Cupric chloride leaching of model sulfur compounds for simple copper ore concentrates
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INTRODUCTION
INTEREST in hydrometallurgical processe~ for treating copper sulfide concentrates continues to be spurred by economic and regulatory factors that require extensive and expensive modifications of existing pyrometallurgy technology. Concerns over air pollution from smelters have led to increasingly stringent regulatory standards which have caused closings at some locations. During the decade of 1970 to 1980, chloride based hydrometallurgical processes gained recognition as potential alternatives to pyrometallurgy in many instances. The status of many of these processes for a variety of metals is reviewed in the Proceedings of an international symposium at Brussels in 1977. l'z Ferric chloride and cupric chloride based aqueous processes, as well as combinations of both, have attracted attention as candidates for processing copper ore and scrap, j-~2 Our own interest in these processes 34 originated from Hoepfner's copper chloride based patent of 1893,s modified recently by Chambers, 6 from the works of Kruesi and coworkers, 7 and from Hayer et al.,8 who emphasized ferric chloride leaching. Both ferric chloride and cupric chloride systems seemingly satisfy bxoad criteria for use in copper processing. Cupric chloride has proven to be an efficient and effective leaching agent when present in excess with copper sulfide ores or for secondary sources of copper such as scrap or cement. 3 Interest in cupric chloride for leaching sulfide concentrates, however, has been moderated by the finding that the leaching process in the presence of sulfur does not proceed with complete reduction of cupric ion. ~'9-]~ Processing modifications can compensate for the incomplete reduction, 4"~J2 but only the ferric chloride based CLEAR process, L~ and the updated Cymet process ~z have been refined to the production stage. G E O R G E W. M c D O N A L D , Graduate R e s e a r c h A s s i s t a n t . and STANLEY H. LANGER, Professor of Chemical Engineering, are with the Department of Chemical Engineering, University of Wisconsin, Madison, WI 53706. Manuscript submitted November 22, 1982. METALLURGICAL TRANSACTIONS B
However, on reviewing a general version of the Hoepfner process as represented by Figure I, the appealing possibility of a cupric chloride based process which could lead to fewer problems with purification and metal winning becomes evident. This would be particularly true in comparison with ferric chloride leaching when nonferrous chalcocite and covellite ores are being processed. With this in mind, the present investigation was directed toward exploring and understanding cupric chloride leaching complications with concentrates using model compounds, as well as identifying possible routes for overcoming these complications. The generalized cupric chloride process of interest, outlined in Figure 2, involves the following four basic steps: Cu C I 2 / N o C I
SOLUTION
or OXIDANT COPPER SULFIDE ORES
] IELECTROLYTE RECYCLE
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LTRAT,ON---[
SULFUR
AQUEOUS NoOH
x
CONCOMITANT METAL HYDROXIDES
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