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 3M. Moreover, the leaching with 3M HCl at 130°C can dissolve Ir from the mixture that was fused at 600°C, regardless of molar ratio of Na2O 2. Ir can also be completely dissolved at 70°C or less when the fused mixture has a 1 : 2:0 ratio. © 2011 The Japan Institute of Metals.