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Insoluble anodes for electrowinning zinc and other metals.

Cole-ER Jr.; O'Keefe-TJ
Rolla, MO: U.S. Department of the Interior, Bureau of Mines, RI 8531, 1981 May; :1-25
This Bureau of Mines investigation was prompted by the need for a stable anode for electrowinning metals, particularly zinc and copper, from acid solutions. The polarization behavior of Pb-Ag (1 pct Ag) anodes in H2SO4 and fluoride solutions was determined as the first step in the development of such an anode. A luggin capillary, DC power supply, high-impedence voltmeter, and other equipment standard to an electrochemical laboratory were used in this study. It was determined that during polarization, a relatively hard, stable coating of pBo2 was formed on the surface of the lead-silver anode and the rate of formation of this coating was considerably enhanced by the presence of fluoride ions in solution. Subsequent investigations at the Bureau of Mines Rolla Research Center resulted in the development of a PbO2-coated titanium PbO2-Ti) anode. Results of this effort were presented in Bureau of Mines Report of Investigations 8111. Additional data resulting from extensive testing of the PbO2-Ti anodes, as well as process improvements and innovations, are included in this report. The anodes were considered generally unsatisfactory for zinc electrowinning because of lower conductivity, higher oxygen overvoltages, and shorter in-cell life as compared with the Pb-Ag anodes now being used in industry. However, the PbO2-Ti anodes were used successfully to oxidize waste chromium solutions and to electrowin copper.
Anodes; Copper; Electrowinning; Lead; Oxide coatings; Polarization; Silver; Titanium; Zinc
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IH; Report of Investigations
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Rolla, MO: U.S. Department of the Interior, Bureau of Mines, RI 8531
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division