Method for synergistically and efficiently extracting lithium from clay type lithium ore clinker and waste lithium iron phosphate

Abstract

The invention relates to the technical field of extraction of lithium from clay type lithium ore and waste lithium iron phosphate, which comprises the following steps: crushing the clay type lithium ore, roasting, dynamically proportioning with the waste lithium iron phosphate to obtain a mixture with the lithium oxide grade of 0.9-1.2%, finely grinding the mixture, stirring and leaching by using dilute sulphuric acid, and finally oxidizing and removing impurities to obtain the clay type lithium ore and waste lithium iron phosphate. The lithium-containing purified liquid is obtained. According to the method, the clay type lithium ore is subjected to coarse crushing and then roasted to complete crystal form conversion, then the clay type lithium ore and the waste lithium iron phosphate are subjected to dynamic matching and mixing according to respective lithium oxide grades, clay type lithium ore coarse particle clinker is used as a rolling grinding medium for fine grinding, and mechanical force is used for inducing lithium iron phosphate amorphization and structural defects, so that the high-quality lithium iron phosphate is obtained. According to the method, the contact sites of the leaching agent are increased, the dynamic conditions of the leaching reaction are adjusted, and the precipitation reaction between impurity ions during leaching of the two materials is utilized, so that the high-lithium and low-impurity leaching solution is obtained, and the efficient extraction of lithium in the clay type lithium ore and the waste lithium iron phosphate under the conditions of low acid consumption and low energy consumption is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of clay-type lithium ore and waste lithium iron phosphate, and particularly relates to a method for synergistically and efficiently extracting lithium from clay-type lithium ore clinker and waste lithium iron phosphate. BACKGROUND

[0002] As a "new energy material in the 21st century", lithium is one of the "high-tech metals" with the fastest market demand growth, and plays an important role in many technology fields such as ceramics, medicine, aerospace, power batteries and the like. In recent years, along with the growth of new energy vehicle production, China has become the world's first lithium resource consumer, but the domestic lithium resources have "inherent deficiency", the salt lake lithium resources are rich but difficult to separate magnesium and lithium, the large-scale development is limited due to strict environmental protection requirements; the spodumene has low grade and poor mining conditions; the lepidolite has many associated elements and a complex refining process, and has great environmental pressure. Therefore, it is urgent to find new lithium resources and new lithium resource development and utilization technologies to ensure the safe and stable supply of lithium resources in China and the sustainable development of the new energy industry.

[0003] Clay-type lithium ore has a wide distribution, easy to exploit, and has good development potential. However, the raw ore grade of clay-type lithium ore is low (<1%), and it is difficult to enrich like spodumene, lepidolite and other ores. At present, some people have carried out efficient lithium extraction research on clay-type lithium ore. For example, patent CN117327919B provides a method for extracting lithium from high-calcium clay-type lithium ore, which specifically includes leaching clay-type lithium ore with 0.63% Li2O content with 1 mol / L hydrochloric acid and then roasting, and then leaching the calcine with 3 mol / L sulfuric acid to obtain a lithium-rich liquor. The lithium leaching rate of this method is >95%; patent CN118724030A discloses a method for extracting lithium from carbonate clay-type lithium ore to prepare lithium carbonate, which specifically includes crushing, grinding, screening and roasting the carbonate clay-type lithium ore, obtaining the roasted clinker, and then acid leaching to obtain a lithium leaching solution. After two times of impurity removal, enrichment and lithium precipitation processes, a lithium carbonate product with a purity of more than 99.0% is finally obtained; patent CN117947286B discloses a method for adding concentrated sulfuric acid with a mass ratio of 1:0.5~1:1 to clay-type lithium ore, acidizing and roasting at 200℃~310℃ for 0.5h-3h, and then water leaching lithium. After solid-liquid separation, the filtrate is impurity-removed, neutralized and precipitated, and filtered to obtain lithium carbonate product and by-products such as alumina and ammonia gas; Wu Lin et al. prepared a mixed acid of sulfuric acid and phosphoric acid in a certain volume ratio in 2016, and carried out a mixed acid leaching verification test on clay-type lithium ore under the conditions of leaching temperature 100℃, leaching time 3h, solid-liquid ratio 1:4 and stirring intensity 300r / min. Finally, the lithium leaching rate can reach 96.67%, but a large amount of aluminum elements are also leached out, with a leaching rate of 88.35%. Although there are some lithium extraction processes for clay-type lithium ore that use sodium salt, sulfuric acid salt and other additives after roasting and water leaching, or blank roasting and using acid with a concentration of >1.5 mol / L for leaching, the lithium leaching rate can reach more than 90%, but a large amount of acid, roasting additives and impurity removal reagents are used in the lithium extraction process. These processes still have problems such as a large amount of impurity elements being leached out, high lithium extraction cost and large fluctuation of lithium extraction process parameters when dealing with clay-type lithium ore with low lithium oxide grade and large content fluctuation in China, which limits the development and utilization process of clay-type lithium ore.

[0004] According to statistics, the loading quantity of lithium iron phosphate power battery accounts for more than 80% of the total loading quantity of new energy vehicle industry, and is the most important battery type in new energy vehicle industry. Therefore, these lithium iron phosphate batteries will become one of the important "urban mine" resources after being retired. At present, many methods for extracting lithium from lithium iron phosphate have been developed. For example, in the patent CN117566709A, waste lithium iron phosphate battery material, 30% hydrogen peroxide and sulfuric acid are mixed and stirred to obtain a leaching solution with a lithium leaching rate of 99% and an aluminum leaching rate of 75%; in the patent CN115287469A, 30% sulfuric acid is used for secondary acid leaching of lithium iron phosphate black powder to recover lithium and phosphorus iron elements; in the patent CN116750740A, waste lithium iron phosphate powder is calcined in a non-oxidizing atmosphere to obtain calcined powder, then pure water is added to the calcined powder for slurry preparation, mixed acid is added to adjust the pH value to 2 for leaching, and the leaching solution and leaching residue are obtained by filtration; and in the patent CN117712531A, a method for recycling waste lithium iron phosphate battery is reported, in which lithium iron phosphate is calcined at 200℃-800℃ in air atmosphere for 1 h, then calcined in reducing atmosphere for 2 h-4 h, and finally leached with 2 mol / L sulfuric acid, with the leaching rates of Li, Fe and P all being >99%. From the above methods, it can be seen that lithium iron phosphate is a very valuable lithium resource. Although the lithium oxide grade in lithium iron phosphate is high, with a content of about 5%-9.5%, direct leaching consumes a lot of acid, and a multi-stage purification and impurity removal process is required to remove Fe, P and other impurities in the leaching solution, which is complex. Selective leaching requires a large amount of oxidizing agent to achieve selective leaching of lithium, which is high in cost.

[0005] Therefore, both clay-type lithium ore clinker and waste lithium iron phosphate need more simple, efficient and low-cost lithium extraction methods to promote the development and utilization of resources and the industrialization process. SUMMARY

[0006] The present application aims to overcome the shortcomings of the prior art and provide a method for synergistically and efficiently extracting lithium from clay-type lithium ore clinker and waste lithium iron phosphate. The method completes the crystal type conversion by calcining the clay-type lithium ore after coarse crushing, then mixes it with waste lithium iron phosphate, dynamically adjusts the ratio, fixes the lithium oxide grade, and activates it by fine grinding to adjust the leaching reaction kinetics. By utilizing the precipitation reaction between impurity ions during leaching of the two materials, a high-lithium and low-impurity leaching solution is obtained, realizing efficient extraction of lithium from clay-type lithium ore and waste lithium iron phosphate under low acid consumption and low energy consumption conditions.

[0007] The purpose of the present application is achieved by the following technical solutions: On the one hand, the present application provides a method for synergistically and efficiently extracting lithium from clay-type lithium ore clinker and waste lithium iron phosphate, comprising the following steps: S1. Coarse crushing: crushing the clay-type lithium ore to -3 mm to obtain clay-type lithium ore coarse particle material; S2. Roasting: roasting the coarse-grained clay-type lithium ore material to obtain coarse-grained clay-type lithium ore clinker; S3. Dynamic proportioning and mixing: dynamically proportioning and mixing the coarse-grained clay-type lithium ore clinker and the waste lithium iron phosphate according to the respective lithium oxide grades to obtain a mixture with a lithium oxide grade of 0.9% to 1.2%; S4. Fine grinding and activation: fine grinding the mixture to 60% to 90% passing -200 mesh to obtain a fine-ground mixture; S5. Dilute acid leaching: adding the fine-ground mixture into a dilute sulfuric acid solution for stirring leaching and first filtration to obtain a lithium-containing leach liquor; S6. Oxidation and impurity removal: adding an oxidizing agent into the lithium-containing leach liquor for oxidation reaction, then adding a pH adjusting agent to adjust the pH value to 6.5 to 7 and performing aging and second filtration to obtain a lithium-containing purified liquor.

[0008] Further, the content of Li2O in the clay-type lithium ore is 0.25% to 0.95%, the content of Al2O3 is 18% to 60%, Li2O / Al2O3 < 0.053, and the content of TFe is 1.2% to 4.2%.

[0009] Further, the content of Li2O in the waste lithium iron phosphate is 5% to 9.5%, the content of TFe is 19% to 36%, and the content of P2O5 is 20% to 45%.

[0010] Further, in S2, the temperature of the roasting is 400°C to 800°C, and the time of the roasting is 30 min to 120 min.

[0011] Further, in S5, the concentration of the dilute sulfuric acid solution is 0.3 mol / L to 1.0 mol / L, and the liquid-solid ratio of the dilute sulfuric acid solution to the fine-ground mixture is 2 L / kg to 6 L / kg.

[0012] Further, the temperature of the stirring leaching is 70°C to 95°C, and the time of the stirring leaching is 0.5 h to 2 h.

[0013] Further, the oxidizing agent includes hydrogen peroxide.

[0014] Illustratively, the amount of the oxidizing agent is 1.0 to 1.2 times the amount required for the complete oxidation of Fe 2+ 1.0 to 1.2 times the amount required for the complete oxidation of Fe

[0015] Further, the pH adjusting agent includes sodium hydroxide.

[0016] Further, the temperature of the oxidation reaction is 20℃-95℃, and the time of the oxidation reaction is 20 min-60 min.

[0017] Further, the temperature of the aging is 80℃-95℃, and the time of the aging is 1 h-4 h.

[0018] In another aspect, the application provides the use of the above method in the preparation of a lithium product, which includes lithium carbonate.

[0019] Further, the step of preparing the lithium carbonate includes: After concentrating the lithium-containing purified solution, a saturated sodium carbonate solution with a lithium excess coefficient of 1.05-1.20 is added dropwise to the concentrated solution to precipitate lithium, followed by a third filtration, and the collected solids are washed and dried to obtain the lithium carbonate.

[0020] Further, the Li concentration in the concentrated solution is greater than 12 g / L.

[0021] Further, the feeding time of the saturated sodium carbonate solution is 0.5 h-2 h.

[0022] Further, the temperature of the lithium precipitation is 90℃-95℃, and the time of the lithium precipitation is 0.5 h-2 h.

[0023] In another aspect, the application provides the use of the above method in the extraction of lithium elements from clay-type lithium ore and waste lithium iron phosphate.

[0024] The principle of the application is: The application uses thermogravimetric-differential scanning calorimetry (TG-DSC) to characterize the thermal behavior of clay-type lithium ore, and draws a TG-DSC curve as shown in Figure 2 It is found that calcination in the temperature range of 400℃-800℃ can destroy the stability of the clay mineral structure in the clay-type lithium ore, causing the collapse of the layered structure, thereby converting the lithium elements in the clay mineral into an acid-soluble state and generating high-activity lithium-containing clay mineral coarse-grained clinker. Then, the coarse-grained clinker is mixed with waste lithium iron phosphate at a dynamic ratio of lithium oxide grade, so that the lithium oxide grade in the mixture is controlled at 0.9%-1.2%, and then the mixture is finely ground and activated. The mechanical force induces the amorphization and structural defects of the lithium iron phosphate, increases the contact sites of the leaching agent, and adjusts the kinetics of the leaching reaction.

[0025] In the leaching process, the early-stage lithium iron phosphate dissolves rapidly in the acid medium, simultaneously releasing a large amount of Li + , Fe 2+ and PO4 3- . In the later stage, PO4 3- and Al 3+Combined, AlPO4 is generated to fix Al in the solution. 3+ This promotes the forward shift of the leaching reaction equilibrium and accelerates the Li + This process releases impurities such as aluminum and phosphorus in the leachate, effectively simplifying subsequent impurity removal procedures.

[0026] In the oxidation and impurity removal process, the leachate contains a large amount of Li. + Fe 2+ And a very small amount of PO4 3- By adding oxidizing agents such as hydrogen peroxide, Fe... 2+ Oxidized to Fe 3+ (2Fe) 2+ +H₂O₂ + 2H₂ + =2Fe 3+ After (+2H2O), Fe 3+ With PO4 3- FePO4 precipitate (Fe) is formed 3+ +PO4 3- =FePO4↓), then use sodium hydroxide to adjust the pH to 6.0~7.5 to further remove Fe. 3+ (Fe) 3+ +OH - =Fe(OH)3), which removes impurities such as Fe and P from the solution. The purified solution obtained after oxidation mainly contains Li. + Na + Two cations and SO4 2- An anion with a simple solution composition can be directly incorporated into the sodium carbonate precipitation process for preparing lithium carbonate products after concentration. This shortens the process flow, reduces reagent usage, and improves the economic efficiency and environmental friendliness of the process, enabling the efficient extraction and utilization of lithium from clay-type lithium ores and waste lithium iron phosphate.

[0027] The beneficial effects of this invention are: 1. This application utilizes waste lithium iron phosphate as a supplementary lithium source, dynamically adjusting the ratio of clay-type lithium ore to waste lithium iron phosphate to overcome the problems of low lithium oxide grade, large content fluctuations, and poor economic efficiency in the development and utilization of clay-type lithium ore; by coarsely crushing and roasting the clay-type lithium ore and then mixing it with waste lithium iron phosphate for fine grinding and activation, the single furnace processing capacity of roasting is increased; using coarse clay-type lithium ore clinker as the rolling grinding medium avoids the easy agglomeration of fine lithium iron phosphate powder and improves grinding efficiency; and by using mechanical force to induce amorphization and structural defects in lithium iron phosphate, the contact points of the leaching agent are increased, improving subsequent leaching conditions.

[0028] 2. This application utilizes Al in clay-type lithium ore. 3+ With PO4 in waste lithium iron phosphate 3-The formation of precipitates promotes a positive shift in the leaching reaction equilibrium, improving lithium leaching efficiency while also achieving synergistic fixation of aluminum and phosphorus impurities. This overcomes the problem of small amounts of Li in the leaching solution from clay-type lithium ores when leaching alone. + With a large amount of Al 3+ Impurities, high impurity removal costs, low lithium recovery rates, and poor economic efficiency are problems. Subsequent addition of hydrogen peroxide and pH adjustment to the leachate promotes the formation of iron phosphate and iron hydroxide precipitates, thus solving the problem of Fe in the leachate during lithium extraction from waste lithium iron phosphate alone. 2+ PO4 3- The problem of high impurity content and high phosphorus content in the effluent is difficult to treat.

[0029] 3. This application innovatively solves the problems of high acid consumption and high energy consumption in the lithium extraction process of clay-type lithium ore by synergistic utilization of clay-type lithium ore and waste lithium iron phosphate. This makes clay-type lithium ore with a lithium oxide grade of only 0.25%~0.95% also have good economic development value. This application adopts a low acid (H2SO4 concentration 0.3 mol / L~1.0 mol / L) synergistic leaching process, combined with precise control of oxidant and pH adjuster, to achieve efficient lithium extraction (recovery rate >90%) and synergistic fixation of impurities. The tailings (mainly containing Al and Si) can be directly used as cement raw materials or engineering backfill materials, providing an efficient lithium extraction path for clay-type lithium ore and waste lithium iron phosphate. Attached Figure Description

[0030] Figure 1 This is a process flow diagram of the synergistic and efficient lithium extraction process from clay-type lithium ore clinker and waste lithium iron phosphate in this application. Figure 2 The results are from TG-DSC analysis of clay-type lithium ore. Detailed Implementation

[0031] The technical solution of this application is described in further detail below with reference to the accompanying drawings, but the scope of protection of this invention is not limited to the following description.

[0032] Example 1 The raw materials are: clay-type lithium ore from a certain region, with a Li2O content of 0.63%, an Al2O3 content of 20.14%, and a TFe content of 4.13%; and waste lithium iron phosphate powder recovered from a certain factory, with a Li2O content of 8.59%, a TFe content of 34.58%, and a P2O5 content of 44.05%.

[0033] Lithium extraction can be achieved by co-extracting lithium from clay-type lithium clinker and waste lithium iron phosphate using the following steps: 1. Coarse crushing: Clay-type lithium ore is crushed to -3 mm (70%) to obtain coarse clay-type lithium ore raw material; 2. Calcination: 200 g of the coarse clay-type lithium ore raw material was calcined at 600℃ for 90 min to obtain 180.8 g of coarse clay-type lithium ore clinker; 3. Dynamic proportioning and mixing: The coarse-particle clinker of clay-type lithium ore is mixed with the recovered waste lithium iron phosphate at a mass ratio of 96.10:3.90 to obtain a mixture with a lithium oxide grade of 1%; 4. Fine grinding and activation: The mixture is finely ground to -200 mesh (60%) to obtain a finely ground mixture; 5. Dilute acid leaching: 50 g of the finely ground mixture was added to a 0.3 mol / L dilute sulfuric acid solution at a liquid-to-solid ratio of 4 L / kg. The mixture was stirred and leached at 95°C for 60 min. After filtration, a lithium-containing leachate and leaching residue were obtained. The lithium-containing leachate was tested and found to contain 1.09 g / L of Li, 4.48 g / L of Fe, 0.43 g / L of Al, and 0.08 g / L of P. Based on the lithium-containing leachate, the leaching rates were 93.41% for Li, 31.22% for Fe, 1.52% for Al, and 4.27% for P. 6. Oxidation and impurity removal: 1 mL of hydrogen peroxide was added to the lithium-containing leachate and oxidized at 95°C for 20 min. Sodium hydroxide was then added to adjust the pH to 6.8. After aging for 1 h, the solution was filtered to obtain a purified lithium-containing solution. Testing revealed that the purified lithium-containing solution contained 1.14 g / L of Li, <0.01 g / L of Fe, <0.01 g / L of Al, and <0.01 g / L of P.

[0034] Example 2 The raw materials are: clay-type lithium ore from a certain region, with a Li2O content of 0.25%, an Al2O3 content of 40.04%, and a TFe content of 2.30%; and waste lithium iron phosphate powder recycled from a certain factory, with a Li2O content of 9.47%, a TFe content of 35.40%, and a P2O5 content of 44.98%.

[0035] Lithium extraction can be achieved by co-extracting lithium from clay-type lithium clinker and waste lithium iron phosphate using the following steps: 1. Coarse crushing: Clay-type lithium ore is crushed to -3 mm (70%) to obtain coarse clay-type lithium ore raw material; 2. Calcination: 200 g of the coarse clay-type lithium ore raw material was calcined at 800℃ for 120 min to obtain 177.4 g of coarse clay-type lithium ore clinker; 3. Dynamic proportioning and mixing: The coarse-particle clinker of clay-type lithium ore is mixed with the recovered waste lithium iron phosphate at a mass ratio of 93.30:6.70 to obtain a mixture with a lithium oxide grade of 0.9%; 4. Fine grinding and activation: The mixture is finely ground to a density of -200 mesh (70%) to obtain a finely ground mixture; 5. Dilute acid leaching: 50 g of the finely ground mixture was added to a 1.0 mol / L dilute sulfuric acid solution at a liquid-to-solid ratio of 2 L / kg. The mixture was stirred and leached at 80°C for 90 min. After filtration, a lithium-containing leachate and leaching residue were obtained. The lithium-containing leachate was tested and found to contain 1.97 g / L of Li, 8.95 g / L of Fe, 1.37 g / L of Al, and 0.32 g / L of P. Based on the lithium-containing leachate, the leaching rates were 94.49% for Li, 37.36% for Fe, 1.23% for Al, and 4.27% for P. 6. Oxidation and impurity removal: 1 mL of hydrogen peroxide was added to the lithium-containing leachate and oxidized at 80°C for 30 min. The temperature was then raised to 90°C, and sodium hydroxide was added to adjust the pH to 6.5. After aging for 2 h, the solution was filtered to obtain a lithium-containing purified solution. Testing revealed that the lithium-containing purified solution contained 2.14 g / L of Li, <0.01 g / L of Fe, and neither Al nor P was detected.

[0036] Example 3 The raw materials are: clay-type lithium ore from a certain region, with a Li2O content of 0.95%, an Al2O3 content of 18.01%, and a TFe content of 1.20%; and waste lithium iron phosphate powder recovered from a certain factory, with a Li2O content of 8.63%, a TFe content of 34.58%, and a P2O5 content of 44.05%.

[0037] Lithium extraction can be achieved by co-extracting lithium from clay-type lithium clinker and waste lithium iron phosphate using the following steps: 1. Coarse crushing: Clay-type lithium ore is crushed to -3 mm (70%) to obtain coarse clay-type lithium ore raw material; 2. Calcination: 200 g of the coarse clay-type lithium ore raw material was calcined at 600℃ for 30 min to obtain 182.3 g of coarse clay-type lithium ore clinker; 3. Dynamic proportioning and mixing: The coarse-particle clinker of clay-type lithium ore is mixed with the recovered waste lithium iron phosphate at a mass ratio of 97.90:2.10 to obtain a mixture with a lithium oxide grade of 1.2%; 4. Fine grinding and activation: The mixture is finely ground to a density of -200 mesh (70%) to obtain a finely ground mixture; 5. Dilute acid leaching: 50 g of the finely ground mixture was added to a 0.3 mol / L dilute sulfuric acid solution at a liquid-to-solid ratio of 6 L / kg. The mixture was stirred and leached at 95°C for 30 min. After filtration, a lithium-containing leachate and leaching residue were obtained. The lithium-containing leachate was tested and found to contain 0.86 g / L of Li, 1.13 g / L of Fe, 0.25 g / L of Al, and 0.03 g / L of P. Based on the lithium-containing leachate, the leaching rates were 92.43% for Li, 33.65% for Fe, 1.47% for Al, and 4.46% for P. 6. Oxidation and impurity removal: 0.5 mL of hydrogen peroxide was added to the lithium-containing leachate and oxidized at 50°C for 40 min. The temperature was then raised to 90°C, and sodium hydroxide was added to adjust the pH to 7.0. After aging for 4 h, the solution was filtered to obtain a purified lithium-containing solution. Testing revealed that the purified lithium-containing solution contained 0.92 g / L Li, <0.01 g / L Fe, <0.01 g / L Al, and <0.01 g / L P.

[0038] Example 4 The raw materials are: clay-type lithium ore from a certain region, with a Li2O content of 0.63%, an Al2O3 content of 20.14%, and a TFe content of 4.13%; and waste lithium iron phosphate powder recycled from a certain factory, with a Li2O content of 5.10%, a TFe content of 19.12%, and a P2O5 content of 20.32%.

[0039] Lithium extraction can be achieved by co-extracting lithium from clay-type lithium clinker and waste lithium iron phosphate using the following steps: 1. Coarse crushing: Clay-type lithium ore is crushed to -3 mm (70%) to obtain coarse clay-type lithium ore raw material; 2. Calcination: 200 g of the coarse clay-type lithium ore raw material was calcined at 400℃ for 120 min to obtain 182.4 g of coarse clay-type lithium ore clinker; 3. Dynamic proportioning and mixing: The coarse-particle clinker of clay-type lithium ore is mixed with the recovered waste lithium iron phosphate at a mass ratio of 96.10:3.90 to obtain a mixture with a lithium oxide grade of 1.0%; 4. Fine grinding and activation: The mixture is finely ground to a density of -200 mesh (90%) to obtain a finely ground mixture; 5. Dilute acid leaching: 50 g of the finely ground mixture was added to a 0.6 mol / L dilute sulfuric acid solution at a liquid-to-solid ratio of 6 L / kg. The mixture was stirred and leached at 70°C for 120 min. After filtration, a lithium-containing leachate and leaching residue were obtained. Analysis of the lithium-containing leachate revealed that the solution contained 0.70 g / L Li, 4.06 g / L Fe, 0.21 g / L Al, and 0.12 g / L P. Based on the lithium-containing leachate, the leaching rates were 92.94% for Li, 34.08% for Fe, 1.12% for Al, and 3.03% for P. 6. Oxidation and impurity removal: 1.2 mL of hydrogen peroxide was added to the lithium-containing leachate and oxidized at 20°C for 60 min. Then, the temperature was raised to 85°C and sodium hydroxide was added to adjust the pH to 7.0. After aging for 4 h, the solution was filtered to obtain a lithium-containing purified solution. The lithium-containing purified solution was found to contain 0.74 g / L of Li, <0.01 g / L of Fe, <0.01 g / L of Al, and <0.01 g / L of P.

[0040] Comparative Example 1 This comparative example uses the same clay-type lithium ore as in Example 1, and performs roasting and acid leaching to extract lithium without the addition of lithium iron phosphate. The specific steps include: 1. Grinding: Crush the clay-type lithium ore and then grind it to -200°C (70%) to obtain coarse clay-type lithium ore raw material; 2. Calcination: 200 g of the coarse clay-type lithium ore raw material was calcined at 600℃ for 90 min to obtain 181 g of coarse clay-type lithium ore clinker; 3. Stirred Leaching: 50 g of the clay-type lithium ore clinker was added to a 0.3 mol / L dilute sulfuric acid solution at a liquid-to-solid ratio of 4 L / kg. The solution was stirred and leached at 95°C for 60 min. After filtration, a lithium-containing leachate and leaching residue were obtained. The lithium-containing leachate was found to contain 0.38 g / L of Li and 2.52 g / L of Al. Based on the lithium-containing leachate, the Li leaching rate was 42.49%, and the Al leaching rate was 7.74%.

[0041] Compared with Example 1, the leaching rate of Li in Comparative Example 1 decreased by 50.92%, the leaching rate of Al increased by 6.22%, the lithium content in the lithium-containing leachate decreased by 1.87 times, and the aluminum impurity content increased by 4.86 times. This is because the absence of lithium iron phosphate to provide phosphate ions prevented aluminum in the solution from forming precipitates under weakly acidic conditions, thus limiting the forward leaching reaction and inhibiting lithium leaching. At the same time, the aluminum impurity in the solution increased significantly, increasing the subsequent impurity removal cost.

[0042] Comparative Example 2 This comparative example uses the same lithium iron phosphate as in Example 1, and performs oxidation and acid leaching to extract lithium without adding clay-type lithium ore. The specific steps include: 1. Grinding: The waste lithium iron phosphate is crushed and then finely ground to -200 mesh (70%) to obtain lithium iron phosphate powder; 2. Oxidative Leaching: 50 g of the lithium iron phosphate powder was added to a 0.3 mol / L dilute sulfuric acid solution at a liquid-to-solid ratio of 4 L / kg. The solution was stirred and leached at 95°C for 60 min. During the leaching process, a total of 20 mL of hydrogen peroxide was slowly added to control the leaching redox potential. After filtration, a lithium-containing leachate and leaching residue were obtained. The lithium-containing leachate was found to contain 5.86 g / L of Li, 0.41 g / L of Fe, and 0.11 g / L of P. Based on the lithium-containing leachate, the leaching rates were 58.73% for Li, 0.47% for Fe, and 0.23% for P.

[0043] Compared to Example 1, Comparative Example 2 showed a 34.68% decrease in Li leaching rate and lower leaching rates for impurities Fe and P. However, the liquid-to-solid ratio in Comparative Example 2 was relatively low, indicating that the lithium leaching effect was actually not good. The results suggest that the Al released during the leaching of clay-type lithium ore in Example 1... 3+ It replaced Fe in the oxidative acid leaching process. 3+ With PO4 in lithium iron phosphate 3- A stable precipitate was formed, which promoted the forward shift of the leaching reaction equilibrium and increased the lithium leaching rate.

[0044] Comparative Example 3 This comparative example uses the same lithium iron phosphate as in Example 1, and performs direct acid leaching for lithium extraction without adding clay-type lithium ore. The specific steps include: 1. Grinding: The waste lithium iron phosphate is crushed and then finely ground to -200 mesh (70%) to obtain lithium iron phosphate powder; 2. Leaching: Take 50 g of the lithium iron phosphate powder and add it to a 0.3 mol / L dilute sulfuric acid solution at a liquid-to-solid ratio of 10 L / kg. Leach at 95°C with stirring for 60 min, and filter to obtain a lithium-containing leachate and leaching residue. Analysis showed that the lithium-containing leachate contained 1.86 g / L of Li, 11.76 g / L of Fe, and 6.11 g / L of P. Based on the lithium-containing leachate, the leaching rate of Li was 46.61%, the leaching rate of Fe was 34.01%, and the leaching rate of P was 31.78%.

[0045] Compared to Example 1, in Comparative Example 3, when waste lithium iron phosphate was directly leached with dilute sulfuric acid, the liquid-to-solid ratio was increased to 10 L / kg to improve lithium extraction efficiency. However, the leaching rate of Li was only 44.84%, and the leaching rates of Fe and P were >30%. This indicates that the direct acid leaching method for extracting lithium from lithium iron phosphate was ineffective, resulting in significant waste of lithium resources. Furthermore, the large-scale leaching of iron and phosphorus led to a surge in subsequent impurity removal load. In addition, the high liquid-to-solid ratio not only failed to effectively improve lithium recovery efficiency but also increased acid consumption and waste liquid treatment costs. In contrast, Example 1, under dilute acid and low liquid-to-solid ratio conditions, significantly improved the lithium extraction efficiency from clay-type lithium ore and lithium iron phosphate, and achieved selective leaching of impurity elements such as aluminum and phosphorus, reducing impurity removal costs. This provides a feasible technical route for the synergistic resource utilization of clay-type lithium ore and waste lithium iron phosphate.

[0046] Experimental Example 1: Preparation of Lithium Carbonate Products The lithium-containing purification solution was prepared using step 1 of Example 1. The lithium-containing purification solution was then concentrated to a Li concentration of 17.52 g / L. A saturated sodium carbonate solution was added dropwise to the solution with an excess coefficient of 1.1 and a feeding time of 1 h. Lithium was then precipitated at 90 ℃ for 2 h. After the precipitation was completed, the solution was filtered to obtain the lithium precipitation mother liquor and the crude product. The crude product was washed and dried once to obtain the lithium carbonate product with a purity of ≥99.5%. The overall Li recovery rate of the entire process was >80%.

[0047] The above description is merely a preferred embodiment of this application. It should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or the technology or knowledge in related fields. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this invention should be within the protection scope of the appended claims.

Claims

1. A method for efficient lithium extraction by synergistic interaction between clay-type lithium ore clinker and waste lithium iron phosphate, characterized in that, Includes the following steps: S1. Coarse crushing: Clay-type lithium ore is crushed to -3 mm to obtain coarse-grained clay-type lithium ore material; S2. Calcination: The coarse clay-type lithium ore material is calcined to obtain coarse clay-type lithium ore clinker; S3. Dynamic proportioning and mixing: The coarse-particle clinker of clay-type lithium ore and waste lithium iron phosphate are dynamically proportioned and mixed according to their respective lithium oxide grades to obtain a mixture with a lithium oxide grade of 0.9% to 1.2%. S4. Fine grinding and activation: The mixture is finely ground to a density of 60% to 90% -200 mesh to obtain a finely ground mixture; S5. Dilute acid leaching: The finely ground mixture is added to a dilute sulfuric acid solution for stirring and leaching, followed by a first filtration, to obtain a lithium-containing leachate; S6. Oxidation and impurity removal: An oxidant is added to the lithium-containing leachate to carry out an oxidation reaction, and then a pH adjuster is added to adjust the pH value to 6.5~7. The solution is then aged and filtered a second time to obtain a lithium-containing purified solution.

2. The method according to claim 1, characterized in that, The clay-type lithium ore contains 0.25%~0.95% Li2O, 18%~60% Al2O3, with a Li2O / Al2O3 ratio <0.053 and a TFe content of 1.2%~4.2%. And / or, the waste lithium iron phosphate contains 5% to 9.5% Li2O, 19% to 36% TFe, and 20% to 45% P2O5.

3. The method according to claim 1, characterized in that, In S2, the calcination temperature is 400℃~800℃, and the calcination time is 30 min~120 min.

4. The method according to claim 1, characterized in that, In S5, the concentration of the dilute sulfuric acid solution is 0.3 mol / L to 1.0 mol / L, and the liquid-to-solid ratio of the dilute sulfuric acid solution to the finely ground mixture is 2 L / kg to 6 L / kg. And / or, the temperature of the stirring leaching is 70℃~95℃, and the stirring leaching time is 0.5 h~2 h.

5. The method according to claim 1, characterized in that, In S6, the oxidant includes hydrogen peroxide; And / or, in S6, the amount of oxidant used is such that the Fe in the lithium-containing leachate is reduced. 2+ The amount required for complete oxidation is 1.0 to 1.2 times. And / or, in S6, the pH adjuster includes sodium hydroxide; And / or, in S6, the temperature of the oxidation reaction is 20°C to 95°C, and the time of the oxidation reaction is 20 min to 60 min; And / or, in S6, the aging temperature is 80℃~95℃, and the aging time is 1 h~4 h.

6. The application of the method according to any one of claims 1 to 5 in the preparation of lithium products, characterized in that, The lithium products include lithium carbonate.

7. The application according to claim 6, characterized in that, The steps for preparing the lithium carbonate include: After concentrating the lithium-containing purified solution, a saturated sodium carbonate solution with a lithium excess coefficient of 1.05~1.20 is added dropwise to the concentrate to precipitate lithium. Then, a third filtration is performed, and the collected solid is washed and dried to obtain the lithium carbonate.

8. The application according to claim 7, characterized in that, The concentration of Li in the concentrate is greater than 12 g / L.

9. The application according to claim 7, characterized in that, The saturated sodium carbonate solution is added over a period of 0.5 h to 2 h. And / or, the lithium deposition temperature is 90℃~95℃, and the lithium deposition time is 0.5 h~2 h.

10. The application of the method according to any one of claims 1 to 5 in the extraction of lithium from clay-type lithium ore and / or waste lithium iron phosphate.

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