Personal Research Database

Full Text: S\Sep Sci Tec38, 2201.pdf

Abstract: The removal of Cr(VI), Mo(VI), or V(V) anions from single metal aqueous solutions was studied. Two alternative treatment methods were applied: (1) sorption of these anions onto commercially available akaganeite (beta-FeOOH) or (2) nanofiltration, using a commercial spiral-wound pilot-scale unit. During sorption experiments, kinetics and equilibrium were mainly studied. A modified second-order kinetic model was found to better fit the kinetic results. Freundlich isotherms better described (slightly) chromium and molybdenum equilibrium sorption experiments, whereas Langmuir isotherm better described vanadium equilibrium. During nanofiltration experiments, the influence of pH and of initial anion concentration was mainly studied, using a fixed background electrolyte concentration.

Keywords: Akaganeite, Removal, Anions, Sorption, Nanofiltration, Chromium, Molybdenum, Vanadium, Hexavalent Chromium, Activated Carbon, Waste-Water, Adsorption, Extraction, Flotation, Chromate, Molybdenum(VI), Vanadium(IV), Groundwater

Machado, R.M., Correia, M.J.N. and Carvalho, J.M.R. (2003), Integrated process for biosorption of copper from liquid effluents using grape stalks. Separation Science and Technology, 38 (10), 2237-2254.

Full Text: S\Sep Sci Tec38, 2237.pdf

Abstract: A multistage process was used for biosorption of heavy metals from liquid effluents using grape stalks as the biosorbent. The biosorption was carried out with a free biomass suspension in a two-stage, countercurrent, stirred batch system. The biomass was separated from the treated effluent using flocculation, sedimentation, and filtering. The filter cake was used, as a small packed column loaded with heavy metals where the elution was performed.

The efficiency of the overall system was studied using three synthetic effluents. The first two effluents labeled in this work as F1 and F2 had 10 and 50 ppm of copper, respectively. The third effluent had a complex metal mixture containing 10 ppm of copper, 50 ppm of zinc, 5 ppm of nickel, 100 ppm of calcium, and 100 ppm of sodium. The biosorption system was able to remove 99% of the copper from the F1 effluent (0.08 ppm of copper in the final effluent), using a biomass concentration of 2 g/L. For the F2 effluent, a biomass concentration of 4 g/L was required to obtain a final copper concentration 0.18 ppm. Copper was also removed from the F3 effluent with an efficiency of 98% (final metal concentration of 0.15 ppm). However, it required a biomass concentration of 6 g/L in the two biosorption stages and the other target metals under study, Zn and Ni, had modest removals of 46% and 35%, respectively.

The results from the elution experiments demonstrate that the key variables to obtain high metal concentration in the eluate are the metal concentration bounded to the biomass, the superficial velocity of the eluant, and the filter cake depth. Using the F2 effluent to load the biomass up to 12.5 mg/g of copper and performing the elution with a superficial velocity of 0.9 cm/min in a filter cake with depth of 10 cm, a copper concentration in the eluate of 1.8 g/L was achieved, which correspond to a concentration factor of 38-fold.

Keywords: Bisorption, Heavy Metals, Biomass, Grape Stalks, Recovery, Cadmium, Biomass, Zinc

Yeon, K.H. and Moon, S.H. (2003), A study on removal of cobalt from a primary coolant by continuous electrodeionization with various conducting spacers. Separation Science and Technology, 38 (10), 2347-2371.

Full Text: S\Sep Sci Tec38, 2347.pdf

Abstract: The production of high purity water in the primary coolant of a nuclear power plant was investigated using a CEDI process with three ion-conducting spacers, i.e., ion-exchange resin (IX), an immobilized ion-exchange polyurethane resin (IEPU), and an ion-exchange textile (IET). The spacers were characterized by varying experimental conditions, e.g., dosage of adsorbent, pH of the solution, contact time, and the porous-plug model. The CEDI stack was assembled as a bed layered with the cation-exchange and anion-exchange materials. The stack configuration was designed to prevent a reaction between the metal ions and hydroxide ions. The performance of the CEDI operation with the layered bed showed more than 99% removal of the ions at a current efficiency ranged from 18 to 24%. In this study, the feasibility of using the CEDI in operations for the removal of heavy metals present at very low concentrations was successfully demonstrated.

Keywords: Ion-Conducting Spacer, Ion-Exchange Resin, Ion-Exchange Polyurethane, Ion-Exchange Textile, Continuous Electrodeionization, Waste-Water, Adsorption

Guibal, E., Guzman, J., Navarro, R. and Revilla, J. (2003), Vanadium extraction from fly ash - Preliminary study of leaching, solvent extraction, and sorption on chitosan. Separation Science and Technology, 38 (12-13), 2881-2899.

Full Text: S\Sep Sci Tec38, 2881.pdf

Abstract: Fly ashes resulting from the combustion of fuel containing high concentrations of vanadium that can be slightly removed by water and more efficiently by alkaline or acid solutions. This uncontrolled release can contaminate water sources and requires appropriate storage of fly ashes. This study investigated the possibility of cleaning the ashes by leaching the material and recovering vanadium by solvent extraction (for metal concentration solutions higher than 200 mg V L^-1) using several amine extractants (Primene JM-T, Amberlite LA-2, Alamine 336, and Alamine 304), a quaternary ammonium salt (Aliquat 336), and by a sorption process (for low-metal concentration solutions) using chitosan. Extraction and stripping were investigated with liquid extractants and showed that Aliquat 336 was the best of these extractants. However, since Aliquat 336 exhibits a greater difficulty at stripping, secondary or tertiary amine extractants appear more suited for the extraction process. Vanadium sorption occurs on chitosan through anion exchange with a maximum sorption capacity of 400 to 450 mg V g^-1 at pH 3. The treatment of acid leachates with chitosan does not appear possible, since it requires a pH control to pH 3, which precipitates ferric ions and coprecipitates vanadium. Alternative routes could be the alkaline leaching of fly ashes and a further pH control.

Keywords: Amine Extractants, Beads, Chitosan, Chitosan Sorption, Coal, Combustion, Equilibrium, Fly Ash, Leaching, Oil, Peat, Solvent Extraction, Sorption, Vanadium, Wood

Guibal, E., McCarrick, P. and Tobin, J.M. (2003), Comparison of the sorption of anionic dyes on activated carbon and chitosan derivatives from dilute solutions. Separation Science and Technology, 38 (12-13), 3049-3073.

Full Text: S\Sep Sci Tec38, 3049.pdf

Abstract: Activated carbon and chitosan were investigated for the sorption of several dyes. While the sorption on activated carbon was largely independent of the pH, the sorption of dyes on chitosan was controlled by the acidity of the solution. Anionic dye sorption onto chitosan occurred through electrostatic attraction on protonated amine groups. Sorption experiments were focused on dilute solutions and sorption capacities ranged between 200 and 2000 mol g^-1 for chitosan and between 50 and 900 mol g^-1 for activated carbon. Since, in most cases, equilibrium was reached within the first 12 hours of contact, sorption kinetics are relatively fast. However, both sorption capacities (sorption isotherms) and kinetics depended on the type of dyes. The attempt to correlate sorption performance to the structure of the dye failed. Sorption kinetics are strongly influenced not only by intraparticle diffusion resistance but also by the affinity of the dye for the sorbent.

Keywords: Chitosan, Activated Carbon, Anionic Dyes, Sorption, Isotherms, Kinetics, Intraparticle Diffusion-Processes, Aqueous-Solutions, Reactive Dyes, Waste-Water, Soluble Chitosans, Color Removal, Adsorption, Chitin, Equilibrium, Isotherms

Chu, K. and Hashim, M. (2003), Modeling batch equilibrium and kinetics of copper removal by crab shell. Separation Science and Technology, 38 (16), 3927-3950.

Full Text: S\Sep Sci Tec38, 3927.pdf

Abstract: The adsorption characteristics of copper from aqueous solutions on crab shell were determined by batch tests. The uptake equilibrium and kinetics were affected by the pH of the sorption system. In the pH range of 3 to 6, the extent of copper removal was found to increase with increasing pH. A Langmuir-Freundlich model with pH-dependent parameters and an extended Langmuir-Freundlich model with pH-independent parameters were found to account very well for the measured constant pH equilibrium isotherms. Four existing rate models (second-order reversible reaction, second-order irreversible reaction, pseudo first-order, and Elovich) were evaluated in simulating transient sorption profiles measured over a pH range of 3 to 6. The rate coefficients of the four models exhibited a linear dependence on the pH of the sorption system. Given the mathematical simplicity of the four rate models and their apparent success in accounting for the experimental observations throughout the whole time course of sorption, any one of the models can be used as a means for predicting the transient behavior of the copper-crab shell sorption system with reasonable accuracy.

Keywords: Adsorption, Chitosan, Crab Shell, Equilibrium, Kinetics, Modeling, Polyaminated Chitosan Beads, Aqueous-Solutions, Activated Carbon, Bone Char, Sorption, Adsorption, Chitin, Thermodynamics, Desorption, Sorbents

Solisio, C., Lodi, A., Converti, A. and Del Borghi, M. (2003), Influence of temperature on cadmium removal by Sphaerotilus natans from acidic solutions. Separation Science and Technology, 38 (16), 3951-3966.

Full Text: S\Sep Sci Tec38, 3951.pdf

Abstract: A culture of Sphaerotilus natans (NCIMB 11196) was used for cadmium removal from acidic solutions, simulating the composition of industrial wastewaters. Tests were carried out at temperatures increasing from 15 up to 40degreesC, to check the actual possibility of utilizing a biological system to remove this heavy metal from water as well as, to shed light on the phenomenon responsible for its uptake. The highest values of the specific growth rate of this microorganism (_mux = 0.11 to 0.13 h^-1) and cadmium removal rate (k_r = 0.15 h^-1) were obtained within 25 to 30degreesC. Under these conditions, biomass was able to increase the pH of the medium from 4.0 up to 7.0 to 7.8. The data of _mux and k_r collected at different temperatures were finally used. to estimate, according to Arrhenius, the thermodynamic parameters of cell growth and cadmium removal as well as of the related thermal inactivations. On the basis of these results, cadmium seemed to be removed by S. natans following a mechanism controlled by cell growth, implying the quick electrostatic attraction of ions to the negative charges present on the cell surface.

Keywords: Cadmium Biosorption, Sphaerotilus Natans, Acidic Solutions, Batch Tests, Temperature, Thermodynamics, Industrial Waste-Water, Ion-Exchange, Heavy-Metals, Fly-Ash, Biosorption, Biomass, Equilibrium, Adsorption, Recovery, Copper

Moreira, R.D.F.P.M., Madeira, V.S., José, H.J. and Humeres, E. (2004), Removal of iron from water using adsorbent carbon. Separation Science and Technology, 39 (2), 271-286.

Full Text: S\Sep Sci Tec39, 271.pdf

Abstract: A novel adsorbent carbon to remove iron from water was evaluated. Bench scale and pilot scale tests were performed to characterize the mechanism of the iron removal. The adsorption equilibrium of iron removal can be described using the Langmuir isotherm, assuming a monolayer. In the absence of dissolved oxygen, Fe²⁺ is adsorbed on the solid surface as a monolayer of 62.7×10^-3 mat-g·g^-1, while the monolayer of oxidized iron coverage in the air-equilibrated system is 72.7×10^-3mat-g·g^-1. The iron removal results from the adsorption of oxygen followed by the oxidation of Fe²⁺ catalyzed by the adsorbent carbon surface. The Fe³⁺ precipitates on the solid, forming a hydrated iron oxide-coated carbon that is also able to adsorb iron. The kinetics of iron removal was modeled using the film and pore diffusion model. Pilot tests performed with and without pre-aeration showed results similar to those observed on the bench scale.

Keywords: Iron Removal, Water, Kinetics, Adsorbent Carbon

Özcan, A.S., Tetik, S. and Özcan, A. (2004), Adsorption of acid dyes from aqueous solutions onto sepiolite. Separation Science and Technology, 39 (2), 301-320.

Full Text: S\Sep Sci Tec39, 301.pdf

Abstract: This research deals with an investigation of the adsorption of two acid dyes, namely Acid Red 57 (AR57) and Acid Blue 294 (AB294) onto sepiolite. Batch kinetics and isotherm studies were carried out. The results indicate that the adsorption of acid dyes obeys Freundlich isotherm and the second-order kinetics model. In addition, the effectiveness of sepiolite on adsorption of AR57 and AB294 from aqueous solution was studied as a function of time, pH, and temperature. Thermodynamic parameters for the adsorption of dyes were calculated and are discussed., The maximum removals of acid dyes was observed around 90% and 75% at pH = 2 for AR57 and AB294, respectively.

Keywords: Adsorption, Acid Dyes, Clays, Isotherm, Sepiolite, Kinetics, Natural Adsorbents, Textile Effluents, Activated Carbons, Methylene-Blue, Color Removal, Basic-Dyes, Fly-Ash, Sorption, Behavior, Clay

Dambies, L. (2004), Existing and prospective sorption technologies for the removal of arsenic in water. Separation Science and Technology, 39 (3), 603-627.

Full Text: S\Sep Sci Tec39, 603.pdf

Abstract: The present article is devoted to a review of existing and emerging sorption technologies for the removal of arsenic in water. After presenting the traditional sorbents used in arsenic removal, experimental studies to characterize the adsorptive capacities of sorbents are detailed. In a second part, metal-loaded polymers, which are among the prospective technologies for arsenate and arsenite removal in drinking water, are introduced. Finally, the design of new metal-loaded polymers to treat arsenic in drinking water is discussed.

Keywords: Arsenic Removal, Arsenate, Arsenite, Adsorption, Ion Exchange, Metal-Loaded Polymers, Water Treatment, Ligand-Exchange Sorption, Hydrous Zirconium-Oxide, Ferric Ion Form, Chelating Resin, Adsorption Characteristics, Activated Carbon, Aqueous-Solution, Anions, Separation, Chitosan

Vaishya, R.C. and Gupta, S.K. (2004), Modeling arsenic(V) removal from water by sulfate modified iron-oxide coated sand (SMIOCS). Separation Science and Technology, 39 (3), 645-666.

Full Text: S\Sep Sci Tec39, 645.pdf

Abstract: The batch kinetics of arsenic(V) on a novel media developed by coating BaSO4 and Fe on quartz sand, known as sulfate modified iron-oxide coated sand (SMIOCS), was investigated. Batch rate data were analyzed using active available site and chemical reaction rate models. The batch kinetic data were a better fit on an active, available site model as compared to a chemical reaction rate model. The media was characterized for certain chemical properties and surface area. The media showed alkali resistance with the presence of iron, barium, and sulfur on the surface. The Langmuir and Freundlich isotherm equations could be used to describe the partitioning behavior of system at different pH. The removal of As(V) on SMIOCS was pH dependent and maximum removal was observed in acidic pH range. The variation in ionic strength and chloride (Cl^-) concentration in the solute do not play a significant role in As(V) removal efficiency but major anions showed some reduction in As(V) removal efficiency. A very small concentration of silica drastically reduced arsenic removal efficiency. However, the presence of Ca²⁺ and Mg²⁺ as cations improved arsenic(V) removal efficiency. The fixed bed studies indicated that the breakthrough time for arsenic(V) removal is dependent on the initial influent arsenic concentrations. These results suggest that arsenate adsorption on SMIOCS media may play an important role for arsenic immmobilization.

Keywords: Arsenic(V) Removal, Water, Sulfate Modified Iron-Oxide Coated Sand, Arsenate Adsorption, Surface-Chemistry, Natural Waters, Ferrihydrite, Goethite, Groundwater, Kinetics

? BišKup, B. and Subotić, B. (2004), Removal of heavy metal ions from solutions using zeolites. III. Influence of sodium ion concentration in the liquid phase on the kinetics of exchange processes between cadmium ions from solution and sodium ions from zeolite A. Separation Science and Technology, 39 (4), 925-940.

Full Text: 2004\Sep Sci Tec39, 925.pdf

Abstract: Kinetics of exchange processes between the sodium ions from zeolite A and cadmium ions from solutions containing different contents of Na⁺ ions was determined by measuring changes in the concentrations of cadmium and sodium ions in both zeolite and the liquid phase during the exchange processes. The exchange kinetics were analyzed in accordance with the kinetic model derived on the basis of the second-order forward reaction between the cadmium ions from solution and the sodium ions from zeolite A and on the second-order backward reaction between sodium ions from solution and cadmium ions from zeolite A. The equilibrium cadmium uptake on zeolite A decreases with increasing concentration of sodium ions in the liquid phase. Agreement between the measured exchange kinetics and the exchange kinetics calculated by numerical solutions of the model equations shows that the exchange process takes place in accordance with the proposed model.

Keywords: Zeolite A, Ion Exchange, Sodium Ions, Cadmium Ions, Exchange Kinetics, Available Synthetic Zeolites, Natural Zeolites, Waste-Water, Cation-Exchange, Self-Diffusion, Lead Removal, Thin-Layers, Na⁺ Ions, Clinoptilolite, Cesium

? Aoyama, M., Kishino, M. and Jo, T.S. (2004), Biosorption of Cr(VI) on Japanese cedar bark. Separation Science and Technology, 39 (5), 1149-1162.

Full Text: 2004\Sep Sci Tec39, 1149.pdf

Abstract: The ability of Japanese cedar (Cryptomeria japonica) bark to remove Cr(VI) from aqueous solutions was investigated. The research parameters included the solution pH, temperature, and initial concentration of Cr(VI) in solution. The removal of Cr(VI) was highly solution pH dependent and adsorbate concentration dependent, and mainly governed by physicochemical adsorption under the weak acidic conditions studied (initial solution pHgreater than or equal to 3). However, the reduction of Cr(VI) to Cr(III) occurred extensively at low solution pH (initial solution pHless than or equal to 2). The equilibrium data at different temperatures fit well in the Langmuir isotherm model. The endothermic nature of the adsorption was confirmed by the positive value of enthalpy change (18.9 kJ mol^-1). The positive value of entropy change (65.2 J mol^-1 K^-1) suggested the increased randomness at the solid-solution interface during the adsorption. The studies showed that Japanese cedar bark can be used as a cost-effective adsorbent for the removal of Cr(VI) from wastewater.

Keywords: Removal of Cr(VI), Cryptomeria Japonica Bark, Adsorption, Langmuir Isotherm, Adsorption Thermodynamics, Wastewater Treatment, Aqueous-Solution, Hexavalent Chromium, Coniferous Leaves, Waste-Water, Removal, Adsorption, Carbon, Ions, Adsorbent, Trivalent

? Basso, M.C., Cerrella, E.G. and Cukierman, A.L. (2004), Cadmium uptake by lignocellulosic materials: Effect of lignin content. Separation Science and Technology, 39 (5), 1163-1175.

Full Text: 2004\Sep Sci Tec39, 1163.pdf

Abstract: Two lignocellulosic materials with different lignin contents (18 and 42%wt) and pure lignin (PL) were evaluated for their effectiveness in binding cadmium from dilute solutions in various concentrations. Maximum sorption capacities (X_m), determined from equilibrium isotherms by applying the Langmuir model, indicated that PL (X_m = 48.3 mg/g) and the sample with the larger lignin content (X_m = 22.2 mg/g) showed a reasonable ability to uptake cadmium. An increasing relationship between X-m and the sample’s lignin content was found, considering the tested materials together with others evaluated earlier under identical conditions. Pure lignin attained the highest value. Accordingly, the lignin content of lignocellulosic materials appears as an indicator of their ability to uptake cadmium. It could facilitate their screening for potential use as alternative cadmium sorbents from dilute wastewater. The effects of the sample’s dose and the solution pH on cadmium uptake also were investigated.

Keywords: Alternative Sorbents, Lignocellulosic Wastes, Heavy Metals Removal, Wastewater Treatment, Aqueous-Solutions, Toxic Metals, Waste-Water, Removal, Carbons, Biosorption, Thermodynamics, Biosorbents, Adsorption, Recovery

? Namasivayam, C. and Kavitha, D. (2004), Adsorptive removal of 2,4-dichlorophenol from aqueous solution by low-cost carbon from an agricultural solid waste: Coconut coir pith. Separation Science and Technology, 39 (6), 1407-1425.

Full Text: 2004\Sep Sci Tec39, 1407.pdf

Abstract: Coconut coir pith, a solid waste generated in coir fibre industries, was carbonized and used as adsorbent for the removal of 2,4-dichlorophenol (2,4-dCP) from water. Varying parameters such as agitation time, 2,4-dCP concentration, adsorbent dose, pH, and temperature were investigated. Adsorption equilibrium reached at 60, 80, 100, and 120 min for 2,4-dCP concentrations of 10, 20, 30, and 40 mg L^-1, respectively. Adsorption followed pseudo-second order kinetics. The adsorption equilibrium data moderately obeyed Langmuir and Freundlich isotherms. The adsorption capacity was found to be 19 mg g^-1 of carbon. Increase of temperature increased adsorption. Acidic pH was favorable for the adsorption of 2,4-dCP. Studies on pH effect and desorption show that both physisorption and chemisorption were involved in the adsorption process.

Keywords: 2,4-Dichlorophenol, Adsorbent, Adsorption, Chlorophenols, Coir Pith Carbon, Desorption Studies, Equilibrium, Isotherms, Kinetics, pH Effect, Phenolic-Compounds, Pseudo-Second-Order, Sorption, Water

? Liao, M.H., Wu, K.Y. and Chen, D.H. (2004), Fast adsorption of crystal violet on polyacrylic acid-bound magnetic nanoparticles. Separation Science and Technology, 39 (7), 1563-1575.

Full Text: 2004\Sep Sci Tec39, 1563.pdf

Abstract: The adsorption of crystal violet from an aqueous solution by polyacrylic acid-bound magnetic nanoparticles was studied. It was shown that the magnetic nano-adsorbent was quite efficient or the adsorption/desorption of crystal violet. In the aqueous solution of crystal violet at 25degreesC, the adsorption behavior followed the Langmuir adsorption isotherm with a maximum adsorption amount of 116 mg g^-1 and a Langmuir adsorption equilibrium constant of 0.005 L mg^-1. In the methanol solution of acetic acid (1.0-8.0%), desorption of crystal violet increased up to 100% with increasing the acetic acid concentration. The reusability of magnetic nano-adsorbent and the effects of temperature, pH, and phosphate on the adsorption of crystal violet were also investigated. Additionally, it was very noteworthy that the adsorption/desorption rate of crystal violet was quite fast (required time < 1 min) clue to the absence of pore-diffusion resistance. The developed magnetic nano-adsorbent will be useful in the removal of cationic dyes from wastewater.

Keywords: Adsorption, Polyacrylic Acid, Crystal Violet, Magnetic Nanoparticles, Nano, Malachite Green, Dye, Adsorbent, Removal, Powder, Water

? Martin-Dupont, F., Gloaguen, V., Granet, R., Guilloton, M. and Krausz, P. (2004), Chemical modifications of Douglas fir bark, a lignocellulosic by-product: Enhancement of their lead(II) binding capacities. Separation Science and Technology,