Method for preparing lithium dihydrogen phosphate by recovering lithium from lithium aluminosilicate impurity residue

Abstract

The present application belongs to the technical field of lithium resource recovery, and relates to a method for recovering lithium from spodumene impurity removal residue to prepare lithium dihydrogen phosphate. The method comprises the following steps: after spodumene acid leaching plate frame impurity removal residue is slurried with water, carbon dioxide is introduced for reaction, solid-liquid separation is performed to obtain a first washing water and a first washing residue; after the first washing residue is added with water for reaction, solid-liquid separation is performed to obtain a second washing liquid and a second washing residue; the first washing water and the second washing water are combined, adsorption and elution are performed by using a titanium ion sieve adsorption column, and a lithium-rich solution is collected; the lithium-rich solution is added with a sodium dihydrogen phosphate solution for reaction and aging, separation is performed, the filter residue is washed with water and dried to obtain white powder lithium dihydrogen phosphate product. The method of the present application improves the solubility of lithium by carbonization with CO2 first, then selectively removes impurities by using a titanium ion sieve, and then directly prepares lithium dihydrogen phosphate from the lithium-rich solution, effectively solving the problems of low lithium recovery rate from spodumene impurity removal plate frame residue, large water resource consumption, and excessive lithium in waste residue.

Description

Technical Field

[0001] This invention belongs to the field of lithium resource recycling technology, and relates to a method for recovering lithium from spodumene impurity removal slag to prepare lithium dihydrogen phosphate. More specifically, it relates to a synergistic treatment method for recovering lithium from the impurity removal plate and frame slag generated during the preparation of lithium carbonate from spodumene, and preparing lithium dihydrogen phosphate. Background Technology

[0002] Spodumene is one of the main lithium-containing minerals. Current lithium extraction processes from spodumene primarily employ the sulfuric acid roasting-water leaching method. The resulting acid leaching brine needs to remove impurities such as calcium and magnesium ions. Typically, sodium hydroxide is added first to remove magnesium, followed by sodium carbonate to remove calcium. The resulting residue, after filtration, is a plate and frame filter press residue, whose main components are magnesium hydroxide, calcium hydroxide, lithium hydroxide, calcium carbonate, and lithium carbonate. This residue has a high lithium content (usually in the form of lithium carbonate), but existing recovery processes often involve multiple water washings, resulting in problems such as high water consumption, low recovery efficiency, excessive residual lithium content in the washing residue, and high environmental pollution risks.

[0003] Lithium carbonate has low solubility in water (approximately 1.33 g / 100 mL, 20 °C), while lithium bicarbonate has extremely high solubility (approximately 32.8 g / 100 mL, 20 °C). Based on this characteristic, related studies have proposed introducing carbon dioxide (CO2) during the washing process to convert lithium carbonate into water-soluble lithium bicarbonate, which can significantly improve lithium dissolution efficiency. However, the lithium ion concentration in the washing solution after conversion is still relatively low and contains various impurity ions, requiring further enrichment and purification.

[0004] Titanium-based lithium-ion sieves (such as H2TiO3 or H4Ti5O) 12 It exhibits high selective adsorption of lithium ions (theoretical adsorption capacity up to 141.81 mg / g), and its ability to achieve Li-ion adsorption is based on the "structural memory effect". + with Na + K + Ca 2+ Mg 2+ It enables efficient separation of impurity ions. Following adsorption, acid elution yields a pure lithium solution, suitable for preparing high-value-added lithium products such as lithium dihydrogen phosphate.

[0005] Currently, there are no reports of a complete process combining carbon dioxide carbonization conversion, titanium-based lithium-ion sieve adsorption and enrichment, and lithium dihydrogen phosphate preparation for the efficient recovery of lithium from spodumene impurity residue. This invention aims to fill this technological gap. Summary of the Invention

[0006] The purpose of this invention is to address the problems of low lithium recovery rate, high water consumption, and excessive residual lithium in waste residue of existing spodumene impurity removal plate frame slag treatment processes, and to provide a method for recovering lithium from spodumene impurity removal slag to prepare lithium dihydrogen phosphate, thereby achieving efficient recovery of lithium resources and compliant discharge of waste residue.

[0007] The purpose of this invention is to provide a method for recovering lithium from spodumene residue to prepare lithium dihydrogen phosphate, the method comprising the following steps: S1. Take a certain amount of spodumene acid leaching plate frame to remove impurities and place it in a stirring device. Add water and stir to form a uniform slurry. Continuously introduce carbon dioxide gas into the slurry to carry out the reaction. After reacting for 1-3 hours, the solid and liquid are separated to obtain a washing water and a washing residue. S2. Transfer the first washing residue to a stirring device, add water, stir and react for 1-2 hours, and then separate the solid and liquid to obtain the second washing liquid and the second washing residue. S3. Combine the first wash water and the second wash water, and pass the mixture through an adsorption column equipped with a titanium ion sieve at a certain flow rate for adsorption. After adsorption, wash the adsorption column with deionized water to remove residual impurity ions. After washing, elute the adsorption column with hydrochloric acid solution and collect the lithium-rich solution. S4. Transfer the lithium-rich solution to a preheated constant temperature water bath and stir. During the stirring process, slowly add sodium dihydrogen phosphate solution to react. After the reaction is completed, cool the slurry to room temperature and age for 2-3 hours. After aging, separate the solid and liquid to obtain filtrate and filter residue. Return the filtrate to S1 for slurry preparation. After washing with water, transfer the filter residue to a vacuum drying oven for drying to obtain a white powdered lithium dihydrogen phosphate product.

[0008] This invention employs a synergistic combination of multiple technologies. First, it utilizes a carbon dioxide carbonization conversion process to convert lithium carbonate into highly soluble lithium carbonate, effectively solving the problems of traditional water washing methods, which require multiple washes due to the low solubility of lithium carbonate, resulting in large water consumption and high lithium residue in the slag. This improves the single-pass leaching rate and reduces the total water consumption. Then, it employs a titanium-based lithium-ion sieve for selective adsorption, utilizing its "structural memory effect" to achieve Li... + Specific adsorption effectively solves the problems of low lithium concentration and low separation efficiency of traditional water washing methods due to many impurities (sodium, potassium, calcium, magnesium, etc.). It has a high impurity removal rate and can save the alkali consumption required for subsequent impurity removal, thus reducing production costs. The lithium-rich solution is then used to prepare lithium dihydrogen phosphate and the reaction conditions are controlled to obtain lithium dihydrogen phosphate with high purity, which can reach battery grade. Overall, it realizes the efficient recovery and utilization of lithium resources.

[0009] Preferably, in the above technical solution S1, the moisture content of the spodumene acid leaching plate and frame slag is 20-40%; the solid-liquid ratio of the spodumene acid leaching plate and frame slag to water is 1:4-5; and the stirring speed is 250-350 rpm. Since the lithium element in the spodumene impurity removal plate and frame slag mainly exists in the form of lithium hydroxide and lithium carbonate, its solubility in water is limited. Leaching lithium by water washing results in a low lithium leaching rate if the solid-liquid ratio is too low, and a high solid-liquid ratio wastes water resources and increases costs. This technical solution effectively balances lithium content and cost by controlling the solid-liquid ratio within a suitable range.

[0010] Preferably, in the above technical solution S1, the flow rate of carbon dioxide is 0.5-1 L / min. Introducing carbon dioxide into the slurry formed by spodumene impurity removal promotes the conversion of insoluble lithium carbonate in the spodumene impurity removal slurry into more soluble lithium bicarbonate, reducing water consumption and increasing the lithium solubility in the washing solution, which is beneficial for improving the lithium leaching rate. However, if the carbon dioxide flow rate is too fast, it will lead to gas waste; if it is too slow, it will slow down the reaction rate and increase the washing time. In this technical solution, by strictly controlling the carbon dioxide flow rate, both lithium leaching rate and cost can be effectively balanced.

[0011] Preferably, in the above technical solution S2, the solid-liquid ratio of the washing residue and water is 1:3-5. This technical solution, by controlling the ratio of the washing residue to water, ensures lithium extraction while ensuring the filter residue meets emission standards.

[0012] Preferably, in the above technical solution S3, the flow rate of the mixed solution through the titanium-based ion sieve adsorption column is 0.5-1 mL / min. This technical solution effectively ensures the adsorption efficiency of lithium ions by controlling the flow rate entering the adsorption column.

[0013] Preferably, in the above technical solution S3, the concentration of the hydrochloric acid solution is 0.5-1 mol / L.

[0014] Preferably, in the above technical solution S4, the water bath temperature is 80-85℃, the stirring speed is 250-350rpm, and the reaction time is 2-3h. In this technical solution, by controlling the temperature of the water bath reaction, the particle morphology and uniformity of lithium dihydrogen phosphate can be ensured, and by carrying out an aging reaction, a more complete reaction can be ensured, thereby improving the recovery rate.

[0015] Preferably, in the above technical solution S4, the concentration of the sodium dihydrogen phosphate solution is 5-6 mol / L; the molar ratio of sodium dihydrogen phosphate to lithium ions in the lithium-rich solution is 1.1-1.2:1. In this technical solution, by adding a slight excess of sodium dihydrogen phosphate, the reaction can be ensured to be more complete, resulting in a purer final product.

[0016] Preferably, in the above technical solution S4, the drying temperature is 100±5℃ and the time is 4-6h.

[0017] Advantages compared to existing technologies: This invention addresses the problems existing in the traditional recovery process of lithium spodumene acid leaching to remove impurities. First, carbon dioxide is introduced into the impurity removal plate and frame slag washing process, utilizing the water-soluble property of lithium carbonate to convert to lithium bicarbonate, significantly improving lithium leaching efficiency, reducing water consumption, and lowering subsequent treatment costs. Then, a titanium-based lithium-ion sieve is used to adsorb lithium from the washing solution. Compared with traditional adsorbents, it has higher selectivity and adsorption capacity, effectively enriching lithium and improving lithium recovery rate. Simultaneously, by optimizing the eluent concentration and subsequent reaction conditions, a highly efficient method for preparing lithium dihydrogen phosphate is developed. The resulting lithium dihydrogen phosphate product has high purity, meeting industrial production needs and increasing the added value of lithium resources. This method is safe, environmentally friendly, and low-cost, with significant economic and environmental benefits, and is suitable for the resource recovery of solid waste from lithium salt production enterprises. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the method for preparing lithium dihydrogen phosphate by recovering lithium from spodumene residue according to the present invention. Detailed Implementation

[0019] The above-described technical features of the present invention and the technical features specifically described below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions. However, the present invention is not limited to these embodiments, nor are these embodiments limited in any way.

[0020] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the formulations involved in the following examples are all commercially available products that can be purchased from the market.

[0021] The present invention will be further described in detail below with reference to embodiments: The main components of the raw material (spodumene impurity removal slag) used in the embodiments of the present invention were detected by atomic absorption spectrometry, and the results are shown in Table 1.

[0022] Table 1 Main components of spodumene residue

[0023] The titanium-based ion sieve used was purchased from Yunnan Gangfeng New Materials Co., Ltd., model G-200.

[0024] Example 1 A method for recovering lithium from spodumene residue to prepare lithium dihydrogen phosphate includes the following steps: S1. Weigh 600g of spodumene acid-leached plate frame slag (moisture content 25%) and place it in a stirring device. Add water at a solid-liquid ratio of 1:5 and stir. Control the stirring speed at 250rpm to form a uniform slurry. Continuously introduce carbon dioxide gas into the slurry at a rate of 0.5L / min to react and fully convert lithium carbonate into lithium bicarbonate. After reacting for 2 hours, separate the solid and liquid to obtain a wash water and a wash residue. S2. Transfer the first washing residue to a stirring device, add water at a solid-liquid ratio of 1:5, stir and react at 250 rpm for 1 hour, dissolve all the remaining lithium in the impurity removal residue, and separate the solid and liquid to obtain the second washing liquid and the second washing residue. The main components of the second washing residue are magnesium carbonate, calcium carbonate and other components, which can be used for desulfurization in the desulfurization tower during the preparation of lithium carbonate from spodumene. S3. Combine the first and second wash waters and pass the mixture through an adsorption column equipped with a titanium ion sieve at a flow rate of 0.5 mL / min. After adsorption, wash the adsorption column with deionized water to remove residual impurity ions. After washing, elute the adsorption column with a 1 mol / L hydrochloric acid solution and collect the lithium-rich solution. S4. Transfer the lithium-rich solution to a constant temperature water bath preheated to 80°C and stir at 250 rpm. During stirring, slowly add a 5 mol / L sodium dihydrogen phosphate solution (controlling the molar ratio of lithium ions to sodium dihydrogen phosphate to be 1:1.1) to react. After the reaction is complete, cool the slurry to room temperature and age for 2 hours. After aging, separate the solid and liquid to obtain filtrate and filter residue. The filtrate can be returned to S1 for slurry preparation. After washing with water, the filter residue is transferred to a vacuum drying oven and dried at 100°C for 4 hours to obtain a white powdered lithium dihydrogen phosphate product.

[0025] Example 2 A method for recovering lithium from spodumene residue to prepare lithium dihydrogen phosphate includes the following steps: S1. Weigh 600g of spodumene acid-leached plate frame slag (moisture content 30%) and place it in a stirring device. Add water at a solid-liquid ratio of 1:4.5 and stir. Control the stirring speed at 300rpm to form a uniform slurry. Continuously introduce carbon dioxide gas into the slurry at a rate of 0.8L / min to react and fully convert lithium carbonate into lithium bicarbonate. After reacting for 3 hours, separate the solid and liquid to obtain a wash water and a wash residue. S2. Transfer the first washing residue to a stirring device, add water at a solid-liquid ratio of 1:4, stir at 300 rpm for 2 hours to dissolve all the remaining lithium in the impurity removal residue, and separate the solid and liquid to obtain the second washing liquid and the second washing residue. The main components of the second washing residue are magnesium carbonate, calcium carbonate and other components, which can be used for desulfurization in the desulfurization tower during the preparation of lithium carbonate from spodumene. S3. Combine the first and second wash waters and pass the mixture through an adsorption column equipped with a titanium ion sieve at a flow rate of 0.8 mL / min. After adsorption, wash the adsorption column with deionized water to remove residual impurity ions. After washing, elute the adsorption column with a 0.7 mol / L hydrochloric acid solution and collect the lithium-rich solution. S4. Transfer the lithium-rich solution to a constant temperature water bath preheated to 85°C and stir at 300 rpm. During stirring, slowly add a 6 mol / L sodium dihydrogen phosphate solution (controlling the molar ratio of lithium ions to sodium dihydrogen phosphate to be 1:1.2) to react. After the reaction is complete, cool the slurry to room temperature and age for 2.5 h. After aging, separate the solid and liquid to obtain filtrate and filter residue. The filtrate can be returned to S1 for slurry preparation. After washing with water, the filter residue is transferred to a vacuum drying oven and dried at 100°C for 6 h to obtain a white powdered lithium dihydrogen phosphate product.

[0026] Example 3 A method for recovering lithium from spodumene residue to prepare lithium dihydrogen phosphate includes the following steps: S1. Weigh 600g of spodumene acid-leached plate frame slag (moisture content 40%) and place it in a stirring device. Add water at a solid-liquid ratio of 1:4 and stir. Control the stirring speed at 350rpm to form a uniform slurry. Continuously introduce carbon dioxide gas into the slurry at a rate of 1L / min to react and fully convert lithium carbonate into lithium bicarbonate. After reacting for 2 hours, separate the solid and liquid to obtain a wash water and a wash residue. S2. Transfer the first washing residue to a stirring device, add water at a solid-liquid ratio of 1:3, stir and react at 350 rpm for 1 hour, dissolve all the remaining lithium in the impurity removal residue, and separate the solid and liquid to obtain the second washing liquid and the second washing residue. The main components of the second washing residue are magnesium carbonate, calcium carbonate and other components, which can be used for desulfurization in the desulfurization tower during the preparation of lithium carbonate from spodumene. S3. Combine the first and second wash waters and pass the mixture through an adsorption column equipped with a titanium ion sieve at a flow rate of 1 mL / min. After adsorption, wash the adsorption column with deionized water to remove residual impurity ions. After washing, elute the adsorption column with a 0.5 mol / L hydrochloric acid solution and collect the lithium-rich solution. S4. Transfer the lithium-rich solution to a constant temperature water bath preheated to 85°C and stir at 350 rpm. During stirring, slowly add a 5 mol / L sodium dihydrogen phosphate solution (controlling the molar ratio of lithium ions to sodium dihydrogen phosphate to be 1:1.2) to react. After the reaction is complete, cool the slurry to room temperature and age for 3 hours. After aging, separate the solid and liquid to obtain filtrate and filter residue. The filtrate can be returned to S1 for slurry preparation. After washing with water, the filter residue is transferred to a vacuum drying oven and dried at 100°C for 5 hours to obtain a white powdered lithium dihydrogen phosphate product.

[0027] Comparative Example 1 A method for recovering lithium from spodumene impurity slag to prepare lithium dihydrogen phosphate differs from Example 2 in that S1 is as follows: 600g of spodumene acid leaching plate frame impurity slag (40% moisture content) is weighed and placed in a stirring device, water is added at a solid-liquid ratio of 1:4 and stirred, and the stirring speed is controlled at 350rpm to form a uniform slurry. After reacting for 2 hours, the solid and liquid are separated to obtain a wash water and a wash slag.

[0028] Comparative Example 2 A method for recovering lithium from spodumene impurity slag to prepare lithium dihydrogen phosphate differs from Example 2 in that S1 is as follows: 600g of spodumene acid-leached plate and frame impurity slag (40% moisture content) is weighed and placed in a stirring device, water is added at a solid-liquid ratio of 1:4 and stirred, and the stirring speed is controlled at 350rpm to form a uniform slurry. Carbon dioxide gas is continuously introduced into the slurry at a rate of 0.3L / min to react, so that lithium carbonate is fully converted into lithium bicarbonate. After reacting for 2 hours, solid and liquid are separated to obtain a wash water and a wash slag.

[0029] Comparative Example 3 A method for recovering lithium from spodumene impurity slag to prepare lithium dihydrogen phosphate differs from Example 2 in that S1 is as follows: 600g of spodumene acid leaching plate frame impurity slag (40% moisture content) is weighed and placed in a stirring device, water is added at a solid-liquid ratio of 1:10 for stirring and washing, the stirring speed is controlled at 350pm to form a uniform slurry, and after reacting for 2 hours, solid and liquid are separated to obtain a washing water and a washing slag. S2 involves transferring the first washing residue to a stirring device, adding water at a solid-liquid ratio of 1:5 for two water washes, and continuing the reaction at a stirring speed of 350 rpm for 1 hour to dissolve all the remaining lithium in the impurity-removing residue. After the reaction is completed, solid-liquid separation is performed to obtain the second washing liquid, the third washing liquid, and the third washing residue. The main components of the third washing residue are magnesium carbonate, calcium carbonate, etc., which can be used for desulfurization in the desulfurization tower during the preparation of lithium carbonate from spodumene.

[0030] Comparative Example 4 A method for recovering lithium from spodumene residue to prepare lithium dihydrogen phosphate differs from Example 2 in that S3 is as follows: the first wash water and the second wash water are combined, and the mixture is passed through an adsorption column equipped with a titanium-based ion sieve at a flow rate of 5 mL / min for adsorption. After adsorption, the adsorption column is washed with deionized water to remove residual impurity ions. After washing, the adsorption column is eluted with a 0.5 mol / L hydrochloric acid solution to collect a lithium-rich solution.

[0031] Comparative Example 5 A method for recovering lithium from spodumene residue to prepare lithium dihydrogen phosphate differs from Example 2 in that S3 is as follows: the first wash water and the second wash water are combined, and the mixture is passed through an adsorption column equipped with a titanium-based ion sieve at a flow rate of 1 mL / min for adsorption. After adsorption, the adsorption column is washed with deionized water to remove residual impurity ions. After washing, the adsorption column is eluted with a 5 mol / L hydrochloric acid solution to collect a lithium-rich solution.

[0032] Comparative Example 6 A method for recovering lithium from spodumene residue to prepare lithium dihydrogen phosphate differs from Example 2 in that S3 involves combining the first and second wash waters, and the mixture is directly introduced into S4 for reaction.

[0033] Comparative Example 7 A method for recovering lithium from spodumene residue to prepare lithium dihydrogen phosphate differs from Example 2 in that S4 is as follows: a lithium-rich solution is transferred to a constant-temperature water bath preheated to 95°C and stirred at 350 rpm. During stirring, a 5 mol / L sodium dihydrogen phosphate solution is slowly added (controlling the molar ratio of lithium ions to sodium dihydrogen phosphate to be 1:1.2) to carry out the reaction. After the reaction is completed, the slurry is cooled to room temperature and aged for 3 hours. After aging, solid and liquid are separated to obtain filtrate and filter residue. The filtrate can be returned to S1 for slurry preparation. The filter residue is washed with water and then transferred to a vacuum drying oven and dried at 100°C for 5 hours to obtain a white powdered lithium dihydrogen phosphate product.

[0034] Comparative Example 8 A method for recovering lithium from spodumene residue to prepare lithium dihydrogen phosphate differs from Example 2 in that S4 is as follows: a lithium-rich solution is transferred to a constant-temperature water bath preheated to 75°C and stirred at 350 rpm. During stirring, a 5 mol / L sodium dihydrogen phosphate solution is slowly added (controlling the molar ratio of lithium ions to sodium dihydrogen phosphate to be 1:1.2) to carry out the reaction. After the reaction is completed, the slurry is cooled to room temperature and aged for 3 hours. After aging, solid and liquid are separated to obtain filtrate and filter residue. The filtrate can be returned to S1 for slurry preparation. The filter residue is washed with water and then transferred to a vacuum drying oven and dried at 100°C for 5 hours to obtain a white powdered lithium dihydrogen phosphate product.

[0035] Comparative Example 9 A method for recovering lithium from spodumene residue to prepare lithium dihydrogen phosphate differs from Example 2 in that S4 is as follows: a lithium-rich solution is transferred to a constant-temperature water bath preheated to 95°C and stirred at 350 rpm. During stirring, a 5 mol / L sodium dihydrogen phosphate solution is slowly added (controlling the molar ratio of lithium ions to sodium dihydrogen phosphate to be 1:1) to carry out the reaction. After the reaction is completed, the slurry is cooled to room temperature and aged for 3 hours. After aging, solid and liquid are separated to obtain filtrate and filter residue. The filtrate can be returned to S1 for slurry preparation. The filter residue is washed with water and then transferred to a vacuum drying oven and dried at 100°C for 5 hours to obtain a white powdered lithium dihydrogen phosphate product.

[0036] Test case The leaching rate, recovery rate, and purity of the final product, lithium dihydrogen phosphate, of lithium recovered in Examples 1-3 and Comparative Examples 1-9 were tested, and the results are shown in Table 2. The lithium leaching rate and recovery rate were determined using the material balance method, and the purity of lithium dihydrogen phosphate was determined using XRD and chemical titration.

[0037] Table 2 Test Results

[0038] As can be seen from the results in Table 2, the lithium recovery rate using the method of the present invention in Examples 1-3 is high, the lithium content in the final washing residue is low, and the purity of the obtained lithium dihydrogen phosphate is above 99.7%. Furthermore, the washing residue can be used as a desulfurization adsorbent for further resource utilization. This method is efficient, environmentally friendly, and feasible. In contrast, in Comparative Examples 1-9, the changes in the recovery method or reaction conditions all affected the final recovery and conversion effect. In Comparative Examples 1-3, the lack of carbon dioxide or the excessively low concentration of carbon dioxide resulted in incomplete lithium carbonate conversion, directly impacting the lithium leaching rate. In particular, Comparative Example 3, despite using a large amount of water for washing and consuming significant water resources, still failed to achieve the recovery effect of Example 2. In Comparative Example 4, although a titanium-based ion sieve was used for adsorption, the excessive flow rate directly affected the lithium recovery rate. In Comparative Example 5, increasing the hydrochloric acid concentration had little impact on lithium recovery, resulting in wasted reagents. In Comparative Example 6, the absence of a titanium-based ion sieve for pre-adsorption of the mixture led to numerous impurities, directly affecting the production and recovery of lithium dihydrogen phosphate. In Comparative Examples 7-8, both excessively high and low reaction temperatures affected the synthesis of lithium dihydrogen phosphate, thus impacting the final lithium recovery rate. In Comparative Example 9, the use of sodium dihydrogen phosphate at a molar concentration equal to that of lithium ions resulted in insufficient reaction, directly affecting the purification of lithium dihydrogen phosphate and the lithium recovery rate.

[0039] In summary, this invention improves lithium solubility through CO2 carbonization, selectively removes impurities using a titanium-based ion sieve, and finally prepares lithium dihydrogen phosphate from the lithium-rich solution. The synergistic operation of these processes effectively solves the problems of low lithium recovery rate, high water consumption, and excessive residual lithium in spodumene-treated plate and frame slag. Compared with traditional processes, this method not only boasts high lithium recovery efficiency (>94%) but also consumes less water, achieves a lithium dihydrogen phosphate product purity of over 99.7%, and realizes the resource utilization of secondary washing slag (as a desulfurization adsorbent). It exhibits significant economic and environmental benefits, providing a practical and feasible technical route for realizing a green circular economy of lithium battery industry waste.

[0040] Finally, it should be emphasized that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recovering lithium from spodumene slag to prepare lithium dihydrogen phosphate, characterized in that, The method includes the following steps: S1. Take a certain amount of spodumene acid leaching plate frame to remove impurities and place it in a stirring device. Add water and stir to form a uniform slurry. Continuously introduce carbon dioxide gas with a flow rate of 0.5-1L / min into the slurry to carry out the reaction. After reacting for 1-3 hours, the solid and liquid are separated to obtain a washing water and a washing residue. S2. Transfer the first washing residue to a stirring device, add water, stir and react for 1-2 hours, and then separate the solid and liquid to obtain the second washing liquid and the second washing residue. S3. Combine the first and second wash waters, and pass the mixture through an adsorption column equipped with a titanium ion sieve at a flow rate of 0.5-1 mL / min. After adsorption, wash the adsorption column with deionized water to remove residual impurity ions. After washing, elute the adsorption column with hydrochloric acid solution and collect the lithium-rich solution. S4. Transfer the lithium-rich solution to a constant temperature water bath preheated to 80-85℃ and stir. During stirring, slowly add sodium dihydrogen phosphate solution to react. After the reaction is complete, cool the slurry to room temperature and age for 2-3 hours. After aging, separate the solid and liquid to obtain filtrate and filter residue. Return the filtrate to S1 for slurry preparation. After washing with water, transfer the filter residue to a vacuum drying oven to dry, and obtain a white powdered lithium dihydrogen phosphate product.

2. The method for recovering lithium from spodumene residue and preparing lithium dihydrogen phosphate according to claim 1, characterized in that, In S1, the moisture content of the spodumene acid-leached plate and frame impurity removal slag is 20-40%; the solid-liquid ratio of the spodumene acid-leached plate and frame impurity removal slag to water is 1:4-5; and the stirring speed is 250-350 rpm.

3. The method for recovering lithium from spodumene slag to prepare lithium dihydrogen phosphate according to claim 1, characterized in that, In S2, the solid-liquid ratio of the washing residue and water is 1:3-5.

4. The method for recovering lithium from spodumene slag and preparing lithium dihydrogen phosphate according to claim 1, characterized in that, In S3, the concentration of the hydrochloric acid solution is 0.5-1 mol / L.

5. The method for recovering lithium from spodumene slag and preparing lithium dihydrogen phosphate according to claim 1, characterized in that, In S4, the stirring speed is 250-350 rpm, and the reaction time is 2-3 hours.

6. The method for recovering lithium from spodumene slag to prepare lithium dihydrogen phosphate according to claim 1, characterized in that, In S4, the concentration of the sodium dihydrogen phosphate solution is 5-6 mol / L; the molar ratio of sodium dihydrogen phosphate to lithium ions in the lithium-rich solution is 1.1-1.2:

1.

7. The method for recovering lithium from spodumene slag to prepare lithium dihydrogen phosphate according to claim 1, characterized in that, In S4, the drying temperature is 100±5℃ and the time is 4-6h.

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