A method for photocatalytic degradation of antibiotics using aged biochar

Abstract

This invention discloses a method for photocatalytic degradation of antibiotics using aged biochar. The method uses aged biochar as a photocatalyst to photocatalytically degrade antibiotics. The aged biochar is prepared from biochar as raw material through hydrogen peroxide modification and freeze-drying. Compared to conventional biochar, the aged biochar used in this invention releases a large amount of dissolved organic matter, absorbs more photons, and generates more reactive oxygen species. Therefore, when using aged biochar as a photocatalyst to degrade antibiotics, it can directly and efficiently degrade antibiotics under visible light conditions. This method for photocatalytic degradation of antibiotics using aged biochar has advantages such as low cost, high treatment efficiency, good removal effect, and no secondary pollution. It is a widely applicable antibiotic degradation method with high practical value and promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of organic pollutant degradation and treatment technology, and relates to a method for photocatalytic degradation of antibiotics, specifically a method for photocatalytic degradation of antibiotics using aged biochar. Background Technology

[0002] Antibiotics are secondary metabolites produced by microorganisms (including bacteria, fungi, and actinomycetes) or higher plants and animals during their life processes. They possess antipathogenic or other activities and can interfere with the developmental functions of other living cells. For example, sulfadimidine is an antibacterial sulfonamide drug suitable for treating infections caused by hemolytic streptococci, meningococci, and pneumococci. It has a long-lasting effect and is widely used in the medical and agricultural fields. In addition, antibiotics are also commonly used as veterinary drugs in animal husbandry and aquaculture, administered to animals through feed additives or direct feeding. However, long-term improper or excessive use of antibiotics can lead to bacterial resistance. Excessive antibiotics can remain directly in the bodies of plants and animals and in the soil, and can also enter natural aquatic environments through medical wastewater or the daily metabolism and material cycling of organisms. This impacts microorganisms in soil and water, disrupts the ecological balance, and affects the diversity and function of microorganisms in the environment. Since the metabolic and degradation capacity of organisms and the environment for antibiotics is limited, antibiotic pollution in the environment further threatens human health and the safety of ecosystems. Therefore, effective methods are needed to achieve the effective removal of antibiotics from the environment.

[0003] Biochar is a product generated from agricultural waste such as wheat straw through low-temperature pyrolysis in an oxygen-deficient environment. It is a multifunctional carbonaceous material with broad application prospects, characterized by abundant sources, low cost, large specific surface area, high porosity, and rich functional groups. As a novel environmentally friendly material, biochar exhibits good adsorption and removal effects on various environmental pollutants. However, the adsorption and removal rate of pollutants using hydrogen peroxide-modified biochar is relatively slow. Furthermore, existing biochar materials can also act as photocatalysts for activated hydrogen peroxide or persulfate to generate active free radicals under irradiation to degrade pollutants. However, when directly using biochar materials to degrade antibiotics in water, the degradation effect is not ideal, and therefore it cannot be directly used for photocatalytic degradation of antibiotics in the environment. Therefore, obtaining a biochar that can be used for photocatalytic degradation of antibiotics is of great significance for promoting the widespread application of biochar in antibiotic degradation. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for the photocatalytic degradation of antibiotics using aged biochar that is low in cost, high in processing efficiency, good in removal effect and free from secondary pollution.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for photocatalytic degradation of antibiotics using aged biochar, wherein the method uses aged biochar as a photocatalyst to photocatalytically degrade antibiotics; the aged biochar is prepared by modifying biochar with hydrogen peroxide and freeze-drying.

[0007] A further improvement to the above-mentioned method for photocatalytic degradation of antibiotics using aged biochar includes the following steps in the preparation method of the aged biochar:

[0008] S1. Mix biochar and hydrogen peroxide solution, shake, and obtain biochar suspension;

[0009] S2. The biochar suspension is heated to obtain a modified biochar suspension;

[0010] S3. The modified biochar suspension is freeze-dried to obtain aged biochar.

[0011] In a further improvement to the above-mentioned method for photocatalytic degradation of antibiotics using aged biochar, in step S3, the freeze-drying is carried out at a temperature of -40℃ to -50℃; and the freeze-drying time is 3 days to 4 days.

[0012] The above-mentioned method for photocatalytic degradation of antibiotics using aged biochar is further improved in step S1, wherein the mass-to-volume ratio of the biochar to the hydrogen peroxide solution is 1:20; the mass concentration of the hydrogen peroxide solution is ≥10%; the oscillation is carried out in a constant temperature oscillation chamber; the rotation speed during the oscillation process is 150 rpm to 200 rpm; and the oscillation time is 20 h to 24 h.

[0013] In a further improvement to the above-mentioned method for photocatalytic degradation of antibiotics using aged biochar, in step S2, the heating is carried out under water bath conditions; the heating involves placing the biochar suspension in a water bath and heating it to 75℃~85℃ in a water bath for 6h~8h; the biochar suspension is continuously stirred during the heating process; the stirring speed is 250rpm~300rpm.

[0014] In a further improvement to the above-mentioned method for photocatalytic degradation of antibiotics using aged biochar, the mass concentration of the hydrogen peroxide solution in step S1 is 15% to 30%.

[0015] In a further improvement to the above-mentioned method for photocatalytic degradation of antibiotics using aged biochar, the mass concentration of the hydrogen peroxide solution in step S1 is 18% to 25%.

[0016] The above-mentioned method for photocatalytic degradation of antibiotics using aged biochar is further improved in that the biochar is prepared by calcining biomass materials; the biomass materials are at least one of wheat straw, corn straw, and rice straw; the heating rate during the calcination process is 8℃ / min to 10℃ / min; the calcination temperature is 300℃ to 500℃; the calcination time is 6h to 8h; and N2 is continuously introduced during the calcination process at a flow rate of 15mL / min to 20mL / min.

[0017] The above-mentioned method for photocatalytic degradation of antibiotics using aged biochar is further improved by using aged biochar as a photocatalyst to photocatalytically degrade antibiotics in water, including the following steps: mixing aged biochar and antibiotic wastewater to carry out a photocatalytic degradation reaction to complete the degradation of antibiotics in the wastewater; the amount of aged biochar added is 0.1g to 0.2g per liter of antibiotic wastewater.

[0018] The above-mentioned method for photocatalytic degradation of antibiotics using aged biochar is further improved in that the antibiotic in the antibiotic wastewater is sulfadiazine or sulfadiazine; the initial concentration of the antibiotic in the antibiotic wastewater is 5 μmol / L to 10 μmol / L; and the pH value of the antibiotic wastewater is 6.5 to 7.5.

[0019] The above-described method for photocatalytic degradation of antibiotics using aged biochar is further improved in that the photocatalytic degradation reaction is carried out under visible light conditions; the wavelength of the visible light is 390 nm to 780 nm; and the photocatalytic degradation reaction time is 2 h to 3 h.

[0020] Compared with the prior art, the advantages of the present invention are as follows:

[0021] (1) In view of the shortcomings of existing biochar or modified biochar, such as poor photocatalytic performance, and the resulting defects such as difficulty in directly using it to degrade antibiotics or poor degradation effect, the present invention creatively provides a method for photocatalytic degradation of antibiotics using aged biochar. The aged biochar is used as a photocatalyst to photocatalytically degrade antibiotics. The aged biochar is prepared by modifying biochar with hydrogen peroxide and freeze-drying. In this invention, modifying biochar with hydrogen peroxide solution improves its electron transfer rate and adsorption capacity, thus enhancing its catalytic performance. Further heating of the modified biochar suspension removes hydrogen peroxide, followed by freeze-drying to remove moisture, achieving aging of the modified biochar. This process loosens the biochar structure, increases pore size, and enhances the number of oxygen-containing groups (especially quinone-like structures) on the surface, providing more adsorption sites and chromophores. Simultaneously, it effectively retains the soluble components of the biochar and improves its polarity and solubility, promoting the release of more dissolved organic matter into the photocatalytic system, increasing its absorbance. This allows the dissolved organic matter to act as a photosensitizer, absorbing more photons and generating a large amount of reactive oxygen species such as hydroxyl groups and singlet oxygen. These reactive oxygen species are then used to effectively degrade antibiotics. Specifically, the higher the degree of aging, the more dissolved organic matter is released, the more photons are absorbed, and the more reactive oxygen species are generated, resulting in better antibiotic degradation. This invention utilizes aged biochar for photocatalytic degradation of antibiotics. It can directly utilize biochar to achieve efficient degradation of antibiotics, and has the advantages of low cost, high treatment efficiency, good removal effect, and no secondary pollution. It is an antibiotic degradation method that can be widely used, with high application value and good application prospects.

[0022] (2) In this invention, by optimizing the freeze-drying conditions, specifically by freeze-drying at a temperature of -40℃ to -50℃ for 3 to 4 days (i.e. 3 to 4 days), the dissolved organic matter in the biochar can be retained as much as possible while effectively removing moisture.

[0023] (3) In this invention, by optimizing the concentration of hydrogen peroxide solution, specifically by optimizing the mass concentration of hydrogen peroxide solution to ≥10%, and especially by optimizing the mass concentration of hydrogen peroxide solution to 18% to 25%, the release of dissolved organic matter and absorbance in the prepared aged biochar are significantly improved, which can improve the photodegradation rate of antibiotics and achieve efficient degradation of antibiotics.

[0024] (4) In this invention, the raw materials for biochar are abundant, and its preparation method and process are relatively simple and the cost is low, which can realize the reuse of agricultural waste.

[0025] (5) In this invention, the aged biochar used achieves photodegradation of antibiotics (such as sulfadiazine) under visible light. Its removal efficiency is significantly improved compared with conventional biochar, and it can effectively utilize solar energy, which is environmentally friendly. Attached Figure Description

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0027] Figure 1 The images show the FTIR spectra of aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) prepared in Example 1 of this invention.

[0028] Figure 2 The image shows the C1s XPS diagrams of aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) prepared in Example 1 of this invention.

[0029] Figure 3 The O1s XPS diagrams are of the aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) prepared in Example 1 of this invention.

[0030] Figure 4 This is a comparison chart showing the TOC content and absorbance of dissolved organic matter released into water by aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) prepared in Example 1 of this invention.

[0031] Figure 5 This is a comparison of the three-dimensional fluorescence spectra of dissolved organic matter released into water by the aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and modified biochar (2%-OBCM, 5%-OBCM, 10%-OBCM, 20%-OBCM) prepared in Example 1 of this invention.

[0032] Figure 6 The image shows the photocatalytic degradation effect of aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) on sulfadiazine in water in Example 1 of this invention.

[0033] Figure 7 The graph shows the photocatalytic degradation rate of sulfadiazine in water by aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) in Example 1 of this invention.

[0034] Figure 8 The graph shows the changes in absorbance and photocatalytic degradation rate of sulfadiazine in water by aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) in Example 1 of this invention.

[0035] Figure 9 The graph shows the adsorption effect of aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) on sulfadiazine in water in Comparative Example 1. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0037] The materials and instruments used in the following examples are all commercially available.

[0038] Example 1:

[0039] A method for photocatalytic degradation of antibiotics using aged biochar, specifically using aged biochar as a photocatalyst to photocatalytically degrade antibiotics in water, includes the following steps:

[0040] The amount of aged biochar was 0.2 g / L. The aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) were added to 50 mL of sulfadiazine solution with pH 7.0 and an initial concentration of 10 μmol / L. The solution was stirred in the dark for 1 h to reach adsorption equilibrium. The solution was then subjected to photocatalytic degradation under visible light irradiation (1000W xenon lamp, wavelength 390 nm to 780 nm) for 2 h to complete the degradation of sulfadiazine in the water.

[0041] Blank control group: No biochar added, all other conditions are the same.

[0042] In this embodiment, the aged biochar used is prepared by modifying biochar with hydrogen peroxide and freeze-drying, including the following steps:

[0043] (1) Preparation of biochar:

[0044] Wheat straw was rinsed with ultrapure water and air-dried at room temperature for 1–2 days. It was then dried in an oven at 80°C for 12 hours. After cooling the dried straw biomass to room temperature, it was chopped and placed in a tube furnace. The furnace was heated to 400°C at an initial temperature of 20–25°C at a rate of 8.5°C / min and maintained at this temperature for 8 hours of pyrolysis. Nitrogen gas was introduced for protection during this period, with a flow rate of 15 mL / min. After cooling to room temperature, the nitrogen gas was removed, and the pyrolyzed char was extracted, ground, and sieved through a 100-mesh sieve to obtain biochar. This biochar was stored in a desiccator for later use. This biochar is designated BC.

[0045] (2) Preparation of aged biochar

[0046] Take 4 portions of biochar (BC) prepared in step (1), each with a mass of 2g, and mix them with 40mL of hydrogen peroxide solutions with mass concentrations of 2%, 5%, 10%, and 20% respectively. Place them in a constant temperature shaking box and shake for 24h at a speed of 180 rpm and a temperature of 25℃ to obtain a biochar suspension. Then, heat the biochar suspension in a water bath magnetic stirrer at a speed of 280 rpm and a temperature of 80℃ for 8h to obtain a modified biochar suspension. Place the modified biochar suspension in a freeze dryer at -40℃ for 3 to 4 days until the moisture is completely removed. Dry it in an oven at 80℃ for 24h, cool it to room temperature, grind it, and pass it through a 100-mesh sieve to obtain different aged biochars with different degrees of aging. In this step, when the mass concentration of hydrogen peroxide solution is 2%, 5%, 10%, and 20%, the corresponding aged biochar is denoted as 2%-OBC, 5%-OBC, 10%-OBC, and 20%-OBC, respectively.

[0047] The elemental content and specific surface area of ​​biochar (BC) and aged biochar (2%-OBC, 5%-OBC, 10%-OBC, and 20%-OBC) were determined using an elemental analyzer (vario ELcube) and a physical adsorption analyzer (ASAP2020PlusHD88), respectively. The results are shown in Table 1.

[0048] Table 1 Physicochemical properties of different biochars

[0049]

[0050] Table 1 shows that when biochar is modified and freeze-dried under different hydrogen peroxide solution concentrations, the degree of aging of biochar increases with the increase of hydrogen peroxide concentration. As the degree of aging of biochar increases, the carbon content of biochar decreases, the oxygen content gradually increases, and the O / C and (O+N) / C ratios are significantly improved. The specific surface area decreases, while the pore volume and most probable pore size increase. This indicates that hydrogen peroxide modification and freeze-drying can achieve the aging treatment of biochar, which increases the oxygen-containing groups on the surface of biochar, increases polarity, makes the structure looser, increases pore size, provides more adsorption sites and space, and increases the solubility of biochar.

[0051] Figure 1 The images show the FTIR spectra of aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) prepared in Example 1 of this invention. Figure 1 It can be seen that biochar is at 1695 cm⁻¹ -1 The absorption peak at that point is -COOH / COO - C=O stretched, 1593cm -1 The absorption peak at 1425 cm⁻¹ is due to the stretching of the C=C / C=O structure conjugated with the aromatic structure. -1 The absorption peak at 1378 cm⁻¹ is due to the stretching vibration of C=C in the aromatic structure. -1 The absorption peak at that location is -COO - The stretching vibration, 1100cm -1 The absorption peak at 1425 cm⁻¹ corresponds to the stretching vibration of CO. As the degree of aging increases, the peak at 1425 cm⁻¹ can be observed to be more pronounced. -1 The absorption peak gradually shifts towards 1378 cm⁻¹ -1 The transfer indicates that hydrogen peroxide modification and freeze-drying treatment transformed the C=C on the surface of biochar into C=O. Overall, the content of oxygen-containing functional groups on the surface of biochar increased, especially carboxyl and carbonyl groups, while quinone-like groups, including aromatic C=O structures, were conducive to the generation of reactive oxygen free radicals in the degradation reaction.

[0052] Figure 2 The image shows the C1s XPS diagrams of aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) prepared in Example 1 of this invention.

[0053] Figure 3 The O1s XPS diagrams are of the aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) prepared in Example 1 of this invention.

[0054] Depend on Figure 2 and Figure 3It can be seen that with the increase of aging degree, the CC / C=C content on the surface of biochar decreases while the content of oxygen-containing functional groups increases, consistent with the FTIR results. The C1s XPS plot shows that compared with the original biochar, the CO content in 20%-OBC increased by 9.84%, and the OC=O content increased by 7.70%. The O1s XPS plot shows that the proportion of OC=O in the oxygen-containing functional groups gradually increases, indicating that hydrogen peroxide modification and freeze-drying treatment convert the CC / C=C on the biochar surface to C=O. Therefore, the O / C ratio of aged biochar also gradually increases, consistent with the elemental analysis results. Furthermore, the carbonyl structure on the biochar surface can promote the generation of reactive oxygen free radicals under light irradiation, thereby promoting the degradation of sulfadiazine.

[0055] Aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) were each prepared into 0.2 g / L biochar suspensions, stirred for 1 h, and then filtered through a 0.45 μm filter membrane. The TOC content was determined using a total organic carbon analyzer (Liqui TOC II), and the absorbance was measured using a UV-Vis spectrophotometer (Shimadzu UV2550). The results are as follows: Figure 4 As shown.

[0056] Figure 4 This is a comparison chart showing the TOC content and absorbance of dissolved organic matter released into water by the aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) prepared in Example 1 of this invention. Figure 4 It can be seen that the aged biochar prepared in this invention releases more dissolved organic matter into the water, and its absorbance also increases with the degree of aging. This indicates that the hydrogen peroxide modification and freeze-drying treatment increases the hydrophilicity of the biochar, allowing more soluble components to enter the aqueous phase. The dissolved biochar is an effective photosensitizer, capable of absorbing photons to generate reactive oxygen species such as hydroxyl groups and singlet oxygen, thereby participating in the degradation reaction of organic matter. Therefore, the higher the degree of aging, the more dissolved organic matter is released, the more photons are absorbed, the more active intermediates are generated, and the better the degradation effect on organic matter.

[0057] In addition, modified biochar (2%-OBCM, 5%-OBCM, 10%-OBCM, 20%-OBCM) was also prepared in this embodiment. The preparation method is basically the same as that of aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC), except that in the preparation method of modified biochar (2%-OBCM, 5%-OBCM, 10%-OBCM, 20%-OBCM), the modified biochar suspension is directly filtered, washed three times with ultrapure water, and then dried to constant weight. Other preparation processes are the same as those for aged biochar.

[0058] In addition, modified biochar (2%-OBCM, 5%-OBCM, 10%-OBCM, 20%-OBCM) and aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) were respectively prepared into 0.2 g / L biochar suspensions. After stirring for 1 h, the suspensions were filtered through a 0.45 μm filter membrane, and 3D-EEM was performed using a Hitachi fluorescence spectrometer (F-4600). The results are as follows: Figure 5 As shown.

[0059] Figure 5 This is a comparison of the three-dimensional fluorescence spectra of dissolved organic matter released into water by the aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and modified biochar (2%-OBCM, 5%-OBCM, 10%-OBCM, 20%-OBCM) prepared in Example 1 of this invention.

[0060] Depend on Figure 5 It can be seen that the EEM spectra of the dissolved substances released by the aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) prepared in this invention are similar to those of the excitation / emission wavelengths (E... x / E m Fluorescent groups are present at both 240 / 420 nm and 300 / 420 nm, which is related to the presence of fulvic acid-like and humic acid-like compounds, respectively. These groups have high photosensitivity, which is conducive to the generation of reactive oxygen species (especially singlet oxygen) under light irradiation. Meanwhile, due to… Figure 5 It can be seen that the fluorescence intensity of the dissolved substances released by modified biochar (2%-OBCM, 5%-OBCM, 10%-OBCM, 20%-OBCM) is significantly lower than that of aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC). The reason may be that the conventional method of treating biochar by filtration and washing will wash away most of the photosensitive dissolved carbon (dissolved organic matter), which is also the fundamental reason why modified biochar prepared by conventional methods does not have excellent photocatalytic performance.

[0061] In this embodiment, during the photocatalytic degradation reaction, 1 mL of the solution to be degraded was taken as a sample at 0, 20, 40, 60, 90, and 120 min, respectively. The samples were filtered through a 0.45 μm filter membrane, and the content of undegraded sulfadiazine in the solution was determined by high-performance liquid chromatography (HPLC). The degradation efficiency of different aged biochars for sulfadiazine in water was calculated, and the results are as follows: Figure 6 As shown.

[0062] Figure 6 The image shows the photocatalytic degradation effect of aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) on sulfadiazine in water in Example 1 of this invention. Figure 6 In the figure, the vertical axis C / C0 represents the residual concentration of sulfadiazine in the sample, and C0 represents the initial concentration of the sulfadiazine solution (C0 = 10 μmol / L). Figure 6 It can be seen that the adsorption and removal efficiency of aged biochar for sulfadiazine was low during the stirring process (first 1 hour). After light irradiation, the degradation efficiency of aged biochar for sulfadiazine was significantly improved. The removal rates of biochar BC, aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) for sulfadiazine under light irradiation were 18.23%, 21.56%, 30.08%, 50.01%, and 77.70%, respectively. This indicates that with the increase of biochar aging degree, aged biochar generates more active intermediates (active oxygen substances) under light irradiation, which can promote the photocatalytic degradation effect of sulfadiazine.

[0063] The relationship between the degradation rate of sulfadiazine by aged biochar and reaction time was reflected using a fitted first-order kinetic model. The equation is as follows:

[0064] C = C0e-kobst(1)

[0065] The transformation yields: Ln(C / C0)=-k obs t(2)

[0066] Figure 7 The graph shows the photocatalytic degradation rate of sulfadiazine in water by aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) in Example 1 of this invention. Figure 7 The corresponding degradation rate was obtained by fitting the experimental results using the above equation (2), where C in the vertical axis ln(C / C0) represents the remaining concentration of sulfadiazine in the sample, and C0 represents the adsorption equilibrium concentration of the sulfadiazine solution. Figure 7 In the figure, the slope represents the pseudo-first-order degradation rate of sulfadiazine, and the calculation results are shown in Table 2.

[0067] Table 2. Pseudo-first-order degradation rates of sulfadiazine by aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC).

[0068]

[0069] Combination Figure 7 As shown in Table 2, when the mass concentration of hydrogen peroxide used for aging treatment is increased to 5%, the photodegradation efficiency of aged biochar for sulfadiazine is significantly improved. As the degree of aging of biochar continues to increase, the degradation rate of sulfadiazine further increases. The degradation rate of sulfadiazine by 20%-OBC is 8 times higher than that of the original biochar.

[0070] Figure 8 This is a graph showing the change in absorbance and photocatalytic degradation rate of sulfadiazine in water by aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) in Example 1 of this invention. Figure 8 As shown, when the mass concentration of hydrogen peroxide increased from 5% to 10%, the absorbance of the dissolved organic matter released by the aged biochar and the degradation rate of SM2 both increased significantly, with growth rates of 3.6 times and 2.3 times respectively. Further increasing the hydrogen peroxide concentration slowed the growth rate, indicating that the antibiotic degradation capacity of the aged biochar reached near saturation at this point. Therefore, when the mass concentration of hydrogen peroxide solution is between 10% and 25%, the release of dissolved organic matter and the absorbance of the prepared aged biochar are significantly improved, which can enhance the photodegradation rate of antibiotics and achieve efficient degradation of antibiotics.

[0071] Comparative Example 1:

[0072] The aged biochar prepared in Example 1 is used to adsorb sulfadiazine in water, including the following steps:

[0073] The amount of aged biochar was 0.2 g / L. The aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) were added to 50 mL of sulfadiazine solution with pH 7.0 and an initial concentration of 10 μmol / L. The solution was stirred in the dark for 3 h to complete the adsorption of sulfadiazine in water.

[0074] After stirring, the sample was filtered through a 0.45 μm filter membrane, and the content of unadsorbed sulfadiazine in the solution was determined by high performance liquid chromatography (HPLC). The adsorption amount was calculated, and the results are shown in Table 3. Figure 8 As shown.

[0075] Table 3 Adsorption data of aged biochar for sulfadiazine

[0076] Biochar BC 2%-OBC 5%-OBC 10% - OBC 20% - OBC Adsorption capacity (μmol / g) 3.238 3.762 5.251 7.369 10.808

[0077] Figure 9 The graph shows the adsorption effect of aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) and biochar (BC) on sulfadiazine in water in Comparative Example 1. Figure 9 In this context, the removal rate R = 1 - C / C0, where C represents the residual concentration of sulfadiazine in the sample, and C0 represents the initial concentration of the sulfadiazine solution (C0 = 10 μmol / L). Figure 9 It can be seen that the adsorption and removal rates of sulfadiazine by biochar (BC) and aged biochar (2%-OBC, 5%-OBC, 10%-OBC, 20%-OBC) are 6.48%, 7.52%, 10.50%, 14.74%, and 21.62%, respectively. According to Table 3, the adsorption effect of aged biochar on sulfadiazine is improved with the increase of aging degree, but it is still relatively low. Therefore, under dark conditions, the overall adsorption and removal efficiency of aged biochar on sulfadiazine is low.

[0078] The results above show that, in this invention, modifying biochar with hydrogen peroxide solution improves the electron transfer rate and adsorption capacity of the biochar, thus enhancing its catalytic performance. Further heating of the modified biochar suspension removes hydrogen peroxide, followed by freeze-drying to remove moisture, achieving aging of the modified biochar. This process, on one hand, loosens the biochar structure, increases pore size, and enhances the number of oxygen-containing groups (especially quinone-like structures) on the surface, providing more adsorption sites and chromophores. On the other hand, it effectively retains the soluble components of the biochar and improves its polarity and solubility, thereby promoting the release of more dissolved organic matter into the photocatalytic system, increasing its absorbance. This allows the dissolved organic matter to act as a photosensitizer, absorbing more photons and generating a large amount of reactive oxygen species such as hydroxyl groups and singlet oxygen. Finally, these reactive oxygen species are used to effectively degrade antibiotics. Specifically, the higher the degree of aging, the more dissolved organic matter is released, the more photons are absorbed, the more reactive oxygen species are generated, and the better the antibiotic degradation effect. This invention utilizes aged biochar for photocatalytic degradation of antibiotics. It can directly utilize biochar to achieve efficient degradation of antibiotics, and has the advantages of low cost, high treatment efficiency, good removal effect, and no secondary pollution. It is an antibiotic degradation method that can be widely used, with high application value and good application prospects.

[0079] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for photocatalytic degradation of antibiotics using aged biochar, characterized in that, The method uses aged biochar as a photocatalyst to photocatalytically degrade antibiotics; the aged biochar is prepared by modifying biochar with hydrogen peroxide and freeze-drying; the preparation method of the aged biochar includes the following steps: S1. Biochar and hydrogen peroxide solution are mixed and shaken to obtain a biochar suspension; the mass-to-volume ratio of biochar to hydrogen peroxide solution is 1:20; the mass concentration of hydrogen peroxide solution is 15%–30%; the biochar is prepared by calcining biomass material; the biomass material is at least one of wheat straw, corn straw, and rice straw; the heating rate during calcination is 8℃ / min–10℃ / min; the calcination temperature is 300℃–500℃; the calcination time is 6h–8h; N2 is continuously introduced during calcination at a flow rate of 15 mL / min–20 mL / min; S2. The biochar suspension is heated to obtain a modified biochar suspension; the heating is carried out under water bath conditions; the heating is performed by placing the biochar suspension under water bath conditions and heating it to 75℃~85℃ in a water bath, and keeping it at that temperature for 6h~8h. S3. The modified biochar suspension is freeze-dried to obtain aged biochar.

2. The method for photocatalytic degradation of antibiotics using aged biochar according to claim 1, characterized in that, In step S3, the freeze-drying is carried out at a temperature of -40℃ to -50℃; the freeze-drying time is 3 days to 4 days.

3. The method for photocatalytic degradation of antibiotics using aged biochar according to claim 2, characterized in that, In step S1, the oscillation is carried out in a constant temperature oscillation chamber; the rotation speed during the oscillation process is 150 rpm to 200 rpm; and the oscillation time is 20 h to 24 h. In step S2, the biochar suspension is continuously stirred during the heating process; the stirring speed is 250 rpm to 300 rpm.

4. The method for photocatalytic degradation of antibiotics using aged biochar according to claim 3, characterized in that, In step S1, the mass concentration of the hydrogen peroxide solution is 18% to 25%.

5. The method for photocatalytic degradation of antibiotics using aged biochar according to any one of claims 1 to 4, characterized in that, The method of using aged biochar as a photocatalyst to photocatalytically degrade antibiotics in water includes the following steps: mixing aged biochar and antibiotic wastewater to carry out a photocatalytic degradation reaction to complete the degradation of antibiotics in the wastewater; the amount of aged biochar added is 0.1g to 0.2g per liter of antibiotic wastewater.

6. The method for photocatalytic degradation of antibiotics using aged biochar according to claim 5, characterized in that, The antibiotics in the antibiotic wastewater are sulfadiazine or sulfadiazine; the initial concentration of the antibiotics in the antibiotic wastewater is 5 μmol / L to 10 μmol / L; and the pH value of the antibiotic wastewater is 6.5 to 7.

5.

7. The method for photocatalytic degradation of antibiotics using aged biochar according to claim 6, characterized in that, The photocatalytic degradation reaction is carried out under visible light conditions; the wavelength of the visible light is 390 nm to 780 nm; and the time of the photocatalytic degradation reaction is 2 h to 3 h.

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