Electrowinning cells

The ease with which the ferrous ion can be oxidized to a ferric ion in the electrowinning cell furthers this reaction. Attack on the copper is most apparent at the solution line, where it results in corrosion of the loops supporting the cathodes, leading to dropped cathodes. 

Monopolar cells operate at low voltages, and may requite high amperages. Industrial citcuits of cells may consist of one hundred or more monopolar cells in series. Monopolar electrodes are used in some membrane chlor-aLkaU cells (Figs. 4 and 5), fluorine cells (Fig. 6), and in metal electrowinning cells (Fig. 7). 

Systems for evaluating electrolytes for metal electrowinning have been developed and are being used commercially in zinc production (96). Computerized mathematical models of zinc electrowinning cells have been developed and vaUdated by comparison with experimental data taken from pilot-plant cells (97). 

The liquor from the first reaction is used as a pregnant liquor to be fed to electrowinning cells. An important electrical current benefit is realized in that it is only necessary to convert cuprous copper (Cu+) to copper rather than the conventional electrowinning process where cupric copper ( - ) is converted to copper. In an alternative process developed by Cymet (6), the cuprous chloride is crystallized from this liquor by cooling. The cuprous chloride is later reduced to copper in a furnace using hydrogen. 

Fig. 7. Sections of metal electrowinning cell without diaphragm (a), end view (b), side view where A is anode and C is cathode.

Deutscher, R.L. and Cathro, K.J (2001) Organochlorine formation in magnesium electrowinning cells. Chemosphere 43, 147-155. 

Metal removal and recovery could be carried out by depositing on a three-dimensional cathode until most of the active surface area of the porous cathode is occupied by the plated metal. The used cathode would then be sent to an electrowinning cell where it would be regenerated by anodically stripping the metal which is deposited onto stainless steel sheets. The metal is then peeled off the sheets as a nontoxic, salable product. Baker Brothers/Systems (Stoughton, MA, USA) currently use this process in their high-surface-area metal recovery systems. 

The controlled grain structure allows forming an adherent protective oxide coating within days when placed in an electrowinning cell without the necessity of being preconditioned [13]. In sulfuric acid electrolytes, the introduction of cobalt ions into the solution reduces the anode overvoltage and the corrosion rate of lead. 

The OMG Harjavalta nickel refinery has 126 electrowinning cells, of which 108 are commercial cells and 18 are starting sheet shells. The older cells have 49 insoluble lead anodes and 48 cathodes and the newer cells have 53 anodes and 52 cathodes each. Figure 20 shows the schematic cell construction used at the Harjavalta nickel refinery. The bagged cathodes are nickel starting sheets made by the deposition of nickel for 48 hours onto a titanium mother blank. The deposits are stripped and automatically made up into starting sheets. The purified solution is fed separately to the cathode compartments at... 

J. Moyes, J. Lam, V. Santos, The intec copper process development of a new electrowinning cell in Copper 2003 - Cobre 2003, (Eds. J. E. Dutrizac, C. G. Clement), Canadian Institute of Mining, Metallurgy and Petroleum, Santiago, Chile, 2003, pp. 487-508. 

C. Frias, M. A. Garcia, G. Diaz, Industrial size PLACID electrowinning cell in Aqueous Electrotechnologies Progress in Theory and Practice 9-13 February 1997, (Ed. D. B. Dreisinger), TMS, Orlando, 1997, pp. 101-113. 

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