Surface interaction of cadmium and zinc metal ions on Al2O3 nanoparticles in aqueous solution.

The adsorbent ability of Al₂O₃ nanoparticles (ANPs) was examined to remove Cd²⁺ and Zn²⁺ from aqueous solution. The sorption of Cd²⁺ and Zn²⁺ on ANPs as a function of pH, ionic strength (IS), humic acid (HA), contact time, foreign ions and the temperature were investigated. It was observed that physico-chemical factors (pH and ionic strength) strongly affect the sorption of Cd²⁺ and Zn²⁺ on ANPs. Comparatively, the sorption of Cd²⁺ and Zn²⁺ dominated by surface complexation of the outer sphere at low pH values (pH < 8.0), while surface complexation of the inner sphere was the major sorption mechanism at elevated pH values (pH > 8.0). The maximum sorption capacity of Cd²⁺ and Zn²⁺ on ANPs calculated from the Langmuir model was 8.40 and 9.00 mg g^–1 respectively at 303 K, exhibiting higher efficiency for Zn²⁺ sorption than Cd²⁺.The thermodynamic parameters (∆H⁰, ∆S⁰ and ∆G⁰) showed that the adsorption of Cd²⁺ and Zn²⁺ was endothermic and spontaneous. This investigation exhibited that ANP is an efficient, inexpensive process and thereby reasonable technology for the elimination of metal ions from the contaminated aqueous source. [ABSTRACT FROM AUTHOR]