Potential of biosorption for the recovery of chromate in industrial wastewaters

A biosorbent's low chemical stability against oxidative attack and its poor regenerability are problems that limit the applicability of biosorption in addressing the problem of recovering chromate in industrial wastewater. To provide a sufficient premise for such an argument, original equilibrium and kinetic data on the biosorption of chromate by the biomass of the brown seaweed Sargassum siliquosum are presented and benchmarked with other related reports. It is established that the optimal condition for chromate biosorption is around pH 2. It is shown that electrochemical reduction of some of the chromate in the solution occurs in parallel with biosorption. Aside from the solution pH, the other factors shown to influence the equilibrium and the kinetics of both biosorption and reduction are the amount of biomass and the total chromate concentration. The chromate bound by the seaweed is found to be difficult to desorb using H2SO4 without first reducing the hexavalent chromate into a trivalent chromium. These findings are shown to be common among other reported studies using different biosorbents. In conclusion, it is argued that biosorption is not a highly viable option for the recovery of chromate in industrial wastewaters.