Competitive Biosorption of Lead Mercury Chromium and Arsenic Ions onto Activated Sludge in Batch Adsorber

Abstract

A wide range of batch experiments were carried out for estimation of the key process parameters in competitive biosorption of Pb²⁺, Hg²⁺, Cr³⁺ and As⁵⁺ from simulated of wastewater onto dry activated sludge in batch adsorber. Eleven isotherm models were used for single component and five models for multi-component systems. The Langmuir model gave the best fit for the data of single component, while the binary, ternary and quaternary systems were fitted successfully with extended Langmuir model. The biosorption capacity for single metal decreased by 11-51 %, 53-88 % and 79-94 % in the binary, ternary and quaternary systems respectively at the optimum agitation speed 600-800 rpm. An order of metal biosorption capacity onto dried activated sludge was the same in the case of competitive multi-metal sorption conditions as it was for single-element sorption, namely Pb²⁺ > Cr³⁺ > Hg²⁺ > As⁵⁺. FT-IR analysis was carried out before and after biosorption to determine which functional groups were responsible for binding the heavy metals. Kinetic study showed that pseudo- second order model was well fitted for all metals ions. R² used to enhance the justification analysis for each used model.