TEMPO-Oxidized Nanocellulose from Sargassum as a Sustainable Material for the Removal of Salicylic Acid in Water

TEMPO-Oxidized Nanocellulose from Sargassum as a Sustainable Material for the Removal of Salicylic Acid in Water | 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 TEMPO-Oxidized Nanocellulose from Sargassum as a Sustainable Material for the Removal of Salicylic Acid in Water B. Portillo-Rodríguez, E. M. Barrera-Rendón, D. A. Solís-Casados, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7336812/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 This work presents the extraction of cellulose from Sargassum and its subsequent conversion into cellulose nanofibril (CNF) using the TEMPO oxidation method. Structural and surface characterizations (XRD, FTIR, FESEM, EDS, AFM, and XPS) confirmed the synthesis, purification, and functionalization of CNF. Compared to purified cellulose (CP), the CNF exhibited higher crystallinity and significantly higher functionalization, particularly with carboxy groups. These carboxy groups played a crucial role in the interaction between cellulose fibers and salicylic acid. UV-Vis and FTIR analyses confirmed the removal of salicylic acid (SA) from water, with only CNF demonstrating effective absorption. UV-Vis analysis showed increased absorption at wavelengths < 250 nm due to interactions between cellulose fragments and SA. To avoid this interference, the adsorption efficiency was determined following the band at 296 nm, where 90% removal of salicylic acid was achieved after 48 h. These findings suggest that NFC from waste biomass is a promising material for water remediation. Saragassum absorption salicylic acid cellulose cellulose nanofibril Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 INTRODUCCION In recent decades, the use of non-steroidal anti-inflammatory drugs (NSAIDs) has increased considerably due to their analgesic, antipyretic, and anti-inflammatory properties (Bindu et al. 2020 ; Lee et al. 2023 ), making them widely used therapeutic agents in human and veterinary medicine (Rana et al. 2019 ; Cook et al. 2024 ). However, this increase in their use has raised environmental concerns because NSAIDs, after use, are excreted by the body and enter aquatic ecosystems (AE) through wastewater effluents. (Schmidt and Redshaw 2015 ; Parolini 2020 ). Due to their high biological activity, these compounds can have toxic effects on aquatic organisms, thereby affecting the trophic chain (Hernández-Tenorio et al. 2022 ; S et al. 2024). One of the most commonly used NSAIDs is acetylsalicylic acid (ASA), commonly known as aspirin, which, when ingested, is metabolized to salicylic acid (SA) (Kraemer and Maurer 2008 ). The presence of SA in AE has been reported to have harmful effects on both flora and fauna (Gómez-Oliván et al. 2014 ; Hernández-Tenorio et al. 2022 ), particularly on crustaceans and algae (Awad et al. 2020 ; Biczak and Pawłowska 2022 ). These effects have prompted the development of efficient strategies for SA removal from water. Techniques such as the Ultra Violet Ozone process (Zhe et al. 2021 ), photocatalysis (Tahir et al. 2019 ), and absorption (Aydın et al. 2023 ) have been explored, with the latter two being the most promising due to their effectiveness. However, materials used for these techniques, such as activated carbon (Otero et al. 2004 ), metal-organic frameworks (MOFs) (Jun et al. 2019 ), and certain metal oxides (Santamaría et al. 2020 ), can be expensive, difficult to synthesize, or have limited availability. At this point, cellulose emerges as an attractive alternative due to its abundance, low cost, biodegradability, and the fact that, owing to the presence of reactive groups on its surface, it is capable of absorbing and/or degrading organic contaminants(Carlsson et al. 2014 ). When cellulose is transformed into cellulose nanofibril (CNF), the material gains a higher surface area and reactivity, which can significantly enhance its ability to adsorb and/or degrade contaminants (Mahfoudhi and Boufi 2017 ; Karzar Jeddi et al. 2019 ). The CNF can be obtained by applying chemical or physical treatments to cellulose (Gupta and Shukla 2020 ). At the same time, cellulose is commonly derived from sources like wood, cotton, and bamboo. Moreover, cellulose can be obtained from non-traditional sources, such as packaging waste (cardboard, paper) (Jiang et al. 2020 ), agricultural waste (fruit peels) (Nasser et al. 2024 ), and even invasive aquatic plants (such as marine sargassum) (Salem and Ismail 2022 ). This study reports the synthesis of cellulose and CNF obtained from Sargassum. The cellulose was extracted via chemical methods and subsequently oxidized using TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl), a nitroxyl radical (N-O•) that allows the oxidation of hydroxy groups (-OH) of cellulose into carboxy groups (-COOH) (Thi Thanh Hop et al. 2022 ). The oxidation not only functionalized the surface of the cellulose but also facilitated the individualization of the fibers, leading to the formation of the CNF. The Cellulose and CNF were evaluated for their ability to remove salicylic acid from water. The results revealed that purified cellulose (CP) primarily absorbed water, whereas the CNF exhibited a high capacity to remove SA. These findings demonstrate the effect of carboxy groups on the removal of organic constituents, as well as the valorization of residual biomass in the development of advanced materials for water treatment. Experimental Materials. The following reagents were used without a prior purification process: Sodium Hydroxide (NaOH ≥ 99.8%, CTR Scientific), 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO, Sigma Aldrich), Sodium Bromide ACS (NaBr ≥ 99.0%, PQM Fermont), Salicylic Acid ACS (C 7 H 6 O 3 ≥ 99.0%, PQM Sigma Aldrich), Sodium Hypochlorite (NaClO ~ 11.0%, PQM Fermont), Acetic Acid (CH₃COOH ~ 5.0% La Costeña). Synthesis of Cellulose. The sargassum samples were collected directly from the beaches of the Mexican Caribbean and sun-dried for a week. To remove traces of sand and debris, the sargassum samples were sieved, washed, and dried for 48 hours at 80°C before being triturated and stored. To remove lignin and hemicellulose from the sargassum, the samples were subjected to a chemical washing process: 5.0 g of triturated sargassum were placed in an Erlenmeyer flask along with 250 mL of a 5.0% by weight NaOH solution and stirred constantly for 2 hours at 80°C. After two hours of washing, the solution changed from a translucent yellow to a dark brown, indicating partial removal of lignin. To ensure the complete lignin removal, a second chemical wash with NaOH was realized. After chemical washing, the samples were filtered and washed repeatedly with deionized water. Subsequently, the bleaching process was carried out by placing the chemically washed sargassum in an Erlenmeyer flask with 250 mL of a 2.0% NaClO solution and 0.1% acetic acid, and stirring for 2 hours at 80°C. At the end of the bleaching process, the samples were filtered and purified by dialysis using dialysis bags with a molecular weight cutoff of 8,000–14,000 for 48 hours. Before use, the dialysis bags were rinsed inside and out with deionized water and then immersed in deionized water for 24 hours to remove any contaminants. During dialysis, the deionized water was repeatedly changed until its pH remained constant. Synthesis of cellulose nanofibril (CNF). The synthesis of CNF was carried out by placing 1.0 g of bleached cellulose in a 500 mL Erlenmeyer flask, to which 250 mL of water was added along with 0.5 g of NaBr, 0.25 g of TEMPO, and 100 mL of 11.0% NaClO. The reaction was carried out at room temperature for 2 hours with magnetic stirring. Throughout the synthesis, the pH of the reaction was frequently monitored to maintain a value between 9.8 and 10.0, which was achieved by adding 0.1 M NaOH dropwise. After two hours of reaction, the precipitate was filtered and purified by dialysis, following the procedure described previously. Salicylic acid (SA) absorption tests. The absorption tests were conducted by dispersing 4.0 mg of cellulose or CNF in 25 mL of an SA solution, which was placed in a 50 mL beaker. To ensure a final concentration of 100 µM SA in the system, the initial SA solution was prepared at a slightly higher concentration, compensating for the dilution caused by the addition of the cellulose or CNF aqueous suspensions obtained from the dialysis purification process. The initial SA concentration thus depended on the concentration of each cellulose or CNF suspension added to the mixture. The mixtures were maintained under constant stirring in a dark chamber for 48 h to avoid photodegradation. Aliquots were extracted at different time intervals and analyzed by UV-Vis spectroscopy to monitor the absorption of SA. Characterization. The characterization techniques employed were X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscopy (AFM), Ultraviolet-Visible Spectroscopy (UV-Vis), and X-ray Photoelectron Spectroscopy (XPS) using the following specifications. X Ray Diffraction (XRD). Cellulose and CNF samples were dried at 60°C for 48 hours before characterization. The XRD patterns were acquired using a Bruker D8 Advance operating in θ–2θ configuration with Bragg–Brentano geometry, a Cu Kα radiation source of (λ = 1.54 Å), and a Linxeye detector, in a scanning range from 10 to 50° of 2Ɵ, with a scanning speed of 2° per minute, and a total acquisition time of 20 minutes per sample. Data were processed by subtracting the baseline to remove background noise, using OriginPro 8.5. No smoothing, deconvolution, or peak fitting was applied, and crystallinity values were estimated directly from the corrected patterns. The crystallinity index was calculated by the Segal method using Eq. 1. \(\:CI=\frac{{I}_{200}-{I}_{am}}{{I}_{200}}*100\) (Eq. 1) (Segal et al. 1959 ; Salem et al. 2023 ) Where I 200 is the intensity of the crystalline peak at the 200 plane, and I am is the intensity of the amorphous contribution. The amorphous halo is typically observed as a broad peak between 15.0° and 21.0° of 2Ɵ; in this study, it was identified at 18.6°. The intensity of the crystalline phase was determined from the maximum of the 200 reflection, in accordance with previous reports (Pham et al. 2022 ; Salem et al. 2023 ). Fourier Transform Infrared Spectroscopy (FTIR). Cellulose and CNF samples were dried at 60°C for 48 hours before FTIR characterization. The analysis was performed using a Bruker Tensor 27 instrument with a mid-infrared (MIR) source and a Bruker Platinum attenuated total reflection (ATR) accessory featuring a diamond crystal, in two different ranges: 4000 − 2000 cm − 1 and 2000 − 500 cm − 1 . Field Emission Scanning Electron Microscopy (FESEM). The cellulose and CNF samples were characterized by FESEM using a JEOL IT710HR Schottky Field Emission Scanning Electron operated at 15 kV and coupled with an X-ray detector. The microscope was used to perform chemical analysis using OXFORD Energy Dispersive Spectroscopy (EDS) with a resolution of 137 eV. Atomic Force Microscopy (AFM). AFM measurements were performed on glass substrates with dimensions of 2.5 cm x 2.5 cm, where 100 µL of a CNF solution was deposited and dried at 60°C for 48 h. Subsequently, they were characterized using ASYLUM RESEARCH equipment, MFP-3D Origin model, in contact mode. The AFM images were processed using WSXM software. Ultraviolet-Visible Spectroscopy (UV-Vis). The AS solutions that were in contact with the cellulose and CNF samples were filtered through a 0.22 µm pore-sized Teflon membrane before the analysis. Measurements were carried out using Perkin Elmer Lambda 35 equipment in a spectral range of 400 to 190 cm − 1 with a scanning speed of 480 nm per minute. X-ray photoelectron spectroscopy (XPS). The measurements of cellulose and CNF samples were performed using a JEOL JPS-9200 X-ray photoelectron spectrometer, equipped with a standard aluminum X-ray source. The spectra were acquired with 15 scans with a pass energy of 20 kV. A Shirley-type model was applied to adjust the baseline, excluding satellite peaks. Results and Discussions To confirm the synthesis of cellulose and CNF, the samples were analyzed by X-ray diffraction (XRD). The diffractograms of all the synthesized samples are shown in Fig. 1 . Analyzing the diffractograms, it was observed that in the case of the cellulose sample that was not subjected to a purification process (CNP) (Fig. 1 a), peaks were observed at 27.3°, 31.5°, and 45.4°, which are associated with the planes 111, 200 and 220, respectively, and which correspond to sodium chloride (NaCl) (Bao et al. 2017 ). The presence of NaCl is due to the precursors used during cellulose synthesis. In the case of the diffractogram of the cellulose sample subjected to a dialysis purification process (CP) (Fig. 1 b), the peaks corresponding to NaCl were not observed, indicating a suitable purification process for the CP. However, new peaks appeared at 13.8°, 22.5°, and 34.8°, associated with the 1–10, 200, and 004 planes, respectively, which are characteristic of cellulose Iβ (Poletto et al. 2013; French 2014 ; Gong et al. 2017 ; Pham et al. 2022 ; Suanto et al. 2022 ; Salem et al. 2023 ; Nang Vu et al. 2024 ). Likewise, a broad, low-intensity peak was observed near 38°, attributed to the presence of some contaminating residue. Analyzing the diffractogram of the CNF sample (Fig. 1 c), the same peaks were observed as in the CP sample, except for the broad peaks observed between 34 and 40°. The elimination of the 004 plane may be due to a disorder of the fibers, probably due to the decrease in the orientation of the fibers, since this plane is associated with ordered cellulose chains (French 2014 ), as well as the elimination of the peak at 38° indicates a successful purification of the material. Another difference observed was the increase in intensity at 15.6° associated with the 110 plane (Poletto et al. 2013), indicating an ordering of the fibers and therefore, an increase in crystallinity in the cellulose fibers (CF) for the CNF sample. This change in crystallinity can be calculated using Eq. 1, where the crystallinity index for the CP and CNF are 78.6% and 93.3%, respectively, indicating an increase in the ordering of the FC for the CNF sample. To explain the structural differences between the synthesized materials, all samples were analyzed by FTIR. The corresponding absorption bands are summarized in Table 1 . Table 1 Assignment of bands observed in the FTIR spectrum for the cellulose and CNF samples. IR Band [cm − 1 ] Assignment Reference 3300 (m) ʋ OH (Agrebi et al. 2019 ; Ria et al. 2022 ; Siddiqui et al. 2024 ) 2900 (w) ʋ s CH (Agrebi et al. 2019 ; Ria et al. 2022 ; Siddiqui et al. 2024 ) 2560 H-O-H (Barannik et al. 2021 ; Krivoshein et al. 2022 ) 2200 CO 2 (Barannik et al. 2021 ; Krivoshein et al. 2022 ) 2000 H-O-H (Barannik et al. 2021 ; Krivoshein et al. 2022 ) 1600 (m) ʋ COOH (Agrebi et al. 2019 ; Ria et al. 2022 ; Siddiqui et al. 2024 ) 1420 (s) σ CH (Agrebi et al. 2019 ; Ria et al. 2022 ; Siddiqui et al. 2024 ) 1040 (s) (ʋ C-C)/(ʋ C-O) (Agrebi et al. 2019 ; Ria et al. 2022 ; Siddiqui et al. 2024 ) 600 (s) oop COOH (Ria et al. 2022 ) The FTIR spectra were analyzed in two central regions: 4000–2000 cm⁻¹ (Fig. 2 a) and 2000–500 cm⁻¹ (Fig. 2 b), where the characteristic cellulose bands were identified in all samples (Agrebi et al. 2019 ; Ria et al. 2022 ; Siddiqui et al. 2024 ), although some notable differences were observed. In the range between 4000 and 2000 cm⁻¹ (Fig. 2 a), prominent bands appeared around 3300 cm⁻¹ and 2900 cm⁻¹, corresponding to hydroxy group stretching (ν OH) and methine group symmetric stretching (νs CH) vibrations, respectively. The unpurified cellulose (CNP) showed lower intensity and definition in these bands, probably due to the presence of contaminating residues from the precursors used in synthesis. In contrast, purified cellulose (CP), which was subjected to dialysis purification treatment and contaminant removal, exhibited a considerable increase in the intensity of these bands, particularly for the ν OH band. Compared to the CP sample, the FTIR spectrum of the CNFs showed a slight decrease in the intensity of the ν OH band, along with an increase in the intensity and greater definition of the ʋ s CH band. These intensity changes are consistent with the TEMPO oxidation process, as the hydroxy group (-OH) present in the hydroxymethyl groups (–CH₂OH) is oxidized to a carboxy group (–COOH), thereby reducing the intensity of the ν OH band. Furthermore, this oxidation decreases the number of hydrogen bonds, thereby increasing the vibrational freedom of the methine group (CH) that remains in the cellulose structure (Soni et al. 2015 ). Additional bands were observed at 2560, 2200, and 2000 cm⁻¹, attributed to absorbed water (H 2 O) at 2560 and 2000 cm⁻¹, and absorbed carbon dioxide (CO₂) at 2200 cm⁻¹ (Barannik et al. 2021 ; Krivoshein et al. 2022 ). In the case of the cellulose spectra (CNP and CP), these bands were more intense than those in the CNF spectra, indicating a greater affinity for humidity and CO₂ in these samples. The increase in the intensity of the CP sample spectrum, relative to the CNP spectrum, may be due to the greater freedom of the functional groups resulting from the removal of impurities in the sample. The highest number of bands was identified in the fingerprint region between 2000 and 500 cm⁻¹ (Fig. 2 b). The band near 1600 cm⁻¹, which corresponds to the stretching vibrations of the carboxy groups (ν COOH), showed a progressive increase in intensity throughout the CNF synthesis process, with the ν COOH band of the CNF sample being the most intense. This trend confirms the successful introduction of carboxy functionalities by the TEMPO oxidation method. The band at 1420 cm⁻¹, associated with the bending vibrations of methine groups (δ CH), showed increased intensity after purification of the CNP sample. However, a decrease was observed following TEMPO oxidation, likely due to partial degradation or modification of aliphatic chains during the oxidation process. A prominent peak at 1040 cm⁻¹, assigned to carbon-carbon (ʋ C–C) and carbon-oxygen (ʋ C–O) stretching vibrations, corresponds to the backbone structure of cellulose. The low intensity observed in the CNP sample was likely due to contamination. In contrast, both CP and CNF samples exhibited similar band intensities, indicating that the cellulose backbone was preserved throughout the purification and oxidation processes. Finally, the band at approximately 600 cm⁻¹, attributed to out-of-plane of carboxy groups (oop COOH), showed a marked increase in intensity in the CP and CNF spectra relative to CNP. This enhancement is associated with the removal of impurities, which facilitates more unrestricted movement of these functional groups. The further increase in CNF may result from reduced fiber dimensions, which enhance molecular flexibility and surface exposure. The FTIR results confirm the production and purification of cellulose as well as the functionalization of carboxy groups (–COOH) using the TEMPO oxidation method, thereby maintaining the structural integrity of the cellulose fibers (Thi Thanh Hop et al. 2022 ). FESEM was used to characterize the morphology and dimensions of the cellulose and CNF samples. The FESEM characterization (Fig. 3 ) was performed using secondary electrons for all samples. The images obtained for the CNP samples (Fig. 3 a and 3a1) show the presence of fibers, as well as some material agglomerations. In the case of the images of the CP sample, which were subjected to the dialysis purification process (Fig. 3 b and 3b1), the CF could be observed clearly. However, taking a closer look at the sample (Fig. 3 b1), the presence of agglomerations was observed again, although in smaller quantities. In the case of the CNF samples (Fig. 3 c and 3c1), to observe the CNF, it was necessary to use higher magnification; however, due to their dimensions, it was impossible to perform adequate characterization. Nevertheless, an evident decrease in the dimension of the CF was observed. To determine the chemical composition of the agglomerations observed by FESEM, an EDS analysis was performed on each sample, with the results presented in Table 2 . The results showed the presence of carbon (C), oxygen (O), sodium (Na), and chlorine (Cl). The presence of C and O in all samples corresponds to the elements from which cellulose is made. In contrast, the presence of Na and Cl is consistent with the chemical composition of the chemical precursors used during the synthesis, so they were classified as contaminants. These contaminating elements precipitated on the CF in the form of NaCl crystals, which were removed after each washing process. The presence and decrease in the percentage by weight of Na and Cl in the samples, after a purification process and the production of CNF, corroborated the results obtained by XRD (Fig. 1 ). Table 2 EDS results in % mass and % atomic of the cellulose and CNF samples. Sample Element % by Mass C O Na Cl CNP 24.33 26.13 26.02 23.52 CP 26.81 30.42 2.79 - CNF 64.78 35.22 - - Sample Element % by Atomic C O Na Cl CNP 37.20 30.00 20.69 12.11 CP 73.35 25.05 1.60 - CNF 71.09 28.91 - - AFM characterized the dimensions and morphology of the CNF. AFM micrographs (Fig. 4 ) showed the fibrous morphology of the CNF, as well as segregation and low ordering of the fibers. Although the CNF samples were not used in film form, the film formed on the surface of the glass substrates exhibited a surface roughness with a mean surface roughness (RMS) value of ~ 10 nm, indicating a relatively smooth structure with slight height variations. When measuring the length of the CNF, an average length of ~ 0.9 µm was obtained (Fig. 4 b), confirming the 1D nanometric morphology. By reducing the measurement scale (Fig. 4 c), the height profile between the carbon fiber edges yielded an average height of ~ 20 nm. In comparison, cross-sectional measurements revealed an average thickness of ~ 50 nm (Fig. 4 d). Once the production of cellulose and carbon fibers was confirmed, SA sorption tests were performed on the CP and CNF samples, since contaminants present in the CNP sample could affect the measurements. The UV-Vis spectra obtained from the SA absorption tests for the CP and CNF samples are shown in Figs. 5 and 6 , respectively. When analyzing the UV-Vis spectra from the absorption tests of the SA solutions in contact with the CP samples (Fig. 5 ), all the characteristic SA bands were observed in the wavelength range from 190 to 400 nm, with absorption bands at 201, 230, and 295 nm, corresponds to electronic transitions within the aromatic ring, to the conjugation between the aromatic ring and the carboxy group (–COOH), and associated with n → π* transitions in the oxygen of the phenolic or hydroxy group respectively (Abounassif et al. 1994 ; Trivedi et al. 2015 ), where the most intense band was observed at 201 nm with an absorbance of 0.36 for a concentration of [10 µM]. The absorption band at 201 nm was initially used to measure the AS absorption process. However, during the first 24 hours of the absorption test, a progressive increase in the intensity of the 201 nm band was observed, which subsequently decreased in intensity until an absorbance similar to that obtained during the first 0.25 hours of the absorption test was reached. In the case of the UV-Vis spectra of the SA solution that was in contact with the CNF sample (Fig. 6 ), a slight increase in the absorptivity could be observed, which was maintained during the first nine hours of the test, from then on the intensity of the absorptivity band began to decrease until after 48 hours where the band of the AS solutions became similar to the CNF solution. The increased band intensity at 201 nm could be attributed to the presence of oligosaccharides, quinones, or carboxylic acids formed during the cellulose purification process. Figure 7 illustrates the possible mechanism of cellulose purification, where the hydroxy groups (-OH) interact with the aromatic rings, thereby fragmenting the cellulose chain. Likewise, the presence of hypochlorous acid breaks the rings and forms quinones and carboxylic acids (Cannella et al. 2012 ; Billès et al. 2017 ; Mankar et al. 2021 ). These compounds were retained in the cellulose solution because, during the dialysis purification process, only small molecules or ions, such as sodium ion (Na + ) and chloride ion (Cl − ), are removed. Therefore, soluble fragments can absorb or interact with the AS molecule in regions smaller than 210 nm due to electronic transitions such as σ→σ* and n→σ* associated with interactions from Carbon–Oxygen or carbonyl (-C = O) bonds (Yu et al. 1983 ), present in all the fragmenting chain compounds, and therefore see this increase in the band without any other process involved. To determine the percentage removal by CP and CNF, a % absorption graph was used (Fig. 8 ), following the absorption bands at 201 nm (Figs. 8 a and 8 c) and 296 nm (Figs. 8 b and 8 d). When analyzing the % removal of the CP sample, following the band at 201 nm (Fig. 8 a), the effect of the interaction of the compounds formed during the cellulose purification process can be observed. Instead of obtaining a % removal, negative values are observed, indicating the presence of a greater amount of AS than at the beginning of the test. Similarly, it was observed that even when following the intensity of the band at 296 nm (Fig. 8 b), there is an effect of the interaction of the AS with the compounds formed during the cellulose purification process, albeit at a lower intensity. In the case of the CNF samples, the interaction of the compounds released from the CNF with salicylic acid was also observed when monitoring the absorption band at 201 nm; however, this interaction was of lower intensity when monitoring the band at 296 nm (Figs. 8 c and 8 d, respectively). Despite this effect, absorption efficiencies of approximately 50% and 90% were observed following the 201 nm and 296 nm bands, respectively. These values are comparable to those obtained with advanced materials and techniques reported in the literature (Table 3 ). Compared to these approaches, TEMPO-oxidized nanocellulose demonstrated competitive efficiency by relying on a low-cost, renewable, and natural biomass precursor. This highlights CNF as a sustainable alternative that combines high performance with environmental and economic benefits, although the observed interferences during monitoring may underestimate its current adsorption capacity. Table 3 Salicylic acid removal table carried out with other elimination techniques and materials. Material Amount of material/Volume of solution [SA] % Removal Equilibrium References UV/O₃ 1000 mL 70 µM 140 µM > 50% > 80% 1 min 10 min (Jing et al. 2020 ) Copolymer (βCD_BDE_Q⁺) 25 mg/25 mL 70 µM 90% 120 min (Cecone et al. 2023 ) Magnetic Ferrite Mg₀.₂Zn₀.₈Fe₂O₄ 10 mg/5 mL 1 µM 90% ≈ 24h (Tatarchuk et al. 2020 ) Microalgae Chlorella sorokiniana (CS), Chlorella vulgaris (CV) and Scenedesmus obliquus (SO) 0.5 g/250 mL 0.75 g/250 mL 1.0 g/250 mL ≈ 180 µM CS ≈ 40% CV ≈ 25% SO > 90% 144h (Escapa et al. 2024 ) Carbon xerogel with ZnO/CuₓO (UV/O₃ solar) 100 mg/500 mL 70 µM > 70% 300 min (de Moraes et al. 2023 ) Titanium with nanoparticles (FeTiO2, AgTiO2) UV-radiation 700 mg/700 mL 30 µM AgTiO2 90% 120 min (Santamaría et al. 2020 ) To corroborate the absorption process by the CNFs, the CP and CNF samples that were in contact with the SA solutions were filtered and dried for FTIR analysis. Figure 9 shows the FTIR spectra of the CP samples before and after the absorption tests (Figs. 9 a and 9 c, respectively), as well as the FTIR spectra of the CNF samples before and after the absorption tests (Figs. 9 b and 9 d, respectively). Analyzing the spectra of the CP sample, it can be seen that all the bands appear to have the same intensity, except the ν OH, (ʋ C–C)/(ʋ C–O), and oop COOH bands. In contrast, the CNF sample showed an increase in intensity in all bands characteristic of cellulose. These results demonstrate that both CP and NFC interact with SA, although the interaction is much more evident in the case of NFC. The changes in the bands suggest the presence of hydrogen bonding and weak electrostatic interactions, particularly with the oxygenated functional groups of SA. To explain this effect of absorption by CNFs, the surface chemical differences between the samples were analyzed using X-ray photoelectron spectroscopy (XPS). The spectra were calibrated using the adventitious carbon at 285.2 eV; the results are shown in Fig. 10 . In the C1s region (Figs. 10 a and 10 c), the CP and CNF samples exhibited five distinct peaks at 283.9, 285.2, 286.4, 287.9, and 289.3 eV. These peaks were assigned to C–H/C–C (aliphatic carbon), C–O (alcohol/ether carbon), C = O (carbonyl carbon), and O–C = O (carboxy/ester carbon), respectively. These assignments are consistent with previous reports (López et al. 1991 ; Haensel et al. 2009 ; Gerullis et al. 2022 ). In the case of the CP sample spectrum (Fig. 10 a), it was observed that all samples presented a relatively high signal intensity, as well as the presence of signals at high binding energy levels such as COOH and C = O. The presence of these last peaks suggests the presence of surface impurities or residual lignin-like structures that contribute to the increase in the aliphatic carbon signal. In contrast, the CNF sample (Fig. 10 c) showed a reduction in the intensity of the C-H and the C-OH peak, indicating that a significant portion of the hydroxy and aliphatic groups were oxidized. A slight decrease in the intensity of the COOH peak was also observed, which can be attributed to the redistribution of the carboxy groups over the cellulose chain, potentially making them less detectable by XPS analysis. Additionally, the C = O peak remained approximately constant in intensity but became broader, suggesting the formation of diverse oxidized carbon resulting from the TEMPO oxidation method. In the O1s region (Figs. 10 b and 10 d), both the CP and CNF samples exhibited five distinct peaks centered at 530.0, 531.4, 532.6, 533.8, and 535.3 eV. These peaks were assigned to O–C = O (carboxyl oxygen), C = O (carbonyl oxygen), C–O (ether/alcohol oxygen), C–OH (hydroxyl oxygen), and adsorbed H₂O, respectively. The presence of these signals in both samples is consistent with the typical oxygen-containing functional groups in polysaccharide structures. Cellulose inherently contains a high density of C–O and C–OH bonds due to its backbone. At the same time, minor signals of C = O and COOH may arise from oxidation during processing or from residual hemicelluloses or lignin fragments. In the CNF sample (Fig. 10 d), a pronounced increase in the intensity of the COOH peak (Jin et al. 2015 ) was observed, indicating the successful formation of carboxylic groups as a result of the TEMPO oxidation. Simultaneously, the intensity of the C–O peak decreased, suggesting a conversion into carboxy groups or removal during the purification steps. The other peaks, associated with C = O, C–OH, and H₂O, remained present in both samples, reflecting the persistent presence of oxygen functionalities and bound or adsorbed water molecules on the hydrophilic cellulose surface. All the spectral changes observed in the CNF sample confirm the successful surface oxidation of cellulose, increasing the density of carboxy functional groups and enhancing the material’s potential for the elimination of salicylic acid from water. Conclusions The results confirmed the production of purified cellulose (CP) and cellulose nanofibrils (CNF) by the TEMPO oxidation process. The CNF exhibited higher crystallinity, more defined functional groups, and a nanometric size, which are favorable characteristics for adsorption. SA adsorption tests demonstrated the efficiency of the CNFs compared to CP. However, we also recognize limitations, such as interferences that occurred during UV-Vis monitoring, as well as the required conditions under which the experiments were performed. For this reason, future work should focus on regeneration, reuse, and testing in real-world wastewater matrices. Declarations Declaration of authorship contribution. B. Portillo-Rodríguez : Writing, Review and Editing, Resources, Project Management, Methodology, Research, Formal Analysis, Conceptualization. E.M. Barrera-Rendón : Resources, Methodology, Formal Analysis, Conceptualization. D. A. Solís-Casados : Writing, Review and Editing, Resources, Methodology, Research, Conceptualization. L. Escobar-Alarcón : Writing, Review and Editing, Resources, Research, Conceptualization. Funds. This research was funded by the Postdoctoral Stays for Mexico grant from the Secretaría de Ciencia, Humanidades, Tecnología e Innovación (SECIHTI). Declaration of conflicts of interest. The authors declare that they have no known financial conflicts of interest or personal relationships that could have influenced the work presented in this article. Acknowledgments. The authors would like to thank LIA Citlalit Martínez Soto, M. in C. Alejandra Núñez, M. in C. Lizbeth Triana, M. in C. Melina Tapia, M. in C. 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sample\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-7336812/v1/2ee39a75bd4485d50c2805d4.png"},{"id":94583549,"identity":"d6a7094f-502f-4fca-87cb-bbb9014a37b8","added_by":"auto","created_at":"2025-10-28 18:14:08","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":20270518,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e FTIR spectrum of the samples: CNP (black), CP (red) and NFC (blue) into range from 4000 to 2000 cm\u003csup\u003e-1\u003c/sup\u003e; \u003cstrong\u003eb\u003c/strong\u003e FTIR spectrum of the samples: CNP (black), CP (red) and NFC (blue) into range from 2000 to 500 cm\u003csup\u003e-1\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-7336812/v1/199c94582d4624b346929f55.png"},{"id":94582837,"identity":"970d0360-25fa-4a47-8dc1-3c15a3e6c1d0","added_by":"auto","created_at":"2025-10-28 18:13:30","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":68623210,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e FESEM images taken with secondary electrons of CNP samples with scale bar of 50µm; \u003cstrong\u003ea\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e1\u003c/strong\u003e\u003c/sub\u003e FESEM images taken with secondary electrons of CNP samples with scale bar of 10µm;\u003cstrong\u003e b\u003c/strong\u003e FESEM images taken with secondary electrons of CP samples with scale bar of 50µm; \u003cstrong\u003eb\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e1\u003c/strong\u003e\u003c/sub\u003e FESEM images taken with secondary electrons of CP samples with scale bar of 10µm; \u003cstrong\u003ec\u003c/strong\u003e FESEM images taken with secondary electrons of CNF samples with scale bar of 1µm; \u003cstrong\u003ec\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e1\u003c/strong\u003e\u003c/sub\u003e FESEM images taken with secondary electrons of CNF samples with scale bar of 500 nm.\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-7336812/v1/6062d01beffec86f7254bd33.png"},{"id":94582841,"identity":"a51f0424-a35e-4ba2-a3ef-5d1a775093e4","added_by":"auto","created_at":"2025-10-28 18:13:31","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":35787143,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea \u003c/strong\u003e2D AFM micrographs of CNF with scale bar of 1µm; \u003cstrong\u003eb \u003c/strong\u003e3D AFM micrographs of CNF and length measurement histogram; \u003cstrong\u003ec\u003c/strong\u003e 2D AFM micrographs of CNF with scale bar of 1µm; \u003cstrong\u003ed\u003c/strong\u003e3D AFM micrographs of CNF and diameter measurement histogram.\u003c/p\u003e","description":"","filename":"Figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-7336812/v1/38c26adfc3100c86dde2d5e8.png"},{"id":94583291,"identity":"7f68d8fa-2a01-4897-8a23-84daf9b6cde6","added_by":"auto","created_at":"2025-10-28 18:13:57","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":7481905,"visible":true,"origin":"","legend":"\u003cp\u003eUV-VIS spectra of salicylic acid [10µm] solutions in contact with CP samples over time.\u003c/p\u003e","description":"","filename":"Figure5.png","url":"https://assets-eu.researchsquare.com/files/rs-7336812/v1/fcbee6101ac1aa809f1cc443.png"},{"id":94582458,"identity":"c464a43c-e002-4a33-94d8-40edffe20b1b","added_by":"auto","created_at":"2025-10-28 18:13:10","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":10251565,"visible":true,"origin":"","legend":"\u003cp\u003eUV-VIS spectra of salicylic acid [10µm] solutions in contact with CNF samples over time.\u003c/p\u003e","description":"","filename":"Figure6.png","url":"https://assets-eu.researchsquare.com/files/rs-7336812/v1/75d981a458be5fc5e35710f9.png"},{"id":94582828,"identity":"d1f3e09d-f506-4ad8-9776-fc9182a9421a","added_by":"auto","created_at":"2025-10-28 18:13:30","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":5161062,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic representation of the cellulose purification process.\u003c/p\u003e","description":"","filename":"Figure7.png","url":"https://assets-eu.researchsquare.com/files/rs-7336812/v1/2dea1c72d4378073e53c526b.png"},{"id":94583684,"identity":"08cd9504-5b79-40e4-8083-daf433edd0a8","added_by":"auto","created_at":"2025-10-28 18:14:23","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":12221849,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea \u003c/strong\u003eAbsorption percentage of salicylic acid [10µm] in contact with CP sample following 201 nm absorbance band; \u003cstrong\u003eb \u003c/strong\u003eAbsorption percentage of salicylic acid [10µm] in contact with CP sample following 296 nm absorbance band; \u003cstrong\u003ec\u003c/strong\u003eAbsorption percentage of salicylic acid [10µm] in contact with CNF sample following 201 nm absorbance band; \u003cstrong\u003ed\u003c/strong\u003e Absorption percentage of salicylic acid [10µm] in contact with CNF sample following 296 nm absorbance band.\u003c/p\u003e","description":"","filename":"Figure8.png","url":"https://assets-eu.researchsquare.com/files/rs-7336812/v1/7f51e64466090d37f92d769f.png"},{"id":94582887,"identity":"3cd8f459-7637-4bc5-9259-1de8b4e49b81","added_by":"auto","created_at":"2025-10-28 18:13:34","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":11222335,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e FTIR spectrum of CP samples before (black) and after 48h of contact(blue), into range from 4000 to 2000 cm\u003csup\u003e-1\u003c/sup\u003e; \u003cstrong\u003eb\u003c/strong\u003e FTIR spectrum of CNF samples before (black) and after 48h of contact(blue), into range from 4000 to 2000 cm\u003csup\u003e-1\u003c/sup\u003e; \u003cstrong\u003ec\u003c/strong\u003e FTIR spectrum of CP samples before (black) and after 48h of contact(blue), into range from 2000 to 500 cm\u003csup\u003e-1\u003c/sup\u003e; \u003cstrong\u003eb\u003c/strong\u003e FTIR spectrum of CNF samples before (black) and after 48h of contact(blue), into range from 2000 to 500 cm\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"Figure9.png","url":"https://assets-eu.researchsquare.com/files/rs-7336812/v1/10ca25425b572db479f49916.png"},{"id":94582946,"identity":"ba69b23d-6ad2-460b-b870-6ed8fad08e96","added_by":"auto","created_at":"2025-10-28 18:13:37","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":16598095,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e C1s XPS spectra of CP; \u003cstrong\u003eb \u003c/strong\u003eO1s XPS spectra of CP; \u003cstrong\u003ec \u003c/strong\u003eC1s XPS spectra of CNF; \u003cstrong\u003ed \u003c/strong\u003eO1s XPS spectra of CNF.\u003c/p\u003e","description":"","filename":"Figure10.png","url":"https://assets-eu.researchsquare.com/files/rs-7336812/v1/623792143dbba793f69c801d.png"},{"id":94542493,"identity":"957054e7-93a9-499d-98fd-0a6113d5b95d","added_by":"auto","created_at":"2025-10-28 17:29:51","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":640321,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7336812/v1/42da1eaf-d00b-48ca-851c-db997589bf24.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"TEMPO-Oxidized Nanocellulose from Sargassum as a Sustainable Material for the Removal of Salicylic Acid in Water","fulltext":[{"header":"INTRODUCCION","content":"\u003cp\u003eIn recent decades, the use of non-steroidal anti-inflammatory drugs (NSAIDs) has increased considerably due to their analgesic, antipyretic, and anti-inflammatory properties (Bindu et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Lee et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), making them widely used therapeutic agents in human and veterinary medicine (Rana et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Cook et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). However, this increase in their use has raised environmental concerns because NSAIDs, after use, are excreted by the body and enter aquatic ecosystems (AE) through wastewater effluents. (Schmidt and Redshaw \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Parolini \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Due to their high biological activity, these compounds can have toxic effects on aquatic organisms, thereby affecting the trophic chain (Hernández-Tenorio et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; S et al. 2024). One of the most commonly used NSAIDs is acetylsalicylic acid (ASA), commonly known as aspirin, which, when ingested, is metabolized to salicylic acid (SA) (Kraemer and Maurer \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). The presence of SA in AE has been reported to have harmful effects on both flora and fauna (Gómez-Oliván et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Hernández-Tenorio et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), particularly on crustaceans and algae (Awad et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Biczak and Pawłowska \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). These effects have prompted the development of efficient strategies for SA removal from water. Techniques such as the Ultra Violet Ozone process (Zhe et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), photocatalysis (Tahir et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), and absorption (Aydın et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) have been explored, with the latter two being the most promising due to their effectiveness.\u003c/p\u003e\u003cp\u003eHowever, materials used for these techniques, such as activated carbon (Otero et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2004\u003c/span\u003e), metal-organic frameworks (MOFs) (Jun et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), and certain metal oxides (Santamaría et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), can be expensive, difficult to synthesize, or have limited availability. At this point, cellulose emerges as an attractive alternative due to its abundance, low cost, biodegradability, and the fact that, owing to the presence of reactive groups on its surface, it is capable of absorbing and/or degrading organic contaminants(Carlsson et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). When cellulose is transformed into cellulose nanofibril (CNF), the material gains a higher surface area and reactivity, which can significantly enhance its ability to adsorb and/or degrade contaminants (Mahfoudhi and Boufi \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Karzar Jeddi et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe CNF can be obtained by applying chemical or physical treatments to cellulose (Gupta and Shukla \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). At the same time, cellulose is commonly derived from sources like wood, cotton, and bamboo. Moreover, cellulose can be obtained from non-traditional sources, such as packaging waste (cardboard, paper) (Jiang et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), agricultural waste (fruit peels) (Nasser et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), and even invasive aquatic plants (such as marine sargassum) (Salem and Ismail \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThis study reports the synthesis of cellulose and CNF obtained from Sargassum. The cellulose was extracted via chemical methods and subsequently oxidized using TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl), a nitroxyl radical (N-O•) that allows the oxidation of hydroxy groups (-OH) of cellulose into carboxy groups (-COOH) (Thi Thanh Hop et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The oxidation not only functionalized the surface of the cellulose but also facilitated the individualization of the fibers, leading to the formation of the CNF.\u003c/p\u003e\u003cp\u003eThe Cellulose and CNF were evaluated for their ability to remove salicylic acid from water. The results revealed that purified cellulose (CP) primarily absorbed water, whereas the CNF exhibited a high capacity to remove SA. These findings demonstrate the effect of carboxy groups on the removal of organic constituents, as well as the valorization of residual biomass in the development of advanced materials for water treatment.\u003c/p\u003e"},{"header":"Experimental","content":"\u003cp\u003eMaterials.\u003c/p\u003e\u003cp\u003eThe following reagents were used without a prior purification process: Sodium Hydroxide (NaOH ≥ 99.8%, CTR Scientific), 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO, Sigma Aldrich), Sodium Bromide ACS (NaBr ≥ 99.0%, PQM Fermont), Salicylic Acid ACS (C\u003csub\u003e7\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e ≥ 99.0%, PQM Sigma Aldrich), Sodium Hypochlorite (NaClO ~ 11.0%, PQM Fermont), Acetic Acid (CH₃COOH ~ 5.0% La Costeña).\u003c/p\u003e\u003cp\u003eSynthesis of Cellulose.\u003c/p\u003e\u003cp\u003eThe sargassum samples were collected directly from the beaches of the Mexican Caribbean and sun-dried for a week. To remove traces of sand and debris, the sargassum samples were sieved, washed, and dried for 48 hours at 80°C before being triturated and stored.\u003c/p\u003e\u003cp\u003eTo remove lignin and hemicellulose from the sargassum, the samples were subjected to a chemical washing process: 5.0 g of triturated sargassum were placed in an Erlenmeyer flask along with 250 mL of a 5.0% by weight NaOH solution and stirred constantly for 2 hours at 80°C. After two hours of washing, the solution changed from a translucent yellow to a dark brown, indicating partial removal of lignin. To ensure the complete lignin removal, a second chemical wash with NaOH was realized. After chemical washing, the samples were filtered and washed repeatedly with deionized water. Subsequently, the bleaching process was carried out by placing the chemically washed sargassum in an Erlenmeyer flask with 250 mL of a 2.0% NaClO solution and 0.1% acetic acid, and stirring for 2 hours at 80°C. At the end of the bleaching process, the samples were filtered and purified by dialysis using dialysis bags with a molecular weight cutoff of 8,000–14,000 for 48 hours. Before use, the dialysis bags were rinsed inside and out with deionized water and then immersed in deionized water for 24 hours to remove any contaminants. During dialysis, the deionized water was repeatedly changed until its pH remained constant.\u003c/p\u003e\u003cp\u003eSynthesis of cellulose nanofibril (CNF).\u003c/p\u003e\u003cp\u003eThe synthesis of CNF was carried out by placing 1.0 g of bleached cellulose in a 500 mL Erlenmeyer flask, to which 250 mL of water was added along with 0.5 g of NaBr, 0.25 g of TEMPO, and 100 mL of 11.0% NaClO. The reaction was carried out at room temperature for 2 hours with magnetic stirring. Throughout the synthesis, the pH of the reaction was frequently monitored to maintain a value between 9.8 and 10.0, which was achieved by adding 0.1 M NaOH dropwise. After two hours of reaction, the precipitate was filtered and purified by dialysis, following the procedure described previously.\u003c/p\u003e\u003cp\u003eSalicylic acid (SA) absorption tests.\u003c/p\u003e\u003cp\u003eThe absorption tests were conducted by dispersing 4.0 mg of cellulose or CNF in 25 mL of an SA solution, which was placed in a 50 mL beaker. To ensure a final concentration of 100 µM SA in the system, the initial SA solution was prepared at a slightly higher concentration, compensating for the dilution caused by the addition of the cellulose or CNF aqueous suspensions obtained from the dialysis purification process. The initial SA concentration thus depended on the concentration of each cellulose or CNF suspension added to the mixture. The mixtures were maintained under constant stirring in a dark chamber for 48 h to avoid photodegradation. Aliquots were extracted at different time intervals and analyzed by UV-Vis spectroscopy to monitor the absorption of SA.\u003c/p\u003e\u003cp\u003eCharacterization.\u003c/p\u003e\u003cp\u003eThe characterization techniques employed were X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscopy (AFM), Ultraviolet-Visible Spectroscopy (UV-Vis), and X-ray Photoelectron Spectroscopy (XPS) using the following specifications.\u003c/p\u003e\u003cp\u003eX Ray Diffraction (XRD).\u003c/p\u003e\u003cp\u003eCellulose and CNF samples were dried at 60°C for 48 hours before characterization. The XRD patterns were acquired using a Bruker D8 Advance operating in θ–2θ configuration with Bragg–Brentano geometry, a Cu Kα radiation source of (λ = 1.54 Å), and a Linxeye detector, in a scanning range from 10 to 50° of 2Ɵ, with a scanning speed of 2° per minute, and a total acquisition time of 20 minutes per sample. Data were processed by subtracting the baseline to remove background noise, using OriginPro 8.5. No smoothing, deconvolution, or peak fitting was applied, and crystallinity values were estimated directly from the corrected patterns. The crystallinity index was calculated by the Segal method using Eq.\u0026nbsp;1.\u003c/p\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:CI=\\frac{{I}_{200}-{I}_{am}}{{I}_{200}}*100\\)\u003c/span\u003e\u003c/span\u003e (Eq.\u0026nbsp;1) (Segal et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e1959\u003c/span\u003e; Salem et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2023\u003c/span\u003e)\u003c/p\u003e\u003cp\u003eWhere I\u003csub\u003e200\u003c/sub\u003e is the intensity of the crystalline peak at the 200 plane, and I\u003csub\u003eam\u003c/sub\u003e is the intensity of the amorphous contribution. The amorphous halo is typically observed as a broad peak between 15.0° and 21.0° of 2Ɵ; in this study, it was identified at 18.6°. The intensity of the crystalline phase was determined from the maximum of the 200 reflection, in accordance with previous reports (Pham et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Salem et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eFourier Transform Infrared Spectroscopy (FTIR).\u003c/p\u003e\u003cp\u003eCellulose and CNF samples were dried at 60°C for 48 hours before FTIR characterization. The analysis was performed using a Bruker Tensor 27 instrument with a mid-infrared (MIR) source and a Bruker Platinum attenuated total reflection (ATR) accessory featuring a diamond crystal, in two different ranges: 4000 − 2000 cm\u003csup\u003e− 1\u003c/sup\u003e and 2000 − 500 cm\u003csup\u003e− 1\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eField Emission Scanning Electron Microscopy (FESEM).\u003c/p\u003e\u003cp\u003eThe cellulose and CNF samples were characterized by FESEM using a JEOL IT710HR Schottky Field Emission Scanning Electron operated at 15 kV and coupled with an X-ray detector. The microscope was used to perform chemical analysis using OXFORD Energy Dispersive Spectroscopy (EDS) with a resolution of 137 eV.\u003c/p\u003e\u003cp\u003eAtomic Force Microscopy (AFM).\u003c/p\u003e\u003cp\u003eAFM measurements were performed on glass substrates with dimensions of 2.5 cm x 2.5 cm, where 100 µL of a CNF solution was deposited and dried at 60°C for 48 h. Subsequently, they were characterized using ASYLUM RESEARCH equipment, MFP-3D Origin model, in contact mode. The AFM images were processed using WSXM software.\u003c/p\u003e\u003cp\u003eUltraviolet-Visible Spectroscopy (UV-Vis).\u003c/p\u003e\u003cp\u003eThe AS solutions that were in contact with the cellulose and CNF samples were filtered through a 0.22 µm pore-sized Teflon membrane before the analysis. Measurements were carried out using Perkin Elmer Lambda 35 equipment in a spectral range of 400 to 190 cm\u003csup\u003e− 1\u003c/sup\u003e with a scanning speed of 480 nm per minute.\u003c/p\u003e\u003cp\u003eX-ray photoelectron spectroscopy (XPS).\u003c/p\u003e\u003cp\u003eThe measurements of cellulose and CNF samples were performed using a JEOL JPS-9200 X-ray photoelectron spectrometer, equipped with a standard aluminum X-ray source. The spectra were acquired with 15 scans with a pass energy of 20 kV. A Shirley-type model was applied to adjust the baseline, excluding satellite peaks.\u003c/p\u003e"},{"header":"Results and Discussions","content":"\u003cp\u003eTo confirm the synthesis of cellulose and CNF, the samples were analyzed by X-ray diffraction (XRD). The diffractograms of all the synthesized samples are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003eAnalyzing the diffractograms, it was observed that in the case of the cellulose sample that was not subjected to a purification process (CNP) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea), peaks were observed at 27.3°, 31.5°, and 45.4°, which are associated with the planes 111, 200 and 220, respectively, and which correspond to sodium chloride (NaCl) (Bao et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). The presence of NaCl is due to the precursors used during cellulose synthesis.\u003c/p\u003e\u003cp\u003eIn the case of the diffractogram of the cellulose sample subjected to a dialysis purification process (CP) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb), the peaks corresponding to NaCl were not observed, indicating a suitable purification process for the CP. However, new peaks appeared at 13.8°, 22.5°, and 34.8°, associated with the 1–10, 200, and 004 planes, respectively, which are characteristic of cellulose Iβ (Poletto et al. 2013; French \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Gong et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Pham et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Suanto et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Salem et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Nang Vu et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Likewise, a broad, low-intensity peak was observed near 38°, attributed to the presence of some contaminating residue.\u003c/p\u003e\u003cp\u003eAnalyzing the diffractogram of the CNF sample (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec), the same peaks were observed as in the CP sample, except for the broad peaks observed between 34 and 40°. The elimination of the 004 plane may be due to a disorder of the fibers, probably due to the decrease in the orientation of the fibers, since this plane is associated with ordered cellulose chains (French \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), as well as the elimination of the peak at 38° indicates a successful purification of the material. Another difference observed was the increase in intensity at 15.6° associated with the 110 plane (Poletto et al. 2013), indicating an ordering of the fibers and therefore, an increase in crystallinity in the cellulose fibers (CF) for the CNF sample. This change in crystallinity can be calculated using Eq.\u0026nbsp;1, where the crystallinity index for the CP and CNF are 78.6% and 93.3%, respectively, indicating an increase in the ordering of the FC for the CNF sample.\u003c/p\u003e\u003cp\u003eTo explain the structural differences between the synthesized materials, all samples were analyzed by\u003c/p\u003e\u003cp\u003eFTIR. The corresponding absorption bands are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eAssignment of bands observed in the FTIR spectrum for the cellulose and CNF samples.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIR Band [cm\u003csup\u003e− 1\u003c/sup\u003e]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAssignment\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eReference\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3300 (m)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eʋ OH\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e(Agrebi et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Ria et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Siddiqui et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2024\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2900 (w)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eʋ\u003csub\u003es\u003c/sub\u003e CH\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e(Agrebi et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Ria et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Siddiqui et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2024\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2560\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eH-O-H\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e(Barannik et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Krivoshein et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2022\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2200\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e(Barannik et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Krivoshein et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2022\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eH-O-H\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e(Barannik et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Krivoshein et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2022\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1600 (m)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eʋ COOH\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e(Agrebi et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Ria et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Siddiqui et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2024\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1420 (s)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eσ CH\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e(Agrebi et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Ria et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Siddiqui et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2024\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1040 (s)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(ʋ C-C)/(ʋ C-O)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e(Agrebi et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Ria et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Siddiqui et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2024\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e600 (s)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003csub\u003eoop\u003c/sub\u003e COOH\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e(Ria et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2022\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e\u003cp\u003eThe FTIR spectra were analyzed in two central regions: 4000–2000 cm⁻¹ (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea) and 2000–500 cm⁻¹ (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb), where the characteristic cellulose bands were identified in all samples (Agrebi et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Ria et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Siddiqui et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), although some notable differences were observed.\u003c/p\u003e\u003cp\u003eIn the range between 4000 and 2000 cm⁻¹ (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea), prominent bands appeared around 3300 cm⁻¹ and 2900 cm⁻¹, corresponding to hydroxy group stretching (ν OH) and methine group symmetric stretching (νs CH) vibrations, respectively. The unpurified cellulose (CNP) showed lower intensity and definition in these bands, probably due to the presence of contaminating residues from the precursors used in synthesis. In contrast, purified cellulose (CP), which was subjected to dialysis purification treatment and contaminant removal, exhibited a considerable increase in the intensity of these bands, particularly for the ν OH band. Compared to the CP sample, the FTIR spectrum of the CNFs showed a slight decrease in the intensity of the ν OH band, along with an increase in the intensity and greater definition of the ʋ\u003csub\u003es\u003c/sub\u003e CH band. These intensity changes are consistent with the TEMPO oxidation process, as the hydroxy group (-OH) present in the hydroxymethyl groups (–CH₂OH) is oxidized to a carboxy group (–COOH), thereby reducing the intensity of the ν OH band. Furthermore, this oxidation decreases the number of hydrogen bonds, thereby increasing the vibrational freedom of the methine group (CH) that remains in the cellulose structure (Soni et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eAdditional bands were observed at 2560, 2200, and 2000 cm⁻¹, attributed to absorbed water (H\u003csub\u003e2\u003c/sub\u003eO) at 2560 and 2000 cm⁻¹, and absorbed carbon dioxide (CO₂) at 2200 cm⁻¹ (Barannik et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Krivoshein et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). In the case of the cellulose spectra (CNP and CP), these bands were more intense than those in the CNF spectra, indicating a greater affinity for humidity and CO₂ in these samples. The increase in the intensity of the CP sample spectrum, relative to the CNP spectrum, may be due to the greater freedom of the functional groups resulting from the removal of impurities in the sample.\u003c/p\u003e\u003cp\u003eThe highest number of bands was identified in the fingerprint region between 2000 and 500 cm⁻¹ (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). The band near 1600 cm⁻¹, which corresponds to the stretching vibrations of the carboxy groups (ν COOH), showed a progressive increase in intensity throughout the CNF synthesis process, with the ν COOH band of the CNF sample being the most intense. This trend confirms the successful introduction of carboxy functionalities by the TEMPO oxidation method.\u003c/p\u003e\u003cp\u003eThe band at 1420 cm⁻¹, associated with the bending vibrations of methine groups (δ CH), showed increased intensity after purification of the CNP sample. However, a decrease was observed following TEMPO oxidation, likely due to partial degradation or modification of aliphatic chains during the oxidation process.\u003c/p\u003e\u003cp\u003eA prominent peak at 1040 cm⁻¹, assigned to carbon-carbon (ʋ C–C) and carbon-oxygen (ʋ C–O) stretching vibrations, corresponds to the backbone structure of cellulose. The low intensity observed in the CNP sample was likely due to contamination. In contrast, both CP and CNF samples exhibited similar band intensities, indicating that the cellulose backbone was preserved throughout the purification and oxidation processes.\u003c/p\u003e\u003cp\u003eFinally, the band at approximately 600 cm⁻¹, attributed to out-of-plane of carboxy groups (oop COOH), showed a marked increase in intensity in the CP and CNF spectra relative to CNP. This enhancement is associated with the removal of impurities, which facilitates more unrestricted movement of these functional groups. The further increase in CNF may result from reduced fiber dimensions, which enhance molecular flexibility and surface exposure.\u003c/p\u003e\u003cp\u003eThe FTIR results confirm the production and purification of cellulose as well as the functionalization of carboxy groups (–COOH) using the TEMPO oxidation method, thereby maintaining the structural integrity of the cellulose fibers (Thi Thanh Hop et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eFESEM was used to characterize the morphology and dimensions of the cellulose and CNF samples. The FESEM characterization (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) was performed using secondary electrons for all samples. The images obtained for the CNP samples (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea and 3a1) show the presence of fibers, as well as some material agglomerations. In the case of the images of the CP sample, which were subjected to the dialysis purification process (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb and 3b1), the CF could be observed clearly. However, taking a closer look at the sample (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb1), the presence of agglomerations was observed again, although in smaller quantities. In the case of the CNF samples (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec and 3c1), to observe the CNF, it was necessary to use higher magnification; however, due to their dimensions, it was impossible to perform adequate characterization. Nevertheless, an evident decrease in the dimension of the CF was observed.\u003c/p\u003e\u003cp\u003eTo determine the chemical composition of the agglomerations observed by FESEM, an EDS analysis was performed on each sample, with the results presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The results showed the presence of carbon (C), oxygen (O), sodium (Na), and chlorine (Cl). The presence of C and O in all samples corresponds to the elements from which cellulose is made. In contrast, the presence of Na and Cl is consistent with the chemical composition of the chemical precursors used during the synthesis, so they were classified as contaminants. These contaminating elements precipitated on the CF in the form of NaCl crystals, which were removed after each washing process. The presence and decrease in the percentage by weight of Na and Cl in the samples, after a purification process and the production of CNF, corroborated the results obtained by XRD (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eEDS results in % mass and % atomic of the cellulose and CNF samples.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eSample\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e\u003cp\u003eElement % by Mass\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eC\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eO\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNa\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eCl\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCNP\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e24.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e26.13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e26.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e23.52\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCP\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e26.81\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e30.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCNF\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e64.78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e35.22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cb\u003eSample\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e\u003cp\u003e\u003cb\u003eElement % by Atomic\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eC\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003eO\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eNa\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eCl\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCNP\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e37.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e30.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e20.69\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e12.11\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCP\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e73.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e25.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCNF\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e71.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e28.91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e\u003cp\u003eAFM characterized the dimensions and morphology of the CNF. AFM micrographs (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) showed the fibrous morphology of the CNF, as well as segregation and low ordering of the fibers. Although the CNF samples were not used in film form, the film formed on the surface of the glass substrates exhibited a surface roughness with a mean surface roughness (RMS) value of ~ 10 nm, indicating a relatively smooth structure with slight height variations. When measuring the length of the CNF, an average length of ~ 0.9 µm was obtained (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb), confirming the 1D nanometric morphology.\u003c/p\u003e\u003cp\u003eBy reducing the measurement scale (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec), the height profile between the carbon fiber edges yielded an average height of ~ 20 nm. In comparison, cross-sectional measurements revealed an average thickness of ~ 50 nm (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed). Once the production of cellulose and carbon fibers was confirmed, SA sorption tests were performed on the CP and CNF samples, since contaminants present in the CNP sample could affect the measurements.\u003c/p\u003e\u003cp\u003eThe UV-Vis spectra obtained from the SA absorption tests for the CP and CNF samples are shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, respectively. When analyzing the UV-Vis spectra from the absorption tests of the SA solutions in contact with the CP samples (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e), all the characteristic SA bands were observed in the wavelength range from 190 to 400 nm, with absorption bands at 201, 230, and 295 nm, corresponds to electronic transitions within the aromatic ring, to the conjugation between the aromatic ring and the carboxy group (–COOH), and associated with n → π* transitions in the oxygen of the phenolic or hydroxy group respectively (Abounassif et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1994\u003c/span\u003e; Trivedi et al. \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), where the most intense band was observed at 201 nm with an absorbance of 0.36 for a concentration of [10 µM]. The absorption band at 201 nm was initially used to measure the AS absorption process. However, during the first 24 hours of the absorption test, a progressive increase in the intensity of the 201 nm band was observed, which subsequently decreased in intensity until an absorbance similar to that obtained during the first 0.25 hours of the absorption test was reached.\u003c/p\u003e\u003cp\u003eIn the case of the UV-Vis spectra of the SA solution that was in contact with the CNF sample (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e), a slight increase in the absorptivity could be observed, which was maintained during the first nine hours of the test, from then on the intensity of the absorptivity band began to decrease until after 48 hours where the band of the AS solutions became similar to the CNF solution.\u003c/p\u003e\u003cp\u003eThe increased band intensity at 201 nm could be attributed to the presence of oligosaccharides, quinones, or carboxylic acids formed during the cellulose purification process. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e illustrates the possible mechanism of cellulose purification, where the hydroxy groups (-OH) interact with the aromatic rings, thereby fragmenting the cellulose chain. Likewise, the presence of hypochlorous acid breaks the rings and forms quinones and carboxylic acids (Cannella et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Billès et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Mankar et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThese compounds were retained in the cellulose solution because, during the dialysis purification process, only small molecules or ions, such as sodium ion (Na\u003csup\u003e+\u003c/sup\u003e) and chloride ion (Cl\u003csup\u003e−\u003c/sup\u003e), are removed. Therefore, soluble fragments can absorb or interact with the AS molecule in regions smaller than 210 nm due to electronic transitions such as σ→σ* and n→σ* associated with interactions from Carbon–Oxygen or carbonyl (-C = O) bonds (Yu et al. \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e1983\u003c/span\u003e), present in all the fragmenting chain compounds, and therefore see this increase in the band without any other process involved.\u003c/p\u003e\u003cp\u003eTo determine the percentage removal by CP and CNF, a % absorption graph was used (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e), following the absorption bands at 201 nm (Figs.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea and \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec) and 296 nm (Figs.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb and \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ed). When analyzing the % removal of the CP sample, following the band at 201 nm (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea), the effect of the interaction of the compounds formed during the cellulose purification process can be observed. Instead of obtaining a % removal, negative values are observed, indicating the presence of a greater amount of AS than at the beginning of the test. Similarly, it was observed that even when following the intensity of the band at 296 nm (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb), there is an effect of the interaction of the AS with the compounds formed during the cellulose purification process, albeit at a lower intensity.\u003c/p\u003e\u003cp\u003eIn the case of the CNF samples, the interaction of the compounds released from the CNF with salicylic acid was also observed when monitoring the absorption band at 201 nm; however, this interaction was of lower intensity when monitoring the band at 296 nm (Figs.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec and \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ed, respectively). Despite this effect, absorption efficiencies of approximately 50% and 90% were observed following the 201 nm and 296 nm bands, respectively. These values are comparable to those obtained with advanced materials and techniques reported in the literature (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Compared to these approaches, TEMPO-oxidized nanocellulose demonstrated competitive efficiency by relying on a low-cost, renewable, and natural biomass precursor. This highlights CNF as a sustainable alternative that combines high performance with environmental and economic benefits, although the observed interferences during monitoring may underestimate its current adsorption capacity.\u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSalicylic acid removal table carried out with other elimination techniques and materials.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMaterial\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAmount of material/Volume of solution\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e[SA]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e% Removal\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eEquilibrium\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eReferences\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eUV/O₃\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1000 mL\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e70 µM\u003c/p\u003e\u003cp\u003e140 µM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026gt; 50%\u003c/p\u003e\u003cp\u003e\u0026gt; 80%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1 min\u003c/p\u003e\u003cp\u003e10 min\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e(Jing et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2020\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCopolymer (βCD_BDE_Q⁺)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e25 mg/25 mL\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e70 µM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e90%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e120 min\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e(Cecone et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2023\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMagnetic Ferrite Mg₀.₂Zn₀.₈Fe₂O₄\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10 mg/5 mL\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1 µM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e90%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e≈ 24h\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e(Tatarchuk et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2020\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMicroalgae \u003cem\u003eChlorella sorokiniana\u003c/em\u003e (CS), \u003cem\u003eChlorella\u003c/em\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003evulgaris\u003c/em\u003e (CV) \u003cem\u003eand Scenedesmus obliquus\u003c/em\u003e (SO)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.5 g/250 mL\u003c/p\u003e\u003cp\u003e0.75 g/250 mL\u003c/p\u003e\u003cp\u003e1.0 g/250 mL\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e≈ 180 µM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCS ≈ 40%\u003c/p\u003e\u003cp\u003eCV ≈ 25%\u003c/p\u003e\u003cp\u003eSO \u0026gt; 90%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e144h\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e(Escapa et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2024\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCarbon xerogel with ZnO/CuₓO (UV/O₃ solar)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e100 mg/500 mL\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e70 µM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026gt; 70%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e300 min\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e(de Moraes et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2023\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTitanium with nanoparticles\u003c/p\u003e\u003cp\u003e(FeTiO2, AgTiO2) UV-radiation\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e700 mg/700 mL\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e30 µM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eAgTiO2 \u0026lt; 2.0%\u003c/p\u003e\u003cp\u003eFeTiO2 ≈ 10%\u003c/p\u003e\u003cp\u003eTiO2 Commercial ≈ 50%\u003c/p\u003e\u003cp\u003eTiO2 synthetized \u0026gt; 90%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e120 min\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e(Santamaría et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2020\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e\u003cp\u003eTo corroborate the absorption process by the CNFs, the CP and CNF samples that were in contact with the SA solutions were filtered and dried for FTIR analysis. Figure\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e shows the FTIR spectra of the CP samples before and after the absorption tests (Figs.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ea and \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ec, respectively), as well as the FTIR spectra of the CNF samples before and after the absorption tests (Figs.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eb and \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ed, respectively). Analyzing the spectra of the CP sample, it can be seen that all the bands appear to have the same intensity, except the ν OH, (ʋ C–C)/(ʋ C–O), and oop COOH bands. In contrast, the CNF sample showed an increase in intensity in all bands characteristic of cellulose. These results demonstrate that both CP and NFC interact with SA, although the interaction is much more evident in the case of NFC. The changes in the bands suggest the presence of hydrogen bonding and weak electrostatic interactions, particularly with the oxygenated functional groups of SA.\u003c/p\u003e\u003cp\u003eTo explain this effect of absorption by CNFs, the surface chemical differences between the samples were analyzed using X-ray photoelectron spectroscopy (XPS). The spectra were calibrated using the adventitious carbon at 285.2 eV; the results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e.\u003c/p\u003e\u003cp\u003eIn the C1s region (Figs.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ea and \u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ec), the CP and CNF samples exhibited five distinct peaks at 283.9, 285.2, 286.4, 287.9, and 289.3 eV. These peaks were assigned to C–H/C–C (aliphatic carbon), C–O (alcohol/ether carbon), C = O (carbonyl carbon), and O–C = O (carboxy/ester carbon), respectively. These assignments are consistent with previous reports (López et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e1991\u003c/span\u003e; Haensel et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Gerullis et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn the case of the CP sample spectrum (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ea), it was observed that all samples presented a relatively high signal intensity, as well as the presence of signals at high binding energy levels such as COOH and C = O. The presence of these last peaks suggests the presence of surface impurities or residual lignin-like structures that contribute to the increase in the aliphatic carbon signal.\u003c/p\u003e\u003cp\u003eIn contrast, the CNF sample (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ec) showed a reduction in the intensity of the C-H and the C-OH peak, indicating that a significant portion of the hydroxy and aliphatic groups were oxidized. A slight decrease in the intensity of the COOH peak was also observed, which can be attributed to the redistribution of the carboxy groups over the cellulose chain, potentially making them less detectable by XPS analysis. Additionally, the C = O peak remained approximately constant in intensity but became broader, suggesting the formation of diverse oxidized carbon resulting from the TEMPO oxidation method.\u003c/p\u003e\u003cp\u003eIn the O1s region (Figs.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003eb and \u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ed), both the CP and CNF samples exhibited five distinct peaks centered at 530.0, 531.4, 532.6, 533.8, and 535.3 eV. These peaks were assigned to O–C = O (carboxyl oxygen), C = O (carbonyl oxygen), C–O (ether/alcohol oxygen), C–OH (hydroxyl oxygen), and adsorbed H₂O, respectively. The presence of these signals in both samples is consistent with the typical oxygen-containing functional groups in polysaccharide structures. Cellulose inherently contains a high density of C–O and C–OH bonds due to its backbone. At the same time, minor signals of C = O and COOH may arise from oxidation during processing or from residual hemicelluloses or lignin fragments.\u003c/p\u003e\u003cp\u003eIn the CNF sample (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ed), a pronounced increase in the intensity of the COOH peak (Jin et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) was observed, indicating the successful formation of carboxylic groups as a result of the TEMPO oxidation. Simultaneously, the intensity of the C–O peak decreased, suggesting a conversion into carboxy groups or removal during the purification steps. The other peaks, associated with C = O, C–OH, and H₂O, remained present in both samples, reflecting the persistent presence of oxygen functionalities and bound or adsorbed water molecules on the hydrophilic cellulose surface.\u003c/p\u003e\u003cp\u003eAll the spectral changes observed in the CNF sample confirm the successful surface oxidation of cellulose, increasing the density of carboxy functional groups and enhancing the material’s potential for the elimination of salicylic acid from water.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThe results confirmed the production of purified cellulose (CP) and cellulose nanofibrils (CNF) by the TEMPO oxidation process. The CNF exhibited higher crystallinity, more defined functional groups, and a nanometric size, which are favorable characteristics for adsorption. SA adsorption tests demonstrated the efficiency of the CNFs compared to CP. However, we also recognize limitations, such as interferences that occurred during UV-Vis monitoring, as well as the required conditions under which the experiments were performed. For this reason, future work should focus on regeneration, reuse, and testing in real-world wastewater matrices.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eDeclaration of authorship contribution.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eB. Portillo-Rodr\u0026iacute;guez\u003c/strong\u003e: Writing, Review and Editing, Resources, Project Management, Methodology, Research, Formal Analysis, Conceptualization. \u003cstrong\u003eE.M. Barrera-Rend\u0026oacute;n\u003c/strong\u003e: Resources, Methodology, Formal Analysis, Conceptualization. \u003cstrong\u003eD. A. Sol\u0026iacute;s-Casados\u003c/strong\u003e: Writing, Review and Editing, Resources, Methodology, Research, Conceptualization. \u003cstrong\u003eL. Escobar-Alarc\u0026oacute;n\u003c/strong\u003e: Writing, Review and Editing, Resources, Research, Conceptualization.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunds.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was funded by the Postdoctoral Stays for Mexico grant from the Secretar\u0026iacute;a de Ciencia, Humanidades, Tecnolog\u0026iacute;a e Innovaci\u0026oacute;n (SECIHTI).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of conflicts of interest.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known financial conflicts of interest or personal relationships that could have influenced the work presented in this article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank LIA Citlalit Mart\u0026iacute;nez Soto, M. in C. Alejandra N\u0026uacute;\u0026ntilde;ez, M. in C. Lizbeth Triana, M. in C. Melina Tapia, M. in C. Nieves Zavala, Dr. Diego Mart\u0026iacute;nez, Dr. Ubaldo Hern\u0026aacute;ndez, and M. in C. Dafne Larissa Ortega Sol\u0026iacute;s for their technical assistance. Benjam\u0026iacute;n Portillo thanks SECIHTI for the postdoctoral fellowship 722355.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAbounassif MA, Mian MS, Mian NAA (1994) Salicylic acid. Anal Profiles Drug Subst Excipients 23:421\u0026ndash;470. https://doi.org/10.1016/S0099-5428(08)60609-7\u003c/li\u003e\n\u003cli\u003eAgrebi F, Ghorbel N, Bresson S, et al (2019) Study of nanocomposites based on cellulose nanoparticles and natural rubber latex by ATR/FTIR spectroscopy: The impact of reinforcement. Polym Compos 40:2076\u0026ndash;2087. https://doi.org/10.1002/pc.24989\u003c/li\u003e\n\u003cli\u003eAwad N, Vega-Est\u0026eacute;vez S, Griffiths G (2020) Salicylic acid and aspirin stimulate growth of Chlamydomonas and inhibit lipoxygenase and chloroplast desaturase pathways. 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J Environ Chem Eng 9:106259. https://doi.org/10.1016/j.jece.2021.106259\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":"Saragassum, absorption, salicylic acid, cellulose, cellulose nanofibril","lastPublishedDoi":"10.21203/rs.3.rs-7336812/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7336812/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis work presents the extraction of cellulose from Sargassum and its subsequent conversion into cellulose nanofibril (CNF) using the TEMPO oxidation method. Structural and surface characterizations (XRD, FTIR, FESEM, EDS, AFM, and XPS) confirmed the synthesis, purification, and functionalization of CNF. Compared to purified cellulose (CP), the CNF exhibited higher crystallinity and significantly higher functionalization, particularly with carboxy groups. These carboxy groups played a crucial role in the interaction between cellulose fibers and salicylic acid. UV-Vis and FTIR analyses confirmed the removal of salicylic acid (SA) from water, with only CNF demonstrating effective absorption. UV-Vis analysis showed increased absorption at wavelengths\u0026thinsp;\u0026lt;\u0026thinsp;250 nm due to interactions between cellulose fragments and SA. To avoid this interference, the adsorption efficiency was determined following the band at 296 nm, where 90% removal of salicylic acid was achieved after 48 h. These findings suggest that NFC from waste biomass is a promising material for water remediation.\u003c/p\u003e","manuscriptTitle":"TEMPO-Oxidized Nanocellulose from Sargassum as a Sustainable Material for the Removal of Salicylic Acid in Water","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-28 16:24:50","doi":"10.21203/rs.3.rs-7336812/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":"8875cccd-15fc-47a7-9b1f-b3a225d82d33","owner":[],"postedDate":"October 28th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-10-28T17:33:41+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-28 16:24:50","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7336812","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7336812","identity":"rs-7336812","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}