Calcium hydroxide / natural zeolite composite humidity control material and preparation method thereof

Abstract

The present application relates to a kind of calcium hydroxide / natural zeolite composite humidity control material and its preparation method, belong to non-metallic mineral functional materials and inorganic humidity control material field.The natural zeolite of the present application is made into ore pulp by adding water, while according to the preset Ca (OH) 2 coating amount and the reaction molar ratio of NaOH and CaCl2 to react to generate Ca (OH) 2 NaOH and CaCl2 are weighed, and water is added to configure into respective uniform solution respectively;After that, NaOH solution and CaCl2 solution are added to natural zeolite ore pulp in parallel flow, and Ca (OH) 2 is uniformly precipitated and coated on the surface of natural zeolite particles;Prepared Ca (OH) 2 / natural zeolite composite powder suspension with certain liquid-solid ratio;Then Ca (OH) 2 / natural zeolite composite powder suspension is hydrothermally reacted;Finally, the hydrothermal reaction product is filtered, washed, dried and depolymerized, and the calcium hydroxide / natural zeolite composite humidity control material is prepared.The present application significantly improves the humidity control performance of natural zeolite, and the preparation method is energy-saving and green environmental protection, has greater application value and good application prospect in the field of building humidity control material.

Description

Technical Field

[0001] This invention relates to a calcium hydroxide / natural zeolite composite humidity-regulating material and its preparation method, belonging to the fields of non-metallic mineral functional materials and inorganic humidity-regulating materials. Background Technology

[0002] Most natural porous minerals possess advantages such as balanced moisture absorption and release properties, inexpensive and readily available raw materials, good chemical stability, and good compatibility with building materials. Environmental humidity has a significant impact on human health. With increasing attention to indoor humidity, mineral-based moisture-regulating materials have gained considerable attention in recent years as indoor building moisture-regulating materials. Currently reported mineral moisture-regulating materials include several natural non-metallic minerals such as diatomaceous earth, sepiolite, zeolite, clay, bentonite, and kaolin. Among them, kaolin, due to its platy structure and relatively few internal pores, has a relatively small moisture absorption and release capacity; bentonite, due to its significant swelling upon contact with water and shrinkage upon loss of water, presents challenges in ensuring workability as a primary material for building moisture regulation; diatomaceous earth, sepiolite, and clay-based natural minerals have well-developed pore structures and good moisture-regulating properties, but their natural resource abundance is relatively lower than that of kaolinite, bentonite, and zeolite. Natural zeolite not only has a well-developed original three-dimensional porous structure, stable physicochemical properties, and reversible water absorption, but also has a wide range of sources and low prices, giving it a significant advantage in the development of indoor building humidity-regulating materials.

[0003] However, most natural zeolites have a large number of micropores, which, while providing strong moisture absorption, are often clogged by impurities or occupied by water molecules due to long-term geological processes. This results in poor interconnectivity between the pores, leading to weak moisture release and overall poor humidity regulation. Furthermore, there are many types of natural zeolites, each exhibiting differences in humidity regulation properties and whiteness. Natural zeolites with weaker humidity regulation properties and lower natural whiteness face significant limitations in their application as humidity-regulating materials. Therefore, optimizing the humidity regulation properties and improving the whiteness of natural zeolites are crucial for their use as indoor humidity-regulating materials in buildings.

[0004] Patent CN105289482A discloses a method for preparing an inorganic humidity-regulating material using zeolite powder as raw material. The specific preparation method involves: first, ball milling the zeolite powder to a certain fineness, drying it, then treating it with an alkali solution of 0.8–1.5 mol / L NaOH, followed by filtration, washing until neutral, drying, and then calcining at 200–400°C for a certain time, followed by rapid cooling to room temperature to obtain the humidity-regulating material. While the humidity-regulating material prepared by this method has good moisture absorption and release properties, the preparation process generates highly alkaline waste liquid, increasing water treatment costs and difficulties, and the calcination process has high energy consumption. Patent CN103318909A discloses a method for improving the humidity-regulating performance of zeolite using microwave-assisted ammonium chloride. The zeolite powder treated by this method also has good humidity-regulating properties, but the preparation process uses ammonium salts, which pose a risk of ammonia release when used as a humidity-regulating material, especially for indoor buildings, under conditions of heating or increased indoor temperature.

[0005] This invention addresses the problems and shortcomings of existing natural zeolite-based inorganic composite humidity-regulating materials, and proposes a healthy and environmentally friendly natural zeolite composite humidity-regulating material and its preparation method based on the characteristics of natural zeolite minerals. This material can effectively improve the humidity-regulating performance of natural zeolite and enhance its whiteness. Summary of the Invention

[0006] The technical solution of this invention is as follows: First, a certain amount of natural zeolite is mixed with water to form a zeolite slurry. Simultaneously, NaOH and dihydrate CaCl2 are weighed according to a preset Ca(OH)2 coating amount and the reaction molar ratio of NaOH to CaCl2 to generate Ca(OH)2, and water is added to each to prepare their respective homogeneous solutions. Then, the NaOH solution and CaCl2 solution are added concurrently to the natural zeolite slurry, uniformly precipitating and coating Ca(OH)2 onto the surface of the natural zeolite particles, thus obtaining a Ca(OH)2 / natural zeolite composite powder suspension with a certain liquid-to-solid ratio. Next, the Ca(OH)2 / natural zeolite composite powder suspension undergoes a hydrothermal reaction. Finally, the hydrothermal reaction product is filtered, washed, dried, and depolymerized to obtain a calcium hydroxide / natural zeolite composite moisture-regulating material.

[0007] The preparation process of the calcium hydroxide / natural zeolite composite humidity-regulating material is as follows:

[0008] (1) Weigh a certain amount of natural zeolite powder, and calculate the required mass of NaOH and CaCl2 dihydrate according to the set amount of Ca(OH)2 coating and the reaction molar ratio of NaOH and CaCl2 to produce Ca(OH)2. Accurately weigh the corresponding mass of NaOH and CaCl2 dihydrate.

[0009] (2) Calculate the required amount of water to be added according to the liquid-solid ratio (3-6):1, and divide the measured amount of water into three equal parts. One part is mixed with the natural zeolite powder weighed in step (1) to form a uniform slurry, and the other two parts are mixed with the NaOH and CaCl2 dihydrate weighed in step (1) to form a uniform NaOH solution and a uniform CaCl2 solution, respectively.

[0010] (3) The NaOH homogeneous solution and CaCl2 homogeneous solution prepared in step (2) are added to the continuously stirred natural zeolite powder slurry using the parallel flow method to carry out the Ca(OH)2 precipitation and coating reaction;

[0011] (4) The Ca(OH)2 precipitate coating product obtained in step (3) is transferred to a hydrothermal reactor for hydrothermal reaction at a temperature of 140℃~170℃ and a time of 2h~5h.

[0012] (5) After cooling the hydrothermal reaction product obtained in step (4), filter, wash, dry, and depolymerize to obtain calcium hydroxide / natural zeolite composite humidity control material.

[0013] The Ca(OH)2 coating amount mentioned in the above technical solution is defined as: Ca(OH)2 coating amount = (theoretical mass of Ca(OH)2 produced by the reaction of NaOH and CaCl2) / mass of natural zeolite weighed; the liquid-solid ratio is defined as: liquid-solid ratio = mass of purified water / (theoretical mass of Ca(OH)2 + mass of natural zeolite).

[0014] The natural zeolite mentioned in the above-mentioned method for preparing calcium hydroxide / natural zeolite composite humidity-regulating material is one of powdered red zeolite, clinoptilolite, or mordenite, or a mixture thereof in any proportion, with a purity of ≥70% zeolite mineral content and a particle size distribution of D. 97 <100μm.

[0015] The NaOH solution and CaCl2 solution are prepared by dissolving industrial-grade NaOH and industrial-grade dihydrate CaCl2 in purified water, respectively.

[0016] The aforementioned calcium hydroxide / natural zeolite composite humidity-regulating material is characterized by a Ca(OH)2 mass content ≤20%, whiteness ≥82%, and a continuous 12-hour humidity regulation capacity (6-hour moisture absorption + 6-hour moisture release) ≥4.9%.

[0017] Compared with existing related technologies, this invention, through the coating of natural zeolite powder with Ca(OH)2 and the chemical fusion with the surface components of natural zeolite under hydrothermal conditions, uniformly generates amorphous calcium silicate gel (CaO·mSiO2·nH2O) on the surface. This results in two main improvements: firstly, it further expands the specific surface area and pore volume of the composite humidity-regulating material (Table 1). Most of the original micropores of the natural zeolite are expanded to mesopores of 2-50 nm after dissolution and coating. Secondly, it significantly increases the number of surface hydroxyl groups in the composite material (Table 2), resulting in a marked optimization of the pore structure and surface properties. Therefore, it significantly improves the humidity-regulating performance of the composite material and greatly enhances the whiteness of the natural zeolite. This makes it more valuable for applications in the field of building humidity-regulating materials. Furthermore, in the preparation method of the calcium hydroxide / natural zeolite composite humidity-regulating material of this invention, the hydrothermal reaction temperature is ≤170℃, the tail liquid is a neutral sodium chloride aqueous solution, and there are no other solid wastes. The entire process is energy-saving and environmentally friendly, with promising application prospects.

[0018] Table 1. Total pore volume, average pore diameter, and specific surface area of ​​natural red zeolite (NS) and calcium hydroxide / natural red zeolite (Ca(OH)2 / NS) of this invention.

[0019]

[0020] Table 2. Number of surface hydroxyl groups in natural red zeolite (NS) and the calcium hydroxide / natural red zeolite (Ca(OH)2 / NS) of this invention.

[0021] Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the preparation process of the calcium hydroxide / natural zeolite composite humidity-regulating material of the present invention.

[0023] Figure 2 The XRD patterns are of natural red zeolite (NS) and the calcium hydroxide / natural red zeolite (Ca(OH)2 / NS) composite humidity-regulating material of the present invention.

[0024] Figure 3 Infrared spectra of natural red zeolite (NS) and the calcium hydroxide / natural red zeolite (Ca(OH)2 / NS) composite humidity-regulating material of the present invention. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments. However, this is not intended to limit the present invention, and any equivalent substitutions made in the art based on the content of the present invention shall fall within the protection scope of the present invention.

[0026] Example 1:

[0027] (1) First weigh 100g of natural red zeolite powder (powder fineness is D). 97 =80μm, powder whiteness (blue light whiteness, the same below) is 89%, XRD quantitative analysis shows that the content of red zeolite mineral in natural red zeolite powder is 94%. The sample (labeled as NS) was added to a 500ml three-necked flask; and the predetermined Ca(OH)2 coating amount was 10%;

[0028] (2) Based on the weighed mass of natural red zeolite powder (100g) and the predetermined Ca(OH)2 coating amount (10%), the theoretical mass of Ca(OH)2 produced by the reaction of NaOH and CaCl2 is calculated to be 10g. Then, based on the reaction molar ratio of NaOH and CaCl2 to produce Ca(OH)2, the required masses of NaOH and CaCl2 dihydrate are calculated to be 10.81g and 19.86g, respectively. The corresponding masses of NaOH and CaCl2 dihydrate are weighed.

[0029] (3) Based on the weighed mass of natural red zeolite powder (100g) and the calculated theoretical mass of Ca(OH)2 (10g), calculate the required mass of water as 330g according to the liquid-solid ratio = 3:1, and accurately weigh the corresponding mass of water.

[0030] (4) Divide 330g of water into 3 equal parts. Mix one part with 100g of weighed natural red zeolite powder to form a uniform slurry. Mix the other two parts with 10.81g of NaOH and 19.86g of CaCl2 dihydrate to form a uniform NaOH solution and a uniform CaCl2 solution, respectively.

[0031] (5) Using the parallel flow method, slowly add the NaOH homogeneous solution and CaCl2 homogeneous solution prepared in step (4) to the homogeneous slurry prepared in step (4) which is under continuous stirring;

[0032] (6) After the uniform NaOH solution and uniform CaCl2 solution are added in parallel, the mixed slurry obtained in step (5) is quickly transferred to the hydrothermal reactor and the stirring is turned on. The hydrothermal reaction is carried out at a hydrothermal temperature of 170°C for 2 hours.

[0033] (7) After the hydrothermal reaction is complete, the slurry is cooled for a period of time, then filtered, washed, dried and depolymerized to obtain calcium hydroxide / natural red zeolite composite humidity conditioning material, and the sample is labeled as C / NS.

[0034] Example 2:

[0035] (1) First weigh 100g of natural clinoptilolite powder (powder fineness is D). 97=100μm, powder whiteness is 78%, XRD quantitative analysis shows that the clinoptilolite mineral content in natural clinoptilolite powder is 85%. The sample (labeled NC) was added to a 1000ml three-necked flask; and the predetermined Ca(OH)2 coating amount was 20%.

[0036] (2) Based on the weighed mass of natural clinoptilolite powder (100g) and the predetermined Ca(OH)2 coating amount (20%), the theoretical mass of Ca(OH)2 produced by the reaction of NaOH and CaCl2 is calculated to be 20g. Then, based on the reaction molar ratio of NaOH and CaCl2 to produce Ca(OH)2, the required masses of NaOH and CaCl2 dihydrate are calculated to be 21.62g and 39.73g, respectively. The corresponding masses of NaOH and CaCl2 dihydrate are weighed.

[0037] (3) Based on the weighed mass of natural clinoptilolite powder (100g) and the calculated theoretical mass of Ca(OH)2 (20g), calculate the required mass of water as 720g according to the liquid-solid ratio = 6:1, and accurately weigh the corresponding mass of water.

[0038] (4) Divide 720g of water into 3 equal parts. Mix one part with 100g of weighed natural clinoptilolite powder to form a uniform slurry. Mix the other two parts with 21.62g of weighed NaOH and 39.73g of CaCl2 dihydrate to form a uniform NaOH solution and a uniform CaCl2 solution, respectively.

[0039] (5) Using a parallel flow method, slowly add the NaOH homogeneous solution and CaCl2 homogeneous solution prepared in step (4) to the homogeneous slurry prepared in step (4) which is under continuous stirring;

[0040] (6) After the NaOH homogeneous solution and CaCl2 homogeneous solution are added in parallel, the mixed slurry obtained in step (5) is quickly transferred to the hydrothermal reactor and the stirring is turned on. The hydrothermal reaction is carried out at a hydrothermal temperature of 140℃ for 5 hours.

[0041] (7) After the hydrothermal reaction is complete, the slurry is cooled for a period of time, then filtered, washed, dried and depolymerized to obtain calcium hydroxide / natural clinoptilolite composite humidity conditioning material, and the sample is marked as C / NC.

[0042] Example 3:

[0043] (1) First weigh 100g of natural zeolite powder (powder fineness is D). 97 =75μm, powder whiteness is 75%, XRD quantitative analysis shows that the total mineral content of clinoptilolite and mordenite in the zeolite powder is 83%. The sample (labeled as NZ) was added to a 1000ml three-necked flask; and the predetermined Ca(OH)2 coating amount was 15%.

[0044] (2) Based on the weighed mass of natural zeolite powder (100g) and the predetermined Ca(OH)2 coating amount (15%), the theoretical mass of Ca(OH)2 produced by the reaction of NaOH and CaCl2 is calculated to be 15g. Then, based on the reaction molar ratio of NaOH and CaCl2 to produce Ca(OH)2, the required masses of NaOH and CaCl2 dihydrate are calculated to be 16.22g and 29.80g, respectively. The corresponding masses of NaOH and CaCl2 dihydrate are weighed.

[0045] (3) Based on the weighed mass of natural zeolite powder (100g) and the calculated theoretical mass of Ca(OH)2 (15g), calculate the required mass of water as 575g according to the liquid-solid ratio = 5:1, and accurately weigh the corresponding mass of water.

[0046] (4) Divide 575g of water into 3 equal parts. Mix one part with 100g of weighed natural zeolite powder to form a uniform slurry. Mix the other two parts with 16.22g of weighed NaOH and 29.80g of CaCl2 dihydrate to form a uniform NaOH solution and a uniform CaCl2 solution, respectively.

[0047] (5) Using the parallel flow method, slowly add the NaOH homogeneous solution and CaCl2 homogeneous solution prepared in step (4) to the homogeneous slurry prepared in step (4) which is under continuous stirring;

[0048] (6) After the uniform NaOH solution and uniform CaCl2 solution are added in parallel, the mixed slurry obtained in step (5) is quickly transferred to the hydrothermal reactor and the stirring is turned on. The hydrothermal reaction is carried out at a hydrothermal temperature of 160°C for 3 hours.

[0049] (7) After the hydrothermal reaction is complete, the slurry is cooled for a period of time, then filtered, washed, dried and depolymerized to obtain calcium hydroxide / natural zeolite composite humidity conditioning material, and the sample is labeled as C / NZ.

[0050] The 6-hour moisture absorption, 6-hour moisture release, continuous 12-hour moisture conditioning capacity, and powder whiteness of the composite humidity conditioning material samples C / NS, C / NC, and C / NZ prepared in Examples 1 to 3 above, as well as their respective control samples NS, NC, and NZ, were tested. The test results are shown in Table 3.

[0051] The testing procedures for the sample's 6-hour moisture absorption, 6-hour moisture release, and continuous 12-hour humidity conditioning were as follows:

[0052] Accurately weigh 1g of sample and place it in a flat glass weighing bottle, spreading it evenly. Then, dry it in a 105℃ oven until constant weight. Record the sample mass as m0. Next, place the sample in a high-humidity and low-humidity desiccator with constant temperature and humidity for moisture absorption and desorption performance testing. The high and low humidity conditions in the desiccator are obtained and maintained stably using saturated NaCl and MgCl2 aqueous solutions at the bottom, respectively. Maintaining a constant ambient temperature of 23℃, the relative humidity of the desiccator is 75% and 33%, respectively. Before performing the moisture absorption test, the dried sample is placed in a low-humidity desiccator with a relative humidity of 33% for 12 hours to achieve moisture equilibration. The sample mass after moisture equilibration is recorded as m0. e Then, the sample was quickly transferred to a high-humidity desiccator with a relative humidity of 75% for 6 hours of continuous moisture absorption, followed by a quick transfer to a low-humidity desiccator with a relative humidity of 33% for 6 hours of continuous moisture release. The mass m of the sample at different times t was recorded. t Then m6 is the mass of the sample after absorbing moisture for 6 hours in an environment with a relative humidity of 75%. 12 The mass of the sample is calculated after it has absorbed moisture for 6 hours at a relative humidity of 75% and then continuously dehumidified for 6 hours in a low-humidity desiccator at a relative humidity of 33%. The balance used for mass measurement must have an accuracy of at least 0.001 g. The 6-hour moisture absorption (a6), 6-hour moisture release (d6), and 12-hour conditioning (s) of the sample are also included. 12 Calculate according to (Equation 1), (Equation 2), and (Equation 3) respectively:

[0053]

[0054]

[0055] s 12 = a6 + d6 (Equation 3)

[0056] Table 3 shows the 6-hour moisture absorption, 6-hour moisture release, continuous 12-hour moisture conditioning capacity, and powder whiteness test results of the composite humidity-regulating material samples prepared in Examples 1 to 3 and their respective comparative samples.

[0057] sample <![CDATA[a6]]> <![CDATA[d6]]> <![CDATA[s 12 ]]> Whiteness C / NS 3.03％ 1.92％ 4.95％ 91％ NS 0.58％ 0.18％ 0.76％ 89％ C / NC 4.35％ 2.36％ 6.71％ 88％ NC 2.75％ 1.03％ 3.78％ 78％ C / NZ 4.01％ 2.08％ 6.09％ 85％ NZ 2.32％ 0.92％ 3.24％ 75％

Claims

1. A method for preparing a calcium hydroxide / natural zeolite composite humidity-regulating material, characterized in that: The calcium hydroxide / natural zeolite composite humidity-regulating material has a Ca(OH)2 content ≤20%, whiteness ≥82%, and a humidity-regulating capacity ≥4.9% after 12 hours. The method for preparing the calcium hydroxide / natural zeolite composite humidity-regulating material is characterized by comprising the following process steps: (1) Weigh a certain amount of natural zeolite powder, and calculate the required mass of NaOH and CaCl2 dihydrate according to the set amount of Ca(OH)2 coating and the reaction molar ratio of NaOH and CaCl2 to produce Ca(OH)2. Weigh the corresponding mass of NaOH and CaCl2 dihydrate. (2) Calculate the required amount of water to be added according to the liquid-solid ratio (3~6):1, and divide the measured amount of water into three equal parts. One part is mixed with the natural zeolite powder weighed in step (1) to form a uniform slurry, and the other two parts are mixed with the NaOH and CaCl2 dihydrate weighed in step (1) to form a uniform NaOH solution and a uniform CaCl2 solution, respectively. (3) The NaOH homogeneous solution and CaCl2 homogeneous solution prepared in step (2) are added to the continuously stirred natural zeolite powder slurry using the co-flow method to carry out the Ca(OH)2 precipitation and coating reaction; (4) The Ca(OH)2 precipitate coating product obtained in step (3) is transferred to a hydrothermal reactor for hydrothermal reaction at a temperature of 140℃~170℃ and a time of 2h~5h. (5) After cooling the hydrothermal reaction product obtained in step (4), filter, wash, dry, and depolymerize to obtain calcium hydroxide / natural zeolite composite humidity conditioning material.

2. The method for preparing a calcium hydroxide / natural zeolite composite humidity-regulating material according to claim 1, characterized in that, The natural zeolite is one of powdered red zeolite, clinoptilolite, or mordenite, or a mixture thereof in any proportion, with a purity of ≥70% zeolite mineral content and a particle size distribution of D97 <100μm.

3. The method for preparing a calcium hydroxide / natural zeolite composite humidity-regulating material according to claim 1, characterized in that, The NaOH solution and CaCl2 solution are prepared by dissolving industrial-grade NaOH and industrial-grade dihydrate CaCl2 in purified water, respectively.

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