High efficiency and flexible construction of hydrophilic polymer brushes on polyether ether ketone hollow-fiber membrane surface for improving permeability separation, and anti-fouling performances

Polyether ether ketone (PEEK) is a high-performance thermoplastic used as a separation membrane for waste-water treatment, purification, and recycling, especially in harsh environments. However, the applications of PEEK membranes are limited by their processing difficulty, low permeability, and membrane fouling. Herein, a PEEK hollow fibre membrane (PHFM) was fabricated by melt-spinning of polyetherimide (PEI)/PEEK blends and extracting PEI. Thereafter, a hydration layer consisting of 2-hydroxylethyl acrylate (HEA) chains was constructed on the PHFM surface based on the surface-initiated atom transfer radical polymerisation method. The grafting density and grafting length of the HEA chains were modulated by varying the bromination time and ATRP reaction time, and the hydrophilicity of the resulting PHFM surface was enhanced significantly without deteriorating its original porous structure. The controllable pores and hydrated layers on the PHFM surface simultaneously improved the permeability, separation performance, and anti-fouling properties of the membrane. Under a bromination time of 6 h and an ATRP reaction time of 8 h, the water flux of the modified PHFM was enhanced by 364 %. The rejection rate of bovine serum albumin (BSA) by the modified membrane exceeded 90 %. According to the extended Derjaguin-Landau-Verwey-Overbeek theory, the improved anti-fouling performance was related to the weakened acid-base attraction between the foulants and membrane with the hydration layer. After multiple separation-washing cycles, the total fouling and irreversible fouling of the modified PHFM were reduced. The normalised water flux and BSA rejection ratio of the modified anti-fouling PHFM remained 216 % and 90 %, respectively.