Preparation method of scale inhibitor for water pollution control

Abstract

The invention discloses a preparation method of a scale inhibitor for water pollution prevention and control, and belongs to the technical field of scale inhibitors, the preparation method comprises the following steps: screening natural diatomite, and modifying with a KH-550 silane coupling agent to obtain modified diatomite; dIC and NHS are used as carboxyl activators, DMPA is used as a basic catalyst, PLGA is converted into an ester intermediate, the ester intermediate and glucosamine are subjected to an amidation reaction, and a modified PLGA copolymer is obtained; dipping the modified PLGA copolymer in the modified diatomite to obtain supported modified PLGA powder; under the action of electrostatic self-assembly, the supported modified PLGA powder is coated with a chitosan shell layer doped with ethidene diamine modified graphene oxide, and the PLGA microcapsule is obtained; the PLGA microcapsules, deionized water, dodecyl polyglucoside and polyethylene glycol are stirred and mixed, and the scale inhibitor for water pollution prevention and control is obtained. The scale inhibitor has stable release, good overall dispersibility and efficient synergistic scale inhibition performance.

Description

Technical Field

[0001] The invention belongs to the technical field of scale inhibitors, and specifically relates to a method for preparing a scale inhibitor for water pollution prevention and control. Background Art

[0002] High-salinity wastewater from the chemical, pharmaceutical, and printing and dyeing industries contains high concentrations of salt and complex pollutants. Direct discharge can seriously harm the aquatic environment and disrupt the aquatic ecosystem. Evaporation and concentration systems are important technologies for treating this type of wastewater, but their operation is often hampered by scaling issues. Calcium, magnesium ions, sulfate, carbonate, and other scaling substances in high-salinity wastewater can form hard scale on the surfaces of equipment such as evaporator heating tubes, significantly reducing heat exchange efficiency. Scale inhibitors, specialized chemical agents that inhibit the crystallization and deposition of scaling substances in water, can effectively prevent the formation of hard scale layers such as calcium and magnesium salts by chelating scaling ions, interfering with crystal growth, or dispersing tiny particles. Chinese patent application publication number CN119191585A discloses a high-salt scale inhibitor suitable for high-salt wastewater multi-evaporation conditions and a method of use. The scale inhibitor consists of 15% polyaspartic acid, 18% polyepoxysuccinic acid, 20% hydroxyethylidene diphosphonic acid, 8% polymaleic anhydride, 12% composite quaternary ammonium salt, 5% 2-phosphate-1,2,4-tricarboxylic acid butane, 3% pH regulator, 5% sodium persulfate, 8% rust inhibitor and 6% preservative. When used, the high-salt wastewater is first pretreated to remove some hardness and impurities, and then the above-mentioned mixed scale inhibitor is added in proportion and evenly dispersed in the wastewater. The scale inhibitor of the invention has excellent scale inhibition performance and can alleviate the accumulation and deposition of salt on the wall of the equipment, thereby extending the service life of the equipment.

[0003] When high-salinity wastewater systems are exposed to high temperatures, the solubility of scale-forming substances changes, making calcium, magnesium, and acid radical ions more susceptible to supersaturation and increasing their crystallization rate. However, at high temperatures, organic scale inhibitors may thermally degrade, resulting in a decrease in their effectiveness. This makes it impossible to effectively mitigate the crystallization and deposition of calcium and magnesium ions on equipment surfaces, exacerbating scaling problems. Therefore, the stability of scale inhibitors in high-temperature applications has become a research priority. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a scale inhibitor for water pollution control. By PLGA coating modification, PLGA microcapsules with slow release and good high-temperature stability are prepared, thereby solving the problem that organic scale inhibitors are easily thermally degraded in high-temperature and high-salt wastewater systems. At the same time, combined with the dispersing effect of dodecyl glucoside, the dispersion stability of the scale inhibitor in high-salt wastewater systems is improved.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A method for preparing a scale inhibitor for water pollution prevention and control comprises the following steps: Step 1: natural diatomaceous earth is sieved and then modified with KH-550 silane coupling agent to obtain modified diatomaceous earth; Step 2: Using DIC and NHS as carboxyl activators and DMPA as a basic catalyst, PLGA is converted into an ester intermediate, which is then amidated with glucosamine to obtain a modified PLGA copolymer; the modified PLGA copolymer is impregnated in modified diatomaceous earth to obtain a loaded modified PLGA powder; Step 3: Through electrostatic self-assembly, the loaded modified PLGA powder is coated in the chitosan shell doped with ethylenediamine-modified graphene oxide to obtain PLGA microcapsules; Step 4: stirring and mixing PLGA microcapsules, deionized water, dodecyl glucoside and polyethylene glycol to obtain a scale inhibitor for water pollution prevention and control.

[0006] Furthermore, the specific preparation process of modified diatomite is as follows: The natural diatomaceous earth is dried at 70-90° C., ground and passed through a 300-mesh sieve, and added to a reactor with a 30wt% sulfuric acid solution, soaked for 20-30 hours, reacted in a water bath at 70-90° C. for 40-60 minutes, filtered after cooling, washed until neutral, dried at 80-100° C., ground again and passed through a 300-mesh sieve, sealed and stored, thereby completing the acid treatment of the diatomaceous earth; the acid-treated diatomaceous earth and deionized water are added to a reactor, silane coupling agent KH-550 and ethanol are added at 70-90° C. with stirring, reacted at 800-1000 rpm for 1-3 hours, filtered, and the filter cake is dried to constant weight to obtain modified diatomaceous earth.

[0007] Furthermore, the usage ratio of natural diatomaceous earth and sulfuric acid is 60-80 g:100-200 mL.

[0008] Furthermore, the mass ratio of the acid-treated diatomaceous earth, deionized water, silane coupling agent and ethanol is 20-30:90-110:0.5-1.5:8-12.

[0009] Furthermore, the specific preparation process of the modified PLGA copolymer is as follows: PLGA and dichloromethane were added to a stirring kettle and stirred at 0-5°C until completely dissolved. N-hydroxysuccinimide, 4-dimethylaminopyridine and N,N-diisopropylcarbodiimide were added in sequence and reacted at 25-35°C for 10-12 hours to form an ester intermediate. Aminoglycosides were dissolved in DMF and added to the reactor and the reaction was continued for 18-24 hours. The reaction system was washed with 5wt% sodium bicarbonate solution and deionized water in sequence, and then dried over anhydrous sodium sulfate, filtered, and the solvent was evaporated under reduced pressure. The crude product was precipitated with glacial ether, and the lower layer was removed and dried under vacuum to obtain a modified PLGA copolymer.

[0010] Furthermore, the usage ratio of PLGA, dichloromethane, N-hydroxysuccinimide, 4-dimethylaminopyridine, N,N-diisopropylcarbodiimide, glucosamine and DMF is 2-4 g: 0.1-0.2 L: 30-50 mg: 6-8 mg: 60-80 μL: 0.5-0.6 g: 20-30 mL.

[0011] Furthermore, the specific preparation process of the loaded modified PLGA powder is as follows: The modified PLGA copolymer was dissolved in a dichloromethane / ethanol mixed solution, the pH value was adjusted to 5.0-6.0 with 0.1M hydrochloric acid, modified diatomaceous earth was added, and ultrasonic dispersion was performed at 25-30°C and 300-500W for 20-30 minutes. The mixture was then stirred at a speed of 200-300 rpm for 8-12 hours, and the solvent was removed by concentration under reduced pressure. The remaining solid was washed with deionized water 3-4 times and dried to constant weight to obtain a loaded modified PLGA powder.

[0012] Furthermore, the usage ratio of the modified PLGA copolymer, dichloromethane / ethanol and modified diatomaceous earth is 2-4 g: 200-400 mL: 10-20 g.

[0013] Furthermore, the specific preparation process of PLGA microcapsules is as follows: The loaded modified PLGA powder, EDA-GO and 0.4 wt% chitosan acetate solution were added to the reactor, stirred at 30-40°C for 2-3 hours, centrifuged and filtered, the filter cake was washed with deionized water 3-4 times, and dried to constant weight to obtain PLGA microcapsules.

[0014] Furthermore, the mass ratio of the loaded modified PLGA powder, EDA-GO, and 0.4 wt % chitosan acetate solution was 5-8: 0.05-0.12: 0.4-0.8.

[0015] Furthermore, the specific preparation process of EDA-GO is as follows: GO and deionized water were added to a reactor and ultrasonically dispersed for 1-3 hours. Ethylenediamine was added at a speed of 200-300 rpm and reacted at 40-50°C for 6-8 hours. Sodium chloride was added as a coagulant and the mixture was centrifuged at 800-1000 rpm for 20-30 minutes. The supernatant was discarded and the lower solid layer was washed 2-3 times with ethanol and deionized water respectively, and dried to constant weight to obtain EDA-GO.

[0016] Furthermore, the mass ratio of GO, deionized water, ethylenediamine and sodium chloride is 5-10:800-1000:5-8:5-10.

[0017] Furthermore, the specific preparation method of the scale inhibitor for water pollution prevention and control is as follows: PLGA microcapsules and deionized water are added into a stirring kettle, heated to 40-60° C., lauryl glucoside and polyethylene glycol are added, stirred for 20-30 minutes, and naturally cooled to room temperature to obtain a scale inhibitor for water pollution prevention and control.

[0018] Furthermore, the mass ratio of PLGA microcapsules, deionized water, dodecyl glucoside and polyethylene glycol is 30-50:20-40:10-13:5-8.

[0019] Beneficial effects of the present invention: 1. In the present invention, glucosamine modification enables a tighter bond between PLGA and modified diatomaceous earth, reducing the rapid detachment of active ingredients. The PLGA microcapsules formed by EDA-GO and chitosan constitute a physical barrier, delaying the diffusion of active ingredients. The density and pore control of the overall structure allow the active ingredients to be released gradually, avoiding waste caused by excessive release and achieving a stable release rate.

[0020] 2. In the present invention, chitosan utilizes its excellent film-forming properties to construct a protective barrier, reducing direct exposure of internal organic scale inhibitors to high temperatures. Modified diatomaceous earth is treated with acid to optimize pores and organic groups are introduced via KH-550, resulting in good compatibility with modified PLGA. As a carrier, it can both reduce damage to PLGA molecular chains caused by high temperatures and enhance the structural stability of the system in high-salt environments. EDA-GO is formed by modifying GO with ethylenediamine, and the surface amino groups improve dispersibility. Its excellent thermal stability, combined with hydrogen bonds with PLGA and chitosan, enhances the heat resistance of the composite system, reduces breakage of PLGA molecular chains caused by high temperatures, and addresses the problem of organic scale inhibitors being easily thermally degraded in high-temperature, high-salt wastewater systems. Because graphene itself has a nanoscale, two-dimensional lamellar structure, the doping of EDA-GO has a debonding and lubricating effect, which can reduce the friction coefficient between PLGA microcapsules and the inner wall of the high-salt wastewater system, thereby effectively reducing the possibility of clogging the evaporation crystallizer.

[0021] 3. The chitosan introduced in the present invention has a natural polysaccharide structure and the natural sugar groups introduced by glucosamine-modified PLGA are both degradable components. As potential substrates for microbial metabolism, they can induce microorganisms to secrete corresponding enzymes to decompose materials to obtain nutrients, thereby promoting the gradual degradation of the materials and ultimately achieving a higher biodegradation rate.

[0022] 4. In the present invention, after PLGA is modified with glucosamine, a large number of amino groups and hydroxyl groups are introduced into the molecular chain. These polar groups can bind to Ca in water through coordination bonds. 2+ 、CO3 2- 、SO4 2- PO4 3-Plasma prevents crystals from agglomerating and growing. The modified diatomaceous earth retains its porous structure and improves its compatibility with other components. The introduced EDA-GO sheet structure has a large specific surface area, and its surface amino groups can be tightly combined with PLGA and chitosan. The addition of chitosan forms a physical barrier for microcapsules, which can hinder the rapid diffusion of components. In addition, dodecyl glucoside, as a surfactant, can improve the dispersibility of the material in water, ensure uniform contact of each scale-inhibiting component, and ultimately achieve efficient synergistic scale inhibition of CaCO3, CaSO4, and CaPO4. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] Example 1: This example provides a method for preparing a scale inhibitor for water pollution control, comprising the following steps: S1: 80g of natural diatomaceous earth was dried at 70°C, ground through a 300-mesh sieve, and added to a reactor with 100mL of a 30wt% sulfuric acid solution, soaked for 20h, reacted in a 70°C water bath for 40min, cooled, filtered, washed until neutral, dried at 80°C, ground through a 300-mesh sieve, and sealed for storage to complete the acid treatment of the diatomaceous earth; 30g of the acid-treated diatomaceous earth and 100g of deionized water were added to a reactor, and a mixture of 1g of a silane coupling agent KH-550 and 8g of ethanol was added at 70°C with stirring. The mixture was stirred at 800rpm for 1h, filtered, and the filter cake was dried to constant weight to obtain modified diatomaceous earth; Impurities were removed and the pore structure of diatomite was optimized through mechanical screening and acid leaching processes. KH-550 silane coupling agent was hydrolyzed in an aqueous phase system to generate silanol groups, which condensed with the silanol groups on the surface of diatomite to form Si-O-Si covalent bonds, thereby achieving the grafting of amino functional groups to obtain modified diatomite.

[0025] S2: Add 20g of poly(lactic acid-co-glycolic acid) (PLGA) (molecular weight of 5000) and 1L of dichloromethane into a stirring vessel and stir at 0°C until completely dissolved. Then, add 500mg of N-hydroxysuccinimide (NHS), 80mg of 4-dimethylaminopyridine (DMAP) and 800μL of N,N-diisopropylcarbodiimide (DIC) in sequence and react at 25°C for 10h. Then, add 5g of glucosamine, dissolve it in DMF and add it to the reactor. Continue to react for 18h. The reaction system is washed with 5wt% sodium bicarbonate solution and deionized water in sequence, then dried over anhydrous sodium sulfate, filtered, and the solvent is evaporated under reduced pressure. The crude product is precipitated with icy ether, and the lower layer is removed and dried under vacuum to obtain a modified PLGA copolymer.

[0026] S3: 10 g of the modified PLGA copolymer was dissolved in 1 L of dichloromethane / ethanol (volume ratio 7:3) solution, and the pH value was adjusted to 5.0 with 0.1 M hydrochloric acid. 40 g of modified diatomaceous earth was added. The mixture was ultrasonically dispersed at 25°C and 300°C for 20 min, and then stirred at 200 rpm for 8 h. The solvent was removed by concentration under reduced pressure. The remaining solid was washed three times with deionized water and dried to constant weight to obtain the loaded modified PLGA powder. The modified PLGA copolymer is dissolved in a dichloromethane / ethanol system, and the pH value of the system is adjusted to protonate the amino group, forming an electrostatic adsorption effect with the silicon oxide anions on the surface of the diatomite. During the impregnation process, the modified PLGA copolymer is loaded both inside and outside the pores of the diatomite to form a loaded modified PLGA powder.

[0027] S4: 5 g of graphene oxide (GO) and 800 g of deionized water were added to a reactor and ultrasonically dispersed for 1 h. 5 g of ethylenediamine (EDA) was added at 200 rpm and reacted at 40°C for 6 h. 5 g of sodium chloride was added as a coagulant and the mixture was centrifuged at 800 rpm for 20 min. The supernatant was discarded and the lower solid layer was washed twice with ethanol and deionized water, respectively, and dried to constant weight to obtain EDA-GO. 5 g of loaded modified PLGA powder, 0.07 g of EDA-GO and 0.4 g of 0.4 wt% chitosan acetate solution were added to a reactor, stirred at 30 °C for 2 h, centrifuged and filtered, the filter cake was washed three times with deionized water, and dried to constant weight to obtain PLGA microcapsules.

[0028] The loaded modified PLGA powder was immersed in a chitosan acetic acid solution containing ethylenediamine modified graphene oxide with a concentration of 0.4wt%. +It forms electrostatic adsorption with the carboxyl / silicon anions on the surface of the copolymer. At the same time, the hydroxyl / amino groups of EDA-GO and the hydroxyl groups of chitosan synergistically enhance the interface binding through hydrogen bonds. Through electrostatic self-assembly, a chitosan shell doped with EDA-GO is finally formed on the surface of the copolymer to obtain PLGA microcapsules.

[0029] S5: 3 g of PLGA microcapsules and 4 g of deionized water were added to a stirred tank, heated to 40° C., 1 g of dodecyl glucoside and 5 g of polyethylene glycol were added, stirred for 20 min, and naturally cooled to room temperature to obtain a scale inhibitor for water pollution control.

[0030] Example 2: This example provides a method for preparing a scale inhibitor for water pollution control, comprising the following steps: S1: 60g of natural diatomaceous earth was dried at 80°C, ground through a 300-mesh sieve, and added to a reactor with 150mL of a 30wt% sulfuric acid solution, soaked for 25h, reacted in an 80°C water bath for 50min, filtered after cooling, washed until neutral, dried at 90°C, ground through a 300-mesh sieve, and sealed for storage to complete the acid treatment of the diatomaceous earth; 20g of the acid-treated diatomaceous earth and 90g of deionized water were added to a reactor, and a mixture of 0.5g of a silane coupling agent KH-550 and 10g of ethanol was added at 80°C with stirring. The mixture was stirred at 900rpm for 2h, filtered, and the filter cake was dried to constant weight to obtain modified diatomaceous earth.

[0031] S2: 30 g of PLGA (molecular weight of 5000) and 1.5 L of dichloromethane were added to a stirring vessel and stirred at 3°C ​​until completely dissolved. 300 mg of N-hydroxysuccinimide, 60 mg of 4-dimethylaminopyridine and 600 μL of N,N-diisopropylcarbodiimide were added in sequence and reacted at 30°C for 11 h to form an ester intermediate. 5.5 g of glucosamine was added and dissolved in DMF and added to the reactor. The reaction was continued for 21 h to complete the amidation. The reaction system was washed with 5 wt% sodium bicarbonate solution and deionized water in sequence, then dried over anhydrous sodium sulfate, filtered, and the solvent was evaporated under reduced pressure. The crude product was precipitated with ice ether, and the lower layer was removed and dried under vacuum to obtain a modified PLGA copolymer.

[0032] S3: Dissolve 20 g of modified PLGA copolymer in 2 L of dichloromethane / ethanol (volume ratio 7:3) solution, adjust the pH to 5.5 with 0.1 M hydrochloric acid, add 60 g of modified diatomaceous earth, and ultrasonically disperse at 28°C and 400 W for 25 minutes. Then stir at 250 rpm for 10 hours, concentrate under reduced pressure to remove the solvent, wash the remaining solid with deionized water three times, and dry to constant weight to obtain loaded modified PLGA powder.

[0033] S4: 8 g GO and 900 g deionized water were added to a reactor and ultrasonically dispersed for 2 h. 8 g ethylenediamine was added at 250 rpm and reacted at 45°C for 7 h. 8 g sodium chloride was added and centrifuged at 900 rpm for 25 min. The supernatant was discarded and the lower solid layer was washed twice with ethanol and deionized water respectively, and dried to constant weight to obtain EDA-GO. 6 g of loaded modified PLGA powder, 0.09 g of EDA-GO and 0.6 g of 0.4 wt% chitosan acetate solution were added to a reactor, stirred at 35 °C for 2.5 h, centrifuged and filtered, the filter cake was washed three times with deionized water, and dried to constant weight to obtain PLGA microcapsules.

[0034] S5: 4 g of PLGA microcapsules and 3 g of deionized water were added to a stirred tank, heated to 50° C., 2 g of dodecyl glucoside and 3 g of polyethylene glycol were added, stirred for 25 min, and naturally cooled to room temperature to obtain a scale inhibitor for water pollution control.

[0035] Example 3: This example provides a method for preparing a scale inhibitor for water pollution control, comprising the following steps: S1: After drying 70g of natural diatomaceous earth at 90°C, grind it through a 300-mesh sieve, add it to a reactor with 200mL of a 30wt% sulfuric acid solution, soak it for 30h, react it in a 90°C water bath for 60min, filter it after cooling, wash it to neutrality, dry it at 100°C, grind it again through a 300-mesh sieve, and seal it for storage to complete the acid treatment of the diatomaceous earth; add 25g of the acid-treated diatomaceous earth and 90g of deionized water to a reactor, add a mixture of 1.5g of silane coupling agent KH-550 and 10g of ethanol at 90°C with stirring, stir and react at 1000rpm for 3h, filter it, and dry the filter cake to constant weight to obtain modified diatomaceous earth.

[0036] S2: 40 g of PLGA (molecular weight of 5000) and 2 L of dichloromethane were added to a stirring vessel and stirred at 5°C until completely dissolved. 400 mg of N-hydroxysuccinimide, 70 mg of 4-dimethylaminopyridine and 700 μL of N,N-diisopropylcarbodiimide were added in sequence and reacted at 35°C for 12 h to form an ester intermediate. 6 g of glucosamine was added and dissolved in DMF and added to the reactor. The reaction was continued for 24 h to complete the amidation. The reaction system was washed with 5 wt% sodium bicarbonate solution and deionized water in sequence, then dried over anhydrous sodium sulfate, filtered, and the solvent was evaporated under reduced pressure. The crude product was precipitated with ice ether, and the lower layer was removed and dried under vacuum to obtain a modified PLGA copolymer.

[0037] S3: Dissolve 30 g of PLGA copolymer in 3 L of dichloromethane / ethanol (volume ratio 7:3) solution, adjust the pH to 6.0 with 0.1 M hydrochloric acid, add 50 g of modified diatomaceous earth, and ultrasonically disperse at 30°C and 500 W for 30 minutes. Then stir at 300 rpm for 12 hours, and concentrate under reduced pressure to remove the solvent. Wash the remaining solid four times with deionized water and dry to constant weight to obtain loaded modified PLGA powder.

[0038] S4: 10 g GO and 1000 g deionized water were added to a reactor and ultrasonically dispersed for 3 h. 6 g ethylenediamine was added at 300 rpm and reacted at 50°C for 8 h. 6 g sodium chloride was added and the mixture was centrifuged at 1000 rpm for 30 min. The supernatant was discarded and the lower solid layer was washed three times with ethanol and deionized water respectively, and dried to constant weight to obtain EDA-GO. 8 g of loaded modified PLGA powder, 0.12 g of EDA-GO and 0.8 g of 0.4 wt% chitosan acetate solution were added to a reactor, stirred at 40 °C for 3 h, centrifuged and filtered, the filter cake was washed four times with deionized water, and dried to constant weight to obtain PLGA microcapsules.

[0039] S5: 5 g of PLGA microcapsules and 2 g of deionized water were added to a stirred tank, heated to 60° C., 3 g of dodecyl glucoside and 6 g of polyethylene glycol were added, stirred for 30 minutes, and then naturally cooled to room temperature to obtain a scale inhibitor for water pollution control.

[0040] Comparative Example 1: The difference from Example 1 is that the step of modifying PLGA with glucosamine in step S2 is omitted, and unmodified PLGA is directly used to be compounded with modified diatomaceous earth in step S3 to prepare a loaded PLGA powder. The other steps remain unchanged to obtain a scale inhibitor for water pollution control.

[0041] Comparative Example 2: The difference from Example 1 is that the loaded modified PLGA powder obtained in step S3 is compounded only with EDA-GO to prepare PLGA microcapsules without chitosan, and the other steps remain unchanged to obtain a scale inhibitor for water pollution control.

[0042] Comparative Example 3: The difference from Example 1 is that the loaded modified PLGA powder obtained in step S3 is compounded only with a chitosan acetate solution with a concentration of 0.4 wt% to prepare PLGA microcapsules without EDA-GO, and the other steps remain unchanged to obtain a scale inhibitor for water pollution control.

[0043] Comparative Example 4: The difference from Example 1 is that in step S4, unmodified GO is used instead of EDA-GO to prepare PLGA microcapsules, and the other steps remain unchanged to obtain a scale inhibitor for water pollution control.

[0044] Comparative Example 5: The difference from Example 1 is that no dodecyl glycoside is added in step S5, and the other steps remain unchanged to prepare a scale inhibitor for water pollution control.

[0045] Performance test experiment: Performance tests were performed on Examples 1 to 3 and Comparative Examples 1 to 5.

[0046] Release rate: 3 g of the scale inhibitors of Examples 1 to 3 and Comparative Examples 1 to 5 were dried to constant weight and placed in a stainless steel cup containing 1 L of high-salt wastewater. The solid samples were allowed to stand at room temperature, and the changes in the solid samples were observed to calculate the release rate.

[0047] Biodegradation rate: The shaking table method was used to culture a mixed solution of scale inhibitors for water pollution control and microbial inoculum. The chemical oxygen demand of the mixed solution was measured on the 28th day, and the biodegradation rate was then calculated based on the change in chemical oxygen demand.

[0048] Dispersion performance test: Take 500mL of simulated high-salt wastewater, add a scale inhibitor with a concentration of 10mg / L, stir evenly, let it stand, take out the upper clear liquid, weigh the mass of the sediment at the bottom, and calculate the sedimentation rate.

[0049] Scale inhibition performance test: Refer to GB / T 16632-2019 to calculate the scale inhibition efficiency for calcium carbonate and calcium sulfate respectively, and refer to the national standard GB / T 22626-2008 to calculate the scale inhibition efficiency for calcium phosphate.

[0050] Table 1 Performance test of various water pollution scale inhibitors

[0051] As can be seen from Table 1, the release rate of Examples 1 to 3 is stable at 2.89-2.96 mg·h -1 Among them, Comparative Example 1 does not use glucosamine to modify PLGA, and the hydrophilicity and binding force with the carrier of PLGA are weak, so the release cannot be delayed. Comparative Example 2 lacks the physical barrier of the microcapsule formed by chitosan, and cannot hinder the rapid diffusion of the ingredients. Comparative Example 3 The sheets and amino groups of EDA-GO can be combined with PLGA and chitosan to form a dense network to delay the release of active ingredients. Comparative Example 3 does not have EDA-GO, so the microcapsule structure is loose, the active ingredient is easy to diffuse, and the release rate is increased. Comparative Example 4 replaces EDA-GO with unmodified GO, and the microcapsule structure is poorly stable, making it difficult to delay the release.

[0052] The biodegradation rates of Examples 1 to 3 are between 84.3% and 85.6%, which are better than those of Comparative Examples 1 to 5. Comparative Example 1 directly uses unmodified PLGA, whose molecular chain has poor hydrophilicity, making it difficult for microorganisms to attach and metabolize, and thus reducing the degradation rate. Chitosan, as a natural degradable polysaccharide, can provide nutrition for microorganisms and promote colonization, thereby enhancing the biocompatibility of the system. Comparative Example 2 lacks chitosan, and the microbial activity is inhibited. In the embodiment, after GO is modified with ethylenediamine, the surface amino groups enhance the binding force with the biocompatible components and reduce the toxicity to microorganisms. In Comparative Example 4, unmodified GO is used, and the surface oxygen-containing groups are prone to induce oxidative stress, inhibiting microbial activity, resulting in a reduced degradation rate. In addition, dodecyl glucoside in the embodiment can improve the dispersibility of the material, allowing microorganisms to more easily access the degradation sites. In Comparative Example 5, due to the lack of this component, the material is prone to agglomeration, making it difficult for microorganisms to fully act, and the degradation rate is also slightly lower than that of the embodiment.

[0053] The sedimentation rates of the scale inhibitors of Examples 1 to 3 were all between 6.2% and 6.5%, and the dispersion performance was excellent. The sedimentation rates of Comparative Examples 1 to 5 increased (7.0%-7.7%) due to the lack of key components or modification steps. In Comparative Example 1, since PLGA was not modified with glucosamine, the hydrophilicity and compatibility of PLGA with other components were greatly reduced, resulting in a significant deterioration in the overall dispersion ability of the scale inhibitor. In Comparative Example 2, since chitosan was not added, the structural stability of the PLGA microcapsules was insufficient, making it difficult to maintain a uniform dispersion state of the particles, and the dispersion effect was weaker than that of the examples. Comparative Example 3 lacked EDA-GO, and lost its function of enhancing interfacial dispersion in the system. Comparative Example 4 used unmodified GO, which had poor dispersion performance and was prone to agglomeration, which led to a significant increase in the overall sedimentation rate of the scale inhibitor. In Comparative Example 5, no dodecyl glycoside was added, and the dispersion stability of the particles decreased, but compared with the case where the structural modification step was missing or the key functional component was omitted, the impact on the dispersion performance was weaker.

[0054] The anti-scaling performance of Examples 1 to 3 and Comparative Examples 1 to 5 is relatively excellent overall. After PLGA is modified with glucosamine, a large number of amino groups and polyhydroxy groups are introduced into the molecular chain. These polar groups can bind to Ca in water through coordination bonds. 2+ 、CO3 2- 、SO4 2- PO4 3-Scale ions such as PLGA and chitosan are prevented from agglomerating and growing. After modification, diatomaceous earth retains its porous structure and improves its compatibility with other components. The lamellar structure of EDA-GO has a large specific surface area, and the surface amino groups can be tightly combined with PLGA and chitosan. The addition of chitosan forms a physical barrier for microcapsules, which hinders the rapid diffusion of components. In addition, dodecyl glucoside, as a surfactant, can improve the dispersibility of the material in water, ensure that each scale-inhibiting component is evenly in contact with scale ions and crystals, and give full play to its role, and ultimately achieve efficient synergistic scale inhibition of CaCO3, CaSO4, and CaPO4. The scale inhibition efficiency of comparative example 1 against calcium phosphate is relatively poor, mainly because it does not modify PLGA with glucosamine. The amino groups and polyhydroxy groups contained in the glucosamine molecules can form stable coordination bonds with calcium ions in calcium phosphate crystals, thereby effectively interfering with the nucleation and growth of calcium phosphate and inhibiting its crystallization precipitation.

[0055] It should be noted that, in this document, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0056] While the embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions, and alterations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a scale inhibitor for water pollution control, characterized in that: The method comprises the following steps: Step 1: natural diatomaceous earth is sieved and then modified with KH-550 silane coupling agent to obtain modified diatomaceous earth; Step 2: Using DIC and NHS as carboxyl activators and DMPA as a basic catalyst, PLGA is converted into an ester intermediate, which is then amidated with glucosamine to obtain a modified PLGA copolymer; the modified PLGA copolymer is impregnated in modified diatomaceous earth to obtain a loaded modified PLGA powder; Step 3: Through electrostatic self-assembly, the loaded modified PLGA powder is coated in the chitosan shell doped with ethylenediamine-modified graphene oxide to obtain PLGA microcapsules; Step 4: stirring and mixing PLGA microcapsules, deionized water, dodecyl glucoside and polyethylene glycol to obtain a scale inhibitor for water pollution prevention and control.

2. The method for preparing a scale inhibitor for water pollution control according to claim 1, characterized in that: The specific preparation process of the modified diatomite is as follows: Add the acid-treated diatomaceous earth and deionized water into a reactor, add the silane coupling agent KH-550 and ethanol at 70-90° C. with stirring, react at 800-1000 rpm for 1-3 hours, filter, and dry the filter cake to constant weight to obtain modified diatomaceous earth; The mass ratio of the acid-treated diatomaceous earth, deionized water, silane coupling agent and ethanol is 20-30:90-110:0.5-1.5:8-12.

3. The method for preparing a scale inhibitor for water pollution control according to claim 2, characterized in that: The acid treatment method of the diatomaceous earth is as follows: The natural diatomaceous earth is dried, ground and passed through a 300-mesh sieve, soaked in a 30 wt% sulfuric acid solution at 20-25°C for 20-30 hours, kept at 70-90°C for 40-60 minutes, cooled, filtered, washed, and dried to complete the acid treatment of the diatomaceous earth; The usage ratio of the natural diatomaceous earth and sulfuric acid is 60-80 g:100-200 mL.

4. The method for preparing a scale inhibitor for water pollution control according to claim 1, characterized in that: The specific preparation process of the modified PLGA copolymer is as follows: PLGA and dichloromethane were added to a stirring kettle and stirred at 0-5°C until completely dissolved. N-hydroxysuccinimide, 4-dimethylaminopyridine and N,N-diisopropylcarbodiimide were added and reacted at 25-35°C for 10-12 hours. Then, aminoglucose was dissolved in DMF and added to the reactor and the reaction was continued for 18-24 hours. The reaction system was washed with 5wt% sodium bicarbonate solution and deionized water in sequence, and then dried with anhydrous sodium sulfate, filtered, and the solvent was evaporated under reduced pressure. The crude product was precipitated with icy ether, and the lower layer was removed and dried under vacuum to obtain a modified PLGA copolymer.

5. The method for preparing a scale inhibitor for water pollution control according to claim 4, characterized in that: The usage ratio of the PLGA, dichloromethane, N-hydroxysuccinimide, 4-dimethylaminopyridine, N,N-diisopropylcarbodiimide, glucosamine and DMF is 2-4 g: 0.1-0.2L: 30-50mg: 6-8mg: 60-80μL: 0.5-0.6g: 20-30mL.

6. The method for preparing a scale inhibitor for water pollution control according to claim 1, characterized in that: The specific preparation process of the loaded modified PLGA powder is as follows: The modified PLGA copolymer was dissolved in a dichloromethane / ethanol mixed solution, the pH value was adjusted to 5.0-6.0 with 0.1M hydrochloric acid, modified diatomaceous earth was added, and ultrasonic dispersion was performed at 25-30°C and 300-500W for 20-30 minutes, and stirring was performed at 200-300 rpm for 8-12 hours. The solvent was removed by concentration under reduced pressure, and the remaining solid was washed and dried to obtain a loaded modified PLGA powder; The usage ratio of the modified PLGA copolymer, dichloromethane / ethanol and modified diatomaceous earth is 2-4 g: 200-400 mL: 10-20 g.

7. The method for preparing a scale inhibitor for water pollution control according to claim 1, characterized in that: The specific preparation process of the PLGA microcapsules is as follows: The loaded modified PLGA powder, EDA-GO and 0.4 wt% chitosan acetate solution were added to a reactor, stirred at 30-40°C for 2-3 hours, centrifuged and filtered, the filter cake was washed with deionized water 3-4 times, and dried to constant weight to obtain PLGA microcapsules; The mass ratio of the loaded modified PLGA powder, EDA-GO and chitosan acetic acid solution is 5-8:0.05-0.12:0.4-0.

8.

8. The method for preparing a scale inhibitor for water pollution control according to claim 7, characterized in that: The EDA-GO is prepared by the following steps: GO and deionized water were added to a reactor, ultrasonically dispersed for 1-3 hours, and then ethylenediamine was added. The mixture was stirred at 40-50°C and 200-300 rpm for 6-8 hours. Then, sodium chloride was added and the mixture was centrifuged at 800-1000 rpm for 20-30 minutes. The lower solid layer was washed with ethanol and deionized water 2-3 times, respectively, and dried to constant weight to obtain EDA-GO. The mass ratio of GO, deionized water, ethylenediamine and sodium chloride is 5-10:800-1000:5-8:5-10.

9. The method for preparing a scale inhibitor for water pollution control according to claim 1, characterized in that: The specific preparation method of the scale inhibitor for water pollution prevention and control is as follows: PLGA microcapsules and deionized water are added into a stirring kettle, and dodecyl glucoside and polyethylene glycol are added at 40-60° C., stirred for 20-30 minutes, and naturally cooled to room temperature to obtain a scale inhibitor for water pollution prevention and control.

10. The method for preparing a scale inhibitor for water pollution control according to claim 9, characterized in that: The mass ratio of the PLGA microcapsules, deionized water, lauryl glucoside and polyethylene glycol is 30-50:20-40:10-13:5-8.

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