Denitrification deep denitrification functional carrier, preparation process and application thereof

Abstract

This invention discloses a functional carrier for deep denitrification, its preparation process, and its application, belonging to the field of water treatment technology. The raw materials for the denitrification functional carrier include the following components in the following proportions: polymer matrix: silane coupling agent-ethanol aqueous solution: mixed adhesive = 100:(4.5-7):(10-13). The magnetic amine cross-linked activated carbon loaded on the carrier of this invention exhibits strong adsorption performance for nitrate ions using the principles of ion exchange and electrostatic adsorption, and demonstrates good biodegradability for low-concentration nitrogen-containing wastewater. The nitrate removal rate is 94.5%-99% in the first two weeks after biofilm formation. The loaded material is mixed with a biodegradable adhesive, resulting in high bioavailability; the carrier mass reduction percentage in the first two weeks is 1%-3.5%; and the formation of a mature biofilm is advanced by 5-23 days.

Description

Technical Field

[0001] This invention belongs to the fields of chemical and environmental protection technology, and relates to the preparation process and application of functional carriers for deep denitrification. Background Technology

[0002] Biofilm technology is currently a research hotspot in the field of water treatment, offering advantages such as low sludge production and high treatment efficiency. It meets the latest emission standards and is highly suitable for deep denitrification. By attaching a biofilm to a carrier surface, a concentration gradient of pollutants exists between the aqueous and biofilm phases, allowing pollutants to enter the biofilm phase and be degraded.

[0003] Currently, there are many types of polymeric biocarriers, mainly made from polymers such as polypropylene, polyethylene, and polyvinyl chloride, blended with some hydrophilic and biocompatible substances to increase the hydrophilicity and biocompatibility of the carrier surface. However, the addition of hydrophilic and biocompatible substances still falls short of practical needs in improving the biofilm formation effect of the carrier. The hydrophilic and biocompatible substances blended within the carrier are not effectively utilized; only the surface functional substances play a role, resulting in resource waste.

[0004] Chinese invention patent CN100537450C discloses a method for preparing a biocompatible carrier by coating natural biological material powder, solvent, coating latex, and other materials onto the surface of a water treatment carrier. This method exhibits good biocompatibility, short biofilm formation time, and good treatment effect. Chinese invention patent CN106430527B discloses a method for preparing a hydrophilic biological carrier by coating natural and synthetic polymer materials onto the surface of a carrier. The carrier prepared by this method not only has good biocompatibility and a short biofilm formation time, but also shows enhanced chemical stability, thermal stability, and mechanical strength compared to the previous invention. However, both of these inventions suffer from insufficient driving force due to the low concentration gradient between the two phases when treating low-concentration wastewater.

[0005] Chinese patent CN110407334B discloses the preparation and application of a biological carrier for simultaneous denitrification and nitrogen removal by adsorbing nitrate ions. The biological packing provided by this invention is made of carbon microspheres with anionic layered magnesium-aluminum compounds loaded on their surface and organically combined with polycaprolactone, which has the functions of actively adsorbing nitrate ions and providing a carbon source for denitrification. However, the use of a non-degradable binder in this packing means that only a portion of the loaded polycaprolactone can be utilized, resulting in waste. Furthermore, the loaded polycaprolactone can cover the adsorption sites for nitrate ions, affecting the adsorption function.

[0006] In summary, the existing biological carriers commonly used in the treatment of low-concentration nitrate nitrogen wastewater have disadvantages such as low utilization rate of loading agents and agent coverage of adsorption sites. Therefore, it is of great significance to develop a packing material with high agent utilization rate and deep denitrification capability. Summary of the Invention

[0007] To address the problem that existing technologies for treating low-concentration nitrate-containing wastewater suffer from issues such as the loading of additives covering adsorption sites and resulting in low additive utilization, this invention provides a functional carrier for deep denitrification. A paste prepared from biodegradable adhesives, magnetic amine cross-linked activated carbon, hydrophilic substances, and biocompatible substances is mixed in a certain proportion and loaded onto the surface of a polymer matrix. This effectively utilizes the additives loaded on the matrix surface and exhibits good treatment results for low-concentration nitrate-containing wastewater.

[0008] This invention uses a polymer material as the matrix and a silane coupling agent as the connecting substance. A paste prepared by mixing magnetic amine cross-linked activated carbon, biocompatible substances, hydrophilic substances, biodegradable adhesives, and ultrapure water in a certain proportion is loaded onto the matrix surface and dried to obtain a biological carrier.

[0009] This invention provides a denitrification functional carrier, wherein the raw materials of the denitrification functional carrier contain a polymer matrix, an ethanol aqueous solution of a silane coupling agent, and a mixed adhesive in a mass ratio of 100:(4.5-7):(10-13); the polymer matrix is ​​selected from at least one of polypropylene, polyethylene, polyvinyl chloride, and polyurethane; the mixed adhesive contains magnetic amine cross-linked activated carbon, a hydrophilic substance, a biocompatible substance, a biodegradable adhesive, and water in a mass ratio of 1:(0.6-0.8):(0.6-0.8):(4-4.5):(5-5.5); the hydrophilic substance is selected from at least one of polyvinyl alcohol, agar, silica gel, and diatomaceous earth; the biocompatible substance is selected from at least one of starch, degummed bone meal, and oyster shell powder.

[0010] Optionally, the shape of the polymer matrix can be selected from cyclic, saddle-shaped, Raschig ring, or hollow sphere. The molecular weight of the polymer matrix is ​​not limited; any molecular weight commonly used in the art may be employed.

[0011] Optionally, the density of the denitrification functional carrier is 0.95–1.1 g / cm³. 3 Preferably, it is 0.98–1.05 g / cm³. 3 .

[0012] Optionally, the biodegradable adhesive is selected from at least one of carboxymethyl polysaccharide adhesives and modified starch adhesives.

[0013] Optionally, the mass ratio of the polymer matrix to the ethanol-water solution of the silane coupling agent is 100:(4.5-7). The silane coupling agent contains two types of groups: one is an organophilic group that bonds to the polymer surface, and the other is an active group that bonds to other groups besides the polymer. This characteristic increases the bonding strength between the loaded mixed adhesive and the polymer matrix.

[0014] Optionally, the silane coupling agent is of type KH550.

[0015] Optionally, the mass concentration of the silane coupling agent in the ethanol aqueous solution is 2-10 g / L, more preferably 4-8 g / L.

[0016] Optionally, the ethanol concentration in the aqueous ethanol solution of the silane coupling agent is 70% to 80% by mass.

[0017] This invention also provides a method for preparing a denitrification functional carrier, the method comprising the steps of:

[0018] S1 pretreatment of the polymer matrix: The polymer matrix is ​​immersed in an ethanol-water solution of silane coupling agent; the ratio of the two is not specifically limited, and the polymer matrix is ​​simply immersed in the ethanol-water solution of silane coupling agent.

[0019] S2 mixes the magnetic amine cross-linked activated carbon, hydrophilic substance, biocompatible substance, biodegradable adhesive and water to obtain a mixed adhesive paste;

[0020] S3 involves immersing the pretreated polymer matrix in the mixed slurry for 3 to 6 hours; after removal, it is dried to form a dense layer of the mixed slurry on the surface of the matrix, thus obtaining the denitrification functional carrier.

[0021] The density of the carrier can be controlled by the number of immersions in S3.

[0022] Optionally, in step S1, the pretreatment time is 1 to 3 hours; preferably, the treatment time is 2 to 3 hours.

[0023] Optionally, in step S2, the mixed adhesive is obtained by stirring at 60-120 r / min for 1 hour, preferably by stirring at 70-100 r / min for 1 hour.

[0024] Optionally, in step S3, the drying temperature is 60–80°C and the drying time is 1–3 hours; preferably, the drying temperature is 70–80°C and the drying time is 2–3 hours.

[0025] The present invention also provides the application of the denitrification functional carrier obtained by any of the above preparation methods in the treatment of nitrate nitrogen wastewater.

[0026] Optionally, the concentration of nitrate ions in the nitrate wastewater is 50 mg / L to 100 mg / L.

[0027] The magnetic amine cross-linked activated carbon consists of mixed solution I and mixed solution II. Mixed solution I consists of activated carbon powder, FeCl3·6H2O, and sodium hydroxide solution; mixed solution II consists of dimethylformamide, ethylenediamine, epichlorohydrin, and triethylamine. The concentration of the sodium hydroxide solution is 4wt%–8wt%. The weight ratio of the activated carbon powder, FeCl3·6H2O, and sodium hydroxide solution is 1:(3–4):(8–10). The volume ratio of the dimethylformamide, ethylenediamine, epichlorohydrin, and triethylamine is 1:(0.9–1.1):(1.2–1.4):(3.1–3.4). The volume ratio of mixed solution I to mixed solution II is 1:(1–2).

[0028] The preparation steps of the magnetic amine crosslinked activated carbon include:

[0029] (1) The activated carbon granules are crushed and passed through a 50-100 mesh sieve, preferably 60-80 mesh;

[0030] (2) Activated carbon pretreatment: The activated carbon is first pyrolyzed, then acid-washed, then washed with deionized water until neutral, and finally dried. The pyrolysis is carried out in a muffle furnace at 350-700℃ for 8-13 hours, preferably at 400-650℃ for 9-11 hours. The acid washing is carried out in 1-3 mol / L nitric acid at 60-85℃ for 1-3 hours, preferably in 1.5-2.5 mol / L nitric acid at 65-80℃ for 1-1.8 hours. The drying is carried out at 70-100℃ for 8-12 hours, preferably at 75-90℃ for 9-11 hours.

[0031] (3) The pretreated activated carbon powder, FeCl3·6H2O and 4-8wt% NaOH solution are mixed in a weight ratio and stirred at 75-85℃ for 4-8h, preferably at 78-83℃ for 5-7h to obtain a mixed solution;

[0032] (4) Mix dimethylformamide, ethylenediamine, epichlorohydrin and triethylamine in a volume ratio and add them to the mixed solution obtained in step (3). Stir at 55-65°C for 4-8 hours, preferably at 60-65°C for 5-7 hours. After centrifugation, wash the product with deionized water and dry at 70-100°C for 3-7 hours, preferably at 70-85°C for 3-5 hours to obtain the magnetic amine crosslinked activated carbon.

[0033] Magnetic amine-crosslinked activated carbon is made by loading Fe3O4 onto the surface of activated carbon through chelation, giving it superparamagnetism. This allows for easy recovery from wastewater using an external magnetic field, and amine functional groups (NH+2Cl) are introduced onto the surface. - It exhibits excellent adsorption performance for nitrate ions; the adsorption principle is based on the Cl- in the amine functional group. -After ion exchange with nitrate ions, Fe is also present in the modified activated carbon. 3+ It has an electrostatic attraction to nitrate ions.

[0034] The denitrification deep nitrogen removal functional carrier of the present invention has the following beneficial effects:

[0035] (1) The adhesive in the mixed adhesive is biodegradable and the loaded functional substances have high utilization rate;

[0036] (2) Magnetic amine cross-linked activated carbon has a good adsorption effect on nitrate in wastewater and can play a good denitrification effect for low-concentration wastewater.

[0037] (3) Bio-friendly and hydrophilic substances are mixed into the mixed adhesive, and the carrier has good bio-friendly and hydrophilic properties;

[0038] (4) Magnetic amine cross-linked activated carbon scattered in water can play a certain role in adsorption and flocculation.

[0039] (5) The magnetic amine cross-linked activated carbon contains Fe3O4 particles, which have a magnetic promoting effect on membrane growth.

[0040] (6) Using silane coupling agent as a "bridge" between the mixed adhesive and the carrier makes the load more secure and less likely to fall off;

[0041] (7) As biocompatible substances are consumed, the surface roughness of the carrier increases, which is conducive to biofilm formation.

[0042] The magnetic amine cross-linked activated carbon loaded on the carrier of this invention has strong adsorption performance for nitrate ions by utilizing the principles of ion exchange and electrostatic adsorption. It also has good biodegradability performance for low-concentration nitrogen-containing wastewater, with a nitrate removal rate of 94.5% to 99% in the first two weeks after biofilm formation. The loading material is mixed with a biodegradable adhesive, resulting in high bioavailability. The carrier mass reduction percentage is 1% to 3.5% in the first two weeks. The formation of a mature biofilm is advanced by 5 to 23 days. Detailed Implementation

[0043] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0044] The present invention will be further described below with reference to embodiments. It should be emphasized that the following description is merely exemplary and not intended to limit the scope and application of the present invention.

[0045] The carrier density test method of this invention is the mass-volume method. The mass of the carrier is directly measured by a balance, and the volume of the carrier is measured by the displacement method. The carrier density is calculated according to the formula ρ=m / V.

[0046] In this invention, a mature biofilm refers to a biofilm content of 150 mg per 1g of carrier.

[0047] The method for testing nitrate is ion chromatography, and the removal rate formula is: (influent nitrate concentration - effluent nitrate concentration) / influent nitrate concentration.

[0048] The wastewater in the following examples and comparative examples is artificially prepared low-concentration nitrate wastewater.

[0049] In this embodiment of the invention, the degummed bone powder was purchased from Jinan Jianhui Chemical Co., Ltd., product number 1130; polyvinyl alcohol was purchased from Beijing Innocare Technology Co., Ltd., product number PVA17-88; agar was purchased from Beijing Innocare Technology Co., Ltd., product number B46657; silica gel was purchased from Beijing Innocare Technology Co., Ltd., product number S157-212; diatomaceous earth was purchased from Beijing Innocare Technology Co., Ltd., product number B42396; starch was purchased from Beijing Innocare Technology Co., Ltd., product number A48874; and oyster shell powder was purchased from Shaanxi Feimi Technology Co., Ltd., product number FM-HKF.

[0050] The modified starch adhesive used in this embodiment of the invention was purchased from Hebei Yanxing Chemical Co., Ltd.; the product model is pregelatinized starch α-starch.

[0051] The carboxymethyl chitosan adhesive used in this embodiment of the invention was purchased from Xi'an Puris Biotechnology Co., Ltd., and its product model is PRS180321.

[0052] The calculation method for carrier weight reduction rate = (weight before use - weight after use) / weight before use. Example 1

[0053] The raw materials for the denitrification functional carrier consist of 100g of polymer matrix, 4.5g of ethanol aqueous solution of silane coupling agent KH550, and 11.2g of mixed adhesive.

[0054] The polymer matrix is ​​hollow spherical polyethylene. The mixed adhesive is a mixture of 0.6g hydrophilic substance, 0.6g biocompatible substance, 4g biodegradable adhesive, 1g magnetic amine cross-linked activated carbon, and 5g ultrapure water. The hydrophilic substance is a mixture of 0.3g polyvinyl alcohol and 0.3g diatomaceous earth. The biocompatible substance is a mixture of 0.3g starch and 0.3g degummed bone meal. The biodegradable adhesive is a modified starch adhesive.

[0055] The preparation method of magnetic amine crosslinked activated carbon is as follows:

[0056] (1) After the activated carbon particles are crushed and passed through a 65-mesh sieve, they are first pyrolyzed in a muffle furnace at 600℃ for 10h, then placed in 2mol / L nitric acid at 75℃ for 1.5h, and finally washed with deionized water until neutral, and dried at 80℃ for 12h to obtain activated carbon powder.

[0057] (2) Mix 1g of activated carbon powder, 3.2g of FeCl3·6H2O and 10ml of 4wt% NaOH solution, and stir at 80℃ for 6h to obtain mixed solution I;

[0058] (3) Mix 2.5 ml dimethylformamide, 2 ml ethylenediamine, 3 ml epichlorohydrin and 8 ml triethylamine to prepare mixed solution II. Mix mixed solution I and mixed solution II are mixed at a volume ratio of 1:1 and stirred at 60°C for 2 h. After centrifugation, the product is washed with deionized water and dried at 100°C for 2 h to obtain magnetic amine crosslinked activated carbon.

[0059] The preparation method of the denitrification functional carrier is as follows:

[0060] Step 1: Immerse the surface of the hollow spherical polyethylene in a 75% ethanol aqueous solution of 5 g / L silane coupling agent for 2 hours.

[0061] Step 2: Mix 1g of magnetic amine cross-linked activated carbon, 0.6g of hydrophilic substance, 0.6g of biocompatible substance, 4g of biodegradable adhesive, and 5g of ultrapure water, and stir at 70r / min for 1h to obtain a mixed slurry.

[0062] Step 3: Immerse the treated hollow spherical polyethylene in the mixed adhesive and stir for 3 hours until the mixed adhesive adheres to the surface of the hollow spherical polyethylene. After removal, dry at 80℃ for 2 hours to form a dense layer of mixed adhesive on the surface of the hollow spherical polyethylene, thus obtaining the denitrification functional carrier. The density of this carrier was tested to be 1.0 g / cm³. 3 .

[0063] The following experiments will verify the nitrate removal rate, mixed slurry utilization rate, and biofilm formation performance of the denitrification functional carrier prepared in the above steps.

[0064] The prepared denitrification functional carrier was loaded into a fixed-bed biofilm reactor, and artificially prepared low-concentration nitrate wastewater (nitrate concentration 51 mg / L) was pumped in from bottom to top. Denitrification sludge from a wastewater treatment plant was used as inoculum. Biofilm formation was initiated at a controlled temperature of 25℃~30℃. Using only hollow spherical polyethylene as a carrier, the time to form a mature biofilm was 23 days. Using the denitrification functional carrier prepared in this embodiment, the time to form a mature biofilm was 8 days, which is 15 days shorter than using hollow spherical polyethylene. In the first two weeks after biofilm formation, the average nitrate removal rate of the denitrification functional carrier in this embodiment was 99%, while the average nitrate removal rate of hollow spherical polyethylene as a carrier was 97.5%, representing an increase of 1.5% in average removal rate. After two weeks, the carrier weight reduction rate was 1.2%.

[0065] Example 2

[0066] The raw materials for the denitrification functional carrier consist of 100g of polymer matrix, 5g of silane coupling agent-ethanol aqueous solution and 11.4g of mixed adhesive.

[0067] The polymer carrier is a Φ25 polypropylene Raschig ring; the mixed adhesive is a mixture of 0.6g hydrophilic substance, 0.6g biocompatible substance, 4.2g biodegradable adhesive, 1g magnetic amine cross-linked activated carbon, and 5g ultrapure water. The hydrophilic substance is a mixture of 0.3g agar and 0.3g silica gel; the biocompatible substance is a mixture of 0.3g starch and 0.3g oyster shell powder; the biodegradable adhesive is carboxymethyl chitosan adhesive.

[0068] The preparation method of magnetic amine crosslinked activated carbon is as follows:

[0069] (1) After the activated carbon particles are crushed and passed through a 70-mesh sieve, they are first pyrolyzed in a muffle furnace at 600℃ for 10.5h, then placed in 2mol / L nitric acid at 75℃ for 1.5h, and finally washed with deionized water until neutral, and dried at 80℃ for 12h to obtain activated carbon powder.

[0070] (2) Mix 1g of activated carbon powder, 4g of FeCl3·6H2O and 6ml of 5wt% NaOH solution, and stir at 80℃ for 6h to obtain mixed solution I;

[0071] (3) Mix 2.5 ml dimethylformamide, 2.5 ml ethylenediamine, 3.5 ml epichlorohydrin and 8 ml triethylamine to prepare mixed solution II. Mix mixed solution I and mixed solution II are mixed at a volume ratio of 1:1.2 and stirred at 60°C for 2 h. After centrifugation, the product is washed with deionized water and dried at 100°C for 2 h to obtain magnetic amine crosslinked activated carbon.

[0072] The preparation method of the denitrification denitrification functional carrier is as follows:

[0073] Step 1: Immerse the surface of the polypropylene Raschig ring in an 80% ethanol aqueous solution of 6 g / L silane coupling agent for 2 hours.

[0074] Step 2: Mix 1g of magnetic amine cross-linked activated carbon, 0.6g of hydrophilic substance, 0.6g of biocompatible substance, 4.2g of biodegradable adhesive, and 5g of ultrapure water, and stir at 80r / min for 1h to obtain a mixed adhesive slurry.

[0075] Step 3: Immerse the treated polypropylene Raschig rings in the mixed slurry and stir for 4 hours until the mixed slurry adheres to the surface of the polypropylene Raschig rings. After removal, dry at 80℃ for 2 hours to form a dense layer of mixed slurry on the surface of the polypropylene Raschig rings, thus obtaining the denitrification functional carrier. The density of this carrier was tested to be 1.01 g / cm³. 3 .

[0076] The following experiments will verify the nitrate removal rate, mixed slurry utilization rate, and biofilm formation ability of the denitrification functional carrier prepared in the above steps.

[0077] The prepared denitrification functional carrier was loaded into a fixed-bed biofilm reactor, and artificially prepared low-concentration nitrate wastewater (nitrate concentration 51 mg / L) was pumped in from bottom to top. Denitrification sludge from a wastewater treatment plant was used as inoculum sludge, and biofilm formation was initiated at a controlled temperature of 30°C. Using only polypropylene Raschig rings as the carrier, the time to form a mature biofilm was 20 days. Using the denitrification functional carrier prepared in this embodiment, the time to form a mature biofilm was 10 days, which is 10 days shorter than using polypropylene Raschig rings. In the first two weeks after biofilm formation, the average nitrate removal rate of the denitrification functional carrier in this embodiment was 98%, while the average nitrate removal rate of polypropylene Raschig rings as the carrier was 96.5%, representing a 2.5% increase in average removal rate. After two weeks, the carrier weight reduction rate was 1.05%.

[0078] Example 3

[0079] The raw materials for the denitrification functional carrier consist of 100g of polymer matrix, 5.5g of silane coupling agent-ethanol aqueous solution, and 11.8g of mixed adhesive. The polymer carrier is saddle-shaped polyvinyl chloride; the mixed adhesive is a mixture of 0.7g of hydrophilic substance, 0.7g of biocompatible substance, 4.4g of biodegradable adhesive, 1g of magnetic amine cross-linked activated carbon, and 5g of ultrapure water. The hydrophilic substance is a mixture of 0.3g of agar and 0.4g of silica gel; the biocompatible substance is a mixture of 0.3g of starch and 0.4g of oyster shell powder; and the biodegradable adhesive is a modified starch adhesive.

[0080] The preparation method of magnetic amine crosslinked activated carbon is as follows:

[0081] (1) After the activated carbon particles are crushed and passed through a 75-mesh sieve, they are first pyrolyzed in a muffle furnace at 600℃ for 11h, then placed in 23mol / L nitric acid at 80℃ for 1.5h, and finally washed with deionized water until neutral, and dried at 80℃ for 12h to obtain activated carbon powder.

[0082] (2) Mix 1g of activated carbon powder, 4g of FeCl3·6H2O and 8ml of 6% (wt) NaOH solution and stir at 80℃ for 6h to obtain mixed solution I;

[0083] (3) Mix 2.5 ml dimethylformamide, 2.8 ml ethylenediamine, 3.3 ml epichlorohydrin and 8 ml triethylamine to prepare mixed solution II. Mix mixed solution I and mixed solution II are mixed at a volume ratio of 1:1.5 and stirred at 60°C for 2 h. After centrifugation, the product is washed with deionized water and dried at 100°C for 2 h to obtain magnetic amine crosslinked activated carbon.

[0084] The preparation method of the denitrification functional carrier is as follows:

[0085] Step 1: Immerse the saddle-shaped polyvinyl chloride surface in a 75% ethanol aqueous solution of 7g / L silane coupling agent for 2 hours.

[0086] Step 2: Mix 1g of magnetic amine cross-linked activated carbon, 0.7g of hydrophilic substance, 0.7g of biocompatible substance, 4.4g of biodegradable adhesive, and 5g of ultrapure water, and stir at 80r / min for 1h to obtain a mixed adhesive slurry.

[0087] Step 3: Immerse the treated saddle-shaped PVC in the mixed adhesive and stir for 5 hours until the mixed adhesive adheres to the surface of the saddle-shaped PVC. After removal, dry at 80℃ for 2 hours to form a dense layer of mixed adhesive on the surface of the saddle-shaped PVC, thus obtaining the denitrification functional carrier. The density of this carrier was tested to be 1.03 g / cm³. 3 .

[0088] The following experiments will verify the nitrate removal rate, mixed slurry utilization rate, and biofilm formation ability of the denitrification functional carrier prepared in the above steps.

[0089] The prepared denitrification functional carrier was loaded into a fixed-bed biofilm reactor. Artificially prepared low-concentration nitrate wastewater (nitrate concentration 50 mg / L, water content and dosage ratio: methanol 333 mg / L, sodium nitrate 303 mg / L, potassium dihydrogen phosphate 4 mg / L, urea 21 mg / L, nitrate concentration 50 mg / L) was pumped in from bottom to top. Denitrification sludge from a wastewater treatment plant was used as inoculum. Biofilm formation was initiated at a controlled temperature of 27°C. Using only saddle-shaped polyvinyl chloride (PVC) as the carrier, the time to form a mature biofilm was 30 days. Using the denitrification functional carrier prepared in this embodiment, the time to form a mature biofilm was 7 days, 23 days shorter than with saddle-shaped PVC. The average nitrate removal rate of the denitrification functional carrier in this embodiment was 98.5% in the first two weeks after biofilm formation, while the average nitrate removal rate of saddle-shaped PVC was 94.5% in the first two weeks, representing a 4% increase in average removal rate. After two weeks, the carrier weight reduction rate was 1.0%.

[0090] Example 4

[0091] The denitrification functional carrier was prepared using essentially the same process as in Example 2, with the only difference being the mass of the magnetic amine cross-linked activated carbon, hydrophilic substance, biocompatible substance, biodegradable adhesive, and ultrapure water in step two: 1 g, 0.6 g, 0.6 g, 4.2 g, and 5.2 g, respectively. The density of the denitrification functional carrier obtained in step three was 1.0 g / cm³. 3 .

[0092] The prepared denitrification functional carrier was loaded into a fixed-bed biofilm reactor, and artificially prepared low-concentration nitrate wastewater (nitrate concentration 52 mg / L) was pumped in from bottom to top. Denitrification sludge from a wastewater treatment plant was used as inoculum sludge. Biofilm formation was initiated at a controlled temperature of 30°C. Using polypropylene Raschig rings as the carrier, the time to form a mature biofilm was 20 days. Using the denitrification functional carrier prepared in this embodiment, the time to form a mature biofilm was 15 days, which is 5 days shorter than using polypropylene Raschig rings. In the first two weeks after biofilm formation, the average nitrate removal rate of the denitrification functional carrier in this embodiment was 98%, while the average nitrate removal rate of polypropylene Raschig rings as the carrier was 96.5% in the first two weeks. The average removal rate in this embodiment increased by 1.5%. After two weeks, the carrier weight reduction rate was 3.5%.

[0093] Example 5

[0094] The denitrification functional carrier was prepared using essentially the same process as in Example 2, except that in step two, the masses of magnetic amine cross-linked activated carbon, hydrophilic substance, biocompatible substance, biodegradable adhesive, and ultrapure water were 1 g, 0.6 g, 0.6 g, 4.4 g, and 5.5 g, respectively. The density of the denitrification functional carrier obtained in step three was 1.03 g / cm³. 3 .

[0095] The prepared denitrification functional carrier was loaded into a fixed-bed biofilm reactor, and artificially prepared low-concentration nitrate wastewater was pumped in from bottom to top. Denitrification sludge from a wastewater treatment plant was used as inoculum sludge. The biofilm formation was initiated at a controlled temperature of 30°C. Using only polypropylene Raschig rings as the carrier, the time to form a mature biofilm was 20 days. Using the denitrification functional carrier prepared in this embodiment, the time to form a mature biofilm was 13 days, which is 7 days shorter than that of polypropylene Raschig rings. In the first two weeks after biofilm formation, the average nitrate removal rate of the denitrification functional carrier in this embodiment was 97%, while the average nitrate removal rate of polypropylene Raschig rings as the carrier was 96.5% in the first two weeks. The average removal rate of this embodiment increased by 0.5%. After two weeks, the carrier weight reduction rate was 1.2%.

[0096] The method for preparing low-concentration denitrification functional carriers according to the above five embodiments provides a carrier suitable for low-concentration nitrate wastewater, fully utilizes the loaded material, allows for adjustable carrier density, and significantly shortens biofilm formation time.

[0097] Example 6

[0098] The same process as in Example 4 was used, but the mass ratio of the polymer matrix, silane coupling agent, ethanol aqueous solution, and mixed adhesive was 100:5:12.

[0099] The prepared denitrification functional carrier was loaded into a fixed-bed biofilm reactor to treat low-concentration nitrogen-containing wastewater. Artificially prepared low-concentration nitrate-containing water (nitrate concentration 53 mg / L) was pumped in from bottom to top. Denitrification sludge from a wastewater treatment plant was used as inoculum. Biofilm formation was initiated at a controlled temperature of 30℃. The time to form a mature biofilm was 14 days, compared to 20 days with polypropylene Raschig ring carrier, a reduction of 6 days. In the first two weeks after biofilm formation, the average nitrate removal rate was 97%, which was 0.5% higher than that with polypropylene Raschig ring as the carrier. After two weeks, the carrier weight reduction rate was 1.1%.

[0100] Example 7

[0101] The same process as in Example 4 was used, but the mass ratio of the polymer matrix, silane coupling agent, ethanol aqueous solution, and mixed adhesive was 100:5:13.

[0102] The prepared denitrification functional carrier was loaded into a fixed-bed biofilm reactor, and artificially prepared low-concentration nitrate wastewater (52 mg / L) was pumped in from bottom to top. Denitrification sludge from a wastewater treatment plant was used as inoculum. Biofilm formation was initiated at a controlled temperature of 30℃, and the time to form a mature biofilm was 16 days, which was 4 days shorter than the 20 days achieved with polypropylene Raschig ring carrier. In the first two weeks after biofilm formation, the average nitrate removal rate was 97.5%, which was 1% higher than that achieved with polypropylene Raschig ring carrier. After two weeks, the carrier weight reduction rate was 2.3%.

[0103] Comparative Example 1

[0104] The denitrification function was prepared using essentially the same process as in Example 1, the only difference being that the carrier surface was not treated with a silane coupling agent-ethanol aqueous solution in step one. This resulted in the mixed slurry failing to adhere to the carrier during impregnation, and the carrier exhibiting low mechanical strength, leading to clump-like detachment during use. Mature biofilm formation took 30 days. The average nitrate removal rate was 75% in the first two weeks after biofilm formation, and the carrier weight reduction rate was 20% after two weeks.

[0105] Comparative Example 2

[0106] The denitrification functional carrier was prepared using a process essentially the same as in Example 2, the only difference being that in step two, instead of adding magnetic amine cross-linked activated carbon, an equal amount of activated carbon was added, thus lacking active adsorption function. It took 15 days to form a mature biofilm. The average nitrate removal rate was 93% in the first two weeks after biofilm formation, and the carrier weight reduction rate was 0.08% after two weeks.

[0107] Comparative Example 3

[0108] The carrier was prepared using the same process as in Example 3, but in step two, the biodegradable adhesive was replaced with non-biodegradable epoxy resin. This is because when epoxy resin is used, only the hydrophilic and biocompatible additives loaded on the surface of the denitrification carrier can participate in the reaction during nitrate treatment, resulting in low carrier utilization. It took 25 days to form a mature biofilm. The average nitrate removal rate was 90% in the first two weeks after biofilm formation, and the carrier weight reduction rate was 0.03% after two weeks.

[0109] Comparative Example 4

[0110] The same process as in Example 4 was used, with the only change being that in step two, the masses of magnetic amine cross-linked activated carbon, hydrophilic substance, biocompatible substance, biodegradable adhesive, and ultrapure water were 0.8 g, 0.6 g, 0.6 g, 4.2 g, and 5.2 g, respectively. The density of the denitrification functional carrier obtained in step three was 1.02 g / cm³. 3 .

[0111] The prepared denitrification functional carrier was loaded into a fixed-bed biofilm reactor to treat low-concentration nitrogen-containing wastewater. Artificially prepared low-concentration nitrate-containing water (nitrate concentration 52 mg / L) was pumped in from bottom to top. Denitrification sludge from a wastewater treatment plant was used as inoculum sludge. The biofilm formation was started at a controlled temperature of 30℃. The time to form a mature biofilm was 18 days. The average nitrate removal rate was 97% in the first two weeks after biofilm formation, and the carrier weight reduction rate was 3% after two weeks.

[0112] Comparative Example 5

[0113] The same process as in Example 4 was used, with the only change being that in step two, the masses of magnetic amine cross-linked activated carbon, hydrophilic substance, biocompatible substance, biodegradable adhesive, and ultrapure water were 0.5 g, 0.6 g, 0.6 g, 4.2 g, and 5.2 g, respectively. The density of the denitrification functional carrier obtained in step three was 1.0 g / cm³. 3 .

[0114] The prepared denitrification functional carrier was loaded into a fixed-bed biofilm reactor to treat low-concentration nitrogen-containing wastewater. Artificially prepared low-concentration nitrate-containing water (nitrate concentration 52 mg / L) was pumped in from bottom to top. Denitrification sludge from a wastewater treatment plant was used as inoculum sludge. The biofilm formation was started at a controlled temperature of 30℃. The time to form a mature biofilm was 20 days. The average nitrate removal rate was 96% in the first two weeks after biofilm formation, and the carrier weight reduction rate was 2.8% after two weeks.

[0115] Comparative Example 6

[0116] The same process as in Example 4 was used, but the mass ratio of the polymer matrix, silane coupling agent, ethanol aqueous solution, and mixed adhesive was 100:5:8.

[0117] The prepared denitrification functional carrier was loaded into a fixed-bed biofilm reactor to treat low-concentration nitrogen-containing wastewater. Artificially prepared low-concentration nitrate-containing water (nitrate concentration 52 mg / L) was pumped in from bottom to top. Denitrification sludge from a wastewater treatment plant was used as inoculum sludge. The biofilm formation was started at a controlled temperature of 30℃. The time to form a mature biofilm was 17 days. The average nitrate removal rate was 96.5% in the first two weeks after biofilm formation, and the carrier weight reduction rate was 2.7% after two weeks.

[0118] Comparative Example 7

[0119] The same process as in Example 4 was used, but the mass ratio of the polymer matrix, silane coupling agent, ethanol aqueous solution, and mixed adhesive was 100:5:5.

[0120] The prepared denitrification functional carrier was loaded into a fixed-bed biofilm reactor to treat low-concentration nitrogen-containing wastewater. Artificially prepared low-concentration nitrate-containing water (nitrate concentration 52 mg / L) was pumped in from bottom to top. Denitrification sludge from a wastewater treatment plant was used as inoculum sludge. The biofilm formation was started at a controlled temperature of 30℃. The time to form a mature biofilm was 15 days. The average nitrate removal rate was 97% in the first two weeks after biofilm formation, and the carrier weight reduction rate was 2.3% after two weeks.

Claims

1. A denitrification functional carrier, characterized in that, The raw materials of the denitrification functional carrier contain a polymer matrix, an ethanol aqueous solution of silane coupling agent, and a mixed adhesive in a mass ratio of 100:(4.5-7):(10-13). The polymer matrix is ​​selected from at least one of polypropylene, polyethylene, polyvinyl chloride, and polyurethane; The mixed adhesive contains magnetic amine cross-linked activated carbon, hydrophilic substances, biocompatible substances, biodegradable adhesives, and water in a mass ratio of 1:(0.6-0.8):(0.6-0.8):(4-4.5):(5-5.5); The hydrophilic substance is selected from at least one of polyvinyl alcohol, agar, silica gel, and diatomaceous earth; The biocompatible substance is selected from at least one of starch, degummed bone meal, and oyster shell powder; The preparation steps of the magnetic amine crosslinked activated carbon include: Step (1) Activated carbon granules are crushed and sieved; Step (2) Activated carbon pretreatment: First, the activated carbon is pyrolyzed, then acid-washed, then washed with deionized water until neutral, and finally dried. Step (3) The pretreated activated carbon powder, FeCl3·6H2O and 4-8 wt% NaOH solution are mixed in a weight ratio and stirred at 75-85℃ for 4-8 hours to obtain a mixed solution; the weight ratio of activated carbon powder, FeCl3·6H2O and sodium hydroxide solution is 1:(3-4):(8-10). Step (4) Mix dimethylformamide, ethylenediamine, epichlorohydrin and triethylamine in volume ratio and add them to the mixed solution obtained in step (3); stir at 55-65℃ for 4-8h; after centrifugation, wash the product with deionized water and dry at 70-100℃ for 3-7h to obtain the magnetic amine crosslinked activated carbon; the volume ratio of dimethylformamide, ethylenediamine, epichlorohydrin and triethylamine is 1:(0.9-1.1):(1.2-1.4):(3.1-3.4).

2. The denitrification functional carrier according to claim 1, characterized in that, In step (1), the sieving is done through a 50-100 mesh sieve; And / or, in step (1), the pyrolysis is performed in a muffle furnace at 350–700°C for 8–13 hours; And / or, in step (2), the pickling is performed by activating the acid in 1-3 mol / L nitric acid at 60-85°C for 1-3 h; And / or, in step (2), the drying is performed at 70-100°C for 8-12 hours; And / or, in step (3), a mixed solution is obtained by stirring at 78-83°C for 5-7 hours; And / or, in step (4), stirring is carried out at 60-65°C for 5-7 hours; And / or, in step (4), drying is carried out at 70-85°C for 3-5 hours; And / or, the density of the denitrification functional carrier is 0.95–1.1 g / cm³. 3 ; And / or, the biodegradable adhesive is selected from at least one of carboxymethyl chitosan adhesive and modified starch adhesive; And / or, the shape of the polymer matrix may be selected from cyclic, saddle-shaped, Raschig ring, or hollow sphere; And / or, the silane coupling agent is of type KH550; And / or, the mass concentration of the silane coupling agent in the ethanol aqueous solution of the silane coupling agent is 2-10 g / L and / or, the mass concentration of ethanol in the ethanol aqueous solution of the silane coupling agent is 70%-80%.

3. The denitrification functional carrier according to claim 1, characterized in that, In step (1), the sieve is 60-80 mesh; And / or, in step (1), the pyrolysis is performed in a muffle furnace at 400-650°C for 9-11 hours; And / or, in step (2), the pickling is performed by activation with 1.5 to 2.5 mol / L nitric acid at 65 to 80°C for 1 to 1.8 hours; And / or, in step (2), the drying is performed at 75-90°C for 9-11 hours; And / or, the density of the denitrification functional carrier is 0.98–1.05 g / cm³. 3 .

4. The denitrification functional carrier according to claim 2, characterized in that, The mass concentration of the silane coupling agent in the ethanol aqueous solution is 4–8 g / L.

5. The method for preparing the denitrification functional carrier according to any one of claims 1-4, characterized in that, The method includes the following steps: S1 Pretreatment of the polymer matrix: The polymer matrix is ​​immersed in an ethanol-water solution of silane coupling agent; S2. The magnetic amine cross-linked activated carbon, hydrophilic substances, biocompatible substances, biodegradable adhesives and water are mixed to obtain a mixed adhesive paste; S3. The pretreated polymer matrix is ​​immersed in the mixed slurry for 3 to 6 hours; after removal, it is dried to form a dense layer of mixed slurry on the surface of the matrix, thus obtaining the denitrification functional carrier.

6. The preparation method according to claim 5, characterized in that, In S1, the pretreatment time is 1 to 3 hours.

7. The preparation method according to claim 5, characterized in that, In S1, the pretreatment time is 2 to 3 hours.

8. The preparation method according to claim 5, characterized in that, In step S2, a mixed mortar is obtained by stirring at 60–120 r / min for 1 hour.

9. The preparation method according to claim 5, characterized in that, In step S2, a mixed mortar is obtained by stirring at 70–100 r / min for 1 hour.

10. The preparation method according to claim 5, characterized in that, In step S3, the drying temperature is 60–80°C and the drying time is 1–3 hours.

11. The preparation method according to claim 5, characterized in that, In step S3, the drying temperature is 70–80°C and the drying time is 2–3 hours.

12. The application of the denitrification functional carrier according to any one of claims 1-4 or the denitrification functional carrier obtained by the preparation method according to any one of claims 5-11 in the treatment of nitrate nitrogen wastewater.

13. The application according to claim 12, characterized in that, The concentration of nitrate ions in the nitrate nitrogen wastewater is 50 mg / L to 100 mg / L.