Reducing Acetochlor Toxicity through Subcritical Hydrolysis Technology: Investigating the Hydrolysis Mechanism

Reducing Acetochlor Toxicity through Subcritical Hydrolysis Technology: Investigating the Hydrolysis Mechanism | 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 Reducing Acetochlor Toxicity through Subcritical Hydrolysis Technology: Investigating the Hydrolysis Mechanism Shuo Pan, Huaiyu Zhou, Shuang Wu, Jingru Bai, Da Cui, Qing Wang, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4575720/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract The primary objective of this investigation was to address the toxicity associated with acetochlor (ACT) through subcritical hydrolysis treatment, assessing the efficacy of this approach in mitigating concerns related to acetochlor's toxicity. Gas chromatography-time-of-flight mass spectrometry (GC × GC-TOFMS), Fourier transform infrared spectrometry (FT-IR), and scanning electron microscopy (SEM) were employed to elucidate distribution patterns, variations in functional groups, and morphological features of the hydrolyzed derivatives of ACT. The hydrolytic transformation pathway and mechanisms of ACT product formation were determined by integrating findings from GC × GC-TOFMS analysis and characterization assessments. The subcritical hydrolysis experiments resulted in the identification of 39 hydrolytic by-products from ACT. The peak hydrolysis rate for ACT was observed at a hydrothermal temperature of 280 °C with a reaction duration of 60 minutes, leading to the complete hydrolysis of toxic by-products. In this study, subcritical hydrolysis technology demonstrated its effectiveness in mitigating the toxicity of ACT, achieving environmentally sustainable treatment, and aiding in the resolution of potential hazards posed by ACT to ecosystems and human health. Acetochlor Subcritical hydrolysis Hydrolysis mechanism GC×GC-TOFMS technique Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction The rapid progress in agriculture has resulted in an increasing reliance on pesticides [1], creating an urgent need for the safe disposal of these agrochemicals [2, 3]. ACT stands out as a globally prevalent herbicide, renowned for its remarkable efficacy, cost-effectiveness, and widespread applicability [4, 5]. Since its introduction and commencement of production in the early 1990s, China has witnessed a consistent surge in ACT production. In 1994, the production of ACT was merely in the kiloton scale. By 1998, it had surged to 10,000 tons, further escalating to approximately 15,000 tons in 2000, peaking at 30,000-40,000 tons in 2003. By 2021, the global sales of ACT had reached an impressive figure of US$530 million [6]. Once introduced into the soil, ACT undergoes continuous transportation, dispersion, and leaching through irrigation and precipitation processes [7]. Consequently, ACT is frequently detected in both soil and water [8], including drinking water sources [9-11]. This emphasizes the urgent need for prudent management of ACT to mitigate its potential repercussions on both the environment and potable water sources. ACT, characterized by a molecular formula of C 14 H 20 ClNO 2 and a molecular weight of 269.8, belongs to the homoamide category of pesticides. It exhibits solubility in organic solvents like benzene and acetone and undergoes decomposition when exposed to strong acids and alkalis. The molecular structure of ACT is illustrated in Fig. 1. As a persistent organic pollutant, ACT inherently displays resilience, posing potential hazards to human health, plants, and animals [12]. Additionally, it carries a conceivable carcinogenic risk for humans [5, 13]. Furthermore, ACT impedes plant growth [14-17], disrupts animal development, and causes damage to the animal nervous system [18-20]. The U.S. Environmental Protection Agency has classified ACT as a B-2 carcinogen and a likely human carcinogen, underscoring its potential harm to ecosystems and human health [21]. However, due to its non-volatile characteristics, challenging photolysis, and limited hydrolysis under natural conditions [22], ACT persists, presenting an ongoing threat to plants, animals, and human health and safety [23]. As one of the most widely used herbicides, addressing the potential hazards posed by ACT to the environment and human health requires concerted efforts [24, 25]. Therefore, conducting an in-depth analysis of the hydrolysis pattern of ACT is crucial to mitigate the risks associated with ACT for environmental safety and human health, among other concerns. Presently, the principal approaches for ACT treatment encompass microbial degradation [4], catalytic oxidation [26-28], and adsorption [29]. Xin et al. [30] employed microbial degradation to treat ACT at 30 °C for 48 hours to produce mainly 2-ethyl-6-methyl-N-methyl-α-chloroacetanilide with low toxicity. Microbial degradation is relatively straightforward to operate, exhibits broad applicability, and boasts low operational costs. Nevertheless, this approach necessitates particular microbial species, entails lengthy processing times, is significantly influenced by environmental factors, and the principal degradation products exhibit marginal toxicity. Fu et al. [31] used catalytic oxidation for the treatment of ACT at 25 °C and 7 h to produce mainly the non-toxic product 1-methyl-3-ving-benzene. Catalytic oxidation offers a broad range of applicability, absence of toxic intermediate by-products, among other advantages. Nonetheless, this technique also confronts challenges such as high catalyst costs, restricted practical application efficiency, organic solvent pollution, and intricate operation. Hou et al. [32] utilized a mixture of calcium peroxide and iron powder for the adsorption of ACT, under conditions of 25 °C temperature and 1 min, resulting in all three degradation products of ACT displaying toxicity. The advantages of adsorption include its simplicity of operation and short processing time. However, this method generates waste, incurs high operating costs, and results in the production of multiple toxic by-products during the degradation process. When contrasted with conventional approaches, subcritical water hydrolysis technology showcases viability in both technical and economic spheres [33-35]. Subcritical hydrolysis technology facilitates the decomposition of organic constituents, expedites methane fermentation, and mitigates the release of harmful gases [36]. Through precise control of reaction parameters, various toxic and stable pesticides can be efficiently processed [37]. Islam et al. [38] employed subcritical water hydrolysis technology to process diazinon, parathion, phenthoat, and EPN pesticides under the conditions of 150 °C and 20 min, thereby transforming these four pesticides and their toxic by-products into harmless compounds. Subcritical hydrolysis represents a "green treatment" utilizing superheated water (100 °C ≤ T ≤ 374 °C and pressure < 22.1 MPa) as a solvent, eliminating the need for organic solvents [39]. Water exhibits increased solubility at elevated temperatures, facilitating the dissolution of ACT. This solubility enables water to serve as a solvent in the reaction, facilitating the dissolution of reactants and catalyzing the reaction. In subcritical hydrolysis experiments treating ACT, the necessity for acid, alkali, and catalysts is eliminated, leaving no solvent residue. The process is non-flammable and non-explosive, effectively reducing the toxicity of ACT [40]. Thus, subcritical hydrolysis technology for ACT treatment boasts high efficiency, minimal pollution, low energy consumption, and straightforward operation. Therefore, subcritical hydrolysis technology emerges as a promising solution, effectively mitigating pesticide toxicity while concurrently degrading and treating hazardous pesticides, ultimately achieving environmentally benign ACT treatment. In this study, the subcritical hydrolysis technique was employed to treat ACT under varying hydrothermal temperatures and reaction times. Initially, the intermediate products resulting from subcritical hydrolysis experiments of ACT underwent a comprehensive analysis using GC×GC-TOFMS. This analysis aimed to elucidate the distribution pattern of the hydrolysis products derived from ACT. Subsequently, FT-IR and SEM techniques were applied for a thorough characterization and analysis of both ACT and the hydrochar. The objective was to gain a comprehensive understanding of the functional group types and morphological features present in ACT and the resulting hydrochar. By integrating the principles of product analysis and characterization, the mechanism of hydrolysis product transformation during subcritical hydrolysis experiments of ACT was unveiled. Ultimately, through the application of subcritical hydrolysis technology, we successfully achieved the environmentally benign treatment of ACT, effectively addressing its potential impact on ecological safety and human health. 2. Materials and methods 2.1 Raw material The ACT employed in this study was obtained from Hubei Weideli Chemical Reagent Co., Ltd., with a purity exceeding 93%, and it manifested as a light yellow liquid. Analytically pure benzene was sourced from Tianjin Damao Chemical Reagent Factory, and analytically pure acetone was procured from Yantai Shuangshuang Chemical Co.. 2.2 Reaction conditions Subcritical hydrolysis experiments were conducted using a 500 mL autoclave reactor (HT-500FJ, Baikal, China), as illustrated in Fig. 2 [ 41 ]. In each trial, 10 g of ACT liquid was mixed with 100 mL of deionized water and subsequently heated to varying temperatures-180°C, 230°C, and 280°C. The autoclave was maintained at the designated temperature for durations of 15 min, 30 min, and 60 min, resulting in a total of nine experimental sets. The pressure within the reactor escalates with ascending temperatures. At reactor temperatures of 180°C, 230°C, and 280°C, the respective pressures amount to 7 bar, 26 bar, and 53 bar, correspondingly. Subsequently, the reactor was cooled to room temperature. Following the hydrothermal reaction, the resulting solid and liquid products (ACT-T-S: ACT-acetochlor; T-temperature; S-time) were filtered and reserved separately. Place the funnel onto the stand, ensuring that the funnel stem is positioned inside the beaker for smooth collection of liquid product. Next, snugly place filter paper against the funnel neck to prevent solid material from entering the liquid product. Subsequently, pour the mixture of solid and liquid into a flat-bottomed funnel and allow it to stand for 1 hour to facilitate the separation of solid and liquid components. 2.3 Determination of ACT hydrolysis products by GC×GC-TOFMS The liquid products resulting from ACT treatment underwent comprehensive analysis using a Gas Chromatography-Time-Of-Flight Mass Spectrometry (GC×GC-TOFMS) analyzer (Clarus SQ8, PerkinElmer, USA). This analytical approach was designed to elucidate the distribution patterns of hydrolysis products arising from ACT, providing insights into the hydrolysis pathways under varying hydrothermal temperatures and reaction durations. The hydrolyzed liquid products, acquired in nine sets, were introduced into a 250 mL separatory funnel. Subsequently, 20 mL of benzene was added, and the mixture underwent vigorous shaking for 10 min, followed by a 5-minute rest period to facilitate stratification. The upper benzene layer was meticulously transferred into a triangular flask. This extraction procedure was iterated three times with the addition of 20 mL of benzene in each repetition. The resulting three extracts were amalgamated in the triangular flask. After dehydration with anhydrous sodium sulfate, the extracts were transferred to a concentration cup, quantitatively reduced to approximately 0.5 mL, and then adjusted to a final volume of 2.0 mL using benzene. Ultimately, the liquid products from the nine sets underwent comprehensive analysis using the GC×GC-TOFMS technique. The gas chromatographic conditions were controlled using a DB-PETRO capillary column (50 m×0.20 mm inner diameter×0.5 µm film thickness). The heating protocol for the column was initiated with an initial temperature of 50 ℃, maintained for 3 min, followed by a gradual increase to 100 ℃ at a rate of 3 ℃·min − 1 , held for an additional 3 min, and subsequently raised to 300 ℃ at a rate of 5 ℃·min − 1 , where it was held for 5 min. Helium served as the carrier gas at a flow rate of 1 mL·min − 1 , and sample injection was executed through a shunt pulse with a shunt ratio of 5:1. The inlet port temperature was sustained at 270 ℃, and the injection volume was set at 1 µl. The mass spectrometric conditions comprised an electron bombardment (EI) source, an ion source temperature of 280 ℃, an ionization energy of 70 eV, a scanning range spanning 35 ~ 500 amu, a quadrupole temperature of 150 ℃, a mass transfer line maintained at 280 ℃, and a solvent delay of 7 min. 2.4 Analytical methods for characterization of ACT and hydrochar Comprehensive characterization and analysis were systematically conducted on both ACT and hydrochar samples to investigate the influence of hydrolysis temperature and reaction time on their elemental composition, surface morphology, pore structure, and surface functional groups in the context of subcritical hydrolysis experiments. The resulting solid products from hydrolysis underwent meticulous drying at 105°C for 12 hours. Subsequently, the nine sets of resulting solid hydrochar were subjected to detailed characterization analyses. In this study, the Nicolet IS10 Fourier Transform Infrared (FT-IR) technique (Thermo Fisher, USA) was employed to characterize the infrared spectra of the ACT chars, facilitating the analysis of variation patterns in characteristic functional groups. Additionally, the Scanning Electron Microscopy (SEM) technique (JSM-7610F, JEOL, Japan) was utilized to scrutinize the external appearance of the ACT and hydrochar, providing insights into alterations in surface structure and solid morphology. 3. Results and discussion 3.1. Product analysis of ACT during subcritical hydrolysis experiments GC×GC-TOFMS technology was employed to analyze the hydrolysis products of ACT under various hydrothermal temperatures and reaction times in subcritical hydrolysis experiments. This analysis successfully determined the molecular and structural formulas of the hydrolysis products, as depicted in Fig. 3 . A total of 39 hydrolysis products were identified during the experiments, as outlined in Table 1 . The hydrolysis products of ACT mainly include aromatic compounds, aliphatic compounds and aliphatic heterocyclic compounds, with aromatic compounds being the main product class. The aromatic products of ACT comprise 33 distinct compounds, falling within various categories such as aromatic phenols, aromatic acyls, aromatic amides, aromatic olefins, halogenated aromatic hydrocarbons, aromatic hydrocarbons, aromatic amines, aromatic esters, aromatic aldehydes, aromatic ketones, and polyphenyl aliphatic hydrocarbons. Among the aromatic phenolic compounds are 2-Ethyl-6-methylphenol (EMP) and Phenol, 2-ethyl-4,5-dimethyl- (PED). Aromatic amides encompass Acetamide, 2-chloro-N-(2,6-diethylphenyl)- (ACD), and 2-Ethyl-6-methyl-2-chloroacetanilide (CMEPA). Halogenated aromatic compounds comprise Chlorobenzene (CBZ). Aromatic hydrocarbons consist of Ethylbenzene (EBZ), O-xylene (OXE), Cumene (CUM), and Benzene, 1-ethyl-2,4,5-trimethyl (BET). Aromatic olefins feature 2,4,6-Trimethylstyrene (TMS). Aromatic amines encompass 2,4,6,N,N-Pentamethylaniline (PMA), 2-Ethyl-6-methylaniline (MEA), 3-Methyl-N,N-dipropylaniline (MDA), N,N,3-triethylaniline (TTA), N,n-diethyl-p-toluidine (DPT), 2,4,6-Trimethylaniline (TEA), N,n-diethyl-2-methyl-benzenamine (DMB), 2,6-Diisopropylaniline (DPA), 1-Ethyl-1,2,3,4-tetrahydroquinolin-7-ol (ETD), 2-(TerT-butyl)-6-methylaniline (TTM), 2,6-Diethylaniline (DYA), 2,6,N,N-Tetramethylaniline (TMA), N,N-Diethylaniline (DFA), Benzenamine, N,N-diethyl-2,6-dimethyl-(DDA), Eseudocumidine (PDC), 2,6-Dimethylaniline (EOT), 2-Isopropyl-6-methylaniline (IMA). Aromatic esters include 2,4,6-Trimethylphenyl isocyanate (TPC) and 2,6-Diethylphenyl isocyanate (DIA). Aromatic aldehydes consist of Benzaldehyde, 4-(dimethylamino)-2-methyl- (BDM) and 4-[(2-Chloroethyl) ethylamino]-benzaldehyde (CBD). Aromatic ketones showcase 4-[4-(Dimethylamino) phenyl] but-3-en-2-one (DPB). Polyphenyl aliphatic hydrocarbon compounds include 3,5,3',5'-Tetramethyl-N4-propyl-biphenyl-4,4'-diamine (TBD). The aliphatic products of ACT encompass four distinct compounds, falling within the categories of both fatty esters and fatty amines. Specifically, the fatty esters comprise Methyl chloroacetate (MCA), Ethyl 2-hydroxyacetate (EHA), and Ethyl chloroacetate (ECA). Meanwhile, the group of fatty amine compounds features Dimethylamine (DTA). Two heterocyclic products originating from ACT lipids were identified, namely (3Z)-3-[4-(Diethylamion) bezylidene]-6-nitro-2-benzofuran-1(3H)-one (DNB) and 5-Methoxy-2-[-4-(2-methoxyphenyl)-5-methyl-1H-pyrazol-3-yl] phenol (MHP). The primary hydrolysis products of ACT in the subcritical hydrolysis experiments comprised 16 species, namely PMA, EOT, TMA, IMA, ETD, DMB, TEA, CBD, DPB, BDM, TTA, ACD, DNB, MHP, TBD, and TPC. As shown in Fig. 3 (d), ACT exhibited a peak at 3174s with the molecular formula C 14 H 20 ClNO 2 . EOT, the demethylation product of TMA, peaked at 2175s with the molecular formula C 9 H 13 N. TMA, the methylation product of MEA, reached a peak at 2284s with the molecular formula C 10 H 15 N. IMA, another methylation product of MEA, reached its peak at 2366s with the molecular formula C 10 H 15 N. ETD, the methylation product of MEA, reached its peak at 2443s. DMB, the demethylation product of DDA, peaked at 2262s, with the molecular formula C 12 H 19 N. CBD, the isomerization and methylation product of ACD, reached its peak at 2867s, with the molecular formula C 11 H 14 ClNO. DPB, the isomerization product of TPC, peaked at 2884s with a molecular formula of C 12 H 15 NO. ACD, the methylation product of CMEPA, exhibited a peak at 3100s with a molecular formula of C 12 H 16 ClNO. As shown in Fig. 3 (a), TEA, the product of TPC, peaked at 2682s, with a molecular formula of C 9 H 13 N. TTA, the methylation product of MDA, peaked at 2979s, with a molecular formula of C 12 H 19 N. PMA, the methylation product of TEA, peaked at 2103s, with a molecular formula of C 11 H 17 ClN. DNB peaked at 3659s, MHP at 3752s, TBD at 3857s, and TPC at 3909s. Illustrated in Fig. 3 (a), (b) and (c), the levels of CBD, DPB, TTA, and TMA exhibited a decline concomitant with the elevation of hydrolysis temperature and reaction duration. Conversely, the quantities of TBD and IMA escalated as the hydrolysis temperature and reaction time experienced an augmentation. The upsurge in TBD could potentially be attributed to the methylation reaction of TEA at 180 ℃. Moreover, the rise in EOT occurred at a hydrolysis temperature of 230 ℃, and its content escalated with the augmentation of both hydrolysis temperature and reaction time. This increase may be attributable to the methylation reactions involving IMA and TMA. Demonstrative evidence reveals that ACT can undergo conversion into a diverse array of hydrolysis products, predominantly encompassing CMEPA, MEA, and others, under natural degradation conditions [ 4 , 42 , 43 ]. Among the 23 hydrolysis products, the presence of ACT's hydrolysis products, namely CMEPA and MEA, was discerned, albeit in limited quantities. CMEPA serves as a demethylation derivative originating from ACT, while MEA is formed through the dechlorination and demethylation reactions of CMEPA. Significantly, not only is ACT itself toxic, but its hydrolysis products, specifically CMEPA, also exhibit toxicity [ 44 ]. Owing to the enduring nature, water solubility, and mobility of these hydrolysis products, their frequent detection in water is attributed. Consequently, to address the ecological threat posed by ACT toxicity, delving into the transformation pathways of ACT and its toxic hydrolysis products in subcritical hydrolysis experiments holds paramount research significance. 3.2 FT-IR analysis of ACT and hydrochar Figure 4 illustrates the FT-IR spectra of ACT and hydrochar, both subjected to diverse processing conditions. The FT-IR technique was employed to investigate alterations in the functional groups on the surfaces of ACT and hydrochar. The examination of the spectra reveals significant changes in the structures of both ACT and hydrochar under varying hydrothermal temperature and reaction time conditions. This observation implies an influence of hydrothermal temperature and reaction time on the functional groups of ACT and hydrochar. These findings contribute to a comprehensive understanding of the chemical transformations occurring during the hydrolysis of ACT and shed light on their consequential impacts on the resultant products. In Fig. 4 (b), (c), and (d), the prominent peaks in the range of 3500 ~ 3100 cm − 1 correspond to -N-H stretching vibrations within the amide group. Additionally, discernible C-H stretching vibrations within the methyl, methylene, and hypromellose groups are observed at wavenumbers 2964, 2934, and 2876 cm − 1 in Fig. 4 (a), (b), (c), and (d), respectively. In Fig. 4 (a), the -C = O stretching vibration within the amide group occurs in the range of 1661 ~ 1591 cm − 1 . Conversely, in Fig. 4 (b), the corresponding -C = O stretching vibration is observed at 1661 − 1621 cm − 1 , while in Fig. 4 (c) and (d), the -C = O stretching vibration within the amide group manifests at 1661 − 1621 cm − 1 . With the temperature elevation to 280°C, the -C = O stretching vibration undergoes a rightward shift from 1681 cm − 1 to 1621 cm − 1 , accompanied by a decrease in the intensity of the -C = O peak. This suggests that an increase in temperature results in a reduction in the polarity of the -C = O bond [ 45 ]. In Fig. 4 (a), the telescopic vibration associated with the -C = C- skeleton is evident within the range of 1463 ~ 1470 cm − 1 , and in Fig. 4 (c) and (d), it is observed within the range of 1482 ~ 1445 cm − 1 . The stretching vibration associated with the -C-N- skeleton occurs at 1373 cm − 1 in all spectra [ 46 ]. In Fig. 4 (a), the telescopic vibration associated with the C-O-C skeleton occurs in the range of 1090 ~ 1019 cm − 1 , and in Fig. 4 (c), (d), it is located at 1060 cm − 1 . Importantly, with the temperature elevation to 280°C, the stretching vibration associated with the C-O-C skeleton undergoes a rightward shift from 1090 cm − 1 to 1060 cm − 1 , accompanied by a decrease in the intensity of the C-O-C peaks. This phenomenon suggests that an increase in temperature results in a reduction in the polarity of the C-O-C bonds. These alterations observed in the FT-IR spectra provide additional insights into the modifications occurring in the molecular structure during the hydrolysis of ACT [ 47 ]. 3.3 SEM analysis of ACT and hydrochar Figure 5 illustrates the external characteristics of ACT's hydrochar under different conditions. By employing SEM techniques, significant changes in the morphology of ACT's hydrochar were observed, particularly in response to variations in temperature and treatment time. At 180°C, ACT undergoes mild hydrolysis, resulting in the development of irregularly shaped, rapid structures of varying sizes on the charcoal surface [ 48 ]. Increasing the temperature to 230°C enhances the distinctiveness of ACT's hydrochar surface texture, accompanied by a moderate degree of hydrolysis [ 49 ]. In comparison to the conditions at 180°C, the hydrochar surface at 230°C exhibits a greater abundance of smaller irregular blocky structures, along with a substantial increase in surface pores [ 50 ]. This observation suggests a more pronounced decomposition of organic components during subcritical hydrolysis [ 51 , 52 ]. Upon further elevation to 280°C, the hydrochar surface becomes rougher, accompanied by a higher number of pores, indicating an intensified hydrolysis process undergone by ACT [ 53 ]. Under constant temperature conditions (180, 230, and 280°C), the surface structure of ACT's hydrochar undergoes substantial changes with the progression of treatment time, ranging from 15 to 60 minutes [ 54 ]. The surface structure exhibits increased roughness as the reaction time extends, leading to the formation of irregularly shaped snap structures with varying sizes and an augmented number of pores [ 48 ]. This implies that the extent of hydrolysis in ACT intensifies with prolonged treatment time [ 45 ]. 3.4 Hydrolytic transformation pathways of ACT during subcritical hydrolysis experiments By synthesizing the results derived from GC×GC-TOFMS analysis and characterization studies, the hydrolytic transformation pathways and mechanisms governing the generation of products from ACT during subcritical hydrolysis experiments were elucidated. Depicted in Fig. 6 are the pathways responsible for the formation of 39 hydrolysis products generated by ACT during subcritical hydrolysis. According to the investigation, the hydrolysis of ACT typically encompasses dechlorination, methylation, amination, hydroxylation, and isomerization reactions. In subcritical hydrolysis experiments, ACT initiates the process by undergoing deethoxymethylation and amide group breakage, ultimately resulting in the formation of CMEPA [ 55 ]. Wang et al. [ 44 ] discovered that CMEPA induces liver damage in zebrafish larvae, underscoring the critical importance of mitigating the risk posed by the metabolic byproduct CMEPA to liver health. The C-N bond within CMEPA underwent cleavage, yielding MEA. Liu et al. [ 56 ] employed radiolytic degradation for ACT, with primary products being CMEPA and MEA. However, when ACT was treated using subcritical water hydrolysis, CMEPA and MEA were minor byproducts, attributable to the higher temperature employed in subcritical water hydrolysis for ACT treatment. Subsequently, MEA underwent further methylation, resulting in the generation of various products, including DYA, IMA, EOT, ETD, TTM, DPA, TMA, DDA, DMB, DFA, and others. DFA experienced both deamination and methylation reactions, leading to the formation of CUM and EBA. ECA arose from the chemotaxis of two small molecule compounds generated by the C-N bond breaking in ACT. The subsequent methylation of ECA resulted in the formation of the product MCA, while EHA was produced through the hydroxylation of ECA. Additionally, EMP was generated by the hydroxylation of MEA, forming phenolic ring compounds. DIA was formed through a process involving dechlorination and methylation of CMEPA, and TPC was produced by the methylation of DIA. Furthermore, DPB and BDM were derived through the processes of methylation and isomerization of TPC, while CBD was formed via the isomerization of CMEPA. CBD underwent dechlorination, methylation, and decarboxylation reactions, resulting in the generation of DPT. Simultaneously, BDM underwent methylation, giving rise to MDA and TTA. TEA was formed through the decarboxylation of TPC, while PMA was produced by the methylation of TEA. TMS was formed through a process involving methylation and isomerization of PMA, and ECA was generated by the isomerization of TEA. Su et al. [ 57 ] employed microbial degradation for ACT treatment. Similarly to the treatment with subcritical water hydrolysis, the hydrolytic products of ACT include CMEPA and DFA. ACT undergoes methylation and dechlorination reactions. Treatment of ACT using subcritical water hydrolysis at a hydrothermal temperature of 280°C and a reaction time of 60 minutes resulted in the lowest ACT content. Furthermore, the toxic hydrolysis products CMEPA underwent complete hydrolysis through subcritical hydrolysis. Consequently, this investigation illustrates that employing subcritical hydrolysis technology proves highly effective in mitigating the risks posed by ACT and its toxic hydrolysis by-products to both the ecosystem and human health. Moreover, it offers a viable solution for the environmentally friendly treatment of ACT. 4. Conclusion This paper discusses the hydrolysis mechanism, decomposition, and transformation pathways of ACT under subcritical conditions. The distribution and identification of hydrolysis products from ACT were elucidated using GC×GC-TOFMS analysis. Employing various analytical techniques, the functional groups and morphological characteristics of both ACT and hydrochar were examined. The hydrolytic transformation pathways of ACT in the subcritical hydrolysis process were determined by integrating results from GC×GC-TOFMS analysis and characterization analysis. The key findings of the study are summarized below: (1) With the increase in temperature and duration, the surface structure of the ACT hydrochar underwent progressive disruption, resulting in a more pronounced texture, indicating an enhancement in the hydrolysis of ACT. The hydrolytic process reached its peak at a hydrothermal temperature of 280 °C with a reaction time of 60 minutes. (2) A decrease in the intensity of the -C=O and C-O-C peaks was observed with increasing temperature, indicating a reduction in the polarity of these two bonds. This phenomenon is primarily attributed to the alterations induced by the hydrolysis of ACT. (3) Utilizing the GC×GC-TOFMS technique, our investigation revealed the emergence of 39 hydrolysis products from ACT during subcritical hydrolysis, predominantly involving dechlorination, hydroxylation, amination, methylation, and isomerization reactions. Notably, at a temperature of 280 °C and a duration of 60 min, the ACT content reached its minimum, and the toxic products CMEPA underwent complete hydrolysis. These findings underscore the efficacy of the subcritical hydrolysis technique in reducing the toxicity of ACT, thereby mitigating the potential environmental and human health risks associated with ACT. 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Isolation and Identification of Endosulfan Degrading Native Bacterial Consortium from Agricultural Soils. Waste and Biomass Valorization. 2020;11(4):3303-3313. Trey M, K DF. Atmospheric OH oxidation chemistry of trifluralin and acetochlor. Environmental science Processes & impacts. 2019; 21(4):650-658. Garrido I, Martínez-Escudero CM, Contreras F, Flores P, Hellín P, Díaz-López M, et al. Degradation of four pesticides by ozonation under field conditions and assessment of its influence on soil microbial activity. Journal of Environmental Chemical Engineering. 2023; 11(3):110027-110034. Bourgin M, Albet J, Violleau F. Study of the degradation of pesticides on loaded seeds by ozonation. Journal of Environmental Chemical Engineering. 2013; 1(4):1004-1012. Weber JB, Peter CJ. Adsorption, Bioactivity, and Evaluation of Soil Tests for Alachlor, Acetochlor, and Metolachlor. Weed Science. 2019; 30(1):14-20. Yu FX, Zhai ZZ, Qu XH. Identification of a Pb-Resistant Acetochlor-Degrading Bacterium for Bioremediation of Soils Contaminated with Herbicides. Water, Air, & Soil Pollution. 2021; 232(2). Fu Y, Li Y, Hu JS, Li S, Qin GW. Photocatalytic degradation of acetochlor by α-Fe 2 O 3 nanoparticles with different morphologies in aqueous solution system. Optik. 2018; 178:36-44. Hou C, Zhao J, Zhang YL, Qian YJ, Chen JB, Yang M, et al. Enhanced simultaneous removal of cadmium, lead, and acetochlor in hyporheic zones with calcium peroxide coupled with zero-valent iron: Mechanisms and application. Chemical Engineering Journal. 2022; 427:130900. Montero GA, Giorgio TD, Schnelle KB. Scale‐up and economic analysis for the design of supercritical fluid extraction equipment for remediation of soil. Environmental Progress & Sustainable Energy. 1996; 15 (2):112-121. Hawthorne SB, Lagadec AJM, Kalderis D, Lilke AV, Miller DJ. Pilot-scale destruction of TNT, RDX, and HMX on contaminated soils using subcritical water. Environmental Science & Technology. 2000; 34 (15):3224-3228. Lagadec AJM, Miller DJ, Lilke AV, Hawthorne SB. Pilot-scale subcritical water remediation of polycyclic aromatic hydrocarbon-and pesticide-contaminated soil. Environmental Science & Technology. 2000; 34 (8):1542-1548. Thompson MT, Young RB, Baroutian S. Efficiency of hydrothermal pretreatment on the anaerobic digestion of pelagic Sargassum for biogas and fertiliser recovery. Fuel. 2020; 279:118515-118527. Islam MN, Park JH, Shin MS, Park HS. Decontamination of PCBs-containing soil using subcritical water extraction process. Chemosphere. 2014; 109:28-33. Islam MN, Jo YT, Jung SK, Park JH. Evaluation of Subcritical Water Extraction Process for Remediation of Pesticide-Contaminated Soil. Water, Air, & Soil Pollution. 2013; 224(8):1652-1658. DeSimone JM. Practical Approaches to Green Solvents. Science. 2002; 297(5582):799-803. Wang; LP, Chang YZ, Li A. Hydrothermal carbonization for energy-efficient processing of sewage sludge: A review. Renewable and Sustainable Energy Reviews. 2019; 108:423-440. Wang Q, Wu S, Cui D, Zhou HY, Wu DY, Pan S, et al. Co-hydrothermal carbonization of organic solid wastes to hydrochar as potential fuel: A review. Science of the Total Environment. 2022; 850:158034. Luo W, Gu QY, Chen WT, Zhu XC, Duan ZB, Yu XB. Biodegradation of acetochlor by a newly isolated Pseudomonas strain. Applied biochemistry and biotechnology. 2015; 176(2):636-644. Ye CM, Wang XJ, Zheng HH. Biodegradation of acetanilide herbicides acetochlor and butachlor in soil. Journal of Environmental Sciences. 2002; (4):524-529. Wang WG, Li MY, Diao L, Zhang C, Tao LM, Zhou WX, et al. The health risk of acetochlor metabolite CMEPA is associated with lipid accumulation induced liver injury. Environmental pollution. 2023; 331:121857. Kocaman K, Yetis U, Dilek FB. Investigating the effect of solids retention time on pesticides removal in an activated sludge process. Sustainable Chemistry and Pharmacy. 2022; 29. Kaluderovic LM, Tomic ZP, Asanin DP, Durovic PRD, Kresovic BJ. Examination of the influence of phenyltrimethylammonium chloride (PTMA) concentration on acetochlor adsorption by modified montmorillonite. Journal of Environmental Science and Health. 2018; 53(8):503-509. Bai XL, Quan BY, Kang CY, Zhang XL, Zheng Y, Song J, et al. Activated carbon from tea residue as efficient absorbents for environmental pollutant removal from wastewater. Biomass Conversion and Biorefinery. 2022;13:13433-13442. Xu QL, Huang HM, Yan J, Wu ZJ, Zhou ZJ, Fang XT, et al. Preparation, characterization and performance analysis of fosthiazate/expanded perlite sustained-release pesticides. Sustainable Chemistry and Pharmacy. 2023; 33:101112-101116. Tien NH, Cuong XN, Phuoc-Cuong L, Tatjana J, Woong CS, Duc ND. Electrochemical degradation of pesticide Padan 95SP by boron-doped diamond electrodes: The role of operating parameters. Journal of Environmental Chemical Engineering. 2021; 9(3):105195-105205. Dagliya M, Satyam N, Garg A. Optimization of growth medium for microbially induced calcium carbonate precipitation(MICP) treatment of desert sand. Journal of Arid Land. 2023; 15(7):797-811. Gai C, Guo Y, Liu T, Peng N, Liu Z. Hydrogen-rich gas production by steam gasification of hydrochar derived from sewage sludge. International Journal of Hydrogen Energy. 2016; 41(5):3363-3372. Nekita B, Sumedha C, Priyanka K. Optimum features of wood-based biochars: A characterization study. Journal of Environmental Chemical Engineering. 2023; 11(3):109971-109976. Liu YT, Qin X, Chen QS, Zhang Q, Yin P, Guo YZ. Effects of moisture and temperature on pesticide stability in corn flour. Journal of the Serbian Chemical Society. 2020; 85(2):191-201. Zhang LH, Gao H, Wang JF, Zhao RF, Wang MM, Hao LY, et al. Plant property regulates soil bacterial community structure under altered precipitation regimes in a semi-arid desert grassland, China. Journal of Arid Land. 2023; 15(5):602-619. Stephane B, Sophie B, Yasmine S, Christophe G, Michel S, Pascal R, et al. GC‐MS and LC‐MS/MS couplings for the identification of degradation products resulting from the ozonation treatment of Acetochlor. Journal of Mass Spectrometry. 2012; 47(4):439-452. Liu SY, Chen YP, Yu HQ. Degradation Pathways of Acetochlor by γ-Radiolysis. Chemistry Letters. 2004; 33(9):1164-1165. Su XN, Zhang JJ, Liu JT, Zhang N, Ma LY, Lu FF, et al. Biodegrading Two Pesticide Residues in Paddy Plants and the Environment by a Genetically Engineered Approach. Journal of agricultural and food chemistry. 2019; 67(17):4947-4957. Table Table 1 is available in the Supplementary Files section. Supplementary Files Table1.docx Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 03 Sep, 2024 Reviewers invited by journal 02 Sep, 2024 Editor invited by journal 16 Jun, 2024 Editor assigned by journal 14 Jun, 2024 First submitted to journal 13 Jun, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4575720","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":348495730,"identity":"c89636ce-0bd7-4c6a-98dd-4200068c179d","order_by":0,"name":"Shuo Pan","email":"","orcid":"","institution":"Northeast Electric Power University","correspondingAuthor":false,"prefix":"","firstName":"Shuo","middleName":"","lastName":"Pan","suffix":""},{"id":348495731,"identity":"2e1e7fe4-5858-404d-a936-8abdbf55ae98","order_by":1,"name":"Huaiyu Zhou","email":"","orcid":"","institution":"Northeast Electric Power University","correspondingAuthor":false,"prefix":"","firstName":"Huaiyu","middleName":"","lastName":"Zhou","suffix":""},{"id":348495732,"identity":"52025cff-71e2-438a-97df-736975d30c99","order_by":2,"name":"Shuang Wu","email":"","orcid":"","institution":"Northeast Electric Power University","correspondingAuthor":false,"prefix":"","firstName":"Shuang","middleName":"","lastName":"Wu","suffix":""},{"id":348495733,"identity":"b5612b8c-c226-4bf3-b9b8-5bf8916a4944","order_by":3,"name":"Jingru Bai","email":"","orcid":"","institution":"Northeast Electric Power University","correspondingAuthor":false,"prefix":"","firstName":"Jingru","middleName":"","lastName":"Bai","suffix":""},{"id":348495734,"identity":"e7131f16-4b47-4b13-b91f-c694c88b3c51","order_by":4,"name":"Da Cui","email":"","orcid":"","institution":"Northeast Electric Power University","correspondingAuthor":false,"prefix":"","firstName":"Da","middleName":"","lastName":"Cui","suffix":""},{"id":348495735,"identity":"29b6bb91-8be1-49cb-a200-33b7eac8f22d","order_by":5,"name":"Qing Wang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAArklEQVRIiWNgGAWjYDACdgbGBx8qbHj42RuI1cLMwGw440yajGTPAeK1sEnzth22MbjhQKQO82YeY6At53kYbjAwfviYQ4QWmcNsiUC/3OZhnN3ALDlzGxFaJJiZDwNtuc3DLHOAjZmXOC2MbUC/nONhk0ggWgvzMaCWAzw8JGhhSwY6LJlHgudgM5F+Ye8xBHrfzt7+ePPBDx+J0YIEGBtIUz8KRsEoGAWjADcAAF73Mb94PbELAAAAAElFTkSuQmCC","orcid":"","institution":"Northeast Electric Power University","correspondingAuthor":true,"prefix":"","firstName":"Qing","middleName":"","lastName":"Wang","suffix":""},{"id":348495736,"identity":"a39d0b83-6b42-42a0-9bf7-01d51483d810","order_by":6,"name":"Faxing Xu","email":"","orcid":"","institution":"Northeast Electric Power University","correspondingAuthor":false,"prefix":"","firstName":"Faxing","middleName":"","lastName":"Xu","suffix":""},{"id":348495737,"identity":"5e8aaff1-26d9-4c8b-81d7-5efffd4f2263","order_by":7,"name":"Zhenye Wang","email":"","orcid":"","institution":"Northeast Electric Power University","correspondingAuthor":false,"prefix":"","firstName":"Zhenye","middleName":"","lastName":"Wang","suffix":""}],"badges":[],"createdAt":"2024-06-13 11:04:32","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4575720/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4575720/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":65835317,"identity":"bbac5147-4700-4bfa-908c-5544c2282c49","added_by":"auto","created_at":"2024-10-03 10:28:35","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":8887,"visible":true,"origin":"","legend":"\u003cp\u003eMolecular structure of ACT\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4575720/v1/450e4d0686f417e881bd4370.jpg"},{"id":65835319,"identity":"0c653ff9-cabf-4550-8792-8b1ff25f6aa5","added_by":"auto","created_at":"2024-10-03 10:28:35","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":72336,"visible":true,"origin":"","legend":"\u003cp\u003eStructure of hydrolysis reactor: (a) Reactor system (1. exhaust cleaning, 2. control system, 3. thermocouple, 4. cooling device, 5. exhaust line, 6. exhaust valve, 7. pressure gauge, 8. magnetic stirrer, 9. fastening bolt, 10. handle, 11. inlet valve, 12. inlet line, 13. nitrogen bottle); (b) Hydrolysis reactor.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4575720/v1/ad86bbff91b4ff714f01b640.jpg"},{"id":65835322,"identity":"20b09acd-56f3-4e1d-8370-eb6050e806dc","added_by":"auto","created_at":"2024-10-03 10:28:35","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":155075,"visible":true,"origin":"","legend":"\u003cp\u003eGC×GC-TOFMS detection mass spectra of ACT and hydrochar: (a)GC×GC-TOFMS detection mass spectra of ACT-280-60; (b) GC×GC-TOFMS detection mass spectra of ACT-180-15, ACT-180-30, and ACT-180-60; (c) GC×GC-TOFMS detection mass spectra of ACT-230-15, ACT-230-30, and ACT-230-60; (d) GC×GC-TOFMS detection mass spectra of ACT-280-15, ACT-280-30, and ACT-280-60.\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4575720/v1/6604d8f12c4fa5297b8e3b85.jpg"},{"id":65835558,"identity":"1c92c995-6b65-4e63-9a99-539bd99617f3","added_by":"auto","created_at":"2024-10-03 10:36:35","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":150517,"visible":true,"origin":"","legend":"\u003cp\u003eFT-IR spectra of ACT and hydrochar: (a) infrared spectra of ACT; (b) infrared spectra of ACT-180-15, ACT-180-30, ACT-180-60; (c) infrared spectra of ACT-230-15, ACT-230-30, ACT-230-60; (d) infrared spectra of ACT-280-15, ACT-280-30, ACT-280-60.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4575720/v1/ee1458fc0acb55c0f24438db.jpg"},{"id":65835324,"identity":"249342fc-6109-48c5-b0eb-5278d00a9936","added_by":"auto","created_at":"2024-10-03 10:28:35","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":97872,"visible":true,"origin":"","legend":"\u003cp\u003eSEM graph of ACT hydrochar\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4575720/v1/fd9d7a3fa4797bddce1273ba.jpg"},{"id":65835320,"identity":"2721d33e-a2d6-44fe-aa64-5e2d92dee606","added_by":"auto","created_at":"2024-10-03 10:28:35","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":221034,"visible":true,"origin":"","legend":"\u003cp\u003eHydrolytic transformation pathway of AT during subcritical hydrolysis\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4575720/v1/0ec4db440a408a4977c1d32d.jpg"},{"id":65836176,"identity":"12d9bafd-8a4f-499e-8ddc-5a804a58d563","added_by":"auto","created_at":"2024-10-03 10:44:38","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1153635,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4575720/v1/4ad05e93-835b-46e9-822c-98f07d56ea9e.pdf"},{"id":65835559,"identity":"365fe5c0-8e5c-466a-998e-a7020bae371a","added_by":"auto","created_at":"2024-10-03 10:36:35","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":152474,"visible":true,"origin":"","legend":"","description":"","filename":"Table1.docx","url":"https://assets-eu.researchsquare.com/files/rs-4575720/v1/511d1e3ba29002614598c4e5.docx"}],"financialInterests":"","formattedTitle":"Reducing Acetochlor Toxicity through Subcritical Hydrolysis Technology: Investigating the Hydrolysis Mechanism","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe rapid progress in agriculture has resulted in an increasing reliance on pesticides [1], creating an urgent need for the safe disposal of these agrochemicals [2, 3]. ACT stands out as a globally prevalent herbicide, renowned for its remarkable efficacy, cost-effectiveness, and widespread applicability [4, 5]. Since its introduction and commencement of production in the early 1990s, China has witnessed a consistent surge in ACT production. In 1994, the production of ACT was merely in the kiloton scale. By 1998, it had surged to 10,000 tons, further escalating to approximately 15,000 tons in 2000, peaking at 30,000-40,000 tons in 2003. By 2021, the global sales of ACT had reached an impressive figure of US$530 million [6]. Once introduced into the soil, ACT undergoes continuous transportation, dispersion, and leaching through irrigation and precipitation processes [7]. Consequently, ACT is frequently detected in both soil and water [8], including drinking water sources [9-11]. This emphasizes the urgent need for prudent management of ACT to mitigate its potential repercussions on both the environment and potable water sources.\u003c/p\u003e\n\u003cp\u003eACT, characterized by a molecular formula of C\u003csub\u003e14\u003c/sub\u003eH\u003csub\u003e20\u003c/sub\u003eClNO\u003csub\u003e2\u003c/sub\u003e and a molecular weight of 269.8, belongs to the homoamide category of pesticides. It exhibits solubility in organic solvents like benzene and acetone and undergoes decomposition when exposed to strong acids and alkalis. The molecular structure of ACT is illustrated in Fig. 1. As a persistent organic pollutant, ACT inherently displays resilience, posing potential hazards to human health, plants, and animals [12]. Additionally, it carries a conceivable carcinogenic risk for humans [5, 13]. Furthermore, ACT impedes plant growth [14-17], disrupts animal development, and causes damage to the animal nervous system [18-20]. The U.S. Environmental Protection Agency has classified ACT as a B-2 carcinogen and a likely human carcinogen, underscoring its potential harm to ecosystems and human health [21]. However, due to its non-volatile characteristics, challenging photolysis, and limited hydrolysis under natural conditions [22], ACT persists, presenting an ongoing threat to plants, animals, and human health and safety [23]. As one of the most widely used herbicides, addressing the potential hazards posed by ACT to the environment and human health requires concerted efforts [24, 25]. Therefore, conducting an in-depth analysis of the hydrolysis pattern of ACT is crucial to mitigate the risks associated with ACT for environmental safety and human health, among other concerns.\u003c/p\u003e\n\u003cp\u003ePresently, the principal approaches for ACT treatment encompass microbial degradation [4], catalytic oxidation [26-28], and adsorption [29]. Xin et al. [30] employed microbial degradation to treat ACT at 30 \u0026deg;C for 48 hours to produce mainly 2-ethyl-6-methyl-N-methyl-\u0026alpha;-chloroacetanilide with low toxicity. Microbial degradation is relatively straightforward to operate, exhibits broad applicability, and boasts low operational costs. Nevertheless, this approach necessitates particular microbial species, entails lengthy processing times, is significantly influenced by environmental factors, and the principal degradation products exhibit marginal toxicity. Fu et al. [31] used catalytic oxidation for the treatment of ACT at 25 \u0026deg;C and 7 h to produce mainly the non-toxic product 1-methyl-3-ving-benzene. Catalytic oxidation offers a broad range of applicability, absence of toxic intermediate by-products, among other advantages. Nonetheless, this technique also confronts challenges such as high catalyst costs, restricted practical application efficiency, organic solvent pollution, and intricate operation. Hou et al. [32] utilized a mixture of calcium peroxide and iron powder for the adsorption of ACT, under conditions of 25 \u0026deg;C temperature and 1 min, resulting in all three degradation products of ACT displaying toxicity. The advantages of adsorption include its simplicity of operation and short processing time. However, this method generates waste, incurs high operating costs, and results in the production of multiple toxic by-products during the degradation process.\u003c/p\u003e\n\u003cp\u003eWhen contrasted with conventional approaches, subcritical water hydrolysis technology showcases viability in both technical and economic spheres [33-35]. Subcritical hydrolysis technology facilitates the decomposition of organic constituents, expedites methane fermentation, and mitigates the release of harmful gases [36]. Through precise control of reaction parameters, various toxic and stable pesticides can be efficiently processed [37]. Islam et al. [38] employed subcritical water hydrolysis technology to process diazinon, parathion, phenthoat, and EPN pesticides under the conditions of 150 \u0026deg;C and 20 min, thereby transforming these four pesticides and their toxic by-products into harmless compounds. Subcritical hydrolysis represents a \u0026quot;green treatment\u0026quot; utilizing superheated water (100 \u0026deg;C \u0026le; T \u0026le; 374 \u0026deg;C and pressure \u0026lt; 22.1 MPa) as a solvent, eliminating the need for organic solvents [39]. Water exhibits increased solubility at elevated temperatures, facilitating the dissolution of ACT. This solubility enables water to serve as a solvent in the reaction, facilitating the dissolution of reactants and catalyzing the reaction. In subcritical hydrolysis experiments treating ACT, the necessity for acid, alkali, and catalysts is eliminated, leaving no solvent residue. The process is non-flammable and non-explosive, effectively reducing the toxicity of ACT [40]. Thus, subcritical hydrolysis technology for ACT treatment boasts high efficiency, minimal pollution, low energy consumption, and straightforward operation. Therefore, subcritical hydrolysis technology emerges as a promising solution, effectively mitigating pesticide toxicity while concurrently degrading and treating hazardous pesticides, ultimately achieving environmentally benign ACT treatment.\u003c/p\u003e\n\u003cp\u003eIn this study, the subcritical hydrolysis technique was employed to treat ACT under varying hydrothermal temperatures and reaction times. Initially, the intermediate products resulting from subcritical hydrolysis experiments of ACT underwent a comprehensive analysis using GC\u0026times;GC-TOFMS. This analysis aimed to elucidate the distribution pattern of the hydrolysis products derived from ACT. Subsequently, FT-IR and SEM techniques were applied for a thorough characterization and analysis of both ACT and the hydrochar. The objective was to gain a comprehensive understanding of the functional group types and morphological features present in ACT and the resulting hydrochar. By integrating the principles of product analysis and characterization, the mechanism of hydrolysis product transformation during subcritical hydrolysis experiments of ACT was unveiled. Ultimately, through the application of subcritical hydrolysis technology, we successfully achieved the environmentally benign treatment of ACT, effectively addressing its potential impact on ecological safety and human health.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec2\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Raw material\u003c/h2\u003e \u003cp\u003eThe ACT employed in this study was obtained from Hubei Weideli Chemical Reagent Co., Ltd., with a purity exceeding 93%, and it manifested as a light yellow liquid. Analytically pure benzene was sourced from Tianjin Damao Chemical Reagent Factory, and analytically pure acetone was procured from Yantai Shuangshuang Chemical Co..\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Reaction conditions\u003c/h2\u003e \u003cp\u003eSubcritical hydrolysis experiments were conducted using a 500 mL autoclave reactor (HT-500FJ, Baikal, China), as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. In each trial, 10 g of ACT liquid was mixed with 100 mL of deionized water and subsequently heated to varying temperatures-180\u0026deg;C, 230\u0026deg;C, and 280\u0026deg;C. The autoclave was maintained at the designated temperature for durations of 15 min, 30 min, and 60 min, resulting in a total of nine experimental sets. The pressure within the reactor escalates with ascending temperatures. At reactor temperatures of 180\u0026deg;C, 230\u0026deg;C, and 280\u0026deg;C, the respective pressures amount to 7 bar, 26 bar, and 53 bar, correspondingly. Subsequently, the reactor was cooled to room temperature. Following the hydrothermal reaction, the resulting solid and liquid products (ACT-T-S: ACT-acetochlor; T-temperature; S-time) were filtered and reserved separately. Place the funnel onto the stand, ensuring that the funnel stem is positioned inside the beaker for smooth collection of liquid product. Next, snugly place filter paper against the funnel neck to prevent solid material from entering the liquid product. Subsequently, pour the mixture of solid and liquid into a flat-bottomed funnel and allow it to stand for 1 hour to facilitate the separation of solid and liquid components.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Determination of ACT hydrolysis products by GC\u0026times;GC-TOFMS\u003c/h2\u003e \u003cp\u003eThe liquid products resulting from ACT treatment underwent comprehensive analysis using a Gas Chromatography-Time-Of-Flight Mass Spectrometry (GC\u0026times;GC-TOFMS) analyzer (Clarus SQ8, PerkinElmer, USA). This analytical approach was designed to elucidate the distribution patterns of hydrolysis products arising from ACT, providing insights into the hydrolysis pathways under varying hydrothermal temperatures and reaction durations.\u003c/p\u003e \u003cp\u003eThe hydrolyzed liquid products, acquired in nine sets, were introduced into a 250 mL separatory funnel. Subsequently, 20 mL of benzene was added, and the mixture underwent vigorous shaking for 10 min, followed by a 5-minute rest period to facilitate stratification. The upper benzene layer was meticulously transferred into a triangular flask. This extraction procedure was iterated three times with the addition of 20 mL of benzene in each repetition. The resulting three extracts were amalgamated in the triangular flask. After dehydration with anhydrous sodium sulfate, the extracts were transferred to a concentration cup, quantitatively reduced to approximately 0.5 mL, and then adjusted to a final volume of 2.0 mL using benzene. Ultimately, the liquid products from the nine sets underwent comprehensive analysis using the GC\u0026times;GC-TOFMS technique.\u003c/p\u003e \u003cp\u003eThe gas chromatographic conditions were controlled using a DB-PETRO capillary column (50 m\u0026times;0.20 mm inner diameter\u0026times;0.5 \u0026micro;m film thickness). The heating protocol for the column was initiated with an initial temperature of 50 ℃, maintained for 3 min, followed by a gradual increase to 100 ℃ at a rate of 3 ℃\u0026middot;min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, held for an additional 3 min, and subsequently raised to 300 ℃ at a rate of 5 ℃\u0026middot;min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, where it was held for 5 min. Helium served as the carrier gas at a flow rate of 1 mL\u0026middot;min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and sample injection was executed through a shunt pulse with a shunt ratio of 5:1. The inlet port temperature was sustained at 270 ℃, and the injection volume was set at 1 \u0026micro;l. The mass spectrometric conditions comprised an electron bombardment (EI) source, an ion source temperature of 280 ℃, an ionization energy of 70 eV, a scanning range spanning 35\u0026thinsp;~\u0026thinsp;500 amu, a quadrupole temperature of 150 ℃, a mass transfer line maintained at 280 ℃, and a solvent delay of 7 min.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Analytical methods for characterization of ACT and hydrochar\u003c/h2\u003e \u003cp\u003eComprehensive characterization and analysis were systematically conducted on both ACT and hydrochar samples to investigate the influence of hydrolysis temperature and reaction time on their elemental composition, surface morphology, pore structure, and surface functional groups in the context of subcritical hydrolysis experiments. The resulting solid products from hydrolysis underwent meticulous drying at 105\u0026deg;C for 12 hours. Subsequently, the nine sets of resulting solid hydrochar were subjected to detailed characterization analyses. In this study, the Nicolet IS10 Fourier Transform Infrared (FT-IR) technique (Thermo Fisher, USA) was employed to characterize the infrared spectra of the ACT chars, facilitating the analysis of variation patterns in characteristic functional groups. Additionally, the Scanning Electron Microscopy (SEM) technique (JSM-7610F, JEOL, Japan) was utilized to scrutinize the external appearance of the ACT and hydrochar, providing insights into alterations in surface structure and solid morphology.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1. Product analysis of ACT during subcritical hydrolysis experiments\u003c/h2\u003e\n \u003cp\u003eGC\u0026times;GC-TOFMS technology was employed to analyze the hydrolysis products of ACT under various hydrothermal temperatures and reaction times in subcritical hydrolysis experiments. This analysis successfully determined the molecular and structural formulas of the hydrolysis products, as depicted in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e. A total of 39 hydrolysis products were identified during the experiments, as outlined in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. The hydrolysis products of ACT mainly include aromatic compounds, aliphatic compounds and aliphatic heterocyclic compounds, with aromatic compounds being the main product class.\u003c/p\u003e\n \u003cp\u003eThe aromatic products of ACT comprise 33 distinct compounds, falling within various categories such as aromatic phenols, aromatic acyls, aromatic amides, aromatic olefins, halogenated aromatic hydrocarbons, aromatic hydrocarbons, aromatic amines, aromatic esters, aromatic aldehydes, aromatic ketones, and polyphenyl aliphatic hydrocarbons. Among the aromatic phenolic compounds are 2-Ethyl-6-methylphenol (EMP) and Phenol, 2-ethyl-4,5-dimethyl- (PED). Aromatic amides encompass Acetamide, 2-chloro-N-(2,6-diethylphenyl)- (ACD), and 2-Ethyl-6-methyl-2-chloroacetanilide (CMEPA). Halogenated aromatic compounds comprise Chlorobenzene (CBZ). Aromatic hydrocarbons consist of Ethylbenzene (EBZ), O-xylene (OXE), Cumene (CUM), and Benzene, 1-ethyl-2,4,5-trimethyl (BET). Aromatic olefins feature 2,4,6-Trimethylstyrene (TMS). Aromatic amines encompass 2,4,6,N,N-Pentamethylaniline (PMA), 2-Ethyl-6-methylaniline (MEA), 3-Methyl-N,N-dipropylaniline (MDA), N,N,3-triethylaniline (TTA), N,n-diethyl-p-toluidine (DPT), 2,4,6-Trimethylaniline (TEA), N,n-diethyl-2-methyl-benzenamine (DMB), 2,6-Diisopropylaniline (DPA), 1-Ethyl-1,2,3,4-tetrahydroquinolin-7-ol (ETD), 2-(TerT-butyl)-6-methylaniline (TTM), 2,6-Diethylaniline (DYA), 2,6,N,N-Tetramethylaniline (TMA), N,N-Diethylaniline (DFA), Benzenamine, N,N-diethyl-2,6-dimethyl-(DDA), Eseudocumidine (PDC), 2,6-Dimethylaniline (EOT), 2-Isopropyl-6-methylaniline (IMA). Aromatic esters include 2,4,6-Trimethylphenyl isocyanate (TPC) and 2,6-Diethylphenyl isocyanate (DIA). Aromatic aldehydes consist of Benzaldehyde, 4-(dimethylamino)-2-methyl- (BDM) and 4-[(2-Chloroethyl) ethylamino]-benzaldehyde (CBD). Aromatic ketones showcase 4-[4-(Dimethylamino) phenyl] but-3-en-2-one (DPB). Polyphenyl aliphatic hydrocarbon compounds include 3,5,3\u0026apos;,5\u0026apos;-Tetramethyl-N4-propyl-biphenyl-4,4\u0026apos;-diamine (TBD).\u003c/p\u003e\n \u003cp\u003eThe aliphatic products of ACT encompass four distinct compounds, falling within the categories of both fatty esters and fatty amines. Specifically, the fatty esters comprise Methyl chloroacetate (MCA), Ethyl 2-hydroxyacetate (EHA), and Ethyl chloroacetate (ECA). Meanwhile, the group of fatty amine compounds features Dimethylamine (DTA). Two heterocyclic products originating from ACT lipids were identified, namely (3Z)-3-[4-(Diethylamion) bezylidene]-6-nitro-2-benzofuran-1(3H)-one (DNB) and 5-Methoxy-2-[-4-(2-methoxyphenyl)-5-methyl-1H-pyrazol-3-yl] phenol (MHP).\u003c/p\u003e\n \u003cp\u003eThe primary hydrolysis products of ACT in the subcritical hydrolysis experiments comprised 16 species, namely PMA, EOT, TMA, IMA, ETD, DMB, TEA, CBD, DPB, BDM, TTA, ACD, DNB, MHP, TBD, and TPC. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e(d), ACT exhibited a peak at 3174s with the molecular formula C\u003csub\u003e14\u003c/sub\u003eH\u003csub\u003e20\u003c/sub\u003eClNO\u003csub\u003e2\u003c/sub\u003e. EOT, the demethylation product of TMA, peaked at 2175s with the molecular formula C\u003csub\u003e9\u003c/sub\u003eH\u003csub\u003e13\u003c/sub\u003eN. TMA, the methylation product of MEA, reached a peak at 2284s with the molecular formula C\u003csub\u003e10\u003c/sub\u003eH\u003csub\u003e15\u003c/sub\u003eN. IMA, another methylation product of MEA, reached its peak at 2366s with the molecular formula C\u003csub\u003e10\u003c/sub\u003eH\u003csub\u003e15\u003c/sub\u003eN. ETD, the methylation product of MEA, reached its peak at 2443s. DMB, the demethylation product of DDA, peaked at 2262s, with the molecular formula C\u003csub\u003e12\u003c/sub\u003eH\u003csub\u003e19\u003c/sub\u003eN. CBD, the isomerization and methylation product of ACD, reached its peak at 2867s, with the molecular formula C\u003csub\u003e11\u003c/sub\u003eH\u003csub\u003e14\u003c/sub\u003eClNO. DPB, the isomerization product of TPC, peaked at 2884s with a molecular formula of C\u003csub\u003e12\u003c/sub\u003eH\u003csub\u003e15\u003c/sub\u003eNO. ACD, the methylation product of CMEPA, exhibited a peak at 3100s with a molecular formula of C\u003csub\u003e12\u003c/sub\u003eH\u003csub\u003e16\u003c/sub\u003eClNO.\u003c/p\u003e\n \u003cp\u003eAs shown in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e(a), TEA, the product of TPC, peaked at 2682s, with a molecular formula of C\u003csub\u003e9\u003c/sub\u003eH\u003csub\u003e13\u003c/sub\u003eN. TTA, the methylation product of MDA, peaked at 2979s, with a molecular formula of C\u003csub\u003e12\u003c/sub\u003eH\u003csub\u003e19\u003c/sub\u003eN. PMA, the methylation product of TEA, peaked at 2103s, with a molecular formula of C\u003csub\u003e11\u003c/sub\u003eH\u003csub\u003e17\u003c/sub\u003eClN. DNB peaked at 3659s, MHP at 3752s, TBD at 3857s, and TPC at 3909s. Illustrated in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e(a), (b) and (c), the levels of CBD, DPB, TTA, and TMA exhibited a decline concomitant with the elevation of hydrolysis temperature and reaction duration. Conversely, the quantities of TBD and IMA escalated as the hydrolysis temperature and reaction time experienced an augmentation. The upsurge in TBD could potentially be attributed to the methylation reaction of TEA at 180 ℃. Moreover, the rise in EOT occurred at a hydrolysis temperature of 230 ℃, and its content escalated with the augmentation of both hydrolysis temperature and reaction time. This increase may be attributable to the methylation reactions involving IMA and TMA.\u003c/p\u003e\n \u003cp\u003eDemonstrative evidence reveals that ACT can undergo conversion into a diverse array of hydrolysis products, predominantly encompassing CMEPA, MEA, and others, under natural degradation conditions [\u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e42\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e43\u003c/span\u003e]. Among the 23 hydrolysis products, the presence of ACT\u0026apos;s hydrolysis products, namely CMEPA and MEA, was discerned, albeit in limited quantities. CMEPA serves as a demethylation derivative originating from ACT, while MEA is formed through the dechlorination and demethylation reactions of CMEPA. Significantly, not only is ACT itself toxic, but its hydrolysis products, specifically CMEPA, also exhibit toxicity [\u003cspan class=\"CitationRef\"\u003e44\u003c/span\u003e]. Owing to the enduring nature, water solubility, and mobility of these hydrolysis products, their frequent detection in water is attributed. Consequently, to address the ecological threat posed by ACT toxicity, delving into the transformation pathways of ACT and its toxic hydrolysis products in subcritical hydrolysis experiments holds paramount research significance.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 FT-IR analysis of ACT and hydrochar\u003c/h2\u003e\n \u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e illustrates the FT-IR spectra of ACT and hydrochar, both subjected to diverse processing conditions. The FT-IR technique was employed to investigate alterations in the functional groups on the surfaces of ACT and hydrochar. The examination of the spectra reveals significant changes in the structures of both ACT and hydrochar under varying hydrothermal temperature and reaction time conditions. This observation implies an influence of hydrothermal temperature and reaction time on the functional groups of ACT and hydrochar. These findings contribute to a comprehensive understanding of the chemical transformations occurring during the hydrolysis of ACT and shed light on their consequential impacts on the resultant products.\u003c/p\u003e\n \u003cp\u003eIn Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(b), (c), and (d), the prominent peaks in the range of 3500\u0026thinsp;~\u0026thinsp;3100 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e correspond to -N-H stretching vibrations within the amide group. Additionally, discernible C-H stretching vibrations within the methyl, methylene, and hypromellose groups are observed at wavenumbers 2964, 2934, and 2876 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(a), (b), (c), and (d), respectively. In Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(a), the -C\u0026thinsp;=\u0026thinsp;O stretching vibration within the amide group occurs in the range of 1661\u0026thinsp;~\u0026thinsp;1591 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Conversely, in Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(b), the corresponding -C\u0026thinsp;=\u0026thinsp;O stretching vibration is observed at 1661\u0026thinsp;\u0026minus;\u0026thinsp;1621 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, while in Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(c) and (d), the -C\u0026thinsp;=\u0026thinsp;O stretching vibration within the amide group manifests at 1661\u0026thinsp;\u0026minus;\u0026thinsp;1621 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. With the temperature elevation to 280\u0026deg;C, the -C\u0026thinsp;=\u0026thinsp;O stretching vibration undergoes a rightward shift from 1681 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 1621 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, accompanied by a decrease in the intensity of the -C\u0026thinsp;=\u0026thinsp;O peak. This suggests that an increase in temperature results in a reduction in the polarity of the -C\u0026thinsp;=\u0026thinsp;O bond [\u003cspan class=\"CitationRef\"\u003e45\u003c/span\u003e]. In Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(a), the telescopic vibration associated with the -C\u0026thinsp;=\u0026thinsp;C- skeleton is evident within the range of 1463\u0026thinsp;~\u0026thinsp;1470 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and in Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(c) and (d), it is observed within the range of 1482\u0026thinsp;~\u0026thinsp;1445 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The stretching vibration associated with the -C-N- skeleton occurs at 1373 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in all spectra [\u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e]. In Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(a), the telescopic vibration associated with the C-O-C skeleton occurs in the range of 1090\u0026thinsp;~\u0026thinsp;1019 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and in Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(c), (d), it is located at 1060 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Importantly, with the temperature elevation to 280\u0026deg;C, the stretching vibration associated with the C-O-C skeleton undergoes a rightward shift from 1090 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 1060 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, accompanied by a decrease in the intensity of the C-O-C peaks. This phenomenon suggests that an increase in temperature results in a reduction in the polarity of the C-O-C bonds. These alterations observed in the FT-IR spectra provide additional insights into the modifications occurring in the molecular structure during the hydrolysis of ACT [\u003cspan class=\"CitationRef\"\u003e47\u003c/span\u003e].\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3 SEM analysis of ACT and hydrochar\u003c/h2\u003e\n \u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e illustrates the external characteristics of ACT\u0026apos;s hydrochar under different conditions. By employing SEM techniques, significant changes in the morphology of ACT\u0026apos;s hydrochar were observed, particularly in response to variations in temperature and treatment time. At 180\u0026deg;C, ACT undergoes mild hydrolysis, resulting in the development of irregularly shaped, rapid structures of varying sizes on the charcoal surface [\u003cspan class=\"CitationRef\"\u003e48\u003c/span\u003e]. Increasing the temperature to 230\u0026deg;C enhances the distinctiveness of ACT\u0026apos;s hydrochar surface texture, accompanied by a moderate degree of hydrolysis [\u003cspan class=\"CitationRef\"\u003e49\u003c/span\u003e]. In comparison to the conditions at 180\u0026deg;C, the hydrochar surface at 230\u0026deg;C exhibits a greater abundance of smaller irregular blocky structures, along with a substantial increase in surface pores [\u003cspan class=\"CitationRef\"\u003e50\u003c/span\u003e]. This observation suggests a more pronounced decomposition of organic components during subcritical hydrolysis [\u003cspan class=\"CitationRef\"\u003e51\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e52\u003c/span\u003e]. Upon further elevation to 280\u0026deg;C, the hydrochar surface becomes rougher, accompanied by a higher number of pores, indicating an intensified hydrolysis process undergone by ACT [\u003cspan class=\"CitationRef\"\u003e53\u003c/span\u003e].\u003c/p\u003e\n \u003cp\u003eUnder constant temperature conditions (180, 230, and 280\u0026deg;C), the surface structure of ACT\u0026apos;s hydrochar undergoes substantial changes with the progression of treatment time, ranging from 15 to 60 minutes [\u003cspan class=\"CitationRef\"\u003e54\u003c/span\u003e]. The surface structure exhibits increased roughness as the reaction time extends, leading to the formation of irregularly shaped snap structures with varying sizes and an augmented number of pores [\u003cspan class=\"CitationRef\"\u003e48\u003c/span\u003e]. This implies that the extent of hydrolysis in ACT intensifies with prolonged treatment time [\u003cspan class=\"CitationRef\"\u003e45\u003c/span\u003e].\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4 Hydrolytic transformation pathways of ACT during subcritical hydrolysis experiments\u003c/h2\u003e\n \u003cp\u003eBy synthesizing the results derived from GC\u0026times;GC-TOFMS analysis and characterization studies, the hydrolytic transformation pathways and mechanisms governing the generation of products from ACT during subcritical hydrolysis experiments were elucidated. Depicted in Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e are the pathways responsible for the formation of 39 hydrolysis products generated by ACT during subcritical hydrolysis. According to the investigation, the hydrolysis of ACT typically encompasses dechlorination, methylation, amination, hydroxylation, and isomerization reactions. In subcritical hydrolysis experiments, ACT initiates the process by undergoing deethoxymethylation and amide group breakage, ultimately resulting in the formation of CMEPA [\u003cspan class=\"CitationRef\"\u003e55\u003c/span\u003e]. Wang et al. [\u003cspan class=\"CitationRef\"\u003e44\u003c/span\u003e] discovered that CMEPA induces liver damage in zebrafish larvae, underscoring the critical importance of mitigating the risk posed by the metabolic byproduct CMEPA to liver health.\u003c/p\u003e\n \u003cp\u003eThe C-N bond within CMEPA underwent cleavage, yielding MEA. Liu et al. [\u003cspan class=\"CitationRef\"\u003e56\u003c/span\u003e] employed radiolytic degradation for ACT, with primary products being CMEPA and MEA. However, when ACT was treated using subcritical water hydrolysis, CMEPA and MEA were minor byproducts, attributable to the higher temperature employed in subcritical water hydrolysis for ACT treatment. Subsequently, MEA underwent further methylation, resulting in the generation of various products, including DYA, IMA, EOT, ETD, TTM, DPA, TMA, DDA, DMB, DFA, and others. DFA experienced both deamination and methylation reactions, leading to the formation of CUM and EBA. ECA arose from the chemotaxis of two small molecule compounds generated by the C-N bond breaking in ACT. The subsequent methylation of ECA resulted in the formation of the product MCA, while EHA was produced through the hydroxylation of ECA. Additionally, EMP was generated by the hydroxylation of MEA, forming phenolic ring compounds.\u003c/p\u003e\n \u003cp\u003eDIA was formed through a process involving dechlorination and methylation of CMEPA, and TPC was produced by the methylation of DIA. Furthermore, DPB and BDM were derived through the processes of methylation and isomerization of TPC, while CBD was formed via the isomerization of CMEPA. CBD underwent dechlorination, methylation, and decarboxylation reactions, resulting in the generation of DPT. Simultaneously, BDM underwent methylation, giving rise to MDA and TTA. TEA was formed through the decarboxylation of TPC, while PMA was produced by the methylation of TEA. TMS was formed through a process involving methylation and isomerization of PMA, and ECA was generated by the isomerization of TEA.\u003c/p\u003e\n \u003cp\u003eSu et al. [\u003cspan class=\"CitationRef\"\u003e57\u003c/span\u003e] employed microbial degradation for ACT treatment. Similarly to the treatment with subcritical water hydrolysis, the hydrolytic products of ACT include CMEPA and DFA. ACT undergoes methylation and dechlorination reactions. Treatment of ACT using subcritical water hydrolysis at a hydrothermal temperature of 280\u0026deg;C and a reaction time of 60 minutes resulted in the lowest ACT content. Furthermore, the toxic hydrolysis products CMEPA underwent complete hydrolysis through subcritical hydrolysis. Consequently, this investigation illustrates that employing subcritical hydrolysis technology proves highly effective in mitigating the risks posed by ACT and its toxic hydrolysis by-products to both the ecosystem and human health. Moreover, it offers a viable solution for the environmentally friendly treatment of ACT.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eThis paper discusses the hydrolysis mechanism, decomposition, and transformation pathways of ACT under subcritical conditions. The distribution and identification of hydrolysis products from ACT were elucidated using GC\u0026times;GC-TOFMS analysis. Employing various analytical techniques, the functional groups and morphological characteristics of both ACT and hydrochar were examined. The hydrolytic transformation pathways of ACT in the subcritical hydrolysis process were determined by integrating results from GC\u0026times;GC-TOFMS analysis and characterization analysis. The key findings of the study are summarized below:\u003c/p\u003e\n\u003cp\u003e(1) With the increase in temperature and duration, the surface structure of the ACT hydrochar underwent progressive disruption, resulting in a more pronounced texture, indicating an enhancement in the hydrolysis of ACT. The hydrolytic process reached its peak at a hydrothermal temperature of 280 \u0026deg;C with a reaction time of 60 minutes.\u003c/p\u003e\n\u003cp\u003e(2) A decrease in the intensity of the -C=O and C-O-C peaks was observed with increasing temperature, indicating a reduction in the polarity of these two bonds. This phenomenon is primarily attributed to the alterations induced by the hydrolysis of ACT.\u003c/p\u003e\n\u003cp\u003e(3) Utilizing the GC\u0026times;GC-TOFMS technique, our investigation revealed the emergence of 39 hydrolysis products from ACT during subcritical hydrolysis, predominantly involving dechlorination, hydroxylation, amination, methylation, and isomerization reactions. Notably, at a temperature of 280 \u0026deg;C and a duration of 60 min, the ACT content reached its minimum, and the toxic products CMEPA underwent complete hydrolysis. These findings underscore the efficacy of the subcritical hydrolysis technique in reducing the toxicity of ACT, thereby mitigating the potential environmental and human health risks associated with ACT.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eDate availability statement:\u003c/h2\u003e \u003cp\u003eThe date that support the findings of this study are available from the corresponding author, [Qing Wang], upon reasonable request.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e \u003cp\u003eThe authors appreciate the support from the Science and Technology Research Program of Jilin Provincial Department of Education (JJKH20230112KJ) and the financial support from the National Natural Science Foundation of China (No.51676032).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eHamrouni R, Molinet J, Dupuy N, Taieb N, Carboue Q, Masmoudi A, et al. 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Journal of agricultural and food chemistry. 2019; 67(17):4947-4957.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Table","content":"\u003cp\u003eTable 1 is available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"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":"waste-and-biomass-valorization","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"wave","sideBox":"Learn more about [Waste and Biomass Valorization](http://link.springer.com/journal/12649)","snPcode":"12649","submissionUrl":"https://submission.nature.com/new-submission/12649/3","title":"Waste and Biomass Valorization","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Acetochlor, Subcritical hydrolysis, Hydrolysis mechanism, GC×GC-TOFMS technique","lastPublishedDoi":"10.21203/rs.3.rs-4575720/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4575720/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe primary objective of this investigation was to address the toxicity associated with acetochlor (ACT) through subcritical hydrolysis treatment, assessing the efficacy of this approach in mitigating concerns related to acetochlor's toxicity. Gas chromatography-time-of-flight mass spectrometry (GC × GC-TOFMS), Fourier transform infrared spectrometry (FT-IR), and scanning electron microscopy (SEM) were employed to elucidate distribution patterns, variations in functional groups, and morphological features of the hydrolyzed derivatives of ACT. The hydrolytic transformation pathway and mechanisms of ACT product formation were determined by integrating findings from GC × GC-TOFMS analysis and characterization assessments. The subcritical hydrolysis experiments resulted in the identification of 39 hydrolytic by-products from ACT. The peak hydrolysis rate for ACT was observed at a hydrothermal temperature of 280 °C with a reaction duration of 60 minutes, leading to the complete hydrolysis of toxic by-products. In this study, subcritical hydrolysis technology demonstrated its effectiveness in mitigating the toxicity of ACT, achieving environmentally sustainable treatment, and aiding in the resolution of potential hazards posed by ACT to ecosystems and human health.\u003c/p\u003e","manuscriptTitle":"Reducing Acetochlor Toxicity through Subcritical Hydrolysis Technology: Investigating the Hydrolysis Mechanism","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-10-03 10:28:30","doi":"10.21203/rs.3.rs-4575720/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2024-09-03T18:54:44+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-09-02T15:13:40+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Waste and Biomass Valorization","date":"2024-06-16T12:51:47+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-06-14T09:22:04+00:00","index":"","fulltext":""},{"type":"submitted","content":"Waste and Biomass Valorization","date":"2024-06-13T07:04:20+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"waste-and-biomass-valorization","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"wave","sideBox":"Learn more about [Waste and Biomass Valorization](http://link.springer.com/journal/12649)","snPcode":"12649","submissionUrl":"https://submission.nature.com/new-submission/12649/3","title":"Waste and Biomass Valorization","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"32dabd87-a47e-4158-85dc-fdbc70f31a5b","owner":[],"postedDate":"October 3rd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2024-10-03T10:28:30+00:00","versionOfRecord":[],"versionCreatedAt":"2024-10-03 10:28:30","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4575720","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4575720","identity":"rs-4575720","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}