Effect of the Zwitterion, p(MAO-DMPA), on the Internal Structure, Fouling Characteristics, and Dye Rejection Mechanism of PVDF Membranes

Abstract

The zwitterion poly-(maleic anhydride-alt-1-octadecene-3-(dimethylamino)-1-propylamine) (p(MAO-DMPA)) synthesized using a ring-opening reaction was used as a poly(vinylidene fluoride) (PVDF) membrane modifier/additive during phase inversion process. The zwitterion was characterized using proton nuclear magnetic resonance (1HNMR) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Atomic force microscopy (AFM), field emission scanning electron microscope (SEM), FTIR, and contact angle measurements were taken for the membranes. The effect of the zwitterionization content on membrane performance indicators such as pure water flux, membrane fouling, and dye rejection was investigated. The morphology of the membranes showed that the increase in the zwitterion amount led to a general decrease in pore size with a concomitant increase in the number of membrane surface pores. The surface roughness was not particularly affected by the amount of the additive; however, the internal structure was greatly influenced, leading to varying rejection mechanisms for the larger dye molecule. On the other hand, the wettability of the membranes initially decreased with increasing content to a certain point and then increased as the membrane homogeneity changed at higher zwitterion percentages. Flux and fouling properties were enhanced through the addition of zwitterion compared to the pristine PVDF membrane. The high (>90%) rejection of anionic dye, Congo red, indicated that these membranes behaved as ultrafiltration (UF). In comparison, the cationic dye, rhodamine 6G, was only rejected to <70%, with rejection being predominantly electrostatic-based. This work shows that zwitterion addition imparted good membrane performance to PVDF membranes up to an optimum content whereby membrane homogeneity was compromised, leading to poor performance at its higher loading.

Advances in Membrane Separation for Biomaterial Dewatering

“…This leads to a decrease in irreversible fouling and higher FRR values . The amphiphilic nature of zwitterionic coatings can provide the intended effect for a broad range of operation conditions. ,− …”

“… 120 The amphiphilic nature of zwitterionic coatings can provide the intended effect for a broad range of operation conditions. 96 , 121 − 127 …”

Ultrafiltration polyanionic poly (3‐sulfopropyl methacrylate) membranes with enhanced antifouling and water flux

“…Various approaches have been employed to mitigate fouling in polyethersulfone membranes, focusing on improving their hydrophilic properties. These methods include incorporating hydrophilic polymers through blending, 18 introducing hydrophilic groups via membrane modification, implementing graft polymerization, 19 utilizing plasma treatment, 20 employing UV‐assisted polymerization, and applying zwitterionic modification 21,22 . The combination of compatible polymer blends provides a pathway to synergistic mechanical capabilities, which frequently outperform those reported by individual component polymers.…”

“…These methods include incorporating hydrophilic polymers through blending, 18 introducing hydrophilic groups via membrane modification, implementing graft polymerization, 19 utilizing plasma treatment, 20 employing UV-assisted polymerization, and applying zwitterionic modification. 21,22 The combination of compatible polymer blends provides a pathway to synergistic mechanical capabilities, which frequently outperform those reported by individual component polymers. This application enables opportunities for beneficial mechanical features that represent unique properties, which are inherent in the individual components.…”