Accurate Determination of Platinum and Rhodium in Spent Automotive Catalyst via Copper Fire Assay Method for Resource Sustainability

Abstract

Spent automotive catalysts (SACs) are the most important secondary resources for recycling platinum-group metals (PGMs). While accurately determining PGM concentrations in SACs is challenging, it is pivotal for effective recycling. Currently, the main methods for determining the PGM concentration in SACs are direct solid sample analysis and microwave dissolution, which face challenges such as matrix interference and the heterogeneity of samples. This study established a method for determining PGMs in SACs by inductively coupled plasma emission spectroscopy (ICP-OES) after the Cu fire assay, to achieve better detection limits for PGMs. The conditions for Cu fire assay were carefully optimized: under the optimal conditions, the losses of Pt, Pd, and Rh in the slag can be minimized to 5 ± 3, 12 ± 9, and 2 ± 2 μg, respectively. The spectral interference of Cu in determining PGMs was avoided by selecting interference-free emission lines. The established method has excellent analytical performance for Rh, with the detection limits for Pt, Pd, and Rh being 1.3, 13.8, and 0.8 g/t, respectively. The precision evaluated within 11 results of repeated measurements of four different types of real SACs ranged from 0.63% to 3.29%. This method provides a clean and reliable approach for determining trace PGMs in SAC and other solid wastes.