Abstract
Removal of Cd2+ and Zn2+ ions from single and binary solutions by dried activated sludge was studied in batch experiments. It was shown that the metal removal is a rapid process significantly influenced by solution pH. Maximum uptake of both Cd and Zn was reached at pH 6.0 and negligible uptake was observed at pH 2.0. The Langmuir isotherm was found to well represent the measured equilibrium sorption data in single metal systems and the maximum sorption capacities Qmax of the activated sludge (d.w.), calculated from Langmuir model were 540 ± 16 μmol/g for Zn2+ and 510 ± 17 μmol/g for Cd2+ ions. The Response surface methodology (RSM) was used for investigation of interaction and competitive effects in binary metal system. It was found that dried activated sludge in binary system Cd-Zn has slightly higher affinity for Cd2+ comparing with Zn2+ ions. Competitive effect of Cd on Zn uptake increased with increasing solution pH and Cd initial concentration. Maximum sorption capacities of the activated sludge were 321 μmol Cd2+/g and 312 μmol Zn2+/g. RSM appears to be a better tool for the evaluation of interaction and competitive effects in binary systems than both the simple extrapolation from single-component systems and experimentally difficult study of multi-component systems.
Highlights
Industrial effluents contain both organic and inorganic pollutants
In order to determine the minimum necessary time to reach the sorption equilibrium, the time-course studies on the biosorption of cadmium and zinc ions from single metal systems by biosorbent prepared from dried activated sludge were performed
They found that zinc adsorption capacity increased obviously during the first 60 min and the final equilibrium was reached within 180 min
Summary
Industrial effluents contain both organic and inorganic pollutants. These pollutants upset natural balance in water ecosystems, interfere with organisms, accumulate in biota and enter into the food chain with human on the top. Contaminants removal by conventional treatment methods, such as chemical precipitation, membrane separation, evaporation and ion-exchange is often limited due to their low efficiency and economic viability (NAYAK and LAHIRI, 2006). There is a need for an effective and economical treatment alternative. Biological processes such as biosorption and bioaccumulation represent possible interactions of toxic pollutants with biological systems in contaminated environment. Current research activity in the field attempts to evaluate whether biosorption may eventually provide such an effective and economical treatment process alternative (NAJA et al, 2010)
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