Key Takeaways & Executive Findings
- •• Mechanical activation significantly reduces particle size and increases surface area and energy of chalcopyrite and pyrite, enhancing their reactivity. • The combined use of mechanically activated chalcopyrite and pyrite boosts copper extraction by 51.8% compared to non-activated mixtures, reaching 63.4%. • Pyrite's catalytic role in chalcopyrite bioleaching is activated by mechanical activation, providing additional oxidants and acting as a cathode in galvanic coupling. • A mechanistic model is proposed to explain how mechanical activation promotes pyrite's role in accelerating chalcopyrite bioleaching.
Abstract
Mechanical activation (MA) is a significant pretreatment technique for enhancing the dissolution of mineral; however, its promotion effect on the role of pyrite during chalcopyrite bioleaching has not been elucidated up to now. In this study, the effect of MA on the role of pyrite on chalcopyrite bioleaching mediated by Acidithiobacillus ferroxidans was investigated by X-ray diffraction, scanning electron microscopy, particle size distribution analysis, and electrochemical measurement. The results showed MA could significantly reduce the minerals particle size, and increase the specific surface area and surface energy of minerals. For example, the d50 of chalcopyrite reduced from 13.40 to 0.31 μm after MA. The copper extraction of mixed MA-chalcopyrite and MA-pyrite system was 63.4%, which exhibited a 51.8% enhancement compared to the non-activated mixed system. Electrochemical experiments identified that the strengthening effect of pyrite on chalcopyrite dissolution was negligible before MA. After MA, the dissolution mechanism of chalcopyrite was not changed, and pyrite could not only provide additional oxidants (acids and iron) but also act as the cathode in the galvanic couple. In this case, the bioleaching of chalcopyrite was accelerated. Therefore, a model of the promotion effect of mechanical activation on the role of pyrite on chalcopyrite bioleaching was proposed.
1. Introduction
Minerals are precious and non-renewable resources given by our Mother Earth. To utilize them, a series of processes have been developed, such as mining, grinding and leaching. After decades of mining activities and human usage, they now became exhausted [1]. With the depletion of high grade, how to process the low and complex minerals has become a research hotspot. Bioleaching has been successfully applied in processing low grade ores to recover metals, such as copper, zinc and refractory gold [2]. Compared with pyrometallurgical process which needs high investment and causes severe environmental pollution, bioleaching is a promising technology for the advantages of low cost and less pollution [3].
Chalcopyrite (commonly regarded as CuFeS2), which is the predominant copper-containing resource, represents approximately 70% of the known copper reserves in the world [4]. However, bioleaching processes have not been widely applied in treating chalcopyrite due to the slow extraction rate. Many previous studies have proposed that the extraction of chalcopyrite was mainly inhibited by the surface passivation film formed on the chalcopyrite surface, and the composition of the passivation layer has been investigated [5 −8]. KLAUBER et al [6] proposed that during acid ferric leaching, the primary constituent of the passivation film was element sulfur (S0) and the second major constituent was disulfide (S2−). SANDSTRÖM et al [7] studied chalcopyrite bioleaching process with extremely thermophilic microorganism and found that, even at low redox potential, element sulfur could be completely oxidized to sulfate (SO4−); hence, the passivation of chalcopyrite was due to the formation of jarosite. To date, there is no consensus on the specific composition of the passivation film, but element sulfur, disulfide, polysulfide and jarosite are regarded as the primary components.
Pyrite (FeS2) is usually associated with chalcopyrite in native deposit [9]. Many studies have found the interactions between pyrite and chalcopyrite in leaching processing, and the promoting effect on chalcopyrite is recognized as galvanic effect [10−14]. In this case, pyrite would act as the cathode and the dissolution of chalcopyrite is enhanced. DIXON et al [10] developed a technology (GalvanoxTM) to increase copper leaching rate at the atmospheric pressure and temperature. NAZARI et al [11, 12] reported that not all pyrite samples have the same promotion effect on chalcopyrite dissolution process, and techniques were investigated to improve the catalytic performance of pyrite. In our previous studies [13, 14], we found that pyrite could enhance chalcopyrite leaching efficiency by changing the redox potential and maintaining it in the appropriate range. In this range, the formation of polysulfide was inhibited, combined with the galvanic effect; thus the chalcopyrite dissolution was promoted.
Mechanical activation (MA), as a pre-treatment technique for mineral processing, has been shown to enhance the reactivity of minerals by increasing their surface area and creating defects. However, its specific effect on the role of pyrite in chalcopyrite bioleaching remains unexplored. This study aims to fill that gap by investigating the influence of mechanical activation on the synergistic interaction between pyrite and chalcopyrite during bioleaching, providing insights for optimizing industrial bioleaching processes.
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LIAO Rui, YU Shi-chao, YANG Bao-jun, SUN Xin, WANG Chen-xu, QIU Guan-zhou, WANG Jun (2025). Promotion effect of mechanical activation on the role of pyrite in chalcopyrite bioleaching. Journal of Central South University. https://doi.org/10.1007/s11771-025-6071-7
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Frequently Asked Questions
What is the main finding of this study?
The study demonstrates that mechanical activation significantly enhances the role of pyrite in promoting chalcopyrite bioleaching, leading to a 51.8% increase in copper extraction compared to non-activated mixtures.
How does mechanical activation affect mineral properties?
Mechanical activation reduces particle size, increases specific surface area and surface energy, thereby enhancing the reactivity of chalcopyrite and pyrite.
What is the role of pyrite in chalcopyrite bioleaching after mechanical activation?
After mechanical activation, pyrite acts as a cathode in galvanic coupling and provides additional oxidants (acids and iron), accelerating the dissolution of chalcopyrite.
What techniques were used in this study?
The study employed X-ray diffraction, scanning electron microscopy, particle size distribution analysis, and electrochemical measurements to investigate the effects.
What is the significance of this research for industrial bioleaching?
The findings suggest that mechanical activation can be a promising pretreatment to improve the efficiency of chalcopyrite bioleaching, potentially making the process more economically viable for low-grade ores.
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