The mineralogical characterization of tellurium in copper anodes
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I.
INTRODUCTION
T E L L U R I U M is a trace constituent of most copper sulphide concentrates, and the tellurium is partly collected in the copper anodes produced in most copper smelters, tu In some operations such as the H o m e Smelter of the Noranda Copper Smelting and Refining Company, t2] gold ores, secondary materials, and electronic scrap are also processed in the smelter, and such practices can result in significantly increased tellurium inputs. Preliminary mineralogical studies of the anodes from several copper refineries indicated that most of the tellurium reported as CuzSe-Cu2Te inclusions concentrated at the grain boundaries of the individual copper crystals. 13'4'5]Rarely, traces of tellurium were detected in some of the complex oxide phases present in the inclusions, but the low tellurium contents could have originated from the closely associated Cu2Se-Cu2Te phase. It is known that small amounts of tellurium and selenium dissolve in solid copper at elevated temperatures, and that some of the solid-solution tellurium can be retained by quenching. [6,7] The solid solubility of tellurium in copper was estimated to be 75 ppm at 800 ~ and 15 ppm at 700 ~ Because commercial copper anodes are cooled relatively rapidly, the possibility exists that part of the tellurium present could occur in dilutemetastable solid solution in the copper metal. Most of the tellurium present in copper anodes reports to the anode slimes generated during commercial electrorefining. The first step in the treatment of the anode slimes is decopperizing, which is commonly affected in C u S O 4 - H 2 S O 4 media. [9,~~ In addition to removing copper, the decopperizing step is often intended to solubilize all of the tellurium while leaving all of the selenium and silver in the slimes for further processing. An impure tellurium product is readily precipitated from the decopperizing leach solution, llu and high-purity tellurium is made from this material. 1~2~The success of the T.T. CHEN and J.E. DUTRIZAC, Research Scientists, are with the Mineral Sciences Laboratories, CANMET, Energy, Mines and Resources Canada, Ottawa, ON, Canada K 1A 0G 1. Manuscript submitted February 8, 1993. METALLURGICAL TRANSACTIONS B
decopperizing process in separating tellurium from selenium and silver in the anode slimes depends on the leaching conditions as well as on the mineral forms of the various elements. Thus, as an initial step in the elucidation of the complex reactions occurring during the decopperizing of copper refinery anode slimes, a systematic mineralogical study of a number of copper anodes was carried out to determine the tellurium carriers, their morphologies, and their relative abundances. A commercial copper anode having a "normal" impurity content as well as six anodes having elevated tellurium and silver contents were examined, and the results are reported in this article. II.
EXPERIMENTAL
A. Samples Seven anodes were supplied for study by the CCR Refinery of the Noranda Copper Smelting and Refining Company. One anode (381) was a no
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