Anthraquinone / reductive graphene oxide mediator membrane as well as preparation method and application thereof

Abstract

The invention belongs to the field of water treatment, and particularly relates to an anthraquinone / reductive graphene oxide mediator membrane as well as a preparation method and application thereof. The anthraquinone / reductive graphene oxide mediator membrane comprises a membrane matrix and amino imidazopyridine modified reductive graphene oxide dispersed in the membrane matrix; the membrane substrate is made of a compound of polyamide and anthraquinone modified polysiloxane; the amino imidazopyridine modified reductive graphene oxide is reductive graphene oxide of which the surface is bonded with a 6-amino imidazopyridine [1, 2-A] pyridine modification unit. The anthraquinone / reductive graphene oxide mediator membrane provided by the invention has very high initial denitrification rate and over-time denitrification rate.

Description

Technical Field

[0001] This invention belongs to the field of water treatment, specifically relating to an anthraquinone / reduced graphene oxide mediator membrane, its preparation method, and its application. Background Technology

[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 essential for all living matter; it is an essential element for proteins, nucleic acids, enzymes, denitrifying bacteria, nitrifying bacteria, and ammonifying bacteria, and is indispensable for plant growth, photosynthesis, energy transfer, and fertilizer synthesis. However, excessive nitrogen release into water damages aquatic ecosystems, leading to eutrophication of amphibian systems, depletion of dissolved oxygen, and the death of fish and other marine life, disrupting the ecological balance and thus 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, making various denitrification technologies increasingly important. Currently, the main denitrification methods for nitrogen removal from nitrogen-containing wastewater can be divided into physical, chemical, and biological methods. Physical methods include ion exchange, physical adsorption, and membrane separation. Chemical methods include chemical precipitation and breakpoint chlorination. However, physical and chemical treatment processes are relatively expensive and can cause secondary pollution, requiring further treatment. In biological denitrification methods, in addition to traditional biological methods, many new biological denitrification theories and processes have emerged both domestically and internationally in recent years. Biological methods use microorganisms to convert organic nitrogen and ammonia nitrogen in wastewater into NO. 2- and NO 3- Then, through ammoniation, nitrification, and denitrification, it is ultimately converted into N2, thus achieving the purpose of nitrogen removal. Compared with physical and chemical methods, biological nitrogen removal 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 cost, while being environmentally friendly and not causing secondary pollution. With the continuous deepening of research and application promotion at home and abroad, traditional biological nitrogen removal processes have gradually been upgraded and developed into various new nitrogen removal processes such as simultaneous nitrification and denitrification, short-cut nitrification and denitrification, and anaerobic ammonium oxidation.

[0004] Traditionally, nitrification and denitrification are thought to occur sequentially, not simultaneously. However, recent research advancements both domestically and internationally have overturned this notion, making simultaneous nitrification and denitrification (SND) a possibility. SND involves a biological nitrogen removal process where nitrification and denitrification reactions occur simultaneously in space and time, directly converting ammonia nitrogen into nitrogen gas. Because the two processes occur concurrently, SND significantly reduces the required reactor volume, saving space and energy. Furthermore, compared to traditional biological nitrogen removal processes, this technology requires minimal aeration and organic carbon, resulting in approximately a 30% reduction in sludge production.

[0005] The key to short-cut nitrification-denitrification processes lies in regulating the nitrification process to stop it at the nitrite stage. The basic principle is to control the reaction parameters to reduce NH4+. + -N is converted to NO2 - -N, and then undergo denitrification to remove NO2 - -N is directly reduced to N2. Compared with traditional nitrification-denitrification processes, this novel biological nitrogen removal technology significantly reduces costs due to its shorter process flow, decreasing aeration requirements by 25% and organic carbon source requirements by 40%. Studies have shown that controlling reaction temperature, pH, 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 production. - Accumulation of -N.

[0006] Anaerobic ammonia oxidation refers to the process of oxidizing nitrogen under strictly anaerobic conditions using NO2. - -N acts as an electron acceptor, NH4 + -N, acting as an electron donor, promotes NH4+ oxidation in anaerobic ammonia-oxidizing bacteria. + -N and NO2 - -N is directly converted to N2. The reaction equation is shown in equation (1-1). Therefore, anaerobic ammonium oxidation is very suitable for treating substances containing NH4+. + -N and NO2 - Wastewater with a nitrogen-to-carbon ratio (C / N) of -N is susceptible to anaerobic oxidation (AMO). Anaerobic ammonia oxidizing bacteria require strictly anaerobic conditions to survive, which helps save energy by reducing aeration requirements. Furthermore, AMO operates as an autotrophic process, requiring no additional organic carbon source, making it particularly suitable for denitrification in wastewater with a low C / N ratio. Therefore, compared to traditional activated sludge systems, AMO has been classified as one of the more cost-effective and environmentally friendly systems, consuming less oxygen for nitrogen removal. However, the sensitivity of AMO bacteria to changes in environmental conditions and their slow growth rate are major limitations restricting the application of AMO in large-scale wastewater treatment.

[0007] NH4 + +1.32NO2- +0.066HCO3 - +0.13H + →1.02N2+0.26NO3 - +0.066CH2O 0.5 N 0.15 +2.03H2O(1-1)

[0008] In recent years, redox mediators (RMs) have been widely used in catalytic biotransformation due to their unique redox properties and biocompatibility, especially RMs containing quinones and carbonyl compounds, which exhibit excellent redox capabilities. As an electron transfer mediator, RMs can lower the activation energy of reactions and accelerate the electron transfer rate, thereby increasing the reduction / oxidation rate of pollutants. Furthermore, they can still promote the biodegradation and transformation of target pollutants under low-temperature conditions. They 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 primarily water-soluble, and directly adding them to wastewater often leads to water runoff and secondary pollution, limiting their practical application. In addition, RMs such as anthraquinones may be reduced or degraded during denitrification, causing them to easily lose their catalytic activity. That is, the denitrification rate of RMs usually decreases with prolonged treatment time. Therefore, improving the initial and sustained denitrification rates of RMs has become an urgent technical problem to be solved. Summary of the Invention

[0009] The primary objective of this invention is to provide a novel anthraquinone / reduced graphene oxide mediator membrane, which exhibits high denitrification efficiency and maintains a high level of denitrification efficiency even after a period of use; that is, it possesses both high initial denitrification rate and high denitrification rate over time.

[0010] A second objective of this invention is to provide a method for preparing the above-mentioned anthraquinone / reduced graphene oxide mediator membrane.

[0011] A third objective of this invention is to provide the application of the above-mentioned anthraquinone / reduced graphene oxide mediator membrane in biological denitrification of wastewater.

[0012] The anthraquinone / reduced graphene oxide mediator membrane provided by the present invention includes a membrane substrate and aminoimidazopyridine-modified reduced graphene oxide dispersed in the membrane substrate; the membrane substrate is a composite of polyamide and anthraquinone-modified polysiloxane; the aminoimidazopyridine-modified reduced graphene oxide is a reduced graphene oxide with 6-aminoimidazo[1,2-A]pyridine modified units bonded to its surface.

[0013] The method for preparing the anthraquinone / reduced graphene oxide mediator membrane provided by the present invention includes: dissolving aminoimidazopyridine-modified reduced graphene oxide in an organic solvent, mixing the resulting solution with polyamide and anthraquinone-modified polysiloxane evenly and then degassing, then placing the resulting casting solution on a substrate and smoothing it with a scraper, and then immersing it in pure water to solidify it into a film, thereby obtaining the anthraquinone / reduced graphene oxide mediator membrane.

[0014] Anthraquinone, as an electron transport mediator, can enhance the reduction / oxidation rate of pollutants, primarily promoting denitrification through electron shuttle and redox mediator interactions. Reduced graphene oxide (GO) exhibits excellent adsorption properties for organic pollutants and enhances the extracellular electron transport capacity of anaerobic microorganisms, achieving denitrification mainly through adsorption and catalysis. In other words, anthraquinone and reduced graphene oxide achieve denitrification via two different pathways, and their combined use can leverage their respective denitrification activities. However, on the one hand, anthraquinone is easily lost with water and readily reduced and degraded, losing its catalytic activity. This leads to a decrease in denitrification rate over time during wastewater treatment. On the other hand, reduced graphene oxide inhibits the activity of denitrifying microorganisms (such as ammonia-oxidizing bacteria (AOB) and denitrifying bacteria), which play a crucial role in the denitrification process. This change in community structure negatively impacts the denitrification process, hindering the improvement of denitrification efficiency. In other words, although anthraquinone and reduced graphene oxide can achieve synergistic denitrification through two pathways, the denitrification rate of both decreases with the extension of treatment time, that is, the denitrification rate will decrease over time.

[0015] Based on this, the inventors of this invention modified the mediator membrane by using a polyamide and anthraquinone-modified polysiloxane as the membrane matrix, and simultaneously using 6-aminoimidazo[1,2-A]pyridine to modify the reduced graphene oxide. The resulting aminoimidazopyridine-modified reduced graphene oxide was then added to the membrane matrix. The resulting anthraquinone / reduced graphene oxide mediator membrane exhibits a high initial denitrification rate and a high denitrification rate over time. The reasons for this are speculated to be as follows: Firstly, the denitrification mechanism of anthraquinone mainly promotes denitrification through electron shuttle and redox mediator interactions, while reduced graphene oxide mainly achieves denitrification through adsorption and catalysis. These two mechanisms can complement each other, resulting in a synergistic denitrification effect. Secondly, the presence of amide bonds in polyamides gives them a certain degree of polarity and hydrogen bond formation ability, limiting their compatibility with polysiloxanes. However, when polyamides are combined with anthraquinone-modified polysiloxanes as a membrane matrix, the surface free energy of the polysiloxanes endows them with surface migration properties, allowing the anthraquinone-modified polysiloxanes to easily migrate and accumulate on the surface of the polyamide. This results in a high anthraquinone content on the polyamide surface, thereby fully utilizing the denitrification effect of anthraquinone and improving the denitrification rate. At the same time, since anthraquinone is chemically bonded to the membrane carrier, the problem of anthraquinone loss with the effluent during the denitrification process can be effectively reduced, thus improving the denitrification rate over time. Furthermore, the introduction of the 6-aminoimidazo[1,2-A]pyridine modification unit can inhibit the adverse effects of reduced graphene oxide 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 denitrification rate of the obtained anthraquinone / reduced graphene oxide mediator membrane over time. Attached Figure Description

[0016] Figure 1 This is the standard curve for nitrate nitrogen. Detailed Implementation

[0017] The anthraquinone / reduced graphene oxide mediator membrane provided by this invention comprises a membrane substrate and aminoimidazopyridine-modified reduced graphene oxide dispersed in the membrane substrate; the membrane substrate is a composite of polyamide and anthraquinone-modified polysiloxane. Preferably, the mass ratio of the polyamide to the anthraquinone-modified polysiloxane is 1:(0.2–0.6), such as 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, or any value between them. Preferably, the mass ratio of the membrane substrate to the aminoimidazopyridine-modified reduced graphene oxide is 100:(5–20), such as 100:5, 100:8, 100:10, 100:12, 100:15, 100:18, 100:20, or any value between them.

[0018] In this invention, the anthraquinone-modified polysiloxane can be commercially available or prepared using various existing methods, such as nucleophilic addition reaction of anthraquinone-2-formyl chloride with an aminopolysiloxane. The preferred structural formula of the aminopolysiloxane is R1SiR`2O(SiOR`2). x (SiOR`R2) y (SiOR`Vi) z In SiR`2R1, R1 is a C1-C5 alkyl, vinyl, or hydroxyl group, R` is a C1-C5 alkyl group, R2 is 3-aminopropyl or N-2-aminoethyl-3-aminopropyl, Vi is vinyl, 20≤x≤200, 3≤y≤9, 2≤z≤7. The resulting anthraquinone-modified polysiloxane also contains vinyl groups that can participate in subsequent crosslinking reactions, enabling the anthraquinone-modified polysiloxane to form an interpenetrating network structure with the polyamide, thus extending its service life. The molar ratio of anthraquinone-2-formyl chloride to the amino group in the amino polysiloxane is preferably 1:(0.8-1.2), such as 1:0.8, 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, 1:1.13, 1:1.15, 1:1.18, 1:1.2 or any value between them.

[0019] In this invention, the aminoimidazopyridine-modified reduced graphene oxide is a reduced graphene oxide with 6-aminoimidazo[1,2-A]pyridine modified units bonded to its surface. The aminoimidazopyridine-modified reduced graphene oxide can be commercially available or prepared using various existing methods. For example, it can be prepared by ultrasonically dispersing reduced graphene oxide in tetrahydrofuran, adding 6-aminoimidazo[1,2-A]pyridine to the resulting dispersion, stirring the reaction for 0.5–5 h, filtering, washing the resulting solid product with anhydrous ethanol, and drying to obtain the aminoimidazopyridine-modified reduced graphene oxide.

[0020] In a preferred embodiment, the membrane substrate further contains dispersed humic substances, which can improve the chemical stability of anthraquinone, making it less susceptible to reduction and degradation, thereby increasing the denitrification rate of the anthraquinone / reduced graphene oxide mediator membrane over time. The preferred mass ratio of the humic substances to the membrane substrate is (2–10):100, such as 2:100, 4:100, 6:100, 8:100, 10:100, or any value between them.

[0021] The method for preparing the anthraquinone / reduced graphene oxide mediator membrane provided by the present invention includes: dissolving aminoimidazopyridine-modified reduced graphene oxide in an organic solvent, mixing the resulting solution with polyamide and anthraquinone-modified polysiloxane evenly and then degassing, then placing the resulting casting solution on a substrate and smoothing it with a scraper, and then immersing it in pure water to solidify it into a film, thereby obtaining the anthraquinone / reduced graphene oxide mediator membrane.

[0022] In the preparation of the anthraquinone / reduced graphene oxide mediator membrane described above, the mass ratio of the polyamide to the anthraquinone-modified polysiloxane is preferably 1:(0.2-0.6), such as 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, or any value between them. The mass ratio of the total amount of the polyamide and the anthraquinone-modified polysiloxane to the aminoimidazopyridine-modified reduced graphene oxide is preferably 100:(5-20), such as 100:5, 100:8, 100:10, 100:12, 100:15, 100:18, 100:20, or any value between them.

[0023] In the preparation of the anthraquinone / reduced graphene oxide mediator membrane described above, the organic solvent is preferably at least one of dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), triethyl phosphate (TEP), and N,N-dimethylformamide (DMF). The density and porosity of the anthraquinone / reduced graphene oxide mediator membrane formed in this case are more conducive to nitrogen removal.

[0024] In the preparation process of the anthraquinone / reduced graphene oxide mediator membrane, it is preferable to further dissolve the humic substance and the aminoimidazopyridine-modified reduced graphene oxide together in an organic solvent. This is more conducive to improving the denitrification rate of the anthraquinone / reduced graphene oxide mediator membrane over time. The preferred mass ratio of the humic substance to the total amount of polyamide and anthraquinone-modified polysiloxane is (2-10):100, such as 2:100, 4:100, 6:100, 8:100, 10:100, or any value between them.

[0025] In the preparation process of the above-mentioned anthraquinone / reduced graphene oxide mediator membrane, the casting solution may also contain at least one of lithium chloride, polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), ethanol, etc.

[0026] The present invention also provides anthraquinone / reduced graphene oxide mediator membrane prepared by the above method.

[0027] Furthermore, the present invention also provides the application of the above-mentioned anthraquinone / reduced graphene oxide mediator membrane in biological denitrification of wastewater.

[0028] The present invention will be described in detail below through embodiments.

[0029] In the following preparation examples and comparative preparation examples, reduced graphene oxide was prepared according to the following methods:

[0030] S1`: Under an ice bath below 0℃, slowly add 10.0g of graphite powder to 230mL of 98% concentrated sulfuric acid while stirring. Mix until homogeneous to obtain mixture A. Add 50.0g of NaNO3 to mixture A and stir for 10min to obtain mixture B. Slowly add 30.0g of KMnO4 to mixture B and mix thoroughly. Then heat to 38℃ and stir for 1h to obtain mixture C. Add 500mL of deionized water to mixture C, heat to 95℃, and stir for 1h to obtain mixture D.

[0031] S2`: Add 100 mL of H2O2 (30%) to the mixture D until the mixture D becomes a golden-brown suspension. After cooling, separate the solid and liquid. Wash the solid with deionized water until the pH of the washing solution is 6 to obtain solid A. Dry solid A at 70℃ for 18 h. Transfer the dried solid A to a muffle furnace for copolymerization annealing treatment at 350℃ for 1 h at a heating rate of 5℃ / min. After cooling, reduced graphene oxide is obtained.

[0032] In the following test cases:

[0033] (1) BTB (bromothymol blue) medium: KNO3 1.0g, agar 20g, KH2PO4 1.0g, FeCl2·6H2O 0.5g, CaCl2·7H2O 0.2g, MgSO4·7H2O 1.0g, sodium succinate 8.5g, BTB (1% dissolved in alcohol) 1mL, distilled water 1000mL, pH=7.2.

[0034] (2) Denitrification medium: KNO3 0.7218g, sodium succinate 2.2g, MgSO4·7H2O 0.2g, K2HPO4 0.5g, distilled water 1000mL, pH=7.2.

[0035] (3) LB medium: 25g LB broth, 1000mL distilled water, pH=7.2.

[0036] (4) Determination of nitrate nitrogen: Nitrate nitrogen (NO3) was determined using an ultraviolet spectrophotometer. - The concentration of NO3- (-N). Specifically, by quantitatively determining NO3- - NO3 was monitored by absorbance at a wavelength of 220 nm. - The concentration of -N is such that soluble organic matter absorbs at wavelengths of 220 nm and 275 nm, while NO3... -There was no absorption at a wavelength of 275 nm, so a second measurement was performed at 275 nm to correct for NO3. - The concentration of -N. The detection limit of this method is 0.08-4 mg / L. The specific operating steps are as follows:

[0037] ① Take an appropriate water sample and transfer it into a 50mL colorimetric tube. Dilute it appropriately according to the detection range and bring the volume to 50mL with distilled water. If the water sample is colored or turbid, add a suspension of 10% zinc sulfate and aluminum hydroxide to pre-treat the water sample by flocculation, and then centrifuge or take the supernatant.

[0038] ② Add 1 mL of 1 mol / L hydrochloric acid and 0.8% aminosulfonic acid to the colorimetric tube, then mix and shake well;

[0039] ③ Use the solution obtained by adding 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, and measure the absorbance at wavelengths of 220 nm and 275 nm using a 10 mm quartz cuvette.

[0040] ④ Determine NO3 according to the above steps. - The absorbance at wavelengths of 220 nm and 275 nm when the concentrations of -N are 0.25 mg / L, 0.5 mg / L, 1 mg / L, 1.5 mg / L and 2 mg / L;

[0041] ⑤NO3 - The formula (1) for calculating the -N content is as follows:

[0042] A 校 =A 220 -2A 275 (1)

[0043] ⑥ NO3 in the water sample - The concentration of -N was determined by the control standard curve ( Figure 1 ) to calculate.

[0044] Preparation Example 1-1: Preparation of Anthraquinone-Modified Polysiloxane

[0045] The structure of aminopolysiloxane is ViSiMe2O(SiOMe2). 103.1 (SiOMeR2) 3.9 (SiOMeVi) 6.5 SiMe2Vi, R2 is 3-aminopropyl, Me is methyl, and Vi is vinyl.

[0046] The aminopolysiloxane and triethylamine were dissolved in tetrahydrofuran to obtain the substrate. Anthraquinone-2-formyl chloride tetrahydrofuran solution was added dropwise under ice bath conditions. After the addition was completed, the mixture was stirred for 8 hours. The temperature was raised to 25°C and the reaction was stirred for 6 hours. The mixture was then filtered to remove the tetrahydrofuran from the filtrate to obtain anthraquinone-modified polysiloxane, denoted as AQ-PSi-1.

[0047] The molar ratio of amino group to anthraquinone-2-formyl chloride in the aminopolysiloxane was 1.2:1. The molar ratio of triethylamine to anthraquinone-2-formyl chloride was 1.15:1. The total concentration of aminopolysiloxane and triethylamine in the substrate was 25 wt%. The concentration of the tetrahydrofuran solution of anthraquinone-2-formyl chloride was 10 wt%.

[0048] Preparation Examples 1-2: Preparation of Anthraquinone-Modified Polysiloxanes

[0049] The structure of aminopolysiloxane is SiMe3O(SiOMe2). 53.5 (SiOMeR2) 3.6 (SiOMeVi) 2.9 SiMe3, R2 is 3-aminopropyl, Me is methyl, and Vi is vinyl.

[0050] The aminopolysiloxane and triethylamine were dissolved in tetrahydrofuran to obtain the substrate. Anthraquinone-2-formyl chloride tetrahydrofuran solution was added dropwise under ice bath conditions. After the addition was completed, the mixture was stirred for 10 h. The temperature was raised to 35 °C and the reaction was stirred for another 2 h. The mixture was then filtered to remove the tetrahydrofuran from the filtrate, and the anthraquinone-modified polysiloxane was obtained, denoted as AQ-PSi-2.

[0051] The molar ratio of amino group to anthraquinone-2-formyl chloride in the aminopolysiloxane was 1.3:1. The molar ratio of triethylamine to anthraquinone-2-formyl chloride was 1.15:1. The total concentration of aminopolysiloxane and triethylamine in the substrate was 25 wt%. The concentration of the tetrahydrofuran solution of anthraquinone-2-formyl chloride was 10 wt%.

[0052] Preparation Examples 1-3: Preparation of Anthraquinone-Modified Polysiloxanes

[0053] The structure of aminopolysiloxane is ViSiMe2O(SiOMe2). 29.4 (SiOMeR2) 7.7 (SiOMeVi) 6.3 SiMe2Vi, R2 is 3-aminopropyl, Me is methyl, and Vi is vinyl.

[0054] The aminopolysiloxane and triethylamine were dissolved in tetrahydrofuran to obtain the substrate. An anthraquinone-2-formyl chloride tetrahydrofuran solution was added dropwise under ice bath conditions. After the addition was complete, the mixture was stirred for 8 hours. The temperature was raised to 20°C and the reaction was stirred for 10 hours. The mixture was then filtered to remove the tetrahydrofuran from the filtrate, and the anthraquinone-modified polysiloxane was obtained, denoted as AQ-PSi-3.

[0055] The molar ratio of amino group to anthraquinone-2-formyl chloride in the aminopolysiloxane was 1.15:1. The molar ratio of triethylamine to anthraquinone-2-formyl chloride was also 1.15:1. The total concentration of aminopolysiloxane and triethylamine in the substrate was 25 wt%. The concentration of the tetrahydrofuran solution of anthraquinone-2-formyl chloride was 10 wt%.

[0056] Preparation Example 2-1: Preparation of Aminoimidazopyridine-Modified Reduced Graphene Oxide

[0057] Ten parts by weight of reduced graphene oxide were ultrasonically dispersed in 500 parts by weight of tetrahydrofuran. Then, 5 parts by weight of 6-aminoimidazo[1,2-A]pyridine were added to the resulting dispersion and the mixture was stirred for 5 hours. After filtration, the resulting solid product was washed with anhydrous ethanol and dried to obtain aminoimidazopyridine-modified reduced graphene oxide, denoted as N-GRO-1.

[0058] Preparation Examples 2-3: Preparation of Aminoimidazopyridine-Modified Reduced Graphene Oxide

[0059] Ten parts by weight of reduced graphene oxide were ultrasonically dispersed in 200 parts by weight of tetrahydrofuran. Then, 15 parts by weight of 6-aminoimidazo[1,2-A]pyridine were added to the resulting dispersion and the mixture was stirred for 20 hours. After filtration, the resulting solid product was washed with anhydrous ethanol and dried to obtain aminoimidazopyridine-modified reduced graphene oxide, denoted as N-GRO-2.

[0060] Preparation Examples 2-3: Preparation of Aminoimidazopyridine-Modified Reduced Graphene Oxide

[0061] Ten parts by weight of reduced graphene oxide were ultrasonically dispersed in 400 parts by weight of tetrahydrofuran. Then, 10 parts by weight of 6-aminoimidazo[1,2-A]pyridine were added to the resulting dispersion and the mixture was stirred for 10 hours. After filtration, the resulting solid product was washed with anhydrous ethanol and dried to obtain aminoimidazopyridine-modified reduced graphene oxide, denoted as N-GRO-3.

[0062] Example 1: Anthraquinone / reduced graphene oxide mediator membrane and its preparation method

[0063] Aminoimidazole-pyridine-modified reduced graphene oxide (N-GRO-1) and humic substances were dissolved in N,N-dimethylacetamide solution. The resulting solution was then mixed with polyamide and anthraquinone-modified polysiloxane (AQ-PSi-1) and degassed. The mass ratio of polyamide to anthraquinone-modified polysiloxane was 1:0.4, the total amount of polyamide and anthraquinone-modified polysiloxane was 100:10, and the mass ratio of humic substances to the total amount of polyamide and anthraquinone-modified polysiloxane was 8:100, resulting in a casting solution with a solid content of 20.2 wt%. Pour casting solution onto a clean glass plate and smooth it with a 5mm clean scraper. Then immerse it in a pure water coagulation bath for 20 hours to solidify into a film. Wash the solidified film with deionized water to remove residual solvent, and obtain anthraquinone / reduced graphene oxide mediator membrane, denoted as M1.

[0064] Example 2: Anthraquinone / reduced graphene oxide mediator membrane and its preparation method

[0065] Aminoimidazole-pyridine-modified reduced graphene oxide (N-GRO-2) and humic substances were dissolved in N,N-dimethylacetamide solution. The resulting solution was then mixed thoroughly with polyamide and anthraquinone-modified polysiloxane (AQ-PSi-2) and degassed. The mass ratio of polyamide to anthraquinone-modified polysiloxane was 1:0.2, the total amount of polyamide and anthraquinone-modified polysiloxane was 100:5, and the mass ratio of humic substances to the total amount of polyamide and anthraquinone-modified polysiloxane was 2:100, resulting in a casting solution with a solid content of 18.1 wt%. The casting solution was poured onto a clean glass plate and leveled with a 5 mm clean doctor blade. The plate was then immersed in a pure water coagulation bath for 20 hours to solidify into a film. The solidified film was washed with deionized water to remove residual solvent, yielding anthraquinone / reduced graphene oxide mediator membrane, denoted as M2.

[0066] Example 3: Anthraquinone / reduced graphene oxide mediator membrane and its preparation method

[0067] Aminoimidazole-pyridine-modified reduced graphene oxide (N-GRO-3) and humic substances were dissolved in N,N-dimethylacetamide solution. The resulting solution was then mixed with polyamide and anthraquinone-modified polysiloxane (AQ-PSi-3) and degassed. The mass ratio of polyamide to anthraquinone-modified polysiloxane was 1:0.6, the total amount of polyamide and anthraquinone-modified polysiloxane was 100:20, and the mass ratio of humic substances to the total amount of polyamide and anthraquinone-modified polysiloxane was 10:100, resulting in a casting solution with a solid content of 19.6 wt%. Pour casting solution onto a clean glass plate and smooth it with a 5mm clean scraper. Then immerse it in a pure water coagulation bath for 20 hours to solidify into a film. Wash the solidified film with deionized water to remove residual solvent, and obtain anthraquinone / reduced graphene oxide mediator film, denoted as M3.

[0068] Example 4: Anthraquinone / reduced graphene oxide mediator membrane and its preparation method

[0069] Anthraquinone / reduced graphene oxide mediator membranes were prepared according to the method of Example 1, except that the humic substance was replaced with the same amount of aminoimidazopyridine-modified reduced graphene oxide (N-GRO-1) by weight, and the other conditions were the same as in Example 1, resulting in an anthraquinone / reduced graphene oxide mediator membrane, denoted as M4.

[0070] Comparative Example 1: Reference anthraquinone / reduced graphene oxide mediator membrane and its preparation method

[0071] Anthraquinone / reduced graphene oxide mediator membranes were prepared according to the method of Example 4, except that the anthraquinone-modified polysiloxane (AQ-PSi-1) was replaced with the same amount of polyamide by weight, and the other conditions were the same as in Example 4, to obtain a reference anthraquinone / reduced graphene oxide mediator membrane, denoted as DM1.

[0072] Comparative Example 2: Reference anthraquinone / reduced graphene oxide mediator membrane and its preparation method

[0073] Anthraquinone / reduced graphene oxide mediator membranes were prepared according to the method of Example 4, except that the anthraquinone-modified polysiloxane (AQ-PSi-1) was replaced with the same parts by weight of aminoimidazopyridine-modified reduced graphene oxide (N-GRO-1), and the other conditions were the same as in Example 4, to obtain a reference anthraquinone / reduced graphene oxide mediator membrane, denoted as DM2.

[0074] Comparative Example 3: Reference Anthraquinone / Reduced Graphene Oxide Mediator Membrane and its Preparation Method

[0075] Anthraquinone / reduced graphene oxide mediator membranes were prepared according to the method of Example 4, except that the anthraquinone-modified polysiloxane was replaced by a mixture of aminopolysiloxane and anthraquinone-2-formyl chloride in the same weight proportions. The structure of the aminopolysiloxane and the molar ratio of aminopolysiloxane to anthraquinone-2-formyl chloride in the mixture were the same as in Preparation Example 1, and the other conditions were the same as in Example 4. A reference anthraquinone / reduced graphene oxide mediator membrane, denoted as DM3, was obtained.

[0076] Comparative Example 4: Reference Anthraquinone / Reduced Graphene Oxide Mediator Membrane and its Preparation Method

[0077] Anthraquinone / reduced graphene oxide mediator membranes were prepared according to the method of Example 4, except that the aminoimidazopyridine-modified reduced graphene oxide (N-GRO-1) was replaced with the same weight of unmodified reduced graphene oxide. The other conditions were the same as in Example 4, and a reference anthraquinone / reduced graphene oxide mediator membrane, denoted as DM4, was obtained.

[0078] Comparative Example 5: Reference anthraquinone / reduced graphene oxide mediator membrane and its preparation method

[0079] Anthraquinone / reduced graphene oxide mediator membranes were prepared according to the method of Example 4, except that the aminoimidazopyridine-modified reduced graphene oxide (N-GRO-1) was replaced with the same parts by weight of anthraquinone-modified polysiloxane (AQ-PSi-1), and the other conditions were the same as in Example 4, to obtain a reference anthraquinone / reduced graphene oxide mediator membrane, denoted as DM5.

[0080] Test case

[0081] Two g of activated sludge from the biochemical treatment tank of a sewage treatment plant in Longyan was added to sterilized LB medium. After sealing with sealing film, the medium was placed in a shaker at 36℃ and 120 r / min for 48 h. 10 mL of the resulting culture solution was added to a new LB medium. The resulting culture solution was then spread and streaked on BTB medium and placed in a constant temperature incubator at 36℃ for 2 days. The most efficient nitrogen-degrading strains were finally screened and stored at -20℃.

[0082] The anthraquinone / reduced graphene oxide mediator membranes obtained in the above examples and comparative examples were respectively loaded into 1000 mL serum bottles. The serum bottles were then filled with water samples to be treated. The selected high-efficiency nitrogen-degrading strains were inoculated into LB medium according to the above method and activated for 48 h in a shaker at 36℃ and 120 rpm. The activated strains were then inoculated into liquid denitrification medium (initial concentration 100 mg / L) at a concentration of 3%, and then added to the serum bottles. The serum bottles were incubated in a shaker at 36℃ and 120 rpm for 24 h. Samples were taken at regular intervals and quantitatively diluted according to the detection range. The NO3 content in the diluted water samples was then measured using a UV spectrophotometer. - Substitute the absorbance value of -N into NO3 - The standard curve of -N Figure 1 The concentration was obtained, and the degradation curve was plotted. The formula (2) for calculating the denitrification rate is as follows:

[0083]

[0084] Where A0 is the initial nitrate nitrogen concentration (mg / L); A t t represents the nitrate nitrogen concentration (mg / L) after time t; r represents the denitrification rate (%). The results are shown in Table 1.

[0085] Ten batches of water samples were treated using anthraquinone / reduced graphene oxide mediator membrane circulation as described above. Each batch was treated continuously for 6 days. The denitrification rates of the first and tenth batches of water samples after 20 hours of treatment were calculated using the above method. The results are shown in Table 1.

[0086] Table 1

[0087]

[0088] The results above show that the anthraquinone / reduced graphene oxide mediator membrane provided by this invention has a high initial denitrification rate and a high denitrification rate over time.

[0089] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. An anthraquinone / reduced graphene oxide mediator membrane, characterized in that, The anthraquinone / graphene oxide mediator membrane includes a membrane substrate and aminoimidazopyridine-modified reduced graphene oxide dispersed in the membrane substrate; the membrane substrate is a composite of polyamide and anthraquinone-modified polysiloxane; the aminoimidazopyridine-modified reduced graphene oxide is a reduced graphene oxide with 6-aminoimidazo[1,2-A]pyridine-modified units bonded to its surface.

2. The anthraquinone / reduced graphene oxide mediator membrane according to claim 1, characterized in that, The mass ratio of the polyamide to the anthraquinone-modified polysiloxane is 1:(0.2-0.6); the mass ratio of the membrane matrix to the aminoimidazopyridine-modified reduced graphene oxide is 100:(5-20).

3. The anthraquinone / reduced graphene oxide mediator membrane according to claim 1, characterized in that, The anthraquinone-modified polysiloxane is obtained by nucleophilic addition reaction of anthraquinone-2-formyl chloride with an aminopolysiloxane; the general structural formula of the aminopolysiloxane is R1SiR`2O(SiOR`2). x (SiOR`R2) y (SiOR`Vi) z SiR`2R1, where R1 is a C1-C5 alkyl, vinyl, or hydroxyl group, R` is a C1-C5 alkyl group, R2 is 3-aminopropyl or N-2-aminoethyl-3-aminopropyl, Vi is vinyl, 20≤x≤200, 3≤y≤9, 2≤z≤7; the molar ratio of anthraquinone-2-formyl chloride to the amino group in the amino polysiloxane is 1:(0.8-1.2).

4. The anthraquinone / reduced graphene oxide mediator membrane according to claim 1, characterized in that, The aminoimidazopyridine-modified reduced graphene oxide was prepared by the following method: the reduced graphene oxide was ultrasonically dispersed in tetrahydrofuran, and then 6-aminoimidazo[1,2-A]pyridine was added to the resulting dispersion and the mixture was stirred for 0.5 to 5 hours. After filtration, the resulting solid product was washed with anhydrous ethanol and dried to obtain the aminoimidazopyridine-modified reduced graphene oxide.

5. The anthraquinone / reduced graphene oxide mediator membrane according to claim 1, characterized in that, The membrane substrate also contains humic substances; the mass ratio of humic substances to the membrane substrate is (2-10):

100.

6. A method for preparing an anthraquinone / reduced graphene oxide mediator membrane, characterized in that, The method includes: dissolving aminoimidazopyridine-modified reduced graphene oxide in an organic solvent, mixing the resulting solution with polyamide and anthraquinone-modified polysiloxane until homogeneous and then degassing, then placing the resulting casting solution on a substrate and smoothing it with a scraper before immersing it in pure water to solidify it into a film, thereby obtaining the anthraquinone / reduced graphene oxide mediator film.

7. The method for preparing the anthraquinone / reduced graphene oxide mediator membrane according to claim 6, characterized in that, The mass ratio of the polyamide to the anthraquinone-modified polysiloxane is 1:(0.2-0.6); the total amount of the polyamide and anthraquinone-modified polysiloxane is used in a mass ratio of 100:(5-20) to the aminoimidazopyridine-modified reduced graphene oxide; the organic solvent is selected from at least one of dimethylacetamide, dimethyl sulfoxide, triethyl phosphate and N,N-dimethylformamide.

8. The method for preparing the anthraquinone / reduced graphene oxide mediator membrane according to claim 6, characterized in that, The method further includes ball milling humic substances together with aminoimidazopyridine-modified reduced graphene oxide; the mass ratio of the amount of humic substances to the total amount of polyamide and anthraquinone-modified polysiloxane is (2-10):

100.

9. The anthraquinone / reduced graphene oxide mediator membrane prepared by the method of claim 6.

10. The application of the anthraquinone / reduced graphene oxide mediator membrane according to claim 1 in biological denitrification of wastewater.

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