Fluorescent imidazolium hydrogels for tracing and recovering platinum with highest purity from spent auto catalyst

In this study, fluorescent polymeric hydrogels were synthesized and engineered to trace and recover platinum with maximum purity from spent auto catalysts by selective coordination. These three-dimensional hydrogels were prepared using a water-soluble polymeric probe [p(DMAA-co-M1), P1, where DMAA = N,N '-dimethyla-crylamide, M1 = quaternized imidazole with anthracene unit] in the presence of N,N '-methylenebisacrylamide as a crosslinker. P1 was extremely selective and sensitive toward platinum ions by fluorescence quenching, with a limit of detection of 0.03 mM. Owing to the high sensitivity and selectivity of P1, the hydrogels derived from P1 exhibited the effective platinum ion detection, followed by the selective recovery from the mixtures of excess amounts of various metal ions. The platinum absorption capacity of the hydrogels from a used auto catalyst leach liquid was 0.2 g platinum/1.0 g hydrogel. Inductively coupled plasma measurements indicated that the purity of the recovered platinum was 95.76%, and the palladium composition was 4.14%. These hydrogels were recycled by thiourea and reused for multiple cycles, indicating that they are a promising candidate for platinum recovery with a contribution to the circular economy.