In this study, nano thin-film composite (n-TFC) membrane was prepared via the interfacial polymerization for organic solvent nanofiltration (OSN) process. Polyetherimide (PEI) / amino-functionalized silica nanocomposite membrane was used as support layer to fabricate n-TFC membrane. In order to obtain the stable support, nanocomposite membranes with different amount of modified silica (0-20 wt. %) were prepared. The resultant membranes were characterized by scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), swelling test and tensile strength techniques. Results showed that mechanical and chemical stability attained their maximum when silica content was 5%. The solvent resistant n-TFC membranes were prepared using interfacial polymerization with m-phenylenediamine (MPD) and trimesoyl chloride (TMC) on the nanocomposite support. The prepared polyamide/ modified PEI nanocomposite membrane was used in a selected OSN. A mixture containing dewaxed oil (Mw≈560 g/mol) and dewaxing solvent (toluene and methyl ethyl ketone) was selected to investigate the separation performance of n-TFC membranes. The oil rejection of 94.72 % and permeation flux of 10.4 L/m2.hr (at 15bar) were achieved which suggest that newly prepared n-TFC membrane has potential in application of the dewaxing solvent separation from the dewaxed lube oil. Pressure dependency of the oil rejection, permeate flux and MEK to toluene mass ratio in permeate of the n-TFC membranes were studied in the pressure range of 10 to 20 bar. The results revealed that the bulk modification has great effect on chemical stability of prepared membrane even at high pressure.

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