The leaching of chalcopyrite with cupric chloride
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I.
INTRODUCTION
CUPRIC chloride is used as a leachant of chalcopyrite in the CLEAR process. 1 As reported by Jones and Peters, 2 cupric chloride is a more reactive oxidant than ferric chloride for chalcopyrite leaching. Also, the present authors and their co-authors ~ pointed out that the cupric chloride accumulated during the leaching of chalcopyrite concentrate with ferric chloride may play an important role in the later stage of leaching. Many researchers have studied the leaching of chalcopyrite in acidic cupric chloride solutions. Some of them postulated that the leaching occurs electrochemically. Papers reported by Bonan et al. 4 and Wilson and Fisher 5 are typical examples, although no direct experimental support has been provided for an electrochemical mechanism of chalcopyrite leaching in the acidic cupric chloride solution. Also, only a limited amount of knowledge about the morphological aspect of chalcopyrite leaching is available. To obtain a fuller understanding of the mechanism of chalcopyrite leaching, we examined chaicopyrite leaching chemically, electrochemically, and morphologically. The correlation between the chemical leaching of chalcopyrite in acidic cupric chloride solutions and the electrochemical leaching of chalcopyrite in acidic chloride media was examined to test the appropriateness of the electrochemical mechanism proposed by previous researchers.
II.
EXPERIMENTAL PROCEDURES
A. Samples and Chemicals Chalcopyrite crystals of museum grade supplied from Shakanai Mine, Akita prefecture, Japan, were used in leaching experiments in this work. Their copper, iron, and sulfur contents were 34.8 pct, 30.4 pct, and 34.8 pct, respectively. The mineral crystals were not associated with any TETSUJI HIRATO, Graduate Student, HIROSHI MAJIMA, Professor, Department of Metallurgy, and YASUHIRO AWAKURA, Lecturer, Department of Metallurgy, are with Kyoto University, Kyoto, Japan 606. Manuscript submitted June 2, 1986. METALLURGICALTRANSACTIONS B
gangue minerals and the purity of the specimens appeared to be good. Disk specimens were prepared by cementing a chalcopyrite crystal in an epoxy resin such that one surface (0.3 to 0.5 cm 2) was exposed to the leaching solution. Moreover, electrical contact was made by soldering copper wire with silver paste on the rear face of each specimen for electrochemical measurements. After fine wet grinding with emery paper, the specimen was subjected to experiments. The exposed surface area was measured prior to each experiment by using a planimeter on an enlarged photograph. Deionized water whose specific resistivity was 5 • 1061) cm and reagent grade chemicals were used to prepare all electrolyte solutions.
B. Leaching Experiments A 0.5 dm 3 glass separable flask with a fitted lid having five necks was used as a reaction vessel for all leaching experiments. The center hole of the lid was used for the accommodation of a rod holding a disk specimen of chalcopyrite. The other four necks were used for the introduction and discharge of nitrogen gas, the accommodation o
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