Demulsification of stable oil-in-water emulsion was studied using powder adsorbent. Among various adsorbents tested, activated carbon was found to be the most efficient regardless of the type of surfactants used. The more dose of activated carbon for the demulsification was required, the higher concentration of the surfactant as well as the larger amount of oil and the bigger size of the lipophilic and hydrophilic groups. Empirical equations were obtained to correlate the dose of activated carbon to the residual concentration of oil as a function of the initial concentration of surfactant.