PREPARATION AND CHARACTERIZATION OF LOW-PRESSURE NANOFILTRATION MEMBRANES BASEDON CROSSLINKED HYPERBRANCHED POLYESTER

Thin-film composite nanofiltration membranes were prepared by a simple dipping and crosslinking process. A polysulfone (PSF) ultrafiltration membrane was used as the support and a crosslinked hyperbranched polyester (HPE) as the active separation layer. The separation layer was immobilized onto the support via the aldol condensation of HPE with glutaraldehyde (GA). The prepared membranes were characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), water contact angle measurements and scanning electron microscopy (SEM). The results of FTIR examination confirmed the existence of crosslinked HPE layer on membrane surface. The results of SEM observation indicated that a thin dense layer of crosslinked HPE was deposited on the support membrane. Water contact angle measurements showed that the membrane hydrophilicity was significantly improved. The effects of HPE concentration and GA concentration during membrane preparation on the separation and permeation properties were investigated. The optimized HPE and GA concentrations were 9.8 g/L and 7.4 g/L, respectively, and the water flux for the resultant membrane reached 69.6 L/(m(2).h), and the Na2SO4 rejection ratio was 93.2% The sequence of rejection ratio to various salts was Na2SO4 > NaCl > MgSO4 > MgCl2, which was characteristic of electronegative nanofiltration membranes. These results showed that a high performance nanofiltration membrane with low operation pressure, high permeability and high rejection could be obtained by the present process.