| 摘要 |
PURPOSE: A refining method of gold by reduction-depositing a gold ion contained in a solution with concentrated sulfuric acid selectively is provided which can refine gold having above 99.9% purity. CONSTITUTION: A base metal having 85-98% of gold content is melted in aqua regia and filtrated to remove silver chloride. The filtrate is added with concentrated sulfuric acid to remove iron, copper, palladium, and platinum, and maintained at 200°C, reduction-depositing a gold ion selectively and generating sulfur dioxide. For an example, 10g base metal having a composition of Au 85.1%, Ag 14.1%, Fe 4,900 ppm, Cu 3,000 ppm, Pd 33 ppm, and Pt 67 ppm is poured in a container, added with 60 ml aqua regia, maintained at 90°C, and filtrated to remove silver chloride. The filtrate is added with 100 ml concentrated sulfuric acid, maintained at 90°C, stirred for 1 hr to remove nitric acid, heated to 200°C at a heating speed of 10°C/min to reduction-deposit a gold ion. The deposited gold contains Ag 59ppm, Pd 23 ppm, and Pt 23 ppm as impurities.
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