Effect of graphite oxide and multi-walled carbon nanotubes on the microstructure and performance of PVDF membranes

Preparation, characterization, and photocatalytic performance of a PVDF/cellulose membrane modified with nano Fe3O4 for removal of methylene blue using RSM under visible light

In this work, a polymeric membrane-based polyvinylidene fluoride coated with cellulose and loaded with iron oxide nanoparticles (PVDF/cellulose/Fe3O4) was synthesized and was characterized using FESEM, XRD, AFM, and contact angle measurements. The activity and modification of the PVDF/cellulose/Fe3O4 membrane under visible light for the removal of methylene blue were studied using the central composite design. The effect of influential variables such as pH, methylene blue concentration, amount of Fe3O4 in the membrane, and irradiation time on MB removal was investigated. Analysis of variance was used to determine the significance of experimental factors and their interactions. About 72.5% methylene blue removal using the PVDF/cellulose/Fe3O4 membrane under visible light was achieved at optimum conditions of a pH of 9, methylene blue concentration of 600 mg L-1, Fe3O4 amount of 0.03 g, and irradiation time of 117 min. Finally, results confirmed that the proposed membrane has good performance for methylene blue removal under visible light.

Removal of propranolol by membranes fabricated with nanocellulose/proanthocyanidin/modified tannic acid: The influence of chemical and morphologic features and mechanism study

Polymer-based membranes containing nanocellulose and natural macromolecules have potential to treat water, however few works have associated the changes in chemical and morphological membrane's features with their performance as adsorbent. Herein, a new green composite based on nanocellulose (NC) and alkylated tannic acid (ATA) and cross-linked with proanthocyanidin was produced and incorporated into polyacrylonitrile (PAN) membranes to eliminate propranolol (PRO) from water. Characterizations revealed that the increasing of NC-ATA content reduced the pore size of the membrane's upper surface and made the finger like structure of the sublayer disappear, due to the formation of hydrophilic domains of NC/ATA which speeds up the external solidification step. The presence of NC-ATA reduced the hydrophilicity, from a water contact angle of 3.65° to 16.51°, the membrane roughness, from 223.5 to 52.0 nm, and the zeta potential from -25.35 to -55.20 mV, improving its features to be a suitable adsorbent of organic molecules. The membranes proved to be excellent green adsorbent, tridimensional, and easy to remove after use, and qmax for PRO was 303 mg·g-1. The adsorption mechanism indicates that H-bonds, ion exchange, and π-π play important role in adsorption. NC-ATA@PAN kept high removal efficiencies after four cycles, evidencing the potential for water purification.

Enhancing the Performance of PVDF/GO Ultrafiltration Membrane via Improving the Dispersion of GO with Homogeniser

In this study, PVDF/GO-h composite membranes were synthesised using a homogeniser to improve the dispersion of GO nanosheets within the composite membrane's structure, and then characterised and contrasted to PVDF/GO-s control samples, which were synthesised via traditional blending method-implementing a magnetic stirrer. By characterizing membrane via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), water contact angle (WCA) and membrane performance. SEM results showed that the number of the finger-like structure channels and pores in the sponge like structure of PVDF/GO-h composite membranes become more compared with PVDF/GO-s membranes. Water contact angle tests showed that the PVDF/GO-h composite membranes have lower contact angle than PVDF/GO-s control, which indicated the PVDF/GO-h composite membranes are more hydrophilic. Results also showed that composite membranes blended using homogeniser exhibited both improved water flux and rejection of target pollutants. In summary, it was shown that the performance of composite membranes could be improved significantly via homogenisation during synthesis, thus outlining the importance of further research into proper mixing.

Impact of a new functionalization of multiwalled carbon nanotubes on antifouling and permeability of PVDF nanocomposite membranes for dye wastewater treatment

Here, novel hydroxyl and carboxyl functionalized multiwalled carbon nanotubes (AHF-MWCNT and ACF-MWCNT) were successfully synthesized and introduced for modification and antifouling improvement of the PVDF membrane. The blending effect of AHF-MWCNT and ACF-MWCNT on the morphology and surface properties of the PVDF membrane was explored by SEM, AFM, water contact angle, and zeta potential analysis. The results indicated that the membrane surface has become more hydrophilic, smoother as well more negative. In addition, the overall porosity and mean pore radius are increased by MWCNTs embedding. The filtration performance, antifouling and dye separation of the nanocomposite membranes were improved by adding any amounts of AHF-MWCNT and ACF-MWCNT in the PVDF membrane matrix. The carboxylic modification presented better performance than the hydroxyl functionalization. The 0.1 wt% ACF-MWCNT blended membrane presented an optimum performance with 46 L m^-2 h^-1 bar^-1 permeability, 93% FRR, and 97.3% dye rejection. Consequently, embedding functionalized MWCNT in the PVDF membrane matrix was led to improvement of membrane characteristics and enhancement of pure water flux, antifouling feature, and dye separation. So, the functionalized MWCNT could be a promising additive for the PVDF membrane modification.

Fabrication and prospective applications of graphene oxide-modified nanocomposites for wastewater remediation

Water bodies have become polluted with heavy metals and hazardous contaminants as a result of fast development. Many strategies have been devised by researchers in order to remove hazardous contaminants from the aquatic environment. Utilizing graphene oxide-based composite materials as efficient adsorbents for waste water treatment, desalination, separation, and purification is gaining attraction nowadays. Some of their defining properties are high mechanical strength, hydrophilicity, remarkable flexibility, ease of synthesis, atomic thickness, and compatibility with other materials. In water treatment, high separation performance and stable graphene-based laminar structures have been the main goals. Magnetic separation is among the methods which received a lot of attention from researchers since it has been shown to be quite effective at removing harmful pollutants from aqueous solution. Graphene oxide-modified nanocomposites have provided optimal performance in water purification. This review article focusses on the fabrication of GO, rGO and MGO nanocomposites as well as the primary characterization tools needed to assess the physiochemical and structural properties of graphene-based nanocomposites. It also discusses the approaches for exploiting graphene oxide (GO), reduced graphene (rGO), and magnetic graphene oxide (MGO) to eliminate contaminants for long-term purification of water. The potential research hurdles for using fabricated MGOs as an adsorbent to remediate water contaminants like hazardous metals, radioactive metal ions, pigments, dyes, and agricultural pollutants are also highlighted.

Enhanced Performance of PVDF Composite Ultrafiltration Membrane via Degradation of Collagen-Modified Graphene Oxide

The collagen obtained from chrome leather waste can be used to modify graphene oxide (GO) to prepare polyvinylidene fluoride (PVDF) composite ultrafiltration membranes, a process that is conducive to the recovery of leather waste, comprehensive utilization of GO and improved performance of the membrane. In this paper, collagen-modified GO (CGO) was prepared by degradation of collagen from chrome leather waste and used to prepare a PVDF composite ultrafiltration membrane. The results show that the carboxyl content of CGO and dispersion were improved. The water flux and flux recovery rate of the modified ultrafiltration membrane were improved. The bovine serum albumin (BSA) intercepted on the membrane surface was easy to clean and the antifouling performance improved. The performance of the membrane decreased when the GO content exceeded 0.75 wt%, while CGO can reach 1.0 wt% without agglomeration due to its good dispersion.

New Understanding of the Difference in Filtration Performance between Anatase and Rutile TiO2 Nanoparticles through Blending into Ultrafiltration PSF Membranes

The blending of nanomaterials into a polymeric matrix is a method known for its ability, under certain circumstances, to lead to an improvement in membrane properties. TiO₂ nanoparticles have been used in membrane research for the last 20 years and have continuously shown promise in this field of research. Polysulfone (PSf) membranes were obtained through the phase inversion method, with different TiO₂ nanoparticle concentrations (0, 0.1, 0.5, and 1 wt.%) and two types of TiO₂ crystalline structure (anatase and rutile), via the addition of commercially available nanopowders. Research showed improvement in all studied properties. In particular, the 0.5 wt.% TiO₂ rutile membrane recorded an increase in permeability of 139.7% compared to the control membrane. In terms of overall performance, the best nanocomposite membrane demonstrated a performance index increase of 71.1% compared with the control membrane.

Development of Multiwalled Carbon Nanotube-Reinforced Biodegradable Polylactic Acid/Polybutylene Succinate Blend Membrane

Currently, gas separation (GS) membranes are produced from petrochemical-based polymers, but their lifespan is severely impacting the environment. Therefore, there has recently been growing interest in developing ecofriendly biodegradable polymer-based GS membranes. This study developed a polylactic acid (PLA)/polybutylene succinate (PBS) blend composite membrane for GS using the dry/wet phase inversion technique. The influence of the multiwalled carbon nanotube (MWCNT) concentration in the PLA/PBS blend was studied by investigating tensile properties, porosity, percentage crystallinity, contact angle, and gas permeance.The obtained results demonstrate that the addition of MWCNT enhances the tensile strength, porosity, and percentage crystallinity, whereas it decreases the contact angle. The pure gas permeation was investigated at pressures of 2-4 bar at 25 °C. The gas permeation study revealed that the PLA/PBS blend with 0.5% wt. MWCNT enhanced the gas permeance and selectivity at 4 bar. The gas permeance acquired at 25 °C and 4 bar for PLA/PBS reinforced with MWCNT was highest in hydrogen followed by carbon dioxide, argon, and nitrogen. Additionally, a study of the membrane morphology illustrated the uniform dispersion of MWCNT in the PLA/PBS blend. The investigation concluded that membranes containing MWCNT are capable of separating gases at the molecular level, thereby reducing energy consumption.

Constructing dense and hydrophilic forward osmosis membrane by cross-linking reaction of graphene quantum dots with monomers for enhanced selectivity and stability

This paper reports a novel thin-film nanocomposite (TFN) membrane with a dense, flat, and hydrophilic polyamide (PA) layer. The atypical PA structure was obtained by the cross-linking reaction of graphene oxide quantum dots containing amino groups (NH₂-GOQDs) with triacyl chloride and polyamide oligomers. And the resulting TFN membrane showed a flat (small-scale ridge structure) and smooth surface. Meanwhile, the introduction of oxygen-containing and amino functional groups increased surface hydrophilicity. The reaction of amino groups on the NH₂-GOQDs with acid chloride groups and the carboxyl groups (in the linear part of the polyamide) enhanced the degree of cross-linking of the PA layer, forming a compact surface. Owning to the dense surface structure, excellent hydrophilicity, and small water transmission distance, the optimized TFN membrane exhibited an enhanced water flux of 26.57 L⋅m^-2⋅h^-1 with a low reverse salt flux of 6.0 g⋅m^-2⋅h^-1. Furthermore, nano-indentation/scratch results showed the interface adhesion between substrate and PA layer was improved due to the physical anchoring of NH₂-GOQDs in the substrate. And in the long-term FO test, the TFN membrane showed stable selectivity. This work proves that the targeted structural design of the PA layer at the nanoscale will have a positive impact on desalination field.

Significantly Improved Dielectric Performance of Poly(1-butene)-Based Composite Films via Filling Polydopamine Modified Ba(Zr0.2Ti0.8)O3-Coated Multiwalled Carbon Nanotubes Nanoparticles

The low dielectric constant of the nonpolar polymer poly(1-butene) (PB-1) limits its application as a diaphragm element in energy storage capacitors. In this work, Ba(Zr_0.2Ti_0.8)O₃-coated multiwalled carbon nanotubes (BZT@MWCNTs) were first prepared by using the sol-gel hydrothermal method and then modified with polydopamine (PDA) via noncovalent polymerization. Finally, PB-1 matrix composite films filled with PDA-modified BZT@MWCNTs nanoparticles were fabricated through a solution-casting method. Results indicated that the PDA-modified BZT@MWCNTs had good dispersion and binding force in the PB-1 matrix. These characteristics improved the dielectric and energy storage performances of the films. Specifically, the PDA-modified 10 vol% BZT@ 0.5 vol% MWCNTs/PB-1 composite film exhibited the best dielectric performance. At 1 kHz, the dielectric constant of this film was 25.43, which was 12.7 times that of pure PB-1 films. Moreover, its dielectric loss was 0.0077. Furthermore, under the weak electric field of 210 MV·m^-1, the highest energy density of the PDA-modified 10 vol% BZT@ 0.5 vol% MWCNTs/PB-1 composite film was 4.57 J·cm^-3, which was over 3.5 times that of PB-1 film (≈1.3 J·cm^-3 at 388 MV·m^-1).

Aging retardation strategy of PVDF membranes: evaluation of free radical scavenging effect of nano-particles

ESR and spectrophotometry proved that nano-particles can effectively remove free radicals produced by NaClO, and analyzed the mechanism of delaying aging.

Carbon nanostructures for advanced nanocomposite mixed matrix membranes: a comprehensive overview

The highly progressive membrane separation technology challenges conventional separation processes such as ion exchange, distillation, precipitation, solvent extraction, and adsorption. The integration of many desired properties such as low energy consumption, high removal efficiency, affordable costs, suitable selectivity, acceptable productivity, ease of scale-up, and being environmentally friendly have made the membranes capable of being replaced with other separation technologies. Combination of membrane technology and nanoscience has revolutionized the nano-engineered materials, e.g. nanocomposites applied in advanced membrane processes. Polymer composites containing carbon nanostructures are promising choices for membrane fabrication owing to their enhanced chemistry, morphology, electromagnetic properties, and physicochemical stability. Carbon nanostructures such as carbon nanotubes (CNTs), nano graphene oxides (NGOs), and fullerenes are among the most popular nanofillers that have been successfully applied in modification of polymer membranes. Literature review shows that there is no comprehensive overview reporting the modification of mixed matrix membranes (MMMs) using carbon nanofibers, nano-activated carbons, and carbon nanospheres. The present overview focuses on the applications of carbon nanostructures mainly CNTs and NGOs in the modification of MMMs and emphasizes on the application of CNTs and NGO particles.

Preparation and performance optimization of PVDF anti-fouling membrane modified by chitin

The poly(vinylidene fluoride) (PVDF)/chitin (CH) blend membranes were prepared by the immersion phase inversion method using N,N-dimethylacetamide (DMAc)/lithium chloride (LiCl) as the co-solvent. It was found that blending CH with PVDF allowed membranes to have a better hydrophilicity, penetrability, antifouling and antibacterial performance. In order to improve the performance of PVDF/CH blend membranes further, water/ethanoic acid (HAc) solutions with different compositions were employed as coagulation baths. The effects of HAc volume percentage in coagulation baths on the surface composition, morphology, wettability, water flux, antifouling and antibacterial property of PVDF/CH membrane were investigated. The results indicated that the content of CH on the surface of the membrane increased with the increase of HAc concentration in coagulation baths, which contributed to an improvement of hydrophilicity. The increasing HAc content in coagulation baths also led to a change from finger-like pores to sponge-like pores and a decrease of porosity for PVDF/CH blend membranes. When increasing HAc concentration, the antifouling performance of the blend membranes was improved. Meanwhile, the amidogen of CH on PVDF/CH membrane surfaces could suppress the growth of bacteria, and the blend membrane showed an improved antibacterial performance with the volume ratio of HAc increasing.