A kind of iron-cobalt modified biochar and its preparation method and application

Abstract

The present invention discloses a kind of iron-cobalt modified biochar and its preparation method and application, and belongs to the technical field of organic pollutant treatment. The iron-cobalt modified biochar of the present invention can not only remove norfloxacin by adsorption, but also activate persulfate to produce sulfate radicals, and then degrade norfloxacin by advanced oxidation process. The Fe and Co on the surface of Co‑Fe‑BC act as catalysts, which can lower the energy threshold of persulfate decomposition to produce sulfate radicals and accelerate the activation rate of persulfate. The generated sulfate radicals have high redox potential and can non-selectively attack norfloxacin molecules, triggering free radical chain reactions through hydrogen atom extraction or electron transfer mechanisms, and ultimately mineralizing norfloxacin into harmless small molecules, such as carbon dioxide and water. This process not only effectively removes norfloxacin, but also reduces the generation of disinfection by-products, thereby improving water quality safety.

Description

Technical Field

[0001] The present invention relates to the technical field of organic pollutant treatment, and in particular to an iron-cobalt modified biochar and a preparation method and application thereof. Background Art

[0002] Norfloxacin, also known as NOR, is a broad-spectrum antibiotic widely used in healthcare and aquaculture. However, it is worth noting that due to excessive use of NOR and its incomplete metabolism in organisms, a large amount of NOR is excreted into the environmental media in the form of parent material or metabolites, which not only poses a potential threat to human health but also affects the balance of the ecosystem. In view of this, the development of effective environmental removal technologies for NOR is particularly urgent. Recent studies have explored a variety of NOR removal technologies, including advanced oxidation processes (AOPs), biological treatment technologies, and adsorption technologies. Among these methods, AOPs are generally regarded as the preferred strategy for treating emerging pollutants in NOR-containing wastewater due to their high removal capacity and economic cost-effectiveness.

[0003] Advanced oxidation technologies (AOPs) utilize strong oxidants to generate highly reactive free radicals to degrade difficult-to-remove organic pollutants in water. These technologies can effectively mineralize or partially oxidize organic pollutants, including pharmaceutical residues, pesticides, dyes, and other persistent organic pollutants. Among AOPs, sulfate radical-based technologies have attracted attention due to their potent oxidative capacity and relatively low environmental impact. Peroxymonosulfate, also known as persulfate (PMS), is a compound containing sulfate radicals. When activated, it can generate sulfate radicals, which rapidly react with organic pollutants, degrading them. PMS itself is a stable compound, relatively safe for use in water treatment, and easy to store. PMS requires an activation process to release sulfate radicals. Existing technologies primarily achieve this activation process through heat, light, metal ions, or catalytic reactions with transition metal ions. However, existing activation methods have low PMS activation rates, and relying solely on activation to generate sulfate radicals to degrade and remove organic pollutants is ineffective. Summary of the Invention

[0004] The present invention provides an iron-cobalt modified biochar, a preparation method and an application thereof, which effectively solve the technical problems of low activation rate of peroxymonosulfate to generate sulfate radicals in existing activation methods and poor removal effect of organic pollutants by relying solely on sulfate radicals. The present invention introduces Fe and Co into biochar by a eutectic solvent method. On the one hand, the biochar is endowed with a high specific surface area and a porous structure, providing abundant adsorption sites for norfloxacin, thereby removing norfloxacin by adsorption. On the other hand, the introduction of Fe and Co into biochar increases the surface functional groups of the biochar. The Fe and Co elements form stable complexes with the carboxyl and ketone groups of norfloxacin through metal coordination bonds. Fe and Co act as catalysts, lowering the energy threshold for persulfate decomposition to generate sulfate radicals, increasing the activation rate of persulfate, and achieving efficient degradation of norfloxacin.

[0005] The first object of the present invention is to provide a method for preparing iron-cobalt modified biochar, comprising the following steps:

[0006] The biomass material is air-dried and crushed to obtain biomass powder.

[0007] Under stirring, add Fe 3+ Source and Co 2+ Source and eutectic solvent, the porous matrix of biomass powder is deconstructed by eutectic solvent, heated to 120℃~150℃, carbonized, and the biomass powder is converted into biochar, while Fe 3+ and Co 2+ The iron and cobalt oxides are converted into iron oxides and cobalt oxides and loaded on the biochar to obtain iron-cobalt modified biochar.

[0008] As a preferred embodiment, the Fe 3+ With Co 2+ The molar ratio is 1.5~2.5:1.

[0009] As a preferred embodiment, the Fe 3+ and Co 2+ The dosage ratio of the eutectic solvent is 0.25g~3.5g:75mL.

[0010] As a preferred embodiment, the eutectic solvent is: choline chloride and oxalic acid dihydrate are mixed in a molar ratio of 1:1 to 1.1, stirred at 75° C. to 80° C. to obtain a transparent liquid, and cooled to room temperature.

[0011] As a preferred embodiment, the carbonization reaction time is 4h~5h.

[0012] As a preferred embodiment, the heating rate is 5°C / min to 6°C / min.

[0013] As a preferred embodiment, after the carbonization reaction is completed, a primary product is obtained, which is rinsed and filtered to obtain a black solid. The black solid is washed with ultrapure water until the washing liquid is neutral to obtain a secondary product. The secondary product is dispersed in anhydrous ethanol, dried, and ground to obtain iron-cobalt modified biochar.

[0014] As a preferred embodiment, the biomass powder is sieved through a 60-mesh sieve.

[0015] The second object of the present invention is to provide an iron-cobalt modified biochar prepared by the above preparation method.

[0016] The third object of the present invention is to provide an application of iron-cobalt modified biochar in removing norfloxacin, characterized in that the application comprises the following steps: adding the iron-cobalt modified biochar to a solution containing norfloxacin for adsorption, and adding a peroxymonosulfate solution for degradation and removal.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The iron-cobalt-modified biochar prepared by the present invention has a high specific surface area and a porous structure, providing abundant adsorption sites for norfloxacin. The introduction of Fe and Co not only increases the surface functional groups of the biochar but also enhances its chemical affinity for norfloxacin. The presence of Fe and Co elements can form complexes with specific functional groups in the norfloxacin molecule, forming stable complexes with the carboxyl and ketone groups of norfloxacin through metal coordination bonds. In addition, the reducibility of Fe and Co enables Co-Fe-BC to destroy the aromatic ring structure of norfloxacin through reduction, further improving the degradation effect of norfloxacin. Under acidic conditions, the functional groups on the surface of Co-Fe-BC are protonated, enhancing the electrostatic attraction to norfloxacin and thus improving the adsorption efficiency. The iron-cobalt-modified biochar not only removes norfloxacin through adsorption but also activates peroxymonosulfate to produce sulfate radicals, which in turn degrades norfloxacin through advanced oxidation processes. The Fe and Co on the surface of Co-Fe-BC act as catalysts, lowering the energy threshold for persulfate decomposition to produce sulfate radicals and accelerating the activation rate of persulfate. Under the catalytic action of Co-Fe-BC, the reaction of persulfate decomposition to produce sulfate radicals is as follows:

[0019]

[0020] The generated sulfate radicals have a high redox potential and can indiscriminately attack norfloxacin molecules, initiating a free radical chain reaction through hydrogen atom abstraction or electron transfer mechanisms, ultimately mineralizing norfloxacin into harmless small molecules such as carbon dioxide and water. This process not only effectively removes norfloxacin but also reduces the formation of disinfection by-products, improving water quality and safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a diagram showing the effect of using iron-cobalt modified biochar with different contents prepared by the present invention to activate persulfate to remove norfloxacin.

[0022] Figure 2 This is a graph showing the pH change when persulfate is activated to remove norfloxacin using iron-cobalt modified biochar with different contents prepared in an embodiment of the present invention.

[0023] Figure 3 This is the adsorption kinetics diagram of the iron-cobalt modified biochar of the present invention.

[0024] Figure 4 This is a fitting diagram of the adsorption isotherm Langmuir model of the iron-cobalt modified biochar of the present invention.

[0025] Figure 5 This is a fitting diagram of the adsorption isotherm Freundlich model of the iron-cobalt modified biochar of the present invention.

[0026] Figure 6 This is a fitting diagram of the adsorption isotherm Temkin model of the iron-cobalt modified biochar of the present invention.

[0027] Figure 7 These are SEM images of the iron-cobalt modified biochar of the present invention, wherein (a) is the iron-cobalt modified biochar prepared by conventional pyrolysis method in Comparative Example 1, (b) is the unmodified biochar prepared by eutectic solvent method in Comparative Example 2, and (c) is the iron-cobalt modified biochar prepared in Example 4.

[0028] Figure 8 These are the SEM images and element distribution MAPPING diagrams of the iron-cobalt modified biochar of Example 4 of the present invention, wherein (a) is the SEM image, (b) is the element distribution MAPPING diagram, and (c) to (e) are the distribution diagrams of the C element, Co element, and Fe element, respectively.

[0029] Figure 9 FTIR graph of the iron-cobalt modified biochar of the present invention, wherein 0% is Comparative Example 2, 5% is Example 1, 30% is Example 2, 50% is Example 3, and 70% is Example 4.

[0030] Figure 10 This is the XRD pattern of the iron-cobalt modified biochar of the present invention.

[0031] Figure 11 N2 adsorption and desorption isotherms of different biochars. Figure 11 The small figure in the figure is a comparison of the BET specific surface areas of different biochars.

[0032] Figure 12 BJH desorption pore size distribution diagram of different biochars.

[0033] Figure 13 This is a diagram showing the elemental analysis results of the iron-cobalt modified biochar with different contents prepared in the present invention. DETAILED DESCRIPTION

[0034] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention is further described below with reference to specific examples, but the examples are not intended to limit the present invention. The following experimental and detection methods are conventional methods unless otherwise specified; the reagents and raw materials are commercially available unless otherwise specified.

[0035] The existing activation methods mentioned in the background of the present invention have a low activation rate for PMS, and the degradation and removal of organic pollutants by simply relying on the generation of sulfate radicals through activation is ineffective. Based on the above technical problems, the present invention provides an iron-cobalt modified biochar and its preparation method and application.

[0036] The technical solution of the present invention is described in detail below.

[0037] The present invention first provides a method for preparing iron-cobalt modified biochar, comprising the following steps:

[0038] The biomass material was air-dried, crushed, and passed through a 60-mesh sieve to obtain biomass powder.

[0039] Under stirring, add Fe 3+ Source and Co 2+ Source and eutectic solvent, the porous matrix of biomass powder is deconstructed by eutectic solvent, the temperature is raised to 120℃~150℃, carbonization reaction is carried out for 4h~5h, the biomass powder is converted into biochar, and Fe 3+ and Co 2+ The iron and cobalt oxides are converted into iron oxides and cobalt oxides and loaded on the biochar to obtain iron-cobalt modified biochar.

[0040] In the above technical solution, Fe and Co are introduced into biochar, giving it a high specific surface area and porous structure, providing abundant adsorption sites for norfloxacin, and removing it through adsorption. The introduction of Fe and Co into biochar increases the biochar's surface functional groups. The Fe and Co elements form stable complexes with the carboxyl and ketone groups of norfloxacin through metal coordination bonds. Acting as catalysts, Fe and Co lower the energy threshold for persulfate decomposition to produce sulfate radicals, increasing the activation rate of persulfate and achieving efficient degradation of norfloxacin. The present invention significantly improves the removal of norfloxacin through the combined action of biochar adsorption and sulfate radical degradation.

[0041] For the above-mentioned carbonization reaction temperature of 120℃~150℃ and carbonization reaction time of 4h~5h, if the carbonization time is less than 4h at a temperature lower than 120℃, the carbonization effect will be poor and biochar with a better pore structure cannot be formed, thereby affecting the adsorption amount of organic pollutants; if the carbonization time is higher than 150℃ for more than 5h, it may cause the microporous structure to collapse and the total pore volume to decrease, which is not conducive to adsorption.

[0042] In order to increase the activation rate of peroxymonosulfate, the Fe 3+ With Co 2+ The molar ratio of iron and cobalt is 1.5~2.5:1. The synergistic effect of iron and cobalt is the key to the activation of peroxymonosulfate. If the molar ratio is 1:1: the iron content is reduced, which destroys the Fe 3+ With Co 2+ The synergistic activation effect of peroxymonosulfate leads to a decrease in the rate of free radical generation. If the molar ratio is 1:3, the excess cobalt covers the iron active sites, causing the metals to agglomerate and form an inert complex of Co-Fe oxides, which in turn inhibits catalytic activity.

[0043] As a preferred embodiment, the Fe 3+ and Co 2+ The dosage ratio of the eutectic solvent is 0.25g to 3.5g:75mL. Excessive eutectic solvent will lead to excessive deposition of iron and cobalt metals on the biochar surface, forming metal particle agglomerates, which not only covers the active sites of the biochar but also reduces the specific surface area and porosity. Insufficient eutectic solvent will destroy the bimetallic synergy, resulting in a decrease in the efficiency of sulfate radical generation.

[0044] It is important to emphasize that the eutectic solvent employed in this invention is prepared by mixing choline chloride and oxalic acid dihydrate in a molar ratio of 1:1 to 1.1, stirring at 80°C to obtain a transparent liquid, and cooling to room temperature. This eutectic solvent decomposes the porous matrix of biomass powder. During pyrolysis, the eutectic solvent acts as a "dynamic template," guiding pore formation through a hydrogen bond network and solvent volatilization. The hydrogen bond donors in the eutectic solvent decompose at high temperatures, releasing gases and promoting the formation of a hierarchical porous structure in the biochar. The micropores (<2 nm) and mesopores (2 nm to 50 nm) within the eutectic solvent are beneficial for the adsorption of small-molecule pollutants, such as heavy metal ions. The ash remaining after carbonization of the eutectic solvent acts as a pore-forming agent, forming continuous macropores (>50 nm), improving mass transfer efficiency.

[0045] In order to avoid the influence of large temperature differences on the pore structure of biochar and the resultant uneven pore distribution, the present invention controls the heating rate to be 5°C / min~6°C / min during the carbonization reaction.

[0046] It should be noted that in order to improve the purity of the final iron-cobalt modified biochar, after the carbonization reaction is completed, the primary product is obtained, rinsed, filtered to obtain a black solid, and the black solid is washed with ultrapure water until the washing liquid is neutral to obtain a secondary product. The secondary product is dispersed in anhydrous ethanol, dried, and ground to obtain iron-cobalt modified biochar.

[0047] The present invention will be described in detail below through the following examples and comparative examples.

[0048] Example 1

[0049] A method for preparing iron-cobalt modified biochar comprises the following steps:

[0050] S1. The biomass material is air-dried, crushed, and passed through a 60-mesh sieve to obtain a biomass powder. Choline chloride and oxalic acid dihydrate are mixed in a molar ratio of 1:1, stirred at 80° C. to obtain a transparent liquid, and cooled to room temperature to obtain a eutectic solvent.

[0051] S2, add 0.25g of Fe with a molar ratio of 2:1 to 5g of the biomass powder under stirring. 3+ Source and Co 2+ source, and then add 75mL of the eutectic solvent to deconstruct the porous matrix of the biomass powder through the eutectic solvent, heat it to 140℃ at a rate of 5℃ / min, and carbonize it for 4h to convert the biomass powder into biochar. 3+ and Co 2+ The iron oxide and cobalt oxide were converted into iron oxide and cobalt oxide and loaded on the biochar. After the carbonization reaction was completed, a primary product was obtained, which was rinsed and filtered to obtain a black solid. The black solid was washed with ultrapure water until the washing liquid was neutral to obtain a secondary product. The secondary product was dispersed in anhydrous ethanol, dried, and ground to obtain iron-cobalt modified biochar, which was recorded as D-140-Co-Fe-5%.

[0052] Example 2

[0053] A method for preparing iron-cobalt modified biochar comprises the following steps:

[0054] S1. The biomass material is air-dried, crushed, and passed through a 60-mesh sieve to obtain a biomass powder. Choline chloride and oxalic acid dihydrate are mixed in a molar ratio of 1:1, stirred at 80° C. to obtain a transparent liquid, and cooled to room temperature to obtain a eutectic solvent.

[0055] S2, under stirring, add 1.5g of Fe with a molar ratio of 2:1 to 5g of the biomass powder. 3+ Source and Co 2+source, and then add 75mL of the eutectic solvent to deconstruct the porous matrix of the biomass powder through the eutectic solvent, heat it to 140℃ at a rate of 5℃ / min, and carbonize it for 4h to convert the biomass powder into biochar. 3+ and Co 2+ The iron oxide and cobalt oxide are converted into iron oxide and cobalt oxide and loaded on the biochar. After the carbonization reaction is completed, a primary product is obtained, which is rinsed and filtered to obtain a black solid. The black solid is washed with ultrapure water until the washing liquid is neutral to obtain a secondary product. The secondary product is dispersed in anhydrous ethanol, dried, and ground to obtain iron-cobalt modified biochar, D-140-Co-Fe-30%.

[0056] Example 3

[0057] A method for preparing iron-cobalt modified biochar comprises the following steps:

[0058] S1. The biomass material is air-dried, crushed, and passed through a 60-mesh sieve to obtain a biomass powder. Choline chloride and oxalic acid dihydrate are mixed in a molar ratio of 1:1, stirred at 80° C. to obtain a transparent liquid, and cooled to room temperature to obtain a eutectic solvent.

[0059] S2, under stirring, add 2.5g of Fe with a molar ratio of 2:1 to 5g of the biomass powder. 3+ Source and Co 2+ source, and then add 75mL of the eutectic solvent to deconstruct the porous matrix of the biomass powder through the eutectic solvent, heat it to 140℃ at a rate of 5℃ / min, and carbonize it for 4h to convert the biomass powder into biochar. 3+ and Co 2+ The iron oxide and cobalt oxide are converted into iron oxide and cobalt oxide and loaded on the biochar. After the carbonization reaction is completed, a primary product is obtained, which is rinsed and filtered to obtain a black solid. The black solid is washed with ultrapure water until the washing liquid is neutral to obtain a secondary product. The secondary product is dispersed in anhydrous ethanol, dried, and ground to obtain iron-cobalt modified biochar, D-140-Co-Fe-50%.

[0060] Example 4

[0061] A method for preparing iron-cobalt modified biochar comprises the following steps:

[0062] S1. The biomass material is air-dried, crushed, and passed through a 60-mesh sieve to obtain a biomass powder. Choline chloride and oxalic acid dihydrate are mixed in a molar ratio of 1:1, stirred at 80° C. to obtain a transparent liquid, and cooled to room temperature to obtain a eutectic solvent.

[0063] S2, under stirring, add Fe with a molar ratio of 2:1 to 5g of the biomass powder3+ Source and Co 2+ source, then add the eutectic solvent, Fe 3+ and Co 2+ The dosage ratio of the eutectic solvent was 3.5 g:75 mL. The porous matrix of the biomass powder was deconstructed by the eutectic solvent. The temperature was raised to 140 ° C at a rate of 5 ° C / min and the carbonization reaction was carried out for 4 hours to convert the biomass powder into biochar. At the same time, Fe 3+ and Co 2+ The iron oxide and cobalt oxide are converted into iron oxide and cobalt oxide and loaded on the biochar. After the carbonization reaction is completed, a primary product is obtained, which is rinsed and filtered to obtain a black solid. The black solid is washed with ultrapure water until the washing liquid is neutral to obtain a secondary product. The secondary product is dispersed in anhydrous ethanol, dried, and ground to obtain iron-cobalt modified biochar, D-140-Co-Fe-70%.

[0064] Example 5

[0065] A method for preparing iron-cobalt modified biochar comprises the following steps:

[0066] S1. The biomass material is air-dried, crushed, and passed through a 60-mesh sieve to obtain a biomass powder. Choline chloride and oxalic acid dihydrate are mixed in a molar ratio of 1:1, stirred at 80° C. to obtain a transparent liquid, and cooled to room temperature to obtain a eutectic solvent.

[0067] S2, under stirring, add 0.25g of Fe with a molar ratio of 1.5:1 to 5g of the biomass powder. 3+ Source and Co 2+ source, and then add 75mL of the eutectic solvent to deconstruct the porous matrix of the biomass powder through the eutectic solvent, heat it to 120℃ at a rate of 5℃ / min, and carbonize it for 5h to convert the biomass powder into biochar. 3+ and Co 2+ The iron oxide and cobalt oxide are converted into iron oxide and cobalt oxide and loaded on the biochar. After the carbonization reaction is completed, a primary product is obtained, which is rinsed and filtered to obtain a black solid. The black solid is washed with ultrapure water until the washing liquid is neutral to obtain a secondary product. The secondary product is dispersed in anhydrous ethanol, dried, and ground to obtain iron-cobalt modified biochar.

[0068] Example 6

[0069] A method for preparing iron-cobalt modified biochar comprises the following steps:

[0070] S1. The biomass material is air-dried, crushed, and passed through a 60-mesh sieve to obtain a biomass powder. Choline chloride and oxalic acid dihydrate are mixed in a molar ratio of 1:1, stirred at 80° C. to obtain a transparent liquid, and cooled to room temperature to obtain a eutectic solvent.

[0071] S2, under stirring, add 0.25g of Fe with a molar ratio of 2.5:1 to 5g of the biomass powder. 3+ Source and Co 2+ source, and then add 75mL of the eutectic solvent to deconstruct the porous matrix of the biomass powder through the eutectic solvent, and heat it to 150℃ at a rate of 5℃ / min, and carbonize it for 4h to convert the biomass powder into biochar. 3+ and Co 2+ The iron oxide and cobalt oxide are converted into iron oxide and cobalt oxide and loaded on the biochar. After the carbonization reaction is completed, a primary product is obtained, which is rinsed and filtered to obtain a black solid. The black solid is washed with ultrapure water until the washing liquid is neutral to obtain a secondary product. The secondary product is dispersed in anhydrous ethanol, dried, and ground to obtain iron-cobalt modified biochar.

[0072] In order to further illustrate the effect of the present invention, the present invention also provides a comparative example, as follows:

[0073] Comparative Example 1

[0074] Compared with Example 1, the difference is that the biochar is prepared by conventional pyrolysis method.

[0075] A method for preparing biochar comprises the following steps:

[0076] S1, air-drying the biomass material, crushing it, and passing it through a 60-mesh sieve to obtain biomass powder.

[0077] S2. Under stirring, 75 mL of ultrapure water was added to 5 g of the biomass powder, and the temperature was raised to 140 ° C at a rate of 5 ° C / min. The carbonization reaction was carried out for 4 hours to convert the biomass powder into biochar. After the carbonization reaction was completed, a primary product was obtained, which was rinsed and filtered to obtain a black solid. The black solid was washed with ultrapure water until the washing liquid was neutral to obtain a secondary product. The secondary product was dispersed in anhydrous ethanol, dried, and ground to obtain unmodified biochar, which was recorded as H-140.

[0078] Comparative Example 2

[0079] Compared with Example 1, the difference is that iron and cobalt are not used for modification.

[0080] A method for preparing biochar comprises the following steps:

[0081] S1. The biomass material is air-dried, crushed, and passed through a 60-mesh sieve to obtain a biomass powder. Choline chloride and oxalic acid dihydrate are mixed in a molar ratio of 1:1, stirred at 80° C. to obtain a transparent liquid, and cooled to room temperature to obtain a eutectic solvent.

[0082] S2. Under stirring, 75 mL of the eutectic solvent was added to 5 g of the biomass powder, and the porous matrix of the biomass powder was deconstructed by the eutectic solvent. The temperature was raised to 140°C at a rate of 5°C / min, and the carbonization reaction was carried out for 4 hours to convert the biomass powder into biochar. After the carbonization reaction, a primary product was obtained, which was rinsed and filtered to obtain a black solid. The black solid was washed with ultrapure water until the washing liquid was neutral to obtain a secondary product. The secondary product was dispersed in anhydrous ethanol, dried, and ground to obtain biochar, which was recorded as D-140.

[0083] The performance of the iron-cobalt modified biochar provided in Examples 1 to 6, the biochar prepared by conventional pyrolysis in Comparative Example 1, and the biochar provided in Comparative Example 2 were tested respectively. The biochar prepared in the above Examples and Comparative Examples were used to remove norfloxacin, and the process and results are as follows.

[0084] Adsorption + activation degradation process of peroxymonosulfate:

[0085] Adsorption: Biochar concentration was 0.5 g / L, 100 mL of 100 mg / L NOR solution was added, and the temperature was set at 25°C in a constant temperature shaker. In the adsorption experiment, 150 mL conical flasks were used and sealed with film. The constant temperature shaker was set at a speed of 200 r / min. Samples of NOR solution were taken at regular intervals and filtered with a 0.22 μm filter membrane. The solution concentration was then determined by HPLC and the adsorption capacity was calculated.

[0086] Activation: After 24 hours of adsorption, add 0.5 mL of 0.1 M PMS solution to the conical flask and seal it with a film. Keep the temperature at 25 ° C and set the shaker speed to 200 r / min to react. Sample the NOR solution at regular intervals and add an equal amount of methanol. Filter with a 0.22 μm filter membrane, and then determine the solution concentration by HPLC and calculate the adsorption capacity.

[0087] Depend on Figure 1 As can be seen, the unmodified biochar of Comparative Example 2 precipitated previously adsorbed norfloxacin after the addition of persulfate, indicating that relying solely on adsorption to remove NOR is unreliable and may also precipitate norfloxacin in actual use, leading to further environmental pollution. The iron-cobalt-modified biochars prepared in Examples 1 to 4 showed improved NOR removal effectiveness as the iron and cobalt content increased. However, NOR adsorption was also affected when the addition amount exceeded 70% of the biochar raw material weight. Therefore, the maximum addition amount of iron-cobalt-modified biochar was 70% of the weight of the biochar raw material powder.

[0088] When simulating pseudo-first-order and pseudo-second-order kinetics, biochar prepared by eutectic solvent method, such as Figure 3As shown in Figure 2, the correlation coefficients R² were 0.65 and 0.86, respectively, indicating that the adsorption of NOR was more consistent with the pseudo-second-order kinetic model, suggesting that the adsorption process may be chemical adsorption. The adsorption of norfloxacin by eutectic solvent carbon showed a large adsorption rate within 500 minutes and continued to increase over time.

[0089] The Langmuir isotherm fitting, Freundlich isotherm fitting and Temkin isotherm fitting of norfloxacin adsorption by the iron-cobalt modified biochar prepared by the eutectic solvent of the present invention are as follows: Figure 4 、 Figure 5 and Figure 6 As shown in the figure, the fitting results indicate that the adsorption of iron-cobalt modified biochar prepared with eutectic solvents under these conditions occurs in both monolayer and multilayer forms. The Temkin model fitting parameter B is greater than 0, indicating that all adsorption is exothermic. The best fitting results from the Freundlich isotherm fitting indicate that the biochar prepared with eutectic solvents has different surface adsorption sites and exhibits multilayer adsorption.

[0090] Figure 7 The microscopic morphology of the iron-cobalt modified biochar prepared by the eutectic solvent method is shown in Figure 2. Figure 7 It can be seen that the biomass structure of the farmland vegetables is gradually destroyed, forming many irregular pore structures and a large number of spherical microspheres. These microspheres are likely to be biochar microspheres synthesized by a series of condensation polymerization reactions of biomass. The microstructure of some previously reported hydrothermal biochar is also similar to this. Figure 8 It can be seen that the iron and cobalt elements are evenly distributed and the content of Fe(III):Co is approximately 2, which meets the initial expected value.

[0091] Figure 9 The FTIR diagram of the iron-cobalt modified biochar of the present invention is shown in FIG. Figure 9 It can be seen that the iron-cobalt modified biochar has abundant functional groups, and the functional groups are of the same type. The vibration peak positions and types of each functional group have been Figure 9 For the iron-cobalt modified biochar prepared by eutectic solvent, the -1 The -OH vibration peaks appearing near 2924 cm -1 and 2860cm -1 The -CHX vibration peak near 1623cm shows a trend of decreasing spectral intensity with increasing temperature. This is because the carbonization degree gradually deepens with increasing temperature, resulting in dehydration and dehydroxylation. -1 The C=C vibration peak near 1554cm -1 The intensity of the C=O vibration peak near 778cm gradually becomes stronger, indicating that one or more sugar molecules dehydrogenate and aromatize with themselves to form aromatic rings during the reaction. -1The vibration peaks appearing nearby are aromatic CH, which also indicates that aromatization reaction has occurred.

[0092] according to Figure 10 The XRD patterns of the iron-cobalt-modified biochars show numerous broad amorphous peaks, indicating that they are amorphous. The differences in the broad peaks observed in the XRD analysis of the various iron-cobalt-modified biochars are primarily observed at 18.8°, 22.9°, and 28.14°. Using Jade 6.0, the diffraction peak at 18.8° likely represents the characteristic peak of iron oxalate, as determined by the reference card PDF#23-0293. The peak intensity at this peak increases with increasing iron and cobalt content, suggesting that the oxalic acid in the DES reacts with the iron minerals in the waste vegetable to form iron oxalate. The diffraction peaks at 22.9° and 28.14° are identifiable as carbon using Jade 6.0, as determined by the reference card PDF#50-0926. These XRD results are highly consistent with those from previous biochar studies, demonstrating that carbonization of waste vegetable biomass using DES at 140°C is feasible. According to the XRD analysis results, the diffraction peaks of iron and cobalt elements correspond to the standard card numbers PDF#34-1266, PDF#23-0293, PDF#21-0920, PDF#50-1674, and PDF#48-1069, respectively, indicating that iron is in the form of Fe+3O(OH), C2Fe+2O4·2H2O, and Fe2O3, and cobalt is in the form of (Co(NH3)4CO3)·0.5H2O, and C2CoO4 in the modified biochar.

[0093] Figure 11 and Figure 12 The N2 adsorption-desorption isotherms and BJH desorption pore size distribution diagrams of biochar prepared at different temperatures are shown. According to the IUPAC classification, the adsorption-desorption isotherms of biochar prepared by eutectic solvent at 140°C can be classified as type IV, which indicates that the prepared biochar has a certain mesoporous structure. Due to the capillary condensation in the mesoporous channel, the adsorption and desorption isotherms do not overlap, and a hysteresis loop appears. The hysteresis loop is classified as type H3. The characteristic of the H3 type hysteresis loop is that the isotherm will not have a platform when the relative pressure is close to the saturated vapor pressure, indicating that the synthetic material has a flat slit structure, crack or wedge-shaped pore structure, etc. It also shows that the pore structure is irregular, which is consistent with the results of biochar scanning electron microscopy. The data related to the specific surface area and pore structure of biochar can be combined Figure 12 According to the BJH desorption pore size distribution, Figure 12It can be seen that the pore structure of the iron-cobalt modified biochar prepared by eutectic solvent has a pore size below 60nm, and the pore size of the biochar prepared by hydrothermal method is below 50nm. According to the IUPAC pore size classification, pores larger than 50nm are macropores, pores between 2nm and 50nm are mesopores, and pores smaller than 2nm are micropores. This shows that the biochar prepared by eutectic solvent has a macropore structure compared with the biochar prepared by hydrothermal method, but the main pores are still concentrated in the mesopore structure of 5nm~25nm.

[0094] Table 1 Elemental analysis results of biochars of the present invention and comparative examples

[0095]

[0096] As shown in Table 1, the biochar H-140 prepared by conventional hydrothermolysis method showed the lowest specific surface area of ​​4.72 m 2 / g, the specific surface area of ​​biochar prepared by eutectic solvent is better than that of H-140, and it can be seen that the specific surface area of ​​biochar prepared by eutectic solvent method is significantly better than that of conventional pyrolysis method. The specific surface area of ​​D-140 prepared at 140℃ is 15.94m 2 / g, which is 3.38 times that of H-140; the total pore volume and specific surface area show the same pattern, with the lowest being 0.018cm in H-140. 3 / g, while D-140 is 0.066cm 3 / g, which is 3.67 times that of H-140; the average pore size results calculated by mesopore size analysis of biochar are not much different, both showing mesoporosity.

[0097] Figure 13 The figure shows the elemental analysis results of biochar modified with different contents of iron and cobalt prepared by the present invention, wherein 5% FeCo is Example 1, 30% FeCo is Example 2, 50% FeCo is Example 3, 70% FeCo is Example 4, and no modification is Comparative Example 2. Figure 13 It can be seen that: Fe / Co content gradient: As the Fe-Co addition ratio increases from 5% to 70%, the bar chart shows that the proportion of Fe and Co increases significantly. The metal is evenly dispersed to form an effective Fe 2+ / Co 3+In the redox cycle, the efficiency of activating PMS to generate sulfate radicals is the highest. The unmodified biochar has the highest carbon content, which is the main force of basic adsorption. With the addition of Fe-Co, the carbon content gradually decreases but still remains dominant. The key turning point is at 30% addition: when C ≥ 50%, sufficient carbon skeleton is retained to support π-π interaction, and the ability to adsorb norfloxacin is stable. When C < 50%, such as the 70% addition group, the carbon skeleton is covered by metal and the adsorption capacity may decrease. The unmodified group has the highest O / C and is rich in hydroxyl / carboxyl groups. The O / C gradually decreases with the addition of metal; the H / C gradually decreases with the addition of metal, indicating that the aliphatic structure decreases and the degree of aromatization increases. The ASH content is < 20%, the pore structure is complete, and the adsorption-catalytic synergistic effect is significant.

[0098] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing iron-cobalt modified biochar, characterized in that: The following steps are involved: Air-drying and crushing the biomass material to obtain biomass powder; Under stirring, add Fe 3+ Source and Co 2+ Source and eutectic solvent, the porous matrix of biomass powder is deconstructed by eutectic solvent, heated to 120℃~150℃, carbonized, and the biomass powder is converted into biochar, while Fe 3+ and Co 2+ Converting into iron oxide and cobalt oxide and loading on the biochar to obtain iron-cobalt modified biochar; The Fe 3+ and Co 2+ The usage ratio of the eutectic solvent is 0.25 g to 3.5 g: 75 mL; the eutectic solvent is: choline chloride and oxalic acid dihydrate are mixed in a molar ratio of 1:1 to 1.1, stirred at 75° C. to 80° C. to obtain a transparent liquid, and cooled to room temperature.

2. The method for preparing iron-cobalt modified biochar according to claim 1, characterized in that: The Fe 3+ With Co 2+ The molar ratio is 1.5~2.5:

1.

3. The method for preparing iron-cobalt modified biochar according to claim 1, characterized in that: The carbonization reaction time is 4h~5h.

4. The method for preparing iron-cobalt modified biochar according to claim 1, characterized in that: The heating rate is 5°C / min to 6°C / min.

5. The method for preparing iron-cobalt modified biochar according to claim 1, characterized in that: After the carbonization reaction is completed, a primary product is obtained, which is rinsed and filtered to obtain a black solid. The black solid is washed with ultrapure water until the washing liquid is neutral to obtain a secondary product. The secondary product is dispersed in anhydrous ethanol, dried, and ground to obtain iron-cobalt modified biochar.

6. The method for preparing iron-cobalt modified biochar according to claim 1, characterized in that: The biomass powder is passed through a 60-mesh sieve.

7. Iron-cobalt modified biochar prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the iron-cobalt modified biochar according to claim 7 in removing norfloxacin, characterized in that: The application comprises the following steps: adding iron-cobalt modified biochar to a solution containing norfloxacin for adsorption, and adding a peroxymonosulfate solution for degradation and removal.

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