A composition and method for lithium extraction from clay-based lithium ores by alkaline leaching

Abstract

The present application relates to a kind of composition and lithium extraction method for clay type lithium ore alkali leaching, the composition for clay type lithium ore alkali leaching includes;Alkaline solution and calcium oxide;The alkaline solution includes sodium hydroxide and alumina;The caustic ratio αK of the alkaline solution is 2-6.The composition for clay type lithium ore alkali leaching provided by the present application, by the reasonable design of leaching reagent component, utilize the synergistic effect of each component in component, realize good leaching effect to clay type lithium ore, can significantly improve the leaching rate of lithium, avoid the leaching of iron and other impurities, it is favorable to the preparation of high-purity lithium carbonate.

Description

Technical Field

[0001] This invention relates to the field of lithium ore extraction technology, specifically to a composition and method for alkaline leaching of clay-type lithium ore. Background Technology

[0002] Currently, lithium carbonate is the main raw material for preparing lithium iron phosphate, the cathode material of batteries. With the increasing demand for lithium-ion batteries, the existing methods for preparing lithium carbonate mainly include the sulfuric acid method, the sulfate limestone sintering method, sodium carbonate pressure leaching, chlorination roasting of spodumene, and the treatment of lithium-containing brine using refining methods.

[0003] For example, CN107640779A discloses a process for producing lithium carbonate from spodumene, including the following steps: crushing, grinding, and sieving spodumene to 100-150 μm to obtain primary raw ore powder; placing the primary raw ore powder in a programmable box-type electric furnace for crystal transformation roasting to obtain primary roasted raw material; grinding the primary roasted raw material, acidifying the clinker, and thermally processing the acidified clinker in a fluidized bed reactor to convert it into a soluble form for lithium separation, then filtering it; transferring the filtered acidified clinker in a process pipeline in a countercurrent manner with the hot process gas removed from the fluidized bed reactor, with the hot gas directly contacting the acidified clinker; introducing carbon dioxide gas into a hydrogenation reactor to convert lithium carbonate into a lithium bicarbonate solution, reacting to obtain a carbonized liquid; heating the purified lithium bicarbonate solution to boiling, filtering, washing, and drying to obtain the desired battery-grade or high-purity lithium carbonate.

[0004] For example, CN113003590A discloses a method for producing lithium carbonate by thermal reduction of α-type spodumene as raw material. This method includes the following steps: mixing α-type spodumene concentrate powder with a reducing agent and a fluxing agent; reducing the lithium in the spodumene to metallic lithium vapor under vacuum and high temperature conditions in a reduction furnace; condensing the vapor to obtain metallic lithium and reduced spodumene slag containing metallic lithium and lithium oxide; leaching the spodumene slag containing metallic lithium and lithium oxide with water to obtain leaching residue and slurry; precipitating and filtering the leaching residue and slurry to remove calcium, and filtering the filtrate as a lithium carbonate raw material solution; further concentrating and precipitating the filtrate to produce battery-grade or high-purity lithium carbonate products. This method is a green and environmentally friendly technology, avoiding the production of hazardous chemicals such as chlorine and the use of sulfuric acid in existing technologies, resulting in a low environmental impact; no environmental pollution or solid waste discharge, good environmental benefits, and good safety.

[0005] However, existing preparation methods for preparing lithium carbonate using clay-type lithium ore still suffer from low lithium recovery rates and low product purity. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a composition and lithium extraction method for alkaline leaching of clay-type lithium ore, so as to solve the problems of low lithium recovery rate and low product purity that still exist in the scheme of preparing lithium carbonate using clay-type lithium ore.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a composition for alkaline leaching of clay-type lithium ore, the composition comprising: an alkaline solution and calcium oxide;

[0009] The alkaline solution includes sodium hydroxide and aluminum oxide;

[0010] The caustic ratio αK of the alkaline solution is 2-6.

[0011] The composition for alkaline leaching of clay-type lithium ore provided by this invention achieves good leaching effect on clay-type lithium ore by rationally designing the leaching reagent components and utilizing the synergistic effect of each component. It can significantly improve the lithium leaching rate, avoid the leaching of iron and other impurities, and is beneficial to the preparation of high-purity lithium carbonate.

[0012] In this invention, the caustic ratio αK of the alkaline solution is 2-6, for example, it can be 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8, 5, 5.2, 5.4, 5.6, 5.8 or 6, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0013] In this invention, controlling a specific caustic ratio is beneficial for achieving efficient leaching of lithium components from minerals. When the caustic ratio is too low, the leaching kinetics of lithium in the minerals cannot be achieved, resulting in low or no lithium leaching. On the other hand, when the caustic ratio is too high, impurity elements in clay-type lithium ores will leach out, resulting in high contents of impurity elements such as Al, K, and Na in the leachate, which is not conducive to the subsequent purification and upgrading of lithium leachate.

[0014] In this invention, the amount of calcium oxide added to the composition is determined based on the mass of clay-type lithium ore, such as 3%-8% of the mass of clay-type lithium ore.

[0015] In this invention, controlling the amount of calcium oxide added is beneficial for the dissolution of lithium from the minerals. When the calcium oxide content is low, the lithium silicate generated in the reaction cannot be dissolved, causing the lithium silicate to enter the slag phase and resulting in lithium loss. When the calcium oxide content is too high, it will inhibit the dissolution of lithium, which is not conducive to lithium leaching, and the amount of slag will increase, thus increasing the cost of slag treatment.

[0016] As a preferred embodiment of the present invention, the alkaline solution contains 250-275 ppm of total alkali, 240-260 ppm of caustic alkali, and 140-160 ppm of Al2O3.

[0017] In this invention, the total alkali content in the alkaline solution is 250-275 ppm, for example, it can be 250 ppm, 251 ppm, 252 ppm, 253 ppm, 254 ppm, 255 ppm, 256 ppm, 257 ppm, 258 ppm, 259 ppm, 260 ppm, 261 ppm, 262 ppm, 263 ppm, 264 ppm, 265 ppm, 266 ppm, 267 ppm, 268 ppm, 269 ppm, 270 ppm, 271 ppm, 272 ppm, 273 ppm, 274 ppm or 275 ppm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] In this invention, the caustic alkali content in the alkaline solution is 240-260 ppm, for example, it can be 240 ppm, 241 ppm, 242 ppm, 243 ppm, 244 ppm, 245 ppm, 246 ppm, 247 ppm, 248 ppm, 249 ppm, 250 ppm, 251 ppm, 252 ppm, 253 ppm, 254 ppm, 255 ppm, 256 ppm, 257 ppm, 258 ppm, 259 ppm or 260 ppm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0019] In this invention, the content of Al2O3 in the alkaline solution is 140-160 ppm, for example, it can be 140 ppm, 141 ppm, 142 ppm, 143 ppm, 144 ppm, 145 ppm, 146 ppm, 147 ppm, 148 ppm, 149 ppm, 150 ppm, 151 ppm, 152 ppm, 153 ppm, 154 ppm, 155 ppm, 156 ppm, 157 ppm, 158 ppm, 159 ppm or 160 ppm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0020] Secondly, the present invention provides the use of the composition for alkaline leaching of clay-type lithium ore as described in the first aspect, specifically a method for lithium extraction from clay-type lithium ore, the lithium extraction method comprising leaching the clay-type lithium ore with the composition for alkaline leaching of clay-type lithium ore as described in the first aspect, specifically including:

[0021] The composition for alkaline leaching of clay-type lithium ore and clay-type lithium ore are placed in a reactor for leaching reaction. The resulting alkaline leaching solution is purified to obtain lithium products.

[0022] In this invention, the leachate obtained by leaching with a specific leaching composition has lower iron, calcium, and magnesium impurity contents (all below 100 ppm) and leaching rates (all <1%) compared to spodumene treated with sulfuric acid. That is, the mixed leachate does not contain difficult-to-treat sulfate, chloride, fluoride, or other ions.

[0023] As a preferred technical solution of the present invention, the solid-liquid ratio of clay-type lithium ore and alkaline solution in the leaching reaction is 1g:(7-9)mL.

[0024] As a preferred technical solution of the present invention, the amount of calcium oxide added in the leaching reaction is 3%-8% of the mass of clay-type lithium ore, for example, it can be 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, 5%, 5.2%, 5.4%, 5.6%, 5.8%, 6%, 6.2%, 6.4%, 6.6%, 6.8%, 7%, 7.2%, 7.4%, 7.6%, 7.8%, or 8%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0025] As a preferred embodiment of the present invention, the leaching reaction temperature is 200-300℃ and the heating rate is 5-10℃ / min.

[0026] In this invention, if the reaction temperature rises too quickly during the leaching process, it will cause uneven temperature inside the vessel, while if it is too slow, it will increase the time cost.

[0027] In this invention, the leaching reaction is carried out in a reaction vessel. When the temperature rises during the reaction, pressure is generated, which is the saturated vapor pressure of water vapor between 200-300°C, corresponding to 1553.6 kPa-8583.6 kPa.

[0028] In this invention, the leaching reaction temperature is 200-300℃, for example, it can be 200℃, 205℃, 210℃, 215℃, 220℃, 225℃, 230℃, 235℃, 240℃, 245℃, 250℃, 255℃, 260℃, 265℃, 270℃, 275℃, 280℃, 285℃, 290℃, 295℃ or 300℃, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0029] In this invention, the heating rate used to reach the leaching reaction temperature is 5-10℃ / min, for example, it can be 5℃ / min, 5.2℃ / min, 5.4℃ / min, 5.6℃ / min, 5.8℃ / min, 6℃ / min, 6.2℃ / min, 6.4℃ / min, 6.6℃ / min, 6.8℃ / min, 7℃ / min, 7.2℃ / min, 7.4℃ / min, 7.6℃ / min, 7.8℃ / min, 8℃ / min, 8.2℃ / min, 8.4℃ / min, 8.6℃ / min, 8.8℃ / min, 9℃ / min, 9.2℃ / min, 9.4℃ / min, 9.6℃ / min, 9.8℃ / min, or 10℃ / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] As a preferred technical solution of the present invention, the holding time for the leaching reaction is 0.5-2h, for example, it can be 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2h, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] As a preferred technical solution of the present invention, the stirring speed in the leaching reaction is 5-30 r / min, for example, it can be 5 r / min, 6 r / min, 7 r / min, 8 r / min, 9 r / min, 10 r / min, 11 r / min, 12 r / min, 13 r / min, 14 r / min, 15 r / min, 16 r / min, 17 r / min, 18 r / min, 19 r / min, 20 r / min, 21 r / min, 22 r / min, 23 r / min, 24 r / min, 25 r / min, 26 r / min, 27 r / min, 28 r / min, 29 r / min or 30 r / min, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0032] As a preferred embodiment of the present invention, the impurity removal includes treating the alkaline leaching solution with a membrane.

[0033] In this invention, the impurity removal treatment is mainly used to separate impurities such as potassium, sodium, calcium, and magnesium. After the impurity removal treatment, the levels of impurities such as potassium, sodium, calcium, and magnesium in the leachate are all less than 50 ppm. Specific treatment parameters can be found in other treatment processes in the field, but it is important to ensure that lithium in the solution is adequately retained during the treatment process.

[0034] Preferably, the membrane treatment includes one or a combination of at least two of nanofiltration membrane treatment, reverse osmosis membrane treatment, or electrodialysis membrane treatment.

[0035] Preferably, the membrane flux of the membrane used in the nanofiltration membrane treatment includes one or at least two combinations of 20, 80, 100 or 500.

[0036] In this invention, the pressure is 4-5 kPa when the temperature is ≤35℃ and 2.7-3 kPa when the temperature is >35℃, and the pH value of the material is 3-9.

[0037] In this invention, the pH value of the material in the reverse osmosis membrane treatment is 1-13, the operating pressure is ≤10 bar, and the operating temperature is <45℃.

[0038] In this invention, the operating temperature during electrodialysis membrane treatment can be controlled at 15-40℃, the resistance of the cation exchange membrane is 4.5-5.5, and the resistance of the anion exchange membrane is 3-3.5.

[0039] As a preferred technical solution of the present invention, the purified liquid obtained after impurity removal is purified and then carbon dioxide is introduced to produce high-purity lithium carbonate.

[0040] In this invention, the solution for carbon dioxide carbonization to precipitate lithium carbonate is a high-purity lithium hydroxide solution after impurity removal, which can be obtained in one step by a comprehensive membrane separation device.

[0041] In this invention, the carbon dioxide introduction rate during the preparation of high-purity lithium carbonate by introducing carbon dioxide is 1-1.5 L / min, and the reaction time is ≥3 h;

[0042] In this invention, the high-purity lithium carbonate refers to lithium carbonate with a purity of ≥99.5%.

[0043] In this invention, the carbon dioxide introduction rate during the preparation of high-purity lithium carbonate is 1-1.5 L / min, for example, it can be 1 L / min, 1.2 L / min, 1.4 L / min, 1.6 L / min, 1.8 L / min, 2 L / min, 2.2 L / min, 2.4 L / min, 2.6 L / min, 2.8 L / min, 3 L / min, 3.2 L / min, 3.4 L / min, 3.6 L / min, 3.8 L / min, 4 L / min, 4.2 L / min, 4.4 L / min, 4.6 L / min, 4.8 L / min, or 5 L / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] In this invention, the time for preparing high-purity lithium carbonate by introducing carbon dioxide is ≥3h, for example, it can be 3h, 3.2h, 3.4h, 3.6h, 3.8h, 4h, 4.2h, 4.4h, 4.6h, 4.8h, 5h or 6h, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] Compared with existing technical solutions, the present invention has the following beneficial effects:

[0046] (1) This invention uses low-grade clay-type lithium ore as raw material and employs alkaline mother liquor for high-pressure selective leaching and membrane separation technology and carbon dioxide carbonization to prepare lithium carbonate to extract lithium from clay-type lithium ore, providing a new lithium extraction process route.

[0047] (2) Traditional lithium extraction methods such as acid extraction and limestone sintering are only applicable to spodumene, lepidolite minerals, and salt lake brines, and are not suitable for new low-grade clay-type lithium ores. They also face challenges such as high cost, limited reserves, and high impurity content. This invention can effectively extract lithium from clay ores with a lithium recovery rate of >85%, low cost, simple process route, and high purity of prepared lithium carbonate.

[0048] (3) The present invention uses alkaline mother liquor reaction vessel selective leaching and membrane separation technology to remove impurities, which is environmentally friendly compared to the traditional sulfuric acid method and chloride method which produce toxic and corrosive gases such as SO3 and HCl.

[0049] (4) The high-purity lithium hydroxide solution obtained by combining high-pressure selective leaching and membrane separation technology can be used to prepare high-purity lithium phosphate, lithium carbonate, etc. Detailed Implementation

[0050] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0051] Example 1

[0052] This embodiment provides an alkaline leaching composition and its specific usage process, as follows:

[0053] (1) Take 13.4g of clay-type lithium ore with a lithium oxide content of 0.38% and place it in the inner liner of a high-pressure hydrothermal reactor. Add 100g of alkaline mother liquor and 1.1g of calcium oxide. The composition of the alkaline mother liquor is: total alkali Na2OT=261.3ppm, caustic alkali Na2OK=254.7ppm, Al2O3=152.1ppm, and caustic ratio αK=4.8.

[0054] (2) Set the temperature of the high pressure vessel in step (1) to 260℃, the heating rate to 5℃ / min, the holding time to 1h, the rotation speed to 8r / min, and start the equipment to perform high pressure selective leaching of lithium and aluminum;

[0055] (3) The slurry obtained in step (2) was filtered by pressure to obtain a mixed leachate containing elements such as aluminum and lithium. The composition of the leachate was determined by ICP-MASS and is shown in Table 1.

[0056] As shown in Table 1, the leaching rate of lithium was 91.49%, the leaching rate of aluminum was 84.84%, the leaching rate of magnesium was 50.31%, iron was almost not leached, and the leaching rate of calcium was 12.21%.

[0057] Table 1

[0058]

[0059] (4) The leachate obtained in step (3) is separated using a comprehensive membrane separation device. First, iron, calcium, magnesium and aluminum are separated using a nanofiltration membrane, and then monovalent sodium and potassium ions are separated and concentrated using reverse osmosis and electrodialysis membranes to obtain a high-purity lithium hydroxide solution.

[0060] The composition of the lithium hydroxide solution determined by ICP-MASS is shown in Table 2.

[0061] Among them, iron, calcium, magnesium and aluminum are completely removed, and potassium and sodium are removed at a rate of more than 99%.

[0062] Table 2

[0063]

[0064]

[0065] (5) Take the high-purity lithium hydroxide solution from step (4) and place it in a 500mL crystallizer. At room temperature, introduce carbon dioxide gas at a flow rate of 1.2L / min and react for 3 hours. After filtering, separating and drying the lithium carbonate mixture, high-purity lithium carbonate is obtained.

[0066] The obtained lithium carbonate has a purity of 99.5% and a lithium recovery rate of 81%, based on the lithium hydroxide solution obtained in step (4).

[0067] Example 2

[0068] This embodiment provides an alkaline leaching composition and its specific usage process, as follows:

[0069] (1) Take 13.1g of clay-type lithium ore with a lithium oxide content of 0.6% and place it in the inner liner of a high-pressure hydrothermal reactor. Add 100g of alkaline mother liquor and 1g of calcium oxide. The composition of the alkaline mother liquor is the same as that in Implementation Case 1.

[0070] (2) Set the temperature of the high pressure vessel in step (1) to 200℃, the heating rate to 10℃ / min, the holding time to 2h, the rotation speed to 30r / min, and start the equipment to perform high pressure selective leaching of lithium and aluminum;

[0071] (3) The slurry obtained in step (2) was filtered by pressure to obtain a mixed leachate containing elements such as aluminum and lithium. The composition and leaching rate of the leachate were determined by ICP-MASS, as shown in Table 3.

[0072] The leaching rate of lithium was 93.28%, the leaching rate of magnesium was 50.2%, the leaching rates of iron, calcium, and magnesium were less than 10%, and the leaching rate of potassium was 70.05%.

[0073] Table 3

[0074]

[0075] (4) The leachate obtained in step (3) is separated using a comprehensive membrane separation device. First, iron, calcium, magnesium and aluminum are separated using a nanofiltration membrane, and then monovalent sodium and potassium ions are separated and concentrated using reverse osmosis and electrodialysis membranes to obtain a high-purity lithium hydroxide solution.

[0076] The composition of the lithium hydroxide solution was determined by ICP-MASS and is shown in Table 4; iron, calcium, magnesium, and aluminum were completely removed, while potassium and sodium were removed at a rate greater than 99.9%.

[0077] Table 4

[0078] exudate 387.7 62460.7 1484.5 11637.2 10.2 6.9 3.7 solution 531.2 / 0.8 16.3 / / /

[0079] (5) Take the high-purity lithium hydroxide solution from step (4) and place it in a 500mL crystallizer. At room temperature, introduce carbon dioxide gas at a flow rate of 1.5L / min and react for 3 hours. After filtering, separating and drying the lithium carbonate mixture, high-purity lithium carbonate is obtained.

[0080] The obtained lithium carbonate has a purity of 99.5% and a lithium recovery rate of 82.3%, based on the lithium hydroxide solution obtained in step (4).

[0081] Example 3

[0082] The only difference from Example 1 is that calcium oxide is not added during the leaching process. The composition of the leachate is detailed in Table 5.

[0083] Table 5

[0084]

[0085] As shown in the table, the lithium leaching rate is only 0.4% without the addition of calcium oxide, which is almost no leaching. Lithium exists in the slag phase in the form of lithium silicate.

[0086] Example 4

[0087] The only difference from Example 1 is that the amount of calcium oxide added during the leaching process is 10% of the mass of the clay-type lithium ore. The composition of the leachate is detailed in Table 6.

[0088] Table 6

[0089]

[0090] As shown in Table 6, when the calcium oxide content is 10%, the lithium leaching rate is 55.58%, which is much lower than the 91.49% in Implementation Case 1. Excessive calcium oxide content will promote aluminum leaching and inhibit Li leaching.

[0091] Based on the results of Examples 5 and 6, it can be seen that the optimal amount of calcium oxide added during the pressure leaching of low-grade lithium clay alkaline mother liquor is 3%-8% of that of clay-type lithium ore.

[0092] Example 5

[0093] This embodiment provides a process for lithium extraction using sulfuric acid, specifically for clay-type lithium ore with a lithium oxide content of 0.6% and a sulfuric acid concentration of 8%. Specific leaching conditions and results are detailed in Table 7.

[0094] Table 7

[0095]

[0096]

[0097] As shown in Table 7, direct leaching of clay-type lithium ore with sulfuric acid results in a low lithium leaching rate of 2.35%; the leaching solution contains high levels of Fe and Ca impurities, with a leaching rate of approximately 60%. Therefore, direct leaching with sulfuric acid is not suitable for low-grade clay-type lithium ore.

[0098] Example 6

[0099] This embodiment provides a process for pressurized leaching of sodium carbonate. Sodium carbonate is leached under alkaline conditions, with Na replacing Li to leach out the Li. The lithium oxide content in the mineral is 0.6%, and the mineral particle size is below a 100-mesh sieve. Specific leaching conditions and results are detailed in Table 8.

[0100] Table 8

[0101]

[0102] As shown in Table 8, direct pressure leaching with sodium carbonate resulted in a Li leaching rate of only 0.82%, almost no leaching. Pressure leaching with sodium carbonate is not suitable for lithium extraction from low-grade clay-type lithium ores.

[0103] The results from the above embodiments show that the composition for alkaline leaching of clay-type lithium ore provided by the present invention, through the rational design of the leaching reagent components and the synergistic effect of each component, achieves a good leaching effect on clay-type lithium ore, can significantly improve the lithium leaching rate, avoid the leaching of iron and other impurities, and is beneficial to the preparation of high-purity lithium carbonate.

[0104] The present invention is described in detail through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0105] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0106] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0107] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A composition for alkaline leaching of clay-type lithium ore, characterized in that, The composition for alkaline leaching of clay-type lithium ore comprises: an alkaline solution and calcium oxide; The alkaline solution includes sodium hydroxide and aluminum oxide; The caustic ratio αK of the alkaline solution is 2-6; the total alkali content in the alkaline solution is 250-275 ppm, the caustic alkali content is 240-260 ppm, and the Al2O3 content is 140-160 ppm.

2. A method for extracting lithium from clay-type lithium ore, characterized in that, The lithium extraction method includes leaching clay-type lithium ore using the composition for alkaline leaching of clay-type lithium ore as described in claim 1, specifically including: The composition for alkaline leaching of clay-type lithium ore and clay-type lithium ore are placed in a reactor for leaching reaction. The resulting alkaline leaching solution is purified to obtain lithium products.

3. The lithium extraction method as described in claim 2, characterized in that, The solid-liquid ratio of clay-type lithium ore and alkaline solution in the leaching reaction is 1 g:(7-9) mL.

4. The lithium extraction method as described in claim 2, characterized in that, The amount of calcium oxide added in the leaching reaction is 3%-8% of the mass of clay-type lithium ore.

5. The lithium extraction method as described in claim 2, characterized in that, The leaching reaction is carried out at a temperature of 200-300℃ and a heating rate of 5-10℃ / min.

6. The lithium extraction method as described in claim 2, characterized in that, The leaching reaction is kept at a temperature of 0.5-2 hours.

7. The lithium extraction method as described in claim 2, characterized in that, The stirring speed during the leaching reaction is 5-30 r / min.

8. The lithium extraction method as described in claim 2, characterized in that, The impurity removal includes treating the alkaline leaching solution with a membrane.

9. The lithium extraction method as described in claim 8, characterized in that, The membrane treatment includes one or a combination of at least two of nanofiltration membrane treatment, reverse osmosis membrane treatment, or electrodialysis membrane treatment.

10. The lithium extraction method as described in claim 9, characterized in that, The membrane flux of the membrane used in the nanofiltration membrane treatment includes one or at least two combinations of 20, 80, 100 or 500.

11. The lithium extraction method as described in claim 2, characterized in that, The purified liquid obtained after impurity removal is then purified by passing carbon dioxide through it to produce lithium carbonate.

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