Circulating water corrosion and scale inhibitor and preparation method thereof

Abstract

The invention belongs to the technical field of water treatment, and particularly relates to a circulating water corrosion and scale inhibitor and a preparation method thereof. The corrosion and scale inhibitor is prepared by compounding N-dodecyl histidine amide grafted polyepoxysuccinic acid, modified chitosan, a glutaraldehyde solution and water, wherein the N-dodecyl histidine amide grafted polyepoxysuccinic acid achieves efficient corrosion inhibition through the strong coordination effect of histidine groups of the N-dodecyl histidine amide grafted polyepoxysuccinic acid and the metal surface and the hydrophobic effect of long-chain alkyl, especially, the N-dodecyl histidine amide grafted polyepoxysuccinic acid has a specific protection effect on copper alloy, and the polyepoxysuccinic acid plays a broad-spectrum scale inhibition role; the modified chitosan is chelated with calcium ions and disperses scale crystals through a multi-functional group; glutaraldehyde is used as a cross-linking agent, and a compact and firm three-dimensional protective film is formed on the metal surface; the corrosion and scale inhibitor has the advantages of no phosphorus, environment friendliness, biodegradability, multiple effects, synergistic enhancement of corrosion and scale inhibition performance and the like, and is suitable for an industrial circulating water system.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a circulating water corrosion and scale inhibitor and its preparation method. Background Technology

[0002] In industrial circulating cooling water systems, continuous evaporation and concentration of water can lead to excessive saturation of dissolved salts, causing them to precipitate and form hard scale that adheres to the inner walls of heat exchangers and pipes. This reduces heat exchange efficiency, increases energy consumption, and shortens equipment lifespan. Simultaneously, the presence of corrosive ions can trigger corrosion of metal equipment, causing perforation damage and even safety accidents. Therefore, adding corrosion and scale inhibitors to the circulating water has become an indispensable key technology for ensuring the safe, stable, and efficient operation of the system.

[0003] Corrosion and scale inhibitors have evolved from inorganic to organic formulations. Currently, organophosphorus corrosion and scale inhibitors have seen rapid development and widespread application over the past few decades due to their excellent corrosion and scale inhibition performance and cost advantages. However, with increasing global environmental awareness, phosphorus emissions are strictly limited, driving the research and development of phosphorus-free, environmentally friendly corrosion and scale inhibitors. Subsequently, biodegradable, environmentally friendly scale inhibitors such as polyaspartic acid and polyepoxysuccinic acid have emerged as leaders, representing the future development direction of water treatment agents. However, corrosion and scale inhibition technologies still face many challenges. The most prominent issue is phosphorus pollution. The use of phosphorus-containing agents leads to eutrophication of discharged water bodies, causing serious environmental and ecological problems. The invention patent with publication number CN113173651A uses a phosphine-containing chelating agent to formulate an effective corrosion and scale inhibitor, but the addition of phosphorus hinders its subsequent application. In addition, many highly efficient non-phosphorus corrosion inhibitors are effective against specific metals but have poor scale inhibition performance, while highly efficient scale inhibitors often lack sufficient corrosion inhibition capacity, making it difficult for a single agent to simultaneously achieve both corrosion inhibition and scale inhibition. The invention patent with publication number CN112573674A uses a phosphorus-free formula and zinc-containing wastewater, reflecting an environmentally friendly development approach, but its formula is complex and cannot efficiently achieve both corrosion inhibition and scale inhibition. Therefore, developing a phosphorus-free, highly efficient, and synergistically effective integrated green formula has become an urgent technical need in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a circulating water corrosion and scale inhibitor and its preparation method to solve the above-mentioned technical problems.

[0005] To achieve the above-mentioned technical objectives, the technical solution of the present invention is as follows: A circulating water corrosion and scale inhibitor, characterized in that, by weight, it comprises the following components: 9-15% modified chitosan, 10-20% N-dodecylhistidine amide grafted polyepoxysuccinic acid, 1-5% 10% glutaraldehyde aqueous solution, and 60-80% deionized water.

[0006] As a further improvement, the modified chitosan structure is as follows: ; Where n is the degree of aggregation, and n is a natural number between 2 and 20.

[0007] As a further improvement, the N-dodecylhistidine amide grafted polyepoxysuccinic acid structure is as follows: ; Where p and np are the degree of aggregation, p < n, p = a natural number from 1 to 5, and n is a natural number from 2 to 10.

[0008] The present invention also provides a method for preparing the circulating water corrosion and scale inhibitor, comprising the following steps: S1. Weigh the modified chitosan, N-dodecylhistidine amide-grafted polyepoxysuccinic acid, 10% glutaraldehyde aqueous solution and deionized water. S2. Dissolve the modified chitosan in a portion of deionized water, heat to 60-70℃, and stir for 30 minutes to obtain a modified chitosan solution. S3. Dissolve N-dodecylhistidine amide-grafted polyepoxysuccinic acid in the remaining deionized water, heat to 60~70℃, stir for 30 min, and obtain N-dodecylhistidine amide-grafted polyepoxysuccinic acid solution. S4. Mix the modified chitosan solution and the N-dodecylhistidine amide-grafted polyepoxysuccinic acid solution and stir for 15-30 minutes to obtain a mixture. S5. Slowly add 10% glutaraldehyde aqueous solution to the mixture, stirring continuously during the addition process. After the addition is completed, continue stirring for 15-30 minutes to obtain a circulating water corrosion and scale inhibitor.

[0009] As a further improvement, in step S2, the modified chitosan is prepared as follows: chitosan is added to an acetic acid solution and stirred until dissolved. NaOH is added dropwise to adjust the pH to 8.0-9.0, and nitrogen gas is passed through for 15 minutes to obtain a chitosan solution. Sodium propylene oxide sulfonate is dissolved in deionized water to obtain a sodium propylene oxide sulfonate solution. The sodium propylene oxide sulfonate solution is added dropwise to the chitosan solution, stirred, and reacted at 60-80℃ for 8-12 hours. After the reaction is completed, a mixture is obtained. Acetone is added to the mixture and stirred until a precipitate appears. The precipitate is collected by suction filtration, washed three times with an ethanol-water solution, and freeze-dried to obtain modified chitosan.

[0010] As a further improvement, the mass ratio of chitosan to sodium propylene oxide sulfonate is 1:3~4; the volume of acetone is 3~5 times the volume of the mixed liquid.

[0011] As a further improvement, in step S3, the preparation method of N-dodecylhistidine amide-grafted polyepoxysuccinic acid is as follows: dissolve polyepoxysuccinic acid in deionized water, stir for 30 min, and prepare a polyepoxysuccinic acid solution with a mass fraction of 5-10%; adjust the pH of the polyepoxysuccinic acid solution to 5.0-5.5 using acetic acid; dissolve N-dodecylhistidine amide in N,N-dimethylformamide to obtain an N-dodecylhistidine amide solution; heat the polyepoxysuccinic acid solution to 95-115℃ and stir continuously, add the N-dodecylhistidine amide solution, and continue to reflux at 95-115℃ for 3-5 h; dialyze using a dialysis bag for 24-48 h; evaporate and concentrate the dialysis product at 40℃; freeze-dry the concentrate to obtain N-dodecylhistidine amide-grafted polyepoxysuccinic acid.

[0012] As a further improvement, the mass ratio of the polyepoxysuccinic acid to N-dodecylhistidine amide is 1:0.5~1.5.

[0013] As a further improvement, the preparation method of the N-dodecylhistidine amide is as follows: histidine is dissolved in anhydrous N,N-dimethylformamide and stirred for 15 min. Then, under an ice bath at 0-4°C, 1-hydroxybenzotriazole and EDC·HCl are added sequentially. After heating to room temperature, the mixture is stirred for 30 min under nitrogen protection to obtain a histidine activation solution. Dodecylamine is dissolved in anhydrous N,N-dimethylformamide to prepare a 1 mol / L dodecylamine solution. The dodecylamine solution is slowly added dropwise to the histidine activation solution under nitrogen protection. Under gas protection, the mixture was stirred at room temperature for 12-16 hours to obtain a reaction solution. The reaction solution was then distilled under reduced pressure at 40-50°C to reduce the volume by half, yielding a concentrated N-dodecylhistidine amide solution. Ten times the volume of ice water was added to the concentrated N-dodecylhistidine amide solution, and the mixture was stirred continuously until a white solid precipitated. The solution was then filtered, and the filter cake was collected. The cake was quickly washed once with 0.1 mol / L dilute hydrochloric acid, washed three times with deionized water at 2-4°C, and dried under vacuum at 40-50°C to obtain N-dodecylhistidine amide.

[0014] As a further improvement, the mass ratio of histidine, 1-hydroxybenzotriazole, EDC·HCl and dodecylamine is 1:1:1.5:1.3~1.5.

[0015] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows: This invention provides a circulating water corrosion and scale inhibitor that exhibits excellent comprehensive performance through the compatibility and synergistic effect of its components. Chitosan, as an environmentally friendly polymer matrix, possesses excellent calcium carbonate scale inhibition and film-forming corrosion inhibition capabilities. By modifying specific sites of its sulfonic acid groups, the solubility of chitosan is increased, and it gains the ability to inhibit calcium phosphate scale, effectively chelating calcium ions and dispersing scale crystals. N-Dodecylhistidine amide grafted polyepoxysuccinic acid is the core functional component. Its unique molecular structure achieves multiple synergistic effects: the polyepoxysuccinic acid framework provides broad-spectrum scale inhibition, especially excellent lattice distortion ability; the grafted dodecyl long chains enhance hydrophobic adsorption on metal surfaces. The system forms a barrier and binds polyepoxysuccinic acid to the metal surface, increasing the local concentration of polyepoxysuccinic acid and enabling it to more effectively exert its scale inhibition properties. Meanwhile, the histidine amide group, with its imidazole ring, achieves targeted and efficient corrosion inhibition of copper alloys through its strong specific coordination with copper ions. Glutaraldehyde is not a traditional corrosion and scale inhibitor; this invention incorporates glutaraldehyde into the system, allowing it to act as a special connecting bridge to locally crosslink chitosan, forming a dense and robust three-dimensional network protective film. This increases the durability and erosion resistance of the protective film, enabling the corrosion and scale inhibitor to function continuously and effectively.

[0016] The advantage of this solution lies in the fact that the corrosion and scale inhibitor of this invention achieves scale inhibition through multiple synergistic mechanisms, namely lattice distortion, chelation, and dispersion, and corrosion inhibition through chemical adsorption, physical barriers, and cross-linking film formation. It possesses strong scale inhibition capabilities against calcium carbonate and calcium phosphate scales, as well as corrosion inhibition against carbon steel and copper materials, making it a multi-effect corrosion and scale inhibitor that simplifies the water treatment process. Furthermore, this corrosion and scale inhibitor is a phosphorus-free and zinc-free green and highly efficient corrosion and scale inhibitor. Its main components are biodegradable, avoiding the ecological risks of eutrophication and heavy metal accumulation in discharged water bodies, aligning with the development direction of green chemistry, and achieving a balance between high efficiency and environmental friendliness. Attached Figure Description

[0017] Figure 1 The graph shows the scale inhibition performance test results of corrosion and scale inhibitors of different concentrations in Example 1, Comparative Example 5 and Comparative Example 6 at 80°C. Figure 2 The graph shows the scale inhibition performance test results of corrosion and scale inhibitors of different concentrations in Example 1, Comparative Example 5 and Comparative Example 6 at 60°C. Figure 3 The images show the SEM scan results of calcium carbonate scale treated with the corrosion and scale inhibitor prepared in Example 1 and the corrosion and scale inhibitor prepared in Comparative Example 5, without the addition of corrosion and scale inhibitor. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0019] Example 1: A method for preparing a corrosion and scale inhibitor for circulating water, specifically including the following steps: S1. Preparation of modified chitosan: Weigh 20g of chitosan and add it to 1% glacial acetic acid. Stir vigorously at room temperature until dissolved. Slowly add 2mol / L NaOH solution to adjust the pH to 8.0. Continuously purge the reaction system with nitrogen gas for 15min to obtain a 2% chitosan solution. Weigh 60g of sodium propylene oxide sulfonate and dissolve it in 200mL of deionized water. Slowly add the solution to the chitosan solution through a dropping funnel. React at 60℃ for 12h. After the reaction is complete, cool to room temperature to obtain a chitosan mixture. Pour the chitosan mixture into 3600mL of acetone and stir continuously until a fibrous precipitate appears. Wash the precipitate three times with an ethanol-water solution (ethanol to water volume ratio of 4:1). Freeze-dry to obtain modified chitosan. The reaction equation is as follows: ; S2. Preparation of N-dodecylhistidine amide: Dissolve 40g of histidine in 400mL of anhydrous N,N-dimethylformamide, stir for 15min, and add 40g of 1-hydroxybenzotriazole and 60g of [unclear text - possibly a specific ingredient or substance] in an ice bath at 0℃. 1-Ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) was heated to room temperature and stirred for 30 min under nitrogen protection to obtain a histidine activation solution. 52 g of dodecylamine solution was added to anhydrous N,N-dimethylformamide and diluted to 280.5 mL to prepare a 1 mol / L dodecylamine solution. The dodecylamine solution was slowly added dropwise to the histidine activation solution, and stirred at room temperature for 12 h under nitrogen protection to obtain a reaction solution. The reaction solution was distilled under reduced pressure at 40 °C until the volume was reduced by half. 4.1 L of ice water was added, and the mixture was stirred continuously until a white solid precipitated. The mixture was filtered to obtain a filter cake, which was quickly washed once with 0.1 mol / L dilute hydrochloric acid, washed three times with deionized water at 2 °C, and dried in a vacuum drying oven at 40 °C to obtain N-dodecylhistidine amide. The reaction equation is as follows: ; S3. Preparation of N-dodecylhistidine amide-grafted polyepoxysuccinic acid: Dissolve 20g of polyepoxysuccinic acid in 380mL of deionized water and stir for 30min to obtain a polyepoxysuccinic acid solution; adjust the pH of the polyepoxysuccinic acid solution to 5.0 using acetic acid; dissolve 10g of N-dodecylhistidine amide in 100mL of N,N-dimethylformamide to obtain an N-dodecylhistidine amide solution; heat the polyepoxysuccinic acid solution to 95℃ and stir continuously; add the N-dodecylhistidine amide solution to the polyepoxysuccinic acid solution; continue the reaction at 95℃ under reflux for 5h; dialyze using a dialysis bag for 24h; evaporate and concentrate the dialysis product at 40℃; freeze-dry the concentrate to obtain N-dodecylhistidine amide-grafted polyepoxysuccinic acid; the reaction equation is as follows: ; S4. Compounding: Dissolve 9g of modified chitosan in 30mL of deionized water, heat to 60℃, and stir for 30min to obtain a modified chitosan solution; dissolve 10g of N-dodecylhistidine amide-grafted polyepoxysuccinic acid in 50mL of deionized water, heat to 60℃, and stir for 30min to obtain an N-dodecylhistidine amide-grafted polyepoxysuccinic acid solution; mix the modified chitosan solution and the N-dodecylhistidine amide-grafted polyepoxysuccinic acid solution, and stir for 15min to obtain a mixed solution; slowly add 1mL of 10% glutaraldehyde aqueous solution to the mixed solution while stirring continuously. After the addition is complete, continue stirring for 15min to obtain a circulating water corrosion and scale inhibitor.

[0020] Example 2: A method for preparing a corrosion and scale inhibitor for circulating water, specifically including the following steps: S1. Preparation of modified chitosan: Weigh 20g of chitosan and add it to 1% glacial acetic acid. Stir vigorously at room temperature until dissolved. Slowly add 2mol / L NaOH solution to adjust the pH to 9.0. Purge the reaction system with nitrogen gas for 15min to obtain a 2% chitosan solution. Weigh 80g of sodium propylene oxide sulfonate and dissolve it in 300mL of deionized water. Slowly add the solution to the chitosan solution through a dropping funnel. React at 80℃ for 8h. After the reaction is complete, cool to room temperature to obtain a chitosan mixture. Pour the chitosan mixture into 6500mL of acetone and stir continuously. A fibrous precipitate appears. Wash the precipitate three times with an ethanol-water solution (ethanol to water volume ratio of 4:1). Freeze-dry to obtain modified chitosan. S2. Preparation of N-dodecylhistidine amide: Dissolve 40g of histidine in 400mL of anhydrous N,N-dimethylformamide and stir for 15min. At 4℃, add 40g of 1-hydroxybenzotriazole and 60g of EDC·HCl sequentially. After heating to room temperature, stir for 30min under nitrogen protection to obtain an activated histidine solution. Add 60g of dodecylamine solution to anhydrous N,N-dimethylformamide and adjust the volume to 324mL to prepare a 1mol / L dodecylamine solution. Slowly add the dodecylamine solution dropwise to the activated histidine solution and stir at room temperature for 16h under nitrogen protection to obtain a reaction solution. Distill the reaction solution under reduced pressure at 50℃ to reduce the volume by half. Add 4.4L of ice water and stir continuously until a white solid precipitates. Filter and collect the filter cake. Wash once quickly with 0.1mol / L dilute hydrochloric acid and three times with deionized water at 4℃. Dry in a vacuum drying oven at 50℃ to obtain N-dodecylhistidine amide. S3. Preparation of N-dodecylhistidine amide-grafted polyepoxysuccinic acid: Dissolve 20g of polyepoxysuccinic acid in 180mL of deionized water and stir for 30min to obtain a polyepoxysuccinic acid solution; adjust the pH of the polyepoxysuccinic acid solution to 5.5 using acetic acid; dissolve 30g of N-dodecylhistidine amide in 150mL of N,N-dimethylformamide to obtain an N-dodecylhistidine amide solution; heat the polyepoxysuccinic acid solution to 115℃ and stir continuously; add the N-dodecylhistidine amide solution to the polyepoxysuccinic acid solution; continue the reaction at 115℃ under reflux for 3h; dialyze using a dialysis bag for 48h; evaporate and concentrate the dialysis product at 40℃; freeze-dry the concentrate to obtain N-dodecylhistidine amide-grafted polyepoxysuccinic acid; S4. Compounding: Dissolve 15g of modified chitosan in 30mL of deionized water, heat to 70℃, and stir for 30min to obtain a modified chitosan solution; dissolve 20g of N-dodecylhistidine amide-grafted polyepoxysuccinic acid in 30mL of deionized water, heat to 70℃, and stir for 30min to obtain an N-dodecylhistidine amide-grafted polyepoxysuccinic acid solution; mix the modified chitosan solution and the N-dodecylhistidine amide-grafted polyepoxysuccinic acid solution, and stir for 30min to obtain a mixed solution; slowly add 5mL of 10% glutaraldehyde aqueous solution to the mixed solution while stirring continuously. After the addition is completed, continue stirring for 30min to obtain a circulating water corrosion and scale inhibitor.

[0021] Example 3 A method for preparing a corrosion and scale inhibitor for circulating water, specifically including the following steps: S1. Preparation of modified chitosan: Weigh 20g of chitosan and add it to 1% glacial acetic acid. Stir vigorously at room temperature until dissolved. Slowly add 2mol / L NaOH solution to adjust the pH to 8.5. Purge the reaction system with nitrogen gas for 15min to obtain a 2% chitosan solution. Weigh 70g of sodium propylene oxide sulfonate and dissolve it in 200mL of deionized water. Slowly add it to the chitosan solution through a dropping funnel. React at 70℃ for 10h. After the reaction is complete, cool to room temperature to obtain a chitosan mixture. Pour the chitosan mixture into 4800mL of acetone and stir continuously. A fibrous precipitate appears. Wash the precipitate three times with ethanol and water at a volume ratio of 4:1. Freeze-dry to obtain modified chitosan. S2. Preparation of N-dodecylhistidine amide: Dissolve 40g of histidine in 400mL of anhydrous N,N-dimethylformamide and stir for 15min. At 0℃, add 40g of 1-hydroxybenzotriazole and 60g of EDC·HCl sequentially. After heating to room temperature, stir for 30min under nitrogen protection to obtain an activated histidine solution. Add 56g of dodecylamine solution to anhydrous N,N-dimethylformamide and adjust the volume to 302mL to prepare a 1mol / L dodecylamine solution. Slowly add the dodecylamine solution dropwise to the activated histidine solution and stir at room temperature for 14h under nitrogen protection to obtain a reaction solution. Distill the reaction solution under reduced pressure at 45℃ to reduce the volume by half. Add 4.25L of ice water and stir continuously until a white solid precipitates. Filter and collect the filter cake. Wash once quickly with 0.1mol / L dilute hydrochloric acid and three times with deionized water at 4℃. Dry in a vacuum drying oven at 45℃ to obtain N-dodecylhistidine amide. S3. Preparation of N-dodecylhistidine amide-grafted polyepoxysuccinic acid: Dissolve 20g of polyepoxysuccinic acid in 200mL of deionized water and stir for 30min to obtain a polyepoxysuccinic acid solution; adjust the pH of the polyepoxysuccinic acid solution to 5.0 using acetic acid; dissolve 20g of N-dodecylhistidine amide in 100mL of N,N-dimethylformamide to obtain an N-dodecylhistidine amide solution; heat the polyepoxysuccinic acid solution to 100℃ and stir continuously; add the N-dodecylhistidine amide solution to the polyepoxysuccinic acid solution; continue the reaction under reflux at 100℃ for 4h; dialyze using a dialysis bag for 36h; evaporate and concentrate the dialysis product at 40℃; freeze-dry the concentrate to obtain N-dodecylhistidine amide-grafted polyepoxysuccinic acid; S4. Compounding: Dissolve 10g of modified chitosan in 25.8mL of deionized water, heat to 60℃, and stir for 30min to obtain a modified chitosan solution; dissolve 15g of N-dodecylhistidine amide-grafted polyepoxysuccinic acid in 46.2mL of deionized water, heat to 60℃, and stir for 30min to obtain an N-dodecylhistidine amide-grafted polyepoxysuccinic acid aqueous solution; mix the modified chitosan solution and the N-dodecylhistidine amide-grafted polyepoxysuccinic acid aqueous solution, and stir for 20min to obtain a mixed solution; slowly add 3mL of 10% glutaraldehyde aqueous solution to the mixed solution while stirring continuously. After the addition is complete, continue stirring for 20min to obtain a circulating water corrosion and scale inhibitor.

[0022] Example 4: A method for preparing a corrosion and scale inhibitor for circulating water, specifically including the following steps: S1. Preparation of modified chitosan: Weigh 20g of chitosan and add it to 1% glacial acetic acid. Stir vigorously at room temperature until dissolved. Slowly add 2mol / L NaOH solution to adjust the pH to 8.0. Purge the reaction system with nitrogen gas for 15min to obtain a 2% chitosan solution. Weigh 65g of sodium propylene oxide sulfonate and dissolve it in 200mL of deionized water. Slowly add the solution to the chitosan solution through a dropping funnel. React at 60℃ for 8h. After the reaction is complete, cool to room temperature to obtain a chitosan mixture. Pour the chitosan mixture into 3600mL of acetone and stir continuously. A fibrous precipitate appears. Wash the precipitate three times with an ethanol-water solution (ethanol to water volume ratio of 4:1). Freeze-dry to obtain modified chitosan. S2. Preparation of N-dodecylhistidine amide: Dissolve 40g of histidine in 400mL of anhydrous N,N-dimethylformamide, stir for 15min, and add 40g of 1-hydroxybenzotriazole and 60g of [unclear text - possibly a specific ingredient or substance] in an ice bath at 2℃. EDC·HCl was heated to room temperature and stirred for 30 min under nitrogen protection to obtain histidine activation solution; 52 g of dodecylamine solution was added to anhydrous N,N-dimethylformamide and diluted to 280.5 mL to prepare a 1 mol / L dodecylamine solution; the dodecylamine solution was slowly added dropwise to the histidine activation solution and stirred at room temperature for 12 h under nitrogen protection to obtain reaction solution; the reaction solution was distilled under reduced pressure at 50 °C to reduce the volume by half, 4.1 L of ice water was added, and the mixture was stirred continuously until a white solid precipitated. The mixture was filtered, the filter cake was collected, and the cake was quickly washed once with 0.1 mol / L dilute hydrochloric acid, washed three times with deionized water at 2 °C, and dried in a vacuum drying oven at 50 °C to obtain N-dodecylhistidine amide; S3. Preparation of N-dodecylhistidine amide-grafted polyepoxysuccinic acid: Dissolve 20g of polyepoxysuccinic acid in 300mL of deionized water and stir for 30min to obtain a polyepoxysuccinic acid solution; adjust the pH of the polyepoxysuccinic acid solution to 5.7 using acetic acid; dissolve 12g of N-dodecylhistidine amide in 100mL of N,N-dimethylformamide to obtain an N-dodecylhistidine amide solution; heat the polyepoxysuccinic acid solution to 105℃ and stir continuously; add the N-dodecylhistidine amide solution to the polyepoxysuccinic acid solution; continue the reaction under reflux at 105℃ for 3.5h; dialyze using a dialysis bag for 30h; evaporate and concentrate the dialysis product at 40℃; freeze-dry the concentrate to obtain N-dodecylhistidine amide-grafted polyepoxysuccinic acid; S4. Compounding: Dissolve 9g of modified chitosan in 30mL of deionized water, heat to 65℃, and stir for 30min to obtain a modified chitosan solution; dissolve 20g of N-dodecylhistidine amide-grafted polyepoxysuccinic acid in 40mL of deionized water, heat to 65℃, and stir for 30min to obtain an N-dodecylhistidine amide-grafted polyepoxysuccinic acid solution; mix the modified chitosan solution and the N-dodecylhistidine amide-grafted polyepoxysuccinic acid aqueous solution, and stir for 15min to obtain a mixed solution; slowly add 1mL of 10% glutaraldehyde aqueous solution to the mixed solution while stirring continuously. After the addition is complete, continue stirring for 15min to obtain a circulating water corrosion and scale inhibitor.

[0023] Comparative Example 1: A method for preparing a corrosion and scale inhibitor for circulating water, differing from Example 1 in that N-dodecylhistidine amide grafted polyepoxysuccinic acid is replaced with polyepoxysuccinic acid, and modified chitosan is replaced with chitosan. The method specifically includes the following steps: Add 9g of chitosan to 30mL of deionized water, heat to 80℃, and stir for 30min to obtain a chitosan solution; dissolve 10g of polyepoxysuccinic acid in 50mL of deionized water and stir evenly to obtain a polyepoxysuccinic acid solution; mix the chitosan solution and the polyepoxysuccinic acid solution and stir for 15min to obtain a mixed solution; slowly add 1mL of 10% glutaraldehyde aqueous solution to the mixed solution while stirring continuously. After the addition is completed, continue stirring for 15min to obtain a circulating water corrosion and scale inhibitor.

[0024] Comparative Example 2: A method for preparing a corrosion and scale inhibitor for circulating water, differing from Example 1 in that N-dodecylhistidine amide grafted with polyepoxysuccinic acid is replaced with polyepoxysuccinic acid, specifically including the following steps: S1. Preparation of modified chitosan: Weigh 20g of chitosan and add it to 1% glacial acetic acid. Stir vigorously at room temperature until dissolved. Slowly add 2mol / L NaOH solution to adjust the pH to 8.0. Purge the reaction system with nitrogen gas for 15min to obtain a 2% chitosan solution. Weigh 60g of sodium propylene oxide sulfonate and dissolve it in 200mL of deionized water. Slowly add it to the chitosan solution through a dropping funnel. React at 60℃ for 12h. After the reaction is complete, cool to room temperature to obtain a chitosan mixture. Pour the chitosan mixture into 3600mL of acetone and stir continuously. A fibrous precipitate appears. Wash the precipitate three times with an ethanol-water solution (ethanol to water volume ratio of 4:1). Freeze-dry to obtain modified chitosan. S2. Compounding: Dissolve 9g of modified chitosan in 30mL of deionized water, heat to 60℃, and stir for 30min to obtain a modified chitosan solution; dissolve 10g of polyepoxysuccinic acid in 50mL of deionized water, heat to 60℃, and stir for 30min to obtain a polyepoxysuccinic acid solution; mix the modified chitosan solution and the polyepoxysuccinic acid solution, and stir for 15min to obtain a mixed solution; slowly add 1mL of 10% glutaraldehyde aqueous solution to the mixed solution while stirring continuously. After the addition is complete, continue stirring for 15min to obtain a circulating water corrosion and scale inhibitor.

[0025] Comparative Example 3: A method for preparing a corrosion and scale inhibitor for circulating water, differing from Example 1 in that modified chitosan is replaced with chitosan, specifically including the following steps: S1. Preparation of N-dodecylhistidine amide: Dissolve 40g of histidine in 400mL of anhydrous N,N-dimethylformamide, stir for 15min, and add 40g of 1-hydroxybenzotriazole and 60g of [unclear text - possibly a specific ingredient or substance] in an ice bath at 0℃. EDC·HCl was heated to room temperature and stirred for 30 min under nitrogen protection to obtain histidine activation solution. 52 g of dodecylamine solution was added to anhydrous N,N-dimethylformamide and the volume was adjusted to 280.5 mL to prepare a 1 mol / L dodecylamine solution. The dodecylamine solution was slowly added dropwise to the histidine activation solution and stirred at room temperature for 12 h under nitrogen protection to obtain a reaction solution. The reaction solution was distilled under reduced pressure at 40 °C to reduce the volume by half. 4.1 L of ice water was added and stirred continuously until a white solid precipitated. The solution was filtered, the filter cake was collected, and the filter cake was quickly washed once with 0.1 mol / L dilute hydrochloric acid and washed three times with deionized water at 2 °C. The filter cake was dried in a vacuum drying oven at 40 °C to obtain N-dodecylhistidine amide. S2. Preparation of N-dodecylhistidine amide-grafted polyepoxysuccinic acid: Dissolve 20g of polyepoxysuccinic acid in 380mL of deionized water and stir for 30min to obtain a polyepoxysuccinic acid solution; adjust the pH of the polyepoxysuccinic acid solution to 5.0 using acetic acid; dissolve 10g of N-dodecylhistidine amide in 100mL of N,N-dimethylformamide to obtain an N-dodecylhistidine amide solution; heat the polyepoxysuccinic acid solution to 95℃ and stir continuously; add the N-dodecylhistidine amide solution to the polyepoxysuccinic acid solution; continue the reaction at 95℃ under reflux for 5h; dialyze using a dialysis bag for 24h; evaporate and concentrate the dialysis product at 40℃; freeze-dry the concentrate to obtain N-dodecylhistidine amide-grafted polyepoxysuccinic acid; S3. Compounding: Add 9g of chitosan to 30mL of deionized water, heat to 80℃, and stir for 30min to obtain a chitosan solution; dissolve 10g of N-dodecylhistidine amide-grafted polyepoxysuccinic acid in 50mL of deionized water, heat to 60℃, and stir for 30min to obtain an N-dodecylhistidine amide-grafted polyepoxysuccinic acid solution; mix the chitosan solution and the N-dodecylhistidine amide-grafted polyepoxysuccinic acid solution, and stir for 15min to obtain a mixed solution; slowly add 1mL of 10% glutaraldehyde aqueous solution to the mixed solution while stirring continuously. After the addition is complete, continue stirring for 15min to obtain a circulating water corrosion and scale inhibitor.

[0026] Comparative Example 4: A method for preparing a corrosion and scale inhibitor for circulating water, which differs from Example 1 in that glutaraldehyde is not added, and specifically includes the following steps: S1. Preparation of modified chitosan: Weigh 20g of chitosan and add it to 1% glacial acetic acid. Stir vigorously at room temperature until dissolved. Slowly add 2mol / L NaOH solution to adjust the pH to 8.0. Purge the reaction system with nitrogen gas for 15min to obtain a 2% chitosan solution. Weigh 60g of sodium propylene oxide sulfonate and dissolve it in 200mL of deionized water. Slowly add it to the chitosan solution through a dropping funnel. React at 60℃ for 12h. After the reaction is complete, cool to room temperature to obtain a chitosan mixture. Pour the chitosan mixture into 3600mL of acetone and stir continuously. A fibrous precipitate appears. Wash the precipitate three times with an ethanol-water solution (ethanol to water volume ratio of 4:1). Freeze-dry to obtain modified chitosan. S2. Preparation of N-dodecylhistidine amide: Dissolve 40g of histidine in 400mL of anhydrous N,N-dimethylformamide, stir for 15min, and add 40g of 1-hydroxybenzotriazole and 60g of [unclear text - possibly a specific ingredient or substance] in an ice bath at 0℃. EDC·HCl was heated to room temperature and stirred for 30 min under nitrogen protection to obtain histidine activation solution. 52 g of dodecylamine solution was added to anhydrous N,N-dimethylformamide and the volume was adjusted to 280.5 mL to prepare a 1 mol / L dodecylamine solution. The dodecylamine solution was slowly added dropwise to the histidine activation solution and stirred at room temperature for 12 h under nitrogen protection to obtain a reaction solution. The reaction solution was distilled under reduced pressure at 40 °C to reduce the volume by half. 4.1 L of ice water was added and stirred continuously until a white solid precipitated. The solution was filtered, the filter cake was collected, and the filter cake was quickly washed once with 0.1 mol / L dilute hydrochloric acid and washed three times with deionized water at 2 °C. The filter cake was dried in a vacuum drying oven at 40 °C to obtain N-dodecylhistidine amide. S3. Preparation of N-dodecylhistidine amide-grafted polyepoxysuccinic acid: Dissolve 20g of polyepoxysuccinic acid in 380mL of deionized water and stir for 30min to obtain a polyepoxysuccinic acid solution; adjust the pH of the polyepoxysuccinic acid solution to 5.0 using acetic acid; dissolve 10g of N-dodecylhistidine amide in 100mL of N,N-dimethylformamide to obtain an N-dodecylhistidine amide solution; heat the polyepoxysuccinic acid solution to 95℃ and stir continuously; add the N-dodecylhistidine amide solution to the polyepoxysuccinic acid solution; continue the reaction at 95℃ under reflux for 5h; dialyze using a dialysis bag for 24h; evaporate and concentrate the dialysis product at 40℃; freeze-dry the concentrate to obtain N-dodecylhistidine amide-grafted polyepoxysuccinic acid; S4. Compounding: Dissolve 9g of modified chitosan in 31mL of deionized water, heat to 60℃, and stir for 30min to obtain a modified chitosan solution; dissolve 10g of N-dodecylhistidine amide-grafted polyepoxysuccinic acid in 50mL of deionized water, heat to 60℃, and stir for 30min to obtain an N-dodecylhistidine amide-grafted polyepoxysuccinic acid solution; mix the modified chitosan solution and the N-dodecylhistidine amide-grafted polyepoxysuccinic acid solution, and stir for 30min to obtain a circulating water corrosion and scale inhibitor.

[0027] Comparative Example 5: A method for preparing a corrosion and scale inhibitor for circulating water, differing from Example 1 in that the corrosion and scale inhibitor is a polyepoxysuccinic acid solution, specifically including the following steps: Dissolve 20g of polyepoxysuccinic acid in 80mL of deionized water and stir for 30min to obtain a circulating water corrosion and scale inhibitor.

[0028] Comparative Example 6: A method for preparing a corrosion and scale inhibitor for circulating water, differing from Example 1 in that the corrosion and scale inhibitor is a modified chitosan solution, specifically including the following steps: S1. Preparation of modified chitosan: Weigh 20g of chitosan and add it to 1% glacial acetic acid. Stir vigorously at room temperature until dissolved. Slowly add 2mol / L NaOH solution to adjust the pH to 8.0. Purge the reaction system with nitrogen gas for 15min to obtain a 2% chitosan solution. Weigh 60g of sodium propylene oxide sulfonate and dissolve it in 200mL of deionized water. Slowly add it to the chitosan solution through a dropping funnel. React at 60℃ for 12h. After the reaction is complete, cool to room temperature to obtain a chitosan mixture. Pour the chitosan mixture into 3600mL of acetone and stir continuously. A fibrous precipitate appears. Wash the precipitate three times with an ethanol-water solution (ethanol to water volume ratio of 4:1). Freeze-dry to obtain modified chitosan. S2. Dissolve 20g of modified chitosan in 80mL of deionized water, heat to 60℃, and stir for 30min to obtain a circulating water corrosion and scale inhibitor.

[0029] Performance testing: The prepared circulating water corrosion and scale inhibitor was used to prepare the test water. The corrosion and scale inhibitor was added to the circulating water sample at a ratio of 10 mg / L, and the scale inhibition performance and corrosion inhibition performance were tested.

[0030] (1) Corrosion inhibition performance test The corrosion inhibition rate of the corrosion and scale inhibitors in the examples and comparative examples was tested according to GB / T 18175-2014 "Determination of Corrosion Inhibition Performance of Water Treatment Agents - Rotary Coated Plate Method"; the experimental conditions were set as follows: temperature 45℃, time 72h; carbon steel and copper test pieces were selected; the test results are shown in Table 1: Table 1. Test results of corrosion inhibition effect of corrosion and scale inhibitors

[0031] As can be seen from Table 1, the corrosion and scale inhibitors prepared in Examples 1-4 have higher corrosion inhibition rates for both carbon steel and copper than those in Comparative Examples 1-4. Specifically, the corrosion inhibition rates of the corrosion and scale inhibitors in Examples 1-4 for carbon steel are all above 98%, and the corrosion and scale inhibition rates for copper are all above 96%, indicating that the corrosion and scale inhibitors prepared using the method of this invention have good corrosion inhibition effects on both carbon steel and copper.

[0032] The corrosion and scale inhibitor prepared using the method of this invention contains an imidazole ring of histidine, which has a strong coordination ability with copper, forming a dense chemical adsorption layer on the surface of copper materials. In addition, the introduction of hydrophobic dodecyl long chains into polyepoxysuccinic acid can form a water-transporting barrier on the metal surface, effectively blocking the penetration of corrosion ions. Furthermore, the aldehyde group in the added glutaraldehyde can partially crosslink chitosan on the metal surface, forming a robust network structure. The synergistic effect of these components, through the dual action of chemical coordination adsorption and physical barrier protection, provides strong protection for the metal material, thereby preventing it from corrosion.

[0033] (2) Scale inhibition efficiency test of calcium carbonate The scale inhibition rates of the corrosion and scale inhibitors in each example and comparative example were tested according to GB / T 16632-2019 "Determination of Scale Inhibition Performance of Water Treatment Agents - Calcium Carbonate Deposition Method"; the experimental conditions were set as follows: temperature 80℃, time 10h; the test results are shown in Table 2. Table 2. Scale inhibition effect test results of corrosion and scale inhibitors

[0034] (3) Scale inhibition efficiency test of calcium phosphate The scale inhibition rates of the corrosion and scale inhibitors in each example and comparative example were tested according to GB / T 22626-2008 "Determination of Scale Inhibition Performance of Water Treatment Agents - Calcium Phosphate Deposition Method"; the experimental conditions were set as follows: temperature 80℃, time 10h; the test results are shown in Table 3. Table 3. Scale inhibition effect test results of corrosion and scale inhibitors

[0035] As can be seen from Tables 2 and 3, Examples 1-4 exhibit stronger scale inhibition effects against both calcium carbonate and calcium phosphate than Comparative Examples 1-4. Specifically, the scale inhibition rate against calcium carbonate reaches over 98%, and the scale inhibition rate against calcium phosphate reaches over 97%. These results demonstrate that the corrosion and scale inhibitor prepared using the method of this invention can achieve good scale inhibition effects against both calcium carbonate and calcium phosphate.

[0036] The corrosion and scale inhibitor prepared by the method of this invention comprises polyepoxysuccinic acid containing a large number of carboxyl groups, and modified chitosan containing sulfonic acid groups and hydroxyl groups. These functional groups can chelate with calcium ions, preventing them from settling and forming precipitates. The carboxyl groups on polyepoxysuccinic acid can also disrupt the crystal structure of calcium carbonate, preventing it from forming a dense scale layer. The dodecyl groups on the modified polyepoxysuccinic acid can form a comb-like structure, and their steric hindrance effect can effectively disperse various scale crystals, preventing scale deposition on the metal surface. For calcium phosphate, the sulfonic acid groups on the modified chitosan play a role, preventing the aggregation of calcium phosphate and its precipitation. Experiments showed that unmodified chitosan had poor water solubility, exhibiting incomplete dissolution, while the chitosan modified by the method of this invention showed good solubility. Therefore, the corrosion and scale inhibitor prepared by the method of this invention, through the synergistic effect of several components, can effectively disperse both calcium carbonate and calcium phosphate, effectively inhibiting the formation of calcium scale.

[0037] (4) Effects of concentration and temperature on the scale inhibition efficiency of corrosion and scale inhibitors Similar tests were conducted using the method described above for testing the scale inhibition efficiency of calcium carbonate. Water samples were prepared with different amounts of corrosion and scale inhibitor added: 2 mg / mL, 4 mg / mL, 6 mg / mL, 8 mg / mL, and 10 mg / mL. Experimental conditions were set as follows: temperature 80℃ or 60℃, time 10 h. The test results are shown below. Figure 1 and Figure 2 , Figure 1 The results were obtained at a temperature of 80℃. Figure 2 The results are from a test conducted at a temperature of 60℃.

[0038] from Figure 1 and Figure 2 As can be seen, at both 80℃ and 60℃, the scale inhibition effect of Example 1 is stronger than that of Comparative Examples 5 and 6, and the scale inhibition efficiency at 60℃ is stronger than that at 80℃. When the scale inhibitor concentration is 6 mg / L, the scale inhibition rate can reach approximately 80%. However, when the scale inhibitor concentration is less than 6 mg / L, the scale inhibition efficiency decreases significantly with decreasing scale inhibitor concentration, but the scale inhibition effect of Example 1 is still stronger than that of the comparative examples.

[0039] (5) SEM scanning detection of calcium carbonate scale Three groups of calcium carbonate scales were prepared on glass slides: one group without corrosion and scale inhibitor, one group using the corrosion and scale inhibitor prepared in Example 1, and one group using the corrosion and scale inhibitor prepared in Comparative Example 5. After drying at 60°C, the glass slides were adhered to conductive adhesive, sputtered with gold, and the images were observed using a scanning electron microscope. The results are as follows. Figure 3As shown, Figure a shows the group without added corrosion and scale inhibitor, Figure b shows the group with corrosion and scale inhibitor prepared in Comparative Example 5, and Figure c shows the group with corrosion and scale inhibitor prepared in Example 1.

[0040] from Figure 3 As can be seen, the calcium carbonate scale without scale inhibitor has a relatively regular shape, appearing as blocky or needle-like distributions; while the sample using polyepoxysuccinic acid as a scale inhibitor has an irregular cloud-like shape with no obvious shape or orientation, irregular crystal form, no obvious edges, and lattice distortion; while the sample using the scale inhibitor prepared by the method of this invention has a very loose calcium carbonate scale structure, with completely broken calcium carbonate crystals, a relatively loose internal structure, and severe lattice distortion. The loose structure allows water flow to easily disperse the calcium scale, thereby inhibiting calcium scale deposition and achieving a better scale inhibition effect.

[0041] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A circulating water corrosion and scale inhibitor, characterized in that, By weight, it comprises the following components: 9-15% modified chitosan, 10-20% N-dodecylhistidine amide grafted polyepoxysuccinic acid, 1-5% 10% glutaraldehyde aqueous solution, and 60-80% deionized water.

2. The preparation method of the circulating water corrosion and scale inhibitor according to claim 1, characterized in that, Includes the following steps: S1. Weigh the modified chitosan, N-dodecylhistidine amide-grafted polyepoxysuccinic acid, 10% glutaraldehyde aqueous solution and deionized water. S2. Dissolve the modified chitosan in a portion of deionized water, heat to 60-70℃, and stir for 30 minutes to obtain a modified chitosan solution. S3. Dissolve N-dodecylhistidine amide-grafted polyepoxysuccinic acid in the remaining deionized water, heat to 60~70℃, stir for 30 min, and obtain N-dodecylhistidine amide-grafted polyepoxysuccinic acid solution. S4. Mix the modified chitosan solution and the N-dodecylhistidine amide-grafted polyepoxysuccinic acid solution and stir for 15-30 minutes to obtain a mixture. S5. Slowly add 10% glutaraldehyde aqueous solution to the mixture, stirring continuously during the addition process. After the addition is completed, continue stirring for 15-30 minutes to obtain a circulating water corrosion and scale inhibitor.

3. The method for preparing the circulating water corrosion and scale inhibitor according to claim 2, characterized in that, The modified chitosan is prepared as follows: chitosan is added to an acetic acid solution and stirred until dissolved. NaOH is added dropwise to adjust the pH to 8.0-9.0, and nitrogen gas is purged for 15 minutes to obtain a chitosan solution. Sodium propylene oxide sulfonate is dissolved in deionized water to obtain a sodium propylene oxide sulfonate solution. The sodium propylene oxide sulfonate solution is added dropwise to the chitosan solution, stirred, and reacted at 60-80℃ for 8-12 hours. After the reaction is completed, a chitosan mixture is obtained. Acetone is added to the chitosan mixture and stirred until a precipitate appears. The precipitate is collected by suction filtration, washed three times with an ethanol aqueous solution, and freeze-dried to obtain modified chitosan.

4. The preparation method of the circulating water corrosion and scale inhibitor according to claim 3, characterized in that, The mass ratio of chitosan to sodium propylene oxide sulfonate is 1:3~4; the volume of acetone is 3~5 times the volume of the chitosan mixture.

5. The method for preparing the circulating water corrosion and scale inhibitor according to claim 2, characterized in that, The preparation method of N-dodecylhistidine amide-grafted polyepoxysuccinic acid is as follows: polyepoxysuccinic acid is dissolved in deionized water and stirred for 30 min to prepare a polyepoxysuccinic acid solution with a mass fraction of 5-10%; the pH of the polyepoxysuccinic acid solution is adjusted to 5.0-5.5 using acetic acid; N-dodecylhistidine amide is dissolved in N,N-dimethylformamide to obtain an N-dodecylhistidine amide solution; the polyepoxysuccinic acid solution is heated to 95-115℃ and stirred continuously, the N-dodecylhistidine amide solution is added, and the reaction is continued at 95-115℃ under reflux for 3-5 h; dialyzed using a dialysis bag for 24-48 h; the dialyzed product is evaporated and concentrated at 40℃; the concentrate is freeze-dried to obtain N-dodecylhistidine amide-grafted polyepoxysuccinic acid.

6. The method for preparing the circulating water corrosion and scale inhibitor according to claim 5, characterized in that, The mass ratio of the polyepoxysuccinic acid to N-dodecylhistidine amide is 1:0.5~1.

5.

7. The method for preparing the circulating water corrosion and scale inhibitor according to claim 5, characterized in that, The preparation method of the N-dodecylhistidine amide is as follows: histidine is dissolved in anhydrous N,N-dimethylformamide and stirred for 15 min. Then, under an ice bath at 0-4℃, 1-hydroxybenzotriazole and EDC·HCl are added sequentially. After heating to room temperature, the mixture is stirred for 30 min under nitrogen protection to obtain an activated histidine solution. Dodecylamine is dissolved in anhydrous N,N-dimethylformamide to prepare a 1 mol / L dodecylamine solution. The dodecylamine solution is added dropwise to the activated histidine solution, and the mixture is stirred under nitrogen protection. Stir at a warm temperature for 12-16 hours to obtain a reaction solution; distill the reaction solution under reduced pressure at 40-50℃ to reduce the volume of the reaction solution by half to obtain a concentrated N-dodecylhistidine amide solution; add 10 times the volume of ice water to the concentrated N-dodecylhistidine amide solution and continue stirring until a white solid precipitates; filter under vacuum, collect the filter cake, rinse once with 0.1mol / L dilute hydrochloric acid, wash three times with deionized water at 2-4℃, and dry under vacuum at 40-50℃ to obtain N-dodecylhistidine amide.

8. The method for preparing the circulating water corrosion and scale inhibitor according to claim 7, characterized in that, The mass ratio of histidine, 1-hydroxybenzotriazole, EDC·HCl and dodecylamine is 1:1:1.5:1.3~1.5.

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