TY - JOUR

T1 - The influence of humic substances on the weathering of PGE in chromitite of the Bushveld Complex: An experimental simulation of the weathering environment

T2 - An experimental simulation of the weathering environment

AU - Kotzé, E.

AU - Schuth, S.

AU - Goldmann, S.

AU - Holtz, F.

N1 - Funding Information: The authors wish to thank the staff of the Thaba Mine and of Mintek South Africa for their help in obtaining samples. We thank Moritz Hill and the Cronimet staff for access to the samples of the Thaba Mine and for permission to publish these results. We are particularly grateful for the assistance of D. Chetty of Mintek (Johannesburg, South Africa) for providing the tailings sample. This research was supported by the German Federal Ministry of Education and Research (BMBF) in the framework of the research and development cooperative project “Applied Mineralogy for the Resource Efficiency of Platinum Metals” (AMREP). Suggestions from the esteemed Dr John F.W. Bowles as well as an anonymous reviewer helped improve the manuscript.

PY - 2022/12/1

Y1 - 2022/12/1

N2 - Organic acids, including humic acid, play a significant role in the weathering of minerals containing metals such as Pt and Pd. They are also among the reactants which are under consideration for new hydrometallurgical methods of liberating unconventional PGE ores (such as the oxidised ores of the Great Dyke, Zimbabwe, and at locations in the Bushveld Complex of South Africa where PGE-bearing layers have been exposed to weathering). In order to better understand the processes operating during weathering of PGE-bearing chromitite seams of the Bushveld Complex, chromite concentrate originating from a South African chromium mine was subjected to reaction with different concentrations of synthetic humic acid. The results confirm the greater mobility of palladium in the environment compared to platinum. Crushed chromite concentrate showed greater mobility of Cr, but not of Pd or Pt, compared to uncrushed concentrate. Increasing the concentration of humic acid increased the amount of Pd and Pt in solution. These experiments give insight into the processes that govern the weathering of chromitite in the Bushveld Complex. The main Pd– and Pt-bearing minerals are not enclosed within chromite but occur at grain boundaries. Thus, they can be liberated by disaggregation of chromite and infiltration of water along chromite grain boundaries. Once in solution, Pd is more mobile than Pt and is dispersed further. Organic acids play an important role during the weathering process as they are capable of enhancing the mobility of the PGE, particularly Pd.

AB - Organic acids, including humic acid, play a significant role in the weathering of minerals containing metals such as Pt and Pd. They are also among the reactants which are under consideration for new hydrometallurgical methods of liberating unconventional PGE ores (such as the oxidised ores of the Great Dyke, Zimbabwe, and at locations in the Bushveld Complex of South Africa where PGE-bearing layers have been exposed to weathering). In order to better understand the processes operating during weathering of PGE-bearing chromitite seams of the Bushveld Complex, chromite concentrate originating from a South African chromium mine was subjected to reaction with different concentrations of synthetic humic acid. The results confirm the greater mobility of palladium in the environment compared to platinum. Crushed chromite concentrate showed greater mobility of Cr, but not of Pd or Pt, compared to uncrushed concentrate. Increasing the concentration of humic acid increased the amount of Pd and Pt in solution. These experiments give insight into the processes that govern the weathering of chromitite in the Bushveld Complex. The main Pd– and Pt-bearing minerals are not enclosed within chromite but occur at grain boundaries. Thus, they can be liberated by disaggregation of chromite and infiltration of water along chromite grain boundaries. Once in solution, Pd is more mobile than Pt and is dispersed further. Organic acids play an important role during the weathering process as they are capable of enhancing the mobility of the PGE, particularly Pd.

UR - http://www.scopus.com/inward/record.url?scp=85143424033&partnerID=8YFLogxK

U2 - 10.25131/sajg.125.0020

DO - 10.25131/sajg.125.0020

M3 - Article

AN - SCOPUS:85143424033

VL - 125

SP - 291

EP - 306

JO - South African Journal of Geology

JF - South African Journal of Geology

SN - 1012-0750

IS - 3-4

ER -