Preparation and characterization of UZM-5/polyamide thin film nanocomposite membrane for dewaxing solvent recovery

Thin-film nanocomposite (TFN) membrane containing amino-functionalized UZM-5 nanoparticles was synthesized by interfacial polymerization on polyetherimide (PEI)/modified SiO2 asymmetric substrate tailored for organic solvent nanofiltration OSN process. m-Phenylenediamine (MPD) with trimesoyl chloride (TMC) was polymerized to prepare polyamide layer. UZM-5 nanoparticles (~73 nm) were synthesized and then functionalized by aminopropylediethoxymethylsilane (APDEMS) and finally incorporated into polyamide (PA) selective layer at concentrations ranging from 0 to 0.2 w/v%. The as-prepared TFN membranes were characterized by scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and contact angle measurements. The performances of membranes were also evaluated through dewaxing solvents (MEK and toluene) recovery from lube oil. FESEM and SEM images clearly confirmed that the polyamide/UZM-5 nanocomposite top layer was formed on the support surface and its morphology was significantly affected by UZM-5 loading. Interaction between functional groups of modified UZM-5 nanoparticles and polyamide matrix was established by ATR-FTIR. AFM results revealed that in the range of 0-0.1 w/v% zeolite loading, the surface roughness of TFN membranes decreased due to the change of polyamide structure while at 0.2 w/v% of zeolite loading, an increase in surface roughness was observed. It also resulted in enhanced hydrophilicity of TFN membranes in the range of 0-0.1 w/v% UZM-5 loading, proved by a decreased water contact angle. The permeation test results indicated that the existence of UZM-5 in the polyamide selective layer improved both oil rejection and permeate flux under optimal concentration (0.02% w/v of UZM-5).