Adsorption of Heavy Metal Cations on Hydrated Oxides and Oxides of Iron and Aluminum with Different Crystallinities

Abstract

The adsorption of Cu²⁺, Zn²⁺, and Mg²⁺ on the hydrated oxides and oxides of iron and aluminum with different crystallinities was investigated. The effects of pH, ionic strength of the bulk solution, competing metal cations, metal cation concentration on the adsorption were evaluated. The adsorption of Cu²⁺, Zn²⁺, and Mg²⁺ on the hydrated oxides and oxides of iron and aluminum increased with increasing pH of the bulk solution, and the adsorption sequence was in the order Cu²⁺>Zn²⁺>Mg²⁺. The ionic strength of the bulk solution did not affect the adsorption of Cu²⁺ and Zn²⁺. Competitive adsorption of Zn²⁺ and Mg²⁺ was observed in the presence of Cu²⁺. The X-ray amorphous hydrated oxides and oxides of iron and aluminum with a low crystallinity showed a larger adsorption capability for heavy metal cations than those with a high crystallinity.