MnFeO / BC / g-CNphotocatalytic material with visible-light response and preparation method of MnFeO / BC / g-CNphotocatalytic material

Abstract

The invention discloses a MnFeO / BC / g-CN photocatalytic material with visible light response and a preparation method thereof, and belongs to the technical field of photocatalytic materials. The method comprises the following steps: firstly, calcining straw-derived biochar (BC) as a carrier together with a manganese source and an iron source by adopting a calcining method to prepare a MnFeO / BC composite material; and loading the MnFeO / BC composite material on graphite-phase carbon nitride (g-CN) through a hydrothermal method to form the ternary composite photocatalytic material. The preparation method effectively solves the problems of easy agglomeration of single MnFeO, low utilization rate of g-CNvisible light and fast carrier recombination. The obtained ternary composite material has excellent visible light response performance, MnFeO, BC and g-CN have a synergistic effect, separation and transmission of photo-induced electron-hole pairs are promoted, and the efficiency of photocatalytic degradation of organic pollutants is remarkably improved; meanwhile, the material has magnetism, can be quickly recycled and recycled through an external magnet, and has a wide application prospect in the field of water treatment.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic materials technology, specifically to a composite photocatalytic material for water treatment with visible light response and its preparation method, particularly a MnFeO2 / BC / g-C3N4 composite material. Background Technology

[0002] Semiconductor-based photocatalysis technology has attracted much attention due to its great potential in the degradation of organic pollutants. However, single-component photocatalysts often suffer from problems such as rapid recombination rates of photogenerated electron-hole pairs, low visible light utilization, easy aggregation, and difficulty in recycling, which limit their practical applications.

[0003] MnFeO2 is a magnetic material with a narrow band gap and good response to visible light, but its small specific surface area makes it prone to aggregation in water, leading to a reduction in active sites. Biochar (BC), derived from biomass, has the advantages of large specific surface area, abundant functional groups, and low cost, and is often used as a catalyst support, but its photocatalytic activity is limited. Graphitic carbon nitride (g-C3N4) is a stable polymer semiconductor, but it has a small specific surface area and rapid carrier recombination.

[0004] Currently, there are no reports on constructing a ternary magnetic photocatalytic system by first loading MnFeO2 onto BC and then combining it with g-C3N4. Therefore, developing a composite material that can synergistically leverage the advantages of all three components and possesses both high catalytic activity and easy recyclability is of significant practical importance. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a MnFeO2 / BC / g-C3N4 photocatalytic material with visible light response and its preparation method. This material can effectively inhibit the aggregation of MnFeO2, improve the utilization rate of visible light and the separation efficiency of photogenerated carriers, and has magnetic recovery capability.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a MnFeO2 / BC / g-C3N4 photocatalytic material with visible light response, characterized by comprising the following steps: S1. Dissolve Mn²⁺ salt, Fe³⁺ salt and biomass carbon source in deionized water, stir and mix, and then freeze dry to obtain a solid precursor; S2. The solid precursor is calcined in an inert atmosphere, cooled, washed, and dried to obtain the MnFeO2 / BC composite material; S3. Disperse g-C3N4 in deionized water to form a dispersion, then add the MnFeO2 / BC composite material, and after ultrasonic dispersion and oscillation mixing, obtain a mixture; S4. The mixture is subjected to a hydrothermal reaction, and the reaction product is washed and dried to obtain the MnFeO2 / BC / g-C3N4 photocatalytic material.

[0007] Furthermore, the Mn²⁺ salt is manganese acetate tetrahydrate, the Fe³⁺ salt is ferric nitrate nonahydrate, and the biomass carbon source is ginger straw powder.

[0008] Furthermore, in step S1, the freeze-drying temperature is -80℃; in step S2, the calcination conditions are: under a nitrogen atmosphere, the temperature is increased to 750℃ at a rate of 5℃ / min and held for 6 hours.

[0009] Furthermore, in step S3, the mass ratio of g-C3N4 to MnFeO2 / BC is 1:1 to 15:1.

[0010] Furthermore, the mass ratio of g-C3N4 to MnFeO2 / BC is 10:1.

[0011] Furthermore, in step S3, the ultrasonic dispersion time of g-C3N4 in deionized water is 3 hours; after adding MnFeO2 / BC, it is first ultrasonically treated for 0.5 hours, and then oscillated for 12 hours.

[0012] Furthermore, in step S4, the conditions for the hydrothermal reaction are: temperature 180℃, pressure 2-3MPa, and reaction time 2h.

[0013] Furthermore, the g-C3N4 is prepared by the following method: melamine is heated to 550°C at a rate of 5°C / min and calcined for 4 hours in an air atmosphere, and then cooled, washed, dried and ground.

[0014] Furthermore, the ginger straw powder is obtained by washing and drying air-dried ginger straw, then crushing it and passing it through an 80-mesh sieve.

[0015] Furthermore, the present invention provides a visible light responsive MnFeO2 / BC / g-C3N4 photocatalytic material prepared by the above preparation method.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: Ternary synergistic enhancement: By first loading MnFeO2 onto BC with a large specific surface area and then combining it with g-C3N4, a heterojunction structure is formed. This structure effectively inhibits the aggregation of MnFeO2 particles and the stacking of g-C3N4 sheets, exposes more active sites, and promotes the transfer of photogenerated electrons between interfaces, significantly reducing the recombination rate of electron-hole pairs, thereby improving the photocatalytic efficiency under visible light.

[0017] Easy to recycle: Due to the magnetic properties of MnFeO2, the final ternary composite material is also magnetic. After the photocatalytic reaction is completed, it can be quickly separated and recovered from the water using an external magnet, greatly improving the catalyst's recyclability and practicality.

[0018] Green and economical: BC is derived from waste biomass (such as straw), realizing resource reuse, reducing catalyst costs, and meeting the requirements of green chemistry and sustainable development.

[0019] The preparation method is controllable: The calcination-hydrothermal process used in this invention is mature, the parameters are controllable, and the repeatability is good, making it suitable for large-scale preparation. Attached Figure Description

[0020] Figure 1 This is a comparison chart of the photocatalytic degradation efficiency of minocycline hydrochloride by the materials prepared in Examples 1, 3, and 4 of this invention and Comparative Examples 1 and 2.

[0021] Figure 2 These are the X-ray diffraction (XRD) spectra of the materials prepared in Example 3 and Comparative Examples 1 and 2 of this invention.

[0022] Figure 3 This is a scanning electron microscope (SEM) image of the MnFeO2 / BC / g-C3N4 photocatalytic material prepared in Example 3 of this invention. Detailed Implementation

[0023] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention. Example 1

[0024] Preparation of g-C3N4: Weigh 5.0g of analytical grade melamine powder and spread it evenly in a 50mL covered porcelain crucible.

[0025] The porcelain crucible was placed in a box-type muffle furnace and calcined in an air atmosphere. The heating program was set as follows: the temperature was increased from room temperature to 550°C at a rate of 5°C / min, and then calcined at 550°C for 4 hours.

[0026] After calcination, the crucible was allowed to cool naturally to room temperature. A large amount of fluffy, pale yellow, blocky solids could be observed inside the crucible.

[0027] Use a medicine spoon to scrape off the solid lumps and transfer them to an agate mortar for initial grinding.

[0028] The pre-ground powder was washed by alternating centrifugation with anhydrous ethanol and deionized water three times each (8000 rpm, 10 min) to remove any possible residual alkaline small molecules.

[0029] The washed product was placed in a vacuum drying oven and dried at 60°C for 8 hours.

[0030] The dried product was removed and ground thoroughly again with an agate mortar and pestle, then passed through a 300-mesh sieve to obtain a light yellow, fine g-C3N4 powder, which was stored in a desiccator for later use. Example 2

[0031] Preparation of straw powder: Collect mature ginger stalks, rinse them with tap water, and then place them in a cool, ventilated place to air dry naturally.

[0032] Soak and rinse the dried ginger stalks in distilled water three times to remove surface residue.

[0033] Place the washed ginger stalks in a vacuum drying oven at 60℃ and dry for 12 hours to completely remove moisture.

[0034] The dried ginger stalks were pulverized using a high-speed universal pulverizer.

[0035] The crushed straw powder is passed through an 80-mesh standard sieve, and the material passing through the sieve is collected to obtain straw powder with uniform particle size. It is then stored in a sealed bag for later use. Example 3

[0036] Preparation of MnFeO2 / BC composite materials: Accurately weigh 10 mmol of manganese acetate tetrahydrate (Mn(CH3COO)2·4H2O) and 10 mmol of ferric nitrate nonahydrate (Fe(NO3)3·9H2O), dissolve them together in 30 mL of deionized water, and stir magnetically for 30 minutes until completely dissolved to obtain a clear solution.

[0037] Add 1.0g of the straw powder prepared in Example 2 to the above solution and stir continuously at 800rpm for 4 hours on a magnetic stirrer to ensure that the metal ions are fully adsorbed and mixed evenly on the straw carrier.

[0038] The obtained homogeneous suspension was transferred to a freeze-drying bottle and pre-frozen in an ultra-low temperature freezer at -80°C for 6 hours. Then it was transferred to a freeze dryer for freeze-drying for 24 hours until all moisture was removed, resulting in a dried solid precursor 1.

[0039] Solid precursor 1 is transferred into a quartz boat and then placed in the center of the quartz tube of a tube furnace.

[0040] High-purity nitrogen (99.99% purity) is introduced into the tubular furnace at a flow rate of 100 mL / min for 30 minutes to completely remove air from the furnace tubes.

[0041] Under nitrogen atmosphere protection, the heating program was set to increase the temperature from room temperature to 750°C at a rate of 5°C / min, and then calcined at 750°C for 6 hours.

[0042] After calcination, the furnace was allowed to cool naturally to room temperature. The calcined product was then removed under a nitrogen atmosphere.

[0043] The calcined product was transferred to a centrifuge tube and washed alternately with deionized water and anhydrous ethanol (3 times each, 8000 rpm, 10 min) until the supernatant became colorless and transparent.

[0044] The washed product was placed in a vacuum drying oven at 60°C and dried for 12 hours.

[0045] The dried block product was ground with an agate mortar to obtain a black, magnetic MnFeO2 / BC composite powder, which was stored for later use. Example 4

[0046] Preparation of MnFeO2 / BC / g-C3N4 photocatalytic material (mass ratio 1:1): Accurately weigh 200 mg of g-C3N4 powder prepared in Example 1 and disperse it in 50 mL of deionized water.

[0047] The above suspension was placed in an ultrasonic cell disruptor and ultrasonically treated in an ice-water bath at 300W power for 3 hours to fully separate and disperse it, forming a uniform mixture A.

[0048] Accurately weigh 200 mg of the MnFeO2 / BC composite material prepared in Example 3 and slowly add it to mixture A.

[0049] The mixture was placed back into the ultrasonic cleaner and ultrasonically treated at room temperature for 30 minutes to achieve initial dispersion.

[0050] Subsequently, the mixture was transferred to a constant temperature shaking incubator and continuously shaken at 25°C and 200 rpm for 12 hours to allow MnFeO2 / BC and g-C3N4 to fully contact and self-assemble, thus obtaining mixture B.

[0051] Transfer all of mixture B into a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene.

[0052] After sealing the high-pressure reactor, place it in a forced-air drying oven and react at 180°C for 2 hours (at which time the pressure inside the reactor will naturally rise to about 2-3 MPa).

[0053] After the reaction is complete, allow it to cool naturally to room temperature. Open the reaction vessel and transfer the reaction products to centrifuge tubes.

[0054] The product was washed three times by alternating centrifugation with deionized water and anhydrous ethanol (8000 rpm, 10 min) until the washing solution was neutral (pH≈7).

[0055] The washed precipitate was dried in a vacuum drying oven at 60°C for 12 hours.

[0056] The dried solid was carefully ground in an agate mortar to obtain the final black powder product, denoted as MFBC / CN-1. Example 5

[0057] Preparation of MnFeO2 / BC / g-C3N4 photocatalytic material (mass ratio 10:1): The steps in this embodiment are exactly the same as in embodiment 4, only the raw material feeding ratio is changed: The dosage of g-C3N4 is 2000mg.

[0058] The dosage of MnFeO2 / BC is 200mg.

[0059] The final product is denoted as MFBC / CN-10.

[0060] Comparative Example 1: Pure g-C3N4: To compare performance, a pure g-C3N4 sample was prepared. 200 mg of g-C3N4 powder prepared in Example 1 was taken and subjected to hydrothermal treatment, washing, and drying under the same conditions as steps 6 to 11 in Example 4. The resulting sample was denoted as CN.

[0061] Comparative Example 2: Pure MnFeO2 / BC: To compare performance, a pure MnFeO2 / BC sample was prepared. 200 mg of the MnFeO2 / BC composite material prepared in Example 3 was dispersed in 50 mL of deionized water and subjected to hydrothermal treatment, washing, and drying under the same conditions as steps 6 to 11 in Example 4. The resulting sample was designated MFBC.

[0062] Performance testing and effect verification: To verify the beneficial effects of the present invention, the performance of the materials prepared above was tested: Photocatalytic degradation experiment: Target contaminant: Minocycline hydrochloride aqueous solution (initial concentration: 20 mg / L, volume: 100 mL).

[0063] Catalyst dosage: 30 mg.

[0064] Procedure: First, the mixture was magnetically stirred in a dark room for 30 minutes to reach adsorption-desorption equilibrium. Then, a 300W xenon lamp (equipped with a 420nm cutoff filter to simulate visible light) was used as the light source, and the reaction was carried out under stirring for 60 minutes. Samples were taken at regular intervals, filtered through a 0.22μm filter membrane, and the concentration of residual pollutants was determined using a UV-Vis spectrophotometer at the maximum absorption wavelength.

[0065] Result: As Figure 1 As shown, the MFBC / CN-10 sample prepared in Example 5 exhibited the highest photocatalytic degradation efficiency, with a degradation rate of over 95% for minocycline hydrochloride within 60 minutes. Its performance was significantly better than that of Comparative Example 1 (CN) and Comparative Example 2 (MFBC), as well as composite materials with other ratios, demonstrating the synergistic effect and optimal mass ratio of the three composites.

[0066] Phase and structure characterization: X-ray diffraction (XRD): Phase analysis of the samples from Example 5 (MFBC / CN-10), Comparative Example 1 (CN), and Comparative Example 2 (MFBC) was performed using an X-ray diffractometer. Results are as follows: Figure 2 As shown, the characteristic diffraction peaks of g-C3N4 (JCPDS87-1526) and MnFeO2 (JCPDS77-2359) were clearly observed in the spectrum of MFBC / CN-10, with no other impurity peaks, confirming the successful preparation and high purity of the composite material.

[0067] Morphological analysis: Scanning electron microscopy (SEM): Morphological observation of sample 5 (MFBC / CN-10). Results are as follows: Figure 3 As shown, MnFeO2 / BC particles are relatively uniformly loaded on the lamellar g-C3N4, and the original agglomeration phenomenon of the latter is significantly improved. This structure is conducive to exposing more active sites and promoting charge separation.

[0068] The above description is only a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. Any equivalent modifications or changes made by those skilled in the art based on the content disclosed in the present invention should be included within the scope of protection set forth in the claims.

Claims

1. A method for preparing a MnFeO2 / BC / g-C3N4 photocatalytic material with visible light response, characterized in that, Includes the following steps: S1. Dissolve Mn²⁺ salt, Fe³⁺ salt and biomass carbon source in deionized water, stir and mix, and then freeze dry to obtain a solid precursor; S2. The solid precursor is calcined in an inert atmosphere, cooled, washed, and dried to obtain the MnFeO2 / BC composite material; S3. Disperse g-C3N4 in deionized water to form a dispersion, then add the MnFeO2 / BC composite material, and after ultrasonic dispersion and oscillation mixing, obtain a mixture; S4. The mixture is subjected to a hydrothermal reaction, and the reaction product is washed and dried to obtain the MnFeO2 / BC / g-C3N4 photocatalytic material.

2. The preparation method according to claim 1, characterized in that, The Mn²⁺ salt is manganese acetate tetrahydrate, and the Fe³⁺ salt is ferric nitrate nonahydrate; the biomass carbon source is ginger straw powder.

3. The preparation method according to claim 1, characterized in that, In step S1, the freeze-drying temperature is -80℃; in step S2, the calcination conditions are: under a nitrogen atmosphere, the temperature is increased to 750℃ at a rate of 5℃ / min and held for 6 hours.

4. The preparation method according to claim 1, characterized in that, In step S3, the mass ratio of g-C3N4 to MnFeO2 / BC is 1:1 to 15:

1.

5. The preparation method according to claim 4, characterized in that, The mass ratio of g-C3N4 to MnFeO2 / BC is 10:

1.

6. The preparation method according to claim 1, characterized in that, In step S3, the ultrasonic dispersion time of g-C3N4 in deionized water is 3h; after adding MnFeO2 / BC, it is first ultrasonically treated for 0.5h, and then oscillated for 12h.

7. The preparation method according to claim 1, characterized in that, In step S4, the conditions for the hydrothermal reaction are: temperature 180℃, pressure 2-3MPa, and reaction time 2h.

8. The preparation method according to claim 1, characterized in that, The g-C3N4 was prepared by the following method: melamine was heated to 550°C at a rate of 5°C / min and calcined for 4 hours in an air atmosphere, and then cooled, washed, dried and ground.

9. The preparation method according to claim 2, characterized in that, The ginger straw powder is obtained by washing and drying air-dried ginger straw, crushing it, and passing it through an 80-mesh sieve.

10. A MnFeO2 / BC / g-C3N4 photocatalytic material with visible light response, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 9.

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