Graphene-based quinone mediator membrane as well as preparation method and application thereof

Abstract

The invention belongs to the field of water treatment, and particularly relates to a graphene-based quinone mediator membrane as well as a preparation method and application thereof. The graphene-based quinone mediator membrane comprises a membrane matrix, and graphene, amino imidazopyridine and humus which are dispersed in the membrane matrix, the membrane substrate is made of polyvinylidene fluoride / butadiene, the polyvinylidene fluoride / butadiene is a random copolymer of polyvinylidene fluoride and butadiene, and an anthraquinone modification unit is bonded on a butadiene structural unit of the random copolymer. The graphene-based quinone mediator membrane provided by the invention has very high initial denitrification rate and over-time denitrification rate.

Description

Technical Field

[0001] The present invention belongs to the field of water treatment, and in particular relates to a graphene-based quinone mediator membrane and a preparation method and application thereof. Background Art

[0002] In recent years, with the rapid development of industry and agriculture and the improvement of living standards, an increasing amount of nitrogen-containing domestic sewage, industrial wastewater, and farmland surface water has been discharged into natural water bodies. Nitrogen is vital to all biological substances. It is an essential element for proteins, nucleic acids, enzymes, denitrifying bacteria, nitrifying bacteria, and ammonifying bacteria. It is also indispensable for plant growth, photosynthesis, energy transfer, and fertilizer synthesis. However, excessive nitrogen released into water can damage aquatic ecosystems, leading to eutrophication of amphibian ecosystems, depletion of dissolved oxygen, and the death of fish and other marine life in the water, disrupting the ecological balance and posing a serious water pollution problem.

[0003] High concentrations of nitrate nitrogen pollution in water bodies not only cause serious harm to the natural environment, but also increasingly erode human health and safety. Various denitrification technologies are becoming more and more worthy of attention. At present, the main denitrification methods for the removal of nitrogen elements in nitrogen-containing wastewater can be divided into physical, chemical and biological methods. Among them, physical methods include physical treatment methods such as ion exchange, physical adsorption and membrane separation. Chemical methods include chemical precipitation and breakpoint chlorination. However, the cost and investment required for physical and chemical treatment processes are relatively expensive, and will cause secondary pollution, which requires further treatment. Among the biological denitrification methods, in addition to traditional biological denitrification methods, many new biological denitrification theories and new biological denitrification processes have emerged at home and abroad in recent years. The biological method converts organic nitrogen and ammonia nitrogen in sewage into NO through the action of microorganisms. 2- and NO 3- , and then through ammonification, nitrification and denitrification, it is finally converted into N2, thereby achieving the purpose of denitrification. Compared with physical and chemical methods, biological denitrification technology is more mature and makes up for the shortcomings and deficiencies of the two. It has the advantages of simple process operation and low operating costs. At the same time, it is environmentally friendly and does not cause secondary pollution. With the continuous deepening of research and application promotion at home and abroad, the traditional biological denitrification process has gradually upgraded its mechanism and developed into various new denitrification processes such as simultaneous nitrification and denitrification, short-range nitrification and denitrification, and anaerobic ammonia oxidation.

[0004] In traditional thinking, nitrification and denitrification cannot occur at the same time and must follow a certain order. However, after years of new research progress at home and abroad, this cognition has been broken, making it possible. Synchronous nitrification and denitrification technology (SND) involves a biological denitrification process in which nitrification and denitrification reactions occur simultaneously in space and time, directly converting ammonia nitrogen into nitrogen gas. Since the nitrification and denitrification processes are carried out simultaneously, the simultaneous nitrification and denitrification process significantly reduces the volume required for the reactor, saving floor space and energy. In addition, compared with traditional biological denitrification processes, this process has minimal demand for aeration and organic carbon, reducing sludge production by approximately 30%.

[0005] The key to the short-range nitrification and denitrification process is to regulate the nitrification process so that it stops at the nitrite stage. The basic principle is to control the reaction parameters to convert NH4 + -N is converted to NO2 - -N, and then denitrification reaction to NO2 - -N is directly reduced to N2. Compared with the traditional nitrification and denitrification process, this new biological denitrification technology greatly saves costs due to the shortened process flow, reduces aeration requirements by 25%, and reduces organic carbon source requirements by 40%. Studies have shown that controlling reaction temperature, pH value, dissolved oxygen (DO) concentration and sludge age can effectively regulate the growth conditions of ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB), thereby promoting NO2 - -N accumulation.

[0006] Anaerobic ammonium oxidation process refers to the use of NO2 - -N as electron acceptor, NH4 + -N acts as an electron donor for anaerobic ammonium oxidizing bacteria, promoting the production of NH4 + -N and NO2 - -N is directly converted into N2. Its reaction equation is as shown in formula (1-1). Therefore, anaerobic ammonium oxidation is very suitable for treating + -N and NO2 - -N wastewater. The living environment of anaerobic ammonium oxidizing bacteria requires strict anaerobic conditions, which helps to save energy by reducing the need for aeration. In addition, the anaerobic ammonium oxidation process operates as an autotrophic process and does not require an additional organic carbon source, making it particularly suitable for denitrification in low carbon-nitrogen ratio wastewater. Therefore, compared with traditional activated sludge systems, anaerobic ammonium oxidation has been classified as one of the more cost-effective and environmentally friendly systems, which consumes less oxygen for the denitrification process. However, the sensitivity of anaerobic ammonium oxidizing bacteria to changes in environmental conditions and their slow growth rate are the main problems limiting the application of anaerobic ammonium oxidation processes in large-scale wastewater treatment.

[0007] NH4 + +1.32NO2- +0.066HCO3 - +0.13H + →

[0008] 1.02N2+0.26NO3 - +0.066CH2O 0.5 N 0.15 +2.03H2O(1-1)

[0009] In recent years, redox mediators (RMs) have been widely used in the field of catalytic biotransformation due to their unique redox properties and biocompatibility. In particular, RMs containing quinones and carbonyl compounds have good redox capabilities. As an electron transfer mediator, RM can reduce the activation energy of the reaction and accelerate the transfer rate of electron transfer, thereby improving the reduction / oxidation rate of pollutants. It can also promote the biodegradation and transformation of target pollutants under low temperature conditions. It can play a catalytic enhancement role in the anaerobic biotransformation and degradation of pollutants such as azo dyes, nitroaromatic amines, polyhalogenated compounds, perchlorates, and heavy metals. However, RMs are basically water-soluble, and directly adding RMs to wastewater often leads to their loss with water and secondary pollution, which limits the practical application of mediator materials. In addition, RMs such as anthraquinone may be reduced or degraded during the denitrification process, causing them to easily lose catalytic activity. That is, the denitrification rate of RMs usually decreases with the extension of treatment time. Therefore, how to improve the initial denitrification rate and the denitrification rate over time of RMs has become a technical problem that needs to be solved urgently. Summary of the Invention

[0010] The first purpose of the present invention is to provide a new graphene-based quinone mediator membrane (AQ-G / PVDF) mediator membrane, which has a high denitrification efficiency and the denitrification efficiency can still be maintained at a high level after a period of use, that is, it has a high initial denitrification rate and a time-dependent denitrification rate.

[0011] A second object of the present invention is to provide a method for preparing the graphene-based quinone mediator film.

[0012] The third object of the present invention is to provide an application of the graphene-based quinone mediator membrane in wastewater denitrification.

[0013] The graphene-based quinone mediator film provided by the present invention includes a membrane matrix and graphene, aminoimidazopyridine and humus dispersed in the membrane matrix; the material of the membrane matrix is ​​polyvinylidene fluoride / butadiene, and the polyvinylidene fluoride / butadiene is a random copolymer of vinylidene fluoride and butadiene, and the butadiene structural unit of the random copolymer is bonded to an anthraquinone modification unit.

[0014] The preparation method of the graphene-based quinone mediator film provided by the present invention comprises:

[0015] S1. The vinylidene fluoride and butadiene are subjected to a free radical polymerization reaction in the presence of a free radical initiator to obtain a prepolymer;

[0016] S2. The prepolymer is subjected to an addition reaction with mercaptoanthraquinone to obtain polyvinylidene fluoride / butadiene;

[0017] S3. dissolving graphene, aminoimidazole pyridine and humus in an organic solvent, uniformly mixing the obtained solution with glutaraldehyde, uniformly mixing the obtained mixture with polyvinylidene fluoride / butadiene and degassing, then placing the obtained casting solution on a substrate and leveling it with a scraper and immersing it in pure water to solidify into a film, thereby obtaining the graphene-based quinone mediator film.

[0018] Anthraquinone, as an electron transfer mediator, can increase the reduction / oxidation rate of pollutants, promoting denitrification primarily through the action of electron shuttles and redox mediators. Graphene (G) has a good adsorption effect on organic pollutants and can enhance the extracellular electron transfer capacity of anaerobic microorganisms, achieving denitrification primarily through adsorption and catalysis. In other words, anthraquinone and graphene achieve denitrification via two different pathways, and their combined use can unleash their denitrification activity. However, on the one hand, anthraquinone is easily lost with water and is easily reduced and degraded, losing its catalytic activity. This results in a decrease in the denitrification rate during wastewater treatment as treatment time increases. On the other hand, graphene can inhibit the activity of denitrifying microorganisms (such as ammonia-oxidizing bacteria (AOB) and denitrifying bacteria), which play a key role in the denitrification process. This change in community structure can adversely affect the denitrification process and hinder the improvement of denitrification efficiency. In other words, although anthraquinone and graphene can achieve synergistic denitrification through two pathways, the denitrification rates of both will decrease with the extension of treatment time, that is, the denitrification rate will decrease over time.

[0019] On this basis, the inventors of the present invention modified the mediator membrane, using a random copolymer of vinylidene fluoride and butadiene as the membrane matrix, and bonding anthraquinone modification units to the membrane matrix. On this basis, graphene was added to the membrane matrix, and aminoimidazole pyridine and humus were additionally added. The resulting graphene-based quinone mediator membrane has a very high initial denitrification rate and time-dependent denitrification rate. The reasons are speculated to be: on the one hand, chemically bonding anthraquinone to the membrane carrier can effectively reduce the problem of anthraquinone being lost with the effluent during the denitrification process, thereby improving the time-dependent denitrification rate. In addition, using a random copolymer of vinylidene fluoride and butadiene as a carrier and bonding anthraquinone to the butadiene structural unit, multiple anthraquinone molecules can be bonded to each copolymer molecular chain, thereby making anthraquinone evenly distributed on the entire side chain of the random copolymer, giving the graphene-based quinone mediator membrane good denitrification ability; on the other hand, the combined addition of aminoimidazole pyridine and humus can not only improve the chemical stability of anthraquinone, making it less likely to degrade and transform, but also inhibit the adverse effects of graphene on the activity of denitrifying microorganisms, improve the composition and structure of the microbial community, and increase the abundance of microorganisms with denitrification function, thereby significantly improving the time-dependent denitrification rate of the resulting graphene-based quinone mediator membrane. DETAILED DESCRIPTION

[0020] The graphene-based quinone mediator film provided by the present invention includes a film matrix and graphene, aminoimidazopyridine and humus dispersed in the film matrix. Wherein, the mass ratio of the film matrix, graphene, aminoimidazopyridine and humus is preferably 100:(10-20):(5-10):(2-10), at which time each substance can play a better synergistic role, which is more conducive to the improvement of the initial denitrification rate and the denitrification rate over time. Specifically, based on the content of the film matrix as 100 parts by weight, the content of the graphene is preferably 10-20 parts by weight, such as 10, 12, 14, 16, 18, 20 parts by weight or any value therebetween; the content of the aminoimidazopyridine is preferably 5-10 parts by weight, such as 5, 6, 7, 8, 9, 10 parts by weight or any value therebetween; the content of the humus is preferably 2-10 parts by weight, such as 2, 4, 6, 8, 10 parts by weight or any value therebetween.

[0021] In the present invention, the material of the membrane substrate is polyvinylidene fluoride / butadiene, which is a random copolymer of vinylidene fluoride and butadiene, and an anthraquinone modification unit is bonded to the butadiene structural unit of the random copolymer.

[0022] In the present invention, the polyvinylidene fluoride / butadiene can be obtained commercially or prepared according to various existing methods. In a preferred embodiment, the polyvinylidene fluoride / butadiene is prepared according to the following method: S1. vinylidene fluoride and butadiene are subjected to a free radical polymerization reaction in the presence of a free radical initiator to obtain a prepolymer; S2. the prepolymer is subjected to an addition reaction with mercaptoanthraquinone to obtain polyvinylidene fluoride / butadiene. Wherein, the molar ratio of the vinylidene fluoride to butadiene is preferably 1:(0.2-0.6), such as 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, 1:0.55, 1:0.6 or any value therebetween. From the perspective of the availability of raw materials, the mercaptoanthraquinone is particularly preferably 1-amino-5-mercaptoanthraquinone. The molar ratio of the mercaptoanthraquinone to butadiene is preferably (0.8-1.2):1, such as 0.8:1, 0.82:1, 0.85:1, 0.88:1, 0.9:1, 0.92:1, 0.95:1, 0.98:1, 1:1, 1.02:1, 1.05:1, 1.08:1, 1.1:1, 1.12:1, 1.15:1, 1.18:1, 1.2:1 or any value therebetween. The conditions for the free radical polymerization reaction preferably include a temperature of 50 to 90° C., such as 50° C., 55° C., 60° C., 65° C., 70° C., 75° C., 80° C., 85° C., 90° C. or any value therebetween; a pressure of 0.05 to 1 MPa, such as 0.05 MPa, 0.1 MPa, 0.2 MPa, 0.4 MPa, 0.6 MPa, 0.8 MPa, 1 MPa or any value therebetween; and a time of 0.5 to 10 h, such as 0.5 h, 1 h, 2 h, 4 h, 6 h, 8 h, 10 h or any value therebetween. The conditions of the addition reaction preferably include a temperature of 70 to 90° C., 70° C., 75° C., 80° C., 85° C., 90° C., or any value therebetween; a pressure of 0.01 to 1 MPa, such as 0.01 MPa, 0.05 MPa, 0.1 MPa, 0.2 MPa, 0.4 MPa, 0.6 MPa, 0.8 MPa, 1 MPa, or any value therebetween; and a time of 0.1 to 24 h, such as 0.1 h, 0.5 h, 1 h, 2 h, 4 h, 6 h, 8 h, 10 h, 12 h, 15 h, 18 h, 20 h, 22 h, 24 h, or any value therebetween. In the present invention, the pressure refers to gauge pressure.

[0023] In the present invention, the aminoimidazopyridine is particularly preferably 6-aminoimidazo[1,2-A]pyridine, which has the structure of formula (1).

[0024]

[0025] The preparation method of the graphene-based quinone mediator film provided by the present invention comprises:

[0026] S1. The vinylidene fluoride and butadiene are subjected to a free radical polymerization reaction in the presence of a free radical initiator to obtain a prepolymer;

[0027] S2. The prepolymer is subjected to an addition reaction with mercaptoanthraquinone to obtain polyvinylidene fluoride / butadiene;

[0028] S3. dissolving graphene, aminoimidazole pyridine and humus in an organic solvent, uniformly mixing the obtained solution with glutaraldehyde, uniformly mixing the obtained mixture with polyvinylidene fluoride / butadiene and degassing, then placing the obtained casting solution on a substrate and leveling it with a scraper and immersing it in pure water to solidify into a film, thereby obtaining the graphene-based quinone mediator film.

[0029] In the preparation process of the above-mentioned graphene-based quinone mediator film, in step S1, the molar ratio of the vinylidene fluoride to butadiene is preferably 1:(0.2~0.6), such as 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, 1:0.55, 1:0.6 or any value therebetween.

[0030] In the preparation process of the above-mentioned graphene-based quinone mediator film, in step S1, the free radical initiator can be at least one of an azo initiator, a peroxide initiator and a redox initiator. Wherein, the azo initiator can be enumerated as at least one of dimethyl azobisisobutyrate, azobisisobutyramidine hydrochloride, azodicarbonamide, azobisisopropylimidazoline hydrochloride, azoisobutylcyanoformamide, azobiscyclohexylcarbonitrile, azobiscyanovaleric acid, azobisisopropylimidazoline, azobisisobutyronitrile, azobisisovaleronitrile and azobisisoheptonitrile. The peroxide initiator can be enumerated as at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, benzoyl peroxide and tert-butyl peroxide. The redox initiator can be enumerated as at least one of sulfate-sulfite, persulfate-thiourea, persulfate-organic salt and ammonium persulfate-fatty amine. The sulfate-sulfite can be selected from at least one of sodium sulfate-sodium sulfite, potassium sulfate-potassium sulfite and ammonium sulfate-ammonium sulfite; the persulfate-thiourea can be selected from at least one of sodium persulfate-thiourea, potassium persulfate-thiourea and ammonium persulfate-thiourea; the persulfate-organic salt can be selected from at least one of sodium persulfate-potassium acetate, potassium persulfate-potassium acetate and ammonium persulfate-ammonium acetate; the ammonium persulfate-fatty amine can be ammonium persulfate-N,N-tetramethylethylenediamine and / or ammonium persulfate-diethylamine.

[0031] In the preparation process of the above-mentioned graphene-based quinone mediator film, in step S2, the molar ratio of the mercaptoanthraquinone to butadiene is preferably (0.8-1.2):1, such as 0.8:1, 0.82:1, 0.85:1, 0.88:1, 0.9:1, 0.92:1, 0.95:1, 0.98:1, 1:1, 1.02:1, 1.05:1, 1.08:1, 1.1:1, 1.12:1, 1.15:1, 1.18:1, 1.2:1 or any value therebetween.

[0032] In the preparation process of the above-mentioned graphene-based quinone mediator film, in step S3, the mass ratio of the polyvinylidene fluoride / butadiene, graphene, aminoimidazopyridine and humic substance is preferably 100:(10-20):(5-10):(2-10). Specifically, based on 100 parts by weight of polyvinylidene fluoride / butadiene, the content of the graphene is preferably 10-20 parts by weight, such as 10, 12, 14, 16, 18, 20 parts by weight or any value therebetween; the content of the aminoimidazopyridine is preferably 5-10 parts by weight, such as 5, 6, 7, 8, 9, 10 parts by weight or any value therebetween; and the content of the humic substance is preferably 2-10 parts by weight, such as 2, 4, 6, 8, 10 parts by weight or any value therebetween. In addition, the mass ratio of glutaraldehyde to polyvinylidene fluoride / butadiene is preferably (1-5):100, such as 1:100, 2:100, 3:100, 4:100, 5:100 or any value therebetween.

[0033] In the preparation process of the above-mentioned graphene-based quinone mediator film, the conditions of the free radical polymerization reaction preferably include a temperature of 50 to 90°C, such as 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C or any value therebetween; a pressure of 0.05 to 1MPa, such as 0.05MPa, 0.1MPa, 0.2MPa, 0.4MPa, 0.6MPa, 0.8MPa, 1MPa or any value therebetween; and a time of 0.5 to 10h, such as 0.5h, 1h, 2h, 4h, 6h, 8h, 10h or any value therebetween.

[0034] In the preparation process of the above-mentioned graphene-based quinone mediator film, the conditions of the addition reaction preferably include a temperature of 70-90°C, 70°C, 75°C, 80°C, 85°C, 90°C or any value therebetween; a pressure of 0.01-1MPa, such as 0.01MPa, 0.05MPa, 0.1MPa, 0.2MPa, 0.4MPa, 0.6MPa, 0.8MPa, 1MPa or any value therebetween; and a time of 0.1-24h, such as 0.1h, 0.5h, 1h, 2h, 4h, 6h, 8h, 10h, 12h, 15h, 18h, 20h, 22h, 24h or any value therebetween.

[0035] The present invention also provides a graphene-based quinone mediator film prepared by the above method.

[0036] In addition, the present invention also provides application of the graphene-based quinone mediator membrane in wastewater denitrification.

[0037] The present invention will be described in detail below through examples.

[0038] In the following test example:

[0039] (1) BTB (bromothymol blue) medium: KNO3 1.0 g, agar 20 g, KH2PO4 1.0 g, FeCl2·6H2O 0.5 g, CaCl2·7H2O 0.2 g, MgSO4·7H2O 1.0 g, sodium succinate 8.5 g, BTB (1% dissolved in alcohol) 1 mL, distilled water 1000 mL, pH = 7.2.

[0040] (2) Denitrification medium: KNO3 0.7218 g, sodium succinate 2.2 g, MgSO4·7H2O 0.2 g, K2HPO4 0.5 g, distilled water 1000 mL, pH = 7.2.

[0041] (3) LB medium: 25 g LB broth, 1000 mL distilled water, pH = 7.2.

[0042] (4) Determination of nitrate nitrogen: Nitrate nitrogen (NO3 - -N) concentration. Specifically, by quantitative determination of NO3 - The absorbance at a wavelength of 220 nm was used to monitor NO3 - -N concentration, soluble organic matter has absorption at wavelengths of 220nm and 275nm, while NO3 - There is no absorption at a wavelength of 275nm, so another measurement is made at a wavelength of 275nm to correct for NO3 - -N concentration. The detection limit of this method is 0.08-4 mg / L. The specific operation steps are as follows:

[0043] ① Take an appropriate amount of water sample and transfer it to a 50mL colorimetric tube. Dilute it appropriately according to the detection range and make up to 50mL with distilled water. If the water sample is colored or turbid, add a 10% suspension of zinc sulfate and aluminum hydroxide to flocculate the sample and then centrifuge or take the supernatant.

[0044] ② Add 1 mL of 1 mol / L hydrochloric acid and 0.8% aminosulfonic acid into the colorimetric tube, then mix and shake well;

[0045] ③ Add 1 mL of hydrochloric acid (1 mol / L) and 0.1 mL of aminosulfonic acid (0.8%) to 50 mL of distilled water as a blank reference. Measure the absorbance at wavelengths of 220 nm and 275 nm using a 10 mm quartz cuvette.

[0046] ④ Determine NO3 according to the above steps - -N concentrations of 0.25 mg / L, 0.5 mg / L, 1 mg / L, 1.5 mg / L, and 2 mg / L at wavelengths of 220 nm and 275 nm;

[0047] ⑤NO3 - The calculation formula (1) of -N content is as follows:

[0048] A 校 =A 220 -2A 275 (1)

[0049] ⑥ NO3 in the water sample tested - The concentration of -N was compared with the standard curve (y = 0.2509x + 0.0006, x is NO3 - -N concentration (mg / L, y is absorbance) to calculate.

[0050] Example 1 Graphene-based quinone mediator film and preparation method thereof

[0051] S1. 2 L of N, N-dimethylacetamide solution and 1.1 g of tetrahydrofurfuryl alcohol ether were added to an autoclave, nitrogen was introduced into the autoclave to reduce the oxygen content to below 20 ppm, and then vinylidene fluoride (VDF) and butadiene were continuously introduced into the autoclave in a molar ratio of 1:0.6. The temperature in the autoclave was then raised to 50 ° C., 1.1 mmol of n-butyl lithium was added, and the pressure was controlled at 1 MPa to initiate the reaction for 2 h to obtain a solution containing a prepolymer;

[0052] S2. To the solution containing the prepolymer obtained in step S1, 1-amino-5-mercaptoanthraquinone was added, and the amount of 1-amino-5-mercaptoanthraquinone was controlled to 0.8 times the molar amount of butadiene used in step S1. After heating to 70° C., 6.7 g of azobisisobutyronitrile was added and the pressure was controlled at 1 MPa to initiate the reaction for 24 hours to obtain a solution containing polyvinylidene fluoride / butadiene;

[0053] S3. Graphene, 6-aminoimidazo[1,2-A]pyridine, and humic acid were dissolved in an N,N-dimethylacetamide solution, the resulting solution was mixed uniformly with glutaraldehyde, and the resulting mixture was mixed uniformly with a solution containing polyvinylidene fluoride / butadiene and then degassed. The mass ratio of polyvinylidene fluoride / butadiene, graphene, aminoimidazopyridine, humic acid, and glutaraldehyde was 100:15:8:6:3, resulting in a casting solution with a solid content of 18.2 wt%. The casting solution was poured onto a clean glass plate and smoothed with a 5 mm clean spatula. The plate was then immersed in a pure water coagulation bath for 24 h to solidify into a film. The cured film was rinsed with deionized water to remove any residual solvent, resulting in a graphene-based quinone mediator film, designated M1.

[0054] Example 2 Graphene-based quinone mediator film and preparation method thereof

[0055] S1. 2L N, N-dimethylacetamide solution and 1.1g tetrahydrofurfuryl alcohol ether were added to an autoclave, nitrogen was introduced into the autoclave to reduce the oxygen content to below 20ppm, and then vinylidene fluoride (VDF) and butadiene were continuously introduced into the autoclave in a molar ratio of 1:0.2. After the temperature in the autoclave was raised to 90°C, 1.1mmol of n-butyl lithium was added and the reaction was initiated at a pressure of 0.1MPa for 10h to obtain a solution containing a prepolymer;

[0056] S2. To the prepolymer solution obtained in step S1, 1-amino-5-mercaptoanthraquinone was added, and the amount of 1-amino-5-mercaptoanthraquinone was controlled to be 1.2 times the molar amount of butadiene used in step S1. After heating to 90° C., 6.7 g of azobisisobutyronitrile was added and the pressure was controlled at 0.1 MPa to initiate the reaction for 1 hour to obtain a solution containing polyvinylidene fluoride / butadiene;

[0057] S3. Graphene, 6-aminoimidazo[1,2-A]pyridine, and humic acid were dissolved in an N,N-dimethylacetamide solution, the resulting solution was mixed uniformly with glutaraldehyde, and the resulting mixture was mixed uniformly with a solution containing polyvinylidene fluoride / butadiene, followed by degassing. The mass ratio of polyvinylidene fluoride / butadiene, graphene, aminoimidazopyridine, humic acid, and glutaraldehyde was 100:10:5:2:1, resulting in a casting solution with a solid content of 16.5 wt%. The casting solution was poured onto a clean glass plate and smoothed with a 5 mm clean spatula. The plate was then immersed in a pure water coagulation bath for 24 h to solidify into a film. The cured film was rinsed with deionized water to remove any residual solvent, resulting in a graphene-based quinone mediator film, designated M2.

[0058] Example 3 Graphene-based quinone mediator film and preparation method thereof

[0059] S1. 2 L of N, N-dimethylacetamide solution and 1.1 g of tetrahydrofurfuryl alcohol ether were added to an autoclave, nitrogen was introduced into the autoclave to reduce the oxygen content to below 20 ppm, and then vinylidene fluoride (VDF) and butadiene were continuously introduced into the autoclave in a molar ratio of 1:0.4. The temperature in the autoclave was then raised to 70 ° C., 1.1 mmol of n-butyl lithium was added, and the reaction was initiated at a pressure of 0.6 MPa for 0.5 h to obtain a solution containing a prepolymer;

[0060] S2. Add 1-amino-5-mercaptoanthraquinone to the prepolymer solution obtained in step S1, and control the amount of 1-amino-5-mercaptoanthraquinone to be 1 times the molar amount of butadiene used in step S1. Then, heat to 70° C., add 6.7 g of azobisisobutyronitrile, and control the pressure at 0.6 MPa to initiate the reaction for 5 hours to obtain a solution containing polyvinylidene fluoride / butadiene;

[0061] S3. Graphene, 6-aminoimidazo[1,2-A]pyridine, and humic acid were dissolved in an N,N-dimethylacetamide solution, the resulting solution was mixed uniformly with glutaraldehyde, and the resulting mixture was mixed uniformly with a solution containing polyvinylidene fluoride / butadiene, followed by degassing. The mass ratio of polyvinylidene fluoride / butadiene, graphene, aminoimidazopyridine, humic acid, and glutaraldehyde was 100:20:10:10:5, resulting in a casting solution with a solid content of 20.6 wt%. The casting solution was poured onto a clean glass plate and smoothed with a 5 mm clean spatula. The plate was then immersed in a pure water coagulation bath for 24 h to solidify into a film. The cured film was rinsed with deionized water to remove any residual solvent, resulting in a graphene-based quinone mediator film, designated M3.

[0062] Comparative Example 1 Reference graphene-based quinone mediator film and its preparation method

[0063] The mediator membrane was prepared according to the method of Example 1, except that graphene, 6-aminoimidazo[1,2-A]pyridine and humic substances were not added to the casting solution. The other conditions were the same as those of Example 1. The specific steps were as follows:

[0064] S1. Same as Example 1;

[0065] S2. Same as Example 1;

[0066] S3. Glutaraldehyde was dissolved in N,N-dimethylacetamide solution. The resulting solution was mixed evenly with a solution containing polyvinylidene fluoride / butadiene and then degassed. The mass ratio of polyvinylidene fluoride / butadiene to glutaraldehyde was 100:3, resulting in a casting solution with a solid content of 18.2 wt%. The casting solution was poured onto a clean glass plate and smoothed with a clean 5 mm spatula. The plate was then immersed in a pure water coagulation bath for 24 hours to solidify into a film. The cured film was rinsed with deionized water to remove any residual solvent, yielding a quinone mediator membrane, designated DM1.

[0067] Comparative Example 2 Reference Graphene-based Quinone Mediator Film and Preparation Method

[0068] A graphene-based quinone mediator film was prepared according to the method of Example 1, except that 6-aminoimidazo[1,2-A]pyridine was replaced by graphene in the same amount by weight. The other conditions were the same as those of Example 1, and a reference graphene-based quinone mediator film was obtained, which was recorded as DM2.

[0069] Comparative Example 3 Reference Graphene-based Quinone Mediator Film and Preparation Method

[0070] A graphene-based quinone mediator film was prepared according to the method of Example 1, except that the humus was replaced by the same weight of graphene. The other conditions were the same as in Example 1, and a reference graphene-based quinone mediator film was obtained, which was recorded as DM3.

[0071] Comparative Example 4 Reference Graphene-based Quinone Mediator Film and Preparation Method Thereof

[0072] A graphene-based quinone mediator film was prepared according to the method of Example 1, except that no butadiene was added during the preparation of the carrier, and 1-amino-5-mercaptoanthraquinone was not bonded to the carrier by an addition reaction, but was directly added to the casting solution. The remaining conditions were the same as those of Example 1, and the specific steps were as follows:

[0073] S1. 2 L of N, N-dimethylacetamide solution and 1.1 g of tetrahydrofurfuryl alcohol ethyl ether were added to an autoclave, and nitrogen was introduced into the autoclave to reduce the oxygen content to below 20 ppm. Vinylidene fluoride (VDF) was then continuously introduced into the autoclave. The temperature of the autoclave was raised to 50° C., 1.1 mmol of n-butyl lithium was added, and the reaction was initiated at a pressure of 1 MPa for 2 h to obtain a solution containing polyvinylidene fluoride.

[0074] S3. Graphene, 6-aminoimidazo[1,2-A]pyridine, humic acid, and 1-amino-5-mercaptoanthraquinone were dissolved in an N,N-dimethylacetamide solution, and the resulting solution was mixed evenly with glutaraldehyde. The resulting mixture was mixed evenly with a solution containing polyvinylidene fluoride and then degassed. The mass ratio of polyvinylidene fluoride, graphene, aminoimidazopyridine, humic acid, and glutaraldehyde was 100:15:8:6:3, and the molar ratio of vinylidene fluoride consumed in the polyvinylidene fluoride production process to 1-amino-5-mercaptoanthraquinone was 1:0.48, resulting in a casting solution with a solid content of 18.2 wt%. The casting solution was poured onto a clean glass plate and smoothed with a 5 mm clean scraper. The plate was then immersed in a pure water coagulation bath for 24 h to solidify into a film. The cured film was washed with deionized water to remove the residual solvent to obtain a graphene-based quinone mediator film, designated as DM4.

[0075] Test Case

[0076] 2 g of activated sludge from the biochemical treatment pool of a sewage plant in Longyan was added to the sterilized LB culture medium. The culture medium was sealed with a sealing film and placed in a shaker at 36°C and 120 r / min for 48 hours. 10 mL of the obtained culture medium was added to new LB culture medium. The obtained culture medium was then spread and streaked on BTB culture medium, and then placed in a constant temperature incubator at 36°C for 2 days. High-efficiency nitrogen-degrading strains were selected and stored at -20°C.

[0077] The mediator membranes obtained in the above embodiments and comparative examples were respectively placed in 1000 mL serum bottles, and the serum bottles were filled with the water sample to be treated. Then, the screened efficient nitrogen degradation strains were inoculated into LB culture medium according to the above method, and activated in a shaker at 36°C and 120 r / min for 48 hours. The activated strains were inoculated into liquid denitrification culture medium (initial concentration was 100 mg / L) with an inoculum size of 3%, and then added to the serum bottle. The serum bottle was placed in a shaker at 36°C and 120 r / min and cultured for 24 hours. Samples were taken at regular intervals and quantitatively diluted according to the detection range, and then the NO3 in the diluted water sample was determined using an ultraviolet spectrophotometer. - -N absorbance value, substitute NO3 - -N standard curve (y=0.2509x+0.0006, x is NO3 - -N concentration (mg / L), y is absorbance) to obtain the concentration and draw the degradation curve. The calculation formula (2) of denitrification rate is as follows:

[0078]

[0079] Where A0 is the initial nitrate nitrogen concentration (mg / L); A tis the nitrate nitrogen concentration after time t (mg / L); r is the denitrification rate (%). The results are shown in Table 1.

[0080] Ten batches of water samples were treated using the graphene-based quinone mediator membrane cycle as described above. Each batch was treated continuously for six days. The denitrification rates for the first and tenth batches of water samples after 24 hours of treatment were calculated using the same method. The results are shown in Table 1.

[0081] Table 1

[0082]

[0083] It can be seen from the above results that the graphene-based quinone mediator film provided by the present invention has a very high initial denitrification rate and a high denitrification rate over time.

[0084] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. A graphene-based quinone mediator film, characterized in that The graphene-based quinone mediator film includes a membrane matrix and graphene, aminoimidazopyridine and humus dispersed in the membrane matrix; the material of the membrane matrix is ​​polyvinylidene fluoride / butadiene, and the polyvinylidene fluoride / butadiene is a random copolymer of vinylidene fluoride and butadiene, and the butadiene structural unit of the random copolymer is bonded to an anthraquinone modification unit.

2. The graphene-based quinone mediator film according to claim 1, characterized in that The mass ratio of the membrane matrix, graphene, aminoimidazopyridine and humus is 100:(10-20):(5-10):(2-10).

3. The graphene-based quinone mediator film according to claim 1, characterized in that The polyvinylidene fluoride / butadiene is prepared according to the following method: S1. The vinylidene fluoride and butadiene are subjected to a free radical polymerization reaction in the presence of a free radical initiator to obtain a prepolymer; S2. The prepolymer is subjected to an addition reaction with mercaptoanthraquinone to obtain polyvinylidene fluoride / butadiene.

4. The graphene-based quinone mediator film according to claim 3, characterized in that The molar ratio of vinylidene fluoride to butadiene is 1:(0.2-0.6); Preferably, the mercaptoanthraquinone is 1-amino-5-mercaptoanthraquinone; Preferably, the molar ratio of mercaptoanthraquinone to butadiene is (0.8-1.2):1; Preferably, the conditions of the free radical polymerization reaction include a temperature of 50 to 90° C., a pressure of 0.05 to 1 MPa, and a time of 0.5 to 10 h; Preferably, the conditions for the addition reaction include a temperature of 70 to 90° C., a pressure of 0.01 to 1 MPa, and a time of 0.1 to 24 h.

5. The graphene-based quinone mediator film according to claim 1, characterized in that The aminoimidazopyridine is 6-aminoimidazo[1,2-A]pyridine.

6. A method for preparing a graphene-based quinone mediator film, characterized in that: The method includes: S1. The vinylidene fluoride and butadiene are subjected to a free radical polymerization reaction in the presence of a free radical initiator to obtain a prepolymer; S2. The prepolymer is subjected to an addition reaction with mercaptoanthraquinone to obtain polyvinylidene fluoride / butadiene; S3. dissolving graphene, aminoimidazole pyridine and humus in an organic solvent, uniformly mixing the obtained solution with glutaraldehyde, uniformly mixing the obtained mixture with polyvinylidene fluoride / butadiene and degassing, then placing the obtained casting solution on a substrate and leveling it with a scraper and immersing it in pure water to solidify into a film, thereby obtaining the graphene-based quinone mediator film.

7. The method for preparing a graphene-based quinone mediator film according to claim 6, wherein: The molar ratio of the vinylidene fluoride to butadiene is 1:(0.2-0.6); the molar ratio of the mercaptoanthraquinone to butadiene is (0.8-1.2):1; the mass ratio of the polyvinylidene fluoride / butadiene, graphene, aminoimidazopyridine and humus is 100:(10-20):(5-10):(2-10); the mass ratio of the glutaraldehyde to polyvinylidene fluoride / butadiene is (1-5):

100.

8. The method for preparing a graphene-based quinone mediator film according to claim 6, wherein: The conditions of the free radical polymerization reaction include a temperature of 50 to 90° C., a pressure of 0.05 to 1 MPa, and a time of 0.5 to 10 h; The conditions of the addition reaction include a temperature of 70 to 90° C., a pressure of 0.01 to 1 MPa, and a time of 0.1 to 24 hours.

9. A graphene-based quinone mediator film prepared by the method according to any one of claims 6 to 8.

10. Use of the graphene-based quinone mediator membrane according to any one of claims 1 to 5 and 9 in wastewater denitrification.

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