The present study is targeted on the effect of pH on solar photocatalytic removal of metal ions from wastewater. Photoreductive deposition and dark adsorption of metal ions Cu(II), Ni(II), Pb(II) and Zn(II), using solar energy irradiated TiO2, has been investigated at pH values 2, 4, 7, 8 and 10. Modeling of metal species at the studied pH values has been performed and speciation is used as a tool for discussing the photodeposition. The decreasing order of metal deposition at pH 2 and 4 was found to be Pb(II) > Cu(H) > Ni(II) congruent to Zn(II). In the neutral and alkaline pH conditions (pH 7, 8 and 10) the order was Cu(II) > Zn(II) > Ni(II) > Pb(II). (C) 2007 Elsevier B.V. All rights reserved.