Cellulose-based composite sponges derived from agricultural wastes for dye removal: Low temperature and non-toxic crosslinking

Cellulose-based composite sponges derived from agricultural wastes for dye removal: Low temperature and non-toxic crosslinking | 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 Cellulose-based composite sponges derived from agricultural wastes for dye removal: Low temperature and non-toxic crosslinking Parita Tanekachon, Worapat Inprasit, Pisutsarun Chitichotpanya, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3045422/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract To enhance the environmental sustainability, the transformation of wastes to be useful aspects have been focused with more attention. In this study, cellulose from residue crops was extracted via microwave-assisted method and fabricated as cellulose/chitosan composite sponges for dye removal. The pore structures with good physical property were introduced via UV crosslinking without heat treatment and followed by freeze-drying method. The optimal crosslinking parameters such as plant types (rice straw, coconut coir, and corn husk), photo-catalyst types (TiO 2 and sodium hypophosphite (SHP)), and UV irradiation time were performed. The results showed that cellulose derived from coconut coir with SHP under 15 min of UV exposure exhibited the porosity more than 90% and pore size in the range of 100–120 µm. The dye adsorption was fitted well with the Langmuir isotherm and provided the highest adsorption capacity at 99.01 mg/g with removal percentages of 96.27 ± 0.17% at an initial dye concentration of 50 mg/L. Thus, the low temperature and non-toxicity of the proposed method in this work has potential for converting wastes into value-added products. Cellulose Chitosan Dye removal Composite sponge Crosslinking Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction The Circular Economy (CE) concept has been mentioned as a renewed interest towards the manipulation of proper resources in order to meet the sustainability and eco-friendliness. This concept is to reduce and optimize the simplified methods based on the ability to recover resources instead of import the resources [ 1 – 2 ]. Reuse and recycle are the main strategies of CE which consist in the use of the pre-processed materials and/or wastes as the raw materials for the diversities of other processes. In the last decade, the agricultural wastes have been mainly emphasized with the attempts to improve and/or modify as the new and value-added materials because the millions of tons each year of these wastes such as the crop residues after harvesting have been noticeable generated and frequently eliminated by burning on farms. These produce the large amounts of greenhouse gases, air pollutants, and volatile organic compounds which cause of the serious environmental pollution resources [ 3 – 5 ]. For sustainable development, the agricultural wastes which are rich in cellulose content are better choices following the CE concept rather than handling as wastes. Cellulose is the one of the most abundant biopolymers which are predominantly found together with hemicellulose and lignin in the cell walls of agricultural wastes. Cellulose is natural resource following the sustainable concept with renewability, reusability, low cost, biodegradability, and eco-friendliness [ 6 ]. Its structure is composed of repeating units of β- D -glucopyranose (a dimer of glucose) which connect through the covalent linkage between the OH group of C4 and C1 carbon atoms known as β-1,4-linkage. The repeating units within the same chain and different chains can be linked by strong hydrogen bonds of the hydroxyl groups. The networks of hydrogen bonds result cellulose having the excellent properties of durable and insoluble in water and most organic solvents [ 7 – 8 ]. As the result of its plentiful hydrophilic hydroxyl groups, cellulose demonstrates considerable potential as a material for adsorbents. However, the its strong hydrogen bonds also entangle cellulose fibrils with hemicellulose and lignin [ 9 – 10 ]. Therefore, the isolation of cellulose from agricultural wastes is accomplished by the removal of the non-cellulosic components by different processes. The extraction is regularly performed by the favorite one of an alkaline treatment to remove complete or partially the non-cellulosic components. Strong bases, such as NaOH, are usually used, followed by neutralizing of pH. However, the conventional cellulose extraction takes long period of time about 8–12 hours. In recent years, irradiation has become well-known and applied for the extraction. Microwave-assisted extraction is a process to achieve high efficiency heating by using microwave which is matched with wavelength of absorption characteristics of the materials. Compared with conventional method, microwave-assisted heating has been performed in reducing reaction time with increasing product yield and purity [ 11 – 12 ]. The contamination by chemical waste in the environment is considerable problem worldwide especially the wastewater from dyestuffs. Most of dyes are synthetic and contain aromatic and azo groups in their structures resulting in toxic and low bio-degradability [ 13 ]. When the effluent containing these dyes released without any treatment, it would cause harmful effects on human health, aquatic organisms, and ecological equilibrium [ 14 – 15 ]. It has been reported that the adsorption by adsorbent is the one of favorite method because of its simplicity, economic feasibility, recyclability, and high efficiency. The cellulose-based adsorbents from agricultural waste have been proposed as the low-cost raw materials with high ability and efficiency for the wastewater treatment. In previous reports, the cellulose extracted from rice husks was modified as cationized-cellulose and applied to remove the Diamine Green B (DG-B), Acid Black 24 (AB-24), and Congo Red (CR) [ 9 ]. The coconut coir dust was also used as low cost adsorbent for the removal of Methylene Blue (MB) [ 16 ]. The corn stalk was modified and studied the adsorption of anionic dyes [ 17 ]. If the cellulose-based adsorbent is directly used without any physical or chemical modification, the capacity and selectivity of adsorption are often low. To overcome its reasonable properties, the cellulose composites have been investigated in various conditions including magnetic cellulose [ 18 ], montmorillonite-cellulose [ 19 ], polyacrylamide-cellulose [ 20 ], and chitosan-cellulose [ 21 ]. Based on the composites mentioned, the blending of cellulose and chitosan with physical modifications have been more attention because of the excellent properties of two compositions. However, chitosan suffers from poor mechanical and chemical stability and is usually leached out in acidic media. The chemical crosslinking under UV irradiation becomes the one of interesting method as its fast and eco-friendliness in the presence of an appropriate photoinitiator and photocatalyst [ 22 – 23 ]. Some researches displayed the crosslinking of cellulose and chitosan based materials by means of poly carboxylic acids with catalysis of TiO 2 and sodium hypophosphite [ 24 – 25 ]. Therefore, the UV-crosslinking is noticeably used in increase of the mechanical and chemical stability, and adsorption capacity through many active functional groups of both cellulose and chitosan. To the best of our knowledge, this study aimed to explore a novel approach to prepare the value-added agricultural residues as the cellulose-based adsorbents following the circular economy concept. Among of all crop residues, rice straw, coconut coir, and corn husk were reported to contain the high content of cellulose as high as 45.0%, 32.6%, and 35.5%, respectively [ 9 , 16 , 26 ]. They were used as raw materials for cellulose and extracted via an environmental-friendly, simple, fast, and efficient microwave-assisted alkali treatment. The extracted cellulose was fabricated as the composite sponges with chitosan under low-temperature and non-toxic photo-crosslinking. The effect of two different types of photo-catalysts, titanium dioxide (TiO 2 ) and sodium hypophosphite (NaH 2 PO 2 ) were investigated. Their morphology, physical and chemical properties with those of different preparations were demonstrated. This research used Methylene blue (MB) as a model to evaluate the adsorption of cationic dye. 2. Materials and methods 2.1 Materials The agricultural wastes including rice straw, coconut coir, and corn husk collected from local area in Pathum Thani, Thailand were used as raw materials for cellulose (CE). Sodium hydroxide (NaOH) from QREC (New Zealand) and 30% hydrogen peroxide (H 2 O 2 ) from Chem-Supply™ (Australia) were used in cellulose extraction. Titanium dioxide (TiO 2 , mixture of rutile and anatase, < 100 nm particle size) from Sigma-Aldrich (Singapore) and sodium hypophosphite monohydrate (SHP, NaH 2 PO 2 ·H 2 O) from KemAus™ (Australia) were applied as the photo-catalysts. Critic acid (CA, HOC(CH 2 CO 2 H) 2 ) from Loba Chemie™ (India) was provided as a non-toxic crosslinker. Sodium dodecyl sulfate (SDS, C 12 H 25 NaO 4 S) from KemAus™ (Australia) was supplied as a pore-forming agent and 2-hydroxy-2-methylpropiophenone (Darocur®1173, C 6 H 5 COC(CH 3 ) 2 OH) from Sigma-Aldrich (Singapore) was used as a photo-initiator. Chitosan (85% deacetylated CS) from Sigma-Aldrich (Singapore), acetic acid (CH 3 COOH) from Carlo Erba (Italy), sodium di-hydrogen phosphate (SDP, NaH 2 PO 4 ·2H 2 O) from KemAus™ (Australia), di-sodium hydrogen phosphate-12-hydrate (DSP, Na 2 HPO 4 ·12H 2 O) from Carlo Erba (Italy), and methylene blue (C 16 H 18 ClN 3 S) from Loba Chemie™ (India) were used without any further purification. Deionized water was used throughout the study. 2.2 Microwave-assisted extraction of cellulose The cellulose extraction was modified from previous work [ 27 ]. Rice straw, coconut coir, and corn husk were cut into the small pieces, cleaned with water, dried overnight at 70°C until constant weights. The dried particles (3 g) were immersed in 100 ml of 5%wt NaOH and were carried under microwave irradiation with 2,400 MHz at 490 W (SHARP R-200WW) for 150 seconds and then took a break for stirred to be good at mixing and further irradiated for 150 seconds to finish each treatment. The samples were filtered and rinsed with DI water to reach neutral pH. After alkali treatment, the extracted sample (10 g) was added in 500 ml of H 2 O 2 at 3:10 volume ratio of H 2 O 2 to DI water. The mixture was continuously stirred during heating at 100°C for 2 hr. The samples were finally filtered and rinsed with DI water to reach neutral pH and dried at 80°C for 24 hr. 2.3 Fabrication and crosslinking of cellulose/chitosan composite sponges The dispersed cellulose (CE) at 5%wt was combined with 1%wt SDS at 1:1 volume ratio. The chitosan (CS) at 2%wt was dissolved in 0.5 M acetic acid and then mixed with 10%wt CA at 2:1 volume ratio. The chitosan solution was gradually added into cellulose mixture at 3:4 volume ratio and vigorously stirred for 24 hr. The catalyst (TiO 2 or SHP) and Darocur®1173 held at 2 and 0.6%wt were further added in the CE/CS mixtures, rapidly and uniformly blended, and then transferred into a Petri dish. To optimize the crosslinking condition, the CE/CS suspensions were exposed to UV-C (200–400 nm) irradiation (4 W, Philips, Poland) with different times of 5, 10, and 15 min and fixed at 20 cm distance. The resultants were subjected to freeze at 4°C to yield an ice gel and was then freeze-dried under vacuum for 24 h on a freeze-drier (Labconco FD5-3, USA) to form the composite sponges. All samples were coded in Table 1 . 2.4 Characterization The presence of functional groups was characterized using Attenuated Total Reflection Fourier Transform Infrared spectroscopy with a resolution of 4 cm -1 over 4000 − 400 cm -1 of wave number range and OMNIC software analysis (ATR-FTIR, Nicolet iS50, Thermo Scientific, USA). The morphology of the composite sponges was examined using a Field Emission Scanning Electron Microscopy with the accelerating voltage of 2–15 kV and PCSEM software analysis (FESEM, JEOL JSM7800F, JAPAN). All samples were coated with Au by vapor deposition with the sputter current and time at 23 mA and 45 sec (QUORUM Q150R ES, UK) before the observations. Porosity was calculated by geometric method with the cylindrical shape of freeze dried samples [ 28 ]. Thermal analysis was conducted on a Thermogravimetric analyzer (TGA2, Mettler Toledo, Switzerland) by heating the sample to 800°C at a rate of 10°C/min under N 2 at a flow rate of 10 ml/min. Table 1 Material compositions for composite sponge fabrication Code Composite composition Photo-crosslinking CE CS Linker (CA) Catalyst Time (min) Rice straw Coconut coir Corn husk TiO 2 SHP 5 10 15 RST5 • • • • • RST10 • • • • • RST15 • • • • • RSS5 • • • • • RSS10 • • • • • RSS15 • • • • • CCT5 • • • • • CCT10 • • • • • CCT15 • • • • • CCS5 • • • • • CCS10 • • • • • CCS15 • • • • • CHT5 • • • • • CHT10 • • • • • CHT15 • • • • • CHS5 • • • • • CHS10 • • • • • CHS15 • • • • • Remark: CE = cellulose, RS = rice straw, CC = coconut coir, CH = corn husk, CS = chitosan, CA = citric acid, and SHP = Sodium hypophosphite 2.5 Adsorption The efficiency of adsorption was investigated through batch method as followed previous reports [ 29 ]. The solution pH was adjusted at 7 with SDP/DSP buffer. Methylene blue (MB) as a model of cationic dye was prepared at 5 concentrations from 2–10 mg/L by dilution of stock solution (10 mg/L) in DI water. The calibration curve and experiment were done using UV-visible spectrophotometry (SHIMADZU-UV-2600) at wavelength of 655 nm. All samples at fixed weight of 300 mg were soaked in 50 ml of MB concentrations (from 5.0 to 50.0 mg/L) with fixed pH 7 and then shaken in a shaker bath (Memmert WME14, Germany) at 30°C. Aliquots of less than 0.5% v/v of the total volume were drawn at specified time intervals up to 60 hours, diluted with DI water. The adsorption capacities were calculated using Eq. ( 1 ): $${q}_{t}= \frac{\left({C}_{0}- {C}_{t}\right) V}{m}$$ 1 where q t (mg•g -1 ) is the amount of MB being absorbed per gram of absorbent at time t (min), C 0 (mg•L -1 ) is the initial MB concentration, C t (mg•L -1 ) is the final MB concentration at time t (min), V (L) is the volume of MB solution, and m is the mass (g) of composite sponges. The adsorption isotherms are obtained and describe the ratio of the adsorbed dye to the remaining dye in the solution at equilibrium. Two models of mathematical expressions, Langmuir and Freundlich, are applied to fit the adsorption isotherms toward MB using Eq. ( 2 ) and Eq. ( 3 ): Langmuir isotherm: $$\frac{1}{{q}_{e}}=\left(\frac{1}{{q}_{max}{K}_{L}}\right)\frac{1}{{C}_{e}}+ \frac{1}{{q}_{max}}$$ 2 Freundlich isotherm: $${log}{q}_{e}=log{K}_{f}+ \frac{1}{n}log{C}_{e}$$ 3 where C e (mg•L -1 ) is the dye concentration at equilibrium, q e (mg•g -1 ) is the amount of dye adsorbed at equilibrium, q max (mg•g -1 ) is the maximum adsorption capacity, and K L (L•mg -1 ) is the Langmuir constant. K f (mg•g -1 ) and n are the Freundlich constant that indicate the adsorption capacity and intensity, respectively. 3. Results and discussion 3.1 Structure and physical properties The physical appearance of the composite sponges had been strongly affected by crosslinking process. Photo-catalysts, TiO 2 and SHP, enhanced the photo-crosslinking between cellulose and chitosan and maintained the composite structure compared to without catalyst. Composite sponges from different cellulose types provided the different surface appearances depending on their characteristics (Fig. S1 ). SEM images of the cross-section sponges prepared by using TiO 2 and SHP as catalysts with different UV irradiated times, 10 and 15 min are shown in Fig. 1 . The randomly distributed and interconnected micro-porous structures were derived in all conditions. The cellulose types were visibly observed to have an impact on the porous morphology of composite sponges. The dispersion of fibers throughout the sponges was obviously seen for RS cellulose (Fig. 1 (a-b and g-h)), while the flake-like structures were found for CC and CH cellulose (Fig. 1 (c-f and i-l)). For CC cellulose (Fig. 1 (c-e and i-j)), the pore structures were clearly established and distinguished with analogous size and shape. It could be caused by the different diameter sizes from large to small ranges of coconut coir (CC), corn husk (CH), and rice straw (RS), respectively [ 27 ], which had strongly affected on their different morphologies. The study of the effect of different photo-catalysts, TiO 2 and SHP, and UV irradiated times toward porosity of crosslinked-sponges is shown in Table S1 . All samples from SHP catalyst exhibited the porosities over 80% when UV irradiated time increased up to 15 min, while only CC cellulose based samples from TiO 2 catalyst reached over 80% porosity at 15 min of UV irradiated time. This indicates that the characteristics of porous structure after photo-crosslinking are consequently upon cellulose and catalyst types with enough UV irradiated time. FTIR spectroscopy was used to characterize the functional group and the structures of the CE/CS composite sponges. All spectra of are quite similar and obviously represent the characteristic peaks of cellulose and chitosan structures (Fig. S2) [ 27 ]. After crosslinking, FTIR spectra of the samples prepared using TiO 2 as photo-catalyst are shown in Fig. 2 a. The characteristic peaks of cellulose and chitosan were found at 3440, 2900, 1559, 1428, 1375, 1246, 1098, and 1061 cm -1 corresponding to O-H (O-H stretching), C-H (C-H stretching), -NH 2 blending, CH 2 (CH 2 scissoring), C-H (C-H deformation), aryl-alkyl ether, C-O-C (C-O-C stretching), and C-C (C-C stretching), while peak at 896 cm -1 is assigned to C-H (aromatic rings) of remaining lignin [ 27 ]. In addition, it is clearly seen the important peak at 1720 cm -1 corresponding to C = O of ester group which is shifted from C = O signal of neat cellulose and chitosan (Fig. S2). This indicates that the crosslinking is successful through ester linkage between –OH group of cellulose and/or chitosan with –COOH group of citric acid which acts as crosslink [ 24 ]. And the board peak at 483 cm − 1 is suggested the formation of Ti-O-C bond from the reaction between TiOH groups on the surface of TiO 2 catalyst and the residual hydroxyl groups of cellulose and chitosan under UV exposure [ 30 ]. When the photo-catalyst was changed to SHP, FTIR spectra of the samples are shown in Fig. 2 b. As prepared samples from SHP show the characteristic peak of C = O of ester group at 1725 cm -1 confirming the crosslinking as explained above. The obvious difference is the signals at 2328 and 814 cm -1 corresponding P-H stretching and bending [ 31 ]. The mechanisms have been suggested that the role of catalysts could be related to some acceleration in the formation of intermediates from a poly carboxylic acid and were subsequently trapped by hydroxyl groups to afford the ester linkages [ 32 ]. For TiO 2 catalyst, the esterification reaction is proposed by Lewis or Bronsted acids as shown in Fig. 3 (a). When TiO 2 is irradiated with UV in the presence of polycarboxylic acid, it leads to the formation of positive holes and protons on TiO 2 surface which may activate the carbonyl group of acid through proton attraction toward the addition of cellulose or chitosan hydroxyl groups to enhance the ester linkages. However, one of the possible mechanisms under UV condition is through free radicals as shown in Fig. 3 (b). The variety of free radicals from citric acid, cellulose, and chitosan is produced and can directly combine to each other and generate the ester linkages [ 33 ]. In case of SHP, the mechanism has been described by the formation of cyclic anhydride as intermediate [ 32 , 34 ]. In general, citric acid is possibly transformed to cyclic anhydride under thermal treatment [ 24 , 35 ]. Similarly, UV irradiation can induce the cyclic anhydride formation which has high reactivity toward hydroxyl groups of cellulose and chitosan [ 36 – 37 ]. This mechanism is expected to start with the formation of a cyclic anhydride intermediate of citric acid and follow by the ring-opening reaction between cyclic anhydride and the hydroxyl groups of cellulose or chitosan. When the first crosslinking occurs, citric acid which is now changed to a bifunctional carboxylic acid will not be reactive enough to undergo the second reaction [ 34 , 38 ]. So, SHP is used to induce the crosslinking with the second cellulose or chitosan chain. The possible mechanism is proposed in Fig. 4 . It can be seen that both TiO 2 and SHP catalysts by using citric acid as cross-linker under the irradiation of UV light for 15 min (without heat treatment) can induce the crosslinking between cellulose and chitosan. The thermal stability of the crosslinked-sponges was studied by TGA and DTG (Fig. 5 ). It found that the similar results of four degradation steps. The first mass losses are at 80–120 °C which attribute to the absorbed moisture in the sponges. The main mass losses are obviously observed at two temperature ranges of 180–210 °C and 300–360 °C corresponding to chitosan and cellulose, respectively [ 39 ]. It can be seen that the losses of chitosan are similar among all samples, while the losses of cellulose are different and reach above 350 °C for as-prepared sponge from coconut coir with TiO 2 catalyst. It could be caused by their properties of different cellulose fibers [ 27 ]. Some losses at 250–270 °C is expected to the decomposition of citric acid. In addition, the losses above 450 °C indicated the decomposition of SHP which usually uses as flame retardant [ 38 ]. These results suggested that the as-prepared sponge from coconut coir provides the highest thermal stability compare to others. 3.2 Adsorption study The investigation of dye removal was done by using the cationic dye (methylene blue, MB) solution in difference of concentration to understand the mechanism of adsorption. The effect of contact of time on MB is shown in Fig. 6 (a). For initial adsorption within 5 min, it increased rapidly because the active sites for MB are empty. After 1 hr, its adsorption became gradually a plateau and reached equilibrium due to the reduction of available sites [ 29 ]. The removal percentages were found to be 91.37 ± 1.94%, 96.27 ± 0.17%, and 90.18 ± 2.09% for the sponge from RS, CC, and CH, respectively, at an initial MB concentration (C 0 ) of 50 mg/L. This was due to the higher porosity of CC-based sponge (Table S1 ). In addition, this could be caused by the characteristic of coconut coir fiber which has a lot of small pore structure along fiber resulting higher availability of adsorption sites as shown in Fig. 6 (b). The adsorption mechanism of dye on the cellulose and chitosan matrix is usually proposed via the hydrogen bonding interaction between the hydroxyl (–OH) groups of the cellulose and chitosan with the nitrogen-containing groups of the MB dye [ 29 ]. Table 2 Adsorption parameters based on the Langmuir and Freundlich isotherms. Samples Langmuir Freundlich q m (mg•g − 1 ) K L (L• mg − 1 ) R 2 n K F (mg•g − 1 ) R 2 RST15 71.94 0.0245 0.9999 1.044 92.64 0.9997 CCT15 86.96 0.0230 0.9999 1.043 105.12 0.9995 CHT15 82.64 0.0213 0.9999 1.041 92.91 0.9996 RSS15 79.37 0.0236 0.9998 1.063 99.42 0.9963 CCS15 99.01 0.0206 0.9999 1.062 107.90 0.9992 CHS15 87.72 0.0215 0.9997 1.063 99.43 0.9978 Furthermore, the Langmuir and Freundlich isotherms were chosen to study equilibrium MB adsorption by the sponges (Eqs. 2 and 3 ). The Langmuir isotherm is mainly applicable to the monolayer of an adsorbate on an adsorbent, while the Freundlich isotherm describes multilayer adsorption under various non-ideal conditions [ 40 ]. The adsorption parameters were determined from these two isotherms are shown in Table 2 . The higher than 0.99 of R 2 values indicate that the experimental results are well-correlated with both isotherms. However, the n value (of Freundlich isotherm) suggested that MB adsorption was favourable as a monolayer because n value is close to 1. In addition, it found that the maximum adsorption capacities of the SHP used sponges are higher than TiO 2 used sponges for both models. The maximum adsorption capacity value was highest at 99.01 mg/g from the Langmuir model of CCS15 sample. The adsorption performance of the composite sponge is comparable to the other reports. Therefore, the cellulose-based sponges from agricultural wastes exhibit the advantage of Circular Economy (CE) concept. 4. Conclusions In summary, the value-added agricultural residues including rice straw, coconut coir, and corn husk were developed as the eco-friendly cellulose-based adsorbents for cationic dye removal. The microwave-assisted treatment was used to isolate cellulose which was improved the adsorption capacity after fabrication as composite sponges with chitosan. Owing to the synergistic property, the UV crosslinking without any heat treatment and toxic chemicals was achieved. However, the different residue type, photo-catalysts, and UV irradiation time yielded the composite sponges with different porosity which had impact on adsorption capacity. The as-prepared sponge from coconut coir using SHP as catalyst under UV exposure for 15 min exhibited the maintained porous structure with the maximum adsorption capacity at 99.01 mg/g from the Langmuir model. The adding value of cellulose from agricultural wastes is very attractive as following Circular Economy (CE) concept and provides the possibility to fabricate as the composite sponges with potential adsorption applications. Declarations Declaration of conflicting interests The authors declare that there are no competing financial interests or personal relationships regarding the publication of this paper. 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Appl Catal A Gen 371:10-16 Gashti MP, Almasian A, Gashti MP (2012) Preparation of electromagnetic reflective wool using nano-ZrO 2 /citric acid as inorganic/organic hybrid coating. Sens Actuator A Phys 187:1-9 Peng H, Yang CQ, Wang X, Wang S (2012) The combination of itaconic acid and sodium hypophosphite as a new cross-linking system for cotton. Ind Eng Chem Res 51:11301-11311 Ye T, Wang B, Liu J, Chen J, Yang Y (2015) Quantitative analysis of citric acid/sodium hypophosphite modifiedcotton by HPLC and conductometric titration. Carbohydr Polym 121:92-98 Molina-Gutiérrez S, Vacche SD, Vitale A, Ladmiral V, Caillol, S, Bongiovanni R, Lacroix-Desmazes P (2020) Photoinduced polymerization of eugenol-derived methacrylates. Molecules 25:3444 Gashti MP, Almasian A (2013) Citric acid/ZrO 2 nanocomposite inducing thermal barrier and self-cleaning properties on protein fibers. Composites Part B 52:340-349 Yang CQ, Chen D, Guan J, He Q (2010) Cross-linking cotton cellulose by the combination of maleic acid and sodium hypophosphite. 1. Fabric wrinkle resistance. Ind Eng Chem Res 49:8325-8332 Kim U-J, Kim HJ, Choi JW, Kimura S, Wada M (2017) Cellulose-chitosan beads crosslinked by dialdehyde cellulose. Cellulose 24:5517-5528 Xu X, Yu J, Liu C, Yang G, Shi L, Zhuang X (2021) Xanthated chitosan/cellulose sponges for the efficient removal of anionic and cationic dyes. React Funct Polym 160:104840 Additional Declarations No competing interests reported. Supplementary Files Supplementary.docx Cite Share Download PDF Status: Posted Version 1 posted 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. 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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-3045422","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":208602948,"identity":"3e58854c-af00-41fc-be2d-8136a8dafd04","order_by":0,"name":"Parita Tanekachon","email":"","orcid":"","institution":"Thammasat University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Parita","middleName":"","lastName":"Tanekachon","suffix":""},{"id":208602949,"identity":"013aa5c9-c52b-431e-af16-5655321579fb","order_by":1,"name":"Worapat Inprasit","email":"","orcid":"","institution":"Phetchaburi Rajabhat University Demonstration School, Phetchaburi Rajabhat University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Worapat","middleName":"","lastName":"Inprasit","suffix":""},{"id":208602954,"identity":"ebe0d7b7-1d1f-4813-834f-bd66c0cb1297","order_by":2,"name":"Pisutsarun Chitichotpanya","email":"","orcid":"","institution":"Thammasat University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Pisutsarun","middleName":"","lastName":"Chitichotpanya","suffix":""},{"id":208602956,"identity":"bba8cbf2-473f-41f6-83e3-991648c3a4d1","order_by":3,"name":"Penwisa Pisitsak","email":"","orcid":"","institution":"Thammasat University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Penwisa","middleName":"","lastName":"Pisitsak","suffix":""},{"id":208602957,"identity":"9eac806c-4add-42f3-9029-d45c1b18085b","order_by":4,"name":"Thitirat Inprasit","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAs0lEQVRIiWNgGAWjYDACCcYGhgQGBjkYP4GgDh6oFmMeCN+AGC0QOrGHaC320s0NDA933EnfL5HA+OEHw588wrbIHGxgSDzzLLdHIoFZsofBoJgIhyUCtbQdBmlhkAY6DMglUks6D9CW3yRpSQBqYSPSlhtgLc8Me848bLPsMTAmrIV9RvoDxp9td+TZ25MP3/hRIUdYC0jXDwaGA0AaGKcMBkSoh4IDxCsdBaNgFIyCkQcAAZE4uTYRS9oAAAAASUVORK5CYII=","orcid":"","institution":"Thammasat University","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Thitirat","middleName":"","lastName":"Inprasit","suffix":""}],"badges":[],"createdAt":"2023-06-10 04:59:07","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3045422/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3045422/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":38479759,"identity":"621b9183-f427-49f8-80fb-fc79380cc9eb","added_by":"auto","created_at":"2023-06-13 15:13:51","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":560873,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of composite sponges prepared using TiO\u003csub\u003e2\u003c/sub\u003e (a) RST10, (b) RST15, (c) CCT10, (d) CCT15, (e) CHT10, (f) CHT15 and SHP (g) RSS10, (h) RSS15, (i) CCS10, (j) CCS15, (k) CHS10, and (l) CHS15 as photo-catalyst with different UV irradiated times.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-3045422/v1/007c3716957d0443a078426a.png"},{"id":38479756,"identity":"3dbf823e-e7f9-4833-8534-85ea9222b42b","added_by":"auto","created_at":"2023-06-13 15:13:50","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":392567,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectra of the CE/CS composite sponges prepared using (a) TiO\u003csub\u003e2\u003c/sub\u003e and (b) SHP as photo-catalysts with UV irradiated time at 15 min.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-3045422/v1/d257aa388535ed17ca4552c9.png"},{"id":38479761,"identity":"98471d38-24ee-479b-b1f3-5cc421a8e953","added_by":"auto","created_at":"2023-06-13 15:13:51","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":133611,"visible":true,"origin":"","legend":"\u003cp\u003eProposed mechanisms of cellulose and chitosan crosslink with citric acid and TiO\u003csub\u003e2\u003c/sub\u003e under UV irradiation: (a) esterification reaction, (b) free radical reaction, (c) crosslinkink between cellulose and chitosan.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-3045422/v1/86a917f409130de886a4f91f.png"},{"id":38480452,"identity":"36538098-7381-483d-9618-7b26b1e49b41","added_by":"auto","created_at":"2023-06-13 15:21:51","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":82478,"visible":true,"origin":"","legend":"\u003cp\u003eProposed mechanisms of cellulose and chitosan crosslink with citric acid and SHP under UV irradiation.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-3045422/v1/7c9936a91619ab0c16360dca.png"},{"id":38479757,"identity":"5fe9fa3e-ff82-49d7-bc05-fb8b0e97d5ba","added_by":"auto","created_at":"2023-06-13 15:13:51","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":391069,"visible":true,"origin":"","legend":"\u003cp\u003eTGA and DTG analysis of as-prepared sponges: (a) rice straw, (b) coconut coir, and (c) corn husk.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-3045422/v1/48c3e13507f8aae9945e39f0.png"},{"id":38479760,"identity":"7cd2769a-7972-4a73-8f73-05edd20f146a","added_by":"auto","created_at":"2023-06-13 15:13:51","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":234810,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Effect of contact time on the MB adsorption (q\u003csub\u003et\u003c/sub\u003e) by the as-prepared sponges, rice straw (RSS15), coconut coir (CCS15), and corn husk (CHS15), and (b) SEM image of cross-section of coconut coir fiber.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-3045422/v1/7635d328485d68ca69a13f47.png"},{"id":38480454,"identity":"3cd33c1c-acd5-4129-9fcd-dad22d5b92a0","added_by":"auto","created_at":"2023-06-13 15:21:57","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1944566,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3045422/v1/c7738ff4-6b22-419c-b0ee-1fc995e9d118.pdf"},{"id":38479762,"identity":"a7067e94-a293-4029-8f3b-3e0bfbb4c693","added_by":"auto","created_at":"2023-06-13 15:13:51","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":2545452,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementary.docx","url":"https://assets-eu.researchsquare.com/files/rs-3045422/v1/c0debc6fef23359c3e7f3e52.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Cellulose-based composite sponges derived from agricultural wastes for dye removal: Low temperature and non-toxic crosslinking","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe Circular Economy (CE) concept has been mentioned as a renewed interest towards the manipulation of proper resources in order to meet the sustainability and eco-friendliness. This concept is to reduce and optimize the simplified methods based on the ability to recover resources instead of import the resources [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Reuse and recycle are the main strategies of CE which consist in the use of the pre-processed materials and/or wastes as the raw materials for the diversities of other processes. In the last decade, the agricultural wastes have been mainly emphasized with the attempts to improve and/or modify as the new and value-added materials because the millions of tons each year of these wastes such as the crop residues after harvesting have been noticeable generated and frequently eliminated by burning on farms. These produce the large amounts of greenhouse gases, air pollutants, and volatile organic compounds which cause of the serious environmental pollution resources [\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. For sustainable development, the agricultural wastes which are rich in cellulose content are better choices following the CE concept rather than handling as wastes.\u003c/p\u003e \u003cp\u003eCellulose is the one of the most abundant biopolymers which are predominantly found together with hemicellulose and lignin in the cell walls of agricultural wastes. Cellulose is natural resource following the sustainable concept with renewability, reusability, low cost, biodegradability, and eco-friendliness [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Its structure is composed of repeating units of β-\u003cem\u003eD\u003c/em\u003e-glucopyranose (a dimer of glucose) which connect through the covalent linkage between the OH group of C4 and C1 carbon atoms known as β-1,4-linkage. The repeating units within the same chain and different chains can be linked by strong hydrogen bonds of the hydroxyl groups. The networks of hydrogen bonds result cellulose having the excellent properties of durable and insoluble in water and most organic solvents [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. As the result of its plentiful hydrophilic hydroxyl groups, cellulose demonstrates considerable potential as a material for adsorbents. However, the its strong hydrogen bonds also entangle cellulose fibrils with hemicellulose and lignin [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Therefore, the isolation of cellulose from agricultural wastes is accomplished by the removal of the non-cellulosic components by different processes. The extraction is regularly performed by the favorite one of an alkaline treatment to remove complete or partially the non-cellulosic components. Strong bases, such as NaOH, are usually used, followed by neutralizing of pH. However, the conventional cellulose extraction takes long period of time about 8\u0026ndash;12 hours. In recent years, irradiation has become well-known and applied for the extraction. Microwave-assisted extraction is a process to achieve high efficiency heating by using microwave which is matched with wavelength of absorption characteristics of the materials. Compared with conventional method, microwave-assisted heating has been performed in reducing reaction time with increasing product yield and purity [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe contamination by chemical waste in the environment is considerable problem worldwide especially the wastewater from dyestuffs. Most of dyes are synthetic and contain aromatic and azo groups in their structures resulting in toxic and low bio-degradability [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. When the effluent containing these dyes released without any treatment, it would cause harmful effects on human health, aquatic organisms, and ecological equilibrium [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. It has been reported that the adsorption by adsorbent is the one of favorite method because of its simplicity, economic feasibility, recyclability, and high efficiency. The cellulose-based adsorbents from agricultural waste have been proposed as the low-cost raw materials with high ability and efficiency for the wastewater treatment. In previous reports, the cellulose extracted from rice husks was modified as cationized-cellulose and applied to remove the Diamine Green B (DG-B), Acid Black 24 (AB-24), and Congo Red (CR) [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The coconut coir dust was also used as low cost adsorbent for the removal of Methylene Blue (MB) [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. The corn stalk was modified and studied the adsorption of anionic dyes [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. If the cellulose-based adsorbent is directly used without any physical or chemical modification, the capacity and selectivity of adsorption are often low. To overcome its reasonable properties, the cellulose composites have been investigated in various conditions including magnetic cellulose [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], montmorillonite-cellulose [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], polyacrylamide-cellulose [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], and chitosan-cellulose [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Based on the composites mentioned, the blending of cellulose and chitosan with physical modifications have been more attention because of the excellent properties of two compositions. However, chitosan suffers from poor mechanical and chemical stability and is usually leached out in acidic media. The chemical crosslinking under UV irradiation becomes the one of interesting method as its fast and eco-friendliness in the presence of an appropriate photoinitiator and photocatalyst [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Some researches displayed the crosslinking of cellulose and chitosan based materials by means of poly carboxylic acids with catalysis of TiO\u003csub\u003e2\u003c/sub\u003e and sodium hypophosphite [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Therefore, the UV-crosslinking is noticeably used in increase of the mechanical and chemical stability, and adsorption capacity through many active functional groups of both cellulose and chitosan.\u003c/p\u003e \u003cp\u003eTo the best of our knowledge, this study aimed to explore a novel approach to prepare the value-added agricultural residues as the cellulose-based adsorbents following the circular economy concept. Among of all crop residues, rice straw, coconut coir, and corn husk were reported to contain the high content of cellulose as high as 45.0%, 32.6%, and 35.5%, respectively [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. They were used as raw materials for cellulose and extracted via an environmental-friendly, simple, fast, and efficient microwave-assisted alkali treatment. The extracted cellulose was fabricated as the composite sponges with chitosan under low-temperature and non-toxic photo-crosslinking. The effect of two different types of photo-catalysts, titanium dioxide (TiO\u003csub\u003e2\u003c/sub\u003e) and sodium hypophosphite (NaH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e2\u003c/sub\u003e) were investigated. Their morphology, physical and chemical properties with those of different preparations were demonstrated. This research used Methylene blue (MB) as a model to evaluate the adsorption of cationic dye.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Materials\u003c/h2\u003e\n \u003cp\u003eThe agricultural wastes including rice straw, coconut coir, and corn husk collected from local area in Pathum Thani, Thailand were used as raw materials for cellulose (CE). Sodium hydroxide (NaOH) from QREC (New Zealand) and 30% hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e) from Chem-Supply\u0026trade; (Australia) were used in cellulose extraction. Titanium dioxide (TiO\u003csub\u003e2\u003c/sub\u003e, mixture of rutile and anatase, \u0026lt;\u0026thinsp;100 nm particle size) from Sigma-Aldrich (Singapore) and sodium hypophosphite monohydrate (SHP, NaH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e2\u003c/sub\u003e\u0026middot;H\u003csub\u003e2\u003c/sub\u003eO) from KemAus\u0026trade; (Australia) were applied as the photo-catalysts. Critic acid (CA, HOC(CH\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e2\u003c/sub\u003eH)\u003csub\u003e2\u003c/sub\u003e) from Loba Chemie\u0026trade; (India) was provided as a non-toxic crosslinker. Sodium dodecyl sulfate (SDS, C\u003csub\u003e12\u003c/sub\u003eH\u003csub\u003e25\u003c/sub\u003eNaO\u003csub\u003e4\u003c/sub\u003eS) from KemAus\u0026trade; (Australia) was supplied as a pore-forming agent and 2-hydroxy-2-methylpropiophenone (Darocur\u0026reg;1173, C\u003csub\u003e6\u003c/sub\u003eH\u003csub\u003e5\u003c/sub\u003eCOC(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003eOH) from Sigma-Aldrich (Singapore) was used as a photo-initiator. Chitosan (85% deacetylated CS) from Sigma-Aldrich (Singapore), acetic acid (CH\u003csub\u003e3\u003c/sub\u003eCOOH) from Carlo Erba (Italy), sodium di-hydrogen phosphate (SDP, NaH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO) from KemAus\u0026trade; (Australia), di-sodium hydrogen phosphate-12-hydrate (DSP, Na\u003csub\u003e2\u003c/sub\u003eHPO\u003csub\u003e4\u003c/sub\u003e\u0026middot;12H\u003csub\u003e2\u003c/sub\u003eO) from Carlo Erba (Italy), and methylene blue (C\u003csub\u003e16\u003c/sub\u003eH\u003csub\u003e18\u003c/sub\u003eClN\u003csub\u003e3\u003c/sub\u003eS) from Loba Chemie\u0026trade; (India) were used without any further purification. Deionized water was used throughout the study.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2 Microwave-assisted extraction of cellulose\u003c/h2\u003e\n \u003cp\u003eThe cellulose extraction was modified from previous work [\u003cspan class=\"CitationRef\"\u003e27\u003c/span\u003e]. Rice straw, coconut coir, and corn husk were cut into the small pieces, cleaned with water, dried overnight at 70\u0026deg;C until constant weights. The dried particles (3 g) were immersed in 100 ml of 5%wt NaOH and were carried under microwave irradiation with 2,400 MHz at 490 W (SHARP R-200WW) for 150 seconds and then took a break for stirred to be good at mixing and further irradiated for 150 seconds to finish each treatment. The samples were filtered and rinsed with DI water to reach neutral pH. After alkali treatment, the extracted sample (10 g) was added in 500 ml of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e at 3:10 volume ratio of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e to DI water. The mixture was continuously stirred during heating at 100\u0026deg;C for 2 hr. The samples were finally filtered and rinsed with DI water to reach neutral pH and dried at 80\u0026deg;C for 24 hr.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3 Fabrication and crosslinking of cellulose/chitosan composite sponges\u003c/h2\u003e\n \u003cp\u003eThe dispersed cellulose (CE) at 5%wt was combined with 1%wt SDS at 1:1 volume ratio. The chitosan (CS) at 2%wt was dissolved in 0.5 M acetic acid and then mixed with 10%wt CA at 2:1 volume ratio. The chitosan solution was gradually added into cellulose mixture at 3:4 volume ratio and vigorously stirred for 24 hr. The catalyst (TiO\u003csub\u003e2\u003c/sub\u003e or SHP) and Darocur\u0026reg;1173 held at 2 and 0.6%wt were further added in the CE/CS mixtures, rapidly and uniformly blended, and then transferred into a Petri dish. To optimize the crosslinking condition, the CE/CS suspensions were exposed to UV-C (200\u0026ndash;400 nm) irradiation (4 W, Philips, Poland) with different times of 5, 10, and 15 min and fixed at 20 cm distance. The resultants were subjected to freeze at 4\u0026deg;C to yield an ice gel and was then freeze-dried under vacuum for 24 h on a freeze-drier (Labconco FD5-3, USA) to form the composite sponges. All samples were coded in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003e2.4 Characterization\u003c/h2\u003e\n \u003cp\u003eThe presence of functional groups was characterized using Attenuated Total Reflection Fourier Transform Infrared spectroscopy with a resolution of 4 cm\u003csup\u003e-1\u003c/sup\u003e over 4000\u0026thinsp;\u0026minus;\u0026thinsp;400 cm\u003csup\u003e-1\u003c/sup\u003e of wave number range and OMNIC software analysis (ATR-FTIR, Nicolet iS50, Thermo Scientific, USA). The morphology of the composite sponges was examined using a Field Emission Scanning Electron Microscopy with the accelerating voltage of 2\u0026ndash;15 kV and PCSEM software analysis (FESEM, JEOL JSM7800F, JAPAN). All samples were coated with Au by vapor deposition with the sputter current and time at 23 mA and 45 sec (QUORUM Q150R ES, UK) before the observations. Porosity was calculated by geometric method with the cylindrical shape of freeze dried samples [\u003cspan class=\"CitationRef\"\u003e28\u003c/span\u003e]. Thermal analysis was conducted on a Thermogravimetric analyzer (TGA2, Mettler Toledo, Switzerland) by heating the sample to 800\u0026deg;C at a rate of 10\u0026deg;C/min under N\u003csub\u003e2\u003c/sub\u003e at a flow rate of 10 ml/min.\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eMaterial compositions for composite sponge fabrication\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"3\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eCode\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"4\" style=\"width: 30.5386%;\"\u003e\n \u003cp\u003eComposite composition\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"6\" style=\"width: 23.0057%;\"\u003e\n \u003cp\u003ePhoto-crosslinking\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colspan=\"3\" style=\"width: 27.7901%;\"\u003e\n \u003cp\u003eCE\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" rowspan=\"2\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003eCS\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" rowspan=\"2\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003eLinker\u003c/p\u003e\n \u003cp\u003e(CA)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\" style=\"width: 8.1436%;\"\u003e\n \u003cp\u003eCatalyst\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\" style=\"width: 9.1616%;\"\u003e\n \u003cp\u003eTime (min)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" style=\"width: 8.6526%;\"\u003e\n \u003cp\u003eRice straw\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" style=\"width: 10.4849%;\"\u003e\n \u003cp\u003eCoconut coir\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" style=\"width: 8.6526%;\"\u003e\n \u003cp\u003eCorn husk\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" style=\"width: 4.2754%;\"\u003e\n \u003cp\u003eTiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" style=\"width: 3.8682%;\"\u003e\n \u003cp\u003eSHP\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" style=\"width: 2.0359%;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" style=\"width: 3.5628%;\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" style=\"width: 3.5628%;\"\u003e\n \u003cp\u003e15\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\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eRST5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eRST10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eRST15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eRSS5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eRSS10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eRSS15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eCCT5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eCCT10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eCCT15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eCCS5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eCCS10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eCCS15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eCHT5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eCHT10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eCHT15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eCHS5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eCHS10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 5.9041%;\"\u003e\n \u003cp\u003eCHS15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 10.4849%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.6526%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.7485%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 5.7005%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 4.2754%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.8682%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 2.0359%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 3.5628%;\"\u003e\n \u003cp\u003e\u0026bull;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"11\" style=\"width: 60.2628%;\"\u003e\n \u003cp\u003eRemark: CE\u0026thinsp;=\u0026thinsp;cellulose, RS\u0026thinsp;=\u0026thinsp;rice straw, CC\u0026thinsp;=\u0026thinsp;coconut coir, CH\u0026thinsp;=\u0026thinsp;corn husk, CS\u0026thinsp;=\u0026thinsp;chitosan,\u003c/p\u003e\n \u003cp\u003eCA\u0026thinsp;=\u0026thinsp;citric acid, and SHP\u0026thinsp;=\u0026thinsp;Sodium hypophosphite\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e2.5 Adsorption\u003c/h2\u003e\n \u003cp\u003eThe efficiency of adsorption was investigated through batch method as followed previous reports [\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e]. The solution pH was adjusted at 7 with SDP/DSP buffer. Methylene blue (MB) as a model of cationic dye was prepared at 5 concentrations from 2\u0026ndash;10 mg/L by dilution of stock solution (10 mg/L) in DI water. The calibration curve and experiment were done using UV-visible spectrophotometry (SHIMADZU-UV-2600) at wavelength of 655 nm. All samples at fixed weight of 300 mg were soaked in 50 ml of MB concentrations (from 5.0 to 50.0 mg/L) with fixed pH 7 and then shaken in a shaker bath (Memmert WME14, Germany) at 30\u0026deg;C. Aliquots of less than 0.5% v/v of the total volume were drawn at specified time intervals up to 60 hours, diluted with DI water. The adsorption capacities were calculated using Eq.\u0026nbsp;(\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e):\u003c/p\u003e\n \u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e$${q}_{t}= \\frac{\\left({C}_{0}- {C}_{t}\\right) V}{m}$$\u003c/div\u003e\n \u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003ewhere q\u003csub\u003et\u003c/sub\u003e (mg\u0026bull;g\u003csup\u003e-1\u003c/sup\u003e) is the amount of MB being absorbed per gram of absorbent at time t (min), C\u003csub\u003e0\u003c/sub\u003e (mg\u0026bull;L\u003csup\u003e-1\u003c/sup\u003e) is the initial MB concentration, C\u003csub\u003et\u003c/sub\u003e (mg\u0026bull;L\u003csup\u003e-1\u003c/sup\u003e) is the final MB concentration at time t (min), V (L) is the volume of MB solution, and m is the mass (g) of composite sponges.\u003c/p\u003e\n \u003cp\u003eThe adsorption isotherms are obtained and describe the ratio of the adsorbed dye to the remaining dye in the solution at equilibrium. Two models of mathematical expressions, Langmuir and Freundlich, are applied to fit the adsorption isotherms toward MB using Eq.\u0026nbsp;(\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e) and Eq.\u0026nbsp;(\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e):\u003c/p\u003e\n \u003cp\u003eLangmuir isotherm:\u003c/p\u003e\n \u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e$$\\frac{1}{{q}_{e}}=\\left(\\frac{1}{{q}_{max}{K}_{L}}\\right)\\frac{1}{{C}_{e}}+ \\frac{1}{{q}_{max}}$$\u003c/div\u003e\n \u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003eFreundlich isotherm:\u003c/p\u003e\n \u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e$${log}{q}_{e}=log{K}_{f}+ \\frac{1}{n}log{C}_{e}$$\u003c/div\u003e\n \u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003ewhere C\u003csub\u003ee\u003c/sub\u003e (mg\u0026bull;L\u003csup\u003e-1\u003c/sup\u003e) is the dye concentration at equilibrium, q\u003csub\u003ee\u003c/sub\u003e (mg\u0026bull;g\u003csup\u003e-1\u003c/sup\u003e) is the amount of dye adsorbed at equilibrium, q\u003csub\u003emax\u003c/sub\u003e (mg\u0026bull;g\u003csup\u003e-1\u003c/sup\u003e) is the maximum adsorption capacity, and K\u003csub\u003eL\u003c/sub\u003e (L\u0026bull;mg\u003csup\u003e-1\u003c/sup\u003e) is the Langmuir constant. K\u003csub\u003ef\u003c/sub\u003e (mg\u0026bull;g\u003csup\u003e-1\u003c/sup\u003e) and n are the Freundlich constant that indicate the adsorption capacity and intensity, respectively.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 Structure and physical properties\u003c/h2\u003e\n \u003cp\u003eThe physical appearance of the composite sponges had been strongly affected by crosslinking process. Photo-catalysts, TiO\u003csub\u003e2\u003c/sub\u003e and SHP, enhanced the photo-crosslinking between cellulose and chitosan and maintained the composite structure compared to without catalyst. Composite sponges from different cellulose types provided the different surface appearances depending on their characteristics (Fig. \u003cspan class=\"InternalRef\"\u003eS1\u003c/span\u003e). SEM images of the cross-section sponges prepared by using TiO\u003csub\u003e2\u003c/sub\u003e and SHP as catalysts with different UV irradiated times, 10 and 15 min are shown in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. The randomly distributed and interconnected micro-porous structures were derived in all conditions. The cellulose types were visibly observed to have an impact on the porous morphology of composite sponges. The dispersion of fibers throughout the sponges was obviously seen for RS cellulose (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e (a-b and g-h)), while the flake-like structures were found for CC and CH cellulose (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e (c-f and i-l)). For CC cellulose (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e (c-e and i-j)), the pore structures were clearly established and distinguished with analogous size and shape. It could be caused by the different diameter sizes from large to small ranges of coconut coir (CC), corn husk (CH), and rice straw (RS), respectively [\u003cspan class=\"CitationRef\"\u003e27\u003c/span\u003e], which had strongly affected on their different morphologies. The study of the effect of different photo-catalysts, TiO\u003csub\u003e2\u003c/sub\u003e and SHP, and UV irradiated times toward porosity of crosslinked-sponges is shown in Table \u003cspan class=\"InternalRef\"\u003eS1\u003c/span\u003e. All samples from SHP catalyst exhibited the porosities over 80% when UV irradiated time increased up to 15 min, while only CC cellulose based samples from TiO\u003csub\u003e2\u003c/sub\u003e catalyst reached over 80% porosity at 15 min of UV irradiated time. This indicates that the characteristics of porous structure after photo-crosslinking are consequently upon cellulose and catalyst types with enough UV irradiated time.\u003c/p\u003e\n \u003cp\u003eFTIR spectroscopy was used to characterize the functional group and the structures of the CE/CS composite sponges. All spectra of are quite similar and obviously represent the characteristic peaks of cellulose and chitosan structures (Fig. S2) [\u003cspan class=\"CitationRef\"\u003e27\u003c/span\u003e]. After crosslinking, FTIR spectra of the samples prepared using TiO\u003csub\u003e2\u003c/sub\u003e as photo-catalyst are shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ea. The characteristic peaks of cellulose and chitosan were found at 3440, 2900, 1559, 1428, 1375, 1246, 1098, and 1061 cm\u003csup\u003e-1\u003c/sup\u003e corresponding to O-H (O-H stretching), C-H (C-H stretching), -NH\u003csub\u003e2\u003c/sub\u003e blending, CH\u003csub\u003e2\u003c/sub\u003e (CH\u003csub\u003e2\u003c/sub\u003e scissoring), C-H (C-H deformation), aryl-alkyl ether, C-O-C (C-O-C stretching), and C-C (C-C stretching), while peak at 896 cm\u003csup\u003e-1\u003c/sup\u003e is assigned to C-H (aromatic rings) of remaining lignin [\u003cspan class=\"CitationRef\"\u003e27\u003c/span\u003e]. In addition, it is clearly seen the important peak at 1720 cm\u003csup\u003e-1\u003c/sup\u003e corresponding to C\u0026thinsp;=\u0026thinsp;O of ester group which is shifted from C\u0026thinsp;=\u0026thinsp;O signal of neat cellulose and chitosan (Fig. S2). This indicates that the crosslinking is successful through ester linkage between \u0026ndash;OH group of cellulose and/or chitosan with \u0026ndash;COOH group of citric acid which acts as crosslink [\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e]. And the board peak at 483 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is suggested the formation of Ti-O-C bond from the reaction between TiOH groups on the surface of TiO\u003csub\u003e2\u003c/sub\u003e catalyst and the residual hydroxyl groups of cellulose and chitosan under UV exposure [\u003cspan class=\"CitationRef\"\u003e30\u003c/span\u003e]. When the photo-catalyst was changed to SHP, FTIR spectra of the samples are shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eb. As prepared samples from SHP show the characteristic peak of C\u0026thinsp;=\u0026thinsp;O of ester group at 1725 cm\u003csup\u003e-1\u003c/sup\u003e confirming the crosslinking as explained above. The obvious difference is the signals at 2328 and 814 cm\u003csup\u003e-1\u003c/sup\u003e corresponding P-H stretching and bending [\u003cspan class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e\n \u003cp\u003eThe mechanisms have been suggested that the role of catalysts could be related to some acceleration in the formation of intermediates from a poly carboxylic acid and were subsequently trapped by hydroxyl groups to afford the ester linkages [\u003cspan class=\"CitationRef\"\u003e32\u003c/span\u003e]. For TiO\u003csub\u003e2\u003c/sub\u003e catalyst, the esterification reaction is proposed by Lewis or Bronsted acids as shown in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e(a). When TiO\u003csub\u003e2\u003c/sub\u003e is irradiated with UV in the presence of polycarboxylic acid, it leads to the formation of positive holes and protons on TiO\u003csub\u003e2\u003c/sub\u003e surface which may activate the carbonyl group of acid through proton attraction toward the addition of cellulose or chitosan hydroxyl groups to enhance the ester linkages. However, one of the possible mechanisms under UV condition is through free radicals as shown in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e(b). The variety of free radicals from citric acid, cellulose, and chitosan is produced and can directly combine to each other and generate the ester linkages [\u003cspan class=\"CitationRef\"\u003e33\u003c/span\u003e]. In case of SHP, the mechanism has been described by the formation of cyclic anhydride as intermediate [\u003cspan class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e]. In general, citric acid is possibly transformed to cyclic anhydride under thermal treatment [\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e35\u003c/span\u003e]. Similarly, UV irradiation can induce the cyclic anhydride formation which has high reactivity toward hydroxyl groups of cellulose and chitosan [\u003cspan class=\"CitationRef\"\u003e36\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e37\u003c/span\u003e]. This mechanism is expected to start with the formation of a cyclic anhydride intermediate of citric acid and follow by the ring-opening reaction between cyclic anhydride and the hydroxyl groups of cellulose or chitosan. When the first crosslinking occurs, citric acid which is now changed to a bifunctional carboxylic acid will not be reactive enough to undergo the second reaction [\u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e]. So, SHP is used to induce the crosslinking with the second cellulose or chitosan chain. The possible mechanism is proposed in Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e. It can be seen that both TiO\u003csub\u003e2\u003c/sub\u003e and SHP catalysts by using citric acid as cross-linker under the irradiation of UV light for 15 min (without heat treatment) can induce the crosslinking between cellulose and chitosan.\u003c/p\u003e\n \u003cp\u003eThe thermal stability of the crosslinked-sponges was studied by TGA and DTG (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e). It found that the similar results of four degradation steps. The first mass losses are at 80\u0026ndash;120 \u0026deg;C which attribute to the absorbed moisture in the sponges. The main mass losses are obviously observed at two temperature ranges of 180\u0026ndash;210 \u0026deg;C and 300\u0026ndash;360 \u0026deg;C corresponding to chitosan and cellulose, respectively [\u003cspan class=\"CitationRef\"\u003e39\u003c/span\u003e]. It can be seen that the losses of chitosan are similar among all samples, while the losses of cellulose are different and reach above 350 \u0026deg;C for as-prepared sponge from coconut coir with TiO\u003csub\u003e2\u003c/sub\u003e catalyst. It could be caused by their properties of different cellulose fibers [\u003cspan class=\"CitationRef\"\u003e27\u003c/span\u003e]. Some losses at 250\u0026ndash;270 \u0026deg;C is expected to the decomposition of citric acid. In addition, the losses above 450 \u0026deg;C indicated the decomposition of SHP which usually uses as flame retardant [\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e]. These results suggested that the as-prepared sponge from coconut coir provides the highest thermal stability compare to others.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 Adsorption study\u003c/h2\u003e\n \u003cp\u003eThe investigation of dye removal was done by using the cationic dye (methylene blue, MB) solution in difference of concentration to understand the mechanism of adsorption. The effect of contact of time on MB is shown in Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e(a). For initial adsorption within 5 min, it increased rapidly because the active sites for MB are empty. After 1 hr, its adsorption became gradually a plateau and reached equilibrium due to the reduction of available sites [\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e]. The removal percentages were found to be 91.37\u0026thinsp;\u0026plusmn;\u0026thinsp;1.94%, 96.27\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17%, and 90.18\u0026thinsp;\u0026plusmn;\u0026thinsp;2.09% for the sponge from RS, CC, and CH, respectively, at an initial MB concentration (C\u003csub\u003e0\u003c/sub\u003e) of 50 mg/L. This was due to the higher porosity of CC-based sponge (Table \u003cspan class=\"InternalRef\"\u003eS1\u003c/span\u003e). In addition, this could be caused by the characteristic of coconut coir fiber which has a lot of small pore structure along fiber resulting higher availability of adsorption sites as shown in Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e(b). The adsorption mechanism of dye on the cellulose and chitosan matrix is usually proposed via the hydrogen bonding interaction between the hydroxyl (\u0026ndash;OH) groups of the cellulose and chitosan with the nitrogen-containing groups of the MB dye [\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e].\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eAdsorption parameters based on the Langmuir and Freundlich isotherms.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\" style=\"width: 10.5495%;\"\u003e\n \u003cp\u003eSamples\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\" style=\"width: 40.6154%;\"\u003e\n \u003cp\u003eLangmuir\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\" style=\"width: 30.9451%;\"\u003e\n \u003cp\u003eFreundlich\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" style=\"width: 15.1209%;\"\u003e\n \u003cp\u003eq\u003csub\u003em\u003c/sub\u003e(mg\u0026bull;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" style=\"width: 17.2308%;\"\u003e\n \u003cp\u003eK\u003csub\u003eL\u003c/sub\u003e (L\u0026bull; mg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" style=\"width: 8.2637%;\"\u003e\n \u003cp\u003eR\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" style=\"width: 6.8571%;\"\u003e\n \u003cp\u003en\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" style=\"width: 15.8242%;\"\u003e\n \u003cp\u003eK\u003csub\u003eF\u003c/sub\u003e (mg\u0026bull;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" style=\"width: 8.2637%;\"\u003e\n \u003cp\u003eR\u003csup\u003e2\u003c/sup\u003e\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\" style=\"width: 10.5495%;\"\u003e\n \u003cp\u003eRST15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 15.1209%;\"\u003e\n \u003cp\u003e71.94\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 17.2308%;\"\u003e\n \u003cp\u003e0.0245\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.2637%;\"\u003e\n \u003cp\u003e0.9999\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 6.8571%;\"\u003e\n \u003cp\u003e1.044\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 15.8242%;\"\u003e\n \u003cp\u003e92.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.2637%;\"\u003e\n \u003cp\u003e0.9997\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 10.5495%;\"\u003e\n \u003cp\u003eCCT15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 15.1209%;\"\u003e\n \u003cp\u003e86.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 17.2308%;\"\u003e\n \u003cp\u003e0.0230\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.2637%;\"\u003e\n \u003cp\u003e0.9999\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 6.8571%;\"\u003e\n \u003cp\u003e1.043\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 15.8242%;\"\u003e\n \u003cp\u003e105.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.2637%;\"\u003e\n \u003cp\u003e0.9995\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 10.5495%;\"\u003e\n \u003cp\u003eCHT15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 15.1209%;\"\u003e\n \u003cp\u003e82.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 17.2308%;\"\u003e\n \u003cp\u003e0.0213\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.2637%;\"\u003e\n \u003cp\u003e0.9999\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 6.8571%;\"\u003e\n \u003cp\u003e1.041\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 15.8242%;\"\u003e\n \u003cp\u003e92.91\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.2637%;\"\u003e\n \u003cp\u003e0.9996\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 10.5495%;\"\u003e\n \u003cp\u003eRSS15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 15.1209%;\"\u003e\n \u003cp\u003e79.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 17.2308%;\"\u003e\n \u003cp\u003e0.0236\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.2637%;\"\u003e\n \u003cp\u003e0.9998\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 6.8571%;\"\u003e\n \u003cp\u003e1.063\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 15.8242%;\"\u003e\n \u003cp\u003e99.42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.2637%;\"\u003e\n \u003cp\u003e0.9963\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 10.5495%;\"\u003e\n \u003cp\u003eCCS15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 15.1209%;\"\u003e\n \u003cp\u003e99.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 17.2308%;\"\u003e\n \u003cp\u003e0.0206\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.2637%;\"\u003e\n \u003cp\u003e0.9999\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 6.8571%;\"\u003e\n \u003cp\u003e1.062\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 15.8242%;\"\u003e\n \u003cp\u003e107.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.2637%;\"\u003e\n \u003cp\u003e0.9992\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" style=\"width: 10.5495%;\"\u003e\n \u003cp\u003eCHS15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 15.1209%;\"\u003e\n \u003cp\u003e87.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 17.2308%;\"\u003e\n \u003cp\u003e0.0215\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.2637%;\"\u003e\n \u003cp\u003e0.9997\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 6.8571%;\"\u003e\n \u003cp\u003e1.063\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 15.8242%;\"\u003e\n \u003cp\u003e99.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" style=\"width: 8.2637%;\"\u003e\n \u003cp\u003e0.9978\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003eFurthermore, the Langmuir and Freundlich isotherms were chosen to study equilibrium MB adsorption by the sponges (Eqs. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e and \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). The Langmuir isotherm is mainly applicable to the monolayer of an adsorbate on an adsorbent, while the Freundlich isotherm describes multilayer adsorption under various non-ideal conditions [\u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e]. The adsorption parameters were determined from these two isotherms are shown in Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e. The higher than 0.99 of R\u003csup\u003e2\u003c/sup\u003e values indicate that the experimental results are well-correlated with both isotherms. However, the n value (of Freundlich isotherm) suggested that MB adsorption was favourable as a monolayer because n value is close to 1. In addition, it found that the maximum adsorption capacities of the SHP used sponges are higher than TiO\u003csub\u003e2\u003c/sub\u003e used sponges for both models. The maximum adsorption capacity value was highest at 99.01 mg/g from the Langmuir model of CCS15 sample. The adsorption performance of the composite sponge is comparable to the other reports. Therefore, the cellulose-based sponges from agricultural wastes exhibit the advantage of Circular Economy (CE) concept.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eIn summary, the value-added agricultural residues including rice straw, coconut coir, and corn husk were developed as the eco-friendly cellulose-based adsorbents for cationic dye removal. The microwave-assisted treatment was used to isolate cellulose which was improved the adsorption capacity after fabrication as composite sponges with chitosan. Owing to the synergistic property, the UV crosslinking without any heat treatment and toxic chemicals was achieved. However, the different residue type, photo-catalysts, and UV irradiation time yielded the composite sponges with different porosity which had impact on adsorption capacity. The as-prepared sponge from coconut coir using SHP as catalyst under UV exposure for 15 min exhibited the maintained porous structure with the maximum adsorption capacity at 99.01 mg/g from the Langmuir model. The adding value of cellulose from agricultural wastes is very attractive as following Circular Economy (CE) concept and provides the possibility to fabricate as the composite sponges with potential adsorption applications.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eDeclaration of conflicting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that there are no competing financial interests or personal relationships regarding the publication of this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Thailand Science Research and Innovation Fundamental Fund fiscal year 2023, and Faculty of Science and Technology, Thammasat University (Grant no. SciGR 8/2564).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eDuque-Acevedo M, Belmonte-Urena LJ, Yakovleva N, Camacho-Ferre F (2020) Analysis of the circular economic production models and their approach in agriculture and agricultural waste biomass management. Int J Environ Res Public Health 17:9545\u003c/li\u003e\n\u003cli\u003eUppal N, Pappu A, Gowri VKS, Thakur VK (2022) Cellulosic fibres-based epoxy composites: From bioresources to a circular economy. Ind Crops Prod 182:114895\u003c/li\u003e\n\u003cli\u003eBarros MV, Salvador R, De Francisco AC, Piekarski CM (2020). Mapping of research lines on circular economy practices in agriculture: From waste to energy. Renew Sust Energ Rev 131:109958\u003c/li\u003e\n\u003cli\u003eLi S, Chen G (2020) Agricultural waste-derived superabsorbent hydrogels: Preparation, performance, and socioeconomic impacts. 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React Funct Polym 160:104840\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Cellulose, Chitosan, Dye removal, Composite sponge, Crosslinking","lastPublishedDoi":"10.21203/rs.3.rs-3045422/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3045422/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eTo enhance the environmental sustainability, the transformation of wastes to be useful aspects have been focused with more attention. In this study, cellulose from residue crops was extracted via microwave-assisted method and fabricated as cellulose/chitosan composite sponges for dye removal. The pore structures with good physical property were introduced via UV crosslinking without heat treatment and followed by freeze-drying method. The optimal crosslinking parameters such as plant types (rice straw, coconut coir, and corn husk), photo-catalyst types (TiO\u003csub\u003e2\u003c/sub\u003e and sodium hypophosphite (SHP)), and UV irradiation time were performed. The results showed that cellulose derived from coconut coir with SHP under 15 min of UV exposure exhibited the porosity more than 90% and pore size in the range of 100\u0026ndash;120 \u0026micro;m. The dye adsorption was fitted well with the Langmuir isotherm and provided the highest adsorption capacity at 99.01 mg/g with removal percentages of 96.27\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17% at an initial dye concentration of 50 mg/L. Thus, the low temperature and non-toxicity of the proposed method in this work has potential for converting wastes into value-added products.\u003c/p\u003e","manuscriptTitle":"Cellulose-based composite sponges derived from agricultural wastes for dye removal: Low temperature and non-toxic crosslinking","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-06-13 15:13:43","doi":"10.21203/rs.3.rs-3045422/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"8669e8a1-de4f-42fd-a140-20712a901527","owner":[],"postedDate":"June 13th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2023-06-13T15:13:46+00:00","versionOfRecord":[],"versionCreatedAt":"2023-06-13 15:13:43","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3045422","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3045422","identity":"rs-3045422","version":["v1"]},"buildId":"WrCJVZZCHTDjtuVLN7oU0","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}