Extraction and separation of multiple platinum group metals from hydrochloric acid solution with sole 1-hexy1-3-methylimidazole-2-thione using microextraction method

In this study, palladium (II), platinum (IV), rhodium (III) and iridium (IV) were sequentially separated with 1-hexyl-3-methylimidazole-2-thione (HMImT) from aqueous hydrochloric acid media by adjustment of hydrochloric acid concentration or in the presence of tin (II) chloride using environmental-friendly microextraction method. It is the first time to use sole extractant to selectively separate four platinum group metals from aqueous solution. Through condition optimization, HMImT shows outstanding extraction capacity (Pd 0.54 mmol/g, Pt 0.14 mmol/g, Rh 0.82 mmol/g) and high extraction percentage to palladium (99.4%), platinum (99.8%), rhodium (99.6%) respectively. The separation coefficient exceeds 10,000 and obtained metals purity reaches 99%. Based on Job's method, FT-IR spectra, UV-vis spectra, H-1 NMR spectra and theoretical natural population analysis (NPA), the anion exchange mechanism of HMImT on Pt (IV) extraction was confirmed. By precipitating calcining method palladium (II), platinum (IV) and rhodium (III) could be recycled in the form of Rh2O3, Pd and Pt2O.