Structurally stable copolymer ultrafiltration membranes prepared via vinyl chloride suspension copolymerization and tannic acid in-situ modification integration

Abstract

Polyvinyl chloride ultrafiltration membranes, widely used in various industries, are hindered by their high susceptibility to contamination. To address this concern, researchers have investigated diverse modification methods, encompassing surface modification and physical blending. Although surface modification provides stability, but it is intricate, expensive, and may result in pore clogging. Physical blending is a simpler approach but lacks durability and stability. Tannic acid (TA), a natural compound, has attracted attention for its potential in membrane modification due to its diverse benefits. However, the existing methods, such as TA-metal networks, encounter challenges of weakened stability and reduced permeability of membrane. To solve these issues, this research presents a novel approach that integrates suspension copolymerization, polyaddition, and a sol–gel process to fabricate structurally stable copolymer ultrafiltration membranes. Active sites for sol–gel reactions were embedded into the copolymer through copolymerization. Subsequently, TA was added to the copolymer casting solution, and isocyanate propyltriethoxysilane was decorated onto TA through a polyaddition reaction. Following this, a non-solvent induced phase separation method was used for membrane fabrication. During the formation of the membrane, a sol–gel reaction occurred between the copolymer and the modified TA, ensuring both stable chemical cross-linking. The membrane demonstrates excellent permeability, fouling resistance, and long-term operational stability. This innovative approach not only addresses compatibility and leakage issues associated with traditional methods but also ensures the stable integration of hydrophilic functional monomers within the copolymer matrix. The proposed method holds promise for advancing applications of ultrafiltration membrane technology in various complex environments.