咪唑类离子液体在蒙脱石上的吸附行为与机理

Adsorption behavior and mechanism of imidazole-based ionic liquids on montmorillonite

研究了钠型蒙脱石对系列咪唑类离子液体(IBILs,烷基链不同,阴离子类型不同)的吸附行为,并通过X射线衍射(XRD)和傅里叶红外光谱(FTIR)及扫描电镜(SEM)等对吸附行为进行了表征.讨论了pH值、离子浓度等对吸附的影响.结果表明,离子液体主要通过静电阳离子交换及烷基疏水作用吸附于蒙脱石之上.阴离子结构变化对吸附影响不大;而烷基链越长,离子液体的吸附量越大,EmimBF_4(1-乙基-3-甲基四氟硼酸盐),BmimBF_4(1-丁基-3-甲基四氟硼酸盐),HmimBF_4(1-己基-3-甲基四氟硼酸盐),OmimBF_4(1-辛基-3-甲基四氟硼酸盐)对应的平衡吸附量分别为33.94,40.48,44.40,53.29mmol/100g.离子液体进入蒙脱石层间后,层间距随着烷基链的增加从12.77A增大至14.41A.降低离子强度或提升pH值都会增强离子液体在蒙脱石上的吸附能力.

Sorption of imidazole-based ionic liquids(IBILs)with different alkyl chain lengths and anions ontoNa-modified montmorillonite(Na/MMT)as affected by ionic strength and solution pH was investigated.The Na/MMT before and after sorption was characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR)and Scanning Electron Microscope(SEM).Sorption of IBILs on Na/MMT was due to the cation exchange interaction and the hydrophobic interaction between IBILs cations and Na/MMT while the effect of IBIL anions was negligible.Furthermore,the adsorption capacities were influenced by the alkyl chain length of IBILs cations.The longer the alkyl chain length,the greater adsorption capacity on the montmorillonite.The equilibrium adsorption of EmimBF4,BmimBF4,HmimBF4and OmimBF4was33.94,40.48,44.40and53.29mmol/100g,respectively.The interlayer spacing of Na/MMT increased from12.77?to14.41?with the increase of the alkyl chain length.Both decreasing background ionic strength and increasing of solution pH will enhance the adsorption of IBILS on montmorillonite.