Sherritt Gordon Mines Limited

Herbert Veltman

Wasyl Kunda

Geoffrey James Mould

Paul Kawulka

Ammonium jarosite is converted to hematite or magnetite and ammonium sulphate. The invention can be used for removing iron from a feed solution containing dissolved ferrous sulphate. The feed solution is treated with ammonium sulphate and oxygen to precipitate ammonium jarosite which is then separated from the treated solution to produce an ammonium jarosite slurry and a separated solution containing sulphate ions. The ammonium jarosite slurry is treated with ammonia to convert the ammonium jarosite to hematite or magnetite and ammonium sulphate solution. The ammonium sulphate solution is separated from the hematite or magnetite, and a portion of the separated ammonium sulphate solution is recycled to the ammonium jarosite precipitation step, the remaining portion of the separated ammonium sulphate solution being recovered.

Recovering magnetite and ammonium sulphate from ammonium jarosite

Direct pressure leaching of zinc and iron containing mineral sulphides in dilute H.sub.2 SO.sub.4 is carried out in a two-stage countercurrent process in which finely divided sulphides are leached in a first leaching stage with solution from the second leaching stage to produce a first stage leach solution containing a high zinc concentration and low iron and H.sub.2 SO.sub.4 concentrations. The first stage solution, after suitable purification treatment, may be treated for zinc recovery by conventional electrowinning. The residue from the first stage leach is pressure leached with return electrolyte from the electrowinning operation with the leach end solution being passed to the first stage leach as already stated. The acid and sulphides concentrations in each of the first and second leaching stage is controlled such that (1) sufficient acid and sulphides enter the leaching circuit to ensure that the final leach solution exiting from the first leaching stage will contain sufficient dissolved zinc, e.g., 140-180 g.p.l., to make it suitable for treatment by electrolysis for recovery of zinc therefrom, (2) the quantity of sulphides entering the first stage leach is in excess of the quantity required to react with all available acid in the solution recycled from the second leaching stage and (3) the quantity of free acid entering the second leaching stage is in excess of the quantity required to react stoichiometrically with all acid reactive constituents in the residue passed from the first leaching stage to the second leaching stage.

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Fort, Canada

Herbert Veltman