BIOSORPTION OF LEAD(II), COPPER(II) AND CADMIUM(II) IONS IN SINGE AND MULTI- METAL SYSTEMS BY PRETREATED AEROBIC GRANULE SLUDGE

Abstract

Heavy metals are present in nature and industrial wastewater; due to their mobility in natural water ecosystems and toxicity, the presence of heavy metals in surface water and ground water has become a major inorganic contamination problem. Discharge and treatment of industrial wastewater containing heavy metals are important issues in environmental protection, if unrecognized or inappropriately treated, heavy-metal toxicity can result in serious hazards. The paper describes the study on the biosorption of Lead (II), Copper (II) and Cadmium (II) ionsfrom single component and multi-component systems in the equilibrium system and in batch sorption experiment using pretreated aerobic granular sludge. The results have shown that Ca-biomass has been an efficient biosorbent for the removal of Pb²⁺, Cu²⁺ and Cd²⁺ ions from an aqueous solution. The single-metal sorption capacity of the aerobic granules for Pb²⁺ has been inhibited by the presence of Cd²⁺ and Cu²⁺ ion; the decreasing affinity of aerobi granular sludge for the three metal ions has been established as: Pb²⁺ > Cu²⁺ > Cd²⁺. Factors such as hydration effect and electronegative charge may contribute to the competitive sorption results. The metal removal capacities of Ca-biomass have been six times higher than those of activated carbon, especially the Cd²⁺ removal capacity. The Langmuir model has been better than the Freundlich model in regard of describing the Pb²⁺, Cu²⁺ and Cd²⁺ ion biosorption based on raw biomass and Ca-biomass; the maximum capacity Qmax determined by the Langmuir model has fitted to the experimental data.