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Sample records for adsorption capacity due

  1. Reduction of adsorption capacity of coconut shell activated carbon for organic vapors due to moisture contents.

    PubMed

    Abiko, Hironobu; Furuse, Mitsuya; Takano, Tsuguo

    2010-01-01

    In occupational hygiene, activated carbon produced from coconut shell is a common adsorbent material for harmful substances including organic vapors due to its outstanding adsorption capacity and cost advantage. However, moisture adsorption of the carbon generally decreases the adsorption capacity for organic vapors. In a previous report, we prepared several coconut shell activated carbons which had been preconditioned by equilibration with moisture at different relative humidities and measured the breakthrough times for 6 kinds of organic vapor, in order to clarify the effect of preliminary moisture content in activated carbon on the adsorption capacity in detail. We found that the relative percent weight increase due to moisture adsorption of the carbon specimen had a quantitative effect, reducing the breakthrough time. In this report, we carried out further measurements of the effect of moisture content on the adsorption of 13 kinds of organic vapor, and investigated the relationship between moisture adsorption and the reduction of the breakthrough time of activated carbon specimens. We also applied the data to the Wood's breakthrough time estimation model which is an extension of the Wheeler-Jonas equation.

  2. Adsorption of heavy metals on to sugar cane bagasse: improvement of adsorption capacities due to anaerobic degradation of the biosorbent.

    PubMed

    Joseph, Osnick; Rouez, Maxime; Métivier-Pignon, Hélène; Bayard, Rémy; Emmanuel, Evens; Gourdon, Rémy

    2009-12-01

    In this work, anaerobic degradation of sugar cane bagasse was studied with a dual objective: the production of biogas and the improvement of the material's characteristics for its implementation in adsorption processes. The biogas production was determined by means of biomethane potential tests carried out over two months of incubation at 35 degrees C. Biogas and methane cumulative productions were assumed to follow a first-order rate of decay. Theoretical cumulative methane and biogas productions were calculated using Buswell's equation. The anaerobic digestion resulted in a 92% decrease in the leachable organic fraction and a 40% mass loss of bagasse. The average productions of biogas and methane from the whole set of experiments were 293 +/- 6 and 122 +/- 4 mL g(-1) of volatile solids, respectively. The anaerobic incubation of the raw material led to an increase in adsorption capacities towards metal ions, which were multiplied by around 2.0 for Zn2+ and 2.3 for Cd2+.

  3. A study of the alumina-silica gel adsorbent for the removal of silicic acid from geothermal water: increase in adsorption capacity of the adsorbent due to formation of amorphous aluminosilicate by adsorption of silicic acid.

    PubMed

    Yokoyama, Takushi; Ueda, Akira; Kato, Koichi; Mogi, Katsumi; Matsuo, Shorin

    2002-08-01

    Two kinds of adsorbents (Si adsorbent and Al adsorbent) for the removal of silicic acid from geothermal water to retard the formation of silica scales were prepared using silicic acid contained in geothermal water. The Si adsorbent was prepared by evaporating geothermal water, and the Al adsorbent was prepared by evaporating geothermal water after the addition of aluminum chloride. The specific surface area of the Si adsorbent was small and it's adsorption capacity of silicic acid was low. Although the specific surface area of the Al adsorbent was also small, it was significantly increased by the adsorption of silicic acid and it's adsorption capacity was high. Based on the change in the local structure of aluminum ion by the adsorption of silicic acid, the Al adsorbent was considered to be silica particles covered with crystalline aluminum hydroxide. Moreover, it was concluded that the increase in the specific surface area of the Al adsorbent and the decrease in the zeta potential were due to the formation of an amorphous aluminosilicate with a large surface area and a negative charge (one 4-coordinated Al) by the reaction between aluminum ions and silicic acids.

  4. Gas adsorption capacity of wood pellets

    DOE PAGES

    Yazdanpanah, F.; Sokhansanj, Shahabaddine; Lim, C. Jim; ...

    2016-02-03

    In this paper, temperature-programmed desorption (TPD) analysis was used to measure and analyze the adsorption of off-gases and oxygen by wood pellets during storage. Such information on how these gases interact with the material helps in the understanding of the purging/stripping behavior of off-gases to develop effective ventilation strategies for wood pellets. Steam-exploded pellets showed the lowest carbon dioxide (CO2) uptake compared to the regular and torrefied pellets. The high CO2 adsorption capacity of the torrefied pellets could be attributed to their porous structure and therefore greater available surface area. Quantifying the uptake of carbon monoxide by pellets was challengingmore » due to chemical adsorption, which formed a strong bond between the material and carbon monoxide. The estimated energy of desorption for CO (97.8 kJ/mol) was very high relative to that for CO2 (7.24 kJ/mol), demonstrating the mechanism of chemical adsorption and physical adsorption for CO and CO2, respectively. As for oxygen, the strong bonds that formed between the material and oxygen verified the existence of chemical adsorption and formation of an intermediate material.« less

  5. Gas adsorption capacity of wood pellets

    SciTech Connect

    Yazdanpanah, F.; Sokhansanj, Shahabaddine; Lim, C. Jim; Lau, A.; Bi, X. T.

    2016-02-03

    In this paper, temperature-programmed desorption (TPD) analysis was used to measure and analyze the adsorption of off-gases and oxygen by wood pellets during storage. Such information on how these gases interact with the material helps in the understanding of the purging/stripping behavior of off-gases to develop effective ventilation strategies for wood pellets. Steam-exploded pellets showed the lowest carbon dioxide (CO2) uptake compared to the regular and torrefied pellets. The high CO2 adsorption capacity of the torrefied pellets could be attributed to their porous structure and therefore greater available surface area. Quantifying the uptake of carbon monoxide by pellets was challenging due to chemical adsorption, which formed a strong bond between the material and carbon monoxide. The estimated energy of desorption for CO (97.8 kJ/mol) was very high relative to that for CO2 (7.24 kJ/mol), demonstrating the mechanism of chemical adsorption and physical adsorption for CO and CO2, respectively. As for oxygen, the strong bonds that formed between the material and oxygen verified the existence of chemical adsorption and formation of an intermediate material.

  6. Predicting protein dynamic binding capacity from batch adsorption tests.

    PubMed

    Carta, Giorgio

    2012-10-01

    The dynamic binding capacity (DBC) and its dependence on residence time influence the design and productivity of adsorption columns used in protein capture applications. This paper offers a very simple approach to predict the DBC of an adsorption column based on a measurement of the equilibrium binding capacity (EBC) and of the time needed to achieve one-half of the EBC in a batch adsorption test. The approach is based on a mass transfer kinetics model that assumes pore diffusion with a rectangular isotherm; however, the same approach is also shown to work for other systems where solute transport inside the particle occurs through other transport mechanisms.

  7. Evaluating the Adsorptive Capacities of Chemsorb 1000 and Chemsorb 1425

    NASA Technical Reports Server (NTRS)

    Monje, Oscar Alberto Monje; Surma, Jan M.; Johnsey, Marissa N.; Melendez, Orlando

    2014-01-01

    The Air Revitalization Lab at KSC tested Chemsorb 1000 and 1425, two candidate sorbents for use in future air revitalization technologies being evaluated by the ARREM project. Chemsorb 1000 and 1425 are granular coconut-shell activated carbon sorbents produced by Molecular Products, Inc. that may be used in the TCCS. Chemsorb 1000 is a high grade activated carbon for organic vapor adsorption. In contrast, Chemsorb 1425 is a high-grade impregnated activated carbon for adsorption of airborne ammonia and amines. Chemsorb 1000 was challenged with simulated spacecraft gas streams in order to determine its adsorptive capacities for mixtures of volatile organics compounds. Chemsorb 1425 was challenged with various NH3 concentrations to determine its adsorptive capacity.

  8. High capacity adsorption media and method of producing

    DOEpatents

    Tranter, Troy J.; Herbst, R. Scott; Mann, Nicholas R.; Todd, Terry A.

    2008-05-06

    A method of producing an adsorption medium to remove at least one constituent from a feed stream. The method comprises dissolving at least one metal compound in a solvent to form a metal solution, dissolving polyacrylonitrile into the metal solution to form a PAN-metal solution, and depositing the PAN-metal solution into a quenching bath to produce the adsorption medium. The at least one constituent, such as arsenic, selenium, or antimony, is removed from the feed stream by passing the feed stream through the adsorption medium. An adsorption medium having an increased metal loading and increased capacity for arresting the at least one constituent to be removed is also disclosed. The adsorption medium includes a polyacrylonitrile matrix and at least one metal hydroxide incorporated into the polyacrylonitrile matrix.

  9. High capacity adsorption media and method of producing

    DOEpatents

    Tranter, Troy J.; Mann, Nicholas R.; Todd, Terry A.; Herbst, Ronald S.

    2010-10-05

    A method of producing an adsorption medium to remove at least one constituent from a feed stream. The method comprises dissolving and/or suspending at least one metal compound in a solvent to form a metal solution, dissolving polyacrylonitrile into the metal solution to form a PAN-metal solution, and depositing the PAN-metal solution into a quenching bath to produce the adsorption medium. The at least one constituent, such as arsenic, selenium, or antimony, is removed from the feed stream by passing the feed stream through the adsorption medium. An adsorption medium having an increased metal loading and increased capacity for arresting the at least one constituent to be removed is also disclosed. The adsorption medium includes a polyacrylonitrile matrix and at least one metal hydroxide incorporated into the polyacrylonitrile matrix.

  10. Novel biosorbent with high adsorption capacity prepared by chemical modification of white pine (Pinus durangensis) sawdust. Adsorption of Pb(II) from aqueous solutions.

    PubMed

    Salazar-Rabago, J J; Leyva-Ramos, R

    2016-03-15

    The natural sawdust (NS) from white pine (Pinus durangensis) was chemically modified by a hydrothermal procedure using citric, malonic and tartaric acids. The adsorption capacity of modified sawdust (MS) towards Pb(II) was considerably enhanced due to the introduction of carboxylic groups on the surface of MS during the modification, and the adsorption capacity was almost linearly dependent on the concentration of carboxylic sites. The NS surface was acidic, and the MS surface became more acidic after the modification. At T = 25 °C and pH = 5, the maximum adsorption capacity of the optimal MS towards Pb(II) was 304 mg/g, which is exceptionally high compared to NS and other MS reported previously. The adsorption capacity of MS was considerably reduced from 304 to 154 mg/g by decreasing the solution pH from 5 to 3 due to electrostatic interactions. The adsorption of Pb(II) on MS was reversible at pH = 2, but not at pH = 5. The contribution percentage of ion exchange to the overall adsorption capacity ranged from 70 to 99% and 10-66% at the initial pH of 3 and 5, respectively. Hence, the adsorption of Pb(II) on MS was mainly due to ion exchange at pH = 3 and to both ion exchange and electrostatic attraction at pH = 5.

  11. Evaluation of the adsorption capacity of alkali-treated waste materials for the adsorption of sulphamethoxazole.

    PubMed

    Kurup, Lisha

    2012-01-01

    The present work is to develop potential adsorbents from waste material and employ them for the removal of a hazardous antibacterial, sulphamethoxazole, from the wastewater by the Adsorption technique. The Adsorption technique was used to impound the dangerous antibiotics from wastewater using Deoiled Soya (DOS), an agricultural waste, and Water Hyacinth (WH), a prolific colonizer. The adsorption capacity of these adsorbents was further enhanced by treating them with sodium hydroxide solution and it was seen that the adsorption capacity increases by 10 to 25%. Hence a comparative account of the adsorption studies of all the four adsorbents, i.e. DOS, Alkali-treated DOS, WH and Alkali-treated Water Hyacinth has been discussed in this paper. Different isotherms like Freundlich, Langmuir and Dubinin-Radushkevich were also deduced from the adsorption data. Isotherm studies were in turn used in estimating the thermodynamic parameters. DOS showed sorption capacity of 0.0007 mol g(-1) while Alkali-treated Deoiled Soya exhibited 0.0011 mol g(-1) of sorption capacity, which reveals that the adsorption is higher in case of alkali-treated adsorbent. The mean sorption energy (E) was obtained between 9 and 12 kJ mol, which shows that the reaction proceeds by ion exchange reaction. Kinetic study reveals that the reaction follows pseudo-second-order rate equation. Moreover, mass transfer studies performed for the ongoing processes show that the mass transfer coefficient obtained for alkali-treated moieties was higher than the parent moieties. The breakthrough curves plotted from the column studies show percentage saturation of 90-98%. About 87-97% of sulphamethoxazole was recovered from column by desorption.

  12. Effect of calcium on adsorption capacity of powdered activated carbon.

    PubMed

    Li, Gang; Shang, Junteng; Wang, Ying; Li, Yansheng; Gao, Hong

    2013-12-01

    We investigated the effect of calcium ion on the adsorption of humic acid (HA) (as a target pollutant) by powered activated carbon. The HA adsorption isotherms at different pH and kinetics of two different solutions including HA alone and HA doped Ca(2+), were performed. It was showed that the adsorption capacity of powdered activated carbon (PAC) for HA was markedly enhanced when Ca(2+) was doped into HA. Also, HA and Ca(2+) taken as nitrate were tested on the uptake of each other respectively and it was showed that the adsorbed amounts of both of them were significantly promoted when HA and calcium co-existed. Furthermore, the adsorbed amount of HA slightly decreased with the increasing of Ca(2+) concentration, whereas the amount of calcium increased with the increasing of HA concentration, but all above the amounts without addition. Finally, the change of pH before and after adsorption process is studied. In the two different solutions including HA alone and HA doped Ca(2+), pH had a small rise, but the extent of pH of later solution was bigger.

  13. Adsorption of selected pharmaceuticals and an endocrine disrupting compound by granular activated carbon. 1. Adsorption capacity and kinetics

    SciTech Connect

    Yu, Z.; Peldszus, S.; Huck, P.M.

    2009-03-01

    The adsorption of two representative PhACs (naproxen and carbamazepine) and one EDC (nonylphenol) were evaluated on two granular activated carbons (GAC) namely coal-based Calgon Filtrasorb 400 and coconut shell-based PICA CTIF TE. The primary objective was to investigate preloading effects by natural organic matter (NOM) on adsorption capacity and kinetics under conditions and concentrations (i.e., ng/L) relevant for drinking water treatment. Isotherms demonstrated that all compounds were significantly negatively impacted by NOM fouling. Adsorption capacity reduction was most severe for the acidic naproxen, followed by the neutral carbamazepine and then the more hydrophobic nonylphenol. The GAC with the wider pore size distribution had considerably greater NOM loading, resulting in lower adsorption capacity. Different patterns for the change in Freundlich KF and 1/n with time revealed different competitive mechanisms for the different compounds. Mass transport coefficients determined by short fixed-bed (SFB) tests with virgin and preloaded GAC demonstrated that film diffusion primarily controls mass transfer on virgin and preloaded carbon. Naproxen suffered the greatest deteriorative effect on kinetic parameters due to preloading, followed by carbamazepine, and then nonylphenol. A type of surface NOM/biofilm, which appeared to add an additional mass transfer resistance layer and thus reduce film diffusion, was observed. In addition, electrostatic interactions between NOM/biofilm and the investigated compounds are proposed to contribute to the reduction of film diffusion. A companion paper building on this work describes treatability studies in pilot-scale GAC adsorbers and the effectiveness of a selected fixed-bed model. 32 refs., 3 figs., 2 tabs.

  14. Proteomic analysis of protein adsorption capacity of different haemodialysis membranes.

    PubMed

    Urbani, Andrea; Lupisella, Santina; Sirolli, Vittorio; Bucci, Sonia; Amoroso, Luigi; Pavone, Barbara; Pieroni, Luisa; Sacchetta, Paolo; Bonomini, Mario

    2012-04-01

    Protein-adsorptive properties are a key feature of membranes used for haemodialysis treatment. Protein adsorption is vital to the biocompatibility of a membrane material and influences membrane's performance. The object of the present study is to investigate membrane biocompatibility by correlating the adsorbed proteome repertoire with chemical feature of the membrane surfaces. Dialyzers composed of either cellulose triacetate (Sureflux 50 L, effective surface area 0.5 m(2); Nipro Corporation, Japan) or the polysulfone-based helixone (FX40, effective surface area 0.4 m(2); Fresenius Medical Care AG, Germany) materials were employed to develop an ex vivo apparatus to study protein adsorption. Adsorbed proteins were eluted by a strong chaotropic buffer condition and investigated by a proteomic approach. The profiling strategy was based on 2D-electrophoresis separation of desorbed protein coupled to MALDI-TOF/TOF analysis. The total protein adsorption was not significantly different between the two materials. An average of 179 protein spots was visualised for helixone membranes while a map of retained proteins of cellulose triacetate membranes was made up of 239 protein spots. The cellulose triacetate material showed a higher binding capacity for albumin and apolipoprotein. In fact, a number of different protein spots belonging to the gene transcript of albumin were visible in the cellulose triacetate map. In contrast, helixone bound only a small proportion of albumin, while proved to be particularly active in retaining protein associated with the coagulation cascade, such as the fibrinogen isoforms. Our data indicate that proteomic techniques are a useful approach for the investigation of proteins surface-adsorbed onto haemodialysis membranes, and may provide a molecular base for the interpretation of the efficacy and safety of anticoagulation treatment during renal replacement therapy.

  15. Chemical modification of oxalate decarboxylase to improve adsorption capacity.

    PubMed

    Lin, Rihui; He, Junbin; Wu, Jia; Cai, Xinghua; Long, Han; Chen, Shengfeng; Liu, Haiqian

    2017-02-03

    In order to enhance the adsorption capacity of oxalate decarboxylase (Oxdc) on calcium oxalate monohydrate crystals and improve the application performance of Oxdc, chemical modification of Oxdc with ethylenediaminetetraacetic dianhydride (EDTAD) was investigated in this work. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and liquid chromatography tandem mass spectrometry (LC/MS) analysis results demonstrated that Oxdc and EDTAD have been covalently bound, and suggested that the chemical modification occurred at the free amino of the side chain and the α-amine of the N-terminus of Oxdc. Fluorescene and circular dichroic measurement showed that the structure and conformation of Oxdc were tinily altered after modification by EDTAD. The optimum pH of EDTAD-modified Oxdc was shifted to the alkaline side about 1.5 unit and it has a higher thermostability. The analysis of kinetic parameters indicated that the EDTAD-modified Oxdc showed a higher affinity towards the substrate. Through modification the adsorption capacity of Oxdc onto CaOx monohydrate crystals was increased by 42.42%.

  16. Adsorption capacities of poly-γ-glutamic acid and its sodium salt for cesium removal from radioactive wastewaters.

    PubMed

    Sakamoto, Shigeki; Kawase, Yoshinori

    2016-12-01

    Cesium removal from radioactive wastewaters was examined using water-insoluble poly-γ-glutamic acid (γ-PGA) and water-soluble sodium salt form poly-γ-L-glutamic acid (γ-PGANa) as biosorbents. The maximum adsorption capacities at equilibrium of γ-PGA and γ-PGANa for Cs were 345 mg-Cs(g-γ-PGA)(-1) at pH 6.0 and 290 mg-Cs(g-γ-PGANa)(-1) at pH 9.0, respectively. At lower pH < pKa, the carboxyl groups of γ-PGA primarily remained in the protonated form and adsorption of Cs only slightly occurred. At higher pH > pKa, the adsorption of Cs was significantly facilitated due to ionization of carboxyl groups to carboxylate ion. Adsorption of Cs at pH > 9.0 was inhibited due to the hydrolysis of Cs. The Langmuir model could successfully describe the isotherm data. For γ-PGA and γ-PGANa, the maximum adsorption capacities at equilibrium in the Langmuir model were 446 and 333 mg-Cs(g-adsorbent)(-1), respectively. The high adsorption capacities confirmed a potential utilization of γ-PGA and γ-PGANa for Cs removal. The adsorption of Cs by both γ-PGA and γ-PGANa attained the equilibrium within 0.5 min. The very quick equilibration is a benefit from the viewpoint of practical application. The spectra of FT-IR and XPS before and after adsorption confirmed the adsorption of Cs onto γ-PGA and γ-PGANa via electrostatic interaction with carboxylate anions.

  17. Enhanced chromium adsorption capacity via plasma modification of natural zeolites

    NASA Astrophysics Data System (ADS)

    Cagomoc, Charisse Marie D.; Vasquez, Magdaleno R., Jr.

    2017-01-01

    Natural zeolites such as mordenite are excellent adsorbents for heavy metals. To enhance the adsorption capacity of zeolite, sodium-exchanged samples were irradiated with 13.56 MHz capacitively coupled radio frequency (RF) argon gas discharge. Hexavalent chromium [Cr(VI)] was used as the test heavy metal. Pristine and plasma-treated zeolite samples were soaked in 50 mg/L Cr solution and the amount of adsorbed Cr(VI) on the zeolites was calculated at predetermined time intervals. Compared with untreated zeolite samples, initial Cr(VI) uptake was 70% higher for plasma-treated zeolite granules (50 W 30 min) after 1 h of soaking. After 24 h, all plasma-treated zeolites showed increased Cr(VI) uptake. For a 2- to 4-month period, Cr(VI) uptake increased about 130% compared with untreated zeolite granules. X-ray diffraction analyses between untreated and treated zeolite samples revealed no major difference in terms of its crystal structure. However, for plasma-treated samples, an increase in the number of surface defects was observed from scanning electron microscopy images. This increase in the number of surface defects induced by plasma exposure played a crucial role in increasing the number of active sorption sites on the zeolite surface.

  18. High-capacity adsorption of aniline using surface modification of lignocellulose-biomass jute fibers.

    PubMed

    Gao, Da-Wen; Hu, Qi; Pan, Hongyu; Jiang, Jiping; Wang, Peng

    2015-10-01

    Pyromellitic dianhydride (PMDA) modified jute fiber (MJF) were prepared with microwave treatment to generate a biosorbent for aniline removal. The characterization of the biosorbent was investigated by SEM, BET and FT-IR analysis to discuss the adsorption mechanism. The studies of various factors influencing the adsorption behavior indicated that the optimum dosage for aniline adsorption was 3g/L, the maximum adsorption capacity was observed at pH 7.0 and the adsorption process is spontaneous and endothermic. The aniline adsorption follows the pseudo second order kinetic model and Langmuir isotherm model. Moreover, the biosorbent could be regenerated through the desorption of aniline by using 0.5M HCl solution, and the adsorption capacity after regeneration is even higher than that of virgin MJF. All these results prove MJF is a promising adsorbent for aniline removal in wastewater.

  19. Estimation of Reduction in Airspace Capacity Due to Convective Weather

    NASA Technical Reports Server (NTRS)

    Sheth, Kapil; Sridhar, Banavar; Namjoshi, Leena

    2006-01-01

    Severe convective weather routinely disrupts normal flow of air traffic in the United States' National Airspace System (NAS). Over the last decade, severe weather has been the most significant cause, accounting for over 70% of air traffic delays in the NAS. Flights incur modification in their nominal routes due to the presence of severe weather, and hence, suffer increased delays. These delays contribute to increased burden on airlines due to extra fuel costs and missed schedules for connecting flights. In this paper, the reduction in air space capacity and the associated air traffic delays due to severe convective weather will be investigated.

  20. Modeling high adsorption capacity and kinetics of organic macromolecules on super-powdered activated carbon.

    PubMed

    Matsui, Yoshihiko; Ando, Naoya; Yoshida, Tomoaki; Kurotobi, Ryuji; Matsushita, Taku; Ohno, Koichi

    2011-02-01

    The capacity to adsorb natural organic matter (NOM) and polystyrene sulfonates (PSSs) on small particle-size activated carbon (super-powdered activated carbon, SPAC) is higher than that on larger particle-size activated carbon (powdered-activated carbon, PAC). Increased adsorption capacity is likely attributable to the larger external surface area because the NOM and PSS molecules do not completely penetrate the adsorbent particle; they preferentially adsorb near the outer surface of the particle. In this study, we propose a new isotherm equation, the Shell Adsorption Model (SAM), to explain the higher adsorption capacity on smaller adsorbent particles and to describe quantitatively adsorption isotherms of activated carbons of different particle sizes: PAC and SPAC. The SAM was verified with the experimental data of PSS adsorption kinetics as well as equilibrium. SAM successfully characterized PSS adsorption isotherm data for SPACs and PAC simultaneously with the same model parameters. When SAM was incorporated into an adsorption kinetic model, kinetic decay curves for PSSs adsorbing onto activated carbons of different particle sizes could be simultaneously described with a single kinetics parameter value. On the other hand, when SAM was not incorporated into such an adsorption kinetic model and instead isotherms were described by the Freundlich model, the kinetic decay curves were not well described. The success of the SAM further supports the adsorption mechanism of PSSs preferentially adsorbing near the outer surface of activated carbon particles.

  1. Adsorption characteristics of adsorbent resins and antioxidant capacity for enrichment of phenolics from two-phase olive waste.

    PubMed

    Wang, Zhihong; Wang, Chengzhang; Yuan, Jiaojiao; Zhang, Changwei

    2017-01-01

    In this study, the adsorption properties of nine resins including polyamide resin (30-60), polyamide resin (60-100) AB-8, S-8, D-101, NKA-9, NKA-II, XDA-1 and XDA-4 for enrichment phenolics of the olive waste were investigated. XDA-1 and NKA-II were chosen for further study due to their outstanding adsorption and desorption capacity. XDA-1 and NKA-II had similar adsorption and desorption behaviors for phenolics of olive waste. The adsorption mechanism could be better explained by pseudo second-order kinetics model and Freundlich isotherm model, and the adsorption processes were spontaneously and exothermic. The experiment of gradient elution were carried out through treated XDA-1 resins column, the result indicated the total phenolics were mainly obtained from the 40% and 60% ethanol fraction. The order of antioxidant capacity by DPPH  , ABTS(+) radical and FRAP assay was similar with the content of phenolics from fraction elution. The compositions of phenolics from different elution fractions were determined by reversed phase-HPLC-DAD method. Gallic acid, hydroxytyrosol, tyrosol and ferulic acid were the major constituent in the fraction elute, and the content of hydroxytyrosol reached to the 41.69mg/g. The above results revealed the synergistic effects of the different phenolics contribute to the antioxidant capacity.

  2. High-capacity hydrogen and nitric oxide adsorption and storage in a metal-organic framework.

    PubMed

    Xiao, Bo; Wheatley, Paul S; Zhao, Xuebo; Fletcher, Ashleigh J; Fox, Sarah; Rossi, Adriano G; Megson, Ian L; Bordiga, S; Regli, L; Thomas, K Mark; Morris, Russell E

    2007-02-07

    Gas adsorption experiments have been carried out on a copper benzene tricarboxylate metal-organic framework material, HKUST-1. Hydrogen adsorption at 1 and 10 bar (both 77 K) gives an adsorption capacity of 11.16 mmol H2 per g of HKUST-1 (22.7 mg g(-)1, 2.27 wt %) at 1 bar and 18 mmol per g (36.28 mg g(-)1, 3.6 wt %) at 10 bar. Adsorption of D2 at 1 bar (77 K) is between 1.09 (at 1 bar) and 1.20(at <100 mbar) times the H2 values depending on the pressure, agreeing with the theoretical expectations. Gravimetric adsorption measurements of NO on HKUST-1 at 196 K (1 bar) gives a large adsorption capacity of approximately 9 mmol g(-1), which is significantly greater than any other adsorption capacity reported on a porous solid. At 298 K the adsorption capacity at 1 bar is just over 3 mmol g(-1). Infra red experiments show that the NO binds to the empty copper metal sites in HKUST-1. Chemiluminescence and platelet aggregometry experiments indicate that the amount of NO recovered on exposure of the resulting complex to water is enough to be biologically active, completely inhibiting platelet aggregation in platelet rich plasma.

  3. Quantitative evaluation of the effect of moisture contents of coconut shell activated carbon used for respirators on adsorption capacity for organic vapors.

    PubMed

    Abiko, Hironobu; Furuse, Mitsuya; Takano, Tsuguo

    2010-01-01

    Activated carbon is an elemental material used for hygienic applications, particularly as an adsorbent for harmful gases and vapors. In Japanese industrial and occupational hygiene, activated carbon produced from coconut shell is a traditional and popular adsorbent material due to its excellent adsorption ability and cost advantage. In this research, in order to clarify the effect of the preliminary content of moisture on the adsorption capacity in detail, we prepared several coconut shell activated carbons which were preconditioned by equilibration with moisture at different relative humidities. We measured their adsorption capacities as breakthrough times for 6 kinds of organic vapor, and attempted to determine the relationships between the relative weight increase of water adsorption and the decrease of adsorption capacities of the activated carbon specimens for the organic vapors. The procedure of the quantitative evaluation of the effect of moisture and the results are useful for practical applications of activated carbon, particularly those used as adsorbents in workplaces.

  4. Methane Adsorption on Aggregates of Fullerenes: Site-Selective Storage Capacities and Adsorption Energies

    PubMed Central

    Kaiser, Alexander; Zöttl, Samuel; Bartl, Peter; Leidlmair, Christian; Mauracher, Andreas; Probst, Michael; Denifl, Stephan; Echt, Olof; Scheier, Paul

    2013-01-01

    Methane adsorption on positively charged aggregates of C60 is investigated by both mass spectrometry and computer simulations. Calculated adsorption energies of 118–281 meV are in the optimal range for high-density storage of natural gas. Groove sites, dimple sites, and the first complete adsorption shells are identified experimentally and confirmed by molecular dynamics simulations, using a newly developed force field for methane–methane and fullerene–methane interaction. The effects of corrugation and curvature are discussed and compared with data for adsorption on graphite, graphene, and carbon nanotubes. PMID:23744834

  5. Methane adsorption on aggregates of fullerenes: site-selective storage capacities and adsorption energies.

    PubMed

    Kaiser, Alexander; Zöttl, Samuel; Bartl, Peter; Leidlmair, Christian; Mauracher, Andreas; Probst, Michael; Denifl, Stephan; Echt, Olof; Scheier, Paul

    2013-07-01

    Methane adsorption on positively charged aggregates of C60 is investigated by both mass spectrometry and computer simulations. Calculated adsorption energies of 118-281 meV are in the optimal range for high-density storage of natural gas. Groove sites, dimple sites, and the first complete adsorption shells are identified experimentally and confirmed by molecular dynamics simulations, using a newly developed force field for methane-methane and fullerene-methane interaction. The effects of corrugation and curvature are discussed and compared with data for adsorption on graphite, graphene, and carbon nanotubes.

  6. Efficient removal and highly selective adsorption of Hg2+ by polydopamine nanospheres with total recycle capacity

    NASA Astrophysics Data System (ADS)

    Zhang, Xiulan; Jia, Xin; Zhang, Guoxiang; Hu, Jiamei; Sheng, Wenbo; Ma, Zhiyuan; Lu, Jianjiang; Liu, Zhiyong

    2014-09-01

    This study reported a new method for efficient removal of Hg2+ from contaminated water using highly selective adsorptive polydopamine (PDA) nanospheres, which were uniform and had a small diameter (150-200 nm). The adsorption isotherms, kinetics, thermodynamics were investigated. Also, the effects of ionic strength, co-existing ions on removing ability of PDA nanospheres for Hg2+ were studied. Adsorption of Hg2+ was very fast and efficient as adsorption equilibrium was completed within 4 h and the maximum adsorption capacities were 1861.72 mg/g, 2037.22 mg/g, and 2076.81 mg/g at 298 K, 313 K, and 328 K respectively, increasing with increasing of temperature. The PDA nanospheres exhibited highly selective adsorption of Hg2+ and had a total desorption capacity of 100% in hydrochloric acid solution, pH 1. The results showed that the structure of PDA nanospheres remained almost unchanged after recycling five times. Furthermore, X-ray photoelectron spectroscopy (XPS) was employed to determine the elements of PDA nanospheres before and after Hg2+ adsorption. Considering their efficient and highly Hg2+ selective adsorption, total recycle capacity, and high stability, PDA nanospheres will be feasible in a number of practical applications.

  7. Structural properties and adsorption capacity of holocellulose aerogels synthesized from an alkali hydroxide-urea solution

    NASA Astrophysics Data System (ADS)

    Kwon, Gu-Joong; Kim, Dae-Young; Hwang, Jae-Hyun; Kang, Joo-Hyon

    2014-05-01

    A tulip tree was used to synthesize a holocellulose aerogel from an aqueous alkali hydroxide-urea solution with the substitution of an organic solvent followed by freeze-drying. For comparison, the synthesized holocellulose aerogels were divided into two groups according to the source of the hydrogel, an upper suspended layer and a bottom concentrated layer of the centrifuged solution of cellulose and NaOH/urea solvents. We investigated the effects of the temperature of the pre-cooled NaOH/urea solution ( i.e., dissolution temperature) on the pore structure and the adsorption capacity of the holocellulose aerogel. A nano-fibrillar network structure of the holocellulose aerogel was observed, with little morphological difference in pore structure for different dissolution temperatures. Both micropores and mesopores were observed in the holocellulose aerogel. The specific surface area of the holocellulose aerogel was generally greater at lower dissolution temperatures. In a series of adsorption tests using methylene blue, the holocellulose aerogel showed the greatest adsorption capacity at the lowest dissolution temperature tested (-2°C). However, the dissolution temperature generally had little effect on the adsorption capacity. The holocellulose aerogel produced from the upper suspended layer of the centrifuged hydrogel solution showed a greater porosity and adsorption capacity than the one produced from the bottom concentrated layer. Overall, the aerogel made by utilizing a delignified tulip tree display a high surface area and a high adsorption property, indicating its possible application in eco-friendly adsorption materials.

  8. Better adsorption capacity of SnO2 nanoparticles with different graphene addition

    NASA Astrophysics Data System (ADS)

    Paramarta, V.; Taufik, A.; Saleh, R.

    2016-11-01

    The adsorption capacity of SnO2 nanoparticle has been studied by graphene and nanographene platelets (NGP) additions using co-precipitation method. The crystalline phase, composition, and morphology of the samples are analyzed using X-Ray Diffraction (XRD), Energy Dispersive X-Ray (EDX), Fourier Transform Infrared Spectroscopy (FT-IR), and Transmission Electron Microscope (TEM). Tetragonal structure of SnO2 is shown for the nanoparticle and its composites. The presence of graphene and NGP is also confirmed. The adsorption capacity of the nanoparticle and its composites are analyzed by observing the degradation of methylene blue (MB) as the organic dye model using UV-Vis Spectroscopy. The result shows that SnO2 composite with graphene achieves higher adsorption capacity of about 20% than the composite with NGP. The fitting of equilibrium adsorption capacity result indicates that the adsorption mechanism of SnO2 composite with graphene tends to follow the Langmuir adsorption-isotherm model.

  9. Enhancement of the anionic dye adsorption capacity of clinoptilolite by Fe(3+)-grafting.

    PubMed

    Akgül, Murat

    2014-02-28

    In this paper, a batch system was applied to study the adsorption behavior of congo red (CR) on raw and modified clinoptilolites. Raw clinoptilolite (Raw-CL) was treated with Fe(NO3)3 in ethanol to obtain its iron-grafted form (Fe-CL). Adsorbents were characterized by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), energy dispersive X-ray spectroscopy (EDX), thermogravimetric/differential thermal analysis (TG/DTA), zeta-potential measurement and N2 gas adsorption-desorption techniques. Effects of the experimental parameters (initial pH, dye concentration, temperature and adsorption time) were investigated to find optimum conditions that result in highest adsorption capacity for CR removal. The obtained results suggest that the solution pH appears to be a key factor of the CR adsorption process. The maximum dye adsorption was achieved with Fe-CL adsorbent at pH ∼6.3 and the corresponding adsorption capacity was found to be 36.7mg/g, which is higher than that of its raw counterpart (16.9mg/g). A significant decrease in CR removal was given by Fe-CL between pH 7 and 11 opposite to Raw-CL which has nearly constant qe in the same pH range. The Fe(3+)-grafting increased the zeta potential of raw clinoptilolite, leading to a higher adsorption capacity compared to that of unfunctionalized adsorbent. Also, temperature change was found to have a significant effect on the adsorption process.

  10. Reservoir capacity estimates in shale plays based on experimental adsorption data

    NASA Astrophysics Data System (ADS)

    Ngo, Tan

    from different measurement techniques using representative fluids (such as CH4 and CO2) at elevated pressures, and the adsorbed density can range anywhere between the liquid and the solid state of the adsorbate. Whether these discrepancies are associated with the inherent heterogeneity of mudrocks and/or with poor data quality requires more experiments under well-controlled conditions. Nevertheless, it has been found in this study that methane GIP estimates can vary between 10-45% and 10-30%, respectively, depending on whether the free or the total amount of gas is considered. Accordingly, CO2 storage estimates range between 30-90% and 15-50%, due to the larger adsorption capacity and gas density at similar pressure and temperature conditions. A manometric system has been designed and built that allows measuring the adsorption of supercritical fluids in microporous materials. Preliminary adsorption tests have been performed using a microporous 13X zeolite and CO 2 as an adsorbing gas at a temperature of 25oC and 35oC and at pressures up to 500 psi. Under these conditions, adsorption is quantified with a precision of +/- 3%. However, relative differences up to 15-20% have been observed with respect to data published in the literature on the same adsorbent and at similar experimental conditions. While it cannot be fully explained with uncertainty analysis, this discrepancy can be reduced by improving experiment practice, thus including the application of a higher adsorbent's regeneration temperature, of longer equilibrium times and of a careful flushing of the system between the various experimental steps. Based on the results on 13X zeolite, virtual tests have been conducted to predict the performance of the manometric system to measure adsorption on less adsorbing materials, such as mudrocks. The results show that uncertainties in the estimated adsorbed amount are much more significant in shale material and they increase with increasing pressure. In fact, relative

  11. Correlation and prediction of adsorption capacity and affinity of aromatic compounds on carbon nanotubes.

    PubMed

    Wu, Wenhao; Yang, Kun; Chen, Wei; Wang, Wendi; Zhang, Jie; Lin, Daohui; Xing, Baoshan

    2016-01-01

    Adsorption of 22 nonpolar and polar aromatic compounds on 10 carbon nanotubes (CNTs) with various diameters, lengths and surface oxygen-containing group contents was investigated to develop predictive correlations for adsorption, using the isotherm fitting of Polanyi theory-based Dubinin-Ashtakhov (DA) model. Adsorption capacity of aromatic compounds on CNTs is negatively correlated with melting points of aromatic compounds, and surface oxygen-containing group contents and surface area ratios of mesopores to total pores of CNTs, but positively correlated with total surface area of CNTs. Adsorption affinity is positively correlated with solvatochromic parameters of aromatic compounds, independent of tube lengths and surface oxygen-containing group contents of CNTs, but negatively correlated with surface area ratios of mesopores to total pores of CNTs. The correlations of adsorption capacity and adsorption affinity with properties of both aromatic compounds and CNTs clearly have physical significance, can be used successfully with DA model to predict adsorption of aromatic compounds on CNTs from the well-known physiochemical properties of aromatic compounds (i.e., solvatochromic parameters, melting points) and CNTs (i.e., surface area and total acidic group contents), and thus can facilitate the environmental application of CNTs as sorbents and environmental risk assessment of both aromatic contaminants and CNTs.

  12. Carbon nanotube membranes with ultrahigh specific adsorption capacity for water desalination and purification.

    PubMed

    Yang, Hui Ying; Han, Zhao Jun; Yu, Siu Fung; Pey, Kin Leong; Ostrikov, Kostya; Karnik, Rohit

    2013-01-01

    Development of technologies for water desalination and purification is critical to meet the global challenges of insufficient water supply and inadequate sanitation, especially for point-of-use applications. Conventional desalination methods are energy and operationally intensive, whereas adsorption-based techniques are simple and easy to use for point-of-use water purification, yet their capacity to remove salts is limited. Here we report that plasma-modified ultralong carbon nanotubes exhibit ultrahigh specific adsorption capacity for salt (exceeding 400% by weight) that is two orders of magnitude higher than that found in the current state-of-the-art activated carbon-based water treatment systems. We exploit this adsorption capacity in ultralong carbon nanotube-based membranes that can remove salt, as well as organic and metal contaminants. These ultralong carbon nanotube-based membranes may lead to next-generation rechargeable, point-of-use potable water purification appliances with superior desalination, disinfection and filtration properties.

  13. High-Capacity and Photoregenerable Composite Material for Efficient Adsorption and Degradation of Phenanthrene in Water.

    PubMed

    Liu, Wen; Cai, Zhengqing; Zhao, Xiao; Wang, Ting; Li, Fan; Zhao, Dongye

    2016-10-18

    We report a novel composite material, referred to as activated charcoal supported titanate nanotubes (TNTs@AC), for highly efficient adsorption and photodegradation of a representative polycyclic aromatic hydrocarbon (PAH), phenanthrene. TNTs@AC was prepared through a one-step hydrothermal method, and is composed of an activated charcoal core and a shell of carbon-coated titanate nanotubes. TNTs@AC offered a maximum Langmuir adsorption capacity of 12.1 mg/g for phenanthrene (a model PAH), which is ∼11 times higher than the parent activated charcoal. Phenanthrene was rapidly concentrated onto TNTs@AC, and subsequently completely photodegraded under UV light within 2 h. The photoregenerated TNTs@AC can then be reused for another adsorption-photodegradation cycle without significant capacity or activity loss. TNTs@AC performed well over a wide range of pH, ionic strength, and dissolved organic matter. Mechanistically, the enhanced adsorption capacity is attributed to the formation of carbon-coated ink-bottle pores of the titanate nanotubes, which are conducive to capillary condensation; in addition, the modified microcarbon facilitates transfer of excited electrons, thereby inhibiting recombination of the electron-hole pairs, resulting in high photocatalytic activity. The combined high adsorption capacity, photocatalytic activity, and regenerability/reusability merit TNTs@AC a very attractive material for concentrating and degrading a host of micropollutants in the environment.

  14. Investigation of Morphology and Hydrogen Adsorption Capacity of Disordered Carbons

    NASA Astrophysics Data System (ADS)

    He, Lilin; Melnichenko, Yuri; Gallego, Nidia; Contescu, Cristian

    2014-03-01

    We have applied small angle neutron scattering (SANS) technique to study the morphologies and hydrogen adsorption capabilities of wood-based ultramicroporous carbon and poly(furfuryl alcohol) derived carbon. The Polydispersed Spherical model and chord length analysis of the scattering profiles were performed to obtain morphological parameters such as average pore size and pore size distribution of the dry carbons, which agreed reasonably well with the independent gas sorption measurements. The hydrogen physisorbed in these two carbons at room temperature and moderate pressures was investigated by In-situ SANS measurements. The experimental data analyzed using a modified Kalliat model for decoupling scattering contributions from pores with different sizes indicates that the molecular hydrogen condenses preferentially in narrow micropores at all measured pressures, which supports the theoretical prediction by quantum mechanical and thermodynamical models.

  15. Influence of clay mineral structure and surfactant nature on the adsorption capacity of surfactants by clays.

    PubMed

    Sánchez-Martín, M J; Dorado, M C; del Hoyo, C; Rodríguez-Cruz, M S

    2008-01-15

    Adsorption of three surfactants of different nature, Triton X-100 (TX100) (non-ionic), sodium dodecylsulphate (SDS) (anionic) and octadecyltrimethylammonium bromide (ODTMA) (cationic) by four layered (montmorillonite, illite, muscovite and kaolinite) and two non-layered (sepiolite and palygorskite) clay minerals was studied. The objective was to improve the understanding of surfactant behaviour in soils for the possible use of these compounds in remediation technologies of contaminated soils by toxic organic compounds. Adsorption isotherms were obtained using surfactant concentrations higher and lower than the critical micelle concentration (cmc). These isotherms showed different adsorption stages of the surfactants by the clay minerals, and were classified in different subgroups of the L-, S- or H-types. An increase in the adsorption of SDS and ODTMA by all clay minerals is observed up to the cmc of the surfactant in the equilibrium solution is reached. However, there was further TX100 adsorption when the equilibrium concentration was well above the cmc. Adsorption constants from Langmuir and Freundlich equations (TX100 and ODTMA) or Freundlich equation (SDS) were used to compare adsorption of different surfactants by clay minerals studied. These constants indicated the surfactant adsorption by clay minerals followed this order ODTMA>TX100>SDS. The adsorption of TX100 and ODTMA was higher by montmorillonite and illite, and the adsorption of SDS was found to be higher by kaolinite and sepiolite. Results obtained show the influence of clay mineral structure and surfactant nature on the adsorption capacity of surfactants by clays, and they indicate the interest to consider the soil mineralogical composition when one surfactant have to be selected in order to establish more efficient strategies for the remediation of soils and water contaminated by toxic organic pollutants.

  16. Predicting CH4 adsorption capacity of microporous carbon using N2 isotherm and a new analytical model

    USGS Publications Warehouse

    Sun, Jielun; Chen, S.; Rostam-Abadi, M.; Rood, M.J.

    1998-01-01

    A new analytical pore size distribution (PSD) model was developed to predict CH4 adsorption (storage) capacity of microporous adsorbent carbon. The model is based on a 3-D adsorption isotherm equation, derived from statistical mechanical principles. Least squares error minimization is used to solve the PSD without any pre-assumed distribution function. In comparison with several well-accepted analytical methods from the literature, this 3-D model offers relatively realistic PSD description for select reference materials, including activated carbon fibers. N2 and CH4 adsorption data were correlated using the 3-D model for commercial carbons BPL and AX-21. Predicted CH4 adsorption isotherms, based on N2 adsorption at 77 K, were in reasonable agreement with the experimental CH4 isotherms. Modeling results indicate that not all the pores contribute the same percentage Vm/Vs for CH4 storage due to different adsorbed CH4 densities. Pores near 8-9 A?? shows higher Vm/Vs on the equivalent volume basis than does larger pores.

  17. Non-contact analysis of the adsorptive ink capacity of nano silica pigments on a printing coating base.

    PubMed

    Jiang, Bo; Huang, Yu Dong

    2014-01-01

    Near infrared spectra combined with partial least squares were proposed as a means of non-contact analysis of the adsorptive ink capacity of recording coating materials in ink jet printing. First, the recording coating materials were prepared based on nano silica pigments. 80 samples of the recording coating materials were selected to develop the calibration of adsorptive ink capacity against ink adsorption (g/m2). The model developed predicted samples in the validation set with r2  = 0.80 and SEP = 1.108, analytical results showed that near infrared spectra had significant potential for the adsorption of ink capacity on the recording coating. The influence of factors such as recording coating thickness, mass ratio silica: binder-polyvinyl alcohol and the solution concentration on the adsorptive ink capacity were studied. With the help of the near infrared spectra, the adsorptive ink capacity of a recording coating material can be rapidly controlled.

  18. [Surface characteristics of alkali modified activated carbon and the adsorption capacity of methane].

    PubMed

    Zhang, Meng-Zhu; Li, Lin; Liu, Jun-Xin; Sun, Yong-Jun; Li, Guo-Bin

    2013-01-01

    Coconut shell based activated carbon was modified by alkali with different concentrations. The surface structures of tested carbons were observed and analyzed by SEM and BET methods. Boehm's titration and SEM/EDS methods were applied to assay the functional groups and elements on the carbon surface. The adsorption of methane on tested carbons was investigated and adsorption behavior was described by the adsorption isotherms. Results showed that surface area and pore volume of modified carbon increased and surface oxygen groups decreased as the concentration of the alkali used increased, with no obvious change in pore size. When concentration of alkali was higher than 3.3 mol x L(-1), the specific surface area and pore volume of modified carbon was larger than that of original carbon. Methane adsorption capacity of alkali modified carbon increased 24%. Enlargement of surface area and pore volume, reduction of surface oxygen groups will benefit to enhance the methane adsorption ability on activated carbon. Adsorption behavior of methane followed the Langmuir isotherm and the adsorption coefficient was 163.7 m3 x mg(-1).

  19. Effect of purity on adsorption capacities of a Mars-like clay mineral at different pressures

    NASA Technical Reports Server (NTRS)

    Jenkins, Traci; Mcdoniel, Bridgett; Bustin, Roberta; Allton, Judith H.

    1992-01-01

    There has been considerable interest in adsorption of carbon dioxide on Marslike clay minerals. Some estimates of the carbon dioxide reservoir capacity of the martian regolith were calculated from the amount of carbon dioxide adsorbed on the ironrich smectite nontronite under martian conditions. The adsorption capacity of pure nontronite could place upper limits on the regolith carbon dioxide reservoir, both at present martian atmospheric pressure and at the postulated higher pressures required to permit liquid water on the surface. Adsorption of carbon dioxide on a Clay Mineral Society standard containing nontronite was studied over a wide range of pressures in the absence of water. Similar experiments were conducted on the pure nontronite extracted from the natural sample. Heating curves were obtained to help characterize and determine the purity of the clay sample.

  20. Assessment of CO₂ adsorption capacity on activated carbons by a combination of batch and dynamic tests.

    PubMed

    Balsamo, Marco; Silvestre-Albero, Ana; Silvestre-Albero, Joaquín; Erto, Alessandro; Rodríguez-Reinoso, Francisco; Lancia, Amedeo

    2014-05-27

    In this work, batch and dynamic adsorption tests are coupled for an accurate evaluation of CO2 adsorption performance of three different activated carbons (AC) obtained from olive stones by chemical activation followed by physical activation with CO2 at varying times (i.e., 20, 40, and 60 h). Kinetic and thermodynamic CO2 adsorption tests from simulated flue gas at different temperatures and CO2 pressures are carried out under both batch (a manometric equipment operating with pure CO2) and dynamic (a lab-scale fixed-bed column operating with a CO2/N2 mixture) conditions. The textural characterization of the AC samples shows a direct dependence of both micropore and ultramicropore volume on the activation time; hence, AC60 has the higher contribution. The adsorption tests conducted at 273 and 293 K showed that when CO2 pressure is lower than 0.3 bar, the lower the activation time, the higher CO2 adsorption capacity; a ranking of ω(eq)(AC20) > ω(eq)(AC40) > ω(eq)(AC60) can be exactly defined when T = 293 K. This result is likely ascribed to the narrower pore size distribution of the AC20 sample, whose smaller pores are more effective for CO2 capture at higher temperature and lower CO2 pressure, the latter representing operating conditions of major interest for decarbonation of flue gas effluent. Moreover, the experimental results obtained from dynamic tests confirm the results derived from the batch tests in terms of CO2 adsorption capacity. It is important to highlight the fact that the adsorption of N2 on the synthesized AC samples can be considered to be negligible. Finally, the importance of proper analysis for data characterization and adsorption experimental results is highlighted for the correct assessment of the CO2 removal performance of activated carbons at different CO2 pressures and operating temperatures.

  1. Fugitive gas adsorption capacity of biomass and animal-manure derived biochars

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This research characterized and investigated ammonia and hydrogen sulfide gas adsorption capacities of low- and high-temperature biochars made from wood shavings and chicken litter. The biochar samples were activated with steam or phosphoric acid. The specific surface areas and pore volumes of the a...

  2. Ammonia adsorption capacity of biomass and animal-manure derived biochars

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this research was to characterize and investigate ammonia and hydrogen sulfide gas adsorption capacities of low- and high-temperature biochars made from wood shavings and chicken litter. The biochar samples were activated with steam or phosphoric acid. The specific surface areas and...

  3. Molecular basis for the high CO2 adsorption capacity of chabazite zeolites.

    PubMed

    Pham, Trong D; Hudson, Matthew R; Brown, Craig M; Lobo, Raul F

    2014-11-01

    CO2 adsorption in Li-, Na-, K-CHA (Si/Al=6,=12), and silica chabazite zeolites was investigated by powder diffraction. Two CO2 adsorption sites were found in all chabazites with CO2 locating in the 8-membered ring (8MR) pore opening being the dominant site. Electric quadrupole-electric field gradient and dispersion interactions drive CO2 adsorption at the middle of the 8 MRs, while CO2 polarization due to interaction with cation sites controls the secondary CO2 site. In Si-CHA, adsorption is dominated by dispersion interactions with CO2 observed on the pore walls and in 8 MRs. CO2 adsorption complexes on dual cation sites were observed on K-CHA, important for K-CHA-6 samples due to a higher probability of two K(+) cations bridging CO2. Trends in isosteric heats of CO2 adsorption based on cation type and concentration can be correlated with adsorption sites and CO2 quantity. A decrease in the hardness of metal cations results in a decrease in the direct interaction of these cations with CO2.

  4. Influence of the inherent properties of drinking water treatment residuals on their phosphorus adsorption capacities.

    PubMed

    Bai, Leilei; Wang, Changhui; He, Liansheng; Pei, Yuansheng

    2014-12-01

    Batch experiments were conducted to investigate the phosphorus (P) adsorption and desorption on five drinking water treatment residuals (WTRs) collected from different regions in China. The physical and chemical characteristics of the five WTRs were determined. Combined with rotated principal component analysis, multiple regression analysis was used to analyze the relationship between the inherent properties of the WTRs and their P adsorption capacities. The results showed that the maximum P adsorption capacities of the five WTRs calculated using the Langmuir isotherm ranged from 4.17 to 8.20mg/g at a pH of 7 and further increased with a decrease in pH. The statistical analysis revealed that a factor related to Al and 200 mmol/L oxalate-extractable Al (Alox) accounted for 36.5% of the variations in the P adsorption. A similar portion (28.5%) was attributed to an integrated factor related to the pH, Fe, 200 mmol/L oxalate-extractable Fe (Feox), surface area and organic matter (OM) of the WTRs. However, factors related to other properties (Ca, P and 5 mmol/L oxalate-extractable Fe and Al) were rejected. In addition, the quantity of P desorption was limited and had a significant negative correlation with the (Feox+Alox) of the WTRs (p<0.05). Overall, WTRs with high contents of Alox, Feox and OM as well as large surface areas were proposed to be the best choice for P adsorption in practical applications.

  5. Effect of surface area and chemisorbed oxygen on the SO2 adsorption capacity of activated char

    USGS Publications Warehouse

    Lizzio, A.A.; DeBarr, J.A.

    1996-01-01

    The objective of this study was to determine whether activated char produced from Illinois coal could be used effectively to remove sulfur dioxide from coal combustion flue gas. Chars were prepared from a high-volatile Illinois bituminous coal under a wide range of pyrolysis and activation conditions. A novel char preparation technique was developed to prepare chars with SO2 adsorption capacities significantly greater than that of a commercial activated carbon. In general, there was no correlation between SO2 adsorption capacity and surface area. Temperature-programmed desorption (TPD) was used to determine the nature and extent of carbon-oxygen (C-O) complexes formed on the char surface. TPD data revealed that SO2 adsorption was inversely proportional to the amount of C-O complex. The formation of a stable C-O complex during char preparation may have served only to occupy carbon sites that were otherwise reactive towards SO2 adsorption. A fleeting C(O) complex formed during SO2 adsorption is postulated to be the reaction intermediate necessary for conversion of SO2 to H2SO4. Copyright ?? 1996 Elsevier Science Ltd.

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

    PubMed

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

    2012-06-01

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

  7. Nanosheet-structured boron nitride spheres with a versatile adsorption capacity for water cleaning.

    PubMed

    Liu, Fei; Yu, Jie; Ji, Xixi; Qian, Muqi

    2015-01-28

    Here, we report the synthesis of nanosheet-structured boron nitride spheres (NSBNSs) by a catalyzing thermal evaporation method from solid B powders. The NSBNSs consist of radially oriented ultrathin nanosheets with the sheet edges oriented on the surface. Formation of this unique structure occurs only at a certain reaction temperature. The diameter from 4 μm to 700 nm and the nanosheet thickness from 9.1 to 3.1 nm of the NSBNSs can be well-controlled by appropriately changing the mass ratio of boron powders and catalyst. The NSBNSs possess versatile adsorption capacity, exhibiting excellent adsorption performance for oil, dyes, and heavy metal ions from water. The oil uptake reaches 7.8 times its own weight. The adsorption capacities for malachite green and methylene blue are 324 and 233 mg/g, while those for Cu(2+), Pb(2+), and Cd(2+) are 678.7, 536.7, and 107.0 mg/g, respectively. The adsorption capacities of the NSBNSs for Cu(2+) and Pb(2+) are higher or much higher than those of the adsorbents reported previously. These results demonstrate the great potential of NSBNSs for water treatment and cleaning.

  8. Effect of heat on the adsorption capacity of an activated carbon for decolorizing/deodorizing yellow zein.

    PubMed

    Sessa, D J; Palmquist, D E

    2008-09-01

    The Freundlich model was evaluated for use to assess the effect of heat on the adsorption capacity of an activated carbon for decolorizing/deodorizing corn zein. Because zein protein and its color/odor components are all adsorbed by activated carbon, a method to monitor their removal was needed. Yellow color is due to xanthophylls; a contributor to off-odor is diferuloylputrescine. The off-odor component absorbs ultraviolet (UV) light at about 325 nm and its removal coincides with removal of yellow color. A spectrophotometric method based on UV absorbances 280 nm for protein and 325 nm for the off-odor component was used to monitor their adsorptions onto activated carbon. Equilibrium studies were performed over temperature range from 25 to 60 degrees C for zein dissolved in 70% aqueous ethanol. Runs made at 55 degrees C adsorbed significantly more of the color/odor components than the protein.

  9. Powder-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

    2016-05-03

    A powder-based adsorbent and a related method of manufacture are provided. The powder-based adsorbent includes polymer powder with grafted side chains and an increased surface area per unit weight to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. A method for forming the powder-based adsorbent includes irradiating polymer powder, grafting with polymerizable reactive monomers, reacting with hydroxylamine, and conditioning with an alkaline solution. Powder-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  10. Foam-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

    2015-06-02

    Foam-based adsorbents and a related method of manufacture are provided. The foam-based adsorbents include polymer foam with grafted side chains and an increased surface area per unit weight to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. A method for forming the foam-based adsorbents includes irradiating polymer foam, grafting with polymerizable reactive monomers, reacting with hydroxylamine, and conditioning with an alkaline solution. Foam-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  11. Adsorption capacity of poly(ether imide) microparticles to uremic toxins.

    PubMed

    Tetali, Sarada D; Jankowski, Vera; Luetzow, Karola; Kratz, Karl; Lendlein, Andreas; Jankowski, Joachim

    2016-01-01

    Uremia is a phenomenon caused by retention of uremic toxins in the plasma due to functional impairment of kidneys in the elimination of urinary waste products. Uremia is presently treated by dialysis techniques like hemofiltration, dialysis or hemodiafiltration. However, these techniques in use are more favorable towards removing hydrophilic than hydrophobic uremic toxins. Hydrophobic uremic toxins, such as hydroxy hipuric acid (OH-HPA), phenylacetic acid (PAA), indoxyl sulfate (IDS) and p-cresylsulfate (pCRS), contribute substantially to the progression of chronic kidney disease (CKD) and cardiovascular disease. Therefore, objective of the present study is to test adsorption capacity of highly porous microparticles prepared from poly(ether imide) (PEI) as an alternative technique for the removal of uremic toxins. Two types of nanoporous, spherically shaped microparticles were prepared from PEI by a spraying/coagulation process.PEI particles were packed into a preparative HPLC column to which a mixture of the four types of uremic toxins was injected and eluted with ethanol. Eluted toxins were quantified by analytical HPLC. PEI particles were able to adsorb all four toxins, with the highest affinity for PAA and pCR. IDS and OH-HPA showed a partially non-reversible binding. In summary, PEI particles are interesting candidates to be explored for future application in CKD.

  12. Synthesis of bilayer MoS{sub 2} nanosheets by a facile hydrothermal method and their methyl orange adsorption capacity

    SciTech Connect

    Ye, Lijuan; Xu, Haiyan; Zhang, Dingke; Chen, Shijian

    2014-07-01

    Highlights: • Hexagonal phase of MoS{sub 2} nanosheets was synthesized by a facile hydrothermal method. • FE-SEM and TEM images show the sheets-like morphology of MoS{sub 2}. • Bilayer MoS{sub 2} can be grown under the optimized mole ratio of 2:1 of S:Mo at 180 °C for 50 h. • The MoS{sub 2} nanosheets possess high methyl orange adsorption capacity due to the large surface area. - Abstract: Molybdenum disulfide (MoS{sub 2}) nanosheets have received significant attention recently due to the potential applications for exciting physics and technology. Here we show that MoS{sub 2} nanosheets can be prepared by a facile hydrothermal method. The study of the properties of the MoS{sub 2} nanosheets prepared at different conditions suggests that the mole ratio of precursors and hydrothermal time significantly influences the purity, crystalline quality and thermal stability of MoS{sub 2}. X-ray diffraction, Raman spectra and transmission electron microscopy results indicate that bilayer MoS{sub 2} can be grown under an optimized mole ratio of 2:1 of S:Mo at 180 °C for 50 h. Moreover, such ultrathin nanosheets exhibit a prominent photoluminescence and possess high methyl orange adsorption capacity due to the large surface area, which can be potentially used in photodevice and photochemical catalyst.

  13. Modified inverse micelle synthesis for mesoporous alumina with a high D4 siloxane adsorption capacity

    SciTech Connect

    Zhong, Wei; Jiang, Ting; Jafari, Tahereh; Poyraz, Altug S.; Wu, Wei; Kriz, David A.; Du, Shoucheng; Biswas, Sourav; Thompson Pettes, Michael; Suib, Steven L.

    2016-10-18

    In this work, mesoporous aluminas (MAs) with uniform and monomodal pores were fabricated via a modified inverse micelle synthesis method, using a non-polar solvent (to minimize the effect of water content) and short reaction time (for a fast evaporation process). The effects of reaction times (4–8 h), surfactant chain lengths (non-ionic surfactants), and calcination temperatures and hold times (450–600 °C; 1–4 h) on the textural properties of MA were studied. Additionally, the targeted pore sizes of MA were obtained in the range of 3.1–5.4 nm by adjusting the surfactant and reaction time. The surface area and pore volume were controlled by the calcination temperature and hold time while maintaining the thermal stability of the materials. The tuned MA of the large mesopore volume achieved 168 mg/g octamethylcyclotetrasiloxane (D4 siloxane) adsorption capacity, a 32% improvement compared to commercially activated alumina. Finally, after three adsorption recycles, the synthesized MA still maintained approximate 85% of its original adsorption capacity, demonstrating a sustainable adsorption performance and high potential for related industrial applications.

  14. Modified inverse micelle synthesis for mesoporous alumina with a high D4 siloxane adsorption capacity

    DOE PAGES

    Zhong, Wei; Jiang, Ting; Jafari, Tahereh; ...

    2016-10-18

    In this work, mesoporous aluminas (MAs) with uniform and monomodal pores were fabricated via a modified inverse micelle synthesis method, using a non-polar solvent (to minimize the effect of water content) and short reaction time (for a fast evaporation process). The effects of reaction times (4–8 h), surfactant chain lengths (non-ionic surfactants), and calcination temperatures and hold times (450–600 °C; 1–4 h) on the textural properties of MA were studied. Additionally, the targeted pore sizes of MA were obtained in the range of 3.1–5.4 nm by adjusting the surfactant and reaction time. The surface area and pore volume were controlledmore » by the calcination temperature and hold time while maintaining the thermal stability of the materials. The tuned MA of the large mesopore volume achieved 168 mg/g octamethylcyclotetrasiloxane (D4 siloxane) adsorption capacity, a 32% improvement compared to commercially activated alumina. Finally, after three adsorption recycles, the synthesized MA still maintained approximate 85% of its original adsorption capacity, demonstrating a sustainable adsorption performance and high potential for related industrial applications.« less

  15. A Porous Aromatic Framework Constructed from Benzene Rings Has a High Adsorption Capacity for Perfluorooctane Sulfonate

    NASA Astrophysics Data System (ADS)

    Luo, Qin; Zhao, Changwei; Liu, Guixia; Ren, Hao

    2016-02-01

    A low-cost and easily constructed porous aromatic framework (PAF-45) was successfully prepared using the Scholl reaction. PAF-45 was, for the first time, used to remove perfluorooctane sulfonate (PFOS) from aqueous solution. Systematic experiments were performed to determine the adsorption capacity of PAF-45 for PFOS and to characterize the kinetics of the adsorption process. The adsorption of PFOS onto PAF-45 reached equilibrium in 30 min, and the adsorption capacity of PAF-45 for PFOS was excellent (5847 mg g‑1 at pH 3). The amount of PFOS adsorbed by PAF-45 increased significantly as the cation (Na+, Mg2+, or Fe3+) concentration increased, which probably occurred because the cations enhanced the interactions between the negatively charged PFOS molecules and the positively charged PAF-45 surface. The cations Na+, Mg2+, and Fe3+ were found to form complexes with PFOS anions in solution. Density functional theory was used to identify the interactions between PFOS and Na+, Mg2+, and Fe3+. We expect that materials of the same type as PAF-45 could be useful adsorbents for removing organic pollutants from industrial wastewater and contaminated surface water.

  16. A Porous Aromatic Framework Constructed from Benzene Rings Has a High Adsorption Capacity for Perfluorooctane Sulfonate

    PubMed Central

    Luo, Qin; Zhao, Changwei; Liu, Guixia; Ren, Hao

    2016-01-01

    A low-cost and easily constructed porous aromatic framework (PAF-45) was successfully prepared using the Scholl reaction. PAF-45 was, for the first time, used to remove perfluorooctane sulfonate (PFOS) from aqueous solution. Systematic experiments were performed to determine the adsorption capacity of PAF-45 for PFOS and to characterize the kinetics of the adsorption process. The adsorption of PFOS onto PAF-45 reached equilibrium in 30 min, and the adsorption capacity of PAF-45 for PFOS was excellent (5847 mg g−1 at pH 3). The amount of PFOS adsorbed by PAF-45 increased significantly as the cation (Na+, Mg2+, or Fe3+) concentration increased, which probably occurred because the cations enhanced the interactions between the negatively charged PFOS molecules and the positively charged PAF-45 surface. The cations Na+, Mg2+, and Fe3+ were found to form complexes with PFOS anions in solution. Density functional theory was used to identify the interactions between PFOS and Na+, Mg2+, and Fe3+. We expect that materials of the same type as PAF-45 could be useful adsorbents for removing organic pollutants from industrial wastewater and contaminated surface water. PMID:26843015

  17. Activated carbons prepared from wood particleboard wastes: characterisation and phenol adsorption capacities.

    PubMed

    Girods, P; Dufour, A; Fierro, V; Rogaume, Y; Rogaume, C; Zoulalian, A; Celzard, A

    2009-07-15

    The problems of valorisation of particleboard wastes on one hand, and contamination of aqueous effluents by phenolic compounds on the other hand, are simultaneously considered in this work. Preparation of activated carbons from a two steps thermo-chemical process, formerly designed for generating combustible gases, is suggested. The resultant carbonaceous residue is activated with steam at 800 degrees C. Depending on the preparation conditions, surface areas within the range 800-1300 m(2)/g are obtained, close to that of a commercial activated carbon (CAC) specially designed for water treatment and used as a reference material. The present work shows that particleboard waste-derived activated carbons (WAC) are efficient adsorbents for the removal of phenol from aqueous solutions, with maximum measured capacities close to 500 mg/g. However, most of times, the adsorption capacities are slightly lower than that of the commercial material in the same conditions, i.e., at equilibrium phenol concentrations below 300 ppm. Given the extremely low cost of activated carbons prepared from particleboard waste, it should not be a problem to use it in somewhat higher amounts than what is required with a more expensive commercial material. Phenol adsorption isotherms at 298 K were correctly fitted by various equations modelling type I and type II isotherms for CAC and WAC, respectively. Phenol adsorption isotherms of type II were justified by a 3-stages adsorption mechanism.

  18. CoFe2O4@MIL-100(Fe) hybrid magnetic nanoparticles exhibit fast and selective adsorption of arsenic with high adsorption capacity

    NASA Astrophysics Data System (ADS)

    Yang, Ji-Chun; Yin, Xue-Bo

    2017-01-01

    In this study, we report the synthesis and application of mesoporous CoFe2O4@MIL-100(Fe) hybrid magnetic nanoparticles (MNPs) for the simultaneous removal of inorganic arsenic (iAs). The hybrid adsorbent had a core-shell and mesoporous structure with an average diameter of 260 nm. The nanoscale size and mesoporous character impart a fast adsorption rate and high adsorption capacity for iAs. In total, 0.1 mg L‑1 As(V) and As(III) could be adsorbed within 2 min, and the maximum adsorption capacities were 114.8 mg g‑1 for As(V) and 143.6 mg g‑1 for As(III), higher than most previously reported adsorbents. The anti-interference capacity for iAs adsorption was improved by the electrostatic repulsion and size exclusion effects of the MIL-100(Fe) shell, which also decreased the zero-charge point of the hybrid absorbent for a broad pH adsorption range. The adsorption mechanisms of iAs on the MNPs are proposed. An Fe-O-As structure was formed on CoFe2O4@MIL-100(Fe) through hydroxyl substitution with the deprotonated iAs species. Monolayer adsorption of As(V) was observed, while hydrogen bonding led to the multi-layer adsorption of neutral As(III) for its high adsorption capacity. The high efficiency and the excellent pH- and interference-tolerance capacities of CoFe2O4@MIL-100(Fe) allowed effective iAs removal from natural water samples, as validated with batch magnetic separation mode and a portable filtration strategy.

  19. CoFe2O4@MIL-100(Fe) hybrid magnetic nanoparticles exhibit fast and selective adsorption of arsenic with high adsorption capacity

    PubMed Central

    Yang, Ji-Chun; Yin, Xue-Bo

    2017-01-01

    In this study, we report the synthesis and application of mesoporous CoFe2O4@MIL-100(Fe) hybrid magnetic nanoparticles (MNPs) for the simultaneous removal of inorganic arsenic (iAs). The hybrid adsorbent had a core-shell and mesoporous structure with an average diameter of 260 nm. The nanoscale size and mesoporous character impart a fast adsorption rate and high adsorption capacity for iAs. In total, 0.1 mg L−1 As(V) and As(III) could be adsorbed within 2 min, and the maximum adsorption capacities were 114.8 mg g−1 for As(V) and 143.6 mg g−1 for As(III), higher than most previously reported adsorbents. The anti-interference capacity for iAs adsorption was improved by the electrostatic repulsion and size exclusion effects of the MIL-100(Fe) shell, which also decreased the zero-charge point of the hybrid absorbent for a broad pH adsorption range. The adsorption mechanisms of iAs on the MNPs are proposed. An Fe-O-As structure was formed on CoFe2O4@MIL-100(Fe) through hydroxyl substitution with the deprotonated iAs species. Monolayer adsorption of As(V) was observed, while hydrogen bonding led to the multi-layer adsorption of neutral As(III) for its high adsorption capacity. The high efficiency and the excellent pH- and interference-tolerance capacities of CoFe2O4@MIL-100(Fe) allowed effective iAs removal from natural water samples, as validated with batch magnetic separation mode and a portable filtration strategy. PMID:28102334

  20. High adsorption capacity of V-doped TiO2 for decolorization of methylene blue

    NASA Astrophysics Data System (ADS)

    Nguyen, Thanh-Binh; Hwang, Moon-Jin; Ryu, Kwang-Sun

    2012-07-01

    In this study, pure TiO2 (V-TiO2-0) and V-doped TiO2 (V-TiO2-x, x = 1-10 mol%) were synthesized using a new sol-gel method. The adsorption capacity of the V-TiO2-x samples was evaluated by measuring the removal of methylene blue (MB) from aqueous solution via decolorization. Since the adsorption capacity was affected by the specific surface area, the interaction between adsorbate (MB) and adsorbent (V-TiO2-x), and the structure of the adsorbent, the physicochemical properties of the samples were investigated. Among the V-doped TiO2-x samples, the V-TiO2-10 sample showed the highest adsorption capacity, which was 11.36 times greater than that of pure TiO2, removing 85.2% of the MB after 2 h. Moreover, changing the molar ratio of the reactants in the V-TiO2-10 sample improved the performance of the material so that 91.6% of the MB was removed after 2 h.

  1. High-capacity adsorption of dissolved hexavalent chromium using amine-functionalized magnetic corn stalk composites.

    PubMed

    Song, Wen; Gao, Baoyu; Zhang, Tengge; Xu, Xing; Huang, Xin; Yu, Huan; Yue, Qinyan

    2015-08-01

    Easily separable amine-functionalized magnetic corn stalk composites (AF-MCS) were employed for effective adsorption and reduction of toxic hexavalent chromium [Cr(VI)] to nontoxic Cr(III). The saturated magnetization of AF-MCS reached 6.2emu/g, and as a result, it could be separated from aqueous solution by a magnetic process for its superparamagnetism. The studies of various factors influencing the sorption behavior indicated that the optimum AF-MCS dosage for Cr(VI) adsorption was 1g/L, and the maximum adsorption capacity was observed at pH 3.0. The chromium adsorption perfectly fitted the Langmuir isotherm model and pseudo second order kinetic model. Furthermore, characterization of AF-MCS was investigated by means of XRD, SEM, TEM, FT-IR, BET, VSM and XPS analysis to discuss the uptake mechanism. Basically, these results demonstrated that AF-MCS prepared in this work has shown its merit in effective removal of Cr(VI) and rapid separation from effluents simultaneously.

  2. Construction of horizontal stratum landform-like composite foams and their methyl orange adsorption capacity

    NASA Astrophysics Data System (ADS)

    Chen, Jiajia; Shi, Xiaowen; Zhan, Yingfei; Qiu, Xiaodan; Du, Yumin; Deng, Hongbing

    2017-03-01

    Chitosan (CS)/rectorite (REC)/carbon nanotubes (CNTs) composite foams with good mechanical properties were successfully fabricated by unidirectional freeze-casting technique. The morphology of the foam showed the well-ordered porous three-dimensional layers and horizontal stratum landform-like structure. The holes on the layers looked like the wings of butterfly. Additionally, the X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy results indicated the successful addition of CNTs and REC. The intercalated REC with CS chains was confirmed by small-angle X-ray diffraction. The surface structure of the foams was also analyzed by Raman spectroscopy. The adsorption experiments showed that when the mass ratio of CS to REC was 10:1 and CNTs content was 20%, the composite foam performed best in adsorbing low concentration methyl orange, and the largest adsorption capacity was 41.65 mg/g.

  3. Determination of Adsorption Capacity and Kinetics of Amidoxime-Based Uranium Adsorbent Braided Material in Unfiltered Seawater Using a Flume Exposure System

    SciTech Connect

    Gill, Gary A.; Kuo, Li-Jung; Strivens, Jonathan E.; Park, Jiyeon; Bonheyo, George T.; Jeters, Robert T.; Schlafer, Nicholas J.; Wood, Jordana R.

    2015-08-31

    amount of biomass increase retained by the adsorbent in the dark flume was only a quarter of that observed in the light exposed flume. Biofouling in sunlit surface seawater has the potential to reduce uranium adsorption capacity by ~ 30% after 42 days of exposure. Minimal or no adsorption loss due to biofouling occurred in the dark flume exposure. Attempts to assess time series measurements of uranium adsorption capacity using “snips” off a master braid are fraught with problems due to the inability to easily determine the mass of the adsorbent material when the biofouling is present. The ability to determine the adsorption of biogenically important trace elements (e.g. Fe, Mn, Zn, Cu, and Sr) on biofouled adsorbents is also problematic.

  4. A review on modification methods to cellulose-based adsorbents to improve adsorption capacity.

    PubMed

    Hokkanen, Sanna; Bhatnagar, Amit; Sillanpää, Mika

    2016-03-15

    In recent decades, increased domestic, agricultural and industrial activities worldwide have led to the release of various pollutants, such as toxic heavy metals, inorganic anions, organics, micropollutants and nutrients into the aquatic environment. The removal of these wide varieties of pollutants for better quality of water for various activities is an emerging issue and a robust and eco-friendly treatment technology is needed for the purpose. It is well known that cellulosic materials can be obtained from various natural sources and can be employed as cheap adsorbents. Their adsorption capacities for heavy metal ions and other aquatic pollutants can be significantly affected upon chemical treatment. In general, chemically modified cellulose exhibits higher adsorption capacities for various aquatic pollutants than their unmodified forms. Numerous chemicals have been used for cellulose modifications which include mineral and organic acids, bases, oxidizing agent, organic compounds, etc. This paper reviews the current state of research on the use of cellulose, a naturally occurring material, its modified forms and their efficacy as adsorbents for the removal of various pollutants from waste streams. In this review, an extensive list of various cellulose-based adsorbents from literature has been compiled and their adsorption capacities under various conditions for the removal of various pollutants, as available in the literature, are presented along with highlighting and discussing the key advancement on the preparation of cellulose-based adsorbents. It is evident from the literature survey presented herein that modified cellulose-based adsorbents exhibit good potential for the removal of various aquatic pollutants. However, still there is a need to find out the practical utility of these adsorbents on a commercial scale, leading to the improvement of pollution control.

  5. Trimodal nanoporous silica as a support for amine-based CO2 adsorbents: Improvement in adsorption capacity and kinetics

    NASA Astrophysics Data System (ADS)

    Chen, Chao; Bhattacharjee, Samiran

    2017-02-01

    A trimodal nanoporous silica (TS) having unique trimodal pore structure viz., internal mesopores, textural mesopores and interconnected macropores, has been functionalized with amine using two different methods covalent grafting and wet impregnation. Both were studied as nanocomposite sorbents for CO2 capture. The effects of the amine loading, immobilization processes and the type of support were investigated. Commercially available silica gel (SG) with a purely mesoporous structure was studied as the support for the amine in order to compare differences in pore structure and amine loading with differences in CO2 adsorption capacity and kinetics. Amine-grafted TS exhibited much faster CO2 adsorption kinetics at 35 °C than amine-grafted SG. At the same amine loading, amine-impregnated TS showed higher CO2 adsorption capacity and faster CO2 adsorption kinetics than amine-impregnated SG. The CO2 adsorption capacity of amine-impregnated TS increased as the amine loading increased until 70%, with the highest value of 172 mg/g, while the amine-impregnated SG reached the highest CO2 adsorption capacity of only 78 mg/g at 40% amine loading. More importantly, amine-impregnated as-prepared TS exhibited even higher CO2 capture capacity than amine-impregnated TS when the amine loading was below 60%. Results suggest that amine-modified trimodal nanoporous silica sorbents meet the challenges of current CO2 capture technology.

  6. Quantitative analysis of the binding strength and adsorption capacity of zinc oxide nanoparticles onto unmodified and modified cotton fiber

    NASA Astrophysics Data System (ADS)

    Printz, Stephen Robert

    Risk of bacterial infection is always a concern in hospitals, so it is important to find ways to minimize this risk. One method for reducing the risk of infection is by using textiles with antimicrobial properties. Zinc oxide nanoparticles have antimicrobial properties, and can be adsorbed onto cotton fibers to pass these properties to the cloth. However, the binding of the zinc oxide nanoparticles to cotton is weak, so the particles desorb from the cloth after repeated washings. The goal of this project was to quantify the binding strength of zinc oxide nanoparticles onto different types of cotton fiber. The cotton was modified by grafting cyclodextrin onto it with citric acid as a crosslinking agent. Adsorption was tested with desized, unbleached cotton print cloth; desized, bleached cotton print cloth; and desized, bleached, mercerized cotton print cloth. As expected, adsorption to unmodified cloth was poor. Unbleached cloth had the highest adsorption capacity (Q 0 = 22 +/- 4 mg ZnO/g cloth), and bleached cloth had the lowest adsorption capacity (Q0 = 17 +/- 4 mg ZnO=g cloth). Mercerized cloth had the lowest strength (b = 0.010 +/- 0.003 ppm-1), and bleached cloth had the highest binding strength (b = 0.04 +/- 0.01 ppm-1). Modification with alpha-cyclodextrin increased adsorption capacity over unmodified cloth by 61, 80, and 70% for mercerized/bleached cloth, bleached cloth, and unbleached cloth, respectively, and increased b by 1601, 126, and 90% respectively. Modification with beta-cyclodextrin increased adsorption capacities by 80, 94, and 112%, respectively, and increased b by 2027, 427, and 46%. As a result, beta-CD modified unbleached cloth had the highest adsorption capacity and one of the lowest binding strengths. However, beta-cyclodextrin modified mercerized cloth has both a high adsorption capacity and a high binding strength, and would likely be the best candidate for use in antimicrobial textiles.

  7. Adsorption capacities of activated carbons for geosmin and 2-methylisoborneol vary with activated carbon particle size: Effects of adsorbent and adsorbate characteristics.

    PubMed

    Matsui, Yoshihiko; Nakao, Soichi; Sakamoto, Asuka; Taniguchi, Takuma; Pan, Long; Matsushita, Taku; Shirasaki, Nobutaka

    2015-11-15

    The adsorption capacities of nine activated carbons for geosmin and 2-methylisoborneol (MIB) were evaluated. For some carbons, adsorption capacity substantially increased when carbon particle diameter was decreased from a few tens of micrometers to a few micrometers, whereas for other carbons, the increase of adsorption capacity was small for MIB and moderate for geosmin. An increase of adsorption capacity was observed for other hydrophobic adsorbates besides geosmin and MIB, but not for hydrophilic adsorbates. The parameter values of a shell adsorption model describing the increase of adsorption capacity were negatively correlated with the oxygen content of the carbon among other characteristics. Low oxygen content indicated low hydrophilicity. The increase of adsorption capacity was related to the hydrophobic properties of both adsorbates and activated carbons. For adsorptive removal of hydrophobic micropollutants such as geosmin, it is therefore recommended that less-hydrophilic activated carbons, such as coconut-shell-based carbons, be microground to a particle diameter of a few micrometers to enhance their equilibrium adsorption capacity. In contrast, adsorption by hydrophilic carbons or adsorption of hydrophilic adsorbates occur in the inner pores, and therefore adsorption capacity is unchanged by particle size reduction.

  8. An adsorbent with a high adsorption capacity obtained from the cellulose sludge of industrial residues.

    PubMed

    Orlandi, Géssica; Cavasotto, Jéssica; Machado, Francisco R S; Colpani, Gustavo L; Magro, Jacir Dal; Dalcanton, Francieli; Mello, Josiane M M; Fiori, Márcio A

    2017-02-01

    One of the major problems in effluent treatment plants of the cellulose and paper industry is the large amount of residual sludge generated. Therefore, this industry is trying to develop new methods to treat such residues and to use them as new products, such as adsorbents. In this regard, the objective of this work was to develop an adsorbent using the raw activated sludge generated by the cellulose and paper industry. The activated cellulose sludge, after being dried, was chemically activated with 42.5% (v/v) phosphoric acid at 85 °C for 1 h and was charred at 500 °C, 600 °C and 700 °C for 2 h. The efficiency of the obtained adsorbent materials was evaluated using kinetic tests with methylene blue solutions. Using the adsorption kinetics, it was verified that the three adsorbents showed the capacity to adsorb dye, and the adsorbent obtained at a temperature of 600 °C showed the highest adsorption capacity of 107.1 mg g(-1). The kinetic model that best fit the experimental data was pseudo-second order. The Langmuir-Freudlich isotherm adequately described the experimental data. As a result, the cellulose sludge generated by the cellulose and paper industries could be used as an adsorbent.

  9. Amine-functionalized PVA-co-PE nanofibrous membrane as affinity membrane with high adsorption capacity for bilirubin.

    PubMed

    Wang, Wenwen; Zhang, Hao; Zhang, Zhifeng; Luo, Mengying; Wang, Yuedan; Liu, Qiongzhen; Chen, Yuanli; Li, Mufang; Wang, Dong

    2017-02-01

    In this study, poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibrous membrane was activated by sodium hydroxide and cyanuric chloride, and then the activated membranes were functionalized by 1,3-propanediamine, hexamethylenediamine and diethylenetriamine to be affinity membranes for bilirubin removal, respectively. The chemical structures and morphologies of membranes were investigated by SEM, FTIR and XPS. And the adsorption ability of different amine-functionalized nanofibrous membranes for bilirubin was characterized. Furthermore, the effects of temperature, initial concentration of bilirubin, NaCl concentration and BSA concentration on the adsorption capacity for bilirubin of diethylenetriamine-functionalized nanofibrous membrane were studied. Results indicated that the adsorption capacity for bilirubin of diethylenetriamine-functionalized nanofibrous membrane could reach 85mg/g membrane when the initial bilirubin concentration was 200mg/L while the adsorption capacity could be increased to 110mg/g membrane if the initial bilirubin concentration was more than 400mg/L. The dynamic adsorption of diethylenetriamine-functionalized nanofibrous membrane showed that the ligands of amine groups on the membrane surface could be used as far as possible by recirculating the plasma with certain flow rates. Therefore, the diethylenetriamine-functionalized PVA-co-PE nanofibrous membrane possessed high adsorption capacity for bilirubin and it can be candidate as affinity membrane for bilirubin removal.

  10. Ultra-high adsorption capacity of zeolitic imidazole framework-67 (ZIF-67) for removal of malachite green from water.

    PubMed

    Lin, Kun-Yi Andrew; Chang, Hsuan-Ang

    2015-11-01

    Zeolitic imidazole frameworks (ZIFs), a new class of adsorbents, are proposed to adsorb Malachite Green (MG) in water. Particularly, ZIF-67 was selected owing to its stability in water and straightforward synthesis. The as-synthesized ZIF-67 was characterized and used to adsorb MG from water. Factors affecting the adsorption capacity were investigated including mixing time, temperature, the presence of salts and pH. The kinetics, adsorption isotherm and thermodynamics of the MG adsorption to ZIF-67 were also studied. The adsorption capacity of ZIF-67 for MG could be as high as 2430mgg(-1) at 20°C, which could be improved at the higher temperatures. Such an ultra-high adsorption capacity of ZIF-67 was almost 10-times of those of conventional adsorbents, including activated carbons and biopolymers. A mechanism for the high adsorption capacity was proposed and possibly attributed to the π-π stacking interaction between MG and ZIF-67. ZIF-67 also could be conveniently regenerated by washing with ethanol and the regeneration efficiency could remain 95% up to 4 cycles of the regeneration. ZIF-67 was also able to remove MG from the aquaculture wastewater, in which MG can be typically found. These features enable ZIF-67 to be one of the most effective and promising adsorbent to remove MG from water.

  11. Influence of Environmental Factors on the Adsorption Capacity and Thermal Conductivity of Silica Nano-Porous Materials.

    PubMed

    Zhang, Hu; Gu, Wei; Li, Ming-Jia; Fang, Wen-Zhen; Li, Zeng-Yao; Tao, Wen-Quan

    2015-04-01

    In this work, the influence of temperature and humidity environment on the water vapor adsorption capacity and effective thermal conductivity of silica nano-porous material is conducted within a relative humidity range from 15% to 90% at 25 °C, 40 °C and 55 °C, respectively. The experiment results show that both the temperature and relative humidity have significant influence on the adsorption capacity and effective thermal conductivity of silica nano-porous materials. The adsorption capacity and effective thermal conductivity increase with humidity because of the increases of water vapor concentration. The effective thermal conductivity increases linearly with adsorption saturation capacity at constant temperature. Because adsorption process is exothermic reaction, the increasing temperature is not conducive to the adsorption. But the effective thermal conductivity increases with the increment of temperature at the same water uptake because of the increment of water thermal conductivity with temperature Geometric models and unit cell structure are adopted to predict the effective thermal conductivity and comparisons with the experimental result are made, and for the case of moist silica nano-porous materials with high porosity no quantitative agreement is found. It is believed that the adsorbed water will fill in the nano-pores and gap and form lots of short cuts, leading to a significant reduction of the thermal resistance.

  12. Hydrophobic interaction chromatography of proteins. IV. Protein adsorption capacity and transport in preparative mode.

    PubMed

    To, Brian C S; Lenhoff, Abraham M

    2011-01-21

    The adsorption isotherms of four model proteins (lysozyme, α-lactalbumin, ovalbumin, and BSA) on eight commercial phenyl hydrophobic interaction chromatography media were measured. The isotherms were softer than those usually seen in ion-exchange chromatography of proteins, and the static capacities of the media were lower, ranging from 30 to 110 mg/mL, depending on the ammonium sulfate concentration and the protein and adsorbent types. The protein-accessible surface area appears to be the main factor determining the binding capacity, and little correlation was seen with the protein affinities of the adsorbents. Breakthrough experiments showed that the dynamic capacities of the adsorbents at 10% breakthrough were 20-80% of the static capacities, depending on adsorbent type. Protein diffusivities in the adsorbents were estimated from batch uptake experiments using the pore diffusion and homogeneous diffusion models. Protein transport was affected by the adsorbent pore structures. Apparent diffusivities were higher at lower salt concentrations and column loadings, suggesting that adsorbed proteins may retard intraparticle protein transport. The diffusivities estimated from the batch uptake experiments were used to predict column breakthrough behavior. Analytical solutions developed for ion-exchange systems were able to provide accurate predictions for lysozyme breakthrough but not for ovalbumin. Impurities in the ovalbumin solutions used for the breakthrough experiments may have affected the ovalbumin uptake and led to the discrepancies between the predictions and the experimental results.

  13. Study on the Adsorption Capacities for Airborne Particulates of Landscape Plants in Different Polluted Regions in Beijing (China).

    PubMed

    Zhang, Wei-Kang; Wang, Bing; Niu, Xiang

    2015-08-14

    Urban landscape plants are an important component of the urban ecosystem, playing a significant role in the adsorption of airborne particulates and air purification. In this study, six common landscape plants in Beijing were chosen as research subjects, and the adsorption capacities for each different plant leaf and the effects of the leaf structures for the adsorption capacities for particulates were determined. Preliminary results show that needle-leaved tree species adsorbed more airborne particulates than broad-leaved tree species for the same leaf area. Pinus tabuliformis exhibits the highest adsorption capacity, at 3.89 ± 0.026 μg·cm(-2), almost two times as much as that of Populus tomentosa (2.00 ± 0.118 μg·cm(-2)). The adsorption capacities for PM10 of the same tree species leaves, in different polluted regions had significant differences, and the adsorption capacities for PM10 of the tree species leaf beside the Fifth Ring Road were higher than those of the tree species leaves in the Botanical Garden, although the adsorption capacities for PM2.5 of the same tree species in different polluted regions had no significant differences. By determining the soluble ion concentrations of the airborne particulates in two regions, it is suggested that the soluble ion concentrations of PM10 in the atmosphere in the Botanical Garden and beside the Fifth Ring Road have significant differences, while those of PM2.5 in the atmosphere had no significant differences. In different polluted regions there are significant adaptive changes to the leaf structures, and when compared with slightly polluted region, in the seriously polluted region the epidermis cells of the plant leaves shrinked, the surface textures of the leaves became rougher, and the stomas' frequency and the pubescence length increased. Even though the plant leaves exposed to the seriously polluted region changed significantly, these plants can still grow normally and healthily.

  14. Study on the Adsorption Capacities for Airborne Particulates of Landscape Plants in Different Polluted Regions in Beijing (China)

    PubMed Central

    Zhang, Wei-Kang; Wang, Bing; Niu, Xiang

    2015-01-01

    Urban landscape plants are an important component of the urban ecosystem, playing a significant role in the adsorption of airborne particulates and air purification. In this study, six common landscape plants in Beijing were chosen as research subjects, and the adsorption capacities for each different plant leaf and the effects of the leaf structures for the adsorption capacities for particulates were determined. Preliminary results show that needle-leaved tree species adsorbed more airborne particulates than broad-leaved tree species for the same leaf area. Pinus tabuliformis exhibits the highest adsorption capacity, at 3.89 ± 0.026 μg·cm−2, almost two times as much as that of Populus tomentosa (2.00 ± 0.118 μg·cm−2). The adsorption capacities for PM10 of the same tree species leaves, in different polluted regions had significant differences, and the adsorption capacities for PM10 of the tree species leaf beside the Fifth Ring Road were higher than those of the tree species leaves in the Botanical Garden, although the adsorption capacities for PM2.5 of the same tree species in different polluted regions had no significant differences. By determining the soluble ion concentrations of the airborne particulates in two regions, it is suggested that the soluble ion concentrations of PM10 in the atmosphere in the Botanical Garden and beside the Fifth Ring Road have significant differences, while those of PM2.5 in the atmosphere had no significant differences. In different polluted regions there are significant adaptive changes to the leaf structures, and when compared with slightly polluted region, in the seriously polluted region the epidermis cells of the plant leaves shrinked, the surface textures of the leaves became rougher, and the stomas’ frequency and the pubescence length increased. Even though the plant leaves exposed to the seriously polluted region changed significantly, these plants can still grow normally and healthily. PMID:26287227

  15. Enhancing adsorption capacity of toxic malachite green dye through chemically modified breadnut peel: equilibrium, thermodynamics, kinetics and regeneration studies.

    PubMed

    Chieng, Hei Ing; Lim, Linda B L; Priyantha, Namal

    2015-01-01

    Breadnut skin, in both its unmodified (KS) and base-modified (BM-KS) forms, was investigated for its potential use as a low-cost adsorbent for the removal of toxic dye, malachite green (MG). Characterization of the adsorbents was carried out using scanning electron microscope, X-ray fluorescence and Fourier transform infra-red spectroscopy. Batch adsorption experiments, carried out under optimized conditions, for the adsorption of MG were fitted using five isotherm models (Langmuir, Freundlich, Dubinin-Radushkevich, Temkin and Sips) and six error functions to determine the best-fit model. The adsorption capacity was greatly enhanced when breadnut skin was chemically modified with NaOH, leading to an adsorption capacity of 353.0 mg g(-1), that was far superior to most reported adsorbents for the removal of MG. Thermodynamics studies indicated that the adsorption of MG was spontaneous on KS and BM-KS, and the reactions were endothermic and exothermic, respectively. Kinetics studies showed that both followed the pseudo-second order. Regeneration experiments on BM-KS indicated that its adsorption capacity was still maintained at>90% even after five cycles. It can be concluded that NaOH-modified breadfruit skin has great potential to be utilized in real-life application as a low-cost adsorbent for the removal of MG in wastewater treatment.

  16. Preparation of a porous clay heterostructure and study of its adsorption capacity of phenol and chlorinated phenols from aqueous solutions.

    PubMed

    Arellano-Cárdenas, Sofía; Gallardo-Velázquez, Tzayhrí; Osorio-Revilla, Guillermo; López-Cortez, Ma del Socorro

    2008-01-01

    A porous clay heterostructure (PCH) from a Mexican clay was prepared and characterized, and its aqueous phenol and dichlorophenols (DCPs) adsorption capacities were studied using a batch equilibrium technique. The PCH displayed a surface area of 305.5 m2/g, 37.2 A average porous diameter, and a basal space of 23.2 A. The adsorption capacity shown by the PCH for both phenol and DCPs from water (14.5 mg/g for phenol; 48.7 mg/g for 3,4-DCP; and 45.5 mg/g for 2,5-DCP) suggests that the PCH has both hydrophobic and hydrophilic characteristics, as a result of the presence of silanol and siloxane groups formed during the pillaring and calcination of the PCH. The values of maximal adsorption capacity for dichlorophenols were higher than those reported for aluminum pillared clays and some inorgano-organo clays and comparable with some ionic exchange resins.

  17. The effects of urease immobilization on the transport characteristics and protein adsorption capacity of cellulose acetate based hemodialysis membranes.

    PubMed

    Mahlicli, Filiz Yasar; Altinkaya, Sacide Alsoy

    2009-10-01

    In this study, cellulose acetate (CA) based hemodialysis membranes were prepared by a dry phase inversion method and the influences of urease immobilization on the clearing performance and protein adsorption capacity of the membranes were investigated. Permeation experiments have shown that modification of CA membranes with urease immobilization not only enhanced the transport rate of urea but also increased the permeation coefficients of uric acid and creatinine by changing the structure of the membrane. Furthermore, the protein adsorption capacity of the CA membranes decreased. On the other hand, the mechanical strength of the modified CA membrane did not change significantly compared with that of the unmodified one. A mathematical model was derived to determine the rate of mass transfer of urea through modified CA membranes. Model predictions along with the experimental data suggest that urease immobilization can be used as an alternative method in preparing CA based hemodialysis membranes with improved transport characteristics and biocompatibility through reduced protein adsorption capacities.

  18. A geometric pore adsorption model for predicting the drug loading capacity of insoluble drugs in mesoporous carbon.

    PubMed

    Gao, Yikun; Zhu, Wenquan; Liu, Jia; Di, Donghua; Chang, Di; Jiang, Tongying; Wang, Siling

    2015-05-15

    In this work, a simple and accurate geometric pore-adsorption model was established and experimentally validated for predicting the drug loading capacity in mesoporous carbon. The model was designed according to the shape of pore channels of mesoporous carbon and the arrangement of drug molecules loaded in the pores. Three different small molecule drugs (celecoxib, fenofibrate and carvedilol) were respectively loaded in mesoporous carbon with different pore sizes. In order to test the accuracy of the established model, nitrogen adsorption-desorption analysis was employed to confirm the pore structure of mesoporous carbon and to calculate the occupation volume of the adsorbed drugs. The adsorption isotherms of celecoxib were systematically investigated to describe the adsorption process. It was found that the experimental results of adsorption capacity were all in the range of the predicted values for all the tested drugs and mesoporous carbon. The occupation volumes calculated from the model also agreed well with the experimental data. These results demonstrated that the established model could accurately provide the range of drug loading capacity, which may provide a useful option for the prediction of the drug loading capacity of small molecule drugs in mesoporous materials.

  19. Fiber-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

    2016-09-06

    A fiber-based adsorbent and a related method of manufacture are provided. The fiber-based adsorbent includes polymer fibers with grafted side chains and an increased surface area per unit weight over known fibers to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. The polymer fibers include a circular morphology in some embodiments, having a mean diameter of less than 15 microns, optionally less than about 1 micron. In other embodiments, the polymer fibers include a non-circular morphology, optionally defining multiple gear-shaped, winged-shaped or lobe-shaped projections along the length of the polymer fibers. A method for forming the fiber-based adsorbents includes irradiating high surface area polymer fibers, grafting with polymerizable reactive monomers, reacting the grafted fibers with hydroxylamine, and conditioning with an alkaline solution. High surface area fiber-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  20. Fiber-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J; Dai, Sheng; Oyola, Yatsandra

    2014-05-13

    A fiber-based adsorbent and a related method of manufacture are provided. The fiber-based adsorbent includes polymer fibers with grafted side chains and an increased surface area per unit weight over known fibers to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. The polymer fibers include a circular morphology in some embodiments, having a mean diameter of less than 15 microns, optionally less than about 1 micron. In other embodiments, the polymer fibers include a non-circular morphology, optionally defining multiple gear-shaped, winged-shaped or lobe-shaped projections along the length of the polymer fibers. A method for forming the fiber-based adsorbents includes irradiating high surface area polymer fibers, grafting with polymerizable reactive monomers, reacting the grafted fibers with hydroxylamine, and conditioning with an alkaline solution. High surface area fiber-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  1. Synthesis of multi-walled carbon nanotubes/β-FeOOH nanocomposites with high adsorption capacity

    NASA Astrophysics Data System (ADS)

    Song, Hao-Jie; Liu, Lei; Jia, Xiao-Hua; Min, Chunying

    2012-12-01

    A hybrid nanostructure of multi-walled carbon nanotubes (CNTs) and β-ferric oxyhydroxide (β-FeOOH) nanoparticles is synthesized by ultrasonic-assisted in situ hydrolysis of the precursor ferric chloride and CNTs. Characterization by X-ray diffraction, scanning electron microscopy , and transmission electron microscopy establishes the nanohybrid structure of the synthesized sample. The results revealed that the surface of CNTs was uniformly assembled by numerous β-FeOOH nanoparticles and had an average diameter of 3 nm. The formation route of anchoring β-FeOOH nanoparticles onto CNTs was proposed as the intercalation and adsorption of iron ions onto the wall of CNTs, followed by the nucleation and growth of β-FeOOH nanoparticles. The values of remanent magnetization ( M r) and coercivity ( H c) of the as-synthesized CNTs/β-FeOOH nanocomposites were 0.1131 emu g, and 490.824 Oe, respectively. Furthermore, CNTs/β-FeOOH nanocomposites showed a very high adsorption capacity of Congo red and thus these nanocomposites can be used as good adsorbents and can be used for the removal of the dye of Congo red from the waste water system.

  2. The adsorptive capacity of vapor-phase mercury chloride onto powdered activated carbon derived from waste tires.

    PubMed

    Lin, Hsun-Yu; Yuan, Chung-Shin; Wu, Chun-Hsin; Hung, Chung-Hsuang

    2006-11-01

    Injection of powdered activated carbon (PAC) upstream of particulate removal devices (such as electrostatic precipitator and baghouses) has been used effectively to remove hazardous air pollutants, particularly mercury-containing pollutants, emitted from combustors and incinerators. Compared with commercial PACs (CPACs), an alternative PAC derived from waste tires (WPAC) was prepared for this study. The equilibrium adsorptive capacity of mercury chloride (HgCl2) vapor onto the WPAC was further evaluated with a self-designed bench-scale adsorption column system. The adsorption temperatures investigated in the adsorption column were controlled at 25 and 150 degrees C. The superficial velocity and residence time of the flow were 0.01 m/sec and 4 sec, respectively. The adsorption column tests were run under nitrogen gas flow. Experimental results showed that WPAC with higher Brunauer-Emmett-Teller (BET) surface area could adsorb more HgCl2 at room temperature. The equilibrium adsorptive capacity of HgCl2 for WPAC measured in this study was 1.49 x 10(-1) mg HgCl2/g PAC at 25 degrees C with an initial HgCI2 concentration of 25 microg/m3. With the increase of adsorption temperature < or = 150 degrees C, the equilibrium adsorptive capacity of HgCl2 for WPAC was decreased to 1.34 x 10(-1) mg HgCl2/g PAC. Furthermore, WPAC with higher sulfur contents could adsorb even more HgCl2 because of the reactions between sulfur and Hg2+ at 150 degrees C. It was demonstrated that the mechanisms for adsorbing HgCl2 onto WPAC were physical adsorption and chemisorption at 25 and 150 degrees C, respectively. Experimental results also indicated that the apparent overall driving force model appeared to have the good correlation with correlation coefficients (r) > 0.998 for HgCl2 adsorption at 25 and 150 degrees C. Moreover, the equilibrium adsorptive capacity of HgCl2 for virgin WPAC was similar to that for CPAC at 25 degrees C, whereas it was slightly higher for sulfurized WPAC than for

  3. Copper Accumulation, Availability and Adsorption Capacity in Sandy Soils of Vineyards with Different Cultivation Duration

    NASA Astrophysics Data System (ADS)

    Mallmann, F. J. K.; Miotto, A.; Bender, M. A.; Gubiani, E.; Rheinheimer, D. D. S.; Kaminski, J.; Ceretta, C. A.; Šimůnek, J.

    2015-12-01

    Bordeaux mixture is a copper-based (Cu) fungicide and bactericide applied in vineyards to control plant diseases. Since it is applied several times per year, it accumulates in large quantities on plants and in soil. This study evaluates the Cu accumulation in, and desorption kinetics and adsorption capability of a sandy Ultisol in a natural field and in 3 vineyards for 5 (V1), 11 (V2), and 31 (V3) years in South of Brazil. Soil samples were collected in 8 depths (0-60 cm) of all four soil profiles, which all displayed similar soil properties. The following soil properties were measured: pH, organic matter (OM), soil bulk density, Cu total concentration, and Cu desorption and adsorption curves. A two first-order reactions model and the Langmuir isotherm were fitted to the desorption and adsorption curves, respectively. An increase in the total mass of Cu in the vineyards followed a linear regression curve, with an average annual increase of 7.15 kg ha-1. Cu accumulated down to a depth of 5, 20, and 30 cm in V1, V2 and V3, respectively, with the highest Cu content reaching 138.4 mg kg-1 in the 0-5 cm soil layer of V3. Cu desorption parameters showed a high correlation with its total concentration. Approximately 57 and 19% of total Cu were immediately and slowly available, respectively, indicating a high potential for plant absorption and/or downward movement. Cu concentrations extracted by EDTA from soil layers not affected by anthropogenic Cu inputs were very low. The maximum Cu adsorption capacity of the 0-5 and 5-10 cm soil layers increased with the vineyard age, reaching concentrations higher than 900 mg kg-1. This increase was highly related to OM and pH, which both increased with cultivation duration. Despite of low clay content of these soils, there is low risk of groundwater Cu contamination for actual conditions. However, high Cu concentrations in the surface layer of the long-term vineyards could cause toxicity problems for this and for companion crops.

  4. Effect of the both texture and electrical properties of activated carbon on the CO{sub 2} adsorption capacity

    SciTech Connect

    Djeridi, W.; Ouederni, A.; Mansour, N.Ben; Llewellyn, P.L.; Alyamani, A.; El Mir, L.

    2016-01-15

    Highlights: • A series of activated carbon pellet without binder was prepared by chemical activation. • Carbon dioxide storage isotherm at 30 °C and up to 25 bars was measured for the microporous carbon. • Adsorption enthalpies have been correlated with the carbon dioxide uptake. • Pyrolysis temperature effect on the electrical conductivity of the samples. • Impact of the both texture and electrical properties on CO{sub 2} adsorption capacity have been deducted - Abstract: A series of activated carbon pellets (ACP) based on olive stones were studied for CO{sub 2} storage application. The surface area, pore volume, and pore diameter were evaluated from the analysis of N{sub 2} adsorption isotherm data. The characterization of carbon materials was performed by scanning electron microscopy (SEM), the powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM). The adsorption enthalpies were obtained by microcalorimetry. The effect of pyrolysis temperature on textural, electrical conductivity and gas adsorption capacities of the ACP were investigated by adsorbing CO{sub 2} at 303 K in the pressure range of 0–2.3 MPa. In fact the electrical conductivity is strongly affected by the microporosity of the samples and the size of the micropore. It increases when the pore size decreases which affect the CO{sub 2} adsorption. Also with increases temperature the free electrons concentration on the surface increases which affect the interaction of the adsorbed gas molecules.

  5. Cu(II) and Zn(II) adsorption capacity of three different clay liner materials.

    PubMed

    Musso, T B; Parolo, M E; Pettinari, G; Francisca, F M

    2014-12-15

    Sorption of Cu(II) and Zn(II) on three natural clays meeting the international requirements for use as liners was evaluated by means of batch tests. The purpose of this research was to determine the retention capacities of the clays for metal cations commonly present in urban solid waste leachates. The pH and ionic strength conditions were set at values frequently found in real leachates. The changes observed in the XRD patterns and FTIR spectra upon adsorption can be considered an evidence of clay-metal electrostatic interaction. The Langmuir model was found to best describe the sorption processes, offering maximum sorption capacities from 8.16 to 56.89 mg/g for Cu(II) and from 49.59 to 103.83 mg/g for Zn(II). All samples remove more Zn(II) than Cu(II), which may be related to the different geometry of the hydrated Cu(II) cation. The total amount of metal sorption was strongly influenced by the total specific surface area, the presence of carbonates and the smectite content of the clays. In addition to their known quality as physical barriers, the adsorbed amounts obtained indicate the suitability of the tested clays to contribute to the retardation of Cu(II) and Zn(II) transport through clay liners.

  6. Expanded porous MOF-505 analogue exhibiting large hydrogen storage capacity and selective carbon dioxide adsorption.

    PubMed

    Zheng, Baishu; Yun, Ruirui; Bai, Junfeng; Lu, Zhiyong; Du, Liting; Li, Yizhi

    2013-03-18

    An expanded 4,4-paddlewheel-connected porous MOF-505-type metal-organic framework (MOF), [Cu2(PDEB)(H2O)2]·xS (NJU-Bai12; NJU-Bai represents the Nanjing University Bai group and S represents noncoordinated solvent molecules) has been designed from a nanosized rectangular diisophthalate linker containing alkyne groups 5,5'-(1,4-phenylenedi-2,1-ethynediyl)bis(1,3-benzenecarboxylic acid). This MOF material possesses permanent microporosity with the highest Brunauer-Emmett-Teller surface area of 3038 m(2)·g(-1) and the largest unsaturated total hydrogen storage capacity of 62.7 mg·g(-1) at 77 K and 20 bar among reported MOF-505 analogues. Additionally, NJU-Bai12 also exhibits excellent carbon dioxide (CO2) uptake capacity (23.83 and 19.85 mmol·g(-1) at 20 bar for 273 and 298 K, respectively) and selective gas adsorption properties with CO2/CH4 selectivity of 5.0 and CO2/N2 selectivity of 24.6 at room temperature.

  7. Synthesis, characterisation and adsorption properties of a porous copper(II) 3D coordination polymer exhibiting strong binding enthalpy and adsorption capacity for carbon dioxide.

    PubMed

    Eckold, Pierre; Gee, William J; Hill, Matthew R; Batten, Stuart R

    2012-11-21

    The synthesis and characterisation of microporous coordination polymers containing copper(II) or cobalt(II) and 2-(pyridin-4-yl)malonaldehyde (Hpma) is described and the gas adsorption properties evaluated. Single-crystal X-ray structure determinations identified the structures as [M(pma)(2)]·2X (M = Cu, 1; Co, 2; X = MeOH, MeCN), which contain 3D networks with rutile topology and continuous 1D rectangular channels with diameters ranging from 3 to 4 Å. The materials exhibit low BET surface areas of 143 m(2) g(-1), but possess large capacities for carbon dioxide capture of 14.1 wt%. The small pore channels are shown to account for this, delivering a particularly strong binding enthalpy to adsorbed CO(2) of 38 kJ mol(-1), and a very large adsorption capacity relative to the low surface area.

  8. High adsorption capacity of heavy metals on two-dimensional MXenes: an ab initio study with molecular dynamics simulation.

    PubMed

    Guo, Xun; Zhang, Xitong; Zhao, Shijun; Huang, Qing; Xue, Jianming

    2016-01-07

    Density functional theory (DFT) calculation is employed to study the adsorption properties of Pb and Cu on recently synthesized two-dimensional materials MXenes, including Ti3C2, V2C1 and Ti2C1. The influence of surface decoration with functional groups such as H, OH and F have also been investigated. Most of these studied MXenes exhibit excellent capability to adsorb Pb and Cu, especially the adsorption capacity of Pb on Ti2C1 is as high as 2560 mg g(-1). Both the binding energies and the adsorption capacities are sensitive to the functional groups attached to the MXenes' surface. Ab initio molecular dynamics (ab-init MD) simulation confirms that Ti2C1 remains stable at room temperature after adsorbing Pb atoms. Our calculations imply that these newly emerging two-dimensional MXenes are promising candidates for wastewater treatment and ion separation.

  9. EFFECT OF MOLECULAR OXYGEN ON ADSORPTIVE CAPACITY AND EXTRACTION EFFICIENCY OF GRANULATED ACTIVATED CARBON FOR THREE ORTHO-SUBSTITUTED PHENOLS

    EPA Science Inventory

    Adsorptive capacity of activated carbon for several organic compounds was found to be strongly influenced by the presence of molecular oxygen. This influence is manifested by the polymerization of adsorbate on the surface of activated carbon. As a result, GAC exhibits much high...

  10. High adsorption capacity NaOH-activated carbon for dye removal from aqueous solution.

    PubMed

    Wu, Feng-Chin; Tseng, Ru-Ling

    2008-04-15

    In this study, the surface coverage ratio (Sc/Sp) and monolayer cover adsorption amount per unit surface area (qmon/Sp) were employed to investigate the adsorption isotherm equilibrium of the adsorption of dyes (AB74, BB1 and MB) on NaOH-activated carbons (FWNa2, FWNa3 and FWNa4); the adsorption rate of the Elovich equation (1/b) and the ratio of 1min adsorption amount of adsorbate to the monolayer cover amount of adsorbate (q1/qmon) were employed to investigate adsorption kinetics. The qmon/Sp of NaOH-activated carbons was better than that of KOH-activated carbons prepared from the same raw material (fir wood). The Sc/Sp values of the adsorption of all adsorbates on adsorbent FWNa3 in this study were found to be higher than those in related literature. Parameters 1/b and q1 of the adsorption of dyes on activated carbons in this study were higher than those on KOH-activated carbons; the q1/qmon value of FWNa3 was the highest. The pore structure and the TPD measurement of the surface oxide groups were employed to explain the superior adsorption performance of FWNa3. A high surface activated carbon (FWNa3) with excellent adsorption performance on dyes with relation to adsorption isotherm equilibrium and kinetics was obtained in this study. Several adsorption data processing methods were employed to describe the adsorption performance.

  11. Efficient Removal of Co2+ from Aqueous Solution by 3-Aminopropyltriethoxysilane Functionalized Montmorillonite with Enhanced Adsorption Capacity

    PubMed Central

    Huang, Zhujian; Gong, Beini; Dai, Yaping; Chiang, Pen-Chi; Lai, Xiaolin; Yu, Guangwei

    2016-01-01

    To achieve a satisfactory removal efficiency of heavy metal ions from wastewater, silane-functionalized montmorillonite with abundant ligand-binding sites (-NH2) was synthesized as an efficient adsorbent. Ca-montmorillonite (Ca-Mt) was functionalized with 3-aminopropyl triethoxysilane (APTES) to obtain the APTES-Mt products (APTES1.0CEC-Mt, APTES2.0CEC-Mt, APTES3.0CEC-Mt, APTES4.0CEC-Mt) with enhanced adsorption capacity for Co2+. The physico-chemical properties of the synthesized adsorbents were characterized by spectroscopic and microscopic methods, and the results demonstrated that APTES was successfully intercalated into the gallery of Ca-Mt or grafted onto the surface of Ca-Mt through Si-O bonds. The effect of solution pH, ionic strength, temperature, initial concentrations and contact time on adsorption of Co2+ by APTES-Mt was evaluated. The results indicated that adsorption of Co2+ onto Ca-Mt, APTES1.0CEC-Mt and APTES2.0CEC-Mt can be considered to be a pseudo-second-order process. In contrast, adsorption of Co2+ onto APTES3.0CEC-Mt and APTES4.0CEC-Mt fitted well with the pseudo-first-order kinetics. The adsorption isotherms were described by the Langmuir model, and the maximum adsorption capacities of APTES1.0CEC-Mt, APTES2.0CEC-Mt, APTES3.0CEC-Mt and APTES4.0CEC-Mt were 25.1, 33.8, 61.6, and 61.9 mg·g-1, respectively. In addition, reaction temperature had no impact on the adsorption capacity, while both the pH and ionic strength significantly affected the adsorption process. A synergistic effect of ion exchange and coordination interactions on adsorption was observed, thereby leading to a significant enhancement of Co2+ adsorption by the composites. Thus, APTES-Mt could be a cost-effective and environmental-friendly adsorbent, with potential for treating Co2+-rich wastewater. PMID:27448094

  12. Cycloadditions on diamond (100) 2 x 1: observation of lowered electron affinity due to hydrocarbon adsorption.

    PubMed

    Ouyang, Ti; Gao, Xingyu; Qi, Dongchen; Wee, Andrew Thye Shen; Loh, Kian Ping

    2006-03-23

    The adsorption of allyl alcohol, acrylic acid, and allyl chloride, as well as unsaturated organic molecules such as acetylene and 1,3 butadiene, on reconstructed diamond (100) 2 x 1 have been investigated using high-resolution electron energy loss (HREELS) spectroscopy and synchrotron radiation spectroscopy. The cycloadditions of these organic molecules produce chemically adsorbed adlayers with varying degree of coverages on the clean diamond. The organic adsorbed surface has a lowered electron affinity and shows a secondary electron yield that varies between 12 and 40% of the yield obtained from a fully hydrogenated diamond surface. The diamond surface can be functionalized with hydroxyl, carboxylic, and chlorine functionalities by the adsorption of these allyl organics. The [2 + 2] adduct of acetylene on the diamond (100) 2 x 1 surface can be observed. 1,3-butadiene attains a higher coverage as well as forms a thermally more stable adlayer on the diamond surface compared to the other organic molecules, due to its ability to undergo [4 + 2] cycloaddition.

  13. Preparation and characterization of a hierarchical porous char from sewage sludge with superior adsorption capacity for toluene by a new two-step pore-fabricating process.

    PubMed

    Kong, Lingjun; Xiong, Ya; Tian, Shuanghong; Luo, Rongshu; He, Chun; Huang, Haibao

    2013-10-01

    A kind of hierarchical porous char (SCCA/Zn) was prepared from sewage sludge by a new two-step pore-fabricating process coupling citric acid (CA) with ZnCl2 in a pyrolysis process. The char was characterized by element analysis, N2-adsorption and mercury intrusion measurement etc. It is found that coupling CA and ZnCl2 can synergistically fabricate pores in the pyrolysis process, resulting in a hierarchical porous char, SCCA/Zn, with the largest SBET of 867.6 m(2) g(-1) due to the fact that the former contributes to the fabrication of macro-pores, which provides more space for fabricating meso- and micro-pores by ZnCl2 activation. Although the SBET of SCCA/Zn was 15% less than that of activated carbon fiber (ACF, SBET=999.5 m(2) g(-1)), SCCA/Zn had a higher toluene adsorption capacity (0.83 g g(-1)) than ACF. The inconsistence between their SBET and adsorption capacity can be ascribed to the strong hydrophobic property of SCCA/Zn.

  14. Effect of different carbon nanotubes on cadmium toxicity to Daphnia magna: The role of catalyst impurities and adsorption capacity.

    PubMed

    Wang, Xinghao; Qu, Ruijuan; Liu, Jiaoqin; Wei, Zhongbo; Wang, Liansheng; Yang, Shaogui; Huang, Qingguo; Wang, Zunyao

    2016-01-01

    Experiments were conducted to investigate the effect of four different carbon nanotubes single- and multi-walled carbon nanotubes (SWCNTs and MWCNTs) and hydroxylated and carboxylated multi-walled carbon nanotubes (OH-MWCNTs and COOH-MWCNTs) on Cd toxicity to the aquatic organism Daphnia magna. The acute toxicity results indicated that all CNTs could enhance the toxicity of Cd to D. magna. Furthermore, the filtrate toxicity and adsorption tests showed that the toxicity-increasing effect of SWCNTs and MWCNTs in the overall system was mainly caused by catalysts impurities from the pristine CNTs, whereas the greater adsorption of Cd onto OH-MWCNTs (30.52 mg/g) and COOH-MWCNTs (24.93 mg/g) was the key factor contributing to the enhanced toxicity. This result raised a concern that the metal catalyst impurities, adsorption capacities, and accumulation of waterborne CNTs were responsible for the toxicity of Cd to aquatic organism.

  15. Dye-adsorption capacity of high surface-area hydrogen titanate nanosheets processed via modified hydrothermal method.

    PubMed

    Padinhattayil, Hareesh; Augustine, Rimesh; Shukla, Satyajit

    2013-04-01

    High surface-area (380 m2 x g(-1)) hydrogen titanate nanosheets (HTNS) processed via the modified hydrothermal method have been utilized for the removal of methylene blue (MB) dye from an aqueous solution via the surface-adsorption process involving the electrostatic attraction mechanism. The HTNS have been characterized using the transmission electron microscope (TEM), selected-area electron diffraction (SAED), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) specific surface-area measurement techniques. The amount of MB dye adsorbed on the surface of HTNS at equilibrium (q(e)) has been examined as a function of contact time, initial dye-concentration, and initial solution-pH. Within the investigated range of initial solution-pH (2.5-11), the MB dye adsorption on the surface of HTNS has been observed to follow the pseudo-second-order kinetics with the dye-adsorption capacity of 119 mg x g(-1) at the initial solution-pH of - 10. The adsorption equilibrium follows the Langmuir isotherm within the initial solution-pH range of 2.5-10. However, in a highly basic solution (initial solution-pH -11), the adsorption equilibrium has been observed to follow the Langmuir, Freundlich, and Dubinin-Kaganer-Radushkevich (DKR) models in the different ranges of initial MB dye concentration. The mere dependence on the DKR model has not been observed within the investigated range of initial solution-pH. The differences in the dye-adsorption characteristics and capacity of HTNS, compared with those of hydrogen titanate nanotubes, have been attributed to the difference in their specific surface-area. Irrespective of the morphology, the maximum coverage of MB dye on the surface of hydrogen titanate has been noted to be the same (52%).

  16. Characterization of the cation-binding capacity of a potassium-adsorption filter used in red blood cell transfusion.

    PubMed

    Suzuki, Takao; Muto, Shigeaki; Miyata, Yukio; Maeda, Takao; Odate, Takayuki; Shimanaka, Kimio; Kusano, Eiji

    2015-06-01

    A K(+) -adsorption filter was developed to exchange K(+) in the supernatant of stored irradiated red blood cells with Na(+) . To date, however, the filter's adsorption capacity for K(+) has not been fully evaluated. Therefore, we characterized the cation-binding capacity of this filter. Artificial solutions containing various cations were continuously passed through the filter in 30 mL of sodium polystyrene sulfonate at 10 mL/min using an infusion pump at room temperature. The cation concentrations were measured before and during filtration. When a single solution containing K(+) , Li(+) , H(+) , Mg(2+) , Ca(2+) , or Al(3+) was continuously passed through the filter, the filter adsorbed K(+) and the other cations in exchange for Na(+) in direct proportion to the valence number. The order of affinity for cation adsorption to the filter was Ca(2+) >Mg(2+) >K(+) >H(+) >Li(+) . In K(+) -saturated conditions, the filter also adsorbed Na(+) . After complete adsorption of these cations on the filter, their concentration in the effluent increased in a sigmoidal manner over time. Cations that were bound to the filter were released if a second cation was passed through the filter, despite the different affinities of the two cations. The ability of the filter to bind cations, especially K(+) , should be helpful when it is used for red blood cell transfusion at the bedside. The filter may also be useful to gain a better understanding of the pharmacological properties of sodium polystyrene sulfonate.

  17. Summary of Adsorption Capacity and Adsorption Kinetics of Uranium and Other Elements on Amidoxime-based Adsorbents from Time Series Marine Testing at the Pacific Northwest National Laboratory

    SciTech Connect

    Gill, Gary A.; Kuo, Li-Jung; Strivens, Jonathan E.; Wood, Jordana R.; Schlafer, Nicholas J.; Janke, Christopher J.; Das, Sadananda; Mayes, Richard; Saito, Tomonori; Brown, Suree S.; Tsouris, Constantinos; Tsouris, Costas; Wai, Chien M.; Pan, Horng-Bin

    2016-09-29

    The Pacific Northwest National Laboratory (PNNL) has been conducting marine testing of uranium adsorbent materials for the Fuel Resources Program, Department of Energy, Office of Nuclear Energy (DOE-NE) beginning in FY 2012. The marine testing program is being conducted at PNNL’s Marine Sciences Laboratory (MSL), located at Sequim Bay, along the coast of Washington. One of the main efforts of the marine testing program is the determination of adsorption capacity and adsorption kinetics for uranium and selected other elements (e.g. vanadium, iron, copper, nickel, and zinc) for adsorbent materials provided primarily by Oak Ridge National Laboratory (ORNL), but also includes other Fuel Resources Program participants. This report summarizes the major marine testing results that have been obtained to date using time series sampling for 42 to 56 days using either flow-through column or recirculating flume exposures. The major results are highlighted in this report, and the full data sets are appended as a series of Excel spreadsheet files. Over the four year period (2012-2016) that marine testing of amidoxime-based polymeric adsorbents was conducted at PNNL’s Marine Science Laboratory, there has been a steady progression of improvement in the 56-day adsorbent capacity from 3.30 g U/kg adsorbent for the ORNL 38H adsorbent to the current best performing adsorbent prepared by a collaboration between the University of Tennessee and ORNL to produce the adsorbent SB12-8, which has an adsorption capacity of 6.56 g U/kg adsorbent. This nearly doubling of the adsorption capacity in four years is a significant advancement in amidoxime-based adsorbent technology and a significant achievement for the Uranium from Seawater program. The achievements are evident when compared to the several decades of work conducted by the Japanese scientists beginning in the 1980’s (Kim et al., 2013). The best adsorbent capacity reported by the Japanese scientists was 3.2 g U/kg adsorbent for a

  18. Relationship between the adsorption capacity of pesticides by wood residues and the properties of woods and pesticides.

    PubMed

    Rodriguez-Cruz, Sonia; Andrades, Maria S; Sanchez-Camazano, Maria; Sanchez-Martin, Maria J

    2007-05-15

    With the aim to explore the potential use of wood residues in technologies aimed at preventing the pollution of soil and water, we studied the adsorption of four non-ionic pesticides (linuron, alachlor, metalaxyl, and chlorpyrifos) and two ionic pesticides (dicamba and paraquat) with a Kow range of -4.5 to 4.7 by nine types of wood with lignin content in the 18.2-26.9% range. The Freundlich Kf values were considered as indicators of the adsorption capacity. A statistical study was carried out using simple and multiple correlations to establish the degree to which the different parameters of the woods and of the pesticides were involved in adsorption. In the case of the non-ionic pesticides, positive and negative significant correlations were observed between Kf and the lignin (r = 0.73-0.83, p < 0.05-0.01), and soluble C contents of the woods (r = 0.66-0.84), p < 0.1-0.01). For dicamba, a correlation between Kf and pH (r = -0.66, p < 0.1) of the woods was found, while for paraquat, this was seen between Kf and the cation exchange capacity (r = 0.71, p < 0.1) of the woods. No significant correlation was observed between Kf and the total C content of the woods. A highly significant correlation between Kf and Kow values (r > or = 0.93, p < 0.01) was found in the adsorption of the pesticides by the woods (with the exception of paraquat) showing that this parameter is very important in this adsorption process. The determination coefficient of the multiple correlation between Kf and the parameters Kow, soluble C, and lignin contents accounts for nearly 100% of the variability in adsorption for non-ionic pesticides. Based on the results of our study and of those of the literature related to the adsorption of aromatic hydrocarbons, we used the Kow values to define a predictive model of adsorption of hydrophobic organic compounds in general by the woods.

  19. Adsorption of Pb(II) on mesoporous activated carbons fabricated from water hyacinth using H3PO4 activation: Adsorption capacity, kinetic and isotherm studies

    NASA Astrophysics Data System (ADS)

    Huang, Yang; Li, Shunxing; Chen, Jianhua; Zhang, Xueliang; Chen, Yiping

    2014-02-01

    Activated carbons with high mesoporosity and abundant oxygen-containing functional groups were prepared from water hyacinth using H3PO4 activation (WHAC) to eliminate Pb(II) in water. Characterizations of the WHAC were performed using Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The BET analysis showed that WHAC possesses a high mesoporosity (93.9%) with a BET surface area of 423.6 m2/g. The presence of oxygen-containing functional groups including hydroxyl, carbonyl, carboxyl and phosphate groups renders the WHAC a favorable adsorbent for Pb(II) with the maximum monolayer capacity (qm) 118.8 mg/g. The adsorption behavior follows pseudo-first order kinetic and Langmuir isotherm. The desorption study demonstrated that the WHAC could be readily regenerated using 0.1 M HCl (pH = 1.0). The desorbed WHAC could be reused at least six times without significant adsorption capacity reduction. The adsorption process was spontaneous and endothermic with ΔG (-0.27, -1.13, -3.02, -3.62, -5.54, and -9.31 kJ/mol) and ΔH (38.72 kJ/mol). Under the optimized conditions, a small amount of the adsorbent (1.0 g/L) could remove as much as 90.1% of Pb(II) (50 mg/L) in 20 min at pH 6.0 and temperature of 298 K. Therefore, the WHAC has a great potential to be an economical and efficient adsorbent in the treatment of lead-contaminated water.

  20. High gas storage capacities and stepwise adsorption in a UiO type metal-organic framework incorporating Lewis basic bipyridyl sites.

    PubMed

    Li, Liangjun; Tang, Sifu; Wang, Chao; Lv, Xiaoxia; Jiang, Min; Wu, Huaizhi; Zhao, Xuebo

    2014-03-04

    A UiO type MOF with Lewis basic bipyridyl sites was synthesized and structurally characterized. After being activated by Soxhlet-extraction, this MOF exhibits high storage capacities for H2, CH4 and CO2, and shows unusual stepwise adsorption for liquid CO2 and solvents, indicating a sequential filling mechanism on different adsorption sites.

  1. Simultaneous activation/sulfurization method for production of sulfurized activated carbons: characterization and Hg(II) adsorption capacity.

    PubMed

    Shamsijazeyi, Hadi; Kaghazchi, Tahereh

    2014-01-01

    As an inexpensive method for modification of activated carbons (ACs), sulfurization has attracted significant attention. However, the resulting sulfurized activated carbons (SACs) often are less porous than the original ACs. In this work, we propose a new method for concurrent sulfurization/activation that can lead to preparation of SACs with more porosity than the corresponding non-sulfurized ACs. By using scanning electron microscopy, nitrogen adsorption/desorption, and iodine number experiments, the porous structure of the SACs has been compared with that of non-sulfurized ACs. The specific surface areas of SACs are higher than the corresponding ACs, regardless of the type of activation agents used. For instance, the specific surface area of SAC and AC activated with phosphoric acid is 1,637 and 1,338 m(2)/g, respectively. Additionally, sulfur contents and surface charges (pHpzc) of the SACs and non-sulfurized ACs are compared. In fact, the SACs have higher sulfur contents and more acidic surfaces. Furthermore, the Hg(II) adsorption capacity of SACs has been compared with the corresponding non-sulfurized ACs. The Hg(II) adsorption isotherms on a selected SAC is measured at different pH values and temperatures. Hg(II) adsorptions as high as 293 mg/g are observed by using SACs prepared by the method proposed in this study.

  2. Effects of Igneous Intrusion on Microporosity and Gas Adsorption Capacity of Coals in the Haizi Mine, China

    PubMed Central

    2014-01-01

    This paper describes the effects of igneous intrusions on pore structure and adsorption capacity of the Permian coals in the Huaibei Coalfield, China. Twelve coal samples were obtained at different distances from a ~120 m extremely thick sill. Comparisons were made between unaltered and heat-affected coals using geochemical data, pore-fracture characteristics, and adsorption properties. Thermal alteration occurs down to ~1.3 × sill thickness. Approaching the sill, the vitrinite reflectance (Ro) increased from 2.30% to 2.78%, forming devolatilization vacuoles and a fine mosaic texture. Volatile matter (VM) decreased from 17.6% to 10.0% and the moisture decreased from 3.0% to 1.6%. With decreasing distance to the sill, the micropore volumes initially increased from 0.0054 cm3/g to a maximum of 0.0146 cm3/g and then decreased to 0.0079 cm3/g. The results show that the thermal evolution of the sill obviously changed the coal geochemistry and increased the micropore volume and adsorption capacity of heat-affected coal (60–160 m from the sill) compared with the unaltered coals. The trap effect of the sill prevented the high-pressure gas from being released, forming gas pocket. Mining activities near the sill created a low pressure zone leading to the rapid accumulation of methane and gas outbursts in the Haizi Mine. PMID:24723841

  3. Effects of igneous intrusion on microporosity and gas adsorption capacity of coals in the Haizi Mine, China.

    PubMed

    Jiang, Jingyu; Cheng, Yuanping

    2014-01-01

    This paper describes the effects of igneous intrusions on pore structure and adsorption capacity of the Permian coals in the Huaibei Coalfield, China. Twelve coal samples were obtained at different distances from a ~120 m extremely thick sill. Comparisons were made between unaltered and heat-affected coals using geochemical data, pore-fracture characteristics, and adsorption properties. Thermal alteration occurs down to ~1.3 × sill thickness. Approaching the sill, the vitrinite reflectance (R(o)) increased from 2.30% to 2.78%, forming devolatilization vacuoles and a fine mosaic texture. Volatile matter (VM) decreased from 17.6% to 10.0% and the moisture decreased from 3.0% to 1.6%. With decreasing distance to the sill, the micropore volumes initially increased from 0.0054 cm(3)/g to a maximum of 0.0146 cm(3)/g and then decreased to 0.0079 cm(3)/g. The results show that the thermal evolution of the sill obviously changed the coal geochemistry and increased the micropore volume and adsorption capacity of heat-affected coal (60-160 m from the sill) compared with the unaltered coals. The trap effect of the sill prevented the high-pressure gas from being released, forming gas pocket. Mining activities near the sill created a low pressure zone leading to the rapid accumulation of methane and gas outbursts in the Haizi Mine.

  4. Loss of factor VIII activity during storage in PVC containers due to adsorption.

    PubMed

    McLeod, A G; Walker, I R; Zheng, S; Hayward, C P

    2000-03-01

    Recombinant factor VIII concentrates are stable when administered in a reconstituted form according to the manufacturer's specifications, and undiluted via infusion with syringe mini-pumps. However many Haemophilia centres administer recombinant factor VIII further diluted in intravenous fluids for greater ease of administration. To investigate the stability of recombinant factor VIII during administration as a diluted infusion, reconstituted factor VIII was stored in polyvinylchloride (PVC) mini-bags undiluted (146 IU mL-1) and at factor VIII concentrations of 10 IU mL-1 and 2 IU mL-1. After 48 h of storage at room temperature in PVC mini-bags, the recoveries of factor VIII activity were 41.9% of the initial activity for the undiluted (146 IU mL-1) product and 43.7% of the initial activity for factor VIII diluted to 10 IU mL-1. For factor VIII diluted to 2 IU mL-1, the amount of factor VIII activity remaining at 48 h was only 1.8% of the initial activity. In contrast, 100% of factor VIII activity was recovered after 48 h when undiluted reconstituted product (146 IU mL-1) was stored in a syringe. To investigate the mechanism of factor VIII activity loss during storage, factor VIII samples collected after 0, 3 and 48 h of storage were analysed by immunoblotting with factor VIII antibodies. No evidence of factor VIII proteolytic degradation during storage was found, however, large amounts of factor VIII antigen were recovered from the empty PVC mini-bags following elution with denaturing detergent. We conclude that clinically significant losses of factor VIII activity occur during storage in PVC mini-bags and that the loss of activity is most likely due to protein adsorption onto the plastic surface. This loss of factor VIII activity during storage in PVC containers may substantially affect the safety and potential cost savings of administering recombinant factor VIII by continuous infusion.

  5. Effect of the concentration of inherent mineral elements on the adsorption capacity of coconut shell-based activated carbons.

    PubMed

    Afrane, G; Achaw, Osei-Wusu

    2008-09-01

    Coconut shells of West Africa Tall, a local variety of the coconut species Cocos nucifera L., were taken from five different geographical locations in Ghana and examined for the presence and concentration levels of some selected mineral elements using atomic absorption spectrometer. Activated carbons were subsequently made from the shells by the physical method. The iodine adsorption characteristics of the activated carbons measured showed a definite relationship to the concentration levels of potassium and other mineral elements in the precursor shell. Samples with lower total minerals content recorded higher iodine numbers. It was observed that the origin of the shells was related to the concentration levels of the analyzed mineral elements in the shells, which in turn affected the adsorption capacity of the activated carbons. The results of this study have important implications for the sourcing of coconuts whose shells are used in the manufacture of activated carbons.

  6. 2,4-D adsorption to biochars: effect of preparation conditions on equilibrium adsorption capacity and comparison with commercial activated carbon literature data.

    PubMed

    Kearns, J P; Wellborn, L S; Summers, R S; Knappe, D R U

    2014-10-01

    Batch isotherm experiments were conducted with chars to study adsorption of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Chars generated from corncobs, bamboo and wood chips in a laboratory pyrolyzer at 400-700 °C were compared with traditional kiln charcoals collected from villages in S/SE Asia and with activated carbons (ACs). 2,4-D uptake by laboratory chars obtained from bamboo and wood chips after 14 h of pyrolysis at 700 °C, from wood chips after 96 h of pyrolysis at 600 °C, and one of the field-collected chars (basudha) was comparable to ACs. H:C and O:C ratios declined with pyrolysis temperature and duration while surface area increased to >500 m(2)/g. Increasing pyrolysis intensity by increasing temperature and/or duration of heating was found to positively influence adsorption capacity yield (mg(2,4-D/g(feedstock))) over the range of conditions studied. Economic analysis showed that high temperature chars can be a cost-effective alternative to ACs for water treatment applications.

  7. PREDICTING THE ADSORPTION CAPACITY OF ACTIVATED CARBON FOR ORGANIC CONTAMINANTS FROM ADSORBENT AND ADSORBATE PROPERTIES

    EPA Science Inventory

    A quantitative structure-property relationship (QSPR) was developed and combined with the Polanyi-Dubinin-Manes model to predict adsorption isotherms of emerging contaminants on activated carbons with a wide range of physico-chemical properties. Affinity coefficients (βl

  8. Properties of poly(1-naphthylamine)/Fe3O4 composites and arsenic adsorption capacity in wastewater

    NASA Astrophysics Data System (ADS)

    Tran, Minh Thi; Nguyen, Thi Huyen Trang; Vu, Quoc Trung; Nguyen, Minh Vuong

    2016-03-01

    The research results of poly(1-naphthylamine)/Fe3O4 (PNA/Fe3O4) nanocomposites synthesized by a chemical method for As(III) wastewater treatment are presented in this paper. XRD patterns and TEM images showed that the Fe3O4 grain size varied from 13 to 20 nm. The results of Raman spectral analysis showed that PNA participated in part of the PNA/Fe3O4 composite samples. The grain size of PNA/Fe3O4 composite samples is about 25-30 nm measured by SEM. The results of vibrating sample magnetometer measurements at room temperature showed that the saturation magnetic moment of PNA/Fe3O4 samples decreased from 63.13 to 43.43 emu/g, while the PNA concentration increased from 5% to 15%. The nitrogen adsorption-desorption isotherm of samples at 77 K at a relative pressure P/ P 0 of about 1 was studied in order to investigate the surface and porous structure of nanoparticles by the BET method. Although the saturation magnetic moments of samples decreased with the polymer concentration increase, the arsenic adsorption capacity of the PNA/Fe3O4 sample with the PNA concentration of 5% is better than that of Fe3O4 in a solution with pH = 7. In the solution with pH > 14, the arsenic adsorption of magnetic nanoparticles is insignificant.

  9. Hyperbranched-polyol-tethered poly (amic acid) electrospun nanofiber membrane with ultrahigh adsorption capacity for boron removal

    NASA Astrophysics Data System (ADS)

    Wang, Zhe; Wu, Zhongyu; Zhang, Yufeng; Meng, Jianqiang

    2017-04-01

    The development of efficient adsorbents with high sorption capacity remains as a challenge for the removal of micropollutants occurred globally in water resources. In this work, poly (amic acid) (PAA) electrospun nanofiber membranes grafted with hyperbranched polyols were synthesized and used for boron removal. The PAA nanofiber was reacted with hyperbranched polyethylenimine (HPEI) and further with glycidol to introduce the vicinal hydroxyl groups. The chemical composition and surface characteristics of the obtained PAA-g-PG membranes were evaluated by FESEM, FTIR, XPS and water contact angles (WCA) measurements. The boron adsorption thermodynamics and kinetics were investigated systematically. The results showed that the PAA nanofiber spun from concentration of 15% had uniform morphology and narrow diameter distribution. The PAA-g-PG nanofiber membrane had a maximum boron uptake of 5.68 mmol/g and could adsorb 0.82 mmol/g boron from a 5 mg/L solution in 15 min. Both the high surface area of nanofibers and the hyperbranched structure should contribute to the high boron uptake and high adsorption rate. The nanofiber membrane obeyed the Langmuir adsorption model and the pseudo-first-order kinetic model. The regeneration efficiency of the nanofiber membrane remained 93.9% after 10 cycled uses, indicating good regenerability of the membrane.

  10. Effects of sulfur impregnation temperature on the properties and mercury adsorption capacities of activated carbon fibers (ACFs)

    USGS Publications Warehouse

    Hsi, H.-C.; Rood, M.J.; Rostam-Abadi, M.; Chen, S.; Chang, R.

    2001-01-01

    Laboratory studies were conducted to determine the role of sulfur functional groups and micropore surface area of carbon-based adsorbents on the adsorption of Hg0 from simulated coal combustion flue gases. In this study, raw activated carbon fibers that are microporous (ACF-20) were impregnated with elemental sulfur between 250 and 650 ??C. The resulting samples were saturated with respect to sulfur content. Total sulfur content of the sulfur impregnated ACF samples decreased with increasing impregnation temperatures from 250 and 500 ??C and then remained constant to 650 ??C. Results from sulfur K-edge X-ray absorption near-edge structure (S-XANES) spectroscopy showed that sulfur impregnated on the ACF samples was in both elemental and organic forms. As sulfur impregnation temperature increased, however, the relative amounts of elemental sulfur decreased with a concomitant increase in the amount of organic sulfur. Thermal analyses and mass spectrometry revealed that sulfur functional groups formed at higher impregnation temperatures were more thermally stable. In general, sulfur impregnation decreased surface area and increased equilibrium Hg0 adsorption capacity when compared to the raw ACF sample. The ACF sample treated with sulfur at 400 ??C had a surface area of only 94 m2/g compared to the raw ACF sample's surface area of 1971 m2/g, but at least 86% of this sample's surface area existed as micropores and it had the largest equilibrium Hg0adsorption capacities (2211-11343 ??g/g). Such a result indicates that 400 ??C is potentially an optimal sulfur impregnation temperature for this ACF. Sulfur impregnated on the ACF that was treated at 400 ??C was in both elemental and organic forms. Thermal analyses and CS2extraction tests suggested that elemental sulfur was the main form of sulfur affecting the Hg0 adsorption capacity. These findings indicate that both the presence of elemental sulfur on the adsorbent and a microporous structure are important properties for

  11. Evaluation of phosphorus adsorption capacity of sesame straw biochar on aqueous solution: influence of activation methods and pyrolysis temperatures.

    PubMed

    Park, J H; Ok, Y S; Kim, S H; Cho, J S; Heo, J S; Delaune, R D; Seo, D C

    2015-12-01

    The phosphorus (P) adsorption characteristic of sesame straw biochar prepared with different activation agents and pyrolysis temperatures was evaluated. Between 0.109 and 0.300 mg L(-1) in the form of inorganic phosphate was released from raw sesame straw biochar in the first 1 h. The release of phosphate was significantly enhanced from 62.6 to 168.2 mg g(-1) as the pyrolysis temperature increased. Therefore, sesame straw biochar cannot be used as an adsorbent for P removal without change in the physicochemical characteristics. To increase the P adsorption of biochar in aqueous solution, various activation agents and pyrolysis temperatures were applied. The amount of P adsorbed from aqueous solution by biochar activated using different activation agents appeared in the order ZnCl2 (9.675 mg g(-1)) > MgO (8.669 mg g(-1)) ⋙ 0.1N-HCl > 0.1N-H2SO4 > K2SO4 ≥ KOH ≥ 0.1N-H3PO4, showing ZnCl2 to be the optimum activation agent. Higher P was adsorbed by the biochar activated using ZnCl2 under different pyrolysis temperatures in the order 600 °C > 500 °C > 400 °C > 300 °C. Finally, the amount of adsorbed P by activated biochar at different ratios of biochar to ZnCl2 appeared in the order 1:3 ≒ 1:1 > 3:1. As a result, the optimum ratio of biochar to ZnCl2 and pyrolysis temperature were found to be 1:1 and 600 °C for P adsorption, respectively. The maximum P adsorption capacity by activated biochar using ZnCl2 (15,460 mg kg(-1)) was higher than that of typical biochar, as determined by the Langmuir adsorption isotherm. Therefore, the ZnCl2 activation of sesame straw biochar was suitable for the preparation of activated biochar for P adsorption.

  12. Experimental studies of the streaming flow due to the adsorption of particles at a liquid surface

    NASA Astrophysics Data System (ADS)

    Singh, Pushpendra; Musunuri, Naga; Fischer, Ian

    2016-11-01

    The particle image velocimetry (PIV) technique is used to study the streaming flow that is induced when particles are adsorbed at a liquid surface. The flow develops within a fraction of second after the adsorption of the particle and persists for several seconds. The fluid directly below the particle rises upward, and near the surface, it moves away from the particle. The flow causes powders sprinkled on a liquid surface to disperse on the surface. The flow strength, and the volume over which it extends, decreases with decreasing particle size. The streaming flow induced by the adsorption of two or more particles is a combination of the flows which they induce individually. The work was supported by National Science Foundation.

  13. Synthesis, characterisation and methyl orange adsorption capacity of ferric oxide-biochar nano-composites derived from pulp and paper sludge

    NASA Astrophysics Data System (ADS)

    Chaukura, Nhamo; Murimba, Edna C.; Gwenzi, Willis

    2016-02-01

    A Fe2O3-biochar nano-composite (Fe2O3-BC) was prepared from FeCl3-impregnated pulp and paper sludge (PPS) by pyrolysis at 750 °C. The characteristics and methyl orange (MO) adsorption capacity of Fe2O3-BC were compared to that of unactivated biochar (BC). X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirmed the composite material was nano-sized. Fourier transform infrared (FTIR) spectroscopy revealed the presence of hydroxyl and aromatic groups on BC and on Fe2O3-BC, but Brunauer-Emmett-Teller (BET) surface area and Barrett-Joyner-Halenda (BJH) porosity were lower for Fe2O3-BC than BC. Despite the lower BET surface area and porosity of Fe2O3-BC, its MO adsorption capacity was 52.79 % higher than that of BC. The equilibrium adsorption data were best represented by the Freundlich model with a maximum adsorption capacity of 20.53 mg g-1 at pH 8 and 30 min contact time. MO adsorption obeyed pseudo-second-order kinetics for both BC and Fe2O3-BC with R 2 values of 0.996 and 0.999, respectively. Higher MO adsorption capacity for Fe2O3-BC was attributed to the hybrid nature of the nano-composites; adsorption occurred on both biochar matrix and Fe2O3 nanocrystals. Gibbs free energy calculations confirmed the adsorption is energetically favourable and spontaneous with a high preference for adsorption on both adsorbents. The nano-composite can be used for the efficient removal of MO (>97 %) from contaminated wastewater.

  14. Zeolite Y Adsorbents with High Vapor Uptake Capacity and Robust Cycling Stability for Potential Applications in Advanced Adsorption Heat Pumps.

    PubMed

    Li, Xiansen; Narayanan, Shankar; Michaelis, Vladimir K; Ong, Ta-Chung; Keeler, Eric G; Kim, Hyunho; McKay, Ian S; Griffin, Robert G; Wang, Evelyn N

    2015-01-01

    Modular and compact adsorption heat pumps (AHPs) promise an energy-efficient alternative to conventional vapor compression based heating, ventilation and air conditioning systems. A key element in the advancement of AHPs is the development of adsorbents with high uptake capacity, fast intracrystalline diffusivity and durable hydrothermal stability. Herein, the ion exchange of NaY zeolites with ingoing Mg(2+) ions is systematically studied to maximize the ion exchange degree (IED) for improved sorption performance. It is found that beyond an ion exchange threshold of 64.1%, deeper ion exchange does not benefit water uptake capacity or characteristic adsorption energy, but does enhance the vapor diffusivity. In addition to using water as an adsorbate, the uptake properties of Mg,Na-Y zeolites were investigated using 20 wt.% MeOH aqueous solution as a novel anti-freeze adsorbate, revealing that the MeOH additive has an insignificant influence on the overall sorption performance. We also demonstrated that the labscale synthetic scalability is robust, and that the tailored zeolites scarcely suffer from hydrothermal stability even after successive 108-fold adsorption/desorption cycles. The samples were analyzed using N2 sorption, (27)Al/(29)Si MAS NMR spectroscopy, ICP-AES, dynamic vapor sorption, SEM, Fick's 2(nd) law and D-R equation regressions. Among these, close examination of sorption isotherms for H2O and N2 adsorbates allows us to decouple and extract some insightful information underlying the complex water uptake phenomena. This work shows the promising performance of our modified zeolites that can be integrated into various AHP designs for buildings, electronics, and transportation applications.

  15. Zeolite Y Adsorbents with High Vapor Uptake Capacity and Robust Cycling Stability for Potential Applications in Advanced Adsorption Heat Pumps

    PubMed Central

    Li, Xiansen; Narayanan, Shankar; Michaelis, Vladimir K.; Ong, Ta-Chung; Keeler, Eric G.; Kim, Hyunho; McKay, Ian S.; Griffin, Robert G.; Wang, Evelyn N.

    2014-01-01

    Modular and compact adsorption heat pumps (AHPs) promise an energy-efficient alternative to conventional vapor compression based heating, ventilation and air conditioning systems. A key element in the advancement of AHPs is the development of adsorbents with high uptake capacity, fast intracrystalline diffusivity and durable hydrothermal stability. Herein, the ion exchange of NaY zeolites with ingoing Mg2+ ions is systematically studied to maximize the ion exchange degree (IED) for improved sorption performance. It is found that beyond an ion exchange threshold of 64.1%, deeper ion exchange does not benefit water uptake capacity or characteristic adsorption energy, but does enhance the vapor diffusivity. In addition to using water as an adsorbate, the uptake properties of Mg,Na-Y zeolites were investigated using 20 wt.% MeOH aqueous solution as a novel anti-freeze adsorbate, revealing that the MeOH additive has an insignificant influence on the overall sorption performance. We also demonstrated that the labscale synthetic scalability is robust, and that the tailored zeolites scarcely suffer from hydrothermal stability even after successive 108-fold adsorption/desorption cycles. The samples were analyzed using N2 sorption, 27Al/29Si MAS NMR spectroscopy, ICP-AES, dynamic vapor sorption, SEM, Fick’s 2nd law and D-R equation regressions. Among these, close examination of sorption isotherms for H2O and N2 adsorbates allows us to decouple and extract some insightful information underlying the complex water uptake phenomena. This work shows the promising performance of our modified zeolites that can be integrated into various AHP designs for buildings, electronics, and transportation applications. PMID:25395877

  16. Zeolite Y adsorbents with high vapor uptake capacity and robust cycling stability for potential applications in advanced adsorption heat pumps

    SciTech Connect

    Li, XS; Narayanan, S; Michaelis, VK; Ong, TC; Keeler, EG; Kim, H; Mckay, IS; Griffin, RG; Wang, EN

    2015-01-01

    Modular and compact adsorption heat pumps (AHPs) promise an energy-efficient alternative to conventional vapor compression based heating, ventilation and air conditioning systems. A key element in the advancement of AHPs is the development of adsorbents with high uptake capacity, fast intracrystalline diffusivity and durable hydrothermal stability. Herein, the ion exchange of NaY zeolites with ingoing Mg2+ ions is systematically studied to maximize the ion exchange degree (IED) for improved sorption performance. It is found that beyond an ion exchange threshold of 64.1%, deeper ion exchange does not benefit water uptake capacity or characteristic adsorption energy, but does enhance the vapor diffusivity. In addition to using water as an adsorbate, the uptake properties of Mg, Na-Y zeolites were investigated using 20 wt.% MeOH aqueous solution as a novel anti-freeze adsorbate, revealing that the MeOH additive has an insignificant influence on the overall sorption performance. We also demonstrated that the lab-scale synthetic scalability is robust, and that the tailored zeolites scarcely suffer from hydrothermal stability even after successive 108-fold adsorption/desorption cycles. The samples were analyzed using N-2 sorption, Al-27/Si-29 MAS NMR spectroscopy, ICP-AES, dynamic vapor sorption, SEM, Fick's 2nd law and D-R equation regressions. Among these, close examination of sorption isotherms for H2O and N-2 adsorbates allows us to decouple and extract some insightful information underlying the complex water uptake phenomena. This work shows the promising performance of our modified zeolites that can be integrated into various AHP designs for buildings, electronics, and transportation applications. (C) 2014 Elsevier Inc. All rights reserved.

  17. Determination of coalbed methane potential and gas adsorption capacity in Western Kentucky coals

    USGS Publications Warehouse

    Mardon, S.M.; Takacs, K.G.; Hower, J.C.; Eble, C.F.; Mastalerz, Maria

    2006-01-01

    The Illinois Basin has not been developed for Coalbed Methane (CBM) production. It is imperative to determine both gas content and other parameters for the Kentucky portion of the Illinois Basin if exploration is to progress and production is to occur in this area. This research is part of a larger project being conducted by the Kentucky Geological Survey to evaluate the CBM production of Pennsylvanian-age western Kentucky coals in Ohio, Webster, and Union counties using methane adsorption isotherms, direct gas desorption measurements, and chemical analyses of coal and gas. This research will investigate relationships between CBM potential and petrographic, surface area, pore size, and gas adsorption isotherm analyses of the coals. Maceral and reflectance analyses are being conducted at the Center for Applied Energy Research. At the Indiana Geological Survey, the surface area and pore size of the coals will be analyzed using a Micrometrics ASAP 2020, and the CO2 isotherm analyses will be conducted using a volumetric adsorption apparatus in a water temperature bath. The aforementioned analyses will be used to determine site specific correlations for the Kentucky part of the Illinois Basin. The data collected will be compared with previous work in the Illinois Basin and will be correlated with data and structural features in the basin. Gas composition and carbon and hydrogen isotopic data suggest mostly thermogenic origin of coalbed gas in coals from Webster and Union Counties, Kentucky, in contrast to the dominantly biogenic character of coalbed gas in Ohio County, Kentucky.

  18. Superfine powdered activated carbon incorporated into electrospun polystyrene fibers preserve adsorption capacity.

    PubMed

    Apul, Onur G; Hoogesteijn von Reitzenstein, Natalia; Schoepf, Jared; Ladner, David; Hristovski, Kiril D; Westerhoff, Paul

    2017-03-17

    A composite material consisted of superfine powdered activated carbon (SPAC) and fibrous polystyrene (PS) was fabricated for the first time by electrospinning. SPAC is produced by pulverizing powdered activated carbon. The diameter of SPAC (100-400nm) is more than one hundred times smaller than conventional powdered activated carbon, but it maintains the internal pore structure based on organic micropollutant adsorption isotherms and specific surface area measurements. Co-spinning SPAC into PS fibers increased specific surface area from 6m(2)/g to 43m(2)/g. Unlike metal oxide nanoparticles, which are non-accessible for sorption from solution, electrospinning with SPAC created porous fibers. Composite SPAC-PS electrospun fibers, containing only 10% SPAC, had 30% greater phenanthrene sorption compared against PS fibers alone. SPAC particles embedded within the polymer were either partially or fully incorporated, and the accessibility of terminal adsorption sites were conserved. Conserving the adsorptive functionality of SPAC particles in electrospun non-woven polymeric fiber scaffolding can enable their application in environmental applications such as drinking water treatment.

  19. Characterization of humic acid reactivity modifications due to adsorption onto α-Al2O3.

    PubMed

    Janot, Noémie; Reiller, Pascal E; Zheng, Xing; Croué, Jean-Philippe; Benedetti, Marc F

    2012-03-01

    Adsorption of purified Aldrich humic acid (PAHA) onto α-Al(2)O(3) is studied by batch experiments at different pH, ionic strength and coverage ratios R (mg of PAHA by m(2) of mineral surface). After equilibration, samples are centrifuged and the concentration of PAHA in the supernatants is measured. The amount of adsorbed PAHA per m(2) of mineral surface is decreasing with increasing pH. At constant pH value, the amount of adsorbed PAHA increases with initial PAHA concentration until a pH-dependent constant value is reached. UV/Visible specific parameters such as specific absorbance SUVA(254), ratio of absorbance values E(2)/E(3) and width of the electron-transfer absorbance band Δ(ET) are calculated for supernatant PAHA fractions of adsorption experiments at pH 6.8, to have an insight on the evolution of PAHA characteristics with varying coverage ratio. No modification is observed compared to original compound for R ≥ 20 mg(PAHA)/g(α)(-)(A)1₂(O)₃. Below this ratio, aromaticity decreases with initial PAHA concentration. Size-exclusion chromatography - organic carbon detection measurements on these supernatants also show a preferential adsorption of more aromatic and higher-sized fractions. Spectrophotometric titrations were done to estimate changes of reactivity of supernatants from adsorption experiments made at pH ≈6.8 and different PAHA concentrations. Evolutions of UV/Visible spectra with varying pH were treated to obtain titration curves that are interpreted within the NICA-Donnan framework. Protonation parameters of non-sorbed PAHA fractions are compared to those obtained for the PAHA before contact with the oxide. The amount of low proton-affinity type of sites and the value of their median affinity constant decrease after adsorption. From PAHA concentration in the supernatant and mass balance calculations, "titration curves" are experimentally proposed for the adsorbed fractions for the first time. These changes in reactivity to our opinion could

  20. Enhancing gas adsorption and separation capacity through ligand functionalization of microporous metal-organic framework structures.

    PubMed

    Zhao, Yonggang; Wu, Haohan; Emge, Thomas J; Gong, Qihan; Nijem, Nour; Chabal, Yves J; Kong, Lingzhu; Langreth, David C; Liu, Hui; Zeng, Heping; Li, Jing

    2011-04-26

    Hydroxyl- and amino- functionalized [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O leads to two new structures, [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O (BDC=terephthalic acid, TED=triethylenediamine, BDC-OH=2-hydroxylterephthalic acid, BDC-NH(2)=2-aminoterephthalic acid). Single-crystal X-ray diffraction and powder X-ray diffraction studies confirmed that the structures of both functionalized compounds are very similar to that of their parent structure. Compound [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O can be considered a 3D porous structure with three interlacing 1D channels, whereas both [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O contain only 1D open channels as a result of functionalization of the BDC ligand by the OH and NH(2) groups. A notable decrease in surface area and pore size is thus observed in both compounds. Consequently, [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O takes up the highest amount of H(2) at low temperatures. Interestingly, however, both [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O show significant enhancement in CO(2) uptake at room temperature, suggesting that the strong interactions between CO(2) and the functionalized ligands, indicating that surface chemistry, rather than porosity, plays a more important role in CO(2) adsorption. A comparison of single-component CO(2), CH(4), CO, N(2), and O(2) adsorption isotherms demonstrates that the adsorption selectivity of CO(2) over other small gases is considerably enhanced through functionalization of the frameworks. Infrared absorption spectroscopic measurements and theoretical calculations are also carried out to assess the effect of functional groups on CO(2) and H(2) adsorption potentials.

  1. Analyte loss due to membrane filter adsorption as determined by high-performance liquid chromatography.

    PubMed

    Carlson, M; Thompson, R D

    2000-02-01

    The phenomenon of membrane filter adsorption in high-performance liquid chromatography (HPLC) is investigated utilizing 16 brands of filters representing 3 polymeric materials: cellulose acetate (CA), nylon, and polyvinylidene difluoride in a variety of diameters (3, 4, 7, 13, and 25 mm). Sixteen compounds commonly encountered in drug preparations are selected as sample analytes and classified as acidic, basic, and neutral in chemical behavior. Six mobile phase/sample solvent mixtures are included: 3 with methanol-water and 3 with acetonitrile-water as major constituents. When using methanol as the mobile phase organic component, CA, nylon, and polyvinylidene difluoride (PVDF) filters exhibit negligible to moderate adsorption levels with regard to the neutral and basic drug compounds. The acidic drug test compounds are adsorbed by 50% of all 3 filter materials tested in methanol-water. In acetonitrile, neutral compounds are affected by 31.4%, basic compounds are affected by 47.0%, and acidic compounds are affected by 53.6% of the nylon and PVDF filters. CA is incompatible with acetonitrile and is excluded from the study with this solvent.

  2. Effect of carboxyethylation degree on the adsorption capacity of Cu(II) by N-(2-carboxyethyl)chitosan from squid pens.

    PubMed

    Huang, Jun; Xie, Haihua; Ye, Hui; Xie, Tian; Lin, Yuecheng; Gong, Jinyan; Jiang, Chengjun; Wu, Yuanfeng; Liu, Shiwang; Cui, Yanli; Mao, Jianwei; Mei, Lehe

    2016-03-15

    Chitosan was prepared by N-deacetylation of squid pens β-chitin, and N-carboxyethylated chitosan (N-CECS) with different degrees of substitution (DS) were synthesized. DS values of N-CECS derivatives calculated by (1)H nuclear magnetic resonance (NMR) spectroscopy were 0.60, 1.02 and 1.46, respectively. The adsorption capacity of Cu(II) by N-CECS correlated well with the DS and pH ranging from 3.2 to 5.8. The maximum Cu(II) adsorption capacity (qm) of all three N-CECS at pH 5.4 was 207.5mg g(-1), which was 1.4-fold higher than that of chitosan. The adsorption equilibrium process was better described by the Langmuir than Freundlich isotherm model. Adsorption of Cu(II) ion onto N-CECS followed a pseudo-second order mechanism with chemisorption as the rate-limiting step. In a ternary adsorption system, the adsorption capacity of Cu(II) by N-CECS also presented high values, and qm for Cu(II), Cd(II), and Pb(II) were 150.2, 28.8, and 187.9mg g(-1), respectively.

  3. One-step synthesis of a novel N-doped microporous biochar derived from crop straws with high dye adsorption capacity.

    PubMed

    Lian, Fei; Cui, Guannan; Liu, Zhongqi; Duo, Lian; Zhang, Guilong; Xing, Baoshan

    2016-07-01

    N-doping is one of the most promising strategies to improve the adsorption capacity and selectivity of carbon adsorbents. Herein, synthesis, characterization and dye adsorption of a novel N-doped microporous biochar derived from direct annealing of crop straws under NH3 is presented. The resultant products exhibit high microporosity (71.5%), atomic percentage of nitrogen (8.81%), and adsorption capacity to dyes, which is about 15-20 times higher than that of original biochar. Specifically, for the sample NBC800-3 pyrolyzed at 800°C in NH3 for 3 h, its adsorption for acid orange 7 (AO7, anionic) and methyl blue (MB, cationic) is up to 292 mg g(-1) and 436 mg g(-1), respectively, which is among the highest ever reported for carbonaceous adsorbents. The influences of N-doping and porous structure on dye adsorption of the synthesized carbons are also discussed, where electrostatic attraction, π-π electron donor-accepter interaction, and Lewis acid-base interaction mainly contribute to AO7 adsorption, and surface area (especially pore-filling) dominates MB adsorption. The N-doped biochar can be effectively regenerated and reused through direct combustion and desorption approaches.

  4. Facile synthesis of hydroxy-modified MOF-5 for improving the adsorption capacity of hydrogen by lithium doping.

    PubMed

    Kubo, Masaru; Hagi, Hayato; Shimojima, Atsushi; Okubo, Tatsuya

    2013-11-01

    A facile synthesis of partially hydroxy-modified MOF-5 and its improved H2-adsorption capacity by lithium doping are reported. The reaction of Zn(NO3)2·6H2O with a mixture of terephthalic acid (H2BDC) and 2-hydroxyterephthalic acid (H2BDC-OH) in DMF gave hydroxy-modified MOF-5 (MOF-5-OH-x), in which the molar fraction (x) of BDC-OH(2-) was up to 0.54 of the whole ligand. The MOF-5-OH-x frameworks had high BET surface areas (about 3300 m(2) g(-1)), which were comparable to that of MOF-5. We suggest that the MOF-5-OH-x frameworks are formed by the secondary growth of BDC(2-)-rich MOF-5 seed crystals, which are nucleated during the early stage of the reaction. Subsequent Li doping into MOF-5-OH-x results in increased H2 uptake at 77 K and 0.1 MPa from 1.23 to 1.39 wt.% and an increased isosteric heat of H2 adsorption from 5.1-4.2 kJ mol(-1) to 5.5-4.4 kJ mol(-1).

  5. MOF-derived ZnO and ZnO@C composites with high photocatalytic activity and adsorption capacity.

    PubMed

    Yang, Seung Jae; Im, Ji Hyuk; Kim, Taehoon; Lee, Kunsil; Park, Chong Rae

    2011-02-15

    Nanostructured ZnO materials have unique and highly attractive properties and have inspired interest in their research and development. This paper presents a facile method for the preparation of novel ZnO-based nanostructured architectures using a metal organic framework (MOF) as a precursor. In this approach, ZnO nanoparticles and ZnO@C hybrid composites were produced under several heating and atmospheric (air or nitrogen) conditions. The resultant ZnO nanoparticles formed hierarchical aggregates with a three-dimensional cubic morphology, whereas ZnO@C hybrid composites consisted of faceted ZnO crystals embedded within a highly porous carbonaceous species, as determined by several characterization methods. The newly synthesized nanomaterials showed relatively high photocatalytic decomposition activity and significantly enhanced adsorption capacities for organic pollutants.

  6. Dendritic silica nanomaterials (KCC-1) with fibrous pore structure possess high DNA adsorption capacity and effectively deliver genes in vitro.

    PubMed

    Huang, Xiaoxi; Tao, Zhimin; Praskavich, John C; Goswami, Anandarup; Al-Sharab, Jafar F; Minko, Tamara; Polshettiwar, Vivek; Asefa, Tewodros

    2014-09-16

    The pore size and pore structure of nanoporous materials can affect the materials' physical properties, as well as potential applications in different areas, including catalysis, drug delivery, and biomolecular therapeutics. KCC-1, one of the newest members of silica nanomaterials, possesses fibrous, large pore, dendritic pore networks with wide pore entrances, large pore size distribution, spacious pore volume and large surface area--structural features that are conducive for adsorption and release of large guest molecules and biomacromolecules (e.g., proteins and DNAs). Here, we report the results of our comparative studies of adsorption of salmon DNA in a series of KCC-1-based nanomaterials that are functionalized with different organoamine groups on different parts of their surfaces (channel walls, external surfaces or both). For comparison the results of our studies of adsorption of salmon DNA in similarly functionalized, MCM-41 mesoporous silica nanomaterials with cylindrical pores, some of the most studied silica nanomaterials for drug/gene delivery, are also included. Our results indicate that, despite their relatively lower specific surface area, the KCC-1-based nanomaterials show high adsorption capacity for DNA than the corresponding MCM-41-based nanomaterials, most likely because of KCC-1's large pores, wide pore mouths, fibrous pore network, and thereby more accessible and amenable structure for DNA molecules to diffuse through. Conversely, the MCM-41-based nanomaterials adsorb much less DNA, presumably because their outer surfaces/cylindrical channel pore entrances can get blocked by the DNA molecules, making the inner parts of the materials inaccessible. Moreover, experiments involving fluorescent dye-tagged DNAs suggest that the amine-grafted KCC-1 materials are better suited for delivering the DNAs adsorbed on their surfaces into cellular environments than their MCM-41 counterparts. Finally, cellular toxicity tests show that the KCC-1-based

  7. Long-Life and High-Areal-Capacity Li-S Batteries Enabled by a Light-Weight Polar Host with Intrinsic Polysulfide Adsorption.

    PubMed

    Pang, Quan; Nazar, Linda F

    2016-04-26

    Lithium-sulfur batteries are attractive electrochemical energy storage systems due to their high theoretical energy density and very high natural abundance of sulfur. However, practically, Li-S batteries suffer from short cycling life and low sulfur utilization, particularly in the case of high-sulfur-loaded cathodes. Here, we report on a light-weight nanoporous graphitic carbon nitride (high-surface-area g-C3N4) that enables a sulfur electrode with an ultralow long-term capacity fade rate of 0.04% per cycle over 1500 cycles at a practical C/2 rate. More importantly, it exhibits good high-sulfur-loading areal capacity (up to 3.5 mAh cm(-2)) with stable cell performance. We demonstrate the strong chemical interaction of g-C3N4 with polysulfides using a combination of spectroscopic experimental studies and first-principles calculations. The 53.5% concentration of accessible pyridinic nitrogen polysulfide adsorption sites is shown to be key for the greatly improved cycling performance compared to that of N-doped carbons.

  8. CO2 Adsorption in Low-Rank Coals: Progress Toward Assessing the National Capacity to Store CO2 in the Subsurface

    NASA Astrophysics Data System (ADS)

    Stanton, R. W.; Burruss, R. C.; Flores, R. M.; Warwick, P. D.

    2001-05-01

    Subsurface environments for geologic storage of CO2 from combustion of fossil fuel include saline formations, depleted oil and gas reservoirs, and unmineable coalbeds. Of these environments, storage in petroleum reservoirs and coal beds offers a potential economic benefit of enhanced recovery of energy resources. Meaningful assessment of the volume and geographic distribution of storage sites requires quantitative estimates of geologic factors that control storage capacity. The factors that control the storage capacity of unmineable coalbeds are poorly understood. In preparation for a USGS assessment of CO2 storage capacity we have begun new measurements of CO2 and CH4 adsorption isotherms of low-rank coal samples from 4 basins. Initial results for 13 samples of low-rank coal beds from the Powder River Basin (9 subbituminous coals), Greater Green River Basin (1 subbituminous coal), Williston Basin (2 lignites) and the Gulf Coast (1 lignite) indicate that their adsorption capacity is up to 10 times higher than it is for CH4. These values contrast with published measurements of the CO2 adsorption capacity of bituminous coals from the Fruitland Formation, San Juan basin, and Gates Formation, British Columbia, that indicate about twice as much carbon dioxide as methane can be adsorbed on coals. Because CH4 adsorption isotherms are commonly measured on coals, CO2 adsorption capacity can be estimated if thecorrect relationship between the gases is known. However, use a factor to predict CO2 adsorption that is twice that of CH4 adsorption, which is common in the published literature, grossly underestimates the storage capacity of widely distributed, thick low-rank coal beds. Complete petrographic and chemical characterization of these low-rank coal samples is in progress. Significant variations in adsorption measurements among samples are depicted depending on the reporting basis used. Properties were measured on an "as received" (moist) basis but can be converted to a

  9. The role of counter ions in nano-hematite synthesis: Implications for surface area and selenium adsorption capacity.

    PubMed

    Lounsbury, Amanda W; Yamani, Jamila S; Johnston, Chad P; Larese-Casanova, Philip; Zimmerman, Julie B

    2016-06-05

    Nano metal oxides are of interest for aqueous selenium (Se) remediation, and as such, nano-hematite (nα-Fe2O3) was examined for use as a Se adsorbent. The effect of surface area on adsorption was also studied. nα-Fe2O3 particles were synthesized from Fe(NO3)3 and FeCl3 via forced hydrolysis. The resulting particles have similar sizes, morphologies, aggregate size, pore size, and PZC. The nα-Fe2O3 from FeCl3 (nα-Fe2O3-C) differs from the nα-Fe2O3 from Fe(NO3)3 (nα-Fe2O3-N) with a ∼25±2m(2)/g greater surface area. Selenite Se(IV) adsorption capacity on nα-Fe2O3 has a qmax ∼17mg/g for the freeze-dried and re-suspended nα-Fe2O3. The Δqmax for nα-Fe2O3 from Fe(NO3)3 and FeCl3 that remained in suspension was 4.6mg/g. For selenate Se(VI), the freeze-dried and re-suspended particles realize a Δqmax= 1.5mg/g for nα-Fe2O3 from Fe(NO3)3 and FeCl3. The nα-Fe2O3 from Fe(NO3)3 and FeCl3 that remained in suspension demonstrated Se(VI) Δqmax=5.4mg/g. In situ ATR-FTIR isotherm measurements completed for Se(VI) at a pH 6 suggest that Se(VI) forms primarily outer-sphere complexes with nα-Fe2O3 synthesized from both salts.

  10. Superb adsorption capacity of hierarchical calcined Ni/Mg/Al layered double hydroxides for Congo red and Cr(VI) ions.

    PubMed

    Lei, Chunsheng; Zhu, Xiaofeng; Zhu, Bicheng; Jiang, Chuanjia; Le, Yao; Yu, Jiaguo

    2017-01-05

    The preparation of hierarchical porous materials as catalysts and sorbents has attracted much attention in the field of environmental pollution control. Herein, Ni/Mg/Al layered double hydroxides (NMA-LDHs) hierarchical flower-like hollow microspheres were synthesized by a hydrothermal method. After the NMA-LDHs was calcined at 600°C, NMA-LDHs transformed into Ni/Mg/Al layered double oxides (NMA-LDOs), which maintained the hierarchical flower-like hollow structure. The crystal phase, morphology, and microstructure of the as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy elemental mapping, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption methods. Both the calcined and non-calcined NMA-LDHs were examined for their performance to remove Congo red (CR) and hexavalent chromium (Cr(VI)) ions in aqueous solution. The maximum monolayer adsorption capacities of CR and Cr(VI) ions over the NMA-LDOs sample were 1250 and 103.4mg/g at 30°C, respectively. Thermodynamic studies indicated that the adsorption process was endothermic in nature. In addition, the addition of coexisting anions negatively influenced the adsorption capacity of Cr(VI) ions, in the following order: CO3(2-)>SO4(2-)>H2PO4(-)>Cl(-). This work will provide new insight into the design and fabrication of advanced adsorption materials for water pollutant removal.

  11. Predicting molecular scale skin-effect in electrochemical impedance due to anomalous subdiffusion mediated adsorption phenomenon

    NASA Astrophysics Data System (ADS)

    Kushagra, Arindam

    2016-02-01

    Anomalous subdiffusion governs the processes which are not energetically driven, on a molecular scale. This paper proposes a model to predict the response of electrochemical impedance due to such diffusion process. Previous works considered the use of fractional calculus to predict the impedance behaviour in response to the anomalous diffusion. Here, we have developed an expression which predicts the skin-effect, marked by an increase in the impedance with increasing frequency, in this regime. Negative inductances have also been predicted as a consequence of the inertial response of adsorbed species upon application of frequency-mediated perturbations. It might help the researchers in the fields of impedimetric sensors to choose the working frequency and those working in the field of batteries to choose the parameters, likewise. This work would shed some light into the molecular mechanisms governing the impedance when exposed to frequency-based perturbations like electromagnetic waves (microwaves to ionizing radiations) and in charge storage devices like batteries etc.

  12. Fourier transform infra-red (FTIR) spectroscopy investigation, dose effect, kinetics and adsorption capacity of phosphate from aqueous solution onto laterite and sandstone.

    PubMed

    Coulibaly, Lassina Sandotin; Akpo, Sylvain Kouakou; Yvon, Jacques; Coulibaly, Lacina

    2016-12-01

    Environmental pollution by phosphate in developing countries is growing with extensive and diffuse pollution. Solving these problem with intensive technologies is very expensive. Using natural sorbent such as laterite and sandstone could be a solution. The main objective of the study is to evaluate the P-removal efficiency of these materials under various solution properties. Laterite and sandstone used mainly contain very high levels of finely grained iron and aluminum oxy-hydroxides and diverse dioctahedral clays. Phosphate adsorption tests were carried out using crushed laterite and sandstone. Optimal doses and pH effects on phosphate adsorption were studied with a potassium hydrogeno-phosphate solution of 5 mg/L at 30 °C. The main results were that the optimal dosage is 15 and 20 mg/L respectively for laterite and sandstone. The phosphate adsorptions efficiency of laterite and sandstone are pH-dependent, they increase when the pH grows up to the Point of Zero Charge (PZC) and slowly decrease beyond. The adsorption capacities of the materials also increase proportionally with the initial phosphate concentration. The pseudo-second-order successfully described the kinetics of the phosphate adsorption on the two adsorbents. With this model, the adsorption capacity values are obtained, which give an idea of the maximum phosphate uptake that the laterite and sandstone could achieve. The changes on the FTIR spectra of raw materials and phosphate adsorbed material confirm the mechanism of chemisorptions. Considering the above, laterite and sandstone could be used as efficient and cheap adsorbent for the removal of phosphate in aqueous solution.

  13. A one-step thermal decomposition method to prepare anatase TiO2 nanosheets with improved adsorption capacities and enhanced photocatalytic activities

    NASA Astrophysics Data System (ADS)

    Li, Wenting; Shang, Chunli; Li, Xue

    2015-12-01

    Anatase TiO2 nanosheets (NSs) with high surface area have been prepared via a one-step thermal decomposition of titanium tetraisopropoxide (TTIP) in oleylamine (OM), and their adsorption capacities and photocatalytic activities are investigated by using methylene blue (MB) and methyl orange (MO) as model pollutants. During the synthesis procedure, only one type of surfactant, oleylamine (OM), is used as capping agents and no other solvents are added. Structure and properties of the TiO2 NSs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption analysis, UV-vis spectrum, X-ray photoelectron spectroscopy (XPS) and Photoluminescence (PL) methods. The results indicate that the TiO2 NSs possess high surface area up to 378 m2 g-1. The concentration of capping agents is found to be a key factor controlling the morphology and crystalline structure of the product. Adsorption and photodegradation experiments reveal that the prepared TiO2 NSs possess high adsorption capacities of model pollutants MB and high photocatalytic activity, showing that TiO2 NSs can be used as efficient pollutant adsorbents and photocatalytic degradation catalysts of MB in wastewater treatment.

  14. An Initial Study of Airport Arrival Heinz Capacity Benefits Due to Improved Scheduling Accuracy

    NASA Technical Reports Server (NTRS)

    Meyn, Larry; Erzberger, Heinz

    2005-01-01

    The long-term growth rate in air-traffic demand leads to future air-traffic densities that are unmanageable by today's air-traffic control system. I n order to accommodate such growth, new technology and operational methods will be needed in the next generation air-traffic control system. One proposal for such a system is the Automated Airspace Concept (AAC). One of the precepts of AAC is to direct aircraft using trajectories that are sent via an air-ground data link. This greatly improves the accuracy in directing aircraft to specific waypoints at specific times. Studies of the Center-TRACON Automation System (CTAS) have shown that increased scheduling accuracy enables increased arrival capacity at CTAS equipped airports.

  15. Adsorption of selected volatile organic vapors on multiwall carbon nanotubes.

    PubMed

    Shih, Yang-hsin; Li, Mei-syue

    2008-06-15

    Carbon nanotubes are expected to play an important role in sensing, pollution treatment and separation techniques. This study examines the adsorption behaviors of volatile organic compounds (VOCs), n-hexane, benzene, trichloroethylene and acetone on two multiwall carbon nanotubes (MWCNTs), CNT1 and CNT2. Among these VOCs, acetone exhibits the highest adsorption capacity. The highest adsorption enthalpies and desorption energies of acetone were also observed. The strong chemical interactions between acetone and both MWCNTs may be the result from chemisorption on the topological defects. The adsorption heats of trichloroethylene, benzene, and n-hexane are indicative of physisorption on the surfaces of both MWCNTs. CNT2 presents a higher adsorption capacity than CNT1 due to the existence of an exterior amorphous carbon layer on CNT2. The amorphous carbon enhances the adsorption capacity of organic chemicals on carbon nanotubes. The morphological and structure order of carbon nanotubes are the primary affects on the adsorption process of organic chemicals.

  16. Electrochemical Surface Potential due to Classical Point Charge Models Drives Anion Adsorption to the Air-Water Interface

    SciTech Connect

    Baer, Marcel D.; Stern, Abraham C.; Levin, Yan; Tobias, Douglas J.; Mundy, Christopher J.

    2012-06-07

    Herein, we present research that suggests that the underlying physics that drive simple empirical models of anions (e.g. point charge, no polarization) to the air-water interface, with water described by SPC/E, or related partial charge models is different than when both ions and water are modeled with quantum mechanical based interactions. Specifically, we will show that the driving force of ions to the air-water interface for point charge models results from both cavitation and the negative electrochemical surface potential. We will demonstrate that we can fully characterize the role of the free energy due to the electrochemical surface potential computed from simple empirical models and its role in ionic adsorption within the context of dielectric continuum theory (DCT). Our research suggests that a significant part of the electrochemical surface potential in empirical models appears to be an artifact of the failure of point charge models in the vicinity of a broken symmetry. This work was supported by the U.S. Department of Energy‘s (DOE) Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences. Pacific Northwest National Laboratory (PNNL) is operated for the Department of Energy by Battelle.

  17. Reduction of load-bearing capacity of all-ceramic crowns due to cement aging.

    PubMed

    Lu, Chenglin; Wang, Raorao; Mao, Shuangshuang; Arola, Dwayne; Zhang, Dongsheng

    2013-01-01

    The purpose of this study was to investigate how water aging of the resin cement influences the stress distribution in all-ceramic crowns and if there is an increase in the propensity for crown failure. The failure of all-ceramic crowns attributed to cement degradation was explored using a combination of experimental and numerical methods. Sectioned all-ceramic crown specimens were fabricated of IPS e.max Ceram/e.max Press (CP) and Vita VM9/Cercon zirconia (VZ), and then stored in either air or distilled water for 30 days. Monotonic contact loads were applied to fracture near the buccal cusp ridge of each sample. Deformation within the crown layers during loading was analyzed by means of Digital Image Correlation (DIC). A 3D finite element model of the restoration including veneer, core, cement and tooth substrate was developed to evaluate the stress distribution in the crowns before and after cement degradation. There was a significant decrease (p<0.001) in the critical fracture load and a change in the fracture mode after cement water absorption in the CP crowns. In contrast, there was no significant influence of cement aging on fracture modes and fracture loads (p>0.05) in the VZ crowns. Finite element analysis showed that regardless of the crown types, the stress distribution is identical by degradation in Young's modulus of the cement. However, core/substrate debonding results in a change of the stress distribution and a significant increase in the magnitude. Water aging causes reduction of stiffness and bonding strength of cement agents. Degradation in bonding strength and stiffness could potentially lead to stress redistribution in the restored crown and reduce the load-bearing capacity of all-ceramic restorations after years of service.

  18. Competitive adsorption of heavy metals onto sesame straw biochar in aqueous solutions.

    PubMed

    Park, Jong-Hwan; Ok, Yong Sik; Kim, Seong-Heon; Cho, Ju-Sik; Heo, Jong-Soo; Delaune, Ronald D; Seo, Dong-Cheol

    2016-01-01

    Objective of this research was to evaluate adsorption of heavy metals in mono and multimetal forms onto sesame straw biochar (SSB). Competitive sorption of metals by SSB has never been reported previously. The maximum adsorption capacities (mgg(-1)) of metals by SSB were in the order of Pb (102)≫Cd (86)≫Cr (65)>Cu (55)≫Zn (34) in the monometal adsorption isotherm and Pb (88)≫Cu (40)≫Cr (21)>Zn (7)⩾Cd (5) in the multimetal adsorption isotherm. Based on data obtained from the distribution coefficients, Freundlich and Langmuir adsorption models, and three-dimensional simulation, multimetal adsorption behaviors differed from monometal adsorption due to competition. Especially, during multimetal adsorption, Cd was easily exchanged and substituted by other metals. Further competitive adsorption studies are necessary in order to accurately estimate the heavy metal adsorption capacity of biochar in natural environments.

  19. Surfactant-free synthesis of octahedral ZnO/ZnFe2O4 heterostructure with ultrahigh and selective adsorption capacity of malachite green

    NASA Astrophysics Data System (ADS)

    Liu, Jue; Zeng, Min; Yu, Ronghai

    2016-05-01

    A new octahedral ZnO/ZnFe2O4 heterostructure has been fabricated through a facile surfactant-free solvothermal method followed by thermal treatment. It exhibits a record-high adsorption capacity (up to 4983.0 mg·g‑1) of malachite green (MG), which is a potentially harmful dye in prevalence and should be removed from wastewater and other aqueous solutions before discharging into the environment. The octahedral ZnO/ZnFe2O4 heterostructure also demonstrates strong selective adsorption towards MG from two kinds of mixed solutions: MG/methyl orange (MO) and MG/rhodamine B (RhB) mixtures, indicating its promise in water treatment.

  20. Ultrasond-assisted synthesis of Fe3O4/SiO2 core/shell with enhanced adsorption capacity for diazinon removal

    NASA Astrophysics Data System (ADS)

    Farmany, Abbas; Mortazavi, Seyede Shima; Mahdavi, Hossein

    2016-10-01

    Fe3O4/SiO2 core/shell nanocrystals were synthesized by ultrasond-assisted procedure. The core/shell nanocrystals were characterized using XRD, FT-IR spectroscopy, SEM and BET. The BET analysis confirmed that iron oxide nanocrystal with the surface area of 208.0 m2/g can be used as an excellent adsorbent for organic and inorganic pollutants. The core/shell nanocrystal was used as an adsorbent for removal of insecticide O,O-diethyl-O[2-isopropyl-6-methylpyridimidinyl] phosphorothioate (diazinon). In continue the influence of different parameters such as pH, adsorbent dosage and shaking time on the adsorption capacity were studied. The experimental data were fitted well with the pseudo-second-order kinetic model (R2=0.9706). The adsorption isotherm was described well by Langmuir isotherm.

  1. Surfactant-free synthesis of octahedral ZnO/ZnFe2O4 heterostructure with ultrahigh and selective adsorption capacity of malachite green

    PubMed Central

    Liu, Jue; Zeng, Min; Yu, Ronghai

    2016-01-01

    A new octahedral ZnO/ZnFe2O4 heterostructure has been fabricated through a facile surfactant-free solvothermal method followed by thermal treatment. It exhibits a record-high adsorption capacity (up to 4983.0 mg·g−1) of malachite green (MG), which is a potentially harmful dye in prevalence and should be removed from wastewater and other aqueous solutions before discharging into the environment. The octahedral ZnO/ZnFe2O4 heterostructure also demonstrates strong selective adsorption towards MG from two kinds of mixed solutions: MG/methyl orange (MO) and MG/rhodamine B (RhB) mixtures, indicating its promise in water treatment. PMID:27142194

  2. PREDICTING THE ADSORPTION CAPACITY OF ACTIVATED CARBON FOR EMERGING ORGANIC CONTAMINANTS FROM FUNDAMENTAL ADSORBENT AND ADSORBATE PROPERTIES - PRESENTATION

    EPA Science Inventory

    A quantitative structure-property relationship (QSPR) was developed and combined with the Polanyi-Dubinin-Manes model to predict adsorption isotherms of emerging contaminants on activated carbons with a wide range of physico-chemical properties. Affinity coefficients (βl

  3. Characterization of biochars derived from agriculture wastes and their adsorptive removal of atrazine from aqueous solution: A comparative study.

    PubMed

    Liu, Na; Charrua, Alberto Bento; Weng, Chih-Huang; Yuan, Xiaoling; Ding, Feng

    2015-12-01

    The physicochemical properties of biochars produced from soybeans (SBB), corn stalks (CSB), rice stalks (RSB), poultry manure (PMB), cattle manure (CMB), and pig manure (PgMB) and their adsorption characteristics of atrazine were investigated. The adsorption capacity increased with the increase of temperature and initial atrazine concentration. More atrazine was removed from basic solutions than acidic solutions, due to the effects of adsorption and hydrolysis. The Freundlich isotherm adsorption parameters indicated that the adsorption capacity decreased in the order SBB>RSB>CMB>CSB>PMB>PgMB, which is associated to the pore volume of biochars. The total pore volume and biochar pH were concluded to play important roles in determining the adsorption capacity, and they may have contributed to physical adsorption mechanisms dominating the overall adsorption process (the low activation energy for all of the biochars). Modified Freundlich and intraparticle diffusion models were used to describe the kinetics of the adsorption process.

  4. Preparation of hybrid organic-inorganic mesoporous silicas applied to mercury removal from aqueous media: Influence of the synthesis route on adsorption capacity and efficiency.

    PubMed

    Pérez-Quintanilla, Damián; Sánchez, Alfredo; Sierra, Isabel

    2016-06-15

    New hybrid organic-inorganic mesoporous silicas were prepared by employing three different synthesis routes and mercury adsorption studies were done in aqueous media using the batch technique. The organic ligands employed for the functionalization were derivatives of 2-mercaptopyrimidine or 2-mercaptothiazoline, and the synthesis pathways used were post-synthesis, post-synthesis with surface ion-imprinting and co-condensation with ion-imprinting. The incorporation of functional groups and the presence of ordered mesopores in the organosilicas was confirmed by XRD, TEM and SEM, nitrogen adsorption-desorption isotherms, (13)C MAS-NMR, (29)Si MAS-NMR, elemental and thermogravimetric analysis. The highest adsorption capacity and selectivity observed was for the material functionalized with 2-mercaptothiazoline ligand by means the co-condensation with ion-imprinting route (1.03 mmol g(-1) at pH 6). The prepared material could be potential sorbent for the extraction of this heavy metal from environmental and drinking waters.

  5. Changing the adsorption capacity of coal-based honeycomb monoliths for pollutant removal from liquid streams by controlling their porosity

    NASA Astrophysics Data System (ADS)

    Gatica, José M.; Harti, Sanae; Vidal, Hilario

    2010-09-01

    Coal-based honeycomb monoliths extruded using methods developed for ceramic materials have been used to retain methylene blue and p-nitrophenol from aqueous solutions. The influence of the filters' thermal treatment on their textural properties and performance as adsorbents was examined. Characterization by N 2 physisorption, mercury porosimetry and scanning electron microscopy along with adsorption tests under dynamic conditions suggest that, depending on the pollutant and its initial concentration, it can be more convenient to previously submit the monoliths to a simple carbonization or to an additional activation, with or without preoxidation, as a consequence of their different resulting pore structures. Infrared spectroscopy indicates that their different adsorption behaviour seems not to be related to differences in their surface chemical groups. In addition, axial crushing tests show that the monoliths have an acceptable mechanical resistance for the application investigated.

  6. Effect of immobilized amine density on cadmium(II) adsorption capacities for ethanediamine-modified magnetic poly-(glycidyl methacrylate) microspheres

    NASA Astrophysics Data System (ADS)

    Dong, Tingting; Yang, Liangrong; Pan, Feng; Xing, Huifang; Wang, Li; Yu, Jiemiao; Qu, Hongnan; Rong, Meng; Liu, Huizhou

    2017-04-01

    A series of ethanediamine (EDA) - modified magnetic poly-(glycidyl methacrylate) (m-PGMA-EDA)microspheres with different amine density were synthesized and their cadmium saturation adsorption capacities were examined. The results showed that the cadmium saturation adsorption capacity increased with the immobilized amine density. However, they did not show strong positive linear correlation in the whole range of amine density examined. The molar ratio of amine groups to the adsorbed cadmium decreased with the increase of amine density and eventually reached a minimum value about 4. It suggested that low immobilized amine density led to low coordination efficiency of the amine. It is hypothesized that the immobilized amine groups needed to be physically close enough to form stable amine-metal complex. When the amine density reached to a critical value 1.25 m mol m-2, stable amine-cadmium complex (4:1 N/Cd) was proposed to form. To illustrate the coordination mechanism (structure and number) of amine and Cd, FT-IR spectra of m-PGMA-EDA and m-PGMA-EDA-Cd , and X-ray photoelectron spectroscopy (XPS) of PGMA-EDA and PGMA-EDA-Cd were examined and analyzed.

  7. Granular activated carbon adsorption of organic micro-pollutants in drinking water and treated wastewater--Aligning breakthrough curves and capacities.

    PubMed

    Zietzschmann, Frederik; Stützer, Christian; Jekel, Martin

    2016-04-01

    Small-scale granular activated carbon (GAC) tests for the adsorption of organic micro-pollutants (OMP) were conducted with drinking water and wastewater treatment plant (WWTP) effluent. In both waters, three influent OMP concentration levels were tested. As long as the influent OMP concentrations are below certain thresholds, the relative breakthrough behavior is not impacted in the respective water. Accordingly, the GAC capacity for OMP is directly proportional to the influent OMP concentration in the corresponding water. The differences between the OMP breakthrough curves in drinking water and WWTP effluent can be attributed to the concentrations of the low molecular weight acid and neutral (LMW) organics of the waters. Presenting the relative OMP concentrations (c/c0) over the specific throughput of the LMW organics (mg LMW organics/g GAC), the OMP breakthrough curves in drinking water and WWTP effluent superimpose each other. This superimposition can be further increased if the UV absorbance at 254 nm (UV254) of the LMW organics is considered. In contrast, using the specific throughput of the dissolved organic carbon (DOC) did not suffice to obtain superimposed breakthrough curves. Thus, the LMW organics are the major water constituent impacting OMP adsorption onto GAC. The results demonstrate that knowing the influent OMP and LMW organics concentrations (and UV254) of different waters, the OMP breakthroughs and GAC capacities corresponding to any water can be applied to all other waters.

  8. Effect of Heat Treatment on the Nitrogen Content and Its Role on the Carbon Dioxide Adsorption Capacity of Highly Ordered Mesoporous Carbon Nitride.

    PubMed

    Lakhi, Kripal S; Park, Dae-Hwan; Joseph, Stalin; Talapaneni, Siddulu N; Ravon, Ugo; Al-Bahily, Khalid; Vinu, Ajayan

    2017-03-02

    Mesoporous carbon nitrides (MCNs) with rod-shaped morphology and tunable nitrogen contents have been synthesized through a calcination-free method by using ethanol-washed mesoporous SBA-15 as templates at different carbonization temperatures. Carbon tetrachloride and ethylenediamine were used as the sources of carbon and nitrogen, respectively. The resulting MCN materials were characterized with low- and high-angle powder XRD, nitrogen adsorption, high-resolution (HR) SEM, HR-TEM, elemental analysis, X-ray photoelectron spectroscopy, and X-ray absorption near-edge structure techniques. The carbonization temperature plays a critical role in controlling not only the crystallinity, but also the nitrogen content and textural parameters of the samples, including specific surface area and specific pore volume. The nitrogen content of MCN decreases with a concomitant increase in specific surface area and specific pore volume, as well as the crystallinity of the samples, as the carbonization temperature is increased. The results also reveal that the structural order of the materials is retained, even after heat treatment at temperatures up to 900 °C with a significant reduction of the nitrogen content, but the structure is partially damaged at 1000 °C. The carbon dioxide adsorption capacity of these materials is not only dependent on the textural parameters, but also on the nitrogen content. The MCN prepared at 900 °C, which has an optimum BET surface area and nitrogen content, registers a carbon dioxide adsorption capacity of 20.1 mmol g(-1) at 273 K and 30 bar, which is much higher than that of mesoporous silica, MCN-1, activated carbon, and multiwalled carbon nanotubes.

  9. Conformational transitions of single polymer adsorption in poor solvent: Wetting transition due to molecular confinement induced line tension

    NASA Astrophysics Data System (ADS)

    Wei, Hsien-Hung; Li, Yen-Ching

    2016-07-01

    We report a theory capable of describing conformational transitions for single polymer adsorption in a poor solvent. We show that an additional molecular confinement effect near the contact line can act exactly like line tension, playing a critical role in the behavior of an absorbed polymer chain. Using this theory, distinct conformational states: desorbed globule (DG), surface attached cap (SAC), and adsorbed lens (AL), can be vividly revealed, resembling the drying-wetting transition of a nanodroplet. But the transitions between these states can behave rather differently from those in the usual wetting transitions. The DG-SAC transition is discrete, occurring at the adsorption threshold when the globule size at the desorbed state is equal to the adsorption blob. The SAC-AL transition is smooth for finite chain lengths, but can change to discontinuous in the infinite chain limit, characterized by the different end-to-end exponent 3/8 and the unique crossover exponent 1/4. Distinctive critical exponents near this transition are also determined, indicating that it is an additional universality class of phase transitions. This work also sheds light on nanodrop spreading, wherein the important role played by line tension might simply be a manifestation of the local molecular confinement near the contact line.

  10. The effect of moisture on the methane adsorption capacity of shales: A study case in the eastern Qaidam Basin in China

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Yu, Qingchun

    2016-11-01

    This study investigated the effects of moisture on high-pressure methane adsorption in carboniferous shales from the Qaidam Basin, China. The shale characteristics, including the organic/inorganic compositions and pore structure (volume and surface) distribution, were obtained using various techniques. Gibbs adsorption measurements were performed over a pressure range up to 6 MPa and temperatures of 308.15 K on dry samples and moisture-equilibrated samples to analyze the correlations between organic/inorganic matter, pore structure, and moisture content on the methane sorption capacity. Compared to dry samples, the sorption capacity of wet samples (0.44-2.52% of water content) is reduced from 19.7 ± 5.3% to 36.1% ± 6.1%. Langmuir fitting is conducted to investigate moisture-dependent variations of adsorbed methane density, Langmuir pressure, and volume. By combining the pore volume and surface distribution analyses, our observations suggested that the main competition sites for CH4-H2O covered pores of approximately 2-7 nm, whereas the effective sites for methane and water were predominantly distributed within smaller (<4 nm) and larger pores (>10 nm), respectively. Regarding the compositional correlations, the impact of moisture on the amount of adsorbed methane shows a roughly linearly decreasing trend with increasing TOC content ranging from 0.62 to 2.88%, whereas the correlation between the moisture effect and various inorganic components is more complicated. Further fitting results indicate that illite/smectite mixed formations are closely related to the methane capacity, whereas the illite content show an evident connection to the pore structural (volume and surface) variations in the presence of moisture.

  11. The Effect of Oxidation on the Surface Chemistry of Sulfur-Containing Carbons and their Arsine Adsorption Capacity

    DTIC Science & Technology

    2010-01-01

    hydrogen sulfide . Carbon 2004;42(3):469–76. Fig. 6 – Water adsorption isotherms of the samples studied. 1786 C A R B O N 4 8 ( 2 0 1 0 ) 1 7 7 9 –1 7 8...that oxygen- and sulfur-containing groups participate in arsine oxida- tion to arsenic tri- and pentoxide and/or in the formation of arsenic sulfides ...technological difficulties, arsine is also a powerful toxin susceptible to oxidation with a strong exothermic effect. Of all the methods to separate

  12. New V(IV)-based metal-organic framework having framework flexibility and high CO2 adsorption capacity.

    PubMed

    Liu, Ying-Ya; Couck, Sarah; Vandichel, Matthias; Grzywa, Maciej; Leus, Karen; Biswas, Shyam; Volkmer, Dirk; Gascon, Jorge; Kapteijn, Freek; Denayer, Joeri F M; Waroquier, Michel; Van Speybroeck, Veronique; Van Der Voort, Pascal

    2013-01-07

    A vanadium based metal-organic framework (MOF), VO(BPDC) (BPDC(2-) = biphenyl-4,4'-dicarboxylate), adopting an expanded MIL-47 structure type, has been synthesized via solvothermal and microwave methods. Its structural and gas/vapor sorption properties have been studied. This compound displays a distinct breathing effect toward certain adsorptives at workable temperatures. The sorption isotherms of CO(2) and CH(4) indicate a different sorption behavior at specific temperatures. In situ synchrotron X-ray powder diffraction measurements and molecular simulations have been utilized to characterize the structural transition. The experimental measurements clearly suggest the existence of both narrow pore and large pore forms. A free energy profile along the pore angle was computationally determined for the empty host framework. Apart from a regular large pore and a regular narrow pore form, an overstretched narrow pore form has also been found. Additionally, a variety of spectroscopic techniques combined with N(2) adsorption/desorption isotherms measured at 77 K demonstrate that the existence of the mixed oxidation states V(III)/V(IV) in the titled MOF structure compared to pure V(IV) increases the difficulty in triggering the flexibility of the framework.

  13. Effect of cetyl trimethyl ammonium bromide concentration on structure, morphology and carbon dioxide adsorption capacity of calcium hydroxide based sorbents

    NASA Astrophysics Data System (ADS)

    Hlaing, Nwe Ni; Vignesh, K.; Sreekantan, Srimala; Pung, Swee-Yong; Hinode, Hirofumi; Kurniawan, Winarto; Othman, Radzali; Thant, Aye Aye; Mohamed, Abdul Rahman; Salim, Chris

    2016-02-01

    Calcium hydroxide (Ca(OH)2) has been proposed as an important material for industrial, architectural, and environmental applications. In this study, calcium acetate was used as a precursor and cetyl trimethyl ammonium bromide (CTAB) was used as a surfactant to synthesize Ca(OH)2 based adsorbents for carbon dioxide (CO2) capture. The effect of CTAB concentration (0.2-0.8 M) on the structure, morphology and CO2 adsorption performance of Ca(OH)2 was studied in detail. The synthesized samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), BET surfaced area and thermogravimetry-differential thermal analysis (TG-DTA) techniques. The phase purity, crystallite size, Brunauer-Emmett-Teller (BET) surface area and CO2 adsorption performance of Ca(OH)2 precursor adsorbents were significantly increased when the concentration of CTAB was increased. XRD results showed that pure Ca(OH)2 phase was obtained at the CTAB concentration of 0.8 M. TGA results exhibited that 0.8 M of CTAB-assisted Ca(OH)2 precursor adsorbent possessed a residual carbonation conversion of ∼56% after 10 cycles.

  14. Predictive Simulation of Gas Adsorption in Fixed-Beds and Limitations due to the Ill-Posed Danckwerts Boundary Condition

    NASA Technical Reports Server (NTRS)

    Knox, James Clinton

    2016-01-01

    The 1-D axially dispersed plug flow model is a mathematical model widely used for the simulation of adsorption processes. Lumped mass transfer coefficients such as the Glueckauf linear driving force (LDF) term and the axial dispersion coefficient are generally obtained by fitting simulation results to the experimental breakthrough test data. An approach is introduced where these parameters, along with the only free parameter in the energy balance equations, are individually fit to specific test data that isolates the appropriate physics. It is shown that with this approach this model provides excellent simulation results for the C02 on zeolite SA sorbent/sorbate system; however, for the H20 on zeolite SA system, non-physical deviations from constant pattern behavior occur when fitting dispersive experimental results with a large axial dispersion coefficient. A method has also been developed that determines a priori what values of the LDF and axial dispersion terms will result in non-physical simulation results for a specific sorbent/sorbate system when using the one-dimensional axially dispersed plug flow model. A relationship between the steepness of the adsorption equilibrium isotherm as indicated by the distribution factor, the magnitude of the axial dispersion and mass transfer coefficient, and the resulting non-physical behavior is derived. This relationship is intended to provide a guide for avoiding non-physical behavior by limiting the magnitude of the axial dispersion term on the basis of the mass transfer coefficient and distribution factor.

  15. Adsorption characteristics of siloxanes in landfill gas by the adsorption equilibrium test

    SciTech Connect

    Nam, Sangchul; Namkoong, Wan; Kang, Jeong-Hee; Park, Jin-Kyu; Lee, Namhoon

    2013-10-15

    Highlights: • Equilibrium test was attempted to evaluate adsorption characteristics of siloxane. • L2 had higher removal efficiency in carbon compared to noncarbon adsorbents. • Total adsorption capacity of siloxane was 300 mg/g by coal activated carbon. • Adsorption characteristics rely on size of siloxane molecule and adsorbent pore. • Conversion of siloxane was caused by adsorption of noncarbon adsorbents. - Abstract: Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed. Coconut activated carbon (CA1), coal activated carbon (CA2), impregnated activated carbon (CA3), silicagel (NCA1), and activated alumina (NCA2) were used for the adsorption of the mixed siloxane which contained hexamethyldisiloxane (L2), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). L2 had higher removal efficiency in noncarbon adsorbents compared to carbon adsorbents. The application of Langmuir and Freundlich adsorption isotherm demonstrated that coconut based CA1 and CA3 provided higher adsorption capacity on L2. And CA2 and NCA1 provided higher adsorption capacity on D4 and D5. Based on the experimental results, L2, D4, and D5 were converted by adsorption and desorption in noncarbon adsorbents. Adsorption affinity of siloxane is considered to be affect by the pore size distribution of the adsorbents and by the molecular size of each siloxane.

  16. Carbon dioxide adsorption in graphene sheets

    NASA Astrophysics Data System (ADS)

    Mishra, Ashish Kumar; Ramaprabhu, Sundara

    2011-09-01

    Control over the CO2 emission via automobiles and industrial exhaust in atmosphere, is one of the major concerns to render environmental friendly milieu. Adsorption can be considered to be one of the more promising methods, offering potential energy savings compared to absorbent systems. Different carbon nanostructures (activated carbon and carbon nanotubes) have attracted attention as CO2 adsorbents due to their unique surface morphology. In the present work, we have demonstrated the CO2 adsorption capacity of graphene, prepared via hydrogen induced exfoliation of graphitic oxide at moderate temperatures. The CO2 adsorption study was performed using high pressure Sieverts apparatus and capacity was calculated by gas equation using van der Waals corrections. Physical adsorption of CO2 molecules in graphene was confirmed by FTIR study. Synthesis of graphene sheets via hydrogen exfoliation is possible at large scale and lower cost and higher adsorption capacity of as prepared graphene compared to other carbon nanostructures suggests its possible use as CO2 adsorbent for industrial application. Maximum adsorption capacity of 21.6 mmole/g was observed at 11 bar pressure and room temperature (25 °C).

  17. Using the fundamentals of adsorption to understand peak distortion due to strong solvent effect in hydrophilic interaction chromatography.

    PubMed

    Gritti, Fabrice; Sehajpal, Jyotsna; Fairchild, Jacob

    2017-03-17

    The peak distortion observed in hydrophilic interaction chromatography (HILIC) may be caused by the sample diluent to mobile phase mismatch. The United States Pharmacopeia (USP) method for organic impurities in cetirizine HCl tablets calls for such a mismatch, having a higher concentration of strong solvent in the sample diluent than in the mobile phase. A significant peak deformation is reported for cetirizine (a second-generation antihistamine) when it is purified on a Ethylene Bridged Hybrid (BEH) HILIC column (4.6mm×100mm, 2.5μm particles) using an acetonitrile-water eluent mixture and a sample diluent containing 7% and 9% water (in volume), respectively. The mechanism and physical origin of such peak distortion are related to (1) the diluent-to-eluent excess of water that propagates along the column at a velocity similar to that of the analyte, (2) the significant drop of the Henry's constant of the analyte upon increasing water concentration in the eluent, (3) the sample volume injected, and (4) to the pre-column sample dilution factor that depends on the characteristics of the LC instrument used. This proposed mechanism is validated from the calculation of the concentration profiles of cetirizine and water by using the equilibrium-dispersive (ED) model of chromatography. The observed distortion of cetirizine peaks is successfully predicted from the measurement of (1) the excess adsorption isotherm of water from acetonitrile onto the BEH HILIC adsorbent, (2) the retention factor of cetirizine as a function of the volume fraction (7, 8, and 9%) of water in the mobile phase, and (3) of the pre-column sample dispersion related to the instrument used (HPLC or UHPLC). The results of the calculations enables the user to anticipate the impacts of the diluent-to-eluent mismatch in water content, the injection volume, the analyte retention under infinite dilution, and of the pre-column sample dispersion on the amplitude of peak distortion in HILIC. Appropriate and

  18. Dynamic and static adsorption and desorption of Hg(II) ions on chitosan membranes and spheres.

    PubMed

    Vieira, Rodrigo S; Beppu, Marisa M

    2006-05-01

    The adsorption and desorption of Hg(II) ions was studied using static and dynamic methods, employing membranes and spheres of chitosan as the adsorbent. The quantity of adsorption was influenced by chitosan crosslinking and by the adsorbent shape. The Langmuir model was applied to fit the experimental equilibrium data. Glutaraldehyde-crosslinked membranes presented a lower desorption capacity, when compared to natural membranes, but could be regenerated for use in successive cycles. Dynamic adsorption experiments suggested that the adsorption capacity depended mainly on adsorbent geometry, due to differences between surface area to mass ratio and initial concentration of Hg(II) ions. The adsorption capacity determined by the dynamic method was 65% and 77% for membranes and spheres, respectively of the value obtained static method results. A process combining dynamic adsorption and static desorption can be used to concentrate the Hg(II) ions by a factor of nearly seven (7x), when compared to the initially treated volume.

  19. Study on Adsorption of Cu(II) on Chitosan Nanofiber Membranes

    NASA Astrophysics Data System (ADS)

    Cao, Jianhua; Li, Dongzhou; Liang, Weihua; Wu, Dayong

    2014-12-01

    Chitosan nanofiber membranes by electrospinning technique were used to remove Cu(II) from aqueous solution. The adsorption kinetics, equilibrium isotherms, and pH effect were investigated in batch experiments. The Langmuir isotherm and pseudo second-order kinetic models agree well with the experimental data. The chitosan nanofiber membranes are effective for Cu(II) adsorption at pH6. Results showed that the maximum adsorption capacity of the chitosan nanofiber membranes with Cu(II) is 118.62 mg g-1. The chitosan nanofiber membranes can be used as an effective adsorbent for the removal of Cu(II) in aqueous solution due to high adsorption capacity.

  20. Competitive adsorption of VOCs and BOM: The role of molecular oxygen

    SciTech Connect

    Sorial, G.A.; Cerminara, P.; Papadimas, S.P.; Suidan, M.T. . Dept. of Civil and Environmental Engineering); Speth, T.F. )

    1994-03-01

    In this study, the presence of background organic matter (BOM) was seen to reduce the adsorptive capacity of carbon for chloroform, chlorobenzene, and dibromochloropropane. Adsorption of these compounds was further reduced under oxic conditions. This additional reduction in capacity was likely due to conglomeration of BOM on the carbon surface, which reduced the available surface area for the target volatile organic chemical (VOC). Adsorption isotherms conducted with constant initial concentration ratios of VOC to BOM showed similar behavior. The ideal adsorbed solution theory (IAST) was found to accurately describe anoxic adsorption isotherms for VOCs in water containing BOM but failed to predict this competition for data collected under oxic conditions.

  1. Porous cellulose spheres: Preparation, modification and adsorption properties.

    PubMed

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

    2016-12-01

    Porous cellulose spheres (PCS) were fabricated by precipitating the spheres from a cellulose ionic liquid solution, followed by freezing, solvent exchange, and drying. PCS had low crystallinity and a large surface area that facilitated modification with trisodium trimetaphosphate (STMP) to introduce phosphate ester groups into the porous structure of the heterogeneous system. The STMP-modified PCS (SPCS) were used to remove heavy metal ions from aqueous solution. With increasing STMP dosage, the adsorption capacity of SPCS obviously improved due to chelation between Pb(2+) and phosphate ester groups. The kinetic adsorption and isotherm data matched the pseudo-second order model and the Langmuir model well. The maximum adsorption capacity reached 150.6 mg g(-1) for SPCS. SPCS were competitive with other absorbents because the phosphate ester groups and porous structure contributed to Pb(2+) adsorption. Moreover, SPCS can be regenerated with ethylenediamine tetraacetic acid disodium salt (EDTA) solution for repetitious adsorption of Pb(2+).

  2. Effects of Humidity Swings on Adsorption Columns for Air Revitalization: Modeling and Experiments

    NASA Technical Reports Server (NTRS)

    LeVan, M. Douglas; Finn, John E.

    1997-01-01

    Air purification systems are necessary to provide clean air in the closed environments aboard spacecraft. Trace contaminants are removed using adsorption. One major factor concerning the removal of trace contaminants is relative humidity. Water can reduce adsorption capacity and, due to constant fluctuations, its presence is difficult to incorporate into adsorption column designs. The purpose of the research was to allow for better design techniques in trace contaminant adsorption systems, especially for feeds with water present. Experiments and mathematical modeling research on effects of humidity swings on adsorption columns for air revitalization were carried out.

  3. Polychelated cryogels: hemoglobin adsorption from human blood.

    PubMed

    Erol, Kadir

    2017-02-01

    The separation and purification methods are extremely important for the hemoglobin (Hb) which is a crucial biomolecule. The adsorption technique is popular among these methods and the cryogels have been used quite much due to their macropores and interconnected flow channels. In this study, the Hb adsorption onto the Cu(II) immobilized poly(2-hydroxyethyl methacrylate-glycidyl methacrylate), poly(HEMA-GMA)-Cu(II), cryogels was investigated under different conditions (pH, interaction time, initial Hb concentration, temperature and ionic strength) to optimize adsorption conditions. The swelling test, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), surface area (BET), elemental and ICP-OES analysis were performed for the characterization of cryogels. Polyethyleneimine (PEI) molecule was used as a Cu(II)-chelating ligand. The Hb adsorption capacity of cryogels was determined as 193.8 mg Hb/g cryogel. The isolation of Hb from human blood was also studied under optimum adsorption conditions determined and the Hb (124.5 mg/g cryogel) was isolated. The adsorption model was investigated in the light of Langmuir and Freundlich adsorption isotherm models and it was determined to be more appropriate to the Langmuir adsorption isotherm model.

  4. Modeling selenium (IV and VI) adsorption envelopes in selected tropical soils using the constant capacitance model

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The adsorption of selenium (Se) on soil is important due to the relevance of Se to environmental and health issues. The adsorption of Se(IV) and Se(VI) was evaluated on soil samples from São Paulo state, Brazil, as a function of varying pH, and the experimental data were fitted to the constant capac...

  5. Bile salt adsorption ability of dietary fiber from named varieties of carrot at different developmental ages.

    PubMed

    Robertson, J A; Eastwood, M A; Yeoman, M M

    1980-06-01

    The adsorption of bile salts to fiber has been measured using fiber prepared from different varieties of carrot at different developmental ages. We investigated the carrot varieties Altrinchan and Chantenay and used the bile salts deoxycholate and glycocholate. The method used to measure adsorption distinguished between true adsorption and apparent adsorption due to bile salts trapped within the interstices of the fiber matrix. Adsorption ability was influenced by the developmental age of the carrot but not by variety. Adsorption ability was at a maximum when the carrot fresh weight was at a maximum. The adsorption ability measured was true adsorption and was not dependent on the water holding capacity of the fiber. Deoxycholate was better adsorbed than glycocholate and the results suggest that the developmental age of a fiber source could be important when formulating diets designed to influence bile salt metabolism.

  6. Equilibrium and kinetic adsorption study of the adsorptive removal of Cr(VI) using modified wheat residue.

    PubMed

    Chen, Suhong; Yue, Qinyan; Gao, Baoyu; Xu, Xing

    2010-09-01

    A new adsorbent modified from wheat residue was synthesized after reaction with epichlorohydrin and triethylamine by using the modifying agents of diethylenetriamine in the presence of organic medium of N,N-dimethylformamide. The performance of the modified wheat straw (MWS) was characterized by Fourier transform infrared spectroscopy and point of zero charge analysis. The adsorption was investigated in a batch adsorption system, including both equilibrium adsorption isotherms and kinetics. Results showed that MWR had great anion-adsorbing capacity, due to the existence of a large number of introduced amino groups, and the value of pH(PZC) was around 5.0. Equilibrium data were analyzed using the Langmuir, Freundlich, and Temkin isotherm models and were found to be best represented by the Freundlich isotherm model. Evaluation of the adsorption process identified its endothermic nature. The maximum adsorption capacity of MWS for the removal of Cr(VI) was 322.58mg/g at 328K, indicating that MWS has high chromium removal efficiency, compared to other adsorbents reported. The kinetics of adsorption followed the pseudo-second-order kinetic equation. The mechanism of adsorption was investigated using the intraparticle diffusion model. Thermodynamic parameters (free energy change, enthalpy change, and entropy change) revealed that the adsorption of Cr(VI) onto MWS was endothermic and spontaneous; additionally, the adsorption can be characterized as an ion-exchange process. The results suggest that MWS is an inexpensive and efficient adsorbent for removing Cr(VI) ions from aqueous solution.

  7. Enhancement of the adsorption capacity of the light-weight expanded clay aggregate surface for the metronidazole antibiotic by coating with MgO nanoparticles: Studies on the kinetic, isotherm, and effects of environmental parameters.

    PubMed

    Kalhori, Ebrahim Mohammadi; Al-Musawi, Tariq J; Ghahramani, Esmaeil; Kazemian, Hossein; Zarrabi, Mansur

    2017-02-09

    The synthesized MgO nanoparticles were used to coat the light-weight expanded clay aggregates (LECA) and as a metronidazole (MNZ) adsorbent. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier-transformed infrared (FTIR) techniques were employed to study the surface morphology and characteristics of the adsorbents. MgO/LECA clearly revealed the advantages of the nanocomposite particles, showing high specific surface area (76.12 m(2)/g), significant adsorption sites and functional groups. Between pH 5 and 9, the MNZ sorption was not significantly affected. Kinetic studies revealed that the MNZ adsorption closely followed the Avrami model, with no dominant process controlling the sorption rate. The study of the effects of foreign ions revealed that the addition of carbonate raised the MNZ removal efficiency of LECA by 8% and the total removal of MNZ by MgO/LECA. Furthermore, nitrate and hardness only marginally influenced the MNZ removal efficiency and their effects can be ranked in the order of carbonate>nitrate>hardness. The isotherm adsorption of MNZ was best fitted with the Langmuir model enlighten the monolayer MNZ adsorption on the homogeneous LECA and MgO/LECA surfaces. The maximum adsorption capacity under optimum conditions was enhanced from 56.31 to 84.55 mg/g for LECA and MgO/LECA, respectively. These findings demonstrated that the MgO/LECA nanocomposite showed potential as an efficient adsorbent for MNZ removal.

  8. Perturbation to global tropospheric oxidizing capacity due to latitudinal redistribution of surface sources of NOx, CH4 and CO

    NASA Astrophysics Data System (ADS)

    Gupta, Mohan L.; Cicerone, Ralph J.; Elliott, Scott

    Economic and social projections indicate that during next several decades there will be major geographical redistribution of surface emissions of O3 precursors, such as NOx, CH4 and CO. A net decrease in their emissions from northern hemispheric mid-latitudes will be accompanied by substantial increases from the tropics. We have investigated a hypothetical scenario of currently underway transition of such emission patterns using a global two-dimensional photochemical model. With overall O3 precursor releases held constant, a simultaneous transfer of their emissions by 25% from the latitude belt 75°N-35°N to 5°S-35°N increases tropospheric oxidizing capacity such that the methane global lifetime and concentrations fall by more than 3%. Seasonally dependent changes in surface O3 concentrations are also calculated. In influencing OH concentration, redistribution of surface NOx emissions is 2-3 orders of magnitude more efficient per unit mass than CO emissions. Shifts in methane sources have insignificant effects on global photochemistry, but lead to a decrease in its interhemispheric gradient.

  9. Brain energy metabolism spurns fatty acids as fuel due to their inherent mitotoxicity and potential capacity to unleash neurodegeneration.

    PubMed

    Schönfeld, Peter; Reiser, Georg

    2017-03-30

    The brain uses long-chain fatty acids (LCFAs) to a negligible extent as fuel for the mitochondrial energy generation, in contrast to other tissues that also demand high energy. Besides this generally accepted view, some studies using cultured neural cells or whole brain indicate a moderately active mitochondrial β-oxidation. Here, we corroborate the conclusion that brain mitochondria are unable to oxidize fatty acids. In contrast, the combustion of liver-derived ketone bodies by neural cells is long-known. Furthermore, new insights indicate the use of odd-numbered medium-chain fatty acids as valuable source for maintaining the level of intermediates of the citric acid cycle in brain mitochondria. Non-esterified LCFAs or their activated forms exert a large variety of harmful side-effects on mitochondria, such as enhancing the mitochondrial ROS generation in distinct steps of the β-oxidation and therefore potentially increasing oxidative stress. Hence, the question arises: Why do in brain energy metabolism mitochondria selectively spurn LCFAs as energy source? The most likely answer are the relatively higher content of peroxidation-sensitive polyunsaturated fatty acids and, the low antioxidative defense in brain tissue. There are two remarkable peroxisomal defects, one relating to α-oxidation of phytanic acid and the other to uptake of very long-chain fatty acids (VLCFAs) which lead to pathologically high tissue levels of such fatty acids. Both, the accumulation of phytanic acid and that of VLCFAs give an enlightening insight into harmful activities of fatty acids on neural cells, which possibly explain why evolution has prevented brain mitochondria from the equipment of with significant β-oxidation enzymatic capacity.

  10. Adsorptive removal of α-endosulfan from water by hydrophobic zeolites. An isothermal study.

    PubMed

    Yonli, Arsène H; Batonneau-Gener, Isabelle; Koulidiati, Jean

    2012-02-15

    This paper deals with the removal of α-endosulfan from water over HY and steamed HBEA zeolites. Experiments were performed to understand the adsorption mechanisms of α-endosulfan on zeolites and to determine the most efficient adsorbent for the purification of water contaminated by this pesticide. The experiments exhibit that α-endosulfan was adsorbed in the micropores. In the case of HY zeolites an adsorption of α-endosulfan molecules on BrØnsted sites was pointed out, due to a preferential water adsorption in mesopores. Moreover a physisorption of α-endosulfan occurred in micropores. For steamed HBEA zeolites physisorption in micropores was pointed out as the adsorption mode. For both types of zeolites a decrease of the adsorption capacities was noticed when the acidity of zeolites increased. There was also a linear relation between the adsorption capacities of α-endosulfan and the hydrophobicity (HI) of the samples and by determining the values of HI for a type of zeolite it was possible to deduce the uptake of α-endosulfan. The HY(40) sample was the most efficient for the removal of α-endosulfan from water because of preferential adsorption of water molecules in mesopores and lower acidity. For this sample the adsorption capacity for α-endosulfan was about 833.33 mg/g where for the most effective HBEA sample (St700(3)) the adsorption capacity was about 793.65 mg/g.

  11. Adsorption of sulfur dioxide on ammonia-treated activated carbon fibers

    USGS Publications Warehouse

    Mangun, C.L.; DeBarr, J.A.; Economy, J.

    2001-01-01

    A series of activated carbon fibers (ACFs) and ammonia-treated ACFs prepared from phenolic fiber precursors have been studied to elucidate the role of pore size, pore volume, and pore surface chemistry on adsorption of sulfur dioxide and its catalytic conversion to sulfuric acid. As expected, the incorporation of basic functional groups into the ACFs was shown as an effective method for increasing adsorption of sulfur dioxide. The adsorption capacity for dry SO2 did not follow specific trends; however the adsorption energies calculated from the DR equation were found to increase linearly with nitrogen content for each series of ACFs. Much higher adsorption capacities were achieved for SO2 in the presence of oxygen and water due to its catalytic conversion to H2SO4. The dominant factor for increasing adsorption of SO2 from simulated flue gas for each series of fibers studied was the weight percent of basic nitrogen groups present. In addition, the adsorption energies calculated for dry SO2 were shown to be linearly related to the adsorption capacity of H2SO4 from this flue gas for all fibers. It was shown that optimization of this parameter along with the pore volume results in higher adsorption capacities for removal of SO2 from flue gases. ?? 2001 Elsevier Science Ltd. All rights reserved.

  12. Adsorption of tetracycline from aqueous solutions onto multi-walled carbon nanotubes with different oxygen contents

    PubMed Central

    Yu, Fei; Ma, Jie; Han, Sheng

    2014-01-01

    Oxidized multi-walled carbon nanotubes (MWCNTs) with different oxygen contents were investigated for the adsorption of tetracycline (TC) from aqueous solutions. As the surface oxygen content of the MWCNTs increased, the maximum adsorption capacity and adsorption coefficient of TC increased to the largest values and then decreased. The relation can be attributed to the interplay between the nanotubes' dispersibility and the water cluster formation upon TC adsorption. The overall adsorption kinetics of TC onto CNTs-3.2%O might be dependent on both intra-particle diffusion and boundary layer diffusion. The maximum adsorption capacity of TC on CNTs-3.2%O was achieved in the pH range of 3.3–8.0 due to formation of water clusters or H-bonds. Furthermore, the presence of Cu2+ could significantly enhanced TC adsorption at pH of 5.0. However, the solution ionic strength did not exhibit remarkable effect on TC adsorption. In addition, when pH is beyond the range (3.3–8.0), the electrostatic interactions caused the decrease of TC adsorption capacity. Our results indicate that surface properties and aqueous solution chemistry play important roles in TC adsorption on MWCNTs. PMID:24937315

  13. Arsenate adsorption onto iron oxide amended rice husk char.

    PubMed

    Cope, Christopher O; Webster, Damon S; Sabatini, David A

    2014-08-01

    In this study, rice husks were charred at 550 °C in a partially sealed ceramic vessel for 30minutes to create a high specific surface area (SSA) rice husk char (RHC). The RHC was then amended with iron oxides using dissolved ferric nitrate, Fe(NO3)3⋅9H2O, to provide a surface chemistry conducive to arsenic adsorption. The 550 °C iron oxide amended rice husk char's (550 IOA-RHC's) SSA was nearly 2.5 orders of magnitude higher and the arsenate adsorptive level was nearly 2 orders of magnitude higher than those reported for iron oxide amended sand, thus indicating a positive relationship between post-amendment SSA and arsenate adsorptive levels. Rice husks were then charred at temperatures ranging from 450 °C to 1050 °C to create an even higher SSA material, which might further increase arsenate adsorptive levels. The 950 °C RHC was chosen for amendment due to its high SSA and feasibility of being produced in the field. Once amended, the 950 °C iron oxide amended rice husk char (950 IOA-RHC) improved the arsenate adsorption capacity by thus confirming a positive relationship, though not a linear relationship, between post-amendment SSA and arsenic adsorptive capacity. Further study demonstrated that post-amendment mesoporous volume and mesoporous surface area appear to be better indicators of arsenic adsorptive capacity than SSA or iron content.

  14. Dynamics and thermodynamics of toxic metals adsorption onto soil-extracted humic acid.

    PubMed

    Shaker, Medhat A; albishri, Hassan M

    2014-09-01

    Humic acids, HA represent a large portion of natural organic matter in soils, sediments and waters. They are environmentally important materials due to their extensive ubiquity and strong complexation ability, which can influence heavy metal removal and transportation in waters. The thermodynamics and kinetics of the adsorption of Cd(II) and Cr(VI) onto solid soil-derived HA have been investigated at optimum conditions of pH (5.5±0.1), metal concentration (10-100mmolL(-1)) and different temperatures (293-323K). The suitability of adsorption models such as Freundlich and Langmuir to equilibrium data was investigated. The adsorption was well described by Langmuir isotherm model in multi-detectable steps. Adsorption sites, i (i=A, B, C) with different capacities, νi are characterized. The stoichiometric site capacity is independent of temperature and equilibrium constant, Ki. Adsorption sites A and B are selectively occupied by Cr(VI) cations while sites A and C are selectively occupied by Cd(II) cations. The thermodynamic parameters of adsorption systems are correlated for each adsorption step. The adsorption is endothermic, spontaneous and favorable. Different kinetic models are applied and the adsorption of these heavy metals onto HA follows pseudo-second-order kinetics and equilibrium is achieved within 24h. The adsorption reaction is controlled by diffusion processes and the type of the adsorption is physical.

  15. CO2 adsorption on chemically modified activated carbon.

    PubMed

    Caglayan, Burcu Selen; Aksoylu, A Erhan

    2013-05-15

    CO2 adsorption capacity of a commercial activated carbon was improved by using HNO3 oxidation, air oxidation, alkali impregnation and heat treatment under helium gas atmosphere. The surface functional groups produced were investigated by diffuse reflectance infrared Fourier transform spectrometer (DRIFTS). CO2 adsorption capacities of the samples were determined by gravimetric analyses for 25-200°C temperature range. DRIFTS studies revealed the formation of carboxylic acid groups on the HNO3 oxidized adsorbents. Increased aromatization and uniform distribution of the Na particles were observed on the samples prepared by Na2CO3 impregnation onto HNO3 oxidized AC support. The adsorption capacities of the nonimpregnated samples were increased by high temperature helium treatments or by increasing the adsorption temperature; both leading to decomposition of surface oxygen groups, forming sites that can easily adsorb CO2. The adsorption capacity loss due to cyclic adsorption/desorption procedures was overcome with further surface stabilization of Na2CO3 modified samples with high temperature He treatments. With Na2CO3 impregnation the mass uptakes of the adsorbents at 20 bars and 25 °C were improved by 8 and 7 folds and at 1 bar were increased 15 and 16 folds, on the average, compared to their air oxidized and nitric acid oxidized supports, respectively.

  16. Electronic storage capacity of ceria: role of peroxide in Aux supported on CeO2(111) facet and CO adsorption.

    PubMed

    Liu, Yinli; Li, Huiying; Yu, Jun; Mao, Dongsen; Lu, Guanzhong

    2015-11-07

    Density functional theory (DFT+U) was used to study the adsorption of Aux (x = 1-4) clusters on the defective CeO2(111) facet and CO adsorption on the corresponding Aux/CeO2-x catalyst, in this work Aux clusters are adsorbed onto the CeO2-x + superoxide/peroxide surface. When Au1 is supported on the CeO2(111) facet with an O vacancy, the strong electronegative Au(δ-) formed is not favorable for CO adsorption. When peroxide is adsorbed on the CeO2(111) facet with the O vacancy, Aux was oxidized, resulting in stable Aux adsorption on the defective ceria surface with peroxide, which promotes CO adsorption on the Aux/CeO2-x catalyst. With more Au atoms in supported Aux clusters, CO adsorption on this surface becomes stronger. During both the Au being supported on CeO2-x and CO being adsorbed on Aux/CeO2-x, CeO2 acts as an electron buffer that can store/release the electrons. These results provide a scientific understanding for the development of high-performance rare earth catalytic materials.

  17. Adsorption of anionic dyes from aqueous solutions using chemically modified straw.

    PubMed

    Zhang, Wenxuan; Li, Haijiang; Kan, Xiaowei; Dong, Lei; Yan, Han; Jiang, Ziwen; Yang, Hu; Li, Aimin; Cheng, Rongshi

    2012-08-01

    The effective disposal of redundant straw is a significant work for environmental protection and full utilization of resource. In this work, the wheat straw has been modified by etherification to prepare a kind of quaternary ammonium straw adsorbents. The adsorption behaviors of the modified straw for methyl orange (MO) and acid green 25(AG25) were studied in both batch and column systems. The adsorption capacity of the straw for both dyes improved evidently after modification. The maximal MO and AG25 uptakes were more than 300 and 950 mg g(-1), respectively. Furthermore, the adsorption equilibrium, kinetics and column studies all indicated that the adsorption behavior was a monolayer chemical adsorption with an ion-exchange process. In addition, after adsorption of anionic dyes, the used adsorbents were successfully applied to adsorb a cationic dye directly at suitable conditions in the secondary adsorption. This was due to the altered surface structures of the used adsorbents.

  18. Sub-ambient carbon dioxide adsorption properties of nitrogen doped graphene

    SciTech Connect

    Tamilarasan, P.; Ramaprabhu, Sundara

    2015-04-14

    Carbon dioxide adsorption on carbon surface can be enhanced by doping the surface with heterogeneous atoms, which can increase local surface affinity. This study presents the carbon dioxide adsorption properties of nitrogen doped graphene at low pressures (<100 kPa). Graphene was exposed to nitrogen plasma, which dopes nitrogen atoms into carbon hexagonal lattice, mainly in pyridinic and pyrrolic forms. It is found that nitrogen doping significantly improves the CO{sub 2} adsorption capacity at all temperatures, due to the enrichment of local Lewis basic sites. In general, isotherm and thermodynamic parameters suggest that doped nitrogen sites have nearly same adsorption energy of surface defects and residual functional groups. The isosteric heat of adsorption remains in physisorption range, which falls with surface coverage, suggesting the distribution of magnitude of adsorption energy. The absolute values of isosteric heat and entropy of adsorption are slightly increased upon nitrogen doping.

  19. Insights into the adsorption capacity and breakthrough properties of a synthetic zeolite against a mixture of various sulfur species at low ppb levels.

    PubMed

    Vellingiri, Kowsalya; Kim, Ki-Hyun; Kwon, Eilhann E; Deep, Akash; Jo, Sang-Hee; Szulejko, Jan E

    2016-01-15

    The sorptive removal properties of a synthetic A4 zeolite were evaluated against sulfur dioxide (SO2) and four reference reduced sulfur compounds (RSC: hydrogen sulfide (H2S), methanethiol (CH3SH), dimethyl sulfide (DMS, (CH3)2S), and dimethyl disulfide (DMDS, CH3SSCH3). To this end, a sorbent bed of untreated (as-received) A4 zeolite was loaded with gaseous standards at four concentration levels (10-100 part-per-billion (ppb (v/v)) at four different volumes (0.1, 0.2, 0.5, and 1 L increments) in both increasing (IO: 0.1-1.0 L) and decreasing volume order (DO: 1.0 to 0.1 L). Morphological properties were characterized by PXRD, FTIR, and BET analysis. The removal efficiency of SO2 decreased from 100% for all concentrations at 0.1 L (initial sample volume) to ∼82% (100 ppb) or ∼96% (10 ppb) at 3.6 L. In contrast, removal efficiency of RSC was near 100% at small loading volumes but then fell sharply, irrespective of concentration (10-100 ppb) (e.g., 32% (DMS) to 52% (H2S) at 100 ppb). The adsorption capacity of zeolite, if expressed in terms of solid-gas partition coefficient (e.g., similar to the Henry's law constant (mmol kg(-1) Pa(-1))), showed moderate variabilities with the standard concentration levels and S compound types such as the minimum of 2.03 for CH3SH (at 20 ppb) to the maximum of 13.9 for SO2 (at 10 ppb). It clearly demonstrated a notable distinction in the removal efficiency of A4 zeolite among the different S species in a mixture with enhanced removal efficiency of SO2 compared to the RSCs.

  20. Characterization of trichloroethylene adsorption onto waste biocover soil in the presence of landfill gas.

    PubMed

    He, Ruo; Su, Yao; Kong, Jiaoyan

    2015-09-15

    Waste biocover soils (WBS) have been demonstrated to have great potential in mitigating trichloroethylene (TCE) emission from landfills, due to the relatively high TCE-degrading capacity. In this study, the characteristics of TCE adsorption on WBS in the presence of the major landfill gas components (i.e., CH4 and CO2) were investigated in soil microcosms. The adsorption isotherm of TCE onto WBS was fitted well with linear model within the TCE concentrations of 7000 ppmv. The adsorption capacity of TCE onto WBS was affected by temperature, soil moisture content and particle size, of which, temperature was the dominant factor. The adsorption capacity of TCE onto the experimental materials increased with the increasing organic matter content. A significantly positive correlation was observed between the adsorption capacity of TCE and the organic matter content of experimental materials that had relatively higher organic content (r = 0.988, P = 0.044). To better understand WBS application in practice, response surface methodology was developed to predict TCE adsorption capacity and emissions through WBS in different landfills in China. These results indicated that WBS had high adsorption capacity of TCE in LFG and temperature should be paid more attention to manipulate WBS to reduce TCE emissions from landfills.

  1. Modeling of the capacity loss of a 12 V automotive lead-acid battery due to ageing and comparison with measurement data

    NASA Astrophysics Data System (ADS)

    Kim, Ui Seong; Shin, Chee Burm; Chung, Seung Myun; Kim, Sung Tae; Cho, Byung Won

    One-dimensional modeling was carried-out to predict the capacity loss of a 12 V automotive lead-acid battery due to ageing. The model not only accounted for electrochemical kinetics and ionic mass transfer in a battery cell, but also considered the anodic corrosion of lead in sulfuric acid. In order to validate the modeling, modeling results were compared with the measurement data of the cycling behaviors of the lead-acid batteries having nominal capacity of 68 Ah that are mounted on the automobiles manufactured by Hyundai Motor Company. The cycling was performed under the protocol of the constant-current discharge and the constant-voltage charge. The discharge rate of C/3 was used. The range of state of charge was between 1 and 0.85. The voltage was kept constant at the gassing voltage until the charge current tapered to 10 mA. The retention capacity of the battery was measured with C/3 discharge rate before the beginning of cycling and after every 40 cycles of cycling. The modeling results were in good agreement with the measurement data.

  2. Adsorption of SO2 onto oxidized and heat-treated activated carbon fibers (ACFs)

    USGS Publications Warehouse

    Daley, M.A.; Mangun, C.L.; DeBarr, J.A.; Riha, S.; Lizzio, A.A.; Donnals, G.L.; Economy, J.

    1997-01-01

    Oxidation of the ACFs, using an aqueous oxidant, decreased their adsorption capacity for SO2 from flue gas due to a decrease in pore volume and repulsion of the SO2 from acidic surface groups. If these samples were heat-treated to desorb the oxygen containing function groups, the amount of SO2 adsorption increased. This increase in adsorption capacity was directly correlated to the amount of CO2 evolved during heat-treatment of the oxidized ACFs. The amount of SO2 adsorbed for these samples was related to the pore size, pore surface chemistry and pore volume. This analysis is explained in more detail in this paper.

  3. Further observations of a decreasing atmospheric CO2 uptake capacity in the Canada Basin (Arctic Ocean) due to sea ice loss

    NASA Astrophysics Data System (ADS)

    Else, Brent G. T.; Galley, R. J.; Lansard, B.; Barber, D. G.; Brown, K.; Miller, L. A.; Mucci, A.; Papakyriakou, T. N.; Tremblay, J.-É.; Rysgaard, S.

    2013-03-01

    data collected in 2009, we evaluated the potential for the southeastern Canada Basin (Arctic Ocean) to act as an atmospheric CO2 sink under the summertime ice-free conditions expected in the near future. Beneath a heavily decayed ice cover, we found surprisingly high pCO2sw (~290-320 µatm), considering that surface water temperatures were low and the influence of ice melt was strong. A simple model simulating melt of the remaining ice and exposure of the surface water for 100 days revealed a weak capacity for atmospheric CO2 uptake (mean flux: -2.4 mmol m-2 d-1), due largely to warming of the shallow mixed layer. Our results confirm a previous finding that the Canada Basin is not a significant sink of atmospheric CO2 under summertime ice-free conditions and that increased ventilation of the surface mixed layer due to sea ice loss is weakening the sink even further.

  4. Development of TREN dendrimers over mesoporous SBA-15 for CO 2 adsorption

    NASA Astrophysics Data System (ADS)

    Bhagiyalakshmi, Margandan; Park, Sang Do; Cha, Wang Seog; Jang, Hyun Tae

    2010-09-01

    Mesoporous SBA-15 was synthesized using rice husk ash (RHA) as the silica source and their defective Si-OH groups were grafted with tris(2-aminoethyl) amine (TREN) dendrimers generation through step-wise growth technique. The X-ray diffraction (XRD) and nitrogen adsorption/desorption results of parent SBA-15 obtained from RHA, suggests its resemblance with SBA-15 synthesized using conventional silica sources. Furthermore, the nitrogen adsorption/desorption results of SBA-15/TREN dendrimer generations (G1-G3) illustrates the growth of dendrimer inside the mesopores of SBA-15 and their CO 2 adsorption capacity was determined at 25 °C. The maximum CO 2 adsorption capacity of 5-6 and 7-8 wt% over second and third dendrimer generation was observed which is discernibly higher than the reported melamine and PAMAM dendrimers. The experimental CO 2 adsorption capacity was found to be less than theoretically calculated CO 2 adsorption capacity due to inter and intra molecular amidation as result of steric hindrance during the dendrimer growth. These SBA-15/TREN dendrimer generations also exhibit thermal stability up to 350 °C and CO 2 adsorption capacity remains unaltered upon seven consecutive runs.

  5. Parametric study of a silica gel-water adsorption refrigeration cycle -- The influence of thermal capacitance and heat exchanger UA-values on cooling capacity, power density, and COP

    SciTech Connect

    Boelman, E.C.; Saha, B.B.; Kashiwagi, Takao

    1997-12-31

    The influence of heat exchanger UA-values (adsorber/desorber, evaporator, and condenser) is investigated for an adsorption chiller, with consideration given to the thermal capacitance of the adsorber/desorber by means of a lumped-parameter cycle simulation model developed by the authors and co-workers for the single-stage silica gel-water adsorption chiller. The closed-cycle-type chiller, for use in air conditioning, is driven by low-grade waste heat (85 C [185 F]) and cooled by water at 31 C (88 F) and operates on relatively short cycle times (420 seconds adsorption/desorption; 30 second adsorber/desorber sensible cooling and heating). The results showed cycle performance to be considerably affected by the thermal capacitance and UA-value of the adsorber/desorber, which is attributed to the severe sensible cooling/heating requirements resulting from batched cycle operation. The model is also sensitive to the evaporator UA-value--but to a lesser extent. The condenser UA-value is the least sensitive parameter due to the working pair adsorption behavior in the temperature range defined for desorption and condensation.

  6. Adsorption of chlorophenols from aqueous solutions by pristine and surface functionalized single-walled carbon nanotubes.

    PubMed

    Ding, Han; Li, Xin; Wang, Jun; Zhang, Xiaojian; Chen, Chao

    2016-05-01

    The adsorption of six kinds of chlorophenols on pristine, hydroxylated and carboxylated single-walled carbon nanotubes (SWCNTs) has been investigated. Pseudo-first order and pseudo-second order models were used to describe the kinetic data. All adsorption isotherms were well fitted with Langmuir, Freundlich and Polanyi-Manes models, due to surface adsorption dominating the adsorption process. The close linear relationship between logKow and logKd suggested that hydrophobicity played an important role in the adsorption. The SWCNTs' adsorption capacity for chlorophenols was weakened by addition of oxygen-containing functional groups on the surface, due to the loss of specific surface area, the increase of hydrophilicity and the reduction of π-π interaction. The best adsorption capacity of pristine SWCNTs, SWCNT-OH and SWCNT-COOH for six chlorophenols varied from 19 to 84mg/g, from 19 to 65mg/g and from 17 to 65mg/g, respectively. The effect of pH on the adsorption of 2,6-dichlorophenol (2,6-DCP), was also studied. When pH is over the pKa of 2,6-dichlorophenol (2,6-DCP), its removal dropped sharply. When ionic strength increased (NaCl or KCl concentration from 0 to 0.02mmol/L), the adsorption capacity of 2,6-DCP on pristine SWCNTs decreased slightly. The comparison of chlorophenols adsorption by SWCNTs, MWCNTs and PAC was made, indicating that the adsorption rate of CNTs was much faster than that of PAC. The results provide useful information about the feasibility of SWCNTs as an adsorbent to remove chlorophenols from aqueous solutions.

  7. Adsorption decontamination of radioactive waste solvent by activated alumina and bauxites

    SciTech Connect

    Hassan, N.M.; Marra, J.C.; Kyser, E.A.

    1994-10-01

    An adsorption process utilizing activated alumina and activated bauxite adsorbents was evaluated as a function of operating parameters for the removal of low level radioactive contaminants from organic waste solvent generated in the fuel reprocessing facilities and support operations at Savannah River Site. The waste solvent, 30% volume tributyl phosphate in n-paraffin diluent, was degraded due to hydrolysis and radiolysis reactions of tributyl phosphate and n-paraffin diluent, producing fission product binding degradation impurities. The process, which has the potential for removing these activity-binding degradation impurities from the solvent, was operated downflow through glass columns packed with activated alumina and activated bauxite adsorbents. Experimental breakthrough curves were obtained under various operating temperatures and flow rates. The results show that the adsorption capacity of the activated alumina was in the order 10{sup 4} dpm/g and the capacity of the activated bauxite was 10{sup 5} dpm/g. The performance of the adsorption process was evaluated in terms of dynamic parameters (i.e. adsorption capacity, the height and the efficiency of adsorption zone) in such a way as to maximize the adsorption capacity and to minimize the height of the mass transfer or adsorption zone.

  8. Simultaneous adsorption of Cd²⁺ and BPA on amphoteric surfactant activated montmorillonite.

    PubMed

    Liu, Chongmin; Wu, Pingxiao; Zhu, Yajie; Tran, Lytuong

    2016-02-01

    The study mainly investigated the simultaneous adsorption of bisphenol A (BPA) and Cd(2+) from aqueous solution on octadecane-betaine modified montmorillonite (BS-Mt). The characteristics of the obtained materials were analyzed by X-ray diffraction (XRD), Fourier-transform infrared (FTIR), Specific surface area (BET) and Scanning electron microscopy/Energy disperse spectroscopy (SEM/EDS), confirming that BS-18 was successfully introduced into Mt. Also, factors including initial solution pH, initial Cd(2+)/BPA concentration, contact time and adsorbent dosage on the adsorption processes were shown to be crucial for Cd(2+) adsorption, whereas had negligible effects on BPA adsorption. In this study, we found that pseudo-second-order model fitted well with the adsorption kinetic studies for both Cd(2+) and BPA with an equilibrium time of 24 h. The Cd(2+) and BPA adsorption isotherm could be well described by Freundlich model and Langmuir model, respectively. On the basis of kinetic models, the maximum adsorption capacity of Cd(2+) in aqueous solution was slightly enhanced after modification, indicating that Cd(2+) adsorption on BS-Mt was mainly attributed to direct electrostatic attraction and the chelate reaction, while the dramatic enhancement of maximum adsorption capacity for BPA was due to the hydrophobic interaction.

  9. Temperature sensitivity of cellulase adsorption on lignin and its impact on enzymatic hydrolysis of lignocellulosic biomass.

    PubMed

    Zheng, Yingfu; Zhang, Songping; Miao, Shida; Su, Zhiguo; Wang, Ping

    2013-07-10

    Unproductive enzyme adsorption is an important factor in addition to steric hindrance of lignin that limits the enzymatic hydrolysis of lignocellulosic biomass. While both are important factors, enzymatic hydrolysis of pretreated biomass is most likely conducted in the presence of certain amount of lignin residues that may not necessarily present accessibility hindrance, but can competitively absorb the enzyme. This paper presents a study with purified lignin samples to elucidate the role of unproductive enzyme adsorption. It appeared that lignin adsorbed cellulase quickly at 4 °C with adsorption equilibrium reached within 1h, similar to that observed for crystalline cellulose. Increasing temperature to 50 °C (typical hydrolytic reaction condition) facilitated the rate of cellulase adsorption on cellulose with a peak of adsorption reached at 0.25 h; however, adsorption on lignin was surprisingly slower and took over 12h to reach equilibrium, which was accompanied with a 10-fold increase in adsorption capacity. Despite the high adsorption capacity of lignin (which is comparable to that of cellulose) at 50 °C, the presence of added lignin imposed only minimal impact on the enzyme apparent activity, most likely due to the slow adsorption kinetics of lignin.

  10. Effect of functionalized groups on gas-adsorption properties: syntheses of functionalized microporous metal-organic frameworks and their high gas-storage capacity.

    PubMed

    Wang, Yanlong; Tan, Chunhong; Sun, Zhihao; Xue, Zhenzhen; Zhu, Qilong; Shen, Chaojun; Wen, Yuehong; Hu, Shengmin; Wang, Yong; Sheng, Tianlu; Wu, Xintao

    2014-01-27

    The microporous metal-organic framework (MMOF) Zn4O(L1)2⋅9 DMF⋅9 H2O (1-H) and its functionalized derivatives Zn4O(L1-CH3)2⋅9 DMF⋅9 H2O (2-CH3) and Zn4O(L1-Cl)2⋅9 DMF⋅9 H2O (3-Cl) have been synthesized and characterized (H3L1=4-[N,N-bis(4-methylbenzoic acid)amino]benzoic acid, H3L1-CH3=4-[N,N-bis(4-methylbenzoic acid)amino]-2-methylbenzoic acid, H3L1-Cl=4-[N,N-bis(4-methylbenzoic acid)amino]-2-chlorobenzoic acid). Single-crystal X-ray diffraction analyses confirmed that the two functionalized MMOFs are isostructural to their parent MMOF, and are twofold interpenetrated three-dimensional (3D) microporous frameworks. All of the samples possess enduring porosity with Langmuir surface areas over 1950 cm(2) g(-1). Their pore volumes and surface areas decrease in the order 1-H>2-CH3 >3-Cl. Gas-adsorption studies show that the H2 uptakes of these samples are among the highest of the MMOFs (2.37 wt% for 3-Cl at 77 K and 1 bar), although their structures are interpenetrating. Furthermore, this work reveals that the adsorbate-adsorbent interaction plays a more important role in the gas-adsorption properties of these samples at low pressure, whereas the effects of the pore volumes and surface areas dominate the gas-adsorption properties at high pressure.

  11. Determination of binding capacity and adsorption enthalpy between Human Glutamate Receptor (GluR1) peptide fragments and kynurenic acid by surface plasmon resonance experiments.

    PubMed

    Csapó, E; Majláth, Z; Juhász, Á; Roósz, B; Hetényi, A; Tóth, G K; Tajti, J; Vécsei, L; Dékány, I

    2014-11-01

    The interaction between kynurenic acid (KYNA) and two peptide fragments (ca. 30 residues) of Human Glutamate Receptor 201-300 (GluR1) using surface plasmon resonance (SPR) spectroscopy was investigated. Because of the medical interest in the neuroscience, GluR1 is one of the important subunits of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPAR). AMPARs are ionotoropic glutamate receptors, which are mediating fast synaptic transmission and are crucial for plasticity in the brain. On the other hand, KYNA has been suggested to have neuroprotective activity and it has been considered for apply in therapy in certain neurobiological disorders. In this article the adsorption of the GluR1201-230 and GluR1231-259 peptides were studied on gold biosensor chip. The peptides were chemically bonded onto the gold surface via thiol group of L-cysteine resulted in the formation of peptide monolayer on the SPR chip surface. Because the GluR1231-259 peptide does not contain L-cysteine the Val256 was replaced by Cys256. The cross sectional area and the surface orientation of the studied peptides were determined by SPR and theoretical calculations (LOMETS) as well. The binding capability of KYNA on the peptide monolayer was studied in the concentration range of 0.1-5.0 mM using 150 mM NaCl ionic strength at pH 7.4 (±0.02) in phosphate buffer solutions. In order to determine the binding enthalpy the experiments were carried out between +10°C and +40°C. The heat of adsorption was calculated by using adsorption isotherms at different surface loading of KYNA on the SPR chip.

  12. Breakthrough CO₂ adsorption in bio-based activated carbons.

    PubMed

    Shahkarami, Sepideh; Azargohar, Ramin; Dalai, Ajay K; Soltan, Jafar

    2015-08-01

    In this work, the effects of different methods of activation on CO2 adsorption performance of activated carbon were studied. Activated carbons were prepared from biochar, obtained from fast pyrolysis of white wood, using three different activation methods of steam activation, CO2 activation and Potassium hydroxide (KOH) activation. CO2 adsorption behavior of the produced activated carbons was studied in a fixed-bed reactor set-up at atmospheric pressure, temperature range of 25-65°C and inlet CO2 concentration range of 10-30 mol% in He to determine the effects of the surface area, porosity and surface chemistry on adsorption capacity of the samples. Characterization of the micropore and mesopore texture was carried out using N2 and CO2 adsorption at 77 and 273 K, respectively. Central composite design was used to evaluate the combined effects of temperature and concentration of CO2 on the adsorption behavior of the adsorbents. The KOH activated carbon with a total micropore volume of 0.62 cm(3)/g and surface area of 1400 m(2)/g had the highest CO2 adsorption capacity of 1.8 mol/kg due to its microporous structure and high surface area under the optimized experimental conditions of 30 mol% CO2 and 25°C. The performance of the adsorbents in multi-cyclic adsorption process was also assessed and the adsorption capacity of KOH and CO2 activated carbons remained remarkably stable after 50 cycles with low temperature (160°C) regeneration.

  13. Enthalpy and entropy effects in hydrogen adsorption on carbon nanotubes.

    PubMed

    Efremenko, Irena; Sheintuch, Moshe

    2005-07-05

    Interaction energies and entropies associated with hydrogen adsorption on the inner and outer surfaces of zigzag single-wall carbon nanotubes (SWCNT) of various diameters are analyzed by means of molecular mechanics, density functional theory, and ab initio calculations. For a single molecule the strongest interaction, which is 3.5 greater than that with the planar graphite sheet, is found inside a (8,0) nanotube. Adsorption on the outer surfaces is weaker than that on graphite. Due to the steric considerations, both processes are accompanied by an extremely strong decline in entropy. Absence of specific adsorption sites and weak attractive interaction between hydrogen molecules within carbon nanotubes results in their close packing at low temperatures. Using the calculated geometric and thermodynamic parameters in Langmuir isotherms we predict the adsorption capacity of SWCNTs at room temperature to be smaller than 1 wt % even at 100 bar.

  14. Preparation of char from lotus seed biomass and the exploration of its dye removal capacity through batch and column adsorption studies.

    PubMed

    Nethaji, S; Sivasamy, A; Kumar, R Vimal; Mandal, A B

    2013-06-01

    Char was obtained from lotus seed biomass by a simple single-step acid treatment process. It was used as an adsorbent for the removal of malachite green dye (MG) from simulated dye bath effluent. The adsorbent was characterized for its surface morphology, surface functionalities, and zero point charge. Batch studies were carried out by varying the parameters such as initial aqueous pH, adsorbent dosage, adsorbent particle size, and initial adsorbate concentration. Langmuir and Freundlich isotherms were used to test the isotherm data and the Freundlich isotherm best fitted the data. Thermodynamic studies were carried out and the thermodynamic parameters such as ∆G, ∆H, and ∆S were evaluated. Adsorption kinetics was carried out and the data were tested with pseudofirst-order model, pseudosecond-order model, and intraparticle diffusion model. Adsorption of MG was not solely by intraparticle diffusion but film diffusion also played a major role. Continuous column experiments were also conducted using microcolumn and the spent adsorbent was regenerated using ethanol and was repeatedly used for three cycles in the column to determine the reusability of the regenerated adsorbent. The column data were modeled with the modeling equations such as Adam-Bohart model, Bed Depth Service Time (BDST) model, and Yoon-Nelson model for all the three cycles.

  15. Evaluation of the adsorptive behavior of cesium and strontium on hydroxyapatite and zeolite for decontamination of radioactive substances.

    PubMed

    Ozeki, K; Aoki, H

    2016-08-12

    Removal of radioactive substances, such as cesium (Cs) and strontium (Sr), has become an emerging issue after the Fukushima Daiichi Nuclear Power Plant Disaster. To assess the possibility that hydroxyapatite (HA) and zeolites can be used for removal of radioactive substances, the adsorption capacities of Cs and Sr on the HA and a zeolite were investigated. The influence of Fe ions on Cs and Sr adsorption on the HA and the zeolite was also evaluated, because Fe ions are the most effective inhibitor of Cs adsorption on the zeolite.In the Cs adsorption process on the HA and the zeolite, the zeolite showed a higher adsorption ratio than the HA, and the maximum sorption capacity of the zeolite was calculated as 196 mg/g, whereas the HA showed a higher Sr adsorption ratio than the zeolite. The maximum sorption capacity of Sr on the HA was 123 mg/g. Under coexistence with Fe, Cs adsorption on the zeolite decreased with increasing Fe concentration, reaching 2.0 ± 0.8% at 0.1 M Fe concentration. In contrast, Cs adsorption on the zeolite was improved by adding the HA. In the case of coexistence of the HA, the Cs adsorption on the mixture of the HA and the zeolite was 52.4% ± 3.6 % at 0.1 M Fe concentration, although Cs adsorption on the HA alone was quite low. In the Fe adsorption processes of the HA and the zeolite, the HA exhibited a maximum sorption capacity of 256 mg/g, which was much higher than that of the zeolite (111 mg/g). The high affinity of Fe on the HA contributes to the improvement of the deteriorated Cs adsorption on the zeolite due to Fe ions.

  16. The rectorite/carbon composites: Fabrication, modification and adsorption.

    PubMed

    Feng, Zhitao; Liu, Dan; Ma, Xiaofei

    2016-02-01

    The rectorite (REC)/carbon composites (RECCs) were prepared with hydrothermal carbonization using starch as carbon source and REC as the template. RECCs were modified with carbon disulfide (CS2) to obtain RECC xanthate (RECCX) composites. The hydrothermal process introduced a large number of oxygen-containing groups by depositing carbon layers onto the surface of REC, and the CS2 modification brought xanthate groups into REC. The adsorption process of Pb(2+) was investigated. Compared with REC, both RECC and RECCX could absorb more Pb(2+). The oxygen-containing groups increased the Pb(2+) adsorption in RECC. With the increasing of CS2 dosages, the adsorption capacities of RECCXs obviously improved due to the formation of the chelation between Pb(2+) and xanthate groups. The kinetic adsorption and the isotherm data matched the pseudo-second-order model and the Langmuir model well. The maximum adsorption capacities could reach 225.7 and 431.0 mg/g for RECC and RECCX, respectively. RECCXs were competitive with other absorbents, because REC, carbon layers and xanthate groups in RECCX composites all contributed to the Pb(2+) adsorption. RECCX could be easily regenerated with ethylenediaminetetraacetic acid disodium salt (EDTA) solution.

  17. Adsorptive removal of cesium using bio fuel extraction microalgal waste.

    PubMed

    Inoue, Katsutoshi; Gurung, Manju; Adhikari, Birendra Babu; Alam, Shafiq; Kawakita, Hidetaka; Ohto, Keisuke; Kurata, Minoru; Atsumi, Kinya

    2014-04-30

    An adsorption gel was prepared from microalgal waste after extracting biodiesel oil by a simple chemical treatment of crosslinking using concentrated sulfuric acid. The adsorbent exhibited notably high selectivity and adsorption capacity towards Cs(+) over Na(+) from aqueous solutions, within the pH range of slightly acidic to neutral. The adsorption followed Langmuir isotherm and the maximum adsorption capacity of the gel for Cs(+) calculated from Langmuir model was found to be 1.36 mol kg(-1). Trace concentration of Cs(+) ions present in aqueous streams was successfully separated from Na(+) ions using a column packed with the adsorbent at pH 6.5. The adsorption capacity of the gel towards Cs(+) in column operation was 0.13 mol kg(-1). Although the adsorbed Cs(+) ions were easily eluted using 1M hydrochloric acid solution, simple incineration is proposed as an alternative for the treatment of adsorbent loaded with radioactive Cs(+) ions due to the combustible characteristics of this adsorbent.

  18. Comparison study of phosphorus adsorption on different waste solids: Fly ash, red mud and ferric-alum water treatment residues.

    PubMed

    Wang, Ying; Yu, Yange; Li, Haiyan; Shen, Chanchan

    2016-12-01

    The adsorption of phosphorus (P) onto three industrial solid wastes (fly ash, red mud and ferric-alum water treatment residual (FAR)) and their modified materials was studied systematically via batch experiments. Compared with two natural adsorbents (zeolite and diatomite), three solid wastes possessed a higher adsorption capacity for P because of the higher Fe, Al and Ca contents. After modification (i.e., the fly ash and red mud modified by FeCl3 and FARs modified by HCl), the adsorption capacity increased, especially for the modified red mud, where more Fe bonded P was observed. The P adsorption kinetics can be satisfactorily fitted using the pseudo-second-order model. The Langmuir model can describe well the P adsorption on all of the samples in our study. pH and dissolved organic matter (DOM) are two important factors for P adsorption. Under neutral conditions, the maximum adsorption amount on the modified materials was observed. With the deviation from pH7, the adsorption amount decreased, which resulted from the change of P species in water and surface charges of the adsorbents. The DOM in water can promote P adsorption, which may be due to the promotion effects of humic-Fe(Al) complexes and the pH buffer function exceeds the depression of competitive adsorption.

  19. Adsorption-desorption reactions of selenium (VI) in tropical cultivated and uncultivated soils under Cerrado biome.

    PubMed

    Lessa, J H L; Araujo, A M; Silva, G N T; Guilherme, L R G; Lopes, G

    2016-12-01

    Soil management may affect selenium (Se) adsorption capacity. This study investigated adsorption and desorption of Se (VI) in selected Brazilian soils from the Cerrado biome, an area of ever increasing importance for agriculture expansion in Brazil. Soil samples were collected from cultivated and uncultivated soils, comprising clayed and sandy soils. Following chemical and mineralogical characterization, soil samples were subjected to Se adsorption and desorption tests. Adsorption was evaluated after a 72-h reaction with increasing concentrations of Se (0-2000 μg L(-1)) added as Na2SeO4 in a NaCl electrolyte solution (pH 5.5; ionic strength 15 mmol L(-1)). Desorption, as well as distribution coefficients (Kd) for selenate were also assessed. Soil management affected Se adsorption capacity, i.e., Se adsorbed amounts were higher for uncultivated soils, when compared to cultivated ones. Such results were also supported by data of Kd and maximum adsorption capacity of Se. This fact was attributed mainly to the presence of greater amounts of competing anions, especially phosphate, in cultivated soils, due to fertilizer application. Phosphate may compete with selenate for adsorption sites, decreasing Se retention. For the same group of soils (cultivated and uncultivated), Se adsorption was greater in the clayed soils compared to sandy ones. Our results support the idea that adding Se (VI) to the soil is a good strategy to increase Se levels in food crops (agronomic biofortification), especially when crops are grown in soils that have been cultivated over the time due to their low Se adsorption capacity (high Se availability).

  20. Cr(VI) Adsorption on Red Mud Modified by Lanthanum: Performance, Kinetics and Mechanisms.

    PubMed

    Cui, You-Wei; Li, Jie; Du, Zhao-Fu; Peng, Yong-Zhen

    Water pollution caused by the highly toxic metal hexavalent chromium (Cr(VI)) creates significant human health and ecological risks. In this study, a novel adsorbent was used to treat Cr(VI)-containing wastewater; the adsorbent was prepared using red mud (RM) generated from the alumina production industry and the rare earth element lanthanum. This study explored adsorption performance, kinetics, and mechanisms. Results showed that the adsorption kinetics of the RM modified by lanthanum (La-RM), followed the pseudo-second-order model, with a rapid adsorption rate. Cr(VI) adsorption was positively associated with the absorbent dose, pH, temperature, and initial Cr(VI) concentration; coexisting anions had little impact. The maximum Cr(VI) adsorption capacity was 17.35 mg/g. Cr(VI) adsorption on La-RM was a mono-layer adsorption pattern, following the Langmuir isotherm model. Thermodynamic parameters showed the adsorption was spontaneous and endothermic. The adsorption of Cr(VI) on La-RM occurred as a result of LaOCl formation on the RM surface, which in turn further reacted with Cr(VI) in the wastewater. This study highlighted a method for converting industrial waste into a valuable material for wastewater treatment. The novel absorbent could be used as a potential adsorbent for treating Cr(VI)-contaminating wastewater, due to its cost-effectiveness and high adsorption capability.

  1. Cr(VI) Adsorption on Red Mud Modified by Lanthanum: Performance, Kinetics and Mechanisms

    PubMed Central

    Cui, You-Wei; Li, Jie; Du, Zhao-Fu; Peng, Yong-Zhen

    2016-01-01

    Water pollution caused by the highly toxic metal hexavalent chromium (Cr(VI)) creates significant human health and ecological risks. In this study, a novel adsorbent was used to treat Cr(VI)-containing wastewater; the adsorbent was prepared using red mud (RM) generated from the alumina production industry and the rare earth element lanthanum. This study explored adsorption performance, kinetics, and mechanisms. Results showed that the adsorption kinetics of the RM modified by lanthanum (La-RM), followed the pseudo-second-order model, with a rapid adsorption rate. Cr(VI) adsorption was positively associated with the absorbent dose, pH, temperature, and initial Cr(VI) concentration; coexisting anions had little impact. The maximum Cr(VI) adsorption capacity was 17.35 mg/g. Cr(VI) adsorption on La-RM was a mono-layer adsorption pattern, following the Langmuir isotherm model. Thermodynamic parameters showed the adsorption was spontaneous and endothermic. The adsorption of Cr(VI) on La-RM occurred as a result of LaOCl formation on the RM surface, which in turn further reacted with Cr(VI) in the wastewater. This study highlighted a method for converting industrial waste into a valuable material for wastewater treatment. The novel absorbent could be used as a potential adsorbent for treating Cr(VI)-contaminating wastewater, due to its cost-effectiveness and high adsorption capability. PMID:27658113

  2. Adsorption removal of tannic acid from aqueous solution by polyaniline: Analysis of operating parameters and mechanism.

    PubMed

    Sun, Chencheng; Xiong, Bowen; Pan, Yang; Cui, Hao

    2017-02-01

    Polyaniline (PANI) prepared by chemical oxidation was studied for adsorption removal of tannic acid (TA) from aqueous solution. Batch adsorption studies were carried out under different adsorbent dosages, pH, ionic strength, initial TA concentration and coexisting anions. Solution pH had an important impact on TA adsorption onto PANI with optimal removal in the pH range of 8-11. TA adsorption on PANI at three ionic strength levels (0.02, 0.2 and 2molL(-1) NaCl) could be well described by Langmuir model (monolayer adsorption process) and the maximum adsorption capacity was 230, 223 and 1023mgg(-1), respectively. Kinetic data showed that TA adsorption on PANI fitted well with pseudo-second-order model (controlled by chemical process). Among the coexisting anions tested, PO4(3-) significantly inhibited TA adsorption due to the enhancement of repulsive interaction. Continuous flow adsorption studies indicated good flexibility and adaptability of the PANI adsorbent under different flow rates and influent TA concentrations. The mechanism controlling TA adsorption onto PANI under different operating conditions was analyzed with the combination of electrostatic interactions, hydrogen bonding, π-π interactions and Van der Waals interactions.

  3. K4Nb6O17·4.5H2O: a novel dual functional material with quick photoreduction of Cr(VI) and high adsorptive capacity of Cr(III).

    PubMed

    Ma, Yuli; Liu, Xiaoqing; Li, Yang; Su, Yiguo; Chai, Zhanli; Wang, Xiaojing

    2014-08-30

    A series of orthorhombic phase K4Nb6O17·4.5H2O was synthesized via a hydrothermal approach. When presented in an acidic pH range, K4Nb6O17·4.5H2O showed a strong ability in quick reduction from Cr(VI) to Cr(III). The resulted Cr(III) ions were removed by an effective adsorption through simply adjusting the solution pH from strong acidity to near neutrality, owing to the sample's unique nano-sheet structure with a wide layer spacing. The Cr(III) ions adsorbed onto samples were released again for reusing by eluting with 1molL(-1) HCl solution, and K4Nb6O17·4.5H2O regenerated by immersing in a KOH solution. The reduction efficiency of Cr(VI) was still up to 98% after irradiation for 60min, and the removal efficiency of Cr(III) ions was as high as 83% even after five cycles. Therefore, K4Nb6O17·4.5H2O is clearly demonstrated to be an excellent dual functional material with quick photoreduction of Cr(VI) and high adsorptive capacity of Cr(III). The relevant materials reported herein might be found various environment-related applications.

  4. Adsorption of aqueous copper on peanut hulls

    NASA Astrophysics Data System (ADS)

    Davis, Kanika Octavia

    A method was established for measuring the adsorption of Cu(II) from aqueous solution to unmodified and modified peanut hulls at constant temperature and pH. Modification of the hulls was performed by oxidation with alkaline hydrogen peroxide. During the modification process, the hydrogen peroxide solubilizes the lignin component, making the surface more porous which increases the availability of binding sites, while simultaneously oxidizing the cellulose. The oxidation of alcohol groups creates more binding sites by creating functional groups such as COO-, which increases chelation to metal ions. Fourier transform infrared spectroscopy confirms delignification of the peanut hulls by the disappearance of carboxyl peaks of the modified hulls, which were originally produced from the lignin content. Although, oxidation is not fully confirmed, it is not ruled out because the expected carboxylate peak (1680 cm-1) maybe overshadowed by a broad peak due to OH bending of water adsorbed to the hulls. Hulls adsorbed copper from solutions in the concentration range of 50-1000 ppm of CuCl2. Concentrations of pre- and post-adsorption solutions were determined using inductively coupled plasma optical emission spectroscopy. The adsorption isotherms were fit to known two and three-parameter models, evaluated and the binding mechanism was inferred. Maximum surface coverage was 3.5 +/- 0.6 mg Cu2+ /g hull for unmodified hulls and 11 +/- 1 mg Cu2+/g hull for modified hulls. The adsorption for the hulls is best described by the Langmuir model, suggesting monolayer, homogeneous adsorption. With a free energy of adsorption of 10.5 +/- 0.9 kJ/mol for unmodified hulls and 14.5 +/-0.4 kJ/mol for modified hulls, the process is categorized as chemisorption for both types of hulls. The adsorption for both hulls is also described by the Redlich-Peterson model, giving beta nearer to 1 than 0, which further suggests homogeneous adsorption described by the Langmuir model. After rinsing the hulls

  5. Acid-base treated vermiculite as high performance adsorbent: Insights into the mechanism of cationic dyes adsorption, regeneration, recyclability and stability studies.

    PubMed

    Stawiński, Wojciech; Węgrzyn, Agnieszka; Dańko, Tomasz; Freitas, Olga; Figueiredo, Sónia; Chmielarz, Lucjan

    2017-04-01

    Additional treatment with NaOH of acid activated vermiculite results in even higher increase in the adsorption capacity in comparison to samples modified only in acidic solution (first step of activation) with respect to raw material. Optimization of treatment conditions and adsorption capacity for two cationic dyes (methylene blue (MB) and astrazon red (AR)), also as binary mixture, was evaluated. The capacity, based on column studies, increased from 48 ± 2 to 203 ± 4 mg g(-1) in the case of methylene blue and from 51 ± 1 to 127 ± 2 mg g(-1) in the case of astrazon red on starting and acid-base treated material, respectively. It was shown that adsorption mechanism changes for both cationic dyes after NaOH treatment and it results in decrease of adsorption rate. In binary mixtures methylene blue is bound stronger by adsorbent and astrazon red may be removed in initial stage of adsorption. Extensive studies on desorption/regeneration process proved high efficiency in recyclable use of all materials. Although cation exchange capacity decreases due to acid treatment, after base treatment exchange properties are used more efficiently. On the other hand, increased specific surface area has less significant contribution into the adsorption potential of studied materials. Obtained adsorbents worked efficiently in 7 adsorption-regeneration cycles and loss of adsorption capacity was observed only in two first cycles.

  6. Adsorption decontamination of radioactive waste solvent by activated alumina and bauxites

    SciTech Connect

    Hassan, N.M.; Matthews, R.S.; Marra, J.C.; Kyser, E.A.

    1995-06-01

    An adsorption process utilizing activated alumina and activated bauxite adsorbents was evaluated as a function of operating parameters for the removal of low level radioactive contaminants from organic waste solvent generated in the fuel reprocessing facilities and support operations at Savannah River Site. The waste solvent, 30 vol% tributyl phosphate in n-paraffin diluent, was degraded due to hydrolysis and radiolysis reaction of tributyl phosphate and n-paraffin diluent, producing fission product binding degradation impurities. The process, which has the potential for removing these activity-binding degradation impurities from the solvent, was operated downflow through glass columns packed with activated alumina and activated bauxite adsorbents. Experimental breakthrough curves were obtained under various operating temperatures and flow rates. The results show that the adsorption capacities of activated alumina and activated bauxite were in the order of 10{sup 4} and 10{sup 5} dpm/g of adsorbent, respectively. The performance of the adsorption process was evaluated in terms of dynamic parameters (i.e., adsorption capacity, the height and the efficiency of adsorption zone) in such a way as to maximize the adsorption capacity and to minimize the height of the mass transfer or adsorption zone.

  7. Dye Adsorption Behavior of Polyvinyl Alcohol/Glutaraldehyde/β-Cyclodextrin Polymer Membranes

    NASA Astrophysics Data System (ADS)

    Ghemati, Dj.; Aliouche, Dj.

    2014-05-01

    Crosslinked polyvinyl alcohol/glutaraldehyde (PVA/GA) membranes were prepared, and attempts to obtain hydrophilic crosslinked PVA membranes were made by adding various amounts of β-cyclodexrin (β-CD), which is a typical cyclic oligosaccharide able to form inclusion complexes with organic host molecules (host-guest complexes). Thus, membranes of PVA/GA/β-CD were synthesized. The membranes were characterized by infrared spectroscopy (FTIR) and swelling measurements. The ability of cyclodextrin to include a wide variety of chemicals was also exploited for the dye adsorption to show the potentialities of the membranes in textile liquid waste processing. Adsorption of reactive methyl orange, and methylene blue dyes on PVA/GA/β-CD membranes was consequently studied using UV-Vis spectroscopy at wavelengths of 547, 463, and 660 nm. Adsorption reached equilibrium after 24 h. Results indicated that there is no covalent bond formation between PVA and β-CD; the β-CD is completely mixed into the PVA matrix polymer. The adsorption capacity increases with increasing amounts of cyclodextrin; the maximum adsorption capacity was obtained with 8% β-CD. Therefore, the change in adsorption capacities may be due to the dye structure effect, and the negative value of free energy indicated the spontaneous nature of adsorption.

  8. Elimination of aromatic pollutants present in wastewater by adsorption over zeolites

    NASA Astrophysics Data System (ADS)

    Koubaissy, Bachar; Toufaily, Joumana; El-murr, Maya; Hamieh, Tayssir; Magnoux, Patrick; Joly, Guy

    Phenol and substituted phenols are toxic organic pollutants commonly present in industrial waste streams especially in industrial wastewater. Water treatment by activated carbon adsorption technique is very advantageous due to their high adsorption capacity and low cost of these materials but it is poorly regenerable In recent years, researchers have focused on class of interesting recyclable adsorbents based on hydrophobic zeolites (Si / Al ratio high) in the field of water treatment. The study on adsorption showed that the affinity of phenol drifts toward the FAU is dependent on the pH solution and on the pollutant solubility in water and finally their economic cost for regeneration after saturation.

  9. Adsorption of SO2 on bituminous coal char and activated carbon fiber prepared from phenol formaldehyde

    USGS Publications Warehouse

    DeBarr, Joseph A.; Lizzio, Anthony A.; Daley, Michael A.

    1996-01-01

    Carbon-based materials are used commercially to remove SO2 from coal combustion flue gases. Historically, these materials have consisted of granular activated carbons prepared from lignite or bituminous coal. Recent studies have reported that activated carbon fibers (ACFs) may have potential in this application due to their relatively high SO2 adsorption capacity. In this paper, a comparison of SO2 adsorption for both coal-based carbons and ACFs is presented, as well as ideas on carbon properties that may influence SO2 adsorption

  10. Quantitative determination of BAF312, a S1P-R modulator, in human urine by LC-MS/MS: prevention and recovery of lost analyte due to container surface adsorption.

    PubMed

    Li, Wenkui; Luo, Suyi; Smith, Harold T; Tse, Francis L S

    2010-02-15

    Analyte loss due to non-specific binding, especially container surface adsorption, is not uncommon in the quantitative analysis of urine samples. In developing a sensitive LC-MS/MS method for the determination of a drug candidate, BAF312, in human urine, a simple procedure was outlined for identification, confirmation and prevention of analyte non-specific binding to a container surface and to recover the 'non-specific loss' of an analyte, if no transfer has occurred to the original urine samples. Non-specific binding or container surface adsorption can be quickly identified by using freshly spiked urine calibration standards and pre-pooled QC samples during a LC-MS/MS feasibility run. The resulting low recovery of an analyte in urine samples can be prevented through the use of additives, such as the non-ionic surfactant Tween-80, CHAPS and others, to the container prior to urine sample collection. If the urine samples have not been transferred from the bulk container, the 'non-specific binding' of an analyte to the container surface can be reversed by the addition of a specified amount of CHAPS, Tween-80 or bovine serum albumin, followed by appropriate mixing. Among the above agents, Tween-80 is the most cost-effective. beta-cyclodextrin may be suitable in stabilizing the analyte of interest in urine via pre-treating the matrix with the agent. However, post-addition of beta-cyclodextrin to untreated urine samples does not recover the 'lost' analyte due to non-specific binding or container surface adsorption. In the case of BAF312, a dynamic range of 0.0200-20.0 ng/ml in human urine was validated with an overall accuracy and precision for QC sample results ranging from -3.2 to 5.1% (bias) and 3.9 to 10.2% (CV), respectively. Pre- and post-addition of 0.5% (v/v) Tween-80 to the container provided excellent overall analyte recovery and minimal MS signal suppression when a liquid-liquid extraction in combination with an isocratic LC separation was employed. The

  11. Development of novel delivery system for warfarin based on mesoporous silica: adsorption characteristics of silica materials for the anticoagulant.

    PubMed

    Dolinina, Ekaterina S; Vorobyeva, Evgeniya V; Parfenyuk, Elena V

    2016-08-01

    The adsorption of the anticoagulant warfarin onto unmodified (UMS) and modified (phenyl (PhMS), methyl (MMS), mercaptopropyl (MPMS)) mesoporous silica materials was studied at pH 1.6 and 7.4 and in the temperature range of 293-325 K. The silica materials were prepared by sol-gel method for further characterization by FTIR spectroscopy, N2 adsorption/desorption method, transmission electron microscopy and zeta potential measurements. The effects of medium pH, temperature and surface modification of mesoporous silica material on their adsorption characteristics (adsorption capacity, thermodynamic parameters of adsorption) relative to anticoagulant warfarin were investigated. It was found that medium acid-base properties strongly affect the adsorption of warfarin due to the pH-dependent structural diversity of the drug and ionization state of the silica surfaces. The adsorption capacity of the silica materials at pH 1.6 decreases in the order: MMS > MPMS > UMS > PhMS. The influence of various non-covalent interactions on the adsorption capacity of the silica materials and energy of the drug-silica interactions is discussed. These results may be useful for the development of a novel delivery system of warfarin.

  12. Two fold modified chitosan for enhanced adsorption of hexavalent chromium from simulated wastewater and industrial effluents.

    PubMed

    Kahu, S S; Shekhawat, A; Saravanan, D; Jugade, R M

    2016-08-01

    Ionic solid (Ethylhexadecyldimethylammoniumbromide) impregnated phosphated chitosan (ISPC) was synthesized and applied for enhanced adsorption of hexavalent chromium from industrial effluent. The compound obtained was extensively characterized using instrumental techniques like FT-IR, TGA-DTA, XRD, SEM, BET and EDX. ISPC showed high adsorption capacity of 266.67mg/g in accordance with Langmuir isotherm model at pH 3.0 due to the presence of multiple sites which contribute for ion pair and electrostatic interactions with Cr(VI) species. The sorption kinetics and thermodynamic studies revealed that adsorption of Cr(VI) followed pseudo-second-order kinetics with exothermic and spontaneous behaviour. Applicability of ISPC for higher sample volumes was discerned through column studies. The real chrome plating industry effluent was effectively treated with total chromium recovery of 94%. The used ISPC was regenerated simply by dilute ammonium hydroxide treatment and tested for ten adsorption-desorption cycles with marginal decrease in adsorption efficiency.

  13. Roles of metal/activated carbon hybridization on elemental mercury adsorption.

    PubMed

    Bae, Kyong-Min; Kim, Byung-Joo; Rhee, Kyong Yop; Park, Soo-Jin

    2014-08-01

    In this study, the elemental mercury removal behavior of metal (copper or nickel)/activated carbon hybrid materials were investigated. The pore structures and total pore volumes of the hybrid materials were analyzed using the N2/77 K adsorption isotherms. The microstructure and surface morphologies of the hybrid materials were characterized by X-ray diffraction and scanning electron microscopy, respectively. In the experimental results, the elemental mercury adsorption capacities of all copper/activated carbon hybrid materials were higher than that of the as-received material despite the decrease in specific surface areas and total pore volumes after the metal loading. All the samples containing the metal particles showed excellent elemental mercury adsorption. The Ni/ACs exhibited superior elemental mercury adsorption to those of Cu/ACs. This suggests that Ni/ACs have better elemental mercury adsorption due to the higher activity of nickel.

  14. Adsorption of tetracycline on kaolinite with pH-dependent surface charges.

    PubMed

    Li, Zhaohui; Schulz, Laura; Ackley, Caren; Fenske, Nancy

    2010-11-01

    Kaolinite is a major type of clay minerals in soils of warm and humid climate. Although it has a much lower cation exchange capacity (CEC) and specific surface area compared to swelling clays, its ubiquitous existence as well as its pH-dependent surface charge makes it an important component to study the interactions between contaminants and soils. Tetracycline (TC) is a group of broad spectrum antibiotics used extensively in human and veterinary medicine. It has a high aqueous solubility and a long environmental half-life. In this study, the interactions between TC and kaolinite in aqueous solution were investigated in batch tests and supplemented by FTIR analyses. The adsorption of TC on kaolinite was mainly on the external surfaces via cation exchange as confirmed by stoichiometric desorption of exchangeable cations and simultaneous adsorption of H(+) rather than due to complexation. Under acidic conditions, a reduction in surface charge, thus the CEC, resulted in more desorption of exchangeable cations compared to TC adsorption. Fitting of the experimental data to the adsorption of different species revealed that TC(+) accounted for 4/5 of the total TC adsorbed with the remaining by zwitterion TC(0), possible via hydrogen bonding. At higher temperature, the pKa2 and pKa3 values seem to shift a pH unit lower. Due to its pH-dependent charge of kaolinite, TC adsorption is more pH dependent. The TC adsorption capacity on kaolinite was much lower compared to that on swelling clays. However, the adsorption rate constant was faster than that on swelling clays owing to surface adsorption instead of intercalation. Despite its low TC adsorption capacity, the ubiquitous existence of kaolinite in soils of warm climate may play a vital role in the fate and transport of TC in these soils.

  15. Investigation of mono/competitive adsorption of environmentally relevant ionized weak acids on graphite: impact of molecular properties and thermodynamics.

    PubMed

    Moustafa, Ahmed M A; McPhedran, Kerry N; Moreira, Jesús; Gamal El-Din, Mohamed

    2014-12-16

    The thermodynamics of adsorption and competitive interactions of five weak acids on a graphite surface was assessed in alkaline solutions. Adsorption of the acids in mono- and multicompound solutions followed their Freundlich isotherms which suggest a diversity of graphite adsorption sites as confirmed by the presence of carboxylic and phenolic groups observed on graphite surfaces. Thermodynamic calculations assigned the formation of the negatively charged assisted hydrogen bond (-CAHB) between ionized solutes and adsorbent surface groups as the possible adsorption mechanism. However, the similar pKa values of current acids resulted in comparable free energies for -CAHB formation (ΔG(-CAHB)) being less than solvation free energies (ΔGSolv). Thus, additional ΔG is supplemented by increased hydrophobicity due to proton exchange of ionized acids with water (ΔΔG Hydrophobicity). Adsorption capacities and competition coefficients indicated that ΔΔG Hydrophobicity values depend on the neutral and ionized acid Kow. Competitive adsorption implies that multilayer adsorption may occur via hydrophobic bonding with the CH3 ends of the self-assembled layer which affects the acid adsorption capacities in mixtures as compared to monocompound solutions. The determination of adsorption mechanisms will assist in understanding of the fate and bioavailability of emerging and classical weak acids released into natural waters.

  16. Influence of pyrolysis temperature on characteristics and phosphate adsorption capability of biochar derived from waste-marine macroalgae (Undaria pinnatifida roots).

    PubMed

    Jung, Kyung-Won; Kim, Kipal; Jeong, Tae-Un; Ahn, Kyu-Hong

    2016-01-01

    The collected roots of Undaria pinnatifida, the main waste in farming sites, accounting for 40-60% of annual production, was pyrolyzed under temperature ranging from 200 to 800°C to evaluate the influence of pyrolysis temperature on biochar properties and phosphate adsorption capacity. It was confirmed that an increase in the pyrolysis temperature led to a decrease of the yield of biochar, while ash content remained almost due to carbonization followed by mineralization. Elemental analysis results indicated an increase in aromaticity and decreased polarity at a high pyrolysis temperature. When the pyrolysis temperature was increased up to 400°C, the phosphate adsorption capacity was enhanced, while a further increase in the pyrolysis temperature lowered the adsorption capacity due to blocked pores in the biochar during pyrolysis. Finally, a pot experiment revealed that biochar derived from waste-marine macroalgae is a potent and eco-friendly alternative material for fertilizer after phosphate adsorption.

  17. Removal of mercury by adsorption: a review.

    PubMed

    Yu, Jin-Gang; Yue, Bao-Yu; Wu, Xiong-Wei; Liu, Qi; Jiao, Fei-Peng; Jiang, Xin-Yu; Chen, Xiao-Qing

    2016-03-01

    Due to natural and production activities, mercury contamination has become one of the major environmental problems over the world. Mercury contamination is a serious threat to human health. Among the existing technologies available for mercury pollution control, the adsorption process can get excellent separation effects and has been further studied. This review is attempted to cover a wide range of adsorbents that were developed for the removal of mercury from the year 2011. Various adsorbents, including the latest adsorbents, are presented along with highlighting and discussing the key advancements on their preparation, modification technologies, and strategies. By comparing their adsorption capacities, it is evident from the literature survey that some adsorbents have shown excellent potential for the removal of mercury. However, there is still a need to develop novel, efficient adsorbents with low cost, high stability, and easy production and manufacture for practical utility.

  18. Adsorption behavior of Zn(II) on calcinated Chinese loess.

    PubMed

    Tang, Xiaowu; Li, Zhenze; Chen, Yunmin

    2009-01-30

    Chinese loess has proven to be effective in removing Zn(II) from aqueous solutions, but the resultant adsorbent-water slurry is difficult to separate. In this paper, the crude loess was calcinated to improve the separation efficiency of slurries in terms of sedimentary rate by increasing the particle sizes of the adsorbent. The sorption capacities of different sorbents, including crude loess, calcinated loess, de-organic crude loess and acid-treated calcinated loess, were obtained and sequenced. The adsorption capacity of the calcinated loess towards Zn(II) was found to be as high as 113.6 mg g(-1). The adsorption isotherms and kinetics of calcinated loess were best-fit with the Freundlich isotherm and the pseudo-second order kinetics, respectively. The thermodynamic analysis revealed that the adsorption was exothermic and spontaneous with a high preference for Zn(II) removal. The adsorption of Zn(II) on calcinated loess implies an ion exchange of the solute with calcite and goethite due to the observed FT-IR and XRD patterns as well as the predicted mean free energies (-11.58 to -9.28 kJ mol(-1) by D-R model). The byproduct of adsorption can be purified and refreshed by using a 0.01 M HCl solution.

  19. Nitroimidazoles adsorption on activated carbon cloth from aqueous solution.

    PubMed

    Ocampo-Pérez, R; Orellana-Garcia, F; Sánchez-Polo, M; Rivera-Utrilla, J; Velo-Gala, I; López-Ramón, M V; Alvarez-Merino, M A

    2013-07-01

    The objective of this study was to analyze the equilibrium and adsorption kinetics of nitroimidazoles on activated carbon cloth (ACC), determining the main interactions responsible for the adsorption process and the diffusion mechanism of these compounds on this material. The influence of the different operational variables, such as ionic strength, pH, temperature, and type of water (ultrapure, surface, and waste), was also studied. The results obtained show that the ACC has a high capacity to adsorb nitroimidazoles in aqueous solution. Electrostatic interactions play an important role at pH<3, which favors the repulsive forces between dimetridazole or metronidazole and the ACC surface. The formation of hydrogen bonds and dispersive interactions play the predominant role at higher pH values. Modifications of the ACC with NH3, K2S2O8, and O3 demonstrated that its surface chemistry plays a predominant role in nitroimidazole adsorption on this material. The adsorption capacity of ACC is considerably high in surface waters and reduced in urban wastewater, due to the levels of alkalinity and dissolved organic matter present in the different types of water. Finally, the results of applying kinetic models revealed that the global adsorption rate of dimetridazole and metronidazole is controlled by intraparticle diffusion.

  20. Nitrogen-doped porous aromatic frameworks for enhanced CO2 adsorption

    DOE PAGES

    Fu, Jia; Wu, Jianzhong; Custelcean, Radu; ...

    2014-10-07

    Recently synthesized porous aromatic frameworks (PAFs) exhibit extremely high surface areas and exceptional thermal and hydrothermal stabilities. Using computer-aided design, we propose new PAFs, designated as NPAFs, by introducing nitrogen-containing groups to the biphenyl unit and predict their CO2 adsorption capacities with grand canonical Monte Carlo (GCMC) simulations. Among various NPAFs considered, one with imidazole groups shows the highest adsorption capacity for CO2 (11.5wt % at 1bar and 298K) , in comparison with 5wt % for the parent PAF (PAF- 1) at the same condition. At higher pressures (around 10bar) ,though, another NPAF with pyridinic N groups performs much bettermore » than the rest due to its greater pore volume in addition to the N functionality. This research suggests that adding N functionality to the organic linkers is a promising way to increase CO2 adsorption capacity of PAFs at ambient condition.« less

  1. Nitrogen-doped porous aromatic frameworks for enhanced CO2 adsorption

    SciTech Connect

    Fu, Jia; Wu, Jianzhong; Custelcean, Radu; Jiang, De-en

    2014-10-07

    Recently synthesized porous aromatic frameworks (PAFs) exhibit extremely high surface areas and exceptional thermal and hydrothermal stabilities. Using computer-aided design, we propose new PAFs, designated as NPAFs, by introducing nitrogen-containing groups to the biphenyl unit and predict their CO2 adsorption capacities with grand canonical Monte Carlo (GCMC) simulations. Among various NPAFs considered, one with imidazole groups shows the highest adsorption capacity for CO2 (11.5wt % at 1bar and 298K) , in comparison with 5wt % for the parent PAF (PAF- 1) at the same condition. At higher pressures (around 10bar) ,though, another NPAF with pyridinic N groups performs much better than the rest due to its greater pore volume in addition to the N functionality. This research suggests that adding N functionality to the organic linkers is a promising way to increase CO2 adsorption capacity of PAFs at ambient condition.

  2. Adsorption of phenanthrene on multilayer graphene as affected by surfactant and exfoliation.

    PubMed

    Zhao, Jian; Wang, Zhenyu; Zhao, Qing; Xing, Baoshan

    2014-01-01

    Surfactant mediated exfoliation of multilayer graphene and its effects on phenanthrene adsorption were investigated using a passive dosing technique. In the absence of surfactant (sodium cholate, NaC), multilayer graphene had higher adsorption capacity for phenanthrene than carbon nanotube and graphite due to the higher surface area and micropore volume. The observed desorption hysteresis is likely caused by the formation of closed interstitial spaces through folding and rearrangement of graphene sheets. In the presence of NaC (both 100 and 8000 mg/L), phenanthrene adsorption on graphene was decreased due to the direct competition of NaC molecules on the graphene surface. With the aid of sonication, multilayer graphene sheets were exfoliated by NaC, leading to better dispersion. The degree of dispersion depended on the graphene-NaC ratio in aqueous solution rather than critical micelle concentration of NaC, and the good dispersion occurred after reaching adsorption saturation of NaC molecules on graphene sheets. In addition, exfoliation weakened the competition between phenanthrene and NaC and enhanced the adsorption capacity of graphene for phenanthrene due to exposed new sites. The findings on exfoliation of graphene sheets and related adsorption properties highlight not only the potential applications of multilayer graphene as efficient adsorbent but also its possible environmental risk.

  3. Batch adsorption of phenol onto physiochemical-activated coconut shell.

    PubMed

    Mohd Din, Azam T; Hameed, B H; Ahmad, Abdul L

    2009-01-30

    The liquid-phase adsorption of phenol onto coconut shell-based activated carbon, CS850A was investigated for its equilibrium studies and kinetic modeling. Coconut shell was converted into high quality activated carbon through physiochemical activation at 850 degrees C under the influence of CO(2) flow. Beforehand, the coconut shell was carbonized at 700 degrees C and the resulted char was impregnated with KOH at 1:1 weight ratio. In order to evaluate the performance of CS850A, a series of batch adsorption experiments were conducted with initial phenol concentrations ranging from 100 to 500 mg l(-1), adsorbent loading of 0.2g and the adsorption process was maintained at 30+/-1 degrees C. The adsorption isotherms were in conformation to both Langmuir and Freundlich isotherm models. Chemical reaction was found to be a rate-controlling parameter to this phenol-CS850A batch adsorption system due to strong agreement with the pseudo-second-order kinetic model. Adsorption capacity for CS850A was found to be 205.8 mg g(-1).

  4. Adsorption and desorption kinetics of carbofuran in acid soils.

    PubMed

    Bermúdez-Couso, Alipio; Fernández-Calviño, David; Pateiro-Moure, Miriam; Nóvoa-Muñoz, Juan Carlos; Simal-Gándara, Jesús; Arias-Estévez, Manuel

    2011-06-15

    Carbofuran adsorption and desorption were investigated in batch and stirred flow chamber (SFC) tests. The carbofuran adsorption capacity of the soils was found to be low and strongly dependent on their clay and organic carbon contents. Carbofuran sorption was due mainly (>80%) to fast adsorption processes governed by intraparticle diffusion. The adsorption kinetic constant for the pesticide ranged from 0.047 to 0.195 min(-1) and was highly correlated with constant n in the Freundlich equation (r=0.965, P<0.05). Batch tests showed carbofuran desorption to be highly variable and negatively correlated with eCEC and the clay content. The SFC tests showed that soil organic carbon (C) plays a key role in the irreversibility of carbofuran adsorption. Carbofuran desorption increased rapidly at C contents below 4%. The desorption kinetic constant for the compound (0.086-0.195 min(-1)) was generally higher than its adsorption kinetic constant; therefore, carbofuran is more rapidly desorbed than it is adsorbed in soil.

  5. Adsorption and adsolubilization of polymerizable surfactants on aluminum oxide.

    PubMed

    Attaphong, Chodchanok; Asnachinda, Emma; Charoensaeng, Ampira; Sabatini, David A; Khaodhiar, Sutha

    2010-04-01

    Surfactant-based adsorption processes have been widely investigated for environmental applications. A major problem facing surfactant-modified adsorbents is surfactant loss from the adsorbent due to loss of monomers from solution and subsequent surfactant desorption. For this study, a bilayer of anionic polymerizable surfactant (Hitenol BC 05, Hitenol BC 10 and Hitenol BC 20) and non-polymerizable surfactant (Hitenol N 08) was adsorbed onto alumina. The results of adsorption studies showed that as the number of ethylene oxide (EO) groups of the surfactants increased, the area per molecule increased and the maximum adsorption decreased. The lowest maximum adsorption onto alumina was for Hitenol BC 20 (20 EO groups) corresponding to 0.08 mmol/g or 0.34 molecule/nm(2) while the highest level of adsorption was 0.30 mmol/g or 1.28 molecule/nm(2) for Hitenol BC 05 (5 EO groups). This variation in adsorption was attributed to the increased bulkiness of the head group with increasing number of EO groups. Relative to the adsolubilization capacity of organic solutes, ethylcyclohexane adsolubilizes more than styrene. Styrene and ethylcyclohexane adsolubilization were both independent of the number of EO groups of the surfactant. For surfactant desorption studies, the polymerization of polymerizable surfactants increased the stability of surfactants adsorbed onto the alumina surface and reduced surfactant desorption from the alumina surface. These results provide useful information on surfactant-based surface modification to enhance contaminant remediation and industrial applications.

  6. Adsorptional photocatalytic degradation of methylene blue onto pectin-CuS nanocomposite under solar light.

    PubMed

    Gupta, Vinod Kumar; Pathania, Deepak; Agarwal, Shilpi; Singh, Pardeep

    2012-12-01

    This study describes the effect of adsorption on methylene blue degradation using pectin-CuS nanocomposite (PCSNC). The nanocomposite was synthesized using co-precipitation methods followed by direct encapsulation with pectin. The synthesized nanocomposite was characterized by SEM, TEM, XRD, FTIR and UV-vis spectral technique. The adsorption and photocatalytic efficiencies of PCSNC were compared with copper sulphide nanoparticle (CSNP). The dye removal was studied under different reaction conditions. The adsorption capacity of pectin based nanocomposite was higher due to other free functional group on pectin surface after connecting to nanoparticles. The simultaneous adsorption and photodegradation process (A+P) was the most efficient process due to rapid destruction of adsorbed dye molecules. The complete COD removal was attained in 10h using PCSNC/A+P process. On comparing with CSNP, pectin-CuS nano composite showed more degradation efficiency and reusability for MB degradation.

  7. Nickel oxide grafted andic soil for efficient cesium removal from aqueous solution: adsorption behavior and mechanisms.

    PubMed

    Ding, Dahu; Lei, Zhongfang; Yang, Yingnan; Feng, Chuanping; Zhang, Zhenya

    2013-10-23

    An andic soil, akadama clay, was modified with nickel oxide and tested for its potential application in the removal of cesium from aqueous solution. Scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), and powder X-ray diffraction (XRD) results revealed the nickel oxide was successfully grafted into akadama clay. N2 adsorption-desorption isotherms indicated the surface area decreased remarkably after modification while the portion of mesopores increased greatly. Thermogravimetric-differential thermal analysis (TG-DTA) showed the modified akadama clay had better thermostability than the pristine akadama clay. Decreases in cation exchange capacity (CEC) and ζ-potential were also detected after the modification. Adsorption kinetic and isotherm studies indicated the adsorption of Cs+ on the modified akadama clay was a monolayer adsorption process. Adsorption capacity was greatly enhanced for the modified akadama clay probably due to the increase in negative surface charge caused by the modification. The adsorption of Cs+ on the modified akadama clay was dominated by an electrostatic adsorption process. Results of this work are of great significance for the application of akadama clay as a promising adsorbent material for cesium removal from aqueous solutions.

  8. Adsorption enhancement of elemental mercury onto sulphur-functionalized silica gel adsorbents.

    PubMed

    Johari, Khairiraihanna; Saman, Norasikin; Mat, Hanapi

    2014-01-01

    In this study, elemental mercury (EM) adsorbents were synthesized using tetraethyl orthosilicate (TEOS) and 3-mercaptopropyl trimethoxysilane as silica precursors. The synthesized silica gel (SG)-TEOS was further functionalized through impregnation with elemental sulphur and carbon disulphide (CS2). The SG adsorbents were then characterized by using scanning electron microscope, Fourier transform infra-red spectrophotometer, nitrogen adsorption/desorption, and energy-dispersive X-ray diffractometer. The EM adsorption of the SG adsorbents was determined using fabricated fixed-bed adsorber. The EM adsorption results showed that the sulphur-functionalized SG adsorbents had a greater Hgo breakthrough adsorption capacity, confirming that the presence of sulphur in silica matrices can improve Hgo adsorption performance due to their high affinity towards mercury. The highest Hgo adsorption capacity was observed for SG-TEOS(CS2) (82.62 microg/g), which was approximately 2.9 times higher than SG-TEOS (28.47 microg/g). The rate of Hgo adsorption was observed higher for sulphur-impregnated adsorbents, and decreased with the increase in the bed temperatures.

  9. Electrostatically mediated adsorption by nanodiamond and nanocarbon particles

    NASA Astrophysics Data System (ADS)

    Gibson, Natalie M.; Luo, Tzy-Jiun Mark; Shenderova, Olga; Koscheev, Alexey P.; Brenner, Donald W.

    2012-03-01

    Nanodiamond (ND) and other nanocarbon particles are popular platforms for the immobilization of molecular species. In the present research, factors affecting adsorption and desorption of propidium iodide (PI) dye, chosen as a charged molecule model, on ND and sp 2 carbon nanoparticles were studied, with a size ranging from 75 to 4,305 nm. It was found that adsorption of PI molecules, as characterized by ultraviolet-visible spectroscopy, on ND particles is strongly influenced by sorbent-sorbate electrostatic interactions. Different types of NDs with a negative zeta potential were found to adsorb positively charged PI molecules, while no PI adsorption was observed for NDs with a positive zeta potential. The type and density of surface groups of negatively charged NDs greatly influenced the degree and capacity of the PI adsorbed. Ozone-purified NDs had the highest capacity for PI adsorption, due to its greater density of oxygen containing groups, i.e., acid anhydrides and carboxyls, as assessed by TDMS and TOF-SIMS. Single wall nanohorns and carbon onion particles were found to adsorb PI regardless of their zeta potential; this is likely due to π bonding between the aromatic rings of PI and the graphitic surface of the materials and the internal cavity of the horns.

  10. Low-temperature adsorption/storage of hydrogen on FAU, MFI, and MOR zeolites with various Si/Al ratios: effect of electrostatic fields and pore structures.

    PubMed

    Jhung, Sung Hwa; Yoon, Ji Woong; Lee, Ji Sun; Chang, Jong-San

    2007-01-01

    Several zeolites, such as faujasite, mordenite, and ZSM-5, with various aluminum contents have been used to analyze the effect of aluminum or cation concentration (strength of electrostatic field) on hydrogen adsorption at low temperature. Irrespective of the zeolite structure, the adsorption capacity, isosteric heat of adsorption (-DeltaHads), surface coverage, and micropore occupancy increase with increasing aluminum content of a zeolite. Zeolites with a higher amount of aluminum favorably adsorb hydrogen at relatively low pressures. For zeolites with similar aluminum contents, the adsorption capacity, isosteric heat of adsorption, surface coverage, and micropore occupancy are in the order of mordenite>ZSM-5>faujasite, probably due to differing pore sizes and the presence or absence of pore intersections. This work demonstrates that zeolites with strong electrostatic fields and narrow pores without intersections are beneficial for high hydrogen uptake.

  11. Mercury adsorption-desorption and transport in soils.

    PubMed

    Liao, Lixia; Selim, H M; Delaune, R D

    2009-01-01

    Kinetic sorption and column miscible displacement transport experiments were performed to quantify the extent of retention/release and the mobility of mercury in different soils. Results indicated that adsorption of mercury was rapid and highly nonlinear with sorption capacities having the following sequence: Sharkey clay > Olivier loam > Windsor sand. Mercury adsorption by all soils was strongly irreversible where the amounts released or desorbed were often less than 1% of that applied. Moreover, the removal of soil organic matter resulted in a decrease of mercury adsorption in all soils. Adsorption was described with limited success using a nonlinear (Freundlich) model. Results from the transport experiments indicated that the mobility of mercury was highly retarded, with extremely low concentrations of mercury in column effluents. Furthermore, mercury breakthrough curves exhibited erratic patterns with ill-distinguished peaks. Therefore, mercury is best regarded as strongly retained and highly "immobile" in the soils investigated. This is most likely due to highly stable complex formation (irreversible forms) and strong binding to high-affinity sites. In a column packed with reference sand material, a symmetric breakthrough curve was obtained where the recovery of mercury in the leachate was only 17.3% of that applied. Mercury retention by the reference sand was likely due to adsorption by quartz and metal-oxides.

  12. Single, competitive, and dynamic adsorption on activated carbon of compounds used as plasticizers and herbicides.

    PubMed

    Abdel daiem, Mahmoud M; Rivera-Utrilla, José; Sánchez-Polo, Manuel; Ocampo-Pérez, Raúl

    2015-12-15

    The main aim of this study was to investigate the single, competitive, and dynamic adsorption of phthalic acid (PA), bisphenol A (BPA), diphenolic acid (DPA), 2,4-dichlorophenoxy-acetic acid (2,4-D), and 4-chloro-2-methylphenoxyacetic acid (MCPA) on two activated carbons with different chemical natures and similar textural characteristics. The adsorption mechanism was also elucidated by analyzing the influence of solution pH and ionic strength. The activated carbons demonstrated high adsorption capacity to remove all micropollutants due to the presence of active sites on their surfaces, which increase dispersive interactions between the activated carbon graphene layers and the aromatic ring of pollutants. The adsorption capacity of the activated carbons increased in the order: DPAadsorption of contaminants is favored at acid pH (pH<5) due to the establishment of attractive electrostatic interactions. In dynamic regime, the amount of pollutant adsorbed was much higher for PA, followed by DPA, and was approximately similar for BPA, 2,4-D, and MCPA. Finally, the amount of BPA and DPA adsorbed on activated carbon decreased by around 50% and 70% in the presence of DPA and BPA, respectively, indicating that both compounds are adsorbed on the same adsorption sites of the activated carbon.

  13. Evaluation of an Absorption Heat Pump to Mitigate Plant Capacity Reduction Due to Ambient Temperature Rise for an Air-Cooled Ammonia and Water Cycle: Preprint

    SciTech Connect

    Bharathan, D.; Nix, G.

    2001-08-06

    Air-cooled geothermal plants suffer substantial decreases in generating capacity at increased ambient temperatures. As the ambient temperature rises by 50 F above a design value of 50 F, at low brine-resource temperatures, the decrease in generating capacity can be more than 50%. This decrease is caused primarily by increased condenser pressure. Using mixed-working fluids has recently drawn considerable attention for use in power cycles. Such cycles are more readily amenable to use of absorption ''heat pumps.'' For a system that uses ammonia and water as the mixed-working fluid, this paper evaluates using an absorption heat pump to reduce condenser backpressure. At high ambient temperatures, part of the turbine exhaust vapor is absorbed into a circulating mixed stream in an absorber in series with the main condenser. This steam is pumped up to a higher pressure and heated to strip the excess vapor, which is recondensed using an additional air-cooled condenser. The operating conditions are chosen to reconstitute this condensate back to the same concentration as drawn from the original system. We analyzed two power plants of nominal 1-megawatt capacity. The design resource temperatures were 250 F and 300 F. Ambient temperature was allowed to rise from a design value of 50 F to 100 F. The analyses indicate that using an absorption heat pump is feasible. For the 300 F resource, an increased brine flow of 30% resulted in a net power increase of 21%. For the 250 F resource, the increase was smaller. However, these results are highly plant- and equipment-specific because evaluations must be carried out at off-design conditions for the condenser. Such studies should be carried out for specific power plants that suffer most from increased ambient temperatures.

  14. Effects of the oxidation degree of graphene oxide on the adsorption of methylene blue.

    PubMed

    Yan, Han; Tao, Xue; Yang, Zhen; Li, Kun; Yang, Hu; Li, Aimin; Cheng, Rongshi

    2014-03-15

    In this current work, a series of graphene oxides (GO) with different oxidation degrees (OD) was prepared using Hummer method. Fundamental adsorption behavior of the GO series for removal of methylene blue (MB) from aqueous solutions has been studied. The GO series shows an overall fast and pH-independent MB adsorption, which is even capable of removing trace levels of dye completely from very dilute solutions. Furthermore, the effects of the oxidation degree (OD) on MB adsorption behavior have been investigated systematically, indicating that the dye uptakes of GO exponentially increase with the increase of OD. Further study on the adsorption mechanism shows that adsorption behavior of GO would change from a Freundlich-type to a Langmuir-type adsorption as the OD increases. It may be due to both the enhanced exfoliation degree of the carbon planes in graphite caused by oxidation and the production of more active adsorption sites. The binding features of the MB loaded GO gradually change from MB molecule parallel stacking on graphite plane through hydrophobic π-π interaction to vertical standing via electrostatic interaction with increasing OD, resulting in a significant improvement of MB uptakes. In addition, the adsorption capacity of the regenerated GO has little loss until four cycles.

  15. Phosphorus adsorption on natural sediments with different pH incorporating surface morphology characterization.

    PubMed

    Huang, Lei; Fang, Hongwei; He, Guojian; Chen, Minghong

    2016-09-01

    Sediment samples from University Lake (U.L.) and Anacostia River (A.R.) were collected to study the phosphorus (P) adsorption with pH at 3.65, 4.75, and 5.65. The surface micro-morphology and pore structures of sediment particles were obtained using a scanning electron microscopy and gas adsorption method, respectively. Fourier analysis was then applied to approximate the surface morphology, which was incorporated into the Langmuir isotherm to directly derive the model parameters for P adsorption simulation. Meanwhile, an empirical function of pH was introduced to represent the pH effect on P adsorption. A stronger P adsorption was observed for the A.R. sediment due to the more clay minerals, smaller median diameter, and a greater percentage of large pores, and the increasing pH resulted in a decrease of adsorption equilibrium constant as well as the P adsorption capacity, which was well reproduced by the adsorption isotherms. This study would benefit the mechanism study of the interactions between sediment particles and pollutants, providing references for understanding the pollutants' transport in aqueous systems.

  16. Kinetic modeling of liquid-phase adsorption of phosphate on dolomite.

    PubMed

    Karaca, S; Gürses, A; Ejder, M; Açikyildiz, M

    2004-09-15

    The adsorption of phosphate from aqueous solution on dolomite was investigated at 20 and 40 degrees C in terms of pseudo-second-order mechanism for chemical adsorption as well as an intraparticle diffusion mechanism process. Adsorption was changed with increased contact time, initial phosphate concentration, temperature, solution pH. A pseudo-second-order model and intraparticle diffusion model have been developed to predict the rate constants of adsorption and equilibrium capacities. The activation energy of adsorption can be evaluated using the pseudo-second-order rate constants. The adsorption of phosphate onto dolomite are an exothermically activated process. A relatively low activation energy and a model highly fitting to intraparticle diffusion suggest that the adsorption of phosphate by dolomite may involve not only physical but also chemisorption. This was likely due to its combined control of chemisorption and intraparticle diffusion. However, for phosphate/dolomite system chemical reaction is important and significant in the rate-controlling step, and for the adsorption of phosphate onto dolomite the pseudo-second-order chemical reaction kinetics provides the best correlation of the experimental data.

  17. Effects of crystalline structures and surface functional groups on the adsorption of haloacetic acids by inorganic materials.

    PubMed

    Punyapalakul, Patiparn; Soonglerdsongpha, Suwat; Kanlayaprasit, Chutima; Ngamcharussrivichai, Chawalit; Khaodhiar, Sutha

    2009-11-15

    The effects of the crystalline structure and surface functional groups of porous inorganic materials on the adsorption of dichloroacetic acid (DCAA) were evaluated by using hexagonal mesoporous silicates (HMS), two surface functional group (3-aminopropyltriethoxy- and 3-mercaptopropyl-) modified HMSs, faujasite Y zeolite and activated alumina as adsorbents, and compared with powdered activated carbon (PAC). Selective adsorption of HAA(5) group was studied by comparing single and multiple-solute solution, including effect of common electrolytes in tap water. Adsorption capacities were significantly affected by the crystalline structure. Hydrogen bonding is suggested to be the most important attractive force. Decreasing the pH lower than the pH(zpc) increased the DCAA adsorption capacities of these adsorbents due to electrostatic interaction and hydrogen bonding caused by protonation of the hydronium ion. Adsorption capacities of HAA(5) on HMS did not relate to molecular structure of HAA(5). Common electrolytes did not affect the adsorption capacities and selectivity of HMS for HAA5, while they affected those of PAC.

  18. Iron [Fe(0)]-rich substrate based on iron-carbon micro-electrolysis for phosphorus adsorption in aqueous solutions.

    PubMed

    Deng, Shihai; Li, Desheng; Yang, Xue; Xing, Wei; Li, Jinlong; Zhang, Qi

    2017-02-01

    The phosphorus (P) adsorption properties of an iron [Fe(0)]-rich substrate (IRS) composed of iron scraps and activated carbon were investigated based on iron-carbon micro-electrolysis (IC-ME) and compared to the substrates commonly used in constructed wetlands (CWs) to provide an initial characterization of the [Fe(0)]-rich substrate. The results showed that P was precipitated by Fe(III) dissolved from the galvanic cell reactions in the IRS and the reaction was suppressed by the pH and stopped when the pH exceeded 8.90 ± 0.09. The adsorption capacity of the IRS decreased by only 4.6% in the second round of adsorption due to Fe(0) consumption in the first round. Substrates with high Ca- and Mg-oxide contents and high Fe- and Al-oxide contents had higher P adsorption capacities at high and low pH values, respectively. Substrates containing high Fe and Al concentrations and low Ca concentrations were more resistant to decreases in the P adsorption capacity resulting from organic matter (OM) accumulation. The IRS with an iron scrap to activated carbon volume ratio of 3:2 resulted in the highest P adsorption capacity (9.34 ± 0.14 g P kg(-1)), with minimal pH change and strong adaptability to OM accumulation. The Fe(0)-rich substrate has the considerable potential for being used as a CW substrate.

  19. Phosphate adsorption on lanthanum loaded biochar.

    PubMed

    Wang, Zhanghong; Shen, Dekui; Shen, Fei; Li, Tianyu

    2016-05-01

    To attain a low-cost and high-efficient phosphate adsorbent, lanthanum (La) loaded biochar (La-BC) prepared by a chemical precipitation method was developed. La-BC and its pristine biochar (CK-BC) were comparatively characterized using zeta potential, BET surface area, scanning electron microscopy/energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The adsorption ability and the mechanisms during adsorption process for the La-BC samples were also investigated. La loaded on the surface of biochar can be termed as La-composites (such as LaOOH, LaONO3 and La(OH)3), leading to the decrease of negative charge and surface area of biochar. La-BC exhibited the high adsorption capacity to phosphate compared to CK-BC. Adsorption isotherm and adsorption kinetic studies showed that the Langmuir isotherm and second order model could well describe the adsorption process of La-BC, indicating that the adsorption was dominated by a homogeneous and chemical process. The calculated maximum adsorption capacity was as high as 46.37 mg g(-1) (computed in P). Thermodynamic analysis revealed that the adsorption was spontaneous and endothermic. SEM, XRD, XPS and FT-IR analysis suggested that the multi-adsorption mechanisms including precipitation, ligand exchange and complexation interactions can be evidenced during the phosphate adsorption process by La-composites in La-BC.

  20. Enhancing adsorption of U(VI) onto EDTA modified L. cylindrica using epichlorohydrin and ethylenediamine as a bridge

    PubMed Central

    Su, Shouzheng; Liu, Qi; Liu, Jingyuan; Zhang, Hongsen; Li, Rumin; Jing, Xiaoyan; Wang, Jun

    2017-01-01

    Benefiting from strong coordination ability and unique vascular structure, EDTA modified L. cylindrica opens up an alternative way for uranium recovery from seawater. However, limitations, such as poor adsorption capacity and slow adsorption rate due to low graft ratio of EDTA via one-step esterification block its practical application. Here, a strategy for increasing the graft ratio is proposed in order to improve the adsorption performance. The strategy initially involves immobilization of epichlorohydrin (EPI) onto L. cylindrica and then ethylenediamine (EDA) is introduced via facile ring-opening reaction. EPI and EDA serve as a bridge between L. cylindrica and EDTA. The graft ratio is promoted (15.01 to 21.44%) contributing to the smaller steric hindrance of EPI and EDA than EDTA and improvement in adsorption performance. In addition, the adsorbent prepared by the new strategy exhibits excellent adsorption properties in simulated seawater. PMID:28272435

  1. Enhancing adsorption of U(VI) onto EDTA modified L. cylindrica using epichlorohydrin and ethylenediamine as a bridge.

    PubMed

    Su, Shouzheng; Liu, Qi; Liu, Jingyuan; Zhang, Hongsen; Li, Rumin; Jing, Xiaoyan; Wang, Jun

    2017-03-08

    Benefiting from strong coordination ability and unique vascular structure, EDTA modified L. cylindrica opens up an alternative way for uranium recovery from seawater. However, limitations, such as poor adsorption capacity and slow adsorption rate due to low graft ratio of EDTA via one-step esterification block its practical application. Here, a strategy for increasing the graft ratio is proposed in order to improve the adsorption performance. The strategy initially involves immobilization of epichlorohydrin (EPI) onto L. cylindrica and then ethylenediamine (EDA) is introduced via facile ring-opening reaction. EPI and EDA serve as a bridge between L. cylindrica and EDTA. The graft ratio is promoted (15.01 to 21.44%) contributing to the smaller steric hindrance of EPI and EDA than EDTA and improvement in adsorption performance. In addition, the adsorbent prepared by the new strategy exhibits excellent adsorption properties in simulated seawater.

  2. Competitive adsorption of Cu(II) and Cd(II) ions by chitosan crosslinked with epichlorohydrin-triphosphate.

    PubMed

    Laus, Rogério; de Fávere, Valfredo Tadeu

    2011-10-01

    In this study, chitosan (CTS) was crosslinked with both epichlorohydrin (ECH) and triphosphate (TPP), by covalent and ionic crosslinking reactions, respectively. The resulting adsorbent (CTS-ECH-TPP) was characterized by SEM, CHN, EDS, FT-IR and TGA analyses, and tested for metal adsorption. The adsorbent was used in batch experiments to evaluate the adsorption of Cu(II) and Cd(II) ions in single and binary metal solutions. In single metal solutions the maximum adsorption capacities for Cu(II) and Cd(II) ions, obtained by Langmuir model, were 130.72 and 83.75 mg g⁻¹, respectively. Adsorption isotherms for binary solutions showed that the presence of Cu(II) decreased Cd(II) adsorption due to a significant competition effect, that is, the adsorbent was selective towards Cu(II) rather than Cd(II).

  3. Enhancing adsorption of U(VI) onto EDTA modified L. cylindrica using epichlorohydrin and ethylenediamine as a bridge

    NASA Astrophysics Data System (ADS)

    Su, Shouzheng; Liu, Qi; Liu, Jingyuan; Zhang, Hongsen; Li, Rumin; Jing, Xiaoyan; Wang, Jun

    2017-03-01

    Benefiting from strong coordination ability and unique vascular structure, EDTA modified L. cylindrica opens up an alternative way for uranium recovery from seawater. However, limitations, such as poor adsorption capacity and slow adsorption rate due to low graft ratio of EDTA via one-step esterification block its practical application. Here, a strategy for increasing the graft ratio is proposed in order to improve the adsorption performance. The strategy initially involves immobilization of epichlorohydrin (EPI) onto L. cylindrica and then ethylenediamine (EDA) is introduced via facile ring-opening reaction. EPI and EDA serve as a bridge between L. cylindrica and EDTA. The graft ratio is promoted (15.01 to 21.44%) contributing to the smaller steric hindrance of EPI and EDA than EDTA and improvement in adsorption performance. In addition, the adsorbent prepared by the new strategy exhibits excellent adsorption properties in simulated seawater.

  4. Effective adsorptive removal of indole from model fuel using a metal-organic framework functionalized with amino groups.

    PubMed

    Ahmed, Imteaz; Jhung, Sung Hwa

    2015-01-01

    Nitrogen-containing compounds (NCCs) should be removed from fuels because of the negative effect of NCCs on the environment and catalyst stability. NCCs are composed of basic materials such as quinoline (QUI) and neutral materials such as indole (IND). The NCCs can be removed by various methods including adsorption. Compared with basic NCCs, neutral NCCs are more difficult to remove through adsorption due to their less affinity toward adsorbents. In this report, adsorption of IND (as one of the representative neutral NCCs) was studied over the metal-organic frameworks (MOFs), UiO-66 and UiO-66-NH2, which contain terephthalate and aminoterephthalate linkers, respectively. In spite of the reduced porosity of UiO-66-NH2, the adsorption capacity of IND was improved upto 46% when compared with pristine UiO-66. Therefore, the additional amino group in the MOF imparts extra adsorption capability on the MOF. For a detailed investigation, adsorption of other NCCs such as QUI, pyrrole, and methylpyrrole was studied. The improved adsorption of IND over amino-functionalized MOFs could be attributed to the improved interaction of IND with the MOF via H-bonding because of the NH2 group. In addition to this remarkable improvement in IND adsorption, UiO-66-NH2 could be regenerated several times for the adsorption of IND by simple solvent washing.

  5. Effects of Reclaimed Water on the Characteristics of Dimethyl Phthalate Adsorption on Sediments.

    PubMed

    Ning, Zigong; Li, Pengxiang; Zhou, Shuang; Li, Yunkai; Ishiguro, Munehide; Zhao, Wei; Wang, Meie

    2017-03-01

    Adsorptions of Dimethyl Phthalate (DMP) on three sediments in both reclaimed and ultrapure water were studied using the batch technique and the effects of reclaimed water on it were clarified. The data were interpreted by using Freundlich and Dubinin-Radushkviech models. The values of 1/n were among 0.207 to 0.766, showing the presence of multiple adsorption sites on sediments. Compared with the ultrapure water as the background solution, the adsorption capacities of sediments for DMP were reduced in case of reclaimed water due to the competition of substances in reclaimed water. The mean adsorption energy, E, is smaller in the reclaimed water than that in ultrapure water.

  6. 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.

  7. Kinetic studies of elemental mercury adsorption in activated carbon fixed bed reactor.

    PubMed

    Skodras, G; Diamantopoulou, Ir; Pantoleontos, G; Sakellaropoulos, G P

    2008-10-01

    Activated carbons are suitable materials for Hg(0) adsorption in fixed bed operation or in injection process. The fixed bed tests provide good indication of activated carbons effectiveness and service lives, which depend on the rates of Hg(0) adsorption. In order to correlate fixed bed properties and operation conditions, with their adsorptive capacity and saturation time, Hg(0) adsorption tests were realized in a bench-scale unit, consisted of F400 activated carbon fixed bed reactor. Hg(0) adsorption tests were conducted at 50 degrees C, under 0.1 and 0.35 ng/cm(3) Hg(0) initial concentrations and with carbon particle sizes ranging between 75-106 and 150-250 microm. Based on the experimental breakthrough data, kinetic studies were performed to investigate the mechanism of adsorption and the rate controlling steps. Kinetic models evaluated include the Fick's intraparticle diffusion equation, the pseudo-first order model, the pseudo-second order model and Elovich kinetic equation. The obtained experimental results revealed that the increase in particle size resulted in significant decrease of breakthrough time and mercury adsorptive capacity, due to the enhanced internal diffusion limitations and smaller external mass transfer coefficients. Additionally, higher initial mercury concentrations resulted in increased breakthrough time and mercury uptake. From the kinetic studies results it was observed that all the examined models describes efficiently Hg(0) breakthrough curves, from breakpoint up to equilibrium time. The most accurate prediction of the experimental data was achieved by second order model, indicating that the chemisorption rate seems to be the controlling step in the procedure. However, the successful attempt to describe mercury uptake with Fick's diffusion model and the first order kinetic model, reveals that the adsorption mechanism studied was complex and followed both surface adsorption and particle diffusion.

  8. Adsorption equilibrium and dynamics of gasoline vapors onto polymeric adsorbents.

    PubMed

    Jia, Lijuan; Yu, Weihua; Long, Chao; Li, Aimin

    2014-03-01

    The emission of gasoline vapors is becoming a significant environmental problem especially for the population-dense area and also results in a significant economic loss. In this study, adsorption equilibrium and dynamics of gasoline vapors onto macroporous and hypercrosslinked polymeric resins at 308 K were investigated and compared with commercial activated carbon (NucharWV-A 1100). The results showed that the equilibrium and breakthrough adsorption capacities of virgin macroporous and hypercrosslinked polymeric resins were lower than virgin-activated carbon. Compared with origin adsorbents, however, the breakthrough adsorption capacities of the regenerated activated carbon for gasoline vapors decreased by 58.5 % and 61.3 % when the initial concentration of gasoline vapors were 700 and 1,400 mg/L, while those of macroporous and hypercrosslinked resins decreased by 17.4 % and 17.5 %, and 46.5 % and 45.5 %, respectively. Due to the specific bimodal property in the region of micropore (0.5-2.0 nm) and meso-macropore (30-70 nm), the regenerated hypercrosslinked polymeric resin exhibited the comparable breakthrough adsorption capacities with the regenerated activated carbon at the initial concentration of 700 mg/L, and even higher when the initial concentration of gasoline vapors was 1,400 mg/L. In addition, 90 % of relative humidity had ignorable effect on the adsorption of gasoline vapors on hypercrosslinked polymeric resin. Taken together, it is expected that hypercrosslinked polymeric adsorbent would be a promising adsorbent for the removal of gasoline vapors from gas streams.

  9. The death of sertoli cells and the capacity to phagocytize elongated spermatids during testicular regression due to short photoperiod in Syrian hamster (Mesocricetus auratus).

    PubMed

    Seco-Rovira, Vicente; Beltrán-Frutos, Esther; Ferrer, Concepción; Sáez, Francisco José; Madrid, Juan Francisco; Pastor, Luis Miguel

    2014-05-01

    In the Syrian hamster (Mesocricetus auratus), an animal that displays testicular regression due to short photoperiod, germ cells are removed by apoptosis during this process and the apoptotic remains are phagocytized by Sertoli cells. The aim of this work was to investigate morphologically whether the testicular regression process due to short photoperiod leads to the apoptosis of Sertoli cells, and whether, during testicular regression, the elongated spermatids are eliminated through phagocytosis by Sertoli cells. To this end, we studied testis sections during testicular regression in Syrian hamster subjected to short photoperiod by means of several morphological techniques using conventional light microscopy (hematoxylin and eosin [H&E], semi-thin section vimentin, immunohistochemistry, SBA lectin, and TUNEL staining), fluorescence microscopy, and transmission electron microscopy (TEM). H&E and semi-thin sections identified Sertoli cells with a degenerated morphology. Greater portion of Sertoli cells that were positive for TUNEL staining were observed especially during the mild regression (MR) and strong regression (SR) phases. In addition, TEM identified the characteristic apoptotic changes in the nucleus and cytoplasm of Sertoli cells. Moreover, during testicular regression and using light microscopy, some elongated spermatids were seen in basal position next to the Sertoli cell nucleus. This Sertoli phagocytic activity was higher in MR and SR phases. TEM confirmed this to be the result of the phagocytic activity of Sertoli cells. In conclusion, during testicular regression in Syrian hamster due to short photoperiod, when germ cells are known to be lost through apoptosis, there is morphological evidences that Sertoli cells are also lost through apoptosis, while some elongated spermatids are phagocytized and eliminated by the Sertoli cells.

  10. Adsorption of bisphenol-A from aqueous solution onto minerals and carbon adsorbents.

    PubMed

    Tsai, Wen-Tien; Lai, Chi-Wei; Su, Ting-Yi

    2006-06-30

    The adsorption behaviors of bisphenol-A, which has been listed as one of endocrine disrupting chemicals, from aqueous solution onto four minerals including andesite, diatomaceous earth, titanium dioxide, and activated bleaching earth, and two activated carbons with coconut-based and coal-based virgins were examined in this work. Based on the adsorption results at the specified conditions, the adsorption capacities of activated carbons are significantly larger than those of mineral adsorbents, implying that the former is effective for removal of the highly hydrophobic adsorbate from the aqueous solution because of its high surface area and low surface polarity. The adsorption capacities of bisphenol-A onto these mineral adsorbents with different pore properties are almost similar in magnitude mainly due to the weakly electrostatic interaction between the mineral surface with negative charge and the target adsorbate with hydrophobic nature. Further, a simplified kinetic model, pseudo-second-order, was tested to investigate the adsorption behaviors of bisphenol-A onto the two common activated carbons at different solution conditions. It was found that the adsorption process could be well described with the pseudo-second-order model. The kinetic parameters of the model obtained in the present work are in line with the pore properties of the two adsorbents.

  11. Simulating effects of land use changes on carbon fluxes: past contributions to atmospheric CO2 increases and future commitments due to losses of terrestrial sink capacity

    NASA Astrophysics Data System (ADS)

    Strassmann, K. M.; Joos, F.; Fischer, G.

    2008-09-01

    The impact of land use on the global carbon cycle and climate is assessed. The Bern carbon cycle-climate model was used with land use maps from HYDE3.0 for 1700 to 2000 A.D. and from post-SRES scenarios for this century. Cropland and pasture expansion each cause about half of the simulated net carbon emissions of 188 GtC over the industrial period and 1.1 GtC yr-1 in the 1990s, implying a residual terrestrial sink of 113 GtC and of 1.8 GtC yr-1, respectively. Direct CO2 emissions due to land conversion as simulated in book-keeping models dominate carbon fluxes due to land use in the past. They are, however, mitigated by 25% through the feedback of increased atmospheric CO2 stimulating uptake. CO2 stimulated sinks are largely lost when natural lands are converted. Past land use change has eliminated potential future carbon sinks equivalent to emissions of 80-150 GtC over this century. They represent a commitment of past land use change, which accounts for 70% of the future land use flux in the scenarios considered. Pre-industrial land use emissions are estimated to 45 GtC at most, implying a maximum change in Holocene atmospheric CO2 of 3 ppm. This is not compatible with the hypothesis that early anthropogenic CO2 emissions prevented a new glacial period.

  12. Multilayer adsorption on fractal surfaces.

    PubMed

    Vajda, Péter; Felinger, Attila

    2014-01-10

    Multilayer adsorption is often observed in liquid chromatography. The most frequently employed model for multilayer adsorption is the BET isotherm equation. In this study we introduce an interpretation of multilayer adsorption measured on liquid chromatographic stationary phases based on the fractal theory. The fractal BET isotherm model was successfully used to determine the apparent fractal dimension of the adsorbent surface. The nonlinear fitting of the fractal BET equation gives us the estimation of the adsorption equilibrium constants and the monolayer saturation capacity of the adsorbent as well. In our experiments, aniline and proline were used as test molecules on reversed phase and normal phase columns, respectively. Our results suggest an apparent fractal dimension 2.88-2.99 in the case of reversed phase adsorbents, in the contrast with a bare silica column with a fractal dimension of 2.54.

  13. The effect of high ionic strength on neptunium (V) adsorption to a halophilic bacterium

    NASA Astrophysics Data System (ADS)

    Ams, David A.; Swanson, Juliet S.; Szymanowski, Jennifer E. S.; Fein, Jeremy B.; Richmann, Michael; Reed, Donald T.

    2013-06-01

    The mobility of neptunium (V) in subsurface high ionic strength aqueous systems may be strongly influenced by adsorption to the cell wall of the halophilic bacteria Chromohalobacter sp. This study is the first to evaluate the adsorption of neptunium (V) to the surface of a halophilic bacterium as a function of pH from approximately 2 to 10 and at ionic strengths of 2 and 4 M. This is also the first study to evaluate the effects of carbonate complexation with neptunium (V) on adsorption to whole bacterial cells under high pH conditions. A thermodynamically-based surface complexation model was adapted to describe experimental adsorption data under high ionic strength conditions where traditional corrections for aqueous ion activity are invalid. Adsorption of neptunium (V) was rapid and reversible under the conditions of the study. Adsorption was significant over the entire pH range evaluated for both ionic strength conditions and was shown to be dependent on the speciation of the sites on the bacterial surface and neptunium (V) in solution. Adsorption behavior was controlled by the relatively strong electrostatic attraction of the positively charged neptunyl ion to the negatively charged bacterial surface at pH below circum-neutral. At pH above circum-neutral, the adsorption behavior was controlled by the presence of negatively charged neptunium (V) carbonate complexes resulting in decreased adsorption, although adsorption was still significant due to the adsorption of negatively charged neptunyl-carbonate species. Adsorption in 4 M NaClO4 was enhanced relative to adsorption in 2 M NaClO4 over the majority of the pH range evaluated, likely due to the effect of increasing aqueous ion activity at high ionic strength. The protonation/deprotonation characteristics of the cell wall of Chromohalobacter sp. were evaluated by potentiometric titrations in 2 and 4 M NaClO4. Bacterial titration results indicated that Chromohalobacter sp. exhibits similar proton buffering

  14. Adsorptive removal of emerging polyfluoroalky substances F-53B and PFOS by anion-exchange resin: A comparative study.

    PubMed

    Gao, Yanxin; Deng, Shubo; Du, Ziwen; Liu, Kai; Yu, Gang

    2017-02-05

    Chrome plating is an important emission source of perfluorinated compounds (PFCs) industrial uses in China, where two commercial products potassium 2-(6-chloro-1,1,2,2,3,3,4,4,5,5,6,6-dodecafluorohexyloxy) (F-53B) and perfluorooctane sulfonate (PFOS) are applied as mist suppressant, causing non-negligible environmental risk. In this paper, anion-exchange resin IRA67 was evaluated for F-53B and PFOS removal from simulated and actual wastewater. Adsorption kinetics exhibited higher adsorption velocity and capacity of IRA67 for PFOS than F-53B due to their difference in molecular structures. Adsorption isotherms demonstrated the adsorption capacity of F-53B and PFOS on IRA67 was 4.2mmol/g and 5.5mmol/g, respectively. Because of the deprotonating of amine groups, solution pH had significant effect on IRA67 at pH>10. The results indicated that besides anion exchange other interactions including hydrophobic interaction and the formation of micelles or hemi-micelles were all involved in adsorption process. Coexisting sulfate and chromate in wastewater decreased adsorption capacities of F-53B and PFOS. The spent resin could be regenerated by the NaCl/NaOH and methanol mixed solution. In the mixed system and actual wastewater IRA67 can simultaneously remove F-53B and PFOS without obvious preference but the removal percent can be affected by competitive effect.

  15. Effects of ammonium hydroxide on the structure and gas adsorption of nanosized Zr-MOFs (UiO-66).

    PubMed

    Abid, Hussein Rasool; Ang, Ha Ming; Wang, Shaobin

    2012-05-21

    Several zirconium-based metal-organic frameworks (Zr-MOFs) have been synthesized using ammonium hydroxide as an additive in the synthesis process. Their physicochemical properties have been characterized by N(2) adsorption/desorption, XRD, SEM, FTIR, and TGA, and their application in CO(2) adsorption was evaluated. It was found that addition of ammonium hydroxide produced some effects on the structure and adsorption behavior of Zr-MOFs. The pore size and pore volume of Zr-MOFs were enhanced with the additive, however, specific surface area of Zr-MOFs was reduced. Using an ammonium hydroxide additive, the crystal size of Zr-MOF was reduced with increasing amount of the additive. All the samples presented strong thermal stability. Adsorption tests showed that capacity of CO(2) adsorption on the Zr-MOFs under standard conditions was reduced due to decreased micropore fractions. However, modified Zr-MOFs had significantly lower adsorption heat. The adsorption capacity of carbon dioxide was increased at high pressure, reaching 8.63 mmol g(-1) at 987 kPa for Zr-MOF-NH(4)-2.

  16. Cu2+, Cd2+ and Pb2+ adsorption from aqueous solutions by pyrite and synthetic iron sulphide.

    PubMed

    Ozverdi, Arzu; Erdem, Mehmet

    2006-09-01

    In this study, removal of Cu(2+), Cd(2+) and Pb(2+) from aqueous solutions by adsorption onto pyrite and synthetic iron sulphide (SIS) was investigated as a function of pH, contact time, adsorbent dosage, initial metal concentration and temperature. It has been determined that the adsorption of metal ions onto both adsorbents is pH dependent and the adsorption capacities increase with the increasing temperature. The mechanisms governing the metal removal processes were determined as chemical precipitation at low pH (<3) due to H(2)S generation and adsorption at high pH (in the range of 3-6). The metal adsorption yields also increased with the increasing adsorbent dosage and contact time and reached to equilibrium for both adsorbents. The Cu(2+), Cd(2+) and Pb(2+) adsorption capacities of both adsorbents decrease in the order of Pb(2+)>Cu(2+)>Cd(2+). Except for cadmium, little fraction of copper and lead in the solid adsorption residues was desorbed in acidic media.

  17. A new porous magnetic chitosan modified by melamine for fast and efficient adsorption of Cu(II) ions.

    PubMed

    Wu, Zhan-Chao; Wang, Zhao-Zhan; Liu, Jie; Yin, Jin-Hua; Kuang, Shao-Ping

    2015-11-01

    A new porous magnetic chitosan modified by melamine (MA-CS/Fe3O4) was synthesized. The compositions and surface topographies were characterized by infrared (IR) spectroscopy, X-ray diffraction (XRD) analysis, thermogravimetric (TG) analysis and scanning electron microscope (SEM), respectively. The results of adsorption kinetics showed the adsorption behavior could be better described by the pseudo-second-order equation (R>0.999). The adsorption isotherm was well fitted by the Langmuir equation (R>0.999), and the values of separation factors were in the range of 0-1.0. The maximum adsorption capacity for Cu(II) was 2.58mmolg(-1) at the optimal experimental conditions, which were pH=5.5, t=25min, C0=5.0mmolL(-1). The rate-controlling step was supposed to be chemical adsorption rather than mass transport. The adsorbent still exhibited high adsorption capacity after five regeneration cycles. The adsorption mechanism was due to coordination between Cu(II) and N atoms.

  18. Activated carbon adsorptive removal of azo dye and peroxydisulfate regeneration: from a batch study to continuous column operation.

    PubMed

    Li, Jing; Du, Yue; Deng, Bin; Zhu, Kangmeng; Zhang, Hui

    2016-12-17

    The performance of activated carbon (AC) for the adsorption of Acid Orange 7 (AO7) was investigated in both batch and column studies. The optimal conditions for adsorption process in batch study were found to be a stirring speed of 500 rpm, AC dosage of 5 g/L, and initial AO7 concentration of 100 mg/L. The spent AC was then treated with peroxydisulfate (PDS), and the regenerated AC was used again to adsorb AO7. Both pseudo-first-order and pseudo-second-order rate models for adsorption kinetics were investigated, and the results showed that the latter model was more appropriate. The effects of regeneration time, PDS concentration, and stirring speed on AO7-spent AC regeneration were investigated in batch studies, and the optimal conditions were time 2 h, stirring speed 700 rpm, and PDS concentration 10 g/L. Under the same adsorption conditions, 89% AO7 could be decolorized by adsorption using regenerated AC. In the column studies, the effect of flow rate was investigated and the adsorption capacity was nearly the same when the flow rate rose from 7.9 to 11.4 mL/min, but it decreased significantly when the flow rate was increased to 15.2 mL/min. The performance of regenerated AC in the column was also investigated, and a slight increase in the adsorption capacity was observed in the second adsorption cycle. However, the adsorption capacity decreased to some extent in the third cycle due to the consumption of C-OH group on the AC surface during PDS regeneration.

  19. 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

  20. Adsorption of Emerging Ionizable Contaminants on Carbon Nanotubes: Advancements and Challenges.

    PubMed

    Ma, Xingmao; Agarwal, Sarang

    2016-05-12

    The superior adsorption capacity of carbon nanotubes has been well recognized and there is a wealth of information in the literature concerning the adsorption of unionized organic pollutants on carbon nanotubes. Recently, the adsorption of emerging environmental pollutants, most of which are ionizable, has attracted increasing attention due to the heightened concerns about the accumulation of these emerging contaminants in the environment. These recent studies suggest that the adsorption of emerging ionizable contaminants on carbon nanotubes exhibit different characteristics than unionized ones. For example, a new charge-assisted intermolecular force has been proposed for ionizable compounds because some adsorption phenomenon cannot be easily explained by the conventional force theory. The adsorption of ionizable compounds also displayed much stronger dependence on solution pH and ionic strength than unionized compounds. This article aims to present a brief review on the current understanding of the adsorption of emerging ionizable contaminants to carbon nanotubes and discuss further research needs required to advance the mechanistic understanding of the interactions between ionizable contaminants and carbon nanotubes.

  1. Adsorption characteristics of diclofenac and sulfamethoxazole to graphene oxide in aqueous solution.

    PubMed

    Nam, Seung-Woo; Jung, Chanil; Li, Hang; Yu, Miao; Flora, Joseph R V; Boateng, Linkel K; Her, Namguk; Zoh, Kyung-Duk; Yoon, Yeomin

    2015-10-01

    The adsorptive properties of graphene oxide (GO) were characterized, and the binding energies of diclofenac (DCF) and sulfamethoxazole (SMX) on GO adsorption were predicted using molecular modeling. The adsorption behaviors of DCF and SMX were investigated in terms of GO dosage, contact time, and pH. Additionally, the effects of sonication on GO adsorption were examined. GO adsorption involves "oxygen-containing functional groups" (OCFGs) such as COOH, which exhibit negative charges over a wide range of pH values (pH 3-11). DCF (-18.8 kcal mol(-1)) had a more favorable binding energy on the GO surface than SMX (-15.9 kcal mol(-1)). Both DCF and SMX were removed from solution (adsorbed to GO), up to 35% and 12%, respectively, within 6h, and an increase in GO dosage enhanced the removal of DCF. Electrostatic repulsion occurred between dissociated DCF/SMX and the more negatively charged GO at basic pH (>pKa). The sonication of GO significantly improved the removal of DCF (75%) and SMX (30%) due to dispersion of exfoliated GO particles and the reduction of OCFGs on the GO surface. Both DCF and SMX in the adsorption isotherm were explained well by the Freundlich model. The results of this study can be used to maximize the adsorption capacities of micropollutants using GO in water treatment processes.

  2. Adsorption of acid dye onto organobentonite.

    PubMed

    Baskaralingam, P; Pulikesi, M; Elango, D; Ramamurthi, V; Sivanesan, S

    2006-02-06

    Removal of Acid Red 151 from aqueous solution at different dye concentrations, adsorbent doses and pH has been studied. The bentonite clay has been modified using cationic surfactants, which has been confirmed using XRD and FT-IR analyses. Experimental result has shown that the acidic pH favours the adsorption. The adsorption isotherms are described by means of Langmuir and Freundlich isotherms. The adsorption capacity has been found to be 357.14 and 416.66 mg g(-1) for the cetyldimethylbenzylammonium chloride-bentonite (CDBA-bent) and cetylpyridinium chloride-bentonite (CP-bent), respectively. Kinetic studies show that the adsorption followed second-order kinetics.

  3. Titania-functionalized graphene oxide for an efficient adsorptive removal of phosphate ions.

    PubMed

    Sakulpaisan, Samita; Vongsetskul, Thammasit; Reamouppaturm, Sakultip; Luangkachao, Jakkrawut; Tantirungrotechai, Jonggol; Tangboriboonrat, Pramuan

    2016-02-01

    Titania-functionalized graphene oxide (T-F GO), synthesized by a sol-gel process, was used as a highly efficient material to remove phosphate ions from the simulated wastewater. X-ray diffraction spectra, Fourier transform infrared spectra and scanning electron micrographs of T-F GO confirmed that titania particles were successfully grown on graphene oxide (GO) surface. The phosphate ion adsorption capacities of GO, titania and T-F GO as a function of the contact time and the pH were investigated by a UV-visible spectrophotometer. Results showed that T-F GO could absorb phosphate ions better than titania and GO could. This indicated the synergistic effect between titania and GO in the phosphate ion adsorption. The pH increment lowered the absorption capacities due to increasing the repulsion between phosphate anions and the charges on the T-F GO surface, whereas the addition of sodium ions increased the adsorption capacities. Also, phosphate ions were absorbed by specific sites of T-F GO and formed a monolayer on its surface. Finally, the maximum adsorption capacity of T-F GO was 33.11 mg/g at pH 6, much higher than those of GO and titania. Therefore, T-F GO could be a promising material to remove phosphate ions from wastewater in the future.

  4. Adsorption of crude oil on anhydrous and hydrophobized vermiculite.

    PubMed

    da Silva, Umberto G; de F Melo, Marcus A; da Silva, Adaílton F; de Farias, Robson F

    2003-04-15

    This publication reports the adsorption of crude oil on vermiculite samples, expanded and hydrophobized with carnauba (Copernícia Cerífera) wax. The adsorption studies were performed by using columns filled with the vermiculite matrices and by dispersion of the vermiculite samples in an oil-water (50 ppm of oil) emulsion. The hydrate vermiculite exhibits a very low adsorption capacity against crude oil. On the other hand, anhydrous (expanded) and hydrophobized matrices show a high adsorption capacity. The 10% hydrophobized matrix show a 50% increased adsorption capacity, in comparison with the expanded one. For adsorption performed in the water-oil emulsion, saturation of the solid hydrophobized matrix is achieved after 60 min. The hydrophobized samples exhibit adsorption factors in the 0.7-1.0 range.

  5. Macromolecule simulation and CH4 adsorption mechanism of coal vitrinite

    NASA Astrophysics Data System (ADS)

    Yu, Song; Yan-ming, Zhu; Wu, Li

    2017-02-01

    The microscopic mechanism of interactions between CH4 and coal macromolecules is of significant practical and theoretical importance in CBM development and methane storage. Under periodic boundary conditions, the optimal energy configuration of coal vitrinite, which has a higher torsion degree and tighter arrangement, can be determined by the calculation of molecular mechanics (MM) and molecular dynamics (MD), and annealing kinetics simulation based on ultimate analysis, 13C NMR, FT IR and HRTEM. Macromolecular stabilization is primarily due to the van der Waals energy and covalent bond energy, mainly consisting of bond torsion energy and bond angle energy. Using the optimal configuration as the adsorbent, GCMC simulation of vitrinite adsorption of CH4 is conducted. A saturated state is reached after absorbing 17 CH4s per coal vitrinite molecule. CH4 is preferentially adsorbed on the edge, and inclined to gathering around the branched chains of the inner vitrinite sites. Finally, the adsorption parameters are calculated through first principle DFT. The adsorbability order is as follows: aromatic structure> heteroatom rings > oxygen functional groups. The adsorption energy order is as follows: Top < Bond < Center, Up < Down. The order of average RDF better reflects the adsorption ability and that of [-COOH] is lower than those of [sbnd Cdbnd O] and [Csbnd Osbnd C]. CH4 distributed in the distance of 0.99-16 Å to functional groups in the type of monolayer adsorption and the average distance order manifest as [sbnd Cdbnd O] (1.64 Å) < [Csbnd Osbnd C] (1.89 Å) < [sbnd COOH] (3.78 Å) < [-CH3] (4.11 Å) according to the average RDF curves. CH4 enriches around [sbnd Cdbnd O] and [Csbnd O-C] whereas is rather dispersed about [-COOH] and [CH3]. Simulation and experiment data are both in strong agreement with the Langmuir and D-A isothermal adsorption model and the D-A model fit better than Langmuir model. Preferential adsorption sites and orientations in vitrinite are

  6. In vitro adsorption of tilidine HCl by activated charcoal.

    PubMed

    Cordonnier, J A; Van den Heede, M A; Heyndrickx, A M

    In vitro studies were carried out in order to determine the adsorption of tilidine HCl, a narcotic analgesic, by activated charcoal (max. adsorption capacity 185.5 mg/g of charcoal). The path of the adsorption isotherms at pH 1.2 and 7.5 suggests that the in vivo adsorption of tilidine HCl may be increased when the drug passes from the stomach to the intestine, unless the intestinal content exerts a displacing effect. Nevertheless, the adsorption was dependent on the quantity of activated charcoal used, becoming more complete when the quantity of activated charcoal was increased. The effects of additives on the adsorption capacity of activated charcoal were also investigated in vitro. Ethanol, sorbitol and sucrose significantly reduced drug adsorption, while cacao powder, milk and starch had no effect on tilidine adsorption. At an acid pH, Federa Activated Charcoal significantly adsorbed more drug than either Norit A or Activated Charcoal Merck.

  7. Efficient adsorption of both methyl orange and chromium from their aqueous mixtures using a quaternary ammonium salt modified chitosan magnetic composite adsorbent.

    PubMed

    Li, Kun; Li, Pei; Cai, Jun; Xiao, Shoujun; Yang, Hu; Li, Aimin

    2016-07-01

    A quaternary ammonium salt modified chitosan magnetic composite adsorbent (CS-CTA-MCM) was prepared by combination of Fe3O4 nanoparticles. Various techniques were used to characterize the molecular structure, surface morphology, and magnetic feature of this composite adsorbent. CS-CTA-MCM was employed for the removal of Cr(VI) and methyl orange (MO), an anionic dye, from water in respective single and binary systems. Compared with chitosan magnetic adsorbent (CS-MCM) without modification, CS-CTA-MCM shows evidently improved adsorption capacities for both pollutants ascribed to the additional quaternary ammonium salt groups. Based on the adsorption equilibrium study, MO bears more affinity to CS-CTA-MCM than Cr(VI) causing a considerable extent of preferential adsorption of dye over metal ions in their aqueous mixture. However, at weak acidic solutions, Cr(VI) adsorption is evidently improved due to more efficient Cr(VI) forms, i.e. dichromate and monovalent chromate, binding to this chitosan-based adsorbent. Thus chromium could be efficient removal together with MO at suitable pH conditions. The adsorption isotherms and kinetics indicate that adsorptions of Cr(VI) and MO by CS-CTA-MCM both follow a homogeneous monolayer chemisorption process. This magnetic adsorbent after saturated adsorption could be rapidly separated from water and easily regenerated using dilute NaOH aqueous solutions then virtually reused with little adsorption capacity loss.

  8. Structure regulation of silica nanotubes and their adsorption behaviors for heavy metal ions: pH effect, kinetics, isotherms and mechanism.

    PubMed

    Wang, Pan; Du, Mingliang; Zhu, Han; Bao, Shiyong; Yang, Tingting; Zou, Meiling

    2015-04-09

    Silica nanotubes (SNTs) with controlled nanotubular structure were synthesized via an electrospinning and calcination process. In this regard, SNTs were found to be ideal adsorbents for Pb(II) removal with a higher adsorption capacity, and surface modification of the SNTs by sym-diphenylcarbazide (SD-SNTs) markedly enhanced the adsorption ability due to the chelating interaction between imino groups and Pb(II). The pH effect, kinetics, isotherms and adsorption mechanism of SNTs and SD-SNTs on Pb(II) adsorption were investigated and discussed detailedly. The adsorption capacity for Pb(II) removal was found to be significantly improved with the decrease of pH value. The Langmuir adsorption model agreed well with the experimental data. As for kinetic study, the adsorption onto SNTs and SD-SNTs could be fitted to pseudo-first-order and pseudo-second-order model, respectively. In addition, the as-prepared SNTs and SD-SNTs also exhibit high adsorption ability for Cd(II) and Co(II). The experimental results demonstrate that the SNTs and SD-SNTs are potential adsorbents and can be used effectively for the treatment of heavy-metal-ions-containing wastewater.

  9. CRYOGENIC ADSORPTION OF HYDROGEN ISOTOPES OVER NANO-STRUCTURED MATERIALS

    SciTech Connect

    Xiao, S.; Heung, L.

    2010-10-07

    Porous materials such as zeolites, activated carbon, silica gels, alumina and a number of industrial catalysts are compared and ranked for hydrogen and deuterium adsorption at liquid nitrogen temperature. All samples show higher D{sub 2} adsorption than that of H{sub 2}, in which a HY sample has the greatest isotopic effect while 13X has the highest hydrogen uptake capacity. Material's moisture content has significant impact to its hydrogen uptake. A material without adequate drying could result in complete loss of its adsorption capacity. Even though some materials present higher H{sub 2} adsorption capacity at full pressure, their adsorption at low vapor pressure may not be as good as others. Adsorption capacity in a dynamic system is much less than in a static system. A sharp desorption is also expected in case of temperature upset.

  10. Adsorption of tetracycline on soil and sediment: effects of pH and the presence of Cu(II).

    PubMed

    Zhang, Zheyun; Sun, Ke; Gao, Bo; Zhang, Guixiang; Liu, Xitao; Zhao, Ye

    2011-06-15

    Tetracycline (TC) is frequently detected in the environment, however, knowledge on the environmental fate and transport of TC is still limited. Batch adsorption experiments of TC by soil and sediment samples were conducted. The distribution of charge and electrostatic potential of individual atoms of various TC species in the aqueous solution were determined using MOPAC version 0.034 W program in ChemBio3D Ultra software. Most of the adsorption isotherms on the soil, river and marine sediments were well fitted with the Freundlich and Polanyi-Manes (PMM) models. The single point organic carbon (OC)-normalized adsorption distribution coefficients (K(OC)) and PMM saturated adsorption capacity (Q(OC)(0)) values of TC were associated with the mesopore volume and clay content to a greater extent, indicating the mesopore volume of the soil and sediments and their clay content possibly influenced the fate and transport of TC in the natural environment. The adsorption of TC on soil and sediments strongly depended on the pH and presence of Cu(II). The presence of Cu(II) facilitated TC adsorption on soil and sediments at low pH (pH<5), possibly due to the metallic complexation and surface-bridging mechanism by Cu(II) adsorption on soil and sediments. The cation exchange interaction, metallic complexation and Coulombic interaction of mechanisms for adsorption of TC to soils and sediments were further supported by quantum chemical calculation of various TC species in different pH.

  11. Protein Adsorption in Three Dimensions

    PubMed Central

    Vogler, Erwin A.

    2011-01-01

    Recent experimental and theoretical work clarifying the physical chemistry of blood-protein adsorption from aqueous-buffer solution to various kinds of surfaces is reviewed and interpreted within the context of biomaterial applications, especially toward development of cardiovascular biomaterials. The importance of this subject in biomaterials surface science is emphasized by reducing the “protein-adsorption problem” to three core questions that require quantitative answer. An overview of the protein-adsorption literature identifies some of the sources of inconsistency among many investigators participating in more than five decades of focused research. A tutorial on the fundamental biophysical chemistry of protein adsorption sets the stage for a detailed discussion of the kinetics and thermodynamics of protein adsorption, including adsorption competition between two proteins for the same adsorbent immersed in a binary-protein mixture. Both kinetics and steady-state adsorption can be rationalized using a single interpretive paradigm asserting that protein molecules partition from solution into a three-dimensional (3D) interphase separating bulk solution from the physical-adsorbent surface. Adsorbed protein collects in one-or-more adsorbed layers, depending on protein size, solution concentration, and adsorbent surface energy (water wettability). The adsorption process begins with the hydration of an adsorbent surface brought into contact with an aqueous-protein solution. Surface hydration reactions instantaneously form a thin, pseudo-2D interface between the adsorbent and protein solution. Protein molecules rapidly diffuse into this newly-formed interface, creating a truly 3D interphase that inflates with arriving proteins and fills to capacity within milliseconds at mg/mL bulk-solution concentrations CB. This inflated interphase subsequently undergoes time-dependent (minutes-to-hours) decrease in volume VI by expulsion of either-or-both interphase water and

  12. Spherical polystyrene-supported chitosan thin film of fast kinetics and high capacity for copper removal.

    PubMed

    Jiang, Wei; Chen, Xubin; Pan, Bingcai; Zhang, Quanxing; Teng, Long; Chen, Yufan; Liu, Lu

    2014-07-15

    In order to accelerate the kinetics and improve the utilization of the surface active groups of chitosan (CS) for heavy metal ion removal, sub-micron-sized polystyrene supported chitosan thin-film was synthesized by the electrostatic assembly method. Glutaraldehyde was used as cross-linking agent. Chitosan thin-film was well coated onto the surface of the polystyrene (PS) beads characterized by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). Their adsorption toward Cu(II) ions was investigated as a function of solution pH, degree of cross-linking, equilibrium Cu(II) ions concentration and contact time. The maximum adsorptive capacity of PS-CS was 99.8 mg/g in the adsorption isotherm study. More attractively, the adsorption equilibrium was achieved in 10 min, which showed superior properties among similar adsorbents. Continuous adsorption-desorption cyclic results demonstrated that Cu(II)-loaded PS-CS can be effectively regenerated by a hydrochloric acid solution (HCl), and the regenerated composite beads could be employed for repeated use without significant capacity loss, indicating the good stability of the adsorbents. The XPS analysis confirmed that the adsorption process was due to surface complexes with atoms of chitosan. Generally, PS beads could be employed as a promising host to fabricate efficient composites that originated from chitosan or other bio-sorbents for environmental remediation.

  13. Protein adsorption to poly(ethylenimine)-modified Sepharose FF: V. Complicated effects of counterions.

    PubMed

    Liu, Na; Yu, Linling; Sun, Yan

    2015-07-24

    In the previous studies on protein adsorption to poly(ethylenimine) (PEI)-grafted Sepharose FF resins, a critical ionic capacity (600mmol/L) of PEI-Sepharose resins was found for the adsorption of bovine serum albumin (BSA), above which both protein capacity and uptake rate increased drastically. In this work, the influence of counterions on the PEI-Sepharose resin with an ionic capacity of 683mmol/L (FF-PEI-L680) was investigated with sodium salts of SCN(-), Cl(-), HPO4(2-) and SO4(2-). Linear gradient elution, batch adsorption and breakthrough experiments showed that counterion preference, effective pore diffusion coefficient (De) and dynamic binding capacity (DBC) values increased in the order of SCN(-), Cl(-), HPO4(2-) and SO4(2-), while static adsorption capacity decreased in this order. It is considered that higher counterion preference of the ion exchange groups resulted in lower protein binding strength and adsorption capacity, while the De value increased due to the enhanced "chain delivery" effect (a kind of surface diffusion). Besides, the DBC value was mainly dependent on De value. In particular, SO4(2-) was the most favorable counterion for the PEI-Sepharose resin, which gave rise to the highest De value (De/D0=1.17, D0 is protein diffusivity in free solution) and DBC value (118mg/mL at a residence time of 2min). Moreover, the effects of counterions on BSA adsorption to DEAE Sepharose FF and Q Sepharose FF, which were non-grafted resins, were also studied for comparisons. It was found that the counterion preferences of the two non-grafted resins were different from each other and also different from that of FF-PEI-L680. The different counterion preferences were attributed to the differences in the ion-exchange ligand chemistries. In addition, the De values for DEAE Sepharose FF and Q Sepharose FF kept unchanged. The low counterion sensitivity of De values could be interpreted as the lack of "chain delivery" effect for the non-grafted resins. The

  14. Siloxane treatment by adsorption into porous materials.

    PubMed

    Ricaurte Ortega, D; Subrenat, A

    2009-09-01

    activated carbon than for the zeolite and silica gel, congruent with the porous structure of the material. Moreover, it was found that D4 is more adsorbable than L2, due to possible interactions between the solid surface and the physical structure of the cyclic compound (D4). The influence of humidity and temperature were also studied. The increase in the temperature reduced the adsorption capacities. The influence of humidity on the adsorption was investigated under dry air and humid air at 70%. No significant difference in the adsorption capacities was found for the activated carbon and for the zeolite, but for the silica gel the mass transfer decreased considerably. For the adsorption isotherms, the maximal capacity of elimination was obtained with the activated carbon materials and was directly related to the porous structure. Thus activated carbon cloth was chosen to design the adsorption-desorption processes in a dynamic system. Thermal heating was used to achieve the regeneration process. Initial cycles have been accomplished and show the stability of the process.

  15. Predicting Multicomponent Adsorption Isotherms in Open-Metal Site Materials Using Force Field Calculations Based on Energy Decomposed Density Functional Theory.

    PubMed

    Heinen, Jurn; Burtch, Nicholas C; Walton, Krista S; Fonseca Guerra, Célia; Dubbeldam, David

    2016-12-12

    For the design of adsorptive-separation units, knowledge is required of the multicomponent adsorption behavior. Ideal adsorbed solution theory (IAST) breaks down for olefin adsorption in open-metal site (OMS) materials due to non-ideal donor-acceptor interactions. Using a density-function-theory-based energy decomposition scheme, we develop a physically justifiable classical force field that incorporates the missing orbital interactions using an appropriate functional form. Our first-principles derived force field shows greatly improved quantitative agreement with the inflection points, initial uptake, saturation capacity, and enthalpies of adsorption obtained from our in-house adsorption experiments. While IAST fails to make accurate predictions, our improved force field model is able to correctly predict the multicomponent behavior. Our approach is also transferable to other OMS structures, allowing the accurate study of their separation performances for olefins/paraffins and further mixtures involving complex donor-acceptor interactions.

  16. Metal adsorption by agricultural biosorbents: Adsorption isotherm, kinetic and biosorbents chemical structures.

    PubMed

    Sadeek, Sadeek A; Negm, Nabel A; Hefni, Hassan H H; Wahab, Mostafa M Abdel

    2015-11-01

    Biosorption of Cu(II), Co(II) and Fe(III) ions from aqueous solutions by rice husk, palm leaf and water hyacinth was investigated as a function of initial pH, initial heavy metal ions concentration and treatment time. The adsorption process was examined by two adsorption isotherms: Langmuir and Freundlich isotherms. The experimental data of biosorption process were analyzed using pseudo-first order, pseudo-second order kinetic models. The equilibrium biosorption isotherms showed that the three studied biosorbents possess high affinity and sorption capacity for Cu(II), Co(II) and Fe(III) ions. Rice husk showed more efficiency than palm leaf and water hyacinth. Adsorption of Cu(II) and Co(II) was more efficient in alkaline medium (pH 9) than neutral medium due to the high solubility of metal ion complexes. The metal removal efficiency of each biosorbent was correlated to its chemical structure. DTA studies showed formation of metal complex between the biosorbents and the metal ions. The obtained results showed that the tested biosorbents are efficient and alternate low-cost biosorbent for removal of heavy metal ions from aqueous media.

  17. The effects of surface chemistry of mesoporous silica materials and solution pH on kinetics of molsidomine adsorption

    SciTech Connect

    Dolinina, E.S.; Parfenyuk, E.V.

    2014-01-15

    Adsorption kinetics of molsidomine on mesoporous silica material (UMS), the phenyl- (PhMS) and mercaptopropyl-functionalized (MMS) derivatives from solution with different pH and 298 K was studied. The adsorption kinetics was found to follow the pseudo-second-order kinetic model for all studied silica materials and pH. Effects of surface functional groups and pH on adsorption efficiency and kinetic adsorption parameters were investigated. At all studied pH, the highest molsidomine amount is adsorbed on PhMS due to π–π interactions and hydrogen bonding between surface groups of PhMS and molsidomine molecules. An increase of pH results in a decrease of the amounts of adsorbed molsidomine onto the silica materials. Furthermore, the highest adsorption rate kinetically evaluated using a pseudo-second-order model, is observed onto UMS and it strongly depends on pH. The mechanism of the adsorption process was determined from the intraparticle diffusion and Boyd kinetic film–diffusion models. The results showed that the molsidomine adsorption on the silica materials is controlled by film diffusion. Effect of pH on the diffusion parameters is discussed. - Graphical abstract: The kinetic study showed that the k{sub 2} value, the rate constant of pseudo-second order kinetic model, is the highest for molsidomine adsorption on UMS and strongly depends on pH because it is determined by availability and accessibility of the reaction sites of the adsorbents molsidomine binding. Display Omitted - Highlights: • The adsorption capacities of UMS, PhMS and MMS were dependent on the pH. • At all studied pH, the highest molsidomine amount is adsorbed on PhMS. • The highest adsorption rate, k{sub 2}, is observed onto UMS and strongly depends on pH. • Film diffusion was the likely rate-limiting step in the adsorption process.

  18. Adsorption of phenolic compound by aged-refuse.

    PubMed

    Xiaoli, Chai; Youcai, Zhao

    2006-09-01

    The adsorption of phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol by aged-refuse has been studied. Adsorption isotherms have been determined for phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol and the data fits well to the Freundlich equation. The chlorinated phenols are absorbed more strongly than the phenol and the adsorption capacity has an oblivious relationship with the numbers and the position of chlorine subsistent. The experiment data suggests that both the partition function and the chemical adsorption involve in the adsorption process. Pseudo-first-order and pseudo-second-order model were applied to investigate the kinetics of the adsorption and the results show that it fit the pseudo-second-order model. More than one step involves in the adsorption process and the overall rate of the adsorption process appears to be controlled by the chemical reaction. The thermodynamic analysis indicates that the adsorption is spontaneous and endothermic.

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

    PubMed

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

    2015-01-01

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

  20. Adsorption of plasmid DNA on anion exchange chromatography media.

    PubMed

    Tarmann, Christina; Jungbauer, Alois

    2008-08-01

    Anion exchange chromatography (AEC) is a useful and effective tool for DNA purification, but due to average pore sizes between 40 and 100 nm most AEC resins lack truly useful binding capacities for plasmid DNA (pDNA). Equilibrium binding capacities and uptake kinetics of AEC media including conventional media (Source 30 Q, Q Sepharose HP), a polymer grafted medium (Fractogel EMD DEAE (M)), media with large pores (Celbeads DEAE, PL SAX 4000 A 30 microm) and a monolithic medium (CIM-DEAE) were investigated by batch uptake or shallow bed experiments at two salt concentrations. Theoretical and experimental binding capacities suggest that the shape of the pDNA molecule can be described by a rod with a length to diameter ratio of 20:1 and that the molecule binds in upright position. The arrangement of DNA like a brush at the surface can be considered as entropy driven, kind of self-assembly process which is inherent to highly and uniformly charged DNA molecules. The initial phase of adsorption is very fast and levels off, associated with a change in mass transfer mechanism. Feed concentrations higher than 0.1 mg/mL pDNA pronounce this effect. Monolithic media showed the fastest adsorption rate and highest binding capacity with 13 mg pDNA per mL.

  1. Graphene oxide/ferroferric oxide/polyethylenimine nanocomposites for Congo red adsorption from water.

    PubMed

    Wang, Lina; Mao, Changming; Sui, Ning; Liu, Manhong; Yu, William W

    2017-04-01

    Graphene oxide/ferroferric oxide/polyethylenimine (GO/Fe3O4/PEI) nanocomposites were synthesized by an in situ growth of Fe3O4 nanoparticles on GO sheets, and then modified by PEI. The GO/Fe3O4/PEI nanocomposites showed extremely high removal efficiency for anionic dye Congo Red (CR) due to the positively charged PEI molecules (methylene blue was also tested but with low adsorption capacity due to its cationic property). The CR removal capacity was 574.7 mg g(-1), higher than most of reported results. The adsorption kinetics could be well described by a pseudo-second-order model. Furthermore, GO/Fe3O4/PEI nanocomposites could be easily recycled by magnetic separation. The removal efficiency remained above 70% after five cycles.

  2. An enhanced hydrogen adsorption enthalpy for fluoride intercalated graphite compounds.

    PubMed

    Cheng, Hansong; Sha, Xianwei; Chen, Liang; Cooper, Alan C; Foo, Maw-Lin; Lau, Garret C; Bailey, Wade H; Pez, Guido P

    2009-12-16

    We present a combined theoretical and experimental study on H(2) physisorption in partially fluorinated graphite. This material, first predicted computationally using ab initio molecular dynamics simulation and subsequently synthesized and characterized experimentally, represents a novel class of "acceptor type" graphite intercalated compounds that exhibit significantly higher isosteric heat of adsorption for H(2) at near ambient temperatures than previously demonstrated for commonly available porous carbon-based materials. The unusually strong interaction arises from the semi-ionic nature of the C-F bonds. Although a high H(2) storage capacity (>4 wt %) at room temperature is predicted not to be feasible due to the low heat of adsorption, enhanced storage properties can be envisaged by doping the graphitic host with appropriate species to promote higher levels of charge transfer from graphene to F(-) anions.

  3. Adsorption of carbon dioxide by MIL-101(Cr): regeneration conditions and influence of flue gas contaminants.

    PubMed

    Liu, Qing; Ning, Liqi; Zheng, Shudong; Tao, Mengna; Shi, Yao; He, Yi

    2013-10-10

    MIL-101(Cr) has drawn much attention due to its high stability compared with other metal-organic frameworks. In this study, three trace flue gas contaminants (H2O, NO, SO2) were each added to a 10 vol% CO2/N2 feed flow and found to have a minimal impact on the adsorption capacity of CO2. In dynamic CO2 regeneration experiments, complete regeneration occurred in 10 min at 328 K for temperature swing adsorption-N2-stripping under a 50 cm(3)/min N2 flow and at 348 K for vacuum-temperature swing adsorption at 20 KPa. Almost 99% of the pre-regeneration adsorption capacity was preserved after 5 cycles of adsorption/desorption under a gas flow of 10 vol% CO2, 100 ppm SO2, 100 ppm NO, and 10% RH, respectively. Strong resistance to flue gas contaminants, mild recovery conditions, and excellent recycling efficiency make MIL-101(Cr) an attractive adsorbent support for CO2 capture.

  4. Adsorption of Carbon Dioxide by MIL-101(Cr): Regeneration Conditions and Influence of Flue Gas Contaminants

    PubMed Central

    Liu, Qing; Ning, Liqi; Zheng, Shudong; Tao, Mengna; Shi, Yao; He, Yi

    2013-01-01

    MIL-101(Cr) has drawn much attention due to its high stability compared with other metal-organic frameworks. In this study, three trace flue gas contaminants (H2O, NO, SO2) were each added to a 10 vol% CO2/N2 feed flow and found to have a minimal impact on the adsorption capacity of CO2. In dynamic CO2 regeneration experiments, complete regeneration occurred in 10 min at 328 K for temperature swing adsorption-N2-stripping under a 50 cm3/min N2 flow and at 348 K for vacuum-temperature swing adsorption at 20 KPa. Almost 99% of the pre-regeneration adsorption capacity was preserved after 5 cycles of adsorption/desorption under a gas flow of 10 vol% CO2, 100 ppm SO2, 100 ppm NO, and 10% RH, respectively. Strong resistance to flue gas contaminants, mild recovery conditions, and excellent recycling efficiency make MIL-101(Cr) an attractive adsorbent support for CO2 capture. PMID:24107974

  5. Adsorption of Carbon Dioxide by MIL-101(Cr): Regeneration Conditions and Influence of Flue Gas Contaminants

    NASA Astrophysics Data System (ADS)

    Liu, Qing; Ning, Liqi; Zheng, Shudong; Tao, Mengna; Shi, Yao; He, Yi

    2013-10-01

    MIL-101(Cr) has drawn much attention due to its high stability compared with other metal-organic frameworks. In this study, three trace flue gas contaminants (H2O, NO, SO2) were each added to a 10 vol% CO2/N2 feed flow and found to have a minimal impact on the adsorption capacity of CO2. In dynamic CO2 regeneration experiments, complete regeneration occurred in 10 min at 328 K for temperature swing adsorption-N2-stripping under a 50 cm3/min N2 flow and at 348 K for vacuum-temperature swing adsorption at 20 KPa. Almost 99% of the pre-regeneration adsorption capacity was preserved after 5 cycles of adsorption/desorption under a gas flow of 10 vol% CO2, 100 ppm SO2, 100 ppm NO, and 10% RH, respectively. Strong resistance to flue gas contaminants, mild recovery conditions, and excellent recycling efficiency make MIL-101(Cr) an attractive adsorbent support for CO2 capture.

  6. Optimizing the lanthanum adsorption process onto chemically modified biomaterials using factorial and response surface design.

    PubMed

    Gabor, Andreea; Davidescu, Corneliu Mircea; Negrea, Adina; Ciopec, Mihaela; Grozav, Ion; Negrea, Petru; Duteanu, Narcis

    2017-01-29

    The rare metals' potential to pollute air, water, soil, and especially groundwater has received lot of attention recently. One of the most common rare earth group elements, lanthanum, is used in many industrial branches, and due to its toxicity, it needs to be eliminated from all residual aqueous solutions. The goal of this study was to evaluate the control of the adsorption process for lanthanum removal from aqueous solutions, using cellulose, a known biomaterial with high adsorbent properties, cheap, and environment friendly. The cellulose was chemically modified by functionalization with sodium β-glycerophosphate. The experimental results obtained after factorial design indicate optimum adsorption parameters as pH 6, contact time 60 min, and temperature 298 K, when the equilibrium concentration of lanthanum was 250 mg L(-1), and the experimental adsorption capacity obtained was 31.58 mg g(-1). Further refinement of the optimization of the adsorption process by response surface design indicates that at pH 6 and the initial concentration of 256 mg L(-1), the adsorption capacity has maximum values between 30.87 and 36.73 mg g(-1).

  7. Phosphate adsorption from sewage sludge filtrate using zinc-aluminum layered double hydroxides.

    PubMed

    Cheng, Xiang; Huang, Xinrui; Wang, Xingzu; Zhao, Bingqing; Chen, Aiyan; Sun, Dezhi

    2009-09-30

    A series of layered double hydroxides (LDHs) with different metal cations were synthesized to remove phosphate in waste sludge filtrate from a municipal wastewater treatment plant for phosphorus recovery and to help control eutrophication. The highest phosphate adsorption capacity was obtained by using Zn-Al-2-300, that is LDHs with Zn/Al molar ratio of 2 and calcined at 300 degrees C for 4h. Circumneutral and mildly alkaline waters appeared suitable for the possible application of Zn-Al LDHs due to the amphoteric nature of aluminum hydroxide. Phosphate adsorption from the sludge filtrate by the LDHs followed pseudo-second-order kinetics, and the adsorption capacity at equilibrium was determined to be approximately 50 mg P/g. Adsorption isotherms showed that phosphate uptake in this study was an endothermic process and had a good fit with a Langmuir-type model. The absorbed phosphate can be effectively desorbed (more than 80%) from LDHs particles by a 5 wt% NaOH solution. The regeneration rate of used LDHs was approximately 60% after six cycles of adsorption-desorption-regeneration.

  8. Removal of chromium from tannery effluents by adsorption.

    PubMed

    Fadali, O A; Magdy, Y H; Daifullah, A A M; Ebrahiem, E E; Nassar, M M

    2004-01-01

    Tannery effluent is characterized not only by heavy loads but also with toxic heavy metals especially chromium ions. Chromium is considered an important source of contamination due to large volume of exhaust liquid discharged and solid sludge produced. Details on adsorption studies were carried out using synthetic chromium salts (chromium chloride) as adsorbate, and cement kiln dust (a waste from white cement industry) as adsorbent. Equilibrium isotherms have been determined for the adsorption of chromium ions on cement kiln dust. Kinetic study provided that the adsorption process is diffusion controlled. The experimental results have been fitted using Freundlich, Langmuir, and Redlich Peterson isotherms. The maximum adsorption capacity of cement kiln dust was found to be 33 mg/g. Industrial tannery effluent (22-mg/L chromium and COD 952 mg/L) was also treated by cement dust. The treated effluent (using 20 g cement dust per 1 L) contains only 0.6 mg/L chromium and COD 200 mg/L.

  9. Functionalized SBA-15 materials for bilirubin adsorption

    NASA Astrophysics Data System (ADS)

    Tang, Tao; Zhao, Yanling; Xu, Yao; Wu, Dong; Xu, Jun; Deng, Feng

    2011-05-01

    To investigate the driving force for bilirubin adsorption on mesoporous materials, a comparative study was carried out between pure siliceous SBA-15 and three functionalized SBA-15 mesoporous materials: CH 3-SBA-15 (MS), NH 2-SBA-15 (AS), and CH 3/NH 2-SBA-15 (AMS) that were synthesized by one-pot method. The obtained materials exhibited large surface areas (553-810 m 2/g) and pore size (6.6-7.1 nm) demonstrated by XRD and N 2-ad/desorption analysis. The SEM images showed that the materials had similar fiberlike morphology. The functionalization extent was calculated according to 29Si MAS NMR spectra and it was close to the designed value (10%). The synthesized mesoporous materials were used as bilirubin adsorbents and showed higher bilirubin adsorption capacities than the commercial active carbon. The adsorption capacities of amine functionalized samples AMS and AS were larger than those of pure siliceous SBA-15 and MS, indicating that electrostatic interaction was the dominant driving force for bilirubin adsorption on mesoporous materials. Increasing the ionic strength of bilirubin solution by adding NaCl would decrease the bilirubin adsorption capacity of mesoporous material, which further demonstrated that the electrostatic interaction was the dominant driving force for bilirubin adsorption. In addition, the hydrophobic interaction provided by methyl groups could promote the bilirubin adsorption.

  10. Adsorption and desorption behavior of copper ions on Na-montmorillonite: effect of rhamnolipids and pH.

    PubMed

    Ozdemir, Günseli; Yapar, Saadet

    2009-07-30

    In this work, the effects of an anionic biosurfactant, rhamnolipid (RL), and pH on the adsorption and desorption of Cu(2+) ions on Na-montmorillonite were investigated. Adsorption studies were conducted through the addition of Cu(2+) to the dispersions containing pristine- and/or RL-modified clay. In the case of pristine clay, RL was also added simultaneously with the Cu(2+). The effect of pH was studied in the range between 1.0 and 8.0. The highest adsorption capacity was obtained at the pH of 4.7-4.8. Among the models including the Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich isotherms; Langmuir isotherm gave a better fit to the experimental data. The most suitable fit for the adsorption kinetics of Cu(2+) was obtained with a pseudo-second-order model. It was determined that the adsorption capacity of the pristine clay is comparable with that of the activated carbon and the modification of clay with RL causes an increase in the adsorption rate due to the distribution of clay platelets in the solution.

  11. Selenium removal from drinking water by adsorption to chitosan-clay composites and oxides: batch and columns tests.

    PubMed

    Bleiman, Nimrod; Mishael, Yael G

    2010-11-15

    Polymer-clay composites were designed to adsorb selenium from water. The highest adsorption efficiency was obtained for chitosan-montmorillonite composites. These composites were characterized by XRD, zeta potential, and FTIR measurements. Adsorption isotherms of selenate on the composite, on Al-oxide and on Fe-oxide were in good agreement with the Langmuir model, yielding a somewhat higher capacity for the composite, 18.4, 17.2 and 8.2 mg/g, respectively. In addition, adsorption by the composite was not pH dependent while its adsorption by the oxides decreased at high pH. Selenium removal from well water (closed due to high selenium concentrations, 0.1 mg/L) by the composite, brought levels to below the WHO limit (0.01 mg/L) and was selective for selenium even in the presence of sulfur (13 mg/L). Selenium adsorption by the composite was higher than by the Al-oxide due to high adsorption of sulfur by the later. Unlike employment in batch Al-oxide is more suitable for employment in filtration columns due to its high hydraulic conductivity. A semi-pilot columns experiment demonstrated selenium removal from the well water below the recommended limit (first 400 pore volumes) by Al-oxide columns. Regeneration of Al-oxide and of the composite was studied and readsorption of selenium was demonstrated.

  12. Adsorption of carbon black using carboxymethyl chitosan in deinking process

    NASA Astrophysics Data System (ADS)

    Muryeti, Budimulyani, Estuti; Sinurat, Ellya

    2017-03-01

    The study about synthesis, characterization, and application carboxymethyl chitosan as adsorbent in deinking process was conducted. Adsorption of carbon black onto carboxymethyl chitosan has been investigated in a batch system. This research was conducted to obtain the adsorption capacity of carboxymethyl chitosan. The experiments were carried out to study the effect of carbon black concentration, contact time and dosage of carboxymethyl chitosan to the adsorption capacity of carboxymethyl chitosan. The optimum condition of carbon black adsorption was achieved at contact time of 60 min and weight doses of 1.0 g. The adsorption capacity of carboxymethyl chitosan was 14.34 mg/g and the adsorption effectivity was 70.54%. The result indicates that carboxymethyl chitosan could be used as adsorbent of carbon black in deinking process.

  13. Comparative study of adsorption of Pb(II) on native garlic peel and mercerized garlic peel.

    PubMed

    Liu, Wei; Liu, Yifeng; Tao, Yaqi; Yu, Youjie; Jiang, Hongmei; Lian, Hongzhen

    2014-02-01

    A comparative study using native garlic peel and mercerized garlic peel as adsorbents for the removal of Pb(2+) has been proposed. Under the optimized pH, contact time, and adsorbent dosage, the adsorption capacity of garlic peel after mercerization was increased 2.1 times and up to 109.05 mg g(-1). The equilibrium sorption data for both garlic peels fitted well with Langmuir adsorption isotherm, and the adsorbent-adsorbate kinetics followed pseudo-second-order model. These both garlic peels were characterized by elemental analysis, Fourier transform infrared spectrometry (FT-IR), and scanning electron microscopy, and the results indicated that mercerized garlic peel offers more little pores acted as adsorption sites than native garlic peel and has lower polymerization and crystalline and more accessible functional hydroxyl groups, which resulted in higher adsorption capacity than native garlic peel. The FT-IR and X-ray photoelectron spectroscopy analyses of both garlic peels before and after loaded with Pb(2+) further illustrated that lead was adsorbed on the through chelation between Pb(2+) and O atom existed on the surface of garlic peels. These results described above showed that garlic peel after mercerization can be a more attractive adsorbent due to its faster sorption uptake and higher capacity.

  14. Competitive adsorption of ibuprofen and amoxicillin mixtures from aqueous solution on activated carbons.

    PubMed

    Mansouri, Hayet; Carmona, Rocio J; Gomis-Berenguer, Alicia; Souissi-Najar, Souad; Ouederni, Abdelmottaleb; Ania, Conchi O

    2015-07-01

    This work investigates the competitive adsorption under dynamic and equilibrium conditions of ibuprofen (IBU) and amoxicillin (AMX), two widely consumed pharmaceuticals, on nanoporous carbons of different characteristics. Batch adsorption experiments of pure components in water and their binary mixtures were carried out to measure both adsorption equilibrium and kinetics, and dynamic tests were performed to validate the simultaneous removal of the mixtures in breakthrough experiments. The equilibrium adsorption capacities evaluated from pure component solutions were higher than those measured in dynamic conditions, and were found to depend on the porous features of the adsorbent and the nature of the specific/dispersive interactions that are controlled by the solution pH, density of surface change on the carbon and ionization of the pollutant. A marked roll-up effect was observed for AMX retention on the hydrophobic carbons, not seen for the functionalized adsorbent likely due to the lower affinity of amoxicillin towards the carbon adsorbent. Dynamic adsorption of binary mixtures from wastewater of high salinity and alkalinity showed a slight increase in IBU uptake and a reduced adsorption of AMX, demonstrating the feasibility of the simultaneous removal of both compounds from complex water matrices.

  15. Treatment of dilute methylene blue-containing wastewater by coupling sawdust adsorption and electrochemical regeneration.

    PubMed

    Bouaziz, I; Chiron, C; Abdelhedi, R; Savall, A; Groenen Serrano, K

    2014-01-01

    In the present work, the coupling of adsorption and electrochemical oxidation on a boron-doped diamond (BDD) electrode to treat solutions containing dyes is studied. This coupling may be convenient for the treatment of diluted pollutant that is limited by the low rate of electrooxidation due to mass-transfer limitation. A pre-concentration step by adsorption could minimize the design of the electrochemical reactor. The adsorbent chosen was mixed with softwood sawdust, and methylene blue was chosen as the model dye molecule. Isotherms of adsorption and kinetics were investigated as well as the effects of current density and regeneration time. The BDD electrochemical oxidation of methylene blue adsorbed onto sawdust led simultaneously to its degradation and sawdust regeneration for the next adsorption. It was observed that multiple adsorption and electrochemical regeneration cycles led to an enhancement of adsorption capacity of the sawdust. This study demonstrated that adsorption–electrochemical degradation coupling offers a promising approach for the efficient elimination of organic dyes from wastewater.

  16. Adsorption of uranium by amidoximated chitosan-grafted polyacrylonitrile, using response surface methodology.

    PubMed

    Xu, Chao; Wang, Jingjing; Yang, Tilong; Chen, Xia; Liu, Xunyue; Ding, Xingcheng

    2015-05-05

    The amidoximated chitosan-grafted polyacrylonitrile (CTS-g-PAO) was prepared for the adsorption of uranium from water. The effects of pH, concentration of uranium and the solid-liquid ratio on the adsorption of uranium by CTS-g-PAO were optimized using Doehlert design of response surface methodology (RSM). The adsorption capacity and removal efficiency achieved 312.06 mg/g and 86.02%, respectively. The adsorption process attained equilibrium only in 120 min. More than 80% of the absorbed uranium could be desorbed by 0.1 mol/l HCl or EDTA-Na, and CTS-g-PAO could be reused at least 3 times. The CTS-g-PAO and U(VI) ions formed a chelate complex due to FTIR spectral analysis. The surface morphology of CTS-g-PAO was also investigated by SEM. The adsorption process was better described by Langmuir isotherm and pseudo second order kinetic model. Results obtained indicated that CTS-g-PAO was very promising in adsorption of uranium from water.

  17. Effect of dispersion on adsorption of atrazine by aqueous suspensions of fullerenes.

    PubMed

    Gai, Ke; Shi, Baoyou; Yan, Xiaomin; Wang, Dongsheng

    2011-07-15

    With the widespread application of fullerenes, it is critical to assess their environmental behaviors and their impacts on the transport and bioavailability of organic contaminants. The effects of fullerene particle size, chemistry of the solution, and natural organic matter on the adsorption of atrazine by aqueous dispersions of fullerenes (C(60)) were investigated in this work. The results showed that the Polanyi-Manes model could fit the adsorption isotherms well. Smaller sizes of fullerene particles led to increased available sites and, consequently, enhanced the adsorption of atrazine on C(60). However, intensely dispersed C(60) systems might not possess suitably high adsorptive capacities due to surface chemistry change. Adsorption of atrazine by aqueous dispersions of C(60) increased with a decrease in the pH of the solution. Introduction of humic acid significantly reduced the size of the C(60) particles, and resulted in the increase of the adsorption amount. Fullerene materials, once released into the aquatic environment, are inclined to form aqueous suspensions with different degrees of dispersion, which would greatly affect the transport and fate of organic contaminants.

  18. Blocking effect of colloids on arsenate adsorption during co-transport through saturated sand columns.

    PubMed

    Ma, Jie; Guo, Huaming; Lei, Mei; Wan, Xiaoming; Zhang, Hanzhi; Feng, Xiaojuan; Wei, Rongfei; Tian, Liyan; Han, Xiaokun

    2016-06-01

    Transport of environmental pollutants through porous media is influenced by colloids. Co-transport of As(V) and soil colloids at different pH were systematically investigated by monitoring breakthrough curves (BTCs) in saturated sand columns. A solute transport model was applied to characterize transport and retention sites of As(V) in saturated sand in the presence of soil colloids. A colloid transport model and the DLVO theory were used to reveal the mechanism and hypothesis of soil colloid-promoted As(V) transport in the columns. Results showed that rapid transport of soil colloids, regulated by pH and ionic strength, promoted As(V) transport by blocking As(V) adsorption onto sand, although soil colloids had low adsorption for As(V). The promoted transport was more significant at higher concentrations of soil colloids (between 25 mg L(-1) and 150 mg L(-1)) due to greater blocking effect on As(V) adsorption onto the sand surfaces. The blocking effect of colloids was explained by the decreases in both instantaneous (equilibrium) As adsorption and first-order kinetic As adsorption on the sand surface sites. The discovery of this blocking effect improves our understanding of colloid-promoted As transport in saturated porous media, which provides new insights into role of colloids, especially colloids with low As adsorption capacity, in As transport and mobilization in soil-groundwater systems.

  19. TREATMENT OF LANDFILL LEACHATE BY COUPLING COAGULATION-FLOCCULATION OR OZONATION TO GRANULAR ACTIVATED CARBON ADSORPTION.

    PubMed

    Oloibiri, Violet; Ufomba, Innocent; Chys, Michael; Audenaert, Wim; Demeestere, Kristof; Van Hulle, Stijn W H

    2015-01-01

    A major concern for landfilling facilities is the treatment of their leachate. To optimize organic matter removal from this leachate, the combination of two or more techniques is preferred in order to meet stringent effluent standards. In our study, coagulation-flocculation and ozonation are compared as pre- treatment steps for stabilized landfill leachate prior to granular activated carbon (GAC) adsorption. The efficiency of the pre treatment techniques is evaluated using COD and UVA254 measurements. For coagulation- flocculation, different chemicals are compared and optimal dosages are determined. After this, iron (III) chloride is selected for subsequent adsorption studies due to its high percentage of COD and UVA254 removal and good sludge settle-ability. Our finding show that ozonation as a single treatment is effective in reducing COD in landfill leachate by 66% compared to coagulation flocculation (33%). Meanwhile, coagulation performs better in UVA254 reduction than ozonation. Subsequent GAC adsorption of ozonated effluent, coagulated effluent and untreated leachate resulted in 77%, 53% and 8% total COD removal respectively (after 6 bed volumes). The effect of the pre-treatment techniques on GAC adsorption properties is evaluated experimentally and mathematically using Thomas and Yoon-Nelson models. Mathematical modelling of the experimental GAC adsorption data shows that ozonation increases the adsorption capacity and break through time with a factor of 2.5 compared to coagulation-flocculation.

  20. Visualization and Measurement of Adsorption/Desorption Process of Ethanol in Activated Carbon Adsorber

    NASA Astrophysics Data System (ADS)

    Asano, Hitoshi; Murata, Kenta; Takenaka, Nobuyuki; Saito, Yasushi

    Adsorption refrigerator is one of the efficient tools for waste heat recovery, because the system is driven by heat at relative low temperature. However, the coefficient of performance is low due to its batch operation and the heat capacity of the adsorber. In order to improve the performance, it is important to optimize the configuration to minimize the amount of driving heat, and to clarify adsorption/desorption phenomena in transient conditions. Neutron radiography was applied to visualize and measure the adsorption amount distribution in an adsorber. The visualization experiments had been performed at the neutron radiography facility of E-2 port of Kyoto University Research Reactor. Activated carbon and ethanol were used as the adsorbent and refrigerant. From the acquired radiographs, adsorption amount was quantitatively measured by applying the umbra method using a checkered neutron absorber with boron powder. Then, transient adsorption and desorption processes of a rectangular adsorber with 84 mm in width, 50 mm in height and 20 mm in depth were visualized. As the result, the effect of fins in the adsorbent layer on the adsorption amount distribution was clearly visualized.

  1. [Adsorption dynamics and breakthrough characteristics based on the fluidization condition].

    PubMed

    Wang, Jun; Wang, Yao; Huang, Xing; Yuan, Yi-Long; Chen, Rui-Hui; Zhou, Hang; Zhou, Dan-Dan

    2014-02-01

    Few studies on the adsorption dynamics and breakthrough characteristics based on the fluidization condition have been reported. In a fluidized bed adsorption reactor with phenol as the adsorbate and granular activated carbon as the adsorbent, the adsorption efficiency, adsorption dynamic characteristics, adsorption breakthrough curves and adsorption capacities were studied and compared with those of a fixed bed operated under the same conditions. The results showed that the adsorption efficiencies exceeded 93% in 5 min in both the fluidized conditions and fixed conditions at the superficial velocities of 8 mm x s(-1) and 13 mm x s(-1). Meanwhile, the above adsorption reactions fitted to Pseudo-second-order with linear correlation coefficients greater than 0.999. The adsorption capacity of fluidized conditions was 8.77 mg x g(-1) and 24.70 mg x g(-1) at the superficial velocities of 6 mm x s(-1) and 8 mm x s(-1). Generally, the fluidized bed reactor showed a higher adsorption efficiency and greater adsorption capacity than the fixed bed reactor.

  2. Adsorption characteristics of acetone, chloroform and acetonitrile on sludge-derived adsorbent, commercial granular activated carbon and activated carbon fibers.

    PubMed

    Tsai, Jiun-Horng; Chiang, Hsiu-Mei; Huang, Guan-Yinag; Chiang, Hung-Lung

    2008-06-15

    The adsorption characteristics of chloroform, acetone, and acetonitrile on commercial activated carbon (C1), two types of activated carbon fibers (F1 and F2), and sludge adsorbent (S1) was investigated. The chloroform influent concentration ranged from 90 to 7800 ppm and the acetone concentration from 80 to 6900 ppm; the sequence of the adsorption capacity of chloroform and acetone on adsorbents was F2>F1 approximately C1 approximately S1. The adsorption capacity of acetonitrile ranged from 4 to 100 mg/g, corresponding to the influent range from 43 to 2700 ppm for C1, S1, and F1. The acetonitrile adsorption capacity of F2 was approximately 20% higher than that of the other adsorbents at temperatures<30 degrees C. The Freundlich equation fit the data better than the Langmuir and Dubinin-Radushkevich (D-R) equations. The adsorption rate of carbon fibers is higher than that of the other adsorbents due to their smaller fiber diameter and higher surface area. The micropore diffusion coefficient of VOC on activated carbon and sludge adsorbent was approximately 10(-4) cm2 s(-1). The diffusion coefficient of VOC on carbon fibers ranged from 10(-8) to 10(-7) cm2 s(-1). The small carbon fiber pore size corresponds to a smaller diffusion coefficient.

  3. COMPETITIVE ADSORPTION OF VOCS AND BOM: THE ROLE OF MOLECULAR OXYGEN

    EPA Science Inventory

    In this study, the presence of background organic matter (BOM) was seen to reduce the adsorptive capacity of carbon for chloroform, chlorobenzene, and dibromochloropropane. Adsorption of these compounds was further reduced under oxic conditions. This additional reduction in cap...

  4. Adsorption of halogenated aliphatic contaminants by graphene nanomaterials.

    PubMed

    Zhou, Yang; Apul, Onur Guven; Karanfil, Tanju

    2015-08-01

    In this study, adsorption of ten environmentally halogenated aliphatic synthetic organic compounds (SOCs) by a pristine graphene nanosheet (GNS) and a reduced graphene oxide (rGO) was examined, and their adsorption behaviors were compared with those of a single-walled carbon nanotube (SWCNT) and a granular activated carbon (GAC). In addition, the impacts of background water components (i.e., natural organic matter (NOM), ionic strength (IS) and pH) on the SOC adsorption behavior were investigated. The results indicated HD3000 and SWCNT with higher microporous volumes exhibited higher adsorption capacities for the selected aliphatic SOCs than graphenes, demonstrating microporosity of carbonaceous adsorbents played an important role in the adsorption. Analysis of adsorption isotherms demonstrated that hydrophobic interactions were the dominant contributor to the adsorption of aliphatic SOCs by graphenes. However, π-π electron donor-acceptor and van der Waals interactions are likely the additional mechanisms contributing to the adsorption of aliphatic SOCs on graphenes. Among the three background solution components examined, NOM showed the most influential effect on adsorption of the selected aliphatic SOCs, while pH and ionic strength had a negligible effects. The NOM competition on aliphatic adsorption was less pronounced on graphenes than SWCNT. Overall, in terms of adsorption capacities, graphenes tested in this study did not exhibit a major advantage over SWCNT and GAC for the adsorption of aliphatic SOCs.

  5. Fluorocarbon Adsorption in Hierarchical Porous Frameworks

    SciTech Connect

    Motkuri, Radha K.; Annapureddy, Harsha V.; Vijayakumar, M.; Schaef, Herbert T.; Martin, P F.; McGrail, B. Peter; Dang, Liem X.; Krishna, Rajamani; Thallapally, Praveen K.

    2014-07-09

    The adsorption behavior of a series of fluorocarbon derivatives was examined on a set of microporous metal organic framework (MOF) sorbents and another set of hierarchical mesoporous MOFs. The microporous M-DOBDC (M = Ni, Co) showed a saturation uptake capacity for R12 of over 4 mmol/g at a very low relative saturation pressure (P/Po) of 0.02. In contrast, the mesoporous MOF MIL-101 showed an exceptionally high uptake capacity reaching over 14 mmol/g at P/Po of 0.4. Adsorption affinity in terms of mass loading and isosteric heats of adsorption were found to generally correlate with the polarizability of the refrigerant with R12 > R22 > R13 > R14 > methane. These results suggest the possibility of exploiting MOFs for separation of azeotropic mixtures of fluorocarbons and use in eco-friendly fluorocarbon-based adsorption cooling and refrigeration applications.

  6. Retention capacities of several bryophytes for Hg(II) with special reference to the elevation and morphology of moss growth.

    PubMed

    Sun, Shou-Qin; Wang, Ding-Yong; He, Ming; Li, Xian-Yuan; Zhang, Cheng

    2007-10-01

    Hg(II) Retention capacities of nine bryophyte species, collected from Jinfo Mountains (JFM) in Chongqing, China, had been investigated with special reference to the effect of morphology and elevation of moss growth. Results indicated that adsorption capacities of bryophytes for Hg(II) became stronger with the increase of multi-branches and leafy-shoots, as well as the elevation of moss growth, which was observed both in adsorption isotherm and adsorption kinetics experiments. Contrarily, the desorption kinetics showed a decrease tendency with the increase of multi-branches and leafy-shoots and the elevation of moss growth. The results demonstrated that bryophytes with higher multi-branches and leafy-shoots and higher growth elevation had a stronger adsorption capacity and a weaker desorption tendency, and therefore had a stronger retention capacity to Hg(II). The results disclosed the different relative sensitivity and retention capacity of mosses to pollution resulting from heavy metals, due to the differences in growth elevation and morphology. These should be considered when bryophytes were chosen as a tool for biomonitoring materials to environmental pollution, especially caused by Hg(II).

  7. [Structural changes of aged biochar and the influence on phenanthrene adsorption].

    PubMed

    Tang, Wei; Guo, Yue; Wu, Jing-Gui; Huang, Zhao-Qin; Dai, Jing-Yu

    2014-07-01

    Biochars prepared by pyrolysis of rice husk at 350 degrees C and 550 degrees C were incubated in the lucifugal thermostat for 300 d. Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), Scanning Electron Microscopy (SEM), and Nuclear Magnetic Resonance (NMR) techniques were applied to explore the structural change before and after incubation. It was found that the oxygen content was increased after incubation, suggesting the formation of oxygen-containing functional groups. Incubation of the biochars also enhanced their nonlinear adsorption of phenanthrene. Structural change subjected to incubation was in fact affected by the pyrolysis temperatures at which the biochars were synthesized. Increase of polarity and decrease of aromaticity were found for biochars prepared at 350 degrees C. In contrast, incubation of biochars prepared at 550 degrees C resulted in increased aliphatic contents and aromaticity, as well as decrease of carboxyl group. The adsorption capacity of phenanthrene predicted by Langmuir model was 3.57 and 2.35 mg x g(-1) for new and aged biochar with lower pyrolysis temperature, respectively. It was assumed that change of the surface structure of the biochars due to aging inhibited the adsorption. On the contrary, aging of biochares prepared at 550 degrees C resulted in enhanced adsorption capacity of phenanthrene from 0.42 to 4.17 mg x (-1), which was probably correlated to the partition effect due to enhanced aromaticity. The data obtained in this research suggested that aging of biochars potentially affected the fate of the pollutants in environment.

  8. Polydopamine-mediated surface functionalization of electrospun nanofibrous membranes: Preparation, characterization and their adsorption properties towards heavy metal ions

    NASA Astrophysics Data System (ADS)

    Wu, Chunlin; Wang, Heyun; Wei, Zhong; Li, Chuan; Luo, Zhidong

    2015-08-01

    In this paper, a simple and versatile approach for the fabrication of a polyethyleneimine (PEI)-functionalized nanofibrous membrane utilizing polydopamine (PDA) as a mediator is proposed. The morphology and structure of the PDA-coated and PEI-grafted nanofibrous membranes were confirmed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Due to a large specific surface area and long fibrous morphology, the synthesized membranes were used as novel adsorbents for copper ion (Cu2+) removal from aqueous solutions. The adsorption of Cu2+ was investigated on the synthesized membranes regarding the membrane dosages, initial solution pH values, initial solution concentrations, contact times and temperatures. In addition, the adsorption equilibrium data of PEI-grafted membranes were well fitted with the Langmuir adsorption isotherm, and a maximum adsorption capacity value of 33.59 mg g-1 was determined (while it was 21.94 mg g-1 for the PDA-coated membranes). The thermodynamic parameters indicated that Cu2+ absorption was a spontaneous and exothermic adsorption process. In addition, XPS peak differentiation imitating analysis permitted the proposal of a copper-amine coordination adsorption mechanism that can be used to explain changes in the adsorption properties compared to PDA coating nanofibrous membranes.

  9. Dynamic adsorption of diarrhetic shellfish poisoning (DSP) toxins in passive sampling relates to pore size distribution of aromatic adsorbent.

    PubMed

    Li, Aifeng; Ma, Feifei; Song, Xiuli; Yu, Rencheng

    2011-03-18

    Solid-phase adsorption toxin tracking (SPATT) technology was developed as an effective passive sampling method for dissolved diarrhetic shellfish poisoning (DSP) toxins in seawater. HP20 and SP700 resins have been reported as preferred adsorption substrates for lipophilic algal toxins and are recommended for use in SPATT testing. However, information on the mechanism of passive adsorption by these polymeric resins is still limited. Described herein is a study on the adsorption of OA and DTX1 toxins extracted from Prorocentrum lima algae by HP20 and SP700 resins. The pore size distribution of the adsorbents was characterized by a nitrogen adsorption method to determine the relationship between adsorption and resin porosity. The Freundlich equation constant showed that the difference in adsorption capacity for OA and DTX1 toxins was not determined by specific surface area, but by the pore size distribution in particular, with micropores playing an especially important role. Additionally, it was found that differences in affinity between OA and DTX1 for aromatic resins were as a result of polarity discrepancies due to DTX1 having an additional methyl moiety.

  10. Preparation and characterization of porous reduced graphene oxide based inverse spinel nickel ferrite nanocomposite for adsorption removal of radionuclides.

    PubMed

    Lingamdinne, Lakshmi Prasanna; Choi, Yu-Lim; Kim, Im-Soon; Yang, Jae-Kyu; Koduru, Janardhan Reddy; Chang, Yoon-Young

    2017-03-15

    For the removal of uranium(VI) (U(VI)) and thorium(IV) (Th(IV)), graphene oxide based inverse spinel nickel ferrite (GONF) nanocomposite and reduced graphene oxide based inverse spinel nickel ferrite (rGONF) nanocomposite were prepared by co-precipitation of GO with nickel and iron salts in one pot. The spectral characterization analyses revealed that GONF and rGONF have a porous surface morphology with an average particle size of 41.41nm and 32.16nm, respectively. The magnetic property measurement system (MPMS) studies confirmed the formation of ferromagnetic GONF and superparamagnetic rGONF. The adsorption kinetics studies found that the pseudo-second-order kinetics was well tune to the U(VI) and Th(IV) adsorption. The results of adsorption isotherms showed that the adsorption of U(VI) and Th(IV) were due to the monolayer on homogeneous surface of the GONF and rGONF. The adsorptions of both U(VI) and Th(IV) were increased with increasing system temperature from 293 to 333±2K. The thermodynamic studies reveal that the U(VI) and Th(IV) adsorption onto GONF and rGONF was endothermic. GONF and rGONF, which could be separated by external magnetic field, were recycled and re-used for up to five cycles without any significant loss of adsorption capacity.

  11. Adsorption of aromatic compounds by carbonaceous adsorbents: a comparative study on granular activated carbon, activated carbon fiber, and carbon nanotubes.

    PubMed

    Zhang, Shujuan; Shao, Ting; Kose, H Selcen; Karanfil, Tanju

    2010-08-15

    Adsorption of three aromatic organic compounds (AOCs) by four types of carbonaceous adsorbents [a granular activated carbon (HD4000), an activated carbon fiber (ACF10), two single-walled carbon nanotubes (SWNT, SWNT-HT), and a multiwalled carbon nanotube (MWNT)] with different structural characteristics but similar surface polarities was examined in aqueous solutions. Isotherm results demonstrated the importance of molecular sieving and micropore effects in the adsorption of AOCs by carbonaceous porous adsorbents. In the absence of the molecular sieving effect, a linear relationship was found between the adsorption capacities of AOCs and the surface areas of adsorbents, independent of the type of adsorbent. On the other hand, the pore volume occupancies of the adsorbents followed the order of ACF10 > HD4000 > SWNT > MWNT, indicating that the availability of adsorption site was related to the pore size distributions of the adsorbents. ACF10 and HD4000 with higher microporous volumes exhibited higher adsorption affinities to low molecular weight AOCs than SWNT and MWNT with higher mesopore and macropore volumes. Due to their larger pore sizes, SWNTs and MWNTs are expected to be more efficient in adsorption of large size molecules. Removal of surface oxygen-containing functional groups from the SWNT enhanced adsorption of AOCs.

  12. Adsorption and desorption of arsenate on sandy sediments from contaminated and uncontaminated saturated zones: Kinetic and equilibrium modeling.

    PubMed

    Hafeznezami, Saeedreza; Zimmer-Faust, Amity G; Dunne, Aislinn; Tran, Tiffany; Yang, Chao; Lam, Jacquelyn R; Reynolds, Matthew D; Davis, James A; Jay, Jennifer A

    2016-08-01

    Application of empirical models to adsorption of contaminants on natural heterogeneous sorbents is often challenging due to the uncertainty associated with fitting experimental data and determining adjustable parameters. Sediment samples from contaminated and uncontaminated portions of a study site in Maine, USA were collected and investigated for adsorption of arsenate [As(V)]. Two kinetic models were used to describe the results of single solute batch adsorption experiments. Piecewise linear regression of data linearized to fit pseudo-first order kinetic model resulted in two distinct rates and a cutoff time point of 14-19 h delineating the biphasic behavior of solute adsorption. During the initial rapid adsorption stage, an average of 60-80% of the total adsorption took place. Pseudo-second order kinetic models provided the best fit to the experimental data (R(2) > 0.99) and were capable of describing the adsorption over the entire range of experiments. Both Langmuir and Freundlich isotherms provided reasonable fits to the adsorption data at equilibrium. Langmuir-derived maximum adsorption capacity (St) of the studied sediments ranged between 29 and 97 mg/kg increasing from contaminated to uncontaminated sites. Solid phase As content of the sediments ranged from 3.8 to 10 mg/kg and the As/Fe ratios were highest in the amorphous phase. High-pH desorption experiments resulted in a greater percentage of solid phase As released into solution from experimentally-loaded sediments than from the unaltered samples suggesting that As(V) adsorption takes place on different reversible and irreversible surface sites.

  13. Adsorption of drinking water fluoride on a micron-sized magnetic Fe3O4@Fe-Ti composite adsorbent

    NASA Astrophysics Data System (ADS)

    Zhang, Chang; Li, Yingzhen; Wang, Ting-Jie; Jiang, Yanping; Wang, Haifeng

    2016-02-01

    A micron-sized magnetic adsorbent (MMA) for fluoride removal from drinking water was prepared by spray drying and subsequent calcination of a magnetic Fe3O4@Fe-Ti core-shell nanoparticle slurry. The MMA granules had high mechanical strength and stability against water scouring, can be easily separated from the water by a magnet, and had a high selectivity for fluoride versus common co-existing ions and high fluoride removal efficiency in a wide range of initial pH of 3-11. Abundant hydroxyl groups on the MMA surface acted as the active sites for fluoride adsorption, which resulted in a high affinity of the MMA for fluoride. The pH in the adsorption process affected the adsorption significantly. At neutral initial pH, the adsorption isotherm was well fitted with the Langmuir model, and the maximum adsorption capacity reached a high value of 41.8 mg/g. At a constant pH of 3, multilayer adsorption of fluoride occurred due to the abundant positive surface charges on the MMA, and the adsorption isotherm was well fitted with the Freundlich model. The MMA had a fast adsorption rate, and adsorption equilibrium was achieved within 2 min. The adsorption kinetics followed a quasi-second order model. The regeneration of the MMA was easy and fast, and can be completed within 2 min. After 10 recycles, the fluoride removal efficiency of the MMA still remained high. These properties showed that the MMA is a promising adsorbent for fluoride removal.

  14. Kinetic and thermodynamic studies of sulforaphane adsorption on macroporous resin.

    PubMed

    Yuanfeng, Wu; Lei, Zhang; Jianwei, Mao; Shiwang, Liu; Jun, Huang; Yuru, You; Lehe, Mei

    2016-08-15

    The adsorption equilibrium, kinetic and thermodynamic of sulforaphane (SF) adsorption onto macroporous resin in aqueous phase were studied. The SP850 resin was screened as the appropriate resin for SF purification. From the equilibrium studies, the Redlich-Peterson model was found to be the best for description of the adsorption behavior of SF onto SP850 resin, followed by the Freundlich model and the Langmuir model. Batch equilibrium experiments demonstrated that, in the examined temperature range, the equilibrium adsorption capacity of SP850 resin decreased with increasing adsorption temperature. Thermodynamics studies indicated that the adsorption of SF was a physical, exothermic, and spontaneous process. The adsorption kinetics revealed that the pseudo-second-order kinetic model was suitable to characterize the kinetics of adsorption of SF onto SP850. Finally, the intra-particle diffusion model demonstrated that SF diffused quickly into macropores, and that diffusion slowed down in the meso- and micropores.

  15. Competitive adsorption of VOCcs and BOM: Oxic and anoxic environments

    SciTech Connect

    Sorial, G.A.; Papadimas, S.P.; Suidan, M.T.; Speth, T.F.

    1994-01-01

    The effect of the presence of molecular oxygen on the adsorption of volatile organic compounds (VOCs) in distilled Milli-Q water and in water supplemented with background organic matter (BOM) is evaluated. Experiments are conducted under conditions where molecular oxygen is present in the test environment (oxic adsorption), and where oxygen is absent from the test environment (anoxic adsorption). Adsorption isotherms for tetrachloroethylene (PCE) and trichloroethylene (TCE) in Milli-Q water showed no impact of the presence of oxygen on their adsorption behavior, while adsorption isotherms for cis-1,2-dichloroethylene (DCE) showed higher capacities under toxic conditions. The Ideal Adsorbed Solution Theory (IAST) successfully predicted the VOCs anoxic adsorption isotherms in BOM. However, the IAST model did not predict the VOCs oxic adsorption isotherms in BOM.

  16. Adsorption of thorium from aqueous solutions by perlite.

    PubMed

    Talip, Z; Eral, M; Hiçsönmez, U

    2009-02-01

    The use of expanded perlite for the adsorption of thorium from aqueous solution by batch technique is presented. The effects of particle size, pH of the solution, initial thorium concentration, shaking time, V/m ratio and temperature were determined. It was found that the adsorption capacity increases by the increase in the pH of the suspensions. The rate of thorium adsorption on expanded perlite was observed to be fast in the first hour of the reaction time. Adsorption isotherms were expressed by Langmuir and Freundlich adsorption models and the adsorption experiments conducted at 30 +/- 1 degrees C showed that the adsorption isotherms correlated well with the Langmuir model. From the adsorption data, thermodynamic parameters such as DeltaG(o), DeltaH(o) and DeltaS(o) were calculated as a function of temperature.

  17. Factors affecting drug adsorption on beta zeolites.

    PubMed

    Pasti, Luisa; Sarti, Elena; Cavazzini, Alberto; Marchetti, Nicola; Dondi, Francesco; Martucci, Annalisa

    2013-05-01

    The adsorption behaviour of three commonly used drugs, namely ketoprofen, hydrochlorothiazide and atenolol, from diluted aqueous solutions on beta zeolites with different SiO2/Al2O3 ratio (i.e. 25, 38 and 360) was investigated by changing the ionic strength and the pH, before and after thermal treatment of the adsorbents. The selective adsorption of drugs was confirmed by thermogravimetry and X-ray diffraction. The adsorption capacity of beta zeolites was strongly dependent on both the solution pH and the alumina content of the adsorbent. Such a remarkable difference was interpreted as a function of the interactions between drug molecules and zeolite surface functional groups. Atenolol was readily adsorbed on the less hydrophobic zeolite, under pH conditions in which electrostatic interactions were predominant. On the other hand, ketoprofen adsorption was mainly driven by hydrophobic interactions. For undissociated molecules the adsorption capability increased with the increase of hydrophobicity.

  18. Magnetically recoverable Fe3O4/graphene nanocomposite towards efficient removal of triazine pesticides from aqueous solution: Investigation of the adsorption phenomenon and specific ion effect.

    PubMed

    Boruah, Purna K; Sharma, Bhagyasmeeta; Hussain, Najrul; Das, Manash R

    2017-02-01

    Spillage of effluents containing high concentration levels of pesticides into water has been considered as one of the serious environmental problems. In this study Fe3O4/reduced graphene oxide (rGO) nanocomposite has been efficiently utilized for the adsorption of five harmful pesticides namely ametryn, prometryn, simazine, simeton and atrazine in an aqueous medium. Electrostatic interaction between the pesticides and Fe3O4/rGO nanocomposite was analyzed by the zeta potential analysis, which is strongly related to the adsorption capacity of the adsorbent. The kinetics parameters of adsorption followed the pseudo second-order linear model. The adsorption isotherm studies show that, the maximum adsorption capacity of 54.8 mg g(-1) is achieved at pH 5 and it was enhanced in the presence of different ions (Mg(2+), Ca(2+), Na(+) and SO4(2)) and maximum (63.7 mg g(-1)) for ametryn adsorption was found in seawater medium. Thermodynamic parameter shows that, the adsorption process is physisorption and spontaneity in nature. The mechanism of the adsorption process was established by the DRIFT spectroscopy analysis. Efficient adsorption (93.61%) of pesticides was observed due to electrostatic, hydrophobic and π-π interactions of composite towards the heterocyclic conjugation of pesticide molecules. Further, Fe3O4/rGO nanocomposite was easily and rapidly separated from an aqueous medium using the external magnet for reuse and 88.66% adsorption efficiency was observed up to seven cycles.

  19. Laboratory study on metal attenuation capacity of fine grained soil near ash pond site.

    PubMed

    Ghosh, Sudipta; Mukherjee, Somnath; Sarkar, Sujoy; Kumar, Sunil

    2008-10-01

    Waste settling tanks of earthen containment nature are common in India for disposal of solid waste in slurry form. For a large pond system, e.g. ash slurry disposal tank of coal base thermal power plant, leachate generation and its migration pose a serious problem. A natural attenuation of controlling the migratory leachate is to use locally available clay material as lining system due to the adsorption properties of soil for reducing some metallic ions. The present investigation was carried out to explore the Ni2+ and Cr6+ removal capacity of surrounding soil of the ash pond site of Super Thermal Power Plant in West Bengal, India through some laboratory scale and field studies. The soil and water samples collected from the site showed the existence of Ni2+ and Cr6+ in excess to permissible limit. A two-dimensional adsorption behaviour of these pollutants through soil was assessed. The results showed that more than 80% of nickel and 72% of chromium were found to be sorbed by the soil corresponding to initial concentrations of two ions, i.e. 1.366 mg/L and 0.76 mg/L respectively. The batch adsorption data are tested Langmuir and Freundlich isotherm models and found reasonably fit. Breakthrough adsorption study uptake also showed a good adsorption capacity of the soil. The experimental results found to fit well with the existing two dimensional (2D) mathematical models as proposed by Fetter (1999).

  20. A COMPUTATIONAL AND EXPERIMENTAL STUDY OF METAL AND COVALENT ORGANIC FRAMEWORKS USED IN ADSORPTION COOLING

    SciTech Connect

    Jenks, Jeromy WJ; TeGrotenhuis, Ward E.; Motkuri, Radha K.; Paul, Brian; McGrail, B. Peter

    2015-07-09

    Metal-organic frameworks (MOFs) have recently attracted enormous interest over the past few years due to their potential applications in energy storage and gas separation. However, there have been few reports on MOFs for adsorption cooling applications. Adsorption cooling technology is an established alternative to mechanical vapor compression refrigeration systems. Adsorption cooling is an excellent alternative in industrial environments where waste heat is available. Applications also include hybrid systems, refrigeration, power-plant dry cooling, cryogenics, vehicular systems and building HVAC. Adsorption based cooling and refrigeration systems have several advantages including few moving parts and negligible power consumption. Key disadvantages include large thermal mass, bulkiness, complex controls, and low COP (0.2-0.5). We explored the use of metal organic frameworks that have very high mass loading and relatively low heats of adsorption, with certain combinations of refrigerants to demonstrate a new type of highly efficient adsorption chiller. An adsorption chiller based on MOFs suggests that a thermally-driven COP>1 may be possible with these materials, which would represent a fundamental breakthrough in performance of adsorption chiller technology. Computational fluid dynamics combined with a system level lumped-parameter model have been used to project size and performance for chillers with a cooling capacity ranging from a few kW to several thousand kW. In addition, a cost model has been developed to project manufactured cost of entire systems. These systems rely on stacked micro/mini-scale architectures to enhance heat and mass transfer. Presented herein are computational and experimental results for hydrophyilic MOFs, fluorophilic MOFs and also flourophilic Covalent-organic frameworks (COFs).

  1. Studies on adsorption-desorption of xenon on surface of BC-404 plastic scintillator based on soaking method

    NASA Astrophysics Data System (ADS)

    Yongchun, Xiang; Tieshuan, Fan; Chuanfei, Zhang; Fei, Luo; Qian, Wang; Rende, Ze; Qingpei, Xiang

    2017-03-01

    The phoswich coincidence detector is used to verify the CTBT treaty by measuring radioxenon and as such needs to possess high detection sensitivity. However, residual xenon adsorbed onto the surface of β detectors greatly influences subsequent measurements of weak samples. In this study, we investigate the adsorption-desorption behavior of xenon on BC-404 scintillator surfaces with different coating thicknesses using the soaking method. The results present the desorption behavior of xenon on a BC-404 surface for the first time. The calculated adsorption capacity for an uncoated surface is consistent with that from previous studies. However, due to factors such as limitations in coating technology, the effectiveness of coating on reducing the "memory effect" of the detector was poor. The proposed method is suitable for studying the adsorption-desorption behavior of gases on solid surfaces due to its simplicity and flexibility.

  2. Adsorption of goethite onto quartz and kaolinite

    USGS Publications Warehouse

    Goldberg, M.C.; Weiner, Eugene R.; Boymel, P.M.

    1984-01-01

    The adsorption of colloidal goethite onto quartz and kaolinite substrates has been studied as a function of pH and NaCl concentration. Goethite adsorption was measured quantitatively by Fourier-transform infrared spectroscopy. The results indicate that adsorption onto both substrates is due primarily to coulombic forces; however, the pH dependence of adsorption is very different for the two substrates. This is explained by the fact that the surface charge on quartz is entirely pH-dependent, while kaolinite has surface faces which carry a permanent negative charge. Adsorption of goethite on to kaolinite increases markedly with increasing NaCl concentration, while adsorption onto quartz is relatively independent of NaCl concentration. This can be explained by the influence of NaCl concentration upon the development of surface charge on the substrates. A method is described for separating surface-bound goethite from free goethite.

  3. Toluene, Methanol and Benzaldehyde Removal from Gas Streams by Adsorption onto Natural Clay and Faujasite-Y type Zeolite.

    PubMed

    Zaitan, Hicham; Mohamed, Elham F; Valdés, Héctor; Nawdali, Mostafa; Rafqah, Salah; Manero, Marie Hélène

    2016-12-01

    A great number of pollution problems come as a result of the emission of Volatile Organic Compounds (VOCs) into the environment and their control becomes a serious challenge for the global chemical industry. Adsorption is a widely used technique for the removal of VOCs due to its high efficiency, low cost, and convenient operation. In this study, the feasibility to use a locally available clay, as adsorbent material to control VOCs emissions is evaluated. Natural clay is characterised by different physical-chemical methods and adsorptive interaction features between VOCs and natural clay are identified. Toluene (T), methanol (M) and benzaldehyde (B) are used here as representatives of three different kinds of VOCs. Adsorption isotherms onto natural clay and faujasite-Y type zeolite (Fau Y) are obtained at room temperature. According to Langmuir model data, maximum adsorption capacities (qm) of Fez natural clay and zeolite toward methanol (M), toluene (T) and benzaldehyde (B) at 300 K are 8, 0.89 and 3.1 mmol g-1, and 15, 1.91 and 13.9 mmol g-1 respectively. In addition, the effect of temperature on the adsorption of toluene onto natural clay is evaluated in the range from 300 to 323K. An increase on temperature reduces the adsorption capacity of natural clay toward toluene, indicating that an exothermic physical adsorption process takes place. The enthalpy of adsorption of toluene onto Fez natural clay was found to be -54 kJ mol-1. A preliminary cost analysis shows that natural clay could be used as an alternative low cost adsorbent in the control of VOCs from contaminated gas streams with a cost of US$ 0.02 kg-1 compared to Fau Y zeolite with US$ 10 kg-1.

  4. Phosphoryl functionalized mesoporous silica for uranium adsorption

    NASA Astrophysics Data System (ADS)

    Xue, Guo; Yurun, Feng; Li, Ma; Dezhi, Gao; Jie, Jing; Jincheng, Yu; Haibin, Sun; Hongyu, Gong; Yujun, Zhang

    2017-04-01

    Phosphoryl functionalized mesoporous silica (TBP-SBA-15) was synthesized by modified mesoporous silica with γ-amino propyl triethoxy silane and tributyl phosphate. The obtained samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), small angle X-ray diffraction (SAXRD), thermo-gravimetric/differential thermalanalyzer (TG/DTA), N2 adsorption-desorption (BET) and Fourier transform infrared spectroscopy (FT-IR) techniques. Results showed that TBP-SBA-15 had large surface areas with ordered channel structure. Moreover, the effects of adsorption time, sorbent dose, solution pH, initial uranium concentration and temperature on the uranium adsorption behaviors were investigated. TBP-SBA-15 showed a high uranium adsorption capacity in a broad range of pH values. The U(VI) adsorption rate of TBP-SBA-15 was fast and nearly achieved completion in 10 min with the sorbent dose of 1 g/L. The U(VI) adsorption of TBP-SBA-15 followed the pseudo-second-order kinetic model and Freundlich isotherm model, indicating that the process was belonged to chemical adsorption. Furthermore, the thermodynamic parameters (ΔG0, ΔH0 and ΔS0) confirmed that the adsorption process was endothermic and spontaneous.

  5. Equilibrium, kinetic and thermodynamic studies on the adsorption of phenol onto graphene

    SciTech Connect

    Li, Yanhui; Du, Qiuju; Liu, Tonghao; Sun, Jiankun; Jiao, Yuqin; Xia, Yanzhi; Xia, Linhua; Wang, Zonghua; Zhang, Wei; Wang, Kunlin; Zhu, Hongwei; Wu, Dehai

    2012-08-15

    Graphical abstract: The effect of temperature on phenol adsorbed by graphene shows that the equilibrium adsorption capacity of phenol increases with the increase in temperature from 285 to 333 K. Increasing adsorption capacities with temperature indicates that the adsorption of phenol is controlled by an endothermic reaction. Highlights: ► The graphene has high phenol adsorption capacity. ► The graphene has a high specific surface area of 305 m{sup 2}/g. ► The adsorption capacity is high at acidic pH range. ► The graphene has rapid phenol adsorption rate. ► Phenol adsorption is a spontaneous and endothermic process. -- Abstract: Graphene, a new member of carbon family, has been prepared, characterized and used as adsorbent to remove phenol from aqueous solution. The effect parameters including pH, dosage, contact time, and temperature on the adsorption properties of phenol onto graphene were investigated. The results showed that the maximum adsorption capacity can reach 28.26 mg/g at the conditions of initial phenol concentration of 50 mg/L, pH 6.3 and 285 K. Adsorption data were well described by both Freundlich and Langmuir models. The kinetic study illustrated that the adsorption of phenol onto graphene fit the pseudo second-order model. The thermodynamic parameters indicated that the adsorption of phenol onto graphene was endothermic and spontaneous.

  6. Enhanced and selective adsorption of mercury ions on chitosan beads grafted with polyacrylamide via surface-initiated atom transfer radical polymerization.

    PubMed

    Li, Nan; Bai, Renbi; Liu, Changkun

    2005-12-06

    Enhanced and selective removal of mercury ions was achieved with chitosan beads grafted with polyacrylamide (chitosan-g-polyacrylamide) via surface-initiated atom transfer radical polymerization (ATRP). The chitosan-g-polyacrylamide beads were found to have significantly greater adsorption capacities and faster adsorption kinetics for mercury ions than the chitosan beads. At pH 4 and with initial mercury concentrations of 10-200 mg/L, the chitosan-g-polyacrylamide beads can achieve a maximum adsorption capacity of up to 322.6 mg/g (in comparison with 181.8 mg/g for the chitosan beads) and displayed a short adsorption equilibrium time of less than 60 min (compared to more than 15 h for the chitosan beads). Coadsorption experiments with both mercury and lead ions showed that the chitosan-g-polyacrylamide beads had excellent selectivity in the adsorption of mercury ions over lead ions at pH < 6, in contrast to the chitosan beads, which did not show clear selectivity for either of the two metal species. Mechanism study suggested that the enhanced mercury adsorption was due to the many amide groups grafted onto the surfaces of the beads, and the selectivity in mercury adsorption can be attributed to the ability of mercury ions to form covalent bonds with the amide. It was found that adsorbed mercury ions on the chitosan-g-polyacrylamide beads can be effectively desorbed in a perchloric acid solution, and the regenerated beads can be reused almost without any loss of adsorption capacity.

  7. Methylene blue adsorption from aqueous solution by activated carbon: effect of acidic and alkaline solution treatments.

    PubMed

    Ijagbemi, Christianah O; Chun, Ji I; Han, Da H; Cho, Hye Y; O, Se J; Kim, Dong S

    2010-01-01

    The removal of Methylene Blue (MB) from aqueous solution using activated carbon (AC) has been investigated. Adsorption experiments were conducted and the maximum adsorption capacity was determined. The effect of experimental parameters such as pH, dye concentration and temperature were studied on the adsorption process. Equilibrium data were mathematically modeled using the Langmuir and Freundlich adsorption models to describe the equilibrium isotherms at different dye concentrations and temperature. Parameters of best-fit model were calculated and discussed. To understand the mechanism of adsorption, kinetic models were employed to follow the adsorption processes; the pseudo-first-order best described the adsorption of MB onto AC. It was found that pH plays a major role in the adsorption process; adsorption capacity was influenced by the physical and surface chemical properties of carbon and the pH of the solution. 99.0% MB removal was achieved at equilibrium.

  8. Adsorption and desorption characteristics of adlay bran free phenolics on macroporous resins.

    PubMed

    Yang, Qingyun; Zhao, Mouming; Lin, Lianzhu

    2016-03-01

    In this study, the adsorption and desorption characteristics of six macroporous resins including XAD-7HP, XAD-16, HP-20, HP-2MGL, SP-207 and SP-825 for enrichment of adlay bran free phenolics were studied. XAD-16, SP-207 and SP-825 were chosen for further study due to their strong adsorption and desorption capacities. XAD-16, SP-207 and SP-825 had similar phenolics adsorption/desorption behaviors. Pseudo-second-order kinetics model and Freundlich isotherm model were suitable for describing the whole exothermic and physical adsorption processes of adlay bran free phenolics on XAD-16, SP-207 and SP-825. After treatment with gradient elution on XAD-16 resin column, the free phenolics were mostly enriched (from 89.61 to 1015.26mg/100g) in 50% ethanol fraction. The oxygen radical absorbance capacity of 50% ethanol fraction was eight times higher than that of the crude extract. Therefore, the production of highly concentrated phenolics might expand the application of adlay bran used as a bioactive ingredient in functional food.

  9. Adsorption of phenolic compounds by organoclays: implications for the removal of organic pollutants from aqueous media.

    PubMed

    Park, Yuri; Ayoko, Godwin A; Kurdi, Róbert; Horváth, Erzsébet; Kristóf, Janos; Frost, Ray L

    2013-09-15

    Montmorillonite (MMT) was converted to organoclays by intercalation of cationic surfactants into its interlayer space. Two types of organoclays were prepared from different surfactants (DDTMA and DDDMA) at different surfactant loadings, and the structural changes in the clays investigated using various techniques. The arrangements of surfactant molecules in the interlayer space was visually aided by molecular mechanical calculation (MM calculation), and the adsorption capacities of MMT and the organoclays for the removal of p-chlorophenol (PCP) and p-nitrophenol (PNP) from aqueous solutions were tested under different conditions. Two adsorption isotherm models (Langmuir and Freundlich isotherms) were used to determine the best fit model and the Freundlich isotherm was found to provide better fit for both PCP and PNP. Due to its hydrophobic properties, the adsorption is more favourable for PNP than PCP. Overall, the adsorption capacity of the organoclays was significantly improved by intercalation with large surfactant molecules as well as highly loaded surfactants as the intercalation with large surfactant molecules created the partitioning phase, which strongly attracted large amounts of organic pollutants. Possible mechanisms and the implications of the results for the use of these organoclays as adsorbents for the removal of phenols from the environment are discussed.

  10. The effect of weathering on charcoal filter performance. 1; The adsorption and desorption behavior of contaminants

    SciTech Connect

    Wren, J.C.; Moore, C.J. )

    1991-05-01

    This paper reports on triethylenediamine (TEDA) impregnated charcoals, used in nuclear reactors to safeguard against the release of airborne radioiodine, which show high efficiency under various reactor operation and accident conditions when the are new. However, during normal operation, charcoal filters are continuously degraded (or weathered) due to the adsorption of moisture and other air contaminants. The effect of weathering on the efficiency of charcoal for removing radioiodine is of great interest. The results of a study on the adsorption behavior of various contaminants NO{sub 2}, SO{sub 2} 2-butanone (methyl-ethyl ketone (MEK)) and NH{sub 3} on TEDA charcoal are presented. This study is an attempt to characterize and quantify the weathering process of TEDA charcoal by these contaminants. The adsorption and desorption of characteristics of these contaminants range from completely irreversible (NO{sub 2}) to completely reversible (NH{sub 3}). The effect of absorbed water (or humidity) on absorption is different for each contaminant. Absorbed water increases the absorption rate and capacity of TEDA charcoal for NO{sub 2}. However, it appears that SO{sub 2} is absorbed as H{sub 2}SO{sub 4} on the wet charcoal. Absorbed water slightly reduces the adsorption capacity of the charcoal for MEK, but does not affect the absorption of NH{sub 3}.

  11. Synthesis of β-Cyclodextrin-Based Electrospun Nanofiber Membranes for Highly Efficient Adsorption and Separation of Methylene Blue.

    PubMed

    Zhao, Rui; Wang, Yong; Li, Xiang; Sun, Bolun; Wang, Ce

    2015-12-09

    Water-insoluble β-cyclodextrin-based fibers were synthesized by electrospinining followed by thermal cross-linking. The fibers were characterized by field-emission scanning electron microscopic (FE-SEM) and Fourier transformed infrared spectrometer (FT-IR). The highly insoluble fraction obtained from different pH values (3-11) indicates successful cross-linking reactions and their usability in aqueous solution. After the cross-linking reaction, the fibers' tensile strength increases significantly and the BET surface area is 19.49 m(2)/g. The cross-linked fibers exhibited high adsorption capacity for cationic dye methylene blue (MB) with good recyclability. The adsorption performance can be fitted well with pseudo-second-order model and Langmuir isotherm model. The maximum adsorption capacity is 826.45 mg/g according to Langmuir fitting. Due to electrostatic repulsion, the fibers show weak adsorption toward negatively charged anionic dye methyl orange (MO). On the basis of the selective adsorption, the fiber membrane can separate the MB/MO mixture solution by dynamic filtration at a high flow rate of 150 mL/min. The fibers can maintain good fibrous morphology and high separation efficiency even after five filtration-regeneration cycles. The obtained results suggested potential applications of β-cyclodextrin-based electrospun fibers in the dye wastewater treatment field.

  12. Polypropylene non-woven meshes with conformal glycosylated layer for lectin affinity adsorption: the effect of side chain length.

    PubMed

    Ye, Xiang-Yu; Huang, Xiao-Jun; Xu, Zhi-Kang

    2014-03-01

    The unique characteristics of polypropylene non-woven meshes (PPNWMs), like random network of overlapped fibers, multiple connected pores and overall high porosity, make them high potentials for use as separation or adsorption media. Meanwhile, carbohydrates can specifically recognize certain lectin through multivalent interactions. Therefore glycosylated PPNWMs, combing the merits of both, can be regarded as superior affinity membranes for lectin adsorption and purification. Here, we describe a versatile strategy for the glycosylation of PPNWMs. Two hydrophilic polymers with different side chain length, poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(oligo(ethylene glycol) methacrylate) (POEGMA), were first conformally tethered on the polypropylene fiber surface by a modified plasma pretreatment and benzophenone (BP) entrapment UV irradiation process. Then glucose ligands were bound through the reaction between the hydroxyl group and acetyl glucose. Chemical changes of the PPNWMs surface were monitored by FT-IR/ATR. SEM pictures show that conformal glucose ligands can be achieved through the modified process. After deprotection, the glycosylated PPNWMs became superhydrophilic and had high specific recognition capability toward Concanavalin A (Con A). Static Con A adsorption experiments were further performed and the results indicate that fast adsorption kinetics and high binding capacity can be accomplished at the same time. We also found that increasing the side chain length of polymer brushes had positive effect on protein binding capacity due to improved chain mobility. Model studies suggest a multilayer adsorption behavior of Con A.

  13. Ciprofloxacin adsorption on graphene and granular activated carbon: kinetics, isotherms, and effects of solution chemistry.

    PubMed

    Zhu, Xuan; Tsang, Daniel C W; Chen, Feng; Li, Shiyu; Yang, Xin

    2015-01-01

    Ciprofloxacin (CIP) is a commonly used antibiotic and widely detected in wastewaters and farmlands nowadays. This study evaluated the efficacy of next-generation adsorbent (graphene) and conventional adsorbent (granular activated carbon, GAC) for CIP removal. Batch experiments and characterization tests were conducted to investigate the adsorption kinetics, equilibrium isotherms, thermodynamic properties, and the influences of solution chemistry (pH, ionic strength, natural organic matter (NOM), and water sources). Compared to GAC, graphene showed significantly faster adsorption and reached equilibrium within 3 min, confirming the rapid access of CIP into the macroporous network of high surface area of graphene as revealed by the Brunner-Emmet-Teller measurements analysis. The kinetics was better described by a pseudo-second-order model, suggesting the importance of the initial CIP concentration related to surface site availability of graphene. The adsorption isotherm on graphene followed Langmuir model with a maximum adsorption capacity of 323 mg/g, which was higher than other reported carbonaceous adsorbents. The CIP adsorption was thermodynamically favourable on graphene and primarily occurred through π - π interaction, according to the FTIR spectroscopy. While the adsorption capacity of graphene decreased with increasing solution pH due to the speciation change of CIP, the adverse effects of ionic strength (0.01-0.5 mol L(-1)), presence of NOM (5 mg L⁻¹), and different water sources (river water or drinking water) were less significant on graphene than GAC. These results indicated that graphene can serve as an alternative adsorbent for CIP removal in commonly encountered field conditions, if proper separation and recovery is available in place.

  14. Room-temperature fabrication of core-shell nano-ZnO/pollen grain biocomposite for adsorptive removal of organic dye from water

    NASA Astrophysics Data System (ADS)

    Tzvetkov, George; Kaneva, Nina; Spassov, Tony

    2017-04-01

    A new core-shell nano-ZnO/pollen grain (n-ZnO/PG) biocomposite has been successfully synthesized via simple and low-temperature two-step liquid precipitation method. The synthetic strategy consists of grafting the surface of pine pollen grains (PG) with Zn2+-organic complexes followed by a treatment in Zn(CH3COO)2/NaOH solution, thus producing a closed n-ZnO shell around the organic core, with a thickness of ∼450 nm. Scanning electron microscopy, X-ray diffraction, FTIR, XPS and UV-vis spectroscopy measurements along with N2 adsorption/desorption were used to characterize the resulting n-ZnO/PG biocomposite. The as-prepared core-shell microparticles are meso-/macro-porous with BET surface area of 25 m2 g-1 and total pore volume of 0.26 cm3 g-1. The adsorption properties of n-ZnO/PG were evaluated through adsorption of Malachite Green (MG) from aqueous medium at room temperature (25 °C). For the sake of comparison, the physico-chemical and adsorptive properties of the raw PG and pure n-ZnO were also examined. Results indicate that n-ZnO/PG is the most favorable for the adsorption of MG under the conditions used in this study. The adsorption kinetic data for PG, n-ZnO and n-ZnO/PG follow the pseudo-second order equation and the maximum adsorption capacity follows an order of n-ZnO/PG > n-ZnO > PG. For n-ZnO/PG an adsorption uptake up to 145.9 mg g-1 is observed. The as-prepared core-shell biocomposite material is a promising cost-effective and environmentally friendly adsorbent due to its textural properties, surface chemistry, adsorption capacity and recyclability.

  15. Adsorption studies of etherdiamine onto modified sugarcane bagasses in aqueous solution.

    PubMed

    Gusmão, Karla Aparecida Guimarães; Gurgel, Leandro Vinícius Alves; Melo, Tânia Márcia Sacramento; Carvalho, Cornélio de Freitas; Gil, Laurent Frédéric

    2014-01-15

    In this study sugarcane bagasse was modified with succinic anhydride and EDTA dianhydride to obtain SCB 2 and EB adsorbents, respectively. These adsorbents were used to remove etherdiamine, which is used for iron ore flotation from single aqueous solutions. The removal and recovery of etherdiamine is important for environmental and economic reasons due to its toxicity and high cost. The results demonstrated that adsorption of etherdiamine by SCB 2 and EB was better fitted by a pseudo-second-order kinetic model than pseudo-first-order and Elovich models. Adsorption isotherms were better fitted by the Langmuir model rather than the Freundlich, Sips, and Temkin models. The maximum adsorption capacities (Qmax) of SCB 2 and EB for etherdiamine adsorption were found to be 869.6 and 1203.5 mg/g, respectively. The calculated ΔG° values for adsorption of etherdiamine on SCB 2 (-22.70 kJ/mol) and EB (-19.10 kJ/mol) suggested that chemisorption is the main mechanism by which etherdiamine is removed from the aqueous solution for both adsorbents. The high Qmax values showed that SCB 2 and EB are potential adsorbents for recovering the etherdiamine and treating effluents produced from iron ore flotation.

  16. Adsorption of crude and engine oils from water using raw rice husk.

    PubMed

    Razavi, Zahra; Mirghaffari, Nourollah; Rezaei, Behzad

    2014-01-01

    The raw rice husk (RRH) was used as a low cost adsorbent to remove three oil compounds with different viscosities (crude oil, engine oil and spent engine oil) from an aqueous environment. Some of the sorbent specifications were characterized using a CHNSO analyzer, Fourier transform infrared, scanning electron microscope and inductively coupled plasma spectroscopy. With decreasing RRH particles size, the oil adsorption percentage was reduced for crude, spent and engine oils from 50 to 30%, 65 to 20% and 70 to 0.01%, respectively. This was probably due to damage of the microcavities. The removal percentage by sorbent at optimized conditions was 88, 80 and 55% for engine, spent and crude oils, respectively, corresponding to their descending viscosity. The adsorption of crude and spent oils on rice husk followed the Freundlich isotherm model, while the adsorption of engine oil was fitted by the Langmuir model. The maximum adsorption capacity (qmax), calculated from the Langmuir model for the adsorption of engine oil on RRH, was 1,250 mg/g.

  17. Preparation and adsorption performance of MnO2/PAC composite towards aqueous glyphosate.

    PubMed

    Cui, Hao; Li, Qin; Qian, Yan; Zhang, Qiu; Zhai, Jianping

    2012-09-01

    Glyphosate (N-phosphonomethylglycine (PMG)) is the organophosphate herbicide most widely used in the world, and industrial production of PMG generates large quantities of wastewater. A manganese dioxide-coated powdered activated carbon (MnO2/PAC) composite was synthesized and investigated for the adsorption of PMG from wastewater. The results of scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectrometry (EDAX) revealed that MnO2 was formed on the surface of the carbon during the modification process. Batch adsorption results showed that the optimal pH for glyphosate adsorption on MnO2/PAC was 3.0. In the range 0.01(-1) molL(-1), glyphosate removal by MnO2/PAC decreased with an increase in ionic strength. Among the coexistent anions, only phosphate showed significant inhibition of PMG removal due to competitive complexation. Batch studies revealed that MnO2/PAC could reach a maximum PMG adsorption capacity of 283 mg g(-1). The Langmuir equilibrium model was found to be suitable for describing PMG sorption, and kinetic studies revealed that adsorption followed second-order rate kinetics. It was also proved that the adsorbed PMG could be effectively desorbed from MnO2/PAC in 1.0 molL(-1) NaOH. All of these results implied that the MnO2/PAC composite may be used as an effective adsorbent for recycling PMG from wastewater.

  18. Investigation of Hexagonal Mesoporous Silica-Supported Composites for Trace Moisture Adsorption.

    PubMed

    Li, Li; Tang, Nian; Wang, Yaxue; Cen, Wanglai; Liu, Jie; Zhou, Yongyan

    2015-12-01

    Moisture control is an important part of effective maintenance program for gas-insulated switchgear (GIS). Herein, hexagonal mesoporous silica (HMS) materials were synthesized by adopting dodecylamine as a structure directing agent, which was then employed as a host for supporting polyethylenimine (PEI) without further calcinations or extraction treatment. The physicochemical properties of the silica support and composites were characterized, and the moisture adsorption capacity of these composites was determined. The reserved template agents resulted in a dramatic improvement in moisture adsorption amount. Among them, 50PEI/DHMS showed the highest adsorption value. The enhanced adsorption could be attributed to the generated hydrogen bonding between amino groups and H2O molecules and the improved diffusion of moisture into the bulk networks of PEI polymers due to its better spatial dispersion imposed by the long alkyl chains of template agents, which was confirmed by thermogravimetry results and hydrogen efficiency analysis. Moreover, the maintained terminal amino groups of templates could also function as active sites for moisture adsorption. The results herein imply that the PEI/DHMS composites could be appealing materials for capturing moisture in GIS.

  19. Reduction of graphene oxide/alginate composite hydrogels for enhanced adsorption of hydrophobic compounds.

    PubMed

    Kim, Semin; Yoo, Youngjae; Kim, Hanbit; Lee, Eunju; Lee, Jae Young

    2015-10-09

    Carbon-based materials, consisting of graphene oxide (GO) or reduced GO (rGO), possess unique abilities to interact with various molecules. In particular, rGO materials hold great promise for adsorption and delivery applications of hydrophobic molecules. However, conventional production and/or usage of rGO in aqueous solution often causes severe aggregation due to its low water solubility and thus difficulties in handling and applications. In our study, to prevent the severe aggregation of GO during reduction and to achieve a high adsorption capacity with hydrophobic compounds, GO/alginate composite hydrogels were first prepared and then reduced in an aqueous ascorbic acid solution at 37 °C. Adsorption studies with a model hydrophobic substance, rhodamine B, revealed that the reduced composite hydrogels are more highly absorbent than the unreduced hydrogels. In addition, the adsorption properties of the composite hydrogels, which are consequences of hydrophobic and ionic interactions, could be modulated by controlling the degree of reduction for the adsorption of different molecules. The composite hydrogels embedding rGO can be very useful in applications related to drug delivery, waste treatment, and biosensing.

  20. Investigation of Hexagonal Mesoporous Silica-Supported Composites for Trace Moisture Adsorption

    NASA Astrophysics Data System (ADS)

    Li, Li; Tang, Nian; Wang, Yaxue; Cen, Wanglai; Liu, Jie; Zhou, Yongyan

    2015-11-01

    Moisture control is an important part of effective maintenance program for gas-insulated switchgear (GIS). Herein, hexagonal mesoporous silica (HMS) materials were synthesized by adopting dodecylamine as a structure directing agent, which was then employed as a host for supporting polyethylenimine (PEI) without further calcinations or extraction treatment. The physicochemical properties of the silica support and composites were characterized, and the moisture adsorption capacity of these composites was determined. The reserved template agents resulted in a dramatic improvement in moisture adsorption amount. Among them, 50PEI/DHMS showed the highest adsorption value. The enhanced adsorption could be attributed to the generated hydrogen bonding between amino groups and H2O molecules and the improved diffusion of moisture into the bulk networks of PEI polymers due to its better spatial dispersion imposed by the long alkyl chains of template agents, which was confirmed by thermogravimetry results and hydrogen efficiency analysis. Moreover, the maintained terminal amino groups of templates could also function as active sites for moisture adsorption. The results herein imply that the PEI/DHMS composites could be appealing materials for capturing moisture in GIS.

  1. Adsorptive removal of phosphate from aqueous solutions using raw and calcinated dolomite.

    PubMed

    Karaca, S; Gürses, A; Ejder, M; Açikyildiz, M

    2006-02-06

    This study explored the feasibility of utilizing raw and calcinated dolomite under CO2 atmosphere for phosphate removal in laboratory experiments. The experimental work emphasized the evaluation of phosphate adsorption characteristics of this adsorbent material. Studies were conducted to delineate the effect of contact time, initial phosphate concentration, temperature, pH, stirring speed, adsorbent dose and calcination temperature. Phosphate removal decreased with increasing temperature and slightly increased with increasing of pH. The observed decrease in the adsorption capacity with increase of the temperature from 20 to 40 and to 60 degrees C indicates that the low temperatures favor the phosphate removal by adsorption onto dolomite. Phosphate removal was seen to decrease with increasing calcination temperature due to the structural changes occurring in the structure and pore size distribution of dolomite samples during calcination. The experimental data obtained were applied to the Freundlich, Langmuir, BET, Halsey, Harkins-Jura, Smith and Henderson isotherm equations to test the fit of these equations to raw and calcinated dolomite samples. By considering the experimental results and adsorption models applied in this study, it can be concluded that adsorption of phosphate occurs predominantly through physical interactions, and the dolomite sample has a heteroporous structure. The large values of the constants for Henderson equation and the high value of y(m) obtained from BET equation indicate the microporous structure is more stable in raw and calcinated dolomite samples.

  2. Adsorption coefficients for TNT on soil and clay minerals

    NASA Astrophysics Data System (ADS)

    Rivera, Rosángela; Pabón, Julissa; Pérez, Omarie; Muñoz, Miguel A.; Mina, Nairmen

    2007-04-01

    To understand the fate and transport mechanisms of TNT from buried landmines is it essential to determine the adsorption process of TNT on soil and clay minerals. In this research, soil samples from horizons Ap and A from Jobos Series at Isabela, Puerto Rico were studied. The clay fractions were separated from the other soil components by centrifugation. Using the hydrometer method the particle size distribution for the soil horizons was obtained. Physical and chemical characterization studies such as cation exchange capacity (CEC), surface area, percent of organic matter and pH were performed for the soil and clay samples. A complete mineralogical characterization of clay fractions using X-ray diffraction analysis reveals the presence of kaolinite, goethite, hematite, gibbsite and quartz. In order to obtain adsorption coefficients (K d values) for the TNT-soil and TNT-clay interactions high performance liquid chromatography (HPLC) was used. The adsorption process for TNT-soil was described by the Langmuir model. A higher adsorption was observed in the Ap horizon. The Freundlich model described the adsorption process for TNT-clay interactions. The affinity and relative adsorption capacity of the clay for TNT were higher in the A horizon. These results suggest that adsorption by soil organic matter predominates over adsorption on clay minerals when significant soil organic matter content is present. It was found that, properties like cation exchange capacity and surface area are important factors in the adsorption of clayey soils.

  3. EFFECT OF GAC CHARACTERISTICS ON ADSORPTION OF ORGANIC POLLUTANTS

    EPA Science Inventory

    The impact of the characteristics of granular activated carbon (GAC) on adsorption capacity and on the potential for polymerization of phenolic compounds on the surface of GAC in the presence of molecular oxygen is evaluated in this study. Adsorption isotherm data were collected...

  4. Defluoridation of drinking water using adsorption processes.

    PubMed

    Loganathan, Paripurnanda; Vigneswaran, Saravanamuthu; Kandasamy, Jaya; Naidu, Ravi

    2013-03-15

    Excessive intake of fluoride (F), mainly through drinking water, is a serious health hazard affecting humans worldwide. There are several methods used for the defluoridation of drinking water, of which adsorption processes are generally considered attractive because of their effectiveness, convenience, ease of operation, simplicity of design, and for economic and environmental reasons. In this paper, we present a comprehensive and a critical literature review on various adsorbents used for defluoridation, their relative effectiveness, mechanisms and thermodynamics of adsorption, and suggestions are made on choice of adsorbents for various circumstances. Effects of pH, temperature, kinetics and co-existing anions on F adsorption are also reviewed. Because the adsorption is very weak in extremely low or high pHs, depending on the adsorbent, acids or alkalis are used to desorb F and regenerate the adsorbents. However, adsorption capacity generally decreases with repeated use of the regenerated adsorbent. Future research needs to explore highly efficient, low cost adsorbents that can be easily regenerated for reuse over several cycles of operations without significant loss of adsorptive capacity and which have good hydraulic conductivity to prevent filter clogging during the fixed-bed treatment process.

  5. BTEX and MTBE adsorption onto raw and thermally modified diatomite.

    PubMed

    Aivalioti, Maria; Vamvasakis, Ioannis; Gidarakos, Evangelos

    2010-06-15

    The removal of BTEX (benzene, toluene, ethyl-benzene and xylenes) and MTBE (methyl tertiary butyl ether) from aqueous solution by raw (D(R)) and thermally modified diatomite at 550, 750 and 950 degrees C (D(550), D(750) and D(950) respectively) was studied. Physical characteristics of both raw and modified diatomite such as specific surface, pore volume distribution, porosity and pH(solution) were determined, indicating important structural changes in the modified diatomite, due to exposure to high temperatures. Both adsorption kinetic and isotherm experiments were carried out. The kinetics data proved a closer fit to the pseudo-second order model. Maximum values for the rate constant, k(2), were obtained for MTBE and benzene (48.9326 and 18.0996 g mg(-1)h(-1), respectively) in sample D(550). The isotherm data proved to fit the Freundlich model more closely, which produced values of the isotherm constant 1/n higher than one, indicating unfavorable adsorption. The highest adsorption capacity, calculated through the values of the isotherm constant k(F), was obtained for MTBE (48.42 mg kg(-1) (mg/L)(n)) in sample D(950).

  6. Polarity control for nonthiolated DNA adsorption onto gold nanoparticles.

    PubMed

    Zhang, Xu; Liu, Biwu; Servos, Mark R; Liu, Juewen

    2013-05-21

    Gold nanoparticles (AuNPs) functionalized with thiolated DNA have enabled many studies in nanoscience. The strong thiol/gold affinity and the nanoscale curvature of AuNPs allow the attached DNA to adapt an upright conformation favorable for hybridization. Recently, it has been shown that nonthiolated DNA can also be attached via DNA base adsorption. Without a thiol label, both ends of the DNA and even internal bases could be adsorbed, decreasing the specificity of subsequent molecular recognition reactions. In this work, we employed a modular sequence design approach to systematically study the effect of DNA sequence on adsorption polarity. A block of poly adenine (poly-A) could be used to achieve a high density of DNA attachment. When the poly-A block length is short (e.g., below 5-7), the loading was independent of the block length, and the conjugate cannot hybridize to its cDNA effectively, suggesting a random attachment controlled by adsorption kinetics. Increasing the block length leads to reduced capacity but improved hybridization, suggesting that more DNA with the desired conformation was adsorbed due to the thermodynamic effects of poly-A binding. The design can be further improved by including capping sequences rich in T or G. Finally, a more general double-stranded DNA approach was described to be suitable for DNA that cannot satisfy the above-mentioned design requirements.

  7. Research and Development of a Small-Scale Adsorption Cooling System

    NASA Astrophysics Data System (ADS)

    Gupta, Yeshpal

    The world is grappling with two serious issues related to energy and climate change. The use of solar energy is receiving much attention due to its potential as one of the solutions. Air conditioning is particularly attractive as a solar energy application because of the near coincidence of peak cooling loads with the available solar power. Recently, researchers have started serious discussions of using adsorptive processes for refrigeration and heat pumps. There is some success for the >100 ton adsorption systems but none exists in the <10 ton size range required for residential air conditioning. There are myriad reasons for the lack of small-scale systems such as low Coefficient of Performance (COP), high capital cost, scalability, and limited performance data. A numerical model to simulate an adsorption system was developed and its performance was compared with similar thermal-powered systems. Results showed that both the adsorption and absorption systems provide equal cooling capacity for a driving temperature range of 70--120 ºC, but the adsorption system is the only system to deliver cooling at temperatures below 65 ºC. Additionally, the absorption and desiccant systems provide better COP at low temperatures, but the COP's of the three systems converge at higher regeneration temperatures. To further investigate the viability of solar-powered heat pump systems, an hourly building load simulation was developed for a single-family house in the Phoenix metropolitan area. Thermal as well as economic performance comparison was conducted for adsorption, absorption, and solar photovoltaic (PV) powered vapor compression systems for a range of solar collector area and storage capacity. The results showed that for a small collector area, solar PV is more cost-effective whereas adsorption is better than absorption for larger collector area. The optimum solar collector area and the storage size were determined for each type of solar system. As part of this dissertation

  8. Study of Adsorption of Copper Species onto Multiwall Carbon Nanotubes

    EPA Science Inventory

    Functionalized CNTs have improved adsorptive capacities over pristine CNTs. These can be used for sensors, membranes, filters and matrix composite enhancements made possible because of their nano-size.

  9. Synthesis and Electrospraying of Nanoscale MOF (Metal Organic Framework) for High-Performance CO2 Adsorption Membrane

    NASA Astrophysics Data System (ADS)

    Wahiduzzaman; Allmond, Kelsey; Stone, John; Harp, Spencer; Mujibur, Khan

    2017-01-01

    We report the sonochemical synthesis of MOF (metal organic framework) nanoparticles of 30-200 nm in size and electrospraying of those particles on electrospun nanofibers to process a MOF-attached nanofibrous membrane. This membrane displayed significant selectivity towards CO2 and capacity of adsorbing with 4000-5000 ppm difference from a mixed gas flow of 1% CO2 and 99% N2. Applying ultrasonic waves during the MOF synthesis offered rapid dispersion and formation of crystalline MOF nanoparticles in room temperature. The MOF nanoparticles of 100-200 nm in size displayed higher surface area and adsorption capacity comparing to that of 30-60 nm in size. Nanofibrous membrane was produced by electrospinning of MOF blended PAN solution followed by electrospraying of additional MOF nanoparticles. This yielded uniform MOF deposition on nanofibers, occurred due to electrostatic attraction between highly charged nanoparticles and conductive nanofibers. A test bench for real-time CO2 adsorption at room temperature was built with non-dispersive Infrared (NDIR) CO2 sensors. Comparative tests were performed on the membrane to investigate its enhanced adsorption capacity. Three layers of the as-produced membranes displayed CO2 adsorption for approximately 2 h. Thermogravimetric analysis (TGA) of the membrane showed the thermal stability of the MOF and PAN up to 290 and 425 °C, respectively.

  10. Synthesis and Electrospraying of Nanoscale MOF (Metal Organic Framework) for High-Performance CO2 Adsorption Membrane.

    PubMed

    Wahiduzzaman; Allmond, Kelsey; Stone, John; Harp, Spencer; Mujibur, Khan

    2017-12-01

    We report the sonochemical synthesis of MOF (metal organic framework) nanoparticles of 30-200 nm in size and electrospraying of those particles on electrospun nanofibers to process a MOF-attached nanofibrous membrane. This membrane displayed significant selectivity towards CO2 and capacity of adsorbing with 4000-5000 ppm difference from a mixed gas flow of 1% CO2 and 99% N2. Applying ultrasonic waves during the MOF synthesis offered rapid dispersion and formation of crystalline MOF nanoparticles in room temperature. The MOF nanoparticles of 100-200 nm in size displayed higher surface area and adsorption capacity comparing to that of 30-60 nm in size. Nanofibrous membrane was produced by electrospinning of MOF blended PAN solution followed by electrospraying of additional MOF nanoparticles. This yielded uniform MOF deposition on nanofibers, occurred due to electrostatic attraction between highly charged nanoparticles and conductive nanofibers. A test bench for real-time CO2 adsorption at room temperature was built with non-dispersive Infrared (NDIR) CO2 sensors. Comparative tests were performed on the membrane to investigate its enhanced adsorption capacity. Three layers of the as-produced membranes displayed CO2 adsorption for approximately 2 h. Thermogravimetric analysis (TGA) of the membrane showed the thermal stability of the MOF and PAN up to 290 and 425 °C, respectively.

  11. Protein adsorption to poly(ethylenimine)-modified Sepharose FF. IV. Dynamic adsorption and elution behaviors.

    PubMed

    Liu, Na; Yu, Lin-Ling; Sun, Yan

    2014-10-03

    We have previously investigated bovine serum albumin (BSA) uptake to poly(ethylenimine) (PEI)-grafted Sepharose FF. It was found that there was a critical ionic capacity (cIC; 600mmol/L) for BSA, above which the protein adsorption capacity and uptake kinetics increased drastically. In this work, two poly(ethylenimine) (PEI)-grafted resins with IC values of 271mmol/L (FF-PEI-L270) and 683mmol/L (FF-PEI-L680), which were below and above the cIC, respectively, were chosen to investigate the breakthrough and linear gradient elution (LGE) behaviors of BSA. Commercially available anion exchanger, Q Sepharose FF, was used for comparison. The DBC values of FF-PEI-L680 were much higher in the entire residence time range (2-10min) than the other two resins due to its high static adsorption capacity and uptake kinetics. At a residence time of 5.0min, the DBC of FF-PEI-L680 (104mg/mL) was about seven times that of FF-PEI-L270 and three times that of Q Sepharose FF. A rise-fall trend of the DBCs with increasing ionic strength (IS) was found for all the three resins studied, indicating the presence of electrostatic exclusion for protein uptake at low IS. With increasing NaCl concentration from 20 to 200mmol/L, FF-PEI-L680 kept very high DBC values (64-114mg/mL). In addition, FF-PEI-L270 showed more favorable adsorption properties than Q Sepharose FF at 100-300mmol/L NaCl. These results proved that the three-dimensional grafting ion exchange layer on the PEI resins enhanced their tolerance to IS. In the study of LGE, the three resins showed similar elution behaviors and no distinct peak tailings were observed. The salt concentrations at the elution peaks (IR) were in the order of FF-PEI-L680>FF-PEI-L270>Q Sepharose FF, indicating that the elution for the PEI resins needed higher salt concentrations, which was also an appearance of the salt-tolerant feature of the PEI resins. When protein loading amount was increased to the value equivalent to the DBC at 10% breakthrough, the

  12. Selective adsorption and recycle of Cu(2+) from aqueous solution by modified sugarcane bagasse under dynamic condition.

    PubMed

    Chen, Jia-Dong; Yu, Jun-Xia; Wang, Fen; Tang, Jia-Qi; Zhang, Yue-Fei; Xu, Yuan-Lai; Chi, Ru-An

    2017-02-20

    Tetraethylenepentamine modified sugarcane bagasse was prepared and applied to test its feasibility in removing and recovering Cu(2+) from wastewater under dynamic condition. Results showed that the Cu(2+) could be selectively absorbed from wastewater by the modified SCB fixed bed column. To understand the adsorption mechanism, Cd(2+) had been selected as the model interfering ion to investigate how co-ions influence the adsorption of Cu(2+) on the sorbent. It was observed that the adsorption capacity of the sorbent for Cu(2+) (0.26 mmol g(-1)) was significantly higher than that of Cd(2+) (0.03 mmol g(-1)), even when the Cd(2+) initial concentration was 100 times higher than that of Cu(2+) in the binary system. This finding indicated that the presence of Cd(2+) in the solution exerted negligible influence on the adsorption of Cu(2+) on the modified SCB. The selectivity of the modified sorbent was further confirmed in the Cu/Cd/Mg/Pb/K quinary system. Further analysis to dynamic adsorption experiment illustrated that, due to the presence of amine groups, the modified SCB showed strong coordination ability to Cu(2+), which allowed the other adsorbed ions (e.g., Cd(2+)) desorbed. This high adsorption selectivity toward Cu(2+) suggested that this prepared sorbent would be a promising candidate for removing and recovering Cu(2+) from wastewater.

  13. Mechanism of highly efficient adsorption of 2-chlorophenol onto ultrasonic graphene materials: Comparison and equilibrium.

    PubMed

    Soltani, Tayyebeh; Lee, Byeong-Kyu

    2016-11-01

    The deficiencies of the recently reported improved Hummers method for the synthesis of graphene oxide (GO), such as high reaction temperature (60°C) and long reaction time (10h), were successfully solved using a low-intensity ultrasonic bath for 30min at 40°C. Furthermore, compared to its conventional synthesis counterpart, a facile and fast, one-step ultrasonic method that excluded hydrazine hydrate was developed to synthesize reduced GO (rGO) from graphite (10min, 50°C) in the presence of hydrazine hydrate (rGO-C, 12h, 90°C). The adsorption characteristics of 2-chlorophenol (2-CP) from an aqueous solution were investigated using rGOs and GOs prepared by ultrasonic (rGO-Us/GO-Us) and conventional (rGO-C/GO-C) methods. Whereas 2-CP was completely removed with rGO-Us after 50min, only 40% of 2-CP was eliminated with rGO-C. The maximum adsorption capacity of 2-CP calculated by the Langmuir model onto rGO-Us (208.67mg/g) was much higher than that onto GO-Us (134.49mg/g). In addition, the ultrasonic graphene adsorption capacities were much higher than the corresponding values of rGO-C (49.9mg/g) and GO-C (32.06mg/g). The enhanced adsorption for rGO-Us and GO-Us is attributed to their greater surface areas, excellent oxygenated groups for GO-Us and superior π-electron-rich matrix for rGO-Us, compared to other adsorbents. The adsorption of 2-CP on the rGO materials increased with increasing solution pH to a maximum around its pKa (pKa=8.85), while the adsorption for the GO materials increased with decreasing solution pH. The adsorption mechanism proceeded via hydrogen bonding in neutral and acidic media, but via π-π electron donor-accepter (EDA) interactions between 2-CP and graphene materials in basic medium. The FTIR spectrum of GO-Us after adsorption indicates that the position and intensity of many peaks of GO-Us were affected due to the adsorption of different 2-CP groups at different pHs.

  14. Peat and coconut fiber as biofilters for chromium adsorption from contaminated wastewaters.

    PubMed

    Henryk, Kołoczek; Jarosław, Chwastowski; Witold, Żukowski

    2016-01-01

    Batch adsorption experiments were performed for the removal of chromium (III) and chromium (VI) ions from aqueous solutions using Canadian peat and coconut fiber. The Langmuir model was used to describe the adsorption isotherm. The maximum adsorption for peat reached 18.75 mg/g for Cr(III) and 8.02 mg/g for Cr(VI), whereas the value for fiber was slightly higher and reached 19.21 mg/g for Cr(III) and 9.54 mg/g for Cr(VI). Both chromium forms could be easily eluted from the materials. The adsorption of chromium forms to organic matter could be explained in terms of formation of donor-acceptor chemical covalent bound with hydroxyl groups as ligands and chromium as the central atom in the formed complex. The chromate-reducing activities were monitored with the use of electron paramagnetic resonance spectroscopy. The results showed that both adsorption and reduction occurred simultaneously and the maximum adsorption capacity of hexavalent chromium being equal to 95% for fiber and 92% for peat was obtained at pH 1.5. The reduction of Cr(VI) in wastewaters began immediately and disappeared after 20 h. Both materials contained yeast and fungi species which can be responsible for reduction of chromium compounds, due to their enzymatic activity (Chwastowski and Koloczek (Acta Biochim Pol 60: 829-834, 2013)). The reduction of Cr(VI) is a two-phase process, the first phase being rapid and based on chemical reaction and the second phase having biological features. After the recovery step, both types of organic materials can be used again for chromium adsorption without any loss in the metal uptake. Both of the materials could be used as biofilters in the wastewater treatment plants.

  15. Ionic Adsorption and Desorption of CNT Nanoropes

    PubMed Central

    Shang, Jun-Jun; Yang, Qing-Sheng; Yan, Xiao-Hui; He, Xiao-Qiao; Liew, Kim-Meow

    2016-01-01

    A nanorope is comprised of several carbon nanotubes (CNTs) with different chiralities. A molecular dynamic model is built to investigate the ionic adsorption and desorption of the CNT nanoropes. The charge distribution on the nanorope is obtained by using a modified gradient method based on classical electrostatic theory. The electrostatic interactions among charged carbon atoms are calculated by using the Coulomb law. It was found here that the charged nanorope can adsorb heavy metal ions, and the adsorption and desorption can be realized by controlling the strength of applied electric field. The distance between the ions and the nanorope as well as the amount of ions have an effect on the adsorption capacity of the nanorope. The desorption process takes less time than that of adsorption. The study indicates that the CNT nanorope can be used as a core element of devices for sewage treatment. PMID:28335306

  16. Synthesis of novel poly(amidoxime) grafted multiwall carbon nanotube gel and uranium adsorption.

    PubMed

    Gopalan, A; Philips, M Francklin; Jeong, Jae-Hong; Lee, Kwang-Pill

    2014-03-01

    This is the first report on the synthesis of a new functional nanocomposite gel containing amidoxime functionalized multiwall carbon nanotube (AO-MWNT-FNC GEL). The surface morphology of AO-MWNT-FNC GEL was investigated by field emission scanning electron microscopy. The modification of gel with amidoxine groups was confirmed by Fourier transform infra red spectroscopy. The AO-MWNT-FNC GEL provides effective binding with uranium ions as was ascertained by X-ray photoelectron spectroscopy. The AO-MWNT-FNC GEL was utilized as the new adsorbent for the recovery of uranium ions from aqueous solution. UV-visible spectroscopy was used to monitor the adsorption capacity of the AO-MWNT-FNC GEL toward uranium ions. The influence of initial uranium ion concentration and solution pH on the adsorption capacity of the AO-MWNT-FNC GEL were studied in batch experiments. The new FNC-GEL designed in this study is distinguished by higher adsorption capacity for uranium ions due to the synergistic contributions from high surface area of MWNT and the functional AO groups in FNC-GEL and exhibits potential for efficient recovery of uranium ions.

  17. Adsorption of bisphenol A to a carbon nanotube reduced its endocrine disrupting effect in mice male offspring.

    PubMed

    Wang, Wenwei; Jiang, Cuijuan; Zhu, Ledong; Liang, Nana; Liu, Xuejiao; Jia, Jianbo; Zhang, Chengke; Zhai, Shumei; Zhang, Bin

    2014-09-10

    Soluble carbon nanotubes (CNTs) have shown promise as materials for adsorption of environmental contaminants such as Bisphenol A (BPA), due to the high adsorption capacity and strong desorption hysteresis of BPA on CNTs. The adsorption of BPA to CNTs may change the properties of both BPA and CNTs, and induce different toxicity to human and living systems from that of BPA and CNTs alone. Herein, we report that oral exposure of BPA/MWCNT-COOH (carboxylated multi-walled carbon nantubes) adduct to mice during gestation and lactation period decreased the male offspring reproductive toxicity compared with those induced by BPA alone. The adduct decreased malondialdehyde (MDA) level in testis and follicle-stimulating hormone (FSH) in serum, but increased the level of serum testosterone in male offspring in comparison to BPA alone. Our investigations broadened the knowledge of nanotoxicity and provided important information on the safe application of CNTs.

  18. Adsorption isotherm of non-azeotropic solution onto porous adsorbents

    NASA Astrophysics Data System (ADS)

    Bono, A.; Ramlan, N. A.; Anisuzzaman, S. M.; Chu, C. M.; Farm, Y. Y.

    2016-06-01

    Adsorption isotherm is essential component in the understanding of the adsorption process. Several methods of the measurements, analysis and interpretation of adsorption from solution have been reported in the literature. Most of the measurements of adsorption isotherm from solution were involved the measurement of excess isotherm conducted at low region of sorbates concentration. Direct interpretation of excess adsorption isotherm as adsorption isotherm is always been practice. Therefore, in this work a study on the measurement of the adsorption isotherm from solution of non-azeotropic organic solvent mixture onto porous adsorbents for whole range of liquid concentration was conducted. The study included the measurement of excess adsorption isotherm using conventional technique. Theoretical analysis and interpretation of adsorption isotherm from the excess isotherm were conducted using Pseudo Ideal Adsorption, Gibbs Dividing Plane Model and Langmuir-Fruendlich binary isotherm model. For organic solvents, acetone and propanol were chosen as the adsorbates due to the non-azeotropic properties in the mixture. Activated carbon and silicalite were chosen as adsorbents due to the different in their porosity such as macro porous and micro porous structure. The result of the study has revealed that the adsorption isotherm of non-azeotropic mixture onto activated carbon and silicalite can be interpreted as monolayer type of adsorption.

  19. Facile and highly efficient removal of trace Gd(III) by adsorption of colloidal graphene oxide suspensions sealed in dialysis bag.

    PubMed

    Chen, Weifan; Wang, Linlin; Zhuo, Mingpeng; Liu, Yue; Wang, Yiping; Li, Yongxiu

    2014-08-30

    A facile, highly efficient and second-pollution-free strategy to remove trace Gd(III) from aqueous solutions by adsorption of colloidal graphene oxide (GO) suspensions in dialysis bag has been developed. The effects of pH, ionic strength and temperature on Gd(III) adsorption, and the pH-dependent desorption were investigated. The maximum adsorption capacity of Gd(III)on GO at pH=5.9±0.1 and T=303K was 286.86mgg(-1), higher than any other currently reported. The Gd(III)-saturated GO suspension could resume colloidal state in 0.1M HNO3 with desorption rate of 85.00% in the fifth adsorption-desorption cycle. Gd(III) adsorption rate on GO was dependent more on pH and ionic strength than on temperature. The abundant oxygen-containing functional groups such as carboxyl and hydroxyl played a vital role on adsorption. The thermodynamics and kinetics investigations revealed that the adsorption of Gd(III) on GO was an endothermic, spontaneous and monolayer absorption process, which well fitted the pseudo-second-order model. GO could be a promising adsorbent applied in the enrichment and removal of lanthanides from aqueous solutions. More significantly, the combination of colloidal GO suspension with dialysis membrane facilely solves the re-pollution of the treated solutions due to the great difficulties in separation and recovery of GO.

  20. Adsorption, desorption and bioregeneration in the treatment of 2-chlorophenol with activated carbon.

    PubMed

    Aktaş, Ozgür; Ceçen, Ferhan

    2007-03-22

    This study aims to clarify the effect of activated carbon type on the extent of adsorbability, desorbability, and bioregenerability in the treatment of 2-chlorophenol. Four different activated carbon types; thermally activated and chemically activated powdered carbons (PAC), and their granular countertypes (GAC) with similar physical characteristics were used. Thermally activated carbons adsorbed 2-chlorophenol much better than chemically activated ones. However, adsorption was more reversible in the case of chemically activated ones. The use of powdered and granular activated carbon countertypes resulted in comparable adsorption and desorption characteristics. For each activated carbon type, 2-chlorophenol exhibited higher adsorbability and lower desorbability than phenol. Biodegradation of 2-chlorophenol took place very slowly when it was used as the sole carbon source in acclimated and non-acclimated activated sludges. Bioregeneration occurred only via desorption due to an initial concentration gradient and no further desorption took place due to low biodegradability. Bioregeneration of activated carbon loaded with 2-chlorophenol was not a suitable option when 2-chlorophenol was the only carbon source. It is suggested to remove 2-chlorophenol via adsorption onto activated carbon rather than applying biological treatment. Also in such cases, the use of thermally activated carbons with higher adsorption and lower desorption capacities is recommended rather than chemically activated carbons.

  1. Adsorption of malathion on thermally treated egg shell material.

    PubMed

    Elwakeel, Khalid Z; Yousif, Ahmed M

    2010-01-01

    Thermally treated egg shell materials were prepared at different temperatures. The samples were investigated by means of FT-IR and thermogravimetric analysis (TGA). The adsorption behaviour of malathion on egg shell and its thermally treated samples was studied using batch method and gave uptake capacities up to 0.964 mmol/g. Adsorption kinetics as well as the adsorption isotherms were discussed. Regeneration of the loaded adsorbent beads towards the successive cycles was also clarified. The adsorption of malathion is maintained until the third cycle without a significant activity loss.

  2. Heavy metal adsorption changes of EAF steel slag after phosphorus adsorption.

    PubMed

    Song, Guanling; Cao, Lijing; Chen, Xiao; Hou, Wenhua; Wang, Qunhui

    2012-01-01

    A kind of electric arc furnace (EAF) steel slag was phosphated, and its isothermal and dynamic adsorptions of copper, cadmium, and lead ions were measured to determine if heavy metal adsorption changes after phosphorus adsorption. The surface area increased greatly after the slag was phosphated. Isothermal adsorption experiments showed that the theoretical Q(max) of the EAF steel slag on Cu(2+), Cd(2+), and Pb(2+) improved 59, 50, and 89% respectively after it was phosphated. Dynamic adsorption results showed that the greatest adsorption capacities of unit volume of Cu(2+), Cd(2+), and Pb(2+) were 2.2, 1.8, and 1.8 times that of the column packed with original EAF steel slag when the column was packed with phosphate EAF steel slag at the same heavy metal ion concentration. The breakthrough time, the exhaustion time and elution efficiency of the column also increased when the column was packed with phosphated EAF steel slag compared with that packed with original EAF steel slag. Phosphorus adsorption could further improve the heavy metal ion adsorption of the EAF steel slag.

  3. Enhanced CO2 adsorptive performance of PEI/SBA-15 adsorbent using phosphate ester based surfactants as additives.

    PubMed

    Cheng, Dandan; Liu, Yue; Wang, Haiqiang; Weng, Xiaole; Wu, Zhongbiao

    2015-12-01

    In this study, a series of polyetherimide/SBA-15: 2-D hexagonal P6mm, Santa Barbara USA (PEI/SBA-15) adsorbents modified by phosphoric ester based surfactants (including tri(2-ethylhexyl) phosphate (TEP), bis(2-ethylhexyl) phosphate (BEP) and trimethyl phosphonoacetate (TMPA)) were prepared for CO2 adsorption. Experimental results indicated that the addition of TEP and BEP had positive effects on CO2 adsorption capacity over PEI/SBA-15. In particular, the CO2 adsorption amount could be improved by around 20% for 45PEI-5TEP/SBA-15 compared to the additive-free adsorbent. This could be attributed to the decrease of CO2 diffusion resistance in the PEI bulk network due to the interactions between TEP and loaded PEI molecules, which was further confirmed by adsorption kinetics results. In addition, it was also found that the cyclic performance of the TEP-modified adsorbent was better than the surfactant-free one. This could be due to two main reasons, based on the results of in situ DRIFT and TG-DSC tests. First and more importantly, adsorbed CO2 species could be desorbed more rapidly over TEP-modified adsorbent during the thermal desorption process. Furthermore, the enhanced thermal stability after TEP addition ensured lower degradation of amine groups during adsorption/desorption cycles.

  4. Centrifugal Adsorption Cartridge System

    NASA Technical Reports Server (NTRS)

    Gonda, Steve R.; Tsao, Yow-Min D.; Lee, Wenshan

    2004-01-01

    The centrifugal adsorption cartridge system (CACS) is an apparatus that recovers one or more bioproduct(s) from a dilute aqueous solution or suspension flowing from a bioreactor. The CACS can be used both on Earth in unit gravity and in space in low gravity. The CACS can be connected downstream from the bioreactor; alternatively, it can be connected into a flow loop that includes the bioreactor so that the liquid can be recycled. A centrifugal adsorption cartridge in the CACS (see figure) includes two concentric cylinders with a spiral ramp between them. The volume between the inner and outer cylinders, and between the turns of the spiral ramp is packed with an adsorbent material. The inner cylinder is a sieve tube covered with a gas-permeable, hydrophobic membrane. During operation, the liquid effluent from the bioreactor is introduced at one end of the spiral ramp, which then constrains the liquid to flow along the spiral path through the adsorbent material. The spiral ramp also makes the flow more nearly uniform than it would otherwise be, and it minimizes any channeling other than that of the spiral flow itself. The adsorbent material is formulated to selectively capture the bioproduct(s) of interest. The bioproduct(s) can then be stored in bound form in the cartridge or else eluted from the cartridge. The centrifugal effect of the spiral flow is utilized to remove gas bubbles from the liquid. The centrifugal effect forces the bubbles radially inward, toward and through the membrane of the inner cylinder. The gas-permeable, hydrophobic membrane allows the bubbles to enter the inner cylinder while keeping the liquid out. The bubbles that thus enter the cylinder are vented to the atmosphere. The spacing between the ramps determines rate of flow along the spiral, and thereby affects the air-bubble-removal efficiency. The spacing between the ramps also determines the length of the fluid path through the cartridge adsorbent, and thus affects the bioproduct

  5. Assessing the Adsorption Properties of Shales

    NASA Astrophysics Data System (ADS)

    Pini, R.

    2014-12-01

    Fine-grained rocks, such as shales, contain a significant amount of nanopores that can significantly contribute to their storage capacity through the mechanism of adsorption. The current ability to extract natural gas that is adsorbed in the rock's matrix is limited and current technology focuses primarily on the free gas in the fractures, thus leading to very low recovery efficiencies. Shales constitute also a great portion of so-called caprocks above potential CO2 sequestration sites; hereby, the adsorption process may limit the CO2 mobility within the cap-rock, thus minimizing leakage phenomena. Whether it is a reservoir or a caprock, understanding and quantifying the mechanisms of adsorption in these natural materials is key to improve the engineering design of subsurface operations. Results will be presented from a laboratory study that combines conventional techniques for the measurement of adsorption isotherms with novel methods that allows for the imaging of adsorption using x-rays. Various nanoporous materials are considered, thus including rocks, such as shales and coals, pure clay minerals and engineered adsorbents with well-defined nanopore structures, such as zeolites. Supercritical CO2 adsorption isotherms have been measured with a Rubotherm Magnetic Suspension balance by covering the pressure range 0.1-20~MPa. A medical x-ray CT scanner has been used to identify three-dimensional patterns of the adsorption properties of a packed-bed of adsorbent, thus enabling to assess the spatial variability of the adsorption isotherm. The data are analyzed by using thermodynamically rigorous measures of adsorption and a graphical method is applied for their interpretation. The density of the adsorbed phase is estimated and compared to data reported in the literature; the latter is key to disclose gas-reserves and/or potential storage capacity estimates. When evaluated against classic adsorbent materials, the adsorption mechanism in shales is further complicated by

  6. Adsorption of bacteriophages on clay minerals

    USGS Publications Warehouse

    Chattopadhyay, Sandip; Puls, Robert W.

    1999-01-01

    The ability to predict the fate of microorganisms in soil is dependent on an understanding of the process of their sorption on soil and subsurface materials. Presently, we have focused on studying the thermodynamics of sorption of bacteriophages (T-2, MS-2, and φX-174) on clays (hectorite, saponite, kaolinite, and clay fraction of samples collected from a landfill site). The thermodynamic study not only determines the feasibility of the process but also provides information on the relative magnitudes of the different forces under a particular set of conditions. The total free energy of interaction during sorption of bacteriophages on clays (ΔG) has been assumed to be the summation of ΔGH (ΔG due to hydrophobic interactions) and ΔGEL (ΔG due to electrostatic interactions). The magnitude of ΔGH was determined from the different interfacial tensions (γ) present in the system, while ΔGEL was calculated from ζ-potentials of the colloidal particles. Calculated results show that surface hydrophobicities of the selected sorbents and sorbates dictate sorption. Among the selected bacteriophages, maximum sorption was observed with T-2, while hectorite has the maximum sorption capacity. Experimental results obtained from the batch adsorption studies also corroborated those obtained from the theoretical study.

  7. Study of Methylene Blue adsorption on keratin nanofibrous membranes.

    PubMed

    Aluigi, A; Rombaldoni, F; Tonetti, C; Jannoke, L

    2014-03-15

    In this work, keratin nanofibrous membranes (mean diameter of about 220nm) were prepared by electrospinning and tested as adsorbents for Methylene Blue through batch adsorption tests. The adsorption capacity of the membranes was evaluated as a function of initial dye concentration, pH, adsorbent dosage, time and temperature. The adsorption capacity increased with increasing the initial dye concentration and pH, while it decreased with increasing the adsorbent dosage and temperature, indicating an exothermic process. The adsorption results indicated that the Langmuir isotherm fitted the experimental data better than the Freundlich and Temkin isotherm models. A mean free energy evaluated through the Dubinin-Radushkevich model of about 16kJmol(-1), indicated a chemisorption process which occurred by ion exchange. The kinetic data were found to fit the pseudo-second-order model better than the pseudo-first-order model. The obtained results suggest that keratin nanofibrous membranes could be promising candidates as dye adsorption filters.

  8. Adsorption of trichlorophenol on zeolite and adsorbent regeneration with ozone.

    PubMed

    Zhang, Yongjun; Mancke, Raoul Georg; Sabelfeld, Marina; Geißen, Sven-Uwe

    2014-04-30

    A FAU-type zeolite was studied as an adsorbent to remove 2,4,6-trichlorophenol (TCP), a frequently detected recalcitrant pollutant in water bodies. Both adsorption isotherm and kinetics were studied with TCP concentrations from 10 to 100mg/L. It was observed that TCP was effectively adsorbed onto the zeolite with a high adsorption capacity and a high kinetic rate. Freundlich model and pseudo-second-order kinetics were successfully applied to describe the experimental data. The influence of solution pH was also studied. Furthermore, ozone was applied to regenerate the loaded zeolite. It was found that an effective adsorption of TCP was kept for at least 8 cycles of adsorption and regeneration. The ozonation also increased the BET specific surface of zeolite by over 60% and consequently enhanced the adsorption capacity.

  9. Adsorption of heavy metal ions using hierarchical CaCO3-maltose meso/macroporous hybrid materials: adsorption isotherms and kinetic studies.

    PubMed

    Ma, Xiaoming; Li, Liping; Yang, Lin; Su, Caiyun; Wang, Kui; Yuan, Shibao; Zhou, Jianguo

    2012-03-30

    Highly ordered hierarchical calcium carbonate is an important phase and has technological interest in the development of functional materials. The work describes hierarchical CaCO(3)-maltose meso/macroporous hybrid materials were synthesized using a simple gas-diffusion method. The uniform hexagonal-shaped CaCO(3)-maltose hybrid materials are formed by the hierarchical assembly of nanoparticles. The pore structure analysis indicates that the sample possesses the macroporous structure of mesoporous framework. The distinguishing features of the hierarchical CaCO(3)-maltose materials in water treatment involve not only high removal capacities, but also decontamination of trace metal ions. Langmuir model fitted the equilibrium data better than the Freundlich isotherm. The maximum removal capacity of the CaCO(3)-maltose hybrid materials for Pb(2+), Cd(2+), Cu(2+), Co(2+), Mn(2+) and Ni(2+) ions was 3242.48, 487.80, 628.93, 393.70, 558.66 and 769.23 mg/g, respectively. Adsorption data were modeled using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics equations. The results indicate that pseudo-second-order kinetic equation and intra-particle diffusion model can better describe the adsorption kinetics. The adsorption and precipitation transformation mechanism can be considered due to hierarchical meso/macroporous structure, rich organic ligands of the CaCO(3)-maltose hybrid materials and the larger solubility product of CaCO(3).

  10. Laboratory study on the adsorption of Mn(2+) on suspended and deposited amorphous Al(OH)(3) in drinking water distribution systems.

    PubMed

    Wang, Wendong; Zhang, Xiaoni; Wang, Hongping; Wang, Xiaochang; Zhou, Lichuan; Liu, Rui; Liang, Yuting

    2012-09-01

    Manganese (II) is commonly present in drinking water. This paper mainly focuses on the adsorption of manganese on suspended and deposited amorphous Al(OH)(3) solids. The effects of water flow rate and water quality parameters, including solution pH and the concentrations of Mn(2+), humic acid, and co-existing cations on adsorption were investigated. It was found that chemical adsorption mainly took place in drinking water with pHs above 7.5; suspended Al(OH)(3) showed strong adsorption capacity for Mn(2+). When the total Mn(2+) input was 3 mg/L, 1.0 g solid could accumulate approximately 24.0 mg of Mn(2+) at 15 °C. In drinking water with pHs below 7.5, because of H(+) inhibition, active reaction sites on amorphous Al(OH)(3) surface were much less. The adsorption of Mn(2+) on Al(OH)(3) changed gradually from chemical coordination to physical adsorption. In drinking water with high concentrations of Ca(2+), Mg(2+), Fe(3+), and HA, the removal of Mn(2+) was enhanced due to the effects of co-precipitation and adsorption. In solution with 1.0 mg/L HA, the residual concentration of Mn(2+) was below 0.005 mg/L, much lower than the limit value required by the Chinese Standard for Drinking Water Quality. Unlike suspended Al(OH)(3), deposited Al(OH)(3) had a much lower adsorption capacity of 0.85 mg/g, and the variation in flow rate and major water quality parameters had little effect on it. Improved managements of water age, pipe flushing and mechanical cleaning were suggested to control residual Mn(2+).

  11. Adsorption of 4-n-Nonylphenol and Bisphenol-A on Magnetic Reduced Graphene Oxides: A Combined Experimental and Theoretical Studies.

    PubMed

    Jin, Zhongxiu; Wang, Xiangxue; Sun, Yubing; Ai, Yuejie; Wang, Xiangke

    2015-08-04

    Adsorption of 4-n-nonylphenol (4-n-NP) and bisphenol A (BPA) on magnetic reduced graphene oxides (rGOs) as a function of contact time, pH, ionic strength and humic acid were investigated by batch techniques. Adsorption of 4-n-NP and BPA were independent of pH at 3.0- 8.0, whereas the slightly decreased adsorption was observed at pH 8.0-11.0. Adsorption kinetics and isotherms of 4-n-NP and BPA on magnetic rGOs can be satisfactorily fitted by pseudo-second-order kinetic and Freundlich model, respectively. The maximum adsorption capacities of magnetic rGOs at pH 6.5 and 293 K were 63.96 and 48.74 mg/g for 4-n-NP and BPA, respectively, which were significantly higher than that of activated carbon. Based on theoretical calculations, the higher adsorption energy of rGOs + 4-n-NP was mainly due to π-π stacking and flexible long alkyl chain of 4-n-NP, whereas adsorption of BPA on rGOs was energetically favored by a lying-down configuration due to π-π stacking and dispersion forces, which was further demonstrated by FTIR analysis. These findings indicate that magnetic rGOs is a promising adsorbent for the efficient elimination of 4-n-NP/BPA from aqueous solutions due to its excellent adsorption performance and simple magnetic separation, which are of great significance for the remediation of endocrine-disrupting chemicals in environmental cleanup.

  12. Evaluation of the isosteric heat of adsorption at zero coverage for hydrogen on activated carbons

    NASA Astrophysics Data System (ADS)

    Dohnke, E.; Beckner, M.; Romanos, J.; Olsen, R.; Wexler, C.; Pfeifer, P.

    2011-03-01

    Activated carbons made from corn cob show promise as materials for high-capacity hydrogen storage. As part of our characterization of these materials, we are interested in learning how different production methods affect the adsorption energies. In this talk, we will show how hydrogen adsorption isotherms may be used to calculate these adsorption energies at zero coverage using Henry's law. We will additionally discuss differences between the binding energy and the isosteric heat of adsorption by applying this analysis at different temperatures.

  13. Determination of binding capacity and adsorption enthalpy between Human Glutamate Receptor (GluR1) peptide fragments and kynurenic acid by surface plasmon resonance experiments. Part 2: Interaction of GluR1270-300 with KYNA.

    PubMed

    Csapó, E; Bogár, F; Juhász, Á; Sebők, D; Szolomájer, J; Tóth, G K; Majláth, Z; Vécsei, L; Dékány, I

    2015-09-01

    In the course of our previous work, the interactions of two peptide fragments (GluR1201-230 and GluR1231-259) of human glutamate receptor (GluR1201-300) polypeptide with kynurenic acid (KYNA) were investigated by surface plasmon resonance (SPR) spectroscopy. Besides quantitation of the interactions, the enthalpies of binding of KYNA on certain peptide fragment-modified gold surfaces were also reported. In the present work, a third peptide fragment (GluR1270-300) of the glutamate receptor was synthesized and its interaction with KYNA was investigated by an SPR technique. This 31-membered peptide was chemically bonded onto a gold-coated SPR chip via a cysteine residue. The peptide-functionalized biosensor chip was analyzed by atomic force microscopy (AFM) and theoretical calculations were performed on the structure and dimensions of the peptide on the gold surface. In order to determine the isosteric heat of adsorption of the binding of KYNA on the peptide-functionalized gold thin film, SPR experiments were carried out between +10°C and +40°C. The results on the GluR1270-300-KYNA system were compared with the previously published binding parameters of the interactions of GluR1201-230 and GluR1231-259 with KYNA. The binding abilities of KYNA with all three peptide fragments immobilized on the gold surface were estimated by a molecular docking procedure and the binding free energies of these AMPA receptor subunits with KYNA were determined.

  14. MOLECULAR OXYGEN AND THE ADSORPTION OF PHENOLS - EFFECT OF FUNCTIONAL GROUPS

    EPA Science Inventory

    This study reveals that the presence of molecular oxygen (oxic conditions) has a significant impact on the exhibited adsorptive capacity of granular activated carbon (GAC) for several phenolic compounds. The increase in the GAC adsorptive capacity under oxic conditions results f...

  15. Phosphorus recovery using pelletized adsorptive materials ...

    EPA Pesticide Factsheets

    Phosphorous (P) is one of the essential nutrients for growth and is generally the most limiting nutrient since, it cannot be fixed from the atmosphere. Methods for recovering phosphorous from water systems already exist, but advances are being made to find a more economic, efficient, effective and easy to use method that can allow for reuse of the recovered P. One area of study is in adsorption, which involves finding the best material for adsorption of phosphorous from water and for releasing it back into the environment through desorption or leaching. The goal of this research was to first optimize the capacity for a pelletized adsorptive material that was synthesized with varying amounts of a binder material from 0-20 % and then to study recovering the phosphate for reuse. The pelletized materials were studied through kinetics experiments as well as isotherm experiments to gain insight into the adsorption capacity and mechanism. Following successful adsorption, a simple leaching study was conducted to see how much phosphate would be released back into water without any added desorption aid. Desorption was then studied by changing the pH of solution. Presenting my thesis work with a poster at ACS.

  16. Sulfate adsorption in Michigan forest soils

    SciTech Connect

    MacDonald, N.W.

    1987-01-01

    The occurrence of acidic atmospheric deposition raised concerns over adverse cation leaching effects on Michigan forest soils with low cation exchange capacities. Leaching effects of acid deposition depend on mobility of sulfate in the soil. Little was known, however, concerning the ability of these soils to adsorb sulfate. The objectives of this study were to determine the ability of representative Michigan forest soils to adsorb sulfate, to relate sulfate adsorption to soil properties, and to develop equations to predict sulfate adsorption in similar forest soils. Frigid zone soil series studied were Grayling (Typic Udipsamments), Rubicon (Entic Haplorthods), Kalkaska (Typic Haplorthods), and Montcalm (Eutric Glossoboralfs). Mesic zone series studied were Spinks (Psammentic Hapludals) and Oshtemo (Typic Hapludalfs). Six randomly located pedons of each series were sampled. Sulfate adsorption was determined by shaking 10 gram soil samples for 24 hours in 50 mL 0.01 M CaCl/sub 2/ solution containing 10 mg SO/sub 4/-S L/sup -1/. Solution filtrates were turbidimetrically analyzed for SO/sub 4/-S and adsorption was calculated from reduction in SO/sub 4/-S concentration. Bw, Bs, and Bh horizons of frigid zone soils and E and Bt horizons of mesic zone soils had the highest sulfate adsorbing abilities. No significant differences were found between series in total sulfate adsorptive capacity.

  17. Adsorption of ammonia by sulfuric acid treated zirconium hydroxide.

    PubMed

    Glover, T Grant; Peterson, Gregory W; DeCoste, Jared B; Browe, Matthew A

    2012-07-17

    The adsorption of ammonia on Zr(OH)(4), as well as Zr(OH)(4) treated with sulfuric acid, were examined. The results show that treating Zr(OH)(4) with sulfuric acid leads to the formation of a sulfate on the surface of the material, and that the sulfate contributes to the ammonia adsorption capacity through the formation of an ammonium sulfates species. Calcination of Zr(OH)(4) decreases the ammonia adsorption capacity of the material and limits the formation of sulfate species. NMR and FTIR spectroscopy results are presented that show the presence of two distinct ammonium species on the surface of the material. The adsorption capacity of the materials is shown to be a complex phenomenon that is impacted by the surface area, the sulfur content, and the pH of the material. The results illustrate that Zr(OH)(4), which is known to adsorb acidic gases, can be modified and used to adsorb basic gases.

  18. Tetraethylenepentamine embedded zeolite A for carbon dioxide adsorption.

    PubMed

    Kim, Young-Ki; Mo, Yong-Hwan; Lee, Jun; You, Hyo-Sang; Yi, Chang-Keun; Park, Young Cheol; Park, Sang-Eon

    2013-04-01

    Tetraethylenepentamine (TEPA) embedded zeolite A crystals were synthesized by using TEPA and the preformed zeolite A precursor under the microwave irradiation. The presence of TEPA in zeolite A crystal was confirmed by TG analysis and FTIR, Raman spectra. The CO2 adsorptive behavior of TEPA embedded zeolite A samples was investigated by CO2 isotherms measured at 25 degrees C comparing with zeolite A. The optimum CO2 sorption capacity was found in the case of 7.5% TEPA embedded zeolite A, which showed 3.75 mmol g(-1) where as the zeolite A showed less CO2 adsorption capacity of 2.88 mmol g(-1). The adsorption capacity of TEPA embedded Zeolite A was sustained up to 90% during 4 cycles of temperature swing adsorption (TSA) from 40 degrees C to 140 degrees C, indicating that the TEPA embedded Zeolite A was found to be useful as one of the application to solid amine adsorbent for CO2.

  19. Three dimensional MOF-sponge for fast dynamic adsorption.

    PubMed

    Li, Huizeng; Li, Mingzhu; Li, Wenbo; Yang, Qiang; Li, Yanan; Gu, Zhenkun; Song, Yanlin

    2017-02-22

    Nowadays, environmental pollution is a big problem. Metal organic frameworks (MOFs) provide a novel strategy for exhaust gases adsorption and toxic pollutants removal. We proposed a facile and versatile method to prepare a highly efficient three dimensional MOF-sponge by coating MOF crystals on polyurethane sponge surface, mimicking the porous structure of the marine animal, sponge. Owing to combination of the spatial structure of the commercial sponge and the excellent adsorption capacity of MOF coatings, the MOF-sponge possessed good permeability and high dynamic adsorption capacity. Dynamic adsorption ability of the prepared Cu3(BTC)2-sponge was demonstrated by flowing gas-mixtures of NH3/N2 and an aquatic solution of Rhodamine B through it, with a capacity of 101.6 mg g(-1) and 8.8 mg g(-1) for NH3 and Rhodamine B, respectively.

  20. Adsorption of Sb(III) and Sb(V) on Freshly Prepared Ferric Hydroxide (FeOxHy).

    PubMed

    He, Zan; Liu, Ruiping; Liu, Huijuan; Qu, Jiuhui

    2015-02-01

    This study prepared fresh ferric hydroxide (in-situ FeOxHy) by the enhanced hydrolysis of Fe(3+) ions, and investigates its adsorptive behaviors toward Sb(III) and Sb(V) through laboratory and pilot-scale studies. A contact time of 120-min was enough to achieve adsorption equilibrium for Sb(III) and Sb(V) on the in-situ FeOxHy, and the Elovich model was best to describe the adsorption kinetics of Sb(III) and Sb(V). The Freundlich model was better than Langmuir model to describe the adsorption of Sb(III) and Sb(V) on the in-situ FeOxHy, and the maximum adsorption capacity of Sb(III) and Sb(V) was determined to be 12.77 and 10.21 mmol/g the in-situ FeOxHy as Fe, respectively. Adsorption of Sb(V) decreased whereas that of Sb(III) increased with elevated pH over pH 3-10, owing to the different electrical properties of Sb(III) and Sb(V). Adsorption of Sb(III) and Sb(V) was slightly affected by ionic strength, and thus indicated the formation of inner sphere complexes between Sb and the adsorbent. Sulfate and carbonate showed little effect on the adsorption of Sb(III) and Sb(V). Phosphate significantly inhibited the adsorption of Sb(V), whereas slightly effected that of Sb(III) due to its similar chemical structure to Sb(V). Pilot-scale continuous experiment indicated the feasibility of using in-situ FeOxHy to remove Sb(V), and equilibrium adsorption capacity at the equilibrium Sb(V) concentration of 10 μg/L was determined to be 0.11, 0.07, 0.07, 0.11, and 0.12 mg/g the in-situ FeOxHy as Fe at equilibrium pH of 7.5-7.7, 6.9-7.0, 6.3-6.6, 5.9-6.4, and 5.2-5.9, respectively.

  1. Adsorption of Sb(III) and Sb(V) on Freshly Prepared Ferric Hydroxide (FeOxHy)

    PubMed Central

    He, Zan; Liu, Ruiping; Liu, Huijuan; Qu, Jiuhui

    2015-01-01

    Abstract This study prepared fresh ferric hydroxide (in-situ FeOxHy) by the enhanced hydrolysis of Fe3+ ions, and investigates its adsorptive behaviors toward Sb(III) and Sb(V) through laboratory and pilot-scale studies. A contact time of 120-min was enough to achieve adsorption equilibrium for Sb(III) and Sb(V) on the in-situ FeOxHy, and the Elovich model was best to describe the adsorption kinetics of Sb(III) and Sb(V). The Freundlich model was better than Langmuir model to describe the adsorption of Sb(III) and Sb(V) on the in-situ FeOxHy, and the maximum adsorption capacity of Sb(III) and Sb(V) was determined to be 12.77 and 10.21 mmol/g the in-situ FeOxHy as Fe, respectively. Adsorption of Sb(V) decreased whereas that of Sb(III) increased with elevated pH over pH 3–10, owing to the different electrical properties of Sb(III) and Sb(V). Adsorption of Sb(III) and Sb(V) was slightly affected by ionic strength, and thus indicated the formation of inner sphere complexes between Sb and the adsorbent. Sulfate and carbonate showed little effect on the adsorption of Sb(III) and Sb(V). Phosphate significantly inhibited the adsorption of Sb(V), whereas slightly effected that of Sb(III) due to its similar chemical structure to Sb(V). Pilot-scale continuous experiment indicated the feasibility of using in-situ FeOxHy to remove Sb(V), and equilibrium adsorption capacity at the equilibrium Sb(V) concentration of 10 μg/L was determined to be 0.11, 0.07, 0.07, 0.11, and 0.12 mg/g the in-situ FeOxHy as Fe at equilibrium pH of 7.5–7.7, 6.9–7.0, 6.3–6.6, 5.9–6.4, and 5.2–5.9, respectively. PMID:25741175

  2. Adsorption studies of methylene blue dye on tunisian activated lignin

    NASA Astrophysics Data System (ADS)

    Kriaa, A.; Hamdi, N.; Srasra, E.

    2011-02-01

    Activated carbon prepared from natural lignin, providing from a geological deposit, was used as the adsorbent for the removal of methylene blue (MB) dye from aqueous solutions. Batch adsorption studies were conducted to evaluate various experimental parameters like pH and contact time for the removal of this dye. Effective pH for MB removal was 11. Kinetic study showed that the adsorption of dye was gradual process. Quasi equilibrium reached in 4 h. Pseudo-first-order, pseudo-second-order were used to fit the experimental data. Pseudo-second-order rate equation was able to provide realistic description of adsorption kinetics. The experimental isotherms data were also modelled by the Langmuir and Freundlich equation of adsorption. Equilibrium data fitted well with the Langmuir model with maximum monolayer adsorption capacity of 147 mg/g. Activated lignin was shown to be a promising material for adsorption of MB from aqueous solutions.

  3. EVALUATING CAPACITIES OF GAC PRELOADED WITH NATURAL WATER

    EPA Science Inventory

    Adsorption studies are conducted to determine how preloading a natural groundwater onto GAC affects the adsorption of cis-1,2-dichloroexthene in small-scale and pilot-scale columns. Capacities are determined from batch-isotherm tests, microcolumns, and pilot columns, which are p...

  4. Modeling adsorption: Investigating adsorbate and adsorbent properties

    NASA Astrophysics Data System (ADS)

    Webster, Charles Edwin

    1999-12-01

    Surface catalyzed reactions play a major role in current chemical production technology. Currently, 90% of all chemicals are produced by heterogeneously catalyzed reactions. Most of these catalyzed reactions involve adsorption, concentrating the substrate(s) (the adsorbate) on the surface of the solid (the adsorbent). Pore volumes, accessible surface areas, and the thermodynamics of adsorption are essential in the understanding of solid surface characteristics fundamental to catalyst and adsorbent screening and selection. Molecular properties such as molecular volumes and projected molecular areas are needed in order to convert moles adsorbed to surface volumes and areas. Generally, these molecular properties have been estimated from bulk properties, but many assumptions are required. As a result, different literature values are employed for these essential molecular properties. Calculated molar volumes and excluded molecular areas are determined and tabulated for a variety of molecules. Molecular dimensions of molecules are important in the understanding of molecular exclusion as well as size and shape selectivity, diffusion, and adsorbent selection. Molecular dimensions can also be used in the determination of the effective catalytic pore size of a catalyst. Adsorption isotherms, on zeolites, (crystalline mineral oxides) and amorphous solids, can be analyzed with the Multiple Equilibrium Analysis (MEA) description of adsorption. The MEA produces equilibrium constants (Ki), capacities (ni), and thermodynamic parameters (enthalpies, ΔHi, and entropies, ΔSi) of adsorption for each process. Pore volumes and accessible surface areas are calculated from the process capacities. Adsorption isotherms can also be predicted for existing and new adsorbate-adsorbent systems with the MEA. The results show that MEA has the potential of becoming a standard characterization method for microporous solids that will lead to an increased understanding of their behavior in gas

  5. Effect of aging process on adsorption of diethyl phthalate in soils amended with bamboo biochar.

    PubMed

    Zhang, Xiaokai; Sarmah, Ajit K; Bolan, Nanthi S; He, Lizhi; Lin, Xiaoming; Che, Lei; Tang, Caixian; Wang, Hailong

    2016-01-01

    Biochar is a carbonaceous sorbent and can be used as a potential material to reduce the bioavailability of organic pollutants in contaminated soils. In the present study, the adsorption and desorption of diethyl phthalate (DEP) onto soils amended with bamboo biochar was investigated with a special focus on the effect of biochar application rates and aging conditions on the adsorption capacity of the soils. Biochar amendment significantly enhanced the soil adsorption of DEP that increased with increasing application rates of biochar. However, the adsorption capacity decreased by two aging processes (alternating wet and dry, and constantly moist). In the soil with low organic carbon (OC) content, the addition of 0.5% biochar (without aging) increased the adsorption by nearly 98 times compared to the control, and exhibited the highest adsorption capacity among all the treatments. In the soil with high OC content, the adsorption capacity in the treatment of 0.5% biochar without aging was 3.5 and 3 times greater than those of the treatments of biochar aged by alternating wet and dry, and constantly moist, respectively. Moreover, constantly moist resulted in a greater adsorption capacity than alternating wet and dry treatments regardless of biochar addition. This study revealed that biochar application enhanced soil sorption of DEP, however, the enhancement of the adsorption capacity was dependent on the soil organic carbon levels, and aging processes of biochar.

  6. Adsorption of ammonium on biochar prepared from giant reed.

    PubMed

    Hou, Jie; Huang, Lei; Yang, Zhimin; Zhao, Yaqi; Deng, Chaoren; Chen, Yucheng; Li, Xin

    2016-10-01

    Giant reed was used as precursor for making biochar in order for the adsorption of NH4 (+)-N from aqueous solution. And the adsorption of the product to NH4 (+)-N was examined. The surface features of biochar were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy/energy dispersive spectrometer (SEM-EDS), and X-ray diffraction (XRD). XRD patterns showed several peaks and correspond to the high amount of crystalline material. The crystals contain KCl, K2O, CaO, MgO, and SiO and possess high surface area which enhances adsorption. The influence of different parameters such as initial concentration, adsorption time, pH, and ionic strength has been carried out. The adsorption could reach equilibrium through 24 h reaction and had the best adsorption amount at the solution pH values from 7 to 9. The cation has great influence on the adsorption of NH4 (+)-N, whereas the anion exerted a weaker effect. The adsorption followed pseudo-first-order and pseudo-second-order models. And the intraparticle diffusion and desorption studies further elucidated that the mechanism of adsorption on the product was ion exchange. The product equilibrium data was well described by the Langmuir and Freundlich model. The maximum adsorption capacities were 1.490 mg/g. Biochar derived from giant reed at 500 °C was suggested as a promising adsorbent for the removal of NH4 (+)-N from slightly polluted wastewater.

  7. Adsorption Behavior of Pb(II) Onto Potassium Polytitanate Nanofibres.

    PubMed

    Shahid, Mohammad; Tiling, Leonard D; El Saliby, Ibrahim; McDonagh, Andrew; Kim, Jong-Beom; Kim, Jong-Ho; Shon, Ho Kyong

    2016-02-01

    Potassium polytitanate nanofibres prepared by a hydrothermal method were investigated for their possible application in removing toxic metals from aqueous solution. Particular attention was paid to employing the titanate as a novel effective adsorbent for the removal of Pb(II). Batch adsorption experiments demonstrated that the adsorption was influenced by various conditions such as solution pH, adsorbent dosage and initial Pb(II) concentration. The results showed that the adsorption rate was faster in the first 5 min and equilibrium was achieved after 180 min. The maximum amount of adsorption was detected at pH 5. Potassium titanate showed much higher adsorption capacity compared to P25. The kinetic studies indicated that the adsorption of Pb(II) onto titanate best fit the pseudo-second-order kinetic model. FTIR spectra revealed that the hydroxyl groups in titanate were responsible for Pb(II) adsorption. The principal mechanism of the adsorption of Pb(II) in the present study is attributed to both ion exchange and oxygen bonding. The adsorption-desorption results demonstrated that the titanate could be readily regenerated after adsorption. Therefore, the present titanate exhibits great potential for the removal of Pb(II) from wastewater.

  8. Adsorption characteristics of activated carbon fibers (ACFs) for toluene: application in respiratory protection.

    PubMed

    Balanay, Jo Anne G; Bartolucci, Alfred A; Lungu, Claudiu T

    2014-01-01

    Granular activated carbon (GAC) is currently the standard adsorbent in respirators against several gases and vapors because of its efficiency, low cost, and available technology. However, a drawback of GAC due to its granular form is its need for containment, adding weight and bulkiness to respirators. This makes respirators uncomfortable to wear, resulting in poor compliance in their use. Activated carbon fibers (ACF) are considered viable alternative adsorbent materials for developing thinner, light-weight, and efficient respirators because of their larger surface area, lighter weight, and fabric form. This study aims to determine the critical bed depth and adsorption capacity of different types of commercially available ACFs for toluene to understand how thin a respirator can be and the service life of the adsorbents, respectively. ACF in cloth (ACFC) and felt (ACFF) forms with three different surface areas per form were tested. Each ACF type was challenged with six concentrations of toluene (50, 100, 200, 300, 400, 500 ppm) at constant air temperature (23°C), relative humidity (50%), and airflow (16 LPM) at different adsorbent weights and bed depths. Breakthrough data were obtained for each adsorbent using gas chromatography with flame ionization detector. The ACFs' surface areas were measured by an automatic physisorption analyzer. The results showed that ACFC has a lower critical bed depth and higher adsorption capacity compared to ACFF with similar surface area for each toluene concentration. Among the ACF types, ACFC2000 (cloth with the highest measured surface area of 1614 ± 5 m(2)/g) has one of the lowest critical bed depths (ranging from 0.11-0.22 cm) and has the highest adsorption capacity (ranging from 595-878 mg/g). Based on these studied adsorption characteristics, it is concluded that ACF has great potential for application in respiratory protection against toluene, particularly the ACFC2000, which is the best candidate for developing thinner and

  9. The Adsorption and Desorption of Pb(2+) and Cd(2+) in Freeze-Thaw Treated Soils.

    PubMed

    Li, Linhui; Ma, Jincai; Xu, Meng; Li, Xu; Tao, Jiahui; Wang, Guanzhu; Yu, Jitong; Guo, Ping

    2016-01-01

    Adsorption and desorption are important processes that influence the potential toxicity and bioavailability of heavy metals in soils. However, information regarding adsorption and desorption behavior of heavy metals in soils subjected to freeze-thaw cycles is poorly understood. In the current study, the effect of freeze-thaw cycles with different freezing temperature (-15, -25, -35°C) on soil properties was investigated. Then the adsorption and desorption behavior of Pb(2+) and Cd(2+) in freeze-thaw treated soils was studied. The adsorption amounts of Pb(2+) and Cd(2+) in freeze-thaw treated soils were smaller than those in unfrozen soils (p < 0.05), due to the fact that pH, cation exchange capacity, organic matter content, free iron oxide content, and CaCO3 content in freeze-thaw treated soils were smaller than those in unfrozen soils. The adsorption amounts of Pb(2+) and Cd(2+) in soils treated with lower freezing temperatures were higher than those in soils treated with higher freezing temperatures. Desorption percentages of Pb(2+) and Cd(2+) in unfrozen soils were smaller than those in freeze-thaw treated soils (p < 0.05). The desorption percentages of Pb(2+) and Cd(2+) were smaller in soils treated with lower freezing temperatures than those in soils treated with higher freezing temperatures. The results obtained highlight the change of the adsorption and desorption behavior of typical heavy metals in freeze-thaw treated soils located in seasonal frozen soils zone in northeast China.

  10. A physical entrapment method for the preparation of carbon nanotube reinforced macroporous adsorption resin with enhanced selective extraction performance

    NASA Astrophysics Data System (ADS)

    Ha, Wei; Song, Xin-Yue; Chen, Juan; Shi, Yan-Ping

    2015-11-01

    In this paper, we demonstrate a novel carbon nanotube (CNT) reinforced macroporous adsorption resin (MAR) for the first time. The CNTs were dispersed in water via sonication, and then in situ physically entrapped in the pores of MAR by capillary forces and sonication. The resulting CNT reinforced MAR (CNT-MAR) was proved by transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM), and subsequently applied to extract a mixture of 8 types, 14 natural products. For comparison, the extraction efficiency of original MAR without CNTs was also evaluated. After extraction, the supernatants were detected via high-performance liquid chromatography (HPLC). The results indicated that the introduction of carbon nanotubes (CNTs) into the pores of MAR can significantly improve the adsorptive selectivity of MAR for natural products. The original MAR without CNTs has almost the same adsorption capacity for selectively extracting 3 types of natural products (phenols, alkaloids and anthraquinones). However, the CNT-MAR only could selectively extract anthraquinones and the adsorption capacity for three anthraquinone natural products is 1.46-1.83 times higher than that of unmodified MAR. In order to achieve the highest extraction efficiency of CNT-MAR for anthraquinone natural products, the main extraction parameters such as the extraction time and the pH value were also optimized. The CNT-MAR demonstrated an excellent ability to extract anthraquinone natural products with high selectivity and adsorption capacity. Due to its low cost, easy preparation and use, and operational characteristics, it shows great potential for selective extraction of natural products.In this paper, we demonstrate a novel carbon nanotube (CNT) reinforced macroporous adsorption resin (MAR) for the first time. The CNTs were dispersed in water via sonication, and then in situ physically entrapped in the pores of MAR by capillary forces and sonication. The resulting CNT reinforced MAR

  11. Adsorptive Removal and Adsorption Kinetics of Fluoroquinolone by Nano-Hydroxyapatite.

    PubMed

    Chen, Yajun; Lan, Tao; Duan, Lunchao; Wang, Fenghe; Zhao, Bin; Zhang, Shengtian; Wei, Wei

    2015-01-01

    Various kinds of antibiotics, especially fluoroquinolone antibiotics (FQs) have been widely used for the therapy of infectious diseases in human and livestock. For their poorly absorbed by living organisms, large-scale misuse or abuse of FQs will foster drug resistance among pathogenic bacteria, as well as a variety of environmental problems when they were released in the environment. In this work, the adsorption properties of two FQs, namely norfloxacin (NOR) and ciprofloxacin (CIP), by nano-hydroxyapatite (n-HAP) were studied by batch adsorption experiments. The adsorption curves of FQs by n-HAP were simulated by Langmuir and Freundlich isotherms. The results shown that NOR and CIP can be adsorbed effectively by the adsorbent of n-HAP, and the adsorption capacity of FQs increase with increasing dosage of n-HAP. The optimum dosage of n-HAP for FQs removal was 20 g · L(-1), in which the removal efficiencies is 51.6% and 47.3%, and an adsorption equilibrium time is 20 min. The maximum removal efficiency occurred when pH is 6 for both FQs. The adsorption isotherm of FQs fits well for both Langmuir and Freundlich equations. The adsorption of both FQs by n-HAP follows second-order kinetics.

  12. Study on the adsorption feature of rutin aqueous solution on macroporous adsorption resins.

    PubMed

    Chen, Zhenbin; Zhang, Anjie; Li, Jie; Dong, Fang; Di, Duolong; Wu, Youzhi

    2010-04-15

    The adsorption feature of different kinds of polystyrene-based macroporous adsorption resins (MARs) was investigated systemically at constant temperature employing Rutin as the adsorbate. Different from traditional adsorption patterns, Langmuir and Freundlich adsorption, and the results showed interesting aspects: (1) With the increase of the volume of the initial solution, the adsorption capacity increased to the maximum, and then decreased gradually. (2) Experimental results clearly verified the opinion that the adsorption process of MARs could be divided into three stages-macropores, mesopores, and micropores-by the capillary effects occurring at the two intersections, and the adsorption feature for every stage could be described well by the fourth type of Brunauer model. (3) The model that the inductive effect transmitted to the first layer could not interpret our experimental results reasonably. Thus, the model that the inductive effect passed on to a higher layer was proposed by investigating regression of the experimental results and the conclusion that the inductive effect transmitted to the third layer was drawn.

  13. Adsorptive Removal and Adsorption Kinetics of Fluoroquinolone by Nano-Hydroxyapatite

    PubMed Central

    Chen, Yajun; Lan, Tao; Duan, Lunchao; Wang, Fenghe; Zhao, Bin; Zhang, Shengtian; Wei, Wei

    2015-01-01

    Various kinds of antibiotics, especially fluoroquinolone antibiotics (FQs) have been widely used for the therapy of infectious diseases in human and livestock. For their poorly absorbed by living organisms, large-scale misuse or abuse of FQs will foster drug resistance among pathogenic bacteria, as well as a variety of environmental problems when they were released in the environment. In this work, the adsorption properties of two FQs, namely norfloxacin (NOR) and ciprofloxacin (CIP), by nano-hydroxyapatite (n-HAP) were studied by batch adsorption experiments. The adsorption curves of FQs by n-HAP were simulated by Langmuir and Freundlich isotherms. The results shown that NOR and CIP can be adsorbed effectively by the adsorbent of n-HAP, and the adsorption capacity of FQs increase with increasing dosage of n-HAP. The optimum dosage of n-HAP for FQs removal was 20 g·L-1, in which the removal efficiencies is 51.6% and 47.3%, and an adsorption equilibrium time is 20 min. The maximum removal efficiency occurred when pH is 6 for both FQs. The adsorption isotherm of FQs fits well for both Langmuir and Freundlich equations. The adsorption of both FQs by n-HAP follows second-order kinetics. PMID:26698573

  14. Parametric and adsorption kinetic studies of methylene blue removal from simulated textile water using durian (Durio zibethinus murray) skin.

    PubMed

    Anisuzzaman, S M; Joseph, Collin G; Krishnaiah, D; Bono, A; Ooi, L C

    2015-01-01

    In this study, durian (Durio zibethinus Murray) skin was examined for its ability to remove methylene blue (MB) dye from simulated textile wastewater. Adsorption equilibrium and kinetics of MB removal from aqueous solutions at different parametric conditions such as different initial concentrations (2-10 mg/L), biosorbent dosages (0.3-0.7 g) and pH solution (4-9) onto durian skin were studied using batch adsorption. The amount of MB adsorbed increased from 3.45 to 17.31 mg/g with the increase in initial concentration of MB dye; whereas biosorbent dosage increased from 1.08 to 2.47 mg/g. Maximum dye adsorption capacity of the durian skin was found to increase from 3.78 to 6.40 mg/g, with increasing solution pH. Equilibrium isotherm data were analyzed according to Langmuir and Freundlich isotherm models. The sorption equilibrium was best described by the Freundlich isotherm model with maximum adsorption capacity of 7.23 mg/g and this was due to the heterogeneous nature of the durian skin surface. Kinetic studies indicated that the sorption of MB dye tended to follow the pseudo second-order kinetic model with promising correlation of 0.9836 < R(2) < 0.9918.

  15. Zinc (hydr)oxide/graphite oxide/AuNPs composites: role of surface features in H₂S reactive adsorption.

    PubMed

    Giannakoudakis, Dimitrios A; Bandosz, Teresa J

    2014-12-15

    Zinc hydroxide/graphite oxide/AuNPs composites with various levels of complexity were synthesized using an in situ precipitation method. Then they were used as H2S adsorbents in visible light. The materials' surfaces were characterized before and after H2S adsorption by various physical and chemical methods (XRD, FTIR, thermal analysis, potentiometric titration, adsorption of nitrogen and SEM/EDX). Significant differences in surface features and synergistic effects were found depending on the materials' composition. Addition of graphite oxide and the deposition of gold nanoparticles resulted in a marked increase in the adsorption capacity in comparison with that on the zinc hydroxide and zinc hydroxide/AuNP. Addition of AuNPs to zinc hydroxide led to a crystalline ZnO/AuNP composite while the zinc hydroxide/graphite oxide/AuNP composite was amorphous. The ZnOH/GO/AuNPs composite exhibited the greatest H2S adsorption capacity due to the increased number of OH terminal groups and the conductive properties of GO that facilitated the electron transfer and consequently the formation of superoxide ions promoting oxidation of hydrogen sulfide. AuNPs present in the composite increased the conductivity, helped with electron transfer to oxygen, and prevented the fast recombination of the electrons and holes.

  16. Effect of pyrolysis temperature on characteristics and aromatic contaminants adsorption behavior of magnetic biochar derived from pyrolysis oil distillation residue.

    PubMed

    Li, Hao; Mahyoub, Samah Awadh Ali; Liao, Wenjie; Xia, Shuqian; Zhao, Hechuan; Guo, Mengya; Ma, Peisheng

    2017-01-01

    The magnetic biochars were easily fabricated by thermal pyrolysis of Fe(NO3)3 and distillation residue derived from rice straw pyrolysis oil at 400, 600 and 800°C. The effects of pyrolysis temperature on characteristics of magnetic biochars as well as adsorption capacity for aromatic contaminants (i.e., anisole, phenol and guaiacol) were investigated carefully. The degree of carbonization of magnetic biochars become higher as pyrolysis temperature increasing. The magnetic biochar reached the largest surface area and pore volume at the pyrolysis temperature of 600°C due to pores blocking in biochar during pyrolysis at 800°C. Based on batch adsorption experiments, the used adsorbent could be magnetically separated and the adsorption capacity of anisole on magnetic biochars was stronger than that of phenol and guaiacol. The properties of magnetic biochar, including surface area, pore volume, aromaticity, grapheme-like-structure and iron oxide (γ-Fe2O3) particles, showed pronounced effects on the adsorption performance of aromatic contaminants.

  17. Direct coupling between stress, strain and adsorption reactions - A study on coal-CO2 systems

    NASA Astrophysics Data System (ADS)

    Hol, S.; Peach, C. J.; Spiers, C. J.

    2012-12-01

    Though it is well-known that adsorption reactions frequently assist deformation of porous rocks, very little understanding exists on the direct coupling with stress state and strain. One of the materials in which adsorption plays a large role is coal, as is observed in the particular case of Enhanced Coalbed Methane Production (ECBM), which involves the geological storage of CO2 and the recovery of CH4. In this case, adsorption and the associated swelling cause significant injectivity problems, which is experienced in almost all pilot field projects to date. This suggests that indeed a strong fundamental coupling exists between CO2 sorption, changes in the mechanical state of the coal matrix and changes in the transport properties of the system, and illustrates the need to understand coupled stress-strain-sorption behaviour. In this contribution, we describe several important observations made on coal-CO2 systems that can learn us about many other natural, stressed adsorbate-adsorbent systems. In our experiments, first of all, the adsorption of CO2 in the coal matrix gave rise to swelling. Although this is well-known, we found that the total volumetric strain occurring under unconfined conditions can be realistically modelled (up to at least 100 MPa) as the sum of an adsorption-related expansion term and an elastic compression term. Second, effective in situ stresses will directly reduce the sorption capacity, and associated swelling of the coal matrix significantly. Our general thermodynamic model for the effect of a 3D stress state on adsorbed CO2 concentration supports this observation, and also shows that "self-stressing", as a result of CO2 adsorption occurring under conditions of restricted or zero strain (i.e. fully constrained conditions), will more than double the expected in situ stresses. A constitutive equation was developed to describe the full coupling between stress state, total strain (i.e. combined strain of adsorption processes and poroelasticity

  18. Adsorption Refrigeration System

    SciTech Connect

    Wang, Kai; Vineyard, Edward Allan

    2011-01-01

    Adsorption refrigeration is an environmentally friendly cooling technology which could be driven by recovered waste heat or low-grade heat such as solar energy. In comparison with absorption system, an adsorption system has no problems such as corrosion at high temperature and salt crystallization. In comparison with vapor compression refrigeration system, it has the advantages of simple control, no moving parts and less noise. This paper introduces the basic theory of adsorption cycle as well as the advanced adsorption cycles such as heat and mass recovery cycle, thermal wave cycle and convection thermal wave cycle. The types, characteristics, advantages and drawbacks of different adsorbents used in adsorption refrigeration systems are also summarized. This article will increase the awareness of this emerging cooling technology among the HVAC engineers and help them select appropriate adsorption systems in energy-efficient building design.

  19. Adsorption of the organic fraction of a tannery sludge by means of organophilic bentonite.

    PubMed

    Cioffi, R; Costanzo, S; Maffucci, L; Santoro, L

    2001-01-01

    Two different organophilic bentonites obtained by cationic exchange with benzyldimethyloctadecylammonium chloride and trimethyloctadecylammonium chloride have been used to adsorb the organic fraction of a tannery sludge. The exchange process was carried out to different extents to obtain bentonite samples with different organophilicities and different interlayer spacings. Before adsorption, the organic matter was extracted by contacting the sludge with a Ca(OH)2 saturated solution. The adsorption capacity was found to increase with the amount of ammonium salt exchanged for both bentonites, but the one exchanged with benzyldimethyloctadecylammonium chloride proved to be more active: up to about 80% TOC could be removed from the contacting solution. The adsorption of the organic matter caused a further increase of the bentonite interlayer spacing. In both cases, the adsorption isotherms were found to be of cooperative type, due to weak adsorbent-adsorbate interactions at low loading followed by increasing adsorbate-adsorbate interactions at increasing loading. The results may be applied to tannery sludge stabilization by cementitious systems.

  20. The characterization of the adsorption of cadmium from aqueous solution using natural fibers treated with nanoparticles

    NASA Astrophysics Data System (ADS)

    Rediske, Nicole M.

    The objective of this research was to characterize natural carbon fibers from coconut husks, both bare and impregnated with metallic nanoparticles, in removing cadmium from aqueous media. The adsorbent load, kinetics, isotherm parameters, removal efficiencies, desorption capacity and possible contaminant removal mechanisms were evaluated. It was found that the fibers treated with metallic nanoparticles performed better than the bare fibers in removing cadmium from water. The ideal conditions were found to be neutral pH with low initial cadmium concentrations. Through the kinetic analyses, the adsorption process was first thought to be pseudo first order with two separate adsorption mechanisms apparent. Upon further analysis, it was seen that the first mechanism does not follow the pseudo first order kinetics model. An increase in calcium and magnesium concentrations was observed as the cadmium concentrations decreases. This increase corresponds with first mechanism. This suggests the cadmium removal in the first mechanism is due to ion exchange. The second mechanism's rate constant was consistently lower than the first mechanisms rate constant by an order of magnitude. This led to the hypothesis that the second mechanism is controlled by van de Waals forces, specifically ion-induced dipole interactions, and physical adsorption. It was also found that the cadmium does not effectively desorb from the wasted fibers in DI water. Keywords: Adsorption; kinetics; pseudo first order; cadmium; metallic nanoparticles; natural fibers; removal efficiencies; ion exchange.

  1. Adsorption of Pb(II) from aqueous solution by Azadirachta indica (Neem) leaf powder.

    PubMed

    Bhattacharyya, Krishna G; Sharma, Arunima

    2004-09-10

    An adsorbent was developed from the mature leaves of the Neem (Azadirachta indica) tree for removing Pb(II) from water. Adsorption was carried out in a batch process with several different concentrations of Pb(II) by varying amount of adsorbent, pH, agitation time and temperature. The uptake of the metal was very fast initially, but gradually slowed down indicating penetration into the interior of the adsorbent particles. Both first-order and second-order kinetics were tested and it was found that the latter gave a better explanation. The experimental data closely followed both Langmuir and Freundlich isotherms. The adsorbent had a considerably high Langmuir monolayer capacity of 300 mg/g. A small amount of the adsorbent (1.2 g/L) could remove as much as 93% of Pb(II) in 300 min from a solution of concentration 100mg/L at 300 K. The adsorption continuously increased in the pH range of 2.0-7.0, beyond which the adsorption could not be carried out due to the precipitation of the metal. The adsorption was exothermic at ambient temperature and the computation of the parameters, DeltaH, DeltaS and DeltaG, indicated the interactions to be thermodynamically favourable.

  2. Recommended volumetric capacity definitions and protocols for accurate, standardized and unambiguous metrics for hydrogen storage materials

    NASA Astrophysics Data System (ADS)

    Parilla, Philip A.; Gross, Karl; Hurst, Katherine; Gennett, Thomas

    2016-03-01

    The ultimate goal of the hydrogen economy is the development of hydrogen storage systems that meet or exceed the US DOE's goals for onboard storage in hydrogen-powered vehicles. In order to develop new materials to meet these goals, it is extremely critical to accurately, uniformly and precisely measure materials' properties relevant to the specific goals. Without this assurance, such measurements are not reliable and, therefore, do not provide a benefit toward the work at hand. In particular, capacity measurements for hydrogen storage materials must be based on valid and accurate results to ensure proper identification of promising materials for further development. Volumetric capacity determinations are becoming increasingly important for identifying promising materials, yet there exists controversy on how such determinations are made and whether such determinations are valid due to differing methodologies to count the hydrogen content. These issues are discussed herein, and we show mathematically that capacity determinations can be made rigorously and unambiguously if the constituent volumes are well defined and measurable in practice. It is widely accepted that this occurs for excess capacity determinations and we show here that this can happen for the total capacity determination. Because the adsorption volume is undefined, the absolute capacity determination remains imprecise. Furthermore, we show that there is a direct relationship between determining the respective capacities and the calibration constants used for the manometric and gravimetric techniques. Several suggested volumetric capacity figure-of-merits are defined, discussed and reporting requirements recommended. Finally, an example is provided to illustrate these protocols and concepts.

  3. Adsorption of Compounds that Mimic Urban Stormwater Dissolved Organic Nitrogen.

    PubMed

    Mohtadi, Mehrdad; James, Bruce R; Davis, Allen P

    2017-02-01

      Stormwater runoff carrying nitrogen can accelerate eutrophication. Bioretention facilities are among low impact development systems which are commonly used to manage urban stormwater quality and quantity. They are, however, not designed to remove dissolved organic nitrogen (DON) and may become a net DON exporter. Adsorption of seven organic nitrogenous compounds onto several adsorbents was examined. Batch adsorption study revealed that coal activated carbon (AC) exhibited the best performance in adsorption of the selected organic nitrogenous compounds. The highest adsorption capacity of coal AC was 0.4 mg N/g for pyrrole at an equilibrium concentration of 0.02 mg N/L, while adsorption was not detectable for urea at the same equilibrium concentration. The fastest compound to reach equilibrium adsorption capacity onto the coal AC was pyrrole (1 hour). The adsorption capacity of the coal AC for pyrrole and N-acetyl-d-glucosamine and 1-hour contact time is recommended for designing bioretention systems targeting organic nitrogenous compounds.

  4. Removal of caffeine from pharmaceutical wastewater by adsorption: influence of NOM, textural and chemical properties of the adsorbent.

    PubMed

    Álvarez-Torrellas, Silvia; Rodríguez, Araceli; Ovejero, Gabriel; Gómez, José María; García, Juan

    2016-01-01

    This work involves the study of the influence of textural and chemical adsorbent properties on natural organic matter (NOM) removal and the simultaneous adsorption of caffeine and NOM in pharmaceutical wastewater. The performance of a microporous activated carbon, Calgon F400, a synthesized mesoporous carbon from peach stones and a commercial sepiolite in the removal of NOM of a WWTP effluent, and the competitive adsorption of caffeine/NOM were evaluated. It was evidenced that the microporous structure of the adsorbents significantly conditioned the removal of NOM, finding that F400 activated carbon (microporous volume of 0.46 cm(3) g(-1)) led to a NOM removal of 45%. The presence of NOM in the aqueous medium led to worse adsorption parameters, including adsorption capacity at breakthrough time, mass transfer zone length and fractional bed utilization. Additionally, an overshooting in the Total Organic Carbon concentration (TOC/TOC0 = 1.05) was observed in the sepiolite adsorption fixed-bed experiment, due to the displacement of the background NOM. The tested adsorbents were efficient in the removal of caffeine from a pharmaceutical wastewater, finding a competitive effect between the target compound and the background NOM for the active sites.

  5. Optimizing the physical-chemical properties of carbon nanotubes (CNT) and graphene nanoplatelets (GNP) on Cu(II) adsorption.

    PubMed

    Rosenzweig, Shirley; Sorial, George A; Sahle-Demessie, Endalkachew; McAvoy, Drew C

    2014-08-30

    Systematic experiments of copper adsorption on 10 different commercially available nanomaterials were studied for the influence of physical-chemical properties and their interactions. Design of experiment and response surface methodology was used to develop a polynomial model to predict maximum copper adsorption (initial concentration, Co=10mg/L) per mass of nanomaterial, qe, using multivariable regression and maximum R-square criterion. The best subsets of properties to predict qe in order of significant contribution to the model were: bulk density, ID, mesopore volume, tube length, pore size, zeta-charge, specific surface area and OD. The highest experimental qe observed was for an alcohol-functionalized MWCNT (16.7mg/g) with relative high bulk density (0.48g/cm(3)), ID (2-5nm), 10-30μm long and OD<8nm. Graphene nanoplatelets (GNP) showed poor adsorptive capacity associated to stacked-nanoplatelets, but good colloidal stability due to high functionalized surface. Good adsorption results for pristine SWCNT indicated that tubes with small diameter were more associated with good adsorption than functionalized surface. XPS and ICP analysis explored surface chemistry and purity, but pHpzc and zeta-charge were ultimately applied to indicate the degree of functionalization. Optimum CNT were identified in the scatter plot, but actual manufacturing processes introduced size and shape variations which interfered with final property results.

  6. Adsorption of mercury on laterite from Guizhou Province, China.

    PubMed

    Yu, Xiaohong; Zhu, Lijun; Guo, Baiwei; He, Shouyang

    2008-01-01

    The adsorption behaviors of Hg(II) on laterite from Guizhou Province, China, were studied and the adsorption mechanism was discussed. The results showed that different mineral compositons in the laterite will cause differences in the adsorption capacity of laterite to Hg(II). Illite and non-crystalloids are the main contributors to enhancing the adsorption capacity of laterite to Hg(II). The pH of the solution is an important factor affecting the adsorption of Hg(II) on laterite. The alkalescent environment (pH 7-9) is favorable to the adsorption of Hg(II). The amount of adsorbed Hg(II) increases with increasing pH. When the pH reaches a certain value, the amount of the adsorbed Hg(II) will reach the maximum level. The amount of adsorbed Hg(II) decreases with increasing pH. The optimal pHs of laterite and kaolinite are 9 and 8, respectively. The optimal initial concentrations of Hg(II) on laterite and kaolinite are 250 and 200 microg/ml, respectively. The adsorption isotherms were described by the Langmuir model. The adsorption of Hg(II) on laterite is a quick process while that of Hg(II) on kaolinite is a slow reaction. Laterite from Guizhou Province is a promising environmental material which can be used in the removal of Hg(II) from wastewater.

  7. Mechanism of amitriptyline adsorption on Ca-montmorillonite (SAz-2).

    PubMed

    Chang, Po-Hsiang; Jiang, Wei-Teh; Li, Zhaohui; Kuo, Chung-Yih; Jean, Jiin-Shuh; Chen, Wan-Ru; Lv, Guocheng

    2014-07-30

    The uptake of amitriptyline (AMI) from aqueous environment by Ca-montmorillonite (SAz-2) was studied in a batch system under different physicochemical conditions. The adsorbent was characterized by X-ray diffraction and Fourier transform infrared (FTIR) analyses. The AMI adsorption on SAz-2 obeyed the Langmuir isotherm with a capacity of 330mg/g (1.05mmol/g) at pH 6-7. The adsorption kinetics was fast, almost reaching equilibrium in 2h, and followed a pseudo-second-order kinetic model. Desorption of exchangeable cations correlated with the AMI adsorption well, indicating that cation exchange was the major mechanism. X-ray diffraction patterns showing significant expansions of the d001 spacing and characteristic FTIR band shifts toward higher frequencies after AMI adsorption onto SAz-2 indicated that the adsorbed AMI molecules were intercalated into the interlayers of the mineral. Thermodynamic parameters based on partitioning coefficients suggested that the AMI adsorption was an endothermic physisorption at high adsorption levels. At low and higher AMI adsorption levels, the intercalated AMI molecules take a horizontal monolayer and bilayer conformation, respectively. The higher adsorption capacity suggested that SAz-2 could be a good candidate to remove AMI from wastewater and would be an important environmental sink for the fate and transport of AMI in soils and groundwater.

  8. Adsorption of soluble oil from water to graphene.

    PubMed

    Wang, Na; Zhang, Yuchang; Zhu, Fuzhen; Li, Jingyi; Liu, Shuaishuai; Na, Ping

    2014-05-01

    The toxicity of soluble oil to the aquatic environment has started to attract wide attention in recent years. In the present work, we prepare graphene according to oxidation and thermal reduction methods for the removal of soluble oil from the solution. Characterization of the as-prepared graphene are performed by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectra, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy, and contact angle analysis. The adsorption behavior of soluble oil on graphene is examined, and the obtained adsorption data are modeled using conventional theoretical models. Adsorption experiments reveal that the adsorption rate of soluble oil on graphene is notably fast, especially for the soluble diesel oil, which could reach equilibrium within 30 min, and the kinetics of adsorption is perfectly consistent with a pseudo-second-order model. Furthermore, it is determined that the adsorption isotherm of soluble diesel oil with graphene fit the Freundlich model best, and graphene has a very strong adsorption capacity for soluble diesel oil in the solution. These results demonstrate that graphene is the material that provided both good adsorptive capacity and good kinetics, implying that it could be used as a promising sorbent for soluble oil removal from wastewater.

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  10. Postsynthetic Functionalization of Mg-MOF-74 with Tetraethylenepentamine: Structural Characterization and Enhanced CO2 Adsorption.

    PubMed

    Su, Xiao; Bromberg, Lev; Martis, Vladimir; Simeon, Fritz; Huq, Ashfia; Hatton, T Alan

    2017-03-15

    Postsynthetic functionalization of magnesium 2,5-dihydroxyterephthalate (Mg-MOF-74) with tetraethylenepentamine (TEPA) resulted in improved CO2 adsorption performance under dry and humid conditions. XPS, elemental analysis, and neutron powder diffraction studies indicated that TEPA was incorporated throughout the MOF particle, although it coordinated preferentially with the unsaturated metal sites located in the immediate proximity to the surface. Neutron and X-ray powder diffraction analyses showed that the MOF structure was preserved after amine incorporation, with slight changes in the lattice parameters. The adsorption capacity of the functionalized amino-Mg-MOF-74 (TEPA-MOF) for CO2 was as high as 26.9 wt % versus 23.4 wt % for the original MOF due to the extra binding sites provided by the multiunit amines. The degree of functionalization with the amines was found to be important in enhancing CO2 adsorption, as the optimal surface coverage improved performance and stability under both pure CO2 and CO2/H2O coadsorption, and with partially saturated surface coverage, optimal CO2 capacity could be achieved under both wet and dry conditions by a synergistic binding of CO2 to the amines as well as metal centers.

  11. The effect of zeolite treatment by acids on sodium adsorption ratio of coal seam gas water.

    PubMed

    Wang, Xiaoyu; Ozdemir, Orhan; Hampton, Marc A; Nguyen, Anh V; Do, Duong D

    2012-10-15

    Many coal seam gas (CSG) waters contain a sodium ion concentration which is too high relative to calcium and magnesium ions for environment acceptance. Natural zeolites can be used as a cheap and effective method to control sodium adsorption ratio (SAR, which is a measure of the relative preponderance of sodium to calcium and magnesium) due to its high cation exchange capacity. In this study, a natural zeolite from Queensland was examined for its potential to treat CSG water to remove sodium ions to lower SAR and reduce the pH value. The results demonstrate that acid activated zeolite at 30%wt solid ratio can reduce the sodium content from 563.0 to 182.7 ppm; the pH from 8.74 to 6.95; and SAR from 70.3 to 18.5. Based on the results of the batch experiments, the sodium adsorption capacity of the acid-treated zeolite is three times greater than that of the untreated zeolite. Both the untreated and acid-treated zeolite samples were characterized using zeta potential, surface characterization, DTA/TG and particle size distribution in order to explain their adsorption behaviours.

  12. A computational study of carbon dioxide adsorption on solid boron.

    PubMed

    Sun, Qiao; Wang, Meng; Li, Zhen; Du, Aijun; Searles, Debra J

    2014-07-07

    Capturing and sequestering carbon dioxide (CO2) can provide a route to partial mitigation of climate change associated with anthropogenic CO2 emissions. Here we report a comprehensive theoretical study of CO2 adsorption on two phases of boron, α-B12 and γ-B28. The theoretical results demonstrate that the electron deficient boron materials, such as α-B12 and γ-B28, can bond strongly with CO2 due to Lewis acid-base interactions because the electron density is higher on their surfaces. In order to evaluate the capacity of these boron materials for CO2 capture, we also performed calculations with various degrees of CO2 coverage. The computational results indicate CO2 capture on the boron phases is a kinetically and thermodynamically feasible process, and therefore from this perspective these boron materials are predicted to be good candidates for CO2 capture.

  13. Delamination behavior of silicate layers by adsorption of cationic surfactants.

    PubMed

    Lee, Seung Yeop; Kim, Soo Jin

    2002-04-15

    Smectite that has reacted for 48 h with hexadecyltrimethylammonium (HDTMA) cations equivalent to 0.01-3.0 times the cation exchange capacity (CEC) converts to HDTMA-smectite. The microstructure of this organoclay is observed using X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). When Na cations in the interlayer of clay are exchanged with HDTMA ions, the changes in internal and external surface configuration are augmented by the intercalation of organic surfactants, showing a heterogeneous increase of interlayer spacings. As HDTMA loading increases, the chance of delaminated layers being developed increases locally in the low-charge interlayer regions by the sufficient adsorption of organic surfactants beyond the CEC due to the tendency of alkyl chain interaction.

  14. Mercury adsorption properties of sulfur-impregnated adsorbents

    USGS Publications Warehouse

    Hsi, N.-C.; Rood, M.J.; Rostam-Abadi, M.; Chen, S.; Chang, R.

    2002-01-01

    Carbonaceous and noncarbonaceous adsorbents were impregnated with elemental sulfur to evaluate the chemical and physical properties of the adsorbents and their equilibrium mercury adsorption capacities. Simulated coal combustion flue gas conditions were used to determine the equilibrium adsorption capacities for Hg0 and HgCl2 gases to better understand how to remove mercury from gas streams generated by coal-fired utility power plants. Sulfur was deposited onto the adsorbents by monolayer surface deposition or volume pore filling. Sulfur impregnation increased the total sulfur content and decreased the total and micropore surface areas and pore volumes for all of the adsorbents tested. Adsorbents with sufficient amounts of active adsorption sites and sufficient microporous structure had mercury adsorption capacities up to 4,509 ??g Hg/g adsorbent. Elemental sulfur, organic sulfur, and sulfate were formed on the adsorbents during sulfur impregnation. Correlations were established with R2>0.92 between the equilibrium Hg0/HgCl2 adsorption capacities and the mass concentrations of elemental and organic sulfur. This result indicates that elemental and organic sulfur are important active adsorption sites for Hg0 and HgCl2.

  15. Single and multi-component adsorption of salicylic acid, clofibric acid, carbamazepine and caffeine from water onto transition metal modified and partially calcined inorganic-organic pillared clay fixed beds.

    PubMed

    Cabrera-Lafaurie, Wilman A; Román, Félix R; Hernández-Maldonado, Arturo J

    2015-01-23

    Fixed-beds of transition metal (Co(2+), Ni(2+) or Cu(2+)) inorganic-organic pillared clays (IOCs) were prepared to study single- and multi-component non-equilibrium adsorption of a set of pharmaceutical and personal care products (PPCPs: salicylic acid, clofibric acid, carbamazepine and caffeine) from water. Adsorption capacities for single components revealed that the copper(II) IOCs have better affinity toward salicylic and clofibric acid. However, multi-component adsorption tests showed a considerable decrease in adsorption capacity for the acids and an unusual selectivity toward carbamazepine depending on the transition metal. This was attributed to a combination of competition between PPCPs for adsorption sites, adsorbate-adsorbate interactions, and plausible pore blocking caused by carbamazepine. The cobalt(II) IOC bed that was partially calcined to fractionate the surfactant moiety showcased the best selectivity toward caffeine, even during multi-component adsorption. This was due to a combination of a mildly hydrophobic surface and interaction between the PPCP and cobalt(II). In general, the tests suggest that these IOCs may be a potential solution for the removal of PPCPs if employed in a layered-bed configuration, to take care of families of adsorbates in a sequence that would produce sharpened concentration wavefronts.

  16. Novel nano bearings constructed by physical adsorption

    NASA Astrophysics Data System (ADS)

    Zhang, Yongbin

    2015-09-01

    The paper proposes a novel nano bearing formed by the physical adsorption of the confined fluid to the solid wall. The bearing is formed between two parallel smooth solid plane walls sliding against one another, where conventional hydrodynamic lubrication theory predicted no lubricating effect. In this bearing, the stationary solid wall is divided into two subzones which respectively have different interaction strengths with the lubricating fluid. It leads to different physical adsorption and slip properties of the lubricating fluid at the stationary solid wall respectively in these two subzones. It was found that a significant load-carrying capacity of the bearing can be generated for low lubricating film thicknesses, because of the strong physical adsorption and non-continuum effects of the lubricating film.

  17. Novel nano bearings constructed by physical adsorption

    PubMed Central

    Zhang, Yongbin

    2015-01-01

    The paper proposes a novel nano bearing formed by the physical adsorption of the confined fluid to the solid wall. The bearing is formed between two parallel smooth solid plane walls sliding against one another, where conventional hydrodynamic lubrication theory predicted no lubricating effect. In this bearing, the stationary solid wall is divided into two subzones which respectively have different interaction strengths with the lubricating fluid. It leads to different physical adsorption and slip properties of the lubricating fluid at the stationary solid wall respectively in these two subzones. It was found that a significant load-carrying capacity of the bearing can be generated for low lubricating film thicknesses, because of the strong physical adsorption and non-continuum effects of the lubricating film. PMID:26412488

  18. Adsorption behavior of EDTA-graphene oxide for Pb (II) removal.

    PubMed

    Madadrang, Clemonne J; Kim, Hyun Yun; Gao, Guihua; Wang, Ning; Zhu, Jun; Feng, Huan; Gorring, Matthew; Kasner, Marc L; Hou, Shifeng

    2012-03-01

    Chelating groups are successfully linked to graphene oxide (GO) surfaces through a silanization reaction between N-(trimethoxysilylpropyl) ethylenediamine triacetic acid (EDTA-silane) and hydroxyl groups on GO surface. EDTA-GO was found to be an ideal adsorbent for Pb(II) removal with a higher adsorption capacity. EDTA-modification enhances the adsorption capacity of GO because of the chelating ability of ethylene diamine triacetic acid. This study investigates the adsorption and desorption behaviors of heavy metal cations and the effects of solution conditions such as pH on Pb(II) removal. The adsorption capacity for Pb(II) removal was found to be 479 ± 46) mg/g at pH 6.8, and the adsorption process was completed within 20 min. The Langmuir adsorption model agrees well with the experimental data. The experimental results suggest that EDTA-GO can be reused after washed with HCl, suggesting potential applications in the environmental cleanup.

  19. Adsorption of congo red by chitosan hydrogel beads impregnated with carbon nanotubes.

    PubMed

    Chatterjee, Sudipta; Lee, Min W; Woo, Seung H

    2010-03-01

    The adsorption performance of chitosan (CS) hydrogel beads was investigated after multiwalled carbon nanotubes (MWCNTs) impregnation for the removal of congo red (CR) as an anionic dye. The study of the adsorption capacity of CS/CNT beads as a function of the CNT concentration indicated that 0.01% CNT impregnation was the most useful for enhancing the adsorption capacity. The sulfur (%) in the CS/CNT beads measured by energy dispersive X-ray (EDX) was 2.5 times higher than that of normal CS beads after CR adsorption. Equilibrium adsorption isotherm data of the CS/CNT beads exhibited better fit to the Langmuir isotherm model than to the Freundlich isotherm model, and the heterogeneity factor (n) value of the CS/CNT beads calculated from the Sips isotherm model was close to unity (0.98). The maximum adsorption capacity of CS/CNT beads obtained from the Langmuir model was 450.4 mg g(-1).

  20. [Adsorption of perchlorate by calcined Mg/Zn/Al layered double hydroxides].

    PubMed

    Wang, Hong-Yu; Liu, Yan

    2014-07-01

    The adsorption capacity of perchlorate by Mg/Zn/Al layered double hydroxides was investigated. The samples were characterized by X-ray diffraction (XRD) and the adsorption isothermal model and dynamic model were discussed. The effect of calcination temperature, Mg/Zn/Al molar ratio, pH value of solution, adsorption time and dosage on the adsorption capacity of samples were studied. The experiment results showed that the removal ratio and adsorption capacity reached the highest and the pH value had good applicability when the molar ratio was Mg/Zn/Al = 2: 1 : 1. The adsorption of perchlorate basically conformed to the pseudo-second kinetics and Langmuir, Freundlich isotherm model.

  1. Adsorption of phenanthrene by quaternary ammonium surfactant modified peat and the mechanism involved.

    PubMed

    Zhou, Y B; Chen, L; Wang, X Q; Xu, Y X; Lu, J

    2012-01-01

    Removal of phenanthrene (PHE) from aqueous solution by adsorption onto quaternary ammonium surfactant modified peat was studied. The results show that surfactant modification enhanced the PHE adsorption capacity of peat. Low temperature and neutral pH favored PHE adsorption. Peat modified with long carbon chain surfactant performed better than peat modified with short carbon chain surfactant. The magnitude of PHE adsorption capacity followed the order of MP-HPB>MP-HTAB>MP-TBAB>RP, ranged from 924 to 1,228 μg g(-1). A negative trend between adsorption capacity (y) and (O+N)/C ratio of biosorbent (x) was observed (y = -1,369.6x + 2,176), which confirmed the negative effect of polarity on polycyclic aromatic hydrocarbon (PAH) removal. The study provides a guide to modify raw materials to enhance adsorption of hydrophobic organics.

  2. C2H2 adsorption in three isostructural metal-organic frameworks: boosting C2H2 uptake by rational arrangement of nitrogen sites.

    PubMed

    Song, Chengling; Jiao, Jingjing; Lin, Qiyi; Liu, Huimin; He, Yabing

    2016-03-21

    Replacing the benzene spacer in the organic linker 5,5'-(benzene-1,4-diyl)diisophthalate with the nitrogen containing heterocyclic rings, namely, pyrazine, pyridazine, and pyrimidine results in three organic linkers, which were reacted with copper ions under solvothermal conditions to form three isostructural metal-organic frameworks (ZJNU-46, ZJNU-47 and ZJNU-48) exhibiting exceptionally high sorption capacities with regard to acetylene due to the simultaneous immobilization of open metal sites and Lewis basic nitrogen sites in the frameworks. At 1 atm and 295 K, the gravimetric C2H2 adsorption uptakes reach 187, 213 and 193 cm(3) (STP) g(-1) for these three compounds. The gravimetric C2H2 adsorption amount of ZJNU-47a is the second highest reported for MOF materials. Notably, despite their same porosities, and densities of open metal sites and uncoordinated nitrogen sites, distinctly different C2H2 adsorption capacities were observed for these three compounds, which we think are mainly associated with the difference in the relative position of nitrogen atoms leading to different binding affinities of the frameworks towards C2H2 guest molecules, and thus different C2H2 adsorptions. This work demonstrates that the rational arrangement of open nitrogen sites will favorably improve the C2H2 uptake and thus provides useful information for future design of porous MOFs with high acetylene storage capacities.

  3. Adsorption of 2,4-dichlorophenoxyacetic acid by mesoporous activated carbon prepared from H3PO4-activated langsat empty fruit bunch.

    PubMed

    Njoku, V O; Islam, Md Azharul; Asif, M; Hameed, B H

    2015-05-01

    The removal of toxic herbicide from wastewater is challenging due to the availability of suitable adsorbents. The Langsat empty fruit bunch is an agricultural waste and was used in this study as a cheap precursor to produce activated carbon for the adsorption of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) at different initial concentrations ranging from 50 to 400 mg/L. The produced Langsat empty fruit bunch activated carbon (LEFBAC) was mesoporous and had high surface area of 1065.65 m(2)/g with different active functional groups. The effect of shaking time, temperature and pH on 2,4-D removal were investigated using the batch technique. The adsorption capacity of 2,4-D by LEFBAC was decreased with increase in pH of solution whereas adsorption capacity increased with temperature. The adsorption data was well described by Langmuir isotherm followed by removal capacity of 261.2 mg/g at 30 °C. The results from this work showed that LEFBAC can be used as outstanding material for anionic herbicide uptake from wastewater.

  4. Functionalized mesoporous silica materials for molsidomine adsorption: Thermodynamic study

    SciTech Connect

    Alyoshina, Nonna A.; Parfenyuk, Elena V.

    2013-09-15

    A series of unmodified and organically modified mesoporous silica materials was prepared. The unmodified mesoporous silica was synthesized via sol–gel synthesis in the presence of D-glucose as pore-forming agent. The functionalized by phenyl, aminopropyl and mercaptopropyl groups silica materials were prepared via grafting. The fabricated adsorbent materials were characterized by Fourier transform infrared spectroscopy (FTIR) analysis, N{sub 2} adsorption/desorption and elemental analysis methods. Then their adsorption properties for mesoionic dug molsidomine were investigated at 290–313 K and physiological pH value. Thermodynamic parameters of molsidomine adsorption on the synthesized materials have been calculated. The obtained results showed that the adsorption process of molsidomine on the phenyl modified silica is the most quantitatively and energetically favorable. The unmodified and mercaptopropyl modified silica materials exhibit significantly higher adsorption capacities and energies for molsidomine than the aminopropyl modified sample. The effects are discussed from the viewpoint of nature of specific interactions responsible for the adsorption. - Graphical abstract: Comparative analysis of the thermodynamic characteristics of molsidomine adsorption showed that the adsorption process on mesoporous silica materials is controlled by chemical nature of surface functional groups. Molsidomine adsorption on the phenyl modified silica is the most quantitatively and energetically favorable. Taking into account ambiguous nature of mesoionic compounds, it was found that molsidomine is rather aromatic than dipolar. Display Omitted - Highlights: • Unmodified and organically modified mesoporous silica materials were prepared. • Molsidomine adsorption on the silica materials was studied. • Phenyl modified silica shows the highest adsorption capacity and favorable energy. • Molsidomine exhibits the lowest affinity to aminopropyl modified silica.

  5. Expanded bed adsorption of human serum albumin from very dense Saccharomyces cerevesiae suspensions on fluoride-modified zirconia.

    PubMed

    Mullick, A; Flickinger, M C

    1999-11-05

    The adsorption of proteins from high cell density yeast suspensions on mixed-mode fluoride-modified zirconia (FmZr) particles (38 to 75 microm, surface area of 29 m(2)/g and density of 2.8 g/cm(3)) was investigated using human serum albumin (HSA) added to Saccharomyces cerevesiae as the model expression host. Because of the high density of the porous zirconia particles, HSA (4 mg/mL) can be adsorbed from a 100 g dry cell weight (DCW)/L yeast suspension in a threefold-expanded bed of FmZr. The expanded bed adsorption of any protein from a suspension containing >50 g DCW/L cells has not been previously reported. The FmZr bed expansion characteristics were well represented by the Richardson-Zaki correlation with a particle terminal velocity of 3.1 mm/s and a bed expansion index of 5.4. Expanded bed hydrodynamics were investigated as a function of bed expansion using residence time distribution studies with sodium nitrite as the tracer. The adsorption of HSA on FmZr exhibited features of multicomponent adsorption due to the presence of dimers. The protein binding capacity at 5% breakthrough decreased from 22 mg HSA/mL settled bed void volume for 20 g DCW/L yeast to 15 mg HSA/mL settled bed void volume for 40 g DCW/L yeast and remained unchanged for the higher yeast concentrations (60 to 100 g DCW/L). However, the batch (or equilibrium) binding capacity decreased monotonically as a function of yeast concentration (20 to 100 g DCW/L) and the binding capacity at 100 g DCW/L yeast was fivefold lower compared with that at 20 g DCW/L yeast. The lower batch binding capacity at high cell concentrations resulted from the adsorption of cells at the surface of the particles restricting access of HSA to the intraparticle surface area. Batch (or equilibrium) and column HSA adsorption results indicated that the adsorption of HSA on FmZr occurred at a time scale that may be much faster than that of yeast cells. The zirconia particles were cleaned of adsorbed HSA and yeast with a

  6. Phenolic resin-based porous carbons for adsorption and energy storage applications

    NASA Astrophysics Data System (ADS)

    Wickramaratne, Nilantha P.

    high Cu2+ ion adsorption capacities. Next, Chapter 5 is devoted to carbon materials for supercapacitors. There are mainly two types of electrochemical capacitors namely EDLC and pseudocapacitors. In EDLC, the energy is stored due to electrochemical attraction between electrode and electrolyte interface. To store more ionic charges on to the carbon electrode, it is essential to have high surface area carbon materials. In the case of pseudocapacitors, the energy is stored due to the redox reaction taking place at the electrode and electrolyte interface. Moreover, conductivity of the electrode is also important for the construction of superior electrode materials. To address these vital issues, the electrode materials has been prepared with special emphasis on the enhancement of their surface area to attract more charges at the electrode-electrolyte interface, introducing graphitic moieties to the carbon matrix to improve the conductivity and doping carbons with metal/heteroatoms to improve both capacitance through pseudocapacitive and conductivity.

  7. Batch studies of adsorption of copper and lead on activated carbon from Eucalyptus camaldulensis dehn. bark.

    PubMed

    Patnukao, Phussadee; Kongsuwan, Apipreeya; Pavasant, Prasert

    2008-01-01

    Powdered activated carbon (PAC) prepared from Eucalyptus camaldulensis Dehn. bark was tested for its adsorption capacity for Cu(II) and Pb(II). The experiment was conducted to investigate the effects of pH, contact time, initial metal concentration, and temperature. The best adsorption of both Cu(II) and Pb(II) occurred at pH 5, where the adsorption reached equilibrium within 45 min for the whole range of initial heavy metal concentrations (0.1-10 mmol/L). The adsorption kinetics was found to follow the pseudo-second order model where equilibrium adsorption capacities and adsorption rate constants increased with initial heavy metal concentrations. The adsorption isotherm followed Langmuir better than Freundlich models within the temperature range (25-60 degrees C). The maximum adsorption capacities (qm) occurred at 60 degrees C, where qm for Cu(II) and Pb(II) were 0.85 and 0.89 mmol/g, respectively. The enthalpies of Cu(II) and Pb(II) adsorption were 43.26 and 58.77 kJ/mol, respectively. The positive enthalpy of adsorption indicated an endothermic nature of the adsorption.

  8. Comparison of monometal and multimetal adsorption in Mississippi River alluvial wetland sediment: batch and column experiments.

    PubMed

    Seo, Dong Cheol; Yu, Kewei; DeLaune, Ronald D

    2008-12-01

    Monometal and multimetal adsorption of selected heavy metals in a sediment from a coastal Louisiana forested swamp used for wastewater treatment was studied. Results from the batch experiments show that the maximum adsorption capacities of the metals by the sediment were in the order of Pb>Hg>Cr>CdCuZn>As based on monometal adsorption isotherm, and Hg>Cr>CuCd approximately Pb>As approximately Zn based on multimetal adsorption isotherm, respectively. Batch experimental data best fit the Langmuir model rather than the Freundlich isotherms. In the column experiments, the maximum adsorption capacities of the metals were in the order of Pb>Hg>Cr>Cd>Cu>Zn>As in monometal conditions, and Hg>Cr>Pb>CuZn approximately Cd>As in multimetal conditions. The metals became more mobile in multimetal than in monometal conditions. Results from both the batch and column experiments show that competitive adsorption among metals increases the mobility of these metals. Particularly, in this study, Pb in multimetal conditions lost it adsorption capacity most significantly. In both monometal and multimetal conditions, the maximum adsorption capacity of the metals in the column experiments was higher than that in the batch experiment indicating other metal retention mechanisms rather than adsorption may be involved. Therefore, both column and batch experiments are needed for estimating retention capacities and removal efficiencies of metals in sediments.

  9. Adsorption of deamidated antibody variants on macroporous and dextran-grafted cation exchangers: II. Adsorption kinetics.

    PubMed

    Tao, Yinying; Carta, Giorgio; Ferreira, Gisela; Robbins, David

    2011-03-18

    Single and multicomponent batch adsorption kinetics were obtained for deamidated mAb variants on two commercial cation exchangers, one with an open macroporous structure--UNOsphere S--and the other with charged dextran grafts--Capto S. The adsorption kinetics for the macroporous matrix was found to be controlled largely by pore diffusion. The effective diffusivity estimated from single component data was a fraction of the mAb free solution diffusivity, and its value could be used to accurately predict the adsorption kinetics for two- and three-component systems. In this case, when two or more variants were adsorbed simultaneously, both experimental and predicted results showed a temporary overshoot of the amount adsorbed above the equilibrium value for the more deamidated variant followed by a gradual approach to equilibrium. Adsorption rates on the dextran grafted material were much faster than those observed for the macroporous matrix for both single component and simultaneous adsorption cases. In this case, no significant overshoot was observed for the more deamidated forms. The Capto S adsorption kinetics could be described well by a diffusion model with an adsorbed phase driving force for single component adsorption and for the simultaneous adsorption of multiple variants. However, this model failed to predict the adsorption kinetics when more deamidated forms pre-adsorbed on the resin were displaced by less deamidated ones. In this case, the kinetics of the displacement process was much slower indicating that the pre-adsorbed components severely hindered transport of the more strongly bound variants. Overall, the results indicate that despite the lower capacity, the macroporous resin may be more efficient in process applications where displacement of one variant by another takes place as a result of the faster and more predictable kinetics.

  10. Adsorption of Gases on Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Mbaye, Mamadou Thiao

    2014-01-01

    This research focus in studying the interaction between various classical and quantum gases with novel carbon nanostructures, mainly carbon nanotubes (CNTs). Since their discovery by the Japanese physicist Sumio Iijima [1] carbon nanotubes have, experimentally and theoretically, been subjected to many scientific investigation. Studies of adsorption on CNTs are particularly directed toward their better usage in gas storage, gas separation, catalyst, drug delivery, and water purification. We explore the adsorption of different gases entrapped in a single, double, or multi-bundles of CNTs using computer simulations. The first system we investigate consists of Ar and Kr films adsorbed on zigzag or armchair nanotubes. Our simulations revealed that Kr atoms on intermediate size zigzag NTs undergo two phase transitions: A liquid-vapor (L→V), and liquid-commensurate (L→CS) with a fractional coverage of one Kr atoms adsorbed for every four carbon atoms. For Ar on zigzag and armchair NTs, the only transition observed is a L→V. In the second problem, we explore the adsorption of CO2 molecules in a nanotube bundle and calculate the isosteric heat of adsorption of the entrapped molecules within the groove. We observed that the lower the temperature, the higher the isosteric of adsorption. Last, we investigate the adsorption of hydrogen, Helium, and Neon gases on the groove site of two parallel nanotubes. At low temperature, the transverse motion on the plane perpendicular to the tubes' axis is frozen out and as a consequence, the heat capacity is reduced to 1/2. At high temperature, the atoms gain more degree of freedom and as a consequence the heat capacity is 5/2.

  11. Adsorption of arsenate on untreated dolomite powder.

    PubMed

    Ayoub, G M; Mehawej, M

    2007-09-05

    Raw dolomite powder was evaluated for its efficiency in adsorbing As(V) from water. An experimental setup comprised of a fluidized dolomite powder bed was used to assess the impact of various test variables on the efficiency of removal of As(V). Test influents including distilled water (DW), synthetic groundwater (SGW) and filtered sewage effluent (FSE) were employed to assess the effect of influent parameters on the adsorption process and the quality of the effluent generated. Dolomite exhibited good As(V) removal levels for distilled water (>92%) and synthetic ground water (>84%) influents at all initial As(V) concentrations tested (0.055-0.600 ppm). Breakthrough of dolomite bed occurred after 45 bed volumes for DW and 20 bed volumes for SGW influents with complete breakthrough taking place at more than 300 bed volumes. As(V) removal from FSE influents was relatively unsuccessful as compared to the DW and SGW influents. Partial removal in the order of 32% from filtered sewage effluent at initial concentration of 0.6 mg/L started at 75 bed volumes and gradually stopped at 165 bed volumes. Varying degrees of As(V) adsorption capacities were observed by the different test influents employed, which indicate that the adsorption of As(V) is adversely affected by competing species, mainly sulfates and phosphates present in the influent. The adsorptive behavior of dolomite was described by fitting data generated from the study into the Langmuir and Freundlich isotherm models. Both models described well the adsorption of dolomite. The average isotherm adsorptive capacity was determined at 5.02 mug/g. Regeneration of the dolomite bed can be achieved with the use of caustic soda solution at a pH of 10.5.

  12. Adsorption of mercury from water by modified multi-walled carbon nanotubes: adsorption behaviour and interference resistance by coexisting anions.

    PubMed

    Chen, Paris Honglay; Hsu, Cheng-Feng; Tsai, David Dah-wei; Lu, Yen-Ming; Huang, Winn-Jung

    2014-08-01

    This investigation reports the use of modified multi-walled carbon nanotubes (MWCNTs) with various functional groups for adsorbing inorganic divalent mercury (Hg(II)) from water samples. To elucidate the behaviours and mechanisms of Hg(II) adsorption by modified MWCNTs, their adsorption capacity was studied by considering adsorption isotherms and kinetics. Particular attention was paid to interference of coexisting inorganic ions with Hg(II) adsorption. The results reveal that functionalization with oxygen-containing groups improved the Hg(II) adsorption capacity of the MWCNTs. Kinetic analysis demonstrated that the adsorption of Hg(II) by MWCNTs was closely described by the pseudo-second-order and Elovich models, suggesting that the adsorption of Hg(II) by MWCNTs was significantly affected by chemical adsorption. The kinetic results were also analysed using the intraparticle diffusion model, which revealed that intraparticle diffusion was not the only rate-controlling mechanism. The adsorption of Hg(II) on MWCNTs fell drastically as the ionic strength increased from 0 to 1.0mol/L chloride ions, and declined significantly as the pH increased from 2.2 to 10.5. The elemental maps obtained by energy-dispersive spectrometer (EDS) revealed the formation of surface complexes of chloride ions with functional groups on MWCNTs, which reduced the number of available sites for the adsorption of Hg(II) and strengthened the repulsive forces between Hg(II) and MWCNTs. The EDS results suggest that chloride ions are important in controlling Hg(II) speciation and adsorption on the surfaces of MWCNTs.

  13. The adsorption mechanism of nortryptiline on C18-bonded discovery

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2005-08-01

    The adsorption isotherms of an ionizable compound, nortriptyline, were accurately measured by frontal analysis (FA) on a C{sub 18}-Discovery column, first without buffer (in an aqueous solution of acetonitrile at 15%, v/v of ACN), then with a buffer (in 28%, v/v ACN solution). The buffers were aqueous solutions containing 20 mM of formic acid or a phosphate buffer at pH 2.70. The linear range of the isotherm could not be reached with the non-buffered mobile phase using a dynamic range larger than 40,000 (from 1.2 x 10{sup -3} g/L to 50 g/L). With a 20 mM buffer in the liquid phase, the isotherm is linear for concentrations of nortriptyline inferior to 10{sup -3} g/L (or 3 {micro} mol/L). The adsorption energy distribution (AED) was calculated to determine the heterogeneity of the adsorption process. AED and FA were consistent and lead to a trimodal distribution. A tri-Moreau and a tri-Langmuir isotherm models accounted the best for the adsorption of nortriptyline without and with buffer, respectively. The nature of the buffer affects significantly the middle-energy sites while the properties of the lowest and highest of the three types of energy sites are almost unchanged. The desorption profiles of nortriptyline show some anomalies in relation with the formation of a complex multilayer adsorbed phase of acetonitrile whose excess isotherm was measured by the minor disturbance method. The C{sub 18}-Discovery column has about the same total saturation capacity, around 200 g of nortriptyline per liter of adsorbent (or 116 mg/g), with or without buffer. About 98-99% of the available surface consists in low energy sites. The coexistence of these different types of sites on the surface solves the McCalley's enigma, that the column efficiency begins to drop rapidly when the analyte concentration reaches values that are almost one hundred times lower than those that could be predicted from the isotherm data acquired under the same experimental conditions. Due to the

  14. Hydrogen Adsorption by Alkali Metal Graphite Intercalation Compounds

    NASA Astrophysics Data System (ADS)

    Purewal, Justin

    Adsorption occurs whenever a solid surface is exposed to a gas or liquid, and is characterized by an increase in fluid density near the interface. Adsorbents have drawn attention in the current effort to engineer materials that store hydrogen at high densities within moderate temperature and pressure regimes. Carbon adsorbents are a logical choice as a storage material due to their low costs and large surface areas. Unfortunately, carbon adsorbents suffer from a low binding enthalpy for H2 (about 5 kJ mol-1), well below the 15 to 18 kJ mol-1) that is considered optimal for hydrogen storage systems. Binding interactions can be increased by the following methods: (1) adjusting the graphite interplanar separation with a pillared structure, and (2) introducing dopant species that interact with H2 molecules by strong electrostatic forces. Graphite intercalation compounds are a class of materials that contain both pillared structures and chemical dopants, making them an excellent model system for studying the fundamentals of hydrogen adsorption in nanostructured carbons. Pressure-composition-temperature diagrams of the MC24(H 2)x graphite intercalation compounds were measured for M = (K, Rb, Cs). Adsorption enthalpies were measured as a function of H2 concentration. Notably, CsC24 had an average adsorption enthalpy of 14.9 kJ mol-1), nearly three times larger than that of pristine graphite. The adsorption enthalpies were found to be positively correlated with the alkali metal size. Adsorption capacities were negatively correlated with the size of the alkali metal. The rate of adsorption is reduced at large H2 compositions, due to the effects of site-blocking and correlation on the H2 diffusion. The strong binding interaction and pronounced molecular-sieving behavior of KC24 is likely to obstruct the translational diffusion of adsorbed H2 molecules. In this work, the diffusion of H2 adsorbed in KC24 was studied by quasielastic neutron scattering measurements and molecular

  15. Mental capacity.

    PubMed

    Williams, Ruth

    2010-02-03

    Three short videos exploring some of the different principles in the Mental Capacity Act 2009 are available on Social Care TV, an online channel intended mainly for the social care sector, although the films are relevant to any professionals whose work is affected by the act. The dramas, which are set in a residential home, a person's own home and a residential school for young people with learning difficulties, concern thedecision-making process and can be viewed at www.scie.org.uk/socialcaretv/topic.asp?guid=377dbe1b-de0c-4d66-bb87-22a243542db2.

  16. Do Forest Age and Soil Depth Affect Carbon and Nitrogen Adsorption in Mineral Horizons?

    NASA Astrophysics Data System (ADS)

    Spina, P. G.; Lovett, G. M.; Fuss, C. B.; Goodale, C. L.; Lang, A.; Fahey, T.

    2015-12-01

    Mineral soils retain large amounts of organic matter through sorption on the surfaces of mineral soils, the largest pools of carbon (C) and nitrogen (N) in the forests of the northeastern U.S. In addition to determining organic matter storage, adsorption and desorption processes are important controllers of runoff chemistry. We are studying adsorption dynamics of mineral soils collected from a chronosequence of hardwood forest sites in the White Mountains, NH to determine how soils vary in their DOM adsorption capacities as a function of effective C and N saturation. We hypothesize that forest age determines proximity to saturation because young forests may need to mine soil organic matter (SOM) in mineral soils to obtain nitrogen to meet growth demands, while the soils of older forests have had time to reaccumulate SOM, eventually reaching C and N saturation. Consequently, we expect adsorption capacities to first increase with forest age in young forests, as the trees mine C and N from mineral surfaces. They will then decrease with forest age in older forests as mining slows and C and N begin to re-accumulate. Batch experiments were conducted with mineral soil samples and dilutions of forest floor leachate. However, preliminary results from a mature forest site (about 100 years old), which we predicted to be a low point of C and N saturation from decades of mining, contradict expectations. Dissolved organic carbon (DOC) adsorption in its shallow mineral soil layers (0-3 cm below E or A horizons) are lower than younger sites ranging from 20 to about 40 years old. In addition to forest age, soil depths also affect N retention dynamics in forest soils. We hypothesized that deeper mineral soils might have greater adsorption capacities due to the fact that they are exposed to less DOC and DON leaching from organic layers and therefore less saturated. Results from the same mature forest site confirm this. Soils from 3-10 cm depth have more potential to adsorb DOC and

  17. A Simple Adsorption Experiment

    ERIC Educational Resources Information Center

    Guirado, Gonzalo; Ayllon, Jose A.

    2011-01-01

    The study of adsorption phenomenon is one of the most relevant and traditional physical chemistry experiments performed by chemistry undergraduate students in laboratory courses. In this article, we describe an easy, inexpensive, and straightforward way to experimentally determine adsorption isotherms using pieces of filter paper as the adsorbent…

  18. Fluorocarbon adsorption in hierarchical porous frameworks

    SciTech Connect

    Motkuri, RK; Annapureddy, HVR; Vijaykumar, M; Schaef, HT; Martin, PF; McGrail, BP; Dang, LX; Krishna, R; Thallapally, PK

    2014-07-09

    Metal-organic frameworks comprise an important class of solid-state materials and have potential for many emerging applications such as energy storage, separation, catalysis and bio-medical. Here we report the adsorption behaviour of a series of fluorocarbon derivatives on a set of microporous and hierarchical mesoporous frameworks. The microporous frameworks show a saturation uptake capacity for dichlorodifluoromethane of >4 mmol g(-1) at a very low relative saturation pressure (P/P-o) of 0.02. In contrast, the mesoporous framework shows an exceptionally high uptake capacity reaching >14 mmol g(-1) at P/P-o of 0.4. Adsorption affinity in terms of mass loading and isosteric heats of adsorption is found to generally correlate with the polarizability and boiling point of the refrigerant, with dichlorodifluoromethane >chlorodifluoromethane >chlorotrifluoromethane >tetrafluoromethane >methane. These results suggest the possibility of exploiting these sorbents for separation of azeotropic mixtures of fluorocarbons and use in eco-friendly fluorocarbon-based adsorption cooling.

  19. Adsorption of dyes on Sahara desert sand.

    PubMed

    Varlikli, Canan; Bekiari, Vlasoula; Kus, Mahmut; Boduroglu, Numan; Oner, Ilker; Lianos, Panagiotis; Lyberatos, Gerasimos; Icli, Siddik

    2009-10-15

    Sahara desert sand (SaDeS) was employed as a mineral sorbent for retaining organic dyes from aqueous solutions. Natural sand has demonstrated a strong affinity for organic dyes but significantly lost its adsorption capacity when it was washed with water. Therefore, characterization of both natural and water washed sand was performed by XRD, BET, SEM and FTIR techniques. It was found that water-soluble kyanite, which is detected in natural sand, is the dominant factor affecting adsorbance of cationic dyes. The sand adsorbs over 75% of cationic dyes but less than 21% for anionic ones. Among the dyes studied, Methylene Blue (MB) demonstrated the strongest affinity for Sahara desert sand (Q(e)=11.98 mg/g, for initial dye solution concentration 3.5 x 10(-5)mol/L). The effects of initial dye concentration, the amount of the adsorbent, the temperature and the pH of the solution on adsorption capacity were tested by using Methylene Blue as model dye. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were applied. It was concluded that adsorption of Methylene Blue on Sahara desert sand followed pseudo-second order kinetics. Gibbs free energy, enthalpy change and entropy change were calculated and found -6411 J/mol, -30360 J/mol and -76.58 J/mol K, respectively. These values indicate that the adsorption is an exothermic process and has a spontaneous nature at low temperatures.

  20. Fluorocarbon adsorption in hierarchical porous frameworks

    NASA Astrophysics Data System (ADS)

    Motkuri, Radha Kishan; Annapureddy, Harsha V. R.; Vijaykumar, M.; Schaef, H. Todd; Martin, Paul F.; McGrail, B. Peter; Dang, Liem X.; Krishna, Rajamani; Thallapally, Praveen K.

    2014-07-01

    Metal-organic frameworks comprise an important class of solid-state materials and have potential for many emerging applications such as energy storage, separation, catalysis and bio-medical. Here we report the adsorption behaviour of a series of fluorocarbon derivatives on a set of microporous and hierarchical mesoporous frameworks. The microporous frameworks show a saturation uptake capacity for dichlorodifluoromethane of >4 mmol g-1 at a very low relative saturation pressure (P/Po) of 0.02. In contrast, the mesoporous framework shows an exceptionally high uptake capacity reaching >14 mmol g-1 at P/Po of 0.4. Adsorption affinity in terms of mass loading and isosteric heats of adsorption is found to generally correlate with the polarizability and boiling point of the refrigerant, with dichlorodifluoromethane >chlorodifluoromethane >chlorotrifluoromethane >tetrafluoromethane >methane. These results suggest the possibility of exploiting these sorbents for separation of azeotropic mixtures of fluorocarbons and use in eco-friendly fluorocarbon-based adsorption cooling.

  1. Adsorption Behavior of Nonplanar Phthalocyanines: Competition of Different Adsorption Conformations

    PubMed Central

    2016-01-01

    Using density functional theory augmented with state-of-the-art van der Waals corrections, we studied the geometric and electronic properties of nonplanar chlorogallium-phthalocyanine GaClPc molecules adsorbed on Cu(111). Comparing these results with published experimental data for adsorption heights, we found indications for breaking of the metal–halogen bond when the molecule is heated during or after the deposition process. Interestingly, the work-function change induced by this dissociated geometry is the same as that computed for an intact adsorbate layer in the “Cl-down” configuration, with both agreeing well with the experimental photoemission data. This is unexpected, as the chemical natures of the adsorbates and the adsorption distances are markedly different in the two cases. The observation is explained as a consequence of Fermi-level pinning due to fractional charge transfer at the interface. Our results show that rationalizing the adsorption configurations on the basis of electronic interface properties alone can be ambiguous and that additional insight from dispersion-corrected DFT simulations is desirable. PMID:27066160

  2. Irreversible adsorption/desorption of PAHs in sediment/water

    SciTech Connect

    Fu, G.; Kan, A.T.; Tomson, M.B.

    1996-10-01

    Successive adsorption isotherm of phenanthrene on soil corresponds to a constant partition of phenanthrene between the bulk solution and solid phase. This shows that the hydrophobic reaction is a dominant mechanism in adsorption process. However, desorption of PAHs appears irreversibility. Cyclic and multiple adsorption and desorption experiments indicated that there is an irreversibly adsorbed intrinsic capacity in the interaction of PAHs (naphthalene and phenanthrene) and soil in aqueous solution. This irreversible fraction for PAHs (naphthalene and phenanthrene) is about 1000-5000 {mu}g/g normalized on the basis of soil organic carbon. The desorption of PAHs from soil appears biphasic when the total adsorbed capacity is greater than the intrinsic irreversibly adsorbed value. In phase, the partitioning coefficient of desorption of PAHs is similar to that of adsorption. However, the other mechanism may be responsible to control the release of PAHs in phase 2.

  3. A review on chitosan-based adsorptive membranes.

    PubMed

    Salehi, Ehsan; Daraei, Parisa; Arabi Shamsabadi, Ahmad

    2016-11-05

    Membrane adsorbents have emerged as powerful and attractive tools for the removal of hazardous materials such as dyes and heavy metal ions, mainly in trace amounts, from water resources. Among membrane adsorbents, those prepared from or modified with chitosan biopolymer and its derivatives are cases of interest because of chitosan advantages including biocompatibility, biodegradability, nontoxicity, reactivity, film and fiber forming capacity and favorable hydrophilicity. This review is oriented to provide a framework for better insight into fabrication methods and applications of chitosan-based adsorptive membranes. Critical aspects including thermokinetic analyses of adsorption and regeneration capacity of the membrane adsorbents have been also overviewed. Future of chitosan-based adsorptive membranes might include efforts for the improvement of mechanical stability and reusability and also most targeted application of appropriate copolymers as well as nanostructures in preparing high performance adsorptive membranes.

  4. Adsorption behaviour of dibutyl phthalate on marine sediments.

    PubMed

    Xu, Xiang-Rong; Li, Xiao-Yan

    2008-01-01

    Laboratory experiments were carried out to investigate the adsorption behaviour of dibutyl phthalate (DBP) on marine sediments collected from five different sites in Victoria Harbour, Hong Kong. DBP adsorption can be well described by the Langmuir isotherm. The maximum DBP adsorption capacity (Q(max)) of the marine sediments ranges from 53 to 79 mg g(-1), which has a positive correlation with their organic content. Around 90% of the organic can be removed from the sediments with treatment by H(2)O(2) oxidation, and the Q(max) then decreases to a range between 13 and 22 mg g(-1). The black carbon content of the sediments has a much greater DBP adsorption capacity than does the natural organic matter of the sediments. The amount of DBP adsorbed on the sediments increases as the salinity of the marine water increases.

  5. Adsorption and photocatalysis of nanocrystalline TiO2 particles for Reactive Red 195 removal: effect of humic acids, anions and scavengers.

    PubMed

    Chládková, B; Evgenidou, E; Kvítek, L; Panáček, A; Zbořil, R; Kovář, P; Lambropoulou, D

    2015-11-01

    In the present study, the coupling of adsorption capacity and photocatalytic efficiency of two different industrially produced titania catalysts was investigated and compared. The azo dye Reactive Red 195 was selected as a model compound. The tested catalysts, PK-10 and PK-180, exhibited different adsorption capacities due to their significant difference in their specific surface, but both have proven to be effective photocatalysts for photodegradation of the studied dye. PK-10 exhibited strong adsorption of the studied dye due to its high specific surface area, while the second studied catalyst, PK-180, demonstrated negligible adsorption of Reactive Red 195. The effect of the pH, the concentration of the catalyst and the initial concentration of the dye appear to affect the photocatalytic rate. The effect of the presence of humic acids and inorganic ions was also examined, while the contribution of various reactive species was indirectly evaluated through the addition of various scavengers. To evaluate the extent of mineralisation of the studied dye, total organic carbon (TOC) measurements during the experiment were also conducted. Besides total colour removal, evident reduction of TOC was also achieved using both catalysts.

  6. Poliovirus Adsorption by 34 Minerals and Soils

    PubMed Central

    Moore, Rebecca S.; Taylor, Dene H.; Sturman, Lawrence S.; Reddy, Michael M.; Fuhs, G. Wolfgang

    1981-01-01

    The adsorption of radiolabeled infectious poliovirus type 2 by 34 well-defined soils and mineral substrates was analyzed in a synthetic freshwater medium containing 1 mM CaCl2 and 1.25 mM NaHCO3 at pH 7. In a model system, adsorption of poliovirus by Ottawa sand was rapid and reached equilibrium within 1 h at 4°C. Near saturation, the adsorption could be described by the Langmuir equation; the apparent surface saturation was 2.5 × 106 plaque-forming units of poliovirus per mg of Ottawa sand. At low surface coverage, adsorption was described by the Freundlich equation. The soils and minerals used ranged from acidic to basic and from high in organic content to organic free. The available negative surface charge on each substrate was measured by the adsorption of a cationic polyelectrolyte, polydiallyldimethylammonium chloride. Most of the substrates adsorbed more than 95% of the virus. In general, soils, in comparison with minerals, were weak adsorbents. Among the soils, muck and Genesee silt loam were the poorest adsorbents; among the minerals, montmorillonite, glauconite, and bituminous shale were the least effective. The most effective adsorbents were magnetite sand and hematite, which are predominantly oxides of iron. Correlation coefficients for substrate properties and virus adsorption revealed that the elemental composition of the adsorbents had little effect on poliovirus uptake. Substrate surface area and pH, by themselves, were not significantly correlated with poliovirus uptake. A strong negative correlation was found between poliovirus adsorption and both the contents of organic matter and the available negative surface charge on the substrates as determined by their capacities for adsorbing the cationic polyelectrolyte, polydiallyldimethylammonium chloride. PMID:6274259

  7. Morphological synthesis of Prussian blue analogue Zn3[Fe(CN)6]2⋅xH2O micro-/nanocrystals and their excellent adsorption performance toward methylene blue.

    PubMed

    Wu, Shikui; Shen, Xiaoping; Zhou, Hu; Zhu, Guoxing; Wang, Rongyan; Ji, Zhenyuan; Chen, Kangmin; Chen, Chaojun

    2016-02-15

    Prussian blue analogue Zn3[Fe(CN)6]2⋅xH2O (Zn-PBA) micro-/nanocrystals with well-defined spherical, cubic and polyhedral morphologies have been successfully synthesized by a simple room-temperature solution method. The morphologies and sizes of the micro-/nanocrystals can be easily tuned by HCl dosage and polymer additive. The as-prepared products are characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis and Brunauer Emmet Teller adsorption-desorption analysis. The possible formation mechanism for these Zn-PBA micro-/nanocrystals is then proposed. In addtion, adsorption performances of these micro-/nanocrystals toward organic dyes are systematically investigated. It is demonstrated that they exhibit strong adsorption selectivity to methylene blue (MB) with an extraordinary adsorption capacity as high as 1.016gg(-1) due to the proper pore size and large specific surface area (643.2m(2)g(-1)) of the product as well as the strong electrostatic interaction between MB molecules and Zn-PBA particles. It is found that the morphology and size of the micro-/nanocrystals have an important effect on their adsorption performance. Moreover, the adsorbed MB dye can be well released in some organic solvents such as ethanol and trichloromethane. The facile morphology-controlled synthesis and excellent adsorption property afford the materials promising application in adsorption related fields.

  8. Adsorption behavior of heavy metals on biomaterials.

    PubMed

    Minamisawa, Mayumi; Minamisawa, Hiroaki; Yoshida, Shoichiro; Takai, Nobuharu

    2004-09-08

    We have investigated adsorption of Cd(II) and Pb(II) at pH 2-6.7 onto the biomaterials chitosan, coffee, green tea, tea, yuzu, aloe, and Japanese coarse tea, and onto the inorganic adsorbents, activated carbon and zeolite. High adsorptive capabilities were observed for all of the biomaterials at pH 4 and 6.7. In the adsorption of Cd(II), blend coffee, tea, green tea, and coarse tea have comparable loading capacities to activated carbon and zeolite. Although activated carbon, zeolite, and chitosan are utilized in a variety of fields such as wastewater treatment, chemical and metallurgical engineering, and analytical chemistry, these adsorbents are costly. On the other hand, processing of the test biomaterials was inexpensive, and all the biomaterials except for chitosan were able to adsorb large amounts of Pb(II) and Cd(II) ions after a convenient pretreatment of washing with water followed by drying. The high adsorption capability of the biomaterials prepared from plant materials is promising in the development of a novel, low-cost adsorbent. From these results, it is concluded that heavy metal removal using biomaterials would be an effective method for the economic treatment of wastewater. The proposed adsorption method was applied to the determination of amounts of Cd(II) and Pb(II) in water samples.

  9. DNA adsorption by indium tin oxide nanoparticles.

    PubMed

    Liu, Biwu; Liu, Juewen

    2015-01-01

    The high conductivity and optical transparency of indium tin oxide (ITO) has made it a popular material in the electronic industry. Recently, its application in biosensors is also explored. To understand its biointerface chemistry, we herein investigate its interaction with fluorescently labeled single-stranded oligonucleotides using ITO nanoparticles (NPs). The fluorescence of DNA is efficiently quenched after adsorption, and the interaction between DNA and ITO NPs is strongly dependent on the surface charge of ITO. At low pH, the ITO surface is positively charged to afford a high DNA adsorption capacity. Adsorption is also influenced by the sequence and length of DNA. For its components, In2O3 adsorbs DNA more strongly while SnO2 repels DNA at neutral pH. The DNA adsorption property of ITO is an averaging result from both components. DNA adsorption is confirmed to be mainly by the phosphate backbone via displacement experiments using free phosphate or DNA bases. Last, DNA-induced DNA desorption by forming duplex DNA is demonstrated on ITO, while the same reaction is more difficult to achieve on other metal oxides including CeO2, TiO2, and Fe3O4 because these particles adsorb DNA more tightly.

  10. Kinetics and equilibrium adsorption studies of dimethylamine (DMA) onto ion-exchange resin.

    PubMed

    Hu, Qinhai; Meng, Yuanyuan; Sun, Tongxi; Mahmood, Qaisar; Wu, Donglei; Zhu, Jianhang; Lu, George

    2011-01-30

    The fine grained resin ZGSPC106 was used to adsorb dimethylamine (DMA) from aqueous solution in the present research. Batch experiments were performed to examine the effects of initial pH of solution and agitation time on the adsorption process. The thermodynamics and kinetics of adsorption were also analyzed. The maximum adsorption was found at natural pH of DMA solution and equilibrium could be attained within 12 min. The equilibrium adsorption data were conformed satisfactorily to the Langmuir equation. The evaluation based on Langmuir isotherm gave the maximal static saturated adsorption capacity of 138.89 mg/g at 293K. Various thermodynamic parameters such as free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) showed that the adsorption was spontaneous, endothermic and feasible. DMA adsorption on ZGSPC106 fitted well to the pseudo-second-order kinetic model. Furthermore, the adsorption mechanism was discussed by Fourier transform infrared spectroscopy (FT-IR) analysis.

  11. Investigation of dye adsorption onto activated carbon from the shells of Macoré fruit.

    PubMed

    Aboua, Kouassi Narcisse; Yobouet, Yao Augustin; Yao, Kouassi Benjamin; Goné, Droh Lanciné; Trokourey, Albert

    2015-06-01

    The activated carbon obtained from the shells of Macoré fruit was used as an adsorbent for the removal of dyes such as methylene blue (MB) and methyl orange (MO) from synthetic contaminated aqueous solutions. It holds that the adsorption is more favourable at acidic pH, with an optimum adsorption at pH = 2. At this pH, the adsorption rate is more than 98% for the two dyes. The sorption capacity was enhanced by increasing the amount of activated carbon. Above room temperature, the adsorption rates remain constant at a value of approximately 99%. The study of the adsorption kinetics indicates that the adsorption on the studied dyes follows second-order kinetics. The isotherm adsorption data were found to be described by both Langmuir and Freundlich. In addition, the thermodynamic studies revealed that the adsorption process is a favourable, endothermic and spontaneous phenomenon.

  12. Adsorption of 2,4,6-trinitrotoluene on carboxylated porous polystyrene microspheres

    NASA Astrophysics Data System (ADS)

    Ye, Zhengfang; Meng, Qingqiang; Lu, Shengtao

    2012-02-01

    Large-pore-size (150 nm) polystyrene (PSt) microspheres were carboxylated with phthalic anhydride (PA) through Friedel-Crafts acetylation to study the adsorption of 2,4,6-trinitrotoluene (TNT) on this material from aqueous solution. The scanning electron microscope (SEM) images and mercury porosimetry measurements (MPM) of the microspheres showed that the pore structure was unchanged during the reaction. High adsorption capacity (11.2 mg g-1 of suction-dried adsorbent) and adsorption rate (33.9 mg g-1 h-1) for TNT were observed during the study. As shown by the adsorption isotherm, the adsorption of TNT on PA-PSt can be described by the Freundlich adsorption equation, indicating heterogeneous adsorption process. On-column adsorption of TNT on PA-PSt and elution indicated that TNT can be completely removed from aqueous solution and condensed into acetone.

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

    PubMed

    Li, Li; Liu, Shuangxi; Zhu, Tan

    2010-01-01

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

  14. Comparative study on composition, structure, and adsorption behavior of activated carbons derived from different synthetic waste polymers.

    PubMed

    Lian, Fei; Xing, Baoshan; Zhu, Lingyan

    2011-08-15

    The composition, structure, and adsorption behavior of activated carbons (ACs) derived from three different types of waste polymers, i.e., tire rubber (TR), polyvinyl chloride (PVC), and polyethyleneterephtalate (PET), by KOH activation were compared. The AC derived from PET exhibited the largest surface area (2831 m(2)/g) and pore volume (1.68 cm(3)/g) due to the homogenous aromatic composition of PET. The AC derived from PVC exhibited relatively lower surface area (2666 m(2)/g) but more narrowed pore size distribution (2-3 nm). The complex composition and high ash content of tire particles resulted in AC product with significantly lower surface area (398.5 m(2)/g) and heterogeneous pore width. Adsorption data of methylene blue (MB) were fitted well by Langmuir equation, indicating monolayer coverage on the ACs. The high oxygen content of PET-derived AC heavily affected its adsorption to MB and iodine. Due to the remarkable surface area and highly mesoporous structures, ACs based on both PET and PVC exhibited much higher adsorption capacities than that of TR and commercial coal-based AC (F400). This study demonstrates that the properties of ACs are highly dependent on their starting polymers and the potential of converting synthetic polymer waste into effective adsorbents for environmental remediation and cleanup.

  15. Adsorption of methylene blue from aqueous solution by graphene.

    PubMed

    Liu, Tonghao; Li, Yanhui; Du, Qiuju; Sun, Jiankun; Jiao, Yuqin; Yang, Guangming; Wang, Zonghua; Xia, Yanzhi; Zhang, Wei; Wang, Kunlin; Zhu, Hongwei; Wu, Dehai

    2012-02-01

    Graphene was prepared using a modified Hummers' method. The physico-chemical properties of graphene were characterized by TEM, BET specific surface area, FTIR, Raman and XRD measurements. The effect factors including pH, contact time, temperature and dosage on the adsorption properties of methylene blue onto graphene were investigated. The experimental data of isotherm followed the Langmuir isotherm model better than the Freundlich model. The maximum adsorption capacity obtained from Langmuir isotherm equation at 293 K was 153.85 mg/g, indicating graphene is a good adsorbent for the adsorption of MB. The kinetic study illustrated that the adsorption of methylene blue onto graphene fit the pseudo second-order model. The thermodynamic parameters indicated that the adsorption of methylene blue onto graphene was an endothermic and spontaneous process.

  16. Adsorption of trihalomethanes from water with carbon nanotubes.

    PubMed

    Lu, Chungsying; Chung, Yao-Lei; Chang, Kuan-Foo

    2005-03-01

    Commercial carbon nanotubes (CNTs) were purified by acid solution and were employed as adsorbents to study adsorption of trihalomethanes (THMs) from water. The properties of CNTs such as purity, structure and nature of the surface were greatly improved after acid treatment which made CNTs become more hydrophilic and suitable for adsorption of low molecular weight and relatively polar THM molecules. The adsorption of THMs onto CNTs fluctuates very little in the pH range 3-7, but decreases with pH value as pH exceeds 7. A comparative study between CNTs and powdered activated carbon (PAC) for adsorption of THMs from water was also conducted. The short time needed to reach equilibrium as well as the high adsorption capacity of CHCl3, which accounts for a significant portion of THMs in the chlorinated drinking water, suggests that CNTs possess highly potential applications for THMs removal from water.

  17. Methane Adsorption on Graphitic Nanostructures: Every Molecule Counts

    PubMed Central

    2012-01-01

    Bundles of single-walled nanotubes are promising candidates for storage of hydrogen, methane, and other hydrogen-rich molecules, but experiments are hindered by nonuniformity of the tubes. We overcome the problem by investigating methane adsorption on aggregates of fullerenes containing up to six C60; the systems feature adsorption sites similar to those of nanotube bundles. Four different types of adsorption sites are distinguished, namely, registered sites above the carbon hexagons and pentagons, groove sites between adjacent fullerenes, dimple sites between three adjacent fullerenes, and exterior sites. The nature and adsorption energies of the sites in C60 aggregates are determined by density functional theory and molecular dynamics (MD) simulations. Excellent agreement between experiment and theory is obtained for the adsorption capacity in these sites. PMID:23378887

  18. Reuse of Solid Waste in Adsorption of the Textile Dye

    NASA Astrophysics Data System (ADS)

    Meziti, Chafika; Boukerroui, Abdelhamid

    This work presents the study of the reuse of a regenerated spent bleaching earth (RSBE). The RSBE material was tested in the removal of a basic textile dye presents in aqueous solution. The effect of physicochemical parameters such as stirring speed, initial concentration, contact time and temperature have been invested and thermodynamic nature of the adsorption process was determined by calculating the ΔH°, ΔS° and ΔG° values The results obtained show that the adsorption mechanism was described by the Langmuir model and the adsorption capacity, qmax (72.41 to 82.37 mg.g-1), increases with temperature (20-50 °C). The thermodynamic parameters show a presence of a strong affinity between two phases (liquid-solid) and an endothermic equilibrium adsorption process. However, the phenomenon of the adsorption kinetic follows the pseudo second order kinetic model.

  19. Adsorption of organic phenols onto hexadecyltrimethylammonium-treated montmorillonite

    SciTech Connect

    Kim, Young S.; Song, Dong I.; Jeon, Young W.; Choi, Sang J.

    1996-12-01

    Montmorillonite used as an adsorbent was organically modified by using a cationic surfactant, hexadecyltrimethylammonium (HDTMA), to enhance the removal capacity of organic phenol contaminants dissolved in an aqueous solution. This modification produces a change of the surface property of montmorillonite from hydrophilic to organophilic. The single- and multicomponent competitive adsorptions were performed in a batch reactor to investigate the removal of three toxic organic phenols, 2-chlorophenol, 3-cyanophenol, and 4-nitrophenol, on the modified HDTMA-montmorillonite. It was observed from the experimental results that the adsorption affinity for HDTMA-montmorillonite was 2-chlorophenol, 4-nitrophenol, 3-cyanophenol in decreasing order. Langmuir and the Redlich-Peterson models were used to analyze the single-component adsorption results, while the IAST and the LCM models predicted the multicomponent adsorption equilibria. These models yielded favorable representations of both individual and competitive adsorption behaviors.

  20. Adsorption of ammonium dinitramide (ADN) from aqueous solutions. 1. Adsorption on powdered activated charcoal.

    PubMed

    Santhosh, G; Venkatachalam, S; Ninan, K N; Sadhana, R; Alwan, S; Abarna, V; Joseph, M A

    2003-03-17

    Investigations on the adsorption of ammonium dinitramide (NH(4)N(NO(2))(2)) (ADN) from aqueous solutions on powdered activated charcoal (PAC) were carried out in order to find out an effective and easier method of separating ADN from aqueous solutions. The effectiveness of PAC in the selective adsorption of ADN from aqueous solutions of ADN (ADN-F) and ADN in presence of sulfate (SO(4)(2-)) and nitrate (NO(3)(-)) ions (ADN-PS) was examined and compared using batch and column methods. The adsorption process follows both Langmuir and Freundlich adsorption isotherms and the isotherm parameters for the models were determined. The observed data favor the formation of monolayer adsorption. The adsorption capacities were found to be 63.3, 119, 105.3 and 82 mg of ADN per g of PAC for ADN-F (batch), ADN-PS (batch), ADN-F (column) and ADN-PS (column), respectively. Break-through curves for ADN-F and ADN-PS were obtained for the optimization of separation of ADN from aqueous solutions. Elution curves were generated for the desorption of ADN from PAC using hot water as eluent.

  1. Hydrogen Adsorption in Carbon nanoparticles

    NASA Astrophysics Data System (ADS)

    Cabrera, A. L.; Rojas, S.; Dias-Droguett, D. E.; Bhuyan, H.; Aomoa, N.; Kakati, M.

    2013-03-01

    We have studied hydrogen adsorption in carbon nanoparticles using a quartz crystal microbalance. The carbon nanoparticles were synthesized from a thermal plasma jet at different pressure (15 - 263 torr) of the reactants and different current (50 - 250 A) to generate the plasma. The as-prepared carbon nanoparticles were directly deposited on top of the gold electrode of a quartz crystal and we monitored in-situ the changes in resonance frequency while the chamber was pressurized at different hydrogen pressures. These changes enabled determination of absorbed hydrogen mass in order to get H/C mass ratio curves as a function of H2 pressure. Adsorption curves obtained in some carbon nanoparticles indicated the formation of hydrogen monolayer inside the pores of the carbon nanoparticles. Using the value of the jump due to the formation of a H2\\ monolayer, a surface area was estimated between 40-60 m2/g for hydrogen adsorption. In other carbon samples, hydrogen uptake curves indicated that H2 was filling the sample's pores when pore volume was large. These observations will be discussed in detail for several carbon nanoparticles samples. Funds provided by VRI Puente 9/2012 and 10/2012

  2. Epoxide-functionalization of polyethyleneimine for synthesis of stable carbon dioxide adsorbent in temperature swing adsorption

    PubMed Central

    Choi, Woosung; Min, Kyungmin; Kim, Chaehoon; Ko, Young Soo; Jeon, Jae Wan; Seo, Hwimin; Park, Yong-Ki; Choi, Minkee

    2016-01-01

    Amine-containing adsorbents have been extensively investigated for post-combustion carbon dioxide capture due to their ability to chemisorb low-concentration carbon dioxide from a wet flue gas. However, earlier studies have focused primarily on the carbon dioxide uptake of adsorbents, and have not demonstrated effective adsorbent regeneration and long-term stability under such conditions. Here, we report the versatile and scalable synthesis of a functionalized-polyethyleneimine (PEI)/silica adsorbent which simultaneously exhibits a large working capacity (2.2 mmol g−1) and long-term stability in a practical temperature swing adsorption process (regeneration under 100% carbon dioxide at 120 °C), enabling the separation of concentrated carbon dioxide. We demonstrate that the functionalization of PEI with 1,2-epoxybutane reduces the heat of adsorption and facilitates carbon dioxide desorption (>99%) during regeneration compared with unmodified PEI (76%). Moreover, the functionalization significantly improves long-term adsorbent stability over repeated temperature swing adsorption cycles due to the suppression of urea formation and oxidative amine degradation. PMID:27572662

  3. Epoxide-functionalization of polyethyleneimine for synthesis of stable carbon dioxide adsorbent in temperature swing adsorption.

    PubMed

    Choi, Woosung; Min, Kyungmin; Kim, Chaehoon; Ko, Young Soo; Jeon, Jae Wan; Seo, Hwimin; Park, Yong-Ki; Choi, Minkee

    2016-08-30

    Amine-containing adsorbents have been extensively investigated for post-combustion carbon dioxide capture due to their ability to chemisorb low-concentration carbon dioxide from a wet flue gas. However, earlier studies have focused primarily on the carbon dioxide uptake of adsorbents, and have not demonstrated effective adsorbent regeneration and long-term stability under such conditions. Here, we report the versatile and scalable synthesis of a functionalized-polyethyleneimine (PEI)/silica adsorbent which simultaneously exhibits a large working capacity (2.2 mmol g(-1)) and long-term stability in a practical temperature swing adsorption process (regeneration under 100% carbon dioxide at 120 °C), enabling the separation of concentrated carbon dioxide. We demonstrate that the functionalization of PEI with 1,2-epoxybutane reduces the heat of adsorption and facilitates carbon dioxide desorption (>99%) during regeneration compared with unmodified PEI (76%). Moreover, the functionalization significantly improves long-term adsorbent stability over repeated temperature swing adsorption cycles due to the suppression of urea formation and oxidative amine degradation.

  4. Epoxide-functionalization of polyethyleneimine for synthesis of stable carbon dioxide adsorbent in temperature swing adsorption

    NASA Astrophysics Data System (ADS)

    Choi, Woosung; Min, Kyungmin; Kim, Chaehoon; Ko, Young Soo; Jeon, Jae Wan; Seo, Hwimin; Park, Yong-Ki; Choi, Minkee

    2016-08-01

    Amine-containing adsorbents have been extensively investigated for post-combustion carbon dioxide capture due to their ability to chemisorb low-concentration carbon dioxide from a wet flue gas. However, earlier studies have focused primarily on the carbon dioxide uptake of adsorbents, and have not demonstrated effective adsorbent regeneration and long-term stability under such conditions. Here, we report the versatile and scalable synthesis of a functionalized-polyethyleneimine (PEI)/silica adsorbent which simultaneously exhibits a large working capacity (2.2 mmol g-1) and long-term stability in a practical temperature swing adsorption process (regeneration under 100% carbon dioxide at 120 °C), enabling the separation of concentrated carbon dioxide. We demonstrate that the functionalization of PEI with 1,2-epoxybutane reduces the heat of adsorption and facilitates carbon dioxide desorption (>99%) during regeneration compared with unmodified PEI (76%). Moreover, the functionalization significantly improves long-term adsorbent stability over repeated temperature swing adsorption cycles due to the suppression of urea formation and oxidative amine degradation.

  5. Trichloroethylene (TCE) adsorption using sustainable organic mulch.

    PubMed

    Wei, Zongsu; Seo, Youngwoo

    2010-09-15

    Soluble substrates (electron donors) have been commonly injected into chlorinated solvent contaminated plume to stimulate reductive dechlorination. Recently, different types of organic mulches with economic advantages and sustainable benefits have received much attention as new supporting materials that can provide long term sources of electron donors for chlorinated solvent bioremediation in engineered biowall systems. However, sorption capacities of organic mulches for chlorinated solvents have not been studied yet. In this study, the physiochemical properties of organic mulches (pine, hardwood and cypress mulches) were measured and their adsorption capacity as a potential media was elucidated. Single, binary and quaternary isotherm tests were conducted with trichloroethylene (TCE), tetrachloroethylene (PCE), trans-dichloroethylene (trans-DCE) and cis-dichloroethylene (cis-DCE). Among the three tested mulches, pine mulch showed the highest sorption capacity for the majority of the tested chemicals in single isotherm test. In binary or quaternary isotherm tests, competition among chemicals appears to diminish the differences in Q(e) for tested mulches. However, pine mulch also showed higher adsorption capacity for most chemicals when compared to hardwood and cypress mulches in the two isotherm tests. Based upon physicochemical properties of the three mulches, higher sorption capacity of pine mulch over hardwood and cypress mulches appears to be attributed to a higher organic carbon content and the lower polarity.

  6. Advances in principal factors influencing carbon dioxide adsorption on zeolites

    PubMed Central

    Bonenfant, Danielle; Kharoune, Mourad; Niquette, Patrick; Mimeault, Murielle; Hausler, Robert

    2008-01-01

    We report the advances in the principal structural and experimental factors that might influence the carbon dioxide (CO2) adsorption on natural and synthetic zeolites. The CO2 adsorption is principally govern by the inclusion of exchangeable cations (countercations) within the cavities of zeolites, which induce basicity and an electric field, two key parameters for CO2 adsorption. More specifically, these two parameters vary with diverse factors including the nature, distribution and number of exchangeable cations. The structure of framework also determines CO2 adsorption on zeolites by influencing the basicity and electric field in their cavities. In fact, the basicity and electric field usually vary inversely with the Si/Al ratio. Furthermore, the CO2 adsorption might be limited by the size of pores within zeolites and by the carbonates formation during the CO2 chemisorption. The polarity of molecules adsorbed on zeolites represents a very important factor that influences their interaction with the electric field. The adsorbates that have the most great quadrupole moment such as the CO2, might interact strongly with the electric field of zeolites and this favors their adsorption. The pressure, temperature and presence of water seem to be the most important experimental conditions that influence the adsorption of CO2. The CO2 adsorption increases with the gas phase pressure and decreases with the rise of temperature. The presence of water significantly decreases adsorption capacity of cationic zeolites by decreasing strength and heterogeneity of the electric field and by favoring the formation of bicarbonates. The optimization of the zeolites structural characteristics and the experimental conditions might enhance substantially their CO2 adsorption capacity and thereby might give rise to the excellent adsorbents that may be used to capturing the industrial emissions of CO2. PMID:27877925

  7. Adsorption behavior of the catechins and caffeine onto polyvinylpolypyrrolidone.

    PubMed

    Dong, Zhan-Bo; Liang, Yue-Rong; Fan, Fang-Yuan; Ye, Jian-Hui; Zheng, Xin-Qiang; Lu, Jian-Liang

    2011-04-27

    Adsorbent is one of the most important factors for separation efficiency in fixed-bed purification techniques. The adsorption behavior of catechins and caffeine onto polyvinylpolypyrrolidone (PVPP) was investigated by static adsorption tests. The results showed that catechins rather than caffeine were preferred to adsorb onto PVPP since the adsorption selectivity coefficient of total catechins vs caffeine was around 22.5, and that adsorption of catechins could be described by the pseudo-second-order model. Adsorption amount of caffeine onto PVPP in green tea extracts solution was much higher than that in purified caffeine solution although the initial concentration of caffeine was similar in the two solutions, indicating the caffeine might be attached with catechins which were adsorbed by PVPP instead of being adsorbed by PVPP directly. The results also showed that the adsorption capacity of catechins and caffeine decreased with an increase in temperature, and that Freundlich and Langmuir models were both suitable for describing the isothermal adsorption of catechins, but not suitable for caffeine. The predicted maximum monolayer adsorption capacity of total catechins by PVPP was 671.77 mg g(-1) at 20 °C, which was significantly higher than that by other reported adsorbents. The thermodynamics analyses indicated that the adsorption of catechins onto PVPP was a spontaneous and exothermic physisorption process, revealing lower temperatur