Process for recovering metal values from materials containing arsenic

A process for recovering metals selected from the group consisting of copper, cadmium, zinc, germanium, indium, antimony, bismuth, lead, silver and gold from a copper smelter flue dust containing arsenic which comprises:

• (a) leaching the flue dust with sulfuric acid at a pH of 0.1-1.5 under oxidizing conditions to convert substantially all of the arsenic to pentavalent arsenic while contacting the leach solution with ferric ions in an amount to precipitate substantially all of the arsenic as a ferric-arsenic compound and to solubilize metals selected from the group consisting of copper, zinc, cadmium, indium and germanium;
• (b) performing a liquids-solids separation on the slurry of step (a) to separate the solids from the solution;
• (c) adjusting the pH of the solution of step (b) to a pH of at least 3 to precipitate the remainder of the arsenic as ferric arsenate and reduce the arsenic content of the solution to no more than about 100 ppm;
• (d) removing the arsenic precipitate from the solution of step (c);
• (e) recovering the metals solubilized in step (a) from the solution of step (d) in substantially arsenic-free form;
• (f) leaching the residue of step (b) with a brine leach in the presence of the ferric-arsenic precipitate to solubilize metals selected from the group consisting of antimony, bismuth, lead, silver and gold;
• (g) performing a liquid-solids separation on the slurry of step (f) to separate the solids from the solution, and
• (h) recovering the metals solubilized in step (f) from the solution of step (g) in substantially arsenic-free form.

A process for recovering at least one of the metals copper, cadmium, zinc, indium and germanium from arsenic-containing flue dust resulting from the pyrometallurgical processing of copper ores comprising:

• (a) leaching the feed material with sulfuric acid at a pH approximately 0.5, at a temperature between about 90.degree. C. and about 130.degree. C. to dissolve the aforesaid metal values, in the presence of oxygen under pressure of between about 25 and about 75 psi to adjust the emf of the system to between about -400 and about -500 mv and sufficient ferric ions to insolubilize all the arsenic as a ferric-arsenic compound;
• (b) allowing the leach materials of step (b) to remain in contact for a period of about 1 to about 3 hours to allow precipitation of arsenic as a ferric arsenic compound;
• (c) filtering the leach materials of step (b);
• (d) neutralizing the liquid of step (c) with calcium carbonate to pH at least about 3.0 and cooling for about one-half hour to precipitate out additional arsenates;
• (e) recovering a metal value or values selected from the group comprising copper, germanium, cadmium, zinc, and indium from the liquid of step (d).

A process for recovering metals selected from the group consisting of copper, zinc, cadmium, indium and germanium from a copper smelter flue dust containing arsenic which comprises:

• (a) leaching the flue dust with sulfuric acid at a pH of 0.1-1.5 under oxidizing conditions to convert substantially all of the arsenic to pentavalent arsenic while contacting the leach solution with ferric ions in an amount to precipitate substantially all of the arsenic as a ferric-arsenic compound, and to solubilize said metals;
• (b) performing a liquid-solids separation on the slurry of step (a) to separate the solids from the solution;
• (c) adjusting the pH of the solution of step (b) to a pH of at least 3 to precipitate the remainder of the arsenic as a ferric-arsenic compound and reduce the arsenic content of the solution to no more than about 100 ppm;
• (d) removing the arsenic precipitate from the solution of step (c);
• and
• (d) recovering the metals solubilized in step (a) from the solution of step (b) in substantially arsenic-free form.

A process for recovering metals selected from the group consisting of antimony, bismuth, lead, silver and gold from a copper smelter flue dust containing arsenic which comprises:

• (a) leaching the flue dust with sulfuric acid at a pH of 0.1-1.5 under oxidizing conditions to convert substantially all of the arsenic to pentavalent arsenic while contacting the leach solution with ferric ions in an amount to precipitate substantially all of the arsenic as a ferric-arsenic compound, and to solubilize said metals;
• (b) performing a liquid-solids separation on the slurry of step (a) to separate the solids from the solution;
• (c) leaching the residue of step (b) with a brine leach in the presence of a ferric-arsenic precipitate to solubilize metals selected from the group consisting of antimony, bismuth, lead, silver and gold;
• (d) performing a liquid-solids separation on the slurry of step (c) to separate to solids from the liquids;
• and
• (e) recovering the metals solubilized in step (c) from the solution of step (d) in substantially arsenic-free form.