Preparation method of heavy metal trapping agent for wastewater treatment

Abstract

The invention relates to the technical field of wastewater treatment, and discloses a preparation method of a heavy metal capturing agent for wastewater treatment, which comprises the following steps: reacting 2-chloroethanol with trimellitic anhydride acyl chloride, and reacting with N, N-dimethyl ethyl trimesoamide to obtain a novel quaternary ammonium salt anhydride intermediate. The three-dimensional hyperbranched molecular chain heavy metal capturing agent contains three anhydride groups which are subjected to amidation polymerization reaction with two amino groups of diaminooxane to obtain the three-dimensional hyperbranched molecular chain heavy metal capturing agent. The heavy metal capturing agent has good adsorption sites, hydrophilicity and dispersibility in water, is not easy to gather, and is beneficial to improving the adsorption performance of the heavy metal capturing agent. Meanwhile, the heavy metal trapping agent contains a large number of carboxyl groups which can be coordinated with Pb < 2 + > and other metal ions, and meanwhile, quaternary ammonium salt cations can be subjected to electrostatic interaction with Cr2O7 < 2-> ions, so that the adsorption capacity of the heavy metal trapping agent on the Pb < 2 + >, Cr2O7 < 2-> and other metal ions is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, in particular to a method for preparing a heavy metal scavenger for wastewater treatment. Background Art

[0003] The development of high-performance adsorbents for the treatment of wastewater containing metal pollutants is a research focus. The molecular chains of hyperbranched polymers are not easily entangled, contain a large amount of active functional groups, have many adsorption sites, and are prepared in a variety of ways. They are widely used in adsorbents and wastewater treatment. Such as hyperbranched polyamides, hyperbranched polyamic acid, hyperbranched polyesters, etc. Patent CN111635530B discloses that trimethylolpropane and citric acid are subjected to melt polycondensation to obtain hyperbranched polycarboxylic acids, which are then grafted onto amination lignin by amidation reaction to obtain hyperbranched alkali lignin-based amphoteric adsorbents, which have good removal rates and adsorption rates for low-concentration multiple anionic and cationic heavy metal ions. Improving the hydrophilicity of hyperbranched polymers can improve their dispersibility in water, help improve adsorption properties, and introducing adsorption groups such as carboxyl groups, quaternary ammonium salts, into hyperbranched polymers can further enhance their adsorption properties to metal ions. Summary of the Invention

[0004] The invention solves the problem that hyperbranched polymers have poor adsorption performance for heavy metal ions.

[0005] Technical solution: A method for preparing a heavy metal scavenger: add a quaternary ammonium hydrochloride intermediate and diaminooxaalkane to N,N-dimethylformamide, react in a nitrogen atmosphere, add methanol after the reaction to precipitate, filter, wash with ethanol, and dry to obtain a heavy metal scavenger. The reaction formula is as follows:

[0006]

[0007] Furthermore, the molar ratio of the quaternary ammonium hydrochloric anhydride intermediate to the diaminooxaalkane is 1:(1.5-1.7).

[0008] Further, the structural formula of diaminooxaalkane is n is any integer from 2 to 4.

[0009] Furthermore, the reaction temperature is 20-35° C., and the reaction time is 8-12 h.

[0010] Further, the preparation method of the quaternary ammonium hydrochloric anhydride intermediate is:

[0011] (1) Add 2-chloroethanol, triethylamine, and 4-dimethylaminopyridine to dichloromethane, and add trimellitic anhydride chloride under ice bath, wherein the molar ratio of 2-chloroethanol, triethylamine, 4-dimethylaminopyridine, and trimellitic anhydride chloride is 1:(1.8-2.2):(0.12-0.16):(1.2-1.4); then stir and react at 20-25°C for 6-9 hours, rotary evaporate the solution, and recrystallize the product with ethyl acetate to obtain 4-chloroethyl formate phthalic anhydride. The reaction formula is:

[0012]

[0013] (2) Add 4-chloroethyl formate, phthalic anhydride, and N,N-dimethylethyl trimesic acid amide in a molar ratio of (3-3.6):1 to acetonitrile, stir and react at 65-75°C for 36-48 hours, rotary evaporate the solution, wash with acetone, dissolve the product in ethyl acetate, heat and volatilize, precipitate, filter, wash with acetone, and dry to obtain a quaternary ammonium hydrochloride intermediate. The reaction formula is:

[0014]

[0015] The technical effect is as follows: the present invention uses triethylamine as an acid-binding agent and 4-dimethylaminopyridine as a catalyst to react 2-chloroethanol and trimellitic anhydride chloride to obtain 4-chloroethyl formate phthalic anhydride; and then reacts with N,N-dimethylethyl trimesic acid amide to obtain a novel quaternary ammonium salt anhydride intermediate. The quaternary ammonium salt contains three anhydride groups, which undergo amidation polymerization with the two amino groups of diaminooxaalkane to obtain a heavy metal scavenger with a three-dimensional hyperbranched molecular chain. The three-dimensional hyperbranched molecular chain structure has more adsorption sites, and the heavy metal scavenger contains hydrophilic ether bonds, quaternary ammonium salts, carboxyl groups and other groups, which have better dispersibility in water and are not easy to aggregate, further increasing the adsorption sites and helping to improve the adsorption performance of the heavy metal scavenger.

[0016] The heavy metal scavenger of the present invention also contains a large number of carboxyl groups, which can react with Pb 2+ The metal ions can coordinate with Cr2O7. 2- The electrostatic interaction between ions significantly improved the heavy metal capture agent's ability to capture Pb 2+ 、Cr2O7 2- The adsorption capacity of metal ions such as iodine and thiazolinone makes heavy metal scavengers have good practical applications in the treatment of metal-containing wastewater. DETAILED DESCRIPTION

[0017] To facilitate understanding of the present invention, preferred embodiments of the present invention are provided below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0018] The structural formula of N,N-dimethylethyl trimesic acid amide is

[0019] The preparation was carried out according to the method of the article "Inorganic–organic hybrid materials based on keggin type polyoxometalates and organic polyammonium cations" in the journal Journal of Molecular Structure, 2003, vol. 656, #1-3, p. 27-35.

[0020] Add 1.88 mmol of trimesoyl chloride to 10 mL of dichloromethane 5.63mmol N,N-dimethylethylenediamine The reaction was stirred at room temperature for 6 h, the solution was rotary evaporated, 15 mL of chloroform and 0.5 g of sodium carbonate were added, and the mixture was stirred and filtered. The filtrate was concentrated, and ether was added to precipitate the precipitate, which was then recrystallized from ethanol to obtain N,N-dimethylethyl trimesic acid amide.

[0021] Example 1

[0022] (1) Add 15 mmol of 2-chloroethanol, 27 mmol of triethylamine, and 2 mmol of 4-dimethylaminopyridine to dichloromethane, and add 21 mmol of trimellitic anhydride chloride under ice bath, then stir and react at 20°C for 9 hours. The solution is rotary evaporated and the product is recrystallized from ethyl acetate to obtain 4-chloroethyl formate phthalic anhydride.

[0023] (2) Add 60 mmol of 4-chloroethyl phthalic anhydride and 20 mmol of N,N-dimethylethyl trimesic acid amide to 120 mL of acetonitrile, stir and react at 75°C for 36 hours, rotary evaporate the solution, wash with acetone, dissolve the product in ethyl acetate, heat and volatilize, precipitate, filter, wash with acetone, and dry to obtain a quaternary ammonium hydrochloric anhydride intermediate.

[0024] (3) Add 40 mmol of quaternary ammonium hydrochloride intermediate and 62 mmol of 1,8-diamino-3,6-dioxaoctane (CAS No. 929-59-9, structural formula: ), stirred and reacted at 20°C in a nitrogen atmosphere for 12 h, and methanol was added after the reaction to precipitate the precipitate, which was filtered, washed with ethanol, and dried to obtain a heavy metal scavenger.

[0025] Example 2

[0026] (1) Add 15 mmol of 2-chloroethanol, 33 mmol of triethylamine, and 1.8 mmol of 4-dimethylaminopyridine to dichloromethane, and add 18 mmol of trimellitic anhydride chloride under ice bath, then stir and react at 25°C for 8 hours. The solution is rotary evaporated and the product is recrystallized from ethyl acetate to obtain 4-chloroethyl formate phthalic anhydride.

[0027] (2) Add 70 mmol of 4-chloroethyl phthalic anhydride and 20 mmol of N,N-dimethylethyl trimesic acid amide to 150 mL of acetonitrile, stir and react at 65 ° C for 48 hours, rotary evaporate the solution, wash with acetone, dissolve the product in ethyl acetate, heat and volatilize, precipitate, filter, wash with acetone, and dry to obtain a quaternary ammonium hydrochloric acid anhydride intermediate.

[0028] (3) Add 40 mmol of quaternary ammonium hydrochloride intermediate and 68 mmol of 1,11-diamino-3,6,9-trioxaundecane (CAS No. 929-75-9, structural formula: ), stirred at 35°C in a nitrogen atmosphere for 8 h, and methanol was added after the reaction to precipitate the precipitate, which was filtered, washed with ethanol, and dried to obtain a heavy metal scavenger.

[0029] Example 3

[0030] (1) Add 15 mmol of 2-chloroethanol, 30 mmol of triethylamine, and 2.4 mmol of 4-dimethylaminopyridine to dichloromethane, and add 18 mmol of trimellitic anhydride chloride under ice bath, then stir and react at 25°C for 6 hours. The solution is rotary evaporated and the product is recrystallized from ethyl acetate to obtain 4-chloroethyl formate phthalic anhydride.

[0031] (2) Add 70 mmol of 4-chloroethyl phthalic anhydride and 20 mmol of N,N-dimethylethyl trimesic acid amide to 150 mL of acetonitrile, stir and react at 70°C for 36 hours, rotary evaporate the solution, wash with acetone, dissolve the product in ethyl acetate, heat and volatilize, precipitate, filter, wash with acetone, and dry to obtain a quaternary ammonium hydrochloric acid anhydride intermediate.

[0032] (3) Add 40 mmol of quaternary ammonium hydrochloride intermediate and 60 mmol of 3,6,9,12-tetrahydrotetradecane-1,4-diamine (CAS No. 68960-97-4, structural formula: ), stirred at 30°C in a nitrogen atmosphere for 12 h, and methanol was added after the reaction to precipitate the precipitate, which was filtered, washed with ethanol, and dried to obtain a heavy metal scavenger.

[0033] Comparative Example 1

[0034] (1) To 500 mL of N,N-dimethylformamide, 40 mmol of a quaternary ammonium hydrochloride intermediate (prepared in the same manner as in Example 1) and 62 mmol of ethylenediamine were added. The mixture was stirred at 20° C. in a nitrogen atmosphere for 12 h. After the reaction, methanol was added to precipitate the precipitate, which was filtered, washed with ethanol, and dried to obtain a heavy metal scavenger.

[0035] Comparative Example 2

[0036] (1) Add 40 mmol of 4,4'-biphenyl ether dianhydride to 500 mL of N,N-dimethylformamide. 62 mmol of 1,8-diamino-3,6-dioxaoctane was stirred and reacted at 20°C for 12 h in a nitrogen atmosphere. After the reaction, methanol was added to precipitate the precipitate, which was filtered, washed with ethanol, and dried to obtain a heavy metal scavenger.

[0037] Comparative Example 3

[0038] (1) Add 40 mmol of 4-chloroethyl formate phthalic anhydride (prepared in the same manner as in Example 1) and 20 mmol of N,N,N',N'-tetramethylethylenediamine to 120 mL of acetonitrile. The reaction was stirred at 75°C for 36 hours, the solution was rotary evaporated, washed, and the product was dissolved in ethyl acetate, heated for volatilization, and the precipitate was filtered and dried to obtain a quaternary ammonium hydrochloride intermediate. The structural formula is

[0039] (2) Add 40 mmol of quaternary ammonium hydrochloride intermediate and 62 mmol of 1,8-diamino-3,6-dioxaoctane to 500 mL of N,N-dimethylformamide, stir and react at 20°C in a nitrogen atmosphere for 12 h, add methanol after the reaction to precipitate, filter, wash with ethanol, and dry to obtain a heavy metal scavenger.

[0040] Add lead nitrate to 1L of distilled water to control Pb 2+ The concentration of the solution was 50 mg / L, the pH of the solution was adjusted to 5, a heavy metal scavenger was added, and the mixture was stirred and adsorbed at 25 °C for 2 h. The supernatant was taken and the Pb content was determined by atomic absorption spectrometry.2+ Calculate the concentration of heavy metal capture agent to Pb 2+ The adsorption capacity Q.

[0041] Q=(C0-C)×V / m. C0 is the Pb content in the solution before adsorption. 2+ The concentration of Pb in the solution after adsorption is C. 2+ The concentration of , V is the volume of the solution, and m is the mass of the heavy metal scavenger. The results are shown in Table 1.

[0042] Table 1 Heavy metal capture agent for Pb 2+ Adsorption capacity test

[0043]

[0044] Add potassium dichromate to 1L distilled water to control Cr2O7 2- The concentration of 50 mg / L was adjusted to pH 5, 50 mg of heavy metal scavenger was added, and the mixture was stirred and adsorbed at 25 °C for 3 h. The supernatant was taken and the Cr2O7 2- Calculate the concentration of heavy metal capture agent to Cr2O7 2- The adsorption capacity Q of the samples was 0.0447 W / m. The results are shown in Table 2.

[0045] Table 2 Effect of heavy metal capture agents on Cr2O7 2- Adsorption capacity test

[0046]

[0047] As shown in Table 1, Examples 1-3 utilize quaternary ammonium anhydride intermediates and diaminooxaalkane to carry out amidation acidification reaction of anhydride and amino groups to obtain heavy metal scavengers with three-dimensional hyperbranched molecular chains, which have more adsorption sites and contain hydrophilic ether bonds, quaternary ammonium salts, carboxyl groups and other groups. They have better dispersibility in water, are not easy to aggregate, and further increase adsorption sites; at the same time, they contain a large number of carboxyl groups, which can react with Pb 2+ The metal ions can coordinate with Cr2O7. 2- The electrostatic interaction between ions significantly improved the heavy metal capture agent's ability to capture Pb 2+ 、Cr2O7 2- The adsorption capacity of metal ions.

[0048] Comparative Example 1 uses a quaternary ammonium anhydride intermediate to react with ethylenediamine to obtain a heavy metal scavenger. The heavy metal scavenger does not contain a hydrophilic ether bond, resulting in a lower hydrophilicity and dispersibility of the heavy metal scavenger in water than in Example 1. It is easy to aggregate in water, reducing the adsorption sites and resulting in a decrease in the adsorption of Pb. 2+ 、Cr2O7 2- The adsorption capacity of metal ions is lower than that in Example 1.

[0049] Comparative Example 2: 4,4'-biphenyl ether dianhydride reacts with 1,8-diamino-3,6-dioxaoctane to obtain a heavy metal scavenger that does not contain a quaternary ammonium salt group, resulting in a low hydrophilicity and low dispersibility of the heavy metal scavenger in water and a low sensitivity to Cr2O7. 2- The adsorption capacity is much lower than that of Example 1.

[0050] Comparative Example 3: 1,8-diamino-3,6-dioxaoctane and quaternary ammonium anhydride intermediate The heavy metal capture agent obtained by the reaction is a linear molecular chain without a three-dimensional hyperbranched molecular chain structure and has fewer adsorption sites. 2+ 、Cr2O7 2- The adsorption capacity of metal ions is lower than that in Example 1.

[0051] The above embodiments merely represent preferred embodiments of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a heavy metal scavenger, characterized in that: The preparation method comprises: adding a quaternary ammonium hydrochloric anhydride intermediate and diaminooxaalkane to N,N-dimethylformamide, reacting in a nitrogen atmosphere, adding methanol to precipitate a precipitate after the reaction, filtering, washing with ethanol, and drying to obtain a heavy metal capture agent; The structural formula of the quaternary ammonium hydrochloric anhydride intermediate is as follows:

2. The method for preparing a heavy metal scavenger according to claim 1, characterized in that: The molar ratio of the quaternary ammonium hydrochloric anhydride intermediate and the diaminooxaalkane is 1:(1.5-1.7).

3. The method for preparing a heavy metal scavenger according to claim 1, characterized in that: The structural formula of the diaminooxaalkane is n is any integer from 2 to 4.

4. The method for preparing a heavy metal scavenger according to claim 1, characterized in that: The reaction temperature is 20-35°C and the reaction time is 8-12h.

5. The method for preparing a heavy metal scavenger according to claim 1, characterized in that: The preparation method of the quaternary ammonium hydrochloric anhydride intermediate is: (1) Add 2-chloroethanol, triethylamine and 4-dimethylaminopyridine to dichloromethane, add trimellitic anhydride chloride under ice bath, and then stir and react at 20-25° C. for 6-9 hours. Rotary evaporate the solution, and recrystallize the product with ethyl acetate to obtain 4-chloroethyl formate phthalic anhydride; (2) Add 4-chloroethyl formate phthalic anhydride and N,N-dimethylethyl trimesic acid amide to acetonitrile, stir to react, rotary evaporate the solution, wash with acetone, dissolve the product in ethyl acetate, heat and volatilize, precipitate, filter, wash with acetone, and dry to obtain a quaternary ammonium hydrochloric acid anhydride intermediate.

6. The method for preparing a heavy metal scavenger according to claim 5, characterized in that: In the above (1), the molar ratio of 2-chloroethanol, triethylamine, 4-dimethylaminopyridine and trimellitic anhydride chloride is 1:(1.8-2.2):(0.12-0.16):(1.2-1.4).

7. The method for preparing a heavy metal scavenger according to claim 5, characterized in that: In the above (2), the molar ratio of 4-chloroethyl formate phthalic anhydride to N,N-dimethylethyl trimesic acid amide is (3-3.6):

1.

8. The method for preparing a heavy metal scavenger according to claim 5, characterized in that: In the step (2), the reaction temperature is 65-75°C and the reaction time is 36-48h.

9. Use of the heavy metal scavenger obtained by the preparation method according to any one of claims 1 to 8 in wastewater treatment.

Images