Improved Antifouling Properties of Polyamide Nanofiltration Membranes by Reducing the Density of Surface Carboxyl Groups (original) (raw)
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RSC Advances, 2018
Membrane fouling is an urgent problem needing to be solved for practical application of nanofiltration membranes. In this study, an amphiphilic nanofiltration membrane with hydrophilic domains as well as low surface energy domains was developed, to integrate a fouling-resistant defense mechanism and a fouling-release defense mechanism. A simple and effective two-step surface modification of a polyamide NF membrane was applied. Firstly, triethanolamine (TEOA) with abundant hydrophilic functional groups was grafted to the membrane surface via reacting with the residual acyl chloride group of the nanofiltration membrane, making the nanofiltration membranes more hydrophilic; secondly, the 1H,1H,2H,2H-perfluorodecyltrichlorosilane (PFTS), well-known as a low surface energy material, was covalently grafted on the hydroxyl functional groups through hydrogen bonding. Filtration experiments with model foulants (bovine serum albumin (BSA) protein solution, humic acid solution (HA) and sodium alginate solution (SA)) were performed to estimate the antifouling properties of the newly developed nanofiltration membranes. As a result of surface modification proposed in this study the antifouling properties of an amphiphilic modified F-PA/PSF membrane were enhanced more than 10% compared to the PA/PSF specimen in terms of flux recovery ratio.
2018
Membrane fouling is an urgent problem needing to be solved for practical application of nanofiltration membranes. In this study, an amphiphilic nanofiltration membrane with hydrophilic domains as well as low surface energy domains was developed, to integrate a fouling-resistant defense mechanism and a fouling-release defense mechanism. A simple and effective two-step surface modification of a polyamide NF membrane was applied. Firstly, triethanolamine (TEOA) with abundant hydrophilic functional groups was grafted to the membrane surface via reacting with the residual acyl chloride group of the nanofiltration membrane, making the nanofiltration membranes more hydrophilic; secondly, the 1H,1H,2H,2H-perfluorodecyltrichlorosilane (PFTS), well-known as a low surface energy material, was covalently grafted on the hydroxyl functional groups through hydrogen bonding. Filtration experiments with model foulants (bovine serum albumin (BSA) protein solution, humic acid solution (HA) and sodium ...
Microporous and Mesoporous Materials, 2017
Polyethersulfone (PES) ultrafiltration membrane with enhanced simultaneous permeability and fouling eresistance property was prepared using a new synthesized aromatic polyamide (PA-6) as an additive. A series of asymmetric membranes were prepared by adding different amounts of PA-6 to the casting solution using the phase inversion induced by immersion precipitation method. Attenuated total reflection-Fourier transform infrared spectra (ATR-FTIR) and water contact angle measurement confirmed the PA-6 enrichment at the membrane surface and increased the membrane hydrophilicity and wettability. The SEM images elucidated the effect of PA-6 addition on the PES membrane morphology by increasing the pore density. The results of filtration performance, which carried out by dead-end filtration of bovine serum albumin (BSA) solution showed that the permeability and fouling resistance property was improved by optimizing the PA-6 content. When the PA-6 content was 2 wt%, the permeability reached approximately 10 times over the pure PES membrane. In comparison to the blend membrane of PES and 2 wt% of polyvinyl pyrrolidone (PVP), the blend membrane of 2 wt% of PA-6 showed significant flux recovery ability. The rejection of all the blended membranes was approximately at high point over 95%. In addition, the results were compared with those obtained using PVP as a usual additive. Although the PVP blended membranes exhibited higher permeability, they showed lower antifouling properties. Finally, a membrane with 1 wt% PVP and 1 wt% PA-6 was prepared and showed the best performance regarding improved permeability and antifouling properties.
Journal of Membrane Science, 2018
In this work, poly[1-vinyl-3(2-carboxyethyl) imidazolium betaine] (PVCIB), as a zwitterionic polyelectrolyte, was tethered onto a commercial thin film composite polyamide (TFC PA) membrane. First, polyvinyl imidazole (PVI) was grafted onto the TFC PA membrane surface by free radical graft polymerization method at various grafting times. Afterwards, one of PVImodified membranes was betainised using 3-bromopropionic acid to obtain PVCIB brushes on the membrane surface. Evaluation of membrane performance through desalination process indicated that despite decrease of salt rejection, water flux increased from 73.4 L/m 2 .h in the PA membrane to 91.6 L/m 2 .h in the PA-PVCIB membrane. Antimicrobial assessment using Escherichia coli showed that PVCIB-modified membrane was able to inhibit bacterial growth by about 98.8%. Antifouling and cleaning abilities of membranes were investigated using BSA and lysozyme at various pH values. It was revealed that hydrophilic PVCIB brushes considerably improved protein-resistant property of the TFC PA membrane. However, considering pHdependent behavior of PVCIB (zwitterionic at alkaline pH or polyelectrolyte at acidic pH), hydration repulsion or electrostatic repulsive forces, respectively, made a contribution to fouling mitigation. Accordingly, PA-PVCIB membrane exhibited remarkable antifouling ability to resist non-specific protein adsorption at neutral and alkaline pHs, whereas both PA-PVI and PA-PVCIB membranes exhibited marked resistance to the positively charged lysozyme adhesion at acidic pH.
Advances and challenges in tailoring antibacterial polyamide thin film composite membranes for water treatment and desalination: A critical review, 2024
Thin film composite (TFC) polyamide membranes have been predominantly utilized in water treatment and desalination and play a significant role in the separation processes. However, the occurrence of fouling, especially biofouling, has a detrimental effect on the efficiency of the membrane. The introduction of nanostructures and other surface modification strategies has paved the way for developing antibacterial TFC membranes, aiming to control and mitigate biofouling to achieve a rational design for practical applications. This comprehensive review introduces and discusses novel antibacterial TFC membranes, including their structure, composition, and performance. Additionally, particular attention is given to understanding the antibacterial mechanism of nanomaterials. To this end, various emerging and prevalent antibacterial nanomaterials are introduced, and their role in the fabrication of TFC membranes is overviewed. Moreover, versatile modification strategies are outlined to impart antibacterial activity into TFC membranes. Finally, the review proposes current challenges and prospects of antibacterial TFC membranes, aiming to provide valuable insights for developing advanced TFC membranes with optimal resistance against biofouling and improved separation performance. This critical review serves as a fundamental guide for designing strategies that surpass the current limitations of TFC membranes' antibacterial agents and nanomaterials, thereby mitigating the tendency of biofouling through tailored membrane surface properties.
Antifouling performance of poly(acrylonitrile)-based membranes: From green synthesis to application
The Journal of Supercritical Fluids, 2011
In order to develop clean ultrafiltration membranes able to prevent the fouling of biological compounds in filtration processes, poly(ethylene glycol) methyl ether acrylate (PEGA) was grafted to poly(acrylonitrile) (PAN) by free-radical polymerization in supercritical carbon dioxide (scCO 2 ) and the grafted copolymer was blended with PAN to fabricate porous membranes using scCO 2 -induced phase inversion method. Fourier transform infrared (FT-IR) analysis, 1 H nuclear magnetic resonance ( 1 H NMR) and differential scanning calorimetry (DSC) confirmed that the poly(acrylonitrile)-graft-poly(ethylene oxide) (PAN-g-PEO) was successfully synthesized, for the first time, in scCO 2 . The effect of increasing PEGA content on the initial monomer feed mixture on graft polymer morphology and average molecular weight was studied. Blended membranes with different PEGA contents were investigated by scanning electron microscopy (SEM), mercury porosimetry and dynamical mechanical analysis (DMA) to characterize their morphological, physico-chemical and mechanical properties. Moreover, water contact angle measurements, pure water permeability and filtration experiments were performed to evaluate membrane hydrophilicity and fouling resistance properties. Permeation experiments of model foulants, bovine serum albumin (BSA) and starch solutions were used to investigate antifouling character of blend membranes at different pHs. PAN: showed to be the ultrafiltration membrane with best performance. Furthermore, comparing with conventional technologies blended membranes of PAN:PAN-g-PEO prepared by a scCO 2assisted process showed enhanced hydrophilicity, larger protein and starch solution permeabilities and good resistance to irreversible fouling, indicating that the technology is an efficient process to prepare fouling resistant membranes for biomacromolecule separations.
Reactive and Functional Polymers, 2020
Poly(vinyl chloride) (PVC) ultrafiltration membranes with improved antifouling and antibiofouling properties were prepared by non-solvent induced phase inversion using a hyperbranched polyamidoamine as additive. PVC reacted into the casting solution with the commercial polyamidoamine nanomaterial Helux-3316 by means of a nucleophilic substitution reaction. The composition of neat and functionalized membranes was studied by ATR-FTIR and elemental composition. Amino groups were tracked using the fluorescent dye fluorescamine. Surface ζ-potential and water contact angles were used to measure surface charge and hydrophilicity of tested membranes. The incorporation of amino groups increased membrane hydrophilicity and surface porosity, which resulted in enhanced permeability. Functionalized membranes displayed antifouling behaviour revealed upon filtering BSA solutions and lower irreversible fouling than PVC membranes. The attachment of Helux moieties to PVC yielded membranes with antibiofouling functionality explained by the interaction of positively charged Helux moieties with the negatively charged cell envelopes. Growth reduction for cells attached to the membrane surface during filtration reached up to 1log for the gram-positive bacterium S. aureus. This investigation revealed that the incorporation of the hyperbranched nanomaterial in concentrations in the order of 1 wt% in the casting solution provides significant benefits to membrane performance, in terms of permeability and antifouling potential.
Effect of pH on the performance of polyamide/polyacrylonitrile based thin film composite membranes
Journal of Membrane Science, 2011
Molecular weight cut off (MWCO) pH Nanofiltration (NF) Interfacial polymerization (IP) Thin film composite (TFC) Glucose Polyethylene glycol (PEG) Donnan steric partitioning pore model (DSPM) a b s t r a c t In this study the effect of pH on the performance of thin film composite (TFC) nanofiltration (NF) membranes has been investigated at the relevant pH conditions, in the range of pH 1-13. TFC polyamide NF membranes have been fabricated on a polyacrylonitrile support via interfacial polymerization between piperazine in an aqueous phase and trimesoyl chloride in an organic phase. Membrane characterization has revealed that the produced membranes show a NaCl retention similar to NF-270 and Desal-5DK, a permeance in between those of NF-270 and Desal-5DK, and a slightly higher iso-electric point than NF-270 and Desal-5DK. The molecular weight cut-off of the membranes appeared to be practically constant in acidic and neutral conditions. At extremely alkaline conditions (pH > 11) an increase in molecular weight cut-off and a reduction in membrane flux has been observed. According to the Donnan steric partitioning pore model (DSPM) the change in performance in alkaline conditions originates from a larger effective average pore size and a larger effective membrane thickness as compared to the other pH conditions.
2014
Thin-film composite (TFC) polyamide reverse osmosis (RO) membranes are prone to biofouling due to their inherent physicochemical surface properties. In order to address the biofouling problem, we have developed novel surface coatings functionalized with biocidal silver nanoparticles (AgNPs) and antifouling polymer brushes via polyelectrolyte layer-by-layer (LBL) self-assembly. The novel surface coating was prepared with polyelectrolyte LBL films containing poly(acrylic acid) (PAA) and poly(ethylene imine) (PEI), with the latter being either pure PEI or silver nanoparticles coated with PEI (Ag-PEI). The coatings were further functionalized by grafting of polymer brushes, using either hydrophilic poly(sulfobetaine) or low surface energy poly(dimethylsiloxane) (PDMS). The presence of both LBL films and sulfobetaine polymer brushes at the interface significantly increased the hydrophilicity of the membrane surface, while PDMS brushes lowered the membrane surface energy. Overall, all surface modifications resulted in significant reduction of irreversible bacterial cell adhesion. In microbial adhesion tests with E. coli bacteria, a normalized cell adhesion in the range of only 4 to 16% on the modified membrane surfaces was observed. Modified surfaces containing silver nanoparticles also exhibited strong antimicrobial activity. Membranes coated with LBL films of PAA/Ag-PEI achieved over 95% inactivation of bacteria attached to the surface within 1 hour of contact time. Both the antifouling and antimicrobial results suggest the potential of using these novel surface coatings in controlling the fouling of RO membranes.
In continuation of work (J. Membr. Sci. 455, 2014, 271) for in situ PEGylation of thin film composite (TFC) membrane, herein, effect of polyethylene glycol (PEG) end-group on the properties and performance of PEGylated TFC nanofiltration (NF) membranes is reported. In situ PEGylation of conventional poly(piperazineamide) TFC NF membranes was performed by interfacial polymerization between TMC and PIP+PIP-terminated polyethylene glycol (PIP-PEG-PIP), PIP+m-phenylenediamine-terminated PEG (MPD-PEG-MPD) and PIP+alkyl amine terminated-PEG (H 2 N-PEG-NH 2 ) mixtures respectively. Among these three processes, PEGylated membranes prepared with TMC and PIP+PIP-PEG-PIP mixture exhibited excellent antifouling property, similar performance, close pore radius and pore structure 2 factor compared to conventional poly(piperazineamide) TFC NF membrane. This is attributed to the closer reactivity of PIP and PIP-PEG-PIP towards TMC. Membranes prepared with TMC and PIP+MPD-PEG-MPD mixtures exhibited superior antifouling property compared to conventional TFC NF membrane, nevertheless, rejection and permeate flux were decreased. TFC membranes prepared with PIP+H 2 N-PEG-NH 2 mixtures/TMC exhibited similar performance compared to conventional membrane with low degree of PEGylation and hence showed only marginal improvement of antifouling property.