Formaldehyde treatment product based on biomass hydrogel as well as preparation method and application of formaldehyde treatment product

Abstract

The invention belongs to the technical field of formaldehyde treatment, and discloses a formaldehyde treatment product based on biomass hydrogel as well as a preparation method and application of the formaldehyde treatment product. The formaldehyde treatment product is biomass hydrogel loaded with Co3O4 and phenolphthalein, the biomass hydrogel is formed by an NC material, and Co3O4 and NC form a Co3O4-coated NC heterojunction. The preparation method comprises the following steps: (1) taking alkali lignin as a carbon source, and calcining the alkali lignin and a nitrogen-rich precursor to prepare NC; (2) uniformly dispersing NC and acrylamide in water, adding an initiator for free radical polymerization reaction, then adding a cross-linking agent for continuous reaction, and after the reaction is finished, washing to obtain biomass hydrogel; and (3) putting the biomass hydrogel into an ethanol solution of cobalt nitrate hexahydrate, carrying out ultrasonic treatment, adjusting the pH value of the system to 9-10, stirring for 4-6 hours, adding phenolphthalein and industrial-grade H2O2, heating for 4-6 hours at 40-60 DEG C, removing supernate, drying, grinding, annealing for 2-3 hours at 150-180 DEG C, and washing. The one-stop formaldehyde treatment device has the three-in-one function of detection, adsorption and degradation, and one-stop formaldehyde treatment is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of formaldehyde treatment, and particularly relates to a formaldehyde treatment product based on biomass hydrogel, its preparation method and application. Background Art

[0002] Indoor formaldehyde pollution has become a major environmental problem threatening public health due to its long-term, hidden and highly carcinogenic nature. The traditional treatment method is physical adsorption first and then chemical decomposition. Therefore, it is necessary to detect first and then select adsorption or decomposition products. This not only has low functional integration and cumbersome processes, but also the physical adsorption is easily saturated, the chemical decomposition is prone to secondary pollution, the removal efficiency of formaldehyde is low, and it is not friendly to the indoor environment. In addition, most of the existing formaldehyde treatment products are synthetic products, which are difficult to degrade and need to be activated under the action of ultraviolet light. Therefore, the existing treatment technologies generally face bottlenecks such as functional fragmentation, strong dependence on ultraviolet light, high risk of secondary pollution and short material life. The detector priced at a thousand yuan can only give an alarm but cannot purify, forming a dilemma of "monitoring-treatment fragmentation".

[0003] Lignin is rich in active functional groups such as phenolic hydroxyl groups and methoxy groups. Its three-dimensional aromatic structure can construct a porous network with a high specific surface area (>300 m² / g) through chemical cross-linking, providing strong adsorption sites for formaldehyde molecules. Compared with traditional gel raw materials (such as chitosan or polyvinyl alcohol), lignin not only has a low cost (3 yuan / kg, only 1 / 5 of petroleum-based materials), but also has natural degradability (the degradation rate >95% in 30 days).

[0004] Under this background, if a formaldehyde treatment product with real-time monitoring, efficient adsorption and degradation can be developed based on lignin, it not only conforms to the concept of green environmental protection, but also has great economic and social significance. Summary of the Invention

[0005] In order to solve the "monitoring-treatment fragmentation" dilemma existing in the formaldehyde treatment products in the prior art, the purpose of the present invention is to provide a formaldehyde treatment product based on biomass hydrogel, its preparation method and application.

[0006] To achieve the above purpose, the technical solutions adopted by the present invention are as follows: A formaldehyde treatment product based on biomass hydrogel, wherein the formaldehyde treatment product is a biomass hydrogel loaded with Co 3 O 4 and phenolphthalein. The biomass hydrogel is formed by NC material. Co 3 O 4 forms a Co 3 O 4 @NC heterojunction with NC, and the NC is a nitrogen-doped modified biomass carbon material.

[0007] To improve the lifespan of the product, it is preferable to form a shell layer on the basis of the above product structure, that is, the formaldehyde treatment product has a core-shell structure, and the shell is CaCO 3 crystals, and the core is a biomass hydrogel loaded with Co 3 O 4 and phenolphthalein. The biomass hydrogel is formed from NC material. Co 3 O 4 forms a Co 3 O 4 @NC heterojunction with NC, and the NC is a nitrogen-doped modified biomass carbon material.

[0008] A preparation method of a formaldehyde treatment product based on biomass hydrogel is as follows: (1) Using alkali lignin (which can be obtained commercially or prepared according to existing techniques) as a carbon source, calcine it together with a nitrogen-rich precursor to prepare NC; (2) Uniformly disperse NC and acrylamide in water, add an initiator to carry out a free radical polymerization reaction, then add a crosslinking agent and continue the reaction. After the reaction ends, soak and wash repeatedly with water to obtain a biomass hydrogel; (3) Place the biomass hydrogel in an ethanol solution of cobalt nitrate hexahydrate, sonicate until cobalt nitrate hexahydrate is completely adsorbed by the biomass hydrogel, then adjust the pH of the system to 9 - 10 with ammonia water, stir at room temperature for 4 - 6 h, add phenolphthalein and industrial-grade H 2 O 2 (concentration 30 ± 2 wt%), heat at 40 - 60 °C for 4 - 6 h, remove the supernatant, dry, grind, anneal in an air atmosphere at 150 - 180 °C for 2 - 3 h, and wash to obtain a biomass hydrogel loaded with Co 3 O 4 and phenolphthalein.

[0009] Preferably, in terms of mass-volume ratio, biomass hydrogel∶cobalt nitrate hexahydrate∶ethanol∶phenolphthalein∶industrial-grade H 2 O 2 =(100 - 150) mg∶(1.5 - 2.0) g∶(10 - 20) mL∶(0.05 - 0.2) g∶(3 - 5) mL.

[0010] Preferably, in step (3), the drying is vacuum drying, and the drying temperature is 35 - 50 °C and the time is 4 - 6 h.

[0011] Preferably, in step (1), the nitrogen-rich precursor is urea; in terms of mass ratio, alkali lignin∶urea = 1∶(1 - 3); the calcination temperature is 700 - 900 °C and the time is 2 - 4 h.

[0012] Preferably, in step (2), the initiator is ammonium persulfate and the crosslinking agent is N,N'-methylenebisacrylamide; by mass-volume ratio, NC∶acrylamide∶water = 1 g∶(5 - 10) g∶(50 - 100) mL; by mass ratio, acrylamide∶initiator∶crosslinking agent = 10∶(0.1 - 0.2)∶(0.1 - 0.2); the temperature of the free radical polymerization reaction is 58 - 62 °C and the time is 1 - 1.5 h; after adding the crosslinking agent, the reaction continues for 2 - 3 h.

[0013] To improve the lifespan of the product, it is preferred to form a shell on the basis of the product structure obtained by the above preparation method. The specific operation process is as follows: in step (3), after annealing, an aqueous dispersion of CaCO 3 crystals or an aqueous solution of a precursor capable of reacting to form CaCO 3 crystals is deposited on the surface of the biomass hydrogel loaded with Co 3 O 4 and phenolphthalein to wrap it, and then it is repeatedly soaked and washed with water and dried to obtain a formaldehyde treatment product with a core-shell structure. In the present invention, when an aqueous dispersion of CaCO 3 crystals or an aqueous solution of a precursor capable of reacting to form CaCO 3 crystals is deposited on the surface of the biomass hydrogel loaded with Co 3 O 4 to wrap it, any form in the prior art can be adopted, preferably spray spraying or microfluidic technology.

[0014] Preferably, in step (3), the deposition thickness of the CaCO 3 crystals is 18 - 20 μm.

[0015] An application of the formaldehyde treatment product based on the biomass hydrogel in formaldehyde treatment. When the formaldehyde treatment product of the present invention is applied in formaldehyde treatment, the formaldehyde treatment product of the present invention can be directly used (the formaldehyde concentration can be monitored in real time by observing the color change of the product), or it can be prepared together with an existing sensor into a finished product that can digitally display the formaldehyde concentration in real time.

[0016] The innovation points of the present invention are as follows: (1) The "detection - adsorption - degradation" trinity function: (1.1) Biomass hydrogel, efficient adsorption and degradation of formaldehyde: The product innovatively uses alkaline lignin to prepare biomass hydrogel as the key material. It has a unique three-dimensional network structure and rich active groups, and has a strong affinity for formaldehyde molecules. On the one hand, it can adsorb a large amount of formaldehyde molecules; on the other hand, the active groups it carries can react chemically with formaldehyde to convert formaldehyde into harmless substances. This biomass hydrogel shows extremely high efficiency in the process of degrading formaldehyde. Compared with traditional materials, it can reduce indoor formaldehyde concentration in a shorter time, and the degradation process is stable and long-lasting, providing a new and efficient solution for indoor formaldehyde control. At the same time, doping Co 3 O 4 Can accelerate the degradation rate, Co 3 O 4 It is a metal oxide with good catalytic performance. In the process of removing formaldehyde, Co 3 O 4 It can catalyze the oxidation reaction of formaldehyde with oxygen in the air, converting formaldehyde into carbon dioxide and water. Its catalytic effect is mainly achieved through the conversion of cobalt ions on the surface between different valence states. During the reaction, cobalt ions can accept and transfer electrons to promote the oxidation reaction of formaldehyde. The introduction of nitrogen atoms can adjust the electronic structure of carbon materials, making them have better electron transfer performance, thereby accelerating electron transfer during the reaction and improving the efficiency of catalytic oxidation. In addition, nitrogen modification can also increase the number of active sites on the surface of carbon materials, providing more reaction sites for the oxidation reaction of formaldehyde. (1.2) Easy to observe color changes and monitor the effect in real time: This product is alkaline as a whole and appears purple-red at the beginning of use. During the process of adsorbing formaldehyde, the pH value decreases due to the generation of the intermediate product formic acid. After reacting with the indicator, the color becomes lighter (light pink). As the formaldehyde degrades, the formic acid is mineralized into carbon dioxide and water. At the same time, as the indoor formaldehyde concentration decreases, the product color gradually changes from light pink to purple, which is slightly lighter than the initial color. Users can easily judge the working status of the product and the changes in indoor formaldehyde concentration through intuitive color changes; the color will appear within 10 minutes of a sudden change in concentration, and the full range will be covered within 30 minutes, which is 3 times faster than traditional test strips (more than 1 hour) and does not require power support. It is suitable for passive scenarios such as home and car. This innovative design makes the formaldehyde treatment effect clear at a glance without the need for complex detection instruments, which greatly facilitates user use and improves the user's sense of control over the indoor environmental quality. (2) Core-shell structure protection to ensure the long-term stability of the product: The active ingredients inside are encapsulated in a "shell" composed of degradable calcium carbonate, which can prevent the internal active ingredients from being interfered with and damaged by external environmental factors, extending the service life of the product. This core-shell structure ensures that the product can still work stably in a complex indoor environment, continuously playing the role of adsorbing and degrading formaldehyde, and guaranteeing the long-term effectiveness and stability of the product in formaldehyde treatment.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) Three-in-one function, one-stop formaldehyde treatment: The formaldehyde treatment product of the present invention innovatively realizes the organic integration of detection, adsorption, and degradation functions, creating a comprehensive indoor formaldehyde treatment solution. This "detection-adsorption-degradation" three-in-one design avoids the cumbersome process of first detecting and then selecting adsorption or decomposition products in traditional treatment methods. It not only achieves efficient removal of formaldehyde but also ensures the continuous safety of the indoor environment, completely solving problems such as the easy saturation of traditional products relying solely on physical adsorption and the easy generation of secondary pollution in chemical decomposition. The three-in-one closed-loop reconstructs the treatment logic, achieving the unity of high efficiency and environmental protection with lignin-based substrates, the colorimetric detection breaking through the user's cognitive threshold, and the core-shell encapsulation overcoming the stability problem. Compared with commercially available products, the products of the present invention have achieved generational leaps in function integration (dual function → triple function), light response range (ultraviolet → visible light), lifespan (3 months → 1 year), and environmental friendliness (synthesis → full degradation), and are expected to lead the indoor air treatment from "passive remediation" into a new era of "intelligent prevention", providing support for a healthy China and a green economy. (2) The combination of innovative core-shell encapsulation technology (CaCO 3 shell) and biomass substrate extends the material lifespan to 12 months, breaking through the bottleneck of short-term failure of traditional materials due to environmental sensitivity. (3) Low cost and high environmental friendliness: Using lignin as the raw material and combining with an all-aqueous green preparation process, it has a low cost and provides an innovative solution for indoor air treatment that combines economy and ecological safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 : XPS diagram of the shell-less formaldehyde treatment product obtained in Example 1 of the present invention.

[0019] Figure 2 : TEM diagram of the shelled formaldehyde treatment product in Example 1 of the present invention.

[0020] Figure 3 : Comparison of the formaldehyde adsorption amounts of different formaldehyde removal products in a short time.

[0021] Figure 4 : Comparison of the formaldehyde adsorption amounts of different formaldehyde removal products within 1 hour.

[0022] Figure 5 : Comparison of the service life of formaldehyde treatment products with / without a shell. Specific implementation manners

[0023] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. Based on the described embodiments, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present invention.

[0024] Example 1

[0025] A preparation method of a formaldehyde treatment product based on biomass hydrogel is as follows: (1). Preparation of NC: Add 2 g of alkali lignin to an aqueous urea solution (4 g of urea, 30 mL of water), stir at room temperature for 6 h, heat to evaporate the water and then dry to obtain a solid sample, and place it in a tubular furnace under a nitrogen atmosphere and heat it to 800 °C at a rate of 5 °C / min and hold for 2 h; (2). Uniformly disperse 1.5 g of NC and 10 g of acrylamide in 80 mL of deionized water, add 0.15 g of initiator ammonium persulfate under a water bath condition of 60 °C to initiate a free radical polymerization reaction for 1 h, and then add 0.15 g of crosslinking agent N,N'-methylenebisacrylamide and continue the reaction for 3 h. After the reaction is completed, repeatedly soak and wash with deionized water to remove unreacted monomers and impurities to obtain a biomass hydrogel; (3). Take 100 mg of the biomass hydrogel and place it in an anhydrous ethanol (15 mL) solution of cobalt nitrate hexahydrate (1.7462 g), ultrasonicate for 30 min to promote adsorption, add ammonia water to adjust the pH to 10, and generate Co(OH) 2 precipitate, stir at room temperature for 4 h, add 0.15 g of phenolphthalein and 3 mL of H 2 O 2 (30 wt%), heat in a water bath at 60 °C for 6 h to oxidize Co(OH) 2 to Co 3 O 4 , remove the supernatant, vacuum dry at 35 °C for 4 h, grind and then anneal in an air atmosphere at 180 °C for 2 h to promote the crystallization of Co 3 O 4 , wash with anhydrous ethanol to remove residual reagents, and obtain a biomass hydrogel loaded with Co 3 O 4 and phenolphthalein (formaldehyde treatment product without a shell); (4). Mix calcium chloride and sodium bicarbonate according to Ca 2+ and HCO 3 -Prepare a mixed aqueous solution in a molar ratio of 1:2, and use a spraying device to atomize the solution into tiny droplets. The spraying pressure is 0.3 MPa, and it is sprayed onto the biomass hydrogel loaded with Co 3 O 4 and phenolphthalein. During the contact process between the droplets and the biomass hydrogel loaded with Co 3 O 4 and phenolphthalein, a reaction occurs to generate CaCO 3 . With continuous spraying, CaCO 3 gradually deposits on the gel surface to form a shell. Spray continuously for 10 min to construct a 20-μm-thick CaCO 3 crystal shell on the gel surface. Then, soak and wash it thoroughly with deionized water again to remove the residual impurities on the surface, and place it in a vacuum drying oven at 40 °C to dry to a constant weight, thus obtaining the shelled formaldehyde treatment product.

[0026] Figure 1 is the XPS diagram of the shell-free formaldehyde treatment product obtained in step (3) of Example 1. As can be seen from Figure 1 : At 800 °C, a composite structure of Co 3 O 4 loaded on nitrogen-doped carbon (NC) (Co 3 O 4 @NC) was successfully synthesized; the chemical states of Co are Co 2+ and Co 3+ coexisting, which is in line with the crystal structure characteristics of Co 3 O 4 ; nitrogen is doped in the form of pyridine nitrogen and graphitic nitrogen, which may improve the electron transport ability and catalytic active site density of the material; the O 1s peak shows that there are lattice oxygen and hydroxyl oxygen on the material surface, indicating its hydrophilicity and potential redox activity, which is suitable for electrochemical or catalytic applications.

[0027] Figure 2 is the TEM diagram of the shelled formaldehyde treatment product obtained in step (4) of Example 1. A core-shell structure can be observed in the figure, where the shell is calcium carbonate, and the Co 3 O 4 @NC heterojunction can be clearly seen inside the core.

[0028] Formaldehyde degradation rate test (I) Experimental process: (1) Sample treatment: Take activated carbon, photocatalyst, and the shelled formaldehyde treatment product obtained in Example 1 of the present invention as test samples, and weigh 0.5 g of each sample and disperse it evenly on the carrier (glass slide); (2) Preparation of initial formaldehyde concentration: Place the carrier with the sample dispersed therein in a closed reaction chamber (glass reactor with temperature and humidity control), then inject formaldehyde gas, and control the initial concentration at 2 ppm (simulating indoor pollution level). Calibrate the initial concentration using a formaldehyde detector (take the average value after repeating 3 times); when the sample is a photocatalyst, irradiate the closed reaction chamber with a UV lamp of 365 nm, and the UV light intensity is 2 mW / cm². When the sample is activated carbon or the shelled formaldehyde treatment product obtained in Example 1 of the present invention, irradiate the closed reaction chamber with visible light, and the visible light intensity is 2 mW / cm²; (3) Sampling at time points: The first 40 minutes is the adsorption stage, and after 40 minutes is the degradation stage. Sampling is performed every 20 minutes (extracting the gas in the chamber), and sampling stops after 2 hours of degradation; during this period, in order to compare the influence of the presence / absence of the CaCO 3 shell on the lifespan of the formaldehyde treatment product of the present invention, use the shell-less formaldehyde treatment product obtained in step (3) of Example 1 as the control sample for the shelled formaldehyde treatment product, and sample when the degradation continues for 2 months, and then sample every 2 months; after each sampling as described above, an equal amount of formaldehyde gas needs to be replenished; (4) Gas chromatography (high precision): Direct injection analysis; (5) Calculate the degradation rate. The degradation rate formula: .

[0029] (2) Experimental results: Figure 3 For the comparison of the formaldehyde adsorption amounts of different formaldehyde removal products in a short time, the adsorption and degradation stages are distinguished by a dashed line in the figure; Figure 4 For the comparison of the formaldehyde adsorption amounts of different formaldehyde removal products within 1 hour. As Figures 3 - 4 can be seen: The degradation rate of activated carbon is very low and basically remains unchanged; the degradation rates of the photocatalyst and the shelled formaldehyde treatment product obtained in Example 1 of the present invention increase with time, and the degradation effect of the shelled formaldehyde treatment product obtained in Example 1 of the present invention is significantly better than that of the photocatalyst; at 1 hour of degradation, the degradation rates of activated carbon and the photocatalyst are 2.06% and 58.31% respectively, both lower than that of the shelled formaldehyde treatment product obtained in Example 1 of the present invention (90.42%).

[0030] Figure 5 For the comparison of the service lives of the formaldehyde treatment products with / without a shell. As Figure 5 can be seen: There is no obvious difference in the degradation rate of the shelled formaldehyde treatment product obtained in Example 1 of the present invention at 2 months and 12 months, indicating that the service life of the shelled formaldehyde treatment product obtained in Example 1 of the present invention can be extended to 12 months.

Claims

1. A formaldehyde treatment product based on biomass hydrogel, characterized by: The formaldehyde treatment product is a biomass hydrogel loaded with Co3O4 and phenolphthalein, the biomass hydrogel is formed by NC material, Co3O4 and NC form a Co3O4@NC heterojunction, and the NC is a nitrogen-doped modified biomass carbon material.

2. The formaldehyde treatment product based on biomass hydrogel according to claim 1, characterized in that: The formaldehyde treatment product has a core-shell structure, the outer shell is CaCO3 crystal, the inner core is a biomass hydrogel loaded with Co3O4 and phenolphthalein, the biomass hydrogel is formed by NC material, Co3O4 and NC form a Co3O4@NC heterojunction, and the NC is a nitrogen-doped modified biomass carbon material.

3. A method for preparing a formaldehyde treatment product based on biomass hydrogel as claimed in claim 1, characterized in that: Here are the steps: (1) Using alkaline lignin as a carbon source, calcining it together with a nitrogen-rich precursor to prepare NC; (2) Dispersing NC and acrylamide uniformly in water, adding an initiator to carry out a free radical polymerization reaction, then adding a crosslinking agent and continuing the reaction. After the reaction is completed, repeatedly soaking and washing with water to obtain a biomass hydrogel; (3) Place the biomass hydrogel in an ethanol solution of cobalt nitrate hexahydrate, and sonicate until the cobalt nitrate hexahydrate is completely adsorbed by the biomass hydrogel. Then, add ammonia water to adjust the pH of the system to 9-10. After stirring at room temperature for 4-6 hours, add phenolphthalein and industrial-grade H2O2, and heat at 40-60°C for 4-6 hours. Remove the supernatant, dry and grind, anneal at 150-180°C in an air atmosphere for 2-3 hours, and wash to obtain a biomass hydrogel loaded with Co3O4 and phenolphthalein.

4. The method for preparing a formaldehyde treatment product based on biomass hydrogel according to claim 3, characterized in that: In step (3), during the hydrothermal reaction, the mass-volume ratio of biomass hydrogel: cobalt nitrate hexahydrate: ethanol: phenolphthalein: industrial grade H2O2 is (100-150) mg: (1.5-2.0) g: (10-20) mL: (0.05-0.2) g: (3-5) mL.

5. The method for preparing a formaldehyde treatment product based on biomass hydrogel according to claim 3, characterized in that: In step (3), the drying is vacuum drying, the drying temperature is 35-50° C., and the drying time is 4-6 hours.

6. The method for preparing a formaldehyde treatment product based on biomass hydrogel according to claim 3, characterized in that: In step (1), the nitrogen-rich precursor is urea; the mass ratio of alkali lignin to urea is 1:(1-3); the calcination temperature is 700-900°C and the calcination time is 2-4h.

7. The method for preparing a formaldehyde treatment product based on biomass hydrogel according to claim 3, characterized in that: In step (2), the initiator is ammonium persulfate, and the cross-linking agent is N,N'-methylenebisacrylamide; in terms of mass-volume ratio, NC: acrylamide: water = 1 g: (5-10) g: (50-100) mL; in terms of mass ratio, acrylamide: initiator: cross-linking agent = 10: (0.1-0.2): (0.1-0.2); the temperature of the free radical polymerization reaction is 58-62°C and the time is 1-1.5 h; after adding the cross-linking agent, the reaction is continued for 2-3 h.

8. The method for preparing a formaldehyde treatment product based on biomass hydrogel according to any one of claims 3 to 7, characterized in that: In step (3), after annealing, an aqueous dispersion of CaCO3 crystals or an aqueous solution of a precursor capable of reacting to form CaCO3 crystals is deposited on the surface of the biomass hydrogel loaded with Co3O4 and phenolphthalein to wrap it, and then repeatedly soaked and washed with water, and dried to obtain a formaldehyde treatment product with a core-shell structure.

9. The method for preparing a formaldehyde treatment product based on biomass hydrogel according to claim 8, characterized in that: In step (3), the deposition thickness of CaCO3 crystals is 18-20 μm.

10. Use of the formaldehyde treatment product based on biomass hydrogel as claimed in claim 1 or 2 in formaldehyde treatment.

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