Sorption of Hg(II) by modified K10 montmorillonite: Influence of pH, ionic strength and the treatment with different cations

This paper describes a treatment of the mineral montmorillonite (MMT) with sodium (MMT-Na), potassium (MMT-K) and calcium (MMT-Ca), aiming the removal of the highly toxic Hg(II) from aqueous medium. An apparent equilibrium near 10 h of contact time was verified, being this time adopted for the sorption studies. The data obtained by this study evidenced that a pseudo-second order was appropriate to describe the model for the three materials. The increase of the ionic strength showed a significant depletion in the Hg(II) sorption, and was more significant for the mineral treated with the monovalent cations. Also, the study showed a high pH-dependency with the better performance close to pH 7.0 that was adopted for the sorption study. The sorption isotherms were carried out between 10.00 and 500.0 mu g L-1, and showed a better Hg(II) sorption for MMT-K, followed by MMT-Na and MMT-Ca, with the maximum sorption values (%) of 94.9, 92.4 and 60.4, respectively, for the concentration of 10.00 mu g L-1. The order of sorption was confirmed by the use of the Langmuir and two-site Langmuir models. The findings suggest this mineral phase as an appropriate sorbent for the removal of Hg(II) from aqueous medium, especially at low concentrations. (C) 2014 Elsevier B.V. All rights reserved.