In-situ synthesis and cross-linking of polyamide thin film composite (TFC) membranes for bioethanol applications

A novel and effective two-step approach has been developed to fabricate cross-linked polyamide thin film composite (TFC) membranes for pervaporation dehydration of bioethanol. The first step is to in situ graft the cross-linker toluene 2,4-diisocyanate (TDI) into the polyamide selective layer during the interfacial polymerization while the second step is to produce the TDI cross-linked TFC membrane by post thermal annealing. The physicochemical properties and membrane structure of the newly developed TFC membranes were investigated in-depth by various characterization techniques such as X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectrometry and positron annihilation spectroscopy (PAS). The cross-linked TFC membranes overcome the swelling issue of conventional TFC membranes and exhibit much enhanced separation performance. The membranes can also function well at elevated temperatures. An impressive flux of 6.80 kg/m2-h with a separation factor of 61 for the dehydration of 85/15 wt% ethanol/water mixtures is achieved at 80 °C. These excellent membranes and the simple processing method may bring about ground-breaking changes to the molecular design of modern pervaporation membranes.