Confined range catalyst suitable for activating persulfate to degrade sulfur-containing malodorous gas as well as preparation and application of limited range catalyst

Abstract

The invention discloses a confinement catalyst suitable for activating persulfate to degrade sulfur-containing malodorous gas and a preparation method and application of the confinement catalyst. The preparation method comprises the following steps: taking activated sludge as a carbon-nitrogen precursor, and adopting hydrothermal pretreatment and a secondary pyrolysis method to obtain the confinement catalyst in which nickel metal is encapsulated in the double-nonmetal doped carbon nanosheet. The limited-range catalyst has good degradation and mineralization performance of persulfate for catalytic oxidation of the sulfur-containing malodorous gas, specifically, to-be-treated gas including the sulfur-containing malodorous gas can be dispersed into microbubbles through a bubbling method, the microbubbles enter a liquid phase system, and the liquid phase system contains the limited-range catalyst and the persulfate; the limited-range catalyst activates the persulfate to degrade the sulfur-containing malodorous gas.

Description

Technical Field

[0001] This invention relates to the field of catalysts, specifically to a nickel-encapsulated bimetallic (boron-nitrogen or phosphorus-nitrogen) doped carbon nanosheet confinement catalyst suitable for activating persulfate to degrade sulfur-containing odorous gases, its preparation method, and its application. Background Technology

[0002] Advanced oxidation technologies (AOPs) offer advantages such as rapid reaction, high degradation efficiency, and simple processes, and are widely used in the degradation of organic pollutants in water. For example, patent specification CN116899604A discloses a method for preparing a metal nitrogen-doped carbon catalyst derived from nickel-containing waste slag. The catalyst obtained can be used to activate sodium persulfate to degrade bisphenol A. Another example is patent specification CN117654571A, which discloses an AOP catalyst with FeNi embedded in two-dimensional nitrogen-doped carbon, its preparation method, and its application. Specifically, the FeNi-embedded two-dimensional nitrogen-doped carbon AOP catalyst and persulfate are added to a tetracycline solution, and the degradation reaction is carried out in the dark.

[0003] Sulfur-containing odorous gases have a low olfactory threshold, significant toxicity and corrosiveness, and harmful effects on air quality and human health. The "Emission Standard for Odor Pollutants" specifies eight main types of odorous gases, five of which are sulfur-containing.

[0004] Currently, research on advanced oxidation technologies for the degradation of gaseous pollutants is still limited. Introducing sulfur-containing odorous gases into a liquid-phase advanced oxidation process allows sulfur species generated on the catalyst surface to dissolve and transfer to the controllable liquid phase, delaying the poisoning of the catalyst and improving catalytic stability. In terms of cost and practical application, persulfate (PDS) is inexpensive and highly stable, showing broad application potential. Therefore, the coupled process of wet scrubbing and advanced oxidation for the removal of sulfur-containing odorous gases has good development prospects and opportunities for widespread adoption. Summary of the Invention

[0005] The design concept of this invention is to prepare a confined catalyst with excellent persulfate activation and sulfur-containing odor gas degradation performance. Existing metal catalysts can effectively activate PDS, but their practical application is limited by secondary pollution caused by metal ion leaching and poor catalyst reusability. Encapsulating metal nanoparticles within carbon nanosheets to construct a nanostructured encapsulated structure is an effective way to reduce the metal dissolution rate and inhibit metal particle aggregation. The layered carbon nanosheets generated by the hydrothermal pyrolysis of activated sludge have internal spaces for encapsulating metals; their large specific surface area promotes mass transfer of reactants, and their excellent conductivity accelerates electron transfer. Furthermore, nitrogen (N) and boron (B) / phosphorus (P) doping will generate more surface active sites, further optimizing electronic conductivity and facilitating catalyst dispersion in water.

[0006] Based on the above analysis, we attempted to combine the synergistic effects of nitrogen, boron / phosphorus, and metal co-doping, and selected a price-advantageous transition metal as the active metal component. Through the selection of metal and support, and the optimization of preparation methods and conditions, we constructed a Ni / M-NC (M is B or P) confined catalyst, which achieved excellent degradation and mineralization capabilities of sulfur-containing odorous gases.

[0007] The specific technical solution of this invention is as follows: In a first aspect, the present invention provides a method for preparing a confined catalyst suitable for activating persulfate to degrade sulfur-containing odorous gases, using activated sludge as a carbon and nitrogen precursor, employing a hydrothermal pretreatment and secondary pyrolysis method, specifically including the following steps: S1, the activated sludge is hydrothermally treated in a closed container at 160~180℃ for 12~16h under autogenous pressure, and the precipitate is dried to obtain activated sludge-derived carbon; based on the dry weight of the activated sludge, the carbon content in the activated sludge is 50%~60% by mass and the nitrogen content is 2%~6% (e.g., 5%) by mass. S2, Boron precursor or phosphorus precursor and activated sludge-derived carbon are mixed and ground and then pyrolyzed in an inert atmosphere to obtain layered double non-metallic doped carbon nanosheets. S3, the double nonmetal-doped carbon nanosheets and nickel precursor are uniformly dispersed in deionized water and ultrasonically stirred for a period of time, then dried and ground into powder. The resulting mixture is pyrolyzed in an inert atmosphere. The pyrolysis product is acid-leached, washed until neutral, and dried to obtain a confined catalyst with nickel metal encapsulated in double nonmetal-doped carbon nanosheets.

[0008] In this invention, the inert atmosphere refers to an atmosphere that does not participate in the reaction, such as a nitrogen atmosphere or a rare gas atmosphere.

[0009] The present invention provides a method for preparing confined catalysts for activating persulfate to degrade sulfur-containing odorous gases. This method has the advantages of simple operation and controllable price. The activity and stability of the catalyst can be improved by adjusting factors such as the active component, the type of precursor and the doping ratio to regulate the metal-support interaction.

[0010] In the confined catalyst of the present invention, metallic Ni particles are confined in a stacked carbon nanosheet catalyst doped with nitrogen and boron or phosphorus, thereby increasing electron transfer capacity, improving mass transfer and enriching active sites, and thus improving catalytic activity.

[0011] In some preferred embodiments, in the method for preparing the confined catalyst suitable for activating persulfate to degrade sulfur-containing odorous gases, the heating rate of the hydrothermal treatment in step S1 is 5°C / min.

[0012] In some preferred embodiments, in the method for preparing the confined catalyst suitable for activating persulfate to degrade sulfur-containing odorous gases, the drying temperature in step S1 is 80°C.

[0013] In some preferred embodiments, in the method for preparing the confined catalyst suitable for activating persulfate to degrade sulfur-containing odorous gases, in step S2, the mass content of the boron precursor or phosphorus precursor is 4% to 6%, for example, 5%, based on the total mass of the boron precursor or phosphorus precursor and activated sludge-derived carbon as 100%.

[0014] In some preferred embodiments, in the method for preparing the confined catalyst suitable for activating persulfate to degrade sulfur-containing odorous gases, in step S2, the boron precursor includes one or more of boric acid, sodium borohydride, and boron oxide.

[0015] In some preferred embodiments, in the method for preparing the confined catalyst suitable for activating persulfate to degrade sulfur-containing odorous gases, in step S2, the phosphorus precursor includes one or more of disodium hydrogen phosphate, sodium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, dipotassium hydrogen phosphate, and potassium dihydrogen phosphate.

[0016] In some preferred embodiments, in the method for preparing the confined catalyst suitable for activating persulfate to degrade sulfur-containing odorous gases, the holding temperature of the pyrolysis in step S2 is 700~900℃, for example 800℃.

[0017] In some preferred embodiments, in the method for preparing the confined catalyst suitable for activating persulfate to degrade sulfur-containing odorous gases, the pyrolysis holding time in step S2 is 2-3 hours.

[0018] In some preferred embodiments, in the method for preparing the confined catalyst suitable for activating persulfate degradation of sulfur-containing odorous gases, in step S2, the pyrolysis heating rate is 5°C / min. In some preferred embodiments, in the method for preparing the confined catalyst suitable for activating persulfate to degrade sulfur-containing malodorous gases, in step S3, the mass content of nickel in the confined catalyst is 0.5% to 2%, for example, 1%.

[0019] In some preferred embodiments, in the method for preparing the confined catalyst suitable for activating persulfate to degrade sulfur-containing malodorous gases, in step S3, the nickel precursor is added at a nickel:double nonmetal doped carbon nanosheet mass ratio of 0.5~2:100, preferably 1:100.

[0020] In some preferred embodiments, in the method for preparing the confined catalyst suitable for activating persulfate to degrade sulfur-containing odorous gases, the ultrasonic time in step S3 is 3 h.

[0021] In some preferred embodiments, in the method for preparing the confined catalyst suitable for activating persulfate to degrade sulfur-containing odorous gases, the stirring time in step S3 is 24 h.

[0022] In some preferred embodiments, in the method for preparing the confined catalyst suitable for activating persulfate to degrade sulfur-containing odorous gases, the holding temperature of the pyrolysis in step S3 is 600~800℃.

[0023] In some preferred embodiments, in the method for preparing the confined catalyst suitable for activating persulfate to degrade sulfur-containing odorous gases, the pyrolysis holding time in step S3 is 6-7 hours.

[0024] Secondly, the present invention provides a confined catalyst suitable for the degradation of sulfur-containing malodorous gases by activated persulfate, prepared by the preparation method described in the first aspect.

[0025] Thirdly, the present invention provides the application of the confined catalyst described in the second aspect in the degradation of sulfur-containing odorous gases by activated persulfate.

[0026] In some preferred embodiments, the application described in the third aspect includes one or more of methanethiol, dimethyl sulfide, dimethyl disulfide, and hydrogen sulfide.

[0027] In some preferred embodiments, the application described in the third aspect includes: dispersing the gas to be treated, including sulfur-containing odorous gas, into microbubbles by bubbling and introducing it into a liquid phase system, the liquid phase system containing the confined catalyst and persulfate, wherein the confined catalyst activates the persulfate to degrade the sulfur-containing odorous gas.

[0028] In some preferred embodiments, in the application described in the third aspect, the content of the confined catalyst in the liquid phase system is 0.15 g / L. -1 .

[0029] In some preferred embodiments, in the application described in the third aspect, the persulfate content in the liquid phase system is 0.5 g / L. -1 .

[0030] In some preferred embodiments, in the application described in the third aspect, the pH of the liquid phase system is 3 to 7, more specifically 5 to 7.

[0031] In some preferred embodiments, in the application described in the third aspect, the flow rate of the gas to be treated entering the liquid phase system is 0.5~2 L / min.

[0032] In some preferred embodiments, in the application described in the third aspect, the concentration of the sulfur-containing odorous gas in the gas to be treated is 40-60 ppmv.

[0033] In some preferred embodiments, in the application described in the third aspect, the confined catalyst activates the persulfate degradation of sulfur-containing odorous gases at room temperature.

[0034] Fourthly, the present invention provides a method for activating persulfate to degrade sulfur-containing odorous gases, comprising: dispersing the gas to be treated, including sulfur-containing odorous gases, into microbubbles by bubbling and introducing them into a liquid phase system, wherein the liquid phase system contains the confined catalyst and persulfate described in the second aspect, and the confined catalyst activates the persulfate to degrade the sulfur-containing odorous gases.

[0035] In some preferred embodiments, the method for degrading sulfur-containing odorous gases by activating persulfate as described in the fourth aspect includes one or more of methanethiol, dimethyl sulfide, dimethyl disulfide, and hydrogen sulfide.

[0036] In some preferred embodiments, in the method for activating persulfate to degrade sulfur-containing malodorous gases according to the fourth aspect, the content of the confined catalyst in the liquid phase system is 0.15 g / L. -1 .

[0037] In some preferred embodiments, in the method for degrading sulfur-containing malodorous gases using activated persulfate according to the fourth aspect, the persulfate content in the liquid phase system is 0.5 g / L. -1 .

[0038] In some preferred embodiments, in the method for degrading sulfur-containing malodorous gases using activated persulfate as described in the fourth aspect, the pH of the liquid phase system is 3 to 7, more specifically 5 to 7.

[0039] In some preferred embodiments, in the method for degrading sulfur-containing malodorous gases by activated persulfate as described in the fourth aspect, the flow rate of the gas to be treated entering the liquid phase system is 0.5~2 L / min.

[0040] In some preferred embodiments, the method for degrading sulfur-containing odorous gases using activated persulfate as described in the fourth aspect, wherein the concentration of the sulfur-containing odorous gas in the gas to be treated is 40-60 ppmv.

[0041] In some preferred embodiments, in the method for activating persulfate to degrade sulfur-containing odorous gases according to the fourth aspect, the temperature at which the confined catalyst activates the persulfate to degrade the sulfur-containing odorous gases is room temperature.

[0042] Compared with the prior art, the beneficial effects of this invention are as follows: This invention presents a confined catalyst, a nickel-encapsulated dual-nonmetallic doped carbon nanosheet catalyst, exhibiting excellent degradation and mineralization performance of persulfate-catalyzed oxidation of sulfur-containing odorous gases. At a gas flow rate of 1 L / min and a methanethiol concentration of 50 ppm, it can degrade over 95% of methanethiol, achieving a mineralization rate of over 90% (sulfur species are completely oxidized to SO4). 2- ).

[0043] The catalytic system of this invention is reusable and has long-term stability, and is minimally affected by water pH and anions. This invention develops an innovative and effective strategy for the deep degradation of sulfur-containing odorous gases. Attached Figure Description

[0044] Figure 1 The images show scanning electron microscope (SEM) images, transmission electron microscope (TEM) images, and elemental distribution maps of the Ni / B-NC catalyst.

[0045] Figure 2 The activity evaluation charts for Ni / B-NC catalysts prepared at different pyrolysis temperatures are shown. The line graph represents the CH3SH removal efficiency of different catalysts, and the bar graph represents the concentration of the byproduct dimethyl disulfide (DMDS). Detailed Implementation

[0046] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0047] Unless otherwise specified, the operating methods in the following examples are generally performed under conventional conditions or as recommended by the manufacturer.

[0048] Example 1: The preparation steps for a catalyst suitable for activating persulfate to degrade sulfur-containing malodorous gases are as follows: Activated sludge (based on the dry weight of the activated sludge, with a carbon content of 50% and a nitrogen content of 5%) was placed in a hydrothermal reactor and hydrothermally treated at 160-180℃ for 12 hours. The resulting precipitate was dried at 80℃ to obtain activated sludge-derived carbon. Boric acid and activated sludge-derived carbon were mixed and ground, and then placed in a muffle furnace, where the boric acid accounted for 5% of the mixture by mass. The mixture was pyrolyzed at 800℃ under a nitrogen atmosphere for 2 hours to obtain layered double non-metallic doped carbon nanosheets. The double non-metallic doped carbon nanosheets and Ni(N) O3)2·6H2O was dispersed in deionized water at a mass ratio of nickel to bimetallic doped carbon nanosheets of 1:100; the resulting mixture was ultrasonicated for 3 h and stirred for 24 h, then dried at 80 °C and ground into fine powder; the resulting mixture was pyrolyzed at 800 °C in a nitrogen atmosphere for 6 h; the resulting black product was soaked in concentrated hydrochloric acid and stirred overnight, then washed several times with deionized water until the pH of the clear solution reached 7, and dried at 80 °C to obtain the catalyst sample Ni / B-NCNT. Figure 1 The SEM, TEM images, and elemental distribution diagrams of the Ni / B-NC catalyst are shown.

[0049] Catalyst evaluation: The main body of the reaction apparatus is a cylindrical plexiglass reactor. Methanethiol (CH3SH) and air at a total flow rate of 1 L / min are thoroughly mixed in a buffer tank to prepare a simulated odor gas with a methanethiol concentration of 50 ppmv. This simulated odor gas is then continuously dispersed into microbubbles through a titanium aeration disc at the bottom of the reactor, ensuring its thorough and uniform distribution throughout the liquid-phase reaction system. The pH of the liquid-phase reaction system is neutral, and the catalyst content is 0.15 g / L. -1 The potassium persulfate content is 0.5 g / L. -1 The catalyst evaluation results are shown in Table 1.

[0050] Table 1 Example 2: The only difference from Example 1 is that the double nonmetal-doped carbon nanosheets and Ni(NO3)2·6H2O are dispersed in deionized water at a nickel:double nonmetal-doped carbon nanosheet mass ratio of 0.5:100. The other preparation and evaluation steps are the same as in Example 1. The resulting catalyst is denoted as 0.5-Ni / B-NC. The catalyst evaluation results are shown in Table 1.

[0051] Example 3: The only difference from Example 1 is that the double nonmetal-doped carbon nanosheets and Ni(NO3)2·6H2O are dispersed in deionized water at a nickel:double nonmetal-doped carbon nanosheet mass ratio of 2:100. The other preparation and evaluation steps are the same as in Example 1. The resulting catalyst is denoted as 2-Ni / B-NC. The catalyst evaluation results are shown in Table 1.

[0052] Example 4: The only difference from Example 1 is that potassium dihydrogen phosphate of equal mass is used instead of boric acid. The other preparation process and evaluation steps are the same as in Example 1. The resulting catalyst is denoted as Ni / P-NC. The catalyst evaluation results are shown in Table 1.

[0053] Example 5: The only difference from Example 1 is that boric acid is not added. The other preparation process and evaluation steps are the same as in Example 1. The obtained catalyst is denoted as Ni / NC. The catalyst evaluation results are shown in Table 1.

[0054] Example 6: The only difference from Example 5 is that Ni(NO3)2·6H2O is not added. The other preparation process and evaluation steps are the same as in Example 1. The obtained catalyst is denoted as NC. The catalyst evaluation results are shown in Table 1.

[0055] Example 7: Referring to Example 1, catalysts with two high-temperature pyrolysis temperatures of 700℃, 800℃, and 900℃ were prepared, and designated as Ni / B-NC-700, Ni / B-NC-800, and Ni / B-NC-900, respectively. Methanethiol degradation was performed according to the catalyst evaluation method of Example 1, and the results are as follows... Figure 2 As shown, the optimal temperature for the two high-temperature pyrolysis processes is 800℃, which results in the highest CH3SH removal efficiency.

[0056] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for preparing a confined catalyst suitable for activating persulfate to degrade sulfur-containing malodorous gases, characterized in that, The preparation method comprises the following steps: S1, hydrothermal treatment of activated sludge at 160-180℃ for 12-16h under self-generated pressure in a closed container to obtain a precipitate, and drying the precipitate to obtain activated sludge derived carbon; the carbon content in the activated sludge is 50%-60% and the nitrogen content is 2%-6% by dry weight of the activated sludge; S2, mixing and grinding boron precursor or phosphorus precursor and activated sludge derived carbon, and then pyrolyzing in an inert atmosphere to obtain laminated double non-metal doped carbon nanosheets; S3, uniformly dispersing double non-metal doped carbon nanosheets and nickel precursor in deionized water and ultrasonic stirring for a period of time, then drying and grinding into powder, and pyrolyzing the mixture in an inert atmosphere, and then acid leaching and washing the pyrolysis product until neutral, and drying to obtain a confined catalyst with nickel metal encapsulated in double non-metal doped carbon nanosheets.

2. The production method according to claim 1, characterized by, In step S1: The heating rate of the hydrothermal treatment is 5℃ / min; The drying temperature is 80℃.

3. The preparation method according to claim 1, characterized in that, In step S2: The mass content of boron precursor or phosphorus precursor is 4%-6%, for example, 5%, based on the total mass of boron precursor or phosphorus precursor and activated sludge derived carbon being 100%; The boron precursor includes one or more of boric acid, sodium borohydride, and boron oxide; The phosphorus precursor includes one or more of disodium hydrogen phosphate, sodium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, dipotassium hydrogen phosphate, and potassium dihydrogen phosphate.

4. The method of claim 1, wherein, In step S2, the holding temperature of the pyrolysis is 700-900℃, for example, 800℃, and the holding time of the pyrolysis is 2-3 hours, and the heating rate of the pyrolysis is 5℃ / min.

5. The preparation method according to claim 1, characterized in that, In step S3: The mass ratio of nickel to double non-metal doped carbon nanosheets is 0.5-2:100, preferably 1:100; The nickel salt includes one or more of nickel nitrate, nickel sulfate, and nickel chloride.

6. The method of claim 1, wherein, In step S3: The ultrasonic time is 3h; The stirring time is 24h; The holding temperature of the pyrolysis is 600-800℃, and the holding time of the pyrolysis is 6-7 hours.

7. The confined catalyst prepared by the preparation method of any one of claims 1-6, which is suitable for activating persulfate to degrade sulfur-containing malodorous gas.

8. The application of the confined catalyst of claim 7 in activating persulfate to degrade sulfur-containing malodorous gas.

9. Use according to claim 8, characterized in that, The sulfur-containing malodorous gas includes one or more of methyl mercaptan, methyl sulfide, dimethyl disulfide, and hydrogen sulfide; The application includes: dispersing the gas to be treated, which includes sulfur-containing malodorous gas, into microbubbles into a liquid phase system by a bubbling method, the liquid phase system containing the confined catalyst and persulfate, and the confined catalyst activating persulfate to degrade sulfur-containing malodorous gas; The content of the confined catalyst in the liquid phase system is 0.15 g / L -1 , and the content of the persulfate is 0.5 g / L -1 . The pH of the liquid phase system is 3-7, further 5-7; The flow rate of the gas to be treated into the liquid phase system is 0.5-2 L / min; The concentration of the sulfur-containing malodorous gas in the gas to be treated is 40-60 ppmv; The temperature of the confined catalyst activating persulfate to degrade sulfur-containing malodorous gas is room temperature.

10. A method of activating persulfate salts to degrade sulfur-containing malodorous gases, characterized by, The preparation method comprises the following steps: The gas to be treated, including a sulfur-containing malodorous gas, is dispersed into microbubbles into a liquid phase system by a bubbling method, the liquid phase system containing a confinement catalyst of claim 7 and a persulfate, the confinement catalyst activating the persulfate to degrade the sulfur-containing malodorous gas.

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