Heavy metal chelating flocculant with double chelating groups and preparation method and application thereof

Abstract

This invention discloses a heavy metal chelating flocculant possessing both dual chelating groups, its preparation method, and its application. First, a polyethylene polyamine undergoes a nucleophilic addition reaction with carbon disulfide in the presence of a base, thereby forming a -CSS... － The acetate group is introduced at the non-terminal position of the polyethylene polyamine molecule, and then, under strongly alkaline conditions, undergoes an electrophilic substitution reaction with a haloacetate to introduce acetate groups at both ends of the molecule, thus giving the molecule both -CSS and ethyl acetate groups. － and —N(CH2COO) － 2. Two strong chelating groups. The two chelating groups in the molecule complement each other, working synergistically to significantly improve the chelation and binding ability and flocculation and precipitation performance of various heavy metal ions, achieving efficient removal of multiple heavy metals in one step. This invention overcomes the shortcomings of common chelating agents, such as single functional groups, weak chelation ability for some ions, and limited applicability; the preparation process is simple, the reaction conditions are mild, the operation and control are easy, the process is environmentally friendly, and it is easy to realize industrial production.

Description

Technical Field

[0001] This invention relates to the fields of heavy metal wastewater treatment and heavy metal fixation in incineration fly ash, specifically to a heavy metal chelating flocculant with dual chelating groups, its preparation method, and its application. Background Technology

[0002] Heavy metals are elements with atomic weights between 63.5 and 200.6 and a specific gravity greater than 5.0 (Srivastava, NK, Majumder, CB, 2008. Novel biofiltration methods for the treatment of heavy metals from industrial wastewater. J. Hazard. Mater. 151, 1-8.). Among them, Zn, Cu, Mo, Cr, Co, and Fe are essential trace elements for the human body, while the vast majority are non-essential and harmful. Even essential heavy metals can cause harm if present in excessive amounts. With the rapid development of industrial and agricultural production, the number of industries involving heavy metals is increasing, especially in mineral mining, smelting, electrolysis, and electroplating, leading to a rise in heavy metal emissions into the environment. Due to their non-biodegradability, the significant biotoxicity even in trace amounts, and their carcinogenic, teratogenic, and mutagenic properties, as well as their insidious and persistent nature, heavy metals pose a serious threat to the ecological environment and human health. Developing new and efficient methods for the prevention and control of heavy metal pollution is of great significance for ecological environmental protection and safeguarding human life.

[0003] Heavy metal wastewater is a significant source of heavy metal pollution and a major form of migration and transformation. Currently, numerous methods have been developed for treating heavy metal wastewater, such as chemical precipitation, adsorption, biological methods, ion exchange, electrochemical methods, membrane filtration, and chelation precipitation (flocculation). However, these methods all have certain drawbacks. For example, while ion exchange offers high material regeneration and metal selectivity, and can exchange anions and cations in solution, it cannot exchange in concentrated metal solutions. The treatment process is overly dependent on pH, and ion exchange resins have low strength, are not heat-resistant, and are prone to oxidation and failure, requiring frequent regeneration and incurring high operating costs. Membrane filtration cannot directly filter heavy metal wastewater and requires supplementary methods such as micelle enhancement or polymer enhancement to increase the particle size of heavy metal pollutants. Furthermore, membrane devices require large investments and suffer from persistent membrane fouling problems, hindering widespread application. Electrochemical methods exhibit metal selectivity, poor adaptability, and are significantly affected by solution pH and current density, resulting in treatment... The cost is relatively high. While adsorption methods are highly adaptable, particularly suitable for advanced wastewater treatment, the use of natural adsorbents results in low adsorption capacity and difficulties in elution and regeneration, leading to large quantities of difficult-to-dispose-of solid hazardous waste. Synthetic adsorbents, although overcoming some of the shortcomings of natural adsorbents, are often expensive to prepare, resulting in high treatment costs, and also suffer from problems related to elution, regeneration, and eluent treatment. Traditional chemical precipitation methods, while simple to operate, consume large amounts of chemical precipitants, often fail to meet treatment standards, and generate large amounts of heavy metal-containing precipitates, becoming difficult-to-dispose-of solid hazardous waste. Because heavy metals are toxic to microorganisms, biological treatment methods lack universality, and many problems remain unresolved, limiting their application. In contrast, chelation precipitation (flocculation) utilizes chelating agents or chelating flocculants to "bind" heavy metal ions from water and separate them through precipitation or flocculation. This method offers high removal efficiency for heavy metal ions, produces less precipitate, and facilitates post-treatment and recovery of heavy metals, making it suitable for large-scale heavy metal wastewater treatment. The key lies in the performance of the chelating agent or chelating flocculant used. Existing chelating agents or chelating flocculants, such as dithiocarbamate (DTC), TMT, sodium thiosulfate, and N,N'-didithiopiperazine carboxylate, all have a single chelating group and weak chelating and binding ability for some heavy metal ions, resulting in poor removal efficiency for some heavy metal ions. Therefore, when treating complex wastewater containing multiple heavy metal ions, a considerable number of heavy metal ions often fail to meet standards. This is because one aminodiacetic acid group [—N(CH2COO] － [2] It can form two stable bonds with most metal ions. It is a five-membered ring, therefore it has a strong chelating ability for most metal ions. However, —N(CH2COO) － A significant portion of the chelates formed by aminodithiocarboxylic acid (-CSS) with metal ions are water-soluble and difficult to separate from water; while aminodithiocarboxylic acid (-CSS) groups... －The chelates formed by the chelation of heavy metal ions are insoluble in water and easily separated from water as precipitates. If CSS, which has a strong chelating ability for heavy metal ions, can be obtained... － and —N(CH2COO) － )2. Combining the same chelating agent molecule to form a heavy metal chelating flocculant with both chelating groups can utilize the strong chelating ability of the two to remove most heavy metals (including CSS). － (Weak chelation) chelates bind together and precipitates from water by forming water-insoluble aminodithiocarbamate chelates, thereby greatly improving the removal efficiency of heavy metals in wastewater. It achieves efficient removal of multiple heavy metal ions in one step, improves the removal effect of complex heavy metal wastewater, simplifies the treatment process, and reduces treatment costs.

[0004] Content of the invention

[0005] To address the technical problem of treating complex heavy metal wastewater, this invention provides a heavy metal chelating flocculant with dual chelating groups, its preparation method, and its application.

[0006] The heavy metal chelating flocculant with dual chelating groups provided by this invention has the structure of its main components as shown in formula (Ⅰ):

[0007]

[0008] In equation (I), 1 ≤ x ≤ 3, 1 ≤ y ≤ x, and x and y are both integers; when y < x, we have x － The y N atoms are connected to H atoms; M is either Na or K;

[0009] The molecules of the above-mentioned main components also possess—CSS － and —N(CH2COO) － Two strong chelating groups complement each other, exhibiting a strong chelating and binding ability for the vast majority of heavy metal ions in water, while also possessing excellent flocculation and sedimentation performance. It is safe, non-toxic, and has a wide range of applications, particularly effective for complex wastewater containing multiple heavy metal ions, achieving highly efficient removal of various heavy metal ions in one step. Furthermore, the preparation method is simple, operation and control are easy, the yield is high, and the process generates virtually no waste, making it easy to popularize, promote, and industrialize.

[0010] The preparation method of the above-mentioned heavy metal chelating flocculant with dual chelating groups includes the following steps:

[0011] (1) Prepare a solution with a mass fraction of 15.00% to 19.20% by adding polyethylene polyamine and distilled water into a reactor at a volume ratio of 1:4 to 5. Then add alkali at a ratio of (n-2) times the amount of polyethylene polyamine to the amount of alkali at 1:0.6 to 1.2, where n represents the number of N atoms in the polyethylene polyamine molecule. Stir at room temperature for 0.5 to 1 h.

[0012] (2) Add carbon disulfide at a ratio of (n-2) times the amount of polyethylene polyamine to the amount of carbon disulfide of 1:0.33-1.05, where n represents the number of N atoms in the polyethylene polyamine molecule. Stir the reaction at room temperature for 3-4 hours until the bottom oil droplets disappear. Then heat the reaction to 50-60℃ for 0.5-1 hours and then cool it down to room temperature to obtain solution A.

[0013] (3) Weigh out the haloacetate and add it to the reactor according to the molar ratio of haloacetate to polyethylene polyamine of 4.0 to 4.2:1, and add distilled water to prepare a solution with a mass fraction of 30% to 35% to obtain solution B.

[0014] (4) Add solution A obtained in step (2) to solution B obtained in step (3) and mix thoroughly; then weigh the alkali according to the molar ratio of alkali to polyethylene polyamine of 4 to 4.2:1, add distilled water to prepare a solution with a mass fraction of 30% to 35%, add it slowly in three batches, and wait until the pH value of the solution drops to 9 to 11 before adding the next batch. After adding all the alkali, continue to react at room temperature for 4 to 6 hours, then raise the temperature to 50 to 60°C and continue to react for 0.5 to 1 hour. Cool to room temperature to obtain a heavy metal chelating flocculant with dual chelating groups.

[0015] Furthermore, the polyethylene polyamine is any one of diethylenetriamine, triethylenetetramine, or tetraethylenepentamine, preferably tetraethylenepentamine.

[0016] Furthermore, in steps (1) and (4), the alkali is NaOH or KOH, preferably NaOH.

[0017] Furthermore, in step (3), the haloacetate is either sodium chloroacetate or sodium bromoacetate, preferably sodium chloroacetate.

[0018] Furthermore, in step (4), the slow addition time is 30 to 60 minutes.

[0019] Furthermore, the polyethylene polyamine, alkali, carbon disulfide, and haloacetate mentioned are all products of industrial grade or higher purity, and no further purification is required before use.

[0020] Furthermore, in steps (1) and (3), the reactors are equipped with mechanical stirring, a dripping funnel, and a reflux condenser.

[0021] The above-mentioned chelating flocculant is applied to the treatment of heavy metals in various types of heavy metal wastewater or incineration fly ash, and the treatment effect is excellent.

[0022] This invention relates to a method for preparing a heavy metal chelating flocculant possessing dual chelating groups. It involves first reacting a polyethylene polyamine with carbon disulfide in the presence of a base, resulting in a nucleophilic addition reaction of the -CSS group. － The acetate group (—CH2COO) is introduced into the non-terminal position of the polyethylene polyamine molecule and then undergoes an electrophilic substitution reaction with a haloacetate under strongly basic conditions. － The ions are introduced at both ends of the molecule to form two sets of -N(CH2COO) － )2, so that the molecule simultaneously possesses —CSS － and —N(CH2COO) － )2 Two strong chelating groups. This invention can achieve —CSS － and —N(CH2COO) － )2 The two chelating groups complement each other, and their synergistic effect significantly improves the chelation and binding ability and flocculation and sedimentation performance of various heavy metal ions in water, achieving efficient removal of various heavy metals in one step.

[0023] The advantages of this invention compared to the prior art are as follows:

[0024] (1) The product of this invention contains CSS. － and —N(CH2COO) － )2 Two strong chelating groups, which can complement each other's strengths, —N(CH2COO － )2 can form stable chelates with most heavy metal ions, which can overcome the -CSS － For some ions (such as Ca) 2+ Mg 2+ The chelating ability of (etc.) is insufficient, while —CSS － It can also solve the problem of —N(CH2COO) － )2. It overcomes the defect of forming soluble chelates with some heavy metal ions and being unable to be separated from water. The two work synergistically to improve the chelation and binding ability of heavy metals in water and the flocculation and sedimentation performance, so as to achieve efficient removal of multiple heavy metal ions in water in one step.

[0025] (2) The method of the present invention first introduces -CSS onto the polyethylene polyamine. － By fully utilizing the fact that nucleophilic addition reactions preferentially occur at the secondary amine position of polyamines, the -CSS － It preferentially occupies its secondary amine site, thereby promoting the introduction of -CH2COO in the subsequent stage through steric hindrance.－ It can only enter the terminal position, which effectively controls the product structure and achieves the successful preparation of the target product.

[0026] (3) The product of this invention is safe and non-toxic, and can react rapidly with most heavy metal ions in wastewater at room temperature to form stable, water-insoluble chelates, making it widely applicable. Because -N(CH2COO-)2 has a strong chelating ability, it can extract heavy metal ions from most heavy metal chelates with slightly weaker chelating abilities. Therefore, it is suitable not only for free heavy metal ions but also for complexed heavy metal ions; it 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.

[0027] (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.

[0028] (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.

[0029] 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

[0030] Figure 1 This is a flowchart of the preparation method of the present invention.

[0031] Figure 2 The infrared spectrum of the heavy metal chelating flocculant (sample of Example 7) that has dual chelating groups is a product of the present invention.

[0032] Figure 3 This is a diagram illustrating the chelation and flocculation mechanism of the product of this invention. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings.

[0034] Examples 1-11 illustrate the preparation methods of the heavy metal chelating flocculant with dual chelating groups of the product of the present invention, and Examples 12-16 illustrate the application examples of the product of the present invention.

[0035] Example 1

[0036] (1) Take 10.9 mL of 99.00% diethylenetriamine and 43.6 mL of distilled water and add them to a 250 mL three-necked flask equipped with a mechanical stirrer, dropping funnel and reflux condenser. Stir to dissolve and prepare a solution with a mass fraction of 19.08%. Then add 4.58 g of 96.00% solid NaOH and stir at room temperature for 0.5 h.

[0037] (2) Take 6.2 mL of carbon disulfide with a mass fraction of 99.00% and slowly add it to the solution in step (1). Stir the reaction at room temperature for 3 hours until the bottom oil droplets disappear. Then heat the solution to 50°C and react for 1 hour. Then cool the solution to room temperature.

[0038] (3) Take 47.54g of sodium chloroacetate with a mass fraction of 98.00% and add it to a 500mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. Add 107.8mL of distilled water to prepare a solution with a mass fraction of 30.00%.

[0039] (4) Add the solution obtained in step (2) to the solution obtained in step (3) and mix thoroughly; weigh 16.67g of solid NaOH with a mass fraction of 96.00%, add 36.7mL of distilled water to dissolve and prepare a solution with a mass fraction of 30.00%, transfer it into a dropping funnel and add it in 3 batches, each batch taking 30min. Add the next batch after the pH value of the reaction solution drops to about 10. After the addition is complete, continue to react at room temperature for 4h, then raise the temperature to 60℃ and continue to react for 0.5h. Cool to room temperature to obtain 239.2mL of orange-red liquid, which is a heavy metal chelating flocculant with dual chelating groups.

[0040] Example 2

[0041] (1) Take 10.9 mL of 99.00% diethylenetriamine and 54.5 mL of distilled water and add them to a 250 mL three-necked flask equipped with a mechanical stirrer, dropping funnel and reflux condenser. Stir to dissolve and prepare a solution with a mass fraction of 15.87%. Then add 5.42 g of 96.00% solid NaOH and stir at room temperature for 1 h.

[0042] (2) Take 6.5 mL of carbon disulfide with a mass fraction of 99.00% and slowly add it to the solution in step (1). Stir the reaction at room temperature for 4 h until the bottom oil droplets disappear. Then heat the solution to 60 °C and react for 0.5 h. Then cool the solution to room temperature.

[0043] (3) Take 49.92g of sodium chloroacetate with a mass fraction of 98.00% and add it to a 500mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. Add 89.9mL of distilled water to prepare a solution with a mass fraction of 35.00%.

[0044] (4) Add the solution obtained in step (2) to the solution obtained in step (3) and mix thoroughly; weigh 17.50g of solid NaOH with a mass fraction of 96.00%, add 30.5mL of distilled water to dissolve and prepare a solution with a mass fraction of 35.00%, transfer it into a dropping funnel and add it in 3 batches, each batch for 30min. Add the next batch after the pH value of the reaction solution drops to about 10. After the addition is complete, continue to react at room temperature for 4h, then raise the temperature to 60℃ and continue to react for 0.5h. Cool to room temperature to obtain 223.7mL of reddish-brown liquid, which is a heavy metal chelating flocculant with dual chelating groups.

[0045] Example 3

[0046] (1) Take 16.2 mL of 95.00% triethylenetetramine and 64.8 mL of distilled water and add them to a 250 mL three-necked flask equipped with a mechanical stirrer, dropping funnel and reflux condenser. Stir to dissolve and prepare a solution with a mass fraction of 18.73%. Then add 5.00 g of 96.00% solid NaOH and stir at room temperature for 1 h.

[0047] (2) Take 6.5 mL of carbon disulfide with a mass fraction of 99.00% and slowly add it to the solution in step (1). Stir the reaction at room temperature for 3.5 h until the bottom oil droplets disappear. Then heat the solution to 55 °C and react for 0.75 h. Then cool the solution to room temperature.

[0048] (3) Take 48.14g of sodium chloroacetate with a mass fraction of 98.00% and add it to a 500mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. Add 110.1mL of distilled water to prepare a solution with a mass fraction of 30.00%.

[0049] (4) Add the solution obtained in step (2) to the solution obtained in step (3) and mix thoroughly; weigh 17.08g of solid NaOH with a mass fraction of 96.00%, add 36.3mL of distilled water to dissolve and prepare a solution with a mass fraction of 32.00%, transfer it into a dropping funnel and add it in 3 batches, each batch taking 40min. Add the next batch after the pH value of the reaction solution drops to about 10. After the addition is complete, continue to react at room temperature for 4.5h, then raise the temperature to 55℃ and continue to react for 0.75h. Cool to room temperature to obtain 252.4mL of orange-red liquid, which is a heavy metal chelating flocculant with dual chelating groups.

[0050] Example 4

[0051] (1) Take 16.2 mL of 95.00% triethylenetetramine and 64.8 mL of distilled water and add them to a 250 mL three-necked flask equipped with a mechanical stirrer, dropping funnel and reflux condenser. Stir to dissolve and prepare a solution with a mass fraction of 17.02%. Then add 9.17 g of 96.00% solid NaOH and stir at room temperature for 0.75 h.

[0052] (2) Take 13.6 mL of carbon disulfide with a mass fraction of 99.00% and slowly add it to the solution in step (1). Stir the reaction at room temperature for 4 hours until the bottom oil droplets disappear. Then heat the solution to 60°C and react for 1 hour. Then cool the solution to room temperature.

[0053] (3) Take 49.92g of sodium chloroacetate with a mass fraction of 98.00% and add it to a 500mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. Add 90.9mL of distilled water to prepare a solution with a mass fraction of 35.00%.

[0054] (4) Add the solution obtained in step (2) to the solution obtained in step (3) and mix thoroughly; weigh 17.50g of solid NaOH with a mass fraction of 96.00%, add 38.5mL of distilled water to dissolve and prepare a solution with a mass fraction of 30.00%, transfer it into a dropping funnel and add it in 3 batches, each batch taking 60min. Add the next batch after the pH of the reaction solution drops to about 10. After the addition is complete, continue to react at room temperature for 6h, then raise the temperature to 50℃ and continue to react for 1h. Cool to room temperature to obtain 249.4mL of orange-red liquid, which is a heavy metal chelating flocculant with dual chelating groups.

[0055] Example 5

[0056] (1) Take 16.2 mL of 95.00% triethylenetetramine and 81.0 mL of distilled water and add them to a 250 mL three-necked flask equipped with a mechanical stirrer, dropping funnel and reflux condenser. Stir to dissolve and prepare a solution with a mass fraction of 15.60%. Then add 7.50 g of 96.00% solid NaOH and stir at room temperature for 1 h.

[0057] (2) Take 9.7 mL of carbon disulfide with a mass fraction of 99.00% and slowly add it to the solution in step (1). Stir the reaction at room temperature for 3 hours until the bottom oil droplets disappear. Then heat the solution to 55°C and react for 1 hour. Then cool the solution to room temperature.

[0058] (3) Take 48.73g of sodium chloroacetate with a mass fraction of 98.00% and add it to a 500mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. Add 110.5mL of distilled water to prepare a solution with a mass fraction of 30.00%.

[0059] (4) Add the solution obtained in step (2) to the solution obtained in step (3) and mix thoroughly; weigh 16.67g of solid NaOH with a mass fraction of 96.00%, add 33.3mL of distilled water to dissolve and prepare a solution with a mass fraction of 32.00%, transfer it into a dropping funnel and add it in 3 batches, each batch taking 50min. Add the next batch after the pH value of the reaction solution drops to about 10. After the addition is complete, continue to react at room temperature for 5.5h, then raise the temperature to 60℃ and continue to react for 0.75h. Cool to room temperature to obtain 264.8mL of reddish-brown liquid, which is a heavy metal chelating flocculant with dual chelating groups.

[0060] Example 6

[0061] (1) Take 20.0 mL of tetraethylenepentamine with a mass fraction of 95.00% and 80.0 mL of distilled water and add them to a 250 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. Stir to dissolve and prepare a solution with a mass fraction of 18.97%. Then add 5.42 g of solid NaOH with a mass fraction of 96.00% and stir at room temperature for 1 h.

[0062] (2) Take 6.5 mL of carbon disulfide with a mass fraction of 99.00% and slowly add it to the solution in step (1). Stir the reaction at room temperature for 3 hours until the bottom oil droplets disappear. Then heat the solution to 50°C and react for 1 hour. Then cool the solution to room temperature.

[0063] (3) Take 47.54g of sodium chloroacetate with a mass fraction of 98.00% and add it to a 500mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. Add 107.8mL of distilled water to prepare a solution with a mass fraction of 30.00%.

[0064] (4) Add the solution obtained in step (2) to the solution obtained in step (3) and mix thoroughly; weigh 17.08g of solid NaOH with a mass fraction of 96.00%, add 37.6mL of distilled water to dissolve and prepare a solution with a mass fraction of 30.00%, transfer it into a dropping funnel and add it in 3 batches, each batch taking 40min. Add the next batch after the pH value of the reaction solution drops to about 10. After the addition is complete, continue to react at room temperature for 6h, then raise the temperature to 50℃ and continue to react for 1h. Cool to room temperature to obtain 263.8mL of orange-red liquid, which is a heavy metal chelating flocculant with dual chelating groups.

[0065] Example 7

[0066] (1) Take 20.0 mL of tetraethylenepentamine with a mass fraction of 95.00% and 100.0 mL of distilled water and add them to a 250 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. Stir to dissolve and prepare a solution with a mass fraction of 15.81%. Then add 10.00 g of solid NaOH with a mass fraction of 96.00% and stir at room temperature for 1 h.

[0067] (2) Take 13.0 mL of carbon disulfide with a mass fraction of 99.00% and slowly add it to the solution in step (1). Stir the reaction at room temperature for 4 hours until the bottom oil droplets disappear. Then heat the solution to 55°C and react for 1 hour. Then cool the solution to room temperature.

[0068] (3) Take 48.73g of sodium chloroacetate with a mass fraction of 98.00% and add it to a 500mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. Add 100.5mL of distilled water to prepare a solution with a mass fraction of 32.00%.

[0069] (4) Add the solution obtained in step (2) to the solution obtained in step (3) and mix thoroughly; weigh 17.50g of solid NaOH with a mass fraction of 96.00%, add 30.5mL of distilled water to dissolve and prepare a solution with a mass fraction of 35.00%, transfer it into a dropping funnel and add it in 3 batches, each batch taking 60min. Add the next batch after the pH of the reaction solution drops to about 10. After the addition is complete, continue to react at room temperature for 6h, then raise the temperature to 60℃ and continue to react for 1h. Cool to room temperature to obtain 276.9mL of reddish-brown liquid, which is a heavy metal chelating flocculant with dual chelating groups, denoted as IDA-TEPA-DTC.

[0070] Using tetraethylenepentamine (TEPA) as raw material, and following the same proportions and preparation conditions as steps (1) to (2) in this embodiment, a tetraethylenepentamine-grafted dithiocarboxylic acid chelating agent was prepared, denoted as TEPA-DTC.

[0071] Example 8

[0072] (1) Take 20.0 mL of tetraethylenepentamine with a mass fraction of 95.00% and 90.0 mL of distilled water and add them to a 250 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. Stir to dissolve and prepare a solution with a mass fraction of 17.24%. Then add 13.75 g of solid NaOH with a mass fraction of 96.00% and stir at room temperature for 1 h.

[0073] (2) Take 19.5 mL of carbon disulfide with a mass fraction of 99.00% and slowly add it to the solution in step (1). Stir the reaction at room temperature for 4 hours until the bottom oil droplets disappear. Then heat the solution to 60°C and react for 1 hour. Then cool the solution to room temperature.

[0074] (3) Take 49.92g of sodium chloroacetate with a mass fraction of 98.00% and add it to a 500mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. Add 89.0mL of distilled water to prepare a solution with a mass fraction of 35.00%.

[0075] (4) Add the solution obtained in step (2) to the solution obtained in step (3) and mix thoroughly; weigh 17.50g of solid NaOH with a mass fraction of 96.00%, add 35.0mL of distilled water to dissolve and prepare a solution with a mass fraction of 32.00%, transfer it into a dropping funnel and add it in 3 batches, each batch taking 60min. Add the next batch after the pH of the reaction solution drops to about 10. After the addition is complete, continue to react at room temperature for 6h, then raise the temperature to 60℃ and continue to react for 1h. Cool to room temperature to obtain 275.9mL of reddish-brown liquid, which is a heavy metal chelating flocculant with dual chelating groups.

[0076] Example 9

[0077] (1) Take 20.0 mL of tetraethylenepentamine with a mass fraction of 95.00% and 100.0 mL of distilled water and add them to a 250 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. Stir to dissolve and prepare a solution with a mass fraction of 15.81%. Then add 14.52 g of solid KOH with a mass fraction of 85.00% and stir at room temperature for 0.75 h.

[0078] (2) Take 13.0 mL of carbon disulfide with a mass fraction of 99.00% and slowly add it to the solution in step (1). Stir the reaction at room temperature for 4 hours until the bottom oil droplets disappear. Then heat the solution to 60°C and react for 1 hour. Then cool the solution to room temperature.

[0079] (3) Take 67.33g of sodium bromoacetate with a mass fraction of 98.00% and add it to a 500mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. Add 152.6mL of distilled water to prepare a solution with a mass fraction of 30.00%.

[0080] (4) Add the solution obtained in step (2) to the solution obtained in step (3) and mix thoroughly; weigh 27.06g of solid KOH with a mass fraction of 85.00%, add 49.6mL of distilled water to dissolve and prepare a solution with a mass fraction of 30.00%, transfer it into a dropping funnel and add it in 3 batches, each batch taking 60min. Add the next batch after the pH value of the reaction solution drops to about 10. After the addition is complete, continue to react at room temperature for 5.5h, then raise the temperature to 55℃ and continue to react for 1h. Cool to room temperature to obtain 366.6mL of orange-red liquid, which is a heavy metal chelating flocculant with dual chelating groups.

[0081] Example 10

[0082] (1) Take 20.0 mL of tetraethylenepentamine with a mass fraction of 95.00% and 100.0 mL of distilled water and add them to a 250 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. Stir to dissolve and prepare a solution with a mass fraction of 15.81%. Then add 10.89 g of solid KOH with a mass fraction of 85.00% and stir at room temperature for 1 h.

[0083] (2) Take 9.7 mL of carbon disulfide with a mass fraction of 99.00% and slowly add it to the solution in step (1). Stir the reaction at room temperature for 3.5 h until the bottom oil droplets disappear. Then heat the solution to 60 °C and react for 0.75 h. Then cool the solution to room temperature.

[0084] (3) Take 66.51g of sodium bromoacetate with a mass fraction of 98.00% and add it to a 500mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. Add 119.7mL of distilled water to prepare a solution with a mass fraction of 35.00%.

[0085] (4) Add the solution obtained in step (2) to the solution obtained in step (3) and mix thoroughly; weigh 27.72g of solid KOH with a mass fraction of 85.00%, add 39.6mL of distilled water to dissolve and prepare a solution with a mass fraction of 35.00%, transfer it into a dropping funnel and add it in 3 batches, each batch for 50min. Add the next batch after the pH value of the reaction solution drops to about 10. After the addition is complete, continue to react at room temperature for 6h, then raise the temperature to 50℃ and continue to react for 1h. Cool to room temperature to obtain 319.7mL of orange-red liquid, which is a heavy metal chelating flocculant with dual chelating groups.

[0086] Example 11

[0087] (1) Take 20.0 mL of tetraethylenepentamine with a mass fraction of 95.00% and 90 mL of distilled water and add them to a 250 mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. Stir to dissolve and prepare a solution with a mass fraction of 17.24%. Then add 10.00 g of solid NaOH with a mass fraction of 96.00% and stir at room temperature for 1 h.

[0088] (2) Take 13.6 mL of carbon disulfide with a mass fraction of 99.00% and slowly add it to the solution in step (1). Stir the reaction at room temperature for 3 hours until the bottom oil droplets disappear. Then heat the solution to 60°C and react for 1 hour. Then cool the solution to room temperature.

[0089] (3) Take 67.33g of sodium bromoacetate with a mass fraction of 98.00% and add it to a 500mL three-necked flask equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. Add 138.9mL of distilled water to prepare a solution with a mass fraction of 32.00%.

[0090] (4) Add the solution obtained in step (2) to the solution obtained in step (3) and mix thoroughly; weigh 16.67g of solid NaOH with a mass fraction of 96.00%, add 36.7mL of distilled water to dissolve and prepare a solution with a mass fraction of 30.00%, transfer it into a dropping funnel and add it in 3 batches, each batch taking 60min. Add the next batch after the pH value of the reaction solution drops to about 10. After the addition is complete, continue to react at room temperature for 6h, then raise the temperature to 60℃ and continue to react for 1h. Cool to room temperature to obtain 325mL of reddish-brown liquid, which is a heavy metal chelating flocculant with dual chelating groups.

[0091] Infrared spectral analysis was performed on the chelating flocculants obtained in Examples 1 to 11, and the results were basically consistent. The infrared spectral analysis results of the chelating flocculant obtained in Example 7 are as follows: Figure 2 As shown. Figure 2 The absorption peaks in the infrared spectrum can be assigned as follows: 3263.68 cm⁻¹ -1 These are the stretching vibration peaks of -OH and -NH in the water content of the sample; at 2927.29 and 2808.67 cm⁻¹. -1 Asymmetric and symmetric stretching vibration peaks of -CH2- appear at 1346.92 cm⁻¹. -1 Its bending vibration peak appears at 1670.24 cm. -1 The strong peak and 1406.94cm -1 The slightly weaker peaks are the asymmetric and symmetric stretching vibrations of the carboxylate group, respectively; 1610.11 cm⁻¹ -1 The absorption peak for bound water molecules is 1474.41 cm⁻¹. -1 It is an aminodithiocarboxylic acid group (N-CSS) - The stretching vibration absorption peaks of CN in the sample are 1291.21, 1201.85, and 1127.21 cm⁻¹. -1 These are the stretching vibration peaks of CO and CN in the molecule; 1016.73 and 964.92 cm⁻¹. -1 For -CSS - The stretching vibration peaks of C=S and CS in the middle; 859.97 cm⁻¹ -1 The deformation vibration peaks can be attributed to —CSS-. Elemental analysis of the above samples showed that the S content was 18.02% and the O content was 17.99%, which translates to —CSS- and —CH2COO-. On average, each chelated flocculant molecule has 1.98 —CSS- and 3.97 —CH2COO- groups. These results indicate that a heavy metal chelating flocculant with dual chelating groups has been successfully synthesized.

[0092] Example 12

[0093] This embodiment demonstrates the treatment effect of the sample from Example 7 on heavy metal wastewater.

[0094] IDA-TEPA-DTC (—CSS) prepared in Example 7 — The content of 2.810 mmol / g and -N(CH2COOH)2 of 2.811 mmol / g) and TEPA-DTC (-CSS) prepared under the same conditions using tetraethylenepentamine (TEPA) as a raw material were compared. — The chelating agent (containing 5.166 mmol / g) was used to prepare 100 mg / L solutions containing Cr. 3+ Pb 2+ Cd 2+ Ni 2+ Mn 2+ Cu 2 + and Zn 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 4.5–7. The reagent was added to a MY3000-6G intelligent color screen coagulation test stirrer (Wuhan Meiyu Instrument Co., Ltd.). The mixture was stirred rapidly at 200–250 r / min for 5 min, then stirred at 100–110 r / min for 10 min, and finally stirred slowly at 50–60 r / min for 7 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.

[0095] Table 1. Removal effect of the product of this invention on free heavy metal ions

[0096]

[0097] As shown in Table 1, under optimal conditions, the product IDA-TEPA-DTC of this invention has a greater effect on free Cr than the control sample TEPA-DTC. 3+ Pb 2+ Cd 2+ Ni 2+ Mn 2+ Cu 2+ and Zn 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 it can even remove Pb. 2+ Cd 2+ and Cu 2+ Completely remove.

[0098] Example 13

[0099] This embodiment illustrates the settling velocity of flocs generated during the treatment of heavy metals in wastewater using the IDA-TEPA-DTC chelation method of the present invention.

[0100] The sample IDA-TEPA-DTC (CSS) obtained in Example 7 — The content was 2.810 mmol / g, and —N(CH2COOH)2 was 2.811 mmol / g) as a chelating agent; TEPA-DTC (—CSS) — The Cd content was 5.166 mmol / g) as the control sample, and 100 mg / L of Cd-containing sample was used as the control sample. 2+ Simulated wastewater was used as the test object. The experiment was first conducted according to the reagent addition amount and flocculation conditions in Example 12. After stirring was stopped, the test solution was quickly transferred into a 500mL graduated cylinder, and the timing was started to record the drop height of the clear and turbid interface at different times. The results are shown in Table 2.

[0101] Table 2. IDA-TEPA-DTC chelated Cd by the product of this invention. 2+ The settling velocity of the generated flocs

[0102]

[0103] As can be seen from the results in Table 2, the product of this invention, IDA-TEPA-DTC, treats Cd-containing substances. 2+ The flocs produced by IDA-TEPA-DTC settled significantly faster than those produced by TEPA-DTC, and after 30 minutes of settling, the height of the clear liquid was greater than that of the TEPA-DTC-treated liquid. During the experiment, it was observed that the flocs produced by IDA-TEPA-DTC were larger and denser than those produced by TEPA-DTC, and the clear liquid had lower turbidity and was clearer. Therefore, the flocs produced by IDA-TEPA-DTC exhibit superior flocculation and sedimentation performance.

[0104] Example 14

[0105] Thiourea-Cd solutions with a molar ratio of 1:1 and a concentration of 50 mg / L were prepared using deionized water. 2+ Citric acid-Cd 2+ Thiourea-Ni 2+ and citric acid-Ni 2+Simulated heavy metal complexation wastewater samples were prepared using the sample obtained in Example 7, commercially available DTCR, and sodium thiram as chelating agents. The agents were added to a MY3000-6G intelligent color screen coagulation test mixer (Wuhan Meiyu Instrument Co., Ltd.). The mixture was rapidly stirred at 200 rpm for 5 minutes, then stirred at 100 rpm for 20 minutes. Polyacrylamide (PAM) was added as a coagulant aid, followed by slow stirring at 60 rpm for 25 minutes. After standing for 30 minutes, the clear liquid at 2 cm below the surface was measured using an AA-7000 atomic absorption spectrophotometer (Shimadzu Corporation, Japan). Turbidity was measured within WZS range. － The results were measured using a Type 185 high turbidity meter (Shanghai Precision Scientific Instruments Co., Ltd.) and are shown in Table 3.

[0106] Table 3. Removal effect of the product of this invention on complexed heavy metal ions

[0107]

[0108]

[0109] Note: Dosage is in the dosage form of the medicine. － CSS － The molar ratio to ions, the concentration unit is mg / L, and the turbidity unit is NTU.

[0110] As can be seen from Table 3, the product of this invention has a good effect on complexing Cu. 2+ Ni 2+ Its removal effect is significantly better than that of commercially available DTCR and sodium thiosulfate.

[0111] Example 15

[0112] Using the IDA-TEPA-DTC obtained in Example 7 as a chelating agent, the wastewater from an electroplating plant was used as the treatment target. The pollutant indicators of the wastewater were: pH value 1.29, turbidity 320.5 NTU, Cu 2+ The concentration was 105.12 mg / L, Ni 2+ The concentration was 25.59 mg / L, the total Cr concentration was 29.27 mg / L, and the Zn concentration was... 2+ The concentration was 434.6 mg / L, Co 2+ The concentration was 10.59 mg / L, Fe 3+ The concentration is 160.54 mg / L. It contains phosphorus compounds and appears as a dark gray turbid substance.

[0113] The product IDA-TEPA-DTC obtained in Example 7, 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 adjusted to approximately 6 with lime milk. The sample was then placed on a MY3000-6G intelligent color screen coagulation test stirrer (Wuhan Meiyu Instrument Co., Ltd.), and certain amounts of chelating agents such as IDA-TEPA-DTC, sodium thimerosal, and TMT-18 were added. The amount of chelating agent added was 1.2 times the stoichiometric ratio, where the stoichiometric ratio of IDA-TEPA-DTC to sodium thimerosal (i.e., the ratio of IDA-TEPA-DTC to sodium thimerosal in either IDA-TEPA-DTC or sodium thimerosal) was... － CSS － The molar ratios of TMT-18 to heavy metal ions were 1.55:1 and 2.25:1, respectively, and the stoichiometric ratio of TMT-18 to metal ions was 2:3. 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, and the endpoint pH value and the concentration of heavy metal ions in the treated water were tested. The results are listed in Table 4.

[0114] Table 4. Removal effect of the product of this invention on comprehensive wastewater from electroplating plants.

[0115]

[0116]

[0117] The results in Table 4 show that the product of this invention, IDA-TEPA-DTC, has a significantly better treatment effect on this type of comprehensive electroplating wastewater than commercially available heavy metal trapping agents such as sodium formaldehyde sulfoxylate and TMT-18. Moreover, it requires a small dosage, results in low turbidity of the treated water, and all pollutant indicators are lower than the limits specified in the "Electroplating Pollutant Discharge Standard" (GB21900-2008).

[0118] Example 16

[0119] Using the product IDA-TEPA-DTC obtained in Example 7, the commercially available heavy metal capture agent sodium thimerosal, and TMT － 18 is a heavy metal stabilizer for incineration fly ash, all prepared as a 5% (w / w) solution. 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 pollutant concentration in the leachate was determined. The results are shown in Table 5.

[0120] Table 5. Effects of the product of this invention and commercially available stabilizers on the treatment of incineration fly ash.

[0121]

[0122] As can be seen from Table 5, the amount of the product IDA-TEPA-DTC used in 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.

[0123] The results of Examples 12-16 show that the product of this invention, IDA-TEPA-DTC, has superior removal efficiency for heavy metal ions in free heavy metal wastewater, complexed heavy metal wastewater, and complex electroplating wastewater compared to the comparative samples. The resulting flocs settle faster and effectively immobilize metal ions in incineration fly ash. This is because IDA-TEPA-DTC contains two types of strong chelating groups—CSS. — And —N(CH2COOH)2, as shown in the attached figure Figure 3 The chelation effect shown: (1) —CSS — It can form water-insoluble disulfide-coordinated four-membered ring structures with most heavy metal ions, while the -N(CH2COOH)2 group can react with most metal ions, including Ca. 2+ and Mg 2+ (1) Difficult-to-coordinate metal ions are generated to form two stable five-membered rings and bind them to the chelating agent molecule; (2) Through two -CSS from different IDA-TEPA-DTC molecules — The chelating group chelates with the same heavy metal ion, linking different molecules together to form a chelate that gradually grows into larger flocs or aggregates of chelate molecules. This improves the performance of chelating and binding metal ions, the settling performance of the flocs, and the stability of the chelate. The synergistic effect of two types of strong chelating groups significantly improves the chelation and removal efficiency of metal ions in wastewater or the stabilization efficiency of metal ions in fly ash.

[0124] 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 variations. For example, within the range of proportions and process conditions given in the present invention, the proportions and process conditions can be combined and varied. Such variations and modifications are all within the scope of the present invention.

Claims

1. A heavy metal chelating flocculant possessing both dual chelating groups, characterized in that, Its main components have the structure shown in formula (Ⅰ): （Ⅰ）； In equation (I), 1≤x≤3, 1≤y≤x, and x and y are both integers; when y<x, x-y N atoms are connected to H atoms; M is Na or K; The chelating flocculant also includes auxiliary components xanthic acid and alkali, and the chelating flocculant is an orange-red or reddish-brown viscous liquid.

2. The method for preparing the heavy metal chelating flocculant with dual chelating groups as described in claim 1, characterized in that, Includes the following steps: (1) Prepare a solution with a mass fraction of 15.00% to 19.20% by adding polyethylene polyamine and distilled water into a reactor at a volume ratio of 1:4 to 5. Then add alkali at a ratio of (n-2) times the amount of polyethylene polyamine to the amount of alkali at 1:0.6 to 1.2, where n represents the number of N atoms in the polyethylene polyamine molecule. Stir at room temperature for 0.5 to 1 h. (2) Add carbon disulfide at a ratio of (n-2) times the amount of polyethylene polyamine to the amount of carbon disulfide of 1:0.33~1.05, where n represents the number of N atoms in the polyethylene polyamine molecule. Stir the reaction at room temperature for 3~4 hours until the bottom oil droplets disappear. Then heat to 50~60℃ and react for 0.5~1 hours. Then cool to room temperature to obtain solution A. (3) Weigh out the haloacetate and add it to the reactor according to the molar ratio of haloacetate to polyethylene polyamine of 4.0~4.2:1, and add distilled water to prepare a solution with a mass fraction of 30%~35% to obtain solution B; (4) Add the solution A obtained in step (2) to the solution B obtained in step (3) and mix thoroughly; then weigh the alkali according to the molar ratio of alkali to polyethylene polyamine of 4~4.2:1, add distilled water to prepare a solution with a mass fraction of 30%~35%, add it slowly in three batches, and wait until the pH value of the solution drops to 9~11 before adding the next batch. After adding, continue to react at room temperature for 4~6 hours, then raise the temperature to 50~60℃ and continue to react for 0.5~1 hours, cool to room temperature, and you will get a heavy metal chelating flocculant with dual chelating groups.

3. The method for preparing the heavy metal chelating flocculant with dual chelating groups according to claim 2, characterized in that, In step (1), the polyethylene polyamine is any one of diethylenetriamine, triethylenetetramine, or tetraethylenepentamine.

4. The method for preparing the heavy metal chelating flocculant with dual chelating groups according to claim 2, characterized in that, In steps (1) and (4), the alkali is NaOH or KOH.

5. The method for preparing the heavy metal chelating flocculant with dual chelating groups according to claim 2, characterized in that, In step (3), the haloacetate is either sodium chloroacetate or sodium bromoacetate.

6. The method for preparing the heavy metal chelating flocculant with dual chelating groups according to claim 2, characterized in that, In step (4), the slow addition time is 30~60 min.

7. The method for preparing the heavy metal chelating flocculant with dual chelating groups according to claim 2, characterized in that, The polyethylene polyamine, alkali, carbon disulfide, and haloacetate mentioned are all products of industrial grade or higher purity and do not require further purification before use.

8. The method for preparing the heavy metal chelating flocculant with dual chelating groups according to claim 2, characterized in that, In steps (1) and (3), the reactors are equipped with mechanical stirring, a dripping funnel, and a reflux condenser.

9. The application of the heavy metal chelating flocculant according to claim 1 or the heavy metal chelating flocculant obtained by 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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