| Abstract: |
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 &eqiuv;AlOH surface sites of all clays. The maximum adsorption density of 9.0 × 10−5 mol m−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: ΓGibbsite Ni > ΓLaterite Ni > ΓNRE > ΓGoethite Ni. In all cases, the estimated Gibb's free energy parameter showed that the Ni(II) adsorption was spontaneous. |
