Intermittent electrocatalytic treatment method for trace estrogen in reclaimed water

Abstract

This invention relates to the field of water treatment technology and discloses an intermittent electrocatalytic treatment method for trace estrogen in reclaimed water. The method is carried out in a three-dimensional electrode reactor. Before formal treatment, a pre-treated water sample containing the estrogen to be removed is used to pre-saturate the particle electrode. Subsequently, reclaimed water containing one or more estrogenic pollutants is continuously introduced into the reactor, operating at a current density of 1.0–10.0 mA / cm², a hydraulic retention time of 5–20 min, and an aeration rate of 0–3.0 L / min. An intermittent power supply mode with alternating power on and off is employed, wherein the ratio of power on time to power off time is 1:1, and the power off time is 2–120 s. During the power off phase, the estrogen to be removed accumulates on the surface of the particle electrode. During the power on phase, the particle electrode repolarizes to form a micro-battery and undergoes electrochemical oxidation in conjunction with the anode, causing direct oxidation and / or indirect oxidation mediated by an electrogenerated oxidant, while the particle electrode achieves in-situ regeneration. The method is applicable to the treatment of trace amounts of estrogens in reclaimed water, preferably one or more of estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-ethinylestradiol (EE2), and bisphenol A (BPA). This invention can reduce the artificially inflated impact of adsorption on the evaluation of treatment effectiveness, and reduce energy consumption while ensuring treatment efficiency.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and specifically to an intermittent electrocatalytic treatment method for trace amounts of estrogen in reclaimed water. Background Technology

[0002] Urban wastewater reuse is an important way to alleviate water shortages and improve water quality. In recent years, trace amounts of emerging pollutants have been frequently detected in the secondary effluent of urban wastewater treatment plants, with estrogen-like pollutants showing a high detection rate. These pollutants can easily have adverse effects on the safety of reclaimed water and the ecological environment. Existing urban wastewater treatment processes are mainly designed for traditional pollution indicators and have limited effectiveness in removing trace amounts of estrogen-like pollutants.

[0003] Three-dimensional electrode technology combines adsorption and electrochemical oxidation, exhibiting higher mass transfer and current efficiency compared to traditional two-dimensional electrodes, thus making it suitable for treating organic pollutants. However, existing three-dimensional electrode treatment technologies are primarily designed for high concentrations of organic pollutants, and the removal of trace estrogens from reclaimed water still faces the following challenges: First, the adsorption effect of the particle electrode significantly impacts the apparent removal rate of trace pollutants; without distinguishing between adsorption and oxidation contributions, it is difficult to objectively evaluate the true treatment effect of the method. Second, continuous power supply operation mode consumes a lot of energy, hindering engineering applications. Third, the particle electrode is prone to long-term stable operation due to adsorption accumulation during the treatment process.

[0004] Therefore, there is an urgent need to provide a three-dimensional electrode treatment method that can take into account the actual removal effect, energy-saving operation and stability, so as to achieve efficient removal of trace estrogen in reclaimed water. Summary of the Invention

[0005] The purpose of this invention is to provide a method for treating trace amounts of estrogen in reclaimed water using intermittent power supply three-dimensional electrode technology, so as to solve the problems of apparent removal rate distortion, high energy consumption and insufficient operational stability in the existing three-dimensional electrode treatment of trace estrogen.

[0006] To achieve the above objectives, the present invention employs the following technical solution: In a three-dimensional electrode reactor comprising an anode plate, a cathode plate, and a particle electrode, the particle electrode is first pre-saturated with a high-concentration pretreated water sample containing the estrogen to be removed, to reduce the interference of adsorption on the evaluation of subsequent treatment effects; subsequently, reclaimed water containing one or more estrogenic pollutants is continuously introduced into the reactor, and electrocatalytic treatment is performed using an intermittent power supply mode. During the power-off phase, the estrogen to be removed accumulates on the surface of the particle electrode; during the power-on phase, the particle electrode repolarizes to form a large number of micro-batteries, which, in conjunction with the anode plate, undergo an electrochemical oxidation reaction, causing the estrogen to be removed to be degraded through direct oxidation and / or indirect oxidation mediated by an electrogenerated oxidant, while the particle electrode is regenerated in situ.

[0007] Preferably, the anode plate is a boron-doped diamond electrode plate, the cathode plate is a stainless steel electrode plate, and the particle electrode is an activated carbon-based tin-antimony-titanium composite catalyst particle electrode.

[0008] Preferably, the distance between the anode plate and the cathode plate is 2 cm, and the stacking height of the particle electrodes in the reactor is 60% to 80% of the effective height of the reactor.

[0009] Preferably, the operating current density is 1.0–10.0 mA / cm², the hydraulic retention time is 5–20 min, and the aeration rate is 0–3.0 L / min. Preferably, in the intermittent power supply mode, the ratio of power-on time to power-off time is 1:1, and the power-off time is 2–120 s.

[0010] Compared with the prior art, the present invention has at least the following beneficial effects: (1) By setting a pre-adsorption saturation step before formal power-on, the present invention can weaken the falsely high removal rate caused by particle electrode adsorption, and make the evaluation of treatment effect closer to the real electrocatalytic contribution; (2) The present invention adopts an intermittent power supply method, which promotes the migration and enrichment of target pollutants to the particle electrode surface during the power-off stage, and achieves efficient oxidation degradation during the power-on stage, thereby reducing system energy consumption while ensuring treatment effect; (3) The present invention takes the treatment method as the core of protection and introduces activated carbon-based tin-antimony-titanium composite catalytic particle electrode as the preferred implementation method, which effectively improves the treatment efficiency.

[0011] (4) This invention is applicable to the removal of trace estrogen in reclaimed water. By regenerating the particle electrode in situ during the treatment process, the frequency of particle electrode replacement and cleaning is reduced, and it has good stability under continuous operation conditions. Attached Figure Description

[0012] Figure 1 This is a schematic flowchart of a method for treating trace amounts of estrogen in reclaimed water according to an embodiment of the present invention.

[0013] Figure 2 This is a schematic diagram of the structure of the activated carbon-based tin-antimony-titanium composite catalytic particle electrode used in one embodiment of the present invention;

[0014] Figure 3 This is a surface microstructure diagram of the activated carbon-based tin-antimony-titanium composite catalytic particle electrode used in one embodiment of the present invention.

[0015] Figure 4 This is a comparative diagram showing the processing effects of intermittent power supply and continuous power supply methods in this invention.

[0016] Figure 5 This is a comparative diagram showing the treatment effect of the activated carbon-based tin-antimony-titanium composite catalytic particle electrode used in this invention compared with other types of particle electrodes.

[0017] Explanation of reference numerals in the attached figures:

[0018] 10-Titanium oxide coating; 20-Tin antimony oxide intermediate layer; 30-Activated carbon carrier. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the reagents, materials and equipment used in the embodiments can be obtained through conventional commercial means, and the experimental methods used are conventional methods in the art.

[0020] like Figure 1 As shown, the method of the present invention includes the following process flow: S1, preparing a composite particle electrode; S2, pre-saturating the particle electrode; S3, electrocatalytically treating the reclaimed water to be treated using an intermittent power supply; S4, detecting the treated effluent; S5, comparing the effects of the method of the present invention with those of a comparative method. Preferably, the present invention employs a continuous flow three-dimensional electrode reaction system. The pre-saturation treatment reduces the interference of the initial adsorption of the particle electrode on the evaluation of the removal rate of the target pollutants. The intermittent power supply is used to achieve the enrichment of the target pollutants during the power-off phase and their oxidative degradation during the power-on phase, while simultaneously achieving in-situ regeneration of the particle electrode. Through the above process flow, stable removal of trace amounts of estrogen from reclaimed water can be achieved, balancing treatment efficiency and energy consumption control.

[0021] Example 1: Preparation of activated carbon-based tin-antimony-titanium composite catalytic particle electrode

[0022] In a preferred embodiment, the composite particle electrode is an activated carbon-based tin-antimony-titanium composite catalytic particle electrode, comprising an activated carbon support 30, a tin-antimony oxide intermediate layer 20 on the surface of the activated carbon support 30, and a titanium oxide coating 10 on the surface of the tin-antimony oxide intermediate layer 20; the preparation method of the particle electrode is as follows:

[0023] Pretreatment of activated carbon carrier 30: Rinse the activated carbon multiple times with deionized water until no floating carbon powder is in the water, then soak it in a dilute methanol solution to remove organic impurities on the surface of the activated carbon; then soak it in a hot alkaline solution to remove oil impurities on the surface of the activated carbon; finally rinse it multiple times with deionized water again, and after the pH of the deionized water has not changed much, dry it in an oven at 80-105℃.

[0024] Tin-antimony oxide intermediate layer 20 loading: Prepare solution A, which is an ethanol solution of SnCl4 and SbCl3, with a tin to antimony concentration ratio of 10:1; immerse the pretreated activated carbon carrier in solution A, place it in a constant temperature shaker to mix thoroughly for 2-3 hours, and then dry it overnight in an oven at 105℃; repeat this step once for secondary loading.

[0025] Titanium oxide coating 10 loading: Solutions B and C were prepared. Solution B was an ethanol solution of tetrabutyl titanate, with a titanium concentration 100 times that of tin in solution A. Solution C was a mixed solution of acetic acid, water, and ethanol, with a volume ratio of 0.3:1:8. Solution C was added dropwise to solution B under high-speed stirring, and stirred thoroughly for 2 hours to form a pale yellow transparent gel solution D. Activated carbon with a tin-antimony oxide intermediate layer was immersed in gel solution D, thoroughly mixed in a constant-temperature shaker, removed, and aged in a fume hood. After removing excess gel, it was dried overnight in a 105°C oven and finally sintered in a muffle furnace at 500°C for 3 hours. This step was repeated once to obtain the activated carbon-based tin-antimony-titanium composite catalytic particle electrode.

[0026] The concentration ratio of tin, antimony, and titanium in the aforementioned particle electrode is 10:1:1000. The composite catalytic coating prepared by a combination of impregnation and sol-gel methods exhibits a relatively dense nanoparticle structure with a particle size of approximately 10-20 nm. Figure 3 As shown.

[0027] Example 2: Construction of the reaction system and intermittent electrocatalytic treatment of reclaimed water

[0028] A continuous-flow three-dimensional electrode reactor was used as the main reaction body. An anode plate, a cathode plate, and particle electrodes were arranged inside the reactor, with the anode and cathode plates vertically positioned within the reactor, and the space between them filled with particle electrodes. In this embodiment, the anode plate was a boron-doped diamond electrode plate, and the cathode plate was a stainless steel electrode plate, with a 2cm distance between them. The particle electrodes were the activated carbon-based tin-antimony-titanium composite catalyst particle electrodes prepared in Example 1, with a stacking height of 60%–80% of the effective height of the reactor. The water sample to be treated was reclaimed water containing E1, E2, E3, EE2, and BPA, with an initial concentration of 1000 μg / L for each target pollutant.

[0029] Before the formal electrolysis begins, to eliminate the artificially inflated contribution of particle electrode adsorption to the system's treatment effect, a pretreated water sample containing a target pollutant concentration greater than 10 mg / L is used to pre-adsorb the particle electrode. When the estrogen concentration in the reactor effluent changes to less than 100 μg / L, the particle electrode is considered to have reached adsorption equilibrium. At this point, pretreatment is stopped and formal electrocatalytic treatment begins.

[0030] After the particle electrode reaches adsorption saturation, an intermittent current is applied to the three-dimensional electrode reactor. The intermittent circulation switch is turned on, and a current is applied between the anode and cathode plates through a DC power supply. The water sample to be treated enters the three-dimensional electrode reactor for electrocatalytic oxidation.

[0031] During the power-off phase, the target pollutants in the water sample diffuse, migrate, and accumulate on the surface of the particle electrode. During the power-on phase, the particle electrode is repolarized under the action of the electric field to form multiple micro-batteries. Under the combined action of the anode plate and the reaction sites on the particle electrode surface, the target pollutants undergo oxidative degradation, while the particle electrode is regenerated in situ.

[0032] The applied current density during the reaction is 1.0-10.0 mA / cm². 2 The hydraulic retention time is 5-20 min, and the aeration rate is 0-3.0 L / min. The power supply is intermittent, with a power-on time to power-off time ratio of 1:1 and a power-off time of 2-120 s.

[0033] The treatment results showed that when the hydraulic retention time was 20 min, the removal rate of the five estrogens in the reclaimed water was all above 99%, with an average removal rate of 99.5% ± 1.03%.

[0034] Comparative Example 1: Electrocatalytic treatment of reclaimed water using a continuous power supply method

[0035] The continuous flow three-dimensional electrode system described in Example 2 was used to treat reclaimed water containing five estrogens (E1, E2, E3, EE2, and BPA), with an initial estrogen concentration of 1000 μg / L. In this example, a continuous power supply was used, i.e., the power outage time was 0, and the applied current density during operation was 2.0 mA / cm². 2 The aeration rate was 0, and the hydraulic retention time was 10 minutes. Under the same operating conditions, the effects of continuous power supply and intermittent power supply on the removal of estrogen from reclaimed water were compared as follows: Figure 4 As shown, the continuous power supply corresponds to T. on / T off The removal effect when T is 0. on / T off When the power supply is 120s / 120s, the system achieves an average removal rate of 84.9% for the five estrogens in the reclaimed water, which is the same as when using continuous power. The removal rates for E3 and BPA even exceed those achieved with continuous power. Using this power supply method, energy consumption is only half that of continuous power.

[0036] Comparative Example 2: Electrocatalytic treatment effect when using other types of particle electrodes

[0037] The continuous flow three-dimensional electrode system described in Example 2 was used to treat reclaimed water containing five estrogens (E1, E2, E3, EE2, and BPA), with an initial estrogen concentration of 1000 μg / L. In this example, the estrogen removal efficiency of different types of particle electrodes was examined under the same operating conditions, including a comparison between the composite particle electrode described in this invention and a composite particle system composed of glass beads and graphite particles. During operation, pre-adsorption treatment was also performed, with an applied current density of 2.0 mA / cm². 2 Aeration rate is 0, hydraulic retention time is 20 min, T on / T off It is 120s / 120s. For example... Figure 5 As shown in the figure, the adsorption process is represented by no power applied from 0-180 min, and the three-dimensional electrolysis process is represented by power applied from 180-420 min. When activated carbon-based particle electrodes are used as particle electrodes, the system's removal rate of estrogen is higher than that of graphite-based particle electrodes. When GAC-type particles are used as particle electrodes, the removal rate of the target estrogen is 93.9%-97.0%; when graphite-type particles are used as particle electrodes, the removal rate of the target estrogen is only 17.6%-19.9%. Using the composite particle electrode described in this invention improves the removal efficiency by more than 80% compared to using graphite particle electrodes, and also has higher stability.

[0038] The above description is merely a preferred embodiment of the present invention. It should be understood that the scope of protection of the present invention is not limited thereto. Any equivalent changes, modifications, substitutions or variations made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for intermittent electrocatalytic treatment of trace estrogen in reclaimed water, characterized in that, The process includes the following steps: (1) providing an electrocatalytic reaction system, which includes an anode plate, a cathode plate, and a particle electrode located between the anode plate and the cathode plate; (2) before treating the reclaimed water, pre-saturating the particle electrode with a pre-treated water sample containing the target estrogen until the particle electrode reaches adsorption equilibrium; (3) introducing the reclaimed water containing one or more trace amounts of estrogen into the electrocatalytic reaction system and performing electrocatalytic treatment under intermittent power supply conditions, wherein, during the power-off phase, the target estrogen migrates to the surface of the particle electrode and accumulates; during the power-on phase, the particle electrode repolarizes to form a micro battery, which, together with the anode plate, causes the target estrogen to undergo electrochemical oxidation degradation and enables the particle electrode to achieve in-situ regeneration; (4) discharging the treated effluent.

2. The method according to claim 1, characterized in that, The target trace estrogen contaminants are one or more of estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-ethinylestradiol (EE2), and bisphenol A (BPA), at a concentration in the μg / L range.

3. The method according to claim 1 or 2, characterized in that, The concentration of estrogen in the pretreated water sample in step (2) is greater than 10 mg / L; when the change in estrogen concentration in the reactor effluent is less than 100 μg / L, the particle electrode is determined to have reached adsorption equilibrium.

4. The method according to any one of claims 1 to 3, characterized in that, The anode plate is a boron-doped diamond electrode plate, and the cathode plate is a stainless steel electrode plate.

5. The method according to any one of claims 1 to 4, characterized in that, The particle electrode is an activated carbon-based tin-antimony-titanium composite catalyst particle electrode, which includes an activated carbon support, a tin-antimony oxide intermediate layer on the surface of the activated carbon support, and a titanium oxide coating on the surface of the tin-antimony oxide intermediate layer.

6. The method according to claim 5, characterized in that, The activated carbon-based tin-antimony-titanium composite catalytic particle electrode is prepared by the following method: first, an intermediate layer of tin-antimony oxide is loaded onto the surface of an activated carbon support by impregnation, and then a titanium oxide coating is loaded by sol-gel method, and sintered at 500-550℃ for 3 h, and the coating is repeated once; wherein, the concentration ratio of tin, antimony and titanium is 10:1:1000.

7. The method according to any one of claims 1 to 5, characterized in that, The distance between the anode plate and the cathode plate is 2 cm; the stacking height of the particle electrodes in the reactor is 60% to 80% of the effective height of the reactor.

8. The method according to any one of claims 1 to 6, characterized in that, The current density during operation of the method is 1.0–10.0 mA / cm², the hydraulic retention time is 5–20 min, and the aeration rate is 0–3.0 L / min; in the intermittent power supply mode, the ratio of power-on time to power-off time is 1:1, and the power-off time is 2–120 s.

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