Recovery of iridium by solvent extraction and direct electrodeposition using phosphonium-based ionic liquids

カリウムベースのイオン液体を用いる溶媒抽出-電解法によるIrの回収

松宮 正彦*; 木下 了磨*; 土田 裕介*; 佐々木 祐二  

Matsumiya, Masahiko*; Kinoshita, Ryoma*; Tsuchida, Yusuke*; Sasaki, Yuji

カリウムベースのイオン液体([P][NTf])中へのIrの溶媒抽出と電解還元について調査した。ボルタモグラムを用いる電気化学分析で、Ir(IV)からIr(0)への還元はIr(IV)Ir(III)とIr(III)Ir(0)の2つのステップがあることを確認した。Ir(IV)の拡散係数は温度範囲、298-373Kの条件下2つの方法で調査し、結果は一致した。Irの抽出と電解を10サイクル連続して実施し、定量的な抽出-電析を達成し、XPS法でIrの金属相を確認した。

The extraction behavior of Ir(IV) in a phosphonium-based ionic liquid (IL) system, triethyl-n-pentyl phosphonium bis(trifluoromethyl-sulfonyl)amide ([P][NTf]), was investigated using an amine extractant. Voltammetry-based electrochemical analysis revealed that the reduction of Ir(IV) proceeded via an intermediate Ir(III) species in two steps, namely, Ir(IV) + e(-) Ir(III) and Ir(III) + 3e(-) Ir(0). Diffusion coefficients of the extracted Ir(IV) species in the IL were determined over the temperature range of 298-373 K using semi-integral and semi-differential analyses, and values obtained from the two analyses were consistent with each other. Furthermore, consecutive solvent extraction and electrodeposition of Ir metal in the IL bath were performed for 10 cycles. The entire Ir electrodeposit was in the metallic state, as is evident from the 4f (7/2) spectrum obtained by XPS.