Carbon fiber aerogel made from raw cotton: a novel, efficient and recyclable sorbent for oils and organic solvents

Preceramic polymer-hybridized phenolic aerogels and the derived ZrC/SiC/C ceramic aerogels with ultrafine nanocrystallines

Phenolic and carbon aerogels have important applications for thermal insulation and ablative resistance materials in aerospace field. However, their antioxidant ability in long-term high-temperature aerobic environments faces serious challenges. To solve this problem, Zr/Si preceramic polymer hybridized phenolic resin (PR-ZS) aerogels were prepared via a facile sol-gel method. Compared with pure phenolic aerogel, the hybrid aerogels possess similar porous microstructure but larger specific surface area, better thermo-oxidative stability, and higher compressive strength. After carbonization at 1700 °C, the hybrid aerogels can be transformed to carbide ceramic aerogels with ultrafine nanocrystalline ZrC and SiC particles embedded in the carbon matrix. Ceramic aerogels exhibit good thermal insulative and anti-ablative properties in a butane torch simulated high-temperature and aerobic environment. The linear ablation rate is as low as 0.017 mm min-1, and the backside temperature is below 330 °C at a 20 mm in-depth position after 300 s of burning test, when the front temperature is approximately 960 °C. This work provides a facile approach to fabricate hybrid phenolic aerogels and derived ZrC/SiC/C ceramic aerogels, which target on applications for extreme environments in aerospace field.

Biomass-Derived Carbon Materials for Electrochemical Sensing: Recent Advances and Future Perspectives

In recent years, biomass carbon materials have received widespread attention in the field of electrochemical sensors. As a new type of renewable green energy, biomass carbon has the advantages of low cost and abundant resources. After special treatment, it can be used as an ideal electrode material. Since biomass carbon materials have diverse sources and their morphology is difficult to control, researchers have conducted in-depth research on their preparation process, morphology regulation and application. This review summarizes different biomass carbon structures and their preparation methods and explores the applications of these materials in electrochemical sensors. Modification of biomass carbon materials through pretreatment, physical and chemical activation, heteroatom doping, metal compound composite and other methods can make up for the deficiencies in its pore structure, electrical conductivity and surface wettability, thereby improving its electrochemical performance. The effects of different biomass sources, functional groups, constituent elements and modification methods on the morphology, structure and electrochemical properties of biomass carbon materials are discussed, and the applications of this type of material in biological molecules, heavy metal ions and pesticide residues are reviewed. Biomass carbon-based materials show great application potential and development prospects in the field of electrochemical sensors.

Superwetting PVA/cellulose aerogel with asymmetric structure for oil/water separation and solar-driven seawater desalination

Extracting clean water from oily wastewater and seawater is one of the effective strategies to alleviate the freshwater crisis. However, achieving both high separation efficiency and excellent salt resistance remain challenges for materials. Herein, a novel methyltrichlorosilane-modified polyvinyl alcohol/cellulose aerogel (MPCA) was prepared by freeze drying, chemical cross-linking, and chemical vapor deposition (CVD) methods. The superwetting MPCA presented an asymmetric structure, in which the small dense pores at the top surface facilitated the efficient separation of water-in-oil (W/O) emulsions and the large pores on the bottom surface were beneficial for brine exchange. The as-prepared superwetting aerogel was suitable for the separation of various W/O emulsions with excellent separation flux (631.9-2368.7 L·m-2·h-1) and outstanding separation efficiency (99.5 %). In addition, MPCA achieved a high evaporation efficiency of 1.39 kg·m-2·h-1 and a satisfactory energy conversion efficiency of 89.7 %. Moreover, the unique asymmetric structure endowed the evaporator excellent salt resistance and could self-dissolve the accumulated salt in 20 min. The as-prepared MPCA could achieve efficient W/O emulsion separation as well as produce freshwater in seawater, providing a new strategy for oily waste seawater purification.

Recent advances in membrane technologies applied in oil-water separation

Effective treatment of oily wastewater, which is toxic and harmful and causes serious environmental pollution and health risks, has become an important research field. Membrane separation technology has emerged as a key area of investigation in oil-water separation research due to its high separation efficiency, low costs, and user-friendly operation. This review aims to report on the advances in the research of various types of separation membranes around emulsion permeance, separation efficiency, antifouling efficiency, and stimulus responsiveness. Meanwhile, the challenges encountered in oil-water separation membranes are examined, and potential research avenues are identified.

Multifunctional elastomeric composites based on 3D graphene porous materials

3D graphene porous materials (3GPM), which have low density, large porosity, excellent compressibility, high conductivity, hold huge promise for a wide range of applications. Nevertheless, most 3GPM have brittle and weak network structures, which limits their widespread use. Therefore, the preparation of a robust and elastic graphene porous network is critical for the functionalization of 3GPM. Herein, the recent research of 3GPM with excellent mechanical properties are summarized and the focus is on the effect factors that affect the mechanical properties of 3GPM. Moreover, the applications of elastic 3GPM in various fields, such as adsorption, energy storage, solar steam generation, sensors, flexible electronics, and electromagnetic wave shielding are comprehensively reviewed. At last, the new challenges and perspective for fabrication and functionalization of robust and elastic 3GPM are outlined. It is expected that the perspective will inspire more new ideas in preparation and functionalization of 3GPM.

Metal-Organic Frameworks Marry Sponge: New Opportunities for Advanced Water Treatment

Metal-organic frameworks (MOFs) have garnered attention across various fields due to their noteworthy features like high specific surface area, substantial porosity, and adjustable performance. In the realm of water treatment, MOFs exhibit great potential for eliminating pollutants such as organics, heavy metals, and oils. Nonetheless, the inherent powder characteristics of MOFs pose challenges in terms of recycling, pipeline blockage, and even secondary pollution in practical applications. Addressing these issues, the incorporation of MOFs into sponges proves to be an effective solution. Strategies like one-pot synthesis, in situ growth, and impregnation are commonly employed for loading MOFs onto sponges. This review comprehensively explores the synthesis strategies of MOFs and sponges, along with their applications in water treatment, aiming to contribute to the ongoing advancement of MOF materials.

Temperature and pH dual response flexible silica aerogel with switchable wettability for selective oil/water separation

Silica aerogels are attractive oil-absorbing agents due to their low density, high porosity. However, how to discharge the oil which adsorbed by silica aerogels is a difficult issue. To address this challenge, new separation strategies with high efficiency are needed. In this study, we prepared the temperature and pH dual response flexible silica aerogel have temperature response and pH response effect, which can change its wettability by adjusting temperature or pH. On the one hand, the temperature and pH responsive flexible silica aerogel can be used to adsorb water at the temperature below 34.73 °C or pH > 7. On the other hand, it can adsorb oil at a temperature above 34.73 °C or pH < 7. The automatic desorption of oil can be achieved without consuming additional energy and damaging the pore structure. Therefore, the sample could continuously adsorb and filtrate efficiently and realize the recovery of oil and adsorption materials.

Bio-Based Aerogels for the Removal of Heavy Metal Ions and Oils from Water: Novel Solutions for Environmental Remediation

Contamination of the aqueous environment caused by the presence of heavy metal ions and oils is a growing concern that must be addressed to reduce their detrimental impact on living organisms and safeguard the environment. Recent efficient and environmentally friendly remediation methods for the treatment of water are based on third-generation bioaerogels as emerging applications for the removal of heavy metal ions and oils from aqueous systems. The peculiarities of these materials are various, considering their high specific surface area and low density, together with a highly porous three-dimensional structure and tunable surface chemistry. This review illustrates the recent progress in aerogels developed from cellulose and chitosan as emerging materials in water treatment. The potential of aerogel-based adsorbents for wastewater treatment is reported in terms of adsorption efficacy and reusability. Despite various gaps affecting the manufacturing and production costs of aerogels that actually limit their successful implementation in the market, the research progress suggests that bio-based aerogels are ready to be used in water-treatment applications in the near future.

Fe3 C/nanocarbon-Enabled Lithium Dendrite Mitigation in Lithium-Sulfur batteries

Lithium dendrite-induced short circuits and material loss are two major obstacles to the commercialization of lithium-sulfur (Li-S) batteries. Here, a nanocarbon composite consisting of cotton-derived Fe3 C-encapsulated multiwalled carbon nanotubes (Fe3 C-MWCNTs) and graphene effectively traps polysulfides to suppress lithium dendrite growth is reported. Machine learning combined with molecular dynamics (MD) simulations unveils a new polysulfide-induced lithium dendrite formation mechanism: the migration of polysulfides away from the anode drags out lithium protrusions through localized lattice distortion of the lithium anode and traps lithium ions in the surrounding electrolyte, leading to lithium dendrite formation. The Li-S battery, constructed using the composite of cotton-derived Fe3 C-MWCNTs and graphene that serves as both the sulfur host and the anode interlayer, exhibits exceptional cycling stability, impressive capacity retention, and effective mitigation of lithium dendrite formation. The findings offer valuable strategies to prevent lithium dendrite formation and enhance understanding of lithium dendrite growth in Li-S batteries.

Natural microfibrils/regenerated cellulose-based carbon aerogel for highly efficient oil/water separation

Cellulose-based carbon aerogels as biodegradable and renewable biomass materials have presented potential applications in oil/water separation. Herein, a novel carbon aerogel composed of natural microfibrils/regenerated cellulose (NM/RCA) was directly prepared by economical hardwood pulp as raw material using a novel co-solvent composed of deep eutectic solvent (DES) and N-methyl morpholine-N-oxide monohydrate (NMMO·H₂O). In addition, the morphology and structure of the filiform natural microfibers could be remained after carbonized at 400 ℃, which resulted in a low density (8-10 mg cm^-3), high specific surface area (768.89 m² g^-1) and high sorption capability. In addition, the aerogel exhibited high compressibility, outstanding elasticity, excellent fatigue resistance, and recyclability (80.5% height recovery after repeating 100 cycles at the strain of 80%). Due to the morphology and composition of the carbonized microfiber surface, the superhydrophobic materials with a water contact angle of 151.5°, could sorb various oils and organic solvents with 65-133 times its own weight and maintain 91.9% sorption capacity after 25 cycles. In addition, the aerogels could achieve the continuous separation of carbon tetrachloride (CCl₄) from water with a high flux rate of 11,718.8 L m^-2 h^-1. Therefore, our prepared NM/RCA aerogels are anticipated to have broad potential applications in oil purification and contaminant remediation.

C-shaped porous polypropylene fibers for rapid oil absorption and effective on-line oil spillage monitoring

Development of efficient absorbent materials for detection and treatment of offshore oil spillages remained a challenge. In this work, C-shaped polypropylene oil-absorbent fibers with sub-micron internal pores were prepared by combining spun-bonding technique and thermally induced phase separation (TIPS). The effect of drawing speed on the phase separation and the porous morphology of the shaped fiber non-woven fabric (NWF) was investigated. C-shaped NWF with porous morphology had large water contact angle, higher porosity, larger specific surface area, and increased oil absorption speed and capacity. An online oil spillage detection system was developed using porous C-shaped NWF and an oxygen sensing probe, showing shorter response time and higher signal-to-noise (STN) ratio. The response time for detecting the spillage of soybean oil and diluted crude oil (0.5 mL/0.8 L) in water were only 24 s and 10 s, respectively. The reliable oil detection low detection limit (RLDL) of the oxygen sensing probe was reduced 173 times (from 36.5 g/L to 0.21 g/L) when combined with C-shaped porous fiber NWF.

Synthesis and Sensing Performance of Chitin Fiber/MoS2 Composites

In this study, chitin fibers (CFs) were combined with molybdenum sulfide (MoS₂) to develop high-performance sensors, and chitin carbon materials were innovatively introduced into the application of gas sensing. MoS₂/CFs composites were synthesized via a one-step hydrothermal method. The surface properties of the composites were greatly improved, and the fire resistance effect was remarkable compared with that of the chitin monomer. In the gas-sensitive performance test, the overall performance of the MoS₂/CFs composite was more than three times better than that of the MoS₂ monomer and showed excellent long-term stability, with less than 10% performance degradation in three months. Extending to the field of strain sensing, MoS₂/CFs composites can realize real-time signal conversion in tensile and motion performance tests, which can help inspectors make analytical judgments in response to the analysis results. The extensive application of sensing materials in more fields is expected to be further developed. Based on the recycling of waste chitin textile materials, this paper expands the potential applications of chitin materials in the fields of gas monitoring, biomedicine, behavioral discrimination and intelligent monitoring.

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.

Biocompatible Material-Based Flexible Biosensors: From Materials Design to Wearable/Implantable Devices and Integrated Sensing Systems

Human beings have a greater need to pursue life and manage personal or family health in the context of the rapid growth of artificial intelligence, big data, the Internet of Things, and 5G/6G technologies. The application of micro biosensing devices is crucial in connecting technology and personalized medicine. Here, the progress and current status from biocompatible inorganic materials to organic materials and composites are reviewed and the material-to-device processing is described. Next, the operating principles of pressure, chemical, optical, and temperature sensors are dissected and the application of these flexible biosensors in wearable/implantable devices is discussed. Different biosensing systems acting in vivo and in vitro, including signal communication and energy supply are then illustrated. The potential of in-sensor computing for applications in sensing systems is also discussed. Finally, some essential needs for commercial translation are highlighted and future opportunities for flexible biosensors are considered.

Cleanup of oils and organic solvents from contaminated water by biomass-based aerogel with adjustable compression elasticity

Leakage of oils and organic solvents poses a significant threat to aquatic environments. Here, low-temperature carbonized aerogels with highly porous and anisotropic structures obtained only from biomass-derived materials were proposed to absorb polymorphic oils from contaminated water. Specifically, carbonized aerogels prepared at temperatures of 300 °C and 350 °C exhibited ultra-high absorption capacities (40‒125 g g^-1) and oil-water separation efficiencies (> 99%) even in harsh environments, which were attributed to their exceptional properties, including high porosity, abundant macropores, excellent thermal stability, and hydrophobicity. Through citric acid crosslinking and low-temperature carbonization, the aerogels exhibited superior compression elasticity and could be cyclically utilized through simple extrusion while realizing the recovery of oils. Moreover, the outstanding photothermal conversion properties obtained through carbonization contributed to the high temperature and fluidity of the oils surrounding the aerogels, which is crucial for improving the absorption performance of high-viscosity oils. Such absorbent materials are used to separate crude oil from oil-water mixtures, which can achieve maximum absorption of 56 g g^-1 and increase the absorption rate (from several days to 10 min) in a low-temperature (4 °C) seawater environment.

Enhanced Sorption for the Oil Spills by SDS-Modified Rice Straw

Frequent oil spills have caused serious consequences to the ecosystem and environment. Therefore, in order to reduce and eliminate the impact of oil spills on biology and the environment, oil spill remediation materials must be considered. As a kind of cheap and biodegradable natural organic cellulose oil-absorbing material, straw has an important practical significance in the treatment of oil spills. In order to improve the ability of rice straw to absorb crude oil, rice straw was first treated with acid and was then modified with sodium dodecyl sulfate (SDS) through a simple charge effect. Finally, the performance of oil absorption was tested and evaluated. The results illustrate that the oil absorption performance was greatly improved under the conditions of 10% H2SO4, for a 90 min reaction at 90 °C, under 2% SDS, and reacted for 120 min at 20 °C, and the rate of adsorption for rice straw to crude oil was raised by 3.33 g/g (0.83 to 4.16). Then, the rice stalks before and after the modification were characterized. Contact angle analysis shows that the modified rice stalks display better hydrophobic–lipophilic properties than unmodified rice stalks. The rice straw was characterized by XRD and TGA, and the surface structure of the rice straw was characterized by FTIR and SEM, which explain the mechanism of surface-modified rice straws with SDS to improve their oil absorption capacity.

Radially aligned hierarchical N-doped porous carbon beads derived from oil-sand asphaltene for long-life water filtration and wastewater treatment

The application of waste-derived highly efficient adsorbent for organic pollutants removal from water and wastewater is presented. Highly porous carbon beads with radially aligned macrochannels were prepared from asphaltene. Well-ordered inwardly aligned macrovoids favored solute diffusion and maximized the liquid accommodation capacity. A further N-doping could modulate the sorbent hydrophilicity leading to an outstanding absorption performance for a range of organic solvents and oily chemicals. N-doped carbon beads were effective sorbents of lopinavir (LNV) and ritonavir (RNV) from water and wastewater. The process of sorption was fast, and the highest removal was noted for RNV than LPV. N-doping favored LNV and RNV adsorption due to the increased porous structure of N-doped asphaltene beads. The chemisorption of both LPV and RTV was a rate-limiting step. The presence of co-pollutants in treated wastewater enhanced LPV and RNV removal and an up to 470 % increase was noted. The presence of LPV or RTV in distilled water was not toxic to Aliivibrio fischeri or even can stimulate their growth. However, after the adsorption process, the solution of RTV reduced its toxicity significantly and the final solution was not toxic. The opposite effect was noted for LPV. Given the repeatability, high removal performance, and cost-effectiveness of the asphaltene-based carbon microtubes when compared to other well-known sorbents such as carbon nanotubes, they demonstrated great potential as a low-cost and effective agent for long-life water filtration and wastewater treatment.

Amphiphilically Modified Porous Polymeric Nanosandwich-Based Membranes for Rapid and Efficient Water Treatment

Low removal efficiency, long treatment time, and high energy consumption hinder advanced and eco-friendly use of traditional adsorbents and separation membranes. Here, a class of amphiphilically modified 2D porous polymeric nanosandwich is designed and is subsequently assembled into adsorptive membranes. The 2D nanosandwich is gifted with high porosity and excellent pore accessibility, demonstrating rapid adsorption kinetics. The as-assembled membrane integrates unimpeded interlayer channels and well-developed, amphiphilic, and highly accessible intralayer nanopores, leading to ultrafast water permeation (1.2 × 10⁴  L m^-2  h^-1  bar^-1 ), high removal efficiency, and easy regeneration. The family of the membrane can be expanded by changing amphiphilic functional groups, further providing treatment of a wide-spectrum of pollutants, including aromatic compounds, pesticide, and pharmaceuticals. It is believed that the novel amphiphilically modified adsorptive membrane offers a distinct water treatment strategy with ultrahigh water permeation and efficient pollutants removal performances, and provides a multiple-in-one solution to the detection and elimination of pollutants.

Closed-Loop Recyclable High-Performance Polyimine Aerogels Derived from Bio-Based Resources

Organic aerogels are an intriguing class of highly porous and ultralight materials which have found widespread applications in thermal insulation, energy storage, and chemical absorption. These fully cross-linked polymeric networks, however, pose environmental concerns as they are typically made from fossil-based feedstock and the recycling back to their original monomers is virtually impossible. In addition, organic aerogels suffer from low thermal stability and potential fire hazard. To overcome these obstacles and create next-generation organic aerogels, a set of polyimine aerogels containing reversible chemical bonds which can selectively be cleaved on demand is prepared. As precursors, different primary amines and cyclophosphazene derivatives made from bio-based reagents (vanillin and 4-hydroxybenzaldehyde) to elevate the thermal stability and reduce the environmental impact are used. The resulting polyimine aerogels exhibit low shrinkage, high porosity, large surface area, as well as pronounced thermal stability and flame resistance. More importantly, the aerogels show excellent recyclability under acidic conditions with high monomer recovery yields and purities. This approach allows for preparation of fresh aerogels from the retrieved building blocks, thus demonstrating efficient closed-loop recycling. These high-performance, recyclable, and bio-based polyimine aerogels pave the way for advanced and sustainable superinsulating materials.

Novel supramolecular organo-oil gelators for fast and effective oil trapping: Mechanism and applications

In this paper, for the sorption of oil from oil polluted soil/water systems, nine new supramolecular organo-oil gelators were synthesized using three distinct diisocyanates and alcohols. The manufactured gelators were characterized using various techniques. The Fourier transform infrared (FTIR) and mass spectra confirmed the successful formation of the oil gelators. The synthesis of the proposed gelators was confirmed by the ¹H NMR, which exhibited three singlets that were attributed to an aliphatic side chain containing 29 protons. The scanning electron microscopy (SEM) analysis exhibited porous, sheets, prisms, and fibrous structures for the supramolecular oil gelators. The oil uptake data analysis was subjected to the Langmuir and Freundlich isotherm models which showed the R² value of 0.99 and a maximum adsorption capacity (q_max) of 45 mLg^-1. From the mechanistic point of view, it was proposed that the organo-oil gel initially leads to self-assembly and further entanglements forming the fibers, which finally make a trap for the oil molecules. Among all the nine gelators and different combinations used, the combination of ditetradecyl (TDI 14: DMI14: HMI 14) gelators in the ratio of 1:2:1 exhibited maximum oil uptake of ∼58% initially which further boosted to ∼99% using gasoline as the co-congealed solvent. Interestingly, the complete gelation of the oil from the oil-water mixture was achieved within 30 min of application with high oil recovery. The presented study confirmed that the oil removal by organo-oil gelator is a simple, novel, and facile technique, which could be employed for treating oil-contaminated soil/water mixture.

Sorption of hazardous industrial organic liquids with environmentally friendly functionalized cellulosic sorbents

The performances of five cellulosic polymers with different functional groups (cellulose, cellulose acetate, cellulose phosphate, chitosan, and chitin) as sorbents of seven frequently used hazardous polar organic liquids (acrolein, butanone peroxide, epichlorohydrin, formaldehyde, furfuryl alcohol, propylene oxide, and vinyl acetate) are investigated in this study. Amongst the cellulosic sorbents, cellulose phosphate exhibited enhanced sorption properties (as high as 3.09–7.03 g/g) against all seven polar organic liquids investigated, and chitosan and chitin also demonstrated comparable sorption efficiencies (2.28–7.72 g/g and 2.55–5.86 g/g, respectively) to those of cellulose phosphate. According to our investigation, the enhanced sorption efficiency could be achieved due to low powder density of cellulose phosphate, which is caused by the weak intramolecular interaction amongst the polymer chains. In addition, cellulose phosphate, chitosan, and chitin also showed enhanced absorbed solvent recovery percents (71.4, 60.6, and 61.1%, respectively, in average) compared with that of pristine cellulose (43.8%). With excellent sorption efficiency, enhanced solvent recovery rate, and reusability after drying, these functionalized cellulosic sorbents can be excellent candidates to replace the conventional carbon and vermiculites-based sorbents, especially for liquid polar organic spill sorption.

Superelastic 3D Assembled Clay/Graphene Aerogels for Continuous Solar Desalination and Oil/Organic Solvent Absorption

Superelastic, arbitrary-shaped, and 3D assembled clay/graphene aerogels (CGAs) are fabricated using commercial foam as sacrificial skeleton. The CGAs possess superelasticity under compressive strain of 95% and compressive stress of 0.09-0.23 MPa. The use of clay as skeletal support significantly reduces the use of graphene by 50%. The hydrophobic CGAs show high solvent absorption capacity of 186-519 times its own weight. Moreover, both the compression and combustion methods can be adopted for reusing the CGAs. In particular, it is demonstrated a design of 3D assembled hydrophilic CGA equipped with salt collection system for continuous solar desalination. Due to energy recovery and brine transport management promoted by this design, the 3D assembled CGA system exhibits an extremely high evaporation rate of 4.11 kg m-2  h-1 and excellent salt-resistant property without salt precipitation even in 20 wt% brine for continuous 36 h illumination (1 kW m-2 ), which is the best reported result from the solar desalination devices. More importantly, salts can be collected conveniently by squeezing and drying the solution out of the salt collection system. The work provides new insights into the design of 3D assembled CGAs and advances their applications in continuous solar desalination and efficient oil/organic solvent adsorption.

Enhanced Crude Oil Sorption by Modified Plant Materials in Oilfield Wastewater Treatment

The treatment of oilfield wastewater with high crude oil content and complex composition is a problem requiring considerable attention. In order to effectively remove crude oil contained in wastewater, in this work, rice straw, as an oil-absorbing material, was modified and used as a sorbent for crude oil. Rice straw was modified with alkali and cetyltrimethylammonium chloride (CTAC) by simple substitution reaction. The adsorption capacity of modified rice straw for oil was evaluated. The results illustrate that the adsorption rate of rice straw for crude oil was increased from 0.83 to 8.49 g/g, with the optimal conditions of 18% NaOH reacted for 90 min at 50 °C and 2% CTAC reacted for 60 min at 20 °C. The proposed modification method could be used for different materials to enhance the adsorption rate. The results of the contact angle test show that the modified straw changed from hydrophilic to hydrophobic, which may be the main reason for the improvement in the oil absorption rate. Finally, the surface structure of rice straw was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and N2 adsorption–desorption isotherms, which further confirmed the hydrophobicity of the modified rice straw.

Aerogels Meet Phase Change Materials: Fundamentals, Advances, and Beyond

Benefiting from the inherent properties of ultralight weight, ultrahigh porosity, ultrahigh specific surface area, adjustable thermal/electrical conductivities, and mechanical flexibility, aerogels are considered ideal supporting alternatives to efficiently encapsulate phase change materials (PCMs) and rationalize phase transformation behaviors. The marriage of versatile aerogels and PCMs is a milestone in pioneering advanced multifunctional composite PCMs. Emerging aerogel-based composite PCMs with high energy storage density are accepted as a cutting-edge thermal energy storage (TES) concept, enabling advanced functionality of PCMs. Considering the lack of a timely and comprehensive review on aerogel-based composite PCMs, herein, we systematically retrospect the state-of-the-art advances of versatile aerogels for high-performance and multifunctional composite PCMs, with particular emphasis on advanced multiple functions, such as acoustic-thermal and solar-thermal-electricity energy conversion strategies, mechanical flexibility, flame retardancy, shape memory, intelligent grippers, and thermal infrared stealth. Emphasis is also given to the versatile roles of different aerogels in composite PCMs and the relationships between their architectures and thermophysical properties. This review also showcases the discovery of an interdisciplinary research field combining aerogels and 3D printing technology, which will contribute to pioneering cutting-edge PCMs. This review aims to arouse wider research interests among interdisciplinary fields and provide insightful guidance for the rational design of advanced multifunctional aerogel-based composite PCMs, thus facilitating the significant breakthroughs in both fundamental research and commercial applications.

Fabrication of Textile Waste Fibers Aerogels with Excellent Oil/Organic Solvent Adsorption and Thermal Properties

In recent years, the treatment of textile waste has attracted more and more attention around the world. The reuse of textile waste can contribute to the reduction of carbon emissions and the sustainable development of the economy. Herein, we proposed a facile and cost-effective approach to fabricating aerogel by using textile waste fibers as the matrix and polyvinyl alcohol (PVA) and glutaraldehyde (GA) as crosslinking agents. After being modified with methyltrimethoxysilane (MTMS) via chemical vapor deposition, both the interior and exterior of the textile waste aerogels exhibit a hydrophobic property with a water contact angle of up to 136.9° ± 2.3°. A comprehensive investigation of the structure, thermal properties, mechanical properties and oil absorption capacity of this aerogel shows its potential for building insulation and oil spill cleanup. The textile waste fibers aerogels have low density and high porosity, good thermal stability and outstanding heat insulation properties (K_avg. = 0.049–0.061 W/m·K). With a maximum oil absorption value of 26.9 ± 0.6 g/g and rapid and effective oil/water mixture separation, the aerogel exhibits competitive commercial application value.

Advanced cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF) aerogels: Bottom-up assembly perspective for production of adsorbents

The most common and abundant polymer in nature is the linear polysaccharide cellulose, but processing it requires a new approach since cellulose degrades before melting and does not dissolve in ordinary organic solvents. Cellulose aerogels are exceptionally porous (>90 %), have a high specific surface area, and have low bulk density (0.0085 mg/cm³), making them suitable for a variety of sophisticated applications including but not limited to adsorbents. The production of materials with different qualities from the nanocellulose based aerogels is possible thanks to the ease with which other chemicals may be included into the structure of nanocellulose based aerogels; despite processing challenges, cellulose can nevertheless be formed into useful, value-added products using a variety of traditional and cutting-edge techniques. To improve the adsorption of these aerogels, rheology, 3-D printing, surface modification, employment of metal organic frameworks, freezing temperature, and freeze casting techniques were all investigated and included. In addition to exploring venues for creation of aerogels, their integration with CNC liquid crystal formation were also explored and examined to pursue "smart adsorbent aerogels". The objective of this endeavour is to provide a concise and in-depth evaluation of recent findings about the conception and understanding of nanocellulose aerogel employing a variety of technologies and examination of intricacies involved in enhancing adsorption properties of these aerogels.

Efficient and recyclable sericin-derived carbon aerogel for oils and organic solvents adsorption

Sericin, an industrial waste of the silk industry, is a promising precursor for adsorbent preparation. In this work, an efficient and novel sericin-derived carbon aerogel (SCA) was used to improve the adsorption efficiency of oils and organic solvents. The SCA demonstrated a high-efficiency sorption capacity of not only soybean oil (adsorption capacity reached up to 167.69 times its weight) but also chloroform and methylene chloride (adsorption capacity of 193.67 g/g and 173.25 g/g respectively). It is observed that SCA could be regenerated multiple times through combustion and after five cycles, its adsorbability to ethanol, dimethyl sulfoxide, and soybean oil remained high at 59.08 g/g, 59.34 g/g, and 137.36 g/g, respectively. The physical and chemical characteristics of sericin and SCA were analyzed using Scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Raman spectra and Fourier transform infrared spectroscopy (FTIR) analysis. The results suggest that SCA is an adsorbent with excellent properties and can significantly increase the adsorption capacity of oils and organic solvents. The overall results indicate that SCA is effectively used as an adsorbent for the adsorption of oils and organic solvents, which will contribute to reduce the discharge of sericin-containing wastewater and alleviate pollution caused by oil and organic solvent leakage.

Fabrication of Carbon Aerogels Derived from Metal-Organic Frameworks/Carbon Nanotubes/Cotton Composites as an Efficient Sorbent for Sustainable Oil–Water Separation

Due to the continuous occurrence of water pollution problems, practical separation methods for oil–water mixtures have attracted more and more attention. To date, different kinds of materials have been developed with good hydrophobic properties and strong separation ability. Carbon aerogels, as a promising ideal adsorbent for dealing with oil-spill accidents, have received extensive attention. In this work, zeolitic imidazolate frameworks (ZIFs), nanoparticles, and carbon nanotubes (CNTs) in the three-dimensional (3D) interconnected network structure of cotton balls (CBs) were successfully prepared by a simple and scalable process. The as-prepared carbonized CBs with carbonized ZIF-8 and CNTs (CZIF-8/CNTs/CCBs) were characterized. The oil–water separation performance of the composite was also measured. The results show that the ZIF-8 clusters intercalated with abundant CNTs are fully loaded into the porous structure of the CBs after the in situ synthesis process. Additionally, ZIF-8/CNTs/CBs was carbonized in nitrogen, leading to the formation of CZIF-8/CNTs/CCBs. The prepared material possesses excellent hydrophobicity with a water contact angle of 152.7°, showing good absorption capacities Q1 in the range of 48 to 84 times its original weight for oil and organic liquids. In addition, CZIF-8/CNTs/CCBs exhibits good recyclability in the absorption–distillation test. In summary, this study proposes a novel and simple method for the preparation of a superhydrophobic material that could have wide application in the separation of oil–water mixtures.

Solar-assisted high-efficient cleanup of viscous crude oil spill using an ink-modified plant fiber sponge

Rapid and efficient clean-up of viscous crude oil spills is still a global challenge due to its high viscous and poor flowability at room temperature. The hydrophobic/oleophilic absorbents with three-dimensional porous structure have been considered as a promising candidate to handle oil spills. However, they still have limited application in recovering the high viscous oil. Inspired by the viscosity of crude oil depended on the temperature, a solar-heated ink modified plant fiber sponge (PFS@GC) is fabricated via a simple and environmentally friendly physical foaming strategy combined with in-situ ink coating treatment. After wrapping by the polydimethylsiloxane (PDMS), the modified PFS@GC (PFS@GC@PDMS) exhibits excellent compressibility, high hydrophobic (141° in water contact angle), solar absorption (> 96.0%), and oil absorptive capacity (12.0-27.8 g/g). Benefiting from the favorable mechanical property and photothermal conversion capacity, PFS@GC@PDMS is demonstrated as a high-performance absorbent for crude oil clean-up and recovery. In addition, PFS@GC@PDMS can also be applied in a continuous absorption system for uninterrupted recovering of oil spills on the water surface. The proposed solar-heated absorbent design provides a new opportunity for exploring biomass in addressing large-scale oil spill disasters.

Facile Construction and Fabrication of a Superhydrophobic and Super Oleophilic Stainless Steel Mesh for Separation of Water and Oil

The fluoride-free fabrication of superhydrophobic materials for the separation of oil/water mixtures has received widespread attention because of frequent offshore oil exploration and chemical leakage. In recent years, oil/water separation materials, based on metal meshes, have drawn much attention, with significant advantages in terms of their high mechanical strength, easy availability, and long durability. However, it is still challenging to prepare superhydrophobic metal meshes with high-separation capacity, low costs, and high recyclability for dealing with oil–water separation. In this work, a superhydrophobic and super oleophilic stainless steel mesh (SSM) was successfully prepared by anchoring Fe₂O₃ nanoclusters (Fe₂O₃-NCs) on SSM via the in-situ flame synthesis method and followed by further modification with octadecyltrimethoxysilane (OTS). The as-prepared SSM with Fe₂O₃-NCs and OTS (OTS@Fe₂O₃-NCs@SSM) was confirmed by a field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectrometer (XPS), and X-ray diffractometer (XRD). The oil–water separation capacity of the sample was also measured. The results show that the interlaced and dense Fe₂O₃-NCs, composed of Fe₂O₃ nanoparticles, were uniformly coated on the surface of the SSM after the immerging-burning process. Additionally, a compact self-assembled OTS layer with low surface energy is coated on the surface of Fe₂O₃-NCs@SSM, leading to the formation of OTS@Fe₂O₃-NCs@SSM. The prepared OTS@Fe₂O₃-NCs@SSM shows excellent superhydrophobicity, with a water static contact angle of 151.3°. The separation efficiencies of OTS@Fe₂O₃-NCs@SSM for the mixtures of oil/water are all above 98.5%, except for corn oil/water (97.5%) because of its high viscosity. Moreover, the modified SSM exhibits excellent stability and recyclability. This work provides a facile approach for the preparation of superhydrophobic and super oleophilic metal meshes, which will lead to advancements in their large-scale applications on separating oil/water mixtures.

Structured Ultra-Flyweight Aerogels by Interfacial Complexation: Self-Assembly Enabling Multiscale Designs

The rapid co-assembly of graphene oxide (GO) nanosheets and a surfactant at the oil/water (O/W) interface is harnessed to develop a new class of soft materials comprising continuous, multilayer, interpenetrated, and tubular structures. The process uses a microfluidic approach that enables interfacial complexation of two-phase systems, herein, termed as "liquid streaming" (LS). LS is demonstrated as a general method to design multifunctional soft materials of specific hierarchical order and morphology, conveniently controlled by the nature of the oil phase and extrusion's injection pressure, print-head speed, and nozzle diameter. The as-obtained LS systems can be readily converted into ultra-flyweight aerogels displaying worm-like morphologies with multiscale porosities (micro- and macro-scaled). The presence of reduced GO nanosheets in such large surface area systems renders materials with outstanding mechanical compressibility and tailorable electrical activity. This platform for engineering soft materials and solid constructs opens up new horizons toward advanced functionality and tunability, as demonstrated here for ultralight printed conductive circuits and electromagnetic interference shields.

Wool-Based Carbon Fiber/MoS2 Composite Prepared by Low-Temperature Catalytic Hydrothermal Method and Its Application in the Field of Gas Sensors

Under the background of the Paris Agreement on reducing greenhouse gases, waste wools were converted into wool carbon fiber (WCF) and WCF-MoS2 composites by low-temperature catalytic hydrothermal carbonization. Their structures and gas-sensing performances were studied for the first time. Due to the existence of heterojunctions, the responses of the WCF-MoS2 composite to the five analytes were 3-400 times those of MoS2 and 2-11 times those of WCF. Interestingly, because of the N, P, and S elements contained in wools, the WCF prepared by the hydrothermal method was realized the doping of N, P, and S, which caused the sensing curves of WCF to have different shapes for different analytes. This characteristic was also well demonstrated by the WCF-MoS2 composite, which inspired us to realize the discriminative detection only by a single WCF-MoS2 sensor and image recognition technology. What's more, the WCF-MoS2 composite also showed a high sensitivity, a high selectivity, and a rapid response to NH3. The response time and the recovery time to 3 ppm NH3 were about 16 and 5 s, respectively. The detection of limit of WCF-MoS2 for NH3 was 19.1 ppb. This work provides a new idea for the development of sensors and the resource utilization of wool waste.

High-throughput production of kilogram-scale nanofibers by Kármán vortex solution blow spinning

The interaction between gas flow and liquid flow, governed by fluid dynamic principles, is of substantial importance in both fundamental science and practical applications. For instance, a precisely designed gas shearing on liquid solution may lead to efficacious production of advanced nanomaterials. Here, we devised a needleless Kármán vortex solution blow spinning system that uses a roll-to-roll nylon thread to deliver spinning solution, coupled with vertically blowing airflow to draw high-quality nanofibers with large throughput. A wide variety of nanofibers including polymers, carbon, ceramics, and composites with tunable diameters were fabricated at ultrahigh rates. The system can be further upgraded from single thread to multiple parallel threads and to the meshes, boosting the production of nanofibers to kilogram scale without compromising their quality.

Hygroscopic holey graphene aerogel fibers enable highly efficient moisture capture, heat allocation and microwave absorption

Aerogel fibers have been recognized as the rising star in the fields of thermal insulation and wearable textiles. Yet, the lack of functionalization in aerogel fibers limits their applications. Herein, we report hygroscopic holey graphene aerogel fibers (LiCl@HGAFs) with integrated functionalities of highly efficient moisture capture, heat allocation, and microwave absorption. LiCl@HGAFs realize the water sorption capacity over 4.15 g g⁻¹, due to the high surface area and high water uptake kinetics. Moreover, the sorbent can be regenerated through both photo-thermal and electro-thermal approaches. Along with the water sorption and desorption, LiCl@HGAFs experience an efficient heat transfer process, with a heat storage capacity of 6.93 kJ g⁻¹. The coefficient of performance in the heating and cooling mode can reach 1.72 and 0.70, respectively. Notably, with the entrapped water, LiCl@HGAFs exhibit broad microwave absorption with a bandwidth of 9.69 GHz, good impedance matching, and a high attenuation constant of 585. In light of these findings, the multifunctional LiCl@HGAFs open an avenue for applications in water harvest, heat allocation, and microwave absorption. This strategy also suggests the possibility to functionalize aerogel fibers towards even broader applications.

Functionalization of aerogel fibers, characterized by high porosity and low thermal conductivity, to obtain multifunctional materials is highly desirable. Here the authors report hygroscopic holey graphene aerogel fibers hosting LiCl salt, enabling moisture capture, heat allocation, and microwave absorption performance.

Emerging Separation Applications of Surface Superwettability

Human beings are facing severe global environmental problems and sustainable development problems. Effective separation technology plays an essential role in solving these challenges. In the past decades, superwettability (e.g., superhydrophobicity and underwater superoleophobicity) has succeeded in achieving oil/water separation. The mixture of oil and water is just the tip of the iceberg of the mixtures that need to be separated, so the wettability-based separation strategy should be extended to treat other kinds of liquid/liquid or liquid/gas mixtures. This review aims at generalizing the approach of the well-developed oil/water separation to separate various multiphase mixtures based on the surface superwettability. Superhydrophobic and even superoleophobic surface microstructures have liquid-repellent properties, making different liquids keep away from them. Inspired by the process of oil/water separation, liquid polymers can be separated from water by using underwater superpolymphobic materials. Meanwhile, the underwater superaerophobic and superaerophilic porous materials are successfully used to collect or remove gas bubbles in a liquid, thus achieving liquid/gas separation. We believe that the diversified wettability-based separation methods can be potentially applied in industrial manufacture, energy use, environmental protection, agricultural production, and so on.