Impact of environmental conditions on the sorption behavior of Co(II) on Na-rectorite studied by batch experiments

Abstract

The sorption of Co(II) from aqueous solution on Na-rectorite was investigated under ambient conditions. Experiments were carried out as a function of contact time, solid content, pH, ionic strength, foreign ions, fulvic acid and temperature. The results indicated that the sorption of Co(II) was strongly dependent on pH. At low pH the sorption was dominated by outer-sphere surface complexation or ion exchange, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models were used to simulate the sorption isotherms at three different temperatures. The thermodynamic data (∆G 0, ∆S 0, ∆H 0) were calculated from the temperature dependent sorption isotherms and the results suggested that the sorption process of Co(II) on Na-rectorite was spontaneous and endothermic. Experimental results indicate that Na-rectorite is a suitable adsorbent for preconcentration and solidification of Co(II) from large volumes of aqueous solutions.