A biological filtration filler for VOCs and malodorous gas treatment and a preparation method thereof

Abstract

The application provides a biological filtration filler for VOCs and malodorous gas treatment and a preparation method, and belongs to the technical field of environmental treatment. The biological filtration filler is composed of organic fillers and inorganic fillers. The organic fillers include tree bark, compost or straw, and the inorganic fillers include zeolite, biological carbon, ceramic granules or shells. The mass ratio of the organic fillers to the inorganic fillers is (1-18):100. The application combines the characteristics of different component fillers and is optimized. A combined biological filtration filler is provided. The filler can provide reasonable environmental conditions for long-term stable growth of degrading bacteria, is beneficial to the proliferation of degrading bacteria on the surface of the filler and the formation of a biological membrane, and is also beneficial to the diffusion of gas on the surface of the biological membrane of the filler. The application overcomes the shortcomings of easy degradation, blockage of voids, large resistance, short gas flow and easy generation of anaerobic zones in local fillers when the organic fillers are used alone.

Description

Technical Field

[0001] This invention relates to the field of environmental remediation technology, specifically to a biological filter media and its preparation method for the treatment of VOCs and malodorous gases. Background Technology

[0002] Odor and volatile organic compound (VOC) pollution are among the main causes of environmental degradation and air quality deterioration. Currently, technologies for treating VOCs and odorous gases are constantly developing both domestically and internationally. This development focuses on optimizing various processes and developing and applying new materials (adsorption materials, catalytic materials, filter materials, biological purification strains, etc.), such as adsorption and catalytic separation processes, adsorption and condensation recovery separation processes, adsorption photocatalysis technology, membrane separation technology, and ion liquid absorption technology. Treatable VOCs mainly include aliphatic hydrocarbons (lower aliphatic hydrocarbons (gasoline), chloroethane, chloromethane), aromatic hydrocarbons (benzene, toluene, xylene, chlorobenzene), oxygen-containing organic compounds (alcohols, ethers, ketones, aldehydes), nitrogen-containing organic compounds (amines), and sulfur-containing organic compounds (thiols, thioethers). Treatable reducing inorganic compounds mainly include hydrogen sulfide, ammonia, and carbon disulfide.

[0003] Currently, there are several main methods for treating organic waste gas and odorous gases: (1) Combustion method: including high-temperature combustion and catalytic combustion. Catalytic combustion is actually complete catalytic oxidation, that is, under the action of a catalyst, the harmful combustible components in the waste gas are completely oxidized into CO2 and H2O. Since most organic matter is combustible, catalytic combustion has become an effective means of purifying waste gas, and can also eliminate some odors. (2) Absorption method: that is, using appropriate absorbents (such as diesel, kerosene, water, etc.) in the absorption tower for absorption. After a certain concentration is reached, the solvent and absorbent are separated, the solvent is recovered, and the absorbent is reused or treated separately. The key to this method is the selection of absorbent. Since the separation of solvent and absorbent is relatively difficult, its application is limited to a certain extent. (3) Activated carbon adsorption: using porous activated carbon or activated carbon fiber to adsorb organic waste gas. After saturation, it is regenerated with low-pressure steam. During regeneration, solvent waste gas is discharged. After condensation and water separation, the solvent is recovered. It is suitable for discontinuous treatment processes, especially for solvent recovery in low-concentration organic waste gas. (4) Condensation method: mainly uses a cold medium to treat high-temperature organic waste gas vapor, which can effectively recover solvents. The treatment effect is related to the temperature of the cold medium. The treatment efficiency is relatively low compared with other methods. It is suitable for the treatment of high-concentration waste gas. (5) Ultraviolet photodegradation method: the mechanism of photodegradation technology is mainly through the hydroxyl radicals generated by the air under light, thereby achieving the degradation of odor substances in the waste gas. (6) Biological purification method: volatile organic compounds (VOCs) or odor substances in the gas enter the microbial suspension or biofilm through the mass transfer process (gas-liquid contact surface or through membrane). Under aerobic conditions, most of the volatile organic compounds or odor substances are degraded into water and carbon dioxide by microorganisms, and a small part is converted into residual bacteria. (7) Low-temperature plasma method: the instantaneous high energy generated by high-frequency discharge is sufficient to open the chemical energy of some harmful gas molecules, so that they are decomposed into elemental atoms or harmless molecules. In addition, the plasma contains a large number of high-energy electrons, positive and negative ions, excited-state particles and free radicals with strong oxidizing properties. These active particles react with some VOCs or odor molecules.

[0004] Domestic and international research and application results show that, compared with other technologies, biological purification technology has outstanding advantages such as high efficiency, low investment and operating costs, convenient process operation and maintenance, and minimal secondary pollution. It is especially suitable for treating large volumes of low-concentration VOCs and odorous gases. When treating low-concentration organic gases and odors, the operating cost of biological methods is 1 / 20 of that of combustion methods, 1 / 10 of adsorption methods, and 1 / 15 of that of chemical absorption methods.

[0005] Packing materials are a core component of biological filtration processes, serving as the carrier for microbial attachment and growth, and significantly influencing the efficiency of pollutant mass transfer and reaction. Currently, common packing materials are broadly classified into two categories: natural organic packing materials and inert inorganic packing materials. Natural organic packing materials generally suffer from drawbacks such as easy compaction and high pressure drop, which are detrimental to the long-term operation of the treatment system. Meanwhile, most inert inorganic packing materials, such as artificial packing materials, have disadvantages such as difficulty in biofilm formation and low purification efficiency. Therefore, developing novel, high-efficiency biological packing materials is of great significance for the widespread application of biological filtration technology. Summary of the Invention

[0006] To address the above problems, this invention provides a biological filter media and its preparation method for the treatment of VOCs and odorous gases.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A biological filter media for the treatment of VOCs and odorous gases, the biological filter media being composed of organic and inorganic fillers, wherein the organic filler includes bark, compost or straw, and the inorganic filler includes zeolite, biochar, ceramsite or seashells, wherein the mass ratio of the organic filler to the inorganic filler is (1-18):100.

[0009] In some preferred embodiments of the present invention, the biological filter media is composed of straw, compost, shells and zeolite in a mass ratio of 2:1:10:30.

[0010] In some preferred embodiments of the present invention, the carbon-to-nitrogen ratio of the biological filter media is 100:(2-10).

[0011] In some preferred embodiments of the present invention, the bulk density of the biological filter media is 400-500 kg / m³. 3 The porosity is 50-60%.

[0012] In some preferred embodiments of the present invention, the particle size of the organic filler and the inorganic filler is 0.1-3 cm.

[0013] In some preferred embodiments of the present invention, the surface of the inorganic filler is coated with a layer of modified porous microspheres, wherein the modified porous microspheres are carbon nanosheets modified with ruthenium phosphide core-shell microspheres coated with silica.

[0014] In some preferred embodiments of the present invention, the method for preparing the modified porous microspheres includes the following steps:

[0015] S1. Weigh phytic acid and ruthenium chloride separately and dissolve them in deionized water. After thorough mixing, add melamine and stir the mixture overnight at 80-100℃. After the reaction is complete, evaporate the solvent to obtain a uniform powder-solid mixture. Under a protective atmosphere, heat the powder-solid mixture to 900℃ and keep it at that temperature for 2 hours. After cooling to room temperature, obtain a black powder. Wash it successively with anhydrous ethanol and deionized water, vacuum dry it overnight, and grind it to obtain product A.

[0016] S2. Dissolve the initiator, catalyst and silane coupling agent in a solvent and mix and disperse them evenly to obtain a mixed solution. Disperse the product A in the mixed solution and stir the reaction overnight at room temperature. Separate the precipitate and wash it with the solvent to obtain product B.

[0017] The mass concentrations of the initiator, catalyst, and silane coupling agent in the mixed solution are (0.1-1) g / mL, (0.1-1) g / mL, and (0.5-2) g / mL, respectively, and the dispersion ratio of product A in the mixed solution is (5-10) g / 100 mL;

[0018] S3. Disperse the product B and carbon nanosheets in styrene emulsion, mix and stir thoroughly until homogeneous, then stir and heat to 80-90℃, keep warm and stir for 1-2 hours, separate the precipitate and wash it with anhydrous ethanol and deionized water in sequence, and dry to obtain product C.

[0019] The dispersion ratios of product B and carbon nanosheets in the styrene emulsion are (5-20) g / 100 mL and (2-6) g / 100 mL, respectively.

[0020] S4. Under ultrasonic conditions, vinyltrimethoxysilane is dissolved in deionized water to obtain a transparent solution with a mass concentration of 5-10 wt%. The product C is dispersed in deionized water to obtain a dispersion solution. The transparent solution and the dispersion solution are mixed, and an ammonia solution is added under stirring. The reaction is continued for 5 hours. After the reaction is completed, the precipitate is separated by centrifugation, washed with anhydrous ethanol, and then soaked in tetrahydrofuran overnight to obtain the product.

[0021] The dispersion ratio of product C is (1-10) g / 100 mL, and the volume ratio of the transparent solution, the dispersion solution, and the ammonia solution is (1-4):10:(1-2).

[0022] In some preferred embodiments of the present invention, the mass ratio of phytic acid to ruthenium chloride and melamine in step S1 is 10:(1.8-3.2):(1.6-2.1).

[0023] In some preferred embodiments of the present invention, the initiator is azobisisobutyronitrile, azobisisoheptanenitrile, or dimethyl azobisisobutyrate; the catalyst is cuprous chloride or cuprous bromide; and the silane coupling agent is γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, or N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane.

[0024] Another aspect of the present invention is to provide a method for preparing the aforementioned biological filter media, comprising the following steps:

[0025] (1) The modified porous microspheres are dispersed in an aqueous polyurethane resin or an aqueous acrylate resin to obtain a coating solution;

[0026] (2) The inorganic filler is dispersed in the coating liquid, and after thorough mixing, the inorganic filler is separated, and after curing and drying, a surface-coated modified inorganic filler is obtained.

[0027] (3) The surface-coated modified inorganic filler and the organic filler are mixed in a mass ratio to obtain the biological filter filler.

[0028] The beneficial effects of this invention are as follows:

[0029] This invention combines and optimizes the characteristics of different component packing materials to provide a combined biological filter packing material. This material provides a suitable environment for the long-term stable growth of degrading bacteria, promoting their proliferation and biofilm formation on the packing surface. It also facilitates gas diffusion across the biofilm, overcoming the drawbacks of using organic packing materials alone, such as easy degradation leading to clogging of pores and high resistance, gas short-circuiting, and the formation of anaerobic zones in certain areas. To further improve the biofilm formation performance of the inorganic packing material, this invention enhances its affinity with microbial strains through surface modification. Specifically, this invention uses phytic acid as the phosphorus source and melamine as the nitrogen source to prepare nitrogen-phosphorus-doped modified ruthenium phosphide, and then sequentially prepares a layer of carbon nanosheets doped on the surface. The polystyrene and silica shells are first processed, and then the polystyrene layer is dissolved to obtain modified microspheres with nitrogen-phosphorus-doped ruthenium phosphide as the core layer, carbon nanosheets as the support, a mesoporous layer, and a surface silica protective layer. On the one hand, the microspheres have a highly mesoporous structure composed of two-dimensional sheet-like structures, which can promote rapid colonization of bacteria and improve biofilm formation. On the other hand, electron transfer is an inherent feature of bacterial metabolism. Bacteria obtain energy for further growth and reproduction through electron transfer. The nitrogen-phosphorus-doped ruthenium phosphide core layer and the carbon nanosheets as the support mesoporous layer can participate in the electron transfer process between VOCs and odorous gases and bacteria, promote the biodegradation process of VOCs and odorous gases, and improve the biological purification efficiency of the packing material. Detailed Implementation

[0030] The present invention will be further described in conjunction with the following embodiments.

[0031] Example 1

[0032] A biological filter media for VOCs and odor gas treatment, comprising straw, compost, seashells, and zeolite in a mass ratio of 2:1:10:30; a carbon-to-nitrogen ratio of 100:5; and a bulk density of 468 kg / m³. 3 The porosity is 54.6%, and the particle size of the biological filter media is 0.1-1 cm.

[0033] Example 2

[0034] A biofilter media for VOCs and odor gas treatment, comprising bark, compost, biochar, and zeolite in a mass ratio of 2:1:10:30; a carbon-to-nitrogen ratio of 100:5; and a bulk density of 439 kg / m³. 3 The porosity is 55.2%, and the particle size of the biological filter media is 0.1-1 cm.

[0035] Example 3

[0036] A biological filter media for VOCs and odor gas treatment, comprising straw, compost, seashells, and zeolite in a mass ratio of 2:1:10:30; a carbon-to-nitrogen ratio of 100:5; and a bulk density of 468 kg / m³. 3 The porosity is 54.6%, and the particle size of the biological filter media is 0.1-1 cm;

[0037] The zeolite is coated with a layer of modified porous microspheres, and its preparation method includes the following steps:

[0038] The modified porous microspheres, hydroxyl-terminated aqueous acrylate resin, aqueous isocyanate, wetting agent, defoamer, and deionized water are mixed to obtain a coating solution; the inorganic filler is dispersed in the coating solution, and after thorough mixing, the inorganic filler is separated, cured, and dried to obtain a surface-coated modified inorganic filler. In this embodiment, the loading of the modified porous microspheres is 0.08 g / g.

[0039] The method for preparing the modified porous microspheres includes the following steps:

[0040] S1. Weigh phytic acid and ruthenium chloride separately and dissolve them in deionized water. After thorough mixing, add melamine and stir the mixture at 85°C overnight. After the reaction is complete, evaporate the solvent to obtain a uniform powder-solid mixture. Under a protective atmosphere, heat the powder-solid mixture to 900°C and keep it at that temperature for 2 hours. After cooling to room temperature, obtain a black powder. Wash the powder with anhydrous ethanol and deionized water in sequence, vacuum dry overnight, and grind it to obtain product A.

[0041] The mass ratio of phytic acid to ruthenium chloride and melamine is 10:2.3:1.8.

[0042] S2. Dissolve the initiator, catalyst and silane coupling agent in a solvent and mix and disperse them evenly to obtain a mixed solution. Disperse the product A in the mixed solution and stir the reaction overnight at room temperature. Separate the precipitate and wash it with the solvent to obtain product B.

[0043] The initiator is azobisisobutyronitrile, the catalyst is cuprous bromide, and the silane coupling agent is γ-aminopropyltriethoxysilane; the mass concentrations are 0.18 g / mL, 0.12 g / mL, and 0.9 g / mL, respectively, and the dispersion ratio of product A in the mixed solution is 6 g / 100 mL;

[0044] S3. Disperse the product B and graphene nanosheets in styrene emulsion, mix and stir thoroughly until homogeneous, then stir and heat to 80-90℃, keep warm and stir for 1-2 hours, separate the precipitate and wash it with anhydrous ethanol and deionized water in sequence, and dry to obtain product C.

[0045] The dispersion ratios of product B and graphene nanosheets in the styrene emulsion are 10 g / 100 mL and 2.5 g / 100 mL, respectively.

[0046] S4. Under ultrasonic conditions, vinyltrimethoxysilane is dissolved in deionized water to obtain a transparent solution with a mass concentration of 6 wt%. The product C is dispersed in deionized water to obtain a dispersion solution. The transparent solution and the dispersion solution are mixed, and an ammonia solution is added under stirring. The reaction is continued for 5 hours. After the reaction is completed, the precipitate is separated by centrifugation, washed with anhydrous ethanol, and then soaked in tetrahydrofuran overnight to obtain the product.

[0047] The dispersion ratio of product C is 2 g / 100 mL, and the volume ratio of the transparent solution, the dispersion solution, and the ammonia solution is 2.2:10:1.2.

[0048] Example 4

[0049] A biological filter media, prepared in the same way as in Example 3, except that product C is replaced by product A.

[0050] Example 5

[0051] A biological filter media, prepared in the same way as in Example 3, except that product C is replaced by graphene nanosheets.

[0052] Experimental Example

[0053] The filtration performance of the biological filter media was determined using a simulated reactor. The simulated reactor was 800 mm high, 190 mm in inner diameter, and the filter media filling height was 340 mm. Wastewater treatment plant secondary sedimentation tank return sludge was used as inoculum sludge. An immersion acclimation method was employed, immersing the sludge solution in the biological filter and acclimating it with gaseous methanol at a concentration of 1500 mg / L. During acclimation, a circulating spray method was used for rinsing. Acclimation was considered complete when the gaseous methanol removal rate reached 60% after removing the sludge solution. The acclimation conditions were: acclimation temperature 30℃, sludge solution pH maintained at 4-8, gas residence time range of 30-50 s, and a spray volume to filter media volume ratio of 1:15. The time to reach 60% gaseous methanol removal rate was recorded, and the biofilm thickness was measured. The results are shown in the table below.

[0054] <![CDATA[Time T 60 (days)]]> 7.5 8 3 5 5 Biofilm thickness (μm) 470 485 390 440 450

[0055] Toluene (import concentration 2.15 mg / m³) 3 ) and hydrogen sulfide (inlet concentration 4.36 mg / m³) 3 To simulate volatile organic waste gas and odor, the waste gas removal effect of the packing materials in each embodiment was measured. The results are as follows:

[0056] Toluene 41.7 39.5 89.4 67.2 60.4 hydrogen sulfide 50.8 45.9 95.4 80.3 76.2

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A biological filter media for the treatment of VOCs and malodorous gases, characterized in that, The biological filter media is composed of organic and inorganic media. The organic media includes bark, compost or straw, and the inorganic media includes zeolite, biochar, ceramsite or seashells. The mass ratio of the organic media to the inorganic media is (1-18):

100. The surface of the inorganic filler is coated with a layer of modified porous microspheres, which are carbon nanosheets modified with ruthenium phosphide core-shell microspheres coated with silica. The method for preparing the modified porous microspheres includes the following steps: S1. Weigh phytic acid and ruthenium chloride separately and dissolve them in deionized water. After thorough mixing, add melamine and stir the mixture overnight at 80-100℃. After the reaction is complete, evaporate the solvent to obtain a uniform powder-solid mixture. Under a protective atmosphere, heat the powder-solid mixture to 900℃ and keep it at that temperature for 2 hours. After cooling to room temperature, obtain a black powder. Wash it successively with anhydrous ethanol and deionized water, vacuum dry it overnight, and grind it to obtain product A. S2. Dissolve the initiator, catalyst and silane coupling agent in a solvent and mix and disperse them evenly to obtain a mixed solution. Disperse the product A in the mixed solution and stir the reaction overnight at room temperature. Separate the precipitate and wash it with the solvent to obtain product B. The mass concentrations of the initiator, catalyst, and silane coupling agent in the mixed solution are (0.1-1) g / mL, (0.1-1) g / mL, and (0.5-2) g / mL, respectively, and the dispersion ratio of product A in the mixed solution is (5-10) g / 100 mL; S3. Disperse the product B and carbon nanosheets in styrene emulsion, mix and stir thoroughly until homogeneous, then stir and heat to 80-90℃, keep warm and stir for 1-2 hours, separate the precipitate and wash it with anhydrous ethanol and deionized water in sequence, and dry to obtain product C. The dispersion ratios of product B and carbon nanosheets in the styrene emulsion are (5-20) g / 100 mL and (2-6) g / 100 mL, respectively. S4. Under ultrasonic conditions, vinyltrimethoxysilane was dissolved in deionized water to obtain a transparent solution with a mass concentration of 5-10 wt%. The product C was dispersed in deionized water to obtain a dispersion solution. The transparent solution and the dispersion solution were mixed, and an ammonia solution was added under stirring. The reaction was continued for 5 hours. After the reaction was completed, the precipitate was separated by centrifugation, washed with anhydrous ethanol, and then soaked in tetrahydrofuran overnight to obtain the final product. Wherein, the dispersion ratio of product C is (1-10) g / 100 mL, and the mixing volume ratio of the transparent solution, the dispersion solution, and the ammonia solution is (1-4):10:(1-2).

2. The biological filter media for VOCs and odor gas treatment according to claim 1, characterized in that, The biological filter media is composed of straw, compost, seashells and zeolite in a mass ratio of 2:1:10:

30.

3. The biological filter media for VOCs and odor gas treatment according to claim 1, characterized in that, The carbon-to-nitrogen ratio of the biological filter media is 100:(2-10).

4. A biological filter media for VOCs and odor gas treatment according to claim 1, characterized in that, The bulk density of the biological filter media is 400-500 kg / m³. 3 The porosity is 50-60%.

5. A biological filter media for VOCs and odor gas treatment according to claim 1, characterized in that, The particle size of the organic filler and the inorganic filler is 0.1-3 cm.

6. A biological filter media for VOCs and odor gas treatment according to claim 1, characterized in that, In step S1, the mass ratio of phytic acid to ruthenium chloride and melamine is 10:(1.8-3.2):(1.6-2.1).

7. A biological filter media for VOCs and odor gas treatment according to claim 1, characterized in that, The initiator is azobisisobutyronitrile, azobisisoheptanenitrile, or dimethyl azobisisobutyrate; the catalyst is cuprous chloride or cuprous bromide; and the silane coupling agent is γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, or N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane.

8. The method for preparing the biological filter media according to any one of claims 1-7, characterized in that, Includes the following steps: (1) The modified porous microspheres are dispersed in an aqueous polyurethane resin or an aqueous acrylic resin to obtain a coating solution; (2) The inorganic filler is dispersed in the coating liquid, and after thorough mixing, the inorganic filler is separated, and after curing and drying, the surface-coated modified inorganic filler is obtained. (3) The surface-coated modified inorganic filler and the organic filler are mixed in a mass ratio to obtain the biological filter filler.