Surface Properties, Free Volume, and Performance for Thin-Film Composite Pervaporation Membranes Fabricated through Interfacial Polymerization Involving Different Organic Solvents

The type of organic solvents used in interfacial polymerization affects the surface property, free volume, and separation performance of the thin-film composite (TFC) polyamide membrane. In this study, TFC polyamide membrane was fabricated through interfacial polymerization between diethylenetriamine (DETA) and trimesoyl chloride (TMC). Four types of organic solvent were explored in the preparation of pervaporation membrane. These are tetralin, toluene, hexane, and isopentane. The solubility parameter distance between organic solvents and DETA follows in increasing order: tetralin (17.07 MPa(1/2)) < toluene (17.31 MPa(1/2)) < hexane (19.86 MPa(1/2)) < isopentane (20.43 MPa(1/2)). Same trend was also observed between the organic solvents and DETA. The larger the solubility parameter distance, the denser and thicker the polyamide. Consequently, field emission scanning electron microscope (FESEM) and positron annihilation spectroscopy (PAS) analysis revealed that TFC(isopentane) had the thickest polyamide layer. It also delivered the highest pervaporation efficiency (permeation flux = 860 ± 71 g m(−2) h(−1); water concentration in permeate = 99.2 ± 0.8 wt%; pervaporation separation index = 959,760) at dehydration of 90 wt% aqueous ethanol solution. Furthermore, TFC(isopentane) also exhibited a high separation efficiency in isopropanol and tert-butanol. Therefore, a suitable organic solvent in preparation of TFC membrane through interfacial polymerization enables high pervaporation efficiency.