Cellulose Nanofiber-Based Aerogels from Wheat Straw: Influence of Surface Load and Lignin Content on Their Properties and Dye Removal Capacity

All-natural aerogel of nanoclay/cellulose nanofibers with hierarchical porous structure for rapid hemostasis

Developing an effective and user-friendly hemostatic agent is highly desired in the treatment of hemorrhage. Inspired by the natural nanostructure and abundant hydroxyl groups of cellulose and clay minerals, we designed an aerogel (HNTs/TOCNs) composed of halloysite nanotubes (HNTs) and TEMPO-oxidized cellulose nanofibers (TOCNs) with a hierarchical porous structure for the treatment of bleeding, using a simple and environmentally friendly self-assembly method. TOCNs formed a three-dimensional porous scaffold with excellent water-holding capacity. The incorporation of HNTs enhanced the hemostatic efficiency and mechanical properties of the 3D framework. The large interlayer spaces and wide channels within the HNTs/TOCNs aerogel provided rapid passage for blood, facilitating blood concentration and offering ample room for interactions between the HNTs/TOCNs aerogel and platelets, erythrocytes, and coagulation factors, thereby promoting hemostasis. Benefiting from the natural hemostatic properties and well-designed structure, the HNTs/TOCNs aerogel displayed excellent hemostatic performance both in vitro and in vivo. Notably, the hemostatic time of HNTs/TOCNs-2 was only 74 ± 8 s, which is approximately 50 % shorter than the blank control (151 ± 20 s) in liver femoral artery injury model. This design of an HNTs/TOCNs aerogel presents a unique opportunity to enhance hemostatic efficacy by synergizing the advantages of natural materials.

Investigating chemical pre-treatment methods: Valorization of wheat straw to enhance polyhydroxyalkanoate (PHA) production with novel isolate Bacillus paranthracis RSKS-3

Wheat is a crucial food crop worldwide, generating straw upon post-harvest. The straw is often burned to enhance soil fertility, leading to massive air pollution. In this study, wheat straw was investigated for the production of Polyhydroxyalkanoate (PHA) using the novel isolate Bacillus paranthracis RSKS-3. The wheat straw was pulverized and valorized with different acids (2 % and 4 % H2SO4, acetic acid, and hydrochloric acid) and alkalis (2 % and 4 % NaOH, calcium carbonate, and potassium hydroxide). The validation of carbohydrates was done using the Molisch test by analyzing purple-ring production and the DNS test which concluded 4 % H2SO4 as an effective treatment with a maximal sugar yield of 5.04 mg/mL at P < 0.05. The bioconversion efficiency of the extract to PHA resulted in 0.87 g/L by Bacillus paranthracis RSKS-3, later characterized by Ultraviolet (UV)-spectroscopy and FT-IR assessment. The findings of the research offer a potential strategy to mitigate airborne pollutants that result from smouldering wheat straw, thereby contributing significant improvements to sustainable development.

Nanostructured Cellulose-Based Aerogels: Influence of Chemical/Mechanical Cascade Processes on Quality Index for Benchmarking Dye Pollutant Adsorbents in Wastewater Treatment

(1) Background: Nanostructured cellulose has emerged as an efficient bio-adsorbent aerogel material, offering biocompatibility and renewable sourcing advantages. This study focuses on isolating (ligno)cellulose nanofibers ((L)CNFs) from barley straw and producing aerogels to develop sustainable and highly efficient decontamination systems. (2) Methods: (Ligno)cellulose pulp has been isolated from barley straw through a pulping process, and was subsequently deconstructed into nanofibers employing various pre-treatment methods (TEMPO-mediated oxidation process or PFI beater mechanical treatment) followed by the high-pressure homogenization (HPH) process. (3) Results: The aerogels made by (L)CNFs, with a higher crystallinity degree, larger aspect ratio, lower shrinkage rate, and higher Young's modulus than cellulose aerogels, successfully adsorb and remove organic dye pollutants from wastewater. (L)CNF-based aerogels, with a quality index (determined using four characterization parameters) above 70%, exhibited outstanding contaminant removal capacity over 80%. The high specific surface area of nanocellulose isolated using the TEMPO oxidation process significantly enhanced the affinity and interactions between hydroxyl and carboxyl groups of nanofibers and cationic groups of contaminants. The efficacy in adsorbing cationic dyes in wastewater onto the aerogels was verified by the Langmuir adsorption isotherm model. (4) Conclusions: This study offers insights into designing and applying advanced (L)CNF-based aerogels as efficient wastewater decontamination and environmental remediation platforms.

Antibacterial Aerogels-Based Membranes by Customized Colloidal Functionalization of TEMPO-Oxidized Cellulose Nanofibers Incorporating CuO

An innovative colloidal approach is proposed here to carry out the customized functionalization of TEMPO-Oxidized Cellulose Nanofibers (CNF) incorporating non-noble inorganic nanoparticles. A heterocoagulation process is applied between the delignified CNF and as-synthetized CuO nanoparticles (CuO NPs) to formulate mixtures which are used in the preparation of aerogels with antibacterial effect, which could be used to manufacture membranes, filters, foams, etc. The involved components of formulated blending, CNF and CuO NPs, were individually obtained by using a biorefinery strategy for agricultural waste valorization, together with an optimized chemical precipitation, assisted by ultrasounds. The optimization of synthesis parameters for CuO NPs has avoided the presence of undesirable species, which usually requires later thermal treatment with associated costs. The aerogels-based structure, obtained by conventional freeze-drying, acted as 3D support for CuO NPs, providing a good dispersion within the cross-linked structure of the nanocellulose and facilitating direct contact of the antibacterial phase against undesirable microorganisms. All samples showed a positive response against Escherichia coli and Staphylococcus aureus. An increase of the antibacterial response of the aerogels, measured by agar disk diffusion test, has been observed with the increase of CuO NPs incorporated, obtaining the width of the antimicrobial "halo" (nwhalo) from 0 to 0.6 and 0.35 for S. aureus and E. coli, respectively. Furthermore, the aerogels have been able to deactivate S. aureus and E. coli in less than 5 h when the antibacterial assays have been analyzed by a broth dilution method. From CNF-50CuO samples, an overlap in the nanoparticle effect produced a decrease of the antimicrobial kinetic.

A review on recent advances towards sustainable development of bio-inspired agri-waste based cellulose aerogels

Cellulose aerogel (CA) is considered to be the most promising material due to its extraordinary properties like unique microstructure, porosity, large specific surface area, biodegradability, renewable nature and lightweight. Cellulosic aerogels are thus found to have potential applications in different fields especially in water purification and biomedical field. Agricultural waste based cellulose aerogels are recently getting wider attention owing to its sustainability. The synthesis methods of agri-waste based cellulose aerogels, its properties and application in different fields especially in the field of water purification are detailed in a comprehensive manner. This review tries to bring light into the commercialization of value-added products from sustainable, cheap agricultural waste material and tries to motivate young researchers.

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.

Bioactive Absorbent Chitosan Aerogels Reinforced with Bay Tree Pruning Waste Nanocellulose with Antioxidant Properties for Burger Meat Preservation

As a transition strategy towards sustainability, food packaging plays a crucial role in the current era. This, carried out in a biorefinery context of agricultural residues, involves not only obtaining desirable products but a comprehensive utilization of biomass that contributes to the circular bioeconomy. The present work proposes the preparation of bioactive absorbent food pads through a multi-product biorefinery approach from bay tree pruning waste (BTPW). In a first step, chitosan aerogels reinforced with lignocellulose and cellulose micro/nanofibers from BTPW were prepared, studying the effect of residual lignin on the material's properties. The presence of micro/nanofibers improved the mechanical performance (up to 60%) in addition to increasing the water uptake (42%) when lignin was present. The second step was to make them bioactive by incorporating bay leaf extract. The residual lignin in the micro/nanofibers was decisive, since when present, the release profiles of the extract were faster, reaching an antioxidant power of more than 85% after only 30 min. Finally, these bioactive aerogels were used as absorbent pads for fresh meat. With the use of the bioactive aerogels (with ≥2% extract), the meat remained fresh for 10 days as a result of delayed oxidation of the food during storage (20% metmyoglobin proportion).

Valorization of wheat straw in food packaging: A source of cellulose

Wheat straw (WS) is one of the abundant categories of agricultural waste, which is usually abandoned and burned yearly, thus creating environmental issues. Traditionally, it is used for low-value purposes, mainly in cattle feeding or agricultural mulch, and the rest is burnt or thrown away. WS is a valuable candidate as raw material for being used as reinforcing fibers to fabricate biocomposites. Among existing strategies, one of the potential strategies to utilize such lignocellulosic biomasses includes the extraction of cellulose as a potential candidate in the fabrication of sustainable packaging. Exploring WS as a valuable source of cellulose could be a key strategy for enabling biopolymers in packaging, which relies on developing tailor-made materials from non-food and low-cost resources. In this regard, the valorization of WSs for packaging can add value to these underutilized residues and successfully contribute to the circular economy concept. The review addresses the valorization of WS as a source of cellulose and its nanostructured forms for food packaging applications. The review also discusses cellulose derivatives extraction using conventional or innovative techniques (microwave-assisted extraction, fractionation, mechanical fibrillation, steam-explosion, microfludization, enzymatic hydrolysis, etc.). The different applications of these extracted biopolymers in the packaging are also summarized.

Biopolymeric Fibrous Aerogels: The Sustainable Alternative for Water Remediation

The increment in water pollution due to the massive development in the industrial sector is a worldwide concern due to its impact on the environment and human health. Therefore, the development of new and sustainable alternatives for water remediation is needed. In this context, aerogels present high porosity, low density, and a remarkable adsorption capacity, making them candidates for remediation applications demonstrating high efficiency in removing pollutants from the air, soil, and water. Specifically, polymer-based aerogels could be modified in their high surface area to integrate functional groups, decrease their hydrophilicity, or increase their lipophilicity, among other variations, expanding and enhancing their efficiency as adsorbents for the removal of various pollutants in water. The aerogels based on natural polymers such as cellulose, chitosan, or alginate processed by different techniques presented high adsorption capacities, efficacy in oil/water separation and dye removal, and excellent recyclability after several cycles. Although there are different reviews based on aerogels, this work gives an overview of just the natural biopolymers employed to elaborate aerogels as an eco-friendly and renewable alternative. In addition, here we show the synthesis methods and applications in water cleaning from pollutants such as dyes, oil, and pharmaceuticals, providing novel information for the future development of biopolymeric-based aerogel.

Extraction of Nanocellulose for Eco-Friendly Biocomposite Adsorbent for Wastewater Treatment

In the present study, nanocellulose was extracted from palm leaves to synthesize nanocellulose/chitosan nanocomposites for the removal of dyes from textile industrial wastewater. Nanocellulose is of interest in water purification technologies because of its high surface area and versatile surface chemistry. Following bleach, alkali, and acid treatments on palm leaves, nanocellulose is obtained as a white powder. The produced nanocellulose was investigated. The adsorption capacity of chitosan, nanocellulose, and novel synthetic nanocellulose/chitosan microbeads (CCMB) for direct blue 78 dye (DB78) removal was studied. A series of batch experiments were conducted in terms of adsorbent concentration, mixing time, pH, dye initial concentration, and nanocellulose concentration in synthetic microbeads. The CCMB was characterized by using physicochemical analysis, namely Brunauer–Emmett–Teller (BET), scanning electron microscope (SEM), zeta potential analysis, and Fourier-transform infrared spectroscopy (FTIR). It was found that the surface area of synthetic CCMB is 10.4 m²/g, with a positive net surface charge. The adsorption tests showed that the dye removal efficiency increases with an increasing adsorbent concentration. The maximum removal efficiencies were 91.5% and 88.4%, using 14 and 9 g/L of CCMB-0.25:1. The initial dye concentrations were 50 and 100 mg/L under acidic conditions (pH = 3.5) and an optimal mixing time of 120 min. The equilibrium studies for CCMB-0.25:1 showed that the equilibrium data were best fitted to Langmuir isothermal model with R² = 0.99. These results revealed that nanocellulose/chitosan microbeads are an effective eco-adsorbent for the removal of direct blue 78 dye and provide a new platform for dye removal.