Electrochemical cathode and anode cooperative treatment method for reverse osmosis concentrated water

Abstract

The invention discloses an electrochemical cathode and anode co-treatment method for reverse osmosis concentrated water, which comprises the following steps: preparing a porous titanium plate with a metal oxide layer loaded on a middle layer for anodic oxidation treatment of the reverse osmosis concentrated water and an anode electrode; preparing a carbon felt material loaded with metal and metal oxide, namely a cathode electrode, for treating reverse osmosis concentrated water by cathode electro-Fenton; a bipolar chamber reactor and the anode / cathode electrode are used for treating reverse osmosis concentrated water through electrochemical cathode and anode cooperation, oxygen generated by the anode increases the dissolved oxygen concentration of the cathode through liquid phase diffusion, cathode two-electron oxygen reduction reaction is promoted to generate hydrogen peroxide, and then the cathode electro-Fenton process is promoted to generate hydroxyl radicals; meanwhile, anode hydrolysis continuously releases hydrogen ions, maintains the acidic environment of the system, inhibits the precipitation of cathode iron ions and strengthens the electro-Fenton reaction of the cathode, so that the effective concentration of hydroxyl radicals is improved compared with that of a monopole system, the electron utilization efficiency is remarkably improved, and the treatment energy consumption is remarkably reduced compared with that of single anode oxidation and cathode electro-Fenton.

Description

Technical Field

[0001] The invention relates to a wastewater treatment method, in particular to an electrochemical treatment method for reverse osmosis concentrated water. Background Art

[0002] Reverse osmosis (RO) technology has been widely used in advanced municipal wastewater treatment and zero-discharge industrial wastewater. In this process, RO effectively removes dissolved salts, organic matter, and microorganisms from wastewater, producing high-quality reclaimed water. This reclaimed water can be reused for municipal water supply, landscape irrigation, and industrial cooling, reducing reliance on freshwater resources and alleviating water shortages. However, the application of RO technology also presents challenges in the treatment of RO brine. RO brine contains high concentrations of organic matter, salts, and other harmful substances. These pollutants are difficult to remove using conventional wastewater treatment methods, making treatment challenging. Furthermore, the treatment process typically requires significant energy and chemical resources, resulting in high treatment costs. Discharging untreated RO brine can have serious negative environmental impacts, such as eutrophication and soil salinization, disrupting ecological balance, and impacting biodiversity. Therefore, further research and solutions are urgently needed to achieve more efficient, economical, and environmentally friendly wastewater treatment.

[0003] Electrochemical oxidation is an effective method for treating reverse osmosis brine. It is gaining increasing attention due to its simple equipment, easy operation, environmental friendliness, and significant degradation effect on poorly biodegradable pollutants. Advanced oxidation technologies include photochemical oxidation, ozonation, electrochemical oxidation, and electro-Fenton oxidation. Among them, electrochemical oxidation technology is particularly suitable for the treatment of high-salinity and high-organic-concentration wastewater such as reverse osmosis brine. In order to overcome the disadvantage of high energy consumption of electrochemical technology, researchers have paid special attention to the combined use of anodic oxidation and cathodic electro-Fenton in recent years. The synergistic effect of the electrochemical cathode and anode can significantly improve the treatment efficiency and economy. Summary of the Invention

[0004] In response to the above-mentioned prior art, the present invention provides an electrochemical anode-cathode coordinated treatment method for reverse osmosis concentrated water, which reduces the power consumption during the treatment process, improves the sewage treatment effect, and enhances the electron utilization rate.

[0005] In order to solve the above technical problems, the present invention proposes an electrochemical cathode-cathode coordinated treatment method for reverse osmosis concentrated water, wherein the treatment method uses cathode electro-Fenton treatment of reverse osmosis concentrated water and anodic oxidation treatment of reverse osmosis concentrated water, and the pollutants in the reverse osmosis concentrated water are refractory organic matter; the method of the present invention comprises:

[0006] Step 1) Preparation of an anode electrode for anodic oxidation treatment of reverse osmosis concentrated water;

[0007] Step 2) Preparation of the cathode electrode used for the cathode electro-Fenton treatment of reverse osmosis concentrated water:

[0008] Step 3) A bipolar chamber reactor is used and the cathode electrode and anode electrode prepared in the present invention are used to electrochemically coordinate the cathode and anode to treat the reverse osmosis concentrated water.

[0009] Step 1) preparing the anode electrode comprises:

[0010] 1-1) Pretreatment of the porous titanium plate: The porous titanium plate was sequentially polished, immersed in a sodium hydroxide solution and heated in a water bath to remove residual impurities, ultrasonically cleaned with acetone and ultrapure water to remove the oxide layer, and immersed in a hydrochloric acid solution and heated in a water bath; finally, the porous titanium plate was transferred to a mixed solution of ultrapure water, hydrochloric acid, and hydrogen peroxide for cleaning to remove residual surface ions;

[0011] 1-2) Synthesis of Enhanced Titanium Dioxide Nanotube Arrays: The pretreated porous titanium plate was immersed in a mixed solution of ammonium fluoride and ethylene glycol and anodized under an applied voltage to form a titanium dioxide nanotube array, which was then calcined in a muffle furnace to obtain an enhanced titanium dioxide nanotube array intermediate layer;

[0012] 1-3) Catalytic layer loading: A metal oxide layer is loaded on the porous titanium plate intermediate layer by a sol-gel method;

[0013] Step 2) preparing the cathode electrode, comprising:

[0014] 2-1) Carbon felt pretreatment: The carbon felt material was ultrasonically cleaned in acetone, anhydrous ethanol, and ultrapure water in sequence, dried at a constant temperature, and then heated in a nitrogen atmosphere to form a graphitized conductive network on the surface of the carbon felt matrix, thereby improving the conductivity of the carbon felt material;

[0015] 2-2) Catalyst loading: The pretreated carbon felt material is immersed in a salt solution containing metal ions and subjected to ultrasound at different frequencies, followed by constant temperature drying to obtain a carbon felt material with metal salt attached thereto;

[0016] 2-3) Thermal shock of the electrode: by controlling the current and voltage, the carbon felt material with the metal salt attached is thermally shocked under suitable temperature and vacuum atmosphere conditions, and the carbon felt material loaded with metal and metal oxides obtained is the cathode electrode;

[0017] Step 3) The electrochemical cathode and anode cooperate to treat reverse osmosis concentrated water:

[0018] 3-1) The reverse osmosis concentrated water is placed in the bipolar chamber reactor, and an electrolyte solution is added to control the initial pH of the solution to 3±0.2; the porous titanium plate with a metal oxide layer loaded on the intermediate layer prepared in step 1) is used as the anode electrode, and the carbon felt material loaded with metal and metal oxide prepared in step 2) is used as the cathode electrode; the volume ratio of the anode and cathode chambers of the bipolar chamber reactor is 1:1, and the current density is 7.5 mA / cm 2 The water sample circulation flow rate is 5 mL / s, and the surface area of the cathode and anode is 20 cm 2 The geometric surface area ratio of the cathode and anode is 1:1; the electrolyte solution is a sodium sulfate solution with a concentration of 0.2 mol / L, and the treatment time is 2 h.

[0019] 3-2) When the power is turned on, the oxygen generated by the hydrolysis reaction at the anode diffuses to the cathode through the liquid phase, where an electro-Fenton reaction occurs to generate hydrogen peroxide; a redox reaction occurs at the anode to treat the reverse osmosis concentrated water.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The method for treating reverse osmosis concentrated water provided by the present invention adopts a cathode-cathode synergistic method to treat organic matter in reverse osmosis concentrated water. The oxygen generated at the anode increases the dissolved oxygen concentration at the cathode through liquid phase diffusion, promotes the cathode two-electron redox reaction to generate hydrogen peroxide, and then promotes the electro-Fenton process to generate hydroxyl groups. At the same time, the anode hydrolysis continuously releases hydrogen ions, maintains the acidic environment of the system, inhibits the precipitation of trivalent iron at the cathode and strengthens the electro-Fenton reaction, so that the effective concentration of hydroxyl groups is increased compared with the monopolar system. The electron utilization efficiency is significantly improved, and the treatment energy consumption is significantly reduced compared with the single treatment method. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 These are digital photos and SEM photos of the MP-Ti-ENTA / SnO2-Sb anode prepared in the present invention, including: (a) digital photo of the MP-Ti-ENTA / SnO2-Sb electrode; (b) SEM photo of the MP-Ti-ENTA / SnO2-Sb electrode after loading the catalytic layer; (c) SEM photo of the cross section of the MP-Ti-ENTA / SnO2-Sb electrode after loading the catalytic layer

[0023] Figure 2 Figure 1 is an EDX spectrum of the MP-Ti-ENTA / SnO2-Sb electrode prepared in the present invention, wherein: (a) SEM image of MP-Ti-ENTA loaded with a catalytic layer; (b) Sb Lα1: distribution of antimony (Sb); (c) Sn Lα1: distribution of tin (Sn); (d) TiKα1: distribution of titanium (Ti); (e) O kα1: distribution of oxygen (O);

[0024] Figure 3is the XRD pattern of the MP-Ti-ENTA / SnO2-Sb electrode prepared in the present invention;

[0025] Figure 4 (a) LSV curve and (b) Nyquist curve of the MP-Ti-ENTA / SnO2-Sb electrode and Ti electrode prepared in the present invention;

[0026] Figure 5 The following are digital photos and SEM photos of the Fe2O3 / CF electrode prepared in the present invention, including: (a) digital photo of the Fe2O3 / CF electrode; (b) SEM image of the electrode CF; (c) SEM image of the Fe2O3 / CF electrode after thermal shock loading with FeCl3·6H2O;

[0027] Figure 6 The EDX spectrum of the Fe2O3 / CF electrode prepared in the present invention, wherein: (a) SEM image of the Fe2O3 / CF electrode; (b) O kα1: oxygen element (O) distribution; (c) C Kα1: carbon element (C) distribution; (d) Fe kα1: iron element (Fe) distribution;

[0028] Figure 7 The XPS spectrum of the Fe2O3 / CF cathode prepared in the present invention, wherein: (a) XPS total spectrum; (b) Fe 2p

[0029] Figure 8 (a) LSV curves and (b) Nyquist curves of the Fe2O3 / CF electrode and the CF electrode prepared in the present invention;

[0030] Figure 9 The removal rate of methylisothiazolinone, a representative pollutant in reverse osmosis concentrate treated by different electrochemical methods;

[0031] Figure 10 This is a diagram showing the effect of removing organic matter from a certain actual chemical reverse osmosis concentrate using different electrochemical methods;

[0032] Figure 11 This is a diagram showing the stability of the electrochemical anode-cathode cooperative system in degrading a certain actual chemical reverse osmosis concentrate. DETAILED DESCRIPTION

[0033] The present invention provides a design concept for an electrochemical cathode-cathode coordinated treatment method for reverse osmosis concentrated water. The oxygen generated at the anode diffuses through the liquid phase to increase the dissolved oxygen concentration at the cathode, promoting the cathode two-electron redox reaction to generate hydrogen peroxide, and further promoting the cathode electro-Fenton process to generate hydroxyl radicals. At the same time, the anode hydrolysis continuously releases hydrogen ions, maintains the acidic environment of the system, inhibits the precipitation of iron ions at the cathode and strengthens the cathode electro-Fenton reaction, so that the effective concentration of hydroxyl radicals is increased compared with the monopolar system, the electron utilization efficiency is significantly improved, and the treatment energy consumption is significantly reduced compared with single anode oxidation and cathode electro-Fenton. In the present invention, reverse osmosis concentrated water is placed in a bipolar chamber reactor, an electrolyte solution is added, and the initial pH of the solution is controlled to 3±0.2; at the same time, a porous titanium plate with a metal oxide layer loaded on the intermediate layer specially prepared by the present invention is used as the anode electrode, and a carbon felt material loaded with metal and metal oxide is used as the cathode electrode. When the power is turned on, the oxygen generated by the anode hydrolysis reaction diffuses through the liquid phase to the cathode, where an electro-Fenton reaction occurs to generate hydrogen peroxide to treat the reverse osmosis concentrated water, and a redox reaction occurs at the anode to treat the reverse osmosis concentrated water.

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the following embodiments are by no means intended to limit the present invention in any way.

[0035] Example 1: Preparation of a porous titanium plate with a metal oxide layer loaded on an intermediate layer as an anode electrode, the steps are as follows:

[0036] (1) A Ø50 mm porous titanium plate was used as the substrate material. It was first polished with 2000 grit sandpaper until the surface was bright. The titanium plate was immersed in a 40% sodium hydroxide solution and treated in an 80°C water bath for 60 minutes to remove residual impurities during the titanium plate processing. Ultrasonic cleaning was performed using acetone and ultrapure water for 30 minutes. To remove the oxide layer, the titanium plate was then placed in an 18% hydrochloric acid solution and reacted in an 85°C water bath for 30 minutes. Finally, the titanium plate was transferred to a solution of H2O, 37% HCl and 30% H2O2 in a volume ratio of 6:1:1 at room temperature for 10 minutes to remove residual ions on the surface.

[0037] (2) The pretreated porous titanium plate was immersed in an ethylene glycol solution containing 0.25 wt.% ammonium fluoride and 2 wt.% ultrapure water, and subjected to initial anodization at 42 V for 6 h to form a titanium dioxide nanotube array. The plate was then calcined in an air environment at 500 ° C for 1 h to obtain an enhanced titanium dioxide nanotube array intermediate layer.

[0038] (3) A metal oxide layer was loaded on the middle layer of the porous titanium plate by the sol-gel method. Citric acid was dissolved in ethylene glycol solution at 60°C and stirred for 30 minutes to promote the hydrolysis reaction to form citrate ester. The solution temperature was raised to 90°C and tin tetrachloride pentahydrate and antimony trichloride were added to form a mixed solution with a preset ratio and boiled for 2 hours. After the gel solution was aged for 3 months, it was used to coat the treated porous titanium plate and dried at 140°C for 10 minutes, followed by annealing at 500°C for 10 minutes. This step was repeated 15 times, and the electrode plate was annealed for 2 hours on the last occasion. After cooling to room temperature, it was ultrasonically cleaned with ultrapure water until the washing liquid was clear, thereby completing the preparation of the porous titanium plate electrode, which was recorded as MP-Ti-ENTA / SnO2-Sb electrode.

[0039] For the MP-Ti-ENTA / SnO2-Sb electrode prepared above, Figure 1 As shown in (a), the MP-Ti-ENTA / SnO2-Sb electrode prepared by anodizing the porous titanium plate electrode and loading the SnO2-Sb catalyst layer has a gray-black macroscopic morphology. Figure 1 (b) shows the surface after the catalytic layer is applied. After multiple coatings, the electrode surface becomes rougher. The catalytic layer particles are evenly distributed on the substrate, and the ENTA is uniformly arranged. The diameter of the ENTA ranges from 80 to 100 nm, indicating a uniform and effective coating process. The presence of the catalytic layer increases the catalytic activity of the material, which has a positive effect on improving reaction efficiency. Figure 1 (c) shows a cross-section of the electrode after the catalyst layer is loaded, revealing the bonding between the catalyst layer and the substrate. The image shows a tight bond between the catalyst layer and the substrate, which is crucial for ensuring the lifespan and stability of the electrode.

[0040] Table 1 Percentage of element content on the electrode surface

[0041] element Atomic percentage (%) Weight percentage (%) Ti 40.01 55.95 O 54.65 25.53 Sn 5.14 17.89 Sb 0.20 0.71

[0042] Figure 2 (a) is the EDX spectrum of the electrode obtained by EDX testing. Figure 2As shown in (b), (c), (d), and (e), oxygen, tin, and antimony are evenly distributed on the electrode surface. Table 1 shows that the atomic percentages of Ti, O, Sn, and Sb are 40.01%, 54.65%, 5.13%, and 0.20%, respectively. The weight percentages of Ti, O, Sn, and Sb are 55.95%, 25.53%, 17.89%, and 0.71%, respectively. These are the main elements in SnO2 and Sb2O3, and their presence increases the conductivity and reaction surface area of the electrode, improving the efficiency of electrochemical treatment. The distribution of titanium reflects its ubiquitous presence as an electrode matrix, providing structural stability to the electrode. The synergistic effect of these elements provides an important guarantee for achieving the electrode's effectiveness in water treatment.

[0043] Figure 3 The sharp peaks observed correspond to the characteristic diffraction peaks of pure Ti or TiO2, indicating the presence of Ti element in the electrode base material and the formation of TiO2 crystal phase. As a material widely used in photocatalysis and electrocatalysis, the integrity of the crystal structure of TiO2 is key to the performance of the electrode. The characteristic peaks of SnO2 and Sb2O3 are also clearly shown in the diffraction peaks, confirming the successful loading and uniform distribution of these oxides. The introduction of SnO2 and Sb2O3 has a significant effect on enhancing the electrochemical activity of the electrode and improving the efficiency of pollutant treatment. Some peaks in the XRD spectrum indicate the presence of composite material phases or alloy phases formed by Ti and Sn or Sb. These composite phases may be formed during the synthesis process and have a positive effect on the chemical stability and electrochemical performance of the electrode. The XRD analysis results show that the electrode has a good crystal structure and composite material characteristics, which provides a material basis for it to exhibit excellent catalytic activity and operational stability in water treatment applications.

[0044] LSV curve is usually used to evaluate the electrocatalytic activity of electrode materials. Figure 4 As shown in (a), under the same voltage change, the current response of the MP-Ti-ENTA / SnO2-Sb electrode is more sensitive than that of the Ti electrode. The enhancement of current sensitivity may be due to the higher surface area and more efficient electron transfer path provided by the MP-Ti-ENTA structure, as well as the synergistic effect of SnO2 and Sb. EIS is an effective tool for studying the electrochemical properties of the interface of electrocatalytic materials and their electron transfer capabilities. In the Nyquist diagram, the arc and oblique line of the compressed semicircle represent the synergistic control process of charge transfer and diffusion during the redox reaction. Figure 4As shown in the Nyquist plot (b), the diameter of the semicircle representing MP-Ti-ENTA / SnO2-Sb is smaller than that of Ti, indicating that MP-Ti-ENTA / SnO2-Sb has lower charge transfer resistance. This is due to the addition of the supported catalytic layer, which improves the charge transfer capacity of the anode and increases the surface reaction rate. In summary, the electrochemical characterization results of the MP-Ti-ENTA / SnO2-Sb electrode reveal its excellent electrocatalytic performance, especially its ability to generate oxidants at high potentials, making it suitable for environmental applications requiring high oxidation performance.

[0045] Example 2: Preparation of a cathode electrode made of a carbon felt material loaded with metals and metal oxides, in the following steps:

[0046] (1) The carbon felt was ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for 30 min, respectively, placed in an oven and dried at 60 °C for 30 min, heated to 1073 K at a heating rate of 5 °C / min, and maintained at this temperature for 2 h.

[0047] (2) The pretreated carbon felt was immersed in a mixed solution containing 50 mM ferric chloride hexahydrate and anhydrous ethanol solution and ultrasonically treated for 120 min. The treatment was divided into three stages. The first stage was 30 min. The solution temperature was maintained at 25 °C and the ultrasonic power density was 1.2 W / cm 2 , to achieve rapid penetration of metal ions in macroscopic pores; the second stage is 30 minutes, the temperature is raised to 40 ° C, and the ultrasonic power density is reduced to 0.5 W / cm 2 , promoting directional migration within the mesoporous channel; the third stage is 60min, applying 20mV / cm 2 A DC bias was applied and ultrasound was applied in intermittent mode, with a 5-second pause followed by a 2-second operation, to complete the anchoring of the nanoparticles in the microporous structure. The carbon felt, which had undergone the ultrasonic treatment, was then placed in an oven and dried at 60°C for 2 hours to obtain a carbon felt with FeCl3 attached.

[0048] (3) The carbon felt with FeCl3 attached was subjected to thermal shock at a current of 60A, a voltage of 32V, a maximum temperature of 1100°C, and a vacuum atmosphere to obtain a carbon felt loaded with metals and metal oxides.

[0049] like Figure 5 As shown in (a), the electrode is prepared by thermal shock method, and its macroscopic morphology is gray-black. Figure 5 The comparison between (b) and (c) shows the changes in the surface of the electrode material before and after treatment. Figure 5As shown in (b), after cleaning and pretreatment, the CF exhibits a clean fiber structure, with individual carbon fibers approximately 5 μm in diameter. The carbon fibers exhibit neat parallel alignment, a smooth surface, and clear fiber outlines. This structural feature provides high surface cleanliness and good mechanical strength, making it suitable as an electrode material and providing a stable electron conduction path. Figure 5 (c) shows an SEM image of the carbon fiber after immersion in a FeCl₃·6H₂O solution and subsequent heat shock treatment. The catalyst particles are evenly and densely dispersed on each carbon fiber, increasing the surface roughness and active area. This surface modification enhances the electrode's electrocatalytic performance and promotes various redox reactions.

[0050] Table 2 Percentage of element content on the surface of Fe2O3 / CF electrode

[0051] element Atomic percentage (%) Weight percentage (%) C 75.73 57.64 O 16.26 16.48 Fe 5.98 21.18

[0052] Figure 6 Shown are the EDX spectrum of Fe2O3 / CF electrode and its corresponding SEM image. Figure 6 (a), (b), and (c) show the detailed chemical composition and surface microstructure of the Fe2O3 / CF electrode, respectively. EDX analysis results show that Fe and O elements are widely distributed on the electrode surface, and these particles are evenly distributed on the CF substrate, demonstrating the successful loading of the catalyst. This distribution is crucial for enhancing the electrochemical activity and catalytic efficiency of the electrode. As shown in Table 2, the atomic percentages of the three elements C, O, and Fe are 74.73%, 16.26%, and 5.98%, respectively. The weight percentages of the three elements C, O, and Fe are 57.64%, 16.48%, and 21.18%, respectively. In addition, the distribution of the Cl element was not found, which may be because the Cl element in FeCl3 evaporates into the air in the form of chlorine gas under ultra-high temperature conditions during the thermal shock process.

[0053] The results of the XPS spectrum further confirmed the presence of C, Fe, and O elements in the electrode, which is consistent with the Figure 6 The results of EDX were consistent. Figure 7 In (b), the peak of Fe element includes Fe 3+ 2p3 / 2(711.0eV), Fe 3+ Comparison of the 2p1 / 2 peak (724.7 eV) and two satellite peaks (715.8 and 730.9 eV) with a standard spectrum shows that these peaks are consistent with the characteristic peaks of Fe2O3, thus concluding that the Fe species supported on the CF is Fe2O3. Based on the above analysis, it can be concluded that the electrode material prepared by the above thermal shock process is Fe2O3 / CF.

[0054] like Figure 8As shown in (a), under the same voltage change, the current response of the Fe2O3 / CF cathode is more sensitive than that of the CF cathode, which shows that the addition of Fe2O3 is beneficial to improving the redox activity of the electrode. Figure 8 As shown in (b), the diameter of the semicircle representing Fe2O3 / CF is smaller than that of CF, indicating that Fe2O3 / CF has a smaller charge transfer resistance. This is because the addition of Fe improves the cathode's charge transfer capacity and increases the surface reaction rate.

[0055] The results of electrochemical characterization show that the Fe2O3 / CF cathode synthesized by thermal shock technology has further improved its electrochemical performance and electrocatalytic activity while maintaining the original characteristics of CF.

[0056] Example 3: Electrochemical cathode-cathode coordinated treatment of reverse osmosis concentrated water and removal rate of methylisothiazolinone, a representative organic compound, in reverse osmosis concentrated water using single anode and single cathode.

[0057] In the electrochemical cathode-cathode coordinated treatment, the porous titanium plate with a metal oxide layer loaded on the intermediate layer prepared in Example 1 is used as the anode electrode, and the carbon felt material loaded with metal and metal oxide prepared in Example 2 is used as the cathode electrode.

[0058] The concentration of methylisothiazolinone was 50 mg / L. The solution pH was selected as 7 and the current density was 7.5 mA / cm 2 The water sample circulation flow rate is 5 mL / s, and the surface area of the cathode and anode is 20 cm 2 The geometric surface area ratio of the cathode and anode is 1:1. The electrolyte solution is a sodium sulfate solution with a concentration of 0.2 mol / L. Under the conditions of treatment time of 2 h, the removal rate of methylisothiazolinone by the synergistic effect of cathode and anode, single anode and single cathode was studied respectively. The results are as follows Figure 9 shown.

[0059] like Figure 9As shown in the methylisothiazolinone degradation experiment, the removal rates of methylisothiazolinone using single anode and single cathode technologies were relatively low. However, using the cathodic synergistic treatment technology, within the same treatment time, the removal rate of methylisothiazolinone was significantly higher, demonstrating that synergistic treatment significantly outperformed single anode or single cathode technologies in organic matter degradation. Furthermore, the sum of the single anode and single cathode treatment effects was less than the synergistic removal rate using the cathodic synergistic treatment, indicating that the synergistic treatment system not only leverages the treatment capabilities of both the cathodic and anodic processes but also directly produces a synergistic effect. This is because the oxygen generated during the anodic oxidation process dissolves in the water and becomes a reactant in the cathodic redox reaction. Dissolved oxygen is reduced at the cathode to form hydrogen peroxide, which promotes the electro-Fenton reaction. The hydrogen ions generated during the anodic reaction migrate to the cathode region and are consumed in the cathodic reaction, thereby maintaining the overall pH balance of the system. This improves the efficiency of the electro-Fenton reaction and increases the concentration of hydroxyl radicals in the system. Furthermore, the complementary reactions between the anode and cathode promote ion circulation in the solution, improving the overall electron utilization efficiency of the electrochemical reaction system. This synergistic effect enables the entire treatment system to more efficiently degrade organic pollutants in water, significantly improving the treatment effect.

[0060] Example 4: Electrochemical anodic and cathodic coordinated treatment of reverse osmosis concentrate and single-anode and single-cathode degradation of reverse osmosis concentrate from a coal chemical industry. In this example, the electrochemical anodic and cathodic coordinated treatment employed the porous titanium plate with a metal oxide layer on the intermediate layer, prepared in Example 1, as the anode electrode, and the metal and metal oxide-loaded carbon felt material, prepared in Example 2, as the cathode electrode.

[0061] The quality of the reverse osmosis concentrated water used in this embodiment is shown in Table 3.

[0062] Table 3 Reverse osmosis concentrated water quality

[0063] index unit value index unit value pH - 9.00 <![CDATA[Cl - ]]> mg / L 1.54×103 Conductivity μS / cm 33,000 <![CDATA[F - ]]> mg / L 55.92 COD mg / L 81.00 <![CDATA[NO 3- ]]> mg / L 955.44 DO mg / L 7.87 <![CDATA[K + ]]> mg / L 231.71 TOC mg / L 32.60 <![CDATA[Br - ]]> mg / L 2.53 TDS g / L 15.85 <![CDATA[Ca 2+ ]]> mg / L 0.57 <![CDATA[Na + ]]> mg / L 1.10×104 <![CDATA[Mg 2+ ]]> mg / L 0.14 <![CDATA[SO4 2- ]]> mg / L 1.64×104

[0064] The initial chemical oxygen demand was 81 mg / L. The solution pH was selected to be 3 and the current density was 7.5 mA / cm 2 The water sample circulation flow rate is 5 mL / s, and the surface area of the cathode and anode is 20 cm 2 Under the conditions of the geometric surface area ratio of anode and cathode being 1:1 and the treatment time being 2h, the removal efficiency of methylisothiazolinone by the synergistic effect of anode and cathode, single anode and single cathode was studied respectively. Figure 10 shown.

[0065] Depend on Figure 10The results show that the synergistic treatment of anodes and cathodes exhibits optimal performance at an initial chemical oxygen demand (COD) concentration of 81 mg / L. The COD concentration significantly drops to approximately 20 mg / L within 120 minutes, achieving a COD removal rate of 74.0% in the reverse osmosis concentrate. This efficiency far exceeds that of either single anodic oxidation or cathodic electro-Fenton. The experimental results demonstrate that the synergistic effect of anodes and cathodes significantly enhances reaction kinetics and pollutant degradation capacity. This synergistic effect increases COD removal by at least 50% compared to single treatment methods, providing key data support for efficient and low-cost wastewater treatment technologies.

[0066] Example 5: Stability of reverse osmosis concentrate from a coal chemical industry by electrochemical cation-cathode synergistic degradation.

[0067] In this embodiment, the porous titanium plate with a metal oxide layer loaded on the intermediate layer prepared in Example 1 is used as the anode electrode, and the carbon felt material loaded with metal and metal oxide prepared in Example 2 is used as the cathode electrode.

[0068] The initial COD concentration was 81 mg / L and the electrode area was 20 cm 2 , the solution volume is 400 mL, and the current density is 7.5 mA / cm 2 , flow rate 5mL / s, initial pH 3.0, cathode and anode area ratio of 1:1. Figure 11 shown.

[0069] like Figure 11 As shown in the figure, after six cycles of experiments within 720 minutes, the COD concentration of the water samples before and after treatment can be steadily reduced from 81 mg / L to about 20 mg / L in each treatment cycle. Although the treatment effect of each cycle decreases slightly, the results of each experiment can still be maintained at the same level. This shows that the system can still ensure the stable performance of the system water treatment after multiple treatments. After multiple cycle experiments, there is no obvious performance degradation of the electrode material, indicating that the anode and cathode materials used can operate for a long time under acidic conditions, verifying the long-term stability of the synergistic system in an acidic environment and ensuring the continuous and efficient operation of the synergistic system.

[0070] In summary, in the method of the present invention, during the preparation of the anode electrode, a mixed solution of ultrapure water, hydrochloric acid, and hydrogen peroxide in a volume ratio of 6:1:1 is used for plate pretreatment and cleaning to fully remove residual ions on the surface. Heat treatment is then performed to form an enhanced titanium dioxide nanotube array intermediate layer. During the preparation of the cathode electrode, ultrasonic treatment at different frequencies is used to adhere FeCl3 to the carbon felt. Furthermore, thermal shock technology is used to further enhance the electrochemical performance and electrocatalytic activity of the Fe2O3 / CF cathode while maintaining the original properties of CF. Oxygen generated during the anodic oxidation process dissolves in water and becomes a reactant in the cathode redox reaction. Dissolved oxygen is reduced at the cathode to form hydrogen peroxide, promoting the electro-Fenton reaction. Hydrogen ions generated during the anodic reaction migrate to the cathode region and are consumed in the cathode reaction, thereby maintaining the overall pH balance of the system, improving the efficiency of the electro-Fenton reaction, and increasing the concentration of hydroxyl radicals in the system. Furthermore, the complementary reactions between the anode and cathode promote ion circulation in the solution, improving the overall electron utilization efficiency of the electrochemical reaction system. This synergistic effect enables the entire treatment system to more efficiently degrade organic pollutants in water, significantly improving the treatment effect.

[0071] Although the present invention has been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments. The above-mentioned specific embodiments are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can make many improvements and changes without departing from the purpose of the present invention, which are all protected by the present invention.

Claims

1. A method for electrochemical cathode-anode coordinated treatment of reverse osmosis concentrated water, characterized in that: The treatment method uses cathode electro-Fenton treatment for reverse osmosis concentrated water and anodic oxidation treatment for reverse osmosis concentrated water. The pollutants in the pre-treated reverse osmosis concentrated water are refractory organic matter. The method includes: Step 1) The preparation of the anode electrode used for the anodic oxidation treatment of reverse osmosis concentrated water comprises: 1-1) Pretreatment of the porous titanium plate: The porous titanium plate was sequentially polished, immersed in a sodium hydroxide solution and heated in a water bath to remove residual impurities, ultrasonically cleaned with acetone and ultrapure water to remove the oxide layer, and immersed in a hydrochloric acid solution and heated in a water bath; finally, the porous titanium plate was transferred to a mixed solution of ultrapure water, hydrochloric acid, and hydrogen peroxide for cleaning to remove residual surface ions; 1-2) Synthesis of Enhanced Titanium Dioxide Nanotube Arrays: The pretreated porous titanium plate was immersed in a mixed solution of ammonium fluoride and ethylene glycol and anodized under an applied voltage to form a titanium dioxide nanotube array, which was then calcined in a muffle furnace to obtain an enhanced titanium dioxide nanotube array intermediate layer; 1-3) Catalytic layer loading: A metal oxide layer is loaded on the porous titanium plate intermediate layer by a sol-gel method; Step 2) The cathode electrode used for the cathode electro-Fenton treatment of reverse osmosis concentrated water is prepared according to the following steps: 2-1) Carbon felt pretreatment: The carbon felt material was ultrasonically cleaned in acetone, anhydrous ethanol, and ultrapure water in sequence, dried at a constant temperature, and then heated in a nitrogen atmosphere to form a graphitized conductive network on the surface of the carbon felt matrix, thereby improving the conductivity of the carbon felt material; 2-2) Catalyst loading: The pretreated carbon felt material is immersed in a salt solution containing metal ions and subjected to ultrasound at different frequencies, followed by constant temperature drying to obtain a carbon felt material with metal salt attached thereto; 2-3) Thermal shock of the electrode: by controlling the current and voltage, the carbon felt material with the metal salt attached is thermally shocked under suitable temperature and vacuum atmosphere conditions, and the carbon felt material loaded with metal and metal oxides obtained is the cathode electrode; Step 3) Electrochemical cathode and anode coordinated treatment of reverse osmosis concentrated water: 3-1) The reverse osmosis concentrated water is placed in the bipolar chamber reactor, and an electrolyte solution is added to control the initial pH of the solution to 3±0.2; the porous titanium plate with a metal oxide layer loaded on the intermediate layer prepared in step 1) is used as the anode electrode, and the carbon felt material loaded with metal and metal oxide prepared in step 2) is used as the cathode electrode; the volume ratio of the anode and cathode chambers of the bipolar chamber reactor is 1:1, and the current density is 7.5 mA / cm 2 The water sample circulation flow rate is 5 mL / s, and the surface area of the cathode and anode is 20 cm 2 The geometric surface area ratio of the cathode and anode is 1:1; the electrolyte solution is a sodium sulfate solution with a concentration of 0.2 mol / L, and the treatment time is 2 h. 3-2) When the power is turned on, the oxygen generated by the hydrolysis reaction at the anode diffuses to the cathode through the liquid phase, where an electro-Fenton reaction occurs to generate hydrogen peroxide; a redox reaction occurs at the anode to treat the reverse osmosis concentrated water.

2. The electrochemical cathode-anode coordinated treatment method for reverse osmosis concentrated water according to claim 1, characterized in that: In step 1-1), the porous titanium plate is polished with 2000-grit sandpaper; the concentration of the sodium hydroxide solution is 40%, the temperature of the water bath heating in the sodium hydroxide solution is 80±2° C., and the heating time is 30 min; the ultrasonic time of acetone and ultrapure water is 30 min; the volume ratio of the components of the mixed solution of ultrapure water, hydrochloric acid, and hydrogen peroxide is 6:1:1, wherein the concentration of hydrochloric acid is 37%, and the concentration of hydrogen peroxide is 30%.

3. The electrochemical cathode-anode coordinated treatment method for reverse osmosis concentrated water according to claim 1, characterized in that: In step 1-2), the volume fraction of ammonium fluoride in the mixed solution of ammonium fluoride and ethylene glycol is 4%, the applied voltage is 42 V, the anodization time is 6 h, the muffle furnace calcination temperature is 500±10° C., and the calcination time is 1 h.

4. The electrochemical cathode-anode coordinated treatment method for reverse osmosis concentrated water according to claim 1, characterized in that: The specific process of loading the metal oxide layer on the middle layer of the porous titanium plate by the sol-gel method in step 1-3) is as follows: dissolving citric acid in a dilute ethylene glycol solution and continuously stirring, heating the solution and adding tin tetrachloride pentahydrate and antimony trichloride and boiling; after aging the gel solution, using it to coat the treated porous titanium plate, and annealing it after drying; repeating the above-mentioned porous titanium plate coating gel solution-annealing process, and after completing the last porous titanium plate coating gel solution-annealing process, annealing the treated porous titanium plate and cooling it to room temperature, and using ultrapure water ultrasonic cleaning until the washing liquid is clear.

5. The electrochemical cathode-anode coordinated treatment method for reverse osmosis concentrated water according to claim 4, characterized in that: In the steps 1-3), the temperature of dissolving the citric acid in the ethylene glycol solution is 60±2°C, the stirring time is 30 minutes, the temperature of adding tin tetrachloride pentahydrate and antimony trichloride to the solution is 90±2°C, and the boiling time is 2 hours; the gel solution is aged for 3 months, the drying temperature is 140±5°C, and the drying time is 10 minutes; the annealing temperature is 500±10°C, the annealing duration is 10 minutes, the gel solution coating-annealing process of the porous titanium plate is repeated 15 times, and the last annealing time is 2 hours.

6. The electrochemical cathode-anode coordinated treatment method for reverse osmosis concentrated water according to claim 1, characterized in that: In step 2-1), the ultrasonic cleaning time in acetone, anhydrous ethanol, and deionized water is 30 minutes respectively; the constant temperature drying is carried out in an oven at a constant temperature of 60±2°C for 30 minutes; and the heating process is carried out in a nitrogen atmosphere at a heating rate of 5°C / min to 1073K and maintained at this temperature for 2 hours.

7. The electrochemical cathode-anode coordinated treatment method for reverse osmosis concentrated water according to claim 1, characterized in that: In step 2-1), the concentration of the metal ion-containing salt solution is 50 mM; the treatment with ultrasound at different frequencies includes three stages, wherein the treatment conditions of the first stage are: the ultrasound power density is 0.8-1.2 W / cm 2 The treatment time is 30 minutes, and the temperature of the salt solution containing metal ions is 25±2℃. This stage realizes the rapid penetration of metal ions in the macropores. The treatment conditions of the second stage are: ultrasonic power density of 0.3-0.5W / cm 2 The treatment time is 30min, and the temperature of the salt solution containing metal ions is 40±2℃. This stage promotes the directional migration in the mesoporous channel. The treatment conditions of the third stage are: applying 10-30mV / cm 2 The DC bias is applied for 60 minutes, and the ultrasonic intermittent mode is selected, with a 2-second pause after every 5-second operation. The nanoparticles in the microporous structure are anchored in this stage. The constant temperature drying is carried out in an oven at a constant temperature of 60±2° C. for 2 hours.

8. The electrochemical cathode-anode coordinated treatment method for reverse osmosis concentrated water according to claim 1, characterized in that: In step 2-3), the current is 60A, the voltage is 32V, and the temperature is 1100±50°C.

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