Bacterial Nanocellulose/MoS2 Hybrid Aerogels as Bifunctional Adsorbent/Photocatalyst Membranes for in-Flow Water Decontamination

Nanocellulose-based porous lightweight materials with flame retardant properties: A review

This review discusses the development and application of nanocellulose (NC)-aerogels, a sustainable and biodegradable biomaterial, with enhanced flame retardant (FR) properties. NC-aerogels combine the excellent physical and mechanical properties of NC with the low density and thermal conductivity of aerogels, making them promising for thermal insulation and other fields. However, the flammability of NC-aerogels limits their use in some applications, such as electromagnetic interference shielding, oil/water separation, and flame-resistant textiles. The review covers the design, fabrication, modification, and working mechanism of NC porous materials, focusing on how advanced technologies can impart FR properties into them. The review also evaluates the FR performance of NC-aerogels by employing widely recognized tests, such as the limited oxygen index, cone calorimeter, and UL-94. The review also explores the integration of innovative and eco-friendly materials, such as MXene, metal-organic frameworks, dopamine, lignin, and alginate, into NC-aerogels, to improve their FR performance and functionality. The review concludes by outlining the potential, challenges, and limitations of future research on FR NC-aerogels, identifying the obstacles and potential solutions, and understanding the current progress and gaps in the field.

Cellulose Membranes: Synthesis and Applications for Water and Gas Separation and Purification

Membranes are a selective barrier that allows certain species (molecules and ions) to pass through while blocking others. Some rely on size exclusion, where larger molecules get stuck while smaller ones permeate through. Others use differences in charge or polarity to attract and repel specific species. Membranes can purify air and water by allowing only air and water molecules to pass through, while preventing contaminants such as microorganisms and particles, or to separate a target gas or vapor, such as H2 and CO2, from other gases. The higher the flux and selectivity, the better a material is for membranes. The desirable performance can be tuned through material type (polymers, ceramics, and biobased materials), microstructure (porosity and tortuosity), and surface chemistry. Most membranes are made from plastic from petroleum-based resources, contributing to global climate change and plastic pollution. Cellulose can be an alternative sustainable resource for making renewable membranes. Cellulose exists in plant cell walls as natural fibers, which can be broken down into smaller components such as cellulose fibrils, nanofibrils, nanocrystals, and cellulose macromolecules through mechanical and chemical processing. Membranes made from reassembling these particles and molecules have variable pore architecture, porosity, and separation properties and, therefore, have a wide range of applications in nano-, micro-, and ultrafiltration and forward osmosis. Despite their advantages, cellulose membranes face some challenges. Improving the selectivity of membranes for specific molecules often comes at the expense of permeability. The stability of cellulose membranes in harsh environments or under continuous operation needs further improvement. Research is ongoing to address these challenges and develop advanced cellulose membranes with enhanced performance. This article reviews the microstructures, fabrication methods, and potential applications of cellulose membranes, providing some critical insights into processing-structure-property relationships for current state-of-the-art cellulosic membranes that could be used to improve their performance.

Catalytic and biomedical applications of nanocelluloses: A review of recent developments

Nanocelluloses exhibit immense potential in catalytic and biomedical applications. Their unique properties, biocompatibility, and versatility make them valuable in various industries, contributing to advancements in environmental sustainability, catalysis, energy conversion, drug delivery, tissue engineering, biosensing/imaging, and wound healing/dressings. Nanocellulose-based catalysts can efficiently remove pollutants from contaminated environments, contributing to sustainable and cleaner ecosystems. These materials can also be utilized as drug carriers, enabling targeted and controlled drug release. Their high surface area allows for efficient loading of therapeutic agents, while their biodegradability ensures safer and gradual release within the body. These targeted drug delivery systems enhance the efficacy of treatments and minimizes side effects. Moreover, nanocelluloses can serve as scaffolds in tissue engineering due to their structural integrity and biocompatibility. They provide a three-dimensional framework for cell growth and tissue regeneration, promoting the development of functional and biologically relevant tissues. Nanocellulose-based dressings have shown great promise in wound healing and dressings. Their ability to absorb exudates, maintain a moist environment, and promote cell proliferation and migration accelerates the wound healing process. Herein, the recent advancements pertaining to the catalytic and biomedical applications of nanocelluloses and their composites are deliberated, focusing on important challenges, advantages, limitations, and future prospects.

Nanocellulose-stabilized nanocomposites for effective Hg(II) removal and detection: a comprehensive review

Mercury pollution, with India ranked as the world's second-largest emitter, poses a critical environmental and public health challenge and underscores the need for rigorous research and effective mitigation strategies. Nanocellulose is derived from cellulose, the most abundant natural polymer on earth, and stands out as an excellent choice for mercury ion remediation due to its remarkable adsorption capacity, which is attributed to its high specific surface area and abundant functional groups, enabling efficient Hg(II) ion removal from contaminated water sources. This review paper investigates the compelling potential of nanocellulose as a scavenging tool for Hg(II) ion contamination. The comprehensive examination encompasses the fundamental attributes of nanocellulose, its diverse fabrication techniques, and the innovative development methods of nanocellulose-based nanocomposites. The paper further delves into the mechanisms that underlie Hg removal using nanocellulose, as well as the integration of nanocellulose in Hg detection methodologies, and also acknowledges the substantial challenges that lie ahead. This review aims to pave the way for sustainable solutions in mitigating Hg contamination using nanocellulose-based nanocomposites to address the global context of this environmental concern.

MoS2-based nanocomposites and aerogels for antibiotic pollutants removal from wastewater by photocatalytic degradation process: A review

Photocatalytic technologies based on molybdenum disulfide (MoS2) catalysts are effective, eco-friendly, and promising for antibiotic pollutants treatment. The technologies used by MoS2-based nanocomposites and aerogels for efficient degradation of antibiotics are reviewed in detail for the first time in this paper. The fundamental aspects of MoS2 were comprehensively scrutinized, encompassing crystal structure, optical properties, and photocatalytic principle. Then, the main synthesized methods and advantages/disadvantages for the preparation of MoS2-based nanocomposites and aerogels were systematically presented. Besides, a comprehensive overview of diverse MoS2-based nanocomposites and aerogels photo-degradation systems that enhanced the degradation of antibiotic pollutants were revealed. Meanwhile, the photo-degradation mechanism concentrated on the photoelectron transfer pathways and reactive oxygen species (ROS) were systematically evaluated. Finally, the challenges and perspectives for deeply development of MoS2-based nanocomposites and aerogels were discussed. This review may help researchers to deeply understand the research status of MoS2-based nanocomposites and aerogels for antibiotics removal, and makes clear the photo-degradation mechanism from photoelectron transfer pathways and ROS aspects of MoS2-based nanocomposites and aerogels.

A sustainable bioprocess to produce bacterial cellulose (BC) using waste streams from wine distilleries and the biodiesel industry: evaluation of BC for adsorption of phenolic compounds, dyes and metals

BACKGROUND

The main challenge for large-scale production of bacterial cellulose (BC) includes high production costs interlinked with raw materials, and low production rates. The valorization of renewable nutrient sources could improve the economic effectiveness of BC fermentation while their direct bioconversion into sustainable biopolymers addresses environmental pollution and/or resource depletion challenges. Herein a green bioprocess was developed to produce BC in high amounts with the rather unexplored bacterial strain Komagataeibacter rhaeticus, using waste streams such as wine distillery effluents (WDE) and biodiesel-derived glycerol. Also, BC was evaluated as a bio-adsorbent for phenolics, dyes and metals removal to enlarge its market diversification.

RESULTS

BC production was significantly affected by the WDE mixing ratio (0-100%), glycerol concentration (20-45 g/L), type of glycerol and media-sterilization method. A maximum BC concentration of 9.0 g/L, with a productivity of 0.90 g/L/day and a water holding capacity of 60.1 g water/g dry BC, was achieved at 100% WDE and ≈30 g/L crude glycerol. BC samples showed typical cellulose vibration bands and average fiber diameters between 37.2 and 89.6 nm. The BC capacity to dephenolize WDE and adsorb phenolics during fermentation reached respectively, up to 50.7% and 26.96 mg gallic acid equivalents/g dry BC (in-situ process). The produced BC was also investigated for dye and metal removal. The highest removal of dye acid yellow 17 (54.3%) was recorded when 5% of BC was applied as the bio-adsorbent. Experiments performed in a multi-metal synthetic wastewater showed that BC could remove up to 96% of Zn and 97% of Cd.

CONCLUSIONS

This work demonstrated a low-carbon approach to produce low-cost, green and biodegradable BC-based bio-adsorbents, without any chemical modification. Their potential in wastewater-treatment-applications was highlighted, promoting closed-loop systems within the circular economy era. This study may serve as an orientation for future research towards competitive or targeted adsorption technologies for wastewater treatment or resources recovery.

An overview of bio-cellulose derived materials for catalytic water treatment

Bio-cellulose derived materials (BCM) exhibit distinct structural and morphologic properties, which make them suitable for catalytic environmental remediation. In the domain of water treatment, the prospects for BCM remain bright, offering new possibilities for the development of advanced materials with low environmental impact. Research on BCM as catalysts or catalyst immobilization platforms for water treatment is still limited, mostly using laboratory-grown biomaterials for the photocatalytic degradation of dyes. BCM production costs can be significant, which can hinder its application. Thus, cost-effective alternatives using waste materials as substrates for BCM culture media are highly desirable to optimize production, while also decreasing food waste. Moreover, advances in biotechnology can enhance BCM production, tailoring its properties to meet specific requirements. Hybrid catalytic BCM composites can be easily developed, due to the straightforward functionalization of the biomaterial's network, promoting the efficiency of a variety of catalytic systems. Still considering the intrinsic features of the biomaterial, membrane development and application pose as an opportunity for continuous flow evaluations, facilitating long-term usage and reusability. Nevertheless, there are still challenges regarding catalytic BCM for water treatment (i.e., cost-effectiveness, scaling up, and consistent performance in diverse treatment scenarios). Addressing these aspects can lead to innovative environmental remediation options.

Noncovalent Self-Assembly of Single-Layer MoS2 Nanosheets and Zinc Porphyrin into Stable SURMOF Nanohybrids with Multimodal Photocatalytic Properties

A noncovalent integration of nanosheets of molybdenum disulfide (MoS2) and the zinc porphyrin complex Zn(II) 5,10,15,20-tetrakis(4-carboxyphenyl)porphine (ZnTCPP) through coordination bonding with metal clusters of zinc acetate (Zn[OAc]2) was applied for synthesis of stable hybrid nanomaterial avoiding surface prefunctionalization. The X-ray powder diffraction in combination with the BET nitrogen adsorption method confirms formation of a ZnTCPP-based surface-attached metal-organic framework (SURMOF) with micropores of 1.63 nm on the MoS2 nanosheets. Fluorescence spectroscopy confirmed Forster resonance energy transfer (FRET) between MoS2 and ZnTCPP without contact quenching. Fluorescent trapping with terephthalic acid for hydroxyl radicals and Sensor Green for singlet oxygen was applied for studying the pathways of photodegradation of model organic pollutant 1,5-dihydroxynaphthalene (DHN) in the presence of SURMOF/MoS2. Visible light initiates sensitization through the excitation of ZnTCPP generating singlet oxygen, whereas UV-light promotes either aerobic FRET-mediated "Z scheme" or anaerobic "Type II heterojunction" mechanisms. Owing to its multimodal photochemistry, the SURMOF/MoS2 hybrid showed comparatively high photocatalytic activity in UV-assisted degradation of DHN (keffUV = 4.0 × 10-2 min-1) as well as the antibacterial activity confirmed by E. coli survival test under visible light. Noncovalent self-assembly utilizing coordination bonding in SURMOFs as supramolecular adhesive to avoid surface premodification provides a basis for new types of multicomponent nanosystems with switchable functionalities by combining different 2D materials and chromophores in one hybrid structure.

Response surface methodology for optimizing methylene blue dye removal by mesoporous activated carbon derived from renewable woody Bambusoideae waste

In this study, the focus was on utilizing tropical plant biomass waste, specifically bamboo (BB), as a sustainable precursor for the production of activated carbon (BBAC) via pyrolysis-induced K2CO3 activation. The potential application of BBAC as an effective adsorbent for the removal of methylene blue (MB) dye from aqueous solutions was investigated. Response surface methodology (RSM) was employed to evaluate key adsorption characteristics, which included BBAC dosage (A: 0.02-0.08 g/L), pH (B: 4-10), and time (C: 2-8 min). The adsorption isotherm analysis revealed that the adsorption of MB followed the Freundlich model. Moreover, the kinetic data were well-described by the pseudo-second-order model, suggesting the role of a chemisorption process. The BBAC demonstrated a notable MB adsorption capacity of 195.8 mg/g, highlighting its effectiveness as an adsorbent. Multiple mechanisms were identified as controlling factors in MB adsorption by BBAC, including electrostatic forces, π-π stacking, and H-bonding interactions. The findings of this study indicate that BBAC derived from bamboo has the potential to be a promising adsorbent for the treatment of wastewater containing organic dyes. The employment of sustainable precursors like bamboo for activated carbon production contributes to environmentally friendly waste management practices and offers a solution for the remediation of dye-contaminated wastewater.

Predicting rejection of emerging contaminants through RO membrane filtration based on ANN-QSAR modeling approach: trends in molecular descriptors and structures towards rejections

In this work, a quantitative structure-activity relationship (QSAR) study was performed on a set of emerging contaminants (ECs) to predict their rejections by reverse osmosis membrane (RO). A wide range of molecular descriptors was calculated by Dragon software for 72 ECs. The QSAR data was analyzed by an artificial neural network method (ANN), in which four out of 3000 theoretical molecular descriptors were chosen and their significance was computed based on the Garson method. The significance trends of descriptors were as follows in descending order: ESpm14u > R2e > SIC1 > EEig03d. The selected descriptors were ranked based on their importance and then an explorative study was conducted on the QSAR data to show the trends in molecular descriptors and structures toward the rejections values of ECs. The MLR algorithm was used to make a linear model and the results were compared with those of the nonlinear ANN algorithm. The comparison results revealed it is necessary to apply the ANN model to this data with non-linear properties. For the whole dataset, the correlation coefficient (R2) and residual mean squared error (RMSE) of the ANN and MLR methods were 0.9528, 6.4224; and 0.8753, 11.3400, respectively. The comparison results showed the superiority of ANN modeling in the analysis of ECs' QSAR data.

Towards Understanding Aerogels' Efficiency for Oil Removal-A Principal Component Analysis Approach

In this study, our aim was to estimate the adsorption potential of three families of aerogels: nanocellulose (NC), chitosan (CS), and graphene (G) oxide-based aerogels. The emphasized efficiency to seek here concerns oil and organic contaminant removal. In order to achieve this goal, principal component analysis (PCA) was used as a data mining tool. PCA showed hidden patterns that were not possible to seek by the bi-dimensional conventional perspective. In fact, higher total variance was scored in this study compared with previous findings (an increase of nearly 15%). Different approaches and data pre-treatments have provided different findings for PCA. When the whole dataset was taken into consideration, PCA was able to reveal the discrepancy between nanocellulose-based aerogel from one part and chitosan-based and graphene-based aerogels from another part. In order to overcome the bias yielded by the outliers and to probably increase the degree of representativeness, a separation of individuals was adopted. This approach allowed an increase in the total variance of the PCA approach from 64.02% (for the whole dataset) to 69.42% (outliers excluded dataset) and 79.82% (outliers only dataset). This reveals the effectiveness of the followed approach and the high bias yielded from the outliers.

Combination strategy of large interlayer spacing and active basal planes for regulating the microwave absorption performance of MoS2/MWCNT composites at thin absorber level

Recently, molybdenum disulfide (MoS₂)/carbon has become a promising candidate for efficient microwave absorption. However, it is still challenging to simultaneously optimize the synergy of impedance matching and loss capability at the level of a thin absorber. Here, a new adjustment strategy is proposed by changing the concentration of precursor l-cysteine for MoS₂/multi-walled carbon nanotubes (MWCNT) composites to unlock the basal plane of MoS₂ and expand the interlayer spacing from 0.62 nm to 0.99 nm, leading to improved packing of MoS₂ nanosheets and more active sites. Therefore, the tailored MoS₂ nanosheets exhibit abundant sulfur-vacancies, lattice-oxygen, more metallic 1T-phase, and higher surface area. Such sulfur-vacancies and lattice-oxygen promote the electronic asymmetric distribution at the solid-air interface of MoS₂ crystals and induce stronger microwave attenuation through interface/dipole polarization, which is further verified by first-principles calculations. In addition, the expansion of the interlayer spacing induces more MoS₂ to deposit on the MWCNT surface and increases the roughness, improving the impedance matching and multiple scattering. Overall, the advantage of this adjustment method is that while optimizing impedance matching at the thin absorber level, composite still maintains a high attenuation capacity, which means enhancing the attenuation performance of MoS₂ itself offsets the weakening of the composite's attenuation ability caused by the decrease in the relative content of MWCNT components. Most importantly, adjusting impedance matching and attenuation ability can be easily implemented by separate control of l-cysteine content. As a result, the MoS₂/MWCNT composites achieve a minimum reflection loss value of -49.38 dB and an effective absorption bandwidth of 4.64 GHz at a thickness of only 1.7 mm. This work provides a new vision for the fabrication of thin MoS₂-carbon absorbers.

Nanocellulose-based aerogels for water purification: A review

Water purification using thin membranes at high pressures through adsorption and size exclusion is the widely used mechanism due to its simplicity and enhanced efficiency compared to other traditional water purification methods. Aerogels have the potential to replace conventional thin membranes considering their unmatched adsorption/absorption capacity and higher water flux due to their unique highly porous (99 %) 3D structure, ultra-low density (~1.1 to 500 mg/cm³), and very high surface area. The availability of a large number of functional groups, surface tunability, hydrophilicity, tensile strength and flexibility of nanocellulose (NC) makes it a potential candidate for aerogel preparation. This review discusses the preparation and employment of NC-based aerogels in the removal of dyes, metal ions and oils/organic solvents. It also offers recent updates on the effect of various parameters that enhance its adsorption/absorption performance. The future perspectives of NC aerogels and their performance with the emerging materials chitosan and graphene oxide are also compared.

Designing Highly Photoactive Hybrid Aerogels for In-Flow Photocatalytic Contaminant Removal Using Silica-Coated Bacterial Nanocellulose Supports

This study explores the use of silica-coated bacterial nanocellulose (BC) scaffolds with bulk macroscopic yet nanometric internal pores/structures as functional supports for high surface area titania aerogel photocatalysts to design flexible, self-standing, porous, and recyclable BC@SiO₂-TiO₂ hybrid organic-inorganic aerogel membranes for effective in-flow photo-assisted removal of organic pollutants. The hybrid aerogels were prepared by sequential sol-gel deposition of the SiO₂ layer over BC, followed by coating of the resulting BC@SiO₂ membranes with a porous titania aerogel overlayer of high surface area using epoxide-driven gelation, hydrothermal crystallization, and subsequent supercritical drying. The silica interlayer between the nanocellulose biopolymer scaffold and the titania photocatalyst was found to greatly influence the structure and composition, particularly the TiO₂ loading, of the prepared hybrid aerogel membranes, allowing the development of photochemically stable aerogel materials with increased surface area/pore volume and higher photocatalytic activity. The optimized BC@SiO₂-TiO₂ hybrid aerogel showed up to 12 times faster in-flow photocatalytic removal of methylene blue dye from aqueous solution in comparison with bare BC/TiO₂ aerogels and outperformed most of the supported-titania materials reported earlier. Moreover, the developed hybrid aerogels were successfully employed to remove sertraline drug, a model emergent contaminant, from aqueous solution, thus further demonstrating their potential for water purification.

Application of Unsupervised Learning for the Evaluation of Aerogels' Efficiency towards Dye Removal-A Principal Component Analysis (PCA) Approach

Water scarcity is a growing global issue, particularly in areas with limited freshwater sources, urging for sustainable water management practices to insure equitable access for all people. One way to address this problem is to implement advanced methods for treating existing contaminated water to offer more clean water. Adsorption through membranes technology is an important water treatment technique, and nanocellulose (NC)-, chitosan (CS)-, and graphene (G)- based aerogels are considered good adsorbents. To estimate the efficiency of dye removal for the mentioned aerogels, we intend to use an unsupervised machine learning approach known as "Principal Component Analysis". PCA showed that the chitosan-based ones have the lowest regeneration efficiencies, along with a moderate number of regenerations. NC2, NC9, and G5 are preferred where there is high adsorption energy to the membrane, and high porosities could be tolerated, but this allows lower removal efficiencies of dye contaminants. NC3, NC5, NC6, and NC11 have high removal efficiencies even with low porosities and surface area. In brief, PCA presents a powerful tool to unravel the efficiency of aerogels towards dye removal. Hence, several conditions need to be considered when employing or even manufacturing the investigated aerogels.

Application of Unsupervised Machine Learning for the Evaluation of Aerogels’ Efficiency towards Ion Removal—A Principal Component Analysis (PCA) Approach

Water scarcity is a global problem affecting millions of people. It can lead to severe economic, social, and environmental consequences. It can also have several impacts on agriculture, industry, and households, leading to a decrease in human quality of life. To address water scarcity, governments, communities, and individuals must work in synergy for the sake of water resources conservation and the implementation of sustainable water management practices. Following this urge, the enhancement of water treatment processes and the development of novel ones is a must. Here, we have investigated the potential of the applicability of “Green Aerogels” in water treatment’s ion removal section. Three families of aerogels originating from nanocellulose (NC), chitosan (CS), and graphene (G) are investigated. In order to reveal the difference between aerogel samples in-hand, a “Principal Component Analysis” (PCA) has been performed on the physical/chemical properties of aerogels, from one side, and the adsorption features, from another side. Several approaches and data pre-treatments have been considered to overcome any bias of the statistical method. Following the different followed approaches, the aerogel samples were located in the center of the biplot and were surrounded by different physical/chemical and adsorption properties. This would probably indicate a similar efficiency in the ion removal of the aerogels in-hand, whether they were nanocellulose-based, chitosan-based, or even graphene-based. In brief, PCA has shown a similar efficiency of all the investigated aerogels towards ion removal. The advantage of this method is its capacity to engage and seek similarities/dissimilarities between multiple factors, with the elimination of the shortcomings for the tedious and time-consuming bidimensional data visualization.

Removal of highly concentrated methylene blue dye by cellulose nanofiber biocomposites

The contamination of water by dyes in high concentrations is a worldwide concern, and it has prompted the development of efficient, economical, and environmentally friendly materials and technologies for water purification. The hydration and adsorption capacity for methylene blue (MB) in biocomposites (BCs) based on cellulose nanofiber (CNF) (0 to 2 wt%) were studied. BCs were synthesized through a simple and straightforward route and characterized by spectroscopy, microscopic techniques and thermogravimetric analysis, among others. Hydration studies showed that BCs prepared with 2 wt% of CNF can absorb large volumes of water, approximately 2274 % in the case of poly 2-acrylamide-2-methyl-1-propanesulfonic acid (PAMPS)-CNF and 2408 % in poly sodium 4-styrene sulfonate (PSSNa)-CNF. These BCs showed outstanding adsorption capacity for highly concentrated MB solutions (4536 mg g^-1 PAMPS-CNF and 11,930 mg g^-1 PSSNa-CNF). It was confirmed that the adsorption mechanism is through electrostatic interactions. Finally, BCs showed high MB adsorption efficiency after several sorption-desorption cycles and on a simulated textile effluent. Furthermore, the theoretical results showed a preferential interaction between MB and the semiflexible polymer chains at the lowest energy setting. The development and study of a new adsorbent material with high MB removal performance that is easy to prepare, economical and reusable for potential use in water purification treatments was successfully achieved.

Structural Engineering of Hierarchical Aerogels Hybrid Networks for Efficient Thermal Comfort Management and Versatile Protection

In recent years, growing concerns regarding energy efficiency and heat mitigation, along with the critical goal of carbon neutrality, have drawn human attention to the zero-energy-consumption cooling technique. Passive daytime radiative cooling (PDRC) can be an invaluable tool for combating climate change by dispersing ambient heat directly into outer space instead of just transferring it across the surface. Although significant progress has been made in cooling mechanisms, materials design, and application exploration, PDRC faces challenges regarding functionality, durability, and commercialization. Herein, a silica nanofiber aerogels (SNAs) functionalized poly(vinylidene fluoride-co-hexafluoropropene) (P(VDF-HFP)) membrane (SFP membrane), inspired by constructional engineering is constructed. As-prepared membranes with flexible network structure combined hierarchical structure design and practicability principal. As the host material for thermal comfort management (TCM) and versatile protection, the SFP membrane features a large surface area, porous structure, and a robust skeleton that can render excellent mechanical properties. Importantly, the SFP membrane can keep exceptional solar reflectivity (0.95) and strong mid-infrared emittance (0.98) drop the temperature to 12.5 °C below ambient and 96 W m^-2 cooling power under typical solar intensities over 910 W m^-2 . This work provides a promising avenue for high performance aerogel membranes that can be created for use in a wide variety of applications.

Cellulose: A Review of Water Interactions, Applications in Composites, and Water Treatment

Cellulose is known to interact well with water, but is insoluble in it. Many polysaccharides such as cellulose are known to have significant hydrogen bond networks joining the molecular chains, and yet they are recalcitrant to aqueous solvents. This review charts the interaction of cellulose with water but with emphasis on the formation of both natural and synthetic fiber composites. Covering studies concerning the interaction of water with wood, the biosynthesis of cellulose in the cell wall, to its dispersion in aqueous suspensions and ultimately in water filtration and fiber-based composite materials this review explores water-cellulose interactions and how they can be exploited for synthetic and natural composites. The suggestion that cellulose is amphiphilic is critically reviewed, with relevance to its processing. Building on this, progress made in using various charged and modified forms of nanocellulose to stabilize oil-water emulsions is addressed. The role of water in the aqueous formation of chiral nematic liquid crystals, and subsequently when dried into composite films is covered. The review will also address the use of cellulose as an aid to water filtration as one area where interactions can be used effectively to prosper human life.

The versatility of nanocellulose, modification strategies, and its current progress in wastewater treatment and environmental remediation

Deterioration in the environmental ecosystems through the depletion of nonrenewable resources and the burden of deleterious contaminants is considered a global concern. To this end, great interest has been shown in the use of renewable and environmentally-friendly reactive materials dually to promote environmental sustainability and cope with harmful contaminants. Among the different available options, the use of nanocellulose (NC) as an environmentally benign and renewable natural nanomaterial is an attractive candidate for environmental remediation owing to its miraculous physicochemical characteristics. This review discusses the intrinsic properties and the structural aspects of different types of NC, including cellulose nanofibrils (CNFs), cellulose nanocrystals (CNCs), and bacterial cellulose (BC) or bacterial nanocellulose (BNC). Also, the different modification strategies involving the functionalization or hybridization of NC by using different functional and reactive materials aimed at wastewater remediation have been elaborated. The modified or hybridized NC has been explored for its applications in the removal or degradation of aquatic contaminants through adsorption, filtration, coagulation, catalysis, photocatalysis, and pollutant sensing. This review highlights the role of NC in the modified composites and describes the underlying mechanisms involved in the removal of contaminants. The life-cycle assessment (LCA) of NC is discussed to unveil the hidden risks associated with its production to the final disposal. Moreover, the contribution of NC in the promotion of waste management at different stages has been described in the form of the five-Rs strategy. In summary, this review provides rational insights to develop NC-based environmentally-friendly reactive materials for the removal and degradation of hazardous aquatic contaminants.

Supported nanostructured photocatalysts: the role of support-photocatalyst interactions

Heterogeneous photocatalysis employing semiconductor oxide photocatalysts is a sustainable and promising method for environmental remediation and clean energy generation. In this context, nanostructured photocatalysts, with at least one dimension in the 1‒100 nm size regime, have attracted ever-growing attention due to their unique and often enhanced size-dependent physicochemical properties. While their reduced size ensures enhanced photocatalytic performance, the same makes it difficult and time/energy-demanding to remove/recover such nanostructured photocatalysts from aqueous media. This fundamental limitation has paved the way towards developing supported nanophotocatalysts where the active photocatalytic nanostructures are coated on the surface of polymeric or inorganic support materials, often in a core@shell conformation. This arrangement solves the problem of photocatalysts' recovery for effective reuse or recycling and leads to improved and desired target properties due to specific photocatalyst-support interactions. While the enhanced physicochemical properties of supported photocatalysts have been widely studied in many target applications, the role of support-photocatalysts interactions in improving these properties remains unexplored. This review article provides an updated viewpoint on the photocatalyst-support interactions and the resulting unique physiochemical properties important for diverse photochemical applications and the design of practical devices. While exploring the properties of supported nanostructured metal oxide/sulfides photocatalysts such as TiO₂ and MoS₂, we also briefly discuss the common strategies employed to coat the active nanomaterials on the surface of different supports (organic/polymeric, inorganic, active, inert, and magnetic).

Nanocellulose-Based Adsorbents for Heavy Metal Ion

Heavy metal ions in industrial sewage constitute a serious threat to human health. Nanocellulose-based adsorbents are emerging as an environmentally friendly material platform for heavy metal ion removal based on their unique properties, which include high specific surface area, excellent mechanical properties, and biocompatibility. In this review, we cover the most recent works on nanocellulose-based adsorbents for heavy metal ion removal and present an in-depth discussion of the modification technologies for nanocellulose in the process of assembling high-performance heavy ion adsorbents. By introducing functional groups, such as amino, carboxyl, aldehyde, and thiol, the assembled nanocellulose-based adsorbents both remove single heavy metal ions and can selectively adsorb multiple heavy ions in water. Finally, the remaining challenges of nanocellulose-based adsorbents are pointed out. We anticipate that this review will provide indispensable guidance on the application of nanocellulose-based adsorbents for the removal of heavy metal ions.

Cellulose nanofiber/molybdenum disulfide aerogels for ultrahigh photothermal effect

The photothermal materials have a broad range of applications in crude oil spills treatment, desalination, and photothermal therapy. However, the rational construction of aerogels with exceptional photothermal performance is highly desired yet still challenging. Herein, a class of stable aerogels comprised of molybdenum disulfide (MoS₂) nanoflowers and cellulose nanofibers (CNFs) was fabricated, affording extraordinary light-to-heat energy conversion capability. Benefiting from the intercalated porous structure, the resultant cellulose nanofibers/molybdenum disulfide (CNF/MoS₂) aerogels deliver an ultrahigh temperature output up to 260.4 °C with near infrared (NIR) laser power densities of 0.8 W cm^-2. Remarkably, when NIR laser power density increased to 1.0 W cm^-2, the aerogels began to burn, achieving the superhigh surface temperature of ∼ 690 °C. The combustion process of CNF/MoS₂ composite aerogels was evaluated in detail. Therefore, this work provides experiment evidence and theoretical basis for the rational applications of photothermal materials at high temperature in future.

Gellan gum/bacterial cellulose hydrogel crosslinked with citric acid as an eco-friendly green adsorbent for safranin and crystal violet dye removal

In this study, ex-situ crosslinked gellan gum (GG)/bacterial cellulose (BC) hydrogels have been investigated as good absorbents for the removal of safranin and crystal violet dye pollutants. The preparation involves a cost-effective and easy-to-perform crosslinking procedure, using citric acid (CA) as a green crosslinker. The physicochemical and mechanical properties of the crosslinked hydrogels were examined by FTIR, TGA, SEM, XRD, and unconfined compression analyses. The swelling capacity of the hydrogels as a function of pH was investigated. CA depicted to improve structural stability as a crosslinker. The dye removal capacity of the hydrogels as good adsorbents was explored and showed higher efficiency in the removal of safranin dye as compared to crystal violet with optimum adsorption capacities obtained as 17.57 and 13.49 mg/g, respectively. Adsorption kinetics and isotherm models as well as thermodynamics examined. Results showed the adsorption process well fitted the pseudo 2nd-order kinetic and Langmuir-Freundlich models while temperature dependence study depicted to be exothermic. Furthermore, no significant loss of removal efficiency of the hydrogel adsorbent was observed even after five adsorption-desorption cycles. Based on the revealed results, the prepared hydrogel may serve as an effective adsorbent for the removal of dyes from the aqueous phase.

Impact of bandgap tuning on ZnS for degradation of environmental pollutants and disinfection

The materials showing multiple applications are appealing for their practical use and industrial production. To realize the suitable property for various applications, we have produced ZnS (sf-ZnS) and metal-doped ZnS nanoflakes (sf-m-ZnS; where m = Cu, Ni, Cd, Bi, or Mn) and correlated their activity with bandgap variation. We obtained all these materials via hexamethyldisilazane (HMDS)-assisted synthetic method without using any surfactants, polymers, or template molecules and characterized them thoroughly using various techniques. Photocatalytic, as well as antibacterial, activities of these materials showed their bifunctional utility. We have demonstrated the effect of doping and consequent extension of absorption band to the visible region and resultant improved photocatalytic activity under sunlight. Thus, the change in bandgap influenced their performance as photocatalysts. Among all materials produced, sf-Cd-ZnS provided superior results as a photocatalyst while degrading two organic pollutants-rhodamine B (RhB) and methylene blue (MB) in water. The antibacterial activity of sf-ZnS and sf-m-ZnS against Gram-positive bacteria, i.e., Staphylococcus aureus (S. aureus), was examined by the zone of inhibition method, wherein sf-Ni-ZnS showed maximum activity. The enhanced activity of these ZnS materials can be attributed to the free surface of nanoparticles without any capping by organic molecules, which provided an intimate interaction of inorganic semiconductor material with organic and biomolecules. Thus, we have demonstrated modification of properties both by bandgap tuning of materials and providing the opportunity for intimate interaction of materials with substrates. The photocatalytic activity and antibacterial action of metal-doped ZnS produced by our method exhibited their potential for environmental remediation, specifically water purification.

Degradation of Toxic Dye and Antimicrobial and Free Radical Potential of Environmental Benign Zinc Oxide Nanoparticles

Several industries have become major contributors to waterbody contamination due to the improper removal of dyes and effluents into water bodies. Due to their carcinogenic properties and low biodegradability, dye degradation is a considerable danger to people, animals, and the oceanic environment. As part of this study, Andrographis paniculata leaf extract was used as a reducing and stabilizing agent to synthesize zinc nanoparticles and degrade dyes such as methyl red and eosin. Zinc oxide nanoparticles (ZnONPs) showed a surface plasmon resonance peak at 430 nm in the UV spectrum. The FTIR result showed a band at 597.93 cm-1 that confirmed the formation of zinc nanoparticles. AFM results revealed spherical ZnONPs. The SEM results predicted an average particle size of 60 nm for crystalline particles. Biologically synthesized zinc nanoparticles exhibited greater antibacterial activity against Pseudomonas spp. and Proteus spp. but lesser activity against Klebsiella spp. and S. aureus. At 1000 μg/ml concentration, ZnONPs had the highest antioxidant activity of 45.34%. An ultraviolet-visible spectrophotometer measured dye degradation progress between 300 and 800 nm. For methyl red, the maximum absorption peak was measured at 415 nm, and for eosin, the maximum peak value was measured between 500 and 515 nm.

ZIF-8-derived photocatalyst membrane for water decontamination: From static adsorption-degradation to dynamic flow removal

Photocatalysis has been considered a promising method for environmental purification. However, powder nanomaterials are not suitable for large-scale application due to the limit of low recyclability and energy-intensive operation. Integrating and depositing powder photocatalysts on monolithic substrates may solve these issues. In this study, a ZIF-8 photocatalyst membrane and its derived product (ZnS photocatalyst membrane) was constructed by a facile in-situ treatment of cellulose-based substrate (take filter paper as an example). Both the two nanomaterials were confirmed to be tightly anchored to filter paper with the aid of chemical interaction. Under visible light irradiation, excellent dynamic-flow photocatalytic removal efficiencies of methylene blue (MB) degradation (97% within 80 min, k = 0.042 ± 0.002 min^-1) and Cr(VI) reduction (100% within 60 min, k = 0.116 ± 0.007 min^-1) were achieved by the prepared ZIF-8 photocatalyst membrane and its derived ZnS photocatalyst, respectively. Considering the high MB adsorption capacity and facile regeneration process of ZIF-8 photocatalyst membrane, the adsorption-degradation strategy was promising for its universal applications. The MB degradation pathway and photocatalytic mechanisms were also explored. Ultimately, a comprehensive discussion on the advantages and implications of prepared photocatalyst membranes for photocatalytic water treatment was rationally proposed. This study provided a promising method for water decontamination and demonstrated the significant superiority of monolithic membrane for photocatalytic water treatment.

Recent advancement in isolation, processing, characterization and applications of emerging nanocellulose: A review

The emergence of nanocellulose from various natural resources as a promising nanomaterial has been gaining interest for a wide range application. Nanocellulose serves as an excellent candidate since it contributes numerous superior properties and functionalities. In this review, details of the three main nanocellulose categorised: cellulose nanocrystal (CNC), cellulose nanofibril (CNF), and bacterial nanocellulose (BNC) have been described. We focused on the preparation and isolation techniques to produce nanocellulose including alkaline pre-treatment, acid hydrolysis, TEMPO-mediated oxidation, and enzymatic hydrolysis. The surface modification of nanocellulose through esterification, silylation, amidation, phosphorylation, and carboxymethylation to improve the diverse applications has also been reviewed. Some invigorating perspectives on the applications, challenges, and future directions on the relevant issues regarding nanocellulose are also presented.

Flexible and Freestanding MoS2 Nanosheet/Carbon Nanotube/Cellulose Nanofibril Hybrid Aerogel Film for High-Performance All-Solid-State Supercapacitors

Flexible supercapacitors assembled with two-dimensional materials have become a research hotspot in recent years. Here, we have prepared two-dimensional nanomaterial MoS₂ and SWCNT, CNF aerogel composite electrode, and its flexible all-solid-state supercapacitor. SWCNT can inhibit the accumulation of MoS₂ nanosheets and enhance the conductivity of the composite electrode. CNF can improve the dispersion uniformity of MoS₂ and SWCNT, and endow the composite electrode with a high specific surface area (328.86 m² g^-1) and excellent flexibility. MoS₂-SWCNT/CNF supercapacitor has a good rectangular CV curve and symmetrical triangular GCD curve. The CV curve of the MoSCF3 supercapacitor with the highest MoS₂-SWCNT content remains rectangular even at the scanning rate of 2000 mV s^-1. Its voltage window can reach 1.5 V. MoS₂-SWCNT/CNF supercapacitor has a specific capacity of 605.32 mF cm^-2 (scanning rate of 2 mV s^-1) and 30.34 F g^-1 (0.01 A g^-1), an area specific energy of 35.61 mWh cm^-2 (area specific power of 0.03 mW cm^-2), and extremely high cycle stability (91.01% specific capacity retention rate after 10 000 cycles) and good flexibility. The fine nanocomposite structure gives MoS₂-SWCNT/CNF supercapacitor impressive electrochemical performance and excellent flexibility, which can be used in the field of portable electronic devices and flexible devices.

Recent Progress of Cellulose-Based Hydrogel Photocatalysts and Their Applications

With the development of science and technology, photocatalytic technology is of great interest. Nanosized photocatalysts are easy to agglomerate in an aqueous solution, which is unfavorable for recycling. Therefore, hydrogel-based photocatalytic composites were born. Compared with other photocatalytic carriers, hydrogels have a three-dimensional network structure, high water absorption, and a controllable shape. Meanwhile, the high permeability of these composites is an effective way to promote photocatalysis technology by inhibiting nanoparticle photo corrosion, while significantly ensuring the catalytic activity of the photocatalysts. With the growing energy crisis and limited reserves of traditional energy sources such as oil, the attention of researchers was drawn to natural polymers. Like almost all abundant natural polymer compounds in the world, cellulose has the advantages of non-toxicity, degradability, and biocompatibility. It is used as a class of reproducible crude material for the preparation of hydrogel photocatalytic composites. The network structure and high hydroxyl active sites of cellulose-based hydrogels improve the adsorption performance of catalysts and avoid nanoparticle collisions, indirectly enhancing their photocatalytic performance. In this paper, we sum up the current research progress of cellulose-based hydrogels. After briefly discussing the properties and preparation methods of cellulose and its descendant hydrogels, we explore the effects of hydrogels on photocatalytic properties. Next, the cellulose-based hydrogel photocatalytic composites are classified according to the type of catalyst, and the research progress in different fields is reviewed. Finally, the challenges they will face are summarized, and the development trends are prospected.

Nanocellulose for Sustainable Water Purification

Nanocelluloses (NC) are nature-based sustainable biomaterials, which not only possess cellulosic properties but also have the important hallmarks of nanomaterials, such as large surface area, versatile reactive sites or functionalities, and scaffolding stability to host inorganic nanoparticles. This class of nanomaterials offers new opportunities for a broad spectrum of applications for clean water production that were once thought impractical. This Review covers substantial discussions based on evaluative judgments of the recent literature and technical advancements in the fields of coagulation/flocculation, adsorption, photocatalysis, and membrane filtration for water decontamination through proper understanding of fundamental knowledge of NC, such as purity, crystallinity, surface chemistry and charge, suspension rheology, morphology, mechanical properties, and film stability. To supplement these, discussions on low-cost and scalable NC extraction, new characterizations including solution small-angle X-ray scattering evaluation, and structure-property relationships of NC are also reviewed. Identifying knowledge gaps and drawing perspectives could generate guidance to overcome uncertainties associated with the adaptation of NC-enabled water purification technologies. Furthermore, the topics of simultaneous removal of multipollutants disposal and proper handling of post/spent NC are discussed. We believe NC-enabled remediation nanomaterials can be integrated into a broad range of water treatments, greatly improving the cost-effectiveness and sustainability of water purification.

Free-standing hybrid film for separation of dye pollutant with self-cleaning ability under visible light

The development of low cost and environmental-friendly materials has long been an ambition for effective removal of dye pollutants in complex water environments. In this study, a free-standing separation film of bacterial cellulose reinforced/functionalized by graphitic phase carbon nitride is developed by a facile suction filtration strategy, of which the former is precoated by polypyrrole, and the latter is pre-doped by oxygen to endow the as-obtained film an enhanced photocatalytic performance and self-cleaning ability. The as-obtained film exhibits a high tensile stress of 51.8 ± 1.1 MPa, and a high resistance to cold, heat, acid and alkali. For typical dyes of methylene blue and rhodamine B, a high dye rejection rate of 99.9% at 138 L/m²•h•bar feed flux is obtained by the as-obtained film. Even at a salt concentration higher than 5%, it still maintained high dye removal rates and achieves effective separation of dye and salt. Simultaneously, a high dye photocatalytic degradation of the composite films rates up to 98% in only 90 min, and a high self-cleaning ability demonstrated by recovery of flux after light treatment in cyclic tests. The density functional theory calculation validates the beneficial effects of improved light response range and separated photogenerated electron/holes for the effective degradation of dyes by oxygen-doped carbon nitride coupled with one-dimensional polypyrrole chains. Overall, this study proposes a new direction for the separation of dye pollutants with a high visible-light self-cleaning capacity by structural tailoring of bacterial cellulose with carbon nitride.

A review on three-dimensional cellulose-based aerogels for the removal of heavy metals from water

Contamination of the aquatic ecosystem by heavy metals is a growing concern that has yet to be addressed with an efficient, cost-effective and environmentally-friendly solution. Heavy metals occur naturally in the earth's crust and also result from anthropogenic activities. Due to the rapid increase in industrialization, there is an increase in consumer demands across various industries such as metal processing, mining sector, agricultural activities, etc. and this has led to an increase in heavy metal concentrations in the aqueous environment. Cellulose-based aerogels are a novel third-generation of aerogels that have recently attracted a lot of attention due to their high adsorption efficiency, eco-friendly prospects and cost effectiveness. In this review, recent literature on cellulose-based aerogel adsorbents used for the removal of heavy metals from aqueous solution has been compiled. The preparation of cellulose-based aerogels, adsorption mechanisms, effects of experimental factors such as pH, temperature, contact time, initial metal concentration and adsorbent dose have been discussed. In addition, cost analysis of cellulose-based adsorbents and some challenges in this research field along with recommendations of improvements have been presented. It can be concluded that functionalizing of cellulose-based aerogels with amine groups, thiol groups, other compounds such as nanobentonite and chitosan results in very high adsorption capacities. The adsorption studies revealed that pseudo-second-order kinetic model was the most commonly encountered adsorption kinetic model, and the most commonly encountered adsorption isotherm model was the Langmuir isotherm model. The main adsorption mechanisms were electrostatic interaction, complexation and ion exchange.

Two-dimensional material-based functional aerogels for treating hazards in the environment: synthesis, functional tailoring, applications, and sustainability analysis

Environmental pollution is a global problem that endangers human health and ecological balance. As a new type of functional material, two-dimensional material (2DM)-based aerogel is one of the most promising candidates for pollutant detection and environmental remediation. The porous, network-like, interconnected three-dimensional (3D) structure of 2DM-based aerogels can not only preserve the characteristics of the original 2DMs, but also bring many distinct physical and chemical properties to offer abundant active sites for adsorbing and combining pollutants, thereby facilitating highly efficient monitoring and treatment of hazardous pollutants. In this review, the synthesis methods of 2DM aerogels and their broad environmental applications, including various sensors, adsorbents, and photocatalysts for the detection and treatment of pollutants, are summarized and discussed. In addition, the sustainability of 2DM aerogels compared to other water purification materials, such as activated carbon, 2DMs, and other aerogels are analyzed by the Sustainability Footprint method. According to the characteristics of different 2DMs, special focuses and perspectives are given on the adsorption properties of graphene, MXene, and boron nitride aerogels, as well as the sensing and photocatalytic properties of transition metal dichalcogenide/oxide and carbon nitride aerogels. This comprehensive work introduces the synthesis, modification, and functional tailoring strategies of different 2DM aerogels, as well as their unique characteristics of adsorption, photocatalysis, and recovery, which will be useful for the readers in various fields of materials science, nanotechnology, environmental science, bioanalysis, and others.

Highly Permeable MoS2 Nanosheet Porous Membrane for Organic Matter Removal

MoS2 nanosheets were synthesized by a bottom-up green chemical process where l-cysteine was used as a sulfur precursor. With specific concentrations, molar ratio of reactants, and pre-mixing conditions, MoS2 nanosheets of 200-300 nm in size and 4.2 nm in average thickness were successfully obtained. Porous membranes were then prepared by depositing the MoS2 nanosheet suspension on a 0.1 μm pore size poly(vinylidene difluoride) membrane filter in a multiple batch procedure. The membrane deposited with 12 batches of MoS2 nanosheets achieved 93.78% removal of bovine serum albumin. Acid red removal of 95.65% was also achieved after the second filtration pass. The porous MoS2 nanosheet membrane also demonstrated a high water flux of 182 ± 2.0 L/(m2 h). This result overcame the trade-off between selectivity and permeability faced by polymeric ultrafiltration membranes. The MoS2 nanosheets as building blocks formed not only intersheet slit pores with a narrow half-width to restrict the passage of organic molecules but also macro-channels allowing easy passage of water. The assembled MoS2 nanosheet membrane delivered promising separation of protein molecules and a high flux, attributing to its porous nanostructure, and could be a potential membrane for various water applications.

Interfacial engineering of vacancy-rich nitrogen-doped FexOy@MoS2 Co-catalytic carbonaceous beads mediated non-radicals for fast catalytic oxidation

How to accelerate the Fe³⁺/Fe²⁺ conversion and fabricate recyclable iron-based catalysts with high reactivity and stability is highly desired yet challenging. Herein, vacancy-rich N@Fe_xO_y@MoS₂ carbonaceous beads were firstly developed via employing sodium alginate, molybdenum disulfide (MoS₂), and Fe-ZIFs through sol-gel self-assembly, followed by in-situ growth and pyrolysis strategies. As expected, A series of characterizations reflected that N@Fe_xO_y@MoS₂ had high dispersibility and conductivity for fast mass and electron transport, and MoS₂ as co-catalyst accelerated the circulation of Fe³⁺ to Fe²⁺ that attained 99.4% (0.345 min^-1) norfloxacin degradation via PMS activation in a synergistic ''adsorption-driven-oxidation'' process, which much outperformed those of pure MoS₂ (32.4%) and N@Fe_xO_y powder catalyst (45.3%). Moreover, confined Fe species, graphitic N, pyrrolic N, pyridinic N, and sulfur/oxygen vacancies were found as highly exposed active sites that contributed to the activation of PMS to dominate non-radicals (¹O₂ and O₂·^-) and other radicals following a contribution order ¹O₂ > O₂·^- > SO₄·^- > ^·OH. More importantly^, a fluidized-bed catalytic unit was evaluated and maintained the continuous zero discharge of NX. Overall, this study offered a generally applicable approach to fabricate removable Fe-based catalysts for contaminants remediation.

Lightweight and broadband 2D MoS2 nanosheets/3D carbon nanofibers hybrid aerogel for high-efficiency microwave absorption

Three-dimensional (3D) porous molybdenum disulfide nanosheets/carbon nanofibers (MoS₂/CNF) hybrid aerogels were synthesized by using solvothermal method and following carbonization, where two-dimensional (2D) MoS₂ nanosheets were homogenously in-situ grown on the interconnected CNF skeleton derived from bacterial cellulose, forming a hierarchical porous structure. This unique heterogeneous structure of the MoS₂/CNF hybrid aerogels were conducive to electromagnetic loss, including conduction, polarization, multi-scatterings, and reflections, thus resulting in a balanced impedance matching and microwave attenuation capacity. It was found that the resulted MoS₂/CNF hybrid aerogels demonstrate excellent microwave absorbing performance when the only 5.0 wt% fillers were loaded in paraffin. Particularly, MoS₂/CNF-2-900 hybrid aerogel displayed an effective absorption bandwidth of 5.68 GHz and minimum reflection loss (RL_min) value of -36.19 dB at a thickness of 2.0 mm. As the thickness increases to 4.4 mm, the RL_min value of MoS₂/CNF-2-900 hybrid aerogel reaches -48.53 dB. Electromagnetic loss mechanism analysis indicates that such improved microwave attenuation is attributed to proper component, multiple heterogenous interface and hierarchical porous structures. All the results in this work pave the avenue for the development of ultralight microwave absorber with high absorption capacity as well as broad effective absorption bandwidth.

Recent Progress in Polysaccharide Aerogels: Their Synthesis, Application, and Future Outlook

Porous polysaccharides have recently attracted attention due to their porosity, abundance, and excellent properties such as sustainability and biocompatibility, thereby resulting in their numerous applications. Recent years have seen a rise in the number of studies on the utilization of polysaccharides such as cellulose, chitosan, chitin, and starch as aerogels due to their unique performance for the fabrication of porous structures. The present review explores recent progress in porous polysaccharides, particularly cellulose and chitosan, including their synthesis, application, and future outlook. Since the synthetic process is an important aspect of aerogel formation, particularly during the drying step, the process is reviewed in some detail, and a comparison is drawn between the supercritical CO2 and freeze drying processes in order to understand the aerogel formation of porous polysaccharides. Finally, the current applications of polysaccharide aerogels in drug delivery, wastewater, wound dressing, and air filtration are explored, and the limitations and outlook of the porous aerogels are discussed with respect to their future commercialization.

Drawing on Membrane Photocatalysis for Fouling Mitigation

Photocatalysis is an effective and environmentally friendly approach for degrading organic pollutants, particularly in scenarios where sunlight can be utilized as the energy source. Opportunities are emerging to apply materials and methods from photocatalytic pollutant degradation to address the challenge of fouling. Membrane fouling, attributed to organic foulants, is a prevalent problem for all membrane-based technologies and represents a major deleterious impact on membrane performance. Integration of tactics developed in photocatalysis more broadly to membranes reveals new strategies for membrane fouling control-an approach taken by an increasing number of researchers. This review summarizes key developments in photocatalytic materials and methods in water treatment and presents recent progress in the development of processes for photocatalytic alleviation of membrane fouling, including photocatalyst design and modification strategies aimed at enhancing photocatalytic efficiency, as well as different configurations of photocatalysis-membrane systems (PMS). Perspectives on future research and development opportunities for photocatalytic membrane fouling control are also provided.

Visible Light-Driven Photocatalytic Rhodamine B Degradation Using CdS Nanorods

In this work, highly crystalline CdS nanorods (NRs) were successfully synthesized by a facile, one-step solvothermal method. The as-prepared CdS NRs powder was characterized by XRD, FESEM, Raman, PL, XPS, BET, and UV-visible techniques to evaluate the structural, morphological, and optical properties. The photocatalytic performance of the as-synthesized CdS NRs was investigated for the photodegradation of RhB dye under visible light irradiations. It has been found that CdS NRs show maximum RhB degradation efficiency of 88.4% in 120 min. The excellent photodegradation ability of the CdS NRs can be attributed to their rod-like structure together with their large surface area and surface state. The kinetic study indicated that the photodegradation process was best described by the pseudo-first-order kinetic model. The possible mechanism for the photodegradation of RhB dye over CdS NRs was proposed in this paper.

Bifunctional Regenerated Cellulose/Polyaniline/Nanosilver Fibers as a Catalyst/Bactericide for Water Decontamination

For antagonizing urgent water pollution and increasing environmental consciousness, the integration of renewable resources and nanotechnologies has become a trend to improve water quality in the ecosystem. Here, we designed a green route to fabricate regenerated cellulose fibers (CFs) with 3D micro- and nanoporous structures in NaOH/urea aqueous solvent systems via a scalable wet-spinning procedure as support materials for nanoparticles (NPs). Modification of CFs with polyaniline@Ag nanocomposites through in situ reduction of the silver ion with aqueous aniline led to enhanced pollutant removal efficiency of functional cellulose-based fibers (FCFs), demonstrating both rapid hydrogenation catalytic performance for the reduction of p-nitrophenol and high antibacterial properties for in-flow water purification. Most importantly, the hierarchically porous structures of FCFs not only provided carrier space but also formed a limiting domain guaranteeing the homogeneity of FCFs even with a Ag NP content as high as 36.47 wt %. The prepared functional fibers show good behavior in in-flow water purification, representing significant advancement in the use of biomass fibers for catalytic and bactericidal applications in liquid media.

Prussian blue as a co-catalyst for enhanced Cr(vi) photocatalytic reduction promoted by titania-based nanoparticles and aerogels

A nanostructured Prussian blue layer deposited on titania-based materials acts as an efficient electron acceptor/mediator greatly enhancing Cr(vi) photocatalytic reduction.

Highly effective catalytic reduction of nitrobenzene compounds with gold nanoparticle-immobilized hydroxyapatite nanowire-sintered porous ceramic beads

A catalytic ceramic bead with micron-sized and interconnected porous channels, adjustable porosity, high catalytic activity, and long-term stability is prepared.