GB425648A - Treatment of ores, metallurgical by-products and the like to effect a separation of selenium from precious metals - Google Patents

Abstract

Ores, metallurgical by-products, and residues such as slimes, sludges, or anode mud containing selenium and precious metals are roasted and leached with sulphuric acid to remove copper, and the residue subjected in the presence of an alkali compound such as caustic soda or soda ash to a controlled oxidizing treatment to convert the selenium to alkali selenite, which is then dissolved out leaving the precious metals as an insoluble residue. Sodium nitrate is the preferred oxidizing agent, but air may also be used, and potassium compounds may replace the sodium compounds referred to above. The alkali selenite solution is neutralized with sulphuric acid to remove lead and tellurium which are filtered off, and then acidified and treated with sulphur dioxide to precipitate red selenium which is boiled with water to obtain black selenium. An example is given of the treatment of anode mud produced in the electrolytic refining of copper. In this case the precious metal residue containing 88 per cent of precious metals is washed, treated with hot dilute sulphuric acid to remove any remaining copper, selenium, and tellurium, and melted down with a small amount of sodium hydroxide-sodium nitrate flux to remove antimony and lead and obtain a product containing 99 per cent of gold and silver.ALSO:Ores, metallurgical by-products, and residues such as slimes, sludges, and anode mud containing selenium and precious metals are roasted and leached with sulphuric acid to remove copper, and the residue subjected to controlled oxidation in the presence of an alkali compound to convert selenium present to alkali selenite, which is then dissolved out leaving the precious metals as an insoluble residue. In the treatment of anode mud produced in the electrolytic refining of copper, the precious metal residue containing 88 per cent of precious metals is washed, treated with hot dilute sulphuric acid to remove any remaining copper, selenium, and tellurium, and melted down with a small amount of sodium hydroxide-sodium nitrate flux to remove antimony and lead and obtain a product containing 99 per cent of gold and silver.