum adsorption conditions were found to be initial CR concentration = 5 mg/L-1, pH = 7, adsorbent dose = 0.125 g and contact time = 45 min. The experimental isotherms data were analyzed using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) isotherm equations and the results indicated that the Freundlich isotherm showed a better fit for CR adsorption. Thermodynamic parameters were calculated from Van't Hoff plot, confirming that the adsorption process was spontaneous and exothermic. The high CR adsorptive removal ability and regeneration efficiency of this adsorbent suggest its applicability in industrial/household systems and data generated would help in further upscaling of the adsorption process.

Facile preparation of polyethylenimine-tannins coated SiO2 hybrid materials for Cu2+ removal

NASA Astrophysics Data System (ADS)

Huang, Qiang; Liu, Meiying; Zhao, Jiao; Chen, Junyu; Zeng, Guangjian; Huang, Hongye; Tian, Jianwen; Wen, Yuanqing; Zhang, Xiaoyong; Wei, Yen

2018-01-01

Polyethylenimine-tannins coated SiO2 (SiO2@PEI-TA) hybrid materials have been prepared via a single-step multifunctional coating with polyethylenimine (PEI) and tannins (TA), and characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The as-prepared SiO2@PEI-TA composites were examined as adsorbents to remove the Cu2+ from aqueous solution. The effects of contact time, initial Cu2+ concentration, solution pH and temperature, on Cu2+ adsorption have been investigated. The results show that the adsorption of Cu2+ onto SiO2@PEI-TA is dependent on the contact time, Cu2+ concentration, pH and temperature. The SiO2@PEI-TA composites show a 2.4-fold increase in adsorption capacity, implying that the introduction of PEI-TA coating is in favor of the Cu2+ adsorption. Based on the analysis of kinetic data, the kinetics of Cu2+ adsorption is more accurately described by the pseudo-second-order model. The equilibrium data are analyzed by Langmuir and Freundlich isotherms. Results of isotherms show that the better agreement is Freundlich isotherm model with correlation coefficient of 0.9914, which suggests that the adsorption of Cu2+ onto SiO2@PEI-TA is mainly a heterogeneous adsorption process. Thermodynamic analyses show that the adsorption interaction is actually a spontaneous and endothermic chemical process, which might involve the chemical chelation between Cu2+ and functional groups (amine and carboxyl groups) on the surface of SiO2@PEI-TA. In addition, the Cu2+ ions could desorb from SiO2@PEI-TA by using acid solution and the adsorption efficiency remains at high level after five adsorption-desorption recycles. These results provide potential applications of these novel adsorbents for the removal of heavy metal Cu2+ from aqueous solution and also provide strong evidence to support the adsorption mechanism proposed in the study.

Competitive removal of hazardous dyes from aqueous solution by MIL-68(Al): Derivative spectrophotometric method and response surface methodology approach

NASA Astrophysics Data System (ADS)

Tehrani, Mahnaz Saghanejhad; Zare-Dorabei, Rouholah

2016-05-01

MIL-68(Al) as a metal-organic framework (MOF) was synthesized and characterized by different techniques such as SEM, BET, FTIR, and XRD analysis. This material was then applied for simulations removal of malachite green (MG) and methylene blue (MB) dyes from aqueous solutions using second order derivative spectrophotometric method (SODS) which was applied to resolve the overlap between the spectra of these dyes. The dependency of dyes removal efficiency in binary solutions was examined and optimized toward various parameters including initial dye concentration, pH of the solution, adsorbent dosage and ultrasonic contact time using central composite design (CCD) under response surface methodology (RSM) approach. The optimized experimental conditions were set as pH 7.78, contact time 5 min, initial MB concentration 22 mg L- 1, initial MG concentration 12 mg L- 1 and adsorbent dosage 0.0055 g. The equilibrium data was fitted to isotherm models such as Langmuir, Freundlich and Tempkin and the results revealed the suitability of the Langmuir model. The maximum adsorption capacity of 666.67 and 153.85 mg g- 1 was obtained for MB and MG removal respectively. Kinetics data fitting to pseudo-first order, pseudo-second order and Elovich models confirmed the applicability of pseudo-second order kinetic model for description of the mechanism and adsorption rate. Dye-loaded MIL-68(Al) can be easily regenerated using methanol and applied for three frequent sorption/desorption cycles with high performance. The impact of ionic strength on removal percentage of both dyes in binary mixture was studied by using NaCl and KCl soluble salts at different concentrations. According to our findings, only small dosage of the proposed MOF is considerably capable to remove large amounts of dyes at room temperature and in very short time that is a big advantage of MIL-68(Al) as a promising adsorbent for adsorptive removal processes.

Evaluation of Sorption Mechanism of Pb (II) and Ni (II) onto Pea (Pisum sativum) Peels.

PubMed

Haq, Atta Ul; Saeed, Muhammad; Anjum, Salma; Bokhari, Tanveer Hussain; Usman, Muhammad; Tubbsum, Saiqa

2017-07-01

The present study was carried out to know the sorption mechanism of Pb (II) and Ni (II) in aqueous solution using pea peels under the influence of sorbent dose, pH, temperature, initial metal ion concentration and contact time. SEM and FTIR were used for characterization of pea peels. The study showed that solution pH affects sorption process and the optimum pH for Pb (II) was 6.0 while for that of Ni (II) was 7.0. Pseudo-second order kinetic model was found to be the most suitable one to explain the kinetic data not only due to high value of R 2 (>0.99) but also due to the closeness of the experimental sorption capacity values to that of calculated sorption capacity values of pseudo second order kinetic model. It can be seen from the results that Freundlich isotherm explains well the equilibrium data (R 2 >0.99). Sorption capacity of pea peels was 140.84 and 32.36 for Pb (II) and Ni (II) mg g -1 respectively. The positive value of ΔH° and negative values of ΔG° suggest that sorption of Pb (II) and Ni (II) onto pea peels is an endothermic and spontaneous process respectively.

Stability of nitroglycerin in intravenous admixtures.

PubMed

Klamerus, K J; Ueda, C T; Newton, D W

1984-02-01

The stability of nitroglycerin in intravenous admixtures was studied. Admixtures containing nitroglycerin 400 micrograms/ml and each of seven injectable drugs in concentrations used clinically were prepared in triplicate in 5% dextrose and 0.9% sodium chloride injections. Admixtures were stored in glass bottles at room temperature for 24 hours in the upright position and then for 24 hours in the inverted position to ensure contact of the solution with the rubber stopper of the container. At 0, 24, and 48 hours, samples of each admixture were assayed by high-performance liquid chromatography for nitroglycerin concentration. The pH of one randomly chosen bottle of each admixture was measured at 0, 24, and 48 hours. A significant loss of nitroglycerin potency at 48 hours was observed only in admixtures containing phenytoin; in these solutions, a 9% decrease in initial nitroglycerin concentration was noted. Phenytoin crystallization was present in all phenytoin admixtures by 24 hours. Compared with initial values, no significant differences in the pH values of any admixture samples assayed at 24 and 48 hours were noted; however, admixtures containing phenytoin had the most alkaline pH values. Under the conditions studied, nitroglycerin concentrations remained above 90% of their initial values for 48 hours in all tested admixtures; however, phenytoin crystallization limits the stability of phenytoin admixtures.

Application of principal component analysis for the optimisation of lead(II) biosorption.

PubMed

Wajda, Łukasz; Duda-Chodak, Aleksandra; Tarko, Tomasz; Kamiński, Paweł

2017-10-03

Current study was focused on optimising lead(II) biosorption carried out by living cells of Arthrospira platensis using Principal Component Analysis. Various experimental conditions were considered: initial metal concentration (50 and 100 mg/l), solution pH (4.0, 4.5, 5.0, 5.5) and contact time (10, 20, 30, 40, 50 and 60 min) at constant rotary speed 200 rpm. It was found that when the biomass was separated from experimental solutions by the filtration, almost 50% of initial metal dose was removed by the filter paper. Moreover, pH was the most important parameter influencing examined processes. The Principal Component Analysis indicated that the most optimum conditions for lead(II) biosorption were metal initial concentration 100 mg/l, pH 4.5 and time 60 min. According to the analysis of the first component it might be stated that the lead(II) uptake increases in time. In overall, it was found to be useful for analysing data obtained in biosorption experiments and eliminating insignificant experimental conditions. Experimental data fitted Langmuir and Dubinin-Radushkevich models indicating that physical and chemical absorption take place at the same time. Further studies are necessary to verify how sorption-desorption cycles affect A. platensis cells.

Adaptive Neuro-Fuzzy Inference system analysis on adsorption studies of Reactive Red 198 from aqueous solution by SBA-15/CTAB composite

NASA Astrophysics Data System (ADS)

Aghajani, Khadijeh; Tayebi, Habib-Allah

2017-01-01

In this study, the Mesoporous material SBA-15 were synthesized and then, the surface was modified by the surfactant Cetyltrimethylammoniumbromide (CTAB). Finally, the obtained adsorbent was used in order to remove Reactive Red 198 (RR 198) from aqueous solution. Transmission electron microscope (TEM), Fourier transform infra-red spectroscopy (FTIR), Thermogravimetric analysis (TGA), X-ray diffraction (XRD), and BET were utilized for the purpose of examining the structural characteristics of obtained adsorbent. Parameters affecting the removal of RR 198 such as pH, the amount of adsorbent, and contact time were investigated at various temperatures and were also optimized. The obtained optimized condition is as follows: pH = 2, time = 60 min and adsorbent dose = 1 g/l. Moreover, a predictive model based on ANFIS for predicting the adsorption amount according to the input variables is presented. The presented model can be used for predicting the adsorption rate based on the input variables include temperature, pH, time, dosage, concentration. The error between actual and approximated output confirm the high accuracy of the proposed model in the prediction process. This fact results in cost reduction because prediction can be done without resorting to costly experimental efforts. SBA-15, CTAB, Reactive Red 198, adsorption study, Adaptive Neuro-Fuzzy Inference systems (ANFIS).

77 FR 8269 - Center for Scientific Review; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-14

.... Place: Mayflower Park Hotel, 405 Olive Way, Seattle, WA 98101. Contact Person: Rebecca Henry, Ph.D... 20814. Contact Person: Melinda Jenkins, Ph.D., Scientific Review Officer, Center for Scientific Review...

Gaz Phase IR and UV Spectroscopy of Neutral Contact Ion Pairs

NASA Astrophysics Data System (ADS)

Habka, Sana; Brenner, Valerie; Mons, Michel; Gloaguen, Eric

2016-06-01

Cations and anions, in solution, tend to pair up forming ion pairs. They play a crucial role in many fundamental processes in ion-concentrated solutions and living organisms. Despite their importance and vast applications in physics, chemistry and biochemistry, they remain difficult to characterize namely because of the coexistence of several types of pairing in solution. However, an interesting alternative consists in applying highly selective gas phase spectroscopy which can offer new insights on these neutral ion pairs. Our study consists in characterizing contact ion pairs (CIPs) in isolated model systems (M+, Ph-(CH2)n-COO- with M=Li, Na, K, Rb, Cs, and n=1-3), to determine their spectral signatures and compare them to ion pairs in solution. We have used laser desorption to vaporize a solid tablet containing the desired salt. Structural information for each system was obtained by mass-selective, UV and IR laser spectroscopy combined with high level quantum chemistry calculations1. Evidence of the presence of neutral CIPs was found by scanning the π-π* transition of the phenyl ring using resonant two-photon ionization (R2PI). Then, conformational selective IR/UV double resonance spectra were recorded in the CO2- stretch region for each conformation detected. The good agreement between theoretical data obtained at the BSSE-corrected-fullCCSD(T)/dhf-TZVPP//B97-D3/dhf-TZVPP level and experimental IR spectra led us to assign the 3D structure for each ion pair formed. Spectral signatures of (M+, Ph-CH2-COO-) pairs, were assigned to a bidentate CIPs between the alkali cation and the carboxylate group. In the case of (Li+, Ph-(CH2)3-COO-) pairs, the presence of a flexible side chain promotes a cation-π interaction leading to a tridentate O-O-π structure with its unique IR and UV signatures. IR spectra obtained on isolated CIPs were found very much alike the ones published on lithium and sodium acetate in solution2. However, in the case of sodium acetate, solution spectra were assigned to solvent shared pairs. Yet, the striking resemblance with our spectral data raises questions about the type assigned, pointing out that CIPs could be more present in these electrolyte solutions than previously thought. The novelty of the gas phase approach to investigate neutral ion pairs, opens the door for various new spectroscopic studies, paving the way to greater knowledge regarding the properties of ion pairs in many scientific fields. 1. Gloaguen, E.; Mons, M.; Topics in Current Chemistry, 2015, Vol 364, 225-270 2. Rudolph, W.W.; Fischer, D.; Irmer, G.; Dalton Transactions 2014, 43, (8), 3174-3185

METHOD OF PROCESSING MONAZITE SAND

DOEpatents

Welt, M.A.; Smutz, M.

1958-08-26

A process is described for recovering thorium, uranium, and rare earth values from monazite sand. The monazite sand is first digested with sulfuric acid and the resulting "monazite sulfate" solution is adjusted to a pH of between 0.4 and 3.0, and oxalate anions are added causing precipitation of the thorium and the rare earths as the oxalates. The oxalate precipitate is separated from the uranium containing supernatant solution, and is dried and calcined to the oxides. The thorium and rare earth oxides are then dissolved in nitric acid and the solution is contacted with tribntyl phosphate whereby an organic extract phase containing the cerium and thorium values is obtained, together with an aqueous raffinate containing the other rare earth values. The organic phase is then separated from the aqueous raffinate and the cerium and thorium are back extracted with an aqueous medium.

Removal of Malachite Green Dye by Mangifera indica Seed Kernel Powder

NASA Astrophysics Data System (ADS)

Singh, Dilbagh; Sowmya, V.; Abinandan, S.; Shanthakumar, S.

2017-11-01

In this study, batch experiments were carried out to study the adsorption of Malachite green dye from aqueous solution by Mangifera indica (mango) seed kernel powder. The mango seed kernel powder was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Effect of various parameters including pH, contact time, adsorbent dosage, initial dye concentration and temperature on adsorption capacity of the adsorbent was observed and the optimized condition for maximum dye removal was identified. Maximum percentage removal of 96% was achieved with an adsorption capacity of 22.8 mg/g at pH 6 with an initial concentration of 100 mg/l. The equilibrium data were examined to fit the Langmuir and Freundlich isotherm models. Thermodynamic parameters for the adsorption process were also calculated.

Atmospheric Pressure Plasma Jet Treatment of Poly-ε-caprolactone Polymer Solutions To Improve Electrospinning.

PubMed

Grande, Silvia; Van Guyse, Joachim; Nikiforov, Anton Y; Onyshchenko, Iuliia; Asadian, Mahtab; Morent, Rino; Hoogenboom, Richard; De Geyter, Nathalie

2017-09-27

An atmospheric pressure plasma jet (APPJ) specifically designed for liquid treatment has been used in this work to improve the electrospinnability of a 5 w/v % solution of poly-ε-caprolactone (PCL) in a mixture of chloroform and N,N-dimethylformamide. Untreated PCL solutions were found to result in nonuniform fibers containing a large number of beads, whereas plasma-treated solutions (exposure time of 2-5 min) enabled the generation of beadless, uniform nanofibers with an average diameter of 450 nm. This enhanced electrospinnability was found to be mainly due to the highly increased conductivity of the plasma-modified PCL solutions. Consequently, more stretching of the polymer jet occurred during electrospinning, leading to the generation of bead-free fibers. Plasma treatment also results in an increased viscosity and decreased pH values. To explain these observed changes, optical emission spectroscopy (OES) has been used to examine the excited species present in the APPJ in contact with the PCL solution. This study revealed that the peaks attributed to H, CH, CH 2 , and C 2 species could be responsible for the degradation of solvent molecules and/or PCL structures during the plasma treatment. Size exclusion chromatography and X-ray photoelectron spectroscopy results showed that the molecular weight and the chemical composition of PCL were not significantly affected by the APPJ treatment. Plasma exposure mainly results in the degradation of the solvent molecules instead of modifying the PCL macromolecules, preserving the original polymer as much as possible. A hypothesis for the observed macroscopic changes in viscosity and pH values could be the generation of new chemical species such as HCl and/or HNO 3 . These species are characterized by their high conductivity, low pH values, and strong polarity and could enhance the solvent quality for PCL, leading to the expansion of the polymer coil, which could in turn explain the observed enhanced viscosity after plasma modification.

In vitro Characteristics of a Glass Ionomer Cement

PubMed Central

Driscoll, Colin L. W.; Green, J. Douglas; Beatty, Charles W.; McCaffrey, Thomas V.; Marrs, Christopher D.

1998-01-01

Glass ionomer cements were first described by Wilson and Kent and have been used in dentistry since 1969. It has been recommended for bridging ossicular chain defects, fixation of ossicular chain prosthesis, anchoring of cochlear implants, mastoid obliteration, and repair of tegmen and posterior canal wall defects. The biocompatability and stability of this material over time is vital to its usefulness in neurotologic surgery. The purpose of this study was to assess the stability of a glass ionomer cement in the presence of bacteria and in different pH environments. We demonstrated that bacteria readily adhere to the surface and their presence is associated with accelerated loss of matrix. We found the cement to be susceptible to low pH and to release a visible cloud of debris upon contact with fluid. Calcium concentration in the solution was elevated at all pH levels. Although we are able to demonstrate these findings in vitro the clinical relevance is unclear. There have been several cases of aseptic meningitis possibly due to intracranial release of components of the cement. Until further studies are done use of the cement in contact with cerebral spinal fluid should be avoided. This cement, or a similar material, would be useful in neurotologic surgery but prior to widespread use further testing should be done to assess safety. ImagesFigure 1Figure 2Figure 3Figure 4Figure 5Figure 9Figure 10Figure 11 PMID:17171062

Equilibrium and thermodynamic studies on biosorption of Pb(II) onto Candida albicans biomass.

PubMed

Baysal, Zübeyde; Cinar, Ercan; Bulut, Yasemin; Alkan, Hüseyin; Dogru, Mehmet

2009-01-15

Biosorption of Pb(II) ions from aqueous solutions was studied in a batch system by using Candida albicans. The optimum conditions of biosorption were determined by investigating the initial metal ion concentration, contact time, temperature, biosorbent dose and pH. The extent of metal ion removed increased with increasing contact time, initial metal ion concentration and temperature. Biosorption equilibrium time was observed in 30min. The Freundlich and Langmuir adsorption models were used for the mathematical description of biosorption equilibrium and isotherm constants were also evaluated. The maximum biosorption capacity of Pb(II) on C. albicans was determined as 828.50+/-1.05, 831.26+/-1.30 and 833.33+/-1.12mgg(-1), respectively, at different temperatures (25, 35 and 45 degrees C). Biosorption showed pseudo second-order rate kinetics at different initial concentration of Pb(II) and different temperatures. The activation energy of the biosorption (Ea) was estimated as 59.04kJmol(-1) from Arrhenius equation. Using the equilibrium constant value obtained at different temperatures, the thermodynamic properties of the biosorption (DeltaG degrees , DeltaH degrees and DeltaS degrees ) were also determined. The results showed that biosorption of Pb(II) ions on C. albicans were endothermic and spontaneous. The optimum initial pH for Pb(II) was determined as pH 5.0. FTIR spectral analysis of Pb(II) adsorbed and unadsorbed C. albicans biomass was also discussed.

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.

77 FR 64814 - National Heart, Lung, and Blood Institute; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-23

... proposals. Place: Bolger Center, 9600 Newbridge Drive, Potomac, MD 20854. Contact Person: Charles Joyce, Ph... proposals. Place: Bolger Center, 9600 Newbridge Drive, Potomac, MD 20854. Contact Person: Charles Joyce, Ph...

77 FR 72364 - National Institute of Allergy and Infectious Diseases; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-05

... Conference Call). Contact Person: Lynn Rust, Ph.D., Scientific Review Officer, Scientific Review Program... Call). Contact Person: Lynn Rust, Ph.D., Scientific Review Officer, Scientific Review Program, Division...

Artificial neural network (ANN) method for modeling of sunset yellow dye adsorption using zinc oxide nanorods loaded on activated carbon: Kinetic and isotherm study.

PubMed

Maghsoudi, M; Ghaedi, M; Zinali, A; Ghaedi, A M; Habibi, M H

2015-01-05

In this research, ZnO nanoparticle loaded on activated carbon (ZnO-NPs-AC) was synthesized simply by a low cost and nontoxic procedure. The characterization and identification have been completed by different techniques such as SEM and XRD analysis. A three layer artificial neural network (ANN) model is applicable for accurate prediction of dye removal percentage from aqueous solution by ZnO-NRs-AC following conduction of 270 experimental data. The network was trained using the obtained experimental data at optimum pH with different ZnO-NRs-AC amount (0.005-0.015 g) and 5-40 mg/L of sunset yellow dye over contact time of 0.5-30 min. The ANN model was applied for prediction of the removal percentage of present systems with Levenberg-Marquardt algorithm (LMA), a linear transfer function (purelin) at output layer and a tangent sigmoid transfer function (tansig) in the hidden layer with 6 neurons. The minimum mean squared error (MSE) of 0.0008 and coefficient of determination (R(2)) of 0.998 were found for prediction and modeling of SY removal. The influence of parameters including adsorbent amount, initial dye concentration, pH and contact time on sunset yellow (SY) removal percentage were investigated and optimal experimental conditions were ascertained. Optimal conditions were set as follows: pH, 2.0; 10 min contact time; an adsorbent dose of 0.015 g. Equilibrium data fitted truly with the Langmuir model with maximum adsorption capacity of 142.85 mg/g for 0.005 g adsorbent. The adsorption of sunset yellow followed the pseudo-second-order rate equation. Copyright © 2014 Elsevier B.V. All rights reserved.

Artificial neural network (ANN) method for modeling of sunset yellow dye adsorption using zinc oxide nanorods loaded on activated carbon: Kinetic and isotherm study

NASA Astrophysics Data System (ADS)

Maghsoudi, M.; Ghaedi, M.; Zinali, A.; Ghaedi, A. M.; Habibi, M. H.

2015-01-01

In this research, ZnO nanoparticle loaded on activated carbon (ZnO-NPs-AC) was synthesized simply by a low cost and nontoxic procedure. The characterization and identification have been completed by different techniques such as SEM and XRD analysis. A three layer artificial neural network (ANN) model is applicable for accurate prediction of dye removal percentage from aqueous solution by ZnO-NRs-AC following conduction of 270 experimental data. The network was trained using the obtained experimental data at optimum pH with different ZnO-NRs-AC amount (0.005-0.015 g) and 5-40 mg/L of sunset yellow dye over contact time of 0.5-30 min. The ANN model was applied for prediction of the removal percentage of present systems with Levenberg-Marquardt algorithm (LMA), a linear transfer function (purelin) at output layer and a tangent sigmoid transfer function (tansig) in the hidden layer with 6 neurons. The minimum mean squared error (MSE) of 0.0008 and coefficient of determination (R2) of 0.998 were found for prediction and modeling of SY removal. The influence of parameters including adsorbent amount, initial dye concentration, pH and contact time on sunset yellow (SY) removal percentage were investigated and optimal experimental conditions were ascertained. Optimal conditions were set as follows: pH, 2.0; 10 min contact time; an adsorbent dose of 0.015 g. Equilibrium data fitted truly with the Langmuir model with maximum adsorption capacity of 142.85 mg/g for 0.005 g adsorbent. The adsorption of sunset yellow followed the pseudo-second-order rate equation.

[Determination of migration of 25 primary aromatic amines from food contact plastic materials by gas chromatography-mass spectrometry].

PubMed

Li, Ying; Li, Chengfa; Xiao, Daoqing; Liang, Feng; Chen, Zhinan; Schen, Xuhui; Sun, Xiaoying; Li, Yongtao

2013-01-01

A solid phase extraction (SPE) combination with gas chromatography-mass spectrometry (GC-MS) was developed for the determination of the migration of 25 primary aromatic amines (PAAs) from food contact plastic materials and articles. The samples were extracted by deionized water and 30 g/L acetic acid, and the pH value of the solution was adjusted to 8 - 10 with ammonia. The extracts were cleaned up and concentrated on an SPE column, then eluted by equal volume of methyl-tert-butyl ether and ethanol. The analysis of the target compounds was performed by GC-MS. The results indicated that the limits of detection were in the range of 0.4 -2.0 microg/kg for different PAAs. The recoveries and relative standard deviations (n = 7) of 10 microg/kg PAAs ranged from 51.6% -118.4% and 0.5% -9.8%, respectively, except the 2,4-diaminoanisole in the acid simulant. The effects of different experimental conditions such as the pH value and volume ratio of methyl-tert-butyl ether and ethanol were studied. The results showed that the method is accurate and stable, and could meet the requirement of the European Commission Regulation (EU) No 10/2011 for the determination of primary aromatic amines. It can be applied in the analysis of the primary aromatic amines in real food contact plastic material and article samples.

Chromium (VI) purification using pine sawdust in batch systems

NASA Astrophysics Data System (ADS)

Politi, Dorothea; Sidiras, Dimitris

2012-12-01

Pine sawdust, a waste generated in furniture industry, has been used as low-cost potential adsorbent. This low-cost adsorbent was used for the removal of chromium (VI) from an aqueous solution. The kinetics of adsorption and extent of adsorption at equilibrium are dependent on the physical and chemical characteristics of the adsorbent and adsorbate. The effect of hydrogen ion concentration, contact time, adsorbent dose and initial concentration of adsorbate on the uptake of chromium were studied in batch experiments. The adsorption data has been correlated with Lagergren - Eldridge pseudofirst order kinetic model. The efficiency of adsorbent material for the removal of Cr(VI) was found to be between 13.1 and 95.6%, respectively. These results depend on the conditions of pH, contact time, sawdust dose and Cr(VI) concentration.

The effect of Coca-Cola and fruit juices on the surface hardness of glass-ionomers and 'compomers'.

PubMed

Aliping-McKenzie, M; Linden, R W A; Nicholson, J W

2004-11-01

The interaction of tooth-coloured dental restorative materials (a conventional glass-ionomer, two resin-modified glass-ionomers and two compomers) with acidic beverages has been studied with the aim of investigating how long-term contact affects solution pH and specimen surface hardness. For each material (ChemFil Superior, ChemFlex, Vitremer Core Build-Up/Restorative, Fuji II LC, Dyract AP and F2000) disc-shaped specimens were prepared and stored in sets of six in the following storage media: 0.9% NaCl (control), Coca-Cola, apple juice and orange juice. After time intervals of 1 day, 1 week, 1 month, 3 months, 4 months, 6 months and 1 year, solution pH and Vickers Hardness Number were determined for each individual specimen. Differences were analysed by anova followed by Student-Newman-Keuls post hoc analysis. All materials were found to reduce the pH of the 0.9% NaCl, but to increase the pH of the acidic beverages. The conventional glass-ionomers dissolved completely in apple juice and orange juice, but survived in Coca-Cola, albeit with a significantly reduced hardness after 1 year. The other materials survived in apple juice and orange juice, but showed greater reductions in surface hardness in these beverages than in Coca-Cola. Fruit juices were thus shown to pose a greater erosive threat to tooth coloured materials than Coca-Cola, a finding which is similar to those concerning dentine and enamel towards these drinks.

Highly efficient and selective adsorption of In{sup 3+} on pristine Zn/Al layered double hydroxide (Zn/Al-LDH) from aqueous solutions

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

Barnabas, Mary Jenisha; Parambadath, Surendran; Mathew, Aneesh

2016-01-15

A pristine Zn/Al-layered double hydroxide (Zn/Al-LDH) showed excellent adsorption ability and selectivity towards In{sup 3+} ions from aqueous solutions. The adsorption behaviour as a function of the contact time, solution pH, ionic strength, and amount of adsorbent under ambient conditions revealed a strong dependency on the pH and ionic strength over In{sup 3+} intake. The structure and properties of Zn/Al-LDH and In{sup 3+} adsorbed Zn/Al-LDH (In–Zn/Al-LDH) were examined carefully by X-ray diffraction, Fourier transform infrared spectroscopy, N{sub 2}-sorption/desorption, UV–vis spectroscopy, and X-ray photoelectron spectroscopy. The adsorbent had a sufficient number of active sites that were responsible for the In{sup 3+}more » adsorption and quite stable even after the adsorption process. The selective adsorption of In{sup 3+} on Zn/Al-LDH was also observed even from a mixture containing competing ions, such as Mn{sup 2+}, Co{sup 2+}, Ni{sup 2+}, Cd{sup 2+}, Pb{sup 2+}, and Cu{sup 2+}. The adsorption experiments showed that Zn/Al-LDH is a promising material for the pre-concentration and selective removal of In{sup 3+} from large volumes of aqueous solutions. - Highlights: • A pristine Zn/Al-layered double hydroxide showed good selectivity for In{sup 3+} ions. • The material exhibited a maximum In{sup 3+} intake of 205 mg g{sup −1} at pH 6. • The materials showed good affinity of In{sup 3+} over Cu{sup 2+} and Pb{sup 2+} from ion mixtures.« less

Coupling the Alkaline-Surfactant-Polymer Technology and The Gelation Technology to Maximize Oil Production

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

Malcolm Pitts; Jie Qi; Dan Wilson

2005-12-01

Gelation technologies have been developed to provide more efficient vertical sweep efficiencies for flooding naturally fractured oil reservoirs or reservoirs with different sand lenses with high permeability contrast. The field proven alkaline-surfactant-polymer technology economically recovers 15% to 25% OOIP more crude oil than waterflooding from swept pore space of an oil reservoir. However, alkaline-surfactant-polymer technology is not amenable to naturally fractured reservoirs or reservoirs with high permeability contrast zones because much of injected solution bypasses target pore space containing oil. This work investigates whether combining these two technologies could broaden applicability of alkaline-surfactant-polymer flooding into these reservoirs. Fluid-fluid interaction withmore » different gel chemical compositions and alkaline-surfactant-polymer solution with pH values ranging from 9.2 to 12.9 have been tested. Aluminum-polyacrylamide gels are not stable to alkaline-surfactant-polymer solutions at any pH. Chromium-polyacrylamide gels with polymer to chromium ion ratios of 25 or greater were stable to alkaline-surfactant-polymer solutions if solution pH was 10.6 or less. When the polymer to chromium ion was 15 or less, chromium-polyacrylamide gels were stable to alkaline-surfactant-polymer solutions with pH values up to 12.9. Chromium-xanthan gum gels were stable to alkaline-surfactant-polymer solutions with pH values of 12.9 at the polymer to chromium ion ratios tested. Silicate-polyacrylamide, resorcinol-formaldehyde, and sulfomethylated resorcinol-formaldehyde gels were also stable to alkaline-surfactant-polymer solutions with pH values ranging from 9.2 to 12.9. Iron-polyacrylamide gels were immediately destroyed when contacted with any of the alkaline-surfactant-polymer solutions with pH values ranging from 9.2 to 12.9. Gel solutions under dynamic conditions of linear corefloods showed similar stability to alkaline-surfactant-polymer solutions as in the fluid-fluid analyses with the exception of the xanthan gum-chromium acetate gels. Aluminum-polyacrylamide flowing gels are not stable to alkaline-surfactant-polymer solutions of either pH 10.5 or 12.9, either in linear corefloods or in dual separate radial core, common manifold corefloods. Chromium acetate-polyacrylamide flowing and rigid tonguing gels are stable to subsequent alkaline-surfactant-polymer solution injection. Rigid tonguing chromium acetate-polyacrylamide gels maintained permeability reduction better than flowing chromium acetate-polyacrylamide gels. Chromium acetate gels were stable to injection of alkaline-surfactant-polymer solutions at 72 F, 125 F and 175 F in linear corefloods. Chromium acetate-polyacrylamide gels maintained diversion capability after injection of an alkaline-surfactant-polymer solution in stacked; radial coreflood with a common well bore. Chromium acetate-polyacrylamide gel used to seal fractured core maintain fracture closure if followed by an alkaline-surfactant-polymer solution. Chromium acetatexanthan gum rigid gels are not stable to subsequent alkaline-surfactant-polymer solution injection at 72, 125, and 175 F. Silicate-polyacrylamide gels are not stable with subsequent injection of either a pH 10.5 or a 12.9 alkaline-surfactant-polymer solution. Resorcinol-formaldehyde gels were stable to subsequent alkaline-surfactant-polymer solution injection. When evaluated in a dual core configuration, injected fluid flows into the core with the greatest effective permeability to the injected fluid. The same gel stability trends to subsequent alkaline-surfactant-polymer injected solution were observed. Aluminum citrate-polyacrylamide, resorcinol-formaldehyde, and the silicate-polyacrylamide gel systems did not produce significant incremental oil in linear corefloods. Both flowing and rigid tonguing chromium acetate-polyacrylamide gels and the xanthan gum-chromium acetate gel system produced incremental oil with the rigid tonguing gel producing the greatest amount. Higher oil recovery could have been due to higher differential pressures across cores. Aluminum citrate-polyacrylamide gels, chromium acetate-polyacrylamide gels, silicate-polymer, and chromium-xanthan gum gels did not alter an alkaline-surfactant-polymer solution's ability to produce incremental oil. Incremental oil was reduced with the resorcinol-formaldehyde gel system. Total waterflood plus chemical flood oil recovery sequence recoveries were generally similar. Performance and produced polymer evaluation of four alkaline-surfactant-polymer projects concluded that only one of the projects could have benefited from combining the alkaline-surfactant-polymer and gelation technologies. Cambridge, the 1993 Daqing, Mellott Ranch, and the Wardlaw alkaline-surfacant-polymer floods were studied. An initial gel treatment followed by an alkaline-surfactant-polymer flood in the Wardlaw field would have been a benefit due to reduction of fracture flow.« less

Evolution of Spatial pH Distribution in Aqueous Solution induced by Atmospheric Pressure Plasma

NASA Astrophysics Data System (ADS)

Takahashi, Shigenori; Mano, Kakeru; Hayashi, Yui; Takada, Noriharu; Kanda, Hideki; Goto, Motonobu

2016-09-01

Discharge plasma at gas-liquid interface produces some active species, and then they affect chemical reactions in aqueous solution, where pH of aqueous solution is changed due to redox species. The pH change of aqueous solution is an important factor for chemical reactions. However, spatial pH distribution in a reactor during the discharge has not been clarified yet. Thus, this work focused on spatial pH distribution of aqueous solution when pulsed discharge plasma was generated from a copper electrode in gas phase to aqueous solution in a reactor. Experiments were conducted using positive unipolar pulsed power. The unipolar pulsed voltage at +8.0 kV was applied to the copper electrode and the bottom of the reactor was grounded. The size of the reactor was 80 mm wide, 10 mm deep, and 40 mm high. The electrode was set at distance of 2 mm from the solution surface. Anthocyanins were contained in the aqueous solution as a pH indicator. The change pH solution spread horizontally, and low pH region of 10 mm in depth was formed. After discharge for 10 minutes, the low pH region was diffused toward the bottom of the reactor. After discharge for 60 minutes, the pH of the whole solution decreased.

Selective Adhesion of Thiobacillus ferrooxidans to Pyrite

PubMed Central

Ohmura, Naoya; Kitamura, Keiko; Saiki, Hiroshi

1993-01-01

Bacterial adhesion to mineral surfaces plays an important role not only in bacterial survival in natural ecosystems, but also in mining industry applications. Selective adhesion was investigated with Thiobacillus ferrooxidans by using four minerals, pyrite, quartz, chalcopyrite, and galena. Escherichia coli was used as a control bacterium. Contact angles were used as indicators of hydrophobicity, which was an important factor in the interaction between minerals and bacteria. The contact angle of E. coli in a 0.5% sodium chloride solution was 31°, and the contact angle of T. ferrooxidans in a pH 2.0 sulfuric acid solution was 23°. E. coli tended to adhere to more hydrophobic minerals by hydrophobic interaction, while T. ferrooxidans selectively adhered to iron-containing minerals, such as pyrite and chalcopyrite. Ferrous ion inhibited the selective adhesion of T. ferrooxidans to pyrite competitively, while ferric ion scarcely inhibited such adhesion. When selective adhesion was quenched by ferrous ion completely, adhesion of T. ferrooxidans was controlled by hydrophilic interactions. Adhesion of E. coli to pyrite exhibited a liner relationship on langmuir isotherm plots, but adhesion of T. ferrooxidans did not. T. ferrooxidans recognized the reduced iron in minerals and selectively adhered to pyrite and chalcopyrite by a strong interaction other than the physical interaction. PMID:16349106

Characterizing the correlation between dephosphorization and solution pH in a calcined water treatment plant sludge.

PubMed

Zhou, Zhenming; Liu, Qidi; Li, Shuwen; Li, Fei; Zou, Jing; Liao, Xiaobin; Yuan, Baoling; Sun, Wenjie

2018-04-26

This study focused on characterizing the correlation between the dephosphorization process of calcined water treatment plant sludge (C-WTPS) and the solution initial pH in batch experiments. The specific aim was to illustrate the effect of different initial pH on the adsorption and desorption of phosphorous in C-WTPS. In addition, the effects of solution initial pH on the release of ammonia nitrogen and total organic carbon (TOC) from C-WTPS and the change of pH after adsorption were also investigated. The results demonstrated that the initial pH significantly influenced the adsorption of phosphorus on C-WTPS. When initial pH was increased from 3 to 10, the phosphorous absorption capacity reduced by 76.5%. Especially, when the initial pH reached to 11, the phosphorus adsorption capacity became a negative value, indicating that C-WTPS released phosphorus into the solution. The addition of C-WTPS to the solution had little impact on the initial pH of the solution. The absorbed phosphorous on C-WTPS was relatively stable in the pH range of 3 to 10. Nevertheless, when the solution pH was higher than 11, it can be easily released into the solution. Furthermore, by comparison with WTPS, C-WTPS released less ammonia nitrogen and TOC into the solution and adsorbed more phosphorus from the solution in the experimental pH range. Therefore, C-WTPS is more suitable to serve as a cost-effective sorbent for phosphorus removal.

Removal of Pb(II) ions from aqueous solution by a waste mud from copper mine industry: equilibrium, kinetic and thermodynamic study.

PubMed

Ozdes, Duygu; Gundogdu, Ali; Kemer, Baris; Duran, Celal; Senturk, Hasan Basri; Soylak, Mustafa

2009-07-30

The objective of this study was to assess the adsorption potential of a waste mud (WM) for the removal of lead (Pb(II)) ions from aqueous solutions. The WM was activated with NaOH in order to increase its adsorption capacity. Adsorption studies were conducted in a batch system as a function of solution pH, contact time, initial Pb(II) concentration, activated-waste mud (a-WM) concentration, temperature, etc. Optimum pH was specified as 4.0. The adsorption kinetic studies indicated that the overall adsorption process was best described by pseudo-second-order kinetics. The equilibrium adsorption capacity of a-WM was obtained by using Langmuir and Freundlich isotherm models and both models fitted well. Adsorption capacity for Pb(II) was found to be 24.4 mg g(-1) for 10 g L(-1) of a-WM concentration. Thermodynamic parameters including the Gibbs free energy (Delta G degrees), enthalpy (Delta H degrees), and entropy (DeltaS degrees) indicated that the adsorption of Pb(II) ions on the a-WM was feasible, spontaneous and endothermic, at temperature range of 0-40 degrees C. Desorption studies were carried out successfully with diluted HCl solutions. The results indicate that a-WM can be used as an effective and no-cost adsorbent for the treatment of industrial wastewaters contaminated with Pb(II) ions.

76 FR 62423 - National Institute on Deafness and Other Communication Disorders; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-07

...., Rockville, MD 20852, (Telephone Conference Call). Contact Person: Melissa Stick, PhD, MPH, Chief, Scientific...., Rockville, MD 20852, (Telephone Conference Call). Contact Person: Melissa Stick, PhD, MPH, Chief, Scientific...

77 FR 70791 - National Institute of Diabetes and Digestive and Kidney Diseases Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-27

..., (Telephone Conference Call). Contact Person: Carol J. Goter-Robinson, Ph.D., Scientific Review Officer... 20037. Contact Person: Carol J. Goter-Robinson, Ph.D., Scientific Review Officer, Review Branch, DEA...

Surface reactions kinetics between nanocrystalline magnetite and uranyl.

PubMed

Missana, Tiziana; Maffiotte, César; García-Gutiérrez, Miguel

2003-05-01

Magnetite is the most important end member of iron corrosion products under reducing environment, which is the condition expected in a deep geological high level radioactive waste disposal. Nanocrystalline magnetite was synthesized in the laboratory and its physicochemical properties were analyzed in detail. The kinetics of the adsorption of U(VI) and the kinetics of the actinide reduction to a lower oxidation state, in presence of the oxide, were studied by means of batch sorption techniques and X-ray photoelectron spectroscopy (XPS) analysis. The results showed that the uranium sorption and reduction processes on the magnetite surface have very fast kinetics (hours), the reduction process being triggered by sorption. XPS measurements showed that the speciation of uranium at the surface does not show significant changes with time (from 1 day to 3 months), as well as the quantity of uranium detected at the surface. The surface speciation depended on the initial pH of the contact solution. Considering that the Eh of equilibrium between magnetite and the solution, under our experimental conditions, is slightly positive (50-100 mV), the uranium reduction would also be thermodynamically possible within the liquid phase. However, the kinetics of reduction in the liquid occur at a much slower rate which, in turn, has to depend on the attainment of the magnetite/solution equilibrium. The decrease of uranium in solution, observed after the uranyl adsorption stage, and particularly at acidic pH, is most probably due to the precipitation of U(IV) formed in the solution.

Synthesis, characterisation of polyaniline-Fe3O4 magnetic nanocomposite and its application for removal of an acid violet 19 dye

NASA Astrophysics Data System (ADS)

Patil, Manohar R.; Khairnar, Subhash D.; Shrivastava, V. S.

2016-04-01

The present work deals with the development of a new method for the removal of dyes from an aqueous solution using polyaniline (PANI)-Fe3O4 magnetic nanocomposite. It is synthesised in situ through self-polymerisation of monomer aniline. Photocatalytic degradation studies were carried out for cationic acid violet 19 (acid fuchsine) dye using PANI-Fe3O4 nanocomposite in aqueous solution. Different parameters like catalyst dose, contact time and pH have been studied to optimise reaction condition. The optimum conditions for the removal of the dye are initial concentration 20 mg/l, adsorbent dose 6 gm/l, pH 7. The EDS technique gives elemental composition of synthesised PANI-Fe3O4. The SEM and XRD studies were carried for morphological feature characteristics of PANI-Fe3O4 nanocomposite. The VSM (vibrating sample magnetometer) gives magnetic property of PANI-Fe3O4 nanocomposite; also FT-IR analysis gives characteristics frequency of synthesised PANI-Fe3O4. Besides the above studies kinetic study has also been carried out.

Synthesis and characterization of Cadmium selenide nanoparticles loaded on activated carbon and its efficient application for removal of Muroxide from aqueous solution

NASA Astrophysics Data System (ADS)

Ghaedi, M.; Amirabad, S. Zamani; Marahel, F.; Nasiri Kokhdan, S.; Sahraei, R.; Nosrati, M.; Daneshfar, A.

2011-12-01

In the first, Cadmium selenide Nanoparticle loaded on activated carbon (CdSe-NP-AC) has been synthesized and characterized by different techniques including XRD and SEM. Then, this new adsorbent successfully has been applied for the removal of muroxide (MO) from aqueous solution in batch studies, while the effect of various experimental parameters like initial pH (pH 0), contact time, amount of (CdSe-NP-AC) and initial MO concentration ( C0) on its removal percentage was examined by one at a time optimization method. It was found following optimization of variable, the adsorption of MO onto (CdSe-NP-AC) followed pseudo-second-order kinetics and show Tempkin and Langmuir models for interpretation of experimental data. It was observed that by increasing the temperature the removal percentage was improved and the positive change in entropy (Δ S°) and heat of adsorption (Δ H°) show the endothermic nature of process, while the high negative value in Gibbs free energy change (Δ G°) indicates the feasible nature of adsorption process.

Competitive adsorption of Pb2+ and Zn2+ ions from aqueous solutions by modified coal fly ash

NASA Astrophysics Data System (ADS)

Astuti, Widi; Martiani, Wulan; Any Ismawati Khair, N.

2017-03-01

Coal fly ash (CFA), which is a solid waste generated in large amounts worldwide, is mainly composed of some oxides having high crystallinity, including quartz (SiO2) and mullite (3Al2O3 2SiO2), and unburned carbon as a mesopore material that enables it to act as a dual site adsorbent. To decrease the crystallinity, CFA was modified by sodium hydroxide treatment. The modified fly ash (MFA) contains lower amount of Si and Al and has a higher specific surface area than the untreated fly ash (CFA). The objective of this study is to investigate the competitive adsorption of Pb2+ and Zn2+ from aqueous solutions by CFA and MFA. The effect of pH, contact time and initial concentration was investigated. Effective pH for Pb2+ and Zn2+ removal was 4. A greater percentage of Pb2+ and Zn2+ was removed with a decrease in the initial concentration of Pb2+ and Zn2+. Quasi-equilibrium reached in 240 min.

Biosorption of praseodymium (III) using Terminalia arjuna bark powder in batch systems: isotherm and kinetic studies.

PubMed

Swain, Krishna Kumari; Mishra, Pravat Manjari; Devi, Aparna Prabha

2018-02-01

The high demand for rare earth elements (REEs) used in various advanced materials implies demand for increased production of REEs or the recycling of solutions to recover the REEs they contain. In this study, the biosorption of Pr(III) from aqueous solution by bark powder of Terminalia arjuna was examined in a batch system as a function of metal concentration, biosorbent dosage, pH and contact time. Results showed that T. arjuna bark powder has a high affinity for adsorbing Pr(III): more than 90% at pH 6.63. The adsorption of Pr(III) by T. arjuna bark powder was investigated by the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. The kinetics of the biosorption process was tested with pseudo-first-order and pseudo-second-order models, and the results showed that the biosorption process was better fitted to the pseudo-second-order model. From Fourier transform infrared spectroscopy (FT-IR) analysis, it is confirmed that the biomolecules of T. arjuna bark powder are involved in the biosorption process of Pr(III) metal ions.

Adsorption behavior of Cr(VI) on modified natural zeolite by a new bolaform N,N,N,N',N',N'-hexamethyl-1,9-nonanediammonium dibromide reagent.

PubMed

Noroozifar, M; Khorasani-Motlagh, M; Gorgij, M N; Naderpour, H R

2008-07-15

The demand for effective adsorbents is to increase in response to the widespread recognition of the deleterious health effects of Cr(VI)-oxyanions exposure through drinking water. In this study, Cr(VI)-oxyanions uptake from aqueous solutions by a new bolaform N,N,N,N',N',N'-hexamethyl-1,9-nonanediammonium dibromide reagent-modified natural zeolitic materials from Zahedan, Iran, was investigated using batch technique. Spectrophotometry method was used for Cr determination. The Cr(VI)-solution concentration varied between 2 and 104 mg L(-1). It was shown that the Cr(VI) uptake strongly depended on pH. The maximum removal of Cr(VI) occurred in acidic media at pH<1.5. The amounts of Cr(VI) adsorbed increased with increase in dose of both adsorbents and their contact time. Based on results an adsorption mechanism has been suggested. The adsorption data for modified zeolite using the amine was consistent with Langmuir isotherm equation and the equilibrium data was analyzed using the Langmuir isotherm.

Functionalized dithiocarbamate chelating resin for the removal of Co2+ from simulated wastewater

NASA Astrophysics Data System (ADS)

Shi, Xuewei; Fu, Linwei; Wu, Yanyang; Zhao, Huiling; Zhao, Shuangliang; Xu, Shouhong

2017-12-01

Industrial wastewater that contains trace amounts of heavy metal ions is often seen in petrochemical industry. While this wastewater can not be directly discharged, it is difficult to treat due to the low concentration of metal ions. Introducing chelating reagents into this wastewater for selective ion adsorption, followed by a mechanical separation process, provides an appealing solution. Toward the success of this technology, the development of effective chelating resins is of key importance. In the present work, a chelating resin containing amino and dithiocarbamate groups was reported for the removal of Co(II) metal ions in trace concentrations from simulated wastewater. By investigating the adsorption performance of the chelating resin at different solution pH values, adsorbent dosages, contact time, initial ion concentrations, and adsorption temperatures, the maximum adsorption capacity of the resin for Co(II) was identified to be 24.89 mg g-1 for a 2 g L-1 adsorbent dosage and a pH value of 5. After four adsorption-desorption cycles, 97% of the adsorption capacity of the resin was maintained. The adsorption kinetics and thermodynamics were analyzed and discussed as well.

pH-sensitive ion-selective field-effect transistor with zirconium dioxide film

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

Vlasov, Yu.G.; Bratov, A.V.; Tarantov, Yu.A.

1988-09-20

Miniature semiconductor pH sensors for liquid media, i.e., ion-selective field-effect transistors (ISFETs), are silicon field-effect transistors with a two-layer dielectric consisting of a passivating SiO/sub 2/ layer adjoining the silicon and a layer of pH-sensitive material in contact with the electrolyte solution to be tested. This study was devoted to the characteristics of pH-sensitive ISFETs with ZrO/sub 2/ films. The base was p-type silicon (KDB-10) with a (100) surface orientation. A ZrO/sub 2/ layer 10-50 nm thick was applied over the SiO/sub 2/ layer by electron-beam deposition. The measurements were made in aqueous KNO/sub 3/ or KCl solutions.

Facile synthesis of stable superhydrophobic nanocomposite based on multi-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Mokarian, Zahra; Rasuli, Reza; Abedini, Yousefali

2016-04-01

A facile approach to fabricate a stable superhydrophobic composite comprising multi-walled carbon nanotubes and silicone rubber has been reported. Contact angle of de-ionized water droplets on the prepared surface was measured with the value of near 159°; while water droplets easily rolled off and bounced on it. Surface free energy of the superhydrophobic coating was examined by three methods about 26 mJ/m2. The prepared film shows good stability under high stress conditions such as ultraviolet exposure, heating, pencil hardness test, attacking with different pH value and ionic-strength solutions. In addition, remarkable stability of the coating was observed after soaking in condensed hydrochloric acid, 5 wt.% NaCl aqueous solution, boiling water and tape test.

Adsorption kinetics, isotherms and thermodynamics of atrazine removal using a banana peel based sorbent.

PubMed

Chaparadza, Allen; Hossenlopp, Jeanne M

2012-01-01

Atrazine removal from water by treated banana peels was studied. The effect of pH, contact time, initial atrazine concentration, and temperature were investigated. Batch experiments demonstrated that 15 g L(-1) adsorbent dosage removed 90-99% of atrazine from 1-150 ppm aqueous solutions. The removal was both pH and temperature dependent with the most atrazine removed between pH 7 and 8.2 and increased with increasing temperature. Equilibrium data fitted well to the Langmuir and Redlich-Peterson models in the concentration and temperature ranges investigated, with a maximum adsorption capacity of 14 mg g(-1). Simple mass transfer models were applied to the experimental data to examine the adsorption mechanism and it was found that both external mass transfer and intraparticle diffusion played important roles in the adsorption mechanisms. The enthalpy of atrazine adsorption was evaluated to be 67.8 ± 6.3 kJ mol(-l) with a Gibbs free energy of -5.7 ± 1.2 kJ mol(-1).

Removal of toxic chemicals from water with activated carbon

USGS Publications Warehouse

Dawson, V.K.; Marking, L.L.; Bills, T.D.

1976-01-01

Activated carbon was effective in removing fish toxicants and anesthetics from water solutions. Its capacity to adsorb 3-trifluoromethyl-4-nitrophenol (TFM), antimycin, NoxfishA? (5% rotenone), Dibrorms, juglone, MSa??222, and benzocaine ranged from 0.1 to 64 mg per gram of carbon. The adsorptive capacity (end point considered as a significant discharge) of activated carbon for removal of TFM was determined at column depths of 15, 30, and 60 cm; temperatures of 7, 12, 17, and 22 C; pH's of 6.5, 7.5, 8.5, and 9.5; and flow rates of 50, 78, 100, 200, and 940 ml/min. Adsorptive capacity increased when the contact time was increased by reducing the flow rate or increasing the column depth. The adsorptive capacity was not significantly influenced by temperature but was substantially higher at pH 6.5 than at the other pH's tested. A practical and efficient filter for purifying chemically treated water was developed.

Study on kinetics of adsorption of humic acid modified by ferric chloride on U(VI)

NASA Astrophysics Data System (ADS)

Zhang, Y. Y.; Lv, J. W.; Song, Y.; Dong, X. J.; Fang, Q.

2017-11-01

In order to reveal the adsorption mechanism of the ferric chloride modified humic acid on uranium, the influence of pH value and contact time of adsorption on uranium was studied through a series of batch experiments. Meanwhile, the adsorption kinetics was analyzed with pseudo-first order kinetic model and pseudo-second order kinetic model. The results show that adsorption is affected by the pH value of the solution and by contract time, and the best condition for adsorption on uranium is at pH=5 and the adsorption equilibrium time is about 80 min. Kinetics of HA-Fe adsorption on uranium accords with pseudo-second order kinetic model. The adsorption is mainly chemical adsorption, and complexes were produced by the reaction between uranium ions and the functional groups on the surface of HA-Fe, which can provide reference for further study of humic acid effecting on the migration of U(VI) in soil.

Antimicrobial Activity and Physicochemical Properties of Calcium Hydroxide Pastes Used as Intracanal Medication.

PubMed

Zancan, Rafaela Fernandes; Vivan, Rodrigo Ricci; Milanda Lopes, Marcelo Ribeiro; Weckwerth, Paulo Henrique; de Andrade, Flaviana Bombarda; Ponce, José Burgos; Duarte, Marco Antonio Hungaro

2016-12-01

The aim of the present study was to evaluate the pH, calcium release, solubility, and antimicrobial action against biofilms of calcium hydroxide + saline solution, Calen (SS White Artigos Dentários Ltd, Rio de Janeiro, Brazil) (CH/P), Calen camphorated paramonochlorophenol (CMCP) (CH/CMPC), and calcium hydroxide + chlorhexidine (CH/CHX) pastes. The pH of the pastes was determined with a calibrated pH meter placed in direct contact with each paste. The root canals of acrylic teeth (N = 10) were filled with the previously mentioned intracanal dressings and immersed in ultrapure water to measure hydroxyl (pH meter) and calcium ion release (atomic absorption spectrophotometer) at time intervals of 3, 7, 15, and 30 days. To assess solubility, the root canals of acrylic teeth (N = 10) were filled with the previously mentioned pastes and scanned by micro-computed tomographic imaging before (initial) and after 7, 15, and 30 days of immersion in ultrapure water. The solubility of each specimen was the difference between the initial and final volume scanning. For antimicrobial analysis, monospecies and dual-species biofilms were in vitro induced on dentin blocks (N = 20). Afterward, they were treated with the pastes for 7 days. Live/dead dye and a confocal microscope were used to measure the percentage of living cells. Data were statistically compared (P < .05). The highest OH - ion release values were found in 3 and 30 days. Ca 2+ releases were greater in CH/CMCP. CH/P and CH/CMCP showed a higher percentage of volume loss values. CH/CHX presented the greatest antimicrobial action. CH/P and CH/CMPC showed higher solubility values in the period analyzed. Seven days of contact may be insufficient for calcium hydroxide + saline solution, CH/P, and CH/CMCP pastes to kill bacterial cells in the biofilms studied. Chlorhexidine added to CH favored greater effectiveness against the previously mentioned bacterial biofilms. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Studies on leaching from spruce twigs and beech leaves.

PubMed

Fritsche, U

1992-01-01

Leaching, depending on the acidity of the eluent, was investigated for K, Mg and Mn. The curves for the leachate concentration versus time could be described by a power function. Leaching from old needles exceeded leaching from young needles to a high degree, but the ratios of the leached elements were almost equal. A method for continuous measurements of pH change in solutions contacting plant materials was developed. The results were in agreement with data on acidity changes in water falling through spruce or beech canopies.

Stable biomimetic super-hydrophobic engineering materials.

PubMed

Guo, Zhiguang; Zhou, Feng; Hao, Jingcheng; Liu, Weimin

2005-11-16

We describe a simple and inexpensive method to produce super-hydrophobic surfaces on aluminum and its alloy by oxidation and chemical modification. Water or aqueous solutions (pH = 1-14) have contact angles of 168 +/- 2 and 161 +/- 2 degrees on the treated surfaces of Al and Al alloy, respectively. The super-hydrophobic surfaces are produced by the cooperation of binary structures at micro- and nanometer scales, thus reducing the energies of the surfaces. Such super-hydrophobic properties will greatly extend the applications of aluminum and its alloy as lubricating materials.

Investigation of pH response and photo-control of wettability on spiropyran-derivatized surfaces

NASA Astrophysics Data System (ADS)

Park, Choong-Do

2009-12-01

One promising method to control a liquid drop on a surface for microfluidic devices is to use the surface tension gradient on a photo-responsive surface by light irradiation. A photo-switchable spiropyran monolayer was prepared on smooth glass or silicon wafers via 3-aminopropylmethyldiethoxysilane linkages. The pH response of the surface-bound spiropyran was investigated by measuring contact angle as a function of pH, since the pH value of the liquids applied to a microfluidic system can vary widely. Based on the contact angle titration and UV-Vis spectroscopic data, a protonation and deprotonation mechanism of the surface-bound spiropyran was proposed. The advancing contact angles under UV and under visible light irradiation at high pH values were about 100 smaller than those at low pH values. The decrease in contact angle under UV light with decreasing pH value was assigned to the protonation of open merocyanine (MC) to MC-OH+. Meanwhile, the decrease in contact angle under visible light was attributed to the protonation of the closed spiropryan (SP), generating a mixed state of MC-OH+ in equilibrium with N-protonated SP-NH+. In order to examine the possibility of light-induced liquid drop motion on the spiropyran-derivatized smooth surfaces, the light-induced surface tension change between SP and MC was estimated using the contact angle hysteresis (CAH) and the Lifshitz---van der Waals/Acid-Base (LWAB) approaches based on the contact angle data. The average light-induced surface energy change between the two isomers under UV and visible light exposure was 1.4 mJ/m 2, implying that the small change in surface tension is not sufficient to move a liquid droplet on the surface. Liquid drop motion requires that the light-induced switching angle be greater than the contact angle hysteresis. However, the light-induced switching angle of the spiropyran-derivatized surface was significantly smaller than the hysteresis. Thus, in order to achieve liquid drop motion on the spiropyran-derivatized surface, a new surface design which employs a combination of chemical modification of a hydrophobic organosilane and micropatterned rough surface morphology was suggested.

75 FR 994 - National Institute of Allergy and Infectious Diseases; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-07

..., 8777 Georgia Avenue, Silver Spring, MD 20910. Contact Person: Lynn Rust, PhD, Scientific Review Officer... of Health, Rockledge 6700, 6700B Rockledge Drive, Bethesda, MD 20817. Contact Person: Lynn Rust, PhD...

Evaluation of biosurfactants grown in corn oil by Rhodococcus rhodochrous on removing of heavy metal ion from aqueous solution

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

Suryanti, Venty, E-mail: venty@mipa.uns.ac.id; Hastuti, Sri; Pujiastuti, Dwi

The potential application of biosurfactants to remove heavy metal ion from aqueous solution by batch technique was examined. The glycolipids type biosurfactants were grown in a media containing of 20% v/v corn oil with 7 days of fermentation by Rhodococcus rhodochrous. The biosurfactants reduced the surface tension of water of about 51% from 62 mN/m to 30 mN/m. The biosurfactant increased the E24 of water-palm oil emulsion of about 55% from 43% to 97% and could maintain this E24 value of above 50% for up to 9 days. Heavy metal ion removal, in this case cadmium ion, by crude andmore » patially purified biosurfactants has been investigated from aqueous solution at pH 6. Adsorption capacity of Cd(II) ion by crude biosurfactant with 5 and 10 minutes of contact times were 1.74 and 1.82 mg/g, respectively. Additionally, the adsorption capacity of Cd(II) ion by partially purified biosurfactant with 5 and 10 minutes of contact times were 0.79 and 1.34 mg/g, respectively. The results demonstrated that the adsorption capacity of Cd(II) ion by crude biosurfactant was higher than that of by partially purified biosurfactant. The results suggested that the biosurfactant could be used in the removal of heavy metal ions from aqueous solution.« less

Evaluation of biosurfactants grown in corn oil by Rhodococcus rhodochrous on removing of heavy metal ion from aqueous solution

NASA Astrophysics Data System (ADS)

Suryanti, Venty; Hastuti, Sri; Pujiastuti, Dwi

2016-02-01

The potential application of biosurfactants to remove heavy metal ion from aqueous solution by batch technique was examined. The glycolipids type biosurfactants were grown in a media containing of 20% v/v corn oil with 7 days of fermentation by Rhodococcus rhodochrous. The biosurfactants reduced the surface tension of water of about 51% from 62 mN/m to 30 mN/m. The biosurfactant increased the E24 of water-palm oil emulsion of about 55% from 43% to 97% and could maintain this E24 value of above 50% for up to 9 days. Heavy metal ion removal, in this case cadmium ion, by crude and patially purified biosurfactants has been investigated from aqueous solution at pH 6. Adsorption capacity of Cd(II) ion by crude biosurfactant with 5 and 10 minutes of contact times were 1.74 and 1.82 mg/g, respectively. Additionally, the adsorption capacity of Cd(II) ion by partially purified biosurfactant with 5 and 10 minutes of contact times were 0.79 and 1.34 mg/g, respectively. The results demonstrated that the adsorption capacity of Cd(II) ion by crude biosurfactant was higher than that of by partially purified biosurfactant. The results suggested that the biosurfactant could be used in the removal of heavy metal ions from aqueous solution.

pH dependent growth of poly( L-lysine)/poly( L-glutamic) acid multilayer films and their cell adhesion properties

NASA Astrophysics Data System (ADS)

Richert, Ludovic; Arntz, Youri; Schaaf, Pierre; Voegel, Jean-Claude; Picart, Catherine

2004-10-01

The short-term interaction of chondrosarcoma cells with (PGA/PLL) polyelectrolyte multilayers was investigated in a serum-containing medium for films built at different pHs and subsequently exposed to the culture medium. The buildup of the films and their stability was first investigated by means of optical waveguide lightmode spectroscopy, quartz crystal microbalance, streaming potential measurements and atomic force microscopy. While film growth is linear at all pHs, after a few layers have been deposited the growth is much larger for the films built at basic pH and even more pronounced for those built at acidic pH. However, these latter films remain stable in the culture medium only if they have been crosslinked prior to the ionic strength and pH jumps. The films built at acidic pH were found to swell in water by about 200% whereas those built at other pHs did not swell in a physiological buffer. For thin films (≈20 nm) built at pH = 7.4, the detachment forces were dependent on the outermost layer, the forces being significantly higher on PLL-ending films than on PGA-ending ones. In contrast, for the thick films built at pH = 4.4 and at pH = 10.4 (thickness of the order of few hundred of nanometers), the detachment forces were independent of the outermost layer of the film. The films built at pH = 10.4, which shrink in contact with salt containing solutions, were highly cell adhesive whereas those built at acidic pH were highly cell resistant. Protein adsorption and film roughness (as measured by AFM) could not explain these striking differences. The high adhesion observed on the film built at pH 10.4 may rather be related to the secondary structure of the film and to its relatively low swellability in water, whereas the cell resistance of the films built at pH 4.4 may be linked to their high swellability. Therefore, for the PGA/PLL films, the cell adhesion properties can be tuned depending on the deposition pH of the polyelectrolyte solutions. This study reveals the importance of the multilayer structure and architecture to control the detachment force of cells onto such films.

Biosorption of heavy metal copper (Cu2+) by Saccharomyces cerevisiae

NASA Astrophysics Data System (ADS)

Ririhena, S. A. J.; Astuti, A. D.; Fachrul, M. F.; Silalahi, M. D. S.; Hadisoebroto, R.; Rinanti, A.

2018-01-01

This research aims to study the optimum effect of contact time and pH adsorption of copper (Cu2+) from electroplating industry waste by dried beer waste S.cerevisiae. This research conducted using batch culture with pH variation 2,3,4,5, and 6, contact time variation 60, 90, 120, 150, 180 minutes, 150 rpm at room temperature (± 28°C), initial Cu2+ concentration 33,746 mg/l, and biosorbent mass 200 mg & 500 mg. The adsorption of heavy metal ions Cu2+ occurs in all variations of pH and contact time at optimum pH. The optimum adsorption occurs at pH 4 with contact time 120 minutes for both 200 mg (41.60%) and 500 mg (61.04%) beer waste biosorbent. Cell morphology seen with Scanning Electron Microscope (SEM) analysis shows the change of cell wall that gets damaged from Cu2+ adsorption. It also proved by the decreased concentration of initial high concentration carboxyl groups. The adsorption process of this research complies to Freundlich Isotherm with R2 value closest to 1 and followed first order kinetic.

Hydroxyapatite-gelatin nanocomposite as a novel adsorbent for nitrobenzene removal from aqueous solution

NASA Astrophysics Data System (ADS)

Wei, Wei; Sun, Rong; Jin, Zhu; Cui, Jing; Wei, Zhenggui

2014-02-01

A novel adsorbent of hydroxyapatite-gelatin (HAP-GEL) nanocomposite was developed for nitrobenzene removal from aqueous solution. The adsorbent was characterized and its performance in nitrobenzene removal was evaluated. The effects of contact time, adsorbent dosage, temperature, pH, ionic strength, humic acid, and the presence of solvent on nitrobenzene adsorption, as well as the thermodynamic parameters for adsorption equilibrium were also investigated. Results showed that HAP-GEL nanocomposite possessed good adsorption ability to nitrobenzene. The adsorption process was fast, and it reached a steady state after only 1 min. Nitrobenzene removal was increased with an increasing amount of adsorbent dosage but decreased as the temperature and pH increased. Meanwhile the amount of nitrobenzene adsorbed decreased with an increase of ionic strength from 0.01 to 1.0 mol/L and humic acid from 10 to 50 mg/L. The adsorption isotherm studies showed that both Langmuir and Freundlich models could fit the experimental data well, and the maximum adsorption capacity was estimated to be 42.373 mg/g. The thermodynamic parameters suggested that the adsorption of nitrobenzene on HAP-GEL nanocomposite was physisorption, spontaneous and exothermic in nature. Findings of this study demonstrated the potential utility of the HAP-GEL nanocomposite as an effective adsorbent for nitrobenzene removal from aqueous solution.

Removal of phenol by activated alumina bed in pulsed high-voltage electric field.

PubMed

Zhu, Li-nan; Ma, Jun; Yang, Shi-dong

2007-01-01

A new process for removing the pollutants in aqueous solution-activated alumina bed in pulsed high-voltage electric field was investigated for the removal of phenol under different conditions. The experimental results indicated the increase in removal rate with increasing applied voltage, increasing pH value of the solution, aeration, and adding Fe2+. The removal rate of phenol could reach 72.1% when air aeration flow rate was 1200 ml/min, and 88.2% when 0.05 mmol/L Fe2+ was added into the solution under the conditions of applied voltage 25 kV, initial phenol concentration of 5 mg/L, and initial pH value 5.5. The addition of sodium carbonate reduced the phenol removal rate. In the pulsed high-voltage electric field, local discharge occurred at the surface of activated alumina, which promoted phenol degradation in the thin water film. At the same time, the space-time distribution of gas-liquid phases was more uniform and the contact areas of the activated species generated from the discharge and the pollutant molecules were much wider due to the effect of the activated alumina bed. The synthetical effects of the pulsed high-voltage electric field and the activated alumina particles accelerated phenol degradation.

Development of a new adsorbent from agro-industrial waste and its potential use in endocrine disruptor compound removal.

PubMed

Rovani, Suzimara; Censi, Monique T; Pedrotti, Sidnei L; Lima, Eder C; Cataluña, Renato; Fernandes, Andreia N

2014-04-30

A new activated carbon (AC) material was prepared by pyrolysis of a mixture of coffee grounds, eucalyptus sawdust, calcium hydroxide and soybean oil at 800°C. This material was used as adsorbent for the removal of the endocrine disruptor compounds 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) from aqueous solutions. The carbon material was characterized by scanning electron microscopy (SEM), infrared spectroscopy (FTIR), N2 adsorption/desorption curves and point of zero charge (pHPZC). Variables including the initial pH of the adsorbate solutions, adsorbent masses and contact time were optimized. The optimum range of initial pH for removal of endocrine disruptor compounds (EDC) was 2.0-11.0. The kinetics of adsorption were investigated using general order, pseudo first-order and pseudo-second order kinetic models. The Sips isotherm model gave the best fits of the equilibrium data (298K). The maximum amounts of E2 and EE2 removed at 298K were 7.584 (E2) and 7.883mgg(-1) (EE2) using the AC as adsorbent. The carbon adsorbent was employed in SPE (solid phase extraction) of E2 and EE2 from aqueous solutions. Copyright © 2014 Elsevier B.V. All rights reserved.

Removal of arsenic from aqueous solutions using waste iron columns inoculated with iron bacteria.

PubMed

Azhdarpoor, Abooalfazl; Nikmanesh, Roya; Samaei, Mohammad Reza

2015-01-01

Arsenic contamination of water resources is one of the serious risks threatening natural ecosystems and human health. This study investigates arsenic removal using a waste iron column with and without iron bacteria in continuous and batch phases. In batch experiments, the effects of pH, contact time, initial concentration of arsenic and adsorbent dose were investigated. Results indicated that the highest arsenate removal efficiency occurred at pH 7 (96.76%). On increasing the amount of waste iron from 0.25 to 1 g, the removal rate changed from about 42.37%-96.70%. The results of continuous experiments on the column containing waste iron showed that as the empty bed contact time increased from 5 to 60 min, the secondary arsenate concentration changed from 23 to 6 µg/l. In experiments involving a waste iron column with iron bacteria, an increase in residence time from 5 to 60 min decreased the secondary arsenate concentration from 14.97 to 4.86 µg/l. The results of this study showed that waste iron containing iron bacteria is a good adsorbent for removal of arsenic from contaminated water.

77 FR 3478 - Center for Scientific Review; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-24

... Marriott Tysons Corner, 1960--A Chain Bridge Road, McLean, VA 22102. Contact Person: Martha M Faraday, Ph.D... Marriott Tysons Corner, 1960-A Chain Bridge Road McLean, VA 22102. Contact Person: Martha M Faraday, Ph.D...

Research of Co(II) Adsorption on Silica Gel Grafted with Dithiocarbamate (DTC-SiO2) in Aqueous Solution

NASA Astrophysics Data System (ADS)

Yao, Qingxu; Xu, Peng; Huo, Yonggang; Shang, Aiguo; Yu, Fengmei

2018-01-01

Dithiocarbamate grafted silica gel (DTC-SiO2) was prepared following two simple reaction steps. The properties of the composite were characterized by FTIR, SEM and element analysis. Its ability to remove Co2+ ions in aqueous solution with low concentration was also studied by static adsorption experiments. The effects of pH value in solution, contact time and temperature were investigated. The results show that the DTC-SiO2 exhibits excellent adsorption property for Co2+. The adsorption kinetics could be well described by pseudo-second-order model and the adsorption isotherms could be depicted by both Freundlich and Dubinin-Radushkevich models. The adsorption process belongs to chemisorption. The slightly influence of common interfering metal ions (Na+, K+, Ca2+ and Mg2+) on the adsorption capacity revealing the synthesized DTC-SiO2 performs excellent selective adsorption to Co2+.

A novel approach for the removal of radiocesium from aqueous solution by ZSM-5 molecular sieve.

PubMed

Gao, Xiaoqing; Zhang, Peng; Yang, Junqiang; Sun, Xuejie; Fu, Yi; Shi, Keliang; Chai, Zhifang; Wu, Wangsuo

2018-05-21

Finding an approach for pretreatment of radionuclides from contaminated water are interesting topics of research. In present work, the ZSM-5 molecular sieve was characterized with different techniques such as zeta potential, SEM, FT-IR and XRD to clarify the surface properties of sample and applied as a sorbent to concentrate and recover Cs(I) from aqueous solution. The effect of environmental conditions such as contact time, ionic strength, content of sorbent and solution pH on Cs(I) uptake were optimized using batch techniques. Different kinetic and isotherm models were utilized to evaluate the experimental data and the correlation parameters were obtained. Based on the sorption/desorption experiment, it can be deduced that the ZSM-5 molecular sieve has potential application for the rapid and quantitative recovery of radiocesium from wastewater. Copyright © 2018 Elsevier Ltd. All rights reserved.

Removal of Congo red dye from aqueous solutions using a halloysite-magnetite-based composite.

PubMed

Ferrarini, F; Bonetto, L R; Crespo, Janaina S; Giovanela, M

2016-01-01

Adsorption has been considered as one of the most effective methods to remove dyes from aqueous solutions due to its ease of operation, high efficiency and wide adaptability. In view of all these aspects, this study aimed to evaluate the adsorption capacity of a halloysite-magnetite-based composite in the removal of Congo red dye from aqueous solutions. The effects of stirring rate, pH, initial dye concentration and contact time were investigated. The results revealed that the adsorption kinetics followed the pseudo-second-order model, and equilibrium was well represented by the Brunauer-Emmett-Teller isotherm. The thermodynamic data showed that dye adsorption onto the composite was spontaneous and endothermic and occurred by physisorption. Finally, the composite could also be regenerated at least four times by calcination and was shown to be a promising adsorbent for the removal of this dye.

Color removal from acid and reactive dye solutions by electrocoagulation and electrocoagulation/adsorption processes.

PubMed

Bellebia, S; Kacha, S; Bouberka, Z; Bouyakoub, A Z; Derriche, Z

2009-04-01

In this study, electrocoagulation of Marine Blue Erionyl MR (acid dye) and electrocoagulation followed by adsorption of Brilliant Blue Levafix E-BRA (reactive dye) from aqueous solutions were investigated, using aluminum electrodes and granular activated carbon (GAC). In the electrocoagulation and adsorption of dyestuff solutions, the effects of current density, loading charge, pH, conductivity, stirring velocity, contact time, and GAC concentration were examined. The optimum conditions for the electrocoagulation process were identified as loading charges 7.46 and 1.49 F/m3, for a maximum abatement of 200 mg/L reactive and acid dye, respectively. The residual reactive dye concentration was completely removed with 700 mg/L GAC. The results of this investigation provide important data for the development of a combined process to remove significant concentrations of recalcitrant dyes from water, using moderate activated carbon energy and aluminum consumption, and thereby lowering the cost of treatment.

Micro-rheology on (polymer-grafted) colloids using optical tweezers.

PubMed

Gutsche, C; Elmahdy, M M; Kegler, K; Semenov, I; Stangner, T; Otto, O; Ueberschär, O; Keyser, U F; Krueger, M; Rauscher, M; Weeber, R; Harting, J; Kim, Y W; Lobaskin, V; Netz, R R; Kremer, F

2011-05-11

Optical tweezers are experimental tools with extraordinary resolution in positioning (± 1 nm) a micron-sized colloid and in the measurement of forces (± 50 fN) acting on it-without any mechanical contact. This enables one to carry out a multitude of novel experiments in nano- and microfluidics, of which the following will be presented in this review: (i) forces within single pairs of colloids in media of varying concentration and valency of the surrounding ionic solution, (ii) measurements of the electrophoretic mobility of single colloids in different solvents (concentration, valency of the ionic solution and pH), (iii) similar experiments as in (i) with DNA-grafted colloids, (iv) the nonlinear response of single DNA-grafted colloids in shear flow and (v) the drag force on single colloids pulled through a polymer solution. The experiments will be described in detail and their analysis discussed.

Effects of Dentin Debris on the Antimicrobial Properties of Sodium Hypochlorite and Etidronic Acid.

PubMed

Arias-Moliz, Maria Teresa; Morago, Ana; Ordinola-Zapata, Ronald; Ferrer-Luque, Carmen María; Ruiz-Linares, Matilde; Baca, Pilar

2016-05-01

The purpose of this study was to determine the influence of dentin powder on the concentration, pH, and antimicrobial activity of sodium hypochlorite (NaOCl) alone and combined with etidronic acid (HEBP). Biofilms of Enterococcus faecalis were grown on the surface of dentin blocks for 5 days and then exposed to 1% and 2.5% NaOCl alone or combined with 9% HEBP for 3 minutes in the absence and presence of dentin powder. The biovolumes of the biofilm were measured using confocal microscopy and the live/dead technique. The available chlorine and pH of the solutions were also measured. Nonparametric tests were used to determine statistical differences (P < .05). The presence of dentin powder resulted in a reduction of the free available chlorine and pH in all the irrigating solutions; 1% NaOCl lost its antimicrobial activity completely in the presence of dentin powder. The antimicrobial activity was significantly reduced in the 2.5% NaOCl and 1% NaOCl/HEBP groups, and it was not affected in the 2.5% NaOCl/HEBP group. The presence of dentin powder significantly decreased the available chlorine and antimicrobial activity of 1% NaOCl, 2.5% NaOCl, and 1% NaOCl/HEBP irrigating solutions. The antimicrobial activity of 2.5% NaOCl/HEBP was not affected by the dentin powder after a 3-minute contact time against E. faecalis biofilms. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Column with CNT/magnesium oxide composite for lead(II) removal from water.

PubMed

Saleh, Tawfik A; Gupta, Vinod K

2012-05-01

In this study, manganese dioxide-coated multiwall carbon nanotube (MnO(2)/CNT) nanocomposite has been successfully synthesized. The as-produced nanocomposite was characterized by different characteristic tools, such as X-ray diffraction, SEM, and FTIR. The MnO(2)/CNT nanocomposite was utilized as a fixed bed in a column system for removal of lead(II) from water. The experimental conditions were investigated and optimized. The pH range between 3 and 7 was studied; the optimum removal was found when the pH was equal to 6 and 7. The thickness of MnO(2)/CNT nanocomposite compact layer was also changed to find the optimum parameter for higher removal. It was observed that the slower the flow rates of the feed solution the higher the removal because of larger contact time.

Comparison of the release behaviors of di (2-ethylhexyl) phthalate and tri(2-ethylhexyl) trimellitate from the polyvinyl-chloride infusion set into pharmaceutical solutions.

PubMed

Zhang, Hong; Yang, Fengmin; Shen, Gang; Yang, Yueyang; Tang, Yalin

2015-05-01

Polyvinyl-chloride (PVC) with plasticizers of di(2-ethylhexyl) phthalate (DEHP) and tris(2-ethyl- hexyl) trimellitate (TOTM) is widely used in medical and paramedical appliances. However, such plasticizers can leach from PVC products into contact solutions. The aim of this study is to investigate the release behaviors of DEHP and TOTM from the PVC intravenous infusion set into various pharmaceutical solutions under the simulated clinical conditions, such as the lipophilic substances (paclitaxel) , parenteral nutrition (fat emulsion injection) , acid and alkali pharmaceutical solution (levofloxacin hydrochloride injection, pH 3.0-5.0 and furosemide, pH 8.0-9.0). A simple and rapid high-performance liquid chromatographic method with UV detection (HPLC-UV) for the determination of DEHP or TOTM released from PVC medical devices into the above intravenous preparations was developed. The cumulative amounts of DEHP or TOTM released in 24 h were in the same following order: paclitaxel > fat emulsion injection levofloxacin hydrochloride > furosemide solution. From a comparison of the cumulative amounts of released DEHP and TOTM from the above solutions, we found that the cumulative amount of TOTM is far less than that of DEHP, under the same conditions. The cumulative amount of the DEHP released in 24 h in the paclitaxel solution was 21. 14 mg, while under the same conditions, the cumulative amount of TOTM was only 0. 078 mg. The cumulative amount of DEHP is assumed to be about 270 times that of the released TOTM. Thus TOTM could be a superior alternative to DEHP for use in medical devices because of its potential lower leachability.

Improved removal of malachite green from aqueous solution using chemically modified cellulose by anhydride.

PubMed

Zhou, Yanmei; Min, Yinghao; Qiao, Han; Huang, Qi; Wang, Enze; Ma, Tongsen

2015-03-01

Cellulose modified with maleic (M) and phthalic (P) anhydride, to be named CMA and CPA, were tested as feasible adsorbents for the removal of malachite green from aqueous solution. At the same time, the uptake ability of natural cellulose was also studied for comparison. The structure of material was characterized by FT-IR and XRD. The effects of solution pH, initial dye concentration, contact time and temperature were investigated in detail by batch adsorption experiments. The kinetic and isotherm studies suggested that the adsorption followed the pseudo-second-order model and Langmuir isotherm. The maximum adsorption capacity on CMA and CPA were 370 mg g(-1) and 111 mg g(-1), respectively. Furthermore, the thermodynamics studies indicated the spontaneous nature of adsorption of malachite green on adsorbents. All the studied results showed that the modified cellulose could be used as effective adsorption material for the removal of malachite green from aqueous solutions. Copyright © 2014 Elsevier B.V. All rights reserved.

Adsorption of crystal violet onto functionalised multi-walled carbon nanotubes: Equilibrium and kinetic studies.

PubMed

Sabna, V; Thampi, Santosh G; Chandrakaran, S

2016-12-01

Synthetic dyes present in effluent from textile, paper and paint industries contain crystal violet (CV), a known carcinogenic agent. This study investigates the modification of multiwalled carbon nanotubes by acid reflux method and equilibrium and kinetic behaviour of adsorption of CV onto functionalized multi-walled carbon nanotubes (fMWNTs) in batch system. High stability of the fMWNTs suspension in water indicates the hydrophilicity of fMWNTs induced due to the formation of functional groups that make hydrogen bonds with water molecules. fMWNTs were characterized by Fourier Transform Infra Red (FTIR) spectroscopy and the functional groups present on the fMWNTs were confirmed. Characteristic variation was observed in the FTIR spectra of fMWNTs after adsorption of crystal violet onto it. Adsorption characteristics were evaluated as a function of system variables such as contact time, dosage of fMWNTs and initial concentration and pH of the crystal violet solution. Adsorption capacity of fMWNTs and percentage removal of the dye increased with increase in contact time, adsorbent dosage and pH but declined with increase in initial concentration of the dye. fMWNTs showed higher adsorption capacity compared to that of pristine MWNTs. Data showed good fit with the Langmuir and Freundlich isotherm models and the pseudo-second order kinetic model; the maximum adsorption capacity was 90.52mg/g. Kinetic parameters such as rate constants, equilibrium adsorption capacities and regression coefficients were estimated. Results indicate that fMWNTs are an effective adsorbent for the removal of crystal violet from aqueous solution. Copyright © 2015 Elsevier Inc. All rights reserved.

Biosorption of Basic Green 4 from aqueous solution by Ananas comosus (pineapple) leaf powder.

PubMed

Chowdhury, Shamik; Chakraborty, Sagnik; Saha, Papita

2011-06-01

Biosorption characteristics of Ananas comosus (pineapple) leaf powder was investigated for decolorization of Basic Green 4 (BG 4), a cationic dye from its aqueous solutions employing a batch experimental set-up. Parameters that influence the sorption process such as pH, biosorbent dosage, contact time, initial dye concentration and temperature were systematically studied. The optimum conditions for removal of BG 4 were found to be pH 9.0, contact time=150 min, biosorbent dosage=5.0 g L(-1), initial dye concentration=50 mg L(-1). The temperature had a strong influence on the biosorption process. Further, the biosorbent was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and Brunauer, Emmett, Teller (BET) surface area and pore size analysis. Experimental biosorption data were modeled by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The biosorption process followed the Langmuir isotherm model with high coefficients of correlation (R(2)>0.99) at different temperatures. The pseudo second order kinetic model fitted well in correlation to the experimental results. Activation energy of the biosorption process (E(a)) was found to be 45.79 kJ mol(-1) by using the Arrhenius equation, indicating chemisorption nature of BG 4 sorption onto pineapple leaf powder. Thermodynamic parameters suggest that the biosorption process is spontaneous and exothermic in nature. Overall, the present findings suggest that this environmentally friendly, efficient and low-cost biosorbent may be useful for the removal of BG 4 from aqueous media. Copyright © 2011 Elsevier B.V. All rights reserved.

77 FR 65570 - Center for Scientific Review; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-29

... Conference Call). Contact Person: Carol Hamelink, Ph.D., Scientific Review Officer, Center for Scientific...--Convention Center, 900 10th Street NW., Washington, DC 20001. Contact Person: Mark P Rubert, Ph.D... for Scientific Review Special Emphasis Panel; Fellowships: Chemistry, Biochemistry and Biophysics...

77 FR 16248 - Center for Scientific Review; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-20

... (Virtual Meeting). Contact Person: Kenneth A Roebuck, Ph.D., Scientific Review Officer, Center for... Rockledge Drive, Bethesda, MD 20892 (Virtual Meeting). Contact Person: Robert Freund, Ph.D., Scientific.... Place: National Institutes of Health, 6701 Rockledge Drive, Bethesda, MD 20892 (Virtual Meeting...

Converter slag-coal cinder columns for the removal of phosphorous and other pollutants.

PubMed

Yang, Jian; Wang, Su; Lu, Zhibo; Yang, Jian; Lou, Shanjie

2009-08-30

A mixture of converter slag and coal cinder as adsorbent for the removal of phosphorous and other pollutants was studied in the paper. The maximum P adsorption capacity, pH of solution, contact time and initial phosphate concentration were evaluated in batch experiments for the two materials firstly. The data of P sorption were best fitted to Langumir equation, and the maximum adsorption capacities of converter slag and coal cinder were 2.417 and 0.398 mg P/g, respectively. The pH of solutions with converter slag and coal cinder changed dramatically with time and closed to 8 in 8h, and the influence of initial pH on phosphate removal by coal cinder was more significant than by converter slag. Phosphate removal rate by converter slag decreased with increase of initial phosphate concentrations. Subsequently, two flow-through columns (Column 1#, V(converter slag):V(coal cinder)=1:5; Column 2#, V(converter slag):V(coal cinder)=1:3) were operated for the removal of phosphorous and other pollutants from the effluents of a vermifilter for nearly eleven months. Results indicated the average removal efficiency of total phosphorus, dissolved phosphorus, COD and NH(4)(+)-N by Column 1# were 44%, 56%, 31% and 67%, and by Column 2# were 42%, 54%, 24% and 57%, respectively. Column 1# had higher removal efficiency for P and other pollutants.

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.

Detoxification of pesticides aqueous solution using horseradish peroxidase.

PubMed

El-Said, Saad Mohamed

2013-03-15

There are pesticide residues in agriculture wastewater and that compounds must be removed before discharge of wastewater in native waters. Thus the aim of this study was to remove toxic pesticide in waste water by the addition of horseradish peroxidase enzyme. The process of pesticide (methyl-parathion (O,O-Diethyl- O-4-nitro-phenylthiophosphate), atrazine (1-chloro-3-ethylamino-5-isopropylamino-2,4,6-triazine) and triazophos (O,O-diethyl O-1-phenyl-1H-1,2,4- triazol-3-yl phosphorothioate) removal from synthetic wastewater using horseradish peroxidase and hydrogen peroxide has been analyzed. The technical feasibility of the process was studied using 0.001-3.0 mM synthetic pesticides solutions. Experiments were carried out at different time, HRP and H2O2 dose and pH to determine the optimum removing conditions. The removal of the three pesticides increases with an increase in HRP and hydrogen peroxide dose. The optimum HRP dose is 2.0 U L(-1) and 10 mM for H2O2. The contact needed to reach equilibrium was found to be 360 min. Maximum removal was achieved up to 74% at pH 8. Also, Chemical Oxygen Demand (COD) of the effluent reduced at the end of 6 h from 2111-221 mg L(-1) (at pH 8). Tests based upon horseradish peroxidase, at optimized parameters, show the reduction of toxicity to non-toxic levels.

Removal of bisphenol A and some heavy metal ions by polydivinylbenzene magnetic latex particles.

PubMed

Marzougui, Zied; Chaabouni, Amel; Elleuch, Boubaker; Elaissari, Abdelhamid

2016-08-01

In this study, magnetic polydivinylbenzene latex particles MPDVB with a core-shell structure were tested for the removal of bisphenol A (BPA), copper Cu(II), lead Pb(II), and zinc Zn(II) from aqueous solutions by a batch-adsorption technique. The effect of different parameters, such as initial concentration of pollutant, contact time, adsorbent dose, and initial pH solution on the adsorption of the different adsorbates considered was investigated. The adsorption of BPA, Cu(II), Pb(II), and Zn(II) was found to be fast, and the equilibrium was achieved within 30 min. The pH 5-5.5 was found to be the most suitable pH for metal removal. The presence of electrolytes and their increasing concentration reduced the metal adsorption capacity of the adsorbent. Whereas, the optimal pH for BPA adsorption was found 7, both hydrogen bonds and π-π interaction were thought responsible for the adsorption of BPA on MPDVB. The adsorption kinetics of BPA, Cu(II), Pb(II), and Zn(II) were found to follow a pseudo-second-order kinetic model. Equilibrium data for BPA, Cu(II), Pb(II), and Zn(II) adsorption were fitted well by the Langmuir isotherm model. Furthermore, the desorption and regeneration studies have proven that MPDVB can be employed repeatedly without impacting its adsorption capacity.

Simultaneous removal of As, Cd, Cr, Cu, Ni and Zn from stormwater using high-efficiency industrial sorbents: Effect of pH, contact time and humic acid.

PubMed

Genç-Fuhrman, Hülya; Mikkelsen, Peter S; Ledin, Anna

2016-10-01

The effect of contact time, solution pH, and the presence of humic acid (HA) on the combined removal of As, Cd, Cr, Cu, Ni and Zn is investigated in batch tests using alumina, granulated activated carbon (GAC), and bauxsol coated sand (BCS) as sorbents. It is found that the equilibrium time for Cd, Cu, Ni and Zn is about 4h, while no clear equilibrium is observed for As and Cr. It is also found that increasing the pH until pH~8 enhanced Cd, Cu, Ni and Zn removal, but increasing the pH above this point had no major effect. In the cases of As and Cr, higher pH values (i.e. >7) decreased their removal. The presence of both 20 and 100mg/L HA suppressed the heavy metal removal except for Cr, and the suppression was higher at the higher HA concentration. Geochemical simulations suggest that this is due to the formation of dissolved HA-metal complexes preventing effective metal sorption. In the case of Cr, the presence of HA increased the removal when using alumina or BCS, while hindering the removal when using GAC. The findings show that the pH-value of the stormwater to be treated must be in the range of 6-7 in order to achieve removal of the full spectrum of metals. The results also show that natural organic matter may severely influence the removal efficiency, such that, for most metals the removal was reduced to the half, while for Cr it was increased to the double for alumina and BCS. Consequently, a properly working filter set up may not work properly anymore when receiving high loads of natural organic acids during the pollen season in spring or during defoliation in autumn and early winter, and during mixing of runoff with snowmelt having a low pH. Copyright © 2016 Elsevier B.V. All rights reserved.

Biosorption studies on copper (II) and cadmium (II) using pretreated rice straw and rice husk.

PubMed

Li, W C; Law, F Y; Chan, Y H M

2017-04-01

This study investigated the adsorption and removal behaviour of copper (Cu) (II) and cadmium (Cd) (II) ions using rice husk and rice straw in aqueous solutions. Different parameters were used to investigate their adsorption performance in saline conditions and the optimal level of biosorption at different pH levels. The main parameters were pH (3, 6 and 9), initial concentration level of heavy metals (Cu (II) 5, 10, 20, 40 and 60 mg/L and Cd (II) 0.5, 1, 2, 4 and 8 mg/L, respectively), salinity (0, 50 and 100 mM NaCl) and contact time (ranging from 3 to 60 min). Langmuir and Freundlich isotherm models were applied to analyse the removal efficiency and sorption capacity of the pretreated rice husk and rice straw. The removal efficiency and adsorption capacity generally increased with the pH and reached a plateau in alkaline conditions. The percentage removal of Cu (II) by rice husk reached 97 % at pH 9 and 95 % by rice straw at pH 6. Biosorption performance increased in the absence of NaCl. Kinetic studies for both metals revealed that the biosorption of Cu (II) and Cd (II) onto rice straw and husk was pseudo-second order.

Inactivation of Template-Directed Misfolding of Infectious Prion Protein by Ozone

PubMed Central

Ding, Ning; Price, Luke M.; Braithwaite, Shannon L.; Balachandran, Aru; Belosevic, Miodrag

2012-01-01

Misfolded prions (PrPSc) are well known for their resistance to conventional decontamination processes. The potential risk of contamination of the water environment, as a result of disposal of specified risk materials (SRM), has raised public concerns. Ozone is commonly utilized in the water industry for inactivation of microbial contaminants and was tested in this study for its ability to inactivate prions (263K hamster scrapie = PrPSc). Treatment variables included initial ozone dose (7.6 to 25.7 mg/liter), contact time (5 s and 5 min), temperature (4°C and 20°C), and pH (pH 4.4, 6.0, and 8.0). Exposure of dilute suspensions of the infected 263K hamster brain homogenates (IBH) (0.01%) to ozone resulted in the in vitro destruction of the templating properties of PrPSc, as measured by the protein misfolding cyclic amplification (PMCA) assay. The highest levels of prion inactivation (≥4 log10) were observed with ozone doses of 13.0 mg/liter, at pH 4.4 and 20°C, resulting in a CT (the product of residual ozone concentration and contact time) value as low as 0.59 mg · liter−1 min. A comparison of ozone CT requirements among various pathogens suggests that prions are more susceptible to ozone degradation than some model bacteria and protozoa and that ozone treatment may be an effective solution for inactivating prions in water and wastewater. PMID:22138993

40 CFR Appendix A to Subpart Ddd... - Free Formaldehyde Analysis of Insulation Resins by the Hydroxylamine Hydrochloride Method

Code of Federal Regulations, 2011 CFR

2011-07-01

..., readable to 0.01 g or better. 3.2pH meter, standardized to pH 4.0 with pH 4.0 buffer and pH 7 with pH 7.0... N sodium hydroxide solution. 4.2Hydroxylamine hydrochloride solution, 100 grams per liter, pH... stirrer. Confirm that the resin has dissolved. 5.4Adjust the resin/solvent solution to pH 4.0, using the...

Removal of lead (II) ions from aqueous solutions onto activated carbon derived from waste biomass.

PubMed

Erdem, Murat; Ucar, Suat; Karagöz, Selhan; Tay, Turgay

2013-01-01

The removal of lead (II) ions from aqueous solutions was carried out using an activated carbon prepared from a waste biomass. The effects of various parameters such as pH, contact time, initial concentration of lead (II) ions, and temperature on the adsorption process were investigated. Energy Dispersive X-Ray Spectroscopy (EDS) analysis after adsorption reveals the accumulation of lead (II) ions onto activated carbon. The Langmuir and Freundlich isotherm models were applied to analyze equilibrium data. The maximum monolayer adsorption capacity of activated carbon was found to be 476.2 mg g⁻¹. The kinetic data were evaluated and the pseudo-second-order equation provided the best correlation. Thermodynamic parameters suggest that the adsorption process is endothermic and spontaneous.

75 FR 4090 - Center for Scientific Review; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-26

... El Camino Real, San Diego, CA 92130. Contact Person: William A. Greenberg, PhD., Scientific Review... (Virtual Meeting). Contact Person: Fouad A. El-Zaatari, PhD., Scientific Review Officer, Center for... for Scientific Review Special Emphasis Panel, Small Business: Experimental Cancer Therapeutics. Date...

75 FR 4094 - National Institute of Allergy And Infectious Diseases; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-26

...). Contact Person: Edward W. Schroder, PhD, Chief, Microbiology Review Branch, Scientific Review Program...). Contact Person: Edward W. Schroder, PhD, Chief, Microbiology Review Branch, Scientific Review Program....855, Allergy, Immunology, and Transplantation Research; 93.856, Microbiology and Infectious Diseases...

Effects of Chlorine Promoted Oxidation on Arsenic Release from Sulfide Minerals

NASA Astrophysics Data System (ADS)

West, N.; Schreiber, M.; Gotkowitz, M.

2007-12-01

High arsenic concentrations (>100 ppb) have been measured in wells completed in the Ordovician St. Peter sandstone aquifer of eastern Wisconsin. The primary source of arsenic is As-bearing sulfide minerals within the aquifer. Periodic disinfection of wells by chlorination may facilitate arsenic release to groundwater by increasing the rate of sulfide mineral oxidation. During typical well disinfection procedures, aquifer solids exposed along uncased portions of wells remain in direct contact with chlorine disinfection solutions for up to twenty-four hours. Due to the redox sensitivity of arsenic mobility in groundwater, it is important to evaluate the effect of repeatedly adding oxidizers to an arsenic impacted aquifer system. This study focuses on abiotic processes that mobilize arsenic from the solid phase during controlled exposure to chlorinated solutions. Two St. Peter samples with As concentrations of 21 and 674 ppm were selected for the experiments. Before reaction, the aquifer mineralogy is characterized using scanning electron microscopy (SEM) and electron microprobe analysis (EMPA). The samples are then reacted with solutions of 60 mg/L free chlorine, 1200 mg/L free chlorine, or nanopure water (control) at pH 7.0 and pH 8.5. These parameters represent typical solution chemistries present within the wells after disinfection. Solutions are sampled periodically during the experiments and analyzed for As, Fe, other trace metals such as Co, Mo, Cr, and Ni, and sulfate. Analysis of the post-reaction solids using SEM, EMPA, laser ablation ICP-MS and Raman techniques are used to document the changes in mineralogy due to chlorination and to document which solid phases contain As.

Perfectly Wetting Mixtures of Surfactants from Renewable Resources: The Interaction and Synergistic Effects on Adsorption and Micellization.

PubMed

Szumała, Patrycja; Mówińska, Alicja

This paper presents a study of the surface properties of mixtures of surfactants originating from renewable sources, i.e., alkylpolyglucoside (APG), ethoxylated fatty alcohol (AE), and sodium soap (Na soap). The main objective was to optimize the surfactant ratio which produces the highest wetting properties during the analysis of the solution of the individual surfactants, two- and three-component mixtures, and at different pH values. The results showed the existence of a synergistic effect in lowering the interfacial tension, critical micelle concentration and the formation of mixed micelles in selected solutions. We found that best wetting properties were measured for the binary AE:APG mixtures. It has been demonstrated that slightly lower contact angles values were observed on Teflon and glass surfaces for the AE:APG:soap mixtures but the results were obtained for higher concentration of the components. In addition, all studied solutions have very good surface properties in acidic, basic and neural media. However, the AE:soap (molar ratio of 1:2), AE:APG (2:1) and AE:APG:soap (1:1:1) compositions improved their wetting power at pH 7 on the aluminium and glass surfaces, as compared to solutions at other pH values tested (selected Θ values close to zero-perfectly wetting liquids). All described effects detected would allow less surfactant to be used to achieve the maximum capacity of washing, wetting or solubilizing while minimizing costs and demonstrating environmental care.

Correlation of Surface Adsorption and Oxidation with a Floatability Difference of Galena and Pyrite in High-Alkaline Lime Systems.

PubMed

Niu, Xiaopeng; Ruan, Renman; Xia, Liuyin; Li, Li; Sun, Heyun; Jia, Yan; Tan, Qiaoyi

2018-02-27

When it comes to Pb-Zn ores with high amounts of pyrite, the major problem encountered is the low separation efficiency between galena and pyrite. By virtue of high dosage of lime and collector sodium diethyl dithiocarbamate (DDTC), pyrite and zinc minerals are depressed, allowing the galena to be floated. However, there have been significant conflicting reports on the flotation behavior of galena at high pH. In this context, correlation of the surface adsorption and oxidation with the floatability difference of galena and pyrite in high-alkaline lime systems would be a key issue for process optimization. Captive bubble contact angle measurements were performed on freshly polished mineral surfaces in situ exposed to lime solutions of varying pH as a function of immersion time. Furthermore, single mineral microflotation tests were conducted. Both tests indicated that the degree of hydrophobicity on the surfaces of galena and pyrite increased in the presence of DDTC at natural or mild pulp pH. While in a saturated lime solution, at pH 12.5, DDTC only worked for galena, but not for pyrite. Surface chemistry analysis by time-of-flight secondary ion mass spectrometry (Tof-SIMS) confirmed the preference of DDTC on the galena surface at pH 12.5, which contributed to a merit recovery. Further important evidence through measurements of Tof-SIMS, ion chromatography, and high-performance liquid chromatography indicated that in high-alkaline lime systems, the merit floatability of galena could exclude the insignificant contribution of elemental sulfur (S 8 ) and was dominantly attributed by the strong adsorption of DDTC. In contrast, the poor flotation response of pyrite at high pH was due to the prevailing adsorption of CaOH + species. This study provides an important surface chemistry evidence for a better understanding of the mechanism on the better selectivity in the galena-pyrite separation adopting high-alkaline lime systems.

Adsorption of mercury from aqueous solutions using palm oil fuel ash as an adsorbent - batch studies

NASA Astrophysics Data System (ADS)

Imla Syafiqah, M. S.; Yussof, H. W.

2018-03-01

Palm oil fuel ash (POFA) is one of the most abundantly produced waste materials. POFA is widely used by the oil palm industry which was collected as ash from the burning of empty fruit bunches fiber (EFB) and palm oil kernel shells (POKS) in the boiler as fuel to generate electricity. Mercury adsorption was conducted in a batch process to study the effects of contact time, initial Hg(II) ion concentration, and temperature. In this study, POFA was prepared and used for the removal of mercury(II) ion from the aqueous phase. The effects of various parameters such as contact time (0- 360 min), temperature (15 – 45 °C) and initial Hg(II) ion concentration (1 – 5 mg/L) for the removal of Hg(II) ion were studied in a batch process. The surface characterization was examined by scanning electron microscopy (SEM) and particle size distribution analysis. From this study, it was found that the highest Hg(II) ion removal was 99.60 % at pH 7, contact time of 4 h, initial Hg(II) ion concentration of 1 mg/L, adsorbent dosage 0.25 g and agitation speed of 100 rpm. The results implied that POFA has the potential as a low-cost and environmental friendly adsorbent for the removal of mercury from aqueous solution.

76 FR 51379 - Center for Scientific Review; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-18

... Drive, Bethesda, MD 20892, (Virtual Meeting). Contact Person: John Bleasdale, PhD, Scientific Review.... Contact Person: Reed A Graves, PhD, Scientific Review Officer, Center for Scientific Review, National... Group Biochemistry and Biophysics of Membranes Study Section. Date: September 26-27, 2011. Time: 8 a.m...

75 FR 9907 - National Heart, Lung, and Blood Institute; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-04

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78 FR 31951 - Center for Scientific Review; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-28

..., Bethesda, MD 20892, (Virtual Meeting). Contact Person: Nuria E Assa-Munt, Ph.D., Scientific Review Officer...; Small Business: Education, Psychology, and Biology in Health Behavior. Date: June 24-25, 2013. Time: 8..., (Virtual Meeting). Contact Person: David R Filpula, Ph.D., Scientific Review Officer, Center for Scientific...

78 FR 51735 - Center For Scientific Review; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-21

...: Biological Chemistry and Macromolecular Biophysics. Date: August 26, 2013. Time: 11:00 a.m. to 12:00 p.m... Drive, Bethesda, MD 20892 (Telephone Conference Call). Contact Person: Nitsa Rosenzweig, Ph.D... Conference Call). Contact Person: Aftab A Ansari, Ph.D., Scientific Review Officer, Center for Scientific...

76 FR 66075 - Center for Scientific Review Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-25

... applications. Place: National Institutes of Health, 6701 Rockledge Drive, Bethesda, MD 20892, (Virtual Meeting..., Bethesda, MD 20892, (Virtual Meeting). Contact Person: Michael H. Chaitin, PhD, Scientific Review Officer... Health, 6701 Rockledge Drive, Bethesda, MD 20892, (Virtual Meeting). Contact Person: John C Pugh, PhD...

Stability of Adrenaline in Irrigating Solution for Intraocular Surgery.

PubMed

Shibata, Yuuka; Kimura, Yasuhiro; Taogoshi, Takanori; Matsuo, Hiroaki; Kihira, Kenji

2016-01-01

Intraocular irrigating solution containing 1 µg/mL adrenaline is widely used during cataract surgery to maintain pupil dilation. Prepared intraocular irrigating solutions are recommended for use within 6 h. After the irrigating solution is admistered for dilution, the adrenaline may become oxidized, and this may result in a decrease in its biological activity. However, the stability of adrenaline in intraocular irrigating solution is not fully understood. The aim of this study was to evaluate the stability of adrenaline in clinically used irrigating solutions of varying pH. Six hours after mixing, the adrenaline percentages remaining were 90.6%±3.7 (pH 7.2), 91.1%±2.2 (pH 7.5), and 65.2%±2.8 (pH 8.0) of the initial concentration. One hour after mixing, the percentages remaining were 97.6%±2.0 (pH 7.2), 97.4%±2.7 (pH 7.5), and 95.6%±3.3 (pH 8.0). The degradation was especially remarkable and time dependent in the solution at pH 8.0. These results indicate that the concentration of adrenaline is decreased after preparation. Moreover, we investigated the influence of sodium bisulfite on adrenaline stability in irrigating solution. The percentage adrenaline remaining at 6 h after mixing in irrigating solution (pH 8.0) containing sodium bisulfite at 0.5 µg/mL (concentration in irrigating solution) or at 500 µg/mL (concentration in the undiluted adrenaline preparation) were 57.5 and 97.3%, respectively. Therefore, the low concentration of sodium bisulfite in the irrigating solution may be a cause of the adrenaline loss. In conclusion, intraocular irrigation solution with adrenaline should be prepared just prior to its use in surgery.

Chromium (VI) ion adsorption by grafted cross-linked chitosan beads in aqueous solution - a mathematical and statistical modeling study.

PubMed

Igberase, E; Osifo, P; Ofomaja, A

2017-12-01

Chitosan outstanding qualities and efficient way of binding metal ions even to near zero concentration is the major reason for special attention. Modification of chitosan allows the polymer to be applied in numerous field of research. Depending on the modification techniques, chitosan possesses increased adsorption capacity. In this study chitosan beads (CS) were formulated from chitosan flakes, the beads were cross-linked with glutaraldehyde and thereafter grafted with ethyldiaminetetraacetic acid. The stability and amine concentration of the beads were determined. The chemical functionalities of the beads were obtained by Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis (TGA). However, in the adsorption studies with Cr(VI), the number of runs in the experiment was obtained by response surface methodology (RSM), and the maximum adsorption capacity (Q m ) from each run was determined from the Langmuir model. The results of the experiment showed that the non-modified beads were soluble at pH 1-4 and insoluble at pH 5, while the modified beads were insoluble at pH 1-6. The amine concentration of CS, CCS and grafted cross-linked chitosan beads (GCCS) were 4.4, 3.8 and 5.0 mmol/g, respectively. The point of zero charge (pH PZC ) of GCCS was found to be 4.4. The quadratic model was significant and adequate in describing the experimental data. The difference between experimental and predicted Q m was negligible. From the design matrix and results, increased Q m was achieved at pH 5, contact time 70 min, temperature 45°C, adsorbent dosage 5 g and initial concentration 70 mg/l. The desorption of the beads loaded with Cr(VI) was successful with 0.5 M HCl eluant and contact time of 180 min, leading to cost minimization.

Postrigor citric acid enhancement can alter cooked color but not fresh color of dark-cutting beef.

PubMed

Stackhouse, R J; Apple, J K; Yancey, J W S; Keys, C A; Johnson, T M; Mehall, L N

2016-04-01

In 2 experiments, dark-cutting (DC) beef strip loins were used to test the effects of citric acid-enhancement pH on visual and instrumental color of fresh and cooked steaks. In Exp. 1 and 2, each DC (mean pH = 6.57 and 6.65, respectively) and normal-pH, low USDA Choice (CH; mean pH = 5.48 and 5.51, respectively) strip loin was cut into 2 equal-length sections, and DC sections were injected to 111% of raw section weight with pH 3.5 to 5.0 (Exp. 1) or pH 2.0 to 3.5 (Exp. 2) solutions made by mixing citric acid in either 0.05% orthophosphate (PO) solution or tap water (HO) base solutions (Exp. 1) and 0.5% PO or 0.5% tripolyphosphate solution base solutions (Exp. 2). After enhancement, sections were cut into steaks, which were assigned to either 5 d of simulated retail display or cooked to 71°C for cooked color measurement. Postenhancement pH of DC steaks enhanced with pH 3.5 to 5.0 solutions did not ( ≥ 0.180) differ from that of nonenhanced DC steaks (Exp. 1) but linearly decreased ( < 0.001) as solution pH decreased from 3.5 to 2.0 (Exp. 2). Even though fresh color scores were increased ( < 0.001) by citric acid enhancement over untreated DC steaks during the first 3 d of display, fresh steak color never ( < 0.001) approached that of nonenhanced CH steaks. When compared with nonenhanced DC steaks, enhancement with pH 3.5 to 5.0 solutions received lower cooked color scores, whereas enhancing DC sections with pH 2.5 solutions produced cooked color and degree-of-doneness scores similar ( ≥ 0.113) to those of nonenhanced CH steaks (Exp. 2). Results indicated that the pH of citric acid enhancement solutions, regardless of base solution, were insufficient to improve the fresh color of DC beef; however, enhancement with pH 2.5 citric acid solutions effectively eliminated the persistent red cooked color typically associated with DC beef comparable with that of normal-pH beef.

FY2016 ILAW Glass Corrosion Testing with the Single-Pass Flow-Through Method

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

Neeway, James J.; Asmussen, Robert M.; Parruzot, Benjamin PG

The inventory of immobilized low-activity waste (ILAW) produced at the Hanford Tank Waste Treatment and Immobilization Plant (WTP) will be disposed of at the near-surface, on-site Integrated Disposal Facility (IDF). When groundwater comes into contact with the waste form, the glass will corrode and radionuclides will be released into the near-field environment. Because the release of the radionuclides is dependent on the dissolution rate of the glass, it is important that the performance assessment (PA) model accounts for the dissolution rate of the glass as a function of various chemical conditions. To accomplish this, an IDF PA model based onmore » Transition State Theory (TST) can be employed. The model is able to account for changes in temperature, exposed surface area, and pH of the contacting solution as well as the effect of silicon concentrations in solution, specifically the activity of orthosilicic acid (H4SiO4), whose concentration is directly linked to the glass dissolution rate. In addition, the IDF PA model accounts for the alkali-ion exchange process as sodium is leached from the glass and into solution. The effect of temperature, pH, H4SiO4 activity, and the rate of ion-exchange can be parameterized and implemented directly into the PA rate law model. The rate law parameters are derived from laboratory tests with the single-pass flow-through (SPFT) method. To date, rate law parameters have been determined for seven ILAW glass compositions, thus additional rate law parameters on a wider range of compositions will supplement the existing body of data for PA maintenance activities. The data provided in this report can be used by ILAW glass scientists to further the understanding of ILAW glass behavior, by IDF PA modelers to use the rate law parameters in PA modeling efforts, and by Department of Energy (DOE) contractors and decision makers as they assess the IDF PA program.« less

Adsorption of ammonium ion by coconut shell-activated carbon from aqueous solution: kinetic, isotherm, and thermodynamic studies.

PubMed

Boopathy, Ramasamy; Karthikeyan, Sekar; Mandal, Asit Baran; Sekaran, Ganesan

2013-01-01

Ammonium ions are one of the most encountered nitrogen species in polluted water bodies. High level of ammonium ion in aqueous solution imparts unpleasant taste and odor problems, which can interfere with the life of aquatics and human population when discharged. Many chemical methods are developed and being used for removal of ammonium ion from aqueous solution. Among various techniques, adsorption was found to be the most feasible and environmentally friendly with the use of natural-activated adsorbents. Hence, in this study, coconut shell-activated carbon (CSAC) was prepared and used for the removal of ammonium ion by adsorption techniques. Ammonium chloride (analytical grade) was purchased from Merck Chemicals for adsorption studies. The CSAC was used to adsorb ammonium ions under stirring at 100 rpm, using orbital shaker in batch experiments. The concentration of ammonium ion was estimated by ammonia distillate, using a Buchi distillation unit. The influence of process parameters such as pH, temperature, and contact time was studied for adsorption of ammonium ion, and kinetic, isotherm models were validated to understand the mechanism of adsorption of ammonium ion by CSAC. Thermodynamic properties such as ∆G, ∆H, and ∆S were determined for the ammonium adsorption, using van't Hoff equation. Further, the adsorption of ammonium ion was confirmed through instrumental analyses such as SEM, XRD, and FTIR. The optimum conditions for the effective adsorption of ammonium ion onto CSAC were found to be pH 9.0, temperature 283 K, and contact time 120 min. The experimental data was best followed by pseudosecond order equation, and the adsorption isotherm model obeyed the Freundlich isotherm. This explains the ammonium ion adsorption onto CSAC which was a multilayer adsorption with intraparticle diffusion. Negative enthalpy confirmed that this adsorption process was exothermic. The instrumental analyses confirmed the adsorption of ammonium ion onto CSAC.

Rise in the pH of an unfrozen solution in ice due to the presence of NaCl and promotion of decomposition of gallic acids owing to a change in the pH.

PubMed

Takenaka, Norimichi; Tanaka, Masayuki; Okitsu, Kenji; Bandow, Hiroshi

2006-09-14

Oxidative decomposition of gallic acid occurs in alkaline solutions but hardly arises in acidic solutions. We have found that the addition of sodium chloride promotes the decomposition of gallic acid caused by freezing even under neutral and acidic conditions. Even at pH 4.5, gallic acid was decomposed by freezing in the presence of NaCl; however, in the absence of NaCl, it was hardly decomposed by freezing at pH lower than 7. Chloride ions are more easily incorporated in ice than sodium ions when the NaCl solution is frozen. The unfrozen solution in ice becomes positively charged, and as a result, protons transfer from the unfrozen solution to the ice. We measured the pH in the unfrozen solution which coexists with single-crystal ice formed from a 5 mmol dm(-3) NaCl solution and determined the pH to be 8.6 at equilibrium with CO(2) of 380 ppm or 11.3 in the absence of CO(2) compared to pH 5.6 in the original solution. From the model calculation performed for gallic acid solution in the presence of 5 mmol dm(-3) NaCl, it can be estimated that the amount of OH(-) transferred from the ice to the solution corresponds to 1.26 x 10(-5) mol dm(-3). The amount of OH(-) transferred is concentrated into the unfrozen solution and affects the pH of the unfrozen solution. Therefore, the pH in an unfrozen gallic acid solution in ice becomes alkaline, and the decomposition of gallic acid proceeds. It is expected that other base-catalyzed reactions in weakly acidic solutions also proceed by freezing in the presence of NaCl without the need for any alkaline reagents.

Effect of pH on the survival of Listeria innocua in calcium ascorbate solutions and on quality of fresh-cut apples.

PubMed

Karaibrahimoglu, Yildiz; Fan, Xuetong; Sapers, Gerald M; Sokorai, Kimberly

2004-04-01

Fresh-cut apple slices were dipped in calcium ascorbate (CaA) solution at pH values ranging from 2.5 to 7.0 to inhibit browning. After treatment, the cut apples were stored at 4 and 10 degrees C for up to 21 days. Color and texture of the apples were determined on days 1, 14, and 21. In a separate experiement, the pH of CaA solution was adjusted with acetic acid to six different pH levels, and the solution was inoculated with Listeria innocua. The survival of the bacterium and the stability of CaA were determined at 0, 20, and 96 h. The cut apples maintained fresh quality when the pH of the CaA solution was above 4.5, but slight discoloration of apple slices dipped in pH 4.5 solution was observed after 14 days at 10 degrees C. At pH 5.0, the CaA dip maintained the quality of the apples at both temperatures for at least 21 days. The L. innocua population was reduced by 4 to 5 log CFU/ml at pH 4.5 after 96 h. At pH 5, the bacterial population in the CaA solution was reduced by approximately 2 log CFU/ml during the same period. The CaA solution was stable at pH 5 for at least 96 h. Reduction of the pH to between 4.5 and 5.0 might reduce the risk of foodborne illness due to consumption of fresh-cut apples treated with a CaA solution contaminated with Listeria.

Evaluation of effects of pH and ionic strength on colloidal stability of IgG solutions by PEG-induced liquid-liquid phase separation.

PubMed

Thompson, Ronald W; Latypov, Ramil F; Wang, Ying; Lomakin, Aleksey; Meyer, Julie A; Vunnum, Suresh; Benedek, George B

2016-11-14

Colloidal stability of IgG antibody solutions is important for pharmaceutical and medicinal applications. Solution pH and ionic strength are two key factors that affect the colloidal stability of protein solutions. In this work, we use a method based on the PEG-induced liquid-liquid phase separation to examine the effects of pH and ionic strength on the colloidal stability of IgG solutions. We found that at high ionic strength (≥0.25M), the colloidal stability of most of our IgGs is insensitive to pH, and at low ionic strength (≤0.15M), all IgG solutions are much more stable at pH 5 than at pH 7. In addition, the PEG-induced depletion force is less efficient in causing phase separation at pH 5 than at pH 7. In contrast to the native inter-protein interaction of IgGs, the effect of depletion force on phase separation of the antibody solutions is insensitive to ionic strength. Our results suggest that the long-range electrostatic inter-protein repulsion at low ionic strength stabilizes the IgG solutions at low pH. At high ionic strength, the short-range electrostatic interactions do not make a significant contribution to the colloidal stability for most IgGs with a few exceptions. The weaker effect of depletion force at lower pH indicates a reduction of protein concentration in the condensed phase. This work advances our basic understanding of the colloidal stability of IgG solutions and also introduces a practical approach to measuring protein colloidal stability under various solution conditions.

Nanoparticle solutions as adhesives for gels and biological tissues

NASA Astrophysics Data System (ADS)

Rose, Séverine; Prevoteau, Alexandre; Elzière, Paul; Hourdet, Dominique; Marcellan, Alba; Leibler, Ludwik

2014-01-01

Adhesives are made of polymers because, unlike other materials, polymers ensure good contact between surfaces by covering asperities, and retard the fracture of adhesive joints by dissipating energy under stress. But using polymers to `glue' together polymer gels is difficult, requiring chemical reactions, heating, pH changes, ultraviolet irradiation or an electric field. Here we show that strong, rapid adhesion between two hydrogels can be achieved at room temperature by spreading a droplet of a nanoparticle solution on one gel's surface and then bringing the other gel into contact with it. The method relies on the nanoparticles' ability to adsorb onto polymer gels and to act as connectors between polymer chains, and on the ability of polymer chains to reorganize and dissipate energy under stress when adsorbed onto nanoparticles. We demonstrate this approach by pressing together pieces of hydrogels, for approximately 30 seconds, that have the same or different chemical properties or rigidities, using various solutions of silica nanoparticles, to achieve a strong bond. Furthermore, we show that carbon nanotubes and cellulose nanocrystals that do not bond hydrogels together become adhesive when their surface chemistry is modified. To illustrate the promise of the method for biological tissues, we also glued together two cut pieces of calf's liver using a solution of silica nanoparticles. As a rapid, simple and efficient way to assemble gels or tissues, this method is desirable for many emerging technological and medical applications such as microfluidics, actuation, tissue engineering and surgery.

Electrocoagulation process to Chemical and Biological Oxygen Demand treatment from carwash grey water in Ahvaz megacity, Iran.

PubMed

Mohammadi, Mohammad Javad; Takdastan, Afshin; Jorfi, Sahand; Neisi, Abdolkazem; Farhadi, Majid; Yari, Ahmad Reza; Dobaradaran, Sina; Khaniabadi, Yusef Omidi

2017-04-01

In this work, we present the result of an electric coagulation process with iron and aluminum electrodes for removal of chemical and biological oxygen demand (COD and BOD) from grey water in different car washes of Ahvaz, Iran. Nowadays, one of the important dangerous that can contaminate water resources for drinking, agriculture and industrial is Car wash effluent [1,2]. In this study, initial COD and BOD concentration, pH of the solution, voltage power and reaction time was investigated. The concentration level of remaining COD and BOD in samples was measured, using DR/5000 UV-vis HACH spectrophotometer [3,4]. The effects of contact time, initial pH, electrical potential and voltage data on removal of COD and BOD were presented. Statistical analysis of the data was carried out using Special Package for Social Sciences (SPSS 16).

Removal of cadmium ions from wastewater using innovative electronic waste-derived material.

PubMed

Xu, Meng; Hadi, Pejman; Chen, Guohua; McKay, Gordon

2014-05-30

Cadmium is a highly toxic heavy metal even at a trace level. In this study, a novel material derived from waste PCBs has been applied as an adsorbent to remove cadmium ions from aqueous solutions. The effects of various factors including contact time, initial cadmium ion concentration, pH and adsorbent dosage have been evaluated. The maximum uptake capacity of the newly derived material for cadmium ions has reached 2.1mmol/g at an initial pH 4. This value shows that this material can effectively remove cadmium ions from effluent. The equilibrium isotherm has been analyzed using several isotherm equations and is best described by the Redlich-Peterson model. Furthermore, different commercial adsorbent resins have been studied for comparison purposes. The results further confirm that this activated material is highly competitive with its commercial counterparts. Copyright © 2014 Elsevier B.V. All rights reserved.

In situ-forming hydrogels for sustained ophthalmic drug delivery.

PubMed

Nanjawade, Basavaraj K; Manvi, F V; Manjappa, A S

2007-09-26

Ophthalmic drug delivery is one of the most interesting and challenging endeavors facing the pharmaceutical scientist. The conventional ocular drug delivery systems like solutions, suspensions, and ointments show drawbacks such as increased precorneal elimination, high variability in efficiency, and blurred vision respectively. In situ-forming hydrogels are liquid upon instillation and undergo phase transition in the ocular cul-de-sac to form visco-elastic gel and this provides a response to environmental changes. In the past few years, an impressive number of novel temperature, pH, and ion induced in situ-forming systems have been reported for sustain ophthalmic drug delivery. Each system has its own advantages and drawbacks. The choice of a particular hydrogel depends on its intrinsic properties and envisaged therapeutic use. This review includes various temperature, pH, and ion induced in situ-forming polymeric systems used to achieve prolonged contact time of drugs with the cornea and increase their bioavailability.

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

Sundaramurthi, Prakash; Suryanarayanan, Raj

To effectively inhibit succinate buffer crystallization and the consequent pH changes in frozen solutions. Using differential scanning calorimetry (DSC) and X-ray diffractometry (XRD), the crystallization behavior of succinate buffer in the presence of either (i) a crystallizing (glycine, mannitol, trehalose) or (ii) a non-crystallizing cosolute (sucrose) was evaluated. Aqueous succinate buffer solutions, 50 or 200 mM, at pH values 4.0 or 6.0 were cooled from room temperature to -25 C at 0.5 C/min. The pH of the solution was measured as a function of temperature using a probe designed to function at low temperatures. The final lyophiles prepared from thesemore » solutions were characterized using synchrotron radiation. When the succinic acid solution buffered to pH 4.0, in the absence of a cosolute, was cooled, there was a pronounced shift in the freeze-concentrate pH. Glycine and mannitol, which have a tendency to crystallize in frozen solutions, remained amorphous when the initial pH was 6.0. Under this condition, they also inhibited buffer crystallization and prevented pH change. At pH 4.0 (50 mM initial concentration), glycine and mannitol crystallized and did not prevent pH change in frozen solutions. While sucrose, a non-crystallizing cosolute, did not completely prevent buffer crystallization, the extent of crystallization was reduced. Sucrose decomposition, based on XRD peaks attributable to {beta}-D-glucose, was observed in frozen buffer solutions with an initial pH of 4.0. Trehalose completely inhibited crystallization of the buffer components when the initial pH was 6.0 but not at pH 4.0. At the lower pH, the crystallization of both trehalose dihydrate and buffer components was evident. When retained amorphous, sucrose and trehalose effectively inhibited succinate buffer component crystallization and the consequent pH shift. However, when trehalose crystallized or sucrose degraded to yield a crystalline decomposition product, crystallization of buffer was observed. Similarly, glycine and mannitol, two widely used bulking agents, inhibited buffer component crystallization only when retained amorphous. In addition to stabilizing the active pharmaceutical ingredient, lyoprotectants may prevent solution pH shift by inhibiting buffer crystallization.« less

Preparation of Zeolite/Zinc Oxide Nanocomposites for toxic metals removal from water

NASA Astrophysics Data System (ADS)

Alswata, Abdullah A.; Ahmad, Mansor Bin; Al-Hada, Naif Mohammed; Kamari, Halimah Mohamed; Hussein, Mohd Zobir Bin; Ibrahim, Nor Azowa

This research work has proposed preparation of Zeolite/Zinc Oxide Nanocomposite (Zeolite/ZnO NCs) by using a co-precipitation method. Then, the prepared Nanocomposite has been tested for adsorption of Lead Pb (II) and Arsenic As (V) from aqueous solution under the room pressure and temperature. After that, the prepared adsorbent has been studied by several techniques. For adsorption process; the effect of the adsorbent masses, contact time, PH and initial metals concentration as well as, the kinetics and isotherm for adsorption process have been investigated. The results revealed that; ZnO nanoparticles (NPs) with average diameter 4.5 nm have successfully been loaded into Zeolite. The optimum parameters for the removal of the toxic metals 93% and 89% of Pb (II) and As (V), respectively, in 100 mg/L aqua solutions were pH4, 0.15 g and 30 min. According to the obtained results; pseudo second-order kinetic and Langmuir isotherm model have higher correlation coefficients and provided a better agreement with the experimental data. The prepared sorbent showed an economical and effective way to remove the heavy toxic metals due to its ambient operation conditions, low- consumption energy and facile regeneration method.

Engineered nano-magnetic iron oxide-urea-activated carbon nanolayer sorbent for potential removal of uranium (VI) from aqueous solution

NASA Astrophysics Data System (ADS)

Mahmoud, Mohamed E.; Khalifa, Mohamed A.; El Wakeel, Yasser M.; Header, Mennatllah S.; Abdel-Fattah, Tarek M.

2017-04-01

A novel magnetic nanosorbent was designed using chemical grafting of nano-magnetite (Nano-Fe3O4) with nanolayer of activated carbon (AC) via urea intermediate for the formation of Nano-Fe3O4-Urea-AC. Characterizing was carried out using FT-IR, SEM, HR-TEM, TGA, point of zero charge (Pzc) and surface area analysis. The designed sorbent maintained its magnetic properties and nanosized structure in the range of 8.7-14.1 nm. The surface area was identified as 389 m2/g based on the BET method. Sorption of uranyl ions from aqueous solutions was studied and evaluated in different experimental conditions. Removal of uranyl ions increased with increasing in pH value and the maximum percentage removal was established at pH 5.0. The removal and sorption processes of uranyl ions by Nano-Fe3O4-Urea-AC sorbent were studied and optimized using the batch technique. The key variables affecting removal of uranyl ions were studied including the effect of the contact time, dosage of Nano-Fe3O4-Urea-AC sorbent, reaction temperature, initial uranyl ions concentration and interfering anions and cations.

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.

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.

Microwave-Hydrothermal Treated Grape Peel as an Efficient Biosorbent for Methylene Blue Removal

PubMed Central

Ma, Lin; Jiang, Chunhai; Lin, Zhenyu; Zou, Zhimin

2018-01-01

Biosorption using agricultural wastes has been proven as a low cost and efficient way for wastewater treatment. Herein, grape peel treated by microwave- and conventional-hydrothermal processes was used as low cost biosorbent to remove methylene blue (MB) from aqueous solutions. The adsorption parameters including the initial pH value, dosage of biosorbents, contact time, and initial MB concentration were investigated to find the optimum adsorption conditions. The biosorbent obtained by microwave-hydrothermal treatment only for 3 min at 180 °C (microwave-hydrothermal treated grape peel, MGP) showed faster kinetics and higher adsorption capability than that produced by a conventional-hydrothermal process (hydrothermal treated grape peel, HGP) with a duration time of 16 h. The maximum adsorption capability of MGP under the optimum conditions (pH = 11, a dosage of 2.50 g/L) as determined with the Langmuir model reached 215.7 mg/g, which was among the best values achieved so far on biosorbents. These results demonstrated that the grape peel treated by a quick microwave-hydrothermal process can be a very promising low cost and efficient biosorbent for organic dye removal from aqueous solutions. PMID:29385041

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.

Comparison of 4-chloro-2-nitrophenol adsorption on single-walled and multi-walled carbon nanotubes

PubMed Central

2012-01-01

The adsorption characteristics of 4-chloro-2-nitrophenol (4C2NP) onto single-walled and multi-walled carbon nanotubes (SWCNTs and MWCNTs) from aqueous solution were investigated with respect to the changes in the contact time, pH of solution, carbon nanotubes dosage and initial 4C2NP concentration. Experimental results showed that the adsorption efficiency of 4C2NP by carbon nanotubes (both of SWCNTs and MWCNTs) increased with increasing the initial 4C2NP concentration. The maximum adsorption took place in the pH range of 2–6. The linear correlation coefficients of different isotherm models were obtained. Results revealed that the Langmuir isotherm fitted the experimental data better than the others and based on the Langmuir model equation, maximum adsorption capacity of 4C2NP onto SWCNTs and MWCNTs were 1.44 and 4.42 mg/g, respectively. The observed changes in the standard Gibbs free energy, standard enthalpy and standard entropy showed that the adsorption of 4C2NP onto SWCNTs and MWCNTs is spontaneous and exothermic in the temperature range of 298–328 K. PMID:23369489

Interfacial activity in alkaline flooding enhanced oil recovery

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

Chan, M.K.

1981-01-01

The ionization of long-chained organic acids in the crude oil to form soaps was shown to be primarily responsible for the lowering of oil-water interfacial tension at alkaline pH. These active acids can be concentrated by silica gel chromatography into a minor polar fraction. An equilibrium chemical model was proposed based on 2 competing reactions: the ionization of acids to form active anions, and the formation of undissociated soap between acid anions and sodium ions. It correlates the interfacial activity with the interfacial concentration of active acid anions which is expressed in terms of the concentrations of the chemical speciesmore » in the system. The model successfully predicts the observed oil-alkaline solution interfacial phenomenon, including its dependence on pH, alkali and salt concentrations, type of acid present and type of soap formed. Flooding at different alkali concentrations to activate different acid species present in the crude was shown to give better recovery than flooding at a single high alkali concentration. Treating the crude oil with a dilute solution of mineral acids liberates additional free active acids and yields better interfacial activity during subsequent alkali contact.« less

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Dynamics of pH modification of an acidic protein bait used for tropical fruit flies (Diptera: Tephritidae).

PubMed

Heath, Robert R; Vazquez, Aime; Schnell, Elena Q; Villareal, Janett; Kendra, Paul E; Epsky, Nancy D

2009-12-01

Several species of Anastrepha and Bactrocera fruit flies (Diptera: Tephritidae) are captured in traps baited with the protein bait NuLure combined with borax (sodium tetraborate decahydrate) in an aqueous solution, typically 9% NuLure (vol:vol) with 3% borax (wt:vol). NuLure is an acid hydrolysate of corn and has an acidic pH. Addition of borax makes the solution more alkaline, and increase in alkalinity results in increase of ammonia release from the bait solution. This is a very dynamic system, with resultant pH affected by factors such as the amount of borax added, the pH of the water used for preparation, the age of the bait solution, and the development of microbial growth. Problems with borax include amount needed to increase alkalinity of NuLure solutions, which creates difficulties in disposing of spent bait in fruit fly trapping programs. Therefore, research was conducted to evaluate NaOH as an alternative method to increase alkalinity of NuLure solutions. Laboratory experiments compared effect of NaOH versus borax for pH modification on changes in pH and ammonia content of NuLure solutions over time. Although NuLure/NaOH solutions could be adjusted to a more alkaline pH than NuLure/borax solutions, borax plays a critical role in pH stability over time. However, the pH of NuLure/NaOH is stabilized when propylene glycol (10% vol:vol) was used to prepare the bait solution. The use of NaOH can provide an alternative to the use of borax to increase bait solution alkalinity.

Molecular Imprinted Polymer of Methacrylic Acid Functionalised β-Cyclodextrin for Selective Removal of 2,4-Dichlorophenol

PubMed Central

Surikumaran, Hemavathy; Mohamad, Sharifah; Sarih, Norazilawati Muhamad

2014-01-01

This work describes methacrylic acid functionalized β-cyclodextrin (MAA-βCD) as a novel functional monomer in the preparation of molecular imprinted polymer (MIP MAA-βCD) for the selective removal of 2,4-dichlorophenol (2,4-DCP). The polymer was characterized using Fourier Transform Infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET) and Field Emission Scanning Electron Microscopy (FESEM) techniques. The influence of parameters such as solution pH, contact time, temperature and initial concentrations towards removal of 2,4-DCP using MIP MAA-βCD have been evaluated. The imprinted material shows fast kinetics and the optimum pH for removal of 2,4-DCP is pH 7. Compared with the corresponding non-imprinted polymer (NIP MAA-βCD), the MIP MAA-βCD exhibited higher adsorption capacity and outstanding selectivity towards 2,4-DCP. Freundlich isotherm best fitted the adsorption equilibrium data of MIP MAA-βCD and the kinetics followed a pseudo-second-order model. The calculated thermodynamic parameters showed that adsorption of 2,4-DCP was spontaneous and exothermic under the examined conditions. PMID:24727378

The amphoteric effect on friction between the bovine cartilage/cartilage surfaces under slightly sheared hydration lubrication mode.

PubMed

Pawlak, Zenon; Gadomski, Adam; Sojka, Michal; Urbaniak, Wieslaw; Bełdowski, Piotr

2016-10-01

The amphoteric effect on the friction between the bovine cartilage/cartilage contacts has been found to be highly sensitive to the pH of an aqueous solution. The cartilage surface was characterized using a combination of the pH, wettability, as well as the interfacial energy and friction coefficient testing methods to support lamellar-repulsive mechanism of hydration lubrication. It has been confirmed experimentally that phospholipidic multi-bilayers are essentially described as lamellar frictionless lubricants protecting the surface of the joints against wear. At the hydrophilicity limit, the low friction would then be due to (a) lamellar slippage of bilayers and (b) a short-range (nanometer-scale) repulsion between the interfaces of negatively charged (PO4(-)) cartilage surfaces, and in addition, contribution of the extracellular matrix (ECM) collagen fibers, hyaluronate, proteoglycans aggregates (PGs), glycoprotein termed lubricin and finally, lamellar PLs phases. In this paper we demonstrate experimentally that the pH sensitivity of cartilage to friction provides a novel concept in joint lubrication on charged surfaces. Copyright © 2016 Elsevier B.V. All rights reserved.

Optical measurement of acidification of human dental plaque in vitro

NASA Astrophysics Data System (ADS)

Graham, Jasmine Y.; Nelson, Leonard Y.; Seibel, Eric J.

2018-02-01

A pH measurement of oral biofilms is helpful for monitoring the impact of acidogenic bacteria in the caries process. Demineralization of dental enamel is closely related to the time dependent pH of human plaque. Therefore, providing a means to easily measure the local pH of biofilms is a useful clinical diagnostic in the arsenal of caries prevention tools. Optical measurement methods of plaque metabolism can use intrinsic fluorescence or extrinsic fluorescence from added dyes. Autofluorescence spectral features of human oral biofilms at green (500 nm) and red (634 nm) fluorescence wavelengths using 405 nm excitation did not demonstrate a spectral or intensity shift between neutral and acidic conditions. Chlorin e6, an ingredient in chlorophyllin food supplement, exhibited a spectral and intensity shift of fluorescence emission in buffered solutions, but this quantitative pH-dependence was not transferable to a human plaque environment. Finally, a ratiometric quantitative pH measure was achieved by exciting (405 nm laser) a mixture of two dyes, fluorescein and rhodamine B. This two-dye mixture produced two strong fluorescent bands centered at 515 nm (fluorescein) and 580 nm (rhodamine B), where the 515 nm band was pH sensitive and the 580 nm band served as a pH insensitive reference. This dual-dye fluorescence ratio exhibited a linear response over pH 7 to 5 in human oral biofilms during a sugar challenge. We have explored methods to use non-contact, optical measures of local acidity levels in difficult to access dental locations such as occlusal fissures using various pH sensitive fluorescent dye systems.

Response surface modeling of boron adsorption from aqueous solution by vermiculite using different adsorption agents: Box-Behnken experimental design.

PubMed

Demirçivi, Pelin; Saygılı, Gülhayat Nasün

2017-07-01

In this study, a different method was applied for boron removal by using vermiculite as the adsorbent. Vermiculite, which was used in the experiments, was not modified with adsorption agents before boron adsorption using a separate process. Hexadecyltrimethylammonium bromide (HDTMA) and Gallic acid (GA) were used as adsorption agents for vermiculite by maintaining the solid/liquid ratio at 12.5 g/L. HDTMA/GA concentration, contact time, pH, initial boron concentration, inert electrolyte and temperature effects on boron adsorption were analyzed. A three-factor, three-level Box-Behnken design model combined with response surface method (RSM) was employed to examine and optimize process variables for boron adsorption from aqueous solution by vermiculite using HDTMA and GA. Solution pH (2-12), temperature (25-60 °C) and initial boron concentration (50-8,000 mg/L) were chosen as independent variables and coded x 1 , x 2 and x 3 at three levels (-1, 0 and 1). Analysis of variance was used to test the significance of variables and their interactions with 95% confidence limit (α = 0.05). According to the regression coefficients, a second-order empirical equation was evaluated between the adsorption capacity (q i ) and the coded variables tested (x i ). Optimum values of the variables were also evaluated for maximum boron adsorption by vermiculite-HDTMA (HDTMA-Verm) and vermiculite-GA (GA-Verm).

Facile functionalized of SBA-15 via a biomimetic coating and its application in efficient removal of uranium ions from aqueous solution.

PubMed

Gao, Jun-Kai; Hou, Li-An; Zhang, Guang-Hui; Gu, Ping

2015-04-09

A novel dopamine-functionalized mesoporous silica (DMS), synthesized by grafting dopamine onto a mesoporous molecular sieve (SBA-15), was developed as a sorbent to extract U(VI) from aqueous solution. The method used to modify SBA-15 was simple, facile and cost-effective. The DMS was characterized by SEM, TEM, XRD and BET, showing that the material had an ordered mesoporous structure and a large surface area. The effect of contact time, pH, ionic strength, temperature, and solid-liquid ratio on the sorption process was investigated. It was demonstrated that the adsorption of U(VI) by DMS was fast and that it can be described by the pseudo-second order-equation where the equilibrium time was 20 min. Additionally, the adsorption isotherm data were fitted well by the Langmuir model with the maximum adsorption capacity of DMS of 196 mg/g at pH 6.0. Furthermore, the influence of the K(+) and Na(+) concentrations and solid-to-liquid ratio on the sorption was very weak, and the values of the thermodynamic parameters revealed that the sorption process was exothermic and spontaneous. All the results suggested that the DMS could be used as an excellent adsorbent to remove U(VI) from aqueous solution. Copyright © 2014 Elsevier B.V. All rights reserved.

Removal of chromium (VI) from aqueous solution using walnut hull.

PubMed

Wang, Xue Song; Li, Zhi Zhong; Tao, Sheng Rong

2009-02-01

In this study, removal of chromium (VI) from aqueous solution by walnut hull (a local low-cost adsorbent) was studied. The extent of adsorption was investigated as a function of solution pH, contact time, adsorbent and adsorbate concentration, reaction temperature and supporting electrolyte (sodium chloride). The Cr (VI) removal was pH-dependent, reaching a maximum (97.3%) at pH 1.0. The kinetic experimental data were fitted to the first-order, modified Freundlich, intraparticle diffusion and Elovich models and the corresponding parameters were obtained. A 102.78 kJ/mol Ea (activation energy) for the reaction of chromium (VI) adsorption onto walnut indicated that the rate-limiting step in this case might be a chemically controlled process. Both the Langmuir and Freundlich isotherms were suitable for describing the biosorption of chromium (VI) onto walnut hull. The uptake of chromium (VI) per weight of adsorbent increased with increasing initial chromium (VI) concentration up to 240-480 mg/L, and decreased sharply with increasing adsorbent concentration ranging from 1.0 to 5.0 g/L. An increase in sodium chloride (as supporting electrolyte) concentration was found to induce a negative effect while an increase in temperature was found to give rise to a positive effect on the chromium (VI) adsorption process. Compared to the various other adsorbents reported in the literature, the walnut hull in this study shows very good promise for practical applicability.

Desorption of 137Cs from Brachythecium mildeanum moss using acid solutions with pH 4.60-6.50

NASA Astrophysics Data System (ADS)

Čučulović, Ana; Veselinović, Dragan

2015-12-01

The desorption of 137Cs from the moss Brachythecium mildeanum (Schimp.) was performed using the following solutions: H2SO4 ( I), HNO3 ( II), H2SO4 + HNO3 ( III) with pH values of 4.60, 5.15, and 5.75, respectively, as well as distilled water (D) with pH 6.50. After five successive desorptions, each lasting 24 h, 20.5-37.6% 137Cs was desorbed from the moss using these solutions, while 30.7% of the starting content was desorbed using distilled water. The first desorption removed the highest percent of the original content of 137Cs in the moss (11.3-18.4%). This was determined by measuring 137Cs activity. If the current results are compared with those obtained earlier it may be concluded that 137Cs desorption from mosses is not species-dependent. The obtained results indicate the necessity of investigating the influence of acid rain, or rather, of H+ ions, on desorption of other ions from biological systems, i.e., the role of H+ ions in spreading other polluting compounds and thus producing secondary environmental pollution. From the results of this study it follows that acid rain will lead, through H+ ion action, to a similar increasing pollution of fallout waters with other ionic compounds which may not be present in the water before the contact with the plants and thus enable the pollution spreading. In the investigated system, the replacement of H+ ions from acid rains by more dangerous radioactive ions occured, increasing the concentration of the radioactive ions in the water, which demonstrates that the same process takes place in fallout water.

Reactive solute transport in streams: A surface complexation approach for trace metal sorption

USGS Publications Warehouse

Runkel, Robert L.; Kimball, Briant A.; McKnight, Diane M.; Bencala, Kenneth E.

1999-01-01

A model for trace metals that considers in-stream transport, metal oxide precipitation-dissolution, and pH-dependent sorption is presented. Linkage between a surface complexation submodel and the stream transport equations provides a framework for modeling sorption onto static and/or dynamic surfaces. A static surface (e.g., an iron- oxide-coated streambed) is defined as a surface with a temporally constant solid concentration. Limited contact between solutes in the water column and the static surface is considered using a pseudokinetic approach. A dynamic surface (e.g., freshly precipitated metal oxides) has a temporally variable solid concentration and is in equilibrium with the water column. Transport and deposition of solute mass sorbed to the dynamic surface is represented in the stream transport equations that include precipitate settling. The model is applied to a pH-modification experiment in an acid mine drainage stream. Dissolved copper concentrations were depressed for a 3 hour period in response to the experimentally elevated pH. After passage of the pH front, copper was desorbed, and dissolved concentrations returned to ambient levels. Copper sorption is modeled by considering sorption to aged hydrous ferric oxide (HFO) on the streambed (static surface) and freshly precipitated HFO in the water column (dynamic surface). Comparison of parameter estimates with reported values suggests that naturally formed iron oxides may be more effective in removing trace metals than synthetic oxides used in laboratory studies. The model's ability to simulate pH, metal oxide precipitation-dissolution, and pH-dependent sorption provides a means of evaluating the complex interactions between trace metal chemistry and hydrologic transport at the field scale.

New analytical methodology for analysing S(IV) species at low pH solutions by one stage titration method (bichromatometry) with a clear colour change. Could potentially replace the state-of-art-method iodometry at low pH analysis due higher accuracy

PubMed Central

Galfi, Istvan; Virtanen, Jorma; Gasik, Michael M.

2017-01-01

A new, faster and more reliable analytical methodology for S(IV) species analysis at low pH solutions by bichromatometry is proposed. For decades the state of the art methodology has been iodometry that is still well justified method for neutral solutions, thus at low pH media possess various side reactions increasing inaccuracy. In contrast, the new methodology has no side reactions at low pH media, requires only one titration step and provides a clear color change if S(IV) species are present in the solution. The method is validated using model solutions with known concentrations and applied to analyses of gaseous SO2 from purged solution in low pH media samples. The results indicate that bichromatometry can accurately analyze SO2 from liquid samples having pH even below 0 relevant to metallurgical industrial processes. PMID:29145479

Considerations on prevention of phlebitis and venous pain from intravenous prostaglandin E(1) administration by adjusting solution pH: in vitro manipulations affecting pH.

PubMed

Kohno, Emiko; Nishikata, Mayumi; Okamura, Noboru; Matsuyama, Kenji

2008-01-01

Prostaglandin E(1) (PGE(1); Alprostadil Alfadex) is a potent vasodilator and inhibitor of platelet aggregation used to treat patients with peripheral vascular disease. The main adverse effects of intravenous PGE(1) administration, phlebitis and venous pain, arise from the unphysiologically low pH of infusion solutions. When PGE(1) infusion solutions with a pH value greater then 6 are used, phlebitis and venous pain are considered to be avoidable. Beginning with a PGE(1) infusion solution with pH greater than 6, we add the amount of 7% sodium bicarbonate needed to bring the solution to pH 7.4 if phlebitis or venous pain develops. In the present study we established a convenient nomogram showing the relationship between the titratable acidity of various infusion solutions and the volume of 7% sodium bicarbonate required to attain pH 7.4 for preventing the phlebitis and venous pain associated with PGE(1) infusion.

Silicate release from glass for pharmaceutical preparations.

PubMed

Bohrer, Denise; Bortoluzzi, Fabiana; Nascimento, Paulo Cícero; Carvalho, Leandro Machado; Ramirez, Adrian Gustavo

2008-05-01

Glass is made of polymeric silica and other minor components, which are necessary for turning the silica into a material more easily moldable and resistant to temperature changes. Glass containers for pharmaceutical usage are classified according to their resistance to a chemical attack, a test carried out in the presence of water and heat. The test is designed to show the released alkalinity, a variable dependent on the amount of sodium oxide, one of the minor components added to the glass mass. In this work, the release of silica from glass by action of constituents from pharmaceutical formulations was investigated. The study included products used in large volumes and usually stored in glass containers. Solutions of amino acids, electrolytes, glucose, oligoelements and others such as heparin and sodium bicarbonate were individually stored in glass containers and heated at 121 degrees C for 30min, as in the water attack test. The test was also carried out only with water, where the pH varied from 2 to 12. The released silicate was measured either by photometry or atomic absorption spectrometry, depending on the nature of the sample. The results showed that silicate is released during the heating cycle even if the contact is with pure water only. The pH exerts a considerable influence on the release, being that the higher the pH, the higher the silica dissolved. An elevated pH, however, is not the only factor responsible for silica dissolution. While in the solutions of NaCl, KCl, Mg Cl2 and ZnSO4 and in most of the amino acids, the concentration of silicate was as high as in pure water (0.1-1.0mg Si/L). In the solutions of sodium acetate, bicarbonate and gluconate, its concentration was much higher, over 30mg Si/L. These results were confirmed by the analysis of commercial products, where in solutions of amino acids the level of silicate ranged from 0.14 to 0.19mg Si/L. On the other hand, calcium gluconate, sodium bicarbonate and potassium phosphate presented silicate levels from 1 to 4mg/L. Although silica is not considered a toxic substance for humans, it is necessary to be aware of its presence in solutions for parenteral nutrition due to the direct introduction into the bloodstream and the large volume usually administrated, even to pre-term infants.

77 FR 64812 - National Institute of General Medical Sciences; Notice of Closed Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-23

... Hilton Bethesda, 8120 Wisconsin Avenue, Bethesda, MD 20814. Contact Person: Saraswathy Seetharam, Ph.D... Drive, Room 3An18K, Bethesda, MD 20892 (Telephone Conference Call). Contact Person: Brian R. Pike, Ph.D... Chemistry Research; 93.862, Genetics and Developmental Biology Research; 93.88, Minority Access to Research...

Rapid and high-performance adsorptive removal of hazardous acridine orange from aqueous environment using Abelmoschus esculentus seed powder: Single- and multi-parameter optimization studies.

PubMed

Nayak, Ashish Kumar; Pal, Anjali

2018-07-01

In this research, the performance of naturally abundant lignocellulosic by-product, Abelmoschus esculentus, and its processed seed powder referred as AESP, as a potential biosorbent for the removal of acridine orange (AO) from the aqueous environment was examined. The AESP biosorbent was characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) analysis, diffuse reflectance spectroscopy (DRS), Fourier transform infrared (FTIR) and pH ZPC analyses. The average size of the biosorbent according to particle size distribution analysis was found to be ∼132 μm. The batch adsorption experiments were conducted by altering the parameters such as contact time, solution pH, biosorbent dosage, initial dye concentration, stirring speed and temperature. Sorption of cationic AO dye onto AESP was found to be rapid, and the equilibrium condition reached within 30 min. The isotherms (Langmuir, Freundlich, Redlich-Peterson and Sips), kinetic models (pseudo-first order, pseudo-second order, Elovich, intra-particle diffusion, Bangham and modified-Freundlich models) and thermodynamic parameters were also evaluated. High values of determination coefficients (R 2 ) and minimal values of non-linear error functions (i.e. HYBRD, RMSE, MPSD, ARE, APE and χ 2 ) indicated that experimental data were best fitted with Sips isotherm and pseudo-second order kinetic model. Accordingly, the maximum loading capacity of AESP was found to be 259.4, 284.3 and 346.5 mg/g for the temperatures of 15, 30 and 45 °C, respectively. The thermodynamic parameters showed that the adsorption of AO onto the AESP surface was an endothermic and spontaneous process. Besides these, the central composite experimental design (CCD) superimposed with response surface methodology (RSM) modeling was also employed to investigate the effect of four significant parameters (solution pH, contact time, initial AO concentration and AESP dosage) and their interaction-term effects on the adsorption capacity of AESP and to formulate the mathematical model for the experimental data using multi-variate statistical analysis. Maximum dye uptake capacity under the optimum conditions of variables (pH 8.96, contact time 32.06 min, initial dye concentration 867.71 mg/L and AESP dosage 1.89 g/L) was 312.1 mg/g at temperature 30 °C, and it was found to be very close to the experimentally determined values (313.4 ± 0.057 mg/g). The promising reusability potential of AESP using 0.1 M HCl, implied that, the lignocellulosic biosorbent AESP might be helpful for the appropriate designing of the environmental-friendly purification systems. Copyright © 2018 Elsevier Ltd. All rights reserved.

Status of the effectiveness of contact lens solutions against keratitis-causing pathogens.

PubMed

Siddiqui, Ruqaiyyah; Lakhundi, Sahreena; Khan, Naveed Ahmed

2015-02-01

The aim of this study was to assess the antimicrobial effects of marketed contact lens disinfecting solutions. Using ISO 14729 Stand-Alone Test for disinfecting solutions, bactericidal, fungicidal and amoebicidal assays of eight different contact lens solutions including: ReNu MultiPlus, DuraPlus, Ultimate Plus, OptiFree Express, Kontex Clean, Kontex Normal, Kontex Multisol extra(+), Kontex Soak were performed. The efficacy of contact lens solutions was determined against keratitis-causing microbes, namely: Pseudomonas aeruginosa, Serratia marcescens, Staphylococcus aureus, Methicillin-resistant Staphylococcus aureus, Fusarium solani and Acanthamoeba castellanii. The results revealed that ReNu MultiPlus, DuraPlus and OptiFree Express were effective in killing bacterial and fungal pathogens as per manufacturer's minimum recommended disinfection time. Ultimate Plus was effective against F. solani and MRSA but ineffective against P. aeruginosa, S. marcescens and S. aureus. Of concern however, is that none of the locally formulated contact lens disinfecting solutions from Pakistan, i.e., Kontex Clean, Kontex Normal, Kontex Multisol extra(+) and Kontex Soak were effective against any of the keratitis-causing organisms tested. All eight contact lens disinfecting solutions were unable to destroy Acanthamoeba cysts. Because such ineffective contact lens disinfection solutions present a major risk to public health, these findings are of great concern to the health officials and to the manufacturers of the contact lens disinfection solutions and effective solutions are needed, along with emphasis on proper hygiene for contact lens care and special guidelines for developing countries regarding the manufacture and storage of contact lens disinfecting solutions. Copyright © 2014 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

21 CFR 800.10 - Contact lens solutions; sterility.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Contact lens solutions; sterility. 800.10 Section...) MEDICAL DEVICES GENERAL Requirements for Specific Medical Devices § 800.10 Contact lens solutions... ophthalmic use, including contact lens solutions, should be sterile. It is further evident that such...

21 CFR 800.10 - Contact lens solutions; sterility.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Contact lens solutions; sterility. 800.10 Section...) MEDICAL DEVICES GENERAL Requirements for Specific Medical Devices § 800.10 Contact lens solutions... ophthalmic use, including contact lens solutions, should be sterile. It is further evident that such...

21 CFR 800.10 - Contact lens solutions; sterility.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Contact lens solutions; sterility. 800.10 Section...) MEDICAL DEVICES GENERAL Requirements for Specific Medical Devices § 800.10 Contact lens solutions... ophthalmic use, including contact lens solutions, should be sterile. It is further evident that such...

21 CFR 800.10 - Contact lens solutions; sterility.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Contact lens solutions; sterility. 800.10 Section...) MEDICAL DEVICES GENERAL Requirements for Specific Medical Devices § 800.10 Contact lens solutions... ophthalmic use, including contact lens solutions, should be sterile. It is further evident that such...

21 CFR 800.10 - Contact lens solutions; sterility.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Contact lens solutions; sterility. 800.10 Section...) MEDICAL DEVICES GENERAL Requirements for Specific Medical Devices § 800.10 Contact lens solutions... ophthalmic use, including contact lens solutions, should be sterile. It is further evident that such...

Electronic control of H+ current in a bioprotonic device with Gramicidin A and Alamethicin

NASA Astrophysics Data System (ADS)

Hemmatian, Zahra; Keene, Scott; Josberger, Erik; Miyake, Takeo; Arboleda, Carina; Soto-Rodríguez, Jessica; Baneyx, François; Rolandi, Marco

2016-10-01

In biological systems, intercellular communication is mediated by membrane proteins and ion channels that regulate traffic of ions and small molecules across cell membranes. A bioelectronic device with ion channels that control ionic flow across a supported lipid bilayer (SLB) should therefore be ideal for interfacing with biological systems. Here, we demonstrate a biotic-abiotic bioprotonic device with Pd contacts that regulates proton (H+) flow across an SLB incorporating the ion channels Gramicidin A (gA) and Alamethicin (ALM). We model the device characteristics using the Goldman-Hodgkin-Katz (GHK) solution to the Nernst-Planck equation for transport across the membrane. We derive the permeability for an SLB integrating gA and ALM and demonstrate pH control as a function of applied voltage and membrane permeability. This work opens the door to integrating more complex H+ channels at the Pd contact interface to produce responsive biotic-abiotic devices with increased functionality.

A dense and strong bonding collagen film for carbon/carbon composites

NASA Astrophysics Data System (ADS)

Cao, Sheng; Li, Hejun; Li, Kezhi; Lu, Jinhua; Zhang, Leilei

2015-08-01

A strong bonding collagen film was successfully prepared on carbon/carbon (C/C) composites. The surface conditions of the modified C/C composites were detected by contact angle measurements, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectra. The roughness, optical morphology, bonding strength and biocompatibility of collagen films at different pH values were detected by confocal laser scanning microscope (CLSM), universal test machine and cytology tests in vitro. After a 4-h modification in 30% H2O2 solution at 100 °C, the contact angle on the surface of C/C composites was decreased from 92.3° to 65.3°. Large quantities of hydroxyl, carboxyl and carbonyl functional groups were formed on the surface of the modified C/C composites. Then a dense and continuous collagen film was prepared on the modified C/C substrate. Bonding strength between collagen film and C/C substrate was reached to 8 MPa level when the pH value of this collagen film was 2.5 after the preparing process. With 2-day dehydrathermal treatment (DHT) crosslinking at 105 °C, the bonding strength was increased to 12 MPa level. At last, the results of in vitro cytological test showed that this collagen film made a great improvement on the biocompatibility on C/C composites.

Sequestration of toxic Pb(II) ions by chemically treated rubber (Hevea brasiliensis) leaf powder.

PubMed

Kamal, Megat Hanafiah Megat Ahmad; Azira, Wan Mat Khalir Wan Khaima; Kasmawati, Mohamed; Haslizaidi, Zakaria; Saime, Wan Ngah Wan

2010-01-01

Rubber leaf powder (an agricultural waste) was treated with potassium permanganate followed by sodium carbonate and its performance in the removal of Pb(II) ions from aqueous solution was evaluated. The interactions between Pb(II) ions and functional groups on the adsorbent surface were confirmed by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) coupled with X-ray energy dispersive spectroscopy (EDX). The effects of several important parameters which can affect adsorption capacity such as pH, adsorbent dosage, initial lead concentration and contact time were studied. The optimum pH range for lead adsorption was 4-5. Even at very low adsorbent dosage of 0.02 g, almost 100% of Pb(II) ions (23 mg/L) could be removed. The adsorption capacity was also dependent on lead concentration and contact time, and relatively a short period of time (60-90 min) was required to reach equilibrium. The equilibrium data were analyzed with Langmuir, Freundlich and Dubinin-Radushkevich isotherms. Based on Langmuir model, the maximum adsorption capacity of lead was 95.3 mg/g. Three kinetic models including pseudo first-order, pseudo second-order and Boyd were used to analyze the lead adsorption process, and the results showed that the pseudo second-order fitted well with correlation coefficients greater than 0.99.

Characterization and evaluation of amorphous carbon thin film (ACTF) for sodium ion adsorption

NASA Astrophysics Data System (ADS)

Fathy, Mahmoud; Mousa, Mahmoud Ahmed; Moghny, Th. Abdel; Awadallah, Ahmed E.

2017-12-01

The removal of sodium ions from aqueous solutions by adsorption onto amorphous carbon thin film (ACTF) has been studied in batch mode. In this work, the ACTF as new adsorbent was synthesized based on rice straw, then its structure and properties were taken into consideration to study its ability to adsorb sodium ions from synthetic water. The influence of pH, contact time, and temperature of the ion adsorption on ACTF was also studied using batch tests. We found that the contact time of sodium adsorption and its isothermal adsorption studied were described by pseudo-second-order kinetic model and Langmuir isotherm, respectively. Our results indicated that the adsorption of sodium ions on ACTF become be stronger and depends on pH, furthermore, the maximum adsorption capacities of sodium on ACTF recorded 107, 120 and 135 mg g-1 at 35, 45, and 65 °C. The thermodynamic parameters explain that the adsorption of sodium ions on ACTF is a spontaneous process and endothermic reaction. According to adsorption studies, we found that the ACTF can be used effectively for ion chromatography or desalinate sodium ion using ion exchange process in the hybrid desalination process with insignificant loss of adsorption capacity. However, the ACTF has better properties than any other carbon materials obtained from an agricultural byproduct.

A Hand-held Fiber-optic Implement for the Site-specific Delivery of Photosensitizer and Singlet Oxygen

PubMed Central

Mahendran, Adaickapillai; Kopkalli, Yasemin; Ghosh, Goutam; Ghogare, Ashwini; Minnis, Mihaela; Kruft, Bonnie I.; Zamadar, Matibur; Aebisher, David; Davenport, Lesley; Greer, Alexander

2012-01-01

We have constructed a fiber optic device that internally flows triplet oxygen and externally produces singlet oxygen, causing a reaction at the (Z)-1,2-dialkoxyethene spacer group, freeing a pheophorbide sensitizer upon the fragmentation of a reactive dioxetane intermediate. The device can be operated and sensitizer photorelease observed using absorption and fluorescence spectroscopy. We demonstrate the preference of sensitizer photorelease when the probe tip is in contact with octanol or lipophilic media. A first-order photocleavage rate constant of 1.13 h−1 was measured in octanol where dye desorption was not accompanied by readsorption. When the probe tip contacts aqueous solution, the photorelease was inefficient because most of the dye adsorbed on the probe tip, even after the covalent ethene spacer bonds have been broken. The observed stability of the free sensitizer in lipophilic media is reasonable even though it is a pyropheophorbide-a derivative that carries a p-formylbenzylic alcohol substituent at the carboxylic acid group. In octanol or lipid systems, we found that the dye was not susceptible to hydrolysis to pyropheophorbide-a, otherwise a pH effect was observed in a binary methanol-water system (9:1) at pH below 2 or above 8. PMID:21790616

Removal of Methylene Blue and Orange-G from Waste Water Using Magnetic Biochar

NASA Astrophysics Data System (ADS)

Mubarak, N. M.; Fo, Y. T.; Al-Salim, Hikmat Said; Sahu, J. N.; Abdullah, E. C.; Nizamuddin, S.; Jayakumar, N. S.; Ganesan, P.

2015-04-01

The study on the removal of methylene blue (MB) and orange-G dyes using magnetic biochar derived from the empty fruit bunch (EFB) was carried out. Process parameters such as pH, adsorbent dosage, agitation speed and contact time were optimized using Design-Expert Software v.6.0.8. The statistical analysis reveals that the optimum conditions for the maximum adsorption of MB are at pH 2 and pH 10, dosage 1.0 g, and agitation speed and contact time of 125 rpm and 120 min respectively. While for orange-G, at pH 2, dosage 1.0 g, and agitation speed and contact time of 125 rpm and 120 min respectively. The maximum adsorption capacity of 31.25 mg/g and 32.36 mg/g for MB and orange-G respectively. The adsorption kinetic for both dyes obeyed pseudo-second order.

Acidic and basic solutions dissolve protein plugs made of lithostathine complicating choledochal cyst/pancreaticobiliary maljunction.

PubMed

Kaneko, Kenitiro; Ono, Yasuyuki; Tainaka, Takahisa; Sumida, Wataru; Ando, Hisami

2009-07-01

Symptoms of choledochal cysts are caused by protein plugs made of lithostathine, which block the long common channel and increase pancreaticobiliary ductal pressure. Agents that dissolve protein plugs can provide relief from or prevent symptoms. In the present study, drugs reportedly effective for pancreatic and biliary stones were used in dissolution tests. Protein plugs were obtained from choledochal cysts during surgery in two children (5- and 6-year-old girls). Plugs approximately 2 mm in diameter were immersed in citric acid, tartaric acid, dimethadione, bromhexine, dehydrocholic acid, sodium citrate, hydrochloric acid, and sodium hydroxide solutions under observation with a digital microscope. The pH of each solution was measured using a pH meter. Plugs dissolved in citric acid (5.2 mM; pH 2.64), tartaric acid (6.7 mM; pH 2.51), dimethadione (75 mM; pH 3.70), hydrochloric acid (0.5 mM; pH 3.13), and sodium hydroxide (75 mM; pH 12.75) solutions. Plugs did not dissolve in dimethadione (7.5 mM; pH 4.31), bromhexine (0.1%; pH 4.68), dehydrocholic acid (5%; pH 7.45), and sodium citrate (75 mM; pH 7.23) solutions. Protein plugs in choledochal cysts are dissolved in acidic and basic solutions, which may eliminate longitudinal electrostatic interactions of the lithostathine protofibrils.

Computer model of hydroponics nutrient solution pH control using ammonium.

PubMed

Pitts, M; Stutte, G

1999-01-01

A computer simulation of a hydroponics-based plant growth chamber using ammonium to control pH was constructed to determine the feasibility of such a system. In nitrate-based recirculating hydroponics systems, the pH will increase as plants release hydroxide ions into the nutrient solution to maintain plant charge balance. Ammonium is an attractive alternative to traditional pH controls in an ALSS, but requires careful monitoring and control to avoid overdosing the plants with ammonium. The primary advantage of using NH4+ for pH control is that it exploits the existing plant nutrient uptake charge balance mechanisms to maintain solution pH. The simulation models growth, nitrogen uptake, and pH of a l-m2 stand of wheat. Simulation results indicated that ammonium-based control of nutrient solution pH is feasible using a proportional integral controller. Use of a 1 mmol/L buffer (Ka = 1.6 x 10(-6)) in the nutrient solution is required.

Method for producing rapid pH changes

DOEpatents

Clark, John H.; Campillo, Anthony J.; Shapiro, Stanley L.; Winn, Kenneth R.

1981-01-01

A method of initiating a rapid pH change in a solution by irradiating the solution with an intense flux of electromagnetic radiation of a frequency which produces a substantial pK change to a compound in solution. To optimize the resulting pH change, the compound being irradiated in solution should have an excited state lifetime substantially longer than the time required to establish an excited state acid-base equilibrium in the solution. Desired pH changes can be accomplished in nanoseconds or less by means of picosecond pulses of laser radiation.

Method for producing rapid pH changes

DOEpatents

Clark, J.H.; Campillo, A.J.; Shapiro, S.L.; Winn, K.R.

A method of initiating a rapid pH change in a solution comprises irradiating the solution with an intense flux of electromagnetic radiation of a frequency which produces a substantial pK change to a compound in solution. To optimize the resulting pH change, the compound being irradiated in solution should have an excited state lifetime substantially longer than the time required to establish an excited state acid-base equilibrium in the solution. Desired pH changes can be accomplished in nanoseconds or less by means of picosecond pulses of laser radiation.

Optimization of thiamethoxam adsorption parameters using multi-walled carbon nanotubes by means of fractional factorial design.

PubMed

Panić, Sanja; Rakić, Dušan; Guzsvány, Valéria; Kiss, Erne; Boskovic, Goran; Kónya, Zoltán; Kukovecz, Ákos

2015-12-01

The aim of this work was to evaluate significant factors affecting the thiamethoxam adsorption efficiency using oxidized multi-walled carbon nanotubes (MWCNTs) as adsorbents. Five factors (initial solution concentration of thiamethoxam in water, temperature, solution pH, MWCNTs weight and contact time) were investigated using 2V(5-1) fractional factorial design. The obtained linear model was statistically tested using analysis of variance (ANOVA) and the analysis of residuals was used to investigate the model validity. It was observed that the factors and their second-order interactions affecting the thiamethoxam removal can be divided into three groups: very important, moderately important and insignificant ones. The initial solution concentration was found to be the most influencing parameter on thiamethoxam adsorption from water. Optimization of the factors levels was carried out by minimizing those parameters which are usually critical in real life: the temperature (energy), contact time (money) and weight of MWCNTs (potential health hazard), in order to maximize the adsorbed amount of the pollutant. The results of maximal adsorbed thiamethoxam amount in both real and optimized experiments indicate that among minimized parameters the adsorption time is one that makes the largest difference. The results of this study indicate that fractional factorial design is very useful tool for screening the higher number of parameters and reducing the number of adsorption experiments. Copyright © 2015 Elsevier Ltd. All rights reserved.

Electropulse treatment of water solution of humic substances in a layer iron granules in process of water treatment

NASA Astrophysics Data System (ADS)

Lobanova, G. L.; Yurmazova, T. A.; Shiyan, L. N.; Machekhina, K. I.

2016-02-01

The present work is a part of a continuations study of the physical and chemical processes complex in natural waters containing humic-type organic substances at the influence of pulsed electrical discharges in a layer of iron pellets. The study of humic substances processing in the iron granules layer by means of pulsed electric discharge for the purpose of water purification from organic compounds humic origin from natural water of the northern regions of Russia is relevant for the water treatment technologies. In case of molar humate sodium - iron ions (II) at the ratio 2:3, reduction of solution colour and chemical oxygen demand occur due to the humate sodium ions and iron (II) participation in oxidation-reduction reactions followed by coagulation insoluble compounds formation at a pH of 6.5. In order to achieve this molar ratio and the time of pulsed electric discharge, equal to 10 seconds is experimentally identified. The role of secondary processes that occur after disconnection of the discharge is shown. The time of contact in active erosion products with sodium humate, equal to 1 hour is established. During this time, the value of permanganate oxidation and iron concentration in solution achieves the value of maximum permissible concentrations and further contact time increase does not lead to the controlled parameters change.

Properties of edible films based on pullulan-chitosan blended film-forming solutions at different pH

USDA-ARS?s Scientific Manuscript database

Influences of solution pH on the properties of pullulan-chitosan blended (Pul-Chi) films and the rheological properties of film-forming solutions were investigated. The extended conformation of chitosan in pH 4.0 solution increased intermolecular interactions with pullulan compared to the more compa...

Assessment of the effectiveness of orange (Citrus reticulata) peel in the recovery of nickel from electroplating wastewater.

PubMed

Hussein, Rim A

2014-12-01

Wastewater discharged from electroplating industry contains different concentrations of heavy metals, which when released into the environment pose a health hazard to human beings. The aim of this study was to assess the effectiveness of orange peel as an adsorbent in the recovery of Nickel (Ni) from electroplating wastewater. The effectiveness of orange peel as an adsorbent was assessed by determining the optimum conditions of adsorption (adsorbent dose, pH, and contact time), calculating the recovery percentage, and characterizing the orange peel sludge resulting from adsorption/desorption process as being hazardous or not. Under optimum conditions for adsorption, orange peel was found to be an effective adsorbent of Ni from electroplating wastewater. It achieved 59.28% removal of the metal from a solution containing 528 mg/l, at a dose of 60 g/l, at pH 7, and for 1-h contact time. The nickel uptake capacity of orange peel was calculated to be 5.2 mg/g. Using HCl for desorption of adsorbed Ni, a recovery of 44.46% of Ni discharged in the wastewater could be reached. Orange peel resulting from the adsorption/desorption process was characterized as being nonhazardous. Orange peel was found to be effective in the recovery of nearly half of the amount of Ni discharged in electroplating wastewater. Further studies are required to determine (a) the impact of the recovered NiCl2 solution on the quality of the plated product, (b) the effect of activation of orange peel on the adsorption process, and (c) the number of cycles during which orange peel can be reused as an effective adsorbent.

FY2017 ILAW Glass Corrosion Testing with the Single-Pass Flow-Through Method

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

Neeway, James J.; Asmussen, Robert M.; Cordova, Elsa

The inventory of immobilized low-activity waste (ILAW) produced at the Hanford Tank Waste Treatment and Immobilization Plant (WTP) will be disposed of at the near-surface, on-site Integrated Disposal Facility (IDF). When groundwater comes into contact with the waste form, the glass will corrode and radionuclides will be released into the near-field environment. Because the release of the radionuclides is dependent on the dissolution rate of the glass, it is important that the performance assessment (PA) model accounts for the dissolution rate of the glass as a function of various conditions. To accomplish this, an IDF PA glass dissolution model basedmore » on Transition State Theory (TST) can be employed. The model is able to account for changes in temperature, exposed surface area, and pH of the contacting solution as well as the effect of silicon solution concentrations, specifically the activity of orthosilicic acid (H4SiO4), whose concentration is directly linked to the glass dissolution rate. In addition, the IDF PA model accounts for the ion exchange process. The effect of temperature, pH, H4SiO4 activity, and the rate of ion exchange can be parameterized and implemented directly into the PA rate model. The rate model parameters are derived from laboratory tests with the single-pass flow-through (SPFT) method. The provided data can be used by glass researchers to further the understanding of ILAW glass behavior, by IDF PA modelers to use the rate model parameters in PA modeling efforts, and by Department of Energy (DOE) contractors and decision makers as they assess the IDF PA program.« less

Tetragonal Chicken Egg White Lysozyme Solubility in Sodium Chloride Solutions

NASA Technical Reports Server (NTRS)

Forsythe, Elizabeth L.; Judge, Russell A.; Pusey, Marc L.

1998-01-01

The solubility of chicken egg white lysozyme, crystallized in the tetragonal form was measured in sodium chloride solutions from 1.6 to 30.7 C, using a miniature column solubility apparatus. Sodium chloride solution concentrations ranged from 1 to 7% (w/v). The solutions were buffered with 0.1 M sodium acetate buffer with the solubility being measured at pH values in 0.2 pH unit increments in the range pH 4.0 to 5.4, with data also included at pH 4.5. Lysozyme solubility was found to increase with increases in temperature and decreasing salt concentration. Solution pH has a varied and unpredictable effect on solubility.

Slip stream apparatus and method for treating water in a circulating water system

DOEpatents

Cleveland, J.R.

1997-03-18

An apparatus is described for treating water in a circulating water system that has a cooling water basin which includes a slip stream conduit in flow communication with the circulating water system, a source of acid solution in flow communication with the slip stream conduit, and a decarbonator in flow communication with the slip stream conduit and the cooling water basin. In use, a slip stream of circulating water is drawn from the circulating water system into the slip stream conduit of the apparatus. The slip stream pH is lowered by contact with an acid solution provided from the source thereof. The slip stream is then passed through a decarbonator to form a treated slip stream, and the treated slip stream is returned to the cooling water basin. 4 figs.

Study of the Adsorption of Fission Products by the Soil of Ezeiza. Report No. 35; ESTUDIO DE LA ADSORCION DE PRODUCTOS DE FISION POR TIERRA DE EZEIZA. INFORME NO. 35

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

Anghileri, L.J.

1960-01-01

A study was made of the adsorptive properties of Ezeiza soil for fission products using an adsorption column technique and adsorption on suspensions. The tests showed that the upper soil level in the zone of Ezeiza is a good adsorber. For fission products in the presence of U, adsorption was over 75% of the activity, the fixation being dependent on the soil concentration, pH of the solution to be decontaminated, and the contact time. For Sr/sup 90/ the values were close to 99% with concentrations of the order of 25 g of soil/100 cc of solution. For Cs/sup 137/ themore » adsorption is almost complete (99%) with 15 g/cc. (J.S.R.)« less

Malachite green "a cationic dye" and its removal from aqueous solution by adsorption

NASA Astrophysics Data System (ADS)

Raval, Nirav P.; Shah, Prapti U.; Shah, Nisha K.

2017-11-01

Adsorption can be efficiently employed for the removal of various toxic dyes from water and wastewater. In this article, the authors reviewed variety of adsorbents used by various researchers for the removal of malachite green (MG) dye from an aqueous environment. The main motto of this review article was to assemble the scattered available information of adsorbents used for the removal of MG to enlighten their wide potential. In addition to this, various optimal experimental conditions (solution pH, equilibrium contact time, amount of adsorbent and temperature) as well as adsorption isotherms, kinetics and thermodynamics data of different adsorbents towards MG were also analyzed and tabulated. Finally, it was concluded that the agricultural solid wastes and biosorbents such as biopolymers and biomass adsorbents have demonstrated outstanding adsorption capabilities for removal of MG dye.

Activated carbon prepared from yerba mate used as a novel adsorbent for removal of tannery dye from aqueous solution.

PubMed

Linhares, Bruno; Weber, Caroline Trevisan; Foletto, Edson Luiz; Paz, Diego Silva; Mazutti, Marcio A; Collazzo, Gabriela Carvalho

2013-01-01

Activated carbon prepared from yerba mate (Ilex paraguariensis) was used as adsorbent for the removal of tannery dye from aqueous solution. The activated carbon was characterized, and it showed a mesoporous texture, with surface area of 537.4 m2 g(-1). The initial dye concentration, contact time and pH influenced the adsorption capacity. The equilibrium data were in good agreement with both Langmuir and Freundlich isotherms. The adsorption kinetics of the tannery dye on activated carbon prepared from yerba mate followed a pseudo-second-order model. The adsorption process was found to be controlled by both external mass-transfer and intraparticle diffusion, but the external diffusion was the dominating process. This work highlights the potential application of activated carbon produced from yerba mate in the field of adsorption.

Biosorption of Azo dyes by spent Rhizopus arrhizus biomass

NASA Astrophysics Data System (ADS)

Salvi, Neeta A.; Chattopadhyay, S.

2017-10-01

In the present study, spent Rhizopus arrhizus biomass was used for the removal of six azo dyes from aqueous solutions. The dye removal capacity of the biomass was evaluated by conducting batch tests as a function of contact time, biomass dosage, pH and initial dye concentrations. The pseudo-second-order kinetic model fitted well with the experimental data with correlation coefficients greater than 0.999, suggesting that chemisorptions might be the rate limiting step. The equilibrium sorption data showed good fit to the Langmuir isotherm model. Among the six dyes tested, the maximum monolayer adsorption capacity for fast red A and metanil yellow was found to be 108.8 and 128.5 mg/g, respectively. These encouraging results suggest that dead Rhizopus arrhizus biomass could be a potential biomaterial for the removal of azo dyes from aqueous dye solution.

A Preliminary Study of Europium Uptake by Yeast Cells. The Case of Kluveromyces Marxianus

NASA Astrophysics Data System (ADS)

Anagnostopoulos, V.; Symeopoulos, B.

2008-08-01

The objective of the present work is an exploration of a cost effective recovery of lanthanides, either for minimizing the industrial processes losses, or for reasons related to Radioactive Waste Management. Specifically, the uptake of europium from aqueous solutions by Kluveromyces marxianus cells was studied. Moreover, this biotechnological approach turns out to be environmental friendly, considering that cells of Kluveromyces marxianus are readily available as wastes from food fermentation industries. Europium [152Eu+154Eu]-labelled solutions were used providing better accuracy and reproducibility of measurements, mainly in low concentration range. The effect of pH, contact time and europium initial concentration were investigated. Adsorption data were fitted to Langmuir and Freundlich sorption models and Scatchard plots were used to reveal the existence of at least two types of binding sites.

Migration of wood-preserving chemicals in contaminated groundwater in a sand aquifer at Pensacola, Florida

USGS Publications Warehouse

Goerlitz, D.F.; Troutman, D.E.; Godsy, E.M.; Franks, B.J.

1985-01-01

Operation of a wood-preserving facility for nearly 80 years at Pensacola, FL, contaminated the near-surface groundwater with creosote and pentachlorophenol. The major source of aquifer contamination was unlined surface impoundments that were in direct hydraulic contact with the groundwater. Episodes of overtopping the impoundments and overland flow of treatment liquor and waste were also significant to the migration and contamination of the groundwater. Solutes contaminating the ground-water are mainly naphthalene and substituted phenols. Sorption did not influence retardation of solutes in transport in the groundwater. Phenol and the mono substituted methylphenols appear to be undergoing bio-transformation. Pentachlorophenol (PCP) was not found in significant concentrations in the groundwater possibly because the solubility of PCP is approximately 5 mg/L at pH 6, near the average acidity for the groundwater.

Magnetic graphene oxide for adsorption of organic dyes from aqueous solution

NASA Astrophysics Data System (ADS)

Drashya, Lal, Shyam; Hooda, Sunita

2018-05-01

Graphene oxide (GO), a 2-D carbon nanomaterial, large surface area, oxygen-containing groups (like: hydroxyl, epoxy and carboxyl) and excellent water dispersibility due to it is good adsorbent dye removal from pollutant water1. But it's difficult to separate GO from water after adsorption. Therefore, Iron oxide was introduced in Graphene oxide by decorating method to make separation more efficient2. We present herein a one step process to prepare Magnetic Graphene oxide (MGO). The Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD) and Raman Spectroscopy characterized the chemical structure of the MGO composite. The adsorption of dyes onto MGO was studied in relation to initial concentration of Dyes, contact time, adsorbent dose, temperature and pH value of solution. We have studied adsorption capacity of different dyes (Methylene blue and crystal violet) by MGO.

Hydrogeochemical processes governing the origin, transport and fate of major and trace elements from mine wastes and mineralized rock to surface waters

USGS Publications Warehouse

Nordstrom, D. Kirk

2011-01-01

Mobility of potential or actual contaminants from mining and mineral processing activities depends on (1) occurrence: is the mineral source of the contaminant actually present? (2) abundance: is the mineral present in sufficient quantity to make a difference? (3) reactivity: what are the energetics, rates, and mechanisms of sorption and mineral dissolution and precipitation relative to the flow rate of the water? and (4) hydrology: what are the main flow paths for contaminated water? Estimates of relative proportions of minerals dissolved and precipitated can be made with mass-balance calculations if minerals and water compositions along a flow path are known. Combined with discharge, these mass-balance estimates quantify the actual weathering rate of pyrite mineralization in the environment and compare reasonably well with laboratory rates of pyrite oxidation except when large quantities of soluble salts and evaporated mine waters have accumulated underground. Quantitative mineralogy with trace-element compositions can substantially improve the identification of source minerals for specific trace elements through mass balances. Post-dissolution sorption and precipitation (attenuation) reactions depend on the chemical behavior of each element, solution composition and pH, aqueous speciation, temperature, and contact-time with mineral surfaces. For example, little metal attenuation occurs in waters of low pH (2, and redox-sensitive oxyanions (As, Sb, Se, Mo, Cr, V). Once dissolved, metal and metalloid concentrations are strongly affected by redox conditions and pH. Iron is the most reactive because it is rapidly oxidized by bacteria and archaea and Fe(III) hydrolyzes and precipitates at low pH (1–3) which is related directly to its first hydrolysis constant, pK1 = 2.2. Several insoluble sulfate minerals precipitate at low pH including anglesite, barite, jarosite, alunite and basaluminite. Aluminum hydrolyzes near pH 5 (pK1 = 5.0) and provides buffering and removal of Al by mineral precipitation from pH 4–5.5. Dissolved sulfate behaves conservatively because the amount removed from solution by precipitation is usually too small relative to the high concentrations in the water column and relative to the flow rate of the water.

Influence of the dentinal wall on the pH of sodium hypochlorite during root canal irrigation.

PubMed

Macedo, Ricardo Gomes; Herrero, Noemi Pascual; Wesselink, Paul; Versluis, Michel; van der Sluis, Luc

2014-07-01

The purpose of this study was to evaluate the influence of dentin on the pH levels of different concentrations of sodium hypochlorite (NaOCl) solutions over time and to evaluate if preconditioning of dentin with 17% EDTA or agitation of the NaOCl solution influences these pH levels. A novel clinically representative model that scales with the ratio of the irrigant volume to the dentin surface area of a human root canal was used. Three standardized bovine dentin bars (2 × 2 × 10 mm) were placed in a plastic test tube. A total of 150 tubes were distributed in 29 groups. In the first experiment, the pH of various NaOCl solutions, with different concentrations (3%, 6%, and 9%) and starting pH levels (5 and 12), was monitored during exposure to dentin between 10 and 300 seconds. In a second experiment, the effect of agitation (45 Hz) and pretreatment of dentin with 17% EDTA on the pH levels of various NaOCl solutions was studied after 30 seconds of exposure to dentin. The short-term chemical stability of the tested solutions was assessed for both the concentration and the pH. The exposure time (P < .001) and concentration of the NaOCl solution (P < .011) significantly influence the pH level after exposure to dentin. However, the change in pH is too small to induce a change in the irrigant antimicrobial/tissue dissolution capacity. Agitation of the irrigant and preconditioning of the dentin did not alter the pH (P > .05). Both the pH 5 and pH 12 solutions were chemically stable for 1 hour. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Burkholderia tropica as a Potential Microalgal Growth-Promoting Bacterium in the Biosorption of Mercury from Aqueous Solutions.

PubMed

ZÁrate, Ana; Florez, July; Angulo, Edgardo; Varela-Prieto, Lourdes; Infante, Cherlys; Barrios, Fredy; Barraza, Beatriz; Gallardo, D I; Valdés, Jorge

2017-06-28

The use of microalgal biomass is an interesting technology for the removal of heavy metals from aqueous solutions owing to its high metal-binding capacity, but the interactions with bacteria as a strategy for the removal of toxic metals have been poorly studied. The goal of the current research was to investigate the potential of Burkholderia tropica co-immobilized with Chlorella sp. in polyurethane discs for the biosorption of Hg(II) from aqueous solutions and to evaluate the influence of different Hg(II) concentrations (0.041, 1.0, and 10 mg/l) and their exposure to different contact times corresponding to intervals of 1, 2, 4, 8, 16, and 32 h. As expected, microalgal bacterial biomass adhered and grew to form a biofilm on the support. The biosorption data followed pseudo-second-order kinetics, and the adsorption equilibrium was well described by either Langmuir or Freundlich adsorption isotherm, reaching equilibrium from 1 h. In both bacterial and microalgal immobilization systems in the coimmobilization of Chlorella sp. and B. tropica to different concentrations of Hg(II), the kinetics of biosorption of Hg(II) was significantly higher before 60 min of contact time. The highest percentage of biosorption of Hg(II) achieved in the co-immobilization system was 95% at pH 6.4, at 3.6 g of biosorbent, 30 ± 1°C, and a mercury concentration of 1 mg/l before 60 min of contact time. This study showed that co-immobilization with B. tropica has synergistic effects on biosorption of Hg(II) ions and merits consideration in the design of future strategies for the removal of toxic metals.

pH modulates the binding of early growth response protein 1 transcription factor to DNA.

PubMed

Mikles, David C; Bhat, Vikas; Schuchardt, Brett J; Deegan, Brian J; Seldeen, Kenneth L; McDonald, Caleb B; Farooq, Amjad

2013-08-01

The transcription factor early growth response protein (EGR)1 orchestrates a plethora of signaling cascades involved in cellular homeostasis, and its downregulation has been implicated in the development of prostate cancer. Herein, using a battery of biophysical tools, we show that the binding of EGR1 to DNA is tightly regulated by solution pH. Importantly, the binding affinity undergoes an enhancement of more than an order of magnitude with an increase in pH from 5 to 8, implying that the deprotonation of an ionizable residue accounts for such behavior. This ionizable residue is identified as His382 by virtue of the fact that its replacement by nonionizable residues abolishes the pH dependence of the binding of EGR1 to DNA. Notably, His382 inserts into the major groove of DNA, and stabilizes the EGR1-DNA interaction via both hydrogen bonding and van der Waals contacts. Remarkably, His382 is mainly conserved across other members of the EGR family, implying that histidine protonation-deprotonation may serve as a molecular switch for modulating the protein-DNA interactions that are central to this family of transcription factors. Collectively, our findings reveal an unexpected but a key step in the molecular recognition of the EGR family of transcription factors, and suggest that they may act as sensors of pH within the intracellular environment. © 2013 FEBS.

Radiation-induced graft polymerization for the preparation of a highly efficient UHMWPE fibrous adsorbent for Cr(VI) removal

NASA Astrophysics Data System (ADS)

Gao, Qianhong; Hua, Jiangtao; Li, Rong; Xing, Zhe; Pang, Lijuan; Zhang, Mingxing; Xu, Lu; Wu, Guozhong

2017-01-01

A novel fibrous adsorbent containing amine and quaternary ammonium groups was prepared by radiation-induced graft of glycidyl methacrylate (GMA) onto ultra-high molecular weight polyethylene (UHMWPE) fiber and further modifying with triethylenetetramine (TETA) and glycidyl trimethylammonium chloride (GTA). The ATR-IR spectra and SEM observation demonstrated that amine and quaternary ammonium groups were immobilized onto the surface of UHMWPE fiber. The principal factors affecting the adsorption of Cr(VI) ions have been investigated including pH of the aqueous solution, contact time, temperature and coexisting anions. This novel fibrous adsorbent could effectively adsorb Cr(VI) in the range of pH 1-9, and the maximum adsorption capacity reached 295 mg/g at pH 3 and 25 °C based on the Langmuir isotherm. It was found that adsorption equilibrium could be achieved within 2 h for initial Cr(VI) of 100 mg/L, following the pseudo-second order model. The effect of coexisting anions (including SO42-, H2PO4-, NO3-and Cl-) on the uptake of Cr(VI) was investigated in detail. Additionally, the adsorption saturated fiber could be regenerated by soaking in 0.5 mol/L NaOH solution, and the adsorption performance of this adsorbent could be maintained at 90% after eight cycles of adsorption-desorption. ATR-IR and XPS analysis revealed that Cr(VI) ions were adsorbed on the fiber adsorbent through ion exchange mechanism.

Removal of lead and zinc ions from water by low cost adsorbents.

PubMed

Mishra, P C; Patel, R K

2009-08-30

In this study, activated carbon, kaolin, bentonite, blast furnace slag and fly ash were used as adsorbent with a particle size between 100 mesh and 200 mesh to remove the lead and zinc ions from water. The concentration of the solutions prepared was in the range of 50-100 mg/L for lead and zinc for single and binary systems which are diluted as required for batch experiments. The effect of contact time, pH and adsorbent dosage on removal of lead and zinc by adsorption was investigated. The equilibrium time was found to be 30 min for activated carbon and 3h for kaolin, bentonite, blast furnace slag and fly ash. The most effective pH value for lead and zinc removal was 6 for activated carbon. pH value did not effect lead and zinc removal significantly for other adsorbents. Adsorbent doses were varied from 5 g/L to 20 g/L for both lead and zinc solutions. An increase in adsorbent doses increases the percent removal of lead and zinc. A series of isotherm studies was undertaken and the data evaluated for compliance was found to match with the Langmuir and Freundlich isotherm models. To investigate the adsorption mechanism, the kinetic models were tested, and it follows second order kinetics. Kinetic studies reveals that blast furnace slag was not effective for lead and zinc removal. The bentonite and fly ash were effective for lead and zinc removal.

Batch and fixed-bed assessment of sulphate removal by the weak base ion exchange resin Amberlyst A21.

PubMed

Guimarães, Damaris; Leão, Versiane A

2014-09-15

This paper investigated sulphate removal from aqueous solutions by Amberlyst A21, a polystyrene weak base ion exchange resin. Both the pH and initial sulphate concentration were observed to strongly affect sorption yields, which were largest in acidic environments. Working under optimum operational conditions, sulphate sorption by Amberlyst A21 was relatively fast and reached equilibrium after 45 min of contact between the solid and liquid phases. Sorption kinetics could be described by either the pseudo-first order (k1=3.05 × 10(-5)s(-1)) or pseudo-second order model (k2=1.67 × 10(-4)s(-1)), and both the Freundlich and Langmuir models successfully fitted the equilibrium data. Sulphate uptake by Amberlyst A21 was a physisorption process (ΔH=-25.06 kJ mol(-1)) that occurred with entropy reduction (ΔS=-0.042 kJ mol(-1)K(-1)). Elution experiments showed that sulphate is easily desorbed (∼ 100%) from the resin by sodium hydroxide solutions at pH 10 or pH 12. Fixed-bed experiments assessed the effects of the initial sulphate concentration, bed height and flow rate on the breakthrough curves and the efficiency of the Amberlyst A21 in the treatment of a real effluent. In all studied conditions, the maximum sulphate loading resin varied between 8 and 40 mg(SO4(2-))mL(resin)(-1). Copyright © 2014 Elsevier B.V. All rights reserved.

Removal of heavy metal from industrial effluents using Baker's yeast

NASA Astrophysics Data System (ADS)

Ferdous, Anika; Maisha, Nuzhat; Sultana, Nayer; Ahmed, Shoeb

2016-07-01

Bioremediation of wastewater containing heavy metals is one of the major challenges in environmental biotechnology. Heavy metals are not degraded and as a result they remain in the ecosystem, and pose serious health hazards as it comes in contact with human due to anthropogenic activities. Biological treatment with various microorganisms has been practiced widely in recent past, however, accessing and maintaining the microorganisms have always been a challenge. Microorganisms like Baker's yeast can be very promising biosorbents as they offer high surface to volume ratio, large availability, rapid kinetics of adsorption and desorption and low cost. The main aim of this study is to evaluate the applicability of the biosorption process using baker's yeast. Here we present an experimental investigation of biosorption of Chromium (Cr) from water using commercial Baker's Yeast. It was envisaged that yeast, dead or alive, would adsorb heavy metals, however, operating parameters could play vital roles in determining the removal efficiency. Parameters, such as incubation time, pH, amount of biosorbent and heavy metal concentration were varied to investigate the impacts of those parameters on removal efficiency. Rate of removal was found to be inversely proportional to the initial Cr (+6) concentrations but the removal rate per unit biomass was a weakly dependent on initial Cr(+6) concentrations. Biosorption process was found to be more efficient at lower pH and it exhibited lower removal with the increase in solution pH. The optimum incubation time was found to be between 6-8 hours and optimum pH for the metal ion solution was 2. The effluents produced in leather industries are the major source of chromium pollution in Bangladesh and this study has presented a very cost effective yet efficient heavy metal removal approach that can be adopted for such kind of wastewater.

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

Polymer-based adsorbent for heavy metals removal from aqueous solution

NASA Astrophysics Data System (ADS)

Mahmud, H. N. M. E.; Huq, A. K. O.; Yahya, R.

2017-06-01

A novel conducting polymer-based adsorbent, polypyrrole (PPy) fine powder has successfully been prepared as a new adsorbent and utilized in the adsorption of heavy metal ions like arsenic, zinc and cadmium ions from aqueous solution. PPy was chemically synthesized by using FeCl3.6H2O as an oxidant. The prepared PPy adsorbent was characterized by Brunauer-Emmet-Teller (BET) surface analysis, field emission scanning electron microscopy (FESEM) and attenuated total reflectance fourier transform infrared ATR-(FTIR) spectroscopy. The adsorption was conducted by varying different parameters such as, contact time, pH and adsorbent dosage. The concentrations of metal ions were measured by inductively coupled plasma mass spectroscopy (ICP-MS). The results show that PPy acts as an effective sorbent for the removal of arsenic, zinc and cadmium ions from aqueous solution. The as-prepared PPy fine powder is easy to prepare and appeared as an effective adsorbent for heavy metal ions particularly arsenic in wastewater treatment.

Starch-g-Poly-(N, N-dimethyl acrylamide-co-acrylic acid): an efficient Cr (VI) ion binder.

PubMed

Kolya, Haradhan; Roy, Anirban; Tripathy, Tridib

2015-01-01

Synthesis of Starch-g-(Poly N, N-dimethylacrylamide-co-acrylic acid) was carried out by solution polymerization technique using potassium perdisulfate (K(2)S(2)O(8)) as the initiator. The graft copolymer was characterized by measuring molecular weight, using size exclusion chromatography (SEC), FTIR spectroscopy and X-ray diffraction (XRD) studies. The synthetic graft copolymer was used for removal of hexavalent chromium ion [Cr (VI)] from its aqueous solution. Various operating variables affecting the metal sorption such as, the amount of adsorbent, solution pH, contact time, temperature and the Cr (VI) solution concentration were extensively investigated. FTIR and UV-VIS spectroscopy, cyclic voltammetry (CV) were employed to study the metal complexation. The adsorption data could be well described by the pseudo-second-order and Langmuir isotherm model which indicate a chemisorption process. Calculation of the various thermodynamic parameters for the adsorption was also done. The negative value of free energy change (ΔG°) indicates the spontaneous nature of the adsorption. Copyright © 2014 Elsevier B.V. All rights reserved.

Engineering cocrystal solubility, stability, and pH(max) by micellar solubilization.

PubMed

Huang, Neal; Rodríguez-Hornedo, Naír

2011-12-01

Cocrystals offer great promise in enhancing drug aqueous solubilities, but face the challenge of conversion to a less soluble drug when in contact with solvent. This manuscript shows that differential solubilization of cocrystal components by micelles can impart thermodynamic stability to otherwise unstable cocrystals. The theoretical foundation for controlling cocrystal solubility and stability is presented by considering the contributions of micellar solubilization and ionization of cocrystal components. A surfactant critical stabilization concentration (CSC) and a solution pH (pH(max)) where cocrystal and drug are thermodynamically stable are shown to characterize cocrystal stability in micellar solutions. The solubility, CSC, and pH(max) of carbamazepine cocrystals in micellar solutions of sodium lauryl sulfate predicted by the models are in very good agreement with experimental measurements. The findings from this work demonstrate that cocrystal CSC and pH(max) can be tailored from the selection of coformer and solubilizing additives such as surfactants, thus providing an unprecedented level of control over cocrystal stability and solubility via solution phase chemistry. Copyright © 2011 Wiley-Liss, Inc.

pH Modulates the Binding of EGR1 Transcription Factor to DNA

PubMed Central

Mikles, David C.; Bhat, Vikas; Schuchardt, Brett J.; Deegan, Brian J.; Seldeen, Kenneth L.; McDonald, Caleb B.; Farooq, Amjad

2013-01-01

EGR1 transcription factor orchestrates a plethora of signaling cascades involved in cellular homeostasis and its down-regulation has been implicated in the development of prostate cancer. Herein, using a battery of biophysical tools, we show that the binding of EGR1 to DNA is tightly regulated by solution pH. Importantly, the binding affinity undergoes an enhancement of more than an order of magnitude with increasing pH from 5 to 8, implying that the deprotonation of an ionizable residue accounts for such behavior. This ionizable residue is identified as H382 by virtue of the fact that its substitution to non-ionizable residues abolishes pH-dependence of the binding of EGR1 to DNA. Notably, H382 inserts into the major groove of DNA and stabilizes the EGR1-DNA interaction via both hydrogen bonding and van der Waals contacts. Remarkably, H382 is predominantly conserved across other members of EGR1 family, implying that histidine protonation-deprotonation may serve as a molecular switch for modulating protein-DNA interactions central to this family of transcription factors. Collectively, our findings uncover an unexpected but a key step in the molecular recognition of EGR1 family of transcription factors and suggest that they may act as sensors of pH within the intracellular environment. PMID:23718776

Characteristics and adsorption study of the activated carbon derived from municipal sewage sludge.

PubMed

Guo, Tiecheng; Yao, Sicong; Chen, Hengli; Yu, Xin; Wang, Meicheng; Chen, Yao

2017-10-01

Sewage sludge-based activated carbon is proved to be an efficient and low-cost adsorbent in treatment of various industrial wastewaters. The produced carbon had a well-developed pore structure and relatively low Brunauer-Emmett-Teller (BET) surface area. Adsorptive capacity of typical pollutants, i.e. copper Cu(II) and methylene blue (MB) on the carbon was studied. Adsorptions were affected by the initial solution pH, contact time and adsorbent dose. Results showed that adsorption of Cu(II) and MB on the produced carbon could reach equilibrium after 240 min. The average removal rate for Cu(II) on the carbon was high, up to 97% in weak acidic conditions (pH = 4-6) and around 98% for MB in a very wide pH range (pH = 2-12). The adsorption kinetics were well fitted by the pseudo-second order model, and both Langmuir and Freundlich isotherm models could well describe the adsorption process at room temperature. The theoretical maximum adsorption capacities of Cu(II) and MB on sewage sludge-based activated carbon were 114.94 mg/g and 125 mg/g, respectively. Compared with commercial carbon, the sewage sludge-based carbon was more suitable for heavy metal ions' removal than dyes'.

Investigation of pH Influence on Skin Permeation Behavior of Weak Acids Using Nonsteroidal Anti-Inflammatory Drugs.

PubMed

Chantasart, Doungdaw; Chootanasoontorn, Siriwan; Suksiriworapong, Jiraphong; Li, S Kevin

2015-10-01

As a continuing effort to understand the skin permeation behavior of weak acids and bases, the objectives of the present study were to evaluate skin permeation of nonsteroidal anti-inflammatory drugs (NSAIDs) under the influence of pH, investigate the mechanism of pH effect, and examine a previous hypothesis that the effective skin pH for drug permeation is different from donor solution pH. In vitro permeability experiments were performed in side-by-side diffusion cells with diclofenac, ibuprofen, flurbiprofen, ketoprofen, and naproxen and human skin. The donor solution pH significantly affected skin permeation of NSAIDs, whereas no effect of the receiver pH was observed. Similar to previous observations, the apparent permeability coefficient versus donor solution pH relationships deviated from the predictions (fractions of unionized NSAIDs) according to the acid/base theory. The influences of the viable epidermis barrier, polar pathway transport, ion permeation across skin, and effective skin pH were investigated. The effective pH values for skin permeation determined using the NSAIDs (weak acids) in this study were different from those obtained previously with a weak base at the same donor solution pH conditions, suggesting that the observed permeability-pH relationships could not be explained solely by possible pH differences between skin and donor solution. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

Biosorption of Copper (II) from Aqueous Solution Using Non-Living Mesorhizobium amorphae Strain CCNWGS0123

PubMed Central

Mohamad, Osama Abdalla; Hao, Xiuli; Xie, Pin; Hatab, Shaimaa; Lin, Yanbing; Wei, Gehong

2012-01-01

The mining industry generates huge amounts of wastewater, containing toxic heavy metals. Treatment to remove heavy metals is necessary and recent work has been focused on finding more environmentally friendly materials for removing heavy metals from wastewater. Biosorption can be an effective process for heavy metal removal from aqueous solutions. Our objectives were to investigate the removal of copper (II) from aqueous solutions using dead cells of Mesorhizobium amorphae CCNWGS0123 under differing levels of pH, agitation speed, temperature, initial copper concentration, biosorbent dose and contact time using flame atomic absorption spectroscopy for metal estimation. The maximum copper removal rate was achieved at pH 5.0, agitation speed 150×g, temperature 28°C and initial Cu (II) concentration of 100 mg L−1. Maximum biosorption capacity was at 0.5 g L−1 and equilibrium was attained within 30 min. Langmuir and Freundlich isotherms showed correlation coefficients of 0.958 and 0.934, respectively. Fourier transform-infrared spectroscopy (FT-IR) analysis indicated that many functional groups, such as O-H, N-H, C-H, C=O, -NH, -CN, C-N, C-O, amide -I, -II, -III and unsaturated alkenes, alkyls and aromatic groups on the cell surface were involved in the interaction between CCNWGS0123 and Cu. Scanning electron microscope and energy dispersive X-ray scanning results showed deformation, aggregation, and cell-surface damage due to the precipitation of copper on the cell surface. Dead cells of CCNWGS0123 showed potential as an efficient biosorbent for the removal of Cu2+ from aqueous solutions. PMID:22353770

The effect of pH on phosphorus availability and speciation in an aquaponics nutrient solution.

PubMed

Cerozi, Brunno da Silva; Fitzsimmons, Kevin

2016-11-01

The interaction between the main ions in aquaponics nutrient solutions affects chemical composition and availability of nutrients, and nutrient uptake by plant roots. This study determined the effect of pH on phosphorus (P) speciation and availability in an aquaponics nutrient solution and used Visual MINTEQ to simulate P species and P activity. In both experimental and simulated results, P availability decreased with increase in pH of aquaponics nutrient solutions. According to simulations, P binds to several cations leaving less free phosphate ions available in solution. High pH values resulted in the formation of insoluble calcium phosphate species. The study also demonstrated the importance of organic matter and alkalinity in keeping free phosphate ions in solution at high pH ranges. It is recommended though that pH in aquaponics systems is maintained at a 5.5-7.2 range for optimal availability and uptake by plants. Copyright © 2016 Elsevier Ltd. All rights reserved.

40 CFR Appendix B to Subpart Nnn... - Free Formaldehyde Analysis of Insulation Resins by Hydroxylamine Hydrochloride

Code of Federal Regulations, 2011 CFR

2011-07-01

... 4.0 with pH 4.0 buffer and pH 7 with pH 7.0 buffer. 3.350-mL burette for 1.0 N sodium hydroxide. 3... hydrochloride solution, 100 grams per liter, pH adjusted to 4.00. 4.3Hydrochloric acid solution, 1.0 N and 0.1 N... magnetic stirrer. Confirm that the resin has dissolved. 5.4Adjust the resin/solvent solution to pH 4.0...

40 CFR Appendix B to Subpart Nnn... - Free Formaldehyde Analysis of Insulation Resins by Hydroxylamine Hydrochloride

Code of Federal Regulations, 2010 CFR

2010-07-01

... 4.0 with pH 4.0 buffer and pH 7 with pH 7.0 buffer. 3.350-mL burette for 1.0 N sodium hydroxide. 3... hydrochloride solution, 100 grams per liter, pH adjusted to 4.00. 4.3Hydrochloric acid solution, 1.0 N and 0.1 N... magnetic stirrer. Confirm that the resin has dissolved. 5.4Adjust the resin/solvent solution to pH 4.0...

Effects of acidic pH on voltage-gated ion channels in rat trigeminal mesencephalic nucleus neurons.

PubMed

Han, Jin-Eon; Cho, Jin-Hwa; Choi, In-Sun; Kim, Do-Yeon; Jang, Il-Sung

2017-03-01

The effects of acidic pH on several voltage-dependent ion channels, such as voltage-dependent K + and Ca 2+ channels, and hyperpolarization-gated and cyclic nucleotide-activated cation (HCN) channels, were examined using a whole-cell patch clamp technique on mechanically isolated rat mesencephalic trigeminal nucleus neurons. The application of a pH 6.5 solution had no effect on the peak amplitude of voltage-dependent K + currents. A pH 6.0 solution slightly, but significantly inhibited the peak amplitude of voltage-dependent K + currents. The pH 6.0 also shifted both the current-voltage and conductance-voltage relationships to the depolarization range. The application of a pH 6.5 solution scarcely affected the peak amplitude of membrane currents mediated by HCN channels, which were profoundly inhibited by the general HCN channel blocker Cs + (1 mM). However, the pH 6.0 solution slightly, but significantly inhibited the peak amplitude of HCN-mediated currents. Although the pH 6.0 solution showed complex modulation of the current-voltage and conductance-voltage relationships, the midpoint voltages for the activation of HCN channels were not changed by acidic pH. On the other hand, voltage-dependent Ca 2+ channels were significantly inhibited by an acidic pH. The application of an acidic pH solution significantly shifted the current-voltage and conductance-voltage relationships to the depolarization range. The modulation of several voltage-dependent ion channels by an acidic pH might affect the excitability of mesencephalic trigeminal nucleus neurons, and thus physiological functions mediated by the mesencephalic trigeminal nucleus could be affected in acidic pH conditions.

Measurements of spectral responses for developing fiber-optic pH sensor

NASA Astrophysics Data System (ADS)

Yoo, Wook Jae; Heo, Ji Yeon; Jang, Kyoung Won; Seo, Jeong Ki; Moon, Jin Soo; Park, Jang-Yeon; Park, Byung Gi; Cho, Seunghyun; Lee, Bongsoo

2011-01-01

In this study, we have fabricated a fiber-optic pH sensor, which is composed of a light source, a pH-sensing probe, plastic optical fibers and a spectrometer, for determining the degree of infection by Helicobacter pylori in the stomach. As pH indicators, phenol red and m-cresol purple are used, and pH liquid solutions are prepared by mixing phenol red or m-cresol purple solutions and various kinds of pH buffer solutions. The light emitted by a light source is guided by plastic optical fibers to the pH liquid solution, and the optical characteristic of a reflected light is changed according to the color variations of the pH indicator in the pH-sensing probe. Therefore, we have measured the intensities and wavelength shifts of the reflected lights, which change according to the color variations of indicators at different pH values, by using a spectrometer for spectral analysis. Also, the relationships between the pH values of liquid solutions and the optical properties of the modulated lights are obtained on the basis of the changes of the colors of indicators.

Bismuth generator method

DOEpatents

Bray, Lane Allan; DesChane, Jaquetta R.

1998-01-01

A method for separating .sup.213 Bi from a solution of radionuclides wherein the solution contains a concentration of the chloride ions and hydrogen ions adjusted to allow the formation of a chloride complex. The solution is then brought into contact with an anion exchange resin, whereupon .sup.213 Bi is absorbed from the solution and adhered onto the anion exchange resin in the chloride complex. Other non-absorbing radionuclides such as .sup.225 Ra, .sup.225 Ac, and .sup.221 Fr, along with HCl are removed from the anion exchange resin with a scrub solution. The .sup.213 Bi is removed from the anion exchange resin by washing the anion exchange resin with a stripping solution free of chloride ions and with a reduced hydrogen ion concentration which breaks the chloride anionic complex, releasing the .sup.213 Bi as a cation. In a preferred embodiment of the present invention, the anion exchange resin is provided as a thin membrane, allowing for extremely rapid adherence and stripping of the .sup.213 Bi. A preferred stripping solution for purification of .sup.213 Bi for use in medical applications includes sodium acetate, pH 5.5. A protein conjugated with bifunctional chelating agents in vivo with the NaOAc, to receive the .sup.213 Bi as it is being released from the anion exchange resin.

Bismuth generator method

DOEpatents

Bray, L.A.; DesChane, J.R.

1998-05-05

A method is described for separating {sup 213}Bi from a solution of radionuclides wherein the solution contains a concentration of the chloride ions and hydrogen ions adjusted to allow the formation of a chloride complex. The solution is then brought into contact with an anion exchange resin, whereupon {sup 213}Bi is absorbed from the solution and adhered onto the anion exchange resin in the chloride complex. Other non-absorbing radionuclides such as {sup 225}Ra, {sup 225}Ac, and {sup 221}Fr, along with HCl are removed from the anion exchange resin with a scrub solution. The {sup 213}Bi is removed from the anion exchange resin by washing the anion exchange resin with a stripping solution free of chloride ions and with a reduced hydrogen ion concentration which breaks the chloride anionic complex, releasing the {sup 213}Bi as a cation. In a preferred embodiment of the present invention, the anion exchange resin is provided as a thin membrane, allowing for extremely rapid adherence and stripping of the {sup 213}Bi. A preferred stripping solution for purification of {sup 213}Bi for use in medical applications includes sodium acetate, pH 5.5. A protein conjugated with bifunctional chelating agents in vivo with the NaOAc receives the {sup 213}Bi as it is being released from the anion exchange resin. 10 figs.

Selective Capture of Cesium and Thallium from Natural Waters and Simulated Wastes with Copper Ferrocyanide Functionalized Mesoporous Silica

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

Sangvanich, Thanapon; Sukwarotwat, Vichaya; Wiacek, Robert J.

2010-10-15

Copper(II) ferrocyanide immobilized inside mesoporous silica MCM-41 supports (Cu-FC-EDA-SAMMSTM) has been evaluated against iron(III) hexacyanoferrate(II) (insoluble Prussian blue) for the sorption of cesium (Cs+) and thallium (Tl+) from natural waters and simulated wastes. The affinities (in term of distribution coefficients, Kd) of both sorbents for Cs and Tl were measured as a function of solution pH, competing cations, and matrices. For the entire pH studied (pH 0.1 to 7.3), Cu-FC-EDA-SAMMS had higher affinities for Cs and Tl (one to two orders of magnitude higher Kd) than Prussian blue and was less negatively impacted by the solution pH, competing cations, andmore » matrices. The adsorption isotherms and kinetics of the two sorbents for Cs and/or Tl were also determined in seawater and simulated acid and alkaline wastes. SAMMS outperformed Prussian blue in terms of maximum adsorption capacity (e.g., 21.7 versus 2.6 mg Cs/g in acid waste stimulant, pH 1.1), and rate (e.g., over 95 wt% of Cs was removed after 2 minutes with SAMMS, while only 75 wt% was removed with Prussian blue). The lower affinity, capacity, and rate of Cs and Tl sorption on Prussian blue than those on Cu-FC-EDA-SAMMS were attributed to the molecular pore sizes, which restrict mass transport, and the insoluble Cs abducts of the Prussian blue, which restrict the ability of neighboring binding sites to further bind Cs ions. On the other hand, the large pores of SAMMS not only enable faster diffusion and faster binding chemistry, but they also allow isolation of binding sites so that one Cs binding event does not impact further Cs binding. In addition, iron (Fe) dissolved from insoluble Prussian blue over 10-fold of that from Cu-FC-EDA-SAMMS after 24 hours of contact time, indicating poorer material stability of Prussian blue.« less

A method for calibrating pH meters using standard solutions with low electrical conductivity

NASA Astrophysics Data System (ADS)

Rodionov, A. K.

2011-07-01

A procedure for obtaining standard solutions with low electrical conductivity that reproduce pH values both in acid and alkali regions is proposed. Estimates of the maximal possible error of reproducing the pH values of these solutions are obtained.

Metal regeneration of iron chelates in nitric oxide scrubbing

DOEpatents

Chang, Shih-Ger; Littlejohn, David; Shi, Yao

1997-08-19

The present invention relates to a process of using metal particles to reduce NO to NH.sub.3. More specifically, the invention concerns an improved process to regenerate iron (II) (CHELATE) by reduction of iron (II) (CHELATE) (NO) complex, which process comprises: a) contacting an aqueous solution containing iron (II) (CHELATE) (NO) with metal particles at between about 20.degree. and 90.degree. C. to reduce NO present, produce ammonia or an ammonium ion, and produce free iron (II) (CHELATE) at a pH of between about 3 and 8. The process is useful to remove NO from flue gas and reduce pollution.

Reforming process

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

Mitsche, R.T.; Pope, G.N.

A process for reforming a naphtha feedstock is disclosed. The reforming process is effected at reforming conditions in contact with a catalyst comprising a platinum group metal component and a group iv-a metal component composited with an alumina support wherein said support is prepared by admixing an alpha alumina monohydrate with an aqueous ammoniacal solution having a ph of at least about 7.5 to form a stable suspension. A salt of a strong acid, e.g., aluminum nitrate, is commingled with the suspension to form an extrudable paste or dough. On extrusion, the extrudate is dried and calcined to form saidmore » alumina support.« less

Characterization of folic acid-PAMAM conjugates: drug loading efficacy and dendrimer morphology.

PubMed

Chanphai, P; Tajmir-Riahi, H A

2018-05-01

We report the loading efficacy of folic acid (FA) by polyamidoamine (PAMAM-G3 and PAMAM-G4) nanoparticles in aqueous solution at physiological pH. Thermodynamic parameters ΔH = -47.57 (kJ Mol -1 ), ΔS = -122.78 (J Mol -1 , K -1 ) and ΔG = -10.96 (kJ Mol -1 ) showed FA-PAMAM bindings occur via H-bonding and van der Waals contacts. The stability of acid-PAMAM conjugate increased as polymer size increased. The acid loading efficacy was 40 to 50%. TEM images exhibited major polymer morphological changes upon acid encapsulation. PAMAM dendrimers are capable of FA delivery in vitro.

Metal regeneration of iron chelates in nitric oxide scrubbing

DOEpatents

Chang, S.G.; Littlejohn, D.; Shi, Y.

1997-08-19

The present invention relates to a process of using metal particles to reduce NO to NH{sub 3}. More specifically, the invention concerns an improved process to regenerate iron (II) (CHELATE) by reduction of iron (II) (CHELATE) (NO) complex, which process comprises: (a) contacting an aqueous solution containing iron (II) (CHELATE) (NO) with metal particles at between about 20 and 90 C to reduce NO present, produce ammonia or an ammonium ion, and produce free iron (II) (CHELATE) at a pH of between about 3 and 8. The process is useful to remove NO from flue gas and reduce pollution. 34 figs.

An Optical Sensor with Polyaniline-Gold Hybrid Nanostructures for Monitoring pH in Saliva.

PubMed

Luo, Chongdai; Wang, Yangyang; Li, Xuemeng; Jiang, Xueqin; Gao, Panpan; Sun, Kang; Zhou, Jianhua; Zhang, Zhiguang; Jiang, Qing

2017-03-17

Saliva contains important personal physiological information that is related to some diseases, and it is a valuable source of biochemical information that can be collected rapidly, frequently, and without stress. In this article, we reported a new and simple localized surface plasmon resonance (LSPR) substrate composed of polyaniline (PANI)-gold hybrid nanostructures as an optical sensor for monitoring the pH of saliva samples. The overall appearance and topography of the substrates, the composition, and the wettability of the LSPR surfaces were characterized by optical and scanning electron microscope (SEM) images, infrared spectra, and contact angles measurement, respectively. The PANI-gold hybrid substrate readily responded to the pH. The response time was very short, which was 3.5 s when the pH switched from 2 to 7, and 4.5 s from 7 to 2. The changes of visible-near-infrared (NIR) spectra of this sensor upon varying pH in solution showed that-for the absorption at given wavelengths of 665 nm and 785 nm-the sensitivities were 0.0299 a.u./pH (a.u. = arbitrary unit) with a linear range of pH = 5-8 and 0.0234 a.u./pH with linear range of pH = 2-8, respectively. By using this new sensor, the pH of a real saliva sample was monitored and was consistent with the parallel measurements with a standard laboratory method. The results suggest that this novel LSPR sensor shows great potential in the field of mobile healthcare and home medical devices, and could also be modified by different sensitive materials to detect various molecules or ions in the future.

Evolution of nano-rheological properties of Nafion¯ thin films during pH modification by strong base treatment: A static and dynamic force spectroscopy study

NASA Astrophysics Data System (ADS)

Eslami, Babak; López-Guerra, Enrique A.; Raftari, Maryam; Solares, Santiago D.

2016-04-01

Addition of a strong base to Nafion® proton exchange membranes is a common practice in industry to increase their overall performance in fuel cells. Here, we investigate the evolution of the nano-rheological properties of Nafion thin films as a function of the casting pH, via characterization with static and dynamic, contact and intermittent-contact atomic force microscopy (AFM) techniques. The addition of KOH causes non-monotonic changes in the viscoelastic properties of the films, which behave as highly dissipative, softer materials near neutral pH values, and as harder, more elastic materials at extreme pH values. We quantify this behavior through calculation of the temporal evolution of the compliance and the glassy compliance under static AFM measurements. We complement these observations with dynamic AFM metrics, including dissipated power and virial (for intermittent-contact-mode measurements), and contact resonance frequency and quality factor (for dynamic contact-mode measurements). We explain the non-monotonic material property behavior in terms of the degree of ionic crosslinking and moisture content of the films, which vary with the addition of KOH. This work focuses on the special case study of the addition of strong bases, but the observed mechanical property changes are broadly related to water plasticizing effects and ionic crosslinking, which are also important in other types of films.

Electrochemical disinfection of bacteria-laden water using antimony-doped tin-tungsten-oxide electrodes.

PubMed

Ghasemian, Saloumeh; Asadishad, Bahareh; Omanovic, Sasha; Tufenkji, Nathalie

2017-12-01

Electrochemical disinfection has been shown to be an efficient method with a shortrequired contact time for treatment of drinking water supplies, industrial raw water supplies, liquid foodstuffs, and wastewater effluents. In the present work, the electrochemical disinfection of saline water contaminated with bacteria was investigated in chloride-containing solutions using Sb-doped Sn 80% -W 20% -oxide anodes. The influence of current density, bacterial load, initial chloride concentration, solution pH, and the type of bacteria (E. coli D21, E. coli O157:H7, and E. faecalis) on disinfection efficacy was systematically examined. The impact of natural organic matter and a radical scavenger on the disinfection process was also examined. The electrochemical system was highly effective in bacterial inactivation for a 0.1 M NaCl solution contaminated with ∼10 7  CFU/mL bacteria by applying a current density ≥1 mA/cm 2 through the cell.100% inactivation of E. coli D21 was achieved with a contact time of less than 60 s and power consumption of 48 Wh/m 3 , by applying a current density of 6 mA/cm 2 in a 0.1 M NaCl solution contaminated with ∼10 7 CFU/mL. Reactive chlorine species as well as reactive oxygen species (e.g. hydroxyl radicals) generated in situ during the electrochemical process were determined to be responsible for inactivation of bacteria. Copyright © 2017 Elsevier Ltd. All rights reserved.

Electrochemical control of pH in a hydroponic nutrient solution

NASA Technical Reports Server (NTRS)

Schwartzkopf, S. H.

1986-01-01

The electrochemical pH control system described was found to provide a feasible alternative method of controlling nutrient solution pH for CELSS applications. The plants grown in nutrient solution in which the pH was controlled electrochemically showed no adverse effects. Further research into the design of a larger capacity electrode bridge for better control is indicated by the results of this experiment, and is currently under way.

Modeling the chemical kinetics of atmospheric plasma for cell treatment in a liquid solution

NASA Astrophysics Data System (ADS)

Kim, H. Y.; Lee, H. W.; Kang, S. K.; Wk. Lee, H.; Kim, G. C.; Lee, J. K.

2012-07-01

Low temperature atmospheric pressure plasmas have been known to be effective for living cell inactivation in a liquid solution but it is not clear yet which species are key factors for the cell treatment. Using a global model, we elucidate the processes through which pH level in the solution is changed from neutral to acidic after plasma exposure and key components with pH and air variation. First, pH level in a liquid solution is changed by He+ and He(21S) radicals. Second, O3 density decreases as pH level in the solution decreases and air concentration decreases. It can be a method of removing O3 that causes chest pain and damages lung tissue when the density is very high. H2O2, HO2, and NO radicals are found to be key factors for cell inactivation in the solution with pH and air variation.

Repertoire of free-living protozoa in contact lens solutions.

PubMed

Bouchoucha, Ibtissem; Aziz, Aurore; Hoffart, Louis; Drancourt, Michel

2016-10-29

The repertoire of free-living protozoa in contact lens solutions is poorly known despite the fact that such protozoa may act as direct pathogens and may harbor intra-cellular pathogens. Between 2009 and 2014, the contact lens solutions collected from patients presenting at our Ophthalmology Department for clinically suspected keratitis, were cultured on non-nutrient agar examined by microscope for the presence of free-living protozoa. All protozoa were identified by 18S rRNA gene sequencing. A total of 20 of 233 (8.6 %) contact lens solution specimens collected from 16 patients were cultured. Acanthamoeba amoeba in 16 solutions (80 %) collected from 12 patients and Colpoda steini, Cercozoa sp., Protostelium sp. and a eukaryotic more closely related to Vermamoeba sp., were each isolated in one solution. Cercozoa sp., Colpoda sp., Protostelium sp. and Vermamoeba sp. are reported for the first time as contaminating contact lens solutions. The repertoire of protozoa in contact lens solutions is larger than previously known.

Study the friction behaviour of poly[2-(dimethylamino)ethyl methacrylate] brush with AFM probes in contact mechanics

NASA Astrophysics Data System (ADS)

Raftari, Maryam; Zhang, Zhenyu; Leggett, Graham J.; Geoghegan, Mark

2011-10-01

We have studied the frictional behaviour of grafted poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) films using friction force microscopy (FFM). The films were prepared on native oxide-terminated silicon substrates using the technique of atom transfer radical polymerization (ATRP). We show that single asperity contact mechanics (Johnson-Kendall-Roberts(JKR) and Derjaguin-Muller-Toporov(DMT)) as well as a linear (Amontons) relation between applied load and frictional load depending on the pH of the FFM probe. Measurements were made using functionalized and unfunctionalized silicon nitride triangular probes. Functionalized probes included gold-coated probes, and ones coated with a self-assembled monolayer of dodecanethiol (DDT). The frictional behaviour between PDMAEMA and all tips immersed in pH from 3 to 11 are corresponded to the DMT or JKR model and are linear in pH=1, 2, and 12. These results show that contact mechanics of polyelectrolytes in water is complex and strongly dependent on the environmental pH.

Inner layer-embedded contact lenses for pH-triggered controlled ocular drug delivery.

PubMed

Zhu, Qiang; Liu, Chang; Sun, Zheng; Zhang, Xiaofei; Liang, Ning; Mao, Shirui

2018-07-01

Contact lenses (CLs) are ideally suited for controlled ocular drug delivery, but are limited by short release duration, poor storage stability and low drug loading. In this study, we present a novel inner layer-embedded contact lens capable of pH-triggered extended ocular drug delivery with good storage stability. Blend film of ethyl cellulose and Eudragit S100 was used as the inner layer, while pHEMA hydrogel was used as outer layer to fabricate inner layer-embedded contact lens. Using diclofenac sodium(DS) as a drug model, influence of polymer ratio in the blend film, EC viscosity, drug/polymer ratio, inner layer thickness and outlayer thickness of pHEMA hydrogel on drug release behavior was studied and optimized for daily use. The pH-triggered drug eluting pattern enables the inner layer-embedded contact lens being stored in phosphate buffer solution pH 6.8 with ignorable drug loss and negligible changes in drug release pattern. In vivo pharmacokinetic study in rabbits showed sustained drug release for over 24 h in tear fluid, indicating significant improvement in drug corneal residence time. A level A IVIVC was established between in vitro drug release and in vivo drug concentration in tear fluid. In conclusion, this inner layer embedded contact lens design could be used as a platform for extended ocular drug delivery with translational potential for both anterior and posterior ocular diseases therapy. Copyright © 2018 Elsevier B.V. All rights reserved.

Composition of incubation solution impacts in vitro protein uptake to silicone hydrogel contact lenses

PubMed Central

Heynen, Miriam; Luensmann, Doerte; Jones, Lyndon

2012-01-01

Purpose To determine the impact of incubation solution composition on protein deposition to silicone hydrogel (SH) contact lenses using a simplistic and a complex model of the tear film. Methods Three SH materials – senofilcon A (SA), lotrafilcon B (LB), and balafilcon A (BA) – were incubated in two different solutions; Solution A was a simplistic augmented buffered saline solution containing a single protein, whereas Solution B was a complex artificial tear solution (ATS), containing the augmented buffered saline solution in addition to proteins, lipids, and mucins (pH=7.4). The proteins of interest (lysozyme, lactoferrin, albumin) were radiolabeled with Iodine-125 (2% protein of interest) and the accumulation of the conjugated protein to the lens materials was determined after 1, 7, 14, and 28 days of incubation. Protein deposition was measured using a gamma counter and the raw data were translated into absolute amounts (µg/lens) via extrapolation from standards. Results After 28 days, lysozyme uptake was significantly lower on BA lenses when incubated in Solution A (33.7 μg) compared to Solution B (56.2 μg), p<0.001. SA lenses deposited similar amounts of lysozyme when incubated in either Solution A (2.6 μg) or Solution B (4.1 μg), p>0.05. LB lenses also deposited similar amounts of lysozyme for both solutions (Solution A: 5.0 μg, Solution B: 4.7 μg, p>0.05). After 28 days, BA lenses accumulated approximately twice the amount of lactoferrin than the other lens materials, with 30.3 μg depositing when exposed to Solution A and 22.0 μg with Solution B. The difference between the two solutions was statistically significant (p<0.001). LB materials deposited significantly greater amounts of lactoferrin when incubated in Solution A (16.6 μg) compared to Solution B (10.3 μg), p<0.001. Similar amounts of lactoferrin were accumulated onto SA lenses regardless of incubation solution composition (Solution A: 8.2 μg, Solution B: 11.2 μg, p>0.05). After 28 days, albumin deposition onto BA lenses was significantly greater when lenses were incubated in Solution B (1.7 μg) compared to Solution A (0.9 μg), p<0.001. Similar amounts of albumin were deposited on SA lenses when incubated in either solution (0.6 μg versus 0.7 μg, p>0.05). LB lenses incubated in Solution A deposited more albumin compared to Solution B (0.9 μg versus 0.6 μg), p=0.003. Discussion Protein deposition onto SH materials varied when contact lenses were incubated in either a complex ATS compared to a single protein solution. More lysozyme accumulated onto BA lenses incubated in a complex analog of the human tear film, whereas lactoferrin deposited onto SA lenses independent of incubation solution composition. To better mimic the ex vivo environment, future studies should use more appropriate analogs of the tear film. PMID:22355245

Biosorption of copper, nickel and manganese using non-living biomass of marine alga, Ulva lactuca.

PubMed

Omar, Hanan Hafez

2008-04-01

The adsorption of Cu2+, Ni2+ and Mn2+ onto the marine algal biomass of Ulva lactuca was investigated in single and multimetal solutions. This study was intended to determine the role of different pH values (2-8) on the biosorption of metals at different concentrations (10, 20 and 30 mg L(-1)). The biosorption capacity of Cu2+, Ni2+ and Mn2+ for 10 mg L(-1) was the same as 20 and 30 mg L(-1), increase with increasing pH up to pH 5.0 and then decreased, in single and multimetal solutions. The optimum pH value was observed in the pH range 4-5 for Cu2+ and pH 5-6 for Ni2+ and Mn2+. The maximum biosorption capacities of tested alga for Cu2+, Ni2+ and Mn2+ were 92, 80 and 75%, respectively in single metal solution at 10 mg L(-1) and pH 5.0. At a further increase of pH (8.0) the biosorption process for Cu2+, Ni2+ and Mn2+ (75, 69 and 63%, respectively at 10 mg L(-1)) was decreased. The minimum biosorptions were 60, 49 and 44% for Cu2+, Ni2+ and Mn2+, respectively in single metal solution at 10 mg L(-1) and pH 2.0. In the multimetal solution, algal biomass exhibited the maximum and the minimum biosorption capacity at different pH values the same as in single metal solution. The inhibitory role of other ions on sorption process can be well observed in multimetal mixture, where biosorption capacity of Cu2+, Ni2+ and Mn2+ were significantly decreased in the multimetal solutions. The maximum biosorption was recorded for Cu2+ (83%) in solution of Cu2+ + Mn2+, Mn2+ (67%) in solution of Ni2 + Mn2+ and for Ni2+ (74%) in solution of Ni2+ + Mn2+ at the concentration 10 mg L(-1) and pH 5.0. The observed reduction in the biosorption of Cu2+, Ni2+ and Mn2+ (65, 57 and 52%, respectively at 10 mg L(-1) and pH 5.0) was more pronounced in the multimetal solution of Cu2 + Ni2+ + Mn2+ as compared with single metal solution. The results demonstrated that the affinity of the tested alga for sorption of the investigated metal ions in single and multimetal solutions runs in the order Cu2+ > Ni2+ > Mn2+. Biosorption equilibrium was established by the Langmuir and Freundlich isotherm models. According to the analyses conducted, the biosorption of Cu2+, Ni2+ and Mn2+ to Ulva lactuca was more consistent with Freundlich isotherm.

Lubrication of nonconformal contacts. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Jeng, Y. R.

1985-01-01

Minimum film thickness results for piezoviscous-rigid regime of lubrication are developed for a compressible Newtonian fluid with Roelands viscosity. The results provide a basis for the analysis and design of a wide range of machine elements operating in the piezoviscous-rigid regime of lubrication. A new numerical method of calculating elastic deformation in contact stresses is developed using a biquadratic polynomial to approximate the pressure distribution on the whole domain analyzed. The deformation of every node is expressed as a linear combination of the nodal pressures whose coefficients can be combined into an influence coefficient matrix. This approach has the advantages of improved numerical accuracy, less computing time and smaller storage size required for influence matrix. The ideal elastohydrodynamic lubrication is extended to real bearing systems in order to gain an understanding of failure mechanisms in machine elements. The improved elastic deformation calculation is successfully incorporated into the EHL numerical scheme. Using this revised numerical technique and the flow factor model developed by Patir and Cheng (1978) the surface roughness effects on the elastohydrodynamic lubrication of point contact is considered. Conditions typical of an EHL contact in the piezoviscous-elastic regime entrained in pure rolling are investigated. Results are compared with the smooth surface solutions. Experiments are conducted to study the transient EHL effects in instrument ball bearings.

Zeolitic imidazolate framework-8 for efficient adsorption and removal of Cr(VI) ions from aqueous solution.

PubMed

Niknam Shahrak, Mahdi; Ghahramaninezhad, Mahboube; Eydifarash, Mohsen

2017-04-01

Heavy metals are emerging toxic pollutants in which the development of advanced materials for their efficient adsorption and separation is thus of great significance in environmental sciences point of view. In this study, one of the zinc-based zeolitic imidazolate framework materials, known as ZIF-8, has been synthesized and used for chromium(VI) contaminant removal from water for the first time. The as-synthesized ZIF-8 adsorbent was characterized with different methodologies such as powder X-ray diffraction (XRD), thermo-gravimetric analysis, FT-IR, nuclear magnetic resonance spectroscopy, and UV-Vis spectra of solid state. Various factors affecting removal percentage (efficiency) are experimentally investigated including pH of solution, adsorbent dosage, contact time and initial concentration of Cr(VI) to achieve the optimal condition. The obtained results indicate that the ZIF-8 shows good performance for the Cr(VI) removal from aqueous solution so that 60 min mixing of 2 g of ZIF-8 adsorbent with the 2.5 ppm of Cr(VI) solution in a neutral environment will result in the highest separation efficiency around 70%. The time needed to reach the equilibrium (maximum separation efficiency) is only 60 min for a concentration of 5 mg L -1 . Structure stability in the presence of water is also carefully examined by XRD determination of ZIF-8 under different contact times in aqueous solution, which suggests that the structure is going to be destructed after 60 min immersed in solution. Electrostatic interaction of Cr(VI) anions by positively charged ZIF-8 is responsible for Cr(VI) adsorption and separation. Moreover, equilibrium adsorption study reveals that the Cr(VI) removal process using ZIF-8 nicely fits the Langmuir and Toth isotherm models which mean the adsorbent has low heterogeneous surface with different distributions of adsorption energies during Cr(VI) adsorption. Equilibrium adsorption capacity is observed around 0.25 for 20 mg L -1 of initial Cr(VI) solutions.

The influence of pH on biotite dissolution and alteration kinetics at low temperature

USGS Publications Warehouse

Acker, James G.; Bricker, O.P.

1992-01-01

Biotite dissolution rates in acidic solutions were determined in fluidized-bed reactors and flowthrough columns. Biotite dissolution rates increased inversely as a linear function of pH in the pH range 3-7, where the rate order n = -0.34. Biotite dissolved incongruently over this pH range, with preferential release of magnesium and iron from the octahedral layer. Release of tetrahedral silicon was much greater at pH 3 than at higher pH. Iron release was significantly enhanced by low pH conditions. Solution compositions from a continuous exposure flow-through column of biotite indicated biotite dissolves incongruently at pH 4, consistent with alteration to a vermiculite-type product. Solution compositions from a second intermittent-flow column exhibited elevated cation release rates upon the initiation of each exposure to solution. The presence of strong oxidizing agents, the mineral surface area, and sample preparation methodology also influenced the dissolution or alteration kinetics of biotite. ?? 1992.

Selective separation of copper over solder alloy from waste printed circuit boards leach solution.

PubMed

Kavousi, Maryam; Sattari, Anahita; Alamdari, Eskandar Keshavarz; Firozi, Sadegh

2017-02-01

The printed circuit boards (PCBs) from electronic waste are important resource, since the PCBs contain precious metals such as gold, copper, tin, silver, platinum and so forth. In addition to the economic point of view, the presence of lead turns this scrap into dangerous to environment. This study was conducted as part of the development of a novel process for selective recovery of copper over tin and lead from printed circuit boards by HBF 4 leaching. In previous study, Copper with solder alloy was associated, simultaneously were leached in HBF 4 solution using hydrogen peroxide as an oxidant at room temperature. The objective of this study is the separation of copper from tin and lead from Fluoroborate media using CP-150 as an extractant. The influence of organic solvent's concentration, pH, temperature and A/O phase ratio was investigated. The possible extraction mechanism and the composition of the extracted species have been determined. The separation factors for these metals using this agent are reported, while efficient methods for separation of Cu (II) from other metal ions are proposed. The treatment of leach liquor for solvent extraction of copper with CP-150 revealed that 20% CP-150 in kerosene, a 30min period of contact time, and a pH of 3 were sufficient for the extraction of Cu(II) and 99.99% copper was recovered from the leached solution. Copyright © 2016. Published by Elsevier Ltd.

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.

Nano-TiO2, ultrasound and sequential nano-TiO2/ultrasonic degradation of N-acetyl-para-aminophenol from aqueous solution.

PubMed

Ayanda, Olushola S; Nelana, Simphiwe M; Petrik, Leslie F; Naidoo, Eliazer B

2017-10-01

The application of nano-TiO 2 as adsorbent combined with ultrasound for the degradation of N-acetyl-para-aminophenol (AAP) from aqueous solution was investigated. The nano-TiO 2 was characterized by means of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR). Experimental results revealed that the adsorption of AAP by nano-TiO 2 fitted the pseudo-second-order kinetic model, the equilibrium could be explained by the Freundlich isotherm and the treatment process is exothermic. The optimum removal efficiency of AAP (128.89 mg/g (77.33%)) was achieved at pH 4 when 0.03 g of nano-TiO 2 was mixed with 50 mL of 100 mg/L AAP aqueous solution at ambient temperature, 60 min contact time, and a stirring speed of 120 rpm. Ultrasound at 20 kHz and pH 3 was favorable and it resulted in 52.61% and 57.43% removal efficiency with and without the addition of nano-TiO 2 , respectively. The degradation of AAP by ultrasound followed by nano-TiO 2 treatment resulted in approximately 99.50% removal efficiency. This study showed that a sequential ultrasound and nano-TiO 2 treatment process could be employed for the removal of AAP or other emerging water and wastewater contaminants.

Development of engineering parameters for the design of metal biosorption waste treatment systems

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

Graham, W.S.

1991-12-03

Untreated landfill leachates and wastes from metal plating and mining operations are sources of environmental contamination by heavy metals. Because of their toxicity and potential for accumulation, the discharge of heavy metals must be controlled. Standard physical and chemical treatments used to remove metals from wastes such as concentration by electro-precipitation, ion exchange, solvent extraction, evaporative recovery, and conventional precipitation, are usually expensive and produce high quantities of sludge. Biosorption is the removal of metals from aqueous solutions by microorganisms. It is called biosorption rather than bioadsorption or bioaccumulation because the mechanisms of removal are not restricted to adsorption ormore » metabolic uptake and so the more general term is preferable and has come to be accepted. In this thesis the focus is one two microorganisms and two metals. However, the possible combinations of conditions such as pH, relative metal molarities, time of contact, and organism are numerous. These experiments are designed to provide optimized parameters to facilitate the design of a functioning biosorption system. The two metals chosen for study are copper and lead in aqueous solution. The two types of microorganisms chosen for testing include an actinomycete and a fungus. The purpose of this research is to identify the significant engineering parameters to be evaluated include reaction rates, equilibrium partitioning of metal ions between those in solution and those removed to the cells, optimum pH for achieving the removal or recovery goal, and biosorption selectivity for one metal over another.« less

Removal of Direct Red 23 from aqueous solution using corn stalks: Isotherms, kinetics and thermodynamic studies

NASA Astrophysics Data System (ADS)

Fathi, M. R.; Asfaram, A.; Farhangi, A.

2015-01-01

The objective of this study was to assess the suitability and efficiency of corn stalk (CS) for the removal of diazo dye Direct Red 23 (DR23) from aqueous solutions. The effect of different variables in the batch method as a function of solution pH, contact time, initial dye concentration, CS amount, temperature, and so forth by the optimization method has been investigated. The color reduction was monitored by spectrophotometry at 503 nm before and after DR23 adsorption on the CS, and the removal percentage was calculated using the difference in absorbance. The sorption processes followed the pseudo second order in addition to intraparticle diffusion kinetics models with a good correlation coefficient with the overall entire adsorption of DR23 on adsorbent. The experimental equilibrium data were tested by four widely used isotherm models namely, Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich (D-R). It was found that adsorption of DR23 on CS well with the Freindlich isotherm model, implying monolayer coverage of dye molecules onto the surface of the adsorbent. More than 99% removal efficiency was obtained within 10 min at adsorbent dose of 0.2 g for initial dye concentration of 10-90 mg L-1 at pH 3. Various thermodynamic parameters, such as Gibbs free energy, entropy, and enthalpy, of the ongoing adsorption process have been calculated. Judgment based on the obtained results of thermodynamic values shows the spontaneous and endothermic nature adsorption processes on adsorbent.

Application of Mn/MCM-41 as an adsorbent to remove methyl blue from aqueous solution.

PubMed

Shao, Yimin; Wang, Xi; Kang, Yuan; Shu, Yuehong; Sun, Qiangqiang; Li, Laisheng

2014-09-01

In this study, the application of Mn loaded MCM-41 (Mn/MCM-41) was reported as a novel adsorbent for methyl blue (MB) from aqueous solution. The mesoporous structure of Mn/MCM-41 was confirmed by XRD technique. Surface area, pore size and wall thickness were calculated from BET equation and BJH method using nitrogen sorption technique. FT-IR studies showed that Mn were loaded on the hexagonal mesoporous structures of MCM-41. It is found that the MCM-41 structure retained after loading of Mn but its surface area and pore diameter decreased due to pore blockage. Adsorption of MB from aqueous solution was investigated by Mn/MCM-41 with changing Mn content, adsorbent dosage, initial MB concentration, contact time, pH and the temperature. Under the chosen condition (25°C, 0.02 g adsorbent dosage, 6.32 pH, 50 mg L(-1) MB, 1 wt.% Mn), a high MB adsorption capacity (45.38 mg g(-1)) was achieved by Mn/MCM-41 process at 120 min, 8.6 times higher than MCM-41. The electrostatic interaction was considered to be the main mechanism for the dye adsorption. The experimental data fitted well to Freundlich and Dubinin-Radushkevich isotherms. The adsorption of MB on Mn/MCM-41 followed pseudo-second-order kinetics. Thermodynamic parameters suggested that the adsorption process is endothermic and spontaneous. Copyright © 2014 Elsevier Inc. All rights reserved.

Slip stream apparatus and method for treating water in a circulating water system

DOEpatents

Cleveland, Joe R.

1997-01-01

An apparatus (10) for treating water in a circulating water system (12) t has a cooling water basin (14) includes a slip stream conduit (16) in flow communication with the circulating water system (12), a source (36) of acid solution in flow communication with the slip stream conduit (16), and a decarbonator (58) in flow communication with the slip stream conduit (16) and the cooling water basin (14). In use, a slip stream of circulating water is drawn from the circulating water system (12) into the slip stream conduit (16) of the apparatus (10). The slip stream pH is lowered by contact with an acid solution provided from the source (36) thereof. The slip stream is then passed through a decarbonator (58) to form a treated slip stream, and the treated slip stream is returned to the cooling water basin (14).

Adsorption Studies of Gadolinium ion on Graphitic Carbon Nitride

NASA Astrophysics Data System (ADS)

Kuila, S. K.; Kundu, T. K.

2018-03-01

Bulk graphitic carbon nitride (g-C3N4) is synthesized by thermal decomposition of urea and used as an adsorbent for gadolinium ion (Gd3+) from aqueous solution. Adsorption capacity of g-C3N4 is found to be influenced by initial Gd3+ concentration, solution pH and contact time. Adsorbed Gd3+is separated from g-C3N4 by ultracentrifuge. Initial and Gd ion accumulated g-C3N4 adsorbent are characterized by X-ray diffraction technique (XRD) for phase identification, UV-visible and Fourier transform infrared (FTIR) spectroscopy for adsorption characteristics and optical property, scanning electron microscopy (SEM) for morphological behaviour along with energy dispersive X-ray spectroscopy (EDS) for elemental study. HNO3(0.1M), NaOH (0.1M) and de-ionized water are used for desorption and around 97% quantitative recovery of Gd ion is observed.

Potential of mean force between two hydrophobic solutes in water.

PubMed

Southall, Noel T; Dill, Ken A

2002-12-10

We study the potential of mean force between two nonpolar solutes in the Mercedes Benz model of water. Using NPT Monte Carlo simulations, we find that the solute size determines the relative preference of two solute molecules to come into contact ('contact minimum') or to be separated by a single layer of water ('solvent-separated minimum'). Larger solutes more strongly prefer the contacting state, while smaller solutes have more tendency to become solvent-separated, particularly in cold water. The thermal driving forces oscillate with solute separation. Contacts are stabilized by entropy, whereas solvent-separated solute pairing is stabilized by enthalpy. The free energy of interaction for small solutes is well-approximated by scaled-particle theory. Copyright 2002 Elsevier Science B.V.

Influence of soil solution cation composition on boron adsorption by soils

USDA-ARS?s Scientific Manuscript database

Boron (B) adsorption on five arid-zone soil samples from California was investigated as a function of solution pH (4-10) and cation composition (Na, Ca, or Mg). Boron adsorption increased with increasing solution pH, reached an adsorption maximum near pH 9, and decreased with further increases with...

A novel biochar derived from cauliflower (Brassica oleracea L.) roots could remove norfloxacin and chlortetracycline efficiently.

PubMed

Qin, Tingting; Wang, Zhaowei; Xie, Xiaoyun; Xie, Chaoran; Zhu, Junmin; Li, Yan

2017-12-01

The biochar was prepared by pyrolyzing the roots of cauliflowers, at a temperature of 500 °C under oxygen-limited conditions. The structure and characteristics of the biochar were examined using scanning electron microscopy, an energy dispersive spectrometer, a zeta potential analyzer, and Fourier transform infrared spectroscopy. The effects of the temperature, the initial pH, antibiotic concentration, and contact time on the adsorption of norfloxacin (NOR) and chlortetracycline (CTC) onto the biochar were investigated. The adsorption kinetics of NOR and CTC onto the biochar followed the pseudo-second-order kinetic and intra-particle diffusion models. The adsorption isotherm experimental data were well fitted to the Langmuir and Freundlich isotherm models. The maximum adsorption capacities of NOR and CTC were 31.15 and 81.30 mg/g, respectively. There was little difference between the effects of initial solution pH (4.0-10.0) on the adsorption of NOR or CTC onto the biochar because of the buffering effect. The biochar could remove NOR and CTC efficiently in aqueous solutions because of its large specific surface area, abundant surface functional groups, and particular porous structure. Therefore, it could be used as an excellent adsorbent material because of its low cost and high efficiency and the extensive availability of the raw materials.

Evaluation of removal efficiency of residual diclofenac in aqueous solution by nanocomposite tungsten-carbon using design of experiment.

PubMed

Salmani, M H; Mokhtari, M; Raeisi, Z; Ehrampoush, M H; Sadeghian, H A

2017-09-01

Wastewater containing pharmaceutical residual components must be treated before being discharged to the environment. This study was conducted to investigate the efficiency of tungsten-carbon nanocomposite in diclofenac removal using design of experiment (DOE). The 27 batch adsorption experiments were done by choosing three effective parameters (pH, adsorbent dose, and initial concentration) at three levels. The nanocomposite was prepared by tungsten oxide and activated carbon powder in a ratio of 1 to 4 mass. The remaining concentration of diclofenac was measured by a spectrometer with adding reagents of 2, 2'-bipyridine, and ferric chloride. Analysis of variance (ANOVA) was applied to determine the main and interaction effects. The equilibrium time for removal process was determined as 30 min. It was observed that the pH had the lowest influence on the removal efficiency of diclofenac. Nanocomposite gave a high removal at low concentration of 5.0 mg/L. The maximum removal for an initial concentration of 5.0 mg/L was 88.0% at contact time of 30 min. The results of ANOVA showed that adsorbent mass was among the most effective variables. Using DOE as an efficient method revealed that tungsten-carbon nanocomposite has high efficiency in the removal of residual diclofenac from the aqueous solution.

Adsorptive removal of Cu(II) from aqueous solution and industrial effluent using natural/agricultural wastes.

PubMed

Singha, Biswajit; Das, Sudip Kumar

2013-07-01

The potentiality of low cost natural/agricultural waste biomasses for the removal of Cu(II) ion from aqueous solution has been investigated in batch experiments. The effect of various physico-chemical parameters such as initial pH, initial Cu(II) concentration, adsorbent dosage, contact time and temperature has been studied. The optimum pH for adsorption was found to be 6 for all adsorbents used. Kinetics data were best described by the pseudo-2nd-order model. The experimental data were fitted well with Freundlich and Halsey isotherm models. The diffusion coefficient and sorption energy indicated that the adsorption process was chemical in nature. Thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated, and it was observed that the adsorption process was spontaneous and endothermic. The mean sorption energy was calculated using Dubinin-Radushkevich isotherm model and it confirmed that the sorption process was chemical in nature. Different active functional groups were identified by FTIR studies which were responsible for Cu(II) ion adsorption process. Application study using electroplating industrial waste water and regeneration experiment of the adsorbent were also investigated. Design procedure for the batch process was also reported. Copyright © 2013 Elsevier B.V. All rights reserved.

Microstructural evolution in a 17-4 PH stainless steel after aging at 400 C

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

Murayama, M.; Hono, K.; Katayama, Y.

1999-02-01

The microstructure of 17-4 PH stainless steel at various stages of heat treatment, i.e., after solution heat treatment, tempering at 580 C, and long-term aging at 400 C, have been studied by atom probe field ion microscopy (APFIM) and transmission electron microscopy (TEM). The solution-treated specimen consists largely of martensite with a small fraction of {delta}-ferrite. No precipitates are present in the martensite phase, while spherical fcc-Cu particles are present in the {delta}-ferrite. No precipitates are present in the martensite phase, while spherical fcc-Cu particles are present in the {delta}-ferrite. After tempering for 4 hours as 580 C, coherent Cumore » particles precipitate in the martensite phase. At this stage, the Cr concentration in the martensite phase is still uniform. After 5000 hours aging at 400 C, the martensite spinodaly decomposes into Fe-rich {alpha} and Cr-enriched {alpha}{prime}. In addition, fine particles of the G-phase (structure type D8{sub a}, space group Fm{bar 3}m) enriched in Si, Ni, and Mn have been found in intimate contact with the Cu precipitates. Following spinodal decomposition of the martensite phase, G-phase precipitation occurs after long-term aging.« less

Upcycling of polypropylene waste by surface modification using radiation-induced grafting

NASA Astrophysics Data System (ADS)

Hassan, Muhammad Inaam ul; Taimur, Shaista; Yasin, Tariq

2017-11-01

In this work, upcycling of polypropylene waste into amidoxime functionalized polypropylene adsorbent was studied using radiation-induced grafting technique. Polypropylene waste (PPw) was resulted from accelerated thermal ageing of polypropylene (PP). Bulk grafting of acrylonitrile (AN) onto PPw was achieved by simultaneous radiation grafting method using gamma rays. Degree of grafting of AN on PPw is affected by absorbed dose and dose rate. The acrylonitrile groups of grafted PPw were chemically converted into amidoxime functionality. Both the acrylonitrile-grafted PP waste and its amidoxime product were investigated by FTIR, XRD, SEM-EDX and TGA techniques. The prepared amidoxime adsorbent with amidoxime group density of 8.06 mmol/g was used for removal of copper ions from aqueous solutions. The effects of various physicochemical conditions such as: solution pH, adsorbent content, initial metal ion concentration and time on adsorption were studied to maximize adsorption of metal ion. Pseudo-first-order, pseudo-second-order and intra-particle diffusion models were applied to study the kinetics of adsorption. Maximum Langmuir adsorption capacity of 208.3 mg/g at pH 5.0 with optimum contact time of 120 min was observed. Utilization of PP waste and its comparable adsorption capacity with existing radiation grafted polymer-based adsorbents provide a new, cheap and cost effective system.

Immobilization of chromate in hyperalkaline waste streams by green rusts and zero-valent iron.

PubMed

Rogers, Christine M; Burke, Ian T; Ahmed, Imad A M; Shaw, Samuel

2014-01-01

Zero-valent iron (ZVI) and green rusts can be used as reductants to convert chromium from soluble, highly toxic Cr(VI) to insoluble Cr(III). This study compared the reduction rates of Cr(VI) by ZVI and two carbonate green rust phases in alkaline/hyperalkaline solutions. Batch experiments were carried out with synthetic chromate solutions at pH 7.7-12.3 and a chromite ore processing residue (COPR) leachate (pH approximately 12.2). Green rust removes chromate from high pH solutions (pH 10-12.5) very rapidly (<400 s). Chromate reduction rates for both green rust phases were consistently higher than for ZVI throughout the pH range studied; the surface area normalized rate constants were two orders of magnitude higher in the COPR leachate solution at pH 12.2. The performances of both green rusts were unaffected by changes in pH. In contrast, ZVI exhibited a marked decline in reduction rate with increasing pH to become almost ineffective above pH12.