Preparation method and application of soap-bark-based Fe / Mn-N co-doped hydrothermal carbon adsorbing antibiotic material

Abstract

The application relates to a preparation method and application of a soapnut-based Fe / Mn-N co-doped hydrothermal carbon adsorbing antibiotic material, and the soapnut is washed and dried, ground, and 80-mesh screening is conducted during grinding to obtain soapnut powder; the soapnut powder, an Fe source and an Mn source are placed in a hydrothermal reaction kettle containing deionized water, and air drying is conducted at 170-180 DEG C for 10-15 h; after being cleaned by ultra-pure water filtration, the hydrothermal carbon is obtained by transferring the hydrothermal carbon to an oven for drying until the weight is constant, grinding by a maragda mortar, and 100-mesh screening; the hydrothermal carbon and urea are placed in a ball mill, and ball milling treatment is conducted at a speed of 500 rpm for 4.5-5.5 h to obtain the soapnut-based Fe / Mn-N co-doped hydrothermal carbon adsorbing antibiotic material. The preparation method is simple, low in cost and low in energy consumption; the prepared Fe / Mn co-doped hydrothermal carbon is loaded with nitrogen atoms after ball milling, the dispersity and stability of the hydrothermal carbon are improved, and the metal self-agglomeration is reduced.

Description

Technical Field

[0001] This invention belongs to the field of hydrothermal carbon adsorption material preparation technology, and relates to a method for preparing and applying a saponin shell-based Fe / Mn-N co-doped hydrothermal carbon adsorbent material, particularly a method for preparing saponin shell-based Fe / Mn-N co-doped hydrothermal carbon and its application in treating tetracycline in water. Background Technology

[0002] Tetracycline (TC) is widely used in medicine, animal husbandry, and agriculture due to its antibacterial and bactericidal properties. Overuse of tetracycline has led to its widespread presence in aquaculture water, rivers, and lakes. Long-term exposure to residual TC can promote the development of antibiotic-resistant bacteria and genes, posing harmful effects on human health and ecological safety. Currently, various materials have been developed for pollutant removal, such as zero-valent metals, metal oxides, biochar, and metal-organic frameworks (MOFs). Metal oxides, especially Fe / Mn oxides, can participate in various pollutant removal technologies, including adsorption, redox, and advanced oxidation, due to their specific nanoscale properties, high specific surface area, low cost, and strong oxidizing and adsorption capabilities.

[0003] Biochar (BC) is widely used as a support for metal oxides due to its high specific surface area, porous structure, low cost, and environmental friendliness, which can improve their dispersibility and electron transfer capabilities. In particular, nitrogen-doped biochar can enhance the stability and adsorption performance of materials. Therefore, bimetallic-supported nitrogen-doped carbon materials can serve as promising adsorbents and oxidants. Currently, the preparation process of metal-nitrogen co-doped biochar is complex, typically involving solution impregnation followed by high-temperature calcination, with the main limitation being high energy consumption.

[0004] Agricultural waste adsorbents have gained widespread attention due to their advantages such as high biomass, low cost, and environmental friendliness. Soapberry, also known as soapberry, is a perennial woody plant of the legume family, widely distributed in my country, and possesses high ecological and economic value. The outer shell of the soapberry contains saponins. Tea saponin, a natural non-compound surfactant, is a pure natural detergent (shampoo, dishwashing liquid) with biodegradability and low toxicity. It can be used to stabilize hydrophobic compounds in various dispersion systems, and surfactant decoration helps prevent Fe aggregation and oxidation. Furthermore, high-pressure autoclave extraction of saponins yields more suitable physicochemical properties and better yields. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing and applying a saponin shell-based Fe / Mn-N co-doped hydrothermal carbon adsorbent antibiotic material, so as to solve the problems of complex preparation process and high energy consumption of metal nitrogen-doped biochar.

[0006] The technical problem solved by this invention is achieved through the following technical solution:

[0007] A method for preparing a saponin shell-based Fe / Mn-N co-doped hydrothermal carbon adsorbent antibiotic material includes the following steps;

[0008] S1. Clean and dry the soapberry shells, then grind them, adding chitosan during grinding, and pass through an 80-mesh sieve to obtain soapberry shell powder; then place the soapberry shell powder, Fe source, and Mn source in a hydrothermal reactor containing deionized water, and hydrothermally react in a forced-air drying oven at 170-180℃ for 10-15 hours. After the reaction is completed, filter and wash with ultrapure water, transfer to an oven to dry to constant weight, grind with an agate mortar, and pass through a 100-mesh sieve to prepare hydrothermal carbon;

[0009] S2. Place hydrothermal carbon and urea in a ball mill and ball mill at 500 rpm for 4.5-5.5 hours to obtain saponin shell-based Fe / Mn-N co-doped hydrothermal carbon adsorbent material.

[0010] Moreover, the weight ratio of soapberry shell to chitosan is 15-35:1.

[0011] Moreover, the weight ratio of the soapberry shell powder:Fe source:Mn source is 25-35:15-25:1-5.

[0012] Moreover, the weight ratio of hydrothermal charcoal to urea is 2:1-2.

[0013] Moreover, the Fe source is FeSO4·7H2O.

[0014] Moreover, the Mn source is MnCl2·4H2O.

[0015] Moreover, the antibiotic in question is tetracycline.

[0016] A method for preparing a saponin shell-based Fe / Mn-N co-doped hydrothermal carbon adsorbent material for the treatment of tetracycline in solution.

[0017] The advantages and positive effects of this invention are:

[0018] 1. The Fe and Mn sources described in this invention are abundant in nature and possess environmentally friendly and redox properties. Soapberry contains surfactants, which can enhance the hydrophobic interaction between biochar and pollutants.

[0019] 2. The preparation method provided by the present invention is simple, low in cost and low in energy consumption. The Fe / Mn co-doped hydrothermal carbon prepared is loaded with nitrogen atoms after ball milling, which improves the dispersibility and stability of Fe / Mn-N co-doped hydrothermal carbon and reduces the agglomeration of the metal itself.

[0020] 3. The ball-milled Fe / Mn-N co-doped hydrothermal carbon of this invention exhibits excellent adsorption capacity for tetracycline in water in terms of pH adaptability, ionic strength resistance, and regenerability. In the adsorption isotherm model, the maximum adsorption capacity (q) of the ball-milled Fe / Mn-N co-doped hydrothermal carbon for tetracycline is [value missing]. m The concentration was 409.07 mg / g. This invention can be considered a promising environmentally friendly adsorbent for wastewater treatment.

[0021] 4. The main purpose of adding chitosan during the grinding of soapberry shells in this invention is to protect the surfactants in the soapberry shells. Soapberry shells contain saponins, tea saponins, and other components, which are natural, non-compound surfactants that are biodegradable and have low toxicity. During the grinding process, the activity of the surfactants may be impaired due to factors such as physical friction and temperature changes. Chitosan can play a protective role, maintaining the performance of the surfactants.

[0022] 5. This invention, by adding chitosan to protect the surfactant in the soapberry shell, indirectly enhances the material's adsorption capacity for tetracycline, enabling more effective removal of pollutants when treating water containing tetracycline. Simultaneously, chitosan itself possesses certain stability and viscosity, helping to maintain the material's structural stability during preparation. In subsequent hydrothermal reactions and ball milling processes, it helps maintain good physical and chemical properties, reducing structural damage during preparation and use, and improving the material's lifespan and reusability.

[0023] 6. In this invention, chitosan also helps to improve the dispersibility of the material. When the material comes into contact with solvents such as water, or when it is mixed with other components during ball milling, chitosan can prevent the agglomeration of material particles, so that the material can be more uniformly dispersed in the system, thereby better exerting its adsorption effect. Attached Figure Description

[0024] Figure 1 This is a scanning electron microscope image of Fe / Mn-BNHS of the present invention.

[0025] Figure 2 This is the elemental distribution diagram of Fe / Mn-BNHS of the present invention.

[0026] Figure 3 The contact angle diagrams for Fe / Mn-HS, Fe / Mn-BHS and Fe / Mn-BNHS of the present invention are shown.

[0027] Figure 4 The diagram shows the removal effect of Fe / Mn-HS, Fe / Mn-BHS and Fe / Mn-BNHS on tetracycline according to the present invention.

[0028] Figure 5This is a graph showing the removal amount of tetracycline by Fe / Mn-HS and Fe / Mn-BNHS at different time points according to the present invention.

[0029] Figure 6 This is a pseudo-first-order kinetic fitting curve of the adsorption of tetracycline by Fe / Mn-BNHS according to the present invention.

[0030] Figure 7 This is a pseudo-second-order kinetic fitting curve of tetracycline adsorption by Fe / Mn-BNHS according to the present invention.

[0031] Figure 8 This is the Freundlich isotherm diagram of tetracycline adsorption by Fe / Mn-BNHS according to the present invention.

[0032] Figure 9 The Langmuir isotherm plot of tetracycline adsorption by Fe / Mn-BNHS according to the present invention is shown.

[0033] Figure 10 The diagram shows the adsorption of tetracycline in the solution by Fe / Mn-BNHS of the present invention at different pH values.

[0034] Figure 11 This is a diagram showing the adsorption of tetracycline in solution by Fe / Mn-BNHS of the present invention at different ion concentrations.

[0035] Figure 12 The diagram shows the effect of Fe / Mn-BNHS of the present invention on tetracycline removal under multiple cycles of use. Detailed Implementation

[0036] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0037] A method for preparing a soapberry shell-based Fe / Mn-N co-doped hydrothermal carbon adsorbent antibiotic material includes the following steps:

[0038] S1. Clean and dry the soapberry shells, then grind them, adding chitosan during grinding, and pass through an 80-mesh sieve to obtain soapberry shell powder; then place the soapberry shell powder, Fe source, and Mn source in a hydrothermal reactor containing deionized water, and hydrothermally react in a forced-air drying oven at 170-180℃ for 10-15 hours. After the reaction is completed, filter and wash with ultrapure water, transfer to an oven to dry to constant weight, grind with an agate mortar, and pass through a 100-mesh sieve to prepare hydrothermal carbon;

[0039] S2. Place hydrothermal carbon and urea in a ball mill and ball mill at 500 rpm for 4.5-5.5 hours to obtain saponin shell-based Fe / Mn-N co-doped hydrothermal carbon adsorbent material.

[0040] Example 1

[0041] Preparation of antibiotic adsorption materials

[0042] A method for preparing a soapberry shell-based Fe / Mn-N co-doped hydrothermal carbon adsorbent antibiotic material includes the following steps:

[0043] S1. Clean and dry the soapberry shells, then grind them, adding 1.6g of chitosan during grinding, and pass through an 80-mesh sieve to obtain soapberry shell powder; place 6g of soapberry shell powder, 4g of FeSO4·7H2O and 0.6g of MnCl2·4H2O in a hydrothermal reactor containing 45ml of deionized water, and hydrothermally react in a 180℃ forced-air drying oven for 12h. After the reaction, filter and wash with ultrapure water, then transfer to a 70℃ oven and dry to constant weight. Grind with an agate mortar and pass through a 100-mesh sieve to obtain Fe / Mn-HS.

[0044] S2. Place 1.2g of hydrothermal charcoal and 1.6g of urea in a ball mill and ball mill at 500rpm for 5h to obtain Fe / Mn-BNHS. Fe / Mn-BHS can be obtained by following the same method without adding urea and chitosan.

[0045] Characterization of adsorption materials

[0046] Figure 1-2 The surface morphology of Fe / Mn-BNHS is shown. Based on the EDX spectrum ( Figure 1 As shown in the figure, Fe, Mn, and N elements have been successfully introduced into the water-carbon. After ball milling, the water-carbon forms a dense stacked structure, and the particle surface becomes smooth. Figure 2 ).

[0047] Figure 3 The hydrophobicity of Fe / Mn-HS, Fe / Mn-BHS, and Fe / Mn-BNHS was demonstrated. Compared to the contact angle of Fe / Mn-HS, ball milling increased the hydrophobicity of the iron-manganese hydrothermal carbon. Furthermore, the addition of urea and chitosan during ball milling introduced nitrogen, which further increased the hydrophobicity of the hydrothermal carbon.

[0048] Example 2

[0049] This example evaluates the adsorption capacity of Fe / Mn-HS and Fe / Mn-BNHS for tetracycline in solution.

[0050] The adsorbent materials (Fe / Mn-HS and Fe / Mn-BNHS) prepared in Example 1 were added to a TC solution with an initial concentration of 50 mg / L, at a dosage of 1 g / L. The reaction temperature was set at 25 °C, and the shaking speed was 180 rpm. Each experiment was performed in triplicate. Samples were taken after 24 hours and filtered through a 0.45 μm filter membrane to determine the residual TC concentration. The results were as follows: Figure 4-5 The diagram shows the adsorption effect of Fe / Mn-HS and Fe / Mn-BNHS on tetracycline in water.

[0051] The removal rate of TC by Fe / Mn-HS was 33.07%. After ball milling, the removal rate of TC by Fe / Mn-BHS increased (54.2%), and the removal rate of TC by Fe / Mn-BNHS further increased (92.2%) after the introduction of nitrogen element in ball milling. Figure 4 Within the first 30 minutes, the adsorption capacity of Fe / Mn-BNHS for TC increased rapidly, then increased slowly, reaching equilibrium after 780 minutes. During the rapid removal phase, the TC removal rate was 76.8%. Figure 5 This result can be attributed to the increase in oxygen-containing functional groups and surface active sites after ball milling. This indicates that combining Fe / Mn-N doped water carbon with ball milling is an effective strategy to improve TC removal efficiency.

[0052] Example 3

[0053] To explain the mechanism of TC adsorption by Fe / Mn-BNHS, pseudo-first-order and pseudo-second-order models were applied to fit the removal kinetics results.

[0054] Fe / Mn-BNHS was added to the above TC solution at a reaction temperature of 25℃, with an addition rate of 1 g / L. The shaking chamber speed was 180 rpm. Each experiment was conducted in triplicate, with samples taken and filtered at 1, 2, 3, 4, 5, 10, 30, 60, 110, 190, 300, 570, 780, and 1200 min to determine the residual concentration of TC. The adsorption kinetics data were fitted using a pseudo-first-order kinetic model, a pseudo-second-order kinetic model, and an intraparticle diffusion model. The relevant equations are shown below. (Pseudo-first-order kinetic model...)

[0055]

[0056] Quasi-second-order dynamic model

[0057]

[0058] Where q t (μg / g) and q e (μg / g) represents the amount of adsorbate adsorbed by the adsorbent at time t (min) and equilibrium, respectively; k1 (min)-1 ) and k2(min -1 ) are the adsorption rate constants for the pseudo-first-order kinetic model and the pseudo-second-order kinetic model, respectively.

[0059] Fitting of dynamic parameters as follows Figure 6 As shown in Table 1. Compared with the pseudo-first-order model (R... 2 =0.8916)( Figure 6 The pseudo-secondary model exhibits a higher correlation coefficient (R²). 2 =0.9997)( Figure 7 The adsorption amount q obtained from the pseudo-second-order model e,cal (mg / g) is closer to the experimental value (q) e,exp Therefore, the pseudo-second-order model can more accurately describe the dynamic process of TC removal by biochar. The results show that the adsorption reaction of biochar on TC is chemisorption, involving electron sharing or exchange between TC and biochar.

[0060] Table 1. Fitting parameters for adsorption kinetics and adsorption isotherm model

[0061]

[0062] Example 4

[0063] To further evaluate the removal performance of Fe / Mn-BNHS for TC (tetracycline) and its adsorption mechanism, two commonly used isotherm models were used to fit the experimental data.

[0064] Fe / Mn-BNHS was added to TC solutions with concentrations of 20, 50, 80, 100, 120, 150, 180, 200, and 250 mg / L, at a dosage of 1 g / L. The reaction temperature was 25℃, and the shaking incubator speed was 180 rpm. Samples were taken and filtered at the equilibrium time, and the residual concentration of TC was determined. Adsorption isotherm experimental data were fitted using Langmuir and Freundlich models, respectively. The Langmuir isotherm model assumes that adsorption is mainly a monolayer chemisorption occurring on the surface of a homogeneous adsorbent, and that there are no transverse or longitudinal forces between the adsorbed molecules. The Freundlich isotherm model assumes that adsorption is a multilayer physisorption and that the adsorbent surface is non-uniform. The specific equations are shown below:

[0065] Langmuir isotherm model:

[0066]

[0067] Freundlich isotherm model:

[0068]

[0069] Where, q m (μg / g) is the theoretical maximum adsorption capacity, K L (L / μg) is the Langmuir constant related to adsorption energy, and C0 (μg / L) and Ce (μg / L) are the concentrations of the adsorbate at the initial and adsorption equilibrium states, respectively. K F (L / μg) and n are Freundlich constants, which are related to the adsorption capacity and adsorption strength of the adsorbent, respectively.

[0070] Compared with the Freundlich model (R 2 =0.95573)( Figure 8 The Langmuir model can fit the experimental data well (R²). 2 =0.9808)( Figure 9 This indicates that the adsorption of TC on biochar follows a monolayer chemisorption mechanism. In the Langmuir model, the maximum adsorption capacity of TC by Fe / Mn-BNHS (q0) is... m The concentration of 409.07 mg / g was significantly higher than that of other adsorbents (Table 2).

[0071] Table 2 Comparison of adsorption capacity of metal-based adsorbent materials

[0072]

[0073] Example 5

[0074] Fe / Mn-BNHS is used to adsorb tetracycline from solutions at different pH values.

[0075] Fe / Mn-BNHS was added to a TC solution with a concentration of 50 mg / L at a dosage of 1 g / L. The pH of the solution was set to 3, 5, 7, 9 and 11, the temperature was set to 25℃, and the shaking speed of the shaker was set to 180 rpm. Samples were taken and filtered at the equilibration time to determine the residual concentration of TC.

[0076] Adsorption capacity of TC at different pH values, such as Figure 10 As shown, the adsorption capacity of TC generally decreases with increasing pH. At pH 5, 7, and 9, the adsorption capacity of Fe / Mn-BNHS for TC remains high, reaching up to 40 mg / g. The results indicate that the Fe / Mn-BNHS hydrothermal carbon provided by this invention has good adaptability over a wide pH range.

[0077] Example 6

[0078] Fe / Mn-BNHS is used to adsorb tetracycline from solutions at different ion concentrations.

[0079] Fe / Mn-BNHS was added to a TC solution with a concentration of 50 mg / L containing NaCl and CaCl2 (CO = 0.001, 0.01 and 0.1 mol / L). The temperature was set to 25℃ and the shaking speed of the incubator was 180 rpm. Samples were taken and filtered at the equilibrium time, and the residual concentration of TC was determined.

[0080] Figure 11 The data shows that, with Na + With increasing concentration, Na + Strength does not affect the adsorption capacity of biochar. However, when Ca... 2+ When the concentration reaches 0.1 mol / L, the adsorption capacity of Fe / Mn-BNHS for TC decreases. This indicates that Fe / Mn-BNHS can maintain a high adsorption capacity for TC in solutions with different ion types, suggesting that this adsorbent is a promising material for purifying practical wastewater.

[0081] Example 7

[0082] Evaluation of the regeneration performance of Fe / Mn-BNHS

[0083] Fe / Mn-BNHS was added to a 50 mg / L TC solution at a dosage of 1 g / L. The temperature was set to 25℃, and the shaking speed was 180 rpm. Samples were taken and filtered at the equilibrium time to determine the residual TC concentration. The adsorbed biochar was then filtered and regenerated with ethanol solution. After filtration and drying, the adsorption experiment was repeated 5 times to determine the regeneration adsorption capacity of Fe / Mn-BNHS.

[0084] like Figure 12 As shown, Fe / Mn-BNHS exhibited high adsorption capacity in both the first and second cycles. The adsorption rate continued to decrease after the second cycle, and even after five cycles, the TC removal rate remained as high as 73%. This indicates that Fe / Mn-BNHS can achieve good regeneration stability and has certain application value in practical processing.

[0085] Although embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments.

Claims

1. A method for preparing a saponin shell-based Fe / Mn-N co-doped hydrothermal carbon adsorbent antibiotic material, characterized in that: Includes the following steps; S1. Wash and dry the soapberry shells, then grind them, adding chitosan during grinding, and pass them through an 80-mesh sieve to obtain soapberry shell powder; then place the soapberry shell powder, Fe source, and Mn source in a hydrothermal reactor containing deionized water, and hydrothermally react in a forced-air drying oven at 170-180℃ for 10-15 hours. After the reaction is completed, filter and wash with ultrapure water, transfer to an oven to dry to constant weight, grind with an agate mortar, and pass through a 100-mesh sieve to prepare hydrothermal carbon; S2. Place hydrothermal carbon and urea in a ball mill and ball mill at 500 rpm for 4.5-5.5 h to obtain a saponin shell-based Fe / Mn-N co-doped hydrothermal carbon adsorbent material.

2. The preparation method of the soapberry shell-based Fe / Mn-N co-doped hydrothermal carbon adsorbent antibiotic material according to claim 1, characterized in that: The weight ratio of soapberry shell to chitosan is 15-35:

1.

3. The preparation method of the saponin shell-based Fe / Mn-N co-doped hydrothermal carbon adsorbent antibiotic material according to claim 1, characterized in that: The weight ratio of the soapberry shell powder, Fe source, and Mn source is 25-35:15-25:1-5.

4. The preparation method of the soapberry shell-based Fe / Mn-N co-doped hydrothermal carbon adsorbent antibiotic material according to claim 1, characterized in that: The weight ratio of hydrothermal charcoal to urea is 2:1-2.

5. The method for preparing the saponin shell-based Fe / Mn-N co-doped hydrothermal carbon adsorbent antibiotic material according to claim 1, characterized in that: The Fe source is FeSO4·7H2O.

6. The method for preparing the saponin shell-based Fe / Mn-N co-doped hydrothermal carbon adsorbent antibiotic material according to claim 1, characterized in that: The Mn source is MnCl2·4H2O.

7. The application of a saponin shell-based Fe / Mn-N co-doped hydrothermal carbon adsorbent material prepared by the method of claim 1 in the treatment of tetracycline in solution.

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