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

Abstract

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.

Liquid‐ and Solid‐based Separations Employing Ionic Liquids for the Recovery of Platinum Group Metals Typically Encountered in Catalytic Converters: A Review

“…While phosphate is not per se toxic, release of excessive amounts into aquatic environments can promote algal growth and lead to eutrophication [245] . Regarding NTf 2 − , which has been reported by many researchers referenced in this review, [142,143,145,150–152,155,157–161,163,184,185–188,195–197] its ecotoxicological potential has been established [246] …”

Complexation–Distribution Separated Solvent Extraction Process Designed for Rapid and Efficient Recovery of Inert Platinum Group Metals

“…Higher E % of Ru(III) and Rh(III) can be actually achieved using ILs as alternative non-aqueous phases. 9 , 10 , 17 , 18 However, much higher cost and difficulty in handling due to higher viscosity compared with ordinary organic solvents are main critical drawbacks of ILs in the solvent extraction. Our current work successfully demonstrated that the solvent extraction of Ru(III) and Rh(III) from HNO 3 (aq) can be facilitated even using an ordinary organic solvent like 1-octanol.…”

Amide-functionalised phosphonium-based ionic liquids as ligands for rhodium(iii) extraction

“…The lifetime of a hydrated H 2 O molecule in the rst coordination sphere (sH 2 O) is a measurable indicator for the lability of metal ions in the innersphere substitution reaction and sH 2 O of Rh(III) is 14 years. 36,56 This low reactivity of Rh(III) is the reason for the extremely slow extraction of Rh(III). An extraction time of more than 3 weeks was required to reach equilibrium, in the following experiments.…”

“…Ionic liquids (ILs) have drawn interest as extractants or diluents in solvent extraction of metal ions; in particular, phosphonium-based ILs have been studied for application to PGM extraction. [30][31][32][33][34][35][36][37][38][39][40] Recently, Papaiconomou and co-workers report highly effective extraction of Rh(III) (>95%) with undiluted trihexyl(tetradecyl)phosphonium chloride ([P 66614 ][Cl]) as the extracting phase. 26,39 However, [P 66614 ][Cl] has a high viscosity (1931 mPa s at 298 K) 35 compared with those of commonly used extractant phases (i.e., a mixture of an extractant and a diluent), owing to the large and bulky cations that have long alkyl chains.…”