Indium Extraction from Sulfate Solutions with a Mixture of Di(2-Ethylhexyl)Phosphoric Acid and Octyl Alcohol

ABSTRACTABSTRACTIn this work, solvent extraction of In(III) from sulfate solutions by using mixtures of D2EHPA with octyl alcohol and octanoic acid was investigated. The introduction of the additives into the organic phase was shown to lead to an antagonistic effect thus facilitating efficient indium stripping from the loaded organic phase. The antagonistic effect is significantly higher in the D2EHPA (HR) and octyl alcohol (HA) mixtures. The formation of stable associates between D2EHPA and HA leads to a decrease in the extraction efficiency of indium. In the presence of alcohol, almost complete stripping of indium from a D2EHPA loaded phase can be achieved to produce a strip liquor containing>33.0 g/L In. Based on the analysis of the extraction data and by using nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy of the organic phases, it was concluded that indium extraction with D2EHPA in octyl alcohol is due to the formation of the extracted compound InR3. The equilibrium constant (logK) for indium extraction with solutions of D2EHPA in octyl alcohol was found to be − 0.12 ± 0.05. Extraction systems containing D2EHPA and octyl alcohol can be used to recover indium from various industrial solutions, in particular from the solutions derived from lead-zinc production and from liquid crystal display panel wastes.KEYWORDS: Sulfate solutionsindiumsolvent extractiondi(2-ethylhexyl)phosphoric acidoctyl alcohol AcknowledgmentsThe authors would like to acknowledge the Multi-Access Chemical Research Center SB RAS (Novosibirsk) for spectral and analytical measurements and the Regional Research Equipment Centre SB RAS (Krasnoyarsk). The authors are also grateful to A.A. Kondrasenko and O.S. Chudina from the Institute of Chemistry and Chemical Technology SB RAS for their help in recording NMR and IR spectra. Appreciation for valuable remarks is extended to Dr. D.S. Flett.Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis research was supported by the Ministry of Science and Higher Education of the Russian Federation [the State Registration Number 1021051503141-0-1.4.1] and funded within the state assignment to the Institute of Chemistry and Chemical Technology SB RAS [Project No. 0287-2021-0014].