Binary composite material for highly efficient removal of formaldehyde by visible light catalysis, preparation method and application thereof

Abstract

The present invention provides a binary composite material for highly efficient visible-light catalytic formaldehyde removal, its preparation method and application, which include the following preparation steps: Using Ce(NO3)3·6H2O as a reaction raw material, CeO2 is obtained by calcination; A basic mixed solution containing CaCl2 and SnCl4·5H2O with a molar ratio of 1:1 is mixed with CeO2, and transferred to a stainless-steel autoclave lined with polytetrafluoroethylene, and hydrothermal reaction is carried out at 180-200 °C. The product is centrifuged, washed, and vacuum dried to obtain CaSn(OH)6 / CeO2; wherein, the molar ratio of CeO2 to CaCl2 is 1:1. The present invention further proves through experiments that when the dosage of CaSn(OH)6 / CeO2, single CaSn(OH)6, and single CeO2 is the same (all 0.2 g), and the formaldehyde content in the sewage to be treated is the same (all 1 ppm), the formaldehyde degradation efficiency of CaSn(OH)6 / CeO2 provided by the embodiment of the present invention reaches 88.9% within 30 min, while the formaldehyde degradation efficiency of the single CaSn(OH)6 semiconductor photocatalytic material is only 4.9% within 30 min, and the formaldehyde degradation efficiency of the single CeO2 photocatalytic material is 39.6% within 30 min.

Description

Technical Field

[0001] The present invention belongs to the field of nanomaterials, and particularly relates to a binary composite material for highly efficient visible-light catalytic formaldehyde removal, a preparation method thereof, and an application thereof. Background Art

[0002] With the development of science, people have a deeper understanding of common chemical substances that affect human health. In modern society, the production of chemical materials has greatly enriched our demand for various products. However, it is precisely due to the abuse of various chemicals that environmental chemical pollution has been caused. Indoor formaldehyde mainly comes from materials containing formaldehyde or substances that are prone to decompose to produce formaldehyde. Common decorative materials and household items are the largest sources of formaldehyde. Some chemicals that can decompose to produce formaldehyde (such as phenolic resin or urea-formaldehyde resin), which have bleaching and shaping functions, also produce formaldehyde when used in food and clothing. This is how formaldehyde, which is extremely harmful to human health, is generated. People usually spend more than 80% of their time in houses / apartments, offices, and cars. Therefore, indoor air quality is crucial for human health. Formaldehyde (HCHO) is considered a major toxic indoor pollutant, which directly affects indoor air quality. A good living environment is related to the physical health of all residents. The problem of indoor formaldehyde pollution urgently needs more exploration and solutions.

[0003] Currently, common methods such as filtration, adsorption, and electrostatic precipitation technologies are mostly used to reduce the harm of formaldehyde to the human body. However, there are also disadvantages such as excessive energy consumption, possible generation of harmful by-products, unsatisfactory removal effects, and difficult operation. From a chemical perspective, we have better methods to solve formaldehyde pollution. Photocatalytic oxidation is a low-cost, green, and effective method for formaldehyde removal, while the existing photocatalytic materials have low formaldehyde removal efficiency. The photocatalytic method has become one of the main research objects due to its advantages such as simple operation, no secondary pollution, and high efficiency.

[0004] Perovskite hydroxide CaSn(OH) 6 has a wide bandgap (about 3.8 eV) and a structure feature of easy self-doping. Its excellent photochemical stability, non-toxicity, and suitable energy band position make it one of the most promising photocatalytic materials for formaldehyde degradation. However, CaSn(OH) 6 The main disadvantage of the semiconductor photocatalyst is that it only absorbs in the ultraviolet region, which limits the application of CaSn(OH) 6 semiconductor photocatalyst in photocatalytic degradation of formaldehyde. Summary of the Invention

[0005] Aiming at the above problems existing in the prior art, the present invention provides a binary composite material for highly efficient visible-light catalytic formaldehyde removal, a preparation method thereof, and an application thereof. By CaSn(OH) 6 and CeO 2Compound, a novel binary composite material with high degradation efficiency for formaldehyde was developed, further improving CaSn(OH) 6 Application of semiconductor photocatalyst in photocatalytic degradation of formaldehyde

[0006] The specific invention content is as follows

[0007] In the first aspect, the present invention provides a preparation method of a binary composite material for efficient visible-light photocatalytic formaldehyde removal. The preparation method of the binary composite material includes the following preparation steps

[0008] S1. Using Ce(NO 3 ) 3 ∙6H 2 O as the reaction raw material, CeO 2 is obtained through calcination

[0009] S2. Mix an alkaline mixed solution containing CaCl 2 and SnCl 4 ∙5H 2 O with a molar ratio of 1:1 with the CeO 2 , and transfer it to a stainless-steel autoclave lined with polytetrafluoroethylene. Hydrothermal reaction is carried out at 180 - 200 °C. The product is centrifuged, washed, and vacuum dried to obtain the binary composite material for efficient visible-light photocatalytic formaldehyde removal - CaSn(OH) 6 / CeO 2 ; wherein, the molar ratio of the CeO 2 to the CaCl 2 is 1:1

[0010] Further, step S1 specifically includes

[0011] S11. Dissolve Ce(NO 3 ) 3 ∙6H 2 O with a mass-volume ratio of 10 mg:1 ml in ethanol, ultrasonically treat it at room temperature, and then transfer it to an environment of 40 - 60 °C to completely volatilize the ethanol to obtain a powdery solid

[0012] S12. Transfer the powdery solid to a muffle furnace and carry out calcination treatment at 300 - 360 °C. After the product is cooled to room temperature, washed and dried, CeO 2 is obtained

[0013] Further, in step S11, the ultrasonication time is 30 - 60 min

[0014] Further, in step S12, the calcination time is 2 - 3 h

[0015] The washing is to wash alternately with deionized water and ethanol for 6 - 10 times;

[0016] The drying is to dry at 40 - 80 °C for 10 - 24 h.

[0017] Further, in step S2, the pH of the alkaline mixed solution is 10 - 12.

[0018] Further, in step S2, the time of the hydrothermal reaction is 24 h.

[0019] Further, in step S2, the washing is to wash alternately with deionized water and ethanol for 6 - 10 times.

[0020] Further, in step S2, the vacuum drying is to dry at 60 - 80 °C for 12 - 24 h in a vacuum environment.

[0021] In the second aspect, the present invention provides a binary composite material with high - efficiency visible - light - catalyzed formaldehyde removal obtained by the preparation method described in the first aspect above.

[0022] In the third aspect, the present invention provides an application of a binary composite material with high - efficiency visible - light - catalyzed formaldehyde removal obtained by the preparation method described in the first aspect above, characterized in that the composite material is used for the degradation of formaldehyde.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] The present invention provides a preparation method of a binary composite material with high - efficiency visible - light - catalyzed formaldehyde removal. By an in - situ one - step hydrothermal synthesis method, CeO 6 is introduced into the CaSn(OH) 2 semiconductor photocatalytic material to form a new CaSn(OH) 6 / CeO 2 binary composite photocatalytic nanomaterial. The introduction of CeO 2 causes the UV - vis of CaSn(OH) 6 to redshift, so that the CaSn(OH) 6 / CeO 2 binary composite photocatalytic nanomaterial has a wider visible - light absorption range than the single CaSn(OH) 6 semiconductor photocatalytic material. Moreover, the introduction of CeO 2 successfully realizes the separation of photo - generated electron - hole pairs of the CaSn(OH) 6 / CeO 2 binary composite photocatalytic nanomaterial at the heterojunction interface (between CaSn(OH) 6 and CeO 2 ), thus avoiding the single CaSn(OH) 6The rapid in-situ recombination of electrons and holes in the band gap of semiconductor photocatalytic materials contributes to the separation of photo-generated carriers and the narrowing of the band gap. Making CaSn(OH) 6 / CeO 2 The binary composite photocatalytic nanomaterial has a much higher degradation efficiency of formaldehyde under visible light irradiation compared to the single CaSn(OH) 6 semiconductor photocatalytic material.

[0025] Furthermore, it is experimentally demonstrated that when the dosages of CaSn(OH) 6 / CeO 2 , single CaSn(OH) 6 , and single CeO 2 are the same (all 0.2 g), and the formaldehyde content in the sewage to be treated is the same (all 1 ppm), the CaSn(OH) 6 / CeO 2 provided by the embodiment of the present invention has a formaldehyde degradation efficiency of 88.9% within 30 min, while the single CaSn(OH) 6 semiconductor photocatalytic material only has a formaldehyde degradation efficiency of 4.9% within 30 min, and the single CeO 2 photocatalytic material has a formaldehyde degradation efficiency of 39.6% within 30 min. Compared with the single CaSn(OH) 6 semiconductor photocatalytic material, the CaSn(OH) 6 / CeO 2 binary composite photocatalytic nanomaterial has a wider visible light absorption range and stronger degradation ability for formaldehyde.

[0026] In addition, the CaSn(OH) 6 / CeO 2 binary composite photocatalytic nanomaterial provided by the present invention does not show a significant decrease in the degradation rate of formaldehyde in 5 consecutive degradation experiments. After 5 cycles, the photocatalyst can still rapidly and effectively remove formaldehyde, and the degradation rate still reaches more than 85%. This indicates that the CaSn(OH) 6 / CeO 2 binary composite photocatalytic nanomaterial has good reusability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 shows the CaSn(OH) provided by the embodiment of the present invention 6 / CeO 2 Flow chart of the preparation method of the composite photocatalytic nanomaterial;

[0029] Figure 2 shows the CaSn(OH) provided by the embodiment of the present invention 6 / CeO 2 SEM image of the CaSn(OH) / CeO composite photocatalytic nanomaterial;

[0030] Figure 3 shows the ultraviolet diffuse reflectance spectrum of the photocatalytic nanomaterial provided by the embodiment of the present invention;

[0031] Figure 4 shows the CaSn(OH) provided by the embodiment of the present invention 6 / CeO 2 N 2 adsorption - desorption isotherm diagram of the composite photocatalytic nanomaterial;

[0032] Figure 5 shows the Fourier transform infrared spectrum of the photocatalytic nanomaterial provided by the embodiment of the present invention;

[0033] Figure 6 shows the performance comparison diagram of the photocatalytic degradation of formaldehyde by the photocatalytic nanomaterial provided by the embodiment of the present invention;

[0034] Figure 7 shows the CaSn(OH) provided by the embodiment of the present invention 6 / CeO 2 Stability evaluation results of the photocatalytic performance of the CaSn(OH) / CeO photocatalytic nanomaterial. Detailed implementation manners

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way restricts the present invention and its application or use. Based on the embodiments of the present invention, any product obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with those of other existing technologies that is the same as or similar to the present invention falls within the protection scope of the present invention. And all other embodiments obtained by those of ordinary skill in the art without creative work also belong to the protection scope of the present invention.

[0036] In the examples, if the specific experimental procedures or conditions are not specified, the operations or conditions of the conventional experimental procedures described in the existing technologies in this field can be followed. For the reagents and other instruments whose manufacturers are not specified, they are all conventional reagent products that can be obtained through commercial purchase. In addition, the drawings are only schematic diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings represent the same or similar parts, and thus the repeated descriptions thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0037] Technologies, methods, and devices known to those of ordinary skill in the relevant fields may not be discussed in detail, but where appropriate, the said technologies, methods, and devices should be regarded as part of the description.

[0038] In the description of the present invention, it should be understood that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Without further statement, the above terms have no special meaning, and thus should not be construed as limiting the protection scope of the present invention.

[0039] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] Before elaborating in detail on a binary composite material for highly efficient visible-light catalytic formaldehyde removal, its preparation method, and its application provided by the present invention, it is necessary to make the following explanations on the relevant technologies:

[0041] Currently, methods such as filtration, adsorption, and electrostatic dust removal are mostly used to reduce the harm of formaldehyde to the human body. These means have disadvantages such as excessive energy consumption or difficult operation. From a chemical perspective, we have better methods to solve formaldehyde pollution. The photocatalysis method has become one of the main research objects due to its advantages such as simple operation, no secondary pollution, and high efficiency. The perovskite-type hydroxide CaSn(OH) 6 has a wide bandgap (about 3.8 eV) and a structure feature of easy self-doping. Its excellent photochemical stability, non-toxicity, and appropriate energy band position make it one of the most promising photocatalytic materials for formaldehyde degradation. However, CaSn(OH) 6 The main disadvantage of semiconductor photocatalytic materials is that they only absorb in the ultraviolet region. This greatly limits the application of CaSn(OH) 6 semiconductor photocatalytic materials in formaldehyde degradation.

[0042] Broadening the light absorption range of CaSn(OH) 6 semiconductor photocatalytic materials can better promote CaSn(OH) 6Application of semiconductor photocatalytic materials in formaldehyde degradation. Therefore, the present invention hopes to form a heterojunction structure by compounding CaSn(OH) 6 semiconductor photocatalytic materials with other semiconductor materials to obtain a wider visible light absorption range and electron transfer efficiency. Through further exploration, it is found that CeO 2 has unique properties such as strong oxygen storage capacity, high catalytic activity, remarkable photothermal conversion ability, and environmental friendliness, and is considered to be one of the most promising transition metal oxide catalysts. The present invention proposes a new strategy for compounding CaSn(OH) 6 with CeO 2 to develop a photocatalytic nanocomposite with a simple preparation method, higher formaldehyde degradation rate, better stability, and reusability in an air medium. Based on this technical concept, the specific implementation content of the present invention is as follows:

[0043] First aspect, the present invention provides a preparation method for a binary composite material with high visible light catalytic efficiency for formaldehyde removal, Figure 1 which shows the flowchart of the preparation method of the CaSn(OH) 6 / CeO 2 composite photocatalytic nanomaterial provided by the embodiment of the present invention. As shown in Figure 1 the preparation method of the binary composite material includes the following preparation steps:

[0044] S1. Using Ce(NO 3 ) 3 ∙6H 2 O as the reaction raw material, CeO 2 is obtained by calcination;

[0045] S2. Mixing an alkaline mixed solution containing CaCl 2 and SnCl 4 ∙5H 2 O with a molar ratio of 1:1 with the CeO 2 , and transferring it to a stainless steel autoclave lined with polytetrafluoroethylene. Hydrothermal reaction is carried out at 180 - 200 °C. The product is centrifuged, washed, and vacuum dried to obtain the binary composite material with high visible light catalytic efficiency for formaldehyde removal - CaSn(OH) 6 / CeO 2 ; wherein, the molar ratio of the CeO 2 to the CaCl 2 is 1:1.

[0046] Specifically in implementation, the present invention first makes Ce(NO 3 ) 3 ∙6H 2 O be converted into CeO 2, further disperse the prepared CeO 2 by ultrasonic in a mixed solution containing CaCl 2 and SnCl 4 ∙5H 2 O to form a mixed system. Since the reaction between CaCl 2 and SnCl 4 ∙5H 2 O must be carried out in an alkaline environment, the pH of the mixed system can be adjusted by means of, such as, NaOH or other alkaline pH regulators. The reaction is carried out at 180 - 200 °C. During the process, when CaCl 2 and SnCl 4 ∙5H 2 O react to form CaSn(OH) 6 , CaSn(OH) 6 constantly composits with CeO 2 , and finally forms a complex CaSn(OH) 6 tightly combined with CeO 2 CaSn(OH) 6 / CeO 2 . That is, during this process, the preparation of CaSn(OH) 6 and the formation of the complex CaSn(OH) 6 / CeO 2 are carried out synchronously, effectively shortening the preparation process and reducing unnecessary raw material waste.

[0047] The present invention provides a preparation method of a binary composite material for highly efficient visible-light catalytic formaldehyde removal. By an in-situ one-step hydrothermal synthesis method, CeO 6 is introduced into the CaSn(OH) 2 semiconductor photocatalytic material to form a new CaSn(OH) 6 / CeO 2 binary composite photocatalytic nanomaterial. The introduction of CeO 2 causes the UV-vis of CaSn(OH) 6 to redshift, making the CaSn(OH) 6 / CeO 2 binary composite photocatalytic nanomaterial have a wider visible-light absorption range than the single CaSn(OH) 6 semiconductor photocatalytic material. Moreover, the introduction of CeO 2 successfully realizes the separation of photo-generated electron-hole pairs of the CaSn(OH) 6 / CeO 2 binary composite photocatalytic nanomaterial at the heterojunction interface (between CaSn(OH) 6 and CeO 2) Separation occurs, thus avoiding a single CaSn(OH) 6 The rapid in-situ recombination of electrons and holes in the bandgap of the semiconductor photocatalytic material contributes to the separation of photo-generated carriers and the narrowing of the bandgap. Making CaSn(OH) 6 / CeO 2 The degradation efficiency of the binary composite photocatalytic nanomaterial for formaldehyde under visible light irradiation is much higher than that of a single CaSn(OH) 6 semiconductor photocatalytic material.

[0048] Furthermore, the above step S1 specifically includes:

[0049] S11. Mix Ce(NO 3 ) 3 ∙6H 2 O and ethanol, perform ultrasonic treatment at room temperature, and then transfer it to an environment of 40 - 60 °C to completely volatilize the ethanol to obtain a powdery solid;

[0050] In this step, with the help of ultrasonic treatment, Ce(NO 3 ) 3 ∙6H 2 O can be better dissolved in the organic solvent ethanol. The ultrasonic treatment time can be controlled within 30 - 60 min; further, the obtained Ce(NO 3 ) 3 ethanol solution is placed in an environment of 40 - 60 °C for evaporation and drying of the ethanol solution to obtain purified Ce(NO 3 ) 3 powder without crystal water. This process can be heated by means of a microwave oven or a water bath to maintain the environmental temperature at 40 - 60 °C.

[0051] S12. Transfer the powdery solid to a muffle furnace and perform calcination treatment at 300 - 360 °C. After the product is cooled to room temperature, it is washed and dried to obtain CeO 2 .

[0052] In this step, the Ce(NO 3 ) 3 solid powder obtained in step S11 is subjected to calcination treatment to convert it into a more stable target product CeO 2 under high temperature. The calcination time is 2 - 3 h; the calcination temperature is preferably 320 °C, and the obtained product after calcination is CeO 2 . To further remove surface impurities of CeO 2 , in the present invention, before using CeO 2 , for CeO 2Washing is carried out, and the specific operation is to wash alternately with deionized water and ethanol for 6 - 10 times; after washing, drying is carried out, and drying can be carried out in air, and the specific operation is to dry at 40 - 80 °C for 10 - 24 h.

[0053] Further, in the above step S2, NaOH or other alkaline pH regulators are used to adjust the pH of the mixed system so that the pH of the mixed system is maintained at 10 - 12.

[0054] Further, in the above step S2, the hydrothermal reaction time is 24 h, and the preferred hydrothermal reaction temperature is 180 °C.

[0055] Further, in the above step S2, after centrifugally collecting the composite material - CaSn(OH) 6 / CeO 2 , further washing treatment is carried out to remove surface impurities. The washing treatment is specifically to wash alternately with deionized water and ethanol for 6 - 10 times. Finally, vacuum drying treatment is carried out to obtain the dry and clean composite material - CaSn(OH) 6 / CeO 2 , and the specific operation is: drying in a vacuum environment at 60 - 80 °C for 12 - 24 h.

[0056] In the second aspect, the present invention provides a binary composite material with high - efficiency visible - light - catalytic formaldehyde removal obtained by the preparation method described in the first aspect above.

[0057] Since CeO 2 has a relatively narrow band gap, it thus has a strong spectral absorption ability. According to the energy band structures of CeO 2 and Ag 3 PO 4 , CeO 2 and CaSn(OH) 6 can form a well - matched heterojunction structure. The present invention introduces mixed - valence CeO 6 into the CaSn(OH) 2 photocatalytic nanomaterial. Constructing a heterojunction can broaden the valence - band width on the basis of a single photocatalytic nanomaterial, promote the high - speed transfer of holes, and thus obtain a composite photocatalytic nanomaterial with high charge - transfer efficiency and photocatalytic reaction performance.

[0058] Figure 2 Figure shows the SEM image of the CaSn(OH) 6 / CeO 2 composite photocatalytic nanomaterial provided by the embodiment of the present invention. As Figure 2 shown, the CaSn(OH) 6 / CeO 2 material is a nanosheet structure.

[0059] In a third aspect, the present invention provides an application of a binary composite material with high visible-light catalytic formaldehyde removal obtained by the preparation method described in the first aspect above, characterized in that the composite material is used for the degradation of formaldehyde.

[0060] The present invention proves through experiments that, under the conditions that the dosages of CaSn(OH) 6 / CeO 2 , single CaSn(OH) 6 , and single CeO 2 are the same (all 0.2 g), and the formaldehyde content in the sewage to be treated is the same (all 1 ppm), the CaSn(OH) 6 / CeO 2 provided in the embodiment of the present invention has a formaldehyde degradation efficiency of 88.9% within 30 minutes, while the formaldehyde degradation efficiency of the single CaSn(OH) 6 semiconductor photocatalytic material is only 4.9% within 30 minutes, and the formaldehyde degradation efficiency of the single CeO 2 photocatalytic material is 39.6% within 30 minutes. Compared with the single CaSn(OH) 6 semiconductor photocatalytic material, the CaSn(OH) 6 / CeO 2 binary composite photocatalytic nanomaterial has a wider visible-light absorption range and stronger formaldehyde degradation ability.

[0061] In addition, the CaSn(OH) 6 / CeO 2 binary composite photocatalytic nanomaterial provided by the present invention does not show an obvious decrease in the formaldehyde degradation rate in 5 consecutive degradation experiments, and the photocatalyst can still quickly and effectively remove formaldehyde after 5 cycles, and the degradation rate still reaches more than 85%. This shows that the CaSn(OH) 6 / CeO 2 binary composite photocatalytic nanomaterial has good reusability.

[0062] To enable those skilled in the art to understand the present invention more clearly, the following examples are now used to elaborate in detail on a binary composite material with high visible-light catalytic formaldehyde removal, its preparation method, and its application described in the present invention.

[0063] Ce(NO 3 ) 3 ∙6H 2 O, CaCl 2 , SnCl 4 ∙5H 2O, NaOH, and ethanol were all purchased from Aladdin (Shanghai, China). All reagents were used without further purification. Deionized water was used in all experiments.

[0064] Example 1

[0065] Step 1: Dissolve 100 mg of Ce(NO 3 ) 3 ∙6H 2 O in 10 mL of ethanol. Ultrasonically treat the solution at room temperature for 60 min, and then heat it in a microwave oven for 10 min to completely volatilize the ethanol. Calcinate the powder product in a muffle furnace at a heating rate of 20 °C min −1 at 320 °C for 2 h. Finally, naturally cool the sample to room temperature, wash and dry it to obtain CeO 2 .

[0066] Step 2: Dissolve 0.4440 g (4 mmol) of CaCl 2 and 1.4024 g (4 mmol) of SnCl 4 ∙5H 2 O in 15 mL of deionized water. After adding 4.5 mol of NaOH solution and stirring for another 2 h, transfer the resulting mixture together with 0.6885 g (4 mmol) of CeO 2 to a stainless-steel autoclave lined with polytetrafluoroethylene, and carry out a hydrothermal reaction at 180 °C for 24 h. Centrifuge to collect the solid precipitate, wash it several times, and dry it under vacuum to obtain CaSn(OH) 6 / CeO 2 .

[0067] Example 2

[0068] Dissolve 100 mg of Ce(NO 3 ) 3 ∙6H 2 O in 10 mL of ethanol. Ultrasonically treat the solution at room temperature for 60 min, and then heat it in a microwave oven for 10 min to completely volatilize the ethanol. Calcinate the powder product in a muffle furnace at a heating rate of 20 °C min −1 at 320 °C for 2 h. Finally, naturally cool the sample to room temperature, wash and dry it to obtain CeO 2 .

[0069] Example 3

[0070] Dissolve 0.4440 g of CaCl 2 and 1.4024 g of SnCl 4 ∙5H 2O was dissolved in 15 mL of deionized water. After adding 4.5 mol of NaOH solution and stirring for another 2 h, the resulting mixture was transferred to a stainless-steel autoclave lined with polytetrafluoroethylene and hydrothermally reacted at 180 °C for 24 h. The solid precipitate was collected by centrifugation, washed repeatedly, and dried in vacuum to obtain CaSn(OH) 6 .

[0071] Figure 2 Figure shows the SEM image of the CaSn(OH) 6 / CeO 2 composite photocatalytic nanomaterial provided by the embodiment of the present invention; as Figure 2 shown, the CaSn(OH) 6 / CeO 2 material has a nanosheet structure.

[0072] Figure 3 Figure shows the ultraviolet diffuse reflectance spectrum of the photocatalytic nanomaterial provided by the embodiment of the present invention, as Figure 3 shown, due to the introduction of CeO 2 , the light absorption edge of the CaSn(OH) 6 / CeO 2 composite photocatalytic nanomaterial is significantly extended to the entire visible spectrum, indicating that the CaSn(OH) 6 / CeO 2 composite photocatalyst can utilize more visible light.

[0073] Figure 4 Figure shows the N 6 / CeO 2 adsorption-desorption isotherm diagram of the CaSn(OH) 2 composite photocatalytic nanomaterial provided by the embodiment of the present invention, as Figure 4 shown, the specific surface area of the CaSn(OH) 6 / CeO 2 composite photocatalytic nanomaterial is 26.9 m 2 / g, indicating a weak adsorption performance for formaldehyde, mainly due to the degradation of formaldehyde by the persistent free radicals generated by photocatalysis.

[0074] Figure 5 Figure shows the Fourier transform infrared spectrum of the photocatalytic nanomaterial provided by the embodiment of the present invention; as Figure 5 shown, FTIR shows that the CeO 2 nanoparticles are located in the infrared bands of 555 cm −1 , 1023 cm −1 , 1415 cm −1 and 1547 cm −1 . Located at 555 cm −1The strong IR band is due to the stretching vibration of metal-oxygen (Ce-O), confirming the formation of CeO bonds in CeO 2 The absorption band at 1547 cm −1 is due to the bending vibration of O-H, which is caused by the adsorption of moisture on the surface of CeO 2 nanoparticles. The FTIR spectrum of CaSn(OH) 6 shows a broad absorption peak at 3303 cm -1 attributed to the O-H stretching vibration, and absorption bands at 1596 cm -1 and 1396 cm -1 due to carbonyl groups, and an absorption band at 1097 cm -1 due to Sn-O and Sn-OH vibrations. It can be seen that the main typical absorption peaks of CaSn(OH) 6 and CeO 2 are all present in the CaSn(OH) 6 / CeO 2 sample, which further indicates the successful synthesis of the CaSn(OH) 6 / CeO 2 composite photocatalytic nanomaterial.

[0075] Experimental Example 1

[0076] This experimental example is used to verify the degradation performance of the CaSn(OH) 6 / CeO 2 composite photocatalytic nanomaterial prepared in Example 1 for formaldehyde.

[0077] Photocatalytic activity evaluation:

[0078] The catalytic activity of the catalyst is measured by the removal rate of formaldehyde under a closed system and visible light irradiation. In all tests, 200 mg of the CaSn(OH) 6 / CeO 2 composite photocatalytic nanomaterial was placed in a glass petri dish, which was placed at the bottom of a reactor with a volume of approximately 216 L (60 × 60 × 60 cm 3 ). A formaldehyde release source (38% formaldehyde solution) was introduced into the reactor. The concentration of gaseous formaldehyde in the reactor was 1 PPM. The reactor was finally sealed with a glass plate to make it a closed system. The photocatalytic degradation reaction of formaldehyde occurred at 25°C. A 350 W xenon lamp was placed vertically outside the photoreactor, and an ultraviolet cut-off filter (420 nm) was used to remove ultraviolet light. A 5 W fan was placed at the bottom of the reactor, and the reaction was terminated when the concentration of gaseous formaldehyde remained unchanged within half an hour. The removal rate of formaldehyde (Y) was calculated as Y (%) = (1 - C / C 0 ) × 100%, where C and C 0The concentrations of formaldehyde at 0 and t min respectively.

[0079] Continuous degradation experiment:

[0080] After the first degradation reaction was completed, the petri dish containing the photocatalyst was dried at 60 °C for 0.5 h, and then put into the reactor again for the next formaldehyde removal reaction. Except for the material, the remaining reaction conditions were the same as those in the first time; after the second reaction was completed, the above steps were repeated for the third degradation experiment. A total of five degradation experiments were carried out.

[0081] The experimental results showed that: under the conditions of visible light (λ>400 nm) with 2 standard sunlight intensities, a catalyst dosage of 0.2 g, an initial formaldehyde concentration of 1 ppm, and an initial temperature of room temperature, CaSn(OH) 6 / CeO 2 The photocatalytic nanomaterial had a formaldehyde degradation efficiency as high as 88.9% after 30 min. In each repeated cycle, there was no obvious loss in the formaldehyde elimination rate, indicating that the catalyst had high durability.

[0082] Figure 6 The performance comparison diagram of the photocatalytic degradation of formaldehyde by the photocatalytic nanomaterial provided in the embodiment of the present invention is shown. As Figure 6 shown, the CeO 2 semiconductor catalytic material provided in Example 2 had a formaldehyde degradation efficiency of 39.6% within 30 min, and the CaSn(OH) 6 semiconductor catalytic material provided in Example 3 had a formaldehyde degradation efficiency of only 4.9% within 30 min. This was because the absorbance of the single CaSn(OH) 6 and CeO 2 semiconductor catalytic materials was limited, and the high recombination rate of photo-generated electron-hole pairs led to poor formaldehyde degradation efficiency. While the CaSn(OH) 6 / CeO 2 composite photocatalytic nanomaterial provided in Example 1 had a formaldehyde degradation efficiency of 88.9% within 30 min. This was because the introduction of CeO 6 in CaSn(OH) 2 broadened the visible light absorption range of the CaSn(OH) 6 photocatalytic nanomaterial, and contributed to the separation of photo-generated carriers and the narrowing of the band gap.

[0083] Figure 7 The stability evaluation results of the photocatalytic performance of the CaSn(OH) 6 / CeO 2 photocatalytic nanomaterial provided in the embodiment of the present invention are shown, as Figure 7As shown, in each repeated cycle, there is no obvious loss in the elimination rate of formaldehyde, and the degradation rate still reaches over 85% after 5 cycles, indicating that the catalyst has high reusability.

[0084] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0085] For method embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present invention is not limited by the described action sequence, because according to the present invention, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0086] The above has introduced in detail a binary composite material for highly efficient removal of formaldehyde by visible light catalysis, its preparation method and application provided by the present invention. Specific examples are used herein to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. Preparation method of a binary composite material for highly efficient removal of formaldehyde by visible light catalysis, characterized in that, the preparation method of the binary composite material comprises the following preparation steps: S1. Using Ce(NO 3 ), 3 ∙6H 2 O as the reaction raw material, CeO 2 is obtained by calcination. The steps specifically include: S11. Mix Ce(NO 3 ), 3 ∙6H 2 O with ethanol, sonicate at room temperature, and then transfer to an environment of 40 - 60 °C to completely evaporate the ethanol to obtain a powdery solid; S12. Transfer the powdery solid to a muffle furnace, conduct a calcination treatment at 300 - 360 °C, cool the product to room temperature, and after washing and drying, obtain CeO 2 ; S2. Mix an alkaline mixed solution containing CaCl and SnCl∙5H₂O with a molar ratio of 1:1 with the CeO₂, and transfer it to a stainless-steel autoclave lined with polytetrafluoroethylene. Carry out a hydrothermal reaction at 180 - 200 °C. The product is centrifuged, washed, and vacuum dried to obtain the binary composite material for highly efficient visible-light catalytic formaldehyde removal, CaSn(OH)₆ / CeO₂; among them, the molar ratio of the CeO₂ to the CaCl₂ is 1:

1. 2 and SnCl 4 ∙5H 2 O with the CeO 2 and transfer to a stainless steel autoclave lined with polytetrafluoroethylene, carry out hydrothermal reaction at 180 - 200 °C, the product is centrifuged, washed, vacuum dried to obtain the binary composite for highly efficient visible light catalytic formaldehyde removal - CaSn(OH) 6 / CeO 2 ; wherein, the molar ratio of the CeO 2 to the CaCl 2 is 1:

1.

2. The preparation method of the binary composite material for highly efficient removal of formaldehyde by visible light catalysis according to claim 1, characterized in that, in step S11, the time of the ultrasonic treatment is 30 - 60 min.

3. The preparation method of the binary composite material for highly efficient removal of formaldehyde by visible light catalysis according to claim 1, characterized in that, in step S12, the time of the calcination is 2 - 3 h; the washing is carried out by alternately washing with deionized water and ethanol for 6 - 10 times; the drying is carried out at 40 - 80 °C for 10 - 24 h.

4. The preparation method of the binary composite material for highly efficient removal of formaldehyde by visible light catalysis according to claim 1, characterized in that, in step S2, the pH of the alkaline mixed solution is 10 - 12.

5. The preparation method of the binary composite material for highly efficient removal of formaldehyde by visible light catalysis according to claim 1, characterized in that, in step S2, the time of the hydrothermal reaction is 24 h.

6. The preparation method of the binary composite material for highly efficient removal of formaldehyde by visible light catalysis according to claim 1, characterized in that, in step S2, the washing is carried out by alternately washing with deionized water and ethanol for 6 - 10 times.

7. The preparation method of the binary composite material for highly efficient removal of formaldehyde by visible light catalysis according to claim 1, characterized in that, in step S2, the vacuum drying is carried out at 60 - 80 °C for 12 - 24 h in a vacuum environment.

8. A binary composite material for highly efficient removal of formaldehyde by visible light catalysis obtained by the preparation method according to any one of claims 1 - 7.

9. Application of a binary composite material for highly efficient removal of formaldehyde by visible light catalysis obtained by the preparation method according to any one of claims 1 - 7, characterized in that, the composite material is used for the degradation of formaldehyde.

Images