Preparation and characterization of poly(phthalazinone ether sulfone ketone) hollow fiber ultrafiltration membranes with excellent thermal stability

Hollow fiber ultrafiltration membranes were prepared successfully from poly(phthalazinone ether sulfone ketone) (PPESK) with a dry/wet phase inversion technique. Ethylene glycol methyl ether, diethylene glycol (DegOH) and methyl ethyl ketone were used as non-solvent additives and N-methyl-2-pyrrolidone used as a solvent in membrane preparation. The effects of PPESK concentration, the type of additives and the concentration of DegOH in casting solution on the morphology and performance of hollow fiber ultrafiltration membranes were investigated, respectively. The structures of PPESK hollow fiber membranes including the cross-section, the inner/outer edge (details of the cross-sections at the inner/outer edge of the membrane), and the external surface were characterized by scanning electron microscope (SEM). It was found that the membrane performance is consistent and agrees with the membrane morphology. With the increase of PPESK concentration in the casting solution, the viscosity strongly increases and it becomes shear-rate dependent. The morphologies of hollow fiber membranes changed from fingerlike structure to sponge-shape structure, and the properties of ultrafiltration membrane showed that the pure water flux was about 159 L m−2 h−1, and PEG10,000 rejection was above 95% under the operating pressure of 0.1 MPa. PPESK hollow fiber ultrafiltration membranes prepared in this work was also investigated the thermal stability at different operating temperature. As a result, when the temperature of feed solution was raised from 15 to 100 °C, the permeation flux increased more than three times without significant change of rejection.