Synergistic roasting-selective lithium extraction method for clay type lithium ore and waste lithium iron phosphate

Abstract

The invention relates to the technical field of efficient lithium extraction of clay-type lithium ore and waste lithium iron phosphate, in particular to a method for collaborative roasting-selective lithium extraction of clay-type lithium ore and waste lithium iron phosphate, which comprises the following steps: respectively crushing and finely grinding clay-type lithium ore and waste lithium iron phosphate until-200 meshes account for 50-90%, dynamically proportioning and mixing to obtain a mixture with Li2O grade of 0.9-1.2%; and then carrying out mixed roasting, adding into a dilute sulphuric acid solution, and carrying out agitation leaching and filtering to obtain a lithium-containing leaching solution. According to the method, the thermodynamic complementation mechanism of the two materials is utilized, the roasting energy consumption is reduced, the double synergistic leaching mechanism is utilized, the leaching of lithium is enhanced, the content of impurities in the leaching solution is reduced, and the efficient selective leaching of the clay type lithium ore and the lithium in the waste lithium iron phosphate is realized.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of efficient lithium extraction from clay-type lithium ore and waste lithium iron phosphate, in particular to a method for selective lithium extraction through clay-type lithium ore and waste lithium iron phosphate synergistic roasting. BACKGROUND

[0002] With the development of science and technology, lithium has become one of the indispensable metal elements in modern industry. In recent years, with the rapid development of the new energy industry, the demand for lithium has surged, and traditional lithium ore resources (such as spodumene, lepidolite, and salt lake lithium) have been difficult to meet the growing demand for lithium. Therefore, new lithium resources need to be developed.

[0003] Clay-type lithium ore is widely distributed and easy to mine, and is a very potential lithium resource. However, due to the low grade of the raw ore (<1%) of clay-type lithium ore, lithium elements are mainly present in clay minerals such as kaolinite, lithium chlorite, and illite, making it difficult to concentrate and enrich. In addition, when extracting lithium from clay-type lithium ore, a large amount of acid, roasting additives, and impurity removal reagents are required, which leads to a large amount of other impurity elements being leached out, high development and utilization costs, and unstable lithium extraction process parameters, thereby limiting the development and utilization process of 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 1 mol / L hydrochloric acid, followed by roasting, and then leaching the roasted sand with 3 mol / L sulfuric acid to obtain a lithium-rich leaching solution. 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 to obtain a roasted clinker, and then acid leaching to obtain a lithium leaching solution. After two impurity removal steps, enrichment, and lithium precipitation processes, a lithium carbonate product with a purity of >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, acid roasting at 200℃~310℃ for 0.5h-3h, and then water leaching to extract lithium. After solid-liquid separation, the filtrate is impurity-removed, neutralized, and precipitated, and then filtered to obtain a lithium carbonate product and by-products such as aluminum oxide and ammonia gas; Wu Lin et al. prepared a mixed acid of sulfuric acid and phosphoric acid with a certain volume ratio in 2016, and conducted a mixed acid leaching verification test on clay-type lithium ore under the following conditions: leaching temperature 100℃, leaching time 3h, solid-liquid ratio 1:4, and stirring intensity 300 r / min. The final lithium leaching rate reached 96.67%, but a large amount of aluminum elements were also leached out, with a leaching rate of 88.35%.

[0004] In the field of new energy vehicles, the cumulative installation volume of lithium iron phosphate batteries accounted for 81.3% of the total installation volume from January to July 2025. In the field of energy storage, the proportion of lithium iron phosphate batteries is over 90%, becoming the first choice in the industry, which means that lithium phosphate iron has become one of the main "urban mines". Currently, the main method for recovering lithium from lithium phosphate iron is acid leaching process. For example, patent CN117566709A mixes waste lithium phosphate iron battery material, 30% hydrogen peroxide and sulfuric acid for stirring, and obtains a leaching solution with a lithium leaching rate of 99% and an aluminum leaching rate of 75%; patent CN115287469A uses 30% sulfuric acid for secondary acid leaching of lithium phosphate iron black powder to recover lithium and phosphorus iron elements; patent CN116750740A discloses roasting waste lithium phosphate iron powder in a non-oxidizing atmosphere to obtain roasted powder, adding pure water to the roasted powder for slurry preparation, adding mixed acid to adjust the pH value to 2 for leaching, and filtering to obtain leaching solution and leaching residue; patent CN117712531A reports a method for recycling waste lithium phosphate iron battery, which roasts lithium phosphate iron at 200-800°C in air atmosphere for 1 h, then roasts in reducing atmosphere for 2-4 h, and finally leaches with 2 mol / L sulfuric acid, with Li, Fe and P leaching rates all >99%. The Li2O grade in waste lithium phosphate iron is relatively high, with a content of about 5%-9.5%, which is a high-value lithium resource for recovery. However, due to the complex sources and various types of waste lithium phosphate iron, the large-scale recovery industry has been slow.

[0005] Therefore, it is of great significance and promoting effect to develop an efficient, short-process and low-cost lithium extraction method combining clay-type lithium ore with high-grade lithium oxide from waste lithium phosphate iron secondary resources. SUMMARY

[0006] The present application aims to overcome the shortcomings of the prior art and provide a method for synergistic roasting and selective lithium extraction of clay-type lithium ore and waste lithium phosphate iron, which mixes clay-type lithium ore and waste lithium phosphate iron for roasting, utilizes the thermodynamic complementary mechanism of the two materials to reduce the roasting energy consumption, utilizes the double synergistic leaching mechanism to strengthen the leaching of lithium and reduce the content of impurities in the leaching solution, and realizes the efficient and selective leaching of lithium in clay-type lithium ore and waste lithium phosphate iron.

[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 synergistic roasting and selective lithium extraction of clay-type lithium ore and waste lithium phosphate iron, which includes the following steps: S11. Grinding: crushing and fine grinding clay-type lithium ore and waste lithium phosphate iron to 50%-90% of -200 mesh, respectively, to obtain clay-type lithium ore powder and waste lithium phosphate iron powder; S12. Dynamic proportioning and mixing: the clay-type lithium ore powder and the waste lithium iron phosphate powder are proportioned and mixed according to the respective lithium oxide grades to obtain a mixture with a Li2O grade of 0.9% to 1.2%; S13. Mixing roasting: the mixture is roasted to obtain converted calcine; S14. Dilute acid leaching: the converted calcine is added into a dilute sulfuric acid solution for stirring leaching and first filtration to obtain a lithium-containing leachate.

[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%, the content of TFe is 1.2% to 4.2%, and Li2O / Al2O3<0.053.

[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 S13, the temperature of the roasting is 450°C to 650°C, and the time of the roasting is 30 min to 120 min.

[0011] In the above technical solution, at the roasting temperature, the lithium iron phosphate will undergo an oxidation exothermic reaction, and the kaolinite in the clay-type lithium ore will undergo a phase change endothermic, so the heat released by the decomposition of the lithium iron phosphate can be used to compensate for the dehydration endothermic of the clay-type lithium ore, thereby reducing the energy demand of the mixture system during roasting.

[0012] Further, in S14, the concentration of the dilute sulfuric acid solution is 0.1 mol / L to 0.5 mol / L, and the liquid-solid ratio of the dilute sulfuric acid solution to the converted calcine is 2 L / kg to 6 L / kg.

[0013] In the above technical solution, there is a double synergistic leaching mechanism between the clay-type lithium ore and the lithium iron phosphate during leaching, which strengthens the leaching of lithium and reduces the content of impurities in the leachate, so a low-concentration dilute sulfuric acid solution can achieve efficient leaching of lithium in the mixture.

[0014] Further, in S14, 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.

[0015] On the other hand, the application provides the use of the above-mentioned method of synergistic roasting of the clay-type lithium ore and the waste lithium iron phosphate for selective lithium extraction in the preparation of lithium products, including lithium carbonate.

[0016] Further, the steps for preparing the lithium carbonate include: S21. Removal of aluminum, iron, and phosphorus: The pH value of the lithium-containing leachate is adjusted to 6.5~7.5 using a pH adjuster, stirred at 80℃~90℃ for 20 min~60 min, and then aged and filtered for 1 h~4 h to obtain a first-grade purified solution. S22. Calcium and magnesium removal: Use calcium-magnesium chelating resin or calcium hydroxide and sodium carbonate to remove calcium from the primary purification solution. 2+ Mg 2+ The secondary purified solution was obtained; S23. Concentration and enrichment: Lithium is concentrated and enriched from the secondary purified liquid to obtain Li. + Lithium concentrate with a concentration of 12 g / L to 20 g / L; S24. Sodium carbonate is added to the lithium concentrate at a molar ratio of 1.05 to 1.15:1. After reacting at 90°C to 95°C for 20 to 40 minutes, the mixture is filtered, washed, and dried to obtain the lithium carbonate.

[0017] Furthermore, in S21, the pH adjuster includes calcium hydroxide or sodium hydroxide.

[0018] Furthermore, in S22, the concentration and enrichment method includes reverse osmosis membrane enrichment, the concentration and enrichment operating pressure is 2.0 MPa to 8.0 MPa, the concentration and enrichment temperature is 10℃ to 40℃, and the empty tower flow rate of the concentration and enrichment is 8 BV / h to 12 BV / h.

[0019] In the above technical solution, because the acid concentration used during leaching is low (0.1 mol / L~0.5 mol / L) and the ionic strength of the leachate is low, it is only necessary to use calcium hydroxide to finely adjust the pH to 6.5~7.5, and then stir and age the solution to promote the transformation of amorphous precipitate into crystalline form. This will remove residual Fe, Al and PO4 from the solution. 3- After thorough precipitation and removal, the purified solution is further purified using calcium-magnesium chelating resin or sodium carbonate and calcium hydroxide to remove calcium and magnesium ions, meeting the separation feed water requirements of the RO membrane. Compared to traditional evaporation concentration, this application utilizes the RO membrane at an operating pressure of 2.0 MPa to 8.0 MPa and a temperature of 20 to 40°C to achieve high-rate lithium concentration, enabling the high concentration of Li... + Concentrating to 12 g / L~20 g / L, the resulting concentrate can be directly used for the preparation of lithium products, significantly reducing concentration energy consumption and lowering the cost of subsequent lithium product preparation.

[0020] Furthermore, in S22, a calcium-magnesium chelating resin is used to remove Ca. 2+ Mg 2+ The operating steps include: The calcium-magnesium chelating resin is added into the primary purified liquid at a liquid-solid ratio of 5 L / kg-15 L / kg, and a chelation reaction is carried out at 25℃-45℃ for 30 min-60 min to obtain the secondary purified liquid.

[0021] Further, in S22, Ca(OH)2 and Na2CO3 are used to remove Ca 2+ , Mg 2+ When S22 is performed, the operation steps include: The primary purified liquid is heated to 40℃-60℃, and then the pH is adjusted to 10.5-11.5 using Ca(OH)2. After stirring for 20 min-40 min, the liquid is filtered. Then, Na2CO3 is added to the filtrate at an excess coefficient of 1.05-1.20, and the liquid is stirred for 30 min-50 min, and then filtered to obtain the secondary purified liquid.

[0022] In the impurity removal process, due to the low acid consumption (0.1 mol / L-0.5 mol / L) in leaching and the low ionic strength of the leaching liquid, the pH value is finely adjusted to 6.5-7.5 using Ca(OH)2. After stirring for 30 min, the liquid is aged for 1 h-4 h to promote the conversion of amorphous precipitate to crystalline state, so that the residual Fe / Al-PO4 can be fully precipitated and removed. After filtration, Ca-Mg chelating resin is used to further adsorb Ca and Mg ions in the purified liquid. The pH of the obtained purified liquid is 6.5-7.5 (the pH tolerance range of the composite nanofiltration membrane is 3-10), which meets the requirements of the reverse osmosis (RO) membrane separation. Compared with the traditional evaporation concentration, the membrane separation concentration can greatly reduce the concentration energy consumption and the cost of lithium carbonate preparation. The reverse osmosis (RO) membrane is used to concentrate Li + to 12 g / L-20 g / L at an operating pressure of 2.0 MPa-8.0 MPa and a temperature of 20℃-40℃. The obtained concentrated liquid can be directly used for lithium precipitation with Na2CO3, and then the lithium carbonate product is prepared. The efficient extraction and utilization of lithium elements in clay-type lithium ore and waste lithium iron phosphate are realized, and the preparation process from raw ore to lithium carbonate is completed.

[0023] In another aspect, the application provides the application of the above-mentioned method for selective lithium extraction by synergistic roasting of clay-type lithium ore and waste lithium iron phosphate in the extraction of lithium elements from clay-type lithium ore and / or waste lithium iron phosphate.

[0024] The principle of the application is as follows: The clay type lithium ore and lithium iron phosphate are crushed and finely ground to 50-90% of -200 mesh, and then dynamically matched according to the Li2O content to obtain a mixture with a Li2O content of 0.9-1.2%, so as to ensure the stability of the subsequent lithium extraction process and avoid the reduction of lithium extraction efficiency caused by the fluctuation of material composition. By performing thermogravimetric analysis (TG) on the clay type lithium ore powder and lithium iron phosphate powder, and using differential scanning calorimetry (DSC) for thermal analysis, the TG-DSC curve as shown in Figure 2 is drawn. It is found that under the calcination environment of 400-600°C, the clay minerals (such as kaolinite) in the clay type lithium ore in the mixture will undergo phase transition endothermic, and the specific chemical reaction is Al2Si2O5(OH)4→Al2O3·2SiO2+2H2O↑, while the lithium iron phosphate will undergo oxidation exothermic reaction, and the specific chemical reaction is 12LiFePO4+3O2=4Li3Fe2(PO4)3+2Fe2O3. The heat released by the decomposition of lithium iron phosphate can compensate for the heat absorbed during the dehydration of clay minerals, so as to reduce the total heat supply demand of the system to the outside world during calcination.

[0025] During the leaching process, the lithium iron phosphate in the converted calcine reacts with acid after release of Fe 3+ and Li + , and the specific chemical reaction is Li3Fe2(PO4)3+9H + =3Li + +2Fe 3+ +3H3PO4. After Fe 3+ enters the solution, part of it replaces Li⁺ in the clay minerals through ion exchange, and the specific chemical reaction is Li + [clay]+Fe 3+ →Fe 3+ [clay]+Li + , thereby improving the leaching rate of lithium in acid; another part of Fe 3+ reacts with PO4 3- and Al 3+ leached from the clay type lithium ore in the solution in weak acid medium to generate mixed precipitates of iron phosphate / aluminum phosphate, and the specific chemical reaction is Fe 3+ +PO4 3- =FePO4↓, Al 3+ +PO4 3- =AlPO4↓. During the precipitation process, the free Fe 3+ , Al 3+ , PO4 3- in the solution can be significantly reduced, and according to the Le Chatelier principle, the leaching reaction equilibrium will move towards the forward reaction direction, so as to realize high-efficiency selective leaching of lithium under low acid concentration conditions.

[0026] The beneficial effects of the present application are: 1、The present application initiatively mixes clay-type lithium ore and waste lithium iron phosphate in a dynamic ratio, fully utilizes the thermodynamic complementary mechanism between the two materials, reduces the roasting energy consumption, and after the dynamic ratio mixing of the clay-type lithium ore and the waste lithium iron phosphate, the content of Li2O in the lithium extraction raw material can be kept stable, solving the problem of low lithium extraction efficiency and poor economy of the clay-type lithium ore due to low raw ore grade and large fluctuation.

[0027] 2、The present application first uses a double synergistic leaching mechanism for efficient lithium extraction from clay-type lithium ore. First, by taking advantage of the characteristics that Li + , Fe 3+ , PO4 3- are released during the leaching of the calcined lithium iron phosphate, the Fe 3+ catalyzes the dissociation of lithium elements in clay minerals, and then by taking advantage of the characteristics that Li + , Al 3+ are released during the leaching of the clay-type lithium ore, the Al 3+ and Fe 3+ , PO4 3- are synergistically precipitated under weak acid conditions, breaking the balance of the conventional leaching system and promoting the leaching reaction balance to move in the positive reaction direction, so as to realize efficient and selective leaching of lithium under low acidity conditions.

[0028] 3、The present application provides a low-acid-consumption lithium extraction technology, the lithium extraction process is simple, the generated wastewater is easy to be treated, the tailings mainly contain Al, Si, Fe, P and other elements, and after grinding, the tailings can be directly used as raw materials for cement or filling materials, providing a new technical route for the full resource utilization of clay-type lithium ore and waste lithium iron phosphate. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is the process flow chart of the method of the present application for synergistic roasting and selective lithium extraction of clay-type lithium ore and waste lithium iron phosphate; Figure 2 is the TG-DSC analysis result of the raw material (a. TG-DSC of clay-type lithium ore; b. TG-DSC of lithium iron phosphate). DETAILED DESCRIPTION

[0030] The technical solutions of the present application will be described in further detail below in combination with the drawings, but the protection scope of the present application is not limited to the following description.

[0031] Example 1 Raw materials: a clay-type lithium ore, wherein the content of Li2O is 0.63%, the content of Al2O3 is 20.14%, and the content of TFe is 4.13%; waste lithium iron phosphate powder recovered from a factory, wherein the content of Li2O is 8.59%, the content of TFe is 34.58%, and the content of P2O5 is 44.05%.

[0032] The clay-type lithium ore and the waste lithium iron phosphate are used to cooperatively extract lithium according to the following steps: 1. Grinding: the clay-type lithium ore and the waste lithium iron phosphate are respectively crushed and finely ground to 50% of -200 mesh, to obtain clay-type lithium ore powder and waste lithium iron phosphate powder; 2. Dynamic proportioning and mixing: the clay-type lithium ore powder and the waste lithium iron phosphate powder are mixed according to a mass ratio of 95.35:4.65, to obtain a mixture with a lithium oxide grade of 1%; 3. Mixed roasting: 200 g of the mixture is roasted at a temperature of 550°C for 90 min, to obtain 182.3 g of converted calcine; 4. Dilute acid leaching: 50 g of the converted calcine is added into a dilute sulfuric acid solution with a concentration of 0.3 mol / L at a liquid-solid ratio of 4 L / kg, and after stirring and leaching at 95°C for 60 min, filtration is performed to obtain a lithium-containing leaching solution and a leaching residue. After detection of the lithium-containing leaching solution, the results show that the content of Li in the solution is 1.21 g / L, the content of Fe is 0.28 g / L, the content of Al is 0.98 g / L, and the content of P is 0.08 g / L. In terms of the lithium-containing leaching solution, the leaching rate of Li is 94.95%, the leaching rate of Fe is 1.84%, the leaching rate of Al is 3.52%, and the leaching rate of P is 3.26%.

[0033] Example 2 Raw materials: a clay-type lithium ore, wherein the content of Li2O is 0.25%, the content of Al2O3 is 40.04%, and the content of TFe is 2.30%; waste lithium iron phosphate powder recovered from a factory, wherein the content of Li2O is 9.47%, the content of TFe is 35.40%, and the content of P2O5 is 44.98%.

[0034] The clay-type lithium ore and the waste lithium iron phosphate are used to cooperatively extract lithium according to the following steps: 1. Grinding: the clay-type lithium ore and the waste lithium iron phosphate are respectively crushed and finely ground to 70% of -200 mesh, to obtain clay-type lithium ore powder and waste lithium iron phosphate powder; 2. Dynamic proportioning and mixing: the clay-type lithium ore powder and the waste lithium iron phosphate powder are mixed according to a mass ratio of 91.01:8.99, to obtain a mixture with a lithium oxide grade of 1%; 3. Mixed roasting: 200 g of the mixture is roasted at a temperature of 450°C for 120 min, to obtain 184.5 g of converted calcine; 4. Dilute acid leaching: 50 g of the converted calcine was added into a dilute sulfuric acid solution with a concentration of 0.5 mol / L at a liquid-solid ratio of 2 L / kg, after stirring and leaching at 80°C for 90 min, filtration was performed to obtain a lithium-containing leaching solution and a leaching residue. After detection of the lithium-containing leaching solution, the results showed that the Li content in the solution was 2.34 g / L, the Fe content was 0.56 g / L, the Al content was 2.77 g / L, and the P content was 0.32 g / L, the Li leaching rate was 93.13%, the Fe leaching rate was 2.07%, the Al leaching rate was 2.62%, and the P leaching rate was 3.71% based on the lithium-containing leaching solution.

[0035] Example 3 The raw materials were: a clay-type lithium ore from a certain place, with a Li2O content of 0.95%, an Al2O3 content of 18.01%, and a TFe content of 1.2%; 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%.

[0036] The clay-type lithium ore and the waste lithium iron phosphate were mixed according to the following steps to cooperatively extract lithium: 1. Grinding: the clay-type lithium ore and the waste lithium iron phosphate were respectively crushed and finely ground to 90% passing 200 mesh to obtain clay-type lithium ore powder and waste lithium iron phosphate powder; 2. Dynamic proportioning and mixing: the clay-type lithium ore powder and the waste lithium iron phosphate powder were mixed according to a mass ratio of 96.75:3.25 to obtain a mixed material with a lithium oxide grade of 1.2%; 3. Mixing and roasting: 200 g of the mixed material was roasted at a temperature of 650°C for 30 min to obtain 183.1 g of converted calcine; 4. Dilute acid leaching: 50 g of the converted calcine was added into a dilute sulfuric acid solution with a concentration of 0.1 mol / L at a liquid-solid ratio of 6 L / kg, after stirring and leaching at 95°C for 30 min, filtration was performed to obtain a lithium-containing leaching solution and a leaching residue. After detection of the lithium-containing leaching solution, the results showed that the Li content in the solution was 0.94 g / L, the Fe content was 0.09 g / L, the Al content was 0.55 g / L, and the P content was 0.04 g / L, the Li leaching rate was 92.75%, the Fe leaching rate was 2.26%, the Al leaching rate was 3.83%, and the P leaching rate was 2.04% based on the lithium-containing leaching solution.

[0037] Example 4 Raw materials: a clay-type lithium ore, wherein the content of Li2O is 0.63%, the content of Al2O3 is 20.14%, and the content of TFe is 4.13%; waste lithium iron phosphate powder recovered from a factory, wherein the content of Li2O is 5.10%, the content of TFe is 19.12%, and the content of P2O5 is 20.32%.

[0038] The clay-type lithium ore and the waste lithium iron phosphate are used to cooperatively extract lithium according to the following steps: 1. Grinding: the clay-type lithium ore and the waste lithium iron phosphate are respectively crushed and finely ground to 70% passing 200 mesh to obtain clay-type lithium ore powder and waste lithium iron phosphate powder; 2. Dynamic proportioning and mixing: the clay-type lithium ore powder and the waste lithium iron phosphate powder are mixed according to a mass ratio of 94.02:5.98 to obtain a mixture with a lithium oxide grade of 0.9%; 3. Mixing roasting: 200 g of the mixture is roasted at a temperature of 550°C for 120 min to obtain 180.1 g of converted calcine; 4. Dilute acid leaching: 50 g of the converted calcine is added into a dilute sulfuric acid solution with a concentration of 0.3 mol / L at a liquid-solid ratio of 6 L / kg, and after stirring and leaching at 70°C for 120 min, filtration is performed to obtain a lithium-containing leaching solution and a leaching residue. After detection of the lithium-containing leaching solution, the results show that the content of Li in the solution is 0.71 g / L, the content of Fe is 0.21 g / L, the content of Al is 0.71 g / L, and the content of P is 0.02 g / L. The leaching rate of Li is 92.01% in the lithium-containing leaching solution, the leaching rate of Fe is 2.26%, the leaching rate of Al is 3.83%, and the leaching rate of P is 2.04%.

[0039] Comparative Example 1 This comparative example uses the same clay-type lithium ore as in Example 1 to roast and leach lithium by acid without adding waste lithium iron phosphate. The specific steps include: 1. Grinding: the clay-type lithium ore is crushed and finely ground to 70% passing 200 mesh to obtain clay-type lithium ore powder; 2. Roasting: 200 g of the clay-type lithium ore powder is roasted at a temperature of 550°C for 90 min to obtain 181 g of converted calcine; 3. Dilute acid leaching: 50 g of the converted calcine is added into a dilute sulfuric acid solution with a concentration of 0.3 mol / L at a liquid-solid ratio of 4 L / kg, and after stirring and leaching at 95°C for 60 min, filtration is performed to obtain a lithium-containing leaching solution and a leaching residue. After detection of the lithium-containing leaching solution, the results show that the content of Li in the solution is 0.58 g / L, and the content of Al is 4.52 g / L. The leaching rate of Li is 45.19% in the lithium-containing leaching solution, and the leaching rate of Al is 16.10%.

[0040] Compared with Example 1, the leaching rate of Li in Comparative Example 1 decreased by 49.76%, the leaching rate of Al increased by 12.58%, the lithium content in the lithium-containing leaching solution decreased by 52.07%, and the impurity aluminum content increased by 361.22%. This is because there is no PO4 3- , which makes the Al 3+ In weak acid conditions, AlPO4 precipitate cannot be generated, which limits the forward progress of the leaching reaction, resulting in inhibition of lithium leaching, while the aluminum impurity in the solution is greatly increased, increasing the cost of subsequent impurity removal.

[0041] Comparative Example 2 This comparative example uses the same waste lithium phosphate iron as Example 1, and does not add clay-type lithium ore for roasting and lithium extraction by acid leaching. The specific steps include: 1. Grinding: crushing and fine grinding the waste lithium phosphate iron to 70% passing -200 mesh to obtain waste lithium phosphate iron powder; 2. Roasting: roasting 200 g of the waste lithium phosphate iron powder at a temperature of 550°C for 90 min to obtain 206 g of converted calcine; 3. Dilute acid leaching: adding 50 g of the converted calcine to a dilute sulfuric acid solution with a concentration of 0.3 mol / L at a liquid-solid ratio of 4 L / kg, stirring and leaching at 95°C for 60 min, and then filtering to obtain a lithium-containing leaching solution and a leaching residue. After detecting the lithium-containing leaching solution, the results showed that the Li content in the solution was 6.86 g / L, the Fe content was 1.41 g / L, and the P content was 2.11 g / L. The Li leaching rate was 32.90%, the Fe leaching rate was 1.68%, and the P leaching rate was 1.97% based on the lithium-containing leaching solution.

[0042] Although the leaching rates of impurities Fe and P in Comparative Example 2 changed little compared with Example 1, the leaching rate of Li decreased by 62.05%. This is because there is no Al 3+ , which makes the PO4 3- In weak acid conditions, AlPO4 precipitate cannot be generated, which limits the forward progress of the leaching reaction, resulting in inhibition of lithium leaching.

[0043] Experimental Example 1: Preparation of lithium carbonate product Method one: the lithium-containing leaching solution is prepared according to the scheme of the present application, then the pH value of the leaching solution is adjusted to 6.5-7.5 using sodium hydroxide, stirred at 80-90°C for 20-60 min, then aged for 1-4 h, then filtered to obtain the purified solution from which aluminum, iron, phosphorus and impurities are removed, then calcium-magnesium chelating resin is added at a liquid-solid ratio of 5-15 L / kg, and after chelation reaction at 25-45°C for 30-60 min, calcium, magnesium and other impurities are removed, then reverse osmosis (RO) membrane is used to concentrate and enrich lithium at an operating pressure of 2.0-8.0 MPa at 10-40°C, the empty column flow rate of concentration and enrichment is 8-12 BV / h, and Li + concentrated solution with a lithium concentration of 12-20 g / L, and finally sodium carbonate is added to the lithium concentrated solution at a molar ratio of 1.05-1.15:1, and after reaction at 90-95°C for 20-60 min, the lithium carbonate product is obtained.

[0044] Method two: the lithium-containing leaching solution is prepared according to the scheme of the present application, then the pH value of the leaching solution is adjusted to 6.5-7.5 using sodium hydroxide, stirred at 80-90°C for 20-60 min, then aged for 1-4 h, then filtered to obtain the purified solution from which aluminum, iron, phosphorus and impurities are removed, then heated to 40-60°C, and the pH value is adjusted to 10.5-11.5 using calcium hydroxide, and after stirring reaction for 20-40 min, filtered to remove magnesium and other impurities, then sodium carbonate is added to the filtrate at a calcium excess coefficient of 1.05-1.20, and after continuing to stir for 30-50 min, filtered to remove calcium and other impurities, finally reverse osmosis (RO) membrane is used to concentrate and enrich lithium in the filtrate at an operating pressure of 2.0-8.0 MPa at 20-40°C, the empty column flow rate of concentration and enrichment is 8-12 BV / h, and Li + concentrated solution with a lithium concentration of 12-20 g / L, and finally sodium carbonate is added to the lithium concentrated solution at a molar ratio of 1.05-1.15:1, and after reaction at 90-95°C for 20-60 min, the lithium carbonate product is obtained.

[0045] For example, the lithium-containing leaching solution prepared in Example 1 is used as raw material, the pH value of the leaching solution is adjusted to 6.5 using sodium hydroxide, stirred at 85°C for 60 min, then aged for 4 h, then filtered to obtain the purified solution, then calcium-magnesium chelating resin is added at a liquid-solid ratio of 5 L / kg, stirred at 25°C for 30 min, then reverse osmosis (RO) membrane is used to concentrate and enrich lithium at an operating pressure of 6.0 MPa at 30°C, and Li +The lithium concentrate solution with the concentration of 16.48 g / L from which calcium and magnesium are removed, finally, sodium carbonate is added to the lithium concentrate solution at a molar ratio of 1.15:1, and the reaction is carried out at 95°C for 60 min. After the completion of lithium precipitation, the lithium precipitation mother liquor and the crude product are obtained by filtration. The crude product is washed once and dried to obtain the lithium carbonate product. The purity of the product is ≥99.5%, and the Li comprehensive recovery rate of the whole process is >80%.

[0046] The above description is merely preferred embodiments of the present application, and it is understood that the present application is not limited to the disclosed forms, and should not be considered as excluding other embodiments, but can be used in various other combinations, modifications and adjustments, and the changes and equivalent replacements made by those skilled in the art without departing from the spirit and scope of the present application, should be within the protection scope of the claims attached to the present application.

Claims

1. A method for selective lithium extraction from the co-combustion of clay-type lithium ores and spent lithium iron phosphate, characterized in that, The method comprises the following steps: S11. Grinding: crushing and fine grinding the clay-type lithium ore and the waste lithium iron phosphate respectively to 50%-90% of -200 mesh, to obtain clay-type lithium ore powder and waste lithium iron phosphate powder; S12. Dynamic proportioning and mixing: dynamically proportioning and mixing the clay-type lithium ore powder and the waste lithium iron phosphate powder according to the lithium oxide grade of each, to obtain a mixture with a Li2O grade of 0.9%-1.2%; S13. Mixing roasting: roasting the mixture to obtain converted calcine; S14. Dilute acid leaching: adding the converted calcine into a dilute sulfuric acid solution for stirring leaching and first filtration, to obtain a lithium-containing leaching solution.

2. The method for synergistic roasting-selective lithium extraction of clay-type lithium ore and waste lithium iron phosphate according to claim 1, characterized in that, The content of Li2O in the clay-type lithium ore is 0.25%-0.95%, the content of Al2O3 is 18%-60%, the content of TFe is 1.2%-4.2%, and Li2O / Al2O3<0.053; And / or, the content of Li2O in the waste lithium iron phosphate is 5%-9.5%, the content of TFe is 19%-36%, and the content of P2O5 is 20%-45%.

3. The method for synergistic roasting-selective lithium extraction of clay-type lithium ore and waste lithium iron phosphate according to claim 1, characterized in that, In S13, the temperature of the roasting is 450°C-650°C, and the time of the roasting is 30-120 min.

4. The method for synergistic roasting-selective lithium extraction of clay-type lithium ore and waste lithium iron phosphate according to claim 1, characterized in that, In S14, the concentration of the dilute sulfuric acid solution is 0.1 mol / L-0.5 mol / L, and the liquid-solid ratio of the dilute sulfuric acid solution to the converted calcine is 2 L / kg-6 L / kg; And / or, in S14, the temperature of the stirring leaching is 70°C-95°C, and the time of the stirring leaching is 0.5 h-2 h.

5. Use of the process according to any one of claims 1 to 4 for the production of lithium products, characterized in that, The lithium product comprises lithium carbonate.

6. Use according to claim 5, characterized in that, The steps for preparing the lithium carbonate comprise: S21. Removing aluminum, iron and phosphorus: adjusting the pH value of the lithium-containing leaching solution to 6.5-7.5 by using a pH regulator, stirring at 80°C-90°C for 20 min-60 min, then aging for 1 h-4 h and performing second filtration, to obtain a first purified solution; S22. Remove calcium and magnesium: use calcium and magnesium chelating resin or calcium hydroxide and calcium carbonate to remove Ca 2+ , Mg 2+ in the primary purified liquid to obtain secondary purified liquid; S23. Concentration enrichment: the secondary purification liquid is subjected to lithium concentration enrichment to obtain Li + lithium concentrated liquid with a concentration of 12 g / L~20 g / L; S24. Adding sodium carbonate to the lithium concentrated solution at a molar ratio of 1.05-1.15:1, and performing filtration, washing and drying after reacting at 90°C-95°C for 20 min-60 min, to obtain the lithium carbonate.

7. Use according to claim 6, characterized in that, In S21, the pH regulator comprises calcium hydroxide or sodium hydroxide; And / or, in S22, the method for concentration and enrichment comprises a reverse osmosis membrane enrichment method, the operation pressure of the concentration and enrichment is 2.0 MPa-8.0 MPa, the temperature of the concentration and enrichment is 10°C-40°C, and the empty tower flow rate of the concentration and enrichment is 8 BV / h-12 BV / h.

8. Use according to claim 6, characterized in that, In S22, calcium-magnesium chelating resin is used to remove Ca. 2+ Mg 2+ The operating steps include: The calcium-magnesium chelation resin is added to the first purified solution at a liquid-solid ratio of 5 L / kg-15 L / kg, and a chelation reaction is performed at 25°C-45°C for 30 min-60 min, to obtain a second purified solution.

9. Use according to claim 6, characterized in that, In S22, Ca is removed using calcium hydroxide and calcium carbonate 2+ , Mg 2+ when, the operating steps include: The primary purification liquid is heated to 40-60 DEG C, then the pH value is adjusted to 10.5-11.5 by using the calcium hydroxide, after stirring for 20-40 min, filtering, then adding sodium carbonate with an excess coefficient of 1.05-1.20 to the filtrate, continuing to stir for 30-50 min, obtaining the secondary purification liquid.

10. Use of the method according to any one of claims 1-4 for extracting lithium from clay-type lithium ore and / or waste lithium iron phosphate.

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