Изучение сорбции высокотоксичных ионов тяжелых металлов природными шунгитами

We have studied the sorption of some highly toxic metal ions such as Hg (II), Tl (I) and Pb (II) by native schungite from Karelia. Native schungite powders with an average particle size below 0.31 μm were used. Black schungite (BS) and grey schungite (GS) samples represent mixtures of different aluminosilicates. Demineralized black schungite (DBS) was obtained by treating BS with HF. The concentrations of Hg (II), Tl (I) and Pb (II) were determined by cathodic electrochemilumnescence technique. For an equilibrium concentration of Hg (II) of 100 mg/liter, the adsorption from 0.05 M HNO3 solution was about 100 mg/g for BS, more than 1000 mg/g for DBS and only 15 mg/g for GS. In the case of DBS, the adsorption kinetics was slow. The obtained data indicate that the centers of Hg (II) adsorption in schungite are associated with free carbon. An increase in the concentration of HNO3 from 0.05 to 0.5 M rather weakly influenced the adsorption of Hg, while the addition of HCl significantly suppressed adsorption. The opposite situation was observed in the case of Tl (I) adsorption. No adsorption of Tl (I) in schungites was observed in strongly acidic media (pH < 2). In slightly acidic or neutral solutions, the adsorption of Tl (I) increased in following sequence: DBS < BS < GS, which indicates that the centers of Tl (I) adsorption in schungite are associated with a mineral component. Similar features were observed for Pb (II) adsorption. The complicated dependence of Pb (II) adsorption from citrate solutions on pH was apparently caused by the influence of pH on the schungite surface and complexation.