A method for extracting lithium from a coal gasification slag chlorination solid phase product

Abstract

The application discloses a method for extracting lithium from coal gasification residue chlorination solid-phase products, and comprises the following steps: under the constant temperature condition of 20-30 DEG C, the coal gasification residue chlorination solid-phase products are mixed with water as raw materials, the solid-liquid ratio is controlled to be 0.56-0.99, and 0.5%-3% of the mass of the raw materials of a complexing agent is added, so that sodium chloride is preferentially precipitated, and lithium ions are enriched in the liquid phase; the complexing agent is an organic carboxylic acid salt or an amino carboxylic acid salt capable of selectively complexing Ca 2+ and Mg 2+ ; the liquid phase is subjected to dynamic adsorption by using an aluminum adsorbent, lithium ions are selectively extracted, and desorption liquid is obtained by desorption; the desorption liquid is evaporated and crystallized under stirring, and anhydrous lithium chloride products are obtained by drying. The method can effectively adapt to the selective separation of lithium resources in a complex chlorination system with high calcium, magnesium and sodium interference, the loss rate of lithium is significantly reduced through the synergistic effect of the solid-liquid ratio and the complexing agent, the lithium recovery rate is greater than or equal to 87%, and a high-purity sodium chloride by-product can also be obtained.

Description

Technical Field

[0001] This invention relates to the field of coal-based solid waste resource utilization technology, and in particular to a method for extracting lithium from the chlorinated solid phase products of coal gasification slag. Background Technology

[0002] Coal gasification technology, as a core process in modern coal chemical industry, generates a large amount of solid waste, including coal gasification slag, annually. This slag contains rare metals such as lithium, gallium, and germanium. While the lithium content is low, the total amount is considerable, making it of significant recycling value. The chlorination roasting process can convert elements such as lithium, sodium, calcium, and magnesium in the coal gasification slag into chlorides, which are then enriched in the solid phase product, creating conditions for subsequent lithium extraction.

[0003] In existing technologies, solid lithium recovery processes are divided into two steps: leaching and extraction. Leaching mainly includes acid methods, alkaline methods, and combined acid-alkaline methods. Lithium extraction methods from leaching solutions include adsorption, carbonization, and extraction.

[0004] A Chinese patent document with publication number CN109777960A discloses a method for separating and recovering lithium and aluminum from fly ash. The method involves leaching with hydrochloric acid, nitric acid, or sulfuric acid, as well as in-situ co-precipitation of aluminum and lithium, to separate aluminum, lithium ions, and a complex leaching solution system into lithium carbonate and alumina. This method is designed for oxide systems, and the co-precipitation of aluminum and lithium can easily lead to lithium loss. The aluminum precipitation process may result in a large loss of Li, resulting in a lithium recovery rate that is usually less than 80%. Furthermore, the acid solution can easily cause equipment corrosion, and the discharge of waste acid can also pose an environmental pollution risk.

[0005] Patent CN105836767A discloses a method for preparing anhydrous lithium chloride from lithium-containing waste liquid. The waste liquid contains at least lithium ions, calcium ions, magnesium ions, sodium ions, potassium ions, sulfate ions, and chloride ions. The method primarily separates calcium and magnesium ions through chemical precipitation, followed by evaporation to allow NaCl to crystallize out. Finally, the high-concentration lithium chloride solution is dried to obtain anhydrous lithium chloride. However, the calcium content in the lithium-containing waste liquid is 0.2-4 g / L, and the magnesium content is 0.1-2 g / L, both low-concentration impurities, making it unsuitable for extracting lithium salts from complex chloride systems with high calcium, magnesium, and sodium interference.

[0006] In the treatment of solid waste from coal gasification slag, the chlorination process yields a mixed chloride rich in calcium chloride and magnesium chloride, with small amounts of lithium chloride and sodium chloride. This complex chloride system is characterized by extremely low lithium content and high calcium, magnesium, and sodium interference. Extracting lithium from this solid phase product of coal gasification slag chlorination presents unique technical challenges. Optimizing the high-calcium and magnesium chloride in the solid phase of coal gasification slag chlorination to achieve selective separation and resource recycling, thereby improving lithium recovery rates, is a pressing technical problem that needs to be solved. Summary of the Invention

[0007] The purpose of this invention is to provide a method for selectively separating and extracting lithium from the chlorination solid-phase products of coal gasification slag. This method is specifically optimized for complex chloride systems with high calcium, magnesium, and sodium interference, in order to achieve the separation of lithium chloride and improve the lithium recovery rate.

[0008] To solve the above-mentioned technical problems, the present invention provides a technical solution as follows: a method for extracting lithium from the chlorination solid-phase product of coal gasification slag, the method comprising the following steps: S1: under constant temperature conditions of 20℃-30℃, the chlorination solid-phase product of coal gasification slag is mixed with water as a raw material, the solid-liquid ratio is controlled at 0.56-0.99, and a complexing agent accounting for 0.5%-3% of the mass of the raw material is added, so that sodium chloride is preferentially precipitated and lithium ions are enriched in the liquid phase; the complexing agent is capable of selectively complexing Ca... 2+ and Mg 2+ S1: Organic carboxylate or aminocarboxylate; S2: Dynamic adsorption of the liquid phase obtained in step S1 using an aluminum-based adsorbent to selectively extract lithium ions, followed by desorption to obtain a lithium desorption solution; S3: Evaporation and crystallization of the desorption solution obtained in step S2 under stirring conditions, followed by drying to obtain anhydrous lithium chloride product.

[0009] Furthermore, the chlorinated solid product of the coal gasification slag is a solid product obtained by chlorination roasting of coal gasification slag, and its chemical composition by mass fraction is: CaCl2 80%-92%, MgCl2 3%-15%, NaCl 1%-6%, LiCl 0.01%-0.1%, with the balance being other impurities.

[0010] Furthermore, the complexing agent mentioned in step S1 is one or more of sodium citrate, sodium gluconate, sodium malate, sodium tartrate, disodium EDTA, and tetrasodium EDTA.

[0011] Furthermore, the sodium chloride obtained in step S1 has a purity of ≥96.2% and a lithium recovery rate of ≥87%.

[0012] Furthermore, the wet density of the aluminum-based adsorbent in step S2 is 0.7 g / ml-0.8 g / ml, and the water content is 30%-40%.

[0013] Furthermore, the operating conditions for dynamic adsorption in step S2 are: adsorption flow rate of 4 BV / h-12 BV / h, water washing flow rate of 8 BV / h-16 BV / h, and desorption flow rate of 4 BV / h-12 BV / h, achieving a lithium utilization rate of 51%-55%.

[0014] Furthermore, the stirring conditions in step S3 are: a stirring rate of 200 rpm to 600 rpm, to achieve an anhydrous lithium chloride purity of ≥99% and a yield of ≥94%.

[0015] Furthermore, the method also includes electrodialysis concentration of the desorption solution in step S2, wherein the electrodialysis uses anion and cation exchange membranes at a voltage of 4V-5V to achieve a lithium ion concentration increase of ≥6 times.

[0016] Furthermore, the method also includes separating calcium and magnesium ions in the tail liquid after liquid-phase adsorption using an aluminum-based adsorbent in step S2, adding sodium carbonate precipitant to the tail liquid, and separating calcium chloride and magnesium chloride byproducts under stirring conditions.

[0017] This invention also provides a method for extracting lithium from the chlorinated solid phase product of coal gasification slag. The method includes the following steps: isothermal dissolution and dual control: under isothermal conditions of 20℃-30℃, the chlorinated solid phase product of coal gasification slag is mixed with water as raw material, the solid-liquid ratio is controlled at 0.56-0.99, and a complexing agent accounting for 0.5%-3% of the mass of the raw material is added, so that sodium chloride is preferentially precipitated, and lithium ions are enriched in the liquid phase, with a lithium recovery rate ≥87%; the complexing agent is capable of selectively complexing Ca... 2+ and Mg 2+ Organic carboxylic acids or aminocarboxylic acids; Dynamic adsorption selective extraction of lithium: The liquid phase obtained in the previous step is dynamically adsorbed using an aluminum-based adsorbent to obtain a tail liquid rich in calcium and magnesium ions after adsorption and a lithium desorption liquid obtained after desorption; Calcium and magnesium ion separation: Sodium carbonate precipitant is added to the above tail liquid, and calcium chloride and magnesium chloride by-products are separated under stirring conditions; Electrodialysis concentration: The lithium desorption liquid is subjected to electrodialysis using anion and cation exchange membranes at a voltage of 4V-5V to achieve a lithium ion concentration increase of ≥6 times; Evaporation crystallization: The desorption liquid after electrodialysis concentration is evaporated and crystallized under stirring conditions, and dried to obtain anhydrous lithium chloride product.

[0018] The method for extracting lithium from the chlorination solid-phase products of coal gasification slag provided by this invention, compared with the prior art, can effectively adapt to complex chloride systems with low lithium grade and high calcium, magnesium, and sodium interference. Through a dual control strategy combining solid-liquid ratio regulation and complexing agent assistance, it selectively complexes Ca while controlling the solution concentration. 2+ and Mg 2+ This resulted in a synergistic effect, significantly reducing lithium loss and achieving a lithium recovery rate of ≥87%, yielding high-purity sodium chloride as a byproduct. Furthermore, by employing aluminum-based adsorbents to dynamically adsorb lithium from a high-calcium-magnesium chloride solution, the aluminum-based adsorbents exhibited a strong effect on Li... + It exhibits high selectivity, and the complexing agent conceals Ca. 2+ and Mg 2+ Subsequently, the adsorption selectivity was further improved, resulting in a lithium utilization rate of ≥51%. In particular, by adding sodium carbonate precipitant to the adsorption tail liquid and by electrodialysis concentration of the lithium desorption liquid, not only can calcium chloride and magnesium chloride byproducts be separated, but the overall lithium recovery rate of the entire process can also be further improved. Attached Figure Description

[0019] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings represent similar elements. Unless otherwise stated, the figures in the drawings do not constitute a limitation on scale.

[0020] Figure 1 This is a schematic flowchart of the method steps for extracting lithium from the chlorinated solid phase product of coal gasification slag in an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the various embodiments of this invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the various embodiments of this invention to facilitate a better understanding of this application. However, the technical solutions claimed in the claims of this application can be implemented even without these technical details and with various variations and modifications based on the following embodiments.

[0022] like Figure 1 As shown, one embodiment of the present invention relates to a method for extracting lithium from the chlorination solid-phase product of coal gasification slag, comprising the following steps: S1: Isothermal Dissolution and Dual Regulation: Using chlorinated solid products from coal gasification slag as raw materials, water was mixed and dissolved under isothermal conditions of 20-30℃ using a dual strategy combining solid-liquid ratio regulation and complexing agent-assisted regulation; the solid-liquid ratio was controlled at 0.56-0.99, and the complexing agent was capable of selectively complexing Ca... 2+ and Mg 2+ The complexing agent is an organic carboxylate or aminocarboxylate, including but not limited to one or more of sodium citrate, sodium gluconate, sodium malate, sodium tartrate, disodium EDTA, and tetrasodium EDTA, with the amount of complexing agent being 0.5%-3% of the raw material mass. Through this dual regulation, sodium chloride is preferentially precipitated, and lithium ions are enriched in the liquid phase. The raw material is a solid product obtained by chlorination roasting of coal gasification slag. In this embodiment, the chemical composition of the chlorinated solid product of coal gasification slag, by mass fraction, is: CaCl2 80%-92%, MgCl2 3%-15%, NaCl 1%-6%, LiCl 0.01%-0.1%, with the remainder being other impurities.

[0023] Effective binding of calcium ions (Ca) in solution using organic carboxylate or aminocarboxylate complexing agents. 2+ ) and magnesium ions (Mg 2+ This effectively reduces the concentration of free calcium and magnesium ions; carboxylate ions have a positive effect on high-valence cations (Ca). 2+Mg 2+ It has a stronger electrostatic attraction and binding ability, while for monovalent Li + and Na + The binding force is very weak, that is, it binds only to monovalent sodium ions (Na+). + ) and lithium ion (Li + The interaction between them is very weak.

[0024] By controlling the specific solid-liquid ratio, sodium chloride can be preferentially precipitated, and Ca can be selectively complexed. 2+ and Mg 2+ The auxiliary regulation suppresses the interference of calcium and magnesium ions, resulting in a lithium recovery rate of ≥87% in this stage. Simultaneously, the selective complexation of calcium and magnesium ions and the preferential precipitation of sodium chloride provide a more favorable low-interference environment for subsequent dynamic lithium adsorption. Here, lithium recovery rate refers to the recovery rate of lithium from the raw material into the liquid phase obtained in step S1.

[0025] S2: Dynamic Adsorption and Selective Lithium Extraction: An aluminum-based adsorbent is used to dynamically adsorb lithium ions from the liquid phase obtained in step S1, selectively extracting lithium ions. Due to the high selectivity of the aluminum-based adsorbent for lithium ions, calcium and magnesium ions are enriched in the tailings. After adsorption-desorption steps, a lithium-rich eluent is obtained. Preferably, the wet density of the aluminum-based adsorbent is 0.7-0.8 g / ml, and the water content is 30-40%. The dynamic adsorption-desorption operating conditions are: adsorption flow rate 4-12 BV / h, water washing flow rate 8-16 BV / h, and desorption flow rate 4-12 BV / h, achieving selective extraction of lithium ions with a lithium utilization rate of 51%-55%. The lithium utilization rate refers to the recovery rate of lithium from the liquid phase obtained in step S1 after adsorption-desorption by the aluminum-based adsorbent into the eluent.

[0026] Aluminum-based adsorbents are suitable for adsorbents containing Cl. - The solution, Cl - Aluminum-based adsorbents, such as those of the LiCl·2Al(OH)3·nH2O type, help maintain the structural stability of the adsorbent by chemically adsorbing Li. + It exhibits high selectivity. Desorption can be performed using dilute hydrochloric acid or water. + Li + Displace it to achieve enrichment.

[0027] After the liquid phase is subjected to dual regulation by isothermal dissolution and complexing agent in step S1, the complexing agent will release free Ca 2+ Mg 2+ The conversion into complex ions reduces their charge density and non-specific adsorption on the adsorbent surface, further significantly improving lithium selectivity; by controlling the solid-liquid ratio, most of NaCl precipitates, and the Na in the liquid phase... + The concentration decreased significantly, reducing competition for adsorption sites and thus lowering the Ca concentration.2+ Mg 2+ Na + Competitive interference with the active sites of the adsorbent to increase the capture of Li by the aluminum-based adsorbent + The efficiency, as measured from the desorption solution, shows that the lithium utilization rate is over 50%.

[0028] S3: Evaporation and Crystallization: The desorbed liquid is evaporated and crystallized at a stirring rate of 200-600 rpm, and then vacuum dried to obtain anhydrous lithium chloride product with a purity ≥99.0% and a yield ≥94%. The yield refers to the percentage of lithium in the desorbed liquid converted into the final anhydrous lithium chloride product.

[0029] One embodiment of the method for extracting lithium from the chlorinated solid phase product of coal gasification slag further includes electrodialysis concentration of the desorption solution obtained in step S2, wherein the electrodialysis uses anion and cation exchange membranes at a voltage of 4V-5V, which can increase the lithium ion concentration by ≥6 times.

[0030] One embodiment relates to a method for extracting lithium from the chlorinated solid phase product of coal gasification slag, which further includes separating calcium and magnesium ions in the tail liquid after selective lithium adsorption in step S2, adding sodium carbonate precipitant to the tail liquid, and separating calcium chloride and magnesium chloride byproducts under stirring conditions.

[0031] One embodiment relates to a method for extracting lithium from the chlorinated solid phase product of coal gasification slag, the method comprising the following steps: isothermal dissolution and dual control: under isothermal conditions of 20℃-30℃, the chlorinated solid phase product of coal gasification slag is mixed with water as raw material, the solid-liquid ratio is controlled at 0.56-0.99, and a complexing agent accounting for 0.5%-3% of the mass of the raw material is added, so that sodium chloride preferentially precipitates, lithium ions are enriched in the liquid phase, and the lithium recovery rate is ≥87%; the complexing agent is an organic carboxylate or aminocarboxylate that can selectively complex Ca2+ and Mg2+; dynamic adsorption selective extraction Lithium extraction: The liquid phase obtained in the previous step is dynamically adsorbed using an aluminum-based adsorbent to obtain a tail liquid rich in calcium and magnesium ions and a lithium desorption liquid obtained after desorption; Calcium and magnesium ion separation: Sodium carbonate precipitant is added to the tail liquid, and calcium chloride and magnesium chloride byproducts are separated under stirring conditions; Electrodialysis concentration: The lithium desorption liquid is subjected to electrodialysis using anion and cation exchange membranes at a voltage of 4V-5V to achieve a lithium ion concentration increase of ≥6 times; Evaporation and crystallization: The desorption liquid after electrodialysis concentration is evaporated and crystallized under stirring conditions, and then dried to obtain anhydrous lithium chloride product.

[0032] The method for extracting lithium from the chlorinated solid-phase products of coal gasification slag provided by this invention employs a dual strategy combining solid-liquid ratio control during the isothermal dissolution step with complexing agent-assisted control. For the chlorinated solid-phase product system dominated by CaCl2 with a mass fraction of 80%-92%, the method selectively complexes CaCl2 while controlling the solution concentration. 2+ and Mg 2+ This technology effectively solves the problem of simultaneously achieving efficient NaCl precipitation and low lithium recovery in complex chloride systems with extremely low lithium grades and high calcium, magnesium, and sodium interference, resulting in an unexpected synergistic effect. This significantly reduces lithium loss, achieving a lithium recovery rate of ≥87% and yielding high-purity sodium chloride as a byproduct. In particular, by adding sodium carbonate precipitant to the adsorption tail liquid and concentrating the lithium desorption liquid through electrodialysis, not only can calcium chloride and magnesium chloride byproducts be separated, but the overall lithium recovery rate of the entire process can also be further improved.

[0033] The method for extracting lithium from the chlorinated solid phase product of coal gasification slag provided by the present invention was experimentally verified.

[0034] Example 1 100g of the chlorinated solid phase product raw material from coal gasification slag obtained through chlorination roasting was taken. The composition of the raw material, by mass fraction, was 80% CaCl2, 12% MgCl2, 6% NaCl, and 0.02% LiCl, with the remainder being other impurities. The lithium chloride extraction process is as follows: Isothermal dissolution and dual control: At 25℃ and with stirring at 500 rpm, 104 ml of deionized water was added at a solid-liquid ratio of 0.96, along with 1.5 g of sodium citrate (1.5% of the raw material mass) as a complexing agent. The mixture was then dissolved at this isothermal temperature for 2.5 hours. After solid-liquid separation, the purity of the precipitated sodium chloride solid was 98.4%, and the lithium recovery rate in the liquid phase was 87.2%.

[0035] Dynamic adsorption selective extraction of lithium: An aluminum-based adsorbent with a wet density of 0.7630 g / ml and a water content of 35.63% was used. The adsorbent was packed into an adsorption column with a diameter of 20 mm and a height of 500 mm. Dynamic adsorption-desorption was performed at an adsorption flow rate of 6 BV / h, a water washing flow rate of 10 BV / h, and a desorption flow rate of 6 BV / h, yielding the adsorption tail liquid and the lithium desorption liquid. Compositional analysis of the lithium desorption liquid showed that the lithium utilization rate in the dynamic adsorption selective extraction step was 53.8%.

[0036] Evaporation and crystallization: The desorbed liquid was evaporated and crystallized at a stirring rate of 400 rpm, and then dried under vacuum to obtain anhydrous lithium chloride product with a purity of 99.41% and a yield of 96.3%.

[0037] The overall lithium recovery rate refers to the total lithium recovery rate from the total lithium in the solid phase product of coal gasification slag chlorination to the final anhydrous lithium chloride product. Measurements show that the overall lithium recovery rate in this embodiment should be the product of the following steps: lithium recovery rate in the liquid phase, lithium utilization rate in the dynamic adsorption selective extraction step, and yield in the evaporation and crystallization step, which is approximately 45.2%.

[0038] Example 2 100g of the chlorinated solid phase product raw material from coal gasification slag obtained by chlorination roasting was taken. The composition of the raw material, by mass fraction, was 92% CaCl2, 3% MgCl2, 1% NaCl, and 0.01% LiCl, with the remainder being other impurities. The lithium chloride extraction process is as follows: Isothermal dissolution and dual control: At 20℃ and with stirring at 500 rpm, 178.6 ml of deionized water was added at a solid-liquid ratio of 0.56, along with 3 g of sodium citrate (3% of the raw material mass) as a complexing agent. The mixture was then dissolved at this temperature for 2 hours. After solid-liquid separation, the purity of the precipitated sodium chloride solid was 96.2%, and the lithium recovery rate in the liquid phase was 98%.

[0039] Selective extraction of lithium by dynamic adsorption: Using the same aluminum-based adsorbent as in Example 1, the adsorption flow rate was adjusted to 4 BV / h, the water washing flow rate to 8 BV / h, and the desorption flow rate to 4 BV / h. The composition analysis of the lithium desorption solution showed that the lithium utilization rate was 55%.

[0040] Evaporation and crystallization: The desorption solution obtained in the above steps is evaporated and crystallized at a stirring rate of 200 rpm. After vacuum drying, anhydrous lithium chloride product is obtained with a purity of 99.0% and a yield of 95%.

[0041] Measurements showed that the overall lithium recovery rate in this embodiment was approximately 51%. This embodiment effectively suppressed magnesium chloride co-precipitation and calcium and magnesium ion interference by using the lowest solid-liquid ratio and the highest amount of complexing agent, achieving the highest recovery rate in the basic process.

[0042] Example 3 100g of the chlorinated solid phase product raw material from coal gasification slag obtained through chlorination roasting was taken. The composition of the raw material, by mass fraction, was 82% CaCl2, 10% MgCl2, 6% NaCl, and 0.01% LiCl, with the remainder being other impurities. The lithium chloride extraction process is as follows: Isothermal dissolution and dual control: At 30℃ and with stirring at 500 rpm, 101 ml of deionized water was added at a solid-liquid ratio of 0.99, along with 0.5 g of sodium citrate (0.5% of the raw material mass) as a complexing agent. The mixture was then dissolved at this isothermal temperature for 3 hours. After solid-liquid separation, the purity of the precipitated sodium chloride solid was 97.5%, and the lithium recovery rate in the liquid phase was 92%.

[0043] Selective extraction of lithium by dynamic adsorption: Using the same aluminum-based adsorbent as in Example 1, the adsorption flow rate was adjusted to 12 BV / h, the water washing flow rate to 16 BV / h, and the desorption flow rate to 12 BV / h. The composition analysis of the lithium desorption solution showed that the lithium utilization rate was 55%.

[0044] Evaporation and crystallization: The desorption solution obtained in the above steps is evaporated and crystallized at a stirring rate of 600 rpm. After vacuum drying, anhydrous lithium chloride product is obtained with a purity of 99.2% and a yield of 94%.

[0045] The overall lithium recovery rate of this embodiment was measured to be approximately 48%.

[0046] Example 4 100g of the chlorinated solid phase product raw material from coal gasification slag obtained through chlorination roasting was taken. The composition of the raw material, by mass fraction, was 82% CaCl2, 15% MgCl2, 3% NaCl, and 0.1% LiCl, with the remainder being other impurities. The lithium chloride extraction process is as follows: Isothermal dissolution and dual control: At 25℃ and with stirring at 500 rpm, 104 ml of deionized water was added at a solid-liquid ratio of 0.96, along with 2 g of sodium citrate (2% of the raw material mass) as a complexing agent. The mixture was then dissolved at an isothermal temperature for 3 hours. After solid-liquid separation, the purity of the precipitated sodium chloride solid was 97.5%, and the lithium recovery rate in the liquid phase was 87%.

[0047] Selective extraction of lithium by dynamic adsorption: Suqing brand aluminum-based adsorbent was used. The wet density of the aluminum-based adsorbent was 0.8 g / ml and the water content was 30%. The adsorption flow rate was adjusted to 6 BV / h, the water washing flow rate was 10 BV / h, and the desorption flow rate was 6 BV / h. The composition analysis of the lithium desorption solution showed that the lithium utilization rate was 51%.

[0048] Evaporation and crystallization: The desorption solution obtained in the above steps is evaporated and crystallized at a stirring rate of 600 rpm. After vacuum drying, anhydrous lithium chloride product is obtained with a purity of 99.3% and a yield of 95%.

[0049] Measurements showed that the overall lithium recovery rate in this embodiment was approximately 42%. However, due to the high MgCl2 content (up to 15%) in the raw materials and significant interference from calcium and magnesium, the overall lithium recovery rate was relatively low compared to other basic processes.

[0050] Example 5 100g of the chlorinated solid phase product raw material from coal gasification slag obtained through chlorination roasting was taken. The composition of the raw material, by mass fraction, was 85% CaCl2, 8% MgCl2, 5% NaCl, and 0.05% LiCl, with the remainder being other impurities. The lithium chloride extraction process is as follows: Isothermal dissolution and dual control: At 25℃ and with stirring at 500 rpm, 111 ml of deionized water was added at a solid-liquid ratio of 0.90, along with 2.5 g of sodium citrate (2.5% of the raw material mass) as a complexing agent. The mixture was then dissolved at this isothermal temperature for 2.5 hours. After solid-liquid separation, the purity of the precipitated sodium chloride solid was 98.5%, and the lithium recovery rate in the liquid phase was 90.2%.

[0051] Selective extraction of lithium by dynamic adsorption: A self-made aluminum-based adsorbent was mixed with Jiuwu brand aluminum-based adsorbent. The wet density of the mixed aluminum-based adsorbent was 0.7 g / ml and the water content was 40%. The adsorption flow rate was adjusted to 8 BV / h, the water washing flow rate was 12 BV / h, and the desorption flow rate was 8 BV / h. The composition analysis of the lithium desorption solution showed that the lithium utilization rate was 52%.

[0052] Evaporation and crystallization: The desorption solution obtained in the above steps is evaporated and crystallized at a stirring rate of 600 rpm. After vacuum drying, anhydrous lithium chloride product is obtained with a purity of 99.3% and a yield of 96%.

[0053] The overall lithium recovery rate of this embodiment was determined to be approximately 45%.

[0054] Example 6 Based on Example 1, before the evaporation and crystallization step, an electrodialysis concentration step was added to the lithium desorption solution obtained in step S2. The electrodialysis used anion and cation exchange membranes, a voltage of 5 V, and an endpoint conductivity of 5 ms / cm. The isothermal dissolution and dual control steps were the same as in Example 1. The purity of the precipitated sodium chloride solid was 98.4%, and the lithium recovery rate in the liquid phase was 87.2%.

[0055] The dynamic adsorption selective extraction of lithium was performed using the same steps as in Example 1, with a lithium utilization rate of 53.8%.

[0056] Electrodialysis concentration step: Lithium ion concentration increased by 6.33 times.

[0057] Evaporation and crystallization step: The desorbed solution concentrated by electrodialysis was evaporated and crystallized at a stirring rate of 400 rpm. After vacuum drying, anhydrous lithium chloride product was obtained with a purity of 99.41% and a yield of 96.3%.

[0058] Based on Example 1, an electrodialysis concentration step was added, increasing the lithium-ion concentration by 6.33 times. Although electrodialysis involves some losses, the significantly increased lithium-ion concentration significantly reduced the energy consumption for subsequent evaporation. Measurements showed that the overall lithium recovery rate in this example still reached 45%.

[0059] Example 7 Based on Example 1, a calcium and magnesium ion separation step was added to the tail liquid after selective lithium adsorption in step S2. Sodium carbonate precipitant was added to the adsorption tail liquid, and the reaction temperature was controlled at 40°C and the stirring intensity at 500 rpm. Calcium and magnesium in the tail liquid exist in the form of complexed ions, which undergo decomplexing and precipitation reactions under the action of sodium carbonate, separating calcium chloride with a purity of 98.2% and magnesium chloride byproducts with a purity of 97.5%. The filtrate was returned to the isothermal dissolution step for recycling.

[0060] Based on Example 1, a calcium and magnesium ion separation step was added to obtain calcium chloride with a purity of 98.2% and magnesium chloride byproducts with a purity of 97.5%. Measurements showed that the overall lithium recovery rate of this example reached 52%, while also achieving resource utilization of the byproducts.

[0061] Example 8 Based on Example 1, an electrodialysis concentration step was added to the lithium desorption solution obtained in the dynamic adsorption selective lithium extraction step. The electrodialysis used anion and cation exchange membranes at a voltage of 4 V, which increased the lithium concentration by 7 times. Calcium and magnesium were separated in the tail liquid of the dynamic adsorption selective lithium extraction step. The reaction temperature was controlled at 50°C and the stirring intensity at 600 rpm. The filtrate was used in the chlorination roasting process to achieve zero waste discharge.

[0062] By simultaneously adding electrodialysis concentration and calcium-magnesium ion separation steps to the process described in Example 1, the lithium ion concentration was increased by 7 times, and the filtrate can be recycled back to the chlorination roasting process. Measurements showed that the overall lithium recovery rate of this example reached 54%, achieving a combination of high recovery rate and zero waste discharge.

[0063] Comparative Example 1 Based on Example 1, in the isothermal dissolution and dual-control steps, the solid-liquid ratio was adjusted to 1.2. Results: Magnesium chloride and sodium chloride precipitated simultaneously, lithium recovery decreased to 60%, and sodium chloride purity reached 80%.

[0064] When the solid-liquid ratio is increased to 1.2, the concentration of each salt in the solution increases significantly, exceeding the solubility of magnesium chloride under these conditions, resulting in a decrease in the lithium recovery rate to 60% in step S1. At the same time, the concentration of residual free magnesium ions in the solution increases, which leads to non-specific competitive adsorption with aluminum-based adsorbents in subsequent dynamic adsorption steps, causing a significant decrease in the lithium utilization rate in step S2, ultimately resulting in a decrease in the overall lithium recovery rate of the entire process.

[0065] Comparative Example 2 Based on Example 1, the adsorption flow rate was adjusted to 2 BV / h in the dynamic adsorption selective lithium extraction step. Results: Adsorption capacity decreased by 15%, and lithium utilization decreased to 40%.

[0066] When the adsorption flow rate is too low, the solution remains in the adsorption column for too long, leading to the loss of some competing ions (such as residual Na+).+ Trace amounts of Ca still exist after complexation 2+ / Mg 2+ This allows for more time to bind to the active sites of aluminum-based adsorbents, reducing the adsorbent's dependence on Li. + Selectivity and effective capacity. At the same time, too low a flow rate will cause uneven fluid distribution within the column, resulting in axial diffusion and channeling, which further weakens the dynamic adsorption efficiency and ultimately leads to a significant decrease in lithium utilization.

[0067] Comparative Example 3 Based on Example 1, the stirring rate was adjusted to 100 rpm during the evaporation and crystallization step. Results: The metastable region width increased, the purity of anhydrous lithium chloride decreased to 98.0%, and the yield decreased to 85%.

[0068] When the stirring rate during evaporation and crystallization is too low, the solution is unevenly mixed, resulting in significant differences in local supersaturation. This leads to an increase in the width of the metastable region, a decrease in the nucleation rate, and uneven crystal growth. Simultaneously, insufficient stirring reduces the mass transfer efficiency at the crystal surface, increases inclusions in the mother liquor, and makes it easier for impurity ions to enter the crystal lattice or be adsorbed by the crystal, thus causing a decrease in the purity and yield of anhydrous lithium chloride.

[0069] Comparative Example 4 Based on Example 1, in the dynamic adsorption selective extraction of lithium step, manganese-based adsorbents (LiMn2O4, Li4Mn5O4) were used. 12 and Li 1.6 Mn 1.6 (O4 type, etc.) replaced aluminum-based adsorbents. Result: Lithium utilization decreased to 35%.

[0070] Li, a manganese-based adsorbent in a high-calcium-magnesium chloride system + The selectivity is significantly lower than that of aluminum-based adsorbents (LiCl·2Al(OH)3·nH2O type). Aluminum-based adsorbents possess a specific layered structure and ion sieving effect, which is beneficial for Li... + It has higher specific recognition ability; while manganese-based adsorbents are easily affected by Ca in this system. 2+ Mg 2+ The competitive adsorption effect and the relatively poor structural stability in chloride media lead to a significant reduction in lithium ion capture efficiency, ultimately resulting in a decrease in lithium utilization.

[0071] Comparative Example 5 Based on Example 1, the amount of complexing agent was reduced to 0.2% in the isothermal dissolution and dual-control steps. Results: Incomplete complexation of calcium and magnesium ions resulted in unrecovered free Ca in the liquid phase. 2+ Mg 2+ The high concentration caused the lithium utilization rate in the dynamic adsorption step to drop to 38%, and the overall lithium recovery rate to drop to 27%.

[0072] When the amount of complexing agent is insufficient (0.2%), it cannot effectively complex the Ca in the solution. 2+ and Mg 2+ This results in a large number of free high-valence cations remaining. These ions compete with aluminum-based adsorbents for adsorption during the dynamic adsorption process, significantly reducing the adsorbent's affinity for Li. + The selectivity and capture efficiency of the complexing agent significantly reduce lithium utilization and overall lithium recovery rate throughout the process. This result demonstrates the necessity of a lower limit of 0.5% for the complexing agent dosage.

[0073] The method for extracting lithium from the chlorination solid-phase products of coal gasification slag provided by this invention is effectively adaptable to complex chloride systems with low lithium content and high calcium, magnesium, and sodium interference. Through a dual control strategy combining solid-liquid ratio regulation and complexing agent assistance, it simultaneously achieves efficient and preferential precipitation of NaCl and Ca. 2+ and Mg 2+ Effective suppression of interference enables selective separation of lithium resources, significantly reducing lithium loss during selective separation and achieving a lithium recovery rate of ≥87%. By employing aluminum-based adsorbents to dynamically adsorb lithium from high-calcium-magnesium chloride solutions, the aluminum-based adsorbents effectively enhance the lithium recovery rate. + It exhibits high selectivity, and the complexing agent conceals Ca. 2+ and Mg 2+ Subsequently, the adsorption selectivity is further improved, resulting in a lithium utilization rate of ≥51%. Finally, crystals are obtained by evaporating and crystallizing the desorption liquid. The crystals are then vacuum dried to obtain a high-purity anhydrous lithium chloride product. In particular, sodium chloride with a purity of ≥96.2% can also be obtained during the lithium chloride extraction process, and calcium chloride and magnesium chloride can be separated and recovered in the tail liquid. No acids, alkalis, or organic solvents are required, and there is no waste acid or alkali discharge, which fully expands the resource recovery benefits and environmental friendliness.

[0074] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be defined by the claims.

Claims

1. A method for extracting lithium from the chlorination solid-phase products of coal gasification slag, characterized in that, The method includes the following steps: S1: Under constant temperature conditions of 20℃-30℃, the chlorinated solid phase product of the coal gasification slag is mixed with water as raw material, the solid-liquid ratio is controlled at 0.56-0.99, and a complexing agent accounting for 0.5%-3% of the mass of the raw material is added to preferentially precipitate sodium chloride and enrich lithium ions in the liquid phase; the complexing agent is capable of selectively complexing Ca... 2+ and Mg 2+ Organic carboxylic acid salts or amino carboxylic acid salts; S2: The liquid phase obtained in step S1 is dynamically adsorbed using an aluminum-based adsorbent to selectively extract lithium ions, and then desorbed to obtain a lithium desorbate; the wet density of the aluminum-based adsorbent is 0.7 g / ml-0.8 g / ml, and the water content is 30%-40%; the operating conditions for dynamic adsorption are: adsorption flow rate 4 BV / h-12 BV / h, water washing flow rate 8 BV / h-16 BV / h, and desorption flow rate 4 BV / h-12 BV / h; S3: The desorption solution obtained in step S2 is evaporated and crystallized under stirring conditions, and then dried to obtain anhydrous lithium chloride product.

2. The method for extracting lithium from the chlorination solid-phase product of coal gasification slag according to claim 1, characterized in that, The chlorinated solid product of the coal gasification slag is a solid product obtained by chlorination roasting of coal gasification slag. Its chemical composition by mass fraction is: CaCl2 80%-92%, MgCl2 3%-15%, NaCl 1%-6%, LiCl 0.01%-0.1%, with the balance being other impurities.

3. The method for extracting lithium from the chlorination solid-phase product of coal gasification slag according to claim 1, characterized in that, The complexing agent mentioned in step S1 is one or more of sodium citrate, sodium gluconate, sodium malate, sodium tartrate, disodium EDTA, and tetrasodium EDTA.

4. The method for extracting lithium from the chlorination solid-phase product of coal gasification slag according to claim 1, characterized in that, The sodium chloride obtained in step S1 has a purity of ≥96.2% and a lithium recovery rate of ≥87%.

5. The method for extracting lithium from the chlorination solid-phase product of coal gasification slag according to claim 1, characterized in that, In step S2, the lithium utilization rate is 51%-55%.

6. The method for extracting lithium from the chlorination solid-phase product of coal gasification slag according to claim 1, characterized in that, The stirring conditions described in step S3 are: a stirring speed of 200 rpm to 600 rpm, to achieve an anhydrous lithium chloride purity of ≥99% and a yield of ≥94%.

7. The method for extracting lithium from the chlorination solid-phase product of coal gasification slag according to claim 1, characterized in that, The method further includes electrodialysis concentration of the desorption solution in step S2, wherein the electrodialysis uses anion and cation exchange membranes and a voltage of 4V-5V to achieve a lithium ion concentration increase of ≥6 times.

8. The method for extracting lithium from the chlorination solid-phase product of coal gasification slag according to claim 1, characterized in that, The method further includes separating calcium and magnesium ions in the tail liquid after liquid-phase adsorption using an aluminum-based adsorbent in step S2, adding sodium carbonate precipitant to the tail liquid, and separating calcium chloride and magnesium chloride byproducts under stirring conditions.

9. A method for extracting lithium from the chlorination solid-phase products of coal gasification slag, characterized in that, The method includes the following steps: Isothermal dissolution and dual regulation: Under isothermal conditions of 20℃-30℃, the chlorinated solid product of the coal gasification slag is mixed with water as raw material, and the solid-liquid ratio is controlled at 0.56-0.

99. A complexing agent accounting for 0.5%-3% of the raw material mass is added to preferentially precipitate sodium chloride and enrich lithium ions in the liquid phase, with a lithium recovery rate ≥87%. The complexing agent is capable of selectively complexing Ca... 2+ and Mg 2+ Organic carboxylic acid salts or amino carboxylic acid salts; Selective extraction of lithium by dynamic adsorption: The liquid phase obtained in the previous step is dynamically adsorbed using an aluminum-based adsorbent to obtain a tail liquid rich in calcium and magnesium ions after adsorption and a lithium desorption solution after desorption. Calcium and magnesium ion separation: Sodium carbonate precipitant is added to the tail liquid, and calcium chloride and magnesium chloride byproducts are separated under stirring conditions; Electrodialysis concentration: The lithium desorption solution is subjected to electrodialysis using anion and cation exchange membranes at a voltage of 4V-5V to achieve a lithium ion concentration increase of ≥6 times. Evaporation crystallization: The desorbed solution after electrodialysis concentration is evaporated and crystallized under stirring conditions, and then dried to obtain anhydrous lithium chloride product.

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