Formaldehyde purifying agent as well as preparation method and application thereof

Abstract

The invention discloses a formaldehyde purifying agent as well as a preparation method and application thereof, and relates to the technical field of air purification. The formaldehyde purifying agent comprises a carrier and delta-MnO2-Ce loaded on the surface of the carrier, the carrier is of a honeycomb structure, and the doping ratio of Ce to Mn is set. The preparation method of the formaldehyde purifying agent provided by the invention is simple and convenient to operate, low in input cost, low in energy consumption in the preparation process and few in by-products; the prepared formaldehyde purifying agent has high selective catalytic efficiency on formaldehyde, has stable purifying efficiency under the conditions of low concentration and long-time operation, is suitable for treating an indoor environment in which formaldehyde is released for a long time and low in concentration, and is expected to be popularized and applied.

Description

Technical Field

[0001] This invention relates to the field of air purification technology, and more specifically, to a formaldehyde purifier, its preparation method, and its application. Background Technology

[0002] With increasing attention being paid to indoor air pollution, formaldehyde (HCHO), a common harmful volatile organic compound in the air, poses a serious threat to human health. Especially in newly renovated buildings or homes, formaldehyde is continuously released from building materials, furniture, paints, and other materials. Long-term exposure to low concentrations can cause various respiratory diseases and even cancer. Therefore, developing efficient and stable formaldehyde purification technologies has become one of the key research directions in environmental functional materials.

[0003] Among numerous air purification materials, manganese dioxide (MnO2) has been widely used in the catalytic degradation of formaldehyde due to its rich crystalline structures, excellent redox properties, and environmentally friendly characteristics. Different crystalline forms of MnO2 (such as α-, β-, γ-, and δ-type) exhibit different catalytic activities and specific surface area characteristics due to differences in their crystal structures, especially δ-MnO2 with its layered or tunnel-like structures.

[0004] Further research shows that metal ion doping can effectively control the electronic structure, oxygen vacancy concentration, and surface reactivity of MnO2. For example, introducing rare earth metal cerium (Ce) with variable valence states, especially trivalent cerium ions (Ce), into δ-MnO2 can effectively control these valence states. 3+ ), can be due to its interaction with tetravalent manganese ions (Mn 4+ The difference in ionic radii between the atoms induces lattice distortion, resulting in a local strain effect. This structural modulation not only helps stabilize the formation of the hydrated manganese oxide-type layered structure, but also promotes the growth of the material in the form of nanospheres, thereby further increasing its specific surface area and surface active site density, enhancing the redox cycle performance of the material, and facilitating the adsorption activation and deep oxidation of formaldehyde molecules at low temperatures. Under laboratory conditions, it exhibits excellent formaldehyde removal potential.

[0005] However, in practical applications, especially in indoor environments where formaldehyde is released over a long period and at low concentrations, existing air purification devices generally rely on traditional activated carbon adsorption or composite catalyst modules, lacking dedicated purification systems designed specifically for such high-performance catalytic materials. Existing formaldehyde purification technologies primarily target high-concentration pollutant environments, employing methods requiring external energy input, such as thermocatalysis or photocatalysis. Furthermore, commercially available air purifiers often focus on particulate filtration or broad-spectrum pollutant removal, resulting in high energy consumption and numerous byproducts. Current technologies also exhibit insufficient selective catalytic efficiency for specific pollutants like formaldehyde, and their purification stability is limited under low-concentration, long-term operating conditions.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a formaldehyde purifier, its preparation method, and its application, so as to solve or improve the above-mentioned technical problems.

[0008] This invention is implemented as follows: In a first aspect, the present invention provides a formaldehyde purifier, the formaldehyde purifier comprising a carrier and δ-MnO2-Ce loaded on the surface of the carrier; The carrier has a honeycomb structure, and the doping ratio of Ce to Mn in δ-MnO2-Ce is 1:20-1:10.

[0009] Secondly, the present invention provides a method for preparing a formaldehyde purifier as described in any of the foregoing embodiments, comprising the following steps: Mix the dissolved manganese source, cerium source and regulator in proportion, react at 85℃-100℃ for 2h-8h and then let stand. After the settling process is completed, the precipitate is collected and dried at a temperature of 100℃-120℃. The redissolved precipitate solution is coated onto the surface of the pretreated carrier to obtain a formaldehyde purifier.

[0010] Thirdly, the present invention provides a purifier comprising a formaldehyde purifier as described in any of the foregoing embodiments or a formaldehyde purifier prepared by any of the foregoing embodiments.

[0011] The present invention has the following beneficial effects: The method for preparing the formaldehyde purifier provided in this invention is simple to operate, has low input cost, and produces few byproducts during the preparation process. The obtained formaldehyde purifier has high selective catalytic efficiency for formaldehyde and has stable purification efficiency under low concentration and long-term operation conditions. It is suitable for treating indoor environments with long-term release and low concentration of formaldehyde and is expected to be widely used. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 For honeycomb structure carriers: the left image is a low magnification, and the right image is a high magnification; Figure 2Molecular sieve support: the left image shows low magnification, and the right image shows high magnification; Figure 3 Activated carbon carrier: the left image shows a low magnification, and the right image shows a high magnification; Figure 4 XRD analysis results of formaldehyde purifiers prepared with different Ce and Mn doping ratios are shown. (a)-(b) Ce to Mn doping ratio is 1:10, (c)-(d) Ce to Mn doping ratio is 1:15, and (e)-(f) Ce to Mn doping ratio is 1:20. (b), (d) and (f) are the fine XRD scan spectra measured at the corresponding doping ratios. Figure 5 The XRD analysis results of formaldehyde purifiers prepared at different reaction times are shown, including (a) 2h, (b) 4h, (c) 6h, (d) 8h, (e) 10h, and (f) 2h-10h. Figure 6 XPS analysis results for Ce and Mn doping ratio of 1:13: (a) full spectrum, (b) O 1s, (c) Mn 2p, (d) Ce 3d; Figure 7 XPS analysis results for Ce and Mn doping ratio of 1:15: (a) full spectrum, (b) O 1s, (c) Mn 2p, (d) Ce 3d. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0015] MnO2 materials themselves already have a certain purification effect on HCHO, but doping with different crystal forms and different interlayer ions will significantly affect its performance. Ce-doped sodium manganese hydrate (δ-MnO2) has superior formaldehyde catalytic activity. δ-MnO2 has a unique tunnel-like crystal structure and high specific surface area, exhibiting excellent adsorption performance and high selectivity for formaldehyde molecules. It can effectively capture and decompose formaldehyde molecules through the synergistic effect of physical adsorption and chemical reaction.

[0016] The typical layered structure of sphagnum molybdenum is a two-dimensional layered structure formed by shared edges of [MnO6] octahedra. Cerium ions (Ce) 3+ The incorporation of ) is due to its interaction with manganese ions (Mn 4+The difference in ionic radius can cause significant lattice distortion. This lattice strain can effectively induce and stabilize the formation of hydrated manganese oxide-type structures and regulate their growth into smaller microsphere structures, thereby significantly increasing the specific surface area.

[0017] In a first aspect, the present invention provides a formaldehyde purifier, the formaldehyde purifier comprising a carrier and δ-MnO2-Ce loaded on the surface of the carrier; The carrier has a honeycomb structure, and the doping ratio of Ce to Mn in δ-MnO2-Ce is 1:20-1:10.

[0018] The formaldehyde purifier provided in this invention has high selective catalytic efficiency for formaldehyde and stable purification efficiency under low concentration and long-term operation conditions, making it suitable for treating indoor environments with long-term release and low concentration of formaldehyde.

[0019] In an optional embodiment, the doping ratio of Ce to Mn in δ-MnO2-Ce is 1:17 to 1:13; Preferably, the manganese source is selected from at least one of potassium permanganate, manganese sulfate, manganese nitrate and manganese chloride; the cerium source is selected from at least one of cerium nitrate hexahydrate, cerium chloride, cerium sulfate and cerium ammonium nitrate.

[0020] It should be noted that the Ce to Mn doping ratio refers to the molar ratio of doping. If the Ce doping amount is too low, the material is closer to pure δ-MnO2, resulting in a limited number of oxygen vacancies and inherent defects. The material exhibits poor structural stability under long-term cycling or harsh reaction conditions, and its performance improvement is limited, approaching that of pure manganese dioxide. Surface properties are difficult to effectively control, and its adsorption and activation capabilities for specific reactants such as formaldehyde are not ideal. If the doping amount is too high, excess cerium may cover the manganese dioxide surface in the form of cerium oxide (CeO2) aggregates, blocking its pores and leading to a decrease in specific surface area. At the same time, excessively dense doping points may disrupt the continuity of the manganese-oxygen framework, hindering electron transport and resulting in a decrease in catalytic activity.

[0021] For example, the doping ratio of Ce to Mn in δ-MnO2-Ce can be selected from any one of 1:17, 1:16, 1:15, 1:14 and 1:13, or other values ​​in the range of 1:17 to 1:13.

[0022] In an optional embodiment, when the carrier is a honeycomb structure, its material includes aluminum and the pore size is 1mm-5mm.

[0023] Furthermore, the carrier is made of highly ductile aluminum and has a honeycomb structure. The honeycomb structure carrier has the following characteristics: low porosity, thin and light material, large surface area, and strong plasticity. It provides more uniform attachment sites for MnO2, significantly increases the loading capacity, and can reduce air resistance, enhance catalytic and adsorption capacity, and improve durability and renewability while ensuring high-efficiency filtration.

[0024] If conventional molecular sieves or activated carbon are used as carriers, the following drawbacks exist: although activated carbon has abundant pores, some micropores may cause MnO2 particles to agglomerate due to pore size limitations, affecting the uniformity of loading; molecular sieves have a weak physical adsorption capacity for MnO2 nanoparticles due to their uniform pore size and small size, resulting in the lowest loading capacity.

[0025] If the pore size of the support is too small, its dense pores result in a very large surface area per unit volume for coating or loading substances, providing a massive number of active sites, which is beneficial for improving the catalytic reaction rate and conversion efficiency, especially crucial for rapid reactions. However, these tiny pores are easily clogged, making the molding, sintering, or processing of fine structures more difficult and costly. If the pore size is too large, there are fewer catalytic reaction sites per unit volume, resulting in lower overall catalytic activity. To achieve a certain conversion rate, a larger volume of support is required, leading to lower mass transfer efficiency and a correspondingly larger required equipment volume.

[0026] Secondly, the present invention provides a method for preparing a formaldehyde purifier as described in any of the foregoing embodiments, comprising the following steps: Mix the dissolved manganese source, cerium source and regulator in proportion, react at 85℃-100℃ for 2h-8h and then let stand. After the settling process is completed, the precipitate is collected and dried at a temperature of 100℃-120℃. The redissolved precipitate solution is coated onto the surface of the pretreated carrier to obtain a formaldehyde purifier.

[0027] In an optional embodiment, the redissolved precipitate solution comprises SiO2, TiO2, δ-MnO2-Ce and deionized water in a mass ratio of (0.5-1.0):(0.8-1.4):(1.7-2.2):(1.2-1.6); Preferably, the mass ratio of SiO2, TiO2, δ-MnO2-Ce and deionized water is (0.5-0.7):(0.8-1.2):(1.8-2.0):(1.4-1.6).

[0028] The redissolved precipitate solution contains both SiO2 and TiO2. TiO2, under light excitation, can completely decompose organic compounds such as formaldehyde into harmless substances. While SiO2 itself does not decompose formaldehyde, its extremely high specific surface area and abundant porous structure allow it to rapidly and massively adsorb formaldehyde molecules from the air, capturing and concentrating them on its surface and within its pores, providing a high-concentration reaction environment for subsequent catalytic decomposition. When SiO2 and TiO2 are used together, the formaldehyde molecules adsorbed by SiO2 are delivered to the active sites on the TiO2 surface, achieving a synergistic process of "adsorption-enrichment-catalytic decomposition," significantly improving overall purification efficiency. Furthermore, the combined use of SiO2 and TiO2 provides a stable skeletal structure for the product, enhancing its mechanical strength and durability.

[0029] In the optimal implementation, the mass ratio of SiO2, TiO2, δ-MnO2-Ce and deionized water is 0.5:1:2:1.5.

[0030] In an optional embodiment, the manganese source and the cerium source are mixed in proportion and then dissolved, and the resulting solution is denoted as solution A; The dissolved regulator solution is denoted as solution B; Solutions A and B were heated to 85℃-100℃ respectively, then mixed and reacted for 2-5 hours before being allowed to stand. Controlling the reaction time provides the necessary conditions for the formation of the layered structure of naphthoore, the intercalation of cerium ions between layers, and the generation of crystal defects (such as oxygen vacancies). The reaction temperature was controlled at 85℃-100℃. Increasing the temperature accelerates the formation rate of naphthoore, but excessively high temperatures will cause the product to transform into manganese oxides or other stable phases, thus reducing the yield.

[0031] Dissolving the raw materials separately, heating them to the reaction temperature separately, and then mixing them together for reaction helps to ensure that the raw materials dissolve completely and the reaction is more thorough.

[0032] Water is used as the solvent in the preparation of solutions A and B. The type of water can be deionized water, purified water, mineral water, or ultrapure water, depending on the requirements. The dissolution time is 1.5-3 hours, respectively, to ensure thorough dissolution. Stirring is performed during the dissolution process to accelerate the process.

[0033] Preferably, the regulator is ammonium oxalate; the mass ratio of the regulator to the manganese source is (4-6):(7-10).

[0034] Furthermore, the mass ratio of the regulator to the manganese source is 5:8.

[0035] The addition of ammonium oxalate has the following characteristics: (1) Complexing cerium ions to improve doping uniformity: oxalate ions (C2O4) 2- ) can be with (Ce3+ / Ce 4+ It forms stable soluble complexes (such as [Ce(C2O4)3]). 3- In the initial stage of the reaction, this complexation prevents cerium ions from locally agglomerating or segregating due to changes in system pH or excessively rapid reaction with the manganese source, allowing cerium ions to be uniformly dispersed in the solution in a complexed state. As the reaction proceeds (e.g., due to temperature increases or pH adjustments), the complex slowly dissociates, and cerium ions gradually and uniformly enter the lattice or interlayer of the naphthoic ore, significantly improving the uniformity of doping and avoiding localized cerium enrichment.

[0036] (2) Regulating precursor morphology and refining grain size: Ammonium oxalate can be used as a soft template and morphology regulator. On the one hand, oxalate can form complex oxalate precursors (such as MnC2O4 and Ce2(C2O4)3) with manganese ions and cerium ions. These precursors decompose during subsequent hydrothermal or calcination processes, which guides the growth of sodium manganese ore grains along specific crystal planes, inhibits excessive grain growth, and ultimately yields products with smaller particle size and larger specific surface area. On the other hand, the gases (CO2 and NH3) produced by the decomposition of ammonium oxalate can form pores on the grain surface, optimize the pore structure of the material, and improve its adsorption or catalytic performance.

[0037] (3) Mildly adjust the redox potential of the system: Oxalate has a certain reducing property and can react with high-valent manganese (such as Mn) in the reaction system. 7+ Mn 4+ A mild redox reaction occurs, slowly reducing some of the high-valence manganese to Mn. 3+ / Mn 2+ This process regulates the valence distribution of manganese in sucralose. Simultaneously, this mild reduction does not disrupt the layered crystal structure of sucralose, avoiding crystal collapse caused by strong reducing agents. For cerium ions, the oxalate complexation also stabilizes Ce. 3+ The valence state is reduced, thus reducing its oxidation to Ce. 4+ The proportion.

[0038] In an optional implementation, the pretreatment of the carrier includes the following steps: Use an alkaline solution to remove oil and oxides from the carrier surface, wash with water until neutral, and then dry. The alkaline solution is selected from sodium hydroxide solution or potassium hydroxide solution; the concentration of the alkaline solution should not be too high to avoid dissolving the effective component aluminum in the carrier. In an optional embodiment, the mass concentration of the alkaline solution is 10%. In other embodiments of the present invention, the concentration of the alkaline solution is reasonably prepared according to actual needs.

[0039] Preferably, when cleaning with an alkaline solution, the carrier is immersed in the alkaline solution for 5-30 minutes to ensure thorough removal of oil and oxide layers from the carrier surface. Rinse with water until neutral to avoid further corrosion of the carrier by residual alkaline solution.

[0040] Preferably, the drying temperature is 220℃-300℃ and the time is 1.5h-3h.

[0041] In an optional implementation, the settling time is 0.5h-1h; And / or, the drying time for the precipitate is 1h-2.5h; And / or, after coating the carrier surface with the redissolved precipitate solution, it is also necessary to perform air drying and baking treatment; wherein the baking treatment is performed at a temperature of 120℃-180℃ for a time of 0.8h-1.5h.

[0042] In other embodiments of the present invention, a vacuum-assisted immersion treatment can also be used, in which the carrier is immersed in the redissolved precipitate solution with the assistance of vacuum, to ensure that the redissolved precipitate solution is in full contact with the carrier and fully penetrates into the pores of the carrier.

[0043] In summary, the preparation method of the formaldehyde purifier provided in this embodiment of the invention specifically includes the following steps: (1) Preparation of solution A After mixing manganese source, cerium source and water in proportion, stir for 1.5h-3h until completely dissolved, and the resulting solution is denoted as solution A; wherein, the doping ratio of Ce to Mn is 1:17-1:13; the manganese source is selected from at least one of potassium permanganate, manganese sulfate, manganese nitrate and manganese chloride; the cerium source is selected from at least one of cerium nitrate hexahydrate, cerium chloride, cerium sulfate and cerium ammonium nitrate.

[0044] (2) Preparation of solution B Add the regulator to water and stir for 1.5-3 hours until completely dissolved. The resulting solution is denoted as solution B. The mass ratio of the regulator to the manganese source is 5:8. The regulator is ammonium oxalate.

[0045] (3) Preparation of δ-MnO2-Ce The solution A obtained in step (1) and the solution B obtained in step (2) are heated to 85℃-100℃ respectively, mixed, reacted for 2h-5h and then allowed to stand; after standing for 0.5h-1h, the supernatant is discarded, the precipitate is collected, and dried at 100℃-120℃ for 1h-2.5h to obtain δ-MnO2-Ce.

[0046] (4) Preparation of formaldehyde purifier The redissolved precipitate solution is coated onto the surface of the pretreated carrier to obtain a formaldehyde purifier.

[0047] The redissolved precipitate solution includes SiO2, TiO2, δ-MnO2-Ce obtained in step (3), and deionized water in a mass ratio of 0.5:1:2:1.5.

[0048] The pretreatment of the carrier includes the following steps: after cutting the carrier to the required specifications, soak it in an alkaline solution with a mass concentration of 0.7‰-1‰ for 25min-30min to remove oil and oxides from the surface of the carrier, wash it with water until neutral, and then dry it at a temperature of 220℃-300℃ for 1.5h-3h.

[0049] After coating the carrier surface with the redissolved precipitate solution, it is necessary to perform air drying and oven drying. Air drying can be done by air drying or drying in an oven at a low temperature (such as 20℃-30℃). The oven drying temperature is 120℃-180℃ and the drying time is 0.8h-1.5h. After the oven drying is completed, it is cooled to room temperature to obtain the formaldehyde purifier.

[0050] Thirdly, the present invention provides a purifier comprising a formaldehyde purifier as described in any of the foregoing embodiments or a formaldehyde purifier prepared by any of the foregoing embodiments.

[0051] In an optional implementation, when the purifier purifies formaldehyde, the initial concentration of formaldehyde is ≤0.70ppm and the purification efficiency is ≥88.46%.

[0052] In an optional implementation, the initial concentration of formaldehyde is 0.65ppm-0.70ppm, and the formaldehyde purification efficiency is ≥88.46%.

[0053] In an optional implementation, the test conditions for formaldehyde purification efficiency are: room temperature (23±2)℃, relative humidity (65±10)%, purification treatment time of 60 min; the test chamber is 3 m³ in volume and is free from external airflow, strong sunlight, and other radiation. 3 .

[0054] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0055] Example 1 This embodiment provides a formaldehyde purifier, the preparation of which includes the following steps: (1) Preparation of solution A After mixing manganese source, cerium source and water in proportion, stir for 2 hours until completely dissolved, and the resulting solution is denoted as solution A; wherein, the doping ratio of Ce to Mn is 1:15; the manganese source is potassium permanganate with a mass of 100 g; and the cerium source is cerium nitrate hexahydrate with a mass of 18.3 g.

[0056] (2) Preparation of solution B Add the regulator to water and stir for 2 hours until completely dissolved. The resulting solution is denoted as solution B. The mass of the regulator is 160 g. The regulator is ammonium oxalate.

[0057] (3) Preparation of δ-MnO2-Ce The solution A obtained in step (1) and the solution B obtained in step (2) were heated to 95°C and then mixed. After reacting for 4 hours, the mixture was allowed to stand. After standing for 1 hour, the supernatant was discarded, the precipitate was collected, and the mixture was dried at 100°C for 2 hours to obtain δ-MnO2-Ce.

[0058] (4) Preparation of formaldehyde purifier The redissolved precipitate solution is coated onto the surface of the pretreated carrier to obtain a formaldehyde purifier.

[0059] The redissolved precipitate solution includes SiO2, TiO2, δ-MnO2-Ce obtained in step (3), and deionized water in a mass ratio of 0.5:1:2:1.5.

[0060] The pretreatment of the carrier includes the following steps: immersing the carrier in a 0.8‰ sodium hydroxide solution for 25 minutes to remove oil and oxides from the carrier surface; rinsing with water until neutral; and then drying at 260℃ for 2 hours. The carrier is made of honeycomb aluminum with a pore size of 3 mm.

[0061] Experimental Example 1 This experimental example is used to investigate the effect of the Ce to Mn doping ratio on the performance of the final product. The steps for preparing the formaldehyde purifier are the same as in Example 1, with the only difference being: (1) Preparation of solution A The Ce to Mn doping ratios are 1:10, 1:13, 1:15 and 1:20.

[0062] The relevant parameters and performance results are summarized in Table 1. The test conditions for formaldehyde purification efficiency were: room temperature (23±2)℃, relative humidity (65±10)%, purification time 60 min; the test was conducted in an experimental chamber with no external airflow, strong sunlight, or other radiation, and the chamber volume was 3 m³. 3 .

[0063] Table 1. Effect of Ce to Mn doping ratio on the performance of the final product

[0064] As shown in Table 1, when the Ce to Mn doping ratio is 1:10 and 1:20, the formaldehyde purification efficiency of the purifier decreases slightly after seven days. However, the purification efficiency of the purifier with a Ce to Mn doping ratio of 1:15 remains essentially unchanged after seven days. The reason for this is that a Ce to Mn doping ratio of 1:15 ensures that Mn... 4+ / Mn 3+ With Ce 4+ / Ce 3+ Highly efficient redox couple cooperation, Mn 4+ Formaldehyde is oxidized to Mn 3+ Ce 4+ Rapidly oxidize and regenerate it into Mn 4+ It reverts to Ce 3+ ; gas phase oxygen then Ce 3+ Oxidized to Ce 4+ This allows for continuous catalytic cycling while maintaining stable catalytic performance.

[0065] Experimental Example 2 This experimental example investigates the effect of different reaction times of solutions A and B on the performance of the final product. The steps for preparing the formaldehyde purifier are the same as in Example 1, with the only difference being: (1) Preparation of solution A The doping ratio of Ce to Mn is 1:20.

[0066] (3) Preparation of δ-MnO2-Ce The solutions A obtained in step (1) and B obtained in step (2) were heated to 95°C and then mixed. The reaction times were 2h, 4h, 6h, 8h and 10h, respectively, and then allowed to stand.

[0067] Experimental Example 3 This experimental example is used to investigate the impact of different types of carriers on the final performance of the product. The steps for preparing the formaldehyde purifier are the same as in Example 1, with the only difference being: (4) Preparation of formaldehyde purifier The carriers consist of a honeycomb structure (pore size of 3 mm), molecular sieves, and activated carbon.

[0068] Test Example 1 This test example analyzes the morphology of formaldehyde purifiers prepared from different types of carriers in Experiment 3. Relevant images are shown below. Figures 1-3 ,in, Figure 1 It is a honeycomb structure carrier: the left image is a small magnification, and the right image is a large magnification; Figure 2 Molecular sieve support: the left image shows low magnification, and the right image shows high magnification; Figure 3 Activated carbon carrier: the left image shows a low magnification, and the right image shows a high magnification.

[0069] Combination Figures 1-3 Morphology analysis results show that all three supports exhibit a nanospherical structure. Among them, the aluminum honeycomb support, due to its higher specific surface area, provides more uniform adhesion sites for MnO2, resulting in a significantly higher loading capacity than other materials. Molecular sieves, with their uniform and small pore size, have a weaker physical adsorption capacity for MnO2 nanoparticles, which affects the loading capacity. Although activated carbon has abundant pores, some micropores may cause MnO2 particle agglomeration due to pore size limitations, affecting the uniformity of the loading.

[0070] Test Example 2 This test example performs XRD analysis on formaldehyde purifiers prepared with different Ce and Mn doping ratios from Experiment 1. Doping ratios of 1:10, 1:15, and 1:20 are used as examples. The analysis results are shown below. Figure 4 In (a)-(b), the Ce to Mn doping ratio is 1:10, in (c)-(d), the Ce to Mn doping ratio is 1:15, and in (e)-(f), the Ce to Mn doping ratio is 1:20; (b), (d), and (f) are the fine XRD scan spectra measured at the corresponding doping ratios.

[0071] from Figure 4 As can be seen, the fine XRD pattern was used to verify whether cerium was completely encapsulated within the manganese dioxide lattice, with a scanning range of 20° to 35°; from Figure 4 It can be seen that when the Ce to Mn doping ratio is 1:10, the XRD pattern shows a CeO2 characteristic peak (111), proving that Ce cannot be completely encapsulated in the manganese dioxide lattice at this doping level. When the Ce to Mn doping ratio is 1:15 and 1:20, no CeO2 characteristic peak appears, proving that Ce is completely encapsulated in the manganese dioxide lattice, and the optimal Ce doping level should be 15:1.

[0072] This test also used XRD to monitor the crystal form of the product at each reaction time point in Experimental Example 2. The optimal reaction time was determined by XRD patterns. The test results are shown in [Figure 1]. Figure 5 .

[0073] from Figure 5 The results show that after a reaction time of 4 h, the three characteristic diffraction peaks of 2θ at 12.5°, 36.5°, and 65.6° in the spectrum are attributed to the characteristic diffraction peaks of the hexagonal naphthoic mineral material, corresponding to the (001), (100), and (110) crystal planes of naphthoic mineral, respectively. Furthermore, the characteristic peaks in the spectrum remained essentially unchanged after 4 h of reaction, confirming that the reaction only needs to proceed for 4 h.

[0074] Test Example 3 This test example performs XPS analysis on formaldehyde purifiers prepared with different Ce to Mn doping ratios from Experiment 1. Doping ratios of 1:13 and 1:15 are used as examples. The analysis results are shown below. Figures 6-7 ,in, Figure 6 The XPS analysis results are as follows: (a) Full spectrum, (b) O 1s, (c) Mn 2p, (d) Ce 3d; Figure 7 The XPS analysis results are as follows: (a) Full spectrum, (b) O 1s, (c) Mn 2p, (d) Ce 3d.

[0075] Combination Figure 6 and Figure 7 The results show that the formaldehyde purification agent preparation process provided by this invention has no problems. Even with slight adjustments to the proportions, it can still ensure that cerium ions are incorporated into the sodium manganese ore. Analysis is as follows: The XPS peaks of Ce 3d can be divided into eight fitted peaks, which are attributed to Ce... 3+ The two fitting peaks of the species and their attribution to Ce 4+ The six fitted peaks of the species, when the Ce to Mn doping ratio is 1:13, Ce 3+ / Ce 4+ = 0.31; When the Ce to Mn doping ratio is 1:15, Ce 3+ / Ce 4+ = 0.32.

[0076] Test Example 4 This test example was used to test the formaldehyde purification efficiency of the formaldehyde purifier prepared in Example 1 under different temperature and humidity conditions. The purification time was 60 minutes. During the test, the test was conducted in an experimental chamber with no external airflow, strong sunlight, or other radiation. The experimental chamber had a volume of 3 m³. 3 The initial concentration of formaldehyde was controlled between 0.65 ppm and 0.70 ppm, and the relevant data are summarized in Table 2.

[0077] Table 2 Formaldehyde purification efficiency under different temperature and humidity conditions

[0078] As can be seen from the test data in Table 2, the formaldehyde purification efficiency can be maintained within the range of temperature 15℃-25℃ and relative humidity 60%-70%. When the temperature increases and the relative humidity decreases, the purification effect is improved to a certain extent. The optimal purification conditions are room temperature (23±2)℃ and relative humidity (65±5)%.

[0079] In summary, the formaldehyde purifier preparation method provided in this embodiment of the invention is simple to operate, has low input cost, and low energy consumption and few by-products during the preparation process. The obtained formaldehyde purifier has high selective catalytic efficiency for formaldehyde and has stable purification efficiency under low concentration and long-term operation conditions. It is suitable for treating indoor environments with long-term release and low concentration of formaldehyde and is expected to be widely used.

[0080] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A formaldehyde scavenger, characterized by comprising: The formaldehyde purifier comprises a carrier and δ-MnO2-Ce loaded on the surface of the carrier; The carrier is a honeycomb structure, and the doping ratio of Ce to Mn in the δ-MnO2-Ce is 1:20-1:

10.

2. The formaldehyde scavenger according to claim 1, characterized in that, The doping ratio of Ce to Mn in the δ-MnO2-Ce is 1:17-1:

13. Preferably, the manganese source is selected from at least one of potassium permanganate, manganese sulfate, manganese nitrate and manganese chloride; and the cerium source is selected from at least one of cerium nitrate hexahydrate, cerium chloride, cerium sulfate and cerium ammonium nitrate.

3. The formaldehyde scavenger according to claim 1, wherein When the carrier is a honeycomb structure, the material of the carrier comprises aluminum, and the pore size is 1mm-5mm.

4. A process for the preparation of a formaldehyde scavenger as claimed in any one of claims 1 to 3, characterized in that, The method comprises the following steps: The dissolved manganese source, cerium source and adjusting agent are mixed in proportion, and after reaction for 2h-8h at a temperature of 85℃-100℃, static treatment is performed; After the static treatment is completed, the precipitate is collected, and drying treatment is performed at a temperature of 100℃-120℃; The resolubilized precipitate solution is coated on the surface of the pretreated carrier to obtain the formaldehyde purifier.

5. The production method according to claim 4, characterized by, The resolubilized precipitate solution comprises SiO2, TiO2, δ-MnO2-Ce and deionized water in a mass ratio of (0.5-1.0):(0.8-1.4):(1.7-2.2):(1.2-1.6). Preferably, the mass ratio of SiO2, TiO2, δ-MnO2-Ce and deionized water is (0.5-0.7):(0.8-1.2):(1.8-2.0):(1.4-1.6).

6. The preparation method according to claim 4, characterized in that, The manganese source and the cerium source are mixed in proportion and then dissolved, and the obtained solution is denoted as solution A; The solution of the dissolved adjusting agent is denoted as solution B; After the solution A and the solution B are heated to 85℃-100℃ respectively, they are mixed, and after reaction for 2h-5h, static treatment is performed; Preferably, the adjusting agent is ammonium oxalate; and the mass ratio of the adjusting agent to the manganese source is (4-6):(7-10).

7. The preparation method according to claim 4, characterized in that, The pretreatment of the carrier comprises the following steps: The oil stains and oxides on the surface of the carrier are removed by an alkaline solution, and after washing with water to neutral, drying treatment is performed; The alkaline solution is selected from sodium hydroxide solution or potassium hydroxide solution; Preferably, when the carrier is washed with the alkaline solution, the carrier is immersed in the alkaline solution for 5min-30min; Preferably, the drying treatment is performed at a temperature of 220℃-300℃ for 1.5h-3h.

8. The preparation method according to claim 4, characterized in that, The time of the static treatment is 0.5h-1h; And / or, the time of the drying treatment of the precipitate is 1h-2.5h; And / or, after the resolubilized precipitate solution is coated on the surface of the carrier, air-drying treatment and drying treatment are further required; wherein the temperature of the drying treatment is 120℃-180℃, and the time is 0.8h-1.5h.

9. A purifier characterized by comprising: The formaldehyde purifier prepared by the method of any one of claims 1-3 or the method of any one of claims 4-8.

10. The purifier of claim 9, wherein, When the purifier purifies formaldehyde, the initial concentration of formaldehyde is ≤0.70ppm, and the purification efficiency of formaldehyde is ≥88.46%.

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