Abstract
Understanding the oxidative mechanisms of chalcopyrite in various hydrothermal fluids is of great significance to improve copper extraction and to model the geochemical cycling of copper, iron, and sulfur. This paper investigated the effect of NaCl on the electrochemical oxidation of chalcopyrite at 340 °C and 21 MPa using polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and Raman spectroscopy. The experimental results showed that NaCl can promote chalcopyrite leaching. As NaCl concentration increases, the protective property of the oxidation layer degraded. In the absence of NaCl, the oxidation layer that consisted of CuSn, (n ≥ 1), probably with some Fe2O3 and Fe(OH)3 and also in the presence of NaCl, Fe2O3, is the principal oxidation product. More rapid ionic diffusion and further chemical reaction contributed to the improvement of chalcopyrite dissolution with increasing NaCl concentration. A dissolution mechanism is proposed in this paper to explain the chalcopyrite leaching processes which is dependent on NaCl concentration.
Highlights
Chalcopyrite (CuFeS2 ) is the most abundant Cu-bearing ore mineral, present in volcanogenic massive sulfide ore deposits and sedimentary exhalative deposits formed by hydrothermal circulation [1,2,3]
The purpose of this study is to reveal the effect of Cl− on the leaching rate and the dissolution pathway of chalcopyrite at 340 ◦ C and 21 MPa by in situ electrochemical measurements and surface characteristics
It was observed that the anodic polarization curves of chalcopyrite in the solutions with various NaCl concentrations
Summary
Chalcopyrite (CuFeS2 ) is the most abundant Cu-bearing ore mineral, present in volcanogenic massive sulfide ore deposits and sedimentary exhalative deposits formed by hydrothermal circulation [1,2,3]. The electrochemical oxidation of chalcopyrite in hydrothermal system affects the dissolved transition metal concentrations and the mineral stabilities in fluids. The element sulfur, and metal-deficient polysulfide have been considered as the possible composition of the passivation layer to inhibit further chalcopyrite oxidation [4,5]. Understanding the chalcopyrite electrochemical processes by hydrometallurgical routes at high temperature and pressure can be achieved by investigating chalcopyrite oxidation products and their leach rate. As Cl− is common in hydrothermal fluids, and investigating the effect of NaCl on the electrochemical oxidation of chalcopyrite at high temperature and pressure could (1) model the geochemical cycling of copper, iron, and sulfur, and (2) provide an alternative way to improve copper extraction. At low temperature and pressure, chloride ions addition can increase the crystallinity
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