Microscopy and XRD investigations of the product layer formed during chalcopyrite leaching in copper(II) chloride solutions
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Outotec Oyj, Base Metals
Aalto University
Mari Lundstrom   

Outotec Oyj, Base Metals P.O. Box 86, 02201 Espoo, Finland
Publication date: 2011-01-01
Physicochem. Probl. Miner. Process. 2011;46(1):263–277
This study presents a microscopy investigation of chalcopyrite surface product layers formed in concentrated cupric chloride solutions, similar to those used in the HydroCopper® process. The physical appearance as well as chemical composition of chalcopyrite reaction product layer was studied as a function of pH (from 1 to 3) and leaching time. Microscopic methods, such as stereo-optical microscopy, scanning electron microscopy (SEM) analyses and X-ray diffraction analyses were applied. To study the chalcopyrite reaction product layers, mineral surface was leached either at open circuit potential (OCP) or treated by anodic polarization. It was shown that at lower pH values a gray elemental sulfur layer was the prevailing phase in the reaction product layer even with longer (22 h) leaching times. With increasing pH (up to from 2 to 3) the reaction product layer became more yellow-brown, and consisted mainly of FeOOH. However, also elemental sulfur was observed at higher pH. At pH 1 the thickness of the reaction product layer increased from ca. 1 to 9 μm with increasing leaching time up to 22 hours. At pH 2 the layer grew up to ca. 10 μm and at pH 3, up to ca. 14 μm.