Novel method for co-extracting lithium, rubidium and cesium by roasting lepidolite through organic sodium salt reinforced sulfate

Abstract

The invention discloses a novel method for co-extracting lithium, rubidium and cesium by roasting lepidolite through organic sodium salt reinforced sulfate, and belongs to the technical field of valuable metal extraction of ores. Thermodynamic analysis is carried out on isomorphic substitution reaction of sodium ions and calcium ions in sulfate, and the sulfate and sodium carboxymethyl cellulose are adopted as co-roasting agents to carry out grinding, roasting and water leaching treatment on lepidolite, so that efficient leaching of lithium, rubidium and cesium is realized. According to the method, due to the introduction of sodium carboxymethyl cellulose, the remarkable effects are achieved: the use amount of a sulfate additive is reduced by 10%-25%, the leaching rates of lithium, rubidium and cesium are improved by 5%-10%, and the leaching residue amount is also reduced by 20%-30%. According to the method, on the basis of a traditional sulfate roasting lithium extraction process, the organic salt sodium carboxymethyl cellulose is creatively selected as a roasting additive, and a new thought and a technical path are provided for subsequent related experimental research.

Description

Technical Field

[0001] This invention belongs to the field of valuable metal extraction technology from ores, specifically relating to a novel method for co-extracting lithium, rubidium, and cesium from lithium mica using organosodium salt-enhanced sulfate roasting. Background Technology

[0002] Lepidolite, as an important lithium resource, has seen its strategic value increasingly prominent with the booming development of related industries. Lithium, with its excellent electrochemical properties (such as high electrochemical activity and high redox potential) and physical characteristics, plays an indispensable role in many key fields, with applications spanning ceramics, specialty glasses, lubricants, and aerospace, especially holding a core position in portable electronic devices and electric vehicle power batteries. In recent years, the rise of the new energy industry has significantly enhanced its importance as a lithium extraction raw material. Furthermore, lepidolite often contains rubidium and cesium metals, which possess excellent photoelectric properties. These two metals are key materials for the development of strategic industries such as aerospace, defense, and new energy. However, existing research mainly focuses on lithium extraction from lepidolite, with relatively little research on the comprehensive recovery and utilization of its associated high-value rubidium and cesium resources. Therefore, developing methods to extract valuable metals such as rubidium and cesium from lepidolite simultaneously with lithium extraction is of great significance to my country's national development.

[0003] Current lepidolite metallurgy mainly focuses on lithium extraction, with limited reports on the extraction of valuable components such as rubidium and cesium. Currently, the technology for extracting lithium, rubidium, and cesium from lepidolite primarily relies on pyrometallurgy. The principle of this process involves mixing and roasting lepidolite with roasting additives at high temperatures, causing lithium to separate from the mineral structure and transform into soluble lithium salts. Subsequently, the roasted product is leached in water to dissolve the soluble lithium salts; the leachate is then treated with a carbonate precipitant to convert the lithium into insoluble lithium carbonate, which is then concentrated by evaporation to crystallize and precipitate. Mainstream pyrometallurgical lithium extraction technologies often use sodium or calcium salts as roasting additives. The mechanism utilizes metal ions (such as Na+) in the additives. + or Ca 2+ Lithium leaching involves ligand exchange with lithium ions in minerals to form water-soluble lithium salts, facilitating subsequent separation and precipitation. However, this technology suffers from drawbacks such as difficulty in extracting valuable metals (especially rubidium and cesium), high additive consumption, and high leaching residue yield. The core root of these problems lies in lepidolite (typically with the chemical formula K(Li₂Al)Si₄O₂). 10 F2 or K(Li) 1.5 Al 1.5 (AlSi3)O 10 The crystal structure of F2 has a strong binding effect on lithium ions, and the isomorphic effect leads to insufficient driving force for the exchange between lithium ions and sodium ions (or other additive ions). Summary of the Invention

[0004] The technical problem to be solved by this invention is how to address the difficulties in extracting valuable metals, high energy consumption, large amount of additives, and high yield of leaching residue in traditional inorganic salt roasting extraction methods.

[0005] The present invention solves the above-mentioned technical problems through the following technical means: The first aspect of this invention provides a method for co-extracting lithium, rubidium, and cesium from lepidolite using organosodium salt-enhanced sulfate roasting, comprising the following steps: Lithium mica is mixed with inorganic and organic salts and calcined to obtain calcined clinker. The calcined clinker is then ground, soaked in water, and filtered to obtain leachate.

[0006] Preferably, the lepidolite contains 0.5-5% Li₂O, 0.05-2% Rb₂O, and 0.05-2% Cs₂O.

[0007] Preferably, the inorganic salt is one or more of sodium sulfate, calcium sulfate, potassium sulfate, magnesium sulfate, ferrous sulfate, sodium bisulfate, aluminum sulfate, sodium carbonate, calcium carbonate, magnesium carbonate, sodium bicarbonate, potassium carbonate, ammonium carbonate, sodium chloride, calcium chloride, potassium chloride, and ferrous sulfide.

[0008] Preferably, the organic salt is one or more of sodium gluconate, sodium salicylate, sodium carboxymethyl cellulose, sodium oxalate, sodium citrate, potassium citrate, sodium acetate, sodium propionate, sodium benzenesulfonate, sodium thiosulfate, ammonium sulfate, and ammonium chloride.

[0009] Preferably, the mass ratio of the lepidolite, inorganic salt and organic salt is 1:(0.5~5):(0.5~1.5); more preferably, the inorganic salt is sodium salt and calcium salt; the mass ratio of sodium salt to calcium salt in the inorganic salt is (1~5):~(1~5).

[0010] Preferably, the calcination conditions are: a temperature of 700~1000℃ and a time of 30~180min.

[0011] Preferably, the liquid-solid mass ratio of water to roasted clinker during the water immersion process is (0.5~20):1.

[0012] Preferably, the water immersion conditions are: immersion temperature of 20~100℃, immersion time of 10~120 min, and rotation speed of 300~700 rpm.

[0013] Mechanism: This invention is based on the principle of organic carbothermal reduction. It introduces organic salts into the traditional inorganic salt additive roasting process. During pyrolysis, the organic salts generate carbonaceous reducing agents and act as electron donors, fully utilizing the carbothermal reduction effect. This process effectively breaks down the silicon-oxygen bonds (Si-O) and aluminum-oxygen bonds (Al-O) in the lithium mica lattice, further deconstructing the mineral lattice, thereby significantly improving the release efficiency and leaching rate of lithium, rubidium, and cesium from the lattice, while simultaneously reducing the roasting temperature and the amount of lithium leaching residue and salt required.

[0014] A second aspect of this invention provides a method for preparing high-purity lithium carbonate from the leachate obtained by the above method, comprising the following steps: (1) Add carbonate to the leachate obtained by the above method to precipitate lithium, filter, wash and dry to obtain lithium carbonate and lithium precipitation mother liquor; (2) The lithium mother liquor was extracted by an organic solution composed of an extractant and a diluent to separate rubidium and cesium solutions. The pH was adjusted with an alkaline solution, and the solution was washed, back-extracted, evaporated and crystallized with hydrochloric acid to prepare rubidium salt and cesium salt.

[0015] Preferably, in step (1), the carbonate is one or more of sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, and calcium bicarbonate.

[0016] Preferably, in step (1), the K in the lithium precipitation mother liquor + Concentrations of 0.1–60 g / L, Rb + Concentrations of 0.5~20 g / L, Cs + The concentration is 0.5~20 g / L.

[0017] Preferably, in step (2), the extractant is one or more of 4-tert-butyl-2-(α-methylbenzyl)phenol, 4-tert-pentyl-2-(α-methylbenzyl)phenol, and 4-tert-heptyl-2-(α-methylbenzyl)phenol.

[0018] Preferably, in step (2), the diluent is one or more of cyclohexane, n-hexane, n-heptane, n-octane, n-nonane, dodecane, benzene, toluene, xylene, n-butanol, n-hexanol, n-octanol, n-nonanol, and n-decanol.

[0019] Preferably, in step (2), the alkaline solution is one or more of sodium hydroxide, potassium hydroxide, and ammonia.

[0020] Preferably, in step (2), the pH is 11 to 13.

[0021] Preferably, in step (2), the extraction is a multi-stage countercurrent extraction, with 2 to 15 stages of countercurrent extraction, and the volume ratio of the organic phase to the aqueous phase in the countercurrent extraction is (1 to 5): 1.

[0022] The beneficial effects of this invention are as follows: (1) The present invention introduces organic salt and inorganic salt to synergistically enhance the extraction of lithium, rubidium and cesium from lepidolite. After the introduction of organic salt, the Gibbs free energy of the reaction between lepidolite and inorganic salt decreases and the reaction trend increases. During the roasting process, the metal ions in the inorganic salt are substituted by isomorphic substitution, making it easier for lithium, rubidium and cesium to leach out. In the preferred embodiment, the leaching rate of lithium can be as high as 100%, while the leaching rates of rubidium and cesium are also 95%.

[0023] (2) Organic salts act as a binder during the roasting process, allowing lepidolite to mix and come into contact with inorganic salts more fully. Thermodynamic analysis and experimental verification show that the roasting temperature is reduced by more than 50°C, which significantly saves energy.

[0024] (3) This scheme introduces organic salts, reduces the amount of inorganic salt additives by 10-20%, and reduces the amount of leaching residue by 20-30%.

[0025] (4) This invention utilizes carbonates to prepare high-purity lithium carbonate products, and uses a mixed phenol extraction system to selectively extract and separate rubidium and cesium from the leachate to prepare rubidium chloride and cesium chloride products, thereby realizing the high-value utilization of lithium mica resources.

[0026] Of course, implementing any product or method of the present invention does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0027] Figure 1 This is the effect of the ratio of lepidolite to inorganic salts on the leaching rates of lithium, rubidium, and cesium in lepidolite ore in Example 2; Figure 2 This is the effect of the ratio of sodium salt to calcium salt in inorganic salts on the leaching rates of lithium, rubidium, and cesium in lepidolite ore, as shown in Example 3. Figure 3 This describes the effect of roasting time on the leaching rates of lithium, rubidium, and cesium in lepidolite ore, as shown in Example 4. Figure 4 XRD patterns of roasted clinker from lepidolite ore at different roasting temperatures in Example 5; Figure 5 This describes the effect of roasting temperature on the leaching rates of lithium, rubidium, and cesium in lepidolite ore, as shown in Example 5. Figure 6 This describes the effect of roasting temperature on the leaching rates of lithium, rubidium, and cesium in lepidolite when Na2SO4 and CaSO4 are used as roasting additives in Comparative Example 1. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. 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. Unless otherwise defined, the technical terms used below have the same meaning as understood by those skilled in the art.

[0029] Unless otherwise specified, the test materials and reagents used in the following examples are commercially available or prepared by known methods.

[0030] Unless otherwise specified, all techniques or conditions described in the embodiments can be performed in accordance with the techniques or conditions described in the literature in this field or in the product manual. Unless otherwise specified, the quantitative experiments in the following embodiments are all repeated three times or more, and the results are averaged.

[0031] Example 1: Sodium sulfate and calcium sulfate were selected as inorganic salts, and sodium carboxymethyl cellulose (CMC-Na) was selected as organic salt to synergistically enhance the sulfate roasting of lepidolite.

[0032] S1. Lithium mica ore is obtained from Jiangxi Province. Lithium mica ore is mixed with sodium sulfate, calcium sulfate and sodium carboxymethyl cellulose (CMC-Na) in a mass ratio of 5:0.9:2.6:0.85. The mixture is placed in a muffle furnace and roasted at 950℃ for 120 minutes. After the reaction is complete, the roasted clinker is obtained. S2. The roasted clinker is cooled to room temperature, ground, and leached with water at a liquid-to-solid mass ratio of 10:1. The leaching temperature is 20℃ and the leaching time is 60 minutes. After filtration, a leaching solution and leaching residue containing lithium, rubidium, and cesium are obtained. The leaching rates of lithium, rubidium, and cesium are 99.84%, 95.16%, and 95.62%, respectively.

[0033] Example 2: Effect of the ratio of lepidolite to inorganic salts on the leaching rates of lithium, rubidium, and cesium in lepidolite Similar to Example 1, lepidolite was mixed with Na₂SO₄, CaSO₄, and sodium carboxymethyl cellulose (CMC-Na) and placed in a muffle furnace. The ratios of lepidolite, Na₂SO₄, CaSO₄, and sodium carboxymethyl cellulose (CMC-Na) were 5:2.5:2.5:1 (1:1), 5:2.25:2.25:0.95 (1:0.9), 5:2:2:0.9 (1:0.8), 5:1.75:1.75:0.85 (1:0.7), 5:1.5:1.5:0.8 (1:0.6), 5:1.25:1.25:0.75 (1:0.5), and 5:1:1:0.7 (1:0.4). The roasting temperature was 950°C, and the roasting time was 120 minutes. After calcination and cooling to room temperature, the mixture was ground and leached and filtered according to the conditions of Example 1 to obtain a solution containing lithium, rubidium, and cesium. The effect of the ratio of lepidolite to inorganic salt on the leaching rates of lithium, rubidium, and cesium is as follows: Figure 1 As shown in the figure, the results indicate that as the ratio of lepidolite to inorganic salts increases, the leaching rates of lithium, rubidium, and cesium show a trend of first increasing and then leveling off. From the perspective of energy conservation, consumption reduction, and reduction of lithium slag, the ratio of lepidolite to inorganic salts of 5:1.75:1.75:0.85 (1:0.7) has the best overall effect.

[0034] Example 3: The effect of the ratio of sodium salts to calcium salts in inorganic salts on the leaching rates of lithium, rubidium, and cesium in lepidolite. Similar to Example 1, lepidolite was mixed with Na₂SO₄, CaSO₄, and sodium carboxymethyl cellulose (CMC-Na) and placed in a muffle furnace. The ratios of lepidolite, Na₂SO₄, CaSO₄, and sodium carboxymethyl cellulose (CMC-Na) were 5:2.8:0.7:0.85 (4:1), 5:2.8:0.8:0.85 (3.5:1), 5:2.7:0.9:0.85 (3:1), 5:2.5:1:0.85 (2.5:1), and 5:2.4:1.2:0.85 (4:1). The following ratios were used: 2:1), 5:2.1:1.4:0.85 (1.5:1), 5:1.75:1.75:0.85 (1:1), 5:1.4:2.1:0.85 (1:1.5), 5:1.2:2.4:0.85 (1:2), 5:1:2.5:0.85 (1:2.5), 5:0.9:2.7:0.85 (1:3), 5:0.8:2.8:0.85 (1:3.5), and 5:0.7:2.8:0.85 (1:4). The calcination temperature was 950℃, and the calcination time was 120 min. After calcination, the solution was cooled to room temperature and ground. It was then leached and filtered according to the conditions of Example 1 to obtain a solution containing lithium, rubidium, and cesium. The effect of the ratio of sodium salt to calcium salt in the inorganic salt on the leaching rate of lithium, rubidium, and cesium is as follows: Figure 2As shown in the figure, the results indicate that as the ratio of sodium salt to calcium salt in inorganic salts increases, the leaching rates of lithium, rubidium, and cesium show a trend of first increasing and then decreasing. From the perspective of energy saving, consumption reduction, and reduction of lithium slag, the ratio of sodium salt to calcium salt in inorganic salts of 5:0.9:2.7:0.85 (1:3) has the best overall effect.

[0035] Example 4: Effect of roasting time on the leaching rates of lithium, rubidium, and cesium in lepidolite ore The lepidolite was prepared in the same manner as in Example 1. Lepidolite was mixed with Na₂SO₄, CaSO₄, and sodium carboxymethyl cellulose (CMC-Na) and placed in a muffle furnace. The mass ratio of lepidolite, Na₂SO₄, CaSO₄, and CMC-Na was 5:0.9:2.6:0.85. The roasting temperature was 950℃, and the roasting times were 10, 20, 30, 40, 50, 60, 90, 120, and 180 min, respectively. After roasting, the mixture was cooled to room temperature and ground. Leaching and filtration were performed according to the conditions in Example 1 to obtain a solution containing lithium, rubidium, and cesium. The effect of roasting time on the leaching rates of lithium, rubidium, and cesium is as follows. Figure 3 As shown in the figure, the leaching rates of lithium, rubidium, and cesium increase with increasing roasting time. When the roasting time exceeds 60 minutes, the leaching rates are all above 90%.

[0036] Example 5: Effect of roasting temperature on the leaching rates of lithium, rubidium, and cesium in lepidolite ore The lepidolite was prepared in the same manner as in Example 1. Lepidolite was mixed with Na₂SO₄, CaSO₄, and sodium carboxymethyl cellulose (CMC-Na) and placed in a muffle furnace. The mass ratio of lepidolite, Na₂SO₄, CaSO₄, and CMC-Na was 5:0.9:2.6:0.85. The calcination time was 120 min, and the calcination temperatures were 700, 750, 800, 850, 900, 950, and 1000 °C. After calcination, the mixture was cooled to room temperature and ground. Leaching and filtration were performed according to the conditions of Example 1 to obtain a solution containing lithium, rubidium, and cesium.

[0037] XRD analysis results are as follows: Figure 4 As shown, with increasing calcination temperature, the structure of lepidolite is destroyed, generating new sodalite, calcium sulfate, and soluble alkali metal salts. This indicates that Na₂SO₄, CaSO₄, and sodium carboxymethyl cellulose can react with lepidolite, promoting the dissolution of lithium, rubidium, and cesium ions from the lepidolite lattice.

[0038] The effect of calcination temperature on the leaching rates of lithium, rubidium, and cesium is as follows: Figure 5As shown in the figure, the leaching rates of lithium, rubidium, and cesium gradually increase with the increase of calcination temperature. When the calcination temperature exceeds 950℃, the leaching rates of lithium, rubidium, and cesium are all greater than 90%.

[0039] Example 6: The amount of lepidolite used in Example 1 was increased to 1000 tons, and the amounts of Na2SO4, CaSO4 and sodium carboxymethyl cellulose (CMC-Na) were increased in the same proportion. Other conditions and steps were the same as in Example 1. The final leaching rates of lithium, rubidium and cesium were still over 90%.

[0040] Comparative Example 1: Na₂SO₄ and CaSO₄ were used as roasting additives in the roasting of lepidolite. The effect of roasting temperature on the leaching rates of lithium, rubidium, and cesium in lepidolite was investigated. The lepidolite used was the same as in Example 1, with Na₂SO₄ and CaSO₄ as the roasting additives. The mass ratio of lepidolite to Na₂SO₄ and CaSO₄ was 5:1.75:1.75. The roasting temperatures were 700, 750, 800, 850, 900, 950, and 1000℃. Other conditions and steps were the same as in Example 1. The results are as follows: Figure 6 As shown in the figure, the leaching rates of lithium, rubidium, and cesium all increase to varying degrees with increasing calcination temperature. The highest leaching rates are achieved at a calcination temperature of 1000℃, with rates of 86.52%, 81.35%, and 80.98%, respectively. Although a relatively high leaching rate can be achieved under these conditions, the calcination temperature and energy consumption are also high.

[0041] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for co-extracting lithium, rubidium, and cesium from lepidolite using organosodium salt-enhanced sulfate roasting, characterized in that, Includes the following steps: Lithium mica is mixed with inorganic and organic salts and calcined to obtain calcined clinker. The calcined clinker is then ground, soaked in water, and filtered to obtain leachate.

2. The method according to claim 1, characterized in that, The lepidolite contains 0.5-5% Li₂O, 0.05-2% Rb₂O, and 0.05-2% Cs₂O.

3. The method according to claim 1, characterized in that, The inorganic salt is one or more of sodium sulfate, calcium sulfate, potassium sulfate, magnesium sulfate, ferrous sulfate, sodium bisulfate, aluminum sulfate, sodium carbonate, calcium carbonate, magnesium carbonate, sodium bicarbonate, potassium carbonate, ammonium carbonate, sodium chloride, calcium chloride, potassium chloride, and ferrous sulfide.

4. The method according to claim 1, characterized in that, The organic salt is one or more of the following: sodium gluconate, sodium salicylate, sodium carboxymethyl cellulose, sodium oxalate, sodium citrate, potassium citrate, sodium acetate, sodium propionate, sodium benzenesulfonate, sodium thiosulfate, ammonium sulfate, and ammonium chloride.

5. The method according to claim 1, characterized in that, The mass ratio of lepidolite, inorganic salt and organic salt is 1:(0.5~5):(0.5~1.5); more preferably, the inorganic salt is sodium salt and calcium salt; the mass ratio of sodium salt to calcium salt in the inorganic salt is (1~5):~(1~5).

6. The method according to claim 1, characterized in that, The roasting conditions are: temperature 700~1000℃, time 30~180min.

7. The method according to claim 1, characterized in that, The liquid-solid mass ratio of water to roasted clinker during the water immersion process is (0.5~20):1; the water immersion conditions are: immersion temperature of 20~100℃, immersion time of 10~120 min, and rotation speed of 300~700 rpm.

8. A method for preparing high-purity lithium carbonate from the leachate obtained by any one of claims 1-7, characterized in that, Includes the following steps: (1) Add carbonate to the leachate to precipitate lithium, filter, wash and dry to obtain lithium carbonate and lithium precipitation mother liquor; (2) The lithium mother liquor was extracted by an organic solution composed of an extractant and a diluent to separate rubidium and cesium solutions. The pH was adjusted with an alkaline solution, and the solution was washed, back-extracted, evaporated and crystallized with hydrochloric acid to prepare rubidium salt and cesium salt.

9. The preparation method according to claim 8, characterized in that, The carbonate is one or more of sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, and calcium bicarbonate; the K in the lithium precipitation mother liquor + Concentrations of 0.1–60 g / L, Rb + Concentrations of 0.5~20 g / L, Cs + The concentration is 0.5~20 g / L.

10. The preparation method according to claim 8, characterized in that, The diluent is one or more of cyclohexane, n-hexane, n-heptane, n-octane, n-nonane, dodecane, benzene, toluene, xylene, n-butanol, n-hexanol, n-octanol, n-nonanol, and n-decanol; the alkaline solution is one or more of sodium hydroxide, potassium hydroxide, and ammonia; the pH is 11-13; the extraction is multi-stage countercurrent extraction, with 2-15 stages, and the volume ratio of the organic phase to the aqueous phase in the countercurrent extraction is (1-5):1.

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