Method for producing a composite water treatment agent

Abstract

This invention discloses a method for producing a composite water treatment agent. It uses a poly(N-isopropylacrylamide-acrylic acid) copolymer as a temperature- and pH-responsive wall material, encapsulating a flocculant core composed of polyferric sulfate and polysilicic acid. After dopamine biomimetic modification, urease is covalently grafted onto the core, which is then combined with sodium alginate and spray-granulated. By setting response thresholds of 18-38℃ and pH 7.0-8.5, precise flocculant dosing is achieved. The method utilizes a synergistic and reversible response sequence of "response-flocculation-pH drop activating enzyme degradation-sedimentation" to correct water quality mismatches, solving problems of inaccurate dosing and residual pollution. This method is suitable for municipal wastewater and industrial cooling water treatment.

Description

Technical Field

[0001] This invention relates to the intersection of intelligent environmental protection materials and water treatment processes, specifically to a method for producing a composite water treatment agent. Background Technology

[0002] In the water treatment industry, composite flocculants are widely used in municipal sewage and industrial cooling water treatment due to their high purification capabilities. However, traditional products have two major pain points: First, the dosage needs to be manually adjusted according to water quality fluctuations, which can easily lead to waste of chemicals or substandard treatment due to inaccurate matching. Second, residual flocculant molecules can easily cause secondary pollution of water bodies, and existing treatment methods are difficult to eradicate at low cost.

[0003] While there have been attempts to use temperature-sensitive and pH-responsive materials for controlled-release agents, these mostly employ single-response mechanisms, lacking sufficient precision to adapt to complex water quality fluctuations. Enzymatic degradation technology, while capable of treating organic residues, suffers from low enzyme loading rates, easy inactivation, and poor synergy with the flocculation process. Furthermore, existing smart water treatment agents lack a sequential synergistic design of "controlled release-degradation-sedimentation," failing to form a closed-loop treatment system. This makes it impossible to simultaneously address issues of dosage accuracy, residual pollution, and treatment efficiency, thus failing to meet the high-efficiency and green requirements of practical water treatment scenarios. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a method for producing a composite water treatment agent. This agent achieves precise controlled release of the flocculation core through a dual temperature- and pH-sensitive response. It combines a dopamine-modified urease-based agent for efficient degradation of residual flocculants with sodium alginate to facilitate rapid floc settling. This forms a closed-loop treatment system with a synergistic "response-flocculation-degradation-sedimentation" sequence. The system exhibits excellent performance in terms of dosage accuracy, residual removal rate, treatment efficiency, and reversible cycle stability, and can meet the high-efficiency and green treatment needs of various complex water quality environments such as municipal wastewater and industrial cooling water.

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

[0006] A composite water treatment agent, said water treatment agent being prepared from the following raw materials in parts by weight:

[0007] 70-80 parts N-isopropylacrylamide monomer, 20-30 parts acrylic acid monomer, 30-50 parts polyferric sulfate, 10-15 parts polysilicic acid, 2-5 parts dopamine, 1-3 parts urease, 5-8 parts sodium alginate, and 280-320 parts deionized water.

[0008] The composite water treatment agent has a particle size of 50-100 μm, and under conditions of 18-38℃ and pH 7.0-8.5, the flocculant release rate is 60%-90%; the residual flocculant degradation rate is 90%-99%; and the floc settling velocity is 2.0-4.0 cm / min.

[0009] Preferably, the preparation method of the composite water treatment agent includes the following specific steps:

[0010] S1. Mix N-isopropylacrylamide monomer and acrylic acid monomer in a molar ratio of 7:3-8:2, dissolve in deionized water, and then add 0.5%-1.5% of ammonium persulfate-sodium bisulfite initiator by mass of total monomers. React at 60-70℃ for 4-6 h to synthesize poly(N-isopropylacrylamide-acrylic acid copolymer).

[0011] S2. Polyferric sulfate and polysilicic acid are mixed in a mass ratio of 3:1-5:1 and stirred evenly to obtain a composite flocculant core.

[0012] S3. The composite flocculant core is dispersed in a poly(N-isopropylacrylamide-acrylic acid copolymer) solution and emulsified for 30-60 min at a stirring speed of 800-1200 rpm and a temperature of 40-50℃ to form a water-in-oil emulsion and obtain the microcapsule precursor.

[0013] S4. Add a dopamine solution with a concentration of 2-5 g / L to the microcapsule precursor at a volume ratio of 1:3-1:5, and react at pH 8.0-8.5 and temperature 25-30℃ for 2-4 h to form a dopamine biomimetic modification layer; then add a urease solution with a concentration of 1000-2000 U / mL and react at 20-25℃ for 1-2 h to covalently graft urease onto the surface of the modification layer.

[0014] S5. Mix the product of S4 with a sodium alginate solution of 1%-3% by mass at a mass ratio of 5:1-8:1, and granulate by spray drying. The inlet air temperature is 120-150℃, the outlet air temperature is 60-80℃, and the feed rate is 5-10 mL / min to obtain a composite water treatment agent.

[0015] Preferably, in step S3, the emulsification method uses a high-shear emulsifier with a shear rate of 10,000-15,000 rpm, and the average particle size of the emulsion after emulsification is 1-5 μm.

[0016] Preferably, the urease loading rate in step S4 is 20%-30%.

[0017] Preferably, the reversible response cycle of the composite water treatment agent is 5-8 times, the urease activity retention rate after the cycle is 70%-90%, and the cumulative release rate of the flocculant core is 95%-99%.

[0018] Preferably, when the water treatment agent treats municipal wastewater with a chemical oxygen demand (COD) of 100-500 mg / L, the COD removal rate is 85%-95%; when treating industrial cooling water with an oil content of 50-100 mg / L, the oil removal rate is 90%-98%.

[0019] Preferably, the storage stability of the water treatment agent is as follows: after being sealed and stored for 6 months at 25°C and 60% relative humidity, the flocculant release rate decreases by 5%-10%, and the urease activity retention rate is 80%-90%.

[0020] Due to the adoption of the above technical solution, the beneficial effects of this invention are as follows: The composite water treatment agent of this invention has temperature-sensitive and pH-responsive characteristics, with a flocculant release rate of 60%-90% under conditions of 18-38℃ and pH 7.0-8.5, and a reversible response cycle of 5-8 times. The residual flocculant degradation rate is 90%-99%, and the floc settling velocity is 2.0-4.0 cm / min, avoiding secondary pollution and improving efficiency. It achieves a removal rate of 85%-95% for municipal wastewater with COD of 100-500 mg / L and a removal rate of 90%-98% for industrial cooling water with an oil content of 50-100 mg / L. After dopamine modification and fixation, its performance remains stable for 6 months of storage at 25℃ and 60% humidity, combining the advantages of high efficiency, greenness, and long-lasting effect. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0022] Figure 1 This is a bar chart showing the flocculant release rate of the sample in Example 1 of the present invention under different temperature and pH conditions;

[0023] Figure 2 This is a bar chart comparing the storage retention rate and cycling retention rate of urease activity in different samples of this invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] Example 1:

[0026] This embodiment 1 describes a composite water treatment agent, which is prepared from the following raw materials in parts by weight:

[0027] 75 parts N-isopropylacrylamide monomer, 25 parts acrylic acid monomer, 40 parts polyferric sulfate, 12 parts polysilicic acid, 3 parts dopamine, 2 parts urease, 6 parts sodium alginate, and 300 parts deionized water.

[0028] The preparation method of the composite water treatment agent in this embodiment includes the following specific steps:

[0029] S1. N-isopropylacrylamide monomer and acrylic acid monomer were mixed at a molar ratio of 7.5:2.5, 150 parts of deionized water were added, and 1.0% of ammonium persulfate-sodium bisulfite initiator by total monomer mass was added. The mixture was reacted at 65°C for 5 h to synthesize poly(N-isopropylacrylamide-acrylic acid copolymer).

[0030] S2. Polyferric sulfate and polysilicic acid are mixed at a mass ratio of 10:3 and stirred evenly to obtain a composite flocculant core.

[0031] S3. The composite flocculant core is dispersed in a poly(N-isopropylacrylamide-acrylic acid copolymer) solution and emulsified at a stirring speed of 1000 rpm and a temperature of 45℃ for 45 min to form a water-in-oil emulsion, thus obtaining the microcapsule precursor.

[0032] S4. Dopamine was dissolved in 10 parts of deionized water to prepare a 3 g / L dopamine solution, which was then added to the microcapsule precursor at a volume ratio of 1:4. The mixture was reacted at pH 8.2 and 28℃ for 3 h to form a dopamine biomimetic modification layer. Urease was then dissolved in 10 parts of deionized water to prepare a 1500 U / mL urease solution, which was added to the system. The mixture was reacted at 22℃ for 1.5 h to covalently graft urease onto the surface of the modification layer, with a urease loading rate of 25%.

[0033] S5. Dissolve sodium alginate in 130 parts of deionized water to prepare a sodium alginate solution with a mass fraction of 2%. Mix this solution with the product of step S4 at a mass ratio of 6:1. Then, granulate by spray drying with an inlet air temperature of 135℃, an outlet air temperature of 70℃, and a feed rate of 8 mL / min to obtain a composite water treatment agent.

[0034] Example 2:

[0035] This embodiment 2 presents a composite water treatment agent, which is prepared from the following raw materials in parts by weight:

[0036] 70 parts N-isopropylacrylamide monomer, 30 parts acrylic acid monomer, 40 parts polyferric sulfate, 12 parts polysilicic acid, 3 parts dopamine, 2 parts urease, 6 parts sodium alginate, and 300 parts deionized water.

[0037] The preparation method of the composite water treatment agent in Example 2 is the same as that in Example 1.

[0038] Example 3:

[0039] This embodiment 3 describes a composite water treatment agent, which is prepared from the following raw materials in parts by weight:

[0040] 75 parts N-isopropylacrylamide monomer, 25 parts acrylic acid monomer, 39 parts polyferric sulfate, 13 parts polysilicic acid, 3 parts dopamine, 2 parts urease, 6 parts sodium alginate, and 300 parts deionized water.

[0041] The preparation method of the composite water treatment agent in Example 3 is the same as that in Example 1, except that the mass ratio of polyferric sulfate to polysilicic acid is adjusted to 3:1.

[0042] Example 4:

[0043] This embodiment 4 describes a composite water treatment agent, which is prepared from the following raw materials in parts by weight:

[0044] 75 parts N-isopropylacrylamide monomer, 25 parts acrylic acid monomer, 40 parts polyferric sulfate, 12 parts polysilicic acid, 2 parts dopamine, 2 parts urease, 6 parts sodium alginate, and 300 parts deionized water.

[0045] The preparation method of the composite water treatment agent in Example 4 is the same as that in Example 1, except that the concentration of dopamine solution is adjusted to 2 g / L.

[0046] Example 5:

[0047] This embodiment 5 describes a composite water treatment agent, which is prepared from the following raw materials in parts by weight:

[0048] 75 parts N-isopropylacrylamide monomer, 25 parts acrylic acid monomer, 40 parts polyferric sulfate, 12 parts polysilicic acid, 3 parts dopamine, 2 parts urease, 3 parts sodium alginate, and 300 parts deionized water.

[0049] The preparation method of the composite water treatment agent in Example 5 is the same as that in Example 1, except that the mass fraction of sodium alginate solution is adjusted to 1%.

[0050] Comparative Example 1:

[0051] This comparative example 1 describes a composite water treatment agent prepared from the following raw materials in parts by weight:

[0052] 75 parts N-isopropylacrylamide monomer, 25 parts acrylic acid monomer, 40 parts polyferric sulfate, 12 parts polysilicic acid, 0 parts dopamine, 2 parts urease, 6 parts sodium alginate, and 300 parts deionized water.

[0053] The preparation method of the composite water treatment agent in Comparative Example 1 is the same as that in Example 1, except that dopamine is not added. Step S4 is adjusted as follows: urease is dissolved in 10 parts of deionized water to prepare a urease solution with a concentration of 1500 U / mL, added to the system, and reacted at 22°C for 1.5 h to fix the urease on the surface of the microcapsules.

[0054] Comparative Example 2:

[0055] This Comparative Example 2 describes a composite water treatment agent prepared from the following raw materials in parts by weight:

[0056] 100 parts N-isopropylacrylamide monomer, 0 parts acrylic acid monomer, 40 parts polyferric sulfate, 12 parts polysilicic acid, 3 parts dopamine, 2 parts urease, 6 parts sodium alginate, and 300 parts deionized water.

[0057] The preparation method of the composite water treatment agent in Comparative Example 2 is the same as that in Example 1, except that acrylic acid monomer is not added.

[0058] Comparative Example 3:

[0059] This comparative example 3 describes a composite water treatment agent prepared from the following raw materials in parts by weight:

[0060] 75 parts N-isopropylacrylamide monomer, 25 parts acrylic acid monomer, 40 parts polyferric sulfate, 12 parts polysilicic acid, 3 parts dopamine, 2 parts urease, 0 parts sodium alginate, and 300 parts deionized water.

[0061] The preparation method of the composite water treatment agent in Comparative Example 3 is the same as that in Example 1, except that sodium alginate is not added.

[0062] Performance testing

[0063] 1. Particle size distribution test

[0064] Using a laser particle size analyzer, the dried particles prepared in the examples and comparative examples were dispersed in deionized water, and the particle size distribution (D50, D90) was tested. Each sample was tested in parallel three times and the average value was taken.

[0065] Table 1. Test data on particle size distribution of each sample

[0066] sample D50 average value (μm) D90 average value (μm) Uniformity coefficient (D90 / D50) Does it conform to the claims (50-100 μm)? Example 1 75.1 98.8 1.32 yes Example 2 77.8 102.7 1.32 yes Example 3 73.4 97.1 1.32 yes Example 4 76.7 100.8 1.31 yes Example 5 78.5 103.8 1.32 yes Comparative Example 1 85.8 115.9 1.40 No (D90 is out of range, particle size distribution is uneven) Comparative Example 2 89.0 122.7 1.38 No (D90 is out of range; lack of acrylic monomers leads to uneven copolymer coating) Comparative Example 3 71.6 108.8 1.52 No (uniformity coefficient exceeds standard, no sodium alginate causing particle agglomeration)

[0067] The water treatment agent particles in the example had a D50 of 73.4-78.5 μm (meeting the requirement of 50-100 μm) and a uniformity coefficient ≤1.32, with a concentrated distribution, thanks to the synergistic effect of copolymer coating, sodium alginate coagulation, and dopamine modification. The comparative example, due to the absence of any core component, showed D90 exceeding the range or uniformity coefficient exceeding the standard, proving that the three are crucial to ensuring particle uniformity.

[0068] 2. Temperature-pH dual-response release rate test

[0069] To verify the release efficiency of the flocculants under target conditions (18-38℃, pH 7.0-8.5) and their stability under non-target conditions, tests were conducted.

[0070] Simulated wastewater configuration:

[0071] Basic simulated wastewater formula (simulated municipal wastewater matrix): Weigh 0.05 g anhydrous calcium chloride, 0.02 g magnesium sulfate, and 0.1 g sodium bicarbonate, dissolve them in 1000 mL deionized water, and stir well to obtain the basic solution;

[0072] Temperature gradient preparation: Take 4 100 mL aliquots of base solution and place them in a constant temperature water bath shaker. Adjust the temperature to 15℃, 25℃, 35℃ and 40℃ respectively, and keep them at the same temperature for 30 min for later use.

[0073] pH gradient preparation: Take four 100 mL aliquots of base solution (at a constant temperature of 25℃), and adjust the pH value to 5.0, 6.0, 7.5, and 9.0 with 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide. Use a pH meter to calibrate in real time, and let stand for 10 min after calibration to stabilize the pH value.

[0074] Composite condition configuration: Additionally, three samples each of simulated wastewater under "target conditions (25℃, pH 7.5)" and "non-target conditions (15℃, pH 5.0)" are configured for parallel testing.

[0075] Standard curve preparation: Prepare 1000 mg / L Fe 3+ Standard stock solutions were diluted to prepare a series of working solutions at concentrations of 1, 5, 10, 50, and 100 mg / L; Fe was determined using ICP-OES preheating for 30 min and deionized water as a blank. 3+ Characteristic emission intensity (259.94 nm), plotted as a standard curve.

[0076] Sample release test: Accurately weigh 0.5 g of sample (±0.0001 g), add simulated wastewater under various conditions (3 replicates); shake at 150 rpm for 2 h (observe every 30 min), centrifuge at 8000 rpm for 10 min after shaking, and filter the supernatant through a 0.45 μm filter membrane;

[0077] ICP-OES determination of Fe in filtrate 3+ Concentration, each filtrate was measured twice in parallel (deviation ≤2%); simulated wastewater without sample was used as a blank, and Fe was subtracted. 3+ Background value; the absence of matrix interference was verified using a blank water treatment agent without polyferric sulfate.

[0078] Table 2. Release rate data (%) of each sample at 15℃ and different pH conditions.

[0079] sample 5.0 6.0 7.5 9.0 Example 1 22.7 45.3 58.6 50.2 Example 2 20.8 42.1 55.3 47.5 Example 3 22.0 43.8 57.2 48.9 Example 4 20.1 40.5 53.8 45.9 Example 5 18.9 38.7 51.5 43.2 Comparative Example 1 28.8 50.2 65.8 58.3 Comparative Example 2 17.6 30.5 38.6 35.2 Comparative Example 3 23.8 44.5 56.9 49.6

[0080] Table 3. Release rate data (%) of each sample under different pH conditions at 25℃.

[0081] sample 5.0 6.0 7.5 9.0 Example 1 24.5 56.8 78.8 65.3 Example 2 22.8 53.6 75.7 62.5 Example 3 23.6 55.2 77.1 63.8 Example 4 21.9 52.3 74.8 61.2 Example 5 20.7 51.1 73.5 59.8 Comparative Example 1 30.2 58.5 72.6 66.1 Comparative Example 2 19.5 38.6 52.4 47.2 Comparative Example 3 25.3 57.2 77.8 64.9

[0082] Table 4. Release rate data (%) of each sample at 35℃ and different pH conditions.

[0083] sample 5.0 6.0 7.5 9.0 Example 1 26.8 62.5 82.4 70.1 Example 2 24.3 59.2 79.6 67.3 Example 3 25.7 60.8 80.9 68.5 Example 4 23.5 57.6 78.3 65.8 Example 5 22.1 55.3 76.7 63.2 Comparative Example 1 32.5 64.3 79.2 72.6 Comparative Example 2 21.8 42.3 56.8 51.5 Comparative Example 3 27.2 61.5 81.6 69.2

[0084] Table 5. Release rate data (%) of various samples at 40℃ and different pH conditions.

[0085] sample 5.0 6.0 7.5 9.0 Example 1 38.6 48.3 42.5 45.7 Example 2 35.8 45.1 39.8 42.5 Example 3 36.5 46.7 41.2 43.9 Example 4 34.2 43.5 38.6 41.3 Example 5 32.9 41.8 36.9 39.5 Comparative Example 1 40.3 52.8 47.6 50.1 Comparative Example 2 29.7 37.2 33.5 35.8 Comparative Example 3 37.8 47.5 42.1 44.7

[0086] The examples showed a release rate of 73.5%-82.4% under target conditions (meeting the 60%-90% requirement) and a release rate of ≤42.5% under non-target conditions, demonstrating excellent response specificity. Comparative Example 2 (without acrylic monomer) showed a significantly deteriorated and irreversible release rate, confirming that the interpenetrating polymer network copolymer is the dual-response core. Comparative Example 1 (without dopamine) showed decreased encapsulation stability, highlighting the role of dopamine modification.

[0087] 3. Residual flocculant degradation rate test

[0088] Simulated wastewater preparation: Dissolve 0.1 g of polyferric sulfate in 1000 mL of simulated wastewater base solution; divide the prepared simulated wastewater into 3 parallel samples, each 200 mL, and preheat in a 25℃ constant temperature water bath for 30 min (matching the target reaction temperature).

[0089] Standard curve preparation: Accurately weigh 0.286 g of ferric sulfate standard, dissolve it in 100 mL of deionized water, and prepare a 1000 mg / L Fe solution. 3+ Standard stock solutions: Transfer 0.2 mL, 0.5 mL, 1.0 mL, 2.0 mL, and 5.0 mL of standard stock solutions to 50 mL colorimetric tubes, respectively, and make up to 20 mL with deionized water. Add 10 mL of sulfosalicylic acid solution, add ammonia dropwise until the solution turns a stable purple-red color, and make up to 50 mL. Let stand for 10 min.

[0090] Using a blank reagent as a reference, the absorbance was measured at a wavelength of 510 nm, with Fe... 3+ Plot a standard curve with concentration on the x-axis and absorbance on the y-axis, and calculate the regression equation.

[0091] Flocculation-degradation reaction: Accurately weigh 0.5 g of each sample (accurate to 0.0001 g) and add them to three parallel simulated wastewater samples. Stir at 25℃ and 150 rpm for 30 min (to complete the flocculation reaction); after stopping stirring, let stand for 1 h, take 50 mL of the supernatant, centrifuge at 8000 rpm for 10 min, and then filter through a 0.45 μm filter membrane to remove flocculent impurities; place the filtrate in a 25℃ constant temperature water bath and keep it at that temperature for 2 h (to allow urease to fully degrade residual Fe³⁺).

[0092] Residual concentration detection: Take 10 mL of the degraded filtrate into a 50 mL colorimetric tube, add the colorimetric reagent according to the standard curve plotting procedure, make up to volume, and let stand for 10 min; measure the absorbance with a spectrophotometer, and substitute it into the regression equation to calculate the residual Fe. 3+ Concentration (each sample was tested in parallel 3 times, with a deviation of ≤2%).

[0093] Table 6 Degradation rate test data for each sample

[0094] sample Initial Fe³⁺ concentration (mg / L) Residual Fe³⁺ concentration (mg / L) Degradation rate (%) Does it meet the requirements (≥90%)? Example 1 245.0 18.9 92.2 yes Example 2 245.0 20.6 91.6 yes Example 3 245.0 19.8 91.9 yes Example 4 245.0 22.0 91.0 yes Example 5 245.0 23.4 90.5 Yes (close to the critical value) Comparative Example 1 245.0 77.1 68.5 No (≤70%, meets degradation requirements) Comparative Example 2 245.0 26.1 89.4 no Comparative Example 3 245.0 21.2 91.4 yes

[0095] Example of residual Fe 3+ The degradation rate was 90.5%-92.2% (≥90%), and the dopamine-modified layer achieved stable fixation of urease. The degradation rate of Comparative Example 1 (without dopamine) was only 68.5%, and urease was easily detached and inactivated. The degradation rates of other comparative examples were close to those of the Example, proving that acrylic monomer and sodium alginate do not affect the urease degradation function.

[0096] 4. COD / Oil Removal Rate Test

[0097] Simulated municipal wastewater (COD=300 mg / L): Accurately weigh 0.0425 g potassium hydrogen phthalate (standard reagent), dissolve in 1000 mL deionized water, stir well and set aside;

[0098] Simulated industrial cooling water (oil content = 80 mg / L): Take 4 mL of petroleum ether (analytical grade), dissolve it in 500 mL of deionized water, ultrasonically disperse for 30 min, prepare simulated wastewater with an oil content of 80 mg / L, and let it stand for 10 min for later use.

[0099] (1) COD removal rate test (potassium dichromate method, GB 11914-89)

[0100] Take 20 mL of simulated municipal wastewater and place it in a 50 mL digestion tube. Add 10 mL of potassium dichromate standard solution and 15 mL of sulfuric acid-silver sulfate catalyst. Shake well and place in a COD digester. Digest at 165℃ for 2 h. After digestion, cool to room temperature, transfer to a 250 mL Erlenmeyer flask, and rinse the digestion tube three times with deionized water. Combine the rinsing solutions (total volume 120-140 mL). Add 3 drops of ferroin indicator and titrate with ferrous ammonium sulfate standard solution until the solution changes from yellow to reddish-brown. Record the volume consumed (the blank experiment is performed using the same procedure). Calculate the COD value according to the formula: COD (mg / L) = (V0-V1)×c×8×1000 / V, where V0 is the blank consumption volume, V1 is the sample consumption volume, c is the ferrous ammonium sulfate concentration (mol / L), and V is the wastewater sampling volume (20 mL). The COD removal rate was calculated by conducting three parallel tests: Removal rate (%) = (Initial COD - Post-treatment COD) / Initial COD × 100%.

[0101] (2) Oil removal rate test (infrared spectrophotometry, GB / T 16488-1996)

[0102] Take 200 mL of simulated industrial cooling water and place it in a 500 mL separatory funnel. Add 20 mL of carbon tetrachloride and extract by shaking for 5 min (inverting the funnel three times to release gas during extraction). Let the mixture stand for 10 min to separate the layers. Filter the lower organic phase through an anhydrous sodium sulfate funnel into a 100 mL colorimetric tube. Wash the separatory funnel and anhydrous sodium sulfate twice with 10 mL of carbon tetrachloride (baking at 550℃ for 2 h to remove moisture and impurities). Combine the filtrates and dilute to 100 mL. Turn on the infrared spectrophotometer and measure the absorbance using carbon tetrachloride as a blank. Substitute the absorbance into the standard curve to calculate the oil content (the standard curve is plotted using a series of oil standard solutions prepared with petroleum ether, R²≥0.999). Take another 200 mL of simulated industrial cooling water and add 0.5 g of the sample to be tested. Stir at 150 rpm for 30 min and let stand for 1 h. Take the supernatant and filter it through a 0.45 μm filter membrane. Measure the oil content after treatment using the above steps. The oil removal rate was calculated by conducting three parallel tests: Removal rate (%) = (Initial oil content - Oil content after treatment) / Initial oil content × 100%.

[0103] Table 7. Test data on COD removal rate of each sample

[0104] sample COD (mg / L) after treatment COD removal rate (%) Does it meet the requirements (≥85%)? Example 1 38.8 87.2 yes Example 2 41.6 86.2 yes Example 3 40.1 86.7 yes Example 4 43.8 85.5 yes Example 5 46.5 84.6 no Comparative Example 1 48.6 83.9 no Comparative Example 2 62.8 79.2 No (Meets degradation requirements) Comparative Example 3 54.0 82.1 No (Meets degradation requirements)

[0105] Table 8. Test data on oil removal rate of each sample

[0106] sample Oil content after treatment (mg / L) Oil removal rate (%) Does it meet the requirements (≥90%)? Example 1 7.3 90.8 yes Example 2 7.9 90.1 yes Example 3 7.6 90.5 yes Example 4 8.4 89.5 no Example 5 8.8 89.0 no Comparative Example 1 9.6 88.0 No (Meets degradation requirements) Comparative Example 2 9.0 88.7 no Comparative Example 3 12.4 84.5 No (Meets degradation requirements)

[0107] Examples 1-4 showed COD removal rates of 85.5%-87.2%, and Examples 1-3 showed oil removal rates of 90.1%-90.8%, demonstrating significant synergistic purification effects. The comparative examples, due to the lack of core components, resulted in insufficient release, incomplete sedimentation, or decreased adsorption, and their removal rates did not meet the standards, thus verifying the necessity of the three components working together to improve purification efficiency.

[0108] 5. Stability and durability testing

[0109] (1) Urease activity retention rate test

[0110] Fresh sample activity test: The urease activity (U / g) of a unit mass of water treatment agent was detected using a urease activity kit.

[0111] Storage stability: The sample was sealed and stored at 25℃ and 60% relative humidity for 6 months, and the urease activity was tested again to calculate the retention rate;

[0112] Cyclic stability: The water treatment agent was repeatedly used to simulate wastewater treatment (centrifuged and recovered after each treatment). After 5-8 cycles, the urease activity was measured and the retention rate was calculated (≥70%).

[0113] (2) Reversible response cyclic test

[0114] Alternate between target conditions (25℃, pH 7.5) and non-target conditions (15℃, pH 5.0), and measure the flocculant release rate after each switch. Repeat this cycle 5-8 times, requiring the release rate to still be ≥60% on the 8th cycle (demonstrating reversibility).

[0115] Table 9. Data on urease activity retention rate of each sample

[0116] sample Urease activity (U / g) in fresh samples Storage retention rate (%) (after 6 months) Cyclic retention rate (%) (after 8 cycles) Example 1 128.8 81.8 71.2 Example 2 126.6 81.4 71.0 Example 3 127.8 81.3 70.8 Example 4 126.1 80.0 70.4 Example 5 124.5 80.4 70.3 Comparative Example 1 124.0 47.4 55.3 Comparative Example 2 125.6 78.8 69.1 Comparative Example 3 127.1 80.0 70.4

[0117] Table 10. Reversible Response Cyclic Test Data for Each Sample (%)

[0118] sample 1 2 3 4 5 6 7 8 Example 1 78.8 77.5 76.3 75.1 74.2 73.5 72.8 71.6 Example 2 75.7 74.3 73.1 72.0 71.2 70.5 69.8 68.9 Example 3 77.1 75.8 74.6 73.5 72.6 71.9 71.2 70.3 Example 4 74.8 73.5 72.3 71.2 70.4 69.7 69.0 68.2 Example 5 73.5 72.2 71.0 69.9 69.1 68.4 67.7 66.9 Comparative Example 1 72.6 71.3 70.1 68.9 68.1 67.4 66.7 65.9 Comparative Example 2 52.4 50.8 49.3 47.7 46.2 44.6 43.1 41.5 Comparative Example 3 77.8 76.5 75.2 74.0 73.1 72.4 71.7 70.9

[0119] In the examples, the urease retention rate after 6 months of storage was ≥80%, the retention rate after 8 cycles was ≥70.3%, and the copolymer reversible response release rate after 8 cycles was ≥66.9%, demonstrating excellent long-term performance. In contrast, the stability of urease in Comparative Example 1 (without dopamine) was significantly deteriorated, while that in Comparative Example 2 (without acrylic monomer) was irreversible, confirming the key role of the core components in stability.

[0120] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite water treatment agent, characterized by comprising: The water treatment agent is prepared from the following raw materials in parts by weight: 70-80 parts N-isopropylacrylamide monomer, 20-30 parts acrylic acid monomer, 30-50 parts polyferric sulfate, 10-15 parts polysilicic acid, 2-5 parts dopamine, 1-3 parts urease, 5-8 parts sodium alginate, and 280-320 parts deionized water. The composite water treatment agent has a particle size of 50-100 μm, and under conditions of 18-38℃ and pH 7.0-8.5, the flocculant release rate is 60%-90%; the residual flocculant degradation rate is 90%-99%; and the floc settling velocity is 2.0-4.0 cm / min.

2. The composite water treatment agent according to claim 1, characterized in that, The reversible response cycle of the composite water treatment agent is 5-8 times, and the urease activity retention rate after the cycle is 70%-90%, while the cumulative release rate of the flocculants is 95%-99%.

3. The composite water treatment agent according to claim 1, characterized in that, When treating municipal wastewater with a chemical oxygen demand (COD) of 100-500 mg / L, the COD removal rate of the water treatment agent is 85%-95%; when treating industrial cooling water with an oil content of 50-100 mg / L, the oil removal rate is 90%-98%.

4. The composite water treatment agent according to claim 1, characterized in that, The storage stability of the water treatment agent is as follows: when sealed and stored for 6 months at 25°C and 60% relative humidity, the flocculant release rate decreases by 5%-10%, and the urease activity retention rate is 80%-90%.

5. A method for preparing a composite water treatment agent, used to prepare the composite water treatment agent according to claims 1-4, characterized in that, The specific preparation steps are as follows: S1. Mix N-isopropylacrylamide monomer and acrylic acid monomer in a molar ratio of 7:3-8:2, dissolve in deionized water, and then add 0.5%-1.5% of ammonium persulfate-sodium bisulfite initiator by mass of total monomers. React at 60-70℃ for 4-6 hours to synthesize poly(N-isopropylacrylamide-acrylic acid copolymer). S2. Polyferric sulfate and polysilicic acid are mixed in a mass ratio of 3:1-5:1 and stirred evenly to obtain a composite flocculant core. S3. The composite flocculant core is dispersed in a poly(N-isopropylacrylamide-acrylic acid copolymer) solution and emulsified for 30-60 min at a stirring speed of 800-1200 rpm and a temperature of 40-50℃ to form a water-in-oil emulsion and obtain the microcapsule precursor. S4. Add a dopamine solution with a concentration of 2-5 g / L to the microcapsule precursor at a volume ratio of 1:3-1:5, and react at pH 8.0-8.5 and temperature 25-30℃ for 2-4 h to form a dopamine biomimetic modification layer; then add a urease solution with a concentration of 1000-2000 U / mL and react at 20-25℃ for 1-2 h to covalently graft urease onto the surface of the modification layer. S5. Mix the product of S4 with a sodium alginate solution of 1%-3% by mass at a mass ratio of 5:1-8:1, and granulate by spray drying. The inlet air temperature is 120-150℃, the outlet air temperature is 60-80℃, and the feed rate is 5-10 mL / min to obtain a composite water treatment agent.

6. The method for preparing a composite water treatment agent according to claim 5, characterized in that, In step S3, the emulsification method uses a high-shear emulsifier with a shear rate of 10,000-15,000 rpm, and the average particle size of the emulsion after emulsification is 1-5 μm.

7. The method for preparing a composite water treatment agent according to claim 5, characterized in that, In step S4, the urease loading rate is 20%-30%.

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