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What happens to impurities during Wohlwill electrorefining of gold?
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gold processing
The Tanami gold mine, Northern Territory, Australia.
In the Wohlwill process, which is used to achieve high-purity gold through electrolysis, impurities are separated from the gold anode in two ways.1
As the impure gold anode dissolves under the influence of an electric current, the impurities either pass directly into the hydrochloric acid and gold chloride electrolyte solution or settle at the bottom of the electrorefining tank as an insoluble slime. This method allows the gold to migrate to the cathode, leaving these impurities behind and resulting in gold with a purity of approximately 99.99 percent.1