A high-performance calcium silicate desiccant prepared by using glass furnace desulfurization waste residue and a preparation method thereof

Abstract

This invention discloses a high-performance calcium silicate desiccant prepared from desulfurization waste residue of a glass furnace and its preparation method, relating to the field of inorganic solid waste material treatment technology. The invention utilizes desulfurization waste residue generated from wet desulfurization of flue gas in a glass furnace as raw material. After pre-oxidation and acid washing to remove impurities, the residue is reacted with sodium silicate under hydrothermal conditions to obtain a calcium silicate desiccant with a specific surface area of ​​230-300 m². 2 / g, with a pore size distribution of 12~16 nm, exhibits a moisture absorption rate ≥19.5% after 24 h at 25 ℃ and 25% relative humidity, and ≥33% after 24 h at 50 ℃ and 50% relative humidity. After 5 cycles of use, the moisture absorption rate retention rate is ≥95%. Because the pre-oxidation oxidizes the sulfite in the desulfurization waste residue to sulfate, no SO2 gas is generated during the entire preparation process. It can be seen that the calcium silicate desiccant preparation method provided by this invention is green and environmentally friendly, and the prepared product has excellent performance.

Description

Technical Field

[0001] This invention relates to the field of inorganic solid waste material treatment technology, specifically to a high-performance calcium silicate desiccant prepared using desulfurization waste residue from glass furnaces and its preparation method. Background Technology

[0002] The glass industry is a high-energy-consuming and high-emission industry. Flue gas from glass furnaces contains a large amount of SO2, and wet desulfurization is one of the main flue gas purification technologies. During the wet desulfurization process in glass furnaces, a large amount of desulfurization waste is generated, mainly composed of calcium sulfate dihydrate (CaSO4·2H2O) and incompletely oxidized calcium sulfite (CaSO3). It also contains glass batch dust (such as quartz sand, soda ash, feldspar, etc.) carried by the flue gas, which contains considerable amounts of active SiO2, Al2O3, Na2O, and other components. Currently, the comprehensive utilization rate of desulfurization waste from glass furnaces is low, with most being disposed of through stockpiling or landfill. This not only occupies a large amount of land resources, but also risks the soluble salts and heavy metals from the waste seeping into the soil and groundwater, causing environmental pollution. Furthermore, calcium sulfite easily decomposes under acidic conditions to produce SO2 gas, posing a secondary pollution risk to the treatment and utilization of the waste. Therefore, developing clean and high-value utilization technologies for desulfurization waste from glass furnaces has significant environmental and economic benefits.

[0003] Calcium silicate materials, due to their unique mesoporous structure and excellent moisture absorption properties, have promising applications in the field of desiccants. In existing technologies, calcium silicate desiccants are mostly prepared using pure chemicals such as limestone and silicates as raw materials, employing chemical precipitation or sol-gel methods. However, their application is limited by their high production costs. The desulfurization waste residue from glass furnaces contains active SiO2 introduced from the glass batching materials, which may be used to prepare calcium silicate desiccants, reducing production costs at the raw material level. Furthermore, if this inherent silicon resource can be fully utilized during the preparation of calcium silicate desiccants, not only can the amount of added sodium silicate be reduced, but the synergistic utilization of calcium and silicon elements in the waste residue can also be achieved. However, the following problems still exist in the existing preparation methods for preparing calcium silicate desiccant using desulfurization waste residue from glass furnaces: (1) The impurities in the desulfurization waste residue are complex (iron, aluminum, magnesium oxides and calcium sulfite, etc.), and directly using it as a calcium source will affect the pore structure of calcium silicate; (2) Calcium sulfite in the desulfurization waste residue will release SO2 gas during acid treatment, causing secondary pollution; (3) The specific surface area and pore volume of the prepared calcium silicate material are limited, and the moisture absorption performance is difficult to meet the requirements of high-requirement application scenarios; (4) The desiccant has insufficient cycle stability, and its performance decays significantly after multiple adsorption and desorption.

[0004] Therefore, the preparation of calcium silicate desiccant from desulfurization waste residue in glass furnaces requires further improvement in order to achieve high-value utilization of desulfurization waste residue in glass furnaces and improve the performance of desiccant products. Summary of the Invention

[0005] This invention provides a high-performance calcium silicate desiccant prepared from desulfurization waste residue of glass furnaces and its preparation method, in order to solve the technical problems existing in the prior art, such as poor pore structure, heavy air pollution, poor moisture absorption performance, and insufficient cycle stability.

[0006] In a first aspect, the present invention provides a method for preparing a high-performance calcium silicate desiccant using desulfurization waste residue from a glass furnace, comprising the following steps: (1) Pre-oxidation treatment: Disperse the desulfurization waste residue of glass furnace in deionized water, add hydrogen peroxide solution, stir and react at 20~80 ℃ for 0.5~2 h to oxidize the sulfite in the desulfurization waste residue to sulfate; (2) Acid washing to remove impurities: The desulfurization waste residue of the glass furnace after oxidation is filtered, and the resulting filter cake is placed in 0.5~0.8mol / L oxalic acid solution and soaked at 60~80 ℃ for 0.5~2 h to remove metal oxide impurities. Then the filter cake obtained by filtration is washed and dried to obtain the purified CaSO4-SiO2 composite precursor. (3) Hydrothermal synthesis: The purified CaSO4-SiO2 composite precursor and sodium silicate are mixed at a mass ratio of 1:0.5~2.0. After mixing, the mixture is dispersed in a mixed solution of water and ethanol with a solid-liquid mass ratio of 1:5~20. The mixture is stirred at 20~60℃ for 8~24 h. Then the mixture is transferred to a hydrothermal reactor and hydrothermally reacted at 100~140℃ for 3~12 h. After the reaction is completed, the mixture is filtered, washed and dried to obtain the calcium silicate precursor. (4) Activation treatment: The obtained calcium silicate precursor is calcined at 200~250 ℃ for 2~8 h to obtain the high-performance calcium silicate desiccant.

[0007] In this invention, hydrogen peroxide is first used to pre-oxidize the desulfurization waste residue from the glass furnace, preventing calcium sulfite (CaSO3) from reacting with oxalic acid to generate SO2 gas during subsequent pickling: CaSO3 + H2C2O4 → CaC2O4 + SO2↑ + H2O. This step oxidizes calcium sulfite to calcium sulfate: CaSO3 + H2O2 → CaSO4 + H2O. The reaction conditions are mild, the reaction rate is fast, and the oxidation is thorough. Furthermore, the hydrogen peroxide decomposes to produce only water, without introducing new impurities. This pre-oxidation treatment eliminates the generation of SO2 gas during pickling at its source, achieving clean production. Then, oxalic acid solution is used to pickle the desulfurization waste residue to remove impurities, effectively dissolving Fe... 3+ Al 3+When metal ions form soluble complexes, impurities can be selectively removed without significant loss of calcium source by controlling the oxalic acid concentration, soaking temperature, and time. The active SiO2 contained in the desulfurization waste residue of glass furnaces is stable in oxalic acid solution and is retained in the solid product after acid washing, forming a calcium sulfate-silica composite precursor. The SiO2 in this precursor can be directly used as the silicon source for subsequent hydrothermal synthesis of calcium silicate. Because SiO2 is insoluble in oxalic acid and remains in the solid product during acid washing, a natural calcium-silica composite precursor is formed. In the subsequent hydrothermal synthesis process, this inherent SiO2 can participate in the reaction to generate calcium silicate, thereby reducing the amount of added sodium silicate. This not only reduces raw material costs but also achieves the synergistic utilization of calcium and silicon elements in the waste residue, embodying the circular economy concept of "using waste to treat waste." In the hydrothermal synthesis step, a mixed solution of ethanol and water is used as the solution medium. Traditional hydrothermal synthesis of calcium silicate is usually carried out in aqueous solution. However, in aqueous systems, the nucleation and growth rate of calcium silicate is relatively fast, easily forming a dense structure and limiting pore development. This invention uses a 1:1 volume ratio of ethanol to water as the reaction medium. The addition of an appropriate amount of ethanol reduces the polarity of the reaction system, slows down the diffusion rate of reactants, and makes the hydrothermal reaction process more mild and controllable, which is conducive to the formation of a precursor with a rich mesoporous structure. In addition, the high volatility of ethanol makes the pores less prone to collapse during the subsequent drying process. Finally, the activation treatment temperature is controlled at 200~250 °C. Within this temperature range, the water of crystallization in the calcium silicate precursor is removed, forming a stable three-dimensional network structure, while generating abundant micropores and mesopores. If the temperature is too low (<200 °C), dehydration is insufficient and pore development is incomplete; if the temperature is too high (>250 °C), it may lead to pore collapse, a decrease in specific surface area, and a reduction in hygroscopic properties.

[0008] Preferably, the desulfurization waste residue of the glass furnace in step (1) is a by-product waste residue generated by the wet desulfurization process of the flue gas of the glass furnace, and its components include 60-80% CaSO4, 5-15% CaSO3 and 5-15% active SiO2 by mass.

[0009] Preferably, the hydrogen peroxide in step (1) has a mass concentration of 10-30%, and 0.5-2.0 mL of hydrogen peroxide is added per gram of desulfurization waste residue. The molar ratio of hydrogen peroxide to sulfite in the desulfurization waste residue is 1.5-3:1.

[0010] Preferably, in the acid washing step (2), 10 mL of oxalic acid solution is added per gram of filter cake.

[0011] Preferably, the washing endpoint of the filter cake in step (2) is to wash it with deionized water until the pH of the filtrate is 6.5~7.5.

[0012] Preferably, in step (3), the volume ratio of water to ethanol in the mixed solution of water and ethanol is 1:1, and the solid-liquid mass ratio is 1:10.

[0013] Preferably, the washing in step (3) involves alternating between anhydrous ethanol and deionized water for 2 to 3 times.

[0014] Preferably, the calcination temperature in step (4) is 220 °C and the calcination time is 4 h.

[0015] In a second aspect, the present invention provides a high-performance calcium silicate desiccant prepared by a preparation method based on the formulation described in the first aspect.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. This invention realizes the high-value utilization of desulfurization waste residue from glass furnaces: using the desulfurization waste residue as a calcium source and part of the silicon source not only solves the environmental problems caused by waste residue storage, but also significantly reduces the production cost of calcium silicate desiccant. In particular, by utilizing the inherent active SiO2 in the waste residue, the synergistic utilization of calcium and silicon elements is achieved, embodying the circular economy concept of "using waste to produce waste".

[0017] 2. The preparation process provided by this invention is clean, environmentally friendly and free of secondary pollution: Through hydrogen peroxide pre-oxidation treatment, calcium sulfite in desulfurization waste residue is converted into calcium sulfate, eliminating the generation of SO2 gas during the pickling process from the source, realizing clean production and ensuring operational safety.

[0018] 3. The preparation process provided by this invention has low energy consumption: it adopts atmospheric pressure pre-oxidation, atmospheric pressure acid washing and low temperature hydrothermal reaction (≤140 ℃), and low calcination temperature (220 ℃). The energy consumption is significantly lower than that of traditional silica gel desiccant (which requires high temperature calcination of 500~600 ℃), and no toxic and harmful reagents are required, making it environmentally friendly. 4. The product prepared by this invention has excellent moisture absorption properties: By improving the purity of raw materials through pre-oxidation and acid washing to remove impurities, and by utilizing the inherent silicon resources of waste residue and controlling the pore structure through hydrothermal synthesis in ethanol medium, the prepared calcium silicate desiccant has a high specific surface area (230~300 m²). 2 With its abundant mesoporous structure (12~16 nm) and various temperature and humidity conditions, it exhibits excellent moisture absorption performance. Under 25 ℃ / 25%RH conditions, the moisture absorption rate can reach more than 19% in 24 h, and under 50 ℃ / 50%RH conditions, the moisture absorption rate can reach more than 33% in 24 h. 5. The product prepared by this invention has good cycle stability: the desiccant can be regenerated and reused after being activated by calcination at 220 ℃. After 5 cycles, the moisture absorption rate retention rate is ≥95%, which is far superior to traditional silica gel desiccant (performance decays by 20-30% after 3-5 cycles).

[0019] 6. The product form prepared by this invention is adjustable: by adjusting the hydrothermal reaction conditions and drying method, powdered or granular products can be obtained to meet the needs of different application scenarios. Attached Figure Description

[0020] Figure 1 A photograph of the high-performance calcium silicate desiccant prepared in Example 1; Figure 2 Microscopic image of the high-performance calcium silicate desiccant prepared in Example 1; Figure 3 A photograph of the acid washing step during the preparation of calcium silicate desiccant in Comparative Example 1; Figure 4 This is a photograph of the calcium silicate desiccant prepared in Comparative Example 1. Figure 5 The image shows the actual product of the calcium silicate desiccant prepared in Comparative Example 2. Figure 6 The image shows the actual product of the calcium silicate desiccant prepared in Comparative Example 3. Figure 7 Microscopic image of the calcium silicate desiccant prepared in Comparative Example 3; Figure 8 The graph shows the moisture absorption rate and retention rate of the calcium silicate desiccant obtained in Example 1 after 5 cycles of use. Detailed Implementation

[0021] The present invention will be described in detail below with reference to specific embodiments and examples, thereby making the advantages and various effects of the present invention more clearly apparent. Those skilled in the art should understand that these specific embodiments and examples are for illustrative purposes only and are not intended to limit the present invention.

[0022] Throughout this specification, unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of any conflict, this specification shall prevail.

[0023] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0024] The present invention will be further illustrated below with reference to specific embodiments.

[0025] Example 1 This embodiment provides a method for preparing high-performance calcium silicate desiccant using desulfurization waste residue from a glass furnace. The preparation process includes the following steps: (1) Pre-oxidation treatment: Take 100 g of wet desulfurization waste residue from a glass furnace of a flat glass enterprise (CaSO4·2H2O mass fraction 72.5%, CaSO3 mass fraction 8.6%, active SiO2 mass fraction 9.2%, Al2O3 mass fraction 2.1%, Fe2O3 mass fraction 1.5%), disperse it in 200 mL of deionized water, add 100 mL of 20% hydrogen peroxide solution, and stir the mixture in a constant temperature water bath at 40 ℃ for 1 h. After the reaction is completed, filter and collect the filter cake.

[0026] (2) Acid washing to remove impurities: The filter cake obtained in step (1) was placed in 500 mL of 0.6 mol / L oxalic acid solution and soaked in a constant temperature water bath at 70℃ for 1 h, with stirring 3 times during the soaking. After soaking, the filter cake was filtered, collected, and repeatedly washed with deionized water until the pH of the filtrate was 7.0. The washed filter cake was then dried in an oven at 105℃ for 6 h to obtain the purified calcium sulfate-silica composite precursor. The mass fraction of CaSO4·2H2O in the composite precursor was 92.5%, the mass fraction of active SiO2 was 11.8%, and the Fe2O3 content was reduced to 0.06%.

[0027] (3) Hydrothermal synthesis: Take 1.0 g of the composite precursor obtained in step (2) and 0.7 g of sodium silicate (modulus 2.8, purity 99%), add them to 17 mL of a mixed solution of ethanol and water in a volume ratio of 1:1, and stir at room temperature for 12 h to make the mixture homogeneous. Transfer the mixture to a 100 mL polytetrafluoroethylene-lined hydrothermal reactor, seal it, and place it in a 120 ℃ oven for hydrothermal reaction for 4 h. After the reaction is completed, cool it naturally to room temperature, filter and collect the product, wash it three times alternately with anhydrous ethanol and deionized water, and dry it in a 105 ℃ oven for 8 h to obtain the calcium silicate precursor.

[0028] (4) Activation treatment: The calcium silicate precursor obtained in step (3) is placed in a muffle furnace and heated to 220 ℃ at a heating rate of 5 ℃ / min. It is then calcined at this temperature for 4 h and naturally cooled to room temperature to obtain a white powdery high-performance calcium silicate desiccant, such as... Figure 1 As shown, its powder is fine and white, and its microscopic image is as follows. Figure 2 As shown, it is evident that it does not have a distinct crystalline structure.

[0029] The calcium silicate desiccant prepared in this embodiment has a specific surface area of ​​292 m², as tested. 2 / g, with an average pore size of 12.1nm and a mesopore volume of 0.51 cm³ / g.

[0030] Example 2 The difference from Example 1 is that: In step (1), the hydrogen peroxide concentration was 10%, and 0.8 mL of hydrogen peroxide was added per gram of desulfurization waste residue. The reaction temperature was 25°C, and the reaction time was 2 h. The remaining conditions were the same as in Example 1.

[0031] The calcium silicate desiccant prepared in this embodiment has a specific surface area of ​​262 m², as tested. 2 / g, with an average pore size of 13.5nm.

[0032] Example 3 The difference from Example 1 is that: In step (1), the hydrogen peroxide concentration was 30%, 1.5 mL of hydrogen peroxide was added per gram of desulfurization waste residue, the reaction temperature was 60℃, and the reaction time was 0.5 h. The remaining conditions were the same as in Example 1.

[0033] The calcium silicate desiccant prepared in this embodiment has a specific surface area of ​​280 m², as determined by testing. 2 / g, with an average pore size of 12.6nm.

[0034] Example 4 The difference from Example 1 is that: In step (2), the concentration of the oxalic acid solution was 0.5 mol / L, the soaking temperature was 80 ℃, and the soaking time was 0.5 h. The remaining conditions were the same as in Example 1.

[0035] The calcium silicate desiccant prepared in this embodiment has a specific surface area of ​​258 m², as tested. 2 / g, with an average pore size of 13.8nm.

[0036] Example 5 The difference from Example 1 is that: In step (2), the concentration of oxalic acid solution was 0.8 mol / L, the soaking temperature was 60 ℃, and the soaking time was 2 h. The remaining conditions were the same as in Example 1.

[0037] The calcium silicate desiccant prepared in this embodiment has a specific surface area of ​​275 m², as tested. 2 / g, with an average pore size of 12.7nm.

[0038] Example 6 The difference from Example 1 is that: In step (3), the mass ratio of the composite precursor to sodium silicate is 1:0.5, the total mass of the mixed solid is 1.5 g, and it is added to 15 mL of a mixed solution of ethanol and water in a volume ratio of 1:1. The mixture is stirred at room temperature for 12 h, the hydrothermal reaction temperature is 140 ℃, and the hydrothermal reaction time is 3 h. The remaining conditions are the same as in Example 1.

[0039] The calcium silicate desiccant prepared in this embodiment has a specific surface area of ​​238 m², as determined by testing. 2 / g, with an average pore size of 15.1nm.

[0040] Example 7 The difference from Example 1 is that: In step (3), the mass ratio of the composite precursor to sodium silicate is 1:1.0, and the total mass of the mixed solid is 2.0 g. 20 mL of a mixed solution of ethanol and water in a volume ratio of 1:1 is added, and the mixture is stirred at room temperature for 12 h. The hydrothermal reaction temperature is 100 ℃, and the hydrothermal reaction time is 6 h. The remaining conditions are the same as in Example 1.

[0041] The calcium silicate desiccant prepared in this embodiment has a specific surface area of ​​286 m², as tested. 2 / g, with an average pore size of 12.0nm.

[0042] Example 8 The difference from Example 1 is that: In step (4), the calcination temperature is 200 °C and the calcination time is 6 h. The remaining conditions are the same as in Example 1.

[0043] The calcium silicate desiccant prepared in this embodiment has a specific surface area of ​​264 m², as tested. 2 / g, with an average pore size of 13.2nm.

[0044] Example 9 The difference from Example 1 is that: In step (4), the calcination temperature is 250 °C and the calcination time is 2 h. The remaining conditions are the same as in Example 1.

[0045] The calcium silicate desiccant prepared in this embodiment has a specific surface area of ​​268 m², as tested. 2 / g, with an average pore size of 12.9nm.

[0046] Example 10 The difference from Example 1 is that: The desulfurization waste residue from another glass company was used, with a CaSO4·2H2O mass fraction of 68.3%, a CaSO3 mass fraction of 12.1%, an active SiO2 mass fraction of 6.5%, an Al2O3 mass fraction of 1.8%, and an Fe2O3 mass fraction of 2.2%. The remaining conditions were the same as in Example 1.

[0047] The calcium silicate desiccant prepared in this embodiment has a specific surface area of ​​271 m², as tested. 2 / g, with an average pore size of 12.8nm.

[0048] Comparative Example 1 This comparative example provides a method for directly preparing calcium silicate desiccant from desulfurization waste residue of glass furnaces without pre-oxidation treatment, including the following steps: (1) Acid washing to remove impurities: Take 100 g of the same desulfurization waste residue from the glass furnace as in Example 1, and place it directly into 500 mL of 0.6 mol / L oxalic acid solution. Soak it in a constant temperature water bath at 70 ℃ for 1 h. Figure 3 As shown, obvious bubbles were observed during the soaking process, and a pungent SO2 odor was emitted. After soaking, the product was filtered, washed, and dried to obtain the acid-washed product.

[0049] (2) Hydrothermal synthesis: Same as step (3) in Example 1.

[0050] (3) Activation treatment: Same as step (4) in Example 1, such as Figure 4 As shown, the obtained calcium silicate desiccant turns yellow and gray.

[0051] The calcium silicate desiccant prepared in this comparative example has a specific surface area of ​​85 m². 2 / g, with an average pore size of 26.5 nm.

[0052] Comparative Example 2 This comparative example provides a method for preparing calcium silicate desiccant from desulfurization waste residue that has not undergone acid washing and impurity removal (but has been pre-oxidized), including the following steps: (1) Pre-oxidation treatment: Same as step (1) in Example 1.

[0053] (2) Direct use: Take 1.0 g of the desulfurization waste residue obtained in step (1) (without acid washing and purification) and 0.7 g of sodium silicate, add them to 17 mL of a 1:1 mixture of ethanol and water, stir at room temperature for 12 h, then transfer the mixture to a hydrothermal reactor and react hydrothermally at 120 ℃ for 4 h. After the reaction is complete, filter, wash and dry to obtain the calcium silicate precursor.

[0054] (3) Activation treatment: Same as step (4) in Example 1, such as Figure 5 As shown, the obtained calcium silicate desiccant turns yellow and gray.

[0055] The calcium silicate desiccant prepared in this comparative example has a specific surface area of ​​105 m². 2 / g, with an average pore size of 23.8nm.

[0056] Comparative Example 3 This comparative example provides a method for preparing calcium silicate desiccant using water as the reaction medium, comprising the following steps: (1) Pre-oxidation treatment: Same as step (1) in Example 1.

[0057] (2) Acid washing to remove impurities: Same as step (2) in Example 1.

[0058] (3) Hydrothermal synthesis: Take 1.0 g of the composite precursor obtained in step (2) and 0.7 g of sodium silicate, add them to 40 mL of deionized water, and stir at room temperature for 12 h. Transfer the mixture to a hydrothermal reactor and hydrothermally react at 120 ℃ for 4 h. After the reaction is complete, filter, wash and dry to obtain the calcium silicate precursor.

[0059] (4) Activation treatment: Same as step (4) in Example 1, such as Figure 6 As shown, the obtained calcium silicate desiccant is relatively white; as Figure 7 As shown, a distinct and coarse crystalline structure is visible.

[0060] The calcium silicate desiccant prepared in this comparative example has a specific surface area of ​​141 m². 2 / g, with an average pore size of 20.5nm.

[0061] Comparative Example 4 This comparative example provides a method for preparing calcium silicate desiccant using different calcination temperatures, including the following steps: (1) Pre-oxidation treatment: Same as step (1) in Example 1.

[0062] (2) Acid washing to remove impurities: Same as step (2) in Example 1.

[0063] (3) Hydrothermal synthesis: Same as step (3) in Example 1.

[0064] (4) Activation treatment: Place the calcium silicate precursor in a muffle furnace and heat it to 400°C at a heating rate of 5°C / min. Hold it at the temperature for 4 hours and then let it cool naturally to room temperature.

[0065] The calcium silicate desiccant prepared in this comparative example has a specific surface area of ​​115 m². 2 / g, with an average pore size of 24.6nm.

[0066] Comparative Example 5 This comparative example provides a commercially available silica gel desiccant (Qingdao Ocean Chemical Co., Ltd., Type A fine-pore silica gel) as a comparison sample.

[0067] Tests showed that the specific surface area of ​​this commercially available silica gel desiccant is 650 m². 2 / g, with an average pore size of 2.2 nm.

[0068] Performance test examples The desiccants prepared in Examples 1-10 and Comparative Examples 1-5 were tested for moisture absorption performance and cyclic stability.

[0069] Test methods (1) Moisture absorption rate test: Weigh approximately 2.0 g of the desiccant sample (accurate to 0.0001 g), place it in a pre-weighed weighing bottle, and dry it in an oven at 105 ℃ until constant weight (recorded as m0). Place the sample in a constant temperature and humidity chamber, setting two conditions: temperature 25℃ and relative humidity 25%, and temperature 50 ℃ and relative humidity 50%. After 24 h, remove and weigh the sample (recorded as m1). The moisture absorption rate is calculated using the following formula: Moisture absorption rate (%) = (m1 - m0) / m0 × 100% The test results are shown in Table 1.

[0070] Table 1. 24-hour moisture absorption rate of different desiccants under conditions of 25 ℃ / 25%RH and 50 ℃ / 50%RH

[0071] As shown in Table 1, the calcium silicate desiccants prepared in Examples 1-10 of this invention exhibited moisture absorption rates exceeding 19% and reaching a maximum of 22.3% under low humidity conditions (25 ℃ / 25%RH) for 24 h; and exceeding 33% and reaching a maximum of 38.0% under high humidity conditions (50 ℃ / 50%RH) for 24 h. These results are significantly superior to the comparative samples prepared without pre-oxidation (Comparative Example 1), without acid washing (Comparative Example 2), hydrothermal synthesis in an aqueous medium (Comparative Example 3), and excessively high calcination temperature (Comparative Example 4). Compared to commercially available silica gel desiccants (Comparative Example 5), although commercially available silica gel desiccants have a higher specific surface area, the desiccants of this invention show slightly better moisture absorption rates under low humidity conditions, and the advantage is more pronounced under high humidity conditions (the moisture absorption rate under high humidity conditions is about 5-9.4 percentage points higher than that of commercially available silica gel). This indicates that specific surface area is not necessarily positively correlated with moisture absorption performance, and the desiccants of this invention exhibit superior moisture absorption performance over a wider range of temperature and humidity.

[0072] (2) Cyclic stability test: The samples that have completed the moisture absorption test were dried in an oven at 220 ℃ for 4 h for regeneration. After cooling to room temperature, the moisture absorption test was repeated (conditions: 25 ℃ / 25%RH, 24h). A total of 5 adsorption-desorption cycles were performed, and the moisture retention rate after each cycle was calculated: Moisture retention rate (%) = (nth moisture absorption rate / first moisture absorption rate) × 100% The test results are shown in Table 2.

[0073] Table 2. Moisture retention rate of different desiccants after 5 cycles (Test conditions: 25 ℃ / 25%RH, 24h)

[0074] As can be seen from the results in Table 2, the calcium silicate desiccants prepared in Examples 1-10 of this invention maintained a moisture absorption rate of 95.9% after five adsorption-desorption cycles. The statistical results of the five moisture absorption tests for the calcium silicate desiccant prepared in Example 1 are shown in Table 2. Figure 8 This demonstrates its excellent cycle stability.

[0075] Finally, it should be noted that the terms "comprising," "including," or any other variations are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make further changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0076] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A preparation method for preparing high-performance calcium silicate desiccant using glass furnace desulfurization waste residue, characterized in that, Includes the following steps: (1) Pre-oxidation treatment: Disperse the desulfurization waste residue of glass furnace in deionized water, add hydrogen peroxide solution, stir and react at 20~80℃ for 0.5~2 h to oxidize the sulfite in the desulfurization waste residue to sulfate; (2) Acid washing to remove impurities: The desulfurization waste residue of the glass furnace after oxidation is filtered, and the resulting filter cake is placed in 0.5~0.8mol / L oxalic acid solution and soaked at 60~80 ℃ for 0.5~2 h to remove metal oxide impurities. Then the filter cake obtained by filtration is washed and dried to obtain the purified CaSO4-SiO2 composite precursor. (3) Hydrothermal synthesis: The purified CaSO4-SiO2 composite precursor and sodium silicate are mixed at a mass ratio of 1:0.5~2.

0. After mixing, the mixture is dispersed in a mixed solution of water and ethanol with a solid-liquid mass ratio of 1:5~20. The mixture is stirred at 20~60 ℃ for 8~24 h. Then the mixture is transferred to a hydrothermal reactor and hydrothermally reacted at 100~140 ℃ for 3~12 h. After the reaction is completed, the mixture is filtered, washed and dried to obtain the calcium silicate precursor. (4) Activation treatment: The obtained calcium silicate precursor is calcined at 200~250 ℃ for 2~8 h to obtain the high-performance calcium silicate desiccant.

2. The production method according to claim 1, characterized by, The desulfurization waste residue of the glass furnace mentioned in step (1) is a by-product waste residue generated by the wet desulfurization process of the flue gas of the glass furnace. Its components include 60-80% CaSO4, 5-15% CaSO3 and 5-15% active SiO2 by mass.

3. The production method according to claim 1, characterized by, The hydrogen peroxide concentration in step (1) is 10-30%, and 0.5-2.0 mL of hydrogen peroxide is added per gram of desulfurization waste residue. The molar ratio of hydrogen peroxide to sulfite in the desulfurization waste residue is 1.5-3:

1.

4. The preparation method according to claim 1, characterized in that, In the acid washing step described in step (2), 10 mL of oxalic acid solution is added per gram of filter cake.

5. The preparation method according to claim 1, characterized in that, The washing endpoint of the filter cake in step (2) is to wash it with deionized water until the pH of the filtrate is 6.5~7.

5.

6. The method of claim 1, wherein, In step (3), the volume ratio of water to ethanol in the mixed solution of water and ethanol is 1:1, and the solid-liquid mass ratio is 1:

10.

7. The preparation method according to claim 1, characterized in that, The washing described in step (3) involves alternating between anhydrous ethanol and deionized water for 2 to 3 washes.

8. The production method according to claim 1, characterized by, The calcination temperature in step (4) is 220 °C and the calcination time is 4 h.

9. A high-performance calcium silicate desiccant prepared according to any one of claims 1 to 8.

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