A method for preparing formaldehyde-removing high-strength gypsum powder, its products and applications

Abstract

This invention discloses a method for preparing formaldehyde-removing high-strength gypsum powder, its product, and its applications. The preparation method includes: (1) mixing zinc salt, titanium salt, organic ligand, organic solvent, and additives, and then performing heat treatment; (2) performing solid-liquid separation on the product of the heat treatment in step (1), then soaking it in an organic solvent, washing, and drying to obtain a metal coordination compound; (3) mixing the metal coordination compound, polyvinyl alcohol, desulfurized gypsum powder, and water, then performing solid-liquid separation, washing, drying, and performing a first heat treatment and a second heat treatment to obtain the formaldehyde-removing high-strength gypsum powder. The high-strength gypsum powder prepared by this invention has a complete morphology, excellent physicochemical and mechanical properties, and possesses photocatalytic formaldehyde decomposition function, making it widely applicable.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building gypsum powder preparation, and particularly relates to a preparation method of net-aldehyde type high-strength gypsum powder, a product thereof and application. BACKGROUND

[0002] Desulfurization gypsum is a byproduct of flue gas desulfurization in coal-fired power plants. Coal-fired power plants use the wet limestone-limestone gypsum method to absorb sulfur dioxide to avoid air pollution by sulfur dioxide, and ultimately generate a byproduct, desulfurization gypsum. With the increase in the flue gas desulfurization treatment capacity of coal-fired power plants, the production of desulfurization gypsum also increases. The accumulation of a large amount of desulfurization gypsum not only occupies land resources, but also easily forms secondary pollution. Therefore, efficient use of desulfurization gypsum to turn waste into treasure has attracted widespread attention. At present, converting desulfurization gypsum into high-strength gypsum to improve its initial setting time and mechanical strength is a good utilization method. However, the crystal type control in the conversion process and the enhancement of the functionality of high-strength gypsum need to be improved and enhanced.

[0003] CN111620642A discloses a net-aldehyde gypsum board and a preparation method thereof. The method mixes and stirs water and modified starch uniformly to obtain wet material, mixes and stirs formaldehyde reagent and zeolite uniformly to obtain an additive, and then mixes and stirs the wet material and the additive uniformly to obtain a premix. The method adds plaster of Paris to the premix to obtain a uniformly mixed slurry, and performs shaping and drying until the slurry is dried to a constant weight, thereby obtaining the net-aldehyde gypsum board. The invention achieves the effect of removing formaldehyde through the chemical reaction between the formaldehyde reagent and formaldehyde. However, as the formaldehyde reagent continuously undergoes chemical reactions, it is gradually consumed and eventually loses the ability to purify formaldehyde. Moreover, the organic ammonia formaldehyde purifying agent itself has certain indoor pollution, which can cause new pollution before reacting with formaldehyde.

[0004] CN105854863A discloses a preparation method of a C / ZnO / TiO2 composite nano photocatalytic material. The method uses a hydrothermal method, takes tetra-n-butyl titanate as a raw material, and takes cetyltrimethylammonium bromide as a surfactant. The tetra-n-butyl titanate is hydrolyzed and stirred at room temperature to obtain a titanium dioxide precursor through hydrothermal treatment, filtration and drying. Second, soluble zinc nitrate and terephthalic acid are dissolved in N,N-dimethylformamide, and MOF-5 is obtained through ultrasonic dispersion and hydrothermal treatment. Finally, the obtained MOF-5 is mixed with the titanium dioxide powder, and the C / ZnO / TiO2 composite nano photocatalytic material is obtained through high-temperature treatment. The material has certain photocatalytic performance, but the titanium dioxide powder and the MOF-5 are only mechanically mixed together. In the high-temperature treatment process, titanium cannot be organically dispersed in the carbon carrier, the effect is not high, and the material is easy to fall off, which is not conducive to long-term use. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a preparation method of high-strength gypsum powder with formaldehyde removal function, a product thereof and an application thereof.The method is simple and green.The high-strength gypsum powder prepared by the method has complete morphology, excellent physicochemical and mechanical properties, and a function of photocatalytic decomposition of formaldehyde, and has a wide range of applications.

[0006] The first aspect of the present application provides a preparation method of high-strength gypsum powder with formaldehyde removal function, comprising the following steps:

[0007] (1) mixing zinc salt, titanium salt, organic ligand, organic solvent and additive, and performing heat treatment;

[0008] (2) performing solid-liquid separation on the product of step (1) heat treatment, then soaking with organic solvent, washing, drying to obtain a metal coordination compound;

[0009] (3) mixing the metal coordination compound, polyvinyl alcohol, desulfurized gypsum powder and water, then performing solid-liquid separation, washing, drying, performing first heat treatment and second heat treatment to obtain the high-strength gypsum powder with formaldehyde removal function.

[0010] Further, in step (1), the zinc salt is selected from at least one of zinc nitrate hexahydrate, zinc acetate dihydrate and zinc sulfate tetrahydrate, preferably zinc nitrate hexahydrate.

[0011] Further, in step (1), the titanium salt is selected from at least one of titanium tetrachloride, titanium acetate and titanium sulfite, preferably titanium tetrachloride.

[0012] Further, in step (1), the organic ligand is selected from at least one of trimesic acid, terephthalic acid and pyromellitic acid, preferably pyromellitic acid.

[0013] Further, in step (1), the organic solvent is selected from at least one of anhydrous ethanol, anhydrous methanol and N,N-dimethylformamide, preferably N,N-dimethylformamide.

[0014] Further, in step (1), the additive is selected from at least one of triethanolamine, polyetheramine D-230 and dimethylacetamide, preferably polyetheramine D-230.

[0015] Further, in step (1), the mass ratio of the zinc salt, titanium salt, organic ligand, organic solvent and additive is 1:(0.28-1.87):(0.15-0.58):(15-70):(0.75-2.87), preferably 1:(0.45-0.79):(0.2-0.4):(25-40):(1.15-1.93).

[0016] Further, in step (1), the heat treatment temperature is 75-150°C, preferably 90-130°C, and the heat treatment time is 8-24h, preferably 12-16h.

[0017] Further, in step (1), the mixing is carried out at room temperature, and the mixing can be carried out by stirring at a speed of 300-500rpm for 25-45min. The reaction vessel is a stainless steel reaction vessel with a polytetrafluoroethylene lining.

[0018] Further, in step (2), the organic solvent is selected from at least one of dichloromethane, anhydrous methanol, and acetonitrile, preferably dichloromethane.

[0019] Further, in step (2), the organic solvent is selected from at least one of dichloromethane, anhydrous methanol, and acetonitrile, preferably dichloromethane.

[0020] Further, in step (2), the drying temperature is 100-200°C, preferably 120-160°C, and the drying time is 10-24h, preferably 14-18h.

[0021] Further, in step (2), the product of step (1) is cooled to room temperature before solid-liquid separation. The room temperature is 20-30°C. The solid-liquid separation and washing can be carried out by conventional methods in the art, such as filtration for solid-liquid separation and repeated washing with anhydrous ethanol until neutral.

[0022] Further, in step (3), the polyvinyl alcohol is selected from any one of water-soluble polyvinyl alcohols, preferably polyvinyl alcohol 17-92.

[0023] Further, in step (3), the desulfurized gypsum powder is desulfurized gypsum produced by a flue gas desulfurization system in a power plant, which is washed with tap water, dried at 50-60°C for 5-6h, and sieved through a 200-mesh sieve to obtain desulfurized gypsum powder.

[0024] Further, in step (3), the mass ratio of the metal complex compound, polyvinyl alcohol, desulfurized gypsum powder, and water is 1:(0.25-0.75):(50-230):(30-170), preferably 1:(0.45-0.6):(100-150):(50-140).

[0025] Further, in step (3), the drying temperature is 80-120°C, preferably 95-110°C, and the drying time is 12-36h, preferably 18-24h.

[0026] Further, after drying, the temperature is decreased to room temperature, and then the first heat treatment is performed.

[0027] Further, in step (3), the first heat treatment temperature is 140-200°C, preferably 160-180°C, the first heat treatment time is 3-10h, preferably 5-8h; the second heat treatment temperature is 280-420°C, preferably 330-370°C, and the second heat treatment time is 1-7h, preferably 2.5-5h.

[0028] Further, in step (3), the temperature increasing rate from room temperature to the first heat treatment temperature is 2.5-6.5°C / min, preferably 3.5-5°C / min, and the temperature increasing rate from the first heat treatment temperature to the second heat treatment temperature is 3-10°C / min, preferably 5-7°C / min.

[0029] Further, in step (3), the first heat treatment and the second heat treatment are performed under inert carrier gas. The inert carrier gas is selected from any one of high-purity nitrogen, high-purity helium and high-purity argon, and the mass of the metal coordination compound to the carrier gas flow rate is 1g: (4-8mL / min).

[0030] Further, in step (3), the mixing is performed at room temperature, and the mixing can be performed by stirring. The room temperature is 20-30°C, and the stirring speed is 500-800rpm for 20-40min.

[0031] Further, in step (3), the solid-liquid separation and washing can be performed by conventional methods in the art, for example, the solid-liquid separation can be performed by filtration, and the washing can be performed by water washing.

[0032] Further, in step (3), the material obtained after drying is placed in a tube furnace for heat treatment.

[0033] The second aspect of the present application provides the net aldehyde type high-strength gypsum powder prepared by the above preparation method.

[0034] Further, the net aldehyde type high-strength gypsum powder is needle-shaped, and the average particle size is 2-4μm, as characterized by a scanning electron microscope.

[0035] Further, the specific surface area of the net aldehyde type high-strength gypsum powder is 87-105m 2 2 ​ / g, the micropore volume is 0.28cm 3 / g~0.35cm 3 / g.

[0036] Further, the net aldehyde type high-strength gypsum powder has 2h flexural strength of 7.5MPa~9.5MPa, 2h compressive strength of 35MPa~40MPa, and dry compressive strength of 65MPa~80MPa.

[0037] The third aspect of the present application provides the application of the net aldehyde type high-strength gypsum powder prepared by the preparation method in the technical field of indoor formaldehyde purification of buildings.

[0038] Further, the net aldehyde type high-strength gypsum powder is used in the conditions of normal temperature, normal pressure and illumination for indoor formaldehyde purification of buildings.

[0039] Compared with the prior art, the present application has the following beneficial effects:

[0040] (1) The net aldehyde type high-strength gypsum powder is obtained by adopting the mode of co-heat treatment of metal coordination compound and desulfurized gypsum powder, in the heat treatment process, the metal coordination compound is carbonized and polycondensed to become high specific surface area activated carbon with photocatalytic active center, which is interwoven with gypsum powder crystals and is not easy to fall off; at the same time, the metal components in the activated carbon can induce the desulfurized gypsum powder crystals to grow into alpha soluble anhydrous high-strength gypsum powder in the dehydration and crystal transformation process, that is, the crystal structure of the gypsum powder is effectively controlled, and the obtained high-strength gypsum powder has high mechanical strength.

[0041] (2) The net aldehyde type high-strength gypsum powder prepared by the present application has high specific surface area, especially micropore volume, which can effectively adsorb small molecular organic gases such as formaldehyde, improve the photocatalytic reaction efficiency, and enhance the targeted processing capacity of the gypsum powder for formaldehyde.

[0042] (3) In the co-heat treatment stage of the metal coordination compound and the desulfurized gypsum powder, polyvinyl alcohol is added, on the one hand, the polyvinyl alcohol can obtain polymers with conjugated diene structure after pyrolysis, thereby improving the formaldehyde adsorption efficiency, and on the other hand, the conjugated diene structure can also constrain the growth space of the gypsum crystals in the heat treatment process, thereby ensuring that the gypsum crystals have a complete needle-like structure. The complete morphology means that the gypsum crystals do not have a large number of broken or broken phenomena under scanning electron microscope observation. BRIEF DESCRIPTION OF DRAWINGS

[0043] Fig. 1 The scanning electron microscope photo of the net aldehyde type high-strength gypsum prepared in Example 1;

[0044] Fig. 2 The scanning electron microscope photo of the net aldehyde type high-strength gypsum prepared in Comparative Example 3;

[0045] Fig. 3 The scanning electron microscope photos of the net aldehyde type high-strength gypsum prepared for Comparative Example 5 are shown in the following. DETAILED DESCRIPTION

[0046] The preparation method and effects of the net aldehyde type high-strength gypsum powder of the present application are further illustrated by the following examples. The examples are implemented on the premise of the technical solutions of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

[0047] In the following examples, the experimental methods are all conventional methods in the art unless otherwise specified. The experimental materials used in the following examples are all purchased from conventional biochemical reagent stores unless otherwise specified.

[0048] In the present application, the Hitachi S-4700 field emission scanning electron microscope (SEM) made in Japan is used to observe the morphology and particle size of the gypsum powder.

[0049] In the present application, the 3H-2000PM2 specific surface tester made by Beijing Bessier Instrument Co., Ltd. is used to determine the specific surface area and pore volume of the gypsum powder. Before testing, the sample is subjected to vacuum degassing treatment at 373K, and the nitrogen adsorption-desorption isotherm curve is tested at 77K, and the specific surface area and pore volume of the sample are analyzed by the BET method.

[0050] In the present application, the XDL 230 X-ray fluorescence spectrometer (XRF) made by Fischer Company in Germany is used to quantitatively analyze the content of each element in the gypsum powder.

[0051] In the present application, the 2h bending resistance, 2h compression resistance and dry compression resistance are all determined according to the standard JC / T 2038-2010.

[0052] In the present application, the formaldehyde removal rate is determined according to the standard JCT 1074-2008 “Indoor air purification function coating material purification performance standard”.

[0053] In the following examples, the desulfurization gypsum powder is desulfurization gypsum produced by the flue gas desulfurization system of a power plant, washed with tap water, dried at 50℃-60℃ for 5h-6h, and obtained by passing through a 200 mesh screen.

[0054] Example 1

[0055] Take 60.5 g of zinc nitrate hexahydrate, 37.8 g of titanium tetrachloride, 17 g of pyromellitic acid and 80 g of polyetheramine D-230 to dissolve in 2000 g of N,N-dimethylformamide, uniformly stirred at 25°C and 400 rpm for 35 min, pour into a reaction kettle with a polytetrafluoroethylene lining, transfer to an oven, heat treat the reaction at 110°C for 14 h, after the heat treatment reaction is completed, take out the reaction kettle, air dry to 25°C and open the reaction kettle, filter, soak in dichloromethane at 55°C for 12 h, then rinse repeatedly with anhydrous ethanol until neutral, transfer to a drying oven, dry at 140°C for 16 h, and obtain a metal coordination compound. Take 10 g of the metal coordination compound, 5 g of polyvinyl alcohol 17-92, 1200 g of desulfurized gypsum powder and 850 g of water, mix at 25°C and 650 rpm for 30 min, filter, wash with tap water, dry at 105°C for 20 h, then reduce to room temperature 25°C, place the material cooled to room temperature in a tube furnace, under the protection of 60 mL / min high-purity nitrogen, two-stage heat treatment, the first stage is to raise the temperature from 25°C to 170°C at a rate of 4°C / min, and stay at 170°C for 6 h, the second stage is to raise the temperature from 170°C to 350°C at a rate of 6°C / min, and stay at 350°C for 3.5 h, to obtain a net aldehyde type high-strength gypsum powder. The morphology and particle size of the gypsum powder crystal are observed by using a Japanese Hitachi S-4700 field emission scanning electron microscope (SEM), as shown in FIG. 1. Fig. 1 .

[0056] Example 2

[0057] Take 60.5 g of zinc nitrate hexahydrate, 27.22 g of titanium tetrachloride, 12 g of pyromellitic acid and 69.57 g of polyetheramine D-230 dissolved in 1512.5 g of N,N-dimethylformamide, uniformly stirred at 20°C and 300 rpm for 25 min, poured into a reaction kettle with a polytetrafluoroethylene lining, transferred to an oven, heat treated at 90°C for 12 h, after the heat treatment reaction is completed, take out the reaction kettle, air to 20°C and open the reaction kettle, filter, soak in dichloromethane at 50°C for 10 h, then repeatedly rinse with anhydrous ethanol to neutral, transfer to a drying box, dry at 120°C for 14 h, to obtain a metal coordination compound. Take 10 g of metal coordination compound, 4.5 g of polyvinyl alcohol 17-92, 1000 g of desulfurized gypsum powder and 500 g of water, mix at 20°C and 500 rpm for 20 min, filter, tap water wash, dry treatment at 95°C for 18 h, then reduce to room temperature 25°C, the material after reducing to room temperature is placed in a tube furnace, under the protection of 40 mL / min high-purity nitrogen, two-stage heat treatment, the first stage is raised from 25°C to 160°C at a rate of 3.5°C / min, and stays at 160°C for 5 h, the second stage is raised from 160°C to 330°C at a rate of 5°C / min, and stays at 330°C for 2.5 h, to obtain a net aldehyde type high-strength gypsum powder.

[0058] Example 3

[0059] Take 60.5 g of zinc nitrate hexahydrate, 27.22 g of titanium tetrachloride, 12 g of pyromellitic acid and 69.57 g of polyetheramine D-230 dissolved in 1512.5 g of N,N-dimethylformamide, uniformly stirred at 20°C and 300 rpm for 25 min, poured into a reaction kettle with a polytetrafluoroethylene lining, transferred to an oven, heat treated at 90°C for 12 h, after the heat treatment reaction is completed, take out the reaction kettle, air to 20°C and open the reaction kettle, filter, soak in dichloromethane at 50°C for 10 h, then repeatedly rinse with anhydrous ethanol to neutral, transfer to a drying box, dry at 120°C for 14 h, to obtain a metal coordination compound. Take 10 g of metal coordination compound, 4.5 g of polyvinyl alcohol 17-92, 1000 g of desulfurized gypsum powder and 500 g of water, mix at 20°C and 500 rpm for 20 min, filter, tap water wash, dry treatment at 95°C for 18 h, then reduce to room temperature 25°C, the material after reducing to room temperature is placed in a tube furnace, under the protection of 40 mL / min high-purity nitrogen, two-stage heat treatment, the first stage is raised from 25°C to 160°C at a rate of 3.5°C / min, and stays at 160°C for 5 h, the second stage is raised from 160°C to 330°C at a rate of 5°C / min, and stays at 330°C for 2.5 h, to obtain a net aldehyde type high-strength gypsum powder.

[0060] Example 4

[0061] The same as example 1, except that zinc acetate dihydrate is used instead of zinc nitrate hexahydrate, to obtain a neat aldehyde type high-strength gypsum powder.

[0062] Example 5

[0063] The same as example 1, except that titanium sulfite is used instead of titanium tetrachloride, to obtain a neat aldehyde type high-strength gypsum powder.

[0064] Example 6

[0065] The same as example 1, except that trimesic acid is used instead of pyromellitic acid, to obtain a neat aldehyde type high-strength gypsum powder.

[0066] Example 7

[0067] The same as example 1, except that absolute ethanol is used instead of N,N- dimethylformamide, to obtain a neat aldehyde type high-strength gypsum powder.

[0068] Example 8

[0069] The same as example 1, except that triethanolamine is used instead of polyetheramine D-230, to obtain a neat aldehyde type high-strength gypsum powder.

[0070] Example 9

[0071] The same as example 1, except that dimethylacetamide is used instead of polyetheramine D-230, to obtain a neat aldehyde type high-strength gypsum powder.

[0072] Example 10

[0073] The same as example 1, except that in the synthesis stage of the metal complexing compound, the temperature of the heat treatment is increased to 150°C and the time is reduced to 8h, to obtain a neat aldehyde type high-strength gypsum powder.

[0074] Example 11

[0075] The same as example 1, except that polyvinyl alcohol 0588 is used instead of polyvinyl alcohol 17-92, to obtain a neat aldehyde type high-strength gypsum powder.

[0076] Example 12

[0077] The same as example 1, except that in the two-stage heat treatment process, the temperature increase rate of the first stage is increased to 6.5°C / min, the first heat treatment temperature is increased to 200°C, and the residence time at the first heat treatment temperature is reduced to 3h, to obtain a neat aldehyde type high-strength gypsum powder.

[0078] Example 13

[0079] The same as example 1, except that the mass of titanium tetrachloride is reduced to 18.15g and the mass of pyromellitic acid is increased to 30.25g, to obtain a neat aldehyde type high-strength gypsum powder.

[0080] Example 14

[0081] The same as Example 1, except that the mass of polyvinyl alcohol, desulfurized gypsum powder and water is reduced to 2.5 g, 500 g and 300 g respectively, to obtain a neat aldehyde type high-strength gypsum powder.

[0082] Comparative Example 1

[0083] The same as Example 1, except that the polyvinyl alcohol is omitted, to obtain a neat aldehyde type high-strength gypsum powder. The morphology and particle size of the gypsum powder crystals are observed by using a Japanese Hitachi S-4700 field emission scanning electron microscope (SEM), as shown in Fig. 2 .

[0084] Comparative Example 2

[0085] The same as Example 1, except that in the preparation stage of the high-strength gypsum powder, the metal complexing compound is omitted, to obtain a neat aldehyde type high-strength gypsum powder.

[0086] Comparative Example 3

[0087] The same as Example 1, except that in the preparation stage of the high-strength gypsum powder, a one-step heat treatment is used instead of a two-stage heat treatment, i.e. the temperature is raised from 25°C to 350°C at a rate of 4°C / min, and the temperature is kept at 350°C for 6h, to obtain a neat aldehyde type high-strength gypsum powder. The morphology and particle size of the gypsum powder crystals are observed by using a Japanese Hitachi S-4700 field emission scanning electron microscope (SEM), as shown in Fig. 3 .

[0088] Comparative Example 4

[0089] According to the method described in CN105854863A, zinc nitrate and terephthalic acid are weighed in a mass ratio of 1:3, dissolved in N,N-dimethylformamide, and then subjected to magnetic stirring and ultrasonic dispersion. After that, the mixture is subjected to hydrothermal reaction at 160°C for 24h in a reaction kettle to obtain MOF-5. 2mL of titanium tetrabutoxide is added to 40mL of distilled water to hydrolyze and filter, and then 60mL of distilled water and 2mL of 0.1mol / L hexadecyl trimethyl ammonium bromide solution are added. The solution is adjusted to pH=3 with HCl:HNO3=1:2, and then subjected to hydrothermal reaction at 180°C in a constant temperature oven for 12h. After filtration, a titanium dioxide precursor is obtained. Then, the MOF-5 and the titanium dioxide precursor are mixed in a mass ratio of 1:1, and then subjected to high temperature treatment at 400°C in a muffle furnace for 2h to obtain a C / ZnO / TiO2 nano photocatalytic material.

[0090] The same as Example 1, except that an equal mass of the C / ZnO / TiO2 nano photocatalytic material is used instead of the metal complexing compound, to obtain a neat aldehyde type high-strength gypsum powder.

[0091] Test Example 1

[0092] The physicochemical properties of the net aldehyde type high-strength gypsum powder in the examples and comparative examples were determined, and the specific results are shown in Table 1.

[0093] Table 1 Performance of net aldehyde type high-strength gypsum prepared in examples and comparative examples

[0094]

[0095]

[0096] From Table 1, Figs. 1-3 It can be seen that the net aldehyde type high-strength gypsum prepared by the present application has good physicochemical properties and needle-like micro-morphology. The BET specific surface area and micropore volume of the sample of Example 1 are 105 m 2 / g and 0.35 cm 3 / g, respectively, while the BET specific surface area and micropore volume of the sample of the comparative example are generally lower than 60 m 2 / g and 0.20 cm 3 / g. Moreover, the sample of the example has a needle-like structure and has a relatively complete crystal structure, while the sample of the comparative example shows different shapes, especially the samples of Comparative Example 1 and Comparative Example 3, which show amorphous structure, i.e., the pore structure performance is affected. This is because in the present application, during the two-stage heat treatment process, the metal complex compound is carbonized and undergoes polycondensation reaction to become high-surface-activity carbon, and the metal components in the activated carbon act as a crystal agent to induce the growth of desulfurized gypsum powder crystals into α-soluble anhydrous high-strength gypsum powder during the dehydration and crystallization process, i.e., effectively regulating the crystal structure of the gypsum powder crystals; the addition of polyvinyl alcohol can constrain the growth space of the gypsum crystals during the heat treatment process, ensuring that they have a complete needle-like structure in morphology.

[0097] Test Example 2

[0098] The mechanical properties and formaldehyde removal rate of the net aldehyde type high-strength gypsum of the examples and comparative examples were determined, and the specific results are shown in Table 2.

[0099] Test conditions: A certain amount of gypsum powder was placed in a transparent and airtight glass reactor, formaldehyde vapor of a specified concentration was introduced, a tungsten lamp was used as a simulated light source at normal temperature and pressure, and the formaldehyde concentration in the reactor was measured after 24 h of continuous irradiation.

[0100] Table 2 Mechanical properties and formaldehyde removal performance of net aldehyde type high-strength gypsum

[0101]

[0102]

[0103] As can be seen from Table 2, the sample of the embodiment has higher mechanical properties and net aldehyde effect and durability. For the sample of Example 1, the formaldehyde removal rate still remains at 96.3% after one year, while the sample of Comparative Example 4, although having higher initial formaldehyde purification effect, the formaldehyde removal rate decreases from 80.5% to 70.2% after one year, that is, the purification durability is insufficient. This is because in the process of preparing the net aldehyde type high-strength gypsum powder, the metal coordination compound of the bimetallic center is first synthesized, and in the high-temperature treatment and carbonization stage, the active metal is organically embedded in the internal structure of the carbon carrier, and is not easy to fall off or lose, and can persistently play the photocatalytic reaction activity, that is, the formaldehyde purification durability is strong. In the preparation of the carbonized material stage of Comparative Example 4, only titanium dioxide is mechanically mixed with MOF-5, and after high-temperature calcination treatment, most of the titanium metal is deposited on the surface of the carbon material, and with the passage of time, separation and falling off and other phenomena are prone to occur, resulting in insufficient net aldehyde durability. At the same time, the net aldehyde type high-strength gypsum powder prepared by the present application adds polyvinyl alcohol, which can obtain a polymer with conjugated diene structure after pyrolysis, which also helps to improve the formaldehyde adsorption efficiency.

Claims

1. A method for preparing a high-strength aldehyde-free gypsum powder, comprising: (1) mixing a zinc salt, a titanium salt, an organic ligand, an organic solvent and an additive, and performing heat treatment; (2) performing solid-liquid separation on the product of the heat treatment in step (1), then soaking with an organic solvent, washing, drying to obtain a metal complex compound; (3) mixing the metal complex compound, polyvinyl alcohol, desulfurized gypsum powder and water, then performing solid-liquid separation, washing, drying, first heat treatment and second heat treatment to obtain the high-strength aldehyde-free gypsum powder; the additive is at least one selected from triethanolamine, polyetheramine D-230 and dimethylacetamide; in step (1), the mass ratio of the zinc salt, the titanium salt, the organic ligand, the organic solvent and the additive is 1: (0.28-1.87) : (0.15-0.58) : (15-70) : (0.75-2.87) ; in step (1), the heat treatment temperature is 75-150℃, and the heat treatment time is 8-24h; in step (3), the mass ratio of the metal complex compound, polyvinyl alcohol, desulfurized gypsum powder and water is 1: (0.25-0.75) : (50-230) : (30-170) ; in step (3), the first heat treatment temperature is 140-200℃, and the first heat treatment time is 3-10h; the second heat treatment temperature is 280-420℃, and the second heat treatment time is 1-7h. in step (1), the zinc salt is at least one selected from zinc nitrate hexahydrate, zinc acetate dihydrate and zinc sulfate tetrahydrate; and the titanium salt is at least one selected from titanium tetrachloride, titanium acetate and titanium sulfite; in step (1), the zinc salt is zinc nitrate hexahydrate, and the titanium salt is titanium tetrachloride; in step (1), the organic ligand is at least one selected from trimesic acid, terephthalic acid and pyromellitic acid; in step (1), the organic ligand is pyromellitic acid; in step (1), the organic solvent is at least one selected from anhydrous ethanol, anhydrous methanol and N, N-dimethylformamide; in step (1), the organic solvent is N, N-dimethylformamide; the additive is polyetheramine D-230; in step (1), the mass ratio of the zinc salt, the titanium salt, the organic ligand, the organic solvent and the additive is 1: (0.45-0.79) : (0.2-0.4) : (25-40) : (1.15-1.93) ; in step (1), the heat treatment temperature is 90-130℃, and the heat treatment time is 12-16h; in step (2), the organic solvent is at least one selected from dichloromethane, anhydrous methanol and acetonitrile; and / or, the organic solvent soaking temperature is 20-80℃, and the soaking time is 5-20h; and / or, the drying temperature is 100-200℃, and the drying time is 10-24h. ​ ​ ​ ​ ​ ​ ​ ​ 2. The production method according to claim 1, characterized by, ​ 3. The preparation method according to claim 2, characterized in that, ​ 4. The method of claim 1, wherein, ​ 5. The preparation method according to claim 4, characterized in that, ​ 6. The method of claim 1, wherein, ​ 7. The preparation method according to claim 6, characterized in that, ​ 8. The method of claim 1, wherein, ​ 9. The method of claim 1, wherein, ​ 10. The method of claim 1, wherein, ​ 11. The method of claim 1, wherein, ​ 12. The method of claim 11, wherein, In step (2), the organic solvent is dichloromethane; and / or, the soaking temperature of the organic solvent is 50-60 ℃, and the soaking time is 10-15 h; and / or, the drying temperature is 120-160 ℃, and the drying time is 14-18 h.

13. The method of claim 1, wherein, In step (3), the polyvinyl alcohol is selected from any one of water-soluble polyvinyl alcohols; and / or, the desulfurized gypsum powder is selected from desulfurized gypsum produced by a flue gas desulfurization system of a power plant, washed with tap water, dried at 50-60 ℃ for 5-6 h, and sieved through a 200-mesh sieve to obtain the desulfurized gypsum powder.

14. The method of claim 13, wherein, In step (3), the polyvinyl alcohol is polyvinyl alcohol 17-92.

15. The method of claim 1, wherein, In step (3), the mass ratio of the metal complex compound, the polyvinyl alcohol, the desulfurized gypsum powder, and the water is 1:(0.45-0.6):(100-150):(50-140).

16. The method of claim 1, wherein, In step (3), the drying temperature is 80-120 ℃, and the drying time is 12-36 h.

17. The method of claim 16, wherein the method further comprises, In step (3), the drying temperature is 95-110 ℃, and the drying time is 18-24 h.

18. The method of claim 16, wherein, In step (3), after drying, the temperature is lowered to room temperature, and then the first heat treatment is performed.

19. The method of claim 1, wherein, In step (3), the first heat treatment temperature is 160-180 ℃, and the first heat treatment time is 5-8 h; the second heat treatment temperature is 330-370 ℃, and the second heat treatment time is 2.5-5 h.

20. The method of claim 1, wherein, In step (3), the temperature is raised from room temperature to the first heat treatment temperature at a rate of 2.5-6.5 ℃ / min, and the temperature is raised from the first heat treatment temperature to the second heat treatment temperature at a rate of 3-10 ℃ / min.

21. The method of claim 20, wherein, In step (3), the temperature is raised from room temperature to the first heat treatment temperature at a rate of 3.5-5 ℃ / min, and the temperature is raised from the first heat treatment temperature to the second heat treatment temperature at a rate of 5-7 ℃ / min.

22. The method of claim 1, wherein, In step (3), the first heat treatment and the second heat treatment are performed under an inert carrier gas; the inert carrier gas is selected from any one of high-purity nitrogen, high-purity helium, and high-purity argon; and the mass of the metal complex compound to the flow rate of the carrier gas is 1 g:(4-8 mL / min).

23. The high-strength gypsum powder prepared by the preparation method of any one of claims 1-22.

24. The net-alkaline high-strength gypsum powder according to claim 23, characterized in that, The high-strength gypsum powder is needle-shaped, and has an average particle size of 2-4 μm.

25. The net-alkaline high-strength gypsum powder according to claim 23, characterized in that, The specific surface area of the net-aldehyde type high-strength gypsum powder is 87m 2 / g~105m 2 / g, the micropore volume is 0.28cm 3 / g~0.35cm 3 / g.

26. The net-alkaline high-strength gypsum powder according to claim 23, characterized in that, The high-strength gypsum powder has a 2-h flexural strength of 7.5-9.5 MPa, a 2-h compressive strength of 35-40 MPa, and a dry compressive strength of 65-80 MPa.

27. The use of the high-strength gypsum powder prepared by the preparation method of any one of claims 1-22 in purifying formaldehyde in a room of a building.

28. The use according to claim 27, characterized in that, The high-strength gypsum powder is used in purifying formaldehyde in a room of a building under the conditions of room temperature, normal pressure, and light.

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