Membranes For Water Treatment Research Articles

Insight Into the Role of Fiber Diameter on Electrospun Polysulfone Mats

ABSTRACTFiber electrospun mats created using cylindrical collectors have been extensively studied as effective membranes for water treatment. However, the relationships between the properties of electrospun mats and the characteristics and performance of membranes are not well‐established. This research examined two samples with average fiber diameters of 1.8 ± 0.49 μm and 0.47 ± 0.26 μm, which were evaluated as supporting substrates for the separation of MgSO4 ions. The variation in fiber diameter resulted from consistent conditions of voltage, distance, and collector rotation speed, while the injection rates were different, set at 2 mL/h and 0.8 mL/h, respectively. The resulting thin‐film composite (TFC) membrane consists of three layers: the first layer is a mesh polyester that underlies a middle hydrophobic electrospun support layer made from a 20 wt.% polysulfone solution. The third layer is a polyamide layer created through interfacial polymerization, involving a reaction between piperazine (PIP) monomers at a concentration of 2% by weight and trimesoyl chloride (TMC) monomers at a concentration of 0.2% by weight. Due to its hydrophobic nature, PSU repels water monomers from its surface during polymerization. Consequently, surface modification using plasma treatment alters the surface characteristics from hydrophobic to hydrophilic, resulting in the formation of a superior polyamide layer. The results indicate that membranes with larger fiber diameters exhibit a rougher texture. Additionally, the increased void space between the fibers in these membranes leads to an increase in pure water flux that is 92% higher compared to membrane samples with smaller fiber diameters; this higher flux is due to larger pore size. Furthermore, membranes with smaller fiber diameters possess a finer pore structure, resulting in a polyamide layer with fewer defects than membranes with larger fibers. This improved structure achieved a separation efficiency of 68% ± 1.02% for MgSO4, while the membrane with an average fiber diameter of 1.80 ± 0.49 μm demonstrated a separation rate of 20% ± 2.26%. These findings provide a step forward in the development of a theoretical framework for engineering TFC membranes with electrospun mats as supports.

Oxygen vacancies-enriched spent lithium-ion battery cathode materials loaded catalytic membrane for effective peracetic acid activation and organic pollutants degradation

Advanced oxidation processes combined with membrane filtration technique offer a promising approach for pollution mitigation and catalyst recovery. Herein, a waste ternary lithium-ion battery cathode material of LiNixCoyMnzO2 (LNCM) loaded polytetrafluoroethylene (PTFE) membrane was synthesized for peracetic acid (PAA) activation (LNCM-PTFE/PAA) and 2,4,6-trichlorophenol (TCP) degradation. Such a novel membrane, with a catalyst loading of 10 mg (0.796 mg/cm2) of LNCM achieved 96.4 % removal of TCP (2 mg/L) within 20 min in neutral pH. The redox cycles of surface metals (such as Co3+/Co2+, Ni3+/Ni2+, and Mn4+/Mn3+/Mn2+) in spent LNCM efficiently enhance charge transfer and mediated PAA activation. And intrinsic oxygen vacancies in LNCM facilitated PAA adsorption and its cleavage. The resulting carbon-centered radicals (R-C•, CH3C(O)OO•) and 1O2 are identified as the primary reactive species that collaboratively participate in TCP degradation. Quantitative structure-activity relationship analysis demonstrated a substantial reduction in product toxicity. The successful practical application of the LNCM-PTFE/PAA membrane was exemplified by treating chlorophenol industrial wastewater. This study presents a new LNCM-PTFE/PAA catalytic membrane for high-efficiency water treatment and a novel perspective for green utilization of waste LNCM.

High performance composite hollow fiber nanofiltration membrane fabricated via the synergistic effect of co-solvent assisted interfacial polymerization and macrocyclic polyamine incorporation

The necessity for high-performance thin film composite (TFC) nanofiltration (NF) membranes for drinking water and wastewater treatment is becoming increasingly apparent in the face of the global water crisis. In this work, co-solvent (acetone) assisted interfacial polymerization (CAIP) and incorporating macrocyclic polyamine (Cyclen) as an aqueous co-monomer were employed to fabricate hollow fiber (HF) NF membrane and to enhance the permeability and the selectivity, respectively, thereby overcoming the inherent trade-off effect. The effects of Cyclen and acetone on the separation performance were comprehensively investigated, and the interfacial polymerization conditions were optimized. The optimal HF NF membrane exhibits a 68.6 % increment in water permeance relative to the baseline membrane while without sacrificing the Na2SO4 rejection which is as high as 99.2 %. In particular, it exhibits a superior high pure water permeability of 222.5 L m−2 h−1 MPa−1, ranking among the highest observed for HF NF membranes in the existing literature. Moreover, it exhibits excellent acid resistance as well as fouling resistance. This research paves a novel approach for developing high-performance HF NF membranes for water and wastewater treatment.

Dual-layer coated photocatalytic membranes for surface water treatment: Insight of membrane fouling restriction

The combination of carbon-based material adsorption and photocatalytic oxidation is a crucial approach to eliminate natural organic substances and mitigate membrane fouling induced by them. In this investigation, Bi2O3-TiO2 (BT) was incorporated with three varieties of carbon-based substances (such as powdered activated carbon (PAC), ordered mesoporous carbon CMK-3 (OMCs), and carbon nanotubes (CNTs)) and employed as a dual-layer coating on the surface of the ultrafiltration membrane to reduce membrane fouling induced by natural organics during the treatment of actual water bodies. Under light conditions, the BT/CMK-3 coating outperforms BT/PAC and BT/CNTs coatings in reducing membrane fouling, with a flux recovery rate of up to 80.4 % and an irreversible fouling rate as low as 19.5 %, while also improving the removal rates of UV254 and DOC to 55.2 % and 77.9 %, respectively. Based on the analyses of three-dimensional fluorescence PARAFAC and liquid chromatography, the BT/CMK-3 coating efficiently removes humic substances and protein-like compounds via adsorption and photocatalytic oxidation, achieving a 24.1 % removal rate of humic acid and a 93.7 % removal rate of low molecular weight neutral substances. Under the synergy of CMK-3 adsorption and BT photocatalytic oxidation, reactive oxygen species effectively degraded and transformed the membrane foulants enriched by CMK-3, reducing and increasing the Zeta potential and free energy on the membrane surface to −4.2 mV and 15.1mJ/m2, respectively. The interaction force between the foulant and the membrane changed into a repulsive force, and the fouling mechanism changed from complete blockage to intermediate blockage, thereby shortening the transition time. This advancement provides significant promise for the development and broader application of photocatalytic membrane filtration technology.

Selective O2-to-H2O2 Electrosynthesis by a High-Performance, Single-Pass Electrofiltration System Using Ibuprofen-Laden CNT Membranes.

Producing H2O2 through a selective, two-electron (2e) oxygen reduction reaction (ORR) is challenging, especially when it serves as an advanced oxidation process (AOP) for cost-effective water decontamination. Herein, we attain a 2e-selectivity H2O2 production using a carbon nanotube electrified membrane with ibuprofen (IBU) molecules laden (IBU@CNT-EM) in an ultrafast, single-pass electrofiltration process. The IBU@CNT-EM can generate H2O2 at a rate of 25.62 mol gCNT-1 h-1 L-1 in the permeate with a residence time of 1.81 s. We demonstrated that an interwoven, hydrophilic-hydrophobic membrane nanostructure offers an excellent air-to-water transport platform for ORR acceleration. The electron transfer number of the ORR for IBU@CNT at neutral pH was confirmed as 2.71, elucidating a near-2e selectivity to H2O2. Density functional theory (DFT) studies validated an exceptional charge distribution of the IBU@CNT for the O2 adsorption. The adsorption energies of the O2 and *OOH intermediates are proportional to the H2O2 selectivity (64.39%), higher than that of the CNT (37.81%). With the simple and durable production of H2O2 by IBU@CNT-EM electrofiltration, the permeate can actuate Fenton oxidation to efficiently decompose emerging pollutants and inactivate bacteria. Our study introduces a new paradigm for developing high-performance H2O2-production membranes for water treatment by reusing environmental functional materials.

Fabrication of ultrafiltration membrane with antibacterial properties by blending Ag/UiO-66-NH2 and bamboo cellulose

Cellulose is a widely available organic substance that forms membranes with excellent hydrophilicity and biocompatibility. However, it is prone to biological contamination because its surface is conducive towards the accumulation of biologically active substances, which has hindered its application potential. In this work, an antimicrobial cellulose-based membrane (Ag/UiO-66-NH2@BCM) with high water flux, high retention rate, and good hydrophilicity was prepared. At an optimal blend ratio of 1 wt% Ag/UiO-66-NH2, the membrane exhibited significant improvements, including a 31% increase in pure water flux, a Bovine Serum Albumin retention rate of 99.6%, and a water flux recovery of 97.4%. Crucially, the membrane demonstrated potent antibacterial, showcasing its broad-spectrum antimicrobial properties. Investigations into the ability of Ag/UiO-66-NH2@BCM to remove Pb2+, Cd2+, and Cr6+ ions from a water column revealed that the maximum adsorption capacity of the monolayer was 405, 390, and 328 mg/g, respectively. The composite membrane demonstrated broad-spectrum and highly effective antimicrobial properties, along with efficient removal of heavy metal ions. The proposed method can be utilized to prepare other composite membranes for water treatment and other fields of membrane separation technology.

Regulating the surface properties and interlamellar spacing of GO-based nanofiltration membrane for efficient water treatment

Regulating the surface properties and interlamellar spacing of GO-based nanofiltration membrane for efficient water treatment

Superhydrophilic‐underwater superoleophobic polyvinyl alcohol membranes for oily water treatment

AbstractPolyvinyl alcohol (PVA) and potato starch‐based porous hydrogels have been fabricated and studied for their wettability. The starting material was crosslinked by glutaraldehyde performed via co‐polymerization reaction at room temperature and low temperature (freeze–thaw). The gels were characterized by Fourier transform infrared (FT‐IR), field emission scanning electron microscope (FE‐SEM), thermogravimetric (TG), and powder X‐ray diffraction (PXRD) analysis. The wetting studies of the gels were evaluated at ambient and submerged conditions by considering both oil and water drops as probe liquids. The gels tend to absorb oil and water in air, however, water‐wet gels demonstrated a very high oil contact angle (>150°). The gels demonstrated superoleophobicity, and the underwater oil CA >172° as the concentration (wt%) of PVA was increased in the gels. Overall, the freeze–thaw gels demonstrated higher underwater oil CA, however, both (room temperature and freeze–thaw fabricated) gels demonstrated similar affinity for under‐oil–water absorption and separation. The hydrogel can retain water easily and thus remove water (even dye dissolved in water) with high separation efficiency and recyclability.

Fabrication and performance evaluation of polycarbonate/polyvinyl alcohol–titanium dioxide thin‐film nanocomposite membranes for water treatment

AbstractIn recent years, there has been growing interest in using polymer nanocomposite membranes as a more advanced method for removing pollutants from water and treating wastewater for various purposes. In this study, thin‐film nanocomposite (TFN) membranes of polycarbonate/polyvinyl alcohol–titanium dioxide thin‐film (PC/PVA–TiO2) were fabricated by dip‐coating a PC substrate in a PVA/TiO2 solution. Various methods, including attenuated total reflectance‐Fourier transform infrared (ATR‐FTIR) spectroscopy, field emission scanning electron microscopy (FE‐SEM), atomic force microscopy (AFM), and water contact angle were utilized to assess the structural characteristics of the produced membranes. The PC/PVA thin‐film composite (TFC) and PC/PVA–TiO2 TFN membranes were then examined in a submerged membrane system to evaluate their effectiveness in filtering humic acid (HA) under various vacuum transmembrane pressure (0.3 and 0.6 bar) condition. The FTIR‐ATR results confirmed the formation of the active layer of PVA/TiO2 nanoparticles (NPs). It was observed that adding 1 wt.% of TiO2 NPs to the active layer of PVA/TiO2 significantly enhanced the water contact angle from 77.5° for PC support to 55.3° for PC/PVA–TiO2 (0.1) TFN membranes. Furthermore, the FE‐SEM results confirmed the formation of an active layer of PVA/TiO2 with a thickness of 237.87 nm. The pure water flux increased from 101.64 L/m2h for the PC/PVA TFC membrane to 144.02 L/m2h and 199.09 L/m2h for the PC/PVA–TiO2 (0.05) and PC/PVA–TiO2 (0.1) TFN membranes, respectively. Also, the results revealed that at lower transmembrane pressure, all membranes showed higher value in HA removal as compared to when higher transmembrane pressure was used.

Sustainable Approaches for the Fabrication of Nanocellulose-Polyamide Membrane Based on Waste Date Palm Leaves for Water Treatment

A vast amount of agricultural waste, such as dried leaves, stems, pits, seeds, etc., are produced by date palm trees in Saudi Arabia each year. This waste is an excellent source of degradable biomass suitable for many uses. Crystalline nanocellulose (CNC) is one of the most important nanomaterials that can be used in various applications. Due to its unique properties, which include biorenewability, optical transparency, high mechanical strengths, and sustainability, nanocrystalline cellulose has become a significant nanomaterial in recent years. In this study, CNC was isolated from the waste date palm leaves and used for the production of PA-modified membranes for water treatment by reverse osmosis membrane technology. The membranes were prepared by surface polymerization with the polyamide as a selective layer on the polysulfone support film. Three membranes were produced, two with 0.01% and 0.02% (w/v) CNC and the third with PA-free CNC for comparison. Each membrane produced was tested using different characterization techniques. The polyamide membrane with 0.01% w/v CNC had a higher water permeability of 43.25 L/m2 h bar than the membranes with 0% w/v CNC (36.25 L/m2 h) and 0.02% w/v CNC (42.85 L/m2 h bar). Under the same conditions, salt retention was also found to be above 98% for both NaCl and MgSO4 for the two modified membranes. The contact angle was found to be 68.04±3.7, 72.83±0.8, and 63.76±5.5 for PA(0%CNC), PA-CNC (0.01% w/v), and PA-CNC (0.02% w/v), respectively. The 0.01% PA-CNC membrane exhibited a higher water contact angle, greater hydrophobicity and lower surface roughness. As a result, the isolated CNC might be appropriate for use as a modifier agent for membrane fabrication and water treatment.

Fabrication of ultra-permeable membranes with antibiofouling capability by incorporating bifunctionalized zeolite

Poor water permeance and biofouling significantly limit the application of nanofiltration (NF) membranes in wastewater treatment and seawater desalination. Herein, bifunctionalized FAU-Ag-OH zeolites, featuring abundant hydroxyl groups and silver ions on their surface, were designed and incorporated into polyamide (PA) layer of a thin-film nanocomposite (TFN) membrane, effectively enhancing the antibiofouling properties and water permeance of membrane. The plentiful hydroxyl groups and well-dispersed silver ions on the bifunctionalized FAU-Ag-OH zeolites impart the membrane with more negative surface charge, increased hydrophilicity, and superior antibiofouling property. Additionally, the doped FAU-Ag-OH zeolites can retard the diffusion of piperazine during interfacial polymerization (IP) process and have improved chemical compatibility with polymers, which results in desirable membrane structure. Consequently, the optimal M–0.05 membrane containing FAU-Ag-OH zeolites exhibited a 2.3-fold increase in water permeance (18.8 ± 2.0 L m−2 h−1 bar−1) and enhanced antibiofouling ability (with antibacterial efficiency up to 95.4 % and flux recovery ratio up to 85 %) compared with the TFC membrane. The successful fabrication of such membrane with enhanced antibiofouling properties and improved water permeance is expected to promote the application of NF membranes in water treatment.

Sustainable Wastewater Treatment with Bi2MoO6/Cellulose Acetate Photocatalytic Membranes

AbstractA major challenge for modern society is securing quality water for various uses. Membrane water treatment will be crucial for drinking water, desalination, and wastewater reuse. The development of bismuth molybdate (Bi2MoO6) nanoparticles has enabled the production of novel Bi2MoO6‐incorporated cellulose acetate (CA) membrane nanocomposite. The synthesized Bi2MoO6/CA nanocomposites are thoroughly examined for their structural, morphological, and photocatalytic characteristics using X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) with energy dispersive X‐ray spectroscopy (EDX) analysis. The photocatalytic properties are determined by evaluating the degradation of Malachite Green (MG) and Rose Bengal (RB) by the nanocomposite membranes under the illumination of a UV light simulator. Notably, the Bi2MoO6/CA nanocomposite membrane displays exceptional and sustained photocatalytic efficiency (78%) and (84%) in MG and RB dye degradation, respectively. Moreover, the effective loading of the Bi2MoO6 onto the CA membrane enhances electron and hole adsorption while facilitating carrier movement. Furthermore, the stability exhibited by the Bi2MoO6/CA nanocomposite photocatalysts remains impressive even after multiple cycles, demonstrating their durability. This research introduces a cutting‐edge semiconductor‐based hybrid nanocomposite material that proves highly efficient in the photocatalytic degradation of organic dyes, showcasing promising advancements in environmental remediation strategies.

The Hidden Role of the Dielectric Effect in Nanofiltration: A Novel Perspective to Unravel New Ion Separation Mechanisms.

Nanofiltration (NF) membranes play a critical role in separation processes, necessitating an in-depth understanding of their selective mechanisms. Existing NF models predominantly include steric and Donnan mechanisms as primary mechanisms. However, these models often fail in elucidating the NF selectivity between ions of similar dimensions and the same valence. To address this gap, an innovative methodology was proposed to unravel new selective mechanisms by quantifying the nominal dielectric effect isolated from steric and Donnan exclusion through fitted pore dielectric constants by regression analysis. We demonstrated that the nominal dielectric effect encompassed unidentified selective mechanisms of significant relevance by establishing the correlation between the fitted pore dielectric constants and these hindrance factors. Our findings revealed that dehydration-induced ion-membrane interaction, rather than ion dehydration, played a pivotal role in ion partitioning within NF membranes. This interaction was closely linked to the nondeformable fraction of hydrated ions. Further delineation of the dielectric effect showed that favorable interactions between ions and membrane functional groups contributed to entropy-driven selectivity, which is a key factor in explaining ion selectivity differences between ions sharing the same size and valence. This study deepens our understanding of NF selectivity and sheds light on the design of highly selective membranes for water and wastewater treatment.

Regulating molecules/ions sieving channels of MXene-based membranes by edge-capping strategy

Regulating molecules/ions transport within two-dimensional (2D) sub-nanometer channels to achieve a higher separation efficiency is of considerable interest for MXene membranes in sustainable water treatment. Herein, sodium tripolyphosphate (STPP) was introduced into Ti3C2Tx nanosheets to construct a series of modified STPP-MXene membranes based on the edge-capping strategy. The critical role of edge-capping in modulating selective molecules/ions separation within 2D sub-nanometer channels was highlighted. The edge-capping method was demonstrated to moderately narrow the shoulder spacing between adjacent Ti3C2Tx nanosheets and impaired their positive electric field intensity. In addition, the DFT results showed that the cations exhibited a much lower relative energy with STPP-Ti3C2Tx (-0.0024 eV) compared to Ti3C2Tx nanosheets (-0.2092 eV), causing cations to permeate more readily through the STPP-MXene membrane. As a result, the appropriately designed and prepared STPP-MXene membrane demonstrated an excellent molecules/ions selectivity (CR/NaCl selectivity = 52.6, CR/Na2SO4 selectivity = 30.3), much higher than that of the pristine MXene membrane. Moreover, by protecting the Ti at the edges of Ti3C2Tx nanosheets, the STPP-MXene membrane retained its original two-dimensional structure to maintain a stable separation performance, even when exposed to a water environment for up to 60 days. In contrast, the pristine MXene membrane was completely oxidized due to its weak stability. This study provides a theoretical basis for the feasibility of edge-capping strategy as a broad modification alternative to design high-efficiency molecular/ionic sieving MXene membranes.

Construction of CS-SDAEM long-chain polysaccharide derivative on TA@CNTs coated PVDF membrane with effective oil-water emulsion purification and low contamination rate

Currently, the most effective way to improve the anti-fouling performance of water treatment separation membrane is to enhance the hydrophilicity of the membrane surface, but it can still cause contamination, leading to the occurrence of flux reduction. The construction of a strong hydration layer to resist wastewater contamination is still a challenging task. In this study, a defect-free hydration layer barrier was achieved by grafting chitosan polysaccharide derivatives (CS-SDAEM) on the membrane, which achieved in effective fouling prevention and low flux decline rate. A layer of tannic acid-coated carbon nanotubes (TA@CNTs) has been uniformly deposited on the commercial PVDF membrane so that the surface was rich in -COOH groups, providing sufficient reaction sites. These reactive groups facilitate the grafting of amphiphilic polymers onto the membrane. This modification strategy achieved in enhancing the antifouling performance. The modified membrane achieved low contamination rate with DR of 16.9 % for wastewater filtration, and the flux recovery rate was above 95 % with PWF of 1100 (L·m−2·h−1). The membrane had excellent anti-fouling performance, which provided a new route for the future development of water treatment membrane.

Dynamic Deposition of PDA on a Hollow Fiber Ceramic Membrane for Oily Water Treatment.

Ceramic membranes have been widely used in oil-water treatment; however, membrane fouling remains a challenge that must be addressed to improve the process feasibility. A thin layer of polydopamine (PDA) was dynamically deposited on the surface of the alumina hollow fiber membranes to reduce oil adhesion. The PDA-alumina membranes were characterized by using SEM-EDS, AFM, and water contact angle measurements. The performance of the modified membranes was evaluated using synthetic crude oil emulsions (100 mg·L-1) in a crossflow system. Membranes modified with PDA exhibited 97% oil rejection, and a stabilized permeate flux of 463 L·h-1·m-2 with a relative flux reduction of 60% and a flux recovery ratio of 75% was observed after cleaning, indicating lower oil adhesion and better fouling reversibility. The most predominant fouling mechanism for the modified membranes seems to be cake filtration because of the reduction in pore size due to the deposition of the PDA layer.

Activating peroxymonosulfate with MOF-derived NiO-NiCo2O4/titanium membrane for water treatment: A non-radical dominated oxidation mechanism

Traditional peroxymonosulfate (PMS) catalytic membranes dominated by radical pathways often face interference from complex components in water bodies. Herein, we employed a controlled electro-deposition technique to coat a Ni-Co metal–organic framework (MOF) precursor onto titanium hollow fiber membrane (THFM), followed by high-temperature calcination to synthesize a MOF-derived NiO-NiCo2O4/THFM (M−NNCO−THFM) PMS catalytic membrane. Then, the M−NNCO−THFM filtration integrated with PMS activation (MFPA process) for water treatment. Experimental results demonstrated that the M−NNCO−THFM MFPA process successfully achieved complete phenol (PE) removal via a non-radical-dominated degradation pathway, involving singlet oxygen (1O2) and electron transfer, while exhibiting wide pH adaptability and exceptional stability in complex water matrices. Mechanism analysis revealed that the electron transfer process was significantly enhanced by the MOF-derived heterojunction structure, which increased the flat-band potential from 0.39 eV to 0.56 eV, thereby facilitating efficient electron transfer for PE removal. The non-radical 1O2 pathway was primarily due to the cycling of metal valence states (Ni2+/Co3+), leading to the reduction of Co2+ and its reaction with PMS, resulting in the generation of reactive species. Furthermore, electrochemical measurements indicated that the M−NNCO−THFM exhibited lower charge transfer resistance and enhanced charge transfer efficiency compared to non-MOF-derived NNCO-THFM, corresponding to the superior catalytic performance and electrochemically active surface area of M−NNCO−THFM.

Phthalocyanine-enabled technologies for water treatment and disinfection strategies

Water treatment and disinfection are critical factors in ensuring a safe and sustainable water supply. Phthalocyanines (Pcs), a class of versatile and robust organic compounds, have garnered significant attention for their application in various water treatment processes. This review paper offers a groundbreaking investigation of Pc-enabled technologies within the domain of water treatment applications. The core aim of this review is to meticulously analyze the chemical and optical properties of Pcs, elucidate their photosensitization mechanism and establish the crucial connection between their chemical structure and photodynamic efficacy. The various modes of Pcs application in water treatment processes - whether in solution, immobilized, or integrated into water treatment membranes - emphasizing the strategies for their integration and effectiveness in disinfection and decontamination has also been extensively investigated. Moreover, it sheds light on the latest advancements and challenges in the field, providing valuable insights into future research for employing Pcs in environmentally sustainable water treatment methods.

Research Progress on Water Treatment Membranes based on New Photocatalytic Materials

Research Progress on Water Treatment Membranes based on New Photocatalytic Materials

Surface Grafting of Magnetic Carbon Nanotubes and Their Vertical Alignment in PVDF Asymmetric Ultrafiltration Membranes for Fast Nanochannel Construction

The application of carbon nanotubes (CNTs) in water treatment membranes can increase the permeability and selectivity of the membranes. However, traditional CNTs are usually affected by van der Waals forces, which makes them prone to agglomerate in polymer membranes, and their non-directional arrangement in the membranes limits their transport efficiency as water channels in the membranes. In this paper, a reversible addition-fragmentation chain transfer (RAFT) polymerization method was used to synthesize propargyl methacrylate - random copolymerization - poly (ethylene glycol) methacrylate - block - polymethyl methacrylate [P(PgMA-r-PEGMA) -b-PMMA]. The P(PgMA-r-PEGMA)-b-PMMA grafting rate was 60.4% on the surface of magnetic sulfhydryl functionalized carbon nanotubes (mCNTs-SH) by click-reaction grafting. Poly (vinylidene fluoride) (PVDF)/CNTs composite ultrafiltration membranes were prepared using vapor-induced phase separation (VIPS) combined with magnetic field arraying. When the mCNTs-g-P(PgMA-r-PEGMA)-b-PMMA were vertically aligned in the PVDF membrane through a magnetic field, the effective construction of the vertical nanochannels was realized, and an increased purified water flux from 25.6 LMH to 35.8 LMH, with the composite ultrafiltration membranes was obtained. In addition, the membranes also showed excellent hydrophilicity, mechanical properties, and polyethylene glycol 1200 (PEG1200) rejection. The water contact angle was reduced from 105° to 79°, the rejection of PEG1200 was increased from 44% to 91% of the 0.5 g/L PEG aqueous solutions, and excellent mechanical properties (tensile strengthes up to 9.3 MPa) were achieved. By designing the interface structure of the CNTs and studying the orientation of the CNTs in PVDF membranes, this work provides a new research idea for the field of water treatment ultrafiltration membranes.