Process integration of sulphuric acid leach and particle size fractionation for cleaner copper concentrate production by enhancing the radionuclide mobility

Abstract

• A process integration of selective H 2 SO 4 leach and particle size fractionation. • Mobility of long-life radionuclides ( 238 U, 230 Th, 226 Ra, 210 Pb, 210 Po) in process. • The underlying mechanism of radionuclide mobility is unveiled. • A conceptual process is proposed for the cleaner Cu production from IOCGU ores. The growing demand of copper metal in the world continues to push the limit of utilization of complex copper resources, among which the iron oxide associated with copper–gold-uranium ore deposits (IOCG-U) contain economic copper and abundant gangues including uranium-bearing minerals that carry naturally occurring radionuclides and pose a challenge for public health and environment. To support the removal of radionuclides from copper flotation concentrate, the particle size fractionation method is integrated into the H 2 SO 4 leach process to illustrate the deportment of long-life radionuclides ( 238 U, 230 Th, 226 Ra, 210 Pb, 210 Po) and other non-copper elements during the process. H 2 SO 4 leach treatment largely dissolved non-copper elements (Fe, Ca, Mg, Al, K, F, U, Th, etc) from the gangue minerals and promoting the further copper phase transformation from the primary chalcopyrite and bornite towards covellite and copper sulphates. In the leach process, over 98% of 238 U and 230 Th were dissolved into H 2 SO 4 leach solution due to the decomposition of uranium-bearing minerals, while the released 226 Ra, 210 Pb and 210 Po from uranium-bearing minerals were largely remobilized, precipitated as insoluble sulphate salts, and accumulated in the small particle size fractions of the H 2 SO 4 leach residue. The underlying mechanism of this deportment is attributed to the mineralogical changes as an increased amount of covellite, digenite and copper sulphate are associated with the small particle size fractions, and serve as preferential hosts for 226 Ra, 210 Pb and 210 Po. Therefore, a conceptual flowsheet which facilitates further removal of 226 Ra, 210 Pb and 210 Po from the H 2 SO 4 leach residue is discussed based on particle size fractionation of the copper concentrate leach residue where radionuclides have been selectively leached or re-distributed.