The removal of lead from chalcopyrite surfaces in relation to radionuclide removal from copper minerals

Surface contaminants, specifically arsenic, mercury, bismuth and radionuclides, present environmental and health concerns and prove challenging to separate in processing plants due to the nature of their association with mineral surfaces. This paper explores alternative methods to the existing hydrometallurgical and pyrometallurgical techniques for separating said radionuclide from economically important copper resources. This study uses Cryogenic X-ray Photoelectron Spectroscopy to determine what species form on the surface of chalcopyrite (a major copper mineral) when it is exposed to lead nitrate, a proxy for radionuclide Pb-210. It then uses Time-of Flight Secondary Ion Mass Spectrometry to investigate the impact of both tumbling and stirred regrinding on the prevalence and distribution by size of lead phases on the chalcopyrite surface. PbS, PbSO3, PbSO4 and PbO were all detected on the chalcopyrite surface throughout the various processing stages. Stirred regrinding removed 38.5% of the lead from the chalcopyrite surface compared to 5.4% of lead removed by tumbling regrinding. Additionally, stirred regrinding caused lead to be concentrated in the fine particle size range (<25 mu m), a phenomenon not observed in the tumbling regrinding scenario. This was attributed to the abrasion breakage mechanism that is dominant in stirred regrinding causing the lead phases to be liberated from the chalcopyrite surface as fine particles. A novel application of stirred regrinding to the removal of strongly-adsorbed radioactive contaminants from copper is proposed to facilitate lead removal with minimal clean chalcopyrite loss. This process could potentially be applied to remove other surface contaminants as well. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study explores alternative methods for separating radionuclides from copper resources, finding that stirred regrinding is more effective in removing lead from chalcopyrite surfaces compared to tumbling regrinding. Stirred regrinding also concentrates lead in fine particles, offering a novel approach for removing radioactive contaminants with minimal chalcopyrite loss.