Separation Of Oil-water Mixtures Research Articles

Amino‐modified banana nanocellulose aerogels with quick pH‐responsive switchable wettability for oil–water separation

AbstractWith the rapid development of the maritime industry, oily wastewater discharges and oil spills cause acute environmental challenges. Currently, cellulosic materials with switchable wettability have received increasing interest for oil–water separation. Moreover, work efficiency needs to be improved with a shorter response time. To realize these, dimethylaminoethyl methacrylate (DMAEMA) and methyltrimethoxysilane (MTMS) synthesized pH‐responsive copolymer (DMAEMA‐co‐MTMS) which grafted banana nanocellulose fiber made from wasted pseudostem to achieve the pH‐responsive aerogel (BCNA‐DcoM). BCNA‐DcoM exhibited hydrophilic/submerged lipophobicity under acidic conditions and hydrophobic/lipophilic under alkaline conditions. A response time of 3 s and a contact angle of 135° were shown when the mass ratio of banana nanocellulose suspension, MTMS, and DMAEMA‐co‐MTMS was 5:3:9. Moreover, BCNA‐DcoM possessed favorable mechanical friction properties, salt resistance (25% NaCl), compression resilience (50 cycles of compression at 60% strain), switchable wettability (>30 cycles), and highly efficient separation performance (>96%). The adsorption capacity of BCNA‐DcoM for oil is 80–184 times the initial weight of the aerogel based on the different oil densities. For practical applications, BCNA‐DcoM could continuously separate oil–water mixtures with the constant‐flow pump. The present work provides more possibilities for rapidly treating industrial oily wastewater with low‐cost and ecological banana pseudostem materials.

A multifunctional Ag NPs/guar gum hydrogel as versatile platform for catalysts, antibacterial agents, and construction of oil-water separation interfaces

The frequently encountered wastewater contaminations, including soluble aromatic compound and dye pollutants, pathogenic bacteria, and insoluble oils, have resulted in significant environmental and human health issues. It poses a challenge to utilize identical materials for the treatment of complex wastewater. Herein, in this research, multifunctional Ag NPs/guar gum hybrid hydrogels were fabricated using a facile in situ reduction and self-crosslinking method for efficient remediation of complex wastewater. The Ag NPs/guar gum hybrid hydrogel showed remarkable remodeling, adhesive, and self-healing characteristics, which was favorable for its versatile applications. The combination of Ag NPs with the guar gum skeleton endowed the hybrid hydrogel with exceptional catalytic activity for reducing aromatic compounds and dye pollutants, as well as remarkable antibacterial efficacy against pathogenic bacteria. In addition, the Ag NPs/guar gum hybrid hydrogel could be employed to coat a variety of substrates, including cotton fabrics and stainless steel meshes. The hydrogel coated cotton fabrics and meshes presented superhydrophilicity/underwater superoleophobicity, excellent antifouling capacity, and outstanding recyclability, which could be successfully applied for efficient separation of oil-water mixtures. The findings of this work provide a feasible and cost-effective approach for the remediation of intricate wastewater.

Cysteine-based antifouling superhydrophilic membranes prepared via facile thiol-ene click chemistry for efficient oil-water separation

Superhydrophilic membranes with underwater superoleophobicity for oil-water separation have been attracted widely attention. Nevertheless, oil contamination of such membranes represents a pressing challenge in this field. Superhydrophilic/underwater superoleophobic membranes with surface zwitterionic moieties are proved to show excellent antifouling properties; however, such zwitterionic surface modifiers adopted previously usually face the problem of cumbersome synthesis relying on expensive reagents and complicated procedures, accompanied with poor acid/alkali resistance due to the unstable linkers, restricting their practical applications. Herein, we describe an alternative strategy for fabricating antifouling superhydrophilic/underwater superoleophobic membranes from a natural amino acid. Sand particle-based sintered glass membranes were firstly coated with silicone nanofilaments using vinyltrichlorosilane as a precursor through chemical vapor deposition; and then the surfaces of silicone nanofilaments were further functionalized with cysteine via thiol-ene click chemistry. The resulting membranes exhibited high separation flux and efficiency for gravity-driven separation of various oil-water mixtures and surfactant-stabilized oil-in-water emulsions. Moreover, such membranes displayed excellent antifouling properties and were reusable for the separation of oil-water mixtures and surfactant-stabilized oil-in-water emulsions. With the advantages of facile fabrication, low-cost, fouling resistance and high separation performance, we believe that cysteine-based glass membranes without any hydrolytic bonds will arouse tremendous attentions for oil-water separation.

Hydrothermally synthetized WO3 coated stainless steel mesh for oil–water separation purposes

To separate oil–water mixtures especially in oil field operations, new energy-efficient methods are urgently required. Conventional separation techniques using demulsifiers for separation of oil–water mixtures or even use of membranes usually suffered from high cost and energy consumption, composition dependency of demulsifiers and fouling or inability of a single membrane to separate all types of oil–water mixtures. This research aimed to synthesize tungsten oxide-coated stainless steel mesh using the hydrothermal method, with a focus on evaluating its effectiveness in oil–water separation. The coating procedure was carried out using hydrothermal techniques, with an emphasis on investigating the impact of precursor concentration, pH levels, reaction temperature and duration, on the separation efficiency of the optimal coating solution. The hydrothermally coated stainless steel mesh was created within a polytetrafluoroethylene reaction vessel, submerged in a 150 ml aqueous solution containing 0.0094 mol of sodium tungstate di-hydrate at pH 3.0, achieved through the addition of hydrochloric acid. Additionally, 1 g of oxalic acid, acting as a chelating agent, was introduced. Subsequently, the mesh underwent a 4 h reaction at 220 °C and was subsequently annealed for 30 min in a 350 °C furnace. Remarkably, the resultant mesh exhibited an exceptional water separation flux of 9870 ± 15 L/hr/m2 when exposed to 1:1 v/v oil–water mixtures. This performance significantly outperformed previous filters designed for similar oil–water separation tasks. The mesh efficiently facilitated the passage of water through the oil–water mixture, achieving an efficiency rate exceeding 98 ± 1%. To gauge its wetting behavior, the hydrophilic/underwater oleophobic filter underwent static contact angle measurements. The filter's wetting mechanism was primarily attributed to its hierarchical surface structure, which enhanced surface hydrophilicity and roughness. Analytical techniques such as XRD, FTIR, and FE-SEM were employed to scrutinize the fabricated filter's composition. These analyses confirmed the successful creation of a nanostructured WO3 coating on both sides of the stainless steel mesh. Moreover, the utilization of commercially available chemicals and straightforward fabrication techniques underscores the promising potential of this approach for large-scale applications.

Robust and flexible polyester fiber membrane with under-liquid dual superlyophobicity for efficient on-demand oil-water separation

Functional materials with under-liquid dual superlyophobicity have generated a great deal of concern from researchers due to their switchable separation ability oil-water mixtures and emulsions. Conceptually, under-liquid dual superlyophobicity is a Cassie state achievable under-liquid through the synergy of an under-liquid double lyophobic surface and the construction of a highly rough surface. However, obtaining an under-liquid dual superlyophobic surface remains difficult due to its thermodynamic contradiction and complex surface composition. Herein, we successfully prepared a functional coating by modifying the mixture of cellulose nanocrystals (CNCs) and nano-TiO2 with perfluorooctanoic acid (PFOA) via a simple method, then obtained a polyester fiber membrane with under-liquid dual superlyophobicity by roll coating method. The surface wettability of the polyester (PET) membrane was altered, transforming it from the original under-water oleophobic/under-oil superhydrophilic state to the under-water superoleophobic/under-oil superhydrophobic state after coated. The resulting membrane was applied to separate oil and water on-demand. The coated PET membrane exhibited high separation efficiency (>99 %) and high separation flux, effectively separating immiscible oil-water systems as well as oil-in-water and water-in-oil emulsions. The coated PET membrane also demonstrated the ability to perform alternate separation of oil-water mixtures through wetting, washing, and rewetting cycles, with repeated processes up to 10 times without significant reduction in separation efficiency. Furthermore, compared with the previous works, our approach offers a simpler and more convenient method for constructing under-liquid dual superlyophobic surface, making it more suitable for continuous corporate production. This study may provide inspiration for the production and application in large-scale of under-liquid dual superlyophobic membranes.

Controllable process to construct robust superhydrophobic membrane with tunable pore size for efficient separation of oil-water mixtures and emulsions

The increase in the discharge of industrial oily wastewater poses a threat to the environment and human health. Thus, the treatment of oily wastewater has become a focus of current research. The superhydrophobic surface derived from the lotus effect provides an effective direction for oil-water separation. Based on this, the authors reported a tunable superhydrophobic stainless steel separation mesh with a water contact angle of 155° through simple electrodeposition and modification with a fluorine-free modifier. The separation mesh with different surface morphology, by controlling different electrodeposition time and current, is able to achieve oil-water separation with super flux up to 51561 L/(m2·h) in heavy oil/water mixture and high-efficiency over 99.5% in water-in-oil emulsion. This controllable process constructs superhydrophobic membrane with tunable pore size, which is capable of separating heavy oil/water mixtures and water-in-oil emulsions depending on the process. This proposal is suggestive in the field of oil-water separation.

Multifunctional amphibious superhydrophilic-oleophobic cellulose nanofiber aerogels for oil and water purification

Aerogels are of a popular choice for oil-water separation and water purification due to their attractive properties, such as lightweight, large surface area, and high porosity. Developing robust aerogels with multifunctional characteristics is highly desirable but remains challenging nowadays. Herein, we develop a facile one-pot condensation strategy for the fabrication of superhydrophilic-oleophobic (SHI-OP) composite aerogels using cellulose nanofibers (CNF), 3-glycidy-loxypropyl trimethoxysilane (GPTMS), polyethyleneimine (PEI) and fluorine-contained compound (FS-60). The resulted aerogels exhibit a directional lamellar structure with interconnected macropores, super-lightweight with high porosity of 98.30 % and low density of 0.0256 g·cm−3. Also, the aerogels are mechanically durable against repeated compression. Meanwhile, the amphibious SHI-OP feature of the composite aerogels in both air and water states enables them to not only absorb trace amount of water from contaminated oils, but also separate oil-water mixtures with separation efficiency of over 99 % and high permeation flux of over 9060 L/m2·h. Moreover, the aerogels also show excellent dye adsorption capability and reusability toward anionic dyes with a maximum adsorption capacity of 1245.68 mg/g. Such robust and multifunctional aerogels with special surface wettability provide good opportunity for liquid purification and dye-containing wastewater treatment.

Sequestration of oils from water using superhydrophobic silanized montmorillonite-KSF nanoclay coated polyurethane foam

Oil spills have disastrous consequences on the environment. Multifarious absorbents have been applied in oil spill remediation; however, the design of cost-effective, dependable, and environmentally benign absorbents is desirable and pressing. Here, a polyurethane foam (PF) with superhydrophobic/superoleophilic properties was fabricated by surface coating of montmorillonite (MMT) nanoclay. Initially, the hydrophobic MMT was obtained by grafting octadecyltrimethoxysilane (ODTMS) onto the surface of the nanoclay and this was then used to modify the foam via a dip-coating technique. This modification produces a superhydrophobic foam with a water contact angle reaching 153.83 ± 1.86°. The as-prepared foam demonstrates high absorption selectivity and excellent absorption capacity of 29.5–66.5 times weight gain for several organic solvents and oils. The efficiency of separation for multiple oil-water mixtures reached 99.87%. After 10 cycles of absorption-desorption studies, such superhydrophobic foam still sustained good oil absorption performance, thus exhibiting outstanding reusability and desirable regeneration for practical applications. The oil and organic solvent samples could swiftly and continuously be retrieved from the water by the modified foam. The fabrication method for the superhydrophobic PF by its modification with natural clay minerals appears to be simple, economical, and promising for expandable applications in the effective separation of oil-water mixtures.

An ultra-thin nickel electrodeposited stainless steel mesh with superhydrophobic property and high mechanical durability for oil-water separation

Oil pollution has a detrimental impact on our water environment. Therefore, developing a durable and high-flux material for separating oil-water mixture is highly desirable. In this study, we present an innovative approach to prepare superhydrophobic-superoleophilic nickel palmitate stainless steel meshes (SNP-SSM) using a one-step electrodeposition method. This method not only creates rough hierarchical micro/nanostructures on the SSM but also reduces the surface free energy of the SSM. The SNP-SSM demonstrates a water contact angle (CA) of 164.98 ± 2.3° and a roll-off angle (ROA) of 4.78 ± 1.3°, enabling effective, long-term separation of oil-water mixtures by gravity. The oil-water separation efficiency (n-hexadecane/water) reaches 98.3%. Furthermore, in various tests, including knife scratching, tape peeling, sandpaper abrasion, bending, heating, and immersion in various liquids, the SNP-SSM exhibits sufficient mechanical, chemical, and thermodynamic robustness, making it suitable for harsh conditions, the as-prepared coatings effectively inhibited the corrosion of the meshes. This study paves the way for advancing technology in challenging oil-water separation scenarios, encompassing mechanical friction, chemical processes, and high-temperature conditions.

Constructing green superhydrophilic and superoleophobic COFs-MOFs hybrid-based membrane for efficiently emulsion separation and synchronous removal of microplastics, dyes, and pesticides

Oil spills and micropollutants have become thorny environmental issues, posing serious threat to ecosystem and human health. To settle such dilemma, this study successfully constructed a robust and environmentally-friendly MOFs-COFs hybrid-based membrane (FS-50/COF(MATPA)-MOF(Zr)/PDA@PVDF) for the first time through solution synthesis and solvothermal method, combined with surface modification of FS-50 molecule. Importantly, we employed a simple two-step strategy to obtain the high-aspect-ratio MOFs fibers: (1) solvent regulation to generate smaller needle-like whiskers during the in-situ growth of MOFs on COFs; (2) high pressure induced directional crystallization in filtration process. The introduction of polydopamine (PDA) greatly improved the adhesion between coating and PVDF membrane. The in-situ growth of high length-diameter ratio MOFs fibers on blocky COFs greatly enhanced the specific surface area of MOFs-COFs hybrid, thus provided sufficient absorption sites. The functional groups of FS-50 endowed the hybrid membrane with superhydrophilicity and superoleophobicity, which facilitated to selectively penetrate water molecules and repel non-polar pollutants. The separation efficiency and decontamination mechanism of hybrid membrane to the simulated oily wastewater (containing various MPs, dyes, and pesticides) were investigated through experiments and theoretical calculations. The hybrid membrane could selectively and synchronously adsorb various dyes (20 mg/L–120 mg/L, almost 100% removal) and pesticides (10 mg/L for DIF and TET, adsorption rates 93.2% and 90.9%, respectively) from oil-water emulsion (50 mL). The large-scale coated sponge (6 cm × 4.5 cm × 3 cm) could quickly achieve separation of oil-water mixture (almost 100%) with a water permeability of more than 162 L m−2·h−1·bar−1, and simultaneously remove various MPs (PP-2000, PP-100, PE-2000, PS-100, 0.2 g/300 mL for each), Sudan Ⅲ (C0 = 200 mg/L), and DIF (C0 = 10 mg/L) from a simulant oily wastewater (300 mL), with the removal rates of almost 100% for MPs, 99.7% for Sudan Ⅲ, and 95.8% for DIF. Furthermore, we elucidated the removal mechanism of pesticide and dyes through simulating the theoretical adsorption energy and potential adsorption sites. The hybrid membrane not only provides a promising candidate for the removal of multiple pollutants from oil-water emulsion, but also opens a new strategy for achieving efficient and clean aquatic environment restoration.

PI nanofiber membranes with pH-responsive wettability fabricated through solution blow spinning for efficient on-demand oil-water separation

Nanofiber membranes (NFMs) are widely used in oil-water separation area due to their unique structure and properties. However, achieving efficient and on-demand separation of oil-water mixtures using NFMs remains a challenge. Herein, we prepared polyimide nanofiber membranes (PI-NFMs) with fluffy structures through solution blow spinning (SBS), and the average diameter of the PI nanofibers was 506.1 ± 75.6 nm. The PI-NFMs exhibited excellent pH responsiveness, demonstrating the ability to swiftly convert their wetting properties between highly hydrophobic and superhydrophilic through a simple acid-alkali treatment. Additionally, the conversion between oil removing model and water removing model according to the type of oil-water mixture was realized. The performance of the membranes in separating oil and water was evaluated using five different densities of oil-water mixtures. Only driven by gravity, the membrane exhibits good separation efficiency and extremely high permeate fluxes with the water and oil fluxes to 37,641.84 and 71,083.16 L·m−2·h−1, respectively, which also shows decent reusability. This work presents a promising solution for the intelligent, efficient, and controllable treatment of industrial oil effluents and oil spills.

Eco-friendly and multifunctional superhydrophilic and underwater superoleophobic materials with adsorption, photodegradation and oil-water separation properties

The frequent water pollution problems have caused serious harm to the ecological environment and human health, among which, a large number of waste water contains heavy metal ions, organic dyes, oil-water emulsion and other pollutants. Therefore, it is particularly important to prepare multifunctional materials that can separate these pollutants and purify wastewater. In this paper, ovalbumin (OVA), phytic acid (PA) and egg shell powder (ESP) and TiO2 particles were used to construct a composite system, which was loaded on fabric, cotton and PVDF membrane by impregnation method. The preparation of OVA-ESP-TiO2-PA modified materials which can efficiently separate various oil-water mixtures and oil-water emulsions were successfully achieved. The modified material could achieve high flux (up to13458 L m−2h−1) and separation efficiency (＞99 %) for various mixtures of oil and water by gravity-driven. Typically, it shows good stability and durability under strong acid and alkali (pH=1–12) and different temperatures (T = 10–60 ℃), and can be reused. What's more, the modified materials can effectively adsorb organic dyes (＞92 %) and heavy metal ions (up to 85 %) and can degrade organic dyes by ultraviolet light. It provides a new idea for the separation of oil-water mixture and the purification of waste liquid containing organic dyes and heavy metal ions, which has a good application prospect in the treatment of industrial wastewater and domestic wastewater.

Spontaneous Separation of Immiscible Organic Droplets on Asymmetric Wedge Channels with Hierarchical Microchannels.

Spontaneous separation of immiscible organic droplets has substantial research implications for environmental protection and resource regeneration. Compared to the widely explored separation of oil-water mixtures, there are fewer reports on separating mixed organic droplets on open surfaces due to the low surface tension differences. Efficient separation of mixed organic liquids by exploiting the rapid spontaneous transport of droplets on open surfaces remains a challenge. Here, through the fusion of inspiration from the fast droplet transport capability of Sarracenia trichome and the asymmetric wedge channel structure of shorebird beaks, this work proposes a spine with hierarchical microchannels and wedge channels (SHMW). Due to the synergistic effect of capillary force and asymmetric Laplace force, the SHMW can rapidly separate mixed organic droplets into two pure phases without requiring additional energy. In particular, the self-spreading of the oil solution on the open channel surface is utilized to amplify the surface energy difference between two droplets, and SHMW achieves the pickup of oil droplets floating on the surface of the organic solution. The maximum separation efficiency on 3-SHMW can reach 99.63%, and it can also realize the antigravity separation of mixed organic droplets with a surface tension difference as low as 0.87 mN·m-1. Furthermore, SHMW performs controllable separation, oil droplet pickup, and continuous separation and collection of mixed organic droplets. It is expected that this cooperative structure composed of hierarchical microchannels and wedge channels will be realized in resource recovery or chemical reactions in industrial production processes.

High efficiency and selective separation of oily wastewater based on superamphiphilic biomass aerogel: Characteristics, mechanisms and application

The design and development of multifunctional materials to meet the sophisticated requirements of oily wastewater treatment is an urgent need and remains a great challenge. Herein, a superamphiphilic bio-aerogel (PTGA) with honeycomb-like porous structure was synthesized. The directional and reversible control of interfacial wettability can be achieved by simple pre-wetting process and solvent replacement method. Combined with the advantages of structure and wettability, PTGA was proved to be ideal for high-efficient oil-water mixture separation (J> 1500 L/m2·h, η > 99.8%), oils absorption (Cabs = 17–26 g/g) and dye selective removal (MO: 73.552 mg/g, MB: 45.876 mg/g). Furthermore, based on the newly developed dynamic separation device and excellent mechanical property of PTGA, enhanced separation of oil-water mixture (J = 3007 L/m2·h) and synergistic removal of co-existing pollutants (MB: 51.274 mg/g) were realized. Mechanism results indicated that the transition of interfacial wetting properties of PTGA was a multi-stage process, while oil/water separation and dye adsorption were two independent processes. Benefit from facile synthesis and unparalleled characteristics, the designed PTGA promise to be reliable and competitive candidates in wastewater remediation.

Recycled waste masks as oil absorbent based on stable SiO2 coating for efficient separation of oil-water mixtures and oil-in-water emulsions

Due to the COVID-19 pandemic, mask contamination has become a global concern, and proper disposal of used masks is crucial. In this study, Waste Masks (WM) were modified into a highly efficient oil adsorption material by in-situ growth of SiO2 and subsequent grafting with Octadecyl trichlorosilane (OTS). The modified masks had a water contact angle of 153.2°, showed attractive adsorption capacity (27.33, 31.84, and 32.81 g·g−1) for soybean oil, lubricating oil and engine oil. The modified WM can adsorb not only the light oil on the water surface but also the heavy oil under water. Furthermore, the modified WM was able to separate oil-in-water emulsions of n-hexane and toluene by adsorbing the oil emulsion droplets. Molecular dynamic (MD) simulation was used to investigate the oil-water separation mechanism and calculate the adsorption energy of oil molecules on the OTS-grafted surface. This study provides an interesting solution to the environmental problems caused by discarded masks and the production of low-cost, reusable, and eco-friendly oil-absorbing materials.

Preparation and characterization of bio-inspired full-biomass-derived aerogel with vertically aligned structure

Using renewable biomass resources to prepare porous materials can reduce the dependence on petroleum-based energy, promote green, low-carbon, and high-quality development, and achieve carbon neutrality. Here, we report a bio-inspired full-biomass-derived aerogel with an ultra-light (10.33–27.77 mg/cm3), highly porous (98.66–99.19 %), and vertically aligned structure. The fabrication involves an ultrasonic-assisted deep eutectic solvent (DES) extraction of cellulose nanofibrils (CNFs)-blending-directional freeze-drying-hydrophobic modification. Initially, CNFs were extracted from corncobs using DES pretreatment. Then, the aerogels were prepared by co-mixing CNFs with alkali lignin and freeze-drying the precursor suspension using the ice-templated method. Finally, the aerogels were modified using trimethoxymethylsilane chemical vapor deposition to render them hydrophobic. The silanization-modified aerogels exhibited superior static and dynamic hydrophobic properties, with a water contact angle of up to 153.4°, and demonstrated self-cleaning properties. These aerogels exhibited adsorption capabilities for various oils and organic solvents (9.6–29.8 g/g) and the ability to separate oil–water mixtures and adsorb methylene blue. Moreover, the aerogels with vertically aligned structures exhibited exceptional axial compression properties (up to 959 kPa), more than four times greater than the radial compression properties. Furthermore, the aerogels exhibited rapid liquid transport properties, with an axial transport rate of soybean oil that was more than 10 times higher than the radial transport rate. This study provides a green, eco-friendly, and sustainable strategy for preparing 3D porous aerogels, paving the way for developing full-biomass-derived aerogels as a promising alternative to petroleum-based adsorbent materials.

Maximizing the benefits of combining fibroin and sericin: Functionalized obsoleted silk cocoon shell for purifying oily wastewater containing Pb2+

Based on the durability of fibroin and the biocompatibility of sericin, researchers are exploring ways to maximize their advantages by combining them in the biomedical field. Fortunately, silk cocoon shell (SC) offers a natural composite material of fibroin and sericin. However, the inherent hydrophobicity of SC, the random arrangement connection of fibers, and the protection provided by the outer sericin limit its application in purifying oil wastewater. In this work, a cost-effective method was developed to improve the hydrophilicity of SC and the mechanical properties of SC by utilizing obsoleted SC as a matrix as well as by dissolving portions of sericin proteins. The polydopamine particle (PDP) was utilized as the intermediate modification layer and a supramolecular gel (SMG) was introduced to the surface of SC, further improving the surface's hydrophilicity of SC. The study indicated that SC@P-SMG has excellent mechanical properties, favorable anti-fouling properties, and superior self-cleaning ability. Furthermore, when the SC@P-SMG was applied in water purification, it could achieve multifunctional applications such as purifying wastewater containing emulsified oil and Pb2+ ions, methylene blue (MB), and oil-water mixture separation. This work provided innovative ideas to maximize the benefits of combining fibroin and sericin.

Layer-by-layer assembly induced strong, hydrophobic and anti-bacterial TEMPO oxidized cellulose nanofibrils films for highly efficient UV-shielding and oil-water separation

Anti-ultraviolet material with cost-effectiveness, environmental friendliness, and multifunction is urgently needed to address the serious problem of ultraviolet radiation. However, traditional anti-ultraviolet products based on plastics are unsustainable and harmful to the environment. Herein, the cellulose films with a sandwich structure using a surface assembly technique were reported. Natural L-phenylalanine was grafted onto cellulose nanofibrils via amidation to enhance their UV-shielding property. To address the hydrophilic nature and limited mechanical strength of cellulose films, we employed octadecyltrichlorosilane and 4ARM-PEG-NH2 for hydrophobic coating and mechanical reinforcement, respectively. In addition to providing complete UV resistance in the wavelength range of 200–320 nm, sample OPT5 exhibited significantly improved tensile stress, Young's modulus, and toughness, measuring 174.09 MPa, 71.11 MPa, and 295.33 MJ/m3, respectively. Furthermore, due to the presence of antibacterial amine groups, the modified film demonstrated a satisfactory inhibitory effect on the growth of Escherichia coli and Bacillus subtilis. Compared to natural cellulose films, the hydrophobically modified material achieved a contact angle of up to 121.1°, which enabled efficient separation of oil-water mixtures with a maximum separation efficiency of 93.87 %. In summary, the proposed TOCNF-based UV-shielding film with multifunctionality holds great potential for replacing petrochemical-derived plastics and serving as an applicable and sustainable membrane material.

Facile fabrication of hydrophobic covalent organic framework decorated melamine sponge for efficient separation of immiscible oil-water mixture and water-in-oil emulsion

Frequent oil spills and oily sewage have caused serious environmental problems. Sponges have attracted great attention in oil-water separation due to their low cost and high porosity, but it still remains challenge to hydrophobic modification of sponge in facile and scalable manner. Here is reported a facile fabrication of porous and hydrophobic sponge composite (MS@COF) with effective oil-water separation by in-situ growth of hydrophobic TFB-BD(Me)2 COF on the surface of melamine sponge. Combining the porous structure of the sponge and hydrophobicity of COF, the composite can separate oil-water mixture and water-in-oil emulsions in a fast way. The prepared MS@COF showed oil adsorption capacity up to 160 g g-1. In addition, continuous separation of oil-water mixture was demonstrated using a peristaltic pump with a separation rate of 50 mL min-1. More importantly, the composite could separate surfactant-stabilized water-in-oil emulsions with separation efficiency of 98.8%. The oil-water mixture and oil-water emulsion separation ability of the composite persisted after 50 separation cycles thereby demonstrating good recyclability. The composite also showed good chemical stability, mechanical and flame retardancy. This work introduces a new approach for the synthesis of hydrophobic sponge decorated with COF nanoparticles for oily wastewater treatment and organic pollutant removal on water surfaces.

Converting pomelo peel biowaste into multifunctional sponges integrated underwater superoleophobicity and catalytic ability for sewage treatment

Fabricating practical multitasking materials integrating efficient oil-water separation ability and excellent catalytic performance is significant for water remediation but challenging for substrates and subsequent surface modification causing high cost, high power consumption, and poor reusability. Herein, a multitasking sponge was designed for water purification by successively modifying the biomass pomelo peel (PP) with polypyrrole (PPy), Au nanoparticles (NPs), and polydopamine (PDA). The cost-effective and renewable PP substrates, facile surface decoration of PP with PPy coating, in-situ spontaneous growth of Au NPs, and the protection of the outermost PDA coating endowed the as-obtained PP/PPy-Au/PDA sponges high sewage treatment efficiency and the potential for large-scale preparation. The PP/PPy-Au/PDA sponges exhibited high catalytic reduction activity for 4-nitrophenol (4-NP) and excellent reusability without remarkable decline in catalytic activity even after 10 recycles due to the synergistic effect among PPy, Au NPs and PDA. In addition, this sponge also displayed superior separation efficiency and high filtration flux towards both immiscible oil-water mixtures and O/W emulsions due to its underwater superoleophobicity. Integrating above properties, the PP/PPy-Au/PDA sponge could perform catalytic degradation of organic molecules and meanwhile separation of oil-water mixtures.