Effect of modification with hydrobromic acid on the performance of activated carbon in the removal of hexavalent chromium from aqueous solution

The ability of activated carbon from coconut shell to adsorb Cr(VI) from aqueous environment has been ameliorated by treating the carbon with hydrobromic acid. The best carbon is gained by soaking activated carbon in 0.3 mol L−1 HBr solution at 80°C for 13 h followed by being carbonized at 600°C in nitrogen for 1.5 h. The Cr(VI) adsorbed at equilibrium by the best as‐prepared carbon is 11.32 mg g−1 while that by the original one is 7.801 mg g−1. Characterization results manifest that the treatment with HBr solution leads to the increase of acidic groups and the decrease of basic groups on the carbon surface. The treatment with HBr solution produces many lactonic groups on the carbon. BET determination indicates that some micropores and mesopores are generated by the treatment with HBr solution. The increase of acidic groups and magnification of surface area is ascribed to the improvement of the ability to adsorb Cr(VI) ions. Lactonic groups and micropores play a key role in adsorbing Cr(VI) from water.