Biosorption behaviors of Cu2+, Zn2+, Cd2+ and mixture by waste activated sludge

Abstract Biosorption of heavy metal ions, such as Cu 2+ , Cd 2+ and Zn 2+ , was carried out using waste activated sludge from municipal sewage treatment plant as adsorption material, and the effects of parameters, such as pH value, temperature, reaction time and sorption duration, were studied in detail. The results indicate that the removal rates of Cu 2+ , Zn 2+ and Cd 2+ with low concentration are 96.47%, 80% and 90%, respectively, adsorbed by waste activated sludge. Little effect of dosage of activated sludge on the adsorption of Cu 2+ and more effects on the adsorption of Zn 2+ and Cd 2+ are observed. Little effect of temperature is observed, while pH value and adsorption time exert important influence on the sorption process. The adsorption behaviors of heavy metal ions all have parabolic relationships with pH value. The optimum pH value is between 6 and 10, and the optimum adsorption time is 1 h. In single heavy metal ion system, the sorption processes of Cu 2+ , Zn 2+ and Cd 2+ are in accordance with Freundlich model, which indicates that it is suitable for the treatment of these three heavy metal ions using intermittent operation. In addition, the sorption capacity of the sludge for Cu 2+ is preferential to the other two ions.