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

• The mineral phase K10 montmorillonite was saturated with Na+, K+ and Ca2 +.
• This material was studied for Hg(II) sorption at low concentration range.
• Two-site Langmuir and Langmuir isotherms were suitable to describe the sorption.
• For Hg(II) concentration of 10.00 μg L− 1, the removal was higher than 90%.

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 μg 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 μg 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.