A water treatment method for removing refractory pesticides in water by an active electrode-mediated peroxide

Abstract

The present invention discloses a water treatment method for purifying refractory pesticides in water mediated by an active electrode. CuBi2O4 rich in oxygen defect structure is loaded on the surfaces of conductive glass, stainless steel, titanium metal, titanium anode coated with metal oxide, and diamond (BDD) electrochemical anode to increase the oxygen evolution potential of the anode, inhibit the oxygen evolution side reaction, adsorb peroxide on the surface, and activate the adsorbed peroxide through the free electrons in the CuBi2O4 structure and the carriers generated by the anode mediation, mediating the generation of active species including hydroxyl radicals, sulfate radicals, superoxide anion radicals, and singlet oxygen, completing the purification of refractory pesticides in pesticide wastewater, high-salt sewage, and runoff rainwater, and having broad application prospects in the field of advanced treatment of sewage and wastewater.

Description

Technical Field

[0001] The present invention relates to a water treatment method for purifying refractory pesticides in water by an active electrode-mediated peroxide, belonging to the field of water pollution control engineering. Background Art

[0002] Due to the large usage amount, high toxicity, and difficult biodegradability of pesticides, the purification of pesticide wastewater has become an environmental problem worthy of attention. By activating peroxides (hydrogen peroxide, persulfate) to generate strongly oxidizing reactive species, and undergoing interfacial redox reactions with organic pollutants to cause the degradation and even mineralization of organic substances, it is expected to be applied to the removal of refractory pesticides in pesticide wastewater. Metal-based catalysts have been widely used in the activation of peroxides due to their high selectivity, reusability, and strong controllability. During the activation of peroxides by metal-based catalysts, the low electron migration rate and slow M (n+1) / M n+ cycle become the rate-limiting step for activating peroxides. Therefore, strengthening the electron migration rate during the activation process, accelerating the M (n+1) / M n+ cycle, and improving the M n+ regeneration efficiency are important measures to improve the oxidation performance of peroxides.

[0003] An electric field can not only directly oxidize organic substances through the reaction with water oxidation reaction, but also activate peroxides to generate reactive species through electron transfer, realizing the synergistic activation of peroxides. On this basis, fixing the catalyst material on the electrode surface with the help of electrochemistry will promote the adsorption of peroxides on the catalyst surface, enhance the activation performance of peroxides and the electron transfer between interfaces. Through the free electrons in the catalyst structure and the carriers generated by anode mediation, the adsorbed peroxides are activated, the adsorbed peroxides are adsorbed on the surface, and reactive oxygen species are mediated to generate, which can realize the purification of refractory pesticides in pesticide wastewater, high-salt sewage, and runoff rainwater.

[0004] Patent CN 114853123 A prepared a composite anode material by loading metal hydroxide on nickel foam. The metal manganese nanodots on the material surface can accelerate the dissociation of water molecules, and the dissociated OH -One electron is lost on the anode surface to generate hydroxyl radicals, thereby achieving the removal of antibiotics in high-concentration wastewater, with the advantages of simple and stable implementation process, high activity, good reproducibility, etc. This patent mainly uses the indirect oxidation of the electrochemical anode to degrade organic pollutants, but the activation of peroxides that can generate multiple reactive species by electrochemistry has not been studied and applied. In addition, nickel foam is easily oxidized and corroded as a carrier in wastewater treatment, and the inevitable leakage during the water treatment process will cause secondary pollution to the environment. It can be seen that means such as optimizing the preparation of electrode materials, strengthening the electrocatalytic efficiency, and increasing the service life of electrode materials can effectively promote the practical application prospect of electrocatalysis in the field of water treatment.

[0005] Patent CN 112062225 A discloses a method for degrading organic matter by three-dimensional electro-activation of persulfate with sulfur-doped activated carbon particle electrodes. By adding sulfur-doped activated carbon particle electrodes to the wastewater to strengthen the purification performance of the anodic oxidation of the wastewater, it is proposed that there is a synergistic effect between three-dimensional electrocatalysis and sulfur-doped activated carbon in the process of activating persulfate, which can effectively improve the degradation rate of pollutants. However, the three-dimensional particle electrodes are small in size, difficult to separate after use, and not easy to recycle. Loading the catalyst on a conductive medium to prepare an electrode material can well solve the problem of catalyst recovery.

[0006] Patent CN114212860B deposits a certain amount of nanosilver particles on the surface of carbon paper through electrochemical deposition technology, with nanosilver-modified carbon paper as anode and stainless steel plate as cathode. In a two-chamber reactor separated by a proton membrane, sodium persulfate is activated by anode electricity, and the generated sulfate radicals, hydroxyl radicals and other active species are used to deeply oxidize and degrade organic pollutants in wastewater, which can improve the activation efficiency of persulfate and the degradation efficiency of pollutants, and achieve the purpose of high-efficiency and low-consumption degradation of organic pollutants in wastewater. However, the nanosilver-modified carbon paper material and the two-chamber reactor separated by the proton membrane are complicated to prepare and expensive, resulting in high processing costs and energy consumption. In addition, the carbon paper anode has the risk of heat and combustion during use, resulting in a reduced life of the carbon paper anode. Patent CN 115069269 A developed a CoMoSxOy electrocatalyst and made it into a membrane anode through vacuum filtration. A porous titanium sheet was used as the cathode. The anode and cathode were assembled together and separated by a rubber plug. Persulfate, electrolyte and pollutant solution were pumped into the filtration reactor. The persulfate was activated on the CoMoSxOy membrane to produce free radicals with strong oxidizing properties, thereby achieving the degradation of organic pollutants. During long-term operation, the CoMoSxOy membrane anode will be blocked and contaminated, resulting in reduced catalytic degradation efficiency and a shorter life of the electrode material. Patent CN113979514B combines spinel-structured CuFe2O4 and electrodes together to exert the synergistic effect of electrochemical activation and CuFe2O4 activation of persulfate, improve activation efficiency, avoid secondary pollution of wastewater, and effectively solve the problems of poor electrode stability and low electrode electrocatalytic activity of titanium-based electrodes during water treatment. However, the electrode material can only generate a single sulfate radical when activating persulfate, and the utilization rate of the catalyst is low when degrading organic pollutants in water bodies with complex components.

[0007] The method reported in the above patent proves the feasibility of the idea proposed in the present invention, and points out that the method of electrochemical activation of peroxide can effectively remove difficult-to-degrade organic matter under certain conditions. However, there are problems such as high cost of raw materials for preparing electrodes, complex preparation process, short service life, single active species produced and limited application range.

[0008] The spinel structure of CuBi2O4 avoids the disadvantages of copper oxide and bismuth oxide existing alone, and is a feasible peroxide activation catalyst. The spinel structure of CuBi2O4 can avoid the leaching of metal ions during use and shows good persulfate activation performance. However, it often has the limitation of slow electron transfer rate during use, which is inevitable for metal oxide catalysts to activate peroxides.

[0009] This patent loads the CuBi2O4 catalyst on the surface of an electroactive anode. This method is easy to operate, safe and reliable, and has good activation performance. It can efficiently degrade various refractory organic compounds without selectivity, improving the operation effect of the traditional metal oxide-activated peroxide water treatment technology. Introducing an electric field can enhance the electrostatic attraction of peroxide on the surface of the CuBi2O4 anode. And CuBi2O4 is rich in oxygen vacancies, which can provide a large number of active sites for the reaction, breaking through the technical bottleneck of slow electron transfer in activating peroxides. This technology promotes the electrostatic attraction of peroxide at the CuBi2O4 anode interface, strengthens its chemical adsorption, generates a transition state peroxide that is easily activated, and mediates the generation of reactive species including hydroxyl radicals, sulfate radicals, superoxide anion radicals, and singlet oxygen, completing the purification of persistent pesticides in pesticide wastewater, high-salt sewage, and runoff rainwater. Summary of the Invention

[0010] The present invention proposes a water treatment method for purifying persistent pesticides in water by an active electrode-mediated peroxide. CuBi2O4 rich in oxygen defect structure is loaded on the surface of an electrochemical anode to increase the oxygen evolution potential of the anode, inhibit the oxygen evolution side reaction, adsorb peroxide on the surface, and activate the adsorbed peroxide through the free electrons in the CuBi2O4 structure and the carriers generated by the anode mediation, mediating the generation of reactive species including hydroxyl radicals, sulfate radicals, superoxide anion radicals, and singlet oxygen, completing the purification of persistent pesticides in pesticide wastewater, high-salt sewage, and runoff rainwater.

[0011] The present invention provides a water treatment method for removing persistent pesticides in water by an active electrode-mediated peroxide, characterized in that (1) the CuBi2O4 anode material can be obtained through the following steps: (1) ultrasonically clean the above-mentioned electrochemical anode with deionized water and absolute ethanol for more than 15 minutes respectively to obtain a surface-clean electrochemical anode; (2) complete the loading of CuBi2O4 on the surface of the electrochemical anode by the precursor drop-casting method. Dissolve 0.2 mmol Bi(NO3)3·5H2O in 2.0 mL acetic acid solution, dissolve 0.1 mmol Cu(NO3)2·3H2O in 8.0 mL absolute ethanol, mix them according to a volume ratio of 1:4 to obtain a precursor of CuBi2O4. At this time, the atomic ratio of Cu to Bi is 1:2. The prepared precursor solution is according to 0.04 mL / cm 2Drop-cast at a ratio on the electrode substrate, repeat the drop-casting three times, transfer it into a muffle furnace, heat it at a heating rate of 5 °C / min to 60 °C, hold for 1 h, then heat it to 500 °C at a heating rate of 2 °C / min and hold for 5 h. After the calcination is completed, cool it naturally to room temperature to obtain the active electrode; (3) Complete the loading of CuBi2O4 on the electrochemical anode surface by the catalyst drop-casting method. Add 18 mmol Bi(NO3)3·5H2O and 9 mmol Cu(NO3)2·3H2O to 20 mL of 10% HNO3 solution in sequence, stir magnetically at room temperature for 1.0 h. After the solution is completely dissolved, add 32.4 mmol of citric acid monohydrate, stir magnetically at room temperature for 1.0 h, heat in a water bath at 75 °C for 2 h and stir magnetically until the solution becomes gel-like, heat at 90 °C for 12 h to obtain a dry gel, transfer it into a muffle furnace, heat it to 500 °C at a heating rate of 2 °C / min and calcine for 5 h. After completion, cool it naturally to room temperature and grind to obtain CuBi2O4 powder. Disperse 218.4 mg of CuBi2O4 powder in 10 mL of absolute ethanol, ultrasonically disperse for 60 min to obtain a uniform suspension, at 0.24 mL / cm 2 Drop-cast at a ratio on the surface of the electrode substrate, dry at room temperature, transfer it into the muffle furnace again, heat it to 450 °C at a heating rate of 10 °C / min and then calcine for 4 h. After completion, cool it naturally to room temperature to obtain the active electrode.

[0012] It is characterized in that (ii) a water treatment method for removing refractory pesticides in water based on the active electrode-mediated peroxide, and the steps for completing the sewage and wastewater treatment application are as follows: The above-mentioned active electrode is combined with a conductive glass, stainless steel, titanium metal, titanium anode coated with metal oxide, diamond, and carbon felt electrochemical cathode. Control the distance between the anode and cathode plates to be 1.0 - 5.0 cm, and the current density between the plates to be 1.0 - 10.0 mA / cm 2 , add 0.325 - 1.3 mmol / L of ozone, hydrogen peroxide, persulfate, potassium permanganate, potassium ferrate. At a residence time of 20 - 60 min and a pH ranging from 3.0 to 11.0, it can purify industrial wastewater, high-salt sewage, and runoff rainwater containing 2.0 - 20.0 mg / L of refractory pesticides, and its removal rates for refractory pesticides and COD exceed 90% and 50% respectively.

[0013] The superior effects of the present invention are as follows: The present invention proposes a water treatment method for removing refractory pesticides in water by an active electrode-mediated peroxide. The CuBi2O4 anode electro-activated peroxide water treatment technology constructed by introducing an electric field has good performance in degrading pollutants; this method increases the oxygen evolution potential of the anode and inhibits the oxygen evolution side reaction; it promotes the interfacial electrostatic attraction of peroxide on the surface of the CuBi2O4 anode, strengthens its chemical adsorption, and generates a transition state peroxide that is easily activated. Through the free electrons in the CuBi2O4 structure and the carriers generated by the anode mediation, the adsorbed peroxide is activated, and active species including hydroxyl radicals, sulfate radicals, superoxide anions, and singlet oxygen are mediated to complete the purification of refractory pesticides in pesticide wastewater, high-salt sewage, and runoff rainwater. Description of the Drawings

[0014] Figure 1 XRD pattern of the CuBi2O4 anode material prepared according to the present invention;

[0015] Figure 2 Scanning electron microscope image of the CuBi2O4 anode material prepared according to the present invention;

[0016] Figure 3 LSV curve diagram of the traditional anode and CuBi2O4 anode materials prepared according to the present invention;

[0017] Figure 4 Degradation effect diagram of the CuBi2O4 anode prepared according to the present invention for the refractory pesticide prometryn;

[0018] Figure 5 Degradation effect diagram of the CuBi2O4 anode prepared according to the present invention for the refractory pesticide prometryn under different current density conditions. Detailed Description of the Invention

[0019] The present invention will be further described in detail with specific embodiments, but the present invention is not limited to the following embodiments.

[0020] Example 1 Preparation Method of CuBi2O4 Anode Material

[0021] The electrode can be obtained through the following steps: (1) ultrasonically clean the above-mentioned electrochemical anode with deionized water and absolute ethanol for more than 15 min respectively to obtain a surface-clean electrochemical anode; (2) complete the loading of CuBi2O4 on the surface of the electrochemical anode by the precursor drop-casting method. Dissolve 0.2 mmol of Bi(NO3)3·5H2O in 2.0 mL of acetic acid solution, and dissolve 0.1 mmol of Cu(NO3)2·3H2O in 8.0 mL of absolute ethanol. Mix them according to a volume ratio of 1:4 to obtain the precursor of CuBi2O4. At this time, the atomic ratio of Cu and Bi is 1:2. Drop-cast the prepared precursor solution on the electrode substrate according to a ratio of 0.04 mL / cm 2 and repeat the drop-casting three times. Transfer it into a muffle furnace, heat it to 60 °C at a heating rate of 5 °C / min, hold for 1 h, then heat it to 500 °C at a heating rate of 2 °C / min, hold for 5 h, and cool it to room temperature naturally after the calcination is completed to obtain an active electrode; (3) complete the loading of CuBi2O4 on the surface of the electrochemical anode by the catalyst drop-casting method. Add 18 mmol of Bi(NO3)3·5H2O and 9 mmol of Cu(NO3)2·3H2O to 20 mL of 10% HNO3 solution in sequence, stir magnetically at room temperature for 1.0 h. After the solution is completely dissolved, add 32.4 mmol of citric acid monohydrate, stir magnetically at room temperature for 1.0 h, heat it in a water bath at 75 °C for 2 h and stir magnetically until the solution becomes gel-like, heat it at 90 °C for 12 h to obtain a dry gel. Transfer it into a muffle furnace, heat it to 500 °C at a heating rate of 2 °C / min and calcine for 5 h, and cool it to room temperature naturally after the end, grind it to obtain CuBi2O4 powder. Disperse 218.4 mg of CuBi2O4 powder in 10 mL of absolute ethanol, ultrasonically disperse for 60 min to obtain a uniform suspension, and drop-cast it on the surface of the electrode substrate according to a ratio of 0.24 mL / cm 2 and dry it at room temperature. Transfer it into a muffle furnace again, heat it to 450 °C at a heating rate of 10 °C / min and then calcine for 4 h, and cool it to room temperature naturally after the end to obtain an active electrode.

[0022] As can be seen from Figure 1 and 2 , the prepared CuBi2O4 anode material has a regular nanoparticle morphology and a loose and porous surface, providing a large number of active sites for the reaction. As can be seen from Figure 3 , the CuBi2O4 material increases the oxygen evolution potential of the traditional anode from 0.49 V to 1.40 V, reduces the occurrence of oxygen evolution side reactions, and improves the degradation performance of organic pollutants.

[0023] Example 2 Treatment of high-salt wastewater with CuBi2O4 anode material

[0024] This process is achieved through the following steps: (1) The cathode used is conductive glass; (2) The distance between the anode and cathode plates is controlled at 1.0 cm; (3) The current density between the plates is 5.0 mA / cm 2 ; (4) The salinity of the high-salt wastewater is 7100 mg / L; (5) The total dissolved solids of the high-salt wastewater is 7.1 g / L; (6) The concentration of organic pollutants in the water to be treated is 10.0 mg / L; (7) The pH range of the reaction system is 5; (8) The contact time is 60 min.

[0025] It is Figure 4 known that when the CuBi2O4 anode is prepared by the catalyst casting method, it has the optimal degradation effect; it is Figure 5 known that when the current density is 5.0 mA / cm 2 , the degradation effect is the best.

[0026] Application of the water treatment method for generating active species by active electrode-mediated peroxide in the purification of runoff rainwater

[0027] This water treatment method can be used for the treatment and resource utilization of runoff rainwater. The "coagulation + precipitation + the technology of the present invention" process is adopted for the advanced treatment of runoff rainwater. The rainwater after the initial runoff is collected through a storage pool, pumped to a filter tank, and coagulants are added to form flocs for direct filtration. After filtration, it is pumped to a chemical oxidation tank. This device uses the new electrode of the present invention, where the electrochemical process structure is divided into 6 - 12 micro-units, which are connected in series in the horizontal direction. Each micro-unit has anode and cathode electrode plates at the same time. The replacement period of the CuBi2O4 anode material is 24 - 46 h. Ozone, hydrogen peroxide, persulfate, potassium permanganate, potassium ferrate peroxide with a concentration of 0.65 mmol / L are added to the chemical oxidation tank. After treatment, it enters a storage pool for various domestic miscellaneous water uses, such as greening and spraying roads.

[0028] Application of the water treatment method for generating active species by active electrode-mediated peroxide in pesticide wastewater

[0029] Pesticide wastewater usually contains refractory pesticides that are difficult to degrade. Conventional sewage treatment processes are difficult to effectively remove them. After biochemical treatment, there are still undegraded organic matters. The technical process proposed in the present invention is set after the secondary sedimentation tank of conventional biochemical treatment to conduct advanced treatment of the wastewater to achieve a better treatment effect.

[0030] The process wastewater flows into the grid well by gravity, enters the regulation tank after intercepting large suspended solids, and is lifted into the anode electro-chemical oxidation tank by a sewage pump. This device uses the new electrode of the present invention as the anode, which is divided into 10 - 18 micro-units. Each micro-unit contains anode and cathode electrode plates, and the micro-units are connected in series horizontally, increasing the hydraulic retention time of the wastewater. The replacement period of the CuBi2O4 anode is 29 - 48 hours. Organic pollutants are degraded under the action of hydroxyl radicals generated in the system, improving the biodegradability of the wastewater. Then it is pumped to an anaerobic reactor to remove a large amount of residual persistent pesticides.

[0031] The specific embodiments described above are only the preferred embodiments of the present invention. However, other aspects and embodiments will be obvious to those skilled in the art. Without departing from the principle of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of this application.

Claims

1. A water treatment method for purifying refractory pesticides in water mediated by an active electrode, characterized in that, Loading CuBi2O4 rich in oxygen defect structures onto the surfaces of conductive glass, stainless steel, titanium metal, titanium anodes coated with metal oxides, and diamond (BDD) electrochemical anodes can increase the oxygen evolution potential of the anodes, inhibit oxygen evolution side reactions, adsorb peroxides on the surface, activate the adsorbed peroxides through the free electrons in the CuBi2O4 structure and the carriers generated by the anodes, mediate the generation of reactive species including hydroxyl radicals, sulfate radicals, superoxide anions, and singlet oxygen, and complete the purification of refractory pesticides in pesticide wastewater, high-salt sewage, and runoff rainwater. It can be achieved through the following specific steps: (1) Ultrasonically clean the above-mentioned electrochemical anodes with deionized water and absolute ethanol for more than 15 minutes each to obtain electrochemically anodes with clean surfaces; (2) The loading of CuBi2O4 on the electrochemical anode surface was completed by the precursor drop-casting method. 0.2 mmol of Bi(NO3)3·5H2O was dissolved in 2.0 mL of acetic acid solution, and 0.1 mmol of Cu(NO3)2·3H2O was dissolved in 8.0 mL of absolute ethanol. They were mixed according to a volume ratio of 1:4 to obtain the precursor of CuBi2O4. At this time, the atomic ratio of Cu to Bi was 1:

2. The prepared precursor solution was drop-cast on the electrode substrate according to a ratio of 0.04 mL / cm 2 and the drop-casting was repeated three times. Then it was transferred into a muffle furnace and heated to 60 °C at a heating rate of 5 °C / min and held for 1 h. Then it was heated to 500 °C at a heating rate of 2 °C / min and held for 5 h. After the calcination was completed, it was naturally cooled to room temperature to obtain the active electrode; (3) The loading of CuBi2O4 on the electrochemical anode surface was completed by the catalyst drop-casting method. 18 mmol of Bi(NO3)3·5H2O and 9 mmol of Cu(NO3)2·3H2O were successively added to 20 mL of 10% HNO3 solution, and magnetically stirred at room temperature for 1.0 h. After the solution was completely dissolved, 32.4 mmol of citric acid monohydrate was added, and magnetically stirred at room temperature for 1.0 h. It was heated in a water bath at 75 °C for 2 h and magnetically stirred until the solution became gel-like, and then heated at 90 °C for 12 h to obtain a dry gel. The dry gel was transferred to a muffle furnace and heated to 500 °C at a heating rate of 2 °C / min for calcination for 5 h. After that, it was naturally cooled to room temperature, and ground to obtain CuBi2O4 powder. 218.4 mg of CuBi2O4 powder was dispersed in 10 mL of absolute ethanol and ultrasonically dispersed for 60 min to obtain a uniform suspension, which was drop-cast on the surface of the electrode substrate at a ratio of 0.24 mL / cm 2 , dried at room temperature, and then transferred to a muffle furnace again. It was heated to 450 °C at a heating rate of 10 °C / min and then calcined for 4 h. After that, it was naturally cooled to room temperature to obtain the active electrode; (4) The oxygen evolution potential of the active electrode prepared by the above method increases from 0.49 V when not loaded with CuBi2O4 to 1.40 V after loading, effectively reducing oxygen evolution side reactions and having good corrosion resistance; (5) The above-mentioned active electrode is combined with conductive glass, stainless steel, titanium metal, titanium anode coated with metal oxide, diamond, and carbon felt electrochemical cathode. The distance between the anode and cathode plates is controlled to be 1.0 - 5.0 cm, and the current density between the plates is 1.0 - 10.0 mA / cm 2 , adding 0.325 - 1.3 mmol / L of ozone, hydrogen peroxide, persulfate, potassium permanganate, potassium ferrate. With a residence time of 20 - 60 min and a pH value ranging from 3.0 to 11.0, it can purify industrial wastewater, high-salt sewage, and runoff rainwater containing persistent pesticides with a concentration of 2.0 - 20.0 mg / L. The removal rates of persistent pesticides and COD exceed 90% and 50% respectively.

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