Rhodium And Iridium Separation Using Solvent Extraction

摘要

The separation and purification of rhodium fromother precious metals is one of the more difficult areas inprecious metal refining, due mainly to the complex solutionchemistry of rhodium. Recovery of rhodium is usuallyachieved through the highly time consuming and inefficientapproach of a series of precipitation and re-dissolution steps.Research at McGill University has focussed on the replacementof this inefficient cycle with a solvent extraction circuit. Thispaper details recent investigations that involve the activation ofrhodium prior to solvent extraction. The role of activation is toconvert the aquochloro complexes of rhodium to a formextractable by conventional solvent extraction reagents. In thenovel separation scheme identified, chloro complexes ofrhodium are converted to bromo complexes, which undergoaquation to a lesser extent, making them more easily extracted.The use of bromide chemistry opens up new options for theseparation of iridium from rhodium, and further work is inprogress in the development of an effective refining process for these metals.