APPLICATION OF THE REAGENTLESS DUAL-TEMPERATURE ION-EXCHANGE TECHNIQUE TO A SELECTIVE SEPARATION AND CONCENTRATION OF COPPER VERSUS ALUMINUM FROM ACIDIC MINE WATERS

Acidic mine waters represent natural effluents from pyritic ore deposi ts and they are mainly characterized by a low pH and a high concentrat ion of metal ions such as Fe3+, Zn2+, Cu2+, Mn2+, Al3+, Ca2+, Mg2+ and Na+. The treatment of these waters is of great economic and ecologica l importance, The present study was targeted at the development of a r eagentless and wasteless dual-temperature ion-exchange technique for c oncentrating copper from the natural acidic mine waters of Rio Tinto a rea (Huelva, Spain). The carboxylic ion er,changer (Lewatit R 250-K) a nd iminodiacetic resin (Lewatit TP-207) were used, Values of the resin capacity towards mine water metal ions and the equilibrium separation factors (alpha) for different metal ion couples have been determined at different temperatures in the range 20-80 degrees C. Acrylic resin has been found to be selective for Al3+ and iminodiacetic resin demons trates high selectivity for Cu2+ Furthermore, the sorbability of Al3increases while that of Cu2+ decreases with temperature for both resin s. This effect gives the possibility for a selective thermostripping o f Cu2+ from the resins pre-equilibrated with cold mine water (at 20 de grees C) using hot mine water at 80 degrees C. The increase in the Cu2 + concentration in the eluate is 30% for acrylic resin and 20% for imi nodiacetic resin. The concentration of Al3+ in the stripping solution drops to 50% in the first case and to 70% in the second.