ABSTRACT
The primary focal point in the fabrication of microfiltration membranes revolves around mitigating issues of low permeability stemming from the initial design as well as countering biofouling tendencies. This work aimed to address these issues by synthesizing an antibacterial capsaicin derivative (CD), which was then grafted to the poly(vinylidene fluoride-co-chlorotrifluoroethylene)-g-polymethacrylic acid (P(VDF-CTFE)-g-PMAA) matrix polymer, resulting in an antibacterial polymer (PD). Notably, both CD and PD demonstrated low cytotoxicities. Utilizing PD, a microfiltration membrane (MA) was successfully prepared through non-solvent-induced phase inversion. The pore sizes of the MA membrane were mainly concentrated at around 436 nm, while the pure water flux of MA reached an impressive value of 62 ± 0.17 Lm-2 h-1 at 0.01 MPa. MA exhibited remarkable efficacy in eradicating both Gram-negative (E. coli) and Gram-positive bacteria (Bacillus subtilis) from its surface. Compared with M1 prepared from P(VDF-CTFE), MA exhibited a lower flux decay rate (41.00% vs. 76.03%) and a higher flux recovery rate (84.95% vs. 46.54%) after three cycles. Overall, this research represents a significant step towards the development of a microfiltration membrane with inherent stable anti-biofouling capability to enhance filtration.
Subject(s)
Anti-Bacterial Agents , Bacillus subtilis , Biofouling , Capsaicin , Escherichia coli , Membranes, Artificial , Biofouling/prevention & control , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/chemical synthesis , Escherichia coli/drug effects , Capsaicin/chemistry , Capsaicin/pharmacology , Bacillus subtilis/drug effects , Microbial Sensitivity Tests , Filtration , Surface Properties , Particle SizeABSTRACT
Inspired by the stomatal feature of plant leaves, a photo-responsive membrane was developed to enhance the removal of irreversible membrane fouling and to control molecule release. Photo-responsive polymers were prepared by reacting the amine group of 4-amineazobenzene with about 3, 5 and 9 out of 12 carboxylic groups of PMAA which was grafted from P(VDF-CTFE) with a certain length. Subsequently, high-flux photo-responsive membranes (PRMs) were prepared from the heterogeneous polymers with different contents of photo-switchable azobenzene following a non-solvent-induced phase-inversion protocol. The pore size and surface hydrophilicity of PRMs could be reversibly increased by switching visible light to UV irradiation, which dramatically enhanced the backflushing efficiency on PRMs under UV irradiation. The "light-cleaning" process could recover more than 90% of the irreversible flux decline caused by typical organic foulant (BSA) and biological foulant (E. coli) on PRMs. The higher the content of azobenzene, the more obvious the pore size and hydrophilicity variation after light switching but the smaller the absolute pore size observed for PRMs. On the other hand, the light-switching gates of PRMs enabled the controlled release of molecules with different sizes. The novel PRM provided an efficient solution to mitigate irreversible membrane fouling and a light-triggered molecule release protocol, which would improve the membrane performance and further expand the application field of the membrane.
Subject(s)
Escherichia coli , Polymers , Hydrophobic and Hydrophilic Interactions , Light , Ultraviolet RaysABSTRACT
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 pH-responsive 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.
