Recovery of precious metals from copper anode slime

A method for recovery of precious metals from copper anode slime, the method comprising:

• leaching a leach liquor out of the copper anode slime by mixing the copper anode slime with an acid mixture with a ratio of between 1:5 and 1:20 (mass of anode slime in grams:total volume of a mixture of the copper anode slime and the acid mixture in milliliters), the acid mixture comprising nitric acid and sulfuric acid;
• separating silver from the leach liquor by:
• forming a silver chloride precipitate in the leach liquor by mixing a supersaturated sodium chloride solution with the leach liquor at room temperature;
• and
• obtaining a first filtrate by filtering the silver chloride precipitate out of the leach liquor;
• separating copper from the first filtrate by:
• forming a copper hydroxide precipitate in the first filtrate by adjusting pH of the first filtrate to 9, the adjusting the pH of the first filtrate comprising adding a sodium hydroxide solution to the first filtrate in a dropwise manner at room temperature;
• and
• obtaining a second filtrate by filtering the copper hydroxide precipitate out of the first filtrate;
• and
• recovering metallic selenium from the second filtrate by:
• forming a reaction mixture by adding L-ascorbic acid (LAA) powder to the second filtrate at room temperature;
• obtaining a first precipitate by adjusting pH of the reaction mixture to a value between 3 and 4, the adjusting the pH of the reaction mixture comprising adding a sulfuric acid solution to the reaction mixture in a dropwise manner while stirring the reaction mixture;
• and
• washing the first precipitate with a nitric acid solution by mixing the first precipitate with the nitric acid solution.