Effect of fulvic acids on sorption of U(VI), Zn, Yb, I and Se(IV) onto oxides of aluminum, iron and silicon

The sorption of Yb³⁺, UO₂/²⁺, Zn²⁺, I^- and SeO₃/^2- onto Al₂O₃3, Fe₂O₃ and SiO₂ were determined by a batch technique in the presence and absence of fulvic acids. The effects of fulvic acid on sorption were compared. The existing general consensus, that humic substances tend to enhance metal cation sorption at low pH, reduce metal cation sorption at high pH and reduce inorganic anion sorption between pH values 3 to 10, was generally shown to be true. However, in this work many exceptions to the general consensus were found. The study indicated that the effect of humic substances on sorption of inorganic cations or anions depends not only on pH, but also on the nature of the oxide, the nature of humic substance, fractionation of the humic substance by sorption, the relative strength of complexes of both soluble and sorbed humic substances, the extent of surface coverage by humic substance, the initial concentration of humic substance and the inorganic electrolyte composition.