Superhydrophilic modification of polytetrafluoroethylene (PTFE) hollow fiber membrane by a novel miniemulsion template method

Abstract

During the hydrophilic modification of PTFE hollow fiber membranes, the modifying substances often block the pores upon crosslinking. This blockage can lead to unsatisfactory water flux, despite the enhanced hydrophilicity of the membranes. Herein, we proposed a miniemulsion template method to solve the above problems, where water soluble polyvinyl alcohol (PVA) and crosslinking agent glutaraldehyde (GA) were selected to modify the PTFE membrane. The PTFE membrane was premoistened with isopropyl alcohol (IPA) and then immersed in a miniemulsion template environment. The miniemulsion droplets and PVA macromolecules gradually diffused into the membrane pores and occupied the membrane voids to realize the displacement with IPA. The PVA macromolecules distributed around the miniemulsion droplets reacted with the crosslinking agent to form a crosslinked network that coated the membrane fibers. After removing the miniemulsion template, the occupied voids were released, thus providing channels for water transport and preventing pore blockage following the crosslinking of the modified substances. The modified PTFE membrane exhibits superior hydrophilicity and high water flux. The water flux can reach 1624.64 ± 20.82 L/(m²·h) at the operating pressure of 0.04 MPa. After 16 days of soaking in strong acid (pH = 2), strong alkali (pH = 12), and a strong oxidizing agent (2000 ppm NaClO), the modified membrane retains its hydrophilic properties, demonstrating excellent chemical stability, better antifouling, and oil-water separation performance. Therefore, the modified PTFE hollow fiber membrane demonstrates significant potential for water treatment applications.