Preparation method of high-stability calcium oxide efficient adsorbent

Abstract

The invention discloses a preparation method of a high-stability calcium oxide high-efficiency adsorbent, which comprises the following steps of: preparing calcium chloride, sodium carbonate and aluminum nitrate which are higher than analytically pure as raw materials, and polyvinyl alcohol and polyethylene glycol as additives to prepare a solution with a specific concentration; carrying out precipitation reaction, and controlling the conditions of aluminum nitrate addition amount, reaction temperature, pH value and the like; and after the reaction is finished, carrying out suction filtration on the precipitate, washing with deionized water, and detecting chloride ions and nitrate ions to ensure that the precipitate is clean. And then drying and calcining can be carried out under inert gas protection or in a vacuum high-temperature furnace. And finally, collecting and detecting the product, analyzing the crystal structure through XRD, measuring the specific surface area and pore size distribution through BET, and measuring the content of aluminum oxide through chemical analysis. Compared with the prior art, the preparation method has the advantages that the calcium oxide adsorbent prepared by accurately controlling all the steps is high in stability and good in adsorption efficiency. The raw materials are common, the cost is low, the preparation process is simple, industrial production is easy, and the application value in the adsorption field is high.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorbent preparation, and specifically refers to a preparation method of a highly stable calcium oxide high-efficiency adsorbent. Background Art

[0002] In many fields such as current industrial production and environmental protection, adsorbents play a crucial role. As a common adsorbent, calcium oxide has been widely studied and applied due to its certain adsorption performance and relatively low cost. However, the calcium oxide adsorbents prepared by traditional methods have certain limitations in terms of stability and adsorption efficiency.

[0003] In the field of gas separation, such as carbon dioxide capture, the adsorption capacity of traditional calcium oxide adsorbents will significantly decrease after multiple cycles of use. This is mainly because during the adsorption-desorption process, phenomena such as sintering and agglomeration of calcium oxide particles occur, resulting in a reduction in its specific surface area and active sites, thereby reducing the adsorption performance. In wastewater treatment, for some wastewater with complex components, traditional calcium oxide adsorbents are difficult to effectively remove various pollutants in it, and the adsorption selectivity and efficiency need to be improved.

[0004] To overcome these problems, researchers have tried to improve the performance of calcium oxide adsorbents by adding additives, changing the preparation process, etc. However, the existing improvement methods still have deficiencies in practical applications. For example, some methods have complex preparation processes and high costs, making it difficult to achieve large-scale industrial production; some methods can improve the adsorption performance to a certain extent, but the improvement in stability is not obvious. Therefore, it is of great practical significance to develop a method that can effectively improve the stability and adsorption efficiency of calcium oxide adsorbents, and has a simple preparation process and moderate cost. Summary of the Invention

[0005] The present invention aims to solve the above technical problems and provides a preparation method of a highly stable calcium oxide high-efficiency adsorbent, which can be used to prepare calcium oxide adsorbents with specific structures and properties, and is widely applied in fields such as gas separation, drying, and wastewater treatment to achieve efficient substance adsorption and separation.

[0006] To solve the above technical problems, the technical solution provided by the present invention is: a preparation method of a highly stable calcium oxide high-efficiency adsorbent, including the following steps:

[0007] S1. Preparation Preparation

[0008] Raw materials: Prepare high-purity calcium chloride and sodium carbonate as the calcium source and precipitating agent, and aluminum nitrate as the additive.

[0009] Additives: Prepare polyvinyl alcohol (PVA) as an additive to control the precipitation structure, and prepare polyethylene glycol as a pore-forming agent.

[0010] Solution preparation: Prepare 0.5 mol / L calcium chloride solution, 0.5 mol / L sodium carbonate solution, 0.05 mol / L aluminum nitrate solution, 2% (by mass) polyvinyl alcohol solution, and 5% (by mass) polyethylene glycol solution respectively;

[0011] S2. Precipitation reaction

[0012] Under stirring conditions, slowly add the aluminum nitrate solution dropwise to the calcium chloride solution. The addition amount of aluminum nitrate is 8% of the amount of substance of the calcium salt. Continuously stir for 30 minutes to evenly disperse the aluminum nitrate in the calcium chloride solution. Then, pour the polyvinyl alcohol solution into the above mixed solution and continue to stir for 30 minutes to fully dissolve the polyvinyl alcohol and mix it evenly with the solution;

[0013] Maintain the stirring state, and slowly add the polyethylene glycol solution to the mixed solution of calcium chloride, aluminum nitrate and polyvinyl alcohol. Then, slowly add the sodium carbonate solution dropwise to the above mixed solution at a slower speed (1 - 2 drops / second). Control the reaction temperature at 30 °C, keep the pH value at 8 - 9, and set the stirring speed at 200 r / min;

[0014] S3. Filtration and washing

[0015] After the reaction is completed, use a Buchner funnel and a suction flask to filter the mixed solution and collect the precipitate;

[0016] Wash the precipitate with deionized water multiple times. After each washing, judge the washing effect by detecting whether there are chloride ions in the washing liquid until no chloride ions can be detected in the washing liquid to remove the impurity ions adsorbed on the surface of the precipitate and at the same time remove the residues of unreacted additives and auxiliaries;

[0017] S4. Drying and calcination

[0018] Drying: Transfer the washed precipitate to an oven and dry it at 100 °C for 18 hours to completely remove the moisture;

[0019] Calcination: Put the dried sample into a high-temperature furnace, heat it to 900 °C at a heating rate of 5 °C / min, and calcine it at this temperature for 2.5 hours;

[0020] S5. Product collection and storage

[0021] After the calcination is completed, wait for the high-temperature furnace to cool to room temperature, take out the prepared calcium oxide adsorbent, and store it sealed in a desiccator to prevent it from absorbing moisture and carbon dioxide in the air and deteriorating;

[0022] S6: Product quality detection

[0023] The product after calcination is detected to see if it is the target product calcium oxide, and whether there are impurity phases is detected, and the specific surface area and pore size distribution of the product are measured.

[0024] Further, the purity of the raw materials in step S1 is above analytical purity, and before use, the purity of calcium chloride, sodium carbonate, and aluminum nitrate is detected by titration or spectroscopic analysis.

[0025] Further, in step S3, the method for detecting whether chloride ions are contained is: adding silver nitrate solution dropwise to the washing liquid, and if no white precipitate is produced, it indicates that the chloride ions have been washed clean.

[0026] Further, during the washing process in step S3, it is also necessary to detect whether nitrate ions are contained. Specifically, the brown ring experiment is used to detect nitrate ions.

[0027] Further, the judgment of the end point of the precipitation reaction in step S2: It is determined by observing that no more precipitate is formed or by taking the supernatant and adding sodium carbonate solution dropwise, and if no new precipitate is produced.

[0028] Further, in step S4, the calcination is carried out under the protection of an inert gas or in a vacuum high-temperature furnace.

[0029] Further, in step S6, the crystal structure of the product is analyzed by XRD (X-ray diffraction) to determine whether it is the target product calcium oxide and to detect whether there are impurity phases;

[0030] The BET (specific surface area and porosity analysis) is used to measure the specific surface area and pore size distribution of the product.

[0031] Further, in step S6, the content of alumina in the product is measured by chemical analysis methods to infer whether the addition amount of aluminum nitrate in step S1 is appropriate.

[0032] The advantages of the present invention compared with the prior art are as follows:

[0033] 1. High stability: By adding aluminum nitrate as an auxiliary agent, the alumina formed after calcination interacts with calcium oxide, effectively inhibiting the sintering and agglomeration phenomena of calcium oxide during use, greatly improving the stability of the adsorbent, and enabling it to still maintain a high adsorption performance after multiple cycles of use.

[0034] 2. High-efficiency adsorption: Using polyvinyl alcohol to control the formation of the precipitation structure to form nano-level precipitates, and polyethylene glycol as a pore-forming agent to generate a porous structure, significantly increasing the specific surface area and adsorption sites of the adsorbent, thereby improving the adsorption efficiency and being able to more effectively adsorb the target substance, showing good adsorption effects in both gas separation and wastewater treatment and other fields.

[0035] 3. Simple preparation process: The operation steps of the preparation method of the present invention are relatively clear and definite. Common equipment is required, such as ovens, high-temperature furnaces, Buchner funnels, etc. It does not require complex instruments and special process conditions, and is easy to realize industrial production.

[0036] 4. Quality controllable: During the preparation process, the purity of raw materials is strictly detected, key parameters such as temperature, pH value, reaction time, etc. in the reaction process are precisely controlled, and comprehensive quality inspections are carried out in the post-treatment stage of the product, including XRD analysis of crystal structure, BET determination of specific surface area and pore size distribution, and chemical analysis for determining alumina content, etc., ensuring the stability and consistency of product quality. Specific embodiments

[0037] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0038] I. Working principle of the present invention:

[0039] S1. Preparation preparation

[0040] Raw materials: High-purity calcium chloride and sodium carbonate are respectively used as the calcium source and precipitating agent, and aluminum nitrate is used as an additive. It is required that the purity of the raw materials is above analytical purity, and the purity of calcium chloride, sodium carbonate, and aluminum nitrate is detected by titration method or spectroscopic analysis before use.

[0041] High-purity raw materials are the basis for ensuring product quality and performance. The presence of impurities may interfere with the subsequent reaction process and product structure. For example, if magnesium ions and other impurities are mixed in calcium chloride, during the precipitation reaction, magnesium ions will react with sodium carbonate to form magnesium carbonate precipitate, which will be mixed into the final product, changing the crystal structure and surface properties of the calcium oxide adsorbent, and thus affecting its adsorption performance. Through strict purity detection, the quality of raw materials can be ensured, laying a foundation for the subsequent preparation of high-performance adsorbents.

[0042] Additives: Prepare polyvinyl alcohol (PVA) as an additive to control the precipitation structure, and polyethylene glycol as a pore-forming agent.

[0043] Solution preparation: Prepare calcium chloride solution with a concentration of 0.5 mol / L, sodium carbonate solution with a concentration of 0.5 mol / L, aluminum nitrate solution with a concentration of 0.05 mol / L, polyvinyl alcohol solution with a mass fraction of 2%, and polyethylene glycol solution with a mass fraction of 5% respectively. Precise preparation of solutions with specific concentrations is to ensure appropriate molar ratios of substances in subsequent reactions, enabling the reaction to proceed as expected. For example, calcium chloride and sodium carbonate solutions with appropriate concentrations can ensure sufficient reaction between calcium ions and carbonate ions to form calcium carbonate precipitate; a specific concentration of aluminum nitrate solution can ensure the introduction of an appropriate amount of aluminum element for subsequent modification of calcium oxide; while polyvinyl alcohol and polyethylene glycol solutions with appropriate mass fractions can respectively achieve the best effects in controlling the precipitate structure and forming a porous structure.

[0044] S2. Precipitation reaction

[0045] Under stirring conditions, slowly add the aluminum nitrate solution to the calcium chloride solution. The addition amount of aluminum nitrate is 8% of the amount of substance of the calcium salt. Continuously stir for 30 minutes to evenly disperse the aluminum nitrate in the calcium chloride solution. Subsequently, pour the polyvinyl alcohol solution into the above mixed solution and continue to stir for 30 minutes to fully dissolve the polyvinyl alcohol and mix it evenly with the solution. Slowly adding and fully stirring the aluminum nitrate can ensure its uniform distribution in the calcium chloride solution, ensuring that aluminum elements can participate in the reaction evenly and be evenly dispersed in the final product in subsequent reactions. When mixed and stirred with the polyvinyl alcohol solution later, due to its dispersion effect in the solution, polyvinyl alcohol adsorbs on the surface of the calcium carbonate precipitate precursor particles, forming a protective film, reducing the mutual attraction between particles, inhibiting the growth and aggregation of particles, and promoting the precipitation to develop towards a nanoscale structure. The nanoscale precipitate can significantly increase the specific surface area of the adsorbent after subsequent conversion to calcium oxide, providing more active sites for the adsorption process, thereby improving the adsorption efficiency.

[0046] Maintain the stirring state and slowly add the polyethylene glycol solution to the mixed solution of calcium chloride, aluminum nitrate and polyvinyl alcohol. Then, dropwise add the sodium carbonate solution to the above mixed solution at a slower speed (1 - 2 drops / second), while controlling the reaction temperature at 30 °C, keeping the pH value at 8 - 9, and setting the stirring speed at 200 r / min. The end point of the precipitation reaction is determined by observing that no more precipitation occurs, or by taking the supernatant and dropping the sodium carbonate solution, and if no new precipitation is produced; polyethylene glycol is used as a pore-forming agent and is evenly distributed around the precipitate particles in the solution. When the sodium carbonate solution is added dropwise at a slower speed, calcium carbonate precipitation can be generated slowly, and polyethylene glycol is wrapped in it during the precipitation formation process. In the subsequent drying and calcination processes, polyethylene glycol decomposes and volatilizes, thus leaving a porous structure inside the adsorbent. This porous structure greatly increases the specific surface area and pore volume of the adsorbent, provides more adsorption channels and sites, and further improves the adsorption performance. Controlling the reaction temperature at 30 °C is because this temperature can not only ensure a moderate reaction rate but also is conducive to the interaction and structure formation among various components. Maintaining the pH value at 8 - 9 can promote the precipitation reaction to proceed smoothly in the direction of generating calcium carbonate precipitation and prevent other side reactions from occurring. A stable stirring speed of 200 r / min helps the substances in the solution to be fully mixed, makes the reaction more uniform, and ensures the consistency of the precipitate structure.

[0047] S3. Filtration and Washing

[0048] After the reaction is completed, use a Buchner funnel and a suction flask to filter the mixed solution and collect the precipitate.

[0049] Wash the precipitate with deionized water multiple times. After each washing, detect whether there are chloride ions by dropping silver nitrate solution into the washing liquid. If no white precipitate is produced, it indicates that the chloride ions have been washed away; at the same time, use the brown ring experiment to detect whether there are nitrate ions in the washing liquid to judge the washing effect of the precipitate until no chloride ions and nitrate ions can be detected, so as to remove the impurity ions adsorbed on the surface of the precipitate and at the same time remove the residues of unreacted additives and auxiliaries.

[0050] Filtration is to separate the generated precipitate from the reaction solution. And the washing process is crucial. If impurity ions such as chloride ions and nitrate ions remain on the surface of the precipitate, it will affect the purity and performance of the adsorbent. By detecting chloride ions and nitrate ions, it is ensured that these impurity ions are completely removed, guaranteeing a pure calcium oxide adsorbent precursor obtained subsequently and avoiding the adverse effects of impurities on the structure and performance of the adsorbent.

[0051] S4. Drying and Calcination

[0052] Drying: Transfer the washed precipitate to an oven and dry it at 100 °C for 18 hours to completely remove moisture. Drying at a lower temperature for a long time can prevent the agglomeration of nanoscale precipitate particles due to high temperature, and at the same time avoid the collapse of the porous structure caused by too fast drying, ensuring that the precipitate particles maintain their original structure and laying a foundation for the subsequent calcination to form an ideal adsorbent structure.

[0053] Calcination: Put the dried sample into a high-temperature furnace and heat it to 900 °C at a heating rate of 5 °C / min, and calcine it at this temperature for 2.5 hours. To prevent calcium oxide from reacting with carbon dioxide in the air at high temperature, calcination can be carried out under the protection of an inert gas or in a vacuum high-temperature furnace. During the calcination process, calcium carbonate undergoes a decomposition reaction to generate calcium oxide and carbon dioxide. At the same time, aluminum hydroxide generated by the reaction of aluminum nitrate in the early stage decomposes into alumina and water, and alumina interacts with calcium oxide to form a structure that helps to improve the stability of calcium oxide. For example, a solid solution may be formed to enhance the stability of the crystal structure; or a coating layer may be formed on the surface of calcium oxide to inhibit the sintering and agglomeration of calcium oxide particles. Selecting an appropriate heating rate, calcination temperature, and time is to ensure the full decomposition of calcium carbonate and the full reaction of alumina with calcium oxide to form a stable structure. The protection of an inert gas or a vacuum environment can prevent calcium oxide from reacting with carbon dioxide to form calcium carbonate, ensuring the purity and performance of the calcium oxide adsorbent.

[0054] S5. Product Collection and Preservation

[0055] After the calcination is completed, wait for the high-temperature furnace to cool to room temperature, take out the prepared calcium oxide adsorbent, and seal it and store it in a desiccator to prevent it from absorbing moisture and carbon dioxide in the air and deteriorating. Calcium oxide adsorbent has strong water absorption and reactivity with carbon dioxide. Sealing and storing it in a desiccator in time after cooling can prevent it from contacting moisture and carbon dioxide in the air, thereby maintaining the stability and activity of the adsorbent and ensuring that its performance is not affected.

[0056] S6. Product Quality Detection

[0057] Conduct various tests on the product after the calcination is completed. Analyze the crystal structure of the product by XRD (X-ray diffraction) to determine whether it is the target product calcium oxide and detect whether there are impurity phases; use BET (specific surface area and porosity analysis) to measure the specific surface area and pore size distribution of the product; use chemical analysis methods to measure the content of alumina to infer whether the addition amount of aluminum nitrate in step S1 is appropriate.

[0058] II. Embodiment:

[0059] Example 1

[0060] S1 Preparation Preparation

[0061] Raw materials: Calcium chloride, sodium carbonate, and aluminum nitrate of analytical reagent grade were purchased. After their purities were detected by titration and spectroscopic analysis and met the requirements, 55.50 g of calcium chloride was accurately weighed using an electronic balance and placed in a 1000 mL volumetric flask. Deionized water was added to dissolve it and diluted to the calibration mark to prepare a 0.5 mol / L calcium chloride solution. Similarly, 53.00 g of sodium carbonate was accurately weighed, put into a 1000 mL volumetric flask, dissolved with deionized water and diluted to the mark to obtain a 0.5 mol / L sodium carbonate solution. 8.82 g of aluminum nitrate was accurately weighed. First, a small amount of dilute nitric acid was added to prevent hydrolysis, and then it was placed in a 500 mL volumetric flask and diluted with deionized water to prepare a 0.05 mol / L aluminum nitrate solution.

[0062] Additives: 2.00 g of polyvinyl alcohol was weighed and added to 98 g of deionized water. It was heated and stirred until completely dissolved to obtain a polyvinyl alcohol solution with a mass fraction of 2%. 5.00 g of polyethylene glycol was weighed and dissolved in 95 g of deionized water to prepare a polyethylene glycol solution with a mass fraction of 5%.

[0063] S2. Precipitation reaction

[0064] In a 2000 mL beaker equipped with a stirrer, 500 mL of the prepared 0.5 mol / L calcium chloride solution was added. The stirrer was turned on, and the stirring speed was set to 200 r / min. 40 mL of 0.05 mol / L aluminum nitrate solution was slowly added dropwise to the calcium chloride solution over approximately 10 minutes. After the addition was complete, stirring was continued for 30 minutes. Then, 50 mL of the 2% polyvinyl alcohol solution was poured into the above mixture, and stirring was continued for 30 minutes.

[0065] While maintaining the stirring state, 50 mL of the 5% polyethylene glycol solution was slowly added. Then, 500 mL of 0.5 mol / L sodium carbonate solution was added dropwise to the above mixture at a rate of 1 - 2 drops per second. At the same time, the pH value of the solution was monitored with a pH meter, and it was fine-tuned by adding dilute hydrochloric acid or sodium hydroxide solution to keep the pH value between 8 - 9. The reaction temperature was controlled at 30 °C using a constant temperature water bath. When it was observed that no more precipitate was formed and no new precipitate was produced when adding sodium carbonate solution to the supernatant, the reaction was determined to have reached the end point.

[0066] S3. Filtration and washing

[0067] After the reaction ended, the mixture was filtered using a Buchner funnel and a suction flask to collect the precipitate.

[0068] Wash the precipitate with 200 mL of deionized water each time. Slowly add deionized water along the glass rod to fully immerse the precipitate. After the water naturally drains out, proceed with the next wash. After each wash, take a small amount of the wash liquor in a test tube, add silver nitrate solution to detect chloride ions, and at the same time use the brown ring experiment to detect nitrate ions. Repeat the washing operation until no chloride ions and nitrate ions can be detected in the wash liquor.

[0069] S4, Drying and Calcination

[0070] Drying: Transfer the washed precipitate to a forced-air drying oven and dry it at 100 °C for 18 hours.

[0071] Calcination: Put the dried sample into a high-temperature furnace, introduce nitrogen as the protective gas, heat it to 900 °C at a heating rate of 5 °C / min, and calcine it at this temperature for 2.5 hours.

[0072] S5, Product Collection and Preservation

[0073] After calcination, wait for the high-temperature furnace to cool to room temperature under nitrogen protection, take out the prepared calcium oxide adsorbent, and seal it and store it in a desiccator.

[0074] S6, Product Quality Detection

[0075] Analyze the crystal structure of the product by XRD. The results show that the product is mainly calcium oxide and there are no obvious impurity phases. Use BET to measure the specific surface area of the product to be 150 m 2 / g, and the pore size distribution is in the range of 5 - 20 nm, indicating that the product has a good porous structure.

[0076] Use chemical analysis methods to measure the content of alumina. After calculation, it is consistent with the theoretical content of alumina converted from the addition amount of aluminum nitrate being 8% of the amount of substance of calcium salt, indicating that the addition amount of aluminum nitrate is appropriate.

[0077] Example 2

[0078] Preparation Preparation: Conduct raw material purity detection and solution preparation in the same way as in Example 1.

[0079] S2, Precipitation Reaction

[0080] The operation process is the same as in Example 1, but when dropping the sodium carbonate solution, strictly control the dropping rate to 1 drop / second to ensure more uniform reaction.

[0081] The judgment of the reaction end point is the same as in Example 1.

[0082] S3, Filtration and Washing

[0083] Conduct suction filtration and washing operations in the same way as in Example 1.

[0084] During the washing process, appropriately increase the amount of deionized water used for each wash to 250 mL to ensure the washing effect.

[0085] S4, Drying and Calcination

[0086] Drying: Use a vacuum drying oven to dry at 100 °C for 18 hours to further ensure the drying effect and prevent particle agglomeration.

[0087] Calcination: Put the dried sample into a vacuum high-temperature furnace, heat it to 900 °C at a heating rate of 5 °C / min, and calcine at this temperature for 2.5 hours.

[0088] S5, Product Collection and Preservation: The same as in Example 1.

[0089] S6, Product Quality Detection

[0090] XRD analysis shows that the product is pure calcium oxide with no impurity phase.

[0091] The BET measurement results show that the specific surface area of the product is 160 m 2 / g, the pore size distribution changes slightly, within the range of 4 - 18 nm, and the adsorption performance has improved.

[0092] Chemical analysis shows that the alumina content is consistent with the theoretical value.

[0093] Example 3

[0094] S1, Preparation Preparation: Conduct raw material purity detection and solution preparation as in Example 1.

[0095] S2, Precipitation Reaction

[0096] When dropping the aluminum nitrate solution, appropriately extend the stirring time to 40 minutes to make the aluminum nitrate disperse more evenly in the calcium chloride solution. Other operations are the same as in Example 1.

[0097] The judgment of the reaction end point is the same as in Example 1.

[0098] S3, Filtration and Washing: The same as in Example 1.

[0099] S4, Drying and Calcination: The same as in Example 1.

[0100] S5, Product Collection and Preservation: The same as in Example 1.

[0101] S6, Product Quality Detection

[0102] XRD analysis shows that the crystal structure of the product is good, it is the target calcium oxide product and has very few impurity phases.

[0103] The BET measurement of the product shows a specific surface area of 155 m 2 / g, with the pore size distribution in the range of 6 - 22 nm, also having a good adsorption structure.

[0104] The determination of the alumina content is consistent with the theoretical value.

[0105] It can be seen from the above three examples that the calcium oxide adsorbent prepared by the precipitation method of the present invention exhibits good performance: through XRD analysis, the product is mainly calcium oxide, and there is no obvious impurity phase or very few impurity phases, indicating that this preparation method can effectively generate the target product with high purity. This benefits from the high purity requirements of the raw materials and the precise control of each reaction step, reducing the introduction of impurities and the occurrence of side reactions.

[0106] The specific surface area of the product in Example 1 is 150 m 2 / g, with the pore size distribution in the range of 5 - 20 nm; the specific surface area of Example 2 is 160 m 2 / g, with the pore size distribution in the range of 4 - 18 nm; the specific surface area of Example 3 is 155 m 2 / g, with the pore size distribution in the range of 6 - 22 nm. The relatively large specific surface area and suitable pore size distribution provide more active sites and channels for adsorption, making the adsorbent have good adsorption performance. This is mainly attributed to the control of the precipitation structure by polyvinyl alcohol to form nano - scale precipitates, and the porous structure generated by polyethylene glycol as a pore - forming agent.

[0107] The content of alumina was determined by chemical analysis methods, and it was all in line with the theoretical content of alumina calculated by converting the addition amount of aluminum nitrate to 8% of the amount of substance of calcium salt, indicating that the addition amount of aluminum nitrate is appropriate and the entire preparation process has good controllability, ensuring the stability of the adsorbent performance

[0108] Comparative example (gel method)

[0109] Preparation of calcium oxide adsorbent by gel method

[0110] Raw material and reagent preparation

[0111] Calcium source: Calcium nitrate [Ca(NO3)2·4H2O] was selected as the calcium source, ensuring that its purity is not lower than the analytical pure level.

[0112] Auxiliary agent: Titanium dioxide (TiO2) was selected as the auxiliary agent, and tetrabutyl titanate [Ti(OC4H9)4] was prepared as the precursor.

[0113] Additive: Citric acid was prepared as a chelating agent, ethylene glycol as a plasticizer, and polyethylene glycol (PEG) as a pore - forming agent.

[0114] Solvent: Absolute ethanol was used as the solvent.

[0115] Preparation of precursor solution

[0116] Calcium source dissolution: In a clean beaker, dissolve a certain amount of calcium nitrate in an appropriate amount of anhydrous ethanol, and stir until completely dissolved to prepare a calcium nitrate ethanol solution with a concentration of 0.3 mol / L.

[0117] Addition of additives: Under stirring, slowly add an appropriate amount of tetrabutyl titanate to the calcium nitrate ethanol solution. The addition amount of tetrabutyl titanate is 8% of the amount of substance of calcium nitrate.

[0118] Addition of chelating agent and plasticizer: Add citric acid and ethylene glycol to the above mixed solution in sequence. The molar ratio of citric acid to calcium nitrate is 1:1, and the addition amount of ethylene glycol is 10% of the total volume of the solution. Continue to stir for 30 minutes after addition.

[0119] Addition of pore-forming agent: Add an appropriate amount of polyethylene glycol to the above solution, and control the mass fraction of polyethylene glycol at 5%. Stir evenly.

[0120] Sol-gel transition

[0121] Initiation of hydrolysis and polycondensation reaction: Dropwise add deionized water to the above mixed solution. The molar ratio of deionized water to tetrabutyl titanate is 4:1, and at the same time, add ammonia water to adjust the pH value of the solution to 7 - 8. Continuously stir under the condition of a constant temperature water bath at 60 °C, control the stirring speed at 300 r / min, and the reaction lasts for 3 - 5 hours. The solution gradually turns into a sol state.

[0122] Gel formation: Let the sol stand and age at 60 °C for 12 - 24 hours to form a gel.

[0123] Drying and calcination

[0124] Drying: Take out the gel from the reaction vessel, put it into an oven, and dry it at 80 °C for 24 - 48 hours.

[0125] Calcination: Transfer the dry gel to a high-temperature furnace, heat it to 600 - 800 °C at a heating rate of 5 °C / min, and calcine it at this temperature for 3 - 5 hours

[0126] The high-stability calcium oxide efficient adsorbent prepared by the precipitation method of the present invention can meet the requirements of efficient adsorption in terms of performance, has a good crystal structure, a large specific surface area and an appropriate pore size distribution, and the alumina content is controllable. Compared with the gel method, it has better economic benefits and lower costs, which are reflected in low raw material costs, savings in equipment and energy consumption costs, and low labor costs. Therefore, the precipitation method of the present invention has significant advantages and high application value in the preparation of high-stability calcium oxide efficient adsorbents, and is expected to be widely applied in related fields such as gas separation, drying, and wastewater treatment.

[0127] The above describes the present invention and its implementation manners. Such description is not restrictive. If those of ordinary skill in the art are inspired by it and, without departing from the gist of the present invention, design similar structural manners and embodiments to this technical solution without creative efforts, they shall fall within the protection scope of the present invention.

Claims

1. A preparation method of a highly stable calcium oxide high-efficiency adsorbent, characterized in that: It includes the following steps: S1. Preparation Preparation Raw materials: Prepare high-purity calcium chloride, sodium carbonate as calcium source and precipitant, and aluminum nitrate as an auxiliary agent; Additives: Prepare polyvinyl alcohol (PVA) as an additive to control the precipitation structure, and prepare polyethylene glycol as a pore-forming agent; Solution preparation: Prepare 0.5 mol / L calcium chloride solution, 0.5 mol / L sodium carbonate solution, 0.05 mol / L aluminum nitrate solution, 2% (mass fraction) polyvinyl alcohol solution, and 5% (mass fraction) polyethylene glycol solution respectively; S2. Precipitation reaction Under stirring conditions, slowly add the aluminum nitrate solution to the calcium chloride solution. The addition amount of aluminum nitrate is 8% of the molar amount of the calcium salt, and continue stirring for 30 minutes to make the aluminum nitrate evenly dispersed in the calcium chloride solution. Then, pour the polyvinyl alcohol solution into the above mixed solution and continue stirring for 30 minutes to fully dissolve the polyvinyl alcohol and mix it evenly with the solution; Maintain the stirring state, and slowly add the polyethylene glycol solution to the mixed solution of calcium chloride, aluminum nitrate and polyvinyl alcohol. Then, slowly add the sodium carbonate solution drop by drop to the above mixed solution at a slower speed (1 - 2 drops / second), control the reaction temperature at 30 °C, keep the pH value at 8 - 9, and set the stirring speed at 200 r / min; S3. Filtration and washing After the reaction is completed, use a Buchner funnel and a suction flask to filter the mixed solution and collect the precipitate; Wash the precipitate with deionized water multiple times. After each washing, judge the washing effect by detecting whether there are chloride ions in the washing solution until no chloride ions are detected in the washing solution to remove the impurity ions adsorbed on the surface of the precipitate, and at the same time remove the residues of unreacted additives and auxiliary agents; S4. Drying and calcination Drying: Transfer the washed precipitate to an oven and dry it at 100 °C for 18 hours to completely remove the moisture; Calcination: Put the dried sample into a high-temperature furnace, heat it to 900 °C at a heating rate of 5 °C / min, and calcine it at this temperature for 2.5 hours; S5. Product collection and storage After the calcination is completed, wait for the high-temperature furnace to cool to room temperature, take out the prepared calcium oxide adsorbent, and store it sealed in a desiccator to prevent it from absorbing moisture and carbon dioxide in the air and deteriorating; S6: Product quality detection Detect whether the product after calcination is the target product calcium oxide, detect whether there are impurity phases, and measure the specific surface area and pore size distribution of the product.

2. The preparation method of a highly stable calcium oxide high-efficiency adsorbent according to claim 1, characterized in that: The purity of the raw materials in step S1 is above analytical purity, and before use, the purity of calcium chloride, sodium carbonate, and aluminum nitrate is detected by titration method or spectroscopic analysis.

3. The preparation method of a highly stable calcium oxide high-efficiency adsorbent according to claim 1, characterized in that: In step S3, the method for detecting whether there are chloride ions is: add silver nitrate solution to the washing solution. If no white precipitate is produced, it indicates that the chloride ions have been washed away.

4. The preparation method of a highly stable calcium oxide high-efficiency adsorbent according to claim 1, characterized in that: During the washing process in step S3, it is also necessary to detect whether there are nitrate ions. Specifically, use the brown ring experiment to detect nitrate ions.

5. The preparation method of a highly stable calcium oxide high-efficiency adsorbent according to claim 1, characterized in that: The judgment of the end point of the precipitation reaction in step S2: It is determined by observing that no more precipitate is formed or taking the supernatant and dropping sodium carbonate solution. If no new precipitate is produced.

6. The preparation method of a highly stable calcium oxide high-efficiency adsorbent according to claim 1, characterized in that: The calcination in step S4 is carried out under the protection of inert gas or in a vacuum high-temperature furnace.

7. The preparation method of a highly stable calcium oxide high-efficiency adsorbent according to claim 1, characterized in that: In step S6, the crystal structure of the product is analyzed by XRD (X-ray diffraction) to determine whether it is the target product calcium oxide and to detect whether there is an impurity phase; BET (specific surface area and porosity analysis) is used to measure the specific surface area and pore size distribution of the product.

8. The preparation method of a highly stable calcium oxide high-efficiency adsorbent according to claim 1, characterized in that: In step S6, the content of alumina in the product is determined by chemical analysis methods, so as to infer whether the addition amount of aluminum nitrate in step S1 is appropriate.