Preparation method of sugarcane peel-based biochar and application of sugarcane peel-based biochar in adsorption of antibiotics

Abstract

The invention belongs to the technical field of biochar preparation, and particularly relates to a preparation method of sugarcane peel-based biochar and application of the sugarcane peel-based biochar in adsorption of antibiotics. According to the invention, the waste sugarcane peel is taken as a raw material, KOH is taken as a modifier, melamine is taken as a nitrogen source, the nitrogen doping amount is changed, a series of active biochar is prepared by a high-temperature cracking method, the high-adsorption-capacity biochar is screened by adopting an ultraviolet spectrophotometric method and a single-factor control variable method, the sugarcane peel is turned into wealth from waste, the utilization value of the sugarcane peel is improved, and the method is suitable for industrial production. And guidance and reference are provided for research and development of novel efficient biochar materials and the problem of antibiotic water pollution.

Description

Technical Field

[0001] This invention belongs to the field of biochar preparation technology, specifically relating to a method for preparing sugarcane peel-based biochar and its application in adsorbing antibiotics. Background Technology

[0002] Antibiotics are chemical substances produced by microorganisms that can inhibit the growth and activity of other microorganisms or even kill them. As broad-spectrum antibacterial drugs, antibiotics are widely used in agriculture, animal husbandry, food processing, and medicine, achieving significant social and economic benefits. However, with the increasing frequency of antibiotic use, antibiotic-related pollution is also increasing. Antibiotics used by the human body cannot be completely absorbed and will be excreted into the aquatic environment. Simultaneously, improper handling of wastewater from antibiotic production in pharmaceutical factories, antibiotics used in laboratories, and unused antibiotics can all easily lead to antibiotic pollution. Residual antibiotics in water can directly harm humans and animals and cause significant environmental damage. Antibiotics in water not only damage the ecological environment and pollute drinking water, but can even affect human life and health. Therefore, the prevention and control of antibiotic pollution in water is urgent. Methods for removing antibiotics from water mainly include biochar adsorption, biodegradation, oxidation-reduction, and ultraviolet treatment, with adsorption generally considered an effective way to remove organic pollutants from aquatic and terrestrial environments. Biochar adsorption is a method that utilizes the adsorption properties of biochar to remove antibiotics from water. Due to its low cost, simple operation, readily available materials, high antibiotic removal efficiency, lack of secondary pollution, and good stability, biochar adsorption is widely used in the treatment of antibiotic-contaminated water bodies.

[0003] Currently, global resources are scarce. Using high-carbon solid wastes such as crop straw, branches, and sugarcane peels as raw materials for biochar production can reduce environmental pollution and create new energy sources, making it an excellent strategy for resource utilization of waste. Using biochar to adsorb antibiotics in water bodies allows for resource reuse and is an effective way to prevent antibiotic-induced water pollution, worthy of widespread application in the treatment of antibiotic-induced water pollution. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing sugarcane peel-based biochar, the prepared biochar having a good ability to adsorb antibiotics.

[0005] This invention provides a method for preparing sugarcane peel-based biochar, the method comprising the following steps: Sugarcane peel powder is carbonized, acid-washed, and dried to obtain mother carbon; the mother carbon is mixed evenly with a modifier, activated at high temperature, and then acid-washed and dried to obtain sugarcane peel-based biochar; the modifier includes melamine and / or KOH, and the mass ratio of the mother carbon to melamine and KOH is 1:0~2:3.

[0006] Preferably, the mass ratio of the mother carbon to melamine and KOH is 1:0:3 or 1:1:3.

[0007] Preferably, the sugarcane peel powder has a particle size ≤0.25mm.

[0008] Preferably, the carbonization temperature is 400℃ and the time is 3 hours; the carbonization heating rate is 5℃ / min.

[0009] Preferably, the acid washing step includes: soaking in dilute HCl, magnetically stirring for 12 hours, then vacuum filtering, and washing with water until neutral.

[0010] Preferably, the drying temperature is 50°C and the drying time is 24 hours.

[0011] Preferably, the high-temperature activation temperature is 800℃, the time is 2 hours, and the high-temperature activation heating rate is 5℃ / min. Preferably, the method of uniformly mixing the mother carbon with melamine and KOH is grinding.

[0012] The present invention also provides the application of sugarcane peel-based biochar prepared by the method described above in the adsorption of antibiotics.

[0013] Preferably, the application includes the prevention and control of antibiotic-induced water pollution.

[0014] Preferably, the antibiotics include tetracycline and / or chloramphenicol.

[0015] The beneficial effects of this invention are: Tetracycline (TC), molecular formula C3 22 H 24 N2O8 (444.45), structural formula as follows:

[0016] Tetracycline and its salts are yellow or pale yellow crystals, readily soluble in water, and extremely stable in a dry state. They are stable in air but sensitive to light. Tetracycline has a long conjugated system in its structure, exhibiting characteristic ultraviolet absorption; the absorbance of its solution can be measured using an ultraviolet spectrophotometer. It contains a large number of hydroxyl groups (-OH), which can form hydrogen bonds with nitrogen (N) and hydrogen (H).

[0017] Chloramphenicol (CHL), molecular formula C 11 H 12 Cl2N2O5 (323.129) has the following structural formula:

[0018] Chloramphenicol is a white crystalline solid, slightly soluble in water, stable in a dry state, and its efficacy is not lost when boiled for 5 hours. It is photosensitive. Chloramphenicol contains a conjugated system in its structure, exhibiting ultraviolet absorption; the absorbance of its solution can be measured using an ultraviolet spectrophotometer. It contains a hydroxyl group (-OH), which can form hydrogen bonds with nitrogen (N) and hydrogen (H).

[0019] Melamine (MA), with the molecular formula C3H6N6(126.12), has the following structural formula:

[0020] Melamine is a triazine-based nitrogen-containing heterocyclic organic compound, a white monoclinic crystal. It is insoluble in water and stable at room temperature. Containing organic nitrogen, it can be added as a nitrogen dopant in the modification of carbon.

[0021] High-temperature pyrolysis is currently the most widely used method for biochar production. High-temperature pyrolysis refers to heating biomass feedstock at high temperatures under anaerobic or oxygen-limited conditions. As the temperature rises, the feedstock undergoes a chemical transformation, breaking down large molecules into smaller molecules, ultimately producing biomass oil, biochar, etc. High-temperature pyrolysis mainly includes rapid pyrolysis, medium-speed pyrolysis, and slow pyrolysis. Slow pyrolysis refers to a pyrolysis reaction occurring at a heating rate of 5-7℃ / min over a relatively long reaction time; medium-speed pyrolysis refers to a pyrolysis reaction occurring at a heating rate of 300℃ / min at a temperature of 400-550℃ for 10-20 seconds; rapid pyrolysis refers to a pyrolysis method occurring at a heating rate of 1000℃ / s at a temperature of 400-550℃ for 1-2 seconds. Although slow pyrolysis is time-consuming, it produces a large yield of solid, liquid, and gaseous pyrolysis products, primarily biochar.

[0022] This invention utilizes KOH to modify the carbonized mother carbon (alkali modification), effectively enhancing its adsorption performance. The adsorption capacity of carbon is related to its specific surface area and macropore volume. Simultaneously, a suitable pore structure plays a crucial role in good adsorption performance, significantly improving the removal rate. Commonly used modification methods include steam / gas modification, ball milling modification, acid modification, alkali modification, organic loading, and inorganic loading. Among these, alkali modification enhances the stability of carbon through bonding, reduces oxygen-containing functional groups on the carbon surface, effectively increases specific surface area and porosity, and promotes hydrogen bonding, π-π conjugation, hydrophobic interactions, and electrostatic interactions between biochar and antibiotics. KOH is commonly used in alkali modification; the chemical reactions involved in its activation modification are as follows: 6KOH + 2C = 2K + 3H₂↑ + 2K₂CO₃ K₂CO₃ + C = K₂O + 2CO↑ K₂O + C = 2K + CO↑ Nitrogen is one of the most popular elements among researchers for its doping and modifying properties. This invention modifies biochar by incorporating melamine, increasing the number of amino functional groups and creating an adsorbent with abundant pores and large pore volumes, thereby enhancing its adsorption performance. Simultaneously, the nitrogen atoms introduced into the biochar increase the number of defect sites, thus enhancing its activity. Melamine contains a significant amount of organic nitrogen, which can be used as a nitrogen source. Using KOH as a modifier, activated carbon is prepared, resulting in nitrogen-doped biochar rich in microporous structures and possessing a large specific surface area. Increased nitrogen doping leads to a larger average pore size, increased pore content, and an increase in nitrogen- and oxygen-containing functional groups, resulting in more surface active sites and a higher maximum adsorption capacity. The nitrogen atoms introduced into the carbon structure significantly improve the affinity between the adsorbent surface and the adsorbate, further providing more active sites. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below.

[0024] Figure 1 A flowchart illustrating the preparation method of sugarcane peel-based biochar provided by this invention; Figure 2 Nitrogen adsorption-desorption isotherms for sugarcane peel-based biochar SC, N0.5, K3, NK0.5, NK1, and NK2; Figure 3 Micropore volume distribution diagrams of sugarcane peel-based biochar SC, N0.5, K3, NK0.5, NK1, and NK2; Figure 4 XPS spectra of biochar SC, K3, and NK1; Figure 5For TC standard curves and CHL standard curves; Figure 6 This represents the maximum adsorption capacity of biochar for TC and CHL. Figure 7 The effect of pH on the adsorption of TC and CHL by NK1 and the isoelectric point of NK1; Figure 8 The effect of initial concentrations of CHL and TC on NK1 adsorption; Figure 9 The effect of carbon addition on the adsorption of CHL and TC by NK1; Figure 10 The effect of temperature on the adsorption of CHL and TC by NK1; Figure 11 Adsorption kinetics curves for K3 and NK1; Figure 12 For pseudo-first-order and pseudo-second-order kinetic fitting of antibiotic adsorption by K3 and NK1; Figure 13 The linear fitting results of NK1 to the Langmuir isotherm adsorption model for TC and CHL, and the linear fitting results of the Freundilich isotherm adsorption model. Figure 14 The results show the linear fitting of K3 to the Langmuir isotherm adsorption model for TC and CHL, and the linear fitting of the Freundilich isotherm adsorption model. Detailed Implementation

[0025] To further illustrate the present invention, the solutions provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0026] In this embodiment of the invention, sugarcane peel was collected from agricultural markets and fruit shops in Haikou City, Hainan Province; tetracycline hydrochloride was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; chloramphenicol was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; melamine was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; potassium hydroxide was purchased from Guangdong Guangshi Reagent Technology Co., Ltd.; hydrochloric acid was purchased from Guangdong Guangshi Reagent Technology Co., Ltd.; and sodium chloride was purchased from Xilong Scientific Co., Ltd.

[0027] Example 1 according to Figure 1 The process shown is used to prepare sugarcane peel-based biochar. Figure 1In the diagram, a represents the washed, trimmed, and dried sugarcane peel; b represents the crushed sugarcane peel powder; c represents the carbonized mother carbon; d represents the mother carbon undergoing acid washing; e represents the mixture obtained by grinding the mother carbon after adding melamine and acid washing; f represents the mixture obtained by grinding the three components after adding KOH to the above mixture; g represents the activated mixture of the three components (activated carbon); h represents the activated carbon undergoing acid washing; and i represents the biochar obtained after filtration to neutrality and drying.

[0028] Wash the collected sugarcane peels, cut them to 3-5cm, and rinse them again with deionized water. Place them in an electric hot air drying oven (60℃) and dry for 18-20 hours (until they are extremely brittle when squeezed). After they are completely dried, crush the sugarcane peels with a high-speed pulverizer, pass the powder through a 0.25mm sieve, and pack them into bags.

[0029] Preparation of mother carbon: Weigh approximately 700 mg of powder into a nickel boat and place it in a tube furnace. Carbonization is carried out under nitrogen atmosphere. The carbonization temperature is 400℃, held at this temperature for 3 hours, and the heating rate is 5℃ / min. The prepared preliminary carbon is placed in dilute HCl and magnetically stirred for 12 hours. It is then vacuum filtered, washed with deionized water until neutral, and dried in a 50℃ oven for 24 hours to obtain mother carbon, denoted as SC.

[0030] Preparation of activated biochar: SC, melamine, and KOH were ground separately at specific mass ratios until homogeneous. The mixture was then placed in a tube furnace and activated under nitrogen atmosphere at 800℃ for 2 hours at a heating rate of 5℃ / min. The prepared biochar was then placed in dilute HCl and magnetically stirred for 12 hours. It was subsequently vacuum filtered, washed with deionized water until neutral, and dried in a 50℃ oven for 24 hours to obtain sugarcane peel-based activated biochar. The mass ratios of SC, melamine, and KOH and the corresponding names of the obtained activated biochars are shown in Table 1 below. Table 1. Correspondence between names of biochar activated under different conditions

[0031] Example 2 Characterization parameters of sugarcane peel-based biochar were determined. Specific surface area and pore volume distribution were measured using a Micromeritics ASAP 2460 instrument. Specific surface area and pore size were calculated using the BET model. Total pore volume and micropore volume were calculated using the single-point adsorption method and t-Plot method, respectively. X-ray photoelectron spectroscopy (XPS) was performed using Scientific K-Alpha from Thermo Fisher Scientific.

[0032] The BET analysis results are shown in Table 2.

[0033] Table 2 Pore characteristics

[0034] As shown in Table 1, the specific surface area of ​​K3 prepared after KOH activation is 2648 m². 2 / g, pore volume is 1.046cm³ 3 / g, which is much larger than that of SC obtained without KOH activation (specific surface area of ​​19m²). 2 / g, pore volume is 0.01994cm³ 3 (g), indicating that KOH can significantly increase the specific surface area and pore volume of the material, making the material's pores more developed. The activated carbons NK0.5, NK1, and NK2, prepared after nitrogen doping with melamine, have specific surface areas of 2648 m² / g, respectively. 2 / g、3409m 2 / g、2627m 2 / g, pore volume is 1.434cm³ 3 / g, 1.936cm 3 / g, 1.371cm 3 The specific surface area and pore volume of NK1 are greater than those of K3 prepared without nitrogen doping with melamine. This indicates that activated carbon prepared using melamine as the nitrogen source and KOH as the modifier has a larger specific surface area and pore volume, thus further improving the adsorption performance of biochar. Furthermore, as shown in the table, among the six types of carbon, NK1 has a significantly larger specific surface area and pore volume, indicating that NK1's adsorption performance is superior to other biochars. NO.5, prepared by nitrogen doping only without KOH modification, has a very small specific surface area and pore volume, indicating that the adsorption performance of biochar prepared without KOH modification is poor.

[0035] Table 1 shows the nitrogen adsorption-desorption isotherms for each biochar (SC, N0.5, K3, NK0.5, NK1, NK2) as follows: Figure 2 As shown.

[0036] Depend on Figure 2 It can be seen that adsorption reaches saturation and tends to equilibrium when the relative pressure P / Po = 0.5. Meanwhile, K3, NK0.5, NK1, and NK2 show a sharp increase in adsorption capacity when the relative pressure P / Po is between 0 and 0.1, demonstrating their rich microporous characteristics. Furthermore, NK1 exhibits extremely strong N2 adsorption capacity, while SC shows almost no N2 adsorption capacity, and N0.5 shows extremely weak adsorption capacity.

[0037] Table 1 shows the micropore volume distribution of each type of biochar. Figure 3 As shown.

[0038] Depend on Figure 3It can be seen that the pore sizes of K3, NK0.5, NK1, and NK2 are mainly 0.4~0.8 nm, with relatively large pore volumes, indicating that KOH mainly plays a role in pore formation during the activation process. NK1 exhibits extremely large pore volumes in the pore size range of 0.5~0.6 nm, while the pore volumes of NK0.5 and NK2 in this range are smaller than those of NK1, and their pore volumes are not as abundant as those of NK1.

[0039] XPS analysis can be used to study the surface composition and chemical state of activated carbon, and can also be used to analyze elements other than H and He, with the same order of magnitude sensitivity. Based on XPS analysis, qualitative analysis of the chemical elements and structure of biochar can be performed. XPS spectra of SC, K3, and NK1 are shown below. Figure 4 As shown.

[0040] Depend on Figure 4 It is known that the main constituent elements of SC, K3, and NK1 are C, O, and N. Among them, the relative content of carbon is large, while the relative content of nitrogen is relatively small. Comparing the relative carbon, oxygen, and nitrogen contents of modified biochar K3 prepared using KOH as a modifier with those of unmodified biochar SC, the relative contents of C, O, and N are not significantly different. However, the modified activated carbon NK1, prepared by nitrogen doping with melamine, shows a significant increase in the relative N content, indicating that melamine was successfully loaded onto the surface of the modified biochar, increasing the nitrogen-containing functional groups on the carbon surface. However, the relative O content is significantly reduced, possibly because after some O volatilization, the volatile substances and fixed carbon residues utilize the remaining space in the matrix to form a better microporous structure.

[0041] Example 3 Plotting CHL and TC standard curves and studying the maximum adsorption capacity of biochar Prepare a series of CHL solutions, measure their absorbance at the maximum absorption wavelength of CHL, and plot a CHL standard curve; prepare a series of TC solutions, measure their absorbance at the maximum absorption wavelength of tetracycline, and plot a TC standard curve.

[0042] The TC standard curve measured at the maximum absorption wavelength of 357 nm is as follows: Figure 5 a. The CHL standard curve measured at the maximum absorption wavelength of 278 nm is as follows: Figure 5 b.

[0043] The adsorption process of antibiotics by sugarcane peel-based biochar mainly consists of a rapid adsorption stage, a slow adsorption stage, and an adsorption-desorption equilibrium stage. In the initial stage of adsorption, many active sites exist on the surface of the modified biochar, and the initial concentration of antibiotics is also relatively high. At this time, the mass transfer driving force of the modified biochar is large, resulting in a high adsorption rate. During this stage, the adsorption capacity increases significantly with time. As the adsorption experiment progresses, the number of active sites on the surface of the modified biochar decreases, the antibiotic concentration decreases, the adsorption rate slows down, and the increase in adsorption capacity becomes more gradual, eventually reaching equilibrium in the adsorption-desorption stage. The maximum adsorption capacities of CHL and TC for the five biochars (K3, N0.5, NK0.5, NK1, and NK2) listed in Table 1 were studied. Take 40 mL of antibiotic solution and add approximately 7 mg of activated biochar to a centrifuge tube. Place the centrifuge tube in a thermostatic mixer, setting the temperature to 25 °C and the rotation speed to 350 rpm. Measure the absorbance of the solution at 5 min, 20 min, 40 min, 1 h, 2 h, 3 h, 4 h, 5 h, and 6 h (until adsorption equilibrium). Calculate the amount of antibiotic adsorbed by the biochar at different time points, Q. t The result is as follows Figure 6 As shown.

[0044] Q t =(C0-C t )*V / m Where C0 is the initial concentration of the antibiotic (mg / L); C t t represents the antibiotic concentration (mg / L) measured at time t; V represents the volume of antibiotic solution added (mL); and m represents the mass of biochar added (mg).

[0045] from Figure 6 It can be seen that during the mixing and oscillation adsorption process, the adsorption capacity of biochar for K3 and NK1 increases with time, and adsorption-desorption equilibrium is basically reached at a mixing time of 3 h. NK1 shows better adsorption performance for TC and CHL than NK0.5, K3, NK2, and NO0.5, which is consistent with the BET analysis results (NK1 has the largest specific surface area and pore volume, and well-developed pores, which is conducive to adsorption). NO0.5, due to the lack of KOH modification and the poor pore-forming ability of melamine, shows extremely poor adsorption capacity for TC and CHL. NK1 adsorbs TC and CHL to a near-equilibrium at t=3 h, while K3 adsorbs TC and CHL to a near-equilibrium at t=4 h.

[0046] Example 4 The initial pH of the antibiotic solution can affect the surface charge of the modified biochar and the ionic valence state of the antibiotic in the solution, which may in turn affect the adsorption performance of NK1. Therefore, the effect of pH on the adsorption of antibiotics by NK1 needs to be further investigated.

[0047] Add 30 mL of 200 mg / L TC to a 50 mL centrifuge tube and adjust the pH of the antibiotic to 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11. Weigh 5.0 mg of NK1 and add it to the centrifuge tube. Place the tube in a constant temperature mixer and set the conditions to 25°C and 350 rpm. Mix for 3 hours. Filter through a 0.45 μm filter membrane and measure the concentration of the filtrate. e Calculate the adsorption amount Q e Perform the experiment in triplicate. Plot the pH-Q curve. e picture.

[0048] Q e =(C0-C e )*V / m Among them, C e This is the concentration measured at equilibrium.

[0049] When the antibiotic is chloramphenicol, the concentration is 150 mg / L, and other procedures are the same as above.

[0050] To measure the isoelectric point of NK1: Take 30 mL of 0.1 mol / L NaCl solution into a 50 mL centrifuge tube and adjust the pH of the solution to 3, 4, 5, 6, 7, and 8. Weigh 5.0 mg of NK1 and add it to the centrifuge tube. Place the tube in a constant temperature mixer and set the conditions to 25℃ and 350 rpm for 6 hours. Filter the mixture through a 0.45 μm filter membrane and measure the pH of the filtrate. e Plot the pH-ΔpH curve. (ΔpH = pH) e -pH0) The effect of pH on the adsorption of TC and CHL by NK1 and the isoelectric point of NK1, as shown in the figure. Figure 7 As shown, a represents the effect of pH on the adsorption of TC and CHL by NK1; b represents the isoelectric point of NK1.

[0051] TC is a weak tetracarboxylic acid that exists in three ionization forms, namely pK a1 (3.30), pK a2 (7.69), pK a3 (9.69). When pH is less than 3.3, TC is converted to TCH. 3+ It exists in various forms; when pH is between 3.3 and 7.7, TC is a zwitterion; at pH 5.5, TC exists almost as an electroneutrally neutral zwitterion. As pH increases, the proportion of negative charge in the TC molecule increases, and when pH is greater than 9, TC exists entirely as an anion. Figure 7 As shown in b, the isoelectric point of NK1 is approximately pH 4.3. When the pH of the antibiotic solution is lower than the isoelectric point of NK1, NK1 carries a negative charge. When the pH of the antibiotic solution is higher than the isoelectric point of NK1, NK1 carries a positive charge.

[0052] Depend on Figure 7 As shown in Figure a, NK1 exhibits good adsorption performance for TC at pH values ​​of 4 and 5. Between pH 2 and 4, the adsorption capacity increases with increasing pH. This is because at pH 2-4, TC is a cation, while NK1 carries a negative charge, leading to mutual attraction and a large adsorption capacity. Between pH 5 and 11, the adsorption capacity decreases with increasing pH. At 25 °C, the initial pH of a 150 mg / L TC solution is approximately 3.6, which is close to its isoelectric point and optimal initial adsorption pH. Therefore, the pH of the TC stock solution was chosen for the adsorption experiment.

[0053] When the initial pH of the CHL solution was between 2 and 11, the adsorption capacity of NK1 for CHL fluctuated around 700 mg / g. This indicates that the pH of the CHL solution has little effect on the adsorption of CHL by NK1. Therefore, the pH of the original CHL solution was chosen for subsequent adsorption experiments.

[0054] Example 5 Effect of concentration on antibiotic adsorption by NK1 Prepare antibiotic solutions of 50 mg / L, 100 mg / L, 150 mg / L, 200 mg / L, and 250 mg / L respectively. Take 30 mL of the antibiotic solution and add it to a 50 mL centrifuge tube. Place the tube in a mixer, set the temperature to 25℃, and the rotation speed to 350 rpm, mix for 3 hours, and filter through a 0.45 μm filter membrane. Measure the concentration (C) of the filtrate. e Calculate the adsorption amount Q e Removal rate E. Three parallel experiments were conducted. CQ plotted. e -E curve.

[0055] E = (C0 - C) e ) / C0*100% Where C0 is the initial concentration of the antibiotic (mg / L); C e The concentration (mg / L) is the concentration measured at equilibrium.

[0056] Prepare CHL concentrations of 90 mg / L, 120 mg / L, 150 mg / L, 180 mg / L, and 210 mg / L, and perform the other procedures as above.

[0057] The effects of initial concentrations of CHL and TC on NK1 adsorption are as follows: Figure 8 As shown.

[0058] Depend on Figure 8It was found that the adsorption capacity of NK1 for CHL increased with increasing CHL concentration, while the removal rate decreased with increasing concentration. At a CHL concentration of 90 mg / L, the removal rate reached 95.8%, but the adsorption capacity was low. At a CHL concentration of 210 mg / L, the adsorption capacity reached 798 mg / g, but the removal rate was still low. At a CHL concentration of 150 mg / L, both the adsorption capacity and removal rate of NK1 for CHL adsorption were ideal. However, when the CHL concentration increased from 150 mg / L to 180 mg / L, the adsorption capacity increased slightly, but the removal rate decreased significantly. Considering all factors, an initial CHL concentration of 150 mg / L was chosen for subsequent experimental studies.

[0059] The adsorption capacity of NK1 for TC increased with increasing TC concentration, while the removal rate decreased with increasing concentration. At a TC concentration of 50 mg / L, the removal rate reached 100%, but the adsorption capacity was low. At a TC concentration of 250 mg / L, the adsorption capacity reached 989 mg / g, but the removal rate was extremely low. Furthermore, at a TC concentration of 150 mg / L, both the adsorption capacity and removal rate of NK1 for CHL were high. However, when the initial TC concentration increased from 150 mg / L to 200 mg / L, the adsorption capacity slightly increased, but the removal rate decreased significantly. Considering all factors, an initial TC concentration of 150 mg / L was chosen for subsequent experimental studies.

[0060] Example 6 Effect of charcoal dosage on antibiotic adsorption by NK1 Take 30 mL of 150 mg / L TC solution and transfer it to a 50 mL centrifuge tube. Weigh out 2.0 mg, 3.5 mg, 5.0 mg, 6.5 mg, and 8.0 mg of NK1 and add them to the centrifuge tube. Place the tube in a mixer and mix at 25°C and 350 rpm for 3 hours. Filter through a 0.45 μm filter membrane and measure the concentration C of the filtrate. e Calculate the adsorption amount Q e Removal rate E. Three parallel experiments were conducted. CQ plotted. e -E curve.

[0061] When the antibiotic is CHL, take 30 mL of 150 mg / L CHL solution into a 50 mL centrifuge tube, and perform the other procedures as above.

[0062] The effect of carbon dosage on the adsorption of CHL and TC by NK1 is as follows: Figure 9 As shown.

[0063] Generally, the removal rate increases with increasing carbon feed amount, while the adsorption capacity decreases with increasing carbon feed amount. Figure 9It is known that when the carbon dosage is 8 mg, the removal rate reaches 96.4%, but the adsorption capacity is extremely low. While the adsorption capacity reaches 1006 mg / g when the carbon dosage is 2 mg, the removal rate is still extremely low. When the carbon dosage increases from 3.5 mg to 5 mg, the removal rate of CHL by NK1 increases significantly, while the adsorption capacity decreases slightly. When the carbon dosage increases from 5 mg to 6.5 mg, the removal rate increases slightly, but the adsorption capacity decreases significantly. Considering all factors, a carbon dosage of 5 mg for NK1 is selected as the optimal dosage for CHL adsorption.

[0064] Keeping other conditions constant, when the carbon dosage is 2 mg, the adsorption capacity of NK1 for TC reaches 968 mg / g, but the removal rate is extremely low. When the carbon dosage is 8 mg, the removal rate reaches 100%, but the adsorption capacity is still low. Increasing the carbon dosage from 3.5 mg to 5 mg results in a sharp increase in removal rate and a slight increase in adsorption capacity. Increasing the carbon dosage from 5 mg to 6.5 mg results in a significant increase in removal rate, but a significant decrease in adsorption capacity. Considering all factors, 5 mg is selected as the optimal carbon dosage for NK1 adsorption of TC.

[0065] Example 7 Effect of temperature on antibiotic adsorption by NK1 Take 30 mL of 150 mg / L TC solution into a 50 mL centrifuge tube, weigh 5.0 mg NK1 and add it to the centrifuge tube. Set the centrifuge speed to 350 rpm and mix for 3 hours. The temperature was set to 15℃, 25℃, 35℃, and 45℃ respectively. Filter through a 0.45 μm filter membrane. Measure the concentration C of the filtrate. e Calculate the adsorption amount Q e The experiment was conducted in three parallel trials. The time-quantitative quotient (TQ) was plotted. e Bar chart.

[0066] When the antibiotic is CHL, take 30 mL of 150 mg / L CHL solution into a 50 mL centrifuge tube, and perform the other procedures as above.

[0067] The effect of temperature on the adsorption of CHL and TC by NK1 is as follows: Figure 10 As shown.

[0068] according to Figure 10 It is known that the adsorption capacity of TC by NK1 increases with increasing temperature. In this experimental study, the adsorption capacity of TC by NK1 reached its maximum at 45℃. The adsorption capacity of CHL by NK1 showed only slight fluctuations with increasing temperature, indicating that temperature has little effect on the adsorption of CHL by NK1. Considering all factors, 35℃ was selected as the optimal adsorption temperature for further research.

[0069] Example 8 Adsorption kinetics of NK1 and K3 40 mL of 150 mg / L TC solution was transferred to a 50 mL centrifuge tube. 6.7 mg of NK1 and K3 were weighed and added to the centrifuge tube, respectively. The mixing temperature was set to 35℃ and the centrifuge speed to 350 rpm. The concentration of the filtrate after filtration through a 0.45 μm filter was measured at 2 min, 5 min, 10 min, 20 min, 40 min, 1 h, 2 h, 3 h, 4 h, 5 h, and 6 h. The adsorption capacity was calculated, and tQ was plotted. t curve.

[0070] Take 40 mL of 150 mg / L CHL solution and add it to a 50 mL centrifuge tube. Weigh 6.7 mg of NK1 and K3 and add them to the centrifuge tube. Set the mixing speed to 350 rpm and mix at 35 °C. Measure the concentration of the filtrate after filtration through a 0.45 μm filter membrane at 5 min, 20 min, 40 min, 1 h, 2 h, 3 h, 4 h, 5 h, and 6 h. Calculate the adsorption capacity and plot tQ. t curve.

[0071] Figure 11 In Figure a, the kinetic curves of CHL adsorption by NK1 and K3 are shown, and in Figure b, the kinetic curves of TC adsorption by NK1 and K3 are shown.

[0072] Depend on Figure 11 It can be seen that within 2 hours, NK1 and K3 modified biochar have many active sites and a high initial concentration, resulting in a large adsorption rate. After 2 hours, the adsorption rate slows down due to the limited number of adsorption sites. After 4 hours, adsorption equilibrium is basically reached.

[0073] To further investigate the adsorption behavior of K3 and NK1, the adsorption data of CHL and TC by K3 and NK1 were fitted using pseudo-first-order and pseudo-second-order kinetic models, respectively. The fitting results are shown in Table 3 and [Table data would be inserted here]. Figure 12 .

[0074] When NK1 adsorbs CHL, the correlation coefficient r of the pseudo-second-order reaction rate equation of NK1 is... 2 (0.9999) is much higher than the correlation coefficient r of the pseudo-first-order reaction rate equation. 2 (0.7816), and Q calculated from the pseudo-second-order reaction rate equation e (657.9 mg / g) and Q obtained from the adsorption experiment results exp (657 mg / g) is very close. This indicates that the pseudo-second-order kinetic model can better describe the adsorption of CHL by NK1. This is because the pseudo-second-order kinetic model includes processes such as external liquid film diffusion, internal diffusion and surface adsorption of particles, and can more accurately reflect its adsorption mechanism, which is mainly chemical adsorption.

[0075] Table 3. Pseudo-first-order and pseudo-second-order kinetic parameters of NK1 and K3 for CHL and TC.

[0076] Figure 12 In the figure, a represents the pseudo-first-order kinetic fit of K3 and NK1 adsorbing CHL; b represents the pseudo-second-order kinetic fit of K3 and NK1 adsorbing CHL; c represents the pseudo-first-order kinetic fit of K3 and NK1 adsorbing TC; and d represents the pseudo-second-order kinetic fit of K3 and NK1 adsorbing TC.

[0077] When K3 adsorbs CHL, the correlation coefficient r of the pseudo-second-order reaction rate equation of K3 is... 2 (0.9971) is greater than the correlation coefficient r of the pseudo-first-order reaction rate equation. 2 (0.9396). Meanwhile, Q, calculated from the pseudo-second-order reaction rate equation... e (617.3 mg / g) and Q obtained from the adsorption experiment results exp (604.0 mg / g) is close. This indicates that the pseudo-second-order kinetic model can better describe the K3 adsorption of CHL process compared to the pseudo-first-order kinetic model, mainly through chemisorption, but also with some physical adsorption.

[0078] When NK1 adsorbs TC, the correlation coefficient r of the pseudo-second-order reaction rate equation for NK1 is... 2 (0.9984) is higher than the correlation coefficient r of the pseudo-first-order reaction rate equation. 2 (0.8345), and Q calculated from the pseudo-second-order reaction rate equation. e (885.0 mg / g) and Q obtained from the adsorption experiment results exp The result (881.0 mg / g) is very close. This indicates that the pseudo-second-order kinetic model can describe the NK1 adsorption of TC, and the adsorption process is mainly chemisorption.

[0079] When K3 adsorbs TC, the correlation coefficient r of the pseudo-second-order reaction rate equation for K3 is... 2 (0.9917) is greater than the correlation coefficient r of the pseudo-first-order reaction rate equation. 2 (0.9118). Meanwhile, Q, calculated from the pseudo-second-order reaction rate equation... e (543.5 mg / g) and Q obtained from the adsorption experiment results exp The result (551.0 mg / g) is quite close. This indicates that the pseudo-second-order kinetic model fits the K3 adsorption of CHL process well, and the adsorption process is mainly chemisorption.

[0080] In summary, the pseudo-second-order kinetic model can fit the adsorption behavior of CHL and TC by K3 and NK1 well, and the adsorption process is mainly chemisorption.

[0081] Example 9 Isothermal thermodynamics of NK1 and K3 Generally, adsorption reactions are exothermic, and lowering the temperature can promote the adsorption of antibiotics by modified biochar. However, before adsorption equilibrium is reached, appropriately increasing the temperature can promote the diffusion of antibiotic molecules to the surface of modified biochar, which is beneficial for adsorption. The Langmuir and Freundlich isotherm adsorption models can be used to explain the adsorption mechanism of the adsorbent on the adsorbate. The Langmuir isotherm adsorption model is suitable for monolayer physical adsorption on a homogeneous surface, while the Freundlich isotherm adsorption model is suitable for multilayer adsorption on a non-homogeneous surface. To further investigate the adsorption behavior of NK1 and K3 on TC and CHL, the Langmuir and Freundlich isotherm adsorption models were used to fit the adsorption equilibrium values ​​of K3 and NK1 at different temperatures for different concentrations of CHL and TC. The specific operations are as follows, and the results are shown in Table 4. Figure 13 and Figure 14 .

[0082] NK1 adsorption of TC: Take 30 mL of TC solutions with initial concentrations of 50 mg / L, 75 mg / L, 100 mg / L, 125 mg / L, and 150 mg / L, place them in 50 mL centrifuge tubes, add 5.0 mg of NK1, and mix at 350 rpm and 25°C for 3 h in a constant temperature mixer. Filter through a 0.45 μm filter membrane, collect the filtrate, and determine the TC concentration. Repeat the above operation at 35°C and 45°C.

[0083] NK1 adsorption of CHL: 30 mL of CHL solutions with initial concentrations of 90 mg / L, 120 mg / L, 150 mg / L, 180 mg / L, and 210 mg / L were placed in 50 mL centrifuge tubes. 5.0 mg of NK1 was added, and the mixture was stirred at 350 rpm for 3 h at 25°C in a constant-temperature mixer. The mixture was filtered through a 0.45 μm filter, and the filtrate was collected to determine the CHL concentration. The reaction temperature was set to 35°C and 45°C, and the above procedure was repeated.

[0084] K3 adsorption of TC: The activated carbon added is K3, and the initial concentrations of the TC solution are 50 mg / L, 75 mg / L, 100 mg / L, 125 mg / L, 150 mg / L, and 175 mg / L. The mixing time is 4 h, and other operations are the same as those for NK1 adsorption of TC.

[0085] K3 adsorption of CHL: K3 was added as the activated carbon, and the mixing time was 4 hours. Other operations were the same as those for NK1 adsorption of CHL.

[0086] Table 4. Langmuir and Freundilich isotherm adsorption models of NK1 and K3 for CHL and TC.

[0087] Fitting of NK1 adsorption TC and CHL isotherm curves Table 4 shows the Langmuir isotherm adsorption model correlation R for NK1 on TC. L 2 The correlation coefficient R between NK1 and TC in the Freundilich isotherm adsorption model (0.9988-0.9952) is greater than that in NK1. F 2 The values ​​(0.9734-0.9653) are more consistent with the Langmuir isothermal adsorption model, indicating that TC molecules are uniformly distributed on the NK1 surface, and the interaction forces between TC molecules are weak, suggesting monolayer adsorption. Furthermore, the adsorption amount increases with increasing temperature, indicating that the adsorption of TC on NK1 is an endothermic reaction.

[0088] Figure 13 The results show the linear fitting of the Langmuir isotherm adsorption model and the Freundilich isotherm adsorption model for NK1 on TC and CHL, respectively. In the figure, a represents the linear fitting of the Langmuir isotherm adsorption model for NK1 on TC; b represents the linear fitting of the Freundilich isotherm adsorption model for NK1 on TC; c represents the linear fitting of the Langmuir isotherm adsorption model for NK1 on CHL; and d represents the linear fitting of the Freundilich isotherm adsorption model for NK1 on CHL.

[0089] Depend on Figure 13 It can be seen that the adsorption capacity of NK1 for CHL first increases and then decreases with increasing temperature, indicating that the adsorption of CHL by NK1 may involve both physical and chemical processes. When the temperature rises, the adsorption rate exceeds the desorption rate, indicating that chemical adsorption is dominant; however, with further increases in temperature, physical adsorption leads to a decrease in the adsorption capacity. At 45℃, the correlation coefficient R0 of the Freundilich isotherm adsorption model for CHL by NK1 is shown. F 2 The value was 0.9990, indicating a high degree of fit. This suggests that under these conditions, the adsorption of CHL by NK1 is a multilayer adsorption, and the interaction between CHL molecules is strong.

[0090] K3 adsorption isotherm fitting of CHL and TC adsorption curves Table 4 shows that the correlation coefficient R between K3 and TC in the Langmuir isotherm adsorption model is... L 2(0.9905-0.9495) is much larger than the correlation coefficient R of the Freundilich isotherm adsorption model for K3 on TC. F 2 (0.2021-0.04523) indicates that the adsorption of TC by K3 conforms to the Langmuir isotherm adsorption model but not to the Freundilich isotherm adsorption model, suggesting that the adsorption of TC by K3 is monolayer adsorption and the adsorption sites of TC molecules on K3 are relatively uniform.

[0091] Figure 14 The linear fittings of K3 to the Langmuir isotherm adsorption model and the Freundilich isotherm adsorption model for TC and CHL are given, where a represents the linear fitting of K3 to the Langmuir isotherm adsorption model for TC; b represents the linear fitting of K3 to the Freundilich isotherm adsorption model for TC; c represents the linear fitting of K3 to the Langmuir isotherm adsorption model for CHL; and d represents the linear fitting of K3 to the Freundilich isotherm adsorption model for CHL.

[0092] The Langmuir isotherm adsorption model of K3 for CHL showed that the adsorption capacity of K3 for CHL decreased with increasing temperature, indicating that the adsorption of CHL by K3 is an exothermic reaction. The correlation coefficient R of the Langmuir isotherm adsorption model of K3 for CHL is... L 2 The correlation coefficient R between K3 and CHL in the Freundilich isotherm adsorption model (0.9978-0.9801) is greater than that in the Freundilich isotherm adsorption model. F 2 (0.9508-0.7791) indicates that the adsorption of CHL on K3 is more consistent with the Langmuir isotherm adsorption model, which is a monolayer adsorption. The adsorption sites of CHL molecules on K3 are relatively uniform, and the interaction forces between CHL molecules are weak.

[0093] As shown in the above examples, using KOH as a modifier can significantly increase the specific surface area and pore volume of biochar, while using melamine as a nitrogen source for nitrogen doping can further increase the specific surface area and pore volume. Among them, NK1 (mother carbon, melamine, and KOH in a mass ratio of 1:1:3) has the largest specific surface area and pore volume, respectively: 3409 m³ / h. 2 / g, 1.936cm 3 / g. At pH 4, NK1 showed the best adsorption effect on TC, while pH had little effect on the adsorption of CHL by NK1. When the initial concentrations of TC and CHL were 150 mg / L and the amount of carbon added was 5 mg, NK1 exhibited good removal rates and adsorption capacities for TC and CHL. The adsorption capacity of NK1 for TC increased with increasing temperature, while temperature had little effect on the adsorption of CHL by NK1. The adsorption behavior of K3 and NK1 for CHL and TC conformed to a pseudo-second-order kinetic model, reflecting that the adsorption process was chemisorption. Thermodynamics basically conformed to the Langmuir isotherm adsorption model, indicating that the adsorption of CHL and TC by K3 and NK1 was mostly monolayer adsorption, with weak interaction forces between adsorbates.

[0094] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing sugarcane peel-based biochar, characterized in that, The method includes the following steps: Sugarcane peel powder is carbonized, acid-washed, and dried to obtain mother carbon; The mother char and the modifier were mixed evenly, activated at high temperature, and then acid washed and dried to obtain sugarcane peel-based biochar. The modifier includes melamine and / or KOH, and the mass ratio of the mother carbon to melamine and KOH is 1:0 to 2:

3.

2. The method according to claim 1, characterized in that, The mass ratio of the mother carbon to melamine and KOH is 1:0:3 or 1:1:

3.

3. The method according to claim 1, characterized in that, The sugarcane peel powder has a particle size ≤0.25mm.

4. The method according to claim 1, characterized in that, The carbonization temperature is 400℃ and the time is 3 hours; the carbonization heating rate is 5℃ / min.

5. The method according to claim 1, characterized in that, The pickling steps include: soaking in dilute HCl, stirring magnetically for 12 hours, then vacuum filtering, and washing with water until neutral.

6. The method according to claim 1, characterized in that, The drying temperature is 50°C and the drying time is 24 hours.

7. The method according to claim 1, characterized in that, The high-temperature activation temperature is 800℃, the time is 2h, and the heating rate of the high-temperature activation is 5℃ / min.

8. The method according to claim 1, characterized in that, The method for uniformly mixing the mother carbon with melamine and KOH is grinding.

9. The use of sugarcane peel-based biochar prepared by the method according to any one of claims 1 to 8 in the adsorption of antibiotics.

10. The application according to claim 9, characterized in that, The antibiotics include tetracycline and / or chloramphenicol.

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