Enhanced antifouling property of poly(aryl ether nitrile) ultrafiltration membranes via copolymerization with phenolphthalin

In this work, phenolphthalin was successfully introduced into the molecule chain of poly(aryl ether nitrile) (PEN) by nucleophilic substitution method in order to get carboxylated PEN (PEN-COOH) copolymers with a controlled carboxylation degree. Then, a series of PEN-COOH ultrafiltration membranes were prepared by immersion precipitation phase inversion method. The influence of the carboxylation degree of PEN-COOH on the structure and performance of the prepared polymeric membrane was studied by scanning electron microscope, atomic force microscope, porosity, contact angle, ultrafiltration and antifouling experiments, etc. The results showed that with the increase of carboxylation degree of polymeric membrane, the surface of PEN-COOH membrane gradually became dense and smooth, and its hydrophilicity increased. Meanwhile, both the pure water flux and permeation flux of the membrane decreased obviously, and the corresponding rejection ratio of bovine serum albumin (BSA) was slightly enhanced. Also, the membrane showed improvement in antifouling property. As the membrane with the best comprehensive performance, PEN-COOH-60% membrane had a BSA rejection ratio as high as 99.3%, while maintaining water flux of 351.7 (L m−2 h−1) and permeation flux of 160.1 (L m−2 h−1). With a water contact angle of 59.7°, the flux recovery rate of PEN-COOH-60% membrane significantly increased 37.1% compared with PEN and basically stable in the three cycles of antifouling experiments. These results proved that the introduction of carboxyl group into PEN molecular chain could effectively improve the antifouling performance of PEN-COOH membrane.