A composite material based on red mud modification and its preparation method

Abstract

This invention belongs to the field of catalytic material synthesis technology, specifically referring to a composite material based on red mud modification and its preparation method. The red mud-modified composite material includes the following raw materials in parts by weight: 0.3-0.5 parts red mud, 0.05-0.1 parts thioacetamide, 0.3-0.6 parts straw, 0.03 parts CTAB, 0.05 parts silane coupling agent, 0.04-0.06 parts polyvinyl alcohol, 0.05-0.08 parts PVP, 0.2-0.3 parts citric acid, and 20 parts alcohol solution. Using red mud as the core, the material is prepared by acid leaching followed by co-calcination with thioacetamide (TAA) and straw under an inert atmosphere. This process achieves iron reduction, pore formation, and atomic doping. The modified material surface becomes positively charged, enabling it to strongly adsorb anionic pollutants and degrade them in situ under visible light through photo-Fenton degradation, thus realizing an integrated wastewater treatment function of "adsorption-enrichment-degradation-regeneration".

Description

Technical Field

[0001] This invention belongs to the field of catalytic material synthesis technology, specifically referring to a composite material based on red mud modification and its preparation method. Background Technology

[0002] The large-scale stockpiling of industrial solid waste, red mud, not only occupies land, but its high alkalinity and potential leaching risks of heavy metals also pose a continuous pressure on the ecological environment. How to achieve high-value-added resource utilization of red mud is an urgent issue of long-term concern in the environmental and materials fields. On the other hand, wastewater containing anionic organic dyes discharged from industries such as printing and dyeing and chemicals has become a challenge in water treatment due to its high color, high toxicity, and difficulty in biodegradation.

[0003] Currently, advanced oxidation technologies based on Fenton or Fenton-like reactions are one of the effective methods for degrading such organic pollutants. Their core lies in the efficient and stable generation of hydroxyl radicals (·OH). Traditional homogeneous Fenton systems use Fe... 2+ Salts present problems such as a narrow pH range, secondary pollution from iron sludge, and the inability to recycle the catalyst. In recent years, the preparation of heterogeneous Fenton catalysts from iron-containing solid waste (such as red mud) has become a research hotspot. However, the direct application of unmodified red mud has obvious drawbacks: firstly, its strong alkalinity consumes the acidity of the reaction system, inhibiting the Fenton reaction; secondly, the iron in it is mainly in the form of inert Fe. 3+ Firstly, the material exists in forms such as Fe2O3, resulting in low catalytic activity. Secondly, the material itself has limited adsorption capacity, leading to poor enrichment of pollutants and low degradation efficiency. Current research on red mud modification mainly focuses on simple acid washing to remove alkali or simple compounding with carbon materials to improve adsorption. These methods fail to effectively activate the iron active sites in red mud at the electronic structure level. 3+ / Fe 2+ The cycle efficiency is low, and the improvement in catalytic performance is limited. At the same time, simply increasing the adsorption capacity will result in pollutants being enriched rather than degraded, posing a desorption and regeneration problem.

[0004] Therefore, developing a red mud-based composite material that can simultaneously achieve strong adsorption, high catalytic activity, and intrinsic active site electronic structure regulation is key to realizing its efficient resource utilization and application in the treatment of recalcitrant wastewater. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention discloses a red mud-based composite material and its preparation method. Using industrial waste red mud as the base material, it undergoes acid leaching pretreatment to remove alkaline impurities and fully expose Fe2O3 active sites. Then, it is compounded with thioacetamide (TAA) and straw, followed by calcination under an inert atmosphere. During calcination, the S2- generated by the pyrolysis of TAA efficiently reduces Fe3+ to Fe2+, while the carbonization of straw simultaneously increases the porosity of the red mud. The N and S elements in TAA achieve atomic-level doping and form stable "Fe-S coordination bonds." The “Fe-SN ternary active center” is subsequently modified with silane coupling agent and CTAB, which significantly enhances the electrostatic adsorption capacity for anionic Congo red under acidic conditions. Under visible light irradiation, the photocatalytic activity of straw charcoal can continuously reduce the Fe3+ generated in the reaction to Fe2+, maintain the stability of the Fe2+ / Fe3+ cycle, and efficiently generate active species such as ·OH through photo-Fenton reaction, ultimately achieving continuous treatment of adsorbed and enriched Congo red molecules through “electrostatic adsorption-pore trapping and enrichment-in-situ photo-Fenton degradation-active center recycling”.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is a composite material based on red mud modification, comprising the following raw materials in parts by weight: 0.3-0.5 parts red mud, 0.05-0.1 parts thioacetamide, 0.3-0.6 parts straw, 0.03 parts CTAB, 0.05 parts silane coupling agent, 0.04-0.06 parts polyvinyl alcohol and 0.05-0.08 parts PVP, 0.2-0.3 parts citric acid and 20 parts alcohol liquid.

[0007] This invention also provides a method for preparing a composite material based on red mud modification, the steps of which are as follows: Step 1: Weigh 0.2-0.3 parts of citric acid and add it to 30 parts of deionized water. Heat at 60℃ for 4 hours. Weigh 0.3-0.5 parts of red mud, sieve it through a 200-mesh screen, and add it to the mixture. Stir at 300 r / min for 2 hours. Filter the mixture using a 0.45-micron filter membrane and wash it 5 times with deionized water. Dry the mixture at 80℃ for 48 hours to obtain the red mud substrate. Step 2: Weigh 0.05-0.1 parts of thioacetamide and 0.3-0.6 parts of straw, crush them, and pre-treat them by sieving through a 100-mesh screen to obtain complex A. Add the obtained complex A and the red mud substrate obtained in Step 1 to 50 parts of deionized water, and ball mill them at a speed of 200 r / min for 2 h. Then dry them at a temperature of 70℃ for 24 h to obtain mixed powder. Step 3: Calcine the mixed powder obtained in Step 2 at a temperature of 500-700℃ for 2.5h, with a heating rate of 5℃ / min, and introduce argon gas (Ar) at a flow rate of 50mL / min. Then, allow it to cool naturally to room temperature to obtain modified red mud powder. Step 4: Weigh 0.05-0.08 parts of PVP and add them to 30 parts of anhydrous ethanol. Sonicate at 20 kHz for 20 min to obtain a dispersion. Add the modified red mud powder obtained in Step 3 to the dispersion. Stir at 300 r / min and heat at 55 ℃ for 2 h to obtain the red mud composite. Step 5: Weigh 0.05 parts of silane coupling agent and add it to 20 parts of alcohol solution, wherein the alcohol solution includes raw materials with the following mass ratio: anhydrous ethanol: deionized water = 9:1. Reflux and heat at 70℃ for 30 min, and stir at 300 r / min. Cool naturally to room temperature to obtain hydrolysate. Step 6: Add the red mud composite obtained in Step 4 to the hydrolysate obtained in Step 5, reflux at 70°C for 2 hours, stir at 500 r / min, weigh out 0.03 parts CTAB and 0.04-0.06 parts polyvinyl alcohol and add them to the mixture, reflux at 90°C for 12 hours, cool naturally to room temperature, wash three times each with deionized water and anhydrous ethanol, and then dry at 65°C for 24 hours to obtain the red mud-modified composite material.

[0008] The beneficial effects achieved by this invention are as follows: The composite material prepared by this invention, based on red mud modification, uses industrial waste red mud as the base material. It is first pretreated with acid leaching to remove alkaline impurities and fully expose Fe2O3 active sites. Then, the pretreated red mud, thioacetamide (TAA), and straw are combined and calcined under an inert atmosphere. During the pyrolysis of TAA, the S2- produced by hydrolysis can efficiently reduce Fe3+ in Fe2O3 of the red mud to Fe2+, providing highly active nuclei for the photo-Fenton reaction. Simultaneously, the carbonization of the straw increases the porosity of the red mud, providing ample adsorption and reaction sites for pollutant molecules. The N and S elements in TAA are simultaneously atomically doped, forming stable "Fe-S coordination bonds" and electronically optimized "Fe-SN ternary active centers" with Fe2+, further enhancing the catalytic stability and surface adsorption characteristics of the material.

[0009] The composite material prepared by this invention, based on red mud modification, is modified by a silane coupling agent, which binds to the hydroxyl groups on the surface of the red mud. Furthermore, CTAB is used to introduce -N+(CH3)3 positively charged groups into the surface of the red mud, significantly improving the surface positive potential of the material under acidic conditions and enhancing its electrostatic adsorption capacity for anionic Congo red. Under visible light irradiation, the straw charcoal also exhibits photocatalytic activity, with its photogenerated electrons continuously reducing Fe3+ generated in the reaction to Fe2+, maintaining the stability of the Fe2+ / Fe3+ cycle. Through photo-Fenton reaction, it efficiently generates ·OH active species, achieving in-situ degradation of adsorbed and enriched Congo red molecules.

[0010] The composite material based on red mud modification prepared by this invention achieves a continuous treatment process of "electrostatic adsorption-pore trapping and enrichment-in-situ photo-Fenton degradation-active center recycling" through the above process. Attached Figure Description

[0011] Figure 1 The diagram shows the preparation method of the composite material based on red mud modification proposed in this application; Figure 2 Here is a SEM image of the red mud in Example 2; Figure 3 TEM image of the red mud-modified composite material prepared in Example 2; Figure 4 The Zeta (Zeta) test results for the red mud and the prepared red mud-modified composite material in Example 2 are shown. Figure 5 Adsorption test diagrams of the red mud-modified composite materials prepared in the examples and comparative examples; Figure 6 Degradation test images of the red mud-modified composite materials prepared in the examples and comparative examples; Figure 7 The H2O2 product test diagrams are shown for the red mud-modified composite materials prepared in the examples and comparative examples. Figure 8 The image shows the OH test result of the red mud-modified composite material prepared in Example 2.

[0012] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0013] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0014] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0015] The preparation method and characterization in the following examples are based on... Figures 1-8 Unless otherwise specified, all methods are conventional. Unless otherwise specified, all parts of the materials used in the following examples are by weight, and all raw materials are new materials purchased from the market. The alcohol solution includes the following raw materials in the following mass ratio: anhydrous ethanol: deionized water = 9:1, silane coupling agent is KH-570, and PVP molecular weight is 10000.

[0016] Example 1: A composite material based on red mud modification, comprising the following raw materials in parts by weight: 0.3 parts red mud, 0.05 parts thioacetamide, 0.3 parts straw, 0.03 parts CTAB, 0.05 parts silane coupling agent, 0.04 parts polyvinyl alcohol and 0.05 parts PVP, 0.2 parts citric acid and 20 parts alcohol liquid.

[0017] This embodiment also provides a method for preparing a composite material based on red mud modification, the steps of which are as follows: Step 1: Weigh 0.2 parts of citric acid and add it to 30 parts of deionized water. Heat at 60℃ for 4 hours. Weigh 0.3 parts of red mud, sieve it through a 200-mesh screen, and add it to the mixture. Stir at 300 r / min for 2 hours. Filter the mixture using a 0.45-micron filter membrane and wash it 5 times with deionized water. Dry the mixture at 80℃ for 48 hours to obtain the red mud substrate. Step 2: Weigh 0.05 parts of thioacetamide and 0.3 parts of straw, crush them, and pre-treat them by sieving through a 100-mesh screen to obtain complex A. Add the obtained complex A and the red mud substrate obtained in Step 1 to 50 parts of deionized water, and ball mill them at a speed of 200 r / min for 2 h. Then dry them at a temperature of 70℃ for 24 h to obtain mixed powder. Step 3: Calcine the mixed powder obtained in Step 2 at 500℃ for 2.5 hours at a heating rate of 5℃ / min, introduce argon gas at a flow rate of 50mL / min, and allow it to cool naturally to room temperature to obtain modified red mud powder. Step 4: Weigh 0.05 parts of PVP and add it to 30 parts of anhydrous ethanol. Sonicate the mixture for 20 minutes at a frequency of 20 kHz to obtain a dispersion. Add the modified red mud powder obtained in Step 3 to the dispersion and stir at a speed of 300 r / min. Heat the mixture at a temperature of 55℃ for 2 hours to obtain the red mud composite. Step 5: Weigh 0.05 parts of silane coupling agent and add it to 20 parts of alcohol solution. Reflux and heat at 70℃ for 30 min, stirring at 300 r / min. Allow to cool naturally to room temperature to obtain the hydrolysate. Step 6: Add the red mud composite obtained in Step 4 to the hydrolysate obtained in Step 5, reflux at 70°C for 2 hours, stir at 500 r / min, weigh out 0.03 parts CTAB and 0.04 parts polyvinyl alcohol and add them to the mixture, reflux at 90°C for 12 hours, cool naturally to room temperature, wash three times each with deionized water and anhydrous ethanol, and then dry at 65°C for 24 hours to obtain the red mud-modified composite material.

[0018] Example 2: A composite material based on red mud modification, comprising the following raw materials in parts by weight: 0.4 parts red mud, 0.08 parts thioacetamide, 0.45 parts straw, 0.03 parts CTAB, 0.05 parts silane coupling agent, 0.05 parts polyvinyl alcohol, 0.065 parts PVP, 0.25 parts citric acid, and 20 parts alcohol liquid.

[0019] This embodiment also provides a method for preparing a composite material based on red mud modification, the steps of which are as follows: Step 1: Weigh 0.25 parts of citric acid and add it to 30 parts of deionized water. Heat at 60℃ for 4 hours. Weigh 0.4 parts of red mud, sieve it through a 200-mesh screen, and add it to the mixture. Stir at 300 r / min for 2 hours. Filter the mixture using a 0.45-micron filter membrane and wash it 5 times with deionized water. Dry the mixture at 80℃ for 48 hours to obtain the red mud substrate. Step 2: Weigh 0.08 parts of thioacetamide and 0.45 parts of straw, crush them, and pre-treat them by sieving through a 100-mesh screen to obtain complex A. Add the obtained complex A and the red mud substrate obtained in Step 1 to 50 parts of deionized water, and ball mill them at a speed of 200 r / min for 2 h. Then dry them at a temperature of 70℃ for 24 h to obtain mixed powder. Step 3: Calcine the mixed powder obtained in Step 2 at 600℃ for 2.5h at a heating rate of 5℃ / min, introduce argon gas at a flow rate of 50mL / min, and allow it to cool naturally to room temperature to obtain modified red mud powder. Step 4: Weigh 0.065 parts of PVP and add it to 30 parts of anhydrous ethanol. Sonicate the mixture for 20 minutes at a frequency of 20 kHz to obtain a dispersion. Add the modified red mud powder obtained in Step 3 to the dispersion and stir at a speed of 300 r / min. Heat the mixture at a temperature of 55℃ for 2 hours to obtain the red mud composite. Step 5: Weigh 0.05 parts of silane coupling agent and add it to 20 parts of alcohol solution. Reflux and heat at 70℃ for 30 min, stirring at 300 r / min. Allow to cool naturally to room temperature to obtain the hydrolysate. Step 6: Add the red mud composite obtained in Step 4 to the hydrolysate obtained in Step 5, reflux at 70°C for 2 hours, stir at 500 r / min, weigh out 0.03 parts CTAB and 0.05 parts polyvinyl alcohol and add them to the mixture, reflux at 90°C for 12 hours, cool naturally to room temperature, wash three times each with deionized water and anhydrous ethanol, and then dry at 65°C for 24 hours to obtain the red mud-modified composite material.

[0020] Example 3: A composite material based on red mud modification, comprising the following raw materials in parts by weight: 0.5 parts red mud, 0.1 parts thioacetamide, 0.6 parts straw, 0.03 parts CTAB, 0.05 parts silane coupling agent, 0.06 parts polyvinyl alcohol and 0.08 parts PVP, 0.3 parts citric acid and 20 parts alcohol liquid.

[0021] This embodiment also provides a method for preparing a composite material based on red mud modification, the steps of which are as follows: Step 1: Weigh 0.3 parts of citric acid and add it to 30 parts of deionized water. Heat at 60℃ for 4 hours. Weigh 0.5 parts of red mud, sieve it through a 200-mesh screen, and add it to the mixture. Stir at 300 r / min for 2 hours. Filter the mixture using a 0.45-micron filter membrane and wash it 5 times with deionized water. Dry the mixture at 80℃ for 48 hours to obtain the red mud substrate. Step 2: Weigh 0.1 parts of thioacetamide and 0.6 parts of straw, crush them, and pre-treat them by sieving through a 100-mesh screen to obtain complex A. Add the obtained complex A and the red mud substrate obtained in Step 1 to 50 parts of deionized water, and ball mill them at a speed of 200 r / min for 2 h. Then dry them at a temperature of 70℃ for 24 h to obtain mixed powder. Step 3: Calcine the mixed powder obtained in Step 2 at 700℃ for 2.5 hours at a heating rate of 5℃ / min, introduce argon gas at a flow rate of 50mL / min, and allow it to cool naturally to room temperature to obtain modified red mud powder. Step 4: Weigh 0.05-0.08 parts of PVP and add them to 30 parts of anhydrous ethanol. Sonicate at 20 kHz for 20 min to obtain a dispersion. Add the modified red mud powder obtained in Step 3 to the dispersion. Stir at 300 r / min and heat at 55 ℃ for 2 h to obtain the red mud composite. Step 5: Weigh 0.05 parts of silane coupling agent and add it to 20 parts of alcohol solution. Reflux and heat at 70℃ for 30 min, stirring at 300 r / min. Allow to cool naturally to room temperature to obtain the hydrolysate. Step 6: Add the red mud composite obtained in Step 4 to the hydrolysate obtained in Step 5, reflux at 70°C for 2 hours, stir at 500 r / min, weigh out 0.03 parts CTAB and 0.06 parts polyvinyl alcohol and add them to the mixture, reflux at 90°C for 12 hours, cool naturally to room temperature, wash three times each with deionized water and anhydrous ethanol, and then dry at 65°C for 24 hours to obtain the red mud-modified composite material.

[0022] Comparative example: The difference between Comparative Example 1 and Example 2 is that TAA was not added; the rest is the same as Example 2. The difference between Comparative Example 2 and Example 2 is that CTAB was not added; the rest is the same as Example 2. The difference between Comparative Example 3 and Example 2 is that TAA and CTAB were not added; the rest are the same as Example 2. Comparative Example 4 was made of red mud and was not further processed.

[0023] The following tests were conducted on the prepared red mud-modified composite materials: Figure 2 The image shows the SEM image of the unmodified red mud in Example 2, which reveals a dense, massive structure. Figure 3 The TEM image of the modified composite material prepared in Example 2 shows that the modified material forms a rich porous structure (derived from the pore regulation during the straw carbonization process), providing sufficient physical adsorption sites for Congo red molecules. Figure 4The figure shows a comparison of the Zeta potentials of unmodified red mud and the modified composite material under pH=5 conditions (consistent with the adsorption-degradation test system). The surface potential of unmodified red mud was 9.3 mV, which increased to 35.4 mV after modification. This increase is attributed to the -N⁺(CH3)3 positively charged group introduced by CTAB, which significantly enhances the electrostatic adsorption of anionic Congo red. Figure 5 The images show the adsorption test results of Congo red on the red mud-modified composite materials prepared in the examples and comparative examples (Congo red concentration was 30 mg / L, pH=5, 50 mg of the prepared red mud-modified composite material was added to 100 mL of Congo red solution for dark reaction adsorption for 30 min). The test results show that the overall adsorption effect of the examples is significantly better than that of the comparative examples. Figure 6 The images show degradation test results of the red mud-modified composite materials prepared in the examples and comparative examples (after the dark reaction, the solution was irradiated with a 300W xenon lamp for 15 minutes, and the concentration of Congo red in the solution was measured using a UV spectrophotometer). The red mud-modified composite material prepared in the examples showed a higher degradation rate of 99.1%. Figure 7 The graph shows the yield of H2O2 catalytically generated from the composite material of Example 2 under 300 W xenon lamp irradiation and pH=5. The results show that the H2O2 yield is 5.1 μmol / g·h, providing sufficient substrate for the photo-Fenton reaction. Furthermore, the ·OH radical activity of the red mud-modified composite material prepared in Example 2 was tested, and the results are as follows... Figure 8 As shown, there is a distinct characteristic signal 10 minutes after the light is turned on, indicating that the catalytic process efficiently generates ・OH strong oxidizing active species, which directly degrades the adsorbed and enriched Congo red molecules.

[0024] Obviously, the above comparative examples and embodiments are only a part of the comparative examples and embodiments of the present invention, and they, along with the comparative examples and embodiments referenced based on such examples, are all within the scope of protection of this invention.

[0025] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0026] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A composite material based on red mud modification, characterized in that, The preparation materials include the following parts by weight: 0.3-0.5 parts red mud, 0.05-0.1 parts thioacetamide, 0.3-0.6 parts straw, 0.03 parts CTAB, 0.05 parts silane coupling agent, 0.04-0.06 parts polyvinyl alcohol and 0.05-0.08 parts PVP, 0.2-0.3 parts citric acid and 20 parts alcohol liquid.

2. The composite material based on red mud modification according to claim 1, characterized in that, The alcohol solution comprises raw materials in the following mass ratio: anhydrous ethanol: deionized water = 9:

1.

3. A method for preparing a composite material based on red mud modification as described in any one of claims 1-2, characterized in that, The steps are as follows: Step 1: Weigh citric acid and add it to water, heat it, weigh red mud and add it, stir, filter, dry, and obtain red mud substrate; Step 2: Weigh thioacetamide and straw pretreatment to obtain complex A. Add complex A and red mud substrate to water, ball mill, dry to obtain mixed powder. Step 3: Calcine the mixed powder and ventilate to obtain modified red mud powder; Step 4: Weigh PVP and add it to ethanol, sonicate to obtain a dispersion, add modified red mud powder to the dispersion, stir, heat to obtain red mud composite. Step 5: Weigh the silane coupling agent and add it to the alcohol solution, heat and stir to obtain the hydrolysate; Step 6: Add the red mud composite to the hydrolysate, heat and stir, weigh CTAB and polyvinyl alcohol, add, heat, wash, and dry to obtain the red mud-modified composite material.

4. The method for preparing a composite material based on red mud modification according to claim 3, characterized in that, The ball milling speed in step two is 200 r / min, and the ball milling time is 2 h.

5. The method for preparing a composite material based on red mud modification according to claim 3, characterized in that, The calcination temperature in step three is 500-700℃, the calcination time is 2.5h, the gas flow rate is 50mL / min, and the gas being circulated is Ar.

6. The method for preparing a composite material based on red mud modification according to claim 3, characterized in that, The frequency of the ultrasound in step four is 20 kHz, and the duration of the ultrasound is 20 minutes.

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