A new approach to recover platinum-group metals from spent catalytic converters via iron matte

Abstract

Decreasing stocks of natural resources and continuously increasing demand for platinum-group metals (PGMs) sustain interest in studies on spent catalytic converters. Recycling spent catalytic converters to extract PGMs not only provides raw materials for the precious metals sector, but also provides a sustainable recycling method for further development. However, recovering PGMs is hard since the catalytic converters contain refractory compounds. In the present study, a pyrometallurgical iron matte process was adopted to separate PGMs from spent catalytic converters. PGM recovery using the classical iron smelting process requires very high temperatures (~2000 °C), but the smelting temperature used in this process was less than 50% that of the classical process. The influences of the B2O3/Na2O ratio, S/Fe ratio, iron source, reaction temperature, and reaction time on the recovery of PGMs from catalytic converters were investigated in detail. The highest recovery percentages were 99% Pt, 99% Pd, and 97% Rh at 950 °C for 75 min. with the addition of 3 times flux (0.72 wt/wt, B2O3/Na2O) of spent catalytic converters and 10 g of FeS2 with a corresponding enrichment factor of around 6.0. In fact, these findings encouraged the further development of the process since no one needs elemental sulfur because SO2 is easily produced from the burning of elemental sulfur with air at low temperatures, and avoiding the recovery of sulfur reduced the process’ energy consumption and was also environmentally friendly.