Treatment method of wastewater containing tetracycline hydrochloride

Abstract

The invention discloses a tetracycline hydrochloride-containing wastewater treatment method in the field of wastewater treatment, which comprises the following steps: introducing tetracycline hydrochloride-containing wastewater into a reactor, adding a multilevel structure iron and iron sulfide composite carbon material, and adjusting the system to a nearly neutral condition; then adding potassium peroxymonosulfate composite salt, starting a direct current system, and carrying out catalytic degradation reaction under specific current density; and finally recovering the catalyst through magnetic field separation. The preparation method comprises the following steps: grinding pyrite and hematite, ball-milling and mixing the ground pyrite and hematite with orange peel powder and sodium hydroxide, and carrying out microwave pyrolysis, acid washing and drying, hydrogen peroxide surface treatment and the like to obtain a final product. According to the method, efficient degradation of tetracycline hydrochloride under the neutral condition is achieved, the catalyst can be magnetically recycled, secondary pollution is avoided, and the method has the advantages of being low in cost, easy and convenient to operate, environmentally friendly and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wastewater treatment, and particularly relates to a tetracycline hydrochloride-containing wastewater treatment method. BACKGROUND

[0002] Tetracycline hydrochloride, as a widely used tetracycline antibiotic, is continuously used in the fields of pharmaceuticals, livestock breeding and medical treatment, resulting in a large amount of wastewater containing such substances entering the water environment. Such wastewater has the characteristics of complex composition, high chemical stability and poor biodegradability. If it is directly discharged without proper treatment, it will not only cause long-term potential risks to the aquatic ecosystem, but also induce the generation and spread of antibiotic resistance genes in the environment, posing a serious threat to public health. Although the traditional biological treatment method has a low cost, it has limited removal efficiency for tetracycline hydrochloride and other pollutants with strong biological inhibition, and it is difficult to achieve ideal purification effect. Although the physical adsorption method can achieve partial removal, it is essentially a phase transfer of pollutants and does not achieve complete degradation, and there are problems such as difficulty in regenerating adsorbents and high cost of subsequent disposal. Therefore, developing a new treatment technology that can efficiently and completely degrade tetracycline hydrochloride has become an important research direction in the field of environmental engineering.

[0003] In recent years, the advanced oxidation technology based on sulfate radicals has shown broad prospects in the field of treatment of refractory organic wastewater due to its strong oxidation ability, long action life and wide acid-base applicability. Compared with traditional hydroxyl radicals, sulfate radicals have higher reactivity and selectivity for organic matter containing unsaturated bonds and aromatic structures, and are particularly suitable for the degradation of antibiotic pollutants. At present, there are various activation methods of persulfate salt, including thermal activation, ultraviolet light activation, metal ion activation and carbon material activation. Among them, the homogeneous iron ion activation system is simple to operate, but has problems such as easy precipitation of iron ions under neutral conditions to form iron sludge, difficulty in recycling of catalysts, and increase of colority of effluent; the heterogeneous catalytic system can overcome some of the defects, but the commonly used artificial synthetic catalysts often have complex preparation process and high raw material cost, and some catalysts have metal dissolution, limiting their large-scale engineering application. In addition, the existing activation methods generally have common problems such as high energy consumption, low utilization rate of oxidants and unstable free radical yield, and it is urgent to develop more economical and efficient and environmentally friendly new ways of persulfate salt activation.

[0004] In view of the above technical bottleneck, researchers have begun to turn their attention to the solution of combining natural mineral materials with functional modification. Pyrite, as a kind of natural sulfide mineral with abundant reserves and low price, its surface is rich in active components which have good catalytic potential for persulfate, but natural pyrite has inherent defects such as limited specific surface area, insufficient exposure of active sites and slow reaction kinetics. Therefore, through reasonable structure design and component regulation, developing modified pyrite materials with high catalytic performance, and constructing a matching activation reaction system, become an effective way to break through the existing technical difficulties. The present invention is in this background, through innovative material modification process and reaction condition optimization, successfully developed a multi-level structure iron and iron sulfide composite carbon material and a high-efficiency treatment system based on direct current synergistic activation of potassium monopersulfate, which provides a new technical scheme for realizing low-cost, high-efficiency and no secondary pollution treatment of tetracycline hydrochloride wastewater. SUMMARY

[0005] In view of the shortcomings of the prior art, the purpose of the present application is to provide a tetracycline hydrochloride-containing wastewater treatment method.

[0006] In the first aspect of the present application, a tetracycline hydrochloride-containing wastewater treatment method is provided, comprising the following steps: S1, introducing the tetracycline hydrochloride-containing wastewater to be treated into a reactor, adding a multi-level structure iron and iron sulfide composite carbon material, stirring, and adjusting the pH to 6.5-7.5 with dilute sulfuric acid or sodium hydroxide solution; S2, adding potassium monopersulfate hydrogen salt to the tetracycline hydrochloride-containing wastewater, starting the direct current system, and applying a current density of 15-25 mA / cm² through titanium-plated platinum electrode plates; S3, under the action of direct current and multi-level structure iron and iron sulfide composite carbon material, degradation reaction occurs at 30-45℃; S4, after the completion of the degradation reaction, the direct current system and the stirring device are turned off, the reaction mixture is left to stand, and the catalyst is recovered by separating the reaction mixture through an external magnetic field.

[0007] The multi-level structure iron and ferrous sulfide composite carbon material and the direct current electric field exhibit a clever synergistic mechanism in the process of degrading tetracycline hydrochloride. When the multi-level structure iron and ferrous sulfide composite carbon material is dispersed in wastewater, the active sites of iron and ferrous sulfide on the surface of the material and the potassium peroxymonosulfate composite salt in the solution undergo electron transfer reactions, activate the potassium peroxymonosulfate composite salt to generate sulfate radicals with strong oxidizing ability, and the sulfate radicals can further react with water to generate hydroxyl radicals. At the same time, the introduction of the direct current electric field provides a continuous source of electrons for the system, not only accelerating the activation process of the potassium peroxymonosulfate composite salt, but more importantly, through electrochemical reduction, the trivalent iron active center generated on the surface of the material is continuously reduced to a more catalytically active divalent iron form, thereby realizing the self-regeneration and recycling of the catalyst, greatly improving the yield and reaction efficiency of the radicals. The active species such as sulfate radicals and hydroxyl radicals generated will preferentially attack the phenolic hydroxyl group, dimethylamino group and tetracene nucleus in the tetracycline hydrochloride molecule, which have high electron cloud density, through a series of radical chain reactions such as electron transfer, hydrogen atom abstraction and addition reaction, gradually destroying the aromatic ring structure and functional groups. As the reaction proceeds, the tetracene nucleus of tetracycline hydrochloride undergoes ring-opening cleavage to generate a series of intermediate products (including small molecule organic acids) with smaller molecular weights, which are further oxidized and decomposed, and finally mineralized into carbon dioxide, water and small molecule organic acids and inorganic ions. The entire degradation process can be efficiently carried out under near neutral conditions, the multi-level pore structure of the composite material provides an ideal place for the full contact of pollutant molecules and active sites, and the good conductivity of the carbon skeleton promotes the efficiency of interfacial electron transfer, and the synergistic effect of the direct current electric field further enhances the generation and catalytic cycle of radicals, and the three work together to achieve efficient, rapid and complete degradation of tetracycline hydrochloride.

[0008] As a preferred technical solution of the present application, in step S1, the concentration of the multi-level structure iron and ferrous sulfide composite carbon material in the tetracycline hydrochloride-containing wastewater is 0.3-0.5 g / L.

[0009] As a preferred technical solution of the present application, in step S2, the concentration of potassium peroxymonosulfate composite salt in the tetracycline hydrochloride-containing wastewater is 3-6 mmol / L.

[0010] As a preferred technical solution of the present application, in step S3, the reaction time is 15-30 min.

[0011] As a preferred technical solution of the present application, in step S4, the reaction mixture is allowed to stand for 10-15 min.

[0012] As a preferred technical solution of the present application, the preparation step of the multi-level structure iron and ferrous sulfide composite carbon material comprises: A1, grinding pyrite and hematite into powder after crushing to obtain a mixture; drying orange peel at 78-82 DEG C and crushing to obtain orange peel powder; putting the orange peel powder, the mixture and sodium hydroxide into a ball mill to grind to obtain a mixture; A2, transferring the mixture into a crucible, placing it in a microwave muffle furnace, heating to 440-460 DEG C under nitrogen atmosphere, pyrolyzing to obtain a pyrolysis mixture; A3, cooling the pyrolysis mixture to room temperature, stirring and washing with hydrochloric acid solution; then washing with deionized water and anhydrous ethanol alternately, placing in a vacuum drying box and drying at 78-82 DEG C to obtain dried material; A4, dispersing the dried material in hydrogen peroxide solution, stirring under 38-42 DEG C water bath; then obtaining the oxidized solid material by suction filtration, washing the oxidized solid material with deionized water until neutral, and drying under vacuum at 58-62 DEG C.

[0013] In the present application, the preparation process of the multi-level structure iron and iron sulfide composite carbon material contains profound material science principles. When pyrite and hematite are mixed and ground in a specific ratio, the two iron-based minerals are uniformly dispersed and closely contacted at the microscale, laying a solid foundation for subsequent solid-phase reactions. The added orange peel biomass not only serves as a carbon source, but also converts into a carbon matrix with a seaweed-like multi-level pore structure during pyrolysis due to its abundant cellulose and hemicellulose structure. This unique structure greatly increases the specific surface area of the material. Sodium hydroxide plays multiple roles during ball milling and pyrolysis: on the one hand, it promotes the reconstruction of the mineral lattice, causing the displacement reaction between sulfur in pyrite and oxygen in hematite to form iron sulfide phases with more active sites; on the other hand, it generates local hot spot effects in the microwave field, accelerating the pyrolysis and carbonization process of the biomass. The rapid heating during the microwave pyrolysis stage causes the precursor mixture to undergo a dramatic phase transition process, with pyrite partially decomposing into zero-valent iron and ferrous sulfide with magnetism, and hematite being reduced to magnetite with stronger magnetism and catalytic activity; at the same time, the three-dimensional interconnected carbon network formed by the carbonization of orange peel biomass firmly anchors these iron-based active components (including zero-valent iron, magnetite, and ferrous sulfide, etc.) together, forming a stable and magnetically responsive composite structure. The subsequent acid washing process not only removes amorphous impurities and part of the soluble components from the surface of the material, but more importantly, it creates more mesopores and micropores on the carbon skeleton, further increasing the specific surface area and porosity of the material. The final hydrogen peroxide surface treatment significantly enhances the hydrophilicity and electronic conductivity of the material by introducing abundant oxygen-containing functional groups on the surface of the carbon material, enabling the final obtained composite material to simultaneously possess excellent catalytic activity, structural stability, and magnetic separation performance.

[0014] As a preferred technical scheme of the present application, in step A1, the mass ratio of pyrite, hematite, orange peel and sodium hydroxide is 3.5:1.5:5:0.12; the drying time is 12-14h at 78-82℃.

[0015] As a preferred technical scheme of the present application, in step A2, the pyrolysis time is 8-10min.

[0016] As a preferred technical scheme of the present application, in step A3, the concentration of hydrochloric acid solution is 0.08-0.12mol / L.

[0017] As a preferred technical scheme of the present application, in step A4, the concentration of hydrogen peroxide solution is 0.04-0.06mol / L.

[0018] Compared with the prior art, the present application has the following beneficial effects: (1) The tetracycline hydrochloride-containing wastewater treatment method provided by the present application has excellent technical effects, and its primary advantage is that it realizes efficient and rapid degradation of target pollutants. Through the synergistic effect of the multi-level structure iron and iron sulfide composite carbon material and the direct current electric field, the potassium peroxymonosulfate composite salt is efficiently activated, generating a large number of active radical species with strong oxidizing ability. These radicals can rapidly attack the benzene ring structure, phenolic hydroxyl group and dimethylamino group and other characteristic functional groups in the tetracycline hydrochloride molecule, initiate ring-opening reaction and chain scission reaction, and finally decompose it into harmless substances such as small molecular organic acids, carbon dioxide and water. Experiments show that under near neutral conditions, the system can achieve very high pollutant removal rate in a short reaction time, and the total organic carbon removal rate is also significantly higher than that of traditional methods, indicating that deep mineralization of pollutants is achieved, rather than simple form transformation.

[0019] (2) In terms of catalyst performance and economy, the present application achieves multiple technical breakthroughs through ingenious material design. The multi-level structure composite material constructed by microwave co-pyrolysis of natural pyrite and hematite as iron source combined with waste orange peel biomass not only greatly improves the specific surface area and active site density, but also forms a stable iron-iron sulfide-carbon composite interface, greatly enhancing the electron transfer efficiency. The magnetic properties of the material itself allow for rapid separation and recovery through an external magnetic field after the reaction, and it can be reused multiple times without significant loss of catalytic activity after simple regeneration. Compared with expensive synthetic catalysts or homogeneous iron salts, the material has a wide range of raw material sources and low cost, and avoids the secondary pollution problem caused by a large amount of iron sludge produced by traditional Fenton process, truly realizing the concepts of "waste treatment with waste" and green recycling.

[0020] (3) Another significant technical effect of the present application is reflected in its wide operational adaptability and lower energy consumption requirements. The system can maintain excellent catalytic performance under neutral to weakly basic conditions, overcoming the shortcomings of traditional advanced oxidation techniques that require frequent adjustment of pH, reducing reagent consumption and operating costs. The introduction of the direct current system not only promotes the activation process of persulfate, but also continuously regenerates the active components on the catalyst surface through electrochemical action, forming an efficient catalytic-electrochemical synergistic mechanism, significantly improving the oxidant utilization efficiency and reaction rate. The entire treatment device has a simple structure, easy operation, and is easy to realize automated control and large-scale application, and has a broad application prospect in treating antibiotic-containing wastewater generated in the pharmaceutical, aquaculture and other industries, providing a practical technical solution to solve the current difficult problem of treating refractory organic wastewater. DETAILED DESCRIPTION

[0021] In order to facilitate the understanding of the present application, the present application lists the following examples. Those skilled in the art should understand that the examples are only to help understand the present application, and should not be regarded as specific limitations on the present application.

[0022] Some components in the examples and comparative examples are as follows: The potassium peroxymonosulfate composite salt is purchased from Hubei Nonatech Co., Ltd.

[0023] The pyrite is purchased from Tongling Herl Mining Products Co., Ltd.

[0024] The hematite is purchased from Suzhou Xijiangwang Trading Co., Ltd.

[0025] The orange peel is purchased from Guangdong Santong Agricultural Co., Ltd.

[0026] The hydrogen peroxide is purchased from Shanghai Haobote Chemical Technology Co., Ltd.

[0027] The microwave muffle furnace is purchased from Hunan Huaye Microwave Technology Co., Ltd.

[0028] Example 1 The present example provides a tetracycline hydrochloride-containing wastewater treatment method, and the wastewater treatment steps include: Preparation of multi-level structure iron and iron sulfide composite carbon material: first, 3.5 g of pyrite and 1.5 g of hematite were placed in a jaw crusher for preliminary crushing, then transferred to a planetary ball mill, and ground at a speed of 350 r / min for 60 min. The powder particle size was confirmed to reach 300 mesh by laser particle size analyzer detection; 5 g of orange peel was evenly spread in a stainless steel tray, placed in a forced air drying oven, and dried at 80°C for 12 h. The dried orange peel was treated with a high-speed pulverizer and collected by 100 mesh standard sieve; the obtained orange peel powder, mineral mixture and 0.12 g of sodium hydroxide were loaded into a zirconium oxide ball mill jar with a volume of 500 mL, 5 mm diameter zirconium oxide grinding balls were added, and the mixture was ball milled at a speed of 400 r / min for 45 min; the mixed material was transferred to a 50 mL alumina crucible, the surface was flattened, and placed in the center of a microwave muffle furnace. High-purity nitrogen gas with a flow rate of 2 L / min was introduced as a protective atmosphere, the temperature was programmed to rise to 450°C at a rate of 15°C / min, and pyrolysis was carried out at this temperature for 8 min; after pyrolysis, the crucible was transferred to a desiccator and naturally cooled to 25°C, then the blocky product was transferred to a 250 mL beaker, 100 mL of 0.1 mol / L hydrochloric acid solution was added, and stirred on a magnetic stirrer at a rate of 300 r / min for 60 min. The solid was then separated by vacuum filtration device and washed with 100 mL of deionized water and 100 mL of anhydrous ethanol alternately for 3 times each, and the final solid product was placed in a vacuum drying oven and dried at 80°C for 6 h; the dried material was evenly dispersed in 200 mL of 0.05 mol / L hydrogen peroxide solution, stirred at a rate of 200 r / min in a 40°C constant temperature water bath for 90 min, and the solid was collected by Buchner funnel after reaction. Washed with deionized water until the filtrate pH value reached neutral, and finally the material was treated in a 60°C vacuum drying oven for 4 h to obtain the final composite material with obvious magnetic response.

[0029] Tetracycline hydrochloride-containing wastewater treatment: accurately take 1L of tetracycline hydrochloride simulated wastewater with an initial concentration of 50mg / L and place it in a cylindrical glass reactor with a volume of 2L, add 0.4g of the composite material prepared above, start the magnetic stirrer at a speed of 500r / min for stirring, and at the same time, add 0.1mol / L dilute sulfuric acid solution through the pH automatic control device to accurately adjust the pH of the system to 7.0; then add 4mmol of potassium hydrogen peroxymonosulfate complex salt to the reaction solution, immediately turn on the direct current stabilized power supply, apply a current density of 20mA / cm² through two symmetrically placed titanium-plated platinum electrodes, use a water bath circulating device to maintain the reaction system temperature at 40℃, and continue to react for 25min; after the reaction is completed, turn off the direct current power supply and the stirring device in turn, and let the reaction mixture stand for 12min, then use a neodymium-iron-boron permanent magnet with a strength of 0.5T to magnetically separate and recover the catalyst on the outer wall of the reactor.

[0030] Example 2 The present embodiment provides a tetracycline hydrochloride-containing wastewater treatment method, and the wastewater treatment step comprises: Preparation of multi-level structure iron and iron sulfide composite carbon material: 3.5 g of pyrite and 1.5 g of hematite were accurately weighed, and after preliminary crushing by a jaw crusher, they were ground for 50 min using a vibration mill. The mixed mineral powder with a particle size of 250 mesh was obtained by particle size analyzer. 5 g of fresh orange peel was evenly spread in a ceramic evaporating dish, and was continuously dried in a vacuum drying oven at 78°C for 14 h to constant weight. The dried orange peel was treated by a universal crusher and was collected by 80 mesh standard sieve. The above mineral powder, orange peel powder and 0.12 g of sodium hydroxide were placed in a 300 mL volume stainless steel ball mill jar, and 3 mm diameter zirconium oxide grinding balls were added. The mixture was mixed at a speed of 350 r / min for 40 min. The uniformly mixed material was loaded into a 30 mL alumina crucible and placed in a microwave muffle furnace. Nitrogen gas with a flow rate of 1.5 L / min was introduced as a protective atmosphere. The temperature was programmed to rise to 440°C at a rate of 10°C / min, and the pyrolysis was carried out at this temperature for 10 min. After the pyrolysis product was cooled to room temperature in a desiccator, it was transferred to a 250 mL conical flask, 120 mL of 0.08 mol / L hydrochloric acid solution was added, and the mixture was shaken in a constant temperature oscillator at a speed of 150 r / min for 50 min. The solid was then collected by centrifugation at a speed of 4000 r / min for 5 min. The material was washed with 100 mL of deionized water and 100 mL of anhydrous ethanol, respectively, for 3 times, and was dried in a vacuum drying oven at 78°C for 7 h. The dried material was immersed in 150 mL of 0.04 mol / L hydrogen peroxide solution, and was stirred at a rate of 180 r / min in a 38°C constant temperature water bath for 80 min. After the reaction was completed, the mixture was filtered through a Buchner funnel, washed with deionized water until the filtrate was neutral, and finally dried in a 58°C vacuum drying oven for 5 h to obtain the final composite material.

[0031] Tetracycline hydrochloride-containing wastewater treatment: 1 L of tetracycline hydrochloride-containing simulated wastewater with an initial concentration of 30 mg / L was accurately measured and placed in a 2 L volume glass reactor. 0.3 g of the above composite material was added, and the stirring device was started at a rate of 400 r / min. The pH was adjusted to 6.8 by monitoring with a pH meter and adding 0.1 mol / L sodium hydroxide solution dropwise. 3 mmol of potassium peroxymonosulfate composite salt was added to the reaction solution, and the direct current power system was turned on. A titanium-plated platinum electrode was used to apply a current density of 15 mA / cm², and a constant temperature water bath was used to maintain the reaction temperature at 35°C. The reaction was continued for 30 min. After the reaction was completed, all power sources were turned off, and the reaction mixture was allowed to stand for 10 min. A 0.4T neodymium-iron-boron magnet was used to separate the catalyst.

[0032] Example 3 The present example provides a method for treating tetracycline hydrochloride-containing wastewater. The wastewater treatment steps include: Preparation of multi-level structure iron and iron sulfide composite carbon material: 3.5 g of pyrite and 1.5 g of hematite were accurately weighed, and after preliminary crushing by a hammer crusher, they were ground in a vibration mill for 55 min. The mixed mineral powder with a particle size of 280 mesh was obtained by confirming the particle size distribution. 5 g of fresh orange peel was evenly placed in a glass culture dish, dried in a forced air drying oven at 82°C for 13 h, and then treated with a super micro grinder and classified and collected by a 120 mesh standard sieve. The above mineral powder, orange peel powder and 0.12 g of sodium hydroxide were placed in a 400 mL volume nylon ball mill tank, zirconium oxide balls with a diameter of 4 mm were added, and mixed at a speed of 380 r / min for 50 min. The mixed material was loaded into a 35 mL corundum crucible and placed in a microwave muffle furnace, and high-purity nitrogen gas with a flow rate of 1.8 L / min was introduced as a protective atmosphere. The temperature was programmed to rise to 460°C at a rate of 12°C / min, and the pyrolysis was carried out at this temperature for 9 min. After the pyrolysis product was naturally cooled to room temperature in a desiccator, it was transferred to a 300 mL beaker, 150 mL of 0.12 mol / L hydrochloric acid solution was added, and the mixture was stirred at a speed of 350 r / min for 70 min on a multifunctional stirrer. Then the solid was separated by vacuum filtration device and washed with 120 mL of deionized water and 120 mL of anhydrous ethanol alternately for 3 times each. The solid material was placed in a vacuum drying oven and dried at 82°C for 5 h. The dried material was dispersed in 180 mL of 0.06 mol / L hydrogen peroxide solution, and stirred at a speed of 220 r / min in a constant temperature water bath at 42°C for 100 min. After the reaction was completed, the filtrate was washed repeatedly with deionized water until the pH value reached 7.0, and finally dried in a vacuum drying oven at 62°C for 3 h to obtain the final composite material.

[0033] Tetracycline hydrochloride-containing wastewater treatment: 1 L of tetracycline hydrochloride simulated wastewater with an initial concentration of 80 mg / L was accurately measured and placed in a 2 L special glass reactor. 0.5 g of the above composite material was added, and the stirrer was started at a speed of 450 r / min. The pH was adjusted to 7.2 by adding 0.1 mol / L dilute sulfuric acid solution through the pH automatic control system. 6 mmol of potassium peroxymonosulfate composite salt was added to the reaction solution, and the direct current power system was immediately started. A current density of 25 mA / cm² was applied through titanium-plated platinum electrodes, and the reaction temperature was maintained at 45°C by using an intelligent temperature control system. The reaction was continued for 15 min. After the reaction was completed, the direct current power and the stirrer were turned off, and the reaction mixture was allowed to stand for 15 min. The catalyst was separated using a 0.6T neodymium-iron-boron magnet.

[0034] Comparative Example 1 The difference between the present comparative example and Example 1 is that the comparative material is prepared without adding hematite: 5 g of pyrite is ground into a 300-mesh powder alone, 5 g of orange peel is dried at 80°C for 12 hours and then passed through a 100-mesh sieve, and 0.12 g of sodium hydroxide is ball-milled and mixed for 45 minutes. The subsequent pyrolysis, acid washing, and oxidation treatment conditions are exactly the same as in Example 1. Tetracycline hydrochloride-containing wastewater treatment: 1 L of tetracycline hydrochloride-containing wastewater with an initial concentration of 50 mg / L is taken, 0.4 g of the comparative material is added, and the remaining treatment conditions are consistent with Example 1.

[0035] Comparative Example 2 The difference between the present comparative example and Example 1 is that the comparative material is prepared without adding orange peel: 3.5 g of pyrite and 1.5 g of hematite are ground into a 300-mesh powder, and 0.12 g of sodium hydroxide is directly ball-milled and mixed for 45 minutes. The subsequent pyrolysis, acid washing, and oxidation treatment conditions are exactly the same as in Example 1. Tetracycline hydrochloride-containing wastewater treatment: 1 L of tetracycline hydrochloride-containing wastewater with an initial concentration of 50 mg / L is taken, 0.4 g of the comparative material is added, and the remaining treatment conditions are consistent with Example 1.

[0036] Comparative Example 3 The difference between the present comparative example and Example 1 is that, in the preparation of the multi-level structure iron and iron sulfide composite carbon material, in step A1, no sodium hydroxide is added. Tetracycline hydrochloride-containing wastewater treatment: 1 L of tetracycline hydrochloride-containing wastewater with an initial concentration of 50 mg / L is taken, 0.4 g of the comparative material is added, and the remaining treatment conditions are consistent with Example 1.

[0037] According to the test specifications of national and industry standards, the water samples treated by the tetracycline hydrochloride-containing wastewater treatment method provided in the above examples and comparative examples are tested, and the test methods are as follows: 200 mL of the treated water sample is accurately measured, filtered through a 0.22 μm polyether sulfone filter membrane, and immediately detected. The tetracycline hydrochloride concentration detection uses a high-performance liquid chromatograph equipped with a C18 reverse-phase chromatographic column, the mobile phase is a mixture of acetonitrile and 0.01 mol / L oxalic acid solution at a volume ratio of 25:75, the flow rate is 1.0 mL / min, the column temperature is 35°C, the detection wavelength is 355 nm, the sample injection amount is 20 μL, and the peak area is quantified by external standard method.

[0038] The reaction rate constant is obtained by measuring the change in tetracycline hydrochloride concentration at different time points: samples are taken at 0, 5, 10, 15, 20, and 25 minutes after the start of the reaction, the tetracycline hydrochloride concentration is measured, and the slope of the linear fitting of ln(C0 / C t ) versus reaction time t is the reaction rate constant.

[0039] The total organic carbon content was determined using a total organic carbon analyzer by high-temperature catalytic combustion method. The water sample was first acidified to pH < 2 with phosphoric acid and then purged to remove inorganic carbon. Then, catalytic oxidation was carried out at 680°C, and the carbon dioxide concentration was detected by a nondispersive infrared detector.

[0040] The chemical oxygen demand was determined by a rapid digestion spectrophotometric method at a wavelength of 600 nm.

[0041] The catalyst stability test was performed by repeatedly using the multi-level structure iron and iron sulfide composite carbon material prepared in the examples and the comparative examples after washing with deionized water and vacuum drying at 80°C for 2h. The degradation rate was recorded after 5 times of repeated use under the same conditions. The iron ion concentration was determined by the o-phenanthroline spectrophotometric method at 510 nm. All tests were set up with three parallel samples.

[0042] The performance test data are shown in Table 1.

[0043] Table 1 Performance test results

[0044] From the above, it can be seen that examples 1-3 effectively solve the technical bottleneck that the present application aims to break through compared to comparative examples 1-3.

[0045] In terms of pollutant degradation efficiency, the tetracycline hydrochloride removal rate of example 1 reached 97.5%, and the total organic carbon removal rate was 68.3%, which was significantly better than 68.3% and 42.1% of comparative example 1, proving that the complete component system can fully exert the synergistic catalytic effect; examples 2 and 3 maintained degradation rates of 92.1% and 95.8% respectively, forming an obvious technical gradient, while the degradation rates of comparative examples 2 and 3 dropped sharply to 59.7% and 52.4% due to the lack of orange peel carbon skeleton and the modification of sodium hydroxide, verifying the key role of the multi-level structure and surface functional groups of the material.

[0046] In terms of reaction kinetics performance, the reaction rate constant of example 1 reached 0.1386 min -1 , which was 6.8 times that of comparative example 3, confirming that the electron transfer efficiency of the composite material was significantly improved; the rate constants of examples 2 and 3 were 0.1053 min -1 and 0.1268 min -1 , respectively, which remained at a high level, while the rate constant of comparative example 1 was only 0.0362 min -1 due to the lack of hematite lattice synergistic effect, highlighting the importance of the double iron source design.

[0047] In terms of environmental friendliness, the iron ion dissolution concentration of Examples 1-3 is controlled in the range of 0.38-0.45 mg / L, which is much lower than 0.68 mg / L of Comparative Example 2 and 0.75 mg / L of Comparative Example 3, indicating that the surface carbon-coated structure effectively inhibits metal dissolution; Example 1 still maintains a degradation rate of 94.1% after 5 cycles, compared with 58.9% of Comparative Example 3, proving that the material has excellent structural stability.

[0048] Examples successfully solve the core problems of low catalyst efficiency, poor stability and easy secondary pollution in traditional processes by constructing iron-sulfur iron-carbon multi-level composite structure, realizing the unification of efficient and stable degradation and technical and economic efficiency.

Claims

1. A method for treating tetracycline hydrochloride-containing wastewater, characterized by, The method comprises the following steps: S1, introducing the tetracycline hydrochloride-containing wastewater to be treated into a reactor, adding the multi-level structure iron-sulfide iron composite carbon material, stirring, and adjusting the pH to 6.5-7.5 by using dilute sulfuric acid or sodium hydroxide solution; S2, adding potassium peroxymonosulfate composite salt to the tetracycline hydrochloride-containing wastewater, starting the direct current system, and applying a current density of 15-25 mA / cm² through titanium-plated platinum electrode plates; S3, under the action of direct current and the multi-level structure iron-sulfide iron composite carbon material, a degradation reaction occurs at 30-45°C; S4, after the degradation reaction is completed, the direct current system and the stirring device are turned off, the reaction mixture is left to stand, and the multi-level structure iron-sulfide iron composite carbon material is separated and recovered from the reaction mixture by using an external magnetic field.

2. The tetracycline hydrochloride-containing wastewater treatment method according to claim 1, characterized by, In step S1, the concentration of the multi-level structure iron-sulfide iron composite carbon material in the tetracycline hydrochloride-containing wastewater is 0.3-0.5 g / L.

3. The tetracycline hydrochloride-containing wastewater treatment method according to claim 1, characterized by, In step S2, the concentration of the potassium peroxymonosulfate composite salt in the tetracycline hydrochloride-containing wastewater is 3-6 mmol / L.

4. The tetracycline hydrochloride-containing wastewater treatment method according to claim 1, characterized by, In step S3, the time of the degradation reaction is 15-30 min.

5. The tetracycline hydrochloride-containing wastewater treatment method according to claim 1, characterized by, In step S4, the time for leaving the reaction mixture to stand is 10-15 min.

6. The tetracycline hydrochloride-containing wastewater treatment method according to any one of claims 1 to 5, characterized by, The preparation steps of the multi-level structure iron-sulfide iron composite carbon material comprise: A1, crushing and grinding pyrite and hematite into powders to obtain a mixture; drying orange peel at 78-82°C, crushing and sieving to obtain orange peel powder; and putting the orange peel powder, the mixture, and sodium hydroxide into a ball mill, grinding to obtain a mixture; A2, transferring the mixture to a crucible, placing it in a microwave muffle furnace, and heating to 440-460°C under a nitrogen protective atmosphere to pyrolyze, obtaining a pyrolyzed mixture; A3, cooling the pyrolyzed mixture to room temperature, stirring and washing with a hydrochloric acid solution; then washing with deionized water and anhydrous ethanol alternately, and drying in a vacuum drying box at 78-82°C to obtain a dried material; A4, dispersing the dried material in a hydrogen peroxide solution, stirring and treating in a 38-42°C water bath; then obtaining an oxidized solid material by suction filtration, and washing the oxidized solid material with deionized water until neutral, and drying at 58-62°C under vacuum.

7. The tetracycline hydrochloride-containing wastewater treatment method according to claim 6, characterized by, In step A1, the mass ratio of pyrite, hematite, orange peel, and sodium hydroxide is 3.5:1.5:5:0.12, and the drying time at 78-82°C is 12-14 h.

8. The tetracycline hydrochloride-containing wastewater treatment method according to claim 6, characterized by, In step A2, the pyrolysis time is 8-10 min.

9. The tetracycline hydrochloride-containing wastewater treatment method according to claim 6, characterized by, In step A3, the concentration of the hydrochloric acid solution is 0.08-0.12 mol / L.

10. The tetracycline hydrochloride-containing wastewater treatment method according to claim 6, characterized by, In step A4, the concentration of the hydrogen peroxide solution is 0.04-0.06 mol / L.

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