Patent ID: 6039790
Filing Date: 2000-03-21
Classification: C22B

Abstract:
A method for recovering nickel and other valuable metals and for precipitating iron from first and second pyrometallurgically produced mattes, wherein the first matte contains a smaller proportion of iron than the second matte, comprising:(a) leaching the first matte in a first leaching cycle including at least one atmospheric leaching step and at least one pressure leaching step each using a leaching solution containing nickel sulfate and sulfuric acid, whereby nickel of the first matte dissolves as nickel sulfate in each leaching step of the first leaching cycle and iron of the first matte dissolves in a leaching step of the first leaching cycle to form an iron-bearing solution,(b) reducing nickel sulfate solution from the first leaching cycle to metallic nickel,(c) leaching the second matte in a second leaching cycle using the iron-bearing solution formed in step (a) with pH adjusted to at least 1, whereby the nickel of the second matte dissolves as nickel sulfate, and(d) using the nickel sulfate solution formed in step (c) as a leaching solution in a leaching step of the first leaching cycle.