Adsorption of elemental mercury on various surfactants was calculated by the DFT/B3LYP method. Mulliken charge analysis was employed to reveal the interaction mechanisms. The results showed that uncharged surfactants have negligible ability to attract mercury, while ionized surfactants presented much stronger interactions. Charge analysis showed that oxidized mercury received significant electrons transferred from the functional groups of the surfactants. A mechanism has been proposed that ionization of these surfactants is required to have significant adsorption of mercury, as supported by experimental observations. (C) 2010 Elsevier Ltd. All rights reserved.