Copper electrorefining

In the copper electrorefining process, fire refined copper or blister copper is cast to form the anodes and the cathode is either a reusable stainless steel sheet or a thin sheet of electro deposited copper which finally becomes a part of the refined cathode. The electrolyte is an acidified solution of copper sulfate. 

The metal deposition rate from aqueous solutions can be expressed as a current density (A m-2 of electrode surface) as the rate is linked to the current density by Faraday s law (1). In modern copper electrorefining and electrowinning, the current density is 300-350 Am-2, while in zinc operations it is greater, 450-500Am-2 or more. According to Faraday s law, enormous amounts of electricity are needed for the tens or hundreds of kilotons of metal produced in a typical electrolysis plant per year. 

Copper electrorefining plays a major role in the production and recycling of copper. In the production of copper, copper-bearing sulfide concentrates are first smelted to copper matte. The molten matte is oxidized to blister copper by a Peirce-Smith converter and the blister copper is fire refined and cast to copper anodes. Blister copper contains about 99% copper and impurities such as arsenic, bismuth, iron, nickel, lead, antimony, selenium, tellurium, and precious metals. It is cast into flat anodes, most often on a rotating horizontal wheel. The mold shape includes lugs by which the anodes are... 

Tab. 6 Typical voltage components in a copper electrorefining cell [5, p. 603]...

Energy Consumption In electrorefining, the thermodynamic cell voltage is zero. An applied voltage is only required to polarize the electrodes and overcome ohmic resistances. The typical voltage components in the copper electrorefining cell are shown in Table 6. 

The removal of lead from the electrolyte is an identical process to decopperizing copper electrorefining electrolyte bleed in liberator cells. 

M. Stelter, H. Bombach, Investigations on copper electrorefining at high current densities, Copper 2003 - Cobre 2003, Canadian Institute of Mining, Metallurgy and Petroleum, Santiago, Chile, 2003, pp. 555-567. 

Copper may also be recovered from leach solutions electrolytically. Electrowinning requires the use of an insoluble anode such as hard lead, comparable to the liberator cell used for liquor purification in copper electrorefining. Consequently, there are net electrochemical reactions involved in electrowinning (Eqs. 13.20 and 13.22), as opposed to the situation with electrorefining, so that about 1.7 V are required for this step. This results in a much higher electrical power consumption of about 2.8 kWh/kg copper for electrowinning, compared to about 0.2 kWh/kg for electrorefining. 

Further, primary current distributions are compared with analytic solutions and some other calculated examples are discussed. To check results of secondary distributions, a copper electrorefining cell was built and quantitative data were obtained. 

Finally, in the case of copper electrorefining, experimentally obtained data of electrode shape changes are compared with calculated values. 

Subsequently several examples are given and quantitative data, obtained in a copper electrorefining cell, are compared with calculated results. 

Electrodeposition and electrode dissolution in copper electrorefining. Numerical and experimental results... 

Figure 2. Schematic diagram of flow sheet to produce electro won nickel fi-om crude nickel sulfate produced fi om a copper electrorefining bleed.

M. Sheedy, P. Pajunen and B. Wesstrom, Control of copper electrolyte impurities -overview of the short bed ion exchange technique and Phelps Dodge El Paso case study, Proceedings of the Sixth International Copper-Cobre Conference Volume V Copper Electrorefining and Electrowinning, eds. G. Houlachi, J. Edwards and T. Robinson (Montreal, Quebec CIM, 2007), 345-357. 

Antimony Separation from Copper Electrorefining Solutions... 

Antimony and its compounds are listed among the most toxic elements of priority pollutants by the U.S. Environmental Protection Agency. Antimony exists in several industrial and mining wastes, such as chemical and allied products, glass products, electrical and electronic equipment, lead acid storage batteries, and copper electrorefining solutions. 

Anode quality is vital in particular, insoluble particulate matter (from soluble Cu anodes) in copper electrorefining or PbSO (from inert Pb- Ag or Pb-Sb) in copper or zinc elect rowinning may cause deleterious deposits. Metallurgically homogeneous, fine-grained soluble anodes are usually preferred via, for example, rolled fabrication techniques. 

Table 4L4 Typical electrolyte conditions for copper electrorefining...

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