D-A type imino conjugated microporous polymer catalyst for persulfate activation as well as preparation method and application of D-A type imino conjugated microporous polymer catalyst

Abstract

The invention relates to a D-A type imino conjugated microporous polymer catalyst for persulfate activation as well as a preparation method and application of the D-A type imino conjugated microporous polymer catalyst. The D-A type imino conjugated microporous polymer catalyst is prepared through a Buchwald-Harwig coupling reaction of a benzothiadiazole monomer and an arylamine monomer. The catalyst prepared by the invention has the characteristics of high-efficiency degradation performance on various organic pollutants, wide applicable pH range, confinement enhanced mass transfer and the like; according to the invention, the catalytic membrane with enhanced mass transfer can be further prepared.

Description

Technical Field

[0001] The invention belongs to the technical field of nano materials and water treatment, and particularly relates to a DA-type imine-based conjugated microporous polymer catalyst for persulfate activation and application of a preparation method thereof. Background Art

[0002] With the development of the times, the industrial level of mankind has gradually improved. The new pollutants contained in the discharged wastewater include persistent organic pollutants (POPs), endocrine disruptors (EDCs), antibiotics, etc., which seriously affect water quality and endanger human health. Advanced oxidation processes (AOPs) based on persulfate are considered to be a potential water treatment technology that can efficiently degrade these pollutants due to their advantages such as multiple reactive oxidative species (ROS), strong oxidizing ability, and easy transportation of persulfate solid powder. Among them, persulfate activation catalysts are the core of this technology. Metal catalysts and non-metallic carbon-based catalysts are the mainstream catalysts currently studied. However, metal catalysts have the problem of secondary pollution caused by metal leakage, and non-metallic carbon-based catalysts have the problem of weak stability of active sites. Therefore, the design and development of new high-performance persulfate activation catalysts is of great research significance to promote the degradation of new pollutants by this technology.

[0003] Polymer-based catalysts have no metal pollution problem, and their molecular design improves the preparation of high-performance persulfates, making them a potential green high-performance activator. However, polymer catalysts are often affected by ·OH and SO4· - In addition, due to the limited mass transfer of pollutants in the fluidized bed process, the utilization rate of the generated free radicals is low, and they will further attack the polymer, resulting in a significant decrease in its stability. Summary of the invention

[0004] The purpose of the present invention is to provide a DA-type imine-based conjugated microporous polymer catalyst for persulfate activation and a preparation method and application thereof, so as to solve the technical problems of poor stability of polymer catalysts and low utilization rate of active free radicals.

[0005] The invention provides a DA-type imine-based conjugated microporous polymer catalyst for persulfate activation. The catalyst is prepared by subjecting a benzothiadiazole monomer and an aromatic amine monomer to a Buchwald-Hartwig coupling reaction to generate the conjugated microporous polymer catalyst.

[0006] Preferably, the benzothiadiazole monomer includes at least one of 4,7-dibromo-2,1,3-benzothiadiazole or 4,7-dibromobenzo[1,2-c:4,5-c']bis([1,2,5]thiadiazole; and the aromatic amine monomer includes tris(4-aminophenyl)amine and the like.

[0007] Preferably, the structure of the catalyst is one of the following structures:

[0008]

[0009] The present invention provides a method for preparing the above-mentioned DA-type imine-based conjugated microporous polymer catalyst for persulfate activation, comprising the following steps: placing a reaction system of a benzothiadiazole monomer, an aromatic amine monomer and a Buchwald-Hartwig coupling reaction in a molar ratio of 2:1-3 in a Schlenk tube, reacting at 60-150°C for 12-72h under a nitrogen atmosphere; then filtering and vacuum drying at a temperature of 25-80°C for 2-72h to obtain a powder catalyst.

[0010] Preferably, the reaction system of the Buchwald-Hartwig coupling reaction is as follows: the solvent used includes at least one of toluene, chloroform, tetrahydrofuran or N,N-dimethylformamide; the palladium catalyst used includes at least one of palladium acetate, tris(dibenzylideneacetone)dipalladium or bis(dibenzylideneacetone)palladium; the ligand used includes at least one of 1,1'-binaphthyl-2,2'-bisdiphenylphosphine, 2-cyclohexylphosphine-2',4',6'-triisopropylbiphenyl or 1,1-bis(diphenylphosphino)ferrocene; and the alkali used includes at least one of sodium tert-butoxide, cesium carbonate, sodium tert-butoxide or potassium tert-butoxide.

[0011] More preferably, during the suction filtration process, the filtrate is washed with anhydrous methanol, chloroform and deionized water in sequence until the filtrate is colorless and transparent.

[0012] The present invention provides an application of the above-mentioned DA-type imine-based conjugated microporous polymer catalyst for persulfate activation in removing organic pollutants, comprising: adding the above-mentioned catalyst to an organic pollutant solution and placing it in a constant temperature oscillator for oscillation, setting the temperature to 5-50°C, the time to 5-60 minutes, and the rotation speed to 100-400 r min -1 The dosage of the catalyst is 0.01 to 0.5 g L -1 .

[0013] Preferably, the organic pollutant solution includes persulfate and organic pollutants, and its pH value is 2-11; the persulfate concentration is 0.1-10 mmol L -1 , including at least one of peroxymonosulfate (PMS) or peroxydisulfate (PDS); the concentration of the organic pollutant is 1 to 50 mg L -1 , including at least one of phenol, tetracycline, acid scarlet or methylene blue and bisphenol A (BPA).

[0014] The present invention also provides a method for preparing a DA-type imine-based conjugated microporous polymer catalytic membrane for persulfate activation, comprising:

[0015] (1) placing the above catalyst in N-methylpyrrolidone, adding carbon nanotubes (CNT), and ultrasonicating to prepare a dispersion;

[0016] (2) The catalytic membrane is prepared by a vacuum filtration method, and after washing, the catalytic membrane is placed in a vacuum drying oven for drying.

[0017] Preferably, in step (1), the dosage of the catalyst is 2-50 mg, the volume of N-methylpyrrolidone is 40-200 mL, the mass ratio of the catalyst to the carbon nanotubes is 1:0.2-4, the ultrasonic temperature is 20-30° C., and the time is 0.5-24 h.

[0018] Preferably, the substrate used to prepare the catalytic membrane in step (2) is an organic Nyon66 microporous filter membrane with a diameter of 30 to 60 mm and a pore size of 0.1 to 0.3 μm; after washing, the catalytic membrane is soaked in deionized water for 3 to 12 hours and then dried at a temperature of 20 to 100° C. for 3 to 24 hours.

[0019] More preferably, the washing comprises washing with anhydrous ethanol, 50% ethanol solvent, and deionized water in sequence until the filtrate does not contain N-methylpyrrolidone.

[0020] The present invention also provides an application of the above catalytic membrane in the continuous flow removal of organic pollutants, comprising: -1 The flow rate flows through the catalytic membrane.

[0021] The present invention is based on the Buchwald-Hartwig coupling reaction of benzothiadiazole electron acceptor (A) and aromatic amine monomer to prepare a DA type imine-based conjugated microporous polymer catalyst having polyaniline-like electron donor (D) characteristics. The polymer catalyst has the following characteristics: (1) The unique redox property of the imine-based conjugated microporous polymer can oxidize persulfate to O2· - and 1 O2, to avoid being oxidized; (2) the DA effect gives the imine-based conjugated microporous polymer a narrow band gap, which is conducive to the rapid transmission of electrons, thus having a kinetic constant comparable to that of metal catalysts; (3) the conjugated characteristics of the polymer make it easy to undergo π-π conjugated self-assembly with carbon nanotubes, which can be further prepared into a catalytic membrane, thereby enhancing the mass transfer of pollutants, effectively preventing the polymer from being attacked by free radicals, and having high stability.

[0022] Beneficial Effects

[0023] (1) The powder catalyst prepared by the present invention has the ability to rapidly degrade pollutants (the removal rate of bisphenol A is nearly 100% within 30 minutes, and the kinetic k value is as high as 0.21min). -1 ), a wide range of applicable pH values, and confined area enhanced mass transfer, and has high efficiency in degrading a variety of organic pollutants.

[0024] (2) The catalytic membrane with enhanced mass transfer prepared by the present invention can maintain a removal rate of bisphenol A above 99.99% during a continuous degradation process of up to 100 hours.

[0025] (3) The present invention provides new ideas for the design and preparation of high-performance non-metallic polymer catalysts and has potential application value in the field of degradation of emerging organic pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a SEM image of the TPBT catalyst in Example 1 of the present invention.

[0027] Figure 2 This is a graph showing the degradation rate of bisphenol A-containing wastewater by the TPBT catalyst in Example 3 of the present invention and the carbon nanotube (CNT) catalyst in Comparative Example 1 over time.

[0028] Figure 3 The treatment flux and degradation rate of bisphenol A-containing wastewater treated by the TPBT@CNT catalytic membrane in Example 5 of the present invention vary with time.

[0029] Figure 4 This is the electron paramagnetic resonance spectrum of the TPBT catalyst in Example 6 of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0031] Example 1

[0032] This embodiment provides a DA-type imine-based conjugated microporous polymer catalyst for persulfate activation, and the preparation method thereof comprises the following steps:

[0033] Tris(4-aminophenyl)amine (95.81 mg, 0.33 mmol, TCI) and 4,7-dibromo-2,1,3-benzothiadiazole (147 mg, 0.5 mmol, Sinopharm) were placed in a Schlenk tube (100 mL), and bis(dibenzylideneacetone)palladium (17.25 mg, 0.03 mmol, TCI), 2-dicyclohexylphosphine-2',4',6'-triisopropylbiphenyl (21.42 mg, 0.45 mmol, TCI), sodium tert-butoxide (336.4 mg, 3.5 mmol, Wokai), sodium fluoride (21 mg, 0.5 mmol, TCl) were added. 50 mL of toluene was added under nitrogen atmosphere, and the coupling reaction was carried out in an oil bath at 110°C for 48 hours. After the reaction was completed, it was washed twice with anhydrous methanol, chloroform, and deionized water at 60°C for two hours each time to remove unreacted raw materials and oligomers. Finally, it was placed in a vacuum oven at 40°C and dried for 24 hours to obtain a polymer catalyst (TPBT, corresponding to the P2 structure in the above structural formula). The SEM image is shown in Figure 1 shown.

[0034] Example 2

[0035] This embodiment provides a DA-type imine-based conjugated microporous polymer catalyst for persulfate activation, and the preparation method thereof comprises the following steps:

[0036] Tri(4-aminophenyl)amine (95.81 mg, 0.33 mmol, TCI) and 4,7-dibromobenzo[1,2-C:4,5-C']bis([1,2,5]thiadiazole) (176 mg, 0.5 mmol, Sinopharm) were placed in a Schlenk tube (100 mL), and bis(dibenzylideneacetone)palladium (17.25 mg, 0.03 mmol, TCI), 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (21.42 mg, 0.45 mmol, TCI), sodium tert-butoxide (336.4 mg, 3.5 mmol, Wokai), and sodium fluoride (21 mg, 0.5 mmol, TCl) were added. 50 mL of toluene was added under nitrogen atmosphere, and the coupling reaction was carried out in an oil bath at 110°C for 48 h. After the reaction, the product was washed twice with anhydrous methanol, chloroform and deionized water at 60°C for two hours each time to remove unreacted raw materials and oligomers. Finally, it was dried in a vacuum oven at 40°C for 24 hours to obtain a polymer catalyst (TPBBT, corresponding to the P4 structure in the above structural formula).

[0037] Example 3

[0038] This embodiment provides an application of a DA-type imine-based conjugated microporous polymer catalyst activated by persulfate in removing organic pollutants, and the specific process includes:

[0039] The polymer catalyst TPBT prepared in Example 1 was added to the organic pollutant solution to obtain a solution containing 25 mg L -1 Organic pollutants, 2mmol L -1 Permonosulfate (PMS), 0.10 g L -1 TPBT, a mixed solution with a pH of 6, was placed in a constant temperature shaking bed at 25°C and shaken at a speed of 300 r / min. Samples were taken at different time points and the concentration of organic pollutants in the solution was determined by high performance liquid chromatography (the mobile phase was 70% methanol and 30% ultrapure water).

[0040] Taking bisphenol A as a model pollutant, samples were taken at 2min, 4min, 6min, 12min, 18min, 24min, and 30min to investigate the degradation effect of the catalyst on organic pollutants within 30min. The experimental results are shown in Figure 2 As shown in the figure, in the TPBT / PMS catalytic system, the degradation rate of bisphenol A by the catalyst within 30 min is kept above 99.99%, and the calculated k is 0.21 min -1 , indicating that the polymer catalyst has a good degradation effect on organic pollutants, indicating that the TPBT / PMS system has good practicality.

[0041] Comparative Example 1

[0042] This comparative example provides an application of a carbon nanotube catalyst in removing organic pollutants. The specific process is referenced to Example 3, except that there is no polymer TPBT and PMS. The degradation rate of bisphenol A is as follows: Figure 2 As shown, the degradation effect of organic pollutants by single carbon nanotube catalyst is significantly worse than that by TPBT / PMS.

[0043] Example 4

[0044] This embodiment provides a method for preparing a DA-type imine-based conjugated microporous polymer catalytic membrane for persulfate activation, which is as follows:

[0045] (1) 15 mg of the polymer catalyst TPBT prepared in Example 1 was added to 200 mL of N-methylpyrrolidone solution, and 20 mg of carbon nanotubes (CNT) were added at the same time, and ultrasonically dispersed at 30° C. for 24 h to prepare a dispersion;

[0046] (2) The catalytic membrane was prepared by vacuum filtration. The membrane substrate used was an organic Nyon66 microporous filter membrane with a diameter of 45 mm and a pore size of 0.2 μm. It was washed with anhydrous ethanol, 50% ethanol solvent, and deionized water in sequence until the filtrate did not contain N-methylpyrrolidone solution. The catalytic membrane was soaked in deionized water for 3 to 12 hours. The membrane after soaking was dried at a drying temperature of 60°C and a drying time of 24 hours. After washing, the catalytic membrane was placed in a vacuum drying oven and dried to obtain a TPBT@CNT catalytic membrane.

[0047] Example 5

[0048] This embodiment provides an application of a DA-type imine-based conjugated microporous polymer catalytic membrane activated by persulfate in continuous flow removal of organic pollutants, specifically including:

[0049] The TPBT@CNT catalytic membrane prepared in Example 4 was placed in a penetration reactor, and the organic pollutant solution (containing 5 mg L -1 Organic pollutants, 1mmol L -1 Permonosulfate (PMS, pH 6) was passed through the catalytic membrane at a pressure of 1 bar, and samples were taken at the outlet at different time points. The concentration of organic pollutants in the solution was determined by high performance liquid chromatography (mobile phase: 70% methanol and 30% ultrapure water).

[0050] Taking bisphenol A as a model pollutant, samples were taken from the outlet after 5min, 10min, 15min, 30min, 45min, 60min, 90min, 120min, 3h, 4h, 5h, 6h, 8h, 10h and then every 5h to investigate the degradation effect of the catalytic membrane on organic pollutants within 100h. The experimental results are shown in Figure 3 As shown, in the catalytic filtration system, the degradation rate of bisphenol A by the catalytic membrane remained above 99.99% within 100 hours, indicating that the catalytic membrane has a good degradation effect on organic pollutants, indicating that the TPBT@CNT catalytic membrane / PMS system has good practicality.

[0051] Example 6

[0052] This embodiment provides a method for detecting active oxygen species in a catalyst activation PMS experiment, which is as follows:

[0053] The polymer catalyst TPBT in Example 1 was added to the organic pollutant solution to obtain a solution containing 25 mg L -1 Organic pollutants, 2mmol L -1 Permonosulfate (PMS), 0.10 g L -1TPBT, pH 6 mixed solution, placed in a 25℃ constant temperature shaker. Sampled at 30min, 40μL sample solution was added to a plastic tube containing 20μL active oxygen species scavenger (free radical scavenger: dimethylpyridine N-oxide (DMPO), singlet oxygen scavenger: 2,2,6,6-tetramethylpiperidine (TEMP), and shaken evenly. The active oxygen species signal intensity was tested using an electron paramagnetic resonance spectrometer (EPR). The results are as follows: Figure 4 As shown in the figure, (a) TMEP captures singlet oxygen, and (b) DMPO captures free radicals. It can be seen from the figure that when DMPO and TEMP are used as capture agents, obvious superoxide free radicals (O2 ·- ) and singlet oxygen ( 1 O2), indicating that superoxide radicals and singlet oxygen are the main active free radicals in the TPBT / PMS system.

Claims

1. A DA-type imine-based conjugated microporous polymer catalyst for persulfate activation, characterized in that: The catalyst is prepared by a Buchwald-Hartwig coupling reaction between a benzothiadiazole monomer and an aromatic amine monomer to generate a conjugated microporous polymer catalyst.

2. The catalyst according to claim 1, characterized in that The benzothiadiazole monomer includes at least one of 4,7-dibromo-2,1,3-benzothiadiazole or 4,7-dibromobenzo[1,2-c:4,5-c']bis([1,2,5]thiadiazole; and the aromatic amine monomer includes tris(4-aminophenyl)amine.

3. The catalyst according to claim 1, characterized in that The structure of the catalyst is one of the following structures:

4. A method for preparing a DA-type imine-based conjugated microporous polymer catalyst for persulfate activation as claimed in claim 1, comprising the following steps: placing a reaction system of a benzothiadiazole monomer, an aromatic amine monomer and a Buchwald-Hartwig coupling reaction in a molar ratio of 2:1-3 in a Schlenk tube, reacting at 60-150°C for 12-72h under a nitrogen atmosphere; then filtering and vacuum drying at a temperature of 25-80°C for 2-72h to obtain a powder catalyst.

5. The preparation method according to claim 4, characterized in that: The reaction system of the Buchwald-Hartwig coupling reaction is as follows: the solvent used includes at least one of toluene, chloroform, tetrahydrofuran or N,N-dimethylformamide; the palladium catalyst used includes at least one of palladium acetate, tris(dibenzylideneacetone)dipalladium or bis(dibenzylideneacetone)palladium; the ligand used includes at least one of 1,1'-binaphthyl-2,2'-bisdiphenylphosphine, 2-cyclohexylphosphine-2',4',6'-triisopropylbiphenyl or 1,1-bis(diphenylphosphino)ferrocene; and the alkali used includes at least one of sodium tert-butoxide, cesium carbonate, sodium tert-butoxide or potassium tert-butoxide.

6. Use of the DA-type imine-based conjugated microporous polymer catalyst for persulfate activation as claimed in claim 1 in removing organic pollutants, characterized in that: The catalyst is added to the organic pollutant solution and placed in a constant temperature oscillator for oscillation, with the temperature set to 5-50°C, the time set to 5-60 minutes, and the speed set to 100-400 rpm. -1 The dosage of the catalyst is 0.01 to 0.5 g L -1 .

7. The use according to claim 6, characterized in that: The organic pollutant solution includes persulfate and organic pollutants, and its pH value is 2-11; the persulfate concentration is 0.1-10 mmol L -1 , including at least one of peroxymonosulfate or peroxydisulfate; the concentration of the organic pollutant is 1 to 50 mg L -1 , including at least one of phenol, tetracycline, acid scarlet or methylene blue and bisphenol A.

8. A method for preparing a DA-type imine-based conjugated microporous polymer catalytic membrane for persulfate activation, comprising the following steps: (1) placing the catalyst as claimed in claim 1 in N-methylpyrrolidone, adding carbon nanotubes, and ultrasonicating to prepare a dispersion; (2) The catalytic membrane is prepared by a vacuum filtration method, and after washing, the catalytic membrane is placed in a vacuum drying oven for drying.

9. The preparation method according to claim 8, characterized in that: In the step (1), the dosage of the catalyst is 2-50 mg, the volume of N-methylpyrrolidone is 40-200 mL, the mass ratio of the catalyst to the carbon nanotubes is 1:0.2-4, the ultrasonic temperature is 20-30° C., and the time is 0.5-24 h.

10. The preparation method according to claim 8, characterized in that: The substrate used for preparing the catalytic membrane in step (2) is an organic Nyon66 microporous filter membrane with a diameter of 30 to 60 mm and a pore size of 0.1 to 0.3 μm; after washing, the catalytic membrane is soaked in deionized water for 3 to 12 hours and then dried at a temperature of 20 to 100° C. for 3 to 24 hours.

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