Electrorefining removes impurities from metals by dissolving them in a liquid solution and re-depositing them in a purer form on a negative electrode. Copper is commonly electrorefined, along with other metals like nickel, silver, gold, and zinc. The process can also be assisted by magnetic fields. Electrorefining is cost-effective and allows for the recovery of precious metals, making it a common method for producing copper and other metals used in various applications.
Electrorefining is the removal of impurities from a metal, achieved by placing two electrodes inside a container filled with liquid. The metal is dissolved by a positive electrode into the solution. It is then re-deposited in a purer form on the negative electrode. Copper is recovered from sulfide ores this way, as part of the smelting process. People started electrorefining metal in Europe in the mid-1800s, when only a few tons per day could be processed. Now, a plant in Chile, South America 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 in the sludge that collects outside the copper electrode. Copper has high electrical and thermal conductivity and is relatively easy to melt, extrude and roll. It is one of the most effective materials for making wire, tube and strip. Generally non-corrosive and non-toxic, copper is suitable for cooking foods and for use in ornaments, alloys and coins.
The use of copper in electrical wires, due to its properties as an electrical conductor, has made electrorefining even more common. Nickel can also be electrorefined, as can lead, silver, gold and zinc. Each of these metals that is removed from the main body of another can be harvested, formed into its own electrode, and further purified.
A liquid medium can be exposed to a combination of electric and magnetic fields. The deposition of pure metal can also be assisted by magnetic fields, in a process known as magneto-electrolysis. The deposition of metal, known as current density, is controlled by the electrode potential and, up to a point, the higher the potential, the faster the deposition rate. The current density limit can increase with magnetic field strength, which varies depending on the design of the electrorefining cell, the composition of the electrolyte solution, and the type of metal being purified.
Metals adhere better to substrates when magnetic fields are applied to the electrode cell design. Electrorefining is an effective process, performed 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 like copper can be manufactured efficiently in qualities and quantities that meet the needs of many different manufacturers and applications.
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