Abstract
The catalytic mechanism of Ag+ for chalcopyrite bioleaching by mesophilic culture (at 30 °C) and thermophilic culture (at 48 °C) was investigated using synchrotron radiation-based X-ray diffraction (SR-XRD) and S K-edge and Fe L-edge X-ray absorption near edge structure (XANES) spectroscopy. Bioleaching experiments showed that copper extraction from chalcopyrite bioleaching by both cultures was promoted significantly by Ag+, with more serious corrosion occurring on the minerals surface. SR-XRD and XANES analyses showed that the intermediates S0, jarosite and secondary minerals (bornite, chalcocite and covellite) formed for all bioleaching experiments. For these secondary minerals, the formation of bornite and covellite was promoted significantly in the presence of Ag+ for both cultures, while Ag+ has almost no effect on the formation of chalcocite. These results provided insight into the catalytic mechanisms of Ag+ to chalcopyrite bioleaching by the mesophilic and thermophilic cultures, which are both probably due to the rapid formation of bornite by Ag+ and the conversion of bornite to covellite.
Highlights
Chalcopyrite is the most abundant copper mineral amongst the copper sulfides and accounts for more than 70% of the copper minerals in the world [1]
Bioleaching experiment has shown that Ag+ can significantly promote the dissolution of chalcopyrite by both mesophilic and thermophilic cultures
The dissolution of chalcopyrite can be more significantly promoted by the thermophilic culture than that by the mesophilic culture, with more serious corrosion on the mineral surfaces
Summary
Chalcopyrite is the most abundant copper mineral amongst the copper sulfides and accounts for more than 70% of the copper minerals in the world [1]. Bioleaching technology is a promising method to recover copper from those ores with advantages such as low-cost and environment-friendly [4]. One common problem limiting the application of this technology to industrial applications is that the copper extraction during bioleaching of chalcopyrite is still low [5,6]. To solve this problem, various methods have been investigated to improve the copper extraction rate in chalcopyrite bioleaching, such as adding catalysts (Ag+ , Cl− or carbon materials [7,8,9]) and Minerals 2018, 8, 382; doi:10.3390/min8090382 www.mdpi.com/journal/minerals. Miller and Portillo [11] first reported the improvement for Ag+ on chalcopyrite dissolution and proposed a direct reaction model to explain the catalytic mechanism (Equations (1) and (2))
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