The present work is aimed at determining the effective surface diffusion coefficients, Ds, and adsorption equilibriums during adsorption of o-chlorobenzoic acid on activated carbon from aqueous solution and alcohol aqueous solution (Methanol, Ethanol and n-Propanol) by batch operation. The solubility of o-chlorobenzoic acid into the alcohol aqueous solution changed about 100-fold as alcohol concentration rose from 0% to 100%. This aim of work is to formulate,by chemical potential theory, adsorption isotherms and Ds during adsorption from alcohol aqueous solution. As a result of this work, the investigated concentration range can be represented by Freundlich type isotherms. Ds depend on the amount of o-chlorobenzoic acid adsorbed and the solubility. The adsorption equilibriums and Ds can be formulated by chemical potential theory.