A chelating agent for fluorine-containing wastewater treatment and a method for preparing the same

Abstract

The present application relates to wastewater treatment technical field, and disclose a kind of fluorine-containing wastewater treatment chelating agent and its preparation method, the present application will boc-amino maleic acid trihydroxymethyl propane ester and the polyethylene glycol polycondensation crosslinking reaction, remove boc protective group, obtain gelatinous fluorine-containing wastewater treatment chelating agent.Chelating agent contains polyether segment, good hydrophilicity, with three-dimensional crosslinking network simultaneously, with spatial network and pore structure, more adsorption chelating site, it is favorable to improve adsorption performance, while chelating agent contains a large number of end carboxyl, amino functional group, copper, lead, cadmium and other metal ions have very strong coordination chelation effect, carboxyl ionization generates H proton in water, and amino combines, makes amino N atom protonation, and F ‑ Ion forms electrostatic effect, thereby improve the adsorption performance of chelating agent to F ‑ In fluorine-containing ion, heavy metal ion wastewater treatment, good practical application.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a chelating agent for treating fluoride-containing wastewater and its preparation method. Background Technology

[0002] Currently, wastewater treatment mainly employs methods such as adsorption, chemical oxidation, precipitation, and microbial degradation.

[0003] Adsorption is a simple and easy-to-operate method, and various adsorption materials are available, such as chelating resins, hydrogels, activated carbon, and molecular sieves. Patent CN120515379B discloses a fluoride adsorbent with multiple metal adsorption sites and its preparation method. This fluoride adsorbent contains active adsorption sites for metals such as Al and Fe, exhibiting a strong affinity for fluoride and thus efficiently removing fluoride pollutants. However, this adsorbent lacks adsorption and chelation properties for heavy metal ions such as copper and lead, limiting its application in the treatment of wastewater containing heavy metals and fluoride. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a chelating agent for treating fluoride-containing wastewater and its preparation method, thus solving the problem of low adsorption performance of chelating agents for fluoride ions.

[0005] The technical solution of this invention is: a method for preparing a chelating agent for treating fluoride-containing wastewater. (1) Trimethylolpropane was added to a flask equipped with a reflux condenser, heated and stirred, p-toluenesulfonic acid was added, maleic anhydride was added dropwise, the reaction was stirred, cooled, and the product was recrystallized in water to obtain trimethylolpropane maleate. The reaction formula is: .

[0006] (2) Add water, trimethylolpropane maleate, and sodium hydroxide to a flask, stir, then add ethanol and N-tert-butoxycarbonyl-diamine monomer, stir to carry out the amino-ene Michael addition reaction, remove ethanol by vacuum distillation, add hydrochloric acid dropwise, precipitate, filter, add the precipitate to water, recrystallize to obtain boc-aminotrimethylolpropane maleate; the reaction formula is: .

[0007] (3) Add polyethylene glycol, trimethylol-boc-aminopropane maleate and p-toluenesulfonic acid to the flask, heat to the reaction temperature, stir for pre-reaction, vacuum, stir for polycondensation reaction, cool, add the product to HCl-ethyl acetate solution, stir to remove boc protecting group, distill under reduced pressure and wash the product with water, dry to obtain fluorine-containing wastewater treatment chelating agent.

[0008] Furthermore, in (1), the molar ratio of trimethylolpropane, p-toluenesulfonic acid, and maleic anhydride is 1:(3-3.3):(0.005-0.006).

[0009] Furthermore, the reaction in (1) is stirred at 85-90℃ for 2.5-3.5h.

[0010] Furthermore, in (2), the molar ratio of trimethylolpropane maleate, sodium hydroxide, and N-tert-butoxycarbonyl-diamine monomer is 1:(3-3.6):(3-3.3).

[0011] Furthermore, in (2), the addition reaction is stirred at 35-50℃ for 3-5 hours.

[0012] Furthermore, the structural formula of the N-tert-butoxycarbonyl-diamine monomer in (2) is as follows: , where a is 2-6.

[0013] Furthermore, in (2), hydrochloric acid is added dropwise to adjust the pH to 2-4, and the mass fraction of hydrochloric acid is 5-37%.

[0014] Furthermore, in (3), the molar ratio of polyethylene glycol, trimethylolpropane maleate, and p-toluenesulfonic acid is (1.32-1.41):1:(0.026-0.03).

[0015] Furthermore, in (3), the molecular weight of polyethylene glycol is 400-2000.

[0016] Furthermore, in (3), the temperature is heated to 185-200℃ and the pre-reaction time is 1-1.5h.

[0017] Furthermore, in (3), the vacuum level is controlled to be 100-300 Pa.

[0018] Furthermore, the stirring polycondensation reaction time in (3) is 8-12h.

[0019] Furthermore, the concentration of the HCl-ethyl acetate solution in (3) is 2.5-4 mol / L.

[0020] Furthermore, in (3), the reaction is carried out by stirring at 20-30℃ for 3-5 hours.

[0021] The beneficial technical effects of this invention are as follows: This invention involves a polycondensation and crosslinking reaction between boc-aminomaleic trimethylolpropane ester containing three carboxyl groups and polyethylene glycol containing two hydroxyl groups, followed by the removal of the boc protecting group to generate an amino group, resulting in a gel-like chelating agent for treating fluoride-containing wastewater. The chelating agent contains polyether segments, exhibiting good hydrophilicity and a three-dimensional crosslinked network with spatial network and porous structure, providing more adsorption and chelation sites, thus improving adsorption performance. Furthermore, the chelating agent contains a large number of terminal carboxyl groups and amino functional groups, exhibiting strong coordination and chelation effects on metal ions such as copper, lead, and cadmium, significantly improving removal rate and adsorption performance. Additionally, the carboxyl groups ionize in water to generate H protons, which combine with the amino group, protonating the N atom of the amino group to form N... + Ions, with F - The ions form an electrostatic interaction, thereby enhancing the chelating agent's ability to bind F. - Its adsorption properties have been well applied in the treatment of wastewater containing fluoride ions and heavy metal ions. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1: (1) 20 mmol of trimethylolpropane was added to a flask equipped with a reflux condenser, heated to 70°C, stirred, and then 0.1 mmol of p-toluenesulfonic acid was added. 60 mmol of maleic anhydride was added dropwise, heated to 90°C, stirred for 3 hours, cooled, and the product was added to water for recrystallization to obtain trimethylolpropane maleate.

[0024] (2) Add 30 mL of water, 15 mmol of trimethylolpropane maleate (total alkenyl molar amount of 45 mmol), and 45 mmol of sodium hydroxide to a flask. After stirring, add 80 mL of ethanol and 45 mmol of N-tert-butoxycarbonyl-1,2-ethylenediamine (total primary amino-NH2 molar amount of 45 mmol). Control the total alkenyl molar amount and the total primary amino-NH2 molar amount ratio to be 1:1. Stir the reaction at 40 °C for 5 h. Remove the ethanol by vacuum distillation. Add 8% hydrochloric acid by mass to adjust the pH to 3. The precipitate is precipitated. Filter the precipitate and add it to water for recrystallization to obtain boc-aminomaleic acid trimethylolpropane.

[0025] (3) Add 13.5 mmol polyethylene glycol 1000 (total hydroxyl molar amount of 27 mmol), 10 mmol trimethylolpropane maleate (total carboxyl molar amount of 30 mmol), and 0.26 mmol p-toluenesulfonic acid to the flask, and control the ratio of total hydroxyl molar amount to total carboxyl molar amount of 0.9:1; heat to 200℃, stir for 1 h, evacuate to control the vacuum degree to 100 Pa, stir for 8 h, cool, add the product to 2.5 mol / L HCl-ethyl acetate solution, stir for 5 h at 25℃, wash the product with water after vacuum distillation, dry, and obtain a gel-like fluoride-containing wastewater treatment chelating agent.

[0026] Example 2: (1) 20 mmol of trimethylolpropane was added to a flask equipped with a reflux condenser, heated to 70°C, stirred, and then 0.12 mmol of p-toluenesulfonic acid was added. 60 mmol of maleic anhydride was added dropwise, heated to 85°C, stirred for 3.5 h, cooled, and the product was added to water for recrystallization to obtain trimethylolpropane maleate.

[0027] (2) Add 30 mL of water, 15 mmol of trimethylolpropane maleate and 45 mmol of sodium hydroxide to the flask, stir, add 90 mL of ethanol and 45 mmol of N-tert-butoxycarbonyl-1,4-butanediamine, stir and react at 50 °C for 3 h, remove ethanol by vacuum distillation, add 5% hydrochloric acid dropwise to adjust pH to 3, precipitate, filter, add the precipitate to water, recrystallize to obtain boc-aminomaleic acid trimethylolpropane.

[0028] (3) Add 13.2 mmol polyethylene glycol 1000, 10 mmol trimethylolpropane maleate-boc-aminopropane ester and 0.26 mmol p-toluenesulfonic acid to the flask, heat to 185 °C, stir for 1.5 h, evacuate to control the vacuum degree to 100 Pa, stir for 12 h, cool, add the product to 2.5 mol / L HCl-ethyl acetate solution, stir for 5 h at 20 °C, wash the product with water after vacuum distillation, dry, and obtain a gel-like fluoride-containing wastewater treatment chelating agent.

[0029] Example 3: (1) Add 14.1 mmol polyethylene glycol 1000, 10 mmol trimethylolpropane maleate (prepared by the same method as in Example 1), and 0.28 mmol p-toluenesulfonic acid to a flask, heat to 190°C, stir for 1 h, evacuate to control the vacuum degree to 100 Pa, stir for 12 h, cool, add the product to a 2.5 mol / L HCl-ethyl acetate solution, stir for 3 h at 30°C, wash the product with water after vacuum distillation, dry, and obtain a gel-like fluoride-containing wastewater treatment chelating agent.

[0030] Example 4: (1) Add 13.5 mmol polyethylene glycol 1000, 10 mmol trimethylolpropane maleate (prepared by the same method as in Example 2), and 0.3 mmol p-toluenesulfonic acid to a flask, heat to 190°C, stir for 1.5 h, evacuate to control the vacuum degree to 150 Pa, stir for 10 h, cool, add the product to a 2.5 mol / L HCl-ethyl acetate solution, stir for 5 h at 20°C, wash the product with water after vacuum distillation, dry, and obtain a gel-like fluoride-containing wastewater treatment chelating agent.

[0031] Comparative Example 1 differs from Example 1 in that trimethylolpropane maleate is used instead of trimethylolpropane-boc-aminopropane maleate.

[0032] (1) Add 13.5 mmol polyethylene glycol 1000, 10 mmol trimethylolpropane maleate and 0.26 mmol p-toluenesulfonic acid to a flask, heat to 200 °C, stir for 1 h, evacuate to control the vacuum degree to 100 Pa, stir for 8 h, cool, add the product to a 2.5 mol / L HCl-ethyl acetate solution, stir at 25 °C for 5 h, it does not contain tert-butyloxycarbonyl, cannot remove the boc protecting group, and cannot generate amino groups, wash the product with water after vacuum distillation, dry, and obtain a gel-like chelating agent.

[0033] Comparative Example 2, the main difference between the comparative example and Example 1 is that succinic anhydride is used instead of maleic anhydride.

[0034] (1) Add 20 mmol of trimethylolpropane to a flask equipped with a reflux condenser, heat to 70°C, stir, add 0.1 mmol of p-toluenesulfonic acid, add 60 mmol of succinic anhydride dropwise, heat to 90°C, stir for 3 h, cool, and recrystallize the product in water to obtain trimethylolpropane succinate, with the structural formula: .

[0035] (2) Add 30 mL of water, 15 mmol of trimethylolpropane succinate, and 45 mmol of sodium hydroxide to a flask. After stirring, add 80 mL of ethanol and 45 mmol of N-tert-butoxycarbonyl-1,2-ethylenediamine. Stir at 40 °C for 5 h. Trimethylolpropane succinate does not contain an alkenyl group and cannot undergo an addition reaction with the primary amino group -NH2 of N-tert-butoxycarbonyl-1,2-ethylenediamine. Remove the ethanol by vacuum distillation, add 8% hydrochloric acid dropwise to adjust the pH to 3, and precipitate. Filter the precipitate and add it to water for recrystallization. The product is still trimethylolpropane succinate.

[0036] (3) Add 13.5 mmol polyethylene glycol 1000, 10 mmol trimethylolpropane succinate, and 0.26 mmol p-toluenesulfonic acid to the flask, heat to 200 °C, stir for 1 h, evacuate to control the vacuum degree to 100 Pa, stir for 8 h, cool, add the product to a 2.5 mol / L HCl-ethyl acetate solution, stir at 25 °C for 5 h, it does not contain tert-butyloxycarbonyl, cannot remove the boc protecting group, and cannot generate amino groups, wash the product with water after vacuum distillation, dry, and obtain a gel-like chelating agent.

[0037] Comparative Example 3: The main difference between the comparative example and Example 1 is that ethylene glycol maleate is used instead of trimethylol-boc-aminopropane maleate.

[0038] (1) Add 30 mL of acetone, 20 mmol of ethylene glycol, 42 mmol of maleic anhydride, and 53.6 mg of sodium acetate to a flask equipped with a reflux condenser. Heat to 55 °C and stir for 1.5 h. Distill under reduced pressure. Recrystallize the product in acetone to obtain ethylene glycol maleate, with the structural formula: .

[0039] (2) Add 30 mL of water, 22.5 mmol of ethylene glycol maleate (total alkenyl molar amount of 45 mmol), and 45 mmol of sodium hydroxide to a flask. After stirring, add 80 mL of ethanol and 45 mmol of N-tert-butoxycarbonyl-1,2-ethylenediamine (total primary amino-NH2 molar amount of 45 mmol). Control the total alkenyl molar amount and the total primary amino-NH2 molar amount ratio to be 1:1. Stir the reaction at 40 °C for 5 h. Remove the ethanol by vacuum distillation. Add 8% hydrochloric acid by mass to adjust the pH to 3. The precipitate is precipitated. Filter the precipitate and add it to water for recrystallization to obtain boc-aminomaleic acid ethylene glycol ester.

[0040] (3) Add 13.5 mmol polyethylene glycol 1000 (total hydroxyl molar amount of 27 mmol), 15 mmol boc-aminomaleic acid ethylene glycol ester (total carboxyl molar amount of 30 mmol), and 0.26 mmol p-toluenesulfonic acid to the flask, and control the ratio of total hydroxyl molar amount to total carboxyl molar amount of 0.9:1; heat to 200℃, stir for 1 h, evacuate to control the vacuum degree to 100 Pa, stir for 8 h, cool, add the product to 2.5 mol / L HCl-ethyl acetate solution, stir at 25℃ for 5 h, wash the product with water after vacuum distillation, and dry to obtain the chelating agent.

[0041] Prepare 1L F with sodium fluoride. - A 10 mg / L (CO) solution was prepared by adding 0.3 g of chelating agent and stirring at 25 °C for 5 h for adsorption. The supernatant was then collected, and the adsorption solution F was tested using an ion-selective electrode method.- The concentration (C) is used as the working electrode, which is a fluoride ion-selective electrode, and the reference electrode is a saturated dry mercury electrode. The removal rate Q is calculated as Q = (C0 - C) / C × 100%.

[0042] 1L Cu configuration 2+ A standard solution with a concentration of 200 mg / L (CO) was mixed with 1.5 g of chelating agent, and the mixture was stirred and adsorbed at 25 °C for 2 h. The supernatant was then collected, and the Cu content of the solution after adsorption was measured by atomic absorption spectrometry. 2+ The concentration (C) is used to calculate the removal rate Q, Q = (C0 - C) / C × 100%.

[0043] 1L Pb configuration 2+ A standard solution with a concentration of 200 mg / L (CO) was mixed with 2.5 g of chelating agent, and the mixture was stirred and adsorbed at 25 °C for 2.5 h. The supernatant was collected, and the Pb content of the adsorbed solution was determined by atomic absorption spectrometry. 2+ The concentration (C) is used to calculate the removal rate Q, Q = (C0 - C) / C × 100%.

[0044] 1L Cd configuration 2+ A standard solution with a concentration of 200 mg / L (CO) was mixed with 2.5 g of chelating agent, and the mixture was stirred and adsorbed at 25 °C for 4 h. The supernatant was collected, and the Cd content of the solution after adsorption was determined by atomic absorption spectrometry. 2+ The concentration (C) is used to calculate the removal rate Q, Q = (C0 - C) / C × 100%.

[0045] Table 1 Removal Rate Test

[0046] Table 1 shows that the chelating agents in each embodiment exhibit good removal rates for fluoride ions, as well as metal ions such as copper, lead, and cadmium, demonstrating excellent adsorption effects. This is mainly because the chelating agents contain polyether segments, which have good hydrophilicity, and possess a three-dimensional cross-linked network with spatial network and porous structure, resulting in more adsorption and chelation sites, thus improving adsorption performance. Furthermore, the presence of numerous terminal carboxyl groups and amino functional groups provides strong coordination and chelation effects for metal ions such as copper, lead, and cadmium, significantly enhancing removal rates and adsorption performance. Additionally, the carboxyl groups ionize in water to generate H protons, which combine with amino groups, protonating the N atom of the amino group to form N... + Ions, with F - The ions form an electrostatic interaction, thereby enhancing the chelating agent's ability to bind F. - Adsorption performance.

[0047] The trimethylolpropane maleate and the chelating agent prepared in Comparative Example 1 do not contain amino groups, and have lower electrostatic and coordination chelating effects on fluoride ions and metal ions such as copper, lead, and cadmium, resulting in a lower removal rate than in Example 1.

[0048] Comparative Example 2, consisting of trimethylolpropane succinate and the prepared chelating agent, does not contain amino groups and exhibits lower electrostatic and coordination chelating effects on fluoride ions and metal ions such as copper, lead, and cadmium, resulting in a lower removal rate than in Example 1.

[0049] Comparative Example 3's boc-aminomaleic acid ethylene glycol ester contains only two carboxyl groups. The chelating agent obtained by polymerization with polyethylene glycol is a linear polymer that does not form a three-dimensional cross-linked network. It does not have a spatial network and porous structure, and has very few adsorption chelation sites. Its adsorption performance and removal rate for fluoride ions, as well as metal ions such as copper, lead, and cadmium, are lower than those in Example 1.

[0050] Regarding the embodiments of this application, it should also be noted that, unless otherwise specified, the embodiments and features described herein can be combined to obtain new embodiments. The above are merely specific implementations of this application, but the scope of protection of this application is not limited thereto; the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing a chelating agent for treating fluoride-containing wastewater, characterized in that, The preparation method is as follows: polyethylene glycol, trimethylolpropane maleate, and p-toluenesulfonic acid are added to a flask in a molar ratio of (1.32-1.41):1:(0.026-0.03), heated to the reaction temperature, stirred for pre-reaction, vacuumed, stirred for polycondensation reaction, cooled, the product is added to HCl-ethyl acetate solution, stirred for reaction, the product is washed after vacuum distillation, dried, and a fluorine-containing wastewater treatment chelating agent is obtained.

2. The preparation method of the chelating agent for fluoride-containing wastewater treatment according to claim 1, characterized in that, The molecular weight of the polyethylene glycol is 400-2000.

3. The preparation method of the chelating agent for fluoride-containing wastewater treatment according to claim 1, characterized in that, The heating to the reaction temperature is 185-200℃, the pre-reaction time is 1-1.5h, and the stirring polycondensation reaction time is 8-12h.

4. The preparation method of the chelating agent for fluoride-containing wastewater treatment according to claim 1, characterized in that, The vacuum level is controlled to be 100-300 Pa.

5. The preparation method of the chelating agent for fluoride-containing wastewater treatment according to claim 1, characterized in that, The concentration of the HCl-ethyl acetate solution is 2.5-4 mol / L.

6. The method for preparing the chelating agent for treating fluoride-containing wastewater according to claim 1, characterized in that, The reaction is carried out at a temperature of 20-30℃ for 3-5 hours.

7. The method for preparing the chelating agent for treating fluoride-containing wastewater according to claim 1, characterized in that, The preparation method of the boc-aminomaleic acid trimethylolpropane ester is as follows: (1) Add trimethylolpropane to a flask equipped with a reflux condenser, heat to 70-75°C, stir, add p-toluenesulfonic acid, add maleic anhydride dropwise, control the molar ratio of trimethylolpropane, p-toluenesulfonic acid, and maleic anhydride to be 1:(3-3.3):(0.005-0.006), heat to 85-90°C, stir for 2.5-3.5 h, cool, recrystallize the product to obtain trimethylolpropane maleate; (2) Add water, trimethylolpropane maleate, and sodium hydroxide to the flask, stir, and then add ethanol and N-tert-butoxycarbonyl-diamine monomer. Control the molar ratio of trimethylolpropane maleate, sodium hydroxide, and N-tert-butoxycarbonyl-diamine monomer to be 1:(3-3.6):(3-3.3). Stir the reaction at 35-50℃ for 3-5 hours, remove ethanol by vacuum distillation, add hydrochloric acid dropwise, precipitate, filter, and recrystallize the precipitate to obtain boc-aminotrimethylolpropane maleate.

8. The method for preparing the chelating agent for treating fluoride-containing wastewater according to claim 7, characterized in that, The structural formula of the N-tert-butoxycarbonyl-diamine monomer is as follows: , where a is 2-6.

9. The method for preparing the chelating agent for treating fluoride-containing wastewater according to claim 7, characterized in that, The pH is adjusted to 2-4 by adding hydrochloric acid, and the mass fraction of the hydrochloric acid is 5-37%.

10. A chelating agent for treating fluoride-containing wastewater obtained by the preparation method according to any one of claims 1-8.

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