Editorial Feature

Electrolytic Refining - Mining Fundamentals

Electrolysis, or electrolytic refining, is a technique used for extraction, as well as purification, of metals obtained by any refining method. In the electro-refining process, a block of impure metal becomes the anode, and a thin sheet of metal becomes the cathode. Both the cathode and anode are dipped in an electrolytic cell containing an aqueous solution of the metal salt. Upon the application of electric current of a suitable voltage, pure metal is deposited at the cathode by the dissolution of impure metal at the anode.

Electrolytic Refining of Minerals

Given below are the electrolytic refining processes of some major minerals:

  • Gold - The electrolytic gold recovery process employs hydrochloric acid as an electrolyte, a thin sheet of gold with more than 99.5% purity as a cathode, and a gold alloy anode. Following the ion transfer, high purity gold is transferred onto the cathode. This process is known as the Wohlwill process. The Miller chlorination process is an economical refining process that separates gold of about 99.5% purity, which can then be electro-refined to improve purity to 99.999%.
  • Silver – The electrolytic silver refining process includes a crude silver anode and a refined silver cathode. The electrolytic process is similar to gold, except that the silver anodes are dissolved in a nitric acid bath. The resulting silver will be about 99.9% pure.
  • Copper – The extraction of copper from other ores through electrolysis involves the deposition of copper on the cathode, and using lead-coated anodes. The purification of copper involves the use of copper sulfate solution as the electrolyte, high purity copper strips as cathodes, and impure copper anodes.

References

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