Carbonized nitrogen quantum dot scale inhibitor with fucoidan carboxylate as stabilizer and preparation method thereof

Abstract

The present invention discloses a carbonized nitrogen quantum dot scale inhibitor using fucoidan carboxylate as a stabilizer and a preparation method thereof. The carbonized nitrogen quantum dot scale inhibitor uses an amino acid polymer as a carbon and nitrogen source and a polysaccharide carboxylate as a stabilizer, and is prepared through a thermal decomposition reaction. Using the amino acid polymer as a carbon and nitrogen source and the polysaccharide carboxylate as a stabilizer, carbonized nitrogen quantum dots with scale inhibition and biodegradability are prepared. These quantum dots can not only effectively inhibit the formation of calcium sulfate scale in cooling circulating water systems but can also naturally degrade in aqueous environments. They can replace currently used synthetic scale inhibitors based on organic phosphonic acid and polyacrylic acid, which do not meet environmental requirements, and have great prospects for industrial application.

Description

Technical Field

[0001] The present invention belongs to the field of advanced materials, and in particular relates to a scale inhibitor using fucoidan carboxylate as a stabilizer and a preparation method thereof. Background Art

[0002] To conserve water resources and save costs, circulating cooling water systems are widely used in various industries. However, this system suffers from a serious scale deposition problem. This is mainly manifested in scale adsorbed on the surface of pipes or equipment, which can hinder heat transfer, reduce water flow, or clog membrane filters. Studies have shown that the addition of scale inhibitors can effectively alleviate scale deposition. Currently, the industry commonly uses low-toxic organic phosphonic acids and polyacrylic acids as scale inhibitors, which pose certain hazards to the ecological environment and can lead to eutrophication of water bodies and microplastic pollution. There is an urgent need to develop green, efficient, and biodegradable scale inhibitors as alternatives. Summary of the Invention

[0003] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0004] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0005] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a carbonized nitrogen quantum dot scale inhibitor using fucoidan carboxylate as a stabilizer.

[0006] As a preferred embodiment of the preparation method of the present invention, the carbonized nitrogen quantum dot scale inhibitor is prepared by thermal decomposition reaction using amino acid polymer as carbon source and nitrogen source and polysaccharide carboxylate as stabilizer.

[0007] As a preferred embodiment of the preparation method of the present invention, the amino acid polymer is obtained by polymerization of aspartic acid; and the polysaccharide carboxylate is obtained by esterification of natural product polysaccharide macromolecules dissolved in imidazoline ionic liquid with amino acid micromolecules.

[0008] As a preferred embodiment of the preparation method of the present invention, the natural product polysaccharide macromolecule includes fucoidan or other water-soluble polysaccharides; the amino acid small molecule includes one of aspartic acid and glutamic acid among the dicarboxylic amino acids; and the imidazoline ionic liquid includes one of imidazoline hexafluorophosphate, imidazoline methanesulfonate, and serine imidazoline.

[0009] As a preferred embodiment of the preparation method of the present invention, the thermal decomposition reaction temperature is 80-95° C. and the reaction time is 12-36 hours.

[0010] As a preferred embodiment of the preparation method of the present invention, the mass ratio of the fucoidan to the dicarboxylic amino acid is 3:1 to 1:1.

[0011] Another object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a carbonized nitrogen quantum dot scale inhibitor using fucoidan carboxylate as a stabilizer.

[0012] As a preferred embodiment of the preparation method of the present invention, the fucoidan is dissolved in an imidazoline ionic liquid to obtain a first solution;

[0013] Adding dicarboxyl amino acid to the first solution, using molecular sieve ZSM-5 as a catalyst, causing esterification reaction in a reactor, centrifuging, washing with ethanol, centrifuging and freeze-drying to obtain a fucoidan carboxylate stabilizer;

[0014] calcining polyaspartic acid at high temperature to obtain carbonized nitrogen quantum dot raw material;

[0015] Dissolving the carbonized nitrogen quantum dot raw material and the fucoidan carboxylate stabilizer in an alkaline aqueous solution to prepare a reaction solution with a mass concentration of 7 to 14 wt % to obtain a second solution;

[0016] The second solution is introduced with oxygen, stirred and heated, subjected to thermal decomposition reaction, centrifuged, purified and freeze-dried to obtain carbonized nitrogen quantum dot scale inhibitor.

[0017] As a preferred embodiment of the preparation method of the present invention, wherein: the dicarboxyl amino acid is added to the first solution, and the mass fraction of fucoidan in the first solution is 3% to 10%.

[0018] As a preferred embodiment of the preparation method of the present invention, the carbonized nitrogen quantum dot raw material and the fucoidan carboxylate stabilizer are dissolved in an alkaline aqueous solution, wherein the mass ratio of the carbonized nitrogen quantum dot raw material to the fucoidan carboxylate stabilizer is 3:1 to 1:1, and the alkaline aqueous solution includes one of sodium hydroxide, sodium carbonate, and sodium bicarbonate, and has a pH of 7.2 to 8.2.

[0019] Another object of the present invention is to overcome the deficiencies in the prior art and provide a carbonized nitrogen quantum dot scale inhibitor with fucoidan carboxylate as a stabilizer for use in alleviating scale deposition.

[0020] As a preferred embodiment of the preparation method of the present invention, the method comprises the following steps: first preparing a mixed solution of calcium chloride and sodium sulfate, then adding 0.1 to 2.5 mg of the prepared green carbonized nitrogen quantum dot scale inhibitor with fucoidan carboxylate as a stabilizer to prepare a scale inhibitor test solution; after the completion of the titration, the remaining Ca in the solution is titrated with EDTA. 2+ The scale inhibition efficiency of carbonized nitrogen quantum dots on calcium sulfate was calculated by the change of calcium ion concentration before and after adding the scale inhibitor.

[0021] As a preferred embodiment of the preparation method of the present invention, the concentration of the scale inhibitor test solution in the application is 1-25 mg / L, the test temperature is 30-60° C., and the temperature is kept constant for 24 hours.

[0022] Beneficial effects of the present invention:

[0023] (1) The present invention uses amino acid polymers as carbon and nitrogen sources and polysaccharide carboxylic acid esters as stabilizers to prepare carbonized nitrogen quantum dots with scale inhibition and biodegradability. These quantum dots can not only effectively inhibit the formation of calcium sulfate scale in cooling circulating water systems, but can also be naturally degraded in water environments. They can replace the currently used organic phosphonic acid and polyacrylic acid synthetic scale inhibitors that do not meet environmental protection requirements, and have great prospects for industrial application.

[0024] (2) The present invention uses the green compound polyaspartic acid as a raw material to obtain a carbon and nitrogen source through a pyrolysis reaction, and uses amino acid-modified polysaccharide macromolecules as a passivator and stabilizer to prepare carboxyl-functionalized carbonized nitrogen quantum dots through a simple pyrolysis reaction. The carbonized nitrogen quantum dots obtained in this embodiment are green and environmentally friendly, with stable fluorescence, good water solubility, and efficient scale inhibition and biodegradability.

[0025] (3) The present invention intends to use natural product polysaccharide macromolecules and amino acid small molecules as raw materials to prepare carbonized nitrogen quantum dot green scale inhibitors through a simple synthesis method. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0027] Figure 1 This is the microscopic morphology of the carboxyl-functionalized carbonitride quantum dots in Example 1 of the present invention.

[0028] Figure 2 is the fluorescence intensity of the carboxyl-functionalized carbonitride quantum dots in Example 1 of the present invention.

[0029] Figure 3 This is the degradation rate of carboxyl-functionalized carbonized nitrogen quantum dots in an aqueous environment according to Example 1 of the present invention.

[0030] Figure 4 This is a graph showing the relationship between the calcium sulfate scale inhibition rate and the addition concentration of carbonized nitrogen quantum dots at different temperatures in Example 9 of the present invention.

[0031] Figure 5 This is a graph showing the relationship between the scale inhibition rate of calcium sulfate and the addition concentration of polyethylene glycol sulfur quantum dots at different temperatures in comparative example 1 of the present invention.

[0032] Figure 6 This is a relationship diagram between the calcium sulfate scale inhibition rate and the addition concentration of citric acid carbon quantum dots at different temperatures in comparative example 2 of the present invention.

[0033] Figure 7 This is a diagram showing the microscopic morphology of calcium sulfate scale before and after adding carboxyl functionalized carbonized nitrogen quantum dots in Example 1 of the present invention. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0035] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0036] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0037] Unless otherwise specified, the following examples are all commercially available products. Fucoidan and other polymers, with molecular weights between 1000 and 10,000 g / mol, were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; imidazoline hexafluorophosphate was purchased from Shandong West Asia Chemical Co., Ltd.; imidazoline methanesulfonate was purchased from Wuhan Smack Biotechnology Co., Ltd.; and serine imidazoline was purchased from Hubei Jiufenglong Chemical Co., Ltd.; and conventional reagents such as polyaspartic acid, aspartic acid, glutamic acid, calcium chloride, sodium sulfate, and EDTA were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0038] Example 1

[0039] The present invention provides a method for preparing a green carbonized nitrogen quantum dot scale inhibitor using fucoidan carboxylate as a stabilizer:

[0040] (1) 3 g of fucoidan was added to 80 mL of imidazoline hexafluorophosphate and stirred thoroughly to dissolve. Then, 1 g of aspartic acid and 0.5 g of ZSM-5 catalyst were added, mixed and stirred evenly, and then transferred to a polytetrafluoroethylene reactor. The mixture was esterified at 90 ° C for 24 h. After centrifugation, the precipitate was collected, washed with anhydrous ethanol, filtered, and freeze-dried to obtain a fucoidan carboxylate stabilizer.

[0041] (2) 10g of polyaspartic acid was placed in a crucible and transferred to a muffle furnace for calcination at 550°C for 12h to obtain a carbonized nitrogen quantum dot raw material. 5g of carbonized nitrogen quantum dot raw material and 3g of fucoidan carboxylate stabilizer were added to 100mL of sodium carbonate aqueous solution with pH=8.0, stirred and dissolved, oxygen was continuously introduced, refluxed and stirred, and thermally decomposed at 90°C for 24h. After the reaction, the lower precipitate was centrifuged and purified with a 300Da dialysis membrane and freeze-dried to obtain a green carbonized nitrogen quantum dot scale inhibitor with fucoidan carboxylate as a stabilizer.

[0042] Depend on Figures 1 to 3 It can be seen that Figure 1 The prepared carbonized nitrogen quantum dots are evenly dispersed, have regular morphology, and exhibit spherical micro-nanostructures with an average diameter of about 3-8 nm. Figure 2 The fluorescence intensity spectrum of the prepared carbonized nitrogen quantum dot solution. Due to the special micro-nano structure of carbonized nitrogen quantum dots, its aqueous solution has fluorescent characteristics. Figure 2 The characteristic fluorescence wavelength of the carbonized nitrogen quantum dot aqueous solution prepared by the above method is around 523 nm, and the fluorescence intensity is proportional to the quantum dot concentration in dilute solution. As the carbonized nitrogen quantum dot concentration increases from 0.2 mg / L to 1.2 mg / L, the fluorescence intensity increases continuously. Figure 3 The graph below shows the relationship between the biodegradation rate of carbonized nitrogen quantum dots and time. 100 mL of carbonized nitrogen quantum dot dilute solution was prepared with a concentration of 1 mg / L and left open at room temperature for 10 days, 20 days, 30 days, 40 days, 50 days and 60 days. Due to the good biodegradability of carbonized nitrogen quantum dots, they will be decomposed and absorbed by microorganisms and lose their fluorescence. Figure 2 It can be seen that the concentration of carbonized nitrogen quantum dots in dilute solution is proportional to the fluorescence intensity. Therefore, the concentration of carbonized nitrogen quantum dots after degradation can be obtained by the change in fluorescence intensity, and the degradation rate can be calculated. Figure 3 It can be seen that carbonized nitrogen quantum dots can be degraded by 90% in an aqueous environment within 60 days, and have good biodegradability.

[0043] Example 2

[0044] The difference from Example 1 is that the imidazoline ionic liquid in step (1) is imidazoline methanesulfonate.

[0045] Example 3

[0046] The difference from Example 1 is that the imidazoline ionic liquid in step (1) is serine imidazoline.

[0047] Example 4

[0048] The difference from Example 1 is that the dicarboxylic amino acid in step (1) is glutamic acid, and the mass is 3 g.

[0049] Example 5

[0050] The difference from Example 1 is that the alkaline aqueous solution in step (2) is sodium hydroxide.

[0051] Example 6

[0052] The difference from Example 1 is that the alkaline aqueous solution in step (2) is sodium bicarbonate.

[0053] Example 7

[0054] The difference from Example 1 is that in step (2), the mass ratio of the carbonized nitrogen quantum dot raw material to the fucoidan carboxylate stabilizer is 3:1.

[0055] Example 8

[0056] The difference from Example 1 is that in step (2), the mass ratio of the carbonized nitrogen quantum dot raw material to the fucoidan carboxylate stabilizer is 1:1.

[0057] Table 1 Yields of stabilizers and scale inhibitors prepared in Examples 1 to 8

[0058]

[0059]

[0060] Example 9

[0061] Application of the green carbonized nitrogen quantum dot scale inhibitor provided in Example 1:

[0062] (1) First, prepare 100 mL of a mixed solution of calcium chloride and sodium sulfate (333 mg of calcium chloride and 385 mg of sodium sulfate). 2+ Concentration 1200mg / L, SO4 2-The concentration was 2600 mg / L, the pH was 6.5, and 0.1 mg, 0.5 mg, 1 mg, 1.5 mg, 2 mg, and 2.5 mg of the green carbonized nitrogen quantum dot scale inhibitor stabilized with fucoidan carboxylate prepared in Example 1 were added to prepare scale inhibitor test solutions with concentrations of 1, 5, 10, 15, 20, and 25 mg / L. The test solutions were maintained at 30, 40, 50, and 60°C for 24 hours.

[0063] (2) After the end, use EDTA to titrate the remaining Ca in the solution 2+ The scale inhibition efficiency of carbonized nitrogen quantum dots on calcium sulfate was calculated by the change of calcium ion concentration before and after adding the scale inhibitor.

[0064] The calculation formula of scale inhibition rate is shown in formula (1):

[0065]

[0066] In formula (1), C0 is the Ca 2+ initial concentration;

[0067] C2 and C1 are the Ca contents in the solution without and with antiscalant. 2+ concentration.

[0068] from Figure 4 It can be seen that as the concentration of carbonized nitrogen quantum dot scale inhibitor increases from 1 mg / L to 25 mg / L, its scale inhibition rate for calcium sulfate also increases, reaching a maximum of 98%. This is because more quantum dots react with water-soluble free Ca 2+ Combined with SO4 2- The reaction forms calcium sulfate precipitation, which reduces scale formation. Figure 4 It can be seen that as the temperature increases from 30℃ to 60℃, the scale inhibition efficiency of quantum dots decreases continuously, which is attributed to the accelerated Ca 2+ and SO4 2- The reaction process reduces the solubility product of calcium sulfate, making it easier for scale to precipitate.

[0069] Comparative Example 1

[0070] The difference from Example 9 is that polyethylene glycol sulfur quantum dots were added in step (1) to prepare scale inhibitor solutions with concentrations of 1, 5, 10, 15, 20, and 25 mg / L. The test solutions were kept at a constant temperature of 30, 40, 50, and 60°C for 24 hours. After the test, the remaining Ca in the solution was titrated with EDTA. 2+ The scale inhibition efficiency of polyethylene glycol sulfur quantum dots on calcium sulfate was calculated by the change of calcium ion concentration before and after adding the scale inhibitor.

[0071] from Figure 5It can be seen that as the concentration of polyethylene glycol sulfur quantum dot scale inhibitor increases from 1 mg / L to 25 mg / L, its scale inhibition rate for calcium sulfate also increases, reaching a maximum of 81%. This is because more quantum dots interact with water-soluble free Ca 2+ Combined with SO4 2- The reaction forms calcium sulfate precipitation, which reduces scale formation. Figure 4 It can be seen that as the temperature increases from 30℃ to 60℃, the scale inhibition efficiency of quantum dots decreases continuously, which is attributed to the accelerated Ca 2+ and SO4 2- The reaction process reduces the solubility product of calcium sulfate, making it easier for scale to precipitate.

[0072] Comparative Example 2

[0073] The difference from Example 9 is that in step (1), a scale inhibitor solution with a concentration of 25 mg / L of citric acid carbon quantum dots was added. The test solution was kept at a constant temperature of 30°C for 24 hours. After the test, the remaining Ca in the solution was titrated with EDTA. 2+ The scale inhibition efficiency of citric acid carbon quantum dots on calcium sulfate was calculated by the change of calcium ion concentration before and after adding the scale inhibitor.

[0074] from Figure 6 It can be seen that as the concentration of citric acid carbon quantum dot scale inhibitor increases from 1 mg / L to 25 mg / L, its scale inhibition rate for calcium sulfate also increases, reaching a maximum of 92%. This is because more quantum dots interact with water-soluble free Ca 2+ Combined with SO4 2- The reaction forms calcium sulfate precipitation, which reduces scale formation. Figure 4 It can be seen that as the temperature increases from 30℃ to 60℃, the scale inhibition efficiency of quantum dots decreases continuously, which is attributed to the accelerated Ca 2+ and SO4 2- The reaction process reduces the solubility product of calcium sulfate, making it easier for scale to precipitate.

[0075] Comparative Example 3

[0076] The difference from Example 1 is that no ZSM-5 catalyst is added in step (1).

[0077] Comparative Example 4

[0078] The difference from Example 1 is that in step (2), the mass ratio of the carbonized nitrogen quantum dot raw material to the fucoidan carboxylate stabilizer is 4:1.

[0079] Comparative Example 5

[0080] The difference from Example 1 is that in step (1), the mass ratio of fucoidan to amino acids is 4:1.

[0081] Comparative Example 6

[0082] The difference from Example 1 is that fucoidan is not added in step (1).

[0083] Comparative Example 7

[0084] The difference from Example 1 is that no dicarboxyl amino acid is added in step (1).

[0085] Table 2 Yields of stabilizers and scale inhibitors prepared in Comparative Examples 3 to 7

[0086] Fucoidan carboxylate stabilizer Green carbonized nitrogen quantum dot scale inhibitor Comparative Example 3 40％ 92％ Comparative Example 4 90％ 80％ Comparative Example 5 85％ 92％ Comparative Example 6 9％ 92％ Comparative Example 7 35％ 76％

[0087] Comparative Example 8

[0088] The difference from Example 9 is that the scale inhibitor solution in step (1) is 30 mg / L.

[0089] The calculated scale inhibition rate at 30 mg / L is 89%.

[0090] Comparative Example 9

[0091] The difference from Example 9 is that the temperature of the test solution in step (1) is 20°C.

[0092] The calculated scale inhibition rates at 1, 5, 10, 15, 20 and 25 mg / L are 32%, 41%, 54%, 63%, 78% and 82% respectively.

[0093] Comparative Example 10

[0094] The difference from Example 9 is that the temperature of the test solution in step (1) is 70°C.

[0095] The calculated scale inhibition rates at 1, 5, 10, 15, 20, and 25 mg / L are 16%, 22%, 27%, 29%, 32%, and 33%, respectively.

[0096] Comparative Example 11

[0097] The difference from Example 1 is that no carbonized nitrogen quantum dot raw material is added in step (2).

[0098] Figure 7 Figure 1 shows the microscopic morphology of calcium sulfate scale without (a) and with (b) a scale inhibitor. As shown in Figure (a), under normal conditions, calcium sulfate scale exhibits a regular cubic structure with dense, smooth, and stable crystals. However, after adding the scale inhibitor, as shown in Figure (b), the calcium sulfate crystal structure undergoes significant changes, with inconsistent morphology, a rough and uneven surface, and a loose and unstable structure. This is due to the adsorption of calcium carbide quantum dots on the surface of the calcium sulfate crystals, which then combine with calcium ions and deposit, affecting the normal growth of the calcium sulfate crystals. This leads to lattice distortion, making it difficult for the crystals to grow and precipitate to form scale.

[0099] Comparative Example 12

[0100] CN 101792504 B Preparation and application method of modified polyaspartic acid scale inhibitor

[0101] (1) Add 29-30 g of maleic anhydride and 55-65 mL of deionized water to a container and stir. After heating to 80-90° C., add 45 mL of 25% ammonia water dropwise. After the addition of ammonia water is complete, a colorless solution is obtained. Stir at 75-85° C. for 2 hours to completely dissolve the suspended matter and obtain a clear homogeneous solution.

[0102] (2) distilling the homogeneous solution obtained in step (1) under reduced pressure at 90° C. to obtain a mixture of white crystals and a small amount of viscous liquid, adding 40-45 mL of deionized water to the mixture and heating it again until the crystals are dissolved into liquid, cooling the liquid in an ice bath, and crystals precipitating after cooling are filtered to obtain white flaky crystals of maleimide;

[0103] (3) Dissolve the white flaky crystalline maleimide obtained in step (2) in 20-30 ml of deionized water, and place it in a methyl silicone oil bath to undergo condensation reaction to obtain a brown solid, namely polysuccinimide; B. Preparation of modified polyaspartic acid 1 / 2 of the mass of the polysuccinimide obtained in step ③ is placed in a three-necked flask, N,N-dimethylformamide solvent is added at a volume of 1 g / 5 mL, 1 g of thiourea is added to the solvent, and stirred with a magnetic stirrer at room temperature for 1.5 hours to obtain a blood-red transparent solution, 3 mol / L sodium hydroxide solution is added to the blood-red transparent solution, and hydrolyzed in a constant temperature water bath at 50°C for 1 hour, and finally the solution is dripped into a beaker to which 3-4 times the volume of ethanol has been added, and precipitated under magnetic stirring to obtain a reddish-brown viscous substance, the supernatant is discarded, and the solution is dried under an infrared drying lamp to finally obtain a light yellow final product, a modified polyaspartic acid scale inhibitor, which is finely ground and sealed for storage.

[0104] Comparative Example 13

[0105] CN201010108127.7 A polyaspartic acid composite for scale inhibitor

[0106] Maleic anhydride (maleic anhydride), ammonia-containing substances and water in a mass ratio of 1:1-1.5:1.2-2.0 are reacted at normal pressure and a temperature of 50°C-80°C for 1-2 hours to synthesize ammonium maleate. Ammonium maleate is polymerized at a temperature of 160°C-200°C under normal pressure to generate polysuccinimide; polysuccinimide is hydrolyzed at a pH of 10-12 and a temperature of 25°C-50°C to generate polyaspartate.

[0107] Comparative Examples 12 and 13 directly use polyaspartic acid as the active ingredient in the scale inhibitor. However, in this solution, the dicarboxylic amino acid aspartic acid is a functional molecule in the carboxylation of the polysaccharide. Polyaspartic acid serves as the carbon and nitrogen source for the quantum dots, not as a direct scale inhibitor. Furthermore, the present invention primarily utilizes polysaccharides to create sulfur and carbon quantum dots, rather than carbonized nitrogen quantum dots. The carbonized nitrogen quantum dots prepared use polysaccharide macromolecules as stabilizers. They are nanoscale functional materials, completely different from traditional scale inhibitors like polyaspartic acid.

[0108] The carbonized nitrogen quantum dots prepared according to this scheme present a regular spherical micro-nano structure with an average diameter of about 3-8nm. The characteristic fluorescence wavelength of its dilute solution is around 523nm, and the fluorescence intensity is proportional to the concentration of the quantum dots. Carbonized nitrogen quantum dots can be degraded by up to 90% in an aqueous environment within 60 days, and have good biodegradability. According to the results of the static scale inhibition test, at 30°C, when the concentration of carbonized nitrogen quantum dots is 25mg / L, the scale inhibition rate for calcium sulfate is as high as 98%, which is much greater than that of polyethylene glycol sulfur quantum dot scale inhibitor and citric acid carbon quantum dot scale inhibitor. In summary, the green carbonized nitrogen quantum dots prepared by this scheme use natural products as raw materials, and the synthesis process is clean and environmentally friendly. It has stable fluorescence and biodegradability, and has efficient scale inhibition performance for calcium sulfate over a wide temperature range.

[0109] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the present invention.

Claims

1. A carbonized nitrogen quantum dot scale inhibitor using fucoidan carboxylate as a stabilizer, characterized by: The carbonized nitrogen quantum dot scale inhibitor is prepared by thermal decomposition reaction using amino acid polymer as carbon source and nitrogen source and polysaccharide carboxylate as stabilizer; The amino acid polymer is obtained by polymerization of aspartic acid; the polysaccharide carboxylate is obtained by esterification of natural product polysaccharide macromolecules dissolved in imidazoline ionic liquid with amino acid micromolecules; The natural product polysaccharide macromolecule includes fucoidan; the amino acid small molecule includes one of aspartic acid and glutamic acid among the dicarboxylic amino acids; the imidazoline ionic liquid includes one of imidazoline hexafluorophosphate, imidazoline methanesulfonate, and serine imidazoline; The thermal decomposition reaction temperature is 80-95°C and the time is 12-36h; The mass ratio of the fucoidan to the dicarboxylic amino acid is 3:1 to 1:

1.

2. The method for preparing the carbonized nitrogen quantum dot scale inhibitor as claimed in claim 1, characterized in that: include, dissolving fucoidan in an imidazoline ionic liquid to obtain a first solution; Adding dicarboxyl amino acid to the first solution, using molecular sieve ZSM-5 as a catalyst, causing esterification reaction in a reactor, centrifuging, washing with ethanol, centrifuging and freeze-drying to obtain a fucoidan carboxylate stabilizer; calcining polyaspartic acid at high temperature to obtain carbonized nitrogen quantum dot raw material; Dissolving the carbonized nitrogen quantum dot raw material and the fucoidan carboxylate stabilizer in an alkaline aqueous solution to prepare a reaction solution with a mass concentration of 7 to 14 wt % to obtain a second solution; The second solution is introduced with oxygen, stirred and heated, subjected to thermal decomposition reaction, centrifuged, purified and freeze-dried to obtain carbonized nitrogen quantum dot scale inhibitor.

3. The preparation method according to claim 2, wherein: The dicarboxyl amino acid is added to the first solution, and the mass fraction of fucoidan in the first solution is 3% to 10%.

4. The preparation method according to claim 2, wherein: The carbonized nitrogen quantum dot raw material and the fucoidan carboxylate stabilizer are dissolved in an alkaline aqueous solution, wherein the mass ratio of the carbonized nitrogen quantum dot raw material to the fucoidan carboxylate stabilizer is 3:1~1:1, the alkaline aqueous solution includes one of sodium hydroxide, sodium carbonate, and sodium bicarbonate, and the pH is 7.2~8.

2.

5. Use of the carbonized nitrogen quantum dot scale inhibitor according to claim 1 in alleviating scale deposition.

6. The use according to claim 5, characterized in that: The method includes preparing a mixed solution of calcium chloride and sodium sulfate, and then adding 0.1-2.5 mg of the prepared green carbonized nitrogen quantum dot scale inhibitor with fucoidan carboxylate as a stabilizer to prepare a scale inhibitor test solution; after the solution is finished, the remaining Ca in the solution is titrated with EDTA. 2+ Concentration, the scale inhibition efficiency of carbonized nitrogen quantum dots on calcium sulfate was calculated by the change of calcium ion concentration before and after the addition of scale inhibitor, wherein the concentration of the scale inhibitor test solution was 1~25mg / L, the test temperature was 30~60℃, and the temperature was kept constant for 24h.

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