The removal of chromium(VI) from dilute aqueous solution by activated carbon

Abstract

The removal of chromium(VI) by activated carbon, filtrasorb 400, is brought by two major interfacial reactions: adsorption and reduction. Chemical factors such as pH and total Cr(VI) that affect the magnitude of Cr(VI) adsorption were investigated. The adsorption of Cr(VI) exhibits a peak value at pH 5–6. The particle size of carbon and the presence of cyanide species do not change the magnitude of chromium removal. The reduced Cr(VI), e.g. Cr(III) is less adsorbable than Cr(VI). The free energy of specific chemical interaction, ΔG chem was computed by the Gouy-Chapman-Stern-Grahame model. The average values of ΔG chem are −5.57 RT and −5.81 RT, respectively, for Cr(VI) and CN. These values are significant enough to influence the overall magnitude of Cr(VI) and CN adsorption. Results also indicate that HCrO − 4 and Cr 2O 2− 7 are the major Cr(VI) species involved in surface association.