A method for treating antibiotic wastewater based on activation of persulfate

Abstract

The present application relates to the technical field of water treatment, and discloses an antibiotic wastewater treatment method based on peroxymonosulfate activation, which comprises the following steps: pumping antibiotic wastewater into a continuous flow fixed bed reactor filled with carbon-coated copper-doped MXene catalyst, and synchronously injecting peroxymonosulfate solution to perform a heterogeneous destruction reaction; draining the water and measuring and controlling the residual peroxymonosulfate in the water phase and the real-time dissolved copper ion concentration; introducing the water into a continuous stirring reaction kettle, reducing the pH value, and compensating copper sulfate as appropriate to establish the total free copper concentration, then adding citric acid and hydrogen peroxide to perform a homogeneous ternary synergistic deep mineralization reaction; and finally, adjusting the alkalinity of the water and performing sedimentation separation. The present application uses the synergy and series connection of heterogeneous interface catalysis and homogeneous body phase, directly converts the dissolved metal into a homogeneous catalytic center, effectively overcomes the incomplete mineralization of a single system and causes the toxicity rebound problem, and realizes the removal of heavy metals and closed loop, thereby avoiding secondary pollution.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a method for treating antibiotic wastewater based on persulfate activation. Background Technology

[0002] The widespread use of antibiotics in the medical and agricultural fields has led to the discharge of large quantities of antibiotic wastewater containing high concentrations of recalcitrant organic matter, placing severe pressure on aquatic ecosystems. Advanced oxidation processes based on persulfate activation are currently widely used in the degradation of antibiotic wastewater due to their strong oxidizing power and relatively mild operating conditions. This process typically employs transition metal-based heterogeneous catalysts to activate persulfate, generating highly reactive species that disrupt the molecular structure of pollutants.

[0003] However, in current practical engineering applications, if only a single heterogeneous catalytic system is used to treat antibiotic wastewater, the oxidation reaction is often limited by the mass transfer resistance at the solid-liquid interface, making it difficult to directly and completely mineralize large-molecule antibiotic pollutants into carbon dioxide and water. After the ring-opening and bond-breaking of large-molecule organic matter, a large number of short-chain aliphatic carboxylic acids and nitrogen-containing organic fragments, which are difficult to degrade, are generated in the aqueous phase. As these intermediates continue to accumulate in the system, considering that their cell membrane permeability is usually higher than that of the parent antibiotic compound, this leads to a thorny problem: the acute biotoxicity of the treated effluent increases instead of decreasing, which is the so-called toxicity rebound phenomenon.

[0004] Besides the toxicity risks from incomplete mineralization, the stability of the catalyst itself is also a major bottleneck in this process. Transition metal catalysts generally face the inherent defect of irreversible dissolution of active metal components in working environments with continuous water flow and strong oxidants. The continuous loss of metal ions not only reduces the effective catalytic centers in the solid-phase catalytic system within the fixed-bed reactor, leading to a decrease in the overall wastewater treatment efficiency of the system; but also, the free heavy metal ions directly discharged with the treated effluent can exceed environmental emission standards, causing significant secondary pollution problems.

[0005] To overcome the limitations of heterogeneous catalysts, the industry often uses two-dimensional layered materials with large specific surface areas (such as MXene) as catalytic frameworks or supports when developing novel catalytic materials. However, in persulfate advanced oxidation systems, the unprotected surface structure of two-dimensional materials is highly susceptible to direct erosion by strong aqueous oxidants. Especially under long-term continuous flow operation, this continuous chemical erosion can damage the layered framework of the material, leading to a decrease in catalyst structural rigidity and even physical collapse. This not only significantly shortens the catalyst's lifespan but also increases the operation and maintenance costs of water treatment systems. Summary of the Invention

[0006] The technical problem solved by this invention is that, in existing advanced oxidation processes for treating antibiotic wastewater, a single heterogeneous catalytic system is insufficient to completely mineralize large molecular pollutants; and the recalcitrant small molecular intermediates generated after the ring-opening degradation of large molecules accumulate, leading to an acute rebound in the biotoxicity of the effluent. Simultaneously, transition metal catalysts have an inherent defect of leaching active components during the reaction, which not only causes secondary heavy metal pollution but also leads to a loss of system catalytic efficiency.

[0007] To address the above problems, the present invention provides the following technical solution: This invention provides a method for treating antibiotic wastewater based on persulfate activation, employing the following technical solution: A method for treating antibiotic wastewater based on persulfate activation, comprising: Antibiotic wastewater is pumped into a continuous flow fixed-bed reactor filled with carbon-coated copper-doped MXene catalyst, and persulfate aqueous solution is injected simultaneously to carry out a heterogeneous ring-breaking reaction to obtain primary treated effluent. The primary treated effluent is diverted to the buffer monitoring and control section to obtain the residual persulfate concentration and real-time dissolved copper ion concentration in the aqueous phase, and the monitored effluent is output. The monitored effluent was introduced into a continuously stirred reactor, and sulfuric acid solution was pumped in to adjust the pH value. When the real-time concentration of dissolved copper ions was lower than the lower limit benchmark, copper sulfate solution was added dropwise to establish the total free copper ion concentration and obtain an acidic substrate mixture. Citric acid solution and hydrogen peroxide solution were added to the acidic substrate mixture to carry out a homogeneous ternary synergistic deep mineralization reaction to obtain deeply mineralized effluent. The deep mineralized effluent overflows into the terminal neutralization reaction tank, where sodium hydroxide solution is added to adjust the pH value and precipitate out the sediment. The clear liquid is then separated to complete the wastewater treatment.

[0008] By adopting the above technical solution, this invention connects heterogeneous interfacial catalysis with a homogeneous phase synergistic process, directly utilizing and converting the metal components dissolved from the fixed bed into homogeneous catalytic centers. Combined with the conversion of a two-stage oxidation mechanism, it achieves deep mineralization of antibiotic pollutants and compliance control of heavy metals. The specific reaction process and mechanism are as follows: In the heterogeneous reaction stage, the surface of the carbon-coated copper-doped MXene catalyst is rich in carbon defects. These defect sites undergo redox reactions with persulfate via a non-radical pathway, primarily generating singlet oxygen. This singlet oxygen can selectively oxidize heterocyclic structures with high electron cloud density in antibiotic molecules, achieving ring-opening and bond breaking of the macromolecular organic framework. This non-radical oxidation pathway exhibits good resistance to background chloride or carbonate ions in the aqueous environment. However, the short-chain aliphatic carboxylic acids and nitrogen-containing organic fragments generated after the ring-opening degradation of macromolecules have cell membrane permeability, which often leads to increased acute biotoxicity in water. Furthermore, some copper active components inevitably dissolve into the aqueous phase during this process.

[0009] Given the aforementioned metal dissolution and intermediate accumulation, the reaction solution subsequently enters a homogeneous ternary synergistic deep mineralization process. The system establishes a baseline concentration of divalent free copper ions through a pre-treatment control and compensation mechanism. Subsequently, citric acid is added under acidic conditions, causing the free divalent copper ions to coordinate with citric acid molecules to form divalent copper coordination compounds. Hydrogen peroxide introduced into the system acts as an electron donor, reducing the divalent copper coordination compounds to highly catalytically active cuprous coordination compounds. These cuprous centers then promote the breaking of peroxy bonds in the residual persulfate in the system, thereby generating sulfate radicals and hydroxyl radicals. These radicals possess strong oxidation potentials, non-selectively breaking and ring-opening bonds in the previously accumulated highly toxic organic fragments, converting the organic carbon skeleton structure into carbon dioxide, effectively interrupting the accumulation process of toxic byproducts. The main chemical reaction equations for this homogeneous activation process are as follows: ; ; After the organic matter has been degraded, the homogeneously generated free radicals not only remove antibiotic fragments from the wastewater, but also simultaneously inorganically degrade citric acid, which acts as a ligand. As the coordination environment is disrupted, copper ions in the aqueous phase enter the terminal neutralization reaction tank with the water flow, and are then converted into copper hydroxide flocculation and sedimentation under alkaline conditions regulated by sodium hydroxide, ultimately completing the closed-loop heavy metal removal of the entire system and ensuring full utilization of the reagents.

[0010] Preferably, when antibiotic wastewater is pumped into a continuous flow fixed-bed reactor filled with carbon-coated copper-doped MXene catalyst, and persulfate aqueous solution is injected simultaneously for heterogeneous ring-breaking reaction, the initial persulfate concentration of the influent mixture is adjusted to 0.3-0.5 mmol / L, sodium hydroxide solution is added to control the pH of the influent to 7.5-8.5, and the influent flow rate is adjusted to maintain the hydraulic residence time of the wastewater in the continuous flow fixed-bed reactor at 15-20 minutes.

[0011] By adopting the above technical solution, maintaining the influent in a weakly alkaline environment helps to generate singlet oxygen at the catalyst interface; in addition, setting a matching hydraulic residence time and oxidant concentration ensures the full destruction of the antibiotic parent molecule structure, while also avoiding the ineffective decomposition of persulfate.

[0012] Preferably, when diverting the primary treated effluent to the buffer monitoring and control pipe section, and obtaining the residual persulfate concentration and real-time dissolved copper ion concentration in the aqueous phase, the residual persulfate concentration is calculated by substituting the initial COD load and hydraulic retention time of the influent into the preset first-order decay kinetic model, and the real-time dissolved copper ion concentration is obtained simultaneously through an online heavy metal detector.

[0013] By adopting the above technical solution and utilizing the coupling of the kinetic model and online detection equipment, the inventory data of key materials in the aqueous phase can be obtained in real time, providing a calculation basis for the accurate addition of acid and alkali reagents and hydrogen peroxide in the downstream homogeneous reactor, and preventing reaction stagnation caused by excessive or insufficient reagents.

[0014] Preferably, the monitored effluent is introduced into a continuously stirred reactor, sulfuric acid solution is pumped in to lower the pH value, and copper sulfate solution is added dropwise when the real-time dissolved copper ion concentration is lower than the lower limit benchmark. When the total free copper ion concentration is established, the pH value of the system is gradually adjusted down to 3.5-4.5. The lower limit benchmark is 0.5-1.0 mg / L, and the compensation bypass is activated to make up the difference when the real-time dissolved copper ion concentration is lower than the lower limit benchmark; otherwise, no dropwise addition is performed.

[0015] By employing the above technical solution, adjusting the gradient down to the acidic range is a thermodynamically necessary condition for maintaining the coordination stability of citric acid and preventing premature precipitation of heavy metals. By establishing a lower limit benchmark for bypass supplementation, the fluctuations caused by the instability of metal dissolution in the heterogeneous stage are compensated, thereby ensuring that there are always sufficient metal catalytic centers in the homogeneous system to initiate the free radical chain reaction.

[0016] Preferably, when adding citric acid solution and hydrogen peroxide solution to the acidic substrate mixture for homogeneous ternary synergistic deep mineralization reaction, the molar ratio of citric acid to total free copper ion concentration is controlled at 1.2 to 2.0:1 to generate complex catalytic centers in situ. Subsequently, hydrogen peroxide solution is injected according to the residual persulfate concentration, and the molar ratio of hydrogen peroxide to residual persulfate is controlled at 1:2 to 5. Mechanical stirring is maintained and the hydraulic residence time is 30 to 45 minutes.

[0017] By adopting the above technical solution, maintaining a slight excess of citric acid can ensure that free copper ions in the aqueous phase are fully coordinated, thus constructing a stable redox electron shuttle channel. Meanwhile, hydrogen peroxide with a specific molar ratio is used only as an inducer to reduce high-valence metal centers. This avoids the situation where excessive dosage leads to direct side reactions with the generated free radicals, resulting in quenching.

[0018] Preferably, the preparation method of the carbon-coated copper-doped MXene catalyst includes: HCl solution and Ti3AlC2 powder were mixed in a specific ratio. LiF powder was added and mixed evenly. Ti3AlC2 powder was then slowly added and in-situ etching was performed by continuous magnetic stirring to obtain the etching product. The etching product was repeatedly centrifuged and washed with deionized water and ultrasonically peeled off. The supernatant was collected by centrifugation to obtain an MXene suspension. Copper sulfate pentahydrate was weighed, dissolved, and added dropwise to the MXene suspension. The mixture was magnetically stirred and adsorbed. A copper-loaded MXene mixture was obtained through ion exchange and electrostatic interaction. Glucose was added as a carbon source precursor to a copper-loaded MXene mixture, and the mixture was continuously stirred to allow glucose molecules to be uniformly physically adsorbed on the surface of the nanosheets, thus obtaining an organic-coated product. The organic-coated product was freeze-dried to remove moisture, then placed in a tube furnace for heat treatment under argon protection, carbonized at a constant temperature, and cooled to room temperature to obtain a carbon-coated copper-doped MXene catalyst.

[0019] By employing the above-mentioned technical solution, an aluminum layer is removed through etching and ultrasonic exfoliation to obtain a two-dimensional layered substrate with a large specific surface area. Subsequently, copper ions are uniformly dispersed on the layered framework through electrostatic adsorption, providing basic catalytic sites. The glucose carbon source is carbonized in situ after heat treatment to form a coating layer. The carbon defects generated within this layer not only constitute the core sites for the activation of persulfate to generate singlet oxygen, but also effectively prevent the direct erosion of the underlying two-dimensional material by the aqueous oxidant, thereby improving the structural rigidity and service life of the catalyst.

[0020] Preferably, when HCl solution and Ti3AlC2 powder are mixed in a specific ratio, LiF powder is added and mixed evenly, and Ti3AlC2 powder is slowly added and in-situ etching is performed by continuous magnetic stirring, the HCl solution with a concentration of 6-9 mol / L is mixed with Ti3AlC2 powder in a specific ratio, and the mass ratio of LiF to Ti3AlC2 is 1-1.5:1, and the mixture is continuously magnetically stirred at 35-45°C for 24-48 hours.

[0021] Preferably, the etching product is repeatedly centrifuged and washed with deionized water and ultrasonically peeled off. When collecting the supernatant after centrifugation to obtain an MXene suspension, the product is repeatedly centrifuged and washed until the pH of the supernatant is >6.0. Then, ultrasonic peeling is performed for 1-2 hours, and samples are taken to determine the solid content to obtain an MXene suspension with a known mass concentration. Copper sulfate pentahydrate is weighed, dissolved, and added dropwise to the MXene suspension. The mixture is magnetically stirred and adsorbed. When obtaining a copper-loaded MXene mixture through ion exchange and electrostatic interaction, the total number of moles of Ti atoms in the system is calculated based on the solid content. Copper sulfate pentahydrate is weighed according to a Cu to Ti molar ratio of 0.2-0.4:1 and magnetically stirred and adsorbed for 12-24 hours.

[0022] Preferably, glucose is added as a carbon source precursor to the copper-loaded MXene mixture, and the glucose molecules are continuously stirred to allow them to be uniformly physically adsorbed on the surface of the nanosheets. The mass ratio of glucose to MXene solid content is controlled to be 0.5 to 1.0:1, and the mixture is continuously stirred for 4 to 8 hours.

[0023] Preferably, the organic coating product is freeze-dried to remove moisture, placed in a tube furnace for heat treatment under argon protection, carbonized at a constant temperature and cooled to room temperature to obtain a carbon-coated copper-doped MXene catalyst. The temperature is then increased to 500-700°C at a heating rate of 2-5°C / min and carbonized at a constant temperature for 2-4 hours.

[0024] By adopting the above technical solution, the boundaries of physicochemical parameters such as concentration, temperature, ratio, and heat treatment process in the catalyst preparation process are defined. The synergistic control of each parameter condition ensures the balance between metal component loading and carbon defect formation, which can avoid structural collapse due to excessively high heat treatment temperature and incomplete carbonization due to excessively low temperature, thus providing a stable solid-phase catalytic material for front-end heterogeneous wastewater treatment.

[0025] This invention provides a method for treating antibiotic wastewater based on persulfate activation. It has the following beneficial effects: 1. This invention combines fixed-bed heterogeneous catalytic ring breaking with homogeneous deep mineralization in a reactor. It utilizes singlet oxygen generated by carbon-coated copper-doped MXene catalyst to achieve ring-opening and bond breaking of antibiotic macromolecules. Subsequently, in the homogeneous stage, sulfate radicals and hydroxyl radicals are excited to non-selectively degrade the remaining small molecule fragments. This process overcomes the defect that a single heterogeneous system cannot completely mineralize, effectively blocks the accumulation process of recalcitrant intermediates, and solves the technical problem of acute biotoxicity rebound in effluent.

[0026] 2. This invention establishes a closed-loop mechanism for in-situ utilization and removal of metal leaching, directly converting copper ions lost in the heterogeneous catalytic stage into catalytic centers for subsequent homogeneous coordination reactions. By combining online monitoring and a compensation bypass to maintain a stable free copper concentration, and after deep mineralization of the wastewater, terminal alkaline neutralization causes copper ions to flocculate and settle. This method transforms the inherent leaching defects of transition metal catalysts into advantageous conditions for initiating homogeneous reactions, avoiding secondary pollution caused by heavy metal loss while ensuring the overall catalytic treatment efficiency of the system.

[0027] 3. The carbon-coated copper-doped MXene catalyst prepared by this invention has good resistance to oxidation and erosion. The coating layer formed by in-situ carbonization of glucose carbon source provides carbon defect sites required for the activation of persulfate. While providing reactivity, this coating structure effectively blocks the direct destruction of the underlying two-dimensional layered material skeleton by strong aqueous oxidants, maintains the structural rigidity of the catalyst under continuous water flow conditions, reduces catalyst loss, and extends the operation and maintenance cycle of the fixed bed reactor. Attached Figure Description

[0028] Figure 1 This is a target identification test curve of the two-stage dynamic evolution of active species in this invention; Figure 2 This is a graph showing the absorbance variation in the acidic system of the present invention, where hydrogen peroxide induces the formation of cuprous complexes. Figure 3 The graph shows the change in total organic carbon accumulation removal rate with process nodes under different reaction systems of the present invention. Figure 4 This is a graph showing the variation of residual persulfate concentration in different reaction systems of the present invention at various process nodes; Figure 5 The graph shows the variation of total copper ion concentration at various process nodes for different reaction systems of the present invention. Figure 6 This is a comparison chart showing the evolution of the acute toxicity inhibition rate of the raw water of the present invention and the primary treated effluent of Comparative Example 1 against luminescent bacteria over exposure time. Figure 7 This is a comparison chart showing the evolution of the acute toxicity inhibition rate of the raw water and the final effluent of the embodiments of the present invention against luminescent bacteria over exposure time. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Preparation Examples 1-3: Preparation Example 1: This preparation example provides a method for preparing a carbon-coated copper-doped MXene catalyst, including the following steps: According to the liquid-solid mass-volume ratio of 20 mL / g, HCl solution with a concentration of 6 mol / L was mixed with Ti3AlC2 powder. LiF powder was added to the HCl solution and mixed evenly. The mass ratio of LiF to Ti3AlC2 was 1:1. Then Ti3AlC2 powder was slowly added and in-situ etching was performed by continuous magnetic stirring at 35°C for 24 hours. The obtained product was repeatedly centrifuged and washed with deionized water until the pH of the supernatant was >6.0. Then, it was ultrasonically exfoliated for 1 hour. The supernatant was collected by centrifugation, and the solid content was measured to obtain a suspension of MXene with a known mass concentration. Based on the total number of Ti atoms in the system according to the solid content conversion, copper sulfate pentahydrate was weighed according to the Cu to Ti molar ratio of 0.2:1, dissolved and added dropwise to MXene suspension, and magnetically stirred for 12 hours at room temperature to adsorb, and copper-loaded MXene mixture was obtained through ion exchange and electrostatic interaction. Glucose was added as a carbon source precursor to a copper-loaded MXene mixture. The mass ratio of glucose to MXene solid content was controlled at 0.5:1. The mixture was stirred continuously for 4 hours to allow glucose molecules to be uniformly physically adsorbed on the surface of the nanosheets, thus obtaining an organic coating product. The organic-coated product was freeze-dried to remove moisture, then placed in a tube furnace and heat-treated under argon protection. The temperature was increased to 500°C at a rate of 2°C / min and held at that temperature for 2 hours to obtain Cu. 0.2 MC catalyst.

[0031] Preparation Example 2: This preparation example provides a method for preparing a carbon-coated copper-doped MXene catalyst, including the following steps: According to the liquid-to-solid mass-to-volume ratio of 20 mL / g, HCl solution with a concentration of 7.5 mol / L was mixed with Ti3AlC2 powder. LiF powder was added to the HCl solution and mixed evenly. The mass ratio of LiF to Ti3AlC2 was 1.25:1. Then Ti3AlC2 powder was slowly added and in-situ etching was performed by continuous magnetic stirring at 40°C for 36 hours. The obtained product was repeatedly centrifuged and washed with deionized water until the pH of the supernatant was >6.0. Then, it was ultrasonically exfoliated for 1.5 hours. The supernatant was collected by centrifugation, and the solid content was measured to obtain a suspension of MXene with a known mass concentration. Based on the total number of Ti atoms in the system according to the solid content conversion, copper sulfate pentahydrate was weighed according to the Cu to Ti molar ratio of 0.3:1, dissolved and added dropwise to MXene suspension, and magnetically stirred for 18 hours at room temperature to adsorb, and copper-loaded MXene mixture was obtained through ion exchange and electrostatic interaction. Glucose was added as a carbon source precursor to a copper-loaded MXene mixture. The mass ratio of glucose to MXene solid content was controlled at 0.75:1. The mixture was stirred continuously for 6 hours to allow glucose molecules to be uniformly physically adsorbed on the surface of the nanosheets, thus obtaining an organic coating product. The organic-coated product was freeze-dried to remove moisture, then placed in a tube furnace and heat-treated under argon protection. The temperature was increased to 600℃ at a rate of 3℃ / min and held at that temperature for 3 hours for carbonization. After cooling to room temperature, Cu was obtained. 0.3 MC catalyst.

[0032] Preparation Example 3: This preparation example provides a method for preparing a carbon-coated copper-doped MXene catalyst, including the following steps: According to the liquid-to-solid mass-to-volume ratio of 20 mL / g, HCl solution with a concentration of 9 mol / L was mixed with Ti3AlC2 powder. LiF powder was added to the HCl solution and mixed evenly. The mass ratio of LiF to Ti3AlC2 was 1.5:1. Then Ti3AlC2 powder was slowly added and in-situ etching was performed by continuous magnetic stirring at 45°C for 48 hours. The obtained product was repeatedly centrifuged and washed with deionized water until the pH of the supernatant was >6.0. Then, it was ultrasonically exfoliated for 2 hours. The supernatant was collected by centrifugation, and the solid content was measured to obtain a suspension of MXene with a known mass concentration. Based on the total number of Ti atoms in the system according to the solid content conversion, copper sulfate pentahydrate was weighed according to the Cu to Ti molar ratio of 0.4:1, dissolved and added dropwise to MXene suspension, and magnetically stirred for 24 hours at room temperature to adsorb, and copper-loaded MXene mixture was obtained through ion exchange and electrostatic interaction. Glucose was added as a carbon source precursor to a copper-loaded MXene mixture. The mass ratio of glucose to MXene solid content was controlled at 1:1. The mixture was stirred continuously for 8 hours to allow glucose molecules to be uniformly physically adsorbed on the surface of the nanosheets, thus obtaining an organic coating product. The organic-coated product was freeze-dried to remove moisture, then placed in a tube furnace and heat-treated under argon protection. The temperature was increased to 700℃ at a rate of 5℃ / min and held at that temperature for 4 hours for carbonization. After cooling to room temperature, Cu was obtained. 0.4 MC catalyst.

[0033] Examples 1-3: Example 1: This embodiment provides a method for treating antibiotic wastewater based on persulfate activation, including the following steps: Antibiotic wastewater containing ofloxacin was pumped into a container filled with Cu obtained in Preparation Example 1. 0.2 In the continuous flow fixed bed reactor of MC catalyst, persulfate aqueous solution is simultaneously injected into the reactor inlet manifold through an online dosing system to adjust the initial persulfate concentration of the inlet mixture to 0.3 mmol / L, and sodium hydroxide solution is added to control the pH value of the inlet to 7.5. The inlet flow rate is adjusted to keep the hydraulic residence time of the wastewater in the reactor at 15 minutes. After the heterogeneous ring-breaking reaction, the primary treated effluent is obtained. The primary treated effluent is diverted to a buffer monitoring and control pipe section equipped with an online oxidation-reduction potential probe and a flow meter. The initial COD load and hydraulic retention time of the influent are substituted into a preset first-order decay kinetic model to calculate the residual persulfate concentration in the aqueous phase. Simultaneously, the real-time dissolved copper ion concentration is obtained through an online heavy metal detector, and the monitored effluent carrying parameter information is output. The monitored effluent was continuously introduced into a continuously stirred reactor equipped with a variable frequency stirrer. Sulfuric acid solution was pumped in to gradually lower the pH value of the system to 3.5 within the first 5 minutes after entering the reactor. When the real-time dissolved copper ion concentration was lower than 0.5 mg / L, the compensation bypass was activated to add copper sulfate solution dropwise into the reactor, with 0.5 mg / L as the lower limit benchmark to make up the difference. Otherwise, no dropwise addition was made. This was used to establish the total free copper ion concentration in the reactor and obtain an acidic substrate mixture. Industrial-grade citric acid solution was added to the acidic substrate mixture, and the molar ratio of citric acid to total free copper ions was controlled at 1.2:1 to generate complex catalytic centers in situ. Subsequently, hydrogen peroxide solution was injected according to the residual persulfate concentration, and the molar ratio of hydrogen peroxide to residual persulfate was controlled at 1:5. Mechanical stirring was maintained and the hydraulic residence time was 30 minutes to carry out a homogeneous ternary synergistic deep mineralization reaction and obtain deeply mineralized effluent. The deep mineralized effluent overflows into the terminal neutralization reaction tank, where sodium hydroxide solution is added to adjust the pH to 7.5 to break down residual trace complexes and precipitate heavy metals. After the metal hydroxides are precipitated in a gravity sedimentation tank, the clear liquid is separated to complete the wastewater treatment.

[0034] Example 2: This embodiment provides a method for treating antibiotic wastewater based on persulfate activation, including the following steps: Antibiotic wastewater containing ofloxacin was pumped into a container filled with Cu obtained in Preparation Example 2. 0.3In the continuous flow fixed-bed reactor of MC catalyst, persulfate aqueous solution is simultaneously injected into the reactor inlet manifold through an online dosing system to adjust the initial persulfate concentration of the inlet mixture to 0.4 mmol / L, and sodium hydroxide solution is added to control the pH value of the inlet to 8.0. The inlet flow rate is adjusted to keep the hydraulic residence time of the wastewater in the reactor at 17.5 minutes. After the heterogeneous ring-breaking reaction, the primary treated effluent is obtained. The primary treated effluent is diverted to a buffer monitoring and control pipe section equipped with an online oxidation-reduction potential probe and a flow meter. The initial COD load and hydraulic retention time of the influent are substituted into a preset first-order decay kinetic model to calculate the residual persulfate concentration in the aqueous phase. Simultaneously, the real-time dissolved copper ion concentration is obtained through an online heavy metal detector, and the monitored effluent carrying parameter information is output. The monitored effluent was continuously introduced into a continuously stirred reactor equipped with a variable frequency stirrer. Sulfuric acid solution was pumped in to gradually lower the pH value of the system to 4.0 within the first 5 minutes after entering the reactor. When the real-time dissolved copper ion concentration was lower than 0.75 mg / L, the compensation bypass was activated to add copper sulfate solution dropwise into the reactor, with 0.75 mg / L as the lower limit benchmark to make up the difference. Otherwise, no dropwise addition was made. This was used to establish the total free copper ion concentration in the reactor and obtain an acidic substrate mixture. Industrial-grade citric acid solution was added to an acidic substrate mixture, and the molar ratio of citric acid to total free copper ions was controlled at 1.6:1 to generate complex catalytic centers in situ. Subsequently, hydrogen peroxide solution was injected according to the residual persulfate concentration, and the molar ratio of hydrogen peroxide to residual persulfate was controlled at 1:3.5. Mechanical stirring was maintained and the hydraulic residence time was 37.5 minutes to carry out a homogeneous ternary synergistic deep mineralization reaction and obtain deeply mineralized effluent. The deep mineralized effluent overflows into the terminal neutralization reaction tank, where sodium hydroxide solution is added to adjust the pH back to 8.0 to break down residual trace complexes and precipitate heavy metals. After the metal hydroxides are precipitated in a gravity sedimentation tank, the clear liquid is separated to complete the wastewater treatment.

[0035] Example 3: This embodiment provides a method for treating antibiotic wastewater based on persulfate activation, including the following steps: Antibiotic wastewater containing ofloxacin was pumped into a container filled with Cu obtained in Preparation Example 3. 0.4 In the continuous flow fixed bed reactor of MC catalyst, persulfate aqueous solution is simultaneously injected into the reactor inlet manifold through an online dosing system to adjust the initial persulfate concentration of the inlet mixture to 0.5 mmol / L, and sodium hydroxide solution is added to control the pH value of the inlet to 8.5. The inlet flow rate is adjusted to keep the hydraulic residence time of the wastewater in the reactor at 20 minutes. After the heterogeneous ring-breaking reaction, the primary treated effluent is obtained. The primary treated effluent is diverted to a buffer monitoring and control pipe section equipped with an online oxidation-reduction potential probe and a flow meter. The initial COD load and hydraulic retention time of the influent are substituted into a preset first-order decay kinetic model to calculate the residual persulfate concentration in the aqueous phase. Simultaneously, the real-time dissolved copper ion concentration is obtained through an online heavy metal detector, and the monitored effluent carrying parameter information is output. The monitored effluent was continuously introduced into a continuously stirred reactor equipped with a variable frequency stirrer. Sulfuric acid solution was pumped in to gradually lower the pH value of the system to 4.5 within the first 5 minutes after entering the reactor. When the real-time dissolved copper ion concentration was lower than 1.0 mg / L, the compensation bypass was activated to add copper sulfate solution dropwise into the reactor, with 1.0 mg / L as the lower limit benchmark to make up the difference. Otherwise, no dropwise addition was made. This was used to establish the total free copper ion concentration in the reactor and obtain an acidic substrate mixture. Industrial-grade citric acid solution was added to the acidic substrate mixture, and the molar ratio of citric acid to total free copper ions was controlled at 2.0:1 to generate complex catalytic centers in situ. Subsequently, hydrogen peroxide solution was injected according to the residual persulfate concentration, and the molar ratio of hydrogen peroxide to residual persulfate was controlled at 1:2. Mechanical stirring was maintained and the hydraulic residence time was 45 minutes to carry out a homogeneous ternary synergistic deep mineralization reaction and obtain deeply mineralized effluent. The deep mineralized effluent overflows into the terminal neutralization reaction tank, where sodium hydroxide solution is added to adjust the pH to 8.5 to break down residual trace complexes and precipitate heavy metals. After the metal hydroxides are precipitated in a gravity sedimentation tank, the clear liquid is separated to complete the wastewater treatment.

[0036] Comparative Examples 1-4: Comparative Example 1: Compared to Example 2, the difference lies in skipping the monitoring and homogeneous ternary synergistic deep mineralization reaction steps. That is, after the wastewater flows out of the fixed-bed reactor to obtain primary treated effluent, it directly enters the terminal neutralization reaction tank, where acid and alkali solutions are added to adjust the pH of the system to a stable level of 8.0 and precipitate separation occurs.

[0037] Comparative Example 2: The difference from Example 2 is that, in the continuously stirred reactor equipped with a variable frequency stirrer, after adding the citric acid solution, hydrogen peroxide solution is not injected. Everything else is the same.

[0038] Comparative Example 3: Compared to Example 2, the difference lies in that, in the continuously stirred reactor equipped with a variable frequency stirrer, after pumping in the sulfuric acid solution and performing copper compensation, the citric acid solution is not added; instead, hydrogen peroxide solution is directly injected. Everything else remains the same.

[0039] Comparative Example 4: The difference from Example 2 is that when injecting the hydrogen peroxide solution into the continuously stirred reactor, the molar ratio of hydrogen peroxide to residual persulfate is significantly increased to 1:1 (or even 2:1). Everything else is the same.

[0040] Test Examples 1-5: Test Example 1: The inlet pipe of the continuous flow fixed bed reactor and the inlet and outlet pipes of the continuous stirred reactor in Example 2 were taken as sampling nodes.

[0041] High-concentration stock solutions of tert-butanol, ethanol, and furfuryl alcohol were prepared using deionized water. The collected antibiotic wastewater was divided into four parallel test groups. The prepared stock solutions of tert-butanol, ethanol, and furfuryl alcohol were added dropwise to each group according to volume ratio, ensuring a final concentration of 100 mmol / L for tert-butanol and ethanol, and a final concentration of 10 mmol / L for furfuryl alcohol. An equal volume of deionized water was added to the blank control system. The influent pump flow rate was adjusted so that the four water samples passed through a container filled with Cu... 0.3 The fixed-bed reactor with MC catalyst maintains a hydraulic retention time of 17.5 minutes.

[0042] Samples were taken periodically at the water outlet, and an excess of sodium thiosulfate solution was added to terminate the reaction. The concentration of ofloxacin in each group of water samples was determined using a high-performance liquid chromatograph equipped with a UV detector.

[0043] The primary effluent from the four fixed-bed treatments was continuously introduced into four simulated continuous stirred reactors. Sulfuric acid was injected to adjust the pH of the system to 4.0, free copper ions were added to 0.75 mg / L, citric acid was added, and hydrogen peroxide was injected in proportion.

[0044] The mechanical stirring speed was maintained to achieve a hydraulic retention time of 37.5 minutes, corresponding to a total reaction time of 55 minutes. Multiple samples were taken during reactor operation. After the reaction was terminated with sodium thiosulfate, the residual concentration of ofloxacin was measured, and the cumulative removal rate at different time points was calculated and recorded.

[0045] Table 1. Cumulative removal rate of ofloxacin at each reaction stage under different quencher systems

[0046] Figure 1 In the diagram, the solid black line marked with a circle represents the blank control group without quencher; the dark gray dashed line marked with a square represents the test group with TBA added; the medium gray dotted line marked with an upper triangle represents the test group with EtOH added; and the light gray dotted line marked with a diamond represents the test group with FFA added. The very light gray background area in the diagram represents the first stage (fixed bed section) of Example 2, and the light gray background area represents the second stage (homogeneous phase section) of Example 2.

[0047] in conclusion: According to Table 1 and Figure 1 The measured data showed that the reaction system exhibited different oxidation characteristics in two gray-scale background regions. During the 0-17.5 minute fixed-bed reaction period corresponding to the very light gray region, the blank control group (represented by the black solid line with circles) removed some of the ofloxacin, while the data for water samples with different quenchers showed divergence. The light gray dotted line (representing FFA with diamonds) was at a low level, with a cumulative removal rate of 16.7%. The curves of the TBA and EtOH groups (represented by the dark gray dashed line with squares and the medium gray dotted line with upward triangles) showed trends similar to the blank control group, indicating that conventional free radical quenchers did not significantly inhibit the reaction at this stage. The presence of chloride or carbonate ions in industrial wastewater typically consumes free radicals. The fixed-bed system was sensitive to FFA but exhibited anti-interference characteristics against TBA and EtOH, verifying that carbon defects on the catalyst surface reacted with persulfate to generate singlet oxygen, consistent with a non-free radical pathway.

[0048] As the reaction solution was introduced into the continuously stirred reactor, the system transitioned to the homogeneous stage corresponding to the light gray background region. In the first stage, the slope of the light gray dotted line at the lower position increased, and the removal rate approached that of the blank group, indicating that singlet oxygen lost its dominant role in the acidic homogeneous environment. The rise of the TBA and EtOH curves slowed down in the second stage. During the experiment, a color change was observed in the reaction solution after hydrogen peroxide was added to the reactor, reflecting the reduction of the complex formed by free copper ions and citric acid to cuprous form. The formed cuprous centers promoted the breaking of the peroxy bonds in the residual persulfate, and the resulting hydroxyl radicals and sulfate radicals degraded the residual antibiotics and intermediates in the wastewater, completing the transformation from interfacial activation to bulk synergistic oxidation.

[0049] Test Example 2: The mixture from the buffer tube section before entering the continuous stirred reactor of Example 2, Comparative Example 2 and Comparative Example 3 was extracted as the initial substrate test sample.

[0050] A 5 mmol / L copper hydroxide colorimetric reagent solution and a 0.1 mol / L acetate-sodium acetate buffer system were prepared to maintain a stable colorimetric environment. The stirring devices of each reactor were started, and reagents were added according to the corresponding parameters. Citric acid solution was added to Example 2 and Comparative Example 2 for in-situ coordination, while no citric acid was added to Comparative Example 3.

[0051] Equal volumes of reaction solution were extracted from each reactor, and buffer solution and copper hydroxide colorimetric reagent were added. After adjusting the volume, the mixture was allowed to stand in the dark, and the results were recorded as the 0-minute baseline sample. Hydrogen peroxide solution of a predetermined ratio was injected into the reactors of Example 2 and Comparative Example 3. No hydrogen peroxide was injected into Comparative Example 2, and an equal volume of deionized water was added to maintain a consistent fluid volume.

[0052] Extract the reaction solution from the reactor at the 2nd, 5th, 10th, and 20th minutes of operation, and quickly transfer it into a colorimetric tube containing the corresponding buffer solution and colorimetric reagent. Shake and protect from light to complete the colorimetric reaction.

[0053] The processed colorimetric solutions at each time point were transferred into quartz cuvettes. Using deionized water as a blank reference, the characteristic absorption peak values ​​at a wavelength of 484 nm were continuously scanned and measured using a UV-Vis spectrophotometer. The absorbance time evolution sequence was then compiled and collected.

[0054] Table 2. Data on the characteristic absorbance of different systems at 484 nm wavelength over time.

[0055] Note: "-" indicates that the absorbance of the reaction system was not measured at this time point due to insufficient sample volume.

[0056] Figure 2 In the diagram, the black dashed line marked with a circle represents Example 2; the dark gray solid line marked with a square represents Comparative Example 2; and the light gray solid line marked with an upper triangle represents Comparative Example 3.

[0057] in conclusion: According to Table 2 and Figure 2 The data shows that the evolution of transition metal valence states varies under different reaction conditions. In practical water treatment analysis, capturing the transient transformation of trace metal ions is challenging. By introducing a copper bath colorimetric reagent, the concentration change of cuprous ions is converted into a quantitative value on the UV-Vis absorption spectrum. The absorbance of each group of reference samples at 0 minutes was at a baseline level of approximately 0.02, indicating that copper initially exists in a divalent form in the homogeneous reactor. Observing the black dashed line marked with a circle, representing Example 2, the absorbance of the system at 484 nm rapidly increased within the first 5 minutes after the injection of hydrogen peroxide, reaching a peak of 0.592. During the experiment, the reaction solution in the reactor showed a slightly reddish hue after the addition of hydrogen peroxide. The increase in the intensity of this absorption peak reflects that, under the acidic citric acid coordination environment, hydrogen peroxide participated in the reaction as an electron donor, converting some of the [Cu(II)-Citrate] into a reddish hue. - It is reduced to [Cu(I)-Citrate], which has catalytic activity. 2- .

[0058] The dark gray solid line with square markings, representing Comparative Example 2, shows that in the control group without hydrogen peroxide injection, the absorbance curve remains flat, with values ​​fluctuating around the baseline. This indicates that citric acid alone cannot spontaneously complete the reduction conversion of valence with divalent copper in the current acidic wastewater. The light gray solid line with upward-pointing triangle markings, representing Comparative Example 3, reflects the reaction without citric acid ligands. In the absence of ligands, even with hydrogen peroxide in the system, free divalent copper ions did not show obvious signs of reduction, with the highest absorbance measured only 0.053. The lack of a complex ligand field resulted in a higher activation energy for free copper ions participating in the redox reaction, and hydrogen peroxide failed to effectively promote the Cu(II) / Cu(I) valence cycle. The above test results cross-validate the indispensable combined role of citric acid coordination and specific proportions of hydrogen peroxide activation in the multinuclear synergistic system.

[0059] Test Example 3: Extract raw antibiotic wastewater and water samples from different reaction time points treated by the processes corresponding to Examples 1 to 3 and Comparative Examples 1 to 4.

[0060] All samples were filtered through a 0.22 μm deactivating glass fiber filter to remove minute suspended matter. Then, excess sodium thiosulfate solution was added to quench any residual oxidants and free radicals in the system, and the samples were stored in a light-protected environment at 4°C.

[0061] A portion of the filtered water sample was injected into a high-performance liquid chromatograph. A C18 reversed-phase column and an ultraviolet detector were used to obtain chromatograms at specific characteristic wavelengths. The residual concentration of ofloxacin was quantitatively analyzed by integral analysis.

[0062] The remaining filtered water sample was introduced into the combustion tube of the total organic carbon analyzer. Under high temperature conditions of 680℃, the organic components in the aqueous phase were completely oxidized into carbon dioxide by a platinum catalyst. The concentration of the generated gas was measured by a non-dispersive infrared detector.

[0063] Based on the initial parameters of the raw water, the total organic carbon cumulative removal rate at each sampling time point was calculated, and the mineralization data of different process systems were recorded.

[0064] Table 3. Evolution of Total Organic Carbon Cumulative Removal Rate with Process Nodes under Different Reaction Systems

[0065] Note: "-" indicates that the reaction system has completed the process at the corresponding sampling node (without undergoing the homogeneous reaction stage) and no sampling and measurement have been performed.

[0066] Figure 3In the diagram, the black dotted line with a five-pointed star represents Example 1; the black dashed line with a circle represents Example 2; the black dotted line with a six-pointed star represents Example 3; the medium gray dashed line with a cross represents Comparative Example 1; the dark gray solid line with a square represents Comparative Example 2; the light gray solid line with an upper triangle represents Comparative Example 3; and the medium gray dotted line with a lower triangle represents Comparative Example 4.

[0067] in conclusion: According to Table 3 and Figure 3 Data shows that the ring-opening mineralization process of antibiotic wastewater exhibits significant differences under different process configurations. During the fixed-bed reaction stage, the cumulative removal rate of total organic carbon in both the example and comparative systems was approximately 25%. Experimental observations combined with chromatographic analysis indicate that the singlet oxygen-dominated non-radical pathway can disrupt the piperazine ring structure with high electron cloud density in the ofloxacin molecule, manifested in a rapid increase in the parent compound removal rate in high-performance liquid chromatography (HPLC). Large molecules in the wastewater are not completely converted into inorganic substances but remain in the aqueous phase as intermediate organic fragments such as short-chain fatty acids. Figure 3 The gray dashed line marked with a cross in Comparative Example 1 stops recording at the fixed-bed effluent node, reflecting the limitation of a single heterogeneous fixed-bed process in the accumulation of recalcitrant organic intermediates without the introduction of a homogeneous synergistic mechanism, thus failing to meet the requirements for deep treatment. After entering the homogeneous acidic reaction stage, the data trends of each system changed.

[0068] Figure 3 The three black curves, representing Examples 1 to 3, with different markings, show an upward trend after crossing the fixed-bed effluent node, reaching removal levels of 84.1%, 89.5%, and 93.2%, respectively, at the final effluent. The cuprous complex generated in the homogeneous system effectively excited the residual persulfate by lowering the activation energy. The hydroxyl radicals and sulfate radicals generated in the system broke bonds and opened rings on organic fragments, completing the conversion of the carbon skeleton to carbon dioxide. The dark gray solid line with square markings and the light gray solid line with upward triangle markings represent Comparative Example 2 and Comparative Example 3, respectively. After entering the homogeneous stage, the removal rate curves were flat, eventually fluctuating around 30%. Without the addition of hydrogen peroxide or in the absence of citric acid coordination, free divalent copper ions could not construct redox electron shuttle channels, and the system lacked the conditions for exciting high-energy free radicals. The gray dotted line with the downward-pointing triangle represents Comparative Example 4, where the removal rate stabilized at 48.6%. Excessive hydrogen peroxide addition consumed the free radicals generated inside the reactor, leading to ineffective decomposition of the oxidant and limiting the mineralization process of the target pollutant. The cross-comparison test results objectively verified the engineering feasibility of the component coupling and proportioning conditions of the multinuclear ternary system in the removal of antibiotic intermediates.

[0069] Test Example 4: Water samples were extracted from four nodes: raw water, effluent from fixed-bed primary treatment, effluent from continuous stirred homogeneous reactor, and effluent from final neutralization and sedimentation in Examples 1 to 3 and Comparative Example 1.

[0070] The collected water samples were filtered through a 0.22 μm pore size filter membrane to remove heterogeneous particulate matter. A portion of the filtrate was taken and an excess of ascorbic acid solution was added to quench residual active free radicals and persulfate. The filtrate was then stored at 4°C in the dark for later use in the total analysis of heavy metals.

[0071] Transfer the remaining unquenched filtrate into an iodine flask, add excess potassium iodide solution and adjust to weak acidity with dilute sulfuric acid, add starch indicator and let stand in the dark for 5 minutes to complete the color development.

[0072] Titrate with a standardized sodium thiosulfate standard solution until the blue color of the solution fades, and calculate the residual persulfate concentration in the aqueous phase at each node based on the volume of titrant consumed.

[0073] Take out the refrigerated quenched water sample, add nitric acid reagent in proportion, and put it into a microwave digester for destructive digestion to deconstruct the complex morphology between organic matter and metal in the water sample.

[0074] After the digestion solution was brought to a fixed volume, it was introduced into the inductively coupled plasma atomic emission spectrometer (ICP-AES) sample introduction system. The total copper ion concentration was measured under the characteristic emission spectrum line. The data were integrated to establish an evolution model of reactant dissipation and metal fate.

[0075] Table 4. Data on the changes in residual persulfate and total copper ion concentrations at each stage of the reaction system

[0076] Note: "-" indicates that the reaction system has been skipped in the process flow at this sampling node (it has not undergone the homogeneous reaction stage) and there is no corresponding measurement data.

[0077] Figure 4 In the diagram, the black dotted line with a pentagram mark represents Example 1; the black dashed line with a circle mark represents Example 2; the black dotted line with a hexagon mark represents Example 3; and the medium gray dashed line with a cross mark represents Comparative Example 1.

[0078] Figure 5 In the diagram, the black dotted line with a pentagram mark represents Example 1; the black dashed line with a circle mark represents Example 2; the black dotted line with a hexagon mark represents Example 3; and the medium gray dashed line with a cross mark represents Comparative Example 1.

[0079] in conclusion: According to Table 4, Figure 4 and Figure 5The data shows that the consumption pathway of persulfate and the fate of heavy metal ions exhibit corresponding changes at different process stages. In actual water treatment projects, metal loss from heterogeneous catalysts often leads to deterioration of effluent quality. (Observation) Figure 4 and Figure 5 The three black curves, marked with pentagrams, circles, and hexagons respectively, represent the three examples of wastewater flowing through the fixed-bed reaction stage. During this process, persulfate was partially consumed, and free copper ions (0.46 to 0.96 mg / L) were detected in the aqueous phase. Upon entering the homogeneous reactor stage, the residual persulfate concentration decreased significantly and approached the instrument detection limit. This consumption process stemmed from the transformation of lost copper ions into homogeneous catalytic active centers under the coordination of citric acid and the induction of trace amounts of hydrogen peroxide, further activating persulfate to generate high-energy free radicals. These free radicals not only degraded antibiotic molecules in the wastewater but also simultaneously mineralized citric acid, which acted as a ligand. With the disruption of the coordination environment, the copper ions, having lost their chelating function, were converted into copper hydroxide and flocculated and settled in the terminal slightly alkaline neutralization tank. Figure 5 Data shows that the final effluent total copper concentration in the embodiments consistently decreased to 0.04 mg / L or below, achieving complete utilization of the reagents and compliance control of heavy metals.

[0080] Unlike the processing in the examples, the medium gray dashed line marked with a cross, representing Comparative Example 1, reflects the operating state lacking homogeneous synergistic process. Figure 4 The results showed that in Comparative Example 1, due to the lack of subsequent homogeneous reaction, the concentration of persulfate in the final effluent remained at 0.23 mmol / L, resulting in the loss of a large amount of unreacted oxidant with the water. Figure 5 The test results further indicate that the total copper concentration in the final effluent of Comparative Example 1 reached 0.62 mg / L. Based on previous chromatographic component scanning data, it is inferred that the short-chain aliphatic carboxylic acids and other incompletely ring-opened organic intermediates produced during the single fixed-bed degradation stage possess strong complexing capabilities, stably retaining the lost copper ions in the aqueous phase and hindering the conventional alkaline precipitation removal process. The above test data validate the closed-loop effect of the multinuclear ternary homogeneous synergistic system in breaking the chelating chain of organic matter, utilizing residual oxidants, and controlling heavy metal emissions.

[0081] Test Example 5: The raw antibiotic wastewater, the terminal neutralization and precipitation effluent of Examples 1 to 3, and the fixed-bed primary treatment effluent of Comparative Example 1 were extracted as toxicity assessment test samples.

[0082] Each water sample was filtered through a 0.22 μm pore size filter membrane, and the pH of the filtrate was adjusted to a neutral range of 6.5 to 8.5 using dilute acid or dilute alkali solutions.

[0083] Sodium chloride was added to the water sample to achieve a salinity of 3% to match the osmotic pressure environment of the luminescent bacteria. The lyophilized luminescent bacteria powder was opened and inoculated into a pre-cooled 3% sodium chloride buffer solution. The suspension was activated at a constant temperature of 15°C for 15 minutes to obtain a bacterial suspension in the logarithmic growth phase.

[0084] The bacterial suspension was aliquoted and injected into test tubes containing different water samples and mixed thoroughly. A prepared pure 3% sodium chloride solution was used as a reference blank control group, and the mixture was placed in the sealed test chamber of the biotoxicity analyzer.

[0085] At exposure time points of 5, 15, 30, and 45 minutes, the luminescence intensity attenuation values ​​of each group of samples were read. Combined with the baseline readings of the blank control group, the relative luminescence inhibition rate of the target water sample as a function of contact time was calculated.

[0086] Table 5. Data on the acute toxicity inhibition rate of different water sample systems against luminescent bacteria at various exposure time periods.

[0087] Figure 6 In the diagram, the dark gray dotted line marked with an asterisk represents the original water; the medium gray dashed line marked with a cross represents Comparative Example 1.

[0088] Figure 7 In the diagram, the dark gray dotted line marked with an asterisk represents the original water; the black dotted line marked with a pentagram represents Example 1; the black dashed line marked with a circle represents Example 2; and the black dotted line marked with a hexagon represents Example 3.

[0089] in conclusion: According to Table 5, Figure 6 and Figure 7 The data showed that the inhibition rates of water samples at different process stages on luminescent bacteria varied, reflecting the evolution of the toxicity of intermediate products during antibiotic degradation. In routine water toxicology analysis, the rebound of toxicity in the primary effluent from advanced oxidation processes is a common assessment phenomenon. Figure 6 Data from Zhongyuan Water showed that the inhibition rate of *Bacillus luminescence* ranged from 68.4% to 74.3% at various exposure times, indicating the background stress of ofloxacin parent organisms on microbial metabolism. After single-bed heterogeneous oxidation treatment of the waste liquid, the gray dashed line marked with a cross (representing Comparative Example 1) deviated from the raw water baseline and rose further, reaching 91.3% at the 45-minute mark. Combined with chromatographic results, it is speculated that singlet oxygen non-radical oxidation cleaved the heterocyclic structure with high electron cloud density, resulting in short-chain aliphatic carboxylic acids and nitrogen-containing organic fragments with high cell membrane permeability. These small molecular intermediates can penetrate the bacterial cell wall and interfere with the internal enzyme system, leading to increased acute biotoxicity.

[0090] To address the increased toxicity caused by the accumulation of these intermediates, a homogeneous free radical oxidation process was introduced into the combined process. (Observation) Figure 7 The curves for Examples 1 to 3, marked with pentagrams, circles, and hexagons respectively, were all controlled below 15%. The sulfate and hydroxyl radicals generated by the cuprous complex and hydrogen peroxide excitation have high oxidation potentials, initiating ring-opening and bond-breaking of previously accumulated highly toxic intermediates. Small organic fragments undergo structural transformation from carbon skeleton to inorganic carbon under the action of free radicals, losing their ability to bind to intracellular receptors. Cross-comparison of data from a single heterogeneous primary treatment with homogeneous synergistic final effluent data demonstrates that the multinuclear deep mineralization process blocks the accumulation chain of toxic byproducts, verifying the technical feasibility of this system in reducing the secondary ecotoxicity derived from antibiotic degradation.

Claims

1. A method for treating antibiotic wastewater based on persulfate activation, characterized in that, include: Antibiotic wastewater is pumped into a continuous flow fixed-bed reactor filled with carbon-coated copper-doped MXene catalyst, and persulfate aqueous solution is injected simultaneously to carry out a heterogeneous ring-breaking reaction to obtain primary treated effluent. The primary treated effluent is diverted to a buffer monitoring and control section to obtain the residual persulfate concentration and real-time dissolved copper ion concentration in the aqueous phase, and the monitored effluent is output. The monitored effluent was introduced into a continuously stirred reactor, sulfuric acid solution was pumped in to adjust the pH value, and copper sulfate solution was added dropwise when the real-time dissolved copper ion concentration was lower than the lower limit benchmark to establish the total free copper ion concentration and obtain an acidic substrate mixture. Citric acid solution and hydrogen peroxide solution were added to the acidic substrate mixture to carry out a homogeneous ternary synergistic deep mineralization reaction to obtain deeply mineralized effluent; The deep mineralized effluent overflows into the terminal neutralization reaction tank, where sodium hydroxide solution is added to adjust the pH value and precipitate out the sediment. The clear liquid is then separated to complete the wastewater treatment.

2. The method for treating antibiotic wastewater based on persulfate activation according to claim 1, characterized in that, Antibiotic wastewater is pumped into the continuous flow fixed-bed reactor containing the carbon-coated copper-doped MXene catalyst. During the heterogeneous ring-breaking reaction, a persulfate aqueous solution is simultaneously injected. The initial persulfate concentration of the influent mixture is adjusted to 0.3–0.5 mmol / L, sodium hydroxide solution is added to control the pH of the influent to 7.5–8.5, and the influent flow rate is adjusted to maintain the hydraulic residence time of the wastewater in the continuous flow fixed-bed reactor at 15–20 minutes.

3. The method for treating antibiotic wastewater based on persulfate activation according to claim 1, characterized in that, When the primary treated effluent is diverted to the buffer monitoring and control pipe section, and the residual persulfate concentration and the real-time dissolved copper ion concentration in the aqueous phase are obtained, the residual persulfate concentration is calculated by substituting the initial COD load and hydraulic retention time of the influent into a preset first-order decay kinetic model, and the real-time dissolved copper ion concentration is obtained simultaneously by an online heavy metal detector.

4. The method for treating antibiotic wastewater based on persulfate activation according to claim 1, characterized in that, The monitored effluent is introduced into the continuously stirred reactor, and sulfuric acid solution is pumped in to adjust the pH value. When the real-time dissolved copper ion concentration is lower than the lower limit benchmark, copper sulfate solution is added dropwise. When the total free copper ion concentration is established, the pH value of the system is gradually adjusted down to 3.5-4.

5. The lower limit benchmark is 0.5-1.0 mg / L. When the real-time dissolved copper ion concentration is lower than the lower limit benchmark, the compensation bypass is activated to make up the difference; otherwise, no dropwise addition is performed.

5. The method for treating antibiotic wastewater based on persulfate activation according to claim 1, characterized in that, When adding citric acid solution and hydrogen peroxide solution to the acidic substrate mixture for homogeneous ternary synergistic deep mineralization reaction, the molar ratio of citric acid to the total free copper ion concentration is controlled at (1.2-2.0):1, to generate complex catalytic centers in situ. Subsequently, hydrogen peroxide solution is injected according to the residual persulfate concentration, and the molar ratio of hydrogen peroxide to the residual persulfate is controlled at 1:(2-5). Mechanical stirring is maintained and the hydraulic residence time is 30-45 minutes.

6. The method for treating antibiotic wastewater based on persulfate activation according to claim 1, characterized in that, The preparation method of the carbon-coated copper-doped MXene catalyst includes: HCl solution and Ti3AlC2 powder were mixed in a specific ratio, and LiF powder was added and mixed evenly. Then, Ti3AlC2 powder was slowly added and in-situ etching was performed by continuous magnetic stirring to obtain the etching product. The etching product was repeatedly centrifuged and washed with deionized water and ultrasonically peeled off. The supernatant was collected by centrifugation to obtain MXene suspension. Copper sulfate pentahydrate was weighed, dissolved, and added dropwise to the MXene suspension. The mixture was magnetically stirred and adsorbed, and a copper-loaded MXene mixture was obtained through ion exchange and electrostatic interaction. Glucose was added as a carbon source precursor to the copper-loaded MXene mixture, and the mixture was continuously stirred to allow glucose molecules to be uniformly physically adsorbed on the surface of the nanosheets, thereby obtaining an organic-coated product. The organic-coated product was freeze-dried to remove moisture, then placed in a tube furnace for heat treatment under argon protection, carbonized at a constant temperature, and cooled to room temperature to obtain the carbon-coated copper-doped MXene catalyst.

7. The method for treating antibiotic wastewater based on persulfate activation according to claim 6, characterized in that, The HCl solution and Ti3AlC2 powder were mixed in a specific ratio. After the LiF powder was added and mixed evenly, the Ti3AlC2 powder was slowly added. During in-situ etching, the HCl solution with a concentration of 6-9 mol / L was mixed with the Ti3AlC2 powder, and the mass ratio of LiF to Ti3AlC2 was (1-1.5):

1. The mixture was continuously magnetically stirred at 35-45°C for 24-48 hours.

8. The method for treating antibiotic wastewater based on persulfate activation according to claim 6, characterized in that, The etching product was repeatedly centrifuged and washed with deionized water and ultrasonically peeled off. When collecting the supernatant by centrifugation to obtain the MXene suspension, the supernatant was repeatedly centrifuged and washed until the pH of the supernatant was >6.

0. Then, ultrasonic peeling was performed for 1 to 2 hours, and the solid content was measured to obtain the MXene suspension with a known mass concentration. After dissolving copper sulfate pentahydrate, it is added dropwise to the MXene suspension and magnetically stirred for adsorption. When obtaining the copper-loaded MXene mixture through ion exchange and electrostatic interaction, the total number of moles of Ti atoms in the system is calculated based on the solid content. Copper sulfate pentahydrate is weighed according to the Cu to Ti molar ratio of (0.2-0.4):1 and magnetically stirred for adsorption for 12-24 hours.

9. The method for treating antibiotic wastewater based on persulfate activation according to claim 6, characterized in that, Glucose was added as a carbon source precursor to the copper-loaded MXene mixture. During continuous stirring, the glucose molecules were uniformly physically adsorbed on the surface of the nanosheets. The mass ratio of glucose to MXene solid content was controlled to be (0.5-1.0):1, and the mixture was stirred continuously for 4-8 hours.

10. The method for treating antibiotic wastewater based on persulfate activation according to claim 6, characterized in that, The organic-coated product is freeze-dried to remove moisture, placed in a tube furnace and heat-treated under argon protection, carbonized at a constant temperature and cooled to room temperature to obtain the carbon-coated copper-doped MXene catalyst. The temperature is increased to 500-700°C at a rate of 2-5°C / min and carbonized at a constant temperature for 2-4 hours.

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