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Production of High-purity Gold from Zinc Precipitates and Steel Wool Cathodes by Hydrometallurgical Refining.
McClelland-GE; Wroblewski-MD; Eisele-JA
MISSING :11 pages
The Bureau of Mines investigated chemical methods for producing high- purity gold from precious-metal-bearing zinc precipitates and steel wool cathodes. Precious-metal-bearing zinc precipitates and steel wool cathodes are unrefined products from conventional cyanidation and heap leaching-cyanidation operations. The zinc precipitates contained 14.40 pct au and 0.35 pct ag. The precious-metal-bearing steel wool cathodes contained 20.65 pct au and 4.84 pct ag. The precipitates and cathodes were treated with dilute acid to solubilize the silver and/or base metals. The gold-bearing residue was leached in dilute aqua regia to solubilize the gold. High- purity gold was precipitated from the aqua regia solution with oxalic acid, sulfurous acid, sodium bisulfite, and gaseous sulfur dioxide. The leaching-precipitation experiments recovered 99.9 pct of the gold. The gold precipitates ranged in fineness from 997 to 999 fine. The chemical refining method provides a viable technique for the smaller operator to produce high-purity gold without using pyrometallurgical refining methods.
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Page last reviewed: March 11, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division