REMOVAL OF CADMIUM IONS FROM AQUEOUS SOLUTIONS BY MICROORGANISMS OF ACTIVATED SLUDGE

In this study, the utilization of dried activated sludge for removal of Cd2+ from aqueous solution in a batch system was investigated. Initial pH, biosorbent dosage, contact time, and initial metal concentration parameters were selected to determine optimal process conditions. The biosorption mechanism was examined by SEM, FTIR and EDX results. The optimum conditions for Cd2+ biosorption were found to be 6.0, 120 mm., 1.2 g.L-1 and 80 mg.L-1, respectively for initial pH, contact time, biosorbent dosage and initial Cd2+ concentration. Langmuir and Freundlich isotherms were used to model the biosorption equilibrium data, and it was determined that the system followed the Langmuir isotherm, and the sorption capacity of the biosorbent was found to be 15.43 mg.g(-1). Biosorption followed a pseudo-second-order rate model. Two main mechanisms of Cd2+ biosorption onto the dried activated sludge were adsorption to the C-H bonds and ion exchange with Na+, K+ and Ca2+ ions.