Abstract: A biomass agricultural waste material, Rice Straw was used for preparation of activated carbons by physical activation and modified with KOH (RSK carbon). Bioremediation of Humic Substance (HS) by RSK carbon was investigated through equilibrium process. The experimental results showed that the equilibrium data fit well Langmuir equation. It was found that for RSK carbon can achieve adsorption of HS at 21.1 mg g-1. The underlying mechanism of HS sorption was discussed. It could be concluded that a mixed effect of electrostatic attraction and surface complex formation is suggested to be responsible for the adsorption of humic substance on the surface of carbon.