Personal Research Database

Full Text: 2007\J Haz Mat140, 369.pdf

Abstract: An application of carbon-coated TiO₂ for decomposition of methylene blue (MB) in a photocatalytic membrane reactor (PMR), coupling photocatalysis and direct contact membrane distillation (DCMD) was investigated. Moreover, photodegradation of a model pollutant in a batch reactor without membrane distillation (MD) was also examined. Carbon-modified TiO₂ catalysts containing different amount of carbon and commercially available TiO₂ (ST-01) were used in this study. The carbon-coated catalyst prepared from a mixture of ST-01 and polyvinyl alcohol in the mass ratio of 70/30 was the most effective in degradation of MB from all of the photocatalysts applied. Photodecomposition of MB on the recovered photocatalysts was lower than on the fresh ones. The photodegradation of MB in the PMR was slower than in the batch reactor, what probably resulted from shorter time of exposure of the catalyst particles to UV irradiation. The MD process could be successfully applied for separation of photocatalyst and by-products from the feed solution. (c) 2006 Elsevier B.V. All rights reserved.

Keywords: Adsorption, Alcohol, Anatase, By-Products, Byproducts, Carbon, Carbon-Coated TiO₂, Catalyst, Catalysts, Coupling, Crystallinity, Decomposition, Degradation, Direct Contact Membrane Distillation, Exposure, Feed, Irradiation, Membrane, Methylene Blue, Mixture, Model, Particles, Performance, Phenol, Photoactivity, Photocatalysis, Photocatalytic Membrane Reactor (PMR), Photodecomposition, Photodegradation, Pollutant, Reactor, Removal, Separation, TiO₂, TiO₂-Mounted Activated Carbon, UV, UV Irradiation, UV-Irradiation, Water-Purification

? Taqvi, S.I.H., Hasany, S.M. and Bhanger, M.Q. (2007), Sorption profile of Cd(II) ions onto beach sand from aqueous solutions. Journal of Hazardous Materials, 141 (1), 37-44.

Full Text: 2007\J Haz Mat141, 37.pdf

Abstract: Sorption of traces of Cd(II) ions onto beach sand is investigated as a function of nature and concentration of electrolyte (10^-4 to 10^-2 M nitric, hydrochloric and perchloric acids, pH 2-10 buffers and deionized water), shaking time 5-40 min, shaking speed 50-200 strokes/min, dosage of sand (50-1000 mg/15cm³), concentration of sorbate (1.0410^-6 to 1.910^-4 M) and temperature (293-323K). Maximum sorption of Cd(II) ions (similar to 66%) is achieved from deionized water using 300mg/15cm³ sand in 20 min. The data are successfully tested by Langmuir, Freundlich and Dubinin-Redushkevich (D-R) sorption isotherms. The values for characteristic Langmuir constants 13.310.20 mol/g and of b = (6.560.53) 10³ dm³/mol, Freundlich constants A = 2.231.16 mmol/g and 1/n = 0.70 0.05 of (D-R) constants beta = -0.0050680.000328 kJ²/mol², X-m = 46.9111.91 mu mol/g and energy E = 9.920.32 kJ/mol have been estimated. Kinetics of sorption has been studied by applying Morris-Weber, Richenberg and Lagergren equations. The sorption follows first order rate equation resulting 0.182±0.004 min^-1 The thermodynamic parameters H = 32.092.92 kJ/mol, S = 111.09.5 J/mol K and G = - 1.680.02 kJ/mol are evaluated. The influence of common ions on the sorption of Cd(II) ions is also examined. Some common ions reduce the sorption while most of the ions have very little effect. It can be concluded that beach sand may be used as an alternative for the expensive synthetic sorbents. (c) 2006 Elsevier B.V. All rights reserved.

Keywords: Acids, Adsorption, Amino, Beach Sand, Cadmium, Cd(II), Cd(II) Ions, Concentration, Dosage, Energy, Freundlich, Freundlich Constants, Isotherms, Kinetics, Langmuir, Langmuir Constants, Parameters, pH, Profile, Rate Equation, Removal, River Sand, Sand, Sorption, Sorption Isotherms, Speed, Surface, Temperature, Thermodynamic, Thermodynamic Parameters, Thermodynamics, Thermodynamics, Waste Material, Water

? Vijayaraghavan, K. and Yun, Y.S. (2007), Utilization of fermentation waste (Corynebacterium glutamicum) for biosorption of Reactive Black 5 from aqueous solution. Journal of Hazardous Materials, 141 (1), 45-52.

Full Text: 2007\J Haz Mat141, 45.pdf

Abstract: A fermentation waste, Corynebacterium glutamicum, was successfully employed as a biosorbent for Reactive Black 5 (RB5) from aqueous solution. This paper initially studied the effect of pretreatment on the biosorption capacity of C. glutamicum toward RB5, using several chemical agents, such as HCl, H₂SO₄, HNO₃, NaOH, Na₂CO₃, CaCl₂ and NaCl. Among these reagents, 0.1 M HNO₃ gave the maximum enhancement of the RB5 uptake, exhibiting 195 mg/g at pH 1 with an initial RB5 concentration of 500 mg/l. The solution pH and temperature were found to affect the biosorption capacity, and the biosorption isotherms derived at different pHs and temperatures revealed that a low pH (pH 1) and high temperature (35 °C) favored biosorption. The biosorption isotherm was well represented using three-parameter models (Redlich–Peterson and Sips) compared to two-parameter models (Langmuir and Freundlich models). As a result, high correlation coefficients and low average percentage error values were observed for three-parameter models. A maximum RB5 uptake of 419 mg/g was obtained at pH 1 and a temperature of 35 °C, according to the Langmuir model. The kinetics of the biosorption process with different initial concentrations (500–2000 mg/l) was also monitored, and the data were analyzed using pseudo-first and pseudo-second order models, with the latter describing the data well. Various thermodynamic parameters, such as ΔG°, ΔH° and ΔS°, were calculated, indicating that the present system was a spontaneous and endothermic process. The use of a 0.1 M NaOH solution successfully desorbed almost all the dye molecules from dye-loaded C. glutamicum biomass at different solid-to-liquid ratios examined.

Keywords: Adsorption, Affect, Agents, Biomass, Biosorbent, Biosorption, Capacity, Chemical, Concentration, Concentrations, Congo-Red, Correlation, Corynebacterium Glutamicum, Dye, Equilibrium, Fermentation, Freundlich, H₂, HCl, HNO₃, Isotherm, Isotherms, Kinetics, Langmuir, Metal-Ions, Model, Models, Paper, Parameters, pH, Pseudo-Second Order, Pseudo-Second-Order, Reactive Dyes, Removal, Rhizopus-Arrhizus, SO₄, Sorption, Temperature, Textile Dyes, Thermodynamic, Thermodynamic Parameters, Tree Fern, Uptake, Waste, Wastewater Treatment

? Ko, I., Davis, A.P., Kim, J.Y. and Kim, K.W. (2007), Effect of contact order on the adsorption of inorganic arsenic species onto hematite in the presence of humic acid. Journal of Hazardous Materials, 141 (1), 53-60.

Full Text: 2007\J Haz Mat141, 53.pdf

Abstract: The speciation of aqueous and adsorbed As forms of arsenic (As) is a major environmental concern in the presence of humic acid (HA). The speciation during As adsorption process by the effect of contact order were evaluated in various equilibrated ternary systems consisting of As, HA and hematite. One ternary system was composed of the preequilibrated As(III)- or As(V)HA complex, with the subsequent addition of hematite ((As-HA)-hematite system), and the other consisted of the preequilibrated HA-hematite, with the addition of As(III) or As(V) (As-(HA-hematite) system). The presence of HA led to a decrease in the As adsorption, opposite to cationic adsorption. The order of the amounts of As adsorption were found to follow as: As(V)-hematite > hematite-(As(V)-HA)> As(V)-(HA-hematite)> As(III)-hematite > hematite-(As(III)-HA)> As(III)-(HA-hematite). Free As(V) and As-HA complex were preferentially adsorbed onto the hematite surface. The immobilization of As can come from adsorbed HA on mineral surfaces, and formation of As-HA complex, following their slow kinetics. (c) 2006 Elsevier B.V. All rights reserved.

Keywords: Adsorption, Arsenic, Binary System, Complex, Environmental, Ferrihydrite, Humic, Humic Acid, Immobilization, Inorganic, Ion-Binding, Kinetics, Mechanisms, Mineral, Molecular-Weight, Natural Organic-Matter, Oxide, Particles, Sorption, Speciation, Surface, Surfaces, Ternary System

? Ru, J., Liu, H.J., Qu, J.H., Wang, A.M. and Dai, R.H. (2007), Removal of dieldrin from aqueous solution by a novel triolein-embedded composite adsorbent. Journal of Hazardous Materials, 141 (1), 61-69.

Full Text: 2007\J Haz Mat141, 61.pdf

Abstract: In this study, a novel triolein-embedded activated carbon composite adsorbent (CA-T) was prepared and applied for the adsorption and removal of dieldrin from aqueous systems. Experiments were carried out to investigate the adsorption behavior of dieldrin on CA-T, including adsorption isotherms, adsorption kinetics, the influence of initial concentration, temperature, shaking speed, pH and the addition of humic acid (HA) on adsorption. The adsorption isotherms accorded with Freundlich equation. Three kinetics models, including pseudo-first-order, pseudo-second-order and intraparticle diffusion models, were used to fit the experimental data. By comparing the correlation coefficients, it was found that both pseudo-second-order and intraparticle diffusion models were used to well describe the adsorption of dieldrin on CA-T. The addition of HA had little effect on dieldrin adsorption by CA-T. Results indicated that CA-T appeared to be a promising adsorbent for removing lipophilic dieldrin in trace amount, which was advantageous over pure granular activated carbon (GAC). The adsorption rate increased with increasing shaking speed, initial concentration and temperature, and remained almost unchanged in the pH range of 4 to 8. Thermodynamic calculations indicated that the adsorption reaction was spontaneous with a high affinity and the adsorption was an endothermic reaction.

Keywords: Activated Carbon, Activated Carbon, Adsorbent, Adsorption, Adsorption, Adsorption Isotherms, Adsorption Kinetics, Adsorption Rate, Behavior, Carbon, Cat, Composite, Composite Adsorbent, Concentration, Correlation, Dieldrin, Diffusion, Freundlich, Gac, Geographical-Distribution, Humic, Humic Acid, Isotherms, Kinetics, Lipophilic, Models, Organochlorine Contaminants, Persistent Organic Pollutants, Persistent Organic Pollutants (POPs), pH, Pops, Pseudo-Second-Order, Range, Reaction, Removal, Sediments, Semipermeable-Membrane Devices, Speed, Temperature, Trends, Triolein, Water

? Ahmad, A.A., Hameed, B.H. and Aziz, N. (2007), Adsorption of direct dye on palm ash: Kinetic and equilibrium modeling. Journal of Hazardous Materials, 141 (1), 70-76.

Full Text: 2007\J Haz Mat141, 70.pdf

Abstract: Palm ash, an agriculture waste residue from palm oil industry in Malaysia, was investigated as a replacement for the current expensive methods of removing direct blue 71 dye from an aqueous solution. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption. Equilibrium data fitted well with Freundlich model in the range of 50-600 mg/L. The equilibrium adsorption capacity of the palm ash was determined with the Langmuir equation and found to be 400.01 mg dye per gram adsorbent at 30 C. The rates of adsorption were found to conform to the pseudo second-order kinetics with good correlation. The results indicate that the palm ash could be employed as a low-cost alternative to commercial activated carbon.

Keywords: Isotherm, Direct Blue Dye, Palm Ash, Kinetics

? Argun, M.E., Dursun, S., Ozdemir, C. and Karatas, M. (2007), Heavy metal adsorption by modified oak sawdust: Thermodynamics and kinetics. Journal of Hazardous Materials, 141 (1), 77-85.

Full Text: 2007\J Haz Mat141, 77.pdf

Abstract: This paper describes the adsorption of heavy metal ions from aqueous solutions by oak (Quercus coccifera) sawdust modified by means of HCl treatment. Our study tested the removal of three heavy metals: Cu, Ni, and Cr. The optimum shaking speed, adsorbent mass, contact time, and pH were determined, and adsorption isotherms were obtained using concentrations of the metal ions ranging from 0.1 to 100 mg L^-1. The adsorption process follows pseudo-second-order reaction kinetics, as well as Langmuir and D-R adsorption isotherms. The paper discusses the thermodynamic parameters of the adsorption (the Gibbs free energy, entropy, and enthalpy). Our results demonstrate that the adsorption process was spontaneous and endothermic under natural conditions. The maximum removal efficiencies were 93% for Cu(II) at pH 4, 82% for Ni(II) at pH 8, and 84% for Cr(VI) at pH 3.

Keywords: Activated Carbon, Adsorbent, Adsorption, Adsorption Isotherms, Aqueous-Solutions, Biosorption, Chromium, Concentrations, Copper(II), Cr(VI), Energy, Entropy, HCl, Heavy Metal, Heavy Metal Ions, Heavy Metals, Ions, Isotherms, Kinetics, Langmuir, Metal, Metal Adsorption, Metal Ions, Metals, Modified, Natural, Nickel Removal, Oak, Paper, Parameters, pH, Pseudo-Second-Order, Quercus, Reaction, Reaction Kinetics, Removal, Sawdust, Speed, Sphagnum Moss Peat, Thermodynamic, Thermodynamic Parameters, Thermodynamics, Treatment, Waste-Water

? Gopal, V. and Elango, K.P. (2007), Equilibrium, kinetic and thermodynamic studies of adsorption of fluoride onto plaster of Paris. Journal of Hazardous Materials, 141 (1), 98-105.

Full Text: 2007\J Haz Mat141, 98.pdf

Abstract: Batch sorption system using plaster of Paris as an adsorbent was investigated to remove fluoride ions from aqueous solutions. The system variables studied include initial concentration of the sorbate, agitation time, adsorbent dose, pH, co-ions and temperature. The experimental data fitted well to the Freundlich and Langmuir isotherms. Thermodynamic parameters such as H, ∆S and ∆G were calculated indicating that the adsorption was a spontaneous, and exothermic. Kinetic studies reveal that the adsorption is first order. A mechanism involving three stages (external surface adsorption, intra particle diffusion and final equilibrium) has been proposed for the adsorption of F- onto plaster of Paris. XRD patterns of the adsorbent were recorded to get a better in sight into the mechanism of adsorption process.

Keywords: Adsorption, Defluoridation, Isotherms, Plaster of Paris, Activated Carbon, Basic-Dyes, Water, Adsorbent, Removal

? Huang, W.J., Cheng, B.L. and Cheng, Y.L. (2007), Adsorption of microcystin-LR by three types of activated carbon. Journal of Hazardous Materials, 141 (1), 115-122.

Full Text: 2007\J Haz Mat141, 115.pdf

Abstract: The effect of carbon properties and water characteristics on the adsorption of m-LR by activated carbon was evaluated using kinetic and isotherm tests. The results showed that both physical and chemical effects simultaneously affect the adsorption process. The activated carbon with a high ratio of mesopore and macropore volume showed an increased m-LR adsorption capacity. The micropores in carbon offer only a nominal internal surface for adsorption. The adsorption capabilities of different activated carbon generally followed their pH(zpc) values. Activated carbons with higher pH(zpc) values exhibit a neutral or positive charge under typical pH conditions, promoting m-LR adsorption on the carbon surface. The competitive effects of natural organic matter (NOM) on activated carbon were evaluated and showed that caused a reduction in the capacity of carbon for m-LR. Furthermore, when pre-chlorination was preceded by adsorption, then the residual chlorine would react with activated carbon caused a decrease in sorption capacity of m-LR, while that chlorine at normal treatment plant dosages is not effective for degrading m-LR. (c) 2006 Elsevier B.V. All rights reserved.

Keywords: Activated Carbon, Adsorption, Adsorption Capacity, Affect, Capacity, Carbon, Chemical, Chlorine, Effects, Hepatotoxin, Hepatotoxins, Isotherm, Kinetic, Kinetics, Matter, Mesopore, Microcystin-LR, Natural, Natural Organic Matter, Nom, Organic, Organic Matter, pH, Physical, Plant, Properties, Reduction, Removal, Sorption, Sorption Capacity, Surface, Surface-Chemistry, Treatment, Water, Water-Treatment Processes

? Koyuncu, H., Kul, A.R., Yıldız, N., Çalımlı, A. and Ceylan, H. (2007), Equilibrium and kinetic studies for the sorption of 3-methoxybenzaldehyde on activated kaolinites. Journal of Hazardous Materials, 141 (1), 128-139.

Full Text: 2007\J Haz Mat141, 128.pdf

Abstract: The sorption of 3-methoxybenzaldehyde on activated kaolinites has been investigated at different temperatures. Two types of activation tests were performed. The sorption equilibrium was studied by sorption isotherms in the temperature range 303-333 K for natural (untreated), thermally and acid activated kaolinites. It was shown that the isotherm shapes were not affected by temperature and activation types of kaolinite. The absorbance data at 312 nm were fitted reasonably well with the Langmuir and Freundlich isotherm models and the model parameters were determined for different temperatures. Thermodynamic quantities such as Gibbs free energy (G), the enthalpy (H) and the entropy change of sorption (S) were determined for natural, thermally and acid activated kaolinites. It was shown that the sorption processes were an endothermic reactions, controlled by physical mechanisms and spontaneously. Adsorption capacity of acid activated kaolinite for 3-methoxybenzaldehyde was higher compared to that of natural and thermally activated kaolinites at various temperatures. The adsorption and desorption rate constants (k(a) and k(d)) were obtained separately by applying a geometric approach to the first order Langmuir model. This method provided good conformity between the K from Langmuir parameters and K-geo (k(a)/k(d)) from geometric approach. (c) 2006 Elsevier B.V. All rights reserved.

Keywords: 3-Methoxybenzaldehyde, Absorbance, Acid, Activation, Adsorption, Aqueous-Solution, Capacity, Clay-Minerals, Desorption, Desorption Hysteresis, Energy, Entropy, Equilibrium, Freundlich, Freundlich Isotherm, Isotherm, Isotherm Models, Isotherms, Kaolinite, Kinetic, Langmuir, Mechanisms, Model, Models, Montmorillonite, Natural, Natural Kaolinite, Parameters, Physical, Potassium Acetate, Range, Sediments, Soils, Sorption, Sorption Equilibrium, Sorption Isotherms, Sorption Kinetics, Temperature

? Han, R.P., Zou, W.H., Yu, W.H., Cheng, S.J., Wang, Y.F. and Shi, J. (2007), Biosorption of Methylene blue from aqueous solution by fallen phoenix tree’s leaves. Journal of Hazardous Materials, 141 (1), 156-162.

Full Text: 2007\J Haz Mat141, 156.pdf

Abstract A new adsorbent, the fallen phoenix tree’s leaf, has been investigated in order to remove methylene blue (MB) from aqueous solutions. Variables of the system, inc luding contact time, leaf dose, solution pH, salt concentration and initial MB concetntrtion, were adopted to study their effects on MB biosorption. The results showed that as the dose of leaf increased, the percentage of MB sorption increased accordingly. There was no significant difference about the quantity of MB adsorbed onto leaf as the pH was within the range 4.5 to 10.0. The salt concentration has negative effect on MB removal. The equilibrium data were analyzed using the Langmuir and the Freundlich isotherms. The results of non-linear regressive analysis are that the Langmuir isotherm are better fit than the Freundlich isotherm at different temperature according to the values of determined coeffic ients (R²) and Chi−square statistic (SS). The Langmuir monolayer saturation capacities of MB adsorbed onto leaf are 80.9, 83.8, 89.7 mg g−1 at 295 K, 309 K and 323 K, respectively. Using the equilibrium concentration contants obtained at different temperatures, various thermodynamic parameters, such as ∆G0, ∆H0 and ∆S0, have been calculated. The thermodynamics parameters of MB/leaf system indicate spontaneous and endothermic process. It was concluded that an increase in temperature be advantage to adsorb MB onto leaf.

Keywords: Phoenix Tree’s Leaf, Biosorption, Methylene Blue, Equilibrium, Thermodynamic

? Li, Q., Zhai, J.P., Zhang, W.Y., Wang, M.M. and Zhou, J. (2007), Kinetic studies of adsorption of Pb(II), Cr(III) and Cu(II) from aqueous solution by sawdust and modified peanut husk. Journal of Hazardous Materials, 141 (1), 163-167.

Full Text: 2007\J Haz Mat141, 163.pdf

Abstract: Sawdust and modified peanut husk were used as adsorbents to remove Pb(II), Cr(III) and Cu(II) from aqueous solution. Results of kinetic experiments demonstrated that the adsorption was effective and rapid. Three different kinds of kinetic models (i.e., intraparticular diffusion model, Lagergren-first-order and second-order equations) were used to investigate the adsorption mechanisms. The adsorption of heavy metals on sawdust and modified peanut husk is not an intraparticular diffusion control. The kinetic adsorption data can be described by the Second-order equation and the adsorption might be a rate-limiting control. The suitability of the adsorbent was tested by fitting the adsorption data with Langmuir and Freundlich isotherms, which gave good fits with both isotherms.

Keywords: Adsorbent, Adsorbents, Adsorption, Carbon, Control, Diffusion, Equilibrium, Freundlich, Heavy Metals, Isotherm, Isotherms, Kinetic, Kinetic Models, Kinetics, Langmuir, Mechanisms, Metals, Methylene-Blue, Model, Models, Modified, Modified Peanut Husk, Pb(II), Peanut, Phenol, Rate Limiting, Removal, Sawdust, Second-Order Equation, Seed Coat, Waste-Water

? Deliyanni, E.A., Peleka, E.N. and Matis, K.A. (2007), Removal of zinc ion from water by sorption onto iron-based nanoadsorbent. Journal of Hazardous Materials, 141 (1), 176-184.

Full Text: 2007\J Haz Mat141, 176.pdf

Abstract: Batch and column experiments were conducted to investigate zinc removal from dilute aqueous solution (i.e. effluent) by sorption onto synthetic nanocrystalline akaganeite. Due to favorite characteristics, this material was shown to be a promising inorganic adsorbent prepared in the laboratory, following a new method of synthesis-previously published. The effects of adsorbent amount, zinc concentration, solution pH value, ionic strength and temperature variation on the treatment process were mainly investigated during this study. Typical adsorption models were determined searching the mechanism of sorption while the bed depth-service time model was applied to column (with granular material) experiments. (c) 2006 Elsevier B.V. All rights reserved.

Keywords: Adsorbent, Adsorption, Akaganeite, Akaganeite, Aqueous-Solutions, Biosorption, Concentration, Copper, Effects, Effluent, Equilibrium, Ferric Hydroxide GFH, Fixed-Beds, Heavy Metals, Industrial Wastewater, Inorganic, Ion, Ionic Strength, Kinetics, Mechanism, Model, Models, Nanocrystalline, Nanocrystals, pH, Removal, Searching, Solution pH, Sorption, Temperature, Treatment, Water, Zinc

? Lee, J.W., Yang, T.H., Shim, W.G., Kwon, T.O. and Moon, I.S. (2007), Equilibria and dynamics of liquid-phase trinitrotoluene adsorption on granular activated carbon: Effect of temperature and pH. Journal of Hazardous Materials, 141 (1), 185-192.

Full Text: 2007\J Haz Mat141, 185.pdf

Abstract: Environmental regulations for removal of trinitrotoluene (TNT) from wastewater have steadily become more stringent. This study focuses on the adsorption equilibrium, kinetics, and column dynamics of TNT on heterogeneous activated carbon. Adsorption equilibrium data obtained in terms of temperature (298.15, 313.15 and 323.15 K) and pH (3, 8 and 10) were correlated by the Langmuir equation. In addition, the adsorption energy distribution functions which describe heterogeneous characteristics of porous solid sorbents were calculated by using the generalized nonlinear regularization method. Adsorption breakthrough curves were studied in activated column under various operating conditions such as temperature, pH, concentration, flow rate, and column length. We found that the effect of pH on adsorption breakthrough curves was considerably higher than other operating conditions. An adsorption model was formulated by employing the surface diffusion model inside the activated carbon particles. The model equation that was solved numerically by an orthogonal collocation method successfully simulated the adsorption breakthrough curves. (c) 2006 Elsevier B.V. All rights reserved.

Keywords: Activated Carbon, Adsorption, Adsorption Energy Distribution, Adsorption Equilibrium, Carbon, Cephalosporin C, Concentration, Desorption, Diffusion, Distribution, Dynamics, Energy, Equilibrium, Flow, Heterogeneous, Heterogeneous Activated Carbon, Kinetics, Langmuir, Langmuir Equation, Model, Operating Conditions, Particles, pH, Phenol, Porous, Removal, Surface, Temperature, TNT, Trinitrotoluene, Waste, Wastewater, Water

? Liu, Y.G., Zhou, M., Zeng, G.M., Li, X., Xu, W.H. and Fan, T. (2007), Effect of solids concentration on removal of heavy metals from mine tailings via bioleaching. Journal of Hazardous Materials,