A foamed carbon-red mud composite material, a preparation method and application thereof

Abstract

The present application belongs to the technical field of sewage purification, and particularly relates to a foamed carbon-red mud composite material and a preparation method and application thereof. The preparation method of the foamed carbon-red mud composite material comprises the following steps: S1, red mud pretreatment; S2, synthesis of foamed carbon: mixing a sodium alginate solution, a calcium chloride solution and melamine foam, standing at room temperature to obtain a pretreatment mixture, and performing annealing treatment on the pretreatment mixture to obtain foamed carbon; and S3, preparation of the foamed carbon-red mud composite material: spraying modified red mud obtained by step S1 after being uniformly dispersed in water onto the surface of the foamed carbon. The foamed carbon-red mud composite material of the present application exhibits good light absorption in the range of 300-800 nm, and has a relatively high local temperature, and has better light absorption capacity and photothermal effect compared with foamed carbon, and can better purify sewage.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sewage purification, and particularly relates to a foamed carbon-red mud composite material and a preparation method and application thereof. BACKGROUND

[0002] Pollutants and pollutant recycling are the key to alleviate environmental problems. Water resources are the foundation of the earth, and evaporation, precipitation, industrial and domestic water, and river and ocean water flow constitute the water cycle on the earth. In the process of industrial and domestic water, water is inevitably contaminated, which has a negative impact on daily life and normal water cycle. Therefore, water purification is a necessary effort. Water purification technologies, such as disinfection, decontamination, and desalination, can solve water quality problems. However, most water purification technologies require complex devices or membranes. Therefore, an economic, green, and environmentally friendly wastewater purification strategy is desirable.

[0003] The photothermal strategy simulates the transpiration process and is a green and simple wastewater purification method. Key materials for solar photothermal steam technology, such as plasmonic materials, semiconductors, and carbon-based materials, have been developed. However, for wastewater containing heavy ions, high concentrations of acids and bases, or high concentrations of organic matter, relying solely on the photothermal transpiration process is insufficient to achieve water purification.

[0004] Therefore, it is necessary to provide an improved technical solution to the above-mentioned deficiencies of the prior art. SUMMARY

[0005] The present application aims to provide a foamed carbon-red mud composite material and a preparation method and application thereof to help solve or improve the problem of poor purification effect of existing photothermal strategies on wastewater.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solution: a preparation method of a foamed carbon-red mud composite material, comprising the following steps: S1, red mud pretreatment: introducing carbon dioxide gas into a red mud dispersion solution until the pH of the red mud solution is less than 8, solid-liquid separation, and drying to obtain modified red mud; S2, synthesis of foamed carbon: mixing sodium alginate solution, calcium chloride solution, and melamine foam, standing at room temperature to obtain a pretreatment mixture, and annealing the pretreatment mixture to obtain foamed carbon; S3, preparation of foamed carbon-red mud composite material: uniformly dispersing the modified red mud obtained by step S1 in water and spraying it on the surface of the foamed carbon, and drying to obtain the foamed carbon-red mud composite material.

[0007] Preferably, in step S2, the pretreatment mixture is heated to 300-500 ℃ for annealing, and the annealing time is 0.5-1 h; the heating rate is 5-15 ℃ / min.

[0008] Preferably, in step S2, the annealing is performed in a muffle furnace.

[0009] Preferably, in step S1, the red mud dispersion liquid is obtained by dispersing red mud particles in deionized water; the particle size of the red mud particles is capable of passing a 100-mesh sieve, and the mass ratio of the red mud dispersion liquid is 1:(2.3-21).

[0010] Preferably, in step S1, the rate of the carbon dioxide gas is 8-12 mL / min; the solid-liquid separation is achieved by centrifugation, the centrifugation speed is 2000-4000 rpm, and the centrifugation time is 10-30 min; the drying temperature is 85-105 ℃, and the drying time is 1-3 h.

[0011] Preferably, in step S2, the concentration of the sodium alginate solution is 40-60 mg / L, the concentration of the calcium chloride solution is 15-25 mg / L, the volume ratio of the sodium alginate solution to the calcium chloride solution is (5-15):(10-30), and the mass ratio of the melamine foam to the sodium alginate in the sodium alginate solution is 9:(10-45); in step S2, the room temperature standing time is 5-36 h.

[0012] Preferably, in step S2, the diameter of the melamine foam is 150-300 μm, and the porosity is 99%.

[0013] The application further provides a foam carbon-red mud composite material prepared by the method.

[0014] The application further provides an application of the foam carbon-red mud composite material, which adopts the technical scheme that the foam carbon-red mud composite material is applied to purify sewage; the sewage contains at least one of organic pollutants, metal ions, and non-metal ions.

[0015] Preferably, the organic pollutants are rhodamine and / or methyl blue; the metal ions are at least one of calcium, magnesium, sodium, potassium, aluminum, iron, and manganese; and the non-metal ions are sulfur and / or silicon.

[0016] Advantages:

[0017] The application takes foam carbon as a basic framework, loads modified red mud (obtained by introducing carbon dioxide into a red mud dispersion liquid to treat the red mud) on the surface of the foam carbon, and forms a foam carbon-red mud composite material with light-heat / photodegradation coupling function.

[0018] In the foamed carbon-red mud composite material of the present invention, the foamed carbon substrate exhibits a porous matrix structure that facilitates water evaporation, coupled with the photodegradation capability of the red mud material, thus realizing the treatment of waste with waste. The excellent light absorption capabilities of both foamed carbon and red mud ensure the photothermal effect and photodegradation performance of the foamed carbon-red mud composite material of the present invention.

[0019] Compared to single inorganic semiconductor photocatalysts, the presence of foamed carbon in the foamed carbon-red mud composite material provided by this invention gives the composite material better adsorption capacity than red mud. Due to the porous structure of the foam, its appropriate tunnel morphology can prevent a large amount of pollution and allow wastewater to pass through the composite material through evaporation. The foamed carbon-red mud composite material of this invention exhibits good light absorption performance in the 300~800 nm range, and also has a higher local temperature, showing better light absorption capacity and photothermal effect than foamed carbon, thus enabling better purification of wastewater.

[0020] In the foamed carbon-red mud composite material of the present invention, the foamed carbon not only serves as a floating matrix material, but also promotes the photodegradation of the red mud catalyst through its photothermal effect, thereby achieving efficient purification of wastewater (e.g., wastewater containing organic pollutants and heavy ions). The red mud, as a catalyst, can further degrade organic pollutants under photothermal assistance, while the photothermal properties of the foamed carbon enhance the overall catalytic performance of the system. This composite material can effectively purify simulated wastewater containing organic pollutants such as rhodamine and methylene blue, as well as actual wastewater containing heavy ions.

[0021] Furthermore, the foamed carbon-red mud composite material of the present invention can be placed directly in the outdoor environment and achieve efficient purification of wastewater by utilizing natural light irradiation, fully demonstrating the feasibility and practicality of the foamed carbon-red mud composite material of the present invention in practical applications. Attached Figure Description

[0022] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0023] Figure 1 The image shows a scanning electron microscope (SEM) image (×20 μm) of the foamed carbon prepared in Comparative Example 1.

[0024] Figure 2 The image shows a scanning electron microscope (SEM) image (×20 μm) of the foamed carbon-red mud composite material prepared in Example 1 of this invention.

[0025] Figure 3The images show the UV-Vis absorption rate test results of the modified red mud (BR) in Example 1 and the foamed carbon-red mud composite material prepared in Example 1, as well as the physical image of the foamed carbon-red mud composite material in Example 1; wherein, (a) is the UV-Vis absorption rate test result image, and (b) is the physical image.

[0026] Figure 4 The figure shows the temperature change test results of the foamed carbon-red mud composite material in Example 1 under standard sunlight irradiation.

[0027] Figure 5 The graph shows the temperature change test results of foamed carbon in Comparative Example 1 under standard sunlight irradiation.

[0028] Figure 6 This is a comparison diagram showing the foamed carbon-red mud composite material prepared in Example 1 of the present invention before and after purification of Rhodamine (RhB) wastewater and methylene blue (MB) wastewater.

[0029] Figure 7 The image shows the UV-Vis spectra of the foamed carbon-red mud composite material prepared in Example 1 of this invention before and after purifying Rhodamine (RhB) wastewater.

[0030] Figure 8 The image shows the UV-Vis spectra of the foamed carbon-red mud composite material prepared in Example 1 of this invention before and after purifying methylene blue (MB) wastewater.

[0031] Figure 9 The graph shows a comparison of the wastewater purification rates of the foamed carbon-red mud composite material prepared in Example 1 and the foamed carbon in Comparative Example 1 under conditions of illumination (one standard sunlight) and under conditions of no illumination.

[0032] Figure 10 The graph shows a comparison of the wastewater purification rates of the foamed carbon-red mud composite material prepared in Example 1 under irradiation with 1 standard sunlight, 1.5 standard sunlight, and 2 standard sunlight.

[0033] Figure 11 The graph shows a comparison of the wastewater purification rates of the foamed carbon-red mud composite material prepared in Example 1 and the foamed carbon in Comparative Example 1 after 6 hours of irradiation under standard sunlight.

[0034] Figure 12 This is a comparison chart of the wastewater purification rates of the foamed carbon-red mud composite materials in Example 1 and Comparative Example 2.

[0035] Figure 13 The graph shows a comparison of the wastewater purification rates of the foamed carbon-red mud composite materials in Example 1 (400 °C), Comparative Example 3 (200 °C), and Comparative Example 4 (600 °C).

[0036] Figure 14 The graphs show a comparison of the wastewater purification rates of foamed carbon-red mud composite materials in Example 1 (red mud loading 5 mg) and Comparative Example 5 (red mud loading 1 mg, red mud loading 3 mg, red mud loading 7 mg, and red mud loading 9 mg); where (a) is a comparison of the purification rates of wastewater containing rhodamine (RhB), and (b) is a comparison of the purification rates of wastewater containing methylene blue (MB).

[0037] Figure 15 The graph shows the wastewater purification rate test results of the foamed carbon-red mud composite material in Comparative Example 6.

[0038] Figure 16 The graph shows the wastewater purification rate test results of the foamed carbon-red mud composite materials in Examples 2-5.

[0039] Figure 17 The graph shows the wastewater purification rate test results of the foamed carbon-red mud composite materials in Examples 6-8. Detailed Implementation

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0041] The present invention will now be described in detail with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0042] The inventors discovered in their research that foamed carbon, due to its porous structure, has advantages in adsorption and can be used for wastewater purification. However, relying solely on the adsorption effect reduces the wastewater purification rate, and there is an urgent need to couple it with materials that have photodegradation properties. Red mud is a solid waste, but it contains a variety of semiconductor materials and has photodegradation properties. Combining treated red mud with foamed carbon can not only dispose of red mud solid waste and promote the construction of a green environment, but also be used for wastewater purification, realizing the treatment of waste with waste.

[0043] This invention addresses the problem of poor wastewater purification effect of current photothermal strategies by providing a method for preparing a foamed carbon-red mud composite material.

[0044] The preparation method of the foamed carbon-red mud composite material of this invention includes the following steps: S1, Red mud pretreatment: Carbon dioxide gas is introduced into the red mud dispersion until the pH of the red mud solution is <8, followed by solid-liquid separation and drying to obtain modified red mud. S2, Foamed carbon synthesis: Sodium alginate solution, calcium chloride solution, and melamine foam are mixed and allowed to stand at room temperature to obtain a pretreated mixture. The pretreated mixture is then annealed to obtain foamed carbon. S3, Preparation of foamed carbon-red mud composite material: The modified red mud obtained in step S1 is uniformly dispersed in water and sprayed onto the surface of the foamed carbon, then dried to obtain the foamed carbon-red mud composite material. If the pH of the modified red mud obtained in step S1 is >8, some metals in the red mud will dissolve, and the red mud itself is highly alkaline, which may ultimately affect the synthesis process and performance of the foamed carbon-red mud composite material of this invention.

[0045] In a preferred embodiment of the preparation method of the foamed carbon-red mud composite material of the present invention, in step S2, the pretreated mixture is heated to 300-500 °C (e.g., 300 °C, 330 °C, 360 °C, 390 °C, 420 °C, 450 °C, 480 °C, or 500 °C) for annealing for 0.5-1 h (e.g., 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, or 1 h); the heating rate is 5-15 °C / min (e.g., 5 °C / min, 7 °C / min, 9 °C / min, 11 °C / min, 13 °C / min, or 15 °C / min). Insufficient annealing time will lead to incomplete decomposition of the precursor, and the pore structure and skeleton strength of the foamed carbon cannot be fully formed, affecting the overall structural stability; excessively long annealing time may cause the pore structure to collapse or shrink, reducing the specific surface area and porosity. Similarly, the heating rate has a significant impact on the pore structure, graphitization degree, mechanical properties, impurity residue, specific surface area, and porosity of carbon foam.

[0046] In a preferred embodiment of the preparation method of the foamed carbon-red mud composite material of the present invention, in step S2, annealing is carried out in a muffle furnace.

[0047] In a preferred embodiment of the preparation method of the foamed carbon-red mud composite material of the present invention, in step S1, the red mud dispersion is obtained by dispersing red mud particles in deionized water; the particle size of the red mud particles is such that they can pass through a 100-mesh sieve, and the mass ratio of the red mud dispersion is 1:(2.3-21) (e.g., 1:2.3, 1:5, 1:10, 1:15, or 1:21). If the red mud particle size is too large, it will lead to problems such as poor interfacial bonding, reduced uniformity, destruction of pore structure, and decreased functional performance.

[0048] In a preferred embodiment of the method for preparing the foamed carbon-red mud composite material of the present invention, in step S1, the carbon dioxide gas introduction rate is 8-12 mL / min (e.g., 8 mL / min, 9 mL / min, 10 mL / min, 11 mL / min or 12 mL / min); solid-liquid separation is achieved by centrifugation at a speed of 2000-4000 rpm (e.g., 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm or 4000 rpm) for a centrifugation time of 10-30 min (e.g., 10 min, 15 min, 20 min, 25 min or 30 min); the drying temperature is 85-105 ℃ (e.g., 85 ℃, 90 ℃, 95 ℃, 100 ℃ or 105 ℃) for a drying time of 1-3 h (e.g., 1 h, 1.5 h, 2 h, 2.5 h or 3 h).

[0049] In a preferred embodiment of the preparation method of the foamed carbon-red mud composite material of the present invention, in step S2, the concentration of sodium alginate solution is 40-60 mg / L (e.g., 40 mg / L, 45 mg / L, 50 mg / L, 55 mg / L or 60 mg / L), the concentration of calcium chloride solution is 15-25 mg / L (e.g., 15 mg / L, 20 mg / L or 25 mg / L), and the volume ratio of sodium alginate solution to calcium chloride solution is (5-15):(10-30) (e.g., 5:10, 5:30, 15:10, 15:30 or 10:20); the mass ratio of melamine foam to sodium alginate in sodium alginate solution is 9:(10-45) (e.g., 9:10, 9:20, 9:30, 9:40 or 9:45); in step S2, the standing time at room temperature is 5-36 h (e.g., 5 h, 8 h, 12 h). (h, 18 h, 24 h, 30 h, or 36 h). Among these, room temperature standing is mainly used for the gelation or stabilization of precursors. If the standing time is too short, it will lead to incomplete gelation, uneven pores, poor mechanical properties, and residual impurities; if the standing time is too long, it may cause over-gelation, difficulty in drying, reduced efficiency, and structural aging.

[0050] In a preferred embodiment of the preparation method of the foamed carbon-red mud composite material of the present invention, in step S2, the diameter of the melamine foam is 150-300 μm and the porosity is 99%.

[0051] In a preferred embodiment of the preparation method of the foamed carbon-red mud composite material of the present invention, in step S3, the drying temperature is 50-70 ℃ (e.g., 50 ℃, 55 ℃, 60 ℃, 65 ℃ or 70 ℃), and the drying time is 6-18 h (e.g., 6 h, 9 h, 12 h, 15 h or 18 h).

[0052] The present invention also proposes a foamed carbon-red mud composite material, which is prepared by the method described above in the embodiments of the present invention.

[0053] The present invention also proposes the application of the foamed carbon-red mud composite material as described above, and the application of the foamed carbon-red mud composite material as described above in the purification of wastewater; the wastewater contains at least one of organic pollutants, metal ions and non-metal ions.

[0054] In a preferred embodiment of the application of the foamed carbon-red mud composite material of the present invention, the organic pollutant is rhodamine and / or methylene blue; the metal ion is at least one of calcium, magnesium, sodium, potassium, aluminum, iron and manganese; and the non-metal ion is sulfur and / or silicon.

[0055] The following detailed description of the foamed carbon-red mud composite material of the present invention, its preparation method, and its application are illustrated through specific embodiments.

[0056] In the following examples, the main raw materials used were sourced as follows: red mud (bauxite slag) from Shanxi Zhongmei Shanxi Aluminum Co., Ltd., China; raw melamine foam from Shandong Shengquan New Material Co., Ltd.; sodium alginate from Shandong Jiejing Group Co., Ltd.; and calcium chloride from Shandong Haihua Group Co., Ltd.

[0057] Example 1

[0058] The preparation method of the foamed carbon-red mud composite material in this embodiment includes the following steps:

[0059] S1. Acid washing of red mud yields BR samples:

[0060] Red mud (bauxite slag) was sourced from Shanxi Zhongmei Shanxi Aluminum Co., Ltd., China. Bauxite residue was pulverized into a fine powder, allowing it to pass through a 100-mesh sieve. 20 g of the sample was mixed with distilled water at a mass ratio of 1:7 and poured into a 1000 mL plastic bottle. The solution was mounted on a mechanical stirrer at room temperature and rotated at a constant stirring speed of 180 rpm / min. CO2 was mixed into the bauxite slag solution at a rotation speed of 10 mL / min using a rotor flow meter until the pH of the bauxite slag suspension dropped to <8. The neutralized bauxite slag was centrifuged at 3000 rpm for 20 minutes and dried in a 95 ℃ air oven for 2 hours to obtain the final treated red mud sample BR (modified red mud).

[0061] S2. Synthesis of foamed carbon: Purchase virgin melamine foam with a diameter of 150-300 µm and a porosity of 99%; mix 10 mL of 50 mg / L sodium alginate solution and 5 mL of 20 mg / L CaCl2 solution with 0.18 mg of virgin melamine foam; after standing at room temperature for 24 h, place the pretreated melamine foam with a thickness of 10 mm into a muffle furnace, heat it to 400 °C at a heating rate of 10 °C / min, and anneal it at 400 °C for 1 h to obtain foamed carbon.

[0062] S3. Preparation of foamed carbon-red mud composite material: Foamed carbon-red mud composite material was prepared by a simple one-step spraying method (spraying modified red mud solution onto the surface of foamed carbon); the prepared foamed carbon was made into a circle with a diameter of 5 cm and a thickness of 5 mm; 5 mg of modified red mud obtained in step S1 was mixed with 30 mL of ultrapure water to obtain a solution as a spray precursor, which was then placed in a spray gun and loaded onto the surface of the foamed carbon; then dried in an oven at 60 ℃ for 12 h to obtain the foamed carbon-red mud composite material of this embodiment.

[0063] Example 2

[0064] The only difference between this embodiment and Embodiment 1 is that the carbon dioxide gas introduction rate in step S1 is 8 mL / min; all other aspects are the same as in Embodiment 1.

[0065] Example 3

[0066] The only difference between this embodiment and Embodiment 1 is that the carbon dioxide gas introduction rate in step S1 is 12 mL / min; all other aspects are the same as in Embodiment 1.

[0067] Example 4

[0068] The only difference between this embodiment and Example 1 is that in step S2, the concentration of sodium alginate solution is 40 mg / L and the volume is 5 mL, and the concentration of calcium chloride solution is 15 mg / L and the volume is 10 mL; all other aspects are the same as in Example 1.

[0069] Example 5

[0070] The only difference between this embodiment and Example 1 is that in step S2, the concentration of sodium alginate solution is 60 mg / L and the volume is 15 mL, and the concentration of calcium chloride solution is 25 mg / L and the volume is 30 mL; all other aspects are the same as in Example 1.

[0071] Example 6

[0072] The only difference between this embodiment and Embodiment 1 is that the room temperature standing time in step S2 is 5 hours; all other aspects are the same as in Embodiment 1.

[0073] Example 7

[0074] The only difference between this embodiment and Embodiment 1 is that the time for standing at room temperature in step S2 is 12 hours; all other aspects are the same as in Embodiment 1.

[0075] Example 8

[0076] The only difference between this embodiment and Embodiment 1 is that the time for standing at room temperature in step S2 is 36 hours; all other aspects are the same as in Embodiment 1.

[0077] Comparative Example 1

[0078] This comparative example provides a foamed carbon, and the preparation method of the foamed carbon is the same as step S2 in Example 1.

[0079] Comparative Example 2

[0080] The only difference between this comparative example and Example 1 is that sodium alginate and calcium chloride in step S2 are omitted (i.e., equal volumes of pure water are used instead of sodium alginate solution and CaCl2 solution, respectively); all other aspects are the same as in Example 1.

[0081] Comparative Example 3

[0082] The only difference between this comparative example and Example 1 is that the annealing temperature in step S2 is 200 °C; all other aspects are the same as in Example 1.

[0083] Comparative Example 4

[0084] The only difference between this comparative example and Example 1 is that the annealing temperature in step S2 is 600 °C; all other aspects are the same as in Example 1.

[0085] Comparative Example 5

[0086] The only difference between this comparative example and Example 1 is that the amount of modified red mud sprayed onto the surface of the foam carbon in step S3 is different from that in Example 1; all other aspects are the same as in Example 1.

[0087] Specifically, foamed carbon-red mud composite materials of this comparative example were obtained when the amount of modified red mud was 1 mg, 3 mg, 7 mg, and 9 mg, respectively (i.e., the amount of modified red mud sprayed on the surface of foamed carbon was 1 mg, 3 mg, 7 mg, and 9 mg, respectively).

[0088] Comparative Example 6

[0089] The only difference between this comparative example and Example 1 is that the pH of the bauxite slag suspension in step S1 is >8 (to reduce the CO2 introduction time); all other aspects are the same as in Example 1.

[0090] Experimental Example

[0091] 1. Scanning electron microscopy observation:

[0092] The scanning electron microscope image of the foamed carbon in Comparative Example 1 is shown below. Figure 1 As shown, the scanning electron microscope image of the foamed carbon-red mud composite material of Example 1 is as follows. Figure 2 As shown:

[0093] from Figure 1 The porous structure of the foamed carbon is visible, and the slightly larger circular nodes observed in the foamed carbon may be caused by the carbonization process and local mass agglomeration. Figure 2 The distribution of red mud in foamed carbon-red mud composite material is shown. The red mud is loaded into the gaps in the foam matrix to maintain the channels of the foamed carbon.

[0094] 2. Ultraviolet-Vis Spectroscopy Test:

[0095] The UV-Vis spectra of the modified red mud (BR) prepared in step S1 of Example 1 and the foamed carbon-red mud composite material of Example 1 were tested: the modified red mud and the foamed carbon-red mud composite material were ground into powder, dispersed in organic solvents such as N,N-dimethylformamide (DMF) or toluene, and ultrasonically stirred for 15 minutes to obtain a stable dispersion. The dispersion was then poured into a cuvette to measure its UV-Vis spectrum.

[0096] Figure 3 In the middle, (a) represents modified red mud (BR) and foamed carbon-red mud composite material ( Figure 3 The UV-Vis absorption rate test results of the "foamed carbon-red mud" composite material show that the light absorption of the foamed carbon-red mud composite material is significantly stronger than that of red mud. Figure 3 (b) is a physical image of the foamed carbon-red mud composite material of Example 1.

[0097] 3. The composite material prepared by this invention was used to test the photocatalytic degradation of organic pollutants. The experimental process was as follows: foam carbon with a diameter of 5 cm and a thickness of 5 mm and foam carbon-red mud composite material were prepared for wastewater purification experiments.

[0098] 2000 mL of wastewater was added to an evaporator (approximately 50 cm × 50 cm). 15 g of the prepared foamed carbon or foamed carbon composite material was added to the evaporator. Simulated sunlight was provided using a Xe light source (PLSSEX300+) with an AM 1.5 G filter. Solar intensity was adjusted using a solar power meter (Thorlabs). The surface temperature of the evaporation interface was recorded in real time using an infrared thermal imager. The mass change of the evaporator during the evaporation process was monitored using an electronic analytical balance. The composition of the collected water vapor was analyzed using ultraviolet-visible and inductively coupled plasma (ICP) measurements.

[0099] (1) The surface temperature of the evaporation interface of the foamed carbon-red mud composite material of Example 1 and the foamed carbon of Comparative Example 1 during wastewater purification was tested using an infrared thermal imager. The test results are as follows: Figure 4 (Foamed carbon-red mud composite material) and Figure 5 As shown in (foamed carbon).

[0100] Depend on Figures 4-5 The comparison shows that the surface temperature of the evaporation interface of the foamed carbon-red mud composite material in Example 1 is significantly higher than that of the foamed carbon in Comparative Example 1 when irradiated by a standard sunlight (100 mW / cm) for 5-8 seconds.

[0101] (2) The foam carbon-red mud composite material of Example 1 was used to purify wastewater containing 200 mg / L Rhodamine (RhB) and methylene blue (MB) under both light conditions (one standard sunlight) and no light conditions, and the wastewater purification efficiency was tested.

[0102] The comparison of wastewater containing rhodamine (RhB) and methylene blue (MB) before and after purification under light conditions (2 h) is shown in the figure below. Figure 6 As shown. By Figure 6 It can be seen that the purified water (i.e., the sample obtained after the collected water vapor is condensed) is colorless and transparent. Due to the photothermal and photocatalytic effects of the foamed carbon-red mud composite material, the wastewater is transformed into pure water.

[0103] Ultraviolet-visible spectroscopy was performed on wastewater containing rhodamine (RhB) before and after purification (samples obtained under light irradiation conditions); the test results are as follows. Figure 7 As shown. Figure 7 The black line corresponds to the sample before purification, and the red line corresponds to the sample after purification. The test results show that after reacting for 2 hours under light conditions, the collected water vapor contains almost no organic molecules.

[0104] Ultraviolet-visible spectroscopy was performed on samples of wastewater containing methylene blue (MB) before and after purification (samples obtained under light irradiation conditions); the test results are as follows. Figure 8 As shown. Figure 8 The black line corresponds to the sample before purification, and the red line corresponds to the sample after purification. The test results show that after reacting for 2 hours under light conditions, the collected water vapor contains almost no organic molecules.

[0105] The test results of wastewater purification efficiency are as follows: Figure 9As shown (the wastewater purification rate was calculated by dividing the mass of the collected condensate at the end of the test by the mass of the foamed carbon-red mud composite material and the test time; the volume of wastewater used in the test was 1 L, the mass of the foamed carbon-red mud composite material was 7.5 g, and the test time was 2 h). Figure 9 It can be seen that the foamed carbon-red mud composite material of Example 1 has a significantly better purification rate for wastewater under light conditions.

[0106] (3) The foamed carbon-red mud composite material of Example 1 was subjected to one standard sunlight (100 mW / cm²) respectively. 2 ), 1.5 standard sunlight (150 mW / cm) 2 ) and 2 standard sunlight (200 mW / cm) 2 Wastewater is purified under irradiation.

[0107] Test results are as follows Figure 10 As shown. By Figure 10 It can be seen that the wastewater purification rate increases with the increase of light intensity.

[0108] (4) The foamed carbon-red mud composite material of Example 1 and the foamed carbon of Comparative Example 1 were used to purify wastewater under one standard sunlight irradiation for 6 hours.

[0109] Test results are as follows Figure 11 As shown. By Figure 11 It can be seen that: the wastewater purification rate of the foamed carbon-red mud composite material in Example 1 remained basically unchanged within the test time of 3 hours, and decreased slightly after 3 hours; while the wastewater purification efficiency of the foamed carbon in Comparative Example 1 continued to decrease significantly during the test; the foamed carbon-red mud composite material in Example 1 has significantly better stability.

[0110] (5) Wastewater was purified by using the foamed carbon-red mud composite materials of Example 1 and Comparative Example 2 under one standard sunlight irradiation.

[0111] Test results are as follows Figure 12 As shown. By Figure 12 It can be seen that: In Example 1, by adding sodium alginate and calcium chloride during the preparation of foamed carbon, the wastewater purification rate of the prepared foamed carbon-red mud composite material was significantly improved.

[0112] (6) Wastewater was purified by using the foamed carbon-red mud composite materials of Example 1, Comparative Example 3 and Comparative Example 4 under one standard sunlight irradiation.

[0113] Test results are as follows Figure 13 As shown. By Figure 13It can be seen that when the annealing temperature in step S2 is 400 ℃, the purification rate of wastewater is significantly higher.

[0114] (7) Wastewater was purified using the foamed carbon-red mud composite materials of Example 1 and Comparative Example 5 under one standard sunlight irradiation; the test results are as follows: Figure 14 As shown.

[0115] Depend on Figure 14 It can be seen that the loading of red mud has a significant impact on the sewage purification effect. When the sludge loading is 5mg (the diameter of the foam carbon is 5 cm and the thickness is 5 mm), the sewage purification effect is optimal.

[0116] (8) Wastewater was purified using the foamed carbon-red mud composite material of Comparative Example 6 under one standard sunlight irradiation (test time 2 h); the wastewater purification rate test results are as follows: Figure 15 As shown.

[0117] from Figure 15 It can be seen that if CO2 is introduced to treat the red mud in step S1, and the pH of the red mud solution is greater than 8, it will have an adverse effect on the wastewater purification performance of the prepared foam carbon-red mud composite material.

[0118] (9) Wastewater was purified using the foamed carbon-red mud composite materials of Examples 2-8 under one standard sunlight irradiation (test time 2 h); the wastewater purification rate test results of Examples 2-5 are as follows. Figure 16 As shown, the wastewater purification rate test results of Examples 6-8 are as follows: Figure 17 As shown.

[0119] (10) The foamed carbon-red mud composite material of Example 1 was used for the purification of wastewater containing metal ions (the mass of wastewater used in the test was 1 L, the amount of foamed carbon-red mud composite material was 7.5 g; the test time was 2 h, and the test conditions were 1 standard light irradiation):

[0120] Test Results: Table 1 shows the comparison of heavy ion concentrations in wastewater before and after purification (the concentration of each element in Table 1 is measured in mg / L). The experiment revealed that harmful elements, such as Ca, Mg, S, Fe, and Mn, were adsorbed onto the foam matrix structure, inhibiting their transport with water molecules. According to ICP measurements, the harmful elements were successfully removed, and no harmful element residues were found in the collected steam.

[0121] Table 1

[0122]

[0123] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of preparing a foamed carbon-red mud composite material, characterized by, The method comprises the following steps: S1, red mud pretreatment: carbon dioxide gas is introduced into a red mud dispersion solution until the pH of the red mud solution is less than 8, solid-liquid separation and drying are performed, and modified red mud is obtained; S2, synthesis of foam carbon: a sodium alginate solution, a calcium chloride solution and melamine foam are mixed, and the mixture is left to stand at room temperature to obtain a pretreatment mixture, the pretreatment mixture is heated to 300-500℃, and annealing treatment is performed for 0.5-1h to obtain foam carbon; S3, preparation of foam carbon-red mud composite material: the modified red mud obtained in step S1 is uniformly dispersed in water and sprayed on the surface of the foam carbon, and drying is performed to obtain the foam carbon-red mud composite material.

2. The method for preparing the foamed carbon-red mud composite material as described in claim 1, characterized in that, The heating rate is 5-15℃ / min.

3. The method for preparing the foamed carbon-red mud composite material as described in claim 1, characterized in that, In step S2, the annealing is performed in a muffle furnace.

4. The method for preparing the foamed carbon-red mud composite material as described in claim 1, characterized in that, In step S1, the red mud dispersion solution is obtained by dispersing red mud particles in deionized water; The particle size of the red mud particles is 100 mesh, and the mass ratio of the red mud dispersion solution is 1:(2.3-21).

5. The method for preparing the foamed carbon-red mud composite material as described in claim 1, characterized in that, In step S1, the introduction rate of the carbon dioxide gas is 8-12mL / min; The solid-liquid separation is achieved by centrifugation, the centrifugal speed is 2000-4000 rpm, and the centrifugation time is 10-30min; The drying temperature is 85-105℃, and the drying time is 1-3h.

6. The method for preparing the foamed carbon-red mud composite material as described in claim 1, characterized in that, In step S2, the concentration of the sodium alginate solution is 40-60 mg / L, the concentration of the calcium chloride solution is 15-25 mg / L, and the volume ratio of the sodium alginate solution to the calcium chloride solution is (5-15):(10-30); The mass ratio of the melamine foam to the sodium alginate in the sodium alginate solution is 9:(10-45); In step S2, the room temperature standing time is 5-36h.

7. The method for preparing the foamed carbon-red mud composite material as described in claim 1, characterized in that, In step S2, the diameter of the melamine foam is 150-300μm, and the porosity is 99%.

8. A foamed carbon-red mud composite material, characterized by, The foam carbon-red mud composite material is prepared by the method of any one of claims 1-7.

9. The foam carbon-red mud composite material of claim 8 for purifying sewage; The sewage contains at least one of organic pollutants, metal ions and non-metal ions.

10. Use according to claim 9, wherein The organic pollutants are rhodamine and / or methyl blue; The metal ions are at least one of calcium, magnesium, sodium, potassium, aluminum, iron and manganese; The non-metal ions are sulfur and / or silicon.

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