Metal leach and recovery process

Abstract

The present invention relates to a metal leach and recovery process. The process involves subjecting a metal bearing material to a reactive process by combining said metal bearing material with a leaching agent to liberate at least one metal value and forming a first aqueous leach pulp. This first aqueous leach pulp is subjected to a solid liquid separation step thereby providing a first clarified aqueous leach solution and a second aqueous leach pulp. The first clarified aqueous leach solution is then subjected to solvent extraction thereby obtaining the first aqueous raffinate. The second aqueous leach pulp is subjected to at least two further solid liquid separation steps of which some or all are in a counter current decantation (CCD) arrangement. Each of the solid liquid separation steps of the CCD arrangement results in an aqueous liquor and aqueous suspension of solids wherein each aqueous suspension of solids resulting from each solid liquid separation step of the CCD arrangement is passed to the subsequent solid liquid separation step and the suspension of solids resulting from the final solid liquid separation step is removed from the process. Further, each aqueous liquor resulting from each solid liquid separation step of the CCD arrangement is passed to the previous solid liquid separation step. The further solid liquid separation steps result in at least one further clarified aqueous leach solution. The at least one further clarified aqueous leach solution is/are subjected to solvent extraction thereby obtaining at least one further aqueous raffinate. At least a portion of the one or more of the at least one further aqueous raffinates is fed into the final solid liquid separation is of the CCD arrangement. The process provides a flocculation system comprising either: (i) addition of an organic polymeric flocculant to or prior to at least one solid liquid separation step, which polymeric flocculant is formed from 2-acrylamido-2-methylpropane sulphonic acid (ATBS) or salts thereof as a homopolymer or copolymer with at least one water-soluble ethylenically unsaturated monomer; or (ii) addition of an organic polymeric flocculant and at least one support agent to or prior to at least one solid liquid separation step, which at least one support agent is selected from at least one of the group consisting of oxidizing agents, reducing agents, irradiation and free radical producing agents. The process provides significantly improved metal extraction and recovery.