Biosorption of Hexavalent Chromium from Aqueous Solutions by Chemically Modified Brown Algae of Sargassum sp. and Dried Activated Sludge

Abstract

The present study deals with the evaluation of biosorptive removal of Cr(VI) ions by pre-treated brown marine algae of Sargassum species and dried activated sludge treated with calcium chloride. Batch kinetics and isotherm experiments were performed in order to examine the effects of contact time, pH, initial metal concentration and biomass concentration, on the removal process. Biosorption of Cr(VI) was rapidly occurred onto biosorbents and most of the sorbed metal was bound within 1 h. The removal performance by the Sargassum sp. was found more than dried activated sludge. Results showed that the uptake of Cr(VI) increased with increasing pH for Sargassum sp. and decreased with increasing pH for dried activated sludge in initial pH from 2 to 6. The capacity of Cr(VI) biosorption at equilibrium increased with the increase of initial Cr(VI) concentration (10-100 mg L^-1) and decreased with the increase of biosorbents dose (0.5-5.5 g L^-1). The results showed that the equilibrium data for Sargassum sp. could be well by the Langmuir isotherm model, whereas the equilibrium data for dried activated sludge fitted the Freundlich isotherm model best within the concentration range studied. From the results obtained, the pseudo-second-order kinetic model best describes the biosorption of Cr(VI) ions.