The application of monmorillonite clays impregnated with organic extractants for the removal of metals from aqueous solution. Part II. The preparation of clays impregnated with commercial solvent extraction reagents and their use for the removal of copper(II)

Selected commercial solvent extraction reagents, Versatic 10, LIX54, Acorga M-5640, Kelex 100, have been adsorbed from water/ethanol solution into the interlayer spaces of two montmorillonite clays containing calcium and tetra-n-propylammonium ions giving high loadings of the reagents (>0.5 mol extractant/kg clay) with both the clays. These intercalated clays were then used to successfully remove copper from dilute aqueous solutions. The results showed that the adsorption was rapid, reaching equilibrium in about 15 min. Extraction isotherms have been obtained for the intercalated clays that demonstrate some interesting behaviour. The isotherms for the calcium-clays show two plateau regions the first signifying the formation of the 1:2 copper: extractant complex and the second at higher loadings of the metal the 1: 1 complex. With the formation of the latter complex, together with the cation exchange of copper for the interlayer calcium ions very high loadings of the clay were obtained approaching I mol copper/kg clay. The clays containing the tetra-n-propylammonium cation behaved in a more normal fashion tending to show only one plateau, and final loadings representing the formation of the 1:2 copper:extractant complex. (C) 2004 Elsevier B.V. All rights reserved.