Significant Acceleration of PGMs Extraction with UCST-Type Thermomorphic Ionic Liquid at Elevated Temperature

Dependency of extraction behavior of inert platinum group metals (PGMs) like Ru(III) and Rh(III) on temperature has been investigated in a biphasic system consisting of HNO3(aq) and betainium bis(trifluoromethylsulfonyl)amide ([Hbet][Tf2N]) ionic liquid. The extraction reactions of Ru(III) and Rh(III) took 3.5 days and 113 days, respectively, at 298 K, while equilibrated within 1 and 3 h to reach 99.2% and 96.5% extraction at 353 K. Further mechanistic studies clarified that the complexation of these PGMs and [Hbet]+ is rate-determining in their extraction and that it is successfully accelerated and enhanced by elevating the temperature.