C - Chemistry – Metallurgy – 22 – B
Patent
C - Chemistry, Metallurgy
22
B
53/289, 53/304,
C22B 15/00 (2006.01)
Patent
CA 1046287
Abstract of Disclosure A method is provided for leaching comminuted nickeli- ferous sulfide matte containing by weight about 20% to 75% nickel, about 5% to 50% copper, non-stoichiometric sulfur in the range of over 4% to about 20%, over 0.5% to about 15 or 20% iron, the sum of the nickel, copper and sulfur contents being at least about 80% of the matte composition, with the balance gangue or slag and incidental impurities. The matte, because of the iron content, is first granu- lated by quenching molten matte from a temperature at least about 10°C above its solidus-liquidus temperature but below its boiling point, following which the matte is comminuted and subjected to atmospheric leaching to dissolve nickel selectively therefrom using a spent copper electrolyte solution containing sulfuric acid having a pH ranging up to about 2 while aerating said solution to cause the pH to rise to above 5 and effect substantial precipi- tation of copper and iron. Preferably, a two-stage atmospheric leaching is employed, the first stage in which the solution is aerated until the solution reaches a pH level of about 3.5 to 4.5 and a second stage atmospheric leaching step in which the aera- tion is replaces with a stronger oxidant, such as oxygen, in order to speed up the atmospheric leaching of the matte and to complete further said atmospheric leaching until the aqueous copper and iron are each reduced to less than 20 ppm as evi- denced by a rise in pH to over about 5. Optionally, the solu- tion with dissolved nickel is separated from the nickel-copper containing residue for nickel recovery and the residue then sub- jected to sulfuric acid leaching at an elevated temperature and pressure to recover metal values therefrom. The pregnant solu- tion from the high pressure leach is subjected to electrowinning to remove copper and the spent electrolyte preferably recycled to the first stage atmospheric leaching step. In a preferred embodiment, the matte may be subjected to an iron preleach step with dilute sulfuric acid prior to the first stage atmospheric leaching step.
233981
Blandon Antonio E.
Queneau Paul B.
Symens Raymond D.
Amax Inc.
Na
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