A green and efficient multi-functional modified environmentally-friendly scale inhibitor for inhibiting calcium sulfate scale formation, and a preparation method and application thereof

Abstract

The application relates to a preparation method and application of a green and efficient multifunctional modified environment-friendly scale inhibitor capable of effectively inhibiting calcium sulfate scale bodies. The scale inhibitor takes starch as a raw material, adopts potassium persulfate as an initiator, introduces glycidyl methacrylate and acrylic acid as grafting monomers through a grafting reaction, and forms a modified scale inhibitor with multiple functions. The grafting chain containing carboxyl, ester and epoxy groups can be introduced on the polysaccharide chain, which endows the scale inhibitor with excellent chelation, dispersion and lattice distortion performance, and can effectively inhibit the formation and growth of scale bodies. The scale inhibitor prepared by the application can not only effectively inhibit the generation of calcium sulfate scale bodies in static water bodies, but also has remarkable application effect in a reverse osmosis system, effectively alleviates the problem of membrane flux decline, and thus improves the stability of a water treatment system. Not only is the water treatment efficiency improved, but also the environment-friendly requirement is met, and a new strategy is provided for the control of calcium sulfate scale bodies.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of green efficient inhibition of calcium sulfate scale formation Multifunctional modified environmentally friendly scale inhibitor and its preparation method and application, belong to water environment processing technical field. BACKGROUND

[0002] With the expansion of global city size and the continuous growth of population, the demand for fresh water is also rising, which undoubtedly further highlights the problem of fresh water resource shortage. 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 desalination process due to its low energy consumption and high desalination efficiency, and is one of the most common desalination technologies. However, reverse osmosis technology faces a series of challenges in practical application. Among them, due to the existence of alkaline earth metals (such as calcium, magnesium, etc.) in water, these alkaline earth metals will react with anions in water in reverse osmosis system, resulting in the formation of scale, especially in the membrane surface or the pores of the membrane. The 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 is also a common problem in the circulating cooling water system in many industrial fields (such as power generation, chemical industry and petroleum industry, etc.), the formation of scale not only affects the heat exchange efficiency and increases the energy consumption, but also may cause potential danger. Therefore, effectively inhibiting the formation of scale has important practical significance in reverse osmosis and circulating cooling water system.

[0003] In reverse osmosis system, direct addition of scale inhibitor is one of the common methods to prevent scale formation, which is popular due to its high efficiency, simple operation and low cost. However, although traditional phosphorus-containing and organic synthetic polymer scale inhibitors perform well in inhibiting scale formation, the environmental problems caused by them cannot be ignored. Especially for phosphorus-containing scale inhibitors, although they have high scale inhibition efficiency, the residual phosphorus elements may cause water eutrophication, which may lead to a series of ecological environmental problems. Therefore, the academic and industrial circles are actively exploring solutions to this problem, and gradually developing towards the research direction of non-phosphorus scale inhibitors, such as organic synthetic polymer scale inhibitors. However, although organic synthetic polymer scale inhibitors perform well in inhibiting scale formation, they are often multi-component copolymers, which not only have high cost and difficult to control molecular structure, but also are difficult to biodegrade in natural environment after being discarded, which also has potential harm to the environment. In recent years, polyaspartic acid as a kind of green scale inhibitor has attracted widespread attention and has great application potential, but it also has the disadvantages of relatively complex preparation conditions, single functional group and containing nutrient element nitrogen in structure. Therefore, developing new type of efficient scale inhibitor with non-phosphorus, non-nitrogen, green environmental protection, biodegradable and good cost performance has become an important topic in this field.

[0004] Natural polymers, such as starch, cellulose, lignin and chitosan, are derived from plants, animals and microorganisms and widely distributed in nature; these materials not only have good biodegradability, but also often have the advantages of economy and environmental friendliness. Although most natural polymers do not have scale inhibition effect, but through appropriate physical and chemical modification methods, they can have good scale inhibition performance. In fact, the research on natural polymer scale inhibitors, such as lignin sulfonate, has attracted widespread attention and application as early as the 1960s. However, it was soon replaced by a large number of synthetic scale inhibitors, such as organic phosphorus scale inhibitors, so the research on natural polymer scale inhibitors is far from systematic and comprehensive, and the scale inhibition performance also needs to be further improved.

[0005] In addition, among different chemical modification methods, graft copolymerization is a commonly used polymer chemical modification method, which can introduce various functional groups on the polymer chain and construct unique branched structure, so that the polymer can have the advantages of both the main chain and the grafted side chain functional groups, and effectively improve its application performance. However, in the past research, after excessive addition of scale inhibitors such as hydroxyethylidene diphosphonic acid and aminotri(methylene) phosphonic acid, the scale inhibitors may be entangled and adsorbed on the surface of the membrane, thereby causing the decrease of membrane flux. SUMMARY

[0006] The technical problem solved by the present application is to provide a natural polymer starch with excellent performance, low price and wide source as a raw material, and through molecular design and functional modification technology, a series of modified environmentally friendly scale inhibitors with excellent scale inhibition effect and environmental protection characteristics are developed, which can effectively inhibit the scaling of calcium sulfate, and can control the membrane pollution in the reverse osmosis system within a wide dosage window. The multi-functional group modified environmentally friendly scale inhibitor can not only effectively inhibit the formation of calcium sulfate scale in static water body, but also effectively alleviate the problem of membrane flux decrease in reverse osmosis system, thereby improving the stability of water treatment system. Due to its non-ionic nature, it is not easy to cause flocculation effect, so as not to pollute the reverse osmosis membrane at high dosage. Through the application in static experiment and reverse osmosis experiment, the formation of calcium sulfate can be effectively inhibited at low and high dosages, showing good scale inhibition performance, which can be applied to control the scaling of circulating cooling water and reverse osmosis system.

[0007] In order to solve the above technical problems, the technical scheme provided by the present application is: a preparation method of a multi-functional group modified environmentally friendly scale inhibitor, taking starch as a raw material, potassium persulfate as an initiator, glycidyl methacrylate GMA and acrylic acid AA as grafting monomers, and obtaining the multi-functional group modified environmentally friendly scale inhibitor through graft copolymerization reaction, and the preparation route is as follows:

[0008]

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

[0010] The specific steps are as follows:

[0011] The starch is dispersed in the sodium hydroxide aqueous solution, and subjected to alkaline gelatinization for 0.5-2 hours; after the alkaline gelatinization treatment, potassium persulfate is added as an initiator; the glycidyl methacrylate and the acrylic acid solution are added into the mixed solution to perform grafting reaction; after the reaction is completed, ethanol or acetone is used as a precipitant to perform separation and precipitation, and a green and efficient multi-functional modified environmental protection scale inhibitor is obtained.

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

[0013] The alkaline gelatinization reaction process controls the reaction temperature to be 60-95 DEG C, and the reaction time is 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] The grafting reaction process controls the reaction temperature to be 50-80 DEG C, and the reaction time is 1-4 hours.

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

[0017] The alkaline gelatinization reaction process controls the reaction temperature to be 75 DEG C, and the reaction time is 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] The grafting reaction process controls the reaction temperature to be 65 DEG C, and the reaction time is 3 hours.

[0020] In order to solve the above technical problems, another technical scheme provided by the application is to prepare the multi-functional modified environmental protection scale inhibitor.

[0021] In order to solve the above technical problems, another technical scheme provided by the application is the application of the multi-functional modified environmental protection scale inhibitor. The multi-functional modified environmental protection scale inhibitor can not only effectively inhibit the generation 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.

[0022] Preferably, first, the starch is mixed with an aqueous sodium hydroxide solution, wherein the mass ratio of starch to sodium hydroxide is 1:0.3, and the starch is stirred at 75°C for 1 hour to allow the starch to be fully gelatinized; after the alkaline gelatinization treatment, potassium persulfate is added as an initiator; subsequently, a mixed aqueous solution of glycidyl methacrylate and acrylic acid with a mass ratio of 1:0.5:0.15 is added dropwise to the reaction system through a constant pressure distribution funnel; after the dropwise addition is completed, the reaction is carried out at 65°C for 3 hours, and the entire reaction is kept 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 multifunctional modified environmentally-friendly scale inhibitor; the multifunctional modified environmentally-friendly scale inhibitor obtained has a CaSO4 static scale inhibition efficiency of 100% when the dosage is 10.0 mg·L -1 , a CaSO4 dynamic scale inhibition efficiency of 100% when the dosage is 5.0 mg·L -1 , and a membrane flux increase of more than 83% after running for 24 hours compared with no scale inhibitor.

[0023] The beneficial effects of the present application are as follows:

[0024] 1. The green and efficient multifunctional modified environmentally-friendly scale inhibitor material obtained by the preparation method has carboxyl, ester and epoxy groups and other functional groups. Unlike the use of a single anionic functional group for modification in the past, the ester and epoxy groups are non-ionic functional groups, which not only can effectively delay the formation of calcium sulfate crystals through chelation, but also exhibit excellent dispersion and lattice distortion effects. Moreover, due to the non-ionic nature, the scale inhibitor is not prone to flocculation, thereby not easily polluting the reverse osmosis membrane at a high dosage. Through static experiments, the scale inhibitor can effectively inhibit the formation of calcium sulfate at a low dosage of 10 mg·L -1 and a high dosage of 80 mg·L -1 , showing good scale inhibition performance. In the application of reverse osmosis experiments, the scale inhibitor can effectively inhibit the formation of calcium sulfate at a low dosage of 2 mg·L -1 and a high dosage of 20 mg·L -1 , showing good scale inhibition performance.

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

[0026] 3. The preparation method of the green and efficient multifunctional modified environmentally-friendly scale inhibitor material is simple to operate, short in synthesis time, low in cost, and suitable for large-scale industrial production, and is an economical preparation method for obtaining a high-quality water treatment agent.

[0027] 4. The green and efficient multifunctional modified environmentally friendly scale inhibitor material of the present invention has good scale inhibition performance. It can interact with scale-forming substances through complexation and dispersion stabilization effects, reduce the crystal nucleation rate, significantly prolong the crystallization induction time, and inhibit the formation of calcium sulfate scale, thereby effectively delaying the scaling and fouling of the membrane surface and alleviating problems such as decreased membrane flux.

[0028] 5. Green and efficient multifunctional modified environmentally friendly scale inhibitor materials have a wide dosage window, and there is no need to strictly control the dosage during use.

[0029] 6. The green and efficient multifunctional modified environmentally friendly scale inhibitor material uses natural high molecular starch as the base material, which is biodegradable, low in cost, and non-toxic, and will not cause secondary pollution to water bodies.

[0030] 7. Example 1 is the best example. Figure 4 This study evaluates the scale inhibition efficiency of a green, efficient, multifunctional modified environmentally friendly scale inhibitor in a static scale inhibition experiment. The scale inhibition performance of this green, efficient, multifunctional modified environmentally friendly scale inhibitor on CaSO4 was assessed using the national standard (GB / T 16632-2019). The dosage was 10.0 mg·L⁻¹. -1 At that time, the static scale inhibition efficiency reached 100% ( Figure 4 ).

[0031] The scale inhibition performance of scale inhibitors in reverse osmosis systems was evaluated using a cross-flow high-pressure flat sheet membrane instrument. The test object was simulated seawater, and the mass of the permeate was automatically recorded using a balance to calculate the permeate flux. Figure 5 It can be seen from the addition of 5.0 mg·L scale inhibitor -1 After 24 hours of operation, the membrane flux increased from 4% to over 83% compared to the untreated scale inhibitor, significantly alleviating membrane fouling. Furthermore, under the same dosage conditions, compared to two commercial scale inhibitors (aminotrimethylenetetramine and polyacrylic acid (weight-average molecular weight 3000)), the green and efficient multifunctional modified environmentally friendly scale inhibitor achieved a final membrane flux of 83.2%, while aminotrimethylenetetramine and polyacrylic acid achieved final membrane fluxes of 74.4% and 70.2%, respectively. Figure 5 This not only achieves better membrane flux, but is also more environmentally friendly because it is phosphorus-free. Figure 6 It can be seen that the green and efficient multifunctional modified environmentally friendly scale inhibitor at 2.0 mg·L⁻¹ -1 At the dosage of [specific dosage], after 3 hours of operation, the membrane flux increased from 27.5% to 93.2% compared to the level without scale inhibitor, at 20.0 mg·L [specific dosage]. -1 Even with excessive dosage, the final membrane flux can still be maintained at 95.5%, thus it has a wide dosage window, which can reduce fouling on the membrane surface within a wide range. Attached Figure Description

[0032] The application will be further described below with reference to the accompanying drawings.

[0033] Figure 1 Synthesis scheme of green and efficient multifunctional modified environmentally friendly scale inhibitor.

[0034] Figure 2 Infrared spectrum of green and efficient multifunctional modified environmentally friendly scale inhibitor material.

[0035] Figure 3 Nuclear magnetic hydrogen spectrum of green and efficient multifunctional modified environmentally friendly scale inhibitor material.

[0036] Figure 4 Inhibition efficiency of green and efficient multifunctional modified environmentally friendly scale inhibitor material in static scale inhibition experiment.

[0037] Figure 5 Effect of no addition and addition of green and efficient multifunctional modified environmentally friendly scale inhibitor material and commercial scale inhibitor on reverse osmosis membrane flux.

[0038] Figure 6 Effect of no addition and different addition amounts of green and efficient multifunctional modified environmentally friendly scale inhibitor material on reverse osmosis membrane flux. DETAILED DESCRIPTION

[0039] The application will be further described below with reference to the accompanying drawings.

[0040] Example 1:

[0041] A green and efficient multifunctional modified environmentally friendly scale inhibitor, which is prepared by using starch as raw material, potassium persulfate as initiator, glycidyl methacrylate (GMA) and acrylic acid (AA) as grafting monomers, and through grafting copolymerization reaction to obtain a green and efficient multifunctional modified environmentally friendly scale inhibitor (weight average molecular weight is about 2.3×10 5 g / mol) for calcium sulfate scale, and the preparation route is as shown below:

[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, wherein the mass ratio of starch to sodium hydroxide is 1:0.3, and stir at 75°C to gelatinize the starch for 1 hour. After the alkaline gelatinization treatment, add potassium persulfate as an initiator. Then, drop a mixed aqueous solution of glycidyl methacrylate and acrylic acid with a mass ratio of 1:0.5:0.15 to the reaction system through a constant pressure distribution funnel. After the drop is completed, react at 65°C for 3 hours, and the entire reaction is kept in a nitrogen atmosphere. After the reaction is completed, adjust the pH of the reaction solution to neutral, then use ethanol or acetone as a precipitant to precipitate and separate the product, and obtain the final product, a green and efficient multifunctional modified environmentally friendly scale inhibitor.

[0045] The infrared spectra of the green and efficient multifunctional modified environmentally friendly scale inhibitor and starch are shown in Figure 2 . As can be seen from Figure 2 , the green and efficient multifunctional modified environmentally friendly scale inhibitor has new characteristic peaks at 1701 cm -1 , 1560 cm -1 and 1255 cm -1 , which correspond to the characteristic peaks of carbonyl, ester and epoxy groups, respectively; thus proving that the green and efficient multifunctional modified environmentally friendly scale inhibitor material is successfully prepared. In addition, as shown in Figure 3 , in the nuclear magnetic hydrogen spectrum, new characteristic peaks appear at 0.93-1.08 ppm, 1.8-2.0 ppm and 5.3-5.7 ppm due to the proton vibration of -CH3, -CH2- and -COOH, respectively.

[0046] Figure 4 The scale inhibition efficiency of the green and efficient multifunctional modified environmentally friendly scale inhibitor material in the static scale inhibition experiment. The national standard (GB / T 16632-2019) was used to evaluate the scale inhibition performance of the green and efficient multifunctional modified environmentally friendly scale inhibitor on CaSO4. 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 was evaluated by a cross-flow high-pressure flat plate membrane instrument, and the object of investigation was simulated seawater. The mass of the permeate was automatically recorded by a balance, which was used to calculate the permeation flux. As can be seen in Figure 5 , the addition of the scale inhibitor 5.0 mg·L -1The membrane flux was increased from 4% to more than 83% compared to the case without scale inhibitor after 24 hours of operation, and the membrane fouling was greatly alleviated. In addition, compared with two commercial scale inhibitors (aminotriphosphoric acid and polyacrylic acid (weight average molecular weight 3000)), the final membrane flux of the green and efficient multifunctional modified environmentally friendly scale inhibitor was 83.2%, while the final membrane flux of aminotriphosphoric acid and polyacrylic acid was 74.4% and 70.2% (Formula 1) Figure 5 ), not only obtaining a better membrane flux, but also being more environmentally friendly due to the absence of phosphorus. Figure 6 It can be seen that the green and efficient multifunctional modified environmentally friendly scale inhibitor has a wide range of dosage windows, and can slow down the scaling on the membrane surface in a wide range. -1 The membrane flux was increased from 27.5% to 93.2% compared to the case without scale inhibitor after 3 hours of operation at a dosage of 2.0 mg·L -1 The final membrane flux can still be maintained at 95.5% at an excess dosage of 20.0 mg·L -1 Therefore, it has a wide range of dosage windows and can slow down the scaling on the membrane surface in a wide range.

[0048] Example 2:

[0049] First, cellulose (sample 2.1) and chitosan (sample 2.2) were mixed with sodium hydroxide aqueous solution as substrates, respectively, with a mass ratio of substrate to sodium hydroxide of 1:0.3, and stirring at 75°C to allow the starch to be fully gelatinized for 1 hour. After the alkaline gelatinization treatment, potassium persulfate was added as an initiator. Subsequently, a mixture of glycidyl methacrylate and acrylic acid with a mass ratio of 1:0.5:0.15 was added to the reaction system through a constant pressure distribution funnel. After the addition was completed, the reaction was carried out at 65°C for 3 hours, and the whole reaction was kept 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 of the green and efficient multifunctional modified environmentally friendly scale inhibitor. The scale inhibition performance of the scale inhibitor on CaSO4 was evaluated according to the national standard (GB / T 16632-2019). The static scale inhibition efficiency of sample 2.1 reached 100% at a dosage of 15.0 mg·L -1 , and the static scale inhibition efficiency of sample 2.2 reached 100% at a dosage of 18.0 mg·L -1 The scale inhibition performance of the scale inhibitor in the reverse osmosis system was evaluated by a cross-flow high-pressure flat plate membrane instrument, and the object of investigation was simulated seawater. The mass of the permeate was automatically recorded by a balance, which was used to calculate the permeation flux. The membrane flux was increased from 4% to more than 72% and 70%, respectively, compared to the case without scale inhibitor after 24 hours of operation at a dosage of 5.0 mg / L of samples 2.1 and 2.2. The green and efficient multifunctional modified environmentally friendly scale inhibitor has a wide range of dosage windows and can slow down the scaling on the membrane surface in a wide range. -1The final membrane fluxes of samples 2.1 and 2.2 were increased by more than 85% and 82% respectively compared to 27.5% without scale inhibitor after 3 hours of operation.

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

[0051] Example 3:

[0052] First, starch was mixed with an aqueous sodium hydroxide solution as a substrate, and the mass ratio of the substrate to sodium hydroxide in sample 3.1 was 1:0.1. The starch was stirred at 75°C for 1 hour to complete gelatinization. In sample 3.2, the mass ratio of the substrate to sodium hydroxide was 1:2, and the starch was stirred at 75°C for 1 hour to complete gelatinization. After the alkaline gelatinization treatment, potassium persulfate was added 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 substrate was added dropwise to the reaction system through a constant pressure distribution funnel. After the dropwise addition was completed, the reaction was carried out at 65°C for 3 hours, and the entire 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, efficient, multi-functional modified environmentally friendly scale inhibitor. The scale inhibition performance of the scale inhibitor on CaSO4 was evaluated according to the national standard (GB / T 16632-2019). When the dosage of sample 3.1 was 30.0 mg·L -1 , the static scale inhibition efficiency reached 100%, and when the dosage 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 by a cross-flow high-pressure flat membrane instrument, and the object of investigation was simulated seawater. The mass of the permeate was automatically recorded by a balance, which was used to calculate the permeation flux. After 24 hours of operation, the membrane fluxes of samples 3.1 and 3.2 were increased by more than 65% and 68% respectively compared to 4% without scale inhibitor. In a wide dosage range of 2.0-20.0 mg·L -1 , the final membrane fluxes of samples 3.1 and 3.2 were increased by more than 76% and 79% respectively compared to 27.5% without scale inhibitor after 3 hours of operation.

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

[0054] Example 4:

[0055] First, starch was mixed with an aqueous sodium hydroxide solution as a base material. In sample 4.1, the mass ratio of the base material to sodium hydroxide was 1:0.3, and the starch was fully gelatinized by stirring at 60 °C for 3 hours. In sample 4.2, the mass ratio of the starch to sodium hydroxide was 1:0.3, and the starch was fully gelatinized by stirring at 95 °C for 0.5 hours. After the alkaline gelatinization treatment, potassium persulfate was added 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 base material was added dropwise to the reaction system through a constant pressure distribution funnel. After the addition was completed, the reaction was carried out at 65 °C for 3 hours, and the entire reaction was maintained in a nitrogen atmosphere. After the reaction was completed, the pH 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, efficient, and multi-functional modified environmentally friendly scale inhibitor. The scale inhibition performance of the scale inhibitor on CaSO4was evaluated according to the national standard (GB / T 16632-2019). The static scale inhibition efficiency of sample 4.1 reached 100% when the dosage was 16.0 mg·L -1 , and the static scale inhibition efficiency of sample 4.2 reached 100% when the dosage was 13.0 mg·L -1 . The scale inhibition performance of the scale inhibitor in a reverse osmosis system was evaluated by a cross-flow high-pressure flat plate membrane instrument, and the object of investigation was simulated seawater. According to the automatic recording of the mass of the permeate by the balance, the permeation flux was calculated. After 24 hours of operation, the membrane flux was increased by more than 72% and 76% compared to the case without adding the scale inhibitor, when 5.0 mg / L of samples 4.1 and 4.2 were added, respectively. In a wide dosage range of 2.0-20.0 mg·L -1 , after 3 hours of operation, the final membrane flux of samples 4.1 and 4.2 was increased by more than 79% and 82% compared to the case without adding the scale inhibitor, respectively.

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

[0057] Example 5:

[0058] First, the starch was mixed with an aqueous solution of sodium hydroxide as the base material, and the mass ratio of the base material to sodium hydroxide was 1:0.3. The starch was fully gelatinized by stirring at 75°C for 1 hour. After the alkaline gelatinization treatment, potassium persulfate was added as an initiator. Subsequently, a mixed aqueous solution of glycidyl methacrylate and acrylic acid with a mass ratio of 1:0.2:0.5 (sample 5.1), 1:2:0.01 (sample 5.2) was added to the reaction system through a constant pressure distribution funnel. After the addition was completed, the reaction was carried out at 65°C for 3 hours, and the whole reaction was kept 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 of green efficient multi-functional modified environmentally friendly scale inhibitor. The scale inhibition performance of the scale inhibitor on CaSO4 was evaluated according to the national standard (GB / T 16632-2019). The static scale inhibition efficiency of sample 5.1 reached 100% when the dosage was 17.0 mg·L -1 , and the static scale inhibition efficiency of sample 5.2 reached 100% when the dosage was 20.0 mg·L -1 . The scale inhibition performance of the scale inhibitor in the reverse osmosis system was evaluated by a cross-flow high-pressure flat plate membrane instrument, and the object of investigation was simulated seawater. According to the automatic recording of the mass of the permeate, the permeation flux was calculated. After adding 5.0 mg / L of samples 5.1 and 5.2 and running for 24 hours, the membrane flux was increased by more than 63% and 77%, respectively, compared with that without adding the scale inhibitor. In the wide dosage range of 2.0-20.0 mg·L -1 , after running for 3 hours, the final membrane flux of samples 5.1 and 5.2 was increased by more than 69% and 86%, respectively, compared with that without adding the scale inhibitor.

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

[0060] Example 6:

[0061] First, the starch was mixed with an aqueous sodium hydroxide solution as a base material, and the mass ratio of the base material to sodium hydroxide was 1:0.3. The starch was fully gelatinized by stirring at 75°C for 1 hour. After the alkaline gelatinization treatment, potassium persulfate was added 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 base material was added dropwise into the reaction system through a constant pressure distribution funnel. Sample 6.1 was reacted at 50°C for 4 hours; sample 6.2 was reacted at 80°C for 1 hour. The entire reaction was maintained in a nitrogen atmosphere. After the reaction was completed, the pH 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, efficient, multi-functional modified environmentally friendly scale inhibitor. The scale inhibitor was evaluated for its scale inhibition performance on CaSO4 using the national standard (GB / T 16632-2019). The static scale inhibition efficiency of sample 6.1 reached 100% when the dosage was 12.0 mg·L -1 , and the static scale inhibition efficiency of sample 6.2 reached 100% when the dosage was 11.0 mg·L -1 . The scale inhibition performance of the scale inhibitor in a reverse osmosis system was evaluated by a cross-flow high-pressure flat plate membrane instrument, and the object of investigation was simulated seawater. The mass of the permeate was automatically recorded by a balance, which was used to calculate the permeation flux. After 24 hours of operation, the membrane flux was increased by more than 76% and 80% compared to the case without adding the scale inhibitor, when 5.0 mg / L of samples 6.1 and 6.2 were added. Within a wide dosage range of 2.0-20.0 mg·L -1 , after 3 hours of operation, the final membrane flux of samples 6.1 and 6.2 was increased by more than 76% and 88% compared to the case without adding the scale inhibitor.

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

[0063] The present application is not limited to the specific technical solutions described in the above examples, and any technical solution formed by equivalent replacement is within the scope of protection required by the present application.

Claims

1. The application of a multifunctional modified environmentally friendly scale inhibitor, characterized in that: First, starch and sodium hydroxide aqueous solution were mixed at a mass ratio of 1:0.

3. The mixture was stirred at 75°C to allow the starch to gelatinize completely for 1 hour. After alkaline gelatinization, potassium persulfate was added as an initiator. Subsequently, a mixed aqueous solution of glycidyl methacrylate and acrylic acid at a mass ratio of 1:0.5:0.15 (to starch) was added dropwise to the reaction system through a constant-pressure distributing funnel. After the addition was completed, the reaction was carried out at 65°C for 3 hours, with the entire reaction maintained under a nitrogen atmosphere. After the reaction was completed, the pH of the reaction solution was adjusted to neutral, and then ethanol or acetone was used as a precipitant to precipitate and separate the product, yielding the final product: a green, efficient, multifunctional modified environmentally friendly scale inhibitor. The obtained multifunctional modified environmentally friendly scale inhibitor was applied at a dosage of 10.0 mg·L⁻¹. -1 At that time, the static scale inhibition efficiency of CaSO4 reached 100% with the addition of 2.0 mg·L⁻¹ scale inhibitor. -1 After 3 hours of operation, the membrane flux increased to 93.2% compared to the untreated membrane, at 20.0 mg·L⁻¹. -1 Even with excessive dosage, the final membrane flux can still be maintained at 95.5%, thus it has a wide dosage window, which can reduce fouling on the membrane surface within a wide range.

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