Patent ID: 6461577
Filing Date: 2002-10-08
Classification: C22B,Y02P

Abstract:
A process for leaching sulphidic material containing metals and arsenic under oxidizing conditions and with the aid of microorganisms, comprising the steps of:a) mixing the material with an acid aqueous solution to obtain a pulp; b) leaching the pulp by conducting a leaching process in a first leaching stage at a pH below 2 and at a temperature ranging from room temperature to a temperature of about 55Â° C. in the presence of an active quantity of microorganisms that are mesophilic and/or moderate thermophilic, wherewith a major part of the arsenic contained in the material is leached-out and oxidized successively to a pentavalent state; c) raising the temperature of the pulp to 60-65Â° C., wherewith an extremely thermophilic microorganism culture present in the pulp is activated and caused to reproduce to form an active quantity; and d) leaching in a second leaching stage the remaining leachable metal content in the material of the pulp in the presence of an active quantity of said extremely thermophilic microorganism under conditions that are favorable to the growth of said extremely thermophilic microorganism.