Hydrophilic and antifouling modification of PVDF membranes by one-step assembly of tannic acid and polyvinylpyrrolidone

Membrane technology has received wide attention as it plays an important role in water treatment process. However, membrane fouling results in a decrease in water permeation flux and separation effect, which lead to degraded membrane lifespan. A facile and novel strategy to form a multifunctional modified coating on the membrane surface by using the one-step assembly coating on the basis of tannin acid had been reported in this work. Tannin acid is a plant-derived polyphenolic substance that is hydrophilic and bactericidal. As a common nonionic polymer, polyvinylpyrrolidone (PVP) has a hydrophobic interaction and hydrogen bonding with TA and is beneficial to improve the hydrophilicity and antifouling performance of the substrate. However, the benefits of coating on the membrane have been limited due to the strong complexing ability of TA and PVP in aqueous solution. Herein, 50% N,N-dimethylformamide (DMF) aqueous solution were found that promoted the co-deposition of TA and PVP on the surface of the membrane. The catechol-rich polyphenol coating provides versatile properties on the membrane surface, including ultra-high pure water flux, high antifouling properties, recyclability, and a certain degree of antimicrobial performance. Moreover, the TA-PVP coating imparts a binding site for binding metal ions that allows it to capture metal ions through complexation and immobilization on the coating. The modified membranes showed more significant antifouling performance after iron ions have been complexed, and showed stronger bactericidal activity after silver ions have been complexed.