Biosorption of hexavalent chromium from aqueous solutions using highly characterised peats

Abstract

This research investigated the biosorption of hexavalent chromium (CrVI) from aqueous solutions by six highly characterised peats. Samples of the peats were tested both in unaltered condition and after being treated with hydrochloric acid (HCl) to free up any occupied exchange sites. Other variables tested were sample dose, contact time, mixing temperature, and the concentrations and pH of the CrVI solution. Desorption studies were also performed, and tests were done to determine whether the peats could be re-used for CrVI biosorption. The results indicate that all six peat types biosorb CrVI from aqueous solution well (42–100 % removal) and that their CrVI removal capacities are affected by manipulation of the various factors. The two factors that had the greatest impact on the CrVI removal capacities of the peats were the concentrations and pH of the CrVI solution. As the CrVI solution concentration and pH were increased, the percent of CrVI removed decreased dramatically (33–56 % decrease for concentration increase; 36–45 % decrease for pH increase with four of the six peat types). The desorption results indicate that it may be possible to recover up to 5 % of the removed CrVI. All of the peat types tested can be repeatedly re-used for additional CrVI biosorption cycles. Hence, their disposal should not become a hazardous waste problem