Magnetic field assisted arrangement of photocatalytic TiO2 particles on membrane surface to enhance membrane antifouling performance for water treatment

Illuminating for purity: Photocatalytic and photothermal membranes for sustainable oil-water separation

The integration of photocatalytic and photothermal materials with oil-water separation membranes marks a significant advancement in sustainable separation technologies. These hybrid membranes exhibit exceptional functionalities, including resistance to oil fouling, self-cleaning, antibacterial properties, and reduced oil viscosity. Based on their reaction mechanisms, current photocatalytic and photothermal membranes are categorized into four types, i.e., photocatalytic membranes, photo-Fenton membranes, PMS-assisted photocatalytic membranes, and photothermal membranes. Under light irradiation, photocatalytically functionalized membranes generate reactive oxygen species (ROS) that degrade organic pollutants and inactivate bacteria on the membrane surfaces, enabling in-situ cleaning and regeneration. In addition to the above benefits, photothermal membranes achieve reduction of oil viscosity for higher membrane permeation and removal of light oil from membrane surfaces through light-induced heating. This review first explores the mechanisms underlying light-driven advanced oxidation processes (AOPs) and photothermal effects, followed by an in-depth discussion on the fabrication methods of these membranes. Additionally, the applications of photocatalytic and photothermal membranes in oil-water separation are examined, with an emphasis on how the photocatalytic and photothermal materials contribute to membrane functionality. Finally, this review presents the challenges currently faced by photocatalytic and photothermal membranes and outlines future research directions.

How can heteroatoms boost the performance of photoactive nanomaterials for wastewater purification?

Photocatalysis, as an alternative for treating persistent water pollutants, holds immense promise. However, limitations hinder sustained treatment and recycling under varying light conditions. This comprehensive review delves into the novel paradigm of metal and non-metal doping to overcome these challenges. It begins by discussing the fundamental principles of photocatalysis and its inherent limitations. Understanding these constraints is crucial for developing effective strategies. Band gap narrowing by metal and non-metal doping modifies the band gap, enabling visible-light absorption. Impurity energy levels and oxygen vacancies influenced the doping energy levels and surface defects. Interfacial electron transfer and charge carrier recombination are the most important factors that impact overall efficiency. The comparative analysis of nanomaterials are reviewed on various, including nanometal oxides, nanocarbon materials, and advanced two-dimensional structures. The synthesis process are narratively presented, emphasizing production yields, selectivity, and efficiency. The review has potential applications in the environment for efficient pollutant removal and water purification, economic cost-effective and scalable production and technological advancement catalyst design, in spite of its challenges in material stability, synthesis methods and optimizing band gaps. The novelty of the review paper is on the proposal of a new paradigm of heterojunctions of doped metal and non-metal photocatalysts to promise highly efficient water treatment. This review bridges the gap between fundamental research and practical applications, offering insights into tailored nano photocatalysts.

A review of experimental Assessment Processes of material resistance to marine and freshwater biofouling

Biofouling presents hazards to a variety of freshwater and marine underwater infrastructures and is one of the direct causes of species invasion. These negative impacts provide a unified goal for both industry practitioners and researchers: the development of novel antifouling materials to prevent the adhesion of biofouling. The prohibition of tributyltin (TBT) by the International Maritime Organization (IMO) in 2001 propelled the research and development of new antifouling materials. However, the evaluation process and framework for these materials remain incomplete and unsystematic. This mini-review starts with the classification and principles of new antifouling materials, discussing and summarizing the methods for assessing their biofouling resistance. The paper also compiles the relevant regulations and environmental requirements from different countries necessary for developing new antifouling materials with commercial potential. It concludes by highlighting the current challenges in antifouling material development and future outlooks. Systematic evaluation of newly developed antifouling materials can lead to the emergence of more genuinely applicable solutions, transitioning from merely laboratory products to materials that can be effectively used in real-world applications.

Membrane processes enhanced by various forms of physical energy: A systematic review on mechanisms, implementation, application and energy efficiency

Membrane technologies in water and wastewater treatment have been eagerly pursued over the past decades, yet membrane fouling remains the major bottleneck to overcome. Membrane fouling control methods which couple membrane processes with online in situ application of external physical energy input (EPEI) are getting closer and closer to reality, thanks to recent advances in novel materials and energy deliverance methods. In this review, we summarized recent studies on membrane fouling control techniques that depend on (i) electric field, (ii) acoustic field, (iii) magnetic field, and (iv) photo-irradiation (mostly ultraviolet or visible light). Mechanisms of each energy input were first reported, which defines the applicability of these methods to certain wastewater matrices. Then, means of implementation were discussed to evaluate the compatibility of these fouling control methods with established membrane techniques. After that, preferred applications of each energy input to different foulant types and membrane processes in the experiment reports were summarized, along with a discussion on the trends and knowledge gaps of such fouling control research. Next, specific energy consumption in membrane fouling control and flux enhancement was estimated and compared, based on the experimental results reported in the literature. Lastly, strength and weakness of these methods and future perspectives were presented as open questions.

Membrane-catalysis integrated system for contaminants degradation and membrane fouling mitigation: A review

The integration of catalytic degradation and membrane separation processes not only enables continuous degradation of contaminants but also effectively alleviates inevitable membrane fouling, demonstrating fascinating practical value for efficient water purification. Such membrane-catalysis integrated system (MCIS) has attracted tremendous research interest from scientists in chemical engineering and environmental science recently. In this review, the advantages of MCIS are discussed, including the membrane structure regulation, stable catalyst loading, nano-confinement effect, and efficient natural organic matter (NOM) exclusion, highlighting the synergistic effect between membrane separation and catalytic process. Subsequently, the design considerations for the fabrication of catalytic membranes, including substrate membrane, catalytic material, and fabrication method, are comprehensively summarized. Afterward, the mechanisms and performance of MCIS based on different catalytic types, including liquid-phase oxidants/reductants involved MCIS, gas involved MCIS, photocatalysis involved MCIS, and electrocatalysis involved MCIS are reviewed in detail. Finally, the research direction and future perspectives of catalytic membranes for water purification are proposed. The current review provides an in-depth understanding of the design of catalytic membranes and facilitates their further development for practical applications in efficient water purification.

Ultrathin g-C3N4 composite Bi2WO6 embedded in PVDF UF membrane with enhanced permeability, anti-fouling performance and durability for efficient removal of atrazine

A novel Bi₂WO₆-g-C₃N₄/polyvinylidene fluoride (PVDF) composite ultrafiltration (UF) membrane (BWO-CN/PVDF) was prepared by microwave hydrothermal and immersion precipitation phase transformation method. The BWO-CN/PVDF-0.10 exhibited an outstanding photocatalytic removal rate of atrazine (ATZ) (97.65 %) under the simulated sunlight and enhanced permeate flux (1356.09 L·m^-2·h^-1). The multiple optical and electrochemical detection confirmed that combining ultrathin g-C₃N₄ and Bi₂WO₆ can increase carrier separation rate and prolong its lifetime. The quenching test revealed that h⁺ and ¹O₂ were the prominent reactive species. Additionally, after a 10-cycle photocatalytic process, the BWO-CN/PVDF membrane presented remarkable reusability and durability. And it showed excellent anti-fouling performance by filtering BSA, HA, SA, and Songhua River under simulated solar irradiation. The molecular dynamic (MD) simulation showed that the combination of g-C₃N₄ and Bi₂WO₆ can enhance the interaction between BWO-CN and PVDF. This work opens up a new idea for designing and constructing a highly efficient photocatalytic membrane for water treatment.

Application of Poly(ether sulfone)-Based Membranes in Clean Energy Technology

Poly(ether sulfone) (PES) is a kind of polymer materials with excellent electrical insulation and acid/alkali stability. PES can be operated at high temperature continuously for a long time and still maintain excellent property stability in the environments with rapidly changed temperature, namely, great thermostability. Moreover, PES has low molding shrinkage, good dimensional stability and excellent film-forming characteristics. Compared with inorganic membranes, PES-based membranes have lower cost, which have received more attention and wide recognition in the field of clean energy technologies in recent years, such as flow batteries, fuel cells, water treatment, and gas separation. Therefore, this review summarizes the research status and prospect of the utilization of PES-based membranes in clean energy fields, in order to further promote their development and application.

Recent Advances on the Fabrication of Antifouling Phase-Inversion Membranes by Physical Blending Modification Method

Membrane technology is an essential tool for water treatment and biomedical applications. Despite their extensive use in these fields, polymeric-based membranes still face several challenges, including instability, low mechanical strength, and propensity to fouling. The latter point has attracted the attention of numerous teams worldwide developing antifouling materials for membranes and interfaces. A convenient method to prepare antifouling membranes is via physical blending (or simply blending), which is a one-step method that consists of mixing the main matrix polymer and the antifouling material prior to casting and film formation by a phase inversion process. This review focuses on the recent development (past 10 years) of antifouling membranes via this method and uses different phase-inversion processes including liquid-induced phase separation, vapor induced phase separation, and thermally induced phase separation. Antifouling materials used in these recent studies including polymers, metals, ceramics, and carbon-based and porous nanomaterials are also surveyed. Furthermore, the assessment of antifouling properties and performances are extensively summarized. Finally, we conclude this review with a list of technical and scientific challenges that still need to be overcome to improve the functional properties and widen the range of applications of antifouling membranes prepared by blending modification.

Reusable composite membranes for highly efficient chromium removal from real water matrixes

Natural or industrial hexavalent chromium water pollution continues to be a worldwide unresolved threat. Today, there is intense research on new active and cost-effective sorbents for Cr(VI), but most still exhibit a critical limitation: their powdered nature makes their recovery from water cost and energy consuming. In this work, Al(OH)₃, MIL-88-B(Fe), and UiO-66-NH₂ Cr(VI) sorbents were immobilized into a poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymeric substrate to develop an easily reactivable and reusable water filtering technology. The immobilization of the sorbents into the PVDF-HFP porous matrix modified the macro and meso-porous structure of the polymeric matrix, tuning in parallel its wettability. Although a partial blocking of the Cr(VI) adsorptive capacity was observed for of Al(OH)₃ and MIL-88-B(Fe) when immobilized into composite membranes, PVDF-HFP/UiO-66-NH₂ filter (i) exceeded the full capacity of the non-immobilized sorbent to trap Cr(VI), (ii) could be reactivated and reusable, and (iii) it was fully functional when applied in real water effluents.

SLAP@g-C3N4 Fluorescent Photocatalytic Composite Powders Enhance the Anti-Bacteria Adhesion Performance and Mechanism of Polydimethylsiloxane Coatings

Fluorescent antifouling and photocatalytic antifouling technologies have shown potential in the field of marine antifouling. SLAP@g-C₃N₄/PDMS (SLAP@CN/PDMS) composite antifouling coatings were designed and prepared using g-C₃N₄, sky-blue long afterglow phosphor (SLAP), and polydimethylsiloxane (PDMS). The fluorescence emitted by SLAP under dark conditions was used to excite g-C₃N₄ for fluorescent photocatalysis and to prolong the photocatalytic activity of g-C₃N₄. Key data were collected by testing and characterization and are presented in this work. The results showed that g-C₃N₄ was successfully coated on the SLAP surface and formed a heterogeneous structure. After the composite powder was added to the PDMS coating, the coating maintained low surface energy but enhanced the surface roughness of the coating. The experimental results of degraded Rhodamine B (RhB) showed that SLAP prolonged the g-C₃N₄ photocatalytic activity time. The anti-marine bacterial adhesion performance of the coating was investigated by bacterial adhesion experiments. The results showed that SLAP@CN could effectively improve the anti-bacterial adhesion performance of PDMS coating, in which the anti-bacterial adhesion performance of SLAP@CN-2.5/PDMS was improved by nearly 19 times. This antifouling coating introduces fluorescent antifouling, photocatalytic antifouling, and fluorescence-driven photocatalytic antifouling based on the low surface energy antifouling of silicones and achieves "all-weather" fluorescent photocatalytic antifouling.

Research progress in external field intensification of forward osmosis process for water treatment: A critical review

Forward osmosis (FO) is an emerging permeation-driven membrane technology that manifests advantages of low energy consumption, low operating pressure, and uncomplicated engineering compared to conventional membrane processes. The key issues that need to be addressed in FO are membrane fouling, concentration polarization (CP) and reverse solute diffusion (RSD). They can lead to problems about loss of draw solutes and reduced membrane lifetime, which not only affect the water treatment effectiveness of FO membranes, but also increase the economic cost. Current research has focused on FO membrane preparation and modification strategies, as well as on the selection of draw solutions. Unfortunately, these intrinsic solutions had limited success in unraveling these phenomena. In this paper, we provide a brief review of the current state of research on existing external field-assisted FO systems (including electric-, pressure-, magnetic-, ultrasonic-, light- and flow-assisted FO system), analyze their mitigation mechanisms for the above key problems, and explore potential research directions to aid in the further development of FO systems. This review aims to reveal the feasibility of the development of external field-assisted FO technology to achieve a more economical and efficient FO treatment process.

Preparation of Ni@UiO-66 incorporated polyethersulfone (PES) membrane by magnetic field assisted strategy to improve permeability and photocatalytic self-cleaning ability

Metal-organic frameworks (MOFs) have been considered as promising nanofillers to fabricate mixed matrix membranes for water treatment. However, manipulating distribution of MOFs nanoparticles in the membrane matrix remains a great challenge. In this study, UiO-66 was firstly coated by magnetic Ni via an in-situ reduction reaction, and then incorporated into polyethersulfone (PES) membrane matrix to prepare PES-Ni@UiO-66 membrane. The magnetic Ni allowed to manipulate the distribution of magnetic Ni@UiO-66 in the phase-inversion process by an external magnetic field. The hydrophilic Ni@UiO-66 can be pulled onto membrane surface by the magnetic force, endowing the prepared membrane with rather higher hydrophilicity. The prepared membrane exhibited superior water permeability with a pure water flux of 611.5 ± 19.8 L·m^-2·h^-1 and improved antifouling performance. Moreover, benifiting from photocatalytic activity of the exposed Ni@UiO-66 on membrane surface, the obtained PES-Ni@UiO-66 membrane demonstrated excellent photocatalytic self-cleaning ability with a flux recovery rate (FRR) higher than 95% under UV irradiation. Analyzing by extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory indicated that the improved antifouling performance could be attributed to less attractive or even repulsive interaction between the prepared membrane and pollutants. This work provided valuable guidance for structural regulation and development of high-performance MOFs-based membranes for water treatment.

Influence of the Zeolite ZSM-22 Precursor on a UF-PES Selective Substrate Layer for Salts Rejection

Fabrication of the ZSM-22/Polyethersulfone (ZSM-22/PES) membranes as selective salt filters represent a growing membrane technological area in separation with the potential of high economic reward based on its low energy requirements. The incorporation of ZSM-22 zeolite material as additives into the PES polymer matrix has the prospective advantage of combining both the zeolite and polymer features while overcoming the limitations associated with both materials. This work investigated the influence of the nature of the silica precursor on ZSM-22 zeolite hydrothermally synthesised using colloidal (C60) and fumed (C60) silica to Si/Al of 60. The successful synthesis of the highly crystalline zeolitic materials was confirmed through XRD, FTIR, and SEM with EDX. The ZSM-22 additives were directly dispersed into a PES polymeric matrix to form a casting solution for the preparation of the ZSM-22/PES selective substrate layers via a phase inversion method for salts rejection. The polymeric PES was selected as an organic network in which the content of the ZSM-22 zeolite (ranging between 0 and 1.0 wt.%), was obtained and characterised by XRD, FTIR, and SEM analysis, as well as water contact angle (WCA) measurement and dead-end filtration cell. The phase inversion preparation method has induced the resulting ZSM-22/PES NF substrates anisotropy, as attributed to a high water flux to the above 700 L·m−2·h−1; high selectivity and rejection of salts to above 80% is revealed by the obtained results. The materials also exhibited improved antifouling behavior to above 70% flux recovery ratios. As such, the nature of the silica precursor influences ZSM-22 zeolite synthesis as a potential additive in the PES polymer matrix and led to the enhanced performance of the pure PES ultrafiltration membrane.

Fabrication of silver vanadate quantum dots/reduced graphene oxide/graphitic carbon nitride Z-scheme heterostructure modified polyvinylidene fluoride self-cleaning membrane for enhancing photocatalysis and mechanism insight

The enhancement of the self-cleaning ability of photocatalytic membranes and their degradation efficiency over tetracycline (TC) still remains a challenge. In this study, an alternative silver vanadate quantum dots (AgVO₃ QDs) doped reduced graphene oxide (RGO) and graphitic carbon nitride (C₃N₄) nanocomposites modified polyvinylidene fluoride (PVDF) membrane (AgVO₃/RGO/C₃N₄-PVDF) was successfully fabricated to enhance the photocatalytic activity. The AgVO₃/RGO/C₃N₄ nanocomposites were functioned as the active component for the photocatalytic membrane. The unique Z-scheme heterostructure of AgVO₃/RGO/C₃N₄ and the porous PVDF framework synergistically enhanced the separation and transport efficiency of photogenerated carriers and facilitated the interaction between the photocatalyst and the pollutant. As a result, the degradation efficiency of TC for the AgVO₃/RGO/C₃N₄-PVDF reached 88.53% within 120 min, which was higher than those of the binary component membranes (64.8% for RGO/C₃N₄-PVDF and 79.18% AgVO₃/C₃N₄-PVDF). In addition, AgVO₃/RGO/C₃N₄-PVDF exhibited high permeability (1977 L·m^-2·h^-1·bar^-1) and excellent antifouling activity. Under visible-light irradiation, the flux recovery rate (FRR) increased from 92.4% to 99.1%. Furthermore, AgVO₃/RGO/C₃N₄-PVDF could reject 97.4% of Escherichia coli (E. coli) owning to its self-cleaning capacity, and eliminated the E. coli under visible-light irradiation trough the photogeneration of h⁺. This study highlights a highly efficient photocatalytic membrane based on a Z-scheme heterostructure, which may have a great potential application in practical wastewater treatment.

Discrepant effects of monovalent cations on membrane fouling induced by colloidal polymer: Evaluation and mechanism investigation

Understanding how ionic conditions affect membrane fouling induced by anionic polyacrylamide (APAM) is important for achieving long-term and stable operation of a polymer flooding produced wastewater (PFPW) membrane separation process. However, there is lack of studies on the effects of monovalent cations (Na⁺ and K⁺) on APAM-based membrane fouling. In this work, the effects of Na⁺ and K⁺ on filtration efficiency, flux decline behavior, fouling resistance, and cleaning efficiency were studied through a series of microfiltration tests. Moreover, the influencing mechanism of membrane fouling was further comprehensively revealed from the aspects of the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, the hydration force, and the microstructure characterizations. The XDLVO theory agreed well with membrane fouling behavior at various ionic strengths. The increase in ionic strength (0-10,000 mg/L) of Na⁺ and K⁺ exacerbated the reduction of relative flux (J/J₀) and the accumulation of fouling resistance, as well as made the porous APAM-induced fouling layer denser and more compact, boosting removal efficiency. Furthermore, K⁺ had a stronger aggravating effect on membrane fouling than Na⁺. Specifically, the final value of J/J₀ for APAM+K⁺ (0.08) was lower than that for APAM + Na⁺ (0.12), and the fouling resistance for APAM+K⁺ (12.25 × 10¹¹ m^-1) was higher than that for APAM + Na⁺ (12.01 × 10¹¹ m^-1) at an ionic strength of 10,000 mg/L, which was owing to the larger hydration force caused by Na⁺ with a smaller ionic radius. This research offers practical guidance for the PFPW membrane filtering process.

Self-cleaning expanded polytetrafluoroethylene-based hybrid membrane for water filtration

Membrane surface fouling is a key problem for water filtration. Compositing photocatalytic substances with a base membrane is a widely used strategy, but most of the membrane will be decomposed by photocatalysis. Herein, expanded polytetrafluoroethylene (ePTFE) with extremely stable chemical properties is grafted with polyacrylic acid (PAA) and then modified with titanium dioxide (TiO2) to realize a self-cleaning TiO2-PAA-ePTFE filtration membrane. It can recover its flux under UV irradiation after fouling. With 20 rounds of self-cleaning, the membrane microstructure still remains intact. Moreover, in addition to retaining bovine serum albumin, TiO2 particles on the membrane surface are capable of absorbing small organic pollutants and degrading them. Thus, this membrane is potentially used as an anti-fouling membrane for water filtration.

Integration of membrane processes for the recovery and separation of polyphenols from winery and olive mill wastes using green solvent-based processing

Winery and olive mill industries generate large amounts of wastes causing important environmental problems. The main aim of this work is the evaluation of different membrane separation processes like microfiltration, ultrafiltration, nanofiltration, and reverse osmosis for the recovery of polyphenols from winery and olive mill wastes in aqueous solutions. Membrane processes were tested separately in a closed-loop system, and by an integration in a concentration mode sequential design (open-loop). Feed flow rate was varied from 1 to 10 mL min^-1, and permeate samples were taken in order to measure the polyphenols concentration. The separation and concentration efficiency were evaluated in terms of total polyphenol content, and by polyphenols families (hydroxybenzoic acids (HB), hydroxycinnamic acids (HC), and flavonoids (F)), using high performance liquid chromatography. Results showed that MF and UF membranes removed suspended solids and colloids from the extracts. NF was useful for polyphenols separation (HB rejections were lower than for HC and F: HB rejections of 50 and 63% for lees filters and olive pomace extracts, respectively), and RO membranes were able to concentrate polyphenols streams (86 and 95% rejection from lees filters and olive pomace, respectively). Membranes sequential designs for lees filters and olive pomace extracts, using a selective membrane train composed by UF, NF and RO membranes, were able to obtain polyphenol rich streams and high-quality water streams for reuse purposes.

Photocatalytic membranes: a new perspective for persistent organic pollutants removal

The presence of conventional and emerging pollutants infiltrating into our water bodies is a course of concern as they have seriously threatened water security. Established techniques such as photocatalysis and membrane technology have proven to be promising in removing various persistent organic pollutants (POP) from wastewaters. The emergence of hybrid photocatalytic membrane which incorporates both photocatalysis and membrane technology has shown greater potential in treating POP laden wastewater based on their synergistic effects. This article provides an in-depth review on the roles of both photocatalysis and membrane technology in hybrid photocatalytic membranes for the treatment of POP containing wastewaters. A concise introduction on POP's in terms of examples, their origins and their effect on a multitude of organisms are critically reviewed. The fundamentals of photocatalytic mechanism, current directions in photocatalyst design and their employment to treat POP's are also discussed. Finally, the challenges and future direction in this field are presented.

Antifouling Fibrous Membrane Enables High Efficiency and High-Flux Microfiltration for Water Treatment

Membrane biofouling has long been a major obstacle to highly efficient water treatment. The modification of the membrane surface with hydrophilic materials can effectively enhance biofouling resistance. However, the water flux of the membranes is often compromised for the improvement of antifouling properties. In this work, a composite membrane composed of a zwitterionic hydrogel and electrospinning fibers was prepared by a spin-coating and UV cross-linking process. At the optimum conditions, the composite membrane could effectively resist the biofouling contaminations, as well as purify polluted water containing bacteria or diatoms with a high flux (1349.2 ± 85.5 L m^-2 h^-1 for 10⁶ CFU mL^-1 of an Escherichia coli solution). Moreover, compared with the commercial poly(ether sulfone) (PES) membrane, the membrane displayed an outstanding long-term filtration performance with a lower water flux decline. Therefore, findings in this work provide an effective antifouling modification strategy for microfiltration membranes and hold great potential for developing antifouling membranes for water treatment.

Fabrication, Optimization, and Performance of a TiO2 Coated Bentonite Membrane for Produced Water Treatment: Effect of Grafting Time

The main problem usually faced by commercial ceramic membranes in the treatment of produced water (PW) is low water flux even though ceramic membrane was well-known with their excellent mechanical, thermal, and chemical properties. In the process of minimizing the problem faced by commercial ceramic membranes, titanium dioxide (TiO₂) nanocomposites, which synthesized via a sol-gel method, were deposited on the active layer of the hydrolysed bentonite membrane. This paper studied the influence of grafting time of TiO₂ nanocomposite on the properties and performance of the coated bentonite membranes. Several characterizations, which are Fourier transform infrared (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray Spectroscopy (EDX), contact angle, porosity, and average pore size, were applied to both pristine and coated bentonite membranes to compare the properties of the membranes. The deposition of TiO₂ nanoparticles on the surface of the coated bentonite membranes was successfully confirmed by the characterization results. The pure water flux performance showed an increment from 262.29 L h⁻¹ m⁻² bar⁻¹ (pristine bentonite membrane) to 337.05 L h⁻¹ m⁻² bar⁻¹ (Ti-Ben 30) and 438.33 L h⁻¹ m⁻² bar⁻¹ (Ti-Ben 60) as the grafting time increase but when the grafting time reached 90 min (Ti-Ben 90), the pure water flux was decreased to 214.22 L h⁻¹ m⁻² bar⁻¹ which is lower than the pristine membrane. The oil rejection performance also revealed an increase in the oil rejection performance from 95 to 99%. These findings can be a good example to further studies and exploit the advantages of modified ceramic membranes in PW treatment.

Magnetic field-influenced nanofiltration membrane blended by CS-EDTA-mGO as multi-functionality green modifier to enhance nanofiltration performance, efficient removal of Na2SO4/Pb2+/RR195 and cyclic wastewater treatment

Magnetic field-influenced nanofiltration membrane by blending of magnetic multi-functionality green modifier (CS-EDTA-mGO) was fabricated via phase inversion processes. Migration of superparamagnetic nanofiller particles into top surface layer of M6 NF-membrane by incorporating external magnetic-filed during casting phase improved the hydrophilicity, as well as formation of large pores diameters (1.57 nm) which offer a flux enhancement (84.2 kg/m²h), excellent fouling resistance (R_r of 26.4%, R_t of 39.4% and R_ir of 25.0%) and highest flux recovery ratio (75.9%). The order of salt rejection for all modified NF-membranes was Na₂SO₄ > MgSO₄ > NaCl and the efficiency of the membranes to reject salts follows the order of M6 > M4 > M0. The performance of M6 as magnetic field-influenced membrane in rejection of RR195 and MB was 21% and 42% higher than unblended membrane (M0), respectively. The highest removal efficiency of Pb²⁺ and Cd²⁺ observed for M6 (98.2% and 93.6%, respectively). M6 was more efficient in concurrent removing pollutants from mixed-solute feed. In this case, the existing of Na₂SO₄ enhanced the retention of RR195 from 97.2% to 99.3%. Long-term operation tests demonstrated the excellent stability of M6 for 18 h filtration with a limited reduction in rejection and water flux of single salt solution. M6 membrane has found potential application in cyclic textile wastewater treatment which the water flux was found to be constant over 3-repeated filtration cycles.

Prospects of Synthesized Magnetic TiO2-Based Membranes for Wastewater Treatment: A Review

Global accessibility to clean water has stressed the need to develop advanced technologies for the removal of toxic organic and inorganic pollutants and pathogens from wastewater to meet stringent discharge water quality limits. Conventionally, the high separation efficiencies, relative low costs, small footprint, and ease of operation associated with integrated photocatalytic-membrane (IPM) technologies are gaining an all-inclusive attention. Conversely, photocatalysis and membrane technologies face some degree of setbacks, which limit their worldwide application in wastewater settings for the treatment of emerging contaminants. Therefore, this review elucidated titanium dioxide (TiO2), based on its unique properties (low cost, non-toxicity, biocompatibility, and high chemical stability), to have great potential in engineering photocatalytic-based membranes for reclamation of wastewater for re-use. The environmental pathway of TiO2 nanoparticles, membranes and configuration types, modification process, characteristics, and applications of IPMs in water settings are discussed. Future research and prospects of magnetized TiO2-based membrane technology is highlighted as a viable water purification technology to mitigate fouling in the membrane process and photocatalyst recoverability. In addition, exploring life cycle assessment research would also aid in utilizing the concept and pressing for large-scale application of this technology.

Drawing on Membrane Photocatalysis for Fouling Mitigation

Photocatalysis is an effective and environmentally friendly approach for degrading organic pollutants, particularly in scenarios where sunlight can be utilized as the energy source. Opportunities are emerging to apply materials and methods from photocatalytic pollutant degradation to address the challenge of fouling. Membrane fouling, attributed to organic foulants, is a prevalent problem for all membrane-based technologies and represents a major deleterious impact on membrane performance. Integration of tactics developed in photocatalysis more broadly to membranes reveals new strategies for membrane fouling control-an approach taken by an increasing number of researchers. This review summarizes key developments in photocatalytic materials and methods in water treatment and presents recent progress in the development of processes for photocatalytic alleviation of membrane fouling, including photocatalyst design and modification strategies aimed at enhancing photocatalytic efficiency, as well as different configurations of photocatalysis-membrane systems (PMS). Perspectives on future research and development opportunities for photocatalytic membrane fouling control are also provided.

Flexible-templated imprinting for fluorine-free, omniphobic plastics with re-entrant structures

HYPOTHESIS

Compared to vertical micro-pillars, re-entrant micro-structures exhibited superior omniphobicity for suspending liquids to Cassie-Baxter state. However, the existing re-entrant structures rely on complex multi-step deposition and etching procedures. The conventional, rigid-templated imprinting would instead damage the re-entrant structures. This leads to the question: is it possible to preserve the re-entrant curvatures by a flexible-templated imprinting?

EXPERIMENTS

We facilely imprinted the re-entrant structures on a plastic substrate using a flexible nylon-mesh template. The effect of imprinting time (15-35 min), temperature (110-120 °C) and pressure (15-50 Bar) was investigated. To further improve the liquid-repellency and abrasion resistance, the silica nanoparticles (30-650 nm) along with epoxy resin binder (10 mg/mL) were pre-coated.

FINDINGS

A one-step imprinting is sufficient to fabricate the re-entrant structures by utilizing flexible nylon-mesh template, without damaging the imprinted structures after the demolding process. The pre-coated silica nanoparticles and epoxy resin (1) improved liquid repellency by introducing hierarchical surface structures (e.g. contact angle hysteresis of olive oil reduced > 10°), and (2) acted as a protective layer against mechanical abrasion (omniphobicity maintained after 25 cycles, ~1.6 kPa sand paper abrasion). Additionally, the fluorine-free post-treatment was sufficient for the omniphobicity on the obtained plastic structures.

Flame-retardant ethylene vinyl acetate composite materials by combining additions of aluminum hydroxide and melamine cyanurate: Preparation and characteristic evaluations

There is a great interest to develop efficient fire-resistant materials. While ethylene vinyl acetate (EVA) is a widely used material, it suffers from the problem of relatively high inflammability which seriously hinders its usage as the product material with a high flame-retardant requirement. In this study, a strategy to combine aluminum hydroxide (ATH) and melamine cyanurate (MCA) with EVA was proposed to prepare the EVA composite materials with high flame resistance. It was found that slight addition of MCA could increase the lubricity of EVA and raise the compatibility between EVA and ATH. Thermogravimetric analysis (TGA) indicated that the thermal stability of EVA was improved via adding MCA, which was evidenced by the delayed thermal decomposition temperature. Moreover, the combustion results indicated that the EVA composite with 60 parts per hundred (phr) ATH and 40 phr MCA addition (EVA-60-40) displayed the optimal isolated layer favoring the fire resistance. In addition, the highest limiting oxygen index (LOI) value (27.5%) and V-0 rating of the EVA-60-40 as compared with other components indicated its incombustible nature. These results suggested the synergetic effect of ATH and MCA additions, the high efficiency of the proposed strategy and the wide application prospect of the produced EVA-ATH-MCA composite materials.