Sorption of Ni(II) on Na-rectorite from aqueous solution: Effect of pH, ionic strength and temperature

Removal of Ni(II) from aqueous solutions by sorption onto Na-rectorite was investigated under ambient conditions. Experiments were carried out as a function of mass content, pH, ionic strength and temperature. The results indicated that the sorption of Ni(II) was strongly dependent on pH value and ionic strength. Sorption of Ni(II) increased with increasing pH and decreasing ionic strength. The sorption of Ni(II) on Na-rectorite was mainly dominated by cation exchange at acidic conditions, whereas surface complexation was the main sorption mechanism at neutral to alkaline pH values. The effect of temperature on Ni(II) sorption on Na-rectorite was negligible at low pH (∼pH < 6), whereas the effect of temperature was obvious at pH > 6. The thermodynamic parameters (ΔH, ΔS, and ΔG) for Ni(II) sorption onto Na-rectorite were calculated from the temperature dependence, and the results suggested that the sorption reaction was endothermic.