Method for strengthening ultraviolet light degradation of methyl mercaptan

Abstract

The invention discloses a method for strengthening ultraviolet light degradation of methyl mercaptan, and belongs to the technical field of atmosphere control and pollution control. The method comprises the following steps: (1) adding water into a dynamic gas-liquid phase photoreaction device; (2) adding a catalyst into water, and adjusting the pH value of the system to a certain range; (3) adding CaSO3 into the water; (4) introducing methyl mercaptan gas; and (5) carrying out a photodegradation reaction by using UVC waveband ultraviolet light to complete the degradation of methyl mercaptan. According to the method disclosed by the invention, an existing ultraviolet light degradation (photooxidation) device can be utilized, required instruments and equipment are simple, the stability of the catalyst is high, the pH range of an applicable absorption aqueous solution is wide, alkali does not need to be additionally added, and the method can be applied at normal temperature and does not involve the use of dangerous chemicals. The method provided by the invention can realize washing absorption-advanced oxidation combined enhanced treatment of methyl mercaptan in waste gas, plays a role in deep degradation and removal of methyl mercaptan odor, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of atmospheric control and pollution treatment technology, and in particular to a method for enhancing the ultraviolet degradation of methanethiol. Background Technology

[0002] Thiols are a class of organic compounds containing a thiol functional group (-SH), usually represented by RSH (R representing alkyl or aromatic groups). Low molecular weight methanethiol is a typical volatile organic compound (VOC). Methanethiol (MeSH) has a strong, unpleasant garlic odor and an extremely low odor threshold, making it one of the major malodorous gases. For example, when the volume fraction of methanethiol in the air reaches 2 × 10⁻⁶... -11 The odor can be detected immediately. Methanethiol is highly volatile, with a vapor pressure of 1510 mm Hg at room temperature, and easily dissipates into the air, producing a foul smell.

[0003] Ultraviolet (UV) photodegradation is a common method for the decomposition of organic matter. The wavelength range of the UV light source used is typically divided into three bands: UVC (200–280 nm), UVB (280–320 nm), and UVA (320–380 nm). For the UV photodegradation of thiols in the liquid phase, some literature reports that 254 nm wavelength UVC light can completely degrade methanethiol dissolved in an alkaline solution (pH=12). However, methanethiol does not absorb UVB and UVA light; therefore, 313 nm wavelength UVB and 365 nm wavelength UVA light cannot degrade methanethiol (Yang Shiying, Wang Leilei, Zhao Lajuan. Wet absorption removal of methanethiol odorous gas using UV / peroxide system [C] / / Chinese Chemical Society, Chinese Solar Energy Society. Proceedings of the 13th National Conference on Solar Photochemistry and Photocatalysis. Key Laboratory of Marine Environment and Ecology, Ministry of Education (Ocean University of China), 2012:192-193.). In an earlier study (Caspari G, Granzow A. The flash photolysis of mercaptans inaqueous solution[J]. The Journal of Physical Chemistry, 1970, 74(4):836-839.), Caspari and Granzow investigated the ultraviolet photolysis of thiols in an oxygen-free aqueous solution, proposing that UVC at 230-270 nm can be absorbed by thiols in water to generate thiol radicals (where R represents alkyl or aromatic groups):

[0004] The resulting thiol free radicals RS• readily recombine to form disulfides (RSSR):

[0005] Therefore, UV photolysis of methanethiol alone cannot mineralize and decompose methanethiol.

[0006] Existing methods for purifying methanethiol include, for example, Chinese invention patent CN10681253A, which discloses a method for treating methanethiol odor. This method involves a series of reactions, including chlorine dioxide oxidation, high-efficiency UV photolysis, and UV-synergistic chlorine dioxide advanced oxidation, to thoroughly remove the methanethiol odor. Chinese invention patent CN112090170A provides a method for preparing a zinc oxide filter material for UV-cooled combustion deodorization. This method utilizes a composite of polyhydrazone and zinc oxide to prepare the zinc oxide filter material, reducing the probability of simple electron-hole recombination and increasing photocatalytic activity. The methanethiol and zinc oxide filter material are photocatalyzed under high-energy, high-ozone UV light irradiation. In Chinese invention patent CN115957749A, a platinum-supported titanium dioxide composite photocatalyst, its preparation method, and its application in the degradation of harmful pollutants are disclosed. In this scheme, platinum is used as the catalyst for the photocatalytic reaction of the supported TiO2 composite material. In the experiment of photocatalytic degradation of harmful pollutants, the composite TiO2 photocatalytic material is solidified on flexible porous fiber cotton. Under the conditions of full-band light irradiation, it can completely degrade harmful pollutants such as methanethiol, formaldehyde, and ammonia in a short time.

[0007] The aforementioned solutions are flawed in terms of both process convenience and safety. In particular, some processes utilize hazardous chemicals such as chlorine dioxide and hydrazine hydrate, posing potential risks to raw material transportation, storage, production, and the environment. Furthermore, according to the "National Pollution Prevention and Control Technology Guidance Catalogue (2024, Restricted and Eliminated Categories)" (draft for public comment) released by the Ministry of Ecology and Environment in September 2024, VOCs photocatalysis and its combined purification technologies, as well as VOCs photolysis (photo-oxidation) and its combined purification technologies, are listed as eliminated technologies. VOCs photocatalysis and its combined purification technologies utilize photocatalysts such as titanium dioxide to activate and oxidize VOCs through ultraviolet and visible light. The reason for their elimination is that the photocatalytic reaction rate is slow, the products are unclear, and the treatment efficiency is low when applied to VOCs treatment, failing to meet treatment requirements. VOCs photolysis (photo-oxidation) and its combined purification technologies utilize pollutant molecules to absorb short-wavelength ultraviolet light, triggering the breakage of chemical bonds in the pollutant molecules. Simultaneously, oxygen or water molecules in the exhaust gas absorb short-wavelength ultraviolet light, generating reactive species, including ozone and hydroxyl radicals, which then undergo degradation reactions with the pollutant molecules. The reasons for phasing out these technologies are: low photoelectric conversion efficiency, generally insufficient effective light radiation energy in the reaction devices, low treatment efficiency when applied to industrial waste gas, and unclear reaction products. Although the above two technologies are not strictly within the scope of elimination for odor control, with the implementation of this catalog, many operating enterprises are actively seeking upgrades and renovations for their VOCs photocatalytic and photolysis (photo-oxidation) treatment facilities, creating a strong demand for new technologies based on existing infrastructure.

[0008] In summary, this method provides a highly applicable, stable, efficient, and safe ultraviolet light degradation method for methanethiol, which is of great significance for the treatment of VOCs. Summary of the Invention

[0009] In view of the above-mentioned deficiencies of the prior art, in a first aspect of the present invention, a method for enhancing the ultraviolet degradation of methanethiol that is simple in process, widely applicable, safe and efficient is provided, comprising the following steps: (1) Add water to the dynamic gas-liquid phase photoreactor; (2) Add a catalyst to the water and adjust the pH of the system to a certain range; (3) Add CaSO3 to the water; (4) Introduce methanethiol gas; (5) Use UVC band ultraviolet light to carry out photodegradation reaction to complete the degradation of methanethiol.

[0010] Preferably, in step (2), the catalyst is selected from CuO, Cu2O, and Al2CuO4.

[0011] Preferably, in step (2), the amount of catalyst added is 0.05~0.3 g / L.

[0012] Preferably, in step (2), the pH range is 3 to 9.

[0013] More preferably, the pH range is 7 to 9.

[0014] Preferably, in step (3), the amount of CaSO3 added is 2~6 mM.

[0015] In a further preferred embodiment, CaSO3 is added in multiple equal additions as the photodegradation reaction proceeds.

[0016] Preferably, in step (4), the initial concentration of methanethiol gas is 75~100 ppmv.

[0017] Preferably, in step (5), the main wavelength of UVC band ultraviolet light is 254 nm.

[0018] In a second aspect of the invention, applications of the first aspect of the invention are provided, including for the degradation of methanethiol in air control or pollution treatment.

[0019] Based on the above technical solutions, the design concept and principle of this invention are as follows: This invention overcomes the technical deficiencies in the reasons given for phasing out two photochemical-related technologies, and its core lies in two aspects: Firstly, there is the transformation of the reaction phase. Methanethiol has a certain degree of water solubility (its solubility in water at room temperature can reach 15.4 g / L). When dissolved in water, it ionizes to release hydrogen ions, making the solution acidic. This makes it easier for it to dissolve in alkaline aqueous solutions (dissolution also applies to acidic solutions, but alkaline solutions are more favorable), thus providing a basis for its liquid-phase oxidation. This scheme utilizes acid-base reactions to enhance the dissolution and washing of VOCs in water, transforming the gas-phase photoreaction into a liquid-phase photoreaction. This increases the reaction concentration of VOCs and extends the reaction time, thereby improving the overall treatment efficiency. Simultaneously, after washing and absorption, the VOCs are converted into a water treatment mode, providing a foundation for subsequent process improvements and achieving deep oxidation.

[0020] Secondly, the composition of the photoreaction system needs updating. Existing photoreaction systems rely solely on the photolysis of TiO2 photocatalysts, oxygen, and water molecules to generate low-concentration gaseous active species, resulting in low photoelectric conversion efficiency. Introducing new oxidant precursors into the photoreaction system, which become the main substances absorbing ultraviolet light, decomposes to generate primary active species. This improves photoelectric conversion efficiency and rapidly generates high-concentration active species, oxidizing and even mineralizing VOCs.

[0021] In the selection of oxidant precursors, this invention considers that the inorganic sulfur-containing products after the photodegradation of thiols may include sulfide ions and their partial oxidation product, sulfite ions (S(Ⅳ)). S(Ⅳ) itself can absorb UVC and undergo photolysis to generate primary sulfoxy radicals—sulfite radicals SO3. ·- It reacts rapidly with dissolved oxygen to produce secondary sulfur radicals—peroxysulfate radicals (SO5). ·- It then reacts with S(IV) to produce sulfate radicals SO4. ·- In slightly alkaline water, hydroxyl radicals HO· can be generated. These secondary radicals can exert a deep oxidizing effect on methanethiol and its degradation products. However, the amount of S(Ⅳ) generated by methanethiol itself is very limited. Therefore, an additional addition of S(Ⅳ) is designed. To control the consumption rate of S(Ⅳ), calcium sulfite (CaSO3), which has a slow-release effect, is chosen as the source of S(Ⅳ). At the same time, CaSO3 is alkaline, and adding a certain amount of CaSO3 can increase the initial pH of the absorption solution, which is beneficial to the washing and absorption of methanethiol.

[0022] Regarding the selection of catalysts, this invention considers the catalytic oxidation reaction characteristics of methanethiol and S(IV). The catalysts meet three conditions: First, they can adsorb methanethiol, such as Cu-based catalysts, which can utilize Cu ions to form complexes with SH to achieve adsorption and surface catalytic reaction of methanethiol, and their catalysts have high stability and low heavy metal leaching; Second, they can activate S(IV) under slightly alkaline pH conditions to generate sulfur-oxygen free radicals; Third, they have certain photocatalytic performance and can enhance the oxidation of S(IV) and thiols.

[0023] Based on the above-mentioned inventive concept, combined with technical background analysis and a large number of exploratory experiments, this invention proposes a new method for the combined enhanced treatment of methanethiol by UVC photocatalytic alumina copper activation alkaline calcium sulfite washing absorption-advanced oxidation. This method can utilize readily available ultraviolet photodegradation (photo-oxidation) devices, requires simple instruments and equipment, and has a good foundation for promotion and application.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects: This invention provides a method for enhancing the ultraviolet degradation of methanethiol. This method is applicable to a wide pH range of absorption aqueous solutions, requires no additional alkali, can be applied at room temperature, does not involve the use of hazardous chemicals, and has the advantages of simple process, wide applicability, safety and high efficiency.

[0025] This invention provides an application of a method for enhancing the ultraviolet degradation of methanethiol, which has broad application prospects in the degradation of methanethiol in air control or pollution treatment. Attached Figure Description

[0026] Figure 1A schematic diagram of the dynamic gas-liquid phase photoreactor used for the photodegradation of methanethiol; Figure 2 Results of methanethiol removal rate tests under different systems; Figure 3 The results show the effect of initial pH on the photodegradation of methanethiol in the UVC / Al2CuO4 / CaSO3 system; Figure 4 The effect of CaSO3 dosage on the photodegradation of methanethiol in the UVC / Al2CuO4 / CaSO3 system; Figure 5 The results show the changes in the concentration of S-form during the photodegradation of methanethiol in the UVC / Al2CuO4 / CaSO3 system. Figure 6 The test results show the photodegradation of different concentrations of methanethiol using the UVC / Al2CuO4 / CaSO3 system. Figure 7 The results show the effect of UVC light intensity on the photodegradation of methanethiol in the UVC / Al2CuO4 / CaSO3 system; Figure 8 The results show the effect of Al2CuO4 catalyst dosage on the photodegradation of methanethiol in the UVC / Al2CuO4 / CaSO3 system; Figure 9 The results show the effect of intermittent CaSO3 addition on the photodegradation of methanethiol in the UVC / Al2CuO4 / CaSO3 system. Figure 10 The results show the stability test results of the Al2CuO4 catalyst in the UVC / Al2CuO4 / CaSO3 system. Figure 11 Scanning electron microscope images of Al2CuO4 before (a) and after (b) the reaction; Figure 12 The results show the effectiveness of different catalysts Al2CuO4, CuO, and Cu2O in the UVC / CaSO3 system. Detailed Implementation

[0027] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0028] In the following embodiments: The photodegradation of methanethiol utilizes a dynamic gas-liquid phase photoreactor, such as... Figure 1As shown in the diagram. The main body of the apparatus is a 1.3 L quartz reaction flask with five holes on the cap: one inlet (5 mm), one outlet (5 mm), one pH probe lead hole (10 mm), one reaction solution sampling hole (10 mm), and one spare hole (10 mm). Before each experiment, the control valve allows 100 ppmv methanethiol gas (diluted with synthetic air at a N2:O2 ratio of 8:2, hereinafter the same) to be directly introduced into the gas chromatography (GC) for analysis. After the signal stabilizes, 1 L of deionized water at 25 °C is added to the quartz reaction flask, the pH is adjusted to the set initial value, and then the set concentration of S(Ⅳ) is added to the reaction solution. The reaction cap is closed, the control valve is opened to allow 100 ppmv methanethiol gas to be introduced into the reaction solution, and the UV lamp is turned on to start the reaction. After the methanethiol is degraded in the reaction flask, the emitted gas enters the GC through the outlet for analysis of the residual methanethiol concentration. Because the retention time of methanethiol is less than 6 minutes, the program is set to inject a gas sample into the GC every 6 minutes, enabling long-term online monitoring of the methanethiol concentration during the reaction process and calculation of the methanethiol removal efficiency. The total reaction time is generally set to 480 minutes.

[0029] Example 1 This embodiment provides a method for enhancing the ultraviolet (UV) degradation of methanethiol, based on a UVC / Al₂CuO₄ / CaSO₃ system. The steps are as follows: (1) 100 ppmv of methanethiol gas was directly introduced into the GC. After the analysis signal stabilized, 1 L of 25 °C deionized water was added to the quartz reaction flask. (2) Add 0.2 g Al2CuO4 and adjust the pH to 7.0; (3) Add CaSO3 solid to make its concentration 4 mM; (4) Quickly seal the reaction cap and control the valve to allow methanethiol gas to enter the reaction flask; (5) Turn on the ultraviolet lamp (light intensity 1.37 µW cm⁻¹) -2 The reaction begins, completing the degradation of methanethiol.

[0030] Furthermore, under the experimental conditions described above, this embodiment reduced one component of the system—UVC, Al2CuO4, or CaSO3—to create Al2CuO4 / CaSO3, UVC / CaSO3, and UVC / Al2CuO4 systems, respectively. Other conditions remained unchanged, and degradation experiments on methanethiol were conducted using different control systems. The methanethiol removal rate test results for different systems are shown below. Figure 2 As shown. According to Figure 2The results show that, except for the UVC / Al2CuO4 system, the other three systems can achieve 100% removal of methanethiol in the first 100 min. However, after 100 min, the removal rate of methanethiol in each system continues to decrease. At 480 min, the removal rates of methanethiol in the four systems are as follows: UVC / Al2CuO4 / CaSO3 system (94.3%) > UVC / CaSO3 system (87.7%) > UVC / Al2CuO4 system (68.8%) > Al2CuO4 / CaSO3 system (0). Only the UVC / Al2CuO4 / CaSO3 system shows a more sustained methanethiol removal efficiency. The above results verify the effectiveness of the present invention.

[0031] Example 2 This embodiment provides a method for enhancing the ultraviolet (UV) degradation of methanethiol. An experiment was conducted to investigate the effect of adjusting the initial pH on the photodegradation of methanethiol in a UVC / Al₂CuO₄ / CaSO₃ system. The steps are as follows: (1) 100 ppmv of methanethiol gas was directly introduced into the GC. After the analysis signal stabilized, 1 L of 25 °C deionized water was added to the quartz reaction flask. (2) Add 0.2 g Al2CuO4, turn on the online pH meter, and adjust the initial pH to 3.0, 7.0 and 9.0 respectively with 0.02 M HCl or NaOH; (3) Add CaSO3 solid to make its concentration 4 mM; (4) Quickly seal the reaction cap with pH probe and control the valve to allow methanethiol gas to enter the reaction bottle; (5) Turn on the ultraviolet lamp (light intensity 1.37 µW cm⁻¹) -2 The timed reaction completes the degradation of methanethiol.

[0032] The effect of initial pH on the photodegradation of methanethiol in the UVC / Al2CuO4 / CaSO3 system is as follows: Figure 3 As shown in the figure, when pH is 3, the breakthrough time is 100 min, and the removal rate of methanethiol is generally below 90% after 200 min. When pH is increased to 7, the breakthrough time does not increase significantly, remaining at 100 min, but the removal rate remains at 90% after 200 min. When pH is increased to 9, the breakthrough time increases to 140 min, and the removal rate remains above 90% after 200 min. Unlike the UVC / CaSO3 system, which is pH-dependent in its degradation of methanethiol (removal rate drops to 60% when pH < 7), the addition of Al2CuO4 improves the system's tolerance to pH changes, enabling it to adapt to the photodegradation of methanethiol under acidic conditions (pH = 3). These results indicate that this scheme has a wider pH range adaptability.

[0033] Example 3 This embodiment provides a method for enhancing the ultraviolet (UV) degradation of methanethiol. An experiment was conducted to investigate the effect of adjusting the amount of CaSO3 added on the photodegradation of methanethiol in a UVC / Al2CuO4 / CaSO3 system. The steps are as follows: (1) 100 ppmv of methanethiol gas was directly introduced into the GC. After the analysis signal stabilized, 1 L of 25°C deionized water was added to the quartz reaction flask. (2) Add 0.2 g Al2CuO4, turn on the online pH meter, and adjust the pH to 7.0; (3) Add CaSO3 solid to make the concentrations 2, 4 and 6 mM respectively; (4) Quickly seal the reaction cap with pH probe and control the valve to allow methanethiol gas to enter the reaction bottle; (5) Turn on the ultraviolet lamp (light intensity 1.37 µW cm⁻¹) -2 The timed reaction completes the degradation of methanethiol.

[0034] The effect of CaSO3 dosage on the photodegradation of methanethiol in the UVC / Al2CuO4 / CaSO3 system is as follows: Figure 4 As shown, when the CaSO3 concentration was 2 mM, the breakthrough time for the photodegradation of methanethiol was 70 min; with the CaSO3 concentration increased to 4 mM and 6 mM, the breakthrough time increased to 100 min and 160 min, respectively. After 200 min, the removal rate was above 90% for all three CaSO3 dosages. These results indicate that the action time of CaSO3 in the UVC / Al2CuO4 / CaSO3 system may be within 200 min, or even less.

[0035] Therefore, this embodiment monitored SO3 during the photodegradation of methanethiol in the UVC / Al2CuO4 / CaSO3 system. 2- and SO4 2- The concentration change. For example... Figure 5 The results showed that CaSO3 with an initial concentration of 4 mM was rapidly consumed within 15 min and almost completely consumed within 30 min. In contrast, in the UV / CaSO3 system, 4 mM S(Ⅳ) was completely consumed within 60 min, while in the UVC / Al2CuO system… 4 / The reason why S(Ⅳ) is consumed faster in the CaSO3 system is that there is a combined effect of UVC and Al2CuO4 on the oxidation and consumption of S(Ⅳ). The reaction time of S(Ⅳ) in the UVC / Al2CuO4 / CaSO3 system is less than 30 min. The later reaction is actually the continued degradation of methanethiol by the UVC / Al2CuO4 system under alkaline conditions.

[0036] SO4 in the UVC / Al2CuO4 / CaSO3 system 2- The concentration of [agent] gradually increased during the reaction, even reaching 4.2 mM at 480 min, exceeding the 4 mMS(IV) added to the system at the beginning of the reaction. This verifies that methanethiol was mineralized into SO4 in this system. 2- Similarly, SO4 was also generated during the photodegradation of methanethiol in the UVC / Al2CuO4 system. 2- The concentration gradually increased from 0 mM at the beginning of the reaction to 0.045 mM at the end, indicating that the active species produced by Al2CuO4 photocatalysis could break the CS bond in methanethiol, thereby mineralizing its organic sulfur to SO4. 2- This also proves that the UVC / Al2CuO4 / CaSO3 system involves the combined effect of multiple oxidation mechanisms.

[0037] Example 4 This embodiment provides a method for enhancing the ultraviolet (UV) degradation of methanethiol. Different concentrations of methanethiol are treated using a UVC / Al₂CuO₄ / CaSO₃ system. The steps are as follows: (1) 50, 75 and 100 ppmv of methanethiol gas were directly introduced into the GC. After the analysis signal stabilized, 1 L of 25℃ deionized water was added to the quartz reaction flask. (2) Add 0.2 g Al2CuO4, turn on the online pH meter, and adjust the pH to 7.0; (3) Add CaSO3 solid to make its concentration 4 mM; (4) Quickly seal the reaction cap with pH probe and control the valve to allow methanethiol gas to enter the reaction bottle; (5) Turn on the ultraviolet lamp (light intensity 1.37 µW cm⁻¹) -2 The timed reaction completes the degradation of methanethiol.

[0038] The test results of photodegradation treatment of different concentrations of methanethiol using the UVC / Al2CuO4 / CaSO3 system are as follows: Figure 6 As shown, when the inlet concentration of methanethiol was 75 ppmv, the breakthrough time was 140 min, while when the concentration increased to 100 ppmv, the breakthrough time decreased to 100 min. After 200 min, the removal rate of methanethiol in the system remained above 90%.

[0039] Example 5 This embodiment provides a method for enhancing the ultraviolet (UV) degradation of methanethiol. An experiment was conducted to investigate the effect of adjusting UVC light intensity on the photodegradation of methanethiol in a UVC / Al₂CuO₄ / CaSO₃ system. The steps are as follows: (1) 100 ppmv of methanethiol gas was directly introduced into the GC analysis. After the signal stabilized, 1 L of 25°C deionized water was added to the quartz reaction flask. (2) Add 0.2 g Al2CuO4, turn on the online pH meter, and adjust the pH to 7.0; (3) Add CaSO3 solid to make its concentration 4 mM; (4) Quickly seal the reaction cap with pH probe and control the valve to allow methanethiol gas to enter the reaction bottle; (5) By covering the outer surface of lamp tubes of different lengths with aluminum foil, light intensities of 0.65, 1.37, and 2.36 µW / cm² were obtained, respectively. -2 The irradiation intensity was measured to conduct experiments on the effect of UVC light intensity; the UV lamp was turned on to time the reaction and complete the degradation of methanethiol.

[0040] The effect of UVC light intensity on the photodegradation of methanethiol in the UVC / Al2CuO4 / CaSO3 system is as follows: Figure 7 As shown, UVC light intensity has a significant impact on the degradation of methanethiol in the system; the higher the light intensity, the higher the methanethiol removal rate within 480 min. When the light intensity increases to 2.36 µW cm⁻¹, the degradation rate increases further. -2 At that time, although the pH was 1.37 µW cm -2 The light intensity decreased more rapidly to 5, and the system maintained a 100% removal rate of methanethiol within 480 min.

[0041] Example 6 This embodiment provides a method for enhancing the ultraviolet (UV) degradation of methanethiol. An experiment was conducted to investigate the effect of adjusting the dosage of the catalyst Al₂CuO₄ on the photodegradation of methanethiol in the UVC / Al₂CuO₄ / CaSO₃ system. The steps are as follows: (1) 100 ppmv of methanethiol gas was directly introduced into the GC analysis. After the signal stabilized, 1 L of 25°C deionized water was added to the quartz reaction flask. (2) Add 0.05, 0.1, 0.2 and 0.3 g of Al2CuO4 respectively, turn on the online pH meter and adjust the pH to 7.0; (3) Add CaSO3 solid to make its concentration 4 mM; (4) Quickly seal the reaction cap with pH probe and control the valve to allow methanethiol gas to enter the reaction bottle; (5) Turn on the ultraviolet lamp (light intensity 1.37 µW cm⁻¹) -2 The timed reaction completes the degradation of methanethiol.

[0042] The effect of Al2CuO4 catalyst dosage on the photodegradation of methanethiol in the UVC / Al2CuO4 / CaSO3 system is as follows: Figure 8As shown, the higher the Al2CuO4 dosage, the higher the efficiency or breakthrough time of the system's photodegradation of methanethiol, the more it initially increases and then decreases. This may be because the number of active sites increases with the dosage. However, excessive catalyst particles may affect the absorption of UVC by CaSO3 or methanethiol, leading to a decrease in removal efficiency. The overall removal efficiency is based on an Al2CuO4 dosage of 0.2 g / L. -1 That would be the best.

[0043] Example 7 This embodiment provides a method for enhancing the ultraviolet degradation of methanethiol, which employs intermittent addition of CaSO3, and the steps are as follows: (1) 100 ppmv of methanethiol gas was directly introduced into the GC analysis. After the signal stabilized, 1 L of 25°C deionized water was added to the quartz reaction flask. (2) Add 0.2 g Al2CuO4, turn on the online pH meter, and adjust the pH to 7.0; (3) Add 1 mM CaSO3; (4) Quickly seal the reaction cap with pH probe and control the valve to allow methanethiol gas to enter the reaction bottle; (5) Turn on the ultraviolet lamp (light intensity 1.37 µW cm⁻¹) -2 The reaction was timed, and 1 mM CaSO3 was added to the reaction flask at 120, 240 and 360 min respectively. The reaction was continued for 480 min to complete the degradation of methanethiol.

[0044] The effect of intermittent CaSO3 addition on the photodegradation of methanethiol in the UVC / Al2CuO4 / CaSO3 system is shown in the figure. Figure 9 As shown, methanethiol was completely removed within 480 min. During the reaction, the pH continuously decreased as the reaction proceeded and rebounded slightly with each addition of CaSO3. In the first 120 min, each addition of CaSO3 had an effect of less than 10 min; while in the subsequent 360 min, each addition of 1 mM CaSO3 had an effect of nearly 30 min. Intermittent addition of CaSO3 could maintain the complete removal of methanethiol for a longer period of time.

[0045] This embodiment differs in the dosing process, replacing the original single 4 mM dosing with four separate 1 mM dosings, while maintaining the same total amount. Therefore, this method allows for flexible adjustments to the dosing method based on different actual needs. For situations requiring long-term maintenance, an intermittent method can be used. However, there is no strict superiority of one method over the other; both can achieve good degradation results.

[0046] Example 8 This embodiment provides a method for enhancing the ultraviolet (UV) degradation of methanethiol. The stability of the Al2CuO4 catalyst in the UVC / Al2CuO4 / CaSO3 system was investigated in practical applications. The steps are as follows: (1) 100 ppmv of methanethiol gas was directly introduced into the GC analysis. After the signal stabilized, 1 L of 25°C deionized water was added to the quartz reaction flask. (2) Add 0.2 g Al2CuO4, turn on the online pH meter, and adjust the pH to 7.0; (3) Add 4 mM CaSO3; (4) Quickly seal the reaction cap with pH probe and control the valve to allow methanethiol gas to enter the reaction bottle; (5) Turn on the ultraviolet lamp (light intensity 1.37 µW cm⁻¹) -2 The reaction was timed and carried out for 480 min. After that, the pH of the reaction solution was adjusted to 7.0, 4 mM CaSO3 was added, methanethiol was introduced, and the reaction was started by turning on the ultraviolet light. The above procedure was repeated 4 times.

[0047] The stability test results of the catalyst Al2CuO4 in the UVC / Al2CuO4 / CaSO3 system are as follows: Figure 10 As shown, the removal rate of methanethiol by Al2CuO4 decreased only slightly (<5%) after four consecutive uses, indicating that Al2CuO4 has good stability. The initial removal rate of less than 100% in the fourth use may be due to the continuous accumulation of CaSO4 precipitate dispersed in the reaction solution, affecting the absorption of UVC by Al2CuO4 and CaSO3. Furthermore, the morphology, specific surface area, and pore size distribution of Al2CuO4 before and after the reaction were observed and tested using scanning electron microscopy (SEM) and a fully automated specific surface area and porosity analyzer (BET analyzer), respectively. Figure 11 As shown, the morphology of Al₂CuO₄ did not change significantly before and after the reaction; the specific surface area increased slightly from 10.7 m². 2 g -1 Slightly increased to 13.1 m 2 g -1 Furthermore, regarding the Cu that may leach out during the reaction process... 2+ Measurements were performed, and no Cu was detected in the reaction solution. 2+ This is partly due to the relative stability of Al₂CuO₄, and partly because the entire system operates under alkaline conditions, Cu 2+ It is not easily dissolved.

[0048] Example 9 This embodiment provides a method for enhancing the ultraviolet (UV) degradation of methanethiol. The differences in the effectiveness of three catalysts—Al₂CuO₄, CuO, and Cu₂O—in enhancing the UVC / CaSO₃ system for methanethiol photodegradation in practical applications were investigated. The steps are as follows: (1) 100 ppmv of methanethiol gas was directly introduced into the GC analysis. After the signal stabilized, 1 L of 25°C deionized water was added to the quartz reaction flask. (2) Add 0.2 g Al2CuO4, CuO or Cu2O, turn on the online pH meter and adjust the pH to 7.0; (3) Add 4 mM CaSO3; (4) Quickly seal the reaction cap and control the valve to allow methanethiol gas to enter the reaction flask; (5) Turn on the ultraviolet lamp (light intensity 1.37 µW cm⁻¹) -2 The reaction begins, completing the degradation of methanethiol.

[0049] The test results of the differences in the effects of three catalysts, Al2CuO4, CuO, and Cu2O, on enhancing the photodegradation of methanethiol in the UVC / CaSO3 system are as follows: Figure 12 As shown, replacing Al2CuO4 with CuO or Cu2O, both systems achieved 100% removal of methanethiol in the first 150 min. At 480 min, the removal rates of methanethiol for the three systems were: UVC / Al2CuO4 / CaSO3 system (94.3%) ≈ UVC / CuO2 / CaSO3 system (94.2%) < UVC / Cu2O / CaSO3 system (95.2%). All three Cu-containing oxide catalysts enhanced methanethiol removal in the UVC / CaSO3 system.

[0050] In summary, the method of this invention utilizes readily available ultraviolet photodegradation (photo-oxidation) equipment, requires simple instruments and equipment, employs a highly stable catalyst, has a wide applicable pH range for the absorption aqueous solution, requires no additional alkali, can be applied at room temperature, and does not involve the use of hazardous chemicals. This invention achieves enhanced treatment of methanethiol in waste gas through a combined process of washing and absorption followed by advanced oxidation, resulting in deep degradation and removal of methanethiol odor.

[0051] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for enhancing the ultraviolet degradation of methanethiol, characterized in that, Includes the following steps: (1) Add water to the dynamic gas-liquid phase photoreactor; (2) Add a catalyst to the water and adjust the pH of the system to a certain range; (3) Add CaSO3 to the water; (4) Introduce methanethiol gas; (5) Use UVC band ultraviolet light to carry out photodegradation reaction to complete the degradation of methanethiol.

2. The method for enhancing the ultraviolet degradation of methanethiol according to claim 1, characterized in that: In step (2), the catalyst is selected from CuO, Cu2O, and Al2CuO4.

3. The method for enhancing the ultraviolet degradation of methanethiol according to claim 1, characterized in that: In step (2), the amount of catalyst added is 0.05~0.3 g / L.

4. The method for enhancing the ultraviolet degradation of methanethiol according to claim 1, characterized in that: In step (2), the pH range is 3 to 9.

5. The method for enhancing the ultraviolet degradation of methanethiol according to claim 4, characterized in that: The pH range is 7 to 9.

6. The method for enhancing the ultraviolet degradation of methanethiol according to claim 1, characterized in that: In step (3), the amount of CaSO3 added is 2~6 mM.

7. The method for enhancing the ultraviolet degradation of methanethiol according to claim 6, characterized in that: As the photodegradation reaction proceeds, CaSO3 is added in multiple equal additions.

8. The method for enhancing the ultraviolet degradation of methanethiol according to claim 1, characterized in that: In step (4), the initial concentration of methanethiol gas is 75~100 ppmv.

9. The method for enhancing the ultraviolet degradation of methanethiol according to claim 1, characterized in that: In step (5), the main wavelength of UVC band ultraviolet light is 254 nm.

10. The application of a method for enhancing the ultraviolet degradation of methanethiol as described in any one of claims 1 to 9, characterized in that, include: Used for the degradation of methanethiol in air control or pollution treatment.

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