A novel nanofiltration concentration separation flux stabilizer and its preparation method

Abstract

The invention discloses a novel nanofiltration concentration separation flux stabilizer and a preparation method thereof, and relates to the field of water treatment. The novel nanofiltration concentration separation flux stabilizer is prepared using a metal compound, an organic acid, an inorganic oxidant, and an organic oxidant, and has a good calcium ion removal effect, so that the nanofiltration membrane can maintain good flux stability. In addition, sodium alginate modified with D-tryptophan methyl ester hydrochloride is added during the preparation process, so that the prepared novel nanofiltration concentration separation flux stabilizer has a better calcium ion removal effect and COD removal effect, and the nanofiltration membrane has a better flux stability.

Description

Technical Field

[0001] The invention belongs to the field of water treatment, and particularly relates to a novel nanofiltration concentration separation flux stabilizer and a preparation method thereof. Background Art

[0002] Nanofiltration is a new membrane technology that originated in the 1970s and developed alongside the advent of low-pressure reverse osmosis. A series of pilot tests and engineering applications have demonstrated that nanofiltration is a reliable and stable membrane filtration technology that can simultaneously intercept multiple organic and inorganic components in water, including polyvalent salts, organic matter, and viruses, achieving water purification.

[0003] During daily operation, nanofiltration membrane systems used to filter high-salt, high-organic liquids are susceptible to membrane flux loss due to surface contamination and clogging, resulting in a decrease in the system's water flux. Contamination of the nanofiltration membrane typically results in a decrease in flux, necessitating frequent shutdowns for chemical cleaning to restore the membrane flux, which reduces the system's operating efficiency. There is a need for a treatment agent that can maintain a stable membrane flux, slowing the decay of the membrane flux and reducing the frequency of membrane cleaning.

[0004] The purpose of the present invention is to provide a method that can delay the accumulation of pollutants on the surface of a nanofiltration membrane and effectively remove specific pollution to achieve the purpose of stabilizing the flux of the nanofiltration membrane. Summary of the Invention

[0005] The object of the present invention is to provide a novel nanofiltration concentration separation flux stabilizer and a preparation method thereof, wherein the novel nanofiltration concentration separation flux stabilizer can maintain good nanofiltration membrane flux stability and has good calcium ion removal effect and COD removal effect.

[0006] The technical solutions adopted by the present invention to achieve the above-mentioned purpose are:

[0007] A novel nanofiltration concentration separation flux stabilizer, comprising:

[0008] A metal compound, wherein the metal is at least one selected from sodium or potassium;

[0009] An organic acid comprising at least modified polyaspartic acid, wherein the modified polyaspartic acid is prepared by modifying polyaspartic acid with ethyl 2-amino-4-methyl-thiophene-3-carboxylate;

[0010] and an oxidant, which contains an inorganic oxidant and an organic oxidant.

[0011] According to an embodiment of the present invention, the organic acid further comprises sulfamic acid and sodium sulfamate; the mass ratio of sulfamic acid to sodium sulfamate is 1:0.8-1.5.

[0012] According to an embodiment of the present invention, the mass ratio of the modified polyaspartic acid to aminosulfonic acid is 1:1-1.5.

[0013] According to an embodiment of the present invention, the metal compound includes at least one of sodium hydroxide and potassium hydroxide.

[0014] According to an embodiment of the present invention, the inorganic oxidant comprises sodium hypochlorite, sodium hypobromite, and hydrogen peroxide; the mass ratio of sodium hypochlorite, sodium hypobromite, and hydrogen peroxide is 1:1-1.7:0.8-1.3.

[0015] According to an embodiment of the present invention, the organic oxidant comprises a nitro oxidant, a nitroso oxidant, and a peroxy organic acid; the mass ratio of the nitro oxidant, the nitroso oxidant, and the peroxy organic acid is 1:0.7-1.2:1-1.5.

[0016] According to an embodiment of the present invention, in the above-mentioned novel nanofiltration concentration separation flux stabilizer, the amount of metal compound is 50-60 parts, the amount of organic acid is 15-20 parts, the amount of inorganic oxidant is 5-10 parts, and the amount of organic oxidant is 2-5 parts, by weight.

[0017] According to an embodiment of the present invention, the novel nanofiltration concentration separation flux stabilizer further comprises deionized water, and the amount of the deionized water is 15-35 parts by weight.

[0018] The present invention also discloses a method for preparing modified polyaspartic acid, comprising: polymerizing aspartic acid to generate polysuccinimide, and then subjecting the polysuccinimide to a ring-opening reaction with ethyl 2-amino-4-methyl-thiophene-3-carboxylate to obtain the modified polyaspartic acid.

[0019] The invention discloses a method for preparing modified polyaspartic acid. The method comprises the following steps: aspartic acid monomers are polymerized to generate polysuccinimide; and then, under alkaline conditions, 2-amino-4-methyl-thiophene-3-carboxylic acid ethyl ester is used as a ring-opening agent to obtain the modified polyaspartic acid. The modified polyaspartic acid is used to prepare a novel nanofiltration concentration and separation flux stabilizer, so that the novel nanofiltration concentration and separation flux stabilizer has a good calcium ion removal effect and enables the nanofiltration membrane to maintain good flux stability. The reason for this may be that oxygen-containing groups, sulfur-containing groups, etc. in the 2-amino-4-methyl-thiophene-3-carboxylic acid ethyl ester enhance the chelating performance for heavy metal ions.

[0020] Specifically, the preparation method of the modified polyaspartic acid comprises the following steps:

[0021] 1) Heat L-aspartic acid at 225-235°C for 5-6 hours, cool to room temperature, add ethanol (the mass volume ratio of L-aspartic acid to ethanol is: 1g:20-25mL), let it settle, and filter to obtain crude polysuccinimide. The crude polysuccinimide is then added to methylformamide, stirred at 38-45°C for 2-2.5 hours, vacuum filtered, and precipitated with ethanol to obtain pure polysuccinimide.

[0022] 2) Deionized water is added to pure polysuccinimide (the mass volume ratio of the two is: 1g:0.5-1mL), stirred and mixed, and then a 10-15wt% sodium hydroxide solution is added, followed by 2-amino-4-methyl-thiophene-3-carboxylic acid ethyl ester. The mixture is stirred and mixed, and the mixture is reacted at 25-30°C for 55-70 minutes. The pH is adjusted to 6-6.5, filtered, purified with ethanol, and the supernatant is poured out. The ethanol is evaporated and then dried to obtain modified polyaspartic acid.

[0023] According to an embodiment of the present invention, the mass volume ratio of the crude polysuccinimide to methylformamide is: 1 g: 3.5-5 mL.

[0024] According to an embodiment of the present invention, the mass volume ratio of the pure polysuccinimide to the sodium hydroxide solution is: 1 g: 3-3.5 mL.

[0025] According to an embodiment of the present invention, the mass ratio of the above-mentioned pure polysuccinimide to 2-amino-4-methyl-thiophene-3-carboxylic acid ethyl ester is: 1:1.5-2.

[0026] The invention also discloses the use of the modified polyaspartic acid obtained by the preparation method in preparing a novel nanofiltration concentration separation flux stabilizer.

[0027] In order to further improve the performance of the novel nanofiltration concentration separation flux stabilizer, the present invention further adds modified sodium alginate to the metal compound of the stabilizer.

[0028] The present invention also provides a method for preparing modified sodium alginate, comprising: subjecting sodium alginate to an amidation reaction with D-tryptophan methyl ester hydrochloride to prepare the modified sodium alginate.

[0029] The invention discloses a preparation method of modified sodium alginate. 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide are used as catalysts, and sodium alginate and D-tryptophan methyl ester hydrochloride are subjected to amidation reaction to obtain the prepared modified sodium alginate. The modified sodium alginate is used for preparing a novel nanofiltration concentration and separation flux stabilizer. The novel nanofiltration concentration and separation flux stabilizer has better calcium ion removal effect and COD removal effect, and the nanofiltration membrane has better flux stability. The reason may be that D-tryptophan methyl ester hydrochloride introduces hydrophobic groups such as benzene rings into sodium alginate, while sodium alginate contains carboxylic acid groups, which can self-assemble to form an amphiphilic structure, thereby effectively removing not only heavy metal cations but also small molecular organic pollutants. In addition, elements such as nitrogen and oxygen in D-tryptophan methyl ester hydrochloride further enhance the chelating performance of sodium alginate for heavy metal ions.

[0030] Specifically, the preparation method of the modified sodium alginate comprises the following steps:

[0031] Sodium alginate was added to a PBS buffer solution (pH of the PBS buffer solution was 6-6.3), and after stirring to dissolve, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride was added at room temperature, and the mixture was fully stirred for 3.5-4.5 hours. N-hydroxysuccinimide and D-tryptophan methyl ester hydrochloride were added, and the reaction was continued with stirring at a constant temperature for 20-24 hours. Anhydrous ethanol was added in an amount of 4-4.5 times the volume, and the mixture was filtered. The precipitate was washed again with anhydrous ethanol for 3-5 times, and then washed by Soxhlet reflux. The precipitate was freeze-dried to obtain modified sodium alginate.

[0032] According to an embodiment of the present invention, the mass volume ratio of the sodium alginate to the PBS buffer solution is: 1 g: 65-80 mL.

[0033] According to an embodiment of the present invention, the mass ratio of the sodium alginate to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 1:0.5-0.55.

[0034] According to an embodiment of the present invention, the mass ratio of the sodium alginate to N-hydroxysuccinimide is 1:0.2-0.3.

[0035] According to an embodiment of the present invention, the molar ratio of the sodium alginate to D-tryptophan methyl ester hydrochloride is 1:2-2.5.

[0036] The invention also discloses the use of the modified sodium alginate prepared by the preparation method in preparing a novel nanofiltration concentration separation flux stabilizer.

[0037] The beneficial effects of the present invention include:

[0038] The present invention provides a novel nanofiltration concentration and separation flux stabilizer and a preparation method thereof. The novel nanofiltration concentration and separation flux stabilizer prepared by using a metal compound, an organic acid including polyaspartic acid modified with 2-amino-4-methyl-thiophene-3-carboxylic acid ethyl ester, an inorganic oxidant, and an organic oxidant has a good calcium ion removal effect, so that the nanofiltration membrane can maintain good flux stability. In addition, sodium alginate modified with D-tryptophan methyl ester hydrochloride is added during the preparation process, so that the prepared novel nanofiltration concentration and separation flux stabilizer has better calcium ion removal effect and COD removal effect, and the nanofiltration membrane has better flux stability.

[0039] Therefore, the present invention provides a novel nanofiltration concentration separation flux stabilizer and a preparation method thereof, wherein the novel nanofiltration concentration separation flux stabilizer can maintain good nanofiltration membrane flux stability and has good calcium ion removal effect and COD removal effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The infrared spectra test results of the modified polyaspartic acid and polyaspartic acid prepared in Example 2;

[0041] Figure 2 These are the infrared spectrum test results of the modified sodium alginate and sodium alginate prepared in Example 4. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention are further described in detail below in conjunction with specific embodiments:

[0043] Example 1:

[0044] A novel preparation method for a nanofiltration concentration and separation flux stabilizer comprises: uniformly mixing a metal compound (comprising sodium hydroxide), an organic acid (comprising sulfamic acid and sodium sulfamic acid, wherein the mass ratio of sulfamic acid to sodium sulfamic acid is 1:1), an inorganic oxidant (comprising sodium hypochlorite, sodium hypobromite, and hydrogen peroxide, wherein the mass ratio of sodium hypochlorite, sodium hypobromite, and hydrogen peroxide is 1:1:1), an organic oxidant (comprising sodium 3-nitrobenzenesulfonate, nitrous tetrafluoroborate, and peracetic acid, wherein the mass ratio of sodium 3-nitrobenzenesulfonate, nitrous tetrafluoroborate, and peracetic acid is 1:1:1), and deionized water to prepare the novel nanofiltration concentration and separation flux stabilizer; wherein, by weight, the metal compound is used in an amount of 50 parts, the organic acid is used in an amount of 15 parts, the inorganic oxidant is used in an amount of 5 parts, the organic oxidant is used in an amount of 2 parts, and the ionized water is used in an amount of 15 parts.

[0045] Example 2:

[0046] The difference between the preparation method of a novel nanofiltration concentration separation flux stabilizer and Example 1 is that modified polyaspartic acid is added to the organic acid, wherein the mass ratio of the modified polyaspartic acid to aminosulfonic acid is 1:1.

[0047] The preparation method of modified polyaspartic acid comprises the following steps:

[0048] 1) L-aspartic acid was heated at 225°C for 6 hours, cooled to room temperature, and ethanol was added (the mass volume ratio of L-aspartic acid to ethanol was 1 g:20 mL). The mixture was allowed to settle and then filtered to obtain crude polysuccinimide. The crude polysuccinimide was then added to methylformamide, stirred at 38°C for 2.5 hours, vacuum filtered, and ethanol precipitated to obtain pure polysuccinimide.

[0049] 2) Deionized water was added to pure polysuccinimide (mass-to-volume ratio: 1 g:0.5 mL), stirred and mixed, and then a 10 wt% sodium hydroxide solution was added, followed by ethyl 2-amino-4-methyl-thiophene-3-carboxylate. The mixture was stirred and mixed, and the mixture was reacted at 25°C for 70 minutes. The pH was adjusted to 6, filtered, purified with ethanol, and the supernatant was poured out. The ethanol was evaporated and dried to obtain modified polyaspartic acid.

[0050] Among them, the mass volume ratio of crude polysuccinimide to methylformamide is: 1g:3.5mL; the mass volume ratio of pure polysuccinimide to sodium hydroxide solution is: 1g:3mL; the mass ratio of pure polysuccinimide to 2-amino-4-methyl-thiophene-3-carboxylic acid ethyl ester is: 1:1.5.

[0051] Example 3:

[0052] The difference between the preparation method of a novel nanofiltration concentration separation flux stabilizer and Example 1 is that polyaspartic acid is used instead of modified polyaspartic acid.

[0053] Example 4:

[0054] The difference between the preparation method of a novel nanofiltration concentration separation flux stabilizer and Example 1 is that modified sodium alginate is added to the metal compound, wherein the mass ratio of the modified sodium alginate to sodium hydroxide is 1:1.

[0055] The preparation method of modified sodium alginate comprises the following steps:

[0056] Sodium alginate was added to PBS buffer solution (pH of PBS buffer solution was 6), stirred to dissolve, and then 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride was added at room temperature, and the mixture was stirred for 3.5 h. N-hydroxysuccinimide and D-tryptophan methyl ester hydrochloride were added, and the mixture was stirred at a constant temperature for 20 h. Four times the volume of anhydrous ethanol was added, and the mixture was filtered. The precipitate was washed again with anhydrous ethanol three times, and then washed with Soxhlet reflux. The precipitate was freeze-dried to obtain modified sodium alginate.

[0057] Among them, the mass volume ratio of sodium alginate to PBS buffer solution is: 1 g:65 mL; the mass ratio of sodium alginate to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is: 1:0.5; the mass ratio of sodium alginate to N-hydroxysuccinimide is: 1:0.2; and the molar ratio of sodium alginate to D-tryptophan methyl ester hydrochloride is: 1:2.

[0058] Example 5:

[0059] The difference between the preparation method of a novel nanofiltration concentration separation flux stabilizer and Example 4 is that sodium alginate is used instead of modified sodium alginate.

[0060] Example 6:

[0061] The difference between the preparation method of a novel nanofiltration concentration separation flux stabilizer and Example 2 is that modified sodium alginate is added to the metal compound, wherein the mass ratio of the modified sodium alginate to sodium hydroxide is 1:1.

[0062] The preparation method of modified sodium alginate is the same as that in Example 4.

[0063] Example 7:

[0064] The difference between the preparation method of a novel nanofiltration concentration separation flux stabilizer and Example 3 is that modified sodium alginate is added to the metal compound, wherein the mass ratio of the modified sodium alginate to sodium hydroxide is 1:1.

[0065] The preparation method of modified sodium alginate is the same as that in Example 4.

[0066] Example 8:

[0067] The difference between the preparation method of a novel nanofiltration concentration separation flux stabilizer and Example 6 is that sodium alginate is used instead of modified sodium alginate.

[0068] Example 9:

[0069] The difference between the preparation method of a novel nanofiltration concentration separation flux stabilizer and Example 7 is that sodium alginate is used instead of modified sodium alginate.

[0070] Test Example 1:

[0071] Infrared spectrum test

[0072] The total reflection Fourier transform infrared spectrometer (Nicolet 6700) was used, which was manufactured by Thermo Fisher Scientific Inc., USA, and was operated at 400-4000 cm -1 The infrared spectrum of the sample was measured within the range.

[0073] The modified polyaspartic acid and polyaspartic acid prepared in Example 2 were tested as above, and the results were as follows: Figure 1 As shown. Figure 1 It can be seen that compared with the infrared spectrum of polyaspartic acid, the infrared spectrum of modified polyaspartic acid is at 905cm -1 There is an infrared characteristic absorption peak of CS bond at 1663cm -1 There is an infrared characteristic absorption peak of C=C bond at , indicating that 2-amino-4-methyl-thiophene-3-carboxylic acid ethyl ester participates in the formation reaction of modified polyaspartic acid.

[0074] The modified sodium alginate and sodium alginate prepared in Example 4 were tested as above. The results are as follows: Figure 2 As shown. Figure 2 It can be seen that compared with the infrared spectrum of sodium alginate, the infrared spectrum of modified sodium alginate is in the range of 1400-1600 cm -1 There is an infrared characteristic absorption peak of benzene ring at 1662cm -1 There is an infrared characteristic absorption peak of C=C bond at , indicating that D-tryptophan methyl ester hydrochloride participates in the formation reaction of modified sodium alginate.

[0075] Test Example 2:

[0076] Calcium ion removal effect test

[0077] A new nanofiltration concentration and separation flux stabilizer was added to sewage with a calcium ion concentration of 80 mg / L at a dosage of 5 ppm. After 30 minutes, the supernatant was taken and treated with a nanofiltration membrane. The calcium ion concentration before and after treatment was measured. The calcium ion removal rate was calculated as follows:

[0078] N / %=[1-(U1 / U0)]×100%

[0079] Wherein, N is the calcium ion removal rate, %; U1 is the concentration of calcium ions in the effluent after treatment, mg / L; U0 is the concentration of calcium ions in the influent, mg / L.

[0080] Table 1 Calcium ion removal rate test results

[0081]

[0082] The above test was performed on the novel nanofiltration concentration separation flux stabilizers prepared in Examples 1 to 9, and the results are shown in Table 1. As can be seen from Table 1, compared with Example 1, the calcium ion removal rate of Example 3 is significantly increased, indicating that the addition of polyaspartic acid in the novel nanofiltration concentration separation flux stabilizer has a good removal effect on calcium ions; compared with Example 1, the calcium ion removal rate of Example 5 is also significantly improved, indicating that the addition of sodium alginate in the novel nanofiltration concentration separation flux stabilizer also has a good removal effect on calcium ions; compared with Example 2 and Example 3, Example 6 and Example 7, and Example 8 and Example 9, the calcium ion removal rate is also increased, indicating that the use of 2-amino-4-methyl-thiophene-3-carboxylic acid ethyl ester to modify polyaspartic acid is used for the preparation of the novel nanofiltration concentration separation flux stabilizer, so that the novel nanofiltration concentration separation flux stabilizer has a good calcium ion removal effect; compared with Example 4 and Example 5, Example 6 and Example 8, and Example 7 and Example 9, the calcium ion removal rate is also improved, indicating that the use of D-tryptophan methyl ester hydrochloride to modify sodium alginate is used for the preparation of the novel nanofiltration concentration separation flux stabilizer, so that the novel nanofiltration concentration separation flux stabilizer also has a good calcium ion removal effect.

[0083] Test Example 3:

[0084] COD removal effect test

[0085] A new nanofiltration concentration and separation flux stabilizer was added to wastewater with a COD concentration of 230 mg / L at a dosage of 5 ppm. After 30 minutes, the supernatant was treated with a nanofiltration membrane and the COD content in the water before and after treatment was tested using the potassium dichromate method. The COD removal rate A was calculated as follows:

[0086] A / %=[(F0-F1) / F0]×100%

[0087] Among them, A is the COD removal rate; F0 is the COD content in the influent of the water recovery system; F1 is the COD content in the effluent of the water recovery system.

[0088] Table 2 COD removal rate test results

[0089]

[0090] The above test was performed on the novel nanofiltration concentration separation flux stabilizer prepared in Examples 1 to 9, and the results are shown in Table 2. As can be seen from Table 2, compared with Example 1, the COD removal rate of Example 3 did not change much, indicating that the addition of polyaspartic acid to the novel nanofiltration concentration separation flux stabilizer had no negative effect on the COD removal effect; compared with Example 1, the COD removal rate of Example 5 was significantly improved, indicating that the addition of sodium alginate to the novel nanofiltration concentration separation flux stabilizer had a good COD removal effect; compared with Example 2 and Example 3, Example 6 and Example 7, and Example 8 and Example 9, the COD removal rate did not change much, indicating that the use of 2-amino-4-methyl- After polyaspartic acid was modified with thiophene-3-carboxylic acid ethyl ester, it was used to prepare a new nanofiltration concentration separation flux stabilizer, so that the new nanofiltration concentration separation flux stabilizer had no negative effect on the COD removal effect; compared with Example 4 and Example 5, Example 6 and Example 8, and Example 7 and Example 9, the COD removal rate was also improved, indicating that after sodium alginate was modified with D-tryptophan methyl ester hydrochloride and used to prepare a new nanofiltration concentration separation flux stabilizer, the new nanofiltration concentration separation flux stabilizer also had a good COD removal effect.

[0091] Test Example 4:

[0092] Membrane flux stability test

[0093] A new nanofiltration concentration separation flux stabilizer was added to the sewage at a dosage of 5 ppm. After 30 minutes, the supernatant was taken and treated with a nanofiltration membrane. The membrane flux was measured after 24 hours of continuous treatment. The membrane flux refers to the amount of fluid passing through a unit membrane area per unit time. The calculation formula is as follows:

[0094] S=M / (D×H)

[0095] Where S is the membrane flux, L·m -2 ·h -1 ; D is the effective area of ​​the membrane, m 2 ; M is the volume of permeate during the collection time, L; H is the collection time, h.

[0096] Table 3 Membrane flux test results

[0097]

[0098] The above test was performed on the novel nanofiltration concentration separation flux stabilizers prepared in Examples 1 to 9, and the results are shown in Table 3. As can be seen from Table 3, compared with Example 1, the membrane flux of Example 3 is significantly increased, indicating that the addition of polyaspartic acid to the novel nanofiltration concentration separation flux stabilizer has good membrane flux stability; compared with Example 1, the membrane flux of Example 5 is also significantly improved, indicating that the addition of sodium alginate to the novel nanofiltration concentration separation flux stabilizer also has good membrane flux stability; compared with Example 2 and Example 3, Example 6 and Example 7, and Example 8 and Example 9, the membrane flux is also increased, indicating that 2-amino-4-methyl-thiophene-3-carboxylic acid ethyl ester is used to modify polyaspartic acid and then used to prepare the novel nanofiltration concentration separation flux stabilizer, so that the novel nanofiltration concentration separation flux stabilizer has good membrane flux stability; compared with Example 4 and Example 5, Example 6 and Example 8, and Example 7 and Example 9, the membrane flux is also improved, indicating that sodium alginate is modified with D-tryptophan methyl ester hydrochloride and then used to prepare the novel nanofiltration concentration separation flux stabilizer, so that the novel nanofiltration concentration separation flux stabilizer also has good membrane flux stability.

[0099] The conventional techniques in the above embodiments are prior arts known to those skilled in the art, and thus will not be described in detail here.

[0100] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A nanofiltration concentration separation flux stabilizer, comprising: A metal compound, wherein the metal is at least one selected from sodium or potassium; An organic acid comprising at least modified polyaspartic acid, wherein the modified polyaspartic acid is prepared by modifying polyaspartic acid with ethyl 2-amino-4-methyl-thiophene-3-carboxylate; and an oxidant, which contains an inorganic oxidant and an organic oxidant.

2. The nanofiltration concentration separation flux stabilizer according to claim 1, characterized in that: The metal compound comprises at least one of sodium hydroxide and potassium hydroxide.

3. The nanofiltration concentration separation flux stabilizer according to claim 1, characterized in that: The inorganic oxidant comprises sodium hypochlorite, sodium hypobromite and hydrogen peroxide.

4. The nanofiltration concentration separation flux stabilizer according to claim 1, characterized in that: The organic oxidant includes a nitro oxidant, a nitroso oxidant, and a peroxy organic acid.

5. The nanofiltration concentration separation flux stabilizer according to claim 1, characterized in that: In the nanofiltration concentration separation flux stabilizer, the amount of the metal compound is 50-60 parts, the amount of the organic acid is 15-20 parts, the amount of the inorganic oxidant is 5-10 parts, and the amount of the organic oxidant is 2-5 parts, calculated by weight.

6. The nanofiltration concentration separation flux stabilizer according to claim 5, characterized in that: The nanofiltration concentration separation flux stabilizer further comprises deionized water, and the amount of the deionized water is 15-35 parts by weight.

7. The method for preparing the modified polyaspartic acid according to claim 1, comprising: Aspartic acid is polymerized to generate polysuccinimide, and then the polysuccinimide is reacted with ethyl 2-amino-4-methyl-thiophene-3-carboxylate to undergo a ring-opening reaction to obtain modified polyaspartic acid.

8. Use of the modified polyaspartic acid obtained by the preparation method according to claim 7 in the preparation of a nanofiltration concentration separation flux stabilizer.

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