Crown ethers assisted cesium extraction from aqueous solutions into a hydrophobic room temperature ionic liquid 1-Butyl-3-methylimidazolium Bis[(Trifluoromethyl)sulfonyl]imide

Abstract

Crown ethers (L) assisted extraction of CsI from aqueous neutral solutions (рН 5-6) into a hydrophobic ionic liquid 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide was studied at 22оС operating with: 12-crown-4 (12С4), 15-crown-5 (15С5), 18-crown-6 (18С6), dibenzo-18-crown-6 (DB18C6), dibenzo-21-crown-7 (DB21C7) and dibenzo-24-crown-8 (DB24C8). The distribution coefficients (logDCsL) are found to increase from 0.30 ∂о 1.7 as the size of L is changing from 15С5 to DB21C7. A further increase of L size (DB24C8) leads to a sufficient decrease of logDCs L up to 0.9. The maximal logDCsL value corresponds to the better cation-crown ether fitting. Well expressed correlation between logDCsL values and stability constants of CsL in ionic liquid (logKCsL) is obtained and is interpreted for the crown ether series.