Enrichment of Platinum Group Metals from Spent Automotive Catalyst Leaching Residue by a Combined Smelting and Wet Extraction Method

Spent automotive catalysts consist of platinum group metals (PGMs) in their leaching residue (LR) after wet extraction and are the leading secondary resource of PGMs. Herein, PGMs were captured from the LR of spent automotive catalysts by NiSO 4 smelting, followed by treatment with sulfuric acid to enrich PGMs from the trap. The effects of the trap, fluxing agent, and slagging agent dosage on the recovery of PGMs were systematically investigated to determine the optimum smelting conditions. The capture efficiency was 90.13, 91.02, and 90.54% for Pt, Pd, and Rh, respectively, under the following conditions: NiSO 4 /LR mass ratio of 3.6, SiO 2 /LR mass ratio of 2.0, CaCO 3 /LR mass ratio of 1.0, Na 2 CO 3 /LR mass ratio of 0.3, Na 2 B 4 O 7 ⋅10H 2 O/LR mass ratio of 0.3, CaF 2 /LR mass ratio of 0.3, and C/LR mass ratio of 0.4 at 1400 °C for 2 h. During the acid leaching enrichment process, the content of PGMs in the enrichment slag was 8.66 times compared with that of the raw materials under the conditions of 14.24 mol/L H 2 SO 4 , liquid–solid ratio of 5:1, 400 rpm, and temperature of 90 °C for 2 h. The method of combined smelting and wet extraction provides a referential value for the enrichment of PGMs from secondary resources. Graphical Abstract