Liquid–liquid extraction of rhenium(VII) from an acidic chloride solution using Cyanex 923

Abstract

The present work addresses the extraction of rhenium(VII) from a HCl solution using Cyanex 923 diluted in kerosene as the extractant. The influence of various parameters on the extraction of rhenium(VII) has been investigated, including the extractant, acid and chloride concentration, and organic-to-aqueous phase ratio. An increase in the HCl concentration leads to a remarkable increase in the extraction efficiency under the studied conditions. The aqueous chemistry of rhenium(VII) revealed that at 2.0mol·L−1 HCl in a leach solution, the HReO4 species becomes solvated and is complexed as HReO4·2[Cyanex 923] in the organic phase. Based on the McCabe–Thiele diagram, a simulation showed that 99.2% extraction efficiency could be attained in a two-stage counter-current extraction with an organic-to-aqueous phase ratio of 2:3. The stripping efficiency of rhenium from a loaded organic was greater than 99% for a 1.5mol·L−1 NH4OH solution at the unit phase ratio and 298K. The study validates Cyanex 923 as a promising extractant for rhenium(VII) from an acidic chloride solution.