A high-efficiency and low-consumption leaching method for smelting slag based on ammonium salt leaching agent circulation

Abstract

The application discloses a kind of based on ammonium salt leaching agent cycle's smelting slag efficient low-consumption leaching method, belong to metallurgical solid waste resource utilization technical field.Water leaching is carried out to smelting slag, and the obtained water leaching residue is subjected to multistage countercurrent leaching using ammonium salt solution to obtain calcium-rich leaching solution, and the calcium-rich leaching solution is subjected to carbon fixation reaction with excess carbon dioxide gas to generate calcium bicarbonate solution;The calcium bicarbonate solution is subjected to neutralization precipitation with the obtained water leaching solution, liquid-solid separation, to obtain light calcium carbonate and ammonium salt solution, and the obtained ammonium salt solution is recycled for multistage countercurrent leaching.The method designs an ammonium salt solution closed-loop process and a calcium carbonate open-loop process, which not only reduces the acid and alkali consumption cost in the smelting slag leaching process, but also produces high-value light calcium carbonate products, realizes the resource utilization of all components of smelting slag, reduces the processing cost of smelting slag, and provides a new way for harmless, efficient and high-value utilization of steel smelting slag.

Description

Technical Field

[0001] This invention relates to a method for treating smelting slag, and particularly to a highly efficient and low-consumption leaching method for smelting slag based on the circulation of ammonium salt leaching agent, belonging to the field of metallurgical solid waste resource utilization technology. Background Technology

[0002] The production of crude steel generates a large amount of smelting slag, primarily solid components discharged during the steelmaking and refining processes to remove harmful impurities, protect molten steel, and reduce furnace lining loss. This slag is rich in various valuable elements such as calcium, magnesium, iron, and aluminum. However, the high content of free CaO and MgO in the slag leads to the hydration of calcium hydroxide and magnesium hydroxide, causing volume expansion and resulting in poor stability and difficulty in utilization.

[0003] Currently, indirect CO2 fixation technology for smelting slag provides an effective way to solve the problem of "dual waste" in the steel industry. Indirect carbon fixation utilizes leaching media such as strong acids, weak acids, and salts to dissolve alkali metal ions such as calcium and magnesium in smelting slag. Under conditions of pH > 7, these ions combine with CO2 to form stable carbonate products. Due to its mild reaction conditions, simple operation, and high carbonation efficiency, indirect carbon fixation shows broad application potential in the field of CO2 mineralization. For example, Chinese patent (CN118745520A) discloses a method for selectively leaching calcium from smelting slag in steps and utilizing all components. The method includes the following steps: 1) stirring and leaching ammonium salt, water, and smelting slag together to obtain leachate I and leaching residue I; 2) stirring and leaching residue I with organic acid to obtain leachate II and leaching residue II; 3) subjecting leaching residue II to strong magnetic separation to obtain magnetically separated iron-rich concentrate and non-magnetic tailings; 4) mixing leachate I and leachate II, and then performing stepwise hydrolysis and precipitation to obtain iron and aluminum precipitates. The precipitate is a calcium-rich solution, which is used to fix carbon dioxide. Although this method achieves full utilization of smelting slag components, it requires the consumption of various acid and alkali leaching agents, and it is difficult to achieve recycling of the leaching agents, resulting in high costs. Furthermore, the leaching selectivity for calcium and magnesium is low. These factors restrict its large-scale industrial application. Summary of the Invention

[0004] To address the technical challenges in the resource utilization of smelting slag in existing technologies, the present invention aims to provide a highly efficient and low-consumption leaching method for smelting slag based on ammonium salt leaching agent recycling. This method, through the design of a reasonable closed-loop circulation process of ammonium salt solution and an open-loop process of calcium carbonate, not only significantly reduces the acid and alkali consumption costs in the smelting slag leaching process, but also produces high-value-added light calcium carbonate as a byproduct. This achieves the resource utilization of all components of smelting slag while reducing the processing cost of smelting slag, providing a new approach for the harmless, efficient, and high-value utilization of smelting slag.

[0005] To achieve the above technical objectives, the present invention provides a highly efficient and low-consumption leaching method for smelting slag based on ammonium salt leaching agent circulation, which includes the following steps:

[0006] (1) The smelting slag is leached with water to obtain a water-leached solution and a water-leached slag;

[0007] (2) The water-leached residue is subjected to multi-stage countercurrent leaching with ammonium salt solution to obtain calcium-rich leachate;

[0008] (3) The calcium-rich leachate is subjected to a carbon fixation reaction with excess carbon dioxide flue gas to obtain a calcium bicarbonate solution;

[0009] (4) The calcium bicarbonate solution and the water leaching solution are subjected to a neutralization and precipitation reaction, and the liquid and solid are separated. The solid product is light calcium carbonate and the liquid product is an ammonium salt solution. The ammonium salt solution is recycled for multi-stage countercurrent leaching.

[0010] The key to the smelting slag leaching method provided by this invention lies in: using ammonium salt solution as the leaching agent for smelting slag, and designing a circulation path for the ammonium salt solution through a leaching process combining water leaching and multi-stage countercurrent leaching with ammonium salt solution. This not only reduces the consumption cost of acid and alkali leaching agents during the smelting slag leaching process, but also improves the leaching selectivity and efficiency of calcium and magnesium in the smelting slag. At the same time, the calcium hydroxide solution obtained from water leaching is used to neutralize the calcium bicarbonate solution obtained from the carbon fixation reaction of excess carbon dioxide, thereby obtaining a high-value-added light calcium carbonate product and achieving open-loop calcium carbonate production. This significantly reduces the calcium ion concentration in the ammonium salt solution, improves the leaching efficiency of calcium and magnesium during subsequent recycling of the ammonium salt solution, and thus improves the recycling rate of the ammonium salt solution. More specifically, this invention first involves water leaching of the smelting slag. The water leaching process mainly involves leaching the active calcium oxide from the smelting slag to obtain a calcium hydroxide solution, which plays an important role in the entire leaching process of the smelting slag. On the one hand, water leaching can obtain a high-purity calcium hydroxide solution, which is an important raw material for subsequent conversion of calcium bicarbonate solution and regeneration of ammonium salt solution. On the other hand, removing the active alkali from the smelting slag can reduce the alkalinity of the smelting slag, which is beneficial to improving the leaching efficiency and leaching selectivity of calcium and magnesium in the smelting slag by the subsequent ammonium salt solution in the multi-stage countercurrent leaching process. The water-leached residue mainly contains bound calcium and magnesium. After multi-stage countercurrent leaching with ammonium salt solution, calcium ions are mainly enriched in the first-stage leachate to obtain a calcium-rich solution. The calcium-rich leachate is then used to absorb carbon dioxide flue gas for carbon fixation. The key to the carbon fixation process is to control the absorption of excess carbon dioxide by the calcium-rich leachate. Excess carbon dioxide causes all calcium ions to be converted into calcium bicarbonate instead of precipitating as calcium carbonate. On this basis, water leachate is added, and the neutralization reaction between calcium bicarbonate and calcium hydroxide completely converts it into calcium carbonate precipitate. The calcium carbonate is then passed through an open circuit, and the remaining liquid is the ammonium salt solution. The ammonium salt solution is directly recycled to the multi-stage countercurrent leaching process, which greatly reduces the consumption of leaching agent.

[0011] In the multi-stage countercurrent leaching process of this invention, a single ammonium salt solution is used as the leaching agent, mainly for leaching bound calcium and magnesium in smelting slag. Under the premise of removing active alkali from smelting slag by water leaching, the ammonium salt solution can ionize to generate ammonium ions and acid ions, and further hydrolyze to form acid molecules and ammonium monohydrate molecules. The acid molecules and the released H⁺ can diffuse to the surface of smelting slag particles, selectively destroying the Ca–Si bonds in bound calcium silicate, thereby achieving effective release of calcium ions. At the same time, the OH⁻ generated by the dissociation of ammonium monohydrate molecules keeps the leachate under alkaline conditions, significantly inhibiting the dissolution of impurity elements such as iron and aluminum, and improving the selectivity of leaching.

[0012] The key to achieving ammonium salt solution recycling in this invention lies in two aspects: First, during the carbon fixation reaction, excess carbon dioxide flue gas is used to fully convert Ca²⁺ in the calcium-rich leachate into Ca(HCO3)2. Second, the calcium hydroxide solution obtained from smelting slag water leaching is used for pH control of the calcium bicarbonate solution, thereby achieving the precipitation conversion of Ca(HCO3)2 to CaCO3. This ensures that calcium ions are completely removed from the ammonium salt solution, effectively preventing the residual Ca²⁺ in the ammonium salt solution from inhibiting the leaching of calcium-containing mineral phases in subsequent recycling processes due to the common ion effect of calcium ions.

[0013] As a preferred embodiment, the smelting slag includes at least one of blast furnace slag, converter slag, electric furnace slag, and ladle refining slag. As a more preferred embodiment, the main components and their mass content in the smelting slag are: Fe₂O₃ 15-25%, CaO 30-60%, SiO₂ 15-20%, MgO 5-10%, and Al₂O₃ 1-3%. Preferably, the smelting slag is rich in alkali metal components such as calcium and magnesium. Preferably, the particle size of the smelting slag is less than 74 μm; smaller particle size is more beneficial to the leaching process.

[0014] As a preferred embodiment, the water leaching conditions are: a solid-liquid ratio of 1 kg: 1~40 L, a temperature of 40~80℃, a time of 30~120 min, and a stirring rate of 100~1200 r / min. Under these preferred water leaching conditions, the active alkaline components in the smelting slag can be efficiently leached. The active alkaline components are mainly calcium oxide, which is beneficial to improving the selectivity and leaching efficiency of the subsequent ammonium salt solution leaching.

[0015] As a preferred embodiment, the ammonium salt solution includes at least one selected from ammonium nitrate solution, ammonium chloride solution, and ammonium acetate solution. As a more preferred embodiment, the concentration of the ammonium salt solution is 0.5~5.0 mol / L. Too low a concentration of the ammonium salt solution will reduce the leaching efficiency of bound calcium and magnesium, while too high a concentration will reduce its leaching selectivity. The ammonium salt solution is further preferably an ammonium acetate solution. The concentration of the ammonium salt solution is further preferably 2.0~4.0 mol / L.

[0016] As a preferred embodiment, the conditions for the multi-stage countercurrent leaching are: 3 or more leaching stages, a solid-liquid ratio of 1 kg: 1~40 L, a temperature of 40~80℃, a time of 30~120 min, and a stirring rate of 100~1200 r / min. The number of stages in the multi-stage countercurrent leaching directly affects the contact time and reaction process between the smelting slag and the ammonium salt solution. Appropriately increasing the number of leaching stages can enhance the interaction between the smelting slag and the leaching medium and increase the leaching rate of calcium-based components. However, excessively high stages will prolong the reaction time and affect the leaching efficiency per unit time. When the number of stages in the multi-stage countercurrent leaching is set to 3, efficient and selective dissolution of calcium-based components can be achieved. Therefore, the preferred number of stages in the multi-stage countercurrent leaching is 3. This invention, by adopting a multi-stage countercurrent leaching method, progressively increases the concentration gradient of the ammonium salt solution and the degree of reaction with the slag, thereby improving leaching efficiency and effectively enriching calcium ions in the leachate, providing an ideal calcium source concentration basis for subsequent carbon fixation reactions.

[0017] As a preferred embodiment, the carbon fixation reaction conditions are: a carbon dioxide volume percentage of 1-30% in the flue gas, a gas flow rate of 40-100 L / min, a reaction temperature of 20-80℃, a reaction time of 60-180 min, and a stirring rate of 100-1200 r / min. The calcium-rich leachate obtained through multi-stage countercurrent leaching in this invention has a pH value in the moderately alkaline range of 9.0-11.5, which can efficiently absorb CO2 and generate carbonic acid, which then ionizes into bicarbonate ions, combining with Ca²⁺ in the solution to form calcium bicarbonate. Carbon dioxide flue gas has a wide range of sources, including sintering flue gas, power plant flue gas, and waste incineration flue gas. Under optimized carbon fixation reaction conditions, the carbon dioxide fixation efficiency can be improved. The conditions of the carbon fixation reaction need to be coordinated and controlled; for example, the concentration of carbon dioxide in the flue gas, the gas flow rate, and the reaction temperature all affect the carbon fixation efficiency.

[0018] The "excess carbon dioxide flue gas" involved in this invention is measured by the theoretical molar amount of carbon dioxide required for calcium ions in the calcium-rich leachate to react with carbon dioxide and convert into calcium bicarbonate. "Excess carbon dioxide flue gas" refers to the amount of carbon dioxide flue gas introduced exceeding the theoretical molar amount. According to common knowledge in this technical field, once the amount of carbon dioxide flue gas introduced reaches the theoretical value, all calcium ions in the calcium-rich leachate are converted into calcium bicarbonate and no longer absorb carbon dioxide, at which point the introduction of carbon dioxide flue gas can be stopped.

[0019] The aqueous extract of this invention has a pH value of 11.8-12.5, exhibiting moderate alkalinity. This alkalinity can be effectively used to control the pH of the calcium bicarbonate solution formed during carbon fixation reactions, providing a favorable chemical environment for the precipitation and transformation of calcium bicarbonate. Therefore, this invention eliminates the need for any external alkaline regulators, relying on the system's own alkaline liquid to achieve pH adjustment, thus reducing the consumption of chemical reagents.

[0020] The leaching residue produced in the final stage of the multi-stage countercurrent leaching process of this invention can be used as a raw material for ironmaking or building materials. More specifically, after magnetic separation, the leaching residue yields iron-rich concentrate and non-magnetic tailings. The iron-rich concentrate can be used as a raw material for ironmaking, and the non-magnetic tailings can be used as a raw material for building materials.

[0021] The lightweight calcium carbonate obtained by this invention has a low impurity content, meets general industrial standards, and can be used as a filler material for rubber and plastics.

[0022] The precipitate obtained by the neutralization and precipitation reaction of this invention has an ammonium salt concentration of 0.3~4.8 mol / L, a pH of 8.0~8.5, and low calcium ion residue, making it suitable for multi-stage countercurrent leaching. Furthermore, the ammonium salt solution does not exhibit significant activity decay or impurity enrichment after multiple rounds of countercurrent leaching-carbon fixation cycles, demonstrating good chemical stability and system purity, and possessing the potential for long-term recycling to meet the requirements of large-scale industrial applications.

[0023] Compared with existing technologies, the beneficial technical effects of the present invention are as follows:

[0024] (1) This invention achieves efficient and selective leaching of calcium and magnesium components in smelting slag by designing a process that combines water leaching and multi-stage countercurrent leaching using a single ammonium salt solution as the leaching agent, while inhibiting the leaching of impurity elements such as iron and aluminum, thus laying a good foundation for the subsequent synthesis of high-purity calcium carbonate products.

[0025] (2) The present invention uses the calcium hydroxide solution obtained by water leaching to neutralize the calcium bicarbonate solution obtained by carbon fixation reaction. This can completely open up the calcium ions in the solution system in the form of calcium carbonate product, effectively remove residual calcium ions in the solution, avoid the interference of calcium ions in the regenerated ammonium salt solution on the subsequent leaching process due to their common ion effect, and ensure the continuous driving force of the leaching reaction.

[0026] (3) The ammonium salt solution regenerated by the neutralization reaction of the present invention is mainly composed of ammonium ions and acid radical ions, which have good chemical stability and system purity. It can be directly reused in the countercurrent leaching stage as an ammonium salt solution leaching agent for recycling. After multiple cycles, it still maintains a suitable concentration and pH, realizing a stable closed-loop circulation system without significant activity decay or impurity accumulation, and significantly reducing the consumption of chemical reagents.

[0027] (4) This invention realizes the resource recycling of smelting slag. The final leaching residue can be used as ironmaking raw material and building material after magnetic separation. The generated solid product is high-value-added light calcium carbonate. It realizes the gradient separation of each component in smelting slag and the resource utilization of all components. The process as a whole is both environmentally friendly and economically feasible.

[0028] In summary, the present invention provides a method for efficient and low-consumption leaching of smelting slag based on ammonium salt leaching agent recycling, which breaks through the limitations of traditional indirect carbon fixation processes for smelting slag in terms of leaching selectivity, resource utilization, and process economy. It provides an efficient, green, and low-cost technical solution for the treatment of calcium-based smelting solid waste and carbon emission reduction, and offers a new approach for the green and low-carbon transformation of the steel industry. Attached Figure Description

[0029] Figure 1 This is a flow chart of the smelting slag leaching process in Embodiment 1 of the present invention. Detailed Implementation

[0030] The following detailed description, in conjunction with the accompanying drawings, clearly and completely illustrates the present invention. Obviously, the described embodiments are merely a part of the embodiments exemplified by the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The main components and mass content of the converter steel slag used in the following examples are: Fe2O3 20%, CaO 45~60%, SiO2 18%, MgO 6%, Al2O3 2%.

[0032] Comparative Example 1

[0033] The only difference from Example 1 is that conventional single-stage leaching is used instead of three-stage countercurrent leaching.

[0034] The results show that:

[0035] The calcium leaching rate in the selected converter steel slag was 56.3%, the calcium leaching selectivity was 97.5%, and the pH value of the resulting calcium-rich leachate was 8.6.

[0036] The final light calcium carbonate had an impurity content lower than the general industrial standard (GB 1886.214–2016). The calcium leaching rate of the ammonium salt solution during the cycle was 51.3–55.7%, decreasing step by step; the calcium leaching selectivity was 97.9–98.7%, increasing step by step, with a final cycle count of 9 times.

[0037] Comparative Example 2

[0038] The only difference from Example 1 is that the steel plant converter slag is directly subjected to a three-stage countercurrent leaching process instead of a water leaching process. Simultaneously, the calcium bicarbonate solution is neutralized and precipitated using a calcium hydroxide solution.

[0039] The results show that:

[0040] The calcium leaching rate in the selected converter steel slag was 75.3%, the calcium leaching selectivity was 94.2%, and the pH value of the resulting calcium-rich leachate was 10.8.

[0041] The final light calcium carbonate had an impurity content lower than the general industrial standard (GB 1886.214–2016), meeting the general industrial standard. The calcium leaching rate of the obtained ammonium salt solution during the cycle was 68.8–73.6%, decreasing step by step; the calcium leaching selectivity was 95.6–96.9%, increasing step by step, with a final cycle count of 7 times.

[0042] Example 1

[0043] 25 kg of converter slag from a steel plant was passed through a 200-mesh sieve, and the total calcium content was 60 wt%. Water leaching was performed at a reaction temperature of 60℃, a leaching time of 60 min, a solid-liquid ratio of 1:20 kg / L, and a stirring speed of 500 r / min. The resulting aqueous leachate had a pH of 12.3. Using a 3.5 mol / L ammonium acetate solution, water leaching of the slag was performed in a three-stage countercurrent process at a reaction temperature of 60℃, a leaching time of 30 min, a solid-liquid ratio of 1:20 kg / L, and a mechanical stirring intensity of 500 r / min (see the three-stage leaching process). Figure 1 Leachate I (calcium-rich leachate) showed a calcium leaching rate of 78.4% and a leaching selectivity of 97.7% in the selected converter slag, with a pH of 11.5. The reaction was carried out at 25℃, with a carbon fixation time of 120 min and a stirring rate of 500 r / min, while a gas containing 25% carbon dioxide was introduced at a rate of 60 L / min. After the reaction, the calcium bicarbonate solution and the aqueous leachate were mixed at a volume ratio of 10:1 for thorough precipitation. After liquid-solid separation, the final light calcium carbonate solution had an impurity content lower than the general industrial standard (GB1886.214–2016), meeting the general industrial standard. During the circulation process, the calcium leaching rate of the resulting ammonium salt solution decreased progressively from 69.4% to 77.6%, while the calcium leaching selectivity increased progressively from 98.1% to 99.2%, with a final circulation count of 12 times.

[0044] Ammonium chloride or ammonium nitrate solutions of the same concentration were used instead of ammonium acetate solution. Other operating steps and conditions were the same as in Example 1. The comparison of leaching cycle effects is shown in Table 1.

[0045]

[0046] Example 2

[0047] 25 kg of converter slag from a steel plant was passed through a 200-mesh sieve, and the total calcium content was 45 wt%. Water leaching was performed at a reaction temperature of 80℃, a leaching time of 120 min, a solid-liquid ratio of 1:40 kg / L, and a stirring speed of 1200 r / min. The pH of the resulting aqueous leachate was 12.5. Using a 5.0 mol / L ammonium acetate solution, under the conditions of a reaction temperature of 80℃, a leaching time of 60 min, a solid-liquid ratio of 1:40 kg / L, and a stirring speed of 1200 r / min, a three-stage countercurrent leaching process was conducted on the water-leached residue (see the three-stage leaching process diagram). Figure 1 Leachate I (calcium-rich leachate) showed a calcium leaching rate of 79.2% and a calcium leaching selectivity of 96.4% in the selected converter slag, with a pH of 10.6. The reaction was carried out at a temperature of 20℃, a carbon fixation time of 180 min, and a stirring rate of 1200 r / min, with a gas flow rate of 80 L / min containing 15% carbon dioxide. After the reaction, the calcium bicarbonate solution and the aqueous leachate were mixed at a volume ratio of 8:1 for thorough precipitation. After liquid-solid separation, the final light calcium carbonate solution had an impurity content lower than the general industrial standard (GB 1886.214–2016), meeting the general industrial standard. During the circulation process, the calcium leaching rate of the resulting ammonium salt solution decreased progressively from 72.1% to 78.4%, while the calcium leaching selectivity increased progressively from 96.9% to 98.4%, with a final circulation count of 10 times.

[0048] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and modifications obtained without departing from the inventive concept should also be considered within the scope of protection of the present invention.

Claims

1. A highly efficient and low-consumption leaching method for smelting slag based on ammonium salt leaching agent circulation, characterized in that: Includes the following steps: (1) The smelting slag is leached with water to obtain a water-leached solution and a water-leached slag; (2) The water-leached residue is subjected to multi-stage countercurrent leaching with ammonium salt solution to obtain calcium-rich leachate; (3) The calcium-rich leachate is subjected to a carbon fixation reaction with excess carbon dioxide flue gas to obtain a calcium bicarbonate solution; (4) The calcium bicarbonate solution and the water leaching solution are subjected to a neutralization and precipitation reaction, and the liquid and solid are separated. The solid product is light calcium carbonate and the liquid product is an ammonium salt solution. The ammonium salt solution is recycled for multi-stage countercurrent leaching.

2. The efficient and low-consumption leaching method for smelting slag based on ammonium salt leaching agent circulation according to claim 1, characterized in that: The smelting slag includes at least one of blast furnace slag, converter steel slag, electric furnace slag, and ladle refining slag.

3. A high-efficiency and low-consumption leaching method for smelting slag based on ammonium salt leaching agent circulation according to claim 1 or 2, characterized in that: The main components and their mass content in the smelting slag are: Fe2O3 15~25%, CaO 30~60%, SiO2 15~20%, MgO 5~10%, Al2O3 1~3%.

4. The efficient and low-consumption leaching method for smelting slag based on ammonium salt leaching agent circulation according to claim 1, characterized in that: The conditions for water leaching are: a solid-liquid ratio of 1 kg: 1~40 L, a temperature of 40~80℃, a time of 30~120 min, and a stirring rate of 100~1200 r / min.

5. The efficient and low-consumption leaching method for smelting slag based on ammonium salt leaching agent circulation according to claim 1, characterized in that: The ammonium salt solution includes at least one of ammonium nitrate solution, ammonium chloride solution, and ammonium acetate solution.

6. A high-efficiency and low-consumption leaching method for smelting slag based on ammonium salt leaching agent circulation according to claim 1 or 5, characterized in that: The concentration of the ammonium salt solution is 0.5~5.0 mol / L.

7. The efficient and low-consumption leaching method for smelting slag based on ammonium salt leaching agent circulation according to claim 1, characterized in that: The conditions for the multi-stage countercurrent leaching are as follows: the number of leaching stages is 3 or more, the solid-liquid ratio is 1kg:1~40L, the temperature is 40~80℃, the time is 30~120min, and the stirring rate is 100~1200r / min.

8. The efficient and low-consumption leaching method for smelting slag based on ammonium salt leaching agent circulation according to claim 1, characterized in that: The conditions for the carbon fixation reaction are as follows: the volume percentage of carbon dioxide in the carbon dioxide flue gas is 1-30%, the gas flow rate is 40-100 L / min, the reaction temperature is 20-80℃, the reaction time is 60-180 min, and the stirring rate is 100-1200 r / min.

9. The efficient and low-consumption leaching method for smelting slag based on ammonium salt leaching agent circulation according to claim 1, characterized in that: The calcium bicarbonate solution and the aqueous extract are mixed at a volume ratio of 5-10:1 to carry out a neutralization and precipitation reaction.

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