Highly selective and antifouling reverse osmosis membrane by crosslinkers induced surface modification (original) (raw)
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Journal of Materials Chemistry, 2010
A new class of surface-structured RO membranes was developed with a hydrophilic brush layer of terminally anchored polymer chains resulting in fouling resistant membranes of low mineral scaling propensity and high permeability. The approach is based on free-radical graft polymerization of a suitable monomer, onto the active polyamide (PA) layer of a thin film composite (PA-TFC) membrane, post-surface activation with an impinging atmospheric pressure plasma source. Two types of nano-structured (SNS) RO membranes (SNS-PA-TFC) were synthesized based on methacrylic acid (MAA-SNS-PA-TFC) and acrylamide (AA-SNS-PA-TFC) graft polymerization. The poly(methacrylic acid) and poly(acrylamide) brush layers, on the PA surface, resulted in RO membranes of significantly lower mineral scaling propensity, evaluated with respect to the mineral scalant calcium sulfate dihydrate, compared with commercial RO membrane (LFC1) of about the same salt rejection ($95%) and surface roughness ($70 nm). Direct membrane surface imaging indicated that the rate of nucleation and thus mineral scaling were reduced owing to the polymer brush layer. Fouling resistance of the SNS-PA-TFC membranes was also demonstrated with respect to model foulants (the protein BSA and alginic acid). The MAA-SNS-PA-TFC and AA-SNS-PA-TFC membranes had a negatively charged and near neutral surfaces, respectively, with water contact angles somewhat lower for the former and higher for the latter membranes relative to the LFC1 membrane. The AA-SNS-PA-TFC membrane displayed lower mineral scaling propensity than the MAA based membrane, although its alginic acid fouling resistance was inferior, despite its lower surface roughness (25-33 nm) relative to the MAA-SNS-PA-RFC
2012
An increase in United States water pollution has been denoted over the past 30 years. With a rise in water pollution, enhanced filtration and heavy metal remediation methods are imperative. Membrane fouling, the process whereby extraneous particles deposit onto a membrane surface and degrade the membrane’s performance, is a major issue facing ultrafiltration. This study’s goals were to enhance membrane flux and anti-fouling performance with a PEGDA filter and to compare the efficiency of PVAm and PEI for heavy metal adsorption. Electrospinning was employed to create membrane platforms for coating and grafting polyethylene glycol diacrylate (PEGDA), N,N’Methylenebisacrylamide (MBAA), cellulose nanofibers (CNF), polyvinyl alcohol (PVAm) and polyethylenimine (PEI). The anti-fouling performance of electrospun PAN membranes was determined by coating the surface with CNF, PEGDA, and MBAA, which were chosen due to their hydrophilic and low-fouling properties. Coating the top layer of the m...
Enhanced resistance to organic fouling in a surface-modified reverse osmosis desalination membrane
Desalination and Water Treatment, 2016
Membrane surface modification with the aim of lowering foulant to surface affinity, has recently gained considerable attention. In this article, we report improved performance (permeate flux, salt rejection, and resistance to alginate fouling) of surface-modified reverse osmosis (RO) membranes, under cross-flow filtration conditions. The surface of RO membranes was modified by amphiphilic hydroxethyl methacrylate-co-perfluorodecyl acrylate (HEMA-co-PFDA) copolymer films. The amphiphilic coatings were deposited via an all-dry and solventless vapor deposition technique, termed as initiated chemical vapor deposition. Scanning electron microscopy revealed that a dense and continuous layer of alginate formed on the surface of the unmodified membranes, whereas foulant deposition on the surface-modified membranes was found to be more sporadic and discontinuous. The coatings were found stable even after 6 h of exposure to sodium alginate at higher pressure (800 psi), as evidenced by ATR-FTIR analysis of the post-fouled membranes.
PEG-coated reverse osmosis membranes: Desalination properties and fouling resistance
Journal of Membrane Science, 2009
This study focuses on the use of surface-coated reverse osmosis (RO) membranes to reduce membrane fouling in produced water purification. A series of crosslinked PEG-based hydrogels were synthesized using poly(ethylene glycol) diacrylate as the crosslinker and poly(ethylene glycol) acrylate, 2-hydroxyethyl acrylate, or acrylic acid as comonomers. The hydrogels were highly water permeable, with water permeabilities ranging from 10.0 to 17.8 (L m)/(m 2 h bar). The hydrogels were applied to a commercial RO membrane (AG brackish water RO membrane from GE Water and Process Technologies). The water flux of coated membranes and a series-resistance model were used to estimate coating thickness; the coatings were approximately 2 m thick. NaCl rejection for both uncoated and coated membranes was 99.0% or greater, and coating the membranes appeared to increase salt rejection, in contrast to predictions from the series-resistance model. Zeta potential measurements showed a small reduction in the negative charge of coated membranes relative to uncoated RO membranes. Model oil/water emulsions were used to probe membrane fouling. Emulsions were prepared with either a cationic or an anionic surfactant. Surfactant charge played a significant role in membrane fouling even in the absence of oil. A cationic surfactant, dodecyltrimethyl ammonium bromide (DTAB), caused a strong decline in water flux while an anionic surfactant, sodium dodecyl sulfate (SDS), resulted in little or no flux decline. In the presence of DTAB, the AG RO membrane water flux immediately dropped to 30% of its initial value, but in the presence of SDS, its water flux gradually decreased to 74% of its initial value after 24 h. DTAB-fouled membranes had lower salt rejection than membranes not exposed to DTAB. In contrast, SDS-fouled membranes had higher salt rejection than membranes not exposed to SDS, with rejection values increasing, in some cases, from 99.0 to 99.8% or higher. In both surfactant tests, coated membranes exhibited less flux decline than uncoated AG RO membranes. Additionally, coated membranes experienced little fouling in the presence of an oil/water emulsion prepared from DTAB and n-decane. For example, after 24 h the water flux of the AG RO membrane fell to 26% of its initial value, while the water flux of a PEGDA-coated AG RO membrane was 73% of its initial value.
Journal of Advanced Research, 2021
Introduction: Nanomaterials aggregation within polyamide (PA) layer of thin film nanocomposite (TFN) membrane is found to be a common issue and can negatively affect membrane filtration performance. Thus, post-treatment on the surface of TFN membrane is one of the strategies to address the problem. Objective: In this study, an eco-friendly surface modification technique based on plasma enhanced chemical vapour deposition (PECVD) was used to deposit hydrophilic acrylic acid (AA) onto the PA surface of TFN membrane with the aims of simultaneously minimizing the PA surface defects caused by nanomaterials incorporation and improving the membrane surface hydrophilicity for reverse osmosis (RO) application. Methods: The TFN membrane was first synthesized by incorporating 0.05 wt% of functionalized titania nanotubes (TNTs) into its PA layer. It was then subjected to 15-s plasma deposition of AA monomer to establish extremely thin hydrophilic layer atop PA nanocomposite layer. PECVD is a promising surface modification method as it offers rapid and solvent-free functionalization for the membranes. Results: The findings clearly showed that the sodium chloride rejection of the plasma-modified TFN membrane was improved with salt passage reduced from 2.43% to 1.50% without significantly altering
Journal of Membrane Science and Research, 2019
During interfacial polymerization (IP) reaction between m-phenylenediamine (MPDA) and trimesoyl chloride (TMC), a by-product, i.e. hydrochloric acid can produce. This produced acid diffuses back in aqueous phase and protonates MPDA and reduces its reactivity that results in lowering of polymer yield and performance of membrane. Further, for getting consistency in reverse osmosis membranes formation, different acid acceptors (AAs) can investigate in the IP to form polyamide-made barrier layer formation. The main objective was to scavenge hydrochloric acid produced during IP and to fabricate membrane having high flux and salt rejection ability. AAs (of varying concentrations) tested were triethylamine-camphorsulfonic acid (TEACSA), triphenyl phosphate (TPP), sodium hydroxide (SH) and trisoduim phosphate (TSP) for studying structure and performance of membranes. The membrane samples were then characterized using surface proflometer, scanning electron microscopy (SEM), Energy-dispersive X-...
Forward osmosis (FO) is an emerging membrane-based water separation process with potential applications in a host of environmental and industrial processes. Nevertheless, membrane fouling remains a technical obstacle affecting this technology, increasing operating costs and decreasing membrane life. This work presents the first fabrication of an antifouling thinfilm composite (TFC) FO membrane by an in situ technique without postfabrication treatment. The membrane was fabricated and modified in situ, grafting Jeffamine, an amine-terminated poly(ethylene glycol) derivative, to dangling acyl chloride surface groups on the nascent polyamide active layer. Surface characterization by contact angle, Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), zeta potential, atomic force microscopy (AFM), and fluorescence microscopy, confirms the presence of Jeffamine on the membrane surface. We demonstrate the improved fouling resistance of the in situ modified membranes through accelerated dynamic fouling FO experiments using a synthetic wastewater feed solution at high concentration (250 mg/L) of alginate, a model macromolecule for the hydrophilic fraction of wastewater effluent organic matter. Our results show a significantly lower flux decline for the in situ modified membranes compared to pristine polyamide (14.3 ± 2.7% vs 2.8 ± 1.4%, respectively). AFM adhesion force measurements between the membrane and a carboxylate-modified latex particle, a surrogate for the organic (alginate) foulant, show weaker foulant− membrane interactions, further confirming the enhanced fouling resistance of the in situ modified membranes.
• Surface modification of commercial RO desalination membranes • p(4VP-co-EGDA) co-polymerization via initiated chemical vapor deposition • Functionalization of the co-polymer to carboxybetaine zwitterion surface moieties • Significant reduction of bacterial cell attachment on modified membrane surface • Perm selectivity under cross flow conditions comparable to virgin membranes a b s t r a c t Copolymer films of poly(4-vinylpyridine-co-ethylene glycol diacrylate) (p(4-VP-co-EGDA)) were synthesized and first deposited on various substrates via initiated chemical vapor deposition (iCVD). As-deposited copolymer films were converted to surface zwitterionic structures containing poly(carboxybetaine acrylic acetate) (pCBAA) units by a quaternization reaction with 3-bromopropionic acid (3-BPA). Conversion to a zwitterionic structure was confirmed by FTIR and high-resolution XPS N1s scans. Biopolymer adsorption of the deposited copolymer coatings was investigated by quartz crystal microbalance with dissipation (QCM-D) using a model foulant‐ bovin serum albumin (BSA). The optimized copolymer films were then deposited onto commercial RO membranes and with subsequent zwitterionicalization. Inertness to bacterial adhesion of the modified membranes was investigated by counting the number of Escherichia coli and Pseudomonas aeruginosa cells attached on the membrane surface under static conditions. Bacterial adhesion studies revealed an almost 98% reduction in microorganism attachment onto the surface of modified membranes compared to bare membranes, which clearly demonstrates the effectiveness and superior performance of the zwitterionic coating against bacterial adhesion. The salt rejection performance of the modified membranes resulted in improved salt rejection (98%); however, permeate flux was slightly compromised compared to virgin membranes. AFM analysis demonstrated that modified membranes showed lower RMS roughness compared to virgin membranes.
Chemical Engineering Research and Design, 2019
In order to address a global issue in regard to the shortage of drinking water resources, reverse osmosis (RO) processes have been considerably attended to provide people with high-quality fresh water. In spite of many efforts carried out for preparation of efficient RO membranes, fouling/biofouling remains as a significant challenge. In this study, antibacterial polyamide thin film composite (PA-TFC) decorated with hydrophilic polyrhodanine (PRh) nanoparticles was fabricated through a novel route of direct filtration method. This method is a facile technique for modification of the membrane surface, in particular, for recovery of the membrane antibacterial agent which is lost during the process. The synthesized membranes were studied for morphology, surface functional groups, hydrophilicity, and surface roughness via FESEM, FTIR, contact angle, and AFM analysis. Both diffusion inhibition zone and colony formation unit tests exhibited excellent biocidal activity of the PRh loaded membranes against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus strains. Moreover, the best fouling resistance was assigned to PA-TFC membrane decorated with 0.5%wt. PRh, and PA-TFC membrane modified with 0.75%wt. PRh revealed the best salt rejection ability.