Membranes For Water Purification Research Articles

Sustainable membrane technology for water purification—Manufacturing, recycling and environmental impacts

Water pollution has become a serious threat to our ecosystem. Water contamination due to human, commercial, and industrial activities has negatively affected the whole world. Owing to the global demanding challenges of water pollution treatments and achieving sustainability, membrane technology has gained increasing research attention. Although numerous membrane materials have focused, the sustainable water purification membranes are most effective for environmental needs. In this regard sustainable, green, and recyclable polymeric and nanocomposite membranes have been developed. Materials fulfilling sustainable environmental demands usually include wide-ranging polyesters, polyamides, polysulfones, and recyclable/biodegradable petroleum polymers plus non-toxic solvents. Consequently, water purification membranes for nanofiltration, microfiltration, reverse osmosis, ultrafiltration, and related filtration processes have been designed. Sustainable polymer membranes for water purification have been manufactured using facile techniques. The resulting membranes have been tested for desalination, dye removal, ion separation, and antibacterial processes for wastewater. Environmental sustainability studies have also pointed towards desired life cycle assessment results for these water purification membranes. Recycling of water treatment membranes have been performed by three major processes mechanical recycling, chemical recycling, or thermal recycling. Moreover, use of sustainable membranes has caused positive environmental impacts for safe waste water treatment. Importantly, worth of sustainable water purification membranes has been analyzed for the environmentally friendly water purification applications. There is vast scope of developing and investigating water purification membranes using countless sustainable polymers, materials, and nanomaterials. Hence, value of sustainable membranes has been analyzed to meet the global demands and challenges to attain future clean water and ecosystem.

Cement based nanofiltration membrane of porous boron nitride and graphene oxide for effective oil/water separation

The development of effective filters for crude oil/water separation presents a critical environmental challenge in the face of oil spills. Porous membrane separation stands as a vital technique for removing organic solvents, oils, and dyes from water. In this study, we designed and fabricated a nanofiltration membrane composed of graphene oxide (GO) and boron nitride (BN) incorporated into a cement-based matrix to enhance the selectivity and efficiency of unidirectional flux transportation. The integration of GO, with its rich functional groups, and BN, known for its hydrophobic properties, within the cement matrix, resulted in an improved water permeation rate. Moreover, the inclusion of BN flakes in the cement matrix significantly enhances its mechanical strength, reaching up to 15.93 MPa (∼35 % greater than pristine cement), establishing it as a robust nanofiltration membrane for simultaneous flux enhancement and water purification. This innovative filter demonstrated remarkable separation efficiency, achieving up to 99 % oil removal while allowing the passage of water. To gain a deeper understanding of our experimental findings, we conducted ab initio investigations into the adsorption behavior of water and oil components, including ethanethiol, thiophene, and toluene molecules, on h-BN, GO, and their defective structures (Stone-Wales defect). Our results affirm that porous h-BN and GO nanosheets, characterized by their high specific surface areas, exhibit remarkable sorption capabilities. This nanoengineered membrane showcases substantial adsorption capacity alongside physisorption characteristics suitable for recycling, thereby holding significant potential for the development of functional porous structural materials in the realm of high-performance, cost-effective, and environmentally sustainable water treatment solutions.

Biodegradable ultrafiltration membrane enhanced with anti-biofouling agent from Anacardium occidentale extract

Our research focuses on developing environmentally friendly biodegradable ultrafiltration (UF) membranes for small-scale water purification in areas lacking infrastructure or during emergencies. To address biofouling challenges without resorting to harmful chemicals, we incorporate bio-based extracts, such as methyl gallate from A. occidentale leaves, a Malaysian ulam herb, known for its quorum sensing inhibition (QSI) properties. The methyl gallate enriched extract was purified by solvent partitioning and integrated into cellulose-based UF membranes (0 to 7.5% w w–1) through phase inversion technique. The resulting membranes exhibited enhanced anti-organic fouling and anti-biofouling properties, with flux recovery ratio (FRR) of 87.84 ± 2.00% against bovine serum albumin and FRRs of 76.67 ± 1.89% and 69.57 ± 1.77% against E. coli and S. aureus, respectively. The CA/MG-5 membrane showed a 224% improvement in pure water flux (PWF) compared to the neat CA membrane. Our innovative approach significantly improves PWF, presenting an environmentally friendly method for biofouling prevention in UF membrane applications.

Hyperbranched polymeric membranes for industrial water purification

This work aims at the preparation and characterization of dual-layer (DL) nano-fibrous mat (NFM) of hydrophobic and mechanical stable polyacrylonitrile (PAN) nano-fibers (NFs), as a supporter, and polyamide 6 (PA)/chitosan (Ch) NFs as a top hydrophilic coating layer.PAN and PA fibers, as residual wastes from textile processes, were collected and dissolved in their proper solvents. PAN was electro-spuned under certain conditions of electro-spinning (voltage, flow rate, and distance between spinneret and collector) to obtain PAN-NFM. Different ratios of PA/Ch composite were prepared and then electro-spun above the PAN-NFM that was previously prepared to obtain hydrophobic/hydrophilic functional dual-layer nano-fibrous membrane (DLNFM). The efficiency of the prepared DLNFM for capturing dye residues and heavy metals from wastewater was investigated.The viscosities of the prepared composite solutions were measured. The prepared dual-layer nano-fiber membranes (DLNFMs) were chemically and physically characterized by Fourier transform infrared spectroscopy, scanning electron microscope, X-ray diffraction, and thermogravimetric analyzer. The potential of the prepared mats for the adsorption of some heavy metal ions, i.e., Cu+2, Cr+3, and Pb+2 cations in addition to dyes from wastewater was evaluated. The effect of using different concentrations of PA/Ch composite as well as the thickness of the obtained DLNFM on the filtration efficiency was studied.The results of this study show the success of functional DLNFM in dye and heavy metal removal. The maximum removal efficiency of acid dyes was reached to 73.4 % and of reactive dye was approximately 61 % for PAN/PA-1.25%Ch DLNFM after 3 days at room temperature. The removal efficiency percent of heavy metal ions reached to 54 % by DLNFM. Additionally, the results showed that 0.08 mm is the ideal thickness for maximum absorption capacity. This value is correlated with the membrane's highest Ch percentage, which is (PAN/PA-1.25%Ch). Furthermore, the results demonstrate that the presence of the Ch polymer strengthened the produced bi-layered membrane to achieve the highest thermal stability when compared to the other nano-fibrous membranes (NFMs), with the breakdown temperature of the Ch functionalized dual-layer membranes (DLMs) reaching approximately 617 °C and a maximum weight loss of 60 %.

Nylons with Applications in Energy Generators, 3D Printing and Biomedicine.

Linear polyamides, known as nylons, are a class of synthetic polymers with a wide range of applications due to their outstanding properties, such as chemical and thermal resistance or mechanical strength. These polymers have been used in various fields: from common and domestic applications, such as socks and fishing nets, to industrial gears or water purification membranes. By their durability, flexibility and wear resistance, nylons are now being used in addictive manufacturing technology as a good material choice to produce sophisticated devices with precise and complex geometric shapes. Furthermore, the emergence of triboelectric nanogenerators and the development of biomaterials have highlighted the versatility and utility of these materials. Due to their ability to enhance triboelectric performance and the range of applications, nylons show a potential use as tribo-positive materials. Because of the easy control of their shape, they can be subsequently integrated into nanogenerators. The use of nylons has also extended into the field of biomaterials, where their biocompatibility, mechanical strength and versatility have paved the way for groundbreaking advances in medical devices as dental implants, catheters and non-absorbable surgical sutures. By means of 3D bioprinting, nylons have been used to develop scaffolds, joint implants and drug carriers with tailored properties for various biomedical applications. The present paper aims to collect evidence of these recently specific applications of nylons by reviewing the literature produced in recent decades, with a special focus on the newer technologies in the field of energy harvesting and biomedicine.

Charge govern ion-selective mechanism of YX2 desalination pore using high-throughput computations and machine learning

Energy-efficient and low-cost desalination of water continues to be a problem that society is facing. With the advances in nanotechnology, a variety of nanopore membranes have emerged for desalination. In particular, YX2 nanopores (YW, Mo, etc. and X = S, Se, Te, etc.) have been considered as promising membranes for water purification. In this work, we used a combination of high-throughput molecular dynamics simulations and machine learning to reveal the nanopore mass transfer mechanism and rationally design the YX2 nanopore. The pore size and the charge of the pore mouth were found to be the main factors affecting water permeation and salt rejection, as discovered through the machine learning study. The physical-chemical analysis provides us with a deep understanding of the charge-governed mechanism on the desalination performance of YX2 nanopores. It revealed that YX2 nanopores with a conical shape and minimized pore charges could be ideal candidates for excellent desalination performance. Based on this, we designed the YX2 pore with a specific charge distribution, which could achieve high water permeation with high salt rejection. Therefore, the combination of machine learning and high-throughput computation methods could aid in designing materials with excellent performance for desalination.

Enhancing Water Purification by Integrating Titanium Dioxide Nanotubes into Polyethersulfone Membranes for Improved Hydrophilicity and Anti-Fouling Performance.

Water pollution remains a critical concern, one necessitated by rapidly increasing industrialization and urbanization. Among the various strategies for water purification, membrane technology stands out, with polyethersulfone (PES) often being the material of choice due to its robust mechanical properties, thermal stability, and chemical resistance. However, PES-based membranes tend to exhibit low hydrophilicity, leading to reduced flux and poor anti-fouling performance. This study addresses these limitations by incorporating titanium dioxide nanotubes (TiO2NTs) into PES nanofiltration membranes to enhance their hydrophilic properties. The TiO2NTs, characterized through FTIR, XRD, BET, and SEM, were embedded in PES at varying concentrations using a non-solvent induced phase inversion (NIPS) method. The fabricated mixed matrix membranes (MMMs) were subjected to testing for water permeability and solute rejection capabilities. Remarkably, membranes with a 1 wt% TiO2NT loading displayed a significant increase in pure water flux, from 36 to 72 L m2 h-1 bar-1, a 300-fold increase in selectivity compared to the pristine sample, and a dye rejection of 99%. Furthermore, long-term stability tests showed only a slight reduction in permeate flux over a time of 36 h, while dye removal efficiency was maintained, thus confirming the membrane's stability. Anti-fouling tests revealed a 93% flux recovery ratio, indicating excellent resistance to fouling. These results suggest that the inclusion of TiO2 NTs offers a promising avenue for the development of efficient and stable anti-fouling PES-based membranes for water purification.

Performance of Teflon- reinforced Nafion against microbes and removal of heavy metal ions from aqueous environment

Considering its promising antimicrobial and metal removal capabilities, water filtration systems have not yet widely used ionic polymer membranes. A textile structure made of Nafion polymer reinforced with Teflon (TFRN) was coated with non-precious metals copper and silver using a chemical decomposition technique. Scanning electron microscopy makes it quite evident that a surface coating was formed with evenly distributed metal particles. Water and moisture uptake capacity for Silver (Ag)-Copper (Cu) coated membrane was reduced by 80 and 67 % respectively compared to pure membrane. Inaddition, Ag–Cu coated membrane showed best performance against Escherichia coli (ATCC25922), and Staphylococcus aureus (ATCC 25923) with 2.04 and 1.7 CFU/ml respectively, by considering below level of Quantification as 1.6 CFU/ml. Pure Nafion membrane at pH 6.5, was used to perform the adsorption studies of transition metal ions like Copper, Nickel, Chromium, Barium, Tin and Arsenic at room temperature. The maximum metal ion removal was about 35 % for Copper followed by Nickel (31 %) and the least adsorption was observed for Barium (13.5 %) from multi-heavy metals solution. The study revealed that the potential of TFRN membrane for water purification in terms of metal and microbial removal process.

Investigation of the adsorption behaviour of toxic heavy metals and bacteria on two allotropes of low dimensional boron nitride: Implications for detection and elimination

In this research, the focus was on two 2D allotropes of boron nitride (BN), specifically Haeck-BN and Twin-BN. They exhibit unique structural and electronic characteristics, making them suitable for sensing applications. High surface area materials offer numerous affinity sites for heavy metal ions and toxic molecules. Using density functional theory (DFT), the adsorption mechanisms of various contaminants in gas (solvent) phase on both pristine and doped Haeck-BN and Twin-BN were investigated. Pronounced adsorption of arsenic (As) and lead (Pb) was observed on pristine Twin-BN sheets, with adsorption energies of −2.83 eV (−2.86 eV) and −2.03 eV (−2.39 eV), respectively. Haeck-BN showed weaker interactions, with adsorption energies of −1.48 eV (−1.55 eV) for As and −0.64 eV (−0.92 eV) for Pb. Significant adsorption of specific amino acids, integral components of bacterial cell walls, was noted on both pristine and silver-modified sheets. The electronic properties showed significant shifts upon molecular adsorption, confirming their sensitivity towards foreign contaminants. The high adsorption energies of amino acids suggest potential applications in efficient bacterial inactivation for water purification. While real-world scenarios pose challenges, the calculations provide valuable insights for potential use of these nanosheets in advanced water purification membrane technology.

Boron Removal Using Spherulitic Polyamide Organic–Inorganic Thin‐Film Nanocomposite Desalination Membranes

AbstractThis research investigates the development of ultrathin polyamide (PA) desalination membranes via electrospray fabrication, balancing the trade‐offs between selectivity and permeability. The unique contribution to the improvement of desalination performance is the integration of protonated montmorillonite nanoclay (MMT‐H+) and hyperbranched amino‐polyol cellulose nanocrystals (APCNC) as co‐nanofillers during the in situ interfacial polymerization process. Synergistic effect of the nanofillers is demonstrated in the resultant spherulitic PA thin‐film nanocomposite (TFN) membrane, achieving salt rejection of up to 99.7% against simulated brackish water. Moreover, the membrane's superior boron removal efficiency at neutral pH, observed at 76.7% in a single‐stage desalination process, is attributed to the reduced membrane pore size, disruption of water‐boron association by the spherulites, and complexation and electrostatic interaction with the abundant hydroxyl and amine groups along the APCNC polymeric chains. This process eliminates the need for pH adjustment, thereby enhancing the membrane's practicality and efficiency. The findings of this study provide significant insights into the interactions between boron and the membrane surface, laying the groundwork for the development of effective TFN desalination membranes for water purification and boron removal. The implication of these findings extends beyond academic interest, offering a promising strategy for addressing the global water scarcity crisis.

Electrochemically assisted preparation of graphitic carbon nitride nanosheet membranes for efficient water purification

The development of a highly effective nanofiltration membrane for water purification is crucial for wastewater recovery. The graphitic carbon nitride (g-C3N4) membrane can be an ideal candidate for advanced water treatment due to its intrinsic porous structure and superior physicochemical stability. However, the developments of the g-C3N4 membranes are limited by their traditional preparation methods involving complicated processes, long reaction time and high-temperature conditions. A simple electrochemical-assisted strategy for the rapid preparation of the g-C3N4 nanosheet membranes at room temperature has been developed in this study. The ultra-thin g-C3N4 membrane with a uniform structure can be synthesized within 40 min, which is at least 7 times quicker compared to the traditional methods. The as-prepared g-C3N4 membrane shows a high water flux rate of ∼ 90 L m−2 h−1 bar−1. Simultaneously, an excellent rejection rate of 99.1% toward Evans blue is achieved based on the synergistic effect of size sieving and electrostatic repulsion. The breakthrough in the preparation method of g-C3N4 nanosheet membranes in this work is of great significance to the development of g-C3N4 membranes in the field of water purification.

Molecular and electrostatic origins of mixed salt partitioning phenomena in uncharged poly(ethylene oxide)-based membranes

Despite the increasing interest in membranes for water purification and resource recovery from aqueous electrolyte mixtures, few studies rigorously investigate the influence of salt solution composition (e.g., mole fraction and total salt concentration) on membrane material properties such as partition coefficients. Here, we systematically investigate the influence of solution composition on the partitioning of ionic species from binary aqueous salt solutions into crosslinked poly(ethylene glycol) diacrylate membranes at fixed ionic strength. These results are compared to partition coefficients observed for pure salt solutions. We observe large systematic deviations between the pure salt and mixed salt ion partition coefficients, indicating that the single salt partition coefficients that are often reported do not describe the more complex and realistic mixed salt scenario. Free energy calculations from molecular dynamics simulations, coupled with equilibrium thermodynamic modeling, indicate that mixed salt partitioning trends result from (i) different ions exhibiting different affinities for the membrane and (ii) the constraint of global electrical neutrality within the membrane. With this physical insight, we develop a simple approach to predicting the concentration of various ions in a membrane equilibrated with a mixed salt solution which requires no adjustable parameters.

Spongy and anti-pollution MXene/Ag2S/cellulose acetate membrane for sustainable solar-driven interfacial evaporation and water purification

Solar-driven interfacial evaporation (SIE) technology stands out as a promising approach for seawater desalination, leveraging solar energy efficiently in an environmentally friendly manner. However, the enrichment of organic pollutants on the interfacial evaporator has posed significant obstacles to the sustained implementation of SIE. Herein, a spongy, anti-pollution cellulose acetate membrane consisting of Ag2S-doping MXene nanosheets (MT-Ag2S/CAM) is proposed for sustainable desalination. The MT-Ag2S/CAM exhibited ultralow water vaporization enthalpy of 1.50 kJ g−1. Meanwhile, the MT-Ag2S/CAM, featured by high porosity (75.25 %), excellent light absorption and salt resistance, demonstrated a notable solar-driven evaporation rate of 1.8 kg m−2h−1 and a remarkable photothermal conversation efficiency of 91.6 % under one sun irradiation. Meanwhile, MT-Ag2S/CAM can realize a removal efficiency of 93.3 % for methylene blue, exhibiting outstanding anti-pollution and self-cleaning capabilities as well as long-term stability due to its strong mechanical properties. Finally, a device for sustainable desalination, water purification and clean water collection is designed and implemented in a practical SIE process.

Innovations in nanomaterial-embedded polymer membranes for water and wastewater treatment: a comprehensive review

Abstract There has been growing interest in advancing nanoparticle-embedded polymeric membranes and their significant utilization in wastewater treatment to address the global water pollution problem. Incorporation of nanomaterials into the membrane matrices not only enhances the physicochemical properties like hydrophilicity, mechanical and thermal stability, porosity, antifouling, and antibacterial properties of the polymers but also influences the membrane permeability, selectivity, and several contaminant removals. This overview highlighted the development of nanomaterials like metal/metal oxide nanoparticles (0D), carbon nanotubes (1D), graphene or graphene oxide (GO) (2D layer materials), zwitterionic, zeolites, and associated structures (3D) blended with significant polymeric materials, along with synthesis and integration techniques for fabricating mixed-matrix nanoparticle-embedded polymer nanocomposite (PNC) membranes. This article also addresses the limitations of conventional water treatment technologies, recent challenges of polymer membrane technology, environmental impact, human considerations, and the prospects of these advanced nanoparticle-embedded polymer membranes for sustainable water and wastewater treatment. The motivation for future research in polymeric materials with embedded nanoparticles and the prediction of novel membranes for water purification will also be provided.

A review on the design and fabrication of polydimethylsiloxane thin-film composite membranes (TFCMs) for alcohol permselective pervaporation

Pervaporation-based membrane technology have gained increasing interest due to their energy efficiency and environmental sustainability. Polydimethylsiloxane (PDMS) thin-film composite membranes (TFCMs) have emerged as promising candidates for alcohol permselective applications. Compared to the development of pervaporation membrane for water purification, the optimization progress with the ethanol recovery membrane has been fairly slow and fails to meet requirements of bio-alcohol production. Despite the continuous efforts on membrane materials, the role of structural, physicochemical properties for the forming progress of selective layer on substrate is not a well-attended topic. This paper summarized the design and construction considerations of PDMS composite membranes for pervaporation from the viewpoint of the transport resistance model, including the effect of selective layer, support layer, and intermediate layer, to deeply understand and precisely regulate the preparation process. We high light the key role of crosslinking and spreading of PDMS on porous support layer in membrane fabrication. The structure-activity relationship between the separation performance of transport structure with the membrane solution properties, substrate pore structure, and the fabrication methods was discussed in detail. It was indicated that the challenges for the TFCMs applied on a pilot or industrial scale include the thickness control, coating and curing time optimization, and solvent issue. Finally, it was expected for further research to optimize the membrane fabrication process, develop novel advanced membrane materials and to explore complex and potential applications the new requirements in industry.

Rapid thermal process for fabricating α-alumina tight ultrafiltration membrane with narrow pore size distribution

The development of tight ceramic ultrafiltration membranes for water purification facilitates is challenging because of high fabrication costs and low permeate flux. In this study, a low-energy rapid thermal process (RTP) was comprehensively investigated for fabricating of high-precision, permeable α-alumina tight ultrafiltration membranes. Compared to the conventional thermal process (CTP), RTP offers an ultra-fast heating rate and shorter holding time, effectively mitigating grain growth and pore aggregation. Moreover, the decomposition of organic matter is delayed during RTP, providing a lower interfacial energy that enables direct formation of α-alumina at a low temperature of 750 °C. During a secondary subsequent RTP, the residual phase is fully converted to α-alumina by the in-situ seeding effect. By utilizing RTP, we successfully prepared α-alumina ultrafiltration membranes within 30 min by calcination, with an average pore size of approximately 6 nm, a narrow pore distribution coefficient of 1.12, and high permeance of 219 L−1·m−2·h−1·bar−1.

A homogeneous carbon nitride nanomodifier for promoting the water permeation of polyamide desalination membranes

Nanomaterial modification provides an effective way to enhance the separation performance of nanofiltration membranes, but the limited hydrophilicity of conventional nanostructures causes their poor solubility in solvents, affecting the quality of polyamide membranes for performance enhancement. Herein, we explored quasi-water soluble carbon nitride as a homogeneous modifier to improve the nanofiltration performance of polyamide membranes. With sufficient hydroxyl, amino, and cyano groups, the introduced quasi-water soluble carbon nitride significantly enhanced the surface hydrophilicity of the support membrane, resulting in the formation of an ultrathin functional layer for high-efficiency desalination. The high permeation flux of 108.64 L m-2h−1 (4 bar) was even twice and three times higher than those of the pristine polyamide membrane and commercial nanofiltration membranes, with a high Na2SO4 barrier rate of 98.84 % and a Cl-/SO42- selectivity of 76. This work provides an effective way to precisely regulate the structure of nanofiltration membranes for high-performance water purification.

Utilizing the oxygen-atom trapping effect of Co3O4 with oxygen vacancies to promote chlorite activation for water decontamination

Heterogeneous high-valent cobalt-oxo [≡Co(IV)=O] is a widely focused reactive species in oxidant activation; however, the relationship between the catalyst interfacial defects and ≡Co(IV)=O formation remains poorly understood. Herein, photoexcited oxygen vacancies (OVs) were introduced into Co3O4 (OV-Co3O4) by a UV-induced modification method to facilitate chlorite (ClO2-) activation. Density functional theory calculations indicate that OVs result in low-coordinated Co atom, which can directionally anchor chlorite under the oxygen-atom trapping effect. Chlorite first undergoes homolytic O-Cl cleavage and transfers the dissociated O atom to the low-coordinated Co atom to form reactive ≡Co(IV)=O with a higher spin state. The reactive ≡Co(IV)=O rapidly extracts one electron from ClO2- to form chlorine dioxide (ClO2), accompanied by the Co atom returning a lower spin state. As a result of the oxygen-atom trapping effect, the OV-Co3O4/chlorite system achieved a 3.5 times higher efficiency of sulfamethoxazole degradation (~0.1331 min-1) than the pristine Co3O4/chlorite system. Besides, the refiled OVs can be easily restored by re-exposure to UV light, indicating the sustainability of the oxygen atom trap. The OV-Co3O4 was further fabricated on a polyacrylonitrile membrane for back-end water purification, achieving continuous flow degradation of pollutants with low cobalt leakage. This work presents an enhancement strategy for constructing OV as an oxygen-atom trapping site in heterogeneous advanced oxidation processes and provides insight into modulating the formation of ≡Co(IV)=O via defect engineering.

Zeolite Imidazolate Frameworks-8@SiO2-ZrO2 Crystal-Amorphous Hybrid Core-Shell Structure as a Building Block for Water Purification Membranes.

Metal-organic frameworks (MOFs) are emerging as promising materials for water purification membranes, owing to their uniform microporous structures and chemical functionalities. Here, we report a simple procedure for depositing MOF-based nanofiltration membranes on commercial TiO2 ceramic tubular supports, completely avoiding the use of dispersants or binders. Zeolite imidazolate frameworks-8 (ZIF-8) nanocrystals were synthesized in methanol at room temperature and subsequently coated with an amorphous SiO2-ZrO2 gel to generate a dispersion of ZIF-8@SiO2-ZrO2 core-shell nanoparticles. The amorphous SiO2-ZrO2 gel served as a binding agent for the ZIF-8 nanocrystals, thus forming a defect-free continuous membrane layer. After repeating the coating twice, the active layer had a thickness of 0.96 μm, presenting a rejection rate >90% for the total organic carbon in an aquaculture effluent and in a wastewater treatment plant, while reducing the concentration of trimethoprim, here used as a target pollutant. Moreover, the oxide gel provided the MOF-based active layer with good adhesion to the support and enhanced its hydrophilicity, resulting in a membrane with excellent mechanical stability and resistance to fouling during the crossflow filtration of the real wastewater samples. These results implied the high potential of the MOF-based nanocomposite membrane for effective treatment of actual wastewater streams.

Role of tea polyphenols in enhancing the performance, sustainability, and catalytic cleaning capability of membrane separation for water-soluble pollutant removal

Tea polyphenols (TPs), like green tea polyphenol (GTP) and black tea polyphenol (BTP), with phenolic hydroxyl structures, form coordination and hydrogen bonds, making them effective for bridging inorganic catalysts and membranes. Here, TPs were employed as interface agents for the preparation of TPs-modified needle-clustered NiCo-layered double hydroxide/graphene oxide membranes (NiCo-LDH-TPs/GO). The incorporation of porous guest material, NiCo-LDH-TPs, facilitated water channel expansion, enhancing membrane permeability and resulting in the development of high-performance, sustainable catalytic cleaning membranes. The introduction of TPs through coordination weakened the surface electronegativity of NiCo-LDH, promoting a uniform mixed dispersion with GO and facilitating membrane self-assembly. NiCo-LDH-GTP/GO-5 and NiCo-LDH-BTP/GO-5 membranes demonstrated permeances of 85.98 and 90.76 L m−2 h−1 bar−1, respectively, with rejections of 98.73% and 99.54% for methylene blue (MB). Notably, the NiCo-LDH-BTP/GO-5 membrane maintained a high rejection of 97.11% even after 18 cycles in the catalytic cleaning process. Furthermore, the modification of GTP and BTP enhanced MB degradation through PMS activation, resulting in a 0.33% and 0.35% increase in the reaction rate constants of NiCo-LDH, respectively, while reducing metal ion spillover. These findings highlighted the potential of TPs in enhancing the efficiency and sustainability of catalytic cleaning GO membranes for water purification and separation processes.