Effects of different ionic liquids as green solvents on the formation and ultrafiltration performance of CA hollow fiber membranes

Ding Yu Xing, Wen Yi Dong, Tai-Shung Chung*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

In this work, we have examined and compared the interactions between cellulose acetate and different ionic liquids at a molecular level and explored their effects on dope rheology, hollow fiber morphology, and performance. Ionic liquid, 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc), was found to interact with cellulose acetate (CA) more closely with intensive hydrogen bonds than 1-ethyl-3-methylimidazolium thiocyanate ([EMIM]SCN). Thus, the CA/[EMIM]OAc solution exhibits a more pronounced charge-ordered network than the CA/[EMIM]SCN solution. In addition, the former does not obey the Cox-Merz rule, whereas the latter obeys the rule with its shear viscosity η identical to its complex viscosity |η∗| at the equivalent shear rate and angular frequency. These dissimilar factors have contributed to an instantaneous liquid-liquid demixing and resulted in a dense outer skin surface and a porous cross-sectional structure comprising macrovoids for the CA/OAc membrane. In contrast, the CA/SCN membrane has a looser interconnected nodular structure resulting from the delayed liquid-liquid demixing. The effects of spinning conditions on membrane properties have been determined. The higher dope flow rate and take-up speed result in smaller pore size. [EMIM]OAc is a more practical solvent than [EMIM]SCN to fabricate CA hollow fibers with a broader choice of spinning parameters. The newly developed CA/OAc membranes have PWP values of 230 and 260 L/(m2 bar h) and pore sizes of 10-27 nm. This work may provide useful insights to develop polymeric membranes using ionic liquids as solvents and facilitate a greener fabrication method in the membrane industry.

Original languageEnglish (US)
Pages (from-to)7505-7513
Number of pages9
JournalIndustrial and Engineering Chemistry Research
Volume55
Issue number27
DOIs
StatePublished - Jul 13 2016

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Industrial and Manufacturing Engineering

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