The mobility of platinum-group elements in humic acid under surficial weathering conditions : an experimenal study

Abstract

Although the platinum-group elements (PGE) are known to be mobile under certain conditions in the surficial weathering environment, their mobilization in the presence of humic substances is poorly constrained. In these experiments, platinum and palladium were mobilized and analyzed in solution using laboratory preparations of humic acid solutions, synthetic minerals, and naturally occurring chromitite samples. The composition of synthetic humic acid is an average of naturally occurring humic substances. Experiments were carried out using humic acid powder (HAP), humic acid sodium salt (HASS) and water as solutions. Synthetic powders of PdS, PtS2, PdTe and PdTe2 were used as substrate for the solutions, along with chromite concentrate and tailings material from the Thaba Mine, South Africa. These substrates were exposed to water, HAP and HASS in different concentrations and for different periods of time.