Abstract
Problem statement: Heavy metals have been one of hazardous components in industrial effluents that can be damaged on the environment by discharging uncontrolled wastewater. The aims of this investigation were biosorption of Cd (II) ions onto pretreated dried activated sludge and determination of kinetic and isotherm of biosorption. Approach: Activated sludge was obtained from Tehran municipal wastewater treatment plant. Activated Sludge was dried and used for biosorbtion of Cd (II) ions from aqueous solution. Dried Activated Sluge (DAS) was pretreated with three different solutions (H2O2, NaOH and ethanol). Biosorption capacity of different types of DAS to remove Cd (II) ions was investigated as a function of Cd (II) concentrations at variable initial Cd (II) concentrations between 10 and 500 mg L−1 with a DAS particle size 0.2-0.3 mm using batch biosorption experiments. Results: Biosorption of Cd (II) by Dried Activated Sludge (DAS) was found to perform better than the others after pretreatment with H2O2. The maximum biosorption capacity was given 256.41, 217.39, 212.77 and 204.08 mg g−1 for the H2O2, NaOH; Ethanol pretreated and untreated DAS, respectively. The pseudo-second order kinetic model was found to be more suitable than the pseudo-first order kinetic model to correlate the experimental data for all types of DAS (R2>0.9). The Freundlich isotherm was found to fit the experimental data slightly better than the Langmuir isotherm model for all pretreated and untreated DAS (R2>0.99). Conclusion: It can be concluded that pretreatment DAS yield higher Cd (II) biosorption capacity, especially DAS that pretreated with H2O2.
Highlights
Heavy metal ions present in some industrial effluents have detrimental effects on the environments such as water and soil[1,2,3,4,5]
Cadmium (II) ion concentration was 50 mg L−1 in this experiment while the Dried Activated Sludge (DAS) concentration and pH were constant at 1gl-1 and 4, respectively
To investigate initial effects of Cd (II) ion concentration a set of experiments was designed with varied ion concentrations between 10 and 500 mg L−1 while the different pretreated DAS concentration and pH were constant at 1 gL−1 and pH 4, respectively
Summary
Heavy metal ions present in some industrial effluents have detrimental effects on the environments such as water and soil[1,2,3,4,5]. Passive binding of heavy metal ions was defined as biosorption and active binding on the cell wall of live organisms defined as bioaccumulation[1,5,10]. Waste activated sludge as a biomaterial, for removal of heavy metal ions can be used because of low cost and its availability[1,11,12,13,14,15]. Bacterial biomass in activated sludge is a natural biosorbent for heavy metal ions because of its negative cell wall charge. Cell wall of bacteria consists of polymeric substances that contain negatively charged functional groups, such as carboxyl, phosphate and Corresponding Author: Ahmad Jonidi Jafari, Department of Environmental Health, School of Public Health, Iran University of Medical Sciences, Argentina Sq., Alvand St., No 52, P.O. Box 15875-4199 Tehran, Iran Tel: +989367254535
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