Magnetic iron oxide catalysts for sludge wet catalytic oxidation and methods of making

Abstract

The application discloses a magnetic iron oxide catalyst for sludge wet catalytic oxidation and a preparation method thereof, and belongs to the field of catalyst material preparation. The specific method is as follows: trivalent iron salt and divalent iron salt are dissolved in water in proportion to obtain a mixed solution; under the protection of an inert gas atmosphere, an alkaline solution is added to the mixed solution, and the pH value is adjusted to 8-12; then, the reaction material is obtained by washing away impurities with water and organic detergent in sequence; and the magnetic iron oxide catalyst is obtained by vacuum drying and grinding the reaction material. The catalyst can effectively reduce the content of organic matter in sludge pyrolysis liquid in the process of catalytic wet oxidation, and has good magnetism and recyclability before and after the reaction. After five cycles, the catalyst still maintains stable organic matter removal effect and good magnetism. The method is expected to be applied to the fields of sludge resource utilization, environmental water pollutant removal and the like.

Description

Technical Field

[0001] This invention belongs to the field of catalyst material preparation, specifically relating to a magnetic iron oxide catalyst for wet catalytic oxidation of sludge and its preparation method. Background Technology

[0002] my country has a huge production of activated sludge, and this production has been steadily increasing in recent years. In 2019, the production of activated sludge reached 60 Mt, and it is projected to exceed 90 Mt (80% water content) by 2025. Therefore, the harmless treatment and resource utilization of activated sludge are particularly crucial. The main components of activated sludge include organic matter, heavy metals, and pathogens, with organic matter content reaching up to 40%.

[0003] Catalytic wet oxidation technology utilizes high temperature, high pressure, and the action of a catalyst to generate strong oxidizing free radicals through oxygen activation, oxidizing pollutants into small-molecule organic or inorganic substances. Compared to traditional sludge treatment methods, this technology can better achieve sludge reduction, harmlessness, and resource recovery. Catalyst selection is crucial in this technology. The catalyst not only needs to be highly efficient but also inexpensive. If the catalyst can be easily recovered and regenerated during use, it will greatly reduce catalyst loss and avoid secondary pollution, thereby reducing remediation costs and improving the atom economy of the catalyst.

[0004] Therefore, there is an urgent need to develop a catalyst that can be recycled and reused and has high efficiency in catalyzing wet oxidation. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and to provide a magnetic iron oxide catalyst for wet catalytic oxidation of sludge and its preparation method.

[0006] The specific technical solution adopted in this invention is as follows:

[0007] In a first aspect, the present invention provides a method for preparing a magnetic iron oxide catalyst for wet catalytic oxidation of sludge, comprising dissolving ferric salt and ferrous salt in water in a certain proportion to obtain a mixed solution; adding an alkaline solution to the mixed solution under an inert gas protective atmosphere to adjust the pH value to alkaline; subsequently washing away impurities with water and an organic detergent to obtain a reactant; and vacuum drying and grinding the reactant to obtain a magnetic iron oxide catalyst.

[0008] Preferably, the molar ratio of ferric ions to ferrous ions in the mixture is (0.1-10):1.

[0009] Preferably, the trivalent ferric salt is ferric chloride hexahydrate or ferric sulfate, and the divalent ferric salt is ferrous chloride tetrahydrate or ferrous sulfate.

[0010] Preferably, the alkaline solution is a sodium hydroxide, potassium hydroxide, or calcium hydroxide solution.

[0011] Furthermore, the concentration of the alkaline solution is 0.01–10 mol / L.

[0012] Preferably, the inert gas is nitrogen or argon.

[0013] Preferably, the pH value is adjusted to a range of 8–12.

[0014] Preferably, the vacuum drying temperature of the reactants is set to 50℃~120℃, and the time is 0.5~12 hours.

[0015] Preferably, the organic detergent is ethanol or acetone.

[0016] In a second aspect, the present invention provides a magnetic iron oxide catalyst obtained by the preparation method described in the first aspect.

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

[0018] The preparation method provided by this invention is simple, uses inexpensive raw materials, and causes minimal environmental pollution. The prepared magnetic iron oxide catalyst can achieve a 40% removal rate of organic matter in sludge pyrolysis liquid, far exceeding the 17% removal rate of the control group without catalyst. Furthermore, this magnetic iron oxide catalyst can be recovered through high-temperature heating, enabling recycling. Experiments show that after five recycling cycles, the magnetic iron oxide catalyst maintains stable organic matter removal performance and good magnetic properties, making it a promising candidate for application in sludge resource recovery processes. Attached Figure Description

[0019] Figure 1 This is a flowchart of the method for preparing magnetic iron oxide catalysts provided by the present invention;

[0020] Figure 2 This is a schematic diagram of the magnetic properties of the magnetic iron oxide catalyst prepared in Example 1.

[0021] Figure 3 The image shows a scanning electron microscope (SEM) image of the magnetic iron oxide catalyst prepared in Example 1.

[0022] Figure 4 The graph shows the effect of the magnetic iron oxide catalyst prepared in Example 1 on the removal rate of organic matter in sludge pyrolysis liquid.

[0023] Figure 5 This is a comparison chart of the removal rates of organic matter in sludge pyrolysis liquid by the magnetic iron oxide catalyst after different cycles in Example 2.

[0024] Figure 6This is a schematic diagram of the magnetic properties of the magnetic iron oxide catalyst after 5 cycles in Example 2.

[0025] Figure 7 This is a scanning electron microscope image of the magnetic iron oxide catalyst after 5 cycles in Example 2. Detailed Implementation

[0026] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly, provided that there is no mutual conflict.

[0027] Example 1

[0028] This embodiment provides a method for preparing a magnetic iron oxide catalyst, as detailed below:

[0029] (1) Dissolve ferric chloride hexahydrate and ferrous chloride tetrahydrate in water to obtain a mixed solution, such that the molar ratio of ferric ions to ferrous ions in the mixed solution is 1:1, and both the ferric chloride solution and the ferrous chloride solution are 0.5 mol / L.

[0030] (2) Under an inert gas protective atmosphere, add a 5 mol / L sodium hydroxide solution to the mixture, adjust the pH value to 10, and carry out the reaction.

[0031] (3) The residual salt ion impurities were then washed away with water and ethanol in sequence to obtain the reactants.

[0032] (4) Place the reactants in a vacuum drying oven, set the drying temperature to 50°C, and the drying time to 12 hours. Finally, grind the reactants to obtain the magnetic iron oxide catalyst.

[0033] like Figure 2 As shown, the magnetic iron oxide catalyst prepared in this embodiment can be adsorbed by a magnet and possesses magnetic properties. Figure 3 This is a scanning electron microscope (SEM) image of the magnetic iron oxide catalyst prepared in this embodiment. Figure 3 It can be seen that the surface of the sample is spherical, which is consistent with the microscopic characteristics of the material.

[0034] To verify the performance of the magnetic iron oxide catalyst prepared in this embodiment for wet catalytic oxidation of sludge, the following experiments were conducted:

[0035] Take 30 mL of sludge pyrolysis liquid and place it in the reactor. Add a certain amount of catalyst, start the pressure control system, set the stirrer speed and reaction temperature, and begin heating. When the target temperature is reached, open the vent valve to allow oxygen to flow into the reactor and begin the reaction. After the reaction is complete, close the oxygen inlet valve and heating switch of the reactor to allow it to cool down.

[0036] according to Figure 4It can be seen that, compared with the absence of catalyst, the degradation rate of organic matter increased from 17% to 38%, which indicates that the addition of magnetic iron oxide catalyst significantly degraded organic matter.

[0037] Example 2

[0038] In this embodiment, the magnetic iron oxide catalyst used in the wet catalytic oxidation of sludge in Example 1 is recovered and then subjected to multiple catalytic cycles. After the reaction, the magnetic iron oxide catalyst is vacuum dried at 50°C for 12 hours and then heated at 450°C for half an hour to complete one cycle of catalyst recovery.

[0039] Figure 5 The graph shows the cyclic effect of the catalyst. As can be seen from the graph, the catalytic effect did not decrease significantly after multiple cycles. Figure 6 This is a schematic diagram of the magnetic properties of the catalyst after 5 cycles. The material still retains strong magnetism after multiple reactions. Figure 7 This is a scanning electron microscope (SEM) schematic diagram of the catalyst after 5 cycles, and... Figure 3 In contrast, the microstructure did not show significant changes, indicating that the catalyst has good recyclability.

[0040] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.

Claims

1. A method for preparing a magnetic iron oxide catalyst for wet catalytic oxidation of sludge, characterized in that, Ferric and divalent iron salts were dissolved in water in a certain proportion to obtain a mixture. Under an inert gas atmosphere, an alkaline solution was added to the mixture to adjust the pH to alkaline. Subsequently, impurities were washed away with water and an organic detergent to obtain the reactant. The reactant was vacuum dried and ground to obtain a magnetic iron oxide catalyst. The molar ratio of ferric and divalent iron ions in the mixture was 1:

1.

2. The method for preparing the magnetic iron oxide catalyst according to claim 1, characterized in that, The trivalent ferric salt is ferric chloride hexahydrate or ferric sulfate, and the divalent ferric salt is ferrous chloride tetrahydrate or ferrous sulfate.

3. The method for preparing the magnetic iron oxide catalyst according to claim 1, characterized in that, The alkaline solution is a sodium hydroxide, potassium hydroxide, or calcium hydroxide solution.

4. The method for preparing the magnetic iron oxide catalyst according to claim 3, characterized in that, The concentration of the alkaline solution is 0.01~10 mol / L.

5. The method for preparing the magnetic iron oxide catalyst according to claim 1, characterized in that, The inert gas is nitrogen or argon.

6. The method for preparing the magnetic iron oxide catalyst according to claim 1, characterized in that, Adjust the pH value to a range of 8-12.

7. The method for preparing the magnetic iron oxide catalyst according to claim 1, characterized in that, The vacuum drying temperature of the reactants is set to 50℃~120℃, and the time is 0.5~12 hours.

8. The method for preparing the magnetic iron oxide catalyst according to claim 1, characterized in that, The organic detergent is ethanol or acetone.

9. A magnetic iron oxide catalyst obtained by any one of the preparation methods described in claims 1 to 8.

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