Scale inhibition and dispersion agent for reverse osmosis membrane as well as preparation method and application of scale inhibition and dispersion agent

Abstract

The invention relates to the technical field of energy conservation and environmental protection, and particularly discloses a scale inhibition and dispersion agent for a reverse osmosis membrane and a preparation method and application of the scale inhibition and dispersion agent. The scale inhibitor for the reverse osmosis membrane, provided by the invention, is obtained by carrying out dehydration condensation reaction on polysuccinimide, carboxylated chitosan and sulfamic acid. The scale inhibition and dispersion agent is suitable for reverse osmosis treatment systems of various water qualities such as municipal wastewater, seawater, brackish water, surface water, underground water and industrial wastewater. Experiments show that the product has excellent scale inhibition performance, the scale inhibition rate can reach 97.4% or above, dirt deposition on the surface of the membrane can be remarkably inhibited, and the service life of the membrane is prolonged. Meanwhile, the preparation process is simple and convenient, the raw material cost is lower, the use is safe and efficient, the biodegradability is good, the influence on the environment is reduced while the stable operation of a reverse osmosis system is ensured, and the popularization and application prospects are good.

Description

Technical Field

[0001] This invention relates to the field of energy conservation and environmental protection technology, and in particular to a scale inhibitor and dispersant for reverse osmosis membranes, its preparation method, and its application. Background Technology

[0002] Reverse osmosis (RO) technology, as a highly efficient membrane separation technology, has become one of the core technologies in the modern water treatment industry due to its excellent performance in water purification, seawater desalination, industrial wastewater treatment, and process water refining. This technology purifies water by efficiently retaining ions, colloidal particles, microorganisms, and other impurities in the water through the reverse osmosis membrane. However, during operation, dissolved metal ions such as calcium, magnesium, and barium in the water easily combine with anions such as carbonate, sulfate, and phosphate to form insoluble salt deposits. Simultaneously, colloidal particles, suspended impurities, and microbial metabolites in the water easily adsorb and accumulate on the membrane surface, leading to membrane fouling. The accumulation of scale and contaminants significantly reduces the membrane's permeate flux and increases operating pressure, not only increasing system energy consumption but also exacerbating physicochemical damage to the membrane and shortening its lifespan. Therefore, the use of scale inhibitors and dispersants in reverse osmosis systems has become a key technical means to ensure stable system operation.

[0003] Scale inhibitors and dispersants can inhibit the formation and growth of scale at the source through chelation, lattice distortion, and dispersion, and stably disperse colloidal particles and suspended impurities in the water, preventing their adsorption and aggregation on the membrane surface. An ideal scale inhibitor and dispersant for reverse osmosis membranes must simultaneously meet multiple requirements, including excellent scale inhibition performance, high-efficiency dispersing ability, good biodegradability, and compatibility with reverse osmosis membranes (i.e., no damage to the membrane structure and no impact on membrane separation performance).

[0004] Currently, commonly used scale inhibitors and dispersants for reverse osmosis membranes in industry mainly include inorganic polyphosphates, organophosphonates, polycarboxylic acids, and modified natural polymers. Inorganic polyphosphates were the most widely used scale inhibitors in the early stages. However, these agents have poor chemical stability and are prone to hydrolysis to form orthophosphates under high temperature, high pH, ​​or long-term storage conditions. This not only causes them to lose their scale inhibitory activity, but the resulting orthophosphates may also combine with calcium ions to form more difficult-to-treat calcium hydroxyphosphate scale. Furthermore, their dispersing properties are weak, and their stabilizing effect on colloidal particles is limited. Organophosphonates have advantages such as high scale inhibition efficiency, high temperature resistance, and acid and alkali resistance, and can effectively inhibit the formation of scale such as calcium carbonate and calcium sulfate. However, the dispersing properties of organophosphonates are generally insufficient, and their stabilizing effect on suspended particles and colloids in water is weak. Moreover, long-term discharge of organophosphonates can accumulate in water bodies, potentially leading to eutrophication and posing a potential threat to the ecological environment. Polycarboxylate scale inhibitors and dispersants possess excellent dispersing properties, but their scale inhibition performance is relatively weak, especially against sparingly soluble sulfate scales such as barium sulfate and strontium sulfate, where their inhibitory effect is far less than that of organophosphonates. When the treated water contains high concentrations of sulfate ions, they struggle to meet the scale inhibition requirements of reverse osmosis systems. While naturally modified polymer scale inhibitors and dispersants (such as starch-modified products and chitosan derivatives) exhibit good biodegradability, their scale inhibition and dispersing properties are generally poor, and their product performance stability is insufficient, making them unsuitable for the complex and variable operating conditions of reverse osmosis water treatment.

[0005] Therefore, developing a scale inhibitor and dispersant for reverse osmosis membranes that combines excellent scale inhibition performance, high efficiency dispersibility, and good biodegradability is of great practical significance and application value for promoting the green development of reverse osmosis water treatment technology and reducing water treatment costs. Summary of the Invention

[0006] In view of the problems that existing scale inhibitors and dispersants for reverse osmosis membranes generally have, such as difficulty in achieving both scale inhibition and dispersion performance, poor chemical stability, and insufficient biodegradability, this invention provides a scale inhibitor and dispersant for reverse osmosis membranes, its preparation method, and its application.

[0007] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: In a first aspect, the present invention provides a scale inhibitor and dispersant for reverse osmosis membranes, the structure of which is shown in Formula I:

[0008] Formula I Where R is M is either Na or K.

[0009] Compared to existing technologies, the scale inhibitor and dispersant provided by this invention achieves highly efficient synergy between scale inhibition and dispersing performance by simultaneously introducing multiple functional groups such as sulfonic acid groups, hydroxyl groups, and carboxyl groups onto the polysuccinimide backbone. Specifically, the strongly hydrophilic sulfonic acid groups effectively enhance the solubility of the molecules in water and, through electrostatic repulsion and steric hindrance, effectively inhibit the agglomeration and deposition of inorganic salt microcrystals, significantly improving the dispersion stability of scale such as calcium carbonate and calcium sulfate, and reducing scale accumulation on the reverse osmosis membrane surface. The carboxyl groups possess excellent chelating ability and can bind with Ca... 2+ Mg 2+ The formation of scale-forming ions into soluble complexes reduces local supersaturation, prevents rapid crystal formation and growth, and inhibits scaling. Simultaneously, the long polysaccharide chains of carboxylated chitosan, being hydrophilic and flexible segments, can fully extend in water, hindering the aggregation of scale particles and colloidal contaminants through steric hindrance. Furthermore, the polysaccharide segments can adsorb onto the reverse osmosis membrane surface via hydrogen bonding, forming a hydrophilic hydration layer that reduces the contact energy between contaminants and the membrane surface, achieving a dual effect of dispersion and membrane protection. In addition, the planar conjugated imide ring structure in the polysuccinimide framework can tightly adsorb onto the scale crystal surface through π-π interactions and van der Waals forces, coating particles and preventing their aggregation and growth. The rigid structure of the imide rings endows the compound with good thermal stability and acid / alkali tolerance, making it suitable for the common operating temperature and pH ranges of reverse osmosis systems.

[0010] The scale inhibitor and dispersant for reverse osmosis membranes provided by this invention achieves a high-efficiency balance between scale inhibition and dispersion performance, while also possessing excellent chemical stability and biodegradability. It is suitable for scale inhibition and dispersion treatment of high-performance, long-life reverse osmosis membrane systems and has significant industrial application value and environmental significance.

[0011] It should be noted that in the above molecular formula, m is the degree of polymerization of carboxylated chitosan, n is the degree of polymerization of polysuccinimide, n1 is the number of ring-opening products of polysuccinimide that react with carboxylated chitosan, n2 is the number of ring-opening products of polysuccinimide that react with aminosulfonic acid, and n-n1-n2 is the number of ring-opening products of polysuccinimide that did not react with carboxylated chitosan and aminosulfonic acid, but cross-linked with the already reacted ring-opening products.

[0012] Secondly, the present invention also provides a method for preparing a scale inhibitor and dispersant for reverse osmosis membranes, wherein the scale inhibitor and dispersant for reverse osmosis membranes is prepared by dehydration condensation reaction using polysuccinimide, carboxylated chitosan and aminosulfonic acid as raw materials.

[0013] The scale inhibitor and dispersant for reverse osmosis membranes provided by this invention is prepared by a one-step dehydration condensation reaction using polysuccinimide, carboxylated chitosan, and aminosulfonic acid as raw materials. This method is simple to operate, operates under mild conditions, and uses readily available raw materials. The resulting product integrates multiple functional groups in its molecular structure. The polysuccinimide framework endows the molecule with a rigid planar conjugated structure, which can be tightly adsorbed onto the scale crystal surface through π-π interactions and van der Waals forces, effectively encapsulating and inhibiting crystal growth, while providing good thermal stability and acid / alkali tolerance, making it suitable for a wide range of operating conditions in reverse osmosis systems. The introduction of carboxylated chitosan groups not only enhances dispersibility and membrane protection through steric hindrance and hydrogen bonding, but also chelates scale ions, reducing local supersaturation and effectively inhibiting scaling. Aminosulfonic acid provides strongly hydrophilic sulfonic acid groups, significantly improving molecular solubility, and further preventing microcrystal aggregation and deposition through electrostatic repulsion, ensuring long-term dispersion stability of the system.

[0014] The scale inhibitor and dispersant prepared by this method achieves an organic combination of rigid skeleton and flexible hydrophilic chain, chelating group and ionizing group in molecular structure, which effectively solves the problems of scale inhibition-dispersion performance imbalance, insufficient chemical stability and poor biodegradability of traditional products, and has outstanding application prospects in the field of reverse osmosis membrane water treatment.

[0015] As a specific embodiment of the present invention, the preparation method of the scale inhibitor and dispersant for reverse osmosis membranes includes the following steps: Step a: Polysuccinimide, aminosulfonic acid and carboxylated chitosan are added to water respectively to obtain polysuccinimide dispersion, aminosulfonic acid aqueous solution and carboxylated chitosan aqueous solution; Step b: The succinimide dispersion and carboxylated chitosan aqueous solution are mixed evenly, and then an aminosulfonic acid aqueous solution and a strong alkali solution are added. A dehydration condensation reaction is carried out at a temperature of pH 8.0–9.5 to obtain a scale inhibitor / dispersant for reverse osmosis membranes; wherein the strong alkali solution is a sodium hydroxide solution or a potassium hydroxide solution. The reaction equation is as follows.

[0016]

[0017] The preparation method of the scale inhibitor and dispersant 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.

[0018] Further, the mass ratio of the polysuccinimide, carboxylated chitosan, and aminosulfonic acid is 1:(0.05~0.2):(0.3~0.5).

[0019] Preferably, the mass ratio of the polysuccinimide, carboxylated chitosan, and aminosulfonic acid is 1:0.1:0.4.

[0020] The optimized ratio ensures the introduction of appropriate amounts of carboxylated chitosan and aminosulfonic acid substituents into the polyimide molecular chain. This allows for the efficient introduction of the chelating scale-inhibiting function of carboxyl groups and the spatial and electrostatic dispersing effects of sulfonic acid groups, while fully preserving the inherent rigid structure and thermal stability of the polysuccinimide backbone. The structural units complement and synergize at the molecular level, simultaneously and significantly improving the scale inhibition efficiency and dispersion stability of the product without weakening the main chain performance. This effectively solves the technical challenge of traditional scale inhibitors and dispersants failing to simultaneously achieve scale inhibition and dispersion performance.

[0021] Further, in step a, the mass concentration of the polysuccinimide dispersion is 5%~10%.

[0022] Further, in step a, the mass concentration of the carboxylated chitosan aqueous solution is 0.4%~1.5%.

[0023] Further, in step a, the mass concentration of the aminosulfonic acid aqueous solution is 3% to 5%.

[0024] Specifically, in step b, the mass concentration of the strong alkali solution is 20% to 30%.

[0025] Furthermore, in step b, the temperature of the dehydration condensation reaction is 35℃~45℃, and the reaction time is 5h~8h.

[0026] Preferably, in step b, the temperature of the dehydration condensation reaction is 40°C and the reaction time is 8 hours.

[0027] The optimized reaction temperature and time ensure a stable and uniform reaction between polysuccinimide, carboxylated chitosan, and aminosulfonic acid, while preventing raw material decomposition or side reactions, thus guaranteeing the reliability and stability of the final product. Furthermore, the mild reaction conditions are easy to control and consume little energy, making them more suitable for practical production applications.

[0028] Furthermore, in step b, the aminosulfonic acid aqueous solution and the strong alkali solution are added simultaneously dropwise over a period of 1 to 1.5 hours.

[0029] Adding aminosulfonic acid and a strong base simultaneously via dropwise addition can effectively maintain the pH stability of the reaction system, avoid local over-acidity or over-alkaliness, and promote a uniform and stable reaction, thereby ensuring the consistency of product performance.

[0030] Furthermore, after the dehydration condensation reaction is completed, a post-treatment process is also included: the reaction solution is cooled to room temperature, acetone is added to precipitate the reactants, the mixture is filtered, washed 3 to 5 times with anhydrous ethanol, vacuum dried, and ground to obtain polysuccinimide-carboxylated chitosan-aminosulfonate.

[0031] Thirdly, as another objective of the present invention, the present invention also provides a scale inhibitor and dispersant composition for reverse osmosis membranes, comprising the above-mentioned scale inhibitor and dispersant for reverse osmosis membranes.

[0032] The scale inhibitor and dispersant provided by this invention can be used in combination with conventional water treatment agents in the art, such as corrosion inhibitors, bactericides, flocculants, or other scale inhibitors and dispersants, as long as the components do not interfere with each other's performance when used together. This combination method can adapt to the comprehensive treatment needs under complex water quality conditions, achieving synergistic effects of scale inhibition, dispersion, corrosion prevention, and microbial control in reverse osmosis systems, thereby improving the overall efficiency and stability of the water treatment solution.

[0033] Fourthly, the present invention also provides the application of the above-mentioned scale inhibitor and dispersant for reverse osmosis membranes in reverse osmosis systems for municipal wastewater, seawater, brackish water, surface water, groundwater or industrial wastewater.

[0034] The scale inhibitor and dispersant provided by this invention has excellent scale inhibition performance, dispersion stability and wide water quality adaptability. It can effectively inhibit membrane fouling, maintain system flux and extend membrane service life in the above-mentioned complex water environment, showing good engineering application potential.

[0035] Furthermore, the amount of antiscalant added to the reverse osmosis membrane is 3 mg / L to 5 mg / L.

[0036] The present invention has the following advantages over the prior art: This invention creatively proposes a novel scale inhibitor and dispersant, obtained through a dehydration condensation reaction of polysuccinimide, carboxylated chitosan, and aminosulfonic acid. This scale inhibitor and dispersant is suitable for reverse osmosis treatment systems handling various water qualities, including municipal wastewater, seawater, brackish water, surface water, groundwater, and industrial wastewater. Experiments show that this product exhibits excellent scale inhibition performance, with a scale inhibition rate exceeding 97.4%, and can significantly inhibit fouling deposition on the membrane surface, extending membrane lifespan. Furthermore, its preparation process is simple, raw material costs are low, it is safe and efficient to use, and it has good biodegradability. While ensuring the stable operation of the reverse osmosis system, it also reduces environmental impact, demonstrating promising prospects for widespread application. Attached Figure Description

[0037] Figure 1 The infrared spectrum of the polysuccinimide-carboxylated chitosan-sodium aminosulfonate product prepared in Example 4; Figure 2 SEM images of the reverse osmosis membranes in the blank group after the scale inhibition test in the reverse osmosis membrane scale inhibition test; Figure 3The image shows a SEM image of the reverse osmosis membrane after a scale inhibition test in a reverse osmosis system, obtained by using the polysuccinimide-carboxylated chitosan-sodium aminosulfonate salt prepared in Example 4 of this invention. Detailed Implementation

[0038] 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.

[0039] To better illustrate the present invention, further examples are provided below.

[0040] Example 1 A method for preparing a scale inhibitor and dispersant for reverse osmosis membranes includes the following steps: Step a: Weigh 5.0 g of polysuccinimide and add it to 60 mL of distilled water to obtain a polysuccinimide dispersion; Weigh 0.25g of carboxylated chitosan and dissolve it in 60mL of distilled water to obtain an aqueous solution of carboxylated chitosan; Weigh 2.4g of sodium hydroxide and dissolve it in 9.6mL of distilled water to obtain an aqueous solution of sodium hydroxide. Weigh 1.5g of aminosulfonic acid and dissolve it in 50mL of distilled water to obtain an aqueous solution of aminosulfonic acid; Step b: Add the prepared polysuccinimide dispersion and carboxylated chitosan aqueous solution to a four-necked flask, start stirring, mix evenly, then slowly add aminosulfonic acid aqueous solution and sodium hydroxide aqueous solution dropwise to the four-necked flask at the same time for 1.0 h, control the reaction temperature at 40℃, continue the reaction for 7.0 h, then precipitate the reactants with acetone, filter, wash three times with anhydrous ethanol, dry under vacuum at 100℃ to constant weight, grind to obtain polysuccinimide-carboxylated chitosan-sodium aminosulfonate.

[0041] Example 2 A method for preparing a scale inhibitor and dispersant for reverse osmosis membranes includes the following steps: Step a: Weigh 5.0 g of polysuccinimide and add it to 55 mL of distilled water to obtain a polysuccinimide dispersion; Weigh 0.5g of carboxylated chitosan and dissolve it in 60mL of distilled water to obtain an aqueous solution of carboxylated chitosan; Weigh 2.4g of sodium hydroxide and dissolve it in 5.6mL of distilled water to obtain an aqueous solution of sodium hydroxide; Weigh 1.5g of aminosulfonic acid and dissolve it in 50mL of distilled water to obtain an aqueous solution of aminosulfonic acid; Step b: Add the prepared polysuccinimide dispersion and carboxylated chitosan aqueous solution to a four-necked flask, start stirring, mix evenly, then slowly add aminosulfonic acid aqueous solution and sodium hydroxide aqueous solution dropwise to the four-necked flask at the same time for 1.0 h, control the reaction temperature at 45℃, continue the reaction for 8.0 h, then precipitate the reactants with acetone, filter, wash three times with anhydrous ethanol, dry under vacuum at 100℃ to constant weight, grind to obtain polysuccinimide-carboxylated chitosan-sodium aminosulfonate.

[0042] Example 3 A method for preparing a scale inhibitor and dispersant for reverse osmosis membranes includes the following steps: Step a: Weigh 5.0 g of polysuccinimide and add it to 95 mL of distilled water to obtain a polysuccinimide dispersion; Weigh 0.75g of carboxylated chitosan and dissolve it in 60mL of distilled water to obtain an aqueous solution of carboxylated chitosan; Weigh 2.4g of sodium hydroxide and dissolve it in 7.2mL of distilled water to obtain an aqueous solution of sodium hydroxide; Weigh 2.0g of aminosulfonic acid and dissolve it in 50mL of distilled water to obtain an aqueous solution of aminosulfonic acid; Step b: Add the prepared polysuccinimide dispersion and carboxylated chitosan aqueous solution to a four-necked flask, start stirring, mix evenly, then slowly add aminosulfonic acid aqueous solution and sodium hydroxide aqueous solution dropwise to the four-necked flask at the same time for 1.0 h, control the reaction temperature at 35℃, continue the reaction for 6.0 h, then precipitate the reactants with acetone, filter, wash three times with anhydrous ethanol, dry under vacuum at 100℃ to constant weight, grind to obtain polysuccinimide-carboxylated chitosan-sodium aminosulfonate.

[0043] Example 4 A method for preparing a scale inhibitor and dispersant for reverse osmosis membranes includes the following steps: Step a: Weigh 5.0 g of polysuccinimide and add it to 60 mL of distilled water to obtain a polysuccinimide dispersion; Weigh 0.5g of carboxylated chitosan and dissolve it in 60mL of distilled water to obtain an aqueous solution of carboxylated chitosan; Weigh 2.4g of sodium hydroxide and dissolve it in 7.2mL of distilled water to obtain an aqueous solution of sodium hydroxide; Weigh 2.0g of aminosulfonic acid and dissolve it in 50mL of distilled water to obtain an aqueous solution of aminosulfonic acid; Step b: Add the prepared polysuccinimide dispersion and carboxylated chitosan aqueous solution to a four-necked flask, start stirring, mix evenly, then slowly add aminosulfonic acid aqueous solution and sodium hydroxide aqueous solution dropwise to the four-necked flask at the same time for 1.0 h, control the reaction temperature at 40℃, continue the reaction for 7.0 h, then precipitate the reactants with acetone, filter, wash three times with anhydrous ethanol, dry under vacuum at 100℃ to constant weight, grind to obtain polysuccinimide-carboxylated chitosan-sodium aminosulfonate.

[0044] The polysuccinimide-carboxylated chitosan-sodium aminosulfonate product prepared in this embodiment was subjected to infrared spectroscopy, and the resulting infrared spectrum is shown below. Figure 1 As shown.

[0045] As can be seen from the figure, polysuccinimide-carboxylated chitosan-sodium aminosulfonate salt at 3282 cm⁻¹ -1 A broad absorption peak appears at 1640 cm⁻¹, which is the stretching vibration absorption peak of -NH. The stretching vibration absorption peak of C=O in the amide is at 1640 cm⁻¹. -1 Location, 1558 cm -1 The peak at 1396 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 1170 cm⁻¹ is the symmetric stretching absorption peak of carboxylic acids. -1 The absorption peak for CN stretching vibration is located at 1068 cm⁻¹. -1 The absorption peak at this point is the symmetric stretching vibration of S=O in the sulfonic acid group, proving the successful synthesis of polysuccinimide-carboxylated chitosan-sodium aminosulfonate.

[0046] Example 5 A method for preparing a scale inhibitor and dispersant for reverse osmosis membranes includes the following steps: Step a: Weigh 5.0 g of polysuccinimide and add it to 45 mL of distilled water to obtain a polysuccinimide dispersion; Weigh 0.75g of carboxylated chitosan and dissolve it in 60mL of distilled water to obtain an aqueous solution of carboxylated chitosan; Weigh 2.4g of sodium hydroxide and dissolve it in 9.6mL of distilled water to obtain an aqueous solution of sodium hydroxide. Weigh 2.5g of aminosulfonic acid and dissolve it in 50mL of distilled water to obtain an aqueous solution of aminosulfonic acid; Step b: Add the prepared polysuccinimide dispersion and carboxylated chitosan aqueous solution to a four-necked flask, start stirring, mix evenly, then slowly add aminosulfonic acid aqueous solution and sodium hydroxide aqueous solution dropwise to the four-necked flask at the same time for 1.0 h, control the reaction temperature at 35℃, continue the reaction for 8.0 h, then precipitate the reactants with acetone, filter, wash three times with anhydrous ethanol, dry under vacuum at 100℃ to constant weight, grind to obtain polysuccinimide-carboxylated chitosan-sodium aminosulfonate.

[0047] Example 6 A method for preparing a scale inhibitor and dispersant for reverse osmosis membranes includes the following steps: Step a: Weigh 5.0 g of polysuccinimide and add it to 70 mL of distilled water to obtain a polysuccinimide dispersion; Weigh 1.0 g of carboxylated chitosan and dissolve it in 70 mL of distilled water to obtain an aqueous solution of carboxylated chitosan; Weigh 2.4g of sodium hydroxide and dissolve it in 5.6mL of distilled water to obtain an aqueous solution of sodium hydroxide; Weigh 2.5g of aminosulfonic acid and dissolve it in 50mL of distilled water to obtain an aqueous solution of aminosulfonic acid; Step b: Add the prepared polysuccinimide dispersion and carboxylated chitosan aqueous solution to a four-necked flask, start stirring, mix evenly, then slowly add aminosulfonic acid aqueous solution and sodium hydroxide aqueous solution dropwise to the four-necked flask at the same time for 1.0 h, control the reaction temperature at 35℃, continue the reaction for 5.0 h, then precipitate the reactants with acetone, filter, wash three times with anhydrous ethanol, dry under vacuum at 100℃ to constant weight, grind to obtain polysuccinimide-carboxylated chitosan-sodium aminosulfonate.

[0048] Example 7 A method for preparing a scale inhibitor and dispersant for reverse osmosis membranes includes the following steps: Step a: Weigh 5.0 g of polysuccinimide and add it to 80 mL of distilled water to obtain a polysuccinimide dispersion; Weigh 0.25g of carboxylated chitosan and dissolve it in 60mL of distilled water to obtain an aqueous solution of carboxylated chitosan; Weigh 2.4g of sodium hydroxide and dissolve it in 7.2mL of distilled water to obtain an aqueous solution of sodium hydroxide; Weigh 2.0g of aminosulfonic acid and dissolve it in 50mL of distilled water to obtain an aqueous solution of aminosulfonic acid; Step b: Add the prepared polysuccinimide dispersion and carboxylated chitosan aqueous solution to a four-necked flask, start stirring, mix evenly, then slowly add aminosulfonic acid aqueous solution and sodium hydroxide aqueous solution dropwise to the four-necked flask at the same time for 1.0 h, control the reaction temperature at 45℃, continue the reaction for 7.0 h, then precipitate the reactants with acetone, filter, wash three times with anhydrous ethanol, dry under vacuum at 100℃ to constant weight, grind to obtain polysuccinimide-carboxylated chitosan-sodium aminosulfonate.

[0049] Scale inhibition performance test 1.1 Static scale inhibition rate test To test the scale inhibition performance of the polysuccinimide-carboxylated chitosan-sodium aminosulfonate salt scale inhibitor in the embodiments of the present invention, the scale inhibitors prepared in Examples 1 to 7 were subjected to scale inhibition tests under the following specific test conditions: Take eight 1000mL beakers and add 750mL of secondary municipal wastewater to each. Then, add the scale inhibitors and dispersants prepared in Examples 1 to 7 to seven of the volumetric flasks, respectively. The remaining volumetric flask is used as a blank test without adding any scale inhibitors and dispersants. 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.

[0050] The formula for calculating the scale inhibition rate is: Scale inhibition rate = (scale amount of blank heating tube - scale amount of chemically treated heating tube) / scale amount of blank heating tube × 100%.

[0051] Table 1

[0052] 1.2 Dynamic scale inhibition rate test To test the scale inhibition effect of the polysuccinimide-carboxylated chitosan-sodium aminosulfonate product prepared in this invention in a reverse osmosis system, the test was conducted using secondary municipal wastewater on a high-pressure flat sheet membrane experimental device.

[0053] Municipal wastewater (secondary discharge) was added to the material tank of the high-pressure flat-sheet membrane experimental equipment, along with the polysuccinimide-carboxylated chitosan-sodium aminosulfonate salt prepared in Example 4 of this invention. The dosage was 4 mg / L, the temperature was controlled at 25°C, and the equipment was run continuously for 168 hours. A blank experimental group was also set up, in which no polysuccinimide-carboxylated chitosan-sodium aminosulfonate salt was added to the material tank, while other operating conditions remained the same.

[0054] During operation, the feed water pressure of the reverse osmosis system membrane in the blank test group gradually increased from the initially set 1.00 MPa to 1.86 MPa, and obvious fouling formed on the reverse osmosis membrane, indicating that the reverse osmosis membrane had become fouled (e.g., Figure 2 (As shown). In the experimental group that incorporated the polysuccinimide-carboxylated chitosan-sodium aminosulfonate prepared in this embodiment of the invention, the feed water pressure of the reverse osmosis membrane system did not increase significantly throughout the entire operation period, remaining basically at 1.00~1.12 MPa. The reverse osmosis membrane was relatively clean, with no obvious fouling formation observed (e.g.). Figure 3(As shown). This demonstrates that the polysuccinimide-carboxylated chitosan-sodium aminosulfonate salt prepared in this invention exhibits excellent scale inhibition performance on reverse osmosis membranes using municipal wastewater secondary discharge as the medium.

[0055] Comparative Example 1 Weigh 5.0 g of polysuccinimide into a four-necked flask, add 60 mL of distilled water to suspend the polysuccinimide in the water, and start stirring. Separately weigh 2.4 g of sodium hydroxide and dissolve it in 7.2 mL of distilled water to obtain an aqueous sodium hydroxide solution. Slowly add the aqueous sodium hydroxide solution dropwise into the four-necked flask over a period of 1.0 h, control the reaction temperature at 40 ℃, and continue the reaction for 6.0 h to obtain the scale inhibitor / dispersant.

[0056] The scale inhibition performance was tested according to the static scale inhibition rate test method in the embodiment. When the dosage was 5 mg / L, the static scale inhibition rate was 64.3%.

[0057] Comparative Example 2 Dissolve 0.5g of carboxylated chitosan in 60mL of distilled water and use the carboxylated chitosan aqueous solution as a scale inhibitor and dispersant.

[0058] The scale inhibition performance was tested according to the static scale inhibition rate test method in the embodiment. When the dosage was 5 mg / L, the static scale inhibition rate was 25.7%.

[0059] Comparative Example 3 Dissolve 2.5g of aminosulfonic acid in 60mL of distilled water, and use the aminosulfonic acid aqueous solution as a scale inhibitor and dispersant.

[0060] The scale inhibition performance was tested according to the static scale inhibition rate test method in the embodiment. When the dosage was 5 mg / L, the static scale inhibition rate was 18.5%.

[0061] Comparative Example 4 Weigh 5.0 g of polysuccinimide into a four-necked flask, add 60 mL of distilled water to suspend the polysuccinimide in the water, and start stirring; separately weigh 2.4 g of sodium hydroxide and dissolve it in 7.2 mL of distilled water to obtain an aqueous sodium hydroxide solution; slowly add the aqueous sodium hydroxide solution dropwise into the four-necked flask over a period of 1.0 h, control the reaction temperature at 40 ℃, and continue the reaction for 6.0 h to obtain solution a; Dissolve 0.5g of carboxylated chitosan in 60mL of distilled water to obtain solution b; Dissolve 2.5g of aminosulfonic acid in 60mL of distilled water to obtain solution c; Mix solutions a, b, and c thoroughly to obtain a scale inhibitor / dispersant.

[0062] The scale inhibition performance was tested according to the static scale inhibition rate test method in the embodiment. When the dosage was 5 mg / L, the static scale inhibition rate was 68.2%.

[0063] Comparative Example 5 This comparative example provides a scale inhibitor and dispersant, which differs from Example 4 only in that aminosulfonic acid is replaced with 2-aminoethanesulfonic acid; otherwise, the steps are exactly the same. The specific steps are as follows: Step a: Weigh 5.0 g of polysuccinimide and add it to 60 mL of distilled water to obtain a polysuccinimide dispersion; Weigh 0.5g of carboxylated chitosan and dissolve it in 60mL of distilled water to obtain an aqueous solution of carboxylated chitosan; Weigh 2.4g of sodium hydroxide and dissolve it in 7.2mL of distilled water to obtain an aqueous solution of sodium hydroxide; Weigh 2.0 g of 2-aminoethanesulfonic acid and dissolve it in 50 mL of distilled water to obtain an aqueous solution of 2-aminoethanesulfonic acid; Step b: Add the prepared polysuccinimide dispersion and carboxylated chitosan aqueous solution to a four-necked flask, start stirring, mix evenly, then slowly add 2-aminoethanesulfonic acid aqueous solution and sodium hydroxide aqueous solution dropwise to the four-necked flask simultaneously over 1.0 h, control the reaction temperature at 40 °C, and continue the reaction for 7.0 h. Then precipitate the reactants with acetone, filter, wash three times with anhydrous ethanol, dry under vacuum at 100 °C to constant weight, grind, and obtain polysuccinimide-carboxylated chitosan-2-aminoethanesulfonate sodium salt.

[0064] The scale inhibition performance was tested according to the static scale inhibition rate test method in the embodiment. When the dosage was 5 mg / L, the static scale inhibition rate was 85.2%.

[0065] The comparison shows that aminosulfonic acid has a significant advantage over 2-aminoethanesulfonic acid in improving scale inhibition and dispersion performance. This is likely because aminosulfonic acid has less steric hindrance, allowing it to integrate more efficiently and uniformly into the polysuccinimide backbone during dehydration condensation reactions. Furthermore, the direct connection between the amino and sulfonic acid groups in aminosulfonic acid results in less steric hindrance, enabling both functional groups to simultaneously form stable multi-coordinate chelates with metal ions such as calcium and magnesium. In contrast, the amino and sulfonic acid groups in 2-aminoethanesulfonic acid are separated by two methylene carbon chains, increasing steric hindrance and significantly weakening the synergistic chelation efficiency of the functional groups. Meanwhile, the electron-donating effect of the amino group in aminosulfonic acid can directly act on adjacent sulfonic acid groups, resulting in a higher charge density after dissociation. This not only enhances the adsorption capacity for metal ions to strengthen the scale inhibition effect, but also stabilizes colloidal particles and scale microcrystals through a stronger electrostatic repulsion effect. In contrast, the electron-donating effect of the carbon chain (alkyl group) in 2-aminoethanesulfonic acid is weaker, resulting in a lower charge density of the sulfonic acid groups. Consequently, its electrostatic dispersion and ion adsorption capabilities are inferior to those of aminosulfonic acid. Furthermore, the more compact molecular structure of aminosulfonic acid makes it easier to embed into the crystal lattice of calcium carbonate, calcium sulfate, and other scale, disrupting their orderly growth. In contrast, the increased carbon chain of 2-aminoethanesulfonic acid increases the molecular volume, reducing the lattice embedding ability and resulting in a weaker lattice distortion effect.

[0066] In summary, the scale inhibitor and dispersant polysuccinimide-carboxylated chitosan-sodium aminosulfonate prepared in the embodiments of the present invention has excellent scale inhibition ability against various scales and 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 can effectively inhibit 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 especially suitable for reverse osmosis treatment systems of various water qualities such as municipal wastewater, seawater, brackish water, surface water, groundwater and industrial wastewater, and has high engineering practical value.

[0067] 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. A scale inhibitor and dispersant for reverse osmosis membranes, characterized in that, The structure of the scale inhibitor and dispersant for the reverse osmosis membrane is shown in Formula I: Formula I Where R is M is either Na or K.

2. The method for preparing the scale inhibitor and dispersant for reverse osmosis membranes according to claim 1, characterized in that, The process includes the following steps: using polysuccinimide, carboxylated chitosan, and aminosulfonic acid as raw materials, a scale inhibitor and dispersant for reverse osmosis membranes is prepared through a dehydration condensation reaction.

3. The method for preparing the scale inhibitor and dispersant for reverse osmosis membranes as described in claim 2, characterized in that, Specifically, the following steps are included: Step a: Polysuccinimide, aminosulfonic acid and carboxylated chitosan are added to water respectively to obtain polysuccinimide dispersion, aminosulfonic acid aqueous solution and carboxylated chitosan aqueous solution; Step b: Mix the succinimide dispersion and carboxylated chitosan aqueous solution evenly, add aminosulfonic acid aqueous solution and strong alkali solution, and carry out dehydration condensation reaction at pH 8.0~9.5 to obtain scale inhibitor and dispersant for reverse osmosis membranes; The strong alkaline solution is either a sodium hydroxide solution or a potassium hydroxide solution.

4. The method for preparing the scale inhibitor and dispersant for reverse osmosis membranes as described in claim 3, characterized in that, The mass ratio of the polysuccinimide, carboxylated chitosan, and aminosulfonic acid is 1:(0.05~0.2):(0.3~0.5).

5. The method for preparing the scale inhibitor and dispersant for reverse osmosis membranes as described in claim 3 or 4, characterized in that, In step a, the mass concentration of the polysuccinimide dispersion is 5%~10%; and / or In step a, the mass concentration of the carboxylated chitosan aqueous solution is 0.4%~1.5%; and / or In step a, the mass concentration of the aminosulfonic acid aqueous solution is 3% to 5%.

6. The method for preparing the scale inhibitor and dispersant for reverse osmosis membranes as described in claim 3, characterized in that, In step b, the mass concentration of the strong alkali solution is 20%~30%.

7. The method for preparing the scale inhibitor and dispersant for reverse osmosis membranes as described in claim 3, characterized in that, In step b, the temperature of the dehydration condensation reaction is 35℃~45℃, and the reaction time is 5h~8h; and / or In step b, the aminosulfonic acid aqueous solution and the strong alkali solution are added simultaneously dropwise over a period of 1 to 1.5 hours.

8. A scale inhibitor and dispersant composition for reverse osmosis membranes, characterized in that, It contains the scale inhibitor and dispersant for reverse osmosis membranes as described in claim 1.

9. The application of the scale inhibitor and dispersant for reverse osmosis membranes as described in claim 1 in reverse osmosis systems for municipal wastewater, seawater, brackish water, surface water, groundwater, or industrial wastewater.

10. The application as described in claim 9, characterized in that, The dosage of the scale inhibitor / dispersant for the reverse osmosis membrane is 3 mg / L to 5 mg / L.

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