Effect of polyvinyl pyrrolidone on chalcopyrite bioleaching with Acidithiobacillus ferrooxidans

Chalcopyrite (CuFeS2) is the most abundant copper-bearing mineral in nature. Large amounts of low-grade chalcopyrite ores cannot easily be utilized due to technical and economic limitations, which lead to an enormous waste of resources. Bioleaching is one of the most common methods to treat low-grade copper ores. However, the low leaching efficiency limits the industrial application of bioleaching chalcopyrite. In this study, polyvinyl pyrrolidone (PVP) was used to intensify the bioleaching of chalcopyrite with Acidithiobacillus ferrooxidans. The bioleaching results showed that PVP increased the bioleaching efficiency and the maximal effect was achieved by adding PVP after 6 days of experimental time. The solid leach residues were investigated using X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectrometry (XPS) analyses to elucidate the role of PVP. Elemental sulfur and jarosite were detected on the chalcopyrite surface. These compounds may have formed a "passivation" layer, thereby hindering bioleaching as described in the literature. Moreover, PVP inhibited the generation of elemental sulfur and weakened the stability of the "passivation" layer. Additionally, PVP may have improved the surface hydrophilicity of chalcopyrite, which probably lead to an enhanced solidliquid mass transfer.