Extraction of lanthanide ions from aqueous solution by bis(2-ethylhexyl)phosphoric acid with room-temperature ionic liquids |
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Authors: | Sang Jun Yoon Jae Goo Lee Hideo Tajima Akihiro Yamasaki Fumio Kiyono Tetsuya Nakazato Hiroaki Tao |
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Affiliation: | 1. Climate Change Technology Research Division, Korea Institute of Energy Research, 71-2 Jang-dong, Yuseong-gu, Daejeon 305-343, Republic of Korea;2. Department of Chemistry and Chemical Engineering, Faculty of Engineering, Nigata University, 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata 950-2181, Japan;3. Department of Materials and Life Science, Faculty of Science and Technology, Seikei University, 3-3-1, Kichijoji-Kitamachi, Musashino-shi Tokyo, 180-8633, Japan;4. Institute for Environmental Management Technology, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8569, Japan |
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Abstract: | Extractions of five kinds of lanthanide metal ions by bis(2-ethylhexyl)phosphoric acid (DEHPA) with [1-Cn-3-methylimidazolium][PF6](Cn = C2, C4) or [1-butyl-4-methylpyridinium][PF6] were carried out under various DEHPA and HNO3 concentrations from 0 to 1 M and under different temperature conditions from 298 to 333 K. These results were compared with those using the conventional organic solvent, hexane, in terms of their distribution coefficient values. Under all of the conditions in this study, the ionic liquid system shows more than three times greater extractability for lanthanide compared to when hexane was used. The distribution coefficient of lanthanide ions decreased as the length of the alkyl chain increased from the ethyl to the butyl. In addition, the imidazolium cation generally shows a higher distribution coefficient compared to the pyridinium cation in an ionic liquid. The concentration ratio of lanthanides and DEHPA resulted in an extraction affinity transition for lanthanides. Also evaluated in this study were issues related to the selectivity associated with the lanthanide mixture and the dependency of the ionic radius during lanthanide extraction. |
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