A star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent and its preparation method and application

Abstract

The present invention discloses a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent, its preparation method, and application. Melamine and formaldehyde are first subjected to an addition reaction under weak alkaline conditions to generate hexahydroxymethylmelamine. Ethylenediamine is added before further dehydration and polycondensation. The ethylenediamine is attached to the melamine through condensation of the hydroxymethyl group and the amino group of the ethylenediamine. The ethylenediamine is then reacted with sodium haloacetate in the presence of an alkali or alkaline salt to attach two -CH2COO groups to the ends of the side chains. － The chelating agent of the present invention can chelate metal ions from different directions, immobilizing them on the molecule and causing them to aggregate. The synergistic chelation of adjacent branches enhances the metal ion chelation capacity and stability of the chelate. The process is simple, the reaction conditions are mild, and the process is environmentally friendly and easy to control, making it easy to implement large-scale production.

Description

Technical Field

[0001] The present invention relates to the field of preparation of chelating agents, and in particular to a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent, a preparation method thereof and an application thereof. Background Art

[0002] Chelating agents, also known as chelating ligands, chelating groups, or polydentate ligands, are characterized by the presence of two or more coordinating atoms in their molecules, which can simultaneously form a chelate ring with a central atom (or ion). Because these molecules resemble the two large "claws" of a crab gripping a metal atom or ion, they are aptly called chelating agents, and the resulting ring-shaped complex is called a chelate. Because two or more coordinating atoms in a chelating agent simultaneously form a chelate ring with a central atom (or ion), the resulting chelate is significantly more stable than non-chelating coordination compounds of similar composition and structure. The vast majority of chelating agents are organic ligands, with oxygen and nitrogen being the most common coordinating atoms, followed by sulfur, phosphorus, and arsenic. Due to their unique structure and properties, chelating agents are widely used in industrial and agricultural production and daily life. For example, the addition of chelating agents can cause metal ions to form chelates with completely different properties. Adding chelating agents in industrial production has become a primary method for reducing and controlling metal ion concentrations. Chelating agents can be used as bleaching aids in chemical, mechanical, and deinked pulp bleaching, using hydrogen peroxide and hypochlorous acid as bleaching agents. Some chelating agents are used medically as antidotes for lead and mercury poisoning. Furthermore, they are widely used in industrial production in areas such as mineral flotation, hydrometallurgy, extraction and separation of metal elements, catalytic synthesis of substances, water softening, electroplating, pharmaceuticals, and dyeing.

[0003] Ethylenediaminetetraacetic acid (sodium) (EDTA) contains two groups of aminodiacetyl groups (-N(CH2COO － )2), can form 4 stable Five-member ring and 1 The five-membered ring has a stronger chelating ability than most other chelating agents, and the chelate formed is more stable. Therefore, it has been widely studied and applied. However, there are only two groups in its molecule - N(CH2COO － )2 chelate groups, and connected by ethylene (-CH2CH2-), the number of chelate groups is small, the spatial structure is not optimal, and the performance is not the best. If more -N(CH2COO － )2 chelating groups are expected to construct new high-efficiency chelating agents, thereby giving chelating agents new properties and obtaining new applications. Melamine is a trimer of aminocyanide, with three amino groups evenly distributed on the triazine nitrogen heterocycle. If the three amino groups evenly distributed on the molecule can be connected to -N(CH2COO－ )2 is expected to construct a melamine-based － )2 groups are distributed in a star-shaped manner. However, due to the special triazine nitrogen heterocyclic structure of melamine, it is only slightly soluble in water, which brings difficulties to its further development, utilization and modification. It is difficult to directly convert -N(CH2COO － )2 modified thereon. Since melamine is a relatively cheap raw material and has the above-mentioned special structure, if the strong chelating group -N(CH2COO － )2 is connected thereto, its structural and price advantages can be fully utilized to construct a high-efficiency chelating agent with a star-shaped structure. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent and a preparation method and application thereof.

[0005] The star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent provided by the present invention has a structure as shown in formula (I):

[0006]

[0007] The above chelating agent uses melamine as the core and grafts 6 branches with aminodiacetic acid (-N(CH2COOH)2) as the end group to form a star-shaped structure. The -N(CH2COOH)2 group on each branch can form two Five-membered ring, and -NH-CH2CH2-N- can also form a Five-membered ring, thus forming a stable chelate; at the same time, the two adjacent -N(CH2COOH)2 can also chelate with the same metal ion to produce a synergistic chelation effect, thereby increasing the chelating ability and the stability of the chelate.

[0008] The preparation method of the star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent comprises the following steps:

[0009] (1) Add formaldehyde solution to a reactor at a molar ratio of melamine to formaldehyde of 1:10-12, adjust the pH to 8.0-9.5 with an alkali or alkaline salt solution, and then add a measured amount of melamine; start the stirrer, raise the temperature to 70-90°C, wait until the reaction mixture turns from turbid to clear, and continue the reaction at this temperature for 20-60 minutes; then preheat distilled water to 70-85°C at a volume ratio of distilled water to formaldehyde solution of 5-8:1, add the distilled water to the reactor, and stir thoroughly;

[0010] (2) adding ethylenediamine dropwise to the solution of step (1) at a molar ratio of ethylenediamine to formaldehyde of 1.0 to 1.1:1, continuing the reaction for 30 to 60 minutes, and then cooling to room temperature;

[0011] (3) adding sodium haloacetate to the solution obtained in step (2) in a molar ratio of sodium haloacetate, alkali or alkaline salt to ethylenediamine of 2.1-2.3:2.3-2.5:1, and after dissolution, slowly adding alkali or alkaline salt solution dropwise in 3-4 batches, adding the next batch after the pH drops to 9-10 after each batch is added, and then maintaining at room temperature for 12-16 hours;

[0012] (4) Raise the temperature to 85-95°C, add activated carbon for decolorization for 1-1.5 hours, then filter and wash the filter residue with distilled water; adjust the pH of the filtrate to 2.5-3.5 with hydrochloric acid solution, evaporate and concentrate, cool to precipitate solid, filter, and wash the filter cake with distilled water until it is free of chlorine. － , and dried at 105-110°C to constant weight to obtain a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

[0013] Furthermore, in step (1), the melamine is a product with a purity of industrial grade or above, and the formaldehyde is a product with a purity of industrial grade or above with a mass fraction of 37-40%.

[0014] Furthermore, in step (1), the alkali or alkaline salt solution is a Na2CO3 solution with a mass fraction of 10% to 15% or a NaOH solution with a mass fraction of 20% to 30%.

[0015] Furthermore, in step (2), the ethylenediamine is a product with a purity above industrial grade.

[0016] Furthermore, in step (3), the sodium haloacetate is either sodium chloroacetate or sodium bromoacetate.

[0017] Furthermore, in step (3), the alkali or alkaline salt solution is a NaOH or KOH solution with a mass fraction of 20% to 30%, or a Na2CO3 solution with a mass fraction of 10% to 15%.

[0018] Furthermore, in step (3), the time for slowly adding the alkali or alkaline salt solution is 40 to 60 minutes.

[0019] Furthermore, in step (4), the mass fraction of the hydrochloric acid solution is 25% to 30%.

[0020] Furthermore, in step (1), the reactors are equipped with mechanical stirring, a dropping funnel and a reflux condenser.

[0021] The above-mentioned chelating agents can be applied to many fields such as chelation of metal ions, regulation of metal ion concentration in industrial production, mining and smelting of minerals, extraction and separation of metal elements, electroplating process, papermaking, pharmaceutical industry or dyeing, with significant effects.

[0022] The present invention relates to a method for preparing a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent. The method firstly reacts melamine with formaldehyde under weak alkaline conditions to generate hexahydroxymethyl melamine, then adds ethylenediamine before further dehydration and polycondensation, so that the hydroxymethyl group condenses with the amino group on the ethylenediamine to connect the ethylenediamine to the amino group of the melamine, and then reacts with sodium haloacetate in the presence of an alkali or an alkaline salt to connect two -CH2COO groups at the end of the chain. － The -N(CH2COOH)2 group forms a molecular structure with melamine as the core and six branches ending in -N(CH2COOH)2 groups arranged in a star shape. The -N(CH2COOH)2 chelates metal ions from different directions, securing them to the molecule. The connecting action of the melamine core brings them together, while the -N(CH2COOH)2 on adjacent branches synergistically chelates them, enhancing the metal ion chelation capacity and stability of the chelate.

[0023] The present invention has the following beneficial effects compared with the prior art:

[0024] (1) The product of the present invention has a melamine core with six branched chains ending in —N(CH2COOH)2) in the molecule, forming a star-shaped structure. The —N(CH2COOH)2) groups on the six branched chains can chelate and bind metal ions over a wide range, and the metal ions chelated and bound by the six branched chains are then aggregated through the melamine ring. The —N(CH2COOH)2 on adjacent branched chains can also produce a synergistic chelation effect. Therefore, the product of the present invention can provide more chelation active sites for metal ions, enhance the chelating ability of the chelating agent and the stability of the chelate, and improve the chelating stability of the chelating agent.

[0025] (2) The method of the present invention adopts the method of diluting the generated hydroxymethyl melamine with water and adding ethylenediamine in time and keeping it in excess before the further dehydration condensation, so as to ensure that the hydroxymethyl and ethylenediamine condense to form a relatively complete 6-branched structure, and play a blocking role on the hydroxymethyl, preventing the condensation between the hydroxymethyl melamine and the melamine, thus overcoming the difficulty of melamine to directly connect to -CH2COO － The difficulty of the groups is effectively prevented, and the problem of easy polycondensation of hydroxymethyl melamine is effectively prevented, thus achieving effective regulation of the molecular structure.

[0026] (3) The unique structure of the product of the present invention not only provides more strong chelating groups and chelating sites for metal ion chelation, but also allows it to contact metal ions from different directions and over a wider range, thereby increasing the speed of the chelation reaction. Furthermore, through the synergistic chelation of -N(CH2COOH)2 on adjacent side chains, it can enhance the chelation of metal ions and the stability of the formed chelate. Therefore, compared with commonly used chelating agents, the product of the present invention has superior chelation ability for metal ions, chelate stability, and chelation reaction speed.

[0027] (4) The preparation process of the present invention is simple, the reaction conditions are mild, the operation control is easy, the process is environmentally friendly, no special equipment is required, the investment is low, and it is easy to realize industrial production, and has broad application prospects.

[0028] The present invention is suitable for the chelation of various metal ions, the regulation of metal ion concentration in industrial production processes, mineral mining and smelting, the extraction and separation of metal elements, electroplating technology, papermaking, pharmaceutical industry, dyeing and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a process flow chart of the preparation method of the present invention.

[0030] Figure 2 This is the infrared spectrum of the star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent (the sample of Example 3).

[0031] Figure 3 Schematic diagram of the chelation mechanism of the product of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the present invention is not limited thereto.

[0033] Examples 1 to 8 are preparation methods of the star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent of the present invention, and Examples 9 to 11 are application examples of the product of the present invention.

[0034] Example 1

[0035] (1) 26.7 mL of 37-40% formaldehyde was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel, and a reflux condenser. A 15.00% Na2CO3 solution was added dropwise to adjust the pH of the formaldehyde solution to 8.0. 3.82 g of 99.00% melamine was then added. The stirrer was started and the temperature was raised to 75°C. When the reaction mixture turned from turbid to clear, the reaction mixture was kept warm and the reaction was continued for 30 min. 133.2 mL of distilled water preheated to 75°C was then added to the reactor and stirred thoroughly.

[0036] (2) adding 24.1 mL of 99.80% ethylenediamine to the solution of step (1), continuing the reaction for 40 min, and then cooling to room temperature;

[0037] (3) Weigh 89.90 g of 98.00% sodium chloroacetate and add it to the solution obtained in step (2). After dissolution, slowly add 165.6 mL of 20.00% NaOH solution dropwise in three batches, with each batch adding for 40 minutes. Add the next batch when the pH value of the reaction solution drops to about 10. After the addition is complete, continue the reaction at room temperature for 12 hours.

[0038] (4) Heat to 90°C, add activated carbon for decolorization for 1 hour, then filter and wash the filter residue with distilled water; adjust the pH of the filtrate to 2.5 with 25.00% hydrochloric acid solution, evaporate and concentrate, cool to precipitate solid, filter, and wash the filter cake with distilled water until it is free of chlorine. － , placed in an oven and dried at 105°C to constant weight to obtain 35.21 g of light yellow powder, which is a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

[0039] Example 2

[0040] (1) 24.4 mL of 37-40% formaldehyde was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel, and a reflux condenser. A 10.00% Na2CO3 solution was added dropwise to adjust the pH of the formaldehyde solution to 8.5. 3.82 g of 99.00% melamine was then added. The stirrer was started and the temperature was raised to 80°C. After the reaction mixture turned from turbid to clear, the temperature was maintained and the reaction was continued for 40 min. 146.5 mL of distilled water preheated to 80°C was then added to the reactor and stirred thoroughly.

[0041] (2) adding 23.2 mL of 99.80% ethylenediamine to the solution of step (1), continuing the reaction for 50 min, and then cooling to room temperature;

[0042] (3) Weigh 90.60 g of 98.00% sodium chloroacetate and add it to the solution obtained in step (2). After dissolution, slowly add 133.0 mL of 25.00% NaOH solution dropwise in three batches, with each batch adding for 50 min. Add the next batch when the pH value of the reaction solution drops to about 10. After the addition is complete, continue the reaction at room temperature for 14 h.

[0043] (4) Heating to 85°C, adding activated carbon for decolorization for 1.5 hours, then filtering, washing the filter residue with distilled water; adjusting the pH of the filtrate to 3.1 with a 28.00% hydrochloric acid solution, evaporating and concentrating, cooling to precipitate solids, filtering, and washing the filter cake with distilled water until it is free of chlorine.－ , placed in an oven and dried at 110°C to constant weight to obtain 34.36 g of light yellow powder, which is a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

[0044] Example 3

[0045] (1) 22.2 mL of 37-40% formaldehyde was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel, and a reflux condenser. 20.00% NaOH solution was added dropwise to adjust the pH of the formaldehyde solution to 9.2. 3.82 g of 99.00% melamine was then added. The stirrer was started and the temperature was raised to 85°C. When the reaction mixture turned from turbid to clear, the reaction mixture was kept warm and the reaction was continued for 50 min. 177.6 mL of distilled water preheated to 85°C was then added to the reactor and stirred thoroughly.

[0046] (2) adding 22.1 mL of 99.80% ethylenediamine to the solution of step (1), continuing the reaction for 60 min, and then cooling to room temperature;

[0047] (3) Weigh 90.21 g of 98.00% sodium chloroacetate and add it to the solution obtained in step (2). After dissolution, slowly add 110.0 mL of 30.00% NaOH solution dropwise in three batches, with each batch adding for 60 min. Add the next batch when the pH value of the reaction solution drops to about 10. After the addition is complete, continue the reaction at room temperature for 16 h.

[0048] (4) Heating to 95°C, adding activated carbon for decolorization for 1 hour, then filtering, washing the filter residue with distilled water; adjusting the pH of the filtrate to 3.5 with a 30.00% hydrochloric acid solution, evaporating and concentrating, cooling to precipitate solids, filtering, and washing the filter cake with distilled water until it is free of chlorine. － , placed in an oven and dried at 110°C to constant weight to obtain 34.25 g of light yellow powder, which is a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

[0049] Example 4

[0050] (1) 24.4 mL of 37-40% formaldehyde was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel, and a reflux condenser. A 25.00% NaOH solution was added dropwise to adjust the pH of the formaldehyde solution to 9.5. 3.82 g of 99.00% melamine was then added. The stirrer was started and the temperature was raised to 90°C. After the reaction mixture turned from turbid to clear, the temperature was maintained and the reaction was continued for 60 min. 170.8 mL of distilled water preheated to 90°C was then added to the reactor and stirred thoroughly.

[0051] (2) adding 23.2 mL of 99.80% ethylenediamine to the solution of step (1), continuing the reaction for 60 min, and then cooling to room temperature;

[0052] (3) Weigh 94.72 g of 98.00% sodium chloroacetate and add it to the solution obtained in step (2). After dissolution, slowly add 115.5 mL of 30.00% NaOH solution dropwise in three batches, with each batch adding for 50 min. Add the next batch when the pH value of the reaction solution drops to about 10. After the addition is complete, continue the reaction at room temperature for 15 h.

[0053] (4) Heating to 90°C, adding activated carbon for decolorization for 1 hour, then filtering, washing the filter residue with distilled water; adjusting the pH of the filtrate to 3.2 with a 26.00% hydrochloric acid solution, evaporating and concentrating, cooling to precipitate solids, filtering, and washing the filter cake with distilled water until it is free of chlorine. － , placed in an oven and dried at 105°C to constant weight to obtain 35.91 g of white powder, which is a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

[0054] Example 5

[0055] (1) 25.5 mL of 37-40% formaldehyde was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel, and a reflux condenser. A 25.00% NaOH solution was added dropwise to adjust the pH of the formaldehyde solution to 8.9. Then, 3.82 g of 99.00% melamine was added. The stirrer was started and the temperature was raised to 85°C. When the reaction mixture turned from turbid to clear, the temperature was kept constant and the reaction was continued for 60 min. Then, 204.2 mL of distilled water preheated to 85°C was added to the reactor and the mixture was thoroughly stirred.

[0056] (2) adding 23.1 mL of 99.80% ethylenediamine to the solution of step (1), continuing the reaction for 60 min, and then cooling to room temperature;

[0057] (3) Weigh 118.97 g of 98.00% sodium bromoacetate and add it to the solution obtained in step (2). After dissolution, slowly add 127.0 mL of 25.00% NaOH solution dropwise in 4 batches, with each batch adding for 50 min. Add the next batch when the pH value of the reaction solution drops to about 10. After the addition is complete, continue the reaction at room temperature for 16 h.

[0058] (4) Heating to 90°C, adding activated carbon for decolorization for 1.5 hours, then filtering, washing the filter residue with distilled water; adjusting the pH of the filtrate to 3.1 with a 25.00% hydrochloric acid solution, evaporating and concentrating, cooling to precipitate solids, filtering, and washing the filter cake with distilled water until it is free of chlorine. －, placed in an oven and dried at 105°C to constant weight to obtain 35.85g of white powder, which is a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

[0059] Example 6

[0060] (1) 23.3 mL of formaldehyde (mass fraction: 37-40%) was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel, and a reflux condenser. 30.00% NaOH solution (mass fraction: 30.00%) was added dropwise to adjust the pH value of the formaldehyde solution to 8.7. 3.82 g of 99.00% melamine (mass fraction: 99.00%) was then added. The stirrer was started and the temperature was raised to 85°C. After the reaction mixture turned from turbid to clear, the temperature was maintained and the reaction was continued for 60 min. 140.0 mL of distilled water (preheated to 85°C) was then added to the reactor and the mixture was thoroughly stirred.

[0061] (2) adding 21.1 mL of 99.80% ethylenediamine to the solution of step (1), continuing the reaction for 60 min, and then cooling to room temperature;

[0062] (3) Weigh 108.63 g of 98.00% sodium bromoacetate and add it to the solution obtained in step (2). After dissolution, slowly add 135.5 mL of 30.00% KOH solution dropwise in 4 batches, with each batch adding for 50 min. Add the next batch when the pH value of the reaction solution drops to about 10. After the addition is complete, continue the reaction at room temperature for 14 h.

[0063] (4) Heating to 85°C, adding activated carbon for decolorization for 1.5 hours, then filtering, washing the filter residue with distilled water; adjusting the pH of the filtrate to 2.9 with a 30.00% hydrochloric acid solution, evaporating and concentrating, cooling to precipitate solids, filtering, and washing the filter cake with distilled water until it is free of chlorine. － , placed in an oven and dried at 105°C to constant weight to obtain 35.02 g of white powder, which is a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

[0064] Example 7

[0065] (1) 26.6 mL of formaldehyde (mass fraction: 37-40%) was added to a 750 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel, and a reflux condenser. A 30.00% mass fraction NaOH solution was added dropwise to adjust the pH value of the formaldehyde solution to 8.3. 3.82 g of 99.00% mass fraction melamine was then added. The stirrer was started and the temperature was raised to 85°C. After the reaction mixture turned from turbid to clear, the reaction mixture was kept warm and the reaction was continued for 60 min. 133 mL of distilled water preheated to 85°C was then added to the reactor and stirred thoroughly.

[0066] (2) adding 24.1 mL of 99.80% ethylenediamine to the solution of step (1), continuing the reaction for 60 min, and then cooling to room temperature;

[0067] (3) Weigh 89.86 g of 98.00% sodium chloroacetate and add it to the solution obtained in step (2). After dissolution, slowly add 457.9 mL of 15.00% Na2CO3 solution dropwise in 4 batches, with each batch adding for 50 min. Add the next batch when the pH value of the reaction solution drops to about 10. After the addition is complete, continue the reaction at room temperature for 15 h.

[0068] (4) Heating to 80°C, adding activated carbon for decolorization for 1.5 hours, then filtering, washing the filter residue with distilled water; adjusting the pH of the filtrate to 2.9 with a 30.00% hydrochloric acid solution, evaporating and concentrating, cooling to precipitate solids, filtering, and washing the filter cake with distilled water until it is free of chlorine. － , placed in an oven and dried at 105°C to constant weight to obtain 34.95g of white powder, which is a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

[0069] Example 8

[0070] (1) 24.4 mL of formaldehyde (mass fraction: 37-40%) was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel, and a reflux condenser. A 25.00% mass fraction NaOH solution was added dropwise to adjust the pH value of the formaldehyde solution to 8.5. 3.82 g of 99.00% mass fraction melamine was then added. The stirrer was started and the temperature was raised to 85°C. After the reaction mixture turned from turbid to clear, the temperature was maintained and the reaction was continued for 60 min. 146.4 mL of distilled water (preheated to 85°C) was then added to the reactor and stirred thoroughly.

[0071] (2) adding 22.1 mL of 99.80% ethylenediamine to the solution of step (1), continuing the reaction for 60 min, and then cooling to room temperature;

[0072] (3) Weigh 82.37 g of 98.00% sodium chloroacetate and add it to the solution obtained in step (2). After dissolution, slowly add 212.9 mL of 20.00% KOH solution dropwise in 4 batches, with each batch adding for 50 min. Add the next batch when the pH value of the reaction solution drops to about 10. After the addition is complete, continue the reaction at room temperature for 15 h.

[0073] (4) Heating to 85°C, adding activated carbon for decolorization for 1.5 hours, then filtering, washing the filter residue with distilled water; adjusting the pH of the filtrate to 3.0 with a 25.00% hydrochloric acid solution, evaporating and concentrating, cooling to precipitate solids, filtering, and washing the filter cake with distilled water until it is free of chlorine. －, placed in an oven and dried at 105°C to constant weight to obtain 35.17 g of white powder, which is a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

[0074] The infrared spectrum analysis of the star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agents obtained in Examples 1 to 8 was performed, and the results were basically the same. The infrared spectrum analysis results of the chelating agent obtained in Example 3 are as follows: Figure 2 shown. Figure 2 The absorption peaks in the infrared spectrum can be assigned as follows: 3294.62 cm -1 The stretching vibration peaks of OH and -NH of water in the sample are at 2965.35 and 2853.74 cm -1 The asymmetric and symmetric stretching vibration peaks of -CH2- appear at 1335.48 cm -1 Its bending vibration peak appears at 1675.28cm -1 The strong peak and 1403.65cm -1 The slightly weaker peaks are the asymmetric stretching and symmetric stretching vibration peaks of carboxylate groups; 1556.99 cm -1 The characteristic absorption peaks of γ(CN) and δ(NH) in the triazine ring, 1468.71 cm -1 is the in-plane stretching vibration peak of the triazine ring, 810.75 cm -1 is the out-of-plane vibration peak of the triazine ring; 1627.59cm -1 The bending vibration peak of -NH and bound water molecule OH; 1447.31cm -1 The deformation vibration peaks of CN are 1215.86, 1118.27 and 1027.08 cm -1 represents the stretching vibration peaks of CO and CN in the molecule. Elemental analysis of the above sample revealed a nitrogen content of 19.98% and an oxygen content of 30.19%, equivalent to 17.89 nitrogen atoms per molecule, close to the theoretical value of 18. If oxygen atoms are converted to -N(CH2COOH)2, each heavy metal chelator molecule carries an average of 5.91 -N(CH2COOH)2 atoms. These results demonstrate the successful synthesis of a star-shaped melamine hexakis(ethylenediamine-N,N-diacetic acid) chelating agent.

[0075] Example 9

[0076] This example demonstrates the effectiveness of using the chelating agent obtained in Example 3 as the primary component of a heavy metal-contaminated soil eluent. The heavy metal content of the soil was as shown in Table 1, along with 16.7% organic matter and a pH of 7.67. 5g of the chelating agent obtained in Example 3, 2g of glycine, and 1g of rhamnolipid were added to 42mL of deionized water and thoroughly stirred to dissolve, yielding a heavy metal eluent. A comparative eluent was prepared by replacing the chelating agent obtained in Example 3 with 5g of disodium ethylenediaminetetraacetic acid (EDTA) according to the aforementioned ratio. 3g of soil was then placed in two 50mL plastic centrifuge tubes, and 30mL of the prepared eluent and the comparative eluent were added, respectively. The samples were shaken at 250 rpm for 12 hours at room temperature (25°C), allowed to stand for another 12 hours, and then filtered. The heavy metal content of the treated soil samples was determined by ICP-OES, and the heavy metal removal efficiency of the eluent was calculated. The results are shown in Table 1.

[0077] Table 1 The leaching effect of the product of the present invention on heavy metal contaminated soil

[0078]

[0079] As can be seen from Table 1, the eluent prepared with the product of the present invention has a significantly higher elution and removal effect on heavy metals in contaminated soil than the eluent prepared with EDTA, and the heavy metal content in the treated soil is lower. The main reason is that the product of the present invention uses melamine as the core and grafts six side chains with aminodiacetic acid (-N(CH2COOH)2) as the end group, forming a unique star-shaped structure. The strong coordination group -N(CH2COOH)2 is numerous and distributed in a star-shaped manner, which is conducive to the reaction with heavy metal ions such as attachment. Figure 3 The chelation effect shown is as follows: (1) the six side chains can contact heavy metal ions from multiple directions, which increases the probability of chelation with heavy metal ions and thus increases the chelation reaction rate; (2) the -N(CH2COOH)2 on each side chain can form two Five-membered ring, and -NH-CH2CH2-N- can also form a The five-membered ring forms a stable chelate; the formed chelate forms a denser chelate or chelate aggregate through the connection of the melamine mother ring; (3) the two -N(CH2COOH)2 groups from different molecules form four The five-membered ring connects the chelates formed by different molecules and gradually grows to form larger aggregates, thereby improving the efficiency of chelating and binding heavy metal ions and the stability of the chelate. 2+ Mg 2+ It also has excellent chelating stabilization effect on metal ions that are difficult to coordinate.

[0080] Example 10

[0081] This example demonstrates the effectiveness of the product of the present invention in deinking and bleaching waste paper. To prepare the deinking solution, dissolve 6g of the product from Example 3, 3.5g of sodium polyacrylate, 4g of hydroxyethylidene diphosphonic acid, and 2.5g of diethylenetriamine penta-methylene phosphonic acid in water. Adjust the pH to approximately 6.0 with NaOH, and dilute to 50mL with water. For comparison, a deinking solution was prepared using sodium ethylenediaminetetraacetic acid (EDTA): 8g of EDTA, 3.5g of sodium polyacrylate, 3g of diethylenetriamine pentaacetic acid, 4g of hydroxyethylidene diphosphonic acid, and 2.5g of diethylenetriamine penta-methylene phosphonic acid were added. Adjust the pH to 6.0-6.5 with NaOH, and dilute to 50mL with water to obtain EDTA deinking solution. To prepare the bleaching solution, mix 2.0g of a 40° Baume NaOH solution, 2.0g of sodium silicate, and 2.5g of hydrogen peroxide to obtain a bleaching solution. Prepare 2 servings. Then, 15g of the prepared deinking solution and EDTA deinking solution were added to each of the two bleaching solutions, stirred evenly, to obtain a deinking and bleaching mixture. 100g of mixed office waste paper was shredded, the pulp concentration controlled to 15%, and the prepared deinking and bleaching mixture was added. The pulp was bleached at 70°C for 80 minutes, then washed with distilled water and its whiteness measured. The optical whiteness of the waste paper pulp treated with the deinking solution prepared by the present invention reached 81.6% ISO, while the whiteness of the pulp treated with EDTA deinking solution was only 76.9% ISO. Therefore, using the waste paper deinking agent prepared by the present invention to deink waste paper increased its whiteness by 4.7%, and eliminated the need for diethylenetriaminepentaacetic acid in the deinking solution formulation, saving reagents and reducing costs.

[0082] Example 11

[0083] This example shows the scale inhibition effect of the product of Example 3. The product of Example 3 was used as a sample, and commercially available EDTA was used as a comparative sample. First, the product of Example 3 and EDTA water treatment agent sample solutions were prepared separately, with a concentration of 0.500 mg / mL; then, the scale inhibition performance was determined according to the method of "Determination of Scale Inhibition Performance of Water Treatment Agents - Calcium Carbonate Deposition Method" (GB / T16632-2019). The scale inhibition experimental conditions were: temperature of 80°C and constant temperature placement time of 10 hours. The scale inhibition rate of the product of Example 3 was determined to be 93.12%, and the scale inhibition rate of commercially available EDTA was 84.95%. Obviously, the scale inhibition performance of the product of Example 3 is significantly better than that of commercially available EDTA.

[0084] The above are merely preferred embodiments of the present invention. Based on the above concept of the present invention, those skilled in the art can also make various modifications and changes thereto. For example, within the range of the ratios and process conditions given in the present invention, the ratios and process conditions can be combined and changed. Similar changes and modifications belong to the essence of the present invention.

Claims

1. A star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent, characterized in that: Its structure is shown in formula (I):

2. The star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent according to claim 1, characterized in that The chelating agent has a star-shaped structure and is in the form of white or light yellow powder.

3. The method for preparing the star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent according to claim 1 or 2, characterized in that: The following steps are involved: (1) Add formaldehyde solution to a reactor at a molar ratio of melamine to formaldehyde of 1:10-12, adjust the pH to 8.0-9.5 with an alkali or alkaline salt solution, and then add a measured amount of melamine; start the stirrer, raise the temperature to 70-90°C, wait until the reaction mixture turns from turbid to clear, and continue the reaction at this temperature for 20-60 minutes; then preheat distilled water to 70-85°C at a volume ratio of distilled water to formaldehyde solution of 5-8:1, add the distilled water to the reactor, and stir thoroughly; (2) adding ethylenediamine dropwise to the solution of step (1) at a molar ratio of ethylenediamine to formaldehyde of 1.0 to 1.1:1, continuing the reaction for 30 to 60 minutes, and then cooling to room temperature; (3) adding sodium haloacetate to the solution obtained in step (2) in a molar ratio of sodium haloacetate, alkali or alkaline salt to ethylenediamine of 2.1-2.3:2.3-2.5:1, and after dissolution, slowly adding alkali or alkaline salt solution dropwise in 3-4 batches, adding the next batch after the pH drops to 9-10 after each batch is added, and then maintaining at room temperature for 12-16 hours; (4) Raise the temperature to 85-95°C, add activated carbon for decolorization for 1-1.5 hours, then filter and wash the filter residue with distilled water; adjust the pH of the filtrate to 2.5-3.5 with hydrochloric acid solution, evaporate and concentrate, cool to precipitate solid, filter, and wash the filter cake with distilled water until it is free of chlorine. － , and dried at 105-110°C to constant weight to obtain a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

4. The method for preparing a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent according to claim 3, wherein: In step (1), the melamine is a product with industrial grade purity or above, and the formaldehyde is a product with industrial grade purity or above with a mass fraction of 37-40%; and the reactors are equipped with mechanical stirring, a dropping funnel and a reflux condenser.

5. The method for preparing a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent according to claim 3, wherein: In step (1), the alkali or alkaline salt solution is a Na2CO3 solution with a mass fraction of 10% to 15% or a NaOH solution with a mass fraction of 20% to 30%.

6. The method for preparing a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent according to claim 3, wherein: In step (2), the ethylenediamine is a product with a purity above industrial grade.

7. The method for preparing a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent according to claim 3, wherein: In step (3), the sodium haloacetate is either sodium chloroacetate or sodium bromoacetate.

8. The method for preparing a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent according to claim 3, wherein: In step (3), the alkali or alkaline salt solution is a NaOH or KOH solution with a mass fraction of 20% to 30%, or a Na2CO3 solution with a mass fraction of 10% to 15%, and the time for slowly adding the alkali or alkaline salt solution is 40 to 60 minutes.

9. The method for preparing a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent according to claim 3, wherein: In step (4), the mass fraction of the hydrochloric acid solution is 25% to 30%.

10. Use of the star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent obtained by the preparation method according to any one of claims 1 to 2 or any one of claims 3 to 9 in the chelation of metal ions, the regulation of metal ion concentration in industrial production processes, the mining and smelting of minerals, the extraction and separation of metal elements, electroplating processes, papermaking, the pharmaceutical industry, or dyeing.

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