Adsorption of Pb(Ⅱ), Cr(Ⅲ), Cu(Ⅱ), Cd(Ⅱ) and Ni(Ⅱ) onto a vanadium mine tailing from aqueous solution

摘要

The adsorption of heavy metal cations Pb(Ⅱ), Cr(Ⅲ), Cu(Ⅱ), Cd(Ⅱ) and Ni(Ⅱ) from aqueous solution by a mine tailing which mainly contains muscovite was investigated. The property of the mineral was investigated by using SEM, FT-IR, XRD and BET analysis. pH_(pzc) was measured by an titration technique to give a value of 5.4 ± 0.1. Kinetics experiments indicated that the processes can be simulated by pseudo-second-order model. Total adsorption amounts of the heavy metal increased, while the adsorption density decreased when the solid-to-liquid ratio (S/L) increased. Grain size did not affect the adsorption capacity significantly. The resulting isotherms can be described by Frendlich relationship. And the maximum adsorption capacity (molar basis) followed the order of Cr(Ⅲ)> Pb(Ⅱ) >Cu(Ⅱ) > Ni(Ⅱ) > Cd(Ⅱ). Thermody-namic analysis showed that the adsorption processed were endothermic and may be chemical in nature with positive △H~0. The positive △S~0 suggested that dissociative processed were involved. Small positive △G~0 suggested that the adsorption processes required a small amount of energy. Adsorption processes were slightly affected by electrolyte ion concentration but strongly dependent on pH value. The most possible mechanism of the adsorption processes involve the inner-sphere-complexions by the aluminol or silanol groups on the surface of the mineral.