Method for mineralizing tetracycline antibiotics based on waste cotton cloth pyrolytic carbon composite material

Abstract

The application discloses a method for mineralizing tetracycline antibiotics based on waste cotton cloth pyrolysis carbon composite material, which comprises the following steps: (1) preparing waste cotton cloth pyrolysis carbon composite material: after pyrolysis of waste cotton cloth, waste cotton cloth pyrolysis carbon BC is prepared, and then iron-copper bimetal is loaded on the pyrolysis carbon BC, and after calcination, the composite material FeCu@BC is prepared; (2) adding the composite material FeCu@BC into a tetracycline antibiotic solution, and stirring under the alternating conditions of light and dark for more than 30 min. The method is simple, low in cost and green and pollution-free. The prepared FeCu@BC can realize effective removal and mineralization of TC under the conditions of dark light series and light-dark series, and the removal rate and mineralization rate can reach 95.10% and 86.65% respectively, and no external strong oxidant is used, which is green and environment-friendly.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental water treatment, and particularly relates to a composite material prepared from waste cotton cloth pyrolysis carbon and a method for removing and mineralizing tetracycline. BACKGROUND

[0002] In recent years, tetracycline antibiotics have been widely used worldwide due to their high antibacterial activity and low cost. Due to the migration, degradation resistance and accumulation of tetracycline (TC), it persists in the environment such as surface water, groundwater and soil, which poses a great threat to human health and ecological safety. In the related art, the heterogeneous advanced oxidation process based on carbon-supported iron-copper bimetallic composite material shows good efficiency in degrading TC. However, the use of strong oxidizing agents such as hydrogen peroxide (H2O2), peroxodisulfate (PDS) and persulfate (PMS) in the advanced oxidation process will bring additional material cost and potential operation risk, which is difficult to meet the needs of green development. Therefore, the technology of using carbon-supported iron-copper bimetallic composite material to degrade TC under sunlight or even dark conditions without strong oxidizing agents has been developed, but there are still problems such as long reaction time and poor mineralization effect of TC, which makes it difficult to achieve green and efficient removal of TC.

[0003] However, the existing literature rarely involves the mineralization rate of tetracycline, or the mineralization rate is low, as shown in Table 1.

[0004] Table 1

[0005]

[0006]

[0007] Among them, the mineralization yield is 100% when the organic matter is completely photocatalytically oxidized into carbon dioxide, water or inorganic matter, but most of the organic matter cannot be completely mineralized, and there are still intermediates or by-products generated, which means that the degradation reaction is not complete, and there is a problem of low mineralization yield. The more by-products generated by photocatalytic oxidation reaction, the lower the mineralization yield. If the carbon in the complete mineralization product of the organic matter exists in the form of carbon dioxide, the mineralization yield is the ratio of the amount of carbon in the generated carbon dioxide to the total amount of carbon in the original organic matter. SUMMARY

[0008] The purpose of the present application is to provide a method for efficiently removing and mineralizing TC without using strong oxidizing agents by using waste cotton cloth pyrolysis carbon-supported iron-copper bimetallic composite material.

[0009] The purpose of the present application is achieved by the following technical solutions:

[0010] A method for mineralizing tetracycline antibiotics based on waste cotton cloth pyrolysis carbon composite material, comprising the following steps:

[0011] (1) Preparation of waste cotton cloth pyrolysis carbon composite material: after pyrolysis of waste cotton cloth, waste cotton cloth pyrolysis carbon BC is prepared, and then iron-copper bimetal is loaded on the pyrolysis carbon BC, and after calcination, a composite material FeCu@BC is prepared;

[0012] (2) The composite material FeCu@BC is added to the tetracycline antibiotic solution, and stirred under alternating light and dark conditions for more than 30 min. The concentration of TC and the total organic carbon (TOC) content in the solution during stirring are measured, and the TC removal rate and mineralization rate are calculated.

[0013] Preferably, the preparation of the waste cotton cloth pyrolysis carbon composite material comprises the following steps:

[0014] (1-1) The waste cotton cloth is heated to 500±50℃ at a heating rate of 10±5℃ / min, and then kept at a constant temperature for 1±0.5h under a protective atmosphere, and then ground and broken to obtain waste cotton cloth pyrolysis carbon BC;

[0015] (1-2) The BC prepared in step (1-1) is added to an oxalate solution, mixed thoroughly, and heated in a water bath to 60±10℃, then an iron-copper mixed solution is added dropwise, and stirred magnetically at 60±10℃ for 0.5±0.2h to obtain an oxalate precipitate-carbon precursor;

[0016] (1-3) The precursor is washed, dried, heated to 350±50℃ at a rate of 10±5℃ / min and calcined for 4±2h, cooled, and ground.

[0017] Preferably, in step (1-2), the molar ratio of Fe 2+ , Cu 2+ and C2O4 2- in the iron-copper mixed solution is 0.5-1.5:0.5-1.5:2-3, and the molar ratio of Fe 2+ to pyrolysis carbon is 1:20-25.

[0018] Preferably, in step (1-2), the iron-copper mixed solution is a FeSO4 solution and a CuSO4 solution, the dropwise addition rate is 5±1mL / min, the molar ratio of Fe 2+ , Cu 2+ and C2O4 2- is 1:1:2-3; and the oxalate is one or more of sodium oxalate, sodium hydrogen oxalate, potassium oxalate, and potassium hydrogen oxalate.

[0019] Preferably, the light exposure time is at least 10 min, and the dark time is at least 10 min.

[0020] Preferably, the light and dark alternation condition is 10-40 min light and 10-40 min dark, or 10-40 min dark and 10-40 min light; and the light is sunlight.

[0021] Preferably, the light time is 20±5 min and the dark time is 20±5 min.

[0022] Preferably, in step (1-3), the drying is freeze-drying under the condition of -40 to -50 DEG C for 24-36 h, and the calcination condition is that air is excluded and then air is introduced to seal the outlet and open the outlet.

[0023] Preferably, in step (1-1), the waste cotton cloth is cut into pieces, washed and dried at 70-80 DEG C for 20-24 h; and the grinding and crushing are followed by sieving through a 100-mesh sieve.

[0024] Preferably, in step (2), the pH value of the tetracycline antibiotic solution is 7.5±1.0; and the dosage of the composite material FeCu@BC is 0.4±0.2 g / L.

[0025] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0026] (1) The present application provides a carbon-supported iron-copper bimetallic composite material prepared from waste cotton cloth pyrolysis carbon, which can efficiently remove and mineralize TC. The present application uses waste cotton cloth as a base material and adopts a co-precipitation-pyrolysis method to synthesize a waste cotton cloth pyrolysis carbon-supported iron-copper bimetallic composite material FeCu@BC with excellent performance. The prepared pyrolysis carbon has a rod-like fiber structure, good dispersibility and rich surface functional groups, and the iron-copper bimetallic oxide contains active components such as Fe3O4, Cu and CuO, which can produce reactive oxygen species to degrade TC through direct electron transfer or indirect activation of dissolved oxygen, but the particles are prone to agglomeration and stacking. The iron-copper bimetallic oxide in the composite material is coated on the waste cotton cloth pyrolysis carbon, has good dispersibility, and can strengthen the direct and indirect degradation of TC through the synergistic effect of carbon functional groups and active metals, thereby improving the removal rate and mineralization rate of TC. The composite material simultaneously realizes the resource utilization of waste cotton cloth pyrolysis carbon and the effective treatment of TC pollution.

[0027] (2) The composite material FeCu@BC has excellent photocatalytic activity. The introduction of waste cotton pyrolysis carbon enhances the separation efficiency of photo-generated electrons and holes in the double metal oxide, and has high photoelectric conversion efficiency. Under the irradiation of sunlight, photo-generated electrons can activate dissolved oxygen to generate free radicals to participate in the degradation process of TC, and photo-generated holes can directly degrade TC, achieving the improvement of TC removal rate and mineralization rate. At the same time, under the complete dark condition, the synergistic effect of waste cotton pyrolysis carbon and iron-copper active metal can also cause the efficient removal and effective mineralization of TC. The present application realizes the effective removal and mineralization of TC under light and dark conditions, which is simple, low in cost, without the use of any external strong oxidizing agent, and green and environmental protection.

[0028] (3) Based on the excellent removal and mineralization ability of the composite material to TC under light and dark conditions, it is found that its mineralization ability is obviously improved under dark-light series and light-dark series. When the light-dark reaction time ratio is 20min:20min under the light-dark series, the removal rate and mineralization rate of the composite material to TC can reach 95.10% and 86.65% respectively, realizing the rapid and efficient removal and mineralization of TC. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The XRD patterns of the waste cotton pyrolysis carbon (BC) prepared in Comparative Example 1, the iron-copper double metal material (FeCu) prepared in Comparative Example 2 and the waste cotton pyrolysis carbon loaded iron-copper double metal composite material (FeCu@BC) prepared in Example 1.

[0030] Figure 2 The scanning electron microscope images of BC (a) prepared in Comparative Example 1, FeCu (b) prepared in Comparative Example 2 and FeCu@BC (c) prepared in Example 1, respectively.

[0031] Figure 3a And Figure 3b The photoluminescence spectra and photocurrent response diagrams of BC prepared in Comparative Example 1, FeCu prepared in Comparative Example 2 and FeCu@BC prepared in Example 1, respectively.

[0032] Figure 4 The effect diagram of the removal of TC by the waste cotton pyrolysis carbon loaded iron-copper double metal composite material (FeCu@BC) in Example 2.

[0033] Figure 5 The effect diagram of the removal and mineralization of TC by the waste cotton pyrolysis carbon loaded iron-copper double metal composite material (FeCu@BC) under light conditions in Example 3.

[0034] Figure 6 The effect diagram of the removal and mineralization of TC by the waste cotton pyrolysis carbon loaded iron-copper double metal composite material (FeCu@BC) under dark conditions in Example 4.

[0035] Figure 7 Figure 4 is a graph showing the effect of different dark-light time ratios on TC removal rate and mineralization rate in the dark-light series of Example 5.

[0036] Figure 8 Figure 5 is a graph showing the effect of different light-dark time ratios on TC removal rate and mineralization rate in the light-dark series of Example 6.

[0037] Figure 9 Figure 6 is a graph showing the effect of different light time on TC removal rate and mineralization rate in the preferred light-dark series of Example 7. DETAILED DESCRIPTION

[0038] The application will be further described in conjunction with the examples and drawings, but the embodiments of the application are not limited thereto.

[0039] Example 1

[0040] The waste cotton cloth pyrolytic carbon-supported iron-copper bimetallic composite material was prepared by the following method:

[0041] (1) The waste cotton cloth was washed, dried at 80°C for 20h, cut into pieces of about 5mm, transferred to a tube furnace, heated to 500°C at a heating rate of 10°C / min under nitrogen atmosphere, kept at constant temperature for 1h, cooled, ground and sieved through a 100 mesh sieve to obtain waste cotton cloth pyrolytic carbon BC.

[0042] (2) 2.1g of BC prepared in step (1) was mixed thoroughly in 50mL of 0.3mol / L sodium oxalate solution, heated to 60°C in a water bath; then 50mL of iron-copper mixed solution containing 0.15mol / L FeSO4·7H2O and 0.15mol / L CuSO4·5H2O was rapidly dropped into the above solution at a rate of 5mL / min by peristaltic pump, magnetically stirred at 60°C for 0.5h, cooled, and centrifuged to obtain a yellow-green oxalate precipitate-carbon precursor. The molar ratio of Fe 2+ , Cu 2+ , C2O4 2- and pyrolytic carbon (BC) was 1:1:2:23.3.

[0043] (3) The above precursor was washed, centrifuged and freeze-dried at -40°C for 24h. Then, after the air in the nitrogen-purged tube furnace was removed, the inlet was closed and the outlet was opened, the precipitate was calcined at 350°C for 4h and then naturally annealed, ground and sieved through a 100 mesh sieve to obtain the waste cotton cloth pyrolytic carbon-supported iron-copper bimetallic composite material FeCu@BC.

[0044] Comparative Example 1

[0045] The waste cotton cloth pyrolytic carbon was prepared by the following method:

[0046] (1) The waste cotton cloth was washed and dried at 80°C for 20 h, cut into pieces of about 5 mm, transferred to a tube furnace, heated to 500°C at a heating rate of 10°C / min in a nitrogen atmosphere, kept at a constant temperature for 1 h, cooled, ground and sieved through a 100 mesh sieve to obtain waste cotton cloth pyrolysis carbon BC.

[0047] Comparative Example 2

[0048] The iron-copper bimetallic material was prepared by the following method:

[0049] (1) 50 mL of an iron-copper mixed solution containing 0.15 mol / L FeSO4·7H2O and 0.15 mol / L CuSO4·5H2O was prepared, wherein the molar ratio of Fe 2+ / Cu 2+ was 1:1; and 50 mL of a 0.3 mol / L sodium oxalate solution was heated to 60°C in a water bath, then the iron-copper mixed solution was quickly dropped into it at a rate of 5 mL / min by a peristaltic pump, and magnetically stirred at 60°C for 0.5 h. After cooling, the yellow-green precipitate was separated by centrifugation;

[0050] (2) The yellow-green precipitate of step (1) was washed with deionized water, centrifuged and freeze-dried at -40°C for 24 h. Subsequently, after the air in the nitrogen-purged tube furnace was removed, the inlet was closed and the outlet was opened, the above-mentioned precipitate was calcined at 350°C for 4 h and then naturally annealed, and then ground through a 100 mesh sieve to obtain an iron-copper bimetallic material FeCu.

[0051] The waste cotton cloth pyrolysis carbon BC prepared in Comparative Example 1 of the present application, the iron-copper bimetallic material FeCu prepared in Comparative Example 2, and the waste cotton cloth pyrolysis carbon loaded iron-copper bimetallic composite material FeCu@BC prepared in Example 1 were subjected to X-ray diffraction characterization analysis, and the results are shown in Figure 1As shown, the single BC has no obvious diffraction peak in the XRD pattern, and a broad peak of graphite carbon appears in the range of 22-27° diffraction angle. After loading FeCu on BC, it is obviously observed that the diffraction peaks of FeCu and FeCu@BC are similar in the XRD pattern. FeCu and FeCu@BC have obvious diffraction peaks at 2θ diffraction angle of 30.11°, 35.47°, 43.11°, 53.48°, 57.01°, 62.60° and 74.06°, which are perfectly matched with the (220), (311), (400), (422), (511), (440) and (533) diffraction crystal faces of Fe3O4, corresponding to the XRD pattern standard card number PDF#89-0691, and have good crystallinity. In addition, the diffraction peaks appearing at 2θ = 43.32°, 50.45° and 74.12° correspond to the (111), (200) and (220) crystal faces of Cu phase (PDF#99-0034), and the diffraction peaks observed at 2θ = 35.54° and 53.35° correspond to the (-111) and (020) crystal faces of CuO (PDF#80-0076), respectively. It is preliminarily inferred that the main phases of FeCu@BC are Fe3O4, Cu and CuO.

[0052] The scanning electron microscopy analysis of the BC prepared in the comparative example 1 of the application, the FeCu prepared in the comparative example 2 and the FeCu@BC prepared in the example 1 was carried out, and the results are shown in Figure 2 . Figure 2 a) It can be observed that the cotton cloth carbon BC retains the fiber structure of the cotton fiber, has no obvious pore structure and has good dispersibility. FeCu presents a stacked state of multiple rod-like particles, has more pores and cracks on the surface, but is easy to agglomerate Figure 2 b). In the scanning electron microscopy image of FeCu@BC, it is observed that the surface of BC is covered with aggregated rod-like crystals and particles of different sizes, indicating that the active metals Fe and Cu are successfully loaded on BC during the pyrolysis process, and FeCu@BC is successfully synthesized Figure 2 c).

[0053] The photoluminescence spectrum analysis and surface photocurrent analysis of the BC prepared in the comparative example 1 of the application, the FeCu prepared in the comparative example 2 and the FeCu@BC prepared in the example 1 were carried out, and the results are shown in Figure 3a and 3b . As can be seen from Figure 3a , the emission peak value of FeCu@BC is obviously weaker, indicating that the introduction of BC enhances the separation efficiency of photo-generated electrons and holes in the double-metal oxide. In addition, the photocurrent intensity generated by FeCu@BC and FeCu materials under the same full spectrum illumination is higher than that of BC prepared in the comparative example 1 Figure 3b), which indicates that FeCu@BC and FeCu materials have high photoelectric conversion efficiency. Based on the above photoelectrochemical characterization, it can be known that the FeCu@BC composite material has excellent photocatalytic activity.

[0054] Example 2

[0055] In order to verify that the FeCu@BC composite material prepared in Example 1 has an advantage in removing TC compared with BC prepared in Comparative Example 1 and FeCu material prepared in Comparative Example 2, comparative experiments of the removal effect of the three under the same conditions were carried out.

[0056] The steps are as follows: the experiment uses a 150 mL conical flask wrapped with tin foil as the reaction container to create a completely light-proof environment, and it is placed in a constant temperature oscillator to initiate the reaction at 150 rpm and 25°C constant stirring. First, dilute the TC mother liquor to 20 mg / L with ultrapure water, and the pH is not adjusted, then transfer 100 mL of the diluted TC solution to the conical flask, and add 0.0056 g of BC, 0.0050 g of FeCu and 0.0106 g of FeCu@BC respectively, and start the reaction. Take samples every certain time, immediately filter with a 0.22 μm polyether sulfone filter membrane, quench the test, and the reaction time is 20 min. The experiment determines the dosage of the three materials by keeping the amount of Fe and Cu metal components consistent. In this implementation, the concentration of residual TC in the test sample is determined at a wavelength of 357 nm by ultraviolet spectrophotometry, and the removal rate of TC is calculated.

[0057] The test results Figure 4 ) show that BC alone has poor removal effect on TC, less than 4%, which can be inferred that the adsorption efficiency of BC on TC is low. The removal rate of FeCu@BC composite material on TC is higher than the sum of the removal rates of BC and FeCu material, which confirms that the removal of TC by the prepared FeCu@BC reaches the effect of "1+1>2", and this promoting effect comes from the synergistic effect between BC and bimetallic particles.

[0058] Example 3

[0059] Under light conditions, the removal and mineralization efficiency of a waste cotton cloth pyrolysis carbon loaded iron-copper bimetallic composite material FeCu@BC prepared in Example 1 on TC were investigated.

[0060] The steps are as follows: the experiment uses a 300W xenon lamp (light current 20A) as a simulated sunlight light source, selects a 250ml jacketed beaker as a container, and circulates cooling water in the reaction container during the process and places it on a magnetic stirrer. 100ml of 20mg / L TC solution is measured in the reaction bottle, and 0.1mol / L NaOH solution is used to adjust the initial pH value of the TC solution to 7.5, which is magnetically stirred at room temperature at a stirring speed of 150rpm, and circulates cooling water to keep the reaction solution constant temperature. 0.4g / L FeCu@BC composite material is added to the above solution, and the light source is turned on, the light current is 21A, and the reaction starts. Take samples every certain time, immediately filter with a 0.22μm polyether sulfone filter membrane, quench the test, the reaction time is 60min, and set 3 groups in parallel. In this embodiment, the concentration of residual TC in the test sample is determined by ultraviolet spectrophotometry at a wavelength of 357nm, and the removal rate of TC is calculated. The TOC analyzer measures the total organic carbon content in the original sample and the test sample, calculates the mineralization rate of total organic carbon in the solution, and thus obtains the mineralization rate of TC.

[0061] The test results Figure 5 ) show that FeCu@BC can quickly remove TC under light conditions, and the removal rate of TC can reach 93.89% at 5min of reaction, and the removal rate of TC can be increased to 96.68% when the reaction time is extended to 60min. In addition, the mineralization rate of TC by FeCu@BC increases with the extension of the reaction time, and the mineralization rate of TC can reach 59.19% at 20min. This shows that under light conditions, the prepared composite material FeCu@BC not only has good removal effect on TC, but also has high mineralization capacity.

[0062] Studies have shown that the removal of TC by FeCu@BC can be attributed to adsorption and degradation, mainly degradation. Adsorption is related to the porosity and dispersity of the material. Degradation includes direct degradation and indirect degradation, direct degradation is caused by the direct action of persistent free radicals and active components such as Fe3O4 in the material on TC, and indirect degradation is the indirect activation of dissolved oxygen by surface functional groups and active metals on the material to produce reactive oxygen species to degrade TC. The mineralization of TC by FeCu@BC refers to the part of TC that is completely degraded into CO2 and H2O. In addition to the degradation described above, under the radiation of sunlight, the photo-generated electrons on the surface of FeCu@BC can activate dissolved oxygen to produce free radicals to participate in the degradation process of TC, and the photo-generated holes can directly degrade TC, thereby achieving high removal and mineralization of TC by FeCu@BC.

[0063] Example 4

[0064] The removal and mineralization efficiency of TC by a waste cotton cloth pyrolysis carbon loaded iron-copper bimetallic composite material FeCu@BC prepared in Example 1 under dark conditions were investigated.

[0065] The steps are as follows: the experiment uses a 150 mL conical flask wrapped with tin foil as the reaction container, creates a completely light-avoiding environment, and places it in a constant temperature oscillator for constant stirring at 150 rpm and 25°C to initiate the reaction. First, 100 mL of a 20 mg / L TC solution is measured in the conical flask, the initial pH value of the TC solution is adjusted to 7.5 with a 0.1 mol / L NaOH solution, then 0.4 g / L FeCu@BC composite material is added, and it is transferred to the constant temperature oscillator to start the reaction. Sample every certain time, immediately filter with a 0.22 μm polyether sulfone filter membrane, quench the test, the reaction time is 60 min, and set 3 groups in parallel. In this embodiment, the concentration of residual TC in the test sample is determined by ultraviolet spectrophotometry at a wavelength of 357 nm, and the removal rate of TC is calculated. The TOC analyzer measures the total organic carbon content in the original sample and the test sample, calculates the mineralization rate of total organic carbon in the solution, and thus obtains the mineralization rate of TC.

[0066] The test results Figure 6 ) show that FeCu@BC can quickly remove TC under dark conditions, and the TC removal rate can reach 94.09% at 5 min of reaction, and the TC removal rate can be improved to 97.96% when the reaction time is extended to 60 min. In addition, the mineralization rate of TC by FeCu@BC increases with the extension of the reaction time, and the TC mineralization rate can reach 40.89% at 40 min. Compared with light conditions, the mineralization rate of TC under dark conditions decreases. Since there is no input of exogenous strong oxidants such as H2O2 and PS, the mineralization of TC by FeCu@BC is limited, and the intermediate products are difficult to be completely mineralized into CO2 and H2O. Overall, FeCu@BC also has good removal and mineralization effect on TC under dark conditions.

[0067] Example 5

[0068] The removal and mineralization efficiency of TC by a waste cotton cloth pyrolysis carbon supported iron-copper bimetallic composite material FeCu@BC prepared in Example 1 under dark-light series conditions is investigated.

[0069] The steps are as follows: the experiment under dark condition uses a 150 mL conical flask wrapped with tin foil as the reaction container to create a completely light-avoiding environment, and it is placed in a constant temperature oscillator to initiate the reaction at 150 rpm and 25°C constant stirring. The experiment under light condition uses a 300 W xenon lamp as a simulated sunlight light source, and a 250 mL jacketed beaker is selected as the container. During the process, the reaction container is circulated with cooling water and placed on a magnetic stirrer. Dark-light series means that the reaction system is first reacted under dark condition for a period of time, and then it is placed under light condition for a period of time. The system is composed as follows: 0.4 g / L FeCu@BC composite material is added to 100 mL of 20 mg / L TC solution with an initial pH value of 7.5. The dark reaction time is controlled to be 10, 20, 30 and 40 min respectively, and the light reaction time is fixed to be 20 min. After the reaction, the sample is taken and immediately filtered with a 0.22 μm polyether sulfone filter membrane, and the test is quenched. Three groups of parallel tests are set. In this embodiment, the concentration of residual TC in the test sample is measured at a wavelength of 357 nm by ultraviolet spectrophotometry, and the removal rate of TC is calculated. The TOC analyzer measures the total organic carbon content in the original sample and the test sample, calculates the mineralization rate of total organic carbon in the solution, and thus obtains the mineralization rate of TC.

[0070] The test results Figure 7 ) show that under the sequence of dark-light, the extension of the dark reaction time has no obvious effect on the removal rate of TC, which is all above 90%. The TC mineralization rate generally shows a trend of first rising and then tending to be flat with the extension of the dark reaction time, which is between 75% and 80%. Compared with pure light condition or pure dark condition, the mineralization rate of TC is improved, and it is inferred that TC undergoes a two-stage degradation process under the condition of dark-light series. That is, FeCu@BC first degrades part of TC and decomposes it into smaller intermediate products under dark condition, and further degrades these intermediate products under light condition and finally mineralizes them into CO2 and H2O, so that the mineralization rate of TC is improved.

[0071] Example 6

[0072] The removal and mineralization efficiency of TC by a waste cotton cloth pyrolysis carbon loaded iron-copper bimetallic composite material FeCu@BC prepared in Example 1 under light-dark series condition are investigated.

[0073] The procedure is as follows: the experiment under light condition uses 300W xenon lamp as simulated sunlight source, selects 250mL jacketed beaker as container, circulates cooling water in the reaction container during the process and places it on a magnetic stirrer. The experiment under dark condition uses 150mL conical flask wrapped with tin foil as reaction container to create a completely light-protected environment, and places it in a constant temperature shaker at 150rpm and 25℃ constant stirring to initiate the reaction. Light-dark series, i.e. first react the reaction system under light condition for a period of time, then place it under dark condition for a period of time. The system composition is as follows: add 0.4g / L FeCu@BC composite material to 100mL of 20mg / L TC solution with initial pH value of 7.5. Fix the light reaction time as 20min, control the dark reaction time as 10, 20, 30 and 40min respectively. After the reaction, take samples, immediately filter with 0.22μm polyether sulfone filter membrane, quench the test, and set 3 groups in parallel. In this embodiment, the concentration of residual TC in the test sample is determined by ultraviolet spectrophotometry at a wavelength of 357nm, and the removal rate of TC is calculated. The TOC analyzer measures the total organic carbon content in the original sample and the test sample, calculates the mineralization rate of total organic carbon in the solution, and thus obtains the mineralization rate of TC.

[0074] The test results Figure 8 ) show that under the order of light first and then dark, with the dark reaction time extending from 10min to 40min, the TC removal rate and mineralization rate both show a trend of first rising and then being flat, and the removal rate and mineralization rate can reach 95.10% and 86.65% respectively when the light-dark time ratio is 20min:20min. Combined with the results of Example 5, the TC mineralization rate is higher when the series order is light first and then dark than when it is dark first and then light, it is inferred that TC also undergoes a two-stage degradation process under the order of light first and then dark, and the high molecular TC is more prone to degradation under light condition, while dark condition is more conducive to the degradation of small molecule intermediates.

[0075] Example 7

[0076] Under the condition of light-dark series, the effect of different light reaction time on the removal and mineralization of TC by the waste cotton cloth pyrolytic carbon loaded iron-copper bimetallic composite material FeCu@BC prepared in Example 1 is investigated.

[0077] The steps are as follows: the experiment under light condition uses a 300W xenon lamp as a simulated sunlight light source, and a 250mL jacketed beaker is selected as a container. During the process, circulating cooling water is circulated in the reaction container and placed on a magnetic stirrer. The experiment under dark condition uses a 150mL conical flask wrapped with tin foil as a reaction container to create a completely light-proof environment, and it is placed in a constant temperature oscillator to stir at 150rpm and 25°C to initiate the reaction. Light-dark series refers to first reacting the reaction system under light condition for a period of time, and then placing it under dark condition for a period of time. The system is composed as follows: 0.4g / L FeCu@BC composite is added to 100mL of 20mg / L TC solution with an initial pH value of 7.5. The light reaction time is controlled to be 10, 15, 20 and 25min respectively, and the dark reaction time is fixed to be 20min. After the reaction is completed, the sample is taken, immediately filtered with a 0.22μm polyether sulfone filter membrane, quenched for testing, and three groups of parallel tests are set. In this embodiment, the concentration of residual TC in the test sample is measured at a wavelength of 357nm by ultraviolet spectrophotometry, and the removal rate of TC is calculated. The TOC analyzer measures the total organic carbon content in the original sample and the test sample, calculates the mineralization rate of total organic carbon in the solution, and thus obtains the mineralization rate of TC.

[0078] The test results Figure 9 ) show that under the light-dark series condition, the removal rate of TC does not change significantly with the prolongation of light reaction time, and is about 95%. The mineralization rate of TC increases first and then tends to be balanced with the prolongation of light reaction time, and can reach 86.65% when the light-dark time ratio is 20min:20min. This shows that under the optimal reaction condition of light-dark series and time ratio of 20min:20min, the removal rate and mineralization rate of TC of the FeCu@BC prepared in Example 1 can reach 95.10% and 86.65% respectively under the total reaction time of 40min, realizing the green, rapid and efficient removal and mineralization of TC.

[0079] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above embodiments, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement modes, and all shall be included in the protection scope of the present application. [1] Liu J.L., Luo K., Li X.M., et al. The biochar-supported iron-copper bimetallic composite activating oxygen system for simultaneous adsorption and degradation of tetracycline [J]. Chemical Engineering Journal, 2020, 402: 126039.

[0080] [2] Xu J., Zhang X.L., Sun C., et al. Insights into removal of tetracycline by persulfate activation with peanut shell biochar coupled with amorphous Cu-doped FeOOH composite in aqueous solution [J]. Environmental Science and Pollution Research, 2019, 26(3): 2820-2834.

[0081] [3] Liu M.E., Xia H, Yang W.X., et al. Novel Cu-Fe bi-metal oxide quantum dots coupled g-C3N4 nanosheets with H2O2 adsorption-activation trade-off for efficient photo-Fenton catalysis [J]. Applied Catalysis B: Environmental, 2022, 301: 120765.

[0082] [4] Lai C., Huang F.L., Zeng G.M., et al. Fabrication of novel magnetic MnFe2O4 / biochar composite and heterogeneous photo-Fenton degradation of tetracycline in near neutral pH [J]. Chemosphere, 2019, 224: 910-921.

[0083] [5] Liu Y, Kong J.J., Yuan J.L., et al. Enhanced photocatalytic activity over flower-like sphere Ag / Ag2CO3 / BiVO4 plasmonic heterojunction photocatalyst for tetracycline degradation [J]. Chemical Engineering Journal, 2018, 331: 242-254.

[0084] [6] Li M.X., Li P., Zhang L., et al. Facile fabrication of ZnO decorated ZnFe-layered double hydroxides@biochar nanocomposites for synergistic photodegradation of tetracycline under visible light [J]. Chemical Engineering Journal, 2022, 434: 134772.

Claims

1. A method for mineralization of tetracycline antibiotics based on pyrolytic carbon composite material from waste cloth, characterized by, The method comprises the following steps: (1) preparing waste cotton cloth pyrolysis carbon composite material: after pyrolysis of waste cotton cloth, waste cotton cloth pyrolysis carbon BC is prepared, and then iron-copper bimetal is loaded on the pyrolysis carbon BC, and after calcination, the composite material FeCu@BC is prepared; (2) adding the composite material FeCu@BC into a tetracycline antibiotic solution, and stirring for more than 30 min under alternating light and dark conditions.

2. The method of claim 1, wherein, The preparation of the waste cotton cloth pyrolysis carbon composite material comprises the following steps: (1-1) heating the waste cotton cloth to 500±50℃ at a heating rate of 10±5℃ / min under a protective atmosphere, and keeping the temperature constant for 1±0.5 h, and then grinding and crushing to obtain waste cotton cloth pyrolysis carbon BC; (1-2) adding the BC prepared in step (1-1) into an oxalate solution, mixing thoroughly, and heating in a water bath to 60±10℃, and then adding an iron-copper mixed solution dropwise, and stirring magnetically at 60±10℃ for 0.5±0.2 h to obtain an oxalate precipitate-carbon precursor; (1-3) washing and drying the precursor, and then heating to 350±50℃ at a rate of 10±5℃ / min and calcining for 4±2 h, and then cooling and grinding.

3. The method of claim 2, wherein, In step (1-2), the molar ratio of Fe 2+ , Cu 2+ to C2O4 2- in the mixed solution of iron and copper is 0.5~1.5: 0.5~1.5:2~3, and the molar ratio of Fe 2+ to pyrolytic carbon is 1:20~25.

4. The method of claim 3, wherein, In step (1-2), the iron-copper mixed solution is FeSO4 solution and CuSO4 solution, the dropping rate is 5±1 mL / min, Fe 2+ , Cu 2+ and C2O4 2- molar ratio is 1:1:2~3; the oxalate is one or more of sodium oxalate, sodium hydrogen oxalate, potassium oxalate, potassium hydrogen oxalate.

5. The method according to any one of claims 1 to 4, characterized in that, The light exposure time is at least 10 min, and the dark time is at least 10 min.

6. The method of claim 5, wherein, The light and dark alternating conditions are first light exposure for 10-40 min and then dark for 10-40 min, or first dark for 10-40 min and then light exposure for 10-40 min; the light is sunlight.

7. The method of claim 6, wherein, The light exposure time is 20±5 min, and the dark time is 20±5 min.

8. The method of any one of claims 2-4, wherein, In step (1-3), the drying is freeze-drying under the condition of -40~-50℃ for 24-36 h, and the calcination condition is that the protective gas is air-excluded, the inlet is closed, and the outlet is open.

9. The method of claim 8, wherein, In step (1-1), the waste cotton cloth is cut into pieces, washed and dried at 70-80℃ for 20-24 h; and after grinding and crushing, it is passed through a 100-mesh sieve.

10. The method of claim 9, wherein, In step (2), the pH value of the tetracycline antibiotic solution is 7.5±1.0; and the dosage of the composite material FeCu@BC is 0.4±0.2 g / L.

Images