Permeability of dilute ionic liquid solutions through a nanofiltration membrane – Effect of ionic liquid concentration, filtration pressure and temperature

• New information about the permeability of IL and glucose water solutions in NF.
• PWP could not be fully recovered after filtration of dilute IL/water solutions.
• Higher T had a stronger negative impact on the PWP than higher IL C.
• Increase in IL C increased its retention as a function of flux.
• Increase in IL C decreased the flux due to the osmotic pressure difference

Nanofiltration is studied to separate glucose from dilute ionic liquid [emim][OAc]–water solutions. The aim of the research is to evaluate the effect of filtration pressure, temperature and ionic liquid (IL) concentration on the separation of ionic liquid and glucose. This kind of separation challenge can be formed in the regeneration of cellulose fibres in a wet spinning bath. The separation tests are done with an NF270 nanofiltration membrane. The tolerance of the NF membrane in ionic liquid is also estimated.Effective osmotic pressures and viscosity were found to have a major role in the permeability of the membrane when filtration was done at dilute IL solutions. Temperature was found to have a significant effect on the flux due to reduced viscosity at higher temperatures. The flux was increased by about 50% when the temperature increased from 20 °C to 40 °C. The best possible separation factor values were achieved when the feed solution contained 1 wt% [emim][OAc] at 20 °C temperature and the filtration pressure was 6 bars. On the basis of the IL concentration and temperature test series, a good separation window for this kind of solution would be at permeate flux values from 50 L m−2 h−1 to 100 L m−2 h−1. After a test series in concentrations of IL from 0.5 wt% to 10 wt%, the pure water permeability (PWP) was reduced by 23% from the original. The decline of PWP during the temperature tests series was 33%.