US2023023272A1 : A Method of Recovering Iridium
Publication Date: 26-Jan 2023
Current Owner: UNIV SYDDANSK
1st Inventor: Shuang Ma Andersen
This month’s EnabledMetals Patent Spotlight comes from the University of Syddansk in Denmark with the topic of recovering iridium. The first inventor is Prof Shuang Ma Andersen.
Iridium recovery requires extensive pyrometallurgy and hydrometallurgy and there is a desire to improve the efficiency, reduce the cost and time required and to diminish the lifecycle footprint of the recovery process. By using a pre-reduction of iridium oxide suspensions with hydrazine, formic acid or sodium borohydride, the subsequent stages can use milder reagents. The best results were obtained with hydrazine which provided almost 100% dissolution of the waste iridium catalyst.
For example, the IrxOy particles are sonicated in hydrazine solution, then reduced in hydrazine solution at 60-100° C for 1-3 h. The reduction takes the oxidation state down from e.g. Ir(IV) to Ir(III) as Ir2O3 for instance. Subsequently the particles are dissolved in HCl 1M and NaCl 3M aqueous solution at 103°C under reflux for 10 mins to 4 h. This solution can be further processed in a number of ways including use directly as a coating, reduction to Ir metal with hydrazine, precipitation as IrxOy with NaOH or treatment with H2O2/NH4Cl 3M to give (NH4)2IrCl6.
Characterisation methods confirm the chemistry described above and indicate that the pre-reduction step improves the subsequent dissolution by several orders of magnitude and in particular for hydrazine