Electrowinning

Updated 2026-07-30

Electrowinning, also called electroextraction, is the electrodeposition of metals from their ores that have been put into solution via a process commonly referred to as leaching. It is an electrolytic process in which an electrical current is passed from an inert anode through a leach solution containing dissolved metal ions, causing the metal to be reduced and deposited as a solid onto the cathode.

Overview

Electrowinning is one of the oldest industrial electrolytic processes. It is distinct from electrorefining, which uses a similar setup but employs an impure metal anode that is oxidized and dissolved, with the overall electron balance being zero. In electrowinning, there is a net positive electron consumption in the overall reaction. Both processes use electroplating on a large scale and are important techniques for the economical purification of non-ferrous metals. Metals produced by this method are said to be electrowon.

History

1807 – English chemist Humphry Davy first obtained sodium metal in elemental form by the electrolysis of molten sodium hydroxide, marking the earliest demonstration of electrowinning.
1847 – Electrorefining of copper was first experimentally demonstrated by Maximilian, Duke of Leuchtenberg.
1865 – James Elkington patented the commercial electrowinning process.
1870 – The first successful plant opened in Pembrey, Wales.
1883 – The first commercial plant in the United States was established by the Balbach and Sons Refining and Smelting Company in Newark, New Jersey.

Process

In a typical electrowinning operation:

Leaching – Ore is treated with a chemical solution (e.g., cyanide for gold, sulfuric acid for copper) to dissolve the metal of interest.
Electrolysis – The leach solution (electrolyte) is placed in a cell containing an inert anode (e.g., lead, titanium, or stainless steel) and a cathode. A direct current is applied.
Deposition – Metal ions (Mⁿ⁺) migrate to the cathode, where they gain electrons and are reduced to their metallic form (M⁰), plating onto the cathode surface.
Recovery – The deposited metal is harvested by mechanical scraping, melting, or other separation methods.

Cathode Types

Flat-plate cathodes – Can be cleaned and reused. Plated metal is recovered by scraping or by heating to the metal's melting point to separate it from the cathode.
Reticulated cathodes – Have a higher surface area, enabling faster deposition rates, but are not reusable and must be sent for recycling.
Starter cathodes – Made of pre-refined metal, they become an integral part of the finished product.

Applications

Electrowinning is used commercially to recover a wide range of metals, including:

Copper – The most common application, often combined with solvent extraction (SX/EW process).
Nickel
Zinc
Cobalt
Manganese
Silver
Gold – Typically from cyanide leach solutions.
Plutonium – The United States extensively used electrorefining with molten salt electrolytes to produce high-purity plutonium for nuclear weapons.

Practical Considerations

In practice, electrowinning is complicated by several factors:

Metal content in leach solutions is often low (a few percent is typical).
Other metals may deposit competitively with the desired metal.
Ores may not be easily or efficiently dissolved.

For these reasons, electrowinning is usually applied only to purified solutions of the target metal, such as cyanide extracts of gold ores or copper sulfate solutions from solvent extraction.