Method for preparing high-purity vaterite based on solid waste carbonization reaction

Abstract

The application relates to the technical field of vaterite, and particularly relates to a method for preparing high-purity vaterite based on solid waste carbonization reaction, which comprises the following steps: A, detecting the content of calcium oxide in steel slag to obtain a detection result; B, the mass ratio of the steel slag, magnesium slag and calcium oxide powder in the composite calcium source is determined according to the detection result; C, a pretreated calcium source is obtained; D, the pretreated calcium source is treated to obtain a leaching solution; E, the leaching solution is treated to obtain a reaction filtrate; F, polyethylene glycol is added into the reaction filtrate to obtain a reaction dispersion liquid; carbonization reaction is carried out by introducing a gas containing carbon dioxide into the reaction dispersion liquid, and then high-purity vaterite is obtained after the reaction dispersion liquid is subjected to filtration, centrifugal separation, washing and drying in sequence. The method for preparing high-purity vaterite based on solid waste carbonization reaction is beneficial to improving the purity, particle size uniformity and yield of vaterite on the premise of enriching the types of calcium sources, so as to overcome the defects in the prior art.

Description

Technical Field

[0001] This invention relates to the field of aragonite technology, and more particularly to a method for preparing high-purity aragonite based on solid waste carbonization reaction. Background Technology

[0002] With the rapid development of modern industry, the annual discharge of industrial solid waste generated by industries such as steel and chemicals is enormous. Taking steel slag as an example, my country, as the world's largest steel producer, discharges more than 100 million tons of steel slag annually, with the accumulated stockpile exceeding one billion tons. In addition, the annual discharge of industrial solid waste such as magnesium slag also reaches tens of millions of tons. The large-scale accumulation of such solid waste not only occupies valuable land resources, but its soluble salts and heavy metals also pollute soil and groundwater through infiltration, posing a serious threat to the ecological environment. At the same time, the large amounts of carbon dioxide emitted during industrial combustion exacerbate global warming. How to achieve the resource utilization of industrial solid waste and the synergistic reduction of carbon dioxide emissions has become a critical issue that urgently needs to be addressed in the environmental field.

[0003] Calcium carbonate, as an important inorganic functional material, has wide applications in rubber, plastics, coatings, papermaking, pharmaceuticals, and building materials. In nature, calcium carbonate mainly exists in its most stable calcite crystal form, while artificially prepared calcium carbonate also includes aragonite and aragonite crystal forms. Among these, aragonite, as a metastable crystal form of calcium carbonate, possesses characteristics such as high specific surface area, high hydrophilicity, good biocompatibility, and a unique spherical porous structure, demonstrating high application value and market prospects in areas such as drug delivery carriers, bioceramics, and precision electronic materials.

[0004] In recent years, the indirect carbonation reaction of calcium resources in industrial solid waste with carbon dioxide to produce calcium carbonate has become a research hotspot. This method can achieve high-value utilization of calcium in solid waste and simultaneously capture and fix carbon dioxide, which is in line with the sustainable development concept of "treating waste with waste and turning waste into treasure". Various technical solutions have emerged for this direction. For example, Chinese invention patent CN117142508A discloses a method for preparing high-purity aragonite using indirect carbonation of steel slag, which involves leaching calcium ions from the steel slag with ammonium chloride and then introducing carbon dioxide for the carbonation reaction. However, this method relies solely on steel slag as the calcium source and does not address the effective removal of impurities such as iron and magnesium ions from the leachate, resulting in limited product purity.

[0005] Furthermore, Chinese invention patent CN111777089A discloses a method for preparing high-purity aragonite-type calcium carbonate microspheres using calcium sulfate as a raw material. This method utilizes leaching aids such as ammonium acetate and ammonium chloride to achieve the preparation of aragonite at low temperature and normal pressure without the need for crystal form control agents. However, while the calcium sulfate raw materials used in this method (such as natural gypsum and industrial by-product gypsum) are widely available, the calcium ion leaching efficiency is limited by the low solubility product of calcium sulfate itself, resulting in a low calcium ion leaching rate. Aragonite, as a metastable crystal form of calcium carbonate (CaCO3), is essentially formed through a process involving calcium ions (CaCO3). 2+ ) and carbonate ions (CO3) 2- The chemical reaction and crystallization process of the product is involved. Therefore, the low calcium ion leaching rate results in a limited product yield. Furthermore, the particle size distribution of the obtained product ranges from 0.3 to 2 μm, exhibiting a large span and poor particle size uniformity.

[0006] In summary, existing technologies for preparing aragonite from industrial solid waste generally suffer from drawbacks such as a single calcium source, low product purity, poor particle size uniformity, and limited yield. Summary of the Invention

[0007] The purpose of this invention is to propose a method for preparing high-purity aragonite based on solid waste carbonization reaction. By optimizing the calcium source system, strengthening impurity removal and controlling particle size distribution, this method can improve the purity, particle size uniformity and yield of aragonite while enriching the types of calcium sources, thus overcoming the shortcomings of the prior art.

[0008] To achieve this objective, the present invention adopts the following technical solution: A method for preparing high-purity aragonite based on solid waste carbonization reaction includes the following steps: A. Detect the calcium oxide content in steel slag and obtain the test results; wherein, the chemical composition of the steel slag includes SiO2, CaO, Al2O3, MgO, Fe2O3, P2O5, Cr2O3 and CuO, and the mineral composition of the steel slag includes tricalcium silicate, dicalcium silicate of β type and dicalcium silicate of γ type. B. Preparation of composite calcium source; the composite calcium source includes steel slag and magnesium slag, or steel slag, magnesium slag and calcium oxide powder, and the mass ratio of steel slag, magnesium slag and calcium oxide powder in the composite calcium source is determined according to the test results; The chemical composition of the magnesium slag includes SiO2, CaO, Al2O3, Fe2O3, MgO and CuO, and the mineral composition of the magnesium slag includes dicalcium silicate of type β and dicalcium silicate of type γ. C. Add the composite calcium source to the sodium sulfide solution, stir and react, then filter to obtain the pretreated calcium source; D. After mechanically activating the pretreated calcium source, mix it evenly with ammonium chloride solution, and then use microwave-assisted leaching to leach calcium ions to obtain leachate; E. After filtering the leachate, the primary filtrate is obtained; Ethylenediaminetetraacetic acid disodium solution, barium chloride solution, and sodium carbonate solution are added sequentially to the primary filtrate to precipitate impurities in the primary filtrate. After filtration through a 0.01–0.02 μm ceramic membrane, a calcium-rich filtrate is obtained. Hydrochloric acid was added to the calcium-rich filtrate to adjust the pH, and the precipitate disodium ethylenediaminetetraacetate was precipitated and recovered to obtain the reaction filtrate. F. Add polyethylene glycol to the reaction filtrate and stir until the polyethylene glycol is completely dispersed to obtain the reaction dispersion. Carbon dioxide gas is introduced into the reaction dispersion to carry out a carbonization reaction, and then high-purity aragonite is obtained after sequential filtration, centrifugation, washing and drying.

[0009] Further, in step B, when the mass percentage of calcium oxide in the steel slag is ≥45%, the composite calcium source includes steel slag and magnesium slag, and the mass ratio of steel slag to magnesium slag is (6.8~7.2):(2.8~3.2). When the mass percentage of calcium oxide in the steel slag is ≥40% and <45%, the composite calcium source includes steel slag and magnesium slag, and the mass ratio of steel slag to magnesium slag is (5.8~6.2):(3.8~4.2). When the mass percentage of calcium oxide in the steel slag is <40%, the composite calcium source includes steel slag, magnesium slag and calcium oxide powder, and the mass ratio of steel slag, magnesium slag and calcium oxide powder is (3.8~4.2):(5.8~6.2):(0.05~0.1).

[0010] Furthermore, in step A, the particle size of the steel slag is ≤3mm; In step B, the particle size of the magnesium slag is ≤1mm, and the mass percentage of calcium oxide in the magnesium slag is ≥40%.

[0011] Further, in step A, the chemical composition of the steel slag, calculated by mass percentage, includes CaO 38-48%, SiO2 20-25%, Fe2O3 15-20%, Al2O3 8-10%, MgO 3-5%, MnO 2-4%, P2O5 2-4%, Cr2O3 1-2%, and CuO 0.5-1.5%, with the remainder being loss on ignition. According to mass percentage, the mineral composition of the steel slag includes 15-25% tricalcium silicate, 20-30% β-type dicalcium silicate, 10-20% γ-type dicalcium silicate, 5-10% free calcium oxide, 2-5% free magnesium oxide, and 5-10% feldspar, with the remainder being glass phase and impurities; In step B, the chemical composition of the magnesium slag, calculated by mass percentage, includes CaO 45-50%, SiO2 25-30%, Fe2O3 4-6%, Al2O3 1-3%, MgO 10-15%, Cr2O3 1-4%, and CuO 2-4%, with the remainder being loss on ignition. The mineral composition of the magnesium slag, calculated by mass percentage, includes 40-50% dicalcium silicate of β type, 25-35% dicalcium silicate of γ type, 8-12% free calcium oxide, and 5-8% periclase, with the remainder being glass phase and impurities.

[0012] Further, in step C, the sodium sulfide solution contains 1 to 2% sodium sulfide by mass.

[0013] Further, step C specifically involves adding the composite calcium source to a sodium sulfide solution and stirring for 40–50 minutes to obtain a solid-liquid mixture. The solid-liquid mixture was placed into a centrifuge tube for centrifugation and the supernatant was removed to obtain a pretreated calcium source.

[0014] Further, step D specifically involves: ball milling the pretreated calcium source at a speed of 200-400 rpm to obtain an activated calcium source; After the activated calcium source and ammonium chloride solution are mixed evenly, the mixture is placed in a microwave field of 200-300W and stirred at 800-1200rpm for 1-2 hours to obtain the leachate.

[0015] Further, in step D, the mass mixing ratio of the activated calcium source to the ammonium chloride solution is 1:(15-20), and the concentration of the ammonium chloride solution is 0.5-1 mol / L.

[0016] Further, the specific method of step E is as follows: filter the leachate to obtain the primary filtrate; Add disodium ethylenediaminetetraacetate solution to the primary filtrate to adjust the pH to 5-6, then stir to obtain the first mixed solution; After adjusting the pH of the first mixed solution to 4-4.5, barium chloride solution was added and stirred to obtain the second mixed solution. Sodium carbonate solution was added to the second mixed solution to adjust the pH to 8-9, and the solution was filtered through a 0.01-0.02 μm ceramic membrane to obtain a calcium-rich filtrate. Hydrochloric acid was added to the calcium-rich filtrate to adjust the pH to 4-5. After the precipitate, disodium ethylenediaminetetraacetate, was precipitated and recovered, the reaction filtrate was obtained.

[0017] Further, in step F, the specific method of filtration is as follows: the mixture of aragonite obtained by carbonizing the reaction dispersion by passing it through a gas containing carbon dioxide is filtered to obtain crude aragonite product. The specific method of centrifugal separation is as follows: disperse the crude aragonite product in anhydrous ethanol, sonicate for 20-30 min, then load it into a centrifuge tube for centrifugal separation, remove the supernatant, and obtain the precipitate; The specific washing method is as follows: wash the precipitate repeatedly with pure water until the washed liquid is colorless and transparent, thus obtaining a solid. The specific drying method is as follows: the solid is dried multiple times, and the weight is weighed after each drying until the weights of two consecutive weighings are consistent, then the drying is complete and high-purity aragonite is obtained.

[0018] The technical solution provided by this invention may include the following beneficial effects: 1. In this technical solution, ammonium chloride provides ammonium ions that regulate crystal form from a thermodynamic and kinetic perspective, enabling the directional growth of aragonite. Specifically, the hydrolysis of ammonium ions makes the system weakly acidic, reducing the overall supersaturation of calcium carbonate and inhibiting the nucleation and growth of calcium carbonate in stable crystal forms such as calcite and aragonite, thus adapting to the low supersaturation nucleation preference of aragonite crystals; simultaneously, ammonium ions react with Ca... 2+ Weak complexation occurs, delaying Ca2+ formation. 2+ With CO3 2- The binding rate is reduced, avoiding localized ion enrichment that induces heterogeneous crystals and creating conditions for the preferential formation of aragonite crystal nuclei. Furthermore, a weakly acidic environment slows the transformation of aragonite crystals into stable crystal forms (such as calcite and aragonite). Combined with the dispersion and particle size control effects of polyethylene glycol, this further blocks the formation and growth path of calcite crystal nuclei, enhancing the kinetic advantage of directional growth of aragonite crystals, achieving stable and uniform formation of aragonite crystals, and obtaining aragonite with uniform particle size.

[0019] 2. This technical solution allows for the recovery and reuse of disodium ethylenediaminetetraacetate precipitate in its acidic form through filtration, while simultaneously obtaining a reaction filtrate rich in calcium ions. This achieves efficient recycling of the complexing agent (recovery rate ≥95%) and pure separation of the target element, calcium. The pure separation of calcium prevents suspended solid particles from becoming heterogeneous nucleation centers, inducing the formation of stable crystal forms such as calcite, and interfering with the formation of metastable aragonite, thus contributing to improved aragonite purity.

[0020] 3. Aragonite, as a metastable crystal form of calcium carbonate (CaCO3), is essentially formed through a process involving calcium ions (CaCO3). 2+) and carbonate ions (CO3) 2- The chemical reaction and crystallization process of aragonite. Therefore, when extremely high calcium ion leaching rates are obtained from steel slag and magnesium slag through pretreatment technologies such as mechanical activation and microwave assistance, it means that the absolute number of calcium ions that can participate in the precipitation reaction in the reaction system increases significantly, which is beneficial to improving the efficiency and yield of aragonite synthesis, and thus improving the yield of aragonite; at the same time, the continuous supply of calcium ions brought about by the high leaching rate is also beneficial to maintaining the stability of the entire precipitation reaction system, reducing the phenomenon of crystal transformation or crystal growth stagnation caused by the depletion of reactants, and further ensuring the yield and stability of aragonite. Detailed Implementation

[0021] This technical solution provides a method for preparing high-purity aragonite based on solid waste carbonization reaction, including the following steps: A. Detect the calcium oxide content in steel slag and obtain the test results; wherein, the chemical composition of the steel slag includes SiO2, CaO, Al2O3, MgO, Fe2O3, P2O5, Cr2O3 and CuO, and the mineral composition of the steel slag includes tricalcium silicate, dicalcium silicate of β type and dicalcium silicate of γ type. B. Preparation of composite calcium source; the composite calcium source includes steel slag and magnesium slag, or steel slag, magnesium slag and calcium oxide powder, and the mass ratio of steel slag, magnesium slag and calcium oxide powder in the composite calcium source is determined according to the test results; The chemical composition of the magnesium slag includes SiO2, CaO, Al2O3, Fe2O3, MgO and CuO, and the mineral composition of the magnesium slag includes dicalcium silicate of type β and dicalcium silicate of type γ. C. Add the composite calcium source to the sodium sulfide solution, stir and react, then filter to obtain the pretreated calcium source; D. After mechanically activating the pretreated calcium source, mix it evenly with ammonium chloride solution, and then use microwave-assisted leaching to leach calcium ions to obtain leachate; E. After filtering the leachate, the primary filtrate is obtained; Ethylenediaminetetraacetic acid disodium solution, barium chloride solution, and sodium carbonate solution are added sequentially to the primary filtrate to precipitate impurities in the primary filtrate. After filtration through a 0.01–0.02 μm ceramic membrane, a calcium-rich filtrate is obtained. Hydrochloric acid was added to the calcium-rich filtrate to adjust the pH, and the precipitate disodium ethylenediaminetetraacetate was precipitated and recovered to obtain the reaction filtrate. F. Add polyethylene glycol to the reaction filtrate and stir until the polyethylene glycol is completely dispersed to obtain the reaction dispersion. Carbon dioxide gas is introduced into the reaction dispersion to carry out a carbonization reaction, and then high-purity aragonite is obtained after sequential filtration, centrifugation, washing and drying.

[0022] To address the shortcomings of existing technologies in preparing aragonite, such as a single calcium source, low product purity, poor particle size uniformity, and limited yield, this technical solution proposes a method for preparing high-purity aragonite based on solid waste carbonization reaction. The method comprises six steps: A (detection), B (preparation of composite calcium source), C (stirring reaction and filtration), D (mechanical activation and microwave-assisted leaching), E (preparation of reaction filtrate), and F (carbonization reaction). By optimizing the calcium source system, enhancing impurity removal, and controlling particle size distribution, this method can improve the purity, particle size uniformity, and yield of aragonite while enriching the types of calcium sources, thus meeting practical application requirements.

[0023] Specifically, the reaction dispersion obtained in step F of this technical solution substantially contains ammonium chloride, polyethylene glycol, and Ca. 2+ During the carbonation reaction, gaseous CO2 is rapidly dissolved in the reaction dispersion to form carbonic acid. Subsequently, the carbonic acid dissociates to generate bicarbonate and carbonate ions; free Ca... 2+ It reacts with bicarbonate / carbonate ions to form calcium carbonate, which exists in the form of aragonite. Simultaneously, the ammonium chloride in this technical solution provides ammonium ions that thermodynamically and kinetically regulate the crystal form, achieving directional growth of aragonite. Specifically, the hydrolysis of ammonium ions makes the system weakly acidic, reducing the overall supersaturation of calcium carbonate and inhibiting the nucleation and growth of calcium carbonate in stable crystal forms such as calcite and aragonite, thus adapting to the low-supersaturation nucleation preference of aragonite; at the same time, ammonium ions react with Ca... 2+ Weak complexation occurs, delaying Ca2+ formation. 2+ With CO3 2- The binding rate is reduced, avoiding localized ion enrichment that induces heterogeneous crystals and creating conditions for the preferential formation of aragonite crystal nuclei. Furthermore, a weakly acidic environment slows the transformation of aragonite crystals into stable crystal forms (such as calcite and aragonite). Combined with the dispersion and particle size control effects of polyethylene glycol, this further blocks the formation and growth path of calcite crystal nuclei, enhancing the kinetic advantage of directional growth of aragonite crystals, achieving stable and uniform formation of aragonite crystals, and obtaining aragonite with uniform particle size.

[0024] In addition, before mixing steel slag, magnesium slag (and calcium oxide powder), the calcium oxide content in the steel slag is first tested, and the mixing ratio of steel slag, magnesium slag and calcium oxide powder is adjusted according to the test results to stabilize the total calcium content in the composite calcium source, thereby offsetting the influence of steel slag composition fluctuations on the calcium ion concentration of the leachate, ensuring the stability of calcium carbonate supersaturation during the subsequent carbonization reaction, and thus achieving precise control of the particle size of the aragonite product, which is beneficial to obtaining aragonite with uniform particle size.

[0025] Secondly, existing technologies typically use steel slag containing Cr₂O₃ and CuO, while magnesium slag contains CuO, resulting in the composite calcium source also containing Cr₂O₃ and CuO. Sodium sulfide is a strong base-weak acid salt, which dissociates in water to release sulfur. 2 This technical solution involves adding sodium sulfide solution to a composite calcium source. The sodium sulfide solution reacts with the Cr₂O₃ and CuO components in the composite calcium source, causing the Cr₂O₃ to ionize. 3+ And Cu in CuO 2+ When heavy metal ions precipitate as heavy metal sulfides, and these precipitates are then removed by filtration, it helps reduce impurities in the pretreated calcium source. Specifically, this technical solution first treats the composite calcium source (i.e., solid slag) with sodium sulfide, converting heavy metals on the solid surface into heavy metal sulfide precipitates that adhere to the composite calcium source. In subsequent step D, mechanical activation may further strip away the sulfide-containing surface layer. After mechanical activation and microwave-assisted leaching in step D, most of the calcium ions in the steel slag and magnesium slag enter the liquid phase of the leachate. However, solid particles such as silicate frameworks, unreacted inert minerals, and heavy metal sulfide precipitates generated in step C are removed by filtration, resulting in a clear liquid rich in calcium ions as the primary filtrate obtained after leaching.

[0026] Furthermore, in step E, a disodium ethylenediaminetetraacetate solution (i.e., disodium EDTA solution) is added to the primary filtrate, utilizing the preferential reaction of disodium ethylenediaminetetraacetate with Al. 3+ Fe 3+ and Mg 2+ A coordination reaction occurs, forming a stable, soluble complex, thus masking iron and magnesium impurities; simultaneously, Ca... 2+ Then some are complexed to form [Ca] EDTA 2 The complex is temporarily stored in solution; subsequently, barium chloride solution is added, causing barium ions to react with phosphate and sulfate ions to form sparingly soluble barium phosphate and barium sulfate precipitates, achieving deep removal of phosphorus and sulfur impurities. It should be noted that phosphate and sulfate ions mainly originate from P2O5 and sulfur-containing components associated with steel slag and magnesium slag. During microwave-assisted leaching after the initial addition of ammonium chloride solution, P2O5 hydrolyzes into phosphate ions, while sulfur-containing components are oxidized into sulfate ions and enter the solution. Afterward, sodium carbonate is added to adjust the pH of the system to 8-9, promoting the removal of trace amounts of uncomplexed Fe. 3+ and Mg 2+Plasma forms hydroxide or basic salt precipitates, while simultaneously promoting the flocculation of EDTA complexes loaded with iron and magnesium impurities with hydroxides and basic salts, forming large-sized flocculent precipitates. These flocs can be effectively retained by ceramic membranes of 0.01–0.02 μm, while soluble small molecules [Ca]... EDTA 2 The complex can pass smoothly through the ceramic membrane into the filtrate, thereby achieving efficient separation of calcium components from impurities and creating conditions for the subsequent recovery of disodium ethylenediaminetetraacetate.

[0027] Subsequently, hydrochloric acid was added to the calcium-rich filtrate for pH adjustment. The high concentration of hydrogen ions strongly competed with the amino and carboxyl groups of EDTA for protonation, causing a sharp decrease in EDTA's ability to complex calcium ions (i.e., the "acid effect"), leading to [Ca... EDTA 2 The complex dissociates, releasing free calcium ions and EDTA. Simultaneously, under adjusted pH conditions, the solubility of the released EDTA in its protonated form (i.e., the acidic form of disodium ethylenediaminetetraacetate) in water is significantly reduced, causing it to crystallize out of the solution as a solid precipitate. The acidic disodium ethylenediaminetetraacetate precipitate can be recovered and reused through filtration, while simultaneously obtaining a calcium-rich reaction filtrate. This achieves efficient recycling of the complexing agent (recovery rate ≥95%) and pure separation of the target element, calcium. The pure separation of the target element, calcium, prevents suspended solid particles from becoming heterogeneous nucleation centers, inducing the formation of stable crystal forms such as calcite, and interfering with the formation of metastable aragonite, thus contributing to improved aragonite purity.

[0028] In addition, this technical solution adjusts the mixing ratio of steel slag, magnesium slag and calcium oxide powder according to the test results to stabilize the total calcium content in the composite calcium source, thereby offsetting the influence of steel slag composition fluctuations on the calcium ion concentration of the leachate, ensuring the stability of calcium carbonate supersaturation during the subsequent carbonization reaction, which is beneficial to avoid crystal transformation caused by raw material fluctuations, and also beneficial to improve the purity of aragonite, making the purity of aragonite ≥99%.

[0029] Finally, as the technical solution shows, the pretreated calcium source is the product of a composite calcium source composed of steel slag and magnesium slag (and calcium oxide powder) treated with sodium sulfide solution. It mainly contains residual components from the steel slag and magnesium slag that have not reacted with sodium sulfide, such as calcium silicate mineral phases. In existing technologies, the mineral composition of steel slag generally contains calcium silicate mineral phases (including tricalcium silicate, β-type dicalcium silicate, and γ-type dicalcium silicate), while the mineral composition of magnesium slag also generally contains calcium silicate mineral phases (including β-type dicalcium silicate and γ-type dicalcium silicate). This technical solution mechanically activates the pretreated calcium source, effectively disrupting the crystal structure of calcium silicate minerals in steel slag and magnesium slag through mechanical activation, causing lattice distortion or amorphization, thereby significantly reducing the resistance to calcium ion leaching from the mineral framework. This results in an activated calcium source with lower calcium ion leaching resistance. Subsequently, the activated calcium source is mixed with ammonium chloride solution, and microwave-assisted technology is introduced. Microwaves can selectively and rapidly heat materials based on the differences in dielectric properties of their components, generating thermal stress within mineral particles. This promotes crack propagation and structural loosening, thereby further enhancing the leaching efficiency of calcium ions. Simultaneously, the high microwave absorption properties of Fe2O3 in steel and magnesium slag create a locally enhanced thermal effect, synergistically promoting the efficient release of calcium ions and ensuring a leaching rate exceeding 92%, demonstrating an extremely high calcium ion leaching efficiency.

[0030] Furthermore, aragonite, as a metastable crystal form of calcium carbonate (CaCO3), is essentially formed through a process involving calcium ions (Ca... 2+ ) and carbonate ions (CO3) 2- The chemical reaction and crystallization process of aragonite. Therefore, when extremely high calcium ion leaching rates are obtained from steel slag and magnesium slag through pretreatment technologies such as mechanical activation and microwave assistance, it means that the absolute number of calcium ions that can participate in the precipitation reaction in the reaction system increases significantly, which is beneficial to improving the efficiency and yield of aragonite synthesis, and thus improving the yield of aragonite; at the same time, the continuous supply of calcium ions brought about by the high leaching rate is also beneficial to maintaining the stability of the entire precipitation reaction system, reducing the phenomenon of crystal transformation or crystal growth stagnation caused by the depletion of reactants, and further ensuring the yield and stability of aragonite.

[0031] Finally, the calcium sources in this technical solution include steel slag, magnesium slag (and calcium oxide powder), which provides abundant calcium sources. This not only helps to overcome the shortcomings of using steel slag as the sole calcium source, but also because both steel slag and magnesium slag are industrial solid wastes, which can help to turn industrial solid waste into valuable resources and make full use of them.

[0032] Preferably, in step F, the carbon dioxide-containing gas can be either carbon dioxide with a purity of ≥99.5% or industrial flue gas, and the carbon dioxide concentration in the industrial flue gas is 10-60%.

[0033] Preferably, in step F, the carbonization reaction is carried out at a temperature of 18–22°C for 1.5–2 hours.

[0034] To further explain, in step B, when the mass percentage of calcium oxide in the steel slag is ≥45%, the composite calcium source includes steel slag and magnesium slag, and the mass ratio of steel slag to magnesium slag is (6.8~7.2):(2.8~3.2). When the mass percentage of calcium oxide in the steel slag is ≥40% and <45%, the composite calcium source includes steel slag and magnesium slag, and the mass ratio of steel slag to magnesium slag is (5.8~6.2):(3.8~4.2). When the mass percentage of calcium oxide in the steel slag is <40%, the composite calcium source includes steel slag, magnesium slag and calcium oxide powder, and the mass ratio of steel slag, magnesium slag and calcium oxide powder is (3.8~4.2):(5.8~6.2):(0.05~0.1).

[0035] This technical solution adjusts the mixing ratio of steel slag, magnesium slag, and calcium oxide powder according to the calcium oxide content in the steel slag to stabilize the total calcium content in the composite calcium source. This offsets the impact of steel slag composition fluctuations on the calcium ion concentration in the leachate, ensuring the stability of calcium carbonate supersaturation during the subsequent carbonization reaction. This enables precise control of the particle size of the aragonite product, avoids crystal transformation caused by raw material fluctuations, and also helps improve the purity of the aragonite.

[0036] To further clarify, in step A, the particle size of the steel slag is ≤3mm; In step B, the particle size of the magnesium slag is ≤1mm, and the mass percentage of calcium oxide in the magnesium slag is ≥40%.

[0037] By controlling the particle size of steel slag and magnesium slag within the above-mentioned range, the solid-liquid reaction contact area is increased, and the diffusion path of ammonium chloride solution into the particle interior is shortened, thereby significantly improving the leaching rate and leaching percentage of calcium.

[0038] Furthermore, by limiting the calcium oxide content in magnesium slag to no less than 40%, on the one hand, the introduction of high-calcium magnesium slag can form a multi-source composite calcium source system with steel slag and calcium oxide powder, effectively broadening the sources of solid waste and reducing raw material costs; on the other hand, when the composition of steel slag fluctuates, resulting in its own low calcium content, the total calcium content of the mixed calcium source can be stabilized by dynamically adjusting the proportion of high-calcium magnesium slag, thereby maintaining a constant calcium ion concentration in the leachate, laying the foundation for subsequent control of particle size uniformity and purity of aragonite products.

[0039] To further explain, in step A, the chemical composition of the steel slag, calculated by mass percentage, includes CaO 38-48%, SiO2 20-25%, Fe2O3 15-20%, Al2O3 8-10%, MgO 3-5%, MnO 2-4%, P2O5 2-4%, Cr2O3 1-2%, and CuO 0.5-1.5%, with the remainder being loss on ignition. According to mass percentage, the mineral composition of the steel slag includes 15-25% tricalcium silicate, 20-30% β-type dicalcium silicate, 10-20% γ-type dicalcium silicate, 5-10% free calcium oxide, 2-5% free magnesium oxide, and 5-10% feldspar, with the remainder being glass phase and impurities; In step B, the chemical composition of the magnesium slag, calculated by mass percentage, includes CaO 45-50%, SiO2 25-30%, Fe2O3 4-6%, Al2O3 1-3%, MgO 10-15%, Cr2O3 1-4%, and CuO 2-4%, with the remainder being loss on ignition. The mineral composition of the magnesium slag, calculated by mass percentage, includes 40-50% dicalcium silicate of β type, 25-35% dicalcium silicate of γ type, 8-12% free calcium oxide, and 5-8% periclase, with the remainder being glass phase and impurities.

[0040] This technology directly determines the supply capacity of target elements such as calcium and the degree of impurity interference by limiting the chemical composition of steel slag and magnesium slag, such as CaO, MgO, and SiO2, which is beneficial to ensuring the calcium ion leaching rate and subsequent impurity removal efficiency.

[0041] Furthermore, the leaching behavior of different mineral phases in ammonium chloride solution varies significantly. For example, free calcium oxide leaches very easily, while silicate minerals such as dicalcium silicate require mechanical activation or microwave assistance to efficiently release calcium ions. Therefore, the limitation of mineral phases such as tricalcium silicate, free calcium oxide, and periclase in this technical solution is beneficial for controlling the leaching behavior of the calcium source, avoiding a decrease in leaching rate or insufficient product purity due to fluctuations in raw material composition, thus providing a reliable raw material guarantee for the stable preparation of high-purity, controllable-particle-size aragonite.

[0042] To further clarify, in step C, the sodium sulfide solution contains 1-2% sodium sulfide by mass.

[0043] This technical solution limits the mass percentage of sodium sulfide in the sodium sulfide solution. On the one hand, this concentration range ensures that the solution has a sufficient concentration of sodium sulfide. 2- Ions that can react with heavy metal ions (such as Cr) in the complex calcium source. 3+ and Cu 2+(etc.) Rapid reaction to generate insoluble sulfide precipitates, achieving deep removal; on the other hand, it avoids the waste of raw materials caused by excessively high concentrations, and at the same time prevents problems such as slow reaction kinetics and incomplete precipitation caused by excessively low concentrations, thus achieving green and low-cost operation of the process while ensuring the impurity removal effect.

[0044] To further explain, step C specifically involves adding the composite calcium source to a sodium sulfide solution and stirring for 40–50 minutes to obtain a solid-liquid mixture. The solid-liquid mixture was placed into a centrifuge tube for centrifugation and the supernatant was removed to obtain a pretreated calcium source.

[0045] This technical solution limits the stirring time to 40–50 minutes, which is S 2－ Ions and heavy metal ions (such as Cr) 3+ and Cu 2+ The reaction process (etc.) provides sufficient kinetic time, overcoming the problem of incomplete reaction caused by localized uneven concentrations during instantaneous precipitation, and ensuring the full formation of heavy metal sulfide precipitates. Simultaneously, the use of centrifugation instead of simple filtration utilizes powerful centrifugal force to thoroughly remove and compact the fine sulfide precipitates (typically small in size and easily suspended) from the liquid phase. Combined with the removal of the supernatant, this effectively prevents the heavy metal sulfide precipitates from re-mixing into the calcium source in subsequent steps, eliminating the risk of secondary contamination. The pretreated calcium source obtained after sufficient reaction and thorough centrifugation has a lower Cr content. 3+ and Cu 2+ The heavy metal content was reduced to extremely low levels, providing a raw material basis for the subsequent preparation of high-purity aragonite.

[0046] To further explain, step D specifically involves: ball milling the pretreated calcium source at a speed of 200–400 rpm to obtain an activated calcium source; After the activated calcium source and ammonium chloride solution are mixed evenly, the mixture is placed in a microwave field of 200-300W and stirred at 800-1200rpm for 1-2 hours to obtain the leachate.

[0047] Low-speed ball milling (200–400 rpm) introduces defects, dislocations, and even localized amorphization into the mineral lattice of calcium source particles (such as steel slag and magnesium slag) through mechanical force. This disrupts the stable phase structure of calcium silicate and other materials, transforming calcium ions that were originally locked in the crystal into an active state that is more easily attacked by ammonium chloride solution, significantly reducing the reaction energy barrier for subsequent chemical leaching.

[0048] Furthermore, this technical solution limits the power of the microwave field. Microwaves have penetrating power and can directly act on the interior of solid particles, creating a "hot inside, cold outside" temperature difference within the particles in the solution. This temperature difference causes thermal stress within the particles, further widening and extending the microcracks formed during the mechanical activation stage, and even causing some particles to "burst" in micro-regions, exposing fresh reaction interfaces. Microwave radiation causes polar molecules (such as water and ammonium ions) to rotate at high speed, producing a "molecular stirring" effect, accelerating the reaction of Ca... 2+ Diffusion from the solid surface into the bulk solution simultaneously promotes the absorption of fresh Cl-. - NH4 + The calcium ions migrate to the reaction interface, thereby significantly increasing the leaching rate and shortening the leaching time to 1-2 hours, which can improve the leaching rate of calcium ions.

[0049] To further explain, in step D, the mass mixing ratio of the activated calcium source to the ammonium chloride solution is 1:(15-20), and the concentration of the ammonium chloride solution is 0.5-1 mol / L.

[0050] Ammonium chloride solution serves as both a leaching agent and a solvent. When the mass ratio of activated calcium source to ammonium chloride solution is too low, the resulting mixed solution has excessive viscosity, hindering ion diffusion. Furthermore, the generated calcium ions tend to saturate on the particle surface, forming a diffusion barrier and inhibiting the continued leaching reaction. Conversely, when the mass ratio is too high, although leaching is more complete, it significantly increases the amount of ammonium chloride solution used, leading to increased energy and water consumption for subsequent treatment of large quantities of dilute solutions, which is neither economical nor environmentally friendly. Therefore, this technical solution uses a mass ratio of activated calcium source to ammonium chloride solution of 1:(15-20), providing a sufficient volume of solution to accommodate the leached calcium ions and ensuring adequate CaO concentration in the solution. 2+ The concentration remains below the saturation point, maintaining the concentration gradient, which is the core driving force of the leaching reaction, thus achieving continuous and efficient dissolution of calcium ions.

[0051] To further explain, the specific method of step E is as follows: filter the leachate to obtain the primary filtrate; Add disodium ethylenediaminetetraacetate solution to the primary filtrate to adjust the pH to 5-6, then stir to obtain the first mixed solution; After adjusting the pH of the first mixed solution to 4-4.5, barium chloride solution was added and stirred to obtain the second mixed solution. Sodium carbonate solution was added to the second mixed solution to adjust the pH to 8-9, and the solution was filtered through a 0.01-0.02 μm ceramic membrane to obtain a calcium-rich filtrate. Hydrochloric acid was added to the calcium-rich filtrate to adjust the pH to 4-5. After the precipitate, disodium ethylenediaminetetraacetate, was precipitated and recovered, the reaction filtrate was obtained.

[0052] This technical solution further refines the specific method of step E, which is conducive to more fully removing various impurities in the leachate, achieving efficient circulation of the complexing agent (recovery rate ≥95%) and pure separation of the target element calcium, thus creating conditions for improving the purity of aragonite.

[0053] To further explain, in step F, the specific method of filtration is as follows: the mixture of aragonite obtained by carbonizing the reaction dispersion by passing it through a gas containing carbon dioxide is filtered to obtain crude aragonite product. The specific method of centrifugal separation is as follows: disperse the crude aragonite product in anhydrous ethanol, sonicate for 20-30 min, then load it into a centrifuge tube for centrifugal separation, remove the supernatant, and obtain the precipitate; The specific washing method is as follows: wash the precipitate repeatedly with pure water until the washed liquid is colorless and transparent, thus obtaining a solid. The specific drying method is as follows: the solid is dried multiple times, and the weight is weighed after each drying until the weights of two consecutive weighings are consistent, then the drying is complete and high-purity aragonite is obtained.

[0054] Optimizing the specific methods of filtration, washing, and drying helps ensure the purity of the obtained aragonite.

[0055] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0056] Example 1 A. The content of calcium oxide in steel slag was detected, and the test results were obtained; the particle size of the steel slag was 3 mm. The chemical composition of steel slag, calculated by mass percentage, includes CaO 38.4%, SiO2 22.2%, Fe2O3 19.6%, Al2O3 9%, MgO 3.7%, MnO 2.7%, P2O5 2%, Cr2O3 1.5%, and CuO 0.6%, with the remainder being loss on ignition. The mineral composition of steel slag, calculated by mass percentage, includes tricalcium silicate 20%, dicalcium β-silicate 25%, dicalcium γ-silicate 18%, free calcium oxide 8%, free magnesium oxide 3%, and feldspar 8%, with the remainder being glassy phase and impurities. B. Preparation of composite calcium source; the composite calcium source includes steel slag, magnesium slag, and calcium oxide powder, and the mass ratio of steel slag, magnesium slag, and calcium oxide powder in the composite calcium source is determined to be 4:6:0.05 according to the test results; the particle size of magnesium slag is 1 mm; the chemical composition of magnesium slag, calculated by mass percentage, includes CaO 45.4%, SiO2 26.8%, Fe2O3 4.9%, Al2O3 1.4%, MgO 10.3%, Cr2O3 2.3%, and CuO 2.7%, with the remainder being loss on ignition; the mineral composition of magnesium slag, calculated by mass percentage, includes 45% β-type dicalcium silicate, 30% γ-type dicalcium silicate, 10% free calcium oxide, and 6% periclase, with the remainder being glass phase and impurities; C. Add the composite calcium source to the sodium sulfide solution and stir for 45 minutes to obtain a solid-liquid mixture; transfer the solid-liquid mixture into a centrifuge tube for centrifugation, remove the supernatant, and obtain the pretreated calcium source; wherein, the mass percentage of sodium sulfide in the sodium sulfide solution is 2%; D. The pretreated calcium source was ball-milled at 300 rpm to obtain an activated calcium source; the activated calcium source was mixed evenly with a 0.8 mol / L ammonium chloride solution and then stirred at 1000 rpm for 2 hours in a 250W microwave field to obtain a leachate; wherein the mass mixing ratio of the activated calcium source to the ammonium chloride solution was 1:18. E. After filtering the leachate, the primary filtrate is obtained; Add disodium ethylenediaminetetraacetate solution to the primary filtrate to adjust the pH to 5, then stir to obtain the first mixed solution; After adjusting the pH of the first mixed solution to 4.5, barium chloride solution was added, and the mixture was stirred to obtain the second mixed solution. Sodium carbonate solution was added to the second mixed solution to adjust the pH to 8, and the solution was filtered through a 0.01 μm ceramic membrane to obtain a calcium-rich filtrate. Hydrochloric acid was added to the calcium-rich filtrate to adjust the pH to 5. After the precipitate disodium ethylenediaminetetraacetate was precipitated and recovered, the reaction filtrate was obtained. F. Add polyethylene glycol to the reaction filtrate and stir until the polyethylene glycol is completely dispersed to obtain the reaction dispersion. Carbonization reaction was carried out by passing a gas of 99.5% purity carbon dioxide into the reaction dispersion to obtain a mixture of aragonite; The mixture of aragonite and spheroidite was filtered to obtain crude aragonite product; The crude aragonite product was dispersed in anhydrous ethanol, sonicated for 30 min, and then placed in a centrifuge tube for centrifugation. The supernatant was removed to obtain the precipitate. Wash the precipitate repeatedly with pure water until the washed liquid is colorless and transparent, thus obtaining a solid. The solid is dried multiple times, and weighed after each drying process, until two consecutive weighings are consistent, at which point the drying process is complete, and high-purity aragonite is obtained.

[0057] The calcium ion content in the composite calcium source was detected by X-ray fluorescence spectroscopy. The total amount of calcium in the composite calcium source was calculated based on the total weight and the calcium ion content. The theoretical mass of aragonite, M1, was then calculated based on the total amount of calcium in the composite calcium source. The obtained high-purity aragonite was weighed to obtain the actual product mass, M2. The yield was calculated according to the formula: Yield = M2 / M1 × 100%. The average value of three measurements was taken as the final test result. The yield of aragonite obtained in this Example 1 was 88.3%.

[0058] The particle size uniformity of the aragonite obtained in Example 1 through the above steps was observed using a scanning electron microscope, and the purity of the aragonite obtained in Example 1 was detected by X-ray diffraction analysis. The results show that the aragonite obtained in Example 1 has high particle size uniformity and a purity of 99.3%.

[0059] Example 2 A. The content of calcium oxide in steel slag was detected, and the test results were obtained; the particle size of the steel slag was 3 mm. The chemical composition of steel slag, calculated by mass percentage, includes CaO 40.3%, SiO2 20.8%, Fe2O3 17.6%, Al2O3 8.3%, MgO 3.2%, MnO 2.4%, P2O5 2.1%, Cr2O3 1%, and CuO 0.8%, with the remainder being loss on ignition. The mineral composition of steel slag, calculated by mass percentage, includes tricalcium silicate 15%, dicalcium β-silicate 30%, dicalcium γ-silicate 20%, free calcium oxide 5%, free magnesium oxide 2%, and feldspar 10%, with the remainder being glassy phase and impurities. B. Preparation of composite calcium source; the composite calcium source includes steel slag and magnesium slag, and the mass ratio of steel slag to magnesium slag in the composite calcium source is determined to be 6:4 according to the test results; the particle size of magnesium slag is 1 mm; the chemical composition of magnesium slag by mass percentage includes CaO 47.3%, SiO2 27.2%, Fe2O3 4%, Al2O3 1.5%, MgO 11.4%, Cr2O3 2.7% and CuO 2.5%, with the remainder being loss on ignition; the mineral composition of magnesium slag by mass percentage includes 40% β-type dicalcium silicate, 35% γ-type dicalcium silicate, 8% free calcium oxide and 8% periclase, with the remainder being glass phase and impurities; C. Add the composite calcium source to the sodium sulfide solution and stir for 40 minutes to obtain a solid-liquid mixture; transfer the solid-liquid mixture into a centrifuge tube for centrifugation, remove the supernatant, and obtain the pretreated calcium source; wherein, the mass percentage of sodium sulfide in the sodium sulfide solution is 2%; D. The pretreated calcium source was ball-milled at 300 rpm to obtain an activated calcium source; the activated calcium source was mixed evenly with a 1 mol / L ammonium chloride solution and then stirred at 1000 rpm for 2 hours in a 300W microwave field to obtain a leachate; wherein the mass mixing ratio of the activated calcium source to the ammonium chloride solution was 1:18. E. After filtering the leachate, the primary filtrate is obtained; Add disodium ethylenediaminetetraacetate solution to the primary filtrate to adjust the pH to 5.5, then stir to obtain the first mixed solution; After adjusting the pH of the first mixed solution to 4.5, barium chloride solution was added, and the mixture was stirred to obtain the second mixed solution. Sodium carbonate solution was added to the second mixed solution to adjust the pH to 9, and the solution was filtered through a 0.02 μm ceramic membrane to obtain a calcium-rich filtrate. Hydrochloric acid was added to the calcium-rich filtrate to adjust the pH to 4. After the precipitate, disodium ethylenediaminetetraacetate, was precipitated and recovered, the reaction filtrate was obtained. F. Add polyethylene glycol to the reaction filtrate and stir until the polyethylene glycol is completely dispersed to obtain the reaction dispersion. A carbonization reaction was carried out by introducing industrial flue gas with a carbon dioxide concentration of 10% into the reaction dispersion to obtain a mixture of aragonite; The mixture of aragonite and spheroidite was filtered to obtain crude aragonite product; The crude aragonite product was dispersed in anhydrous ethanol, sonicated for 20 min, and then placed in a centrifuge tube for centrifugation. The supernatant was removed to obtain the precipitate. Wash the precipitate repeatedly with pure water until the washed liquid is colorless and transparent, thus obtaining a solid. The solid is dried multiple times, and weighed after each drying process, until two consecutive weighings are consistent, at which point the drying process is complete, and high-purity aragonite is obtained.

[0060] The calcium ion content in the composite calcium source was detected by X-ray fluorescence spectroscopy. The total amount of calcium in the composite calcium source was calculated based on the total weight and the calcium ion content. The theoretical mass of aragonite, M1, was then calculated based on the total amount of calcium in the composite calcium source. The obtained high-purity aragonite was weighed to obtain the actual product mass, M2. The yield was calculated according to the formula: Yield = M2 / M1 × 100%. The average value of the three measurements was taken as the final test result. The result showed that the yield of aragonite obtained in this Example 2 was 87.8%.

[0061] The particle size uniformity of the aragonite obtained in Example 2 through the above steps was observed using a scanning electron microscope, and the purity of the aragonite obtained in Example 2 was detected by X-ray diffraction analysis. The results show that the aragonite obtained in Example 2 has high particle size uniformity and a purity of 99.1%.

[0062] Example 3 A. The content of calcium oxide in steel slag was detected, and the test results were obtained; the particle size of the steel slag was 2 mm. The chemical composition of steel slag, calculated by mass percentage, includes CaO 45.2%, SiO2 20.4%, Fe2O3 15.3%, Al2O3 8.1%, MgO 3.4%, MnO 2.5%, P2O5 2.3%, Cr2O3 1%, and CuO 0.5%, with the remainder being loss on ignition. The mineral composition of steel slag, calculated by mass percentage, includes tricalcium silicate 25%, dicalcium β-silicate 20%, dicalcium γ-silicate 13%, free calcium oxide 10%, free magnesium oxide 5%, and feldspar 8%, with the remainder being glassy phase and impurities. B. Preparation of composite calcium source; the composite calcium source includes steel slag and magnesium slag, and the mass ratio of steel slag to magnesium slag in the composite calcium source is determined to be 7:3 according to the test results; wherein, the particle size of magnesium slag is 1mm; The chemical composition of magnesium slag, calculated by mass percentage, includes CaO 48.3%, SiO2 25.2%, Fe2O3 6%, Al2O3 1.2%, MgO 10.6%, Cr2O3 2.4%, and CuO 2.5%, with the remainder being loss on ignition. The mineral composition of magnesium slag, calculated by mass percentage, includes 50% β-type dicalcium silicate, 25% γ-type dicalcium silicate, 12% free calcium oxide, and 5% periclase, with the remainder being glassy phase and impurities. B. After uniformly mixing steel slag, magnesium slag and calcium oxide powder according to the mixing ratio dynamically adjusted in step A, a composite calcium source is obtained. C. Add the composite calcium source to the sodium sulfide solution and stir for 50 minutes to obtain a solid-liquid mixture; transfer the solid-liquid mixture into a centrifuge tube for centrifugation, remove the supernatant, and obtain the pretreated calcium source; wherein, the mass percentage of sodium sulfide in the sodium sulfide solution is 1.5%; D. The pretreated calcium source was ball-milled at 400 rpm to obtain an activated calcium source; the activated calcium source was mixed evenly with a 1 mol / L ammonium chloride solution and then stirred at 1200 rpm for 2 hours in a 300W microwave field to obtain a leachate; wherein the mass mixing ratio of the activated calcium source to the ammonium chloride solution was 1:20. E. After filtering the leachate, the primary filtrate is obtained; Add disodium ethylenediaminetetraacetate solution to the primary filtrate to adjust the pH to 6, then stir to obtain the first mixed solution; After adjusting the pH of the first mixed solution to 4.5, barium chloride solution was added, and the mixture was stirred to obtain the second mixed solution. Sodium carbonate solution was added to the second mixed solution to adjust the pH to 8, and the solution was filtered through a 0.01 μm ceramic membrane to obtain a calcium-rich filtrate. Hydrochloric acid was added to the calcium-rich filtrate to adjust the pH to 5. After the precipitate disodium ethylenediaminetetraacetate was precipitated and recovered, the reaction filtrate was obtained. F. Add polyethylene glycol to the reaction filtrate and stir until the polyethylene glycol is completely dispersed to obtain the reaction dispersion. Carbon dioxide gas with a purity of 99.5% was introduced into the reaction dispersion to carry out a carbonization reaction, yielding a mixture of aragonite; the aragonite mixture was then filtered to obtain crude aragonite product. The crude aragonite product was dispersed in anhydrous ethanol, sonicated for 25 min, and then placed in a centrifuge tube for centrifugation. The supernatant was removed to obtain the precipitate. Wash the precipitate repeatedly with pure water until the washed liquid is colorless and transparent, thus obtaining a solid. The solid is dried multiple times, and weighed after each drying process, until two consecutive weighings are consistent, at which point the drying process is complete, and high-purity aragonite is obtained.

[0063] The calcium ion content in the composite calcium source was detected by X-ray fluorescence spectroscopy. The total amount of calcium in the composite calcium source was calculated based on the total weight and the calcium ion content. The theoretical mass of aragonite, M1, was then calculated based on the total amount of calcium in the composite calcium source. The obtained high-purity aragonite was weighed to obtain the actual product mass, M2. The yield was calculated according to the formula: Yield = M2 / M1 × 100%. The average value of the three measurements was taken as the final test result. The yield of aragonite obtained in this Example 3 was 86.6%.

[0064] The particle size uniformity of the aragonite obtained in Example 3 through the above steps was observed using a scanning electron microscope, and the purity of the aragonite obtained in Example 3 was detected by X-ray diffraction analysis. The results show that the aragonite obtained in Example 3 has high particle size uniformity and a purity of 99.1%.

[0065] Comparative Example 1 The preparation methods, steps AD and F, and raw materials of this comparative example are the same as those of Example 1. The difference is that in step E of this comparative example, the primary filtrate is not further treated. That is, step E of Comparative Example 1 is: E. After filtering the leachate, a primary filtrate is obtained, and the primary filtrate is used as the reaction filtrate.

[0066] The calcium ion content in the composite calcium source was detected by X-ray fluorescence spectroscopy. The total amount of calcium in the composite calcium source was calculated based on the total weight and the calcium ion content. The theoretical mass of aragonite, M1, was then calculated based on the total amount of calcium in the composite calcium source. The obtained high-purity aragonite was weighed to obtain the actual product mass, M2. The yield was calculated using the formula: Yield = M2 / M1 × 100%. The average of the three measurements was taken as the final test result. The yield of aragonite obtained in this comparative example 1 was 85.3%.

[0067] The particle size uniformity of the aragonite obtained in Comparative Example 1 through the above steps was observed using a scanning electron microscope, and the purity of the aragonite obtained in Comparative Example 1 was detected by X-ray diffraction analysis. The results showed that the aragonite obtained in Comparative Example 1 had high particle size uniformity and a purity of 75.3%.

[0068] Comparative Example 2 The preparation methods, steps AC and EF, and raw materials in this comparative example are the same as in Example 1. The difference is that in step D of this comparative example, only the pretreated calcium source is leached using microwave-assisted leaching to extract calcium ions. That is, step D of Comparative Example 2 is: D. After mixing the pretreated calcium source with a 0.8 mol / L ammonium chloride solution, place it in a 250W microwave field and stir at 1000 rpm for 2 hours to obtain the leachate. The calcium ion content in the composite calcium source was detected by X-ray fluorescence spectroscopy. The total amount of calcium in the composite calcium source was calculated based on the total weight and the calcium ion content. The theoretical mass of aragonite, M1, was then calculated based on the total amount of calcium in the composite calcium source. The obtained high-purity aragonite was weighed to obtain the actual product mass, M2. The yield was calculated using the formula: Yield = M2 / M1 × 100%. The average of the three measurements was taken as the final test result. The yield of aragonite obtained in this comparative example 2 was 65.8%.

[0069] The particle size uniformity of the aragonite obtained in Comparative Example 2 through the above steps was observed using a scanning electron microscope, and the purity of the aragonite obtained in Comparative Example 2 was detected by X-ray diffraction analysis. The results showed that the aragonite obtained in Comparative Example 2 had high particle size uniformity and a purity of 99.1%.

[0070] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A method for preparing high-purity aragonite based on solid waste carbonization reaction, characterized in that, Includes the following steps: A. Detect the calcium oxide content in steel slag and obtain the test results; wherein, the chemical composition of the steel slag includes SiO2, CaO, Al2O3, MgO, Fe2O3, P2O5, Cr2O3 and CuO, and the mineral composition of the steel slag includes tricalcium silicate, dicalcium silicate of β type and dicalcium silicate of γ type. B. Preparation of composite calcium source; the composite calcium source includes steel slag and magnesium slag, or steel slag, magnesium slag and calcium oxide powder, and the mass ratio of steel slag, magnesium slag and calcium oxide powder in the composite calcium source is determined according to the test results; The chemical composition of the magnesium slag includes SiO2, CaO, Al2O3, Fe2O3, MgO and CuO, and the mineral composition of the magnesium slag includes dicalcium silicate of type β and dicalcium silicate of type γ. C. Add the composite calcium source to the sodium sulfide solution, stir and react, then filter to obtain the pretreated calcium source; D. After mechanically activating the pretreated calcium source, mix it evenly with ammonium chloride solution, and then use microwave-assisted leaching to leach calcium ions to obtain leachate; E. After filtering the leachate, the primary filtrate is obtained; Ethylenediaminetetraacetic acid disodium solution, barium chloride solution, and sodium carbonate solution are added sequentially to the primary filtrate to precipitate impurities in the primary filtrate. After filtration through a 0.01–0.02 μm ceramic membrane, a calcium-rich filtrate is obtained. Hydrochloric acid was added to the calcium-rich filtrate to adjust the pH, and the precipitate disodium ethylenediaminetetraacetate was precipitated and recovered to obtain the reaction filtrate. F. Add polyethylene glycol to the reaction filtrate and stir until the polyethylene glycol is completely dispersed to obtain the reaction dispersion. Carbon dioxide gas is introduced into the reaction dispersion to carry out a carbonization reaction, and then high-purity aragonite is obtained after sequential filtration, centrifugation, washing and drying.

2. The method for preparing high-purity aragonite based on solid waste carbonization reaction according to claim 1, characterized in that, In step B, when the mass percentage of calcium oxide in the steel slag is ≥45%, the composite calcium source includes steel slag and magnesium slag, and the mass ratio of steel slag to magnesium slag is (6.8~7.2):(2.8~3.2). When the mass percentage of calcium oxide in the steel slag is ≥40% and <45%, the composite calcium source includes steel slag and magnesium slag, and the mass ratio of steel slag to magnesium slag is (5.8~6.2):(3.8~4.2). When the mass percentage of calcium oxide in the steel slag is <40%, the composite calcium source includes steel slag, magnesium slag and calcium oxide powder, and the mass ratio of steel slag, magnesium slag and calcium oxide powder is (3.8~4.2):(5.8~6.2):(0.05~0.1).

3. The method for preparing high-purity aragonite based on solid waste carbonization reaction according to claim 1, characterized in that, In step A, the particle size of the steel slag is ≤3mm; In step B, the particle size of the magnesium slag is ≤1mm, and the mass percentage of calcium oxide in the magnesium slag is ≥40%.

4. The method for preparing high-purity aragonite based on solid waste carbonization reaction according to claim 3, wherein in step A, the chemical composition of the steel slag, calculated by mass percentage, includes CaO 38-48%, SiO2 20-25%, Fe2O3 15-20%, Al2O3 8-10%, MgO 3-5%, MnO 2-4%, P2O5 2-4%, Cr2O3 1-2%, and CuO 0.5-1.5%, with the remainder being loss on ignition; According to mass percentage, the mineral composition of the steel slag includes 15-25% tricalcium silicate, 20-30% β-type dicalcium silicate, 10-20% γ-type dicalcium silicate, 5-10% free calcium oxide, 2-5% free magnesium oxide, and 5-10% feldspar, with the remainder being glass phase and impurities; In step B, the chemical composition of the magnesium slag, calculated by mass percentage, includes CaO 45-50%, SiO2 25-30%, Fe2O3 4-6%, Al2O3 1-3%, MgO 10-15%, Cr2O3 1-4%, and CuO 2-4%, with the remainder being loss on ignition. The mineral composition of the magnesium slag, calculated by mass percentage, includes 40-50% dicalcium silicate of β type, 25-35% dicalcium silicate of γ type, 8-12% free calcium oxide, and 5-8% periclase, with the remainder being glass phase and impurities.

5. The method for preparing high-purity aragonite based on solid waste carbonization reaction according to claim 1, characterized in that, In step C, the sodium sulfide solution contains 1-2% sodium sulfide by mass.

6. The method for preparing high-purity aragonite based on solid waste carbonization reaction according to claim 1, characterized in that, Step C is as follows: the composite calcium source is added to the sodium sulfide solution and stirred for 40-50 minutes to obtain a solid-liquid mixture; The solid-liquid mixture was placed into a centrifuge tube for centrifugation and the supernatant was removed to obtain a pretreated calcium source.

7. The method for preparing high-purity aragonite based on solid waste carbonization reaction according to claim 1, characterized in that, Step D specifically involves: ball milling the pretreated calcium source at a speed of 200–400 rpm to obtain an activated calcium source; After the activated calcium source and ammonium chloride solution are mixed evenly, the mixture is placed in a microwave field of 200-300W and stirred at 800-1200rpm for 1-2 hours to obtain the leachate.

8. The method for preparing high-purity aragonite based on solid waste carbonization reaction according to claim 7, characterized in that, In step D, the mass mixing ratio of the activated calcium source to the ammonium chloride solution is 1:(15-20), and the concentration of the ammonium chloride solution is 0.5-1 mol / L.

9. The method for preparing high-purity aragonite based on solid waste carbonization reaction according to claim 1, characterized in that, The specific method for step E is as follows: filter the leachate to obtain the primary filtrate; Add disodium ethylenediaminetetraacetate solution to the primary filtrate to adjust the pH to 5-6, then stir to obtain the first mixed solution; After adjusting the pH of the first mixed solution to 4-4.5, barium chloride solution was added and stirred to obtain the second mixed solution. Sodium carbonate solution was added to the second mixed solution to adjust the pH to 8-9, and the solution was filtered through a 0.01-0.02 μm ceramic membrane to obtain a calcium-rich filtrate. Hydrochloric acid was added to the calcium-rich filtrate to adjust the pH to 4-5. After the precipitate, disodium ethylenediaminetetraacetate, was precipitated and recovered, the reaction filtrate was obtained.

10. The method for preparing high-purity aragonite based on solid waste carbonization reaction according to claim 1, characterized in that, In step F, the specific method of filtration is as follows: the mixture of aragonite obtained by carbonizing the reaction dispersion by passing a gas containing carbon dioxide is filtered to obtain crude aragonite product. The specific method of centrifugal separation is as follows: disperse the crude aragonite product in anhydrous ethanol, sonicate for 20-30 min, then load it into a centrifuge tube for centrifugal separation, remove the supernatant, and obtain the precipitate; The specific washing method is as follows: wash the precipitate repeatedly with pure water until the washed liquid is colorless and transparent, thus obtaining a solid. The specific drying method is as follows: the solid is dried multiple times, and the weight is weighed after each drying until the weights of two consecutive weighings are consistent, then the drying is complete and high-purity aragonite is obtained.