High-Flux pH-Responsive Ultrafiltration Membrane for Efficient Nanoparticle Fractionation

Abstract

Fractionation of nanoparticles with different sizes from the mixture by using a single membrane would reduce the membrane cost and enhance the efficiency. In this study, an amphiphilic pH-responsive copolymer was prepared by grafting a pHresponsive hydrophilic polymethacrylic acid (PMAA) side chain from a hydrophobic poly(vinylidene fluoride-co-chlorotrifluoroethylene), P(VDF-CTFE) backbone. Subsequently, the isoporous pH-responsive membranes (PPMs) were prepared from the functional copolymers with different PMAA chain lengths. PPM indicated reversible pore size decreasing with the increasing pH of the feed. Moreover, the membrane pore size variation range was further extended by adjusting the PMAA side chain length of the copolymer to reach a wide range from 10.2 to 34.5 nm. Owning to the amphiphilic nature of the copolymer, PPM showed a narrow pore size distribution which is responsible for the much higher pure water flux of PPM than the conventional UF membrane with similar retention capability. In the fractionation test, the mixed 20 and 30 nm polystyrene nanoparticles were penetrating PPM at pH 11 and 3, respectively. The pH-responsive PPM indicated great potential for nanoparticle fractionation, while the uniform pores of PPM further enhanced the membrane performance in terms of permeability and selectivity.

Enhancing biofouling resistance in microfiltration membranes through capsaicin-derivative functionalization

“…Second, P(VDF-CTFE)-g-PMAA was synthesized, following our previous study. 33 In brief, tert-butyl methacrylate (tBMA) was grafted from the P(VDF-CTFE) backbone using atom transfer radical polymerization (ATRP); subsequently, the tert-butyl This journal is © The Royal Society of Chemistry 2024 alcohol group was detached through hydrolysis to obtain P(VDF-CTFE)-g-PMAA with the carboxyl groups. The detailed synthesis procedure is provided in Text S1 (ESI †).…”

“…10 For example, poly(vinylidene fluorideco-chlorotrifluoroethylene) P(VDF-CTFE), which was widely adopted for MF membrane preparation because of the high stability and facile posttreatment, was introduced with hydrophilic functional groups. 11 However, hydrophilic modification may not be sufficient to completely prevent membrane biofouling because bacteria could transport and multiply on the membrane surface. 12 Alternative approaches include the incorporation of biocides into the membrane matrix to kill the attached microbes.…”

Temperature-Responsive Separation Membrane with High Antifouling Performance for Efficient Separation

“…In recent years, membranes capable of intelligent responses to various stimuli, including temperature [17], pH [18,19], pressure [20], light [21], electricity [22], and magnetic fields [23], have been developed [24]. Such innovations not only diminish membrane operational costs but also broaden their applications [25]. Shen et al enhanced a hydrophobic PVDF membrane's filtration efficacy by rendering it both hydrophilic and pH-sensitive through surface modification [26].…”

Bioinspired Redox-Responsive Graphene Oxide Membrane Based on Supramolecular Host–Guest Interaction for Tunable Molecular Separation

“…Up to now, extensive bioinspired intelligent responsive membranes, which can respond to environmental stimuli, including pH, ionic strength, light, temperature, and electricity, − have been fabricated by introducing stimuli-responsive agents into a porous membrane substrate. When receiving stimulus signals from the external environment, these stimuli-responsive agents can change their conformation and structure, thereby causing changes in the effective pore size or surface properties of the separation membrane. , The molecular chain or agglomeration structure in traditional polymer membranes is conducive to structure design and introduction of stimuli-responsive agents. , However, a stimuli-responsive membrane based on a traditional polymer substrate is still limited by the heterogeneous pore structure, complex modification strategies, and masking of partial stimuli-responsive agents, resulting in unsatisfactory response performance and limited application prospects.…”

“…14,15 The molecular chain or agglomeration structure in traditional polymer membranes is conducive to structure design and introduction of stimuli-responsive agents. 8,16 However, a stimuli-responsive membrane based on a traditional polymer substrate is still limited by the heterogeneous pore structure, complex modification strategies, and masking of partial stimuli-responsive agents, resulting in unsatisfactory response performance and limited application prospects. Two-dimensional lamellar membranes, represented by graphene oxide (GO) membranes, have recently emerged as promising advanced membrane materials due to their unique water transport properties.…”