Preparation of Interconnected Biomimetic Poly(vinylidene fluoride-co-chlorotrifluoroethylene) Hydrophobic Membrane by Tuning the Two-Stage Phase Inversion Process

Abstract

A facile strategy was applied for poly(vinylidene fluoride-cochlorotrifluoroethylene) (PVDF-CTFE) hydrophobic membrane preparation by tuning the two-stage phase inversion process. The exposure stage was found to benefit the solid−liquid demixing process (gelation/crystallization) induced by the solvent evaporation and the subsequent phase inversion induced by immersion benefit the liquid−liquid demixing. It was confirmed that the electrospun nanostructure-like biomimetic surface and interconnected pore structure can be expected by controlling the exposure duration, and 300 s was considered as the inflection point of exposure duration for PVDF-CTFE membrane through which a tremendous variation would show. The micro/ nanohierarchical structure in the membrane surface owing to the crystallization of PVDF-CTFE copolymer was responsible for the improvement of membrane roughness and hydrophobicity. Meanwhile, the interconnected pore structure in both the surface and the cross-section, which were formed because of the crystallization process, offers more mass transfer passages and enhances the permeate flux. The membrane then showed excellent MD performance with high permeate flux, high salt rejection, and relatively high stability during a 48 h continuous DCMD operation, according to the morphology, pore structure, and properties, which can be a substitute for hydrophobic membrane application.

Preparation of N-MG-modified PVDF-CTFE substrate composite nanofiltration membrane and its selective separation of salt and dye

“…15 This copolymer introduces CTFE segments into the PVDF chain, exhibiting superior chemical resistance, better resistance to polar organic solvents, and higher mechanical strength compared to PVDF. 16,17 Thus, it is an ideal material for water treatment in complex environments such as dyeing and printing wastewater. However, its hydrophobicity increases further with an increase in the relative content of C-F bonds, 15,18 posing challenges when used as an NF substrate membrane.…”