TY - JOUR

T1 - Mobility and distribution of palladium and platinum in soils above lower and middle group chromitites of the western bushveld complex, South Africa

AU - Oppermann, L.

AU - Junge, Malte

AU - Schuth, Stephan

AU - Holtz, F.

AU - Schwarz-Schampera, U.

AU - Sauheitl, Leopold

N1 - Funding Information: We are very thankful to the staff and management of Cronimet Chrome Mining SA for the possibility of sampling at Thaba Mine and logistic support by Deshenthree Chetty, Mintek, Johannesburg, South Africa. A special thanks is given to Moritz Hill of Cronimet for his support for this project. Pieter Wiese is thanked for his help with analysis at the Institute of Soil Science (Leibniz Universität Hannover) and Alexandra Tangen for assistance in the clean lab at the Institute for Mineralogy (Leibniz Universität Hannover). Many thanks for the critical and helpful input of journal reviewers Jens Gutzmer and Bertus Smith, which together with the constructive comments of SAJG Editor Stephen McCourt improved the quality and clarity of argumentation of our presentation. This study was part of the project “Applied Mineralogy for Resource Efficiency of Platinum Metals” (AMREP, working package B-2, grant number BMBF 033R119E), which is funded by the German Ministry of Education and Research (BMBF), and was also supported by the graduate school "Geofluxes" at the Leibniz Universität Hannover. Publisher Copyright: © 2017 December Geological Society of South Africa. Copyright: Copyright 2019 Elsevier B.V., All rights reserved.

PY - 2017/12/1

Y1 - 2017/12/1

N2 - Weathered chromitite layers from the Lower Group (LG) and Middle Group (MG) of the Bushveld Complex in South Africa are mined for chromite but have the potential to be processed for platinum-group elements (PGE) as a byproduct. However, recovery rates of PGE from weathered PGE ores are apparently low because of the supergene redistribution of PGE. Thus, understanding the processes that are responsible for PGE mobilization during weathering processes is useful to assess the PGE potential in weathered chromitites. In this study the distribution of platinum (Pt) and palladium (Pd) in soil samples from the LG and MG chromitites of the Thaba Mine (western Bushveld Complex) is investigated, with a special focus on the influence of organic matter on Pt and Pd mobilization. For this purpose, the soil samples were treated with different chemical digestion methods (aqua regia digestion and total digestion), and the Pt and Pd concentrations in humic and fulvic acids extracted from the soils were determined. The average total Pt and Pd concentrations of the soil samples (integrated over the whole soil horizons) are up to 62 ng/g and 128 ng/g, respectively, and their concentrations increase towards the topsoil. The humic acid extracts contain up to 0.04 ng/g Pt and up to 6.78 ng/g Pd and the fulvic acid extracts contain up to 0.16 ng/g Pt and up to 2.72 ng/g Pd. Up to 1% of the total Pt present in the soil is bound to fulvic acids, whereas up to 7% Pd is bound to humic acids. Palladium is mobilized equally by humic and fulvic acids, whereas the transport of Pt occurs preferentially by fulvic acids, indicating a higher mobility of Pd compared to Pt under supergene conditions during soil formation.

AB - Weathered chromitite layers from the Lower Group (LG) and Middle Group (MG) of the Bushveld Complex in South Africa are mined for chromite but have the potential to be processed for platinum-group elements (PGE) as a byproduct. However, recovery rates of PGE from weathered PGE ores are apparently low because of the supergene redistribution of PGE. Thus, understanding the processes that are responsible for PGE mobilization during weathering processes is useful to assess the PGE potential in weathered chromitites. In this study the distribution of platinum (Pt) and palladium (Pd) in soil samples from the LG and MG chromitites of the Thaba Mine (western Bushveld Complex) is investigated, with a special focus on the influence of organic matter on Pt and Pd mobilization. For this purpose, the soil samples were treated with different chemical digestion methods (aqua regia digestion and total digestion), and the Pt and Pd concentrations in humic and fulvic acids extracted from the soils were determined. The average total Pt and Pd concentrations of the soil samples (integrated over the whole soil horizons) are up to 62 ng/g and 128 ng/g, respectively, and their concentrations increase towards the topsoil. The humic acid extracts contain up to 0.04 ng/g Pt and up to 6.78 ng/g Pd and the fulvic acid extracts contain up to 0.16 ng/g Pt and up to 2.72 ng/g Pd. Up to 1% of the total Pt present in the soil is bound to fulvic acids, whereas up to 7% Pd is bound to humic acids. Palladium is mobilized equally by humic and fulvic acids, whereas the transport of Pt occurs preferentially by fulvic acids, indicating a higher mobility of Pd compared to Pt under supergene conditions during soil formation.

UR - http://www.scopus.com/inward/record.url?scp=85055860689&partnerID=8YFLogxK

U2 - 10.25131/gssajg.120.4.511

DO - 10.25131/gssajg.120.4.511

M3 - Article

AN - SCOPUS:85055860689

VL - 120

SP - 511

EP - 524

JO - South African Journal of Geology

JF - South African Journal of Geology

SN - 1012-0750

IS - 4

ER -