Green and efficient polyfunctional group modified environment-friendly scale inhibitor for inhibiting calcium sulfate scaling as well as preparation method and application of scale inhibitor

Abstract

The invention relates to a preparation method and application of a green and efficient polyfunctional group modified environment-friendly scale inhibitor capable of effectively inhibiting calcium sulfate scale. According to the scale inhibitor, starch serves as a raw material, potassium persulfate serves as an initiator, glycidyl methacrylate and acrylic acid are introduced through a grafting reaction to serve as grafting monomers, and the modified scale inhibitor with multiple functions is formed. A grafted chain containing carboxyl, ester group and epoxy group can be introduced to a polysaccharide chain, so that the scale inhibitor is endowed with excellent chelation, dispersion and lattice distortion properties, and the formation and growth of scale bodies can be effectively inhibited. The prepared scale inhibitor can effectively inhibit generation of calcium sulfate scale in a static water body, has a remarkable application effect in a reverse osmosis system, and effectively relieves the problem of reduction of membrane flux, so that the stability of a water treatment system is improved. The water treatment efficiency is improved, the requirement for environmental friendliness is met, and a new strategy is provided for calcium sulfate scale control.

Description

Technical Field

[0001] The present invention relates to a multi-functional group modified environmental-friendly scale inhibitor for green and efficient inhibition of calcium sulfate scaling, its preparation method and application, belonging to the technical field of water environment treatment. Background Art

[0002] With the expansion of the global urban scale and the continuous growth of the population, the demand for fresh water is also continuously rising, which undoubtedly further highlights the shortage of fresh water resources. The desalination technology of seawater and brackish water has become one of the important means to solve the problem of fresh water shortage. Reverse osmosis technology is widely used in the desalination process due to its low energy consumption and high desalination efficiency, and it is one of the most common desalination technologies at present. However, reverse osmosis technology faces a series of challenges in practical applications. Among them, due to the presence of alkaline earth metals (such as calcium, magnesium, etc.) in water, these alkaline earth metals will undergo chemical reactions with anions in the reverse osmosis system, resulting in the formation of scale, especially the formation of deposits on the membrane surface or in the pores of the membrane. This kind of scale not only affects the permeability of the membrane, but also increases the energy consumption and operating cost of the membrane system. In addition, scale formation is also a common problem in the circulating cooling water systems of many industrial fields (such as power generation, chemical industry, and petroleum industries). The formation of scale not only affects the heat transfer efficiency and increases energy consumption, but may even pose potential risks. Therefore, effectively inhibiting the formation of scale is of great practical significance in both reverse osmosis and circulating cooling water systems.

[0003] In the reverse osmosis system, directly adding a scale inhibitor is one of the common methods to prevent scaling, and this strategy is widely popular because of its high efficiency, simple operation and low cost. However, although traditional phosphorus-containing and organic synthetic polymer scale inhibitors perform well in inhibiting scaling, the environmental problems they cause cannot be ignored. Especially phosphorus-containing scale inhibitors, although they have high scale inhibition efficiency, the residual phosphorus elements may lead to eutrophication of water bodies, thus triggering a series of ecological and environmental problems. Therefore, both academia and industry are actively exploring solutions to this problem and gradually developing towards the research direction of phosphorus-free scale inhibitors, such as organic synthetic polymer scale inhibitors. However, although organic synthetic polymer scale inhibitors perform well in inhibiting scaling, they are often multi-component copolymers, which not only have deficiencies such as high cost and difficult molecular structure regulation, but also are difficult to biodegrade in the natural environment after being discarded, and pose potential hazards to the environment. In recent years, polyaspartic acid has received extensive attention as a green scale inhibitor and has great application potential, but it also has deficiencies such as relatively complex preparation conditions, single functional groups, and the presence of nutrient element nitrogen in its structure. Therefore, developing a new type of high-efficiency scale inhibitor that is phosphorus-free, nitrogen-free, green and environmentally friendly, biodegradable and has good cost performance has become an important research topic in this field.

[0004] Natural polymers, such as starch, cellulose, lignin, and chitosan, are derived from organisms such as plants, animals, and microorganisms and are widely distributed in nature. These materials not only have good biodegradability but also often possess advantages such as economy and environmental friendliness. Although most natural polymers do not inherently have scale inhibition properties, through appropriate physicochemical modification methods, they can be made to have good scale inhibition performance. In fact, the research on natural polymer scale inhibitors, such as lignosulfonates, has attracted extensive attention and application as early as the 1960s. However, it was soon replaced by a large number of newly discovered synthetic scale inhibitors, such as organophosphorus scale inhibitors. Therefore, the research on natural polymer scale inhibitors is far from systematic and comprehensive, and the scale inhibition performance still needs to be further improved.

[0005] In addition, among different chemical modification methods, graft copolymerization is a commonly used polymer chemical modification method. It can introduce various functional groups onto the polymer chain and construct a unique branched-chain structure, enabling the polymer to possess the advantages of both the main chain of the raw material and the functional groups of the grafted side chain, effectively improving its application performance. However, in past studies, after excessive dosing of scale inhibitors such as hydroxyethylidene diphosphonic acid and amino trimethylene phosphonic acid, the scale inhibitors may entangle and adsorb on the surface of the membrane, resulting in a decrease in membrane flux. Summary of the Invention

[0006] The technical problem solved by the present invention is: to propose a series of modified environmentally friendly scale inhibitors with excellent scale inhibition effects and environmental protection characteristics, which are made from natural polymer starch with excellent performance, low price, and wide sources through molecular design and functionalization modification technology, effectively inhibiting the scaling of calcium sulfate and controlling membrane fouling in the reverse osmosis system within a wide dosing window. The multi-functional group modified environmentally friendly scale inhibitor can not only effectively inhibit the formation of calcium sulfate scale in static water bodies but also effectively alleviate the problem of membrane flux decline in the reverse osmosis system, thereby improving the stability of the water treatment system. Due to its non-ionic nature, it is not easy to produce a flocculation effect and is not easy to contaminate the reverse osmosis membrane at high dosing amounts. Through application in static experiments and reverse osmosis experiments, it can effectively inhibit the formation of calcium sulfate at both low and high dosing amounts, showing good scale inhibition performance and can be applied to control the scaling of circulating cooling water and reverse osmosis systems.

[0007] To solve the above technical problems, the technical solution proposed by the present invention is: A preparation method of a multi-functional group modified environmentally friendly scale inhibitor, using starch as the raw material, potassium persulfate as the initiator, glycidyl methacrylate (GMA) and acrylic acid (AA) as graft monomers, and obtaining the multi-functional group modified environmentally friendly scale inhibitor through graft copolymerization reaction. The preparation route is as follows:

[0008]

[0009] Wherein: m and n are positive integers;

[0010] The specific steps are as follows:

[0011] Disperse starch in an aqueous sodium hydroxide solution, and conduct alkaline gelatinization for 0.5 - 2 h. After the alkaline gelatinization treatment, add potassium persulfate as an initiator; add glycidyl methacrylate and acrylic acid solution to the mixture for grafting reaction. After the reaction is completed, use ethanol or acetone as a precipitant for precipitation separation to obtain a green and highly efficient multi-functional modified environmental scale inhibitor.

[0012] Preferably, the mass ratio of the starch to the sodium hydroxide is 1:0.1 - 1:2;

[0013] During the alkaline gelatinization reaction process, control the reaction temperature at 60 - 95 °C and the reaction time at 0.5 - 3 hours;

[0014] The mass ratio of the starch to the glycidyl methacrylate is 1:0.2 - 1:2, and the mass ratio of the starch to the acrylic acid is 1:0.01 - 1:0.5;

[0015] During the grafting reaction process, control the reaction temperature at 50 - 80 °C and the reaction time at 1 - 4 hours.

[0016] Preferably, the mass ratio of the starch to the sodium hydroxide is 1:0.3;

[0017] During the alkaline gelatinization reaction process, control the reaction temperature at 75 °C and the reaction time at 1 hour;

[0018] The mass ratio of the starch to the glycidyl methacrylate is 1:0.5, and the mass ratio of the starch to the acrylic acid is 1:0.15;

[0019] During the grafting reaction process, control the reaction temperature at 65 °C and the reaction time at 3 hours.

[0020] To solve the above technical problems, another technical solution proposed by the present invention is: preparing a multi-functional modified environmental scale inhibitor.

[0021] To solve the above technical problems, another technical solution proposed by the present invention is: the application of the multi-functional modified environmental scale inhibitor. The multi-functional modified environmental scale inhibitor can not only effectively inhibit the formation of calcium sulfate scale in static water bodies, but also effectively alleviate the problem of the decline of membrane flux in the reverse osmosis system, thereby improving the stability of the water treatment system.

[0022] Preferably, first mix starch with an aqueous sodium hydroxide solution, where the mass ratio of starch to sodium hydroxide is 1:0.3, and stir at 75 °C for 1 hour to fully gelatinize the starch; after alkaline gelatinization treatment, add potassium persulfate as an initiator; subsequently, dropwise add an aqueous solution of glycidyl methacrylate and acrylic acid with a mass ratio of 1:0.5:0.15 to the starch into the reaction system through a constant-pressure dropping funnel; after the dropping is completed, react at 65 °C for 3 hours, and keep the whole reaction in a nitrogen atmosphere; after the reaction is completed, adjust the pH value of the reaction solution to neutral, and then use ethanol or acetone as a precipitant to precipitate and separate the product to obtain the final product, a green and highly efficient multi-functional group modified environmental protection scale inhibitor; when the dosage of the obtained multi-functional group modified environmental protection scale inhibitor is 10.0 mg·L -1 , the static scale inhibition efficiency of CaSO 4 reaches 100%, and when 5.0 mg·L -1 of the scale inhibitor is added and the membrane flux rises to more than 83% compared with that without the scale inhibitor after running for 24 hours.

[0023] Advantages of the present invention:

[0024] 1. The green and highly efficient multi-functional group modified environmental protection scale inhibitor material obtained by the preparation method of the present invention has multiple functional groups such as carboxyl, ester group and epoxy group. Different from the previous use of single anion functional group modification, the ester group and epoxy group are non-ionic functional groups. These functional groups can not only effectively delay the formation of calcium sulfate crystals through chelation, but also show excellent dispersion and lattice distortion effects. And due to its non-ionic nature, it is not easy to produce a flocculation effect, so it is not easy to pollute the reverse osmosis membrane at a high dosage. Through static experiments, it can effectively inhibit the formation of calcium sulfate at both a lower dosage of 10 mg·L -1 and a higher dosage of 80 mg·L -1 , showing good scale inhibition performance. In the application of reverse osmosis experiments, it can effectively inhibit the formation of calcium sulfate at both a lower dosage of 2 mg·L -1 and a higher dosage of 20 mg·L -1 , showing good scale inhibition performance.

[0025] 2. The present invention can not only be used in cooling circulating water in high-temperature and high-hardness environments, but also be applicable to reverse osmosis treatment under high pressure, can cope with different ions and pollutants, and is not easy to cause secondary pollution to the membrane.

[0026] 3. The preparation method of the green and highly efficient multi-functional group modified environmental protection scale inhibitor material of the present invention has simple operation, short synthesis time, and the main raw materials used are natural polymer products with rich sources and low cost, which is suitable for large-scale industrial production and is an economical preparation method for obtaining high-quality water treatment agents.

[0027] 4. The green and highly efficient multi-functional group modified environmental protection scale inhibitor material of the present invention has good scale inhibition performance, can act with scale-forming substances through complexation and dispersion stabilization effects, reduce the crystal nucleation rate, significantly extend the crystallization induction time, inhibit the formation of calcium sulfate scale bodies, and thus effectively delay the fouling and pollution on the membrane surface and alleviate problems such as the decline of membrane flux.

[0028] 5. The green and highly efficient multi-functional group modified environmental protection scale inhibitor material has a wide dosing window and does not require strict control of the dosage during use.

[0029] 6. The green and highly efficient multi-functional group modified environmental protection scale inhibitor material selects natural polymer starch as the substrate, has biodegradability, low cost, and is non-toxic itself, and will not cause secondary pollution to the water body.

[0030] 7. Example 1 is the best example, Figure 4 which is the scale inhibition efficiency of the green and highly efficient multi-functional group modified environmental protection scale inhibitor material in the static scale inhibition experiment. The national standard (GB / T 16632-2019) is adopted to evaluate the scale inhibition performance of the green and highly efficient multi-functional group modified environmental protection scale inhibitor against CaSO 4 . When the dosing amount is 10.0 mg·L -1 , the efficiency of static scale inhibition reaches 100% ( Figure 4 ).

[0031] The scale inhibition performance of the scale inhibitor in the reverse osmosis system is evaluated through a cross-flow high-pressure flat membrane instrument. The object under investigation is simulated seawater, and the mass of the permeate is automatically recorded by a balance for calculating the permeation flux. Figure 5 It can be seen from -1 that after running for 24 hours with the addition of 5.0 mg·L Figure 5 of the scale inhibitor, the membrane flux is increased from 4% to more than 83% compared with that without the scale inhibitor, and the membrane fouling situation is greatly alleviated. In addition, under the condition of the same dosing amount, compared with 2 commercial scale inhibitors (aminotrimethylene phosphonic acid and polyacrylic acid (weight average molecular weight is 3000)), the final membrane flux of the green and highly efficient multi-functional group modified environmental protection scale inhibitor is 83.2%, and the final membrane fluxes of aminotrimethylene phosphonic acid and polyacrylic acid are 74.4% and 70.2% ( Figure 6 ), not only obtaining better membrane flux, but also being more environmentally friendly because it does not contain phosphorus. -1 It can be seen that with the addition of 2.0 mg·L -1 of the scale inhibitor, after running for 3 hours, the membrane flux is increased from 27.5% to 93.2% compared with that without the scale inhibitor. Under the excessive dosing amount of 20.0 mg·L Brief Description of the Drawings

[0032] The present invention will be further described below in conjunction with the accompanying drawings.

[0033] Figure 1 Schematic diagram of the synthesis of a green and highly efficient multi-functional group modified environmental scale inhibitor.

[0034] Figure 2 Infrared spectrum of the green and highly efficient multi-functional group modified environmental scale inhibitor material.

[0035] Figure 3 1H NMR spectrum of the green and highly efficient multi-functional group modified environmental scale inhibitor material.

[0036] Figure 4 Scale inhibition efficiency of the green and highly efficient multi-functional group modified environmental scale inhibitor material in static scale inhibition experiments.

[0037] Figure 5 Effect of adding and not adding the green and highly efficient multi-functional group modified environmental scale inhibitor material and commercial scale inhibitor on the reverse osmosis membrane flux.

[0038] Figure 6 Effect of adding and not adding the green and highly efficient multi-functional group modified environmental scale inhibitor material at different dosages on the reverse osmosis membrane flux. Detailed Embodiments

[0039] The present invention will be further illustrated by the following examples. It should be understood that these examples are illustrative and explanatory of the present invention and do not limit the scope of the present invention in any way.

[0040] Example 1:

[0041] A green and highly efficient multi-functional group modified environmental scale inhibitor is prepared from starch as the raw material, potassium persulfate as the initiator, glycidyl methacrylate (GMA) and acrylic acid (AA) as graft monomers through a graft copolymerization reaction to obtain a green and highly efficient multi-functional group modified environmental scale inhibitor for calcium sulfate scale (weight average molecular weight is about 2.3×10 5 g / mol). The preparation route is as follows:

[0042]

[0043] Wherein: m and n are positive integers;

[0044] The specific steps are as follows: First, mix starch with an aqueous sodium hydroxide solution, where the mass ratio of starch to sodium hydroxide is 1:0.3, and stir at 75 °C for 1 hour to fully gelatinize the starch. After alkaline gelatinization treatment, add potassium persulfate as an initiator. Subsequently, a mixed aqueous solution of glycidyl methacrylate and acrylic acid with a mass ratio of 1:0.5:0.15 to the starch is dropped into the reaction system through a constant-pressure dropping funnel. After the dropping is completed, react at 65 °C for 3 hours, and keep the whole reaction in a nitrogen atmosphere. After the reaction is completed, adjust the pH value of the reaction solution to neutral, and then use ethanol or acetone as a precipitant to precipitate and separate the product to obtain the final product, a green and highly efficient multi-functional group modified environmentally friendly scale inhibitor.

[0045] The infrared spectra of the green and highly efficient multi-functional group modified environmentally friendly scale inhibitor and starch are shown in Figure 2 . From Figure 2 it can be seen that the green and highly efficient multi-functional group modified environmentally friendly scale inhibitor shows new characteristic peaks at 1701 cm -1 , 1560 cm -1 and 1255 cm -1 , which respectively correspond to the characteristic peaks of carbonyl, ester group and epoxy group; thus proving the successful preparation of the green and highly efficient multi-functional group modified environmentally friendly scale inhibitor material. In addition, as Figure 3 shown, in the proton nuclear magnetic resonance spectrum, due to the proton vibrations of -CH 3 , -CH 2 - and -COOH, new characteristic peaks appear at 0.93 - 1.08 ppm, 1.8 - 2.0 ppm and 5.3 - 5.7 ppm respectively.

[0046] Figure 4 shows the scale inhibition efficiency of the green and highly efficient multi-functional group modified environmentally friendly scale inhibitor material in the static scale inhibition experiment. The national standard (GB / T 16632 - 2019) is used to evaluate the scale inhibition performance of the green and highly efficient multi-functional group modified environmentally friendly scale inhibitor against CaSO 4 . When the dosage is 10.0 mg·L -1 , the static scale inhibition efficiency reaches 100% ( Figure 4 ).

[0047] The scale inhibition performance of the scale inhibitor in the reverse osmosis system is evaluated through a cross-flow high-pressure flat membrane instrument. The object under investigation is simulated seawater, and the mass of the permeate is automatically recorded by an electronic balance for calculating the permeation flux. Figure 5 It can be seen from -1After running for 24 hours, the membrane flux increased from 4% to over 83% compared to the case without the scale inhibitor, and the membrane fouling situation was greatly alleviated. In addition, under the condition of the same dosage, compared with two commercial scale inhibitors (aminotrimethylene phosphonic acid and polyacrylic acid (weight-average molecular weight of 3000)), the final membrane flux of the green and highly efficient multi-functional group modified environmental-friendly scale inhibitor was 83.2%, while those of aminotrimethylene phosphonic acid and polyacrylic acid were 74.4% and 70.2% ( Figure 5 ), not only achieving a better membrane flux, but also being more environmentally friendly due to being phosphorus-free. Figure 6 It can be seen that at a dosage of 2.0 mg·L -1 , after running for 3 hours, the membrane flux increased from 27.5% to 93.2% compared to the case without the scale inhibitor. At an excessive dosage of 20.0 mg·L -1 , the final membrane flux could still be maintained at 95.5%. Therefore, it has a wide dosage window and can slow down the scaling on the membrane surface within a wide range.

[0048] Example 2:

[0049] First, cellulose (Sample 2.1) and chitosan (Sample 2.2) were used as substrates and mixed with an aqueous sodium hydroxide solution respectively, where the mass ratio of the substrate to sodium hydroxide was 1:0.3, and stirred at 75 °C for 1 hour to fully gelatinize the starch. After the alkaline gelatinization treatment, potassium persulfate was added as an initiator. Subsequently, an aqueous solution mixture of glycidyl methacrylate and acrylic acid with a mass ratio of 1:0.5:0.15 to the substrate was dropped into the reaction system through a constant-pressure dropping funnel. After the dropping was completed, the reaction was carried out at 65 °C for 3 hours, and the whole reaction was maintained in a nitrogen atmosphere. After the reaction ended, the pH value of the reaction solution was adjusted to neutral, and then ethanol or acetone was used as a precipitant to precipitate and separate the product, obtaining the final product, the green and highly efficient multi-functional group modified environmental-friendly scale inhibitor. The scale inhibition performance of the scale inhibitor on CaSO 4 was evaluated using the national standard (GB / T 16632-2019). Among them, when the dosage of Sample 2.1 was 15.0 mg·L -1 , the static scale inhibition efficiency reached 100%. When the dosage of Sample 2.2 was 18.0 mg·L -1 , the static scale inhibition efficiency reached 100%. The scale inhibition performance of the scale inhibitor in the reverse osmosis system was evaluated through a cross-flow high-pressure flat membrane instrument, and the object under investigation was simulated seawater. The mass of the permeate was automatically recorded by a balance for calculating the permeation flux. When adding 5.0 mg / L of Sample 2.1 and 2.2, after running for 24 hours, the membrane flux increased from 4% to above 72% and 70% respectively compared to the case without the scale inhibitor. At 2.0 - 20.0 mg·L -1In the wide dosing range, after running for 3 hours, the final membrane fluxes of Samples 2.1 and 2.2 increased from 27.5% to over 85% and 82% respectively compared to those without the scale inhibitor.

[0050] Compared with Example 1, changing the type of substrate will reduce the scale inhibition efficiency of the scale inhibitor.

[0051] Example 3:

[0052] First, starch was used as the substrate and mixed with an aqueous sodium hydroxide solution respectively. The mass ratio of the substrate to sodium hydroxide in Sample 3.1 was 1:0.1, and it was stirred at 75 °C for 1 hour to fully gelatinize the starch; the mass ratio of the substrate to sodium hydroxide in Sample 3.2 was 1:2, and it was stirred at 75 °C for 1 hour to fully gelatinize the starch. After alkaline gelatinization treatment, potassium persulfate was added as an initiator. Subsequently, an aqueous solution of glycidyl methacrylate and acrylic acid with a mass ratio of 1:0.5:0.15 to the substrate was dropped into the reaction system through a constant pressure dropping funnel. After the dropping was completed, the reaction was carried out at 65 °C for 3 hours, and the whole reaction was maintained in a nitrogen atmosphere. After the reaction ended, the pH value of the reaction solution was adjusted to neutral, and then ethanol or acetone was used as a precipitant to precipitate and separate the product, obtaining the final product, a green and efficient multi-functional modified environmental scale inhibitor. The scale inhibition performance of the scale inhibitor on CaSO 4 was evaluated using the national standard (GB / T 16632-2019). Among them, when the dosing amount of Sample 3.1 was 30.0 mg·L -1 , the static scale inhibition efficiency reached 100%. When the dosing amount of Sample 3.2 was 25.0 mg·L -1 , the static scale inhibition efficiency reached 100%. The scale inhibition performance of the scale inhibitor in the reverse osmosis system was evaluated through a cross-flow high-pressure flat membrane instrument. The object under investigation was simulated seawater, and the mass of the permeate was automatically recorded by a balance for calculating the permeation flux. Samples 3.1 and 3.2 were added at 5.0 mg / L. After running for 24 hours, the membrane fluxes increased from 4% to over 65% and 68% respectively compared to those without the scale inhibitor. In the wide dosing range of 2.0-20.0 mg·L -1 , after running for 3 hours, the final membrane fluxes of Samples 3.1 and 3.2 increased from 27.5% to over 76% and 79% respectively compared to those without the scale inhibitor.

[0053] Compared with Example 1, changing the mass of sodium hydroxide in the alkaline gelatinization will reduce the scale inhibition efficiency of the scale inhibitor.

[0054] Example 4:

[0055] First, starch was used as the base material and mixed with an aqueous sodium hydroxide solution respectively. In Sample 4.1, the mass ratio of the base material to sodium hydroxide was 1:0.3, and it was stirred at 60 °C for 3 hours to fully gelatinize the starch; in Sample 4.2, the mass ratio of starch to sodium hydroxide was 1:0.3, and it was stirred at 95 °C for 0.5 hours to fully gelatinize the starch. After alkaline gelatinization treatment, potassium persulfate was added as an initiator. Subsequently, an aqueous solution of glycidyl methacrylate and acrylic acid with a mass ratio of 1:0.5:0.15 to the base material was added dropwise to the reaction system through a constant-pressure dropping funnel. After the dropping was completed, the reaction was carried out at 65 °C for 3 hours, and the whole reaction was maintained in a nitrogen atmosphere. After the reaction was completed, the pH value of the reaction solution was adjusted to neutral, and then ethanol or acetone was used as a precipitant to precipitate and separate the product, obtaining the final product, a green and highly efficient multi-functional modified environmental scale inhibitor. The scale inhibition performance of the scale inhibitor against CaSO 4 was evaluated using the national standard (GB / T 16632-2019). Among them, when the dosage of Sample 4.1 was 16.0 mg·L -1 , the static scale inhibition efficiency reached 100%; when the dosage of Sample 4.2 was 13.0 mg·L -1 , the static scale inhibition efficiency reached 100%. The scale inhibition performance of the scale inhibitor in the reverse osmosis system was evaluated through a cross-flow high-pressure flat membrane instrument. The object of investigation was simulated seawater, and the mass of the permeate was automatically recorded by an electronic balance for calculating the permeation flux. When Samples 4.1 and 4.2 were added at 5.0 mg / L and the operation was carried out for 24 hours, the membrane fluxes increased from 4% to more than 72% and 76% respectively compared with that without the scale inhibitor. In the wide dosage range of 2.0 - 20.0 mg·L -1 , after the operation for 3 hours, the final membrane fluxes of Samples 4.1 and 4.2 increased from 27.5% to more than 79% and 82% respectively compared with that without the scale inhibitor.

[0056] Compared with Example 1, changing the temperature and time in alkaline gelatinization would reduce the scale inhibition efficiency of the scale inhibitor.

[0057] Example 5:

[0058] First, starch was used as the base material and mixed with an aqueous sodium hydroxide solution respectively. The mass ratio of the base material to sodium hydroxide was 1:0.3, and it was stirred at 75 °C for 1 hour to fully gelatinize the starch. After alkaline gelatinization treatment, potassium persulfate was added as an initiator. Subsequently, an aqueous solution of glycidyl methacrylate and acrylic acid with a mass ratio of 1:0.2:0.5 (Sample 5.1) and 1:2:0.01 (Sample 5.2) to the base material was added dropwise to the reaction system through a constant-pressure dropping funnel. After the dropping was completed, the reaction was carried out at 65 °C for 3 hours, and the whole reaction was maintained in a nitrogen atmosphere. After the reaction was completed, the pH value of the reaction solution was adjusted to neutral, and then ethanol or acetone was used as a precipitant to precipitate and separate the product, obtaining the final product, a green and efficient multi-functional modified environmental scale inhibitor. The scale inhibition performance of the scale inhibitor against CaSO 4 was evaluated using the national standard (GB / T 16632-2019). Among them, when the dosage of Sample 5.1 was 17.0 mg·L -1 , the static scale inhibition efficiency reached 100%. When the dosage of Sample 5.2 was 20.0 mg·L -1 , the static scale inhibition efficiency reached 100%. The scale inhibition performance of the scale inhibitor in the reverse osmosis system was evaluated by a cross-flow high-pressure flat membrane instrument. The object of investigation was simulated seawater, and the mass of the permeate was automatically recorded by a balance for calculating the permeation flux. When Samples 5.1 and 5.2 were added at 5.0 mg / L and the operation was carried out for 24 hours, the membrane fluxes increased from 4% to more than 63% and 77% respectively compared with that without the scale inhibitor. In the wide dosage range of 2.0 - 20.0 mg·L -1 , after the operation for 3 hours, the final membrane fluxes of Samples 5.1 and 5.2 increased from 27.5% to more than 69% and 86% respectively compared with that without the scale inhibitor.

[0059] Compared with Example 1, changing the mass ratio of the feed will reduce the scale inhibition efficiency of the scale inhibitor.

[0060] Example 6:

[0061] First, starch was used as a substrate and mixed with an aqueous sodium hydroxide solution respectively. The mass ratio of the substrate to sodium hydroxide was 1:0.3, and stirring was carried out at 75 °C for 1 hour to fully gelatinize the starch. After alkaline gelatinization treatment, potassium persulfate was added as an initiator. Subsequently, an aqueous solution of glycidyl methacrylate and acrylic acid with a mass ratio of 1:0.5:0.15 to the substrate was added dropwise to the reaction system through a constant-pressure dropping funnel. Sample 6.1 was reacted at 50 °C for 4 hours; Sample 6.2 was reacted at 80 °C for 1 hour. The whole reaction was maintained in a nitrogen atmosphere. After the reaction, the pH value of the reaction solution was adjusted to neutral, and then ethanol or acetone was used as a precipitant to precipitate and separate the product, obtaining the final product, a green and highly efficient multi-functional modified environmental scale inhibitor. The national standard (GB / T 16632-2019) was used to evaluate the scale inhibition performance of the scale inhibitor against CaSO 4 The scale inhibition performance of 4 was evaluated. Among them, when the dosage of Sample 6.1 was 12.0 mg·L -1 , the static scale inhibition efficiency reached 100%. When the dosage of Sample 6.2 was 11.0mg·L -1 , the static scale inhibition efficiency reached 100%. The scale inhibition performance of the scale inhibitor in the reverse osmosis system was evaluated by a cross-flow high-pressure flat membrane instrument. The object of investigation was simulated seawater, and the mass of the permeate was automatically recorded by a balance for calculating the permeation flux. When Samples 6.1 and 6.2 were added at 5.0 mg / L and operated for 24 hours, the membrane flux increased from 4% to over 76% and 80% respectively compared with that without the scale inhibitor. In the wide dosage range of 2.0 - 20.0 mg·L -1 , after operating for 3 hours, the final membrane fluxes of Samples 6.1 and 6.2 increased from 27.5% to over 76% and 88% respectively compared with that without the scale inhibitor.

[0062] Compared with Example 1, changing the temperature and time of the grafting reaction will reduce the scale inhibition efficiency of the scale inhibitor.

[0063] The present invention is not limited to the specific technical solutions described in the above embodiments. Any technical solutions formed by equivalent substitution are within the protection scope required by the present invention.

Claims

1. A method for preparing a multi-functional modified environmentally friendly antiscalant, characterized in that : Using starch as raw material, potassium persulfate as initiator, glycidyl methacrylate GMA and acrylic acid AA as grafting monomers, a multifunctional modified environmentally friendly scale inhibitor is obtained through graft copolymerization. The preparation route is as follows: Where: m and n are positive integers; The specific steps are as follows: The starch is dispersed in an aqueous sodium hydroxide solution and alkaline gelatinized for 0.5 to 2 hours. After alkaline gelatinization, potassium persulfate is added as an initiator. Glycidyl methacrylate and acrylic acid solution are added to the mixed solution for grafting reaction. After the reaction is completed, ethanol or acetone is used as a precipitant for precipitation and separation to obtain a green and efficient multi-functional modified environmentally friendly scale inhibitor.

2. The method for preparing a multifunctional modified environmentally friendly antiscalant according to claim 1, characterized in that : The mass ratio of the starch to the sodium hydroxide is 1:0.1 to 1:2; The alkaline gelatinization reaction process controls the reaction temperature to be 60-95°C and the reaction time to be 0.5-3 hours; The mass ratio of the starch to the glycidyl methacrylate is 1:0.2 to 1:2, and the mass ratio of the starch to the acrylic acid is 1:0.01 to 1:0.5; The grafting reaction process controls the reaction temperature to be 50-80° C. and the reaction time to be 1-4 hours.

3. The method for preparing a multifunctional modified environmentally friendly antiscalant according to claim 1, characterized in that : The mass ratio of the starch to the sodium hydroxide is 1:0.3; The alkaline gelatinization reaction process controls the reaction temperature to 75°C and the reaction time to 1 hour; The mass ratio of the starch to the glycidyl methacrylate is 1:0.5, and the mass ratio of the starch to the acrylic acid is 1:0.15; The grafting reaction process controlled the reaction temperature to be 65° C. and the reaction time to be 3 hours.

4. A multi-functional modified environmentally friendly antiscalant prepared according to any one of the preparation methods of claims 1-3.

5. The use of the multifunctional modified environmentally friendly antiscalant according to claim 4, characterized in that : The multi-functional modified environmentally friendly antiscalant can not only effectively inhibit the formation of calcium sulfate scale in static water bodies, but also effectively alleviate the problem of membrane flux decline in reverse osmosis systems, thereby improving the stability of water treatment systems.

6. The use of the multifunctional modified environmentally friendly antiscalant according to claim 3, characterized in that : First, starch is mixed with an aqueous solution of sodium hydroxide, wherein the mass ratio of starch to sodium hydroxide is 1:0.3, and the mixture is stirred at 75°C to fully gelatinize the starch for 1 hour; after alkaline gelatinization treatment, potassium persulfate is added as an initiator; subsequently, a mixed aqueous solution of glycidyl methacrylate and acrylic acid in a mass ratio of 1:0.5:0.15 to starch is added dropwise to the reaction system through a constant pressure distribution funnel; after the addition is completed, the mixture is reacted at 65°C for 3 hours, and the entire reaction is maintained in a nitrogen atmosphere; after the reaction is completed, the pH value of the reaction solution is adjusted to neutral, and then ethanol or acetone is used as a precipitant to precipitate and separate the product, thereby obtaining the final product, a green and efficient multi-functional modified environmentally friendly scale inhibitor; The obtained multifunctional modified environmentally friendly antiscalant has a dosage of 10.0 mg·L -1 When the static scale inhibition efficiency of CaSO4 reaches 100%, the scale inhibitor 5.0 mg·L -1 After 24 hours of operation, the membrane flux increased to more than 83% compared with that without adding antiscalant.

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