Reduction Kinetics of Hexavalent Chromium during Biosorption onto the Protonated Ecklonia Biomass

Hexavalent chromium was removed by means of biosorption onto the protonated brown seaweed biomass. During the biosorption Cr(VI) was reduced to Cr(III), which resulted in accumulation of Cr(III) in the solution. The Cr(VI) reduction rate increased with increases of initial Cr(VI) and biosorbent concentrations and decrease of solution pH. Based upon the experimental results at various conditions, we suggested the mechanism for the chromium removal as following serial reactions: (1) sorption of anionic Cr(VI) onto the positively charged site of biomass, (2) reduction of Cr(VI) to Cr(III) on the positively charged site, (3) desorption of Cr(III) from the positively charged site, and (4) sorption of cationic Cr(III) onto the negatively charged site of biomass.