Using zinc cathodes for zinc electrowinning.
Cole-ER Jr.; Smith-LL; Fine-MM
Rolla, MO: U.S. Department of the Interior, Bureau of Mines, RI 8344, 1979 Jan; :1-19
The Bureau of Mines developed a procedure that enables substitution of zinc cathodes for the aluminum cathodes normally used in commercial zinc electrowinning. Using zinc cathodes eliminates the necessity for stripping and makes it possible to electrowin zinc from solutions derived from material containing excessive amounts of soluble fluorides; for example, zinc concentrates obtained as a byproduct of fluorspar mining in Kentucky and Illinois. To demonstrate the viability of using zinc cathodes, fluoride-containing zinc concentrate was roasted, leached, and purified according to current commerical practice. Electrolysis was carried out in 0.8-, 1-, 5-, and 10-liter cells at 35 deg to 40 deg c with a cathode-current density of 8 amp/dm2 in a solution containing 65 g/l Zn++ and 200 g/l H2SO4 using PbO2 anodes. Zinc deposits were produced on zinc cathodes with good morphology and excellent current efficiency (90 to 94 pct) in solutions containing enough fluoride (x0.5 G/l, F-) to cause sticking of zinc to aluminum cathodes. The approach described has failed previously because of severe solution-level corrosion of the zinc cathodes. The present investigation found that the use of a simple mechanical barrier to prevent oxygen migration from the anode was sufficient to prevent solution-level corrosion of the zinc cathode starting sheet.
Cathodes; Concentrates; Electrolysis; Electrolytes; Electrowinning; Fluorides; Zinc
IH; Report of Investigations
NTIS Accession No.
Rolla, MO: U.S. Department of the Interior, Bureau of Mines, RI 8344