The application of montmorillonite clays impregnated with organic extractants for the removal of metals from aqueous solution Part I. The preparation of clays impregnated with di-(2-ethylhexyl) phosphoric acid and their use for the removal of copper(II)

The adsorption of di-(2-ethylhexyl)phosphoric acid (DEHPA) into montmorillonite clays containing various interstitial (interlayer) inorganic and organic cations is described. The adsorption isotherms follow a step-like pattern with loadings, depending on the cation, approaching a maximum of 3 mol kg(-1). The clay impregnated with DEHPA has been used successfully to remove copper(H) ions from aqueous solutions. The extraction isotherms also show a step-like pattern with the formation of both 2:1 and 1: 1 extractant:copper complexes giving maximum loadings of about 0.5 mol kg(-1) for a clay containing approximately 0.5 mol kg(-1) DEHPA. The rate of extraction is reasonably fast with 15 min to reach equilibrium. Losses of DEHPA from the impregnated clay under the conditions of extractant are also dependent on the nature of the interstitial cation and losses of < 10 ppm can be readily obtained. Such losses indicate the potential for use in hydrometallurgical circuits and control of aqueous effluents from industry or land-fill sites. (C) 2001 Elsevier Science BN. All rights reserved.