Patent ID: 6342189
Filing Date: 2002-01-29
Classification: C22B,Y02P

Abstract:
A method for the precipitation of valuable metals from a leaching solution that has been acidified with sulphuric acid and that is substantially free from impurities, by neutralization with lime and/or limestone, comprising the steps of:a) conducting the neutralization in at least two stages wherein only partial precipitation is effected in the first stage and wherein extensive precipitation of the remaining valuable metal content is effected in the last stage by adding a surplus of neutralization agent; b) forming a slurry of precipitate, solid neutralization agent and leaching solution in the last stage of the neutralization process; c) returning the slurry, formed in the last stage, to the first neutralization stage, wherein the amount of slurry returned together with neutralizing agent added to the first stage provides the partial precipitation of the valuable metal content; d) forming precipitate in the first stage that contains valuable metal, but is substantially free from neutralization agent; and e) separating the valuable metal containing precipitate in the first stage that is substantially free from neutralization agent from a liquid effluent wherein the liquid effluent is passed to a subsequent neutralization stage.