Chemical Dissolution of Iridium Powder Using Alkali Fusion Followed by High-Temperature Leaching

Abstract

The dissolution of iridium has been investigated with an alkali fusion treatment with Na₂O₂ followed by leaching in HCl solution. Alkali fusion with Na₂O₂ allows Ir to be easily oxidized to IrO₂, which is transformed to a high oxidation state through the binding of Na-Ir-O at 600°C for 4 h. From the fused mixture, with molar ratio of 1:2.0 (Ir:Na₂O₂), Ir can be leached completely at 130°C using an HCl solution with a concentration above 3 M. Moreover, the leaching with 3 M HCl at 130°C can dissolve Ir from the mixture that was fused at 600°C, regardless of molar ratio of Na₂O₂. Ir can also be completely dissolved at 70°C or less when the fused mixture has a 1:2.0 ratio.