阅读说明：本技术 一种高效处理四环素类抗生素有机废水的方法 (Method for efficiently treating tetracycline antibiotic organic wastewater ) 是由 林鑫辰 于 2021-09-29 设计创作，主要内容包括：本发明涉及一种高效处理四环素类抗生素有机废水的方法,包括：制备Fe-(3)O-(4)@MSTSC和TiO-(2)/Fe-(3)O-(4)@MSTSC；分别对材料的各项属性进行表征,并建立光助类Fenton催化氧化体系和光催化与类Fenton协同催化氧化体系；进行光助类Fenton催化氧化单因素测试及动力学分析；检测光助类Fenton催化氧化体系的稳定性；进行自由基定性检测,结合强氧化性自由基的淬灭实验分别各体系分析降解四环素的反应机制并分别建立机理模型。本发明在传统高级氧化技术的Fenton技术基础上,使用以Fe-(3)O-(4)为催化剂的非均相类Fenton法解决传统工艺产生含铁污泥、pH值适用范围窄(pH≈3)和催化剂不可回收利用等问题。(The invention relates to a method for efficiently treating tetracycline antibiotic organic wastewater, which comprises the following steps: preparation of Fe 3 O 4 @ MSTSC and TiO 2 /Fe 3 O 4 @ MSTSC; respectively characterizing each attribute of the material, and establishing a photo-assisted Fenton-like catalytic oxidation system and a photo-catalytic and Fenton-like synergistic catalytic oxidation system; carrying out photo-assisted Fenton catalytic oxidation single-factor test and kinetic analysis; detecting the stability of the photo-assisted Fenton catalytic oxidation system; carrying out qualitative detection on free radicals, and analyzing degradation of each system by combining quenching experiments of strong oxidizing free radicalsThe reaction mechanism of tetracycline is respectively built up. The invention uses Fe based on Fenton technology of traditional advanced oxidation technology 3 O 4 The heterogeneous Fenton-like method for the catalyst solves the problems that the traditional process generates iron-containing sludge, the pH value application range is narrow (pH is approximately equal to 3), the catalyst cannot be recycled and the like.)

1. A method for efficiently treating tetracycline antibiotic organic wastewater is characterized by comprising the following steps:

step 1: preparation of Fe₃O₄@ MSTSC catalyst and TiO with different molar ratios₂And Fe₃O₄Preparation of TiO₂/Fe₃O₄@ MSTSC catalyst;

step 2: respectively to Fe₃O₄@ MSTSC and TiO₂/Fe₃O₄The various attributes of @ MSTSC are characterized and Fe is characterized based on the characterization₃O₄@ MSTSC establishes photo-assisted Fenton catalytic oxidation system and TiO catalytic oxidation system₂/Fe₃O₄@ MSTSC establishes a photocatalytic and Fenton-like synergistic catalytic oxidation system;

and step 3: according to the tetracycline concentration, pH value and H₂O₂The addition amount and the catalyst addition amount are adjusted according to the Fe₃O₄@ MSTSC is used for photo-assisted Fenton catalytic oxidation single-factor test and kinetic analysis, and TiO is determined according to degradation effect of tetracycline₂/Fe₃O₄@ MSTSC optimum TiO₂/Fe₃O₄Molar ratio;

and 4, step 4: detecting the stability of the photo-assisted Fenton catalytic oxidation system through magnetic recovery, a repeatability experiment and iron dissolution and precipitation amount;

and 5: and (3) respectively carrying out qualitative detection on free radicals of a photo-assisted Fenton-like catalytic oxidation system and a photo-catalytic and Fenton-like synergistic catalytic oxidation system by using an electron paramagnetic resonance spectroscopy technology, and respectively analyzing a reaction mechanism for degrading tetracycline and respectively establishing a mechanism model by combining quenching experiments of strong oxidizing free radicals.

2. The method for treating tetracycline antibiotic organic wastewater with high efficiency of claim 1, wherein in step 2, Fe is treated separately₃O₄@ MSTSC and TiO₂/Fe₃O₄@ MSTSC was subjected to multiple tests and based on the test results, Fe was tested separately₃O₄@ MSTSC and TiO₂/Fe₃O₄The various attributes of the @ MSTSC are characterized; wherein, for Fe₃O₄The testing items of @ MSTSC include powder X-ray diffraction test, X-ray photoelectron spectroscopy, field emission scanning electron microscope, X-ray energy dispersion spectroscopy, transmission electron microscope, high resolution transmission electron microscope, selected area electron diffraction, solid ultraviolet-visible diffuse reflectance spectroscopy, Brunauer-Emmett-Teller specific surface area test, Barrett-Joyner-Halendal total pore volume and pore size distribution test and vibration sample magnetometer; for TiO₂/Fe₃O₄The test items of @ MSTSC include powder X-ray diffraction testing, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, X-ray energy dispersion spectroscopy, transmission electron microscopy, high resolution transmission electron microscopy, selected area electron diffraction, Brunauer-Emmett-Teller specific surface area testing, Barrett-Joyner-Halendal total pore volume and pore size distribution testing, and vibrating sample magnetometers.

3. The method for treating tetracycline antibiotic organic wastewater with high efficiency of claim 2, characterized in that the Fe is treated₃O₄In the X-ray diffraction test of @ MSTSC, Fe was measured by an X-ray diffractometer₃O₄Analysis of phase, crystal structure, etc. of @ MSTSC₃O₄@ MSTSC samples were ground to a fine powder and placed in a background-free clear glass slide for X-ray diffraction experiments, Fe₃O₄The characteristic diffraction peaks of the @ MSTSC sample were compared with X-ray diffraction standard cards to determine the phase of the sample, the grain size of the sample was calculated using the Scherrer formula: k λ/(β cos θ), wherein D is the crystal grain sizeK is the Scherrer constant, K is 0.89, λ is the incident wavelength of the X-ray source used,beta is the half-peak width of the diffraction peak of the tested sample, and theta is the diffraction angle.

4. The method for treating tetracycline antibiotic organic wastewater with high efficiency of claim 2, characterized in that the Fe is treated₃O₄@ MSTSC for X-ray photoelectron spectroscopy, Fe was characterized by using an X-ray photoelectron spectrometer₃O₄@ MSTSC surface elemental characterization, chemical valence states and chemical environment, X-ray photoelectron spectrometer using AlK α radiation source and equipped with dual X-ray source, data corrected with C1s (284.60eV) as reference.

5. The method for treating tetracycline antibiotic organic wastewater with high efficiency of claim 2, characterized in that the Fe is treated₃O₄@ MSTSC for analysis of Fe by means of a field emission scanning electron microscope equipped with an energy dispersive spectrometer, while carrying out field emission scanning electron microscopy and X-ray energy dispersive spectroscopy₃O₄Surface and morphological characteristics of @ MSTSC materials, without taking samples of Fe before observation₃O₄@ MSTSC is treated with metal spraying; the magnetic sample needs to be fixed using a duplex copper mesh to prevent the sample from damaging the device.

6. The method for efficiently treating tetracycline antibiotic organic wastewater according to claim 2,in the pair of Fe₃O₄@ MSTSC for Electron diffraction in Transmission Electron microscope and selected region, Fe was observed with a Transmission Electron microscope₃O₄The microstructure of @ MSTSC and high-resolution transmission electron microscope observation and selective area electron diffraction of the sample, observing Fe₃O₄、TiO₂Size, lattice and diffraction analysis of; the magnetic sample needs to be fixed using a duplex copper mesh to prevent the sample from damaging the device.

7. The method for treating tetracycline antibiotic organic wastewater with high efficiency of claim 2, characterized in that Fe is measured by using a specific surface area and porosity measurement system₃O₄Testing the specific surface area, N2 adsorption and desorption curves, pore volume and pore size distribution of the @ MSTSC sample; mixing Fe₃O₄The sample of @ MSTSC is put into a nitrogen atmosphere system, the surface of the material is biologically adsorbed under the condition of liquid nitrogen temperature, and when the physical adsorption is balanced, the Fe is determined by measuring the adsorption pressure and the volume of the adsorbed gas during balance₃O₄The monomolecular layer adsorption capacity of the @ MSTSC material, the specific surface area of the sample was calculated according to the Brunauer-Emmett-Teller theory, and the average pore diameter and pore size distribution in the sample were calculated by using the Barrett-Joyner-Halenda method and the average pore volume was calculated.

8. The method for treating tetracycline-based antibiotic organic wastewater with high efficiency as claimed in claim 1, wherein in the qualitative detection of free radicals in photo-assisted Fenton catalytic oxidation system using electron paramagnetic resonance spectroscopy, an electron spin paramagnetic resonance spectrometer is used to qualitatively detect hydroxyl free radicals HO and superoxide free radicals O during the photo-Fenton catalytic process₂-generation of; using DMPO as a capture agent of strong oxidizing free radicals to obtain an EPR result of the paramagnetic substance captured by spin; HO is tested in an ultra pure water environment and O2 is tested in a chromatographically pure methanol phase environment.

9. The efficient treatment of tetracycline antibiotic organic waste of claim 1A water method is characterized in that when a quenching experiment of strong oxidizing free radicals is carried out, excessive tertiary butanol, p-benzoquinone, sodium azide and ammonium oxalate are respectively used as hydroxyl free radicals HO & lt- & gt and superoxide free radicals O & lt- & gt in a light-type Fenton system₂-singlet oxygen O₂ ¹And a cavity h⁺The default scavenger can effectively scavenge the corresponding free radical, and has small damage to other free radicals; evaluating the existence of the 4 free radicals according to the degradation rate and the degradation speed of the tetracycline, and checking the free radical free radicals and the types of the dominant reactions; the tetracycline concentration is detected by using a high performance liquid chromatograph to remove the influence of benzoquinone and sodium azide on the spectrophotometric detection of tetracycline.

Technical Field

The invention relates to the technical field of tetracycline antibiotic wastewater treatment, in particular to a method for efficiently treating tetracycline antibiotic organic wastewater.

Background

Antibiotics, one of the most important medical findings of the 20 th century, have not only contributed greatly to the treatment of bacterial infections in humans and animals, but have long been used in the animal husbandry as a feed additive to stimulate growth and prevent diseases. Up to 90% of veterinary antibiotics are not assimilated by the animal and may be excreted from the body via urine or faeces. Although european countries banned the use of veterinary antibiotics as feed additives as early as 1998, their use in china and the united states is still widespread. The wide application of antibiotics in the medical industry and the veterinary industry, and the discharge of industrial wastewater is a main source of antibiotic wastewater. After industrial wastewater is treated and discharged and the incomplete metabolism links of human and animal bodies are carried out, antibiotics can be finally collected into the water environment of the nature in various ways, so that water resources are polluted. After the antibiotics enter the water body, certain biological activity still exists, the antibiotics threaten an ecological system and are beneficial to the development of resistant bacteria and resistant genes, and even if the residual quantity is within the level range of mu g/L, the antibiotics also can have some potential influences and even harm on the ecology and the human health.

The tetracycline antibiotics are a broad-spectrum antibiotic produced by actinomycete streptomycete discovered in 40 th of the 20 th century, have common phenanthrene (parent nucleus), have tetracene basic skeleton in structure, and form different tetracycline medicaments comprising aureomycin, terramycin, tetracycline, demeclocycline and the like due to different substituents in molecular structures. The tetracycline antibiotics have similar physical and chemical properties, are yellow crystalline powder, are bitter in taste, and have low solubility in water. The compound contains phenolic hydroxyl and enol hydroxyl in the molecule, is weak acidic, contains dimethylamino and is weak alkaline, so the compound is an amphoteric compound, can be dissolved in alkali or acid liquor, and is hydrochloride which is widely used in clinic.

Tetracycline antibiotics are widely used in the prevention and control of human diseases and the treatment of infectious diseases in animals due to their low cost and broad antimicrobial spectrum, or as growth promoters added to animal feeds. An investigation conducted by the U.S. department of agriculture shows that approximately 93% of pigs are fed daily with antibiotics during the growth of the breed, with Tetracycline (TC) accounting for 15.8%. Tetracycline, one of the most commonly used antibiotics, is not only widely used to protect humans from infectious diseases, but also covers over 60% of the animal disease treatment industry. This leaves a large amount of tetracycline antibiotics in production, use, and environment.

The removal of the hazards of tetracycline antibiotic contamination is essential. The Hamscher and Boxall et al team have detected concentrations of tetracycline, oxytetracycline, and aureomycin in soil as high as 0.2, 0.3, and 0.039mg/kg, respectively. The tetracycline antibiotics can generate toxic action to various degrees on a plurality of aquatic organisms in the water body, such as zebra fish, daphnia magna, crucian and the like. In addition, more than 40 tetracycline antibiotic resistance genes are discovered at present, which affects the human health and ecological health development.

In the prior art, Fe is used₃O₄The heterogeneous Fenton-like method for the catalyst is used for treating the tetracycline antibiotic organic wastewater, but the problems of iron-containing sludge generated in the traditional process, narrow pH value application range (pH is approximately equal to 3), unrecoverable catalyst and the like are solved in the treatment process.

Disclosure of Invention

Therefore, the invention provides a method for efficiently treating tetracycline antibiotic organic wastewater, which is used for overcoming the defect that Fe is used in the prior art₃O₄The heterogeneous Fenton-like method of the catalyst solves the problem of narrow pH value application range in the traditional process.

In order to achieve the above object, the present invention provides a method for efficiently treating tetracycline antibiotic organic wastewater, comprising:

step 1: preparation of Fe₃O₄@ MSTSC catalyst and TiO with different molar ratios₂And Fe₃O₄Preparation of TiO₂/Fe₃O₄@ MSTSC catalyst;

step 2: respectively to Fe₃O₄@ MSTSC and TiO₂/Fe₃O₄The various attributes of @ MSTSC are characterized and Fe is characterized based on the characterization₃O₄@ MSTSC establishes photo-assisted Fenton catalytic oxidation system and TiO catalytic oxidation system₂/Fe₃O₄@ MSTSC establishes a photocatalytic and Fenton-like synergistic catalytic oxidation system;

and step 3: according to the tetracycline concentration, pH value and H₂O₂The addition amount and the catalyst addition amount are adjusted according to the Fe₃O₄The @ MSTSC is used for photo-assisted Fenton catalytic oxidation single-factor test and kinetic analysis according toDetermination of the Effect of Tetracycline degradation TiO₂/Fe₃O₄@ MSTSC optimum TiO₂/Fe₃O₄Molar ratio;

and 4, step 4: detecting the stability of the photo-assisted Fenton catalytic oxidation system through magnetic recovery, a repeatability experiment and iron dissolution and precipitation amount;

and 5: and (3) respectively carrying out qualitative detection on free radicals of a photo-assisted Fenton-like catalytic oxidation system and a photo-catalytic and Fenton-like synergistic catalytic oxidation system by using an electron paramagnetic resonance spectroscopy technology, and respectively analyzing a reaction mechanism for degrading tetracycline and respectively establishing a mechanism model by combining quenching experiments of strong oxidizing free radicals.

Further, in the step 2, Fe is separately treated₃O₄@ MSTSC and TiO₂/Fe₃O₄@ MSTSC was subjected to multiple tests and based on the test results, Fe was tested separately₃O₄@ MSTSC and TiO₂/Fe₃O₄The various attributes of the @ MSTSC are characterized; wherein, for Fe₃O₄The testing items of @ MSTSC include powder X-ray diffraction test, X-ray photoelectron spectroscopy, field emission scanning electron microscope, X-ray energy dispersion spectroscopy, transmission electron microscope, high resolution transmission electron microscope, selected area electron diffraction, solid ultraviolet-visible diffuse reflectance spectroscopy, Brunauer-Emmett-Teller specific surface area test, Barrett-Joyner-Halendal total pore volume and pore size distribution test and vibration sample magnetometer; for TiO₂/Fe₃O₄The test items of @ MSTSC include powder X-ray diffraction testing, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, X-ray energy dispersion spectroscopy, transmission electron microscopy, high resolution transmission electron microscopy, selected area electron diffraction, Brunauer-Emmett-Teller specific surface area testing, Barrett-Joyner-Halendal total pore volume and pore size distribution testing, and vibrating sample magnetometers.

Further, in the case of Fe₃O₄In the X-ray diffraction test of @ MSTSC, Fe was measured by an X-ray diffractometer₃O₄Analysis of phase, crystal structure, etc. of @ MSTSC₃O₄@ MSTSC samples were ground to a fine powder and placed in a background-free clear glass slide for X-ray diffraction experiments, Fe₃O₄The characteristic diffraction peaks of the @ MSTSC sample were compared with X-ray diffraction standard cards to determine the phase of the sample, the grain size of the sample was calculated using the Scherrer formula: k λ/(β cos θ), wherein D is the crystal grain sizeK is the Scherrer constant, K is 0.89, λ is the incident wavelength of the X-ray source used,beta is the half-peak width of the diffraction peak of the tested sample, and theta is the diffraction angle.

Further, in the case of Fe₃O₄@ MSTSC for X-ray photoelectron spectroscopy, Fe was characterized by using an X-ray photoelectron spectrometer₃O₄@ MSTSC surface elemental characterization, chemical valence states and chemical environment, X-ray photoelectron spectrometer using AlK α radiation source and equipped with dual X-ray source, data corrected with C1s (284.60eV) as reference.

Further, in the case of Fe₃O₄@ MSTSC for analysis of Fe by means of a field emission scanning electron microscope equipped with an energy dispersive spectrometer, while carrying out field emission scanning electron microscopy and X-ray energy dispersive spectroscopy₃O₄Surface and morphological characteristics of @ MSTSC materials, without taking samples of Fe before observation₃O₄@ MSTSC is treated with metal spraying; the magnetic sample needs to be fixed using a duplex copper mesh to prevent the sample from damaging the device.

Further, in the case of Fe₃O₄@ MSTSC for Electron diffraction in Transmission Electron microscope and selected region, Fe was observed with a Transmission Electron microscope₃O₄The microstructure of @ MSTSC and high-resolution transmission electron microscope observation and selective area electron diffraction of the sample, observing Fe₃O₄、TiO₂Size, lattice and diffraction analysis of; the magnetic sample needs to be fixed using a duplex copper mesh to prevent the sample from damaging the device.

Further, Fe was measured by using a specific surface area and porosity measurement system₃O₄Testing the specific surface area, N2 adsorption and desorption curves, pore volume and pore size distribution of the @ MSTSC sample; mixing Fe₃O₄The sample of @ MSTSC is put into a nitrogen atmosphere system, the surface of the material is biologically adsorbed under the condition of liquid nitrogen temperature, and when the physical adsorption is balanced, the Fe is determined by measuring the adsorption pressure and the volume of the adsorbed gas during balance₃O₄The monomolecular layer adsorption capacity of the @ MSTSC material, the specific surface area of the sample was calculated according to the Brunauer-Emmett-Teller theory, and the average pore diameter and pore size distribution in the sample were calculated by using the Barrett-Joyner-Halenda method and the average pore volume was calculated.

Further, when the electron paramagnetic resonance spectroscopy technology is used for qualitatively detecting the free radicals of the photo-assisted Fenton catalytic oxidation system, an electron spin paramagnetic resonance spectrometer is used for qualitatively detecting the hydroxyl free radicals HO & and the superoxide free radicals O in the photo-Fenton catalytic process₂-generation of; using DMPO as a capture agent of strong oxidizing free radicals to obtain an EPR result of the paramagnetic substance captured by spin; HO is tested in an ultra pure water environment and O2 is tested in a chromatographically pure methanol phase environment.

Further, in the quenching experiment of the strong oxidizing free radical, excessive tertiary butanol, p-benzoquinone, sodium azide and ammonium oxalate are respectively used as a hydroxyl free radical HO & lt + & gt and a superoxide free radical O in a photo-Fenton-like system₂-singlet oxygen O₂ ¹And a cavity h⁺The default scavenger can effectively scavenge the corresponding free radical, and has small damage to other free radicals; evaluating the existence of the 4 free radicals according to the degradation rate and the degradation speed of the tetracycline, and checking the free radical free radicals and the types of the dominant reactions; the tetracycline concentration is detected by using a high performance liquid chromatograph to remove the influence of benzoquinone and sodium azide on the spectrophotometric detection of tetracycline.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention is based on the Fenton technology of the traditional advanced oxidation technologyAbove, use Fe₃O₄The heterogeneous Fenton-like method for the catalyst solves the problems that the traditional process generates iron-containing sludge, the pH value application range is narrow (pH is approximately equal to 3), the catalyst cannot be recycled and the like.

2. The invention introduces UV light, establishes a photo-assisted Fenton-like catalytic oxidation system, and solves the problem that a large amount of H is required to be added in a heterogeneous Fenton-like system₂O₂And H₂O₂Low efficiency of use and Fe³⁺Reduction to Fe²⁺The problem of too small an amount, using photolysis H₂O₂The process fully increases the hydroxyl radical HO of the high-activity strong oxidant in the system.

3. The invention aims to solve the problems of low ultraviolet light use efficiency and low light quantum yield of a photo-assisted Fenton catalytic oxidation system, and uses a special photo-catalytic advanced oxidation method to oxidize TiO₂The semiconductor is introduced into the system to form a photocatalysis and Fenton-like concerted catalysis oxidation system, and then the photocatalysis TiO is further utilized₂Generated e^-Reduction of Fe³⁺And using the light h⁺More hydroxyl radicals HO. are produced.

4. To solve the problem of Fe caused by magnetic and Van der Waals force₃O₄、TiO₂The invention increases the specific surface area and the dispersion stability of the material, supplements catalytic reaction active sites, and loads the material on the corn straw template skeleton carbon by a one-step synthesis method.

Drawings

FIG. 1 is a flow chart of the method for efficiently treating tetracycline antibiotic organic wastewater according to the present invention;

FIG. 2 shows Fe according to the present invention₃O₄@ MSTSC and coprecipitated Fe₃O₄An XRD pattern of (a);

FIG. 3 shows Fe according to the present invention₃O₄XPS measurement spectra for @ MSTSC and high resolution XPS spectra for the Fe 2p, C1s and O1s regions;

FIG. 4 shows Fe according to the present invention₃O₄FE-SEM image and coprecipitated Fe of @ MSTSC₃O₄FE-SEM image of (1);

FIG. 5 shows Fe according to the present invention₃O₄@ MSTSC EDS mapping image;

FIG. 6 shows Fe according to the present invention₃O₄TEM, HRTEM, and sea images of @ MSTSC;

FIG. 7 shows Fe according to the present invention₃O₄@ MSTSC and coprecipitated Fe₃O₄The solid ultraviolet-visible diffuse reflection spectrogram of (1);

FIG. 8 shows Fe according to the present invention₃O₄@ MSTSC and coprecipitated Fe₃O₄N of (A)₂Adsorption-desorption isotherms and pore size profiles;

FIG. 9 shows Fe according to the present invention₃O₄@ MSTSC and coprecipitated Fe₃O₄Magnetic hysteresis loop of (1) and Fe dispersed in solution₃O₄@ MSTSC separation scheme under external magnetic field conditions;

FIG. 10 is a UV-visible full scan of the tetracycline of the invention and its concentration-absorbance standard curve;

FIG. 11 is a graph of the effect of initial tetracycline concentration on the photo-Fenton-like system of the present invention;

FIG. 12 is a graph of the effect of initial pH on a photo-Fenton-like system according to the present invention;

FIG. 13 shows the initial H of the present invention₂O₂Influence of the addition amount on the light-type Fenton system;

FIG. 14 is a graph of the effect of initial catalyst dosage on photo-Fenton-like systems according to the present invention;

FIG. 15 shows Fe according to the present invention₃O₄The EPR spectrum result of the @ MSTSC photo-assisted Fenton catalytic oxidation system;

FIG. 16 is a graph of tetracycline degradation efficiency and degradation kinetics for different systems according to the present invention;

FIG. 17 shows Fe according to the present invention₃O₄@ MSTSC recycling effect and XRD result;

FIG. 18 shows Fe according to the present invention₃O₄The experimental result of quenching of the free radical of the @ MSTSC photo-assisted Fenton catalytic oxidation system;

FIG. 19 shows Fe according to the present invention₃O₄@ MSTSC with co-precipitated Fe₃O₄Performance comparison and kinetic fitting of the degraded tetracycline;

FIG. 20 is a comparison of tetracycline degradation performance and corresponding kinetic fit for adsorbed tetracycline and unadsorbed tetracycline according to the invention.

Detailed Description

In order that the objects and advantages of the invention will be more clearly understood, the invention is further described below with reference to examples; it should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only for explaining the technical principle of the present invention, and do not limit the scope of the present invention.

Please refer to the drawings, which are a flow chart of the method for efficiently treating tetracycline antibiotic organic wastewater of the present invention, the method of the present invention comprises:

step 1: preparation of Fe₃O₄@ MSTSC catalyst and TiO with different molar ratios₂And Fe₃O₄Preparation of TiO₂/Fe₃O₄@ MSTSC catalyst;

step 2: respectively to Fe₃O₄@ MSTSC and TiO₂/Fe₃O₄The various attributes of @ MSTSC are characterized and Fe is characterized based on the characterization₃O₄@ MSTSC establishes photo-assisted Fenton catalytic oxidation system and TiO catalytic oxidation system₂/Fe₃O₄@ MSTSC establishes a photocatalytic and Fenton-like synergistic catalytic oxidation system;

and step 3: according to the tetracycline concentration, pH value and H₂O₂The addition amount and the catalyst addition amount are adjusted according to the Fe₃O₄@ MSTSC is used for photo-assisted Fenton catalytic oxidation single-factor test and kinetic analysis, and TiO is determined according to degradation effect of tetracycline₂/Fe₃O₄@ MSTSC optimum TiO₂/Fe₃O₄Molar ratio;

and 4, step 4: detecting the stability of the photo-assisted Fenton catalytic oxidation system through magnetic recovery, a repeatability experiment and iron dissolution and precipitation amount;

and 5: and (3) respectively carrying out qualitative detection on free radicals of a photo-assisted Fenton-like catalytic oxidation system and a photo-catalytic and Fenton-like synergistic catalytic oxidation system by using an electron paramagnetic resonance spectroscopy technology, and respectively analyzing a reaction mechanism for degrading tetracycline and respectively establishing a mechanism model by combining quenching experiments of strong oxidizing free radicals.

In particular, in the preparation of Fe₃O₄@ MSTSC and TiO₂/Fe₃O₄Before @ MSTSC, pretreatment is carried out on the corn straws. The corn straw is used as a biological material, wherein the components are complex, and the pore channels contain substances such as grease, wax, resin and the like. In order to open the pore channel, the corn straw needs to be pretreated by an ammoniation extraction method or an alkali liquor soaking method to improve the soaking effect. The pretreatment effect is similar, and the ammonification method is easy to operate and has lower cost, so the ammonification extraction method is used for pretreating the corn straws. Firstly, the hard outer layer of the corn straw is removed, and the inner part of the corn straw is observed to have a porous structure. Corn straw small disks, peeled and cut to a thickness of 1mm, were dried in an oven at 60 ℃ for 6 hours. The volume ratio of the later use is 1: 4 NH 3. H2O and deionized water as extracting solution, heating and extracting for 4 hours in an extracting device matched with a constant temperature electrothermal sleeve, a Soxhlet extraction tube, a condensing tube and a round bottom flask, washing with ultrapure water until the pH value of the corn stalk is about 7 after the extraction is finished, and then placing in an oven at 60 ℃ for drying for 6 hours for later use.

In particular, in the preparation of Fe₃O₄@ MSTSC, FeCl is first introduced under a nitrogen atmosphere₃·6H₂O (5.404g) and FeCl₂·4H₂O (1.988g) was dissolved in 100mL of ultrapure water with mechanical stirring to give a yellow solution. The extracted 1.0g of corn stalks are soaked in the obtained yellow solution for 24 hours at room temperature, so that the precursor solution is completely absorbed by the stalks. Note that the beaker was completely sealed during the soaking process, allowing no air to flow in.

Then, 40mL of 25% NH₃·H₂O is added to the solid-liquid mixture at a rate of one second drop and the reaction is completed (i.e. co-precipitated Fe is formed) while continuing mechanical stirring₃O₄) And forming a black solid-liquid mixture. After this operation, the beaker was again tightly sealed and then heated in a water bath at 60 ℃ for 40 minutes. The mixture is black and has a pH of about 11 to 13. After cooling to room temperature, the filtered black corn stover was washed alternately with ultrapure water and ethanol until the pH became neutral, and then dried in a vacuum oven at 60 ℃ for 6 hours. In this way, the preparation of the calcined precursor is completed.

Finally, a dry synthesis atmosphere (10% O) was passed through a tube furnace₂，90％N₂) Heating the precursor to 300 ℃ at the speed of 10 ℃/min, keeping the temperature at 300 ℃ for 2h, and then normally cooling to indoor environment temperature to prepare Fe₃O₄@ MSTSC photo-assisted Fenton-like catalytic material.

In particular, in the preparation of TiO₂/Fe₃O₄@ MSTSC, first, with Fe₃O₄@ MSTSC was prepared identically by mixing 5.404g FeCl₂·4H₂O and 1.988g FeCl₃·6H₂O was dissolved in 100mL of ultrapure water under nitrogen blanket to form a yellow solution. 1.0g of corn stalks which are subjected to extraction pretreatment are immersed in the solution for 24 hours under a sealed condition.

Next, 40mL of NH was added thereto₃·H₂O, Fe is formed after fully stirring₃O₄Black mixture attached to the straw. After washing several times with ethanol and ultrapure water to a pH of about 7, it was dried in a vacuum oven at 60 ℃ for 6 hours.

Thirdly, 25mL of tetrabutyl titanate solution is dissolved in 75mL of absolute ethanol, and 1mL of glacial acetic acid is added to prevent hydrolysis, so that a precursor solution is prepared. Vacuum drying to obtain Fe₃O₄According to TiO, the corn stalks₂With Fe₃O₄Are arranged at a molar ratio of 1:1, 1:2, 1:5, 1:10 and 10:1, respectively, and are immersed in the precursor solution for 24 hours.

Finally, in the synthesis atmosphere (10% O)₂，90％N₂) Placing the precursor in a tubular roasting furnace, roasting at 300 ℃ for 2h (heating at 10 ℃/min), then heating to 550 ℃ at the same speed, roasting for 4h, naturally cooling, and taking out to obtain TiO₂/Fe₃O₄@ MSTSC composite.

With continuing reference to FIG. 1, in step 2, Fe is treated separately₃O₄@ MSTSC and TiO₂/Fe₃O₄@ MSTSC was subjected to multiple tests and based on the test results, Fe was tested separately₃O₄@ MSTSC and TiO₂/Fe₃O₄The various attributes of the @ MSTSC are characterized; wherein, for Fe₃O₄Test items of @ MSTSC include powder X-ray diffraction test (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FE-SEM), X-ray Energy Dispersion Spectroscopy (EDS), Transmission Electron Microscope (TEM), High Resolution Transmission Electron Microscope (HRTEM), selected area electron diffraction (SEAD), solid ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), Brunauer-Emmett-Teller specific surface area test (BET), Barrett-Joyner-Halendal Total pore volume and pore size distribution test (BJH), and Vibrating Sample Magnetometer (VSM); for TiO₂/Fe₃O₄Test items of @ MSTSC include XRD, XPS, FE-SEM, EDS, TEM, HRTEM, SEAD, BET, BJH, and VSM.

Specifically, in the case of Fe₃O₄@ MSTSC, for X-ray diffraction testing

Equipped with Ni filtration at Cu K αAs a radiation source, an X-ray diffractometer with a current of 30mA and an acceleration voltage of 40kV is used for measuring Fe₃O₄Analyzing the phase, crystal structure and the like of the @ MSTSC, wherein the scanning angle range is 20-80 DEG, and the scanning speed is 3 DEG min^-1(step size of sampling angle interval is 0.05 DEG, one step per second), mixing Fe₃O₄@ MSTSC samples were ground to a fine powder and placed in a background-free clear glass slide for X-ray diffraction experiments, Fe₃O₄Characteristic diffraction peak and X-ray diffraction standard card pair of @ MSTSC sampleThe phase of the sample is determined by comparing the grain size of the sample using the Scherrer equation: k λ/(β cos θ), wherein D is the crystal grain sizeK is the Scherrer constant, K is 0.89, λ is the incident wavelength of the X-ray source used,beta is the half-peak width of the diffraction peak of the tested sample, and theta is the diffraction angle.

Fe₃O₄@ MSTSC and coprecipitated Fe₃O₄The XRD pattern of (A) is shown in figure 2. The XRD intensity peaks of [email protected] MSTSC represent the 30.121 ° (220), 35.479 ° (311), 43.119 ° (400), 53.495 ° (422), 57.026 ° (511), 62.622 ° (440) and 74.086 ° (533) planes belonging to cubic (isometric) magnetite Fe3O4(PDF # 88-0866). Pure crystalline phase Fe is obtained₃O₄And the corn stalk template skeleton carbon without causing Fe₃O₄Phase transition of (2). Fe₃O₄XRD pattern of @ MSTSC and co-precipitated Fe₃O₄The XRD patterns of the maize straws have no significant difference, but the former has a little more noise under the same test conditions, which is mainly the influence of the carbon structure of the template framework of the maize straws. In addition, the higher peak intensity of the spectrum indicates that highly crystalline Fe is synthesized₃O₄。

In Fe₃O₄No characteristic peak of graphite structure is found in the XRD spectrum of @ MSTSC, which indicates that the prepared corn straw template skeleton carbon is amorphous carbon. gamma-Fe₂O₃With Fe₃O₄Have similar XRD patterns, but do not exist at high temperatures. Furthermore, although gamma-Fe₂O₃Diffraction pattern of (3) and Fe₃O₄Similar, but they have different space groups (Fe)₃O₄Is Fd-3m, gamma-Fe₂O₃P4132) and lattice parameter (Fe)₃O₄Corresponding to PDF #88-0866, gamma-Fe₂O₃Corresponding to PDF # 39-1346). Fe₃O₄Will be re-determined from the XPS spectrum of the Fe 2p orbit (FIG. 3-b)And (5) performing secondary verification.

Estimation of Fe by Scherrer's equation₃O₄@ MSTSC has an average grain size of about 3.28-18.42nm, and coprecipitates Fe₃O₄Has a slightly larger particle size of 10.31-157.68nm, which indicates Fe₃O₄@ MSTSC has a finer crystal structure, which confirms the influence of the biomass structure on the crystal growth process, especially the nucleation process, and the grain size of the product is also controlled, which is a control method for the microscopic fine structure change caused by macroscopic variables. Most of Fe₃O₄@ MSTSC has a particle size in the range of 9-13nm, while Fe is coprecipitated₃O₄The particle size of (A) is 40-60 nm.

Specifically, in the case of Fe₃O₄@ MSTSC for X-ray photoelectron spectroscopy, Fe was characterized by using an X-ray photoelectron spectrometer₃O₄@ MSTSC surface elemental characterization, chemical valence states and chemical environment, X-ray photoelectron spectrometer using AlK α radiation source and equipped with dual X-ray source, data corrected with C1s (284.60eV) as reference.

The XPS technology is used for analyzing the surface element composition and the element valence state of the [email protected] MSTSC in the energy range of 0-1200eV, and the test result is shown in figure 3. The measured full-scan spectrum (FIG. 3-a) shows that the material contains three elements: fe, C and O.

FIG. 3-b shows Fe₃O₄Fine scanning XPS Spectroscopy of Fe 2p orbital of @ MSTSC, the two main peaks at 710.8eV and 724.0eV correspond to Fe 2p1/2 and Fe 2p3/2, respectively, where no representation of Fe alone was found₂O₃(Fe³⁺) The satellite peak of (a). The Fe 2p1/2 and Fe 2p3/2 peaks may be deconvoluted to Fe respectively³⁺724.4eV, 711.1eV and Fe²⁺723.1eV, 709.1eV, respectively, with a coverage area (integral) ratio of about 2: 1, which is identical with the pure phase Fe3O4 compound, shows that no gamma-Fe exists in the material₂O₃This is consistent with the results of the XRD patterns.

As shown in FIG. 3-C, the binding energy peaks for 284.8eV and 285.3eV are generated from the C1s orbital, due to the relatively large content of C-C bonds and C-O bonds, respectively. The O1s orbital XPS spectrum (FIG. 3-d) can be deconvoluted into three peaks at 530.3eV, 531.6eV and 532.3 eV. The main peaks are lattice oxygen (Fe-O bond) of 530.3eV and surface hydroxyl (O-H bond) of 531.6eV, and the integral amounts of O-H and Fe-O on the surface of the catalyst are almost equal, indicating that the number of hydroxyl on the surface of the catalyst is larger, which leads to an increase in the catalytic activity of the catalyst material.

Specifically, in the case of Fe₃O₄@ MSTSC for analysis of Fe by means of a field emission scanning electron microscope equipped with an energy dispersive spectrometer, while carrying out field emission scanning electron microscopy and X-ray energy dispersive spectroscopy₃O₄Surface and morphological characteristics of @ MSTSC materials, without taking samples of Fe before observation₃O₄@ MSTSC is treated with metal spraying; the magnetic sample needs to be fixed using a duplex copper mesh to prevent the sample from damaging the device.

FIGS. 4-a and 4-b show Fe₃O₄@ MSTSC FE-SEM image. It can be seen that the material exhibits a good microscopic channel-like porous structural framework, which is attributed to the corn stover template skeleton carbon and exhibits a distinct metallic texture, indicating that the characteristic morphology of corn stover was successfully replicated. This change in structure, texture and texture accounts for Fe₃O₄And the interaction with the biological carbon material structure. The channels are of different sizes and it also provides the material with a greater pore volume. In fact, as can be seen from FIG. 4-b, much Fe₃O₄The nanoparticles are more uniformly loaded on the straw carbon. Due to surface Fe₃O₄，Fe₃O₄The outer surface of @ MSTSC is rough and irregular, and has fine holes, which indicates that the synthetic material has the potential of adsorbing TC. Most of Fe₃O₄@ MSTSC Fe₃O₄Particle size in the range of 9-13nm, while most of the co-precipitated Fe₃O₄The particle size of (A) is 40-60nm, as can be seen in FIG. 4-c.

The EDS element mapping (figure 5) of a sample is analyzed by using an on-board energy dispersion spectrometer, the material has three elements of carbon (C), oxygen (O) and iron (Fe), and the sample contains a small amount of FeCl from a precursor liquid₃·6H₂O and FeCl₂·4H₂Chlorine (Cl) element of O. Most of Fe and O unitsThe element is due to Fe₃O₄Their distribution is exactly identical to that of the C element, which, on the one hand, proves the presence of carbon as framework and, on the other hand, also proves the presence of highly dispersed Fe₃O₄The nanoparticles are stably supported on the backbone carbon. Analysis in combination with FE-SEM demonstrated Fe₃O₄The interaction between the nano particles and the corn straw template carbon skeleton is stable and firm.

Specifically, in the case of Fe₃O₄In the case of transmission electron microscope and selective area electron diffraction using @ MSTSC, Fe was observed using a transmission electron microscope with an acceleration voltage of 200kV₃O₄The microstructure of @ MSTSC and high-resolution transmission electron microscope observation and selective area electron diffraction of the sample, observing Fe₃O₄、TiO₂Size, lattice and diffraction analysis of; the magnetic sample needs to be fixed using a duplex copper mesh to prevent the sample from damaging the device.

TEM (FIGS. 6-a and 6-b) and HRTEM (FIG. 6-c) analysis of the samples were performed using transmission electron microscopy to identify morphology, morphology and size of the material. It can be clearly seen that Fe₃O₄The shape of the nanoparticles was a cubic (isometric) structure of 3.28 to 18.42nm, further confirming that these particle materials were of nanoscale size, which is consistent with the results of XRD analysis, and Fe₃O₄The particles are well dispersed on the surface of the framework. The occurrence of the massive contrast in FIGS. 6-a and 6-b is due to Fe on the carbon skeleton₃O₄The nanoparticles are more prominent than the backbone plane, resulting in an increase in thickness making the image appear black. The uniformly distributed protrusions increase the surface area of the material, using Fe₃O₄The larger binding energy between the nanoparticles and the carbon skeleton can resist Fe₃O₄Magnetic attraction among each other reduces Fe₃O₄And exhibit a large number of nano-mesoporous structures.

Diffraction contrast of HRTEM image shows Fe₃O₄Has interplanar spacing values of 0.296nm, 0.253nm and 0.148nm, respectively, and cubic system (isometric system) Fe₃O₄Three major XRD peaks of phases (220), (311) and (440) are very consistent, different crystal planes of different grains can be observed at the same angle, and the three major XRD peaks are typical of a homogeneous multi-orientation polycrystalline structure.

Selective area electron diffraction of the material, SEAD image (FIG. 6-d) verifies Fe₃O₄The polycrystalline structure of the @ MSTSC sample, the major crystallographic planes (220), (311), (400), (422), (511) and (440) are clearly visible.

In particular, solid uv-vis diffuse reflectance spectroscopy is a technical method for studying the optical absorption properties of solid materials in the uv-visible region. The samples were subjected to solid ultraviolet-visible diffuse reflectance spectral analysis by a solid ultraviolet-visible spectrophotometer (U-4100, Shimazu, Japan) to test the optical absorption properties of the samples in the wavelength range of 200-800nm using high mesh ground size Al2O3 as a background reference standard.

Ultraviolet-visible diffuse reflectance spectrum test of the catalyst using an ultraviolet-visible spectrophotometer for investigating the photophysical properties of the catalyst, co-precipitating Fe as shown in FIG. 7₃O₄And Fe₃O₄The @ MSTSC sample has wide-range light absorption in the range of 200-₃O₄Does not significantly affect the light absorption of Fe, and further does not affect Fe³⁺The light absorption and the light reaction of the catalyst enable the photo-assisted Fenton catalytic oxidation system to be durable and continuous.

In particular, Fe is measured by using a specific surface area and porosity measurement system₃O₄Testing the specific surface area, N2 adsorption and desorption curves, pore volume and pore size distribution of the @ MSTSC sample; mixing Fe₃O₄The sample of @ MSTSC is put into a nitrogen atmosphere system, the surface of the material is biologically adsorbed under the condition of liquid nitrogen temperature, and when the physical adsorption is balanced, the Fe is determined by measuring the adsorption pressure and the volume of the adsorbed gas during balance₃O₄The monomolecular layer adsorption capacity of the @ MSTSC material is calculated according to the Brunauer-Emmett-Teller theory to calculate the specific surface area of the sample, and the average pore diameter and the pore diameter distribution in the sample are calculated by using the Barrett-Joyner-Halenda method and the average pore is calculatedVolume.

Fe was analyzed using a specific surface area and porosimetry system₃O₄@ MSTSC and coprecipitated Fe₃O₄Specific surface area, particle size distribution, pore structure, etc., and the detailed data are shown in table 1.

TABLE 3-1 Fe₃O₄@ MSTSC and coprecipitated Fe₃O₄Specific surface area, particle size distribution, pore structure and other properties

N₂The adsorption-desorption isotherm (fig. 8-a) can characterize the large specific surface area of the material, which is an important indicator of catalytic activity. According to the IUPAC classification, hysteresis loops of the IVH3 type, between 0.5 and 1.0 at relative pressure (P/P0), were identified, demonstrating the presence of mesoporous structures (pore size 2-50nm) in the material. With co-precipitating Fe₃O₄(33.7135m2/g) in comparison with Fe₃O₄@ MSTSC has a larger BET specific surface area value (120.0948m 2/g). Mesopores were readily wetted and therefore [email protected] MSTSC was hydrophilic and well dispersed in aqueous solution, a phenomenon that could, of course, be attributed to the use of corn stover template framework carbon.

The Barret-Joyner-Halenda (BJH) method (FIG. 8-b) is more suitable for mesoporous structures. Calculation of Fe by BJH model₃O₄@ MSTSC has an average pore diameter of 3.92nm, and Fe is coprecipitated₃O₄6.52nm and pore volumes estimated at 0.23cc/g and 0.12cc/g, respectively, the pore volumes of which differ by nearly a factor of two under the same conditions.

Specifically, a vibration sample magnetometer (SQUID-VSM, Quantum Design, America) was used to analyze the magnetic hysteresis loop and the magnetic strength of a catalyst sample at room temperature in a magnetic field of ± 10000Oe, and the recycling efficiency was analyzed.

The magnetization curve of the sample (M-H curve) as a function of the magnetic field strength is shown in FIG. 9, and Fe is measured₃O₄The saturation magnetization value of @ MSTSC in the magnetic field of +/-10000 Oe is 34.60emu/g, which is weaker than that of pure coprecipitation Fe₃O₄(44.29emu/g), the decrease in saturation magnetization (Ms) is due to the presence of the nonmagnetic material corn stover template backbone carbon. Despite Fe₃O₄The magnetic properties of @ MSTSC have decreased but are still sufficient for magnetic separation. FIG. 9-b already demonstrates that Fe₃O₄@ MSTSC can be easily and quickly separated from an aqueous solution without leaving a residue, even in the absence of an external magnetic field, Fe₃O₄@ MSTSC remains magnetic.

Specifically, the photo-Fenton degradation rate of the tetracycline in the aqueous solution is obtained by monitoring the residual amount of the tetracycline, and the performance of the catalyst material is further evaluated. A certain amount of tetracycline was dissolved in 250mL of ultrapure water, charged into a 250mL beaker covered with aluminum foil, and passed through H₂SO₄And NaOH to adjust the pH of the TC solution, and its specific value was measured using a pH meter. An ultraviolet lamp (length 120mm, width 10mm, wavelength 220 nm and power 10W) was inserted in the center of a beaker, and a predetermined amount of a catalyst sample (Fe)₃O₄@ MSTSC, coprecipitated Fe₃O₄Commercial product Fe₃O₄And TiO with different molar ratios₂/Fe₃O₄@ MSTSC) is added into a tetracycline reactor, a magnetic stirrer (the rotating speed is 500 r.min < -1 >) is opened to be evenly mixed, and a certain amount of H is added₂O₂Starting the ultraviolet lamp tube to initiate degradation reaction, and timing.

At a specific time, a solution sample in a reactor of about 4mL is measured by a disposable sterile syringe, and the catalyst is filtered by a polyether sulfone (PES) membrane of 450nm/13mm to detect the concentration of tetracycline.

By detecting the solution by using an ultraviolet-visible spectrophotometer, the ultraviolet-visible light full-scan absorption spectrum of the tetracycline hydrochloride aqueous solution shown in figure 10-a can observe that the absorption peaks of tetracycline at 275nm and 357nm are strongest and can be used as the characteristic peaks. Tetracycline solutions with concentrations of 5mg/L, 10mg/L, 20mg/L, 30mg/L, 40mg/L, and 50mg/L, respectively, were prepared, and absorbance was measured at a wavelength of 357nm using deionized water as a reference, and a standard curve of tetracycline concentration (mg/L) -absorbance was plotted, as shown in FIG. 10-b.

The decrease of the absorption peak at 357nm is used to indicate the degradation of tetracycline^[43]And Fe was evaluated by measuring the rate of tetracycline degradation₃O₄@ MSTSC, coprecipitated Fe₃O₄Commercial product Fe₃O₄And TiO with different molar ratios₂/Fe₃O₄@ MSTSC.

The tetracycline degradation rate was calculated as follows:

ε＝[(C₀–C)/C₀]×100％

in the formula C₀The initial concentration of tetracycline (mg/L);

c is the tetracycline concentration (mg/L) at a particular detection time;

ε is the degradation rate (%) of tetracycline

Plotting the residual ratio C/C of tetracycline₀Graph relating to reaction time for analysis of tetracycline degradation process within 90 minutes. The experimental data result shows that the tetracycline degradation kinetic equation can be expressed as a quasi-first order kinetic equation model:

-ln(C/C₀)＝Kt+b

in the formula C₀The initial concentration of tetracycline (mg/L);

c is the tetracycline concentration (mg/L) at a particular detection time;

k is kinetic constant (min)^-1)；

t is reaction time (min);

b is the intercept constant.

FIG. 11-a shows Fe₃O₄The ability of @ MSTSC to degrade tetracycline of different concentrations in a photo-assisted Fenton catalytic oxidation system. When the pH is 7.0, the adding amount of the catalyst is 0.3g/L and 10mmol/L H is added₂O₂The maximum concentration of degradable tetracycline is reached. When the concentration of the tetracycline is 25mg/L and 50mg/L, the tetracycline can be degraded by about 94 percent in 40 minutes,and near complete degradation at 60 deg.f. The rate constants observed at 25mg/L and 50mg/L were almost the same in FIG. 11-b, 0.10542 min^-1And 0.10647min^-1. At tetracycline concentrations above 50mg/L, the reaction rate slowed down under the same conditions. For subsequent experiments, we selected 50mg/L tetracycline as the degradation target.

The pH value of the solution is an important parameter in a photo-assisted Fenton catalytic oxidation system, the degradation of tetracycline in 50mg/L simulated wastewater with the pH values of 3.0, 5.0, 7.0 and 9.0 is researched and monitored, and the result is shown in a figure 12. Experimental results show that the photo-assisted Fenton catalytic oxidation system is effective in the pH range of 3.0-7.0, which proves that the tetracycline can be degraded in acidic and neutral solutions at high efficiency, and the system can degrade tetracycline wastewater under the condition of not adjusting the pH. Of course, when the pH was 9.0, the degradation effect was 93% after 90 minutes of the reaction.

HO is a core element initiating tetracycline degradation, thus H₂O₂The concentration has a significant influence on the reaction. First, a large amount of H can be directly reacted₂O₂Photolysis to produce more HO. Second, H₂O₂With Fe²⁺By reaction with HO, possibly also with Fe³⁺The reaction produces hydroperoxyl radicals (HO)₂Cndot.). Finally, H₂O₂Can react with HO, so excess H₂O₂Can be used as a scavenger of HO & to reduce the degradation efficiency of TC.

In organic matter degradation systems, HO₂The rate constant for degradation of the reactants is much smaller than HO, the contribution of which is approximately negligible. As can be seen in FIG. 13-b, the low concentration (5mM) of H₂O₂Poor effect, more than 10mM H₂O₂The kinetic constants of the system are almost equal and are all about 0.107min^-1。

Fe₃O₄The effect of the amount of @ MSTSC on degradation efficiency is shown in FIG. 14. The degradation efficiency increases with increasing catalyst content and no longer increases any significantly after reaching 0.3g/L, which may be due to the fact that a large amount of catalyst makes the solution too turbid and the UV irradiation efficiency naturally decreases, which leads to the photolysis of hydroxyl radicalsThe amount of (c) is reduced. Therefore, 0.3g/L catalyst was selected as the experimental condition in the subsequent experiments.

Specifically, an electron spin paramagnetic resonance spectrometer (A200, Bruker, Germany) was used to qualitatively detect hydroxyl radicals (HO. cndot.) and superoxide radicals (O. cndot.) in the photo-Fenton-like catalytic process₂·^-) Is generated. Experiments using DMPO as a capture agent for strongly oxidizing radicals, results were obtained for the spin-captured paramagnetic species EPR. The presence of HO & was examined in an ultrapure water environment and O was examined in a chromatographically pure methanol phase environment₂·^-Are present. The experimental conditions were: [ TC ]]₀＝50mg/L， pH＝7.0，[H₂O₂]₀＝10mM，[Fe₃O₄@MSTSC]₀0.3g/L and T22 ± 1 ℃.

Detection conditions of the photo-assisted Fenton catalytic oxidation system are as follows: the central field strength is 3470G; the scanning width is 60G; the microwave frequency is 9.75 GHz; the power is 6.33 mW; the detection conditions of photocatalysis and Fenton-like concerted catalytic oxidation are as follows: the central field intensity is 3510G; the scanning width is 100G; the microwave frequency is 9.75 GHz; the power was 6.33 mW.

Fe₃O₄The electron paramagnetic resonance spectrum analysis of the @ MSTSC photo-assisted Fenton catalytic oxidation reaction system is shown in figure 15. The EPR spectrum shows that the solution of the system exhibits 1: 2: 2: type 1 typically has a 4 fold peak, which contrasts sharply with dark conditions, which qualitatively illustrates the generation of HO.

And no HO was observed in a short time₂·(·O₂ ^-) DMPO-O with DMPO₂(H) Presence of characteristic peaks, description O₂ ^-Is difficult to be in Fe₃O₄Monitoring in a @ MSTSC photo-assisted Fenton catalytic oxidation reaction system to obtain O₂ ^-Is not the hypothesis of the free radicals that dominate the oxidation reaction.

Specifically, to illustrate the synergistic effect and mechanism of photochemical reaction and Fenton-like reaction, 0.3g/L Fe was added at pH 7.0₃O₄@MSTSC，10mM H₂O₂At room temperature (22 +/-)50mg/L tetracycline was degraded at 1 ℃ and a series of control experiments (including under dark conditions) were performed, the results of which are shown in FIG. 16.

Using addition of ultraviolet light alone or H alone₂O₂As a reaction limitation, the tetracycline in the system is hardly oxidized, probably because the UV light is not effective in destroying tetracycline, and H₂O₂Has a redox potential lower than HO. When Fe is added separately₃O₄@ MSTSC, Fe can be considered₃O₄The absorbance decrease phenomenon is dominated by the adsorption of @ MSTSC to tetracycline. In this case, the addition of ultraviolet rays does not have a significant accelerating effect.

Addition of catalyst and H₂O₂Formed Fenton-like reaction and addition of UV light and H₂O₂Formed photolysis H₂O₂The reaction significantly increased the degradation of TC by 47.8% and 90.1% at 60min, respectively. Single Fenton-like systems in dark conditions without UV light assistance to increase Fe³⁺/Fe²⁺Circulation velocity, so that it is higher than photolysis H₂O₂The process produces less HO.

In summary, the photo-assisted Fenton-like catalytic oxidation reaction showed a higher degradation rate, which degraded 98.1% of the target pollutant in about 40 minutes and degraded almost all the target pollutant in the system at 60 minutes with a kinetic constant of 0.10647min^-1(FIG. 16-b), these experiments demonstrate that the photo-assisted Fenton-like synergy is of great significance.

Specifically, a catalyst that can be reused many times is undoubtedly cost-effective, and can be effectively reused is also one of important indicators of a catalyst. Here, after the previous experiment was completed, Fe was separated using an external magnetic field₃O₄The material @ MSTSC, dried after collection and re-tested under the same reaction conditions, the stability of the catalyst was evaluated by five consecutive experiments and the catalyst was XRD tested before and after five reactions, the results of which are shown in figure 17.

The results show that after five cycles Fe₃O₄Drop of @ MSTSCThe solution efficiency was still about 94%. There was no shift in XRD characteristic peak (FIG. 17-b) before and after the reaction, and the decrease in peak height was probably due to Fe₃O₄And (4) reducing the content. HO-Effect on catalyst surface can increase Fe²⁺、Fe³⁺And the solubility of amorphous iron oxide, coupled with ultraviolet light corrosion, results in reduced catalyst stability. With decreasing pH, H₂O₂The number of cycles is increased, the concentration of leached iron is increased, and the repeated oxidation process produces incompatible but easily soluble iron (hydroxide)^[55]This should also be the reason for the degradation capacity. In all experiments, Fe in solution²⁺And Fe³⁺The sum of the concentrations of (A) and (B) is 0.163mg/L, which is far lower than 2.0mg/L of EU standard. Fe₃O₄@ MSTSC has high catalytic efficiency, less leached iron, good stability and a simple recovery method.

Specifically, in the quenching experiment of the strong oxidizing free radical, excessive tertiary butanol, p-benzoquinone, sodium azide and ammonium oxalate are respectively used as a hydroxyl free radical HO and a superoxide free radical O in a light-type Fenton system₂-singlet oxygen O₂ ¹And a cavity h⁺The default scavenger can effectively scavenge the corresponding free radical, and has small damage to other free radicals; evaluating the existence of the 4 free radicals according to the degradation rate and the degradation speed of the tetracycline, and checking the free radical free radicals and the types of the dominant reactions; the tetracycline concentration is detected by using a high performance liquid chromatograph to remove the influence of benzoquinone and sodium azide on the spectrophotometric detection of tetracycline.

To determine Fe₃O₄The @ MSTSC photo-assisted Fenton catalytic oxidation reaction system degrades main active free radical substances of tetracycline, a free radical quenching experiment is carried out on the system, the default quencher can effectively remove corresponding free radicals, and damage to other free radical components can be ignored. The experimental conditions were: [ TC ]]₀＝50mg/L，pH＝7.0，[H₂O₂]₀＝10mM，[Fe₃O₄@MSTSC]₀0.3g/L and T22 ± 1 ℃.

Wherein the sodium azide quenches singlet oxygen (O)₂ ¹) And ammonium oxalate quenching the cavity (h)⁺) The experimental data are not shown in the chart because the former should have a small content or an insignificant oxidation effect, and the latter should not appear in the system, which has little effect on the degradation effect of tetracycline.

The use of tert-butanol and p-benzoquinone as HO & HO, respectively₂The quencher of (1) to remove the corresponding free radical, the experimental results are shown in FIG. 18. It was shown that the removal of HO significantly reduces the efficiency of the tetracycline degradation reaction, while HO₂·(·O₂ ^-) The removal had no significant effect on the reaction. This illustrates the synchronized generation of HO with conventional homogeneous Fenton₂·(·O₂ ^-) Different from HO, Fe₃O₄HO is not directly generated in the photo-assisted Fenton catalytic oxidation reaction of @ MSTSC₂·(·O₂ ^-) Only HO. is a direct product, and HO₂·(· O₂ ^-) Is an indirect product and has no significant effect on the catalytic oxidation reaction.

Specifically, to clarify the importance of skeletal carbon and the superiority of the new materials prepared, Fe was compared₃O₄@ MSTSC and coprecipitated Fe₃O₄The difference in the ability of the material to degrade tetracycline is shown in FIGS. 19-a and 19-b (kinetic studies). The experimental conditions were: the initial concentration of tetracycline is 50mg/L, H₂O₂The initial concentration was 10mmol/L, the catalyst dosage was about 0.3mg/L, and the initial pH was about 7.0.

Under the condition of the same quality of catalyst, the coprecipitation Fe is caused due to the magnetic agglomeration phenomenon and the like₃O₄Exhibits a low specific surface area, H₂O₂Adsorption on Fe₃O₄Fe having a reduced ability to generate HO on the surface and solving the above problems₃O₄The @ MSTSC mesoporous material can promote tetracycline and H₂O₂And the molecules diffuse into their pores. Although Fe is coprecipitated₃O₄Containing more Fe₃O₄However, for the reasons mentioned above, its adsorption capacity for tetracycline is much smaller than that for Fe₃O₄Suction of @ MSTSCThe catalyst has the advantages of capacity attachment and fewer Fenton reaction active sites. Therefore, the corn straw carbon skeleton material with larger specific surface area and high reactivity is self-evident for improving the tetracycline degradation performance.

Specifically, studies compared Fe₃O₄The change of degradation efficiency after the @ MSTSC catalyst adsorbs tetracycline and does not adsorb tetracycline further illustrates that the increase of surface reaction after adsorption leads to the improvement of tetracycline degradation effect, and shows the synergistic effect of adsorption removal and surface degradation, particularly as shown in FIGS. 20-a and 20-b (kinetics research). After 60 minutes of adsorption, 50mg/L tetracycline was reduced by 17%, after sufficient adsorption, the rate of tetracycline degradation was significantly increased with a kinetic constant of 0.10647min^-1Increasing the temperature to 0.16161min^-1The directional attack capability of the microreactor on the adsorbed tetracycline is embodied.

Fe₃O₄@ MSTSC has certain adsorption capacity on tetracycline, and the large specific surface area of the @ MSTSC has great influence on degradation of tetracycline. The porous structure of the corn straw template skeleton carbon can form a microreactor, can degrade tetracycline and can strike pollutants in a targeted manner. The combination of surface degradation after adsorption and degradation in solution after desorption allows for faster degradation of tetracycline^[56]. First, Fe₃O₄The ability of @ MSTSC to decompose pollutants is superior to that of coprecipitation Fe₃O₄. Second, Fe₃O₄After the @ MSTSC adsorbs tetracycline for 60 minutes, the degradation efficiency is obviously higher than that of an unadsorbed system.

The degradation mechanism of the tetracycline can be presumed, and the system comprehensively treats the tetracycline wastewater by using hydroxyl free radicals generated by Fenton-like reaction, hydroxyl free radicals generated by hydrogen peroxide photolysis and surface degradation reaction promoted by the material to adsorb the tetracycline. The UV light effectively promotes Fe as compared to the Fenton-like reaction alone³⁺Reduction to Fe²⁺The cyclic process of (2). Fe₃O₄The nano particles are highly dispersed on the carbon skeleton, so that the magnetic agglomeration phenomenon is reduced, and the specific surface area is increased. Due to Fe₃O₄The tetracycline molecule can be successfully enrichedCollected in a cavity and provided with a microreactor to eliminate reactants.

In summary, the present invention concludes as follows:

1.Fe₃O₄@ MSTSC maintains the micro-morphology of corn stover, with Fe₃O₄The phase is of cubic (isometric) magnetite type, and the skeletal carbon is amorphous carbon. Fe₃O₄The average grain size is 3.28-18.42nm, which shows that the skeleton carbon controls the growth of semiconductor crystal, and the carbon skeleton does not influence Fe obviously₃O₄Light absorption of (2). The BET specific surface area of the material was 120.0948m²The magnetic material has the advantages of a specific volume, a specific magnetic property, a specific volume, and a specific magnetic property.

2. The process of degrading tetracycline by the photo-assisted Fenton catalytic oxidation system is very effective and accords with quasi-first-order kinetics, and the kinetic constant is 0.10647min^-1. Single factor experiment confirms that the optimal conditions of room temperature (22 +/-1 ℃) experiment are that the initial tetracycline concentration is 50mg/L, the pH is 7.0, and H₂O₂The dosage is 10mmol/L, Fe₃O₄The dosage of @ MSTSC is 0.3 g/L.

3. The performance and dynamics of tetracycline degradation of different systems are compared, and the results are obtained by using Fe₃O₄The photo-assisted Fenton catalytic oxidation system with the @ MSTSC as the catalyst has the best effect, and the ultraviolet light has an obvious promotion effect on the Fenton-like process.

4. Fe after five cycles₃O₄The degradation efficiency of @ MSTSC can still be kept about 94%, XRD has no obvious change, the concentration of iron in the solution is 0.163mg/L, and the material has performance, chemical stability and reutilization capability.

5.Fe₃O₄Qualitative detection of hydroxyl radical containing HO & lt- & gt in @ MSTSC photo-assisted Fenton catalytic oxidation reaction system, wherein the reaction system is an oxidation reaction taking HO & lt- & gt as a main component, HO & lt- & gt is a direct product, and the super-oxygen radical HO & lt- & gt is HO & lt- & gt₂·(·O₂ ^-) Is an indirect product, singlet oxygen O₂ ¹The effect of (c) is negligible.

So far, the technical solutions of the present invention have been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of the present invention is obviously not limited to these specific embodiments. Equivalent changes or substitutions of related technical features can be made by those skilled in the art without departing from the principle of the invention, and the technical scheme after the changes or substitutions can fall into the protection scope of the invention.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention; various modifications and alterations to this invention will become apparent to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.