Foamy carbon-red mud composite material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of sewage purification, and particularly relates to a foamy carbon-red mud composite material as well as a preparation method and application thereof. The preparation method of the foamy carbon-red mud composite material comprises the following steps: S1, pretreating red mud; s2, synthesis of foamy carbon: mixing a sodium alginate solution, a calcium chloride solution and melamine foam, standing at room temperature to obtain a pretreated mixture, and annealing the pretreated mixture to obtain the foamy carbon; and S3, preparation of a foamy carbon-red mud composite material: uniformly dispersing the modified red mud treated in the step S1 in water, and then spraying on the surface of the foamy carbon. The foamy carbon-red mud composite material shows good light absorption in a range of 300-800 nm, has high local temperature, has better light absorption capability and photothermal effect compared with foamy carbon, and can better purify sewage.

Description

Technical Field

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

[0002] Recycling and reuse of pollutants is key to alleviating environmental problems. Water resources are the foundation of the Earth; evaporation, precipitation, industrial and domestic water use, and river and ocean flows constitute the Earth's water cycle. During industrial and domestic water use, water inevitably becomes polluted, negatively impacting daily life and the normal water cycle. Therefore, water purification is a necessary endeavor. Water purification technologies, such as disinfection, decontamination, and desalination, can address water quality issues. However, most water purification technologies require complex devices or membranes. Therefore, an economical, green, and environmentally friendly wastewater purification strategy is desirable.

[0003] Photothermal strategies mimic the evaporation process and are a green and simple method for wastewater purification. Key materials for solar thermal steam technology, such as plasma 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 photothermal evaporation is insufficient for water purification.

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

[0005] The purpose of the present invention is to provide a foam carbon-red mud composite material and its preparation method and application, so as to help solve or improve the problem that the existing photothermal strategy has poor purification effect on sewage.

[0006] In order to achieve the above-mentioned object, the present invention provides the following technical scheme: A method for preparing a foamed carbon-red mud composite material, comprising the following steps: S1, red mud pretreatment: introducing carbon dioxide gas into a red mud dispersion 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 a sodium alginate solution, a calcium chloride solution, and a melamine foam, and standing at room temperature to obtain a pretreated mixture, and annealing the pretreated mixture to obtain foamed carbon; S3, preparation of a foamed carbon-red mud composite material: uniformly dispersing the modified red mud obtained by the treatment in step S1 in water, spraying the mixture on the surface of the foamed carbon, and drying to obtain the foamed carbon-red mud composite material.

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

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

[0009] Preferably, 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).

[0010] Preferably, in step S1, the carbon dioxide gas is introduced at a rate of 8-12 mL / min; the solid-liquid separation is achieved by centrifugation, the centrifugal speed is 2000-4000 rpm, and the centrifugation time is 10-30 min; the drying temperature is 85-105 ° C, 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, 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 standing time at room temperature 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 present invention also provides a foamed carbon-red mud composite material, which adopts the following technical solution: a foamed carbon-red mud composite material, wherein the foamed carbon-red mud composite material is prepared by the method described above.

[0014] The present invention also provides an application of a foamed carbon-red mud composite material, which adopts the following technical solution: application of the foamed carbon-red mud composite material as described above in purifying sewage; the sewage contains at least one of organic pollutants, metal ions and non-metallic ions.

[0015] Preferably, the organic pollutant is rhodamine and / or methyl 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.

[0016] Beneficial effects: The present invention uses foamed carbon as a basic framework and forms a foamed carbon-red mud composite material with photothermal / photodegradation coupling function by loading modified red mud (obtained by treating the red mud by introducing carbon dioxide into a red mud dispersion) on its surface.

[0017] The foamed carbon-red mud composite material of the present invention exhibits a porous matrix structure that facilitates water evaporation, coupled with the photodegradation ability of the red mud material, achieving a waste treatment using waste. The excellent light absorption capacity of the foamed carbon and red mud ensures the photothermal effect and photodegradation performance of the foamed carbon-red mud composite material of the present invention.

[0018] Compared to a single inorganic semiconductor photocatalyst, the presence of the foamed carbon in the foamed carbon-red mud composite material provides the composite with superior adsorption capacity compared to red mud. Due to the porous structure of the foam, the appropriate tunnel morphology within it prevents significant pollution and allows wastewater to pass through the composite via transpiration. The foamed carbon-red mud composite material exhibits excellent light absorption properties within the 300-800 nm range and possesses a higher local temperature. Compared to foamed carbon, it has superior light absorption and photothermal effects, enabling improved wastewater purification.

[0019] In the carbon foam-red mud composite material of this invention, the carbon foam not only serves as a floating matrix 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 catalyst can further degrade organic pollutants with the aid of photothermal energy, while the carbon foam's photothermal properties enhance the overall catalytic performance of the system. This composite material can effectively purify simulated wastewater containing organic pollutants such as rhodamine and methyl blue, as well as actual wastewater containing heavy ions.

[0020] In addition, the foamed carbon-red mud composite material of the present invention can be directly placed in an outdoor environment and utilize natural light to achieve efficient purification of sewage, fully demonstrating the feasibility and practicality of the foamed carbon-red mud composite material of the present invention in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. Among them: Figure 1 This is a scanning electron microscope image (×20 μm) of the foamed carbon prepared in Comparative Example 1.

[0022] Figure 2 This is a scanning electron microscope image (×20 μm) of the foamed carbon-red mud composite material prepared in Example 1 of the present invention.

[0023] Figure 3These are the UV-visible light absorption test result graphs of the modified red mud (BR) in Example 1 and the foamed carbon-red mud composite material prepared in Example 1, and a physical picture of the foamed carbon-red mud composite material in Example 1; wherein, (a) is the UV-visible light absorption test result graph, and (b) is the physical picture.

[0024] Figure 4 This is a graph showing the temperature change test results of the foamed carbon-red mud composite material of Example 1 under standard sunlight.

[0025] Figure 5 This is a temperature change test result diagram of the foam carbon of Comparative Example 1 under standard sunlight.

[0026] Figure 6 This is a comparison diagram of the carbon foam-red mud composite material prepared in Example 1 of the present invention before and after being used for the purification of rhodamine (RhB) wastewater and methyl blue (MB) wastewater.

[0027] Figure 7 This is a UV-visible spectrum of the foamed carbon-red mud composite material prepared in Example 1 of the present invention before and after purification of rhodamine (RhB) wastewater.

[0028] Figure 8 The UV-visible spectra of the foamed carbon-red mud composite material prepared in Example 1 of the present invention before and after purification of methyl blue (MB) wastewater are shown.

[0029] Figure 9 This is a comparison chart of the sewage purification rates of the foamed carbon-red mud composite material prepared in Example 1 and the foamed carbon of Comparative Example 1 under illumination conditions (1 standard sunlight) and no illumination conditions, respectively.

[0030] Figure 10 This is a comparison chart of the sewage purification rates of the foamed carbon-red mud composite material prepared in Example 1 under 1 standard sunlight, 1.5 standard sunlight, and 2 standard sunlight, respectively.

[0031] Figure 11 This is a comparison chart of the sewage purification rates of the foamed carbon-red mud composite material prepared in Example 1 and the foamed carbon of Comparative Example 1, respectively, after being irradiated with one standard sunlight for 6 h.

[0032] Figure 12 This is a comparison chart of the sewage purification rates of the foamed carbon-red mud composite material of Example 1 and Comparative Example 2.

[0033] Figure 13 1 is a comparison chart of the sewage purification rates of the foamed carbon-red mud composite materials of Example 1 (400°C), Comparative Example 3 (200°C) and Comparative Example 4 (600°C).

[0034] Figure 14 The figures are a comparison of the sewage purification rates of the foamed carbon-red mud composite materials of 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); wherein, (a) is a comparison of the purification rates for sewage containing rhodamine (RhB), and (b) is a comparison of the purification rates for sewage containing methyl blue (MB).

[0035] Figure 15 This is a graph showing the sewage purification rate test results of the foamed carbon-red mud composite material of Comparative Example 6.

[0036] Figure 16 This is a graph showing the sewage purification rate test results of the foamed carbon-red mud composite material of Examples 2-5.

[0037] Figure 17 Graph showing the sewage purification rate test results of the foamed carbon-red mud composite material of Examples 6-8. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention are within the scope of protection of the present invention.

[0039] The present invention will be described in detail below with reference to the embodiments. It should be noted that the embodiments and features of the embodiments of the present invention can be combined with each other without conflict.

[0040] During their research, the inventors discovered that foamed carbon can be used for sewage purification due to its advantages in adsorption due to its porous structure; however, relying solely on the adsorption effect reduces the sewage purification rate, and it is urgent to couple it with materials with photodegradation properties; red mud is a solid waste, but it contains a variety of semiconductor materials and has photodegradation properties; combining the treated red mud with foamed carbon can not only dispose of red mud solid waste and promote green environmental construction, but can also be used for sewage purification, achieving "waste" treatment.

[0041] In view of the problem that the existing photothermal strategy has poor purification effect on sewage, the present invention provides a method for preparing a foamed carbon-red mud composite material.

[0042] The preparation method of the foamed carbon-red mud composite material of the embodiment of the present invention comprises the following steps: S1, red mud pretreatment: introducing carbon dioxide gas into the red mud dispersion until the pH of the red mud solution is less than 8, separating the solid and liquid, 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 pretreated mixture, and annealing the pretreated mixture to obtain foamed carbon; S3, preparation of foamed carbon-red mud composite material: uniformly dispersing the modified red mud obtained by the treatment of step S1 in water and spraying it on the surface of the foamed carbon, drying to obtain the foamed carbon-red mud composite material. Among them, if the pH of the modified red mud obtained in step S1 is greater than 8, some metals in the red mud will dissolve, and the red mud itself is highly alkaline, which may eventually affect the synthesis process and performance of the foamed carbon-red mud composite material of the present invention.

[0043] In a preferred embodiment of the method for preparing 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. The annealing time is 0.5-1 h (e.g., 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, or 1 h), and 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 may result in incomplete decomposition of the precursor, preventing the pore structure and skeleton strength of the foamed carbon from being fully formed, thereby affecting the overall structural stability. Excessive annealing time may cause the pore structure to collapse or shrink, reducing the specific surface area and porosity. Similarly, the heating rate has an important influence on the pore structure, graphitization degree, mechanical properties, impurity residue, specific surface area and porosity of foamed carbon.

[0044] In a preferred embodiment of the method for preparing the foamed carbon-red mud composite material of the present invention, in step S2, annealing is performed in a muffle furnace.

[0045] In a preferred embodiment of the method for preparing the foamed carbon-red mud composite material of the present invention, in step S1, a red mud dispersion is prepared by dispersing red mud particles in deionized water; the red mud particles have a particle size that can pass through a 100-mesh sieve, and the mass ratio of the red mud dispersion to the red mud is 1:(2.3-21) (e.g., 1:2.3, 1:5, 1:10, 1:15, or 1:21). Excessively large red mud particle size can lead to poor interfacial bonding, reduced uniformity, disrupted pore structure, and decreased functional performance.

[0046] In a preferred embodiment of the method for preparing the foamed carbon-red mud composite material of the present invention, in step S1, the introduction rate of carbon dioxide gas is 8-12 mL / min (for example, 8 mL / min, 9 mL / min, 10 mL / min, 11 mL / min or 12 mL / min); solid-liquid separation is achieved by centrifugation, the centrifugal speed is 2000-4000 rpm (for example, 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm or 4000 rpm), and the centrifugation time is 10-30 min (for example, 10 min, 15 min, 20 min, 25 min or 30 min); the drying temperature is 85-105 ° C (for example, 85 ° C, 90 ° C, 95 ° C, 100 ° C or 105 ° C), and the drying time is 1-3 h (for example, 1 h, 1.5 h, 2 h, 2.5 h or 3 h).

[0047] In a preferred embodiment of the method for preparing the foamed carbon-red mud composite material of the present invention, in step S2, the concentration of the sodium alginate solution is 40-60 mg / L (for example, 40 mg / L, 45 mg / L, 50 mg / L, 55 mg / L or 60 mg / L), the concentration of the calcium chloride solution is 15-25 mg / L (for example, 15 mg / L, 20 mg / L or 25 mg / L), and the volume ratio of the sodium alginate solution to the calcium chloride solution is (5-15):(10-30) (for example, 5:10, 5:30, 15:10, 15:30 or 10:20); the mass ratio of the melamine foam to the sodium alginate in the sodium alginate solution is 9:(10-45) (for example, 9:10, 9:20, 9:30, 9:40 or 9:45); in step S2, the standing time at room temperature is 5-36 h (for example, 5 h, 8 h, 12 h, 18 h, 20 h, 30 h, 40 h, 50 h, 60 h, 70 h, 80 h, 90 h, 90 h, 100 h, 150 h, 100 h, 150 h, 150 h, 150 h, 150 h, 150 h, 150 h, 150 h, 150 h, 150 h, 150 h, 150 h, 150 h, 150 h, 150 h, 150 h, 150 h, 150 h, h, 18 h, 24 h, 30 h or 36 h). Among them, standing at room temperature is mainly used for gelation or stabilization of the precursor. Too short a standing time will lead to incomplete gelation, uneven pores, poor mechanical properties and impurity residues; too long a standing time may cause excessive gelation, drying difficulties, reduced efficiency and structural aging.

[0048] In a preferred embodiment of the method for preparing 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%.

[0049] In a preferred embodiment of the method for preparing the foamed carbon-red mud composite material of the present invention, in step S3, the drying temperature is 50-70°C (for example, 50°C, 55°C, 60°C, 65°C or 70°C), and the drying time is 6-18 h (for example, 6 h, 9 h, 12 h, 15 h or 18 h).

[0050] The present invention also provides a foamed carbon-red mud composite material. The foamed carbon-red mud composite material in the embodiment of the present invention is prepared by the method described above.

[0051] The present invention also proposes the use of the foamed carbon-red mud composite material as described above, and the use of the foamed carbon-red mud composite material as described above in purifying sewage; the sewage contains at least one of organic pollutants, metal ions and non-metallic ions.

[0052] 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 methyl blue; the metal ion is at least one of calcium, magnesium, sodium, potassium, aluminum, iron and manganese; and the non-metallic ion is sulfur and / or silicon.

[0053] The foamed carbon-red mud composite material of the present invention, its preparation method and application are described in detail below through specific examples.

[0054] In the following examples, the sources of the main raw materials used are: red mud (bauxite slag) from Shanxi Zhongmei Shanxi Aluminum Co., Ltd., China; original melamine foam purchased from Shandong Shengquan New Materials Co., Ltd.; sodium alginate purchased from Shandong Jiejing Group Co., Ltd.; calcium chloride purchased from Shandong Haihua Group Co., Ltd.

[0055] Example 1 The preparation method of the foamed carbon-red mud composite material of this embodiment includes the following steps: S1. Acid washing of red mud to obtain BR sample: Red mud (bauxite slag) was obtained from Shanxi Zhongmei Shanxi Aluminum Co., Ltd., Shanxi, China. The bauxite residue was crushed into a fine powder that could pass through a 100-mesh sieve. Twenty grams of this 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 and rotated at a constant stirring speed of 180 rpm / min at room temperature. CO₂ was introduced into the bauxite slag solution through a rotor flowmeter at a rate of 10 mL / min 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 an air oven at 95°C for 2 hours to obtain the treated red mud sample BR (modified red mud).

[0056] S2. Synthesis of foamed carbon: Purchase pristine 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 the pristine melamine foam; after standing at room temperature for 24 h, place the pretreated melamine foam with a thickness of 10 mm in 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.

[0057] S3. Preparation of foamed carbon-red mud composite material: A foamed carbon-red mud composite material was prepared by a simple one-step spraying method (spraying the modified red mud solution on the surface of the foamed carbon); the prepared foamed carbon was formed into a circle with a diameter of 5 cm (thickness of 5 mm), 5 mg of the modified red mud obtained by the treatment 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; and then dried in an oven at 60°C for 12 h to obtain the foamed carbon-red mud composite material of this embodiment.

[0058] Example 2 The only difference between this embodiment and embodiment 1 is that the introduction rate of carbon dioxide gas in step S1 is 8 mL / min; the rest are consistent with embodiment 1.

[0059] Example 3 The only difference between this embodiment and embodiment 1 is that the introduction rate of carbon dioxide gas in step S1 is 12 mL / min; the rest are consistent with embodiment 1.

[0060] Example 4 The only difference between this embodiment and embodiment 1 is that in step S2, the concentration of the sodium alginate solution is 40 mg / L and the volume is 5 mL, and the concentration of the calcium chloride solution is 15 mg / L and the volume is 10 mL; the rest are consistent with embodiment 1.

[0061] Example 5 The only difference between this embodiment and embodiment 1 is that in step S2, the concentration of the sodium alginate solution is 60 mg / L and the volume is 15 mL, and the concentration of the calcium chloride solution is 25 mg / L and the volume is 30 mL; the rest are consistent with embodiment 1.

[0062] Example 6 The only difference between this embodiment and embodiment 1 is that the standing time at room temperature in step S2 is 5 h; the rest is consistent with embodiment 1.

[0063] Example 7 The only difference between this embodiment and embodiment 1 is that the standing time at room temperature in step S2 is 12 h; the rest is consistent with embodiment 1.

[0064] Example 8 The only difference between this embodiment and embodiment 1 is that the standing time at room temperature in step S2 is 36 h; the rest is consistent with embodiment 1.

[0065] Comparative Example 1 This comparative example provides a foamed carbon, and the preparation method of the foamed carbon is the same as step S2 in Example 1.

[0066] Comparative Example 2 The only difference between this comparative example and Example 1 is that sodium alginate and calcium chloride in step S2 are omitted (ie, equal volumes of pure water are used instead of sodium alginate solution and CaCl2 solution, respectively); the rest are consistent with Example 1.

[0067] Comparative Example 3 The only difference between this comparative example and Example 1 is that the annealing temperature in step S2 is 200° C.; the rest are consistent with Example 1.

[0068] Comparative Example 4 The only difference between this comparative example and Example 1 is that the annealing temperature in step S2 is 600° C.; the rest are consistent with Example 1.

[0069] Comparative Example 5 The only difference between this comparative example and Example 1 is that the amount of modified red mud sprayed on the surface of the foamed carbon in step S3 is different from that in Example 1; the rest is consistent with Example 1.

[0070] Specifically, the foamed carbon-red mud composite material of this comparative example was 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 the foamed carbon was 1 mg, 3 mg, 7 mg, and 9 mg, respectively).

[0071] Comparative Example 6 The only difference between this comparative example and Example 1 is that the pH of the bauxite slag suspension in step S1 is greater than 8 (to reduce the CO2 introduction time); the rest are consistent with Example 1.

[0072] Experimental example 1. Scanning electron microscopy observation: The scanning electron microscope image of the foam carbon of Comparative Example 1 is as follows: Figure 1 As shown, the scanning electron microscope image of the foam carbon-red mud composite material of Example 1 is as follows Figure 2 As shown: from Figure 1The porous structure of the carbon foam can be seen, and the slightly larger round nodes observed in the carbon foam may be generated by the carbonization process and local mass agglomeration; Figure 2 The distribution of red mud in the foam carbon-red mud composite material is shown. The red mud is loaded in the gaps of the foam matrix and maintains the channels of the foam carbon.

[0073] 2. UV-visible spectrum test: The UV-visible 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 an organic solvent such as N,N-dimethylformamide (DMF) or toluene, and ultrasonically stirred for 15 minutes to obtain a stable dispersion. The dispersion was poured into a cuvette to measure its UV-visible spectrum.

[0074] Figure 3 Among them, (a) is modified red mud (BR) and foam carbon-red mud composite material ( Figure 3 From the UV-visible light absorption test results of "foam carbon-red mud"), it can be seen that the light absorption of the foam carbon-red mud composite material is significantly stronger than that of red mud. Figure 3 (b) is a physical picture of the foamed carbon-red mud composite material of Example 1.

[0075] 3. The composite material prepared by the present invention was used to conduct a photocatalytic degradation test of organic pollutants. The experimental process was as follows: foamed carbon and foamed carbon-red mud composite materials with a diameter of 5 cm and a thickness of 5 mm were prepared and used in sewage purification experiments.

[0076] 2000 mL of wastewater was added to an evaporator (approximately 50 cm × 50 cm in area). 15 g of the prepared carbon foam or carbon foam composite was added to the evaporator. A Xe light source (PLSSEX300+) equipped with an AM 1.5 G filter provided simulated solar light. A solar meter (Thorlabs) was used to adjust the solar intensity. The surface temperature of the evaporation interface was recorded in real time using an infrared thermal imager. An electronic analytical balance monitored the mass change of the evaporator during the evaporation process. The composition of the collected water vapor was analyzed using UV-Vis and inductively coupled plasma (ICP) spectroscopy.

[0077] (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 when purifying sewage was tested using an infrared thermal imager. The test results are as follows: Figure 4 (carbon foam-red mud composite material) and Figure 5 (carbon foam) shown.

[0078] Depend on Figure 4-5By comparison, the surface temperature of the evaporation interface of the foamed carbon-red mud composite material of Example 1 under the irradiation of standard sunlight (100 mW / cm) for 5s-8s is significantly higher than that of the foamed carbon of Comparative Example 1.

[0079] (2) The carbon foam-red mud composite material of Example 1 was used to purify wastewater containing rhodamine (RhB) and methyl blue (MB) at a concentration of 200 mg / L under illumination conditions (one standard sunlight) and no illumination conditions, respectively, to test the wastewater purification efficiency.

[0080] Under light conditions (2 h), the comparison of sewage containing rhodamine (RhB) and methyl blue (MB) before and after purification is shown in the figure. Figure 6 As shown. Figure 6 The purified water (i.e., the sample obtained by condensing the collected water vapor) is colorless and transparent. The wastewater is converted into pure water due to the photothermal and photocatalytic effects of the carbon foam-red mud composite.

[0081] UV-visible spectroscopy was performed on the samples of sewage containing rhodamine (RhB) before and after purification (samples purified under light conditions); the test results are as follows: Figure 7 shown. Figure 7 The black line in the figure corresponds to the sample before purification, and the red line corresponds to the sample after purification. The test results show that after a 2-hour reaction under illumination, the collected water vapor contains almost no organic molecules.

[0082] UV-visible spectroscopy was performed on the samples of wastewater containing methyl blue (MB) before and after purification (samples purified under light conditions); the test results are as follows: Figure 8 shown. Figure 8 The black line in the figure corresponds to the sample before purification, and the red line corresponds to the sample after purification. The test results show that after a 2-hour reaction under illumination, the collected water vapor contains almost no organic molecules.

[0083] The test results of sewage purification efficiency are as follows: Figure 9 As shown (the sewage purification rate is calculated by dividing the mass of the condensed water collected at the end of the test by the mass of the foam carbon-red mud composite material and the test time; the sewage volume used in the test is 1 L, the mass of the foam carbon-red mud composite material is 7.5 g; the test time is 2 h). Figure 9 It can be seen that the foam carbon-red mud composite material of Example 1 has a significantly better purification rate for sewage under light conditions.

[0084] (3) The foamed carbon-red mud composite material of Example 1 was used to generate a 1 standard sunlight (100 mW / cm 2), 1.5 standard suns (150 mW / cm 2 ) and 2 standard suns (200 mW / cm 2 ) to purify sewage under irradiation.

[0085] The test results are as follows Figure 10 As shown. Figure 10 It can be seen that the sewage purification rate increases with the increase of light intensity.

[0086] (4) The foamed carbon-red mud composite material of Example 1 and the foamed carbon of Comparative Example 1 were used to purify sewage under 1 standard sunlight, and the test time was 6 h.

[0087] The test results are as follows Figure 11 As shown. Figure 11 It can be seen that the sewage purification rate of the foamed carbon-red mud composite material of Example 1 remained basically unchanged within the test time of 3 hours, and decreased slightly after 3 hours; while the sewage purification efficiency of the foamed carbon of Comparative Example 1 continued to decrease significantly during the test process; the foamed carbon-red mud composite material of Example 1 has significantly better stability.

[0088] (5) The carbon foam-red mud composite materials of Example 1 and Comparative Example 2 were used to purify sewage under the irradiation of one standard sun.

[0089] The test results are as follows Figure 12 As shown. Figure 12 It can be seen that in Example 1, by adding sodium alginate and calcium chloride during the preparation of foamed carbon, the sewage purification rate of the prepared foamed carbon-red mud composite material was significantly improved.

[0090] (6) The carbon foam-red mud composite materials of Example 1, Comparative Example 3 and Comparative Example 4 were used to purify sewage under irradiation of one standard sun.

[0091] The test results are as follows Figure 13 As shown. Figure 13 It can be seen that when the annealing temperature in step S2 is 400°C, the purification rate of sewage is significantly higher.

[0092] (7) The carbon foam-red mud composite materials of Example 1 and Comparative Example 5 were used to purify sewage under 1 standard sunlight; the test results are as follows: Figure 14 shown.

[0093] Depend on Figure 14 It can be seen that the loading amount of red mud will have a significant impact on the sewage purification effect. When the sludge loading amount is 5 mg (the diameter of the foam carbon is 5 cm and the thickness is 5 mm), the sewage purification effect is optimal.

[0094] (8) The foam carbon-red mud composite material of Comparative Example 6 was used to purify sewage under 1 standard sunlight (test time 2 h); the sewage purification rate test results are as follows Figure 15 shown.

[0095] from Figure 15 It can be seen that if the pH of the red mud solution is greater than 8 after the red mud is treated by introducing CO2 in step S1, the sewage purification performance of the prepared foamed carbon-red mud composite material will be adversely affected.

[0096] (9) The foamed carbon-red mud composite materials of Examples 2-8 were used to purify sewage under 1 standard sunlight (test time 2 h); the sewage purification rate test results of Example 2-5 are as follows: Figure 16 As shown, the test results of sewage purification rate of Examples 6-8 are as follows Figure 17 shown.

[0097] (10) The foamed carbon-red mud composite material of Example 1 was used to purify wastewater containing metal ions (the wastewater mass used in the test was 1 L, the amount of the foamed carbon-red mud composite material used was 7.5 g; the test time was 2 h, and the test condition was 1 standard light): Test Results: Table 1 compares the heavy ion removal results before and after purification (element concentrations in Table 1 are in mg / L). The experiment revealed that harmful elements, such as Ca, Mg, S, Fe, and Mn, were adsorbed onto the foam matrix, inhibiting their transport with water molecules. ICP measurements confirmed successful removal of these harmful elements, with no residual residue in the collected steam.

[0098] Table 1

[0099] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a foamed carbon-red mud composite material, characterized in that: The steps include: S1. Red mud pretreatment: introducing carbon dioxide gas into the red mud dispersion until the pH of the red mud solution is less than 8, performing solid-liquid separation and drying to obtain modified red mud; S2. Synthesis of foamed carbon: mixing a sodium alginate solution, a calcium chloride solution and melamine foam, and allowing to stand at room temperature to obtain a pretreated mixture, and annealing the pretreated mixture to obtain foamed carbon; S3. Preparation of foamed carbon-red mud composite material: The modified red mud obtained by the treatment in step S1 is uniformly dispersed in water and then sprayed on the surface of the foamed carbon, and dried to obtain the foamed carbon-red mud composite material.

2. The method for preparing the foamed carbon-red mud composite material according to claim 1, wherein: In step S2, the pretreated mixture is heated to 300-500° C. for annealing, and the annealing time is 0.5-1 h; The heating rate is 5-15°C / min.

3. The method for preparing the foamed carbon-red mud composite material according to claim 1, wherein: In step S2, the annealing is performed in a muffle furnace.

4. The method for preparing the foamed carbon-red mud composite material according to claim 1, wherein: 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).

5. The method for preparing the foamed carbon-red mud composite material according to claim 1, wherein: In step S1, the carbon dioxide gas is introduced at a rate of 8-12 mL / min; The solid-liquid separation is achieved by centrifugation, the centrifugal speed is 2000-4000 rpm, and the centrifugal time is 10-30 min; The drying temperature is 85-105° C., and the drying time is 1-3 h.

6. The method for preparing the foamed carbon-red mud composite material according to claim 1, wherein: 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 standing time at room temperature is 5-36 h.

7. The method for preparing the foamed carbon-red mud composite material according to claim 1, wherein: In step S2, the diameter of the melamine foam is 150-300 μm and the porosity is 99%.

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

9. Use of the foamed carbon-red mud composite material according to claim 8 in purifying sewage; The sewage contains at least one of organic pollutants, metal ions and non-metal ions.

10. The use according to claim 9, characterized in that The organic pollutants are rhodamine and / or methylene blue; The metal ion is 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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