Adsorption of transition metal chlorides by silica with grafted 1-n-Propyl-3-Methylimidazolium Chloride

Abstract

Silica with grafted 1-n-propyl-3-methylimidazolium chloride was investigated as adsorbent for the removal of cobalt(II), copper(II), zinc(II), cadmium(II) and mercury(II) chlorides from alcoholic and aqueous solutions. The adsorption proceeds via the formation of metal-chloride anionic complexes detained near the grafted organic cations as counterions. This conclusion is corroborated by the electronic and Raman spectra. The high removal degrees of the metal chlorides from solutions are easily reached. The adequate models of adsorption equilibria consider dissociation and auto-complexation of chlorides in solutions and formation of tri- and tetrachlorometallate anions in the solid phase. Also, the equilibrium constants for the CoCl2 and CuCl2 adsorption by several materials containing grafted organic cations and chloride counterions were recalculated in the framework of this model. The weak dependence of equilibrium constants on the nature of immobilized cations and carriers agrees with the established chemistry of metal chlorides fixation.