Single-multicomponent biosorption of lead mercury chromium and arsenic onto activated sludge in batch and fixed-bed 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 isotherm models for multicomponent 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. An order of metal biosorption capacity onto dried activated sludge was found to be Pb²⁺ > Hg²⁺ > Cr³⁺ > As⁵⁺. FTIR analysis was carried out before and after biosorption. Pore diffusion coefficients required for fixed-bed design were determined by matching batch experimental data with the film-pore diffusion model at optimum agitation speed, 600 rpm and optimum weight of sewage sludge biomass. A general multicomponent rate model has been utilized to predict the fixed-bed breakthrough curves for multicomponent systems. Good agreement between the predicted theoretical breakthrough curves and the experimental results was observed. Results confirmed, from the feed containing Pb²⁺, Hg²⁺, Cr³⁺, and As⁵⁺, arsenic breakthrough from the column appeared first with higher overshoot, followed by chromium, mercury, and finally lead cations with no overshoot. COMSOL multiphysics software was used to solve the batch and fixed-bed models.

Keywords:

• Activated sludge
• Batch
• Fixed-bed adsorber
• Multicomponent system
• COMSOL software