Process and mechanism of electrolytic enrichment of PGMs from Fe-PGMs alloy

摘要

The secondary production of platinum group metals (PGMs) occupies a 30% proportion of the global supply. The iron-capturing recycling technology produces Fe-PGMs alloy, of which PGMs need further enrichment for purification. We applied electrolytic refining method on Fe-PGMs alloy for separating PGMs from iron. Fe-PGMs alloy and titanium plates are used as anode and cathode. The main electrolyte is ferrous sulfate. During electrolysis, iron is electrolytically migrated to the cathode and electro-deposited, while PGMs settle to form anode slime. An appropriate parameters range for electrolysis is potential (0.5-0.8 V), concentration of Fe2+ (1.0-1.5 mol/L), temperature (60-80 degrees C), pH (3.0-3.5). The impurities like carbon and phosphorous can promote the dissolution of iron in the early electrolysis by expanding the coverage of reaction intermediates adsorbed on the anode surface but will hinder the dissolution and enrichment if forming a film layer. After electrolysis at 0.7 V constant voltage, PGMs were separated from the iron matrix and enriched in the anode slime (85-90%) and residual anode (10-15%). The recovery efficiency reached nearly 100%. Pure iron was prepared on the cathode and the electrolytic liquid can be reused. This electrolytic enrichment process has lower energy consumption, less wastewater, and higher recovery efficiency. (C) 2020 Elsevier Ltd. All rights reserved.