A method for removing tetracycline from water

Abstract

The present invention relates to the field of environmental protection and discloses a method for removing tetracycline from water. The method uses an iron single-atom material to adsorb tetracycline in water. The iron single-atom material is prepared according to the following steps: (1) mixing ethanol, dimethylformamide, ammonia water, and water to obtain a mixed solution; (2) mixing zinc chloride, iron triacetylacetonate, and triazole with the mixed solution, stirring and reacting, to obtain an iron-doped metal-organic framework material; and (3) pyrolyzing the iron-doped metal-organic framework material at 850 to 950° C. under a protective gas atmosphere to obtain the iron single-atom material. The method provided by the present invention can be applied in complex water environments and has great significance for environmental protection. At the same time, the present invention proposes for the first time the use of an iron single-atom material as an adsorbent for adsorbing tetracycline in water, providing a new application for the iron single-atom material.

Description

Technical Field

[0001] The invention relates to the technical field of environmental protection, and in particular to a method for removing tetracycline in water. Background Art

[0002] Tetracycline (TC), a broad-spectrum antibiotic, is widely used in human disease treatment and livestock production due to its low cost and minimal toxicity. However, due to its overuse, large amounts of tetracycline are released into the environment in various forms and remain there for extended periods. Its poor biodegradability has led to serious soil and groundwater contamination. Furthermore, long-term consumption of water containing tetracycline can lead to bacterial growth, gastrointestinal discomfort, liver damage, and even impaired bone growth. Therefore, it is crucial to find an effective method to remove tetracycline from the environment.

[0003] Adsorption is considered the most promising method due to its simplicity, high removal efficiency, and the fact that it does not degrade and produce larger toxins. The key to adsorption lies in the choice of adsorbent, with activated carbon, silica gel, and carbon-based materials currently being commonly used. Among these materials, carbon-based materials have been extensively studied due to their rich pore structure, large specific surface area, and good stability. More importantly, carbon-based materials have π-π electron interactions with tetracycline antibiotics, which gives them a good adsorption capacity for tetracycline antibiotics. However, this increased adsorption capacity makes desorption by washing difficult, resulting in reduced cyclic stability and hindering their practical application.

[0004] Therefore, designing an adsorbent with high adsorption capacity and high cyclic stability is of great significance for environmental protection. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems existing in the prior art and provide a method for removing tetracycline in water. The method uses an iron single-atom material as an adsorbent to adsorb tetracycline. The preparation process of the iron single-atom material is simple, the removal efficiency of the tetracycline antibiotic is high, and the material is reusable.

[0006] In order to achieve the above object, the present invention provides a method for removing tetracycline in water, which uses iron single atom material to adsorb tetracycline in water.

[0007] Wherein, the iron single atom material is prepared according to the following process:

[0008] (1) mixing ethanol, dimethylformamide, ammonia water and water to obtain a mixed solution;

[0009] (2) mixing zinc chloride, iron triacetylacetonate, and triazole with the mixed solution, and then stirring to react to obtain an iron-doped metal-organic framework material;

[0010] (3) Under a protective gas atmosphere, the iron-doped metal-organic framework material is subjected to high-temperature pyrolysis at 850-950° C. to obtain an iron single-atom material.

[0011] Preferably, in step (1), the volume ratio of ethanol, dimethylformamide, water and ammonia water is 20:15-25:25-35:5-10.

[0012] Preferably, in step (2), the usage ratio of zinc chloride, ferric triacetylacetonate and triazole is 2 g: 23-30 g: 1-5 mL.

[0013] Preferably, in step (2), the ratio of zinc chloride to the mixed solution is 2 g: 65-90 mL.

[0014] Preferably, in step (2), the stirring reaction time is 20 to 30 hours and the temperature is 20 to 30°C.

[0015] Preferably, in step (2), the step of mixing zinc chloride, ferric triacetylacetonate, and triazole with the mixed solution comprises:

[0016] Dissolve zinc chloride in the mixed solution, then add ferric triacetylacetonate and stir for 5 to 15 minutes, and then dropwise add triazole.

[0017] Preferably, in step (2), after the stirring reaction step, the method further comprises: separating the reaction liquid obtained by the stirring reaction into solid-liquid form, and washing and drying the obtained solid matter.

[0018] Preferably, the drying temperature is 60-100° C., and the drying time is 10-15 hours.

[0019] Preferably, in step (3), the protective gas is nitrogen or argon.

[0020] Preferably, in step (3), the heating rate during the pyrolysis process is 3 to 7°C / min.

[0021] Preferably, in step (3), the pyrolysis time is 2 to 5 hours.

[0022] Preferably, after the pyrolysis step, the method further comprises: grinding the pyrolysis product.

[0023] Preferably, in step (3), the pyrolysis temperature is 850-950°C.

[0024] Preferably, the method comprises: mixing the iron single atom material with water containing tetracycline, and stirring the mixture to react so as to remove the tetracycline in the water.

[0025] The present invention proposes for the first time the use of single-atom iron materials as adsorbents for tetracycline adsorption in water, providing a new application for single-atom iron materials. Because the single-atom iron material exhibits high adsorption and removal efficiency for tetracycline antibiotics, along with broad pH applicability (adsorption varies minimally at pH values ​​between 3 and 10), good resistance to ion interference (tetracycline removal rates remain above 70% even under 10 mmol / L anion interference), and excellent cycling performance, the method for removing tetracycline from water provided by the present invention can be applied in complex water environments, offering low cost, high efficiency, and significant competitive advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The X-ray diffraction patterns (a) and Raman spectra (b) of the materials prepared in Example 1 and Comparative Examples 1-3 are shown;

[0027] Figure 2 TEM (a), high-resolution TEM (b), high-angle annular dark-field scanning TEM (c), and corresponding EDX mapping (d) of the iron single-atom material SA-Fe / NC prepared in Example 1;

[0028] Figure 3 N2 adsorption-desorption isotherms (a) and pore size distribution diagrams (b) of the materials prepared in Example 1 and Comparative Examples 1-3;

[0029] Figure 4 The adsorption kinetics curves (a) and adsorption capacity bar graphs (b) of the materials prepared in Example 1 and Comparative Examples 1-4, as well as commercial activated carbon;

[0030] Figure 5 are the adsorption isotherms of the materials prepared in Example 1 and Comparative Examples 1-4, and commercial activated carbon;

[0031] Figure 6 is the adsorption amount and Zeta potential of the iron single atom material SA-Fe / NC prepared in Example 1 at different pH values;

[0032] Figure 7 is the removal rate of tetracycline by the iron single atom material SA-Fe / NC prepared in Example 1 in the presence of different anions;

[0033] Figure 8 This is a graph showing the cycling experimental results of the iron single-atom material SA-Fe / NC prepared in Example 1. DETAILED DESCRIPTION

[0034] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0035] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0036] The present invention provides a method for removing tetracycline in water, which is characterized in that the tetracycline in the water is adsorbed by using an iron single atom material.

[0037] Wherein, the iron single atom material is prepared according to the following process:

[0038] (1) mixing ethanol, dimethylformamide (DMF), ammonia water and water to obtain a mixed solution;

[0039] (2) mixing zinc chloride, iron triacetylacetonate, and triazole with the mixed solution, and then stirring to react to obtain a nitrogen-doped graphitic carbon-supported iron-doped metal-organic framework material;

[0040] (3) Under a protective gas atmosphere, the iron-doped metal-organic framework material is subjected to high-temperature pyrolysis at 850-950° C. to obtain an iron single-atom material.

[0041] In the present invention, an iron ion-doped metal-organic framework material is first prepared by a simple one-pot solvothermal method. Then, through a pyrolysis reaction, the precursor is carbonized to form a material in which Fe single atoms are anchored on nitrogen-doped carbon, thereby obtaining a nitrogen-doped graphitic carbon-loaded iron single atom material, i.e., an iron single atom material.

[0042] The present invention found that the single-atom Fe-N4 site enhances charge localization, which is beneficial to the π-π electron interaction between the carbon substrate and tetracycline, thereby enhancing the adsorption of tetracycline by the iron single-atom material.

[0043] The iron single-atom material prepared by the present invention has a high specific surface area and a porous structure, which enables it to have a large number of adsorption sites for adsorbing tetracycline antibiotics; and the iron single-atom material has a highly graphitized structure and a large number of atomic sites, which significantly enhances the π-π electron interaction between the carbon substrate and tetracycline, thereby improving the adsorption capacity of the iron single-atom material for tetracycline.

[0044] It should be noted that the pyrolysis temperature in step (3) is much higher than the decomposition temperature of tetracycline (175°C), and the preparation of single atoms can undergo a high-temperature process. Therefore, in the cyclic experiment, only a simple pyrolysis treatment is required to remove the tetracycline adsorbed in the iron single-atom material, but the structure and properties of the material itself will not change. Therefore, the iron single-atom material can be cyclically removed of tetracycline.

[0045] In a preferred embodiment, after ethanol, dimethylformamide (DMF), ammonia water and water are added into a container, stirring is required to mix them evenly.

[0046] In a preferred embodiment, in step (1), the volume ratio of ethanol, dimethylformamide, water and ammonia water is 20:15-25:25-35:5-10, specifically, for example, it can be 20:15:25:5, 20:15:27:6, 20:17:25:7, 20:20:30:8, 20:20:32:9, 20:25:32:10 or 20:25:35:10, and most preferably it is 20:20:30:8.

[0047] In a preferred embodiment, in step (2), the usage ratio of zinc chloride, ferric triacetylacetonate and triazole is 2g:23-30g:1-5mL, specifically, for example, it can be 2g:23g:1mL, 2g:23g:4mL, 2g:25g:1mL, 2g:25g:5mL, 2g:26g:2.5mL, 2g:28g:5mL or 2g:30g:3mL, and most preferably it is 2g:26g:2.5mL.

[0048] In a preferred embodiment, in step (2), the dosage ratio of zinc chloride to the mixed solution is 2 g:65-90 mL, specifically, for example, 2 g:65 mL, 2 g:68 mL, 2 g:75 mL, 2 g:78 mL, 2 g:80 mL, 2 g:82 mL, 2 g:87 mL or 2 g:90 mL.

[0049] In a preferred embodiment, in step (2), the stirring reaction time is 20 to 30 hours, more preferably 22 to 26 hours; the reaction temperature is 20 to 30°C, more preferably 25 to 28°C.

[0050] In the present invention, step (2) specifically comprises: dissolving zinc chloride in the mixed solution, then adding ferric triacetylacetonate and stirring for 5 to 15 minutes, then dropwise adding triazole, and then stirring to react.

[0051] In a preferred embodiment, in step (2), after the stirring reaction step, the step further includes: solid-liquid separation of the reaction liquid obtained by the stirring reaction, and washing and drying the obtained solid.

[0052] More preferably, the washing step comprises: washing the obtained solid with water and ethanol 1 to 4 times each. Specifically, washing with water 1 to 4 times first, and then washing with ethanol 1 to 4 times.

[0053] More preferably, the drying temperature is 60-100° C., more preferably 70-90° C.; and the drying time is 10-15 hours.

[0054] In order to facilitate the pyrolysis reaction, in the present invention, the iron-doped metal organic framework material is first ground into powder and then subjected to pyrolysis reaction.

[0055] In a preferred embodiment, in step (3), the protective gas is argon or nitrogen.

[0056] In a preferred embodiment, in step (3), the heating rate during the pyrolysis process is 3 to 7°C / min.

[0057] In a preferred embodiment, in step (3), the pyrolysis time is 2 to 5 hours, specifically, for example, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours or 5 hours.

[0058] In a preferred embodiment, after the pyrolysis step, the method further comprises: grinding the pyrolysis product to make the particle size uniform.

[0059] In a more preferred embodiment, in step (3), the pyrolysis temperature is 900-950°C, specifically, for example, 900°C, 920°C, 930°C, 940°C or 950°C, and most preferably 920°C.

[0060] In a preferred embodiment, the method for removing tetracycline from water comprises: mixing the iron single atom material with water containing tetracycline, and stirring the mixture to react, so as to remove the tetracycline from the water.

[0061] The iron single-atom material has a high adsorption capacity and removal efficiency for tetracycline antibiotics. It also has a wide pH applicability (adsorption capacity changes very little at pH = 3 to 10) and good resistance to ion interference (the tetracycline removal rate can remain above 70% under 10 mmol / L anion interference). Most importantly, the iron single-atom material has excellent recycling performance. After each adsorption of the pollutant (tetracycline), a simple pyrolysis treatment is required to maintain the adsorption performance of the iron single-atom material at its initial state, and the material structure does not change.

[0062] The present invention will be described in detail below through examples, but the scope of protection of the present invention is not limited thereto. In the following examples, room temperature refers to 25°C.

[0063] Example 1

[0064] This example is used to illustrate the preparation method of the iron single-atom material of the present invention.

[0065] (1) Mix 20 mL of ethanol, 20 mL of DMF, 30 mL of ultrapure water, and 8 mL of aqueous ammonia, and stir to obtain a mixed solution;

[0066] (2) 2 g of zinc chloride was dissolved in the mixed solution (i.e., the ratio of zinc chloride to the mixed solution was 2 g:78 mL), stirred and ultrasonically mixed to make it uniform, then 26 mg of ferric triacetylacetonate was added and stirred for 10 min, then 2.5 mL of triazole was added dropwise, and the obtained solution was stirred and reacted at room temperature for 24 h, and then the obtained reaction solution was centrifuged to separate the solid matter, and the solid matter was washed twice with water and then washed twice with ethanol, and finally dried at 80 ° C for 12 h to obtain an iron-doped metal organic framework material, recorded as Fe@MOF; after testing, Fe@MOF was a rhombic octahedral structure with a specific surface area of ​​85.2 m 2 / g;

[0067] (3) Grind the Fe@MOF into powder, take 200 mg of Fe@MOF powder and transfer it to a porcelain boat, and calcine it in a tube furnace (under argon atmosphere, heating rate 5°C / min, calcination at 920°C for 3h). After cooling to room temperature, grind the obtained powder evenly to obtain the iron single atom material SA-Fe / NC.

[0068] Example 2

[0069] This example is used to illustrate the preparation method of the iron single-atom material of the present invention.

[0070] (1) 20 mL of ethanol, 15 mL of DMF, 27 mL of ultrapure water, and 6 mL of aqueous ammonia were mixed and then stirred to obtain a mixed solution;

[0071] (2) 2 g of zinc chloride was dissolved in the mixed solution (i.e., the ratio of zinc chloride to the mixed solution was 2 g: 68 mL), stirred and ultrasonically mixed to make it uniform, then 23 mg of ferric triacetylacetonate was added and stirred for 12 min, followed by dropwise addition of 4 mL of triazole, the resulting solution was stirred and reacted at room temperature for 26 h, and the resulting reaction solution was centrifuged to separate the solid matter, which was first washed twice with water and then twice with ethanol, and finally dried at 90 ° C for 10 h to obtain an iron-doped metal organic framework material, recorded as Fe@MOF;

[0072] (3) Grind the Fe@MOF into powder, take 200 mg of Fe@MOF powder and transfer it to a porcelain boat, and calcine it in a tube furnace (under the conditions of argon atmosphere, heating rate of 4°C / min, and calcination at 900°C for 4h). After cooling to room temperature, grind the obtained powder evenly to obtain iron single-atom material.

[0073] Example 3

[0074] This example is used to illustrate the preparation method of the iron single-atom material of the present invention.

[0075] (1) Mix 20 mL of ethanol, 25 mL of DMF, 32 mL of ultrapure water, and 10 mL of aqueous ammonia, and stir to obtain a mixed solution;

[0076] (2) 2 g of zinc chloride was dissolved in the mixed solution (i.e., the ratio of zinc chloride to the mixed solution was 2 g: 87 mL), stirred and ultrasonically mixed to make it uniform, then 30 mg of ferric triacetylacetonate was added and stirred for 7 min, followed by dropwise addition of 3 mL of triazole, and the resulting solution was stirred and reacted at room temperature for 24 h. The resulting reaction solution was then centrifuged to separate the solid matter, which was first washed twice with water and then twice with ethanol, and finally dried at 70 ° C for 14 h to obtain an iron-doped metal organic framework material, recorded as Fe@MOF;

[0077] (3) Grind the Fe@MOF into powder, take 200 mg of Fe@MOF powder and transfer it to a porcelain boat, and calcine it in a tube furnace (under argon atmosphere, heating rate 6°C / min, calcination at 950°C for 2h). After cooling to room temperature, grind the obtained powder evenly to obtain iron single-atom material.

[0078] Comparative Example 1

[0079] The method described in Example 1 was followed, except that ferric triacetylacetonate was not added, to obtain material NC;

[0080] Specifically, the preparation method of NC includes the following steps:

[0081] (1) Mix 20 mL of ethanol, 20 mL of DMF, 30 mL of ultrapure water, and 8 mL of aqueous ammonia, and stir to obtain a mixed solution;

[0082] (2) 2 g of zinc chloride was dissolved in the mixed solution, stirred and ultrasonicated to mix uniformly, and then 2.5 mL of triazole was added dropwise. The resulting solution was stirred and reacted at room temperature for 24 h. The resulting reaction solution was then centrifuged to separate the solid matter. The solid matter was first washed twice with water and then twice with ethanol, and finally dried at 80° C. for 12 h to obtain a metal organic framework material, which was recorded as MOF.

[0083] (3) The MOF was ground into powder, 200 mg of MOF powder was transferred to a porcelain boat, and calcined in a tube furnace (under argon atmosphere, heating rate of 5 °C / min, and calcination at 920 °C for 3 h). After cooling to room temperature, the obtained powder was ground uniformly to obtain material NC.

[0084] Comparative Example 2

[0085] The method described in Example 1 was followed, except that the pyrolysis temperature in step (3) was 500° C. to obtain the material Fe / NC-500.

[0086] Comparative Example 3

[0087] The method described in Example 1 was followed, except that the pyrolysis temperature in step (3) was 700° C. to obtain the material Fe / NC-700.

[0088] Comparative Example 4

[0089] The method described in Example 1 was followed, except that the amount of ferric triacetylacetonate added was 104 mg, to obtain a material Fe NPs / NC, in which Fe nanoparticles were supported on nitrogen-doped carbon;

[0090] Specifically, the preparation method of Fe NPs / NC includes the following steps:

[0091] (1) Mix 20 mL of ethanol, 20 mL of DMF, 30 mL of ultrapure water, and 8 mL of aqueous ammonia, and stir to obtain a mixed solution;

[0092] (2) 2 g of zinc chloride was dissolved in the mixed solution, stirred and ultrasonically mixed to make it uniform, and then 104 mg of ferric triacetylacetonate was added and stirred for 10 min, followed by dropwise addition of 2.5 mL of triazole. The obtained solution was stirred and reacted at room temperature for 24 h, and the obtained reaction solution was centrifuged to separate the solid. The solid was first washed with water twice, then washed with ethanol twice, and finally dried at 80 ° C for 12 h to obtain an iron-doped metal organic framework material, recorded as Fe2@MOF;

[0093] (3) The Fe2@MOF was ground into powder, 200 mg of Fe2@MOF powder was transferred to a porcelain boat, and calcined in a tube furnace (under argon atmosphere, heating rate of 5°C / min, and calcination at 920°C for 3 h). After cooling to room temperature, the obtained powder was ground evenly to obtain the material Fe NPs / NC.

[0094] Test Example 1

[0095] This test example is used to illustrate the characterization results of the materials prepared in the examples and comparative examples.

[0096] 1. The materials prepared in Example 1 and Comparative Examples 1-3 were subjected to X-ray diffraction (XRD) and Raman spectroscopy (Raman patterns) analysis. The results are as follows: Figure 1 As shown, Figure 1 a is the XRD pattern, Figure 1 b is the Raman spectrum.

[0097] Figure 1 a shows that SA-Fe / NC and NC have only two peaks at 26° and 44°, corresponding to the (002) and (101) phases of graphitic carbon, respectively. This indicates that there is no obvious metal agglomeration during the pyrolysis process and no iron particles are formed. For Fe / NC-500 and Fe / NC-700, Zn is not completely removed because the pyrolysis temperature is not high enough.

[0098] Figure 1 b shows the I of SA-Fe / NC D / I G The value is 1.00, which is lower than that of Fe / NC-500 (1.01) and Fe / NC-700 (1.07), indicating that its defect degree is greater and it can anchor more metal single atoms.

[0099] 2. The iron single atom material SA-Fe / NC prepared in Example 1 was characterized using an electron microscope. The results are as follows: Figure 2 As shown, Figure 2 a is the transmission electron microscopy (TEM) image of SA-Fe / NC, Figure 2 b is the high-resolution transmission electron microscopy (HR-TEM) image of SA-Fe / NC. Figure 2 c is the high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) image of SA-Fe / NC, Figure 2 d is the corresponding energy dispersive X-ray fluorescence (EDX) mapping.

[0100] Figure 2 a and Figure 2 The characterization results in b further show that there are no metal particles or clusters in SA-Fe / NC, indicating that Fe exists in the form of single atoms.

[0101] Figure 2 c and Figure 2 d shows the uniform distribution of Fe, N, O, and C elements in SA-Fe / NC.

[0102] 3. The materials obtained in Example 1 and Comparative Examples 1-3 were analyzed and tested using a BET surface analyzer. The N2 adsorption-desorption isotherms and pore size distributions were as follows: Figure 3 shown.

[0103] The test results show that the specific surface area of ​​SA-Fe / NC is 837.7m 2 g -1 The average pore size is 15.4 nm; the specific surface area of ​​Fe / NC-500 is 128.7 m 2 g -1 The average pore size is 44.9 nm; the specific surface area of ​​Fe / NC-700 is 405.5 m 2 g -1 The average pore size is 21.1 nm; the specific surface area of ​​NC is 1162.4 m 2 g -1 , with an average pore size of 16.3 nm; the specific surface area and pore size of NC are both larger than those of SA-Fe / NC, but combined with the tetracycline adsorption data below, it can be seen that the adsorption capacity of SA-Fe / NC is more than twice that of NC, which indicates that the specific surface area and pore size are not the main reasons for the high adsorption capacity of tetracycline by SA-Fe / NC.

[0104] Test Example 2

[0105] This test example is used to illustrate the advantages and characteristics of the method for removing tetracycline in water provided by the present invention.

[0106] 1. Investigation of adsorption performance

[0107] (1) The materials (i.e., adsorbents) prepared in Example 1 and Comparative Examples 1-4, as well as commercial activated carbon (AC), were subjected to adsorption kinetics experiments. The experimental process was as follows:

[0108] 6 mg of tetracycline hydrochloride was dissolved in 200 mL of deionized water to prepare a 30 mg / L tetracycline solution. The pH was adjusted before adding the adsorbent. 10 mg of adsorbent (50 mg / L) was added and the reaction was initiated with a stirrer at 298 K. At fixed intervals (0, 3 min, 10 min, 30 min, 60 min, 120 min, 180 min, 300 min, 420 min, 540 min, 660 min, and 780 min), 2.5 mL of the solution was drawn up with a syringe and filtered through a 0.22 μm filter membrane. The residual tetracycline concentration was measured at 355 nm using a UV-visible spectrophotometer (UV-8000A, Shanghai, China). That is, the reaction conditions were: 30 mg / L tetracycline, 50 mg / L adsorbent, pH 4.4, and reaction time 13 h. The calculation formula used was:

[0109]

[0110] Among them, C0 and C t Represent the initial and t time tetracycline concentrations, V represents the volume of the solution, and m represents the mass of the adsorbent. Figure 4 shown.

[0111] Depend on Figure 4 As can be seen in the adsorption kinetics experiments, the equilibrium adsorption capacities of the SA-Fe / NC prepared in the Examples were higher than those of the adsorbents prepared in Comparative Examples 1-4 and commercial activated carbon. In particular, the SA-Fe / NC prepared in Example 1 exhibited an equilibrium adsorption capacity of 491.3 mg / g, which is 8.9 times that of commercial activated carbon (AC). This demonstrates that the iron single-atom material prepared using the method provided by the present invention exhibits superior adsorption performance.

[0112] (2) The materials prepared in Example 1 and Comparative Examples 1-4, as well as commercial activated carbon (AC), were subjected to adsorption isotherm experiments according to the above experimental method. The reaction conditions were: the concentration of tetracycline hydrochloride was 20-45 mg L -1 , adsorbent 50 mg / L, pH 4.4, reaction time 13 h, obtained Figure 5 The adsorption isotherms are shown and the adsorption isotherm fitting parameters are shown in Table 1.

[0113] Table 1 Adsorption isotherm fitting parameters

[0114]

[0115]

[0116] As can be seen from Table 1, among the parameters fitted by the Langmuir model, SA-Fe / NC (Example 1) exhibits a maximum adsorption capacity of 573.6 mg / g; among the parameters fitted by the Friedrich model, SA-Fe / NC (Example 1) exhibits a maximum adsorption capacity of 368.5 mg / g.

[0117] 2. PH applicability investigation

[0118] Take the SA-Fe / NC prepared in Example 1, refer to the above experimental method, adjust the pH to 2-10, and explore the effect of different pH on adsorption. The reaction conditions are: 30 mg / L tetracycline, 50 mg / L adsorbent, pH 4.4, reaction time 13 h, and the test results are as follows: Figure 6 shown.

[0119] Depend on Figure 6 It can be seen that in the adsorption experiments at different pH, the adsorption amount of SA-Fe / NC changes very little in the range of pH = 3 to 10, indicating that SA-Fe / NC has a wide pH applicability.

[0120] 3. Investigation of anti-ion interference

[0121] Taking the SA-Fe / NC prepared in Example 1, referring to the above experimental method, the effects of five different anions on adsorption (NaCl, NaNO3, NaCO3, Na2SO4, Na3PO4) were explored. The reaction conditions were: tetracycline 10 mg / L, adsorbent 50 mg / L, pH 4.4, reaction time 1.5 h, and the experimental results were as follows: Figure 7 shown. Figure 7 In the table, the control group refers to the group without added interfering ions, the 1mol / L group refers to the group with an interfering ion concentration of 1mol / L, and the 10mol / L group refers to the group with an interfering ion concentration of 10mol / L.

[0122] Depend on Figure 7 It can be seen that under different anion interferences, the removal rate of tetracycline by SA-Fe / NC always remains above 70%, indicating that it has good resistance to ion interference.

[0123] 4. Cyclic stability investigation

[0124] The SA-Fe / NC prepared in Example 1 was tested for cyclic performance according to the above experimental method. In the cyclic experiment, the solution after each adsorption was centrifuged, washed twice with ethanol, dried at 60°C, and then heat-treated at 920°C for 1 hour. The obtained adsorbent was subjected to the next cycle, wherein the reaction conditions were: 10 mg / L tetracycline, 50 mg / L adsorbent, pH 4.4, and reaction time 1.5 hours. The test results are shown in Figure 2. Figure 8 shown.

[0125] Depend on Figure 8 It can be seen that after six cycles, the removal rate of tetracycline by SA-Fe / NC is still above 94%, indicating that SA-Fe / NC has excellent recyclability.

[0126] In summary, the iron single-atom material provided by the present invention has wide pH applicability, good resistance to ion interference, and excellent circulation performance, and can effectively remove tetracycline from water. Therefore, the method provided by the present invention has great application potential in the treatment of tetracycline-containing wastewater.

[0127] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for removing tetracycline from water, characterized in that: Use iron single atom materials to adsorb tetracycline in water. Wherein, the iron single atom material is prepared according to the following process: (1) mixing ethanol, dimethylformamide, ammonia water and water to obtain a mixed solution; (2) mixing zinc chloride, iron triacetylacetonate, and triazole with the mixed solution, and then stirring to react to obtain an iron-doped metal-organic framework material; (3) pyrolyzing the iron-doped metal-organic framework material at 920-950° C. under a protective gas atmosphere to obtain an iron single-atom material; Wherein, in step (2), the usage ratio of zinc chloride, ferric triacetylacetonate and triazole is 2g:23-30mg:1-5mL.

2. The method according to claim 1, characterized in that In step (1), the volume ratio of ethanol, dimethylformamide, water and ammonia water is 20:15-25:25-35:5-10.

3. The method according to claim 1, characterized in that In step (2), the dosage ratio of zinc chloride to the mixed solution is 2g:65-90mL.

4. The method according to claim 1 or 3, characterized in that In step (2), the stirring reaction time is 20 to 30 hours, and the temperature is 20 to 30°C.

5. The method according to claim 1, wherein In step (2), the step of mixing zinc chloride, ferric triacetylacetonate, and triazole with the mixed solution comprises: Dissolve zinc chloride in the mixed solution, then add ferric triacetylacetonate and stir for 5 to 15 minutes, and then dropwise add triazole.

6. The method according to claim 1, characterized in that In step (2), after the stirring reaction step, the method further comprises: separating the reaction liquid obtained by the stirring reaction into solid and liquid, and washing and drying the obtained solid.

7. The method according to claim 6, characterized in that The drying temperature is 60-100° C., and the drying time is 10-15 hours.

8. The method according to claim 1, characterized in that In step (3), the protective gas is nitrogen or argon.

9. The method according to claim 1 or 8, characterized in that In step (3), the heating rate during the pyrolysis process is 3 to 7°C / min.

10. The method according to claim 1 or 8, characterized in that In step (3), the pyrolysis time is 2 to 5 hours.

11. The method according to claim 1 or 8, characterized in that After the pyrolysis step, the method further comprises grinding the pyrolysis product.

12. The method according to claim 1, characterized in that The method comprises: mixing iron single-atom material with water containing tetracycline, and stirring to react so as to remove the tetracycline in the water.

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