The Wohlwill process has been used extensively to refine gold. The main objective of electrorefining is to obtain a gold bar as pure as 99.99% in order to cover the requirements of the users. Essentially, the electrorefining process is operated at steady state in a gold chloride/hydrochloric electrolyte. During the process impure gold of 93% is dissolved at the anode and gold is deposited on the cathode. It is important to indicate that base metals or copper in the anode will increase their content and soluble chlorides and silver will form silver chloride that is retained in anodic bags. Some particles of gold are formed on the cell walls due to low current efficiency and unbalanced reactions of monovalent gold.
Anodes are cast plates of gold and cathodes are sheets of titanium plates. The cathodic deposit is removed periodically by scrapping. The solution is bled and processed for impurities removal. Initially gold is reduced and removed and the remaining solution is treated by other recovery processes considering the metallic content of the solution. The gold and silver chlorides are returned to the Miller Process. Once the solution has no high levels or precious metal is removed and a new fresh electrolyte containing gold chloride is sent to the electrolytic cell. If the solution has a high level of impurities, the cost of treatment and bleeding tend to increase.
Gold refining around Wohlwill Process