Composite filler, method for preparing same and use thereof

Abstract

The present application relates to a kind of composite filler and its preparation method and application, including (1) biomass raw material ball milling pyrolysis and is prepared biochar, into water and is made into biochar suspension;(2) polyurethane is impregnated into biochar suspension, after reaction, drying is obtained composite filler.The composite filler provided by the present application is used as the filler of biological trickling filter device to treat VOCs, can improve the adhesion of microorganism in reactor to quickly generate biofilm, shorten the time of membrane formation and start, maintain long-term stable operation of device.

Description

Technical Field

[0001] This invention relates to a composite packing material, its preparation method, and its application; more specifically, it relates to a composite packing material, its preparation method, and its application in treating VOCs in a bio-trickling filter. Background Technology

[0002] Volatile organic compounds (VOCs) are among the major pollutants in the atmosphere, characterized by their wide range of sources, high volatility, and easy diffusion. Traditional technologies such as oxidation, absorption, adsorption, and condensation are energy-intensive and generate byproducts. Biological treatment utilizes microorganisms to convert VOCs into H2O and CO2, offering advantages such as high removal rates, no byproducts, and low investment and operating costs. Currently, biotrickling filtration systems are widely used in biological treatment due to their high economic efficiency and relatively small footprint. In biotrickling filtration systems, the packing material is the core of the bioreactor, serving as a carrier for microbial attachment, growth, and mass transfer, directly affecting the pollutant removal efficiency. Polyurethane, as a porous carrier, can enrich microorganisms and can be used as packing material for biofilm attachment in biotrickling filtration systems.

[0003] CN108722169A discloses a method for degrading VOCs and a dedicated miniaturized bio-trickling filter device. The method includes (1) placing a microbial composite agent for degrading VOCs and a packing material in water for aeration and biofilm formation to obtain a biofilm; (2) contacting the biofilm with VOCs gas from bottom to top, and spraying a rinsing solution from top to bottom onto the packing material, wherein the rinsing solution includes a circulating nutrient solution and an emulsifier. However, directly using polyurethane as the packing material results in poor biocompatibility, a long initial biofilm formation time for microorganisms, and a reduction in VOCs degradation efficiency during long-term operation or when the substrate density is high. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a composite packing material, its preparation method, and its application in treating VOCs in a biotrickling filtration system. The composite packing material provided by this invention, when used as a packing material in a biotrickling filtration system to treat VOCs, can improve the adhesion of microorganisms within the reactor to rapidly generate a biofilm, shorten the biofilm formation and start-up time, and maintain long-term stable operation of the system.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0006] The first aspect of this invention provides a method for preparing a composite filler, comprising the following steps:

[0007] (1) Biochar is obtained by ball milling and pyrolysis of biomass raw materials, and then added to water to make a biochar suspension.

[0008] (2) Polyurethane was impregnated into a biochar suspension, and the reaction was followed by drying to obtain a composite filler.

[0009] Furthermore, the biomass mentioned in step (1) can be any common biomass raw material, including but not limited to any one or more of agricultural and forestry waste, animal manure, plant roots and stems, sawdust and straw.

[0010] Furthermore, the ball milling time in step (1) is 20-60 minutes, and the ball milling speed is 100-800 rpm. It is generally carried out in a ball mill.

[0011] Furthermore, the temperature of biomass pyrolysis in step (1) is 400-800℃, the heating rate of pyrolysis is 3-5℃ / min, and pyrolysis is carried out for 2-8 hours after reaching the reaction temperature.

[0012] Furthermore, the specific surface area of ​​the biochar in step (1) is 800-1000 m². 2 / g, with an average pore size of 2.2-2.6 nm and a pore volume of 0.6-1.0 cm³. 3 / g.

[0013] Further, the concentration of the biochar suspension in step (1) is 1-10 g / L, preferably 3-6 g / L. Preferably, the suspension can be prepared using water or a buffer solution, wherein the buffer solution is a 0.05-0.20 mol / L phosphate buffer solution.

[0014] Further, in step (1), a certain amount of polyacetylimide is added to the biochar suspension, the amount being 0.1%-0.5% of the biochar suspension.

[0015] Further, the polyurethane in step (2) is in block form with a size less than 10 mm. It is washed with ethanol and then dried at a temperature of 120-140℃ for 6-12 hours. After drying, it is immersed in a biochar suspension. The mass-to-volume ratio of polyurethane to biochar suspension is 1 g: 5-15 mL.

[0016] Furthermore, the reaction described in step (2) is carried out under stirring for 1-4 hours at a speed of 50-200 rpm.

[0017] Furthermore, the drying temperature in step (2) is 105-150℃, and the drying time is 4-24h.

[0018] A second aspect of this invention provides a composite filler prepared using the method described above. The prepared composite filler is a polyurethane-biochar composite material, wherein the mass fraction of biochar is 5%-40%.

[0019] The third aspect of the present invention provides a method for treating VOCs-containing gases using a bio-trickling filter device, wherein the bio-trickling filter device is filled with the composite packing material provided by the present invention, and the specific process is divided into a biofilm formation stage and an operation stage.

[0020] Furthermore, the biofilm formation stage can be specifically described as follows: VOCs-degrading bacterial solution and composite packing material are placed in an inorganic nutrient solution for aeration and biofilm formation. The loading volume of the composite packing material is 20%-40%. The VOCs-degrading bacterial solution is an activated sludge suspension capable of degrading VOCs, used at a sludge concentration of 10-40 mg / L. The biofilm formation conditions are: aeration to achieve a dissolved oxygen concentration of 1-5 mg / L and a pH of 6-9. Once a biofilm with a thickness of 2 mm or more is formed, the system can transition to a continuous operation stage.

[0021] Furthermore, the specific process during the operation phase can be as follows: VOC-containing gas is introduced into the bio-trickling filter, where it contacts the biofilm to degrade the VOCs. The inlet concentration of VOC-containing gas is 200-800 mg / m³. 3 The concentration of toluene was 150-600 mg / m³. 3 The dwell time is 40-80 seconds.

[0022] Furthermore, the spray solution is an inorganic culture medium that provides nutrients for microorganisms. The spray solution is circulated and sprayed onto the packing material from top to bottom, with a spraying rate of 50-150 mL / h.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention loads biochar onto polyurethane to prepare a composite filler that has both a well-developed pore structure and good biocompatibility. It can not only provide a carrier with excellent affinity for the proliferation and metabolism of microorganisms, but also the redox active groups and aromatic structures (benzene rings) on the surface of biochar can be used by microorganisms as electron shuttles, promoting the extracellular electron migration of microorganisms, which is beneficial to the rapid start-up of membrane reactors and the degradation of pollutants.

[0025] (2) The composite filler prepared by the method of the present invention has a certain amount of hydroxyl functional groups on its surface, which can interact with the proteins on the surface of microorganisms through hydrogen bonding or van der Waals forces, thereby improving the biocompatibility of polyurethane and reducing the shedding of microorganisms during the reaction process.

[0026] (3) The present invention uses polyacetylimine, which not only further enhances the attachment and growth of microorganisms, but also helps to improve the degradation effect of VOCs.

[0027] (4) The composite packing provided by the present invention can be used as a packing material for a biological trickling filter device to treat VOCs-containing gases. It can improve the attachment of dominant microorganisms in the reactor to quickly generate biofilm, shorten the biofilm formation and device start-up time, and maintain the long-term stable operation of the device. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the bio-trickling filtration device of the present invention.

[0029] Figure 2 The infrared spectrum of the composite filler prepared in Example 1 of this invention. Detailed Implementation

[0030] The technical solution of the present invention and its application effects are further illustrated below with reference to specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0031] Unless otherwise specified, the experimental methods used in the embodiments of this invention are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments can be purchased from biochemical reagent stores.

[0032] In this embodiment of the invention, the waste activated sludge comes from the secondary sedimentation tank sludge of a wastewater treatment plant. The screening and acclimatization method of the activated sludge is as follows: the sludge suspension and inorganic culture medium are mixed at a volume ratio of 1:5 and loaded into a reactor. Toluene is then added at a volume ratio of 600:1 and the reactor is sealed. It is cultured in a shaker at 30°C and 120 rpm for 48 hours, and the toluene concentration is measured every 6 hours until the toluene is completely degraded. Then, 10% of the inoculum is transferred to fresh inorganic culture medium and cultured for another 48 hours. The enriched bacterial culture is spread on an agar plate and cultured at 30°C for 24 hours. Then, a single colony is picked and inoculated into sterilized inorganic culture medium and cultured in a shaker at 30°C and 120 rpm for 12 hours. After detection and analysis, the composition of the degrading bacteria is mainly Pseudomonas, Sphingolipids, Bacillus, Mycobacterium, Rhodococcus, and Geobacterium, with a relative abundance ratio of 32:19:4:3:5:2. The inorganic culture medium consists of: glucose 1.5 g / L, anhydrous calcium chloride 0.12 g / L, ammonium chloride 0.28 g / L, magnesium chloride 0.25 g / L, dipotassium hydrogen phosphate 0.8 g / L, sodium dihydrogen phosphate 0.6 g / L, manganese sulfate 0.4 g / L, anhydrous copper sulfate 0.02 g / L, zinc sulfate heptahydrate 0.03 g / L, and ferrous sulfate heptahydrate 0.04 g / L.

[0033] In this embodiment of the invention, COD concentration was determined using GB11914-89 "Water Quality - Determination of Chemical Oxygen Demand - Dichromate Method". VOCs concentration was determined using a GC-9790II gas chromatograph.

[0034] Example 1

[0035] Straw was ball-milled at 400 rpm for 40 minutes, then placed in a muffle furnace and pyrolyzed at 600℃ for 5 hours at a heating rate of 4℃ / min to obtain straw biochar. The specific surface area of ​​the biochar was 983.5 m². 2 / g, with an average pore size of 2.26nm and a pore volume of 0.94cm³. 3 / g. Add biochar to water to prepare a 5g / L biochar suspension.

[0036] Polyurethane blocks approximately 5 mm in size were washed with anhydrous ethanol and then dried at 135°C for 12 hours. After drying, they were immersed in a biochar suspension at a mass-to-volume ratio of 1 g:15 mL. The mixture was stirred at 150 rpm for 2 hours and then dried at 120°C for 12 hours to obtain the polyurethane-biochar composite filler. The biochar content in the composite material was 37% by mass.

[0037] Infrared characterization tests were performed on the polyurethane-biochar composite material, and the results are as follows: Figure 1 As shown, the wavelength is at 3380cm. -1 The characteristic peak for hydroxyl groups is located at 1586 cm⁻¹. -1 1410cm -1 1032cm -1 and 863cm -1 The four characteristic peaks of the benzene ring are the CH in-plane bending vibration peak, the C=C double bond absorption peak, the CH out-of-plane bending vibration peak, and the CH single bond absorption peak, indicating that the surface of the composite packing contains a certain amount of hydroxyl and aromatic groups. The hydroxyl groups can form chemical bonds with proteins on the surface of microorganisms, improving the biocompatibility and binding force of the packing, while the aromatic groups can promote extracellular electron transfer in microorganisms, thus benefiting microbial proliferation.

[0038] Example 2

[0039] Peach pits were ball-milled at 200 rpm for 20 minutes, then placed in a muffle furnace and pyrolyzed at 450℃ for 2.5 hours at a heating rate of 3℃ / min to obtain straw biochar. The specific surface area of ​​the biochar was 817.6 m². 2 / g, average pore size is 2.52nm, pore volume is 0.65cm³. 3 / g. Biochar was added to water to prepare a 3g / L biochar suspension. Approximately 3mm thick polyurethane blocks were washed with anhydrous ethanol and then dried at 130℃ for 10 hours. After drying, the polyurethane was immersed in the biochar suspension at a mass-to-volume ratio of 1g:5mL. The mixture was stirred at 100rpm for 1 hour and dried at 110℃ for 10 hours to obtain a polyurethane-biochar composite filler, in which the biochar mass fraction was 6%.

[0040] Example 3

[0041] Bamboo was ball-milled at 700 rpm for 50 minutes, then placed in a muffle furnace and pyrolyzed at a rate of 6℃ / min for 8 hours at a controlled temperature of 750℃ to obtain straw biochar. The specific surface area of ​​the biochar was 918.4 m². 2 / g, average pore size 2.42nm, pore volume 0.72cm³ 3 / g. Add biochar to water to prepare a 4 g / L biochar suspension.

[0042] Polyurethane blocks approximately 8 mm in size were washed with anhydrous ethanol and then dried at 120°C for 7 hours. After drying, they were immersed in a biochar suspension at a mass-to-volume ratio of 1 g:10 mL. The mixture was stirred at 180 rpm for 3.5 hours and then dried at 140°C for 6 hours to obtain a polyurethane-biochar composite filler, in which the biochar mass fraction was 22%.

[0043] Example 4

[0044] Same as Example 1, except that: a 0.1 mol / L phosphate buffer solution was used instead of water, including equimolar amounts of disodium hydrogen phosphate and sodium dihydrogen phosphate, to finally prepare the composite filler.

[0045] Example 5

[0046] Similar to Example 1, except that a certain amount of polyacetylimide was added to the biochar suspension, at a concentration of 0.2% of the biochar suspension. The resulting composite filler was thus prepared.

[0047] Comparative Example 1

[0048] Same as Example 1, except that the packing material inside the bio-trickling filter device is only polyurethane.

[0049] Comparative Example 2

[0050] Same as Example 1, except that the packing material in the bio-trickling filter device is only the biochar obtained by pyrolysis in step (1).

[0051] Test case

[0052] The bioreactor uses a horizontal biological trickling filter tower, with an actual packing volume of V = 4608 cm³ per section. 3 (Reactor dimensions: length 18.0cm, width 16.0cm, height 18.0cm), the total volume of the two packing sections is V. 总 =9216cm 3 ,like Figure 2 The main components of the reactor shown include a gas distribution system, a purification system, and a nutrient solution spraying system. Composite packing material is fixed inside the reactor in a tightly stacked arrangement, allowing microorganisms to attach to it. The gas intake and composition are controlled by an injection pump and a gas flow controller, ensuring the gas flows laterally through the packing layer.

[0053] The packing material, VOCs-degrading bacterial solution, and inorganic nutrient solution from the examples and comparative examples were placed in a horizontal biological trickling filter for aeration and biofilm formation. The composite packing material was filled to 30% of the filter. The VOCs-degrading bacterial solution was an activated sludge suspension for VOCs degradation, used at a sludge concentration of 30 mg / L. The biofilm formation conditions were: aeration to achieve a dissolved oxygen concentration of 2-3 mg / L and a pH of 7-7.5. Once a biofilm with a thickness of 2 mm or more was formed, the filter was ready for operation.

[0054] During operation, the VOCs concentration in the introduced gas is 400 mg / m³. 3 The concentration of toluene was 300 mg / m³. 3 The gas residence time is 48s. The inorganic nutrient solution is sprayed intermittently in a circulating manner, with a 5-minute interval between sprays and a 5-minute interval. The spray rate is 50mL / h. The daily load of inorganic nutrient solution added to the reactor is equivalent to 418mg COD / L·d. After the spray wets the packing material, it flows out from the bottom of the tower and returns to the water storage tank at the bottom of the tower. Then, the nutrient solution is pumped to the top of the tower for recycling.

[0055] Table 1. Test results of different embodiments and comparative examples

[0056]

Claims

1. A method for preparing a composite filler, characterized in that... The steps include: (1) Biochar is obtained by ball milling and pyrolysis of biomass raw materials, and then added to water to form a biochar suspension; (2) Polyurethane is impregnated into the biochar suspension, and after reaction, it is dried to obtain a composite filler.

2. The method according to claim 1, characterized in that: The biomass mentioned in step (1) is selected from any one or more of agricultural and forestry waste, animal manure, plant roots and stems, sawdust and straw.

3. The method according to claim 1, characterized in that: The ball milling time in step (1) is 20-60 min, and the ball milling speed is 100-800 rpm.

4. The method according to claim 1, characterized in that: The temperature of biomass pyrolysis in step (1) is 400-800℃, the heating rate of pyrolysis is 3-5℃ / min, and pyrolysis is carried out for 2-8 hours after reaching the reaction temperature.

5. The method according to claim 1, characterized in that: The specific surface area of ​​the biochar in step (1) is 800-1000 m². 2 / g, with an average pore size of 2.2-2.6 nm and a pore volume of 0.6-1.0 cm³. 3 / g.

6. The method according to claim 1, characterized in that: The concentration of the biochar suspension in step (1) is 1-10 g / L, preferably 3-6 g / L.

7. The method according to claim 1 or 6, characterized in that: Step (1) Prepare a suspension using water or a buffer solution, wherein the buffer solution is a phosphate buffer solution of 0.05-0.20 mol / L.

8. The method according to claim 1, characterized in that: Step (1) Add polyacetylation to the biochar suspension in an amount of 0.1%-0.5% of the biochar suspension.

9. The method according to claim 1, characterized in that: The polyurethane in step (2) is in block form with a size of less than 10 mm; it is washed with ethanol and then dried at a temperature of 120-140℃ for 6-12 hours; after drying, it is then immersed in a biochar suspension.

10. The method according to claim 1, 8, or 9, characterized in that: Step (2) The mass-to-volume ratio of polyurethane to biochar suspension is 1g: 5-15mL.

11. The method according to claim 1, characterized in that: The reaction in step (2) is carried out under stirring for 1-4 hours at a speed of 50-200 rpm; the drying temperature is 105-150℃ and the drying time is 4-24 hours.

12. A composite packing material, characterized in that... It is prepared using the method described in any one of claims 1-11.

13. A method for treating VOC-containing gases using a bio-trickling filtration device, characterized in that: The bio-trickling filter device is filled with the composite packing material prepared by any one of claims 1-11 or as described in claim 12. The specific process is divided into a biofilm formation stage and an operation stage.

14. The method according to claim 13, characterized in that: The biofilm formation stage is specifically as follows: VOCs-degrading bacterial solution and composite packing material are placed in an inorganic nutrient solution for aeration and biofilm formation; the filling amount of composite packing material is 20%-40%; the VOCs-degrading bacterial solution is an activated sludge suspension capable of degrading VOCs, and the dosage is based on a sludge concentration of 10-40 mg / L; the biofilm formation conditions are: aeration to achieve a dissolved oxygen concentration of 1-5 mg / L and a pH of 6-9; once a biofilm with a thickness of more than 2 mm is formed, the system can be switched to the continuous operation stage.

15. The method according to claim 13, characterized in that: The specific process during the operation phase is as follows: VOCs-containing gas is sent into the bio-trickling filter device to contact the biofilm to degrade the VOCs.

16. The method according to claim 13, characterized in that: The inlet gas concentration containing VOCs is 200-800 mg / m³. 3 The concentration of toluene was 150-600 mg / m³. 3 The dwell time is 40-80 seconds.

17. The method according to claim 13, characterized in that: The spray solution is an inorganic culture medium that provides nutrients for microorganisms. The spray solution is circulated and sprayed onto the packing material from top to bottom, with a spraying rate of 50-150 mL / h.

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