The present work deals with the synthesis, characterization and cadmium adsorption studies on SiO2, Fe(OH)(3) and their mixed oxides. Mixed oxides of iron and silicon of composition [0.5M SiO2:0.5 M Fe(OH)(3)] were prepared by physical mixing (M-1) and sequential precipitation methods (M-2). The selectivity of adsorbents towards Cd2+ ion was found to be in the order M-2 > M-1 = Fe(OH)(3) > silica. Dissolution of silica, mixed oxides M-1 and M-2 was also investigated in the pH range 3-10. The greater dissolution of mixed oxide M-2, along with the higher selectivity towards Cd2+ ions showed the formation of the ternary complexes on the surface of M-2. The complex formation was also confirmed by IR studies and by the increase in Cd2+ sorption with the addition of the silicates anions in the medium. The thermodynamic parameters showed the Cd2+ sorption to be endothermic and spontaneous in nature. (C) 2009 Elsevier B. V. All rights reserved.