Recovery of platinum group metal value via potassium iodide leaching

Platinum recovery from secondary sources such as end-of-life polymer electrolyte fuel cells (PEMFCs) via electrowinning and chemical dissolution in deoxygenated 4 M potassium iodide with varying added iodine content was investigated. Previous research in this field has shown that complete platinum recovery from model systems is possible, but further study was necessary to determine the process viability with Pt containing devices. The work presented here investigated the leach rate of platinum black deposited on an electrochemical quartz crystal microbalance (EQCM) as well as the effective recovery of Pt from untested and end-of-life polymer electrolyte membrane fuel cells. Platinum black dissolution rates were found to be dependent on added iodine content, with higher concentrations accelerating the reaction. Platinum recovery from leached materials, as determined by aqua regia digestion, was found to be 98.7% and 96.7% for untested and end-of-life PEMFCs, respectively. Results indicate that higher iodine concentrations continuously improved recovery efficiency, but increasing iodine concentration above 5 mM resulted in comparatively minor improvements.