Method for removing pollutants in water by coupling selective adsorption with electrocatalysis

Abstract

The invention discloses a method for removing pollutants in water by coupling selective adsorption with electrocatalysis. The method comprises the following steps: calcining a graphite electrode plate at 180-300 DEG C; the method comprises the following steps: mixing a functional monomer and a target pollutant according to a molar ratio of (1-2): 1, dissolving in an acetonitrile or methanol solution containing an organic electrolyte, stirring and standing overnight to obtain a functional monomer-pollutant compound; taking a graphite flake as a working electrode and a silver electrode filled with an organic electrolyte solution as a reference electrode, cleaning after electropolymerization is completed to obtain a molecularly imprinted electrode, and soaking the molecularly imprinted electrode in water for later use; placing the molecularly imprinted electrode in a formic acid-acetonitrile solution, and cleaning after ultrasonic treatment to complete removal of template molecules; putting into a new pollutant aqueous solution, stirring with small magnetons, and carrying out selective adsorption; after adsorption is completed, constant voltage is applied to the molecularly imprinted electrode, and pollutants are continuously degraded. Pollutants containing-OH or-NH2 can be degraded, new pollutants are adsorbed in advance, and the electro-catalysis cost is reduced.

Description

Technical Field

[0001] The present invention relates to a method for removing pollutants, in particular to a method for removing pollutants in water by selective adsorption coupled electrocatalysis. Background Art

[0002] Given that the biological methods commonly used in traditional sewage treatment plants have poor effects on the removal of new pollutants, and even negative removal rates are frequently reported in global studies (Bioresource Technology, 2022, 352: 127054), it is necessary to develop physical and chemical technologies to make up for this shortcoming. The concentration of new pollutants in sewage is extremely low (ng / L~μg / L), which leads to limited diffusion and mass transfer, low direct electrocatalytic efficiency, high energy consumption, and is not suitable for large-scale application. In view of this situation, the adsorption method has great potential.

[0003] There are many types of new pollutants in sewage, and there are interferences from other pollutants such as humus and salt ions. Existing treatment technologies lack selectivity. Removing one or several new pollutants requires a large amount of adsorbents and their adsorption capacity. Therefore, it is necessary to develop selective adsorbents for specific new pollutants. Molecularly imprinted polymers are customized adsorbents constructed with target pollutants as templates, which can achieve efficient selective adsorption for different pollutants (Chemical Reviews, 2019, 119 (1): 94-119). However, adsorption only completes the phase transfer of new pollutants, and does not completely degrade them. Therefore, selective adsorption coupled with electrocatalytic degradation is expected to perfectly solve this problem and achieve efficient and economical removal of new pollutants.

[0004] Existing new pollutant removal technologies are mainly biodegradation, membrane separation, electrocatalytic degradation and adsorption, among which the biodegradation effect is poor, the membrane separation technology equipment and operating costs are extremely high, and the electrocatalytic degradation is inefficient and energy-consuming for low-concentration new pollutants. The development of adsorbent materials at this stage mainly focuses on the modification of specific surface area, hydrophilicity, special groups, etc. The developed adsorbent has poor selectivity for new pollutants and cannot be targeted to enrich specific new pollutants. On the other hand, the adsorbent constructed by existing molecular imprinting polymers has poor electrical conductivity and cannot be directly used as an electrocatalytic electrode. Publication No. CN118771540A discloses a molecular imprinting polymer electrocatalytic plate and its preparation method and application, but it relies on the matching relationship of boric acid based on the ortho-hydroxyl group of azithromycin, so it is only applicable to azithromycin, a new pollutant, and is greatly limited in actual use. In addition, in the existing pollutant removal process, there are also problems such as limited diffusion mass transfer, many interferences, and high operating energy consumption. Summary of the invention

[0005] Purpose of the invention: In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a method for removing pollutants from water by selective adsorption coupled electrocatalysis, which can selectively enrich pollutants and remove them at low cost.

[0006] Technical solution: The method for removing pollutants from water by selective adsorption coupled electrocatalysis according to the present invention comprises the following steps:

[0007] Step 1, calcining the graphite electrode sheet at 180-300° C.;

[0008] Step 2: mixing the functional monomer and the target pollutant in a molar ratio of 1 to 2:1, dissolving them in an acetonitrile or methanol solution containing an organic electrolyte, stirring and standing overnight to obtain a functional monomer-pollutant complex;

[0009] Step 3, using the calcined graphite sheet obtained in step 1 as a working electrode and a silver electrode filled with an organic electrolyte solution as a reference electrode, electropolymerization is performed using scanning cyclic voltammetry, wherein the working solution includes an acetonitrile or methanol solution of a functional monomer-pollutant complex and a bithiophene cross-linking monomer, and after the polymerization is completed, washing is performed to obtain a molecularly imprinted electrode, which is then immersed in water for standby use;

[0010] Step 4: placing the molecularly imprinted electrode in a formic acid-acetonitrile solution, washing with ultrapure water after ultrasonication, and completing the removal of the template molecule;

[0011] Step 5, placing the product obtained in step 5 into a new pollutant aqueous solution, stirring with a small magnetic particle, and performing selective adsorption;

[0012] Step six: After adsorption is completed, a constant voltage is applied to the molecular imprinting electrode to continuously degrade the pollutants.

[0013] Furthermore, in step 1, the calcination time is 2 to 12 hours. Calcination is beneficial to remove organic matter remaining on the surface of the plate and slightly increase the specific surface area.

[0014] Furthermore, in step 2, the functional monomer is a borate thiophene or carboxy thiophene monomer. The target pollutant is a pollutant containing -OH or -NH2.

[0015] Preferably, when the target pollutant is a macrolide antibiotic containing an ortho-hydroxyl group, the functional monomer is a borate-based thiophene; when the target pollutant is bisphenol A, carbamazepine, or tetracycline containing a hydroxyl or amino group, the functional monomer is a carboxylated thiophene.

[0016] Furthermore, in step 3, the concentration of the functional monomer-pollutant complex is 0.5-10 mM, and the concentration of the acetonitrile or methanol solution of the bithiophene cross-linking monomer is 0.25-5 mM. The scanning potential window of the electropolymerization is 0-2.3 V, the scanning rate is 10-100 mV / s, and the number of scanning cycles is 1-10.

[0017] Preferably, the concentration of the functional monomer-pollutant complex is 4 mM, the concentration of the acetonitrile or methanol solution of the bithiophene cross-linking monomer is 2 mM, the scanning rate is 50 mV / s, and the number of scanning cycles is 5.

[0018] Furthermore, in step 4, in the formic acid-acetonitrile solution, the volume ratio of formic acid to acetonitrile is 1:8 to 10. The ultrasonic power is 80 to 320 W, and the ultrasonic time is 30 to 40 minutes.

[0019] Preferably, the volume ratio of formic acid to acetonitrile is 1:9.

[0020] Furthermore, in step five, the rotation speed of the small magnetic stirring is 500-600 rpm, and the stirring time is 20-120 minutes.

[0021] Furthermore, in step six, the constant voltage is 0.9-1.65V.

[0022] Preparation principle: The method of removing new pollutants by selective adsorption coupled electrocatalysis is based on the selective adsorption capacity and conductivity of the prepared molecular imprinting polymer electrode. It can quickly and selectively adsorb low-concentration new pollutants in water into the cavities on the electrode surface. Subsequently, voltage is applied with the electrode as the anode to directly oxidize and degrade the new pollutants, achieving selective and efficient removal.

[0023] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0024] 1. It can degrade pollutants containing -OH or -NH2, pre-adsorb new pollutants to the electrode surface, and reduce the cost of electrocatalysis;

[0025] 2. Molecularly imprinted polymers are used to adsorb new pollutants with high selectivity;

[0026] 3. The electrodes are constructed using conductive molecular imprinted polymers, which can be directly coupled to the electrocatalytic process after the adsorption process;

[0027] 4. By replacing the template, selective adsorption coupled electrocatalytic plates for a variety of new pollutants can be constructed;

[0028] 5. After the degradation is completed, there is no need to remove the template molecules again, and new pollutants can continue to be selectively adsorbed and electrocatalyzed. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a preparation flow chart of the present invention;

[0030] Figure 2 This is a graph showing the change in azithromycin concentration in water during the selective adsorption coupled electrocatalysis process of molecular imprinting electrodes;

[0031] Figure 3 is the adsorption capacity of blank graphite electrode and molecular imprinted electrode for carbamazepine at 20 min and 120 min;

[0032] Figure 4 It is the linear voltammetric scan of blank graphite electrode and molecular imprinted electrode in aqueous solution;

[0033] Figure 5 This is a comparison chart of the adsorption capacity of molecular imprinting electrodes for new pollutants such as azithromycin (AZN), roxithromycin (ROX), clarithromycin (CLA), carbamazepine (CBZ), tetracycline (OTC), and ciprofloxacin (CIP);

[0034] Figure 6 It is a comparison of the adsorption and removal effects of azithromycin by molecular imprinting electrode and non-molecular imprinting electrode;

[0035] Figure 7 The cyclic voltammetry scans of molecular imprinted electrodes prepared using carboxypyrrole (A) and 3-boronic acid thiophene (B) in potassium ferrocyanide solution. DETAILED DESCRIPTION

[0036] Example 1

[0037] like Figure 1 As shown, a method for selective adsorption coupled electrocatalysis to remove pollutants from water comprises the following steps:

[0038] (1) Calcination of electrode plates: Place the graphite electrode sheet in a muffle furnace and calcine at 180°C for 12 h.

[0039] (2) Preparation of functional monomer-azithromycin complex: Boronic acid-based thiophene monomer (3-thiophene boronic acid) is used as a functional monomer, mixed with azithromycin in a molar ratio of 1:1, dissolved in an acetonitrile solution containing an organic electrolyte, stirred and allowed to stand overnight to obtain a functional monomer-azithromycin complex.

[0040] (3) Electropolymerization to prepare molecular imprinted electrodes: The graphite sheet calcined in (1) was used as the working electrode, and the silver electrode filled with organic electrolyte solution was used as the reference electrode for electropolymerization. The working solution was an acetonitrile solution containing 0.5 mM functional monomer-azithromycin complex and 0.25 mM 2,2'-bithiophene cross-linking monomer. Electropolymerization was performed using scanning cyclic voltammetry, and the parameters were set as follows: scanning potential window of 0-2.3 V, scanning rate of 100 mV / s, and scanning number of 10. After the polymerization was completed, it was washed with acetonitrile and ultrapure water, and then soaked in water for use.

[0041] (4) Removal of molecular imprinting template: The prepared molecular imprinting electrode was placed in a formic acid-acetonitrile solution with a volume ratio of 1:9, ultrasonicated at a power of 320 W for 30 minutes, and then washed with ultrapure water to complete the removal of the template molecule.

[0042] (5) Selective adsorption: The prepared molecular imprinted electrode was placed in an aqueous solution of azithromycin and stirred at 500 rpm for 120 min using a small magnetic stirrer.

[0043] (6) Electrocatalytic removal of new pollutants: After adsorption, a constant voltage of 1.2 V was applied to the molecularly imprinted electrode to continuously degrade azithromycin.

[0044] like Figure 3 As shown, nearly 60% of azithromycin in water was rapidly removed in 2 h of selective adsorption, and the removal rate of azithromycin reached 99% in the subsequent 4 h of electrocatalysis.

[0045] Example 2

[0046] A method for removing pollutants from water by selective adsorption coupled electrocatalysis comprises the following steps:

[0047] (1) Calcination of electrode plates: Place the graphite electrode sheet in a muffle furnace and calcine at 300°C for 2 h.

[0048] (2) Preparation of functional monomer-new pollutant complex: A carboxythiophene monomer (3-carboxythiophene) is used as a functional monomer, mixed with a target new pollutant (carbamazepine) at a molar ratio of 2:1, dissolved in an acetonitrile solution containing an organic electrolyte, stirred and allowed to stand overnight to obtain a functional monomer-carbamazepine complex.

[0049] (3) Electropolymerization to prepare molecular imprinted electrodes: The graphite sheet calcined in (1) was used as the working electrode, and the silver electrode filled with organic electrolyte solution was used as the reference electrode for electropolymerization. The working solution was an acetonitrile solution containing 10 mM functional monomer-carbamazepine complex and 5 mM cross-linking monomer (3,3'-bithiophene). Scanning cyclic voltammetry was used for electropolymerization, and the parameters were set as follows: scanning potential window of 0-2.0 V, scanning rate of 10 mV / s, and scanning number of 1. After the polymerization was completed, it was washed with acetonitrile and ultrapure water, and then soaked in water for use.

[0050] (4) Removal of molecular imprinting template: The prepared molecular imprinting electrode was placed in a formic acid-acetonitrile solution with a volume ratio of 1:9, ultrasonicated at a power of 120 W for 30 minutes, and then washed with ultrapure water to complete the removal of the template molecules.

[0051] (5) Selective adsorption: The prepared molecular imprinted electrode was placed in a 5 mg / L carbamazepine aqueous solution and stirred at 500 rpm with a small magnetic stirrer for 120 min.

[0052] (6) Electrocatalytic removal of new pollutants: After adsorption, a constant voltage of 1.2 V was applied to the molecularly imprinted electrode to continuously degrade carbamazepine.

[0053] like Figure 4 As shown, in the 120-minute selective adsorption, the molecularly imprinted electrode adsorbed 7.79 times and 6.83 times more than the blank graphite electrode at 20 minutes and 120 minutes, respectively, indicating that the molecularly imprinted catalytic electrode has a large adsorption capacity and can quickly adsorb new pollutants.

[0054] like Figure 5 As shown, the oxygen evolution potentials of the prepared molecular imprinted catalytic electrode and the blank graphite electrode are 1.68 V and 1.60 V, respectively, indicating that the potential of the electrocatalytic oxidation can be set to a maximum of 1.65 V.

[0055] Example 3

[0056] A method for removing pollutants from water by selective adsorption coupled electrocatalysis comprises the following steps:

[0057] (1) Calcination of electrode plates: Place the graphite electrode sheet in a muffle furnace and calcine at 300°C for 2 h.

[0058] (2) Preparation of functional monomer-new pollutant complex: Boric acid-based thiophene monomer (benzoboronic acid-3-thiophene) is used as a functional monomer, mixed with azithromycin in a molar ratio of 1:1, dissolved in a methanol solution containing an organic electrolyte, stirred and allowed to stand overnight to obtain a functional monomer-new pollutant complex.

[0059] (3) Electropolymerization to prepare molecular imprinted electrodes: The graphite sheet calcined in (1) was used as the working electrode, and the silver electrode filled with organic electrolyte solution was used as the reference electrode for electropolymerization. The working solution was a methanol solution containing 4 mM functional monomer-new pollutant complex and 2 mM cross-linking monomer (3,3'-bithiophene). Scanning cyclic voltammetry was used for electropolymerization, and the parameters were set as follows: scanning potential window of 0-1.6 V, scanning rate of 50 mV / s, and scanning number of 5. After the polymerization was completed, it was washed with acetonitrile and ultrapure water, and then soaked in water for use.

[0060] (4) Removal of molecular imprinting template: The prepared molecular imprinting electrode was placed in a formic acid-acetonitrile solution with a volume ratio of 1:9, ultrasonicated at a power of 80 W for 30 minutes, and then washed with ultrapure water to complete the removal of the template molecules.

[0061] (5) Selective adsorption: The prepared molecular imprinted electrode was placed in an aqueous solution of azithromycin (AZN), roxithromycin (ROX), clarithromycin (CLA), carbamazepine (CBZ), tetracycline (OTC), and ciprofloxacin (CIP), and stirred at 500 rpm with a small magnetic stirrer for 20 min.

[0062] (6) Electrocatalytic removal of new pollutants: After adsorption, a constant voltage of 1.2 V was applied to the molecularly imprinted electrode to continuously degrade azithromycin.

[0063] like Figure 6 As shown, in the 20-minute selective adsorption, the removal rate of azithromycin in water was the highest, while the amount of other new pollutants adsorbed and removed was less than 10% of azithromycin, which illustrates the superior selectivity of the molecular imprinting catalytic electrode.

[0064] Example 4

[0065] A method for removing pollutants from water by selective adsorption coupled electrocatalysis comprises the following steps:

[0066] (1) Calcination of electrode plates: Place the graphite electrode sheet in a muffle furnace and calcine at 200°C for 3 h.

[0067] (2) Preparation of functional monomer-new pollutant complex: Carboxythiophene monomer (thiophene-3,4-dicarboxylic acid) is used as the functional monomer, mixed with the target new pollutant (bisphenol A) at a molar ratio of 2:1, dissolved in an acetonitrile solution containing an organic electrolyte, stirred and allowed to stand overnight to obtain a functional monomer-bisphenol A complex.

[0068] (3) Electropolymerization to prepare molecular imprinting electrodes: The calcined graphite sheet from (1) was used as the working electrode, and the silver electrode filled with an organic electrolyte solution was used as the reference electrode for electropolymerization. The working solution was an acetonitrile solution containing 10 mM functional monomer-bisphenol A complex and 5 mM cross-linking monomer (2,2'-bithiophene). Scanning cyclic voltammetry was used for electropolymerization, and the parameters were set as follows: scanning potential window of 0-2.0 V, scanning rate of 50 mV / s, and scanning number of 5. After the polymerization was completed, it was washed with acetonitrile and ultrapure water, and then soaked in water for use. The structure of the obtained molecular imprinting polymer electrode is as follows: Figure 7 shown.

[0069] (4) Removal of molecular imprinting template: The prepared molecular imprinting electrode was placed in a formic acid-acetonitrile solution with a volume ratio of 1:8, ultrasonicated at a power of 80 W for 40 minutes, and then washed with ultrapure water to complete the removal of the template molecules.

[0070] (5) Selective adsorption: The prepared molecular imprinted electrode was placed in the bisphenol A-containing wastewater to be treated and stirred at 500 rpm with a small magnetic stirrer for 120 minutes.

[0071] (6) Electrocatalytic removal of new pollutants: After 2 h of adsorption, a constant voltage of 0.9 V was applied to the molecularly imprinted electrode to continuously degrade bisphenol A.

[0072] Example 5

[0073] A method for removing pollutants from water by selective adsorption coupled electrocatalysis comprises the following steps:

[0074] (1) Calcination of electrode plates: Place the graphite electrode sheet in a muffle furnace and calcine at 120°C for 12 h.

[0075] (2) Preparation of functional monomer-new pollutant complex: A carboxythiophene monomer (3-carboxythiophene) is used as a functional monomer, mixed with a target new pollutant (tetracycline) at a molar ratio of 2:1, dissolved in an acetonitrile solution containing an organic electrolyte, stirred and allowed to stand overnight to obtain a functional monomer-tetracycline complex.

[0076] (3) Electropolymerization to prepare molecular imprinted electrodes: The graphite sheet calcined in (1) was used as the working electrode, and the silver electrode filled with organic electrolyte solution was used as the reference electrode for electropolymerization. The working solution was an acetonitrile solution containing 4 mM functional monomer-tetracycline complex and 2 mM cross-linking monomer (3,3'-bithiophene). Scanning cyclic voltammetry was used for electropolymerization, and the parameters were set as follows: scanning potential window of 0-2.0 V, scanning rate of 20 mV / s, and scanning number of 2. After the polymerization was completed, it was washed with acetonitrile and ultrapure water, and then soaked in water for use.

[0077] (4) Removal of molecular imprinting template: The prepared molecular imprinting electrode was placed in a formic acid-acetonitrile solution with a volume ratio of 1:10, ultrasonicated at a power of 80 W for 30 minutes, and then washed with ultrapure water to complete the removal of the template molecule.

[0078] (5) Selective adsorption: The prepared molecular imprinted electrode was placed in the wastewater containing tetracycline to be treated and stirred at 600 rpm with a small magnetic stirrer for 20 minutes.

[0079] (6) Electrocatalytic removal of new pollutants: After 2 h of adsorption, a constant voltage of 1.65 V was applied to the molecularly imprinted electrode to continuously degrade tetracycline.

[0080] Among the above embodiments, the best embodiment is embodiment 3.

[0081] Comparative Example 1

[0082] The remaining steps of this comparative example are the same as those of Example 3, except that azithromycin is not used in the electrode synthesis in step (2), and the adsorption-electrocatalysis experiment is performed using the obtained non-molecularly imprinted electrode. The results show that the adsorption removal rate of azithromycin by the non-molecularly imprinted electrode is low and does not have a rapid removal effect. Figure 6 shown.

[0083] Comparative Example 2

[0084] The remaining steps of this comparative example are the same as those of Example 3, except that the functional monomer in step (2) is replaced by carboxypyrrole. The results show that the obtained molecular imprinted electrode has poor electrochemical stability and exhibits a significant change in the redox peak in the presence of an electrochemical redox probe. Figure 7 As shown, the selected thiophene functional monomers have good electrochemical stability and are suitable for the selective adsorption-electrocatalytic removal of new pollutants.

Claims

1. A method for removing pollutants from water by selective adsorption coupled electrocatalysis, characterized in that: The following steps are involved: Step 1, calcining the graphite electrode sheet at 180-300° C.; Step 2: mixing the functional monomer and the target pollutant in a molar ratio of 1 to 2:1, dissolving them in an acetonitrile or methanol solution containing an organic electrolyte, stirring and standing overnight to obtain a functional monomer-pollutant complex; Step 3, using the calcined graphite sheet obtained in step 1 as a working electrode and a silver electrode filled with an organic electrolyte solution as a reference electrode, electropolymerization is performed using scanning cyclic voltammetry, wherein the working solution includes an acetonitrile or methanol solution of a functional monomer-pollutant complex and a bithiophene cross-linking monomer, and after the polymerization is completed, washing is performed to obtain a molecularly imprinted electrode, which is then immersed in water for standby use; Step 4: placing the molecularly imprinted electrode in a formic acid-acetonitrile solution, washing with ultrapure water after ultrasonication, and completing the removal of the template molecule; Step 5, placing the product obtained in step 5 into a new pollutant aqueous solution, stirring with a small magnetic particle, and performing selective adsorption; Step six: After adsorption is completed, a constant voltage is applied to the molecular imprinting electrode to continuously degrade the pollutants.

2. The method for removing pollutants from water by selective adsorption coupled electrocatalysis according to claim 1, characterized in that: In the step 1, the calcination time is 2 to 12 hours.

3. The method for removing pollutants from water by selective adsorption coupled electrocatalysis according to claim 1, characterized in that: In the step 2, the functional monomer is a borate thiophene or carboxy thiophene monomer.

4. The method for removing pollutants from water by selective adsorption coupled electrocatalysis according to claim 1, characterized in that: In the step 2, the target pollutant is a pollutant containing -OH or -NH2.

5. The method for removing pollutants from water by selective adsorption coupled electrocatalysis according to claim 1, characterized in that: In the step three, the concentration of the functional monomer-pollutant complex is 0.5-10 mM, and the concentration of the acetonitrile or methanol solution of the bithiophene cross-linking monomer is 0.25-5 mM.

6. The method for removing pollutants from water by selective adsorption coupled electrocatalysis according to claim 1, characterized in that: In the step 3, the scanning potential window of electropolymerization is 0-2.3V, the scanning rate is 10-100mV / s, and the number of scanning cycles is 1-10.

7. The method for removing pollutants from water by selective adsorption coupled electrocatalysis according to claim 1, characterized in that: In the step 4, in the formic acid-acetonitrile solution, the volume ratio of formic acid to acetonitrile is 1:8-10.

8. The method for removing pollutants from water by selective adsorption coupled electrocatalysis according to claim 1, characterized in that: In the step 4, the ultrasonic power is 80 to 320 W, and the ultrasonic time is 30 to 40 minutes.

9. The method for removing pollutants from water by selective adsorption coupled electrocatalysis according to claim 1, characterized in that: In the step 5, the rotation speed of the small magnetic stirring is 500-600 rpm, and the stirring time is 20-120 minutes.

10. The method for removing pollutants from water by selective adsorption coupled electrocatalysis according to claim 1, characterized in that: In the step six, the constant voltage is 0.9-1.65V.

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