Surface complexation of nickel on iron and aluminum oxides: A comparative study with single and dual site clays

Ni adsorption on various single and dual site clays (gibbsite, goethite, natural red earth and leterite) was determined using batch experiments as a function of pH, background electrolyte concentration and adsorbate loading. The experimental data was quantified by 2-pK surface complexation modeling using monodentate and bidentate surface reactions. Gibbsite and laterite showed higher retention of Ni compared to natural red earth (NRE) and goethite indicating high affinity to AlOH surface sites of all clays. The maximum adsorption density of 9.0×10^-5molm^-2 was reported for gibbsite. All four sorbents showed a negligible variation with ionic strength. The Ni adsorption capacity, i.e., ΓNi, varied with the type of sorbents used in accordance with the following order: Γ_Gibbsite Ni>Γ_Laterite Ni>Γ_NRE>Γ_Goethite Ni. In all cases, the estimated Gibb's free energy parameter showed that the Ni(II) adsorption was spontaneous.