CN110078456B

CN110078456B - Gypsum fiberboard with adsorption and photocatalytic performances and preparation method and application thereof

Info

Publication number: CN110078456B
Application number: CN201910410735.4A
Authority: CN
Inventors: 刘荣; 杨锡红; 曹云; 韩燕�; 徐悦清
Original assignee: Nanjing Jinghuanre Metallurgy Engineering Co ltd; Nanjing Normal University
Current assignee: Nanjing Jinghuanre Metallurgy Engineering Co ltd
Priority date: 2019-05-16
Filing date: 2019-05-16
Publication date: 2021-10-19
Anticipated expiration: 2039-05-16
Also published as: CN110078456A

Abstract

The invention discloses a gypsum fiberboard with adsorption and photocatalytic performances and a preparation method and application thereof, wherein the gypsum fiberboard is mainly prepared from the following raw materials in percentage by weight: 3-10% of high titanium slag-based mineral cotton fiber, 65-68% of building gypsum powder and 22-32% of water. The high-titanium slag-based mineral slag cotton gypsum fiberboard material prepared by the invention has double effects of adsorbing and photocatalytic degradation of formaldehyde, increases the functionality of the gypsum board material, can adsorb and photocatalytic degrade indoor formaldehyde gas, effectively improves the indoor air quality, improves the competitiveness of the product market, and can bring good economic benefits; meanwhile, the method provided by the invention has the advantages of simple process, low cost and low energy consumption, can change waste into valuable, is expected to realize large-scale preparation of the high-titanium slag-based mineral cotton gypsum fiberboard, meets the requirement of industrial production, and accords with the development trend of national green ecological building materials.

Description

Gypsum fiberboard with adsorption and photocatalytic performances and preparation method and application thereof

Technical Field

The invention belongs to the technical field of multifunctional building materials and building energy conservation, and particularly relates to a high-titanium slag-based mineral cotton gypsum fiberboard with adsorption and photocatalytic performances, and a preparation method and application thereof.

Background

With the continuous advance of city modernization in recent years, the use of decorative materials for houses and public places is gradually increased year by year. However, these building materials and furniture will release many toxic and harmful gases, such as formaldehyde, ammonia, benzene and benzene series, etc. volatile gases, and indoor air pollution is pushed up to the wind opening wave tip. Based on the rising concern of the public on indoor air pollution, the research and development of novel building materials with the function of environmental pollution control has become a focus of attention of a large number of scholars at home and abroad.

The formaldehyde is taken as a main indoor pollutant, is a carcinogen recognized by the world health organization, and is of great importance for purifying the formaldehyde. At present, the main purification modes at home and abroad are as follows: physical adsorption, plant purification, chemical absorption, catalytic oxidation, photocatalysis and the like. Wherein, the photocatalyst technology can continuously react at normal temperature and normal pressure, the photocatalyst does not generate loss during the reaction, and the final product is CO₂And H₂And O, the reaction condition is mild, secondary pollution is not generated, the operation is simple and convenient, and the method is widely researched and applied in recent years. Titanium dioxide becomes an application hotspot in the field of photocatalysis due to good chemical stability and catalytic performance.

Today, the iron-making section of the Chinese iron and steel company produces about 360 million tons of high titanium slag (TiO) each year₂The content is more than or equal to 22 percent), and the high titanium slag is used as a byproduct in the metallurgical industry and has great potential value. A large amount of high-titanium slag can not be utilized or can only be used as a building material additive for rough utilization every year, so that serious resource waste and environmental pollution are caused, and a scientific and reasonable new way for resource utilization of the high-titanium slag is urgently needed to be developed. A large number of researchers at home and abroad mainly aim at recovering and extracting titanium element from high-titanium slag, and the method has low efficiency, produces a large amount of waste acid, waste alkali and the like during extraction and causes secondary pollution.

Disclosure of Invention

The purpose of the invention is as follows: the problems existing in the prior art are as follows: 1. at present, gypsum boards for indoor decoration mainly have a decoration effect, and meanwhile, the surfaces of gypsum boards have a certain adsorption effect on indoor formaldehyde gas, but after the surfaces are adsorbed and saturated, the adsorbed gas is desorbed again, and the purpose of completely and thoroughly purifying and removing the formaldehyde gas in a closed indoor space cannot be achieved; 2. at present, the high titanium slag is roughly utilized and stockpiled in occupied area, so that the resource waste and secondary pollution of valuable titanium resources in the slag are caused. The invention provides a gypsum fiberboard with adsorption and photocatalytic performances, which has the synergistic purification and removal effects of adsorption and photocatalytic degradation on indoor formaldehyde gas, effectively improves the indoor air quality, and realizes the overall resource utilization of high-titanium slag; the problem of environmental pollution caused by waste or waste accumulation of valuable titanium resources in high-titanium slag is solved, the gypsum board has the effect which is not possessed by the traditional gypsum board, and the problem of environmental pollution caused by overproof formaldehyde in the current home decoration material is solved.

The invention also provides a preparation method and application of the gypsum fiberboard with adsorption and photocatalytic performances.

The technical scheme is as follows: in order to achieve the purpose, the gypsum fiberboard with adsorption and photocatalytic performance is characterized by being mainly prepared from the following raw materials in percentage by weight:

3 to 10 percent of high titanium slag-based mineral cotton fiber

65 to 68 percent of building gypsum powder

22 to 32 percent of water.

Wherein the high titanium slag-based mineral cotton fiber is cotton-like fiber prepared by blowing molten high titanium slag with compressed air, and TiO in the molten high titanium slag₂The content (mass fraction) is 22-25%. The high titanium slag of the invention is TiO₂The titanium-containing blast furnace slag with the content of more than or equal to 22 percent has the advantages of high titanium content and the existing titanium is in a perovskite phase (CaTiO)₃) Has good photocatalytic properties.

Wherein the average diameter of the high-titanium slag-based mineral cotton fiber is 1.30-3.60 mu m, and the average length is 35-45 mm.

Preferably, the building gypsum powder is alpha-hemihydrate gypsum powder (high-strength gypsum).

Wherein the water is tap water.

The preparation method of the gypsum fiberboard with adsorption and photocatalytic performances comprises the following steps:

(1) placing the high-titanium slag-based mineral cotton fiber into an ultrasonic cleaning machine for ultrasonic cleaning, removing slag balls, cleaning and drying;

(2) mixing the cleaned and dried high-titanium slag-based mineral cotton fiber with building gypsum powder, and uniformly stirring to prepare a dry mixed material;

(3) adding water into the dry mixture, and uniformly stirring to prepare slurry;

(4) pouring the slurry obtained in the step (3) into a mould to prepare a wet plate blank;

(5) and (3) drying the wet blank at room temperature in the air, and drying to form the gypsum fiberboard with adsorption and photocatalytic performance.

Preferably, the ultrasonic treatment in the step (1) is carried out for 1-2 hours, and the slag balls on the surface of the mineral wool are removed according to the principle that the gravity and the resistance of the slag balls and the fibers are different when the slag balls and the fibers move in water.

Preferably, the wet blank in the step (5) is dried in the air at room temperature for 24 hours and then dried at 110 ℃ for 2-3 hours.

The gypsum fiberboard with the adsorption and photocatalytic performances is applied to the preparation and production of green ecological environment-friendly building materials.

The green ecological environment-friendly building material can adsorb and photocatalytically degrade indoor formaldehyde gas, and effectively improves indoor air quality.

The invention takes high titanium slag-based mineral cotton fiber, building gypsum powder and water as raw materials; aims to change the high titanium slag into valuable, and simultaneously, the titanium content in the high titanium slag is fully utilized to carry out photocatalytic degradation on indoor formaldehyde. The high titanium slag-based mineral cotton fiber is prepared by blowing molten high titanium slag with compressed air, wherein titanium is in perovskite phase (CaTiO)₃) The photocatalyst has the advantages of being light in weight, good in heat insulation and chemical stability and the like, and can be used as an excellent photocatalyst due to the special fiber structure and good adsorption performance.

According to the invention, the high-titanium slag-based mineral cotton and the gypsum are mixed, and a large amount of experimental research is carried out, so that the high-titanium slag-based mineral cotton gypsum fiberboard material with adsorption and photocatalytic performances is prepared, waste utilization and effective formaldehyde purification can be realized, and the high-titanium slag-based mineral cotton gypsum fiberboard material has a very good commercial application prospect; similar methods are not reported at home and abroad, and a brand-new gypsum fiberboard with adsorption and photocatalysis performances, which is formed by mixing high-titanium slag-based mineral wool and gypsum, is disclosed for the first time.

The scientific principle of the invention is as follows:

the mechanism of formaldehyde adsorption: under the condition of no illumination, the high titanium slag-based mineral slag cotton gypsum fiberboard adsorbs formaldehyde and is highly fitted with a quasi-first order kinetic equation, so that the adsorption process is simple physical adsorption and mainly depends on Van der Waals force generated between formaldehyde molecules and the surface of the gypsum fiberboard; the formaldehyde molecules are influenced by Van der Waals force and are adsorbed to the surface of the gypsum fiber board, so that the aim of adsorbing the formaldehyde is fulfilled.

The mechanism of photocatalytic degradation of formaldehyde is as follows: the high titanium slag-based mineral wool fiber contains a perovskite phase, and when the high titanium slag-based mineral wool fiber is irradiated by ultraviolet light, the light energy can effectively promote the perovskite phase on the surface of the high titanium slag-based mineral wool to be excited to generate a large number of electron-hole pairs (e)^-，h⁺) And H₂The OH can oxidize the formaldehyde adsorbed on the surface of the slag wool with high titanium slag base into CHO, the generated CHO further reacts to generate intermediate product HCOOH, and the HCOOH is finally oxidized into non-toxic CO₂And H₂O, and no secondary pollution is generated. The reaction steps of the process can be summarized as:

CaTiO₃+hv→e^-+h⁺

h⁺+H₂O→·OH+H⁺

HCHO+·OH→·CHO+H₂O

·CHO+·OH→HCOOH

wherein e^-Is a conduction band electron, h⁺Is a valence band hole.

In the above reaction step, the reactant is formaldehyde solution, and H in the solution₂Decomposition of O to H⁺Is beneficial to the generation of OH.

The building gypsum powder of the invention is alpha-type semi-hydrated gypsum powder (high-strength gypsum powder) which is available on the market.

The slag wool is made up by using molten slag (blast furnace slag, copper slag and aluminium slag, etc.) as main raw material and adopting compressed air or high-pressure steam as blowing medium to blow molten slag into cotton-like inorganic fibre (reference: blast furnace slag-making slag wool process and its product application, the authors: wonderful property, etc., Shanghai metal, No. 36, No. 2, 3.2014., No. 36, and the ② blowing process parameters, whose effects on the quality of slag wool, the authors: Zhang Hangjin, etc., material and metallurgical science report, No. 15, No. 1, 3.2016). The preparation method of the high titanium slag-based slag cotton fiber in the invention refers to the preparation method of the slag cotton in the above documents, and can also adopt other slag cotton blowing preparation methods in the prior art, except that the TiO of the molten slag is used as the blowing preparation method₂The high titanium slag-based mineral cotton fiber is obtained by using the high titanium slag which is the raw material of titanium-containing blast furnace slag with the content of 22-25 percent and cotton-like fibers which are prepared by blowing compressed air.

Has the advantages that: compared with the prior art, the invention has the following advantages:

1. the gypsum fiberboard material with adsorption and photocatalytic performances prepared by the invention has the advantages of simple preparation process and no pollution, realizes the reutilization of waste resources, has the formaldehyde adsorption efficiency of more than 25 percent, and can decompose formaldehyde gas adsorbed on the surface of the board into CO through the photocatalytic action₂And H₂O (wherein the photocatalytic degradation purification removal efficiency is more than or equal to 7 percent), realizes the thorough purification removal (rather than single adsorption) of formaldehyde gas, increases the functionality of the gypsum board material, improves the competitiveness of the product market, and can bring good economic benefit;

2. the gypsum fiberboard material prepared by the invention meets the requirements of national green ecological building materials, can be applied to the preparation and production of green ecological environment-friendly building materials, particularly to the production of building materials which have the characteristics of adsorption, synergistic purification of photocatalytic degradation of indoor formaldehyde gas, effective improvement of indoor air quality and development of a new way of functional gypsum fiberboard materials.

3. The high-titanium slag-based mineral slag cotton gypsum fiberboard material prepared by utilizing the high-titanium slag has double effects of adsorbing and photocatalytic degradation of formaldehyde, and efficiently utilizes titanium resources to adsorb, remove and purify the formaldehyde indoors.

Drawings

FIG. 1 is a photograph of a high titanium slag-based mineral wool fiber material object used in the present invention;

FIG. 2 is a photograph of a gypsum fiber board with adsorption and photocatalytic properties prepared by the present invention;

FIG. 3 is a schematic diagram of an experimental apparatus for photocatalytic degradation of formaldehyde under a simulated ultraviolet light source; (a) a photocatalytic experimental device; (b) single physical adsorption experimental apparatus.

Detailed Description

The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the present invention is not limited to the following embodiments.

The invention is further illustrated by the following figures and examples.

In each embodiment of the invention, the high titanium slag-based mineral cotton fiber is cotton-like fiber prepared by blowing molten high titanium slag through compressed air, and TiO in the molten high titanium slag₂The content is 22 to 25 percent; the average diameter of the high titanium slag-based mineral cotton fiber is 1.30-3.60 mu m, and the average length is 35-45 mm; as shown in fig. 1.

The building gypsum powder is alpha-type semi-hydrated gypsum powder.

The water is tap water.

Example 1

The components used for preparing 15g of the product of the invention and the mass ratio thereof are as follows:

high titanium slag-based mineral cotton fiber 10%

66.7 percent of building gypsum powder

23.3 percent of water

Placing the high-titanium slag-based slag cotton fiber in an ultrasonic cleaning machine for ultrasonic treatment for 1-2 h to remove slag balls on the surface of the slag cotton, cleaning and drying; weighing 1.5g of cleaned and dried high-titanium slag-based mineral cotton fiber, putting the high-titanium slag-based mineral cotton fiber into 10.0g of building gypsum powder, uniformly stirring to obtain a mixture, adding 3.5g of water into the mixture, and continuously and uniformly stirring to obtain slurry; then, the slurry was poured into a 7cm × 7cm × 1cm mold to prepare a wet plate blank. And (3) drying the wet blank at room temperature for 24 hours, then placing the wet blank in an electric heating air blast drying oven, and drying the wet blank at 110 ℃ for 2-3 hours to form the gypsum fiberboard with adsorption and photocatalytic performance.

Example 2

high titanium slag-based mineral cotton fiber 6.7%

66.7 percent of building gypsum powder

26.6 percent of water

Placing the high-titanium slag-based slag wool fiber in an ultrasonic cleaning machine for ultrasonic treatment for 1-2 hours to remove slag balls on the surface of the slag wool; weighing 1.0g of cleaned and dried high-titanium slag-based mineral cotton fiber, putting the high-titanium slag-based mineral cotton fiber into 10.0g of building gypsum powder, uniformly stirring to obtain a mixture, adding 4.0g of water into the mixture, and continuously and uniformly stirring to obtain slurry; then, the slurry was poured into a 7cm × 7cm × 1cm mold to prepare a wet plate blank. And (3) drying the wet blank at room temperature for 24 hours, then placing the wet blank in an electric heating air blast drying oven, and drying the wet blank at 110 ℃ for 2-3 hours to form the gypsum fiberboard with adsorption and photocatalytic performance.

Example 3

3.3 percent of high titanium slag-based mineral cotton fiber

66.7 percent of building gypsum powder

30 percent of water

Placing the high-titanium slag-based slag wool fiber in an ultrasonic cleaning machine for ultrasonic treatment for 1-2 hours to remove slag balls on the surface of the slag wool; weighing 0.5g of cleaned and dried high-titanium slag-based mineral cotton fiber, putting the high-titanium slag-based mineral cotton fiber into 10g of building gypsum powder, uniformly stirring to obtain a mixture, adding 4.5g of water into the mixture, and continuously and uniformly stirring to obtain slurry; then, the slurry was poured into a 7cm × 7cm × 1cm mold to prepare a wet plate blank. And (3) drying the wet blank at room temperature for 24 hours, then placing the wet blank in an electric heating air blast drying oven, and drying the wet blank at 110 ℃ for 2-3 hours to form the gypsum fiberboard with adsorption and photocatalytic performance. The prepared gypsum fiber board with adsorption and photocatalytic performance prepared in this example is shown in fig. 2.

Example 4

In example 4, the components used for preparing the product of the invention and the mass ratio thereof are as follows: 3% of high titanium slag-based mineral cotton fiber; 68% of building gypsum powder; 29% of water; the other preparation process is the same as example 3.

3 percent of high titanium slag-based mineral cotton fiber

66.7 percent of building gypsum powder

30.3 percent of water

Placing the high-titanium slag-based slag wool fiber in an ultrasonic cleaning machine for ultrasonic treatment for 1-2 hours to remove slag balls on the surface of the slag wool; weighing 0.45g of cleaned and dried high-titanium slag-based mineral cotton fiber, putting the high-titanium slag-based mineral cotton fiber into 10.0g of building gypsum powder, uniformly stirring to obtain a mixture, adding 4.55g of water into the mixture, and continuously and uniformly stirring to obtain slurry; then, the slurry was poured into a 7cm × 7cm × 1cm mold to prepare a wet plate blank. And (3) drying the wet blank at room temperature for 24 hours, then placing the wet blank in an electric heating air blast drying oven, and drying the wet blank at 110 ℃ for 2-3 hours to form the gypsum fiberboard with adsorption and photocatalytic performance.

Example 5

In example 5, the components used for preparing the product of the invention and the mass ratio thereof are as follows: 3% of high titanium slag-based mineral cotton fiber; 65% of building gypsum powder; 32% of water; the other preparation process is the same as example 3.

Example 6

In example 6, the components used for preparing the product of the invention and the mass ratio thereof are as follows: 10% of high titanium slag-based mineral cotton fiber; 68% of building gypsum powder; 22% of water; the other preparation process is the same as example 3.

Test example 1

The performance of the gypsum fiber board with adsorption and photocatalytic performances prepared by the invention is tested.

The gypsum fiber board with photocatalytic performance of the embodiment 1 to 4 is subjected to a formaldehyde photocatalytic degradation performance test, and the process is as follows:

a formaldehyde solution with the concentration of 8 mug/L is prepared by using a 37-40% formaldehyde analytical pure solution as a reaction solution. The photocatalytic experiment was carried out in a light-shielded closed experimental apparatus shown in FIG. 3. The gypsum fiber board with adsorption and photocatalytic performance of the examples 1 to 4 was cut into 1cm × 1cm × 1cm cubes, placed in a quartz glass bottle, added with 400ml of formaldehyde solution with a concentration of 8 μ g/L, and reacted with an ultraviolet light source at room temperature. Wherein the ultraviolet light source in the device shown in FIG. 3(a) adopts 10 ultraviolet lamp tubes (15W, wavelength 254nm) with the same specification arranged in pairs at two sides to ensure that the gypsum fiber board uniformly irradiates ultraviolet light with the ultraviolet light irradiation intensity of 2.5mW/cm²The suspension state of the gypsum fiber board in the bottle is maintained by magnetic stirring. In the experiment, samples are taken every 1h, and the formaldehyde concentration in the reacted solution is measured by adopting a phenol reagent spectrophotometry, so that the formaldehyde removal efficiency of the gypsum fiber board with adsorption and photocatalytic performances is calculated.

In addition, four sets of single physical adsorption experiments (fig. 3 (b)) were set to be performed simultaneously with the photocatalytic experiment under the light-shielding condition, and the gypsum fiber sheets having adsorption and photocatalytic performances of examples 1 to 4 were cut into 1cm × 1cm × 1cm square pieces and placed in a narrow-mouth brown bottle. Except no ultraviolet irradiation, the components proportion of the gypsum fiber board, the concentration of formaldehyde solution, the sampling time and the test method of the concentration of formaldehyde are all consistent with those of the photocatalysis experiment. The difference value of the photocatalytic degradation experiment and the single physical adsorption experiment result is the photocatalytic degradation rate of the gypsum fiber board to formaldehyde.

TABLE 1 removal of formaldehyde from gypsum fiberboard material having photocatalytic properties (%)

As can be seen from Table 1, the formaldehyde adsorption removal rate increases with the mass percentage of the high titanium slag-based slag wool; in the photocatalysis experiment, the total removal rate is reduced along with the increase of the mass percentage of the high-titanium slag-based slag wool, so the photocatalytic degradation rate shows the trend of reducing along with the increase of the mass percentage of the high-titanium slag-based slag wool. Along with the increase of the mass percentage of the high-titanium slag-based mineral wool, the content of the formaldehyde-adsorbing components of the high-titanium slag-based mineral wool gypsum board is increased, the adsorption point positions provided by the high-titanium slag-based mineral wool gypsum board are increased, the high-titanium slag-based mineral wool gypsum board is favorable for adsorbing formaldehyde, and therefore the adsorption removal rate is increased accordingly. From the analysis of the photocatalytic mechanism, it is known that the photocatalytic degradation of formaldehyde is related to the number of electron-hole pairs generated by the catalyst. Although increasing the mass percentage of high titanium slag-based slag wool in gypsum board theoretically increases the number of electron-hole pairs produced. And the high-titanium slag-based mineral wool is mixed in the high-titanium slag-based mineral wool gypsum board, when the volume of the high-titanium slag-based mineral wool gypsum board is not changed, the mass percentage of the high-titanium slag-based mineral wool is increased, so that the high-titanium slag-based mineral wool has poor dispersibility in the high-titanium slag-based mineral wool gypsum board, and agglomeration occurs, so that a part of the high-titanium slag-based mineral wool cannot irradiate ultraviolet light, the number of electron-hole pairs generated by the high-titanium slag-based mineral wool is reduced, and the photocatalytic degradation rate is reduced. Therefore, the gypsum board with 3-10% of high titanium slag-based mineral wool fiber content has the best total formaldehyde removal effect.

The gypsum fiber board prepared in the embodiment of the invention performs resource utilization on the high-titanium slag-based mineral wool, wherein a perovskite phase (CaTiO)₃) Has photocatalysis performance, and the prepared high titanium slag-based mineral slag cotton gypsum fiberboard material has double effects of adsorbing and degrading formaldehyde through photocatalysis. At room temperatureThe high titanium slag-based slag cotton gypsum board only containing 3 percent of high titanium slag-based slag cotton has the illumination intensity of 2.5mW/cm²Under the irradiation of ultraviolet light, the total removal rate of formaldehyde solution with the concentration of 8.0 mu g/L can reach 25.79 percent, wherein the photocatalytic degradation rate is 10.84 percent, which accounts for 42.03 percent of the total removal rate, and the effect is very obvious.

Claims

1. A gypsum fiberboard with adsorption and photocatalytic performances is characterized by being prepared from the following raw materials in percentage by weight:

3-10% of high-titanium slag-based mineral cotton fiber

65-68% of building gypsum powder

22% -32% of water;

the preparation method of the gypsum fiberboard with adsorption and photocatalytic properties comprises the following steps:

(1) ultrasonically cleaning the high-titanium slag-based mineral cotton fiber, removing slag balls, cleaning and drying;

(5) drying the wet blank at room temperature in the air, and drying to form a gypsum fiberboard with adsorption and photocatalytic performance;

the high titanium slag-based mineral cotton fiber is cotton-like fiber prepared by blowing molten high titanium slag through compressed air, wherein TiO in the molten high titanium slag₂The content is 22% -25%; the average diameter of the high-titanium slag-based mineral cotton fiber is 1.30-3.60 mu m, and the average length of the high-titanium slag-based mineral cotton fiber is 35-45 mm.

2. The gypsum fiberboard of claim 1, wherein the building gypsum powder is alpha hemihydrate gypsum powder.

3. The gypsum fiberboard of claim 1, wherein the water is tap water.

4. A method for preparing the gypsum fiberboard with adsorption and photocatalytic properties according to claim 1, comprising the following steps:

5. The preparation method of the gypsum fiberboard with adsorption and photocatalytic properties as claimed in claim 1, wherein the ultrasound in step (1) is performed for 1-2 hours, and the slag balls on the surface of the mineral wool are removed according to the principle that the gravity and the resistance of the slag balls and the fibers are different when the slag balls and the fibers move in water.

6. The method for preparing the gypsum fiberboard with adsorption and photocatalytic properties according to claim 1, wherein the wet blank obtained in the step (5) is dried at 110 ℃ for 2-3 hours after being air-dried at room temperature for 24 hours.

7. Use of the gypsum fiberboard with adsorption and photocatalytic properties as described in claim 1 in the preparation and production of green ecological environment-friendly building materials.

8. The application of claim 7, wherein the green ecological environment-friendly building material is a building material capable of adsorbing and photocatalytic degrading indoor formaldehyde gas and effectively improving indoor air quality.