PES membrane surface modification via layer-by-layer self-assembly of GO@TiO2 for improved photocatalytic performance

Composite aerogel membranes with well dispersed nano M-TiO2@GO for efficient photocatalysis

Photocatalytic technology plays a crucial role in addressing energy shortages and environmental pollution. TiO2 has been widely applied in photocatalysis but encounters several issues, such as the easy recombination of photoexcited electrons and holes, the poor dispersion uniformity, the wide band gap, and the complex recovery process. In this work, a recyclable M-TiO2@GO/modified chitosan composite aerogel membrane was designed and prepared for photocatalytic application, with TiO2 nanoparticles generated by MXene oxidation (M-TiO2) serving as the photocatalyst and modified chitosan acting as the matrix. The experimental results demonstrated that M-TiO2 nanoparticles were in situ generated on the surface of graphene oxide (GO) nanosheets, forming M-TiO2@GO nanoparticles with a 0D@2D structure. Due to the combined effects of M-TiO2 and carbon (another product resulting from the oxidation of MXene), the band gap of M-TiO2 nanoparticles was decreased from 3.10 eV to 2.06 eV, which significantly enhanced the photocatalytic efficiency of TiO2. When the photocatalytic degradation performance of the aerogel membrane containing M-TiO2@GO nanoparticles was evaluated, the sample C15M15G5 (containing modified chitosan 15 mg/M-TiO2 15 mg/GO 5 mg) demonstrated nearly complete degradation of Rhodamine B and Acid Blue 1 within 120 min, exhibiting excellent photocatalytic performance. In addition, the antibacterial properties of C15M15G5 were examined and found that the antibacterial rate reached 100% following ultraviolet irradiation. In summary, this study presents an innovative strategy to obtain well-dispersed nano TiO2, which can be used to prepare composite photocatalytic aerogel membranes with excellent catalytic performance and complete recyclability.

Critical review on emerging photocatalytic membranes for pollutant removal: From preparation to application

Due to synergistically enhanced separation and degradation performances, photocatalytic membranes offer an environmentally friendly and energy-sustainable method for water purification. However, a comprehensive review on preparation and application of photocatalytic membranes is still lacking. Systematically comparing different photocatalytic membrane fabrication methods and revealing the underlying mechanisms of their respective applications are of particular interest. In this review, we first discuss the common preparation methods for photocatalytic membranes in detail, focusing on the main approaches to improve their photocatalytic performance. We elucidate the mechanisms of photocatalytic membrane-based degradation processes, and describe some representative applications of photocatalytic membranes in water treatment. At the same time, the influencing factors that are critical for achieving high removal efficiency are also proposed. In the end, the practical applications and the perspectives for future studies and implementation of photocatalytic membranes are evaluated. This review will serve as a summary to advance researchers' understanding of the advantages of photocatalytic membranes, with the ultimate goal of achieving large-scale relevant applications of photocatalytic membranes in water treatment.

Ultrahigh antifouling ultrafiltration membrane based on Ag NPs photoreduction modified PVP/BiOCl nanoflower for efficient membrane fouling removal

Polyethersulfone (PES) is widely used as an ultrafiltration (UF) membrane material in industrial production due to its excellent performance. However, its inherent hydrophobicity leads to severe membrane fouling issues during practical operation. In this study, focusing on the fouling issues of PES UF membrane, bismuth oxychloride (BiOCl) was chosen as the main nanomaterial. Ag NPs were introduced via photoreduction into BiOCl at the optimal ratio of polyvinylpyrrolidone (PVP) and BiOCl (wt%-0.3:100), resulting in the synthesis of Ag@BiOCl nanoparticles. These nanoparticles were then blended into the PES casting solution and fabricated into composite UF membranes using the reverse thermally induced phase separation (RTIPS) method. Analysis of UV-vis characterization results revealed that the introduction of Ag NPs widened the visible light absorption range of the composite material from 414.30 nm to 508.62 nm. PL spectroscopy results indicated that Ag NPs effectively inhibited the recombination of photogenerated electron-hole pairs, significantly enhancing the photocatalytic activity of Ag@BiOCl. Additionally, the introduction of Ag NPs induced the generation of oxygen vacancies (OVs) on the surface of the composite membrane. Under visible light, the contaminated composite membrane drove the OVs in the photocatalytic material to generate hot electrons (h+-e-). These h+-e- promoted the generation of more active oxygen species, thereby improving the efficiency of membrane fouling removal. The optimal membrane in the PES/Ag@BiOCl series, AGMC5-2 exhibited a pure water flux of 3960.43 L m-2 h-1, a humic acid (HA) rejection rate of 95.00%, and a flux recovery rate of 85.98%. The antibacterial rates against E. coli and S. aureus were 79.07% and 82.33%, respectively. In this study, the PES/Ag@BiOCl composite membrane demonstrated outstanding pure water flux, excellent pollutant rejection rates, significant self-cleaning, and antibacterial properties, effectively addressing membrane fouling issues caused by the inherent hydrophobicity of PES. The successful preparation of the PES/Ag@BiOCl composite membrane lays the foundation for the application of photocatalytic membranes in the field of water treatment.

Fabrication of anti-fouling and self-cleaning PHI modified PVDF membranes for high-flux dye removal

The large pore size of ultrafiltration membranes presents a challenge in rejecting small molecules and the accumulated contaminants on the membrane surface severely restrict the treatment efficiency and shorten the lifespan of separation membranes. Herein, poly(heptazine imide) (PHI) is utilized as a modifier to fabricate anti-fouling and self-cleaning polyvinylidene fluoride (PVDF) membranes for high-flux dye removal. The introduction of PHI does not affect the rejection performance of bovine serum albumin (>97%), whilst improving the water permeability and mechanical strength of membranes. The anti-fouling ability is also significantly enhanced with a flux recovery ratio of 91.61%. In addition, the rejection performance of PHI modified PVDF (PHI/PVDF) membranes for anionic dyes, especially for those of low molecular weight, is obviously improved. The rejection ratios of Congo red (CR) and orange G are 99.8% and 87.4%, respectively, and rejection performance for methyl orange is increased from 22.0% (pure PVDF membrane) to 62.5% (M3 membrane with 3 g PHI added). Furthermore, in the presence of anionic dye (such as CR), 99.3% of methylene blue, 91.8% of malachite green and 95.9% of basic red 46 can be rejected and approximately 613 L m-2 of 50 mg per L CR solution can be processed after 2 h of operation, with the rejection ratio consistently above 98%. The accumulated CR dyes on PHI/PVDF membranes can be easily self-cleaned within 60 min by the H2O2-assisted photocatalytic reaction, effectively solving the problem of membrane fouling.

Bifunctional photocatalyst/hydrogel composites: Synergistic effects and degradation mechanisms for the degradation of benzo(a)pyrene in smoked sausages

Benzo(a)pyrene (B(a)P) is a structurally stable and carcinogenic compound, and B(a)P deposition and transport from smoking environment particulates to smoked meat products is a global challenge. In this study, a novel photosensitive bifunctional composite gel (ST/SiO2-Mn) was successfully synthesized as a reliable material for reducing PM2.5-B(a)P in the smoke environment. B(a)P removal experiments demonstrated that the adsorption and filtration properties of the gel effectively reduced the emission of PM2.5-B(a)P in smoke environment. The ST/SiO2-Mn gel removed 88.5 % of PM2.5-B(a)P in 240 min, which further led to a 59.7 % decrease in B(a)P on the sausage surface. In addition, photocatalytic experiments demonstrated that the ST/SiO2-Mn composite could effectively remove B(a)P, and 50 μg/mL B(a)P could be completely degraded within 20 min. Free radical trapping experiments showed that superoxide radicals (•O2-) contributed significantly to the degradation process. In conclusion, this study provides valuable insights for effective PM2.5-B(a)P degradation without increasing economic burden.

Enhanced activation of peroxymonosulfate by ZIF-67/g-C3N4 S-scheme photocatalyst under visible light assistance for degradation of polyethylene terephthalate

Photocatalyst-activated peroxymonosulfate (PMS) degradation of pollutants is already widely used for wastewater treatment under visible light. Polyethylene terephthalate (PET) is widely used in daily life, but waste plastics have an irreversible negative impact on the environment. In this paper, the ZIF-67/g-C3N4 S-scheme heterojunction catalyst was synthesized as a photocatalyst to achieve a good effect on PET degradation in coordination with PMS. The results indicated that PET could be degraded up to 60.63 ± 2.12 % under the combined effect of catalyst, PMS, and light. In this experiment, the influence of catalyst-to-plastic ratio, PMS concentration, aqueous pH, and inorganic anions on plastic degradation by the photocatalytic synergistic PMS system was discussed, and the excellent performance of this system for degrading PET was highlighted through a comparative test. Electron spin resonance (ESR) and free radical quenching experiments demonstrated that SO4•- contributes the largest amount to the PET degradation performance. Furthermore, results from gas chromatography and liquid chromatography-mass spectrometry (LC-MS) indicated that the plastic degradation products include CO, CH4, and organic small-molecule liquid fuels. Finally, a possible mechanism for the light/PMS system to degrade PET in water was suggested. This paper provides a feasible solution to treat waste microplastics in water.

The Application of TiO2/ZrO2-Modified Nanocomposite PES Membrane for Improved Permeability of Textile Dye in Water

This study investigates the modification of polyethersulfone (PES) membranes with 1 wt% titanium dioxide (TiO2), zirconium dioxide (ZrO2) and a nanocomposite of TiO2/ZrO2. The aim was to efficiently remove Rhodamine B (RhB) from water using a threefold approach of adsorption, filtration and photodegradation. Among the modified membranes (TiO2, ZrO2 and TiO2/ZrO2), the TiO2/ZrO2-PES nanocomposite membrane showed a better performance in rejection of RhB than other membranes with the rejection efficiency of 96.5%. The TiO2/ZrO2-PES membrane was found to possess a thicker selective layer and reduced mean pore radius, which contributed to its improved rejection. The TiO2/ZrO2 nanocomposite membrane also showed high bulk porosity and a slightly lower contact angle of 69.88° compared to pristine PES with a value of 73°, indicating an improvement in hydrophilicity. Additionally, the TiO2/ZrO2-PES nanocomposite membrane demonstrated a relatively lower surface roughness (Sa) of 8.53 nm, which offers the membrane antifouling properties. The TiO2/ZrO2-PES membrane showed flux recovery ratio (FRR), total fouling (Rt), reversible fouling (Rr) and irreversible fouling (Rir) of 48.0%, 88.7%, 36,8% and 52.9%, respectively. For the photocatalytic degradation performance, the removal efficiency of RhB followed this order TiO2 > TiO2/ZrO2 > ZrO2 (87.6%, 85.7%, 67.8%). The tensile strength and elongation were found to be compromised with the addition of nanoparticles and nanocomposites. This indicates the necessity to further modify and optimise membrane fabrication to achieve improved mechanical strength of the membranes. At low pressure, the overall findings suggest that the TiO2/ZrO2 nanocomposite has the potential to offer significant improvements in membrane performance (water flux) compared to other modifications.

Innovative Graphene-Based Nanocomposites for Improvement of Electrochemical Sensors: Synthesis, Characterization, and Applications

Graphene, renowned for its exceptional physicochemical attributes, has emerged as a favored substrate for integrating a wide array of inorganic and organic materials in scientific endeavors and innovations. Electrochemical graphene-based nanocomposite sensors have been developed by incorporating diverse nanoparticles into graphene, effectively immobilized onto electrodes through various techniques. These graphene-based nanocomposite sensors have effectively detected and quantified various electroactive species in samples. This review delves into using graphene nanocomposites to fabricate electrochemical sensors, leveraging the exceptional electrical, mechanical, and thermal properties inherent to graphene derivatives. These nanocomposites showcase electrocatalytic activity, substantial surface area, superior electrical conductivity, adsorption capabilities, and notable porosity, which are highly advantageous for sensing applications. A myriad of characterization techniques, including Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET surface area analysis, and X-ray diffraction (XRD), have proven effective in exploring the properties of graphene nanocomposites and validating the adjustable formation of these nanomaterials with graphene. The applicability of these sensors across various matrices, encompassing environmental, food, and biological domains, has been evaluated through electrochemical measurements, such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). This review provides a comprehensive overview of synthesis methods, characterization techniques, and sensor applications pertinent to graphene-based nanocomposites. Furthermore, it deliberates on the challenges and future prospects within this burgeoning field.

Synthesis and characterization of nanocomposite based polymeric membrane (PES/PVP/GO-TiO2) and performance evaluation for the removal of various antibiotics (amoxicillin, azithromycin & ciprofloxacin) from aqueous solution

The escalating global concern regarding antibiotic pollution necessitates the development of advanced water treatment strategies. This study presents an innovative approach through the fabrication and evaluation of a Polyethersulfone (PES) membrane adorned with GO-TiO2 nanocomposites. The objective is to enhance the removal efficiency of various antibiotics, addressing the challenge of emerging organic compounds (EOCs) in water systems. The nanocomposite membranes, synthesized via the phase inversion method, incorporate hydrophilic agents, specifically GO-TiO2 nanocomposites and Polyvinylpyrrolidone (PVP). The resultant membranes underwent comprehensive characterization employing AFM, EDS, tensile strength testing, water contact angle measurements, and FESEM to elucidate their properties. Analysis revealed a substantial improvement in the hydrophilicity of the modified membranes attributed to the presence of hydroxyl groups within the GO-TiO2 structure. AFM images demonstrated an augmentation in surface roughness with increasing nanocomposite content. FESEM images unveiled structural modifications, leading to enhanced porosity and augmented water flux. The pure water flux elevated from 0.980 L/m2.h-1 for unmodified membranes to approximately 6.85 L/m2.h-1 for membranes modified with 2 wt% nanocomposites. Membrane performance analysis indicated a direct correlation between nanocomposite content and antibiotic removal efficiency, ranging from 66.52% to 89.81% with 4 wt% nanocomposite content. Furthermore, the nanocomposite-modified membrane exhibited heightened resistance to fouling. The efficacy of the membrane extended to displaying potent antibacterial properties against microbial strains, including S. aureus, E. coli, and Candida. This study underscores the immense potential of GO-TiO2 decorated PES membranes as a sustainable and efficient solution for mitigating antibiotic contamination in water systems. The utilization of nanocomposite membranes emerges as a promising technique to combat the presence of EOC pollutants, particularly antibiotics, in water bodies, thus addressing a critical environmental concern.

Layer-by-layer assembled graphitic carbon nitride membranes for water treatment

Meeting societal demand for potable water supply remains one of the prioritized challenges faced in the modern era. The anthropogenic intervention has led to a dire situation threatening ecological balance and human health. There is an inevitable need for the development of new technologies and innovations in existing technologies for water treatment. Photocatalytic Membrane technology, encompassing the merits of membrane filtration and photocatalytic degradation has evolved as a potential and reliable technology for sustainable water treatment. Innovations in photocatalytic materials and membrane fabrication techniques can lead to the goal of commercialization of membrane water treatment technology. Herein, we demonstrate the potential of graphitic carbon nitride (g-C3N4) and its functionalized analog as photocatalytic membranes for sustainable water treatment. g-C3N4 and Tetracarboxyphenylporphyrin sensitized g-C3N4 (g-C3N4/TCPP) was introduced onto commercial nylon membrane surface via a layer-by-layer (LBL) assembly method using chitosan and sodium salt of polystyrene sulphonic acid as polyelectrolytes. The fabricated membranes were characterized to ensure the integration of the photocatalysts. The performance of the membranes for water treatment was assessed by selecting some common dyes as model pollutants. The modified membranes exhibited excellent flux recovery and could afford high rejection rates upon irradiation indicating the prospects for sustainable filtration.

Introducing self-healing properties to polyethersulfone (PES) membrane via poly(vinyl alcohol)/ polyacrylic acid (PVA/PAA) surface coating

During membrane filtration, it is inevitable that a membrane will experience physical damage, leading to a loss of its integrity and a decrease in separation efficiency. Hence, the development of a water-responsive membrane capable of healing itself autonomously after physical damage is significantly important in the field of water filtration. Herein, a water-enabled self-healing composite polyethersulfone (PES) membrane was synthesized by coating the membrane surface using a mixed solution composed of poly (vinyl alcohol) and polyacrylic acid (PVA-PAA). The self-healing efficiency of the coated PES membrane was examined based on the changes in water flux at three stages which are pre-damaged, post-damaged, and post-healing. The self-healing process was initiated by the swelling of the water-responsive PVA and PAA, followed by the formation of reversible hydrogen bonds, completing the self-healing process. The coated PES membrane with three layers of PVA-PAA coatings (at 3:1 ratio) demonstrated high water flux and remarkable self-healing efficiency of up to 98.3%. The self-healing capability was evidenced by the morphology of the membrane observed via scanning electron microscope (SEM). The findings of this investigation present a novel architecture approach for fabricating self-healing membranes using PVA-PAA, in addition to other relevant parameters as reported.

Separation performance of graphene oxide nanofiltration membrane intercalated by MWCNTs and α -Fe2O3 nanoparticles

Nanofiltration (NF) technology is used in the field of water treatment due to its advantages of low energy consumption, high efficiency, and simple process flow. However, the problems of membrane fouling and trade-off (i.e., high flux with low rejection or high rejection with low flux) exist in NF technology, which limit its wide-scale popularization and application. The emphasis of this work is to improve the performance of graphene oxide (GO)-based NF membranes. Multi-walled carbon nanotubes (MWCNTs) and α-Fe2O3 were selected to modify the GO-based membrane by expanding the interlayer spacing and enhancing its antifouling and rejection abilities. Our composite membranes exhibit an increased interlayer spacing of 0.787 nm to 1.1 nm, achieving a high pure water permeation flux of 138.96 Lm-2 h-1, as well as satisfactory rejection rates for salts and dyes (Na2SO4, NaCl, MgCl2, Congo red, and methylene blue). Additionally, the membranes exhibit a relatively good antifouling property. After five cycles of rejection tests, the flux and rejection rate could be recovered to 90 % from 80 % with a 4-h irradiation under visible light. This study provides valuable insights into the development of high-efficiency and advanced NF membranes.

Construction of carbon nitride/zeolitic imidazolate framework-67 heterojunctions on carbon fiber cloth as the photocatalyst for various pollutants removal and hydrogen production

With the macroscale and conductive carbon fiber cloth (CFC) as the substrate, the obtained self-supported photocatalysts hold great promise for enhancing the separation of generated carriers and the recyclability of catalysts, thereby improving the photocatalytic performance and practicality in various applications. Additionally, decorating metal-organic frameworks (MOFs) with ultrahigh surface area on the surface of effective semiconductors is a promising method to enhance the adsorption capacity and photocatalytic performance. Herein, zeolitic imidazolate framework-67 (ZIF-67) as a typical MOFs was applied to modify carbon nitride (C3N4) on the surface of macroscale and conductive CFC. CFC/C3N4/ZIF-67 (4 × 4 cm2) was obtained by a thermal condensation-chemical bath deposition two-step route, and it shows superior adsorption and photocatalytic activity toward bisphenol A (BPA), levofloxacin (LVFX), ciprofloxacin (CIP) and good hydrogen evolution activity. Besides, the recycling test for four cycles indicates the high stability of CFC/C3N4/ZIF-67 with an easy recycling process. In this study, CFC/C3N4/ZIF-67 was prepared through the hydrothermal and chemical bath deposition two-step method, which enhances light absorption and photocatalytic performance, as well as recyclability for solving environmental and energy issues.

Multifunctional Ti3C2Tx MXene/Silver Nanowire Membranes with Excellent Catalytic, Antifouling, and Antibacterial Properties for Nitrophenol-Containing Water Purification

The uncontrolled release of nitrophenol and dye pollutants into water systems is an increasingly serious worldwide concern, and thus efficient wastewater treatment technologies are urgently needed. Herein we report a novel two-dimensional (2D) transition metal carbides and/or nitrides (Ti3C2Tx MXene) membrane modified with silver nanowires (AgNWs) by vacuum assisted filtration technology for the ultrafast nitrophenol catalysis and water purification applications. Regular and controllable membrane transport channels were constructed by stacking Ti3C2Tx MXene nanosheets. Furthermore, the intercalation of AgNWs into the Ti3C2Tx MXene interlayer greatly enlarged the interlayer spacing, resulting in more gaps for fast and selective molecular transport. The optimized Ti3C2Tx MXene@AgNWs (M@A) membrane exhibited a water flux up to ∼191.9 L/(m2 h) while maintaining a high bovine serum albumin (BSA) rejection of ∼95.4%. We emphatically used M@A membranes as efficient catalysts for the reduction of 4-nitrophenol (4-NP), and the results indicated that M@A-12% membrane exhibited the greatest catalytic reduction ability, and recycling utilization. M@A-12% membrane also had an antibacterial rate of more than 99% against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). This work provides a possibility to expand the application of 2D multifunctional M@A membranes in wastewater treatment and pollutant catalytic degradation.

Anti-fouling PVDF membranes incorporating photocatalytic biochar-TiO2 composite for lignin recycle

In this study, a photocatalytic biochar-TiO₂ (C-Ti) composite was prepared using lignin as carbon precursor, and blended with PVDF polymer to fabricate PVDF/C-Ti MMMs via non-solvent induced phase inversion. The prepared membrane demonstrates both 1.5 times higher initial and recovered fluxes than the similarly prepared PVDF/TiO₂ membrane, suggesting the C-Ti composite can help maintain higher photodegradation efficiency and better anti-fouling performance. In addition, the comparison of PVDF/C-Ti membrane against pristine PVDF membrane show that the reversible fouling and photodegradation reversible fouling of BSA increased from 10.1% to 6.4%-35.1% and 26.6%, respectively. And the FRR of PVDF/C-Ti membrane was 62.12%, 1.8 times that of PVDF membrane. The PVDF/C-Ti membrane was also applied for lignin separation, where the rejection to sodium lignin sulfonate was maintained at about 75%, and the flux recovery ratio after UV irradiation reached 90%. The demonstrated the advantages of PVDF/C-Ti membrane in photocatalytic degradation and antifouling performance.

Constructing Z-Scheme 0D/2D TiO2 Nanoparticles/Bi2O3 Nanosheet Heterojunctions with Enhanced Visible Light Induced Photocatalytic Antibiotics Degradation and Hydrogen Evolution

Photocatalysis has been regarded as a promising technology for degrading organic pollutants in wastewater and producing hydrogen. In this paper, TiO2 nanoparticles (NPs) were synthesized to improve the visible light absorption of TiO2, which were further combined with Bi2O3 nanosheets to synthesize a series of 0D/2D TiO2 NPs/Bi2O3 nanosheet heterojunctions. The visible light induced photocatalytic activities of the as-synthesized TiO2/Bi2O3 heterojunctions were studied. The optimized catalyst TB-3 with 15 wt% of Bi2O3/TiO2 exhibited the best photocatalytic degradation of tetracycline hydrochloride (TC). The degradation rate constant k of TC over TB-3 was approximately eight times and 39 times greater than that of P25 and Bi2O3, respectively. Additionally, TB-3 showed the highest amount of hydrogen evolution, while that of Bi2O3 was almost zero. The enhancement of photocatalytic performances was ascribed to the improved visible light absorption and the Z-scheme charge transfer path of the TiO2/Bi2O3 heterojunctions, which enhanced the separation efficiency and reduced recombination of photogenerated charge carries, as evidenced by UV–Visible diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and electrochemistry measurements. The active species trapping experiments and the electron spin resonance (ESR) results revealed that ·O2− was the main active substance in the photocatalytic degradation. The possible degradation pathway and intermediate products of TC have been proposed. This work provides experimental evidence supporting the construction of Z-scheme heterojunctions to achieve excellent visible light induced photocatalytic activity.

Simultaneous degradation and separation of antibiotics in sewage effluent by photocatalytic nanofiltration membrane in a continuous dynamic process

Bifunctional photocatalytic nanofiltration (PNF) membrane is increasingly concerned in practical micro-polluted water purification, but there are still several bottlenecks that inhibit its practicality. In this context, the feasibility of a novel metal-free and visible light-responsive surface-anchored PNF membrane for simultaneously removing target antibiotics in real sewage effluent in a continuous dynamic process was explored. The results showed that the optimal PNF-4 membrane was expectedly consisted of an inside tight sub-nanopore structured separation layer and an outside thinner, smoother, super hydrophilic mesoporous degradation layer, respectively. Consequently, the activated PNF-4 membrane could synergistically reduce trimethoprim and sulfamethoxazole concentrations to below two orders of magnitude, accompanying with almost constant high water permeability, suggesting that the hydrophilic modification of the mesoporous degradation layer basically offsets its inherent hydraulic resistance. Also, after repeating the fouling-physical rinsing process three times lasted for 78 h, only sporadic adherent contaminants remained onto the top surface, together with the minimal total and irreversible fouling ratios (as low as 7.2% and 1.2%, respectively), strongly demonstrated that PNF-4 membrane displayed good self-cleaning performance. Undoubtedly, this will significantly reduce its potential cleaning frequency and maintenance cost in long-term operation. Meanwhile, the acute and chronic biotoxicities of its permeate to Virbrio qinghaiensis sp. -67 were also reduced sharply to 2.22% and 0.45%, respectively. All of these evidences suggest that the dual functions of PNF-4 membrane are synergetic in an uninterrupted permeating process. It will provide useful insights for continuously enhancing the practicality and effectiveness of PNF membrane in actual micro-polluted water purification scenarios.

Advanced Polymeric Nanocomposite Membranes for Water and Wastewater Treatment: A Comprehensive Review

Nanomaterials have been extensively used in polymer nanocomposite membranes due to the inclusion of unique features that enhance water and wastewater treatment performance. Compared to the pristine membranes, the incorporation of nanomodifiers not only improves membrane performance (water permeability, salt rejection, contaminant removal, selectivity), but also the intrinsic properties (hydrophilicity, porosity, antifouling properties, antimicrobial properties, mechanical, thermal, and chemical stability) of these membranes. This review focuses on applications of different types of nanomaterials: zero-dimensional (metal/metal oxide nanoparticles), one-dimensional (carbon nanotubes), two-dimensional (graphene and associated structures), and three-dimensional (zeolites and associated frameworks) nanomaterials combined with polymers towards novel polymeric nanocomposites for water and wastewater treatment applications. This review will show that combinations of nanomaterials and polymers impart enhanced features into the pristine membrane; however, the underlying issues associated with the modification processes and environmental impact of these membranes are less obvious. This review also highlights the utility of computational methods toward understanding the structural and functional properties of the membranes. Here, we highlight the fabrication methods, advantages, challenges, environmental impact, and future scope of these advanced polymeric nanocomposite membrane based systems for water and wastewater treatment applications.