Chromium(VI) removal using in-situ nitrogenized activated carbon prepared from Brewers' spent grain

In-situ nitrogenised activated carbons (ACs) are prepared from brewers' spent grain (BSG) using different activation procedures. Cr(VI) adsorption (10 mg/L, pH 2) on these ACs is compared to adsorption on commercial Norit GAC 1240 and Filtrasorb F400. The adsorption isotherms for both Cr(VI) and Cr total (Cr-tot) are determined for each AC, of which the best performing ones are chosen for kinetic experiments. The adsorption mechanism towards Cr(VI) is accompanied by its reduction to Cr(III), removing almost all Cr(VI) even at low dosages for all tested ACs. An optimal dosage (0.75 g/L) is found for each AC. For the best performing AC this dosage results in removal rates of over 99% of Cr(VI) and 88% of Cr-tot. The amount of reduced Cr(VI) increases with AC dosage, resulting in a higher Cr(III) equilibrium concentration above this optimal dosage. The redox reaction is more dominant in the commercial ACs. However, a faster removal rate for the ACBSGs for both Cr(VI) and Cr-tot is demonstrated.