Scale inhibitor for reverse osmosis membrane as well as preparation method and application of scale inhibitor

Abstract

The invention relates to the technical field of scale inhibitors, and particularly discloses a scale inhibitor for a reverse osmosis membrane as well as a preparation method and application of the scale inhibitor. The scale inhibitor for the reverse osmosis membrane, provided by the invention, is obtained by carrying out dehydration condensation reaction on carboxylated chitosan and 2-phosphonobutane-1, 2, 4-tricarboxylic acid serving as raw materials. The scale inhibitor for the reverse osmosis membrane has excellent scale inhibition performance, the scale inhibition rate can reach 95% or above, meanwhile, the scale inhibitor has the advantages of being low in cost, easy to operate, safe, efficient and the like, scale can be effectively inhibited in the long-term use process, meanwhile, the structural integrity and performance stability of the reverse osmosis membrane can be kept, and the service life of the reverse osmosis membrane is prolonged. And the reverse osmosis system can be efficiently, continuously and stably operated, can be applied to reverse osmosis systems with different water source characteristics, is particularly suitable for reverse osmosis systems for advanced treatment of municipal wastewater secondary discharge water, reuse of reclaimed water, seawater desalination and the like, and has a relatively high engineering practical value.

Description

Technical Field

[0001] The invention relates to the technical field of scale inhibitors, and in particular to a scale inhibitor for a reverse osmosis membrane and a preparation method and application thereof. Background Art

[0002] Reverse osmosis (RO) is a highly efficient membrane separation technology that is widely used in many fields. It relies on the characteristics of a semipermeable membrane to drive the solvent (usually water) from the high-concentration side through the membrane to the low-concentration side under pressure, while the solute is retained, achieving the purpose of concentrating, purifying or separating the solution. Reverse osmosis technology occupies an extremely important position in industries such as seawater desalination, brackish water desalination, pure water preparation, industrial wastewater treatment and reuse.

[0003] In recent years, the issue of water reuse has received more and more attention. At present, part of the effluent from urban sewage treatment plants is used as a supplementary water source for natural water systems (such as rivers, lakes, and reservoirs), and the other part is used as the second water source for cities after deep treatment. Reverse osmosis membranes can achieve deep purification of sewage and improve water quality. Therefore, they have been widely used in the field of water reuse. Although reverse osmosis membrane treatment technology has significant advantages in the deep treatment of urban sewage, it also faces some challenges. During the membrane treatment process, impurities such as ions in the water will cause dirt to deposit on the membrane surface, significantly reducing water treatment efficiency, increasing energy consumption, shortening the service life of the reverse osmosis membrane, and even causing equipment shutdown and safety problems. Therefore, the membrane scaling problem 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 a certain extent, but the scale inhibition effect of reverse osmosis membranes for municipal wastewater with high hardness, high salt content, and complex ions, water reuse, and seawater desalination is poor. Therefore, it is of great significance to develop an environmentally friendly scale inhibitor suitable for municipal wastewater, reclaimed water reuse, seawater desalination and other systems. Summary of the invention

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

[0005] In order to solve the above technical problems, the technical solution provided by the present invention is: In a first aspect, the present invention provides a scale inhibitor for a reverse osmosis membrane, wherein the structure of the scale inhibitor for a reverse osmosis membrane is shown in Formula I:

[0006] Formula I Among them, R 1 , R 2 , R 3 for or M, and R 1 , R 2 , R 3 Not M at the same time; M is Na or K.

[0007] Compared with the prior art, the scale inhibitor for reverse osmosis membrane provided by the present invention has good solubility in water, and contains carboxyl, phosphate, amino and hydroxyl groups in its molecular structure, which can attract and stably chelate various metal ions to form stable chelates, prevent the contact between scale-forming cations and scale-forming anions (such as carbonate, phosphate, sulfate, etc.), thereby significantly reducing the probability of scale formation; at the same time, it can also be adsorbed on the surface of scale-forming particles, and through the dual effects of steric hindrance and electrostatic repulsion, prevent the mutual contact and aggregation of scale-forming particles, so that they remain in a dispersed state, thereby preventing the growth of scale; in addition, even if a small amount of scale-forming particles have formed tiny aggregates, the scale inhibitor can further disperse them to prevent them from continuing to grow and deposit on the surface of the reverse osmosis membrane; in addition, the scale inhibitor of the present invention can be adsorbed on the surface of the reverse osmosis membrane to form a protective film, reduce the direct contact and friction between the scale and the membrane surface, reduce the physical damage of the membrane, and extend the service life of the reverse osmosis membrane, thereby reducing the operation and maintenance cost of the reverse osmosis membrane system.

[0008] In a second aspect, the present invention also provides a method for preparing a scale inhibitor for a reverse osmosis membrane, using carboxylated chitosan and 2-phosphonobutane-1,2,4-tricarboxylic acid as raw materials, and preparing the scale inhibitor for a reverse osmosis membrane through a dehydration condensation reaction.

[0009] As a specific embodiment of the present invention, the preparation method of the scale inhibitor for reverse osmosis membrane comprises the following steps: Step a, dissolving 2-phosphonobutane-1,2,4-tricarboxylic acid and carboxylated chitosan in water respectively to obtain 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution and carboxylated chitosan aqueous solution; Step b, adding a strong base solution to the 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution to obtain a 2-phosphonobutane-1,2,4-tricarboxylate salt solution; Step c, uniformly mixing the 2-phosphonic acid butane-1,2,4-tricarboxylate solution and the carboxylated chitosan aqueous solution, adding a strong alkali solution to adjust the pH to 9-10, heating to carry out a dehydration condensation reaction, and obtaining a scale inhibitor for reverse osmosis membrane as shown in Formula I, namely, carboxylated chitosan-2-phosphonic acid butane-1,2,4-tricarboxylate sodium salt (CCS-PBTCA); wherein the strong alkali solution is a sodium hydroxide solution or a potassium hydroxide solution. The reaction equation is as follows.

[0010]

[0011] R represents carboxylated chitosan, with the structural formula .

[0012] The preparation method of the scale inhibitor for reverse osmosis membrane provided by the present invention is simple, the reaction conditions are mild, the operation is simple and convenient, and the product yield is high, so it is easy to realize large-scale production and application.

[0013] Furthermore, the mass ratio of the 2-phosphonobutane-1,2,4-tricarboxylic acid to the carboxylated chitosan is 0.15:1 to 0.5:1.

[0014] Preferably, the mass ratio of the 2-phosphonobutane-1,2,4-tricarboxylic acid to the carboxylated chitosan is 0.4:1.

[0015] The preferred addition ratio of each substance can improve the conversion rate of carboxylated chitosan units, so that the prepared scale inhibitor has a suitable molecular structure, thereby having a higher scale inhibition performance in the reverse osmosis system. If the mass ratio is too low, the carboxylated chitosan cannot be effectively grafted, and the scale inhibition rate is limited; if the mass ratio is too high, the grafting rate is too high, the molecular weight is too large, and it is not conducive to improving the scale inhibition rate.

[0016] Furthermore, in step a, the mass concentration of the 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution is 48% to 52%.

[0017] Furthermore, in step a, the mass concentration of the carboxylated chitosan aqueous solution is 4% to 10%.

[0018] Furthermore, 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.

[0019] Specifically, in step b, the mass concentration of the strong alkaline solution is 15% to 20%.

[0020] Furthermore, in step c, the temperature of the dehydration condensation reaction is 40° C. to 50° C., and the reaction time is 6 h to 8 h.

[0021] Preferably, in step c, the temperature of the dehydration condensation reaction is 45° C. and the reaction time is 7 h.

[0022] Furthermore, in step c, the strong base solution is added by slow dropwise addition, and the dropwise addition time is 2.0h~2.5h.

[0023] Specifically, in step c, the mass concentration of the strong alkaline solution is 15% to 20%.

[0024] The preferred addition ratio of the various substances, 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.

[0025] Furthermore, after the addition reaction is completed, a post-treatment process is also included: cooling the reaction solution to room temperature, adding acetone, filtering, washing with anhydrous ethanol for 5 times, drying, and grinding to obtain a carboxylated chitosan-2-phosphonic acid butane-1,2,4-tricarboxylic acid sodium salt product.

[0026] In a third aspect, as another object of the present invention, the present invention further provides an antiscalant composition for a reverse osmosis membrane, comprising the above-mentioned antiscalant for a reverse osmosis membrane.

[0027] The scale inhibitor can be used in combination with conventional water treatment agents in the art as long as there is no adverse effect between the components.

[0028] In a fourth aspect, the present invention also provides the use of the above-mentioned scale inhibitor for reverse osmosis membrane in the deep treatment of secondary discharge water of municipal wastewater, reuse of reclaimed water or reverse osmosis system for seawater desalination.

[0029] Furthermore, the addition amount of the scale inhibitor for the reverse osmosis membrane is 4 mg / L to 6 mg / L.

[0030] Compared with the prior art, the present invention has the following beneficial effects: The present invention creatively proposes a novel scale inhibitor, which is obtained by dehydration condensation reaction of carboxylated chitosan and 2-phosphonobutane-1,2,4-tricarboxylic acid. The novel scale inhibitor is suitable for reverse osmosis systems such as deep treatment of secondary discharge water of municipal wastewater, reuse of reclaimed water, and desalination of seawater. The novel scale inhibitor has excellent scale inhibition performance, and the scale inhibition rate can reach more than 95%. At the same time, the novel scale inhibitor also has the advantages of low cost, simple operation, safety and high efficiency, etc., which effectively ensures the normal operation of the reverse osmosis membrane, significantly reduces the risk of membrane pollution, and has good biodegradability, thereby reducing pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the infrared spectrum of the carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt product prepared in Example 1. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] In order to better illustrate the present invention, further examples are given below.

[0034] Example 1 A method for preparing a scale inhibitor for a reverse osmosis membrane comprises the following steps: Weigh 3.0 g of a 50% by mass 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution into a beaker for later use; weigh 1.125 g of sodium hydroxide and dissolve it in 6.375 g of distilled water to obtain a sodium hydroxide aqueous solution; and slowly pour the sodium hydroxide aqueous solution into the 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution while stirring continuously to generate a 2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt solution.

[0035] Weigh 10g of carboxylated chitosan and dissolve it in 150mL of distilled water to obtain a carboxylated chitosan aqueous solution. Add the carboxylated chitosan aqueous solution and 2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt solution into a four-necked flask, start stirring, slowly drop a 20wt% sodium hydroxide aqueous solution for 2.0h, adjust the pH value of the system to 9.6, react at 40°C for 6.0h, stop stirring, and then precipitate the reactant with acetone, filter, wash with anhydrous ethanol 5 times, vacuum dry at 80°C to constant weight, grind, and obtain carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt (CCS-PBTCA).

[0036] The carboxylated chitosan-2-phosphonic acid butane-1,2,4-tricarboxylic acid sodium salt product obtained in this example was subjected to infrared measurement, and the obtained infrared spectrum was as follows: Figure 1 shown.

[0037] As can be seen from the figure, carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt is at 3253 cm -1 A broad absorption peak appears at the position, which is the stretching vibration absorption peak of -NH in the copolymer, while -NH 2 At 3400~3500cm -1 There are two stretching vibration absorption peaks between them, indicating that -NH 2 The carboxyl group of 2-phosphonobutane-1,2,4-tricarboxylic acid was grafted; the stretching vibration absorption peak of C=O in the amide is at 1642cm -1 1582cm -1 The absorption peak at 1391 cm is the overlapping absorption peak of the antisymmetric stretching vibration of carboxylic acid and the NH bending vibration of amide. -1 The symmetrical stretching absorption peak of carboxylic acid is 1071 cm -1 The peak at the center is the CN stretching vibration absorption peak, which proves that the sodium salt of carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylic acid has been successfully synthesized.

[0038] Example 2 A method for preparing a scale inhibitor for a reverse osmosis membrane comprises the following steps: Weigh 6.0 g of a 50% by mass 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution into a beaker for later use; weigh 2.22 g of sodium hydroxide and dissolve it in 8.88 g of distilled water to obtain a sodium hydroxide aqueous solution; and slowly pour the sodium hydroxide aqueous solution into the 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution while stirring continuously to generate a 2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt solution.

[0039] Weigh 10g of carboxylated chitosan and dissolve it in 150mL of distilled water to obtain a carboxylated chitosan aqueous solution. Add the carboxylated chitosan aqueous solution and 2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt solution into a four-necked flask, start stirring, slowly drop a 20wt% sodium hydroxide aqueous solution for 2.0h, adjust the pH value of the system to 9.5, react at 50°C for 6.0h, stop stirring, and then precipitate the reactant with acetone, filter, wash with anhydrous ethanol 5 times, vacuum dry at 80°C to constant weight, grind, and obtain carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt (CCS-PBTCA).

[0040] Example 3 A method for preparing a scale inhibitor for a reverse osmosis membrane comprises the following steps: Weigh 8.0 g of a 50% by mass 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution into a beaker for later use; weigh 2.96 g of sodium hydroxide and dissolve it in 11.84 g of distilled water to obtain a sodium hydroxide aqueous solution; and slowly pour the sodium hydroxide aqueous solution into the 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution while stirring continuously to generate a 2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt solution.

[0041] Weigh 10g of carboxylated chitosan and dissolve it in 150mL of distilled water to obtain a carboxylated chitosan aqueous solution. Add the carboxylated chitosan aqueous solution and 2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt solution into a four-necked flask, start stirring, slowly drop a 20wt% sodium hydroxide aqueous solution for 2.0h, adjust the pH value of the system to 9.3, react at 45°C for 6.0h, stop stirring, and then precipitate the reactant with acetone, filter, wash with anhydrous ethanol 5 times, vacuum dry at 80°C to constant weight, grind, and obtain carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt (CCS-PBTCA).

[0042] Example 4 A method for preparing a scale inhibitor for a reverse osmosis membrane comprises the following steps: Weigh 8.0 g of a 50% by mass 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution into a beaker for later use; weigh 2.96 g of sodium hydroxide and dissolve it in 11.84 g of distilled water to obtain a sodium hydroxide aqueous solution; and slowly pour the sodium hydroxide aqueous solution into the 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution while stirring continuously to generate a 2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt solution.

[0043] Weigh 10g of carboxylated chitosan and dissolve it in 150mL of distilled water to obtain a carboxylated chitosan aqueous solution. Add the carboxylated chitosan aqueous solution and 2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt solution into a four-necked flask, start stirring, slowly drop a 20wt% sodium hydroxide aqueous solution for 2.0h, adjust the pH value of the system to 9.0, react at 45°C for 7.0h, stop stirring, and then precipitate the reactant with acetone, filter, wash with anhydrous ethanol 5 times, vacuum dry at 80°C to constant weight, grind, and obtain carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt (CCS-PBTCA).

[0044] Example 5 A method for preparing a scale inhibitor for a reverse osmosis membrane comprises the following steps: Weigh 10.0 g of a 50% by mass 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution into a beaker for later use; weigh 3.0 g of sodium hydroxide and dissolve it in 12 g of distilled water to obtain a sodium hydroxide aqueous solution; and slowly pour the sodium hydroxide aqueous solution into the 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution while stirring continuously to generate a 2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt solution.

[0045] Weigh 10g of carboxylated chitosan and dissolve it in 90mL of distilled water to obtain a carboxylated chitosan aqueous solution. Add the carboxylated chitosan aqueous solution and 2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt solution into a four-necked flask, start stirring, slowly drop a 20wt% sodium hydroxide aqueous solution for 2.5h, adjust the pH value of the system to 10.0, react at 40°C for 8.0h, stop stirring, and then precipitate the reactant with acetone, filter, wash with anhydrous ethanol 5 times, vacuum dry at 80°C to constant weight, grind, and obtain carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt (CCS-PBTCA).

[0046] Example 6 A method for preparing a scale inhibitor for a reverse osmosis membrane comprises the following steps: Weigh 10.0 g of a 50% by mass 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution into a beaker for later use; weigh 5.0 g of sodium hydroxide and dissolve it in 20.0 g of distilled water to obtain a sodium hydroxide aqueous solution; and slowly pour the sodium hydroxide aqueous solution into the 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution while stirring continuously to generate a 2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt solution.

[0047] Weigh 10g of carboxylated chitosan and dissolve it in 200mL of distilled water to obtain a carboxylated chitosan aqueous solution. Add the carboxylated chitosan aqueous solution and 2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt solution into a four-necked flask, start stirring, slowly drop a 20wt% sodium hydroxide aqueous solution for 2.0h, adjust the pH value of the system to 9.5, react at 50°C for 8.0h, stop stirring, and then precipitate the reactant with acetone, filter, wash with anhydrous ethanol 5 times, vacuum dry at 80°C to constant weight, grind, and obtain carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt (CCS-PBTCA).

[0048] Scale inhibition performance test 1.1 Static scale inhibition rate test In order to test the scale inhibition performance of the scale inhibitor carboxylated chitosan-2-phosphonic acid butane-1,2,4-tricarboxylic acid sodium salt in the embodiment of the present invention, the scale inhibitors prepared in Examples 1 to 6 were subjected to a scale inhibition test, and the specific test conditions were as follows: Take 7 1000mL beakers, add 750mL of municipal wastewater secondary discharge water respectively, and then add the scale inhibitors prepared in Examples 1 to 6 to 6 of the volumetric flasks respectively. The remaining 1 volumetric flask is not added with scale inhibitor as a blank test and placed in a constant temperature water bath at 80°C. When the water in the beaker is evaporated and concentrated to about 500mL, take the beaker out of the water bath, cool it to room temperature, pour the water in the beaker into a 500mL volumetric flask, and make up to 500mL with a small amount of distilled water, then put the volumetric flask into a constant temperature water bath at 80°C, continue the water bath for 10 hours, and then measure its calcium scale inhibition rate after cooling to room temperature. The test results are shown in Table 1.

[0049] The calculation formula of scale inhibition rate is: Scale inhibition rate = (scaling amount of blank heating tube - scaling amount of added heating tube) / scaling amount of blank heating tube × 100%.

[0050] Table 1

[0051] When the scale inhibitors prepared in Examples 1 to 6 were added to the secondary discharge water of municipal wastewater without evaporation and concentration, and the dosage was 3 mg / L, the average scale inhibition rate of Examples 1 to 6 was 96.4%.

[0052] 1.2 Dynamic scale inhibition rate test In order to test the scale inhibition effect of the carboxylated chitosan-2-phosphonic acid butane-1,2,4-tricarboxylic acid sodium salt product prepared in Examples 1 to 6 of the present invention in the reverse osmosis system, the test water used in this test is municipal wastewater secondary discharge water, and the scale inhibition test method adopts a dynamic scale inhibition test method. Municipal wastewater secondary discharge water is added to the water supply tank of the microfiltration-ultrafiltration-reverse osmosis experimental device (microfiltration uses a precision filter, the filter element model is 20 inches 5μm; ultrafiltration uses Huamo UF-4040; reverse osmosis membrane uses Huamo ULPHM-4040), and the carboxylated chitosan-2-phosphonic acid butane-1,2,4-tricarboxylic acid sodium salt product prepared in the embodiment of the present invention is added to the water supply tank, the dosage is 4mg / L, and it is continuously operated for 1 month. At the same time, a blank experiment is performed, no agent is added to the water supply tank, and other operating conditions are the same.

[0053] The results show that during the operation of the blank experiment, the conductivity of the produced water gradually increased from 32µs / cm to 50µs / cm, and the desalination rate of the reverse osmosis membrane dropped to about 95%. At the same time, the water inlet pressure of the reverse osmosis system membrane also increased to 0.95MPa, and the water production flow rate was between 330~350L / h, indicating that the reverse osmosis membrane has been scaled. In the experiment of adding the membrane scale inhibitor prepared by the embodiment of the present invention, the conductivity of the produced water remained almost unchanged during the entire operation, maintained between 30~34µs / cm, the desalination rate of the membrane was always above 99.5%, and at the same time, the water inlet pressure of the reverse osmosis system membrane remained unchanged at 0.92MPa, and the water production flow rate was always between 360~380L / h, and the whole system operated normally. It shows that the carboxylated chitosan-2-phosphonic acid butane-1,2,4-tricarboxylic acid sodium salt prepared by the present invention has excellent scale inhibition effect in the reverse osmosis system of municipal wastewater secondary discharge water.

[0054] Comparative Example 1 10 g of carboxylated chitosan was weighed and dissolved in 150 mL of distilled water to obtain a carboxylated chitosan aqueous solution as a scale inhibitor a.

[0055] The scale inhibition performance was tested according to the test method of static scale inhibition rate in the embodiment. When the dosage was 6 mg / L, the static scale inhibition rate was 26.4%.

[0056] Comparative Example 2 A 50% by mass 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution was used as the scale inhibitor b.

[0057] The scale inhibition performance was tested according to the test method of static scale inhibition rate in the embodiment. When the dosage was 6 mg / L, the static scale inhibition rate was 76.1%.

[0058] Comparative Example 3 Weigh 8.0 g of a 50% by mass 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution into a beaker for later use; weigh 2.96 g of sodium hydroxide and dissolve it in 11.84 g of distilled water to obtain a sodium hydroxide aqueous solution; and slowly pour the sodium hydroxide aqueous solution into the 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution while stirring continuously to generate a 2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt solution.

[0059] Weigh 10 g of carboxylated chitosan and dissolve it in 150 mL of distilled water to obtain a carboxylated chitosan aqueous solution.

[0060] The 2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt solution and the carboxylated chitosan aqueous solution are uniformly mixed to obtain scale inhibitor C.

[0061] The scale inhibition performance was tested according to the test method of static scale inhibition rate in the embodiment. When the dosage was 6 mg / L, the static scale inhibition rate was 79.5%.

[0062] Comparative Example 4 Weigh 8.0 g of a 50% 2-hydroxyphosphonoacetic acid aqueous solution into a beaker for later use; weigh 2.96 g of sodium hydroxide and dissolve it in 11.84 g of distilled water to obtain a sodium hydroxide aqueous solution, and slowly pour the sodium hydroxide aqueous solution into the 2-hydroxyphosphonoacetic acid aqueous solution while stirring continuously to generate a 2-hydroxyphosphonoacetic acid sodium salt solution.

[0063] Weigh 10g of carboxylated chitosan and dissolve it in 150mL of distilled water to obtain a carboxylated chitosan aqueous solution. Add the carboxylated chitosan aqueous solution and 2-hydroxyphosphonic acid acetic acid sodium salt solution into a four-necked flask, start stirring, slowly drop a 20wt% sodium hydroxide aqueous solution for 2.0h, adjust the pH value of the system to 9.0, react at 45°C for 7.0h, stop stirring, and then precipitate the reactant with acetone, filter, wash with anhydrous ethanol 5 times, vacuum dry at 80°C to constant weight, grind, and obtain carboxylated chitosan-2-hydroxyphosphonic acid acetic acid sodium salt as scale inhibitor d.

[0064] The scale inhibition performance was tested according to the test method of static scale inhibition rate in the embodiment. When the dosage was 6 mg / L, the static scale inhibition rate was 64.1%.

[0065] In summary, the scale inhibitor carboxylated chitosan-2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt prepared in the embodiment of the present invention has excellent scale inhibition ability against a variety of scales, and has excellent compatibility with various types of reverse osmosis membranes, and will not cause the physical and chemical properties of the reverse osmosis membrane to decrease. 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, and can be applied to reverse osmosis systems with different water source characteristics, especially suitable for reverse osmosis systems such as deep treatment of secondary discharge water of municipal wastewater, reuse of reclaimed water, and desalination of seawater, and has high engineering practical value.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A scale inhibitor for reverse osmosis membrane, characterized in that: The structure of the antiscalant for reverse osmosis membrane is shown in Formula I: Formula I Among them, R1, R2, and R3 are Or M, and R1, R2, R3 are not M at the same time; M is Na or K.

2. The method for preparing the scale inhibitor for reverse osmosis membrane according to claim 1, characterized in that: The method comprises the following steps: using carboxylated chitosan and 2-phosphonobutane-1,2,4-tricarboxylic acid as raw materials, and preparing a scale inhibitor for a reverse osmosis membrane through a dehydration condensation reaction.

3. The method for preparing a scale inhibitor for a reverse osmosis membrane according to claim 2, characterized in that: The specific steps include: Step a, dissolving 2-phosphonobutane-1,2,4-tricarboxylic acid and carboxylated chitosan in water respectively to obtain 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution and carboxylated chitosan aqueous solution; Step b, adding a strong base solution to the 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution to obtain a 2-phosphonobutane-1,2,4-tricarboxylate salt solution; Step c, mixing the 2-phosphonobutane-1,2,4-tricarboxylate solution and the carboxylated chitosan aqueous solution evenly, adding a strong alkaline solution to adjust the pH to 9-10, heating to carry out a dehydration condensation reaction, and obtaining a scale inhibitor for reverse osmosis membrane as shown in Formula I; Wherein, the strong alkaline solution is sodium hydroxide solution or potassium hydroxide solution.

4. The method for preparing a scale inhibitor for reverse osmosis membrane according to claim 3, characterized in that: The mass ratio of the 2-phosphonobutane-1,2,4-tricarboxylic acid to the carboxylated chitosan is 0.15:1 to 0.5:

1.

5. The method for preparing a scale inhibitor for reverse osmosis membrane according to claim 3 or 4, characterized in that: In step a, the mass concentration of the 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution is 48% to 52%; and / or In step a, the mass concentration of the carboxylated chitosan aqueous solution is 4% to 10%.

6. The method for preparing a scale inhibitor for reverse osmosis membrane according to 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 method for preparing a scale inhibitor for a reverse osmosis membrane according to claim 3, characterized in that: In step c, the temperature of the dehydration condensation reaction is 40°C to 50°C, and the reaction time is 6h to 8h; and / or In step c, the strong base solution is added in a slow dropwise manner for 2.0 h to 2.5 h.

8. A scale inhibitor composition for reverse osmosis membrane, characterized in that: The invention comprises the antiscalant for reverse osmosis membrane according to claim 1.

9. Use of the scale inhibitor for reverse osmosis membrane according to claim 1 in deep treatment of secondary discharge water of municipal wastewater, reuse of reclaimed water or reverse osmosis system for desalination of seawater.

10. The use according to claim 9, characterized in that The added amount of the scale inhibitor for reverse osmosis membrane is 4 mg / L to 6 mg / L.

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