Adsorption of metal ion and aromatic compounds by anionic surfactant-coated particles of titanium dioxide

Adsorption of Cu2+ and 2-naphthol from aqueous solutions was examined by anionic surfactant (sodium dodecyl sulfate, SDS) adsorbed on titanium dioxide, Two types of titanium dioxide were used one was untreated and the other was hydrophobic with dodecyl chain groups, At pH 3, 4 and 5, the adsorption of Cu2+ increased with increasing SDS concentration and then decreased slightly on untreated titanium dioxide; the adsorption of Cu2+ decreased in a following order, pH 5 > pH 4 > pH 3. The adsorption behavior of Cu2+ by the SDS adsorbed on hydrophobic titanium dioxide was similar to that on untreated titanium dioxide. although the amount of SDS adsorbed on the former was half as that on the latter. This difference derives from different adsorption states of SDS. In addition, simultaneous adsorption of Cu2+ and 2-naphthol on both untreated and hydrophobic titanium dioxides by addition of SDS was performed at pH 5; the amount of Cu2+ adsorbed was almost the same as those without 2-naphthol for both titanium dioxides and the amount of SDS adsorbed was enhanced in the presence of 2-naphthol where 2-naphthol was adsolubilized more efficiently in the SDS adsorbed layer on hydrophobic titanium dioxide than on untreated titanium dioxide. This anionic surfactant-adsorbed layer can remove both metal ions and the nonionic aromatic compound simultaneously. (C) 1998 Elsevier Science B.V. All rights reserved.