Mechanically Tough and Regenerable Antibacterial Nanofibrillated Cellulose-Based Aerogels for Oil/Water Separation

Bioaerogels from biomass waste: An alternative sustainable approach for wastewater treatment

The generation of municipal solid waste is projected to increase from 2.1 billion tonnes in 2023 to 3.8 billion tonnes by 2050. In 2020, the direct global cost of managing this waste was approximately USD 252 billion. When considering additional hidden costs-such as those arising from pollution, adverse health effects, and climate change due to inadequate waste disposal-the total cost escalates to USD 361 billion. Without significant improvements in waste management practices, this figure could nearly double by 2050, reaching an estimated USD 640.3 billion annually. Among municipal solid waste, biowaste accounts for roughly 44 % of the global municipal solid waste, translating to about 840 million tonnes annually. They are widely accessible and economical, offering a cost-effective alternative to traditional treatment materials. Transforming biomass waste into carbon-based materials (e.g., bioaerogels) is a sustainable practice that reduces waste and repurposes it for environmental remediation. This approach not only decreases the volume of waste directed to landfills and mitigates harmful greenhouse gas emissions from decomposition but also aligns with the principles of a circular economy. Furthermore, it supports sustainable development goals by addressing issues such as water scarcity and pollution while promoting waste valorization and resource efficiency. The unique properties of bioaerogels-including their porosity, multi-layered structure, and chemical adaptability-make them highly effective for the remediation of different water pollutants from aquatic bodies. This review article comprehensively delves into multifaceted wastewater remediation strategies -based bioaerogels such as coagulation and flocculation, advanced oxidation processes, membrane filtration, catalytic processes, water disinfection, Oil-water separation, biodegradation, and adsorption. Additionally, it examines different mechanisms of interaction such as surface adsorption, electrostatic interaction, van der Waals forces, ion exchange, surface precipitation, complexation, pore-filling, hydrophobic interactions, and π-π stacking. Moreover, it conducts an integrated techno-economic evaluation to assess their feasibility in wastewater treatment. By valorizing biomass waste, a closed-loop system can be established, where waste is transformed into valuable bioaerogels. This approach not only addresses challenges related to effluent pollution but also generates economic, environmental, and social benefits. Ultimately, the review underscores the transformative potential of bioaerogels in wastewater treatment, emphasizing their crucial role in supporting long-term environmental goals and advancing the principles of resource circularity.

A Comparative Study of Structural Contribution to Biocidability via Immobilization of Fluorinated and Nonfluorinated Quaternary Ammonium Salts on Top Surfaces

Higher biocidability of fluorinated quaternary ammonium salt (QAS) is usually contributed to its preferential segregation to the surface to better contact with and kill bacteria. However, whether its structure also elicits better performance is still unclear. Herein, the same amount of a fluorinated QAS and its nonfluorinated counterpart are both immobilized on the top surface to eliminate the effect of concentration distribution to only study their structure-biocidability relationship. Briefly, the fluorinated and nonfluorinated QASs were synthesized by quaternization of N,N-dimethylethanolamine with 2-(perfluorooctyl)ethyl bromide that was prepared by bromination of 2-(perfluorooctyl)ethanol and 1-bromodecane, respectively. Polystyrene (PS) and diblock copolymer poly(styrene)-b-poly(tert-butyl acrylate) (PS-PtBA) were successively spin coated on SiO2 wafers at different concentrations to form bilayer structures that have a PS base layer and a PtBA top layer. The tert-butyl acrylate groups of the PtBA layer of 0.9 nm were converted to carboxylic acid groups with trifluoroacetic acid for respective esterification with the two hydroxy-containing QASs. It was observed that the fluorinated and nonfluorinated surfaces fabricated at the maximum comparable esterification yield of 63.5% fully eradicated ∼104 CFU of Staphylococcus aureus and Escherichia coli in 120 and 150 min, respectively, indicating that the fluorocarbon chain is more biocidal through better interpenetration into bacterial membranes. Immobilization of a functionality on top surface provides a universal strategy to study its structural contribution to activity without interference of the concentration distribution.

Research Progress on Membrane Separation Technology for Oily Wastewater Treatment

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

A review of various dimensional superwetting materials for oil-water separation

In recent years, the application and fabrication technologies of superwetting materials in the field of oil-water separation have become a research hotspot, aiming to address challenges in marine oil spill response and oily wastewater treatment. Simultaneously, the fabrication technologies and related applications of superwetting materials have been increasingly diversified. This paper systematically reviews the sources and hazards of oily wastewater and oil-water emulsions, several traditional oil-water separation methods, and their limitations, thereby highlighting the advantages of superwetting materials. Additionally, this paper provides an overview of the fundamental theories of wetting and conducts a microanalysis of the penetration mechanism based on Laplace pressure at the gas-liquid-solid three-phase interface. Following this, the latest advances in superwetting oil-water separation materials are elucidated, focusing on five categories: (i) superhydrophobic-superoleophilic materials; (ii) superhydrophilic-underwater superoleophobic materials; (iii) superhydrophobic-superoleophobic materials; (iv) "special" superwetting materials; and (v) smart switchable superwetting materials. This paper innovatively discusses these materials from the perspectives of two-dimensional and three-dimensional materials, deeply studying the mechanisms of oil-water separation and using data to quantify the separation efficiency. Comparative discussions are conducted on the materials from various dimensions, including different substrates, innovations in existing technologies, and fabrication methods as discussed in various articles, followed by corresponding summaries. Finally, the existing shortcomings and challenges of current superwetting materials are summarized, and prospects are proposed. We firmly believe that developing low-cost, stable, environmentally friendly, and practical large-scale superwetting oil-water separation materials will have broad application prospects and potential in the future.

Promising adsorbent for dye detoxification: Exploring the potential of chitosan sodium carboxymethylcellulose silk fibroin aerogel

The main goal of this study is to create a CS-CMC-SF aerogel consisting of chitosan sodium carboxymethylcellulose and silk fibroin. The aerogel is designed to remove types of dyes from water while also being environmentally friendly. This innovative adsorbent has been optimized for extracting both cationic and anionic dyes from solutions. It incorporates chitosan sodium carboxymethylcellulose and silk filament fibers to enhance its strength. Experimental data illustrates that the CS-CMC-SF aerogel possesses remarkable adsorption capabilities - 5461.77 mg/g for Congo Red (CR), 2392.83 mg/g for Malachite Green (MG), and 1262.20 mg/g for Crystal Violet (CV). A kinetic study aligns with the pseudo-second-order kinetic model suggesting predominant chemisorption phenomena occur during adsorption process. Isotherm analysis further identifies multilayered adsorption occurring on irregularly shaped surfaces of the aerogel while thermodynamic assessments validate exothermic and spontaneous characteristics inherent in its absorption mechanism. Several analytical methods such as SEM, FT-IR, XRD, and XPS were employed to examine physicochemical attributes tied to this unique material design conceptually; identifying mechanisms including pore filling, π-π interactions, ion exchange activity, electrostatic connections along with hydrogen bonding inducing overall superior performance output. Furthermore substantial soil biodegradability alongside compostable features associated with our proposed CS-CMC-SF aerogels established it's potential suitability within applications demanding sustainable options thereby validating its underlying ecological credibility.

Construction of durable antibacterial cellulose textiles through grafting dynamic disulfide-containing amino-compound and nanosilver deposition

Cotton textile is very comfortable to wear, and also provides an ideal environment for bacterial propagation, easily causing harm to human health. In order to address this issue, various antibacterial techniques are employed for cotton finishing. However, some processes are complex and involve the use of environmentally unfriendly chemicals. In this work, a durable and efficient antibacterial cotton fabric was prepared via grafting of an amino-compound containing dynamic disulfide bonds, and then in-situ deposition of silver nanoparticles (AgNPs). Briefly, the reactive α-lipoic acid-modified polyethyleneimine (mPEI) was introduced to the cotton fibers via thiol-ene click reaction. Subsequently, the amino groups and dynamically-generated sulfhydryl groups in the mPEI molecules were used to initiate the ultrafast reduction of silver ions without the participation of additional reductant, constructing a stable antibacterial layer on fiber surface. The results reveal that the amino and thiol groups of mPEI could form coordination bonds with the deposited silver nanoparticles, and the antibacterial ability of AgNP@cotton-g-mPEI fabric remains at a high level even after 20 washing cycles. After 30 min of contact with Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), the antibacterial rates against both bacteria reached 99.99 %. Meanwhile, the network matrix constructed by the recombination of the dynamic disulfide bonds in mPEI endows the cotton fabric with detectable wrinkle resistance and encouraging anti-ultraviolet effect. The present work provides a novel alternative for preparation of durable and efficient antibacterial textiles.

Robust functionalized cellulose-based porous composite for efficient capture and ultra-fast desorption of aqueous heavy metal pollution

The heavy metal pollution control industry requires convenient and cost-effective solutions to address complex aqueous environment. Adsorption method can be an effective strategy to realize these goals. Considering the importance of environmental and sustainable development strategies, there is an urgent need to develop efficient, green and non-toxic heavy metal adsorbents. In this work, a robust aminated cellulose-based porous adsorbent (PGPW) was developed from delignified wood and amino-rich polymer using a solvent-free, mild, simple and efficient preparation method. Such adsorbent exhibited excellent adsorption capacity (188.68 mg g-1) for Cu(II), and its adsorption behavior was consistent with pseudo-second order kinetic and Langmuir isotherm models. Notably, PGPW with superior compressibility could be squeezed to achieve rapid desorption and reach equilibrium within 5 min, while still retaining 87 % adsorption efficiency after 50 cycles. In addition, PGPW showed remarkable selectivity towards various coexisting ionic systems and demonstrated a considerable adsorption capacity in natural water applications. The adsorption mechanism of heavy metal ions on porous adsorption material was elucidated. This approach provides a simple, gentle and sustainable strategy for preparing functionalized wood-based composites with efficient adsorption and ultra-fast desorption of heavy metal ions.

Ultra-flexible silver/iron nanowire decorated melamine composite foams for high-efficiency electromagnetic wave absorption and thermal management

Nowadays, functional electronic devices with excellent flexibility and thermal management capability for effective electromagnetic wave absorption are urgently in demand. Herein, a novel and highly flexible silver nanowire (AgNW)/iron nanowire (FeNW) decorated melamine composite foam (AgFe-MF) was prepared via simple dip-coating process. Owing to optimal impedance matching, synergistic dielectric and magnetic losses as well as three-dimensional porous structure, the AgFe-MF with an ultra-low filler content (0.22 vol%) exhibited an outstanding minimum reflection loss of -69.61 dB, and the best effective absorption bandwidth (EAB) could reach up to 6.37 GHz. Importantly, the EAB of long-time working AgFe-MF was enhanced to 7.01 GHz after 1000 compress-release cycles under 40 % strain. Besides, it also featured considerate Joule heating capacity and achieved a saturation temperature of over 85.7 ℃ under 2.6 V voltage. The impressive thermal isolation and long-term stability ensured the safety used as portable heater. Therefore, this work will provide a vital slight for fabricating smart wearable electronic devices with integrated anti-electromagnetic radiation and personalized thermal management performances towards potential thermal and health threats.

Highly elastic photothermal nanofibrillated cellulose aerogels for solar-assisted efficient cleanup of viscous oil spill

Frequent oil spills and illegal industrial pollutant discharge cause ecological and resource damages, so it is necessary to establish efficient adsorption and recovery strategies for oils in wastewater. Herein, inspired by solar-driven viscosity-breaking, we propose a facile approach to fabricate multifunctional nanofibrillated cellulose-based aerogel with high elasticity, excellent photothermal conversion, efficient selective oil adsorption and antibacterial properties. Firstly, copper sulfide (CuS) nanoparticles were in situ deposited on the template of oxidative nanofibrillated cellulose (ONC), aiming at achieving efficient photothermal effect and antibacterial properties. Ethylene glycol diglycidyl ether (EGDE) was employed to establish multiple crosslinking network between CuS@ONC and polyethyleneimine (PEI). A thin hydrophobic PMTS layer deposited on the surface of aerogel via a facile gas-solid reaction ensured stable oil selectivity. The resulting composite aerogel can rapidly adsorb oil under solar self-heating, significantly reducing the adsorption time from 25 to 5 min. Furthermore, it exhibits excellent adsorption capacities for various oils, retaining over 92 % of its initial capacity even after 20 adsorption-desorption cycles, and the antibacterial properties extend its lifespan. This work offers a promising method for constructing multifunctional aerogels for efficient oil-water separation, especially beneficial for high-viscosity and high-melting-point oil cleanup.

Preparation of Nanocellulose-Based Aerogel and Its Research Progress in Wastewater Treatment

Nowadays, the fast expansion of the economy and industry results in a considerable volume of wastewater being released, severely affecting water quality and the environment. It has a significant influence on the biological environment, both terrestrial and aquatic plant and animal life, and human health. Therefore, wastewater treatment is a global issue of great concern. Nanocellulose's hydrophilicity, easy surface modification, rich functional groups, and biocompatibility make it a candidate material for the preparation of aerogels. The third generation of aerogel is a nanocellulose-based aerogel. It has unique advantages such as a high specific surface area, a three-dimensional structure, is biodegradable, has a low density, has high porosity, and is renewable. It has the opportunity to replace traditional adsorbents (activated carbon, activated zeolite, etc.). This paper reviews the fabrication of nanocellulose-based aerogels. The preparation process is divided into four main steps: the preparation of nanocellulose, gelation of nanocellulose, solvent replacement of nanocellulose wet gel, and drying of nanocellulose wet aerogel. Furthermore, the research progress of the application of nanocellulose-based aerogels in the adsorption of dyes, heavy metal ions, antibiotics, organic solvents, and oil-water separation is reviewed. Finally, the development prospects and future challenges of nanocellulose-based aerogels are discussed.

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.