Flux Recovery Ratio Research Articles

Novel in-situ zwitterionization of carbon quantum dots on membrane surface for oil/water separation

Industrial growth led to an increase in the release of hazardous oily wastewater that seriously threatens human health and the ecosystem. Developing polymeric membranes for treating such wastewater has garnered significant attention, yet their fouling resistance remains a challenge. In this study, an anti-fouling zwitterionic cellulose acetate (CA) membrane, called ZQDs-g-CA, was fabricated by grafting carbon quantum dots (CQDs) on the surface of the CA membrane, followed by zwitterionization of CQDs (Zwitterionic carbon quantum dots, ZQDs). The grafting of ZQDs increased the hydrophilicity and oleophobicity of the membrane due to the hydrophilic functional groups present in the nanomaterial. The surface roughness was increased, allowing a greater surface area for contact between water molecules and the membrane. The modified CA membrane demonstrated excellent water flux (602.2 ± 30.2 L m−1 h−1 bar−1 (LMHB)) and oil/water emulsion separation performance, with a permeation flux of 426.1 ± 9.6 LMHB and oil rejection of 99.4 %. Additionally, the anti-fouling tests demonstrated remarkable performance with more than 96 % flux recovery ratio (FRR), 30.35 % reversible fouling ratio (Rr), and 3.05 % irreversible fouling ratio (Rir). The results showed that the in-situ ZQDs on the CA membrane exceeded the 96 % rejection rate for different oil/water emulsions. ZQDs were successfully applied on the CA membrane, which would provide a reference for the application of ZQDs-g-CA in oil/water separation.

Development and Study of Novel Ultrafiltration Membranes Based on Cellulose Acetate.

Recently, increasing attention of researchers in the field of membrane technology has been paid to the development of membranes based on biopolymers. One of the well-proven polymers for the development of porous membranes is cellulose acetate (CA). This paper is devoted to the study of the influence of different parameters on ultrafiltration CA membrane formation and their transport properties, such as the variation in coagulation bath temperature, membrane shrinkage (post-treatment at 80 °C), introduction to casting CA solution of polymers (polyethylene glycol (PEG), polysulfone (PS), and Pluronic F127 (PL)) and carbon nanoparticles (SWCNTs, MWCNTs, GO, and C60). The structural and physicochemical properties of developed membranes were studied by scanning electron and atomic force microscopies, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and contact angle measurements. The transport properties of developed CA-based membranes were evaluated in ultrafiltration of bovine serum albumin (BSA), dextran 110 and PVP K-90. All developed membranes rejected 90% compounds with a molecular weight from ~270,000 g/mol. It was shown that the combination of modifications (addition of PEG, PS, PL, PS-PL, and 0.5 wt% C60) led to an increase in the fluxes and BSA rejection coefficients with slight decrease in the flux recovery ratio. These changes were due to an increased macrovoid number, formation of a more open porous structure and/or thinner top selective, and decreased surface roughness and hydrophobization during C60 modification of blend membranes. Optimal transport properties were found for CA-PEG+C60 (the highest water-394 L/(m2h) and BSA-212 L/(m2h) fluxes) and CA-PS+C60 (maximal rejection coefficient of BSA-59%) membranes.

Preparation of Antioxidant and Antifouling Ultrafiltration Membrane by Co-blending Eugenol with Polyethylene Glycol-Modified Polyvinylidene Fluoride

Polyvinylidene fluoride-graft-polyethylene glycol methyl acrylate (PVDF-g-PEGMA) was prepared by grafting PEGMA onto PVDF using a homogeneous irradiation grafting method. After incorporating various concentrations of eugenol, a natural antioxidant component of clove oil, the membranes were fabricated through non-solvent induced phase separation. The results indicated that the addition of eugenol did not alter the inherent properties of the membrane but slightly reduced the pore size and water flux. The cyclic flux test showed that eugenol did not compromise the anti-fouling performance of the membrane, with the flux recovery ratio exceeding 93%. The antioxidant performance test revealed that eugenol enhanced the membrane’s capacity to remove free radicals and imparted oxidation resistance in NaClO solution, making the modified membrane suitable for use in oxidizing environments. This study successfully demonstrated a simple method to prepare a bifunctional membrane with anti-fouling and antioxidant properties, potentially extending its service life and applicability in oxidative contexts.

Green polycaprolactone/sulfonated kraft lignin phase inversion membrane for dye/salt separation

Exploring environmentally friendly, renewable, and cost-effective raw materials is essential in sustainable membrane fabrication. This study presents a facile and scalable method for fabricating a green and biodegradable tight ultrafiltration membrane for dye/salt separation. This involves simply blending biodegradable polycaprolactone (PCL) with the low-cost biobased sulfonated kraft lignin (SKL) additive. Additionally, we employed acetic acid as a green alternative solvent to enhance the sustainability of the membrane fabrication process. The incorporation of hydrophilic SKL into the PCL matrix resulted in increased hydrophilicity (water contact angle changed from 72° to 56°), surface roughness (increased from 29 nm to 43.5 nm), and enhanced negative electrostatic charge of the membrane (−40 mV to −45 mV). The optimized PCL/SKL membrane (M3) exhibited excellent water flux (∼45 LMH) under 40 psi hydraulic pressure coupled with ∼98 % and ∼10 % rejection rates for reactive red (RR) dye and NaCl, respectively. Moreover, the M3 membrane maintained its exceptional dye/salt fractionation performance while separating the mixtures at low salt concentrations. However, with increasing salt concentration (1–50 g/L), the membrane's RR dye rejection declined from ∼90 % to ∼50 %, with a significant reduction in NaCl and Na2SO4 salts rejection (from ∼14 % to ∼1 % and ∼22 % to –∼1 %, respectively). The M3 membrane exhibited remarkable antifouling properties during dye and humic acid filtration with a high flux recovery ratio (>98 %) and low flux decline rate (<7 %). The PCL/SKL membrane also showed excellent stability and maintained consistent separation performance over a long period. Overall, the novel biodegradable PCL/SKL membrane prepared in this study presents a promising avenue toward sustainable membrane fabrication for wastewater treatment applications.

Biochar decorated with metal–organic framework nanoparticles as robust modifier to manipulate nanofiltration mixed matrix membranes characteristics and performance

UiO-66-NH2 metal–organic framework nanoparticles and carbonaceous biochar prepared from the pyrolysis of Cladophora glomerata alga are introduced as novel modifiers and employed to manipulate polyethersulfone (PES) mixed matrix membranes. The membranes were fabricated through immersion precipitation method and fully assessed through X-ray diffraction pattern, field emission scanning electron microscopy, contact angle, atomic force microscopy, and zeta potential analysis. The membrane performances were also examined by water flux, fouling resistance, and solute rejection. The results indicated that the modified membranes manipulated by 0.2–0.8 wt% of modifier had smoother surfaces than the pristine PES membrane. Moreover, by loading the modifiers in the membrane bulk, the zeta potential was changed from negative to positive values. All the modified membranes revealed superior filtration performance compared to that of the pristine PES membrane. In the modified membrane of the best performance, water flux was increased to up to 85% and contact angle was decreased to 43°. Due to the uniform distribution of modifiers on the membrane surface, and thereby, formation of a barrier layer, up to 98.5% of Reactive Blue 50 dye was rejected by the modified membranes. Salt rejections were also improved in the membranes tailored by the introduced modifiers. Furthermore, through the fouling experiments conducted by humic acid and bovine serum albumin, just 12.9 and 34% reductions in water fluxes were recorded for the modified membrane of the best performance. The experimental results indicated that the higher flux recovery ratios could also be expected for all the membranes modified by the novel hydrophilic modifiers.

Antifouling macrocyclic-engineered PVDF membrane for the low-pressure separation of surfactant-stabilized oily wastewater

Fouling is a common phenomenon which affects the long-term efficacy of membranes in the practical treatment of oily wastewater. It often results in a dramatic decline in flux, and a consequent increase in maintenance and operational cost. To address this, various substrates have been incorporated during membrane fabrication to enhance the fouling resistance, and improve the separation efficiency. Herein, we report the fabrication of a novel symmetrical ball-copper phthalocyanine incorporated PVDF membrane (CuPc@PVDF) for the effective separation of surfactant-stabilized oil-in-water emulsions. The symmetrical ball-Cu phthalocyanine with four non-peripheral substituents synthesized ab-initio and characterized using UV–vis, FT-IR, 1H NMR, and MALDI-TOF spectroscopies was added to the casting solution during membrane fabrication resulting in the formation of highly hydrophilic and anti-fouling CuPc@PVDF membrane. In contrast to the PVDF membrane, having a water contact angle of 82.3° ± 0.7°, the CuPc@PVDF membrane demonstrated high hydrophilicity with a contact angle of 55.5° ± 0.5°, and pure water permeance up to 768 LMH at 3 bar. It further achieved 99.9 % rejection of oil with size in the range of 50–450 nm at 1 bar, and demonstrated high stability and excellent anti-fouling property during 10 cycles of continuous demulsification, with a flux recovery ratio (FRR) of 98.5 %, and extremely low irreversible flux of 1.5 %. Similarly, the CuPc@PVDF membrane exhibited high resistance to accelerated organic fouling, maintaining a steady flux and an FRR of 93.0 % during 1 hour of continuous operation with 10 ppm sodium alginate and Ca2+ ions. This study reports a novel strategy to enhance the fouling resistance of demulsification membranes, and could be further explored in the design of next generation of advanced membranes for the purification of oily wastewater.

Antifouling performance enhancement of PES membranes using hydrophilic nanoparticles of poly(dopamine-acrylate) for oil/water separation

Polydopamine-acrylate (P(A-D)x) nanoparticles were blended with polyethersulfone (PES) to fabricate a high-performance hybrid ultrafiltration (UF) membrane for the separation of water from oily wastewater. In tris-alkaline buffer solution at room temperature, P(A-D)x nanoparticles were synthesized by intramolecular Michael addition of dopamine with acrylic acid (AA) monomers. Hybrid PES membranes were prepared using P(A-D)x at 0.05–0.4 wt% and characterized using various assays including Field emission scanning electron microscopy (FESEM), Thermogravimetric analysis (TGA), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and water contact angle (WCA). The membranes showed a significant increase in hydrophilicity, water permeability, and oil rejection (R). The primary and secondary pure water fluxes of the membrane with 0.2 wt% P(A-D)0.25 were 45% and 110.78% higher than those of neat PES membrane, respectively. For 3300 ppm oil feed solution, water flux during water/oil separation increased by 107%, while the oil rejection (R) remained at 99.08%. The surface of membrane was markedly hydrophilic, with a WCA about 40°, much lower than that of the neat PES membrane (80.67°). UF hybrid membranes also showed a remarkable reduction in oil adhesion on the membrane surface as well as superior antifouling performance for membranes containing 0.2 wt% P(A-D)0.25, flux recovery ratio (FRR) = 84.88 ± 3.27%, reversible fouling (Rr) = 51.12 ± 1.09%, and irreversible fouling (Rir) = 15.12 ± 3.27%. In addition, the pure water flux was 446% higher than that of the unmodified membrane after five cycles (900 minutes).

PolyMOF interlayers modulated interfacial polymerization of ultra-thin nanofiltration membranes with efficient and stable desalination performance

Ultra-thin nanofiltration (NF) membranes exhibit excellent potential in the high-efficiency removal of ions due to their superior water permeability and selectivity. However, the stability of these membranes under pressure still poses a significant challenge. In this study, we have developed an innovative polyMOF interlayer using trimesoyl chloride (TMC) cross-linked UiO-66-NH2 (denoted as UiO-66-NH2-TMC) to bolster the construction of a pressure-resistant and ultra-thin polyamide (PA) membrane, achieving stable and high-permeance desalination performance. The introduced hydrophilic and structurally reinforced UiO-66-NH2-TMC interlayer with high pore density and narrow pore size distribution provides essential benefits: (1) it ensures a uniform distribution of amine monomers, which are critical for creating defect-free PA membranes; (2) it optimizes the diffusion of amine monomers, encouraging the formation of an ultra-thin PA membrane; and (3) it enhances the overall compatibility and structural support of the membrane, significantly improving pressure resistance. Consequently, our interlayer-modulated thin-film composite (i-TFC) membrane, with 13 nm thickness, demonstrates exceptional water permeance at 25 L m−2 h−1⋅bar−1 and maintains a high sodium sulfate (Na2SO4) rejection of 96 %. Moreover, the i-TFC membranes exhibit stable performance under pressures ranging from 2 to 10 bar, display excellent long-term operational stability over 36 h, and show an anti-fouling propensity with a notable flux recovery ratio of 81.5 %. This research offers a novel approach to polyMOF interlayer application, carving a path toward designing and fabricating ultra-thin NF membranes with efficient and stable desalination properties.

The removal of pathogenic bacteria and dissolved organic matter from freshwater using microporous membranes: insights into biofilm formation and fouling reversibility

Pathogenic bacteria in drinking-water pose a health risk to consumers, as they compromise the quality of portable water. Chemical disinfection of water containing dissolved organic matter (DOM) causes harmful disinfection by-products. In this work, 4-hydroxybenzoic acid (4-HBA) blended polyethersulfone membranes were fabricated and characterised using microscopic and spectroscopic techniques. The membranes were evaluated for the removal of bacteria and DOM from synthetic and environmental water. Permeate flux increased from 287.30 to 374.60 l m−2 h−1 at 3 bars when 4-HBA increased from 0 to 1.5 wt.%, suggesting that 4-HBA influenced the membrane’s affinity for water. Furthermore, 4-HBA demonstrated antimicrobial properties by inhibiting bacterial growth. The membrane with 1 wt.% 4-HBA recorded 99.4 and 100% bacteria removal in synthetic and environmental water, respectively. Additionally, DOM removal of 55–73% was achieved. A flux recovery ratio (FRR) of 94.6% was obtained when a mixture of bacteria and humic acid was filtered, implying better fouling layer reversibility during cleaning. Furthermore, 100% FRR was achieved when a multimedia granular filtration step was installed prior to membrane filtration. The results illustrated that the membranes had a high permeate flux with low irreversible fouling. This indicated the potential of the membranes in treating complex feed streams using simple cleaning protocols.

High performance and antifouling zeolite@polyethersulfone/cellulose acetate asymmetric membrane for efficient separation of oily wastewater

Microfiltration membranes have emerged as a promising alternative for oily wastewater treatment due to their high efficiency, low cost, and ease of operation. In this study, polyethersulfone (PES), cellulose acetate (CA), and 4A zeolite were blended to fabricate asymmetric membranes by the phase inversion technique and examined in oily wastewater treatment. Kerosene was chosen as a model polluting oil. The fabricated pure PES membrane (P), PES membranes incorporating 4A zeolite (ZP), PES membrane blended with CA (PC), and PES/CA blended membranes with 4A zeolite (ZPC) were characterized using field emission scanning electron microscopy, atomic force microscopy, Fourier-transform infrared spectroscopy, porosity, and contact angle to study the structure properties of these membranes. The performance of membranes was examined by water permeation, oil permeation flux, oil rejection, flux recovery ratio, and relative flux reduction. The ZPC membranes showed the highest performance in comparison with other prepared membranes. Incorporating 4A zeolite nanoparticles with 0.5 wt% into the PES/CA blended membrane significantly enhanced the microfiltration performance and decreased the contact angle of the P membrane from 70° to 29.8°. The effect of operation parameters such as transmembrane pressure (1–4 bar), feed temperature (25–50 ºC), and concentration of oil feed solution (250–1000 mg/L) on the permeation flux and oil rejection was studied on the PES/CA blended membrane containing 0.5 wt% 4A zeolite (0.5%ZPC). The 0.5%ZPC membrane showed improved porosity of 87.7% and it gave the highest value of pure water flux of 91.1 L/m2.h, oil permeation flux of 75.55 L/m2.h, maximum oil rejection of 98.8%, flux recovery ratio of 97.7%, and relative flux reduction of 21.8%. The permeation flux given by the 0.5%ZPC membrane was improved by about 8 times that of the P membrane. Re-usability studies verified the durability of the blended membranes and their performance in oily wastewater treatment.

2D/2D nanohybrid of MoS2/g-C3N4 engineered polysulfone (PSF) membrane with enhanced filtration and anti-fouling performance

The rational design of 2D hybrid materials has gained substantial attention in the field of membrane-based water treatment. In this study, a hierarchical flower-like MoS2/g-C3N4 (Hf-MoCN) hybrid has been reported as a modifier for antifouling and performance enhancement of polysulfone (PSF) membranes. PSF membranes modified with 0.1, 0.3, and 0.5 wt% of Hf-MoCN were prepared by phase inversion technique. The prepared membranes were examined for their morphology, contact angle, pore size, and porosity. Further, the ultrafiltration performance and antifouling ability of the PSF/ Hf-MoCN were examined through BSA filtration studies. The contact angle dropped from 78° to 55° when 0.3 wt% of Hf-MoCN was incorporated into the PSF matrix. Moreover, the pure water and BSA fluxes of this modified membrane were improved by 2.1 and 3.6 folds, respectively, compared to the bare membrane. Besides, all Hf-MoCN modified membranes showed higher BSA rejection efficiency than the unmodified membrane. Flux recovery ratio studies showed that the membrane modified with 0.3 wt% of Hf-MoCN had better antifouling ability than the other membranes. Thus, the study showed that the incorporation of Hf-MoCN provided the membrane with a versatile transport pathway and desirable surface properties, thus improving its wettability, filtration performance and antifouling ability.

Enhanced Photocatalytic and Filtration Performance of TiO2-Ag Composite-Coated Membrane Used for the Separation of Oil Emulsions

Polyvinylidene fluoride (PVDF) membranes were coated with TiO2 and TiO2-Ag to enhance their efficiency for oil-in-water emulsion separation. The photocatalytic activities of the two modified membranes and their filtration performances were compared in detail. The significantly enhanced photocatalytic activity of the TiO2-Ag composite was proved using a methyl orange (MO) solution (c = 10−5 M) and a crude oil emulsion (c = 50 mg·L−1). The TiO2-Ag-coated membrane reduced the MO concentration by 87%, whereas the TiO2-modified membrane reached only a 46% decomposition. The photocatalytic reduction in the chemical oxygen demand of the emulsion was also ~50% higher using the TiO2-Ag-coated membrane compared to that of the TiO2-coated membrane. The photoluminescence measurements demonstrated a reduced electron/hole recombination, achieved by the Ag nanoparticle addition (TiO2-Ag), which also explained the enhanced photocatalytic activity. A significant improvement in the oil separation performance with the TiO2-Ag-coated membrane was also demonstrated: a substantial increase in the flux and flux recovery ratio (up to 92.4%) was achieved, together with a notable reduction in the flux decay ratio and the irreversible filtration resistance. Furthermore, the purification efficiency was also enhanced (achieving 98.5% and 99.9% COD and turbidity reductions, respectively). Contact angle, zeta potential, scanning electron microscopy (SEM), and atomic force microscopy (AFM) measurements were carried out to explain the results. SEM and AFM images revealed that on the TiO2-Ag-coated membrane, a less aggregated, more continuous, homogeneous, and smoother nanolayer was formed due to the ~50% more negative zeta potential of the TiO2-Ag nanocomposite compared to that of the TiO2. In summary, via Ag addition, a sufficiently hydrophilic, beneficially negatively charged, and homogeneous TiO2-Ag-coated PVDF membrane surface was achieved, which resulted in the presented advantageous filtration properties beyond the photocatalytic activity enhancement.

Synthesis of MOF-5/polyethersulfone (PES) mixed matrix membranes for enhancing membrane filtration performance in polyphenol purification

The various apple products industries produce a large amount of apple residue, which is easily fermented, causes environmental pollution, and its disposal cost is high, but is rich in nutrients, such as polyphenols. Polyphenols can be purified to realize high-value deep processing of apple pomace and to promote energy reuse of food waste. In this study, the highly selective purification of polyphenols was achieved by membrane filtration using prepared Metal-organic framework (MOF)-5/PES mixed matrix membranes with apple peels as raw material. The polyethersulfone mixed matrix membrane was loaded with MOF-5 by the phase inversion method, and their structural and physicochemical properties were characterized by scanning electron microscopy (SEM), and X-ray diffraction (XRD). Zeta potential and specific surface area of MOF-5 particles were measured, as well as the water contact angle and anti-fouling properties of the mixed matrix membrane were analyzed. It was confirmed that the membrane loaded with MOF-5 showed better hydrophilicity and mechanical properties compared with the pristine polyether sulfone membrane. Under practical conditions, the increased hydrophilicity could enhance the anti-fouling properties of membranes, which would improve the flux recovery ratio of membranes. In addition, the prepared MOF-5/PES mixed matrix membrane was applied to the purification of polyphenols, showing excellent purification performance of polyphenols. In particular, the purity of polyphenol after membrane filtration could reach 70.45% when the additional amount of MOF-5 was 10%. This research provides a method to prepare MOF-5/PES mixed matrix membranes, which effectively solves the problem of unstable and unsatisfactory purification effect of commercially available membranes, promotes the development of new materials in membrane science, and realizes high-value deep processing and comprehensive resource development of food waste using membrane filtration.

Pressure-driven membranes for advanced treatment of textile wastewater: Dye/salt fractionation, concentration, and cleaning strategies

Textile wastewater commonly contains various organic compounds and salt mixtures, potentially raising serious environmental and health concerns. Traditional treatment approaches are hindered by high salinity; consequently, membrane separation technologies have attracted increasing attention over the past few decades. Herein, four commercial pressure-driven membranes with molecular weight cut-off (MWCO) gradients were employed for the advanced treatment of different types of textile wastewater. Specifically, these membranes were initially subjected to a fractionation test toward the dye/salt mixtures, followed by deep concentration of the dye molecules. Using Congo red (CR), methyl blue (MB), NaCl, and Na2SO4 as representative dyes and salts, the results indicated that all membranes could effectively separate dye/salt mixtures and further conduct a deep concentration process toward the separated dye solutions. However, their efficiency and effectiveness largely depend on the membrane pore size and solution characteristics. For instance, membranes with lower MWCOs experience less fouling and shorter operation durations when treating CR-related solutions. All membranes showed improved fractionation efficiency toward MB/salt mixtures, requiring only approximately 10.2–42.9 % of the operation duration compared to CR-related solutions. The loose nanofiltration membrane proved superior to tight ultrafiltration membranes in both fractionation and concentration processes. Further research on cleaning methodologies demonstrated that both alkali and ethanol cleaning were influential in restoring the membrane performance. An appropriate ethanol/water concentration can effectively regenerate severely fouled membranes, achieving a high flux recovery ratio of ∼95 %. This study evaluated state-of-the-art pressure-driven membranes for textile wastewater treatment and guided cleaning strategies for optimal performance recovery.

Effects of coagulant bath temperature toward separation performance and antifouling properties of PVDF/CA membranes for filtration of dyes

Phase inversion is used to prepare poly(vinylidene fluoride) (PVDF) microfiltration membranes by combining it with the hydrophilic polymer additive cellulose acetate (CA). For the filtration of methylene blue (MB) and acid yellow 17 (AY17), the effects of coagulant bath temperature (CBT) on the separation performance and antifouling properties are thoroughly investigated. SEM analysis shows that the membrane at higher CBT has a larger pore diameter than at lower CBT, resulting in differences in membrane surface hydrophilicity. It is found that the increase in surface hydrophilicity causes the permeability of PVDF/CA membranes to be higher at higher CBT than at lower CBT. Rejection values above 90% indicate that the membranes are more effective for MB separation at both lower and higher CBT. Otherwise, lower CBT provides better AC rejection than higher CBT. The Flux Recovery Ratio, which is higher at higher CBT, remains in the 75–95% range at lower CBT. As a result, lower CBT is better for membrane fouling resistance than higher CBT. In addition, the fouling observed at lower CBT is similar to the fouling observed at higher CBT, but lower CBT has a higher percentage of reversible fouling than higher CBT. The membranes with more reversible fouling are therefore easier to clean using the backwashing process. As a result, PVDF/CA membranes manufactured at lower CBT have better separation performance and antifouling characteristics than those manufactured at higher CBT.

Novel MXene/PVDF nanocomposite ultrafiltration membranes for optimized Eriochrome black T (azo dye) removal

In the context of recycling and reusing textile wastewater, the quest for a membrane possessing superior efficiency has garnered considerable attention. This research endeavors to advance this objective by introducing a novel asymmetric ultrafiltration membrane constructed from PVDF (Polyvinylidene Fluoride) modified with MXene through bulk modification, thereby augmenting its resistance to fouling for textile wastewater treatment applications. The investigation employed a comprehensive array of characterization techniques. The proposed interaction mechanism between the contents of PVDF/MXene and the interaction mechanism of composite membrane with water molecules were also presented. Comparative analysis with pure membranes revealed that the incorporation of MXene resulted in enhanced hydrophilicity and porosity, concurrently reducing its surface roughness when compared to a pristine membrane. The lowest water contact angle about 38.5 (⁰) was observed in the mixed matrix membrane containing 0.5 wt% MXene. The developed membranes exhibited a maximum pure water flux of 538 LMH and a flux of 467.8 LMH for EBT dye solution. Furthermore, optimization of the nanocomposite membrane composition led to nearly complete rejection of Eriochrome black T (EBT). A continuous improvement in the flux recovery ratio (FRR%) culminating in a peak value of 85.6% for the MMMs prepared from 0.5 wt% MXene.

Spray coating vapor-phase interfacial polymerization: A new approach for developing 2D nanosheet enabled thin film nanocomposite membranes to remove heavy metal ions

Alternate to the conventional dip coating method, a new eco-friendly approach has been used to develop thin-film nanocomposite (TFN) membranes in this research work, all while preserving the exceptional separation capabilities of TFN membranes. The methodology is altered by employing spray coating and implementing vapor-phase interfacial polymerization (VP-IP) to craft thin-film nanocomposite membranes. This innovative approach significantly reduces reagent consumption and eliminates the need for organic solvent (n-hexane). By incorporating amine-functionalized graphene oxide (GO-NH-NH2) as a nanofiller, we have fabricated both thin-film nanocomposite (TFN) and thin-film composite (TFC, without nanofiller) membranes. Developed membranes were characterized with various physicochemical characterization techniques and tested against heavy metal ions. The membranes demonstrated outstanding performance, with ∼ 96 % rejection of Na2SO4, ∼95 % rejection of Pb(NO3)2, ∼94 % rejection of CuSO4, and ∼ 92 % rejection of CdSO4 salt with highest pure water flux 46.57 Lm2h−1. The antifouling characteristics and antibacterial activity of the membrane were also assessed, revealing that including nanosheets has substantially elevated the antifouling properties, notably by increasing the flux recovery ratio. Furthermore, the prepared membranes exhibited enhanced antibacterial performance after incorporating these nanosheets.

Photocatalysis and PMS activation caused by CuO/TiO2 photocatalyst coated on PVDF membrane for mitigating membrane fouling

BackgroundOne direction to mitigate membrane fouling is to create anti-fouling photocatalytic membranes. The photocatalysts’ hydrophilicity reduces the interaction of the membrane with hydrophobic foulants and the photocatalysis decomposes membrane fouling. Another noteworthy point is that PMS (peroxymonosulfate) can be activated by photocatalysts to decompose foulants and membrane fouling more intensely. MethodsThe CuO/TiO2 was prepared by deposition of Cu(OH)2 onto TiO2 followed by heat treatments. Their catalytic performances were tested by the degradation of Acid Blue 260 by photocatalysis and PMS activation. The best CuO/TiO2 was then coated onto PVDF membranes through a PAA binding layer. Their antifouling performance was examined through simulated foulants such as sodium alginate. The photocatalysts and membranes were characterized using FTIR, SEM-EDS, TEM, XRD, BET, UV–Vis DRS, XPS, ESR, and AFM. Significant FindingsThe CuO/TiO2 possessed a lower bandgap, high surface area (60.7 m2/g), and low particle sizes (30–60 nm). The 25%CuO/TiO2 possesses the highest photocatalytic degradation efficiency of 39.0% under UV irradiation; further PMS activation caused the removal efficiency to reach 90.0%. The degradation efficiency by the membrane was 100% after five cycles. The membranes indicated a decrease of 18.9% in water flux but remained very high. The membrane flux recovery ratio (FRR) was 98.8%.

Permeate flux recovery and removal foulant performances of hollow fiber polyvinylidene fluoride membrane bioreactor with peroxodisulfate activated iron (II) sulfate as a chemical cleaning agent

The main challenge with membrane bioreactors is fouling, which leads to decreased flux performance and a shortened membrane lifespan. This study aims to provide a solution for the flux recovery and removal of irreversible fouling on Polyvinylidene Fluoride (PVDF) membranes without damaging their structure using sulfate radicals. Sulfate radicals are formed via peroxodisulfate precursors that are activated by Fe2+. The membrane flux recovery and irreversible fouling ratio were 88.45-99.04% and 11.60-0.96%, respectively, at operating temperatures of 298-308 K. The PVDF membrane has been tested for microfiltration and washed up to 6 times per cycle. The mechanical properties, XRD, SEM-EDX, and ATR-FTIR characterization of the PVDF membrane after washing with PDS/Fe2+ did not show a negative effect on the PVDF structure. Additionally, the results of the kinetic and thermodynamic studies showed that washing with PDS/Fe2+ inhibited the formation of fouling particles on the membrane surface. Based on this study, sulfate radical oxidants with PDS precursors activated by Fe2+ can be applied as cleaning chemicals for PVDF membranes without damaging their structures.

Electro‐Conductive Ti3C2 MXene Multilayered Membranes: Dye Removal and Antifouling Performance

AbstractThis work describes the fabrication of a novel electroconductive membrane made of Ti3C2Tx (MXene) nanosheet coating through a one‐step pressure‐assisted technique. Ti3C2‐MXene is firmly attached over a polyamide–imide (PAI) microfilter by employing a binder composed of carboxymethyl cellulose (CMC)/glutaraldehyde (GA). Through coating a proper amount of multilayer Ti3C2‐MXene, the electrical conductivity of 174 ± 0.16 S m−1 is achieved. The rejection rates of reactive red 120 (RR120), reactive black (RB), and methyl orange (MO) by the pristine PAI membrane are 45.2%, 40.81%, and 33.65%, respectively. However, rejection rates significantly improve with the Ti3C2 MXene coating to over 99.71%, 97.95%, and 68.91% for RR120, RB, and MO. Applying a 4 V cathodic potential resulted in a flux recovery ratio (FRR) of 99.83% and a flux decline rate (FDR) of less than 1% during humic acid (HA) filtration. Without applying voltage, the MXene‐coated membrane shows an FRR and FDR of 92.51% and 45.56%, respectively. Surface energy analysis reveals strong repulsive interactions between foulants and the membrane surface. Moreover, the surface free energy indicates that foulants such as sodium alginate (SA) and bovine serum albumin (BSA) exhibit stronger adhesion to the membrane than HA, consistent with the fouling experiment results.