In situ metal-polyphenol interfacial assembly tailored superwetting PES/SPES/MPN membranes for oil-in-water emulsion separation

Solvation enabled highly efficient gradient assembly creates robust metal-phenolic coatings

Metal-phenolic networks (MPNs) are supramolecular materials that have received interest in various fields, including biomedicine, separations, environmental remediation, and catalysis. Despite recent advances, the construction of thick and robust MPN coatings that withstand harsh conditions (e.g., acidic, alkaline) remains challenging. In addition, the interfacial assembly of MPNs in mixed solvents (e.g., water and nonaqueous solvents) has not been investigated. Herein, a solvent-regulated (water/ethylene glycol) gradient assembly strategy that can regulate the coordination kinetics of MPNs to realize thick (up to 1.5 μm) and robust MPN coatings on various substrates is presented. Through mediating interactions between polyphenols, a balance is achieved between the aggregation, precipitation, and continuous assembly of well-dispersed precursors. The gradient assembly of polyphenols and metal ions results in lateral and longitudinal cross-linking leading to the formation of robust MPN coatings. The potential application of the coatings in oil/water separation is demonstrated by their excellent performance (oil intrusion pressure of 2.0 kPa and water flux of 2.59 × 105 L m-2h-1), long-term stability, tolerance to various harsh conditions, and thick oil fouling. This study provides further insight into the assembly mechanism of MPNs.

Preparation of hydrophilic PVDF membranes through in situ assembly of phytate-polyethyleneimine-Fe3+ for efficient separation of herbal volatile oil from oily water

In the realm of oil-water separation technologies, membrane-based separation emerges as an efficacious approach. Nevertheless, crafting a hydrophilic membrane capable of effectively segregating herbal volatile oil remains a formidable challenge. Our study introduces a facile in situ assembly strategy for fabricating a double-crosslinked composite coating comprising phytate (PA)-polyethyleneimine (PEI) polyelectrolyte complexes and PA-Fe3⁺ assemblies. The PA within the PA-PEI/Fe3⁺ coatings form a double cross-linking layer through interactions with amine groups and metal ions, thereby enhancing interfacial interactions and structural integrity of the membranes. Consequently, the resultant PVDF/PA-PEI/Fe3⁺ membranes exhibit improved coating stability, pronounced hydrophilicity, and exceptional antifouling capabilities, rendering them highly suitable for the separation of diverse herbal volatile oil-in-water emulsions. Furthermore, they possess the capability for reuse with an average retention ratio exceeding 90% and a pure water flux reaching up to 3200 L·m⁻2·h⁻1. Additionally, they demonstrate long-term stability and resistance to corrosion. With a simplistic yet efficient preparation process, the PVDF/PA-PEI/Fe3⁺ membrane holds significant potential for the extraction of oils from herbal volatile oil-in-water emulsions.

Research Progress on Membrane Separation Technology for Oily Wastewater Treatment

This paper presents the research progress and future prospects of membrane separation technology for treating oily wastewater. It discusses various treatment methods tailored to different sources and characteristics of oily wastewater, summarizing the features of different membrane separation technologies and the latest advancements in their application. The paper concludes by emphasizing the need for future research to focus on developing environmentally friendly and efficient coupled membrane treatment technologies, optimizing membrane material design and enhancing the environmental benefits of oily wastewater treatment.

A pH-Responsive Drug-Delivery System Based on Apatinib-Loaded Metal-Organic Frameworks for Ferroptosis-Targeted Synergistic Anti-Tumor Therapy

Purpose

The efficacy of systemic therapy for hepatocellular carcinoma (HCC) is limited mainly by the complex tumor defense mechanism and the severe toxic side-effects of drugs. The efficacy of apatinib (Apa), a key liver cancer treatment, is unsatisfactory due to inadequate targeting and is accompanied by notable side-effects. Leveraging nanomaterials to enhance its targeting represents a crucial strategy for improving the effectiveness of liver cancer therapy.

Patients and Methods

A metal polyphenol network-coated apatinib-loaded metal-organic framework-based multifunctional drug-delivery system (MIL-100@Apa@MPN) was prepared by using metal-organic frameworks (MOFs) as carriers. The nanoparticles (NPs) were subsequently characterized using techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), zeta potential measurements, and particle size analysis. In vitro experiments were conducted to observe the drug release kinetics and cytotoxic effects of MIL-100@Apa@MPN on HepG2 cells. The in vivo anti-tumor efficacy of MIL-100@Apa@MPN was evaluated using the H22 tumor-bearing mouse model.

Results

The formulated MIL-100@Apa@MPN demonstrates remarkable thermal stability and possesses a uniform structure, with measured drug-loading (DL) and encapsulation efficiency (EE) rates of 28.33% and 85.01%, respectively. In vitro studies demonstrated that HepG2 cells efficiently uptake coumarin-6-loaded NPs, and a significant increase in cumulative drug release was observed under lower pH conditions (pH 5.0), leading to the release of approximately 73.72% of Apa. In HepG2 cells, MIL-100@Apa@MPN exhibited more significant antiproliferative activity compared to free Apa. In vivo, MIL-100@Apa@MPN significantly inhibited tumor growth, attenuated side-effects, and enhanced therapeutic effects in H22 tumor-bearing mice compared to other groups.

Conclusion

We have successfully constructed a MOF delivery system with excellent safety, sustained-release capability, pH-targeting, and improved anti-tumor efficacy, highlighting its potential as a therapeutic approach for the treatment of HCC.

Chelation-directed interface engineering of in-place self-cleaning membranes

Water-energy sustainability will depend upon the rapid development of advanced pressure-driven separation membranes. Although energy-efficient, water-treatment membranes are constrained by ubiquitous fouling, which may be alleviated by engineering self-cleaning membrane interfaces. In this study, a metal-polyphenol network was designed to direct the armorization of catalytic nanofilms (ca. 18 nm) on inert polymeric membranes. The chelation-directed mineralized coating exhibits high polarity, superhydrophilicity, and ultralow adhesion to crude oil, enabling cyclable crude oil-in-water emulsion separation. The in-place flux recovery rate exceeded 99.9%, alleviating the need for traditional ex situ cleaning. The chelation-directed nanoarmored membrane exhibited 48-fold and 6.8-fold figures of merit for in-place self-cleaning regeneration compared to the control membrane and simple hydraulic cleaning, respectively. Precursor interaction mechanisms were identified by density functional theory calculations. Chelation-directed armorization offers promise for sustainable applications in catalysis, biomedicine, environmental remediation, and beyond.

Engineering In Situ Catalytic Cleaning Membrane Via Prebiotic-Chemistry-Inspired Mineralization

Pressure-driven membrane separation promises a sustainable energy-water nexus but is hindered by ubiquitous fouling. Natural systems evolved from prebiotic chemistry offer a glimpse of creative solutions. Herein, a prebiotic-chemistry-inspired aminomalononitrile (AMN)/Mn2+ -mediated mineralization method is reported for universally engineering a superhydrophilic hierarchical MnO2 nanocoating to endow hydrophobic polymeric membranes with exceptional catalytic cleaning ability. Green hydrogen peroxide catalytically triggered in-situ cleaning of the mineralized membrane and enabled operando flux recovery to reach 99.8%. The mineralized membrane exhibited a 9-fold higher recovery compared to the unmineralized membrane, which is attributed to active catalytic antifouling coupled with passive hydration antifouling. Electron density differences derived from the precursor interaction during mediated mineralization unveiled an electron-rich bell-like structure with an inner electron-deficient Mn core. This work paves the way to construct multifunctional engineered materials for energy-efficient water treatment as well as for diverse promising applications in catalysis, solar steam generation, biomedicine, and beyond.

Separation Performance of Membranes Containing Ultrathin Surface Coating of Metal-Polyphenol Network

Metal-polyphenol networks (MPNs) are being used as versatile coatings for regulating membrane surface chemistry and for the formation of thin separation layers. The intrinsic nature of plant polyphenols and their coordination with transition metal ions provide a green synthesis procedure of thin films, which enhance membrane hydrophilicity and fouling resistance. MPNs have been used to fabricate tailorable coating layers for high-performance membranes desirable for a wide range of applications. Here, we present the recent progress of the use of MPNs in membrane materials and processes with a special focus on the important roles of tannic acid-metal ion (TA-Mⁿ⁺) coordination for thin film formation. This review introduces the most recent advances in the fabrication techniques and the application areas of TA-Mⁿ⁺ containing membranes. In addition, this paper outlines the latest research progress of the TA-metal ion containing membranes and summarizes the role of MPNs in membrane performance. The impact of fabrication parameters, as well as the stability of the synthesized films, is discussed. Finally, the remaining challenges that the field still faces and potential future opportunities are illustrated.

Interfacial Polymerization on Polyethersulfone Ultrafiltration Membrane to Prepare Nanofiltration Layers for Dye Separation

Nanofiltration membranes are of great significance to the treatment of dye wastewater. Interfacial polymerization is a widely used method to fabricate nanofiltration membranes. In this study, the interaction of tannic acid-assisted polyethylene polyamine (PEPA) with terephthalaldehyde (TPAL) was performed on PES ultrafiltration membranes using novel nitrogen-rich amine monomers and relatively less reactive aldehyde-based monomers. A new nanofiltration membrane ((T-P-T)/PES) was prepared by interfacial polymerization. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy were used to analyze the elemental composition, bonding state, and surface morphology of the membrane surface. The effects of the PEPA deposition time, TPAL concentration, interfacial reaction time, and curing time on the nanofiltration layer were investigated. The modified membrane, prepared under optimal conditions, showed strong dye separation ability. The permeation of the modified membrane could reach 68.68 L·m^-2·h^-1·bar^-1, and the rejection of various dyes was above 99%. In addition, the (T-P-T)/PES membrane showed good stability during long-term dye separation.

A high-protein retained PES hemodialysis membrane with tannic acid as a multifunctional modifier

A high protein retention polyethersulfone (PES) membrane was prepared by nonsolvent-induced phase separation and surface coating, which exhibited enhanced hemocompatibility and antioxidant stress performance. The cross-linked network was constructed by tannic acid (TA) and alpha-lipoic acid (α-LA) on the surface of the membrane, which controlled the pores to a reasonable size. The enrichment of heparin-like groups on the membrane surface, implemented by "hydrophobic interaction" and "click reaction", confers anticoagulant properties; the presence of a large number of phenolic hydroxyl groups from TA and the introduction of α-LA allows the modified membranes to intervene in oxidative stress. The hemocompatibility characterizations included plasma recalcification time (PRT), activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT) and hemolysis rate (HR). Additionally, the DPPH ABTS radical scavenging capacity was tested to evaluate the antioxidant performance. The results show that the modified membrane presents an outstanding protein retention rate (99.3%) along with permeability. In addition, the PRT is prolonged to 341.7 s, and the DPPH• scavenging ability reaches 0.74 µmol•cm-2. The membranes can be easily prepared and present excellent comprehensive performance. This work provides a simple and facile strategy for the fabrication of hemodialysis membranes with controllable pore sizes.

Preparation of Porous Silicate Cement Membranes via a One-Step Water-Based Hot-Dry Casting Method

A commercial interest in the improvement in the separation performance and permeability of porous materials is driving efforts to deeply explore new preparation methods. In this study, the porous silicate cement membranes (PSCMs) were successfully prepared through an adjustable combination of hot-dry casting and a cement hydration process. The obtained membrane channel was unidirectional, and the surface layer was dense. The physical characteristics of the PSCMs including their pore morphology, porosity, and compressive strength, were diversified by adjusting the solid content and hot-dry temperature. The results indicated that with the solid content increasing from 40 wt. % to 60 wt. %, the porosity decreased by 8.07%, while the compressive strength improved by 12.46%. As the hot-dry temperature increased from 40 °C to 100 °C, the porosity improved by 23.04% and the BET specific surface area and total pore volume enlarged significantly, while the compressive strength decreased by 27.03%. The pore size distribution of the PSCMs exhibited a layered structure of macropores and mesopores, and the pore size increased with the hot-dry temperature. Overall, the PSCMs, which had typical structures and adjustable physical characteristics, exhibited excellent permeability and separation performance.

Metal Ion-Directed Functional Metal-Phenolic Materials

Metal ions are ubiquitous in nature and play significant roles in assembling functional materials in fields spanning chemistry, biology, and materials science. Metal-phenolic materials are assembled from phenolic components in the presence of metal ions through the formation of metal-organic complexes. Alkali, alkali-earth, transition, and noble metal ions as well as metalloids interacting with phenolic building blocks have been widely exploited to generate diverse hybrid materials. Despite extensive studies on the synthesis of metal-phenolic materials, a comprehensive summary of how metal ions guide the assembly of phenolic compounds is lacking. A fundamental understanding of the roles of metal ions in metal-phenolic materials engineering will facilitate the assembly of materials with specific and functional properties. In this review, we focus on the diversity and function of metal ions in metal-phenolic material engineering and emerging applications. Specifically, we discuss the range of underlying interactions, including (i) cation-π, (ii) coordination, (iii) redox, and (iv) dynamic covalent interactions, and highlight the wide range of material properties resulting from these interactions. Applications (e.g., biological, catalytic, and environmental) and perspectives of metal-phenolic materials are also highlighted.

Antifouling BaTiO3/PVDF piezoelectric membrane for ultrafiltration of oily bilge water

Barium titanate/polyvinylidene fluoride (BaTiO₃/PVDF) piezoelectric membrane was successfully prepared and generated in-situ vibrations to reduce membrane fouling by applying alternating current (AC) signal for oily bilge water ultrafiltration. The effect of in-situ vibration on membrane fouling was investigated through changing in the excitation alternating voltage and its frequency, pH, crossflow rate. The results indicated that the piezoelectric membrane by applying AC signal remarkably alleviated the membrane fouling for bilge water ultrafiltration. The membrane fouling decreased with increasing the AC signal voltage. The final steady-state permeate flux from the piezoelectric membrane for bilge water ultrafiltration increased with the AC signal voltage, raising it by up to 63.4% at AC signal voltage of 20 V compared to that of the membrane without applying AC voltage. The high permeate flux was obtained at the resonant frequency of 220 kHz. During the 50-h ultrafiltration of bilge water with the piezoelectric membrane excited at 220 kHz and 15 V, the permeate flux from the membrane was stable. The oil concentration in outflow from the piezoelectric membrane was below 14 ppm, which met the discharged level required by IMO convention. The total organic carbon removal rate in bilge water was over 94%.

Modified Polyethersulfone Ultrafiltration Membrane for Enhanced Antifouling Capacity and Dye Catalytic Degradation Efficiency

Catalytic membranes, as a combination of heterogeneous advanced oxidation and membrane technology reaction systems, have important application prospects in the treatment of dyes and other organics. In practical applications, it is still challenging to construct catalytic membranes with excellent removal efficiency and fouling mitigation. Herein, molybdenum disulfide-iron oxyhydroxide (MoS2-FeOOH) was fabricated using iron oxide and MoS2 nanoflakes, which were synthesized by the hydrothermal method. Furthermore, by changing the concentration of MoS2-FeOOH, the MoS2-FeOOH/polyethersulfone (PES) composite ultrafiltration membrane was obtained with improved hydrophilicity, permeability, and antifouling capacity. The pure water flux of the composite membrane reached 385.3 L/(m2 h), which was 1.7 times that of the blank PES membrane. Compared with the blank membrane, with the increase of MoS2-FeOOH content, the MoS2-FeOOH/PES composite membranes had better adsorption capacity and catalytic performance, and the membrane with 3.0% MoS2-FeOOH content (M4) could be achieved at a 60.2% methylene blue (MB) degradation rate. In addition, the membrane flux recovery ratio (FRR) of the composite membrane also increased from 25.6% of blank PES membrane (M0) to more than 70% after two cycles of bovine serum albumin (BSA) filtration and hydraulic cleaning. The membrane with 2.25% MoS2-FeOOH content (M3) had the best antifouling performance, with the largest FRR and the smallest irreversible ratio (Rir). Catalytic self-cleaning of the composite membrane M3 recovered 95% of the initial flux with 0.1 mol/L H2O2 cleaning. The MoS2-FeOOH/PES composite membranes with the functions of excellent rejection and antifouling capacity have a good prospect in the treatment of printing and dyeing wastewater composed of soluble dyes.

Superhydrophilic polyethersulfone (PES) membranes with high scale inhibition properties obtained through bionic mineralization and RTIPS

Reverse thermally induced separation (RTIPS) was used to obtain a separation membrane with a better internal structure for a higher water flux and a surface that could easily form a hydration layer. In comparison to the traditional modification method, this work focused on the aspect that the internal structure obtained by changing the membrane-making method provided easier adhesion conditions for the dopamine/TiO₂ hybrid nanoparticles (DA/TiO₂ HNPs) obtained by biomimetic mineralization. It provided a basis for exploring the variation in adhesion with the water bath temperature and the amount of titanium added through the study of turbidity point, SEM images, water contact angle, thermogravimetric test, EDX, AFM, XPS, FTIR and other test results. The SEM images proved that the membrane obtained through the RTIPS method had a porous surface and spongy internal structure, furthermore, additional polymers were adsorbed. Use of EDX demonstrated that biomimetic mineralization prevented the production of agglomerated titanium dioxide. XPS and FTIR spectra confirmed the introduction and immobilization of HNP aggregation. Moreover, a decrease in the surface roughness and water contact angle further suggested an improvement in the hydrophilicity of the modified membrane. The introduction of HNP at a higher water bath temperature helped increase the water flux up to ten times, moreover, the oil-water separation efficiency could still reach over 99.50%. Lastly, a cycle test of the modified membrane under the optimal conditions helped confirm that the membrane forming conditions at this time could provide a better environment for the formation of the hydrophilic layer, which was conducive to the recycling of the separation membrane. In summary, more fixed more hydrophilic particles could be obtained through the RTIPS method based on biomimetic mineralization to prevent the accumulation of titanium dioxide, thus helping improve permeability and anti-fouling of the membrane.

Recent Progress in Microfiltration/Ultrafiltration Membranes for Separation of Oil and Water Emulsions

Oily wastewater has become one of the leading causes of environmental pollution. A massive quantity of oily wastewater is released from industries, oil spills, and routine activities, endangering the ecosystem's sustainability. Due to the enormous negative impact, researchers put strenuous efforts into developing a sustainable solution to treat oily wastewater. Microfiltration/ultrafiltration membranes are considered an efficient solution to treat oily wastewater due to their low cost, small footprint, facile operation, and high separation efficiencies. However, membranes severely fouled during the separation process due to oil's adsorption and cake layer formation, which shortens the membranes' life. This review has critically discussed the microfiltration/ultrafiltration membrane synthesizing methods and their emulsion's separation performance. In the end, key challenges and their possible solutions are highlighted to provide future direction to synthesize next-generation membranes.

Bimetallic polyphenol networks structure modified polyethersulfone membrane with hydrophilic and anti-fouling properties based on reverse thermally induced phase separation method

In order to improve the hydrophobicity of traditional polyethersulfone (PES) membranes, this study combined the reverse thermally induced phase separation (RTIPS) method with the constructed bimetallic polyphenol networks (BMPNs) to prepare hydrophilic anti-fouling membranes. As for BMPNs, tannic acid (TA) was served as an intermediate to construct both the inner and surface hydrophilic layers of the PES membranes. On the one hand, etching Zeolitic imidazolate framework-8 (EZIF-8) with synergistic etching and surface functionalization via TA not only retained the high pore structure of MOFs, but also had good hydrophilicity. On the other hand, the MPN hydrophilic layer was formed on the membrane surface by the combination of TA from the surface of EZIF-8 and iron ions in the coagulation bath. Therefore, BMPNs structure penetrated the interior and surface of PES membrane, which greatly improved the hydrophilic properties. In addition, the membrane with porous surfaces and spongy cross sections by RTIPS method improved the permeability and mechanical properties of the membrane by several times compared with the membrane via NIPS method. The obtained membranes in this experiment showed excellent permeability, just like pure water flux reached 1662.16 L/m² h, while BSA rejection rate remained at 92.78%. Compared with pure membrane, it showed a better flux recovery rate (FRR = 83.33%) after cleaning, and the reduction of irreversible (R_ir = 16.67%) fouling indexes indicated that the adsorption of protein was inhibited. These results suggested that the hydrophilic anti-fouling PES membranes prepared by this method possessed great application potential in membrane separation technology.

Tannic acid-based functional coating: surface engineering of membranes for oil-in-water emulsion separation

Recent progress in the tannic acid-based functional coating for surface engineering of membranes toward oil-in-water emulsion separation is summarized.

Comprehensive Electrokinetic-Assisted Separation of Oil Emulsion with Ultrahigh Flux

Many industries have a significant but largely unmet need for efficient and high-flux emulsion separation, particularly for nanoemulsions. Conventional separation membranes rely on size-based separation mainly utilizing a sieving mechanism plus a wetting phenomenon, resulting in a dramatic trade-off between separation efficiency and separation flux. Herein we address this challenge by adapting electrokinetics to membrane-based separation, using a charge-based mechanism capable of separating even nanoemulsions with a demonstrated separation efficiency of >99% and ultrahigh flux up to 40 000 L/H·m². Our device arrests nano-oil droplets, allowing them to coalesce into larger droplets which are then able to be filtered by coarser membranes. This hybrid technology makes electrokinetic-assisted filtration scalable and commercially viable and allows for a better understanding of the multiphysics underlying dynamic separation.

A dual-functional layer modified GO@SiO2 membrane with excellent anti-fouling performance for continuous separation of oil-in-water emulsion

As the most significant target of membrane separation, the inadequacy of permeability and anti-fouling frequently constrain the application of the membrane in actual oily wastewater. Herein, a novel concept of membrane surface construction was proposed to mitigate this intractable problem, using SiO₂ as the support layer and graphene oxide (GO) as the isolation layer. The best co-localization proportion of the support layer (56 mg/L) and isolation layer (3.5 mg/L) was determined by the separation performance of the modified membranes for the simulated emulsion. The thin GO layer could effectively prevent contaminants from entering the membrane pores without affecting its roughness. Based on the synergistic action of the isolation layer and support layer, the GO@SiO₂ membrane could well implement emulsion purification with a stable permeability (654.11 LMHB) and high separation efficiency (99.41%). The superior anti-fouling performance of the membrane ensures its long-term cycling stability, with the permeability recovery rate of 89.75% (low-density oil) and 90.41% (high-density oil) after 10 repeated cycles. The storage stability also indirectly increases its value in practical applications. More importantly, the GO@SiO₂ membrane also shows great potential for industrial emulsion treatment with excellent purification and cycling stability (permeability recovery rate of 84.01%).

Mussel-inspired triple bionic adsorbent: Facile preparation of layered double hydroxide@polydopamine@metal-polyphenol networks and their selective adsorption of dyes in single and binary systems

To effectively address the serious human health challenges and ecological damage caused by organic dyes in wastewater, we developed a novel bionic adsorbent (LDH@PDA@MPNs) for the selective adsorption and removal of malachite green (MG) and crystalline violet (CV). The adsorbent was prepared using a facile two-step method based on mussel-inspired chemistry and metal complexation. The physicochemical structure, surface morphology, and composition of the LDH@PDA@MPNs were characterized by scanning electron microscopy, Fourier-transform infrared spectrometry, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Adsorption of MG and CV with the LDH@PDA@MPNs was evaluated. Under optimal conditions, the maximum adsorption of MG and CV by the adsorbent was 89.608 and 40.481 mg/g, respectively. The adsorption kinetics showed that the experimental data were in good agreement with the pseudo-second-order kinetic model, and the equilibrium adsorption isotherm data fitted well with the Freundlich model. The thermodynamic results indicated that the adsorption of the dyes on LDH@PDA@MPNs was a spontaneous endothermic process. Importantly, the bionic adsorbent not only shows high removal efficiency by easy regeneration with low-cost reagents but also exhibits high selectivity for dyes in both single and binary systems. Therefore, LDH@PDA@MPNs have the potential to adsorb and remove dyes from complex wastewater solutions.

Efficient Fenton-Like Catalysis Boosting the Antifouling Performance of the Heterostructured Membranes Fabricated via Vapor-Induced Phase Separation and In Situ Mineralization

A photocatalytic membrane with significant degradation and antifouling performance has become an important part in wastewater treatment. However, the low catalyst loading on the polymer membrane limits its performance improvement. Herein, we fabricated poly(vinylidene fluoride) (PVDF) and poly(acrylic acid) (PAA) blend membranes with a rough surface via a vapor-induced phase separation (VIPS) process. Then Fe³⁺ was cross-linked with the carboxyl groups on the membrane surface and further in situ mineralized into β-FeOOH nanorods. The resultant membranes exhibit not only hydrophilicity and underwater superoleophobicity but also favorable separation efficiency and high water flux in oil-in-water emulsions separation. Under visible light irradiation, the membrane can degrade methylene blue (MB) to 95.2% in 180 min. More importantly, the membrane has a significant photocatalytic self-cleaning ability for crude oil with a flux recovery ratio (FRR) as high as 94.1%. This work brings a new strategy to fabricate the rough and porous surface for high loading of the hydrophilic photo-Fenton catalyst, improving the oil/water emulsion separation and antifouling performance of the membranes.

Influence of UV-irradiation intensity and exposure duration on the hemobiocompatibility enhancement of a novel synthesized phosphobetaine zwitterions polyethersulfone clinical hemodialysis membranes

To improve the biocompatibility of polyethersulfone (PES) membranes utilized for biomedical hemodialysis (HD) applications, surface grafting with hydrophilic polymers has become a reliable modification strategy. Like most photochemical catalyzed reactions, UV-assisted grafting is distinctly advantageous for inducing permanent surface chemistry, enhancing hydrophilicity, improving morphology, and surface charge of membranes. PES membranes may be hydrophilic and chemically stable; however, they also have low protein-binding capacity and very susceptible to fouling and target analyte binding. In this study, novel zwitterionic polymers (PVP-ZW) have been synthesized by UV-assisted grafting PVP to a phosphobetaine monomer in a reaction involving dimethylamino and dioxaphospholane-2-oxide terminal groups in an NVP monomer solution at varying UV exposure conditions. The highlight of the present study is the investigation of the hemocompatibility of coated PES HD membranes at varying UV exposure conditions with respect to membrane chemistry and morphology and its influence on human serum protein adsorption. A clinical investigation of inflammatory biomarker release from incubated coated membranes within uremic blood samples of HD patients reveals they are weak complement and coagulation activators compared to bare PES membrane. The trend of fibrinogen adsorption on coated PES membranes was observed to increase with reducing UV intensity and exposure duration. Fibrinogen adhesion only increased with roughened membrane surfaces, and this also led to the formation of biological activation pathways hindering biocompatibility. Resistance against fibrinogen absorption on zwitterionic modified PES membrane could be linked with the creation of electrostatically induced neutral zwitterionic PVP-phosphobetaine hydration layer with hydrophilic character. Experimental results are accompanied by spectroscopic and morphological imaging evidence. Zwitterion coated PES membranes (PES-PVP-ZW) fabricated from higher UV intensities through longer exposure durations showed significant presence of surface deformations in the forms of inherent exfoliations due to harsh UV reaction conditions. The zeta potential and surface roughness of coated membranes also played significant role in the fibrinogen adsorption on PES membranes during ultrafiltration.

Synchronous removal of emulsions and organic dye over palladium nanoparticles anchored cellulose-based membrane

Membrane is a considerable precursor for emulsions separation and organic dyes degradation used in water purification and oil reclamation. However, the tedious preparation method, the surface smears easily, and low degradation efficiency, these characteristics usually significantly hinder its applicability toward wastewater governance. Herein, a green, facile, and efficient fabrication strategy to prepare a bi-functional palladium nanoparticles (PdNPs)-loaded bacterial cellulose membrane (BCMPd) is proposed. A tri-functional bacterial cellulose membrane (BCM) was obtained by percolating bacterial cellulose (BC) on a basal membrane, and BCM served as a support, reducing agent, and stabilizer in the subsequent reduction of PdNPs. Bi-functional BCMPd was successfully obtained and used for continuously removing emulsions and reducing methylene blue (MB) from simulated wastewater via the integration of physical sieving and chemical reaction. Meanwhile, the enhancement factors for the water transfer ability and demulsification capacity correlated directly with the wettability and surface structure of BCMPd. Furthermore, the dosage of BC was adjusted to reveal the mechanism for the enhanced water transferability and demulsification capacity. Notably, PdNPs of BCMPd decreased Fermi potential difference between BH_4- and MB, accelerating the electron transfer of the reduction reaction and thus exhibiting a remarkable MB degradation efficiency. Together, the information obtained in this work can be useful for comprehensively addressing the bottleneck of forming a cost-effective, eco-friendly, and bi-functional membrane reactor, providing an alternative approach for better treatment of complex wastewater.

Incorporation of lanthanum particles to polyethersulfone ultrafiltration membrane for specific phosphorus uptake: Method comparison and performance assessment

It is known that phosphorus is a major contributor to the occurrence of eutrophication. As such, it is of importance to remove it from water. Nanofiltration (NF) has low phosphorus selectivity and requires a relatively high pressure to achieve the separation, though it is capable of removing phosphorus. In this paper, we report our findings of method development on fabrication and application of a lanthanum (La)-incorporated polyethersulfone (PES)/sulfonated polyphenylenesulfone membrane for phosphorus treatment. The performances of membranes fabricated by the in situ and ex situ methods were examined in a series of batch adsorption and dead-end filtration experiments. The membrane fabricated by the in situ method demonstrated higher adsorption capacity (48.0 mg/g), faster kinetics (equilibrium in 6 h) and higher water permeance (>100 LMH/bar), which outperformed that by the ex situ method. Furthermore, the PES/La (in situ) membrane showed a comparable phosphate removal with a much higher permeance (about 20 times) than the NF90 (a nanofiltration commercial membrane). Moreover, the multiple cycles of filtration study showed that the membrane was reused satisfactorily in treating low-phosphate contaminated water and meeting the stringent phosphate standard limit of 0.15 mg/L. The removal of phosphate by the membranes was attributed to the mechanisms of ion exchange and electrostatic attraction/complexation. The study reported here provides a better approach in fabrication of functionalized membrane for water treatment, such as phosphate removal in either batch adsorption or membrane filtration process.