Caracterización mineralógica preliminar de residuos generados en un tratamiento de aguas ácidas tipo sustrato alcalino disperso

Abstract

The acid waters generation in the exploitation of sulphide deposits is a great global environmental problem. For 7 months, the acid mine waters generated in the Zaruma-Portovelo mining area (Ecuador) were satisfactory treated in labo- ratory. However, these systems produce a solid residue with high concentrations of potentially toxic elements that must be properly managed. This work aims to develop a preliminary mineralogical characterization of these solid wastes. Initially, at low pH the chemistry of Fe controlled by low crystallinity oxyhydroxysulphates precipitates (jarosite, schwertmannite and ferrihydrite) will give way to the formation of Al-rich (Alunite / basaluminite) phase precipitation. Subsequently, at pH > 6, the high availability of CO32- ion will condition the presence of divalent metal carbonates (Fe, Cu, Mn, Mg and to a lesser extent Zn). The partition of Zn to the solid phase seems to be the last through the formation of carbonates (smithsonite) and sulphates with substitutions of Zn-Cu (bianchite or melanterite group). The results show the mineralogical complexity of these systems. In addition, complementary techniques to characterize the low crystallinity minerals are necessary to unders- tand the geochemical behavior of metals and the environmental implications that such solid wastes could generate without proper management.