Crystalline nuclei-templated PVDF/PAN_PVDF ultrafiltration membranes prepared via a dual-casting technique: High water permeation with improved anti-fouling and flux recovery

Abstract

The combined crystallization and diffusion (CCD) method has been introduced in recent years to produce polyvinylidene fluoride (PVDF) and other polymeric ultrafiltration (UF) membranes with high permeation/separation performance. However, the CCD PVDF membranes can easily be fouled by protein adsorption, which deteriorates their permeance over time. This study addresses this issue by incorporating polyacrylonitrile (PAN) into PVDF in the separation layer at different percentages via a dual-casting technique in the CCD method to prevent irreversible fouling. The anisotropic CCD membrane morphology with interconnected microchannels was preserved after PAN was blended in the separation layer without phase separation or delamination, as determined by scanning electron microscopy (SEM). Antifouling studies revealed that even after two fouling cycles, the 10 % PAN-doped dual-cast PVDF membrane presented very high pure water permeance (PWP) at 640 L per square meter membrane area per hour (LMH) under 1 bar pressure difference across the membrane (LMH bar⁻¹), that is over 4 times greater than the initial water permeance of well-known commercial PVDF membranes from industry leaders (∼150 LMH bar⁻¹) at the same mean flow pore size range (30–35 nm). This research provides an efficient and facile route for fabricating high-performance ultrafiltration membranes with superior antifouling and flux recovery characteristics for long-term operation.