Ionic liquid induced removal of Rhodamine B from water

In this communication we are reporting ionic liquid induced removal of Rhodamine B from water which interestingly depends on the identity of the IL. Specifically, we found that addition of small amount of non-aromatic cation containing IL,1-butyl-1-methypyrrolidinium bis(trifluoromethylsulfonyl)imide [bmpyrr] [Tf2N] in aqueous Rhodamine B solutions causes dramatic decrease in absorbance as well as fluorescence emission intensity. The decrease in absorbance and fluorescence emission could be attributed to precipitation of Rhodamine B dye from aqueous solution. No such precipitation of the dye was observed when small amount of other aromatic cation containing ILs such as 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4] and 1-butyl-3-methylimidazolium hexaflurophosphate [bmim][PF6] were added to aqueous solution of the dye. Furthermore, the extent of precipitation increased with the amount of added IL [bmpyrr][Tf2N] in aqueous Rhodamine B solutions and more than 98% of dye could be precipitated out from the aqueous Rhodamine B (5 mu M) solution with the help of small amount (0.8 wt%) of added [bmpyrr][Tf2N]. These findings could contribute to the technological applications for removal of even trace amount of Rhodamine B dye from waste water. (C) 2020 Elsevier B.V. All rights reserved.