Good Antifouling Performance Research Articles

Mechanically durable and self-healing super-hydrophobic coating with hierarchically structured KH570 modified SiO2-decorated aligned carbon nanotube bundles

We prepared stably and hierarchically structured particles (ACNTB-SiO2-KH570) composed of silane coupling agent 3-methacryloxypropyltrimethoxysilane (KH570) modified nano-SiO2 and aligned carbon nanotube bundles (ACNTB), and developed a mechanically durable super-hydrophobic composite coating from epoxy (EP) adhesive precursor and ACNTB-SiO2-KH570 by dripping method, without using any fluoro-containing compounds. The results show that ACNTB-SiO2-KH570 particle film possesses excellent super-hydrophobicity because of the complicated nanotexture of ACNTB-SiO2-KH570. The composite coating with a very small content (4.3%) of ACNTB-SiO2-KH570 can show excellent super-hydrophobicity owing to the formation of rough surface with micro/nanoscale hierarchical structure. The water contact angle (CA) and sliding angle (SA) of the composite coating can reach 158.8 ± 2.5° and 2.5 ± 0.5°, respectively. Moreover, the composite coating not only displays good antifouling and self-cleaning performance, but also retains super-hydrophobicity after sand falling test, water jet impact and sandpaper abrasion cycles. The excellent mechanical durability of the composite coating is attributed to the synergistic effects of high strength and toughness ACNTB-SiO2-KH570 and the good interface interaction of the different components in coating. The composite coating can show good adhesions to various substrate and exhibit super-hydrophobicity. Furthermore, the damaged composite coating can recover its super-hydrophobicity after being heated to 300 °C, owing to the combination of the decomposition of partial EP polymers and the migration of SiO2 to the coating surface.

PVDF-CaAlg nanofiltration membranes with dual thin-film-composite (TFC) structure and high permeation flux for dye removal

Novel polyvinylidene fluoride-calcium alginate (PVDF-CaAlg) nanofiltration (NF) membranes were prepared by impregnating electrospun PVDF substrates with sodium alginate solution and crosslinking with CaCl2 solution. The NF membranes were characterized via field emission scanning electron microscopy (FESEM) equipped with an energy-dispersive spectrometry (EDS), attenuated total reflectance Fourier transform infrared spectra (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). The results show that the prepared PVDF-CaAlg NF membranes exhibit dual thin-film-composite (TFC) structure and superior surface hydrophilicity. The highest pure water flux can achieve 63.8 L·m−2·h−1·bar−1 accompanied with a 98.5% rejection rate for methyl blue (MB), which is superior to many polymeric NF membranes. The prepared PVDF-CaAlg NF membranes exhibit much higher rejections for seven typical dyes, and the rejection slightly rises with the increase of impregnating time. In the long-term filtration process, the permeation flux for dye solution remains stable. PVDF-CaAlg NF membranes show good anti-fouling performance to BSA protein and lactobacillus.

Flexible, fouling-resistant and self-cleaning Ti3C2Tx-derivated hydrophilic nanofiltration membrane for highly efficient rejection of organic molecules from wastewater

Up to now, the applications of nanofiltration membranes for removal of organic molecules from wastewater have still be restricted due to the improper channel distribution, inherent low chemical stability and easy fouling of the membranes. In this study, a new kind of Ti3C2Tx-deviated hybrid nanomaterial membranes is fabricated by a vacuum-filtration strategy on a cellulose acetate support. Ti3C2Tx nanosheets, together with the self-derivated TiO2, are found to play a key role to establish continuous water transmission channels. With the incorporation of TiO2 nanoparticles, the surface roughness of the prepared membranes also decreases apparently. By this new design, the water flux of the Ti3C2Tx-TiO2 membrane increases to a maximum value of 75.4 L/m2 h bar 4 times higher than that of the pristine Ti3C2Tx membrane, together with a high removal ratio of above 99% for one typical small molecule organic contaminant of rhodamine B (RhB). The composite membranes also exhibit a good anti-fouling performance, since the adsorption tendency of pollutants on the surface of the membrane or the blockage of the pores was decreased. In addition, the excellent photocatalytic self-cleaning ability of the membranes under UV light, with the improved possibility of highly efficient recycling, was also validated, which was ascribed to the in situ formation of Ti3C2Tx/TiO2 heterojunctions. This study provides a new prospective for providing multi-functional nanofiltration membranes in the field of wastewater treatment.

High-performance chlorinated polyvinyl chloride ultrafiltration membranes prepared by compound additives regulated non-solvent induced phase separation

To enable wider deployment of ultrafiltration (UF) membrane technology, novel advanced membrane materials are still highly desired. Chlorinated polyvinyl chloride (CPVC) shares most of the outstanding features of polyvinyl chloride (PVC) and possesses improved thermal stability, indicating a promising material for UF membrane. To date, however, the separation performance of the current CPVC UF membranes is far below the requirements for application. In this study, propylene glycol and polyoxyethylene-20-sorbaitan monolaurate (Tween-20) were selected as compound additives to manipulate the structure and separation performance of CPVC membrane fabricated by the non-solvent induced phase separation process. The results demonstrated that the synergistic effect of compound additives led to instantaneous demixing to increase the ratio of polymer lean phase in the initial casting film, and the rapid precipitation fixed the phase separation structure immediately. Consequently, the prepared membranes possessed improved porosity and pore size uniformity. The obtained CPVC UF membranes exhibited a high pure water flux up to 955.2 L m-2 h-1·bar-1 with a BSA rejection above 95.0%, which is 11 times higher than CPVC membrane fabricated without additive and comparable to that of commercial UF membranes. In addition, thanks to the more uniform pore size distribution and smooth top surface, the obtained CPVC membranes also exhibited good antifouling performance. Moreover, the CPVC UF membrane showed good thermal stability and reuse performance, which would facilitate its post-functionalization and practical application.

Construction of superhydrophilic/underwater superoleophobic polydopamine‐modified h‐BN/poly(arylene ether nitrile) composite membrane for stable oil‐water emulsions separation

Oil/water emulsion separation in harsh environments remains a big challenge. Herein, a double layered nanofibrous composite membrane was developed by assembly of polydopamine‐modified hexagonal boron nitride (h‐BN‐PDA) onto a poly(arylene ether nitrile) (PEN) nanofibrous mat. Owing to the synergistic effect of a h‐BN‐PDA skin layer and a PEN nanofibrous mat supporting layer, as‐prepared composite membrane exhibited high thermal stability, corrosion resistance, and superhydrophilic/underwater superoleophobic property. Consequently, the PEN composite membrane showed good antifouling performance and a high rejection ratio (>99.0%) for various oil/water emulsions. After 10 cycles, the separation flux of PEN composite membrane still reached 588.1 L/m2 h under the operating pressure of 0.04 MPa. Furthermore, the PEN composite membrane could still achieve high separation efficiency and high flux in high‐temperature (65 °C) and strongly corrosive conditions (pH = 1‐13). Therefore, the stable and efficient h‐BN‐PDA/PEN composite membrane showed potential application for treating oily wastewater in harsh environments.

Surface Interactions between Water-in-Oil Emulsions with Asphaltenes and Electroless Nickel-Phosphorus Coating.

Surface interactions between emulsion drops and substrate surfaces play an important role in many phenomena in industrial processes, such as fouling issues in oil production. Investigating the interaction forces between the water-in-oil emulsion drops with interfacially adsorbed asphaltenes and various substrates is of fundamental and practical importance in understanding the fouling mechanisms and developing efficient antifouling strategies. In this work, the surface interactions between water drops with asphaltenes and Fe substrates with or without an electroless nickel-phosphorus (EN) coating in organic media have been directly quantified using the atomic force microscope drop probe technique. The effects of asphaltene concentration, organic solvent type, aging time, contact time, and loading force were investigated. The results demonstrated that the adhesion between water drops and the substrates was enhanced with higher asphaltene concentration, better organic solvent to asphaltenes, longer aging time, longer contact time, and stronger loading force, which was due to the growing amount and conformational change of asphaltenes adsorbed at the water/oil interface. Meanwhile, the adhesion between the water drop and the EN substrate was much weaker than that with the Fe substrate. The bulk fouling tests also showed that EN coating had a very good antifouling performance, which was in consistence with the force measurement results. Our work sheds light on the fundamental understanding of emulsion-related fouling mechanisms in the oil industry and provides useful information for developing new coatings with antifouling performances.

Hierarchically Assembled Graphene Oxide Composite Membrane with Self-Healing and High-Efficiency Water Purification Performance.

Graphene oxide (GO) with a two-dimensional lamellar structure and single-atom thickness has exhibited advantages in water purification by stacking to a continuous membrane. However, a proper method to further increase the separation property of the GO membrane is still urgently needed. Besides, damage to the membrane during the full-scale application processes and the resulted consequential loss are prevalent problems need to be solved. Here, a hierarchically assembled GO composite membrane was developed that can achieve high-efficiency water purification performance and self-healing property via the synergistic effect of the metal-organic framework (MOF) and the coated hydrophilic layer of chitosan. The intercalated MOF effectively expanded the channel space of GO and endowed the channels with molecular-sieving property. Meanwhile, the coated chitosan layer can selectively adsorb water and achieve self-healing through the cross-linking reaction. The prepared GO composite membrane shows largely improved water flux (14.62 L m-2 h-1 bar-1), increased 344% than the water flux of the GO membrane, high rejection ratio (>99% for dyes), and good antifouling performance. In addition, the damaged GO composite membrane can recover its water flux (95%) and rejection ratio (96%) through a facile self-healing process.

Construction of Antifouling Membrane Surfaces through Layer-by-Layer Self-Assembly of Lignosulfonate and Polyethyleneimine.

Lignin is the second most abundant and low-cost natural polymer, but its high value-added utilization is still lack of effective and economic ways. In this paper, waste lignosulfonate (LS) was introduced to fabricate antifouling membrane surfaces via layer-by-layer self-assembly with polyethyleneimine (PEI). The LS/PEI multilayers were successfully deposited on the polysulfone (PSf) membrane, as demonstrated by ATR-FTIR, XPS, Zeta potential measurements, AFM, and SEM. Meanwhile, the effect of the number of bilayers was investigated in detail on the composition, morphologies, hydrophilicity, and antifouling performance of the membrane surface. As a result, with the bilayer numbers increase to 5, the PSf membrane shows smooth surface with small roughness, and its water contact angle reduces to 44.1°, indicating the improved hydrophilicity. Accordingly, the modified PSf membrane with 5 LS/PEI bilayers repels the adsorption of protein, resulting in good antifouling performance. This work provides a green, facile, and low-cost strategy to construct antifouling membrane surfaces.

Hierarchically Stabilized PAN/β-FeOOH Nanofibrous Membrane for Efficient Water Purification with Excellent Antifouling Performance and Robust Solvent Resistance.

Filtration membranes, with good antifouling performance and robust solvent resistance (e.g., organic solvents or highly acidic/alkaline/saline solvents), that can effectively purify complex polluted water systems are especially demanded in practice but present a challenge to be conquered. Herein, a simple method has been demonstrated to address the obstacles, applying the stabilized polyacrylonitrile (SPAN) nanofiber/β-FeOOH nanorod composite membrane as a model. In this work, simply stabilizing PAN nanofibers in air can achieve robust solvent resistance against organic solvents and strong inorganic acidic/alkaline/saline solutions. Hydrophilic β-FeOOH nanorods were anchored onto SPAN nanofibers of our electrospun membrane and achieve superhydrophilicity (0°)/underwater superoleophobicity (>155°) for various oils. More importantly, the SPAN/β-FeOOH nanofibrous membrane exhibits robust mechanical strength (274 MPa of Young's modulus), excellent chemical stability, fast separation flux (2532-10146 L m-2 h-1), and satisfying removal ratio (>98.2%) against insoluble oils and soluble cationic dyes. In addition, good photocatalytic activity against organic pollutants provides our membranes with excellent flux restorability and a long-term use capacity. These outstanding performances endow our membrane with a great potential application in purifying polluted aquatic systems in worldly harsh conditions.

One-pot route to synthesize HNTs@PVDF membrane for rapid and effective separation of emulsion-oil and dyes from waste water.

Water-purification membranes with high water flux, excellent recycling ability, good anti-fouling property, wide range for different oil/water emulsions separation, and strong water-soluble dyes removal ability are highly desirable for water purification but still a challenge to be realized. In this work, we show a simple method to address this challenge, in which halloysite nanotubes (HNTs) have been decorated on the poly (vinylidene fluoride) (PVDF) membrane surface through one-pot method via the aid of KH550 and dopamine. The HNTs@PVDF composite membrane exhibits superhydrophilic and under-water superoleophobic performance. In addition, our membrane can separate wide oil/water emulsions (including surfactant-stabilized and surfactant-free emulsions) from wastewater with high efficiency (>99.65%), outstanding recycle ability with good flux recovery rate (FRR > 95%) and good anti-fouling performance (the underwater oil contact angle (OCA) is 155.8 ± 1.8° with low oil adhesion) and high water flux (7994 ± 150 L m-2 h-1). Interestingly, our membrane also removes different water-soluble dyes (e.g., Congo red, methylene blue, and rhodamine B) from waste water by simply filtering. Those outstanding properties make our membrane hold great potential applications in real-world water purification and environmental protection.

Green synthesis of TiO2 nanoparticles using Cajanus cajan extract and their use in controlling the fouling of ultrafiltration PVDF membranes

Polyvinylidene fluoride (PVDF)/TiO2 composite ultrafiltration membranes were fabricated using different loadings of TiO2 NPs synthesized by the green route using an extract of Cajanus cajan. XRD analysis confirmed the synthesis of TiO2 nanoparticles of size 10 nm using Debye Scherrer’s equation. High hydrophobicity of PVDF restricts its successful application due to fouling in the membrane. Therefore, composite membranes were prepared via the phase inversion route and characterized by contact angle and permeation tests. The BSA filtration experiments revealed that membrane with 0.5 wt% of TiO2 exhibits excellent hydrophilicity, permeation flux, high rejection ratio, and good antifouling performance. It was observed that the fouling characteristic of the membrane is governed by the surface roughness of the membrane, and with increasing loading of TiO2 the surface roughness decreases indirectly enhancing the antifouling property of membranes. The adsorption capacity of bovine serum albumin on the membrane surface decreased from 2.85 to 2.15 mg cm−2 as the TiO2 loading increased from 0 to 0.02 g TiO2/g PVDF. Fouling was found due to cake formation in ultrafiltration and can be explained by Hermia’s fouling model suggesting that the solutes are not deposited into the pores, which indicates that the fouling process is physically reversible.

The construction of electrochemical aptasensor based on coral-like poly-aniline and Au nano-particles for the sensitive detection of prostate specific antigen

Prostate specific antigen (PSA), as the significant biomarker of prostate cancer, has aroused widespread concern. However, constructing the PSA aptasensor with high sensitivity and low detection limit is still facing huge challenges. In this study, a sensitive electrochemical aptasensor for detecting PSA based on coral-like poly-aniline (PANI)/gold nano-particles (AuNPs) and the peptides was constructed. Coral-like PANI and AuNPs with the diameter of 50–80 nm, as the substrate materials, were directly deposited on glass carbon electrode (GCE) by electrodeposited method. Then, the peptides, as the antifouling materials, were anchored on the modified-electrode, which not only can form antifouling surface to reduce nonspecific adsorption, but also can be as a medium between the modified-electrode and PSA aptamer. Finally, the PSA aptamer was immobilized on the electrode. Based on the synergistic effect of excellent conductivity and special morphology of the substrate materials, and the antifouling ability of peptides, the aptasensor exhibited a high sensitivity of 462.7 μA(ng mL−1)−1 cm−2, wide linear range from 0.1 pg mL-1 to 100 ng mL-1, low limit of detection (LOD) of 0.085 pg mL-1 and good antifouling performance. The aptasensor also possessed outstanding selectivity, reproducibility and stability. Moreover, the aptasensor can directly detect PSA in 10% human serum solutions.

Metal–organic framework-based ultrafiltration membrane separation with capacitive-type for enhanced phosphate removal

The great potential of ultrafiltration (UF) membranes for phosphate rejection has been challenged by the selectivity-permeability trade-off. Here, we propose a filtration system based on a novel dual-layer UF mixed matrix membrane (MMM) with a capacity for capacitive deionization (CDI), which was fabricated by incorporating NH2-MIL-101 into a polyethersulfone (PES) polymer matrix and the in-situ combination of carbon cloth (CC). The MMM exhibited an improved porosity of 85.52%, a declined water contact angle of 53.25°, and a 5.7% increase in water permeability in comparison to those of the PES membrane due to the hydrophilic and mesoporous NH2-MIL-101 particles. While incorporating the CC provided the non-conductive PES polymer with high electroconductivity. As an electrode, the CC/MMM exhibited a relatively high permeance of 424.63 L/h MPa m2, good antifouling performance, and remarkable phosphate rejection that reached 100% during the 2-h filtration period in the electrically-enhanced dead-end filtration cell. The removal capacity of the cell exceeded 22.51% and 74.0% for the energized CC/PES membrane and uncharged CC/MMM, respectively, due to the superior phosphate adsorption ability of NH2-MIL-101 and enhanced deionization capacity due to the electric field. UF MMM separation coupled with the electrochemical technique exhibited great potential to enhance the selective rejection of phosphate ions at low levels, while maintaining high membrane permeability and shortening the treatment time required by the CDI technique.

A loose NF membrane by grafting TiO2-HMDI nanoparticles on PES/β-CD substrate for dye/salt separation

In this study, a high flux loose nanofiltration (NF) membrane was fabricated for the desalination of dye wastewater through a facile method which combined doping and surface grafting. First, PES ultrafiltration substrate was prepared via non-solvent induced phase separation by introducing multi-hydroxyl β-cyclodextrin (β-CD) into the casting solution as hydrophilic additive. Then, titanium dioxide (TiO2) nanoparticles were grafted uniformly on membrane surface with the assistance of 1, 6-hexamethylene diisocyanate (HMDI), resulting in the enhancement of surface hydrophilicity and separation performance of the resultant membranes. Remarkably, the membrane prepared at optimized conditions achieved a high pure water flux (52.0 L·m−2·h−1 at 0.2 MPa) and high permeate flux for dyes (e.g. 30.5 L·m−2·h−1 for Congo Red at 0.2 MPa). It also exhibited high rejection for dyes (e.g. 97.4% for Congo Red) and high transmittance of salts (e.g. 94.0% for Na2SO4). Moreover, the membrane possessed good antifouling performance with a high flux recovery ratio of 93.7% after fouled by humic acid (HA). The results indicated that the novel loose NF membrane had an impressive potential application for dye wastewater treatment.

A modified, mussel-inspired method to fabricate polyvinylidene fluoride membranes filled with halloysite nanotubes modified with dopamine, iron oxide, and silane for oil–water separation

Polyvinylidene fluoride is an excellent membrane separation material, but its hydrophilicity is weak, which makes the membrane susceptible to contamination during use. In this study, a novel composite nanomaterial was prepared to improve the hydrophilicity of the polyvinylidene fluoride membrane, so that it can efficiently separate the oil–water emulsion. The nanophase material crystal structure was studied by X-ray diffraction, and the Fourier transform infrared spectroscopy revealed polar moieties (–OH, –NH2) on the membrane surface. The results show that the hydrophilic nanomaterials have been successfully prepared. The membrane surface morphology and the pore structure were analyzed by scanning electron microscopy and atomic force microscopy. It can be observed that the surface of the modified membrane is more orderly than the original polyvinylidene fluoride membrane. The polyvinylidene fluoride composite membrane’s pure water flux was investigated by using a cup ultrafiltration device to characterize the permeability. The pure water contact angle was measured by a contact angle meter to characterize the membrane’s hydrophilicity. The results show that the modified membrane has good hydrophilicity compared with the original polyvinylidene fluoride membrane. In addition, the oil–water separation performance was studied using four different types of oil/water emulsions. The experimental results showed that the membrane had a good performance in separating the emulsified oils with a highest oil removal rate of 97.2%. At the same time, the polyvinylidene fluoride membrane had good anti-fouling performance. After three pollution/washing cycles, the flux recovery rate still reached 84.6%. Under the long-term testing conditions, the performance of the membrane was relatively stable.

Polyurethane films modified with polyaniline-zinc oxide nanocomposites for biofouling mitigation

Eco-friendly antifouling coatings are considered to be superior alternatives over conventional biocidal agents that affect marine life adversely. Considering this fact, polyurethane (PU) films modified with a novel pigment [Polyaniline-Zinc oxide (PANI-ZnO) nanocomposites, 1–2% w/w] and phytic acid as a chelating dopant have been developed. The structure has been elucidated using Infrared Spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and the surface properties of the films were explored by using atomic force microscopy, contact angle measurements, and swelling ratios. PANI-ZnO nanocomposite particles conferred excellent chemical, mechanical and thermal properties to the PU films. The antifouling properties of the modified PU films were tested against marine bacteria (Gram negative: Vibrio harveyi and Gram positive: Bacillus licheniformis) both qualitatively and quantitatively (80 to 12% for V. harveyi and 75 to 20% for B. licheniformis). In-vitro studies displayed good antifouling performance of the modified PU-PANI-ZnO films. The present study offers a simple, moreover a passive (green) technology that allows restoration of submerged surfaces with minimal detrimental effect on marine flora and fauna.

Functional, Degradable Zwitterionic Polyphosphoesters as Biocompatible Coating Materials for Metal Nanostructures.

A zwitterionic polyphosphoester (zPPE), specifically l-cysteine-functionalized poly(but-3-yn-1-yloxy)-2-oxo-1,3,2-dioxaphospholane (zPBYP), has been developed as a poly(ethylene glycol) (PEG) alternative coating material for gold nanoparticles (AuNPs), the most extensively investigated metal nanoparticulate platform toward molecular imaging, photothermal therapy, and drug delivery applications. Thiol-yne conjugation of cysteine transformed an initial azido-terminated and alkynyl-functionalized PBYP homopolymer into zPBYP, offering hydrolytic degradability, biocompatibility, and versatile reactive moieties for installation of a range of functional groups. Despite minor degradation during purification, zPPEs were able to stabilize AuNPs presumably through multivalent interactions between combinations of the side chain zwitterions (thioether and phosphoester groups of the zPPEs with the AuNPs). 31P NMR studies in D2O revealed ca. 20% hydrolysis of the phosphoester moieties of the repeat units had occurred during the workup and purification by aqueous dialysis at pH 3 over ca. 1 d, as observed by the 31P signal of the phosphotriesters resonating at ca. -0.5 to -1.7 shifting downfield to ca. 1.1 to -0.4 ppm, attributed to transformation to phosphates. Further hydrolysis of side chain and backbone units proceeded to an extent of ca. 75% over the next 2 d in nanopure water (pH 5-6). The NMR degradation results were consistent with the broadening and red-shift of the surface plasmon resonance (SPR) observed by UV-vis spectroscopy of the zPPE-coated AuNPs in water over time. All AuNP formulations in this study, including those with citrate, PEG, and zPPE coatings, exhibited negligible immunotoxicity, as determined by cytokine overexpression in the presence of the nanostructures relative to those in cell culture medium. Notably, the zPPE-coated AuNPs displayed superior antifouling properties, as assessed by the extent of cytokine adsorption relative to both the PEGylated and citrate-coated AuNPs. Taken together, the physicochemical and biological evaluations of zPPE-coated AuNPs in conjunction with PEGylated and citrate-coated analogues indicate the promise of zPPEs as favorable alternatives to PEG coatings, with negligible immunotoxicity, good antifouling performance, and versatile reactive groups that enable the preparation of highly tailored nanomaterials for diverse applications.

Novel thin‐film composite nanofiltration membranes fabricated via the incorporation of ssDNA for highly efficient desalination

ABSTRACTIn this work, the biomacromolecule, single‐stranded deoxyribonucleic acid (ssDNA) was innovatively incorporated into the polyamide layer to tailor the permeate flux and antifouling performance of the nanofiltration (NF) membranes. With active amines groups, the ssDNA was as the aqueous phase monomers along with piperazine (PIP), and reacted with trimesoyl chloride on polyethersulfone substrate to fabricate thin‐film composite (TFC) NF membranes. The NF membrane prepared under optimal ratio of ssDNA/PIP had a pure water permeability of 75.8 L m−2 h−1 (improved 58% compared to PIP NF membrane) and Na2SO4 rejection of 98.0% at 6.0 bar. The rejections for different inorganic salts were the order: Na2SO4 (98.0%) > MgSO4 (89.2%) > MgCl2 (72.8%) > NaCl (23.0%). Furthermore, the TFC NF membranes showed good antifouling performance in long‐term running with 300 ppm bovine serum albumin and humic acid solution. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 47102.

Synergistic effect of welding electrospun fibers and MWCNT reinforcement on strength enhancement of PAN–PVC non-woven mats for water filtration

Typical electrospun polymer mats exhibit poor mechanical properties, undesirable for pressure-driven water filtration. Herein, strength enhancement of polyacrylonitrile–poly(vinyl chloride) (PAN–PVC) electrospun mats is demonstrated with a synergistic approach, using solvent vapor-induced welding of the polymer fibers at their cross points and reinforcement of the fibers by unfunctionalized multi-walled carbon nanotubes (MWCNTs). Tensile strength and Young’s modulus of the as-spun PAN–PVC mats are increased by 127% and 175% respectively via welding effects, and are further enhanced to 205% and 314% increments respectively, using 1 wt% MWCNTs. The post-treated composite mats achieve over four-fold the modulus predicted by the modified Halpin–Tsai model. With a slight total reduction in pure water flux (8%), water permeability is not greatly suppressed by welding the polymer fibers or by the presence of MWCNTs in the fibers. The two strength-enhancing strategies also allow recyclability of the post-treated composite mats with high particulate (25 nm–5 μm) filtration efficiency of nearly 100% and good antifouling performance (flux recovery of >93%) throughout the 10 tested filtration cycles.

Calcium alginate-coated electrospun polyhydroxybutyrate/carbon nanotubes composite nanofibers as nanofiltration membrane for dye removal

A novel nanofiber composite nanofiltration membrane was fabricated through coating calcium alginate hydrogel on electrospun polyhydroxybutyrate/carbon nanotubes (CaAlg-c-PHB/CNT) nanofiber membrane. The CaAlg-c-PHB/CNT nanofiber composite membrane was investigated by means of SEM, FTIR, Raman, XRD, DSC, TGA, zeta potential and water contact angle (WCA) measurements. The tensile tests of the CaAlg-c-PHB/CNT nanofiber composite membrane were performed in dry and wet state. The filtration properties of the CaAlg-c-PHB/CNT nanofiber composite membrane were measured in term of flux and rejection rate at operation pressure ranged from 0.1 to 0.7 MPa. The antifouling properties were investigated by emulsified oil–water and BSA solution separation. Results showed that the CaAlg-c-PHB/CNT nanofiber composite membrane with 1 wt% CNT had the highest tensile strength and initial Modulus with the value of 6.14, 5.12 and 142.64, 127.5 MPa in dry and wet state, respectively. The water contact angle was decreased remarkably from 83.6° to 17.8° after calcium alginate hydrogel coating. The pure water flux (PWF) was increased from 68.61 to 150.72 L/m2 h with operation pressure increased from 0.1 to 0.7 MPa. Five dyes with different molecular weight ranged from 400 to 900 g/mol were selected for filtration test. The rejection rate could maintain over 90% for dyes with the molecular weight higher than 600 g/mol under 0.5 MPa. The CaAlg-c-PHB/CNT nanofiber composite membrane showed good antifouling performance for both oil and protein. These results indicated that the CaAlg-c-PHB/CNT composite nanofiber membrane can be used as an effective nanofiltration membrane operated at high pressure for dye removal.