Comparison of the Bioleaching Effect of Mesophilic (35°C) and Thermophilic (45°C) Bacteria on the TIZAPA Tailings

Abstract

The exploitation of mineral deposits generates large amounts of wastes such as fine size particles, known as tailings. Mine wastes are characterized by the presence of pyrite, pyrrotite, galene, sphalerite, chalcopyrite and arsenopyrite. One of the most important environmental problems derived from the treatment and disposition of mining tailings is acid mine drainage (AMD) which results from the oxidation of the sulfurous minerals contained in these tailings. The acid generated is produced by a series of complex chemical reactions; the production rate is controlled by leaching microorganisms, which are present mining processes. In this work the bioleaching kinetics of heavy metals such as Cu, Fe, Zn, Cd, Pb, Ni and As, from a Tizapa tailing sample in presence of mesophilic and moderately thermophilic bacteria were studied and compared. The microorganisms used in this work were previously adapted to the tailing sample by the conventional method of successive steps. The percentage of dissolution of heavy metals at 45°C was smaller than at 35°C and the value of parameters such as redox potential and bacterial growth increased with temperature. Bioleaching studies were compared with the corresponding control systems.