Method for selective adsorption coupled with electrocatalytic removal of pollutants from water

Abstract

The application discloses a method for removing pollutants in water by selective adsorption and coupling electrocatalysis, comprising the following steps: calcining a graphite electrode sheet at 180-300 DEG C; mixing a functional monomer and target pollutants at 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 the graphite sheet as a working electrode, taking a silver electrode filled with an organic electrolyte solution as a reference electrode, washing after electro-polymerization to obtain a molecularly imprinted electrode, and soaking in water for use; placing the molecularly imprinted electrode in a formic acid-acetonitrile solution, washing after ultrasonic treatment to remove the template molecules; placing in a new pollutant aqueous solution, stirring with a small magnet, and performing selective adsorption; after adsorption, applying a constant voltage to the molecularly imprinted electrode to continuously degrade the pollutants. The application can degrade pollutants containing -OH or -NH2, pre-adsorb new pollutants, and reduce the cost of electrocatalysis.

Description

Technical Field

[0001] This invention pertains to pollutant removal methods, specifically a method for selectively adsorbing and coupling electrocatalysis to remove pollutants from water. Background Technology

[0002] Given that traditional biological methods commonly used in wastewater treatment plants are ineffective at removing novel pollutants, with negative removal rates frequently reported in global studies (Bioresource Technology, 2022, 352:127054), there is a need to develop physicochemical technologies to address this shortcoming. The extremely low concentrations of novel pollutants in wastewater (ng / L to μg / L) limit their diffusion and mass transfer, resulting in low efficiency and high energy consumption in direct electrocatalysis, making it unsuitable for large-scale applications. Adsorption methods show great potential in addressing this situation.

[0003] Wastewater contains a wide variety of new pollutants, which are also interfering with other pollutants such as humic substances and salt ions. Existing treatment technologies lack selectivity, and removing one or a few new pollutants requires consuming large amounts of adsorbent and its adsorption capacity. Therefore, it is necessary to develop selective adsorbents for specific new pollutants. Molecularly imprinted polymers are custom adsorbents constructed using target pollutants as templates, which can achieve highly 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 technologies for removing novel pollutants mainly include biodegradation, membrane separation, electrocatalytic degradation, and adsorption. Biodegradation has relatively poor performance, membrane separation technology has extremely high equipment and operating costs, and electrocatalytic degradation is inefficient and energy-intensive for low-concentration novel pollutants. Current development of adsorption materials focuses on modifying specific surface area, hydrophilicity / hydrophobicity, and special functional groups. However, the developed adsorbents have poor selectivity for novel pollutants and cannot specifically enrich them. Furthermore, existing adsorbents constructed from molecularly imprinted polymers have poor conductivity and cannot be directly used as electrocatalytic electrodes. CN118771540A discloses a molecularly imprinted polymer electrocatalytic electrode plate, its preparation method, and its application; however, it relies on the matching relationship between boric acid and the ortho-hydroxyl group of azithromycin, thus it is only applicable to azithromycin, a novel pollutant, and its practical application is significantly limited. In addition, existing pollutant removal processes also suffer from limited diffusion and mass transfer, numerous interfering substances, and high operating energy consumption. Summary of the Invention

[0005] Purpose of the invention: In order to overcome the shortcomings of the existing technology, the purpose of this invention is to provide a method for selectively enriching pollutants and removing pollutants from water by selective adsorption coupled with electrocatalysis at low cost.

[0006] Technical solution: The present invention provides a method for selectively adsorbing and coupling electrocatalysis to remove pollutants from water, comprising the following steps:

[0007] Step 1: Calcine the graphite electrode sheet at 180–300°C;

[0008] Step 2: Mix the functional monomer and the target pollutant at a molar ratio of 1 to 2:1, dissolve them in an acetonitrile or methanol solution containing an organic electrolyte, stir and let stand overnight to obtain the functional monomer-pollutant complex.

[0009] Step 3: Using the calcined graphite sheet obtained in Step 1 as the working electrode and the silver electrode filled with organic electrolyte solution as the reference electrode, electropolymerization is carried out using scanning cyclic voltammetry. The working solution includes acetonitrile or methanol solution of functional monomer-pollutant complex and bithiophene crosslinking monomer. After polymerization, the electrode is washed to obtain a molecularly imprinted electrode, which is then soaked in water for later use.

[0010] Step 4: Place the molecularly imprinted electrode in a formic acid-acetonitrile solution, sonicate, and then wash with ultrapure water to complete the removal of template molecules.

[0011] Step 5: Place the product obtained in Step 5 into the aqueous solution of the new pollutant and stir with a small magnetic stirrer to carry out selective adsorption;

[0012] Step six: After adsorption is complete, a constant voltage is applied to the molecularly imprinted electrode to continuously degrade pollutants.

[0013] Furthermore, in step one, the calcination time is 2 to 12 hours. Calcination helps to remove residual organic matter on the surface of the electrode plate and slightly increases the specific surface area.

[0014] Furthermore, in step two, the functional monomer is a borate-based thiophene or a carboxy-based 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 borate thiophene; when the target pollutant is bisphenol A, carbamazepine, or tetracycline containing hydroxyl or amino groups, the functional monomer is carboxythiophene.

[0016] Further, in step three, the concentration of the functional monomer-contaminant complex is 0.5–10 mM, and the concentration of the acetonitrile or methanol solution of the bithiophene crosslinking monomer is 0.25–5 mM. The scanning potential window for electropolymerization is 0–2.3 V, the scanning rate is 10–100 mV / s, and the number of scan cycles is 1–10.

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

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

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

[0020] Furthermore, in step five, the small magnetic stirrer is rotated at 500–600 rpm for 20–120 minutes.

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

[0022] Preparation principle: The selective adsorption coupled with electrocatalysis method for removing new pollutants is based on the selective adsorption capacity and conductivity of the prepared molecularly imprinted polymer electrode. It can quickly and selectively adsorb low concentrations of new pollutants in water into the cavities on the electrode surface. Then, a voltage is applied to 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 onto the electrode surface, and reduce the cost of electrocatalysis;

[0025] 2. It employs molecularly imprinted polymers to adsorb new pollutants, exhibiting high selectivity;

[0026] 3. Electrodes constructed using conductive molecularly imprinted polymers can be directly coupled to electrocatalytic processes after the adsorption process;

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

[0028] 5. After degradation, there is no need to remove template molecules again; new pollutants can continue to be selectively adsorbed and electrocatalyzed for removal. Attached Figure Description

[0029] Figure 1 This is a flowchart of the preparation process of the present invention;

[0030] Figure 2 This is a graph showing the change in azithromycin concentration in water during selective adsorption coupled with electrocatalysis using a molecularly imprinted electrode.

[0031] Figure 3 The adsorption capacity of blank graphite electrode and molecularly imprinted electrode for carbamazepine is shown at 20 minutes and 120 minutes.

[0032] Figure 4 These are linear voltammetric scans of a blank graphite electrode and a molecularly imprinted electrode in aqueous solution;

[0033] Figure 5 This is a comparison chart of the adsorption capacities of molecularly imprinted electrodes for novel pollutants azithromycin (AZN), roxithromycin (ROX), clarithromycin (CLA), carbamazepine (CBZ), tetracycline (OTC), and ciprofloxacin (CIP).

[0034] Figure 6 This is a comparison of the adsorption and removal effects of molecularly imprinted electrodes and non-molecularly imprinted electrodes on azithromycin.

[0035] Figure 7 These are cyclic voltammetric scans of molecularly imprinted electrodes prepared using carboxypyrrole (A) and thiophene 3-borate (B), respectively, in potassium ferricyanide solution. Detailed Implementation

[0036] Example 1

[0037] like Figure 1 As shown, a method for selectively adsorbing and coupling electrocatalysis to remove pollutants from water includes the following steps:

[0038] (1) Calcination of the electrode plate: The graphite electrode plate is placed in a muffle furnace and calcined at 180°C for 12 hours.

[0039] (2) Preparation of functional monomer-azithiamycin complex: Boric acid thiophene monomer (3-thiophene boric acid) was used as the functional monomer and mixed with azithiamycin at a molar ratio of 1:1. The mixture was dissolved in acetonitrile solution containing organic electrolyte, stirred and allowed to stand overnight to obtain functional monomer-azithiamycin complex.

[0040] (3) Electropolymerization for the preparation of molecularly imprinted electrodes: The calcined graphite sheet from (1) was used as the working electrode, and a silver electrode filled with an organic electrolyte solution was used as the reference electrode for electropolymerization. The working solution was an acetonitrile solution containing 0.5 mM functional monomer-azithiomycin complex and 0.25 mM 2,2'-bithiophene crosslinking monomer. Electropolymerization was performed using scanning cyclic voltammetry with the following parameters: scanning potential window of 0–2.3 V, scanning rate of 100 mV / s, and 10 scan cycles. After polymerization, the electrodes were washed with acetonitrile and ultrapure water, and then immersed in water for later use.

[0041] (4) Removal of molecular imprinted template: The prepared molecular imprinted electrode was placed in a formic acid-acetonitrile solution with a volume ratio of 1:9 and sonicated at 320W for 30 minutes. Then it was washed with ultrapure water to complete the removal of template molecules.

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

[0043] (6) Electrocatalytic removal of new pollutants: After adsorption is completed, a constant voltage of 1.2V is 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 during 2 hours of selective adsorption, and the removal rate of azithromycin reached 99% during the subsequent 4 hours of electrocatalysis.

[0045] Example 2

[0046] A method for selectively adsorbing and coupling electrocatalysis to remove pollutants from water includes the following steps:

[0047] (1) Calcination of the electrode plate: The graphite electrode plate is placed in a muffle furnace and calcined at 300℃ for 2 hours.

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

[0049] (3) Electropolymerization for the preparation of molecularly imprinted electrodes: The calcined graphite sheet from (1) was used as the working electrode, and a 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 of the functional monomer-carbamazepine complex and 5 mM of the crosslinking monomer (3,3'-bithiophene). Electropolymerization was performed using scanning cyclic voltammetry with the following parameters: scanning potential window of 0–2.0 V, scanning rate of 10 mV / s, and 1 scan cycle. After polymerization, the electrodes were washed with acetonitrile and ultrapure water, and then immersed in water for later use.

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

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

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

[0053] like Figure 4 As shown, in the selective adsorption of 120 minutes, 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 rapidly adsorb new pollutants.

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

[0055] Example 3

[0056] A method for selectively adsorbing and coupling electrocatalysis to remove pollutants from water includes the following steps:

[0057] (1) Calcination of the electrode plate: The graphite electrode plate is placed in a muffle furnace and calcined at 300℃ for 2 hours.

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

[0059] (3) Electropolymerization for the preparation of molecularly imprinted electrodes: The calcined graphite sheet from (1) was used as the working electrode, and a silver electrode filled with an organic electrolyte solution was used as the reference electrode for electropolymerization. The working solution was a methanol solution containing 4 mM of the functional monomer-new pollutant complex and 2 mM of the crosslinking monomer (3,3'-bithiophene). Electropolymerization was performed using scanning cyclic voltammetry with the following parameters: scanning potential window of 0–1.6 V, scanning rate of 50 mV / s, and 5 scan cycles. After polymerization, the electrodes were washed with acetonitrile and ultrapure water, and then immersed in water for later use.

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

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

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

[0063] like Figure 6 As shown, during 20 minutes of selective adsorption, azithromycin in water was removed at the highest rate, while the amount of other new pollutants removed by adsorption was less than 10% of that of azithromycin, demonstrating the superior selectivity of this molecularly imprinted catalytic electrode.

[0064] Example 4

[0065] A method for selectively adsorbing and coupling electrocatalysis to remove pollutants from water includes the following steps:

[0066] (1) Calcination of the electrode plate: The graphite electrode sheet is placed in a muffle furnace and calcined at 200°C for 3 hours.

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

[0068] (3) Electropolymerization for preparing molecularly imprinted electrodes: Calcinated graphite sheets (1) were used as the working electrode, and a 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 of the functional monomer-bisphenol A complex and 5 mM of the crosslinking monomer (2,2'-bithiophene). Electropolymerization was performed using scanning cyclic voltammetry with the following parameters: scanning potential window of 0–2.0 V, scanning rate of 50 mV / s, and 5 scan cycles. After polymerization, the electrodes were washed with acetonitrile and ultrapure water, and then immersed in water for later use. The resulting molecularly imprinted polymer electrode structure is shown below. Figure 7 As shown.

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

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

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

[0072] Example 5

[0073] A method for selectively adsorbing and coupling electrocatalysis to remove pollutants from water includes the following steps:

[0074] (1) Calcination of the electrode plate: The graphite electrode sheet is placed in a muffle furnace and calcined at 120°C for 12 hours.

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

[0076] (3) Electropolymerization for the preparation of molecularly imprinted electrodes: The calcined graphite sheet from (1) was used as the working electrode, and a silver electrode filled with an organic electrolyte solution was used as the reference electrode for electropolymerization. The working solution was an acetonitrile solution containing 4 mM of the functional monomer-tetracycline complex and 2 mM of the crosslinking monomer (3,3'-bithiophene). Electropolymerization was performed using scanning cyclic voltammetry with the following parameters: scanning potential window of 0–2.0 V, scanning rate of 20 mV / s, and 2 scan cycles. After polymerization, the electrodes were washed with acetonitrile and ultrapure water, and then immersed in water for later use.

[0077] (4) Removal of molecular imprinted template: The prepared molecular imprinted electrode was placed in a formic acid-acetonitrile solution with a volume ratio of 1:10 and sonicated at 80W for 30 minutes. Then it was washed with ultrapure water to complete the removal of template molecules.

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

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

[0080] Of the above embodiments, the preferred embodiment is Embodiment 3.

[0081] Comparative Example 1

[0082] The remaining steps of this comparative example are the same as those in Example 3, except that azithromycin is not used in the electrode synthesis in step (2), and the obtained non-molecularly imprinted electrode is used for adsorption-electrocatalysis experiments. The results showed that the non-molecularly imprinted electrode had a low adsorption and removal rate for azithromycin and did not exhibit rapid removal efficiency. Figure 6 As shown.

[0083] Comparative Example 2

[0084] The remaining steps of this comparative example are the same as those in Example 3, except that the functional monomer in step (2) is replaced with carboxypyrrole. The results showed that the obtained molecularly imprinted electrode had poor electrochemical stability and exhibited significant changes in redox peaks during cyclic voltammetry scans in the presence of the electrochemical redox probe, such as... Figure 7 As shown, the selected thiophene functional monomers exhibit good electrochemical stability, making them suitable for the selective adsorption-electrocatalytic removal of novel pollutants.

Claims

1. A method for selectively adsorbing and coupling electrocatalysis to remove pollutants from water, characterized in that, Includes the following steps: Step 1: Calcine the graphite electrode sheet at 180~300 ℃; Step 2: Mix the functional monomer and the target pollutant at a molar ratio of 1 to 2:1, dissolve them in an acetonitrile or methanol solution containing an organic electrolyte, stir and let stand overnight to obtain the functional monomer-pollutant complex. Step 3: Using the calcined graphite sheet obtained in Step 1 as the working electrode and the silver electrode filled with organic electrolyte solution as the reference electrode, electropolymerization is carried out using scanning cyclic voltammetry. The working solution includes acetonitrile or methanol solution of functional monomer-pollutant complex and bithiophene crosslinking monomer. After polymerization, the electrode is washed to obtain a molecularly imprinted electrode, which is then soaked in water for later use. Step 4: Place the molecularly imprinted electrode in a formic acid-acetonitrile solution, sonicate, and then wash with ultrapure water to complete the removal of template molecules. Step 5: Place the substance obtained in Step 4 into the aqueous solution of the new pollutant and stir with a small magnetic stirrer to carry out selective adsorption; Step 6: After adsorption is complete, a constant voltage is applied to the molecularly imprinted electrode to continuously degrade pollutants; In step one, the calcination time is 2~12 h; In step four, the volume ratio of formic acid to acetonitrile in the formic acid-acetonitrile solution is 1:8~10, the ultrasonic power is 80~320W, and the ultrasonic time is 30~40 minutes. The target pollutant is bisphenol A, carbamazepine, or tetracycline, and the functional monomer is a carboxythiophene monomer.

2. The method for selective adsorption coupled with electrocatalysis to remove pollutants from water according to claim 1, characterized in that: In 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 crosslinking monomer is 0.25~5 mM.

3. The method for selective adsorption coupled with electrocatalysis to remove pollutants from water according to claim 1, characterized in that: In step three, the scanning potential window for electropolymerization is 0~2.3 V, excluding 0 V, the scanning rate is 10~100 mV / s, and the number of scans is 1~10.

4. The method for selective adsorption coupled with electrocatalysis to remove pollutants from water according to claim 1, characterized in that: In step five, the stirring speed of the small magnetic stirrer is 500~600 rpm, and the time is 20~120 minutes.

5. The method for selective adsorption coupled with electrocatalysis to remove pollutants from water according to claim 1, characterized in that: In step six, the constant voltage is 0.9~1.65 V.

Images