Personal Research Database

Full Text: 2009\J Haz Mat171, 386.pdf

Abstract: Wine-processing waste sludge (WPWS) has been shown to have powerful potential for sorption of some heavy metals (i.e., chromium, lead and nickel) in single-component aqueous solutions. But although most industrial wastewater contains two or more toxic metals, there are few sorption studies on multicomponent metals by WPWS. This study has two goals: (i) conduct competitive adsorption using Cr, Cu and Zn as sorbates and examine their interaction in binary or ternary systems: and (II) determine the effects of temperature on the kinetic sorption reaction. The sludge tested contained a high amount of organic matter (38%) and had a high cation exchange capacity (CEC, 255 cmol(c) kg^-1). Infrared analysis reveals that carboxyl is the main functional group in this WPWS. The C-13 NMR determination indicates alkyl-C and carboxyl-C are major organic functional groups. At steady state, there are about 40.4% (Cr), 35.0% (Cu) and 21.9% (Zn) sorbed in the initial 6.12 mM of single-component solutions. Only pseudo-second-order sorption kinetic model successfully describes the kinetics of sorption for all experimental metals. The rate constants, k(2), of Cr, Cu and Zn in single-component solutions are 0.016, 0.030 and 0.154 g mg^-1 min^-1, respectively. The sorption of metals by WPWS in this competitive system shows the trend: Cr > Cu > Zn. Ions of charge, hydrated radius and electronic configuration are main factors affecting sorption capacity. The least sorption for Zn in this competitive system can be attributed to its full orbital and largest hydrated radius. Though the effect of temperature on Zn sorption is insignificant, high temperature favors the other metallic sorptions, in particular for Cr. However, the Cr sorption is lower than Cu at 10°C. The Cr sorption by WPWS can be higher than that of Cu at 30° and 50°C. (C) 2009 Elsevier B.V. All rights reserved.

Keywords: Adsorption, Analysis, Aqueous Solutions, Aqueous-Solutions, Biosorption, C-13, Cadmium Ions, Capacity, Cation, Cation Exchange, Cec, Charge, Chromium, Competitive, Competitive Adsorption, Competitive Sorption, Copper, Cu, Experimental, Fly Ashes, Functional Group, Functional Groups, Heavy Metals, Heavy-Metals, Industrial Wastewater, Interaction, Kinetic, Kinetic Model, Kinetic Sorption, Kinetics, Lead, Mechanism, Metals, Model, Nickel, NMR, NOV, Organic, Organic Matter, Potential, Pseudo Second Order, Pseudo-Second-Order, Rate Constants, Rights, Selectivity, Sludge, Soils, Solutions, Sorption, Sorption Capacity, Sorption Studies, State, Steady State, Systems, Temperature, Toxic, Toxic Metals, Trend, Waste, Waste Sludge, Wastewater, Zinc

? Ely, A., Baudu, M., Basly, J.P. and Kankou, M.O.S.O. (2009), Copper and nitrophenol pollutants removal by Na-montmorillonite/alginate microcapsules. Journal of Hazardous Materials, 171 (1-3), 405-409.

Full Text: 2009\J Haz Mat171, 405.pdf

Abstract: The use of renewable bioresources allows the development of low cost adsorbents that are versatile. In the present paper, the affinity and the removal capacity of montmorillonite/alginate microcapsules for a hydrophobic organic pollutant (4-nitrophenol) and an inorganic pollutant (copper) were evaluated. The physicochemical processes through sorption and kinetic experiments under different ratios of montmorillonite vs. alginate and initial contaminant concentrations were investigated. The total weight loss and diameter decrease during the drying process were 90-96% and 64%, respectively. A significant decrease in beads diameter, related to water elimination, has been observed during the first 24 h. Structural modifications that occur during the drying process were evaluated using thermal analysis. From correlation coefficients. the second-order equation depicts properly the adsorption of copper by the microbeads adsorption capacity increases to saturation with time: 3 and 6 h were needed to reach equilibrium on wet and dry mixed microcapsules. The pseudo-second order model properly depicts the adsorption process of 4-NP onto Na-mont and (Na-mont/SA) mixed rnicrocapsules but failed to reproduce the data observed for the alginate beads. Isotherms data were fitted with good correlation using the Langmuir model: alginate and montmorillonite adsorption capacities (q(m)/wet beads) agree with those obtained by various studies. (C) 2009 Elsevier B.V. All rights reserved.

Keywords: 4-Nitrophenol, Activated Carbon, Adsorbents, Adsorption, Adsorption, Adsorption Capacities, Adsorption Capacity, Alginate, Analysis, Beads, Biosorption, Calcium Alginate Beads, Capacity, Chitosan, Contaminant, Copper, Correlation, Cost, Data, Dehydration, Development, Encapsulation, Equilibrium, Experiments, First, Gel Beads, Heavy-Metals, Isotherms, Kinetic, Langmuir, Langmuir Model, Low Cost, Low Cost Adsorbents, Model, Montmorillonite, Na-Montmorillonite (Na-Mont), NOV, Organic, Organic Pollutant, Paranitrophenol (4-Np), Pervaporation, Pollutants, Pseudo Second Order, Pseudo-Second Order, Pseudo-Second Order Model, Pseudo-Second-Order, Removal, Rights, Saturation, Second Order, Second-Order, Second-Order Equation, Sodium Alginate, Sodium Alginate (SA), Sorption, Thermal Analysis, Water

? Mohapatra, M., Rout, K. and Anand, S. (2009), Synthesis of Mg(II) doped goethite and its cation sorption behaviour. Journal of Hazardous Materials, 171 (1-3), 417-423.

Full Text: 2009\J Haz Mat171, 417.pdf

Abstract: Modified goethite samples were prepared with Mg(II) content varying in the range of 0-1.36%. A typical TEM of Mg(II) doped sample showed needle shaped goethite particles having 10-30 nm width and 100-400 nm length. Sorption studies of cations namely Pb(II), Cu(II), Cd(II), Zn(II) and Fe(III) were conducted onto the Mg(II) doped modified goethite surface. Goethite doping with 0.18 M Mg (CMg2) showed better sorption capacity for Pb(II), Cu(II) and Cd(II). Therefore, the effect of contact time, solution pH, sorbate and sorbent concentrations on the sorption of various metal ions was studied on this sample in batch experiments. The time data fitted to pseudo-second-order kinetics for all the metal ions. Sorption on GMg(2) sample for the metal ions increased with the increase in pH from 2 to 4. The isothermic data showed good fit to both Langmuir and Freundlich isotherms except for Cd(II) which followed only the later model. The sorption capacities with respect to Pb(II), Cd(II), Zn(II), Cu(B) and Fe(III) were found to be 87.7,153.25, 86.25, 33.4 and 72.5 mg/g respectively. The results of sorption studies on GMg(2) from binary and ternary solutions have also been presented. The XRD patterns of metal ion loaded GMg(2) samples confirmed that metal ion adsorption resulted in shifting of d-values/altering of relative intensity (RI) of major planes of goethite. (C) 2009 Elsevier B.V. All rights reserved.

Keywords: Adsorption, Batch, Batch Experiments, Behaviour, Capacity, Cation, Cation Sorption, Cations, Cd, Cd(II), Cu, Cu(II), Data, Experiments, Fe(III), Freundlich, Freundlich Isotherms, Goethite, Ions, Isotherms, Kinetics, Langmuir, Langmuir and Freundlich Isotherms, Lead, Length, Metal, Metal Ion, Metal Ions, Metal-Ions, Mg(II) Doped Goethite, Model, Modified, NOV, Particles, Pb, Pb(II), pH, Pseudo Second Order, Pseudo Second Order Kinetics, Pseudo-Second-Order, Pseudo-Second-Order Kinetics, Rights, Solution, Solutions, Sorbate, Sorbent, Sorption, Sorption Capacity, Sorption Studies, Surface, Synthesis, TEM, XRD, Zinc, Zn(II)

? Sari, A. and Tuzen, M. (2009), Removal of mercury(II) from aqueous solution using moss (Drepanocladus revolvens) biomass: Equilibrium, thermodynamic and kinetic studies. Journal of Hazardous Materials, 171 (1-3), 500-507.

Full Text: 2009\J Haz Mat171, 500.pdf

Abstract: The equilibrium, thermodynamics and kinetics of the biosorption of Hg(II) onto moss (Drepanocladus revolvens) biomass from aqueous solution were investigated. Optimum experimental parameters were determined to be pH 5.5, contact time 60 min, biomass concentration 4 gL^-1 of solution, and temperature 20°C. From the Langmuir model the maximum biosorption capacity of the moss biomass was found to be 94.4 mg g^-1. The mean free energy value (10.2 kJ mol^-1) evaluated by using the Dubinin-Radushkevich (D-R) model indicated that the biosorption of mercury ions onto D. revolvens was taken place by chemical ion-exchange. The kinetic studies indicated that the biosorption process of mercury ions followed well pseudo-second-order model. The calculated thermodynamic parameters (ΔGº, ΔSº, ΔHº) showed the biosorption to be exothermic and spontaneous with decreased randomness at the solid-solution interface. The recovery of the Hg(II) from D. revolvens biomass was found to be 99% using 1 M HCl. It was concluded that the D. revolvens biomass can be used as biosorbent for the treatment of wastewaters containing Hg(II) ions. (C) 2009 Elsevier B.V. All rights reserved.

Keywords: Activated Carbon, Aqueous Solution, Aspergillus-niger, Biomass, Biosorbent, Biosorption, Capacity, Chemical, Concentration, D. revolvens, Energy, Equilibrium, Exothermic, Experimental, Fontinalis-Antipyretica, Fungal Biomass, Heavy-Metals, Hg(II), Hg(II) Ions, Inorganic Mercury, Interface, Ion Exchange, Ion-Exchange, Ionexchange, Ions, Isotherm, Kinetic, Kinetic Studies, Kinetics, Langmuir, Langmuir Model, Macroalga Cystoseira-Baccata, Mercury, Mercury Ion, Mercury(II), Microalgae Chlamydomonas-Reinhardtii, Model, NOV, pH, Pseudo Second Order, Pseudo-Second-Order, Pseudo-Second-Order Model, Randomness, Recovery, Removal, Rights, Solution, Sphagnum Moss, Spontaneous, Temperature, Thermodynamic, Thermodynamic Parameters, Thermodynamics, Treatment, Value, Waste-Water, Wastewaters

? Guerra, D.L., Pinto, A.A., Viana, R.R. and Airoldi, C. (2009), Layer silicates modified with 1,4-bis(3-aminopropyl)piperazine for the removal of Th(IV), U(VI) and Eu(III) from aqueous media. Journal of Hazardous Materials, 171 (1-3), 514-523.

Full Text: 2009\J Haz Mat171, 514.pdf

Abstract: Natural montmorillonite (M) and synthetic kanemite (K) have been functionalized with 1,4-bis(3-aminopropyl)piperazine reacted with methylacrylate to yield new inorganic-organic chelating materials. The original and modified materials were characterized by X-ray diffractometry, textural analysis, SEM and nuclear magnetic nuclei of carbon-13 and silicon-29. The chemically modified clay samples (M-APPMA and K-APPMA) showed modification of its physical-chemical properties including: specific area 45.0 m² g^-1 (M) to 978.8 m² g^-1 (M-APPMA) and 23.5 m² g^-1 (K) to 898.9 m² g^-1 (K-APPMA). The ability of these materials to remove thorium(IV), uranyl(VI) and europium(III) from aqueous solution was followed by a series of adsorption isotherms, which were fitted to non-linear Sips adsorption isotherm model. To achieve the best adsorption conditions the influence of pH and variation of metal concentration were investigated. The energetic effects (H°_int, G°_int and S°_int) caused by metal ions adsorption were determined through calorimetric titrations. (C) 2009 Published by Elsevier B.V.

Keywords: Acid Activation, Adsorption, Adsorption Isotherm, Adsorption Isotherms, Adsorption Process, Aqueous, Clay, Elsevier, Gel, Hexagonal Mesoporous Silicas, Intercalation, Ionic-Strength, Isotherm, Isotherms, Kanemite, Metal, Metal Ions, Metals Uptake, Montmorillonite, pH, Radionuclide, Removal, Sem, Sorption, Thermochemical Data, Thermodynamic, Waste

? Yetilmezsoy, K., Demirel, S. and Vanderbei, R.J. (2009), Response surface modeling of Pb(II) removal from aqueous solution by Pistacia vera L.: Box-Behnken experimental design. Journal of Hazardous Materials, 171 (1-3), 551-562.

Full Text: 2009\J Haz Mat171, 551.pdf

Abstract: A three factor, three-level Box-Behnken experimental design combining with response surface modeling (RSM) and quadratic programming (QP) was employed for maximizing Pb(II) removal from aqueous solution by Antep pistachio (Pistacia vera L) shells based on 17 different experimental data obtained in a lab-scale batch study. Three independent variables (initial pH of solution (pH(0)) ranging from 2.0 to 5.5, initial concentration of Pb(II) ions (C(0)) ranging from 5 to 50 ppm, and contact time (t(c)) ranging from 5 to 120 min) were consecutively coded as x(1), x(2) and x(3) at three levels (-1, 0 and 1), and a second-order polynomial regression equation was then derived to predict responses. The significance of independent variables and their interactions were tested by means of the analysis of variance (ANOVA) with 95% confidence limits (alpha = 0.05). The standardized effects of the independent variables and their interactions on the dependent variable were also investigated by preparing a Pareto chart. The optimum values of the selected variables were obtained by solving the quadratic regression model, as well as by analysing the response surface contour plots. The optimum coded values of three test variables were computed as x(1) = 0.125, x(2) = 0.707, and x(3) = 0.107 by using a LOQO, AMPL optimization algorithm. The experimental conditions at this global point were determined to be pH(0) = 3.97, C(0) = 43.4 ppm, and t(c) = 68.7 min, and the corresponding Pb(II) removal efficiency was found to be about 100%. (C) 2009 Elsevier B.V. All rights reserved.

Keywords: Acid, Adsorption, Adsorption, Analysis, Antep Pistachio Shells, Batch Study, Box-Behnken Experimental Design, Design, Enhanced Removal, Experimental, Ions, Lead Removal, Metal-Ions, Methodology, Model, Modeling, Neural-Network, Optimization, Pb(II), Pb(II) Ions, Pb(II) Removal, pH, Precipitation, Removal, Response Surface Modeling, RSM, Shells, Waste-Water

? Wu, Z.S. and Li, C. (2009), Kinetics and thermodynamics of beta-carotene and chlorophyll adsorption onto acid-activated bentonite from Xinjiang in xylene solution. Journal of Hazardous Materials, 171 (1-3), 582-587.

Full Text: 2009\J Haz Mat171, 582.pdf

Abstract: The kinetics and thermodynamics of beta-carotene and chlorophyll adsorption from xylene solution onto acid-activated bentonite (AAB) within the temperature range 65-95°C were investigated. Adsorption of beta-carotene was described well with the Langmuir isotherm, whereas chlorophyll adsorption was determined well with the Freundlich isotherm, and the experimental data on chlorophyll adsorption were also fitted by the Langmuir isotherm to a certain extent, as reflected by correlation coefficients (R-2) over 0.9865. In addition, the adsorption of beta-carotene and chlorophyll onto AAB are favorable. The pseudo-second-order model was found to explain the kinetics of adsorption of both pigments more effectively. increase of temperature enhanced the adsorption rate and equilibrium adsorption capacity of beta-carotene and chlorophyll on AAB. The activation energy for the sorption of beta-carotene and chlorophyll on AAB was 19.808 kJ/mol and 16.475 kJ/mol, respectively. The thermodynamic parameters H°, S° and G°, computed from K-F of the adsorption isotherm constant, were 21.766 kJ/mol, 92.244J/K moll and -9.554 kJ/mol respectively for the adsorption of beta-carotene on AAB at 65°C, and for adsorption of chlorophyll on AAB at 65°C were 31.051 kJ/mol, 93.549J/K mol and -0.729 kJ/mol, respectively. The adsorption of beta-carotene and chlorophyll in xylene solution on AAB was a spontaneous and endothermic process with increasing in the randomness at the solid-solution interface. (C) 2009 Elsevier B.V. All rights reserved.

Keywords: Acid-Activated Bentonite, Activation, Activation Energy, Adsorption, Adsorption Capacity, Adsorption Isotherm, Adsorption Rate, Bentonite, Beta Carotene, Beta-Carotene, Bleaching Earth, Capacity, Chlorophyll, Correlation, Data, Decolorization, Endothermic, Energy, Equilibrium, Experimental, Freundlich, Freundlich Isotherm, Interface, Isotherm, Kinetics, Kinetics and Thermodynamics, Kinetics of Adsorption, Langmuir, Langmuir Isotherm, Mechanism, Model, Montmorillonite Clay, NOV, Palm Oil, Pseudo Second Order, Pseudo-Second-Order, Pseudo-Second-Order Model, Randomness, Rights, Solution, Sorption, Spontaneous, Temperature, Thermodynamic, Thermodynamic Parameters, Thermodynamics, Vegetable-Oils, Xylene, Xylene Solution

? Ozmen, M., Can, K., Akin, I., Arslan, G., Tor, A., Cengeloglu, Y. and Ersoz, M. (2009), Surface modification of glass beads with glutaraldehyde: Characterization and their adsorption property for metal ions. Journal of Hazardous Materials, 171 (1-3), 594-600.

Full Text: 2009\J Haz Mat171, 594.pdf

Abstract: In this study, a new material that adsorbs the metal ions was prepared by modification of the glass beads surfaces with glutaraldehyde. First, the glass beads were etched with 4 M NaOH solution. Then, they were reacted with 3-aminopropyl-triethoxysilane (APTES). Finally, silanized glass beads were treated with 25% of glutaraldehyde solution. The characterization studies by using Fourier Transform Infrared Spectroscopy (FT-IR),Thermal Gravimetric Analysis (TGA), elemental analysis and Scanning Electron Microscopy (SEM) indicated that modification of the glass bead surfaces was successfully performed. The adsorption studies exhibited that the modified glass beads could be efficiently used for the removal of the metal cations and anion (chromate ion) from aqueous solutions via chelation and ion-exchange mechanisms. For both Pb(II) and Cr(VI), selected as model ions, the adsorption equilibrium was achieved in 60 min and adsorption of both ions followed the second-order kinetic model. It was found that the sorption data was better represented by the Freundlich isotherm in comparison to the Langmuir and Redlich-Peterson isotherm models. The maximum adsorption capacities for Pb(II) and Cr(VI) were 9.947 and 11.571 mg/g, respectively. The regeneration studies also showed that modified glass beads could be re-used for the adsorption of Pb(II) and Cr(VI) from aqueous solutions over three cycles. (C) 2009 Elsevier B.V. All rights reserved.

Keywords: Adsorption, Adsorption Capacities, Adsorption Equilibrium, Analysis, Aptes, Aqueous Solutions, Aqueous-Solutions, Beads, Characterization, Chelation, Chromate, Comparison, Cr(VI), Data, Equilibrium, Exchange Membranes, Freundlich, Freundlich Isotherm, Glass, Glass Beads, Glutaraldehyde, Heavy Metal Ions, Hexavalent Chromium, Ion Exchange, Ion-Exchange, Ionexchange, Ions, Isotherm, Isotherm Models, Kinetic, Kinetic Model, Langmuir, Magnetic Nano-Adsorbent, Mechanisms, Metal, Metal Ions, Model, Models, Modification, Modified, NaOH, NOV, Pb(II), Property, Redlich-Peterson, Redlich-Peterson Isotherm, Regeneration, Removal, Rights, Second Order, Second-Order, SEM, Silica-Gel, Solution, Solutions, Sorption, Surface Modification, Surfaces, TGA, Transport

? Zhao, Y.J., Chen, Y., Li, M.S., Zhou, S.Y., Xue, A.L. and Xing, W.H. (2009), Adsorption of Hg²⁺ from aqueous solution onto polyacrylamide/attapulgite. Journal of Hazardous Materials, 171 (1-3), 640-646.

Full Text: 2009\J Haz Mat171, 640.pdf

Abstract: Polyacrylamide/attapulgite (PAM/ATP) was prepared by the solution polymerization of acrylamide (AM) onto gamma-methacryloxypropyl trimethoxy silane (KH-570)-modifled attapulgite (ATP). PAM/ATP was characterized using Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The effects of contact time, adsorbent dosage, and pH of the initial solution on the adsorption capacities for Hg²⁺ were investigated. The adsorption process was rapid; 88% of adsorption occurred within 5 min and equilibrium was achieved at around 40 min. The equilibrium data fitted the Langmuir sorption isotherms well, and the maximum adsorption capacity of Hg²⁺ onto PAM/ATP was found to be 192.5 mg g(-1). The adsorption kinetics of PAM/ATP fitted a pseudo-second-order kinetic model. Our results suggest that chemisorption processes could be the rate-limiting steps in the process of Hg²⁺ adsorption. Hg²⁺ adsorbed onto PAM/ATP could be effectively desorbed in hot acetic acid solution, and the adsorption capacity of the regenerated adsorbents could still be maintained at 95% by the sixth cycle. (C) 2009 Elsevier B.V. All rights reserved.

Keywords: Activated Palygorskite, Adsorbent, Adsorbent Dosage, Adsorbents, Adsorption, Adsorption Capacities, Adsorption Capacity, Adsorption Kinetics, Am, Aqueous Solution, Atp, Attapulgite, Capacity, Chemisorption, Chitosan Beads, Data, Equilibrium, FTIR, Grafted Attapulgite, Heavy-Metals, Ions, Isotherm, Isotherms, Kinetic, Kinetic Model, Kinetics, Langmuir, Mercury Adsorption, Mercury Removal, Model, NOV, pH, Polyacrylamide, Polymerization, Pseudo Second Order, Pseudo-Second-Order, Pseudo-Second-Order Kinetic Model, Rights, Selective Adsorption, Solution, Sorption, Sorption Isotherms, Spectroscopy, Transfer Radical Polymerization, Waste-Water, X-Ray, X-Ray Photoelectron Spectroscopy, XPS

? Türk, T., Alp, İ. and Deveci, H. (2009), Adsorption of As(V) from water using Mg-Fe-based hydrotalcite (FeHT). Journal of Hazardous Materials, 171 (1-3), 665-670.

Full Text: 2009\J Haz Mat171, 665.pdf

Abstract: This paper describes a study of the sorptive removal of arsenate (As(V)) from aqueous solutions by synthetically prepared Mg-Fe-based hydrotalcites (FeHT) as layered double hydroxide (LDH) adsorbents. The synthesis of Fe³⁺-substituted hydrotalcites (FeHT) with the chemical formula [Mg(II)₆Fe(II)₂(OH)₁₆]²⁺ [CO₃×yH₂O]^2- was achieved by a co-precipitation method. The reaction products were characterized by powder X-ray diffraction analysis. The influences of solution pH, initial arsenate (As(V)) concentration, and sorbent concentration were investigated in multiple kinetic runs. The adsorption rates and isotherms were investigated in batch experiments. The pseudo-first-order and second-order kinetic models were tested and the latter was found to fit better to the experimental data. Langmuir and Freundlich isotherms were used to describe the adsorption data from equilibrium experiments. The results have shown that FeHT has a high arsenate removal efficiency, with the ability to reduce the concentration of arsenate in the aqueous Solution from an initial value of 330 mu g/l to <10 mu g/l (i.e. below the limit value specified by WHO). (C) 2009 Elsevier B.V. All rights reserved.

Keywords: Adsorbents, Adsorption, Analysis, Aqueous Solutions, Aqueous-Solutions, Arsenate, Arsenate Removal, Arsenic Removal, As(V), Batch, Batch Experiments, Chemical, Clay, Concentration, Coprecipitation, Data, Double Hydroxide, Efficiency, Equilibrium, Experimental, Experiments, Freundlich, Freundlich Isotherms, Hydrotalcite, Hydrotalcites, Hydroxide, Iron, Isotherm, Isotherms, Kinetic, Kinetic Models, Kinetics, Langmuir, Langmuir and Freundlich Isotherms, Layered Double Hydroxide, Layered Double Hydroxide (LDH), Layered Double Hydroxides, Mg-Fe-Based Hydrotalcites (FEHT), Models, NOV, pH, Pseudo First Order, Pseudo-First-Order, Rates, Red, Removal, Removal Efficiency, Rights, Second Order, Second-Order, Selenium, Solution, Solutions, Sorbent, Synthesis, Value, Water, X-Ray, X-Ray Diffraction

? Božić, D., Stanković, V., Gorgievski, M., Bogdanović, G. and Kovačević, R. (2009), Adsorption of heavy metal ions by sawdust of deciduous trees. Journal of Hazardous Materials, 171 (1-3), 684-692.

Full Text: 2009\J Haz Mat171, 684.pdf

Abstract: The adsorption of heavy metal ions from synthetic solutions was performed using sawdust of beech, linden and poplar trees. The adsorption depends on the process time, pH of the solution, type of ions, initial concentration of metals and the sawdust concentration in suspension. The kinetics of adsorption was relatively fast, reaching equilibrium for less than 20 min. The adsorption equilibrium follows Langmuir adsorption model. The ion exchange mechanism was confirmed assuming that the alkali-earth metals from the adsorbent are substituted by heavy metal ions and protons. On lowering the initial pH, the adsorption capacity decreased, achieving a zero value at a pH close to unity. The maximum adsorption capacity (7-8 mg g^-1 of sawdust) was achieved at a pH between 3.5 and 5 for all the studied kinds of sawdust. The initial concentration of the adsorbate and the concentration of sawdust strongly affect the process. No influence of particles size was evidenced. A degree of adsorption higher than 80% can be achieved for Cu²⁺ ions but it is very low for Fe²⁺ ions, not exceeding 10%. (C) 2009 Elsevier B.V. All rights reserved.

Keywords: Adsorbent, Adsorption, Adsorption Capacity, Adsorption Equilibrium, Adsorption Isotherms, Adsorption Kinetics, Aqueous-Solutions, Biosorbent, Biosorption, Biosorption, Capacity, Concentration, Copper, Cu(II), Cu²⁺, Equilibrium, Heavy Metal, Heavy Metal Ions, Heavy Metals, Industrial Effluents, Ion Exchange, Ion-Exchange, Ions, Kinetics, Kinetics of Adsorption, Langmuir, Mechanism, Metal, Metal Ions, Metals, Model, NOV, Particles, pH, Removal, Rights, Sawdust, Size, Solution, Solutions, Sorption, Suspension, Trees, Value, Waste-Water

? Bulut, Y., Akçay, G., Elma, D. and Serhatlı, I.E. (2009), Synthesis of clay-based superabsorbent composite and its sorption capability. Journal of Hazardous Materials,