Inkjet printing of dopamine followed by UV light irradiation to modify mussel-inspired PVDF membrane for efficient oil-water separation

Empowering TiO2-coated PVDF membranes stability with polyaniline and polydopamine for synergistic separation and photocatalytic enhancement in dye wastewater purification

Photocatalytic membranes are effective in removing organic dyes, but their low UV resistance poses a challenge. To address this, self-protected photocatalytic PVDF membranes were developed using polyaniline (PANI) and polydopamine (PDA), whaich are anti-oxidation polymers, as interlayers between the membrane and TiO2. PVDF membranes were first modified by a self-polymerization layer of either PANI or PDA and then coated with titanium dioxide (TiO2). The TiO2 remained firmly attached to the PANI and PDA layer, regardless of sonication and prolonged usage. The PANI and PDA layers enhanced the durability of PVDF membrane under UV/TiO2 activation. After 72 h of irradiation, PVDF-PDA-TiO2 and PVDF-PANI-TiO2 membranes exhibited no significant change. This process improved both separation and photocatalytic activity in dye wastewater treatment. The PVDF-PDA-TiO2 and PVDF-PANI-TiO2 membranes showed enhanced membrane hydrophilicity, aiding in the rejection of organic pollutants and reducing fouling. The modified membranes exhibited a significant improvement in the flux recovery rate, attributed to the synergistic effects of high hydrophilicity and photocatalytic activity. Specially, the flux recovery rate increased from 17.7% (original PVDF) to 56.3% and 37.1% for the PVDF-PDA-TiO2 membrane and PVDF-PANI-TiO2 membrane. In dye rejection tests, the PVDF‒PDA‒TiO2 membrane achieved 88% efficiency, while the PVDF‒PANI‒TiO2 reached 95.7%. Additionally, the photodegradation of Reactive Red 239 (RR239) by these membranes further improved dye removal. Despite an 11% reduction in flux, the PVDF-PDA-TiO2 membrane demonstrated greater durability and longevity. The assistance of PANI and PDA in TiO2 coating also improved COD removal (from 33 to 58-68%) and provided self-protection for photocatalytic membranes, indicating that these photocatalytic membranes can contribute to more sustainable wastewater treatment processes.

Asymmetric Wettability Janus Mesh via Electrostatic Printing for Selective Oil-Water and Emulsion Separation

Janus mesh with two-sided asymmetric wettability shows high potential for selective oil-water and emulsion separation. However, it remains a challenge to construct Janus mesh structures with good stability and extremely asymmetric wettability. Herein, a novel Janus mesh with asymmetric wettability was structured by two different precursors, polydimethylsiloxane/zinc oxide (PDMS/ZnO) and zinc oxide-polyacrylonitrile/N,N-dimethylformamide (ZnO-PAN/DMF), by electrostatic printing, including electrostatic air spraying and electrostatic spinning. The prepared Janus mesh has special micro-nanostructures on two sides, including PDMS@ZnO and ZnO@PAN. On the basis of gravity, when the placement direction is changed, Janus mesh can effectively separate oil-water mixtures of different densities and surfactant-stabilized oil-water emulsions. Meanwhile, the obtained Janus mesh exhibited good separation efficiency (>96.3%) for various oil-water mixtures, and the flux was up to 2621 ± 30 L m-2 h-1. The Janus mesh was cycled 20 times with no weakening in separation efficiency, indicating satisfactory cycling stability. The Janus mesh displayed good stability under harsh conditions (acidic, alkaline, and high temperature). The Janus mesh can realize low energy input and long-lasting oil-water separation, which has widespread application prospects in intelligent oil-water separation. This top-down electrostatic printing strategy provides a way to construct Janus interface materials with practical applications.

Zero-Oil-Fouling Membrane With High Coverage of Grafted Zwitterionic Polymer for Separation of Oil-in-Water Emulsions

Current hydrophilic modification strategies improve the antifouling ability of membranes but fail to completely eliminate the fouling of emulsified oil droplets with a wide size distribution. Constructing membranes with superior anti-oil-fouling ability to resist various oil droplets especially at high permeation fluxes is challenging. Here, the fabrication of a zero-oil-fouling membrane by grafting considerably high coverage of zwitterionic polymer and building defect-free hydration defense barrier on the surface is reported. A uniform layer of protocatechuic acid with COOH as abundant as existing in every molecule is stably deposited on the membrane so as to provide sufficient reactive sites and achieve dense grafting of the zwitterionic polymer. The coverage of zwitterionic polymer on the membrane plays a crucial role in promoting the antifouling ability to emulsified oil droplets. The poly(vinylidene fluoride) membrane with 93% coverage of the zwitterionic polymer exhibits zero oil fouling when separating multitudinous oil-in-water emulsions with ≈0% flux decline, ≈100% flux recovery, and a high water flux of ≈800 L m-2 h-1 bar-1. This membrane outperforms almost all of the reported membranes in terms of the comprehensive antifouling performance. This work provides a feasible route for manufacturing super-antifouling membranes toward oil/water separation application.

Ozone-Induced Rapid and Green Synthesis of Polydopamine Coatings with High Uniformity and Enhanced Stability

The development of green, controllable, and simplified pathways for rapid dopamine polymerization holds significant importance in the field of polydopamine (PDA) surface chemistry. In this study, a green strategy is successfully devised to accelerate and control the polymerization of dopamine through the introduction of ozone (O3 ). The findings reveal that ozone serves as an eco-friendly trigger, significantly accelerating the dopamine polymerization process across a broad pH range, spanning from 4.0 to 10.0. Notably, the deposition rate of PDA coatings on a silicon wafer reaches an impressive value of ≈64.8 nm h-1 (pH 8.5), which is 30 times higher than that of traditional air-assisted PDA and comparable to the fastest reported method. Furthermore, ozone exhibits the ability to accelerate dopamine polymerization even under low temperatures. It also enables control over the inhibition-initiation of the polymerization process by regulating the "ON/OFF" mode of the ozone gas. Moreover, the ozone-induced PDA coatings demonstrate exceptional characteristics, including high homogeneity, good hydrophilicity, and remarkable chemical and mechanical stability. Additionally, the ozone-induced PDA coatings can be rapidly and effectively deposited onto a wide range of substrates, particularly those that are adhesion-resistant, such as polytetrafluoroethylene (PTFE).

A comprehensive review on state-of-the-art antifouling super(wetting and anti-wetting) membranes for oily wastewater treatment

One of the most dangerous types of pollution to the environment is oily wastewater, which is produced from a number of industrial sources and can cause damage to the environment, people, and creatures. To overcome this issue, membrane technology as an advanced method has been considered for treating oily wastewater due to its stability, high removal efficiency, and simplicity in scaling up. Membrane fouling, or the accumulation of oil droplets at or within the membrane pores, compromises the efficiency of membrane separation and water flux. In the last decade, the fabrication of membranes with specific wettability to reduce fouling has received much consideration. The purpose of this article is to offer a literature overview of all fabricated anti-fouling super(wetting and anti-wetting) membranes for applicable membrane processes for the separation of immiscible and emulsified oil/water mixtures. In this review, we first explain membrane fouling and discuss methods for preventing it. Afterwards, in all membrane separation processes, including pressure-driven, gravity-driven, and thermal-driven, membranes based on the form and density of oil are categorized as oil-removing or water-removing with special wettability, and then their wettability modification with different materials is particularly discussed. Finally, the prospect of anti-fouling membrane fabrication in the future is presented.

Melt-blown fiber felt for efficient all-weather recovery of viscous oil spills by Joule heating and photothermal effect

Adsorbents play a vital role in responding to marine oil spills, yet effectively cleaning up viscous oil spills remains a technical challenge. Herein, we present a superhydrophobic oil-adsorbing felt prepared using melt-blown technology and functionally enhanced with a photoelectric composite CNT/PANI coating for effectively cleaning up high-viscosity oil spills. By virtue of its superior solar/Joule heating ability and thermally conductive fiber network, p-CNT/PANI@PP notably reduced crude oil viscosity and enhanced the oil diffusion coefficient within pores. Leveraging primarily solar heating and supplemented by Joule heating, p-CNT/PANI@PP demonstrates an impressive in-situ adsorption rate of up to 560 g/h for ultra-high-viscosity crude oil (c.a. 138000 mPa·s), alongside an adsorption capacity of 15.57 g/g. This measure enables efficient viscosity reduction and continuous day-and-night recovery of viscous crude oil, addressing the challenges posed by seasonal fluctuations in seawater temperature and adverse weather conditions. Moreover, a conveyorized collector integrated with an oil-adsorbing felt realizes continuous recovery of viscous oil spills with speed control to tackle varying thicknesses of oil film. Given the top-down material design, superior functionality, and applicability to applications, this work provides a comprehensive and feasible solution to catastrophic large-area viscous oil spills.

High performance forward osmosis membrane with ultrathin hydrophobic nanofibrous interlayer

The novel thin film composite (TFC) forward osmosis (FO) membrane with electrospinning nanofibers as support layer can alleviate internal concentration polarization (ICP). While the macropores of the nanofiber support layer cause defects in the polyamide (PA) layer. Therefore, hydrophobic polyvinylidene fluoride (PVDF) fine nanofibers were used as an interlayer to modulate the process of interfacial polymerization (IP) in this study. The results showed that the introduction of the interlayer improved the hydrophobicity of the support layer for achieving uniform, thin and defect-free selective polyamide (PA) layer. The water flux of TFC-PVDF was 58.26 LMH in the FO mode of 2 M NaCl, which was two times higher than that of the unmodified FO membrane. Lower reverse salt flux (4.91 gMH) and structural parameter (179.43 μm) alleviated the ICP. In addition, TFC-PVDF membrane showed good anti-fouling performance for SA (flux recovery ratio of 93.97%) due to high hydrophilicity, low zeta potential and low roughness. This study provides an easy and promising method to prepare defect-free PA selective layer on the macropores nanofiber support layer. The novel FO membrane shows high desalination performance and anti-fouling properties.

Rapid Construction of Caffeic Acid/p-Phenylenediamine Antifouling Hydrophilic Coating on a PVDF Membrane for Emulsion Separation

The current methods of constructing modification strategies for hydrophilic membranes are time-consuming, complex in operation, and poor in universality, which limit their application on membranes. In this work, inspired by the adhesion properties and versatility of caffeic acid (CA) and p-phenylenediamine (PPDA), a simple, rapid, and universal method was designed for the separation of oil-in-water emulsion by preparing a stable hydrophilic coating separation membrane. The preparation time of the membrane was shortened to 40 min. The developed PVDF-PCA/PPDA membrane showed superhydrophilic and underwater superoleophobic properties. When applied to petroleum ether-in-water emulsion, isooctane-in-water emulsion, and dodecane-in-water emulsion separation, the oil rejection was more than 99.0%. In the circulating separation of 10 g/L soybean oil-in-water emulsion, the oil rejection was more than 99.3%, and the highest flux was 1036 L·m-2·h-1. The prepared PVDF-PCA/PPDA membrane performed well in the separation test of oily wastewater. The proposed strategy is simple and rapid; it may become a universal method for preparing membranes with super strong antifouling properties against viscous oil and accelerate the research progress of membrane separation of oil-in-water emulsions.

Durably dual superlyophobic cationic guar gum‑calcium complex decorated cellulose fabrics for on-demand oil/water separation

The removal to oils from water has become a global issue because of the growing of wastewater discharge and unceasing appearance of oil leaks. Herein, a kind of durably dual superlyophobic (superhydrophobic under oil and superoleophobic under water) cotton fabric (CF) was fabricated via simple assembly route that introduced guar hydroxypropyltrimonium chloride‑calcium (GHTC-Ca) chelate compound on the fabric surface. The coated CF exhibits good resistance to mechanical abrasion, corrosive aqueous solution, high temperature, and organic solvent immersion. Furthermore, due to prewetting-caused superoleophobicity underwater and superhydrophobicity underoil, the as-prepared CF can selectively separate both heavy oils and light oils in water under extremely harsh conditions with separation efficiencies as high as 98.7 % and 98.4 %, respectively. More importantly, the as-prepared fabrics are able to remove dispersed oil droplets from oil-in-water emulsions and water droplets from water-in-oil emulsions with separation efficiency of over 89 % and 91.4 %, respectively. Hence, this prominent separation performance suggests a good application prospect of GHTC-Ca functionalized CF in oily water purification.

Self-Assembly of Shark Scale-Patterned Tunable Superhydrophobic/Antifouling Structures with Visual Color Response

The stacked riblet-like shark scales, also known as dermal denticles, allow them to control the boundary layer flow over the skin and to reduce interactions with any biomaterial attached, which guide the design of antifouling coatings. Interestingly, shark scales are with a wide variation in geometry both across species and body locations, thereby displaying diversified antifouling capabilities. Inspired by the multifarious denticles, a stretchable shark scale-patterned silica hollow sphere colloidal crystal/polyperfluoroether acrylate-polyurethane acrylate composite film is engineered through a scalable self-assembly approach. Upon stretching, the patterned photonic crystals feature different short-term antibacterial and long-term anti-biofilm performances with a distinguished color response under varied elongation ratios. To gain a better understanding, the dependence of elongation ratio on antiwetting behaviors, antifouling performances, and structural color changes has also been investigated in this research.

Efficient oily wastewater treatment by a novel electroflotation-membrane separation system consisting a Ni-Cu-P membrane prepared by electroless nickel plating

Electroflotation-membrane separation system with a conductive membrane has recently emerged as a promising technology for oily wastewater treatment. However, the conductive membrane prepared by electroless plating often suffers the problems of low stability and high activation cost. To solve these problems, this work proposed a new strategy regarding surface metallization of polymeric membrane by surface nickel-catalyzed electroless nickel plating of nickel‑copper‑phosphorus alloys for the first time. It was found that, addition of copper source remarkably enhanced the membranes' hydrophilicity, corrosion resistance and fouling resistance. The Ni-Cu-P membrane had an underwater oil contact angle of up to 140°, and simultaneously possessed rejection rate > 98 % with rather high flux of 65,663.0 L·m^-2·h^-1 and excellent cycling stability when separating n-hexane/water mixtures under gravity drive. The permeability is higher than the state-of-the-art membranes for oil/water separation. The Ni-Cu-P membrane as the cathode can be assembled into an electroflotation-membrane separation system, allowing to separate oil-in-water emulsion with 99 % rejection. Meanwhile, the applied electric field significantly improved membrane flux and fouling resistance (flux recovery up to 91 %) when separate kaolin suspensions. Polarization curve and Nyquist curve analysis further confirmed that addition of Cu element obviously enhanced corrosion resistance of the Ni modified membrane. This work provided a novel strategy to make up high-efficiency membranes for oily wastewater treatment.

Amphiphilic Grafted Polymers Based on Citric Acid and Aniline Used to Enhance the Antifouling and Permeability Properties of PES Membranes

Water treatment technology based on ultrafiltration (UF) faces the problem of severe membrane fouling due to its inherent hydrophobicity. The use of amphiphilic polymers that possess both hydrophobic and hydrophilic chain segments can be advantageous for the hydrophilic modification of UF membranes due to their excellent combination in the membrane matrix. In the present study, we examined a novel amphiphilic CA-g-AN material, constructed by grafting citric acid (CA) to aniline (AN), as a modified material to improve the hydrophilicity of a PES membrane. This material was more compatible with the polymer membrane matrix than a pure hydrophilic modified material. The polyethersulfone (PES) membranes modified by amphiphilic CA-g-AN demonstrated a higher water flux (290.13 L·m^-2·h^-1), which was more than eight times higher than that of the pure PES membrane. Furthermore, the flux recovery ratio (FRR) of the modified membrane could reach 83.24% and the value of the water contact angle (WCA) was 76.43°, demonstrating the enhanced hydrophilicity and antifouling ability of the modified membranes. With this study, we aimed to develop a new amphiphilic polymer to improve the antifouling property and permeability of polymer-based UF membranes to remove organic pollutants from water.

Efficient oil-water emulsion treatment via novel composite membranes fabricated by CaCO3-based biomineralization and TA-Ti(IV) coating strategy

Continuous increasing discharge of industrial oily wastewater and frequent occurrence of oil spill accidents have taken heavy tolls on global environment and human health. Organic-inorganic modifications can fabricate superhydrophilic/submerged superoleophobic membranes for efficient oil-water separation/treatment though they still suffer from complex operation, non-environmental friendliness, expensive cost or uneven distribution. Herein, a new strategy regarding tannic acid (TA)-Ti(IV) coating and CaCO₃-based biomineralization through simple inkjet printing processes was proposed to modify polyvinylidene fluoride (PVDF) membrane, endowing the membrane with high hydrophilicity (water contact angle (WCA) decreased from 86.01° to 14.94°) and underwater superoleophobicity (underwater contact angle (UOCA) > 155°). The optimized TA-Ti(IV)-CaCO₃ modified membrane possessed perfect water permeation to various oil/water emulsions (e.g., 355.7 L·m^-2·h^-1 for gasoline emulsion) under gravity with superior separation efficiency (>98.8 %), leading the way in oil/water emulsion separation performance of PVDF membranes modified with polyphenolic surfaces to our knowledge. Moreover, the modified membrane displayed rather high flux recovery after eight cycles of filtration while maintaining the original excellent separation efficiency. The modification process proposed in this study is almost independent of the nature of the substrate, and meets the demand for simple, inexpensive, rapid preparation of highly hydrophilic antifouling membranes, showing abroad application prospect for oil-water emulsion separation/treatment.

Hemin-Modified Multi-Walled Carbon Nanotube-Incorporated PVDF Membranes: Computational and Experimental Studies on Oil-Water Emulsion Separations

The separation of oil/water emulsions has attracted considerable attention for decades due to the negative environmental impacts brought by wastewater. Among the various membranes investigated for separation, polyvinylidene fluoride (PVDF) membranes have shown significant advantages of ease of fabrication, high selectivity, and fair pore distribution. However, PVDF membranes are hydrophobic and suffer from severe fouling resulting in substantial flux decline. Meanwhile, the incorporation of wettable substrates during fabrication has significantly impacted the membrane performance by lowering the fouling propensity. Herein, we report the fabrication of an iron-containing porphyrin (hemin)-modified multi-walled carbon nanotube incorporated PVDF membrane (HA-MWCNT) to enhance fouling resistance and the effective separation of oil-in-water emulsions. The fabricated membrane was thoroughly investigated using the FTIR, SEM, EDX, AFM, and contact angle (CA) analysis. The HA-MWCNT membrane exhibited a water CA of 62° ± 0.5 and excellent pure water permeance of 300.5 L/m2h at 3.0 bar (400% increment), in contrast to the pristine PVDF, which recorded a CA of 82° ± 0.8 and water permeance of 59.9 L/m2h. The hydrophilic HA-MWCNT membrane further showed an excellent oil rejection of >99% in the transmembrane pressure range of 0.5−2.5 bar and a superb flux recovery ratio (FRR) of 82%. Meanwhile, the classical molecular dynamics (MD) simulations revealed that the HA-MWCNT membrane had greater solvent-accessible pores, which enhanced water permeance while blocking the hydrocarbons. The incorporation of the hemin-modified MWCNT is thus an excellent strategy and could be adopted in the design of advanced membranes for oil/water separation.

Designing of nanotextured inorganic-organic hybrid PVDF membrane for efficient separation of the oil-in-water emulsions

The separation of the emulsified oil/water is one of the critical environmental challenges. The PVDF membranes have been found helpful for separation, but rapid fouling makes them less attractive in treating oil-in-water emulsions. The design of antifouling membranes has become an area of deep interest. Herein, developing a novel modified PVDF ultrafiltration membrane was reported by doping the pyrrole and solidifying it in a ferric-containing coagulation bath, resulting in a unique nanotextured PVDF membrane (CCB-Fe/PP_np-PVDF) to separate the oil/water emulsions. The resultant CCB-Fe/PP_np-PVDF membrane was thoroughly characterized using the FTIR, FE-SEM, EDX, mapping, AFM, and contact analyzer. The hydrophilicity of the CCB-Fe/PP_np-PVDF was substantially improved, and the water contact angle was reduced from 81֯ ± 0.9֯ to 44֯ ± 1.7֯. The CCB-Fe/PPnp-PVDF membrane flux increased by 121% compared to the pristine PVDF membrane, with high separation efficiency of 99%. The hydrophilic nanotextured surface of the CCB-Fe/PP_np-PVDF membrane showed good antifouling behavior, with a flux recovery ratio (FRR) of more than 96%. Irreversible flux was just less than 4%. The high flux recovery ratio indicated that the nanotextured surface produced by the Fe/PP_np had prevented the blockage of the membrane pores and compact cake layer formation, which makes it an excellent membrane for oil/water emulsion separation. This strategy can be adopted for designing advanced membranes for separation applications.

Surface Modification of Ultrafiltration Membranes with 1,4-Benzoquinone and Polyetheramines to Improve Fouling Resistance

Membrane fouling remains a key challenge for membrane separations. Hydrophilic membrane surface modification can mitigate irreversible foulant deposition, thereby improving fouling resistance. We report new hydrophilic membrane coatings based on 1,4-benzoquinone and various commercially available polyetheramines. These coatings, prepared from 1,4-benzoquinone and Jeffamine EDR 148, poly(benzoquinone-Jeffamine EDR 148) (p(BQ-EDR 148)), were used to modify polysulfone (PS) ultrafiltration membranes. In fouling experiments using an oil/water emulsion, membranes exhibited comparable fouling resistance to that of polydopamine (pDA)-modified membranes. Based on contact angle measurements, p(BQ-EDR 148) and pDA-modified membranes have similar levels of hydrophilicity, and both exhibited higher threshold flux values than those of their unmodified analogues. Based on their similar threshold flux values, p(BQ-EDR 148)-modified (76 LMH) and pDA-modified membranes (74 LMH) should have similar fouling resistance. Moreover, the mean pore size of p(BQ-EDR 148)-modified membranes can be tuned, while keeping the pure water permeance constant, by changing the deposition time and molar ratio of benzoquinone to EDR 148 in the modification solution.

Impacts of Calcium Addition on Humic Acid Fouling and the Related Mechanism in Ultrafiltration Process for Water Treatment

Humic acid (HA) is a major natural organic pollutant widely coexisting with calcium ions (Ca²⁺) in natural water and wastewater bodies, and the coagulation-ultrafiltration process is the most typical solution for surface water treatment. However, little is known about the influences of Ca²⁺ on HA fouling in the ultrafiltration process. This study explored the roles of Ca²⁺ addition in HA fouling and the potential of Ca²⁺ addition for fouling mitigation in the coagulation-ultrafiltration process. It was found that the filtration flux of HA solution rose when Ca²⁺ concentration increased from 0 to 5.0 mM, corresponding to the reduction of the hydraulic filtration resistance. However, the proportion and contribution of each resistance component in the total hydraulic filtration resistance have different variation trends with Ca²⁺ concentration. An increase in Ca²⁺ addition (0 to 5.0 mM) weakened the role of internal blocking resistance (9.02% to 4.81%) and concentration polarization resistance (50.73% to 32.17%) in the total hydraulic resistance but enhanced membrane surface deposit resistance (33.93% to 44.32%). A series of characterizations and thermodynamic analyses consistently suggest that the enlarged particle size caused by the Ca²⁺ bridging effect was the main reason for the decreased filtration resistance of the HA solution. This work revealed the impacts of Ca²⁺ on HA fouling and demonstrated the feasibility to mitigate fouling by adding Ca²⁺ in the ultrafiltration process to treat HA pollutants.

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.

Gold Nanocluster-Encapsulated Hyperbranched Polyethyleneimine for Selective and Ratiometric Dopamine Analyses by Enhanced Self-Polymerization

The exploitation of selective and sensitive dopamine (DA) sensors is essential to more deeply understand its biological function and diagnosis of related diseases. In this study, gold nanocluster-encapsulated hyperbranched polyethyleneimine (hPEI-Au NCs) has been explored as the specific and ratiometric DA nanoprobe through hPEI-assisted DA self-polymerization reactions. The Au NCs encapsulation not only provides a fluorescent internal reference but also enhances the DA self-polymerization by weakening the proton sponge effect of the hPEI layer. Rapid and sensitive DA detection is realized through the proposed hPEI-Au NC nanoprobe with a limit of detection of 10 nM. The favorable selectivity over other possible interferents including amino acids, sugars, and salts is due to the specific self-polymerization reaction. The DA analysis in urine samples with small relative standard deviations has been accomplished with an hPEI-Au NC nanoprobe.

Novel fabrication of hydrophobic/oleophilic human hair fiber for efficient oil/water separation through one-pot dip-coating synthesis route

Frequent oil spill accidents and industrial wastewater discharge has always been one of the most severe worldwide environmental problems. To cope with this problem, many fluorine-containing and high-cost materials with superwettability have been extensively applied for oil-water separation, which hinders its large-scale application. In this work, a novel human hair fiber (HHF)-polymerized octadecylsiloxane (PODS) fiber was fabricated with a facile one-pot dip-coating synthesis approach, inspired by the self-assembly performance and hydrophobicity of OTS modification. The benefits of prominent hydrophobic/lipophilic behavior lie in the low surface energy, and a rough PODS coating was rationally adhered on the surface of HHF. Driven solely by gravity and capillary force, the HHF-PODS showed excellent oil/water separation efficiency (> 99.0%) for a wide range of heavy and light oil/water mixtures. In addition, HHF-PODS demonstrated durability toward different harsh environments like alkaline, acid, and salty solutions.

Novel dopamine-modified cellulose acetate ultrafiltration membranes with improved separation and antifouling performances

Cellulose acetate (CA) is widely used in the preparation of ultrafiltration membranes due to its many excellent characteristics, especially chemical activity and biodegradability. To improve the inherent hydrophobic and antifouling properties of CA membrane, in this work, CA was successfully modified with dopamine (CA-2,3-DA) through selective oxidation and Schiff base reactions, which was confirmed by FTIR and ¹H NMR measurements. Then, CA-2,3-DA membrane with high water permeability and excellent antifouling property was prepared by the phase inversion method. Compared with the original CA membrane, the CA-2,3-DA membrane maintained a higher rejection ratio for BSA (92.5%) with a greatly increased pure water flux (167.3 L m^-2 h^-1), which could overcome the trade-off between permeability and selectivity of the traditional CA membrane to a certain extent. According to static protein adsorption and three-cycle dynamic ultrafiltration experiments, the CA-2,3-DA membrane showed good antifouling performance and superior long-term performance stability, as supported by the experimental results, including flux recovery ratio, flux decline ratio, and filtration resistance. It is expected that this approach can greatly expand the high-value utilization of modified natural organic polysaccharides in separation engineering.

Polymeric Membranes for Oil-Water Separation: A Review

This review is devoted to the application of bulk synthetic polymers such as polysulfone (PSf), polyethersulfone (PES), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF) for the separation of oil-water emulsions. Due to the high hydrophobicity of the presented polymers and their tendency to be contaminated with water-oil emulsions, methods for the hydrophilization of membranes based on them were analyzed: the mixing of polymers, the introduction of inorganic additives, and surface modification. In addition, membranes based on natural hydrophilic materials (cellulose and its derivatives) are given as a comparison.

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.

A novel composite membrane for simultaneous separation and catalytic degradation of oil/water emulsion with high performance

It is of great significance to develop novel membranes with dual-function of simultaneously separating oil/water emulsion and degrading the contained water-miscible toxic organic components. To meet this requirement, a dual-functional Ni nanoparticles (NPs)@Ag/C-carbon nanotubes (CNTs) composite membrane was fabricated via electroless nickel plating strategy in this study. The as-prepared composite membrane possessed superhydrophilicity with water contact angle of 0° and splendid underwater oleophobic property with oil contact angle of 142°. When the membrane was applied for separation of surfactant stabilized oil-in-water emulsion, high permeate flux (about 97 L m^-2·h^-1 under gravity), oil rejection (about 98.8%) and antifouling property were achieved. Benefitting from the NiNPs@Ag/C-CNTs layer on membrane surface, the composite membrane exhibited high catalytic degradation activity for water-miscible toxic organic pollutant (4-nitrophenol) with addition of NaBH₄ in a flow-through mode. Meanwhile, the NiNPs@Ag/C-CNTs composite membrane possessed excellent durability, which was verified by the good structural integrity even under ultrasonic treatment. The cost-efficiency, high separation and degradation performance of the prepared membrane suggested its great potential for treatment of oily wastewater.