Electrocatalytic oxidation method, system and applications

Abstract

The application discloses an electro-catalytic oxidation method, system and application, and relates to the technical field of electro-catalytic oxidation, and in particular relates to an electro-catalytic oxidation method, system and application. The method comprises the following steps: controlling an electro-catalytic oxidation system to adopt a low current density for treatment under a reverse current condition, so that cathode dissolution transition metal ions form transition metal-organic acid complexes with low-molecular organic acids in wastewater; switching the current direction of the electro-catalytic oxidation system to a forward direction, and adopting a first current density for electro-catalytic oxidation; keeping the forward current direction, starting a pulse power supply, and adopting a second current density for electro-catalytic oxidation to break the transition metal-organic acid complexes, so that the problems of low degradation efficiency and high treatment cost of industrial wastewater are solved.

Description

Technical Field

[0001] This application relates to an electrocatalytic oxidation method, system, and application, belonging to the field of wastewater treatment technology. Background Technology

[0002] With rapid industrialization, the discharge of industrial wastewater has been increasing, and the large amount of toxic and harmful organic pollutants contained therein poses a serious threat to the environment and human health. In recent years, new pollutants have emerged rapidly due to their characteristics of biotoxicity, environmental persistence, and bioaccumulation, attracting global attention. In the biochemical effluents of key industries such as chemical, electroplating, pharmaceutical, and dyeing, as well as centralized wastewater treatment plants, in addition to incompletely treated degradation intermediates such as low-molecular-weight organic acids, low concentrations of persistent new pollutants, including antibiotics, endocrine disruptors, pesticides, bisphenols, and perfluorinated compounds, often remain, ranging from 10 ng / L to 100 mg / L, and usually coexisting with low-molecular-weight organic acids.

[0003] Due to their complex molecular structures, high bond energies, and difficulty in degradation, novel pollutants require advanced oxidation technologies such as electrocatalytic oxidation and Fenton oxidation for the deep treatment of industrial wastewater. These technologies primarily rely on reactive species like hydroxyl radicals to indiscriminately attack organic pollutants. However, due to the non-selectivity of radical reactions, in treating complex systems containing multiple pollutants, the oxidation process often preferentially targets easily degradable low-molecular-weight organic acids, resulting in lower degradation efficiency for novel pollutants with complex structures and high bond energies. This necessitates the addition of excessive chemical reagents and higher energy consumption in practical applications, increasing treatment costs and hindering the achievement of low-consumption, high-efficiency pollution reduction and deep detoxification. Summary of the Invention

[0004] The purpose of this application is to overcome the shortcomings of the prior art and provide an electrocatalytic oxidation method, system and application to solve the technical problems of low degradation efficiency and high treatment cost of industrial wastewater.

[0005] To achieve the above objectives, the technical solution adopted in this application is as follows:

[0006] In a first aspect, this application provides an electrocatalytic oxidation method, comprising: controlling the electrocatalytic oxidation system under reverse current conditions and using a low current density for treatment, so that transition metal ions are dissolved at the cathode and form transition metal-organic acid complexes with low molecular weight organic acids in wastewater, thereby protecting the low molecular weight organic acids from preferential oxidation in subsequent steps;

[0007] The current direction of the electrocatalytic oxidation system is switched to the positive direction, and the first current density is used for electrocatalytic oxidation to preferentially degrade the recalcitrant characteristic pollutants in the wastewater.

[0008] Maintaining the positive current direction, the pulse power supply is turned on, and electrocatalytic oxidation is performed using the second current density to break down the transition metal-organic acid complex and oxidize and degrade the released low-molecular-weight organic acids.

[0009] In conjunction with the first aspect, further, the range of the low current density is 0.1 mA / cm². 2 Up to 1mA / cm 2 .

[0010] Furthermore, the first current density ranges from 1 mA / cm² to 10 mA / cm²; the second current density ranges from 10 mA / cm² to 30 mA / cm².

[0011] In a first aspect, this application provides an electrocatalytic oxidation system, characterized in that it comprises:

[0012] A reactor is used to contain wastewater to be treated.

[0013] Anode and cathode are installed inside the reactor, and a pulsed power supply is electrically connected to the anode and cathode;

[0014] The control unit is configured to perform the following operations: control the pulse power supply to sequentially output a reverse low current density, a forward first current density, and a forward second current density.

[0015] In conjunction with the second aspect, furthermore, the substrate of the anode is titanium metal, and its surface has a titanium dioxide nanotube modified layer and a metal oxide coating.

[0016] Furthermore, the metal oxide coating comprises any one or more of ruthenium, iridium, tantalum, and lead dioxide.

[0017] Furthermore, the cathode substrate is a steel material containing at least one of iron, cobalt, copper, nickel, and zinc.

[0018] Furthermore, the steel material containing iron is any one or more of carbon steel, stainless steel 304, and stainless steel 316L.

[0019] Thirdly, this application provides an application of an electrocatalytic oxidation method in the deep treatment of industrial wastewater, characterized in that it is used to synergistically remove characteristic pollutants and low-molecular-weight organic acids from wastewater.

[0020] In conjunction with the third aspect, the characteristic contaminant further includes at least one of antibiotics, endocrine disruptors, pesticides, bisphenols, and perfluorinated compounds.

[0021] Compared with the prior art, the beneficial effects achieved by this application are as follows:

[0022] This application utilizes a combination of electrocatalytic oxidation with forward and reverse reversal and a "DC-directional pulse" method to comprehensively generate a transition metal-organic acid complexation mechanism, high current density anodic complex breaking, and cathodic reduction, thereby achieving the synergistic removal of novel pollutants with low residual and high toxicity characteristics and low molecular weight organic carboxylic acids. Attached Figure Description

[0023] Figure 1 This is a comparison chart of COD removal efficiency in various embodiments of this application;

[0024] Figure 2 This application provides a comparison of acute toxicity tests on effluent organisms treated in various embodiments.

[0025] Figure 3 This application describes the removal of novel pollutants characteristic of the influent and effluent from a centralized wastewater treatment plant in a chemical industrial park using an electrocatalytic oxidation method.

[0026] Figure 4 This application describes the removal of novel pollutants characteristic of the influent and effluent from a wastewater treatment plant for a dyeing and printing enterprise using an electrocatalytic oxidation method. Detailed Implementation

[0027] The present application will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and should not be used to limit the scope of protection of the present application.

[0028] This application provides an electrocatalytic oxidation method for the deep treatment of industrial wastewater, comprising the following steps:

[0029] S1: The current direction is reversed, the positive terminal of the power supply is connected to the cathode, and the negative terminal is connected to the anode. A low current density of 0.1 mA / cm² is used. 2 Up to 1mA / cm 2 The reaction time is 0.5-2h, which allows the transition metal ions at the cathode to dissolve into the system and complex with low molecular weight organic acids in the wastewater to form transition metal-organic acid complexes. The complex bonds of the transition metal-organic acid complexes are difficult to break at low current densities. At current densities below 1mA / cm², the degradation rate of the complexes is lower than the oxidation rate of the organic acids, thus protecting the low molecular weight organic acids from oxidation.

[0030] Transition metal ions include, but are not limited to, ions that can be dissolved and form complexes with organic acids, such as iron ions, cobalt ions, nickel ions, copper ions, and zinc ions, with iron ions being preferred.

[0031] S2: Current direction adjusted to positive, positive terminal of power supply connected to anode, negative terminal of power supply connected to cathode, current density 1~10mA / cm² 2The reaction time is 1-3 hours. Anodizing degrades the macromolecular toxic pollutants in the system into low-molecular-weight organic acids. For example, ferrous ions are partially oxidized to ferric ions. The low-molecular-weight organic acids produced by degradation form ferrous-organic acid complexes with ferrous ions and ferric-low-molecular-weight organic acid complexes with ferric ions, thus being protected from further degradation and mineralization.

[0032] S3: Keep the current direction positive, turn on the pulse power supply, and increase the current density to 10~30mA / cm². 2 The reaction time is 1.5-3 hours. Under the action of strong current in the system, a complex-breaking reaction occurs, and ferrous iron is converted into ferric iron ions. Only low-molecular-weight organic acids remain in the system. The low-molecular-weight organic acids are further removed under the action of direct oxidation at the anode and indirect oxidation by free radicals. During this process, electrons gradually accumulate, and ferric iron is reduced to elemental iron at the cathode.

[0033] S4: The reaction is complete, and water is discharged.

[0034] The reaction principle of this application is as follows: In the reaction process of electrochemical oxidation coupled with Fenton oxidation, the following reaction exists:

[0035]

[0036] This refers to iron(III)-carboxylate complexes and iron(II)-carboxylate complexes generated during electrocatalysis and Fenton coupling, where R refers to a group attached to carbon. Because the complexes protect the carboxylate, their degradation rate is very slow. In an electrochemical oxidation system, by combining forward and reverse electrocatalytic oxidation with a combination of "DC-directional pulse," iron ions are generated using an iron sacrificial anode. This first causes low-molecular-weight organic carboxylic acids to form complexes with iron, thus protecting the organic carboxylic acids from degradation. This promotes the preferential removal of residual characteristic pollutants through direct and indirect electrocatalytic oxidation. Then, high current density is used to break down the iron-organic carboxylic acid complexes, thereby removing low-molecular-weight organic carboxylic acids. This method improves the selective removal rate of characteristic pollutants and achieves efficient pollution reduction and deep detoxification.

[0037] This application also provides an electrocatalytic oxidation system, comprising: a reactor for containing wastewater to be treated.

[0038] An anode and cathode are disposed within the reactor, a pulsed power supply electrically connected to the anode and cathode, and a control unit configured to perform the following operations: controlling the pulsed power supply to sequentially output a reverse low current density, a forward first current density, and a forward second current density.

[0039] The control unit is a programmable logic controller or microprocessor, with preset programs for current direction switching and current density adjustment.

[0040] In an feasible electrocatalytic oxidation system, the anode substrate is titanium metal, and its surface is modified with titanium dioxide nanotubes and coated with a metal oxide coating, wherein the metal oxide includes any one or more of ruthenium, iridium, tantalum, and lead dioxide.

[0041] The cathode substrate is a steel material containing at least one of iron, cobalt, copper, nickel, and zinc, wherein the steel material containing iron is any one or more of carbon steel, stainless steel 304, and stainless steel 316L.

[0042] Under the specified initial conditions, the anode is connected to the positive terminal of the power supply, and the cathode is connected to the negative terminal of the power supply; this direction is considered positive.

[0043] Example 1:

[0044] In the initial state of the electrocatalytic oxidation system in this embodiment, the anode is connected to the positive terminal of the power supply, and the cathode is the negative terminal of the power supply; this direction is positive.

[0045] An electrocatalytic oxidation method for deep treatment of industrial wastewater, comprising the following specific steps, characterized in that:

[0046] S1: The current direction is reversed, the positive terminal of the power supply is connected to the cathode, and the negative terminal is connected to the anode, using a low current density of 0.1 mA / cm². 2 The reaction time is 2 hours, allowing the Fe at the cathode to react. 2+ When dissolved into the system, it complexes with low-molecular-weight organic acids in the wastewater. The low current density makes it difficult to break the complexation bond of the transition metal-organic acid complex, thus protecting the low-molecular-weight organic acids from oxidation.

[0047] S2: The current direction is adjusted to positive, the positive terminal of the power supply is connected to the anode, and the negative terminal is connected to the cathode. The current density is 1 mA / cm². 2 The reaction time is 3 hours. Anodizing degrades the macromolecular toxic pollutants in the system into low-molecular organic acids. Ferrous ions are partially oxidized to ferric ions. The low-molecular organic acids produced by degradation form ferrous-organic acid complexes with ferrous ions and ferric-low-molecular organic acid complexes with ferric ions, thus protecting them from further degradation and mineralization.

[0048] S3: Keep the current direction positive, turn on the pulse power supply, and increase the current density to 10mA / cm². 2 The reaction time is 3 hours. Under the action of strong current in the system, the complex breaking reaction occurs, and ferrous iron is converted into ferric iron ions. Only low molecular weight organic acids remain in the system. The low molecular weight organic acids are further removed under the action of direct oxidation at the anode and indirect oxidation by free radicals. During this process, electrons gradually accumulate, and ferric iron is reduced to elemental iron at the cathode.

[0049] S4: The reaction is complete, and water is discharged.

[0050] This application constructs a method that combines forward and reverse electrocatalytic oxidation with "DC-directional pulse" to generate iron ions using an iron sacrificial anode. This first forms a complex between low-molecular-weight organic carboxylic acids and iron, protecting the organic carboxylic acids from degradation. This allows residual characteristic pollutants to be preferentially removed through direct and indirect electrocatalytic oxidation. Then, a high current density is used to break down the iron-organic carboxylic acid complex, thereby removing low-molecular-weight organic carboxylic acids. This method improves the selective removal rate of characteristic pollutants and achieves efficient pollution reduction and deep detoxification.

[0051] Example 2:

[0052] S1: The current direction is reversed, the positive terminal of the power supply is connected to the cathode, and the negative terminal is connected to the anode, using a low current density of 0.5 mA / cm². 2 The reaction time is 1 hour, allowing the Fe at the cathode to react. 2+ When dissolved into the system, it complexes with low-molecular-weight organic acids in the wastewater. The low current density makes it difficult to break the complexation bond of the transition metal-organic acid complex, thus protecting the low-molecular-weight organic acids from oxidation.

[0053] S2: The current direction is adjusted to positive, the positive terminal of the power supply is connected to the anode, and the negative terminal is connected to the cathode. The current density is 5 mA / cm². 2 The reaction time is 2 hours. Anodizing degrades the macromolecular toxic pollutants in the system into low-molecular organic acids. Ferrous ions are partially oxidized to ferric ions. The low-molecular organic acids produced by degradation form ferrous-organic acid complexes with ferrous ions and ferric-low-molecular organic acid complexes with ferric ions, thus protecting them from further degradation and mineralization.

[0054] S3: Keep the current direction positive, turn on the pulse power supply, and increase the current density to 20mA / cm². 2 The reaction time is 2 hours. Under the action of strong current in the system, the complex breaking reaction occurs, and ferrous iron is converted into ferric iron ions. Only low molecular weight organic acids remain in the system. The low molecular weight organic acids are further removed under the action of direct oxidation at the anode and indirect oxidation by free radicals. During this process, electrons gradually accumulate, and ferric iron is reduced to elemental iron at the cathode.

[0055] S4: The reaction is complete, and water is discharged.

[0056] Example 3:

[0057] S1: The current direction is reversed; the positive terminal of the power supply is connected to the cathode, and the negative terminal is connected to the anode. A low current density of 1 mA / cm² is used. 2 The reaction time is 0.5 h, allowing Fe at the cathode to react. 2+When dissolved into the system, it complexes with low-molecular-weight organic acids in the wastewater. The low current density makes it difficult to break the complexation bond of the transition metal-organic acid complex, thus protecting the low-molecular-weight organic acids from oxidation.

[0058] S2: The current direction is adjusted to positive, the positive terminal of the power supply is connected to the anode, and the negative terminal is connected to the cathode. The current density is 10 mA / cm². 2 The reaction time is 1 hour. Anodizing degrades the macromolecular toxic pollutants in the system into low-molecular organic acids. Ferrous ions are partially oxidized to ferric ions. The low-molecular organic acids produced by degradation form ferrous-organic acid complexes with ferrous ions and ferric-low-molecular organic acid complexes with ferric ions, thus protecting them from further degradation and mineralization.

[0059] S3: Keep the current direction positive, turn on the pulse power supply, and increase the current density to 30mA / cm². 2 The reaction time is 1.5 hours. Under the action of strong current in the system, the complex breaking reaction occurs, and ferrous iron is converted into ferric iron ions. Only low molecular weight organic acids remain in the system. The low molecular weight organic acids are further removed under the action of direct oxidation at the anode and indirect oxidation by free radicals. During this process, electrons gradually accumulate, and ferric iron is reduced to elemental iron at the cathode.

[0060] S4: The reaction is complete, and water is discharged.

[0061] Example 4:

[0062] This example serves as control group one, using the same electrocatalytic oxidation system and water quality as in example one, but differing in the operating parameters, as follows:

[0063] The current direction is positive, the positive terminal of the power supply is connected to the anode, the negative terminal is connected to the cathode, and the current density is 10 mA / cm². 2 The reaction was carried out for 8 hours, and water was discharged after the reaction was completed.

[0064] Example 5:

[0065] This example serves as control group two, employing the same electrocatalytic oxidation system and water quality as in example one, with the difference being the operating parameters, as follows:

[0066] The current direction is positive, the positive terminal of the power supply is connected to the anode, and the negative terminal is connected to the cathode. The current density is 30 mA / cm². 2 The reaction was carried out for 5 hours. After the reaction was completed, water was discharged.

[0067] like Figure 1 The figure shown is a comparison chart of COD removal efficiency for each embodiment. Figure 2 For the comparison of acute toxicity tests on effluent organisms in each embodiment, the experiment was conducted continuously for 48 hours, and EC was observed and calculated. 50 Value, EC in the figure 50,48hThe higher the value, the lower the biotoxicity.

[0068] according to Figure 1 and Figure 2 As can be seen, the electrocatalytic oxidation method described in this application has demonstrated high COD removal efficiency in multiple embodiments, and the treated effluent has significantly reduced acute biological toxicity (EC50). 50 The higher 48h value indicates that this method can not only effectively degrade organic matter, but also significantly reduce the toxicity of effluent, possessing the dual advantages of high efficiency and low toxicity, and is suitable for the deep treatment of industrial wastewater.

[0069] This application provides an application of an electrocatalytic oxidation method in the advanced treatment of industrial wastewater, used to synergistically remove characteristic pollutants and low-molecular-weight organic acids from wastewater, wherein the characteristic pollutants include at least one of antibiotics, endocrine disruptors, pesticides, bisphenols, and perfluorinated compounds.

[0070] The application includes: controlling the electrocatalytic oxidation system to operate under reverse current conditions, causing the cathode to dissolve transition metal ions, which then form transition metal-organic acid complexes with low-molecular-weight organic acids in wastewater;

[0071] The current direction of the electrocatalytic oxidation system is switched to the positive direction, and the first current density is used for electrocatalytic oxidation to degrade the macromolecular toxic pollutants in the wastewater into low-molecular organic acids. The low-molecular organic acids complex with transition metal ions in the system; at the same time, some transition metal ions are oxidized.

[0072] Maintaining the positive current direction, the pulse power supply is turned on, and electrocatalytic oxidation is performed using the second current density to break down the transition metal-organic acid complex and oxidize and degrade the released low-molecular-weight organic acids. At the same time, the transition metal ions are reduced at the cathode.

[0073] like Figure 3 , Figure 4 The figures show the removal of characteristic new pollutants from the influent and effluent of a centralized wastewater treatment plant in a chemical industrial park and a wastewater treatment plant for printing and dyeing enterprises using the electrocatalytic oxidation method provided in this application. Figure 3 and Figure 4 It is evident that the method described in this application demonstrates efficient and broad-spectrum removal capabilities for a variety of novel pollutants when treating actual industrial wastewater.

[0074] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. An electrocatalytic oxidation method, characterized by, The method comprises: The control electro-catalytic oxidation system is treated under reverse current condition with low current density, so that the transition metal ions dissolved from cathode form transition metal-organic acid complex with low molecular organic acid in waste water; the low current density ranges from 0.1 mA / cm 2 to 1 mA / cm 2 ; switching the current direction of the electro-catalytic oxidation system to positive, and performing electro-catalytic oxidation at a first current density in the range of 1 mA / cm² to 10 mA / cm²; maintaining the positive current direction, turning on the pulse power, and performing electro-catalytic oxidation at a second current density in the range of 10 mA / cm² to 30 mA / cm² to break the transition metal-organic acid complex.

2. An electro-catalytic oxidation system for carrying out the method of claim 1, characterized in that, The method comprises: a reactor for containing wastewater to be treated; an anode and a cathode arranged in the reactor, and a pulse power electrically connected to the anode and the cathode; and a control unit configured to control the pulse power to sequentially output a reverse low current density, a positive first current density, and a positive second current density.

3. The system of claim 2, wherein, The substrate of the anode is titanium metal, and the surface thereof has a titanium dioxide nanotube modified layer and a metal oxide coating.

4. The system of claim 3, wherein, The metal oxide coating comprises any one or more of ruthenium, iridium, tantalum, and lead dioxide.

5. The system of claim 2, wherein, The substrate of the cathode is a steel material comprising at least one of iron, cobalt, copper, nickel, and zinc.

6. The system of claim 5, wherein, The steel material comprising iron is any one or more of carbon steel, stainless steel 304, and stainless steel 316L.

7. Use of the method according to claim 1 in the advanced treatment of industrial wastewater, characterized in that, The method is used for synergistically removing characteristic pollutants and low-molecular organic acids in wastewater.

8. Use according to claim 7, characterized in that, The characteristic pollutants include at least one of antibiotics, endocrine disruptors, pesticides, bisphenols, and perfluorinated compounds.

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