Preparation of a composite electrode and its application in treatment of wastewater by coupling dielectric barrier plasma discharge

Abstract

The application discloses a preparation of a composite electrode and application of the composite electrode in treatment of wastewater by coupling dielectric barrier plasma discharge, and is characterized in that: a conductive carbon cloth is used as a substrate, a non-metallic compound g-C3N4 and a metallic compound CuS are in-situ loaded on the carbon cloth by a high-temperature calcination method and a hydrothermal method, and silver nanoparticles are doped in a precursor electrode by a soaking-reduction method, so that the photoelectric response performance of the composite electrode is improved; the prepared composite electrode is used as a reaction electrode and is placed in a reaction container, wastewater to be treated is immersed in the composite electrode, then the reaction container containing the composite electrode and the wastewater to be treated is placed in a dielectric barrier discharge area of a dielectric barrier discharge reactor, a discharge voltage is adjusted, and reaction is carried out. The prepared composite electrode is combined with the dielectric barrier plasma, and the silver-doped non-metallic compound / metallic compound has good adaptability and degradation effect on sterilization of bacteria and degradation of antibiotics in the plasma discharge system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pollutant degradation, and in particular to a preparation method of a composite electrode loaded with silver-doped non-metallic compound graphite carbon nitride (g-C3N4) and silver-doped metallic compound copper sulfide (CuS) on a carbon cloth (CC) substrate and application of the composite electrode coupled with dielectric barrier plasma discharge in bacterial disinfection and tetracycline degradation. BACKGROUND

[0002] Nowadays, the safety of drinking water has become a global public health issue of great concern. Waterborne diseases caused by pathogenic microorganisms are increasing, and water bodies contaminated by pathogenic microorganisms contain a large number of pathogenic bacteria, viruses, etc. Some pathogenic microorganisms (Escherichia coli, Enterococcus faecalis, Vibrio cholerae, etc.) can survive and reproduce in the water environment and eventually spread widely through the water environment, leading to large-scale outbreaks of epidemics and causing great threats to the ecological system and human health.

[0003] The persistence of antibiotics in living organisms can cause biological accumulation. Residual antibiotics in the human body can disrupt the balance of the normal flora system and even cause damage to organs such as the kidneys and liver, and trigger allergic reactions and carcinogenesis and teratogenesis. Antibiotics in the environment can induce the emergence of drug-resistant bacteria and transfer antibiotic resistance genes between the environment, animals and humans, posing a threat to human and animal health.

[0004] The removal of antibiotics and bacterial disinfection from contaminated water is extremely important for drinking water safety. DBD plasma technology has been widely used in new fields such as oxidation-reduction, sterilization and disinfection, material preparation and energy production, and has achieved certain results. DBD generates a large number of active substances (·OH, O3, O2· - , etc.) through discharge, which is an effective means of degrading organic pollutants and destroying microbial cell structures.

[0005] For example, the patent specification with publication number CN207079039U discloses a kind of plasma water disinfection device. Among them, the device is made of water inlet area, disinfection area and water storage area, high activity particle is generated by installing plasma generating device in disinfection area, and high-efficiency water disinfection is realized by using the dual action of active substance and strong electric field. The patent specification with publication number CN 110201667A discloses a kind of Ag / GO photocatalytic material for sterilization. Among them, graphite powder is used to prepare graphene by Hummers method;A certain amount of nanosheet graphene is uniformly mixed with a certain amount of AgNO3 powder by mortar grinding;The mixture is placed in a tube furnace and calcined at 500 DEG C under nitrogen atmosphere for 6h, and Ag / GO is obtained after natural cooling. The natural bactericidal effect of nano-silver is used to explore the antibacterial and disinfection performance in water environment. But generally, nano-silver is mainly in powder form, and nano-silver powder is not easy to recycle, and potential biological toxicity also causes some concerns. SUMMARY

[0006] The present application provides a kind of silver-doped non-metallic compound / metallic compound composite electrode for bacterial disinfection and degradation of antibiotic and its preparation method and application, carbon cloth can firmly fix catalyst on carbon fiber, simplify the process of material recycling. In addition, carbon cloth plays an important role in the separation efficiency of electric charge and the durability of material in the reaction due to its excellent conductivity and stability. By loading silver-doped non-metallic compound / metallic compound on carbon cloth substrate, the application of different composite electrode materials in bacterial disinfection and antibiotic degradation in dielectric barrier plasma discharge system is explored.

[0007] A method for treating E. coli or / and tetracycline in wastewater by composite electrode coupled dielectric barrier plasma discharge, comprising:

[0008] The composite electrode is placed as a reaction electrode in a reaction vessel, the composite electrode is immersed in the wastewater to be treated, then the reaction vessel containing the composite electrode and the wastewater to be treated is placed in the dielectric barrier discharge area of the dielectric barrier discharge reactor, the discharge voltage is adjusted, and the reaction is carried out.

[0009] The composite electrode is silver-doped non-metallic compound graphite carbon nitride composite carbon cloth electrode (Ag / g-C3N4 / CC electrode) or silver-doped metallic compound copper sulfide composite carbon cloth electrode (Ag / CuS / CC electrode).

[0010] The preparation process of the Ag / g-C3N4 / CC electrode includes:

[0011] High-temperature thermal polymerization: carbon cloth electrode (CC) is coated in melamine, and g-C3N4 / CC electrode is obtained by calcination treatment.

[0012] Soaking-reduction: the g-C3N4 / CC electrode was immersed in AgNO3 suspension, and then was taken out and dried, and then was immersed in sodium borohydride solution to obtain Ag / g-C3N4 / CC electrode;

[0013] The preparation process of the Ag / CuS / CC electrode comprises:

[0014] Hydrothermal method: the carbon cloth CC electrode was placed in a mixed solution A of copper sulfate pentahydrate and thioacetamide, and a CuS / CC electrode was obtained by hydrothermal method;

[0015] Soaking-reduction: the CuS / CC electrode was immersed in a mixed aqueous solution B of AgNO3 and glucose, and an Ag / CuS / CC electrode was obtained by reaction.

[0016] In the preparation of the composite electrode of the application, the non-metallic compound g-C3N4 is loaded on the carbon cloth electrode by high-temperature thermal polymerization. After high-temperature thermal polymerization, a layer of granular g-C3N4 is attached to the carbon fiber, and these particles are distributed closely and uniformly, which is conducive to light absorption and charge separation. The metallic compound CuS is loaded on the carbon cloth electrode by hydrothermal method. The rice-shaped CuS nanoparticles have a high specific surface area, which is conducive to enhancing the light absorption capacity. Finally, Ag nanoparticles are compounded in the electrode by soaking-reduction method. Since Ag has excellent electrical conductivity and better morphology, the composite of g-C3N4, CuS further improves the photoelectric performance of the electrode. The obtained composite electrode is coupled with a dielectric barrier plasma discharge device for treating Escherichia coli and tetracycline in wastewater, and has a significant purification effect. Compared with the g-C3N4 / CC and CuS / CC electrodes alone, the silver-doped composite electrode has higher light response capacity, smaller impedance and better stability.

[0017] The following also provides several optional modes, but not as an additional limitation to the above overall scheme, just a further supplement or preferred, without technical or logical contradiction, each optional mode can be combined with the above overall scheme, and can also be combined between multiple optional modes.

[0018] Optionally, the carbon cloth used in the application is a commercially available carbon cloth (CC) electrode with high light transmittance, low resistance and high conductivity.

[0019] Optionally, to remove surface impurities, a brand new CC electrode was placed in acetone, ethanol and distilled water respectively, and was ultrasonically washed and dried after washing, ready for the next experiment.

[0020] In the high-temperature thermal polymerization step, the CC electrode is wrapped in melamine, and it is appropriate to completely wrap the CC electrode with melamine. Alternatively, half the amount of melamine is first laid flat on the bottom of a square quartz dish (100 mm x 40 mm x 15 mm) and compacted; then the pretreated CC electrode is laid flat on the melamine, and an equal amount of melamine is weighed and used to cover and wrap the CC electrode; the treated electrode is moved into a tube furnace for calcination.

[0021] In the preparation process of the Ag / g-C3N4 / CC electrode:

[0022] Alternatively, the calcination temperature is 500-600°C, and the calcination time is 3-5 h.

[0023] Alternatively, the mass of the single layer of melamine is controlled to be 0.75-1.5 g, and the cutting size of the CC electrode is 3 x 6 cm.

[0024] Further, the mass of the single layer of melamine is controlled to be 1.25 g, the cutting size of the CC electrode is 3 x 6 cm, the tube furnace calcination temperature is controlled to be 550°C, and the reaction time is controlled to be 4 h.

[0025] In the step of preparing the Ag / g-C3N4 / CC electrode, the prepared g-C3N4 / CC electrode is immersed in an AgNO3 suspension, the g-C3N4 / CC with Ag precursor is immersed in a sodium borohydride solution, and the Ag / g-C3N4 / CC electrode is obtained by immersion-reduction.

[0026] Alternatively, the concentration of AgNO3 is 5-20 g / L, the g-C3N4 / CC electrode immersion time is 5-15 min, the concentration of the sodium borohydride solution is 0.07-0.08 g / 20 ml, and the reduction time of the g-C3N4 / CC with Ag precursor in the sodium borohydride solution is 1-2 h.

[0027] Further, the concentration of AgNO3 is 10 g / L, the g-C3N4 / CC electrode immersion time is 10 min, the concentration of the sodium borohydride solution is 0.076 g / 20 ml, and the reduction time of the g-C3N4 / CC with Ag precursor in the sodium borohydride solution is 1.5 h.

[0028] Alternatively, after immersion in the AgNO3 suspension, the sample is placed in a 70°C oven and dried for 10 min.

[0029] In the preparation process of the Ag / CuS / CC electrode:

[0030] In the hydrothermal method step, a certain mass of copper sulfate pentahydrate and a certain mass of thioacetamide are dissolved in a mixed solution of distilled water and ethylene glycol. The treated CC electrode is immersed in the mixed solution and moved to a polytetrafluoroethylene-lined hydrothermal kettle for hydrothermal reaction.

[0031] Optionally, the concentration of copper sulfate pentahydrate in the mixed solution A is 1.5g-2g / 100ml, and the concentration of thioacetamide is 1.5g-2g / 100ml. Further, the mass of copper sulfate pentahydrate is controlled at 1.87g, the mass of thioacetamide is controlled at 1.69g, the volume of distilled water is controlled at 39ml, and the volume of ethylene glycol is controlled at 81ml.

[0032] Optionally, the temperature of the hydrothermal treatment is 150-200℃, and the time of the hydrothermal treatment is 2-8h. Further, the temperature of the hydrothermal reaction is 180℃, and the time of the reaction is 4h.

[0033] Optionally, the concentration ratio of AgNO3 and glucose in the mixed solution B is 1-3:1, and the concentration of glucose is 10mM-30mM.

[0034] Optionally, after the CuS / CC electrode is immersed in the mixed solution B, the CuS / CC electrode is sequentially subjected to ultrasonic treatment, standing aging, and washing and drying treatment, the time of the ultrasonic treatment is 10min-50min, and the time of the standing aging is 2-8h.

[0035] Further, the concentration ratio of AgNO3 and glucose in the mixed aqueous solution is controlled at 2:1, the concentration of glucose is 22.5mM, the volume of the mixed solution is controlled at 15ml, the time of the ultrasonic treatment is controlled at 30min, and the time of the standing aging is controlled at 6h.

[0036] Bactericidal and antibiotic degradation:

[0037] Optionally, the concentration of the living Escherichia coli in the wastewater to be treated is 0.5-1.5×10 7 CFU / mL, and the concentration of tetracycline is 15-25mg / L.

[0038] Further, the concentration of the living Escherichia coli in the wastewater to be treated is 1.5×10 7 CFU / mL, and the concentration of tetracycline is 20mg / L.

[0039] Optionally, the discharge voltage is adjusted to be 20-40V, the discharge gap is adjusted to be 2-4mm, and the reaction time in the dielectric barrier discharge reactor is 5-40min.

[0040] Further, the discharge voltage is adjusted to be 25V, the discharge gap is adjusted to be 3mm, and the reaction time in the dielectric barrier discharge reactor is 30min.

[0041] Optionally, the wastewater to be treated can be one of pharmaceutical wastewater, aquaculture wastewater, tetracycline solution (20 mg / L), amoxicillin solution (20 mg / L), and E. coli bacterial solution.

[0042] The application further provides a preparation method of the Ag / g-C3N4 / CC electrode, comprising the following steps:

[0043] The CC electrode is coated in melamine, and the g-C3N4 / CC electrode is obtained through calcination treatment;

[0044] The g-C3N4 / CC electrode is immersed in an AgNO3 suspension, and then taken out and dried, and then immersed in a sodium borohydride solution, so as to obtain the Ag / g-C3N4 / CC electrode.

[0045] The application further provides an Ag / g-C3N4 / CC electrode prepared by the preparation method.

[0046] The application further provides a preparation method of the Ag / CuS / CC electrode, comprising the following steps:

[0047] The carbon cloth CC electrode is placed in a mixed solution A of copper sulfate pentahydrate and thioacetamide, and the CuS / CC electrode is obtained through hydrothermal treatment;

[0048] The CuS / CC electrode is immersed in a mixed aqueous solution B of AgNO3 and glucose, so as to obtain the Ag / CuS / CC electrode.

[0049] The application further provides an Ag / CuS / CC electrode prepared by the preparation method.

[0050] The application further provides an application of the Ag / g-C3N4 / CC electrode or the Ag / CuS / CC electrode in degradation of pollutants contained in wastewater through coupling of dielectric barrier plasma discharge, wherein the pollutants are E. coli and / or tetracycline. The prepared composite electrode is combined with the dielectric barrier plasma, and the silver-doped nonmetal / metal compound has good adaptability and degradation effect on bacterial disinfection and antibiotic degradation in the plasma discharge system, which widens the thought of coupling of different catalytic materials and plasma discharge. Finally, the biocompatibility of the wastewater treated through coupling of the composite electrode material and plasma discharge is investigated, and the result shows that the water sample treated through the plasma has small biological toxicity, which is helpful to improve the biological compatibility of the actual wastewater.

[0051] Compared with the prior art, the application has at least one of the following advantages:

[0052] (1) In the present application, the silver-doped metal / non-metal compound composite is made by a simple process, with conductive CC as the substrate, silver and non-metallic compound graphite carbon nitride (g-C3N4) / metallic compound (CuS) composite strengthening the photoelectrocatalytic activity of the material, thereby improving the effect of bacterial disinfection and antibiotic degradation.

[0053] (2) The present application combines photocatalysis with dielectric barrier plasma, synergistically disinfects bacteria and degrades antibiotics, and achieves good degradation effect in a short time.

[0054] (3) In the present application, silver-doped non-metallic / metallic compounds have good adaptability and degradation effect in the plasma discharge system, which widens the thinking of coupling plasma discharge with catalytic materials.

[0055] (4) The sewage mixture in the present application can come from laboratory simulation and can also come from actual wastewater, which has strong practical significance.

[0056] (5) The present application is simple to operate, easy to prepare electrodes, easy to build devices, and has wide application scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0057] Fig. 1(a) and Fig. 1(b) are treatment result graphs in Example 1;

[0058] Figure 2 Fig. 2(a) and Fig. 2(b) are treatment result graphs in Example 2;

[0059] Figure 3 Fig. 3(a) and Fig. 3(b) are treatment result graphs in Example 3;

[0060] Figure 4 Fig. 4(a) and Fig. 4(b) are treatment result graphs in Example 4. DETAILED DESCRIPTION

[0061] The technical solutions of the present application will be described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0062] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing the specific embodiments and are not intended to limit the present application.

[0063] Example 1

[0064] The preparation method of the Ag / g-C3N4 / CC electrode of the embodiment and its application in sterilization specifically includes the following steps:

[0065] I. The preparation process of the g-C3N4 / CC electrode is as follows:

[0066] (1) Removal of impurities on the surface of the CC electrode: sequentially clean the CC with acetone, ethanol, and distilled water by ultrasonic cleaning.

[0067] (2) Dosage of melamine: weigh 1.25 g of melamine and lay it on the bottom of a square quartz dish (100 mm x 40 mm x 15 mm), and compact it; weigh an equal amount of melamine again for standby use.

[0068] (3) Preparation of g-C3N4 / CC: take the pretreated CC electrode and lay it on the melamine, weigh 1.25 g of melamine again to cover and wrap the CC electrode; move the treated electrode into a tube furnace for calcination at 550°C for 4 h to obtain the g-C3N4 / CC electrode.

[0069] II. The preparation process of the Ag / g-C3N4 / CC electrode is as follows:

[0070] (1) Preparation of the solution: weigh 0.1 g of AgNO3 in a beaker, add 10 ml of distilled water, stir to dissolve as AgNO3 solution; weigh 0.076 g of sodium borohydride in a beaker, add 20 ml of distilled water, and stir to form a sodium borohydride solution.

[0071] (2) Soaking: immerse the g-C3N4 / CC electrode prepared in the previous step in the AgNO3 solution for 10 min.

[0072] (3) Drying: take out the soaked electrode and place it in a 70°C oven for 10 min to obtain g-C3N4 / CC with Ag precursor.

[0073] (4) Soaking: soak the g-C3N4 / CC with Ag precursor in the sodium borohydride solution for 1.5 h.

[0074] (5) Drying: take out the soaked electrode and place it in a 70°C oven for 10 min to obtain the Ag / g-C3N4 / CC electrode.

[0075] III. Degradation of E. coli by Ag / g-C3N4 / CC electrode coupled with dielectric barrier plasma discharge:

[0076] (1) Take the E. coli liquid for activation, inoculate the E. coli into the liquid medium, and place it in a shaking incubator for 24 h; the shaking incubator parameters are: 120 rmp, 37°C.

[0077] (2) Prepare two 50ml centrifuge tubes, take 10ml of the prepared bacterial solution and centrifuge at 8000rmp for 5min; discard the supernatant of the centrifuged bacterial solution, and add 100ml of physiological saline to prepare the bacterial solution to be treated.

[0078] (3) Set up three control groups, respectively: Ag / g-C3N4 / CC electrode sterilization experiment without discharge; CC electrode sterilization experiment with discharge gap of 3mm and discharge voltage of 25V; and pure plasma discharge sterilization experiment with discharge gap of 3mm and discharge voltage of 25V.

[0079] (4) Ag / g-C3N4 / CC electrode coupled dielectric barrier plasma discharge sterilization experiment (i.e. experimental group): take 4 pieces of Ag / g-C3N4 / CC electrode (splicing size of 6x6cm) and 100ml of E. coli solution, and place them in a quartz reaction dish, and fix them under the dielectric barrier quartz glass plate in the dielectric barrier plasma reactor, so that the distance between the liquid surface and the upper quartz glass plate is controlled at 3mm; when the voltage is adjusted to 25V, blue-purple streamers are generated between the liquid surface and the upper plate (i.e. discharge gap), and the streamer phenomenon tends to be uniform and stable as the voltage rises; the discharge gap is 3mm and the discharge voltage is 25V.

[0080] (5) The discharge time is controlled at 30min, and the sampling is 5min / group, with a total of 6 groups.

[0081] (6) E. coli counting method: dilute the E. coli solution to ~1.5x10 7 , count using the dilution plate method, set up control groups, and each group corresponds to a dilution factor repeated three times.

[0082] (7) Seal the coated samples with sealing tape and place them in a constant temperature incubator for 24h.

[0083] The treatment results are shown in Figures 1(a) and 1(b). First, using Ag / g-C3N4 / CC electrode without the effect of plasma discharge at room temperature for E. coli disinfection, it can be observed that the sterilization efficiency is low (Ag / g-C3N4 / CC in Figure 1(a)). Pure plasma discharge has a certain improvement on E. coli disinfection, but it fails to achieve a sterilization efficiency of 99.99% within 30min (Without catalyst 25V in Figure 1(a)).

[0084] The present embodiment also examines the difference of single loading g-C3N4, Ag and g-C3N4, Ag loading sequence on sterilization effect, from Figure 1(a) can be seen that the sterilization efficiency of Ag and g-C3N4 two composite is significantly better than single loading, which shows that there is a synergistic effect between Ag and g-C3N4. At the same time, the loading sequence of Ag and g-C3N4 has a more obvious gap on the sterilization of E. coli, from the results in Figure 1(b) can be seen that the loading of g-C3N4 first and then loading Ag is reasonable (Ag / g-C3N4 / CC25V in Figure 1(b)), the sterilization effect is significantly better than loading Ag first and then loading g-C3N4, and the introduction of Ag / g-C3N4 / CC electrode coupled with plasma discharge has a significant improvement on the degradation of E. coli, and reaches 99.99% sterilization efficiency in 15 min, and finally realizes >5.5log10 CFU mL -1 of E. coli removal efficiency in 30 min.

[0085] Example 2

[0086] Degradation of tetracycline by Ag / g-C3N4 / CC electrode coupled with dielectric barrier plasma discharge:

[0087] (1) Take 4 pieces of Ag / g-C3N4 / CC electrode (prepared in Example 1, the size of the spliced electrode is 6x6cm) and 200ml tetracycline solution (10mg / 500ml) into the quartz reaction dish, and fix it in the dielectric barrier plasma reactor; when the voltage is adjusted to 25V, blue-purple streamer is generated between the liquid surface and the upper electrode plate (i.e. discharge gap), and the streamer phenomenon tends to be uniform and stable with the increase of voltage; the discharge gap is 3mm, and the discharge voltage is 30V.

[0088] (2) The discharge time is controlled at 30min, and the sampling is 5min / group, and a total of 6 groups are sampled.

[0089] (3) Detection of tetracycline: the change of TC concentration was determined by high performance liquid chromatograph (HPLC) equipped with C18 column (4.6x150mm, 5μm). The mobile phase was mixed by 0.01M oxalic acid solution and methanol (v:v=53:47), the flow rate was 0.6ml / min, and the ultraviolet detector was adjusted to 355nm.

[0090] The results are as follows Figure 2As shown, without electrode, the DBD discharge reaction effect is low, and the removal efficiency of TC is only 58.68%. This is because the energy utilization efficiency of the system is low, and the oxidation and reduction free radicals in the solution not only have low yield, but also cannot be effectively separated. After adding the CC electrode, the removal performance is improved, which benefits from the good conductivity of CC and the small amount of adsorption of pollutants, so that the active substances can quickly react with the pollutants, reducing the loss caused by the migration of pollutants in the solution. After introducing g-C3N4 / CC, the oxidation and reduction performance of the DBD system is further improved, because the granular g-C3N4 improves the discharge condition of the system, and at the same time, the material surface electron-hole pairs (e - -h + ) are separated, which are used for reduction and oxidation reactions, respectively. With the loading of Ag, the degradation rate of TC is greatly improved from 61.73% to 91.63% at 15 min.

[0091] Example 3

[0092] The preparation method of the Ag / CuS / CC electrode of the present example specifically includes the following steps:

[0093] I. The preparation method of the CuS / CC electrode is as follows:

[0094] (1) Removal of impurities on the surface of the CC electrode: sequentially clean the CC with acetone, ethanol, and distilled water under ultrasonic.

[0095] (2) Preparation of CuS / CC: Dissolve 1.87 g of copper sulfate pentahydrate and 1.69 g of thioacetamide in 39 mL of water and 81 mL of ethylene glycol, respectively. After the solids in the solution are completely dissolved, add the ethylene glycol solution dropwise to the copper sulfate aqueous solution. During this process, the solution changes from blue to dark green rapidly, and finally to red-brown. Transfer a CC with a size of 3x3 cm and 20 mL of the above mixture to a polytetrafluoroethylene-lined autoclave, and hydrothermal at 180℃ for 6 h. After the reaction is completed, naturally cool to room temperature, and clean repeatedly with ethanol and distilled water for several times, and dry at 70℃.

[0096] II. The preparation method of the Ag / CuS / CC electrode is as follows:

[0097] (1) Preparation of solution: Prepare a mixed aqueous solution of AgNO3 and glucose (concentration ratio of 2:1) and stir for 5 min. The concentrations of AgNO3 and glucose are 45 mM and 22.5 mM, respectively.

[0098] (2) Soaking: Soak a piece of CuS / CC electrode (prepared in the previous step) in 15 mL of the above mixed aqueous solution of AgNO3 and glucose (concentration ratio of 2:1) for 30 min.

[0099] (3) Static aging: The static aging time is 6h

[0100] (4) Washing and drying: The electrode after soaking is taken out, the surface loose particles are washed with distilled water, and the final Ag / CuS / CC electrode is dried at 70°C.

[0101] III. Degradation of tetracycline by Ag / CuS / CC electrode coupled with dielectric barrier plasma discharge:

[0102] (1) 4 pieces of Ag / CuS / CC electrodes (prepared in Example 3, with a spliced size of 6x6 cm) and 200 ml of tetracycline solution (10 mg / 500 ml) are placed in a quartz reaction dish and fixed in a dielectric barrier plasma reactor. When the voltage is adjusted to 25 V, a blue-purple glow is generated between the liquid surface and the upper electrode plate (i.e. the discharge gap), and the glow phenomenon tends to be uniform and stable as the voltage rises. The discharge gap is 3 mm and the discharge voltage is 30 V.

[0103] (2) The discharge time is controlled at 30 min, and the sampling is 5 min / group, with a total of 6 groups.

[0104] (3) Detection of tetracycline: The concentration change of TC was determined by high performance liquid chromatography (HPLC) equipped with a C18 column (4.6x150 mm, 5 μm). The mobile phase was a mixture of 0.01 M oxalic acid solution and methanol (v:v=53:47), the flow rate was 0.6 ml / min, and the ultraviolet detector was adjusted to 355 nm.

[0105] The results are shown in Figure 3 It can be seen that without the addition of electrodes, the oxidation efficiency of TC is very low, only 58.68% within 30 min. After the addition of CC, the oxidation effect is improved due to the enhancement of electrical conductivity and the acceleration of charge transfer. When CuS is loaded on CC, the removal rate of TC is significantly improved, because the rice-shaped CuS nanoparticles are uniformly and orderly distributed on the carbon fiber, which effectively utilizes the input energy of DBD discharge and also undergoes photocatalytic reaction under ultraviolet-visible light irradiation. The addition of Ag further improves the pollutant treatment performance of CuS / CC electrode, and the removal rate of TC can reach 98.74% after 15 min of reaction. The doping modification of Ag has a positive effect on the electrical conductivity, light responsiveness and structure regulation of the material.

[0106] Example 4

[0107] Bactericidal effect of Ag / CuS / CC electrode coupled with dielectric barrier plasma discharge on aquaculture wastewater:

[0108] (1) Select 100 ml of actual wastewater sample (aquaculture wastewater).

[0109] (2) Take 4 pieces of Ag / CuS / CC electrodes (prepared in Example 3, splicing size of 6 x 6 cm) and 200 mL of tetracycline solution (10 mg / 500 ml) into a quartz reaction vessel, and fix it in the dielectric barrier plasma reactor; when the voltage is adjusted to 25 V, blue-purple streamers are generated between the liquid surface and the upper electrode plate (i.e. discharge gap), and the streamer phenomenon tends to be uniform and stable as the voltage rises; the discharge gap is 3 mm, the discharge voltage is 30 V, and the discharge time is controlled for 60 min.

[0110] (3) Take 1 ml of water sample at 0 min, 30 min and 60 min.

[0111] (4) Dilute and plate the obtained water samples, and repeat the plating three times for each corresponding dilution factor.

[0112] (5) Seal the plated samples with sealing tape and place them in a constant temperature incubator for 24 h. The results are shown in Table 1. Figure 4 As shown in Table 1, the number of bacteria in the initial aquaculture wastewater is very large, reaching 2.9 x 10 4 CFU / mL. After 30 min of discharge reaction, the number of surviving bacteria in the solution is significantly reduced, only 1.6 x 10 3 CFU / mL, removing nearly 95%. After 60 min of treatment, the sterilization efficiency has exceeded 99%, which reflects the excellent sterilization performance of the catalytic system.

[0113] The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as limiting the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are all within the scope of protection of the present application. Therefore, the protection scope of the present patent should be subject to the appended claims.

Claims

1. A method for treating E. coli or / and tetracycline in wastewater by a composite electrode coupled dielectric barrier plasma discharge, characterized in that, The application relates to a method for treating wastewater by using a composite electrode. The method comprises the following steps: placing a composite electrode as a reaction electrode in a reaction container, immersing the composite electrode in wastewater to be treated, placing the reaction container with the composite electrode and the wastewater to be treated in a dielectric barrier discharge region of a dielectric barrier discharge reactor, adjusting a discharge voltage, and performing a reaction. The composite electrode is an Ag / g-C3N4 / CC electrode or an Ag / CuS / CC electrode. The preparation process of the Ag / g-C3N4 / CC electrode comprises the following steps: The g-C3N4 / CC electrode is obtained by coating a carbon cloth (CC) electrode in melamine and performing calcination treatment. The Ag / g-C3N4 / CC electrode is obtained by immersing the g-C3N4 / CC electrode in an AgNO3 suspension, taking out and drying, and then immersing the g-C3N4 / CC electrode in a sodium borohydride solution. The preparation process of the Ag / CuS / CC electrode comprises the following steps: The CuS / CC electrode is obtained by placing a carbon cloth (CC) electrode in a mixed solution A of copper sulfate pentahydrate and thioacetamide and performing hydrothermal treatment. The Ag / CuS / CC electrode is obtained by immersing the CuS / CC electrode in a mixed aqueous solution B of AgNO3 and glucose.

2. The method of claim 1, wherein, The viable cell concentration of the E. coli in the wastewater to be treated is 0.5-1.5×10 7 CFU / mL; and the concentration of the tetracycline is 5-20 mg / L.

3. The method of claim 1, wherein, The discharge voltage is adjusted to be 20-40 V, the discharge gap is adjusted to be 2-4 mm, and the reaction time in the dielectric barrier discharge reactor is 5-40 min.

4. The method of claim 1, wherein, In the preparation process of the Ag / g-C3N4 / CC electrode: The calcination treatment is performed at a temperature of 500-600 DEG C for 3-5 h. The concentration of the AgNO3 suspension is 0.05-0.15 g / 10 ml, and the immersion time in the AgNO3 suspension is 8-12 min. The concentration of the sodium borohydride solution is 0.07-0.08 g / 20 ml, and the immersion time in the sodium borohydride solution is 1-2 h.

5. The method of claim 1, wherein, In the preparation process of the Ag / CuS / CC electrode: The concentration of the copper sulfate pentahydrate in the mixed solution A is 1.5 g-2 g / 100 ml, and the concentration of the thioacetamide is 1.5 g-2 g / 100 ml. The hydrothermal treatment is performed at a temperature of 150-200 DEG C for 2-8 h. The concentration ratio of AgNO3 to glucose in the mixed solution B is 1-3:1, and the concentration of the glucose is 10 mM-30 mM. After the CuS / CC electrode is immersed in the mixed solution B, the CuS / CC electrode is sequentially subjected to ultrasonic treatment, standing and aging, and washing and drying treatment, the ultrasonic treatment time is 10 min-50 min, and the standing and aging time is 2-8 h.

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