A method for preparing a quaternary ammonium-based hydrogel and its application in removing perchlorate in water

Abstract

This invention discloses a method for preparing a quaternary ammonium-based hydrogel and its application in removing perchlorate from water, belonging to the field of water quality monitoring and treatment. The method for preparing the quaternary ammonium-based hydrogel includes step S1: dissolving N,N'-methylenebisacrylamide in deionized water, adding 2-(methacryloyloxy)ethyltrimethylammonium chloride, shaking until completely dissolved, and carrying out a cross-linking reaction in water; step S2: adding a catalyst and an initiator sequentially to the resulting dissolved solution, initiating a free radical polymerization reaction by vortexing, and then solidifying at room temperature (25°C) for 24 hours to obtain the quaternary ammonium-based hydrogel. The cross-linking reaction is carried out by cross-linking N,N'-methylenebisacrylamide and 2-(methacryloyloxy)ethyltrimethylammonium chloride in water in a specific ratio. After the cross-linking reaction is completed, tetramethylethylenediamine and potassium persulfate are added sequentially. This adsorbent can efficiently adsorb perchlorate in water.

Description

Technical Field

[0001] This invention relates to the field of water quality monitoring and treatment technology, and in particular to a method for preparing a quaternary ammonium-based hydrogel and its application in removing perchlorate from water. Background Technology

[0002] In recent years, perchlorate, as a persistent and highly water-soluble inorganic pollutant, has been prevalent in water bodies worldwide. As a strong oxidant, it is widely used in the military and aerospace industries, fireworks manufacturing, and serves as an essential additive in the production of leather tanning agents, rubber products, lubricants, and magnesium batteries. Its discharge has led to the frequent detection of high concentrations of perchlorate in surface water, groundwater, and even drinking water. Because perchlorate is not easily degraded in water and is prone to diffusion, its environmental pollution problems have attracted widespread attention.

[0003] Perchlorate not only originates from industrial production but is also part of the natural chlorine cycle. In terms of health risks, studies have shown that perchlorate can compete with iodide ions, significantly inhibiting the absorption of iodine in the thyroid gland, thereby interfering with the synthesis and secretion of thyroid hormones (T3 and T4) and leading to thyroid dysfunction. This effect is particularly detrimental to sensitive populations such as children, pregnant women, and newborns, and may cause metabolic disorders, growth retardation, and other related health risks.

[0004] Meanwhile, due to the extremely high water solubility and stability of perchlorate, conventional water treatment processes have limited effectiveness in removing it. Summary of the Invention

[0005] The purpose of this invention is to solve the problem of difficulty in removing perchlorate in water treatment in the prior art, and to propose a method for preparing quaternary ammonium hydrogels and their application in removing perchlorate from water.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a quaternary ammonium hydrogel includes the following steps:

[0008] Step S1: Dissolve N,N'-methylenebisacrylamide in deionized water, add 2-(methacryloyloxy)ethyltrimethylammonium chloride, shake until completely dissolved, and carry out the cross-linking reaction in water;

[0009] Step S2: Add the catalyst and initiator to the obtained dissolved solution in sequence, initiate the free radical polymerization reaction by vortex oscillation, and solidify at room temperature (25°C) for 24 hours to obtain quaternary ammonium hydrogel.

[0010] Preferably, the catalyst in step S2 is tetramethylethylenediamine, and the initiator is potassium persulfate.

[0011] Furthermore, in step S1, the amount of N,N'-methylenebisacrylamide is 40 mg, the amount of deionized water is 1 ml, and the vortex oscillation time is 30 seconds.

[0012] Furthermore, the 2-(methacryloyloxy)ethyltrimethylammonium chloride in step S1 is 400 μL, and the eddy current oscillation time is 30 seconds.

[0013] Furthermore, in step S2, the potassium persulfate is 50 μL with a concentration of 40 g / L, added in two portions of 25 μL each time, with each vortex oscillation lasting 15 seconds.

[0014] Preferably, the quaternary ammonium hydrogel obtained in step S2 is cut into uniform 4mm*4mm cubes, soaked in deionized water for a period of time to remove unreacted monomers, and then freeze-dried to obtain freeze-dried hydrogel.

[0015] Furthermore, the quaternary ammonium hydrogel was soaked for 24 hours after being cut into pieces, with the water changed every 8 hours. The freeze-drying temperature was -75℃ and the time was 24 hours. The freeze-dried small pieces of hydrogel were then thoroughly ground to obtain hydrogel powder.

[0016] Application of a quaternary ammonium hydrogel in the removal of perchlorate from water.

[0017] Compared with the prior art, the present invention provides a method for preparing quaternary ammonium hydrogels and their application in removing perchlorate from water, which has the following beneficial effects:

[0018] 1. A quaternary ammonium-based hydrogel adsorbent was obtained by crosslinking N,N'-methylenebisacrylamide with 2-(methacryloyloxy)ethyltrimethylammonium chloride in water in a certain proportion. After the crosslinking reaction was completed, tetramethylethylenediamine and potassium persulfate were added in sequence, and free radical polymerization was initiated by eddy current oscillation. The resulting solution solidified at room temperature. This adsorbent can efficiently adsorb perchlorate in water and has strong practicality, good treatment effect and good commercial application prospects.

[0019] 2. Since 2-(methacryloyloxy)ethyltrimethylammonium chloride only crosslinks with N,N'-methylenebisacrylamide, thus retaining the quaternary ammonium group with adsorption activity, the hydrogel adsorbent can provide a high density of adsorption sites, so that the maximum adsorption capacity for perchlorate can reach 432.11 mg / g.

[0020] 3. Quaternary ammonium hydrogels can effectively adsorb perchlorate. When the initial concentration of perchlorate is 5 mg / L, the hydrogel can achieve more than 95% ClO4 adsorption in just 20 minutes. -The removal rate effectively achieved rapid and efficient removal of ClO4. - The target is its rough surface structure and abundant quaternary ammonium groups, which provide a large number of active sites for the adsorption process; in addition, the hydrogen bonds and electrostatic adsorption between perchlorate and the functional groups on the hydrogel surface further enhance the adsorption rate. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the synthesis of the quaternary ammonium group of the present invention;

[0022] Figure 2 The graph shows the effect of different material ratios of hydrogels prepared in the embodiments and comparative examples of the present invention on the adsorption and removal rate of perchlorate.

[0023] Figure 3 This is a SEM scan of the cross-section of the hydrogel prepared according to an embodiment of the present invention;

[0024] Figure 4 The image shows the XRD pattern of the hydrogel powder prepared in an embodiment of the present invention.

[0025] Figure 5 The infrared characteristic image is shown for the hydrogel powder prepared according to an embodiment of the present invention.

[0026] Figure 6 This is a contact angle diagram of the hydrogel material prepared according to an embodiment of the present invention;

[0027] Figure 7 This is a graph showing the adsorption capacity of hydrogel powder prepared in the embodiments of the present invention for perchlorate at different initial concentrations;

[0028] Figure 8 This is a graph showing the adsorption rate of perchlorate on the hydrogel powder prepared in an embodiment of the present invention.

[0029] Figure 9 The graph shows the adsorption and removal rate of perchlorate by the hydrogel prepared in the embodiments of the present invention under the presence of different coexisting ions. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Unless otherwise specified, the raw materials used are all conventional products purchased from the market.

[0031] Example:

[0032] Reference Figure 1 A method for preparing a quaternary ammonium hydrogel, specifically including the following steps:

[0033] Step S1: Pipette 1 ml of deionized water into a 2 ml centrifuge tube, weigh 40 mg of N,N'-methylenebisacrylamide powder and dissolve it in the centrifuge tube, vortex for 30 seconds; Pipette 400 μl of 2-(methacryloyloxy)ethyltrimethylammonium chloride solution to allow the cross-linking reaction to occur, vortex for 30 seconds.

[0034] Step S2: Use 5 μL of tetramethylethylenediamine as a catalyst, vortex for 30 s, and finally take 50 μL of 40 g / L potassium persulfate solution, vortex for 15 s to initiate free radical polymerization reaction and obtain a clear and transparent solution.

[0035] Step S3: Place the solution in the centrifuge tube at room temperature for 24 hours to obtain a transparent quaternary ammonium hydrogel. Cut the hydrogel into small pieces and soak them in deionized water for 24 hours. Change the water every 8 hours to remove unreacted monomers and obtain a swollen hydrogel.

[0036] Step S4: Freeze the swollen hydrogel in an ultra-low temperature freezer at -75°C for 24 hours, and freeze-dry it to obtain a pure white adsorbent; it should also be noted that in this embodiment, the mass ratio of 2-(methacryloyloxy)ethyltrimethylammonium chloride to N,N'-methylenebisacrylamide is 8:1.

[0037] Comparative example:

[0038] Please refer to Figure 2 This invention investigates the adsorption effect of different ratios of 2-(methacryloyloxy)ethyltrimethylammonium chloride to N,N'-methylenebisacrylamide on perchlorate in hydrogels. Using the methods described in the above embodiments, other quaternary ammonium hydrogels with different mass ratios of 2-(methacryloyloxy)ethyltrimethylammonium chloride / N,N'-methylenebisacrylamide were synthesized at ratios of 1:10, 1:2, 1:1, 2:1, 4:1, and 8:1.

[0039] A quaternary ammonium-based hydrogel adsorbent for removing perchlorate from water was prepared using the above method. The prepared adsorbent was characterized experimentally, as detailed below.

[0040] SEM characterization:

[0041] The prepared adsorbent powder was characterized by SEM, and the data are as follows: Figure 3 As shown; according to Figure 3 It can be seen that the hydrogel prepared in the examples has a rich fissure structure and excellent swelling properties.

[0042] XRD characterization:

[0043] The prepared adsorbent powder was characterized by XRD, and the data are as follows: Figure 4 As shown, according to Figure 4 It can be seen that the spectrum has a gentle "bow-shaped" background, with a broad peak appearing in the 2θ = 15°–30° region, proving that the material is a typical amorphous polymer.

[0044] Infrared FT-IR characterization:

[0045] The prepared adsorbent material was characterized by infrared FT-IR, and the data are as follows: Figure 5 As shown. By Figure 5 It can be seen that the hydrogel prepared in the examples has a structure rich in polar functional groups, which can undergo electrostatic adsorption, hydrogen bonding or ion exchange reaction with anions, and has a good adsorption effect on perchlorate.

[0046] Contact angle characterization:

[0047] The hydrophilicity / hydrophobicity of the prepared adsorbent material was tested by the contact angle, such as... Figure 6 As shown, the hydrogel prepared in the example has a contact angle of 26.26°, which is a superhydrophilic material.

[0048] Experimental Example 1:

[0049] Adsorption capacity test

[0050] Take 5 mg of the prepared adsorbent powder and add it to a 100 mL Erlenmeyer flask. Add perchlorate solutions of different concentrations to the Erlenmeyer flask until the volume reaches 50 mL. Figure 7 The concentration shown is 5-500 mg / L. Place the conical flask in a water bath shaker and shake for 24 hours until adsorption equilibrium is reached. Take a sample and measure the perchlorate concentration at this point. Then, repeat the experiment at different temperatures and calculate the equilibrium concentration. With adsorption capacity The fitted curve was obtained Figure 7 The content shown is included. The calculation formula is as follows:

[0051]

[0052] in and (mg / L) represents the initial and equilibrium concentrations of perchlorate; V(L) is the volume of the reaction solution; m(g) is the mass of the adsorbent. (mg / g) is the adsorption capacity.

[0053] Experimental Example 2:

[0054] Adsorption rate test

[0055] Take 10 mg of the prepared adsorbent powder and add it to a 100 ml beaker. Add perchlorate solutions of different concentrations to the beaker until the volume reaches 50 ml. Figure 8The concentration is shown as 5-20 mg / L. The beaker was placed on a magnetic stirrer and stirred. Perchlorate concentration was measured at specific time intervals up to 30 minutes. The fitted curve was obtained. Figure 8 The content shown.

[0056] Experimental Example 3:

[0057] Experiment on the effect of coexisting ions on perchlorate adsorption:

[0058] Adsorption efficiency was tested under conditions where different ions (chloride, nitrate, sulfate, and carbonate ions) coexisted. 10 mg of the prepared adsorbent powder was added to a 100 mL beaker. Then, 5 mg / L perchlorate and other anion solutions were added to the beaker until the volume reached 50 mL. The concentration of the other anions was 25 mg / L. Figure 9 As shown. The allocation coefficients are... The calculation formula is as follows:

[0059]

[0060] in and (mg / L) represents the initial and equilibrium concentrations of perchlorate; V(L) represents the volume of the reaction solution; and m(g) represents the mass of the adsorbent.

[0061] Experimental results: Figure 9 It can be seen that when the concentration of coexisting ions is five times that of perchlorate ions, the distribution coefficient of perchlorate is much higher than that of coexisting anions, indicating that the adsorbent provided by the present invention is selective for perchlorate.

[0062] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a quaternary ammonium-based hydrogel, characterized in that, Includes the following steps: Step S1: Dissolve N,N'-methylenebisacrylamide in deionized water, add 2-(methacryloyloxy)ethyltrimethylammonium chloride, and shake until completely dissolved; the mass ratio of 2-(methacryloyloxy)ethyltrimethylammonium chloride to N,N'-methylenebisacrylamide is 1:1, 2:1, 4:1, or 8:

1. Step S2: Add the catalyst and initiator to the obtained dissolved solution in sequence, shake, and solidify at room temperature to obtain a quaternary ammonium hydrogel.

2. The method for preparing the quaternary ammonium hydrogel according to claim 1, characterized in that, The catalyst in step S2 is tetramethylethylenediamine, and the initiator is potassium persulfate.

3. The method for preparing the quaternary ammonium hydrogel according to claim 2, characterized in that, In step S1, the amount of N,N'-methylenebisacrylamide is 40 mg and the amount of deionized water is 1 ml.

4. The method for preparing the quaternary ammonium hydrogel according to claim 3, characterized in that, The 2-(methacryloyloxy)ethyltrimethylammonium chloride mentioned in step S1 is 400 μL.

5. The method for preparing the quaternary ammonium hydrogel according to claim 4, characterized in that, The potassium persulfate in step S2 is 50 μL, with a concentration of 40 g / L.

6. The method for preparing the quaternary ammonium hydrogel according to claim 1, characterized in that, The quaternary ammonium hydrogel obtained in step S2 is cut into pieces, soaked in deionized water for a period of time, and then freeze-dried to obtain freeze-dried hydrogel.

7. The method for preparing the quaternary ammonium hydrogel according to claim 6, characterized in that, The quaternary ammonium hydrogel was soaked for 24 hours after being cut into pieces, and then freeze-dried at -75℃ for 24 hours.

8. The method for preparing the quaternary ammonium hydrogel according to claim 7, characterized in that, The freeze-dried small pieces of hydrogel were thoroughly ground to obtain hydrogel powder.

9. An application of a quaternary ammonium hydrogel prepared by the method of claim 1 in the removal of perchlorate from water.

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