Method for separating and enriching lithium ions in spodumene by using fulvic acid gradient and application thereof

Abstract

This invention discloses a method and application for the stepwise separation and enrichment of lithium ions in spodumene ore using fulvic acid. First, the spodumene ore undergoes high-temperature conversion roasting. Then, the converted β-spodumene is mixed with sulfuric acid and subjected to sulfation roasting. A lithium leachate containing aluminum, iron, magnesium, and calcium impurities is prepared by water leaching. The pH of the solution is adjusted stepwise to 6.5 to precipitate and remove aluminum and iron ions. An anionic polyacrylamide flocculant is added to achieve solid-liquid separation. The pH is then adjusted to 12 to precipitate and remove magnesium and calcium ions, completing preliminary impurity removal. Next, 0.25-3 g / L fulvic acid is added to the filtrate for selective impurity removal via a complexation reaction. Finally, flocculation is performed using polyaluminum chloride solution, and solid-liquid separation yields a high-purity lithium-containing filtrate. This invention, through stepwise pH adjustment for preliminary impurity removal, selective complexation with fulvic acid for deep impurity removal, and synergistic flocculation with polyaluminum chloride, can efficiently remove aluminum, iron, magnesium, and calcium impurities from lithium leachate. The impurity removal effect is good, and the lithium ion enrichment purity and recovery rate are high, making it suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of lithium extraction technology from spodumene ore, specifically relating to a method and application for the stepwise separation and enrichment of lithium ions in spodumene ore using humic acid. Background Technology

[0002] Lithium, as a strategic key metal, plays an irreplaceable role in strategic emerging industries such as new energy vehicles and large-scale energy storage. my country's dependence on imported lithium resources has long been high, making the development of efficient and green lithium extraction technologies crucial for ensuring national resource security.

[0003] The sulfuric acid process is currently the most widely used method for lithium extraction from spodumene. Its basic principle involves high-temperature transformation roasting of spodumene to convert α-spodumene into β-spodumene, followed by sulfation roasting and water leaching, allowing lithium to enter the solution as lithium sulfate. However, the traditional sulfuric acid process suffers from a series of prominent problems: firstly, significant lithium entrainment loss occurs during neutralization and impurity removal; secondly, calcium and magnesium ions are difficult to remove deeply, affecting the purity of the final lithium carbonate product; and thirdly, reagent consumption is high, and waste residue treatment costs are high. These problems severely restrict the technological upgrading and green development of the spodumene lithium extraction industry.

[0004] In existing technologies, impurity removal methods for spodumene leaching solutions mainly include chemical precipitation, ion exchange, complexation masking, and filtration. Chemical precipitation adjusts the pH to precipitate impurity ions as hydroxides, but this method has limited effectiveness in removing calcium and magnesium ions and easily leads to lithium co-precipitation loss. While ion exchange has good impurity removal efficiency, resin regeneration is costly and the operation is complex. Complexation masking utilizes complexing agents to form stable complexes with impurity ions, but traditional complexing agents lack selectivity, making it difficult to selectively remove target ions under conditions where multiple impurity ions coexist.

[0005] Therefore, developing a deep purification technology that can achieve efficient and selective separation of lithium and impurity ions under conditions of coexistence of multivalent dissimilar metal ions has important theoretical significance and application value. Summary of the Invention

[0006] The purpose of this invention is to provide a method and application for the stepwise separation and enrichment of lithium ions in spodumene ore using fulvic acid. Specifically, it utilizes fulvic acid to selectively complex and capture impurity ions such as calcium, magnesium, aluminum, and iron, while simultaneously using polyaluminum chloride to synergistically flocculate and enrich lithium ions from the spodumene leachate. This method has significant advantages such as mild operating conditions, environmentally friendly reagents, high impurity removal efficiency, and low lithium loss rate. It has important theoretical significance and application value for promoting the green transformation of spodumene lithium extraction processes, and is particularly suitable for the production of battery-grade lithium carbonate and lithium hydroxide.

[0007] A method for the stepwise separation and enrichment of lithium ions in spodumene ore using humic acid includes the following steps:

[0008] (1) High-temperature transformation roasting

[0009] The spodumene ore is subjected to high-temperature transformation roasting to transform the α-spodumene crystal form into β-spodumene.

[0010] (2) Sulphation roasting

[0011] The transformed β-spodumene was mixed with sulfuric acid in a certain proportion and placed in a sulfation roasting furnace. The mixture was then sulfated and roasted at 230-280℃ for 10-80 min to obtain the sulfation roasting product.

[0012] (3) Water leaching

[0013] The sulfation-calcined product was added to deionized water and leached at 25-65℃ for 15-65 min to allow lithium sulfate to fully dissolve and enter the liquid phase, yielding a Li-containing product. + and including Al 3+ Fe 3+ Mg 2+ Ca 2+ Lithium leaching solution containing polyvalent impurity ions;

[0014] (4) Preliminary impurity removal by stepwise pH adjustment

[0015] Adjust the pH of the lithium leaching solution to 6.5 to allow Al to... 3+ and Fe 3+ Initial precipitation is achieved by adding 0.2-0.8‰ flocculant by mass of the solution to achieve preliminary solid-liquid separation; the pH of the filtrate is adjusted to 12 to allow Mg to settle. 2+ and Ca 2+ A hydroxide precipitate is formed, which is then separated by filtration.

[0016] (5) Selective complexation of fulvic acid for deep impurity removal

[0017] Add fulvic acid to the filtrate after preliminary impurity removal at a concentration of 0.25-3 g / L, adjust the pH of the system to 3-11, and react at 15-75℃ for 30-180 min to obtain the solution after complexation reaction.

[0018] (6) Polyaluminum chloride synergistic flocculation

[0019] Add polyaluminum chloride solution to the solution after complexation reaction; the polyaluminum chloride solution has a pH range of 2-7, a polyaluminum chloride concentration of 10%, and a volume ratio of polyaluminum chloride solution to the solution after complexation reaction of 1:5-3:5. Stir and mix, and flocculate to obtain a flocculated mixed system.

[0020] (7) Solid-liquid separation

[0021] The flocculated mixture was subjected to solid-liquid separation to obtain purified lithium-containing filtrate.

[0022] Further, in step (1), the high-temperature transformation roasting process is to place the product in a roasting furnace, set the heating rate to 5-15°C / min, and keep it at 900-1050°C for 15-45min.

[0023] Furthermore, in step (2), the amount of sulfuric acid used is 1.1-1.5 times the theoretical amount.

[0024] Further, in step (3), the sulfation roasting product is added to deionized water at a liquid-to-solid ratio of 1.0:1 to 4.0:1.

[0025] Furthermore, in step (4), NaOH is added to adjust the pH value to alkaline, and the flocculant is an anionic polyacrylamide flocculant.

[0026] Further, in step (4), the anionic polyacrylamide flocculant is a polyacrylamide-sodium acrylate copolymer.

[0027] Furthermore, the polyaluminum chloride solution has a pH range of 2-7 and a polyaluminum chloride concentration of 10%.

[0028] Further, in step (6), the flocculation process is carried out by rapidly stirring at 150-200 r / min for 1-2 min to fully mix the flocculant with the solution; then the stirring is adjusted to 40-60 r / min for 10-15 min to promote floc growth; finally, stirring is stopped and the mixture is allowed to settle.

[0029] Furthermore, it also includes a post-processing step, in which the purified lithium-containing filtrate is concentrated by evaporation at 60°C, cooled to precipitate sodium, and then carbonized and thermally decomposed to obtain lithium carbonate product.

[0030] Another objective of this application is to provide a method for the stepwise separation and enrichment of lithium ions in spodumene ore using humic acid, and its application in the process of separating and enriching lithium ions in spodumene ore.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. Excellent impurity removal effect and low lithium loss rate: This invention utilizes fulvic acid to remove Fe 3+ Mg 2+ Ca 2+ Selective complexation of Li + The ability to complex with extremely weak properties was achieved under optimized conditions, thus realizing Al 3+ Removal rate up to 98.97%, Fe 3+ Removal rate up to 99.19%, Mg 2+Removal rate up to 99.02%, Ca 2+ With a removal rate of up to 99.39% and a lithium loss of less than 5%, it is significantly better than the traditional chemical precipitation method. At the same time, it ensures that lithium is basically retained in the liquid phase during the impurity removal process, effectively solving the problem of serious lithium entrainment loss in the traditional neutralization and impurity removal process.

[0033] 2. Two-stage regulation of stepwise pH control and fulvic acid complexation, resulting in high impurity removal efficiency: It fully utilizes the differences in solubility products of different metal ions and hydroxides to remove iron, magnesium, calcium, and aluminum impurities. The remaining impurities then combine with fulvic acid to form colloidal substances, resulting in better subsequent flocculation and precipitation effects. The impurity removal efficiency is far higher than that of single precipitation methods. At the same time, this application uses anionic polyacrylamide flocculant to improve sedimentation and filtration performance, thereby comprehensively reducing lithium ion adsorption and entrainment losses during the impurity removal process.

[0034] 3. Green and environmentally friendly reagent: Fulvic acid is a natural organic polymer with wide sources and is biodegradable. Compared with traditional chemical reagents, it is more environmentally friendly and in line with the development direction of green chemical industry.

[0035] 4. Excellent solid-liquid separation effect: Polyaluminum chloride and fulvic acid form an "aluminum-humic" composite network and clustered dense flocs through the synergistic effect of charge neutralization and adsorption bridging, which have excellent settling performance and achieve efficient solid-liquid separation.

[0036] 5. High product purity: The lithium carbonate product obtained by post-processing the purified lithium-containing filtrate has a pure phase and regular crystal shape. XRD analysis confirms that there are no obvious impurity phases, which can meet the quality requirements of battery-grade lithium carbonate.

[0037] 6. High degree of process integration: This invention organically integrates unit operations such as high-temperature transformation roasting, sulfation roasting, water leaching, stepwise pH control for impurity removal, selective complexation of fulvic acid, synergistic flocculation of polyaluminum chloride, and lithium carbonate preparation, forming a complete cascade separation, enrichment and lithium extraction process, which is convenient for industrial promotion and application. Attached Figure Description

[0038] Figure 1 The FTIR infrared spectrum of the humic acid complex described in Example 1;

[0039] Figure 2 The XRD pattern of the lithium carbonate product described in Example 1;

[0040] Figure 3 The diagram shows the flocculation effect of adding polyacrylamide flocculant as described in Comparative Example 3. a is the complexing liquid; b is the solution with added polyacrylamide flocculant. Detailed Implementation

[0041] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings, but the present invention is not limited to the following embodiments.

[0042] Example 1

[0043] (1) High-temperature transformation roasting

[0044] Take 200g of spodumene ore sample, place it in a muffle furnace, heat it to 1050℃ at a heating rate of 5℃ / min, hold it at that temperature for 30min, and then let it cool naturally to room temperature to obtain the transformed β-spodumene.

[0045] High-temperature conversion is a key pre-step in the sulfuric acid process for lithium extraction. β-spodumene has higher chemical reactivity, which is beneficial for the efficient leaching of lithium during the subsequent sulfation roasting process.

[0046] (2) Sulphation roasting

[0047] The transformed spodumene was mixed with concentrated sulfuric acid in a specific ratio (the amount of sulfuric acid was 1.2 times the theoretical amount; in this embodiment, the transformed spodumene and concentrated sulfuric acid were mixed at a mass ratio of 1:1.12), and placed in a calcining furnace. The temperature was increased to 250°C at a rate of 5°C / min and held for 70 min to obtain the sulfation calcination product. Under these conditions, the lithium in β-spodumene reacts with sulfuric acid to form soluble lithium sulfate, while the silicon component is converted into an insoluble substance.

[0048] (3) Water leaching

[0049] The sulfation-calcined product was added to deionized water at a liquid-to-solid ratio of 3.5:1, and leaching was carried out at 25°C and 200 rpm for 50 min with stirring. After leaching, the mixture was filtered to obtain a lithium leaching solution containing impurities. ICP-OES analysis showed that the leaching solution contained Li... + The concentration was 302.46 mg / L, Al 3+ The concentration was 59.37 mg / L, Fe 3+ The concentration was 32.28 mg / L, Mg 2+ The concentration was 212.66 mg / L, Ca 2+ The concentration was 924.99 mg / L.

[0050] (4) Preliminary impurity removal by stepwise pH adjustment

[0051] Under stirring conditions, the lithium leaching solution was adjusted to a pH of 6.5 to allow Fe... 3+ And Al 3+ Preliminary precipitation, followed by Al separation 3 + Add 0.5‰ anionic polyacrylamide flocculant to achieve preliminary solid-liquid separation. Slowly add NaOH solution (5 mol / L concentration) to the lithium leachate, continuously adjusting the pH from 6.5 to 12, so that Mg... 2+ Ca 2+Preliminary precipitation occurs sequentially. The mixture is then filtered and the filtrate is collected. Al in the filtrate... 3+ The concentration was 6.63 mg / L, Fe 3+ The concentration was 1.48 mg / L, Mg 2+ The concentration was 65.25 mg / L, Ca 2+ The concentration was 243.16 mg / L.

[0052] (5) Selective complexation of fulvic acid for deep impurity removal

[0053] Fulvic acid (FA) was added to the filtrate after preliminary impurity removal at a concentration of 1.65 g / L. Under stirring conditions, the pH of the system was adjusted to 10 with NaOH solution (concentration 1 mol / L), the temperature was raised to 45℃, and the reaction was maintained at this temperature for 135 min to obtain the solution after the fulvic acid complexation reaction.

[0054] Under these conditions, the carboxyl group (-COOH) and phenolic hydroxyl group (-OH) in the fulvic acid molecule serve as the core active sites for the complexation reaction, coordinating with Fe in a bridging coordination mode. 3+ Mg 2+ Ca 2+ Selective formation of stable coordination structures, while Li + Due to differences in charge density and ionic radius, it is difficult for lithium to form stable complexes with fulvic acid, thus achieving efficient and selective separation of lithium from impurity ions. FTIR and XPS were used to analyze the structural changes of fulvic acid before and after complexation. Figure 1 FTIR spectra show that at 1595.11 cm⁻¹ -1 and 1416.70cm -1 The newly emerging strong absorption peaks correspond to the asymmetric and symmetric stretching vibrations of the carboxylate group -COO-, respectively, indicating that the free carboxyl group in the fulvic acid molecule has undergone deprotonation and coordinated with the metal ion as a core binding site. Simultaneously, the CO stretching vibration peak at 1098.98 cm⁻¹... -1 A significant redshift was observed at 1035.44 cm. -1 Combined with 3286.35cm -1 The presence of a broad -OH peak and a low-frequency region at 590.63 cm⁻¹ -1 The generation of MO bond vibration signals jointly confirmed that the phenolic hydroxyl group also participated in the complexation process. XPS analysis further confirmed that the carboxylate group and the phenolic hydroxyl group formed a stable coordination structure with the metal ion in a bridging coordination mode.

[0055] (6) Polyaluminum chloride synergistic flocculation

[0056] Add 20 mL of polyaluminum chloride (PAC) solution to 50 mL of solution with pH adjusted to 7 after the complexation reaction, stir, and allow to settle. Dense, clustered flocs form in the solution, settling rapidly. PAC reduces the surface charge of the fulvic acid-metal ion complex through charge neutralization, and simultaneously connects the dispersed complex particles through adsorption bridging, forming an "aluminum-humic" complex network with fulvic acid. This promotes the aggregation of the complex into dense, clustered flocs, creating favorable conditions for subsequent solid-liquid separation.

[0057] (7) Solid-liquid separation

[0058] The dense, amorphous composite flocs formed by polyaluminum chloride and humic acid exhibit excellent settling properties, enabling efficient solid-liquid separation. The flocculated mixture was then separated by vacuum filtration to obtain a purified lithium-containing filtrate. The filtrate was clear and transparent, with a significantly reduced content of impurity ions. ICP-OES analysis of the sample revealed that Al... 3+ The concentration was 0.61 mg / L, Fe 3+ The concentration is 0.26 mg / L, Mg 2+ The concentration was 2.08 mg / L, Ca 2+ The concentration was 5.63 mg / L. After a two-step impurity removal process, Al... 3+ The removal rate reached 98.97%, Fe 3+ The removal rate was 99.19%, Mg 2+ The removal rate reached 99.02%, Ca 2+ The removal rate reached 99.39%, Li + The loss rate was 3.82%.

[0059] (8) Post-processing to prepare lithium carbonate

[0060] The purified lithium-containing filtrate was placed in an evaporator and concentrated at 60°C. The concentrate was cooled to room temperature, precipitating sodium salt (mainly Na₂SO₄), which was then separated by filtration. CO₂ gas was passed through the sodium-removed concentrate to initiate a carbonation reaction, generating a lithium bicarbonate solution. The lithium bicarbonate solution was heated to 90°C for thermal decomposition, precipitating lithium carbonate. The precipitate was then filtered, washed, and dried to obtain the lithium carbonate product. Figure 2 As shown, XRD analysis revealed no obvious diffraction peaks of impurity phases, indicating that the product phase was pure Li2CO3 without any impurity phases. The purity was found to be higher than 99.5% by acid-base titration. SEM observation showed that the product exhibited rod-shaped and short columnar crystal forms.

[0061] Example 2

[0062] The difference between this embodiment and Example 1 is that the amount of fulvic acid added is 2.25 g / L, pH=9, temperature is 65℃, and reaction time is 105 min; other conditions are the same as in Example 1. The results show that Al3+ The removal rate reached 98.05%, Fe 3+ The removal rate reached 98.81%, Mg 2+ The removal rate reached 98.90%, Ca 2+ The removal rate reached 99.13%, Li + The loss rate was 4.25%.

[0063] Example 3

[0064] The difference between this embodiment and Example 1 is that the amount of fulvic acid added is 1.5 g / L, pH=7, temperature is 50℃, and reaction time is 165 min; other conditions are the same as in Example 1. The results show that Al 3+ The removal rate reached 98.16%, Fe 3+ The removal rate reached 98.85%, Mg 2+ The removal rate reached 97.76%, Ca 2+ The removal rate reached 97.92%, Li + The loss rate was 4.88%.

[0065] Comparative Example 1

[0066] The traditional chemical precipitation method was used for impurity removal: lime milk was added to the lithium leaching solution to adjust the pH to 10.5-11.0, so that Mg... 2+ Ca 2+ It precipitated as a hydroxide under the same conditions as in Example 1. The results showed that Mg... 2+ The removal rate is approximately 85%, Ca 2+ The removal rate is approximately 70%, which is far lower than the removal effect of the embodiments of the present invention, and the lithium entrainment loss rate is as high as 15-20%.

[0067] Comparative Example 2

[0068] The difference between this embodiment and Embodiment 1 is that in the stepwise pH control preliminary impurity removal step, during the precipitation and separation of Al... 3+ When dealing with iron ions, no 0.5‰ anionic polyacrylamide flocculant was added, and other conditions were the same as in Example 1. The results showed that Al... 3+ The removal rate reached 98.73%, Fe 3+ The removal rate was 99.10%, Mg 2+ The removal rate reached 98.96%, Ca 2+ The removal rate reached 99.38%, Li + The loss rate was 8.67%.

[0069] This application uses anionic polyacrylamide flocculant, unlike nonionic or cationic polyacrylamide. At around pH 6.5, aluminum ions in the solution mainly form positively charged aluminum hydroxide (Al(OH)3) colloidal particles, which is the fundamental reason for its strong adsorption capacity and difficulty in filtration. In this embodiment, anionic polyacrylamide is added. Through bridging, the fine aluminum hydroxide colloids are linked into larger flocs, reducing the adsorption specific surface area. Simultaneously, the anionic polyacrylamide neutralizes the positively charged aluminum hydroxide colloids, reducing electrostatic repulsion between colloids. These two effects result in denser and more rigid flocs formed from aluminum and iron colloidal precipitates during filtration, significantly improving filter cake permeability and filterability, thereby significantly reducing the physical encapsulation, entrainment, and adsorption of lithium ions, ultimately reducing lithium loss in the impurity removal process. In an environment of pH 6.5, nonionic or cationic polyacrylamide generally has lower flocculation efficiency and floc density compared to anionic polyacrylamide flocculants for strongly charged aluminum hydroxide colloids.

[0070] Comparative Example 3

[0071] This comparative example used PAM flocculation after fulvic acid complexation, with other experimental procedures remaining unchanged. 100 mL of the leachate containing the fulvic acid complex was measured and placed in a beaker. An appropriate amount of PAM solution was added to the leachate, and the mixture was slowly stirred to ensure full contact between the fulvic acid-metal complex colloids in the water sample. The mixture was then allowed to stand for 1 hour to allow the flocs to separate from the supernatant. Figure 3 As shown, by comparing the changes in the leachate before and after the addition of PAM, it can be seen that flocs were formed in the solution after the addition of PAM flocculant, indicating that some fulvic acid complexes were effectively flocculated and precipitated. After standing for 1 hour, a clear supernatant was obtained by centrifugation and filtration. However, during the subsequent evaporation and concentration process, viscous substances appeared in the concentrate, indicating that PAM flocculant still remained in the filtered supernatant, resulting in unsatisfactory flocculation and limited separation efficiency. Therefore, PAM was not selected as the flocculant in this study.

[0072] Comparative Example 4

[0073] This study investigated the effect of different polyaluminum chloride (PAC) dosages on flocculation. Too low a dosage resulted in incomplete flocculation, while too high a dosage could lead to restabilization of the colloids (particles regaining a positive charge and becoming suspended), thus reducing treatment effectiveness and increasing the risk of aluminum residue. To examine the effect of PAC dosage on the flocculation effect of the leachate, 50 mL of a fulvic acid complex solution with a pH of 7.0 was measured and placed in three identical beakers. 10, 20, and 30 mL of 10% PAC solution were added sequentially. The beakers were placed on a magnetic stirrer and first stirred rapidly at 150-200 rpm for 1-2 minutes to ensure thorough mixing of the flocculant and solution. Then, the stirring speed was reduced to 40-60 rpm for 10-15 minutes to promote floc growth. Finally, stirring was stopped, and the mixture was allowed to settle. Observe the morphology and settling properties of the flocs in each beaker, compare the changes in floc size, density, settling speed, clarity and color of the supernatant, and determine the optimal dosage of polyaluminum chloride based on the flocculation effect.

[0074] Comparative Examples 3 and 4 explored the effects of different flocculants and different flocculant dosages on sedimentation performance. This application improved sedimentation and filtration performance by adding 0.2-0.8‰ anionic polyacrylamide flocculant, thereby comprehensively reducing lithium ion adsorption and entrainment losses during the impurity removal process. Other flocculants did not have ideal effects.

[0075] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for the stepwise separation and enrichment of lithium ions in spodumene ore using humic acid, characterized in that, Includes the following steps: (1) High-temperature transformation roasting The spodumene ore is subjected to high-temperature transformation roasting to transform the α-spodumene crystal form into β-spodumene. (2) Sulphation roasting The transformed β-spodumene was mixed with sulfuric acid in a certain proportion and placed in a sulfation roasting furnace. The mixture was then sulfated and roasted at 230-280℃ for 10-80 min to obtain the sulfation roasting product. (3) Water leaching The sulfation-calcined product was added to deionized water and leached at 25-65℃ for 15-65 min to allow lithium sulfate to fully dissolve and enter the liquid phase, yielding a Li-containing product. + and including Al 3+ Fe 3+ Mg 2+ Ca 2+ Lithium leaching solution containing polyvalent impurity ions; (4) Preliminary impurity removal by stepwise pH adjustment Adjust the pH of the lithium leaching solution to 6.5 to allow Al to... 3+ and Fe 3+ Initial precipitation is achieved by adding 0.2-0.8‰ flocculant by mass of the solution to achieve preliminary solid-liquid separation; the pH of the filtrate is adjusted to 12 to allow Mg to settle. 2+ and Ca 2+ A hydroxide precipitate is formed, which is then separated by filtration. (5) Selective complexation of fulvic acid for deep impurity removal Add fulvic acid to the filtrate after preliminary impurity removal at a concentration of 0.25-3 g / L, adjust the pH of the system to 3-11, and react at 15-75℃ for 30-180 min to obtain the solution after complexation reaction. (6) Polyaluminum chloride synergistic flocculation Add polyaluminum chloride solution to the solution after complexation reaction; the volume ratio of polyaluminum chloride solution to the solution after complexation reaction is 1:5-3:5, stir and mix, and flocculate to obtain a flocculated mixed system. (7) Solid-liquid separation The flocculated mixture was subjected to solid-liquid separation to obtain purified lithium-containing filtrate.

2. The method for the stepwise separation and enrichment of lithium ions in spodumene ore using humic acid according to claim 1, characterized in that, In step (1), the high-temperature transformation roasting process is to place the product in a roasting furnace, set the heating rate to 5-15°C / min, and keep it at 900-1050°C for 15-45min.

3. The method for the stepwise separation and enrichment of lithium ions in spodumene ore using humic acid according to claim 1, characterized in that, In step (2), the amount of sulfuric acid used is 1.1-1.5 times the theoretical amount.

4. The method for the stepwise separation and enrichment of lithium ions in spodumene ore using humic acid according to claim 1, characterized in that, In step (3), the sulfation roasting product is added to deionized water at a liquid-solid ratio of 1.0:1 to 4.0:

1.

5. The method for the stepwise separation and enrichment of lithium ions in spodumene ore using humic acid according to claim 1, characterized in that, In step (4), NaOH is added to adjust the pH value to alkaline, and the flocculant is an anionic polyacrylamide flocculant.

6. The method for the stepwise separation and enrichment of lithium ions in spodumene ore using humic acid according to claim 1, characterized in that, The anionic polyacrylamide flocculant is a polyacrylamide-sodium acrylate copolymer.

7. The method for the stepwise separation and enrichment of lithium ions in spodumene ore using humic acid according to claim 1, characterized in that, The polyaluminum chloride solution has a pH range of 2-7 and a polyaluminum chloride concentration of 10%.

8. The method for the stepwise separation and enrichment of lithium ions in spodumene ore using humic acid according to claim 1, characterized in that, In step (6), the flocculation process is carried out by stirring rapidly at 150-200 r / min for 1-2 min to fully mix the flocculant with the solution; then the stirring is adjusted to 40-60 r / min for 10-15 min to promote floc growth; finally, the stirring is stopped and the mixture is allowed to settle.

9. The method for the stepwise separation and enrichment of lithium ions in spodumene ore using humic acid according to claim 1, characterized in that, It also includes a post-processing step, in which the purified lithium-containing filtrate is concentrated by evaporation at 60°C, cooled to precipitate sodium, and then carbonized and thermally decomposed to obtain lithium carbonate product.

10. The application of the method for separating and enriching lithium ions in spodumene ore using humic acid in a stepwise manner according to claims 1-9 in the process of separating and enriching lithium ions in spodumene ore.

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