Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Group ib metal
Patent
1985-10-29
1987-06-09
Doll, John
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Group ib metal
423 34, 423 36, 423 38, 423 41, 423 42, 423 45, 423 46, 423 92, 423 94, 423 98, 423101, 423103, 423106, 423109, 423140, 423146, 423147, 423150, 75 2, 75101R, 75108, 75111, 75115, 75117, 75118R, 75120, 75121, 204106, 204107, 204108, C01G 300
Patent
active
046719458
DESCRIPTION:
BRIEF SUMMARY
SUMMARY OF THE INVENTION
This invention deals with a method for the separation of the valuable metals zinc, lead and silver from copper and iron in complex metal sulphides which contains one or more of these valuable metals. Normally this is about the impure chalcopyrite concentrates. Further this invention is about a complete leaching of the copper and at the same time an almost fully reduced cuprous chloride and ferrous chloride solution is produced, from which the copper is recovered by electrolysis. The iron is removed from the solution by oxidation using air in the presence of cuprous chloride applying well known methods.
The new in this invention lies in the first separation technique, (the separation of zinc, lead and silver from copper and iron), and the following leaching of copper in a simplified effective leach operation. This excludes such operations as solvent extraction (Elkem) for zinc, and the leach operation for copper needs only one stage for 100% leaching, compared to others which needs 2 stages (Elkem) or only leaches 50-60% (Duval).
The separation and leaching is done by the cupric chloride/sulphate solution which is made by the oxidation of the solution coming from the copper electrolysis stage. This cupricchloride/sulphate solution is separated into two parts-solution. One part, and normally the smallest one (1-2% of the main part) goes to a metathesis stage where the copper in solution is exchanged with the zinc, the lead and the silver in the fresh metal sulphide material which is added.
These reactions only proceed by deliberately controlling the total chloride concentration in the solution to normally about 250 g/l, by injection of water or dilute filtrates to the stage, from washing operations of filter presses etc.
Then the zinc, the lead and the silver is dissolved as the copper in the solution is precipitated as a sulphide. The sulphur which the copper needs to make sulphides comes from the sulphur liberated when zinc, lead and silver is dissolved. It is important that at all time having an excess of elemental suphur (S.sup.o) present for an effective precipitation of CuS. This can easiest be done by recycling some residue from the copper leach stage, a residue containing 70-80% elemental sulphur. The metals zinc, lead and silver can be separated from the solution by a number of different methods. Here an ordinary hydroxide precipitation is chosen. The leaching of copper and some of the iron from the chalcopyrite is in great contrast to the metathesis. The solution used in the metathesis stage, containing some 250 g/l chorides cannot be used in the leaching. One has to increase this intentionally to some 350 g/l for a complete leaching and reduction of the solution. The leaching can, of course, take place at lower choride concentrations, but then you do not get a reduced solution (Duval).
Duval only manages 50-60% leaching in their main leach stage and does the rest of the leaching in oxidation autoclave.
Elkem uses about 400 g/l chlorides and get a very reduced leach solution of ferrous chloride with some cuprous chloride. They need two leach stages for a complete leaching and simultaneously producing an almost fully reduced leach solution. Elkems ferric-chloride solution cannot be used for the metathesis reactions. The inventors have found a new way of combining known chemistry and chemical reactions, by intentionally separating the strong cupric chloride/sulphate solution from the oxidation/iron precipitation stage (containing some 350 g/l chlorides) into two part-solutions. The other part, and normally the largest part goes to the leach stage. Here the chloride concentration is kept on about 350 g/l by regulating the evaporation of water in an amount equal to the volume of water in the wash water/thin filtrates added in the metathesis stage. Thus the reaction between the copper in the leach stage and the copper in the leach residuc forming a copper sulphide is avoided, and an almost fully reduced solution is obtained.
Most of the known type of continous reactors (stirred
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Kostol Carl O.
Thomassen Thomas
Doll John
Stoll Robert L.
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