Preparation method of composite water treatment agent for aquaculture wastewater treatment

Abstract

The invention discloses a preparation method of a composite water treatment agent for aquaculture wastewater treatment. The preparation method comprises the following steps: preparing nitrogen-phosphorus-sulfur ternary doped carbon spheres; carrying out ionic liquid functionalization treatment; growing an inner layer Cu-MOF (Metal Organic Framework); growing Zn / Cu-MOF on the outer layer; performing plasma treatment; the composite water treatment agent is obtained. According to the ternary-doped carbon sphere core in the composite water treatment, rich active sites are provided through N, P and S synergistic doping, the hydrophilicity and ion exchange capacity of the material are remarkably improved through ionic liquid functionalization, rapid diffusion and adsorption of pollutants are promoted, organic matter is efficiently degraded through the catalytic oxidation effect of MOF in an inner layer Cu-rich area, and the composite water treatment efficiency is improved. Meanwhile, ammonia nitrogen is cooperatively treated; phosphate ions are preferentially removed from the Zn-rich area on the outer layer. When the compound water treatment agent is used for treating aquaculture wastewater, organic pollutants and harmful substances such as nitrogen and phosphorus can be effectively removed.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a method for preparing a composite water treatment agent for aquaculture wastewater treatment. Background Art

[0002] With the continuous expansion of the aquaculture industry, the problem of aquaculture wastewater discharge is becoming increasingly serious. Aquaculture wastewater usually contains a large amount of organic matter, nitrogen, phosphorus, antibiotics and other harmful substances. If it is discharged directly without effective treatment, it will cause serious pollution to the water environment, soil and ecosystem, and even threaten human health. Therefore, how to efficiently and economically treat aquaculture wastewater has become an urgent problem to be solved in the field of environmental protection today.

[0003] At present, the methods for treating aquaculture wastewater mainly include physical method, chemical method and biological method. The physical method removes suspended matter and solid particles in the wastewater by filtration, precipitation, adsorption and other means, but the removal effect of pollutants such as organic matter and antibiotics dissolved in water is poor. The chemical method removes harmful substances in the water by adding chemical agents to react with pollutants in the wastewater, but this method may cause secondary pollution and has high operating costs. The biological method relies on the metabolism of microorganisms to degrade organic matter in the water and can effectively remove pollutants such as nitrogen and phosphorus, but the treatment cycle is long and has high requirements for water quality, temperature and environmental conditions.

[0004] Although the existing technology has solved the problem of nitrogen and phosphorus removal in aquaculture wastewater to a certain extent, it is still difficult to remove antibiotics, organic matter and complex pollutants in wastewater. The existing water treatment methods are single and lack effective synergy, and cannot solve the problem of removing multiple pollutants at the same time. Therefore, it is urgent to develop a new, composite water treatment agent that can form a synergistic effect between different pollutants, improve the efficiency of wastewater treatment, reduce costs, and avoid the generation of secondary pollution. Summary of the invention

[0005] Based on the problems existing in the background technology, the present invention provides a method for preparing a composite water treatment agent for aquaculture wastewater treatment. Using the composite water treatment agent of the present invention to treat aquaculture wastewater can effectively remove organic pollutants and harmful substances such as nitrogen and phosphorus, thereby improving water quality and reducing the impact of pollutants on the aquatic ecological environment.

[0006] The present invention is implemented by the following technical solutions:

[0007] A method for preparing a composite water treatment agent for aquaculture wastewater treatment comprises the following steps:

[0008] S1. Soak corn cob powder in thiourea and urea aqueous solution, stir, continue to add ammonium dihydrogen phosphate aqueous solution, stir, and dry to obtain a mixture; place the mixture in a tube furnace, heat treat it in a nitrogen atmosphere, and cool it to room temperature to obtain nitrogen, phosphorus and sulfur ternary doped carbon spheres;

[0009] S2. Prepare an ethanol solution of ionic liquid, add nitrogen, phosphorus and sulfur ternary doped carbon spheres thereto, ultrasonically disperse, stir, filter, wash and dry to obtain functionalized carbon spheres;

[0010] S3. dissolving copper acetate in a mixed solution of ethanol and water, adding the functionalized carbon spheres thereto, dispersing by ultrasonication, then dropping an ethanol solution containing 1,3,5-benzenetricarboxylic acid, heating and stirring to react, obtaining a dispersion, centrifuging, and washing with ethanol to obtain surface Cu-MOF-coated carbon spheres;

[0011] S4. Dissolve zinc acetate and copper acetate in a mixed solution of ethanol and water, add the surface Cu-MOF coated carbon spheres thereto, disperse by ultrasonication, then dropwise add an ethanol solution containing 1,3,5-benzenetricarboxylic acid, heat and stir to react, obtain a dispersion, centrifuge, wash with ethanol, and vacuum dry to obtain a prefabricated composite water treatment agent;

[0012] S5. The prefabricated composite water treatment agent is subjected to plasma treatment to obtain the composite water treatment agent.

[0013] Furthermore, in step S1, the mass ratio of corn cob powder, thiourea and urea is 1:(0.4-0.8):(0.4-0.8); and the concentration of thiourea and urea aqueous solution is 0.1-0.2 g / mL.

[0014] Furthermore, in step S2, the mass ratio of the amount of diammonium phosphate to the amount of corn cob powder is (0.4-0.8):1.

[0015] Furthermore, the conditions for the heat treatment in the tubular furnace in step S1 are specifically as follows: heating to 500-550° C. at 5° C. / min, keeping the temperature for 2 hours, and naturally cooling to room temperature.

[0016] Further, in step S2, the ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid, and the concentration is 0.05-0.1 g / mL;

[0017] The mass ratio of ionic liquid to nitrogen, phosphorus and sulfur ternary doped carbon balls is (0.2-0.3):1.

[0018] Furthermore, in step S3, the mass ratio of copper acetate, 1,3,5-benzenetricarboxylic acid and functionalized carbon spheres is (0.8-0.95):(0.2-0.3):1.

[0019] Furthermore, in step S3, the volume ratio of ethanol to water is 3:1; the concentration of the copper acetate mixed solution is 0.07-0.1 g / mL; the concentration of the 1,3,5-benzenetricarboxylic acid ethanol solution is 0.04-0.06 g / mL; and the heating temperature is 60°C.

[0020] Furthermore, in step S4, the molar ratio of zinc acetate to copper acetate is (2-4):1; the mass ratio of the total amount of zinc acetate and copper acetate, 1,3,5-benzenetricarboxylic acid and the surface Cu-MOF coated carbon balls is (0.2-0.4):(0.1-0.2):1.

[0021] Furthermore, in step S4, the volume ratio of ethanol to water is 3:1; the concentration of zinc acetate is 0.03-0.06 g / mL; the concentration of 1,3,5-benzenetricarboxylic acid ethanol solution is 0.04-0.06 g / mL; and the heating temperature is 70°C.

[0022] Furthermore, the specific conditions of the plasma treatment in step S5 are: in an oxygen atmosphere, at a flow rate of 50 mL / min and a power of 200 W for 5 min.

[0023] Beneficial effects of the present invention:

[0024] The ternary doped carbon sphere core in the composite water treatment of this application provides abundant active sites through the synergistic doping of N, P, and S, wherein the N doped sites promote the adsorption of ammonium ions, the P doped sites selectively bind metal ions, and the S doping enhances the electron transfer and heavy metal chelation capabilities. The ionic liquid functionalization significantly improves the hydrophilicity and ion exchange capacity of the material, and promotes the rapid diffusion and adsorption of pollutants. The MOF in the inner Cu-rich region efficiently degrades organic matter through catalytic oxidation, while synergistically treating ammonia nitrogen; the outer Zn-rich region preferentially removes phosphate ions. This spatially separated structural design avoids mutual interference between different treatment processes and achieves the synergistic removal of pollutants. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the following embodiments.

[0026] Example 1

[0027] A method for preparing a composite water treatment agent for aquaculture wastewater treatment comprises the following steps:

[0028] S1. Dissolve 100g of thiourea and 100g of urea in 1L of deionized water, add 200g of corn cob powder, stir at room temperature for 12h, continue to add 100g of ammonium dihydrogen phosphate, stir at room temperature for 4h, and dry at 80°C to obtain a mixture; place the mixture in a tube furnace and heat treat it in a nitrogen atmosphere, that is, heat it to 500°C at 5°C / min, keep it warm for 2h, and naturally cool it to room temperature to obtain nitrogen-phosphorus-sulfur ternary doped carbon spheres;

[0029] S2.25 g of 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid was dissolved in 1 L of anhydrous ethanol, and 100 g of nitrogen, phosphorus and sulfur ternary doped carbon spheres were added thereto, ultrasonically dispersed, stirred, filtered, washed and dried to obtain functionalized carbon spheres;

[0030] S3. Dissolve 75g of copper acetate in a mixed solution of 750mL of ethanol and 250mL of water, add 80g of functionalized carbon spheres, disperse by ultrasonication, then drop 400mL of an ethanol solution containing 21g of 1,3,5-benzenetricarboxylic acid, heat to 60°C and stir to react to obtain a dispersion, centrifuge, and wash with ethanol to obtain surface Cu-MOF-coated carbon spheres;

[0031] S4. Dissolve 18g of zinc acetate and 9g of copper acetate in a mixed solution of 300mL of ethanol and 100mL of water, add the surface Cu-MOF coated carbon spheres thereto, disperse by ultrasonication, then drop 250mL of an ethanol solution containing 12g of 1,3,5-benzenetricarboxylic acid, heat to 70°C and stir to react, obtain a dispersion, centrifuge, wash with ethanol, and vacuum dry to obtain a prefabricated composite water treatment agent;

[0032] S5. The prefabricated composite water treatment agent is subjected to plasma treatment, that is, the composite water treatment agent is obtained by treating the prefabricated composite water treatment agent under oxygen atmosphere at a flow rate of 50 mL / min and a power of 200 W for 5 minutes.

[0033] Example 2

[0034] The difference between this embodiment and embodiment 1 is that in step S4, the amount of zinc acetate used is 19.5 g, the amount of copper acetate used is 7.5 g, and the remaining steps are the same as in embodiment 1.

[0035] Example 3

[0036] Preferably, in S2, S3 and / or S4, after adding carbon spheres to the corresponding solution and performing ultrasonic dispersion, a preset volume of the target solution is taken for DLS (Dynamic Light Scattering) test:

[0037] irradiating the target solution to be tested with laser;

[0038] The scattered light signal is collected by a photomultiplier tube or an avalanche photodiode, wherein the sampling time interval is in the order of nanoseconds or microseconds;

[0039] A light intensity-time image is constructed based on the collected scattered light signal, and a post-sampling signal after a preset time length is compared with the initial sampling signal to obtain a comparison result;

[0040] Based on the intensity-time image and the comparison results, the autocorrelation function C(T) is constructed to determine the particle decay constant T;

[0041] Determine the diffusion coefficient D based on the particle decay constant T:

[0042] 1 / T=2DK

[0043] Where K is the scattered light wave vector;

[0044] Furthermore, Where n is the refractive index of the solvent; λ is the laser wavelength; θ is the scattering angle, and in DLS, θ = 90°;

[0045] According to the diffusion coefficient D, the particle size is determined, and it is judged whether the particle size meets the preset size threshold; if so, ultrasonic dispersion is stopped and the preparation process is continued; if not, ultrasonic dispersion and DLS test are performed again until the particle size in the solution meets the preset size threshold.

[0046] Comparative Example 1

[0047] The difference between this comparative example and Example 1 is that in step S1, 300 g of urea is dissolved in 1 L of deionized water, 200 g of corn cob powder is added, and the mixture is stirred at room temperature for 12 h. The remaining steps are the same as in Example 1.

[0048] Comparative Example 2

[0049] The difference between this comparative example and Example 1 is that step S2 is not included, that is, after obtaining nitrogen, phosphorus and sulfur ternary doped carbon spheres, they are directly added to a mixed solution of copper acetate in ethanol and water to prepare surface Cu-MOF coated carbon spheres; and ionic liquid surface functionalization treatment is not included.

[0050] Comparative Example 3

[0051] The difference between this comparative example and Example 1 is that step S4 is not included, that is, plasma treatment is directly performed after the surface Cu-MOF coated carbon spheres are obtained.

[0052] Comparative Example 4

[0053] The difference between this comparative example and Example 1 is that step S1 and step S2 are the same as those in Example 1.

[0054] The specific operation of step S3 is as follows: 84g of copper acetate and 18g of zinc acetate are dissolved in a mixed solution of 750mL of ethanol and 250mL of water, 80g of functionalized carbon spheres are added thereto, ultrasonically dispersed, and then 600mL of an ethanol solution containing 33g of 1,3,5-benzenetricarboxylic acid is added dropwise, heated to 70°C and stirred for reaction to obtain a dispersion, centrifuged, and washed with ethanol to obtain a prefabricated composite water treatment agent;

[0055] S5. The prefabricated composite water treatment agent is subjected to plasma treatment, that is, the composite water treatment agent is obtained by treating the prefabricated composite water treatment agent under oxygen atmosphere at a flow rate of 50 mL / min and a power of 200 W for 5 minutes.

[0056] Test example

[0057] Treatment effect of water treatment agents on aquaculture wastewater in Examples 1-2 and Comparative Examples 1-4

[0058] Artificially prepared aquaculture wastewater was used, in which the concentrations of major pollutants were as follows: total phosphorus concentration 10 mg / L, ammonia nitrogen concentration 20 mg / L, COD 300 mg / L, ciprofloxacin concentration 10 mg / L, and its composition and prepared substance concentrations were specifically: glucose 500 mg / L, ammonium sulfate 94.38 mg / L, potassium dihydrogen phosphate 14.32 mg / L and ciprofloxacin 10 mg / L.

[0059] Determination of pollutants in aquaculture wastewater

[0060] (1) Ammonia nitrogen: Determined according to the national standard Nessler's reagent spectrophotometric method HJ535-2009.

[0061] (2) Total phosphorus: Determined according to the ammonium molybdate photometric method of French standard GB 11893-1989.

[0062] (3) COD: determined according to the national standard HJ 828-2017 for alkaline potassium permanganate.

[0063] (4) Ciprofloxacin: High performance liquid chromatography, using a C-18 solid phase extraction column, with a mobile phase of 0.025 mol·L -1 Phosphoric acid aqueous solution: acetonitrile = 87:13 (V:V) flow rate is 1.5 ml min -1 , and detected at a wavelength of 278 nm.

[0064] According to the feeding amount of 2g per liter of wastewater, the water treatment agent in Examples 1-2 and Comparative Examples 1-4 was mixed with the prepared aquaculture wastewater, stirred at room temperature, and sampled after reacting for 2h. The contents of ammonia nitrogen, total phosphorus, COD and ciprofloxacin in the water samples were determined, and the removal rates of ammonia nitrogen, total phosphorus, COD and ciprofloxacin were calculated. The specific results are shown in Table 1.

[0065] Table 1

[0066]

[0067]

[0068] As can be seen from the results in Table 1, the use of the composite water treatment agent prepared by the present invention to treat aquaculture wastewater can effectively remove organic pollutants and harmful substances such as nitrogen and phosphorus, thereby improving water quality and reducing the impact of pollutants on aquatic ecological environment. The composite water treatment agent is also tested for recycling performance in the present invention. The material has excellent reusability. After simple regeneration treatment (acid washing-alkali washing-water washing), the material can be recycled for 8-10 times. After the 10th use, the removal rates of ammonia nitrogen, total phosphorus, COD and ciprofloxacin are still maintained at more than 88%.

[0069] In Comparative Example 1, only urea was used to treat corn cob powder, and thiourea was not added. The carbon balls in the composite water treatment agent finally prepared did not contain sulfur doping. In terms of ammonia nitrogen treatment, the lack of sulfur doping caused the synergistic effect of sulfur doping on improving the electrical conductivity of the material to disappear, reducing the electron transfer efficiency and reducing the catalytic oxidation conversion rate of ammonia nitrogen. The total phosphorus removal performance was not greatly affected initially. Although the phosphate adsorption mechanism of the outer Zn-MOF did not change, the lack of sulfur doping weakened the overall stability of the material, which may cause the loss of part of the MOF structure and affect the long-term operation effect. It was found through the cycle test that the total phosphorus removal rate was 85.57% after 10 cycles. In terms of COD treatment, the lack of sulfur doping reduced the electronic conductivity of the material, affected the efficiency of the Cu active center to produce active oxygen, and reduced the COD removal capacity. The composite water treatment lacking sulfur doping has a reduced selective adsorption capacity for antibiotics, and the removal rate of antibiotics will also be reduced.

[0070] In Comparative Example 2, no ionic liquid functionalization treatment was performed, which would directly affect the interface properties of the material and the wastewater treatment effect. In terms of ammonia nitrogen treatment, due to the lack of additional ion exchange sites provided by ionic liquids, the ammonia nitrogen adsorption capacity was reduced. At the same time, the surface hydrophilicity of the water treatment agent was reduced, affecting NH 4+ Diffusion and contact efficiency. In terms of total phosphorus, due to the reduced surface hydrophilicity of the water treatment agent, the dispersion performance of the water treatment agent in the aqueous phase is reduced, and it is easy to agglomerate, resulting in a certain reduction in the total phosphorus removal rate. In the scheme of the present invention, ionic liquids promote the contact between organic molecules and catalytic active sites by enhancing the hydrophilicity of the material and providing ion channels. Without ionic liquid functionalization, the surface hydrophobicity of the water treatment agent is enhanced, and it is difficult for organic pollutants to effectively contact the Cu active center, affecting the catalytic oxidation efficiency, thereby resulting in a decrease in the COD treatment rate. The imidazole ring structure of the ionic liquid can enhance the adsorption of aromatic ring antibiotics through π-π stacking, and at the same time, BF 4-The charge provided by anions helps the binding of polar antibiotics. After losing this interface functionalization, the selective adsorption capacity of the material for tetracycline and quinolone antibiotics is greatly reduced.

[0071] In comparative example 3, the outer Zn / Cu-MOF growth layer is missing. In terms of ammonia nitrogen treatment, only the Cu-MOF layer can still achieve ammonium ion adsorption and conversion through the synergistic effect of Cu active centers and N doping sites, and the ammonia nitrogen removal rate is reduced to a certain extent. Without the outer Zn-rich region, the material loses the active site for efficient chelation of phosphate. Although Cu-MOF also has a certain adsorption capacity for phosphate, its selectivity and binding stability are much lower than those of Zn-MOF, and the removal rate of total phosphorus decreases significantly. The COD removal rate did not change significantly in the early stage. Cu-MOF has good catalytic oxidation performance and can produce sufficient active oxygen species to degrade organic matter after plasma activation. However, due to the lack of the protective effect of the outer MOF, the active components are easily lost. After 10 cycles, the COD removal rate is only 84.14%. The performance in antibiotic removal is also reduced to a certain extent. In the scheme of the present invention, the bimetallic MOF structure provides multiple action sites, the inner Cu-MOF degrades antibiotics by catalytic oxidation, and the outer Zn-MOF achieves adsorption through coordination. After losing this synergistic effect, the antibiotic removal rate is reduced.

[0072] In comparative example 4, Cu and Zn were introduced at one time for MOF growth. In terms of ammonia nitrogen treatment, due to the random distribution of Cu and Zn active sites, the catalytic oxidation efficiency of the Cu active center is disturbed by Zn, and the advantage of spatial separation is lost, resulting in a decrease in ammonia nitrogen removal rate. In addition, the competitive coordination phenomenon of metal ions is prone to occur during the treatment process, affecting the stability of the treatment effect. The randomly distributed metal sites weaken the coordination effect of Zn and phosphate, and the presence of Cu interferes with the selective binding of phosphate, so the total phosphorus removal effect is reduced. The Cu active center is diluted by Zn, the ability to produce active oxygen is weakened, and the deep oxidation effect of the inner Cu enriched area is lost, so the treatment of COD is significantly affected. In terms of antibiotic treatment, the dual action mechanism of spatial separation is lost, and the catalytic degradation effect of Cu can neither be fully exerted nor the selective adsorption of Zn is lacking. The selectivity of water treatment agents for antibiotics is significantly reduced, the treatment efficiency is unstable, and it is easily affected by water quality fluctuations.

[0073] Finally, it should be noted that the above-mentioned embodiments only express several implementation methods of the present invention and are not intended to limit the invention. For those skilled in the art, any modification, equivalent replacement, improvement, etc. made without departing from the concept of the present invention should be included in the protection scope of the invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a composite water treatment agent for aquaculture wastewater treatment, characterized in that: The following steps are involved: S1. Soak corn cob powder in thiourea and urea aqueous solution, stir, continue to add ammonium dihydrogen phosphate aqueous solution, stir, and dry to obtain a mixture; place the mixture in a tube furnace, heat treat it in a nitrogen atmosphere, and cool it to room temperature to obtain nitrogen, phosphorus and sulfur ternary doped carbon spheres; S2. Prepare an ethanol solution of ionic liquid, add nitrogen, phosphorus and sulfur ternary doped carbon spheres thereto, ultrasonically disperse, stir, filter, wash and dry to obtain functionalized carbon spheres; S3. dissolving copper acetate in a mixed solution of ethanol and water, adding the functionalized carbon spheres thereto, dispersing by ultrasonication, then dropping an ethanol solution containing 1,3,5-benzenetricarboxylic acid, heating and stirring to react, obtaining a dispersion, centrifuging, and washing with ethanol to obtain surface Cu-MOF-coated carbon spheres; S4. Dissolve zinc acetate and copper acetate in a mixed solution of ethanol and water, add the surface Cu-MOF coated carbon spheres thereto, disperse by ultrasonication, then dropwise add an ethanol solution containing 1,3,5-benzenetricarboxylic acid, heat and stir to react, obtain a dispersion, centrifuge, wash with ethanol, and vacuum dry to obtain a prefabricated composite water treatment agent; S5. The prefabricated composite water treatment agent is subjected to plasma treatment to obtain the composite water treatment agent.

2. The method for preparing the composite water treatment agent for aquaculture wastewater treatment according to claim 1, characterized in that: In step S1, the mass ratio of corn cob powder, thiourea and urea is 1:(0.4-0.8):(0.4-0.8); the concentration of thiourea and urea aqueous solution is 0.1-0.2 g / mL.

3. The method for preparing the composite water treatment agent for aquaculture wastewater treatment according to claim 1, characterized in that: The mass ratio of the amount of diammonium phosphate to the amount of corn cob powder in step S2 is (0.4-0.8):

1.

4. The method for preparing the composite water treatment agent for aquaculture wastewater treatment according to claim 1, characterized in that: The specific conditions of the tube furnace heat treatment in step S1 are: heating to 500-550° C. at 5° C. / min, keeping the temperature for 2 hours, and naturally cooling to room temperature.

5. The method for preparing the composite water treatment agent for aquaculture wastewater treatment according to claim 1, characterized in that: In step S2, the ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid with a concentration of 0.05-0.1 g / mL; The mass ratio of ionic liquid to nitrogen, phosphorus and sulfur ternary doped carbon balls is (0.2-0.3):

1.

6. The method for preparing the composite water treatment agent for aquaculture wastewater treatment according to claim 1, characterized in that: In step S3, the mass ratio of copper acetate, 1,3,5-benzenetricarboxylic acid and functionalized carbon spheres is (0.8-0.95):(0.2-0.3):

1.

7. The method for preparing a composite water treatment agent for aquaculture wastewater treatment according to claim 1, characterized in that: In step S3, the volume ratio of ethanol to water is 3:1; the concentration of the copper acetate mixed solution is 0.07-0.1 g / mL; the concentration of the 1,3,5-benzenetricarboxylic acid ethanol solution is 0.04-0.06 g / mL; and the heating temperature is 60°C.

8. The method for preparing the composite water treatment agent for aquaculture wastewater treatment according to claim 1, characterized in that: In step S4, the molar ratio of zinc acetate to copper acetate is (2-4):1; the mass ratio of the total amount of zinc acetate and copper acetate, 1,3,5-benzenetricarboxylic acid and the surface Cu-MOF coated carbon balls is (0.2-0.4):(0.1-0.2):

1.

9. The method for preparing the composite water treatment agent for aquaculture wastewater treatment according to claim 1, characterized in that: In step S4, the volume ratio of ethanol to water is 3:1; the concentration of zinc acetate is 0.03-0.06 g / mL; the concentration of 1,3,5-benzenetricarboxylic acid ethanol solution is 0.04-0.06 g / mL; and the heating temperature is 70°C.

10. The method for preparing the composite water treatment agent for aquaculture wastewater treatment according to claim 1, characterized in that: The specific conditions of the plasma treatment in step S5 are: in an oxygen atmosphere, at a flow rate of 50 mL / min and a power of 200 W for 5 min.

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