Star-shaped melamine hexa (ethylenediamine-N, N-diacetic acid) chelating agent as well as preparation method and application thereof

Abstract

The invention discloses a star-shaped melamine hexa (ethylenediamine-N, N-diacetic acid) chelating agent as well as a preparation method and application thereof. The preparation method comprises the following steps: firstly, carrying out addition reaction on melamine and formaldehyde under a weakly alkaline condition to generate hexamethylol melamine, adding ethidene diamine before further dehydration polycondensation, and connecting ethidene diamine to melamine through condensation of hydroxymethyl and amino of ethidene diamine; and reacting with halogenated sodium acetate in the presence of alkali or alkaline salt, and grafting two-CH2COO-groups to the tail end of each branched chain to form a molecular structure which takes melamine as a mother nucleus and six branched chains with-N (CH2COOH) 2 groups at the tail ends and is distributed in a star shape. The chelating agent provided by the invention can chelate metal ions from different directions, fix the metal ions on molecules and aggregate the metal ions, and the synergistic chelating effect of adjacent branched chains enhances the chelating ability to the metal ions and the stability of the chelate. The method has the advantages of simple process, mild reaction conditions, environment-friendly and easy-to-control process, and easy realization of large-scale production.

Description

Technical Field

[0001] The 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 and a preparation method and application thereof. Background Art

[0002] Chelating agents are also called chelating ligands, chelating groups or multidentate ligands. They are characterized by containing more than two coordinating atoms in the molecule and being able to simultaneously form a chelating ring with a central atom (or ion). Since this type of molecular structure is very similar to the two large "claws" of a "crab" clamping metal atoms or ions, it is figuratively called a chelating agent, and the complex with a ring structure formed is called a chelate. Since two or more coordinating atoms in the chelating agent simultaneously form a chelating ring with a central atom (or ion), the stability of the formed chelate is significantly improved compared to non-chelating coordination compounds with similar composition and structure. The vast majority of chelating agents are organic ligands, and the most common coordinating atoms among them are oxygen and nitrogen, followed by sulfur, phosphorus, arsenic, etc. Due to the special structure and properties of chelating agents, they are widely used in industrial and agricultural production and daily life. For example, adding chelating agents can make metal ions generate chelates with completely different properties. Adding chelating agents in industrial production has become the main method to reduce and control the concentration of metal ions; chelating agents can be used as bleaching aids for chemical, mechanical and deinked pulp with hydrogen peroxide and hypochlorous acid as bleaching agents; some chelating agents can be used as antidotes for lead and mercury poisoning in medicine. In addition, in industrial production, it can also be widely used in mineral flotation, hydrometallurgy, extraction and separation of metal elements, catalytic synthesis of substances, water softening, electroplating technology, pharmaceutical industry and dyeing process.

[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 optimal. If more —N(CH2COO － )2 chelating group, it is expected to construct a new type of high-efficiency chelating agent, thereby giving the chelating agent new properties and obtaining new applications. Melamine is a trimer of aminocyanide, with three amino groups evenly distributed on the triazine nitrogen heterocyclic ring. If the three amino groups evenly distributed on its molecule can be connected to -N(CH2COO－ )2 is expected to construct a melamine-based system with multiple—N(CH2COO － )2 groups are distributed in a star shape. 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 and modification. It is difficult to directly convert -N(CH2COO － )2 is modified on it. 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 view of 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 terminal group to form a star-shaped structure. The -N(CH2COOH)2 group on each branch can form 2 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 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) Adding formaldehyde solution into a reactor at a molar ratio of melamine to formaldehyde of 1:10-12, adjusting the pH value to 8.0-9.5 with an alkali or alkaline salt solution, and then adding a measured amount of melamine; starting the stirrer, heating to 70-90° C., and waiting for the reaction mixture to turn from turbid to clear, keeping the temperature and continuing the reaction for 20-60 minutes; then preheating distilled water to 70-85° C. at a volume ratio of distilled water to formaldehyde solution of 5-8:1, adding the distilled water to the reactor, and stirring 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 keeping 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 higher than industrial grade, and the formaldehyde is a product with a purity higher than industrial grade 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 the chelation of metal ions, the regulation of metal ion concentration in industrial production, the mining and smelting of minerals, the extraction and separation of metal elements, electroplating technology, papermaking, pharmaceutical industry or dyeing, etc., with remarkable effects.

[0022] The present invention relates to a method for preparing a star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent. First, melamine and formaldehyde are subjected to addition reaction under weak alkaline conditions to generate hexahydroxymethyl melamine, and then ethylenediamine is added before further dehydration and polycondensation, so that the hydroxymethyl group and the amino group on the ethylenediamine are condensed to connect the ethylenediamine to the amino group of the melamine, and then the chelating agent is reacted with sodium haloacetate in the presence of an alkali or an alkaline salt to connect two -CH2COO at the end of the chain. － It forms -N(CH2COOH)2 groups, forming a molecular structure with melamine as the parent core and 6 branches with -N(CH2COOH)2 groups at the ends, which are distributed in a star shape. The metal ions are chelated and fixed on the molecule from different directions by -N(CH2COOH)2, and the metal ions are aggregated together by the connecting effect of the melamine parent core, and the chelating ability of metal ions and the stability of the chelate are enhanced by the synergistic chelation of -N(CH2COOH)2 on the adjacent branches.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The product of the present invention has a melamine core and six branched chains with -N(CH2COOH)2) at the ends, forming a star-shaped structure. The -N(CH2COOH)2) groups on the six branched chains can chelate and bind metal ions from a wider range, and then the metal ions chelated and bound by the six branched chains are aggregated through the melamine ring, and 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 adding water to dilute the generated hydroxymethyl melamine before further dehydration condensation and timely adding ethylenediamine and maintaining its excess, so as to ensure that the hydroxymethyl group and ethylenediamine condense to form a relatively complete six-branched structure, and play a sealing role on the hydroxymethyl group to prevent 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 was effectively prevented, and the problem of easy polycondensation of hydroxymethyl melamine was effectively prevented, thus achieving effective regulation of the molecular structure.

[0026] (3) The special structure of the product of the present invention can not only provide more strong chelating groups and chelating sites for the chelation of metal ions, but also make it contact with metal ions from different directions and in a wider range, thereby increasing the speed of the chelation reaction, and can enhance the chelation of metal ions and the stability of the formed chelate through the synergistic chelation of -N(CH2COOH)2 on the adjacent side chains. Therefore, compared with the commonly used chelating agents, the product of the present invention has a better chelating ability for metal ions, chelate stability and chelate 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 invention is suitable for the chelation of various metal ions, the regulation of metal ion concentration in industrial production, the mining and smelting of minerals, the extraction and separation of metal elements, electroplating technology, papermaking, pharmaceutical industry, dyeing and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

[0034] Example 1

[0035] (1) Take 26.7 mL of formaldehyde with a mass fraction of 37-40% and add it to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, add a 15.00% Na2CO3 solution dropwise to adjust the pH value of the formaldehyde solution to 8.0, then add 3.82 g of 99.00% melamine, start the stirrer, raise the temperature to 75°C, wait for the reaction mixture to turn from turbid to clear, keep the temperature and continue the reaction for 30 minutes; then add 133.2 mL of distilled water preheated to 75°C to the reactor and stir 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. The addition time for each batch is 40 min. When the pH value of the reaction solution drops to about 10, add the next batch. After the addition is complete, continue to react at room temperature for 12 h.

[0038] (4) Raise the temperature 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 a 25.00% hydrochloric acid solution, evaporate and concentrate, cool to precipitate solids, filter, and wash the filter cake with distilled water until there is no chlorine. － , placed in an oven and dried at 105°C to constant weight to obtain 35.21 g of light yellow powder, i.e., star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

[0039] Example 2

[0040] (1) Take 24.4 mL of formaldehyde with a mass fraction of 37-40% and add it to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, add a 10.00% Na2CO3 solution dropwise to adjust the pH value of the formaldehyde solution to 8.5, then add 3.82 g of 99.00% melamine, start the stirrer, raise the temperature to 80°C, wait for the reaction mixture to turn from turbid to clear, keep the temperature and continue the reaction for 40 minutes; then add 146.5 mL of distilled water preheated to 80°C to the reactor and stir 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 3 batches, with each batch adding for 50 min. When the pH value of the reaction solution drops to about 10, add the next batch, and continue to react at room temperature for 14 h after the addition is complete;

[0043] (4) Raise the temperature to 85°C, add activated carbon for decolorization for 1.5 hours, then filter, and wash the filter residue with distilled water; adjust the pH of the filtrate to 3.1 with a 28.00% hydrochloric acid solution, evaporate and concentrate, cool to precipitate solids, filter, and wash the filter cake with distilled water until there is no chlorine.－ , placed in an oven and dried at 110°C to constant weight to obtain 34.36 g of light yellow powder, i.e., star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

[0044] Example 3

[0045] (1) 22.2 mL of formaldehyde with a mass fraction of 37-40% was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and a 20.00% NaOH solution was added dropwise to adjust the pH value of the formaldehyde solution to 9.2, and 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 reaction was continued for 50 min at the temperature; then 177.6 mL of distilled water preheated to 85° C. was 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 3 batches. The addition time of each batch is 60 min. When the pH value of the reaction solution drops to about 10, add the next batch. After the addition is complete, continue to react at room temperature for 16 h.

[0048] (4) Raise the temperature to 95°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 3.5 with a 30.00% hydrochloric acid solution, evaporate and concentrate, cool to precipitate solids, filter, and wash the filter cake with distilled water until there is no chlorine. － , placed in an oven and dried at 110°C to constant weight to obtain 34.25 g of light yellow powder, i.e., star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

[0049] Example 4

[0050] (1) 24.4 mL of formaldehyde with a mass fraction of 37-40% was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and a 25.00% NaOH solution was added dropwise to adjust the pH value of the formaldehyde solution to 9.5, and then 3.82 g of 99.00% melamine was added, the stirrer was started, the temperature was raised to 90° C., and the reaction mixture was kept warm until it turned clear from turbidity, and the reaction was continued for 60 min; then 170.8 mL of distilled water preheated to 90° C. was 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 3 batches, with each batch adding for 50 min. When the pH value of the reaction solution drops to about 10, add the next batch, and continue to react at room temperature for 15 h after the addition is complete;

[0053] (4) Raise the temperature 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 3.2 with a 26.00% hydrochloric acid solution, evaporate and concentrate, cool to precipitate solids, filter, and wash the filter cake with distilled water until there is no chlorine. － , placed in an oven and dried at 105°C to constant weight to obtain 35.91 g of white powder, i.e., star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

[0054] Example 5

[0055] (1) Take 25.5 mL of formaldehyde with a mass fraction of 37-40% and add it to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, add a 25.00% NaOH solution dropwise to adjust the pH value of the formaldehyde solution to 8.9, then add 3.82 g of 99.00% melamine, start the stirrer, raise the temperature to 85°C, wait for the reaction mixture to turn from turbid to clear, keep the temperature and continue the reaction for 60 minutes; then add 204.2 mL of distilled water preheated to 85°C to the reactor and stir thoroughly;

[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. The addition time of each batch is 50 min. When the pH value of the reaction solution drops to about 10, add the next batch. After the addition is complete, continue to react at room temperature for 16 h.

[0058] (4) Raise the temperature to 90°C, add activated carbon for decolorization for 1.5 hours, then filter, and wash the filter residue with distilled water; adjust the pH of the filtrate to 3.1 with a 25.00% hydrochloric acid solution, evaporate and concentrate, cool to precipitate solids, filter, and wash the filter cake with distilled water until there is no chlorine. －, placed in an oven and dried at 105°C to constant weight to obtain 35.85 g of white powder, i.e., star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

[0059] Example 6

[0060] (1) 23.3 mL of formaldehyde with a mass fraction of 37-40% was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and a 30.00% NaOH solution was added dropwise to adjust the pH value of the formaldehyde solution to 8.7, and 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 reaction was continued for 60 min at the temperature; then 140.0 mL of distilled water preheated to 85° C. was added to the reactor and stirred thoroughly;

[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. The addition time of each batch is 50 min. When the pH value of the reaction solution drops to about 10, add the next batch. After the addition is complete, continue to react at room temperature for 14 h;

[0063] (4) Raise the temperature to 85°C, add activated carbon for decolorization for 1.5 hours, then filter, and wash the filter residue with distilled water; adjust the pH of the filtrate to 2.9 with a 30.00% hydrochloric acid solution, evaporate and concentrate, cool to precipitate solids, filter, and wash the filter cake with distilled water until there is no chlorine. － , placed in an oven and dried at 105°C to constant weight to obtain 35.02 g of white powder, i.e., star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

[0064] Example 7

[0065] (1) 26.6 mL of formaldehyde with a mass fraction of 37-40% was added to a 750 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and a 30.00% NaOH solution was added dropwise to adjust the pH value of the formaldehyde solution to 8.3, and then 3.82 g of 99.00% melamine was added, the stirrer was started, and the temperature was raised to 85° C., and the reaction mixture was kept warm until it turned clear from turbidity and continued to react for 60 min; then 133 mL of distilled water preheated to 85° C. was 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. The addition time of each batch is 50 min. When the pH value of the reaction solution drops to about 10, add the next batch. After the addition is complete, continue to react at room temperature for 15 h;

[0068] (4) Raise the temperature to 80°C, add activated carbon for decolorization for 1.5 hours, then filter, and wash the filter residue with distilled water; adjust the pH of the filtrate to 2.9 with a 30.00% hydrochloric acid solution, evaporate and concentrate, cool to precipitate solids, filter, and wash the filter cake with distilled water until there is no chlorine. － , placed in an oven and dried at 105°C to constant weight to obtain 34.95 g of white powder, i.e., star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

[0069] Example 8

[0070] (1) 24.4 mL of formaldehyde with a mass fraction of 37-40% was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and a 25.00% NaOH solution was added dropwise to adjust the pH value of the formaldehyde solution to 8.5, and 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 reaction was continued for 60 min at the temperature; then 146.4 mL of distilled water preheated to 85° C. was 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. The addition time of each batch is 50 min. When the pH value of the reaction solution drops to about 10, add the next batch. After the addition is complete, continue to react at room temperature for 15 h.

[0073] (4) Raise the temperature to 85°C, add activated carbon for decolorization for 1.5 hours, then filter, and wash the filter residue with distilled water; adjust the pH of the filtrate to 3.0 with a 25.00% hydrochloric acid solution, evaporate and concentrate, cool to precipitate solids, filter, and wash the filter cake with distilled water until there is no chlorine. －, placed in an oven and dried at 105°C to constant weight to obtain 35.17 g of white powder, i.e., star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent.

[0074] The infrared spectroscopy 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 obtained were basically the same. The infrared spectroscopy 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 attributed as follows: 3294.62cm -1 The stretching vibration peaks of OH and -NH 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 The 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; 1556.99cm -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 It is the bending vibration peak of -NH and bound water molecule OH; 1447.31cm -1 are the deformation vibration peaks of CN; 1215.86, 1118.27 and 1027.08 cm -1 It is the stretching vibration peak of CO and CN in the molecule. The elemental analysis of the above samples shows that the N content is 19.98%, and the O content is 30.19%, which is equivalent to 17.89 N atoms in each molecule, close to the theoretical value of 18; O atoms are converted to -N(CH2COOH)2, so each heavy metal chelating agent molecule is connected with an average of 5.91 -N(CH2COOH)2. The above results show that the star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent has been successfully synthesized.

[0075] Example 9

[0076] This example shows the effect of using the chelating agent obtained in Example 3 as the main component of the heavy metal contaminated soil eluent. A heavy metal contaminated soil, wherein the heavy metal content is shown in Table 1, the organic matter is 16.7%, and the pH value is 7.67. Take 5g of the chelating agent obtained in Example 3, 2g of glycine, and 1g of rhamnolipid, add them to 42mL of deionized water, stir and dissolve them thoroughly to obtain a heavy metal eluent. Preparation of comparative eluent: replace the chelating agent obtained in Example 3 with 5g of disodium ethylenediaminetetraacetic acid (EDTA), and prepare a comparative sample eluent according to the above ratio. Then take 3g of soil and place it in 2 50mL plastic centrifuge tubes, add 30mL of the prepared eluent and comparative eluent respectively; at room temperature (25°C), shake at a speed of 250r / min for 12h, let it stand for 12h and then filter, use plasma emission spectroscopy (ICP-OES) to determine the content of various heavy metals in the treated soil sample, calculate the removal rate of heavy metals by the eluent, and 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 elution liquid prepared with the product of the present invention has a significantly higher elution removal effect on heavy metals in contaminated soil than the elution liquid prepared with EDTA, and the heavy metal content in the soil after treatment is lower. The main reason is that the product of the present invention is based on melamine as the core, grafted with 6 side chains with aminodiacetic acid (-N(CH2COOH)2) as the end group, forming a unique star-shaped structure, with a large number of strong coordination groups -N(CH2COOH)2, and a star-shaped distribution, 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, increasing the probability of chelation with heavy metal ions, thereby increasing 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 more compact chelate or chelate aggregate through the connection of the melamine mother ring; (3) 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 shows the effect of the product of the present invention on the deinking and bleaching of waste paper. Preparation of deinking liquid: Take 6g of the product of Example 3, 3.5g of sodium polyacrylate, 4g of hydroxyethylidene diphosphonic acid, and 2.5g of diethylenetriamine penta methylene phosphonic acid, add water to dissolve, adjust the pH to about 6.0 with NaOH, and dilute with water to a volume of 50mL to obtain. In addition, sodium ethylenediaminetetraacetic acid (EDTA) is used to prepare deinking liquid for comparison: Take 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, adjust the pH to 6.0-6.5 with NaOH, and dilute with water to a volume of 50mL to obtain EDTA deinking liquid. Preparation of bleaching liquid: Take 2.0g of 40 degrees Baume NaOH solution, 2.0g of sodium silicate and 2.5g of hydrogen peroxide and mix them evenly to obtain bleaching liquid, and prepare 2 portions. Then, 15g of the prepared deinking liquid and EDTA deinking liquid of the present invention are added to 2 parts of bleaching liquid respectively, and stirred evenly to obtain a deinking and bleaching mixed liquid. Take 100g of mixed office waste paper and shred it, control the pulp concentration to 15%, add the above-prepared deinking and bleaching mixed liquid, bleach it at 70°C for 80 minutes, then wash it with distilled water, and measure its whiteness. The optical whiteness value of the waste paper pulp treated with the deinking liquid prepared by the product of the present invention reaches 81.6% ISO, while the whiteness value of the EDTA deinking liquid only reaches 76.9% ISO. Therefore, the waste paper deinking agent prepared by the product of the present invention is used to deink waste paper, and the whiteness is increased by 4.7%, and diethylenetriaminepentaacetic acid does not need to be added to the deinking liquid formula, which saves reagents and reduces costs.

[0082] Embodiment 11

[0083] This example is the scale inhibition effect of the product of Example 3. The product of Example 3 is used as a sample, and commercially available EDTA is used as a comparative sample. First, the product of Example 3 and the EDTA water treatment agent sample solution are prepared respectively, with a concentration of 0.500 mg / mL; then the scale inhibition performance is determined according to the method of "Determination of Scale Inhibition Performance of Water Treatment Agents-Calcium Carbonate Deposition Method" (GB / T16632-2019), and the scale inhibition experimental conditions are: temperature is 80°C, and constant temperature placement time is 10h. The scale inhibition rate of the product of Example 3 is determined to be 93.12%, and the scale inhibition rate of commercially available EDTA is 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) Adding formaldehyde solution into a belt reactor at a molar ratio of melamine to formaldehyde of 1:10-12, adjusting the pH value to 8.0-9.5 with an alkali or alkaline salt solution, and then adding a measured amount of melamine; starting the stirrer, heating to 70-90°C, and waiting for the reaction mixture to turn from turbid to clear, keeping the temperature and continuing the reaction for 20-60 minutes; then preheating distilled water to 70-85°C at a volume ratio of distilled water to formaldehyde solution of 5-8:1, adding the distilled water to the reactor, and stirring 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 keeping 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 the star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent according to claim 3, characterized in that: In step (1), the melamine is a product with a purity higher than industrial grade, and the formaldehyde is a product with a purity higher than industrial grade 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 the star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent according to claim 3, characterized in that: 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 the star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent according to claim 3, characterized in that: In step (2), the ethylenediamine is a product with a purity above industrial grade.

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

8. The method for preparing the star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent according to claim 3, characterized in that: 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 the star-shaped melamine hexa(ethylenediamine-N,N-diacetic acid) chelating agent according to claim 3, characterized in that: 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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