A Novel Freeze-Drying-Free Strategy to Fabricate a Biobased Tough Aerogel for Separation of Oil/Water Mixtures

Efficient oil spill cleanup from water: Investigating the effectiveness of a sustainable anti-swelling hydrogel for rapid water repellency and oil absorption

Considering the significant harm caused to aquatic ecosystems and marine life by oil spills and the discharge of oily wastewater, there is a pressing need to address this issue to protect our environment and prevent the wastage of valuable resources. We introduced a two-step approach to create an anti-swelling, water-repellent sorbent using a green polysaccharide called gum gellan, functionalized with Octadecyl trichlorosilane (OTS) through dip coating method. Natural gums like gellan have high absorption capability due to their large surface area. However, they are hydrophilic, which means they can only absorb water. This property makes them unsuitable for oil spill applications. To make gum gellan suitable for oil spill applications, we have modified it in this study. We have introduced a material called octadecyltrichlorosilane, which has low surface energy and hierarchical roughness. This modification changes the wettability of gellan from hydrophilic to hydrophobic/oleophilic, allowing it to absorb oil and repel water. The sorbent is analyzed using several techniques, such as FTIR, XRD, TGA, FE-SEM, BET, Raman, EDX, and H1-NMR. The hydrophobic sorbent obtained demonstrates low density, high surface area, and high porosity. These characteristics give it excellent floatability and immediate and exceptional selectivity for absorbing oil from water. Additionally, it does not absorb any detectable amount of water. The sorbent exhibited a water contact angle (WCA) of 140 ± 3 ° and an oil contact angle (OCA) of 0° for various oils and organic solvents. It has rapid oil absorption capacity of 3.72 g/g for diesel, and can be easily recovered after use. The BET analysis revealed that after the modification with OTS, the sorbent's total surface area increased from 0.579 m2/g to 4.713 m2/g. This indicates that the OTS modification greatly enhances the surface area and pore volume of the, thus improving its ability to absorb oil. This sorbent efficiently separates oil-in-water emulsions, both surfactant-stabilized and surfactant-free, achieving over 90% separation through gravity alone. Moreover, the sorbent can sustain its wettability even under harsh environmental conditions, including exposure to acids, alkalis, and salts. The absorption data predominantly aligned with the pseudo-2nd-order model. Thus, this sorbent provides a cost-effective alternative for efficiently absorbing and separating oil-water emulsions in households and industries.

Elastic SiC Aerogel for Thermal Insulation: A Systematic Review

SiC aerogels with their lightweight nature and exceptional thermal insulation properties have emerged as the most ideal materials for thermal protection in hypersonic vehicles; However, conventional SiC aerogels are prone to brittleness and mechanical degradation when exposed to complex loads such as shock and mechanical vibration. Hence, preserving the structural integrity of aerogels under the combined influence of thermal and mechanical external forces is crucial not only for stabling their thermal insulation performance but also for determining their practicality in harsh environments. This review focuses on the optimization of design based on the structure-performance of SiC aerogels, providing a comprehensive review of the inherent correlations among structural stability, mechanical properties, and insulation performance. First, the thermal transfer mechanism of aerogels from a microstructural perspective is studied, followed by the relationship between the building blocks of SiC aerogels (0D particles, 1D nanowires/nanofibers) and their compression performance (including compressive resilience, compressive strength, and fatigue resistance). Moreover, the strategy to improve the high-temperature oxidation resistance and insulation performance of SiC aerogels is explored. Lastly, the challenges and future breakthrough directions for SiC aerogels are presented.

Trichome-Like Biomimetic Air Filters via Templated Silicone Nanofilaments

Air pollution threats to human health have increased awareness of the role of filter units in air cleaning applications. As an ideal energy-saving strategy for air filters, the slip effect on nanofiber surfaces can potentially overcome the trade-off between filtration efficiency and pressure drop. However, the potential of the slip effect in nanofibrous structures is significantly limited by the tight nanofiber stacks. In this study, trichome-like biomimetic (TLB) air filters with 3D-templated silicone nanofilaments (average diameter: ≈74 nm) are prepared based on an in situ chemical vapor deposition (CVD) method inspired by plant purification. Theoretical modeling and experimental results indicate that TLB air filters make significant use of the slip effect to overcome the efficiency-resistance tradeoff. The selectable filter class (up to U15, ≈99.9995%) allows TLB air filters to meet various requirements, and their integral filtration performance surpasses that of most commodity air filters, including melt-blown cloth, ePTFE membranes, electrospun mats, and glass fiber paper. The proposed strategy directly transforms commercial filter media and filters into TLB air filters using a bottom-up, one-step approach. As a proof-of-concept, reusable N95 respirators and air purifiers equipped with TLB air filters are fabricated, overcoming the limitations of existing filter designs and fabrication methods.

Bioinspired Structures Made of Silicone Nanofilaments for Upcycling Waste Masks to Reusable N95 Respirators

The increasing demand for personal protective equipment such as single-use masks has led to large amounts of nondegradable plastic waste, aggravating economic and environmental burdens. This study reports a simple and scalable approach for upcycling waste masks via a chemical vapor deposition technique, realizing a trichome-like biomimetic (TLB) N95 respirator with superhydrophobicity (water contact angle ≥150°), N95-level protection, and reusability. The TLB N95 respirator comprising templated silicone nanofilaments with an average diameter of ∼150 nm offers N95-level protection and breathability comparable to those of commercial N95 respirators. The TLB N95 respirator can still maintain its N95-level protection against particulate matter and viruses after 10 disinfection treatment cycles (i.e., ultraviolet irradiation, microwave irradiation, dry heating, and autoclaving), demonstrating durable reusability. The proposed strategy provides new insight into upcycle waste masks, breaking the existing design and preparation concept of reusable masks.

Transfer Printing of Ordered Plasmonic Nanoparticles at Hard and Soft Interfaces with Increased Fidelity and Biocompatibility Supports a Surface Lattice Resonance

Transfer printing, the relocation of structures assembled on one surface to a different substrate by adjusting adhesive forces at the surface-substrate interface, is widely used to print electronic circuits on biological substrates like human skin and plant leaves. The fidelity of original structures must be preserved to maintain the functionality of transfer-printed circuits. This work developed new biocompatible methods to transfer a nanoscale square lattice of plasmon resonant nanoparticles from a lithographed surface onto leaf and glass substrates. The fidelity of the ordered nanoparticles was preserved across a large area in order to yield, for the first time, an optical surface lattice resonance on glass substrates. To effect the transfer, interfacial adhesion was adjusted by using laser induction of plasmons or unmounted adhesive. Optical and confocal laser scanning microscopy showed that submicron spacing of the square lattice was preserved in ≥90% of transfer-printed areas up to 4 mm2. Up to 90% of ordered nanoparticles were transferred, yielding a surface lattice resonance measured by transmission UV-vis spectroscopy.

Environmentally Friendly Plastic Boats - A Facile Strategy for Cleaning Oil Spills on Water with Excellent Efficiency

In this report, we demonstrate a novel plastic boat capable of selectively and efficiently collecting spilled oils while floating on water. The boat has macroscopic openings in its vertical and curved sidewalls. It is easily, quickly, and inexpensively fabricated using an environmentally friendly polymer via a three-dimensional printing technique. Its surface is sequentially coated with nano-ceramic coating liquid and oil, which imparts favorable hydrophobic, oleophilic, and high oil-wettability properties. Using the boat prototype, a small pump system, and an oil boom-like device, we demonstrate that spilled oils with a wide range of viscosities (2.0-1000 cSt at 25-40 °C) are rapidly collected from the surface of both pure water and seawater. Remarkably, it efficiently collects oil spills on seawater under wavy conditions, and the retrieved oil does not mix with any drop of water. Moreover, the boat can be scaled up to a large size easily and has a long-term usage. By exhibiting these characteristics, our developed boat is a prominent potential device for practical oil retrieval applications.

Stainless Steel Screen Modified with Renatured Xerogel for Efficient and Highly Stable Oil/Water Separation via Gravity

The application of hydrogel coatings to surface-modified metallic materials has gained considerable attention in engineering practice such as water-oil separation. However, the low coating adhesion and poor coating stability restrict its application. In this study, to obtain special wettability and durable filter materials, polyacrylamide (PAM)/sodium alginate (SA) xerogel particles were first prepared and adhered to a stainless steel screen by using an epoxy resin as a linker. Subsequently, the xerogel particles of the screen rehydrates in water to form a PAM-SA double-network hydrogel. The results show that the screen modified by PAM-SA xerogel of 20-30 μm particle size and a linker concentration of 0.1 g/mL resulted in a chimeric structure and subsequently transformed a uniform double-network hydrogel coating in water. According to the experimental results, the rough hydrogel coating exhibits superhydrophilicity and superoleophobicity under water; in particular, it has excellent wear resistance as well as physical and chemical stability. Under gravity-driven action, the PAM-SA-modified screen demonstrates high separation efficiency values of up to 99% in separating a wide range of oil/water mixtures and maintaining a water flux of (2-6) × 10⁴ L·m^-2·h^-1. There was no significant reduction in efficiency of separation and water flux after 10 cycles, indicating that the PAM-SA-modified screen is capable of offering outstanding separation performance and durability. Moreover, the hydrogel-modified screen demonstrated corrosion and swelling resistance in some extreme environments, paving a way for practical applications in water treatment. The novel hydrogel-coating-modified screen with ease of preparation holds great promise for oil/water separation and other engineering applications.

Special Superwetting Materials from Bioinspired to Intelligent Surface for On-Demand Oil/Water Separation: A Comprehensive Review

Since superwetting surfaces have emerged, on-demand oil/water separation materials serve as a new direction for meeting practical needs. This new separation mode uses a single porous material to allow oil-removing and water-removing to be achieved alternately. In this review, the fundamentals of wettability are systematically summarized in oil/water separation. Most importantly, the two states, bioinspired surface and intelligent surface, are summarized for on-demand oil/water separation. Specifically, bioinspired surfaces include micro/nanostructures, bioinspired chemistry, Janus-featured surfaces, and dual-superlyophobic surfaces that these superwetting materials can possess asymmetric wettability in one structure system or opposite underliquid wettability by prewetting. Furthermore, an intelligent surface can be adopted by various triggers such as pH, thermal and photo stimuli, etc., to control wettability for switchable oil/water separation reversibly, expressing a thought beyond nature to realize innovative oil/water separation by external stimuli. Remarkably, this review also discusses the advantages of all the materials mentioned above, expanding the separation scope from the on-demand oil/water mixtures to the multiphase immiscible liquid-liquid mixtures. Finally, the prospects of on-demand oil/water separation materials are also concluded.

Sulfolane Crystal Templating: A One-Step and Tunable Polarity Approach for Self-Assembled Super-Macroporous Hydrophobic Monoliths

Freeze-casting (ice templating) is generally used to prepare super-macroporous materials. However, water solubility limits the application of freeze-casting in hydrophobic material fabrication. In the present work, inexpensive and low-toxic sulfolane was used as a novel crystallization-induced porogen (sulfolane crystal templating) to prepare super-macroporous hydrophobic monoliths (cryogels) with tunable polarity. The phase transition of sulfolane consisted of reversible processes in the liquid, semi-crystalline, and crystalline states. Because of the density change during phase transition, liquid sulfolane experienced a 16.4% volume shrinkage per unit mass. Thus, the cryogels obtained using the conventional freezing method contained obvious hollow-shaped defects. Furthermore, a novel route of pre-cooling, pre-crystallization, crystal growth, freezing, and thawing (PPCFT) was employed to prepare cryogels with defect-free macroscopic morphology and uniform pore structure. The as-obtained cryogels were composed of a super-macroporous structures and interconnected channels, and their porosity ranged between 85 and 97%. Moreover, the cryogels manifested good hydrophobicity (contact angle = 120-130°) and had absorption capacities greater than 10 g g^-1 for oils and organic liquids. The maximum absorption capacities of the resultant cryogels in dichloromethane, ethyl acetate, and liquid paraffin were 60.3, 35.8, and 15.2 g g^-1, respectively. Moreover, sulfolane could conveniently dissolve hydrophobic and hydrophilic monomers to generate amphiphilic cryogels (contact angle = 130-0°). Therefore, sulfolane crystal templating is a potential fabrication method for super-macroporous hydrophobic materials with tunable polarity.

A novel approach for authentication of shellac resin in the shellac-based edible coatings: Contain shellac or not in the fruit wax preservative coating

•

A novel approach based on targeted metabolomics for the authentication of shellac resin in shellac-based coating solution was established for the first time.

•

The authentication of shellac resin was skillfully transformed by means of taking monomer compounds constituting shellac resin (fatty acids and terpenic acids) as targeted metabolites.

•

The feasibility of the authenticated approach of shellac resin in commercial coating solution products for fruit preservation was verified by taking common metabolites as the biomarkers.

As an edible coating substrate, the detection of shellac resin has always been an intractable problem. In this paper, an authentication method of shellac resin in shellac-based edible coatings was established. Results showed that the authentication of shellac resin could be skillfully transformed as the identification of 13 targeted metabolites which were monomer compounds of shellac resin. The 13 targeted metabolites were further divided into 6 differential metabolites and 7 common metabolites with the metabonomic method and difference analysis of targeted metabolite contents. Then, four commercial soi-disant shellac-based coating solutions were selected to verify the feasibility of this method, and 7 common metabolites were detected in only one commercial sample, highly consistent with the results of shellac resin. All the above results indicated that the targeted metabolomics approach established in this study could provide a scientific basis for the qualitative authentication of shellac resin in the preservation coating.

Fabrication and Characterization of Quercetagetin-Loaded Nanoparticles Based on Shellac and Quaternized Chitosan: Improvement of Encapsulation Efficiency and Acid and Storage Stabilities

Shellac can be used as an ideal delivery vehicle to deliver and protect the hydrophobic quercetagetin; the barriers such as low acid stability and encapsulation efficiency, however, heavily impede the application of shellac. The purpose of this work is to prepare quercetagetin-loaded shellac-quaternized chitosan nanoparticles (Que-Sh-QCS NPs) to overcome these challenges. Herein, quaternized chitosan, with 14% degree of substitution, was successfully synthesized via a quaternization modification. The concentration of quaternized chitosan over 0.05% can prevent the aggregation of shellac nanoparticles at the acid. The encapsulation efficiency of quercetagetin obviously increased from 37.92 to 65.48% with the concentration of QCS varying from 0 to 0.05%. Meanwhile, Que-Sh-QCS_0.05 NPs possessed good storage stability, antioxidant property, biocompatibility, and controlled release. Therefore, quaternized chitosan can improve the encapsulation efficiency and acid and storage stabilities of nutraceutical-loaded shellac nanoparticles, providing a new insight into the application of shellac in cosmetics, pharmaceuticals, and food.

Removal of Oily Contaminants from Water by Using the Hydrophobic Ag Nanoparticles Incorporated Dopamine Modified Cellulose Foam

The presence of oil-related contaminants in water has emerged as a severe threat to the environment. The separation of these contaminants from water has become a great challenge, and extensive efforts are being made to develop suitable, environmentally friendly materials. Highly hydrophobic materials are effective in the selective separation of oil from water. In this work, silver (Ag)-incorporated, highly hydrophobic dopamine-modified cellulose sponge was prepared by functionalizing with the range of alkyl silanes. The Ag nanoparticle-incorporated dopamine provided the appropriate roughness, whereas the alkyl component provided the low surface energy that made it selective towards oil. It was found that the alkyl groups with a longer chain length were more effective in enhancing the hydrophobicity of the Ag nanoparticle-incorporated, dopamine-modified cellulose. The developed materials were characterized by Fourier transform infrared spectroscopy (FTIR), field emission-scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), elemental mapping, and contact angle goniometry. The maximum water contact angle on the functionalized surfaces was observed at 148.4°. The surface of the C18s-Ag-DA-Cell-F showed excellent selectivity towards the oily component that rapidly permeated, and water was rejected wholly. The developed material showed a separation efficiency of 96.2% for the oil/water mixture. The C18s-Ag-DA-Cell-F material showed excellent reusability. Due to their environmentally friendly nature, excellent selectivity, and good separation efficiency, the functionalized cellulose materials can be used to separate oil and water effectively.

Advanced super-hydrophobic polymer-based porous absorbents for the treatment of oil-polluted water

The threat of environmental pollution caused by spilled oil is rapidly increasing along with the expansion of oil exploration, the development of maritime activities and industrial growth. Oil spill incidents usually affect seriously the ecosystem and human life. Therefore, the treatment and recovery of the oil spill have been considered as an ultra-important issue to protect the environment and to minimize its negative impacts on socio-economic activities. Among methods of oil spill recovery, porous materials have emerged as potential absorbents possessing the capacity of absorbing spilled oil at a fast rate, high adsorption capacity, good selectivity, and high reusability. In this review paper, two types of polymer-based porous absorbents modified surface and structure were introduced for the treatment strategy of the oil-polluted water. In addition, the absorption mechanism and factors affecting the adsorption capacity for oils and organic solvents were thoroughly analyzed. More importantly, characteristics of polymer-based porous materials were discussed in detail based on microstructure analysis, absorption efficiency, and reusability. In general, this paper has provided an overview and a comprehensive assessment of the use of advanced polymer-based porous materials for the treatment of oil-polluted water, although the impacts of environmental factors such as wind, wave, and temperature should be further investigated in the future.

Formation Mechanism of Bleaching Damage for a Biopolymer: Differences between Sodium Hypochlorite and Hydrogen Peroxide Bleaching Methods for Shellac

Bleached shellac, a widely used material in food processing and products, was deeply affected in terms of structures and properties by the bleaching method. In the present study, a marked difference was observed between the damage performances of sodium hypochlorite-bleached shellac (SHBS) and hydrogen peroxide-bleached shellac (HPBS). The main bleaching damage reactions of sodium hypochlorite were the addition of double bonds to generate chlorine and the oxidation of hydroxyl to form aldehydes or ketones. In the case of hydrogen peroxide, degradation of shellac resin was caused by the hydrolysis of ester bonds and the oxidation of hydroxyl groups to form aldehydes and ketones, as well as carboxylic acids with deep oxidation. Based on the structural characterization of shellac resin, the bleaching damages were affected by the bleaching agent via the oxidizable groups, such as the unsaturated double bonds, hydroxyl and aldehyde groups in cyclic terpenes, and fatty acid chains. The differences could be attributed to the action of sodium hypochlorite on the hydroxyl group of aldehyde or ketone. Conversely, hydrogen peroxide bleaching oxidized the hydroxyl group and aldehyde group to carboxylic acid and initiated the hydrolysis reaction of the ester bond of the shellac resin, leading to the degradation of the resin. Thus, understanding the mechanism underlying the bleaching damage could provide a scientific basis for the subsequent targeted regulation of bleaching damage.

Ultralight Magnetic Nanofibrous GdPO4 Aerogel

Anisotropic aerogels are promising bulk materials with a porous 3D structure, best known for their large surface area, low density, and extremely low thermal conductivity. Herein, we report the synthesis and some properties of ultralight magnetic nanofibrous GdPO₄ aerogels. Our proposed GdPO₄ aerogel synthesis route is eco-friendly and does not require any harsh precursors or conditions. The most common route for magnetic aerogel preparation is the introduction of magnetic nanoparticles into the structure during the synthesis procedure. However, the nanofibrous GdPO₄ aerogel reported in this work is magnetic by itself already and no additives are required. The hydrogel used for nanofibrous GdPO₄ aerogel preparation was synthesized via a hydrothermal route. The hydrogel was freeze-dried and heat-treated to induce a phase transformation from the nonmagnetic trigonal to magnetic monoclinic phase. Density of the obtained magnetic nanofibrous monoclinic GdPO₄ aerogel is only ca. 8 mg/cm³.