Modication of activated carbons from brewers’ spent for chromium(VI) adsorption

Abstract

In-situ nitrogenised activated carbons (ACs) were prepared from brewers’ spent grain (BSG) using different activation procedures. Cr(VI) adsorption on these ACs was compared to commercial ACs. Two modification methods were used to enhance the adsorption properties of selected ACs. The first consisted of an oxidation of the surface using acidic and basic reagents. The second incorporated an amino-crosslinked copolymer with a quaternary ammonium end group on the surface of the AC. Adsorption isotherms of unmodified ACs showed that the adsorption mechanism towards Cr(VI) was accompanied by its reduction to Cr(III). Even al low dosage, almost all Cr(VI) was removed. Increasing AC dosage enhanced the reduction process, resulting in higher Cr(III) end concentrations in the solution. The copolymer modification caused a drastic increase in qe values (mg Cr(VI)/g AC) by a factor of 5 compared to the unmodified and commercial ACs. Oxidised AC performed worse.