Sludge-based composite adsorbent and preparation method and application thereof

Abstract

This invention discloses a sludge-based composite adsorbent, its preparation method, and its application, relating to the field of solid waste resource utilization technology. The sludge-based composite adsorbent comprises sludge-based molecular sieves, sludge-based perovskite, and sludge ash-modified sludge-based pyrolytic carbon. This invention fully utilizes elements such as silicon, aluminum, iron, and carbon in sludge, transforming them into material components with special structures and functions through pyrolysis and hydrothermal methods. The components are then composited in a "sandwich" structure, significantly improving the moisture and high-temperature resistance of biochar. It has the advantages of low cost and high adsorption efficiency for odorous gases from dried sludge at high temperatures and humidity, thus achieving waste-to-waste treatment.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, specifically to a sludge-based composite adsorbent, its preparation method, and its application. Background Technology

[0002] With the continuous development of society, economy, and people's living standards, the production of sewage sludge is increasing daily. Sludge contains organic matter and minerals, and can be used as an alternative raw material and fuel in the cement industry, realizing the resource utilization of solid waste. However, the high water content of sludge (over 80%) means that directly feeding it into cement kilns will reduce cement yield and quality. Therefore, sludge must be dried. The sludge drying process produces and emits large amounts of malodorous gases, primarily ammonia, which harm human health. Given the increasing environmental and health awareness throughout society, purifying the malodorous gases from sludge drying is a critical problem that urgently needs to be solved.

[0003] Considering overall purification efficiency, economic cost, and process flow, using activated carbon as the primary adsorbent for the adsorption and purification of odorous gases from sludge drying is currently the main treatment method. However, activated carbon is often expensive, leading to increased costs. Although some patented technologies use biochar prepared from solid waste as an adsorbent to reduce costs, the odorous gases from sludge drying are characterized by high humidity and high temperature. High humidity causes a large number of adsorption sites on the adsorbent to be occupied by water molecules, and high temperature makes the adsorbate molecules have high kinetic energy, making them difficult to capture by the adsorption sites, resulting in a significant decrease in the adsorption efficiency, capacity, and lifespan of activated carbon. At the same time, some patented technologies modify biochar, but most of them improve adsorption capacity by expanding pores. Since biochar lacks adsorption selectivity, it is only a temporary solution under the high humidity and high temperature characteristics of odorous gases from sludge drying. The modification process requires the use of some reagents, which also increases costs. In addition, some patented technologies cool and dry the odorous gases, but the drying process increases costs and energy consumption, and cooling causes some harmful gas molecules to condense and enter the water along with the moisture, requiring the deployment of wastewater treatment processes and equipment.

[0004] Therefore, in view of the high temperature and high humidity characteristics of odorous gases from sludge drying, it is necessary to develop a moisture-resistant and high-temperature-resistant biochar-like adsorbent. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing biochar adsorbents in adsorbing and purifying odorous gases from high-temperature and high-humidity sludge drying, and to provide a sludge-based composite adsorbent. This adsorbent fully utilizes elements such as silicon, aluminum, iron, and carbon in sludge, and transforms them into material components with special structures and functions through pyrolysis and hydrothermal methods. The adsorbent is then composited in a "sandwich" structure, which significantly improves the moisture resistance and high-temperature resistance of biochar. It has the advantages of low cost and high adsorption efficiency for odorous gases from high-temperature and high-humidity sludge drying, thus achieving waste treatment.

[0006] The technical problem to be solved by this invention is achieved by the following technical solution:

[0007] One objective of this invention is to provide a sludge-based composite adsorbent, comprising sludge-based molecular sieves, sludge-based perovskite, and sludge ash-modified sludge-based pyrolytic carbon.

[0008] A second objective of this invention is to provide a method for preparing the sludge-based composite adsorbent, comprising the following steps:

[0009] (1) Sludge-based molecular sieves, sludge-based perovskite, and sludge-ash-modified sludge-based pyrolytic carbon were mixed with dispersants and binders respectively to prepare slurry A, slurry B, and slurry C;

[0010] (2) Spray slurry C, slurry B and slurry A onto the substrate in sequence and dry them to obtain the sludge-based composite adsorbent.

[0011] A third objective of this invention is to provide the application of the sludge-based composite adsorbent in purifying odorous gases from sludge drying.

[0012] The beneficial effects of this invention are:

[0013] 1. The main gain components of the sludge-based composite adsorbent described in this invention are all derived from the sludge and incineration ash of wastewater treatment plants. This represents the resource utilization of solid waste, achieving waste-to-waste treatment and effectively reducing the production cost of the adsorbent. It has broad market application prospects.

[0014] 2. The sludge-based composite adsorbent of the present invention can effectively adapt to high temperature and high humidity environments, and is particularly suitable for the field of odor adsorption and purification of sludge drying.

[0015] 3. The preparation method of the sludge-based composite adsorbent provided by the present invention has the advantages of simple operation and cheap and readily available raw materials, and is suitable for industrial production. Detailed Implementation

[0016] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0017] This invention provides a sludge-based composite adsorbent, comprising sludge-based molecular sieves, sludge-based perovskite, and sludge ash-modified sludge-based pyrolytic carbon.

[0018] Furthermore, the sludge-based molecular sieve, sludge-based perovskite, and sludge ash-modified sludge-based pyrolytic carbon are combined in a "sandwich" structure.

[0019] Furthermore, based on the total amount of the sludge-based composite adsorbent, the sludge-based composite adsorbent comprises 20-30% by weight of sludge-based molecular sieve and 20-30% by weight of sludge-based perovskite, with the remainder being sludge ash modified sludge-based pyrolytic carbon.

[0020] This invention provides a method for preparing the sludge-based composite adsorbent, comprising the following steps:

[0021] (1) Sludge-based molecular sieves, sludge-based perovskite, and sludge-ash-modified sludge-based pyrolytic carbon were mixed with dispersants and binders respectively to prepare slurry A, slurry B, and slurry C;

[0022] (2) Spray slurry C, slurry B and slurry A onto the substrate in sequence and dry them to obtain the sludge-based composite adsorbent.

[0023] Furthermore, in order to satisfy the dispersibility and binding properties of the slurry, the dispersant is ethanol; the binder is Nafion solution.

[0024] Preferably, the ratio of the sludge-based molecular sieve to ethanol and Nafion solution is (2-3) g:10 mL:1 mL; the ratio of the sludge-based perovskite to ethanol and Nafion solution is (2-3) g:10 mL:1 mL; and the ratio of the sludge ash-modified sludge-based pyrolytic carbon to ethanol and Nafion solution is (4-6) g:10 mL:1 mL. More preferably, the ratio of the sludge-based molecular sieve to ethanol and Nafion solution is 3 g:10 mL:1 mL; the ratio of the sludge-based perovskite to ethanol and Nafion solution is 2 g:10 mL:1 mL; and the ratio of the sludge ash-modified sludge-based pyrolytic carbon to ethanol and Nafion solution is 5 g:10 mL:1 mL.

[0025] In order to ensure that the adsorbent has good mechanical and purification properties during use, the three components of the adsorbent need to be sprayed onto the substrate in the following order: sludge ash modified sludge-based pyrolytic carbon, sludge-based perovskite, and sludge-based molecular sieve, in a "sandwich" microstructure.

[0026] Furthermore, the substrate is one of nickel foam, carbon cloth, or honeycomb ceramic.

[0027] Further, the preparation method of the sludge-based molecular sieve is as follows: Sludge ash is taken, and dilute hydrochloric acid is added to adjust the pH value to 1-2. The mixture is stirred, filtered, and the filter residue is dried to obtain conditioned sludge ash. Conditioned sludge ash is taken, and sodium hydroxide solid is added. The mixture is ground and then calcined in a tube furnace under air atmosphere. The resulting calcined solid is added to distilled water for hydrothermal crystallization, filtered, and the filter residue is dried to obtain the sludge-based molecular sieve. Preferably, the mass ratio of the conditioned sludge ash to sodium hydroxide solid is 1:(1-5); the calcination temperature is 600-900℃, and the calcination time is 1-3 hours; the mass ratio of the calcined solid to distilled water is 1:(5-20); the hydrothermal temperature is 80-120℃, and the hydrothermal time is 6-12 hours. More preferably, the mass ratio of the conditioned sludge ash to sodium hydroxide solid is 1:2; the calcination temperature is 700℃, and the calcination time is 1.5h; the mass ratio of the calcined solid to distilled water is 1:10; and the hydrothermal temperature is 100℃, and the hydrothermal time is 10h. In this invention, sodium hydroxide is used for hot alkaline activation to ensure the activity of the conditioned sludge ash components. The addition of distilled water to the hot alkaline activated conditioned sludge ash for hydrothermal treatment ensures a suitable growth environment for the sludge-based molecular sieve.

[0028] Further, the preparation method of the sludge-based perovskite is as follows: Sludge ash is taken, and dilute nitric acid is added to adjust the pH to 1-2. The mixture is stirred, filtered, and polytitanium chloride is added to the filtrate. The mixture is then mixed, dehydrated, and the resulting mixture is pyrolyzed under a nitrogen atmosphere to obtain sludge-based perovskite. Preferably, the concentration of the dilute nitric acid is 0.5–2 mol / L; the mass ratio of polytitanium chloride to the filtrate is (1–6):1; the pyrolysis temperature is 300–500℃, and the pyrolysis time is 2–6 h. More preferably, the concentration of the dilute nitric acid is 1 mol / L; the mass ratio of polytitanium chloride to the filtrate is 3:1; the pyrolysis temperature is 450℃, and the pyrolysis time is 3 h. In this invention, dilute nitric acid is added to the sludge ash to obtain a filtrate containing ferric nitrate as one of the raw materials for perovskite; and to ensure that the sludge-based perovskite has a suitable growth environment and structure, the ratio of polytitanium chloride to the filtrate needs to be controlled.

[0029] Further, the preparation method of the sludge ash modified sludge-based pyrolytic carbon is as follows: sludge ash and sludge powder are mixed, and dilute hydrochloric acid is added to adjust the pH value to 1-2. The mixture is stirred, filtered, and the resulting solid is placed in a tube furnace and calcined under a nitrogen atmosphere to obtain sludge ash modified sludge-based pyrolytic carbon. Preferably, the mass ratio of sludge ash to sludge powder is 1:(5-10); the concentration of dilute hydrochloric acid is 0.5-2 mol / L; the calcination temperature is 500-700℃, and the calcination time is 1-3 h. More preferably, the mass ratio of sludge ash to sludge powder is 1:7; the concentration of dilute hydrochloric acid is 1 mol / L; the calcination temperature is 600℃, and the calcination time is 2 h. In this invention, a certain proportion of sludge ash and sludge powder are treated with dilute hydrochloric acid and then co-pyrolyzed to ensure that the sludge pyrolytic carbon has suitable hydrophobicity and pore volume.

[0030] Further, the method for preparing the sludge ash is as follows: municipal sludge is calcined in air and then ground to obtain sludge ash. Preferably, the calcination temperature is 700–900℃ and the calcination time is 4–6 hours. More preferably, the calcination temperature is 800℃ and the calcination time is 5 hours. The total mass fraction of silicon compounds and aluminum compounds in the sludge ash is ≥50%, and the mass fraction of iron compounds is ≥7%.

[0031] Further, the method for preparing the sludge powder is as follows: drying and grinding municipal sludge to obtain sludge powder. Preferably, the drying temperature is 100-120℃. More preferably, the drying temperature is 105℃. In this invention, the purpose of drying the municipal sludge is to facilitate grinding, and the purpose of calcination is to remove the organic matter while ensuring that the active components remain relatively stable during use.

[0032] This invention provides the application of the sludge-based composite adsorbent in purifying odorous gases from sludge drying.

[0033] This invention utilizes the main elements such as silicon, aluminum, iron, and carbon in sludge and its incineration ash, transforming them into material components with special structures and functions through pyrolysis and hydrothermal methods. These components primarily consist of sludge-based molecular sieves, sludge-based perovskite, and sludge ash-modified pyrolytic carbon, arranged in a spatially oriented "sandwich" structure. Leveraging the hygroscopic properties of sludge-based molecular sieves and the endothermic phase transition properties of sludge-based perovskite, high-temperature, high-humidity odors are transformed into room-temperature, low-humidity odors after passing through the sludge-based molecular sieves and perovskite sequentially. Simultaneously, the pyrolytic carbon prepared by co-pyrolyzing sludge ash and sludge contains some silicon oxide, further enhancing the hydrophobicity of the pyrolytic carbon and significantly improving the moisture and high-temperature resistance of the biochar, thereby increasing its adsorption capacity for dried sludge odors under high-humidity and high-temperature environments.

[0034] Example 1

[0035] (1) The sludge was dried at 105℃, ground, and passed through a 20-mesh sieve to obtain sludge powder, which was set aside for later use. Municipal sludge was calcined at 800℃ in air for 5 hours, and after cooling to room temperature, it was taken out, ground, and passed through a 20-mesh sieve to obtain sludge ash, which was set aside for later use. The sludge ash was found to contain 38.4% silicon dioxide, 7.34% iron oxide, and 17.1% aluminum oxide.

[0036] (2) Take 10g of sludge ash and 70g of sludge powder, mix them evenly, add 1mol / L dilute hydrochloric acid to adjust the pH to 1-2 and stir for 30min, filter, and calcine the resulting solid in a nitrogen atmosphere at 600℃ for 2h to obtain sludge ash modified sludge-based pyrolytic carbon.

[0037] (3) Take 10g of sludge ash, add 1mol / L dilute hydrochloric acid to adjust the pH to 1-2 and stir for 30min, filter to obtain conditioned sludge ash; mix the conditioned sludge ash with sodium hydroxide solid at a mass ratio of 1:2 and grind, then calcine in air at 700℃ for 1.5h, mix the calcined solid with distilled water at a mass ratio of 1:10, hydrothermally treat at 100℃ for 10h, filter, dry the filter residue to obtain sludge-based molecular sieve.

[0038] (4) Take 10g of sludge ash, add 1mol / L dilute nitric acid to adjust the pH to 1-2 and stir for 30min, filter to obtain filtrate; mix polytitanium chloride with filtrate at a mass ratio of 3:1, dehydrate, and then pyrolyze in a nitrogen atmosphere at 450℃ for 3h to obtain sludge-based perovskite.

[0039] (5) Take 3g of sludge-based molecular sieve, 2g of sludge-based perovskite, and 5g of sludge ash-modified sludge-based pyrolytic carbon in a mass ratio of 3:2:5 and mix them with 10mL of ethanol and 1mL of Nafion solution to prepare a slurry. Spray the slurry onto the nickel foam in the order of sludge ash-modified sludge-based pyrolytic carbon, sludge-based perovskite, and sludge-based molecular sieve, and dry it to obtain the sludge-based composite adsorbent.

[0040] Performance testing: The obtained sludge-based composite adsorbent was placed in an adsorption testing device, and 100 ppm of room-temperature dry ammonia gas was introduced as a simulated odor. The results showed that after 98 minutes of adsorption, the ammonia concentration at the outlet reached 95% of the initial concentration, indicating adsorption saturation.

[0041] Example 2

[0042] The preparation method of the sludge-based composite adsorbent in this embodiment is the same as in Example 1.

[0043] The performance testing conditions were the same as in Example 1, except that the 100 ppm room temperature ammonia gas was replaced with ammonia gas at 90% relative humidity and 60°C to simulate high-temperature and high-humidity odor. The results showed that after 93 minutes of adsorption, the ammonia concentration at the outlet reached 95% of the initial concentration, indicating adsorption saturation. Compared to room temperature dry ammonia gas, the adsorption breakthrough time was only shortened by 5 minutes.

[0044] Example 3

[0045] In this embodiment, the preparation method of the sludge-based composite adsorbent is the same as in Example 2, except that in step (2), the mass ratio of sludge ash to sludge powder is adjusted to 1:10.

[0046] The performance test conditions were the same as in Example 2. The results showed that the adsorption saturated after 89 minutes.

[0047] Example 4

[0048] In this embodiment, the preparation method of the sludge-based composite adsorbent is the same as in Example 2, except that in step (3), the mass ratio of conditioned sludge ash to sodium hydroxide solid is adjusted to 1:1.

[0049] The performance test conditions were the same as in Example 2. The results showed that the adsorption saturated after 91 minutes.

[0050] Example 5

[0051] In this embodiment, the preparation method of the sludge-based composite adsorbent is the same as in Example 2, except that in step (5), the mass ratio of sludge-based molecular sieve, sludge-based perovskite, and sludge ash-modified sludge-based pyrolytic carbon is adjusted to 3:3:4.

[0052] The performance test conditions were the same as in Example 2, except that the ammonia temperature was adjusted to 70°C. The results showed that the adsorption was saturated after 86 minutes.

[0053] Comparative Example 1

[0054] In this comparative example, the preparation method of the sludge-based composite adsorbent is the same as that in Example 2, except that in step (5), the mass ratio of sludge-based perovskite and sludge ash-modified sludge-based pyrolytic carbon is adjusted to 2:8, and sludge-based molecular sieves are not used.

[0055] The performance test conditions were the same as in Example 2. The results showed that the adsorption was saturated after 40 minutes of adsorption.

[0056] Comparative Example 2

[0057] In this comparative example, the preparation method of the sludge-based composite adsorbent is the same as that in Example 2, except that in step (5), the ratio of sludge-based molecular sieve and sludge ash-modified sludge-based pyrolytic carbon is adjusted to 3:7, and sludge-based perovskite is not used.

[0058] The performance test conditions were the same as in Example 2. The results showed that the adsorption was saturated after 45 minutes.

[0059] Comparative Example 3

[0060] The preparation method of the sludge-based composite adsorbent in this comparative example is the same as that in Example 2, except that sludge ash is not added in step (2) but sludge powder is directly pyrolyzed.

[0061] The performance test conditions were the same as in Example 2. The results showed that the adsorption was saturated after 68 minutes.

[0062] Comparative Example 4

[0063] The preparation method of the sludge-based composite adsorbent in this comparative example is the same as that in Example 2, except that in step (5), the mass ratio of sludge-based molecular sieve, sludge-based perovskite, and sludge ash-modified sludge-based pyrolytic carbon is adjusted to 1:1:8.

[0064] The performance test conditions were the same as in Example 2. The results showed that the adsorption was saturated after 74 minutes.

[0065] Comparative Example 5

[0066] The preparation method of the sludge-based composite adsorbent in this comparative example is the same as that in Example 2, except that the three slurries are mixed and sprayed in step (5).

[0067] The performance test conditions were the same as in Example 2. The results showed that the adsorption saturated after 61 minutes.

[0068] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A sludge-based composite adsorbent, characterized in that: The sludge-based composite adsorbent includes sludge-based molecular sieves, sludge-based perovskite, and sludge ash-modified sludge-based pyrolytic carbon. The sludge-based molecular sieve, sludge-based perovskite, and sludge ash-modified sludge-based pyrolytic carbon are combined in a "sandwich" structure. Based on the total amount of the sludge-based composite adsorbent, the sludge-based composite adsorbent contains 20-30% by weight of sludge-based molecular sieve and 20-30% by weight of sludge-based perovskite, with the remainder being sludge ash modified sludge-based pyrolytic carbon. The preparation method of the sludge-based molecular sieve is as follows: take sludge ash, add dilute hydrochloric acid to adjust the pH value to 1-2, stir, filter, dry the filter residue to obtain conditioned sludge ash; take conditioned sludge ash, add sodium hydroxide solid, grind and put it into a tube furnace for calcination in air atmosphere, add distilled water to the obtained calcined solid for hydrothermal crystallization, filter, dry the filter residue to obtain sludge-based molecular sieve. The preparation method of the sludge-based perovskite is as follows: take sludge ash, add dilute nitric acid to adjust the pH to 1-2, stir, filter, add polytitanium chloride to the filtrate, mix well, dehydrate, and pyrolyze the resulting mixture under a nitrogen atmosphere to obtain sludge-based perovskite. The preparation method of the sludge ash modified sludge-based pyrolytic carbon is as follows: take sludge ash and sludge powder, mix them evenly, add dilute hydrochloric acid to adjust the pH value to 1-2, stir, filter, and put the obtained solid into a tube furnace for calcination under a nitrogen atmosphere to obtain sludge ash modified sludge-based pyrolytic carbon.

2. The sludge-based composite adsorbent according to claim 1, characterized in that: In the preparation method of the sludge-based molecular sieve, the mass ratio of the conditioned sludge ash to sodium hydroxide solid is 1:(1~5); the calcination temperature is 600~900℃, and the calcination time is 1~3 h; the mass ratio of the calcined solid to distilled water is 1:(5~20); the hydrothermal temperature is 80~120℃, and the hydrothermal time is 6~12 h.

3. The sludge-based composite adsorbent according to claim 2, characterized in that: The mass ratio of the conditioned sludge ash to sodium hydroxide solid is 1:2; the calcination temperature is 700℃ and the calcination time is 1.5 h; the mass ratio of the calcined solid to distilled water is 1:10; the hydrothermal temperature is 100℃ and the hydrothermal time is 10 h.

4. The sludge-based composite adsorbent according to claim 1, characterized in that: In the preparation method of the sludge-based perovskite, the concentration of the dilute nitric acid is 0.5~2 mol / L; the mass ratio of the polytitanium chloride to the filtrate is (1~6):1; the pyrolysis temperature is 300~500℃, and the pyrolysis time is 2~6 h.

5. The sludge-based composite adsorbent according to claim 4, characterized in that: The concentration of the dilute nitric acid is 1 mol / L; the mass ratio of the polytitanium chloride to the filtrate is 3:1; the pyrolysis temperature is 450℃ and the pyrolysis time is 3 h.

6. The sludge-based composite adsorbent according to claim 1, characterized in that: In the method for preparing sludge-based pyrolytic carbon modified with sludge ash, the mass ratio of sludge ash to sludge powder is 1:(5~10); the concentration of dilute hydrochloric acid is 0.5~2 mol / L; the calcination temperature is 500~700℃, and the calcination time is 1~3 h.

7. The sludge-based composite adsorbent according to claim 6, characterized in that: The mass ratio of sludge ash to sludge powder is 1:7; the concentration of the dilute hydrochloric acid is 1 mol / L; the calcination temperature is 600℃ and the calcination time is 2 h.

8. The sludge-based composite adsorbent according to claim 1, characterized in that: The method for preparing the sludge ash is as follows: municipal sludge is calcined in air and ground to obtain sludge ash; The total mass fraction of silicon and aluminum compounds in the sludge ash is ≥50%, and the mass fraction of iron compounds is ≥7%.

9. The sludge-based composite adsorbent according to claim 1, characterized in that: The method for preparing the sludge powder is as follows: municipal sludge is dried and ground to obtain sludge powder.

10. The sludge-based composite adsorbent according to claim 8, characterized in that: In the method for preparing the sludge powder, the calcination temperature is 700~900℃ and the calcination time is 4~6 h.

11. The sludge-based composite adsorbent according to claim 10, characterized in that: The calcination temperature is 800℃ and the calcination time is 5 h.

12. The sludge-based composite adsorbent according to claim 9, characterized in that: The drying temperature is 100~120℃.

13. The sludge-based composite adsorbent according to claim 12, characterized in that: The drying temperature is 105℃.

14. A method for preparing the sludge-based composite adsorbent according to any one of claims 1 to 13, characterized in that, The preparation method includes the following steps: (1) Sludge-based molecular sieves, sludge-based perovskite, and sludge-ash-modified sludge-based pyrolytic carbon were mixed with dispersants and binders respectively to prepare slurry A, slurry B, and slurry C; (2) Spray slurry C, slurry B and slurry A onto the substrate in sequence and dry them to obtain the sludge-based composite adsorbent.

15. The preparation method according to claim 14, characterized in that: The dispersant is ethanol; the binder is Nafion solution.

16. The preparation method according to claim 15, characterized in that: The ratio of the sludge-based molecular sieve to ethanol and Nafion solution is (2~3) g : 10 mL : 1 mL; the ratio of the sludge-based perovskite to ethanol and Nafion solution is (2~3) g : 10 mL : 1 mL; and the ratio of the sludge ash-modified sludge-based pyrolytic carbon to ethanol and Nafion solution is (4~6) g : 10 mL : 1 mL.

17. The preparation method according to claim 16, characterized in that: The ratio of the sludge-based molecular sieve to ethanol and Nafion solution is 3 g : 10 mL : 1 mL; the ratio of the sludge-based perovskite to ethanol and Nafion solution is 2 g : 10 mL : 1 mL; and the ratio of the sludge ash-modified sludge-based pyrolytic carbon to ethanol and Nafion solution is 5 g : 10 mL : 1 mL.

18. The preparation method according to claim 14, characterized in that: The substrate is one of nickel foam, carbon cloth, or honeycomb ceramic.

19. The application of the sludge-based composite adsorbent according to any one of claims 1 to 13 or the sludge-based composite adsorbent obtained by the preparation method according to any one of claims 14 to 18 in purifying odorous gases from sludge drying.