Photo-thermal micro-electrolysis floating material as well as preparation method and application thereof

Abstract

The invention discloses a photo-thermal micro-electrolysis floating material as well as a preparation method and application thereof, and relates to the technical field of photo-thermal interface water evaporation. The floating material is prepared from iron-carbon composite powder, fly ash floating beads, a binder, a pore forming agent and deionized water according to a specific ratio. The preparation method comprises the following steps: preparing iron-carbon composite powder, preparing forming slurry, forming a mold, spraying carbon dots, drying and sintering. Meanwhile, the invention also provides application of the photo-thermal type micro-electrolysis floating material or the photo-thermal type micro-electrolysis floating material prepared by the preparation method in wastewater purification. The floating material has excellent photo-thermal conversion performance and micro-electrolysis performance and good floatability and mechanical strength, VOCs / water separation in the wastewater distillation and purification process can be efficiently promoted through solar energy, the wastewater treatment efficiency is improved, and the wastewater treatment energy consumption is reduced. The preparation method is simple and easy to operate, the raw materials are obtained from the coal-series solid waste, the cost is low, and recycling of the coal-series solid waste can be promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-carbon environmental protection, and particularly relates to the technology of photothermal interfacial water evaporation. Specifically, it is a photothermal microelectrolysis floating material and its preparation method and application. Background Technique

[0002] Coal chemical wastewater has complex components, strong toxicity and high treatment difficulty, seriously threatening the ecological environment and public health. During the wastewater treatment process, a large amount of organic pollutants still remain in the coal chemical wastewater after secondary biochemical treatment, making it difficult to meet the discharge standards and requiring advanced treatment. Traditional advanced wastewater treatment methods include coagulation sedimentation, adsorption, catalytic oxidation and membrane treatment, etc. These methods are often accompanied by problems such as high cost, extensive use of chemical reagents and membrane fouling. Therefore, finding a low-cost, simple process, environmentally friendly and highly efficient coal chemical wastewater advanced treatment technology has become an important research goal.

[0003] In recent years, the photothermal interfacial water evaporation technology has shown broad application prospects in the field of wastewater treatment due to its unique advantages of efficiently utilizing solar energy to drive water evaporation and simultaneously accelerating the interfacial physical and chemical reactions through heat convection. This technology is not only low-carbon and environmentally friendly, but also has the characteristics of low maintenance and operation costs and high-performance and stable performance. Through reasonable design of the morphology and composition of the photothermal material, the photothermal interfacial water evaporation rate can reach more than 3.0 kg•m -2 •h -1 above, and a significant water distillation and purification rate can be obtained. However, the single photothermal interfacial water evaporation technology still has certain limitations in the advanced treatment of coal chemical wastewater. Especially in the separation of VOCs / water, due to the significant volatility of VOCs, it is difficult for single photothermal interfacial water evaporation to achieve efficient VOCs / water separation, and even the phenomenon of VOCs enrichment in distilled water occurs. Therefore, how to prepare advanced photothermal interfacial water evaporation materials and improve the VOCs / water separation efficiency has become an important current research direction. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art, and provide a photothermal microelectrolysis floating material and its preparation method and application. The present invention couples photothermal interfacial water evaporation with microelectrolysis, improves the VOCs / water separation efficiency, and provides a new technical solution for the advanced treatment of coal chemical wastewater.

[0005] The present invention is achieved by the following technical solutions: A photothermal microelectrolysis floating material is made from the following raw materials in parts by weight: 25 - 30 parts of iron-carbon composite powder, 55 - 60 parts of fly ash cenospheres, 10 - 20 parts of binder, 5 - 10 parts of pore-forming agent, and 30 - 40 parts of deionized water.

[0006] Preferably, the iron-carbon composite powder is composed of nano-powders with high iron content, coal-based carbon dot powder, and nano-titanium dioxide powder in any proportion. The nano-powders with high iron content are high-purity nano-iron powder or high-purity nano-stainless steel powder; the fly ash cenospheres are hollow spherical particles with a size in the range of 200-500 mesh; the binder is bentonite; the pore-forming agent is sodium bicarbonate or sodium carbonate or ammonium bicarbonate.

[0007] Preferably, the iron-carbon composite powder is composed of 50-55 parts by weight of nano-powders with high iron content, 10-15 parts by weight of coal-based carbon dot powder, and 30-35 parts by weight of nano-titanium dioxide powder.

[0008] Preferably, the preparation method of the coal-based carbon dot powder is as follows: etching waste coal tar pitch in formic acid and hydrogen peroxide, with the volume ratio of formic acid to hydrogen peroxide being 8-12 and the etching time being 20-25 h. After the etching is completed, centrifugation and rotary evaporation drying are carried out to obtain the coal-based carbon dot powder.

[0009] Furthermore, the present invention also provides a preparation method of the above-mentioned photothermal micro-electrolysis floating material, which specifically includes the following steps: 1) Preparation of the iron-carbon composite powder: Mix the nano-powders with high iron content, coal-based carbon dot powder, and nano-titanium dioxide powder, first carry out ball milling treatment, then carry out high-temperature calcination, and finally prepare the iron-carbon composite powder.

[0010] 2) Preparation of the molding slurry: Mix the iron-carbon composite powder, fly ash cenospheres, binder, and pore-forming agent, then add deionized water and stir well to finally prepare the molding slurry.

[0011] 3) Molding with a mold: Pour the uniformly mixed molding slurry into a stainless steel mold and carry out molding under a fixed pressure, and finally demold to obtain the floating material blank.

[0012] 4) Spraying carbon dots: Disperse the coal-based carbon dot powder in absolute ethanol to obtain a coal-based carbon dot ethanol dispersion, and then spray the coal-based carbon dot ethanol dispersion on the upper surface of the floating material blank by spraying method.

[0013] 5) Drying and sintering: Dry the floating material blank under natural conditions, then place it in an argon atmosphere for sintering, and after the sintering is completed, the above-mentioned photothermal micro-electrolysis floating material is obtained.

[0014] Preferably, in step 1) of the above preparation method, the ball milling speed is 350-400 r / min, the ball milling time is 0.4-0.6 h; the temperature of high-temperature calcination is 350-450 °C, the calcination time is 1.5-2.5 h, and the calcination atmosphere is argon.

[0015] Preferably, in step 3) of the above preparation method, the fixed pressure during molding is (1.5-2.0)×105 Pa.

[0016] Preferably, in step 4) of the above preparation method, the coal-based carbon dot powder is added to absolute ethanol at a concentration of 10 g / L, magnetically stirred at 600 rpm for 30 min, and ultrasonically treated at 60 Hz for 10 min to obtain a homogeneous and stable coal-based carbon dot ethanol dispersion; the spraying amount of the coal-based carbon dot ethanol dispersion on the upper surface of the floating material blank is controlled at 25-30 mg / cm 2 .

[0017] Preferably, in step 5) of the above preparation method, the sintering temperature is 750-850 °C, the sintering time is 1.0-1.5 h, and the sintering atmosphere is argon.

[0018] Furthermore, the present invention also provides the application of the above photothermal microelectrolysis floating material or the photothermal microelectrolysis floating material prepared by the above preparation method in wastewater purification.

[0019] In summary, the present invention provides a photothermal microelectrolysis floating material, its preparation method and application. The floating material of the present invention uses metal nanoflakes with high iron content, coal-based carbon dot powder, nano-titanium dioxide powder and fly ash cenospheres as key raw materials, supplemented with bentonite, etc. as binders, and sodium bicarbonate, sodium carbonate, etc. as pore-forming agents, and adopts a slurry forming and high-temperature sintering process to prepare a floating composite material with both photothermal and microelectrolysis functions. The composite material of the present invention can float on the water surface, efficiently utilize solar energy for photothermal interfacial water evaporation, and at the same time exert its microelectrolysis characteristics to degrade volatile organic pollutants (VOCs). Finally, water and VOCs can be effectively separated to achieve efficient purification of wastewater. Experimental results show that the composite material of the present invention has a water evaporation rate of up to 1.72 kg•m -2 under simulated solar light irradiation, and the removal rate of volatile organic matter phenol in distilled water reaches 92.0%, realizing the synergistic effect of photothermal interfacial water evaporation and microelectrolysis in wastewater treatment, which is beneficial to the advanced treatment of industrial wastewater. In addition, the fly ash cenospheres involved in the present invention are extracted from power plant fly ash, and the coal-based carbon dots are derived from waste coal tar pitch. Both power plant fly ash and waste coal tar pitch are coal-based solid wastes. Therefore, the implementation of the present invention also promotes the reuse of coal-based solid wastes. -2 •h -1 -2, and the removal rate of volatile organic matter phenol in distilled water reaches 92.0%, realizing the synergistic effect of photothermal interfacial water evaporation and microelectrolysis in wastewater treatment, which is beneficial to the advanced treatment of industrial wastewater. In addition, the fly ash cenospheres involved in the present invention are extracted from power plant fly ash, and the coal-based carbon dots are derived from waste coal tar pitch. Both power plant fly ash and waste coal tar pitch are coal-based solid wastes. Therefore, the implementation of the present invention also promotes the reuse of coal-based solid wastes.

[0020] Compared with the prior art, the floating material of the present invention has excellent photothermal conversion performance, microelectrolysis performance, good floating property and mechanical strength, can efficiently promote the VOCs / water separation in the wastewater distillation purification process by using solar energy, improve the wastewater treatment efficiency, and reduce the energy consumption of wastewater treatment. The floating material preparation method provided by the present invention is simple and easy to operate, uses coal-based solid wastes as raw materials, has a low cost, can promote the reuse of coal-based solid wastes, and protects the environment. Description of the Drawings

[0021] The drawings herein are used to provide further illustration of the present invention and constitute a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and shall not unduly limit the present invention.

[0022] Figure 1 It is a physical diagram of the photothermal microelectrolysis floating material prepared in Example 1 and a schematic diagram of it floating on the water surface.

[0023] Figure 2 It is a scanning electron microscope image of the photothermal microelectrolysis floating material prepared in Example 1.

[0024] Figure 3 It is a transmission electron microscope image of the iron-carbon composite powder prepared in Example 1.

[0025] Figure 4 It is an ultraviolet-visible-near infrared absorption spectrum of the photothermal microelectrolysis floating material prepared in Example 1.

[0026] Figure 5 It is the surface temperature-time curve of the photothermal microelectrolysis floating material prepared in Example 1 under simulated sunlight irradiation of 1.0 kW•m -2 simulated sunlight irradiation.

[0027] Figure 6 It is a schematic diagram of the device structure when testing the performance of the photothermal microelectrolysis floating material prepared in Example 1 for treating phenol wastewater with solar energy.

[0028] Figure 7 It is the ultraviolet-visible absorption spectrum of the photothermal microelectrolysis floating material prepared in Example 1 for treating phenol wastewater and the obtained distilled water under simulated sunlight of 1.0 kW•m -2 simulated sunlight irradiation.

[0029] Figure 8 It is the ultraviolet-visible absorption spectrum of the photothermal microelectrolysis floating material prepared in Example 2 for treating phenol wastewater and the obtained distilled water under simulated sunlight of 1.0 kW•m -2 simulated sunlight irradiation.

[0030] Figure 9 It is the ultraviolet-visible absorption spectrum of the photothermal microelectrolysis floating material prepared in Example 3 for treating phenol wastewater and the obtained distilled water under simulated sunlight of 1.0 kW•m -2 simulated sunlight irradiation.

[0031] Figure 10 It is the ultraviolet-visible absorption spectrum of the photothermal microelectrolysis floating material prepared in Example 4 for treating phenol wastewater and the obtained distilled water under simulated sunlight of 1.0 kW•m -2 simulated sunlight irradiation.

[0032] Figure 11 The photothermal micro-electrolysis floating material prepared in Example 5 is 1.0 kW•m -2 UV-visible absorption spectra of phenol wastewater treated under simulated sunlight and the resulting distilled water.

[0033] Figure 12 The photothermal micro-electrolysis floating material prepared in Example 6 is 1.0 kW•m -2 UV-visible absorption spectra of phenol wastewater treated under simulated sunlight and the resulting distilled water.

[0034] Figure 13 The photothermal micro-electrolysis floating material prepared in Example 7 is 1.0 kW•m -2 UV-visible absorption spectra of phenol wastewater treated under simulated sunlight and the resulting distilled water.

[0035] Figure 14 This is a physical picture of the photothermal micro-electrolysis floating material prepared in Example 8 and a schematic diagram of it sinking to the bottom of the water.

[0036] Figure 15 The photothermal micro-electrolysis floating material prepared in Example 9 is a real picture of the photothermal micro-electrolysis floating material prepared in Example 9 and its performance at 1.0 kW•m -2 UV-visible absorption spectra of phenol wastewater treated under simulated sunlight and the resulting distilled water.

[0037] Figure 16 The photothermal micro-electrolysis floating material prepared in Example 10 is shown in Figure 11. -2 UV-visible absorption spectra of phenol wastewater treated under simulated sunlight and the resulting distilled water. DETAILED DESCRIPTION

[0038] The invention provides a photothermal micro-electrolysis floating material, a preparation method and an application thereof.

[0039] The described photothermal microelectrolysis floating material is made from the following raw materials in parts by weight: 25-30 parts of iron-carbon composite powder, 55-60 parts of fly ash cenospheres, 10-20 parts of binder, 5-10 parts of pore former, and 30-40 parts of deionized water. Among them, the iron-carbon composite powder is composed of nano-powders with high iron content, coal-based carbon dot powders, and nano-titanium dioxide powders in any proportion. Preferably, the iron-carbon composite powder can be composed of 50-55 parts by weight of nano-powders with high iron content, 10-15 parts by weight of coal-based carbon dot powders, and 30-35 parts by weight of nano-titanium dioxide powders. The preparation method of the coal-based carbon dot powder is as follows: etching waste coal tar pitch in formic acid and hydrogen peroxide, with the volume ratio of formic acid to hydrogen peroxide being 8-12, the etching time being 20-25 h. After the etching is completed, centrifugation and rotary evaporation drying are carried out to obtain the coal-based carbon dot powder. The coal-based carbon dot powder is prepared with waste coal tar pitch as the precursor and has excellent photothermal conversion performance; the nano-powders with high iron content are high-purity nano-iron powder or high-purity nano-stainless steel powder, which can provide electrons in the microelectrolysis reaction; the nano-titanium dioxide powder is commercial P25 powder, which has excellent hydrophilic performance and can ensure the transmission of water; the fly ash cenospheres adopt hollow spherical particles with a size in the range of 200-500 mesh and have the characteristics of light weight and floating; the binder is bentonite; the pore former is sodium bicarbonate or sodium carbonate or ammonium bicarbonate.

[0040] The preparation method of the described photothermal microelectrolysis floating material specifically includes the following steps: 1) Preparation of iron-carbon composite powder: Mix the nano-powders with high iron content, coal-based carbon dot powders, and nano-titanium dioxide powders, first carry out ball milling treatment, then carry out high-temperature calcination, and finally prepare the iron-carbon composite powder; in this step, the ball milling speed is 350-400 r / min, and the ball milling time is 0.4-0.6 h; the temperature of the high-temperature calcination is 350-450 °C, the calcination time is 1.5-2.5 h, and the calcination atmosphere is argon.

[0041] 2) Preparation of the forming slurry: Mix the iron-carbon composite powder, fly ash cenospheres, binder, and pore former, then add deionized water and stir well to finally prepare the forming slurry.

[0042] 3) Molding with a mold: Pour the uniformly mixed forming slurry into a stainless steel mold and carry out molding under a fixed pressure, and finally demold to obtain the floating material blank; in this step, the fixed pressure during the molding under pressure is (1.5-2.0)×10 5 Pa.

[0043] 4) Carbon dot spraying: Disperse the coal-based carbon dot powder in absolute ethanol to obtain a coal-based carbon dot ethanol dispersion, and then spray the coal-based carbon dot ethanol dispersion on the upper surface of the floating material blank by spraying method; in this step, add the coal-based carbon dot powder into absolute ethanol at a concentration of 10 g / L, stir magnetically at 600 rpm for 30 min, and perform ultrasonic treatment at 60 Hz for 10 min to obtain a uniform and stable coal-based carbon dot ethanol dispersion; the spraying amount of the coal-based carbon dot ethanol dispersion on the upper surface of the floating material blank is controlled at 25-30 mg / cm 2 .

[0044] 5) Drying and sintering: Dry the floating material blank under natural conditions, and then place it in an argon atmosphere for sintering. After the sintering is completed, the described photothermal microelectrolysis floating material is obtained; in this step, the sintering temperature is 750-850 °C, the sintering time is 1.0-1.5 h, and the sintering atmosphere is argon.

[0045] Application of the described photothermal microelectrolysis floating material or the photothermal microelectrolysis floating material prepared by the described preparation method in wastewater purification.

[0046] To enable those skilled in the art to better understand the present invention, the present invention will be further clearly and completely described below in conjunction with the reference drawings and embodiments. It should be noted that, without conflict, the implementation manners and features in the embodiments of the present application can be combined with each other. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Example 1

[0047] A preparation method of a photothermal microelectrolysis floating material specifically includes the following steps: 1) Weigh the weight ratio of high-purity nano iron powder, coal-based carbon dot powder and nano titanium dioxide powder as 52:13:32.5. After mixing, transfer it to a planetary ball mill, with a ball-to-material ratio of 40:3, and ball mill at a ball mill speed of 368 r / min for 0.5 h. After the ball milling is completed, calcine the obtained powder at 400 o °C in an argon atmosphere for 2.0 h to obtain an iron-carbon composite powder.

[0048] 2) Weigh the weight ratio of the iron-carbon composite powder, fly ash cenosphere, bentonite, sodium bicarbonate and deionized water as 25:55:15:5:40, and mix and stir for 0.5 h to obtain a molding slurry.

[0049] 3) Weigh 1.0 g of the molding slurry and add it to a circular mold, control the pressure to be 1.6×10 5 Pa, demold after molding for 10 min to obtain a floating material blank with a blank diameter of 2 cm and a thickness of 5 mm.

[0050] 4) Add the coal-based carbon dot powder into absolute ethanol at a concentration of 10 g / L, magnetically stir for 30 min at 600 rpm, and ultrasonically treat for 10 min at 60 Hz to obtain a homogeneous and stable coal-based carbon dot ethanol dispersion; spray the coal-based carbon dot ethanol dispersion onto the surface of the floating material blank by the spraying method, and the carbon dot spraying amount is 28 mg / cm 2 .

[0051] 5) Dry the floating material blank under natural conditions for 24 h, transfer it to a tubular atmosphere sintering furnace, and under an argon atmosphere, set the heating rate to 15 o °C / min, heat up to 800 o °C and hold for 1.0 h, and take it out after cooling to obtain the described photothermal microelectrolysis floating material.

[0052] The obtained photothermal microelectrolysis floating material presents a loose and porous structure and can stably float on the water surface. As Figure 1 shown, a shows the loose and porous structure of the photothermal microelectrolysis floating material, and b shows that the photothermal microelectrolysis floating material can stably float on the water surface; the photothermal microelectrolysis floating material contains a large number of micropores and mesopores inside. As Figure 2 and Figure 3 shown,[[]] Figure 2 in a is the low-magnification SEM image of the photothermal microelectrolysis floating material, b is the medium-magnification SEM image of the photothermal microelectrolysis floating material, and c is the high-magnification SEM image of the photothermal microelectrolysis floating material,[[]] Figure 3 in a is the low-magnification TEM image of the iron-carbon composite powder, and b is the high-magnification TEM image of the iron-carbon composite powder; the absorption rate of the photothermal microelectrolysis floating material in the ultraviolet-visible-near-infrared region can reach more than 80%. As Figure 4 shown. Under the irradiation of simulated sunlight at 1.0 kW•m -2 , the surface temperature of the photothermal microelectrolysis floating material rises from 20 o °C to 60 o °C within 20 minutes, showing its excellent photothermal conversion performance. As Figure 5 shown. Use the device as Figure 6 shown to conduct an experiment on solar treatment of phenol wastewater (phenol concentration: 100 mg / L). The measured water evaporation rate is 1.72 kg•m -2 •h -1 , and the phenol removal rate in the obtained distilled water can reach 92.0%, showing its excellent performance in solar treatment of phenol wastewater. As Figure 7 shown. Example 2

[0053] A preparation method of a photothermal microelectrolysis floating material specifically includes the following steps: 1) Weigh the weight ratio of high-purity nano iron powder and coal-based carbon dot powder as 4:1. After mixing, transfer it to a planetary ball mill. The ball-to-material ratio is 40:3, and ball mill for 0.5 h at a ball milling speed of 368 r / min. After ball milling, calcine the obtained powder at 400 o C for 2.0 h under an argon atmosphere to obtain iron-carbon composite powder.

[0054] 2) Weigh the weight ratio of iron-carbon composite powder, fly ash cenospheres, bentonite, sodium bicarbonate and deionized water as 25:55:15:5:40. After mixing and stirring for 0.5 h, obtain the forming slurry.

[0055] 3) Weigh 1.0 g of the forming slurry and add it to a circular mold. Control the pressure to 1.6×10 5 Pa, demold after molding for 10 min to obtain a floating material blank. The diameter of the blank is 2 cm and the thickness is 5 mm.

[0056] 4) Add the coal-based carbon dot powder to absolute ethanol at a concentration of 10 g / L, stir magnetically at 600 rpm for 30 min, and ultrasonically treat at 60 Hz for 10 min to obtain a homogeneous and stable coal-based carbon dot ethanol dispersion; use the spraying method to spray the coal-based carbon dot ethanol dispersion onto the surface of the floating material blank, and the carbon dot spraying amount is 28 mg / cm 2 .

[0057] 5) Dry the floating material blank under natural conditions for 24 h, transfer it to a tube-type atmosphere sintering furnace. Under an argon atmosphere, set the heating rate to 15 o C / min, heat up to 800 o C and hold for 1.0 h, and take it out after cooling to obtain the described photothermal microelectrolysis floating material.

[0058] Conduct an experiment on treating phenol wastewater (phenol concentration: 100 mg / L) with solar energy using the obtained above-mentioned photothermal microelectrolysis floating material. Measure the water evaporation rate as 1.45 kg•m -2 •h -1 , and the phenol removal rate in the obtained distilled water can reach 62.41%. Compared with the performance of the photothermal microelectrolysis floating material obtained in Example 1 for treating phenol wastewater with solar energy, there is a significant decrease, as Figure 8 shown, indicating the importance of nano-titanium dioxide powder (P25 titanium dioxide nano-powder) as a raw material. Example 3

[0059] A preparation method of a photothermal microelectrolysis floating material, which is different from the preparation method of Example 1 in that kaolin is used instead of bentonite to prepare the photothermal microelectrolysis floating material.

[0060] The above-mentioned photo-thermal micro-electrolysis floating material obtained was used for the experiment of treating phenol wastewater by solar energy (phenol concentration: 100 mg•L -1 ). The water evaporation rate was measured to be 1.61 kg•m -2 •h -1 . The phenol removal rate in the obtained distilled water could reach 76.1%, showing a significant decrease compared with the performance of the photo-thermal micro-electrolysis floating material obtained in Example 1 for treating phenol wastewater by solar energy. As Figure 9 shown, it indicates that bentonite is more effective than kaolin as a raw material. Example 4

[0061] A preparation method of a photo-thermal micro-electrolysis floating material, which is different from the preparation method of Example 1 in that sodium carbonate is used to replace sodium bicarbonate to prepare the photo-thermal micro-electrolysis floating material.

[0062] The above-mentioned photo-thermal micro-electrolysis floating material obtained was used for the experiment of treating phenol wastewater by solar energy (phenol concentration: 100 mg•L -1 ). The water evaporation rate was measured to be 1.70 kg•m -2 •h -1 . The phenol removal rate in the obtained distilled water could reach 89.3%, showing no significant decrease compared with the performance of the photo-thermal micro-electrolysis floating material obtained in Example 1 for treating phenol wastewater by solar energy. As Figure 10 shown, it indicates the feasibility of using sodium carbonate as a raw material. Example 5

[0063] A preparation method of a photo-thermal micro-electrolysis floating material, which is different from the preparation method of Example 1 in that ammonium bicarbonate is used to replace sodium bicarbonate to prepare the photo-thermal micro-electrolysis floating material.

[0064] The above-mentioned photo-thermal micro-electrolysis floating material obtained was used for the experiment of treating phenol wastewater by solar energy (phenol concentration: 100 mg•L -1 ). The water evaporation rate was measured to be 1.64 kg•m -2 •h -1 . The phenol removal rate in the obtained distilled water could reach 89.2%, showing no significant decrease compared with the performance of the photo-thermal micro-electrolysis floating material obtained in Example 1 for treating phenol wastewater by solar energy. As Figure 11 shown, it indicates the feasibility of using ammonium bicarbonate as a raw material. Example 6

[0065] A preparation method of a photo-thermal micro-electrolysis floating material, which is different from the preparation method of Example 1 in that after the floating material blank is obtained by slurry molding, the coal-based carbon dot ethanol dispersion liquid is not sprayed on the surface of the floating material blank, and other process parameters and operation steps are exactly the same as those in Example 1.

[0066] The above-mentioned photothermal microelectrolysis floating material obtained was used for the experiment of treating phenol wastewater by solar energy (phenol concentration: 100 mg•L -1 ). The water evaporation rate was measured to be 1.62 kg•m -2 •h -1 . The phenol removal rate in the obtained distilled water could reach 71.4%, showing a significant decrease compared with the performance of the photothermal microelectrolysis floating material obtained in Example 1 for treating phenol wastewater by solar energy. As Figure 12 shown, it indicates the necessity of spraying the ethanol dispersion of coal-based carbon dots on the surface of the floating material blank. Example 7

[0067] A preparation method of a photothermal microelectrolysis floating material is different from the preparation method of Example 1 in that high-purity nano stainless steel powder is used to replace high-purity nano iron powder, and other process parameters and operation steps are exactly the same as those in Example 1.

[0068] The above-mentioned photothermal microelectrolysis floating material obtained was used for the experiment of treating phenol wastewater by solar energy (phenol concentration: 100 mg•L -1 ). The water evaporation rate was measured to be 1.67 kg•m -2 •h -1 . The phenol removal rate in the obtained distilled water could reach 85.3%, showing no significant decrease compared with the performance of the photothermal microelectrolysis floating material obtained in Example 1 for treating phenol wastewater by solar energy. As Figure 13 shown, it indicates the feasibility of using high-purity nano stainless steel powder as the raw material. Example 8

[0069] A preparation method of a photothermal microelectrolysis floating material is different from the preparation method of Example 1 in that during the slurry molding process, the pressure is adjusted to 2.1×10 5 Pa, and other process parameters and operation steps are the same as those in Example 1.

[0070] The above-mentioned photothermal microelectrolysis floating material obtained presented a dense structure and could not float on the water surface. As Figure 14 shown, a is the photothermal microelectrolysis floating material presenting a dense structure, and b is the photothermal microelectrolysis floating material that could not float on the water surface, indicating that the molding pressure should be less than 2.0×10 5 Pa. Example 9

[0071] A preparation method of a photothermal microelectrolysis floating material is different from the preparation method of Example 1 in that in step 1), the weight ratio of high-purity nano iron powder, coal-based carbon dot powder, and nano titanium dioxide powder is 50:15:35, the ball milling speed is 400 r / min, the ball milling time is 0.4 h, and after the ball milling is completed, the obtained powder is heated at 450 oC, calcined for 1.5 h under an argon atmosphere; in step 2), the weight ratio of the iron-carbon composite powder, fly ash cenospheres, bentonite, sodium bicarbonate and deionized water is 28:60:10:10:35; in step 3), the pressure is controlled to be 1.5×10 5 Pa; in step 4), the carbon dot spraying amount is 30 mg / cm 2 ; in step 5), the temperature is raised to 750 o C and maintained for 1.2 h. Other process parameters and operation steps are exactly the same as those in Example 1.

[0072] The obtained photothermal microelectrolysis floating material presents a loose and porous structure and can stably float on the water surface, as shown in a of Figure 15 ; the obtained photothermal microelectrolysis floating material is used for the experiment of treating phenol wastewater by solar energy (phenol concentration: 100 mg•L -1 ), and the measured water evaporation rate is 1.70 kg•m -2 •h -1 , and the phenol removal rate in the obtained distilled water can reach 91.5%, showing its excellent performance in treating phenol wastewater by solar energy, as shown in b of Figure 15 . Example 10

[0073] A preparation method of a photothermal microelectrolysis floating material, which is different from the preparation method of Example 1 in that: in step 1), the weight ratio of high-purity nano iron powder, coal-based carbon dot powder and nano titanium dioxide powder is 55:10:30, the ball milling speed is 350 r / min, the ball milling time is 0.6 h, and after the ball milling is completed, the obtained powder is calcined at 350 o C under an argon atmosphere for 2.5 h; in step 2), the weight ratio of the iron-carbon composite powder, fly ash cenospheres, bentonite, sodium bicarbonate and deionized water is 30:57:20:8:30; in step 3), the pressure is controlled to be 2.0×10 5 Pa; in step 4), the carbon dot spraying amount is 25 mg / cm 2 ; in step 5), the temperature is raised to 850 o C and maintained for 1.5 h. Other process parameters and operation steps are exactly the same as those in Example 1.

[0074] The obtained photothermal microelectrolysis floating material presents a loose and porous structure and can stably float on the water surface, as shown in a of Figure 16 ; the obtained photothermal microelectrolysis floating material is used for the experiment of treating phenol wastewater by solar energy (phenol concentration: 100 mg•L -1 ), and the measured water evaporation rate is 1.69 kg•m -2 •h -1, the removal rate of phenol in the obtained distilled water can reach 91.0%, showing its excellent performance in treating phenol wastewater by solar energy, as shown in Figure 16 shown in b of

[0075] The above-described embodiments only represent the optimal implementation modes of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A photothermal microelectrolysis floating material, characterized in that, It is made from the following raw materials in parts by weight: 25 - 30 parts of iron-carbon composite powder, 55 - 60 parts of fly ash cenospheres, 10 - 20 parts of binder, 5 - 10 parts of pore former, and 30 - 40 parts of deionized water.

2. The photothermal microelectrolysis floating material according to claim 1, characterized in that: The iron-carbon composite powder is composed of nano powder with high iron content, coal-based carbon dot powder, and nano titanium dioxide powder in any proportion. The nano powder with high iron content is high-purity nano iron powder or high-purity nano stainless steel powder; the fly ash cenospheres are hollow spherical particles with a size in the range of 200 - 500 mesh; the binder is bentonite; the pore former is sodium bicarbonate or sodium carbonate or ammonium bicarbonate.

3. The photothermal microelectrolysis floating material according to claim 1, wherein: The iron-carbon composite powder is composed of 50 - 55 parts by weight of nano powder with high iron content, 10 - 15 parts by weight of coal-based carbon dot powder, and 30 - 35 parts by weight of nano titanium dioxide powder.

4. The photothermal microelectrolysis floating material according to claim 2 or 3, characterized in that: The preparation method of the coal-based carbon dot powder is: etching waste coal tar pitch in formic acid and hydrogen peroxide, the volume ratio of formic acid to hydrogen peroxide is 8 - 12, the etching time is 20 - 25 h, after the etching is completed, centrifugation and rotary evaporation drying are carried out to obtain the coal-based carbon dot powder.

5. The preparation method of the photothermal micro-electrolysis floating material according to claim 4, characterized in that, It includes the following steps: 1) Prepare the iron-carbon composite powder: Mix the nano powder with high iron content, coal-based carbon dot powder, and nano titanium dioxide powder, first carry out ball milling treatment, then carry out high-temperature calcination, and finally prepare the iron-carbon composite powder; 2) Prepare the forming slurry: Mix the iron-carbon composite powder, fly ash cenospheres, binder, and pore former, then add deionized water and stir well to finally prepare the forming slurry; 3) Mold forming: Pour the uniformly mixed forming slurry into a stainless steel mold and carry out molding under a fixed pressure, and finally demold to obtain the floating material blank; 4) Carbon dot spraying: Disperse the coal-based carbon dot powder in absolute ethanol to obtain a coal-based carbon dot ethanol dispersion liquid, and then spray the coal-based carbon dot ethanol dispersion liquid on the upper surface of the floating material blank by spraying method; 5) Drying and sintering: Dry the floating material blank under natural conditions, then place it in an argon atmosphere for sintering, and after the sintering is completed, the described photothermal microelectrolysis floating material is obtained.

6. The preparation method of the photothermal micro-electrolysis floating material according to claim 5, characterized in that: In step 1), the ball milling speed is 350 - 400 r / min, and the ball milling time is 0.4 - 0.6 h; the temperature of the high-temperature calcination is 350 - 450 °C, the calcination time is 1.5 - 2.5 h, and the calcination atmosphere is argon.

7. The preparation method of the photothermal micro-electrolysis floating material according to claim 5, characterized in that: In step 3), the fixed pressure during compression molding is (1.5~2.0)×10 5 Pa.

8. The preparation method of the photothermal microelectrolysis floating material according to claim 5, characterized in that: In step 4), the coal-based carbon dot powder is added to absolute ethanol at a concentration of 10 g / L, magnetically stirred at 600 rpm for 30 min, and ultrasonically treated at 60 Hz for 10 min to obtain a homogeneous and stable coal-based carbon dot ethanol dispersion; the spraying amount of the coal-based carbon dot ethanol dispersion on the upper surface of the floating material blank is controlled at 25-30 mg / cm 2 .

9. The preparation method of the photothermal micro-electrolysis floating material according to claim 5, characterized in that: In step 5), the sintering temperature is 750 - 850 °C, the sintering time is 1.0 - 1.5 h, and the sintering atmosphere is argon.

10. The application of the photothermal microelectrolysis floating material according to any one of claims 1 - 3 or the photothermal microelectrolysis floating material according to claim 4 or the photothermal microelectrolysis floating material prepared by the preparation method according to claim 5 in wastewater purification.

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