A method for preparing Fe-CaTiO3 heterogeneous visible-light Fenton catalyst from vanadium-titanium magnetite

Abstract

The application discloses a method for preparing Fe-CaTiO3 heterogeneous visible light Fenton catalyst from vanadium-titanium magnetite, and comprises the following steps: (1) vanadium-titanium magnetite powder, bentonite, slaked lime and water are mixed according to a proportion, and then enter a disc balling machine to be balling to prepare green balls; (2) the green balls prepared in the step (1) are dried and roasted to prepare oxidized pellets; (3) the oxidized pellets are reduced in a hydrogen-rich reducing atmosphere to obtain direct reduced iron (DRI) containing CaTiO3; (4) the DRI is cooled to below 50 DEG C under the protection of inert gas; and (5) the cooled DRI is crushed and ball milled, and thus Fe-CaTiO3 is obtained. The prepared Fe-CaTiO3, H2O2 and visible light constitute a photo-assisted heterogeneous Fenton reaction system, which can efficiently catalyze degradation of organic pollutants in wastewater; and the method has the advantages of low preparation cost, high catalytic activity, easy recovery and reusability.

Description

Technical Field

[0001] This invention relates to the fields of comprehensive utilization of vanadium-titanium magnetite resources and organic wastewater treatment technology, specifically to a method for preparing Fe-CaTiO3 heterogeneous visible light Fenton catalyst from vanadium-titanium magnetite. Background Technology

[0002] With rapid industrial development, the types and quantities of organic pollutants generated are increasing daily. Wastewater with complex chemical structures, low concentrations, and high toxicity is difficult to remove effectively using traditional physicochemical methods or biodegradation. Therefore, the treatment of recalcitrant organic wastewater has become a research hotspot in environmental science. The Fenton oxidation process (Fe...) 2+ The H2O2 system generates highly oxidizing hydroxyl radicals (·OH). As a highly efficient and practical deep oxidation treatment technology, it is widely used in the treatment of wastewater in industries such as pharmaceuticals, printing and dyeing, and petrochemicals due to its advantages such as simple operation and high reaction efficiency. However, it also has disadvantages such as a narrow reaction pH range (2-3) and easy generation of iron-containing sludge precipitation, which limits its wider application.

[0003] Using iron-containing solids to replace Fe 2+ The heterogeneous Fenton-like reaction system with H2O2 has seen rapid development in recent years due to its ability to broaden the reaction pH range and reduce the generation of iron-containing sludge. Zero-valent iron (ZFI) possesses good catalytic activity and magnetism, ensuring rapid and efficient separation of the catalyst from the reaction medium using a magnetic field after the reaction. The combination of ZFI and semiconductors in the light + H2O2 system can synergistically enhance the degradation of organic pollutants. This is attributed to the strong oxidizing properties of photogenerated holes in semiconductors, which have a degrading effect on pollutants, and the photogenerated electrons, which can accelerate the degradation of Fe. 3+ To Fe 2+ The transformation of ·OH groups facilitates the production of more ·OH groups, synergistically accelerating the degradation of organic matter. To date, reported composite catalysts such as Fe / TiO2, Fe / N3C4, Fe / ZnFe2O4, Fe / Cu2O, and Fe / ZnS have exhibited good catalytic activity. However, most of these catalysts are prepared using pure reagents as raw materials through relatively stringent hydrometallurgical methods (including hydrothermal, sol-gel, and co-precipitation methods). Reports on the direct one-step preparation of Fe / semiconductor photo-assisted heterogeneous Fenton catalysts from inexpensive minerals are rare.

[0004] Vanadium-titanium magnetite is the main form of vanadium-titanium ore. Currently, vanadium-titanium magnetite is mainly smelted using blast furnace technology. The main problem is that almost all the titanium in the titanium magnetite ends up in the blast furnace slag. However, due to the low titanium grade (TiO2 content 10%–25%) and poor activity, the titanium resources are not effectively utilized. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing Fe-CaTiO3 heterogeneous visible light Fenton catalyst from vanadium-titanium magnetite. By adding slaked lime, the Ti element in vanadium-titanium magnetite is transformed into CaTiO3 semiconductor material with visible light response, which forms a synergistic effect with Fe in direct reduction of iron, accelerating the generation rate of ·OH in the H2O2 / Vis system, thereby enhancing the degradation of organic pollutants in wastewater. Compared with the blast furnace smelting process of vanadium-titanium magnetite, carbon emissions are reduced by more than 50%, and 100% utilization of valuable elements in vanadium-titanium magnetite is achieved.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] A method for preparing Fe-CaTiO3 heterogeneous visible-light Fenton catalyst from vanadium-titanium magnetite includes the following steps:

[0008] (1) Vanadium-titanium magnetite is mixed with bentonite, slaked lime and water in a certain proportion, and then fed into a disc pelletizer to make green pellets.

[0009] (2) The green pellets prepared in step (1) are dried and calcined to prepare oxidized pellets;

[0010] (3) Reduce the oxidized pellets in a hydrogen-rich reducing atmosphere to obtain direct reduced iron (DRI) containing CaTiO3;

[0011] (4) Cool the DRI prepared in step (3) to below 50°C under inert gas protection;

[0012] (5) The cooled DRI was crushed and ball-milled to obtain the Fe-CaTiO3 heterogeneous visible light Fenton catalyst.

[0013] Furthermore, in step (1) of the present invention, the TiO2 content in the vanadium-titanium magnetite is 5% to 20%, and the Fe content is 40% to 65%; the portion of the vanadium-titanium magnetite below 200 mesh accounts for more than 80% of the total.

[0014] Furthermore, in step (1) of the present invention, the mass ratio of the amount of quicklime added to TiO2 in vanadium-titanium magnetite is 0.9 to 1.1:1, the mass ratio of vanadium-titanium magnetite to bentonite is 100:1 to 2, and the mass percentage of moisture in the mixture is 9% to 11%.

[0015] Furthermore, the green pellets prepared in step (1) of the present invention have a particle size of 8 to 16 mm.

[0016] Furthermore, the drying temperature in step (2) of the present invention is 300-400℃; the calcination temperature is 1150-1250℃, and the calcination time is 20-30 min.

[0017] Furthermore, the hydrogen-rich gas mentioned in step (3) of the present invention is coke oven gas, wherein (H2+CO+CH4)>85% and H2 / CO≥4.

[0018] Furthermore, the reduction temperature of the reduction reaction in step (3) of the present invention is 950-1050°C, and the reduction time is 1-2 hours.

[0019] Furthermore, in step (5) of the present invention, 100% of the ball milled DRI particles are less than 100 mesh.

[0020] The technical solution of this invention has the following beneficial technical effects:

[0021] This invention uses vanadium-titanium magnetite as raw material and employs a pellet preparation-hydrogen-rich gas direct reduction method to prepare Fe-CaTiO3 heterogeneous visible-light Fenton catalyst. The prepared Fe-CaTiO3, together with H2O2 and visible light, constitutes a photo-assisted heterogeneous Fenton reaction system (Fe-CaTiO3 / H2O2 / Vis), which can efficiently catalyze the degradation of organic pollutants in wastewater, such as antibiotics and organic dyes.

[0022] The Fe-CaTiO3 heterogeneous visible light Fenton catalyst prepared by this invention can be recovered and reused through a magnetic field.

[0023] The catalyst prepared by the method of this invention has the advantages of low preparation cost, high catalytic activity, easy recovery, and reusability, and has good application prospects.

[0024] Compared with the blast furnace smelting process of vanadium-titanium magnetite, the method of this invention reduces carbon emissions by more than 50% and achieves 100% utilization of valuable elements in vanadium-titanium magnetite. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the method of the present invention. Detailed Implementation

[0026] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention. Example 1

[0027] A method for preparing Fe-CaTiO3 heterogeneous visible-light Fenton catalyst from vanadium-titanium magnetite, the process flow is as follows: Figure 1 As shown, the details are as follows:

[0028] (1) Select vanadium-titanium magnetite with TiO2 content of 18.8% and total iron content of 42.6%; grind the selected vanadium-titanium magnetite, and after grinding, the part below 200 mesh accounts for 85% of the total; mix the ground vanadium-titanium magnetite with bentonite, slaked lime and water in a certain proportion; the mass ratio of vanadium-titanium magnetite to bentonite in the mixture is 100:1, the mass ratio of vanadium-titanium magnetite to slaked lime is 100:18, and the moisture content in the mixture is 11%; then put the mixture into a disc pelletizer for pelletizing, and control the green pellet size to be 8-16 mm;

[0029] (2) The green pellets prepared in step (1) are dried and calcined to prepare oxidized pellets; the drying temperature is 300℃, the calcination temperature is 1150℃, the calcination time is 30min, and the average compressive strength of the pellets is 2050N.

[0030] (3) The pellets were reduced by coke oven gas at 950°C for 2 hours to obtain DRI containing CaTiO3; wherein (H2+CO+CH4)=91% and H2 / CO=8 in the coke oven gas.

[0031] (4) Cool the DRI containing CaTiO3 to 50°C under the protection of inert gas.

[0032] (5) After cooling, the DRI containing CaTiO3 is crushed and ball-milled until the proportion of particles smaller than 100 mesh is 100% to obtain Fe-CaTiO3 heterogeneous visible light Fenton catalyst.

[0033] The Fe-CaTiO3 prepared in this embodiment was added to a reaction system consisting of organic wastewater, H2O2, and Vis. The concentration of tetracycline in the wastewater was 20 mg / L, the pH of the solution was 3.5, the catalyst dosage was 1 g / L, the H2O2 concentration was 30 mM, and the visible light intensity was 200 mW / cm². 2 Within 90 minutes, the degradation rate of tetracycline reached 98.5%, and the total organic carbon (TOC) removal rate reached 85%. After being recycled 10 times using magnetic field recovery, the degradation rate of tetracycline by Fe-CaTiO3 could still reach 95%, demonstrating good stability.

[0034] Compared to the blast furnace smelting process for vanadium-titanium magnetite, this embodiment reduces CO2 emissions by 77% and increases Ti utilization from ineffective to 100%. Example 2

[0035] A method for preparing Fe-CaTiO3 heterogeneous visible-light Fenton catalyst from vanadium-titanium magnetite, the process flow is as follows: Figure 1 As shown, the details are as follows:

[0036] (1) Select vanadium-titanium magnetite with TiO2 content of 12.5% ​​and total iron content of 54.3%; grind the selected vanadium-titanium magnetite, and after grinding, the part below 200 mesh accounts for 82% of the total; mix the ground vanadium-titanium magnetite with bentonite, slaked lime and water in a certain proportion; the mass ratio of vanadium-titanium magnetite to bentonite in the mixture is 100:1.5, the mass ratio of vanadium-titanium magnetite to slaked lime is 100:12, and the moisture content in the mixture is 10%; then put the mixture into a disc pelletizer for pelletizing, and control the green pellet size to be 8-16 mm;

[0037] (2) The green pellets prepared in step (1) are dried and calcined to prepare oxidized pellets; the drying temperature is 350℃, the calcination temperature is 1200℃, the calcination time is 25min, and the average compressive strength of the pellets is 2190N.

[0038] (3) The pellets were reduced by coke oven gas at 1000℃ for 1.5h to obtain DRI containing CaTiO3; wherein (H2+CO+CH4)=88% and H2 / CO=6 in the coke oven gas.

[0039] (4) Cool the DRI containing CaTiO3 to 47°C under the protection of inert gas.

[0040] (5) After cooling, the DRI containing CaTiO3 is crushed and ball-milled until the proportion of particles smaller than 100 mesh is 100% to obtain Fe-CaTiO3 heterogeneous visible light Fenton catalyst.

[0041] The Fe-CaTiO3 prepared in this embodiment was added to a reaction system consisting of organic wastewater, H2O2, and Vis. The concentration of methyl orange in the wastewater was 15 mg / L, the pH of the solution was 6.5, the catalyst dosage was 1.25 g / L, the H2O2 concentration was 25 mM, and the visible light intensity was 150 mW / cm². 2 Within 80 minutes, the degradation rate of methyl orange reached 97.0%, and the total organic carbon (TOC) removal rate reached 83%. After being recycled 10 times by magnetic field recovery, the degradation rate of methyl orange by Fe-CaTiO3 could still reach 93%, demonstrating good stability.

[0042] Compared to the blast furnace smelting process for vanadium-titanium magnetite, this embodiment reduces CO2 emissions by 66% and increases Ti utilization from ineffective to 100%. Example 3

[0043] A method for preparing Fe-CaTiO3 heterogeneous visible-light Fenton catalyst from vanadium-titanium magnetite, the process flow is as follows: Figure 1 As shown, the details are as follows:

[0044] (1) Select vanadium-titanium magnetite with TiO2 content of 6.5% and total iron content of 61.5%; grind the selected vanadium-titanium magnetite to a size of less than 200 mesh, with the portion accounting for 80% of the total; mix the ground vanadium-titanium magnetite with bentonite, slaked lime and water in a certain proportion; the mass ratio of vanadium-titanium magnetite to bentonite in the mixture is 100:2, the mass ratio of vanadium-titanium magnetite to slaked lime is 100:6, and the moisture content in the mixture is 9%; then put the mixture into a disc pelletizer for pelletizing, and control the green pellet size to be 8-16 mm;

[0045] (2) The green pellets prepared in step (1) are dried and calcined to prepare oxidized pellets; the drying temperature is 400℃, the calcination temperature is 1250℃, the calcination time is 20min, and the average compressive strength of the pellets is 2506N.

[0046] (3) The pellets were reduced by coke oven gas at 1050℃ for 1 hour to obtain DRI containing CaTiO3; wherein (H2+CO+CH4)=87% and H2 / CO=4 in the coke oven gas.

[0047] (4) Cool the DRI containing CaTiO3 to 45°C under the protection of inert gas.

[0048] (5) After cooling, the DRI containing CaTiO3 is crushed and ball-milled until the proportion of particles smaller than 100 mesh is 100% to obtain Fe-CaTiO3 heterogeneous visible light Fenton catalyst.

[0049] The Fe-CaTiO3 prepared in this embodiment was added to a reaction system consisting of organic wastewater, H2O2, and Vis. The concentration of Rhodamine B in the wastewater was 10 mg / L, the pH of the solution was 9.5, the catalyst dosage was 0.5 g / L, the H2O2 concentration was 15 mM, and the visible light intensity was 100 mW / cm². 2 Within 60 minutes, the degradation rate of Rhodamine B reached 99.5%, and the total organic carbon (TOC) removal rate reached 80%. After being recycled 10 times using magnetic field recovery, the degradation efficiency of Fe-CaTiO3 for Rhodamine B still reached 96%, demonstrating good stability.

[0050] Compared to the blast furnace smelting process for vanadium-titanium magnetite, this embodiment reduces CO2 emissions by 50% and increases Ti utilization from ineffective to 100%.

Claims

1. A method for preparing Fe-CaTiO3 heterogeneous visible-light Fenton catalyst from vanadium-titanium magnetite, characterized in that, Includes the following steps: (1) Vanadium-titanium magnetite is mixed with bentonite, slaked lime and water in a certain proportion, and then fed into a disc pelletizer to make green pellets. (2) The green pellets prepared in step (1) are dried and calcined to prepare oxidized pellets; (3) Reduce the oxidized pellets in a hydrogen-rich reducing atmosphere to obtain direct reduced iron (DRI) containing CaTiO3; (4) Cool the DRI obtained in step (3) to below 50°C under inert gas protection; (5) The cooled DRI was crushed and ball-milled to obtain the Fe-CaTiO3 heterogeneous visible light Fenton catalyst.

2. The method for preparing Fe-CaTiO3 heterogeneous visible-light Fenton catalyst from vanadium-titanium magnetite according to claim 1, characterized in that, In step (1), the TiO2 content in the vanadium-titanium magnetite is 5% to 20%, and the Fe content is 40% to 65%; the portion of the vanadium-titanium magnetite below 200 mesh accounts for more than 80% of the total.

3. The method for preparing Fe-CaTiO3 heterogeneous visible-light Fenton catalyst from vanadium-titanium magnetite according to claim 1, characterized in that, In step (1), the mass ratio of the amount of quicklime added to TiO2 in vanadium-titanium magnetite is 0.9 to 1.1:1, the mass ratio of vanadium-titanium magnetite to bentonite is 100:1 to 2, and the mass percentage of moisture in the mixture is 9% to 11%.

4. The method for preparing Fe-CaTiO3 heterogeneous visible-light Fenton catalyst from vanadium-titanium magnetite according to claim 1, characterized in that, The green pellets prepared in step (1) have a particle size of 8 to 16 mm.

5. The method for preparing Fe-CaTiO3 heterogeneous visible-light Fenton catalyst from vanadium-titanium magnetite according to claim 1, characterized in that, The drying temperature in step (2) is 300-400℃; the calcination temperature is 1150-1250℃, and the calcination time is 20-30 min.

6. The method for preparing Fe-CaTiO3 heterogeneous visible-light Fenton catalyst from vanadium-titanium magnetite according to claim 1, characterized in that, The hydrogen-rich gas mentioned in step (3) is coke oven gas, wherein (H2+CO+CH4)>85% and H2 / CO≥4.

7. The method for preparing Fe-CaTiO3 heterogeneous visible-light Fenton catalyst from vanadium-titanium magnetite according to claim 1, characterized in that, The reduction temperature of the reduction reaction in step (3) is 950-1050℃, and the reduction time is 1-2h.

8. The method for preparing Fe-CaTiO3 heterogeneous visible-light Fenton catalyst from vanadium-titanium magnetite according to claim 1, characterized in that, In step (5), the Fe-CaTiO3 heterogeneous visible light Fenton catalyst with a particle size of less than 100 mesh accounts for 100%.

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