Modification of Supramolecular Membranes with 3D Hydrophilic Slide-Rings for the Improvement of Antifouling Properties and Effective Separation

A Wide-Spectrum Oil/Water Separation Scenario Enhanced by a Chitosan-Based Superwetting Membrane with a Tunable Microstructure and Powerful Photocatalytic Self-Cleaning Capability

Oil spills and industrial oily wastewater pose serious threats to the environment. A series of modified membranes with special wettability have been widely used for separating oil/water mixtures and emulsions. However, these membranes still face challenges such as the detachment of the modified coatings and membrane fouling. Here, a freestanding biobased superwetting nanofibrous membrane for oil/water mixture separation was electrospun with chitosan (CS) and poly(vinyl alcohol) (PVA) as precursors, followed by chemical cross-linking and in situ growth of β-FeOOH nanoparticles on the surface. Moreover, by precisely controlling both the cross-linking time between CS and PVA and the growth time of β-FeOOH nanoparticles, the nanosize apertures and rough structures on the membrane surface can be regulated toward a wide range of oil/water separation scenarios. As a result, FeOOH@CS/PVA-4-12 demonstrated superwettability, with a water contact angle of 9.5 ± 3.5° in air and an underwater-oil contact angle above 140°, achieving a separation efficiency of 98.5% and a water permeation flux of 2350 L·m-2·h-1 for n-heptane/water mixtures. The membrane FeOOH@CS/PVA-24-24 exhibited exceptional oil-in-water emulsion separation performance with a separation efficiency of up to 99.9% for water/n-heptane emulsions. Additionally, the membrane exhibited remarkable antifouling properties, attributed to its superwetting surface and the photocatalytic ability of β-FeOOH nanoparticles. After five photocatalytic self-cleaning cycles, the water permeation flux and separation efficiency remained almost unchanged, demonstrating its great potential for practical application.

Polymerization-Achieved Cyclodextrin Slide-Ring Supramolecular Hydrogel Self-Generating Flexible Electronic Device

Supramolecular flexible electronic devices are one of the research hotspots due to their application in the fields of chemistry, biology, and materials. Herein, we reported a slide-ring supramolecular flexible electronic device, which is constructed by acrylamide (AAm), acrylic acid (AA), carboxymethyl-α-cyclodextrin (CM-α-CD), PEG20000 diacrylate (PEG20000DA), and calcium chloride via the photoinitiated polymerization, displaying not only the mechanical force-responded self-generation but also the human-computer information transfer. As compared with the polymer hydrogel, the addition of α-CD polypseudorotaxane to the hydrogel has notably enhanced both the tensile length and the tensile toughness, making it more suitable for flexible electronic device applications. The hydrogel can be stretched to ca. 15 times its original length and quickly recovers after the external force is removed. In addition, it also exhibits a conductivity of 0.21 S/m, demonstrating good electrical conductivity. Significantly, based on the slide-ring supramolecular array for energy harvesting, it can generate an open-circuit voltage of 420 V using the contact separation method for testing, which can be used as a flexible electronic device for human-computer information transfer.

PDMS/magnetic lignin sponge for oil/water separation

Recyclable, non-toxic, and degradable biological substrates contribute significantly to super-wetting surfaces. In this work, we prepared magnetic micro-nano super-hydrophobic surfaces through a robust solution with magnetic modified lignin particles as the supporting structure. A novel PDMS (polydimethylsiloxane)/magnetic lignin particle (lignin@Fe3O4)/PDA sponge composite was fabricated. Through dopamine (DA) self-polymerization, covalent deposition of magnetic lignin (ML), and PDMS silane modification, the magnetic super-hydrophobic polyurethane sponge composite (Sponge-P) was synthesized so that the Fe3O4 nanoscale microspheres wrapped with microscale lignin magnetic particles adhered to the sponge surface tighter and were barely dislodged. The as-prepared Sponge-P displayed excellent flexibility and a water contact angle of up to 152.2°. The super-hydrophobic sponge prepared with the proposed method was acid-base stable (pH = 2-12), self-cleaning, and suitable for high-salinity seawater. The magnetic super-hydrophobic sponge has good oil-water separation ability and can absorb 43 times its own weight of oil. In the meantime, due to the introduction of magnetic materials into lignin, we not only constructed micro-nanostructures to improve the surface super-hydrophobicity, but also made Sponge-P have the function of magnetic recovery, which has a unique advantage in treating oily wastewater.

Self-Assembled CMC/UiO-66-NH2 Membrane with Anti-Crude Oil Adhesion Property for Highly Efficient Oil-Water Separation

Developing the high-anti-fouling membrane has kept continuous attention in oil/water emulsion treatment. However, the majority of works on anti-fouling membranes mainly focused on low-viscosity oils, which greatly limited the development and application of a membrane to face the real crude oil wastewater. Inspired by the hydrophilicity of sodium carboxymethyl cellulose (CMC) and zirconium base metal-organic frame (Zr-MOF), an anti-oil-fouling CMC/UiO-66-NH₂ composite membrane was constructed by a self-assembly method. Profiting from the hydrophilicity and micro-nanostructure of the CMC/UiO-66-NH₂ layer, the obtained CMC/UiO-66-NH₂ membranes displayed underwater superoleophobicity and desired oil resistance. It could display the effective separation capability with 1282 ± 62 to 6160 ± 81 L/(m²·h·bar) and above 99.08% toward the different light oil emulsions. More importantly, the CMC/UiO-66-NH₂ membrane displayed ultralow crude oil adhesion behaviors toward the crude oil emulsions, which could achieve a considerably high flux (746 ± 60 to 5224 ± 87 L/(m²·h·bar)). Furthermore, electrostatic interaction and physical enwinding-wrapping between CMC and UiO-66-NH₂ also endowed the composite membranes with outstanding stability. After immersing the as-prepared membranes into the harsh environments for 24 h, the membranes still maintained high underwater-oil contact angles (UWOCA > 155°) and separation ability (oil rejection was above 99.0%). Therefore, CMC/UiO-66-NH₂ composite membranes could demonstrate promising prospects in real oily emulsion treatment.

Efficacy of MOF-199 in improvement of permeation, morphological, antifouling and antibacterial characteristics of polyvinylidene fluoride membranes

Metal–organic frameworks (MOFs) are widely explored for advances in hybrid membranes because of their bonding and fondness in polymers.

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.

Design of nanoengineered antibacterial polymers for biomedical applications

Pathogenic bacteria have become global threats to public health. Since the advent of antibiotics about 100 years ago, their use has been embraced with great enthusiasm because of their effective treatment of bacterial infections. However, the evolution of pathogenic bacteria with resistance to conventional antibiotics has resulted in an urgent need for the development of a new generation of antibiotics. The use of antimicrobial polymers offers the promise of enhancing the efficacy of antimicrobial agents. Of the various antibacterial polymers that effectively eradicate pathogenic bacteria, those that are nanoengineered have garnered significant research interest in their design and biomedical applications. Because of their high surface area and high reactivity, these polymers show greater antibacterial activity than conventional antibacterial agents, by inhibiting the growth or destroying the cell membrane of pathogenic bacteria. This review summarizes several strategies for designing nanoengineered antibacterial polymers, explores the factors that affect their antibacterial properties, and examines key features of their design. It then comments briefly on the future prospects for nanoengineered antibacterial polymers. This review thus provides a feasible guide to developing nanoengineered antibacterial polymers by presenting both broad and in-depth bench research, and it offers suggestions for their potential in biomedical applications.

Fabrication of pH-Sensitive Superhydrophilic/Underwater Superoleophobic Poly(vinylidene fluoride)-graft-(SiO2 Nanoparticles and PAMAM Dendrimers) Membranes for Oil-Water Separation

The efficient treatment of oil-water emulsions under acidic condition remains a widespread concern. Poly(amidoamine) (PAMAM) dendrimer with hyperbranched structures and a large amount of primary and tertiary amino groups has exhibited advantages to solve this issue. Here, a novel poly(vinylidene fluoride)-graft-(SiO₂ nanoparticles and PAMAM dendrimers) (PVDF-g-SiO₂ NPs/PAMAM) membrane was fabricated using a surface-grafting strategy. SiO₂ NPs were immobilized on PVDF-g-poly(acrylic acid) (PAA) membranes for improving the surface roughness, and PAMAM dendrimers were further immobilized on the membrane surface by interfacial polymerization (IP) for improving the surface energy. The obtained membrane demonstrated a water contact angle and a stable underwater-oil contact angle of 0° and >150°, respectively. These characteristics endowed the membrane with excellent water permeability [>3100 L/(m²·h) at 0.9 bar] and separation efficiency (>99%) during oil-water separation. Furthermore, the PAMAM chain will extend from a collapsed state into a fully extension state because of the protonation of amine groups under acidic condition, thus achieving a low underwater oil-adhesion property, fouling resistance, desirable stability, and recyclability (over 12 cycles) during usage. This work shows a promising prospect for the treatment of corrosive emulsions under acidic condition.

Superwetting Oil/Water Separation Membrane Constructed from In Situ Assembled Metal-Phenolic Networks and Metal-Organic Frameworks

Superwetting membranes with opposite wettability to oil and water have drawn intense attention in recent years for oil/water separation. Superhydrophilic and underwater superoleophobic membranes have shown unique advantages in the efficient treatment of oily wastewater containing oil-in-water emulsions. Facile interfacial engineering and microstructural design of the hierarchical architectures and the hydrophilic chemistry is of significance but still challenging. In this study, a hydrophilic hierarchical hybrid layer derived from metal-phenolic network (MPN)/metal-organic framework (MOF) synergy is constructed on the membrane surface via a proposed coordination-directed alternating assembly strategy. The assembly of MPN multilayers provides a hydrophilic chemical basis, and the assembly of MOF nanocrystals provides a hierarchical structural basis. Notably, the coordination interfacial interaction enables the formation of well-defined hydrophilic hierarchical architectures. The obtained membrane is thus endowed with robust superhydrophilicity, underwater superoleophobicity, and anti-oil-adhesion capability, which make it capable of highly efficient oil-water separation with high water permeance (above 6300 L/m² h), high oil rejection (above 99.4%), and recyclable antifouling property. The high performance of the developed superwetting membrane makes it a competitive candidate for oil/water separation. Additionally, the demonstrated MPN/MOF assembly strategy may offer new prospects for the facile and versatile design of other superwetting materials.