Preparation method and application of iron-molybdenum co-loaded biochar catalyst

Abstract

The invention relates to the technical field of biochar catalyst preparation, in particular to a preparation method and application of an iron-molybdenum co-loaded biochar catalyst, and the preparation method comprises the following preparation steps: S1, preparing a biochar precursor; s2, introduction of iron and molybdenum elements; s3, carrying out load modification; s4, modifying a pore structure; and S5, carrying out secondary pyrolysis. According to the method, tetracycline in water can be degraded more quickly and efficiently, the treatment efficiency is greatly improved, and the method has important significance for solving the problem of antibiotic pollution in water. Besides, the process also shows a good degradation effect when being applied to an actual water body, the tetracycline degradation rate can reach 98.8%, the content of tetracycline in water is effectively reduced, and potential hazards of antibiotics to the environment and the ecological system are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of biochar catalyst preparation, and in particular to a method for preparing an iron-molybdenum co-loaded biochar catalyst and application thereof. Background Art

[0002] Antibiotics are used in livestock farms to increase production or prevent infection. Livestock manure containing residual antibiotics is further used as fertilizer for crop production and aquaculture, leading to the entry of antibiotics into soil, groundwater and aquatic ecosystems. At the same time, due to the high solubility characteristics of antibiotics and the lack of effective treatment measures, antibiotics are directly or indirectly released into different environments.

[0003] Tetracycline (TC) is one of the most widely used antibiotics in the world. The use of a large amount of tetracycline has led to its frequent detection in the environment. It is light yellow crystal or powder, odorless, bitter, hygroscopic, and gradually darkens when exposed to light. Tetracycline antibiotics include tetracycline, doxycycline, minocycline, tigecycline, oxytetracycline, and chlortetracycline. Due to the widespread use of tetracycline antibiotics and the series of environmental safety risks they can cause, the removal of tetracycline using biological methods, physical adsorption, and advanced oxidation methods has been widely reported.

[0004] Among the advanced oxidation processes, the ozone / permonosulfate (O3 / PMS) combined process was first proposed by Professor Ma Jun of Harbin Institute of Technology, and achieved efficient degradation of atrazine in a short period of time. Although the ozone / permonosulfate process shows high efficiency in degrading organic pollutants, it still has some limitations in practical applications. First, when ozone or permonosulfate is used alone, the utilization rate of the oxidant is low and the degradation efficiency is limited. Secondly, the reaction rate of ozone and permonosulfate is slow, especially in complex water bodies, which are easily interfered by inorganic ions and organic matter, resulting in a decrease in degradation effect. In addition, the reaction conditions of ozone and permonosulfate (such as pH, temperature, etc.) have a great influence on the degradation efficiency, which limits its application in practical engineering. In order to improve the degradation efficiency of the ozone / permonosulfate process, researchers have tried to introduce catalysts to accelerate the activation of oxidants and the generation of free radicals. Transition metal catalysts (such as iron, molybdenum, etc.) have become a hot topic of research due to their good catalytic performance and low cost. However, existing iron-molybdenum catalysts have problems such as uneven loading and unstable catalytic activity during the preparation process, which limits their promotion in practical applications. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing an iron-molybdenum co-loaded biochar catalyst and its application, which can significantly enhance the degradation efficiency by using the iron-molybdenum co-loaded biochar catalyst, thereby solving the problems in the prior art such as low utilization rate of ozone and permonosulfate, and the degradation efficiency being greatly affected by the complex components of the water body.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing an iron-molybdenum co-loaded biochar catalyst comprises the following preparation steps:

[0008] S1. Preparation of biochar precursor: washing, drying, and crushing carbon-containing organic matter into powder, passing through a 100-mesh sieve, and then pyrolyzing the powder once in a nitrogen atmosphere to obtain a biochar precursor;

[0009] S2. Introduction of iron and molybdenum elements: The biochar precursor, ferric chloride and sodium molybdate were mixed in a mass ratio of 1:1:1.5 and immersed in a 50% acetone solution, stirred at a speed of 100-200 r / min for 22-24 hours, filtered and dried to obtain primary biochar;

[0010] S3. Load modification: adding the primary biochar obtained in step S2 to the primary modification liquid, stirring at 20-30°C and 150-250r / min for 1-2h to obtain a primary modified biochar;

[0011] S4. Pore structure modification: adding the primary modified biochar obtained in step S3 to the secondary modified liquid, stirring at 200-300 r / min for 2.5-3.5 h at 50-60° C., filtering and drying to obtain secondary modified biochar;

[0012] S5. Secondary pyrolysis: The secondary modified biochar obtained in step S4 is subjected to secondary pyrolysis at 500-600°C for 1.5-2h to obtain an iron-molybdenum co-loaded biochar catalyst.

[0013] Preferably, the carbon-containing organic matter is one or more of corn straw, wheat straw, and rice straw.

[0014] Preferably, the primary pyrolysis temperature is controlled at 500-600°C, and the pyrolysis time is 1.5-2h.

[0015] Preferably, in step S3, the primary modification liquid is a mixed solution of 5% hexadecyltrimethylammonium bromide solution and polyaspartic acid, wherein the mass ratio of the 5% hexadecyltrimethylammonium bromide solution to polyaspartic acid is 10:1.

[0016] Preferably, in step S4, the secondary modification liquid is a mixed solution of 5% disodium ethylenediaminetetraacetic acid solution and polymaleic anhydride, wherein the mass ratio of the 5% disodium ethylenediaminetetraacetic acid solution to the polymaleic anhydride is 8:1.

[0017] Preferably, in step S3, the mass ratio of primary biochar to primary modified liquid is 1:3.

[0018] Preferably, in step S4, the mass ratio of the primary modified biochar to the secondary modified liquid is 1:1.

[0019] Preferably, in step S2, the drying temperature is 60-70°C and the drying time is 10-12 hours.

[0020] Preferably, in step S4, the drying temperature is 80-90° C. and the drying time is 5-8 h.

[0021] An application of an iron-molybdenum co-loaded biochar catalyst prepared according to the above preparation method in degrading tetracycline in water.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The primary modified liquid in the present invention can make the iron and molybdenum ions more evenly dispersed on the surface of biochar, increase the number of active sites, and make the iron and molybdenum ions more fully enter the pores of biochar, achieve more uniform and deeper loading, and thus improve the catalytic efficiency and catalytic performance of the catalyst. The polyaspartic acid contains multiple carboxyl groups, which can form stable chelates with various metal ions, making the metal ions evenly dispersed on the surface of biochar, enhancing the binding ability of metal ions with the functional groups on the surface of biochar, and improving the loading efficiency.

[0024] 2. The adsorption of the secondary modified liquid on the surface of biochar in the present invention helps to improve the pore structure of biochar, making its pores more uniform and open, which is beneficial to the loading of metal ions. It complements the primary modified liquid and better improves the catalytic efficiency and catalytic performance of the catalyst.

[0025] 3. The present invention can degrade tetracycline in water more quickly and efficiently, greatly improving the treatment efficiency, which is of great significance for solving the problem of antibiotic pollution in water. In addition, the application of this process in actual water bodies also shows a good degradation effect, and the degradation rate of tetracycline can reach 98.8%, which effectively reduces the content of tetracycline in water and reduces the potential harm of antibiotics to the environment and ecosystem. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a process flow chart for preparing the iron-molybdenum co-loaded biochar catalyst of the present invention;

[0027] Figure 2The three-dimensional fluorescence spectrum of tetracycline water samples is configured for the water samples at the fine grid of the Southeast Wastewater Treatment Plant, where a is the three-dimensional fluorescence spectrum of the untreated water sample without tetracycline, b is the three-dimensional fluorescence spectrum of the untreated water sample containing tetracycline, c is the three-dimensional fluorescence spectrum of the water sample after treatment for 20 minutes, and d is the three-dimensional fluorescence spectrum of the water sample after treatment for 60 minutes;

[0028] Figure 3 It is a line graph showing the effect of the iron-molybdenum co-loaded biochar catalyst of the present invention in degrading tetracycline water samples under different water quality conditions;

[0029] Figure 4 Schematic diagram of the structure of the iron-molybdenum co-loaded biochar catalyst obtained in Example 1 and Comparative Examples 1-3 of the present invention under an electron microscope, wherein a, b, and c are the observation results of the product obtained in Comparative Example 1 at 3000 times, 2000 times, and 1000 times magnification, respectively, d, e, and f are the observation results of the product obtained in Comparative Example 2 at 20000 times, 5000 times, and 2000 times magnification, respectively, g, h, and i are the observations of the product obtained in Comparative Example 3 at 5000 times, 3000 times, and 2000 times magnification, respectively, j, k, and l are the observations of the newly obtained product in Example 1 at 20000 times, 5000 times, and 2000 times magnification, respectively, and m, n, and o are the observations of the product obtained in Example 1 and after use at 20000 times, 10000 times, and 2000 times magnification, respectively;

[0030] Figure 5 This is the EDS spectrum of the iron-molybdenum co-loaded biochar catalyst obtained in Example 1 of the present invention;

[0031] Figure 6 The graph is a nitrogen adsorption-desorption isotherm curve of BC, FeBC, MoBC, FeMoBC (new) and FeMoBC (used), wherein BC is the product obtained in Comparative Example 1, FeBC is the product obtained in Comparative Example 2, MoBC is the product obtained in Comparative Example 3, FeMoBC (new) is the iron-molybdenum co-loaded biochar catalyst prepared in Example 1, and FeMoBC (used) is the used iron-molybdenum co-loaded biochar catalyst;

[0032] Figure 7 The XRD spectra of the iron-molybdenum co-loaded biochar catalyst obtained in Example 1 of the present invention and after use, wherein FeMoBC (new) is the iron-molybdenum co-loaded biochar catalyst prepared in Example 1, and FeMoBC (used) is the used iron-molybdenum co-loaded biochar catalyst;

[0033] Figure 8This is a full spectrum of newly prepared and used materials of the iron-molybdenum co-loaded biochar catalyst obtained in Example 1 of the present invention, wherein FeMoBC (new) is the iron-molybdenum co-loaded biochar catalyst prepared in Example 1, and FeMoBC (used) is the product of Example 1 after use;

[0034] Fig. 9 The XPS analysis spectra of the newly prepared and used elements of the iron-molybdenum co-loaded biochar catalyst obtained in Example 1 of the present invention, wherein a is the XPS analysis spectrum of the newly prepared product in Example 1 for the C1 orbital electrons of the C element, b is the XPS analysis spectrum of the used product in Example 1 for the C1 orbital electrons of the C element, c is the XPS analysis spectrum of the newly prepared product in Example 1 for the 2p orbital electrons of the Fe element, d is the XPS analysis spectrum of the used product in Example 1 for the 2p orbital electrons of the Fe element, e is the XPS analysis spectrum of the newly prepared product in Example 1 for the 3d orbital electrons of the Mo element, and f is the XPS analysis spectrum of the used product in Example 1 for the 3d orbital electrons of the Mo element;

[0035] Fig.10 Kinetic fitting diagram to explore the effect of the dosage of the iron-molybdenum co-loaded biochar catalyst on the degradation efficiency of tetracycline;

[0036] Fig.11 This is a kinetic fitting diagram for exploring the effect of the concentration of potassium persulfate solution on the degradation efficiency of tetracycline in the present invention;

[0037] Fig.12 The kinetic fitting diagram for exploring the effect of initial concentration of tetracycline on degradation efficiency in the present invention;

[0038] Fig.13 The kinetic fitting diagram of the present invention in exploring the effect of ozone concentration on tetracycline degradation efficiency;

[0039] Fig.14 This is a kinetic fitting diagram for exploring the effect of pH value of water environment on the degradation efficiency of tetracycline in the present invention;

[0040] Fig.15 This is a reaction flow chart of the O3 / PMS / FeMoBC system in the study of the effect of the O3 / PMS / FeMoBC system on tetracycline degradation in the performance test of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] See also Figure 1-15 , the present invention provides a technical solution:

[0043] Example 1

[0044] A method for preparing an iron-molybdenum co-loaded biochar catalyst:

[0045] S1. Preparation of biochar precursor: The carbon-containing organic matter was washed, dried, crushed into powder, passed through a 100-mesh sieve, and then pyrolyzed once in a nitrogen atmosphere. The pyrolysis temperature was controlled at 500°C and the pyrolysis time was 1.5 h to obtain a biochar precursor;

[0046] S2. Introduction of iron and molybdenum elements: 100 g of biochar precursor, 100 g of ferric chloride, and 150 g of sodium molybdate were mixed and immersed in 500 mL of 50% acetone solution by mass, stirred at a speed of 100 r / min for 22 h, filtered, and dried at a drying temperature of 60 ° C for 10 h to obtain primary biochar;

[0047] S3. Load modification: adding the primary biochar obtained in step S2 to a primary modification liquid 3 times the mass of the primary biochar, stirring at 150 r / min for 1 h at 20° C. to obtain a primary modified biochar;

[0048] S4. Pore structure modification: adding the primary modified biochar obtained in step S3 to the secondary modified liquid, stirring at 200 r / min at 50°C for 2.5h, filtering and drying at 80°C for 5h to obtain secondary modified biochar;

[0049] S5. Secondary pyrolysis: The secondary modified biochar obtained in step S4 is subjected to secondary pyrolysis at 500° C. for 1.5 h to obtain an iron-molybdenum co-loaded biochar catalyst.

[0050] Example 2

[0051] A method for preparing an iron-molybdenum co-loaded biochar catalyst:

[0052] S1. Preparation of biochar precursor: The carbon-containing organic matter was washed, dried, crushed into powder, passed through a 100-mesh sieve, and then pyrolyzed once in a nitrogen atmosphere. The pyrolysis temperature was controlled at 600°C and the pyrolysis time was 2 h to obtain a biochar precursor;

[0053] S2. Introduction of iron and molybdenum elements: 90 g of biochar precursor, 90 g of ferric chloride and 135 g of sodium molybdate were mixed and immersed in a 50% by mass acetone solution, stirred at a speed of 200 r / min for 24 h, filtered and dried at a drying temperature of 70 ° C for 12 h to obtain primary biochar;

[0054] S3. Load modification: adding the primary biochar obtained in step S2 to a primary modification liquid 3 times the mass of the primary biochar, stirring at 250 r / min at 30° C. for 2 h to obtain a primary modified biochar;

[0055] S4. Pore structure modification: adding the primary modified biochar obtained in step S3 to a secondary modified liquid of the same mass as the primary modified biochar, stirring at 300 r / min at 60°C for 3.5 hours, filtering and drying at 90°C for 8 hours to obtain a secondary modified biochar;

[0056] S5. Secondary pyrolysis: The secondary modified biochar obtained in step S4 is subjected to secondary pyrolysis at 600° C. for 2 h to obtain an iron-molybdenum co-loaded biochar catalyst.

[0057] Example 3

[0058] A method for preparing an iron-molybdenum co-loaded biochar catalyst:

[0059] S1. Preparation of biochar precursor: The carbon-containing organic matter was washed, dried, crushed into powder, passed through a 100-mesh sieve, and then pyrolyzed once in a nitrogen atmosphere. The pyrolysis temperature was controlled at 550°C and the pyrolysis time was 1.7 h to obtain a biochar precursor;

[0060] S2. Introduction of iron and molybdenum elements: 95 g of biochar precursor, 95 g of ferric chloride, and 142.5 g of sodium molybdate were mixed and immersed in a 50% by mass acetone solution, stirred at a speed of 150 r / min for 23 h, filtered, and dried at a drying temperature of 63 ° C for 11 h to obtain primary biochar;

[0061] S3. Load modification: The primary biochar obtained in step S2 is added to a primary modification liquid having a mass three times that of the primary biochar, and stirred at 200 r / min for 1.5 h at 25° C. to obtain a primary modified biochar;

[0062] S4. Pore structure modification: adding the primary modified biochar obtained in step S3 to a secondary modified liquid of the same mass as the primary modified biochar, stirring at 250 r / min at 55°C for 3 hours, filtering and drying at a drying temperature of 85°C for 6 hours to obtain a secondary modified biochar;

[0063] S5. Secondary pyrolysis: The secondary modified biochar obtained in step S4 is subjected to secondary pyrolysis at 550°C for 1.7 hours to obtain an iron-molybdenum co-loaded biochar catalyst.

[0064] Example 4

[0065] A method for preparing an iron-molybdenum co-loaded biochar catalyst:

[0066] S1. Preparation of biochar precursor: The carbon-containing organic matter was washed, dried, crushed into powder, passed through a 100-mesh sieve, and then pyrolyzed once in a nitrogen atmosphere. The pyrolysis temperature was controlled at 580°C and the pyrolysis time was 1.9 h to obtain a biochar precursor;

[0067] S2. Introduction of iron and molybdenum elements: 100 g of biochar precursor, 100 g of ferric chloride and 150 g of sodium molybdate were mixed and immersed in a 50% by mass acetone solution, stirred at a speed of 180 r / min for 23.5 h, filtered and dried at a drying temperature of 68 ° C for 11.5 h to obtain primary biochar;

[0068] S3. Load modification: The primary biochar obtained in step S2 is added to a primary modification liquid having a mass three times that of the primary biochar, and stirred at 230 r / min at 28° C. for 1.8 h to obtain a primary modified biochar;

[0069] S4. Pore structure modification: adding the primary modified biochar obtained in step S3 to a secondary modified liquid of the same mass as the primary modified biochar, stirring at 280 r / min at 58°C for 3.3 h, filtering and drying at a drying temperature of 88°C for 7 h to obtain a secondary modified biochar;

[0070] S5. Secondary pyrolysis: The secondary modified biochar obtained in step S4 is subjected to secondary pyrolysis at 580°C for 1.8 hours to obtain an iron-molybdenum co-loaded biochar catalyst.

[0071] Comparative Example 1

[0072] Comparative Example 1 is different from Example 1 in that sodium molybdate and ferric chloride are not added in step S2, and the remaining steps are exactly the same in Comparative Example 1 and Example 1.

[0073] Comparative Example 2

[0074] Comparative Example 2 is different from Example 1 in that sodium molybdate is not added in step S2, and the remaining steps are exactly the same in Comparative Example 2 and Example 1.

[0075] Comparative Example 3

[0076] Comparative Example 3 is different from Example 1 in that ferric chloride is not added in step S2, and the remaining steps are exactly the same in Comparative Example 3 and Example 1.

[0077] Performance Test:

[0078] In order to verify the degradation ability of the iron-molybdenum co-loaded biochar catalyst in actual complex water bodies, the water sample at the fine grid in the Southeast Wastewater Treatment Plant in Changchun City, Jilin Province was used for the experiment. After the raw water was allowed to stand for 24 hours, it was filtered using a 50μm qualitative filter paper and filtered twice. A 30μM tetracycline solution was prepared as a solvent. At the same time, an ultraviolet spectrophotometer and a three-dimensional fluorescence instrument were used to detect the water sample parameters. The water quality analysis structure and the three-dimensional fluorescence distribution method results are shown in Tables 1 and 2 below:

[0079] Table 1 Water quality analysis results of water samples at the fine screen of Southeast Wastewater Treatment Plant

[0080] Water quality indicators Before treatment (containing tetracycline) After treatment COD 204.68mg / L 45.61mg / L TN 39.68mg / L 25.06mg / L NH3-N 33.93mg / L 21.24mg / L TP 5.59mg / L 4.55mg / L pH 7.41 6.48

[0081] Table 2 Three-dimensional fluorescence distribution method

[0082]

[0083] The three-dimensional fluorescence spectrum of the water sample is shown in the attached figure. Figure 2 As shown, the organic matter in the solution mainly exists between regions III, IV and V (240-400nm / 350-550nm), and is judged to be aromatic protein or phenolic substances (Fulvic acid) and humic acid substances. Figure 2 In the experiment, after 20 minutes of treatment with the Fe-Mo co-loaded biochar catalyst, the fluorescent substances in the raw water sample were greatly reduced; in the 60-minute water sample, the fluorescent area in the three-dimensional fluorescence spectrum almost disappeared, indicating that most fluorescent organic matter was degraded to below the detection limit. As the oxidative degradation proceeded, the content of related organic matter gradually decreased.

[0084] Attached Figure 3The figure is a line graph showing the effect of the iron-molybdenum co-loaded biochar catalyst on the degradation of tetracycline water samples under different water quality conditions. Compared with the deionized water sample, the time required to degrade the target pollutant dissolved in the raw water sample to less than 90% increased by 6 minutes. Complex water samples have a certain impact on the degradation efficiency of the iron-molybdenum co-loaded biochar catalyst. The main reason is that the raw water sample contains many types of inorganic salts and other complex organic matter. During the oxidative degradation process, they interfere by quenching active oxidizing substances and competing with the target pollutants for active oxidizing substances, but still have a 98.8% degradation rate for tetracycline in water. This result further shows that the present invention has a certain applicability in the degradation of tetracycline in the presence of actual water bodies.

[0085] 1. Electron microscope-energy spectrometer characterization analysis

[0086] Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS) Characterization Analysis The morphology and energy dispersive spectrometer test of the iron-molybdenum co-loaded biochar catalysts obtained in Example 1 and Comparative Examples 1-3 were performed using a TESCAN MIRA LMS scanning electron microscope. The results are shown in the attached Figure 4 As shown in the figure, a, b, c are the observation results of the product obtained in comparative example 1 at magnifications of 3000 times, 2000 times, and 1000 times, respectively; d, e, and f are the observation results of the product obtained in comparative example 2 at magnifications of 20000 times, 5000 times, and 2000 times, respectively; g, h, and i are the observation results of the product obtained in comparative example 3 at magnifications of 5000 times, 3000 times, and 2000 times, respectively; j, k, and l are the observation results of the newly obtained product in Example 1 at magnifications of 20000 times, 5000 times, and 2000 times, respectively; and m, n, and o are the observation results of the product obtained in Example 1 and used at magnifications of 20000 times, 10000 times, and 2000 times, respectively. The elemental composition of the iron-molybdenum co-loaded biochar catalyst was clarified by EDS analysis. As shown in the attached figure Figure 5 As shown, the iron-molybdenum co-loaded biochar catalyst contains carbon, oxygen, iron and molybdenum elements, whose mass proportions are 41.56%, 26.31%, 18.82% and 13.31% respectively; their atomic weight proportions are 62.03%, 29.45%, 6.02% and 2.5% respectively.

[0087] 2. Specific surface area and pore structure analysis

[0088] Specific surface area and pore structure analysis (BET analysis) Micromeritics ASAP2460 fully automatic specific surface area and porosity analyzer was used to measure the total specific surface area, total pore volume and pore size of the material. The results are shown in the attached figure. Figure 6 Attached Figure 6The nitrogen adsorption-desorption isotherm curves of BC, FeBC, MoBC, FeMoBC (new) and FeMoBC (used), wherein BC is the product obtained in Comparative Example 1, FeBC is the product obtained in Comparative Example 2, MoBC is the product obtained in Comparative Example 3, FeMoBC (new) is the iron-molybdenum co-loaded biochar catalyst prepared in Example 1, and FeMoBC (used) is the used iron-molybdenum co-loaded biochar catalyst. The curve has a slowly rising trend, which reflects that the catalyst has more mesoporous structures.

[0089] 3. X-ray diffraction analysis

[0090] X-ray diffraction analysis (XRD analysis) is to characterize the solid phase crystal structure of biochar. The crystal structure of the iron-molybdenum co-loaded biochar catalyst before and after use was determined by XRD patterns. The iron-molybdenum co-loaded biochar catalyst obtained in Example 1 was measured using a Rigaku SmartLabSE instrument from Japan. The results are shown in the attached figure. Figure 7 XRD analysis results show that the synthesis of Fe-Mo co-loaded biochar catalyst is successful. 4. X-ray photoelectron spectroscopy analysis

[0091] X-ray photoelectron spectroscopy (XPS) analysis was performed using a Thermo Scientific K-Alpha XPS instrument. The results are shown in the attached Figure 8 and attached Fig. 9 As shown, Figure 8 This is a full spectrum of newly prepared and used materials of the iron-molybdenum co-loaded biochar catalyst obtained in Example 1; Fig. 9 a is the XPS spectrum analysis of the newly prepared product of Example 1 on the C1 orbital electron of the C element, b is the XPS spectrum analysis of the used product of Example 1 on the C1 orbital electron of the C element, c is the XPS spectrum analysis of the newly prepared product of Example 1 on the 2p orbital electron of the Fe element, d is the XPS spectrum analysis of the used product of Example 1 on the 2p orbital electron of the Fe element, e is the XPS spectrum analysis of the newly prepared product of Example 1 on the 3d orbital electron of the Mo element, and f is the XPS spectrum analysis of the used product of Example 1 on the 3d orbital electron of the Mo element. XPS results show that various valence states of FeO x and MoO x The surface of the iron-molybdenum co-loaded biochar catalyst doped in Example 1 is consistent with the XRD detection results, further illustrating the successful synthesis of the iron-molybdenum co-loaded biochar catalyst.

[0092] 5. Investigate the effect of the dosage of Fe-Mo co-loaded biochar catalyst on the degradation efficiency of tetracycline (TC)

[0093] Water was taken from the fine grid in the Southeast Wastewater Treatment Plant in Changchun City, Jilin Province. Under the conditions of water phase temperature of 25±1℃, permonosulfate (PMS) concentration of 30μM, gaseous ozone concentration of 3.6mg / L, tetracycline solution concentration of 0.03mM, and solution pH of 6.8±0.1, the material dosage was controlled to be 50, 100, 200, 300, and 500mg / L respectively. The effect of functional material dosage on TC degradation efficiency in the O3 / PMS / FeMoBC process was investigated. The reaction flow chart of the O3 / PMS / FeMoBC system is shown in the attached figure. Fig.15 shown.

[0094] The results are attached Fig.10 As shown in the figure, the reaction rate of O3 / PMS / FeMoBC system is significantly improved compared with O3 and O3 / PMS. obs The values ​​are greatly improved. Under the same conditions, O3 / PMS / FeMoBC is higher than the single O3 and O3 / PMS processes. When the catalyst dosage is 200 mg / L, the degradation rate reaches 94.3% at 8 minutes, while the time point for O3 and O3 / PMS to reach this degradation rate under the same conditions is 20 minutes. When the dosage is increased from 50 mg / L to 200 mg / L, the degradation rate increases from 89% in 14 minutes to 98.6%. However, when the dosage is increased from 200 mg / L to 500 mg / L, the increase in degradation efficiency is very small. It is speculated that the added material is not evenly diffused into the reactor, resulting in a slow increase in its degradation efficiency. Therefore, in order to remove tetracycline from water and save costs, this experiment sets the material dosage to 200 mg / L when considering other influencing factors.

[0095] 6. Investigate the effect of the concentration of potassium persulfate solution (PMS) on the degradation efficiency of tetracycline (TC)

[0096] Water was taken from the fine screen in the Southeast Wastewater Treatment Plant in Changchun City, Jilin Province. The water phase temperature was controlled at 25±1℃, the gaseous ozone concentration was 3.6mg / L, the FeMoBC material dosage was 200mg / L, the concentration of the solution containing tetracycline was 30μM, and the solution pH was 6.8±0.1. The PMS concentration was controlled at 5μM, 10μM, 30μM, 50μM and 80μM to investigate the effect of PMS concentration on the degradation efficiency under the O3 / PMS / FeMoBC process.

[0097] The results are attached Fig.11 As shown in Figure 2, the influence trend of PMS concentration on O3 / PMS / FeMoBC is consistent with that of O3 / PMS process. When the PMS concentration increases from 5μM to 50μM, its k obsThe value gradually increases, and more PMS in the system increases the overall reaction rate. This shows that within a certain concentration range, the increase in PMS value is positively correlated with the catalytic efficiency of FeMoBC.

[0098] 7. Investigate the effect of initial concentration of tetracycline (TC) on degradation efficiency

[0099] Water was taken from the fine screen in the Southeast Wastewater Treatment Plant in Changchun City, Jilin Province. The experiment was carried out under the conditions of controlled water phase temperature at 25±1℃, potassium bisulfate solution concentration at 30μM, gaseous ozone concentration at 3.6mg / L, FeMoBC material dosage at 200mg / L, and solution pH at 6.8±0.1. The initial concentration of tetracycline was controlled at 0.01mM, 0.02mM, 0.03mM, 0.04mM and 0.05mM to investigate the effect of initial concentration of tetracycline on the degradation efficiency under O3 / PMS / FeMoBC process.

[0100] The results are attached Fig.12 As shown in Figure 2, the degradation rate of the O3 / PMS / FeMoBC system is higher than that of the single O3 and O3 / PMS methods, and the reaction rate decreases with the increase of TC concentration. obs =0.307min -1 , which was 141.7% and 65.05% higher than that of O3 and O3 / PMS processes, respectively. Even at a TC concentration of 0.05 mM, the process still achieved a degradation rate of 99% within 20 min.

[0101] 8. Investigate the effect of ozone concentration on the degradation efficiency of tetracycline (TC)

[0102] The water was taken from the fine grid in the Southeast Wastewater Treatment Plant in Changchun City, Jilin Province. The water phase temperature was controlled at 25±1°C, the concentration of potassium bisulfate solution was 30μM, the solution pH was 6.8±0.1, the FeMoBC material dosage was 200mg / L, and the concentration of the solution containing tetracycline was 0.03mM. The experiment was carried out under the conditions of controlling the gaseous ozone concentration to 1.2mg / L, 2.4mg / L, 3.6mg / L, 4.8mg / L, 6mg / L and Air (air was introduced) to investigate the effect of gaseous ozone concentration on degradation efficiency under the O3 / PMS / FeMoBC process. Among them, the control group with air introduced only adjusted the ozone generator current to zero, and the other parameters were consistent with O3=6mg / L.

[0103] The results are attached Fig.13 As shown in Figure 2, the effect of gaseous ozone concentration on degradation efficiency in the O3 / PMS / FeMoBC process is similar to that in the O3 and O3 / PMS processes. With the increase of ozone concentration, the k obsThe main reason is that the half-life of ·OH is short, and self-quenching and free radical competition are less likely to occur. In addition, the increase in ·OH concentration also helps to increase SO4 ·- The concentration of FeMoBC can enhance the decomposition ability of PMS and further improve the utilization rate of oxidant. obs The value was greatly improved, confirming that FeMoBC has high catalytic efficiency. In addition, in the Air group, we further clarified the key role of O3 in O3 / PMS / FeMoBC.

[0104] 8. Explore the effect of water environment pH on degradation efficiency

[0105] Water was taken from the fine screen in the Southeast Wastewater Treatment Plant in Changchun City, Jilin Province. The water phase temperature was controlled at 25±1℃, the concentration of potassium bisulfate solution was 30μM, the gaseous ozone concentration was 3.6mg / L, the FeMoBC material dosage was 200mg / L, the solution pH was 6.8±0.1, and the concentration of the solution containing tetracycline was 0.03mM. The experiment was carried out under the conditions of controlling the solution pH to 3.0, 5.0, 7.0, 9.0 and 11.0 to investigate the effect of water environment pH on the degradation efficiency under the O3 / PMS / FeMoBC process.

[0106] The results are attached Fig.14 As shown in the figure, in the process of the pH in the reaction system changing from acidic to neutral and then to weakly alkaline, the degradation of tetracycline by O3 / PMS / FeMoBC first increased and then decreased. At pH = 5, the degradation rate reached the maximum, which shows that acidic conditions are not conducive to the production of hydroxyl groups, but are conducive to the circulation of iron ions. The optimal pH is between 5-7. Within this range, the solubility of iron ions is high, which is conducive to the reaction; the stability of ozone molecules is better, which will also improve the efficiency of oxidative decomposition. In addition, the pH adaptability range of O3 / PMS / FeMoBC is wider than that of O3 and O3 / PMS processes. Even in the worst case of pH = 11 (k obs =0.18113min -1 ), as shown in its kinetic fitting diagram, its fluctuation range is still smaller than that of O3 and O3 / PMS processes.

[0107] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an iron-molybdenum co-loaded biochar catalyst, characterized in that: The method comprises the following preparation steps: S1. Preparation of biochar precursor: washing, drying, and crushing carbon-containing organic matter into powder, passing through a 100-mesh sieve, and then pyrolyzing the powder once in a nitrogen atmosphere to obtain a biochar precursor; S2. Introduction of iron and molybdenum elements: The biochar precursor, ferric chloride and sodium molybdate were mixed in a mass ratio of 1:1:1.5 and immersed in a 50% acetone solution, stirred at a speed of 100-200 r / min for 22-24 hours, filtered and dried to obtain primary biochar; S3. Load modification: adding the primary biochar obtained in step S2 to the primary modification liquid, stirring at 20-30°C and 150-250r / min for 1-2h to obtain a primary modified biochar; S4. Pore structure modification: adding the primary modified biochar obtained in step S3 to the secondary modified liquid, stirring at 200-300 r / min for 2.5-3.5 h at 50-60° C., filtering and drying to obtain secondary modified biochar; S5. Secondary pyrolysis: The secondary modified biochar obtained in step S4 is subjected to secondary pyrolysis at 500-600°C for 1.5-2h to obtain an iron-molybdenum co-loaded biochar catalyst.

2. The method for preparing an iron-molybdenum co-loaded biochar catalyst according to claim 1, characterized in that: The carbon-containing organic matter is one or more of corn straw, wheat straw and rice straw.

3. The method for preparing an iron-molybdenum co-loaded biochar catalyst according to claim 1, characterized in that: In step S1, the primary pyrolysis temperature is controlled at 500-600°C, and the pyrolysis time is 1.5-2h.

4. The method for preparing an iron-molybdenum co-loaded biochar catalyst according to claim 1, characterized in that: In step S3, the primary modification solution is a mixed solution of 5% hexadecyltrimethylammonium bromide solution and polyaspartic acid, wherein the mass ratio of the 5% hexadecyltrimethylammonium bromide solution to the polyaspartic acid is 10:

1.

5. The method for preparing an iron-molybdenum co-loaded biochar catalyst according to claim 1, characterized in that: In step S4, the secondary modification liquid is a mixed solution of 5% disodium ethylenediaminetetraacetic acid solution and polymaleic anhydride, wherein the mass ratio of the 5% disodium ethylenediaminetetraacetic acid solution to the polymaleic anhydride is 8:

1.

6. The method for preparing an iron-molybdenum co-loaded biochar catalyst according to claim 1, characterized in that: In step S3, the mass ratio of primary biochar to primary modified liquid is 1:

3.

7. The method for preparing an iron-molybdenum co-loaded biochar catalyst according to claim 1, characterized in that: In step S4, the mass ratio of the primary modified biochar to the secondary modified liquid is 1:

1.

8. The method for preparing an iron-molybdenum co-loaded biochar catalyst according to claim 1, characterized in that: In step S2, the drying temperature is 60-70°C and the drying time is 10-12 hours.

9. The method for preparing an iron-molybdenum co-loaded biochar catalyst according to claim 1, characterized in that: In step S4, the drying temperature is 80-90° C. and the drying time is 5-8 hours.

10. Use of an iron-molybdenum co-loaded biochar catalyst prepared according to the preparation method according to any one of claims 1 to 9 in degrading tetracycline in water.

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