Method for preparing composite material for adsorbing methylene blue in printing and dyeing wastewater by modifying red mud and application thereof

Abstract

This invention discloses a method and application for preparing novel composite materials using modified red mud, belonging to the field of solid waste resource utilization technology. The technical solution of this invention is as follows: red mud is dried, ground, and calcined to obtain magnetic red mud. Sucrose and humic acid are mixed with the magnetic red mud, ultrasonically dispersed, and magnetically stirred to ensure thorough mixing. The resulting mixture is placed in a reaction vessel for hydrothermal reaction. After the reaction is complete, the solution is cooled, filtered, washed, and dried to obtain a hydrothermal carbon-humic acid red mud composite material. This invention transforms industrial solid waste red mud into an adsorbent material through a simple calcination and hydrothermal method, achieving synergistic solid-liquid treatment and providing a new approach for the resource utilization of red mud. The novel composite material prepared by this invention using red mud doped with sucrose and humic acid has better pore structure and selectivity compared to traditional adsorbents, achieving the goal of treating waste with waste.

Description

Technical Field

[0001] This invention relates to a method and application of preparing a composite material for adsorbing methylene blue in dyeing and printing wastewater by modifying red mud, belonging to the field of solid waste resource utilization technology. Background Technology

[0002] Red mud, a major solid waste generated during alumina production, can be categorized into Bayer process red mud, sintering process red mud, and combined process red mud based on alumina quality and production technology. Red mud contains large amounts of metal oxides such as Fe2O3, Al2O3, and TiO2, making it a potential effective material for treating water pollutants. In 2022, China's alumina production increased to over 80 million tons, with red mud production exceeding 100 million tons and utilization reaching over 8 million tons, an increase of nearly 40% compared to 2021. Reports indicate that by 2025, the comprehensive utilization rate of newly generated major solid wastes should reach 60%. However, red mud, as one of the most difficult-to-treat major solid wastes, currently has a comprehensive utilization rate of only 7-8%, far lower than other major industrial solid wastes. Large amounts of red mud cannot be effectively recycled and are instead dumped, wasting land resources. If the comprehensive utilization rate of red mud cannot be significantly improved, it will have a significant impact on industry, hindering normal production. Furthermore, improperly treated red mud can cause serious pollution to soil, water resources, and the atmosphere. Therefore, improving its comprehensive utilization rate is key to solving the problem of large-scale red mud accumulation.

[0003] Dyeing and printing wastewater refers to the wastewater generated during the dyeing and printing processes in the dyeing and printing industry. It contains large amounts of organic dyes and other harmful substances, posing serious threats to the environment and human health. Organic dyes are organic compounds containing numerous benzene rings, phenolic hydroxyl groups, and amino groups, exhibiting strong toxicity and bioaccumulation. Their main hazards are as follows: First, organic dyes contain large amounts of benzene ring compounds and phenolic hydroxyl groups, which are highly toxic and carcinogenic, causing long-term harm to the environment and human health. Second, the discharge of organic dyes into dyeing and printing wastewater leads to changes in water color and increases in COD (chemical oxygen demand), affecting water transparency and quality, and causing water pollution. Therefore, effective measures are needed to mitigate the environmental pollution caused by dyeing and printing wastewater.

[0004] Treatment methods for dye wastewater include physical, chemical, and biological methods. Among these, biological methods are currently considered the most effective and environmentally friendly, encompassing traditional activated sludge processes, biofilm processes, and microbial combustion technologies. In recent years, research on biological methods has increasingly focused on the screening and improvement of microorganisms to enhance treatment efficiency and reduce costs. Chemical methods are also effective for dye wastewater treatment. These methods primarily decompose dye molecules through oxidation and reduction reactions, but they require significant energy and chemical consumption, and the resulting waste also necessitates treatment, leading to higher costs. In contrast, physical methods are simpler to operate, requiring less complex equipment and technology, and allowing for the selection of different physical treatment methods, such as filtration, sedimentation, and adsorption, depending on the specific circumstances. However, their treatment efficiency is lower, and they are typically used as supplementary methods to other treatment approaches. In conclusion, while dye wastewater treatment technologies have seen significant development and application, issues such as low efficiency and high costs persist. Therefore, continuous research and innovation are needed to improve treatment efficiency, reduce costs, minimize environmental impact, and achieve efficient treatment and resource utilization of dye wastewater.

[0005] For example, patent CN106669751A discloses a method for treating methylene blue dye wastewater, which requires acid-base modification of red mud, potentially generating secondary pollutants and harming the environment. Patent document CN113351173A discloses a humic acid-containing magnetic adsorbent material and its preparation method and application, using red mud or sludge as the iron source. The prepared adsorbent material exhibits excellent magnetic properties, strong chemical stability, and superior regeneration performance; however, the preparation process is cumbersome, requiring modification treatment under three different thermal environments, resulting in high energy consumption. Therefore, a method for preparing and applying a hydrothermal carbon-humic acid-red mud composite material has been developed. This method is not only simple but also avoids the use of oxidants or organic solvents, preventing secondary pollution. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for preparing a novel composite material from red mud combined with sucrose and humic acid, and for adsorbing and treating methylene blue (MB) in dyeing and printing wastewater. The method employs hydrothermal synthesis, utilizing the abundant metal oxides in red mud and the hydrothermal carbon material formed by sucrose, along with humic acid for doping, followed by activation to enhance the active sites, thereby purifying the methylene blue in dyeing and printing wastewater.

[0007] To address the issue of low utilization rate of red mud, this invention uses red mud as raw material, adds sucrose and humic acid, and prepares a novel adsorbent through simple hydrothermal carbonization and activation. This adsorbent has better adsorption properties, effectively removing methylene blue from dyeing and printing wastewater, reducing red mud pollution, lowering environmental remediation costs, and realizing the resource utilization of red mud.

[0008] A composite material for adsorbing methylene blue in dyeing and printing wastewater was prepared by combining red mud with sucrose and humic acid. The specific preparation steps are as follows:

[0009] (1) Dry the red mud in an oven to constant weight, grind the dried red mud and pass it through a 100-mesh sieve to obtain red mud powder for later use.

[0010] (2) The red mud powder from step (1) is roasted and activated to obtain magnetic red mud.

[0011] (3) Mix the magnetic red mud from step (2) with sucrose and humic acid and add deionized water (there are no special requirements for the amount of deionized water used as a solvent; just make sure that the magnetic red mud, sucrose and humic acid are fully mixed). After ultrasonic dispersion, place it in a constant temperature magnetic stirrer at room temperature.

[0012] (4) Place the mixture in step (3) into a reaction vessel for hydrothermal reaction. After the reaction is completed, cool it naturally to obtain a reaction solution. Filter, wash, dry and grind the reaction solution to obtain a hydrothermal carbon-humic acid red mud composite material.

[0013] Preferably, the drying temperature of the red mud in step (1) is 100~110℃.

[0014] Preferably, the calcination activation in step (2) is carried out under N2 atmosphere, with the temperature increased to 400-600℃ at a heating rate of 5℃ / min for 2 hours.

[0015] Preferably, the mass ratio of red mud, humic acid and sucrose in step (3) is 1:0.1~1:1~2.

[0016] Preferably, the ultrasonic dispersion time in step (3) is 10 to 30 minutes and the stirring time is 1 to 2 hours.

[0017] Preferably, the magnetic stirring speed in step (3) is 300-500 rpm.

[0018] Preferably, the hydrothermal reaction in step (4) is carried out at 140-220℃ for 8-16 hours.

[0019] Preferably, the drying in step (4) is carried out at 60-100°C for 12 hours; the washing in step (4) is carried out using deionized water until the washing liquid is clear.

[0020] The hydrothermal carbon-humic acid red mud composite material prepared by this invention can adsorb methylene blue in dyeing and printing wastewater. The process includes the following steps: adding the hydrothermal carbon-humic acid red mud composite material to wastewater containing methylene blue, with an addition amount of 0.1 g / L to 0.5 g / L and an adsorption time of 10 h to 12 h.

[0021] Beneficial effects of the present invention

[0022] (1) This invention utilizes red mud loaded with sucrose and humic acid carbon materials to adsorb and treat methylene blue in dyeing and printing wastewater. Compared with hydrothermal carbon adsorbent materials formed by red mud or sucrose alone, it has better pore structure and selectivity, which can improve the removal rate of methylene blue wastewater and provide a new method for the resource utilization of red mud.

[0023] (2) The preparation method of the present invention is simple, the material is magnetic and easy to recycle, the preparation process does not produce toxic and harmful by-products, it can be mass-produced and meets the requirements of environmental protection.

[0024] (3) The addition of humic acid in this invention promotes the formation of hydrothermal carbon, which enables sucrose humic acid to better modify the red mud and load it onto the red mud, thereby enhancing the surface area and active sites of the material and further improving the adsorption effect.

[0025] (4) The present invention utilizes the method of “using waste to treat waste”, which not only improves the utilization rate of red mud, but also reduces the process cost and reduces the pollution to the environment.

[0026] (5) The addition of renewable carbon precursor sucrose in this invention provides a richer carbon source, which improves the adsorption effect and has significant properties such as environmental protection, low cost and easy production.

[0027] (6) The preparation process of this invention only requires treatment in two thermal environments, which is relatively simple, saves energy, and does not affect the adsorption effect of hydrothermal carbon-humic acid red mud composite material on methylene blue. Attached Figure Description

[0028] Figure 1 A method for preparing novel composite materials by modifying red mud and a process flow diagram for treating dyeing and printing wastewater.

[0029] Figure 2 XRD pattern analysis of the original red mud sample.

[0030] Figure 3 FT-IR image of a novel composite material prepared by modifying red mud.

[0031] Figure 4 This is a diagram showing the effect of red mud modification in preparing a novel composite material for adsorbing methylene blue. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following embodiments are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims. Reagents or instruments used in the embodiments whose manufacturers are not specified can be commercially available conventional products.

[0033] The red mud used in this embodiment of the invention comes from an aluminum company in Wenshan City, Yunnan Province.

[0034] Example 1

[0035] A method for preparing a composite material for adsorbing methylene blue in dyeing and printing wastewater using modified red mud, the process is as follows: Figure 1 As shown, the specific steps are as follows:

[0036] (1) Red mud from an aluminum company in Wenshan City, Yunnan Province was placed in an oven and dried at 100°C to constant weight, and then ground through a 100-mesh sieve to obtain red mud powder for later use.

[0037] (2) The red mud powder obtained in step (1) is placed in a tube furnace and heated to 600°C for 2 hours under N2 atmosphere at a heating rate of 5°C / min to activate it, thereby obtaining magnetic red mud.

[0038] (3) Add 1g of magnetic red mud, 1g of sucrose and 0.5g of humic acid obtained in step (2) to deionized water, sonicate for 30 minutes in an ultrasonic cleaner to disperse evenly, and stir for 1 hour in a magnetic stirrer with a speed of 500 rpm.

[0039] (4) The mixed solution obtained in step (3) was transferred into a stainless steel reactor with a polytetrafluoroethylene liner and reacted at 180°C for 12 hours. After the reaction was completed, the mixture was cooled naturally. The filter residue obtained by vacuum filtration was washed with deionized water until the washing liquid was clear. The residue was dried at 60°C for 12 hours to obtain the hydrothermal carbon-humic acid red mud composite material.

[0040] The original red mud sample was subjected to XRD analysis, such as... Figure 2 As shown, it contains a large amount of metal oxides such as Fe2O3 and Al2O3. The prepared red mud-modified novel composite material was subjected to FT-IR spectroscopy, and the results are as follows... Figure 3 As shown in the figure (a represents a novel composite material of red mud, b represents humic acid, c represents hydrothermal carbon formed by hydrothermal treatment of sucrose alone, and d represents red mud calcined at 600℃), the spectrum of d is recorded at 996 cm⁻¹. -1 The dominant wavelength band can be attributed to Si-O-Si bonds. Furthermore, the broadband observed at ~3450 nm is a sign of -OH stretching. In the spectrum of c, at 1630 cm⁻¹... ‐1The vibrations of the C=C (aromatic ring) group observed at this wavelength are related to the vibrations observed at 1386 cm⁻¹. In the spectrum of b, at 1386 cm⁻¹... ‐1 and 2915 cm ‐1 The observed bands are -COO and CH bonds. Characteristic bands of b, c, and d were found in the spectrum of a, indicating that the composite material preparation method was successful.

[0041] Example 2

[0042] A method for preparing a composite material for adsorbing methylene blue in dyeing and printing wastewater using modified red mud, the specific steps of which are as follows:

[0043] (1) Red mud from an aluminum company in Wenshan City, Yunnan Province was placed in an oven and dried at 100°C to constant weight, and then ground through a 100-mesh sieve to obtain red mud powder for later use.

[0044] (2) The red mud powder obtained in step (1) is placed in a tube furnace and roasted at 500°C for 2 hours under N2 atmosphere at a heating rate of 5°C / min to obtain magnetic red mud.

[0045] (3) Add 1g of magnetic red mud, 0.5g of sucrose and 1g of humic acid obtained in step (2) to deionized water, sonicate for 20min in an ultrasonic cleaner to disperse evenly, and stir for 2h in a magnetic stirrer with a stirring speed of 300rpm.

[0046] (4) The mixed solution obtained in step (3) is transferred into a stainless steel reactor with a polytetrafluoroethylene liner and reacted at 180°C for 12 hours. After the reaction is completed, the mixture is cooled naturally. The filter residue obtained by suction filtration is washed with deionized water until the washing liquid is clear. It is then dried at 80°C for 12 hours to obtain a hydrothermal carbon-humic acid red mud composite material.

[0047] Example 3

[0048] A method for preparing a composite material for adsorbing methylene blue in dyeing and printing wastewater using modified red mud, the specific steps of which are as follows:

[0049] (1) Red mud from an aluminum company in Wenshan City, Yunnan Province was placed in an oven and dried at 100°C to constant weight, and then ground through a 100-mesh sieve to obtain red mud powder for later use.

[0050] (2) The red mud powder obtained in step (1) is placed in a tube furnace and roasted at 400°C for 2 hours under N2 atmosphere at a heating rate of 5°C / min to obtain magnetic red mud.

[0051] (3) Add 1g of magnetic red mud, 2g of sucrose and 1g of humic acid obtained in step (2) to deionized water, sonicate for 10min in an ultrasonic cleaner to disperse them evenly, and stir for 2h in a magnetic stirrer with a stirring speed of 300rpm.

[0052] (4) The mixed solution obtained in step (3) was transferred into a stainless steel reactor with a polytetrafluoroethylene liner and reacted at 160°C for 16 hours. After the reaction was completed, the mixture was cooled naturally. The filter residue obtained by vacuum filtration was washed with deionized water until the washing liquid was clear. It was then dried at 100°C for 12 hours to obtain the hydrothermal carbon-humic acid red mud composite material.

[0053] Example 4

[0054] A method for preparing a composite material for adsorbing methylene blue in dyeing and printing wastewater using modified red mud, the specific steps of which are as follows:

[0055] (1) Red mud from an aluminum company in Wenshan City, Yunnan Province was placed in an oven and dried at 100°C to constant weight, and then ground through a 100-mesh sieve to obtain red mud powder for later use.

[0056] (2) The red mud powder obtained in step (1) is placed in a tube furnace and roasted at 600°C for 2 hours under N2 atmosphere at a heating rate of 5°C / min to obtain magnetic red mud.

[0057] (3) Add 1g of magnetic red mud, 2g of sucrose and 0.3g of humic acid obtained in step (2) to deionized water, sonicate for 20min in an ultrasonic cleaner to disperse evenly, and stir for 1h in a magnetic stirrer with a stirring speed of 500rpm.

[0058] (4) The mixed solution obtained in step (3) was transferred into a stainless steel reactor with a polytetrafluoroethylene liner and reacted at 220°C for 12 hours. After the reaction was completed, the mixture was cooled naturally. The filter residue obtained by vacuum filtration was washed with deionized water until the washing liquid was clear. The residue was dried at 100°C for 12 hours to obtain the hydrothermal carbon-humic acid red mud composite material.

[0059] Example 5

[0060] A method for preparing a composite material for adsorbing methylene blue in dyeing and printing wastewater using modified red mud, the specific steps of which are as follows:

[0061] (1) Red mud from an aluminum company in Wenshan City, Yunnan Province was placed in an oven and dried at 105°C to constant weight, and then ground through a 100-mesh sieve to obtain red mud powder for later use.

[0062] (2) The red mud powder obtained in step (1) is placed in a tube furnace and roasted at 600°C for 2 hours under N2 atmosphere at a heating rate of 5°C / min to obtain magnetic red mud.

[0063] (3) Add 1g of magnetic red mud, 1.5g of sucrose and 0.1g of humic acid obtained in step (2) to deionized water, sonicate for 20min in an ultrasonic cleaner to disperse evenly, and stir for 1h in a magnetic stirrer with a stirring speed of 500rpm.

[0064] (4) The mixed solution obtained in step (3) was transferred into a stainless steel reactor with a polytetrafluoroethylene liner and reacted at 140°C for 8 hours. After the reaction was completed, the mixture was cooled naturally. The filter residue obtained by suction filtration was washed with deionized water until the washing liquid was clear. The residue was dried at 100°C for 12 hours to obtain the hydrothermal carbon-humic acid red mud composite material.

[0065] Example 6

[0066] A method for preparing a composite material for adsorbing methylene blue in dyeing and printing wastewater using modified red mud, the specific steps of which are as follows:

[0067] (1) Red mud from an aluminum company in Wenshan City, Yunnan Province was placed in an oven and dried at 110°C to constant weight, and then ground and passed through a 100-mesh sieve to obtain red mud powder for later use.

[0068] (2) The red mud powder obtained in step (1) is placed in a tube furnace and roasted at 600°C for 2 hours under N2 atmosphere at a heating rate of 5°C / min to obtain magnetic red mud.

[0069] (3) Add 1g of magnetic red mud, 1g of sucrose and 0.1g of humic acid obtained in step (2) to deionized water, mix them evenly under magnetic stirring, and then sonicate them evenly in an ultrasonic cleaner for 20 minutes.

[0070] (4) The mixed solution obtained in step (3) was transferred into a stainless steel reactor with a polytetrafluoroethylene liner and reacted at 180°C for 8 hours. After the reaction was completed, the mixture was cooled naturally. The filter residue obtained by vacuum filtration was washed with deionized water until the washing liquid was clear. The residue was dried at 100°C to obtain hydrothermal carbon-humic acid red mud composite material.

[0071] Comparative Example 1

[0072] As a comparison, this comparative example differs from Example 1 in that humic acid is not added. The specific steps are as follows:

[0073] (1) Red mud from an aluminum company in Wenshan City, Yunnan Province was placed in an oven and dried at 100°C to constant weight, and then ground through a 100-mesh sieve to obtain red mud powder for later use.

[0074] (2) The red mud powder obtained in step (1) is placed in a tube furnace and heated to 600°C for 2 hours under N2 atmosphere at a heating rate of 5°C / min to activate it, thereby obtaining magnetic red mud.

[0075] (3) Add 1g of magnetic red mud and 1g of sucrose obtained in step (2) to deionized water, mix them evenly under magnetic stirring, and then sonicate them evenly in an ultrasonic cleaner for 30 minutes.

[0076] (4) The mixed solution obtained in step (3) was transferred into a stainless steel reactor with a polytetrafluoroethylene liner and reacted at 180°C for 12 hours. After the reaction was completed, the mixture was cooled naturally. The filter residue obtained by vacuum filtration was washed with deionized water until the washing liquid was clear. The residue was dried at 60°C to obtain a hydrothermal carbon-red mud composite material.

[0077] Comparative Example 2

[0078] As a comparison, this comparative example differs from Example 1 in that no sucrose is added. The specific steps are as follows:

[0079] (1) Red mud from an aluminum company in Wenshan City, Yunnan Province was placed in an oven and dried at 100°C to constant weight, and then ground through a 100-mesh sieve to obtain red mud powder for later use.

[0080] (2) The red mud powder obtained in step (1) is placed in a tube furnace and heated to 600°C for 2 hours under N2 atmosphere at a heating rate of 5°C / min to activate it, thereby obtaining magnetic red mud.

[0081] (3) Add 1g of magnetic red mud and 0.5g of humic acid obtained in step (2) to deionized water, mix them evenly under magnetic stirring, and then sonicate them evenly in an ultrasonic cleaner for 30 minutes.

[0082] (4) The mixed solution obtained in step (3) is transferred into a stainless steel reactor with a polytetrafluoroethylene liner and reacted at 180°C for 12 hours. After the reaction is completed, the mixture is cooled naturally, and the filter residue obtained by vacuum filtration is washed with deionized water until the washing liquid is clear. The residue is then dried at 60°C to obtain humic acid red mud composite material.

[0083] Comparative Example 3

[0084] As a comparison, this comparative example differs from Example 1 in that the hydrothermal reaction in step (4) is replaced by calcination, and the specific steps are as follows:

[0085] (1) Red mud from an aluminum company in Wenshan City, Yunnan Province was placed in an oven and dried at 100°C to constant weight, and then ground through a 100-mesh sieve to obtain red mud powder for later use.

[0086] (2) The red mud powder obtained in step (1) is placed in a tube furnace and heated to 600°C for 2 hours under N2 atmosphere at a heating rate of 5°C / min to activate it, thereby obtaining magnetic red mud.

[0087] (3) Add 1g of magnetic red mud, 1g of sucrose and 0.5g of humic acid obtained in step (2) to deionized water, mix them evenly under magnetic stirring, and then sonicate them evenly in an ultrasonic cleaner for 30 minutes.

[0088] (4) The mixed solution obtained in step (3) is dried in an oven at 60°C for 10 hours, placed in a tube furnace and heated to 600°C for 2 hours at a heating rate of 5°C / min under N2 atmosphere to obtain carbon-red mud composite material.

[0089] Example 7

[0090] The effect of different mass ratios of red mud-modified novel composite materials on methylene blue removal rate.

[0091] The materials prepared using Examples 1-6 and Comparative Examples 1-3 were tested. The application of the novel red mud-modified composite material in the adsorption of methylene blue in wastewater treatment specifically involves using the prepared composite material to treat methylene blue in wastewater, including the following steps:

[0092] 40 mg of the novel red mud-modified composite material was placed in 100 ml of a solution with a methylene blue concentration of 50 mg / L. The mixture was reacted for 10 h under light-protected conditions. The concentration of methylene blue in the solution was measured, and the removal efficiency of the novel red mud-modified composite material for methylene blue was calculated. The results are as follows: Figure 4 The graphs show the adsorption effect of different modified red mud composite materials on methylene blue, and Table 1 shows the effect of red mud modified new composite materials obtained from raw materials with different mass ratios on the methylene blue removal rate.

[0093] Table 1

[0094]

[0095] Examples 1, 2, and 3 considered the effect of red mud roasting temperature on adsorbent performance and determined that 600℃ was the optimal roasting temperature for carbon materials.

[0096] From Table 1 and Figure 4 It is known that different mass ratios, loading amounts, and addition amounts lead to different results. When sucrose and humic acid are added simultaneously, and the ratio of red mud, sucrose, and humic acid is 1:1:0.5, the removal rate reaches over 97%. This indicates that the novel red mud-modified composite material prepared by this invention can significantly reduce the concentration of methylene blue in water pollution and reduce environmental damage.

Claims

1. A method for preparing a composite material for adsorbing methylene blue from dyeing and printing wastewater using modified red mud, characterized in that: The specific steps are as follows: (1) Dry the red mud in an oven to constant weight, grind the dried red mud and pass it through a 100-mesh sieve to obtain red mud powder for later use; (2) The red mud powder from step (1) is roasted and activated to obtain magnetic red mud; (3) Mix the magnetic red mud from step (2) with sucrose and humic acid and add deionized water. After ultrasonic dispersion, place it in a constant temperature magnetic stirrer and stir at room temperature. (4) Place the mixture in step (3) into a reaction vessel for hydrothermal reaction. After the reaction is completed, cool it naturally to obtain a reaction solution. Filter, wash, dry and grind the reaction solution to obtain a hydrothermal carbon-humic acid red mud composite material. In step (2), the calcination activation is carried out under N2 atmosphere, with the temperature increased to 400-600℃ at a heating rate of 5℃ / min for 2 hours; The mass ratio of red mud, sucrose and humic acid in step (3) is 1:0.5:0.1 to 1:2:1; The hydrothermal reaction described in step (4) is carried out at 160~180℃ for 12~16h.

2. The method for preparing a composite material for adsorbing methylene blue in dyeing and printing wastewater using red mud modification according to claim 1, characterized in that: The drying temperature of the red mud in step (1) is 100~110℃.

3. The method for preparing a composite material for adsorbing methylene blue in dyeing and printing wastewater using red mud modification according to claim 1, characterized in that: (3) The ultrasonic dispersion time is 10-30 min and the stirring time is 1-2 h.

4. The method for preparing a composite material for adsorbing methylene blue in dyeing and printing wastewater using red mud modification according to claim 1, characterized in that: In step (3), the magnetic stirring speed is 300-500 rpm.

5. The method for preparing a composite material for adsorbing methylene blue in dyeing and printing wastewater using red mud modification according to claim 1, characterized in that: The drying in step (4) is carried out at 60-100℃ for 12 hours; the washing in step (4) is carried out using deionized water until the washing liquid is clear.

6. The application of the composite material prepared according to claim 1 in the adsorption of methylene blue in dyeing and printing wastewater.

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