Corrosion and scale inhibitor for water treatment and preparation method thereof

Abstract

The application discloses a kind of water treatment corrosion and scale inhibitor and preparation method thereof, first, guanidine group is introduced by the reaction of chitosan and thiourea trioxide, then carboxyl group is introduced by the reaction of composition containing carboxylic acid group in alkaline solution and isopropanol solution, and double modified chitosan composition is prepared, finally, modified chitosan is compounded with composition containing carboxylic acid to obtain the product.The product prepared by the application has excellent performance of corrosion inhibition, scale inhibition, antibacterial, non-toxic and easy degradation, and has strong comprehensive water treatment ability.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a corrosion and scale inhibitor for water treatment and its preparation method. Background Technology

[0002] After long-term circulation of cooling water, three problems will inevitably arise: sediment adhesion, metal corrosion, and microbial growth. To solve these three problems, it is necessary to select a comprehensive water treatment agent composed of scale inhibitors, corrosion inhibitors, and bactericides to add to the circulating water. This process formula can effectively control the formation of scale, prevent corrosion of pipelines and equipment, and effectively control the growth of microorganisms.

[0003] Existing water treatment agents mostly use phosphorus-based scale inhibitors containing organophosphonic acids. However, organophosphonic acids have a high phosphorus content, which can lead to eutrophication of water bodies, promote algae growth, and cause phenomena such as phosphorus scale and red tides. In contrast, polycarboxylic acid scale inhibitors are phosphorus-free, non-toxic, and pollution-free environmentally friendly products, with overall performance superior to phosphorus-based scale inhibitors. In addition, bactericides mostly use isoxazolinones, chlorine-based agents, quaternary ammonium salts, etc., but they have extremely strong irritant, corrosive, and toxic properties, which harm human health and pollute the environment.

[0004] Chitosan is a natural alkaline polysaccharide obtained by deacetylation of chitin contained in the shells of crustaceans such as shrimp and crabs, as well as fungal cell walls. Chitosan possesses excellent biocompatibility and biodegradability, making it easy to formulate various derivatives. Its biodegradability, biocompatibility, non-toxicity, and antibacterial activity allow it to be used as a natural antibacterial agent. However, the presence of numerous hydrogen bonds within and between chitosan molecules, its high crystallinity, poor water solubility (only dissolving in certain dilute acid solutions), and other factors significantly limit its widespread application as an antibacterial agent.

[0005] Therefore, it is urgently needed to develop a non-toxic, pollution-free, biodegradable, and highly effective corrosion and scale inhibitor. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a corrosion and scale inhibitor for water treatment.

[0007] One objective of this invention is to provide a method for preparing a corrosion and scale inhibitor for water treatment, which is obtained by following these steps:

[0008] 1) Dissolve chitosan in an acidic solution to prepare a chitosan solution, and heat it to 45-60 degrees Celsius;

[0009] 2) Slowly add thiourea trioxide dropwise to the chitosan solution and continue heating and stirring for 1 hour;

[0010] 3) After the reaction is complete and cooled to room temperature, the solution is precipitated with ethanol, filtered, washed, and vacuum dried;

[0011] 4) Dissolve the obtained product in water and heat it again to 45-60 degrees Celsius;

[0012] 5) Add acid to the solution obtained in step 4) and stir for 2-3 hours, filter, wash and then vacuum dry;

[0013] 6) Dissolve the product obtained in step 5) in an alkaline solution and isopropanol;

[0014] 7) Slowly add the carboxylic acid-containing composition at 60-70 degrees Celsius and stir the reaction for 2-3 hours;

[0015] 8) After stirring, adjust to neutral with acid, filter, wash with ethanol, and then vacuum dry;

[0016] 9) Dissolve the product obtained in step 8) in a carboxylic acid-containing composition to obtain the final product.

[0017] Preferably, the chitosan used in step 1 has a degree of deacetylation greater than 95%.

[0018] Preferably, the acid in step 1) and step 5) is one or more of hydrochloric acid, acetic acid or lactic acid.

[0019] Preferably, the alkaline solution in step 6) is one or a mixture of potassium hydroxide and sodium hydroxide.

[0020] Preferably, the carboxylic acid-containing composition in steps 7) and 9) is one or more of polyacrylic acid, maleic acid-acrylic acid copolymer, polyepoxysuccinic acid, and polyaspartic acid.

[0021] The second objective of this invention is to provide a corrosion and scale inhibitor for water treatment, comprising at least the modified chitosan and a carboxylic acid-containing composition prepared in step 9).

[0022] Preferably, the modified chitosan and the carboxylic acid-containing composition are compounded in a ratio of 1:20 to 1:35.

[0023] This invention has the following advantages: It provides a method for sequentially grafting guanidine and carboxyl groups onto chitosan. First, the amino groups on chitosan react with thiourea trioxide to generate guanidine groups, which are then grafted onto the chitosan. The introduction of guanidine groups improves the antibacterial and antimicrobial properties of chitosan. Then, under alkaline conditions, the hydroxyl groups on chitosan are made more active than the amino groups, causing the hydroxyl groups to condense with the carboxyl groups, and the carboxyl groups are grafted onto the chitosan. The introduction of carboxyl groups improves the solubility of chitosan, enabling the chitosan to possess both enhanced antibacterial properties and biocompatibility with low cytotoxicity. The carboxyl groups grafted onto the chitosan are... Compared to simply grafting carboxyl groups, high molecular weight polycarboxylic acid compositions enhance the water solubility of chitosan more effectively. Furthermore, the modified chitosan, with its abundant carboxyl groups, retains the excellent corrosion and scale inhibition capabilities of these groups. This results in a dual-modified chitosan that integrates antibacterial, slow-release, scale inhibition, non-toxicity, and easy biodegradability properties, solving the problem of traditional slow-release scale inhibitors requiring multiple formulations. It possesses superior comprehensive capabilities. The preparation process of this slow-release scale inhibitor is simple, the reaction conditions are mild, and it can be grafted and compounded with various polycarboxylic acid compositions, facilitating large-scale application. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0025] Example 1: Preparation of modified chitosan, which was carried out according to the following steps.

[0026] 1) Weigh 30g of chitosan with a molecular weight of 2×105Da and a degree of deacetylation of 99% and add it to the hydrochloric acid solution. Heat the solution in a water bath to 45 degrees Celsius and stir until the chitosan is completely dissolved.

[0027] 2) Slowly add 27g of thiourea trioxide to the chitosan solution while stirring, and continue adding for 1 hour. The pH of the reaction solution is 6.2.

[0028] 3) After cooling to room temperature, filter under reduced pressure. Precipitate the filtrate with anhydrous ethanol. After filtration, wash with anhydrous ethanol 2-3 times again. Finally, put it into a vacuum dryer for drying at room temperature. The product obtained at this time is chitosan guanidine bisulfite.

[0029] 4) Dissolve the obtained product in distilled water and heat to 50 degrees Celsius;

[0030] 5) Add hydrochloric acid to the chitosan guanidine bisulfite solution, continue stirring for 3 hours, filter under reduced pressure, wash the product 2-3 times with anhydrous ethanol, and dry it at room temperature in a vacuum dryer. The product obtained after drying is chitosan guanidine hydrochloride powder.

[0031] 6) Dissolve 10g of chitosan guanidine hydrochloride powder and 100ml of isopropanol in a 40% sodium hydroxide solution, heat to 65 degrees Celsius, and then add polyacrylic acid solution dropwise while stirring for 2 hours. Control the pH of the reaction solution to 8-10 and keep warm for 1 hour.

[0032] 7) After the reaction is complete, adjust the solution to neutral with hydrochloric acid, filter under reduced pressure, wash the product 2-3 times with anhydrous ethanol, and dry it in a vacuum dryer at 45 degrees Celsius to obtain chitosan with guanidine and carboxyl groups.

[0033] A corrosion and scale inhibitor was prepared by dissolving 5g of double-modified chitosan in 100g of polyacrylic acid solution.

[0034] Example 2, Preparation of modified chitosan, was carried out according to the following steps:

[0035] 1) Weigh 30g of chitosan with a molecular weight of 2×105Da and a degree of deacetylation of 99% and add it to the acetic acid solution. Heat the solution in a water bath to 50 degrees Celsius and stir until the chitosan is completely dissolved.

[0036] 2) Slowly add 27g of thiourea trioxide to the chitosan solution while stirring, and continue adding for 1 hour. The pH of the reaction solution is 6.3.

[0037] 3) After cooling to room temperature, filter under reduced pressure. Precipitate the filtrate with anhydrous ethanol. After filtration, wash with anhydrous ethanol 2-3 times again. Finally, put it into a vacuum dryer for drying at room temperature. The product obtained at this time is chitosan guanidine bisulfite.

[0038] 4) Dissolve the obtained product in distilled water and heat to 55 degrees Celsius;

[0039] 5) Add hydrochloric acid to the chitosan guanidine bisulfite solution, continue stirring for 2 hours, filter under reduced pressure, wash the product 2-3 times with anhydrous ethanol, and dry it at room temperature in a vacuum dryer. The product obtained after drying is chitosan guanidine hydrochloride powder.

[0040] 6) Dissolve 10g of chitosan guanidine hydrochloride powder and 100ml of isopropanol in a 35% sodium hydroxide solution, heat to 70 degrees Celsius, and then add polyepoxysuccinic acid solution dropwise while stirring for 3 hours. Control the pH of the reaction solution to 8-10 and keep warm for 1 hour.

[0041] 7) After the reaction is complete, adjust the solution to neutral with polyepoxysuccinic acid, filter under reduced pressure, wash the product 2-3 times with anhydrous ethanol, and dry it in a vacuum dryer at 45 degrees Celsius to obtain chitosan with guanidine and carboxyl groups.

[0042] A corrosion and scale inhibitor was prepared by dissolving 5g of double-modified chitosan in 150g of polyepoxysuccinic acid.

[0043] Example 3, Preparation of modified chitosan, was carried out according to the following steps:

[0044] 1) Weigh 30g of chitosan with a molecular weight of 2×105Da and a degree of deacetylation of 99% and add it to the lactic acid solution. Heat the solution in a water bath to 60 degrees Celsius and stir until the chitosan is completely dissolved.

[0045] 2) Slowly add 27g of thiourea trioxide to the chitosan solution while stirring, and continue adding for 1 hour. The pH of the reaction solution is 6.5.

[0046] 3) After cooling to room temperature, filter under reduced pressure. Precipitate the filtrate with anhydrous ethanol. After filtration, wash with anhydrous ethanol 2-3 times again. Finally, put it into a vacuum dryer for drying at room temperature. The product obtained at this time is chitosan guanidine bisulfite.

[0047] 4) Dissolve the obtained product in distilled water and heat to 60 degrees Celsius;

[0048] 5) Add hydrochloric acid to the chitosan guanidine bisulfite solution, continue stirring for 2 hours, filter under reduced pressure, wash the product 2-3 times with anhydrous ethanol, and dry it at room temperature in a vacuum dryer. The product obtained after drying is chitosan guanidine hydrochloride powder.

[0049] 6) Dissolve 10g of chitosan guanidine hydrochloride powder and 100ml of isopropanol in a 45% sodium hydroxide solution, heat to 60 degrees Celsius, and then add maleic acid acrylic acid copolymer solution dropwise while stirring for 2 hours. Control the pH of the reaction solution to 8-10 and keep warm for 1 hour.

[0050] 7) After the reaction is complete, adjust the solution to neutral with maleic acid-acrylic acid copolymer, filter under reduced pressure, wash the product 2-3 times with anhydrous ethanol, and dry it in a vacuum dryer at 45 degrees Celsius to obtain chitosan with guanidine and carboxyl groups.

[0051] A corrosion and scale inhibitor was prepared by dissolving 10g of double-modified chitosan in 350g of maleic acid-acrylic acid copolymer.

[0052] According to the requirements of "General Technical Conditions for Oilfield Injection Water" SY / T 5757-2010, the corrosion and scale inhibitors prepared in Examples 1-3 were subjected to antibacterial experiments. The test temperature was 40℃, and the dosage was 50 mg / L. The experimental results are as follows:

[0053] Inoculation with experimental bacteria Bacterial content in water samples Example 1 Example 2 Example 3 saprophytic bacteria / ml 450 0.3 0.6 0.3 sulfate-reducing bacteria / ml 250 0 0 0 Iron bacteria / ml 950 0 0.6 0.6

[0054] Scale inhibition, corrosion inhibition, and antibacterial experiments were conducted on Examples 1-3. Corrosion tests were performed using carbon steel inserts. Scale inhibition performance was determined according to "Determination of Scale Inhibition Performance of Water Treatment Agents - Calcium Carbonate Deposition Method" (GB / T16632-2008). Corrosion tests were conducted according to "Determination of Corrosion Inhibition Performance of Water Treatment Agents - Rotary Insert Method" (GB / T18175-2000). The test temperature was 40℃, the insert rotation speed was 80 rpm, and the test time was 72 hours. The dosage was 30 mg / L for all tests.

[0055] Example 1 Example 2 Example 3 Corrosion inhibition rate / % 94.6 93.4 92.3 Scale inhibition rate / % 96.6 97.4 98.3

[0056] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for the preparation of corrosion and scale inhibitor for water treatment, characterized in that, The method comprises the following steps: 1) dissolving chitosan in an acid solution to form a chitosan solution, and heating to 45-60 degrees Celsius; 2) slowly adding thiourea trioxide to the chitosan solution, and continuing to heat and stir for 1 hour; 3) after the reaction is completed and the solution is cooled to room temperature, the solution is precipitated with ethanol, filtered and washed, and vacuum dried; 4) dissolving the obtained product in water and heating to 45-60 degrees Celsius again; 5) adding hydrochloric acid to the solution prepared in step 4) and stirring for 2-3 hours, filtering and washing, and vacuum drying; 6) dissolving the product prepared in step 5) in a basic solution and isopropyl alcohol; 7) slowly adding a carboxylic acid group-containing composition at 60-70 degrees Celsius, and stirring for 2-3 hours; 8) after stirring is completed, adjusting to neutral with an acid, filtering, and washing with ethanol, and vacuum drying; 9) dissolving the product obtained in step 8) in a carboxylic acid group-containing composition.

2. The method for preparing a corrosion and scale inhibitor for water treatment according to claim 1, characterized in that: The chitosan used in step 1) has a deacetylation degree of greater than 95%.

3. The method of claim 1, wherein the method is characterized by: The basic solution in step 6) is a mixture of one or both of potassium hydroxide and sodium hydroxide.

4. The method for preparing the corrosion and scale inhibitor for water treatment according to claim 1, characterized in that: The carboxylic acid group-containing composition in steps 7) and 9) is one or more of polyacrylic acid, maleic acid-acrylic acid copolymer, polyepoxysuccinic acid, and polyaspartic acid.

5. The corrosion and scale inhibitor for water treatment prepared according to the method of any one of claims 1-3, characterized in that, At least the modified chitosan prepared in step 9) and the carboxylic acid group-containing composition.

6. The corrosion and scale inhibitor for water treatment prepared according to claim 5, characterized in that, The modified chitosan and the carboxylic acid group-containing composition are compounded in a ratio of 1:20-1:35.