2-(N-dithioformate) amino-3-mercaptopropionic acid chelating agent as well as preparation method and application thereof

Abstract

The invention discloses a 2-(N-dithioformate) amino-3-thiohydracrylic acid chelating agent as well as a preparation method and application of the 2-(N-dithioformate) amino-3-thiohydracrylic acid chelating agent. The method comprises the following steps: breaking an inner salt bond in 2-amino-3-mercaptopropionic acid by using a strong base, removing H < + > from-NH2 in molecules under the action of the strong base to form negative ions of ammonia, and carrying out nucleophilic addition reaction on the negative ions and carbon disulfide in the presence of the strong base to generate the 2-(N-dithioformate) amino-3-mercaptopropionic acid chelating agent. The molecule of the product has three coordination groups such as-CSS <->,-COO <-> and-SH, the chelating removal efficiency of heavy metal ions in wastewater can be improved through the synergistic effect of the three coordination groups, and the range of adapting to the heavy metal ions is widened. The product disclosed by the invention has an excellent removal effect on divalent and trivalent heavy metal ions and monovalent heavy metal ions such as Ag < + >, Hg < + > and Cu < + >. The method is simple in process, mild in reaction condition, easy to control operation, environment-friendly in process and easy to realize industrial production.

Description

Technical Field

[0001] The invention relates to the preparation of heavy metal chelating agents and the field of heavy metal wastewater treatment, and in particular to a 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent and a preparation method and application thereof. Background Art

[0002] Heavy metals exist naturally in almost all aquatic systems at trace levels. Although some of these heavy metals, such as Zn, Cu, Mo, Cr, Co, Fe, etc., are essential trace nutrients for the human body, they are difficult to biodegrade, highly toxic, bioaccumulate, and biomagnify. Even at low concentrations, they may cause serious potential harm to the ecological environment system, pose a serious threat to human health, and seriously affect the sustainable development of the economy and society. With the rapid development of modern industries such as mineral mining, metallurgy, battery manufacturing, chemical industry, metal electroplating, electronics, and instrumentation, the types and quantities of heavy metal wastewater are increasing, the composition is becoming more and more complex, and the difficulty of treatment is increasing. How to efficiently and low-costly treat heavy metal wastewater has become a major environmental problem that environmental protection workers around the world urgently need to work hard to solve.

[0003] The developed heavy metal wastewater treatment technologies mainly include traditional chemical precipitation, ion exchange, adsorption, ion flotation, electrochemical method, membrane filtration and chelate precipitation (flocculation) method. Among them, the chelate precipitation (flocculation) method has become the heavy metal wastewater treatment method that the environmental protection industry is competing to develop and promote for application due to its simple treatment process, high efficiency, low cost, small amount of sediment produced, easy post-treatment and recovery and utilization of heavy metals, and suitable for large-scale heavy metal wastewater treatment. The mechanism of chelate precipitation (flocculation) method to remove heavy metal ions from wastewater is to "bind" the heavy metal ions to the chelate molecules through the chelate groups of the chelate or chelate flocculant to form coordination bonds with the heavy metal ions, thereby forming microflocculations and further growing into flocs (or with the assistance of flocculants), and then separated from the water body by precipitation or flocculation. The key to using chelate precipitation (flocculation) method to treat heavy metal wastewater is the performance of the chelate or chelate flocculant used, which mainly depends on the chelate group and its distribution on the chelate molecule and the spatial structure of the molecule. Research and practice have shown that carboxyl (—COO － ), amino (—NH2), imino (—NH—), sulfhydryl (—SH), hydroxyl (—OH) and aminodithiocarboxylic acid (—CSS － ) have certain coordination binding effects on heavy metals, especially CSS － , —SH and —COO － The coordination binding ability to heavy metals is strong, typical examples include TMT, sodium thiamethoxam, ethylthiocyanate and sodium N,N'-dithiopiperazine formate. The former contains -SH, and the latter three all contain -CSS －Studies have shown that a single coordination (chelating) group cannot adapt to all heavy metals and it is difficult to achieve the expected effect in treating complex wastewater containing multiple heavy metals, such as CSS － Chelating agents containing -SH groups do not have strong chelating ability for Cr, Zn and Ni; however, treatment agents containing -SH groups, such as TMT, can chelate Ag. + , Hg + , Cu + Therefore, by integrating multiple chelating groups into the same chelating agent molecule and optimizing its structure, it is expected to complement each other, significantly improve the chelating and binding ability of heavy metals, and expand the scope of application of chelating agents, so as to achieve the purpose of effectively removing multiple heavy metal ions in one step.

[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 metal ions, the present invention provides a 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent and a preparation method and application thereof.

[0006] The chelating agent 2-(N-dithioformate)amino-3-mercaptopropionic acid provided by the present invention has a structure as shown in formula (I):

[0007]

[0008] In formula (I), M is Na or K;

[0009] The molecule is based on 2-amino-3-mercaptopropionic acid, with an aminodithiocarboxylic acid group (—CSS) grafted onto the amino group. － ), so that the molecule has both - CSS － , —COO － The three coordination groups, including -SH and -SH, complement each other and work synergistically to enhance the binding ability to heavy metal ions in wastewater, improve the removal effect of heavy metal ions in wastewater, and broaden the adaptability to heavy metal wastewater.

[0010] The preparation method of the above-mentioned 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent comprises the following steps:

[0011] (1) Add 2-amino-3-mercaptopropionic acid and distilled water into a reactor in a mass ratio of 2-amino-3-mercaptopropionic acid, alkali and distilled water of 1:0.38-0.85:15-25, stir and 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 ion;

[0012] (2) slowly adding carbon disulfide dropwise at a mass ratio of carbon disulfide to 2-amino-3-mercaptopropionic acid of 0.63 to 0.83:1, and continuing the reaction at room temperature for 4 to 6 hours after the addition is complete;

[0013] (3) Raise the temperature to 45-55°C and continue the reaction for 2-2.5 hours until the oil droplets disappear completely. Cool to room temperature to obtain an orange-red to reddish brown liquid, i.e., the product 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent.

[0014] Furthermore, in step (1), the 2-amino-3-mercaptopropionic 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 30 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 preparation method of a 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent. First, the internal salt bond of 2-amino-3-mercaptopropionic acid is broken by using a strong base, and then the -NH2 in the molecule is dehydrated under the action of the strong base. + The negative ions of ammonia (negative ammonia ionization) are formed, 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-(N-dithioformate)amino-3-mercaptopropionic acid. The present invention makes full use of the -NH2, -COOH and -SH of 2-amino-3-mercaptopropionic acid and its unique structure, and connects -CSS to -NH2. － Make the prepared product have both - CSS － , —COO － The chelating and removal performance of heavy metals in wastewater and the adaptability to heavy metals are improved through the synergistic effect of the three coordination groups.

[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-mercaptopropionic acid molecules as the basic skeleton, making full use of the -COO － , -NH2, -SH and other functional groups and their structural characteristics make the chelating agent molecule have both -CSS － , —COO － and -SH, forming a specific spatial structure and distribution of coordination / chelating groups. － It reacts with most heavy metal ions to form a stable and water-insoluble disulfide coordinated four-membered ring (—CSS － )2M, and -SH forms water-insoluble thiolate with some heavy metal ions to chelate and bind heavy metal ions. － The synergistic effect of the auxiliary and optimized spatial structure of the chelating agent improves the binding capacity of heavy metals in wastewater. － The product of the present invention overcomes the defects of common aminodithiocarboxylate chelating agents, such as insufficient chelating and binding ability to 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-mercaptopropionic acid, and then fully removes the H in the -NH2 in the molecule under the strong base condition. + The formation of ammonia anions (negative ammonia ionization) creates 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 the present invention can react rapidly with most heavy metal ions in wastewater at room temperature to form stable water-insoluble chelates, and because the molecule contains -CSS － , —COO － and -SH, which broadened its adaptability to heavy metal ions, especially to Ag. + , Hg + , Cu + The removal of monovalent heavy metals is also effective. － Strong chelating ability, can capture heavy metal ions from most heavy metal chelates that are slightly weaker than it. Therefore, the product of the present invention is not only suitable for the removal of free heavy metal ions, but also suitable for the removal of complexed heavy metal ions. The product of the present invention can chelate with multiple heavy metal ions in water, and is particularly suitable for the treatment of complex wastewater containing multiple heavy metal ions, and realizes the efficient removal of multiple heavy metal ions in one step.

[0025] (4) The product of the present invention is used to treat heavy metal wastewater. The process 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 generate insoluble flocs, which can then be separated by sedimentation or filtration 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 This is the infrared spectrum of the product of the present invention, 2-(N-dithioformate)amino-3-mercaptopropionic acid 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 preparation methods of the product 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent of the present invention, and Examples 8 to 11 are application examples of the product of the present invention.

[0033] Example 1

[0034] (1) 12.2374 g of 99.00% 2-amino-3-mercaptopropionic acid was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and then 183.5 mL of distilled water was added and stirred to dissolve; then 4.5833 g of 96.00% NaOH was added and stirred for 1 h after dissolution;

[0035] (2) adding 6.2 mL of 99.00% carbon disulfide dropwise to the solution obtained in step (1) within 30 min, and continuing the reaction at room temperature for 4 h;

[0036] (3) The temperature was raised to 45°C and the reaction was continued for 2.5 h until the oil droplets disappeared completely. The mixture was cooled to room temperature to obtain 198.0 mL of an orange-red liquid, i.e., the product 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent.

[0037] Example 2

[0038] (1) 12.2374 g of 99.00% 2-amino-3-mercaptopropionic acid was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and then 220.3 mL of distilled water was added and stirred to dissolve; then 5.5003 g of 96.00% NaOH was added and stirred for 1.5 h after dissolution;

[0039] (2) adding 6.8 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;

[0040] (3) The temperature was raised to 50°C and the reaction was continued for 2 h until the oil droplets disappeared completely. The mixture was cooled to room temperature to obtain 238.0 mL of an orange-red liquid, i.e., the product 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent.

[0041] Example 3

[0042] (1) 12.2374 g of 99.00% 2-amino-3-mercaptopropionic acid was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and then 244.7 mL of distilled water was added and stirred to dissolve; then 6.5000 g of 96.00% NaOH was added and stirred for 2 h after dissolution;

[0043] (2) taking 7.4 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 50 min, and the reaction was continued at room temperature for 6 h;

[0044] (3) The temperature was raised to 55°C and the reaction was continued for 2 h until the oil droplets disappeared completely. The mixture was cooled to room temperature to obtain 262.2 mL of an orange-red liquid, i.e., the product 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent.

[0045] Example 4

[0046] (1) 12.2374 g of 99.00% 2-amino-3-mercaptopropionic acid was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and then 220.3 mL of distilled water was added and stirred to dissolve; then 7.0417 g of 96.00% NaOH was added and stirred for 2 h after dissolution;

[0047] (2) adding 8.1 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 6 h;

[0048] (3) The temperature was raised to 55° C. and the reaction was continued for 2.5 h until the oil droplets disappeared completely. The mixture was cooled to room temperature to obtain 237.8 mL of an orange-red liquid, i.e., the product 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent.

[0049] Example 5

[0050] (1) 12.2374 g of 99.00% 2-amino-3-mercaptopropionic acid was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and then 305.9 mL of distilled water was added and stirred to dissolve; then 7.2613 g of 85.00% KOH was added and stirred for 2 h after dissolution;

[0051] (2) adding 6.2 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 4.5 h;

[0052] (3) The temperature was raised to 45°C and the reaction was continued for 2.5 h until the oil droplets disappeared completely. The mixture was cooled to room temperature to obtain 320.3 mL of orange-red liquid, i.e., the product 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent.

[0053] Example 6

[0054] (1) 12.2374 g of 99.00% 2-amino-3-mercaptopropionic acid was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and then 195.8 mL of distilled water was added and stirred to dissolve; then 8.7136 g of 85.00% KOH was added and stirred for 1.5 h after dissolution;

[0055] (2) adding 6.8 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 h;

[0056] (3) The temperature was raised to 50°C and the reaction was continued for 2.25 h until the oil droplets disappeared completely. The mixture was cooled to room temperature to obtain 208.5 mL of a reddish brown liquid, i.e., the product 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent.

[0057] Example 7

[0058] (1) 12.2374 g of 99.00% 2-amino-3-mercaptopropionic acid was added to a 500 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser, and then 220.3 mL of distilled water was added and stirred to dissolve; then 10.2978 g of 85.00% KOH was added and stirred for 2 h after dissolution;

[0059] (2) taking 7.4 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 50 min, and the reaction was continued at room temperature for 6 h;

[0060] (3) The temperature was raised to 55°C and the reaction was continued for 2 h until the oil droplets disappeared completely. The mixture was cooled to room temperature to obtain 233.4 mL of a reddish brown liquid, i.e., the product 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent.

[0061] The infrared spectroscopy analysis of the 2-(N-dithioformate)amino-3-mercaptopropionic acid 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 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: 3169.89cm -1 The stretching vibration peaks of OH and -NH in the sample; at 2979.11 cm -1 The weak peaks at -CH2- and The asymmetric stretching vibration peak of -1 Its bending vibration peak appears at 2545.38cm -1 is the stretching vibration peak of SH; 2082.62cm -1 The weak peaks are the angular vibration peaks of sulfamide NC=S; 1619.35 and 1443.01 cm -1 The asymmetric and symmetric bending vibration peaks of -NH; 1520.43 and 1406.45 cm -1 The peaks at 1451.65cm are the asymmetric stretching and symmetric stretching vibration peaks of carboxylate groups. -1 N-CSS - ) CN stretching vibration absorption peaks; 1296.77 and 1150.53 cm -1 The stretching vibration peaks of CN and CO in the molecule; 1066.67 and 937.63 cm -1 for-css - The stretching vibration peak of C=S and CS in the middle; 870.96cm -1 For — CSS － Deformation vibration peak; 660.20cm-1 The element analysis of the above samples showed that the S content was 39.73%, which is equivalent to CSS. － Each chelating agent molecule contains an average of 0.995 CSS － The above results show that the chelating agent 2-(N-dithiocarbamate)amino-3-mercaptopropionic acid has been successfully synthesized.

[0062] Example 8

[0063] This example shows the treatment effect of the sample of Example 3 on heavy metal wastewater. The samples obtained in Example 3 (referred to as CYS-DTC, -CSS － The content of Cu was 4.123mmol / g) and commercially available sodium thiamethoxam were used as chelating agents to prepare 100mg / L 2 + 、Ni 2+ , Pb 2+ 、Cd 2+ 、Ag + and Hg + Simulated heavy metal water samples. Flocculation test conditions: Take 500mL simulated heavy metal water samples respectively, adjust the pH value to about 6, 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), and 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]

[0067] It can be seen from Table 1 that under the optimal conditions, the product CYS-DTC of the present invention is significantly better than the commercially available comparative sample sodium fumarate in terms of free Cu 2+ 、Ni 2+ , Pb 2+ 、Cd 2+ 、Ag + and Hg + 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 CYS-DTC contains -SH, -COO — , —CSS —There are three functional groups, while sodium fumei only has -CSS — The three groups in CYS-DTC work synergistically to enhance the removal effect of heavy metal ions. In particular, for Ag + and Hg + For monovalent heavy metal ions, CYS-DTC has a more significant advantage, which is that -SH can react with Ag + and Hg + The formation of stable insoluble thiolate promotes the reaction of monovalent Ag + and Hg + removal.

[0068] Example 9

[0069] The CYS-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 and cyanide compounds and is grayish white and turbid.

[0070] The product CYS-DTC obtained in Example 3, the commercially available heavy metal scavenger sodium ferram and TMT-18 were used as reagents. 200 mL of wastewater sample was taken, the pH was first adjusted to about 6 with lime milk, and then placed on the MY3000-6G intelligent color screen coagulation test stirring instrument (Wuhan Meiyu Instrument Co., Ltd.), and a certain amount of CYS-DTC, sodium ferram and TMT-18 chelating agents were added respectively. The stoichiometric ratio of CYS-DTC and sodium ferram (i.e., the ratio of CSS-1 in CYS-DTC or sodium ferram) was 1:1. － The molar ratio of TMT-18 to heavy metal ions was 1.75:1 and 2.30:1 respectively, and the molar ratio of TMT-18 to metal ions was 1:2. 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.

[0071] Table 2 Removal effect of the product of the present invention on comprehensive wastewater from electroplating plants

[0072]

[0073]

[0074] The results in Table 2 show that the product CYS-DTC of the present invention has a significantly better treatment effect on this comprehensive electroplating wastewater than the commonly used heavy metal scavengers sodium thiamethoxam 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).

[0075] Example 10

[0076] The CYS-DTC obtained in Example 3 was used as a chelating agent, and the cobalt concentrate of a copper foil production plant was treated. Its pollutant indicators are shown in Table 3, which contains pyrophosphate and is light green and transparent. The product CYS-DTC obtained in Example 3, the commercially available heavy metal scavengers sodium formate and TMT-18 were used as reagents respectively. Take 200 mL of the wastewater sample, first adjust the pH to about 5.5 with sulfuric acid, 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 CYS-DTC, sodium formate and TMT-18 chelating agents respectively. The stoichiometric ratio of CYS-DTC and sodium formate (i.e., the CSS in CYS-DTC or sodium formate) is 1:1. － The molar ratio of TMT-18 to heavy metal ions) is 1.85:1 and 2.1:1 respectively, and the stoichiometric ratio of TMT-18 is 1:1.5. The chelating agent was added under stirring at 220 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 test the concentration of heavy metal ions in the treated water. The results are listed in Table 3.

[0077] Table 3 The removal effect of the product of the present invention on cobalt concentrated water of a copper foil production plant

[0078]

[0079]

[0080] The results in Table 3 show that the treatment effect of the product CYS-DTC of the present invention on this kind of wastewater is significantly better than that of the commonly used heavy metal scavengers sodium thiamethoxam and TMT-18 on the market. 2+ 、Co 2+ , Fe 3+ The three ions are completely removed, and Zn 2+ Cr 3+ 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).

[0081] Embodiment 11

[0082] The product CYS-DTC obtained in Example 3, the commercial heavy metal scavenger sodium fumei and TMT-18 were used as stabilizers for heavy metals in incineration fly ash, and all were prepared into solutions 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 reaction was stirred and kneaded for 20 minutes, and then the reaction was continued for 2 hours, and then the sample was taken for leaching experiment 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.

[0083] Table 4 Effects of the products of the present invention and commercially available stabilizers on incineration fly ash treatment

[0084]

[0085] As can be seen from Table 4, the dosage of the product CYS-DTC of 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.

[0086] The results of Examples 8 to 11 show that the product CYS-DTC of the present invention has better removal efficiency for free heavy metal wastewater and complex 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 CYS-DTC contains CSS — , —COO — (N—CH—COO — ) and -SH, which are easy to react with heavy metal ions in water to form Figure 3 Chelation shown: (1)—CSS — It is easy to chelate with heavy metal ions to form a water-insoluble disulfide coordinated four-membered ring chelate, -COO — Cooperate with -NH- to form a stable Five-membered chelate ring, and -SH can bind heavy metal ions, especially Hg + 、Ag + and Cu + The monovalent ions form water-insoluble thiolates, and the three groups work synergistically to improve the chelating and binding ability of heavy metal ions; (2) two CSS — 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.

[0087] 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-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent, characterized in that: Its structure is shown in formula (I): In formula (I), M is Na or K.

2. The method for preparing the 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent according to claim 1, characterized in that: The following steps are involved: (1) Add 2-amino-3-mercaptopropionic acid and distilled water into a reactor in a mass ratio of 2-amino-3-mercaptopropionic acid, alkali and distilled water of 1:0.38-0.85:15-25, stir and 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 ion; (2) slowly adding carbon disulfide dropwise at a mass ratio of carbon disulfide to 2-amino-3-mercaptopropionic acid of 0.63 to 0.83:1, and continuing the reaction at room temperature for 4 to 6 hours after the addition is complete; (3) Raise the temperature to 45-55°C and continue the reaction for 2-2.5 hours until the oil droplets disappear completely. Cool to room temperature to obtain an orange-red to reddish brown liquid, i.e., the product 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent.

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

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

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

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

7. The method for preparing the 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent according to claim 2, characterized in that: In step (2), the carbon disulfide is a product with a purity above industrial grade.

8. The method for preparing the 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent according to claim 2, characterized in that: In step (2), the time for slowly adding carbon disulfide is 30 to 60 minutes.

9. Use of the 2-(N-dithioformate)amino-3-mercaptopropionic acid chelating agent obtained by the preparation method according to claim 1 or any one of claims 2 to 8 in the treatment of heavy metals in heavy metal wastewater or incineration fly ash.

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