Development of dynamic pH and temperature-responsive smart membranes via immobilization of chitosan-graft-poly(N-isopropylacrylamide-co-methacrylic acid) hydrogels on microfiltration membrane-support

Abstract Ultrafiltration is a pressure-driven membrane process which is widely used for water treatment and separations in biotechnology, chemical, pharmaceutical and food industries. The study deals with the development of novel smart membranes for ultrafiltration which reversibly change flux and human serum albumin (HSA) rejection as a response to the change of the pH and temperature of the feed solution. Smart membranes were prepared via immobilization of cross-linked dual-responsive chitosan-graft-poly(N-isopropylacrylamide (NIPAM)-co-methacrylic acid) hydrogels on the surface of the microfiltration membrane via filtration in dead-end mode. It was shown that pure water flux (PWF) increases by 1.8–4.7 times upon the temperature increase from 25 °C to 50 °C due to the conformational changes of poly(NIPAM) chains grafted to chitosan at temperature higher than lower critical solution temperature. It was shown that PWF increases by 8.7 times at T = 25 °C and 16.5 times at T = 50 °C when pH of the feed water decreases from 10 to 3. The developed smart membranes demonstrate extremely high cleaning efficiency and can be simply washed by distilled water at T = 50 °C after ultrafiltration of HSA solution (pH = 3). It was shown that PWF of smart membrane is restored by 1154% compared to 67% for reference microfiltration membrane.