A method for activating persulfate for improving degradation performance of organic pollutants based on flow-through electrocatalytic membrane

Abstract

The application discloses a method for activating persulfate for improving the degradation performance of organic pollutants based on a flow-through electrocatalytic membrane, which comprises two steps of preparing a boron nitride electrocatalytic membrane loaded with bimetallic nanoparticles and carrying out a flow-through degradation reaction. Compared with a traditional mode, the flow-through mode provided by the application realizes effective coupling of a membrane catalytic system and a conventional electro-activated persulfate system, breaks through the limitation of low mass transfer efficiency, significantly improves the utilization rate of persulfate, and thus improves the degradation efficiency of organic pollutants. The flow-through reactor provided by the application has the advantages of simple structure, strong operability, low catalyst loss and good stability, has a wide industrial application prospect, and provides an efficient, economical and sustainable solution for the degradation of organic pollutants.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of environmental remediation materials, and relates to organic pollutant treatment, in particular to a method for improving the degradation performance of organic pollutants based on flow-type electrocatalytic membrane activated persulfate. BACKGROUND

[0002] The long-term existence of organic pollutants in the water environment has become a major global water pollution problem, and the development of efficient and environmentally friendly water treatment technology has become the focus of current research, especially for organic pollutants such as antibiotics, dyes, and drug residues. The advanced oxidation technology based on persulfate has gradually become an effective method for treating organic pollutants, because it can generate active species (such as SO4 ·- and · OH) with strong oxidation ability.

[0003] Because the rate of generating active species by persulfate self-decomposition is low, external catalysts or external energy are often added to activate it quickly. External catalysts include transition metals, carbon-based materials, metal-organic frameworks, etc. At present, transition metal-based catalysts are recognized as one of the most effective ways to activate persulfate. Single-metal catalysts have poor activation effect because there is no synergistic effect between metals, so double-metal catalysts are considered as a worthy consideration for persulfate activators. In addition, transition metals are prone to release metal ions into the water environment when they activate persulfate, which can easily cause secondary pollution of the water environment. Therefore, it is still challenging to seek a stable and efficient transition metal-based catalyst to improve the activation effect of persulfate while ensuring the stability of the catalyst.

[0004] Electro-activation is another way to apply external energy to activate persulfate, and this method is often used in combination with transition metal catalysts to synergistically promote the activation of persulfate and accelerate the degradation of pollutants, that is, a high-activity transition metal-based electrode material is prepared by loading a transition metal-based catalyst on a common electrode substrate. The traditional electro-activated persulfate system is usually carried out in a homogeneous system with limited mass transfer, which limits the mass transfer efficiency between persulfate, pollutants, and electro-catalysts, resulting in low utilization efficiency of persulfate oxidants and affecting the treatment effect of pollutants. Unlike this, the catalytic membrane system can improve the mass transfer efficiency of the reaction system by forced convection, thereby improving the controllability of the catalytic reaction time and the long-term stability of the system. However, how to effectively couple the catalytic membrane system with the traditional electro-activated persulfate system, and how to achieve effective activation of persulfate by optimizing the fluid dynamics process of the reaction system, in order to achieve efficient degradation of pollutants, is still a technical problem that needs to be overcome. SUMMARY

[0005] The application aims to provide a method for activating persulfate based on a flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants.

[0006] The application achieves the above application purposes by adopting the following technical solutions:

[0007] The application provides a method for activating persulfate based on a flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants, wherein the flow-through electrocatalytic membrane is a boron nitride electrocatalytic membrane loaded with bimetallic nanoparticles, and the method specifically comprises the following steps:

[0008] Step one, preparing a boron nitride electrocatalytic membrane loaded with bimetallic nanoparticles;

[0009] Step 1.1, preparing boron nitride:

[0010] Boric acid and melamine are dispersed in deionized water, and the obtained product is dried and ground after reaction in a constant-temperature high-pressure reaction kettle, and then boron nitride (BN) is obtained through pyrolysis;

[0011] Step 1.2, preparing boron nitride loaded with bimetallic nanoparticles:

[0012] The BN prepared in step 1.1 is dispersed in ethanol, and a cobalt chloride hexahydrate solution and a molybdate ammonium heptahydrate solution are added, then a sodium borohydride solution is added after mixing, and after stirring, centrifugation, washing and drying, boron nitride loaded with bimetallic nanoparticles (CoMo@BN) is obtained through pyrolysis;

[0013] Step 1.3, preparing an electrocatalytic membrane loaded with CoMo@BN:

[0014] The CoMo@BN prepared in step 1.2 is dispersed in ethanol, and a conductive acetylene black and a polyvinylidene fluoride solution are added, and then the mixture is uniformly mixed by ultrasonic mixing and is loaded on a nylon membrane by a negative pressure filtration method, and an electrocatalytic membrane loaded with CoMo@BN is obtained after drying;

[0015] Step two, performing a flow-through degradation reaction: persulfate is added to organic wastewater containing electrolyte and pollutants to form a reaction system; the degradation process is carried out in a flow-through electroactivated persulfate reactor under a constant direct current voltage in a dead-end filtration mode, the electrocatalytic membrane loaded with CoMo@BN is used as a working electrode, and a platinum wire ring is used as a counter electrode; the reaction system is pumped into the reactor at a constant flow rate by a peristaltic pump to realize a flow-through pollutant degradation process, and the reaction time is 60-180 min.

[0016] Preferably, the mass ratio between boric acid and melamine in step 1.1 is 1:1, the concentration of boric acid is 1.2M; the temperature in the high-pressure reactor is 105℃, and the reaction time is 3h; the pyrolysis process is: heating at a rate of 5℃·min -1 to 900-1100℃ under nitrogen atmosphere, and continuing the pyrolysis at the temperature for 2-4h.

[0017] Preferably, in step 1.2, the mass of BN and the volume of ethanol are in a ratio of 10g:1L; the molar ratio of cobalt chloride hexahydrate and ammonium heptamolybdate tetrahydrate is 8:1, and the concentration of cobalt chloride hexahydrate is 0.025M; the concentration of sodium borohydride solution is 0.1M; the pyrolysis process is: heating at a rate of 5℃·min -1 to 400℃ under nitrogen atmosphere, and keeping the temperature for 2-4h.

[0018] Preferably, in step 1.3, the mass of CoMo@BN and the volume of ethanol are in a ratio of 15g:1L, the mass fraction of polyvinylidene fluoride is 3-6wt%, and the mass fraction of conductive acetylene black is 10-15wt%.

[0019] Preferably, in step two, the pollutants are tetracycline, oxytetracycline, aureomycin, rhodamine B, methylene blue, methyl orange, and orange G; the concentration of the pollutants is 20mg·L -1 .

[0020] Preferably, in step two, the electrolyte is sodium sulfate solution; the concentration of the electrolyte is 50mM.

[0021] Preferably, in step two, the concentration of the persulfate salt is 0.1-0.5mM.

[0022] Preferably, in step two, the pH value of the reaction system is 3-9.

[0023] Preferably, in step two, the direct current voltage is 1-2V; the flow rate is 1-7mL·min -1 .

[0024] Compared with the prior art, the application has the beneficial technical effects that:

[0025] (1) The application provides a boron nitride electrocatalytic film loaded with bimetallic nanoparticles for activating persulfate, which can efficiently degrade pollutants in a wide pH range and completely remove the pollutants in less than 50min.

[0026] (2) The application significantly improves the utilization rate of persulfate, thereby accelerating the degradation efficiency of organic pollutants; the method breaks through the low mass transfer efficiency between pollutants, persulfate and electrocatalyst in the traditional mode, optimizes the material exchange process in the reaction system, so that the electro-activated persulfate has a wide application prospect in the treatment of organic pollutant wastewater.

[0027] (3) The flow-through electro-activated persulfate reactor provided by the application has simple structure and simple reaction device, can effectively avoid the loss of catalyst, has good operability and stability, and is therefore beneficial to industrial production and popularization, and provides a more efficient, economic and sustainable solution for the degradation of organic pollutants. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 SEM image of CoMo@BN prepared in Example 1.

[0029] Figure 2 XRD test image of CoMo@BN prepared in Example 1.

[0030] Figure 3 Electrochemical performance test image of BN prepared in Comparative Example 1, Mo@BN prepared in Comparative Example 2, Co@BN prepared in Comparative Example 3 and CoMo@BN electrocatalytic film prepared in Example 1; wherein (a) is a CV test image, and (b) is an EIS test image.

[0031] Figure 4 It is a schematic diagram of the reaction device and the structure of the flow-through reactor; in the structure of the flow-through reactor, 1 is a quartz shell, 2 is a waterproof rubber sealing ring, 3 is a nylon film, 4 is a CoMo@BN loaded electrocatalytic film, 5 is a nylon film, and 6 is a platinum wire ring.

[0032] Figure 5 It is a degradation curve of tetracycline by different electrocatalytic films as persulfate activators.

[0033] Figure 6 It is a degradation curve of tetracycline by CoMo@BN loaded electrocatalytic film as persulfate activator under different voltages.

[0034] Figure 7 It is a degradation curve of tetracycline by CoMo@BN loaded electrocatalytic film as persulfate activator under different concentrations of persulfate.

[0035] Figure 8 It is a degradation curve of tetracycline by CoMo@BN loaded electrocatalytic film as persulfate activator under different flow rates.

[0036] Figure 9Degradation curves of tetracycline by CoMo@BN loaded electrocatalytic membrane as activator of persulfate under different pH conditions.

[0037] Figure 10 System stability test chart of CoMo@BN loaded flow-through electrocatalytic membrane for activating persulfate to degrade organic pollutants.

[0038] Figure 11 Efficiency chart of CoMo@BN loaded flow-through electrocatalytic membrane for activating persulfate to degrade different types of organic pollutants.

[0039] Figure 12 Comparison chart of degradation performance of tetracycline by CoMo@BN loaded electrocatalytic membrane as activator of persulfate under flow-through and traditional modes; wherein (a) is a degradation curve chart, and (b) is a fitting chart of first-order rate constant k.

[0040] Figure 13 Comparison chart of persulfate utilization rate by CoMo@BN loaded electrocatalytic membrane as activator of persulfate under flow-through and traditional modes.

[0041] Figure 14 Comparison chart of TOC removal efficiency of pollutant solution by CoMo@BN loaded electrocatalytic membrane as activator of persulfate under flow-through and traditional modes. DETAILED DESCRIPTION

[0042] The technical solutions of the present application are further described below in combination with examples.

[0043] It should be noted that all the raw materials used in the present application are known in the art unless otherwise specified.

[0044] In accordance with the above technical solutions, the following specific embodiments of the present application are given. It should be noted that the present application is not limited to the following specific embodiments, and any equivalent variations made on the basis of the technical solutions of the present application fall within the scope of protection of the present application.

[0045] Example 1

[0046] A method for improving the degradation performance of organic pollutants based on flow-through electrocatalytic membrane activated persulfate, the flow-through electrocatalytic membrane is a boron nitride electrocatalytic membrane loaded with bimetallic nanoparticles, which specifically comprises the following steps:

[0047] Step one, preparation of boron nitride (CoMo@BN) electrocatalytic membrane loaded with bimetallic nanoparticles;

[0048] Step 1.1, preparation of boron nitride (BN):

[0049] 7.42 g of boric acid and 7.42 g of melamine were added to 100 mL of deionized water, and the mixture was placed in a high-pressure reactor and reacted at 105 °C for 3 h. The resulting product was dried in an oven at 60 °C for 24 h. Subsequently, the dried flakes were ground uniformly and placed in a tube furnace, and then reacted at 5 °C / min under a nitrogen atmosphere. -1 The temperature was increased to 1000℃ at a certain rate and held for 3 hours to obtain BN;

[0050] Step 1.2, Preparation of boron nitride (CoMo@BN) loaded with bimetallic nanoparticles:

[0051] The BN (0.5 g) obtained in step 1.1 was dispersed in 50 mL of ethanol, referred to as solution A; simultaneously, 0.476 g of cobalt chloride hexahydrate and 0.309 g of ammonium heptamolybdate tetrahydrate (molar ratio 8:1) were dissolved in 80 mL of deionized water, referred to as solution B; solutions A and B were mixed and magnetically stirred for 30 min; then, 20 mL of sodium borohydride solution (0.1 M) was added dropwise, and magnetic stirring was continued for 2 h. After centrifugation, the mixture was washed three times with ethanol and deionized water, respectively, and placed in an oven at 60 °C for 24 h; subsequently, the resulting powder was dried under a nitrogen atmosphere at 5 °C·min. -1 The temperature was increased to 400℃ at a certain rate and held for 3 hours to obtain boron nitride CoMo@BN loaded with bimetallic nanoparticles.

[0052] Step 1.3, Preparation of the CoMo@BN-supported electrocatalytic membrane:

[0053] 15 mg of CoMo@BN prepared in step 1.2 was dispersed in ethanol and sonicated for 10 min. Then, conductive acetylene black (12 wt%) and polyvinylidene fluoride (5 wt%) were added, and the mixture was sonicated for another 10 min. The resulting mixture was then loaded onto a nylon membrane by negative pressure filtration and dried at 60 °C for 24 h to obtain an electrocatalytic membrane loaded with CoMo@BN.

[0054] The material prepared in step one of this embodiment is characterized as follows:

[0055] from Figure 1 As can be observed in the SEM image, CoMo@BN shows a layer of flocculent material loaded on BN with a rough surface and irregular cavity structure.

[0056] Figure 2XRD pattern of CoMo@BN. A characteristic peak was observed at 26.7°, which corresponds to BN (PDF #45-0895). In addition, characteristic peaks corresponding to the (100) and (102) planes of MoO2 (PDF #50-0739) were observed at 36.5° and 53.8°, respectively, and characteristic peaks corresponding to the (111) and (200) planes of Co (PDF #15-0806) were observed at 44.2° and 51.5°, respectively. This clearly indicates that the main components of the active material loaded on the BN surface are Co and MoO2.

[0057] Figure 3 The CV curve of CoMo@BN shown in (a) exhibits the largest internal area, indicating a higher double-layer capacitance, greater charge storage capacity, and superior redox characteristics. Figure 3 The Nyquist plot of CoMo@BN shown in (b) exhibits a smaller semicircle, indicating that it has the lowest charge transfer resistance.

[0058] Step two, flow-through degradation reaction:

[0059] The persulfate salt was added to a total of 100 mL of tetracycline organic wastewater containing 50 mM Na2SO4 (electrolyte) and 20 mg·L -1 The reaction system was formed, and the concentration of the persulfate salt in the reaction system was 0.4 mM, and the natural pH value of the reaction system was 7. The degradation experiment was carried out in a flow-through reactor with an effective reaction area of 3 cm x 3 cm. The CoMo@BN-loaded electrocatalytic film was used as the working electrode, and a platinum wire ring was used as the counter electrode. A constant direct current voltage of 1.5 V was applied. At room temperature of 25°C, the reaction system was pumped into the reactor at a flow rate of 5 mL·min -1 The solution flowed through the reactor from bottom to top, ensuring that the electrodes were fully immersed in the solution for dead-end filtration. The treated solution was pumped back into the original container to form a circulating flow-through reaction device, and the reaction time was 60 min.

[0060] The reactor structure and reaction device are shown in Figure 4 The device adopts an up-and-down flow-through structure, and the reaction cavity is constructed with a quartz shell, which has excellent corrosion resistance and visibility. The two electrodes are installed in parallel inside the cavity, and the electrode part is led out of the cavity to connect the direct current power supply. The anode of the electrocatalytic film is covered with a nylon film on both sides to inhibit catalyst loss and promote uniform liquid flow. A certain thickness of waterproof rubber sealing ring is provided on both sides of the electrode, which has the functions of sealing and insulating between the electrodes.

[0061] In this embodiment, the tetracycline concentration in the reaction system was tested at fixed time during the degradation reaction. After the completion of the degradation reaction, the reaction time was taken as the horizontal coordinate, and the ratio of the tetracycline concentration before and after the degradation of the reaction system was taken as the vertical coordinate, to draw a curve as shown in Figure 5 .

[0062] Comparative Example 1

[0063] This comparative example gives a method for activating persulfate based on flow-through electrocatalytic membrane for degrading organic pollutants, which is basically the same as Example 1, the only difference is that in step one, the prepared is BN loaded electrocatalytic membrane, step 1.1 preparation of BN is consistent with Example 1, omit step 1.2 in Example 1, and the BN loaded electrocatalytic membrane is prepared by referring to the method of step 1.3 in Example 1; in step two, replace the "CoMo@BN loaded electrocatalytic membrane" in Example 1 with "BN loaded electrocatalytic membrane". In this embodiment, the final tetracycline degradation curve is shown in Figure 5 .

[0064] Comparative Example 2

[0065] This comparative example gives a method for activating persulfate based on flow-through electrocatalytic membrane for degrading organic pollutants, which is basically the same as Example 1, the only difference is that in step one, the prepared is Mo@BN loaded electrocatalytic membrane, step 1.1 preparation of BN is consistent with Example 1; in step 1.2, the raw material cobalt chloride hexahydrate is omitted, and Mo@BN is prepared by referring to step 1.2 in Example 1; the Mo@BN loaded electrocatalytic membrane is prepared by referring to the method of step 1.3 in Example 1; in step two, replace the "CoMo@BN loaded electrocatalytic membrane" in Example 1 with "Mo@BN loaded electrocatalytic membrane". In this embodiment, the final tetracycline degradation curve is shown in Figure 5 .

[0066] Comparative Example 3

[0067] This comparative example gives a method for activating persulfate based on flow-through electrocatalytic membrane for degrading organic pollutants, which is basically the same as Example 1, the only difference is that in step one, the prepared is Co@BN loaded electrocatalytic membrane, step 1.1 preparation of BN is consistent with Example 1; in step 1.2, the raw material ammonium heptamolybdate tetrahydrate is omitted, and Co@BN is prepared by referring to step 1.2 in Example 1; the Co@BN loaded electrocatalytic membrane is prepared by referring to the method of step 1.3 in Example 1; in step two, replace the "CoMo@BN loaded electrocatalytic membrane" in Example 1 with "Co@BN loaded electrocatalytic membrane". In this embodiment, the final tetracycline degradation curve is shown in Figure 5 .

[0068] Example 2

[0069] This example gives a method for activating persulfate based on flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants. In step two of the method, "a constant direct current voltage of 1 V is applied", and other processes remain consistent with Example 1. In this example, the final tetracycline degradation curve is shown as Figure 6 .

[0070] Example 3

[0071] This example gives a method for activating persulfate based on flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants. In step two of the method, "a constant direct current voltage of 2 V is applied", and other processes remain consistent with Example 1. In this example, the final tetracycline degradation curve is shown as Figure 6 .

[0072] Comparative Example 4

[0073] This comparative example gives a method for activating persulfate based on flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants. In step two of the method, "no constant direct current voltage is applied (open circuit state)", and other processes remain consistent with Example 1. In this example, the final tetracycline degradation curve is shown as Figure 6 .

[0074] Example 4

[0075] This example gives a method for activating persulfate based on flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants. In step two of the method, "the concentration of persulfate in the reaction system is 0.3 mM", and other processes remain consistent with Example 1. In this example, the final tetracycline degradation curve is shown as Figure 7 .

[0076] Example 5

[0077] This example gives a method for activating persulfate based on flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants. In step two of the method, "the concentration of persulfate in the reaction system is 0.5 mM", and other processes remain consistent with Example 1. In this example, the final tetracycline degradation curve is shown as Figure 7 .

[0078] Example 6

[0079] This example gives a method for activating persulfate based on flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants. In step two of the method, "the concentration of persulfate in the reaction system is 0.1 mM", and other processes remain consistent with Example 1. In this example, the final tetracycline degradation curve is shown as Figure 7 .

[0080] Comparative Example 5

[0081] The present comparative example gives a method for degrading organic pollutants based on flow-through electrocatalytic membrane, and the method step two is "the reaction system does not contain persulfate", and other processes remain consistent with example 1. In this example, the final tetracycline degradation curve is shown as Figure 7 .

[0082] Example 7

[0083] The present example gives a method for activating persulfate based on flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants, and the method step two is "use peristaltic pump to pump the reaction system into the reactor at a flow rate of 7 mL·min -1 ", and other processes remain consistent with example 1. In this example, the final tetracycline degradation curve is shown as Figure 8 .

[0084] Example 8

[0085] The present example gives a method for activating persulfate based on flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants, and the method step two is "use peristaltic pump to pump the reaction system into the reactor at a flow rate of 3 mL·min -1 ", and other processes remain consistent with example 1. In this example, the final tetracycline degradation curve is shown as Figure 8 .

[0086] Example 9

[0087] The present example gives a method for activating persulfate based on flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants, and the method step two is "use peristaltic pump to pump the reaction system into the reactor at a flow rate of 1 mL·min -1 ", and other processes remain consistent with example 1. In this example, the final tetracycline degradation curve is shown as Figure 8 .

[0088] Example 10

[0089] The present example gives a method for activating persulfate based on flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants, and the method step two is "use dilute H2SO4 to adjust the pH value of the reaction system to 3", and other processes remain consistent with example 1. In this example, the final tetracycline degradation curve is shown as Figure 9 .

[0090] Example 11

[0091] The embodiment gives a method for activating persulfate based on flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants. In step two, the pH value of the reaction system is adjusted to 5 by using dilute H2SO4. The other processes are consistent with example 1. In this embodiment, the final tetracycline degradation curve is shown in Figure 9 .

[0092] Example 12

[0093] The embodiment gives a method for activating persulfate based on flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants. In step two, the pH value of the reaction system is adjusted to 9 by using NaOH. The other processes are consistent with example 1. In this embodiment, the final tetracycline degradation curve is shown in Figure 9 .

[0094] Example 13

[0095] The embodiment gives a method for activating persulfate based on flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants. In step two, the treated solution is not pumped back to the original container to form a continuous flow-through reaction device, and the reaction time is 1080 min. The other processes are consistent with example 1.

[0096] In this embodiment, during the degradation reaction, the tetracycline concentration in the reaction system is tested every 60 min at the water outlet. After the completion of the degradation reaction, the reaction time is taken as the horizontal coordinate, and the degradation efficiency of tetracycline before and after the degradation of the reaction system is taken as the vertical coordinate, and a column chart is drawn, as shown in Figure 10 .

[0097] Example 14

[0098] The embodiment gives a method for activating persulfate based on flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants. In step two, the pollutants are terramycin, aureomycin, rhodamine B, methylene blue, methyl orange, and orange G. The other processes are consistent with example 1.

[0099] In this embodiment, after the completion of the degradation reaction, the pollutant concentration in the reaction system is tested, the degradation efficiency of the pollutant before and after the degradation of the reaction system is calculated, and a column chart is drawn, as shown in Figure 11 .

[0100] Example 15

[0101] The embodiment gives a method for activating persulfate based on flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants. In step two, the reaction system of step two is stirred by using a magnetic stirrer at a speed of 250 rpm, and the reaction system is pumped at a flow rate of 5 mL·min-1 The flow rate of the solution was pumped into the reactor, and other processes were consistent with Example 1.

[0102] In this example, the tetracycline concentration and persulfate content in the reaction system were tested at fixed time points during the degradation reaction. After the completion of the degradation reaction, a curve was plotted with the reaction time as the horizontal coordinate and the ratio of the tetracycline concentration before and after the degradation of the reaction system as the vertical coordinate, as shown in FIG. Figure 12 (a); and the first-order reaction rate constant k calculated is shown in FIG. Figure 12 (b). Figure 12

[0103] Comparative Example 6

[0104] This comparative example gives a method for electro-activated persulfate degradation of organic pollutants, which specifically comprises the following steps:

[0105] Step 1, preparation of a double-metal nanoparticle-loaded boron nitride (CoMo@BN) electrocatalytic film, which is consistent with Example 1;

[0106] Step 2, degradation reaction:

[0107] The persulfate was added to 100 mL of tetracycline organic wastewater containing 50 mM Na2SO4 (electrolyte) and 20 mg·L -1 The concentration of persulfate in the reaction system was 0.4 mM, and the natural pH value of the reaction system was 7. The degradation process was carried out in a 200 mL beaker containing the reaction system. The CoMo@BN-loaded electrocatalytic film was used as the working electrode, and the platinum wire ring was used as the counter electrode. The two electrodes were vertically placed in the solution, and the electrode distance was 2 cm. A constant direct current voltage of 1.5 V was applied. The reaction system was stirred at a speed of 250 rpm using a magnetic stirrer at room temperature of 25°C, and the reaction time was 60 min.

[0108] In this comparative example, the tetracycline concentration and persulfate content in the reaction system were tested at fixed time points during the degradation reaction. After the completion of the degradation reaction, a curve was plotted with the reaction time as the horizontal coordinate and the ratio of the tetracycline concentration before and after the degradation of the reaction system as the vertical coordinate, as shown in FIG. Figure 12 (a); and the first-order reaction rate constant k calculated is shown in FIG. Figure 12 (b). Figure 13

[0109] Example 16​​

[0110] The embodiment gives a method for activating persulfate based on flow-through electrocatalytic membrane to improve the degradation performance of organic pollutants. In step two of the method, the "reaction time is 180 min", and other processes remain consistent with example 15.

[0111] In the embodiment, the total organic carbon (TOC) content in the reaction system is sampled and tested at fixed time during the degradation reaction. After the completion of the degradation reaction, the reaction time is taken as the horizontal coordinate, and the removal efficiency of TOC before and after the degradation of the reaction system is taken as the vertical coordinate, and a curve graph is drawn as shown in Figure 14 .

[0112] Comparative Example 7

[0113] The comparative example gives a method for degrading organic pollutants by electro-activated persulfate. In step two of the method, the "reaction time is 180 min", and other processes remain consistent with comparative example 6.

[0114] In the comparative example, the total organic carbon (TOC) content in the reaction system is sampled and tested at fixed time during the degradation reaction. After the completion of the degradation reaction, the reaction time is taken as the horizontal coordinate, and the removal efficiency of TOC before and after the degradation of the reaction system is taken as the vertical coordinate, and a curve graph is drawn as shown in Figure 14 .

[0115] From the above examples and comparative examples, the following conclusions are obtained:

[0116] (A) From comparative examples 1 to 3 and example 1, it can be seen that:

[0117] From Figure 5 , it can be seen that when the bimetallic nanoparticles are loaded on boron nitride (CoMo@BN), the degradation rate of tetracycline by the electrocatalytic membrane activated persulfate prepared reaches 100% within less than 50 min of reaction time. When no metal or single metal nanoparticles are loaded on boron nitride (BN, Mo@BN and Co@BN), the degradation rates of tetracycline by the electrocatalytic membrane activated persulfate prepared are 60.05%, 78.36% and 92.08% respectively within 60 min of reaction time. The results show that transition metals Co and Mo nanoparticles can improve the catalytic efficiency of persulfate, and the synergistic effect of bimetallic can further improve the catalytic efficiency, thereby efficiently degrading tetracycline.

[0118] (B) From comparative example 4 and examples 1 to 3, it can be seen that:

[0119] From Figure 6It can be seen that when no voltage is applied to the CoMo@BN electrocatalytic film, 1V, 1.5V and 2V voltage is applied, the degradation rate of tetracycline is 82.95%, 88.93%, 100% and 98.13% respectively. From the results, it can be seen that as the applied voltage value increases, the degradation efficiency of tetracycline gradually improves, however, when the voltage reaches 1.5V, continuing to increase the voltage size has an adverse effect on the degradation efficiency, so 1.5V is the best voltage value.

[0120] (C) It can be seen from Comparative Example 5, Example 1 and Examples 4-6 that:

[0121] From Figure 7 It can be seen that when the concentration of persulfate in the reaction system is 0.3mM, 0.4mM and 0.5mM respectively, the degradation efficiency of tetracycline is 94.03%, 100% and 98.93% respectively after 60min of reaction, and the degradation efficiency is only 54.05% and 78.02% without adding or only adding 0.1mM persulfate. From the results, it can be seen that when the CoMo@BN loaded electrocatalytic film is used as an activator, adding higher concentration of persulfate within a certain range will improve the degradation efficiency of pollutants, but too high concentration will not be conducive to the degradation of pollutants.

[0122] (D) It can be seen from Example 1 and Examples 7-9 that:

[0123] From Figure 8 It can be seen that when the flow rate of the reaction system solution pumped into the reactor by the peristaltic pump is 1mL·min -1 , 3mL·min -1 , 5mL·min -1 and 7mL·min -1 , the degradation efficiency of tetracycline is 63.24%, 86.24%, 100% and 100% respectively. The results show that as the flow rate increases, the degradation efficiency of tetracycline also increases, and since energy consumption is considered, 5mL·min -1 is determined as the best flow rate.

[0124] (E) It can be seen from Example 1 and Examples 10-12 that:

[0125] From Figure 9 It can be seen that when the pH is 3, 5, 7 and 9 respectively, the degradation efficiency of tetracycline is 98.05%, 97.16%, 100% and 97.71% respectively. The results show that the degradation rate of tetracycline in the reaction system is more than 97% in a wide pH value range, indicating that the reaction system can adapt to a wide range of pH.

[0126] (F) It can be seen from Example 13 that:

[0127] From Figure 10It can be seen that when the CoMo@BN loaded electrocatalytic membrane is used as a persulfate activator, the degradation efficiency of tetracycline in the continuous flow mode is not less than 93% after 1080 min of operation, indicating that the reaction system has good running stability.

[0128] (G) It can be seen from Example 14 that:

[0129] It can be seen from Figure 11 that when the CoMo@BN loaded electrocatalytic membrane is used as a persulfate activator, the degradation efficiencies of oxytetracycline (OTC), chlortetracycline (CTC), rhodamine B (RhB), methylene blue (MB), methyl orange (MO) and orange G (OG) are 94.63%, 96.42%, 100%, 100%, 99.84% and 100% respectively within 60 min in the flow mode. The results show that the degradation rates of the above pollutants in the reaction system are all more than 94% when the CoMo@BN loaded electrocatalytic membrane is used as a persulfate activator, indicating that the electrocatalytic membrane is suitable for the degradation of a wide variety of pollutants.

[0130] (H) It can be seen from Comparative Example 6 and Example 15 that:

[0131] It can be seen from Figure 12 (a) and 12(b) that when the CoMo@BN loaded electrocatalytic membrane is used as a persulfate activator, the degradation efficiency of tetracycline is 100% within 60 min in the flow mode, and the first-order rate constant k is 0.159 min -1 . The degradation efficiency of tetracycline is only 85.71% in the traditional degradation mode, and the first-order rate constant k is 0.089 min -1 . The results show that the flow mode constructed by the reactor and reaction device in Figure 4 significantly improves the catalytic efficiency of persulfate, accelerates the degradation rate of tetracycline, and increases the degradation efficiency to 100%.

[0132] It can be seen from Figure 13 that when the CoMo@BN loaded electrocatalytic membrane is used as a persulfate activator, the utilization rate of persulfate in the reaction system continues to increase in the flow mode and the traditional degradation mode with the extension of reaction time. The utilization rate of persulfate in the flow mode is always higher than that in the traditional degradation mode. The utilization rate of persulfate in the flow mode is 93.69% within 60 min, while the value in the traditional degradation mode is 73.89%. The results show that the CoMo@BN loaded electrocatalytic membrane is a high-efficiency activator of persulfate, and compared with the traditional degradation mode, the flow mode constructed by the reactor and reaction device in Figure 4 can significantly improve the utilization rate of persulfate.

[0133] (I) It can be seen from Comparative Example 7 and Example 16 that:

[0134] As can be seen from Figure 14 , when the CoMo@BN loaded electrocatalytic film is used as a persulfate activator, the TOC removal rate of the reaction system in the flow-through mode is always higher than that in the traditional degradation mode. The TOC removal rate of the reaction system in the flow-through mode within 180 min is 77.51%, but that in the traditional degradation mode is only 54.36%. The results show that the flow-through mode constructed by the reactor and reaction device in Figure 4 has a higher TOC removal rate of the reaction system and shows a higher removal effect than the traditional degradation mode.

[0135] In summary, the results of (A) to (E) above are as follows: The CoMo@BN loaded electrocatalytic film can be used as a high-efficiency activator of persulfate to degrade tetracycline. The finally determined optimal reaction system of the present application is that the concentration of tetracycline in the reaction system is 20 mg·L -1 , the concentration of persulfate is 0.4 mM, the applied anode voltage is 1.5 V, the rate of the peristaltic pump pumping the solution into the reactor is 5 mL·min -1 , and the applicable pH value range is 3-9.

[0136] In summary, the results of (F) to (G) above are as follows: The CoMo@BN loaded electrocatalytic film as a persulfate activator has good running stability and is suitable for the degradation of a wide range of different types of pollutants by using the flow-through mode constructed by the reactor and reaction device in Figure 4 .

[0137] In summary, the results of (H) to (I) above are as follows: When the CoMo@BN loaded electrocatalytic film is used as a persulfate activator, the flow-through mode constructed by the reactor and reaction device in Figure 4 significantly improves the degradation efficiency and rate of pollutants, the TOC removal rate, and the utilization rate of persulfate compared with the traditional degradation mode.

Claims

1. A method for activating persulfate for enhanced degradation of organic pollutants based on flow-through electrocatalytic membrane, characterized in that, The flow-through electro-catalytic membrane is a boron nitride electro-catalytic membrane loaded with bimetallic nanoparticles, and the method specifically comprises the following steps: Step one, preparation of a boron nitride electro-catalytic membrane loaded with bimetallic nanoparticles; Step 1.1, preparation of boron nitride: Disperse boric acid and melamine in deionized water, then place in a constant-temperature high-pressure reactor for reaction, dry the obtained product, then grind, and then pyrolyze to obtain boron nitride BN; Step 1.2, preparation of boron nitride loaded with bimetallic nanoparticles: Disperse the BN prepared in step 1.1 in ethanol, and simultaneously add a cobalt chloride hexahydrate and ammonium heptamolybdate tetrahydrate aqueous solution, then add a sodium borohydride solution after mixing, and then centrifuge, wash and dry in sequence after stirring, and then pyrolyze to obtain boron nitride loaded with bimetallic nanoparticles CoMo@BN; Step 1.3, preparation of an electro-catalytic membrane loaded with CoMo@BN: Disperse the CoMo@BN prepared in step 1.2 in ethanol, add conductive acetylene black and a polyvinylidene fluoride solution, uniformly mix after ultrasonic mixing, and then load onto a nylon membrane by a negative pressure filtration method, and obtain an electro-catalytic membrane loaded with CoMo@BN after drying; Step two, flow-through degradation reaction: add persulfate to organic wastewater containing electrolyte and pollutants to form a reaction system; the degradation process is carried out in a flow-through electro-activated persulfate reactor under a constant direct current voltage dead-end filtration, the electro-catalytic membrane loaded with CoMo@BN is used as a working electrode, a platinum wire ring is used as a counter electrode, the reaction system is pumped into the reactor at a constant flow rate by a peristaltic pump to realize a flow-through pollutant degradation process, and the reaction time is 60-180 min.

2. A method for enhancing the degradation of organic pollutants using activated persulfate based on flow-through electrocatalytic membrane according to claim 1, characterized in that, The mass ratio between boric acid and melamine in step 1.1 is 1:1; the temperature in the high-pressure reactor is 105°C, the boric acid concentration is 1.2 M, and the reaction time is 3 h; the pyrolysis process is: heating at a rate of 5°C·min -1 to 900-1100°C under a nitrogen atmosphere, and continuing the pyrolysis at this temperature for 2-4 h.

3. A method for activation of persulfate for enhanced degradation of organic pollutants based on flow-through electrocatalytic membrane as claimed in claim 1, wherein, In Step 1.2, the ratio between the mass of BN and the volume of ethanol was 10 g: 1 L; the molar ratio of the cobalt chloride hexahydrate and ammonium heptamolybdate tetrahydrate was 8: 1, and the concentration of cobalt chloride hexahydrate was 0.025 M; the concentration of sodium borohydride solution was 0.1 M; and the pyrolysis process was: heating at a rate of 5 °C·min -1 to 400 °C under a nitrogen atmosphere and maintaining for 2-4 h.

4. A method for enhancing the degradation of organic pollutants using activated persulfate based on flow-through electrocatalytic membrane according to claim 1, characterized in that, In step 1.3, the ratio between the mass of CoMo@BN and the volume of ethanol is 15 g:1 L, the mass fraction of the polyvinylidene fluoride is 3-6 wt%, and the mass fraction of the conductive acetylene black is 10-15 wt%.

5. A method for activation of persulfate for enhanced degradation of organic pollutants based on flow-through electrocatalytic membrane as claimed in claim 1, wherein, In step two, the pollutants are tetracycline, terramycin, aureomycin, rhodamine B, methylene blue, methyl orange, orange G; the concentration of the pollutants is 20 mg·L -1 .

6. A method for enhancing the degradation of organic pollutants using activated persulfate based on flow-through electrocatalytic membrane according to claim 1, characterized in that, In step two, the electrolyte is sodium sulfate; and the concentration of the electrolyte is 50 mM.

7. A method for activating persulfate for enhanced degradation of organic pollutants based on flow-through electrocatalytic membrane according to claim 1, characterized in that, In step two, the concentration of the persulfate is 0.1-0.5 mM.

8. A method for activating persulfate for enhanced degradation of organic pollutants based on flow-through electrocatalytic membrane according to claim 1, characterized in that, In step two, the pH value of the reaction system is 3-9.

9. A method for activating persulfate for enhanced degradation of organic pollutants based on flow-through electrocatalytic membrane according to claim 1, characterized in that, In step two, the direct current voltage is 1-2 V; the flow rate is 1-7 mL·min -1 .

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