Method for degrading micro-plastics through electrocatalytic oxidation

Abstract

The invention discloses a method for degrading micro-plastics through electrocatalytic oxidation, which comprises the following steps: water sample pretreatment: separating out suspended solids in a water sample containing micro-plastics, so that the particle size of the suspended solids in the water sample is less than or equal to 1 mu m; diluting the water sample until the concentration of suspended matters in the water sample is less than or equal to 120mg / L, and adjusting the pH value of the water sample to 6.5-7.5 by using inorganic acid or inorganic base to obtain a water body to be treated; electrocatalytic oxidation: putting an oxidizing agent into the water body to be treated until the concentration of the oxidizing agent is less than or equal to 0.2 mmol / L; direct-current voltage is applied to the to-be-treated water body for electro-catalysis treatment, the current density is smaller than or equal to 45 mA / cm < 2 >, and the degraded water body is obtained; the oxidizing agent can form free sulfate radicals after meeting water, and the electro-catalysis treatment temperature is lower than or equal to 45 DEG C. The method for degrading the micro-plastics through electrocatalytic oxidation has the effects of inhibiting oxygen evolution reaction and improving the degradation rate of the micro-plastics.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a method for electrocatalytic oxidation degradation of microplastics. Background Art

[0002] Microplastics, as a type of plastic particles or fragments with a diameter of less than 5 mm, are of various types, including but not limited to polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET), etc. These tiny plastic particles are widely distributed in oceans, lakes, rivers and even soil environments. They not only act as carriers of heavy metal ions and persistent organic pollutants, but may also become breeding platforms for potential pathogens, posing a significant threat to the balance of the ecological environment and human health and safety. In view of this, researchers are actively engaged in exploring efficient strategies for the management of microplastics in water bodies.

[0003] At present, the treatment technology for microplastics has shown a diversified trend, mainly including adsorption, electrocoagulation, membrane separation, biodegradation, oxidant treatment and electrochemical oxidation.

[0004] Adsorption technology, by virtue of its rich pore structure and specific chemical properties on the surface of adsorbents (such as activated carbon, zeolite, biomass materials, etc.), can effectively adsorb and fix microplastics from water bodies to achieve the purpose of separation and removal. However, this technology is limited by the limited adsorption capacity of the adsorbent, which is easy to reach saturation and requires frequent replacement or regeneration. In addition, further treatment measures are still required for the adsorbed microplastics, otherwise it may cause secondary pollution problems.

[0005] Electrocoagulation technology uses electrolysis to generate metal hydroxide flocs on the electrode surface. These flocs can absorb microplastics and form larger particles, which are then removed by precipitation or filtration. However, this technology still faces challenges such as high energy consumption, high operating costs, and easy loss of electrode materials.

[0006] Membrane separation technology uses the principle of selective permeability of the membrane to trap microplastics on the surface of the membrane by physical filtration, thereby achieving effective separation. Commonly used membrane technologies include microfiltration, ultrafiltration and nanofiltration. However, membrane separation technology has also exposed shortcomings in the application process, such as easy clogging, low removal efficiency of small-size microplastics (especially nano-sized) and high cost of membrane materials.

[0007] Biodegradation technology mainly relies on microorganisms (such as bacteria and fungi) or their secreted enzymes to decompose microplastics into low molecular weight compounds or achieve complete mineralization. However, this method has problems such as slow degradation rate, low universality and unstable degradation efficiency, which limits its widespread application.

[0008] Oxidant treatment technology uses strong oxidants to decompose microplastics into small molecular compounds through oxidation reactions. However, oxidants are usually expensive. In addition, some types of microplastics (such as polyethylene and polypropylene) are highly resistant to oxidants and are difficult to completely degrade, which may lead to residual problems.

[0009] As a means of degrading pollutants through electrochemical reactions, the basic principle of electrochemical oxidation technology is to use strong oxidizing substances (such as hydroxyl radicals, hydrogen peroxide, ozone, etc.) produced by electrodes (especially anodes) to oxidize and decompose microplastics into small molecular compounds, or even mineralize them into carbon dioxide and water. Although this technology has achieved certain results, it still has limitations such as serious oxygen evolution side reactions, high energy consumption, low degradation rate, and susceptibility to interference from water quality factors (such as anion suppression). Summary of the invention

[0010] In view of the deficiencies of the prior art, the object of the present invention is to provide a method for electrocatalytic oxidation degradation of microplastics.

[0011] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes: A method for electrocatalytic oxidation degradation of microplastics, comprising the following steps: Water sample pretreatment: Separate the suspended matter in the water sample containing microplastics so that the particle size of the suspended matter in the water sample is ≤1μm; then dilute the water sample to a suspended matter concentration of ≤120mg / L, and then adjust the pH of the water sample to 6.5-7.5 with inorganic acid or inorganic base to obtain the water body to be treated; Electrocatalytic oxidation: Add oxidant to the water to be treated until the concentration of oxidant is ≤0.2mmol / L; then apply 3~5V DC voltage to the water to be treated for electrocatalytic treatment, and the current density is ≤45mA / cm 2 , and obtain the degraded water body; The oxidant can form sulfate radicals when in contact with water, and the electrocatalytic treatment temperature is ≤45°C.

[0012] In the present invention, the inorganic acid is selected from one or both of hydrochloric acid (HCl) and sulfuric acid (H2SO4).

[0013] In the present invention, the inorganic base is selected from one or both of sodium hydroxide (NaOH) and potassium hydroxide (KOH).

[0014] In the present invention, sulfate radical (SO4 － ·) It can quickly capture electrons in the electrochemical reaction to generate stable sulfate ions. This process competes with the electron transfer pathway involved in the oxygen evolution reaction, thereby reducing the number of electrons available for the oxygen evolution reaction and inhibiting the generation of oxygen.

[0015] In the present invention, the electrochemical catalysis and the oxidant themselves can degrade microplastics. In addition, the synergistic effect of the electrochemical catalysis and the oxidant can activate the oxidant electrochemically, thereby further improving the degradation rate of the microplastics.

[0016] In the present invention, the oxidant cannot be chlorate, hypochlorite, chlorite, permanganate, or perchlorate, as these substances have the following disadvantages when used as oxidants: ① Chlorate / hypochlorite / chlorite: easily react with organic matter in water to produce toxic by-products (such as chlorinated organic matter); ② Permanganate: It has strong oxidizing properties, but it will generate MnO2 precipitation, which increases the difficulty of solid waste treatment; ③Perchlorate: It has weak oxidizing properties and high stability and cannot effectively activate to generate free radicals.

[0017] In the present invention, the oxidant is not suitable to contain ammonium ions, because ammonium ions are prone to produce side reactions under electrochemical catalysis and oxidation conditions and release irritating gases.

[0018] In the present invention, when the concentration of the oxidant is greater than 0.2 mmol / L, sulfate radical quenching will occur.

[0019] Preferably, in the water sample pretreatment step, the water sample is first diluted until the microplastic content in the water sample is ≤160±10 mg / L, and then the suspended matter in the water sample containing microplastics is separated.

[0020] In the present invention, the water sample is first diluted until the microplastic content in the water sample is ≤160±10 mg / L, which can prevent the electrolysis device from being blocked by excessive microplastic concentration.

[0021] Preferably, the oxidant is selected from one or both of peroxymonosulfate (PMS) and peroxydisulfate (PDS).

[0022] Preferably, the oxidant is selected from peroxymonosulfate, and the concentration of the oxidant is 0.15 mmol / L.

[0023] Preferably, the DC voltage is 3-5V.

[0024] Preferably, the current density is 20 mA / cm 2 ~40mA / cm 2 .

[0025] Preferably, the electrocatalytic treatment temperature is 35°C to 45°C.

[0026] In the present invention, when the electrocatalytic treatment temperature is lower than 35°C, the degradation rate of microplastics is slow; when the electrocatalytic treatment temperature is higher than 45°C, the side reactions between microplastics and oxidants will be accelerated, and the side reactions may produce toxic byproducts.

[0027] Preferably, the concentration of the oxidant is 0.1 mmol / L to 0.2 mmol / L.

[0028] Preferably, in the electrocatalytic oxidation step, the anode is cleaned once every 0.5 h to 1 h.

[0029] In the present invention, cleaning the anode once every 0.5h to 1h helps to maintain the electrochemical performance of the anode.

[0030] Preferably, in the water sample pretreatment step, the water sample is diluted until the suspended matter concentration in the water sample is 80 mg / L to 120 mg / L.

[0031] Preferably, the method further comprises the steps of: Electrolysis system buffering: After the electrocatalytic treatment is completed, the cooling rate of the degraded water is controlled to be ≤2℃ / min to room temperature.

[0032] The present invention is helpful to avoid stress cracking caused by excessive temperature difference between the inside and outside of the electrode or cell material due to too fast a cooling rate.

[0033] Compared with the prior art, the advantages of the present invention include: (1) The present invention provides a method for electrocatalytic oxidation degradation of microplastics, wherein the sulfate radicals generated by the oxidant help to inhibit the oxygen evolution reaction; (2) The present invention provides a method for electrocatalytic oxidation degradation of microplastics, in which electrochemistry activates the oxidant, which is beneficial to improving the degradation rate of microplastics. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 It is a direct view of the data of degradation rates obtained in Comparative Example 4, Comparative Example 3, Comparative Example 2, Comparative Example 1, Example 5, Example 4, and Example 3 in the present invention; Figure 2 It is a data intuitive diagram of dissolved organic carbon in solution measured in Examples 3 to 5 and Comparative Examples 1 to 4 of the present invention; Figure 3 It is a data intuitive diagram of the residual oxidant concentration measured in Example 3 and Comparative Example 2 of the present invention; Figure 4The data relationship diagram of the degradation rate and the current density measured in Example 3 and Examples 6 to 9 of the present invention; Figure 5 The data relationship diagram of the degradation rate and the oxidant concentration measured in Examples 10 to 15 of the present invention; Figure 6 This is a data relationship diagram of the degradation rate and the type of microplastics measured in Examples 3 and 16 to 19 of the present invention; Figure 7 It is a data relationship diagram of the degradation rates measured in Example 3 and Examples 1-2 of the present invention. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to understand the characteristics and effects of the present application, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein have the common meanings understood by those skilled in the art for the present application. In case of conflict, the definitions in this specification shall prevail.

[0037] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present application in any way, that is, the content of the present application can be implemented without being limited by any specific theory or mechanism.

[0038] As used herein, "this application" means "the present invention" or "the present disclosure".

[0039] The use of "one", "an", "a kind" or similar expressions to describe the components and technical features described in this application is merely for the convenience of expression and to provide a general meaning to the scope of this application. Therefore, such description should be understood to include one or at least one, and the singular also includes the plural, unless it is obvious that it refers to another meaning.

[0040] In this document, "or its combination" means "or any combination thereof", and "any one", "any one" means "any one", "any one" or "any one".

[0041] In this article, the terms "comprise", "include", "have", "contain" or any other similar terms are open-ended transitional phrases, which are intended to cover non-exclusive inclusions. For example, a composition or product containing multiple elements is not limited to the elements listed in this article, but may also include other elements that are not explicitly listed but are generally inherent to the composition or product. In addition, unless otherwise explicitly stated, the term "or" refers to an inclusive "or" rather than an exclusive "or". For example, any of the following situations satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), A and B are both true (or exist). In addition, in this article, the interpretation of the terms "comprise", "include", "have", and "contain" should be considered to have been specifically disclosed and simultaneously cover closed transitional phrases such as "consisting of", "consisting of", "the balance is", and "substantially consisting of", "mainly consisting of", "mainly consisting of", "basically containing", "basically consisting of", "basically consisting of", "essentially containing" and other transitional phrases.

[0042] In this article, all features or conditions such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are only for simplicity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be deemed to have covered and specifically disclosed all possible sub-ranges and individual values ​​within the range (including integers and fractions), especially integer values. For example, the range description of "1.0 to 8.0" or "between 1.0 and 8.0" or "between 1.0 and 8.0" should be deemed to have specifically disclosed all sub-ranges such as 1.0 to 8.0, 1.0 to 7.0, 2.0 to 8.0, 2.0 to 6.0, 3.0 to 6.0, 4.0 to 8.0, 3.0 to 8.0, etc., and should be deemed to cover endpoint values, especially sub-ranges defined by integer values, and should be deemed to have specifically disclosed individual values ​​such as 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, etc. Unless otherwise indicated, the foregoing method of interpretation applies to all contents of the entire application, regardless of whether the scope is broad or not.

[0043] If the quantity, concentration or other numerical value or parameter is expressed as a range, a preferred range (or a better range) or a series of upper and lower limits, it should be understood that all ranges consisting of any pair of the upper limit or preferred value (or a better value) of the range and the lower limit or preferred value (or a better value) of the range have been specifically disclosed herein, regardless of whether these ranges are disclosed separately. In addition, if a numerical range is mentioned herein, unless otherwise specified, the range should include its endpoints and all integers and fractions within the range.

[0044] In this document, numerical values ​​should be understood to have the accuracy of the number of significant digits of the numerical value, provided that the purpose of the invention can be achieved. For example, the number 40.0 should be understood to cover the range of 39.50 to 40.49.

[0045] Unless otherwise specified, in this application, parts by weight represent relative parts by weight in a composition, which may be any weight unit, such as but not limited to kilograms, kilograms, grams, pounds, etc. For example, 100 parts by weight of polyphenylene ether resin may represent 100 kilograms of polyphenylene ether resin or 100 pounds of polyphenylene ether resin.

[0046] It should be understood that the features disclosed in the various embodiments herein may be arbitrarily combined to form the technical solution of the present application, as long as there is no contradiction in the combination of these features.

[0047] The present application will be described below with specific implementations and examples. It should be understood that these specific implementations and examples are merely illustrative and are not intended to limit the scope of the present application and its use.

[0048] Unless otherwise stated, the methods, reagents and conditions used in the following preparation examples, comparative examples and examples are conventional methods, reagents and conditions in the art.

[0049] In the following descriptions: Potassium persulfate (K2S2O8): content ≥99%; Potassium peroxymonosulfate (KHSO5): content ≥99%.

[0050] Preparation Example Preparation Example 1 The preparation method of this preparation example includes: Z1. Mix PE microplastics in water to obtain a water sample containing microplastics, and filter the water sample containing microplastics through a microporous filter membrane, wherein the filter particle size of the microporous filter membrane is 1 μm; Z2. Dilute the filtered water sample with water. During the dilution process, use a laser particle size analyzer to detect the concentration of suspended matter in the water sample. Dilute the filtered water sample with water until the concentration of suspended matter is 81±1 mg / L. Z3. Adjust the pH of the diluted water sample to 6.5 using dilute hydrochloric acid to obtain the water to be treated.

[0051] Preparation Example 2 The difference between this preparation example and preparation example 1 is that in step Z2, the filtered water sample is diluted with water to a suspended matter concentration of 119±1 mg / L, and in step Z3, the pH of the diluted water sample is adjusted to 7.5 by sodium hydroxide solution.

[0052] Preparation Example 3 The preparation method of this preparation example includes: Z1. Dilute the water sample containing microplastics with water. During the dilution process, use a laser particle size analyzer to detect the concentration of suspended matter in the water sample. Dilute the filtered water sample with water to a suspended matter concentration of 160±10 mg / L, and then filter it through a microporous filter membrane with a filtration particle size of 1 μm. Z2. Dilute the filtered water sample with water. During the dilution process, use a laser particle size analyzer to detect the concentration of suspended matter in the water sample. Dilute the filtered water sample with water until the concentration of suspended matter is 100±1 mg / L. Z3. Adjust the pH of the diluted water sample to 7.0 by sodium hydroxide solution to obtain the water body to be treated.

[0053] Preparation Example 4 The difference between this preparation example and preparation example 3 is that the type of microplastic is PVC.

[0054] Preparation Example 5 The difference between this preparation example and preparation example 3 is that the type of microplastic is PS.

[0055] Preparation Example 6 The difference between this preparation example and preparation example 3 is that the type of microplastic is PP.

[0056] Preparation Example 7 The difference between this preparation example and preparation example 3 is that the type of microplastic is PET.

[0057] Example Example 1 The preparation method of this embodiment includes: S1. Add potassium peroxymonosulfate to the water to be treated obtained in Preparation Example 1 at 25° C., and slowly stir until the concentration of potassium peroxymonosulfate reaches 0.2 mmol / L; S2. After heating the water to 35°C, control the water temperature to 35±0.5°C, and then apply 5V DC voltage to the water to be treated, with a current density of 40mA / cm 2 , the anode was washed with deionized water every 0.5 h, the electrocatalytic treatment time was 6 h, and the degraded water was obtained; S3. Control the cooling rate of the degradation water body to ≤2℃ / min to room temperature.

[0058] Example 2 The difference between this embodiment and embodiment 1 is that: S1. At 25° C., potassium peroxymonosulfate and potassium peroxydisulfate were added to the water to be treated obtained in Preparation Example 2, with slow stirring during the process until the concentrations of potassium peroxymonosulfate and potassium peroxydisulfate were both 0.1 mmol / L.

[0059] Example 3 The preparation method of this embodiment includes: S1. Add potassium peroxymonosulfate to the water to be treated obtained in Preparation Example 3 at 25° C., and slowly stir until the concentration of potassium peroxymonosulfate reaches 0.2 mmol / L; S2. After heating the water to 40℃, control the water temperature to 40±0.5℃, and then apply 4V DC voltage to the water to be treated, with a current density of 40mA / cm 2 The anode was washed with deionized water every 0.5 h, and a sample was taken every h to test the dissolved organic carbon content in the solution by a TOC instrument, the residual oxidant concentration was detected by titration, and the degradation rate was detected by Fourier transform infrared spectroscopy. The electrocatalytic treatment time was 6 h to obtain the degraded water body; S3. Control the cooling rate of the degradation water body to ≤2℃ / min to room temperature.

[0060] Example 4 The difference between this embodiment and embodiment 3 is that: S1. Add potassium persulfate to the water to be treated obtained in Preparation Example 2 at 25° C., stirring slowly during the process until the concentration of potassium persulfate reaches 0.2 mmol / L; S2. After heating the water to 40℃, control the water temperature to 40±0.5℃, and then apply 4V DC voltage to the water to be treated, with a current density of 40mA / cm 2 , the anode was washed with deionized water once every 0.5 h, and a sample was taken every h to test the dissolved organic carbon content in the solution through a TOC instrument. The electrocatalytic treatment time was 6 h to obtain the degraded water body; Example 5 The preparation method of this embodiment includes: S1.1. At 25°C, PE microplastics were mixed in water to obtain a water sample containing microplastics, and the water sample containing microplastics was filtered through a microporous filter membrane, wherein the filter particle size of the microporous filter membrane was 1 μm; S1.2. At 25°C, add the filtered water sample to a 50wt% hydrogen peroxide (H2O2) solution until the concentration of hydrogen peroxide in the water sample is 0.2mmol / L; then dilute with hydrogen peroxide at a concentration of 0.2mmol / L, and use a laser particle size analyzer to detect the concentration of suspended matter in the water sample during the dilution process. Dilute the filtered water sample with water to a suspended matter concentration of 100±1mg / L; S1.3, at 25°C, adjusting the pH of the diluted water sample to 7.0 with a sodium hydroxide solution to obtain water to be treated; S2. After heating the water to 40℃, control the water temperature to 40±0.5℃, and then apply 4V DC voltage to the water to be treated, with a current density of 40mA / cm2 , the anode was washed with deionized water every 0.5 h, the electrocatalytic treatment time was 6 h, and the degraded water was obtained; S3. Control the cooling rate of the degradation water body to ≤2℃ / min to room temperature.

[0061] Example 6 The difference between this embodiment and embodiment 3 is that in step S2, the current density is 10 mA / cm 2 , there is no need to test the dissolved organic carbon content, residual oxidant concentration, and degradation rate in the solution.

[0062] Example 7 The difference between this embodiment and embodiment 6 is that in step S2, the current density is 20 mA / cm 2 .

[0063] Example 8 The difference between this embodiment and embodiment 6 is that in step S2, the current density is 30 mA / cm 2 .

[0064] Example 9 The difference between this embodiment and embodiment 3 is that in step S2, the current density is 50 mA / cm 2 .

[0065] Example 10 The difference between this embodiment and embodiment 6 is that the concentration of potassium sulfate in step S1 is 0.05 mmol / L, and in step S2, the DC voltage is 3 V and the current density is 45 mA / cm 2 .

[0066] Embodiment 11 The difference between this embodiment and embodiment 10 is that the concentration of potassium sulfate in step S1 is 0.10 mmol / L.

[0067] Example 12 The difference between this embodiment and embodiment 10 is that the concentration of potassium sulfate in step S1 is 0.15 mmol / L.

[0068] Example 13 The difference between this embodiment and embodiment 10 is that the concentration of potassium sulfate in step S1 is 0.20 mmol / L.

[0069] Embodiment 14 The difference between this embodiment and embodiment 10 is that the concentration of potassium sulfate in step S1 is 0.25 mmol / L.

[0070] Embodiment 15 The difference between this embodiment and embodiment 10 is that the concentration of potassium sulfate in step S1 is 0.30 mmol / L.

[0071] Example 16 The difference between this embodiment and embodiment 3 is that the water body to be treated in step S1 comes from preparation example 4, and there is no need to test the dissolved organic carbon content, residual oxidant concentration, and degradation rate in the solution.

[0072] Embodiment 17 The difference between this embodiment and Embodiment 16 is that the water to be treated in step S1 comes from Preparation Example 5.

[0073] Embodiment 18 The difference between this embodiment and Embodiment 16 is that the water to be treated in step S1 comes from Preparation Example 6.

[0074] Embodiment 19 The difference between this embodiment and Embodiment 16 is that the water to be treated in step S1 comes from Preparation Example 7.

[0075] Comparative Example Comparative Example 1 The preparation method of this comparative example comprises: D1. After heating the water body to be treated obtained in Preparation Example 3 to a temperature of 40°C, the water body temperature was controlled to be 40±0.5°C, and then a 4V DC voltage was applied to the water body to be treated, and the current density was 40mA / cm 2 The anode was washed with deionized water every 0.5 h, and a sample was taken every h to test the dissolved organic carbon content in the solution by a TOC instrument and the degradation rate was detected by Fourier transform infrared spectroscopy. The electrocatalytic treatment time was 6 h to obtain the degraded water body; D2. Control the cooling rate of the degradation water body to ≤2℃ / min to room temperature.

[0076] Comparative Example 2 The preparation method of this comparative example comprises: D1. Add potassium peroxymonosulfate to the water to be treated obtained in Preparation Example 3 at 25° C., and slowly stir until the concentration of potassium peroxymonosulfate reaches 0.2 mmol / L; D2. After heating the water to 40°C, control the water temperature to 40±0.5°C for 6 hours, take a sample every hour to test the dissolved organic carbon content in the solution by TOC instrument, detect the residual oxidant concentration by titration, and detect the degradation rate by Fourier transform infrared spectroscopy to obtain the degraded water; D3. Control the cooling rate of the degradation water body to ≤2℃ / min to room temperature.

[0077] Comparative Example 3 The difference between this comparative example and comparative example 2 is: D1. At 25° C., potassium persulfate was added to the water to be treated obtained in Preparation Example 3, and the mixture was slowly stirred until the concentration of potassium persulfate reached 0.2 mmol / L.

[0078] D2. After heating the water to 40°C, control the water temperature to 40±0.5°C for 6 hours. Take a sample every hour and use a TOC meter to test the dissolved organic carbon content in the solution to obtain the degraded water.

[0079] Comparative Example 4 The preparation method of this comparative example comprises: D1.1. At 25°C, PE microplastics were mixed in water to obtain a water sample containing microplastics, and the water sample containing microplastics was filtered through a microporous filter membrane with a filtration particle size of 1 μm; D1.2. At 25°C, add the filtered water sample to a 50wt% hydrogen peroxide (H2O2) solution until the concentration of hydrogen peroxide in the water sample is 0.2mmol / L; then dilute with 0.2mmol / L hydrogen peroxide, and use a laser particle size analyzer to detect the concentration of suspended matter in the water sample during the dilution process. Dilute the filtered water sample with water until the concentration of suspended matter is 100±1mg / L; D1.3. At 25°C, adjust the pH of the diluted water sample to 7.0 with sodium hydroxide solution to obtain the water to be treated; D2. After heating the water to 40°C, control the water temperature to 40±0.5°C for 6 hours, take a sample every hour and test the dissolved organic carbon content in the solution with a TOC instrument to obtain the degraded water; D3. Control the cooling rate of the degradation water body to ≤2℃ / min to room temperature. Performance Testing The degradation rates of microplastics in water samples and the obtained degraded water bodies were detected by Fourier transform infrared spectroscopy in Examples 1 to 19 and Comparative Examples 1 to 4, unit: %: Table 1 Differences between the processes of Examples 1 to 19 and Comparative Examples 1 to 4 It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it accordingly. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, some simple deductions or substitutions can be made without departing from the concept of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for electrocatalytic oxidation degradation of microplastics, characterized in that: The steps include: Water sample pretreatment: Separate the suspended matter in the water sample containing microplastics so that the particle size of the suspended matter in the water sample is ≤1μm; then dilute the water sample to a suspended matter concentration of ≤120mg / L, and then adjust the pH of the water sample to 6.5-7.5 with inorganic acid or inorganic base to obtain the water body to be treated; Electrocatalytic oxidation: Add oxidant to the water to be treated until the concentration of oxidant is ≤0.2mmol / L; then apply DC voltage to the water to be treated for electrocatalytic treatment, with a current density of ≤45mA / cm 2 , and obtain the degraded water body; The oxidant can form sulfate radicals when in contact with water, and the electrocatalytic treatment temperature is ≤45°C.

2. The method for electrocatalytic oxidation degradation of microplastics according to claim 1, characterized in that: In the water sample pretreatment step, the water sample is first diluted until the microplastic content in the water sample is ≤160±10 mg / L, and then the suspended matter in the water sample containing microplastics is separated.

3. The method for electrocatalytic oxidation degradation of microplastics according to claim 1, characterized in that: The oxidant is selected from one or both of peroxydisulfate and peroxymonosulfate.

4. The method for electrocatalytic oxidation degradation of microplastics according to claim 3, characterized in that: The oxidant is selected from peroxodisulfate, and the concentration of the oxidant is 0.15 mmol / L.

5. The method for electrocatalytic oxidation degradation of microplastics according to claim 1, characterized in that: The DC voltage is 3 to 5V; And / or, the current density is 20 mA / cm 2 ~40mA / cm 2 ; And / or, the electrocatalytic treatment temperature is 35°C to 45°C; And / or, the concentration of the oxidant is 0.1 mmol / L to 0.2 mmol / L.

6. The method for electrocatalytic oxidation degradation of microplastics according to claim 1, characterized in that: In the electrocatalytic oxidation step, the anode is cleaned once every 0.5 h to 1 h.

7. The method for electrocatalytic oxidation degradation of microplastics according to claim 1, characterized in that: In the water sample pretreatment step, the water sample is diluted until the suspended matter concentration in the water sample is 80 mg / L to 120 mg / L.

8. The method for electrocatalytic oxidation degradation of microplastics according to claim 1, characterized in that: Also includes the steps: Electrolysis system buffering: After the electrocatalytic treatment is completed, the cooling rate of the degraded water is controlled to be ≤2℃ / min to room temperature.

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