A scale inhibitor for reverse osmosis membranes, and a preparation method and application thereof

Abstract

The present application relates to the technical field of scale inhibitors, and specifically discloses a scale inhibitor for reverse osmosis membranes, a preparation method and application thereof. The scale inhibitor for reverse osmosis membranes is obtained by a dehydration condensation reaction of carboxylated chitosan and 2-phosphonate butane-1,2,4-tricarboxylic acid as raw materials. The scale inhibitor for reverse osmosis membranes has excellent scale inhibition performance, and the scale inhibition rate can reach more than 95%. Meanwhile, the scale inhibitor has the advantages of low cost, simple operation, high safety and efficiency, etc. In the long-term use process, the scale inhibitor can effectively inhibit scale while maintaining the structural integrity and performance stability of the reverse osmosis membrane, ensuring the efficient and stable operation of the reverse osmosis system. The scale inhibitor can be applied to reverse osmosis systems with different water source characteristics, especially in the reverse osmosis systems for the advanced treatment of municipal wastewater with secondary discharge, water reuse, seawater desalination, etc., and has high engineering practical value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of scale inhibitors, in particular to a scale inhibitor for reverse osmosis membranes and a preparation method and application thereof. BACKGROUND

[0002] Reverse osmosis (RO) is a highly efficient membrane separation technology with wide applications in many fields. It is a process that takes advantage of the properties of semi-permeable membranes to separate solutes from a solution under pressure, resulting in the transfer of solvent (usually water) from the high concentration side to the low concentration side through the membrane, while the solutes are retained, achieving the purposes of concentration, purification or separation of the solution. Reverse osmosis technology plays an extremely important role in seawater desalination, brackish water desalination, pure water preparation, industrial wastewater treatment and reuse, etc.

[0003] In recent years, the problem of reclaimed water reuse has been getting more and more attention. At present, part of the discharge water from municipal wastewater treatment plants is used as a supplement to natural water systems (such as rivers, lakes, and reservoirs), and another part is treated to a high degree and used as a second water source for towns. Reverse osmosis membranes can achieve deep purification and water quality improvement of wastewater, and therefore have been widely used in the field of reclaimed water reuse. Although reverse osmosis membrane treatment technology has significant advantages in the deep treatment of municipal wastewater, it also faces some challenges. During the membrane treatment process, impurities such as ions in the water can cause scale to deposit on the membrane surface, significantly reducing the water treatment efficiency, increasing the energy consumption, shortening the service life of the reverse osmosis membrane, and even causing equipment downtime and safety problems. Therefore, the problem of membrane fouling has become a bottleneck problem in the industrial application of membrane treatment technology. Traditional scale inhibitors such as polyphosphates and organic phosphates can inhibit the formation of scale to some extent, but their scale inhibition effect on reverse osmosis membranes for municipal wastewater, reclaimed water reuse, and seawater desalination systems with high hardness, high salt content, and complex ions is poor. Therefore, it is of great significance to develop a scale inhibitor suitable for municipal wastewater, reclaimed water reuse, and seawater desalination systems, and friendly to the environment. SUMMARY

[0004] In view of the poor scale inhibition performance of the scale inhibitors in the prior art on reverse osmosis membranes for municipal wastewater, reclaimed water reuse, and seawater desalination systems, the present application provides a scale inhibitor for reverse osmosis membranes and a preparation method and application thereof.

[0005] To solve the above technical problems, the technical solution provided by the present application is as follows:

[0006] In a first aspect, the present application provides a scale inhibitor for reverse osmosis membranes, the structure of the scale inhibitor for reverse osmosis membranes is shown as formula I:

[0007]

[0008] Formula I

[0009] wherein R1, R2, R3 are or M, and R1, R2, R3 are not simultaneously M; M is Na or K.

[0010] Compared with the prior art, the scale inhibitor for reverse osmosis membranes provided by the application has good solubility in water, and contains carboxyl, phosphoric acid group, amino and hydroxyl groups in the molecular structure, can attract and stabilize chelation of various metal ions, form stable chelates, prevent contact of scale-forming cations and scale-forming anions (such as carbonate, phosphate, sulfate, etc.), and thus significantly reduce the probability of scale formation; at the same time, the scale inhibitor can also be adsorbed on the surface of scale-forming particles, prevent mutual contact and agglomeration of the scale-forming particles through the dual action of steric hindrance and electrostatic repulsion, and make the scale-forming particles maintain a dispersed state, thereby preventing scale growth; in addition, even if a small amount of scale-forming particles have formed a small aggregate, the scale inhibitor can further disperse the small aggregate, prevent the small aggregate from continuing to grow and depositing on the surface of the reverse osmosis membrane; in addition, the scale inhibitor can be adsorbed on the surface of the reverse osmosis membrane to form a protective film, reduce direct contact and friction between scale and the membrane surface, reduce physical damage to the membrane, and prolong the service life of the reverse osmosis membrane, thereby reducing the operation and maintenance cost of the reverse osmosis membrane system.

[0011] In a second aspect, the application further provides a preparation method of the scale inhibitor for reverse osmosis membranes, which uses carboxylated chitosan and 2-phosphonobutane-1,2,4-tricarboxylic acid as raw materials and prepares the scale inhibitor for reverse osmosis membranes through dehydration condensation reaction.

[0012] As a specific embodiment of the application, the preparation method of the scale inhibitor for reverse osmosis membranes comprises the following steps:

[0013] In step a, 2-phosphonobutane-1,2,4-tricarboxylic acid and carboxylated chitosan are respectively dissolved in water to obtain a 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution and a carboxylated chitosan aqueous solution.

[0014] In step b, a strong alkali solution is added to the 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution to obtain a 2-phosphonobutane-1,2,4-tricarboxylic acid salt solution.

[0015] In step c, the 2-phosphonobutane-1,2,4-tricarboxylic acid salt solution and the carboxylated chitosan aqueous solution are uniformly mixed, a strong alkali solution is added to adjust the pH to 9-10, and then the temperature is increased to perform dehydration condensation reaction, so as to obtain the scale inhibitor for reverse osmosis membranes, i.e., carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt (CCS-PBTCA), as shown in formula I; the strong alkali solution is a sodium hydroxide solution or a potassium hydroxide solution. The reaction equation is as follows.

[0016]

[0017] R represents carboxylated chitosan, with the structural formula as follows: .

[0018] The preparation method of the antiscalant for reverse osmosis membranes provided by this invention is simple, the reaction conditions are mild, the operation is easy, and the product yield is high, which facilitates large-scale production and application.

[0019] Furthermore, the mass ratio of 2-phosphonobutane-1,2,4-tricarboxylic acid to carboxylated chitosan is 0.15:1 to 0.5:1.

[0020] Preferably, the mass ratio of 2-phosphonobutane-1,2,4-tricarboxylic acid to carboxylated chitosan is 0.4:1.

[0021] The optimal ratio of each substance can improve the conversion rate of carboxylated chitosan units, resulting in a suitable molecular structure for the prepared scale inhibitor, thus achieving high scale inhibition performance in reverse osmosis systems. If the mass ratio is too low, effective grafting of carboxylated chitosan is impossible, limiting the improvement in scale inhibition rate; if the mass ratio is too high, the grafting rate is too high, and the molecular weight is too large, which is also detrimental to improving the scale inhibition rate.

[0022] Further, in step a, the mass concentration of the aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid is 48%~52%.

[0023] Further, in step a, the mass concentration of the carboxylated chitosan aqueous solution is 4%~10%.

[0024] Further, in step b, the molar ratio of the alkali to 2-phosphonobutane-1,2,4-tricarboxylic acid in the strong alkali solution is 4:1 to 7:1.

[0025] Specifically, in step b, the mass concentration of the strong alkali solution is 15% to 20%.

[0026] Furthermore, in step c, the temperature of the dehydration condensation reaction is 40℃~50℃, and the reaction time is 6h~8h.

[0027] Preferably, in step c, the temperature of the dehydration condensation reaction is 45°C and the reaction time is 7 hours.

[0028] Furthermore, in step c, the strong alkali solution is added slowly dropwise over a period of 2.0 to 2.5 hours.

[0029] Specifically, in step c, the mass concentration of the strong alkali solution is 15% to 20%.

[0030] The preferred ratio of each substance, as well as the preferred reaction temperature, time, and pH value, can promote the full reaction of 2-phosphonobutane-1,2,4-tricarboxylate and carboxylated chitosan, reduce the occurrence of side reactions, and thus improve the yield and purity of the carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylate sodium salt product.

[0031] Furthermore, after the addition reaction is completed, a post-processing procedure is also included: the reaction solution is cooled to room temperature, acetone is added, the mixture is filtered, washed five times with anhydrous ethanol, dried, and ground to obtain the carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt product.

[0032] Thirdly, as another objective of the present invention, the present invention also provides a scale inhibitor composition for reverse osmosis membranes, comprising the above-described scale inhibitor for reverse osmosis membranes.

[0033] This scale inhibitor can be used in combination with conventional water treatment agents in the art, as long as there is no adverse interaction between the components.

[0034] Fourthly, the present invention also provides the application of the above-mentioned antiscalant for reverse osmosis membranes in advanced treatment of secondary wastewater discharge, reclaimed water reuse, or seawater desalination reverse osmosis systems.

[0035] Furthermore, the amount of scale inhibitor added to the reverse osmosis membrane is 4 mg / L to 6 mg / L.

[0036] The present invention has the following advantages over the prior art:

[0037] This invention creatively proposes a novel scale inhibitor, which is obtained through a dehydration condensation reaction of carboxylated chitosan and 2-phosphonobutane-1,2,4-tricarboxylic acid. It is suitable for reverse osmosis systems such as secondary wastewater treatment, greywater reuse, and seawater desalination, and has excellent scale inhibition performance, with a scale inhibition rate of over 95%. At the same time, it also has the advantages of low cost, simple operation, safety and high efficiency, effectively ensuring the normal operation of reverse osmosis membranes, significantly reducing the risk of membrane fouling, and has good biodegradability, reducing environmental pollution. Attached Figure Description

[0038] Figure 1 The infrared spectrum of the carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt product prepared in Example 1 is shown. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] To better illustrate the present invention, further examples are provided below.

[0041] Example 1

[0042] A method for preparing a scale inhibitor for reverse osmosis membranes includes the following steps:

[0043] Weigh 3.0 g of a 50% aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid into a beaker and set aside. Separately, weigh 1.125 g of sodium hydroxide and dissolve it in 6.375 g of distilled water to obtain an aqueous solution of sodium hydroxide. Slowly pour the aqueous solution of sodium hydroxide into the aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid while stirring continuously to generate a sodium salt solution of 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0044] 10g of carboxylated chitosan was dissolved in 150mL of distilled water to obtain an aqueous solution of carboxylated chitosan. The aqueous solution of carboxylated chitosan and a solution of sodium 2-phosphonobutane-1,2,4-tricarboxylate were added to a four-necked flask. Stirring was started, and a 20wt% sodium hydroxide aqueous solution was slowly added dropwise over 2.0h. The pH of the system was adjusted to 9.6, and the reaction was carried out at 40℃ for 6.0h. Stirring was stopped, and the reactants were precipitated with acetone, filtered, washed five times with anhydrous ethanol, and dried under vacuum at 80℃ to constant weight. The mixture was then ground to obtain sodium carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylate (CCS-PBTCA).

[0045] The carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt product obtained in this example was subjected to infrared spectroscopy, and the resulting infrared spectrum is shown below. Figure 1 As shown.

[0046] As can be seen from the figure, carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylate sodium salt at 3253 cm⁻¹ -1 A broad absorption peak appears at 3400-3500 cm⁻¹, which is the stretching vibration absorption peak of -NH in the copolymer, while -NH₂ has a peak at 3400-3500 cm⁻¹. -1 The presence of two stretching vibration absorption peaks indicates that the -NH2 group in the carboxylated chitosan molecule is grafted with the carboxyl group of 2-phosphonobutane-1,2,4-tricarboxylic acid; the stretching vibration absorption peak of C=O in the amide is at 1642 cm⁻¹. -1 Location; 1582cm -1 The peak at 1391 cm⁻¹ is an absorption peak resulting from the overlap of the antisymmetric stretching of carboxylic acids and the NH bending vibration of amides. -1 The peak at 1071 cm⁻¹ is the symmetric stretching absorption peak of carboxylic acids. -1 The absorption peak at this point is the CN stretching vibration, proving the successful synthesis of carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt.

[0047] Example 2

[0048] A method for preparing a scale inhibitor for reverse osmosis membranes includes the following steps:

[0049] Weigh 6.0 g of a 50% aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid into a beaker and set aside. Separately, weigh 2.22 g of sodium hydroxide and dissolve it in 8.88 g of distilled water to obtain an aqueous solution of sodium hydroxide. Slowly pour the aqueous solution of sodium hydroxide into the aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid while stirring continuously to generate a sodium salt solution of 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0050] 10 g of carboxylated chitosan was dissolved in 150 mL of distilled water to obtain an aqueous solution of carboxylated chitosan. The aqueous solution of carboxylated chitosan and a solution of sodium 2-phosphonobutane-1,2,4-tricarboxylate were added to a four-necked flask. Stirring was started, and a 20 wt% sodium hydroxide aqueous solution was slowly added dropwise over 2.0 h. The pH of the system was adjusted to 9.5, and the reaction was carried out at 50 °C for 6.0 h. Stirring was then stopped, and the reactants were precipitated with acetone, filtered, washed five times with anhydrous ethanol, and dried under vacuum at 80 °C to constant weight. The mixture was then ground to obtain sodium carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylate (CCS-PBTCA).

[0051] Example 3

[0052] A method for preparing a scale inhibitor for reverse osmosis membranes includes the following steps:

[0053] Weigh 8.0 g of a 50% aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid into a beaker and set aside. Separately, weigh 2.96 g of sodium hydroxide and dissolve it in 11.84 g of distilled water to obtain an aqueous solution of sodium hydroxide. Slowly pour the aqueous solution of sodium hydroxide into the aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid while stirring continuously to generate a sodium salt solution of 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0054] 10 g of carboxylated chitosan was dissolved in 150 mL of distilled water to obtain an aqueous solution of carboxylated chitosan. The aqueous solution of carboxylated chitosan and a solution of sodium 2-phosphonobutane-1,2,4-tricarboxylate were added to a four-necked flask. Stirring was started, and a 20 wt% sodium hydroxide aqueous solution was slowly added dropwise over 2.0 h. The pH of the system was adjusted to 9.3, and the reaction was carried out at 45 °C for 6.0 h. Stirring was then stopped, and the reactants were precipitated with acetone, filtered, washed five times with anhydrous ethanol, and dried under vacuum at 80 °C to constant weight. The mixture was then ground to obtain sodium carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylate (CCS-PBTCA).

[0055] Example 4

[0056] A method for preparing a scale inhibitor for reverse osmosis membranes includes the following steps:

[0057] Weigh 8.0 g of a 50% aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid into a beaker and set aside. Separately, weigh 2.96 g of sodium hydroxide and dissolve it in 11.84 g of distilled water to obtain an aqueous solution of sodium hydroxide. Slowly pour the aqueous solution of sodium hydroxide into the aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid while stirring continuously to generate a sodium salt solution of 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0058] 10 g of carboxylated chitosan was dissolved in 150 mL of distilled water to obtain an aqueous solution of carboxylated chitosan. The aqueous solution of carboxylated chitosan and a solution of sodium 2-phosphonobutane-1,2,4-tricarboxylate were added to a four-necked flask. Stirring was started, and a 20 wt% sodium hydroxide aqueous solution was slowly added dropwise over 2.0 h. The pH of the system was adjusted to 9.0, and the reaction was carried out at 45 °C for 7.0 h. Stirring was then stopped, and the reactants were precipitated with acetone, filtered, washed five times with anhydrous ethanol, and dried under vacuum at 80 °C to constant weight. The mixture was then ground to obtain sodium carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylate (CCS-PBTCA).

[0059] Example 5

[0060] A method for preparing a scale inhibitor for reverse osmosis membranes includes the following steps:

[0061] Weigh 10.0 g of a 50% aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid into a beaker for later use; separately weigh 3.0 g of sodium hydroxide and dissolve it in 12 g of distilled water to obtain an aqueous solution of sodium hydroxide; slowly pour the aqueous solution of sodium hydroxide into the aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid while stirring continuously to generate a sodium salt solution of 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0062] 10g of carboxylated chitosan was dissolved in 90mL of distilled water to obtain an aqueous solution of carboxylated chitosan. The aqueous solution of carboxylated chitosan and a solution of sodium 2-phosphonobutane-1,2,4-tricarboxylate were added to a four-necked flask. Stirring was started, and a 20wt% sodium hydroxide aqueous solution was slowly added dropwise over 2.5 hours. The pH of the system was adjusted to 10.0, and the reaction was carried out at 40℃ for 8.0 hours. Stirring was stopped, and the reactants were precipitated with acetone, filtered, washed five times with anhydrous ethanol, and dried under vacuum at 80℃ to constant weight. The mixture was then ground to obtain sodium carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylate (CCS-PBTCA).

[0063] Example 6

[0064] A method for preparing a scale inhibitor for reverse osmosis membranes includes the following steps:

[0065] Weigh 10.0 g of a 50% aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid into a beaker and set aside. Separately, weigh 5.0 g of sodium hydroxide and dissolve it in 20.0 g of distilled water to obtain an aqueous solution of sodium hydroxide. Slowly pour the aqueous solution of sodium hydroxide into the aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid while stirring continuously to generate a sodium salt solution of 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0066] 10 g of carboxylated chitosan was dissolved in 200 mL of distilled water to obtain an aqueous solution of carboxylated chitosan. The aqueous solution of carboxylated chitosan and a solution of sodium 2-phosphonobutane-1,2,4-tricarboxylate were added to a four-necked flask. Stirring was started, and a 20 wt% sodium hydroxide aqueous solution was slowly added dropwise over 2.0 h. The pH of the system was adjusted to 9.5, and the reaction was carried out at 50 °C for 8.0 h. Stirring was then stopped, and the reactants were precipitated with acetone, filtered, washed five times with anhydrous ethanol, and dried under vacuum at 80 °C to constant weight. The mixture was then ground to obtain sodium carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylate (CCS-PBTCA).

[0067] Scale inhibition performance test

[0068] 1.1 Static scale inhibition rate test

[0069] To test the scale inhibition performance of the carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylate sodium salt of the scale inhibitor in the embodiments of the present invention, the scale inhibitors prepared in Examples 1 to 6 were subjected to scale inhibition tests under the following specific test conditions:

[0070] Take seven 1000mL beakers and add 750mL of secondary municipal wastewater to each. Then, add the scale inhibitors prepared in Examples 1 to 6 to six of the volumetric flasks, and leave the remaining volumetric flask without scale inhibitor as a blank test. Place the flasks in an 80℃ constant temperature water bath. When the water in the beakers evaporates and concentrates to about 500mL, remove the beakers from the water bath and cool them to room temperature. Pour the water from the beakers into a 500mL volumetric flask and make up to 500mL with a small amount of distilled water. Then put the volumetric flasks back into the 80℃ constant temperature water bath and continue the water bath for 10 hours. After cooling to room temperature, measure the calcium scale inhibition rate. The test results are shown in Table 1.

[0071] The formula for calculating the scale inhibition rate is:

[0072] Scale inhibition rate = (scale amount of blank heating tube - scale amount of chemically treated heating tube) / scale amount of blank heating tube × 100%.

[0073] Table 1

[0074]

[0075] When the scale inhibitors prepared in Examples 1 to 6 were added to the secondary discharge water of municipal wastewater that was not concentrated by evaporation, the average scale inhibition rate of Examples 1 to 6 was 96.4% when the dosage was 3 mg / L.

[0076] 1.2 Dynamic scale inhibition rate test

[0077] To test the scale inhibition effect of the carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylate sodium salt product prepared in Examples 1-6 of this invention in a reverse osmosis system, the water used in this experiment was secondary municipal wastewater discharge, and the scale inhibition test method adopted was the dynamic scale inhibition test method. Secondary municipal wastewater discharge was added to the makeup water tank of the microfiltration-ultrafiltration-reverse osmosis experimental device (microfiltration used a precision filter with a 20-inch 5μm filter element; ultrafiltration used Huamo UF-4040; reverse osmosis membrane used Huamo ULPHM-4040), and the carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylate sodium salt product prepared in the examples of this invention was added to the makeup water tank at a dosage of 4 mg / L, and the system was run continuously for one month. A blank experiment was also conducted simultaneously, in which no reagent was added to the makeup water tank, and all other operating conditions were the same.

[0078] The results showed that in the blank experiment, the permeate conductivity gradually increased from 32 µS / cm to 50 µS / cm during operation, and the desalination rate of the reverse osmosis membrane decreased to about 95%. Simultaneously, the feed water pressure of the reverse osmosis system membrane also increased to 0.95 MPa, and the permeate flow rate was between 330 and 350 L / h, indicating that the reverse osmosis membrane had formed scale. However, in the experiment with the membrane antiscalant prepared according to the embodiments of this invention, the permeate conductivity remained almost unchanged throughout the operation, maintaining between 30 and 34 µS / cm, the membrane desalination rate remained above 99.5%, the feed water pressure of the reverse osmosis system membrane remained constant at 0.92 MPa, and the permeate flow rate remained between 360 and 380 L / h, indicating that the entire system operated normally. This demonstrates that the carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt prepared according to this invention has excellent scale inhibition effect in the reverse osmosis system for secondary municipal wastewater discharge.

[0079] Comparative Example 1

[0080] Weigh 10g of carboxylated chitosan and dissolve it in 150mL of distilled water to obtain an aqueous solution of carboxylated chitosan, which is used as scale inhibitor a.

[0081] The scale inhibition performance was tested according to the static scale inhibition rate test method in the embodiment. When the dosage was 6 mg / L, the static scale inhibition rate was 26.4%.

[0082] Comparative Example 2

[0083] A 50% aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid was used as scale inhibitor b.

[0084] The scale inhibition performance was tested according to the static scale inhibition rate test method in the embodiment. When the dosage was 6 mg / L, the static scale inhibition rate was 76.1%.

[0085] Comparative Example 3

[0086] Weigh 8.0 g of a 50% aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid into a beaker and set aside. Separately, weigh 2.96 g of sodium hydroxide and dissolve it in 11.84 g of distilled water to obtain an aqueous solution of sodium hydroxide. Slowly pour the aqueous solution of sodium hydroxide into the aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid while stirring continuously to generate a sodium salt solution of 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0087] Weigh 10g of carboxylated chitosan and dissolve it in 150mL of distilled water to obtain an aqueous solution of carboxylated chitosan.

[0088] The above-mentioned sodium 2-phosphonobutane-1,2,4-tricarboxylic acid salt solution and carboxylated chitosan aqueous solution were mixed evenly to obtain scale inhibitor c.

[0089] The scale inhibition performance was tested according to the static scale inhibition rate test method in the embodiment. When the dosage was 6 mg / L, the static scale inhibition rate was 79.5%.

[0090] Comparative Example 4

[0091] Weigh 8.0g of a 50% aqueous solution of 2-hydroxyphosphonic acid in a beaker and set aside. Separately, weigh 2.96g of sodium hydroxide and dissolve it in 11.84g of distilled water to obtain an aqueous solution of sodium hydroxide. Slowly pour the sodium hydroxide solution into the aqueous solution of 2-hydroxyphosphonic acid while stirring continuously to form a sodium 2-hydroxyphosphonic acid salt solution.

[0092] 10g of carboxylated chitosan was dissolved in 150mL of distilled water to obtain an aqueous solution of carboxylated chitosan. The aqueous solution of carboxylated chitosan and a sodium 2-hydroxyphosphonoacetate solution were added to a four-necked flask. Stirring was started, and a 20wt% sodium hydroxide aqueous solution was slowly added dropwise over 2.0h. The pH of the system was adjusted to 9.0, and the reaction was carried out at 45℃ for 7.0h. Stirring was stopped, and the reactants were precipitated with acetone, filtered, washed five times with anhydrous ethanol, and dried under vacuum at 80℃ to constant weight. The product was then ground to obtain carboxylated chitosan-2-hydroxyphosphonoacetate sodium salt, which was used as a scale inhibitor (d).

[0093] The scale inhibition performance was tested according to the static scale inhibition rate test method in the embodiment. When the dosage was 6 mg / L, the static scale inhibition rate was 64.1%.

[0094] In summary, the scale inhibitor prepared in this embodiment of the invention, carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt, exhibits excellent scale inhibition capabilities against various scale types and demonstrates excellent compatibility with various reverse osmosis membranes. It does not cause a decline in the physicochemical properties of the reverse osmosis membrane. During long-term use, it effectively inhibits scale while maintaining the structural integrity and performance stability of the reverse osmosis membrane, ensuring the efficient, continuous, and stable operation of the reverse osmosis system. It can be applied to reverse osmosis systems with different water source characteristics, and is particularly suitable for advanced treatment of secondary municipal wastewater discharge, reclaimed water reuse, and seawater desalination systems, demonstrating high engineering practical value.

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. The application of a scale inhibitor for reverse osmosis membranes in municipal wastewater secondary discharge deep treatment, reclaimed water reuse, or seawater desalination reverse osmosis systems, characterized in that, The structure of the antiscalant for the reverse osmosis membrane is shown in Formula I: Formula I Among them, R1, R2, and R3 are Or M, and R1, R2, and R3 are not all M at the same time; M is Na or K; The method for preparing the antiscalant for reverse osmosis membranes includes the following steps: A scale inhibitor for reverse osmosis membranes was prepared by dehydration condensation reaction using carboxylated chitosan and 2-phosphonobutane-1,2,4-tricarboxylic acid as raw materials.

2. The application according to claim 1, characterized in that, The preparation method of the antiscalant for reverse osmosis membranes includes the following steps: using carboxylated chitosan and 2-phosphonobutane-1,2,4-tricarboxylic acid as raw materials, the antiscalant for reverse osmosis membranes is prepared by dehydration condensation reaction.

3. The application as described in claim 2, characterized in that, The preparation method of the antiscalant for reverse osmosis membranes specifically includes the following steps: Step a: Dissolve 2-phosphonobutane-1,2,4-tricarboxylic acid and carboxylated chitosan in water to obtain aqueous solutions of 2-phosphonobutane-1,2,4-tricarboxylic acid and carboxylated chitosan, respectively. Step b: Add a strong alkali solution to the aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid to obtain a 2-phosphonobutane-1,2,4-tricarboxylic acid salt solution; Step c: Mix the 2-phosphonobutane-1,2,4-tricarboxylate solution and carboxylated chitosan aqueous solution evenly, add a strong alkali solution to adjust the pH to 9-10, and heat to carry out a dehydration condensation reaction to obtain a scale inhibitor for reverse osmosis membranes as shown in Formula I. The strong alkaline solution is either a sodium hydroxide solution or a potassium hydroxide solution.

4. The application as described in claim 3, characterized in that, The mass ratio of 2-phosphonobutane-1,2,4-tricarboxylic acid to carboxylated chitosan is 0.15:1 to 0.5:

1.

5. The application as described in claim 3 or 4, characterized in that, In step a, the mass concentration of the aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid is 48%~52%; and / or In step a, the mass concentration of the carboxylated chitosan aqueous solution is 4% to 10%.

6. The application as described in claim 3, characterized in that, In step b, the molar ratio of the alkali to 2-phosphonobutane-1,2,4-tricarboxylic acid in the strong alkali solution is 4:1 to 7:

1.

7. The application as described in claim 3, characterized in that, In step c, the temperature of the dehydration condensation reaction is 40℃~50℃, and the reaction time is 6h~8h; and / or In step c, the strong alkali solution is added slowly dropwise over a period of 2.0 to 2.5 hours.

8. The application as described in claim 1, characterized in that, The amount of antiscalant added to the reverse osmosis membrane is 4 mg / L to 6 mg / L.

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