Fe2O3 composite loquat leaf biochar and its preparation method and application

Abstract

This application relates to the field of organic wastewater treatment technology and specifically discloses an Fe2O3-composite loquat leaf biochar, its preparation method, and application. The preparation method comprises the following steps: drying loquat leaves and crushing them into powder to obtain a precursor; carbonizing the resulting precursor to obtain loquat leaf biochar (TBC); ball milling the TBC to obtain ultrafine particles (MTBC); placing the MTBC and FeCl3·6H2O in a crucible, adding deionized water, stirring, and drying; then heating the crucible to 240-260°C and maintaining the temperature at 50-70°C, washing with water, and drying to obtain the Fe2O3-composite loquat leaf biochar. By organically combining biochar with Fe2O3, the application significantly improves its activation properties and enhances the material's adsorption capacity, thereby increasing the removal rate of 2-fluorophenol (2-FP) from wastewater.

Description

Technical Field

[0001] The present application relates to the technical field of organic wastewater treatment, and more specifically, to a Fe2O3 composite loquat leaf biochar and its preparation method and application. Background Art

[0002] o-Fluorophenol (2-fluorophenol) is an important intermediate in pesticides and agrochemicals, used in the synthesis of fungicides and herbicides, as well as in the synthesis of dye liquids, plastics, and rubber additives. It has caused serious pollution to the aquatic environment. Compared with traditional physical, chemical, and biological treatment methods, advanced oxidation processes (ADPs) offer strong oxidizing power, high reaction rates, and robust resistance to environmental interference. Advanced oxidation technology based on peroxymonosulfate (PMS) is considered an emerging and promising technology for treating organic pollutants. PMS activation can generate sulfate radicals (SO4· - ). Compared with hydroxyl radical (·OH), SO4· - It has advantages such as higher redox potential (2.5-3.1V), longer half-life (30-40μs), and wider acid and alkali resistance range (2.0-8.0), and has broad application prospects in practical applications.

[0003] PMS can be activated through UV, heat, ultrasound, transition metals (Co, Cu, Fe, and Mn), and biochar. Biochar, with its strong adsorption capacity, well-developed pore structure, and high specific surface area, is widely available and diverse in structure, making it a promising candidate for wastewater treatment. Fe₂O₃ has attracted attention for its excellent catalytic properties, non-toxicity, and low cost. The Fe atoms in Fe₂O₃ possess a strong oxygen storage capacity, providing a continuous oxygen supply between the biochar and PMS, ensuring stable activation of the biochar. Biochar, with its large specific surface area and stable graphite structure, can disperse the metal load, preventing metal aggregation and increasing the number of active sites exposed on the biochar surface.

[0004] Therefore, it is of great significance to organically combine biochar with Fe2O3 to prepare biochar-Fe2O3 composite carbon materials, thereby improving the activation effect of biochar on PMS. Summary of the Invention

[0005] In order to organically combine biochar and Fe2O3, the present application provides a Fe2O3 composite loquat leaf biochar, a preparation method and application thereof. The porous biochar prepared thereby has high porosity, abundant surface activation sites and significantly improved degradation rate.

[0006] In the first aspect, the present application provides a method for preparing Fe2O3-composite loquat leaf biochar, which adopts the following technical solution:

[0007] A method for preparing Fe2O3 composite loquat leaf biochar comprises the following steps:

[0008] Step 1: Loquat leaves are washed, dried, and crushed into powder to obtain a precursor, which is then carbonized to obtain loquat leaf biochar (TBC);

[0009] Step 2: ball milling the TBC to obtain ultrafine particles (MTBC);

[0010] Step 3: Put the MTBC and FeCl3·6H2O into a crucible, add deionized water, stir and dry; then, heat to 240-260°C and keep warm for 50-70 minutes, wash with water and dry to obtain Fe2O3 composite loquat leaf biochar.

[0011] By adopting the above technical solution, loquat leaves are used as a biomass carbon source because they are rich in volatile oils, triterpenoids, sesquiterpenes, flavonoids, polyphenols, organic acids and various vitamins, and contain rich carbon skeletons. They can be used as carbon precursors to provide a rich carbon source, and the loquat leaf biochar formed after carbonization will produce a specific mineralogical crystal structure Ca(OH)2. At the same time, due to the mechanical force during the ball milling process, the surface of MTBC is rough and porous, which may provide more specific surface area for the subsequent loading of Fe2O3. During the secondary calcination of MTBC and FeCl3, Ca(OH)2 reacts with CO2 in the air and is converted into CaCO3. FeCl3 is hydrolyzed to be acidic, and the H + Reacts with CaCO3 to generate CO2, which promotes Fe 3+ Converted to Fe(OH)3. At high temperatures, Fe(OH)3 is further converted to Fe2O3 and composited on the biochar surface. The organic combination of biochar and Fe2O3 not only utilizes the rich pore structure and specific surface area of ​​loquat leaf biochar to disperse Fe2O3 particles, preventing their agglomeration and increasing the reactive sites on the loquat leaf biochar surface, but also utilizes the strong hydrogen storage capacity of Fe2O3 to continuously supply oxygen between the carbon material and PMS, ensuring its stable catalytic performance, significantly improving its activation performance, and enhancing the material's adsorption capacity, thereby improving the removal rate of 2-fluorophenol (2-FP) in wastewater.

[0012] In a specific embodiment, the mass ratio of MTBC to FeCl3·6H2O is (1-9): (9-1).

[0013] In a specific embodiment, the mass ratio of MTBC to FeCl3·6H2O is (3-5): (5-7).

[0014] By adopting the above technical solution, FeCl3 is hydrolyzed into acidic state, wherein H +Reacts with CaCO3 to generate CO2, which promotes Fe 3+ Converted to Fe(OH)3. At high temperatures, Fe(OH)3 is further converted to Fe2O3 and composited on the biochar surface. A small amount of FeCl3 forms less Fe2O3. An appropriate amount of FeCl3 can promote hydrolysis to Fe2O3 through reaction with CaCO3, while an excess of FeCl3 reduces the degree of hydrolysis, resulting in a small amount of Fe2O3. The above ratio in this application allows for a greater Fe2O3 loading.

[0015] In a specific embodiment, the step 1 is specifically as follows: the loquat leaves are washed, dried, and crushed into powder to obtain a precursor, and the obtained precursor is heated to 800°C in a tube furnace at a heating rate of 5°C / min in a N2 atmosphere and kept warm for 2 hours to obtain loquat leaf biochar (TBC).

[0016] By adopting the above technical solution, the conditions for preparing biochar, such as temperature and time, have a significant impact on the active organic carbon, ecological characteristics, and trace chemistry of the biochar. Biochar produced at low temperatures produces oxalates, while at high temperatures, it primarily produces carbonates.

[0017] The organic matter content of loquat leaf biochar decreases with increasing carbonization temperature. This is likely due to the accelerated decomposition of organic matter at higher carbonization temperatures, which increases the pyrolysis loss of carbonaceous substances and low-molecular organic compounds in the loquat leaves. Furthermore, the organic matter content of loquat leaf biochar decreases with increasing carbonization time. pH is a key property of biomass carbonization to biochar. Loquat leaf carbonization forms a large amount of carbonates, and its pH increases with increasing carbonization temperature.

[0018] Based on the specific biomass loquat leaves, the inventors optimized the process parameters during the carbonization process to obtain loquat leaf biochar with better physical and chemical properties.

[0019] In a specific embodiment, in step 2, the mass ratio of the TBC to the balls is 1:30.

[0020] By adopting the above technical solution, selecting a suitable ball-to-material mass ratio not only helps to obtain a suitable powder particle size, but also improves the grinding efficiency.

[0021] In a specific embodiment, the method for preparing the Fe2O3 composite loquat leaf biochar comprises the following steps:

[0022] Step 1: Mixing and drying dried and crushed loquat leaves, melamine, and deionized water to obtain a precursor, and carbonizing the obtained precursor to obtain loquat leaf biochar (TBC);

[0023] Step 2: The TBC and the activator are mixed, deionized water is added, and the mixture is heated and ultrasonically activated under a nitrogen atmosphere to obtain material A; material A is added to an acidic solution until neutralized and dried to obtain material B, and material B is ball-milled to obtain ultrafine particles (MTBC);

[0024] Step 3: MTBC and FeCl3·6H2O were placed in a crucible, stirred with deionized water, and dried; subsequently, the temperature was raised to 250°C and kept for 1 hour, and Fe2O3 composite loquat leaf biochar was obtained after washing and drying.

[0025] By adopting the above technical solution, ultrasonic activation can not only make biochar have a porous structure and a higher specific surface area, but also reduce the use of activator. The activator can produce a large number of micropores due to its etching effect. Melamine decomposes under nitrogen and high temperature conditions to produce a large amount of gas. During the activation process, mesopores and macropores are formed as the nitrogen flow leaves, so that a multi-level pore structure is formed on the TBC surface, allowing iron ions to better enter the pores of the biochar material, forming more adsorption sites on the biochar surface, improving the adsorption capacity of the material, and thus improving the removal rate of 2-fluorophenol (2-FP) in wastewater.

[0026] In a specific embodiment, the activator is a mixture of KOH, polyethylene glycol-modified cyclodextrin, and thiourea in a mass ratio of 5:(1-4):(1-4).

[0027] By adopting the above technical scheme, polyethylene glycol-modified cyclodextrin can effectively improve the problem of poor water solubility of cyclodextrin, which is conducive to a more uniform distribution of the activator in TBC. Polyethylene glycol has a pore-forming effect and can form new pores in situ on biochar to alternately compound with the original pores of biochar, which not only increases the pore diameter, but also forms a larger number of pores. At the same time, combined with the effect of KOH, the mesopore distribution amount is increased. The pyrolysis of cyclodextrin increases the micropore volume of the carbon material, so that macropores, mesopores and micropores are alternately distributed, and the biochar has multi-level pore size and high specific surface area; thiourea provides nitrogen and sulfur sources, and through high-temperature thermal cracking, nitrogen atoms and sulfur atoms are doped in porous carbon, which can effectively change the morphology, structure and chemical properties of the carbon material, thereby improving the adsorption and separation effect of the material, thereby improving the adsorption capacity of the carbon material.

[0028] In a specific implementation plan, the step three is specifically as follows: MTBC and FeCl3·6H2O of different mass ratios (10:0, 9:1, 7:3, 5:5, 3:7, 1:9, 0:10) are placed in a crucible, deionized water is added and stirred for 12 hours, and then placed in a vacuum drying oven to dry at 60°C; then, the temperature is increased to 250°C in a tube furnace at a heating rate of 5°C / min in an air atmosphere and kept warm for 1 hour; after washing and drying, Fe2O3 composite loquat leaf biochar is obtained and named MTBC-x (x=0, 1, 3, 5, 7, 9, 10), where x represents the proportion of FeCl3·6H2O during the preparation process.

[0029] In a second aspect, the present application provides a Fe2O3 composite loquat leaf biochar, which adopts the following technical solution:

[0030] A Fe2O3 composite loquat leaf biochar is prepared by adopting the above preparation method.

[0031] By adopting the above technical solution, the preparation method of loquat leaf biochar involved in the present invention is simple, reliable, easy to control, low cost, and Fe2O3 is non-toxic and will not cause pollution to humans and the ecological environment.

[0032] In a third aspect, the present application provides an application of Fe2O3 composite loquat leaf biochar, using the following technical solution:

[0033] A Fe2O3-composite loquat leaf biochar, combined with PMS, is used to degrade 2-FP in organic wastewater.

[0034] By adopting the above technical solution, the Fe2O3 composite loquat leaf biochar prepared in this application has a high removal rate for 2-FP in organic wastewater.

[0035] In summary, this application has the following beneficial effects:

[0036] 1. This application forms Fe2O3 composite loquat leaf biochar by effectively combining loquat leaf biochar with Fe2O3. This can not only utilize the rich pore structure and specific surface area of ​​biochar to disperse Fe2O3 particles, prevent their agglomeration and increase the reactive sites on the surface of biochar, but also utilize the strong hydrogen storage capacity of Fe2O3 to continuously supply oxygen between the carbon material and PMS, ensuring its stable catalytic performance, significantly improving its activation performance, and enhancing the adsorption capacity of the material.

[0037] 2. This application activates loquat leaf biochar by combining ultrasonic physics and activator chemistry to give the biochar a porous structure and a high specific surface area. At the same time, the activator can produce a large number of micropores due to its etching effect. Melamine decomposes under nitrogen and high temperature conditions, producing a large number of small molecules that leave with the nitrogen flow during the activation process, forming mesopores and macropores. This creates a multi-level pore structure on the TBC surface, allowing iron ions to better enter the pores of the biochar material, forming more adsorption sites on the biochar surface, and improving the adsorption capacity of the material.

[0038] 3. The activator of this application utilizes KOH, polyethylene glycol-modified cyclodextrin and thiourea, which interact with each other to jointly improve the adsorption effect of the carbon material;

[0039] 4. The preparation method of loquat leaf biochar of the present application is simple, reliable, easy to control, low-cost, and Fe2O3 is non-toxic and will not cause pollution to humans and the ecological environment;

[0040] 5. The Fe2O3 composite loquat leaf biochar prepared in this application has a high removal rate for 2-FP in organic wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Figure (a) is a 5000x magnified SEM image of MTBC in Example 3; Figure (b) is a 5000x magnified SEM image of MTBC-5 in Example 3; Figure (c) is a 50x magnified SEM image of MTBC-5 in Example 3;

[0042] Figure 2 XRD patterns of TBC, MTBC, MTBC-0, MTBC-1, MTBC-3, MTBC-5, MTBC-7, MTBC-9, and MTBC-10 in Examples 1-5 and Comparative Examples 1-2;

[0043] Figure 3 The time-degradation graph of MTBC-x / PMS system for 2-FP in Examples 1-5 and Comparative Examples 1-2;

[0044] Figure 4 This is the time-degradation diagram of different organic pollutants in organic wastewater by the MTBC-5 / PMS system in Example 3;

[0045] Figure 5 This is the time-degradation graph of 2-FP in organic wastewater with different pH values ​​by the MTBC-5 / PMS system in Example 3;

[0046] Figure 6 This is the time-degradation graph of 2-FP by the MTBC-5 / PMS system in the presence of different ions in Example 3;

[0047] Figure 7 This is the time-degradation diagram of 2-FP in the MTBC-5 / PMS system in three cycle tests in Example 3. DETAILED DESCRIPTION

[0048] The following examples and appendix Figure 1-7 The present application is further described in detail. The raw materials involved in the present application can be obtained commercially.

[0049] Example

[0050] Example 1

[0051] In this embodiment, Fe2O3 composite loquat leaf biochar was prepared according to the following steps:

[0052] (1) 10 g of loquat leaves were washed, dried, and crushed into powder to obtain a precursor. The precursor was heated to 800 °C in a tube furnace at a heating rate of 5 °C / min under a nitrogen atmosphere and kept at this temperature for 2 h to obtain loquat leaf biochar (TBC).

[0053] (2) 10 g of TBC (TBC to ball mass ratio of 1:30) was mechanically ground in a planetary ball mill equipped with a ball mill at a speed of 500 r / min for 4 h to obtain ultrafine particles (MTBC);

[0054] (3) 1.8 g of MTBC and 0.2 g of FeCl3·6H2O were added to 4 mL of deionized water and stirred for 12 h. The mixture was then dried in a vacuum drying oven at 60 °C. Subsequently, the temperature was increased to 250 °C in a tube furnace at a heating rate of 5 °C / min in air atmosphere and kept at this temperature for 1 h. MTBC-1 was obtained after washing and drying.

[0055] Example 2

[0056] The difference between this embodiment and embodiment 1 is that in step (3), 1.4 g of MTBC and 0.6 g of FeCl3·6H2O were added to 4 mL of deionized water, stirred for 12 h, and then placed in a vacuum drying oven to dry at 60°C; then, the temperature was increased to 250°C in a tube furnace at a heating rate of 5°C / min in an air atmosphere and kept at this temperature for 1 h; and MTBC-3 was obtained after washing and drying.

[0057] Example 3

[0058] The difference between this embodiment and embodiment 1 is that, in step (3), 1 g of MTBC and 1 g of FeCl3·6H2O were added to 4 mL of deionized water, stirred for 12 h, and then placed in a vacuum drying oven to dry at 60°C; then, the mixture was heated to 250°C in a tube furnace at a heating rate of 5°C / min in an air atmosphere and kept at this temperature for 1 h; and MTBC-5 was obtained after washing with water and drying.

[0059] Example 4

[0060] The difference between this embodiment and embodiment 1 is that in step (3), 0.6 g of MTBC and 1.4 g of FeCl3·6H2O were added to 4 mL of deionized water, stirred for 12 h, and then placed in a vacuum drying oven to dry at 60°C; then, the temperature was increased to 250°C in a tube furnace at a heating rate of 5°C / min in an air atmosphere and kept at this temperature for 1 h; and MTBC-7 was obtained after washing with water and drying.

[0061] Example 5

[0062] The difference between this embodiment and embodiment 1 is that in step (3), 0.2 g of MTBC and 1.8 g of FeCl3·6H2O were added to 4 mL of deionized water, stirred for 12 h, and then placed in a vacuum drying oven to dry at 60°C; then, the temperature was increased to 250°C in a tube furnace at a heating rate of 5°C / min in an air atmosphere and kept at this temperature for 1 h; and MTBC-9 was obtained after washing with water and drying.

[0063] Example 6

[0064] In this embodiment, Fe2O3 composite loquat leaf biochar was prepared according to the following steps:

[0065] (1) 10 g of loquat leaves were washed, dried, crushed into powder, mixed with 20 g of melamine, and added with 60 ml of deionized water to mix thoroughly. After standing at room temperature for 12 h, the mixture was transferred to a 105 °C forced air drying oven and dried for 12 h to obtain a precursor. The obtained precursor was heated to 800 °C in a tube furnace at a heating rate of 5 °C / min in a nitrogen atmosphere and kept at this temperature for 2 h to obtain porous loquat leaf biochar (P-TBC);

[0066] (2) 10 g of P-TBC was mixed with 4 g of active agent (2 g of KOH solid, 0.4 g of polyethylene glycol-modified cyclodextrin and 1.6 g of thiourea) in a reaction vessel, and then 100 ml of deionized water was added and stirred thoroughly to mix. The mixture was allowed to stand at room temperature for 10 h to obtain a mixture. The mixture was ultrasonically treated at a frequency of 50 kHz, a power of 500 W, a time of 10 h, and a temperature of 50 ° C. The mixture was heated from room temperature to 700 ° C at a heating rate of 5 ° C / min for 2 h under the protection of nitrogen gas and then naturally cooled to room temperature to obtain material A. Material A was transferred to a reaction vessel and a molar concentration of 1% was added. The mixture was immersed in a 2 mol / L hydrochloric acid solution for 12 hours, then washed with high-purity water until the pH of the filtrate was neutral, and then dried at 105°C for 12 hours to obtain material B. 10 g of material B (mass ratio of material B to balls was 1:30) was mechanically ground in a planetary ball mill equipped with a ball mill at 500 rpm for 4 hours to obtain ultrafine particles (P-MTBC). The polyethylene glycol-modified cyclodextrin was prepared by dissolving 4.5 g of β-cyclodextrin in 50 ml of water at 65°C, mixing, then adding 8 g of PEG (molecular weight 2000), stirring for 1 hour, and allowing to stand. The precipitate was vacuum filtered and then vacuum dried at 30°C to constant weight.

[0067] (3) 1 g of P-MTBC and 1 g of FeCl3·6H2O were added to 4 mL of deionized water and stirred for 12 h. The mixture was then dried in a vacuum drying oven at 60 °C. Subsequently, the mixture was heated to 250 °C in an air atmosphere at a heating rate of 5 °C / min in a tube furnace and kept at this temperature for 1 h. P-MTBC was obtained after washing and drying.

[0068] Example 7

[0069] The only difference between this embodiment and embodiment 6 is that, in step (2), 10 g of P-TBC and 4 g of active agent (2 g of KOH solid, 1.2 g of polyethylene glycol-modified cyclodextrin and 0.8 g of thiourea) are mixed in a reaction vessel, 100 ml of deionized water is added and the mixture is thoroughly stirred and mixed, and the mixture is allowed to stand at room temperature for 10 h to obtain a mixture; the mixture is ultrasonically treated at a frequency of 50 kHz, a power of 500 W, a time of 10 h, and a temperature of 50°C and is heated at 5°C / m The heating rate of in was increased from room temperature to 700°C for activation treatment for 2 hours, and then naturally cooled to room temperature to obtain material A; material A was transferred to a reaction vessel and added with a hydrochloric acid solution with a molar concentration of 2 mol / L and soaked for 12 hours, then washed with high-purity water until the pH of the filtrate was neutral, and then dried at 105°C for 12 hours to obtain material B; 10 g of material B (the mass ratio of material B to balls was 1:30) was mechanically ground at a speed of 500 r / min in a planetary ball mill equipped with a ball milling jar for 4 hours to obtain ultrafine particles (P-MTBC).

[0070] Example 8

[0071] The only difference between this embodiment and embodiment 6 is that, in step (2), 10 g of P-TBC and 4 g of active agent (2 g of KOH solid, 1.6 g of polyethylene glycol-modified cyclodextrin and 0.4 g of thiourea) are mixed in a reaction vessel, 100 ml of deionized water is added and the mixture is thoroughly stirred and mixed, and the mixture is allowed to stand at room temperature for 10 h to obtain a mixture; the mixture is ultrasonically treated at a frequency of 50 kHz, a power of 500 W, a time of 10 h, and a temperature of 50°C, and is heated at 5°C / m The heating rate of in was increased from room temperature to 700°C for activation treatment for 2 hours, and then naturally cooled to room temperature to obtain material A; material A was transferred to a reaction vessel and added with a hydrochloric acid solution with a molar concentration of 2 mol / L and soaked for 12 hours, then washed with high-purity water until the pH of the filtrate was neutral, and then dried at 105°C for 12 hours to obtain material B; 10 g of material B (the mass ratio of material B to balls was 1:30) was mechanically ground at a speed of 500 r / min in a planetary ball mill equipped with a ball milling jar for 4 hours to obtain ultrafine particles (P-MTBC).

[0072] Example 9

[0073] The only difference between this embodiment and embodiment 6 is that in step (1), 10 g of loquat leaves were washed, dried, crushed into powder, and added with 20 ml of deionized water to mix thoroughly. The mixture was then allowed to stand at room temperature for 12 h and then transferred to a 105°C forced air drying oven for 12 h to obtain a precursor. The obtained precursor was heated to 800°C in a tube furnace at a heating rate of 5°C / min in an N2 atmosphere and kept at this temperature for 2 h to obtain loquat leaf biochar (TBC).

[0074] Example 10

[0075] The only difference between this embodiment and embodiment 6 is that, in step (2), 10 g of P-TBC and 4 g of active agent (2 g of KOH solid and 2 g of polyethylene glycol-modified cyclodextrin) were mixed in a reaction vessel, 100 ml of deionized water was added and the mixture was thoroughly stirred and mixed, and the mixture was allowed to stand at room temperature for 10 h to obtain a mixture; the mixture was ultrasonically treated at a frequency of 50 kHz, a power of 500 W, a time of 10 h, and a temperature of 50°C, and the mixture was heated at a rate of 5°C / min under the protection of nitrogen gas. The temperature was raised from room temperature to 700°C for activation treatment for 2 hours, and then naturally cooled to room temperature to obtain material A; material A was transferred to a reaction vessel and added with a hydrochloric acid solution with a molar concentration of 2 mol / L to soak for 12 hours, then washed with high-purity water until the pH of the filtrate was neutral, and then dried at 105°C for 12 hours to obtain material B; 10 g of material B (the mass ratio of material B to balls was 1:30) was mechanically ground at a speed of 500 r / min for 4 hours in a planetary ball mill equipped with a ball milling jar to obtain ultrafine particles (P-MTBC).

[0076] Example 11

[0077] The only difference between this embodiment and embodiment 6 is that, in step (2), 10 g of P-TBC and 4 g of active agent (2 g of KOH solid and 2 g of thiourea) were mixed in a reaction vessel, 100 ml of deionized water was added and the mixture was thoroughly stirred and mixed, and the mixture was allowed to stand at room temperature for 10 h to obtain a mixture; the mixture was ultrasonically treated at a frequency of 50 kHz, a power of 500 W, a time of 10 h, and a temperature of 50°C, and the temperature was increased at a rate of 5°C / min from 0.5 to 1.5 °C under the protection of nitrogen gas. The room temperature was heated to 700°C for activation treatment for 2 hours, and then naturally cooled to room temperature to obtain material A; material A was transferred to a reaction vessel and added with a hydrochloric acid solution with a molar concentration of 2 mol / L and soaked for 12 hours, then washed with high-purity water until the pH of the filtrate was neutral, and then dried at 105°C for 12 hours to obtain material B; 10 g of material B (the mass ratio of material B to balls was 1:30) was mechanically ground in a planetary ball mill equipped with a ball mill at a speed of 500 r / min for 4 hours to obtain ultrafine particles (P-MTBC).

[0078] Example 12

[0079] The only difference between this embodiment and embodiment 6 is that, in step (2), 10 g of P-TBC and 4 g of active agent (2 g of polyethylene glycol-modified cyclodextrin and 2 g of thiourea) were mixed in a reaction vessel, 100 ml of deionized water was added and the mixture was thoroughly stirred and mixed, and the mixture was allowed to stand at room temperature for 10 h to obtain a mixture; the mixture was ultrasonically treated at a frequency of 50 kHz, a power of 500 W, a time of 10 h, and a temperature of 50°C, and the temperature was increased at a rate of 5°C / min under the protection of nitrogen gas. The temperature was raised from room temperature to 700°C for activation treatment for 2 hours, and then naturally cooled to room temperature to obtain material A; material A was transferred to a reaction vessel and added with a hydrochloric acid solution with a molar concentration of 2 mol / L to soak for 12 hours, then washed with high-purity water until the pH of the filtrate was neutral, and then dried at 105°C for 12 hours to obtain material B; 10 g of material B (the mass ratio of material B to balls was 1:30) was mechanically ground at a speed of 500 r / min for 4 hours in a planetary ball mill equipped with a ball milling jar to obtain ultrafine particles (P-MTBC).

[0080] Example 13

[0081] The only difference between this embodiment and embodiment 6 is that, in step (2), 10 g of P-TBC and 4 g of active agent (2 g of KOH solid, 0.2 g of polyethylene glycol, 0.2 g of cyclodextrin and 1.6 g of thiourea) were mixed in a reaction vessel, 100 ml of deionized water was added and the mixture was thoroughly stirred and mixed, and the mixture was allowed to stand at room temperature for 10 h to obtain a mixture, and the mixture was ultrasonically treated at a frequency of 50 kHz, a power of 500 W, a time of 10 h, and a temperature of 50°C and under the protection of nitrogen gas at 5°C / min. The material A was activated by heating from room temperature to 700°C at a heating rate of 10.5 min for 2 h, and then naturally cooled to room temperature to obtain material A. Material A was transferred to a reaction vessel and soaked in a hydrochloric acid solution with a molar concentration of 2 mol / L for 12 h, then washed with high-purity water until the pH of the filtrate was neutral, and then dried at 105°C for 12 h to obtain material B. 10 g of material B (the mass ratio of material B to balls was 1:30) was mechanically ground at a speed of 500 r / min for 4 h in a planetary ball mill equipped with a ball milling jar to obtain ultrafine particles (P-MTBC).

[0082] Example 14

[0083] The only difference between this embodiment and embodiment 6 is that, in step (2), 10 g of P-TBC and 4 g of active agent (2 g of KOH solid, 0.4 g of polyethylene glycol-modified cyclodextrin and 1.6 g of thiourea) are mixed in a reaction vessel, 100 ml of deionized water is added and the mixture is thoroughly stirred and mixed, and the mixture is allowed to stand at room temperature for 10 h to obtain a mixture, the mixture is heated from room temperature to 700° C. at a heating rate of 5° C. / min under the protection of nitrogen gas for activation treatment for 2 h, and then naturally cooled to room temperature to obtain material A; material A is transferred to a reaction vessel and added with a hydrochloric acid solution with a molar concentration of 2 mol / L and soaked for 12 h, then washed with high-purity water until the pH of the filtrate is neutral, and then dried at 105° C. for 12 h to obtain material B; 10 g of material B (the mass ratio of material B to balls is 1:30) is mechanically ground at a speed of 500 r / min for 4 h in a planetary ball mill equipped with a ball milling jar to obtain ultrafine particles (P-MTBC).

[0084] Example 15

[0085] The only difference between this example and Example 6 is that in step (2), 10 g of P-TBC (the mass ratio of P-TBC to balls is 1:30) is mechanically ground in a planetary ball mill equipped with a ball mill at a speed of 500 r / min for 4 h to obtain ultrafine particles (P-MTBC).

[0086] Comparative Example

[0087] Comparative Example 1

[0088] The difference between this comparative example and Example 1 is that in step (3), 2 g of MTBC was added to 4 mL of deionized water, stirred for 12 h, and then placed in a vacuum drying oven to dry at 60°C; then, the temperature was increased to 250°C in a tube furnace at a heating rate of 5°C / min in an air atmosphere and kept at this temperature for 1 h; MTBC-0 was obtained after washing with water and drying.

[0089] Comparative Example 2

[0090] This comparative example differs from Example 1 in that MTBC-10 was prepared according to the following steps: 2 g of FeCl₃·6H₂O was added to 4 mL of deionized water, stirred for 12 hours, and then dried in a vacuum drying oven at 60°C. Subsequently, the temperature was increased in a tube furnace at a rate of 5°C / min to 250°C under air atmosphere and maintained at this temperature for 1 hour. MTBC-10 was then washed and dried to obtain the product. It should be understood that MTBC-10 in this example was prepared for data processing purposes and does not contain MTBC itself.

[0091] Characterization and performance testing

[0092] 1. Surface morphology of biochar was observed by field emission scanning electron microscopy

[0093] Scanning electron microscopy (SEM) images of MTBC and MTBC-5 in Example 3 are shown in FIG. Figure 1 As shown in Figures (a) and (b), the MTBC surface is rough and porous due to the mechanical forces during ball milling, potentially providing more surface area for subsequent Fe loading. In contrast, the surface of MTBC-5 is smooth and contains numerous tiny protrusions, which is due to the Fe modification occupying the pores of the MTBC. Furthermore, distinct Fe₂O₃ particles can be observed on the MTBC-5 surface, demonstrating the successful incorporation of Fe₂O₃ onto the MTBC surface. Transmission electron microscopy (TEM) also confirms the successful preparation of the composite biochar. As shown in Figure (c), calculated lattice spacing of MTBC-5 is 0.368 nm, corresponding to the (0 1 2) crystal plane of Fe₂O₃, indicating a tight bond between Fe₂O₃ and MTBC.

[0094] 2. The crystal structure characteristics of biochar were analyzed by X-ray diffractometer (XRD)

[0095] The XRD patterns of TBC, MTBC, MTBC-0, MTBC-1, MTBC-3, MTBC-5, MTBC-7, MTBC-9 and MTBC-10 in Examples 1-5 and Comparative Examples 1-2 are as follows: Figure 2 As shown. The diffraction peaks at 18.1°, 28.7°, 34.2°, 47.2°, 50.9°, and 54.5° for TBC and MTBC correspond to different crystal planes of Ca(OH)2, which is attributed to the specific mineralogical crystal structure of loquat leaf biochar. In contrast, the diffraction peaks at 23.1°, 29.4°, 36.0°, 39.4°, 43.2°, 47.5°, and 48.5° for MTBC-0, MTBC-1, and MTBC-3 belong to different crystal planes of CaCO3. The main reason for this change is that during the secondary calcination process, Ca(OH)2 reacts with CO2 in the air and is converted into CaCO3. In addition, the diffraction peaks of Fe2O3 can be observed at 24.1°, 33.1°, 35.6°, 40.8°, 49.4°, 54.0°, 62.4° and 63.9° in MTBC-5 and MTBC-7, which is consistent with the results of electron microscopy. + Reacts with CaCO3 to generate CO2, which promotes Fe 3+Converted to Fe(OH)3. At high temperatures, Fe(OH)3 further converts to Fe2O3, which forms a complex on the biochar surface. This also explains the disappearance of the CaCO3 diffraction peak in the XRD patterns of MTBC-5 and MTBC-7. A small amount of FeCl3 cannot form Fe2O3. An appropriate amount of FeCl3 can promote hydrolysis to Fe2O3 through reaction with CaCO3, while an excessive amount of FeCl3 reduces the degree of hydrolysis and prevents the formation of Fe2O3.

[0096] 3. Test of catalytic adsorption performance of biochar

[0097] 1. The removal efficiency of 2-fluorophenol (2-FP) by the prepared catalyst MTBC-x with different iron-carbon ratios is as follows Figure 3 As shown. All MTBC-x showed different degrees of adsorption effect on 2-FP, and with the gradual increase of the iron-carbon ratio, the ability of MTBC-x to activate PMS to degrade 2-FP showed a trend of first increasing and then decreasing. Compared with PMS (11.4%), TBC / PMS (12.3%), MTBC / PMS (13.5%) and Fe2O3 / PMS (28.6%) systems, the MTBC-5 / PMS system had the best effect, which could remove 97.3% of 2-FP within 15 minutes (19.1% was removed by pre-adsorption in the first 30 minutes). In addition, as Figure 4 , the system can also maintain good removal effects on other common organic pollutants (RhB, NPX, DCF and TC).

[0098] 2. To evaluate the application of the MTBC-5 / PMS system in actual wastewater, the initial pH of the 2-FP solution was adjusted, and common anions and natural macromolecular organic matter humic acid (HA) were introduced. Figure 5 The removal of 2-FP was not affected in the pH range of 3-9, and even showed a slight promotion effect. It was only significantly inhibited at pH 11, with the removal rate dropping to 47.3%. This is mainly due to the inactivation of Fe sites by converting to Fe(OH)3 in a strong alkaline environment and the self-decomposition of PMS into SO5 with a lower oxidation potential. 2- .

[0099] 3. Such as Figure 6 , add 10 mM Cl - It has almost no effect on the degradation of 2-FP. - The slight decrease in removal efficiency (7.7%) under the presence of SO4 was also attributed to the slight inhibition of the pre-adsorption process (8.3%). 2-The negligible inhibitory effect of H2PO4 may be due to the fact that sulfate enters the pore structure of the catalyst, which increases the negative charge on the surface of MTBC-5 and generates electrostatic repulsion with PMS, reducing the utilization rate of PMS. - The introduction of H2PO4 and HA reduced the removal efficiency by 17.3% and 23.1%, respectively. - It can form complexes with Fe sites, while HA is easily adsorbed on the catalyst surface to cover the reaction sites. 2- and HCO3 - Significantly inhibit the reaction. Among them, HCO3 - Promote the adsorption, on the contrary, CO3 2- It shows inhibition of the adsorption process. This is also the reason for the difference in pollutant removal rates between them. 2- and HCO 3- It will increase the pH of the solution, and alkaline conditions are not conducive to the degradation of 2-FP.

[0100] 4. Secondary pollution caused by metal dissolution is a common problem of metal-based catalysts. Figure 7 After three cycles, MTBC-5 achieved a 52.4% 2-FP removal rate, with metal release remaining well below the national standard of 0.3 mg / L. This demonstrates its reusability and environmental impact.

[0101] 5. In a 250 ml beaker, with continuous magnetic stirring at 500 rpm at room temperature, a certain amount of PMS was added to 100 ml of 2-FP solution (CO 20 mg / L), and then the Fe2O3 composite loquat leaf biochar prepared in Examples 3 and 6-15 was immediately added to initiate the reaction. Samples were taken every 0.5 ml and immediately quenched with 0.5 ml of methanol. The samples were filtered through a 0.45 μm filter membrane and then quantified by HPLC. The 2-FP concentration C in the examples was determined at 1093 min using a high performance liquid chromatograph (HPLC, RIGOL L-3000, Beijing, China) equipped with an Agilent C18 column (150 mm × 4.6 mm, 5 μm). The C / CO value corresponding to each example was calculated. The results are shown in Table 1.

[0102] Table 1 Performance test data of Example 3 and Examples 6-15

[0103]

[0104] Combining Example 3 and Example 6 and referring to Table 1, it can be seen that the present application activates the loquat leaf biochar to form a multi-level pore structure on the TBC surface, so that iron ions can better enter the pores of the biochar material, and more adsorption sites are formed on the biochar surface, thereby improving the adsorption capacity of the material.

[0105] In combination with Example 6 and Example 9 and with reference to Table 1, it can be seen that when the loquat leaf biochar is activated in the present application, the activator and melamine have a mutually promoting effect on the activation of the loquat leaf biochar. The activator can produce a large number of micropores due to its etching effect. Melamine decomposes under nitrogen and high temperature conditions to produce a large amount of gas. During the activation process, it leaves with the nitrogen flow to form mesopores and macropores, so that a multi-level pore structure is formed on the surface of the TBC, so that iron ions can better enter the pores of the biochar material, and more adsorption sites are formed on the surface of the biochar, thereby improving the adsorption capacity of the material.

[0106] Combining Example 6 with Examples 10-12 and referring to Table 1, it can be seen that the activator of the present application utilizes KOH, polyethylene glycol-modified cyclodextrin and thiourea to exert a synergistic effect, thereby jointly improving the adsorption effect of the carbon material.

[0107] Combining Example 6 and Example 13 and referring to Table 1, it can be seen that the use of polyethylene glycol-modified cyclodextrin in the activator of the present application makes up for the poor water solubility of cyclodextrin by utilizing the good water solubility of polyethylene glycol. Compared with the addition of polyethylene glycol and cyclodextrin separately, the water solubility is better, the activation effect is improved, and thus the adsorption of biochar is improved.

[0108] From Example 6 and Examples 14-15 and referring to Table 1, it can be seen that when activating loquat leaf biochar, the present application utilizes the principle of combining ultrasonic physics and activator chemistry to make the biochar have a porous structure and a higher specific surface area, thereby further improving the adsorption capacity of the biochar.

[0109] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing Fe2O3 composite loquat leaf biochar, characterized in that: The following steps are involved: Step 1: Powder obtained by drying and crushing loquat leaves, melamine, and deionized water are mixed and dried to obtain a precursor, and the obtained precursor is carbonized to obtain loquat leaf biochar (TBC); Step 2: The TBC is mixed with an activator, deionized water is added, and the mixture is heated and activated under a nitrogen atmosphere to obtain material A; material A is added to an acidic solution until neutralized and dried to obtain material B, and material B is ball-milled to obtain ultrafine particles (MTBC); The activator is a mixture of KOH, polyethylene glycol-modified cyclodextrin and thiourea in a mass ratio of 5:(1-4):(1-4); Step 3: Put the MTBC and FeCl3·6H2O into a crucible, add deionized water, stir and dry; then, heat to 250°C and keep warm for 1 hour, wash and dry to obtain Fe2O3 composite loquat leaf biochar; The mass ratio of the MTBC to FeCl 3 ·6H 2 O is (1-9): (9-1).

2. The method for preparing Fe2O3 composite loquat leaf biochar according to claim 1, characterized in that: The mass ratio of the MTBC to FeCl 3 ·6H 2 O is (3-5): (5-7).

3. The method for preparing Fe2O3 composite loquat leaf biochar according to claim 1, characterized in that: In the step 1, the obtained precursor is heated to 800° C. in a tube furnace at a heating rate of 5° C. / min under a N 2 atmosphere and kept at this temperature for 2 h to obtain loquat leaf biochar (TBC).

4. The method for preparing Fe2O3 composite loquat leaf biochar according to claim 1, characterized in that: In the step 2, during the ball milling, the mass ratio of material B to balls is 1:

30.

5. The method for preparing Fe2O3 composite loquat leaf biochar according to claim 1, characterized in that: The third step is specifically as follows: MTBC and FeCl3·6H2O are placed in a crucible, deionized water is added, stirred for 12 hours, and then placed in a vacuum drying oven for drying at 60°C; then, the temperature is increased to 250°C in a tube furnace at a heating rate of 5°C / min in an air atmosphere and kept at this temperature for 1 hour; and Fe2O3 composite loquat leaf biochar is obtained after washing and drying.

6. A Fe2O3 composite loquat leaf biochar, characterized in that: The biochar is prepared by the preparation method of Fe2O3 composite loquat leaf biochar according to any one of claims 1 to 5.

7. An application of Fe2O3 composite loquat leaf biochar, characterized in that: The Fe2O3 composite loquat leaf biochar described in claim 6 is used in combination with PMS to degrade 2-FP in organic wastewater.

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