Impregnation of different ionic liquids onto cationic starch and their comparison in the extraction of Th(IV)

Cationic starch (CS) was prepared by using epichlorohydrin (EPI) and 3-chloro-2-hydroxypropyltrimethy- lammonium chloride (CHPTMA) and ionic liquids (ILs) having different anionic groups [1-butyl-3-methyl imidazolium tetrafluoroborate (BMI$^{+}$BF$_{4}^{-})$, 1-butyl-3-methyl imidazolium bromide (BMI$^{+}$Br$^{-})$, 1-butyl-3-methyl imidazolium hexafluorophosphate (BMI$^{+}$PF$_{6}^{-})$, and 1-butyl-3-methyl imidazolium bis-[(trifluoromethyl)sulfonyl]imide (BMI$^{+}$ [(TF)$_{2}$N]$^{-})$] were impregnated onto CS. Thorium(IV) ions were preconcentrated by using IL impregnated CS. The effects of ILs were investigated for extraction of Th(IV) by CS and the results were compared. Th(IV) was preconcentrated with approximately 73{\%} sorption capacity by CS and increased up to 98{\%}--100{\%} for IL impregnated sorbents at pH 7.0. The sorption capacities of Th(IV) were 0.453 mmol g$^{-1}$, 0.399 mmol g$^{-1}$, 0.281 mmol g$^{-1}$, and 0.183 mmol g$^{-1}$ for CS--BMI$^{+}$Br$^{-}$, CS--BMI$^{+}$[(TF)$_{2}$N], CS--BMI$^{+}$PF$_{6}^{-}$ and CS--BMI$^{+}$BF$_{4}^{-}$, respectively. The elution occurred with HCl and NaOH solutions at pH 7.0.