Biosorption of Zinc on Immobilized Green Algae: Equilibrium and Dynamics Studies

Abstract

The efficacy of using blank alginate beads and immobilized dead algal cells for the removal of zinc ions from aqueous solutions was investigated. It was found that the sorption capacities were significantly affected by solution pH; with higher pH favoring higher zinc ion uptake. Dynamics and isotherm experiments were carried out at the optimal pH 5.0. Zinc uptake on either sorbent was found to be rapid where approximately 90% of the maximum zinc uptake occurred within the first 30 min in both cases of blank alginate and immobilized algal cells. The equilibrium data for the biosorption of zinc ions onto both sorbents were fitted to the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm equations. The presence of copper and nickel in aqueous solutions was found to suppress the sorption process. The results of the dynamics studies revealed that the biosorption of zinc on immobilized dead algal cells followed pseudo-second order kinetics with little intraparticle diffusion mechanism contribution.