Oxidative Transformation of Sugarcane Bagasse by Plasma-Activated Water

Oxidative Transformation of Sugarcane Bagasse by Plasma-Activated 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 Oxidative Transformation of Sugarcane Bagasse by Plasma-Activated Water Confidence Chinechectam Uzoma, Brenda Freires Ferreira, Maria Girlânia Freires Matos, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9117765/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 study investigates the interaction between plasma-activated water (PAW) and sugarcane bagasse (SCB), focusing on the chemical effects of reactive oxygen and nitrogen species generated during plasma–liquid interactions on lignocellulosic biomass. Initially, atmospheric cold plasma was employed as a strategy for the direct and indirect activation of SCB aiming at improving its performance in the removal of methyl orange from aqueous solutions. Direct activation was performed by exposing SCB to a helium plasma jet, while indirect activation involved treating deionized water with the plasma jet under two configurations: plasma exposure at the liquid surface and plasma treatment with gas bubbling, generating PAW with different chemical reactivities. Unexpectedly, the results indicated that PAW did not significantly enhance the dye removal capacity of the biomass. Instead, spectroscopic analyses revealed that reactive species dissolved in PAW promoted oxidation, fragmentation, and partial solubilization of lignocellulosic components, particularly lignin-derived aromatic structures. UV–Vis measurements of the liquid phase suggested the release of soluble organic compounds from the biomass, indicating chemical modification of the lignocellulosic matrix. These findings demonstrate that PAW acts not only as an oxidizing medium for pollutant degradation but also as an effective agent for the chemical pretreatment of lignocellulosic biomass. The observed oxidative transformation of SCB suggests potential applications of plasma-activated water in biomass processing and pretreatment strategies relevant to emerging biorefinery concepts. This study therefore provides new insights into plasma–biomass interactions and highlights the versatility of plasma-liquid systems for sustainable biomass valorization. plasma-activated water lignocellulosic biomass sugarcane bagasse plasma–liquid interaction biomass pretreatment Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction The increasing generation of agro-industrial residues and the contamination of water bodies by organic pollutants represent significant environmental challenges associated with the current industrial production model [ 1 ]. In the Brazilian context, the sugarcane agro-energy sector stands out not only for its economic relevance but also for the large volume of sugarcane bagasse (SCB) generated as a by-product, whose destination remains largely restricted to combustion for energy cogeneration or low value-added disposal [ 2 ]. The valorization of this abundant and renewable lignocellulosic residue is therefore strategic for mitigating environmental impacts and fostering practices aligned with the principles of the circular economy. In parallel, synthetic dyes such as methyl orange are widely used in the textile, food, and chemical industries and are frequently detected in industrial effluents. Even at low concentrations, these compounds can cause adverse aesthetic, ecological, and toxicological effects, in addition to exhibiting high chemical stability, which hinders their degradation by conventional wastewater treatment processes[ 3 ]. In this context, the development of sustainable, efficient, and low-cost materials for the removal of such contaminants has attracted considerable research interest. State-of-the-art studies identify lignocellulosic agro-industrial residues, such as SCB, as promising candidates for adsorption-based pollutant removal due to their porous structure, relatively high surface area, and the presence of functional groups such as hydroxyl, carboxyl, and phenolic moieties [ 4 , 5 ]. Several modification strategies have been explored to enhance the affinity of these materials for dissolved organic species, including chemical (acidic, alkaline, and oxidative), thermal, and biological treatments. However, many of these approaches involve aggressive reagents, multiple processing steps, the generation of secondary effluents, and increased operational costs, which limit their large-scale applicability[ 6 , 7 ]. These drawbacks highlight the need for alternative surface activation routes that are efficient, clean, and compatible with natural matrices. In this context, atmospheric cold plasma has emerged as a promising technology for material processing and surface modification. Plasma–liquid interactions are known to generate a variety of reactive oxygen and nitrogen species (RONS), including hydrogen peroxide, hydroxyl radicals, nitrites, and nitrates. When dissolved in water, these species produce plasma-activated water (PAW), a chemically reactive medium capable of inducing oxidation reactions in organic compounds. Because of its high oxidative potential and absence of chemical additives, PAW has attracted increasing interest for applications in environmental remediation, agriculture, and biomass processing [ 8 , 9 ]. Plasma–surface interactions lead to the generation of reactive species, low-intensity UV radiation, and transient electric fields, which can introduce oxygen-containing functional groups, induce mild surface etching, and increase wettability and surface energy without the use of additional chemical reagents [ 9 – 11 ]. Beyond surface activation, recent studies have also demonstrated that reactive species generated in plasma–liquid systems can interact with complex biopolymers, promoting oxidative modification of lignocellulosic structures. In particular, reactive oxygen species are capable of oxidizing phenolic groups and cleaving ether linkages in lignin, leading to partial depolymerization and solubilization of aromatic fragments[ 12 – 15 ]. Such processes are of particular interest in the context of lignocellulosic biomass pretreatment, a key step in emerging biorefinery strategies aimed at improving the accessibility of cellulose and hemicellulose for subsequent conversion processes [ 16 ]. Therefore, plasma-based approaches may simultaneously contribute to environmental remediation and biomass valorization. Accordingly, the activation of SCB by atmospheric cold plasma—either through direct exposure or via plasma-activated water—was initially expected to generate more reactive and functionalized surfaces capable of enhancing the removal of organic dyes from aqueous solutions. However, the interaction between PAW and lignocellulosic biomass may also induce oxidative transformations within the lignin–carbohydrate matrix, potentially leading to structural modification and partial solubilization of biomass components. Experimental Setup and Methods Optical Characterization of the Plasma An experimental setup was assembled for the electrical and optical characterization of the plasma. For each technological application, the voltage, current, frequency, and applied power used to generate the plasma were monitored with the aid of an oscilloscope. Plasma active species were also monitored using an optical emission spectrometer (OES) operating in the spectral range from 200 to 1100 nm. Optical emission was collected and transmitted to the optical emission spectrometer (USB Ocean Optics, SpectraSuite, USA). The acquired spectra were analyzed by evaluating the relative intensities of the detected species. The emission peaks corresponding to the identified species were compared with atomic transition data available in the database of the National Institute of Standards and Technology (NIST)[ 17 ]. SCB Activation Plasma activation was carried out using an adjustable high-frequency (25–45 kHz) and high-voltage (0–20 kV) power supply. The high-voltage (HV) source was connected to a stainless-steel tube positioned inside a glass tube, while a grounded metallic ring was fixed to the outer surface of the glass tube, configuring a dielectric barrier discharge (DBD) arrangement (Fig. 1 A). A continuous flow of helium was guided through the stainless-steel tube and, upon exiting the nozzle region, was subjected to the electric discharge established between the inner electrode and the grounded ring, resulting in the formation of a stable atmospheric cold plasma jet used for surface activation of the samples. For direct activation, a helium plasma jet with a flow rate of 1 L·min⁻¹ was applied directly onto the SCB surface (Fig. 1 B). For indirect activation, deionized water was first treated by plasma and subsequently applied to the BCA. In each indirect activation procedure, 15 mL of deionized water was exposed to a helium plasma jet for 10 min (10 kV, 26.3 kHz) under two different configurations: plasma treatment at the liquid surface in a Petri dish (Fig. 1 C) and plasma treatment via gas bubbling, achieved by inserting a tube connected to the plasma jet into the liquid at a flow rate of 1 L·min⁻¹ (Fig. 1 D). The sugarcane bagasse (SCB) was obtained as a residue from sugarcane juice extraction. Initially, the material was thoroughly washed with deionized water to remove soluble impurities and residual sugars, followed by drying in an oven at 60°C until constant mass. The dried material was then ground using a knife mill and sieved through a set of standardized sieves. The particle size fraction between 65 and 100 mesh was selected for the experiments in order to ensure sample homogeneity. For each treatment condition, 50 mg of SCB were accurately weighed. The samples were then subjected to different activation procedures involving direct plasma exposure or indirect treatment using plasma-activated water (PAW). The experimental conditions are summarized in Table 1 . Table 1 Experimental conditions for plasma activation of SCB Condition Description of treatment Control 50 mg of SCB soaked with one drop of deionized water DA (Direct Activation) 50 mg of SCB directly exposed to plasma and subsequently soaked with one drop of deionized water ISA (Indirect Surface Activation) 50 mg of SCB soaked with one drop of plasma-activated water produced by plasma interaction at the liquid surface (PAW-S) IBA (Indirect Bubble Activation) 50 mg of SCB soaked with one drop of plasma-activated water produced by plasma bubbling through the liquid (PAW-B) Analysis of Plasma-Activated Water (PAW) The concentrations of reactive species NO₂⁻, NO₃⁻, and H₂O₂ in deionized water and plasma-treated water were evaluated by qualitative UV–Vis spectroscopic analysis using a Thermo Scientific GENESYS 180 Spectrophotometer, operating in the wavelength range of 190–800 nm. This approach is widely employed to identify plasma-generated reactive species in aqueous media, as these compounds exhibit characteristic absorption bands in the ultraviolet region[ 18 – 20 ]. All measurements were performed using quartz cuvettes with an optical path length of 10 mm. Influence of BCA on Methyl Orange Degradation Three working dye solutions (WDS) were prepared to assess the effect of plasma activation on dye degradation. P1 was obtained by diluting 1 mL of WDS in 19 mL of deionized water; P2 by diluting 1 mL of WDS in 19 mL of plasma-activated water produced by surface treatment (PAW-S); and P3 by diluting 1 mL of WDS in 19 mL of plasma-activated water produced by gas bubbling (PAW-B). The influence of SCB in different activation states—control, DA, ISA, and IBA—was subsequently evaluated by incorporating the material into the dye solutions to obtain filtrate samples. Four experimental systems were prepared, each with a total volume of 20 mL: F1, filtrate from untreated BCA in P1; F2, filtrate from DA-treated BCA in P1; F3, filtrate from ISA-treated BCA in P2; and F4, filtrate from IBA-treated BCA in P3. All suspensions were stirred for 30 min to ensure sufficient contact between the dye solution and the solid phase. The solid material was then removed by filtration, and the UV–Vis spectra of the filtrates were recorded using deionized water as the blank. All measurements were performed under identical optical path length and spectral range conditions to ensure consistency and comparability. Fourier-transform infrared (FTIR) spectra were collected using an Agilent Cary 630 spectrometer equipped with an attenuated total reflectance (ATR) accessory with a diamond crystal and ZnSe optics. Measurements were carried out in the 4000–650 cm⁻¹ spectral range with a resolution of 4 cm⁻¹, averaging eight scans per sample at room temperature. Results and Discussions Optical Characterization of the Plasma Jet The optical emission spectrum (OES) exhibited a prominent peak at approximately 588 nm, attributed to the He I transition, indicating the occurrence of excitation processes driven by electron–helium collisions within the discharge. Additional emission bands observed in the 350–434 nm region were assigned to molecular nitrogen species, corresponding to the second positive (C³Π u → B³Πg) and first negative (B²Σ u ⁺ → X²Σg⁺) systems of N₂/N₂⁺, in agreement with spectra typically reported for atmospheric-pressure helium plasmas in the literature [ 21 ]. In the spectral region above 657 nm, several bands were attributed to the first positive system of N₂ (B³Πg → A³Σ u ⁺), except for the emissions at 706 nm and 777 nm, which were associated with the He I and O I transitions, respectively. In addition, the emission line observed around 656 nm was attributed to the Hα transition of the Balmer series of atomic hydrogen, as commonly reported in optical emission spectroscopy studies of atmospheric-pressure plasmas [ 22 ]. The presence of these excited and ionized species indicates the generation of reactive oxygen and nitrogen species (RONS) during the discharge, which can interact with the surrounding air, with water, or directly with solid surfaces [ 23 – 26 ]. In the case of lignocellulosic solid surfaces, such interactions promote surface oxidation processes, resulting in chemical modifications in the outermost layers of the material[ 16 ]. Under the direct activation (DA) mechanism, plasma-generated reactive species interact directly with the surface of SCB, inducing chemical modifications subsequently identified by FTIR analysis. In contrast, during indirect activation, these species dissolve in water during plasma treatment, leading to the formation of plasma-activated water (PAW) enriched with oxidizing agents, such as oxygen- and nitrogen-based species[ 27 ]. These species present in PAW subsequently interact with the SCB surface, promoting chemical modifications similar to those observed under direct activation conditions. Physicochemical Analysis and Reactive Species of PAW The analysis of reactive species was also carried out by UV–Vis spectroscopy[ 18 , 28 ]. The UV–Vis absorption spectra of deionized water (H₂O-DI) and plasma-activated water obtained by surface treatment (PAW-S) and gas bubbling (PAW-B) reveal significant differences in the ultraviolet region (Fig. 3 ). While H₂O-DI exhibits virtually no absorption over the entire analyzed spectral range, the PAW samples display intense absorption bands below 250 nm, indicating the formation of plasma-induced reactive chemical species. The strong absorption observed in the 190–230 nm range is characteristic of nitrate (NO₃⁻), whose π→π* electronic transition typically shows a maximum around 200–205 nm[ 29 – 31 ]. The higher intensity of this band in the PAW-S sample indicates a greater concentration of oxidized nitrogen species when activation occurs at the plasma–liquid interface, a condition that favors the incorporation of gaseous nitrogen oxides (NOₓ) into the aqueous medium. This behavior is consistent with the increased direct exposure of the liquid surface to plasma-generated reactive species. In addition, contributions in the 210–230 nm region may be associated with the presence of nitrite (NO₂⁻), which exhibits weaker and broader absorption in this spectral range[ 32 ]. Although the overlap between nitrate and nitrite bands hinders their quantitative discrimination by UV–Vis spectroscopy alone, the broadening and asymmetry of the absorption profile suggest the coexistence of both species, particularly in the plasma-activated samples. The presence of hydrogen peroxide (H₂O₂) may also contribute to absorption in the deep-UV region [ 29 , 33 , 34 ]. Consistent reports in the literature associate absorption bands in the ≈ 260–280 nm region with hydrogen peroxide in aqueous solutions, attributed to the n→σ* electronic transition of the O–O bond [ 29 , 34 , 35 ]. This result can be understood in terms of the different mechanisms governing the generation and consumption of reactive species under the two activation configurations. During bubbling, excited species and radicals produced in the plasma interact directly with the liquid bulk, favoring recombination reactions of hydroxyl radicals (•OH) that lead to H₂O₂ formation[ 33 ]. Moreover, the reduced direct exposure of the liquid surface to gaseous nitrogen oxides limits strong acidification of the medium, which can enhance hydrogen peroxide stability and reduce its decomposition. In contrast, under surface-treatment conditions (PAW-S), although there is greater incorporation of reactive nitrogen species such as nitrate and nitrite, the more oxidizing and acidic environment tends to promote competitive reactions that consume H₂O₂, including nitrogen-species-catalyzed decomposition or conversion into secondary products[ 33 , 34 , 36 ]. This explains the absence of a discernible absorption peak above 250 nm in this sample, despite the higher absorbance observed in the deep-UV region. Thus, the exclusive presence of the absorption band above 250 nm in PAW-B reinforces that the plasma activation mode not only affects the total amount of reactive species generated but also significantly alters their predominant chemical nature. While surface activation favors the formation of oxidized nitrogen species, bubbling proves to be more efficient for the generation and stabilization of H₂O₂, which may be decisive for specific PAW applications, particularly those that rely on controlled oxidative potential and the prolonged action of hydrogen peroxide. UV–Vis analysis of dye solutions The UV–Vis absorption spectra of solutions P1 (dye in deionized water), P2 (dye in plasma-activated water obtained by surface treatment, PAW-S), and P3 (dye in plasma-activated water obtained by gas bubbling, PAW-B) reveal clear differences in both the ultraviolet and visible regions, reflecting the effect of plasma activation on the chemical stability of the dye. Sample P1 exhibits an intense absorption band in the deep-UV region, with a maximum around 200 nm and a shoulder near 280 nm. These bands are attributed to π → π* electronic transitions associated with aromatic rings and unsaturated groups present in the molecular structure of the dye[ 37 ]. A distinct absorption band appears in the visible region, with a maximum at 464 nm, corresponding to the dye’s conjugated chromophoric system. In contrast, samples P2 and P3 show a significant reduction in the intensity of this visible band, indicating partial degradation of the chromophore upon contact with plasma-activated water. The more pronounced decrease in absorbance observed for P3 suggests a higher oxidative efficiency of PAW-B, consistent with the greater incorporation of reactive species into the aqueous medium during the bubbling process. In the deep-UV region (≈ 200 nm), a marked increase in absorbance is observed for samples P2 and P3 compared to P1. This behavior is attributed to the presence of reactive species such as NO₃⁻, NO₂⁻, and H₂O₂, as discussed previously. Between 250 and 350 nm, subtle spectral differences among the samples indicate the coexistence of degradation intermediates and nitrogen-containing species, reinforcing that dye degradation proceeds progressively through disruption of the conjugated system and the formation of less complex compounds. Overall, the UV–Vis results demonstrate that plasma-activated water exhibits sufficient oxidative capacity to promote the initial degradation of the dye already during the solution preparation stage, with this effect being more pronounced under the bubbling condition. These findings corroborate the role of PAW as an active agent in the chemical modification of organic pollutants, supporting its application as a preliminary or complementary step in contaminant removal and wastewater treatment processes, as well as in the chemical activation of lignocellulosic materials such as SCB. Analysis of plasma-activated SCB samples The Control, DA, ISA, and IBA samples were analyzed by FTIR immediately after treatment (Fig. 4 ). In the O–H stretching region (3600–3000 cm⁻¹), all samples exhibit a broad band characteristic of hydroxyl groups associated with cellulose, hemicellulose, and lignin [ 8 , 38 , 39 ]. However, the ISA and IBA samples show increased intensity and band broadening, with a more pronounced effect for the IBA configuration. This behavior indicates an increase in the density of polar groups and hydrogen-bonding capacity, associated with the incorporation of reactive oxygen-containing species generated during plasma treatment [ 39 ]. The bands attributed to C–H stretching vibrations of –CH₂ and –CH₃ groups (3000–2800 cm⁻¹) display a relative decrease in intensity in the plasma-treated samples, particularly those subjected to PAW activation (ISA and IBA). This reduction suggests partial oxidation of aliphatic chains and possible removal of amorphous, carbon-rich components, resulting from plasma-induced chemical and structural reorganization of the SCB surface[ 4 , 6 ]. In the 1750–1600 cm⁻¹ region, the FTIR spectra reveal clear differences between SCB immersed in deionized water (Control) and that treated with plasma-activated water (PAW), indicating modifications in functional groups associated with C = O and C = C bonds, which are typical of plasma-induced surface oxidation processes[ 40 , 41 ]. For the control sample, a weak band is observed around 1730 cm⁻¹, attributed to the C = O stretching of ester and acetyl groups of hemicellulose, as well as a stable band between 1650–1600 cm⁻¹, associated with the aromatic C = C vibrations of lignin, indicating that the treatment essentially promotes physical hydration, without significant chemical modifications of the lignocellulosic matrix [ 38 , 39 ]. In contrast, the bagasse soaked in plasma-activated water (PAW) shows an increase in intensity and broadening of the band at ~ 1730–1715 cm⁻¹, indicating the formation of new carbonyl groups resulting from oxidative processes[ 38 , 42 ]. These changes are attributed to the action of reactive species dissolved in PAW, such as H₂O₂, •OH, and reactive nitrogen species, formed during the plasma–water interaction, which promote the oxidation of cellulose hydroxyl groups and lignin side chains[27, 43]. Concomitant modifications in the 1650–1600 cm⁻¹ region suggest partial oxidation of lignin and an increased contribution of strongly bound water, reflecting the enhanced surface polarity of the material[ 38 ]. These results confirm that, unlike deionized water, PAW promotes effective oxidative functionalization of the sugarcane bagasse surface, in agreement with studies reporting plasma-induced chemical modifications in lignocellulosic materials, resulting in increased hydrophilicity and surface reactivity[ 42 ]. UV–Vis analysis of the filtrates after interaction with activated SCB The analysis of the filtrates was used to study the effect of SCB plasma activation on removal and/or dye degradation efficiency when SCB (plasma activated or not) is mixing with a solution containing water deionized or plasma-activated water (PAW) (Fig. 6 ). The samples F1, filtrate from untreated BCA in P1; F2, filtrate from DA-treated BCA in P1; F3, filtrate from ISA-treated BCA in P2; and F4, filtrate from IBA-treated BCA in P3. Comparing the spectra obtained for P1, P2, and P3 in the absence of SCB (Fig. 4 ), a substantial increase in absorbance is observed in the 200–260 nm range, with intensities approximately 4–6 times higher. This increment cannot be explained solely by the presence of inorganic species generated by the plasma, such as NO₃⁻, NO₂⁻, and H₂O₂, since these species are also present in the system without SCB and, individually, do not account for the magnitude of the observed increase. The introduction of SCB significantly alters the chemical composition of the medium, indicating that the lignocellulosic material does not act merely as an adsorptive phase but also as a source of UV-active organic compounds. Under the action of reactive oxygen and nitrogen species (RONS) formed in the plasma, structural components of the bagasse — particularly lignin — undergo oxidation, fragmentation, and solubilization processes. These reactions may release phenolic compounds, partially oxidized aromatic structures, quinones, and low-molecular-weight organic acids, all of which are characterized by strong absorption in the deep UV region[39, 44, 45]. In particular, lignin exhibits pronounced absorption bands below 280 nm, associated with π→π* electronic transitions in conjugated aromatic systems. Oxidation of these structures tends to broaden and intensify absorption in this region, which is consistent with the spectral broadening and increased intensity observed experimentally. Therefore, the spectral behavior suggests that the plasma–SCB system functions as an active reaction environment, promoting chemical transformations in the biomass that significantly contribute to the resulting UV–Vis profile. At the characteristic absorption wavelength of the dye (464 nm), sample F1 exhibited the highest absorbance (0.211), identical to that observed for solution P1 (Fig. 4 ), indicating that untreated SCB was ineffective in promoting dye degradation. The use of SCB directly treated with plasma (F2) resulted in absorbance values comparable to those obtained for the other filtrates (F3 and F4). Notably, these values are also similar to those observed for P2 and P3 in Fig. 4 . This behavior indicates that neither direct nor indirect plasma activation of SCB significantly enhances dye adsorption or degradation under the studied conditions.In fact, the results suggest that plasma-activated water — whether interacting directly with SCB or indirectly through the treated solution — primarily promotes oxidation, fragmentation, and solubilization of the lignocellulosic material itself. This interpretation is consistent with the observed increase in UV absorption, which is more likely associated with the release of oxidized organic compounds from SCB rather than with improved dye removal efficiency. Final Considerations Although the primary objective of this study was to evaluate the influence of sugarcane bagasse on the degradation of methyl orange, the results revealed a distinct and scientifically meaningful phenomenon. Rather than enhancing dye removal, the interaction between plasma-activated water (PAW) and the lignocellulosic matrix promoted oxidation, fragmentation, and partial solubilization of structural components of the biomass, particularly lignin-derived aromatic structures. This unexpected outcome provides valuable insight into the chemical reactivity of PAW toward complex biopolymers and demonstrates that plasma–liquid systems can actively modify lignocellulosic materials. The release of UV-active aromatic compounds observed in the filtrates indicates that reactive species generated during plasma–water interactions are capable of inducing oxidative depolymerization and structural rearrangements within the biomass matrix. From a broader perspective, these processes resemble key steps involved in biomass pretreatment strategies aimed at disrupting the lignin–carbohydrate complex and increasing the accessibility of cellulose and hemicellulose. Therefore, beyond its initial scope in dye removal, this work highlights the potential of plasma-activated water as a mild, reagent-free, and environmentally compatible approach for the chemical pretreatment of lignocellulosic biomass. Such a mechanism may be particularly relevant for emerging biorefinery concepts, where controlled lignin modification or extraction is desirable to enable downstream conversion processes, including enzymatic hydrolysis, production of biofuels, and valorization of lignin-derived aromatic compounds. In this context, the findings reported here contribute to expanding the understanding of plasma-based technologies as versatile tools not only for environmental remediation but also for the sustainable processing and valorization of agro-industrial residues within integrated biomass conversion platforms. Declarations Author Contribution Conceptualization: C.A.J.;J.C.P.B.Methodology: C.C.U.; J.O.V; Investigation: C.C.U.; B.F.F; M.G.F.M; F.L.G.MData curation: C.C.U.; B.F.F; M.G.F.MFormal analysis: C.A.J.; J.C.P.BVisualization: C.A.J.; J.C.P.B; F.L.G.MWriting – original draft preparation: C.C.U.; B.F.F; M.G.F.M; F.L.G.M review and editing: C.A.J., Supervision: C.A.J.;Project administration: C.A.J. Acknowledgments This project was funded by the National Council for Scientific and Technological Development (CNPq- 402536/2021-5 and 304422/2021-5), and National Council for the Improvement of Higher Education (CAPES). Data Availability The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request. The original experimental records are documented in the laboratory notebook of the research group. 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Carbohydr Polym 165:429–436. https://doi.org/10.1016/j.carbpol.2017.02.042 Brisset JL, Pawlat J (2016) Chemical Effects of Air Plasma Species on Aqueous Solutes in Direct and Delayed Exposure Modes: Discharge, Post-discharge and Plasma Activated Water. Plasma Chem Plasma Process 36:355–381. https://doi.org/10.1007/s11090-015-9653-6 Thøgersen J, Réhault J, Odelius M, Ogden T, Jena NK, Jensen SJK, Keiding SR, Helbing J (2013) Hydration dynamics of aqueous nitrate. J Phys Chem B 117:3376–3388. https://doi.org/10.1021/jp310090u Wu J (2000) Bubbles produced by breaking waves in fresh and salt waters. J Phys Oceanogr 30:1809–1813. https://doi.org/10.1175/1520-0485(2000)030%3C1809:BPBBWI%3E2.0.CO;2 Chen Z, Bononi FC, Sievers CA, Kong WY, Donadio D (2022) UV-Visible Absorption Spectra of Solvated Molecules by Quantum Chemical Machine Learning. J Chem Theory Comput 18:4891–4902. https://doi.org/10.1021/acs.jctc.1c01181 He B, Ma Y, Gong X, Long Z, Li J, Xiong Q, Liu H, Chen Q, Zhang X, Yang S, Liu QH (2017) Simultaneous quantification of aqueous peroxide, nitrate, and nitrite during the plasma-liquid interactions by derivative absorption spectrophotometry. J Phys D Appl Phys 50. https://doi.org/10.1088/1361-6463/aa8819 Direct determination of nitrate in natural water by ultraviolet first derivative spectrophotometry, n.d Drolc A, Vrtovšek J (2010) Nitrate and nitrite nitrogen determination in waste water using on-line UV spectrometric method. Bioresour Technol 101:4228–4233. https://doi.org/10.1016/j.biortech.2010.01.015 Zheng H, Guan X, Mao X, Zhu Z, Yang C, Qiu H, Hu S (2018) Determination of nitrite in water samples using atmospheric pressure glow discharge microplasma emission and chemical vapor generation of NO species. Anal Chim Acta 1001:100–105. https://doi.org/10.1016/j.aca.2017.11.060 Liu J, He B, Chen Q, Li J, Xiong Q, Yue G, Zhang X, Yang S, Liu H, Liu QH (2016) Direct synthesis of hydrogen peroxide from plasma-water interactions. Sci Rep 6:1–7. https://doi.org/10.1038/srep38454 Zhao YY, Wang T, Wilson MP, MacGregor SJ, Timoshkin IV, Ren QC (2016) Hydroxyl Radicals and Hydrogen Peroxide Formation at Nonthermal Plasma-Water Interface. IEEE Trans Plasma Sci 44:2084–2091. https://doi.org/10.1109/TPS.2016.2547841 Locke BR, Shih KY (2011) Review of the methods to form hydrogen peroxide in electrical discharge plasma with liquid water. Plasma Sources Sci Technol 20. https://doi.org/10.1088/0963-0252/20/3/034006 Volkov AG, Bookal A, Hairston JS, Roberts J, Taengwa G, Patel D (2021) Mechanisms of multielectron reactions at the plasma/water interface: Interfacial catalysis, RONS, nitrogen fixation, and plasma activated water. Electrochim Acta 385. https://doi.org/10.1016/j.electacta.2021.138441 spectrometric-identification-of-organic- compounds-silverstein , (n.d.) Emmanuel V, Odile B, Céline R (2015) FTIR spectroscopy of woods: A new approach to study the weathering of the carving face of a sculpture, Spectrochim. Acta Mol Biomol Spectrosc 136:1255–1259. https://doi.org/10.1016/j.saa.2014.10.011 -Alla A, Nada MA, El-Sakhawy M, Kamel SM Infra-red spectroscopic study of lignins, n.d Masruroh DJDH, Santjojo, Abdurrouf MA, Abdillah MC, Padaga SP, Sakti (2019) Effect of Electron Density and Temperature in Oxygen Plasma Treatment of Polystyrene Surface. IOP Conf Ser Mater Sci Eng Inst Phys Publishing. https://doi.org/10.1088/1757-899X/515/1/012061 B.H. Stuart, Infrared Spectroscopy: Fundamentals and Applications, n.d Brisset JL, Pawlat J (2016) Chemical Effects of Air Plasma Species on Aqueous Solutes in Direct and Delayed Exposure Modes: Discharge, Post-discharge and Plasma Activated Water. Plasma Chem Plasma Process 36:355–381. https://doi.org/10.1007/s11090-015-9653-6 Kruszelnicki J, Lietz AM, Kushner MJ (2019) Atmospheric pressure plasma activation of water droplets. J Phys D Appl Phys 52:355207. https://doi.org/10.1088/1361-6463/ab25dc Santacruz-Salas AP, Antunes MLP, Rangel EC, Watanabe CH, Rosa AH (2024) Plasma-engineered sugarcane bagasse: a novel strategy for efficient mercury removal from aqueous solutions. Environ Sci Pollut Res 31:65606–65626. https://doi.org/10.1007/s11356-024-35585-9 Dermawan D, Satriavi AD, Nurhidayati DI, Firnandi R, Mayangsari NE, Ramadani TA, Widiana DR, Juniani AI, Mujiyanti DR, Wang YF (2025) Composite adsorbent from sugarcane (Saccharum officinarum) bagasse biochar generated from atmospheric pressure microwave plasma pyrolysis process and nano zero valent iron (nZVI) for rapid and highly efficient Cr(VI) adsorption, Case Studies in Chemical and Environmental Engineering 11 https://doi.org/10.1016/j.cscee.2025.101123 Thapa A, Gohain RB, Talukdar P, Kundu S, Manna P, Biswas S (2025) DBD plasma induced degradation of anionic and cationic dyes: An insight into the fragmentation pathway of dye degradation. Chem Eng J Adv 24. https://doi.org/10.1016/j.ceja.2025.100869 Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9117765","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":609505511,"identity":"bf307a0f-9c61-4adc-a6fc-80bef764a69f","order_by":0,"name":"Confidence Chinechectam Uzoma","email":"","orcid":"","institution":"Universidade Federal Rural do Semi-Árido","correspondingAuthor":false,"prefix":"","firstName":"Confidence","middleName":"Chinechectam","lastName":"Uzoma","suffix":""},{"id":609505513,"identity":"72fdd712-b772-4023-bf1a-2594bda34531","order_by":1,"name":"Brenda Freires Ferreira","email":"","orcid":"","institution":"Universidade Federal Rural do Semi-Árido","correspondingAuthor":false,"prefix":"","firstName":"Brenda","middleName":"Freires","lastName":"Ferreira","suffix":""},{"id":609505514,"identity":"957e4c9d-73ac-4e6a-995e-d22240d59139","order_by":2,"name":"Maria Girlânia Freires Matos","email":"","orcid":"","institution":"Universidade Federal Rural do Semi-Árido","correspondingAuthor":false,"prefix":"","firstName":"Maria","middleName":"Girlânia Freires","lastName":"Matos","suffix":""},{"id":609505515,"identity":"1e3f7f3b-1f0a-471b-b0bb-223081aaaff9","order_by":3,"name":"Francisco Leonardo Gomes Menezes","email":"","orcid":"","institution":"Universidade Federal Rural do Semi-Árido","correspondingAuthor":false,"prefix":"","firstName":"Francisco","middleName":"Leonardo Gomes","lastName":"Menezes","suffix":""},{"id":609505516,"identity":"6873ed7e-5178-460b-a01c-ede003171c8f","order_by":4,"name":"Jussier Oliveira Vitoriano","email":"","orcid":"","institution":"Universidade Federal Rural do Semi-Árido","correspondingAuthor":false,"prefix":"","firstName":"Jussier","middleName":"Oliveira","lastName":"Vitoriano","suffix":""},{"id":609505517,"identity":"9ff87665-c1cb-4266-b8c1-41acdf0154fd","order_by":5,"name":"Júlio Cesar Pereira Barbosa","email":"","orcid":"","institution":"Universidade Federal Rural do Semi-Árido","correspondingAuthor":false,"prefix":"","firstName":"Júlio","middleName":"Cesar Pereira","lastName":"Barbosa","suffix":""},{"id":609505518,"identity":"f044484b-5360-45f6-a43b-21de38dafaf7","order_by":6,"name":"Clodomiro Alves-Junior","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAUlEQVRIie2Qv0vDQBTHv+GgWa7celKJ/8KTgvEQ/5fIgS4pdspohcC5BF2v+Fe4ZE7J0EUyd+zkHHHpoGCQ+qOQYEbB+3APvjzeB949wOH4i/iA/HhAhBrBtj0AqEthPxTPYtxb2WbeRxEpW6ye4+NLATy9nBoKwrtyjTopEY6KVkWWA63muVTza+j7iaHx/uqcPFuVULdRq0KMH42GuSQqoNnEvJ5Z2TSHpgQ9ti+2qyhDMyuWNXvrrXiGIomYmtCtfP6F9lJoL6vo0Mp4usiqC66yjovdpM3F8isSfqaxSehAiuXDepOcBCFvV75hPPrKRVO/Cg1+0WPI4XA4/iPvWY9Ot5XNSr0AAAAASUVORK5CYII=","orcid":"","institution":"Universidade Federal Rural do Semi-Árido","correspondingAuthor":true,"prefix":"","firstName":"Clodomiro","middleName":"","lastName":"Alves-Junior","suffix":""}],"badges":[],"createdAt":"2026-03-13 19:53:19","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9117765/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9117765/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":105300737,"identity":"d97c8191-ac99-4488-a722-4886ce330706","added_by":"auto","created_at":"2026-03-24 13:45:38","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":74623,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(A) \u003c/strong\u003eHelium plasma configurations used for activation; \u003cstrong\u003e(B)\u003c/strong\u003e direct activation of SCB (DA); \u003cstrong\u003e(C)\u003c/strong\u003e indirect activation at the surface of deionized water (PAW-S);\u003cstrong\u003e(D)\u003c/strong\u003e indirect activation within the liquid by gas bubbling (PAW-B).\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9117765/v1/0eeb77f518f6fd7a67726637.jpg"},{"id":105564741,"identity":"720719fa-6f7d-4f1c-8397-96a2803b329a","added_by":"auto","created_at":"2026-03-27 12:50:43","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":98548,"visible":true,"origin":"","legend":"\u003cp\u003eOESspectrum showing the reactive species generated in the helium plasma jet.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9117765/v1/03b549dc1fa88c3f3845d89c.jpg"},{"id":105300736,"identity":"25331ddd-0a27-4770-a560-3cdde3453e84","added_by":"auto","created_at":"2026-03-24 13:45:38","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":82698,"visible":true,"origin":"","legend":"\u003cp\u003eUV–Vis absorbance spectra of deionized water (H₂O-DI), plasma-activated water by surface treatment (PAW-S), and plasma-activated water by gas bubbling (PAW-B)\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9117765/v1/03346cda6d9f96397e1fd343.jpg"},{"id":105300735,"identity":"20074864-ad1e-43ed-a301-c3387306b8ce","added_by":"auto","created_at":"2026-03-24 13:45:38","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":94833,"visible":true,"origin":"","legend":"\u003cp\u003eUV–Vis absorption spectra of P1, P2, and P3 illustrating the stability of the dye in plasma-activated water.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9117765/v1/26b734510abfbfe695aab7bc.jpg"},{"id":105300742,"identity":"0d0eb381-76c7-49ce-be41-9c1766b8eb64","added_by":"auto","created_at":"2026-03-24 13:45:38","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":131554,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectra of SCB under control conditions, direct activation (DA), indirect surface activation (ISA), and indirect bubbling activation (IBA).\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9117765/v1/61dff56dc2ed04b6c68dc117.jpg"},{"id":105300740,"identity":"72e4f6cb-d0fa-4ccb-8690-30d296df8526","added_by":"auto","created_at":"2026-03-24 13:45:38","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":74797,"visible":true,"origin":"","legend":"\u003cp\u003eAdsorption performance of the filtrated samples evaluating the effects of plasma-induced surface modification and pre-oxidation by plasma-activated water (PAW).\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9117765/v1/93792f29036cdafc8aa00e55.jpg"},{"id":108491981,"identity":"3dd59f2c-07e5-4da8-9ea6-3e6652326165","added_by":"auto","created_at":"2026-05-05 09:56:31","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":784337,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9117765/v1/05ea0f01-f62f-4b28-903b-4343c1e7cbb3.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Oxidative Transformation of Sugarcane Bagasse by Plasma-Activated Water","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe increasing generation of agro-industrial residues and the contamination of water bodies by organic pollutants represent significant environmental challenges associated with the current industrial production model [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. In the Brazilian context, the sugarcane agro-energy sector stands out not only for its economic relevance but also for the large volume of sugarcane bagasse (SCB) generated as a by-product, whose destination remains largely restricted to combustion for energy cogeneration or low value-added disposal [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. The valorization of this abundant and renewable lignocellulosic residue is therefore strategic for mitigating environmental impacts and fostering practices aligned with the principles of the circular economy.\u003c/p\u003e \u003cp\u003eIn parallel, synthetic dyes such as methyl orange are widely used in the textile, food, and chemical industries and are frequently detected in industrial effluents. Even at low concentrations, these compounds can cause adverse aesthetic, ecological, and toxicological effects, in addition to exhibiting high chemical stability, which hinders their degradation by conventional wastewater treatment processes[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. In this context, the development of sustainable, efficient, and low-cost materials for the removal of such contaminants has attracted considerable research interest.\u003c/p\u003e \u003cp\u003eState-of-the-art studies identify lignocellulosic agro-industrial residues, such as SCB, as promising candidates for adsorption-based pollutant removal due to their porous structure, relatively high surface area, and the presence of functional groups such as hydroxyl, carboxyl, and phenolic moieties [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Several modification strategies have been explored to enhance the affinity of these materials for dissolved organic species, including chemical (acidic, alkaline, and oxidative), thermal, and biological treatments. However, many of these approaches involve aggressive reagents, multiple processing steps, the generation of secondary effluents, and increased operational costs, which limit their large-scale applicability[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. These drawbacks highlight the need for alternative surface activation routes that are efficient, clean, and compatible with natural matrices.\u003c/p\u003e \u003cp\u003eIn this context, atmospheric cold plasma has emerged as a promising technology for material processing and surface modification. Plasma\u0026ndash;liquid interactions are known to generate a variety of reactive oxygen and nitrogen species (RONS), including hydrogen peroxide, hydroxyl radicals, nitrites, and nitrates. When dissolved in water, these species produce plasma-activated water (PAW), a chemically reactive medium capable of inducing oxidation reactions in organic compounds. Because of its high oxidative potential and absence of chemical additives, PAW has attracted increasing interest for applications in environmental remediation, agriculture, and biomass processing [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Plasma\u0026ndash;surface interactions lead to the generation of reactive species, low-intensity UV radiation, and transient electric fields, which can introduce oxygen-containing functional groups, induce mild surface etching, and increase wettability and surface energy without the use of additional chemical reagents [\u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Beyond surface activation, recent studies have also demonstrated that reactive species generated in plasma\u0026ndash;liquid systems can interact with complex biopolymers, promoting oxidative modification of lignocellulosic structures. In particular, reactive oxygen species are capable of oxidizing phenolic groups and cleaving ether linkages in lignin, leading to partial depolymerization and solubilization of aromatic fragments[\u003cspan additionalcitationids=\"CR13 CR14\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Such processes are of particular interest in the context of lignocellulosic biomass pretreatment, a key step in emerging biorefinery strategies aimed at improving the accessibility of cellulose and hemicellulose for subsequent conversion processes [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Therefore, plasma-based approaches may simultaneously contribute to environmental remediation and biomass valorization. Accordingly, the activation of SCB by atmospheric cold plasma\u0026mdash;either through direct exposure or via plasma-activated water\u0026mdash;was initially expected to generate more reactive and functionalized surfaces capable of enhancing the removal of organic dyes from aqueous solutions. However, the interaction between PAW and lignocellulosic biomass may also induce oxidative transformations within the lignin\u0026ndash;carbohydrate matrix, potentially leading to structural modification and partial solubilization of biomass components.\u003c/p\u003e"},{"header":"Experimental Setup and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eOptical Characterization of the Plasma\u003c/h2\u003e \u003cp\u003eAn experimental setup was assembled for the electrical and optical characterization of the plasma. For each technological application, the voltage, current, frequency, and applied power used to generate the plasma were monitored with the aid of an oscilloscope. Plasma active species were also monitored using an optical emission spectrometer (OES) operating in the spectral range from 200 to 1100 nm. Optical emission was collected and transmitted to the optical emission spectrometer (USB Ocean Optics, SpectraSuite, USA). The acquired spectra were analyzed by evaluating the relative intensities of the detected species. The emission peaks corresponding to the identified species were compared with atomic transition data available in the database of the National Institute of Standards and Technology (NIST)[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSCB Activation\u003c/h3\u003e\n\u003cp\u003ePlasma activation was carried out using an adjustable high-frequency (25\u0026ndash;45 kHz) and high-voltage (0\u0026ndash;20 kV) power supply. The high-voltage (HV) source was connected to a stainless-steel tube positioned inside a glass tube, while a grounded metallic ring was fixed to the outer surface of the glass tube, configuring a dielectric barrier discharge (DBD) arrangement (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA). A continuous flow of helium was guided through the stainless-steel tube and, upon exiting the nozzle region, was subjected to the electric discharge established between the inner electrode and the grounded ring, resulting in the formation of a stable atmospheric cold plasma jet used for surface activation of the samples. For direct activation, a helium plasma jet with a flow rate of 1 L\u0026middot;min⁻\u0026sup1; was applied directly onto the SCB surface (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB). For indirect activation, deionized water was first treated by plasma and subsequently applied to the BCA. In each indirect activation procedure, 15 mL of deionized water was exposed to a helium plasma jet for 10 min (10 kV, 26.3 kHz) under two different configurations: plasma treatment at the liquid surface in a Petri dish (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC) and plasma treatment via gas bubbling, achieved by inserting a tube connected to the plasma jet into the liquid at a flow rate of 1 L\u0026middot;min⁻\u0026sup1; (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eD).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe sugarcane bagasse (SCB) was obtained as a residue from sugarcane juice extraction. Initially, the material was thoroughly washed with deionized water to remove soluble impurities and residual sugars, followed by drying in an oven at 60\u0026deg;C until constant mass. The dried material was then ground using a knife mill and sieved through a set of standardized sieves. The particle size fraction between 65 and 100 mesh was selected for the experiments in order to ensure sample homogeneity. For each treatment condition, 50 mg of SCB were accurately weighed. The samples were then subjected to different activation procedures involving direct plasma exposure or indirect treatment using plasma-activated water (PAW). The experimental conditions are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\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\u003eExperimental conditions for plasma activation of SCB\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCondition\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDescription of treatment\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\u003eControl\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e50 mg of SCB soaked with one drop of deionized water\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDA (Direct Activation)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e50 mg of SCB directly exposed to plasma and subsequently soaked with one drop of deionized water\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eISA (Indirect Surface Activation)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e50 mg of SCB soaked with one drop of plasma-activated water produced by plasma interaction at the liquid surface (PAW-S)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eIBA (Indirect Bubble Activation)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e50 mg of SCB soaked with one drop of plasma-activated water produced by plasma bubbling through the liquid (PAW-B)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e\n\u003ch3\u003eAnalysis of Plasma-Activated Water (PAW)\u003c/h3\u003e\n\u003cp\u003eThe concentrations of reactive species NO₂⁻, NO₃⁻, and H₂O₂ in deionized water and plasma-treated water were evaluated by qualitative UV\u0026ndash;Vis spectroscopic analysis using a Thermo Scientific GENESYS 180 Spectrophotometer, operating in the wavelength range of 190\u0026ndash;800 nm. This approach is widely employed to identify plasma-generated reactive species in aqueous media, as these compounds exhibit characteristic absorption bands in the ultraviolet region[\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. All measurements were performed using quartz cuvettes with an optical path length of 10 mm.\u003c/p\u003e\n\u003ch3\u003eInfluence of BCA on Methyl Orange Degradation\u003c/h3\u003e\n\u003cp\u003eThree working dye solutions (WDS) were prepared to assess the effect of plasma activation on dye degradation. P1 was obtained by diluting 1 mL of WDS in 19 mL of deionized water; P2 by diluting 1 mL of WDS in 19 mL of plasma-activated water produced by surface treatment (PAW-S); and P3 by diluting 1 mL of WDS in 19 mL of plasma-activated water produced by gas bubbling (PAW-B). The influence of SCB in different activation states\u0026mdash;control, DA, ISA, and IBA\u0026mdash;was subsequently evaluated by incorporating the material into the dye solutions to obtain filtrate samples. Four experimental systems were prepared, each with a total volume of 20 mL: F1, filtrate from untreated BCA in P1; F2, filtrate from DA-treated BCA in P1; F3, filtrate from ISA-treated BCA in P2; and F4, filtrate from IBA-treated BCA in P3. All suspensions were stirred for 30 min to ensure sufficient contact between the dye solution and the solid phase. The solid material was then removed by filtration, and the UV\u0026ndash;Vis spectra of the filtrates were recorded using deionized water as the blank. All measurements were performed under identical optical path length and spectral range conditions to ensure consistency and comparability. Fourier-transform infrared (FTIR) spectra were collected using an Agilent Cary 630 spectrometer equipped with an attenuated total reflectance (ATR) accessory with a diamond crystal and ZnSe optics. Measurements were carried out in the 4000\u0026ndash;650 cm⁻\u0026sup1; spectral range with a resolution of 4 cm⁻\u0026sup1;, averaging eight scans per sample at room temperature.\u003c/p\u003e"},{"header":"Results and Discussions","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eOptical Characterization of the Plasma Jet\u003c/h2\u003e \u003cp\u003eThe optical emission spectrum (OES) exhibited a prominent peak at approximately 588 nm, attributed to the He I transition, indicating the occurrence of excitation processes driven by electron\u0026ndash;helium collisions within the discharge. Additional emission bands observed in the 350\u0026ndash;434 nm region were assigned to molecular nitrogen species, corresponding to the second positive (C\u0026sup3;Π\u003csub\u003eu\u003c/sub\u003e \u0026rarr; B\u0026sup3;Πg) and first negative (B\u0026sup2;Σ\u003csub\u003eu\u003c/sub\u003e⁺ \u0026rarr; X\u0026sup2;Σg⁺) systems of N₂/N₂⁺, in agreement with spectra typically reported for atmospheric-pressure helium plasmas in the literature [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. In the spectral region above 657 nm, several bands were attributed to the first positive system of N₂ (B\u0026sup3;Πg \u0026rarr; A\u0026sup3;Σ\u003csub\u003eu\u003c/sub\u003e⁺), except for the emissions at 706 nm and 777 nm, which were associated with the He I and O I transitions, respectively. In addition, the emission line observed around 656 nm was attributed to the Hα transition of the Balmer series of atomic hydrogen, as commonly reported in optical emission spectroscopy studies of atmospheric-pressure plasmas [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The presence of these excited and ionized species indicates the generation of reactive oxygen and nitrogen species (RONS) during the discharge, which can interact with the surrounding air, with water, or directly with solid surfaces [\u003cspan additionalcitationids=\"CR24 CR25\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. In the case of lignocellulosic solid surfaces, such interactions promote surface oxidation processes, resulting in chemical modifications in the outermost layers of the material[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Under the direct activation (DA) mechanism, plasma-generated reactive species interact directly with the surface of SCB, inducing chemical modifications subsequently identified by FTIR analysis. In contrast, during indirect activation, these species dissolve in water during plasma treatment, leading to the formation of plasma-activated water (PAW) enriched with oxidizing agents, such as oxygen- and nitrogen-based species[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. These species present in PAW subsequently interact with the SCB surface, promoting chemical modifications similar to those observed under direct activation conditions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003ePhysicochemical Analysis and Reactive Species of PAW\u003c/h3\u003e\n\u003cp\u003eThe analysis of reactive species was also carried out by UV\u0026ndash;Vis spectroscopy[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. The UV\u0026ndash;Vis absorption spectra of deionized water (H₂O-DI) and plasma-activated water obtained by surface treatment (PAW-S) and gas bubbling (PAW-B) reveal significant differences in the ultraviolet region (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). While H₂O-DI exhibits virtually no absorption over the entire analyzed spectral range, the PAW samples display intense absorption bands below 250 nm, indicating the formation of plasma-induced reactive chemical species. The strong absorption observed in the 190\u0026ndash;230 nm range is characteristic of nitrate (NO₃⁻), whose π\u0026rarr;π* electronic transition typically shows a maximum around 200\u0026ndash;205 nm[\u003cspan additionalcitationids=\"CR30\" citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. The higher intensity of this band in the PAW-S sample indicates a greater concentration of oxidized nitrogen species when activation occurs at the plasma\u0026ndash;liquid interface, a condition that favors the incorporation of gaseous nitrogen oxides (NOₓ) into the aqueous medium. This behavior is consistent with the increased direct exposure of the liquid surface to plasma-generated reactive species. In addition, contributions in the 210\u0026ndash;230 nm region may be associated with the presence of nitrite (NO₂⁻), which exhibits weaker and broader absorption in this spectral range[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Although the overlap between nitrate and nitrite bands hinders their quantitative discrimination by UV\u0026ndash;Vis spectroscopy alone, the broadening and asymmetry of the absorption profile suggest the coexistence of both species, particularly in the plasma-activated samples. The presence of hydrogen peroxide (H₂O₂) may also contribute to absorption in the deep-UV region [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Consistent reports in the literature associate absorption bands in the \u0026asymp;\u0026thinsp;260\u0026ndash;280 nm region with hydrogen peroxide in aqueous solutions, attributed to the n\u0026rarr;σ* electronic transition of the O\u0026ndash;O bond [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. This result can be understood in terms of the different mechanisms governing the generation and consumption of reactive species under the two activation configurations. During bubbling, excited species and radicals produced in the plasma interact directly with the liquid bulk, favoring recombination reactions of hydroxyl radicals (\u0026bull;OH) that lead to H₂O₂ formation[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Moreover, the reduced direct exposure of the liquid surface to gaseous nitrogen oxides limits strong acidification of the medium, which can enhance hydrogen peroxide stability and reduce its decomposition. In contrast, under surface-treatment conditions (PAW-S), although there is greater incorporation of reactive nitrogen species such as nitrate and nitrite, the more oxidizing and acidic environment tends to promote competitive reactions that consume H₂O₂, including nitrogen-species-catalyzed decomposition or conversion into secondary products[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. This explains the absence of a discernible absorption peak above 250 nm in this sample, despite the higher absorbance observed in the deep-UV region. Thus, the exclusive presence of the absorption band above 250 nm in PAW-B reinforces that the plasma activation mode not only affects the total amount of reactive species generated but also significantly alters their predominant chemical nature. While surface activation favors the formation of oxidized nitrogen species, bubbling proves to be more efficient for the generation and stabilization of H₂O₂, which may be decisive for specific PAW applications, particularly those that rely on controlled oxidative potential and the prolonged action of hydrogen peroxide.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eUV–Vis analysis of dye solutions\u003c/h3\u003e\n\u003cp\u003eThe UV\u0026ndash;Vis absorption spectra of solutions P1 (dye in deionized water), P2 (dye in plasma-activated water obtained by surface treatment, PAW-S), and P3 (dye in plasma-activated water obtained by gas bubbling, PAW-B) reveal clear differences in both the ultraviolet and visible regions, reflecting the effect of plasma activation on the chemical stability of the dye. Sample P1 exhibits an intense absorption band in the deep-UV region, with a maximum around 200 nm and a shoulder near 280 nm. These bands are attributed to π \u0026rarr; π* electronic transitions associated with aromatic rings and unsaturated groups present in the molecular structure of the dye[\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. A distinct absorption band appears in the visible region, with a maximum at 464 nm, corresponding to the dye\u0026rsquo;s conjugated chromophoric system. In contrast, samples P2 and P3 show a significant reduction in the intensity of this visible band, indicating partial degradation of the chromophore upon contact with plasma-activated water. The more pronounced decrease in absorbance observed for P3 suggests a higher oxidative efficiency of PAW-B, consistent with the greater incorporation of reactive species into the aqueous medium during the bubbling process. In the deep-UV region (\u0026asymp;\u0026thinsp;200 nm), a marked increase in absorbance is observed for samples P2 and P3 compared to P1. This behavior is attributed to the presence of reactive species such as NO₃⁻, NO₂⁻, and H₂O₂, as discussed previously. Between 250 and 350 nm, subtle spectral differences among the samples indicate the coexistence of degradation intermediates and nitrogen-containing species, reinforcing that dye degradation proceeds progressively through disruption of the conjugated system and the formation of less complex compounds. Overall, the UV\u0026ndash;Vis results demonstrate that plasma-activated water exhibits sufficient oxidative capacity to promote the initial degradation of the dye already during the solution preparation stage, with this effect being more pronounced under the bubbling condition. These findings corroborate the role of PAW as an active agent in the chemical modification of organic pollutants, supporting its application as a preliminary or complementary step in contaminant removal and wastewater treatment processes, as well as in the chemical activation of lignocellulosic materials such as SCB.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eAnalysis of plasma-activated SCB samples\u003c/h2\u003e \u003cp\u003eThe Control, DA, ISA, and IBA samples were analyzed by FTIR immediately after treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). In the O\u0026ndash;H stretching region (3600\u0026ndash;3000 cm⁻\u0026sup1;), all samples exhibit a broad band characteristic of hydroxyl groups associated with cellulose, hemicellulose, and lignin [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. However, the ISA and IBA samples show increased intensity and band broadening, with a more pronounced effect for the IBA configuration. This behavior indicates an increase in the density of polar groups and hydrogen-bonding capacity, associated with the incorporation of reactive oxygen-containing species generated during plasma treatment [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. The bands attributed to C\u0026ndash;H stretching vibrations of \u0026ndash;CH₂ and \u0026ndash;CH₃ groups (3000\u0026ndash;2800 cm⁻\u0026sup1;) display a relative decrease in intensity in the plasma-treated samples, particularly those subjected to PAW activation (ISA and IBA). This reduction suggests partial oxidation of aliphatic chains and possible removal of amorphous, carbon-rich components, resulting from plasma-induced chemical and structural reorganization of the SCB surface[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. In the 1750\u0026ndash;1600 cm⁻\u0026sup1; region, the FTIR spectra reveal clear differences between SCB immersed in deionized water (Control) and that treated with plasma-activated water (PAW), indicating modifications in functional groups associated with C\u0026thinsp;=\u0026thinsp;O and C\u0026thinsp;=\u0026thinsp;C bonds, which are typical of plasma-induced surface oxidation processes[\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFor the control sample, a weak band is observed around 1730 cm⁻\u0026sup1;, attributed to the C\u0026thinsp;=\u0026thinsp;O stretching of ester and acetyl groups of hemicellulose, as well as a stable band between 1650\u0026ndash;1600 cm⁻\u0026sup1;, associated with the aromatic C\u0026thinsp;=\u0026thinsp;C vibrations of lignin, indicating that the treatment essentially promotes physical hydration, without significant chemical modifications of the lignocellulosic matrix [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. In contrast, the bagasse soaked in plasma-activated water (PAW) shows an increase in intensity and broadening of the band at ~\u0026thinsp;1730\u0026ndash;1715 cm⁻\u0026sup1;, indicating the formation of new carbonyl groups resulting from oxidative processes[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. These changes are attributed to the action of reactive species dissolved in PAW, such as H₂O₂, \u0026bull;OH, and reactive nitrogen species, formed during the plasma\u0026ndash;water interaction, which promote the oxidation of cellulose hydroxyl groups and lignin side chains[27, 43]. Concomitant modifications in the 1650\u0026ndash;1600 cm⁻\u0026sup1; region suggest partial oxidation of lignin and an increased contribution of strongly bound water, reflecting the enhanced surface polarity of the material[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. These results confirm that, unlike deionized water, PAW promotes effective oxidative functionalization of the sugarcane bagasse surface, in agreement with studies reporting plasma-induced chemical modifications in lignocellulosic materials, resulting in increased hydrophilicity and surface reactivity[\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eUV\u0026ndash;Vis analysis of the filtrates after interaction with activated SCB\u003c/h2\u003e \u003cp\u003eThe analysis of the filtrates was used to study the effect of SCB plasma activation on removal and/or dye degradation efficiency when SCB (plasma activated or not) is mixing with a solution containing water deionized or plasma-activated water (PAW) (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). The samples F1, filtrate from untreated BCA in P1; F2, filtrate from DA-treated BCA in P1; F3, filtrate from ISA-treated BCA in P2; and F4, filtrate from IBA-treated BCA in P3. Comparing the spectra obtained for P1, P2, and P3 in the absence of SCB (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), a substantial increase in absorbance is observed in the 200\u0026ndash;260 nm range, with intensities approximately 4\u0026ndash;6 times higher. This increment cannot be explained solely by the presence of inorganic species generated by the plasma, such as NO₃⁻, NO₂⁻, and H₂O₂, since these species are also present in the system without SCB and, individually, do not account for the magnitude of the observed increase. The introduction of SCB significantly alters the chemical composition of the medium, indicating that the lignocellulosic material does not act merely as an adsorptive phase but also as a source of UV-active organic compounds. Under the action of reactive oxygen and nitrogen species (RONS) formed in the plasma, structural components of the bagasse \u0026mdash; particularly lignin \u0026mdash; undergo oxidation, fragmentation, and solubilization processes. These reactions may release phenolic compounds, partially oxidized aromatic structures, quinones, and low-molecular-weight organic acids, all of which are characterized by strong absorption in the deep UV region[39, 44, 45]. In particular, lignin exhibits pronounced absorption bands below 280 nm, associated with π\u0026rarr;π* electronic transitions in conjugated aromatic systems. Oxidation of these structures tends to broaden and intensify absorption in this region, which is consistent with the spectral broadening and increased intensity observed experimentally. Therefore, the spectral behavior suggests that the plasma\u0026ndash;SCB system functions as an active reaction environment, promoting chemical transformations in the biomass that significantly contribute to the resulting UV\u0026ndash;Vis profile. At the characteristic absorption wavelength of the dye (464 nm), sample F1 exhibited the highest absorbance (0.211), identical to that observed for solution P1 (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), indicating that untreated SCB was ineffective in promoting dye degradation. The use of SCB directly treated with plasma (F2) resulted in absorbance values comparable to those obtained for the other filtrates (F3 and F4). Notably, these values are also similar to those observed for P2 and P3 in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. This behavior indicates that neither direct nor indirect plasma activation of SCB significantly enhances dye adsorption or degradation under the studied conditions.In fact, the results suggest that plasma-activated water \u0026mdash; whether interacting directly with SCB or indirectly through the treated solution \u0026mdash; primarily promotes oxidation, fragmentation, and solubilization of the lignocellulosic material itself. This interpretation is consistent with the observed increase in UV absorption, which is more likely associated with the release of oxidized organic compounds from SCB rather than with improved dye removal efficiency.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eFinal Considerations\u003c/h2\u003e \u003cp\u003eAlthough the primary objective of this study was to evaluate the influence of sugarcane bagasse on the degradation of methyl orange, the results revealed a distinct and scientifically meaningful phenomenon. Rather than enhancing dye removal, the interaction between plasma-activated water (PAW) and the lignocellulosic matrix promoted oxidation, fragmentation, and partial solubilization of structural components of the biomass, particularly lignin-derived aromatic structures. This unexpected outcome provides valuable insight into the chemical reactivity of PAW toward complex biopolymers and demonstrates that plasma\u0026ndash;liquid systems can actively modify lignocellulosic materials. The release of UV-active aromatic compounds observed in the filtrates indicates that reactive species generated during plasma\u0026ndash;water interactions are capable of inducing oxidative depolymerization and structural rearrangements within the biomass matrix. From a broader perspective, these processes resemble key steps involved in biomass pretreatment strategies aimed at disrupting the lignin\u0026ndash;carbohydrate complex and increasing the accessibility of cellulose and hemicellulose. Therefore, beyond its initial scope in dye removal, this work highlights the potential of plasma-activated water as a mild, reagent-free, and environmentally compatible approach for the chemical pretreatment of lignocellulosic biomass. Such a mechanism may be particularly relevant for emerging biorefinery concepts, where controlled lignin modification or extraction is desirable to enable downstream conversion processes, including enzymatic hydrolysis, production of biofuels, and valorization of lignin-derived aromatic compounds. In this context, the findings reported here contribute to expanding the understanding of plasma-based technologies as versatile tools not only for environmental remediation but also for the sustainable processing and valorization of agro-industrial residues within integrated biomass conversion platforms.\u003c/p\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eConceptualization: C.A.J.;J.C.P.B.Methodology: C.C.U.; J.O.V; Investigation: C.C.U.; B.F.F; M.G.F.M; F.L.G.MData curation: C.C.U.; B.F.F; M.G.F.MFormal analysis: C.A.J.; J.C.P.BVisualization: C.A.J.; J.C.P.B; F.L.G.MWriting \u0026ndash; original draft preparation: C.C.U.; B.F.F; M.G.F.M; F.L.G.M review and editing: C.A.J., Supervision: C.A.J.;Project administration: C.A.J.\u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e \u003cp\u003eThis project was funded by the National Council for Scientific and Technological Development (CNPq- 402536/2021-5 and 304422/2021-5), and National Council for the Improvement of Higher Education (CAPES).\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request. The original experimental records are documented in the laboratory notebook of the research group.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMartinez-Burgos WJ, Bittencourt Sydney E, Bianchi Pedroni Medeiros A, Magalh\u0026atilde;es AI, de Carvalho JC, Karp SG, Porto de Souza L, Vandenberghe LA, Junior Letti V, Thomaz Soccol GV, de Melo Pereira C, Rodrigues A, Lorenci Woiciechowski CR, Soccol (2021) Agro-industrial wastewater in a circular economy: Characteristics, impacts and applications for bioenergy and biochemicals. 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J Phys D Appl Phys 52:355207. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1088/1361-6463/ab25dc\u003c/span\u003e\u003cspan address=\"10.1088/1361-6463/ab25dc\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSantacruz-Salas AP, Antunes MLP, Rangel EC, Watanabe CH, Rosa AH (2024) Plasma-engineered sugarcane bagasse: a novel strategy for efficient mercury removal from aqueous solutions. Environ Sci Pollut Res 31:65606\u0026ndash;65626. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11356-024-35585-9\u003c/span\u003e\u003cspan address=\"10.1007/s11356-024-35585-9\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDermawan D, Satriavi AD, Nurhidayati DI, Firnandi R, Mayangsari NE, Ramadani TA, Widiana DR, Juniani AI, Mujiyanti DR, Wang YF (2025) Composite adsorbent from sugarcane (Saccharum officinarum) bagasse biochar generated from atmospheric pressure microwave plasma pyrolysis process and nano zero valent iron (nZVI) for rapid and highly efficient Cr(VI) adsorption, Case Studies in Chemical and Environmental Engineering 11 \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.cscee.2025.101123\u003c/span\u003e\u003cspan address=\"10.1016/j.cscee.2025.101123\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eThapa A, Gohain RB, Talukdar P, Kundu S, Manna P, Biswas S (2025) DBD plasma induced degradation of anionic and cationic dyes: An insight into the fragmentation pathway of dye degradation. Chem Eng J Adv 24. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.ceja.2025.100869\u003c/span\u003e\u003cspan address=\"10.1016/j.ceja.2025.100869\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\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":"plasma-activated water, lignocellulosic biomass, sugarcane bagasse, plasma–liquid interaction, biomass pretreatment","lastPublishedDoi":"10.21203/rs.3.rs-9117765/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9117765/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study investigates the interaction between plasma-activated water (PAW) and sugarcane bagasse (SCB), focusing on the chemical effects of reactive oxygen and nitrogen species generated during plasma\u0026ndash;liquid interactions on lignocellulosic biomass. Initially, atmospheric cold plasma was employed as a strategy for the direct and indirect activation of SCB aiming at improving its performance in the removal of methyl orange from aqueous solutions. Direct activation was performed by exposing SCB to a helium plasma jet, while indirect activation involved treating deionized water with the plasma jet under two configurations: plasma exposure at the liquid surface and plasma treatment with gas bubbling, generating PAW with different chemical reactivities. Unexpectedly, the results indicated that PAW did not significantly enhance the dye removal capacity of the biomass. Instead, spectroscopic analyses revealed that reactive species dissolved in PAW promoted oxidation, fragmentation, and partial solubilization of lignocellulosic components, particularly lignin-derived aromatic structures. UV\u0026ndash;Vis measurements of the liquid phase suggested the release of soluble organic compounds from the biomass, indicating chemical modification of the lignocellulosic matrix. These findings demonstrate that PAW acts not only as an oxidizing medium for pollutant degradation but also as an effective agent for the chemical pretreatment of lignocellulosic biomass. The observed oxidative transformation of SCB suggests potential applications of plasma-activated water in biomass processing and pretreatment strategies relevant to emerging biorefinery concepts. This study therefore provides new insights into plasma\u0026ndash;biomass interactions and highlights the versatility of plasma-liquid systems for sustainable biomass valorization.\u003c/p\u003e","manuscriptTitle":"Oxidative Transformation of Sugarcane Bagasse by Plasma-Activated Water","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-24 13:45:32","doi":"10.21203/rs.3.rs-9117765/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":"c9e78c98-34a3-4f36-b402-b61737be1f58","owner":[],"postedDate":"March 24th, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Rejected","date":"2026-05-02T07:57:05+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-01T15:04:02+00:00","index":12,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-05-02T08:09:57+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-24 13:45:32","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9117765","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9117765","identity":"rs-9117765","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}