XDLVO理论解析膜蒸馏回收离子液体过程中的膜污染研究

Analysis of membrane fouling by XDLVO theory in vacuum membrane distillation for ionic liquid recycling

应用XDLVO(Extended Derjaguin-Landau-Verwey-Overbeek)理论定量解析了真空膜蒸馏(VMD)回收离子液体水溶液过程中的膜污染行为.通过XDLVO理论,计算了聚四氟乙烯(PTFE)膜与3种不同离子液体如1丁基3甲基咪唑氯盐([Bmim]Cl)、1丁基3甲基咪唑甲磺酸盐([Bmim][MeSO 3])、1己基3甲基咪唑氯盐([Hmim]Cl)之间的相互作用能,分析了3种相互作用能[范德华能(LW)、静电作用能(EL)、极性作用能(AB)]在膜污染形成过程中的贡献.结果表明,LW和EL作用能均为正值,表现为排斥作用;AB作用能为负值,表现为吸引作用,且AB作用能是引起膜污染的主要作用能.此外,3种离子液体引起膜污染的难易程度为[Hmim]Cl>[Bmim][MeSO 3]>[Bmim]Cl.界面相互作用能与膜污染程度相关性分析表明,XDLVO理论可以合理预测不同离子液体的膜污染行为.基于污染实验和计算结果,采用间歇式浓缩方式,发现PTFE膜可将质量分数20%的[Bmim]Cl水溶液浓缩至86.2%,[Bmim]Cl截留率稳定在99.9%以上,[Bmim]Cl总回收率可达99.98%.

The extended Derjaguin-Landau-Verwey-Overbeek(XDLVO)theory was used to quantitatively analyze the interfacial interactions of polytetrafluoroethylene(PTFE)membrane with different ionic liquids[1-butyl-3-methylimidazolium chloride([Bmim]Cl),1-butyl-3-methylimidazolium methanesulfonate([Bmim][MeSO 3])and 1-hexyl-3-methylimidazolium chloride([Hmim]Cl)]in vacuum membrane distillation(VMD).The relative contributions of Lifshitz van der Waals(LW),acid-base(AB)and electrostatic(EL)interaction energies between PTFE membrane and ionic liquid were evaluated.The results showed that the LW and EL energies were positive(repulsion),while the AB interaction energy was negative(attraction).And the AB interaction energy played a dominant role in membrane fouling by each ionic liquid.Moreover,the least membrane fouling was caused by[Bmim]Cl,followed by[Bmim][MeSO 3]and[Hmim]Cl.The membrane fouling predictions was in accordance with the experimental results,revealing that the XDLVO theory has a great potential for predicting membrane fouling behavior.Based on the fouling analysis,timely cleaning could improve the VMD concentration process,and a final[Bmim]Cl concentration as high as 86.2%(mass fraction)with a total[Bmim]Cl recovery over 99.98%was achieved.