Abstract
Equilibrium and kinetics of Cadmium (II) biosorption onto acclimatized activated sludge (AAS) were studied. Activated sludge (AS) obtained from a domestic sewage treatment plant was acclimatized using expired skimmed powdered milk as a model for simulated pharmaceutical wastewater (SPWW) to improve its performance as a biosorbent. The present study seeks to investigate the potential of using AAS as a biosorbent for removing hazardous Cd ions from industrial wastewater effluents. Up to about 99% of Cd was removed from aqueous solutions of 200 mg L−1 initial concentration using 1 g L−1 AAS and pH 5·5. The corresponding uptake capacity was 197 mg g−1. By comparing the results of AAS to that of non-acclimatized activated sludge, acclimatization proved to be beneficial in enhancing Cd removal by more than ten-fold. Furthermore, biosorption followed a Langmuirian type behavior and the kinetics was best described by the pseudo-second order model. AAS promises to be a cost effective eco-friendly biosorbent for Cd removal. The current batch studies lay a foundation for further investigating biosorption on pilot and industrial scales in both batch and continuous modes.