Zinc hydrometallurgical process
AssigneeTexasgulf Canada Ltd.
InventorsGeorge M. Freeman, John E. Dulson, Monica F. Morris
Life of this patent
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Abstract
Hydrometallurgical process for the recovery of copper arsenate from zinc plant cement copper residues and the use thereof in the purification of zinc electrolyte, with the attendant upgrading of the copper value in the treated cement copper residues.
Claims19
In a process for electrowinning zinc metal wherein copper, cadmium and cobalt contaminants are removed from the impure electrolyte prior to electrolysis, including the formation of a cement copper cake residue fraction, the improvement comprising:
- a. subjecting said cement copper cake to an acid leach followed by an alkali addition to extract substantial amounts of zinc, cadmium and cobalt in solution and provide a copper-enriched residue;
- b. precipitating cobalt from the extraction solution of step (a);
- c. separating the precipitated cobalt from the solution in step (b);
- d. subjecting said copper-enriched residue of step (a) to a caustic leach to extract arsenic in solution therefrom and provide a copper-enriched cement copper cake product;
- e. reacting the arsenic-containing solution from step (d) with a copper salt to form copper arsenate residue and leave a zinc-containing solution;
- f. treating said impure electrolyte with said copper arsenate residue to remove said contaminants.
A process for recovery of arsenic from cement copper cake which comprises the steps of:
- a. leaching cement copper cake with hot acid to form a slurry and thereafter neutralizing said slurry to a pH of about 3.5 to 4.0;
- b. dividing said slurry into its solution and residue fractions;
- c. caustic leaching the residue fraction from step (b) to form a slurry;
- d. dividing the slurry from step (c) into its solution and residue fractions;
- e. treating the solution fraction from step (d) to remove arsenic as copper arsenate.
The process of purifying zinc electrolyte prior to electrolysis thereof in the electrowinning of metallic zinc comprising maintaining said electrolyte at a temperature of about 90.degree.-95.degree. C., adding zinc dust in an amount of about 1.5 to 2.5 grams per liter and copper arsenate in an amount of about 0.25 grams per liter until the cobalt level of said electrolyte is less than 0.1 ppm, and adjusting the pH to about 4.0 removing the solids from said electrolyte.
In a process for electrowinning zinc metal wherein copper, cadmium and cobalt contaminants are removed from the impure electrolyte prior to electrolysis, including the formation of a cement copper cake residue fraction, the improvement comprising:
- a. subjecting said cement copper cake to an acid leach followed by an alkali addition to extract substantial amounts of zinc, cadmium and cobalt in solution and provide a copper-enriched residue;
- b. precipitating cobalt from the extraction solution of step (a) by the addition of potassium permanganate;
- c. separating the precipitated cobalt from the solution in step (b);
- d. subjecting said copper-enriched residue of step (a) to a caustic leach to extract arsenic in solution therefrom and provide a copper-enriched cement copper cake product;
- e. reacting the arsenic-containing solution from step (d) with a copper salt to form copper arsenate residue and leave a zinc-containing solution;
- f. treating said impure electrolyte with said copper arsenate residue to remove said contaminants.
A composition of matter comprised of a major amount of copper arsenate of the general chemical formula Cu.sub.3 (AsO.sub.4).sub.2 4H.sub.2 O and including additional precipitated materials in the ionized state analyzing by weight of the total composition approximately as follows:
- ______________________________________ Zinc 1.3% Cadmium 10 parts per million Cobalt 10 parts per million Manganese 10 parts per million Sodium 2.2% Calcium 4.3% Sulfate 8.9% ______________________________________
Dependencies are inferred from the claim text.