2-amino-3-(4-imidazolyl) propionic acid dithioformate chelating agent as well as preparation method and application thereof

Abstract

The invention discloses a 2-amino-3-(4-imidazolyl) propionic acid dithioformate chelating agent as well as a preparation method and application of the 2-amino-3-(4-imidazolyl) propionic acid dithioformate chelating agent. The preparation method comprises the following steps: reacting 2-amino-3-(4-imidazolyl) propionic acid with alkali to break inner salt bonds in molecules, and removing H < + > from amino under the action of strong alkali to realize negative ammonia ionization; and then carrying out nucleophilic addition reaction on the 2-amino-3-(4-imidazolyl) propionate dithioformate and carbon disulfide in the presence of strong base to generate the 2-amino-3-(4-imidazolyl) propionate dithioformate chelating agent. The chelating agent disclosed by the invention has two coordination groups, namely-CSS-and-COO-, forms a specific space structure and chelating group distribution, and overcomes the defects that a common aminodithioformate chelating agent is insufficient in heavy metal ion chelating and binding capability, poor in treatment effect and the like due to single chelating group and poor molecular structure. The method is simple in process, mild in reaction condition, simple and convenient to operate and control, free of three wastes and easy to realize industrial production.

Description

Technical Field

[0001] The invention relates to the fields of preparation of chelating agents, treatment of heavy metal wastewater and immobilization of heavy metals in fly ash, and in particular to a 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agent and a preparation method and application thereof. Background Art

[0002] Due to population growth, rapid upgrading of agricultural and industrial activities, various pollutants discharged into the environment have increased dramatically around the world. 2+ 、Cd 2+ , Hg 2+ Cr 3+ 、Ni 2+ , Cu 2+ and Co 2+ Heavy metals such as chlorinated metals are not only highly toxic to human health and the ecosystem, but also cannot be naturally degraded. Therefore, they pose a severe challenge to public health and the environment. With the increasing attention and awareness of heavy metal hazards, it is urgent 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 the chemical precipitation method has disadvantages such as unsatisfactory treatment effect, large sludge volume, and heavy metal dissolution, it is still widely used in the treatment of high-concentration heavy metal wastewater at home and abroad due to technical or economic reasons. Adsorption is a more commonly used treatment method, but it often has problems such as low adsorption capacity, difficulty in elution and regeneration, and easy generation of a large amount of hazardous waste containing heavy metals, causing serious secondary pollution. The operating cost is high and it is only suitable for the treatment of low-concentration heavy metal wastewater and deep treatment of wastewater. The ion exchange method has high equipment investment costs, small ion exchange capacity, and elution and regeneration are prone to produce high-concentration waste liquid, which is not suitable for the treatment of high-concentration large-scale heavy metal wastewater. The electrolysis method refers to the removal of heavy metal ions in wastewater through a series of oxidation-reduction reactions under the action of electric current. Although the removal rate is fast, the coordination bonds of the coordinated heavy metals can be destroyed, and the heavy metals are easy to recycle, the floor space is small, and the amount of sludge is small, but the plate consumption is fast, the power consumption is large, and the removal effect of low-concentration heavy metal wastewater is poor. It is only suitable for small and medium-sized heavy metal wastewater treatment, such as electroplating wastewater treatment. The chelation precipitation (flocculation) method is based on the traditional chemical precipitation method. It uses the basic principles of coordination chemistry to chelate and bind heavy metal ions in the wastewater through chelating agents to form precipitates (flocs) and separate them from the wastewater. Compared with the traditional chemical precipitation method, the chelation precipitation (flocculation) method has a stronger chelation and binding ability for heavy metals, better removal effect, and produces less precipitates (flocs). It is convenient for post-processing, conducive to recycling, and suitable for a wide range of heavy metal ion concentrations, especially for the treatment of large-scale heavy metal wastewater. Therefore, it has become one of the key points and hotspots in the field of heavy metal wastewater treatment. The key to treating heavy metal wastewater by chelation precipitation (flocculation) is the performance of the chelating agent, which determines the treatment effect, efficiency, treatment cost and post-treatment of sediment. Therefore, the research and development of chelating agents with excellent performance and low cost has become an urgent task in this field. At present, widely used chelating agents such as TMT series, aminodithiocarboxylic acid (CSS) － ) chelating agents have the problems of single chelating group and limited chelating and binding ability to some heavy metal ions. Research and practice have shown that the performance of chelating agents is not only related to the type of chelating group, but also to the molecular structure of the chelating agent, especially the distribution of the chelating group on the molecule. Therefore, how to construct a chelating group with excellent performance and optimize the spatial structure of the chelating agent plays a vital role in improving the performance of the chelating agent. By making multiple chelating (coordination) groups compatible in the same chelating agent molecule and optimizing its structure, it is expected that the chelating groups can complement each other, and further promote the chelating and binding effect on heavy metal ions through the optimized structure, thereby improving the treatment efficiency of heavy metal wastewater.

[0004] Summary of the invention

[0005] In view of the technical problem that the above-mentioned single chelating group has poor effect in treating complex wastewater containing multiple heavy metals, the present invention provides a 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agent and a preparation method and application thereof.

[0006] The 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agent provided by the present invention has a structure of the 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 a H atom;

[0009] The above main component is based on 2-amino-3-(4-imidazolyl) propionic acid, on which 1 to 2 aminodithiocarboxylic acid groups (-CSS － ), so that the molecule has both - CSS － and—COO － The two coordination groups, and one imidazole ring, form a special molecular structure and chelating group distribution. The two coordination groups complement each other, broaden the scope of adaptation to heavy metal ions, and enhance the binding ability of heavy metal ions in wastewater through the synergistic effect of chelating groups, thereby improving the treatment efficiency of heavy metal wastewater; the auxiliary components are xanthogenic acid and alkali; the appearance is light red to orange-red liquid.

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

[0011] (1) Add 2-amino-3-(4-imidazolyl)propionic acid and distilled water into a reactor in a mass ratio of 2-amino-3-(4-imidazolyl)propionic acid, alkali and distilled water of 1:0.60-1.64:25-30, stir to dissolve, then add alkali, and continue stirring for 1-2 hours after the alkali is dissolved to break the internal salt bond in the molecule and dehydrogenate the amino group into negative ammonia ions;

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

[0013] (3) Raise the temperature to 55-65°C and continue the reaction for 1.5-2 hours until the oil droplets disappear completely. Cool to room temperature to obtain a light red to orange-red liquid, i.e., the product 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agent.

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

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

[0016] Furthermore, in step (1), the reactors are equipped with mechanical stirring, a dropping funnel and a reflux condenser.

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

[0018] Furthermore, in step (2), the time for slowly adding carbon disulfide is 40 to 60 minutes.

[0019] The above chelating agent is used to treat various heavy metal wastewaters or heavy metals in incineration fly ash, and the treatment effect is excellent.

[0020] The present invention relates to a method for preparing 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate. The method firstly reacts 2-amino-3-(4-imidazolyl) propionic acid with a base to break the internal salt bond of the 2-amino-3-(4-imidazolyl) propionic acid, and then removes the H from the amino group in the molecule under the action of a strong base. + The negative ions of ammonia are formed (negative ammonium ionization), so that when carbon disulfide is added, the carbon atoms with partial positive charge of carbon disulfide are effectively attacked to generate a nucleophilic addition reaction, thereby generating a chelating agent of 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate. The present invention makes full use of the amino group, carboxyl group and imidazole ring of 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate and its structural characteristics, and connects a CSS － Make the prepared product have both - CSS － and—COO － The synergistic effect of the two coordination groups significantly improves the chelating removal performance of heavy metal ions in wastewater.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The product of the present invention uses 2-amino-3-(4-imidazolyl) propionic acid molecules as the basic skeleton, making full use of the -COO － , amino, imidazole ring and other functional groups and their structural characteristics make the chelating agent molecules have both - CSS － , —COO － The two strong coordination groups, such as CSS, form a specific spatial structure and chelating group distribution. － It reacts with most heavy metal ions to form a stable and water-insoluble disulfide coordinated four-membered ring (—CSS －)2M structure to chelate heavy metal ions, in -COO － The binding capacity of heavy metals in wastewater is improved by the synergistic effect of auxiliary and optimized spatial structure of chelating agents; through the -CSS from different molecules － It chelates with the same heavy metal ions to form macromolecules, allowing the formed microflocs to gradually grow and form macroflocs and be separated from the water body, thereby improving the treatment effect of heavy metal wastewater and overcoming the defects of commonly used aminodithiocarboxylate chelating agents such as insufficient chelating and binding ability for some heavy metal ions and poor treatment effect due to the single chelating group and poor molecular structure.

[0023] (2) The method of the present invention firstly strengthens the base to break the inner salt bond of 2-amino-3-(4-imidazolyl) propionic acid, and then fully removes the H in the amino group of the molecule under the strong base condition. + The formation of an ammonia ion (negative ammonia ionization) provides sufficient conditions for further nucleophilic attack on the partially positively charged C atom 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 the present invention can react rapidly with most heavy metal ions in wastewater at room temperature to generate stable water-insoluble chelates, which have a wide range of applications. － The strong chelating ability of the product can capture heavy metal ions from most heavy metal complexes that are slightly weaker than it. Therefore, it is suitable for the removal of not only free heavy metal ions but also complexed heavy metal ions. The product of the present invention can chelate with a variety of heavy metal ions in water, and is particularly suitable for the treatment of complex wastewater containing a variety of heavy metal ions, achieving efficient removal of a variety of heavy metal ions in one step.

[0025] (4) The process of using the product of the present invention to treat heavy metal wastewater is simple. It only requires adding a certain amount of the product of the present invention to the heavy metal wastewater and stirring it sufficiently to quickly produce insoluble flocs, which can then be separated by sedimentation and filtered without the need for complicated equipment and processes.

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

[0027] The invention is suitable for treating various heavy metal wastewaters and fixing heavy metals in incineration fly ash, and is particularly suitable for removing heavy metal ions in industrial wastewater and domestic sewage, especially complex wastewater containing multiple heavy metal ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The figure is a process flow chart of the preparation method of the present invention.

[0029] Figure 2 It is the infrared spectrum of the product of the present invention, 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agent (sample of Example 3).

[0030] Figure 3 This is a diagram showing the chelating flocculation mechanism of the product of the present invention. DETAILED DESCRIPTION

[0031] 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.

[0032] Examples 1 to 7 are methods for preparing the product of the present invention, 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate, and Examples 8 to 11 are application examples of the product of the present invention.

[0033] Example 1

[0034] (1) 9.4036 g of 2-amino-3-(4-imidazolyl)propionic acid (mass fraction 99.00%) was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and then 235.1 mL of distilled water was added and stirred to dissolve; then 5.6422 g of NaOH (mass fraction 96.00%) was added and stirred for 1 h after dissolution;

[0035] (2) adding 3.7 mL of 99.00% carbon disulfide dropwise to the solution obtained in step (1) within 40 min, and continuing the reaction at room temperature for 5 h;

[0036] (3) The temperature was raised to 55° C. and the reaction was continued for 1.5 h until the oil droplets disappeared completely. The mixture was cooled to room temperature to obtain 242.6 mL of a light red liquid, i.e., the product 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agent.

[0037] Example 2

[0038] (1) 9.4036 g of 99.00% 2-amino-3-(4-imidazolyl)propionic acid was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and then 235.1 mL of distilled water was added and stirred to dissolve; then 5.6422 g of 96.00% NaOH was added and stirred for 1.5 h after dissolution;

[0039] (2) adding 3.7 mL of 99.00% carbon disulfide dropwise to the solution obtained in step (1) within 50 min, and continuing the reaction at room temperature for 5.5 h;

[0040] (3) The temperature was raised to 60° C. and the reaction was continued for 1.5 h until the oil droplets disappeared completely. The mixture was cooled to room temperature to obtain 264.7 mL of a light red liquid, i.e., the product 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agent.

[0041] Example 3

[0042] (1) 9.4036 g of 99.00% 2-amino-3-(4-imidazolyl)propionic acid was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and then 282.1 mL of distilled water was added and stirred to dissolve; then 9.0246 g of 96.00% NaOH was added and stirred for 2 h after dissolution;

[0043] (2) adding 7.5 mL of 99.00% carbon disulfide dropwise to the solution obtained in step (1) within 60 min, and continuing the reaction at room temperature for 5.5 h;

[0044] (3) The temperature was raised to 65° C. and the reaction was continued for 1.5 h until the oil droplets disappeared completely. The mixture was cooled to room temperature to obtain 295.1 mL of a light red liquid, i.e., the product 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agent.

[0045] Example 4

[0046] (1) 9.4036 g of 99.00% 2-amino-3-(4-imidazolyl)propionic acid was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and then 263.3 mL of distilled water was added and stirred to dissolve; then 8.3692 g of 96.00% NaOH was added and stirred for 1.5 h after dissolution;

[0047] (2) adding 6.7 mL of 99.00% carbon disulfide dropwise to the solution obtained in step (1) within 50 min, and continuing the reaction at room temperature for 6 h;

[0048] (3) The temperature was raised to 60° C. and the reaction was continued for 2 h until the oil droplets disappeared completely. The mixture was cooled to room temperature to obtain 275.6 mL of a light red liquid, i.e., the product 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agent.

[0049] Example 5

[0050] (1) 9.4036 g of 2-amino-3-(4-imidazolyl)propionic acid (mass fraction: 99.00%) was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and then 244.5 mL of distilled water was added and stirred to dissolve; then 9.1096 g of KOH (mass fraction: 85.00%) was added and stirred for 1 h after dissolution;

[0051] (2) adding 3.7 mL of 99.00% carbon disulfide dropwise to the solution obtained in step (1) within 40 min, and continuing the reaction at room temperature for 5 h;

[0052] (3) The temperature was raised to 55° C. and the reaction was continued for 1.5 h until the oil droplets disappeared completely. The mixture was cooled to room temperature to obtain 252.1 mL of a red liquid, i.e., the product 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agent.

[0053] Example 6

[0054] (1) 9.4036 g of 2-amino-3-(4-imidazolyl)propionic acid (mass fraction 99.00%) was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and then 272.7 mL of distilled water was added and stirred to dissolve; then 12.8722 g of KOH (mass fraction 85.00%) was added and stirred for 1.5 h after dissolution;

[0055] (2) adding 5.6 mL of 99.00% carbon disulfide dropwise to the solution obtained in step (1) within 50 min, and continuing the reaction at room temperature for 5.5 h;

[0056] (3) The temperature was raised to 60° C. and the reaction was continued for 1.75 h until the oil droplets completely disappeared. The mixture was cooled to room temperature to obtain 284.8 mL of a red liquid, i.e., the product 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agent.

[0057] Example 7

[0058] (1) 9.4036 g of 99.00% 2-amino-3-(4-imidazolyl)propionic acid was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and then 244.5 mL of distilled water was added and stirred to dissolve; then 15.4467 g of 85.00% KOH was added and stirred for 2 h after dissolution;

[0059] (2) taking 7.8 mL of carbon disulfide with a mass fraction of 99.00% and adding it dropwise to the solution obtained in step (1), the addition was completed within 60 minutes, and the reaction was continued at room temperature for 6 hours;

[0060] (3) The temperature was raised to 65° C. and the reaction was continued for 2 h until the oil droplets disappeared completely. The mixture was cooled to room temperature to obtain 258.4 mL of an orange-red liquid, i.e., the product 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agent.

[0061] The infrared spectroscopy analysis of the 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agents obtained in Examples 1 to 7 was performed, and the results obtained were basically the same. The infrared spectroscopy analysis results of the 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate (referred to as HIS-DTC) obtained in Example 3 are as follows: Figure 2 shown. Figure 2 The absorption peaks in the infrared spectrum can be attributed as follows: 3201.99cm -1 The stretching vibration peaks of OH and -NH in the sample are at 2976.63 and 286.84 cm -1 The weak peaks at 1333.78 and 1300.86 cm-1 are the asymmetric and symmetric stretching vibration peaks of -CH2-. -1 Its bending vibration peak appears at 2073.17cm -1 The weak peaks are the angular vibration peaks of sulfamide NC=S; 1627.22 and 1486.21 cm -1 The asymmetric and symmetric bending vibration peaks of -NH and the corresponding bending vibration peaks of water are 1627-1580cm -1 Covered by the strong peaks of 1580.85 and 1403.20cm -1 The peaks at 1448.32cm are the asymmetric stretching and symmetric stretching vibration peaks of carboxylate groups. -1 N-CSS - ) CN stretching vibration absorption peaks; 1262.13 and 1131.06 cm -1 The stretching vibration peaks of CO and CN in the molecule; 1048.52 and 960.41 cm -1 for-css - The stretching vibration peak of C=S and CS in the middle; 897.91cm -1 Attributable to — CSS － Deformation vibration peak; 800cm -1 The following weak peaks are deformation vibration peaks of the imidazole ring in the molecule. The above samples were analyzed for elemental content, and the S content was 36.21%, which is equivalent to -CSS － Each chelating agent molecule contains an average of 1.98 CSS － The above results show that the chelating agent of 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate has been successfully synthesized.

[0062] Example 8

[0063] This example shows the treatment effect of the sample from Example 3 on heavy metal wastewater. － The content of Cd was 5.646mmol / g) and commercially available sodium thiamethoxam were used as chelating agents to prepare 100mg / L 2 + 、Ni 2+ , Pb 2+ , Cu 2+ Cr 3+ and Mn 2+ Simulated heavy metal water samples. Flocculation test conditions: Take 500mL simulated heavy metal water samples respectively, adjust the pH value to about 6.0, add chelating agent on MY3000-6G intelligent color screen coagulation test stirring instrument (Wuhan Meiyu Instrument Co., Ltd.), stir quickly at 220r / min for 5min, stir at 100r / min for 10min, and then stir slowly at 60r / min for 15min, let it stand for 20min, take the clear liquid 2cm below the liquid surface and measure it on AA-7000 atomic absorption spectrophotometer (Japan, Shimadzu Corporation), the treatment effect is shown in Table 1.

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

[0065]

[0066] It can be seen from Table 1 that under the optimal conditions, the product HIS-DTC of the present invention has a significantly higher affinity for free Cd than the commercially available comparative sample sodium thiamethoxam. 2+ 、Ni 2+ , Pb 2+ , Cu 2+ Cr 3+ and Mn 2+ The plasma removal effect is good, and the residual ion concentration is far lower than the first-level standard of the "Comprehensive Wastewater Discharge Standard" (GB8978-1996), and the dosage is lower. This is because HIS-DTC contains -COO — and — CSS — There are two functional groups, while sodium fumei only has -CSS — Due to the special 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] The HIS-DTC obtained in Example 3 was used as a chelating agent to treat the comprehensive wastewater of a certain electroplating plant. The pollutant indicators of the comprehensive wastewater are shown in Table 2. The comprehensive wastewater contains phosphorus compounds and is gray-green turbid.

[0069] The product HIS-DTC obtained in Example 3, the commercially available heavy metal scavenger sodium fumei and TMT-18 were used as reagents. Take 200 mL of wastewater sample, adjust the pH to about 6.0 with lime milk, and then place it on the MY3000-6G intelligent color screen coagulation test stirring instrument (Wuhan Meiyu Instrument Co., Ltd.), and add a certain amount of HIS-DTC, sodium fumei and TMT-18 chelating agents. The stoichiometric ratio of HIS-DTC and sodium fumei (i.e., the ratio of CSS-1 in HIS-DTC or sodium fumei) is 1:1. － The molar ratio of TMT-18 to heavy metal ions was 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 under stirring at 250 r / min and stirred for 5 min; then stirred at 100 r / min for 20 min (when stirring for 10 min, add appropriate amount of polyacrylamide PAM), and then stirred at 60 r / min for 15 min, and allowed to stand for 20 min, and 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 the present invention on comprehensive wastewater from electroplating plants

[0071]

[0072] The results in Table 2 show that the product HIS-DTC of the present invention has a significantly better treatment effect on this comprehensive electroplating wastewater than the commonly used heavy metal scavengers sodium fumei and TMT-18 on the market, and the dosage is small, the turbidity of the treated water is low, and the pollutant indicators are all lower than the limit values ​​specified in the "Emission Standard of Pollutants for Electroplating" (GB21900-2008).

[0073] Example 10

[0074] The HIS-DTC obtained in Example 3 was used as a chelating agent, and the comprehensive wastewater of a copper foil production plant was treated. The pollutant indicators are shown in Table 3. It contains pyrophosphate and is light yellow and slightly turbid. The product HIS-DTC obtained in Example 3, the commercially available heavy metal scavengers sodium forme and TMT-18 were used as reagents. Take 200 mL of the wastewater sample, first adjust the pH to about 6.0 with lime milk, and then place it on the MY3000-6G intelligent color screen coagulation test stirring instrument (Wuhan Meiyu Instrument Co., Ltd.), and add a certain amount of HIS-DTC, sodium forme and TMT-18 chelating agents respectively. The stoichiometric ratio of HIS-DTC and sodium forme (that is, the stoichiometric ratio of HIS-DTC or sodium forme) is 1:1. －The molar ratio of TMT-18 to heavy metal ions was 1.85:1 and 2.1:1 respectively, and the stoichiometric ratio of TMT-18 was 1:1.5. The chelating agent was added under stirring at 200 r / min and stirred for 5 min; then stirred at 100 r / min for 20 min (adding an appropriate amount of polyacrylamide PAM during stirring for 10 min), and then stirred at 60 r / min for 20 min, and allowed to stand for 20 min, and samples were taken for analysis to determine the concentration of heavy metal ions in the treated water. The results are listed in Table 3.

[0075] Table 3 Removal effect of the product of the present invention on the comprehensive wastewater of the copper foil production plant

[0076]

[0077]

[0078] The results in Table 3 show that the treatment effect of the product HIS-DTC of the present invention on this kind of wastewater is significantly better than that of the common heavy metal scavengers sodium fumei and TMT-18 on the market. 2+ 、Co 2+ , Fe 3+ The three ions are completely removed, and Cr 3+ and Zn 2+ It can also remove pollutants to very low concentrations, and the pollutant indicators are all lower than the limit values ​​specified in the "Electroplating Pollutant Emission Standard" (GB21900-2008).

[0079] Embodiment 11

[0080] The product HIS-DTC obtained in Example 3, the commercial heavy metal scavenger sodium fumei and TMT-18 were used as heavy metal stabilizers for incineration fly ash, and all were prepared into a solution with a mass fraction of 5%. During the test, 250g of fly ash from a garbage incineration plant was added to a reaction kneader, and then stabilizer and water were added according to the mass ratio of fly ash: stabilizer: water = 100: 1-3: 20, and the mixture was fully stirred and kneaded for reaction for 20 minutes, and then the reaction was continued for 2 hours, and then samples were taken for leaching experiments according to the method specified in HJ / T300-2007, and the pollutant concentration in the leaching solution was determined. The results are shown in Table 4.

[0081] Table 4 Effects of the products of the present invention and commercially available stabilizers on incineration fly ash treatment

[0082]

[0083]

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

[0085] The results of Examples 8 to 11 show that the product HIS-DTC of the present invention has better removal efficiency for free heavy metal wastewater and complex actual electroplating wastewater and heavy metal ions in copper foil production wastewater than the comparative samples, and has better chelating and stabilizing effect on incineration fly ash. The reason is that HIS-DTC contains 1 to 2 CSS — and 1—COO — (N—CH—COO — ), which is easy to react with heavy metal ions in water Figure 3 Chelation shown: (1) 2 in 1 molecule—CSS — Chelate with heavy metal ions to form a water-insoluble disulfide coordinated four-membered ring chelate, or it can be two CSS from different HIS-DTC molecules — Chelates with heavy metal ions to form a water-insoluble disulfide-coordinated four-membered ring chelate; one molecule contains two CSS — Can be connected to two CSS of another HIS-DTC at the same time — It can chelate with heavy metal ions to form two disulfide coordinated four-membered ring chelates, and can also chelate with two CSS from different HIS-DTC molecules. — Chelate with heavy metal ions to form two disulfide coordinated four-membered ring chelates; (2) can be obtained through two CSS from different HIS-DTC molecules — Group or N—CH—COO — Chelate with the same heavy metal ion to form a water-insoluble disulfide coordinated four-membered ring chelate or two The five-membered chelate ring connects the chelates formed by different molecules and gradually grows to form larger flocs, thereby improving the efficiency of chelating and binding heavy metal ions and the stability of the chelate.

[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 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 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agent, characterized in that: The structure of its main component is shown in formula (I): In formula (I), M is Na or K; x=0 or 1. When x=0, the N atom is connected to a H atom.

2. The 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agent according to claim 1, characterized in that: The chelate also includes auxiliary ingredients of xanthogenic acid and alkali; the appearance of the chelate is light red to orange-red liquid.

3. The method for preparing the 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agent according to claim 1 or 2, characterized in that: The following steps are involved: (1) Add 2-amino-3-(4-imidazolyl)propionic acid and distilled water into a reactor in a mass ratio of 2-amino-3-(4-imidazolyl)propionic acid, alkali and distilled water of 1:0.60-1.64:25-30, stir to dissolve, then add alkali, and continue stirring for 1-2 hours after the alkali is dissolved to break the internal salt bond in the molecule and dehydrogenate the amino group into negative ammonia ions; (2) slowly adding carbon disulfide dropwise at a mass ratio of carbon disulfide to 2-amino-3-(4-imidazolyl)propionic acid of 0.56 to 1.08:1, and continuing the reaction at room temperature for 5 to 6 hours after the addition is complete; (3) Raise the temperature to 55-65°C and continue the reaction for 1.5-2 hours until the oil droplets disappear completely. Cool to room temperature to obtain a light red to orange-red liquid, i.e., the product 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agent.

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

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

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

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

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

9. The method for preparing the 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate chelating agent according to claim 3, characterized in that: In step (2), the time for slowly adding carbon disulfide is 30 to 60 minutes.

10. Use of the 2-amino-3-(4-imidazolyl) propionic acid dithiocarboxylate 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 treatment of heavy metals in heavy metal wastewater or incineration fly ash.

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