Highly selective extraction of platinum group metals with silica-based (poly)amine ion exchangers applied to industrial metal refinery effluents

Batches of authentic industrial base metal refinery (BMR) and precious metal refinery (PMR) effluents containing large amounts of Ni, Cu and Fe ions and relatively small amounts of the valuable Pt, Pd and Rh metal ions have been treated with silica-based (poly)amine anion exchangers. In most cases, notably with the PMR effluents, the extraction of Pt and Pd appeared to be very effective, with recuperation of more than 95% from some of the effluents, while an increase in temperature was not necessary to obtain maximum metal ion uptake. Successive Rh extraction from the BMR effluents resulted in a maximum removal of 22% of the metal ions initially present. A higher percentage could not be reached apparently due to the presence of large amounts of competing sulphate and chloride counter ions. The removal of Rh from PMR effluents containing smaller amounts of other transition metal ions was somewhat more effective. Despite the large amounts of Ni, Cu and Fe in many of the tested effluents, no uptake of any of these metal ions has been observed. The platinum group metal (PGM) selectivity of these ion exchangers over the other transition metals has thus proven to be very high.