Purification of Impure Copper can be Achieved by Electrolytic Refining
What is impure copper: The smelting process takes copper ore and processes it into metal. This metal (sometimes called “blister copper” contains other metals (impurities) which often include valuable metals as gold, silver, arsenic, platinum and others. We all know that pure copper is important in making electrical wire, but copper wires’ electrical conductivity can be dramatically reduced by those impurities if not well purified.
Electrolytic refining (electrorefining) is a process used to make impure copper pure. Unlike aluminum, copper metal is fairly easy to obtain chemically from its ores. By electrolysis, it can be refined and made very pure—up to 99.999%. The electrorefining is at the heart of not only copper purification, but the production of sodium hydroxide and chlorine.
Copper Electrolytic Refining Process
In the electrolytic refining of copper, a thin sheet of high-purity Cu serves as the cathode. The blister copper plates are taken and used as anodes in an electrolyte bath of copper sulfate, CuSO4, and sulfuric acid H2SO4. As current is passed through the solution, pure copper from the anodes is plated out onto pure copper cathodes and the foreign metals accumulate as “anode sludge” in the bottom of the anode compartment of the electrorefining cell–The oxidation of copper is more facile than the oxidation of water so metallic copper dissolves into solution as copper(II) ions, leaving behind many of the impurities (less active metals). The cathode increases in size, and the anode erodes away, thereby building up more and more pure copper on the cathode.
Copper Electrolysis Machines
Electrolysis of copper transfers copper atoms from an impure copper anode to a pure copper cathode, leaving the impurities behind. A series of equipment are installed in the plant. Next, Whirlston Metal Recycling Machinery will detail more information on the cost-effective setup.
Copper Anodes: In copper processing, a copper anode is an intermediate product from the smelting furnaces which is used as a copper source from which to make copper cathodes during electrolysis. In electrolysis, it is the positive terminal. Oxidation occurs at the anode. The anode is replaced when it’s been eroded too far and risk falling apart. The remainder of the anodes are melted and cast into new full-size anodes. The electrolyte is monitored until too much impurities have built up, then it is replaced with fresh electrolyte while the old is treated to recover the dissolved metals. In large copper plants the main contaminant in the electrolyte is nickel.
Copper Cathode Sheets: also called “the negative terminal”. Thin “starter sheets” of highly pure copper foil (sometimes stainless steel sheet) are used as the cathodes, placed in between the anodes. When current is applied (over 200 amperes), copper (as well as other metals) leaves the anode and moves through the solution toward the cathode — Copper (99.99% pure copper) is deposited to the cathode sheet over a number of weeks until a thick enough layer of pure copper has been built up and the cathode is replaced.
Electrolytic Copper Refining Tank: the anodes of impure copper are refined by electrolytic means to the pure cathode copper in the refining tank. It is filled with a solution of sulfuric acid and copper(II) sulfate, in which the anodes and cathodes are interleaved and immersed — between anodes are suspended starting sheets which are thin sheets of electrolytic copper. The cathode sheets remain in the tank until sufficient copper from the anode has been deposited on the cathode. Impurities which is below copper stay as metal and fall to the bottom of the refining tank as “anode sludge”.
Off-gas Treatment System: The whole plant should include a dust collection system.
Technical Specification of Copper Electrolytic Refining Plant
|Impure copper powder||500kg/day||1000kg/day||2000kg/day||5000kg/day|
|Copper electrolysis cycle||15 days/48 hour||15 days/48 hour||15 days/48 hour||15 days/48 hour|
|Production capacity of pure copper||370kg||750kg||1500kg||3750kg|