Method for preparing vaterite type nano calcium carbonate from calcium carbide purified ash

Abstract

The invention discloses a method for preparing vaterite type nano calcium carbonate by using calcium carbide purified ash, which comprises the following steps: adding amino acid into a calcium carbide purified ash solution, and reacting to obtain an amino acid calcium solution; then adding an amino silane coupling agent into the amino acid calcium solution to obtain a modified amino acid calcium solution; mixing and stirring an ammonium carbonate solution and the modified amino acid calcium solution to completely react, washing and filtering to obtain vaterite type nano calcium carbonate and an ammonium salt solution; and finally, heating the filtered ammonium salt solution, and recovering ammonia gas and amino acid. Amino acid calcium is modified through the amino silane coupling agent, then calcium carbonate is prepared, modification can be conducted from the molecular level, the better modification effect is achieved, nanoscale vaterite type calcium carbonate with the small particle size and high purity can be obtained, and the tensile strength of calcium carbonate is remarkably enhanced.

Description

Technical Field

[0001] This invention relates to the field of calcium carbonate preparation technology, and more specifically, to a method for preparing aragonite-type nano-calcium carbonate using calcium carbide purification ash. Background Technology

[0002] Currently, most domestic calcium carbide production involves a chemical reaction in a closed furnace using quicklime and coke as raw materials, at temperatures ranging from 1800 to 2200°C. This process produces calcium carbide and releases furnace exhaust gas. After purification, this exhaust gas generates solid waste, known as calcium carbide purification ash. This treated exhaust gas contains a large amount of carbon dioxide, and direct emission of this gas would have adverse effects on the atmosphere. The treatment of calcium carbide purification ash and carbon dioxide has long been a challenge for clean production and environmental protection efforts in calcium carbide enterprises. Specifically, the production of one ton of calcium carbide generates approximately 400 cubic meters of carbon dioxide in the furnace. 3 The calcium carbide industry typically treats its calcium carbide purification ash by transporting it off-site and then landfilling it. During unloading, transportation, and dumping, the dust easily becomes airborne, causing air pollution. Carbon dioxide is treated by adsorbing impurities to meet emission standards before release, resulting in significantly increased economic costs. Therefore, effectively disposing of calcium carbide purification ash and carbon dioxide, eliminating safety hazards while meeting environmental protection requirements, has always been a challenge for the calcium carbide industry.

[0003] Calcium carbide purification ash is used in the industry as a raw material for the preparation of calcium carbonate. It is usually prepared by liquid phase method, which is simple, produces uniform particle size, and causes less pollution. At the same time, the quality of the product can be affected by controlling the reaction conditions. For example, the article "Process and Mechanism for Preparing Spherical Cascade Calcium Carbonate from Calcium Carbide Slag" discloses the preparation of high-purity spherical cascade calcium carbonate using calcium carbide slag as raw material and glycine as an additive under normal pressure via a calcium carbide slag-CO2 reaction method. The method involves using untreated calcium carbide slag, CO2, and glycine as raw materials to prepare a calcium carbide slag suspension with a Ca(OH)2 concentration of 0.5 mol / L. When the suspension temperature reaches 15℃, glycine is added to the suspension according to the n(Gly) / n(Ca) (0~3.0) value. After stirring, CO2 is introduced, and the reaction is terminated when the pH value is suitable. The mixture is then filtered, washed, and dried to obtain well-dispersed spherical cascade calcium carbonate with a rough, protruding surface, a particle size of 1~10μm, and a purity of approximately 93%. However, its particle size, purity, and other properties still need further improvement.

[0004] For example, invention patent CN107381611A discloses a method for preparing modified nano-calcium carbonate powder for artificial stone. The method involves reacting a carbide slag solution and an ammonium chloride solution to obtain a calcium chloride solution. Then, an ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate, is added to the calcium chloride solution. After thorough mixing, an ammonium bicarbonate solution is added to the solution, and a microwave-catalyzed synthesis reaction is performed to obtain a suspension. The suspension is then ultrasonically dispersed, and 5–15 wt% of a modifier is added. The mixture is then ultrasonically sonicated, filtered, and dried to obtain modified nano-calcium carbonate powder for artificial stone. This method modifies calcium carbonate, improving its dispersibility, compatibility, and impact resistance. However, calcium carbonate is difficult to modify at the molecular level; most modifications can only be achieved through physical blending, resulting in poor modification effects.

[0005] For example, the invention patent with publication number CN109809442A discloses a system and method for producing magnesium hydroxide and light calcium carbonate by purifying ash residue in a calcium carbide furnace. The method produces light calcium carbonate and uses hydrochloric acid to dissolve calcium ions to obtain calcite-type calcium carbonate. The accumulation of chloride ions will lead to excessive impurity content in the product, reducing the product value, and the raw materials cannot be recycled, resulting in relatively high costs.

[0006] Most existing processing technologies are not only energy-intensive and environmentally unfriendly, but also have poor overall economic benefits. The resulting nano-calcium carbonate is mostly calcite-type, while aragonite-type nano-calcium carbonate has advantages that other crystalline calcium carbonate types do not possess. Aragonite-type calcium carbonate has advantages such as hollow or porous structure, uniform particle size distribution, micro-nano size, high hydrophilicity, large specific surface area, good solubility and dispersibility, good biocompatibility and safety, good degradability, strong phase transformation ability, good mechanical properties and thermal stability, and spherical distribution. Therefore, aragonite-type calcium carbonate has great application prospects and economic benefits in the fields of daily use, biomedicine, and new materials. How to prepare high-performance aragonite-type calcium carbonate is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of the above, the present invention provides a method for preparing aragonite-type nano-calcium carbonate using calcium carbide purification ash, which can modify calcium carbonate at the molecular level to obtain high-performance aragonite-type calcium carbonate with nano-size, high purity and good tensile strength.

[0008] This invention provides a method for preparing aragonite-type nano-calcium carbonate using calcium carbide purification ash, comprising the following steps:

[0009] (1) Dissolve calcium carbide purification ash in water, filter and obtain calcium carbide purification ash solution; then add amino acids to calcium carbide purification ash solution and react to obtain amino acid calcium solution;

[0010] (2) Add aminosilane coupling agent to amino acid calcium solution to obtain modified amino acid calcium solution;

[0011] (3) React ammonia water and carbon dioxide to produce ammonium carbonate solution;

[0012] (4) After the ammonium carbonate solution and the modified amino acid calcium solution are mixed and stirred until the reaction is complete, the mixture is washed and filtered to obtain aragonite-type nano-calcium carbonate and ammonium salt solution.

[0013] (5) The filtered ammonium salt solution is heated to recover ammonia and amino acids.

[0014] This invention utilizes the hydrolysis of organosilicon in aminosilane coupling agents and the Ca in amino acid calcium. 2+ Complexation is used to modify amino acid calcium. Because amino acid calcium has excellent water solubility and biocompatibility, adding aminosilane coupling agents can effectively modify it at the molecular level. The aminosilane coupling agent, when linked to the amino acid calcium, achieves better modification and dispersibility. In subsequent reactions, the aminosilane coupling agent can be more tightly bound to the final product, calcium carbonate, enhancing its tensile strength and other properties. Furthermore, in the subsequent use of calcium carbonate, when used in combination with organic compounds depending on the application, the organic functional groups in the aminosilane coupling agent will tightly connect with the organic compound, promoting interfacial fusion and increasing the strength and other properties of the applied material.

[0015] Among them, according to amino acids and Ca 2+ Amino acids were added to the calcium carbide purification ash solution at a molar ratio of 2.0 to 2.2:1.

[0016] amino acids and Ca 2+ The reaction is carried out according to stoichiometric ratios, with a slight excess of amino acids to ensure complete formation of calcium amino acids, thereby improving the product's formation rate and utilization. However, the excess should not be too much, as this will not only increase production costs but also affect the purity of the product and subsequent reactions, increasing the probability of side reactions and impacting the formation, yield, and purity of the target product.

[0017] The calcium carbide purification ash solution and amino acids react at 90℃~110℃ to obtain an amino acid calcium solution.

[0018] A suitable reaction temperature can improve the yield and rate of calcium amino acid formation, ensuring the quality of the calcium amino acid. Excessively high temperatures may cause the reaction rate to be too fast and difficult to control, potentially even triggering side reactions, altering the properties of amino acids, and affecting the formation and yield of calcium amino acid. It may also lead to the decomposition or structural changes of the formed calcium amino acid, reducing the purity and quality of the product. Conversely, excessively low temperatures will result in a slow reaction rate, leading to excessively long reaction times and low production efficiency. Therefore, controlling the temperature within the range of 90℃ to 110℃ ensures that the reaction is completed within a reasonable time, ensuring reaction efficiency, improving reaction selectivity, avoiding excessively vigorous reactions that could trigger side reactions, ensuring product purity, and helping to maintain the structural stability of the calcium amino acid, thus ensuring the quality and stability of the product.

[0019] In this process, an aminosilane coupling agent is added to an amino acid calcium solution at a temperature of 60℃ to 80℃.

[0020] The modification process of amino acid calcium requires a suitable temperature. At an appropriate temperature, the hydrolysis of organosilicon in the aminosilane coupling agent and the Ca in the amino acid calcium react... 2+ Complexation forms a stable complex, and excessively high or low temperatures can affect the performance of the final product.

[0021] Excessive temperature can cause the aminosilane coupling agent to decompose or turn yellow, destroying the formed coupling bonds and affecting the coupling effect. Insufficient temperature can affect the coupling rate, and due to the low activity of the aminosilane coupling agent molecules, the reaction with amino calcium may be insufficient, resulting in poor coupling effect and failing to effectively improve the performance of amino calcium. Moreover, temperature affects the solubility and dispersibility of aminosilane coupling agent and amino calcium in solution. Appropriate temperature can improve the solubility of the substance, allowing the aminosilane coupling agent to be better dispersed in the amino calcium solution, which is beneficial to the reaction. However, excessive temperature may cause the volatilization or precipitation of some components in the solution, affecting the homogeneity of the system and the reaction. Insufficient temperature is not conducive to the dissolution and reaction of the substance.

[0022] The amount of aminosilane coupling agent added is Ca 2+ Content: 2-3 wt%.

[0023] An appropriate amount of aminosilane coupling agent can effectively enhance the mechanical properties of the final product, such as tensile strength, as well as improve the dispersibility of the coupled substances and the processing performance of the product. However, adding too much aminosilane coupling agent will reduce the mechanical properties and stability of the final product and make it difficult to process. Adding too little aminosilane coupling agent will result in insufficient compatibility between the product and other products.

[0024] The molar ratio of ammonia to carbon dioxide is 2.0 to 2.2:1.

[0025] The resulting aragonite-type nano-calcium carbonate has a particle size range of 10 nm to 100 nm.

[0026] The resulting aragonite-type nano-calcium carbonate has a particle size range of 10 nm to 30 nm.

[0027] The purity of the obtained aragonite-type nano-calcium carbonate is ≥95%.

[0028] The tensile strength of the obtained aragonite-type nano-calcium carbonate is ≥20 MPa.

[0029] The aragonite-type nano-calcium carbonate prepared by the method of this invention has the advantages of small particle size and narrow distribution range. The reaction raw materials are simple and clean, avoiding interference from impurities and side reactions. The obtained aragonite-type nano-calcium carbonate has high purity and high tensile strength.

[0030] The beneficial effects of this technical solution are as follows:

[0031] (1) In this invention, aminosilane coupling agent is first used to modify amino acid calcium, and then calcium carbonate is prepared. This can modify the calcium carbonate at the molecular level, which has a better modification effect. Small-sized nano-sized aragonite-type calcium carbonate with high purity can be obtained, and the tensile strength of calcium carbonate is significantly enhanced.

[0032] (2) The present invention uses a liquid phase method, which has mild reaction conditions and does not require high temperature, high pressure and other conditions, thus reducing production costs and safety risks;

[0033] (3) The preparation method of the present invention is simple and easy to mass-produce, which meets the needs of industrial production and is conducive to promoting the widespread application of aragonite-type nano-sized calcium carbonate. Attached Figure Description

[0034] Figure 1 The images show the XRD patterns of calcium carbonate obtained in Comparative Examples 1 and 2 and Example 1. Detailed Implementation

[0035] The embodiments of this application will now be described in more detail. This application can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to provide a more thorough and complete understanding of the application. It should be understood that the embodiments of this application are for illustrative purposes only and are not intended to limit the scope of protection of this application.

[0036] Embodiments 1 to 6 of the present invention are implemented according to the following technical solutions, including the following steps:

[0037] (1) Dissolve the calcium carbide purification ash in water, filter, and obtain a calcium carbide purification ash solution; then, according to the amino acid and Ca... 2+Amino acids are added to the calcium carbide purification ash solution at a molar ratio of 2.0 to 2.2:1. The calcium carbide purification ash solution and amino acids react at 90℃ to 110℃ to obtain an amino acid calcium solution.

[0038] (2) An aminosilane coupling agent was added to an amino acid calcium solution at a temperature of 60℃~80℃ to obtain a modified amino acid calcium solution; wherein the amount of aminosilane coupling agent added was Ca 2+ Content 2-3 wt%;

[0039] (3) Ammonia water and carbon dioxide are reacted to produce ammonium carbonate solution; wherein the molar ratio of ammonia water to carbon dioxide is 2.0 to 2.2:1;

[0040] (4) After the ammonium carbonate solution and the modified amino acid calcium solution are mixed and stirred until the reaction is complete, the mixture is washed and filtered to obtain aragonite-type nano-calcium carbonate and ammonium salt solution.

[0041] (5) The filtered ammonium salt solution is heated to obtain gaseous ammonia and liquid amino acids, which are then fed into a storage tank for recycling.

[0042] Comparative Example 1:

[0043] (1) Take 80g of calcium carbide purification ash whose main component is 70wt% calcium oxide, 1000g of water and 200g of hydrochloric acid (37wt%) and mix them at 110℃. Filter to obtain calcium chloride solution.

[0044] (2) Ammonia and carbon dioxide are reacted to produce an ammonium carbonate solution; the molar ratio of ammonia to carbon dioxide is 2.0:1.

[0045] (3) After the calcium chloride solution and ammonium carbonate solution are stirred and reacted completely, the solid and liquid are separated. After the filter cake is washed and dried, calcite-type calcium carbonate product and ammonium chloride solution are obtained.

[0046] (4) The ammonia and hydrochloric acid were recovered by heating the ammonium chloride solution. However, the hydrochloric acid was too acidic and could not be completely recovered.

[0047] Comparative Example 2:

[0048] (1) Take 80g of calcium carbide purification ash whose main component is 70wt% calcium oxide, 1000g of water and 120g of acetic acid, mix and react at 110℃, filter, and obtain calcium acetate solution;

[0049] (2) Ammonia and carbon dioxide are reacted to produce an ammonium carbonate solution; the molar ratio of ammonia to carbon dioxide is 2.0:1.

[0050] (3) Add aminosilane coupling agent KBE-573 to the prepared calcium acetate aqueous solution, wherein KBE-573 is Ca2+ The content is 2.5 wt%, and after stirring evenly, a modified calcium acetate solution is obtained;

[0051] (4) After the ammonium carbonate solution and the modified calcium acetate solution are mixed and stirred until the reaction is complete, the solid and liquid are separated. After the filter cake is washed and dried, calcite-type light calcium carbonate product and ammonium salt solution are obtained.

[0052] (5) The ammonium salt solution is heated and stirred at 80°C to obtain gaseous ammonia and liquid acetic acid, which are then introduced into a storage tank for recycling.

[0053] Comparative Example 3:

[0054] (1) Dissolve the calcium carbide purification ash in water, filter, and obtain a calcium carbide purification ash solution; then, according to the amino acid and Ca... 2+ Amino acids were added to the calcium carbide purification ash solution at a molar ratio of 2.0:1, and the reaction was carried out at 110℃ to obtain an amino acid calcium solution.

[0055] (2) Ammonia and carbon dioxide are reacted to produce an ammonium carbonate solution; the molar ratio of ammonia to carbon dioxide is 2.0:1.

[0056] (3) After the ammonium carbonate solution and the amino acid calcium solution are mixed and stirred until the reaction is complete, the mixture is washed and dried to obtain the aragonite-type nano calcium carbonate product and the ammonium salt solution.

[0057] (4) The ammonium salt solution is heated and stirred at 80°C to obtain gaseous ammonia and liquid aspartic acid, which are then introduced into a storage tank for recycling.

[0058] Comparative Example 4:

[0059] (1) Dissolve the calcium carbide purification ash in water, filter, and obtain a calcium carbide purification ash solution; then, according to the amino acid and Ca... 2+ Amino acids were added to the calcium carbide purification ash solution at a molar ratio of 2.0:1, and the reaction was carried out at 110℃ to obtain an amino acid calcium solution.

[0060] (2) Ammonia and carbon dioxide are reacted to produce an ammonium carbonate solution; the molar ratio of ammonia to carbon dioxide is 2.0:1.

[0061] (3) After the ammonium carbonate solution and the amino acid calcium solution are mixed and stirred until the reaction is complete, aminosilane coupling agent KBE-573 is added, wherein KBE-573 is Ca 2+ The content is 3wt%, and after washing and drying, modified aragonite-type nano calcium carbonate product and ammonium salt solution are obtained;

[0062] (4) The ammonium salt solution is heated and stirred at 80°C to obtain gaseous ammonia and liquid aspartic acid, which are then introduced into a storage tank for recycling.

[0063] Table 1 shows the specific implementation conditions of the embodiments of the present invention, and Table 2 shows the test results of the products obtained from the embodiments and comparative examples of the present invention. In Comparative Example 1, hydrochloric acid was used as the raw material, and the calcium chloride aqueous solution did not contain organic matter, so the aminosilane coupling agent could not modify it, resulting in calcite-type calcium carbonate with low tensile strength of only 12 MPa. In Comparative Example 2, acetic acid was used as the raw material. Although calcium acetate could be modified by the aminosilane coupling agent, the resulting calcium carbonate was calcite-type with a large particle size of 0.5 μm to 1 μm, and only had a tensile strength of 16 MPa. Figure 1 The XRD patterns also show that Comparative Examples 1 and 2 are calcite-type calcium carbonate, while the calcium carbonate obtained in the embodiments of the present invention is aragonite-type. Comparative Example 3 is modified with amino acid calcium without the addition of aminosilane coupling agent, resulting in aragonite-type nano-calcium carbonate, but its tensile strength is significantly reduced to only 15 MPa. The calcium carbonate prepared by the method of the present invention is aragonite-type nano-calcium carbonate, which has the advantages of small particle size, high purity and high calcium recovery rate, and also has high tensile strength, all greater than 20 MPa. The experiment proves that the method of the present invention can obtain small-particle-size nano-sized aragonite-type calcium carbonate and significantly enhance the tensile strength of calcium carbonate.

[0064] Furthermore, Comparative Example 4 first obtained calcium carbonate and then modified it with an aminosilane coupling agent. As can be seen from the test results in Table 2, its performance was worse than that of the calcium carbonate obtained by modifying amino acid calcium in this invention. This proves that the present invention first modifies amino acid calcium with an aminosilane coupling agent and then prepares calcium carbonate, which can modify it at the molecular level and has a better modification effect than directly modifying calcium carbonate. The resulting nanosphere aragonite-type calcium carbonate has a smaller particle size, higher purity, and greater tensile strength.

[0065] Table 1 Specific Implementation Conditions of the Embodiments

[0066]

[0067] Table 2. Test results of products obtained from the examples and comparative examples.

[0068] Case Particle size range purity Calcium recovery rate tensile strength Example 1 10nm~30nm 99％ 98％ 23Mpa Example 2 10nm~50nm 95％ 96％ 21 MPa Example 3 10nm~80nm 97％ 95％ 21.5 MPa Example 4 20nm~50nm 96％ 98％ 22Mpa Example 5 20nm~80nm 96％ 98％ 20Mpa Example 6 20nm~100nm 95％ 97％ 22Mpa Comparative Example 1 20nm~100um 94％ 96％ 12Mpa Comparative Example 2 0.5um~1um 96％ 94％ 16Mpa Comparative Example 3 20nm~100um 96％ 94％ 15Mpa Comparative Example 4 20nm~100um 96％ 94％ 20Mpa

[0069] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of protection of the claims.

Claims

1. A method for preparing spheroidal aragonite-type nano-calcium carbonate using calcium carbide purification ash, characterized in that, The following steps are involved: (1) Dissolve calcium carbide purification ash in water, filter and obtain calcium carbide purification ash solution; then add amino acids to calcium carbide purification ash solution and react to obtain amino acid calcium solution; (2) Add aminosilane coupling agent to amino acid calcium solution to obtain modified amino acid calcium solution; (3) React ammonia water and carbon dioxide to produce ammonium carbonate solution; (4) After the ammonium carbonate solution and the modified amino acid calcium solution are mixed and stirred until the reaction is complete, the mixture is washed and filtered to obtain aragonite-type nano-calcium carbonate and ammonium salt solution. (5) The filtered ammonium salt solution is heated to recover ammonia and amino acids.

2. The method for preparing spheroidal aragonite-type nano-calcium carbonate using calcium carbide purified ash according to claim 1, characterized in that, According to amino acids and Ca 2+ Amino acids were added to the calcium carbide purification ash solution at a molar ratio of 2.0 to 2.2:

1.

3. The method for preparing spheroidal aragonite-type nano-calcium carbonate using calcium carbide purified ash according to claim 1, characterized in that, An amino acid calcium solution is obtained by reacting calcium carbide purification ash solution and amino acids at 90℃~110℃.

4. The method for preparing spheroidal aragonite-type nano-calcium carbonate using calcium carbide purification ash according to claim 1, characterized in that, An aminosilane coupling agent is added to an amino acid calcium solution at a temperature of 60℃~80℃.

5. The method for preparing spheroidal aragonite-type nano-calcium carbonate using calcium carbide purification ash according to claim 1, characterized in that, The amount of aminosilane coupling agent added is Ca 2+ Content: 2-3 wt%.

6. The method for preparing spheroidal aragonite-type nano-calcium carbonate using calcium carbide purified ash according to claim 1, characterized in that, The molar ratio of ammonia to carbon dioxide is 2.0 to 2.2:

1.

7. A method for preparing spheroidal aragonite-type nano-calcium carbonate using calcium carbide purified ash according to any one of claims 1 to 6, characterized in that, The resulting spheroidal aragonite-type nano-calcium carbonate has a particle size range of 10 nm to 100 nm.

8. The method for preparing spheroidal aragonite-type nano-calcium carbonate using calcium carbide purified ash according to claim 7, characterized in that, The resulting spheroidal aragonite-type nano-calcium carbonate has a particle size range of 10 nm to 30 nm.

9. A method for preparing spheroidal aragonite-type nano-calcium carbonate using calcium carbide purified ash according to any one of claims 1 to 6, characterized in that, The purity of the obtained aragonite-type nano-calcium carbonate is ≥95%.

10. A method for preparing spheroidal aragonite-type nano-calcium carbonate using calcium carbide purified ash according to any one of claims 1 to 6, characterized in that, The tensile strength of the obtained aragonite-type nano-calcium carbonate is ≥20 MPa.

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