A porous core-shell Fenton catalyst, its preparation method and application

Abstract

This invention discloses a porous core-shell Fenton catalyst, its preparation method, and its application in water treatment. The preparation method includes the following steps: 1) extruding a core paste as a core and two outer shell pastes on both sides into a sandwich-shaped paste; the raw material composition of the core paste includes steel slag, clay, a first activator, and water; the raw material composition of the outer shell paste includes fly ash, clay, a second activator, a pore-forming agent, and water; 2) sealing and rounding the sandwich-shaped paste by extending the outer shell paste, cutting it into spheres, polishing, drying, and calcining to obtain the porous core-shell Fenton catalyst.

Description

Technical Field

[0001] This invention relates to the field of Fenton catalyst technology, specifically to a porous core-shell structure Fenton catalyst, its preparation method, and its application. Background Technology

[0002] Fly ash and steel slag are common industrial solid wastes. Because they contain effective components such as SiO2 and Al2O3, they can be prepared into ceramsite, which is widely used in wastewater, waste gas and building materials.

[0003] Chinese patent application CN201610101449.6 discloses a porous ceramsite Fenton catalyst and its preparation method. The catalyst uses municipal sludge, clay, kaolin, fly ash, silicon source, copper-containing compounds, and iron-containing compounds as raw materials, and is prepared by high-temperature sintering. However, this preparation method requires a large variety of raw materials and necessitates the addition of copper-containing and iron-containing compounds as active ingredients, resulting in high preparation costs.

[0004] Chinese patent application CN202211101596.5 discloses a method for preparing composite multivalent Fenton catalysts using a hydrothermal synthesis method. This method uses diatomaceous earth, fly ash, and cement as raw materials, with copper sulfate and manganese sulfate added as active substances. First, core spheres are prepared by rolling on a pelletizing disc, then shell materials are added to form an outer shell layer on the surface, resulting in a core-shell structure. This is followed by 48 hours of curing and 10 hours of hydrothermal reaction. However, this preparation method is complex, time-consuming, requires the addition of active substances, and has high production costs.

[0005] Therefore, there is a need to develop a Fenton catalyst that can effectively utilize the active components in fly ash and can efficiently and for a long lifespan catalyze H2O2 to remove pollutants. Summary of the Invention

[0006] To address the aforementioned technical problems and shortcomings in the field, this invention provides a method for preparing a porous core-shell structured Fenton catalyst, which solves the problems of low utilization rate of active components, complex preparation methods, and high costs of existing catalysts prepared based on fly ash. The resulting Fenton catalyst has high strength and structural stability, and exhibits excellent catalytic activity and stability.

[0007] A method for preparing a porous core-shell structured Fenton catalyst, comprising the following steps:

[0008] 1) The core paste is sandwiched between two outer shell pastes and squeezed into a sandwich shape;

[0009] The raw material composition of the core paste includes steel slag, clay, a first activator, and water;

[0010] The raw material composition of the outer shell paste includes fly ash, clay, a second activator, a pore-forming agent, and water;

[0011] 2) The sandwich-shaped paste is sealed and rolled into a ball by extending the outer shell paste, cut into balls, polished, dried, and calcined to obtain the porous core-shell structure Fenton catalyst.

[0012] This invention uses industrial solid waste fly ash and steel slag as raw materials to produce a porous core-shell structure Fenton catalyst by extrusion, cutting, polishing to form balls, and then high-temperature calcination. The preparation method is simple and allows for waste recycling.

[0013] The inventors discovered that without an extrusion process, the contact between fly ash and the activator is insufficient, limiting the dissolution of active substances Al2O3 and SiO2 from the original glassy structure of the fly ash. This, in turn, affects the formation of a new glassy framework structure during subsequent calcination, reducing the compressive strength of the Fenton catalyst and impacting its stability, lifespan, and catalytic performance. Furthermore, if a fly ash shell structure is not constructed and steel slag is used directly as the Fenton catalyst, the insufficient content of active substances Al2O3 and SiO2 in the steel slag prevents the formation of a sufficient glassy structure to guarantee the compressive strength of the Fenton catalyst.

[0014] Based on this, the inventors first prepared the outer shell paste and the core paste, and then pressed, cut, polished and sphericalized them under certain pressure and calcined them at high temperature. This made the fly ash outer shell form a solid glassy structure to ensure the structural stability of the Fenton catalyst, while the steel slag core, being rich in Fe, can efficiently catalyze H2O2 to carry out the Fenton reaction.

[0015] In step 1), the pressure of the extrusion can be 1 to 2 MPa.

[0016] In step 1), the thickness of the core paste in the sandwich-shaped paste can be 2-4 mm, and the thickness of the outer shell paste on both sides can be 1-3 mm on each side.

[0017] In step 1), the mass fraction of Fe2O3 in the steel slag can be 18% to 30%.

[0018] In step 1), the first activator may include sodium metasilicate, etc. Sodium metasilicate can also act as a binder and a glass frame forming aid.

[0019] In step 1), the mass fraction of Fe2O3 in the fly ash can be 10% to 15%.

[0020] In step 1), the second activator may include sodium metasilicate, etc. Sodium metasilicate can also act as a binder and a glass frame forming aid.

[0021] In step 1), the pore-forming agent may include sodium bicarbonate, etc.

[0022] In step 1), the raw material composition of the core paste, by mass parts, may include:

[0023]

[0024]

[0025] In step 1), the raw material composition of the outer shell paste, by weight, may include:

[0026]

[0027] In step 1), the mass ratio of the core paste to the outer shell paste can be 1:1 to 3.

[0028] In step 2), the diameter of the rounded paste can be 3-6 mm.

[0029] In step 2), the diameter of the sphere obtained by cutting can be 3 to 6 mm.

[0030] In step 2), the polishing time can be 10 to 20 minutes.

[0031] In step 2), the calcination may include two stages, wherein:

[0032] The first stage is pre-calcination, with a calcination temperature of 500-600℃ and a calcination time of 20-40 minutes;

[0033] The calcination temperature in the second stage can be 1000–1150℃, and the calcination time can be 20–40 minutes.

[0034] The present invention also provides a porous core-shell structured Fenton catalyst prepared by the aforementioned preparation method.

[0035] The present invention also provides the application of the porous core-shell structured Fenton catalyst in water treatment.

[0036] In the Fenton catalyst of the present invention, fly ash and steel slag are iron-containing raw materials, and clay is a molding aid.

[0037] The Fenton catalyst of the present invention comprises a fly ash raw material outer shell layer and a steel slag raw material inner core layer. Fly ash contains active substances Al2O3 and SiO2 that form a glassy body, which can provide a glass framework structure for the Fenton catalyst. Fe2O3 contained in fly ash can directly contact H2O2 and generate ·OH through a heterogeneous catalytic reaction. Fe2O3 in steel slag can further catalyze H2O2 through a slow release effect. Thus, the catalyst can efficiently and effectively catalyze the generation of ·OH from H2O2, and the removal rate of pollutants such as rifampicin can reach up to 97%.

[0038] The porous core-shell structure Fenton catalyst of the present invention can achieve a removal rate of up to 97% for pollutants such as rifampicin through a mechanism of heterogeneous reaction and slow-release Fe to achieve homogeneous reaction, which is conducive to the promotion of practical application.

[0039] Compared with the prior art, the beneficial effects of this invention are as follows:

[0040] This invention produces a porous core-shell Fenton catalyst by extrusion, cutting, polishing to form spheres, followed by high-temperature calcination. The preparation method is simple and allows for waste recycling. Using fly ash and steel slag as raw materials, the fly ash is excited to form a glass framework structure, ensuring the structural stability of the Fenton catalyst. At the same time, the Fe in the fly ash and steel slag is used to carry out heterogeneous and homogeneous reactions, thereby efficiently and with a long lifespan catalyzing the generation of ·OH from H2O2, achieving the goal of efficiently removing pollutants such as rifampicin.

[0041] Moreover, the porous core-shell structure Fenton catalyst of the present invention has good removal effect on pollutants such as rifampicin and has practical application value. Attached Figure Description

[0042] Figure 1 A cross-sectional photograph of the porous core-shell Fenton catalyst prepared in Example 1.

[0043] Figure 2 Scanning electron microscope image of the porous core-shell Fenton catalyst prepared in Example 1.

[0044] Figure 3 The figure shows the stability test results of the porous core-shell Fenton catalyst prepared in Example 1.

[0045] Figure 4 Scanning electron microscope image of the porous core-shell Fenton catalyst prepared in Example 2.

[0046] Figure 5 Scanning electron microscope image of the porous core-shell Fenton catalyst prepared in Example 3.

[0047] Figure 6 The compressive strength diagrams are for the comparative examples and Fenton catalysts prepared in Examples 1-3.

[0048] Figure 7 The image shows the removal effect of the Fenton catalyst prepared in comparative examples and Examples 1-3 on rifampicin. Detailed Implementation

[0049] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0050] Unless otherwise specified, "parts" in the following embodiments and comparative examples refer to parts by mass.

[0051] Example 1

[0052] The preparation method of the porous core-shell structure Fenton catalyst in this embodiment is carried out according to the following steps:

[0053] (1) Mix 10 parts of fly ash with a mass fraction of 11% Fe2O3, 10 parts of clay, 4 parts of sodium metasilicate and 1 part of sodium bicarbonate with 7.5 parts of water to form a shell paste.

[0054] (2) Mix 5 parts of steel slag with a mass fraction of 19% Fe2O3, 5 parts of clay, and 2 parts of sodium metasilicate with 2 parts of water to form a core paste.

[0055] (3) The core paste is sandwiched between two outer shell pastes. The mass ratio of the core paste to the outer shell paste is 1:1. The paste is squeezed into a strip-shaped sandwich shape under a pressure of 1.5MPa. After squeezing, the thickness of the core in the sandwich structure is 3mm and the thickness of the outer layer is 1.2mm.

[0056] (4) Seal and roll the strip-shaped sandwich-like paste by extending the outer layer of paste, with a paste diameter of 5mm;

[0057] (5) Cut the paste into 5mm diameter balls using a 5mm axial cutter, and polish them for 10 minutes.

[0058] (6) The dried raw material balls were calcined at a pre-calcination temperature of 600℃ for 20 min and a calcination time of 1100℃ for 20 min to obtain a porous core-shell Fenton catalyst.

[0059] A cross-sectional photograph of the porous core-shell Fenton catalyst prepared in Example 1 is shown below. Figure 1 As shown, from Figure 1 It can be seen that the Fenton catalyst has a porous and core-shell structure.

[0060] Scanning electron microscope (SEM) images of the porous core-shell Fenton catalyst prepared in Example 1 are shown below. Figure 2 As shown, from Figure 2 It can be seen that both the core and shell of the Fenton catalyst have abundant pores.

[0061] 0.3 g of the porous core-shell Fenton catalyst prepared in Example 1 was added to 100 mL of 10 mg / L solution at pH 3. -1 The rifampicin wastewater was mechanically stirred at 200 rpm, and then H2O2 was added to bring the initial concentration of H2O2 to 8 mmol / L before the reaction. -1 After stirring for 60 minutes, repeatability experiments were conducted and the amount of Fe dissolved from the porous core-shell Fenton catalyst was measured to examine the catalyst's performance stability and Fe slow-release capacity. Figure 3 It can be seen that after 6 uses, the catalyst still achieved a 95% removal rate of rifampicin, indicating that its catalytic performance is high and stable, and the sustained-release Fe concentration range is 0.91–1.40 mg / L. -1 The catalyst has the ability to release Fe slowly and sustainably, and has a long service life.

[0062] Example 2

[0063] The preparation method of the porous core-shell structure Fenton catalyst in this embodiment is carried out according to the following steps:

[0064] (1) Mix 10.5 parts of fly ash with a mass fraction of 11% Fe2O3, 10.5 parts of clay, 3 parts of sodium metasilicate and 1 part of sodium bicarbonate with 7.5 parts of water to form a shell paste.

[0065] (2) Mix 5 parts of steel slag with a mass fraction of 19% Fe2O3, 5 parts of clay, and 2 parts of sodium metasilicate with 2 parts of water to form a core paste.

[0066] (3) The core paste is used as the sandwich, and the outer shell paste is used on both sides. The mass ratio of the core paste to the outer shell paste is 1:2.5. Apply 2MPa pressure to compress into a strip sandwich-shaped paste. After compression, the thickness of the sandwich structure is 2mm and the thickness of the outer layer is 2mm.

[0067] (4) Seal and roll the strip-shaped sandwich-like paste by extending the outer layer of paste, with a paste diameter of 5mm;

[0068] (5) Cut the paste into 5mm diameter balls using a 5mm axial cutter, and polish them for 15 minutes.

[0069] (6) The dried raw material balls were calcined at a pre-calcination temperature of 600℃ for 30 min and a calcination temperature of 1100℃ for 30 min to obtain a porous core-shell structure Fenton catalyst.

[0070] Scanning electron microscope (SEM) images of the porous core-shell Fenton catalyst prepared in Example 2 are shown below. Figure 4 As shown, from Figure 4 It can be seen that both the core and shell of the Fenton catalyst have abundant pores.

[0071] Example 3

[0072] The preparation method of the porous core-shell structure Fenton catalyst in this embodiment is carried out according to the following steps:

[0073] (1) Mix 11 parts of fly ash with a mass fraction of 11% Fe2O3, 11 parts of clay, 2 parts of sodium metasilicate and 1 part of sodium bicarbonate with 7 parts of water to form a shell paste.

[0074] (2) Mix 4 parts of steel slag with a mass fraction of 19% Fe2O3, 4 parts of clay, 2 parts of sodium metasilicate, and 2 parts of water evenly to form a core paste.

[0075] (3) The core paste is sandwiched between two outer shell pastes. The mass ratio of the core paste to the outer shell paste is 1:1. The paste is squeezed into a strip-shaped sandwich shape under a pressure of 1.5MPa. After squeezing, the thickness of the core in the sandwich structure is 3mm and the thickness of the outer layer is 1.2mm.

[0076] (4) Seal and roll the strip-shaped sandwich-like paste by extending the outer layer of paste, with a paste diameter of 5mm;

[0077] (5) Cut the paste into 5mm diameter balls using a 5mm axial cutter, and polish them for 15 minutes.

[0078] (6) The dried raw material balls were calcined at a pre-calcination temperature of 500℃ and a calcination time of 30 min, and at a calcination temperature of 1000℃ and a calcination time of 30 min to obtain a porous core-shell structure Fenton catalyst.

[0079] Scanning electron microscope (SEM) images of the porous core-shell Fenton catalyst prepared in Example 3 are shown below. Figure 5 As shown, from Figure 5 It can be seen that both the core and shell of the Fenton catalyst have abundant pores.

[0080] Comparative Example

[0081] The preparation method of the Fenton catalyst in this comparative example is carried out according to the following steps:

[0082] (1) Mix 5 parts of steel slag with a mass fraction of 19% Fe2O3, 5 parts of clay and 2 parts of sodium metasilicate evenly, and granulate the core by spraying water in a disc granulator to achieve a diameter of 3mm.

[0083] (2) Mix 11 parts of fly ash with a mass fraction of 11% Fe2O3, 11 parts of clay, 2 parts of sodium metasilicate and 1 part of sodium bicarbonate evenly as shell material; granulate the core and shell structure on the basis of the core by a disc granulator and water spraying, so that the diameter of the core and shell structure is 5mm; the mass ratio of core material to shell material is 1:1.3.

[0084] (3) The dried raw material balls were calcined at a pre-calcination temperature of 500℃ for 30 min and a calcination temperature of 1000℃ for 30 min to obtain the Fenton catalyst.

[0085] Test case

[0086] The compressive strength of the catalysts prepared in the comparative examples and Examples 1-3 was tested by applying a certain pressure to them in order to examine the structural stability of the catalysts. Figure 6 As shown, if disc granulation is used, the compressive strength of the catalyst prepared in the comparative example is only 4 MPa, while the compressive strength of the catalysts prepared in Examples 1-3 reaches 9-18 MPa due to the improved preparation method. The present invention significantly improves the structural stability of the catalyst.

[0087] 0.3 g of Fenton catalyst prepared in comparative examples and Examples 1-3 was added to 100 mL of 10 mg L solution at pH 3. -1 The rifampicin wastewater was mechanically stirred at 200 rpm, and then H2O2 was added to bring the initial concentration of H2O2 to 8 mmol / L before the reaction. -1 After stirring for 60 minutes, from Figure 7 It can be seen that if the porous core-shell structure Fenton catalyst is prepared by the traditional disc granulation method, its removal rate is only 83%, while the catalysts in Examples 1-3 have a removal rate of 90%-97% for rifampicin. The present invention significantly improves the catalytic performance.

[0088] As can be seen from the above embodiments, the porous core-shell Fenton catalyst prepared by the present invention not only has good structural and performance stability, but also can efficiently catalyze the removal of rifampicin from H2O2, making it suitable for application in actual water treatment processes.

[0089] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for preparing a porous core-shell structured Fenton catalyst, characterized in that, Including the following steps: 1) The core paste is sandwiched between two outer shell pastes, and then squeezed into a sandwich-shaped paste. The raw material composition of the core paste includes steel slag, clay, a first activator, and water; the first activator includes sodium metasilicate. The raw material composition of the outer shell paste includes fly ash, clay, a second activator, a pore-forming agent, and water; the second activator includes sodium metasilicate. 2) The sandwich-shaped paste is sealed and rolled into a ball by extending the outer shell paste, cut into balls, polished, dried, and calcined to obtain the porous core-shell structure Fenton catalyst.

2. The preparation method according to claim 1, characterized in that, In step 1): The extrusion pressure is 1~2 MPa; In the sandwich-shaped paste, the core paste has a thickness of 2-4 mm, and the outer shell paste on both sides has a thickness of 1-3 mm on each side.

3. The preparation method according to claim 1, characterized in that, In step 1): The mass fraction of Fe2O3 in the steel slag is 18%~30%; The mass fraction of Fe2O3 in the fly ash is 10%~15%; The pore-forming agent includes sodium bicarbonate.

4. The preparation method according to claim 1, characterized in that, In step 1), the raw material composition of the core paste, by mass parts, includes: 2-5 parts steel slag, 2-5 parts clay, 1-2 parts first activator, and 2-2.5 parts water.

5. The preparation method according to claim 1, characterized in that, In step 1), the raw material composition of the outer shell paste, by mass parts, includes: 10-15 parts fly ash, 10-15 parts clay, 2-5 parts second activator, 1-2 parts pore-forming agent, and 7-9 parts water.

6. The preparation method according to claim 1, characterized in that, In step 1), the mass ratio of the core paste to the outer shell paste is 1:1~3.

7. The preparation method according to claim 1, characterized in that, In step 2): The diameter of the rounded paste is 3~6 mm; The diameter of the sphere obtained by cutting is 3~6 mm; Polishing time is 10~20 minutes.

8. The preparation method according to claim 1, characterized in that, In step 2), the calcination includes two stages, wherein: The first stage is pre-calcination, with a calcination temperature of 500~600℃ and a calcination time of 20~40 min; The second stage of calcination is carried out at a temperature of 1000~1150℃ for a duration of 20~40 min.

9. The porous core-shell Fenton catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the porous core-shell structure Fenton catalyst according to claim 9 in water treatment.

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