Fly-Ash based Flame-Retardant Cellulose Materials for Strengthening and Value-Added Utilization in Industrial Solid Wastes

Fly-Ash based Flame-Retardant Cellulose Materials for Strengthening and Value-Added Utilization in Industrial Solid Wastes | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Fly-Ash based Flame-Retardant Cellulose Materials for Strengthening and Value-Added Utilization in Industrial Solid Wastes Wentao He, Lei Tan, Yongjia Wu, Yongchun Wei, Yiyang Chen, Dan Li, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4185593/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 04 Feb, 2025 Read the published version in Cellulose → Version 1 posted 4 You are reading this latest preprint version Abstract Cellulose, a bio-based material, is increasingly researched and valued for its abundant availability and exceptional characteristics. However, Cellulose has a flammable problem. This study addresses this issue by integrating it with industrial waste fly ash (FA) to overcome its natural flammability. By solution compounding, the study successfully developed cellulose/FA films and porous structures, significantly boosting the material's flame-retardant capabilities. This innovation not only enhances the practical application of cellulose but also promotes the high-value reuse of FA, resonating with the principles of sustainable development. The cellulose/FA hydrogel, characterized by a homogeneous and stable blend of FA particles and cellulose, achieves this through effective affinity and hydrogen bonding, ensuring optimal miscibility and encapsulation. In terms of thermal properties, the modified composites (C-F10, C-F20 and C-F30) demonstrate a substantial increase in initial decomposition temperatures, approximately 26℃ higher than pure cellulose, ranging between 282℃ and 302℃. This enhancement is attributed to the formation of an inorganic protective layer on the cellulose matrix, which significantly improves thermal stability while maintaining key mechanical properties. Remarkably, the flame retardancy of these materials shows notable improvement, particularly at a 30wt% FA concentration, with the limiting oxygen index (LOI) of the porous and film structures reaching around 29% and 31%, respectively. This advancement greatly elevates their flame resistance. Overall, this study presents a pioneering approach in developing eco-friendly, flame-retardant materials by repurposing industrial waste, marking a significant stride in sustainable material innovation. Cellulose Fly-Ash Flame-Retardance Strengthening Value-Added Utilization of Industrial Waste Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction The current scarcity of petroleum resources, coupled with the excessive waste of petroleum-derived products, is exerting severe environmental stress. In the quest to promote sustainable development and tackle environmental challenges stemming from the non-degradable nature and toxic emissions during combustion of many discarded petroleum-based substances, bio-based materials have received significant focus in both industrial and academic spheres (Jiang et al. 2018 ; Long et al. 2018 ). Cellulose, a linear copolymer composed of D -anhydroglucopyranose units linked by β -(1→4)-glycosidic bonds, stands out as an exemplary bio-based material. It offers numerous benefits, including affordability, low density, renewability, and biocompatibility-advantages that are particularly notable in comparison to petroleum-based polymers (Habibi et al. 2010 ; Suflet et al. 2006 ). However, cellulose's solubility is restricted to certain solvents, a consequence of its robust inter- and intra-molecular hydrogen bonding. By modifying cellulose through the addition of functional groups or the adsorption of nanoparticles, its range of applications can be substantially broadened (Zhao et al. 2018 ). The current focus on developing composites with diverse structures and functionalities, utilizing cellulose as a core material, is a critical approach to replacing various fossil-based products and mitigating environmental pollution (Suflet et al. 2006 ). However, a significant challenge is that cellulose shares the same flammability traits as many traditional polymers in natural environments, primarily due to its low limiting oxygen index. When ignited, cellulose and its derivatives undergo thermal decomposition, releasing a large number of volatile compounds, which raises safety concerns during their manufacturing and usage, consequently hindering the advancement of cellulose-based products (Aoki et al. 2010). At present, enhancing the flame retardancy of cellulose typically involves integrating various types of flame retardants into the gel matrix, encompassing inorganic, halogenated organic, organic phosphorus, nitrogen, and silicon-based compounds (Chang et al. 2014 ; Gong et al. 2019 ). Nevertheless, the use of conventional halogenated flame retardants poses environmental concerns, as they emit toxic substances when burned. This situation underscores the necessity for employing eco-friendly, cellulose-compatible flame retardants (Han et al. 2015 ). Currently, there is a growing body of research exploring the utilization of nitrogen and phosphorus-based flame retardants, alongside eco-friendly inorganic alternatives, to replace conventional halogenated and boron-based retardants (Aoki et al. 2010; Han et al. 2015 ). Especially inorganic flame retardants, with the development of surface treatment technology and today's nano research, the market has launched a number of new efficient inorganic flame retardants, inorganic flame retardants began to emerge. Inorganic flame retardants are gaining attention for their exceptional thermal stability, cost-effectiveness, non-toxic nature, and lack of secondary pollution (Nine et al. 2015 ). For instance, Wang et al ( 2015 ) have successfully created cellulose/montmorillonite (MMT) bio-based plastics using a cellulose solution and MMT suspension, processed through hot pressing. This composite material exhibited notable thermal stability and flame-retardant properties. Similarly, Chen et al. ( 2022 ) developed cellulose/bentonite (Cel/BT) foam from Cel solution and BT powder, facilitated by environmental natural drying and chemical cross-linking with 1,4-butanediol diether. This product demonstrated biodegradability and superior mechanical characteristics. These inorganic fillers not only impart flame-retardant properties but also enhance the base material's features. Thus, enhancing flame-retardant capabilities while maintaining the material's inherent structural qualities is becoming a preferable approach for practical applications (Zhang et al. 2023 ). The widespread utilization of coal since the 1920s has led to the production of a significant quantity of FA and its related by-products. Annually, over 500 million tons of FA are produced globally due to coal combustion in electricity generation, but only about 20–30% of this is repurposed in various regions. The predominant method of managing FA involves land deposition or landfilling, which consumes considerable land resources. Additionally, improper disposal of FA, particularly its heavy metal contents, poses a serious threat to the natural ecosystem. This can result in the degradation of plant and microbial life, further exacerbating environmental pollution (Adamczuk et al. 2015; Luo et al. 2021 ; Wang et al. 2022 ; Xu et al. 2018). Moreover, with the annual increase in FA production, the costs associated with its management are escalating. Given this context, it's critical to implement cost-effective strategies for FA utilization. FA, a conventional industrial by-product, is a powdery solid residue derived from coal combustion. Characterized by a surface rich in hydroxyl groups, FA demonstrates excellent permeability when in a loose state. Its composition includes a variety of oxides such as silica (SiO 2 ), alumina (Al 2 O 3 ), and trace amounts of ferrous oxide (FeO), ferric oxide (Fe 2 O 3 ), calcium oxide (CaO), magnesium oxide (MgO), sulfur trioxide (SO 3 ), and titanium dioxide (TiO 2 ), among others (Bao et al. 2023 ). In recent years, integrating FA into polymer-based composite materials has become a significant method to address inherent polymer shortcomings and enhance specific characteristics. This strategy is pivotal in recycling industrial residual waste and reducing raw material expenses. For example, Li et al. ( 2022 ) incorporated FA with an aluminum salt coupling agent, PVC, and various additives. Through a series of processing and molding techniques, they developed polyvinyl chloride/fly ash composite materials exhibiting superior mechanical properties. Similarly, Prabhu et al. ( 2021 ) dispersed nano FA, polyaniline (PANI), and benzoyl peroxide in a chloroform system, creating PANI-nano FA composite materials using reverse-phase emulsion polymerization. These materials demonstrated greater thermal stability compared to pure PANI. Given the high thermal stability of FA's inorganic constituents like SiO 2 and Al 2 O 3 , leveraging FA as an efficient, cost-effective inorganic flame retardant is highly promising. The advancement of FA into valuable flame-retardant materials represents an innovative approach to waste utilization, potentially leading to the creation of affordable, high-performance materials. This development not only maximizes the use of industrial waste but also could increase the commercial attractiveness of these materials, offering environmental and economic benefits. In our research, we employed hot pressing and freeze-drying methods to fabricate cellulose-based FA film and porous materials. During this process, FA particles were efficiently captured and firmly bound to the regenerated cellulose fibers through interfacial interactions. This resulted in a homogeneous dispersion and encapsulation within the cellulose, significantly improving the flame-retardant properties of the base material and leading to the formation of a stable cellulose/FA composite hydrogel (Abdel-Halim et al. 2011; Wang et al. 2015 ). Notably, in the fabrication of film materials, we maintained a careful balance between cost-efficiency and performance. The process was conducted without additional additives, yet the resulting film materials exhibited an admirable synergy of structural integrity and functionality. This approach not only reinforces the material's structural stability but also augments its practical utility. The development of these cellulose-based fly ash materials not only broadens the scope of flame-retardant cellulose applications but also achieves high-value utilization of FA, presenting a viable solution to environmental challenges posed by FA accumulation. Material For our research, the cellulose sample was sourced from Jiangxi Province Huazhong Spinning and Chemical Co., specifically utilizing cotton pulp. The fly ash used in our experiments was obtained from Dawukou Power Plant located in Shizuishan City, Ningxia Province. The chemicals employed in the process, including urea and sodium hydroxide, were acquired from J&K Scientific Co., Ltd. The ionic liquid used, AmimCl, was sourced from Shandong Henglian New Materials Co., Ltd. Additionally, sulfuric acid and sodium sulfate of analytical purity were purchased from Sinopharm Chemical Reagent Co., Ltd. Lastly, epichlorohydrin (ECH) was procured from Aladdin Reagent Co., Ltd. Preparation of Cellulose/FA Film Materials (C1-FX) During the fabrication of the Cellulose/FA film materials (C1-FX), we prepared FA suspensions in concentrations of 10wt%, 20wt%, and 30wt%, relative to the cellulose mass, designated as F10, F20, and F30, respectively. The cellulose was dissolved in an AmimCl solution and then combined with the FA suspension to create a cellulose/FA hydrogel (Wan et al. 2021 ). Notably, this process did not require any additional additives, thereby preserving the eco-friendly nature of the materials. Following this, the mixture was converted into thin films using the bar coating technique. These films were subsequently immersed in distilled water to remove any residual impurities (Vehviläinen et al. 2015 ). The final stage involved subjecting the films to hot pressing at 110℃, which yielded cellulose/FA film materials characterized by structural stability and enhanced flame-retardant properties. Preparation of Cellulose/FA Porous Materials (C2-FX) For the production of Cellulose/FA porous materials (C2-FX), we adopted a distinct approach. Initially, FA suspensions with concentrations of 10wt%, 20wt%, and 30wt% (labeled F10, F20, F30) were prepared, based on the cellulose mass ratio, and mixed with the cellulose solution. A key step involved the in situ alkali treatment of FA during its dissolution in the NaOH/urea solution, which effectively enhanced the hydroxyl active sites on the FA surface. This step was critical as it strengthened the hydrogen bonding between FA and cellulose, thereby streamlining the processing stages (Cai et al. 2005; Palomo et al. 1999 ). Following this, 5 ml of epichlorohydrin (ECH) was added to the mixture and stirred for 10 minutes. The resultant hydrogels were then subjected to a freeze-drying process at temperatures below − 20℃ for three days, aimed at removing moisture and forming a consistent porous structure. This careful freeze-drying process was crucial to prevent pore collapse due to tension, ensuring the material maintained uniform porosity(Mao et al. 2008 ; Zeng et al. 2021). Experimental characterization Fourier Transform Infrared Spectroscopy (FTIR) analysis was performed using a Nicolet Nexus-670 FTIR spectrometer from Thermo Fisher, USA. The procedure was executed at ambient temperature. It involved grinding and pressing a blend of 50 mg of potassium bromide (KBr) powder with an adequate quantity of the sample. The spectral scanning range was set from 400 to 4000 cm − 1 . X-ray diffraction (XRD) patterns were obtained using a Shimadzu XRD-6000 (3 kW) X-ray diffractometer. The measurements were taken at a scan rate of 2° per minute, within a 2θ range of 10° to 50°. Thermal gravimetric analysis (TGA) and Differential Thermogravimetric Analysis (DTGA) were conducted using a Q50 TGA instrument from TA Instruments/Oster China Co., Ltd., USA. This analysis involved a heating rate of 10°C per minute, within a temperature range of 30°C to 600°C, under a nitrogen atmosphere. The sample weight was approximately 5 mg. Tensile and compression properties of the samples were evaluated using a UTM4304 electronic universal testing machine from Shenzhen Sanen Zongheng Technology Co., Ltd., with a testing speed of 1 mm per minute. Field emission scanning electron microscopy (FE-SEM) analysis was performed with a SIGMA-500 type field emission scanning electron microscope from Zeiss, Germany, to examine the surface morphology of the samples. The limiting oxygen index (LOI) was determined in accordance with GB2406-80 standards, using a JT-C2 LOI tester from Dongguan Jint Instrument Co., Ltd. Results and discussion Structure and Miscibility of Cellulose/FA Composite Material Figure 1a delineates the fabrication process of cellulose/FA materials. The procedure commenced with blending a specific quantity of FA suspension with the cellulose solution to create a cellulose/FA mixture. Subsequent heating and stirring facilitated the formation of a cellulose/FA composite hydrogel, which displayed a homogenous gray-black hue, signifying effective dispersion of FA within the cellulose matrix. A notable aspect is the denser structure of the film material compared to the porous variant, negating the need for additional cross-linking agents. Following this, flexible cellulose/FA film materials and uniformly porous cellulose/FA materials were produced via thermal pressing and freeze-drying techniques. Surface examination confirmed excellent compatibility and uniform distribution between cellulose and FA in both materials. Figure 1b and Fig. 1c showcase the macroscopic appearances of the cellulose/FA film and porous materials, respectively. In Fig. 1b, the film material maintained a consistent thickness of approximately 0.3 ± 0.05 mm. The pure cellulose film exhibited notable transparency and flexibility, whereas the addition of FA to the cellulose/FA film resulted in a gray-black coloration but retained foldability and flexibility. The surface of the unpressed cellulose/FA film material appeared wrinkled, highlighting uneven FA distribution, particularly along the edges, which led to visible defects and structural irregularities. Conversely, Fig. 1c reveals that both the cellulose porous material and the cellulose/FA porous variant possessed dense pore structures. The addition of FA to the latter increased its inorganic content, thereby enhancing structural stability and reducing the likelihood of pore collapse (Wei et al. 2021 ). Overall, the comparison suggests effective FA dispersion in cellulose, indicating an advancement in the material's overall performance. From Fig. 2 a we can see the peak value corresponding to the characteristic peak of cellulose markedly diminishes with the inclusion of fly ash (FA), and in samples C-F20, C-F30, and C-F40, the cellulose characteristic peaks are virtually absent. This indicates that the addition of FA disrupts cellulose's original crystalline structure, resulting in a reduction of crystallinity among the cellulose fibers. Such a change in crystallinity is indicative of the effective encapsulation of cellulose by FA. Particularly at higher FA concentrations, the cellulose matrix can be completely enveloped by FA. Furthermore, FA serves as a physical barrier within the structure, offering additional protection to the underlying cellulose matrix. This physical barrier effect of FA contributes to the overall structural integrity and protective quality of the composite material. Figure 2 b displays the FT-IR spectra for cellulose, fly ash (FA), and the C-F10 composite. In FA's FT-IR spectrum, the peaks at 550.5 cm − 1 and 1057 cm − 1 are attributed to the stretching vibrations of Si-O-Si and Al-O bonds, respectively. The spectra of cellulose and C-F10 show characteristic peaks between 3300–3500 cm − 1 , indicative of hydroxyl group (-OH) stretching vibrations. Notably, there is a peak shift from 3363.2 cm − 1 in cellulose to 3434.5 cm − 1 in C-F10, suggesting enhanced hydrogen bonding and indicating interactions between cellulose and FA(Spinella et al. 2016 ). This shift in the infrared spectrum corroborates the strong hydrogen bond interactions between cellulose and FA, leading to the uniform dispersion of FA within the cellulose matrix and excellent miscibility of the two components in the cellulose/FA material. Figure 2 c reveals that the interplay between FA and cellulose extends beyond simple mixing. The presence of hydrogen bonds not only strengthens the bond between cellulose and FA but also ensures that FA is firmly adhered to the cellulose base. This interaction boosts the overall performance of the material and theoretically validates the exceptional compatibility between cellulose and FA. Moreover, this composite formation method enables the high-value utilization of FA, enhancing the material's functional and environmental merits. Figure 3 a and Fig. 3 a' clearly show that the cellulose porous materials have a loosely arranged porous architecture. This design not only provides a high specific surface area favorable for the even adherence of FA particles but also effectively prevents their agglomeration, ensuring a uniform distribution (Wang et al. 2014 ). In Fig. 3 b, Fig. 3 b', Fig. 3 c, and Fig. 3 c', which are SEM images of C2-F10 and C2-F20 respectively, there is a noticeable enhancement in the pore structure. Compared to the pore structure of pure cellulose, the cellulose/FA porous materials exhibit more complete pore structures as FA content increases, a change attributed to the disruption of cellulose's original crystalline structure by FA, as supported by FT-IR and XRD analysis(Song et al. 2022 ).Furthermore, the strong hydrogen bonding interactions between FA and cellulose enable large areas of FA particles to adhere, not only reinforcing the pore structure but also facilitating the reconnection of some cellulose fibers. This leads to the creation of a dense formation with a complete pore structure. Additional examination of Fig. 3 d and Fig. 3 d' reveals that even with a 30% FA addition, the FA particles remain uniformly dispersed on the cellulose pore structure's surface. The material's pore structure progressively becomes more compact and three-dimensional, avoiding any collapse. This observation further substantiates the hydrogen bonding interactions between FA and cellulose, which permit a widespread uniform adherence and dense dispersion of FA. This interaction underpins the formation of the porous material's structure, yielding a complete and three-dimensional pore configuration. During the development of cellulose/FA porous materials, the introduction of a cross-linking agent was deemed essential for providing necessary structural support. Without it, the porous materials often exhibited structural disintegration post-freeze-drying, as evidenced by the compromised integrity of their pore structures. On the other hand, cellulose film materials, upon FA addition, developed a denser structure facilitated by the hydrogen bonding between FA and cellulose. This bonding obviated the need for extra cross-linking agents, allowing the film materials to attain the required stability and structural integrity during their formation. Figure 3 f showcases the cross-section of the cellulose/FA film, where, despite some FA particles being visible on the cellulose surface, they remained firmly attached, underscoring the robust interfacial compatibility and efficient hydrogen bonding between cellulose and FA. Post-hot pressing, the cellulose film's surface exhibited a curved and fibrous appearance, with microfiber alignment parallel to the surface, indicative of a certain level of orientation. However, this structured orientation almost vanished with the incorporation of FA. As inferred from XRD analysis, the disruption of cellulose's original crystalline structure by FA could be responsible for this alteration, leading to a denser structure distinct from that of the cellulose film materials. In Fig. 3 f', although some small holes were observed on the surface, likely due to low-temperature cracking in liquid nitrogen, the overall structure remained densely packed (Ou et al. 2023 ). In the C1-F20 sample, FA was evenly interspersed among the cellulose fibers and firmly encapsulated by them, demonstrating good compatibility. Figure 3 g displays the SEM-EDS spectra for C2-F20, highlighting elements such as Si, Al, Ca, and Fe. This indicated a uniform distribution of FA within C2-F20's three-dimensional network, crucial for thermal stability and flame retardancy. The combination of XRD analysis and SEM images further validated that FA's characteristic elements, including Si, Al, and Ca, were uniformly dispersed within the network. This uniform dispersion not only bolstered the material's overall stability but also potentially enhanced its mechanical strength and thermal stability. Consequently, the successful fabrication of cellulose/FA film opens up new avenues for the high-quality utilization of FA, underscoring its potential in advanced material applications. Figure 4 a illustrates the stress-strain curves for various film materials during tensile testing. The stress recorded for the pure cellulose film was 88.9 MPa. In comparison, the stresses for C1-F10, C1-F20, and C1-F30 were 89.2 MPa, 64.5 MPa, and 51.1 MPa, respectively. These results suggest that the mechanical properties of the films generally diminish as the proportion of FA increases. However, a certain level of FA addition, as seen in C1-F10, can actually optimize and enhance the mechanical performance. This variation in mechanical properties is primarily attributed to the excessive addition of FA, which disrupts the original crystalline structure of cellulose. Increased surface defects and a more pronounced steric hindrance effect, outweighing the benefits of hydrogen bonding interactions, lead to spatial structural defects in cellulose. This adversely impacts the binding efficacy between cellulose and FA, thereby affecting the tensile strength of the cellulose/FA films (Aruniit et al. 2012 ). Despite the fact that an excessive FA addition induces defects in the cellulose's crystal structure, a 10% FA addition level seems to strike a balance. At this level, the hydrogen bonding interactions between cellulose and FA can offset some of the performance degradation caused by defects in the cellulose crystals. Consequently, an opportune addition of FA can preserve the original mechanical properties of the film while potentially imparting flame retardancy. This finding highlights the delicate balance between maintaining structural integrity and enhancing functional properties in composite materials. Figure 4 b showcases the stress-strain curves for porous materials under compression testing. The graph illustrates that pure cellulose exhibits a compressive stress of 0.05 MPa at 20% compression. However, the addition of FA leads to a significant increase in compressive stress for samples C2-F10, C2-F20, and C2-F30. Closer examination, in conjunction with SEM images, indicates that the incorporation of FA enhances the three-dimensional spatial structure of cellulose, rendering it completer and more stable. This enhancement is attributed to FA adhering to the cellulose's pore structure via strong hydrogen bond interactions. FA effectively forms an inorganic coating skeleton around the pores, providing crucial support and reinforcement (Lee et al. 2022). As a result, with increasing FA content, the area of adhesion between FA and cellulose also expands, consequently boosting the compressive strength of the porous material (Donius et al. 2014 ). A comprehensive evaluation of the mechanical properties of both film and porous materials suggests that a moderate addition of FA to cellulose not only ensures uniform FA distribution within the cellulose matrix but also improves its mechanical properties. This finding underscores the potential for broadening the application spectrum of cellulose, paving the way for more diverse and high-value uses of FA. Such developments are significant in material science, as they expand the scope of cellulose applications and demonstrate effective strategies for the high-value utilization of industrial by-products like FA. Flame Retardancy and Thermal Stability Table 1 LOI data of cellulose and cellulose-based fly ash composite materials Sample LOI (%) Sample LOI (%) Cellulose Membrane 15 Cellulose Porous 15 C1-F10 27 C2-F10 25 C1-F20 28 C2-F20 27 C1-F30 31 C2-F30 29 LOI is a critical metric for assessing the flame retardancy of materials, representing the minimum concentration of oxygen needed to sustain the combustion of a polymer in an environment consisting solely of oxygen and nitrogen gases (Camino et al 1988 ; Rosa et al 1999 ; Wang et al 2022 ). Figure 5c and Table 1 illustrates a notable variance in the LOI values among different cellulose materials. The LOI value for cellulose film material stands at 15%, whereas the LOI values for FA-modified cellulose film materials, namely C1-F10, C1-F20, and C1-F30, are 27%, 28%, and 31% respectively. Similarly, the LOI value for cellulose porous material is 15%, with its FA-modified versions, C2-F10, C2-F20, and C2-F30, exhibiting LOI values of 25%, 27%, and 29% respectively. This data indicates that FA incorporation significantly enhances the flame retardancy of cellulose materials. Figure 5a and Fig. 5b displays photographs capturing the combustion stages of cellulose/FA film and porous materials. These images, alongside combustion experiments, affirm that increasing FA content markedly improves the flame retardancy of cellulose/FA materials. Due to their denser structure, film materials exhibit higher flame retardancy compared to porous materials. A thorough analysis of the burning behavior of cellulose/FA material reveals two key mechanisms enhancing its flame retardancy. Firstly, during the combustion of internal cellulose, Al 2 O 3 and SiO 2 in FA forms an inorganic protective layer on the surface, effectively encapsulating the combustible cellulose matrix. This barrier impedes direct combustion and heat transfer, delaying the release of pyrolysis products, SEM analysis confirms this protective layer's effectiveness in enhancing the flame retardancy of the cellulose matrix and plays a flame retardant effect. (Lange et al 2003; Park et al 2022 ). Secondly, FA's high specific surface area and the abundance of hydroxyl groups (-OH) on its surface post-alkali treatment play a crucial role. These features enable FA to adsorb or hinder the release and diffusion of volatiles during cellulose combustion. Consequently, the addition of FA to cellulose not only isolates it from oxygen but also provides protective shielding. This dual mechanism significantly contributes to the enhanced flame retardancy of cellulose materials, offering new possibilities in material development for applications requiring high flame resistance (Kandola et al 1996 ; Xu et al 2023 ). Table 2 TG data of cellulose and cellulose-based fly ash composite materials Sample No. Ta do ( o C) Tb dp ( o C) Mass loss (%) Cellulose 276 303 77 C-F10 282 313 61 C-F20 299 325 58 C-F30 FA 302 ~ 329 ~ 56 0 a : The onset decomposition temperature; b : The fastest decomposition temperature; To delve deeper into the thermal stability of the materials, TGA was conducted on cellulose, FA, and the cellulose/FA composites C-F10, C-F20, and C-F30 under a nitrogen (N 2 ) atmosphere. Figure 5d and Fig. 5e, along with Table 2 , display the TGA and DTGA curves, providing specific TG data for these materials. Under N 2 protection, the thermal degradation of the cellulose/FA materials predominantly occurs due to cellulose's thermal decomposition, with the major weight loss happening between 260℃ and 400℃ (Park et al 2022 ). Notably, the initial decomposition temperatures for C-F10, C-F20, and C-F30 are observed at 282℃, 299℃, and 302℃, respectively. The incorporation of FA raises the onset temperature of cellulose decomposition from 282℃ to 302℃. Pure cellulose experiences a weight loss of up to 76.71%, but this value significantly reduces upon FA addition, further decreasing as the FA content increases, from 76.71–55.51%. This reduction is ascribed to the increased inorganic content within the cellulose matrix due to the addition of FA. Cellulose/FA composites start decomposing around 290℃, indicating enhanced thermal stability compared to many polymer materials(He et al 2020 ). Moreover, the inclusion of FA substantially slows down the rate of thermal decomposition in the cellulose matrix. This effect can be explained by the formation of an "inorganic encapsulation" layer around the cellulose matrix, induced by FA, which acts as a thermal barrier, significantly slowing down the decomposition process. SEM and XRD analyses corroborate this finding, demonstrating that within a certain range of FA content, the thermal stability of cellulose/FA materials is indeed improved. This enhancement in thermal stability is crucial for applications where resistance to high temperatures is required, and it also validates the effectiveness of FA as a reinforcing agent in improving the thermal properties of cellulose-based materials. Conclusion This study successfully developed cellulose/FA porous and film materials using the NaOH/urea low-temperature dissolution system and AmimCl solution, combined with freeze-drying and hot pressing techniques. FT-IR analysis verified the presence of hydrogen bonding between cellulose and FA, which significantly enhanced their compatibility. SEM imaging demonstrated a uniform dispersion of FA within the cellulose matrix, effectively covering the cellulose surface. This encapsulation strengthens the mechanical properties of the material to a certain extent and provides a physical barrier, augmenting the flame retardancy of the cellulose. A comprehensive evaluation of the mechanical properties of both film and porous materials suggests that a moderate addition of FA to cellulose not only ensures uniform FA distribution within the cellulose matrix but also improves its mechanical properties. The initial thermal decomposition temperatures for samples C-F10, C-F20, and C-F30 were recorded at 282℃, 299℃, and 302℃, respectively, representing an increase of approximately 26℃ compared to pure cellulose. LOI of these materials reached up to 31%, clearly demonstrating that FA incorporation markedly improves both the thermal stability and flame retardancy of the cellulose matrix. The experimental approach outlined in this research significantly boosts the flame retardancy of cellulose-based composite materials. This method offers several advantages: it utilizes abundant, easily accessible raw materials, and employs non-toxic, efficient processes that are suitable for large-scale industrial production. Crucially, this technique not only enhances the potential of cellulose-based materials for fire protection applications but also achieves high-value utilization of FA industrial waste. This contributes substantially to environmental protection and supports the establishment of a more sustainable and eco-friendly development model. The findings and methodologies of this study are pivotal in advancing the field of material science, particularly in developing sustainable, flame-retardant materials that are both environmentally responsible and industrially feasible. Declarations Conflicts of interest There are no conflicts to declare. Supporting Information Supporting Information is available from th SpringerLink Online Library. Author Contribution Conceptualization: Yongqiang Qian, Wentao He, Lei Tan,Dan Li and Shengwei Guo; Methodology: Yongqiang Qian and Wentao He; Data curation: Yongqiang Qian, Wentao He and Lei Tan; Formal Analysis: Yongqiang Qian, Lei Tan and Wentao He; Validation: Wentao He, Lei Tan, and Yongjia Wu; Visualization: Lei Tan and Wentao He; Investigation: Lei Tan and Yiyang Chen; Resources: Yongqiang Qian, Li Dan and Guxia Wang; Funding acquisition: Yongqiang Qian and Shengwei Guo; Writing – original draft: Yongqiang Qian and Wentao He; Writing – review & editing: Shengwei Guo. All authors reviewed the manuscript. Acknowledgements This work was supported by North Minzu University College Students' Innovative Entrepreneurial Training Plan Program (S202311407038), the Natural Science Foundation of Ningxia (Grant No. 2023AAC03283), the Fundamental Research Funds for the Central Universities, North Minzu University (Grant No. 2021KYQD11 and 2022XYZCL03), and the National Natural Science Foundation of China (Grant Nos. 52263021). Wentao He and Lei Tan contributed equally to this work. All authors discussed the results commented on the manuscript and approved the final version of this manuscript. References Abdel-Halim E S, Al-Deyab S S (2011) Removal of heavy metals from their aqueous solutions through adsorption onto natural polymers. Carbohydrate Polymers 84 (1), 454-458. Adamczuk A, Kołodyńska D (2015) Equilibrium, thermodynamic and kinetic studies on removal of chromium, copper, zinc and arsenic from aqueous solutions onto fly ash coated by chitosan. Chemical Engineering Journal 274 , 200-212. Aoki D, Nishio Y (2010) Phosphorylated cellulose propionate derivatives as thermoplastic flame resistant/retardant materials: influence of regioselective phosphorylation on their thermal degradation behaviour. Cellulose 17 , 963-976. Aruniit A, Kers J, Majak J,Tall K (2012) Influence of hollow glass microspheres on the mechanical and physical properties and cost of particle reinforced polymer composites. Proceedings of the Estonian Academy of Sciences 61 (3), 160. Bao J, Lao J, Hu Y, Song Y, Xu M, Niu F (2023) Facile surface modification of fly ash to obtain flexible cellulose composite dielectric films with enhanced breakdown strength and energy storage density. Cellulose 30 (8), 5259-5271. Cai J, Zhang L (2005) Rapid dissolution of cellulose in LiOH/urea and NaOH/urea aqueous solutions. Macromolecular bioscience 5 (6), 539-548. Camino G, Costa L, Casorati E, Bertelli G, Locatelli R (1988) The oxygen index method in fire retardance studies of polymeric materials. Journal of Applied Polymer Science 35 (7), 1863-1876. Chang SC, Slopek RP, Condon B, JC Grunlan (2014) Surface coating for flame-retardant behavior of cotton fabric using a continuous layer-by-layer process. Industrial & Engineering Chemistry Research 53 (10), 3805-3812. Chen L, Wang S, Wang S, Chen C, Qi L, Yu L, Lu Z, Huang J, Chen J, Wang Z, Shi XW, Song Z, Liu H, Chen C (2022) Scalable production of biodegradable, recyclable, sustainable cellulose–mineral foams via coordination interaction assisted ambient drying. ACS nano 16 (10), 16414-16425. Donius AE, Liu A, Berglund LA, Wegst UGK (2014) Superior mechanical performance of highly porous, anisotropic nanocellulose–montmorillonite aerogels prepared by freeze casting. Journal of the mechanical behavior of biomedical materials 37 , 88-99. Gong J, Chen X, Tang T (2019) Recent progress in controlled carbonization of (waste) polymers. Progress in Polymer Science 94 , 1-32. Habibi Y, Lucia L A, Rojas O J (2010) Cellulose nanocrystals: chemistry, self-assembly, and applications. Chemical reviews 110 (6), 3479-3500. Han Y, Zhang X, Wu X, Lu C (2015) Flame retardant, heat insulating cellulose aerogels from waste cotton fabrics by in situ formation of magnesium hydroxide nanoparticles in cellulose gel nanostructures. ACS Sustainable Chemistry & Engineering 3 (8), 1853-1859. He W, Song P, Yu B, Fang Z, Wang H (2020) Flame retardant polymeric nanocomposites through the combination of nanomaterials and conventional flame retardants. Progress in Materials Science 114 , 100687. Jiang F, Li T, Li Y, Zhang Y, Gong A, Dai J, Hitz E, Luo W, Hu L (2018) Wood‐based nanotechnologies toward sustainability. Advanced Materials 30 (1), 1703453. Kandola BK, Horrocks AR, Price D, Coleman GV (1996) Flame-retardant treatments of cellulose and their influence on the mechanism of cellulose pyrolysis. Journal of Macromolecular Science, Part C: Polymer Reviews 36 (4), 721-794. La Rosa AD, Recca A, Carter JT, McGrail PT (1999) An oxygen index evaluation of flammability on modified epoxy/polyester systems. Polymer 40 (14), 4093-4098. Lange J, Wyser Y. (2003) Recent innovations in barrier technologies for plastic packaging—a review Packaging. Technology and Science: An International Journal 16 (4), 149-158. Lee H J, Kang S W (2022) Improvement of stability for cellulose polymer by calcium oxide for application to porous materials. Cellulose 29 (15), 8319-8327. Li Z, Wang G, Yan J, Qian Y, Guo S, Liu Y, Li D (2022) Value-added utilization of coal fly ash and recycled polyvinyl chloride in door or window sub-frame composites. Green Processing and Synthesis 12 (1), 20230002. Long LY, Weng YX, Wang YZ (2018) Cellulose aerogels: Synthesis, applications, and prospects. Polymers 10 (6), 623. Luo Y, Wu Y, Ma S, Zheng S, Zhang Y, Chu PK (2021) Utilization of coal fly ash in China: a mini-review on challenges and future directions. Environmental Science and Pollution Research 28 , 18727-18740. Mao J, Grgic B, Finlay WH, Kadla JF, Kerekes RJ (2008) Wood pulp based filters for removal of sub-micrometer aerosol particles. Nordic Pulp & Paper Research Journal 23 (4), 420-425. Nine MJ, Cole MA, Tran DNH, Losic D (2015) Graphene: a multipurpose material for protective coatings. Journal of Materials Chemistry A 3 (24), 12580-12602. Ou J, Hu S, Yao L, Chen Y, Qi H, Yue F (2023) Simultaneous strengthening and toughening lignin/cellulose nanofibril composite films: Effects from flexible hydrogen bonds. Chemical Engineering Journal 453 , 139770. Palomo A, Grutzeck MW, Blanco MT (1999) Alkali-activated fly ashes: A cement for the future. Cement and concrete research 29 (8), 1323-1329. Park S Y, Lee K, Shin H, Youn HJ (2022) Eco-friendly flame retardant foam prepared by oven drying of pickering stabilized carboxymethylated cellulose nanofibril/nanoclay wet foam. Cellulose 29 (18), 9693-9705. Prabhu R, Jeevananda T, Reddy KR, Raghu AV (2021) Polyaniline-fly ash nanocomposites synthesized via emulsion polymerization: Physicochemical, thermal and dielectric properties. Materials Science for Energy Technologies 4 , 107-112. Song D, Wang B, Tao W, Wang X, Zhang W, Dai M, Li J, Zhou Z (2022) Synergistic reinforcement mechanism of basalt fiber/cellulose nanocrystals/polypropylene composites. Nanotechnology Reviews 11 (1), 3020-3030. Spinella S, Maiorana A, Qian Q, Dawson NJ, Hepworth V, McCallum, Scott A, Ganesh M, Singer KD, Gross RA (2016) Concurrent cellulose hydrolysis and esterification to prepare a surface-modified cellulose nanocrystal decorated with carboxylic acid moieties. ACS Sustainable Chemistry & Engineering 4 (3), 1538-1550. Suflet DM, Chitanu GC, Popa VI (2006) Phosphorylation of polysaccharides: New results on synthesis and characterisation of phosphorylated cellulose. Reactive and Functional Polymers 66 (11), 1240-1249. Vehviläinen M, Kamppuri T, Grönqvist S, Rissanen M, Maloney T, Honkanen M, Nousiainen P (2015) Dissolution of enzyme-treated cellulose using freezing–thawing method and the properties of fibres regenerated from the solution. Cellulose 22 , 1653-1674. Wan J, Diao H, Yu J, Song G, Zhang J (2021) A biaxially stretched cellulose film prepared from ionic liquid solution. Carbohydrate Polymers 260 , 117816. Wang Q, Guo J, Xu D, Cai J, Qiu Y, Ren J, Zhang L (2015) Facile construction of cellulose/montmorillonite nanocomposite biobased plastics with flame retardant and gas barrier properties. Cellulose 22 , 3799-3810. Wang X, Fu C, Feng Z, Huo H, Yin X, Gao G, Yin G, Ci L, Tong Y, Jiang Z, Wang J (2022) Flyash/polymer composite electrolyte with internal binding interaction enables highly-stable extrinsic-interfaces of all-solid-state lithium batteries. Chemical Engineering Journal 428 , 131041. Wang Y, Feng T, Piao J, Ren J, Ou M, Wang Y, Lian R, Cui J, Guan H, Jiao C, Chen X (2022) Surface modification of epichlorohydrin‐modified aramid nanofibers using ionic liquid to improve the fire safety and tensile strength of cotton fabrics. Polymers for Advanced Technologies 33 (12), 4302-4316. Wang Z, Fan X, He M, Chen Z, Wang Y, Ye Q, Zhang H, Zhang L (2014) Construction of cellulose–phosphor hybrid hydrogels and their application for bioimaging. Journal of Materials Chemistry B 2 (43), 7559-7566. Wei Y, Chai J, Qin Y, Li Y, Xu Z, Li Y, Ma Y (2021) Effect of fly ash on mechanical properties and microstructure of cellulose fiber-reinforced concrete under sulfate dry–wet cycle attack. 302 , 124207. Xu G, Shi X (2018) Characteristics and applications of fly ash as a sustainable construction material: A state-of-the-art review. Resources, conservation and recycling 136 , 95-109. Xu S, Han Y, Zhou C, Li J, Shen L, Lin H (2023) A biobased flame retardant towards improvement of flame retardancy and mechanical property of ethylene vinyl acetate. Chinese Chemical Letters 34 (1), 107202. Zeng B, Byrne N (2021) The effect of drying method on the porosity of regenerated cellulose fibres. Cellulose 28 (13), 8333-8342. Zhang C, Hu Y, Shao J, Pan H (2023) Flame retardant cellulose/polyvinyl alcohol/sodium alginate composite aerogels crosslinked by metal ions for flame resistance materials. Cellulose 30 (11), 7079-7093. Zhao S, Malfait WJ, Guerrero‐Alburquerque N, Koebel MM, Nyström G (2018) Biopolymer aerogels and foams: Chemistry, properties, and applications. Angewandte Chemie International Edition 57 (26), 7580-7608. Additional Declarations No competing interests reported. Supplementary Files VideoS1C1F10.mp4 VideoS2C1F20.mp4 VideoS3C1F30.mp4 VideoS4C2F10.mp4 VideoS5C2F20.mp4 VideoS6C2F30.mp4 VideoS7CelluloseFoam.mp4 VideoS8Cellulosemembrane.mp4 Cite Share Download PDF Status: Published Journal Publication published 04 Feb, 2025 Read the published version in Cellulose → Version 1 posted Editorial decision: Revision requested 31 Mar, 2024 Submission checks completed at journal 29 Mar, 2024 Editor assigned by journal 29 Mar, 2024 First submitted to journal 29 Mar, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4185593","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":285901241,"identity":"fa53c611-1318-45b5-a125-e7e5b51e0e8e","order_by":0,"name":"Wentao He","email":"","orcid":"","institution":"North Minzu University","correspondingAuthor":false,"prefix":"","firstName":"Wentao","middleName":"","lastName":"He","suffix":""},{"id":285901242,"identity":"54d92058-82dd-422c-8d7b-9ce5a53ed6fa","order_by":1,"name":"Lei Tan","email":"","orcid":"","institution":"North Minzu University","correspondingAuthor":false,"prefix":"","firstName":"Lei","middleName":"","lastName":"Tan","suffix":""},{"id":285901243,"identity":"1f3a6477-b4ed-42a8-aeff-64afc684a312","order_by":2,"name":"Yongjia Wu","email":"","orcid":"","institution":"North Minzu University","correspondingAuthor":false,"prefix":"","firstName":"Yongjia","middleName":"","lastName":"Wu","suffix":""},{"id":285901244,"identity":"811afb9f-a825-4a97-a59e-7c013fc5ff46","order_by":3,"name":"Yongchun Wei","email":"","orcid":"","institution":"North Minzu University","correspondingAuthor":false,"prefix":"","firstName":"Yongchun","middleName":"","lastName":"Wei","suffix":""},{"id":285901245,"identity":"82c6a123-9ba1-4d39-8d23-edd415686fce","order_by":4,"name":"Yiyang Chen","email":"","orcid":"","institution":"North Minzu University","correspondingAuthor":false,"prefix":"","firstName":"Yiyang","middleName":"","lastName":"Chen","suffix":""},{"id":285901246,"identity":"eb121bd0-13e9-4f08-90aa-db3176300d87","order_by":5,"name":"Dan Li","email":"","orcid":"","institution":"North Minzu University","correspondingAuthor":false,"prefix":"","firstName":"Dan","middleName":"","lastName":"Li","suffix":""},{"id":285901247,"identity":"ca4fabac-92fb-4c96-8d23-5745a5d6b8c8","order_by":6,"name":"Guxia Wang","email":"","orcid":"","institution":"North Minzu University","correspondingAuthor":false,"prefix":"","firstName":"Guxia","middleName":"","lastName":"Wang","suffix":""},{"id":285901249,"identity":"525c8b37-a520-49de-ac6e-85b0dd902639","order_by":7,"name":"Yongqiang Qian","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA8klEQVRIiWNgGAWjYDACZhRGBYQtQYKWM8RoQQGMbURo4TvO/OwxT8Uduz4g4+HXeXcStzMwH7zNw2CXh0uL5GE2c2OeM8+SZ4IYstueJe5sYEu25mFILsalxeAwg5k0b9vhZDBDctvhxA0HeMykeRgOJDbg1ML+DaoFyJCcA9LC/42AFh6wLXYghuTHBrAtbHi1SB7mKZOcc+ZwAoghzXDssPGGw2zGlnMMknFq4Tt/fJvEm4rD9iCG5I+aw7Ibjjc/vPGmwg6nFoYDDAxMPAwMiQ1ABjMPSAQcpwa41EO0MP5gYLCHMUbBKBgFo2AUYAAAs6padQLUnpIAAAAASUVORK5CYII=","orcid":"","institution":"North Minzu University","correspondingAuthor":true,"prefix":"","firstName":"Yongqiang","middleName":"","lastName":"Qian","suffix":""},{"id":285901252,"identity":"480856c1-5c5a-41ac-affd-8cbe707dd40a","order_by":8,"name":"Shengwei Guo","email":"","orcid":"","institution":"North Minzu University","correspondingAuthor":false,"prefix":"","firstName":"Shengwei","middleName":"","lastName":"Guo","suffix":""}],"badges":[],"createdAt":"2024-03-29 04:14:27","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4185593/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4185593/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10570-025-06411-3","type":"published","date":"2025-02-04T15:57:25+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":54038390,"identity":"1ff8822b-4bfd-4c0c-90a5-eee8636e0521","added_by":"auto","created_at":"2024-04-03 17:15:08","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":592654,"visible":true,"origin":"","legend":"\u003cp\u003e(\u003cstrong\u003ea\u003c/strong\u003e) Preparation schematic diagram of cellulose-based FA composite material, (b)\u003cstrong\u003e \u003c/strong\u003eAppearance diagram of membrane material, (c) Appearance diagram of porous materials\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4185593/v1/cb447b2f4d8a8b02b6001376.png"},{"id":54038391,"identity":"07537c62-2ee7-4361-a828-c64fd96ba827","added_by":"auto","created_at":"2024-04-03 17:15:08","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":332938,"visible":true,"origin":"","legend":"\u003cp\u003e(\u003cstrong\u003ea)\u003c/strong\u003e XRD spectra of FA, C-F10, C-F20, C-F30,\u003cstrong\u003e (b) \u003c/strong\u003eFT-IR spectra of FA, cellulose, and C-F10,\u003cstrong\u003ec \u003c/strong\u003eHydrogen Bond Interaction Diagram between Cellulose and FA\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-4185593/v1/b66389500d2bd82ce2d6438e.png"},{"id":54038392,"identity":"05207737-3d84-4626-a16e-d2bc9d1c7e62","added_by":"auto","created_at":"2024-04-03 17:15:08","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":2229577,"visible":true,"origin":"","legend":"\u003cp\u003e(a)\u003cstrong\u003e \u003c/strong\u003eSEM images of cellulose porous materials, (b) SEM images of C2-F10, (c) SEM images of C2-F20,(d) SEM images of C2-F30, (e) SEM images of the cross-section of cellulose membrane materials, (f) SEM images of the cross-section of C1-F20 membrane material, (a'), (b'), (c '), (d'), (e'), and (f') are correspondingly higher magnification SEM images, (g) The figure shows the SEM images and SEM-EDX spectra of Si, Al, Ca, Fe in C2-F20.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-4185593/v1/d9e0efe5cecc359c37b82dc9.png"},{"id":54038395,"identity":"b307adfe-6020-4934-a558-2e7b6ed89888","added_by":"auto","created_at":"2024-04-03 17:15:09","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":34131,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Stress-strain curve of the film material (C1-Fx) and (b) stress-strain curve of the porous material (C2-Fx)\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-4185593/v1/3f784ca69d3a295e419aae58.png"},{"id":54038393,"identity":"fdf52b76-3119-470b-8cad-547e59708933","added_by":"auto","created_at":"2024-04-03 17:15:09","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":704102,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Digital photographs of the combustion of cellulose film materials and cellulose/FA film materials,\u003cstrong\u003e \u003c/strong\u003e(b) Digital photographs of the combustion of cellulose porous materials and cellulose/FA porous materials, (c) The limiting oxygen index of cellulose and cellulose/fly ash composite materials, (d) TGA image of cellulose/FA materials, (e) DTGA image of cellulose/FA materials.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-4185593/v1/2394c718bbc473ae088fb0e6.png"},{"id":75930858,"identity":"cbbfd642-a423-47a7-91d8-12cb934afce8","added_by":"auto","created_at":"2025-02-10 16:13:42","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5344381,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4185593/v1/1f449898-995a-46ae-aa7a-6c9180daa69e.pdf"},{"id":54038394,"identity":"364e000a-d8dd-4076-ba90-a503d296493f","added_by":"auto","created_at":"2024-04-03 17:15:09","extension":"mp4","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":51072555,"visible":true,"origin":"","legend":"","description":"","filename":"VideoS1C1F10.mp4","url":"https://assets-eu.researchsquare.com/files/rs-4185593/v1/a2edc900c797bfd661b2c1e4.mp4"},{"id":54038403,"identity":"894e2066-ef51-415a-8452-04a1d1d4bad9","added_by":"auto","created_at":"2024-04-03 17:15:12","extension":"mp4","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":86593024,"visible":true,"origin":"","legend":"","description":"","filename":"VideoS2C1F20.mp4","url":"https://assets-eu.researchsquare.com/files/rs-4185593/v1/0108a2d2e38f3640e6ebebe7.mp4"},{"id":54038396,"identity":"73e96348-fa8e-4d76-a80f-cd3232fed25d","added_by":"auto","created_at":"2024-04-03 17:15:09","extension":"mp4","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":43208441,"visible":true,"origin":"","legend":"","description":"","filename":"VideoS3C1F30.mp4","url":"https://assets-eu.researchsquare.com/files/rs-4185593/v1/eada7da64f9ef110d69f8c25.mp4"},{"id":54038398,"identity":"f86a2237-a1ee-40b1-8358-c24779d05ed5","added_by":"auto","created_at":"2024-04-03 17:15:09","extension":"mp4","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":49410254,"visible":true,"origin":"","legend":"","description":"","filename":"VideoS4C2F10.mp4","url":"https://assets-eu.researchsquare.com/files/rs-4185593/v1/a436ebb884947e6d4d4c8cd2.mp4"},{"id":54038397,"identity":"4d1e632f-1df9-4b64-8385-eaab55cba624","added_by":"auto","created_at":"2024-04-03 17:15:09","extension":"mp4","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":3203139,"visible":true,"origin":"","legend":"","description":"","filename":"VideoS5C2F20.mp4","url":"https://assets-eu.researchsquare.com/files/rs-4185593/v1/1900b641ab4222bd8ff7767c.mp4"},{"id":54038401,"identity":"62ffe97e-d296-49c8-90f0-152337d4c537","added_by":"auto","created_at":"2024-04-03 17:15:11","extension":"mp4","order_by":6,"title":"","display":"","copyAsset":false,"role":"supplement","size":35702201,"visible":true,"origin":"","legend":"","description":"","filename":"VideoS6C2F30.mp4","url":"https://assets-eu.researchsquare.com/files/rs-4185593/v1/c262f49b16afb0ffee1c2d82.mp4"},{"id":54038482,"identity":"5ffa3455-b4e4-4c03-aec9-09f49dee6ad7","added_by":"auto","created_at":"2024-04-03 17:15:28","extension":"mp4","order_by":7,"title":"","display":"","copyAsset":false,"role":"supplement","size":238533894,"visible":true,"origin":"","legend":"","description":"","filename":"VideoS7CelluloseFoam.mp4","url":"https://assets-eu.researchsquare.com/files/rs-4185593/v1/5e930d313ac147cbc457e6c2.mp4"},{"id":54038453,"identity":"9c6959d0-cddb-430d-99ee-26742e326ef5","added_by":"auto","created_at":"2024-04-03 17:15:21","extension":"mp4","order_by":8,"title":"","display":"","copyAsset":false,"role":"supplement","size":91359520,"visible":true,"origin":"","legend":"","description":"","filename":"VideoS8Cellulosemembrane.mp4","url":"https://assets-eu.researchsquare.com/files/rs-4185593/v1/35c177225ecf0bba8183c06e.mp4"}],"financialInterests":"No competing interests reported.","formattedTitle":"Fly-Ash based Flame-Retardant Cellulose Materials for Strengthening and Value-Added Utilization in Industrial Solid Wastes","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe current scarcity of petroleum resources, coupled with the excessive waste of petroleum-derived products, is exerting severe environmental stress. In the quest to promote sustainable development and tackle environmental challenges stemming from the non-degradable nature and toxic emissions during combustion of many discarded petroleum-based substances, bio-based materials have received significant focus in both industrial and academic spheres (Jiang et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Long et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Cellulose, a linear copolymer composed of \u003cem\u003eD\u003c/em\u003e-anhydroglucopyranose units linked by \u003cem\u003eβ\u003c/em\u003e-(1\u0026rarr;4)-glycosidic bonds, stands out as an exemplary bio-based material. It offers numerous benefits, including affordability, low density, renewability, and biocompatibility-advantages that are particularly notable in comparison to petroleum-based polymers (Habibi et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Suflet et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). However, cellulose's solubility is restricted to certain solvents, a consequence of its robust inter- and intra-molecular hydrogen bonding. By modifying cellulose through the addition of functional groups or the adsorption of nanoparticles, its range of applications can be substantially broadened (Zhao et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe current focus on developing composites with diverse structures and functionalities, utilizing cellulose as a core material, is a critical approach to replacing various fossil-based products and mitigating environmental pollution (Suflet et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). However, a significant challenge is that cellulose shares the same flammability traits as many traditional polymers in natural environments, primarily due to its low limiting oxygen index. When ignited, cellulose and its derivatives undergo thermal decomposition, releasing a large number of volatile compounds, which raises safety concerns during their manufacturing and usage, consequently hindering the advancement of cellulose-based products (Aoki et al. 2010). At present, enhancing the flame retardancy of cellulose typically involves integrating various types of flame retardants into the gel matrix, encompassing inorganic, halogenated organic, organic phosphorus, nitrogen, and silicon-based compounds (Chang et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Gong et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Nevertheless, the use of conventional halogenated flame retardants poses environmental concerns, as they emit toxic substances when burned. This situation underscores the necessity for employing eco-friendly, cellulose-compatible flame retardants (Han et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eCurrently, there is a growing body of research exploring the utilization of nitrogen and phosphorus-based flame retardants, alongside eco-friendly inorganic alternatives, to replace conventional halogenated and boron-based retardants (Aoki et al. 2010; Han et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Especially inorganic flame retardants, with the development of surface treatment technology and today's nano research, the market has launched a number of new efficient inorganic flame retardants, inorganic flame retardants began to emerge. Inorganic flame retardants are gaining attention for their exceptional thermal stability, cost-effectiveness, non-toxic nature, and lack of secondary pollution (Nine et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). For instance, Wang et al (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) have successfully created cellulose/montmorillonite (MMT) bio-based plastics using a cellulose solution and MMT suspension, processed through hot pressing. This composite material exhibited notable thermal stability and flame-retardant properties. Similarly, Chen et al. (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) developed cellulose/bentonite (Cel/BT) foam from Cel solution and BT powder, facilitated by environmental natural drying and chemical cross-linking with 1,4-butanediol diether. This product demonstrated biodegradability and superior mechanical characteristics. These inorganic fillers not only impart flame-retardant properties but also enhance the base material's features. Thus, enhancing flame-retardant capabilities while maintaining the material's inherent structural qualities is becoming a preferable approach for practical applications (Zhang et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe widespread utilization of coal since the 1920s has led to the production of a significant quantity of FA and its related by-products. Annually, over 500\u0026nbsp;million tons of FA are produced globally due to coal combustion in electricity generation, but only about 20\u0026ndash;30% of this is repurposed in various regions. The predominant method of managing FA involves land deposition or landfilling, which consumes considerable land resources. Additionally, improper disposal of FA, particularly its heavy metal contents, poses a serious threat to the natural ecosystem. This can result in the degradation of plant and microbial life, further exacerbating environmental pollution (Adamczuk et al. 2015; Luo et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Wang et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Xu et al. 2018). Moreover, with the annual increase in FA production, the costs associated with its management are escalating. Given this context, it's critical to implement cost-effective strategies for FA utilization. FA, a conventional industrial by-product, is a powdery solid residue derived from coal combustion. Characterized by a surface rich in hydroxyl groups, FA demonstrates excellent permeability when in a loose state. Its composition includes a variety of oxides such as silica (SiO\u003csub\u003e2\u003c/sub\u003e), alumina (Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e), and trace amounts of ferrous oxide (FeO), ferric oxide (Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e), calcium oxide (CaO), magnesium oxide (MgO), sulfur trioxide (SO\u003csub\u003e3\u003c/sub\u003e), and titanium dioxide (TiO\u003csub\u003e2\u003c/sub\u003e), among others (Bao et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). In recent years, integrating FA into polymer-based composite materials has become a significant method to address inherent polymer shortcomings and enhance specific characteristics. This strategy is pivotal in recycling industrial residual waste and reducing raw material expenses. For example, Li et al. (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) incorporated FA with an aluminum salt coupling agent, PVC, and various additives. Through a series of processing and molding techniques, they developed polyvinyl chloride/fly ash composite materials exhibiting superior mechanical properties. Similarly, Prabhu et al. (\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) dispersed nano FA, polyaniline (PANI), and benzoyl peroxide in a chloroform system, creating PANI-nano FA composite materials using reverse-phase emulsion polymerization. These materials demonstrated greater thermal stability compared to pure PANI. Given the high thermal stability of FA's inorganic constituents like SiO\u003csub\u003e2\u003c/sub\u003e and Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, leveraging FA as an efficient, cost-effective inorganic flame retardant is highly promising. The advancement of FA into valuable flame-retardant materials represents an innovative approach to waste utilization, potentially leading to the creation of affordable, high-performance materials. This development not only maximizes the use of industrial waste but also could increase the commercial attractiveness of these materials, offering environmental and economic benefits.\u003c/p\u003e \u003cp\u003eIn our research, we employed hot pressing and freeze-drying methods to fabricate cellulose-based FA film and porous materials. During this process, FA particles were efficiently captured and firmly bound to the regenerated cellulose fibers through interfacial interactions. This resulted in a homogeneous dispersion and encapsulation within the cellulose, significantly improving the flame-retardant properties of the base material and leading to the formation of a stable cellulose/FA composite hydrogel (Abdel-Halim et al. 2011; Wang et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Notably, in the fabrication of film materials, we maintained a careful balance between cost-efficiency and performance. The process was conducted without additional additives, yet the resulting film materials exhibited an admirable synergy of structural integrity and functionality. This approach not only reinforces the material's structural stability but also augments its practical utility. The development of these cellulose-based fly ash materials not only broadens the scope of flame-retardant cellulose applications but also achieves high-value utilization of FA, presenting a viable solution to environmental challenges posed by FA accumulation.\u003c/p\u003e"},{"header":"Material","content":"\u003cp\u003eFor our research, the cellulose sample was sourced from Jiangxi Province Huazhong Spinning and Chemical Co., specifically utilizing cotton pulp. The fly ash used in our experiments was obtained from Dawukou Power Plant located in Shizuishan City, Ningxia Province. The chemicals employed in the process, including urea and sodium hydroxide, were acquired from J\u0026amp;K Scientific Co., Ltd. The ionic liquid used, AmimCl, was sourced from Shandong Henglian New Materials Co., Ltd. Additionally, sulfuric acid and sodium sulfate of analytical purity were purchased from Sinopharm Chemical Reagent Co., Ltd. Lastly, epichlorohydrin (ECH) was procured from Aladdin Reagent Co., Ltd.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003ePreparation of Cellulose/FA Film Materials (C1-FX)\u003c/h2\u003e \u003cp\u003eDuring the fabrication of the Cellulose/FA film materials (C1-FX), we prepared FA suspensions in concentrations of 10wt%, 20wt%, and 30wt%, relative to the cellulose mass, designated as F10, F20, and F30, respectively. The cellulose was dissolved in an AmimCl solution and then combined with the FA suspension to create a cellulose/FA hydrogel (Wan et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Notably, this process did not require any additional additives, thereby preserving the eco-friendly nature of the materials. Following this, the mixture was converted into thin films using the bar coating technique. These films were subsequently immersed in distilled water to remove any residual impurities (Vehvil\u0026auml;inen et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The final stage involved subjecting the films to hot pressing at 110℃, which yielded cellulose/FA film materials characterized by structural stability and enhanced flame-retardant properties.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003ePreparation of Cellulose/FA Porous Materials (C2-FX)\u003c/h2\u003e \u003cp\u003eFor the production of Cellulose/FA porous materials (C2-FX), we adopted a distinct approach. Initially, FA suspensions with concentrations of 10wt%, 20wt%, and 30wt% (labeled F10, F20, F30) were prepared, based on the cellulose mass ratio, and mixed with the cellulose solution. A key step involved the in situ alkali treatment of FA during its dissolution in the NaOH/urea solution, which effectively enhanced the hydroxyl active sites on the FA surface. This step was critical as it strengthened the hydrogen bonding between FA and cellulose, thereby streamlining the processing stages (Cai et al. 2005; Palomo et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1999\u003c/span\u003e). Following this, 5 ml of epichlorohydrin (ECH) was added to the mixture and stirred for 10 minutes. The resultant hydrogels were then subjected to a freeze-drying process at temperatures below \u0026minus;\u0026thinsp;20℃ for three days, aimed at removing moisture and forming a consistent porous structure. This careful freeze-drying process was crucial to prevent pore collapse due to tension, ensuring the material maintained uniform porosity(Mao et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Zeng et al. 2021).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eExperimental characterization\u003c/h2\u003e \u003cp\u003eFourier Transform Infrared Spectroscopy (FTIR) analysis was performed using a Nicolet Nexus-670 FTIR spectrometer from Thermo Fisher, USA. The procedure was executed at ambient temperature. It involved grinding and pressing a blend of 50 mg of potassium bromide (KBr) powder with an adequate quantity of the sample. The spectral scanning range was set from 400 to 4000 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. X-ray diffraction (XRD) patterns were obtained using a Shimadzu XRD-6000 (3 kW) X-ray diffractometer. The measurements were taken at a scan rate of 2\u0026deg; per minute, within a 2θ range of 10\u0026deg; to 50\u0026deg;. Thermal gravimetric analysis (TGA) and Differential Thermogravimetric Analysis (DTGA) were conducted using a Q50 TGA instrument from TA Instruments/Oster China Co., Ltd., USA. This analysis involved a heating rate of 10\u0026deg;C per minute, within a temperature range of 30\u0026deg;C to 600\u0026deg;C, under a nitrogen atmosphere. The sample weight was approximately 5 mg. Tensile and compression properties of the samples were evaluated using a UTM4304 electronic universal testing machine from Shenzhen Sanen Zongheng Technology Co., Ltd., with a testing speed of 1 mm per minute. Field emission scanning electron microscopy (FE-SEM) analysis was performed with a SIGMA-500 type field emission scanning electron microscope from Zeiss, Germany, to examine the surface morphology of the samples. The limiting oxygen index (LOI) was determined in accordance with GB2406-80 standards, using a JT-C2 LOI tester from Dongguan Jint Instrument Co., Ltd.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results and discussion","content":"\u003cp\u003e\u003cstrong\u003eStructure and Miscibility of Cellulose/FA Composite Material\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFigure\u0026nbsp;1a delineates the fabrication process of cellulose/FA materials. The procedure commenced with blending a specific quantity of FA suspension with the cellulose solution to create a cellulose/FA mixture. Subsequent heating and stirring facilitated the formation of a cellulose/FA composite hydrogel, which displayed a homogenous gray-black hue, signifying effective dispersion of FA within the cellulose matrix. A notable aspect is the denser structure of the film material compared to the porous variant, negating the need for additional cross-linking agents. Following this, flexible cellulose/FA film materials and uniformly porous cellulose/FA materials were produced via thermal pressing and freeze-drying techniques. Surface examination confirmed excellent compatibility and uniform distribution between cellulose and FA in both materials. Figure\u0026nbsp;1b and Fig.\u0026nbsp;1c showcase the macroscopic appearances of the cellulose/FA film and porous materials, respectively. In Fig.\u0026nbsp;1b, the film material maintained a consistent thickness of approximately 0.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05 mm. The pure cellulose film exhibited notable transparency and flexibility, whereas the addition of FA to the cellulose/FA film resulted in a gray-black coloration but retained foldability and flexibility. The surface of the unpressed cellulose/FA film material appeared wrinkled, highlighting uneven FA distribution, particularly along the edges, which led to visible defects and structural irregularities. Conversely, Fig.\u0026nbsp;1c reveals that both the cellulose porous material and the cellulose/FA porous variant possessed dense pore structures. The addition of FA to the latter increased its inorganic content, thereby enhancing structural stability and reducing the likelihood of pore collapse (Wei et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e). Overall, the comparison suggests effective FA dispersion in cellulose, indicating an advancement in the material's overall performance.\u003c/p\u003e\n\u003cp\u003eFrom Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ea we can see the peak value corresponding to the characteristic peak of cellulose markedly diminishes with the inclusion of fly ash (FA), and in samples C-F20, C-F30, and C-F40, the cellulose characteristic peaks are virtually absent. This indicates that the addition of FA disrupts cellulose's original crystalline structure, resulting in a reduction of crystallinity among the cellulose fibers. Such a change in crystallinity is indicative of the effective encapsulation of cellulose by FA. Particularly at higher FA concentrations, the cellulose matrix can be completely enveloped by FA. Furthermore, FA serves as a physical barrier within the structure, offering additional protection to the underlying cellulose matrix. This physical barrier effect of FA contributes to the overall structural integrity and protective quality of the composite material.\u003c/p\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eb displays the FT-IR spectra for cellulose, fly ash (FA), and the C-F10 composite. In FA's FT-IR spectrum, the peaks at 550.5 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1057 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are attributed to the stretching vibrations of Si-O-Si and Al-O bonds, respectively. The spectra of cellulose and C-F10 show characteristic peaks between 3300\u0026ndash;3500 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, indicative of hydroxyl group (-OH) stretching vibrations. Notably, there is a peak shift from 3363.2 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in cellulose to 3434.5 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in C-F10, suggesting enhanced hydrogen bonding and indicating interactions between cellulose and FA(Spinella et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e). This shift in the infrared spectrum corroborates the strong hydrogen bond interactions between cellulose and FA, leading to the uniform dispersion of FA within the cellulose matrix and excellent miscibility of the two components in the cellulose/FA material. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ec reveals that the interplay between FA and cellulose extends beyond simple mixing. The presence of hydrogen bonds not only strengthens the bond between cellulose and FA but also ensures that FA is firmly adhered to the cellulose base. This interaction boosts the overall performance of the material and theoretically validates the exceptional compatibility between cellulose and FA. Moreover, this composite formation method enables the high-value utilization of FA, enhancing the material's functional and environmental merits.\u003c/p\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ea and Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ea' clearly show that the cellulose porous materials have a loosely arranged porous architecture. This design not only provides a high specific surface area favorable for the even adherence of FA particles but also effectively prevents their agglomeration, ensuring a uniform distribution (Wang et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e). In Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eb, Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eb', Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ec, and Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ec', which are SEM images of C2-F10 and C2-F20 respectively, there is a noticeable enhancement in the pore structure. Compared to the pore structure of pure cellulose, the cellulose/FA porous materials exhibit more complete pore structures as FA content increases, a change attributed to the disruption of cellulose's original crystalline structure by FA, as supported by FT-IR and XRD analysis(Song et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e).Furthermore, the strong hydrogen bonding interactions between FA and cellulose enable large areas of FA particles to adhere, not only reinforcing the pore structure but also facilitating the reconnection of some cellulose fibers. This leads to the creation of a dense formation with a complete pore structure. Additional examination of Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ed and Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ed' reveals that even with a 30% FA addition, the FA particles remain uniformly dispersed on the cellulose pore structure's surface. The material's pore structure progressively becomes more compact and three-dimensional, avoiding any collapse. This observation further substantiates the hydrogen bonding interactions between FA and cellulose, which permit a widespread uniform adherence and dense dispersion of FA. This interaction underpins the formation of the porous material's structure, yielding a complete and three-dimensional pore configuration.\u003c/p\u003e\n\u003cp\u003eDuring the development of cellulose/FA porous materials, the introduction of a cross-linking agent was deemed essential for providing necessary structural support. Without it, the porous materials often exhibited structural disintegration post-freeze-drying, as evidenced by the compromised integrity of their pore structures. On the other hand, cellulose film materials, upon FA addition, developed a denser structure facilitated by the hydrogen bonding between FA and cellulose. This bonding obviated the need for extra cross-linking agents, allowing the film materials to attain the required stability and structural integrity during their formation. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ef showcases the cross-section of the cellulose/FA film, where, despite some FA particles being visible on the cellulose surface, they remained firmly attached, underscoring the robust interfacial compatibility and efficient hydrogen bonding between cellulose and FA. Post-hot pressing, the cellulose film's surface exhibited a curved and fibrous appearance, with microfiber alignment parallel to the surface, indicative of a certain level of orientation. However, this structured orientation almost vanished with the incorporation of FA. As inferred from XRD analysis, the disruption of cellulose's original crystalline structure by FA could be responsible for this alteration, leading to a denser structure distinct from that of the cellulose film materials. In Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ef', although some small holes were observed on the surface, likely due to low-temperature cracking in liquid nitrogen, the overall structure remained densely packed (Ou et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e). In the C1-F20 sample, FA was evenly interspersed among the cellulose fibers and firmly encapsulated by them, demonstrating good compatibility. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eg displays the SEM-EDS spectra for C2-F20, highlighting elements such as Si, Al, Ca, and Fe. This indicated a uniform distribution of FA within C2-F20's three-dimensional network, crucial for thermal stability and flame retardancy. The combination of XRD analysis and SEM images further validated that FA's characteristic elements, including Si, Al, and Ca, were uniformly dispersed within the network. This uniform dispersion not only bolstered the material's overall stability but also potentially enhanced its mechanical strength and thermal stability. Consequently, the successful fabrication of cellulose/FA film opens up new avenues for the high-quality utilization of FA, underscoring its potential in advanced material applications.\u003c/p\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ea illustrates the stress-strain curves for various film materials during tensile testing. The stress recorded for the pure cellulose film was 88.9 MPa. In comparison, the stresses for C1-F10, C1-F20, and C1-F30 were 89.2 MPa, 64.5 MPa, and 51.1 MPa, respectively. These results suggest that the mechanical properties of the films generally diminish as the proportion of FA increases. However, a certain level of FA addition, as seen in C1-F10, can actually optimize and enhance the mechanical performance. This variation in mechanical properties is primarily attributed to the excessive addition of FA, which disrupts the original crystalline structure of cellulose. Increased surface defects and a more pronounced steric hindrance effect, outweighing the benefits of hydrogen bonding interactions, lead to spatial structural defects in cellulose. This adversely impacts the binding efficacy between cellulose and FA, thereby affecting the tensile strength of the cellulose/FA films (Aruniit et al. \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e). Despite the fact that an excessive FA addition induces defects in the cellulose's crystal structure, a 10% FA addition level seems to strike a balance. At this level, the hydrogen bonding interactions between cellulose and FA can offset some of the performance degradation caused by defects in the cellulose crystals. Consequently, an opportune addition of FA can preserve the original mechanical properties of the film while potentially imparting flame retardancy. This finding highlights the delicate balance between maintaining structural integrity and enhancing functional properties in composite materials.\u003c/p\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eb showcases the stress-strain curves for porous materials under compression testing. The graph illustrates that pure cellulose exhibits a compressive stress of 0.05 MPa at 20% compression. However, the addition of FA leads to a significant increase in compressive stress for samples C2-F10, C2-F20, and C2-F30. Closer examination, in conjunction with SEM images, indicates that the incorporation of FA enhances the three-dimensional spatial structure of cellulose, rendering it completer and more stable. This enhancement is attributed to FA adhering to the cellulose's pore structure via strong hydrogen bond interactions. FA effectively forms an inorganic coating skeleton around the pores, providing crucial support and reinforcement (Lee et al. 2022). As a result, with increasing FA content, the area of adhesion between FA and cellulose also expands, consequently boosting the compressive strength of the porous material (Donius et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e). A comprehensive evaluation of the mechanical properties of both film and porous materials suggests that a moderate addition of FA to cellulose not only ensures uniform FA distribution within the cellulose matrix but also improves its mechanical properties. This finding underscores the potential for broadening the application spectrum of cellulose, paving the way for more diverse and high-value uses of FA. Such developments are significant in material science, as they expand the scope of cellulose applications and demonstrate effective strategies for the high-value utilization of industrial by-products like FA.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFlame Retardancy and Thermal Stability\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab1\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eLOI data of cellulose and cellulose-based fly ash composite materials\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSample\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eLOI (%)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSample\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eLOI (%)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eCellulose Membrane\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e15\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eCellulose Porous\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e15\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eC1-F10\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e27\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eC2-F10\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e25\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eC1-F20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e28\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eC2-F20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e27\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eC1-F30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e31\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eC2-F30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e29\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eLOI is a critical metric for assessing the flame retardancy of materials, representing the minimum concentration of oxygen needed to sustain the combustion of a polymer in an environment consisting solely of oxygen and nitrogen gases (Camino et al \u003cspan class=\"CitationRef\"\u003e1988\u003c/span\u003e; Rosa et al \u003cspan class=\"CitationRef\"\u003e1999\u003c/span\u003e; Wang et al \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e). Figure\u0026nbsp;5c and Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e illustrates a notable variance in the LOI values among different cellulose materials. The LOI value for cellulose film material stands at 15%, whereas the LOI values for FA-modified cellulose film materials, namely C1-F10, C1-F20, and C1-F30, are 27%, 28%, and 31% respectively. Similarly, the LOI value for cellulose porous material is 15%, with its FA-modified versions, C2-F10, C2-F20, and C2-F30, exhibiting LOI values of 25%, 27%, and 29% respectively. This data indicates that FA incorporation significantly enhances the flame retardancy of cellulose materials. Figure\u0026nbsp;5a and Fig.\u0026nbsp;5b displays photographs capturing the combustion stages of cellulose/FA film and porous materials. These images, alongside combustion experiments, affirm that increasing FA content markedly improves the flame retardancy of cellulose/FA materials. Due to their denser structure, film materials exhibit higher flame retardancy compared to porous materials. A thorough analysis of the burning behavior of cellulose/FA material reveals two key mechanisms enhancing its flame retardancy. Firstly, during the combustion of internal cellulose, Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and SiO\u003csub\u003e2\u003c/sub\u003e in FA forms an inorganic protective layer on the surface, effectively encapsulating the combustible cellulose matrix. This barrier impedes direct combustion and heat transfer, delaying the release of pyrolysis products, SEM analysis confirms this protective layer's effectiveness in enhancing the flame retardancy of the cellulose matrix and plays a flame retardant effect. (Lange et al 2003; Park et al \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e). Secondly, FA's high specific surface area and the abundance of hydroxyl groups (-OH) on its surface post-alkali treatment play a crucial role. These features enable FA to adsorb or hinder the release and diffusion of volatiles during cellulose combustion. Consequently, the addition of FA to cellulose not only isolates it from oxygen but also provides protective shielding. This dual mechanism significantly contributes to the enhanced flame retardancy of cellulose materials, offering new possibilities in material development for applications requiring high flame resistance (Kandola et al \u003cspan class=\"CitationRef\"\u003e1996\u003c/span\u003e; Xu et al \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab2\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eTG data of cellulose and cellulose-based fly ash composite materials\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSample No.\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eTa do (\u003csup\u003eo\u003c/sup\u003eC)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eTb dp (\u003csup\u003eo\u003c/sup\u003eC)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eMass loss (%)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eCellulose\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e276\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e303\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e77\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eC-F10\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e282\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e313\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e61\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eC-F20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e299\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e325\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e58\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eC-F30\u003c/p\u003e\n\u003cp\u003eFA\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e302\u003c/p\u003e\n\u003cp\u003e~\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e329\u003c/p\u003e\n\u003cp\u003e~\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e56\u003c/p\u003e\n\u003cp\u003e0\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003ctfoot\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\"\u003e\u003csup\u003ea\u003c/sup\u003e: The onset decomposition temperature; \u003csup\u003eb\u003c/sup\u003e: The fastest decomposition temperature;\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tfoot\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eTo delve deeper into the thermal stability of the materials, TGA was conducted on cellulose, FA, and the cellulose/FA composites C-F10, C-F20, and C-F30 under a nitrogen (N\u003csub\u003e2\u003c/sub\u003e) atmosphere. Figure\u0026nbsp;5d and Fig.\u0026nbsp;5e, along with Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e, display the TGA and DTGA curves, providing specific TG data for these materials. Under N\u003csub\u003e2\u003c/sub\u003e protection, the thermal degradation of the cellulose/FA materials predominantly occurs due to cellulose's thermal decomposition, with the major weight loss happening between 260℃ and 400℃ (Park et al \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e). Notably, the initial decomposition temperatures for C-F10, C-F20, and C-F30 are observed at 282℃, 299℃, and 302℃, respectively. The incorporation of FA raises the onset temperature of cellulose decomposition from 282℃ to 302℃. Pure cellulose experiences a weight loss of up to 76.71%, but this value significantly reduces upon FA addition, further decreasing as the FA content increases, from 76.71\u0026ndash;55.51%. This reduction is ascribed to the increased inorganic content within the cellulose matrix due to the addition of FA. Cellulose/FA composites start decomposing around 290℃, indicating enhanced thermal stability compared to many polymer materials(He et al \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). Moreover, the inclusion of FA substantially slows down the rate of thermal decomposition in the cellulose matrix. This effect can be explained by the formation of an \"inorganic encapsulation\" layer around the cellulose matrix, induced by FA, which acts as a thermal barrier, significantly slowing down the decomposition process. SEM and XRD analyses corroborate this finding, demonstrating that within a certain range of FA content, the thermal stability of cellulose/FA materials is indeed improved. This enhancement in thermal stability is crucial for applications where resistance to high temperatures is required, and it also validates the effectiveness of FA as a reinforcing agent in improving the thermal properties of cellulose-based materials.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis study successfully developed cellulose/FA porous and film materials using the NaOH/urea low-temperature dissolution system and AmimCl solution, combined with freeze-drying and hot pressing techniques. FT-IR analysis verified the presence of hydrogen bonding between cellulose and FA, which significantly enhanced their compatibility. SEM imaging demonstrated a uniform dispersion of FA within the cellulose matrix, effectively covering the cellulose surface. This encapsulation strengthens the mechanical properties of the material to a certain extent and provides a physical barrier, augmenting the flame retardancy of the cellulose. A comprehensive evaluation of the mechanical properties of both film and porous materials suggests that a moderate addition of FA to cellulose not only ensures uniform FA distribution within the cellulose matrix but also improves its mechanical properties. The initial thermal decomposition temperatures for samples C-F10, C-F20, and C-F30 were recorded at 282℃, 299℃, and 302℃, respectively, representing an increase of approximately 26℃ compared to pure cellulose. LOI of these materials reached up to 31%, clearly demonstrating that FA incorporation markedly improves both the thermal stability and flame retardancy of the cellulose matrix. The experimental approach outlined in this research significantly boosts the flame retardancy of cellulose-based composite materials. This method offers several advantages: it utilizes abundant, easily accessible raw materials, and employs non-toxic, efficient processes that are suitable for large-scale industrial production.\u003c/p\u003e \u003cp\u003eCrucially, this technique not only enhances the potential of cellulose-based materials for fire protection applications but also achieves high-value utilization of FA industrial waste. This contributes substantially to environmental protection and supports the establishment of a more sustainable and eco-friendly development model. The findings and methodologies of this study are pivotal in advancing the field of material science, particularly in developing sustainable, flame-retardant materials that are both environmentally responsible and industrially feasible.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eConflicts of interest\u003c/h2\u003e \u003cp\u003eThere are no conflicts to declare.\u003c/p\u003e \u003ch2\u003eSupporting Information\u003c/h2\u003e \u003cp\u003eSupporting Information is available from th SpringerLink Online Library.\u003c/p\u003e \u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eConceptualization: Yongqiang Qian, Wentao He, Lei Tan,Dan Li and Shengwei Guo; Methodology: Yongqiang Qian and Wentao He; Data curation: Yongqiang Qian, Wentao He and Lei Tan; Formal Analysis: Yongqiang Qian, Lei Tan and Wentao He; Validation: Wentao He, Lei Tan, and Yongjia Wu; Visualization: Lei Tan and Wentao He; Investigation: Lei Tan and Yiyang Chen; Resources: Yongqiang Qian, Li Dan and Guxia Wang; Funding acquisition: Yongqiang Qian and Shengwei Guo; Writing \u0026ndash; original draft: Yongqiang Qian and Wentao He; Writing \u0026ndash; review \u0026amp; editing: Shengwei Guo. All authors reviewed the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eThis work was supported by North Minzu University College Students' Innovative Entrepreneurial Training Plan Program (S202311407038), the Natural Science Foundation of Ningxia (Grant No. 2023AAC03283), the Fundamental Research Funds for the Central Universities, North Minzu University (Grant No. 2021KYQD11 and 2022XYZCL03), and the National Natural Science Foundation of China (Grant Nos. 52263021). Wentao He and Lei Tan contributed equally to this work. All authors discussed the results commented on the manuscript and approved the final version of this manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAbdel-Halim E S, Al-Deyab S S (2011) Removal of heavy metals from their aqueous solutions through adsorption onto natural polymers. Carbohydrate Polymers\u003cem\u003e 84\u003c/em\u003e(1), 454-458.\u003c/li\u003e\n\u003cli\u003eAdamczuk A, Kołodyńska D (2015) Equilibrium, thermodynamic and kinetic studies on removal of chromium, copper, zinc and arsenic from aqueous solutions onto fly ash coated by chitosan. Chemical Engineering Journal\u003cem\u003e 274\u003c/em\u003e, 200-212.\u003c/li\u003e\n\u003cli\u003eAoki D, Nishio Y (2010) Phosphorylated cellulose propionate derivatives as thermoplastic flame resistant/retardant materials: influence of regioselective phosphorylation on their thermal degradation behaviour. Cellulose\u003cem\u003e 17\u003c/em\u003e, 963-976.\u003c/li\u003e\n\u003cli\u003eAruniit A, Kers J, Majak J,Tall K (2012) Influence of hollow glass microspheres on the mechanical and physical properties and cost of particle reinforced polymer composites. Proceedings of the Estonian Academy of Sciences\u003cem\u003e 61\u003c/em\u003e(3), 160.\u003c/li\u003e\n\u003cli\u003eBao J, Lao J, Hu Y, Song Y, Xu M, Niu F (2023) Facile surface modification of fly ash to obtain flexible cellulose composite dielectric films with enhanced breakdown strength and energy storage density. Cellulose\u003cem\u003e 30\u003c/em\u003e(8), 5259-5271.\u003c/li\u003e\n\u003cli\u003eCai J, Zhang L (2005) Rapid dissolution of cellulose in LiOH/urea and NaOH/urea aqueous solutions. Macromolecular bioscience\u003cem\u003e 5\u003c/em\u003e(6), 539-548.\u003c/li\u003e\n\u003cli\u003eCamino G, Costa L, Casorati E, Bertelli G, Locatelli R (1988) The oxygen index method in fire retardance studies of polymeric materials. Journal of Applied Polymer Science\u003cem\u003e 35\u003c/em\u003e(7), 1863-1876.\u003c/li\u003e\n\u003cli\u003eChang SC, Slopek RP, Condon B, JC Grunlan (2014) Surface coating for flame-retardant behavior of cotton fabric using a continuous layer-by-layer process. Industrial \u0026amp; Engineering Chemistry Research\u003cem\u003e 53\u003c/em\u003e(10), 3805-3812.\u003c/li\u003e\n\u003cli\u003eChen L, Wang S, Wang S, Chen C, Qi L, Yu L, Lu Z, Huang J, Chen J, Wang Z, Shi XW, Song Z, Liu H, Chen C (2022) Scalable production of biodegradable, recyclable, sustainable cellulose\u0026ndash;mineral foams via coordination interaction assisted ambient drying. ACS nano\u003cem\u003e 16\u003c/em\u003e(10), 16414-16425.\u003c/li\u003e\n\u003cli\u003eDonius AE, Liu A, Berglund LA, Wegst UGK (2014) Superior mechanical performance of highly porous, anisotropic nanocellulose\u0026ndash;montmorillonite aerogels prepared by freeze casting. Journal of the mechanical behavior of biomedical materials\u003cem\u003e 37\u003c/em\u003e, 88-99.\u003c/li\u003e\n\u003cli\u003eGong J, Chen X, Tang T (2019) Recent progress in controlled carbonization of (waste) polymers. Progress in Polymer Science\u003cem\u003e 94\u003c/em\u003e, 1-32.\u003c/li\u003e\n\u003cli\u003eHabibi Y, Lucia L A, Rojas O J (2010) Cellulose nanocrystals: chemistry, self-assembly, and applications. Chemical reviews\u003cem\u003e 110\u003c/em\u003e(6), 3479-3500.\u003c/li\u003e\n\u003cli\u003eHan Y, Zhang X, Wu X, Lu C (2015) Flame retardant, heat insulating cellulose aerogels from waste cotton fabrics by in situ formation of magnesium hydroxide nanoparticles in cellulose gel nanostructures. ACS Sustainable Chemistry \u0026amp; Engineering\u003cem\u003e 3\u003c/em\u003e(8), 1853-1859.\u003c/li\u003e\n\u003cli\u003eHe W, Song P, Yu B, Fang Z, Wang H (2020) Flame retardant polymeric nanocomposites through the combination of nanomaterials and conventional flame retardants. Progress in Materials Science\u003cem\u003e 114\u003c/em\u003e, 100687.\u003c/li\u003e\n\u003cli\u003eJiang F, Li T, Li Y, Zhang Y, Gong A, Dai J, Hitz E, Luo W, Hu L (2018) Wood‐based nanotechnologies toward sustainability. Advanced Materials\u003cem\u003e 30\u003c/em\u003e(1), 1703453.\u003c/li\u003e\n\u003cli\u003eKandola BK, Horrocks AR, Price D, Coleman GV (1996) Flame-retardant treatments of cellulose and their influence on the mechanism of cellulose pyrolysis. Journal of Macromolecular Science, Part C: Polymer Reviews\u003cem\u003e 36\u003c/em\u003e(4), 721-794.\u003c/li\u003e\n\u003cli\u003eLa Rosa AD, Recca A, Carter JT, McGrail PT (1999) An oxygen index evaluation of flammability on modified epoxy/polyester systems. Polymer\u003cem\u003e 40\u003c/em\u003e(14), 4093-4098.\u003c/li\u003e\n\u003cli\u003eLange J, Wyser Y. (2003) Recent innovations in barrier technologies for plastic packaging\u0026mdash;a review Packaging. Technology and Science: An International Journal\u003cem\u003e 16\u003c/em\u003e(4), 149-158.\u003c/li\u003e\n\u003cli\u003eLee H J, Kang S W (2022) Improvement of stability for cellulose polymer by calcium oxide for application to porous materials. Cellulose\u003cem\u003e 29\u003c/em\u003e(15), 8319-8327.\u003c/li\u003e\n\u003cli\u003eLi Z, Wang G, Yan J, Qian Y, Guo S, Liu Y, Li D (2022) Value-added utilization of coal fly ash and recycled polyvinyl chloride in door or window sub-frame composites. Green Processing and Synthesis\u003cem\u003e 12\u003c/em\u003e(1), 20230002. \u003c/li\u003e\n\u003cli\u003eLong LY, Weng YX, Wang YZ (2018) Cellulose aerogels: Synthesis, applications, and prospects. Polymers\u003cem\u003e 10\u003c/em\u003e(6), 623.\u003c/li\u003e\n\u003cli\u003eLuo Y, Wu Y, Ma S, Zheng S, Zhang Y, Chu PK (2021) Utilization of coal fly ash in China: a mini-review on challenges and future directions. Environmental Science and Pollution Research\u003cem\u003e \u003c/em\u003e\u003cem\u003e28\u003c/em\u003e, 18727-18740.\u003c/li\u003e\n\u003cli\u003eMao J, Grgic B, Finlay WH, Kadla JF, Kerekes RJ (2008) Wood pulp based filters for removal of sub-micrometer aerosol particles. Nordic Pulp \u0026amp; Paper Research Journal\u003cem\u003e 23\u003c/em\u003e(4), 420-425.\u003c/li\u003e\n\u003cli\u003eNine MJ, Cole MA, Tran DNH, Losic D (2015) Graphene: a multipurpose material for protective coatings. Journal of Materials Chemistry A\u003cem\u003e 3\u003c/em\u003e(24), 12580-12602.\u003c/li\u003e\n\u003cli\u003eOu J, Hu S, Yao L, Chen Y, Qi H, Yue F (2023) Simultaneous strengthening and toughening lignin/cellulose nanofibril composite films: Effects from flexible hydrogen bonds. Chemical Engineering Journal\u003cem\u003e 453\u003c/em\u003e, 139770.\u003c/li\u003e\n\u003cli\u003ePalomo A, Grutzeck MW, Blanco MT (1999) Alkali-activated fly ashes: A cement for the future. Cement and concrete research\u003cem\u003e 29\u003c/em\u003e(8), 1323-1329.\u003c/li\u003e\n\u003cli\u003ePark S Y, Lee K, Shin H, Youn HJ (2022) Eco-friendly flame retardant foam prepared by oven drying of pickering stabilized carboxymethylated cellulose nanofibril/nanoclay wet foam. Cellulose\u003cem\u003e 29\u003c/em\u003e(18), 9693-9705.\u003c/li\u003e\n\u003cli\u003ePrabhu R, Jeevananda T, Reddy KR, Raghu AV (2021) Polyaniline-fly ash nanocomposites synthesized via emulsion polymerization: Physicochemical, thermal and dielectric properties. Materials Science for Energy Technologies\u003cem\u003e 4\u003c/em\u003e, 107-112.\u003c/li\u003e\n\u003cli\u003eSong D, Wang B, Tao W, Wang X, Zhang W, Dai M, Li J, Zhou Z (2022) Synergistic reinforcement mechanism of basalt fiber/cellulose nanocrystals/polypropylene composites. Nanotechnology Reviews\u003cem\u003e 11\u003c/em\u003e(1), 3020-3030.\u003c/li\u003e\n\u003cli\u003eSpinella S, Maiorana A, Qian Q, Dawson NJ, Hepworth V, McCallum, Scott A, Ganesh M, Singer KD, Gross RA (2016) Concurrent cellulose hydrolysis and esterification to prepare a surface-modified cellulose nanocrystal decorated with carboxylic acid moieties. ACS Sustainable Chemistry \u0026amp; Engineering\u003cem\u003e 4\u003c/em\u003e(3), 1538-1550.\u003c/li\u003e\n\u003cli\u003eSuflet DM, Chitanu GC, Popa VI (2006) Phosphorylation of polysaccharides: New results on synthesis and characterisation of phosphorylated cellulose. Reactive and Functional Polymers\u003cem\u003e 66\u003c/em\u003e(11), 1240-1249.\u003c/li\u003e\n\u003cli\u003eVehvil\u0026auml;inen M, Kamppuri T, Gr\u0026ouml;nqvist S, Rissanen M, Maloney T, Honkanen M, Nousiainen P (2015) Dissolution of enzyme-treated cellulose using freezing\u0026ndash;thawing method and the properties of fibres regenerated from the solution. Cellulose\u003cem\u003e 22\u003c/em\u003e, 1653-1674.\u003c/li\u003e\n\u003cli\u003eWan J, Diao H, Yu J, Song G, Zhang J (2021) A biaxially stretched cellulose film prepared from ionic liquid solution. Carbohydrate Polymers\u003cem\u003e 260\u003c/em\u003e, 117816.\u003c/li\u003e\n\u003cli\u003eWang Q, Guo J, Xu D, Cai J, Qiu Y, Ren J, Zhang L (2015) Facile construction of cellulose/montmorillonite nanocomposite biobased plastics with flame retardant and gas barrier properties. Cellulose\u003cem\u003e 22\u003c/em\u003e, 3799-3810.\u003c/li\u003e\n\u003cli\u003eWang X, Fu C, Feng Z, Huo H, Yin X, Gao G, Yin G, Ci L, Tong Y, Jiang Z, Wang J (2022) Flyash/polymer composite electrolyte with internal binding interaction enables highly-stable extrinsic-interfaces of all-solid-state lithium batteries. Chemical Engineering Journal\u003cem\u003e 428\u003c/em\u003e, 131041.\u003c/li\u003e\n\u003cli\u003eWang Y, Feng T, Piao J, Ren J, Ou M, Wang Y, Lian R, Cui J, Guan H, Jiao C, Chen X (2022) Surface modification of epichlorohydrin‐modified aramid nanofibers using ionic liquid to improve the fire safety and tensile strength of cotton fabrics. Polymers for Advanced Technologies\u003cem\u003e 33\u003c/em\u003e(12), 4302-4316.\u003c/li\u003e\n\u003cli\u003eWang Z, Fan X, He M, Chen Z, Wang Y, Ye Q, Zhang H, Zhang L (2014) Construction of cellulose\u0026ndash;phosphor hybrid hydrogels and their application for bioimaging. Journal of Materials Chemistry B\u003cem\u003e 2\u003c/em\u003e(43), 7559-7566.\u003c/li\u003e\n\u003cli\u003eWei Y, Chai J, Qin Y, Li Y, Xu Z, Li Y, Ma Y (2021) Effect of fly ash on mechanical properties and microstructure of cellulose fiber-reinforced concrete under sulfate dry\u0026ndash;wet cycle attack.\u003cem\u003e 302\u003c/em\u003e, 124207.\u003c/li\u003e\n\u003cli\u003eXu G, Shi X (2018) Characteristics and applications of fly ash as a sustainable construction material: A state-of-the-art review. Resources, conservation and recycling\u003cem\u003e 136\u003c/em\u003e, 95-109.\u003c/li\u003e\n\u003cli\u003eXu S, Han Y, Zhou C, Li J, Shen L, Lin H (2023) A biobased flame retardant towards improvement of flame retardancy and mechanical property of ethylene vinyl acetate. Chinese Chemical Letters\u003cem\u003e 34\u003c/em\u003e(1), 107202.\u003c/li\u003e\n\u003cli\u003eZeng B, Byrne N (2021) The effect of drying method on the porosity of regenerated cellulose fibres. Cellulose\u003cem\u003e 28\u003c/em\u003e(13), 8333-8342.\u003c/li\u003e\n\u003cli\u003eZhang C, Hu Y, Shao J, Pan H (2023) Flame retardant cellulose/polyvinyl alcohol/sodium alginate composite aerogels crosslinked by metal ions for flame resistance materials. Cellulose\u003cem\u003e 30\u003c/em\u003e(11), 7079-7093.\u003c/li\u003e\n\u003cli\u003eZhao S, Malfait WJ, Guerrero‐Alburquerque N, Koebel MM, Nystr\u0026ouml;m G (2018) Biopolymer aerogels and foams: Chemistry, properties, and applications. Angewandte Chemie International Edition\u003cem\u003e 57\u003c/em\u003e(26), 7580-7608.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"cellulose","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"cels","sideBox":"Learn more about [Cellulose](https://www.springer.com/journal/10570)","snPcode":"10570","submissionUrl":"https://submission.nature.com/new-submission/10570/3","title":"Cellulose","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Cellulose, Fly-Ash, Flame-Retardance, Strengthening, Value-Added Utilization of Industrial Waste","lastPublishedDoi":"10.21203/rs.3.rs-4185593/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4185593/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eCellulose, a bio-based material, is increasingly researched and valued for its abundant availability and exceptional characteristics. However, Cellulose has a flammable problem. This study addresses this issue by integrating it with industrial waste fly ash (FA) to overcome its natural flammability. By solution compounding, the study successfully developed cellulose/FA films and porous structures, significantly boosting the material's flame-retardant capabilities. This innovation not only enhances the practical application of cellulose but also promotes the high-value reuse of FA, resonating with the principles of sustainable development. The cellulose/FA hydrogel, characterized by a homogeneous and stable blend of FA particles and cellulose, achieves this through effective affinity and hydrogen bonding, ensuring optimal miscibility and encapsulation. In terms of thermal properties, the modified composites (C-F10, C-F20 and C-F30) demonstrate a substantial increase in initial decomposition temperatures, approximately 26℃ higher than pure cellulose, ranging between 282℃ and 302℃. This enhancement is attributed to the formation of an inorganic protective layer on the cellulose matrix, which significantly improves thermal stability while maintaining key mechanical properties. Remarkably, the flame retardancy of these materials shows notable improvement, particularly at a 30wt% FA concentration, with the limiting oxygen index (LOI) of the porous and film structures reaching around 29% and 31%, respectively. This advancement greatly elevates their flame resistance. Overall, this study presents a pioneering approach in developing eco-friendly, flame-retardant materials by repurposing industrial waste, marking a significant stride in sustainable material innovation.\u003c/p\u003e","manuscriptTitle":"Fly-Ash based Flame-Retardant Cellulose Materials for Strengthening and Value-Added Utilization in Industrial Solid Wastes","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-03 17:15:00","doi":"10.21203/rs.3.rs-4185593/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-03-31T18:37:50+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-03-29T12:14:57+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-03-29T12:14:57+00:00","index":"","fulltext":""},{"type":"submitted","content":"Cellulose","date":"2024-03-29T04:10:08+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"cellulose","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"cels","sideBox":"Learn more about [Cellulose](https://www.springer.com/journal/10570)","snPcode":"10570","submissionUrl":"https://submission.nature.com/new-submission/10570/3","title":"Cellulose","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"4c651d53-4b47-4a1d-907e-cf708618efaf","owner":[],"postedDate":"April 3rd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-02-10T16:07:21+00:00","versionOfRecord":{"articleIdentity":"rs-4185593","link":"https://doi.org/10.1007/s10570-025-06411-3","journal":{"identity":"cellulose","isVorOnly":false,"title":"Cellulose"},"publishedOn":"2025-02-04 15:57:25","publishedOnDateReadable":"February 4th, 2025"},"versionCreatedAt":"2024-04-03 17:15:00","video":"","vorDoi":"10.1007/s10570-025-06411-3","vorDoiUrl":"https://doi.org/10.1007/s10570-025-06411-3","workflowStages":[]},"version":"v1","identity":"rs-4185593","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4185593","identity":"rs-4185593","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}