Adsorption of Cr(VI) ions on the activated carbon derived from oxalic acid treated coconut shell

The activated carbon from coconut shell has been treated with oxalic acid to enhance its capability to adsorb Cr(VI) ions from waste water. The experiments manifest that the uptake of Cr(VI) at equilibrium on the best carbon prepared by immersing activated carbon in 0.5 mol l−1 oxalic acid solution at 60°C for 24 h, followed by being calcined at 500°C in nitrogen for 2 h is 10.52 mg g−1 while that on the original one is 7.80 mg g−1. FT-IR, XPS and Boehm titration characterisation demonstrate that the treatment with oxalic acid results in the increase of carboxyl and phenolic hydroxyl groups on the carbon. BET determination demonstrates that the treatment with oxalic acid produces more micropores and mesopores. The amelioration of the adsorbing Cr(VI) capacity of the carbon lies on the increase of acid functional groups and enlargement of surface area.