Electrorefining is the removal of impurities from a metal, accomplished through the placement of two electrodes within a fluid-filled container. The metal is dissolved from a positive electrode in the solution. It is then re-deposited in purer form on the negative electrode. Copper is recovered from sulfide ores this way, as part of the smelting process. People first began electrorefining metal in Europe in the mid-1800s, when just a few tons per day could be processed. Now, a plant in Chile, South American can electrorefine up to 1,700 tons per day of copper.
Most of the world’s copper is produced through electrorefining, which removes silver, gold, and platinum metals as well as nickel. The precious metals that are separated can be recovered within the sludge that collects outside the copper electrode. Copper is high in electrical and thermal conductivity and is relatively easy to cast, extrude, and roll. It is one of the most effective materials for making wires, tubes, and strips. Generally non-corrosive and not toxic, copper is suited for cooking food and for use in ornaments, alloys, and coins.
The use of copper in electrical wire, because of its properties as an electrical conductor, has made electrorefining even more commonplace. Nickel can also be electrorefined, as well as lead, silver, gold, and zinc. Any of these metals that are removed from the main body of another can be collected, formed into their own electrode, and further purified.
A liquid medium can be exposed to a combination of electric and magnetic fields. The deposition of the pure metal can also be assisted by magnetic fields, in a process known as magnetoelectrolysis. Metal deposition, known as current density, is controlled by the electrode’s potential and, up to a point, the higher the potential, the higher the rate of deposition. The current density limit can increase with the magnetic field’s strength, which varies depending on the design of the electrorefining cell, composition of the electrolyte solution, and the type of metal being purified.
Metals adhere to substrates better when magnetic fields are applied to the electrode cell design. Electrorefining is an effective process, carried out in open tank electrolytic cells, which is also cost effective. When other precious metals are recovered and used or sold, this can result in sales that exceed the cost of electrorefining the original substance. Materials such as copper can be efficiently manufactured at qualities and quantities that meet the demands of many different manufacturers and applications.