TY - JOUR
T1 - Counteranion-dependent sorption of imidazolium- and benzimidazolium-based ionic liquids by soot
AU - Li, Yue
AU - Wei, Li
AU - Zhang, Wen
AU - Dong, Zhiqiang
AU - Qiu, Yuping
N1 - Funding Information:
This research was supported by the National Natural Science Foundation of China ( 21677108 , 21377093 ).
Publisher Copyright:
© 2018 Elsevier Ltd
PY - 2018/7
Y1 - 2018/7
N2 - Sorption of ionic liquids (ILs) to soil and porous materials as affected by anions was observed, but scarce effort has been focused on addressing the role of counteranions in sorption and the associated underlying mechanisms. In this work, two series of 1-butyl-3-methylimidazolium- (Bmim-) and N-butyl, methyl-benzimidazolium-based (Bmbim-based) ILs coupled with different counteranions were prepared to investigate the effect of anions on IL sorption by soot. The octanol–water partition coefficient (Kow) and the ion-pair formation constant at infinite dilution in water (KIP°) of ILs were independently measured to explore the contribution of counteranion-dependent hydrophobicity and ion-pair. A wide range of sorption coefficients (Kd) of ILs were achieved with values varying from 59.8 to 344.3 L·kg−1 for Bmbim-based ILs and from 253.4 to 489.7 L kg−1 for Bmbim-based ILs. Compared with other anions, bis(trifluoromethanesulphonyl)imide ([Tf2N]–) and hexafluorophosphate ([PF6]−) exhibit tighter association with IL cations in aqueous solution due to their larger Kow and higher KIP°. Positive linear relationships between log KIP° and Kd and between log Kow and Kd evidenced that the counteranion-dependent sorption of ILs relies on the association strengths of IL cations and counteranions, which further influence the hydrophobicity/hydrophilicity of ion pairs. Compared with that of strongly coordinating anions (such as [CH3SO3]−, [CF3COO]−, [BF4]−, [CF3SO3]−, and [Cl]−), the addition of weakly coordinating anions (such as [Tf2N]– and [PF6]–) in solution contributes to markedly large sorption enhancement of ILs. Consequently, the contribution of different counteranions on IL sorption is essentially based on the formation of ion pair with different KIP° and Kow in aqueous solution.
AB - Sorption of ionic liquids (ILs) to soil and porous materials as affected by anions was observed, but scarce effort has been focused on addressing the role of counteranions in sorption and the associated underlying mechanisms. In this work, two series of 1-butyl-3-methylimidazolium- (Bmim-) and N-butyl, methyl-benzimidazolium-based (Bmbim-based) ILs coupled with different counteranions were prepared to investigate the effect of anions on IL sorption by soot. The octanol–water partition coefficient (Kow) and the ion-pair formation constant at infinite dilution in water (KIP°) of ILs were independently measured to explore the contribution of counteranion-dependent hydrophobicity and ion-pair. A wide range of sorption coefficients (Kd) of ILs were achieved with values varying from 59.8 to 344.3 L·kg−1 for Bmbim-based ILs and from 253.4 to 489.7 L kg−1 for Bmbim-based ILs. Compared with other anions, bis(trifluoromethanesulphonyl)imide ([Tf2N]–) and hexafluorophosphate ([PF6]−) exhibit tighter association with IL cations in aqueous solution due to their larger Kow and higher KIP°. Positive linear relationships between log KIP° and Kd and between log Kow and Kd evidenced that the counteranion-dependent sorption of ILs relies on the association strengths of IL cations and counteranions, which further influence the hydrophobicity/hydrophilicity of ion pairs. Compared with that of strongly coordinating anions (such as [CH3SO3]−, [CF3COO]−, [BF4]−, [CF3SO3]−, and [Cl]−), the addition of weakly coordinating anions (such as [Tf2N]– and [PF6]–) in solution contributes to markedly large sorption enhancement of ILs. Consequently, the contribution of different counteranions on IL sorption is essentially based on the formation of ion pair with different KIP° and Kow in aqueous solution.
KW - Counteranion
KW - Ion-pair formation constant
KW - Ionic liquids
KW - Sorption
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U2 - 10.1016/j.chemosphere.2018.03.092
DO - 10.1016/j.chemosphere.2018.03.092
M3 - Article
C2 - 29571147
AN - SCOPUS:85047455564
SN - 0045-6535
VL - 202
SP - 264
EP - 271
JO - Chemosphere
JF - Chemosphere
ER -