Selective separation of tanshinone homologs by biocomposite membranes based on poly(ionic liquids) and natural fibers

Membranes have been used as versatile tools for the separation of various natural products; however, the selective separation of structural analogs of natural products using membranes remains challenging. In this study, biocomposite membranes based on poly(ionic liquids) and different natural fibers (jute, cotton, or wool) were successfully prepared. Natural fibers can regulate the microstructure and improve the mechanical properties of membranes. Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, Brunauer-Emmett-Teller analysis, and thermo gravimetric analysis were used to characterize the membranes. The membranes were used to separate tanshinone homologs (tanshinone I, tanshinone IIA, cryptotanshinone, and dihydrotanshinone I), allowing cryptotanshinone to penetrate the membrane while rejecting tanshinone I. A maximal selectivity of 44.57 % was obtained for the tanshinone homologs using a one-step separation protocol. These poly(ionic liquids)/natural fiber membranes possess high water flux, good self-cleaning, and good antibacterial properties. The membranes were effective in separating tanshinone homologs and have the potential to separate other natural homologs.