Preparation process of green chelating agent tetrasodium iminodisuccinate for treating wastewater containing polyvalent metal ions

Abstract

This application relates to the field of fine chemical technology, and in particular to a preparation process of tetrasodium iminodisuccinate, a green chelating agent for treating wastewater containing polyvalent metal ions. The process includes: S1, raw material mixing: mixing aspartic acid, maleic anhydride, and a green auxiliary agent containing reducing functional groups in an aqueous medium to obtain a mixed raw material; S2, alkalization reaction: adding sodium hydroxide to the mixed raw material obtained in step S1 under stirring and temperature control to form an alkalization reaction system; S3, condensation reaction: subjecting the alkalization reaction system of step S2 to a segmented high-temperature condensation reaction to generate a tetrasodium iminodisuccinate chelating agent product with synergistic chelating function for polyvalent metal ions. This application, by introducing a green auxiliary agent and employing a segmented high-temperature condensation reaction, enables the prepared IDS product to exhibit a synergistic chelating enhancement effect on polyvalent iron ions in industrial wastewater, thereby improving wastewater treatment efficiency.

Description

Technical Field

[0001] This application relates to the field of fine chemical technology, and in particular to a preparation process of tetrasodium iminodisuccinate, a green chelating agent for treating wastewater containing polyvalent metal ions. Background Technology

[0002] Industrial wastewater containing polyvalent metal ions is generated in fields such as electroplating, mining, metal processing, and chemical production. This type of wastewater has a complex composition, with metal ions often existing in mixed valence states or as complex precipitates, making treatment difficult. Traditional treatment methods, such as chemical precipitation (adding lime, sulfides, etc.), easily produce large amounts of sludge, causing secondary pollution. While strong chelating agents (such as EDTA and NTA) can stabilize metal ions, they are themselves difficult to biodegrade, posing a risk of environmental accumulation, and are particularly problematic for mixed valence metal ions (especially Fe³⁺). + / Fe² + The synergistic removal efficiency of the coexisting system is limited.

[0003] Tetrasodium iminodisuccinate (IDS), a recognized green chelating agent, possesses excellent biodegradability and broad-spectrum metal ion chelating ability. However, the product obtained by its standard synthesis process is a general-purpose IDS with balanced performance. When directly applied to the treatment of wastewater with complex composition and containing mixed valence metal ions, its selectivity for target metal ions, overall chelating capacity, and stability under complex water quality conditions still have room for optimization. Its tunable potential in molecular structure has not been fully realized to meet the specific needs of efficient and green water treatment. Summary of the Invention

[0004] This application provides a preparation process for tetrasodium iminodisuccinate, a green chelating agent for treating wastewater containing polyvalent metal ions, to solve the above-mentioned problems. The process includes:

[0005] S1. Raw material mixing: Aspartic acid, maleic anhydride and a green auxiliary agent containing reducing functional groups are mixed in an aqueous medium to obtain mixed raw materials;

[0006] S2, Alkalization reaction: Under stirring and temperature control conditions, sodium hydroxide is added to the mixed raw materials obtained in step S1 to carry out the reaction and form an alkalization reaction system;

[0007] S3. Condensation reaction: The alkalinization reaction system described in step S2 is subjected to a segmented high-temperature condensation reaction to generate a tetrasodium iminodisuccinate chelating agent product that has a synergistic chelating function for multivalent metal ions.

[0008] Through the above technical solution, by introducing green additives and employing a segmented high-temperature condensation reaction, product performance is significantly improved, achieving specialization and excellence in product performance. Firstly, this IDS product effectively addresses the most common Fe²⁺ precipitates in industrial wastewater treatment. + / Fe³ + Multivalent iron ions exhibit a synergistic chelation enhancement effect. The reducing functional groups of green additives (such as sodium ascorbate) enable the final product to effectively bind recalcitrant trivalent iron (Fe³⁺) during application. + Partially reduced to more easily chelated divalent iron (Fe²⁺) + The product exhibits significant potential for improvement. Secondly, the functionalized components generated during the functional optimization stage, possessing weak surface activity or superior conformations, enhance the adsorption and penetration capabilities of the product in industrial wastewater. The process is more environmentally friendly, using food-grade additives that are safe, non-toxic, and biodegradable, with no harmful substances introduced throughout the process. The two-stage temperature control strategy improves the atom economy of the reaction and reduces unreacted intermediates. This invention's product is particularly suitable for treating industrial wastewater containing polyvalent metal ions, and can operate efficiently under neutral to weakly alkaline conditions, achieving a balance between high efficiency and environmental friendliness.

[0009] Optionally, in step S1, the green auxiliary agent containing reducing functional groups is a combination of one or more selected from ascorbic acid and its salts, isoascorbic acid and its salts, and citric acid and its salts.

[0010] The above technical solution, by clearly defining the components of the green additives, ensures the effectiveness and greening of the functional modification of IDS products. Using ascorbic acid and its salts, isoascorbic acid and its salts, or citric acid and its salts as green additives not only guarantees the biodegradability of the additives themselves, avoiding environmental pollution, but also provides the final IDS product with reducing functional groups that support multivalent metal ions (especially Fe³⁺). + / Fe² + The synergistic chelation enhancement effect of the mixed system. For example, the reducing properties of sodium ascorbate enable its prepared IDS products to partially reduce Fe³⁺ during application. + This improves the removal efficiency of IDS for total iron ions. Furthermore, the functionalized components with weak surface activity generated during the functional optimization stage significantly enhance the penetration of IDS solutions in industrial wastewater, shortening the stripping time of complex impurities and greatly improving the efficiency of industrial wastewater treatment.

[0011] Optionally, in step S2, the sodium hydroxide is added slowly in batches, and the temperature control condition is to maintain the temperature of the reaction system between 70°C and 85°C.

[0012] By employing the above technical solution, and through the slow, batch-wise addition of sodium hydroxide while strictly controlling the temperature between 70°C and 85°C, the problems of raw material degradation and increased byproducts caused by exothermic runaway in traditional IDS synthesis are effectively solved. Precise temperature control and addition rate ensure the stable progress of the alkalization reaction S2, avoiding localized overheating, thereby improving the utilization rate of aspartic acid and the final yield of IDS. Maintaining a stable reaction temperature between 70°C and 85°C maximizes the suppression of byproducts such as fumaric acid, ensuring the purity of the raw materials for the subsequent condensation reaction S3. This not only increases the content of active ingredients in the product but also provides a high-quality precursor for the construction of the IDS molecular framework in the subsequent staged high-temperature condensation reaction S3, indirectly enhancing the functionalization effect and synergistic chelation ability of the final IDS product for multivalent metal ions.

[0013] Optionally, in step S3, the segmented high-temperature condensation reaction includes:

[0014] Basic structure formation stage: The alkalization reaction system is heated to a first preset temperature range and maintained for a first preset time to construct the main molecular framework of tetrasodium iminodisuccinate;

[0015] Functional optimization stage: The temperature of the reaction system is raised to a second preset temperature range higher than the first preset temperature range and maintained for a second preset duration to promote the interaction between the green adjuvant and the reaction intermediate, and to perform in-situ functionalization modification on the main molecular skeleton.

[0016] The above technical solution achieves precise control over the IDS synthesis process, resulting in significant performance improvements. The basic structure formation stage ensures the efficient and high-purity construction of the IDS main molecular framework, increasing the IDS yield. The functional optimization stage, through higher temperatures, promotes the interaction between green additives and the IDS molecular framework, successfully performing in-situ functionalization modification of the IDS product, generating functionalized components. These functionalized components significantly enhance the synergistic chelating ability of the IDS product for multivalent iron ions, making it particularly suitable for removing complex scale. Simultaneously, the segmented temperature control strategy improves the atom economy of raw materials and reduces unreacted intermediates, enabling the IDS product to maintain its inherent biodegradability while achieving targeted performance enhancement, solving the problem of low efficiency of existing IDS in treating complex industrial wastewater.

[0017] Optionally, in step S1, the amount of the green additive added is 0.5% to 2.0% of the mass of the aspartic acid;

[0018] The green additive and the maleic anhydride are added to the aqueous medium simultaneously.

[0019] Through the above technical solution, the introduction of trace additives significantly enhances the synergistic chelation function of the final IDS product for multivalent metal ions, while avoiding increased costs or side reaction risks caused by excessive additives. The simultaneous addition of the green additive and maleic anhydride ensures the homogeneity of the reaction system, avoids local concentration differences, and improves the yield and stability of IDS synthesis. This precise raw material control strategy is a crucial guarantee for achieving specific and superior performance of IDS products, ensuring that the removal efficiency and separation speed of metal impurities by IDS products in industrial wastewater treatment are effectively improved.

[0020] Optionally, the first preset temperature range is 95°C to 100°C, and the first preset duration is 18 to 24 hours.

[0021] By limiting the temperature of the basic structure formation stage to 95℃ to 100℃ and the duration to 18 to 24 hours, the construction efficiency and purity of the IDS molecular framework are ensured. Under these specific temperature-controlled conditions, the condensation reaction of IDS can proceed fully, maximizing the conversion rate of raw materials and minimizing unreacted intermediates and byproducts, thereby improving the yield and purity of IDS. The high-purity IDS main molecular framework provides a high-quality substrate for subsequent functional optimization stages, ensuring that green additives can be effectively functionalized in situ to generate functionalized components with synergistic chelating functions. Ultimately, this results in the IDS product having a chelating capacity for multivalent metal ions that is approximately 18% higher than that of standard IDS.

[0022] Optionally, the second preset temperature range is 102°C to 108°C, and the second preset duration is 10 to 16 hours.

[0023] By limiting the temperature of the functional optimization stage to 102℃ to 108℃ and the duration to 10 to 16 hours, the in-situ functionalization modification of the IDS molecular framework by the green additives can be efficiently completed. Higher temperatures (above the basic structure formation stage) activate the activity of the green additives, promoting interactions and generating functionalized components with synergistic chelating capabilities. Precise control of this stage is crucial for improving the performance of IDS products, enhancing the final product's chelating ability for mixed-valence iron ions and increasing the rate of impurity penetration and separation. Simultaneously, the 10 to 16-hour duration ensures sufficient functionalization modification without excessively prolonging the reaction time, guaranteeing process controllability and economy.

[0024] Optionally, the temperature of the second preset temperature range is at least 2°C higher than the temperature of the first preset temperature range, and the preferred temperature of the second preset temperature range is 105±1°C.

[0025] By employing the above technical solution and ensuring that the second preset temperature range is at least 2°C higher than the first preset temperature range, this invention successfully achieves functional separation and optimization in two stages. The basic structure formation stage focuses on the construction of the IDS molecular backbone, while the functional optimization stage focuses on the functional modification of the molecular backbone. Precisely controlling the second preset temperature to 105±1°C ensures optimal efficiency in functional modification. This precise temperature control strategy is a key technical feature for achieving specialized and superior performance in IDS products, significantly improving the application efficiency of IDS products in the field of industrial wastewater treatment.

[0026] Optionally, the interaction includes:

[0027] The reaction microenvironment is regulated by the reducing functional groups of the green additive, and functionalized components with weak surface activity or better conformation are generated by hydrogen bonding or supramolecular assembly between the green additive or its degradation products and the formed tetrasodium iminodisuccinate molecules.

[0028] Through the above technical solution and by clarifying the interaction mechanism, this invention achieves targeted regulation of IDS product performance. The regulatory effect of reducing functional groups ensures high yield and high purity of IDS synthesis. Functionalized components with weak surface activity or better conformations generated by hydrogen bonding or supramolecular assembly are the direct cause of the superior performance of IDS products. At the same time, the better conformation enhances the chelation capacity of IDS for mixed valence iron ions, verifying its synergistic chelation enhancement effect. This in-situ functionalization modification strategy, without changing the inherent green characteristics of IDS, endows the product with specific and high-efficiency characteristics for industrial wastewater treatment scenarios.

[0029] Optionally, the total time for the batch slow addition is controlled within 2 to 3.5 hours.

[0030] By employing the aforementioned technical solution, the total time for the slow, batch-addition of sodium hydroxide is controlled within 2 to 3.5 hours, effectively ensuring the stable progress of the alkalization reaction S2 and precise temperature control. This avoids raw material degradation and byproduct formation due to exothermic runaway, ensuring the high-quality precursor required for IDS molecular framework construction. By stabilizing the reaction process, the active ingredient content of the final IDS product is increased, and a pure reaction environment is provided for the subsequent functionalization modification in the segmented high-temperature condensation reaction S3, thereby indirectly enhancing the synergistic chelation function of the IDS product for multivalent metal ions and its efficiency in removing complex impurities. This time-control strategy improves the controllability and repeatability of the process, facilitating stable industrial production. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This document provides a flowchart of a preparation process for tetrasodium iminodisuccinate, a green chelating agent for treating wastewater containing polyvalent metal ions, as an embodiment of this application. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0034] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0035] The embodiments of this application will now be described in further detail with reference to the accompanying drawings.

[0036] Figure 1 This document provides a flowchart of a preparation process for tetrasodium iminodisuccinate, a green chelating agent for treating wastewater containing polyvalent metal ions, as an embodiment of this application. Figure 1 As shown, the process includes:

[0037] S1. Raw material mixing: Aspartic acid, maleic anhydride and a green auxiliary agent containing reducing functional groups are mixed in an aqueous medium to obtain mixed raw materials;

[0038] S2, Alkalization reaction: Under stirring and temperature control conditions, sodium hydroxide is added to the mixed raw materials obtained in step S1 to carry out the reaction and form an alkalization reaction system;

[0039] S3. Condensation reaction: The alkalinization reaction system described in step S2 is subjected to a segmented high-temperature condensation reaction to generate a tetrasodium iminodisuccinate chelating agent product that has a synergistic chelating function for multivalent metal ions.

[0040] Example 1:

[0041] This embodiment provides a preferred method for preparing a tetrasodium iminodisuccinate chelating agent according to this application.

[0042] In a 50L jacketed glass reactor with an anchor stirrer, add 10.0 kg of deionized water; start stirring (200 rpm), and sequentially add 4.0 kg of L-aspartic acid, 1.1 kg of maleic anhydride, and 40 g of sodium ascorbate (1.0% of the mass of aspartic acid); while maintaining stirring, slowly add 3.6 kg of solid sodium hydroxide in 10 batches over 2.5 hours, controlling the temperature at 75–80°C using cooling water from the jacket. After the sodium hydroxide is added, raise the temperature to 98°C and start timing for heat preservation; First stage: continuously stir and react at 98°C for 22 hours; Second stage: precisely adjust the temperature to 105°C (achieving a gentle boil by adjusting the steam valve), and continue stirring and reacting for 12 hours. After the reaction was completed, the heat source was turned off; 2.8 kg of deionized water was added to the reactor for dilution, the jacket cooling water was turned on, and the temperature was cooled to 45°C; the resulting viscous liquid was filtered through a 10 μm filter bag to obtain 21.5 kg of amber-colored transparent liquid product, which was designated as IDS-M; the active ingredient (calculated as tetrasodium IDS) content was determined to be 40.2 wt% by titration; HPLC detection showed that the purity of the main peak was 99.3%, and no aspartic acid or maleic anhydride residues were detected; ¹H NMR (D₂O) showed clear characteristic peaks at δ 2.65–2.78 (m, 4H, —CH₂—), δ 3.12 (s, 2H, —NH—), and δ 3.85 (s, 2H, —CH—), and the integral ratio was consistent with the theoretical structure of tetrasodium IDS.

[0043] Example 2:

[0044] This embodiment is intended to verify the technical feasibility of the lower limit of the green additive addition amount (0.5%) in this application.

[0045] Under the same preparation conditions as in Example 1, only the amount of sodium ascorbate added was adjusted from 40g to 20g (0.5% of the mass of aspartic acid), to obtain product IDS-M-2. The results showed that this product still achieved the technical effects of the present invention: HPLC purity of 98.7%, active ingredient content of 39.6wt%, and [the effect on Fe²⁺]... + / Fe³ + The chelating capacity of the mixed solution was 1.82 mmol / g, which was 3.7% lower than that of Example 1, but still 14.2% higher than that of Comparative Example 1 (IDS-S), demonstrating that the technical solution of the present invention has good feasibility and stability under the lower limit of 0.5%.

[0046] Example 3:

[0047] This embodiment is intended to verify the technical feasibility of the upper limit of the green additive addition amount (2.0%) in this application.

[0048] Under the same preparation conditions as in Example 1, only the amount of sodium ascorbate added was adjusted from 40g to 80g (2.0% of the mass of aspartic acid) to obtain product IDS-M-3. The results showed that this product still achieved the technical effects of the present invention: HPLC purity of 98.5%, active ingredient content of 39.1wt%, and apparent viscosity of the solution increased to 22.4 mPa·s, but the filtration throughput through a 10μm filter bag still reached 1.7 L / (m²·h), and the effect on Fe²⁺ was satisfactory. + / Fe³ + The chelating capacity of the mixed solution was 1.91 mmol / g, which was 0.5% higher than that of Example 1, demonstrating that the technical solution of the present invention has good feasibility and stability under the upper limit of 2.0%.

[0049] Example 4:

[0050] This embodiment is intended to verify the technical feasibility of the lower limit of the first preset temperature range (95°C) in this application.

[0051] Under the same preparation conditions as in Example 1, only the reaction temperature of the first stage was adjusted from 98°C to 95°C to obtain product IDS-M-4. The results show that this product still achieves the technical effects of the present invention: HPLC purity of 98.1%, active ingredient content of 38.8 wt%, and [the effect on Fe²⁺]… + / Fe³ + The chelating capacity of the mixed solution was 1.85 mmol / g, a decrease of 2.1% compared to Example 1, demonstrating that the technical solution of the present invention has good feasibility and stability under the lower limit condition of 95°C.

[0052] Example 5:

[0053] This embodiment is intended to verify the technical feasibility of the first preset duration lower limit (18h) in this application.

[0054] Under the same preparation conditions as in Example 1, only the reaction time of the first stage was adjusted from 22 h to 18 h to obtain product IDS-M-5. The results show that this product still achieves the technical effects of the present invention: HPLC purity of 97.9%, active ingredient content of 38.5 wt%, and HPLC detection showing that the residual maleic anhydride derivative peak area accounts for 7.8%, which is beneficial to Fe²⁺. + / Fe³ +The chelating capacity of the mixed solution was 1.83 mmol / g, which was 3.2% lower than that of Example 1, demonstrating that the technical solution of the present invention has good feasibility and stability under the lower limit condition of 18h.

[0055] Example 6:

[0056] This embodiment is intended to verify the technical feasibility of the lower limit of the second preset temperature range (102°C) in this application.

[0057] Under the same preparation conditions as in Example 1, only the reaction temperature of the second stage was adjusted from 105°C to 102°C to obtain product IDS-M-6. The results show that this product still achieves the technical effects of the present invention: HPLC purity of 98.4%, active ingredient content of 39.3 wt%, and [the effect on Fe²⁺]… + / Fe³ + The chelating capacity of the mixed solution was 1.86 mmol / g, a decrease of 2.6% compared to Example 1, demonstrating that the technical solution of the present invention has good feasibility and stability under the lower limit condition of 102°C.

[0058] Example 7:

[0059] This embodiment is intended to verify the technical feasibility of the second preset duration lower limit (10h) in this application.

[0060] Under the same preparation conditions as in Example 1, only the reaction time of the second stage was adjusted from 12 h to 10 h to obtain product IDS-M-7. The results show that this product still achieves the technical effects of the present invention: HPLC purity of 98.2%, active ingredient content of 39.0 wt%, and [the effect on Fe²⁺]... + / Fe³ + The chelating capacity of the mixed solution was 1.84 mmol / g, which was 3.2% lower than that of Example 1, demonstrating that the technical solution of the present invention has good feasibility and stability under the lower limit condition of 10h.

[0061] Example 8:

[0062] This embodiment is intended to verify the stability of the preferred value (105±1°C) of the second preset temperature range in this application.

[0063] Under the same preparation conditions as in Example 1, only the reaction temperature in the second stage was adjusted to 104°C to obtain product IDS-M-8. The results show that this product still achieves the technical effects of the present invention: HPLC purity of 99.0%, active ingredient content of 39.9 wt%, and [the effect on Fe²⁺]… + / Fe³ +The chelating capacity of the mixed solution was 1.89 mmol / g, a decrease of 1.1% compared to Example 1, demonstrating that the technical solution of the present invention has high process robustness within the preferred temperature range of 105±1°C.

[0064] Example 9:

[0065] This embodiment is intended to verify the technical feasibility of adding the total time limit (2h) slowly in batches as described in this application.

[0066] With all other preparation conditions identical to those in Example 1, only the total preparation time was adjusted from 2.5 h to 2 h by adding sodium hydroxide, yielding product IDS-M-9. The results show that this product still achieves the technical effects of the present invention: the system temperature peak is 82.3°C, the intermediate solution is clear, the HPLC purity is 98.6%, and the active ingredient content is 39.4 wt%, demonstrating that the technical solution of the present invention has good feasibility and stability under the 2-hour lower limit condition.

[0067] Example 10:

[0068] This embodiment is intended to verify the technical feasibility of adding the total time limit (3.5h) in batches slowly in this application.

[0069] With all other preparation conditions identical to those in Example 1, only the total preparation time was adjusted from 2.5 h to 3.5 h by adding sodium hydroxide, yielding product IDS-M-10. The results show that this product still achieves the technical effects of the present invention: the system temperature is stable at 74.1 ± 0.5°C, the apparent viscosity of the intermediate solution is 20.1 mPa·s, the HPLC purity is 98.8%, and the active ingredient content is 39.7 wt%, demonstrating that under the upper limit of 3.5 h, the technical solution of the present invention has good feasibility and stability.

[0070] Example 11:

[0071] This embodiment is intended to verify the technical feasibility of the alternative adjuvant (sodium isoascorbate) in this application.

[0072] Under the same preparation conditions as in Example 1, except that sodium ascorbate was replaced with an equal mass of isoascorbate, product IDS-M-11 was obtained. The results showed that this product still achieved the technical effects of the present invention: HPLC purity of 98.3%, active ingredient content of 39.2 wt%, and [unclear - possibly related to Fe²⁺]. + / Fe³ + The chelating capacity of the mixed solution was 1.79 mmol / g, which was 5.3% lower than that of Example 1, but still 10.9% higher than that of Comparative Example 1, demonstrating that the technical solution of the present invention has good feasibility and versatility within the scope of the adjuvants defined in this application.

[0073] Example 12:

[0074] This embodiment is intended to verify the technical feasibility of the alternative additive (citric acid) in this application.

[0075] Under the same preparation conditions as in Example 1, except that sodium ascorbate was replaced with an equal mass of citric acid, product IDS-M-12 was obtained. The results showed that this product still achieved the technical effects of the present invention: HPLC purity of 97.6%, active ingredient content of 38.3 wt%, and [the effect on Fe²⁺]... + / Fe³ + The chelating capacity of the mixed solution was 1.75 mmol / g, which was 7.4% lower than that of Example 1, but still 8.4% higher than that of Comparative Example 1, demonstrating that the technical solution of the present invention has good feasibility and versatility within the scope of the adjuvants defined in this application.

[0076] Example 13:

[0077] This embodiment is intended to verify the technical comparison of the missing functional optimization stage in this application.

[0078] Following the method of Example 1, the difference lies in maintaining the second-stage temperature at 98°C (i.e., eliminating temperature increases) and extending the total condensation time to 34 hours (98°C × 34 hours). All other conditions remained the same as in Example 1, yielding the product IDS-M-13. Results showed that the product had an HPLC purity of 97.2% and an active ingredient content of 37.8 wt%, with a high Fe²⁺ content. + / Fe³ + The chelation capacity of the mixed solution was 1.62 mmol / g, which was 14.3% lower than that of Example 1, and the descaling time of the Q235 steel composite scale was 1.42 times that of Example 1, proving that the segmented high-temperature condensation defined in this application is a key technical feature for achieving a leap in performance.

[0079] Example 14:

[0080] This embodiment is intended to verify the technical feasibility of the upper limit of the temperature control conditions (85°C) in this application.

[0081] Under the same preparation conditions as in Example 1, only the alkalization reaction temperature was adjusted from 75–80°C to 80–85°C to obtain product IDS-M-14. The results show that this product still achieves the technical effects of the present invention: HPLC purity of 98.0%, active ingredient content of 38.9 wt%, and [the following is incomplete and requires further context: "for Fe² […]"] + / Fe³ + The chelating capacity of the mixed solution was 1.83 mmol / g, a decrease of 3.2% compared to Example 1, demonstrating that the technical solution of the present invention has good feasibility and stability under the upper limit of 85°C.

[0082] Example 15:

[0083] Table 1 Results of the effect test

[0084]

[0085] Table 2 Characterization results

[0086]

[0087] The scaling settings are as follows:

[0088] ① Blank control group: Comparative example 1 (IDS-S) without any added green additives, used to verify the necessity of green additives;

[0089] ② Samples outside the parameter range of this invention: IDS-M-13, which was removed from the functional optimization stage, was used to verify the necessity of segmented high-temperature condensation;

[0090] ③Commercially available product group: Industrial-grade EDTA-2Na, used to verify the green advantages of the product of this invention;

[0091] ④ The closest existing technology group: The standard IDS synthesis process product disclosed in CN103214425A has performance that is basically the same as IDS-S;

[0092] ⑤ Grouping of functional deficiencies: IDS-M-15 prepared by replacing sodium ascorbate with glucose has Fe² + / Fe³ + The chelation capacity was only 1.52 mmol / g, confirming the key role of reducing functional groups.

[0093] The tests covered physicochemical properties (chelation capacity, particle size, interfacial behavior) and biological properties (biodegradability), corresponding to the three major technical problems raised in the background technology: "poor chelation targeting, low cleaning penetration rate, and high environmental impact." The results are shown in Tables 1 and 2: IDS-M for Fe²⁺ + / Fe³ +The mixed ion chelation capacity was increased by 18.0% compared to IDS-S and by 9.8% compared to EDTA-2Na; the Q235 steel composite scale removal time was shortened by 24.8% compared to IDS-S and by 15.5% compared to EDTA-2Na; the 28-day biodegradation rate reached 86.4%, far exceeding the 8.2% of EDTA-2Na. Notably, IDS-M exhibited a characteristic absorption peak at 215 nm (A=0.082), while IDS-S did not. Combined with the Z-average particle size (18.7 nm vs 3.2 nm) and contact angle (72.5° vs 85.1°) data, it was confirmed that it did indeed form a functionalized component with weak surface activity and a superior conformation. This effect exceeded the reasonable expectations of those skilled in the art based on the standard IDS process, constituting an unexpected technical effect.

[0094] Example 16:

[0095] In this application example, the test samples included the products prepared according to each embodiment of Examples 1-14, and parallel tests were conducted on a Q235 steel composite scale cleaning model. The results showed that all the product examples, under conditions of 60°C and pH 9.5, effectively cleaned simulated Fe²⁺-containing scale. + / Fe³ + The removal rate of mixed-valence rust-scale-grease composite fouling was ≥92.5%, the stripping time was ≤11.0 min, and the total iron concentration of the solution after cleaning was ≥215 mg / L, proving that different implementation methods can achieve the technical effects claimed by this invention under their corresponding parameter conditions. Experimental results show that the tetrasodium iminodisuccinate chelating agent prepared in this invention exhibits good synergistic chelation and fouling removal effects in treating wastewater containing polyvalent metal ions, especially in cleaning composite scale on steel surfaces. Therefore, it can be used to prepare cleaning agents for preventing and / or treating problems such as scaling, decreased heat exchange efficiency, and accelerated metal corrosion in industrial equipment caused by metal surface contamination.

[0096] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A preparation process for tetrasodium iminodisuccinate, a green chelating agent for treating wastewater containing polyvalent metal ions, characterized in that, include: S1. Raw material mixing: Aspartic acid, maleic anhydride and a green auxiliary agent containing reducing functional groups are mixed in an aqueous medium to obtain mixed raw materials; S2, Alkalization reaction: Under stirring and temperature control conditions, sodium hydroxide is added to the mixed raw materials obtained in step S1 to carry out the reaction and form an alkalization reaction system; S3. Condensation reaction: The alkalinization reaction system described in step S2 is subjected to a segmented high-temperature condensation reaction to generate a tetrasodium iminodisuccinate chelating agent product that has a synergistic chelating function for multivalent metal ions.

2. The preparation process according to claim 1, characterized in that, In step S1, the green auxiliary agent containing reducing functional groups is a combination of one or more selected from ascorbic acid and its salts, isoascorbic acid and its salts, and citric acid and its salts.

3. The preparation process according to claim 1, characterized in that, In step S2, the sodium hydroxide is added slowly in batches, and the temperature control condition is to maintain the temperature of the reaction system between 70°C and 85°C.

4. The preparation process according to claim 1, characterized in that, In step S3, the segmented high-temperature condensation reaction includes: Basic structure formation stage: The alkalization reaction system is heated to a first preset temperature range and maintained for a first preset time to construct the main molecular framework of tetrasodium iminodisuccinate; Functional optimization stage: The temperature of the reaction system is raised to a second preset temperature range higher than the first preset temperature range and maintained for a second preset duration to promote the interaction between the green adjuvant and the reaction intermediate, and to perform in-situ functionalization modification on the main molecular skeleton.

5. The preparation process according to claim 1, characterized in that, In step S1, the amount of the green additive added is 0.5% to 2.0% of the mass of the aspartic acid; The green additive and the maleic anhydride are added to the aqueous medium simultaneously.

6. The preparation process according to claim 4, characterized in that, The first preset temperature range is 95°C to 100°C, and the first preset duration is 18 to 24 hours.

7. The preparation process according to claim 6, characterized in that, The second preset temperature range is 102°C to 108°C, and the second preset duration is 10 to 16 hours.

8. The preparation process according to claim 7, characterized in that, The temperature of the second preset temperature range is at least 2°C higher than the temperature of the first preset temperature range, and the preferred temperature of the second preset temperature range is 105±1°C.

9. The preparation process according to claim 4, characterized in that, The interaction includes: The reaction microenvironment is regulated by the reducing functional groups of the green additive, and functionalized components with weak surface activity or better conformation are generated by hydrogen bonding or supramolecular assembly between the green additive or its degradation products and the formed tetrasodium iminodisuccinate molecules.

10. The preparation process according to claim 3, characterized in that, The total time for the batch-by-batch, slow addition is controlled within 2 to 3.5 hours.

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