Multi-type pollutant selective treatment method based on electrochemical-ozone coupling

Abstract

The invention relates to the technical field of wastewater treatment, in particular to a multi-type pollutant selective treatment method based on electrochemical-ozone coupling. According to the invention, a cathode and anode double-chamber structure separated by a porous water-permeable membrane is adopted, when electron-deficient pollutants are treated, ozone is activated into hydroxyl radicals by adopting cathode water inlet and anode water outlet and utilizing an alkaline environment of a cathode chamber and H2O2 generated in situ, so that rapid degradation of the pollutants and subsequent anode mineralization are realized; when electron-rich pollutants are treated, anode water inlet and cathode water outlet are adopted, pollutant structures are damaged by direct selective oxidation of dissolved ozone, and deep mineralization is performed through non-selective free radical oxidation in a cathode chamber. Targeted reinforced removal of pollutants with different electronic properties by the same device is realized, the removal efficiency and the mineralization rate are remarkably improved, the unit energy consumption is reduced, a low-cost carbon fiber membrane compartment material is adopted, and the device has a good engineering application prospect.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically to a method for selective treatment of multiple types of pollutants based on electrochemical-ozone coupling. Background Technology

[0002] Electrochemical-ozone coupling technology is an advanced oxidation method that combines electrochemical processes with ozone oxidation. It aims to enhance the removal efficiency of recalcitrant organic pollutants through the synergistic effect of electrochemically generated active substances and applied ozone. In this coupling system, ozone not only directly participates in pollutant oxidation but also generates highly oxidizing species such as hydroxyl radicals through reduction reactions on the cathode surface. Simultaneously, hydrogen peroxide generated by the electrochemical reaction and the specific electrode interface environment help promote the decomposition and activation of ozone, thereby increasing the steady-state concentration of reactive oxygen species in the system. Compared to single processes, this coupling technology combines the selectivity of direct ozone oxidation with the broad spectrum of hydroxyl radical oxidation, and has shown promising application potential in trace organic pollutant reduction and advanced wastewater treatment in recent years.

[0003] However, existing electrochemical-ozone coupling systems face a technical bottleneck of insufficient selectivity when treating practical wastewater. The reactivity of organic pollutants is closely related to their electronic structure: electron-deficient pollutants (such as aromatic compounds containing nitro or carboxyl groups) have low direct reaction rate constants with ozone molecules, and their degradation mainly depends on hydroxyl radicals generated by ozone activation in the system; while electron-rich pollutants (such as aromatic or heterocyclic compounds containing amino or hydroxyl groups) are easily attacked directly by ozone molecules, preferentially completing the initial structural breakage through selective oxidation pathways. Current studies mostly adopt sequencing batch operation or single-chamber continuous flow modes, which cannot flexibly adjust the ozone activation pathway and oxide species composition according to the differences in the electronic characteristics of influent pollutants.

[0004] Therefore, achieving selective and enhanced removal of electron-deficient and electron-rich pollutants has become a key challenge for the precise and efficient application of this technology. Based on this, this invention aims to provide an electrochemical-ozone coupling treatment method using a porous, permeable membrane with compartments. By constructing a cathode-cathode partitioned configuration and flexibly switching the influent mode, it utilizes the hydrogen peroxide enriched in the cathode compartment and the alkaline conditions, as well as the strong oxidation potential in the anode compartment, to achieve differentiated and efficient degradation of electron-deficient and electron-rich pollutants. Summary of the Invention

[0005] The purpose of this invention is to provide a method for selective treatment of multiple types of pollutants based on electrochemical-ozone coupling, in order to solve the problem that existing electrochemical-ozone coupling systems cannot achieve selective enhanced removal of electron-deficient and electron-rich pollutants in the same device.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for selective treatment of multiple types of pollutants based on electrochemical-ozone coupling, which constructs a dual-chamber reactor with a cathode chamber and an anode chamber separated, wherein a mixture of oxygen and ozone is introduced into both the cathode chamber and the anode chamber, and the direction of water inflow is selected according to the electronic properties of the target pollutant; When treating electron-deficient pollutants, a cathode-inlet-anode-outlet operation mode is adopted, so that the water to be treated first enters the cathode chamber, where hydrogen peroxide generated in situ at the cathode activates ozone under alkaline conditions to generate hydroxyl radicals for non-selective degradation, and then enters the anode chamber for deep mineralization. When treating electron-rich pollutants, an anode-cathode water-inlet operation mode is adopted, in which the water to be treated first enters the anode chamber, where dissolved ozone is used to selectively oxidize and destroy the structure of the pollutants, and then enters the cathode chamber for free radical oxidation and deep mineralization.

[0007] Furthermore, the separating material between the cathode chamber and the anode chamber includes a carbon fiber membrane.

[0008] Furthermore, the separating material between the cathode chamber and the anode chamber is a porous, water-permeable separating membrane, including a polytetrafluoroethylene membrane, a bipolar membrane, or a carbon fiber membrane.

[0009] Furthermore, the cathode is a porous electrode that produces hydrogen peroxide, and the anode is a titanium-based noble metal oxide coated electrode.

[0010] Furthermore, the supporting electrolytic cell includes a sodium sulfate solution.

[0011] Furthermore, the cathode chamber maintains an alkaline environment with a pH range of 10.0 to 11.0; the anode chamber maintains an acidic environment with a pH range of 3.0 to 5.0.

[0012] Furthermore, the electron-deficient pollutants include ibuprofen and / or nitrobenzene; the electron-rich pollutants include benzotriazole and / or sulfamethoxazole.

[0013] Furthermore, the current density is controlled at 5~20 mA / cm during the treatment process. 2 The flow rate of the introduced O2 / O3 mixed gas is 0.2~1.0L / min, the ozone concentration is 10~30mg / L, and the hydraulic retention time is 40~80min.

[0014] Furthermore, when using the cathode inlet-anode outlet mode to treat electron-deficient pollutants, the steady-state removal rate of pollutants is not less than 83%, and the total organic carbon mineralization rate is not less than 31%; when using the anode inlet-cathode outlet mode to treat electron-rich pollutants, the steady-state removal rate of pollutants is not less than 96%, and the total organic carbon mineralization rate is not less than 52%.

[0015] An electrochemical-ozone coupled two-chamber reactor employing the above method.

[0016] The beneficial effects of this invention are: 1. This invention achieves targeted degradation of pollutants with different electronic properties through different influent modes. For electron-deficient pollutants, such as ibuprofen and nitrobenzene, the cathode influent-anode effluent mode achieves steady-state removal rates of 95% and 83.3%, respectively, representing increases of 12.7% and 6.5% compared to the reverse influent mode; mineralization rates reach 38.2% and 31.9%, respectively, representing increases of 6.8% and 8.7%. For electron-rich pollutants, such as benzotriazole and sulfamethoxazole, the anode influent-cathode effluent mode achieves steady-state removal rates of 96.2% and 100%, respectively, representing increases of 6.2% and 4.4%; mineralization rates reach 52.3% and 62.5%, respectively, representing increases of 7.3% and 16.7%.

[0017] 2. After matching the appropriate water inlet method, the energy consumption per ton of water for electron-deficient pollutants ibuprofen and nitrobenzene is reduced to 0.0171 kWh·m³, respectively. -3 ·order -1 and 0.0303 kWh·m -3 ·order -1 The energy consumption per ton of water for electron-rich pollutants benzotriazole and sulfamethoxazole was reduced to 0.0159 kWh·m³, respectively. -3 ·order -1 and 0.00791 kWh·m -3 ·order -1 The efficiency was significantly lower than that of the non-matching water intake mode, greatly reducing the energy consumption of the treatment and achieving efficient energy utilization.

[0018] 3. This invention utilizes a porous, water-permeable membrane to separate the anode and cathode chambers, which not only maintains an alkaline environment conducive to the reduction of oxygen with two electrons in the cathode chamber and increases the in-situ concentration of H2O2, but also increases the steady-state concentration of hydroxyl radicals in the system, effectively enhancing the non-selective oxidation potential of the system.

[0019] 4. This invention uses a porous permeable membrane as the compartment material, which significantly reduces the replacement frequency and maintenance cost caused by membrane fouling and material loss, and avoids the secondary environmental risks that perfluorinated compounds may cause, thereby reducing operation and maintenance costs and environmental risks, and improving the feasibility of the technology in engineering applications. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the reaction apparatus involved in the present invention; Figure 2 This is a graph showing the removal efficiency of the present invention for different types of pollutants when (a) the cathode water inlet and (b) the anode water inlet; Figure 3 This is a diagram showing the mineralization efficiency of different types of pollutants during cathode and anode water inlet processes according to the present invention. Figure 4 This is a reaction energy consumption diagram of the present invention for removing different types of pollutants during cathode water inlet and anode water inlet; Figure 5 The graph shows a comparison of hydrogen peroxide concentration under different treatment methods (a), and a graph showing pH changes under cathode inlet and anode inlet conditions (b). Figure 6 The graph shows a comparison of hydroxyl radical concentrations under different treatment methods (a), and EPR spectra of hydroxyl radical signals under different treatment methods (b). Figure 7 This is a comparison chart of the removal efficiency of ibuprofen and benzotriazole under different treatment methods. Detailed Implementation

[0021] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention.

[0022] This invention utilizes a porous, water-permeable membrane to construct a compartmentalized electrochemical reactor. By changing the direction of the continuous flow of influent, the activation pathway and oxide species composition of ozone in the anode and cathode chambers are controlled, thereby achieving selective and enhanced removal of pollutants with different electronic properties.

[0023] 1. Mechanism of ozone activation and free radical generation in the cathode chamber In the cathode chamber, introduced oxygen (O2) undergoes a two-electron oxygen reduction reaction (2e) on the surface of the hydrogen peroxide-producing porous electrode. - ORR (Ortho-Repair) generates hydrogen peroxide (H2O2) in situ, and the reaction equation is as follows: O2 + 2H2O + 2e - →H₂O₂ + 2OH⁻ - Meanwhile, the electrochemical hydrogen evolution reaction and oxygen reduction process consume H2. + This creates an alkaline environment in the cathode chamber. Under alkaline conditions, the in-situ generated H2O2 is converted into hydrogen peroxide ions (HO2). - It exists in the form of ) and undergoes a rapid perozonation reaction with dissolved ozone (O3) to efficiently generate hydroxyl radicals (·OH). The reaction equation is as follows: H2O2 HO2 - +H + HO2 - +O3→·OH+O2· - +O2 In addition, ozone can also directly accept electrons on the cathode surface to undergo electrochemical reduction, generating ·OH: O3+e - +H₂O→·OH⁺OH - +O2 2. Direct ozone oxidation mechanism in the anode chamber In the anode chamber, the oxygen evolution reaction mainly occurs at the anode (titanium-based noble metal electrode), accompanied by the direct dissolution of ozone. Due to the acidic environment of the anode chamber, the H2O2 yield is extremely low, ozone activation is inhibited, and the oxide species in the system are mainly in the molecular state of O3. Electron-rich pollutants have a high direct reaction rate constant with O3 and can undergo selective electrophilic attack, leading to the initial breakage of the aromatic ring or heterocyclic structure of the pollutants.

[0024] 3. Differentiated removal principle based on inlet water direction control Cathode-Anode Inlet / Outlet Mode (for electron-deficient pollutants): The treated water first enters the cathode chamber, where the high concentration of ·OH in the cathode chamber rapidly and non-selectively degrades the electron-deficient pollutants, achieving deep destruction of their initial structure. It then enters the anode chamber, where the direct electron transfer oxidation at the anode further mineralizes the intermediate products, as shown in the following reaction: Pollutant + ·OH → Intermediate product → CO2 + H2O + Inorganic ions Anode-cathode water intake mode (for electron-rich pollutants): The treated water first enters the anode chamber, where the selective oxidation of dissolved O3 efficiently attacks electron-rich sites, achieving rapid breakage of the pollutant's parent structure; then it enters the cathode chamber, where residual intermediate products and some unreacted pollutants undergo non-selective oxidation under the action of ·OH, completing deep mineralization.

[0025] 4. The key role of porous permeable membranes in compartmentalization The porous, permeable membrane, serving as the separator between the anode and cathode chambers, allows ions to migrate directionally under the influence of an electric field to maintain the loop current. Simultaneously, it effectively prevents macroscopic mixing of the electrolytes in both chambers, maintaining the differentiated chemical environment between the alkaline (pH > 9) cathode chamber and the acidic (pH < 5) anode chamber. This pH gradient is a crucial prerequisite for the efficient production of H₂O₂ and the activation of O₃ to generate ·OH in the cathode chamber, and is also the core guarantee for selectively removing pollutants of different properties by controlling the direction of the influent.

[0026] Example 1 This embodiment uses a two-chamber electrochemical reactor with dimensions of 5cm in length, 7cm in width, and 10cm in height. Figure 1As shown, the cathode is a graphite felt electrode (5cm×10cm, 5mm thick), and the anode is a DSA electrode (Ti / IrO2-Ta2O5 coating, 5cm×10cm). The anode and cathode chambers are separated by a porous water-permeable membrane with a width of 6.5cm, a height of 9cm, and a thickness of about 0.5mm, and the distance between the electrodes is 3cm. Microporous aeration heads are installed at the bottom of both chambers to introduce O2 / O3 mixed gas.

[0027] The experimental conditions were: current density 10 mA / cm² 2 The O2 / O3 gas flow rate was 0.5 L / min, the O3 concentration was 20 mg / L, and the water inlet method was pumped in from the bottom of the cathode chamber and pumped out from the top of the anode chamber (cathode inlet type - over-ozone technology), with an inlet flow rate of 5 mL / min and a hydraulic retention time (HRT) of 60 min. The target pollutants were ibuprofen (IBP) and nitrobenzene (NB), both electron-deficient representatives, with an initial concentration of 0.05 mM. The supporting electrolyte was 50 mM Na2SO4, and the system operated at room temperature.

[0028] The system was continuously run for 3 HRTs until steady state, and then samples were taken for analysis, such as... Figure 2-4 As shown, the results indicate that the ibuprofen removal rate reached 95%, the TOC mineralization rate was 38.2%, and the energy consumption per ton of water was 0.0171 kWh·m³. -3 ·order -1 Nitrobenzene removal rate: 83.3%; TOC mineralization rate: 31.9%; Energy consumption per ton of water: 0.0303 kWh·m³ -3 ·order -1 .

[0029] Example 2 The dual-chamber electrochemical reactor in this embodiment is the same as in Example 1. The water inlet method is pumped in from the bottom of the anode chamber and pumped out from the top of the cathode chamber (anode-inlet type - ozone technology); the target pollutants are electron-rich representative benzotriazole (BTA) and sulfamethoxazole (SMX), respectively, with an initial concentration of 0.05 mM for both, and the supporting electrolyte is 50 mM Na2SO4, operating at room temperature; other experimental conditions are the same as in Example 1.

[0030] The system was continuously run for 3 HRTs until steady state, and then samples were taken for analysis, such as... Figure 2-4 As shown, the results indicate that the benzotriazole removal rate reached 96.2%, the TOC mineralization rate was 52.3%, and the energy consumption per ton of water was 0.0159 kWh·m³. -3 ·order -1 The removal rate of sulfamethoxazole reached 100%, the TOC mineralization rate was 62.5%, and the energy consumption per ton of water was 0.00791 kWh·m³. -3 ·order -1 .

[0031] Example 3 The dual-chamber electrochemical reactor in this embodiment is the same as in Example 1. The target pollutants are ibuprofen (IBP), a representative of the electron-deficient type, and benzotriazole (BTA), a representative of the electron-rich type, respectively, with an initial concentration of 0.05 mM for both. The supporting electrolyte is 50 mM Na2SO4, and the operation is at room temperature. A segmented control strategy is adopted: the first 3 HRT cycles are operated in cathode-inlet mode, and the valve is switched to anode-inlet mode in the last 3 HRT cycles. Other experimental conditions are the same as in Example 1.

[0032] like Figure 2-4 As shown, the results indicate that in the anode-feed mode, the ibuprofen removal rate is 82.3%, the TOC mineralization rate is 31.4%, and the energy consumption per ton of water is 0.0295 kWh·m³. -3 ·order -1 Compared to the cathode-feed mode, the removal rate decreased by 12.7%, the mineralization rate decreased by 6.8%, and the energy consumption per ton of water was significantly higher; under the cathode-feed mode, the benzotriazole removal rate was 90.0%, the TOC mineralization rate was 45.0%, and the energy consumption per ton of water was 0.0228 kWh·m³. -3 ·order -1 Compared to the anode-inlet mode, the removal rate is reduced by 6.2%, the mineralization rate is reduced by 7.3%, and the energy consumption per ton of water is significantly higher.

[0033] like Figure 5 As shown, for ibuprofen, when using the cathode-inlet mode, the steady-state concentration of H2O2 in the cathode chamber reaches 9.25 mg / L, the pH of the cathode chamber is stable at 10.0-11.0, and the pH of the anode chamber is stable at 4.0-5.0; for benzotriazole, when using the anode-inlet mode, the steady-state concentration of H2O2 in the cathode chamber reaches 6.4 mg / L, the dissolved O3 in the anode chamber is fully utilized, and the direct ozone oxidation and chain breaking of pollutants are preferentially achieved, the pH of the cathode chamber is stable at 10.0-11.0, and the pH of the anode chamber is stable at 3.0-4.0.

[0034] Comparative Example 1 In this comparative example, conventional electro-ozone technology, anodic inlet type and cathodic inlet type electro-ozone technology were used to treat the inlet water of ibuprofen and benzotriazole separately. Other experimental conditions were the same as in Example 1.

[0035] like Figure 6 As shown, when ibuprofen is treated using cathode-inlet electro-ozone technology, the steady-state concentration of hydroxyl radicals in the system is 0.09 × 10⁻⁶. -10 M -1 When benzotriazole is treated using an anolyte-inlet electro-ozone technology, the steady-state concentration of hydroxyl radicals in the system is 0.074 × 10⁻⁶. -10 M -1 This is significantly higher than the 0.05×10⁻⁶ of traditional electro-ozone technology.-10 M -1 The three systems exhibited distinct characteristic peaks of hydroxyl radicals.

[0036] like Figure 7 As shown in the comparative example, the removal rates of ibuprofen by the traditional electro-ozone technology, the anode-inlet type, and the cathode-inlet type electro-ozone technology were 78.6%, 82.2%, and 95%, respectively; and the removal rates of benzotriazole were 83.5%, 96.5%, and 89.8%, respectively. It can be seen that, compared with the traditional single-chamber electro-ozone technology, the degradation efficiency of ibuprofen and benzotriazole by the compartment electro-ozone technology of the present invention is significantly higher than that of the traditional single-chamber electro-ozone technology.

[0037] This invention is not limited to the preferred embodiments described above. Anyone can derive other forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A method for selective treatment of multiple types of pollutants based on electrochemical-ozone coupling, characterized in that: A dual-chamber reactor with a cathode chamber and an anode chamber was constructed. A mixture of oxygen and ozone was introduced into both the cathode chamber and the anode chamber. The direction of water inlet was selected based on the electronic properties of the target pollutant. When treating electron-deficient pollutants, a cathode-inlet-anode-outlet operation mode is adopted, so that the water to be treated first enters the cathode chamber, where hydrogen peroxide generated in situ at the cathode activates ozone under alkaline conditions to generate hydroxyl radicals for non-selective degradation, and then enters the anode chamber for deep mineralization. When treating electron-rich pollutants, an anode-cathode water-inlet operation mode is adopted, in which the water to be treated first enters the anode chamber, where dissolved ozone is used to selectively oxidize and destroy the structure of the pollutants, and then enters the cathode chamber for free radical oxidation and deep mineralization.

2. The method for selective treatment of multiple types of pollutants based on electrochemical-ozone coupling according to claim 1, characterized in that: The separating material between the cathode chamber and the anode chamber is a porous, water-permeable separating membrane, including a polytetrafluoroethylene membrane, a bipolar membrane, or a carbon fiber membrane.

3. The method for selective treatment of multiple types of pollutants based on electrochemical-ozone coupling according to claim 1, characterized in that: The cathode is a porous electrode that produces hydrogen peroxide, and the anode is a titanium-based noble metal oxide coated electrode.

4. The method for selective treatment of multiple types of pollutants based on electrochemical-ozone coupling according to claim 3, characterized in that: The cathode is a graphite felt electrode; the anode is a DSA electrode with a Ti / IrO2-Ta2O5 coating.

5. The method for selective treatment of multiple types of pollutants based on electrochemical-ozone coupling according to claim 3, characterized in that: The supporting electrolytic cell includes a sodium sulfate solution.

6. The method for selective treatment of multiple types of pollutants based on electrochemical-ozone coupling according to claim 1, characterized in that: The cathode chamber maintains an alkaline environment with a pH range of 10.0 to 11.0; the anode chamber maintains an acidic environment with a pH range of 3.0 to 5.

0.

7. The method for selective treatment of multiple types of pollutants based on electrochemical-ozone coupling according to claim 1, characterized in that: The electron-deficient pollutants include ibuprofen and / or nitrobenzene; the electron-rich pollutants include benzotriazole and / or sulfamethoxazole.

8. The method for selective treatment of multiple types of pollutants based on electrochemical-ozone coupling according to claim 1, characterized in that: The current density is controlled at 5~20 mA / cm during the process. 2 The flow rate of the introduced O2 / O3 mixed gas is 0.2~1.0L / min, the ozone concentration is 10~30mg / L, and the hydraulic retention time is 40~80min.

9. The method for selective treatment of multiple types of pollutants based on electrochemical-ozone coupling according to claim 1, characterized in that: When using the cathode-inlet-anode-outlet mode to treat electron-deficient pollutants, the steady-state removal rate of pollutants is not less than 83%, and the total organic carbon mineralization rate is not less than 31%; when using the anode-inlet-cathode-outlet mode to treat electron-rich pollutants, the steady-state removal rate of pollutants is not less than 96%, and the total organic carbon mineralization rate is not less than 52%.

10. An electrochemical-ozone coupled two-chamber reactor employing the method of any one of claims 1-9.

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