Bio-enzyme color-changing formaldehyde-removing tablet and preparation method thereof

Abstract

The invention belongs to the technical field of formaldehyde removal materials, and particularly provides a biological enzyme color-changing formaldehyde removal sheet and a preparation method thereof.The biological enzyme color-changing formaldehyde removal sheet is composed of a formaldehyde removal agent and an inert base material, and the formaldehyde removal agent is prepared from, by weight, 60-80 parts of active components, 1-3 parts of pigment, 18-28 parts of binder, 30-40 parts of solvent and 0.05-1 part of pH indicator; wherein the active component is a composition of biological enzyme, a first amino compound and modified chitosan. The biological enzyme color-changing formaldehyde removal sheet can efficiently catalyze and decompose formaldehyde pollutants, can reduce the concentration of indoor pollutants to a safe level in a short time, is mild in action condition, changes color along with the formaldehyde removal progress, and is convenient to use, green and safe.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aldehyde removal materials, and specifically provides a biological enzyme color-changing aldehyde removal sheet and a preparation method thereof. BACKGROUND

[0002] Indoor formaldehyde pollution has become a key problem to be solved in modern living environment, which is mainly derived from artificial board, furniture paint, adhesive and other decoration and decoration materials. The release period in indoor environment can be as long as 3-15 years, and long-term exposure can cause serious harm to human respiratory system, nervous system and immune system, and even induce cancer and other malignant diseases. With the improvement of people's health consciousness and the increasing demand for indoor air quality, the development of efficient, safe and long-lasting formaldehyde purification technology has become the research focus in the field of environmental governance.

[0003] Traditional formaldehyde treatment technologies mainly include physical adsorption method, chemical decomposition method and photocatalytic method. The physical adsorption method is represented by activated carbon, which adsorbs formaldehyde molecules in the air through porous structure, but has the problems of limited adsorption capacity, easy saturation and possible secondary pollution after saturation. It is usually necessary to frequently replace the material, and it is difficult to achieve long-term purification effect. The chemical decomposition method mainly uses oxidizing agents (such as chlorine dioxide and ozone) or amine compounds to react with formaldehyde. Although it can quickly reduce the concentration of formaldehyde, some chemical reagents themselves have irritating odor or corrosive property, which may pose potential risks to indoor environment and human health, and the safety of reaction products also needs further verification. The photocatalytic method takes titanium dioxide as the core, which can decompose formaldehyde into carbon dioxide and water under ultraviolet irradiation. However, this technology has strong dependence on light conditions, and the catalytic efficiency is greatly reduced in indoor weak light or no light environment. At the same time, the catalyst is easy to aggregate and deactivate, which is difficult to meet the purification demand of actual living scene.

[0004] In this context, bio-enzyme technology has gradually become a research hotspot in the field of formaldehyde treatment due to its environmental friendliness, high efficiency, and sustainability. Bio-enzyme is a catalytically active protein produced by living cells. Its nature determines that it can exert catalytic action at normal temperature and pressure, and the reaction products are usually harmless small molecular substances (such as carbon dioxide and water), which will not cause secondary pollution. Early bio-enzyme de-aldehyde technology mainly applied in the form of liquid enzyme preparation, through spraying method to attach enzyme liquid on the surface of pollution source, but there are problems such as enzyme activity is easily affected by temperature, humidity and other environmental factors, and liquid preparation has poor storage stability and short shelf life, which limits its large-scale popularization and application. In order to solve the above defects, researchers began to explore the immobilization technology of enzyme, by loading bio-enzyme on the surface or inside of porous carrier material, to construct solid-state de-aldehyde product, namely bio-enzyme color-changing de-aldehyde sheet. This dosage form not only can effectively protect the spatial structure of enzyme, improve the stability and service life of enzyme in complex environment, but also can enrich formaldehyde molecules through the adsorption of carrier material, improve the contact efficiency of bio-enzyme and formaldehyde, and then enhance the formaldehyde purification effect, which provides a new technical direction for long-term treatment of indoor formaldehyde pollution.

[0005] The application patent CN110141954A discloses a de-aldehyde solution, its loading carrier, preparation method and de-aldehyde filter core. The de-aldehyde solution and its loading carrier of the application are obtained by adding amine substances, cosolvents, compounds containing active alpha hydrogen atoms and solvents into a reaction kettle in a certain proportion, then immersing formaldehyde adsorbent into the de-aldehyde solution to obtain a carrier loaded with the de-aldehyde solution. The de-aldehyde solution uses the principle of aldehyde amine carboxyl reaction, and realizes the non-toxic and harmless treatment of formaldehyde by changing the amine substance group. However, its rapid decomposition efficiency still has room for improvement compared with the new de-aldehyde agent added with bio-enzyme. At present, the requirements for green safety, convenient use and stable use are becoming higher and higher, and the traditional de-aldehyde products cannot meet the requirements. In addition, when using the traditional de-aldehyde products, the user cannot intuitively see the formaldehyde absorption and removal effect, which will cause the replacement of the de-aldehyde products beyond the period, and will endanger the health and safety of the user. SUMMARY

[0006] In view of the existing technical problems, the purpose of the present application is to provide a bio-enzyme color-changing de-aldehyde sheet and a preparation method thereof. The bio-enzyme color-changing de-aldehyde sheet of the present application can efficiently catalyze and decompose formaldehyde pollutants, and can reduce the indoor pollutant concentration to a safe level in a short time. It has mild action conditions, is convenient to use, and is green and safe.

[0007] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: The first aspect of the present application provides a biological enzyme discoloring aldehyde-removing sheet, which is composed of an aldehyde-removing agent and an inert substrate, the aldehyde-removing agent comprising the following raw materials by weight: 60-80 parts of an active component, 1-3 parts of a pigment, 18-28 parts of a binder, 30-40 parts of a solvent, and 0.05-1 parts of a pH indicator; wherein the active component is a combination of biological enzymes, a first amino compound, and modified chitosan.

[0008] In some embodiments of the present application, the biological enzymes are one or more of formaldehyde dehydrogenase, catalase, ethanol oxidase, and protease.

[0009] In some embodiments of the present application, the first amino compound is one or more of propylene diamine, butylene diamine, and triethylamine.

[0010] In some embodiments of the present application, the modified chitosan is prepared by the following steps: (1) mixing amino-protected chitosan and dimethyl sulfoxide, then adding epichlorohydrin and stirring uniformly, heating to 60-80°C under an inert atmosphere for 3-4h, cooling, separating, washing, and drying to obtain pretreated chitosan; (2) mixing the pretreated chitosan of step (1) and N,N-dimethylformamide, then adding a second amino compound, heating to 70-85°C under stirring for 8-10h, precipitating, filtering, washing, and drying to obtain pre-modified chitosan; (3) mixing the pre-modified chitosan of step (2) and anhydrous ethanol, slowly adding vanillin, heating to 65-68°C for 5-6h, then cooling the reaction mixture, mixing with water under stirring, adding saturated sodium bicarbonate solution to adjust the pH to 7-8, stirring for 1-3h, filtering, washing, dialyzing, and drying to obtain the modified chitosan.

[0011] In some embodiments of the present application, the mass ratio of the amino-protected chitosan to epichlorohydrin in step (1) is 1:(3-3.5).

[0012] In some embodiments of the present application, the mass ratio of the pretreated chitosan to the second amino compound in step (2) is 1:(3-6).

[0013] In some embodiments of the present application, the second amino compound in step (2) is ethylenediamine and / or diethylenetriamine.

[0014] In some embodiments of the present application, the mass ratio of the pre-modified chitosan to vanillin in step (3) is 1:(1.2-1.5).

[0015] In some embodiments of the present application, the degree of deacetylation of the chitosan is ≥ 95%, and the viscosity-average molecular weight is 1.05 x 10 6 .

[0016] In some embodiments of the present application, the mass ratio of the biological enzyme, the first amino compound and the modified chitosan in the active component is 1: (10-15): (1-3).

[0017] In the present application, the biological enzyme, the amino compound are mixed as the active component. The biological enzyme is a protein with catalytic function produced by living cells. The aldehyde removal process is essentially a highly efficient biological catalytic reaction, which can significantly reduce the activation energy required for chemical reaction, and can quickly decompose formaldehyde molecules into harmless carbon dioxide and water at normal temperature and pressure. It is safe and non-toxic, and does not produce secondary pollution. At the same time, due to the nucleophilic property of the amino group, the amino compound reacts with the carbonyl group with strong polarity in the formaldehyde molecule to produce hydroxymethyl derivatives or more stable imine products, avoiding the risk of re-release of adsorbed formaldehyde in the existing technology, and achieving the purpose of removing formaldehyde.

[0018] The present application further modifies the chitosan to obtain a modified chitosan. When the modified chitosan is blended with the biological enzyme and the amino compound in a specific ratio, the decomposition efficiency of the biological enzyme discoloring formaldehyde removal sheet to formaldehyde concentration is greatly improved. The applicant speculates that on the one hand, the addition of the modified chitosan helps the binder to ensure the uniformity of the distribution of the formaldehyde removal agent on the inert substrate and the structural stability, which is conducive to the efficient and stable performance of the active component. On the other hand, the specific network structure avoids the adverse hindrance to air circulation while adsorbing formaldehyde, so that the pollutants such as formaldehyde are adsorbed and captured by the active component and fully contacted, thereby improving the formaldehyde removal efficiency of the biological enzyme discoloring formaldehyde removal sheet. Specifically, by modifying the chitosan, the present application optimizes the specific second amino compound to retain sufficient active sites under specific conditions, so that the biological enzyme discoloring formaldehyde removal sheet achieves rapid and efficient formaldehyde removal effect. At the same time, the film-forming property of the chitosan is also retained and balanced in a suitable range, which improves the structural stability while avoiding the adverse hindrance to air circulation.

[0019] In some embodiments of the present application, the binder is hydroxypropyl methyl cellulose and / or polyvinylpyrrolidone.

[0020] In some embodiments of the present application, the solvent is N, N-dimethylformamide or water.

[0021] In some embodiments of the present application, the pH indicator is one or more of litmus, bromocresol purple, bromothymol blue and phenol red.

[0022] The present application realizes the visual removal of formaldehyde by the color change of the pH indicator, and achieves the effect of discoloring removal.

[0023] The second aspect of the present application also provides a preparation method of the biological enzyme discoloring aldehyde-removing sheet, comprising the following steps: (1) mixing the active component, pigment, adhesive, pH indicator and solvent, and stirring to obtain an aldehyde-removing agent; (2) uniformly coating the aldehyde-removing agent obtained in step (1) on an inert substrate by a coating process, drying and cutting to obtain the biological enzyme discoloring aldehyde-removing sheet.

[0024] In some embodiments of the present application, the inert substrate is a polyester non-woven fabric.

[0025] In some embodiments of the present application, the coating amount of the aldehyde-removing agent is 20-40 mL / m 2 .

[0026] Compared with the prior art, the present application has the following advantages: 1. The biological enzyme discoloring aldehyde-removing sheet of the present application can efficiently catalyze and decompose formaldehyde pollutants, and can reduce the indoor pollutant concentration to a safe level in a short time. The action condition is mild, and the sheet appears discoloration with the progress of aldehyde removal, is convenient to use, and is green and safe.

[0027] 2. In the present application, the biological enzyme and the amino compound are mixed as the active component, which can quickly decompose formaldehyde molecules into harmless carbon dioxide and water at normal temperature and pressure, and is safe and non-toxic without secondary pollution. At the same time, due to the nucleophilic property of the amino group, the amino compound reacts with the carbonyl group with strong polarity in the formaldehyde molecule to generate hydroxymethyl derivatives or more stable imine products, avoiding the risk of re-release of adsorbed formaldehyde in the existing technology, and achieving the purpose of aldehyde removal.

[0028] 3. In the present application, the modified chitosan is obtained by modifying chitosan, and when it is blended with the biological enzyme and the amino compound at a specific ratio, the decomposition efficiency of the biological enzyme discoloring aldehyde-removing sheet to formaldehyde concentration is greatly improved. The addition of the modified chitosan helps the adhesive to ensure the uniformity and structural stability of the aldehyde-removing agent on the inert substrate, which is beneficial to the efficient and stable exertion of the active component, and at the same time avoids the adverse hindrance to air circulation, so that the pollutants such as formaldehyde are adsorbed and captured by the active component and fully contacted, which improves the aldehyde-removing efficiency of the biological enzyme discoloring aldehyde-removing sheet. DETAILED DESCRIPTION

[0029] The present application will be described below in conjunction with specific embodiments. It should be noted that the following examples are only used to illustrate the present application, but not to limit the present application. Other combinations and various modifications within the concept of the present application can be made without departing from the spirit or scope of the present application.

[0030] For the convenience of the person skilled in the art to implement the present application, the sources of some raw materials in the following specific embodiments are described as follows: the degree of deacetylation of chitosan is ≥95%, and the viscosity-average molecular weight is 1.05×10 6 ; other raw materials are not specially mentioned and can be purchased from the market.

[0031] In the following specific embodiments, the post-treatment steps such as "cooling", "separation", "washing", "drying" and "dialysis" are the routine operations of the person skilled in the art, which are selected according to the actual operation.

[0032] Preparation Example 1 The preparation method of the amino-protected chitosan comprises the following steps: Chitosan and 1wt% acetic acid aqueous solution are mixed to prepare a 2% (w / v) chitosan acetic acid aqueous solution, and 1.2 times the molar amount of trifluoroacetic anhydride of the amino molar amount in chitosan is added, which is treated at 0℃ for 1.5h to obtain the amino-protected chitosan.

[0033] Preparation Example 2 The preparation steps of the modified chitosan are as follows: (1) 10g of the amino-protected chitosan (obtained from Preparation Example 1) and 200mL of dimethyl sulfoxide are mixed, and then 33g of epichlorohydrin is added and stirred uniformly, and then the temperature is raised to 70℃ under nitrogen atmosphere for 3.5h, and then cooled to room temperature, separated, washed and dried to obtain the pretreated chitosan; (2) 5g of the pretreated chitosan of step (1) and 100mL of N,N-dimethylformamide are mixed, and then 22.5g of diethylenetriamine is added, and then the temperature is raised to 78℃ under stirring for 9h, and then precipitated, filtered, washed and dried to obtain the pre-modified chitosan; (3) 5g of the pre-modified chitosan of step (2) and 100mL of anhydrous ethanol are mixed, and then 6.5g of vanillin is slowly added dropwise, and then the temperature is raised to 66℃ for 5.5h, and then the reaction is cooled, and then mixed with 500mL of water under stirring, and then saturated sodium bicarbonate solution is added to adjust the pH to 7.5, and then stirred for 2h, and then filtered, washed, dialyzed and dried to obtain the modified chitosan.

[0034] Preparation Example 3 The specific preparation steps of the modified chitosan are the same as those of Preparation Example 2, except that the amount of diethylenetriamine added in step (2) of the present preparation example is 32.5g.

[0035] Preparation Example 4 The specific preparation steps of the modified chitosan are the same as those of Preparation Example 2, except that ethylenediamine is used to replace diethylenetriamine in step (2) of the present preparation example.

[0036] Preparation Example 5 The specific preparation steps of the modified chitosan are the same as those in Preparation Example 2, except that the amount of vanillin added in step (3) of the present preparation example is 8 g.

[0037] Preparation Example 6 The preparation steps of the modified chitosan are as follows: (1) 10 g of the amino-protected chitosan (obtained in Preparation Example 1) and 200 mL of dimethyl sulfoxide were mixed, and then 33 g of epichlorohydrin was added and stirred uniformly. The mixture was heated to 70°C under a nitrogen atmosphere and reacted for 3.5 h. After cooling to room temperature, the product was separated, washed and dried to obtain the pretreated chitosan; (2) 5 g of the pretreated chitosan obtained in step (1) and 100 mL of N,N-dimethylformamide were mixed, and then 22.5 g of diethylenetriamine was added. The mixture was heated to 78°C under stirring and reacted for 9 h. After cooling, the reaction product was mixed with 500 mL of water under stirring, and saturated sodium bicarbonate solution was added to adjust the pH to 7.5. The mixture was stirred for 2 h, and then filtered, washed, dialyzed and dried to obtain the pre-modified chitosan.

[0038] In the following specific embodiments, unless otherwise specified, the pigment used is sodium copper chlorophyll, the binder used is hydroxypropyl methylcellulose (type E15), the biological enzyme used is formaldehyde dehydrogenase, the first amino compound used is butanediamine, the solvent used is water, the pH indicator used is bromothymol blue, and the inert substrate used is polyester non-woven fabric (fiber diameter of 20±5 μm).

[0039] Example 1 A biological enzyme discoloring and aldehyde-removing sheet, which is composed of an aldehyde-removing agent and an inert substrate, the aldehyde-removing agent comprises the following raw materials by weight: active component 70 parts, pigment 2 parts, binder 20 parts, solvent 35 parts and pH indicator 0.08 parts; wherein the active component is a composition of biological enzyme, first amino compound and modified chitosan in a mass ratio of 1:12:2.

[0040] The preparation method of the biological enzyme discoloring and aldehyde-removing sheet of the present example comprises the following steps: (1) mixing the active component, pigment, binder, pH indicator and solvent, and stirring to obtain an aldehyde-removing agent; (2) uniformly coating the aldehyde-removing agent obtained in step (1) on the inert substrate by coating process, and drying and cutting to obtain the biological enzyme discoloring and aldehyde-removing sheet.

[0041] The coating amount of the aldehyde-removing agent is 30 mL / m 2 .

[0042] The modified chitosan is obtained from Preparation Example 2.

[0043] Example 2 The bio-enzyme discoloring aldehyde-removing sheet is composed of an aldehyde-removing agent and an inert substrate, and the aldehyde-removing agent comprises the following raw materials in parts by weight: 60 parts of an active component, 1 part of a pigment, 18 parts of a binder, 30 parts of a solvent and 0.05 parts of a pH indicator; wherein the active component is a combination of bio-enzyme, a first amino compound and modified chitosan in a mass ratio of 1:12:2.

[0044] The preparation method of the bio-enzyme discoloring aldehyde-removing sheet comprises the following steps: (1) mixing, stirring the active component, the pigment, the binder, the pH indicator and the solvent to obtain the aldehyde-removing agent; (2) uniformly coating the aldehyde-removing agent obtained in step (1) on the inert substrate by coating process, drying and cutting to obtain the bio-enzyme discoloring aldehyde-removing sheet.

[0045] The coating amount of the aldehyde-removing agent is 30 mL / m 2 .

[0046] The modified chitosan is obtained from Preparation Example 2.

[0047] Example 3 The bio-enzyme discoloring aldehyde-removing sheet is composed of an aldehyde-removing agent and an inert substrate, and the aldehyde-removing agent comprises the following raw materials in parts by weight: 60 parts of an active component, 1 part of a pigment, 18 parts of a binder, 30 parts of a solvent and 0.05 parts of a pH indicator; wherein the active component is a combination of bio-enzyme, a first amino compound and modified chitosan in a mass ratio of 1:12:2.

[0048] The preparation method of the bio-enzyme discoloring aldehyde-removing sheet comprises the following steps: (1) mixing, stirring the active component, the pigment, the binder, the pH indicator and the solvent to obtain the aldehyde-removing agent; (2) uniformly coating the aldehyde-removing agent obtained in step (1) on the inert substrate by coating process, drying and cutting to obtain the bio-enzyme discoloring aldehyde-removing sheet.

[0049] The coating amount of the aldehyde-removing agent is 30 mL / m 2 .

[0050] The modified chitosan is obtained from Preparation Example 2.

[0051] Example 4 The bio-enzyme discoloring aldehyde-removing sheet and the preparation method thereof are the same as those in Example 1, except that the modified chitosan in the present example is obtained from Preparation Example 3.

[0052] Example 5 A biological enzyme color-changing aldehyde removal tablet and a preparation method thereof, the specific implementation manner is the same as that of embodiment 1, the difference lies in that the modified chitosan in the embodiment is obtained from preparation example 4.

[0053] Embodiment 6 A biological enzyme color-changing aldehyde removal tablet and a preparation method thereof, the specific implementation manner is the same as that of embodiment 1, the difference lies in that the modified chitosan in the embodiment is obtained from preparation example 5.

[0054] Embodiment 7 A biological enzyme color-changing aldehyde removal tablet and a preparation method thereof, the specific implementation manner is the same as that of embodiment 1, the difference lies in that the modified chitosan in the embodiment is obtained from preparation example 6.

[0055] Embodiment 8 A biological enzyme color-changing aldehyde removal tablet and a preparation method thereof, the specific implementation manner is the same as that of embodiment 1, the difference lies in that the mass ratio of the biological enzyme, the amino compound and the modified chitosan in the active component in the embodiment is 1:12:3.5.

[0056] Embodiment 9 A biological enzyme color-changing aldehyde removal tablet and a preparation method thereof, the specific implementation manner is the same as that of embodiment 1, the difference lies in that the modified chitosan used in the embodiment is chitosan.

[0057] Comparative example 1 A biological enzyme color-changing aldehyde removal tablet and a preparation method thereof, the specific implementation manner is the same as that of embodiment 1, the difference lies in that the modified chitosan obtained from preparation example 2 is not added.

[0058] Performance test: The biological enzyme color-changing aldehyde removal tablets prepared in the above embodiments 1-9 and comparative example 1 were cut into samples of 15 cm x 45 cm, which were respectively placed in a drawer containing 2.0 mg / m 3 Formaldehyde concentration of 0.1 m 3 In the closed drawer (4 samples were respectively placed along the drawer wall in each group), samples were taken at intervals of 0 h, 5 h, 12 h and 24 h for detection, and the specific reference was QB / T2761-2024, the formaldehyde removal effect at 0 h was 0, and the specific results are shown in Table 1.

[0059] Table 1 From the results in Table 1, it can be seen that the biological enzyme color-changing aldehyde removal tablets prepared in embodiments 1-3 have better formaldehyde removal effect.

[0060] Compared with embodiment 1, in the preparation of the modified chitosan, the amount of diethylenetriamine added is changed, the formaldehyde removal effect of the biological enzyme color-changing aldehyde removal tablet at 5 h and 12 h is significantly enhanced, but the formaldehyde removal effect at 24 h is negatively affected, which may hinder the formaldehyde removal effect of the biological enzyme.

[0061] Example 5, compared with Example 1, when ethylenediamine is used to replace diethylenetriamine in the preparation of modified chitosan, the initial aldehyde removal effect of the bio-enzyme color-changing aldehyde removal sheet is not high, which may be affected by the active site.

[0062] Example 6, compared with Example 1, the amount of vanillin added in the preparation of modified chitosan is changed, although the final de-aldehyde effect is improved, but the early aldehyde removal efficiency is slow due to the steric hindrance.

[0063] Example 7, compared with Example 1, no vanillin is further introduced in the preparation of modified chitosan, which affects the de-aldehyde effect of the bio-enzyme color-changing aldehyde removal sheet.

[0064] Example 8, compared with Example 1, when the proportion of active components, specifically the proportion of modified chitosan, is changed, the adsorption and capture of formaldehyde by the active components are affected, and then the de-aldehyde effect of the bio-enzyme color-changing aldehyde removal sheet is affected.

[0065] Example 9, compared with Example 1, the synergistic effect of the active components obtained by mixing unmodified chitosan, bio-enzyme and amino compound is affected, and the de-aldehyde effect is decreased.

[0066] Comparative Example 1, compared with Example 1, when no modified chitosan is added, the de-aldehyde effect of the bio-enzyme color-changing aldehyde removal sheet is obviously insufficient, which may be affected by the decrease of structural stability.

[0067] The above is only the preferred embodiment of the present application, and does not limit the application in any form. Although the above application is disclosed as the preferred embodiment, it does not limit the application. Any skilled person in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the application, and the equivalent embodiments are also included. Any simple modification, equivalent change and modification made according to the technical essence of the application to the above embodiments are still within the scope of the technical solution.

Claims

1. A bio-enzyme color-changing formaldehyde-removing tablet, characterized in that, The bio-enzyme color-changing formaldehyde removal tablet is composed of a formaldehyde removal agent and an inert substrate. The formaldehyde removal agent contains the following raw materials in parts by weight: 60-80 parts of active component, 1-3 parts of pigment, 18-28 parts of binder, 30-40 parts of solvent and 0.05-1 parts of pH indicator; wherein, the active component is a composition of bio-enzyme, first amino compound and modified chitosan.

2. The bio-enzyme color-changing formaldehyde-removing tablet according to claim 1, characterized in that, The bioenzyme is one or more of formaldehyde dehydrogenase, catalase, ethanol oxidase, and protease.

3. The bio-enzyme color-changing formaldehyde-removing tablet according to claim 1, characterized in that, The first amino compound is one or more of propylenediamine, butanediamine, and triethylamine.

4. The bio-enzyme color-changing formaldehyde-removing tablet according to claim 1, characterized in that, The preparation steps of the modified chitosan are as follows: (1) Mix amino-protected chitosan and dimethyl sulfoxide, then add epichlorohydrin and stir until homogeneous. Under an inert atmosphere, heat to 60-80℃ and react for 3-4 hours. After cooling, separation, washing and drying, pretreated chitosan is obtained. (2) The pretreated chitosan from step (1) and N,N-dimethylformamide are mixed, and then the second amino compound is added. The mixture is heated to 70-85°C under stirring and reacted for 8-10 hours. After precipitation, filtration, washing and drying, pre-modified chitosan is obtained. (3) Take the pre-modified chitosan from step (2) and anhydrous ethanol, slowly add vanillin, heat to 65~68℃ and react for 5~6h, then cool the reactants and mix with water under stirring, adjust the pH to 7~8, stir for 1~3h, filter, wash, dialyze and dry to obtain the modified chitosan.

5. The bio-enzyme color-changing formaldehyde-removing tablet according to claim 4, characterized in that, The mass ratio of the pretreated chitosan and the second amino compound in step (2) is 1:(3-6).

6. The bio-enzyme color-changing formaldehyde-removing tablet according to claim 5, characterized in that, In step (2), the second amino compound is ethylenediamine and / or diethylenetriamine.

7. The bio-enzyme color-changing formaldehyde-removing tablet according to claim 4, characterized in that, The mass ratio of the pre-modified chitosan to vanillin in step (3) is 1:(1.2-1.5).

8. The bio-enzyme color-changing formaldehyde-removing tablet according to claim 1, characterized in that, The mass ratio of the bio-enzyme, the first amino compound, and the modified chitosan in the active component is 1:(10-15):(1-3).

9. The bio-enzyme color-changing formaldehyde-removing tablet according to claim 1, characterized in that, The adhesive is hydroxypropyl methylcellulose and / or polyvinylpyrrolidone.

10. A method for preparing a bio-enzyme color-changing aldehyde-removing tablet according to any one of claims 1-9, characterized in that, It includes the following steps: (1) Mix the active ingredients, pigments, binders, pH indicators and solvents, and stir to obtain a formaldehyde removal agent; (2) The formaldehyde removal agent obtained in step (1) is uniformly coated on an inert substrate by a coating process, and after drying and cutting, the bio-enzyme color-changing formaldehyde removal tablet is obtained.

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