A method for preparing high aspect ratio calcium carbonate whiskers by carbon fixation in steel smelting slag leachate

Abstract

The invention discloses a method for preparing high aspect ratio calcium carbonate whiskers by carbon fixation in steel smelting slag leachate, belonging to the technical field of solid waste resource utilization. The method comprises the following steps: leaching steel smelting slag to obtain calcium-magnesium leachate and leach slag; removing impurities from the calcium-magnesium leachate by a pH swing method to obtain a calcium-magnesium purified solution; capturing the gas containing carbon dioxide by an alkaline solution to obtain a carbonated solution; adjusting the pH of the calcium-magnesium purified solution to convert magnesium ions into magnesium hydroxide, placing the solution in an ultrasonic field, adding the carbonated solution to carry out a carbon fixation reaction, and washing and drying the precipitate obtained by the reaction to obtain calcium carbonate whiskers. The method not only successfully realizes the efficient resource utilization of two wastes, steel smelting slag and carbon dioxide flue gas, but also produces high value-added calcium carbonate whisker products while stably fixing carbon dioxide, and has broad application prospects and environmental value.

Description

Technical Field

[0001] The invention relates to a method for treating steel smelting slag, in particular to a method for preparing high aspect ratio calcium carbonate whiskers by carbon fixation in steel smelting slag leaching liquid, belonging to the technical field of solid waste resource utilization. Background Art

[0002] In the traditional steel smelting industry, a large amount of smelting slag is produced. These solid slags are usually regarded as waste, and their treatment and disposal require a lot of resources and costs. With the increasing global attention to environmental protection and sustainable development, the efficient utilization of steel smelting slag has become an urgent issue. At the same time, global attention to greenhouse gas emissions is increasing. Carbon dioxide, as one of the main greenhouse gases, has an adverse impact on climate change and environmental health. Therefore, developing a method to fix carbon dioxide in steel smelting slag and convert it into valuable products has become an important research direction.

[0003] There are literature reports on the use of steel slag to fix carbon dioxide at home and abroad. For example, the literature (“Direct Gas–Solid Carbonation Kinetics of Steel Slag and the Contribution to In situ Sequestration of Flue Gas CO2 in Steel-Making Plants”, Sicong Tian et al. ChemSusChem, 2013, 6, 2348 – 2355) discloses the use of steel slag as a raw material to directly react with carbon dioxide to achieve carbon fixation. The purpose of the literature is to study the effects of different temperatures and CO2 concentrations on the carbon fixation efficiency of steel slag. The results show that 88.5 kg CO2 can be fixed per ton of steel slag, but the literature does not involve how to make high-value use of the products after the carbonization of steel slag. As for the current method of directly fixing carbon dioxide with smelting slag, although the process is simple, its reaction conditions are relatively harsh, usually requiring high temperature and high pressure, and its solidification efficiency is low, and the added value of the solidified products produced is not high.

[0004] There are related technologies of ultrasound-assisted carbonation reaction in the prior art, such as European patent (publication number EP2238077A4) discloses a method and equipment for producing precipitated calcium carbonate (PCC) or its composite with some other materials in a continuous process, which is specifically disclosed in a small reactor to produce PCC in a continuous manner, and the small reactor is easy to achieve pressurization, and high shear rate and ultrasonic wave breakdown CO2 bubbles are small bubbles, these factors jointly improve the mass transfer from gas phase to water phase, improve the solubility of CO2 in water, thereby accelerating the carbonation reaction rate. This technology is essentially to utilize high pressure conditions to realize the gas-solid reaction between carbon dioxide gas and calcium hydroxide slurry to realize carbonation reaction, and to accelerate the carbonation reaction and realize the particle size control of calcium carbonate crystals by adding high energy conditions (such as high shear or ultrasound). This patented technology is mainly to obtain calcium carbonate fillers whose size and morphology meet the requirements of papermaking. For example, a Chinese patent (publication number CN115744954A) discloses the use of ultrasound to assist carbon fixation reaction, which can not only improve the efficiency of carbon fixation reaction, but also convert the alkaline calcium source in the fly ash of garbage incineration into ultrafine calcium carbonate (the particle size can be controlled within the range of 1 to 7 μm) to obtain high-value calcium carbonate products. The role of ultrasound is to break carbon dioxide bubbles into micro-nano bubbles to enhance the solubility of carbon dioxide gas in the slurry, while preventing calcium carbonate crystals from agglomerating to control the acquisition of micron-sized calcium carbonate crystals. In summary, the main purpose of the ultrasound-assisted carbonation reaction between carbon dioxide and calcium hydroxide in the prior art is to improve the efficiency of gas-solid reaction and obtain calcium carbonate with a smaller particle size, rather than to control the formation of calcium carbonate nuclei and whisker growth to obtain high-purity, high aspect ratio calcium carbonate whisker products. Summary of the invention

[0005] In view of the technical problems existing in the method of fixing carbon dioxide using steel smelting slag in the prior art, the purpose of the present invention is to provide a method for preparing calcium carbonate whiskers with high aspect ratio by fixing carbon with steel smelting slag leachate. The method uses steel smelting slag leachate to fix carbon dioxide flue gas, which can not only achieve efficient fixation of carbon dioxide and reduce greenhouse gas emissions, but also obtain calcium carbonate whisker products with high aspect ratio, realize the comprehensive utilization of steel smelting slag solid waste, and has broad application prospects. The method is simple, efficient, low-cost, and meets the needs of large-scale industrial production.

[0006] In order to achieve the above technical purpose, the present invention provides a method for preparing high aspect ratio calcium carbonate whiskers by carbon fixation in steel smelting slag leachate, the method comprising the following steps:

[0007] 1) Leaching the steel smelting slag to obtain calcium magnesium leaching solution and leaching slag;

[0008] 2) removing impurities from the calcium and magnesium leaching solution by a pH swing method to obtain a calcium and magnesium purified solution; during the impurity removal process by the pH swing method, the pH value is controlled in the range of 9.2 to 11.1, and the total concentration of iron ions and aluminum ions in the calcium and magnesium purified solution is controlled to be less than 1×10 -5 mol / L, the molar ratio of calcium ion to magnesium ion is between 4 / 1 and 50 / 1;

[0009] 3) Capturing the gas containing carbon dioxide through an alkaline solution to obtain a carbonated solution;

[0010] 4) The pH of the calcium-magnesium purified solution is adjusted to 10-11.3 to convert magnesium ions into magnesium hydroxide, and then placed in an ultrasonic field, and the carbonation solution is added to carry out a carbon fixation reaction. The precipitate obtained by the reaction is washed with water and dried in turn to obtain calcium carbonate whiskers. The conditions of the carbon fixation reaction are: the reaction temperature is 60-80° C., the addition time of the carbonation solution is less than 1 min, and the reaction time is 10-120 min.

[0011] The high aspect ratio calcium carbonate whisker of the present invention is generally considered to have an aspect ratio of 7 or more, preferably 7 to 150, and more preferably 20 to 140.

[0012] The method for preparing high aspect ratio calcium carbonate whiskers by carbon fixation using steel smelting slag leachate provided by the present invention uses steel smelting slag as raw material, firstly efficiently and selectively leaches calcium and magnesium therein, and then removes a small amount of iron and aluminum impurities in the form of precipitation by pH swing method, and controls iron and aluminum at a relatively low level, which is conducive to obtaining calcium carbonate whiskers with low impurity content, and at the same time regulates the calcium-magnesium ratio in the solution system, which is conducive to the subsequent formation process of calcium carbonate whiskers. The high calcium-magnesium purified solution after impurity removal is mainly regulated by pH to selectively convert magnesium ions into magnesium hydroxide, and the presence of magnesium hydroxide is the key to the subsequent growth of calcium carbonate crystals into whiskers. Under the action of ultrasound, the cavitation core in the solution system obtains ultrasonic energy to form a large number of cavitation bubble nuclei. As the ultrasound is transmitted in the leachate, since the size of the cavitation bubble nucleus is smaller than the resonance size, resonance begins to occur, and positive and negative pressure areas are quickly formed. In the negative pressure area, the pressure in the bubble nucleus is less than the static pressure at equilibrium, and it grows rapidly. When the bubble grows to a certain extent, the cavitation bubble collapses and explodes rapidly, and a mechanical force is generated. At this time, a carbonated solution rich in carbonate ions is quickly added to react with calcium ions in the solution to form calcium carbonate seeds, and under the mechanical force generated by the ultrasonic cavitation bubble explosion, the calcium carbonate seeds explode and diffuse to the surroundings. The magnesium hydroxide in the solution system is highly dispersed under the action of ultrasound and adheres to the surface of the calcium carbonate crystal, which can inhibit the radial growth of calcium carbonate and make the calcium carbonate crystal particles grow in the length direction to form calcium carbonate whiskers. After the calcium carbonate whiskers are generated, the ultrasonic action can promote the magnesium hydroxide to fall off from the surface of the calcium carbonate whiskers, which is conducive to obtaining calcium carbonate whiskers with higher purity.

[0013] As a preferred solution, the total mass content of calcium and magnesium in the steel smelting slag is 30-60%, and its particle size is less than 74 μm. The steel smelting slag is waste slag or by-product produced in the steel smelting process, mainly composed of impurities, slag and other non-metallic components in the smelting raw materials, and the total content of calcium and magnesium is 30-60%. The present invention mainly realizes the recovery and utilization of metals such as calcium and magnesium in steel smelting slag.

[0014] As a preferred solution, the leaching conditions are: using an organic carboxylic acid solution or an ammonium salt solution as a leaching agent, a leaching temperature of 60-90°C, a leaching time of 0.5-2 h, and a leaching liquid-solid ratio of 20-100 L / kg.

[0015] As a preferred solution, the ammonium salt solution includes at least one of ammonium acetate solution, ammonium nitrate solution and ammonium chloride solution. The concentration of the ammonium salt solution is 0.1-1 mol / L; the further preferred concentration is 0.3-0.7 mol / L. The concentration of the organic carboxylic acid solution is 0.1-1 mol / L; the further preferred concentration is 0.3-0.7 mol / L. The organic carboxylic acid in the organic carboxylic acid solution is a unit acid or a polyacid having 1-5 carbon atoms. Under preferred leaching conditions, high selective leaching of calcium and magnesium in steel smelting slag can be achieved, and the selectivity is higher than 90%. Organic acids such as acetic acid, propionic acid, etc.

[0016] In the pH swing method impurity removal process of the present invention, at least one of calcium hydroxide, magnesium hydroxide, sodium hydroxide and ammonia is used to regulate pH. The regulation of pH value is very important for the regulation of impurity removal and magnesium ion content. If pH is too low, iron ion and aluminum ion precipitation will be incomplete, and if pH is too high, a large amount of magnesium ion precipitation will be caused, which is unfavorable for the preparation of subsequent calcium carbonate whiskers. In addition, magnesium concentration is too high, and too much magnesium will prevent the growth of primary calcium carbonate whiskers in radial and long directions, and will inhibit the growth of calcium carbonate whiskers, resulting in the formation of irregular calcium carbonate, while magnesium concentration is too low to be enough to effectively control crystal morphology, and it is difficult to inhibit the radial growth of primary calcium carbonate crystals towards the higher surface energy, resulting in less whisker generation. Therefore, the molar ratio of calcium ion to magnesium ion is further preferably between 8 and 20.

[0017] As a preferred solution, the alkaline solution is an ammonia solution. The ammonia solution can be industrial ammonia water or ammonia wastewater. Ammonia water is used to absorb carbon dioxide to mainly form ammonium carbonate without introducing new impurity ions.

[0018] As a preferred solution, the pH value of the carbonated solution is controlled to be in the range of 8 to 10. The solution is kept in a weakly alkaline environment to prevent carbon dioxide from escaping.

[0019] As a preferred solution, the volume concentration of carbon dioxide in the carbon dioxide-containing gas is greater than 3%. Carbon dioxide-containing gas, such as flue gas, mainly comes from the calcination of carbonate minerals, the combustion of fossil fuels, smelting flue gas or waste incineration flue gas, etc.

[0020] The pH of the calcium-magnesium purification solution of the present invention is adjusted to 10-11.3. pH=11.3 is the critical value at which magnesium ions are precipitated in large quantities but calcium ions are not precipitated, so the pH is controlled below 11.3 to selectively convert magnesium ions into magnesium hydroxide precipitates.

[0021] As a preferred solution, the ultrasonic power of the ultrasonic field is 200-1500 W. Under appropriate ultrasonic action, on the one hand, it is conducive to the high dispersion of magnesium hydroxide, which is conducive to the subsequent action on the calcium carbonate crystal nucleus to induce its growth. On the other hand, it is conducive to explosive nucleation to quickly form a uniform and large amount of calcium carbonate crystal nuclei. On the third aspect, it is conducive to the subsequent magnesium hydroxide falling off on the calcium carbonate whisker to improve the purity of the calcium carbonate whisker. The ultrasonic power of the ultrasonic field is further 400-800 W.

[0022] The present invention can realize explosive nucleation under the action of ultrasound by controlling the feeding rate and time, forming a large number of uniform crystal nuclei, and then controlling the uniform growth of calcium carbonate crystals and regulating the crystal phase at an appropriate temperature and reaction time. Of course, the faster the addition rate of the carbonated solution and the shorter the addition time, the more crystal nuclei are formed. The addition rate of the carbonated solution is further preferably 1 to 1000 L / min. The addition time is further preferably <40s.

[0023] The solution for separating calcium carbonate whiskers after the carbon fixation reaction of the present invention is mainly an organic acid salt solution or an ammonium salt solution, which can be recycled as a leaching agent for steel smelting slag, thereby reducing the use of leaching reagents.

[0024] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0025] The present invention utilizes steel smelting slag leachate to achieve the fixation of carbon dioxide flue gas, thereby achieving efficient utilization of waste resources, reducing resource waste, and converting waste slag into products with high added value, which effectively reduces the environmental burden of waste slag treatment and provides solid support for sustainable development.

[0026] The present invention utilizes magnesium leached from smelting slag as a crystal surfactant, and effectively controls the morphology and size of calcium carbonate crystals by regulating the concentration change and distribution of magnesium ions during the synthesis of calcium carbonate whiskers. In this process, magnesium ions not only promote the nucleation of calcium carbonate, but also affect the growth direction and rate of crystals, so that the final product has a more uniform whisker-like structure with a high aspect ratio.

[0027] The present invention not only effectively fixes carbon dioxide, but also converts it into a high-value-added calcium carbonate whisker product. This treatment method helps reduce greenhouse gas emissions and effectively prevents carbon dioxide from being emitted into the atmosphere by stably fixing it. This has a far-reaching positive impact on addressing climate change and environmental protection.

[0028] The low-carbon chain acid salt remaining after the precipitation of calcium carbonate reaction is completed can be used as a leaching agent for steel smelting slag, thereby further saving the use of reagents and improving the process economy.

[0029] The present invention uses ultrasonic wave to strengthen the reaction, and the obtained calcium carbonate whisker product has high purity. This high-quality product has wide applications in multiple industrial fields, such as building materials, plastic fillers and coatings. This not only improves the market competitiveness of the product, but also opens up new possibilities for the further development of the industry.

[0030] The indirect method used in the present invention in combination with the ultrasonic strengthening technology significantly reduces the energy consumption of the entire curing reaction, which not only reduces production costs, but also improves the effective use of energy, creating favorable conditions for sustainable production.

[0031] In summary, the technical solution of the present invention shows obvious advantages in the utilization of steel smelting slag resources, carbon dioxide emission reduction, calcium carbonate product quality and energy efficiency, provides strong support for environmental protection technology, and is expected to have a broad and positive impact in the fields of industrial production and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The XRD diffraction pattern of the calcium carbonate whisker product of Example 1 is shown in FIG.

[0033] Figure 2 This is the microscopic morphology of the calcium carbonate whisker product of Example 1.

[0034] Figure 3 The XRD diffraction pattern of the calcium carbonate whisker product of Comparative Example 1 is shown.

[0035] Figure 4 The microstructure of the calcium carbonate whisker product of Comparative Example 1.

[0036] Figure 5 The XRD diffraction pattern of the calcium carbonate whisker product of Example 2 is shown in FIG.

[0037] Figure 6 This is the microscopic morphology of the calcium carbonate whisker product of Example 2.

[0038] Figure 7 The XRD diffraction pattern of the calcium carbonate whisker product of Example 3 is shown in FIG.

[0039] Figure 8This is the microscopic morphology structure of the calcium carbonate whisker product of Example 3.

[0040] Fig. 9 The XRD diffraction pattern of the calcium carbonate whisker product of Example 4 is shown in FIG.

[0041] Fig.10 This is the microscopic morphology structure of the calcium carbonate whisker product of Example 4.

[0042] according to Figures 1 to 9 It can be seen that the crystal phases of calcium carbonate include aragonite whiskers, vaterite and calcite, etc. Figure 3 The diffraction peak intensity of Chinese quartz whiskers is low, and it mainly exists in vaterite and calcite. Figure 1 , Figure 5 , Figure 7 and Fig. 9 The diffraction peak intensity of aragonite whiskers is high, indicating that its calcium carbonate whisker content is high. DETAILED DESCRIPTION

[0043] The technical solution of the present invention will be clearly and completely described below through embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0044] Example 1

[0045] Take 5 kg of converter slag from a steel plant and pass it through a 200 mesh sieve. The total content of calcium and magnesium is 60 wt%. Select 0.5 mol / L ammonium acetate solution as the leaching agent, and leach the converter slag under the conditions of reaction temperature of 80 ℃, leaching time of 2h, and liquid-solid ratio of 100 L / kg. The total selectivity of calcium and magnesium in the selected converter slag is 98%. The obtained leachate is adjusted to pH 10.3 by 12 wt% ammonia water to remove impurities, so that the molar ratio of calcium and magnesium in the leachate is 10. After liquid-solid separation, add ammonia solution to make the pH value 11.3, and obtain a turbid solution of calcium-containing magnesium hydroxide. In addition, a carbon dioxide flue gas with a concentration of 3 vol% is passed into ammonia wastewater with a concentration of 12% at 0.1 L / min to obtain an ammonium bicarbonate solution, and its pH value is controlled to be 8. At a reaction temperature of 70°C and an ultrasonic power of 600 W, the carbonized solution was pumped into the turbid solution containing magnesium hydroxide at a rate of 1 L / min for 30 seconds, and the equal volumes were mixed and reacted for 15 minutes. After the reaction, the liquid and solid were separated, and the obtained calcium carbonate whisker had a content of 93% and an aspect ratio of 30-120.

[0046] Comparative Example 1

[0047] Compared with Example 1, the only difference is that the ultrasonic power is 0 W. The obtained calcium carbonate whisker content is 44%, and the aspect ratio is 5-37.

[0048] Example 2

[0049] Take 5 kg of refined slag from a steel plant and pass it through a 200-mesh sieve. The total content of calcium and magnesium is 55 wt%. 0.5 mol / L acetic acid solution is selected as the leaching agent. The reaction temperature is 60 ° C, the leaching time is 2 h, and the liquid-to-solid ratio is 20 L kg -1 The slag was leached under the conditions of 12 wt% ammonia water, and the total selectivity of calcium and magnesium in the selected slag was 91%. The obtained leachate was adjusted to pH 9.2 by 12 wt% ammonia water to remove impurities, so that the molar ratio of calcium and magnesium in the leachate was 4. After liquid-solid separation, ammonia solution was added to make the pH value 11.3, and a turbid solution of magnesium hydroxide containing calcium was obtained. In addition, carbon dioxide flue gas with a concentration of 10 vol% was passed into ammonia wastewater with a concentration of 12% at 3 L / min to obtain an ammonium carbonate solution, and the pH value was controlled to be 10. Under the conditions of reaction temperature of 60 ° C and ultrasonic power of 1500 W, the carbonized solution was pumped into the turbid solution containing magnesium hydroxide at 1 L / min, the pumping time was 33s, and the equal volumes were mixed for 10 min. After the reaction, liquid-solid separation was carried out, and the obtained calcium carbonate whisker content was 83% and the aspect ratio was 23~140.

[0050] Since the magnesium concentration in this embodiment is relatively low, it is not enough to effectively control the growth morphology of calcium carbonate crystals and it is difficult to inhibit the radial growth of primary calcium carbonate crystals with higher surface energy, resulting in slightly less whisker generation. However, its calcium carbonate whisker content is 83%, which still meets the application requirements in most fields.

[0051] Example 3

[0052] 5 kg of converter slag from a steel plant was taken and passed through a 200-mesh sieve. The total calcium and magnesium content was 30 wt%. 0.5 mol / L ammonium acetate solution was selected as the leaching agent. The reaction temperature was 90 °C, the leaching time was 0.5 h, and the liquid-to-solid ratio was 80 L∙kg -1The converter slag was leached under the conditions of 12 wt% ammonia water, and the total selectivity of calcium and magnesium in the selected converter slag was 94%. The obtained leachate was slowly adjusted to pH 11.1 by 12 wt% ammonia water to remove impurities, so that the molar ratio of calcium and magnesium in the leachate was 50. After liquid-solid separation, ammonia solution was added to make the pH value 11.3, and a turbid solution of magnesium hydroxide containing calcium was obtained. In addition, carbon dioxide flue gas with a concentration of 20 vol% was passed into the ammonia-containing wastewater at 1.5 L / min to obtain an ammonium bicarbonate solution, and the pH value was controlled to be 9. Under the conditions of a reaction temperature of 80°C and an ultrasonic power of 200 W, the carbonized solution was pumped into the turbid solution containing magnesium hydroxide at 1 L / min, the pumping time was 42s, and the equal volumes were mixed and reacted for 120 min. After the reaction, the liquid and solid were separated, and the obtained calcium carbonate whisker content was 80%, and the aspect ratio was 7~25.

[0053] In this embodiment, due to the relatively high magnesium concentration, excessive magnesium will prevent the growth of primary calcium carbonate whiskers in the radial and longitudinal directions, and will inhibit the growth of calcium carbonate whiskers, resulting in a slight decrease in the number of calcium carbonate whiskers. However, its calcium carbonate whisker content is 80%, which still meets the application requirements in most fields.

[0054] Example 4

[0055] 5 kg of converter slag from a steel plant was taken and passed through a 200-mesh sieve. The total calcium and magnesium content was 48 wt%. 0.5 mol / L ammonium acetate solution was selected as the leaching agent. The reaction temperature was 85 °C, the leaching time was 1.5 h, and the liquid-to-solid ratio was 40 L∙kg -1 The converter slag was leached under the conditions of 12 wt% ammonia water, and the total selectivity of calcium and magnesium in the selected converter slag was 93%. The obtained leachate was adjusted to pH 10.5 by 12 wt% ammonia water to remove impurities, so that the molar ratio of calcium and magnesium in the leachate was 12. After liquid-solid separation, ammonia solution was added to make the pH value 11.3, and a turbid solution of magnesium hydroxide containing calcium was obtained. In addition, carbon dioxide flue gas with a concentration of 20 vol% was passed into the ammonia-containing wastewater at 1.5 L / min to obtain an ammonium bicarbonate solution, and the pH value was controlled to be 8. Under the conditions of reaction temperature of 70°C and ultrasonic power of 600 W, the carbonized solution was pumped into the turbid solution containing magnesium hydroxide at 1 L / min, the pumping time was 50s, and the equal volumes were mixed for reaction for 12 min. After the reaction, liquid-solid separation was performed, and the obtained calcium carbonate whisker content was 95% and the aspect ratio was 50~150.

[0056] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and changes obtained without departing from the technical concept of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing high aspect ratio calcium carbonate whiskers by carbon fixation in steel smelting slag leachate, characterized in that: The following steps are involved: 1) Leaching the steel smelting slag to obtain calcium magnesium leaching solution and leaching slag; 2) removing impurities from the calcium and magnesium leaching solution by a pH swing method to obtain a calcium and magnesium purified solution; during the impurity removal process by the pH swing method, the pH value is controlled in the range of 9.2 to 11.1, and the total concentration of iron ions and aluminum ions in the calcium and magnesium purified solution is controlled to be less than 1×10 -5 mol / L, the molar ratio of calcium ion to magnesium ion is between 8 / 1 and 20 / 1; 3) Capturing the gas containing carbon dioxide through an alkaline solution to obtain a carbonated solution; 4) The pH of the calcium-magnesium purified solution is adjusted to 10-11.3 to convert magnesium ions into magnesium hydroxide, and then placed in an ultrasonic field, and the carbonation solution is added to carry out a carbon fixation reaction. The precipitate obtained by the reaction is washed with water and dried in sequence to obtain calcium carbonate whiskers. The conditions of the carbon fixation reaction are: the reaction temperature is 60-80° C., the addition time of the carbonation solution is less than 1 min, and the reaction time is 10-120 min.

2. The method for preparing high aspect ratio calcium carbonate whiskers by carbon fixation in steel smelting slag leachate according to claim 1, characterized in that: The total mass content of calcium and magnesium in the steel smelting slag is 30-60%, and the particle size is less than 74 μm.

3. The method for preparing high aspect ratio calcium carbonate whiskers by carbon fixation in steel smelting slag leachate according to claim 1, characterized in that: The leaching conditions are: using an organic carboxylic acid solution or an ammonium salt solution as a leaching agent, a leaching temperature of 60-90° C., a leaching time of 0.5-2 h, and a leaching liquid-solid ratio of 20-100 L / kg.

4. The method for preparing high aspect ratio calcium carbonate whiskers by carbon fixation in a steel smelting slag leachate according to claim 3, characterized in that: The ammonium salt solution includes at least one of ammonium acetate solution, ammonium nitrate solution and ammonium chloride solution; The concentration of the ammonium salt solution is 0.1-1 mol / L; The concentration of the organic carboxylic acid solution is 0.1-1 mol / L; the organic carboxylic acid in the organic carboxylic acid solution is a unit acid or a polyacid having 1-5 carbon atoms.

5. The method for preparing high aspect ratio calcium carbonate whiskers by carbon fixation in steel smelting slag leachate according to claim 1, characterized in that: The alkaline solution is an ammonia solution.

6. The method for preparing high aspect ratio calcium carbonate whiskers by carbon fixation in steel smelting slag leachate according to claim 1, characterized in that: The pH value of the carbonated solution is controlled in the range of 8 to 10.

7. The method for preparing high aspect ratio calcium carbonate whiskers by carbon fixation in steel smelting slag leachate according to claim 1, characterized in that: The ultrasonic power of the ultrasonic field is 200-1500W.

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