Sulfate removal from aqueous solutions by hydrous iron oxide freshly prepared in the presence of some heavy metals cations and some anions has been investigated in batch systems by varying the pH and concentrations of various ions. Infrared spectroscopic analyses have been performed to characterize the effect of these ions on the mechanism of sulfate interaction with the surface of the hydrous oxide. The results of macroscopic studies show that in the binary systems, copper and zinc ions inhibit the sulfate removal at pH higher than 5.5. In the presence of oxalate and phosphate ions. significant competitive effects are observed contrary to acetate ions. The IR spectra of the solids obtained show that among the studied ions, only phosphate ions have an effect on the sulfate interaction with the surface of the oxide. In their presence, the formation of outer sphere complex is more probable. (C) 2009 Elsevier B.V. All rights reserved.