Rate phenomena involved in the dissolution of chalcopyrite in chloride bearing lixiviants
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THE dissolution of chalcopyrite in chloride-bearing lixiviants has been studied by several investigators who have shown that reaction occurs rapidly when finelydivided material is involved. 1-9 For example, Haver and Wong 7 found that essentially complete reaction is obtained in two hours when 3.8 micron chalcopyrite is reacted with ferric chloride at 106 ~ With regard to rate phenomena, Jones and Peters8 observed linear kinetics and found that leaching takes place via the reaction, CuFeS2(s) + 4Fe(+,~--* Cu(+~q2) + 5Fe(+aq ~) + 2S(s)
[1] These authors postulated that dissolution occurs electrochemically and measured the mixed potential of chalcopyrite in contact with lixiviants containing ferric sulfate, ferric chloride and cupric chloride. The variation of the mixed potential with ferric iron addition was found to be 72 my/decade in chloride media and 65 mv/decade in a sulfate-bearing solution. Linear kinetics were also observed by Dutrizac? The effect of rate on ferric chloride concentration was investigated, and 0.8 power dependence was observed. Rate was found to increase initially with chloride concentration but became independent of this quantity for values greater than about two molar. An activation energy of 41 kJ/mol was observed. As is apparent, both the electrochemistry and the kinetics of chalcopyrite dissolution with ferric chloride have been examined independently. However, the electrochemical aspects of dissolution have never been incorporated in the rate model for this system. In this view it was the purpose of the present investigation to B. R. PALMER is Professor and M. C. FUERSTENAU is Professor and Head, Department of Metallurgical Engineering, South Dakota School of Mines and Technology, Rapid City, SD. C. O. NEBO, formerly AMAX Fellow, Department of Metallurgical Engineering, South Dakota School of Mines and Technology, is currently Research Metallurgist, Duval Corporation, Sahuarita, AZ. M. F. RAU, formerly Teaching Assistant, Department of Metallurgical Engineering, South Dakota School of Mines and Technology, is currently Graduate Research Assistant, Department of Metallurgy and Materials Science, University of California, Berkeley, CA. Manuscript submitted August 18, 1980. METALLURGICAL TRANSACTIONS B
develop an electrochemical rate model of the dissolution of chalcopyrite with ferric chloride. EXPERIMENTAL MATERIALS AND REAGENTS Massive samples of chalcopyrite from Temagami, Ontario were used in this investigation. The copper, iron and sulfur contents were 33.06, 29.04 and 33.25 percent, respectively. Reagent-grade materials were used in preparation of the lixiviants. The water used in lhis study was prepared by passing distilled water through a mixed-bed ion exchange column. The leaching of chalcopyrite was effected in a covered two-liter glass reaction vessel. Openings were incorporated in the cover for admission of a stirring rod, a thermometer, a gas dispersion tube, and a sampling device. The sampling apparatus contained a glass tube through which oxygen-free purging gas was admit
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