Defect mnO-doped biochar modified red mud catalyst, and preparation method and application thereof

Abstract

The present application relates to the field of waste resource and environmental catalysis technology, and particularly relates to a defect MnO doped biochar modified red mud catalyst, a preparation method and application thereof. The present application first converts the red mud from alkaline to neutral through a hydrothermal reaction, and then reduces the hematite in the red mud to Fe3O4 by using the reducing gas released by coffee grounds in the pyrolysis process, simultaneously generates biomass carbon, and further forms defect MnO through step pyrolysis to prepare the defect MnO doped biochar modified red mud catalyst. The catalyst has a suitable specific surface area, adjustable pore structure, and can activate persulfate to degrade organic pollutants in water at room temperature. The synergistic effect of the biochar and the defect MnO electronic additive significantly improves the activity of the modified red mud catalyst, realizes efficient degradation of organic matter in wastewater, and realizes high-value utilization of red mud solid waste.

Description

Technical Field

[0001] This invention belongs to the field of waste resource utilization and environmental catalysis technology, and particularly relates to a defective MnO-doped biochar modified red mud catalyst, its preparation method and application. Background Technology

[0002] Red mud is a polluting waste residue discharged after alumina extraction from bauxite. As of 2018, my country's accumulated red mud reached 790 million tons. The dumping of red mud not only occupies a large amount of land but also seriously harms the soil environment of the storage sites. Currently, red mud has a wide range of applications, but it is mainly concentrated in the preparation of cement building materials and as roadbed materials, with a very low proportion of refined and high-value utilization.

[0003] Red mud's main components include SiO2, Al2O3, CaO, and Fe2O3. Utilizing red mud to prepare high-value-added products can not only alleviate the environmental pressure caused by red mud dumping but also realize the resource utilization of solid waste, thus attracting the attention of experts and scholars both domestically and internationally. Red mud contains a high content of Fe2O3, making it a potential substitute for iron-containing reagents in the synthesis of Fenton-like catalysts. Invention patent CN116139863A, "A Red Mud-Based PBA-Derived Metal Oxide Fenton Catalyst and Its Preparation Method and Application," discloses a red mud-based PBA-derived metal oxide Fenton catalyst and its preparation method; the prepared material can activate H2O2 to degrade organic pollutants in water. Invention patent CN114984958B, "A Red Mud-Based Solid Waste Catalyst and Its Preparation Method and a Method for Remediating Soil Polycyclic Aromatic Hydrocarbon Pollution," discloses a red mud-based solid waste catalyst and its preparation method, as well as a method for remediating soil polycyclic aromatic hydrocarbon pollution, which can effectively degrade organic pollutants in soil. In summary, existing methods for preparing catalysts using red mud can all obtain iron-based catalysts. However, due to the high alkalinity and small specific surface area of ​​red mud, the catalyst prepared has low catalytic activity. Summary of the Invention

[0004] The purpose of this invention is to provide a defective MnO-doped biochar-modified red mud catalyst, its preparation method, and its application, so as to solve the problems existing in the prior art.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a defect-MnO-doped biochar-modified red mud catalyst, comprising the following steps:

[0007] (1) After grinding and mixing red mud and coffee grounds, a hydrothermal reaction was carried out. After centrifugation and drying, a biomass-modified red mud precursor was obtained.

[0008] (2) The biomass-modified red mud precursor was impregnated with manganese nitrate solution and then calcined to obtain biomass-modified red mud loaded with manganese precursor material.

[0009] (3) The biomass-modified red mud loaded with manganese precursor was pyrolyzed at high temperature under a nitrogen atmosphere to obtain a defect MnO-doped biochar-modified red mud catalyst, denoted as MnO / C@RM.

[0010] Preferably, in step (1), the mass ratio of coffee grounds to red mud is 0.5 to 4:1, and the ratio of coffee grounds and red mud to water is 5 to 10 g: 50 mL.

[0011] Preferably, the temperature of the hydrothermal reaction in step (1) is 140-200℃ and the time is 6-10h.

[0012] Preferably, the pH value of the leachate obtained in step (1) of the biomass-modified red mud precursor is 6.8 to 7.0.

[0013] Preferably, in step (2), the mass ratio of manganese nitrate to biomass-modified red mud precursor is 1:10, the calcination temperature is 350℃, and the time is 1.5h.

[0014] Preferably, in step (3), the pyrolysis is carried out by heating to 500°C at a rate of 5°C / min, holding for 1 hour, and then heating to 600°C and holding for 2 to 5 hours.

[0015] The present invention also provides a defect-MnO-doped biochar-modified red mud catalyst prepared by the above preparation method.

[0016] This invention also provides the application of the aforementioned defective MnO-doped biochar-modified red mud catalyst in the activation of persulfate degradation of organic pollutants in water.

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

[0018] This invention first transforms red mud from alkaline to neutral through a hydrothermal reaction. Then, the reducing gas released during the pyrolysis of coffee grounds reduces hematite in the red mud to Fe3O4, simultaneously generating biomass carbon. Further stepwise pyrolysis forms defective MnO, resulting in a defective MnO-doped biochar-modified red mud catalyst. This catalyst possesses a suitable specific surface area and tunable pore structure, enabling activation at room temperature to degrade organic pollutants in water using persulfate. The synergistic effect of biochar improving the catalyst's specific surface area and the defective MnO electronic additive significantly enhances the activity of the modified red mud catalyst, achieving highly efficient degradation of organic matter in wastewater and realizing the high-value utilization of red mud solid waste. Attached Figure Description

[0019] Figure 1The image shows the X-ray diffraction pattern of the MnO / C@RM catalyst prepared in Example 1.

[0020] Figure 2 The image shows the effect of the MnO / C@RM catalyst prepared in Example 1 on the activation of PMS for the degradation of Rhodamine B.

[0021] Figure 3 The graph shows a comparison of the performance of the MnO / C@RM catalyst prepared in Example 1 and the catalyst prepared in Comparative Example 1 in activating persulfate to degrade Rhodamine B.

[0022] Figure 4 The graph shows a comparison of the performance of the MnO / C@RM catalyst prepared in Example 1 and the catalyst prepared in Comparative Example 2 in activating persulfate to degrade Rhodamine B.

[0023] Figure 5 The graphs show the effect of the MnO / C@RM catalysts prepared in Examples 2-6 on the activation of PMS for the degradation of Rhodamine B. Detailed Implementation

[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. However, the present invention is not limited to these embodiments.

[0025] Example 1

[0026] 6.0g of coffee grounds dried to constant weight were ground and mixed evenly with 3.0g of red mud. 50ml of deionized water was added and stirred for 30min. The mixture was then placed in a reactor and kept at 180℃ for 8h. After removal, the mixture was centrifuged and dried to obtain a biomass-modified red mud precursor. 0.26ml of 50% manganese nitrate solution was diluted to 1.4ml and impregnated with an equal volume of 2g of biomass-modified red mud precursor. After standing for 6h, the mixture was dried and then calcined at 350℃ for 1.5h to obtain a biomass-modified red mud supported manganese precursor material. The biomass-modified red mud supported manganese precursor was placed in a tube furnace and heated to 500℃ at a rate of 5℃ / min under a nitrogen atmosphere. The temperature was held for 1h, and then increased to 600℃ and held for 4h to obtain a defect MnO-doped biochar-modified red mud catalyst, denoted as MnO / C@RM.

[0027] Figure 1 The XRD pattern of the MnO / C@RM catalyst prepared in Example 1 is shown. It can be seen that the diffraction peak at approximately 35.4° corresponds to Fe3O4, indicating that hematite in the red mud was reduced to Fe3O4 during pyrolysis. Meanwhile, the diffraction peak appearing at 40.7° is a characteristic peak of MnO.

[0028] Comparative Example 1

[0029] In a comparative example of this invention, the preparation method of the catalyst differs from Example 1 in that the coffee grounds and red mud are not subjected to hydrothermal treatment after mixing; instead, they are directly impregnated with an equal volume of manganese nitrate solution. The remaining preparation methods are identical to those in Example 1. 6.0 g of coffee grounds dried to constant weight are ground and mixed evenly with 3.0 g of red mud. 0.26 ml of a 50% manganese nitrate solution is diluted to 1.4 ml and impregnated with an equal volume of 2 g of biomass-modified red mud precursor. After standing for 6 hours, the mixture is dried and then calcined at 350°C for 1.5 hours to obtain a biomass-modified red mud-supported manganese precursor material. The biomass-modified red mud-supported manganese precursor is placed in a tube furnace and heated to 500°C at a rate of 5°C / min under a nitrogen atmosphere, held for 1 hour, and then heated to 600°C and held for 4 hours to obtain a defect-MnO-doped biochar-modified red mud catalyst.

[0030] Comparative Example 2

[0031] In a comparative example of the present invention, the preparation method of the catalyst differs from that of Example 1 in that the coffee grounds and red mud are hydrothermally treated without impregnation with manganese nitrate solution, while the rest of the preparation method is exactly the same as in Example 1. 6.0 g of coffee grounds dried to constant weight are ground and mixed evenly with 3.0 g of red mud. 50 ml of deionized water is added and stirred for 30 min, then placed in a reaction vessel and kept at 180°C for 8 h. After removal, the mixture is centrifuged and dried to obtain a biomass-modified red mud precursor. The biomass-modified red mud precursor is placed in a tube furnace and heated to 500°C at a rate of 5°C / min under a nitrogen atmosphere, held for 1 h, and then heated to 600°C and held for 4 h to obtain a biochar-modified red mud catalyst.

[0032] Example 2

[0033] The preparation conditions of Example 1 were used, except that the coffee grounds weighed 3.0g. 3.0g of coffee grounds dried to constant weight were ground and mixed evenly with 3.0g of red mud. 50ml of deionized water was added and stirred for 30min. The mixture was then placed in a reactor and kept at 180℃ for 8h. After removal, it was centrifuged and dried to obtain a biomass-modified red mud precursor. 0.26ml of a 50% manganese nitrate solution was diluted to 1.4ml and an equal volume was impregnated onto 2g of the biomass-modified red mud precursor. After standing for 6h, it was dried and then calcined at 350℃ for 1.5h to obtain a biomass-modified red mud-supported manganese precursor material. The biomass-modified red mud-supported manganese precursor was placed in a tube furnace and heated to 500℃ at a rate of 5℃ / min under a nitrogen atmosphere, held for 1h, and then heated to 600℃ and held for 4h to obtain a defect-MnO-doped biochar-modified red mud catalyst.

[0034] Example 3

[0035] The preparation conditions of Example 1 were used, except that the hydrothermal reaction temperature was 160℃. 6.0g of coffee grounds dried to constant weight were ground and mixed evenly with 3.0g of red mud. 50ml of deionized water was added and stirred for 30min. The mixture was then placed in a reaction vessel and kept at 160℃ for 8h. After removal, it was centrifuged and dried to obtain a biomass-modified red mud precursor. 0.26ml of a 50% manganese nitrate solution was diluted to 1.4ml and an equal volume was impregnated onto 2g of the biomass-modified red mud precursor. After standing for 6h, it was dried and then calcined at 350℃ for 1.5h to obtain a biomass-modified red mud-supported manganese precursor material. The biomass-modified red mud-supported manganese precursor was placed in a tube furnace and heated to 500℃ at a rate of 5℃ / min under a nitrogen atmosphere, held for 1h, and then heated to 600℃ and held for 4h to obtain a defect-MnO-doped biochar-modified red mud catalyst.

[0036] Example 4

[0037] The preparation conditions of Example 1 were used, except that the pyrolysis process was carried out at 600℃ for 6 hours. 6.0g of coffee grounds dried to constant weight were ground and mixed evenly with 3.0g of red mud. 50ml of deionized water was added and stirred for 30 minutes. The mixture was then placed in a reactor and kept at 180℃ for 8 hours. After removal, it was centrifuged and dried to obtain a biomass-modified red mud precursor. 0.26ml of a 50% manganese nitrate solution was diluted to 1.4ml and impregnated with an equal volume of 2g of the biomass-modified red mud precursor. After standing for 6 hours, it was dried and then calcined at 350℃ for 1.5 hours to obtain a biomass-modified red mud-supported manganese precursor material. The biomass-modified red mud-supported manganese precursor was placed in a tube furnace and heated to 500℃ at a rate of 5℃ / min under a nitrogen atmosphere, held for 1 hour, and then heated to 600℃ and held for 6 hours to obtain a defect-MnO-doped biochar-modified red mud catalyst.

[0038] Example 5

[0039] The preparation conditions of Example 2 were used, except that the hydrothermal reaction temperature was 160℃. 3.0g of coffee grounds dried to constant weight were ground and mixed evenly with 3.0g of red mud. 50ml of deionized water was added and stirred for 30min. The mixture was then placed in a reaction vessel and kept at 160℃ for 8h. After removal, it was centrifuged and dried to obtain a biomass-modified red mud precursor. 0.26ml of a 50% manganese nitrate solution was diluted to 1.4ml and an equal volume was impregnated onto 2g of the biomass-modified red mud precursor. After standing for 6h, it was dried and then calcined at 350℃ for 1.5h to obtain a biomass-modified red mud-supported manganese precursor material. The biomass-modified red mud-supported manganese precursor was placed in a tube furnace and heated to 500℃ at a rate of 5℃ / min under a nitrogen atmosphere, held for 1h, and then heated to 600℃ and held for 4h to obtain a defect-MnO-doped biochar-modified red mud catalyst.

[0040] Example 6

[0041] The preparation conditions of Example 2 were used, except that the pyrolysis process was carried out at 600℃ for 6 hours. 3.0g of coffee grounds dried to constant weight were ground and mixed evenly with 3.0g of red mud. 50ml of deionized water was added and stirred for 30 minutes. The mixture was then placed in a reactor and kept at 180℃ for 8 hours. After removal, it was centrifuged and dried to obtain a biomass-modified red mud precursor. 0.26ml of a 50% manganese nitrate solution was diluted to 1.4ml and an equal volume was impregnated onto 2g of the biomass-modified red mud precursor. After standing for 6 hours, it was dried and then calcined at 350℃ for 1.5 hours to obtain a biomass-modified red mud-supported manganese precursor material. The biomass-modified red mud-supported manganese precursor was placed in a tube furnace and heated to 500℃ at a rate of 5℃ / min under a nitrogen atmosphere, held for 1 hour, and then heated to 600℃ and held for 6 hours to obtain a defect-MnO-doped biochar-modified red mud catalyst.

[0042] Catalytic effect experiment

[0043] Take 0.5 mL of 0.1 mol / L PMS solution and 0.01 g of catalyst and add them to 50 mL of 50 mg / L Rhodamine B solution. Place the solution in a 30 °C constant temperature water bath. After the reaction starts, filter the solution through a 0.45 μm polytetrafluoroethylene syringe membrane filter at 2.5, 5, 10, 20, 40 and 60 min respectively. Measure the absorbance of the solution at 554 nm using a UV spectrophotometer.

[0044] Figure 2 The graph shows the effect of the MnO / C@RM catalyst prepared in Example 1 on the degradation of Rhodamine B by PMS. It can be seen that without the catalyst, the removal rate of Rhodamine B within 60 min is only 14.8% due to thermal activation of PMS, while the removal rate of Rhodamine B reaches 95.9% after using the catalyst. Therefore, the MnO / C@RM catalyst significantly improves the degradation effect of the system on Rhodamine B.

[0045] Figure 3 The graph shows a comparison of the performance of the MnO / C@RM catalyst prepared in Example 1 and the catalyst prepared in Comparative Example 1 in activating persulfate to degrade Rhodamine B. It can be seen that the hydrothermal treatment of coffee grounds and red mud in this technical solution has a significant effect on improving the catalyst performance.

[0046] Figure 4 The graph shows a comparison of the performance of the MnO / C@RM catalyst prepared in Example 1 and the catalyst prepared in Comparative Example 2 in activating persulfate to degrade Rhodamine B. It can be seen that defective MnO doping has a significant effect on improving catalyst performance.

[0047] Figure 5The graphs show the effect of the MnO / C@RM catalysts prepared in Examples 2-6 on the degradation of Rhodamine B by PMS. It can be seen that the removal rate of Rhodamine B exceeds 95% in all cases.

[0048] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of the present invention in any way. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by the present invention.

Claims

1. A method for preparing a defect-MnO-doped biochar-modified red mud catalyst, characterized in that, Includes the following steps: (1) After grinding and mixing red mud and coffee grounds, a hydrothermal reaction was carried out. After centrifugation and drying, a biomass-modified red mud precursor was obtained. (2) The biomass-modified red mud precursor was impregnated with manganese nitrate solution and then calcined to obtain biomass-modified red mud loaded with manganese precursor material. (3) The biomass-modified red mud loaded with manganese precursor was pyrolyzed at high temperature under a nitrogen atmosphere to obtain a defect MnO-doped biochar-modified red mud catalyst, denoted as MnO / C@RM.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of coffee grounds to red mud is 0.5 to 4:1, and the ratio of coffee grounds and red mud to water is 5 to 10 g: 50 mL.

3. The preparation method according to claim 1, characterized in that: In step (1), the hydrothermal reaction temperature is 140–200℃ and the time is 6–10h.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The pH value of the leachate obtained from the biomass-modified red mud precursor in step (1) is 6.8 to 7.

0.

5. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of manganese nitrate to biomass-modified red mud precursor is 1:10, the calcination temperature is 350℃, and the time is 1.5h.

6. The preparation method according to claim 1, characterized in that, In step (3), the pyrolysis involves heating the temperature to 500℃ at a rate of 5℃ / min, holding it at that temperature for 1 hour, and then heating it to 600℃ and holding it at that temperature for 2 to 5 hours.

7. The defect MnO-doped biochar-modified red mud catalyst prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the defective MnO-doped biochar-modified red mud catalyst according to claim 7 in the activation of persulfate degradation of organic pollutants in water.

9. The application according to claim 8, characterized in that, The organic pollutant is at least one of Rhodamine B, Acid Orange 7, and Methyl Blue.

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