Study on the activity of doped metal-modified water-sodium- manganese ore catalyst to catalyze the degradation of dimethylamine

Study on the activity of doped metal-modified water-sodium- manganese ore catalyst to catalyze the degradation of dimethylamine | 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 Study on the activity of doped metal-modified water-sodium- manganese ore catalyst to catalyze the degradation of dimethylamine Jia Wei, Chengxun Deng, Mengnan Yu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7291479/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 15 You are reading this latest preprint version Abstract Improving the degradation efficiency of VOCs remains a challenge for our industry. Among them, catalytic degradation is an efficient VOCs degradation technology. The synthesis of doped metal-modified water-sodium-manganese mineral catalysts with efficient catalytic performance and stability remains a challenge for the complete degradation of VOPs. Different water-sodium-manganese ore manganese dioxide were prepared by high-temperature calcination and solvent method, and modified by doped metals (Al, Ce, K), and the results showed that the K 2 SO 4- MnO 2 -M2 catalyst prepared by solvent method had good catalytic activity. By adjusting the metal doping ratio of manganese to potassium and changing the crystal structure of the catalyst, the results showed that the K 2 SO 4- MnO 2 -M2 (6:10) type had the best catalytic activity. The results showed that the K 2 SO 4- MnO 2 -M2 catalyst introduced K + ions into the original crystal structure, and it was observed that the ratio of Mn 3+ to Mn 4+ increased with the insertion of K + , indicating that there were more oxygen vacancies, and the concentration of adsorbed oxygen and lattice oxygen increased, which was conducive to catalytic performance and catalytic stability. This study provides a reference for the degradation of volatile organic pollutants by doped modified water-sodium-manganese ore catalysts. catalyst VOCs Water sodium manganese ore Modified materials Degrade ethyl acetate Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 1 Introduction Volatile organic compounds (VOCs) are considered to be one of the major air pollutants, which are not only harmful to human health, but also harmful to the environment.At present, effective removal methods for VOCs include adsorption method, catalytic method, biofilm separation method, photocatalytic method, and plasma method(He et al., 2009 ).Among them, catalytic oxidation has been widely used because of its good degradation effect and high stability. In order to catalyze the degradation of VOCs, catalysts are often used(Y. Sun et al., 2023 ),and studies have shown that the effects of different catalysts for catalytic degradation of VOCs are significantly different(Liu et al., 2019 ). The research of (Du et al,2023)shows that TiO 2 catalyst, as the most mature photocatalyst, has the characteristics of high catalytic efficiency and low cost, but due to the low optical quantum efficiency of TiO 2 , the easy recombination of electron-hole pairs, and the inability to produce visible light response, TiO 2 photochemical materials cannot be widely and efficiently used. Consult the literature (Wang et al,2024) used the CeO 2 catalyst, and the results showed that CeO 2 has the characteristics of visible light response, high chemical stability, and strong photogenerated hole oxidation ability, but CeO 2 has shortcomings such as photogenerated electron/hole pair easy recombination and low photocatalytic efficiency, which limits its practical application. Consult the literature (Ren Lei et al,2024) used a Pt-based catalyst to catalyze the degradation of VOCs, and the results showed that the catalyst had higher lattice oxygen content and stronger redox ability, which was conducive to improving the catalytic degradation ability of VOCs, but the precious metal was expensive and difficult to prepare. As a ubiquitous manganese oxide mineral in nature, its unique two-dimensional layered structure makes it have excellent physical and chemical properties. After reviewing the literature, it was found that the water-sodium manganese ore catalyst prepared by (Zhang et al,2015) had the highest catalytic activity, simple operation and good stability. By reviewing the literature, it can be seen that (J. Zhang et al., 2015a ) a single manganese oxide catalyst has shortcomings such as low degradation efficiency and intermediate products, so on this basis, scholars have tried to load manganese dioxide materials on other stable supports to obtain the modified water-sodium manganese ore catalyst. At present, there have been many reports on sodium manganese ore, but there are few studies on the adsorption mechanism of sodium manganese ore and transition metal-doped sodium manganese ore on VOCs. After reviewing the literature, it can be seen that the metal doping the catalyst has a significant effect on the degradation of VOCs, and through the literature review, it can be found that(Yang et al., 2020 )doped and modified the water sodium manganese ore with K ions to obtain the K-ion water sodium manganese ore material. Consult the literature (Tang et al., 2006 ) prepared a water-sow-manganese ore catalyst doped with Ce ions. Consult the literature(Drits et al., 1997 ) showed that with the increase of doping amount, the octahedral vacancy decreased, and the adsorption effect of the material gradually increased. Therefore, the catalyst prepared by doping modified water-sodium manganese ore material can enhance its catalytic oxidation. In this paper, the modified sodium manganese rock catalysts with good catalytic activity and good stability were screened by studying the doping modificatio Potassium, aluminum, and cerium metal oxide catalysts were prepared on a solvent method to prepare sodium water manganese ore substrates (J. Zhang et al., 2015b )and K/Al/Ce-MnOx composite catalysts were prepared to explore the effect of modified water sodium manganese ore catalysts with different doped metals on the catalytic degradation of dimethylamine, and the optimal catalyst was selected, and the optimal ratio of modified materials was explored by adjusting the ratio of metal to manganese to the optimal catalyst, and the optimal reaction conditions were screened out. According to the characterization and activity results, it was found that the binding of K ions to p-water sodium manganese ore significantly improved the redox property of the catalyst, and the activity of the catalyst was optimal when K/Mn:6/10, which significantly improved the catalytic degradation of dimethylamine by the catalyst. This study provides a new method for catalyzing the oxidative degradation of dimethylamine by doped metal-modified water-sodium manganese ore catalysts. n of different metals (Al, Ce, K). 2 Experiments 2.1 Experimental materials and instruments Dimethylamine solution (CH 3 ) 2 NH, Shanghai Maclean's Biochemical Technology Co., Ltd.; Potassium nitrate (KNO 3 ), Beijing Beihua Fine Chemicals Co., Ltd.; Aluminum nitrate (Al(NO 3 ) 3 ·9H 2 O), Tianjin Damao Chemical Reagent Factory; Cerium nitrate (Ce(NO 3 ) 3 ·6H 2 O), Sinopharm Chemical Reagent Co., Ltd.; Potassium sulfate (K 2 SO 4 ) Tianjin Damao Chemical Reagent Factory; Tube furnace, Hefei Kejing Material Technology Co., Ltd.; Mass Flow Meter, Beijing Qixing Huachuang Flow Meter Co., Ltd.; Potassium permanganate (KMn0 4 ), Wuxi Zhan Zhan Chemical Reagent Co., Ltd.; Vortex air pump, Sensen Group Co., Ltd.; Oven, muffle furnace, crucible, constant temperature water bath shaker, Shanghai Nanrong Laboratory Equipment Co., Ltd.; Gas chromatograph (Shimadzu Instruments (Suzhou) Co., Ltd.). 2.2 Preparation of catalysts Sodium manganese ore material is prepared by calcination at high temperature, 1 gram of potassium permanganate is fully ground and then put into the muffle furnace for calcination, the reaction condition is 10°C/min, burned to 1000°C, kept warm for 5 hours, and the water sodium manganese ore material is obtained by centrifugal filtration after cooling, which is recorded as MnO 2 -M1 Sodium manganese ore material was prepared by solvent method, 1g of potassium permanganate and 0.6g of ammonium oxalate were put into an Erlenmeyer flask, dissolved in 150ml of deionized water, kept warm at 150 rpm at 90°C for 12h in a water bath shaker, centrifuged and washed with deionized water after the end, and the prepared sodium manganese ore material was recorded as MnO 2 -M2. Follow-up experiments confirmed that the activity of the water-sodium manganese ore material (M2) prepared by solvent method was better, so the doped metal modification of M2 was carried out on this basis. Preparation of modified water sodium manganese ore materials: On the basis of the solvent method, Al(NO 3 ) 3 ·9H 2 O, Ce(NO 3 ) 3 ·6H 2 O, KNO 3 and K 2 SO 4 were dissolved into Erlenmeyer flasks, and the doped molar ratio was 1:10 (metal: Mn), and the reaction conditions were consistent with those of the solvent method, which were recorded as Al-MnO 2 -M2, Ce-MnO 2 -M2, KNO 3 -MnO 2 -M2 and K 2 SO 4 -MnO 2 -M2, respectively. The experimental results show that K 2 SO 4 -MnO 2 -M2 is the optimal catalyst for metal doping. By adjusting the molar ratio (Mn/K) of the doped metal (Mn/K) 0.5:10, 1:10, 3:10, 6:10, 8:10 and 10:10 corresponding masses of K2SO4, the K-doped modified water sodium manganese ore materials were named K 2 SO 4 -MnO 2 -M2 (0.5:10), K 2 SO4-MnO 2 -M2 (1:10), K 2 SO 4 -MnO 2 -M2 (3:10), K 2 SO 4 -MnO 2 -M2 (6:10), K 2 SO 4 -MnO 2 -M2 (8:10) vs. K 2 SO 4 -MnO 2 -M2 (10:10). 2.3 Characterization of catalysts Using an XRD diffractometer (D8-Advance X-ray diffraction device manufactured by Bruker, Germany, with a wavelength of 0.154 nm) selected as the radiation source, the experimental conditions were set as follows: operating voltage 40 kV, current 40 mA, scanning angle extended from 5 ° to 80 °, scanning interval of 0.02 ° per step, and scanning speed of 10 °/min. In this study, a Sigma 300 field emission scanning electron microscope (SEM) from Carl Zeiss in Germany was used, and the SEM was set to 5 kV and all samples were subjected to a 45-second gold spray with a Quorum SC7620 sputter coater at a current of 10 mA before characterization. The ASAP 2460 multi-station automatic specific surface area analyzer of Micromeritics was used to estimate the specific surface area of the material according to the multi-point BET theory, and the measured P/P0 value range was set between 0.10 and 0.35 to ensure the accuracy of the nitrogen adsorption and desorption process, and the sample was degassed at a temperature of 200°C for 4 hours. The BelCAT-II automatic chemical adsorption instrument provided by MicrotracBEL was used for experimental analysis. The experimental procedure was as follows: 100 mg of the sample was placed in a U-shaped quartz tube, and then pretreated with helium (He) at a flow rate of 50 mL/min at 105°C for 1 hour to remove surface contaminants and residual gases. After the system cooled to room temperature, a 5% hydrogen/argon (5% H2/Ar) gas mixture was introduced, the flow rate was set at 60 mL/min, and the heating rate was increased from 40°C to 500°C at a 5°C/min heating rate. In this experiment, Thermo Fisher's ESCALAB 250Xi photoelectron spectrometer was used for testing and analysis, and the Kα ray of Al was selected as the excitation source, and the energy flux was set to 30 eV. All spectral calibrations refer to the binding energies of C1s, which is standard 284.8 eV. In the experiment, HORIBA's in-situ confocal Raman microscope was used, the Ar + laser (λ = 514.5 nm) was selected as the excitation source, the laser intensity was set to 0.1%, and a cumulative of 500 scans was performed. 2.4 Catalyst activity evaluation In this study, in order to explore the catalytic performance of the modified sodium manganese ore catalyst, a simple catalytic oxidation reaction device was established according to the principle of fixed-bed reactor, which was mainly composed of a blower, a mass flow meter I., a dimethylamine reactor heated by a water bath, a buffer bottle, a mass flow meter II., a tube furnace, and a mass flow meter III. The experimental equipment is shown in Fig. 1 , in this experiment, the initial concentration of dimethylamine is controlled by the mass flow meter I., and the different reaction space velocities when dimethylamine enters the catalytic oxidation device are obtained by adjusting the mass flow meter II. rotary gauge, the tail is carried out by the gas collection device, and the gas is sampled by the gas absorption bottle, so that the gas continues to pass through the absorption bottle containing 50 ml of absorption solution for 20 min, and 0.12 mol/L hydrochloric acid is used as the absorption solution. The gas absorption bottle is shown in Fig. 2 . During the experiment, gas chromatography was used to analyze and determine the degradation effect. The catalytic degradation activity of the catalyst to dimethylamine was evaluated by the degradation rate, which was expressed by Eq. ( 1 ). $$\:\eta\:=\frac{{C}_{in}-{C}_{0ut}}{{C}_{{i}^{n}}}$$ 1 Equation ( 1 ): η—degradation rate (%); Cin—dimethylamine inlet concentration (mg/m3); Cout—Dimethylamine outlet concentration (mg/m3). 3 Results and Discussion 3.1 XRD analysis of sodium water manganese rock catalysts The XRD characterization results of the sodium manganese ore material prepared by calcination are shown in Fig. 1 A, and the XRD pattern of the standard card JCPDS No.80-1098 shows that the peak values of sodium water manganese ore prepared by calcination method in this study are (~ 12.5°), (~ 25.2°), (~ 36.5°), and (~ 65.5). The peak values of sodium manganese ore studied by (Zhu Lin et al,2017) were (~ 12.3°), (~ 25.2°), (~ 36.5°), and (~ 65.5°), which coincided, indicating that the minerals prepared by calcination were mainly sodium manganese ore with a good crystal structure (Peng Xin et al,2021) As can be seen from Fig. 1 B, the peak values of sodium manganese ore doped by Al(NO 3 ) 3 ·9H 2 O, Ce(NO 3 ) 3 ·6H 2 O, KNO 3 and K 2 SO 4 are basically the same, and they are all structures of sodium manganese. The (001), (002), (100) and (110) planes of sodium manganese ore at ~ 12.3°, ~ 24.6°, ~ 36.5° and ~ 65.5° correspond to the materials, respectively. In this study (Yin Hongling et al,2003; Wang Haoyu et al,2023; Xu Jiali et al,2013) it can be seen from Figure B that the peak value of the sodium manganese ore material prepared by the solvent method is weak at 65.5°, so it indicates that the crystallinity of the sodium manganese ore catalyst prepared by the solvent method is poor. The results of (Zhu Lin et al,2017) showed that the crystallinity of the material was not directly related to the catalytic effect on dimethylamine. Therefore, although the crystallinity of the water-sodium manganese ore material prepared by solvent method is poor, the subsequent catalytic effect should be experimentally explored. 3.2 Characterization of different molar ratios of potassium doped water sodium manganese ore catalysts Figure 2 is an XRD of different molar ratios of potassium-doped sodium manganese ore materials, and it can be seen that when K is incorporated, the main diffraction peaks are consistent with those of sodium manganese, indicating that the layered structure of K elements does not change when they are incorporated(J. Wang, Zhang, et al., 2015 ) When the K doping concentration increases, the intensity of the diffraction peak decreases at 12.3°, and the diffraction peak increases at half height and width. According to the Scherrer equation, the addition of K will reduce the crystallinity of the material and make the grain smaller. As shown in Fig. 3 XRD comparison of MnO2, the characteristic peak gradually shifted to 12° as the molar ratio of K increased by 12.3°, indicating that the crystal spacing of the material gradually increased when the molar ratio of K increased, which may be due to the displacement of Mn 4+ and Mn 3+ in the crystal by K + ions with larger ionic radius. According to(J. Wang, Li, et al., 2015 ) K+, as an interlayer ion, promotes the replenishment of surface hydroxyl groups by activating water molecules, thereby enhancing surface oxygen activity. In this study, it is possible to increase the activity of the catalyst by doping K ions, which is more conducive to the catalytic degradation of VOCs. 3.3 SEM images of sodium water manganese ore and its different molar ratio potassium modified materials As can be seen from Fig. 4 , the above catalytic materials are all spherical structures composed of nanorods, which are consistent with the morphology of sodium manganese, and the higher the potassium content, the worse the crystallinity, and the more obvious the spherical nanorod-like structure is formed. It can be seen that the particle size gradually decreases from 300 nm to 90 nm, and when too much potassium is added, K2SO4-MnO2-M2 (10:10) is irregular spherical in shape, indicating that the structure of the substance has been destroyed. As can be seen from the SEM images, the crystal morphology of the material is consistent with the XRD analysis. Since the grain boundary interface structure composed of different crystal forms has an important influence on the catalytic reaction, there are a large number of coordination unsaturated ions near the crystal interface, which is conducive to increasing the oxygen defect concentration of materials and promoting the activation process of acting molecular oxygen(Hojo et al., 2010 ; Royer et al., 2005 ; Vidruk et al., 2009 ). 3.4 XPS full spectrum of sodium water manganese ore and modified materials From Fig. 5 , it can be seen that the XPS full spectrum can obtain the elements and their valence state analysis of the material, and it can be seen from the figure that K, Mn and O elements are urged in the modified material, indicating that K element is successfully doped into the water sodium manganese ore material. The curve of 01s is shown in Fig. 6 (A), and the O1s curve can be divided into three fitting peaks, which correspond to the three species existing on the surface of the catalyst, namely lattice oxygen (Olatt.), adsorbed oxygen (Oadds.), and chemisorption water (Ow)(Mathew et al., 2012 ; C. Zhang et al., 2012 ). The specific results of the peaks are shown in Table 1 , including the elemental valence states and surface chemical compositions of different molar ratios of water sodium manganese ore materials doped with K ions, from Table 1 , it can be seen that the Oadds./Olatt. ratio of K 2 SO 4 -MnO 2 -M2 (6:10) is the highest (0.35), according to the study of (Over H et al,2003) and (Jia et al., 2016 ),when Oadds./ When the ratio of Olatt. is high, it indicates that the catalyst has more active sites and the activity of the catalyst is better. In this study, subsequent catalyst activity experiments also proved that the K 2 SO 4 -MnO 2 -M2 (6:10) catalyst had the best activity. The XPS spectrum of Mn 2p is shown in Fig. 6 (B), and there are two typical peaks of Mn 2p1/2 and Mn 2p3/2, and the binding energies are concentrated in the range of 642.5 eV and 653.7 eV, respectively, so the split energy difference between the spin orbit is about 11.2 eV, which is in line with the conclusion of the existing study(Niu et al., 2021 ). According to the study (Biesinger et al., 2011; Mathew et al., 2012 ) K + was introduced into the original lattice, so that K + embedded more oxygen vacancies in the lattice, thereby reducing the peak position of adsorbed water and increasing the adsorbed oxygen and lattice oxygen, and the ratio of Mn 3+ to Mn 4+ was (a): MnO 2 was 3.00, (b) K 2 SO 4 -MnO 2 -M2 (1:10) was 3.19, and (c) K 2 SO 4 -MnO 2 -M2 (3:10) 3.64, (d) K 2 SO 4 -MnO 2 -M2 (6:10) is 4.94, (e): K 2 SO 4 -MnO 2 -M2 (10:10) is 1.90, according to (Liu et al., 2019 ) The results show that when the ratio of the two is higher, it indicates that the material has more active sites for catalytic oxidation, and in this study, K 2 SO 4 -MnO 2 -M2 (6:10) was found in several modified materials The ratio was the highest (4.94), which may indicate that the material has more active sites than other modified materials, and has a better catalytic degradation effect on dimethylamine. From Fig. 6 (C), the XPS diagram of Mn3s in the modified material shows that Mn 3s is considered to be used to distinguish the oxidation state of Mn more accurately, according to (M. Sun et al., 2013 )The average oxidation valence state of Mn is calculated as: AOS = 8.95–1.13ΔE3s, from which it can be seen that (a), (b), (c), (d), The binding energy difference between the two peaks is 4.74 eV, 4.76 Ev, 4.87 eV, 4.9 eV, and 4.71 eV, and the AOS value of K 2 SO 4 -MnO 2 -M2 (6:10) is the smallest, only 3.41, and according to the study of(Jia et al., 2016 ), based on the principle of electric neutrality, the smallest value indicates that it contains the most abundant oxygen gap, and also indicates that the modified material has abundant active sites. The XPS spectrum of K2p is shown in Fig. 6 (D). The XPS peaks of K2p can be divided into two typical characteristic peaks, K 2p1/2 and K 2p3/2, corresponding to binding energies of ~ 295.7 eV and ~ 292.9 eV, respectively, which are attributed to K+. It can be seen from Table 1 that when the K doping amount is 5.9, the relative elemental content of O and Mn is 43.78 and 14.69, when the K doping is 6.01, the relative elemental content of O and Mn is 43.86 and 15.55, when the K doping amount is 6.12, the relative elemental content of O and Mn is 43.87 and 16.43, and when the K doping is 6.57, the relative elemental content of O and Mn is 44.21 and 16.97. It can be seen that with the increase of K doping, the relative content of O and Mn increases gradually. This result proves that the potassium type on the surface of the composite material has not changed, and its properties and valence state are stable, which is a good support type (Kruse & Chenakin, 2011 ). Table 1 Surface chemical composition and element valence distribution of birnessite and its modified materials Catalyst materials K 2p/% 2p(At%) O 1s/% O adds ./O latt . Mn 2p/% Mn 3+ /Mn 4+ MnO 2 / 43.7 0.26 14.56 3.00 K 2 SO 4 -MnO 2 -M2(1:10) 5.9 43.78 0.30 14.69 3.19 K 2 SO 4 -MnO 2 -M2(3:10) 6.01 43.86 0.34 15.55 3.64 K 2 SO 4 -MnO 2 -M2(6:10) 6.12 43.87 0.35 16.43 4.94 K 2 SO 4 -MnO 2 -M2(10:10) 6.57 44.21 0.25 16.97 1.90 3.5 H2-TPR analysis Table 2 Summary of H 2 -TPR data for three birnessite materials Catalyst materials Reduction temperature(℃) Total hydrogen consumption(mmol/g) A B MnO 2 322.6 — 6.49 K 2 SO 4 -MnO 2 -M2(1:10) 234.9 329.9 4.52 K 2 SO 4 -MnO 2 -M2(6:10) 231.7 314.3 4.50 In order to study the reducibility of the catalyst, H2-TPR tests were carried out on MnO 2 -M2, K 2 SO 4 -MnO 2 -M2 (1:10) and K 2 SO 4 -MnO 2 -M2 (6:10), as shown in Fig. 7 , the MnO 2 catalyst only had a reduction peak at 322.6°C, while the modified sodium water manganese ore materials K 2 SO 4 -MnO 2 -M2 (1:10) and K 2 SO 4 -MnO 2 -M2 (6:10) A low peak appeared at 230°C, followed by a peak similar to MnO 2 -M2 at 320°C. Based on the doping ratio of the catalyst and the strength of the metal reduction, it was determined that the former peak (A) was attributed to the reduction of K + to potassium, and the latter peak (B) was due to the reduction of Mn 4+ and Mn 3+ to Mn 3+ and Mn 2+ , respectively (Araújo Melo et al., 2002 ) At the same time, with the increase of potassium doping, the reduction peak temperature of the material decreased, and the peak value also decreased, and the reduction capacity of the three was K 2 SO 4 -MnO 2 -M2 (6:10) > K 2 SO 4 -MnO 2 -M2 (1:10) > MnO 2 -M2, which was also consistent with the order of catalytic performance. In addition, the total hydrogen consumption of the above three catalyst materials is calculated in Table 2 , and the total hydrogen consumption of catalyst K 2 SO 4 -MnO 2 -M2 (6:10) is at least 4.50 mmol/g, indicating that it has the lowest AOS and the lowest proportion of Mn 4+ . Good low temperature (231.7-329.9°C) reducibility corresponds to strong lattice oxygen (Olatt.) species mobility (Si et al., 2015 )which is conducive to accelerating the redox process and enhancing the catalytic activity of K 2 SO 4 -MnO 2 -M2 (6:10) in the catalytic reaction of dimethylamine. 3.6 Nitrogen adsorption-desorption assay (BET) analysis The physical properties of the materials were analyzed by nitrogen adsorption-desorption experiment (BET), and the results of BET determination are shown in Table 3 . Table 3 Specific surface area of MnO 2 and its modified materials Catalyst materials Specific surface area(m 2 /g) MnO 2 20.94 K 2 SO 4 -MnO 2 -M2(1:10) 22.47 K 2 SO 4 -MnO 2 -M2(3:10) 23.88 K 2 SO 4 -MnO 2 -M2(6:10) 25.86 K 2 SO 4 -MnO 2 -M2(10:10) 21.60 As shown in the SEM images above, the particle size of the modified material decreases and the specific surface area increases, and the crystallinity of the catalyst material decreases from 300 nm to 140 nm of the K 2 SO 4 -MnO 2 -M2 (6:10) material after potassium doping. The analysis found that this was due to the lattice distortion caused by the difference in the radius between the two ions after the introduction of new ions to replace Mn 4+ , which affected the crystal growth process, thereby reducing the size of the material and increasing the specific surface area. Combined with Table 2 , the specific surface area of MnO 2 was the lowest, only 20.94 m2/g. When the doping ratio gradually increased from 1:10 to 6:10, the specific surface area increased to 22.47, 23.88 and 25.86 m2/g, respectively. However, when the doping ratio continued to increase to 10:10, part of the sodium manganese ore structure in the material was destroyed, and the morphology of the material showed an irregular structure, which reduced the specific surface area of the modified material to 21.6 m2/g, but it was still higher than that of the MnO 2 material. Therefore, the doping of K element makes the particle size of the modified material smaller, the specific surface area increases, and the catalyst has more active sites, so that the catalyst has a better catalytic effect on dimethylamine(J. Wang, Zhang, et al., 2015 ). 3.7 Raman spectrum analysis The structural changes of sodium manganese dioxide after potassium modification were compared by Raman spectroscopy, and the test results are shown in Fig. 8 . As can be seen from Fig. 8 δ-MnO 2 is mainly presented as three sets of broad and weak characteristic Raman peaks, all corresponding to M-O bonds, located at 501.2, 574.1 and 648.5 cm-1, respectively, according to the study of (Julien, 2003 ) these three sites correspond to the bending vibration of the Mn-O-Mn bond in the MnO 6 group, the ν3(Mn-O) expansion vibration caused by Mn 4+ on the bottom surface of the [MnO 6 ] octahedron, and the ν2(Mn-O) in the [MnO 6 ] structure Asymmetrical telescopic vibration. It can be seen from Fig. 8 that the strength of each characteristic peak of the modified sodium manganese ore material gradually weakens with the increase of K doping, and the ν3(Mn-O) expansion vibration characteristic peak in the material shows a redshift phenomenon when the K doping ratio is 10:10, and the main reason for this phenomenon is that the addition of K element causes more defects in the crystal, which causes the stress in the crystal and the distortion of the crystal lattice. In summary, the increase of internal defects in the crystal caused by K doping increased the oxygen defect content on the surface of the modified manganese dioxide catalyst and enhanced its catalytic degradation efficiency. 3.8 Catalytic activity test As shown in Fig. 9 -A, degradation begins at 150°C with empty tower conditions, and the degradation rate reaches 50% at 280°C. The degradation rate is slowed down at 400°C-500°C, and the degradation rate reaches 90% when the temperature reaches 550°C. Under the condition of MnO2-M1, the degradation rate of dimethylamine reached 28.2% at 150°C, which was about 20% higher than that of empty tower, and the degradation rate of dimethylamine reached 90% at 490°C. Under the condition of MnO 2 -M2, the degradation rate of dimethylamine is more than 50% at the temperature of 150°C, and the degradation effect is significantly higher than that of MnO 2 -M1. From Fig. 10 -A, it can be clearly seen that with the increase of temperature, the degradation effect of catalyst MnO 2 -M2 on dimethylamine is significantly superior to that of MnO 2 -M1. Therefore, it can be concluded that the order of reactivity of the three should be: MnO 2 -M2 > MnO 2 -M1 > empty tower. It can be seen that the catalyst MnO 2 -M2 prepared by potassium permanganate and ammonium oxalate solvent method (M2) has a significant effect on the catalytic oxidation of dimethylamine. As shown in Fig. 9 -B, the degradation rate of Ce-MnO 2 -M2 with the lowest activity was 66.1%, and the degradation rate of the best K 2 SO 4 -MnO 2 -M2 was 73.57% at 150°C, compared with the degradation of dimethylamine by empty towers, which had just reached the critical pyrolysis temperature of dimethylamine degradation in the empty tower. Among them, the degradation temperatures of MnO 2 -M2, Al-MnO 2 -M2, Ce-MnO 2 -M2, KNO 3 -MnO 2 -M2 and K 2 SO 4 -MnO 2 -M2 were 298°C, 200°C, 253°C, 205°C and 185°C when the degradation rate of dimethylamine reached 80%, respectively. At 50–200°C, the catalytic activities were K 2 SO 4 -MnO 2 -M2 > Al-MnO 2 -M2 > KNO 3 -MnO 2 -M2 > Ce-MnO 2 -M2 > MnO 2 -M2。 Based on the above data, K 2 SO 4 -MnO 2 -M2 was selected as the optimal metal doping catalyst. As can be seen from Fig. 9 -(a), with the increase of molar ratio, the degradation temperature of K 2 SO 4 -MnO 2 -M2 (0.5:10) to K 2 SO 4 -MnO 2 -M2 (10:10) catalyst is 110°C, 76°C, 63°C, 52°C, 107°C and 119°C when the molar ratio increases, and the degradation temperature is 362°C, 304°C, 295°C, 243°C, 312°C and 326°C when the degradation rate reaches 90%. K 2 SO 4 -MnO 2 -M2 (6:10) has a higher degradation rate (81.7%) at 150°C, and when the temperature reaches 200°C, the degradation efficiency of different proportions of catalysts gradually decreases, while the K 2 SO 4 -MnO 2 -M2 (0.5:10), K 2 SO 4 -MnO 2 -M2 (8:10) and K 2 SO 4 -MnO 2 -M2 (10:10) catalysts have similar trends in the whole catalytic degradation of dimethylamine. It can be seen from Fig. 10 -(b) that at 100°C, the degradation rate of the unmodified catalyst MnO2-M2 for dimethylamine is only about 15%, the modified catalysts K 2 SO 4 -MnO 2 -M2 (6:10) and K 2 SO 4 -MnO 2 -M2 (1:10) are both above 60%, and the degradation rate of the K 2 SO 4 -MnO 2 -M2 (6:10) catalyst even reaches 69.75%, which is about 4 times higher than that of MnO 2 -M2. Therefore, from the comprehensive data, the catalyst K 2 SO 4 -MnO 2 -M2 (6:10) has the best effect on the degradation of dimethylamine. 3.9 Effect of reaction conditions on catalytic activity and stability test As shown in Fig. 10 -A, the degradation rate of dimethylamine at low concentration (150 mg/L) began to occur at low temperature (50°C), and the degradation rate was 4.33%, and the degradation rate of medium and high concentration (650, 1500 mg/L) did not begin to degrade until the reaction temperature increased to 100°C, and the degradation effect of high concentration (1500 mg/L) dimethylamine was significantly lower than that of medium and low concentration dimethylamine in the temperature range of 150–500°C. At 500°C, the difference in the degradation rate of 150, 650 and 1500 mg/L dimethylamine gradually narrowed to about 1%, which was 75.15%, 74.09% and 74.93%, respectively. With the increase of temperature, the degradation trend of the three is gradually consistent. When the temperature reaches 600°C, the degradation rate of dimethylamine has exceeded 90%, and the complete transformation is basically realized. According to (W. Wang et al., 2016 ) the concentration of dimethylamine is too high to increase the critical temperature of thermal decomposition, and the degradation effect is not obvious, and with the increase of reaction temperature, C-N gradually breaks down, which promotes the deep oxidative decomposition of dimethylamine. Figure 10 -B shows the influence of airspeed under the condition of empty tower, when the airspeed is large (350000 mL/gcat∙h), the degradation rate reaches 50% and 90% at 398°C and 564.2°C, respectively. Dimethylamine began to degrade at 100°C at 45000 and 150000 mL/gcat∙h at space speeds, and the degradation rates reached 246°C and 284°C at 50%, respectively, and reached more than 90% at 550°C, with 95.18% and 91.15°C, respectively. Based on the above data, it can be seen that the degradation effect of dimethylamine in the empty tower is in the order of low air velocity (45000 mL/gcat∙h) > medium air velocity (150000 mL/gcat∙h) > maximum space velocity (350000 mL/gcat∙h). Figure 10 -C shows the effect of different concentrations on the catalyst activity of K 2 SO 4 -MnO 2 -M2 (6:10) catalyst, and it can be seen from Fig. 10 -C that the temperature of dimethylamine degradation reaches 50% at 150, 650 and 1500 mg/L, respectively. The degradation rate reached 90% at 241°C, 299°C and 293°C, respectively. According to the research of (Zhang Huai et al,2017) it was also shown that the catalyst had better catalytic performance for low concentrations of dimethylamine. Based on the above data, it can be seen that at low temperature (50°C-300°C), K 2 SO 4 -MnO 2 -M2 (6:10) has obvious advantages in the catalytic effect of medium and low concentrations of dimethylamine, but the advantage gradually decreases with the increase of temperature. As shown in Fig. 10 , the mass of K 2 SO 4 -MnO 2 -M2 (6:10) catalyst is 20, 60 and 100 mg, respectively, and the temperatures corresponding to dimethylamine degradation efficiency reach 50% are 219, 153 and 139°C, respectively, and the temperature of dimethylamine degradation efficiency is 322, 264 and 250°C, respectively. As can be seen from Fig. 10 -D, the catalytic degradation efficiency of dimethylamine at 20 mg is significantly lower than that at 60 and 100 mg. However, the degradation of dimethylamine was similar between 60 and 100 mg of catalyst K 2 SO 4 -MnO 2 -M2 (6:10). It can be seen that the larger the amount of non-catalyst under the same reaction conditions, the better the catalytic decomposition effect, which is in line with the research law of (Xie Wengong et al,2025) Fig. 10 (a)(b) shows that compared with the degradation effect of dimethylamine under the empty tower at the air velocity, the addition of the catalyst significantly reduces the degradation temperature of dimethylamine, that is, when the reaction condition is T = 150°C and the reaction space velocity is 45000 mL/gcat·h, the dimethylamine reaches the critical pyrolysis temperature under the empty tower condition, and the dimethylamine has begun to degrade after the addition of the catalyst, and the degradation rate reaches about 50%. Similarly, the degradation effect was the worst when the space velocity was 350000 mL/gcat·h under the condition of empty tower, and the degradation began at close to 300°C, while the pyrolysis temperature was reached after 100°C after the catalyst was added, and the degradation rate reached 90% at 300°C. Therefore, the superiority of the catalyst K 2 SO 4 -MnO 2 -M2 (6:10) in the degradation of dimethylamine can be fully demonstrated. As shown in Fig. 10 (a), the removal rate of dimethylamine by K 2 SO 4 -MnO 2 -M2 (6:10) increases with the increase of temperature under different space velocity conditions, and shows a similar trend. However, with the increase of space velocity, the degradation effect of K 2 SO 4 -MnO 2 -M2 (6:10) on dimethylamine gradually weakened at the same reaction temperature. According to the inference of(Danita Patricia & Vijay Solomon, 2025 ) it may be that when the space velocity is small, it can fully contact with the surface of the catalyst and the residence time is longer, so the catalytic degradation effect is better. Figure 10 (b) shows the variation trend of T40, T50 and T90 with reaction space velocity, with the increase of space velocity, the temperature of T40 degradation rate decreases first and then increases, the T50 degradation rate is less affected by temperature, and the T90 degradation rate curve of T90 shows an upward trend, compared with high air velocity, the T40 and T90 of dimethylamine increase by about 70°C at 45000 mL/gcat·h space velocity. It is further proved that the degradation effect of K 2 SO 4 -MnO 2 -M2 (6:10) on dimethylamine gradually weakens with the increase of space velocity. As shown in Fig. 10 (c)(d), the catalytic stability of K 2 SO 4 -MnO 2 -M2 (6:10) at 100°C, 300°C and 450°C was compared. It can be seen from Figure c that the experimental fluctuations are very large at 100°C, and the degradation effect of dimethylamine decreases with the increase of the number of cycles, but the degradation effect of dimethylamine is stable with the increase of the number of cycles at 300°C and 450°C, and the difference between the first and tenth degradation rates of dimethylamine is 8.55%, 5.59% and 3.12%, respectively, corresponding to the reaction temperature conditions of 100°C, 300°C and 450°C, respectively, according to the study of (Meng et al., 2025 )and the above data, The cycling stability of the K 2 SO 4 -MnO 2 -M2 (6:10) catalyst catalyzed dimethylamine oxide was affected at low temperature, while the catalyst could be stable at high temperature. In summary, dimethylamine can maintain high catalytic degradation efficiency after 10 cycles at high temperature (300–450°C), so the catalyst has high stability. As shown in Fig. 10 (d), the stability of the optimal catalyst K 2 SO 4 -MnO 2 -M2 (6:10) at the optimal reaction temperature (300°C) decreases the decomposition of dimethylamine, and it can be seen that the degradation efficiency of the K 2 SO 4 -MnO 2 -M2 (6:10) catalyst for dimethylamine gas is about 95%, the highest degradation rate of dimethylamine is 97.81% at 11h, and the lowest degradation rate of dimethylamine is 92.68% at 19h. In summary, the catalyst K 2 SO 4 -MnO 2 -M2 (6:10) has high stability. 3.10 Possible Reaction Mechanisms Figure 11 shows the XPS spectra of the K 2 SO 4 -MnO 2 -M2 (6:10) catalyst before and after use, showing the relationship between the content of Ow/Oadds./Olatt., Mn3 + /Mn4 + , and K + and the catalytic performance of K 2 SO 4 -MnO 2 -M2 (6:10). As can be seen from Fig. 11 (A), the content of adsorbed oxygen (Oadds.) and lattice oxygen (Olatt.) on the surface of the K 2 SO 4 -MnO 2 -M2 catalyst increased relatively well, which may be due to the higher catalytic temperature, which causes more oxygen to be adsorbed during the catalytic process, which is conducive to the stability of the catalyst (Huang et al., 2014 ) As can be seen in Fig. 11 (B), the ratio of Mn 3+ /Mn 4+ in the catalyst decreases after use, and part of the Mn 3+ on the surface of the catalyst is oxidized to Mn 4+ . Figure 11 (C) shows the XPS spectrum of Mn 3s, which shows that there is no difference between before and after use, indicating that the surface of the material remains rich in oxygen and the catalytic activity of the catalyst is stable(Hou et al., 2014 )Fig. 11 (D) shows that the characteristic peak of K + does not change, but the K + content of the catalyst decreases after use, which may be due to the loss caused by the oxidation of O2 during catalytic oxidation. From the changes before and after the use of the catalyst reflected in the XPS spectrum, as well as the study of (Lourenço et al., 2021 )it is possible to infer the valence changes of the elements within the catalyst: Mn 3+ +K + +O 2 ⟷ Mn 4+ +nK + +mO 2− The above possible changes lead to the occurrence of redox reactions, where Mn 3+ is oxidized to Mn 4+ due to the addition of K + ions, so that dimethylamine gas is continuously oxidized and degraded by catalysts. According to the above experiments, the analysis of the oxidative degradation of dimethylamine follows the Mars-van Krevelen (MVK) mechanism. Firstly, the K 2 SO 4 -MnO 2 -M2 (6:10) catalyst is heated to activate the reactive oxygen species on the surface, while the dimethylamine gas is adsorbed on the surface of the catalyst and reacts with the adsorbed oxygen and lattice oxygen on the surface, resulting in the reduction of metal oxides in the catalyst. According to V. The study of (Santos et al., 2010 ) suggests that during the reaction, the dimethylamine molecule is oxidized to break the C-N bond, resulting in the catalytic degradation of dimethylamine. Through the analysis of XPS, BET and H 2 -TPR, it was revealed that K 2 SO 4 -MnO 2 -M2 (6:10) had a large oxygen capacity and a high specific surface, so as to achieve the uniform distribution of Mn, K, O and other elements on the catalyst, promote the rapid transfer between it and O 2 , improve the catalytic activity and stability of the catalyst, and improve its long-lasting catalytic oxidation ability of dimethylamine. 4 Conclusion The potassium modified water sodium manganese ore catalyst (K 2 SO 4 -MnO 2 -M2) was prepared by solvent method with potassium sulfate as the carrier and the molar ratio of K to Mn was adjusted to adjust the lattice defect and oxygen vacancy concentration by adjusting the molar ratio. The results showed that K 2 SO 4 -MnO 2 -M2 had the highest catalytic decomposition performance for dimethylamine. The high specific surface area and total pore volume of K 2 SO 4 -MnO 2 -M2 catalyst promoted the adsorption of dimethylamine and molecular oxygen by the active site of the catalyst, and the surface of K 2 SO 4 -MnO 2 -M2 catalyst was rich in adsorbed oxygen and lattice oxygen, which was dominated by adsorbed oxygen and crystalline oxygen, which enhanced the catalytic oxidation of dimethylamine. At the same time, K 2 SO 4 -MnO 2 -M2 has better redox performance, and a more stable catalyst is obtained through multiple redox cycles. XPS analysis showed that the oxidation of dimethylamine catalyzed by K 2 SO 4 -MnO 2 -M2 followed the M-vK mechanism. In this study, an efficient and stable K 2 SO 4 -MnO 2 -M2 catalyst for dimethylamine combustion was synthesized, and its catalytic effect and reaction mechanism were clarified, which provided a reference for the application of efficient removal of volatile organic compounds by supported transition metal catalysts. The optimal reaction conditions were selected as follows: gas flow rate of 0.35 L/min (space velocity of 350000 mL/gcat·h), dimethylamine concentration of 150 mg/L, reaction temperature of 300°C, and catalyst mass of 0.06 g. Declarations Funding Statement This work was supported by Chengxun Deng. The funder had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results. Conflict of interest The authors declare no competing interests. Ethical approval This article does not contain any studies with human participants or animals performed by any of the authors. Consent to participate Not applicable. This study did not involve human participants. Consent to publish Not applicable. Data availability All data generated or analysed during this study are included in this published article References Araújo Melo, D. M., Ruiz, J. A. C., Melo, M. A. F., Sobrinho, E. V., & Martinelli, A. 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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-7291479","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":500020458,"identity":"760ec3c1-e20d-4caa-9a46-558faa6c57ba","order_by":0,"name":"Jia Wei","email":"","orcid":"","institution":"Hefei University","correspondingAuthor":false,"prefix":"","firstName":"Jia","middleName":"","lastName":"Wei","suffix":""},{"id":500020459,"identity":"e3db9fb2-807a-4fc8-9cb3-a9a96b2df081","order_by":1,"name":"Chengxun Deng","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzUlEQVRIie3PvQqCUBjG8VcO6PK6v6DgLSiCNBzwQlqOBE4GQdDk4OTkBRhdhUvzAaMWL8DG8AYcm/qApiaPW9D5z89veAB0uh8sbpls7/hEzypUzaVMBnCZG1RSlXRdGAJnHHqhKIw6i5xNZqKxH5oecr6cJIzSnVN3iJaTbhdwTtfFFDFpdSS7IjQOWURG0U4TJBGR/fARrp0iITyFIaJA6FGR+FaZ3GqUGFTvL0Lli8+YlCPK2LPaph9zPk2+OIk58w+ZK3Q6ne4/egGM5TvSo4MCBgAAAABJRU5ErkJggg==","orcid":"","institution":"Hefei University","correspondingAuthor":true,"prefix":"","firstName":"Chengxun","middleName":"","lastName":"Deng","suffix":""},{"id":500020460,"identity":"e4954de5-8073-47eb-8026-56d06e2dca11","order_by":2,"name":"Mengnan Yu","email":"","orcid":"","institution":"Hefei University","correspondingAuthor":false,"prefix":"","firstName":"Mengnan","middleName":"","lastName":"Yu","suffix":""}],"badges":[],"createdAt":"2025-08-04 13:08:19","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7291479/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7291479/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":89402431,"identity":"b0b7dd15-a7cb-4305-a210-5071d50e8b8b","added_by":"auto","created_at":"2025-08-19 14:32:25","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":19134,"visible":true,"origin":"","legend":"\u003cp\u003eReaction diagram of dimethylamine catalytic oxidation device\u003c/p\u003e\n\u003cp\u003e1. Blower 2. Rotameter I. 3. Montessori Bottle Washing 4. Water Heater 5. Magnetic Stirrer 6. Gas Mixing Bottle 7. Buffer Bottle 8. Rotameter II. 9. Tubular Furnace Thermal Catalytic Oxidation Reaction Device 10. Headspace Injector 11. Gas chromatography\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7291479/v1/7db6a78933af1574ac4b4336.jpg"},{"id":89401966,"identity":"3f5f1ea1-6534-4b36-9508-dbcc7554e025","added_by":"auto","created_at":"2025-08-19 14:24:25","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":31390,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig. 1 A: \u003c/strong\u003eXRD spectra of water-sodium-manganese ore materials prepared by calcination\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFig.1 B: \u003c/strong\u003eXRD spectra of water-sow-manganese ore materials and modified materials prepared by solvent method\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7291479/v1/458ef5d147c563d007c2bcc5.png"},{"id":89403424,"identity":"d94da20f-2381-4eb0-acfc-fc7988d245bd","added_by":"auto","created_at":"2025-08-19 14:40:25","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":61922,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig. 2 \u003c/strong\u003eXRD patterns of K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 materials with different molar ratios\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7291479/v1/a8df42dd26e158fc501363f3.png"},{"id":89401969,"identity":"f3844d11-d422-410d-9975-be9a196ff27a","added_by":"auto","created_at":"2025-08-19 14:24:25","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":53673,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig. 3\u003c/strong\u003e XRD comparison of potassium doped materials with different molar ratios and MnO\u003csub\u003e2\u003c/sub\u003e at ~ 12.3 °\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7291479/v1/1cfc9631d9e0fa65d40c4cb6.png"},{"id":89402435,"identity":"d8ea3055-0dca-444a-9e68-975b80197f7a","added_by":"auto","created_at":"2025-08-19 14:32:26","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":492721,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig. 4 \u003c/strong\u003eis the SEM image of birnessite and its modified materials doped with different molar ratios of potassium\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7291479/v1/b3a364c8353b65fdce9505be.png"},{"id":89402432,"identity":"416aefca-585c-464d-8a7d-18ee46e060b8","added_by":"auto","created_at":"2025-08-19 14:32:25","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":54201,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig. 5 \u003c/strong\u003eXPS full spectrum of birnessite and its potassium modified material\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7291479/v1/03ae05e87558b047b0a20fec.png"},{"id":89401974,"identity":"84c6416d-e934-4aef-9930-48a3d23a9a90","added_by":"auto","created_at":"2025-08-19 14:24:26","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":323049,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 6: \u003c/strong\u003eXPS images of each element in sodium manganese ore and its modified materials\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7291479/v1/83c7209578a50c70c51de67a.png"},{"id":89401992,"identity":"ea1f1acb-f1b8-423a-8651-083c35d73650","added_by":"auto","created_at":"2025-08-19 14:24:27","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":40231,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig. 7\u003c/strong\u003e The H\u003csub\u003e2\u003c/sub\u003e-TPR spectra of MnO\u003csub\u003e2\u003c/sub\u003e-M2、K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2(1:10) and K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2(6:10)\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7291479/v1/daea66164911865caba30ad9.png"},{"id":89402443,"identity":"e04f1340-e14b-4a8e-967d-4aee68dab1f8","added_by":"auto","created_at":"2025-08-19 14:32:27","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":45586,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig. 8 \u003c/strong\u003eRaman spectra of birnessite and its potassium modified materials\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-7291479/v1/b3825d2b90e3e8f8292c1181.png"},{"id":89401980,"identity":"dba7f5e8-03c3-4fb2-8538-6aa2d7ad2fa1","added_by":"auto","created_at":"2025-08-19 14:24:26","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":88214,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig.9 A: \u003c/strong\u003eReactivity of MnO2-M1, MnO2-M2 and empty column catalytic oxidation\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eB:\u003c/strong\u003eReactivity of MnO2-M2 and Al/Ce/KNO3/K2SO4-MnO2-M2 for the catalytic oxidation of dimethylamine\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(a):\u003c/strong\u003eCatalyst K2SO4-MnO2-M2: 0.5, 1, 3, 6, 8, 10:10 doping ratio Reactivity of catalytic oxidation\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(b):\u003c/strong\u003eCatalyst K2SO4-MnO2-M2, MnO2-M2 and blank controlled trial\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-7291479/v1/6619230f89a314f008822401.png"},{"id":89401984,"identity":"79c5a6d9-e997-4b86-89c6-2df19db24584","added_by":"auto","created_at":"2025-08-19 14:24:26","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":133585,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig.10\u003c/strong\u003e Analysis of factors catalyzed degradation of dimethylamine\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eA:\u003c/strong\u003e Effect of dimethylamine concentration under empty tower conditions;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eB. \u003c/strong\u003eEffect of airspeed under empty tower conditions;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eC:\u003c/strong\u003e Effect of dimethylamine at different concentrations; D: Effect of catalyst quality\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFig. 10, (c) (d): \u003c/strong\u003eCyclic and operational stability of K2SO4-MnO2-M2 (6:10) catalyzed degradation of dimethylamine\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-7291479/v1/719e6ea87c82b53e9e5c4cef.png"},{"id":89402439,"identity":"8f979518-7e3d-4e38-a15b-b82c3b38bf8b","added_by":"auto","created_at":"2025-08-19 14:32:26","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":145501,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig. 11 \u003c/strong\u003eXPS Spectra of K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2(6:10)Catalysts before and after Usage:\u003c/p\u003e\n\u003cp\u003e(A)O 1s;(B)Mn 2p; (C)Mn 3s; (D)K 2p\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-7291479/v1/a34bd8b1753d89277d49e4e5.png"},{"id":89403709,"identity":"440e4c8f-ad59-4bcd-a734-8be623ab3d64","added_by":"auto","created_at":"2025-08-19 14:48:27","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2526062,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7291479/v1/c1debf7f-2622-455d-85ee-b274923fbf7a.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Study on the activity of doped metal-modified water-sodium- manganese ore catalyst to catalyze the degradation of dimethylamine","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eVolatile organic compounds (VOCs) are considered to be one of the major air pollutants, which are not only harmful to human health, but also harmful to the environment.At present, effective removal methods for VOCs include adsorption method, catalytic method, biofilm separation method, photocatalytic method, and plasma method(He et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2009\u003c/span\u003e).Among them, catalytic oxidation has been widely used because of its good degradation effect and high stability.\u003c/p\u003e\u003cp\u003eIn order to catalyze the degradation of VOCs, catalysts are often used(Y. Sun et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2023\u003c/span\u003e),and studies have shown that the effects of different catalysts for catalytic degradation of VOCs are significantly different(Liu et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The research of (Du et al,2023)shows that TiO\u003csub\u003e2\u003c/sub\u003e catalyst, as the most mature photocatalyst, has the characteristics of high catalytic efficiency and low cost, but due to the low optical quantum efficiency of TiO\u003csub\u003e2\u003c/sub\u003e, the easy recombination of electron-hole pairs, and the inability to produce visible light response, TiO\u003csub\u003e2\u003c/sub\u003e photochemical materials cannot be widely and efficiently used. Consult the literature (Wang et al,2024) used the CeO\u003csub\u003e2\u003c/sub\u003e catalyst, and the results showed that CeO\u003csub\u003e2\u003c/sub\u003e has the characteristics of visible light response, high chemical stability, and strong photogenerated hole oxidation ability, but CeO\u003csub\u003e2\u003c/sub\u003e has shortcomings such as photogenerated electron/hole pair easy recombination and low photocatalytic efficiency, which limits its practical application. Consult the literature (Ren Lei et al,2024) used a Pt-based catalyst to catalyze the degradation of VOCs, and the results showed that the catalyst had higher lattice oxygen content and stronger redox ability, which was conducive to improving the catalytic degradation ability of VOCs, but the precious metal was expensive and difficult to prepare. As a ubiquitous manganese oxide mineral in nature, its unique two-dimensional layered structure makes it have excellent physical and chemical properties. After reviewing the literature, it was found that the water-sodium manganese ore catalyst prepared by (Zhang et al,2015) had the highest catalytic activity, simple operation and good stability. By reviewing the literature, it can be seen that (J. Zhang et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2015a\u003c/span\u003e)\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003ea\u003c/span\u003e single manganese oxide catalyst has shortcomings such as low degradation efficiency and intermediate products, so on this basis, scholars have tried to load manganese dioxide materials on other stable supports to obtain the modified water-sodium manganese ore catalyst.\u003c/p\u003e\u003cp\u003eAt present, there have been many reports on sodium manganese ore, but there are few studies on the adsorption mechanism of sodium manganese ore and transition metal-doped sodium manganese ore on VOCs. After reviewing the literature, it can be seen that the metal doping the catalyst has a significant effect on the degradation of VOCs, and through the literature review, it can be found that(Yang et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2020\u003c/span\u003e)doped and modified the water sodium manganese ore with K ions to obtain the K-ion water sodium manganese ore material. Consult the literature (Tang et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2006\u003c/span\u003e) prepared a water-sow-manganese ore catalyst doped with Ce ions. Consult the literature(Drits et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1997\u003c/span\u003e) showed that with the increase of doping amount, the octahedral vacancy decreased, and the adsorption effect of the material gradually increased. Therefore, the catalyst prepared by doping modified water-sodium manganese ore material can enhance its catalytic oxidation. In this paper, the modified sodium manganese rock catalysts with good catalytic activity and good stability were screened by studying the doping modificatio Potassium, aluminum, and cerium metal oxide catalysts were prepared on a solvent method to prepare sodium water manganese ore substrates (J. Zhang et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2015b\u003c/span\u003e)and K/Al/Ce-MnOx composite catalysts were prepared to explore the effect of modified water sodium manganese ore catalysts with different doped metals on the catalytic degradation of dimethylamine, and the optimal catalyst was selected, and the optimal ratio of modified materials was explored by adjusting the ratio of metal to manganese to the optimal catalyst, and the optimal reaction conditions were screened out. According to the characterization and activity results, it was found that the binding of K ions to p-water sodium manganese ore significantly improved the redox property of the catalyst, and the activity of the catalyst was optimal when K/Mn:6/10, which significantly improved the catalytic degradation of dimethylamine by the catalyst. This study provides a new method for catalyzing the oxidative degradation of dimethylamine by doped metal-modified water-sodium manganese ore catalysts.\u003c/p\u003e\u003cp\u003en of different metals (Al, Ce, K).\u003c/p\u003e"},{"header":"2 Experiments","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Experimental materials and instruments\u003c/h2\u003e\n \u003cp\u003eDimethylamine solution (CH\u003csub\u003e3\u003c/sub\u003e) \u003csub\u003e2\u003c/sub\u003eNH, Shanghai Maclean\u0026apos;s Biochemical Technology Co., Ltd.; Potassium nitrate (KNO\u003csub\u003e3\u003c/sub\u003e), Beijing Beihua Fine Chemicals Co., Ltd.; Aluminum nitrate (Al(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e\u0026middot;9H\u003csub\u003e2\u003c/sub\u003eO), Tianjin Damao Chemical Reagent Factory; Cerium nitrate (Ce(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO), Sinopharm Chemical Reagent Co., Ltd.; Potassium sulfate (K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e) Tianjin Damao Chemical Reagent Factory; Tube furnace, Hefei Kejing Material Technology Co., Ltd.; Mass Flow Meter, Beijing Qixing Huachuang Flow Meter Co., Ltd.; Potassium permanganate (KMn0\u003csub\u003e4\u003c/sub\u003e), Wuxi Zhan Zhan Chemical Reagent Co., Ltd.; Vortex air pump, Sensen Group Co., Ltd.; Oven, muffle furnace, crucible, constant temperature water bath shaker, Shanghai Nanrong Laboratory Equipment Co., Ltd.; Gas chromatograph (Shimadzu Instruments (Suzhou) Co., Ltd.).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2 Preparation of catalysts\u003c/h2\u003e\n \u003cp\u003eSodium manganese ore material is prepared by calcination at high temperature, 1 gram of potassium permanganate is fully ground and then put into the muffle furnace for calcination, the reaction condition is 10\u0026deg;C/min, burned to 1000\u0026deg;C, kept warm for 5 hours, and the water sodium manganese ore material is obtained by centrifugal filtration after cooling, which is recorded as MnO\u003csub\u003e2\u003c/sub\u003e-M1\u003c/p\u003e\n \u003cp\u003eSodium manganese ore material was prepared by solvent method, 1g of potassium permanganate and 0.6g of ammonium oxalate were put into an Erlenmeyer flask, dissolved in 150ml of deionized water, kept warm at 150 rpm at 90\u0026deg;C for 12h in a water bath shaker, centrifuged and washed with deionized water after the end, and the prepared sodium manganese ore material was recorded as MnO\u003csub\u003e2\u003c/sub\u003e-M2. Follow-up experiments confirmed that the activity of the water-sodium manganese ore material (M2) prepared by solvent method was better, so the doped metal modification of M2 was carried out on this basis. Preparation of modified water sodium manganese ore materials: On the basis of the solvent method, Al(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e\u0026middot;9H\u003csub\u003e2\u003c/sub\u003eO, Ce(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO, KNO\u003csub\u003e3\u003c/sub\u003e and K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e were dissolved into Erlenmeyer flasks, and the doped molar ratio was 1:10 (metal: Mn), and the reaction conditions were consistent with those of the solvent method, which were recorded as Al-MnO\u003csub\u003e2\u003c/sub\u003e-M2, Ce-MnO\u003csub\u003e2\u003c/sub\u003e-M2, KNO\u003csub\u003e3\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 and K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2, respectively. The experimental results show that K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 is the optimal catalyst for metal doping. By adjusting the molar ratio (Mn/K) of the doped metal (Mn/K) 0.5:10, 1:10, 3:10, 6:10, 8:10 and 10:10 corresponding masses of K2SO4, the K-doped modified water sodium manganese ore materials were named K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (0.5:10), K\u003csub\u003e2\u003c/sub\u003eSO4-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (1:10), K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (3:10), K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10), K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (8:10) vs. K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (10:10).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3 Characterization of catalysts\u003c/h2\u003e\n \u003cp\u003eUsing an XRD diffractometer (D8-Advance X-ray diffraction device manufactured by Bruker, Germany, with a wavelength of 0.154 nm) selected as the radiation source, the experimental conditions were set as follows: operating voltage 40 kV, current 40 mA, scanning angle extended from 5 \u0026deg; to 80 \u0026deg;, scanning interval of 0.02 \u0026deg; per step, and scanning speed of 10 \u0026deg;/min. In this study, a Sigma 300 field emission scanning electron microscope (SEM) from Carl Zeiss in Germany was used, and the SEM was set to 5 kV and all samples were subjected to a 45-second gold spray with a Quorum SC7620 sputter coater at a current of 10 mA before characterization. The ASAP 2460 multi-station automatic specific surface area analyzer of Micromeritics was used to estimate the specific surface area of the material according to the multi-point BET theory, and the measured P/P0 value range was set between 0.10 and 0.35 to ensure the accuracy of the nitrogen adsorption and desorption process, and the sample was degassed at a temperature of 200\u0026deg;C for 4 hours. The BelCAT-II automatic chemical adsorption instrument provided by MicrotracBEL was used for experimental analysis. The experimental procedure was as follows: 100 mg of the sample was placed in a U-shaped quartz tube, and then pretreated with helium (He) at a flow rate of 50 mL/min at 105\u0026deg;C for 1 hour to remove surface contaminants and residual gases. After the system cooled to room temperature, a 5% hydrogen/argon (5% H2/Ar) gas mixture was introduced, the flow rate was set at 60 mL/min, and the heating rate was increased from 40\u0026deg;C to 500\u0026deg;C at a 5\u0026deg;C/min heating rate. In this experiment, Thermo Fisher\u0026apos;s ESCALAB 250Xi photoelectron spectrometer was used for testing and analysis, and the K\u0026alpha; ray of Al was selected as the excitation source, and the energy flux was set to 30 eV. All spectral calibrations refer to the binding energies of C1s, which is standard 284.8 eV. In the experiment, HORIBA\u0026apos;s in-situ confocal Raman microscope was used, the Ar\u0026thinsp;+\u0026thinsp;laser (\u0026lambda;\u0026thinsp;=\u0026thinsp;514.5 nm) was selected as the excitation source, the laser intensity was set to 0.1%, and a cumulative of 500 scans was performed.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003e2.4 Catalyst activity evaluation\u003c/h2\u003e\n \u003cp\u003eIn this study, in order to explore the catalytic performance of the modified sodium manganese ore catalyst, a simple catalytic oxidation reaction device was established according to the principle of fixed-bed reactor, which was mainly composed of a blower, a mass flow meter I., a dimethylamine reactor heated by a water bath, a buffer bottle, a mass flow meter II., a tube furnace, and a mass flow meter III. The experimental equipment is shown in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e, in this experiment, the initial concentration of dimethylamine is controlled by the mass flow meter I., and the different reaction space velocities when dimethylamine enters the catalytic oxidation device are obtained by adjusting the mass flow meter II. rotary gauge, the tail is carried out by the gas collection device, and the gas is sampled by the gas absorption bottle, so that the gas continues to pass through the absorption bottle containing 50 ml of absorption solution for 20 min, and 0.12 mol/L hydrochloric acid is used as the absorption solution. The gas absorption bottle is shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e. During the experiment, gas chromatography was used to analyze and determine the degradation effect. The catalytic degradation activity of the catalyst to dimethylamine was evaluated by the degradation rate, which was expressed by Eq.\u0026nbsp;(\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n \u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e$$\\:\\eta\\:=\\frac{{C}_{in}-{C}_{0ut}}{{C}_{{i}^{n}}}$$\u003c/div\u003e\n \u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003eEquation (\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e): \u0026eta;\u0026mdash;degradation rate (%); Cin\u0026mdash;dimethylamine inlet concentration (mg/m3); Cout\u0026mdash;Dimethylamine outlet concentration (mg/m3).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3 Results and Discussion","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 XRD analysis of sodium water manganese rock catalysts\u003c/h2\u003e\n \u003cp\u003eThe XRD characterization results of the sodium manganese ore material prepared by calcination are shown in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eA, and the XRD pattern of the standard card JCPDS No.80-1098 shows that the peak values of sodium water manganese ore prepared by calcination method in this study are (~\u0026thinsp;12.5\u0026deg;), (~\u0026thinsp;25.2\u0026deg;), (~\u0026thinsp;36.5\u0026deg;), and (~\u0026thinsp;65.5). The peak values of sodium manganese ore studied by (Zhu Lin et al,2017) were (~\u0026thinsp;12.3\u0026deg;), (~\u0026thinsp;25.2\u0026deg;), (~\u0026thinsp;36.5\u0026deg;), and (~\u0026thinsp;65.5\u0026deg;), which coincided, indicating that the minerals prepared by calcination were mainly sodium manganese ore with a good crystal structure (Peng Xin et al,2021) As can be seen from Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eB, the peak values of sodium manganese ore doped by Al(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e\u0026middot;9H\u003csub\u003e2\u003c/sub\u003eO, Ce(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO, KNO\u003csub\u003e3\u003c/sub\u003e and K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e are basically the same, and they are all structures of sodium manganese. The (001), (002), (100) and (110) planes of sodium manganese ore at ~\u0026thinsp;12.3\u0026deg;, ~\u0026thinsp;24.6\u0026deg;, ~\u0026thinsp;36.5\u0026deg; and ~\u0026thinsp;65.5\u0026deg; correspond to the materials, respectively. In this study (Yin Hongling et al,2003; Wang Haoyu et al,2023; Xu Jiali et al,2013) it can be seen from Figure B that the peak value of the sodium manganese ore material prepared by the solvent method is weak at 65.5\u0026deg;, so it indicates that the crystallinity of the sodium manganese ore catalyst prepared by the solvent method is poor. The results of (Zhu Lin et al,2017) showed that the crystallinity of the material was not directly related to the catalytic effect on dimethylamine. Therefore, although the crystallinity of the water-sodium manganese ore material prepared by solvent method is poor, the subsequent catalytic effect should be experimentally explored.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 Characterization of different molar ratios of potassium doped water sodium manganese ore catalysts\u003c/h2\u003e\n \u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e is an XRD of different molar ratios of potassium-doped sodium manganese ore materials, and it can be seen that when K is incorporated, the main diffraction peaks are consistent with those of sodium manganese, indicating that the layered structure of K elements does not change when they are incorporated(J. Wang, Zhang, et al., \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e) When the K doping concentration increases, the intensity of the diffraction peak decreases at 12.3\u0026deg;, and the diffraction peak increases at half height and width. According to the Scherrer equation, the addition of K will reduce the crystallinity of the material and make the grain smaller. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e XRD comparison of MnO2, the characteristic peak gradually shifted to 12\u0026deg; as the molar ratio of K increased by 12.3\u0026deg;, indicating that the crystal spacing of the material gradually increased when the molar ratio of K increased, which may be due to the displacement of Mn\u003csup\u003e4+\u003c/sup\u003e and Mn\u003csup\u003e3+\u003c/sup\u003e in the crystal by K\u003csup\u003e+\u003c/sup\u003e ions with larger ionic radius. According to(J. Wang, Li, et al., \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e) K+, as an interlayer ion, promotes the replenishment of surface hydroxyl groups by activating water molecules, thereby enhancing surface oxygen activity. In this study, it is possible to increase the activity of the catalyst by doping K ions, which is more conducive to the catalytic degradation of VOCs.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3 SEM images of sodium water manganese ore and its different molar ratio potassium modified materials\u003c/h2\u003e\n \u003cp\u003eAs can be seen from Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e, the above catalytic materials are all spherical structures composed of nanorods, which are consistent with the morphology of sodium manganese, and the higher the potassium content, the worse the crystallinity, and the more obvious the spherical nanorod-like structure is formed. It can be seen that the particle size gradually decreases from 300 nm to 90 nm, and when too much potassium is added, K2SO4-MnO2-M2 (10:10) is irregular spherical in shape, indicating that the structure of the substance has been destroyed. As can be seen from the SEM images, the crystal morphology of the material is consistent with the XRD analysis. Since the grain boundary interface structure composed of different crystal forms has an important influence on the catalytic reaction, there are a large number of coordination unsaturated ions near the crystal interface, which is conducive to increasing the oxygen defect concentration of materials and promoting the activation process of acting molecular oxygen(Hojo et al., \u003cspan class=\"CitationRef\"\u003e2010\u003c/span\u003e; Royer et al., \u003cspan class=\"CitationRef\"\u003e2005\u003c/span\u003e; Vidruk et al., \u003cspan class=\"CitationRef\"\u003e2009\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4 XPS full spectrum of sodium water manganese ore and modified materials\u003c/h2\u003e\n \u003cp\u003eFrom Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e, it can be seen that the XPS full spectrum can obtain the elements and their valence state analysis of the material, and it can be seen from the figure that K, Mn and O elements are urged in the modified material, indicating that K element is successfully doped into the water sodium manganese ore material. The curve of 01s is shown in Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e(A), and the O1s curve can be divided into three fitting peaks, which correspond to the three species existing on the surface of the catalyst, namely lattice oxygen (Olatt.), adsorbed oxygen (Oadds.), and chemisorption water (Ow)(Mathew et al., \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e; C. Zhang et al., \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e). The specific results of the peaks are shown in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e, including the elemental valence states and surface chemical compositions of different molar ratios of water sodium manganese ore materials doped with K ions, from Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e, it can be seen that the Oadds./Olatt. ratio of K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) is the highest (0.35), according to the study of (Over H et al,2003) and (Jia et al., \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e),when Oadds./ When the ratio of Olatt. is high, it indicates that the catalyst has more active sites and the activity of the catalyst is better. In this study, subsequent catalyst activity experiments also proved that the K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) catalyst had the best activity. The XPS spectrum of Mn 2p is shown in Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e(B), and there are two typical peaks of Mn 2p1/2 and Mn 2p3/2, and the binding energies are concentrated in the range of 642.5 eV and 653.7 eV, respectively, so the split energy difference between the spin orbit is about 11.2 eV, which is in line with the conclusion of the existing study(Niu et al., \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e). According to the study (Biesinger et al., 2011; Mathew et al., \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e) K\u003csup\u003e+\u003c/sup\u003e was introduced into the original lattice, so that K\u003csup\u003e+\u003c/sup\u003e embedded more oxygen vacancies in the lattice, thereby reducing the peak position of adsorbed water and increasing the adsorbed oxygen and lattice oxygen, and the ratio of Mn\u003csup\u003e3+\u003c/sup\u003e to Mn\u003csup\u003e4+\u003c/sup\u003e was (a): MnO\u003csub\u003e2\u003c/sub\u003e was 3.00, (b) K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (1:10) was 3.19, and (c) K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (3:10) 3.64, (d) K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) is 4.94, (e): K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (10:10) is 1.90, according to (Liu et al., \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e) The results show that when the ratio of the two is higher, it indicates that the material has more active sites for catalytic oxidation, and in this study, K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) was found in several modified materials The ratio was the highest (4.94), which may indicate that the material has more active sites than other modified materials, and has a better catalytic degradation effect on dimethylamine. From Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e(C), the XPS diagram of Mn3s in the modified material shows that Mn 3s is considered to be used to distinguish the oxidation state of Mn more accurately, according to (M. Sun et al., \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e)The average oxidation valence state of Mn is calculated as: AOS\u0026thinsp;=\u0026thinsp;8.95\u0026ndash;1.13\u0026Delta;E3s, from which it can be seen that (a), (b), (c), (d), The binding energy difference between the two peaks is 4.74 eV, 4.76 Ev, 4.87 eV, 4.9 eV, and 4.71 eV, and the AOS value of K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) is the smallest, only 3.41, and according to the study of(Jia et al., \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e), based on the principle of electric neutrality, the smallest value indicates that it contains the most abundant oxygen gap, and also indicates that the modified material has abundant active sites. The XPS spectrum of K2p is shown in Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e (D). The XPS peaks of K2p can be divided into two typical characteristic peaks, K 2p1/2 and K 2p3/2, corresponding to binding energies of ~\u0026thinsp;295.7 eV and ~\u0026thinsp;292.9 eV, respectively, which are attributed to K+. It can be seen from Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e that when the K doping amount is 5.9, the relative elemental content of O and Mn is 43.78 and 14.69, when the K doping is 6.01, the relative elemental content of O and Mn is 43.86 and 15.55, when the K doping amount is 6.12, the relative elemental content of O and Mn is 43.87 and 16.43, and when the K doping is 6.57, the relative elemental content of O and Mn is 44.21 and 16.97. It can be seen that with the increase of K doping, the relative content of O and Mn increases gradually. This result proves that the potassium type on the surface of the composite material has not changed, and its properties and valence state are stable, which is a good support type (Kruse \u0026amp; Chenakin,\u0026nbsp;\u003cspan class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eSurface chemical composition and element valence distribution of birnessite and its modified materials\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCatalyst materials\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eK 2p/% 2p(At%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eO 1s/%\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eO\u003csub\u003eadds\u003c/sub\u003e./O\u003csub\u003elatt\u003c/sub\u003e.\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMn 2p/%\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMn\u003csup\u003e3+\u003c/sup\u003e/Mn\u003csup\u003e4+\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMnO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e43.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eK\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2(1:10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e43.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.19\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eK\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2(3:10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e43.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e15.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.64\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eK\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2(6:10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e43.87\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e16.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.94\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eK\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2(10:10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.57\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e44.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e16.97\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.90\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003e3.5 H2-TPR analysis\u003c/h2\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eSummary of H\u003csub\u003e2\u003c/sub\u003e-TPR data for three birnessite materials\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eCatalyst materials\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eReduction temperature(℃)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eTotal hydrogen consumption(mmol/g)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eA\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eB\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMnO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e322.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.49\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eK\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2(1:10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e234.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e329.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.52\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eK\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2(6:10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e231.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e314.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eIn order to study the reducibility of the catalyst, H2-TPR tests were carried out on MnO\u003csub\u003e2\u003c/sub\u003e-M2, K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (1:10) and K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10), as shown in Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e, the MnO\u003csub\u003e2\u003c/sub\u003e catalyst only had a reduction peak at 322.6\u0026deg;C, while the modified sodium water manganese ore materials K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (1:10) and K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) A low peak appeared at 230\u0026deg;C, followed by a peak similar to MnO\u003csub\u003e2\u003c/sub\u003e-M2 at 320\u0026deg;C. Based on the doping ratio of the catalyst and the strength of the metal reduction, it was determined that the former peak (A) was attributed to the reduction of K\u003csup\u003e+\u003c/sup\u003e to potassium, and the latter peak (B) was due to the reduction of Mn\u003csup\u003e4+\u003c/sup\u003e and Mn\u003csup\u003e3+\u003c/sup\u003e to Mn\u003csup\u003e3+\u003c/sup\u003e and Mn\u003csup\u003e2+\u003c/sup\u003e, respectively (Ara\u0026uacute;jo Melo et al., \u003cspan class=\"CitationRef\"\u003e2002\u003c/span\u003e) At the same time, with the increase of potassium doping, the reduction peak temperature of the material decreased, and the peak value also decreased, and the reduction capacity of the three was K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10)\u0026thinsp;\u0026gt;\u0026thinsp;K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (1:10)\u0026thinsp;\u0026gt;\u0026thinsp;MnO\u003csub\u003e2\u003c/sub\u003e-M2, which was also consistent with the order of catalytic performance. In addition, the total hydrogen consumption of the above three catalyst materials is calculated in Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e, and the total hydrogen consumption of catalyst K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) is at least 4.50 mmol/g, indicating that it has the lowest AOS and the lowest proportion of Mn\u003csup\u003e4+\u003c/sup\u003e. Good low temperature (231.7-329.9\u0026deg;C) reducibility corresponds to strong lattice oxygen (Olatt.) species mobility (Si et al., \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e)which is conducive to accelerating the redox process and enhancing the catalytic activity of K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) in the catalytic reaction of dimethylamine.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003e3.6 Nitrogen adsorption-desorption assay (BET) analysis\u003c/h2\u003e\n \u003cp\u003eThe physical properties of the materials were analyzed by nitrogen adsorption-desorption experiment (BET), and the results of BET determination are shown in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"char\" class=\"colspec\"\u003e\u003cbr\u003e\u003c/div\u003e\n \u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eSpecific surface area of MnO\u003csub\u003e2\u003c/sub\u003e and its modified materials\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCatalyst materials\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSpecific surface area(m\u003csup\u003e2\u003c/sup\u003e/g)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMnO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e20.94\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eK\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2(1:10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e22.47\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eK\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2(3:10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e23.88\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eK\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2(6:10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e25.86\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eK\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2(10:10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e21.60\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eAs shown in the SEM images above, the particle size of the modified material decreases and the specific surface area increases, and the crystallinity of the catalyst material decreases from 300 nm to 140 nm of the K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) material after potassium doping. The analysis found that this was due to the lattice distortion caused by the difference in the radius between the two ions after the introduction of new ions to replace Mn\u003csup\u003e4+\u003c/sup\u003e, which affected the crystal growth process, thereby reducing the size of the material and increasing the specific surface area. Combined with Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e, the specific surface area of MnO\u003csub\u003e2\u003c/sub\u003e was the lowest, only 20.94 m2/g. When the doping ratio gradually increased from 1:10 to 6:10, the specific surface area increased to 22.47, 23.88 and 25.86 m2/g, respectively. However, when the doping ratio continued to increase to 10:10, part of the sodium manganese ore structure in the material was destroyed, and the morphology of the material showed an irregular structure, which reduced the specific surface area of the modified material to 21.6 m2/g, but it was still higher than that of the MnO\u003csub\u003e2\u003c/sub\u003e material. Therefore, the doping of K element makes the particle size of the modified material smaller, the specific surface area increases, and the catalyst has more active sites, so that the catalyst has a better catalytic effect on dimethylamine(J. Wang, Zhang, et al., \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n \u003ch2\u003e3.7 Raman spectrum analysis\u003c/h2\u003e\n \u003cp\u003eThe structural changes of sodium manganese dioxide after potassium modification were compared by Raman spectroscopy, and the test results are shown in Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e. As can be seen from Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e \u0026delta;-MnO\u003csub\u003e2\u003c/sub\u003e is mainly presented as three sets of broad and weak characteristic Raman peaks, all corresponding to M-O bonds, located at 501.2, 574.1 and 648.5 cm-1, respectively, according to the study of (Julien, \u003cspan class=\"CitationRef\"\u003e2003\u003c/span\u003e) these three sites correspond to the bending vibration of the Mn-O-Mn bond in the MnO\u003csub\u003e6\u003c/sub\u003e group, the \u0026nu;3(Mn-O) expansion vibration caused by Mn\u003csup\u003e4+\u003c/sup\u003e on the bottom surface of the [MnO\u003csub\u003e6\u003c/sub\u003e] octahedron, and the \u0026nu;2(Mn-O) in the [MnO\u003csub\u003e6\u003c/sub\u003e] structure Asymmetrical telescopic vibration. It can be seen from Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e that the strength of each characteristic peak of the modified sodium manganese ore material gradually weakens with the increase of K doping, and the \u0026nu;3(Mn-O) expansion vibration characteristic peak in the material shows a redshift phenomenon when the K doping ratio is 10:10, and the main reason for this phenomenon is that the addition of K element causes more defects in the crystal, which causes the stress in the crystal and the distortion of the crystal lattice. In summary, the increase of internal defects in the crystal caused by K doping increased the oxygen defect content on the surface of the modified manganese dioxide catalyst and enhanced its catalytic degradation efficiency.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\n \u003ch2\u003e3.8 Catalytic activity test\u003c/h2\u003e\n \u003cp\u003eAs shown in Fig. \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e-A, degradation begins at 150\u0026deg;C with empty tower conditions, and the degradation rate reaches 50% at 280\u0026deg;C. The degradation rate is slowed down at 400\u0026deg;C-500\u0026deg;C, and the degradation rate reaches 90% when the temperature reaches 550\u0026deg;C. Under the condition of MnO2-M1, the degradation rate of dimethylamine reached 28.2% at 150\u0026deg;C, which was about 20% higher than that of empty tower, and the degradation rate of dimethylamine reached 90% at 490\u0026deg;C. Under the condition of MnO\u003csub\u003e2\u003c/sub\u003e-M2, the degradation rate of dimethylamine is more than 50% at the temperature of 150\u0026deg;C, and the degradation effect is significantly higher than that of MnO\u003csub\u003e2\u003c/sub\u003e-M1. From Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e-A, it can be clearly seen that with the increase of temperature, the degradation effect of catalyst MnO\u003csub\u003e2\u003c/sub\u003e-M2 on dimethylamine is significantly superior to that of MnO\u003csub\u003e2\u003c/sub\u003e-M1. Therefore, it can be concluded that the order of reactivity of the three should be: MnO\u003csub\u003e2\u003c/sub\u003e-M2\u0026thinsp;\u0026gt;\u0026thinsp;MnO\u003csub\u003e2\u003c/sub\u003e-M1\u0026thinsp;\u0026gt;\u0026thinsp;empty tower. It can be seen that the catalyst MnO\u003csub\u003e2\u003c/sub\u003e-M2 prepared by potassium permanganate and ammonium oxalate solvent method (M2) has a significant effect on the catalytic oxidation of dimethylamine. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e-B, the degradation rate of Ce-MnO\u003csub\u003e2\u003c/sub\u003e-M2 with the lowest activity was 66.1%, and the degradation rate of the best K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 was 73.57% at 150\u0026deg;C, compared with the degradation of dimethylamine by empty towers, which had just reached the critical pyrolysis temperature of dimethylamine degradation in the empty tower. Among them, the degradation temperatures of MnO\u003csub\u003e2\u003c/sub\u003e-M2, Al-MnO\u003csub\u003e2\u003c/sub\u003e-M2, Ce-MnO\u003csub\u003e2\u003c/sub\u003e-M2, KNO\u003csub\u003e3\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 and K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 were 298\u0026deg;C, 200\u0026deg;C, 253\u0026deg;C, 205\u0026deg;C and 185\u0026deg;C when the degradation rate of dimethylamine reached 80%, respectively. At 50\u0026ndash;200\u0026deg;C, the catalytic activities were K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2\u0026thinsp;\u0026gt;\u0026thinsp;Al-MnO\u003csub\u003e2\u003c/sub\u003e-M2\u0026thinsp;\u0026gt;\u0026thinsp;KNO\u003csub\u003e3\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2\u0026thinsp;\u0026gt;\u0026thinsp;Ce-MnO\u003csub\u003e2\u003c/sub\u003e-M2\u0026thinsp;\u0026gt;\u0026thinsp;MnO\u003csub\u003e2\u003c/sub\u003e-M2。 Based on the above data, K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 was selected as the optimal metal doping catalyst. As can be seen from Fig. \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e-(a), with the increase of molar ratio, the degradation temperature of K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (0.5:10) to K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (10:10) catalyst is 110\u0026deg;C, 76\u0026deg;C, 63\u0026deg;C, 52\u0026deg;C, 107\u0026deg;C and 119\u0026deg;C when the molar ratio increases, and the degradation temperature is 362\u0026deg;C, 304\u0026deg;C, 295\u0026deg;C, 243\u0026deg;C, 312\u0026deg;C and 326\u0026deg;C when the degradation rate reaches 90%. K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) has a higher degradation rate (81.7%) at 150\u0026deg;C, and when the temperature reaches 200\u0026deg;C, the degradation efficiency of different proportions of catalysts gradually decreases, while the K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (0.5:10), K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (8:10) and K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (10:10) catalysts have similar trends in the whole catalytic degradation of dimethylamine. It can be seen from Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e-(b) that at 100\u0026deg;C, the degradation rate of the unmodified catalyst MnO2-M2 for dimethylamine is only about 15%, the modified catalysts K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) and K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (1:10) are both above 60%, and the degradation rate of the K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e-M2 (6:10) catalyst even reaches 69.75%, which is about 4 times higher than that of MnO\u003csub\u003e2\u003c/sub\u003e-M2. Therefore, from the comprehensive data, the catalyst K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) has the best effect on the degradation of dimethylamine.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\n \u003ch2\u003e3.9 Effect of reaction conditions on catalytic activity and stability test\u003c/h2\u003e\n \u003cp\u003eAs shown in Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e-A, the degradation rate of dimethylamine at low concentration (150 mg/L) began to occur at low temperature (50\u0026deg;C), and the degradation rate was 4.33%, and the degradation rate of medium and high concentration (650, 1500 mg/L) did not begin to degrade until the reaction temperature increased to 100\u0026deg;C, and the degradation effect of high concentration (1500 mg/L) dimethylamine was significantly lower than that of medium and low concentration dimethylamine in the temperature range of 150\u0026ndash;500\u0026deg;C. At 500\u0026deg;C, the difference in the degradation rate of 150, 650 and 1500 mg/L dimethylamine gradually narrowed to about 1%, which was 75.15%, 74.09% and 74.93%, respectively. With the increase of temperature, the degradation trend of the three is gradually consistent. When the temperature reaches 600\u0026deg;C, the degradation rate of dimethylamine has exceeded 90%, and the complete transformation is basically realized. According to (W. Wang et al., \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e) the concentration of dimethylamine is too high to increase the critical temperature of thermal decomposition, and the degradation effect is not obvious, and with the increase of reaction temperature, C-N gradually breaks down, which promotes the deep oxidative decomposition of dimethylamine.\u003c/p\u003e\n \u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e-B shows the influence of airspeed under the condition of empty tower, when the airspeed is large (350000 mL/gcat∙h), the degradation rate reaches 50% and 90% at 398\u0026deg;C and 564.2\u0026deg;C, respectively. Dimethylamine began to degrade at 100\u0026deg;C at 45000 and 150000 mL/gcat∙h at space speeds, and the degradation rates reached 246\u0026deg;C and 284\u0026deg;C at 50%, respectively, and reached more than 90% at 550\u0026deg;C, with 95.18% and 91.15\u0026deg;C, respectively. Based on the above data, it can be seen that the degradation effect of dimethylamine in the empty tower is in the order of low air velocity (45000 mL/gcat∙h)\u0026thinsp;\u0026gt;\u0026thinsp;medium air velocity (150000 mL/gcat∙h)\u0026thinsp;\u0026gt;\u0026thinsp;maximum space velocity (350000 mL/gcat∙h).\u003c/p\u003e\n \u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e-C shows the effect of different concentrations on the catalyst activity of K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) catalyst, and it can be seen from Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e-C that the temperature of dimethylamine degradation reaches 50% at 150, 650 and 1500 mg/L, respectively. The degradation rate reached 90% at 241\u0026deg;C, 299\u0026deg;C and 293\u0026deg;C, respectively. According to the research of (Zhang Huai et al,2017) it was also shown that the catalyst had better catalytic performance for low concentrations of dimethylamine. Based on the above data, it can be seen that at low temperature (50\u0026deg;C-300\u0026deg;C), K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) has obvious advantages in the catalytic effect of medium and low concentrations of dimethylamine, but the advantage gradually decreases with the increase of temperature. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e, the mass of K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) catalyst is 20, 60 and 100 mg, respectively, and the temperatures corresponding to dimethylamine degradation efficiency reach 50% are 219, 153 and 139\u0026deg;C, respectively, and the temperature of dimethylamine degradation efficiency is 322, 264 and 250\u0026deg;C, respectively.\u003c/p\u003e\n \u003cp\u003eAs can be seen from Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e-D, the catalytic degradation efficiency of dimethylamine at 20 mg is significantly lower than that at 60 and 100 mg. However, the degradation of dimethylamine was similar between 60 and 100 mg of catalyst K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10). It can be seen that the larger the amount of non-catalyst under the same reaction conditions, the better the catalytic decomposition effect, which is in line with the research law of (Xie Wengong et al,2025) Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e(a)(b) shows that compared with the degradation effect of dimethylamine under the empty tower at the air velocity, the addition of the catalyst significantly reduces the degradation temperature of dimethylamine, that is, when the reaction condition is T\u0026thinsp;=\u0026thinsp;150\u0026deg;C and the reaction space velocity is 45000 mL/gcat\u0026middot;h, the dimethylamine reaches the critical pyrolysis temperature under the empty tower condition, and the dimethylamine has begun to degrade after the addition of the catalyst, and the degradation rate reaches about 50%. Similarly, the degradation effect was the worst when the space velocity was 350000 mL/gcat\u0026middot;h under the condition of empty tower, and the degradation began at close to 300\u0026deg;C, while the pyrolysis temperature was reached after 100\u0026deg;C after the catalyst was added, and the degradation rate reached 90% at 300\u0026deg;C. Therefore, the superiority of the catalyst K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) in the degradation of dimethylamine can be fully demonstrated.\u003c/p\u003e\n \u003cp\u003eAs shown in Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e(a), the removal rate of dimethylamine by K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) increases with the increase of temperature under different space velocity conditions, and shows a similar trend. However, with the increase of space velocity, the degradation effect of K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) on dimethylamine gradually weakened at the same reaction temperature. According to the inference of(Danita Patricia \u0026amp; Vijay Solomon, \u003cspan class=\"CitationRef\"\u003e2025\u003c/span\u003e) it may be that when the space velocity is small, it can fully contact with the surface of the catalyst and the residence time is longer, so the catalytic degradation effect is better.\u003c/p\u003e\n \u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e(b) shows the variation trend of T40, T50 and T90 with reaction space velocity, with the increase of space velocity, the temperature of T40 degradation rate decreases first and then increases, the T50 degradation rate is less affected by temperature, and the T90 degradation rate curve of T90 shows an upward trend, compared with high air velocity, the T40 and T90 of dimethylamine increase by about 70\u0026deg;C at 45000 mL/gcat\u0026middot;h space velocity. It is further proved that the degradation effect of K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) on dimethylamine gradually weakens with the increase of space velocity.\u003c/p\u003e\n \u003cp\u003eAs shown in Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e(c)(d), the catalytic stability of K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) at 100\u0026deg;C, 300\u0026deg;C and 450\u0026deg;C was compared. It can be seen from Figure c that the experimental fluctuations are very large at 100\u0026deg;C, and the degradation effect of dimethylamine decreases with the increase of the number of cycles, but the degradation effect of dimethylamine is stable with the increase of the number of cycles at 300\u0026deg;C and 450\u0026deg;C, and the difference between the first and tenth degradation rates of dimethylamine is 8.55%, 5.59% and 3.12%, respectively, corresponding to the reaction temperature conditions of 100\u0026deg;C, 300\u0026deg;C and 450\u0026deg;C, respectively, according to the study of (Meng et al., \u003cspan class=\"CitationRef\"\u003e2025\u003c/span\u003e)and the above data, The cycling stability of the K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) catalyst catalyzed dimethylamine oxide was affected at low temperature, while the catalyst could be stable at high temperature. In summary, dimethylamine can maintain high catalytic degradation efficiency after 10 cycles at high temperature (300\u0026ndash;450\u0026deg;C), so the catalyst has high stability. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e(d), the stability of the optimal catalyst K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) at the optimal reaction temperature (300\u0026deg;C) decreases the decomposition of dimethylamine, and it can be seen that the degradation efficiency of the K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) catalyst for dimethylamine gas is about 95%, the highest degradation rate of dimethylamine is 97.81% at 11h, and the lowest degradation rate of dimethylamine is 92.68% at 19h. In summary, the catalyst K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) has high stability.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\n \u003ch2\u003e3.10 Possible Reaction Mechanisms\u003c/h2\u003e\n \u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e shows the XPS spectra of the K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) catalyst before and after use, showing the relationship between the content of Ow/Oadds./Olatt., Mn3\u003csup\u003e+\u003c/sup\u003e/Mn4\u003csup\u003e+\u003c/sup\u003e, and K\u003csup\u003e+\u003c/sup\u003e and the catalytic performance of K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10). As can be seen from Fig. \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e(A), the content of adsorbed oxygen (Oadds.) and lattice oxygen (Olatt.) on the surface of the K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 catalyst increased relatively well, which may be due to the higher catalytic temperature, which causes more oxygen to be adsorbed during the catalytic process, which is conducive to the stability of the catalyst (Huang et al., \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e) As can be seen in Fig. \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e(B), the ratio of Mn\u003csup\u003e3+\u003c/sup\u003e/Mn\u003csup\u003e4+\u003c/sup\u003e in the catalyst decreases after use, and part of the Mn\u003csup\u003e3+\u003c/sup\u003e on the surface of the catalyst is oxidized to Mn\u003csup\u003e4+\u003c/sup\u003e. Figure \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e(C) shows the XPS spectrum of Mn 3s, which shows that there is no difference between before and after use, indicating that the surface of the material remains rich in oxygen and the catalytic activity of the catalyst is stable(Hou et al., \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e)Fig. \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e(D) shows that the characteristic peak of K\u003csup\u003e+\u003c/sup\u003e does not change, but the K\u003csup\u003e+\u003c/sup\u003e content of the catalyst decreases after use, which may be due to the loss caused by the oxidation of O2 during catalytic oxidation. From the changes before and after the use of the catalyst reflected in the XPS spectrum, as well as the study of (Louren\u0026ccedil;o et al., \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e)it is possible to infer the valence changes of the elements within the catalyst: Mn\u003csup\u003e3+\u003c/sup\u003e+K\u003csup\u003e+\u003c/sup\u003e+O\u003csub\u003e2\u003c/sub\u003e ⟷ Mn\u003csup\u003e4+\u003c/sup\u003e+nK\u003csup\u003e+\u003c/sup\u003e+mO\u003csup\u003e2\u0026minus;\u003c/sup\u003e The above possible changes lead to the occurrence of redox reactions, where Mn\u003csup\u003e3+\u003c/sup\u003e is oxidized to Mn\u003csup\u003e4+\u003c/sup\u003e due to the addition of K\u003csup\u003e+\u003c/sup\u003e ions, so that dimethylamine gas is continuously oxidized and degraded by catalysts. According to the above experiments, the analysis of the oxidative degradation of dimethylamine follows the Mars-van Krevelen (MVK) mechanism. Firstly, the K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) catalyst is heated to activate the reactive oxygen species on the surface, while the dimethylamine gas is adsorbed on the surface of the catalyst and reacts with the adsorbed oxygen and lattice oxygen on the surface, resulting in the reduction of metal oxides in the catalyst. According to V. The study of (Santos et al., \u003cspan class=\"CitationRef\"\u003e2010\u003c/span\u003e) suggests that during the reaction, the dimethylamine molecule is oxidized to break the C-N bond, resulting in the catalytic degradation of dimethylamine. Through the analysis of XPS, BET and H\u003csub\u003e2\u003c/sub\u003e-TPR, it was revealed that K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) had a large oxygen capacity and a high specific surface, so as to achieve the uniform distribution of Mn, K, O and other elements on the catalyst, promote the rapid transfer between it and O\u003csub\u003e2\u003c/sub\u003e, improve the catalytic activity and stability of the catalyst, and improve its long-lasting catalytic oxidation ability of dimethylamine.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4 Conclusion","content":"\u003cp\u003eThe potassium modified water sodium manganese ore catalyst (K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2) was prepared by solvent method with potassium sulfate as the carrier and the molar ratio of K to Mn was adjusted to adjust the lattice defect and oxygen vacancy concentration by adjusting the molar ratio. The results showed that K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 had the highest catalytic decomposition performance for dimethylamine. The high specific surface area and total pore volume of K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 catalyst promoted the adsorption of dimethylamine and molecular oxygen by the active site of the catalyst, and the surface of K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 catalyst was rich in adsorbed oxygen and lattice oxygen, which was dominated by adsorbed oxygen and crystalline oxygen, which enhanced the catalytic oxidation of dimethylamine. At the same time, K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 has better redox performance, and a more stable catalyst is obtained through multiple redox cycles. XPS analysis showed that the oxidation of dimethylamine catalyzed by K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 followed the M-vK mechanism. In this study, an efficient and stable K\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e-M2 catalyst for dimethylamine combustion was synthesized, and its catalytic effect and reaction mechanism were clarified, which provided a reference for the application of efficient removal of volatile organic compounds by supported transition metal catalysts. The optimal reaction conditions were selected as follows: gas flow rate of 0.35 L/min (space velocity of 350000 mL/gcat·h), dimethylamine concentration of 150 mg/L, reaction temperature of 300°C, and catalyst mass of 0.06 g.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by Chengxun Deng. The funder had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis article does not contain any studies with human participants or animals performed by any of the authors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable. This study did not involve human participants.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to publish\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analysed during this study are included in this published article\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAra\u0026uacute;jo Melo, D. M., Ruiz, J. A. C., Melo, M. A. F., Sobrinho, E. V., \u0026amp; Martinelli, A. E. (2002). Preparation and characterization of lanthanum palygorskite clays as acid catalysts. \u003cem\u003eJournal of Alloys and Compounds\u003c/em\u003e, \u003cem\u003e344\u003c/em\u003e(1\u0026ndash;2), 352\u0026ndash;355. https://doi.org/10.1016/S0925-8388(02)00384-5\u003c/li\u003e\n \u003cli\u003eDanita Patricia, P., \u0026amp; Vijay Solomon, R. (2025). 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Kinetic Characteristics of Alkaline Water Sodium Manganese Ore Oxidation of As(III.) and Cr(III.) with Different Degrees of Oxidation[J]. Journal of Petromineralogy, 2013, 32( 6): 975-984\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eZhang Huan, Fu Min, Wei Junfu, et al. Degradation of trace nitrosodimethylamine in water by Pd/Fe0 bimetallic composite catalytic fibers[J].Environmental Science,2017,38(07):2868-2874.DOI:10.13227/j.hjkx.201701194.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eXie Wengong, Wu Tiantian, Yan Feng. Catalytic Synthesis of Ethyl Acetate by Binary S2O82-/TiO2-Fe3O4 Solid Super Acid Catalyst[J].Petrochemical Technology and Application,2025,43(02):105-110.DOI:10.19909/j.cnki.ISSN1009-0045.2025.02.0105.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"discover-chemistry","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Chemistry](https://link.springer.com/journal/44371)","snPcode":"44371","submissionUrl":"https://submission.nature.com/new-submission/44371/3","title":"Discover Chemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"catalyst, VOCs, Water sodium manganese ore, Modified materials, Degrade ethyl acetate","lastPublishedDoi":"10.21203/rs.3.rs-7291479/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7291479/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eImproving the degradation efficiency of VOCs remains a challenge for our industry. Among them, catalytic degradation is an efficient VOCs degradation technology. The synthesis of doped metal-modified water-sodium-manganese mineral catalysts with efficient catalytic performance and stability remains a challenge for the complete degradation of VOPs. Different water-sodium-manganese ore manganese dioxide were prepared by high-temperature calcination and solvent method, and modified by doped metals (Al, Ce, K), and the results showed that the K\u003csub\u003e2\u003c/sub\u003eSO\u003csup\u003e4-\u003c/sup\u003eMnO\u003csub\u003e2\u003c/sub\u003e-M2 catalyst prepared by solvent method had good catalytic activity. By adjusting the metal doping ratio of manganese to potassium and changing the crystal structure of the catalyst, the results showed that the K\u003csub\u003e2\u003c/sub\u003eSO\u003csup\u003e4-\u003c/sup\u003eMnO\u003csub\u003e2\u003c/sub\u003e-M2 (6:10) type had the best catalytic activity. The results showed that the K\u003csub\u003e2\u003c/sub\u003eSO\u003csup\u003e4-\u003c/sup\u003eMnO\u003csub\u003e2\u003c/sub\u003e-M2 catalyst introduced K\u003csup\u003e+\u003c/sup\u003e ions into the original crystal structure, and it was observed that the ratio of Mn\u003csup\u003e3+\u003c/sup\u003e to Mn\u003csup\u003e4+\u003c/sup\u003e increased with the insertion of K\u003csup\u003e+\u003c/sup\u003e, indicating that there were more oxygen vacancies, and the concentration of adsorbed oxygen and lattice oxygen increased, which was conducive to catalytic performance and catalytic stability. This study provides a reference for the degradation of volatile organic pollutants by doped modified water-sodium-manganese ore catalysts.\u003c/p\u003e","manuscriptTitle":"Study on the activity of doped metal-modified water-sodium- manganese ore catalyst to catalyze the degradation of dimethylamine","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-19 14:24:21","doi":"10.21203/rs.3.rs-7291479/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-08-25T11:54:44+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-24T14:52:58+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"315831947393232138477533547165388515916","date":"2025-08-22T17:15:55+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"29915952691968294421169077343459000966","date":"2025-08-22T16:02:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"86321897671739857401159755531710842787","date":"2025-08-22T12:39:56+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"36691519114655700719513921345474519355","date":"2025-08-22T09:49:52+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-21T11:30:48+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"224207088471272995354414476960295927587","date":"2025-08-21T11:14:51+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-21T04:48:45+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"120330664175227954516531288179338248820","date":"2025-08-19T07:52:08+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-08-11T11:34:45+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-08-11T11:12:51+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-08-11T11:04:34+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-08-11T09:44:18+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Chemistry","date":"2025-08-11T09:40:15+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-chemistry","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Chemistry](https://link.springer.com/journal/44371)","snPcode":"44371","submissionUrl":"https://submission.nature.com/new-submission/44371/3","title":"Discover Chemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"d43034d8-753d-44a8-bc9c-cfc9411760e2","owner":[],"postedDate":"August 19th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-11-07T07:38:07+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-19 14:24:21","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7291479","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7291479","identity":"rs-7291479","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}