Method for controllably preparing nano calcium carbonate by leaching acetylene sludge with maleic acid and indirectly mineralizing CO2
By using maleic acid as a leaching agent to react with carbide slag, combined with pH adjustment and CO2 carbonation, the problems of uneven particle size and incomplete impurity separation in the preparation of calcium carbonate from carbide slag were solved, achieving efficient preparation of nano-calcium carbonate, which is suitable for large-scale production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-03-27
AI Technical Summary
The existing process for preparing calcium carbonate from carbide slag has problems such as uneven particle size distribution of calcium carbonate, incomplete separation of impurities, long leaching time, and poor economic efficiency. In particular, when using carbide slag to indirectly mineralize CO2 to prepare nano-calcium carbonate, there are environmental problems such as high consumption of leaching agent and ammonia volatilization.
Using maleic acid as the leaching agent, it is mixed with carbide slag and a pH adjuster is added. By adjusting the pH value and introducing CO2 gas, a carbonation reaction is carried out to prepare nano-calcium carbonate. The process is simple, has high leaching efficiency, and is suitable for large-scale production.
This method achieves efficient leaching of calcium ions from carbide slag, producing nano-calcium carbonate products that meet commercial requirements. It solves the problems of uneven particle size distribution and incomplete impurity separation, and features environmental friendliness and low energy consumption.
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Figure CN121735289A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to CO2 capture, utilization and storage technology, solid waste resource utilization and chemical process materials technology, specifically to a method for the indirect mineralization of CO2 from carbide slag by maleic acid leaching to controllably prepare nano-calcium carbonate. Background Technology
[0002] Carbon capture, utilization, and storage (CCUS) technology is considered a highly promising carbon reduction technology. Compared to marine and geological storage, mineral carbon sequestration based on alkaline solid waste has become a highly promising carbon sequestration pathway due to its advantages such as low raw material costs, mild reaction conditions, and stable storage. This technology achieves the safest long-term storage by converting CO2 into thermodynamically stable carbonate minerals. It not only provides a feasible solution but also has significant economic benefits, making it an effective way to synergistically promote solid waste resource utilization and carbon reduction.
[0003] The mineralization of industrial solid waste can be divided into two pathways: direct mineralization and indirect mineralization. Direct mineralization involves the direct contact and reaction of CO2 with solid particles, completing CO2 absorption and mineralization in one step. This process is simple, but it suffers from slow reaction kinetics and limited mineralization efficiency due to the low reactivity of the solids. Furthermore, co-precipitation of impurities easily leads to low product purity and difficult morphology control, and the separation of mineralized products from unreacted raw materials is challenging. In contrast, the indirect method divides the CO2 mineralization reaction into two steps: calcium ion extraction and CO2 absorption mineralization. The indirect mineralization method completes the leaching of Ca and CO2 absorption and conversion through two steps of leaching and mineralization. This not only improves adaptability to low-reactivity minerals but also achieves high mineralization efficiency, producing high-purity, high-value-added calcium carbonate products with controllable morphology. However, this method requires addressing the consumption, recycling, and recovery of the leaching agent.
[0004] Calcium carbide slag (CS) is a byproduct of calcium carbide hydrolysis, producing approximately 1.2 tons of dry-basis calcium carbide slag for every ton of calcium carbide produced. Currently, calcium carbide slag is mainly used in building materials, chemicals, and landfill, but large quantities remain stockpiled, impacting the environment. Due to its high calcium hydroxide content, CS is a typical calcium-based alkaline industrial solid waste and an ideal raw material for CO2 mineralization. Increasingly, researchers are proposing using calcium carbide slag as a calcium source to produce high-value-added calcium carbonate products through CO2 mineralization technology, while simultaneously achieving permanent CO2 fixation, providing a new approach to reducing anthropogenic carbon emissions and utilizing waste resources.
[0005] Domestic and foreign scholars have conducted extensive research on the two-step indirect mineralization of CO2 to prepare nano-calcium carbonate using carbide slag. It can be roughly divided into the following categories: (1) Using acid / alkali leaching process, firstly, acid / alkali (such as HCl, acetic acid, NaOH, etc.) is used to pretreat carbide slag, and then CO2 is introduced to carry out mineralization reaction. Although the pretreatment with hydrochloric acid can promote the agglomeration of calcium carbonate whiskers and help to synthesize uniformly distributed aragonite-type calcium carbonate whiskers, problems such as low conversion rate, long reaction time and difficulty in product separation will occur. (2) Using inorganic ammonium salts (such as ammonium chloride, ammonium carbonate, ammonium nitrate, etc.) as leaching agents for carbide slag, nano-calcium carbonate is prepared by carbonation. The utilization rate of carbide slag under this process can reach more than 90%, the purity and whiteness of the prepared product are extremely high, and it has a significant effect on separating impurities in carbide slag. However, it will bring problems and challenges such as chlorine wastewater treatment and ammonia volatilization. (3) Using amino acids to indirectly mineralize CO2 in conjunction with calcium carbide slag. Compared with other leaching agents, amino acids have the advantages of being green, environmentally friendly, and recyclable. They also have a better leaching effect on calcium in calcium carbide slag and can affect the growth of calcium carbonate crystal nuclei to prepare nano-calcium carbonate. However, there are still problems such as the energy consumption of amino acid regeneration and high cost.
[0006] In existing technologies, the direct CO2 carbonation method using calcium carbide slag to produce calcium carbonate results in a large particle size distribution and incomplete impurity separation, leading to a product purity lower than that of commercially available carbonation products. While the indirect carbonation method using calcium carbide slag can yield fine or nano-sized calcium carbonate, the calcium leaching time is long, and there are also problems such as difficulty in treating chlorine-containing wastewater and poor economic efficiency. Summary of the Invention
[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for the controllable preparation of nano-calcium carbonate by indirect CO2 mineralization of calcium carbide slag using maleic acid leaching. This method first mixes calcium carbide slag with maleic acid leaching agent, stirs and reacts, then filters to obtain a calcium-rich leaching solution. Next, a pH adjuster is added to the calcium-rich leaching solution to adjust the pH value. After aging, CO2 gas is introduced and the reaction is continuously stirred. Finally, the reaction is terminated, and solid-liquid separation is performed to obtain nano-calcium carbonate. This method uses maleic acid as the calcium carbide slag leaching agent to prepare nano-calcium carbonate through a two-step indirect mineralization process. The leaching agent used is green and environmentally friendly, enhances the leaching of calcium ions, and can obtain nano-sized calcium carbonate that meets the requirements of commercial products. This solves the problems of uneven particle size distribution and incomplete separation of impurities in calcium carbide slag in existing calcium carbonate preparation processes. The mineralization process is simple, the leaching-mineralization cycle is short, and it is suitable for the large-scale industrial production of nano-calcium carbonate.
[0008] To achieve the above technical effects, the following technical solution is adopted: A method for the controllable preparation of nano-calcium carbonate by indirect CO2 mineralization from calcium carbide slag using maleic acid leaching includes the following steps: Step S1: Leaching of active calcium components from carbide slag The calcium carbide slag was mixed with maleic acid leaching agent (pH 2-5), stirred and reacted, and then filtered to obtain a calcium-rich leaching solution. Step S2: CO2 carbonation reaction of calcium-rich extract A pH adjuster is added to the calcium-rich leachate obtained in step S1 to adjust the pH value. After aging, CO2 gas is introduced and the reaction is continuously stirred. At the same time, the pH change during the reaction is monitored and recorded. When the pH endpoint is reached, the reaction ends and solid-liquid separation is performed. The solid phase is dried and ground to obtain the nano-calcium carbonate.
[0009] Furthermore, the carbide slag pretreatment process is as follows: The carbide slag is first dried at 105℃ for 1-2 h, and then mechanically crushed to obtain solid particles with a particle size of less than 150 μm. The carbide slag has a moisture content of 8 wt%-12 wt% and a CaO content of 65 wt%-72 wt%.
[0010] Furthermore, the concentration of maleic acid leaching agent in step S1 is 0.8~1.4 mol / L.
[0011] Furthermore, in step S1, the solid-liquid ratio of calcium carbide slag to maleic acid leaching agent is 30~70 g / L.
[0012] Furthermore, the stirring reaction conditions in step S1 are as follows: Stir the mixture at 300-700 rpm for 2-45 minutes at 20-85℃.
[0013] Furthermore, in step S2, the pH adjuster adjusts the pH value to 9-14.
[0014] Furthermore, the reaction conditions in step S2 are specifically as follows: Carbonation is carried out by introducing CO2 gas at a flow rate of 100-700 mL / min at 25-85℃ for 5-60 min. A chemical precipitation method is used, with CO2 gas introduced into the bottom of the reactor.
[0015] Furthermore, the pH endpoint in step S2 is 7-10.
[0016] Furthermore, the pH adjuster in step S2 is NaOH.
[0017] Furthermore, the average particle size distribution of the nano-calcium carbonate after drying and grinding is 50~300 nm.
[0018] The calcium carbide slag is a byproduct of calcium carbide hydrolysis. Approximately 1.2 tons of dry calcium carbide slag are generated for every ton of calcium carbide produced. It is characterized by high alkalinity and high calcium content.
[0019] The beneficial effects of this invention are as follows: (1) Calcium carbide slag is an industrial solid waste with a high calcium content. By using maleic acid leaching, no less than 95% of the calcium content can be leached out within 5 minutes under normal temperature and pressure and gentle stirring. (2) The calcium-rich leaching solution can achieve a carbonation efficiency of not less than 90% and meet the requirements of commercially viable nano-calcium carbonate products within a reaction time of 40 min at room temperature and pressure. (3) Using unsaturated organic acids as leaching agents solves the problems of uneven particle size distribution of calcium carbonate and incomplete separation of impurities in calcium carbide slag in the existing calcium carbonate preparation process. (4) The process is simple, with high leaching and mineralization efficiency, low energy consumption, low equipment investment and operating costs, and the product meets the commercialization requirements of nano-calcium carbonate. It can achieve the dual benefits of high-value utilization of carbide slag and permanent CO2 sequestration and emission reduction, and is an environmentally friendly process. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of the entire process of preparing nano-calcium carbonate by indirect CO2 mineralization of carbide slag in an embodiment of the invention; Figure 2 This is a mineral composition diagram of the calcium carbonate products prepared in some embodiments of the present invention; Figure 3 This is a microscopic morphology image of the calcium carbonate product prepared in Example 1 of the present invention; Figure 4 This is a surface microstructure image of the calcium carbonate product prepared in Example 5 of the present invention; Figure 5 This is a microscopic morphology image of the calcium carbonate product prepared in Example 6 of the present invention; Figure 6 This is a microscopic morphology diagram of the calcium carbonate product prepared in Example 7 of the present invention. Detailed Implementation
[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0022] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, 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.
[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.
[0024] This invention relates to a method for the controllable preparation of nano-calcium carbonate by indirect CO2 mineralization of carbide slag based on the action of unsaturated acids, comprising the following steps: (1) Leaching of active calcium components in carbide slag: Carbide slag is mixed with maleic acid leaching agent, stirred and reacted, and then filtered to obtain calcium-rich leaching solution; (2) CO2 carbonation reaction of calcium-rich extract: Add pH adjuster to calcium-rich extract in step (1), and after aging for a period of time, introduce CO2 gas and stir continuously to react. At the same time, monitor and record the pH change during the reaction. After a period of time, the reaction ends and solid-liquid separation is carried out. The solid phase is dried and ground to obtain nano-calcium carbonate.
[0025] In some embodiments, during leaching, the solid-liquid ratio of the leaching agent solution to the calcium carbide slag is 30-70 g / L, and the concentration of the leaching agent is 0.8-1.4 mol / L. Specifically, the leaching effect of calcium ions is better when the concentration of the leaching agent solution is 1.0-1.2 mol / L.
[0026] In some embodiments, the leaching temperature is 20~85°C and the leaching time is 2~40 min. Specifically, the calcium ion leaching effect is better when the leaching temperature is 20~40°C.
[0027] In some embodiments, adding a pH adjuster to adjust the pH to 12-14 in the calcium-rich extract can significantly improve the carbonation efficiency.
[0028] In some embodiments, the carbonation reaction temperature is 25-85°C, the CO2 flow rate is 100-700 mL / min, and the carbonation time is 5-60 min. Specifically, the carbonation temperature is preferably 25-75°C. Specifically, the CO2 flow rate is preferably 300-500 mL / min. Specifically, the carbonation time is preferably 25-40 min. Studies have shown that carbonation efficiency is higher under these conditions.
[0029] In some embodiments, after the carbonation reaction is completed, solid-liquid separation is performed, and the separated solid phase is dried and ground to obtain nano-calcium carbonate with an average particle size distribution of 50~300 nm.
[0030] Example 1: In this embodiment, the carbide slag used has a moisture content of approximately 10 wt% and a CaO content of approximately 68%. The specific operating process is as follows: (1) Dry the carbide slag at 105℃ for 2 h and then mechanically crush and screen it to a particle size of less than 150 μm; (2) Prepare a 1.0 mol / L maleic acid solution as a leaching agent for the calcium component of carbide slag; (3) Add 5 g of carbide slag from step (1) and the maleic acid solution from step (2) to a magnetically stirred water bath at a solid-liquid ratio of 40 g / L. Stir and mix thoroughly at 400 rpm for 40 min at 25°C. After the reaction is complete, a calcium ion leaching solution is obtained with a leaching rate of 98.77%. (4) Add 10 g of NaOH solid to the calcium leaching solution in step (3) to adjust the pH to 9~14, stir thoroughly at 400 rpm at 35℃, and introduce CO2 gas at a flow rate of 500 mL / min to carry out the carbonation reaction. (5) The pH change was monitored throughout the carbonation reaction. After the mineralization reaction was carried out for 35 min, the reaction was terminated when the pH stabilized at 8-9. The reaction product was separated into solid and liquid phases. The solid phase was dried, ground and tested. The solid product was nano-calcite type calcium carbonate with a single crystal particle size of about 50 nm and a carbonation efficiency of 85.12%.
[0031] Example 2 In this embodiment, the carbide slag used has a moisture content of approximately 10 wt% and a CaO content of approximately 68%. The specific operating process is as follows: (1) Dry the carbide slag at 105℃ for 2 h and then mechanically crush and screen it to a particle size of less than 150 μm; (2) Prepare a 1.2 mol / L maleic acid solution as a leaching agent for the calcium component of carbide slag; (3) Add 5 g of carbide slag from step (1) and the maleic acid solution from step (2) to a magnetically stirred water bath at a solid-liquid ratio of 40 g / L. Mix thoroughly at 400 rpm for 40 min at 25°C. After the reaction, a calcium ion leaching solution is obtained with a leaching efficiency of 80.54%. (4) Add 10 g of NaOH solid to the calcium leaching solution in step (3) to adjust the pH to 9~14, stir thoroughly at 400 rpm at 35℃, and introduce CO2 gas at a flow rate of 500 mL / min to carry out the carbonation reaction. (5) The pH change was monitored throughout the carbonation reaction. After the mineralization reaction was carried out for 35 minutes, the reaction was terminated when the pH stabilized at 8-9. The reaction product was separated into solid and liquid phases. The solid phase was dried, ground and tested. The solid product was nano-calcite type calcium carbonate with a single crystal particle size of about 50 nm and a carbonation efficiency of 79.05%.
[0032] Example 3 In this embodiment, the carbide slag used has a moisture content of approximately 10 wt% and a CaO content of approximately 68%. The specific operating process is as follows: (1) Dry the carbide slag at 105℃ for 2 h and then mechanically crush and screen it to a particle size of less than 150 μm; (2) Prepare a 1.0 mol / L maleic acid solution as a leaching agent for the calcium component of carbide slag; (3) Add 5 g of carbide slag from step (1) and the maleic acid solution from step (2) to a magnetically stirred water bath at a solid-liquid ratio of 40 g / L. Stir and mix thoroughly at 400 rpm for 5 min at 25℃. After the reaction is complete, a calcium ion leaching solution is obtained with a leaching efficiency of 97.89%. (4) Add 10 g of NaOH solid to the calcium leaching solution in step (3) to adjust the pH to 9~14, stir thoroughly at 400 rpm at 35℃, and introduce CO2 gas at a flow rate of 500 mL / min to carry out the carbonation reaction. (5) The pH change was monitored throughout the carbonation reaction. After the mineralization reaction was carried out for 35 minutes, the reaction was terminated when the pH stabilized at 8-9. The reaction product was separated into solid and liquid phases. The solid phase was dried, ground and tested. The solid product was nano-calcite type calcium carbonate with a single crystal particle size of about 50 nm and a carbonation efficiency of 84.85%.
[0033] Example 4 In this embodiment, the carbide slag used has a moisture content of approximately 10 wt% and a CaO content of approximately 68%. The specific operating process is as follows: (1) Dry the carbide slag at 105℃ for 2 h and then mechanically crush and screen it to a particle size of less than 150 μm; (2) Prepare a 1.0 mol / L maleic acid solution as a leaching agent for the calcium component of carbide slag; (3) Add 5 g of carbide slag from step (1) and the maleic acid solution from step (2) to a magnetically stirred water bath at a solid-liquid ratio of 40 g / L. Stir and mix thoroughly at 400 rpm for 40 min at 35℃. After the reaction is complete, a calcium ion leaching solution is obtained with a leaching efficiency of 97.72%. (4) Add 10 g of NaOH solid to the calcium leaching solution in step (3) to adjust the pH to 9~14, stir thoroughly at 400 rpm at 35℃, and introduce CO2 gas at a flow rate of 500 mL / min to carry out the carbonation reaction. (5) The pH change was monitored throughout the carbonation reaction. After the mineralization reaction was carried out for 35 minutes, the reaction was terminated when the pH stabilized at 8-9. The reaction product was separated into solid and liquid phases. The solid phase was dried, ground and tested. The solid product was nano-calcite type calcium carbonate with a single crystal particle size of about 50 nm and a carbonation efficiency of 84.55%.
[0034] Example 5 In this embodiment, the carbide slag used has a moisture content of approximately 10 wt% and a CaO content of approximately 68%. The specific operating process is as follows: (1) Dry the carbide slag at 105℃ for 2 h and then mechanically crush and screen it to a particle size of less than 150 μm; (2) Prepare a 1.0 mol / L maleic acid solution as a leaching agent for the calcium component of carbide slag; (3) Add 5 g of carbide slag from step (1) and the maleic acid solution from step (2) to a magnetically stirred water bath at a solid-liquid ratio of 40 g / L. Stir and mix thoroughly at 400 rpm for 40 min at 25℃. After the reaction is complete, a calcium ion leaching solution is obtained with a leaching efficiency of 98.77%. (4) Add 10 g of NaOH solid to the calcium leaching solution in step (3) to adjust the pH to 9~14, stir thoroughly at 400 rpm at 35℃, and introduce CO2 gas at a flow rate of 500 mL / min to carry out the carbonation reaction.
[0035] (5) The pH change was monitored throughout the carbonation reaction. After the mineralization reaction was carried out for 25 minutes, the reaction was terminated when the pH stabilized at 8-9. The reaction product was separated into solid and liquid phases. The solid phase was dried, ground and tested. The solid product was nano-calcite type calcium carbonate with a single crystal particle size of about 50 nm and a carbonation efficiency of 80.15%.
[0036] Example 6 In this embodiment, the carbide slag used has a moisture content of approximately 10 wt% and a CaO content of approximately 68%. The specific operating process is as follows: (1) Dry the carbide slag at 105℃ for 2 h and then mechanically crush and screen it to a particle size of less than 150 μm; (2) Prepare a 1.0 mol / L maleic acid solution as a leaching agent for the calcium component of carbide slag; (3) Add 5 g of carbide slag from step (1) and the maleic acid solution from step (2) to a magnetically stirred water bath at a solid-liquid ratio of 40 g / L. Stir and mix thoroughly at 400 rpm for 40 min at 25℃. After the reaction is complete, a calcium ion leaching solution is obtained with a leaching efficiency of 98.77%. (4) Add 10 g of NaOH solid to the calcium leaching solution in step (3) to adjust the pH to 9~14, stir thoroughly at 400 rpm at 35℃, and introduce CO2 gas at a flow rate of 300 mL / min to carry out the carbonation reaction.
[0037] (5) The pH change was monitored throughout the carbonation reaction. After the mineralization reaction was carried out for 35 minutes, the reaction was terminated when the pH stabilized at 8-9. The reaction product was separated into solid and liquid phases. The solid phase was dried, ground and tested. The solid product was nano-calcite type calcium carbonate with a single crystal particle size of about 50 nm and a carbonation efficiency of 84.82%.
[0038] Example 7 In this embodiment, the carbide slag used has a moisture content of approximately 10 wt% and a CaO content of approximately 68%. The specific operating process is as follows: (1) Dry the carbide slag at 105℃ for 2 h and then mechanically crush and screen it to a particle size of less than 150 μm; (2) Prepare a 1.0 mol / L maleic acid solution as a leaching agent for the calcium component of carbide slag; (3) Add 5 g of carbide slag from step (1) and the maleic acid solution from step (2) to a magnetically stirred water bath at a solid-liquid ratio of 40 g / L. Stir and mix thoroughly at 400 rpm for 40 min at 25℃. After the reaction is complete, a calcium ion leaching solution is obtained with a leaching efficiency of 98.77%. (4) Add 10 g of NaOH solid to the calcium leaching solution in step (3) to adjust the pH to 9~14, stir thoroughly at 400 rpm at 75℃, and introduce CO2 gas at a flow rate of 500 mL / min to carry out the carbonation reaction.
[0039] (5) The pH change was monitored throughout the carbonation reaction. After the mineralization reaction was carried out for 35 minutes, the reaction was terminated when the pH stabilized at 8-9. The reaction product was separated into solid and liquid phases. The solid phase was dried, ground and tested. The solid product was aragonite-calcite mixed calcium carbonate with a single crystal size of about 50 nm and a carbonation efficiency of 91.35%.
[0040] To fully verify the excellent leaching performance and high leaching rate of the leaching agent selected in this application for calcium ions in carbide slag, succinic acid and citric acid, two commonly used leaching agents for indirect mineralization of carbide slag, were selected as comparative references. Parallel comparative leaching and mineralization experiments were conducted on carbide slag samples under strictly controlled leaching conditions (including key parameters such as solid-liquid ratio, temperature, and time). The specific procedures are as follows: Comparative Example 1: The carbide slag used in this comparative example has a moisture content of approximately 10 wt% and a CaO content of approximately 68%. The specific operating process is as follows: (1) Dry the carbide slag at 105℃ for 2 h and then mechanically crush and screen it to a particle size of less than 150 μm; (2) Prepare a 1.0 mol / L succinic acid solution as the leaching agent for the calcium component of carbide slag; (3) Add 5 g of carbide slag from step (1) and the maleic acid solution from step (2) to a magnetically stirred water bath at a solid-liquid ratio of 40 g / L. Stir and mix thoroughly at 400 rpm for 40 min at 25°C. After the reaction is complete, a calcium ion leaching solution is obtained with a leaching rate of 71.78%.
[0041] (4) Add 10 g of NaOH solid to the calcium leaching solution in step (3) to adjust the pH to 9~14, stir thoroughly at 400 rpm at 35℃, and introduce CO2 gas at a flow rate of 500 mL / min to carry out the carbonation reaction. (5) The pH change was monitored throughout the carbonation reaction. After the mineralization reaction was carried out for 35 minutes, the reaction was terminated when the pH stabilized at 8-9. The reaction product was separated into solid and liquid phases. The solid phase was dried, ground and tested. The solid product was nano-calcite type calcium carbonate with a single crystal particle size of about 50-200 nm. The particle size distribution range was large and the carbonation efficiency was 76.47%.
[0042] Comparative Example 2: The carbide slag used in this comparative example has a moisture content of approximately 10 wt% and a CaO content of approximately 68%. The specific operating process is as follows: (1) Dry the carbide slag at 105℃ for 2 h and then mechanically crush and screen it to a particle size of less than 150 μm; (2) Prepare a 1.0 mol / L citric acid solution as the leaching agent for the calcium component of carbide slag; (3) Add 5 g of carbide slag from step (1) and the citric acid solution from step (2) to a magnetically stirred water bath at a solid-liquid ratio of 40 g / L. Stir and mix thoroughly at 400 rpm for 40 min at 25℃. After the reaction is complete, a calcium ion leaching solution is obtained with a leaching rate of 90.38%. (4) Add 10 g of NaOH solid to the calcium leaching solution in step (3) to adjust the pH to 9~14, stir thoroughly at 400 rpm at 35℃, and introduce CO2 gas at a flow rate of 500 mL / min to carry out the carbonation reaction. (5) The pH change was monitored throughout the carbonation reaction. After the mineralization reaction was carried out for 35 minutes, the reaction was terminated when the pH stabilized at 8-9. The reaction product was separated into solid and liquid phases. The solid phase was dried, ground and tested. The solid product was nano-calcite type calcium carbonate with a single crystal particle size of about 50-200 nm. The particle size distribution range was large and the carbonation efficiency was 34.59%.
[0043] In summary, this invention discloses a method for the controllable preparation of nano-calcium carbonate by indirect CO2 mineralization of calcium carbide slag using maleic acid leaching. The method first mixes calcium carbide slag with maleic acid leaching agent, stirs and reacts, then filters to obtain a calcium-rich leaching solution. Next, a pH adjuster is added to the calcium-rich leaching solution to adjust the pH value. After aging, CO2 gas is introduced and the reaction is continuously stirred. Finally, the reaction is terminated, and solid-liquid separation is performed to obtain nano-calcium carbonate. This method uses maleic acid as the calcium carbide slag leaching agent to prepare nano-calcium carbonate through a two-step indirect mineralization process. The leaching agent used is environmentally friendly and can enhance the leaching of calcium ions. It also solves the problems of uneven particle size distribution, large particle size range, low carbonation efficiency, and incomplete separation of impurities in calcium carbide slag in existing calcium carbonate preparation processes. The mineralization process is simple, the leaching-mineralization cycle is short, and it is suitable for the large-scale industrial production of nano-calcium carbonate.
[0044] Therefore, those skilled in the art will recognize that although embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Therefore, the scope of the present invention should be understood and recognized as covering all such other variations or modifications.
Claims
1. A method for the controllable preparation of nano-calcium carbonate by indirect CO2 mineralization from calcium carbide slag using maleic acid leaching, characterized in that, The method includes the following steps: Step S1: Leaching of active calcium components from carbide slag The calcium carbide slag was mixed with maleic acid leaching agent, stirred and reacted, and then filtered to obtain a calcium-rich leaching solution. Step S2: CO2 carbonation reaction of calcium-rich leachate A pH adjuster is added to the calcium-rich leachate obtained in step S1 to adjust the pH value. After aging, CO2 gas is introduced and the reaction is continuously stirred. At the same time, the pH change during the reaction is monitored and recorded. When the pH reaches the endpoint, the reaction ends and solid-liquid separation is performed. The solid phase is dried and ground to obtain the nano-calcium carbonate.
2. The method for controlling the preparation of nano-calcium carbonate by indirect CO2 mineralization from carbide slag using maleic acid leaching as described in claim 1, characterized in that... The carbide slag pretreatment process is as follows: The carbide slag is first dried at 105℃ for 1-2 hours, and then mechanically crushed to obtain solid particles with a particle size of less than 150 μm. The water content of the carbide slag is 8wt%-12wt%, and the CaO content is 65wt%-72wt%.
3. The method for controlling the preparation of nano-calcium carbonate by indirect CO2 mineralization from carbide slag using maleic acid leaching as described in claim 1, characterized in that... The concentration of maleic acid leaching agent in step S1 is 0.8~1.4 mol / L.
4. The method for controlling the preparation of nano-calcium carbonate by indirect CO2 mineralization from carbide slag using maleic acid leaching as described in claim 1, characterized in that... In step S1, the solid-liquid ratio of calcium carbide slag to maleic acid leaching agent is 30~70 g / L.
5. The method for controlling the preparation of nano-calcium carbonate by indirect CO2 mineralization from carbide slag using maleic acid leaching as described in claim 1, characterized in that... The stirring reaction conditions in step S1 are as follows: Stir the mixture at 300-700 rpm for 2-45 minutes at 20-85℃.
6. The method for controlling the preparation of nano-calcium carbonate by indirect CO2 mineralization from carbide slag using maleic acid leaching as described in claim 1, characterized in that... In step S2, the pH adjuster adjusts the pH value to 9-14.
7. The method for controlling the preparation of nano-calcium carbonate by indirect CO2 mineralization from carbide slag using maleic acid leaching as described in claim 1, characterized in that... The specific reaction conditions in step S2 are as follows: Carbonation reaction is carried out by introducing CO2 gas at a flow rate of 100-700 mL / min at 25-85℃ for 5-60 min.
8. The method for controlling the preparation of nano-calcium carbonate by indirect CO2 mineralization from carbide slag using maleic acid leaching as described in claim 1, characterized in that... The pH endpoint in step S2 is 7-10.
9. The method for controlling the preparation of nano-calcium carbonate by indirect CO2 mineralization from carbide slag using maleic acid leaching as described in claim 1, characterized in that... In step S2, the pH adjuster is NaOH.
10. The method for controlling the preparation of nano-calcium carbonate by indirect CO2 mineralization from carbide slag using maleic acid leaching as described in claim 1, characterized in that... The average particle size distribution of the dried and ground nano-calcium carbonate is 50~300 nm.