The mineralogical deportment of germanium in the Clarksville Electrolytic Zinc Plant of Savage Zinc Inc.
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INTRODUCTION
GERMANIUM is a strategic element which is widely used for infrared night vision systems, fiber optics, gammaray detectors, semiconductors, catalysts, and phosphors. In 1992, world production capacity was estimated to be 270 t Ge/year, but consumption was only - 6 5 t Ge/year. The reported price of germanium metal ranged from $350/kg to $1000/kg depending on the contractual arrangement.I~] Germanium is recovered from the dusts and residues generated during the processing of certain complex Zn-Cu-Pb sulfide ores or low-temperature sphalerite ores. The germanium is commonly concentrated in the sulfide minerals and their oxidation products. For example, at the Apex mine (St. George, Utah), Ge is found in the hematite and goethite oxidation products in concentrations up to 1.0 pct Ge but not in the associated quartz.t2.31 Germanium substitutes in the structure of some sphalerites, especially those from lowtemperature epigenetic deposits in sedimentary rocks; concentrations of several hundred parts per million Ge are common in such sphalerites. [4j Although the form of Ge in the sphalerite remains unresolved, possible mechanisms include the coupled substitution of a Ge4+ ion and a vacancy for two Zn 2+ sites or the substitution of uncharged Ge atoms on both the zinc and sulfur sublattices71 The Gordonsville mine is located about 60 km east of Nashville on the northern flank of the Nashville dome in central Tennessee.E61The mine is currently owned by Savage Zinc Inc., which was formerly Jersey Miniere Zinc. Sphalerite is the major ore mineral, and the resulting zinc concentrate is Ge rich; it has an average Ge content of - 4 0 0 ppm.iT.81 Although the mineral form of Ge in the zinc con-
J.E. DUTRIZAC and T.T. CHEN, Research Scientists, are with the Mineral Sciences Laboratories, CANMET, Ottawa, ON, Canada KIA0GI. R.J. LONGTON, Engineering Superintendent, is with Savage Zinc Inc., Clarksville, TN 37041. Manuscript submitted February 27, 1995. METALLURGICAL AND MATERIALS TRANSACTIONS B
centrate has not been reported, it is assumed that most of the Ge occurs in solid solution in the sphalerite structure, as is the situation at the nearby Hoover and Knight deposits.[ 91 The Gordonsville zinc concentrate is processed at the 98,000 t/year Clarksville Electrolytic Zinc Plant of Savage Zinc Inc.tT.sJ The concentrate is oxidized in a Lurgi fluid bed roaster, and the resulting calcine, which contains virtually all of the germanium in the concentrate feed, is subjected to neutral and weak acid leaching. Because of the low Fe content of the calcine, no hot acid leaching circuit is employed. In the leach plant, spent electrolyte and other recycled process streams are mixed with purchased ferrous sulfate and MnO: to produce an Fe-bearing acid solution. This solution is contacted with the roaster calcine in a 30 m 3 pulping tank. The resulting slurry overflows to the neutral leaching circuit which consists of a series of five 80 m 3 tanks operating at 72 ~ to 73 ~ Spent electrolyte is added to the first and third tan
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