Study on a functionalized ionic liquid [BIim][Cl3] for efficient dissolution of precious metals (Pd, Pt, Au, Rh)

The development of industrial technology has significantly promoted the production and accumulation of spent precious metal-based catalysts. This work describes the synthesis of an ionic liquid – [BIim][Cl 3 ] and its application as an alternative to toxic and corrosive reagents for precious metal leaching from waste catalysts. The leaching process using [BIim][Cl 3 ] is proved to be safe and green. It offers a higher stability and higher leaching efficiency compared to other reagents used in previous publications. The ionic liquid [BIim][Cl 3 ] enabled the efficient leaching of Pd and Au, as well as the extremely stable precious metals Pt, Rh under mild conditions. The highest leaching efficiencies achieved by [BIim][Cl 3 ] were 99.9 %, 98.5 %, 98.6 % and 90.6 % for Pd, Au, Pt and Rh under the optimal leaching conditions, respectively. In order to reveal the leaching mechanism, XPS, far infrared (FIR), NMR, and EDS were used to demonstrate the importance of imidazolium cations in the leaching process. The leaching pathway was proposed based on the DFT calculation results on transition state energy barrier.