A 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate chelating agent, its preparation and use

Abstract

This invention discloses a chelating agent for 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate, its preparation method, and its application. First, 2-amino-3-(4-imidazolyl)propionic acid is reacted with a base to break the internal salt bond in the molecule. Then, under the action of a strong base, the amino group loses its hydrogen atom. + The ammonia is ionized and then undergoes a nucleophilic addition reaction with carbon disulfide in the presence of a strong base to generate a chelating agent, 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate. The chelating agent obtained in this invention possesses both -CSS... － and —COO － Two coordinating groups constitute a specific spatial structure and chelating group distribution, overcoming the shortcomings of commonly used aminodithiocarbamate chelating agents, such as insufficient chelating and binding capacity for heavy metal ions due to their single chelating group and suboptimal molecular structure, resulting in poor treatment effects. This invention features a simple process, mild reaction conditions, easy operation and control, no waste generation, and is easily scalable for industrial production.

Description

Technical Field

[0001] This invention relates to the fields of chelating agent preparation, heavy metal wastewater treatment, and heavy metal immobilization in fly ash, specifically to a 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate chelating agent, its preparation method, and its application. Background Technology

[0002] Due to population growth and the rapid upgrading of agricultural and industrial activities, the emission of various pollutants into the environment worldwide has increased dramatically. Among them, Pb... 2+ Cd 2+ Hg 2+ Cr 3+ Ni 2+ Cu 2+ and Co 2+ Heavy metals, including certain heavy metals, are highly toxic even in trace amounts to human health and ecosystems, and they cannot be naturally degraded. Therefore, they pose a serious challenge to public health and the environment. With increasing public awareness and concern about the hazards of heavy metals, there is an urgent need to develop new and efficient treatment methods and technologies to eliminate heavy metal pollution.

[0003] Common terminal heavy metal wastewater treatment methods mainly include chemical precipitation, adsorption, ion exchange, and electrolysis. Although chemical precipitation has drawbacks such as unsatisfactory treatment effects, large sludge volume, and heavy metal dissolution, it is still widely used domestically and internationally for treating high-concentration heavy metal wastewater due to technical or economic reasons. Adsorption is a commonly used method, but it often suffers from low adsorption capacity, difficulty in elution and regeneration, and the generation of large amounts of hazardous waste containing heavy metals, causing serious secondary pollution. Its operating costs are also high, making it only suitable for treating low-concentration heavy metal wastewater and for advanced wastewater treatment. Ion exchange has high equipment investment costs, limited ion exchange capacity, and the tendency to generate high-concentration wastewater during elution and regeneration, making it unsuitable for treating large-scale, high-concentration heavy metal wastewater. Electrolysis involves the removal of heavy metal ions from wastewater through a series of oxidation-reduction reactions under the influence of an electric current. Although it offers rapid removal rates, breaks the coordination bonds of complexed heavy metals, facilitates heavy metal recycling, requires little space, and produces minimal sludge, it suffers from rapid plate consumption, high power consumption, and poor removal efficiency for low-concentration heavy metal wastewater. It is only suitable for small to medium-scale heavy metal wastewater treatment, such as electroplating wastewater. Chelation precipitation (flocculation), based on traditional chemical precipitation, utilizes the fundamental principles of coordination chemistry. It separates heavy metal ions from wastewater by chelating them with chelating agents, forming precipitates (flocculations). Compared to traditional chemical precipitation, chelation precipitation (flocculation) has a stronger chelating and binding capacity for heavy metals, resulting in better removal efficiency, less precipitate (flocculation), easier post-treatment, and easier recycling. It is suitable for a wide range of heavy metal ion concentrations, especially for large-scale heavy metal wastewater treatment. Therefore, it has become one of the key research areas and hot topics in the field of heavy metal wastewater treatment. The key to treating heavy metal wastewater using chelation precipitation (flocculation) lies in the performance of the chelating agent, which determines the treatment effect, efficiency, cost, and post-treatment of the sludge. Therefore, developing high-performance and inexpensive chelating agents has become an urgent task in this field. Currently, widely used chelating agents include the TMT series and aminodithiocarbamate-based (-CSS) chelating agents. － Traditional chelating agents, such as those containing only one type of chelating group, suffer from limited chelating ability for certain heavy metal ions. Research and practice show that the performance of chelating agents is not only related to the type of chelating group but also to their molecular structure, particularly the distribution of the chelating groups within the molecule. Therefore, constructing high-performance chelating groups and optimizing the spatial structure of chelating agents are crucial for improving their performance. Integrating multiple chelating (coordination) groups within the same chelating agent molecule and optimizing its structure can leverage the strengths of each group and further enhance the chelating and binding effect on heavy metal ions, thereby improving the treatment efficiency of heavy metal wastewater.

[0004] Content of the invention

[0005] To address the technical problem that a single chelating group is ineffective in treating complex wastewater containing multiple heavy metals, this invention provides a 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate chelating agent, its preparation method, and its application.

[0006] The 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate chelating agent provided by this invention has the structure of its main component as shown in formula (I):

[0007]

[0008] In formula (I), M is Na or K; x = 0 or 1, when x = 0, the N atom is connected to the H atom;

[0009] The above-mentioned main components are based on 2-amino-3-(4-imidazolyl)propionic acid, with 1-2 aminodithiocarboxylic acid groups (-CSS) grafted onto it. － This allows the molecule to contain both -CSS and other related elements. － and —COO － It contains two coordinating groups and one imidazole ring, forming a unique molecular structure and chelating group distribution. The two coordinating groups complement each other, broadening the range of adaptability to heavy metal ions, and through the synergistic effect of the chelating groups, enhancing the binding capacity of heavy metal ions in wastewater, thereby improving the treatment efficiency of heavy metal wastewater; the auxiliary components are xanthic acid and alkali; the appearance is a light red to orange-red liquid.

[0010] The preparation method of the above-mentioned 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate chelating agent includes the following steps:

[0011] (1) 2-amino-3-(4-imidazolyl)propionic acid, alkali and distilled water are added to the reactor at a mass ratio of 1:0.60 to 1.64:25 to 30. After stirring and dissolving, alkali is added. After the alkali dissolves, stirring is continued for 1 to 2 hours to break the internal salt bond in the molecule and dehydrogenate the amino group into anionic ions.

[0012] (2) Add carbon disulfide slowly dropwise at a mass ratio of 0.56 to 1.08:1 to 2-amino-3-(4-imidazolyl)propionic acid. After the addition is complete, continue the reaction at room temperature for 5 to 6 hours.

[0013] (3) Heat to 55-65℃ and continue the reaction for 1.5-2 hours until the oil droplets completely disappear. Cool to room temperature to obtain a light red to orange-red liquid, which is the product 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate chelating agent.

[0014] Furthermore, in step (1), the 2-amino-3-(4-imidazolyl)propionic acid is a product with a purity of industrial grade or higher.

[0015] Furthermore, in step (1), the alkali is NaOH or KOH, and the NaOH or KOH is a product with a purity of industrial grade or higher.

[0016] Furthermore, in step (1), the reactors are equipped with mechanical stirrers, dripping funnels, and reflux condensers.

[0017] Furthermore, in step (2), the carbon disulfide is a product with a purity of industrial grade or higher.

[0018] Furthermore, in step (2), the slow addition of carbon disulfide takes 40 to 60 minutes.

[0019] The above-mentioned chelating agents are applied to the treatment of heavy metals in various types of heavy metal wastewater or incineration fly ash, and the treatment effect is excellent.

[0020] This invention relates to a method for preparing 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate. The method involves first reacting 2-amino-3-(4-imidazolyl)propionic acid with a base to break the inner salt bond of the 2-amino-3-(4-imidazolyl)propionic acid, and then removing the hydrogen atom from the amino group of the molecule under the action of a strong base. + The formation of ammonia anions (ammonia ionization) allows for effective nucleophilic addition of the partially positively charged carbon atoms of carbon disulfide upon its addition, resulting in the formation of a chelating agent for 2-amino-3-(4-imidazolyl)propionic acid dithiocarboxylate. This invention fully utilizes the amino, carboxyl, and imidazolium rings of 2-amino-3-(4-imidazolyl)propionic acid dithiocarboxylate, along with its structural characteristics, by attaching a -CSS group to the amino group. － The prepared product possesses both -CSS － and —COO － Two coordinating groups, through their synergistic effect, significantly improve the chelation and removal performance of heavy metal ions in wastewater.

[0021] The advantages of this invention compared to the prior art are as follows:

[0022] (1) The product of this invention uses 2-amino-3-(4-imidazolyl)propionic acid molecule as the basic skeleton, making full use of the -COO of 2-amino-3-(4-imidazolyl)propionic acid molecule. － The functional groups such as amino and imidazole rings, along with their structural characteristics, give chelating agent molecules the characteristics of -CSS. － —COO － Two strong coordinating groups, namely -CSS, constitute a specific spatial structure and chelating group distribution. This is achieved through the -CSS groups in the molecule. － It forms stable, water-insoluble disulfide-coordinated four-membered rings (—CSS) with most heavy metal ions. －The 2M structure chelates and binds heavy metal ions in the -COO region. － The synergistic effect of auxiliary agents and chelating agents in optimizing the spatial structure enhances the binding capacity of heavy metals in wastewater; through the -CSS of different molecules － It chelates with the same heavy metal ions to form macromolecules, causing the micro flocs to gradually grow and form large flocs that are then separated from the water, thereby improving the treatment effect on heavy metal wastewater. This overcomes the shortcomings of commonly used aminodithiocarbamate chelating agents, such as insufficient chelating and binding ability for some heavy metal ions due to their single chelating group and suboptimal molecular structure, resulting in poor treatment effect.

[0023] (2) The method of the present invention first uses a strong base to break the inner salt bond of 2-amino-3-(4-imidazolyl)propionic acid, and then, under strong base conditions, fully removes the H from the amino group in the molecule. + The formation of ammonium anions (ammonium anionization) provides sufficient conditions for further nucleophilic attack on the partially positively charged C atoms on carbon disulfide, effectively ensuring the smooth progress of the nucleophilic addition reaction and the successful synthesis of the product.

[0024] (3) The product of this invention can react rapidly with most heavy metal ions in wastewater at room temperature to form stable, water-insoluble chelates, thus having a wide range of applications. Due to —CSS － Its strong chelating ability allows it to extract heavy metal ions from most heavy metal complexes that are slightly weaker than itself. Therefore, it is suitable not only for removing free heavy metal ions but also for removing heavy metal ions in complexed states. The product of this invention can chelate with multiple heavy metal ions in water, making it particularly suitable for treating complex wastewater containing multiple heavy metal ions, achieving highly efficient removal of multiple heavy metal ions in one step.

[0025] (4) The product of this invention is simple to use for treating heavy metal wastewater. It only requires adding a certain amount of the product of this invention to the heavy metal wastewater and stirring it thoroughly to quickly generate insoluble flocs, which can then be separated by sedimentation and filtration. No complicated equipment or procedures are required.

[0026] (5) The preparation method of the present invention is simple, the reaction conditions are mild, the operation is easy to control, no "three wastes" are generated, the required equipment is conventional equipment, it is easy to realize industrial production, and it has broad application prospects.

[0027] This invention is suitable for the treatment of various heavy metal wastewaters and the fixation of heavy metals in incineration fly ash, and is especially suitable for removing heavy metal ions from industrial wastewater and domestic sewage, particularly complex wastewater containing multiple heavy metal ions. Attached Figure Description

[0028] Figure 1 This is a flowchart of the preparation method of the present invention.

[0029] Figure 2 The infrared spectrum of the chelating agent 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate (sample of Example 3) is shown.

[0030] Figure 3 This is a diagram illustrating the chelation and flocculation mechanism of the product of this invention. Detailed Implementation

[0031] 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.

[0032] Examples 1-7 illustrate the preparation method of the product of the present invention, 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate, and Examples 8-11 illustrate the application examples of the product of the present invention.

[0033] Example 1

[0034] (1) Take 9.4036 g of 99.00% 2-amino-3-(4-imidazolyl)propionic acid and add it to a 500 mL three-necked flask equipped with a mechanical stirrer, dropping funnel and reflux condenser. Then add 235.1 mL of distilled water and stir to dissolve. Then add 5.6422 g of 96.00% NaOH, dissolve and continue stirring for 1 h.

[0035] (2) Take 3.7 mL of carbon disulfide with a mass fraction of 99.00% and add it dropwise to the solution obtained in step (1). The addition is completed within 40 min, and the reaction continues at room temperature for 5 h.

[0036] (3) Heat to 55℃ and continue the reaction for 1.5h until the oil droplets completely disappear. Cool to room temperature to obtain 242.6mL of light red liquid, which is the chelating agent of 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate.

[0037] Example 2

[0038] (1) Take 9.4036 g of 99.00% 2-amino-3-(4-imidazolyl)propionic acid and add it to a 500 mL three-necked flask equipped with a mechanical stirrer, dropping funnel and reflux condenser. Then add 235.1 mL of distilled water and stir to dissolve. Then add 5.6422 g of 96.00% NaOH, dissolve and continue stirring for 1.5 h.

[0039] (2) Take 3.7 mL of 99.00% carbon disulfide and add it dropwise to the solution obtained in step (1). The addition should be completed within 50 min, and the reaction should continue at room temperature for 5.5 h.

[0040] (3) Heat to 60℃ and continue the reaction for 1.5h until the oil droplets completely disappear. Cool to room temperature to obtain 264.7mL of light red liquid, which is the chelating agent of 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate.

[0041] Example 3

[0042] (1) Take 9.4036 g of 99.00% 2-amino-3-(4-imidazolyl)propionic acid and add it to a 500 mL three-necked flask equipped with a mechanical stirrer, dropping funnel and reflux condenser. Then add 282.1 mL of distilled water and stir to dissolve. Then add 9.0246 g of 96.00% NaOH, dissolve and continue stirring for 2 h.

[0043] (2) Take 7.5 mL of carbon disulfide with a mass fraction of 99.00% and add it dropwise to the solution obtained in step (1). The addition should be completed within 60 min, and the reaction should continue at room temperature for 5.5 h.

[0044] (3) Heat to 65℃ and continue the reaction for 1.5h until the oil droplets completely disappear. Cool to room temperature to obtain 295.1mL of light red liquid, which is the chelating agent of 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate.

[0045] Example 4

[0046] (1) Take 9.4036 g of 99.00% 2-amino-3-(4-imidazolyl)propionic acid and add it to a 500 mL three-necked flask equipped with a mechanical stirrer, dropping funnel and reflux condenser. Then add 263.3 mL of distilled water and stir to dissolve. Then add 8.3692 g of 96.00% NaOH, dissolve and continue stirring for 1.5 h.

[0047] (2) Take 6.7 mL of carbon disulfide with a mass fraction of 99.00% and add it dropwise to the solution obtained in step (1). The addition is completed within 50 min, and the reaction continues at room temperature for 6 h.

[0048] (3) Heat to 60℃ and continue the reaction for 2 hours until the oil droplets completely disappear. Cool to room temperature to obtain 275.6 mL of light red liquid, which is the chelating agent of 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate.

[0049] Example 5

[0050] (1) Take 9.4036 g of 99.00% 2-amino-3-(4-imidazolyl)propionic acid and add it to a 500 mL three-necked flask equipped with a mechanical stirrer, dropping funnel and reflux condenser. Then add 244.5 mL of distilled water and stir to dissolve. Then add 9.1096 g of 85.00% KOH, dissolve and continue stirring for 1 h.

[0051] (2) Take 3.7 mL of carbon disulfide with a mass fraction of 99.00% and add it dropwise to the solution obtained in step (1). The addition is completed within 40 min, and the reaction continues at room temperature for 5 h.

[0052] (3) Heat to 55℃ and continue the reaction for 1.5h until the oil droplets completely disappear. Cool to room temperature to obtain 252.1mL of red liquid, which is the chelating agent of 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate.

[0053] Example 6

[0054] (1) Take 9.4036 g of 99.00% 2-amino-3-(4-imidazolyl)propionic acid and add it to a 500 mL three-necked flask equipped with a mechanical stirrer, dropping funnel and reflux condenser. Then add 272.7 mL of distilled water and stir to dissolve. Then add 12.8722 g of 85.00% KOH and stir for 1.5 h after dissolving.

[0055] (2) Take 5.6 mL of 99.00% carbon disulfide and add it dropwise to the solution obtained in step (1). The addition should be completed within 50 min, and the reaction should continue at room temperature for 5.5 h.

[0056] (3) Heat to 60℃ and continue the reaction for 1.75h until the oil droplets completely disappear. Cool to room temperature to obtain 284.8mL of red liquid, which is the chelating agent of 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate.

[0057] Example 7

[0058] (1) Take 9.4036 g of 99.00% 2-amino-3-(4-imidazolyl)propionic acid and add it to a 500 mL three-necked flask equipped with a mechanical stirrer, dropping funnel and reflux condenser. Then add 244.5 mL of distilled water and stir to dissolve. Then add 15.4467 g of 85.00% KOH, dissolve and continue stirring for 2 h.

[0059] (2) Take 7.8 mL of carbon disulfide with a mass fraction of 99.00% and add it dropwise to the solution obtained in step (1). The addition should be completed within 60 min, and the reaction should continue at room temperature for 6 h.

[0060] (3) Heat to 65℃ and continue the reaction for 2 hours until the oil droplets completely disappear. Cool to room temperature to obtain 258.4 mL of orange-red liquid, which is the chelating agent of 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate.

[0061] Infrared spectroscopy analysis was performed on the chelating agents of 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate obtained in Examples 1 to 7, and the results were basically consistent. The infrared spectral analysis results of the 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate (denoted as HIS-DTC) obtained in Example 3 are as follows: Figure 2 As shown. Figure 2 The absorption peaks in the infrared spectrum can be assigned as follows: 3201.99 cm⁻¹ -1 These are the stretching vibration peaks of OH and -NH in the water content of the sample; at 2976.63 and 286.84 cm⁻¹. -1 The weak peaks at these locations are the asymmetric and symmetric stretching vibration peaks of -CH2-, corresponding to 1333.78 and 1300.86 cm⁻¹. -1 Its bending vibration peak appears at 2073.17 cm. -1 The weak peaks are the angular vibrational peaks of thioamide NC=S; 1627.22 and 1486.21 cm⁻¹. -1 The peaks represent the asymmetric and symmetric bending vibrations of -NH, with the corresponding water bending vibration peaks at 1627–1580 cm⁻¹. -1 The strong peaks are obscured; 1580.85 and 1403.20 cm. -1 The peaks at 1448.32 cm⁻¹ represent the asymmetric and symmetric stretching vibrations of the carboxylate group, respectively. -1 It is an aminodithiocarboxylic acid group (N-CSS) - The stretching vibration absorption peaks of CN in the sample are at 1262.13 and 1131.06 cm⁻¹. -1 These are the stretching vibration peaks of CO and CN in the molecule; 1048.52 and 960.41 cm⁻¹. -1 For -CSS - The stretching vibration peaks of C=S and CS in the middle; 897.91 cm. -1 It can be categorized as CSS － Deformation vibration peak; 800cm -1 The following weak peaks are deformation vibration peaks of the imidazole ring in the molecule. Elemental analysis of the above sample showed that the sulfur content was 36.21%, converted to -CSS... － Each chelating agent molecule contains an average of 1.98 -CSS molecules. － The above results indicate that the chelating agent of 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate has been successfully synthesized.

[0062] Example 8

[0063] This embodiment demonstrates the treatment effect of the sample from Example 3 on heavy metal wastewater. The samples obtained in Example 3 (denoted as HIS-DTC, —CSS) were compared. － Using sodium thiram (containing 5.646 mmol / g) and commercially available sodium thiram as chelating agents, 100 mg / L solutions containing Cd were prepared. 2 + Ni 2+ Pb 2+ Cu 2+ Cr 3+ and Mn 2+ Simulated heavy metal water samples were used. Flocculation test conditions: 500 mL of simulated heavy metal water samples were taken, and the pH value was adjusted to approximately 6.0. Chelating agents were added to the MY3000-6G intelligent color screen coagulation test stirrer (Wuhan Meiyu Instrument Co., Ltd.). The mixture was stirred rapidly at 220 r / min for 5 min, then at 100 r / min for 10 min, followed by slow stirring at 60 r / min for 15 min. After standing for 20 min, the clear liquid at 2 cm below the surface was measured using an AA-7000 atomic absorption spectrophotometer (Shimadzu Corporation, Japan). The treatment results are shown in Table 1.

[0064] Table 1. Removal effect of the product of this invention on free heavy metal ions

[0065]

[0066] As can be seen from Table 1, under optimal conditions, the product HIS-DTC of this invention is significantly more effective than the commercially available comparative sample sodium fumarate in controlling free Cd. 2+ Ni 2+ Pb 2+ Cu 2+ Cr 3+ and Mn 2+ Plasma removal is highly effective, with residual ion concentrations far below the Class I standard of the "Integrated Wastewater Discharge Standard" (GB8978-1996), and the dosage is also lower. This is because HIS-DTC contains -COO- — and CSS — It contains two functional groups, while sodium thiamethoxam only contains -CSS. — Due to the unique molecular spatial structure of HIS-DTC and the synergistic effect of the two groups, the removal effect of heavy metal ions is enhanced.

[0067] Example 9

[0068] Using HIS-DTC obtained in Example 3 as a chelating agent, the wastewater from a certain electroplating plant was used as the treatment target. The pollutant indicators of the wastewater are shown in Table 2. It contains phosphorus compounds and is grayish-green and turbid.

[0069] The product HIS-DTC obtained in Example 3, commercially available heavy metal chelating agents sodium thimerosal and TMT-18 were used as reagents. 200 mL of wastewater sample was taken, and the pH was first adjusted to approximately 6.0 with lime slurry. Then, it was placed on a MY3000-6G intelligent color screen coagulation test stirrer (Wuhan Meiyu Instrument Co., Ltd.), and certain amounts of chelating agents such as HIS-DTC, sodium thimerosal, and TMT-18 were added. The stoichiometric ratio of HIS-DTC to sodium thimerosal (i.e., the ratio of HIS-DTC to sodium thimerosal - CSS) was determined. － The molar ratios of the chelating agent to heavy metal ions were 1.70:1 and 2.25:1, respectively, and the molar ratio of TMT-18 to metal ions was 1:1.5. The chelating agent was added with stirring at 250 rpm for 5 min; then stirred at 100 rpm for 20 min (adding an appropriate amount of polyacrylamide PAM after 10 min of stirring), followed by stirring at 60 rpm for 15 min, and allowed to stand for 20 min. Samples were taken for analysis, and the endpoint pH value and the concentration of heavy metal ions in the treated water were tested. The results are listed in Table 2.

[0070] Table 2. Removal effect of the product of this invention on comprehensive wastewater from electroplating plants.

[0071]

[0072] The results in Table 2 show that the product HIS-DTC of this invention has a significantly better treatment effect on this type of comprehensive electroplating wastewater than commercially available heavy metal capture agents such as sodium fumarate and TMT-18. Moreover, it requires less dosage, has lower turbidity in the treated water, and all pollutant indicators are lower than the limits specified in the "Electroplating Pollutant Discharge Standard" (GB21900-2008).

[0073] Example 10

[0074] Using HIS-DTC obtained in Example 3 as the chelating agent, the wastewater from a copper foil manufacturing plant was used as the treatment target. The pollutant indicators are shown in Table 3, containing pyrophosphate and appearing pale yellow and slightly turbid. The product HIS-DTC obtained in Example 3, commercially available heavy metal trapping agents sodium thimerosal and TMT-18 were used as reagents. 200 mL of wastewater sample was taken, and the pH was first adjusted to approximately 6.0 with lime milk. Then, it was placed on a MY3000-6G intelligent color screen coagulation test stirring instrument (Wuhan Meiyu Instrument Co., Ltd.), and certain amounts of HIS-DTC, sodium thimerosal, and TMT-18 were added respectively. The stoichiometric ratio of HIS-DTC to sodium thimerosal (i.e., the ratio of HIS-DTC to sodium thimerosal in HIS-DTC or sodium thimerosal) was determined. －The molar ratios of TMT-18 to heavy metal ions were 1.85:1 and 2.1:1, respectively, and the stoichiometric ratio of TMT-18 to metal ions was 1:1.5. The chelating agent was added with stirring at 200 rpm for 5 min; then stirred at 100 rpm for 20 min (adding an appropriate amount of polyacrylamide PAM after 10 min of stirring), followed by stirring at 60 rpm for 20 min, and allowed to stand for 20 min. Samples were taken for analysis to determine the concentration of heavy metal ions in the treated water, and the results are listed in Table 3.

[0075] Table 3. Removal effect of the product of this invention on the comprehensive wastewater of copper foil manufacturing plant.

[0076]

[0077]

[0078] Table 3 shows that the product HIS-DTC of this invention has a significantly better treatment effect on this wastewater than commercially available heavy metal capture agents such as sodium fumarate and TMT-18. It can not only remove Cu... 2+ Co 2+ Fe 3+ All three ions were completely removed, and for Cr 3+ and Zn 2+ It can also remove pollutants to very low concentrations, and all pollutant indicators are lower than the limits specified in the "Electroplating Pollutant Emission Standard" (GB21900-2008).

[0079] Example 11

[0080] HIS-DTC, the product obtained in Example 3, sodium formaldehyde sulfoxylate, a commercially available heavy metal trapping agent, and TMT-18 were used as heavy metal stabilizers in incineration fly ash, and solutions with a mass fraction of 5% were prepared. During the experiment, 250g of fly ash from a waste incineration plant was added to a reaction kneader. Then, stabilizer and water were added at a mass ratio of fly ash: stabilizer: water = 100:1 to 3:20. After thorough stirring and kneading for 20 minutes, the reaction continued for 2 hours. Samples were then taken for leaching experiments according to the method specified in HJ / T300-2007, and the concentration of pollutants in the leachate was determined. The results are shown in Table 4.

[0081] Table 4. Effects of the product of this invention and commercially available stabilizers on the treatment of incineration fly ash.

[0082]

[0083]

[0084] As can be seen from Table 4, the amount of HIS-DTC, the product of this invention, is less than that of sodium fumarate and TMT-18, and it has a stronger stabilizing effect on metal ions in fly ash. The concentration of metal elements in the leachate of the stabilized fly ash is lower than the limit specified in the "Standard for Pollution Control of Municipal Solid Waste Landfill" (GB16889-2008), and it can be safely landfilled in the landfill.

[0085] The results of Examples 8-11 show that the product HIS-DTC of this invention has superior removal efficiency for heavy metal ions in free heavy metal wastewater and complex actual electroplating wastewater and copper foil production wastewater compared to the comparative samples, and exhibits better chelation and stabilization effects on incineration fly ash. This is because HIS-DTC contains 1-2 -CSS groups. — And 1—COO — (N—CH—COO — It readily reacts with heavy metal ions in water, as shown in the attached image. Figure 3 The chelation effect shown: (1) Two -CSS molecules in one molecule — It can chelate with heavy metal ions to form water-insoluble disulfide-coordinated four-membered ring chelates, or it can be derived from two —CSS groups in different HIS-DTC molecules. — It chelates with heavy metal ions to form water-insoluble disulfide-coordinated four-membered ring chelates; two —CSS groups per molecule — It can simultaneously interact with two CSSs of another HIS-DTC. — It can chelate with heavy metal ions to form chelates with two disulfide-coordinated four-membered ring structures, and can also chelate with two -CSS from different HIS-DTC molecules. — (2) It can chelate with heavy metal ions to form a chelate with two disulfide-coordinated four-membered ring structures; (3) it can be chelated by two -CSS from different HIS-DTC molecules. — Group or N-CH-COO — It chelates with the same heavy metal ion to form one water-insoluble disulfide-coordinated four-membered ring chelate or two... The five-membered chelating ring connects chelates formed by different molecules, allowing them to grow gradually and form larger flocs, thereby improving the efficiency of chelating and binding heavy metal ions and the stability of the chelates.

[0086] 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 make various modifications and transformations. For example, within the range of proportions and process conditions given in the present invention, the proportions and process conditions can be combined and transformed. Such transformations and modifications are all within the scope of the present invention.

Claims

1. A chelating agent for 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate, characterized in that, Its main components have the structure shown in formula (Ⅰ): （Ⅰ）， In equation (I), M is Na or K; x=1.

2. The method for preparing the chelating agent of 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate according to claim 1, characterized in that, Includes the following steps: (1) 2-amino-3-(4-imidazolyl)propionic acid, alkali and distilled water are added to the reactor at a mass ratio of 1:0.60~1.64:25~30. After stirring and dissolving, alkali is added. After the alkali dissolves, stirring is continued for 1~2 hours to break the internal salt bond in the molecule and make the amino dehydrogenated and ionized. (2) Add carbon disulfide slowly dropwise at a mass ratio of 0.56 to 1.08:1 for carbon disulfide and 2-amino-3-(4-imidazolyl)propionic acid. After the addition is complete, continue the reaction at room temperature for 5 to 6 hours. (3) Heat to 55~65℃ and continue the reaction for 1.5~2h until the oil droplets disappear completely. Cool to room temperature to obtain a light red to orange-red liquid, which is the product 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate chelating agent.

3. The method for preparing the chelating agent of 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate according to claim 2, characterized in that, In step (1), the 2-amino-3-(4-imidazolyl)propionic acid is a product with industrial grade or higher purity.

4. The method for preparing the chelating agent of 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate according to claim 2, characterized in that, In step (1), the alkali is NaOH or KOH.

5. The method for preparing the chelating agent of 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate according to claim 4, characterized in that, The NaOH or KOH is a product of industrial grade or higher purity.

6. The method for preparing the chelating agent of 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate according to claim 2, characterized in that, In step (1), the reactors are equipped with mechanical stirring, a dripping funnel, and a reflux condenser.

7. The method for preparing the chelating agent of 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate according to claim 2, characterized in that, In step (2), the carbon disulfide is a product with a purity of industrial grade or higher.

8. The method for preparing the chelating agent of 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate according to claim 2, characterized in that, In step (2), the slow addition of carbon disulfide takes 30 to 60 minutes.

9. The application of the 2-amino-3-(4-imidazolyl)propionic acid dithiocarbamate chelating agent according to claim 1 in the treatment of heavy metals in heavy metal wastewater or incineration fly ash.

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