An ultrapermeable thin film composite membrane supported by green nanofibrous polyimide substrate for polar aprotic organic solvent recovery

The preparation of polymeric-based thin film composite (TFC) membrane with high permeance and superior solvent resistance in organic solvent nanofiltration (OSN) applications always involves the consumption of toxic chemicals or high energy, which does not meet the requirements of green chemistry. In this work, intrinsic insoluble polyimide (PI) nanofiber substrates were obtained by a two-step method including electrospinning of poly (amic acid) synthesized by polycondensation reaction between various monomers and subsequent thermal imidization, and the optimized one with low thermal imidization temperature was employed as substrate for TFC membrane in strong polar aprotic solvents recovery, therefore achieving the green process. The effects of different dianhydride and diamine monomers and different thermal imidization temperatures on the solvent resistance and microscopic morphology of nanofiber substrates are also studied. The optimized monomers in this work contribute to a low-temperature imidization of PI nanofiber substrate. The solvent permeance of corre-sponding TFC OSN membrane with the insoluble PI nanofiber substrate reaches up to 11.2 L m(-2) h(-1) bar(-1) with 99.7% rejection in rose bengal/DMF system, and good long-term stability. This work provides potential guide-lines for developing next-generation OSN membranes under a green process.

Automated summary

This study presents a green process for the preparation of polymeric-based thin film composite (TFC) membrane with high permeance and superior solvent resistance in organic solvent nanofiltration (OSN) applications. Intrinsic insoluble polyimide (PI) nanofiber substrates were obtained by electrospinning of poly (amic acid) and subsequent thermal imidization. The optimized monomers contribute to a low-temperature imidization of PI nanofiber substrate. The resulting TFC OSN membrane showed high solvent permeance and rejection, along with good long-term stability.