Electroconductivities of the Organic Extraction System Containing Di-(2-ethylhexyl) Phosphoric Acid (P204)

Abstract

How to greenly and economically extract high-value elements from a complex matrix is the focus of current separation techniques. The combination between solvent extraction and electrodeposition technique was proposed in this work. In order to realize the electrodeposition of metal ions from the extraction organic phase, the electroconductivities of the commonly used extraction system containing di-(2-ethylhexyl) phosphoric acid (P204) were investigated in detail. The results showed that the traditional P204 extraction system is not electroconductive even after the extraction of metal ions, but this problem was effectively solved by the addition of ionic liquids (ILs) especially the tributylhexylphosphonium bis(trifluoromethyl sulfonyl)imide ([P4446][NTf₂]). Different diluents have significant effects on the electroconductivity, among which methyl isobutyl ketone (MIBK) is the best to obtain a high electroconductivity. The electroconductivity-composition diagram of the P204+MIBK+[P4446][NTf₂] system at room temperature indicates that both the MIBK and [P4446][NTf₂] contribute to improving the electroconductivity of this system. All these findings provide the feasibility of electrodeposition from the extraction organic system containing P204.