Method for extracting lithium from lithium-containing resource

Abstract

The invention discloses a method for extracting lithium from lithium-containing resources, and belongs to the technical field of lithium extraction processes. The method comprises the following steps: firstly, mixing a lithium-containing material with composite salt to prepare powder, then pressing into blocks, roasting to obtain block materials, carrying out ball-milling crushing on the block materials, adding dilute sulphuric acid, carrying out wet milling, filtering to obtain filtrate, then measuring the concentration of each metal ion in the filtrate and combining related thermodynamic data, calculating the amount of a precipitant required by impurity removal and the optimal pH value of impurity precipitation, finally adding the precipitant into the filtrate according to a calculation result, adjusting the pH value, and filtering to obtain a purified lithium solution; according to the method, the composite salt and the lithium-containing material are jointly roasted, the roasting temperature is effectively reduced through low-melting-point persulfate, the energy consumption is reduced, the optimal impurity removal condition can be obtained innovatively through calculation, a large amount of early-stage exploration experiment cost and time are saved, and the method is suitable for industrial production. And the lithium element is retained to the maximum extent while the impurities are removed to the maximum extent, and the method has wide adaptability.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium extraction technology, and specifically relates to a method for extracting lithium from lithium-containing resources. Background Art

[0002] As the global demand for clean energy and electric vehicles continues to grow, the production and consumption of lithium-ion batteries are also continuing to rise. As the key raw material of lithium-ion batteries, the demand for lithium has also increased significantly. At present, the extraction of lithium resources mainly depends on lithium ore. Among the many lithium ore extraction technologies, sulfate roasting has been widely used in industrial production due to its high efficiency, strong adaptability and high lithium extraction rate.

[0003] The core of the sulfate roasting method is to roast lithium-containing minerals and sulfate at high temperature, convert lithium elements into soluble lithium sulfate through chemical reactions, and then transfer lithium-containing components from the solid phase to the liquid phase through the acid leaching step to form a lithium-containing filtrate; however, the sulfate roasting method still faces some problems in actual operation: in order to achieve a better lithium extraction effect, the roasting process temperature is usually as high as 1000°C or above [1-4] , which greatly increases the energy consumption in the lithium extraction process; more importantly, after the roasting is completed, the lithium-containing filtrate obtained by acid leaching often contains a certain concentration of impurity elements such as magnesium, calcium, iron, and aluminum. These impurity elements mainly come from the exchange reaction between the relevant elements in the lithium-containing material and the metal ions in the sulfate during the roasting process, as well as the dissolution of relevant elements during acid leaching. The presence of impurities not only affects the purity of lithium, but may also have an adverse effect on the subsequent lithium recovery and reuse process.

[0004] In order to maximize the removal of impurities while ensuring the maximum retention of lithium, existing research usually relies on a large number of exploratory experiments to optimize the optimal impurity removal conditions, such as the amount of precipitant added and the pH value setting during the precipitation process. [5-9] ; However, in practical applications, the optimal impurity removal conditions determined by exploratory experiments have certain limitations: existing exploratory experiments are usually carried out on specific types of lithium-containing raw materials. When the type or composition of the raw materials changes, the impurity content inside them will also change accordingly. This requires re-exploratory experiments to determine new optimal impurity removal conditions. This process not only consumes a lot of experimental resources, but also increases time costs. If the impurities are removed according to the original conditions, the lithium element may precipitate along with the impurities due to excessive pH value or excessive amount of precipitant, resulting in a significant reduction in the lithium content in the filtrate; conversely, if the pH value is too low or the amount of precipitant is insufficient, the impurities may not be fully removed, affecting the purity of the final product.

[0005] [1]Setoudeh N., Nosrati A., Welham N. J. Lithium extraction from mechanically activated of petalite-Na 2 SO 4 mixtures after isothermal heating[J]. Minerals Engineering, 2020, 151.

[0006] [2]Qiu S. B., Sun T. Y., Zhu Y., et al. Direct Preparation of Water-Soluble Lithium Salts from α-Spodumene by Roasting with Different Sulfates[J]. Industrial & Engineering Chemistry Research, 2023, 62(1): 685-97.

[0007] [3]Liu Chenglin, Qiu Shengbo, Sun Tianyu, et al. A method for producing lithium sulfate solution by roasting spodumene with sulfate[Z]. 2022

[0008] [4]Li Xiang, Xu Lijuan, Meng Xiangke, et al. A method for extracting lithium from lithium ore leaching residue[Z]. 2022

[0009] [5]Zhu Jun, Li Xiaopeng, Liu Xinhai, et al. Experimental study on purification of crude lithium phosphate produced in salt lake[J]. Mining and Metallurgical Engineering, 2023, 43(3): 101-5.

[0010] [6]Tang Yaochuan, Dai Yujia, Wu Linhong, et al. Study on the process for removing calcium and magnesium ions from high-calcium and high-lithium brine to produce lithium carbonate[J]. Nonferrous Metals Engineering, 2024, 14(5): 49-55.

[0011] [7]Kang Min, Wu Tianjiao, Zhao Xiaoyi, et al. Study on the process for removing calcium and magnesium from leaching solution of lepidolite ore[J]. Mining and Metallurgical Engineering, 2023, 43(4): 135-8.

[0012] [8]Liu J. C., Zhang Y. B., Miao Y., et al. Alkaline Resins Enhancing Li + / H +Ion Exchange for Lithium Recovery from Brines Using Granular Titanium-Type Lithium Ion-Sieves[J].Industrial & Engineering Chemistry Research,2021,60(45):16457-68.

[0013] [9]Liu T.C.,Chen J.,Li H.L.,et al.High-Efficiency Removal of Calcium and Magnesium from Lithium-Concentrated Solution via Counter-Current Extraction Using Di-(2-ethylhexyl)phosphinic Acid[J].ACS Sustainable Chemistry & Engineering,2022,10(2):967-74. Summary of the Invention

[0014] The purpose of the present invention is to provide a method for extracting lithium from lithium-containing resources to solve the problems in the above-mentioned background technology.

[0015] To achieve the above purpose, the present invention provides the following technical solutions:

[0016] A method for extracting lithium from lithium-containing resources, comprising the following steps:

[0017] 1) Mix the lithium-containing material with a composite salt and perform ball milling and screening multiple times to obtain a powder. The composite salt is obtained by mixing a sulfate and a persulfate;

[0018] 2) Press the powder obtained in step 1) into blocks, calcine to obtain block materials, and then ball mill and screen the block materials to obtain a powder;

[0019] 3) Add dilute sulfuric acid to the powder obtained in step 2) for wet milling, and filter to obtain a lithium-containing filtrate;

[0020] 4) Measure the volume of the lithium-containing filtrate obtained in step 3) and the concentrations of various metal elements in the lithium-containing filtrate, calculate the dosage of the precipitant required for impurity removal and the optimal pH value for impurity precipitation, then add the precipitant to the lithium-containing filtrate and adjust the pH value, and filter to obtain a purified lithium solution;

[0021] Among them, the calculation method for the dosage of the precipitant required for impurity removal in step 4) is as follows:

[0022] a. According to the following formula (1) and the measured concentrations of various metal impurity elements Calculate the concentration of the precipitant anion and The unit is mol / L;

[0023]

[0024] In the formula, n represents the number of types of metal impurity elements, represents the concentration of the i-th metal impurity ion, x i is the charge number of the i-th metal impurity element ion, and y is the charge number of the precipitant anion;

[0025] b. With the general formula of the precipitant being R c N d , according to the following formula (2), the volume V of the lithium-containing filtrate measured L , and the concentration of the precipitant anion calculated in step a above Calculate the dosage m of the precipitant;

[0026]

[0027] In the formula, is the molecular weight of the selected precipitant, with the unit g / mol;

[0028] Among them, the calculation method for the optimal pH value of impurity precipitation in step 4) is:

[0029] c. According to the following formulas (3) and (4), and the hydrolysis constants of various metal ions at the current reaction temperature and the hydrolysis constant of the precipitant anion (n is an integer starting from 1), calculate the distribution coefficients x+ of various metal ions (W and the distribution coefficient y- ) of the precipitant anion (N

[0030]

[0031]

[0032] d. According to the following formula (5), the solubility products of the insoluble salts formed by various metal ions and the precipitant anion at the current reaction temperature The concentration of the precipitant anion calculated in step a above and the distribution coefficients of the precipitant anion and various metal ions calculated in step c above, calculate the critical concentration [W] of various metal elements in the solutionL ;

[0033]

[0034] e. According to the following formula (6) and the measured concentrations of each metal element and the critical concentration [W] of each metal element calculated in step d above L , calculate the theoretical precipitation rate ε of each metal element at different pH values [W] ;

[0035]

[0036] f. According to the theoretical precipitation rate ε of each metal element at different pH values calculated in step e [W] , plot the curve relationship between the theoretical precipitation rate and the pH value, and calculate the minimum pH value that can make the precipitation rate of all metal impurity elements greater than 99.9%. This pH value is the optimal pH value for the impurity removal process.

[0037] Preferably, in step 1), the mass ratio of sulfate and persulfate in the composite salt is 1-4:1, and the molar ratio of the total metal elements in the composite salt to the lithium element in the lithium-containing material is 0.5-4:1.

[0038] Preferably, the particle size of the powder obtained in step 1) and step 2) is <30 μm.

[0039] Preferably, in the ball milling process of step 1) and step 2), the mass ratio of the grinding beads to the solid is 1-10:1, the rotation speed is 300-1000 rpm, and the time is 2-12 h.

[0040] Preferably, in step 2), the roasting reaction temperature is 700-850 °C and the time is 0.5-3 h.

[0041] Preferably, in step 3), the concentration of the dilute sulfuric acid is 0.05-0.25 mol / L, and the mass ratio of the dilute sulfuric acid solution to the powder solid is 2-4:1.

[0042] Preferably, in the wet milling process of step 3), the mass ratio of the grinding beads to the slurry is 1-10:1, the rotation speed is 300-1000 rpm, the time is 4-12 h, and the pore size of the filter membrane used in the filtration process is 0.22 μm.

[0043] Preferably, in the step 4), the precipitant is one or more of sodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium carbonate, sodium bicarbonate, sodium oxalate, sodium hydroxide, potassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium carbonate, potassium bicarbonate, potassium oxalate, potassium hydroxide, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium carbonate, ammonium bicarbonate, ammonium oxalate, and the actual dosage of the precipitant is 1.02 - 1.2 times the calculated dosage of the precipitant required for impurity removal.

[0044] Preferably, in the step 4), the reagent used to adjust the pH value is one or more of saturated sodium hydroxide solution, potassium hydroxide, ammonia water, concentrated sulfuric acid, and the pore size of the filter membrane used in the filtration process is 0.22 μm.

[0045] The beneficial effects of the present invention are as follows:

[0046] 1. The present invention innovatively uses the method of co - roasting composite salts with lithium - containing materials to achieve efficient conversion of lithium elements in lithium - containing materials. The low - melting - point persulfate in the composite salts changes the original phase equilibrium state during the roasting reaction process, effectively reducing the temperature required for the roasting process, thereby effectively reducing energy consumption and production costs. In addition, persulfate will decompose at high temperatures to generate highly reactive O - O free radicals, which can accelerate the breaking of chemical bonds in lithium - containing materials, thereby promoting the release and conversion of lithium elements, enabling lithium elements to be more efficiently converted into soluble lithium sulfate, and improving the production efficiency of the overall lithium extraction process;

[0047] 2. By measuring the concentrations of various metal ions in the filtrate and combining relevant thermodynamic data, the present invention can accurately calculate the dosage of the precipitant required for impurity removal and the optimal pH value for impurity precipitation, greatly improving the accuracy and efficiency of impurity removal, ensuring the maximum removal of impurity elements while maximizing the retention of lithium elements, effectively improving the comprehensive yield and purity of the final lithium salt. The method of the present invention is applicable to lithium - containing raw materials of different types and compositions, with wide adaptability. When the type or composition of the raw materials changes, only by calculating and adjusting according to the concentrations of various metal ions in the actual filtrate, the new optimal impurity - removal conditions can be quickly determined without the need to conduct a large number of exploratory experiments again, saving experimental resources and time costs, and improving process flexibility;

[0048] 3. By mixing the lithium - containing materials with composite salts for multiple ball - milling and screening, the present invention not only ensures uniform mixing between the materials, but also significantly reduces the particle size of the materials, greatly increasing their specific surface area, thereby promoting the full reaction between the lithium - containing materials and the composite salts during the roasting process, improving the roasting efficiency and effect; by further ball - milling and screening the roasted lumps, the powder is further refined, which is beneficial to the full leaching of soluble lithium during the subsequent wet - milling leaching process, thereby improving the lithium extraction efficiency. Description of the Drawings

[0049] Figure 1 Process flow diagram of the method for extracting lithium from lithium-containing resources according to the present invention;

[0050] Figure 2 In (a), it is the critical concentration of metal elements in the lithium-containing filtrate obtained in Example 1 at different pH values, and in (b), it is the theoretical precipitation rate of metal elements in the lithium-containing filtrate obtained in Example 1 at different pH values (the optimal leaching pH value is shown in the figure);

[0051] Figure 3 In (a), it is the critical concentration of metal elements in the lithium-containing filtrate obtained in Example 2 at different pH values, and in (b), it is the theoretical precipitation rate of metal elements in the lithium-containing filtrate obtained in Example 2 at different pH values (the optimal leaching pH value is shown in the figure);

[0052] Figure 4 In (a), it is the critical concentration of metal elements in the lithium-containing filtrate obtained in Example 3 at different pH values, and in (b), it is the theoretical precipitation rate of metal elements in the lithium-containing filtrate obtained in Example 3 at different pH values (the optimal leaching pH value is shown in the figure); Detailed implementation manners

[0053] The present invention will be specifically described below through examples. It is necessary to point out here that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the protection scope of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention according to the above content of the present invention. In the following examples, reagents and instruments not specifically stated can be obtained commercially, and experimental operations not specifically stated are carried out according to the manufacturer's instructions or conventional techniques in the art. Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to the described content can be applied to the present invention; the endpoints and any values within the ranges disclosed herein are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, between the endpoints of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0054] 1) Mix the lithium-containing material with the composite salt and conduct multiple ball milling and screening to obtain a powder. The composite salt is obtained by mixing a sulfate and a persulfate;

[0055] 2) Press the powder obtained in step 1) into blocks, roast to obtain block materials, and then ball mill and screen the block materials to obtain a powder;

[0056] 3) Add dilute sulfuric acid to the powder obtained in step 2) for wet grinding, and filter to obtain the lithium-containing filtrate;

[0057] 4) Measure the volume of the lithium-containing filtrate obtained in step 3) and the concentrations of various metal elements in the lithium-containing filtrate. Calculate the dosage of the precipitant required for impurity removal and the optimal pH value for metal impurity precipitation. Then add the precipitant to the lithium-containing filtrate and adjust the pH value, and filter to obtain the purified lithium solution;

[0058] Among them, the calculation method for the dosage of the precipitant required for impurity removal in step 4) is as follows:

[0059] a. According to the following formula (1) and the measured concentrations of various metal impurity elements Calculate the concentration of the precipitant anion required and The units are both mol / L;

[0060]

[0061] In the formula, n represents the number of types of metal impurity elements, represents the concentration of the i-th metal impurity ion, x i is the charge number of the i-th metal impurity element ion, and y is the charge number of the precipitant anion;

[0062] b. With the general formula of the precipitant being R c N d , according to the following formula (2), the measured volume V of the lithium-containing filtrate L , and the concentration of the precipitant anion calculated in step a above Calculate the dosage m of the precipitant;

[0063]

[0064] In the formula, is the molecular weight of the selected precipitant, with the unit g / mol;

[0065] Among them, the calculation method for the optimal pH value for impurity precipitation in step 4) is as follows:

[0066] c. According to the following formulas (3) and (4), and the hydrolysis constants of various metal ions and the hydrolysis constant of the precipitant anion at the current reaction temperature and (n is an integer starting from 1), calculate the distribution coefficients x+ of various metal ions (W ) and the distribution coefficients y- of the precipitant anion (N

[0067]

[0068] d. According to the following formula (5), the solubility product of the insoluble salts formed by each metal ion and the precipitating agent anion at the current reaction temperature The concentration of the precipitating agent anion calculated in step a above And the distribution coefficients of the precipitating agent anion and each metal ion calculated in step c above, calculate the critical concentration [W] of each metal element in the solution L ;

[0069]

[0070] e. According to the following formula (6), the measured concentration of each metal element And the critical concentration [W] of each metal element calculated in step d above L , calculate the theoretical precipitation rate ε of each metal element at different pH values [W] ;

[0071]

[0072] f. According to the theoretical precipitation rate ε of each metal element at different pH values calculated in step e [W] , plot the curve relationship diagram between the theoretical precipitation rate and the pH value, calculate the minimum pH value that can make the precipitation rate of all metal impurity elements greater than 99.9%, and this pH value is the optimal pH value for the impurity removal process.

[0073] In some preferred embodiments of the present invention, in step 1), the mass ratio of sulfate to persulfate in the composite salt is 1-4:1, and the molar ratio of the total metal element in the composite salt to the lithium element of the lithium-containing material is 0.5-4:1. Among them, the composite salt can be further preferably sodium sulfate and sodium persulfate with lower cost. The mass ratio of sulfate to persulfate in the composite salt can also be selected as 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1; the molar ratio of the total metal element in the composite salt to the lithium element of the lithium-containing material can also be selected as 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1.

[0074] In some preferred embodiments of the present invention, the particle size of the powder obtained in step 1) and step 2) is <30 μm. The lithium-containing material and the lump material need to be ball-milled and screened multiple times, and the mesh number of the sieve used in the screening process decreases sequentially, with a range of 40-500 meshes.

[0075] In some preferred embodiments of the present invention, in the ball milling processes of step 1) and step 2), the mass ratio of grinding beads to solid is 1-10:1, the rotation speed is 300-1000 rpm, and the time is 2-12 h; the mass ratio of grinding beads to slurry in the ball milling process can also be selected as 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1; the rotation speed can also be selected as 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm; the time can also be selected as 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h.

[0076] In some preferred embodiments of the present invention, in step 2), the roasting reaction temperature is 700-850 °C and the time is 0.5-3 h; the roasting reaction temperature can also be selected as 720 °C, 740 °C, 760 °C, 780 °C, 800 °C, 820 °C, 840 °C; the time can also be selected as 1 h, 1.5 h, 2 h, 2.5 h.

[0077] The reaction principle of the roasting process is as follows:

[0078] In the process of heating the lithium-containing material and the composite salt for roasting, since the sodium persulfate in the composite salt has a relatively low melting point, it can start to melt at a relatively low temperature and undergo an ion exchange reaction with the lithium-containing material, thereby significantly reducing the roasting temperature required. During the high-temperature roasting process, the sodium ions in sodium sulfate and sodium persulfate exchange with the lithium ions in the lithium-containing material to form soluble lithium sulfate. The ion exchange reaction can be represented by the following general formula:

[0079] Li 2 O·nM x O y +Na 2 SO 4 →Na 2 O·nM x O y +Li 2 SO 4

[0080] 2Li 2 O·nM x O y +2Na 2 S 2 O 8 →2Na 2 O·nM x O y +2Li 2 SO 4 +2SO 3 ↑+O 2 ↑

[0081] In the formula: M refers to elements such as magnesium, calcium, iron, and aluminum in the lithium-containing material; in addition, elements such as magnesium, calcium, and aluminum in the lithium-containing material may also react with the composite salt to form soluble metal salts and enter the solution during the wet grinding process.

[0082] In some preferred embodiments of the present invention, in step 3), the concentration of dilute sulfuric acid is 0.05 - 0.25 mol / L, and the mass ratio of the dilute sulfuric acid solution to the powder solid is 2 - 4:1; the concentration of dilute sulfuric acid can also be selected as 0.1 mol / L, 0.15 mol / L, 0.2 mol / L; the mass ratio of the solution to the solid can also be selected as 2.5:1, 3:1, 3.5:1.

[0083] In some preferred embodiments of the present invention, in the wet grinding process of step 3), the mass ratio of the grinding beads to the slurry is 1 - 10:1, the rotation speed is 300 - 1000 rpm, the time is 4 - 12 h, and the pore size of the filter membrane used in the filtration process is 0.22 μm; in the wet grinding process, the mass ratio of the grinding beads to the slurry can also be selected as 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1; the rotation speed can also be selected as 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm; the time can also be selected as 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h.

[0084] In some preferred embodiments of the present invention, in step 4), the precipitating agent is one or more of sodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium carbonate, sodium bicarbonate, sodium oxalate, sodium hydroxide, potassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium carbonate, potassium bicarbonate, potassium oxalate, potassium hydroxide, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium carbonate, ammonium bicarbonate, ammonium oxalate, and the amount of the precipitating agent used is 1.02 - 1.2 times the theoretical amount for removing impurity ions, and the amount of the precipitating agent used can also be selected as 1.05 times, 1.1 times, 1.15 times the theoretical amount for removing impurity ions.

[0085] In some preferred embodiments of the present invention, in step 4), the reagent used to adjust the pH value is one or more of saturated sodium hydroxide solution, potassium hydroxide, ammonia water, concentrated sulfuric acid, and the pore size of the filter membrane used in the filtration process is 0.22 μm.

[0086] Now, taking the metal impurity elements in the lithium-containing filtrate described in step 4) as magnesium, calcium, iron, and aluminum, and using sodium phosphate (molecular formula Na 3 PO 4 ·12H 2 O) as an example, the steps of the calculation process in step 4) are as follows:

[0087] The calculation method for the amount of precipitating agent required for impurity removal is:

[0088] a. Calculate the concentration of phosphate ions required based on the concentrations of various metal impurity elements in the lithium-containing filtrate:

[0089]

[0090] Among them, and are the concentrations of magnesium, calcium, iron, and aluminum in the lithium-containing filtrate respectively, is the concentration of phosphate ions;

[0091] b. Then calculate the mass m of sodium phosphate required based on the measured volume V L of the lithium-containing filtrate, the molecular weight of sodium phosphate and the concentration of phosphate ions ;

[0092]

[0093] The calculation method for the optimal pH value for metal impurity precipitation is as follows:

[0094] c. According to the "Lange's Handbook of Chemistry" and relevant information, at 25 °C, the hydrolysis constant of magnesium ions in the solution is and the hydrolysis constant of calcium ions is and the hydrolysis constant of iron ions is and the hydrolysis constant of aluminum ions is and the hydrolysis constant of phosphate ions is and The solubility products of magnesium phosphate, calcium phosphate, iron phosphate, aluminum phosphate, and lithium phosphate are and

[0095] Since there are hydrolysis equilibria of metal ions and phosphate ions in the solution, which will affect the precipitation-dissolution equilibrium of related phosphates, it is necessary to first calculate the distribution coefficients of these ions at different pH values according to the hydrolysis constants of related ions:

[0096]

[0097]

[0098] In the above formulas, and are the distribution coefficients of magnesium ions, calcium ions, iron ions, aluminum ions, and phosphate ions respectively;

[0099] d. According to the solubility product of phosphates corresponding to metal impurities, the concentration of phosphate ions calculated in step a above The distribution coefficients of magnesium ions, calcium ions, iron ions, aluminum ions and phosphate ions calculated in step c above are used to calculate the critical concentrations of various metal elements in the solution, [Mg] L , [Ca] L , [Fe] L and [Al] L , and their expressions are:

[0100]

[0101] Since there is also a dissolution-precipitation equilibrium of lithium phosphate in the solution, the critical concentration of lithium element in the solution is calculated as [Li] L :

[0102]

[0103] e. According to the measured concentrations of magnesium, calcium, iron, aluminum and lithium in the lithium-containing filtrate, and the critical concentrations of various metal ions calculated in step d above, the theoretical precipitation rates ε of various metal elements at different pH values are calculated [W] ;

[0104]

[0105] In the formula, W refers to magnesium, calcium, iron, aluminum and lithium elements in the solution;

[0106] f. According to the calculation results, draw the curves of the critical concentrations and theoretical precipitation rates of metal elements in the solution at different pH values, and select the minimum pH value that can make the precipitation rates of all metal impurity ions greater than 99.9% as the optimal pH value for the impurity removal process.

[0107] It should be noted that in the embodiments of the present invention, the performance and efficiency of the lithium extraction process are further evaluated by calculating the lithium extraction rate and the removal rate of metal elements;

[0108] Among them, the calculation formula of the lithium extraction rate is as follows:

[0109] ε = 1 - m L ω L / m S ω S (7)

[0110] In the formula, ε is the lithium extraction rate, ω L and ω S are the lithium element contents in the lithium-containing filtrate and the lithium-containing material respectively, dimensionless, m L and m S are the masses of the lithium-containing filtrate and the lithium-containing material respectively.

[0111] Among them, the calculation formula for the removal rate of metal elements is as follows:

[0112]

[0113] In the formula, λ M is the leaching rate of Mg, Ca, Fe, Al, and Li, dimensionless, and are the contents of relevant elements in the lithium-containing filtrate and the purified lithium solution, respectively, and are the masses of the lithium-containing filtrate and the purified lithium solution, respectively.

[0114] It should be noted that in the present invention, the ICP (Inductively Coupled Plasma Emission Spectrometer), which is commonly used in the prior art, is used to measure the concentrations of various metal elements in the lithium-containing filtrate and the purified lithium solution.

[0115] The following are specific examples:

[0116] Example 1

[0117] 1) First, weigh 600 g of lithium-containing material #1 with a lithium content of 1.43%, mix it with 149.8 g of composite salt, and then perform multiple ball milling and screening under the conditions of a grinding bead to solid mass ratio of 3:1, a rotation speed of 600 rpm, and a time of 2 h to obtain a powder with a particle size less than 30 μm; the molar ratio of Na element in the composite salt to Li element in the lithium-containing material is 1.5:1, the composite salt is composed of sodium sulfate and sodium persulfate, and the mass fraction of sodium persulfate is 30%;

[0118] 2) Press the powder obtained in step 1) into a block, then calcine it at 850 °C for 1 h to obtain a calcined block material, and then perform ball milling and screening on the calcined block material under the conditions of a grinding bead to solid mass ratio of 3:1, a rotation speed of 600 rpm, and a time of 2 h to obtain a powder with a particle size less than 30 μm;

[0119] 3) Add the powder obtained in step 2) to a dilute sulfuric acid solution with a concentration of 0.1 mol / L, and the mass ratio of the dilute sulfuric acid solution to the powder solid is 4:1. Then perform wet milling under the conditions of a grinding bead to solid mass ratio of 3:1, a rotation speed of 600 rpm, and a time of 8 h. After wet milling is completed, filter the slurry with a filter membrane with a pore size of 0.22 μm to obtain a lithium-containing filtrate;

[0120] 4) Measure the volume of the lithium-containing filtrate obtained in step 3) and the concentrations of various metal elements in the lithium-containing filtrate. The measurement results are shown in Table 1. Then, according to the above formulas (1)-(2) and the data in Table 1, calculate the precipitating agent sodium phosphate (molecular formula Na 3 PO 4 ·12H 2The theoretical dosage of (O) is 49.41 g. According to the above formulas (3)-(6), the theoretical precipitation rate ε of each metal element at different pH values under the current reaction temperature is calculated. [M] , and a curve relationship diagram of the theoretical precipitation rate and pH value as shown in Figure 1 is plotted. According to Figure 1 , it can be known that the minimum pH value that can make the precipitation rate of all metal impurity elements greater than 99.9% under the current reaction temperature is 9.61; according to the above formula (7) and the lithium element content in the data in Table 1, the lithium element extraction rate is calculated, and the results are shown in Table 3;

[0121] 5) Add 51.88 g of sodium phosphate to the lithium-containing filtrate according to 1.05 times the theoretical dosage of sodium phosphate, adjust the pH value to 9.61 with sulfuric acid, and then filter with a filter membrane with a pore size of 0.22 μm to obtain the purified lithium solution; measure the content of each metal element in the purified lithium solution, and calculate the removal rate of each metal element according to formula (8), and the results are shown in Table 2.

[0122] Example 2

[0123] 1) First, weigh 600 g of lithium-containing material #2 with a lithium content of 1.63%, mix it with 170.4 g of composite salt, and then under the conditions of a grinding bead to solid mass ratio of 3:1, a rotation speed of 600 rpm, and a time of 2 h, perform multiple ball milling and screening to obtain a powder with a particle size less than 30 μm; the molar ratio of Na element in the composite salt to Li element in the lithium-containing material is 1.5:1, the composite salt is composed of sodium sulfate and sodium persulfate, and the mass fraction of sodium persulfate is 30%;

[0124] 2) Press the powder prepared in step 1) into blocks, then calcine at 850 °C for 1 h to obtain calcined block materials, and then under the conditions of a grinding bead to solid mass ratio of 3:1, a rotation speed of 600 rpm, and a time of 2 h, ball mill and screen the calcined block materials to obtain a powder with a particle size less than 30 μm;

[0125] 3) Add the powder prepared in step 2) to a dilute sulfuric acid solution with a concentration of 0.1 mol / L, and the mass ratio of the dilute sulfuric acid solution to the powder solid is 4:1. Then, under the conditions of a grinding bead to solid mass ratio of 3:1, a rotation speed of 600 rpm, and a time of 8 h, perform wet grinding. After wet grinding is completed, filter the slurry with a filter membrane with a pore size of 0.22 μm to obtain a lithium-containing filtrate;

[0126] 4) Measure the volume of the lithium-containing filtrate obtained in step 3) and the concentration of each metal element in the lithium-containing filtrate. The measurement results are shown in Table 1. Then, according to the above formulas (1)-(2) and the data in Table 1, calculate the precipitant sodium phosphate (molecular formula Na 3 PO 4 ·12H 2O) The theoretical dosage is 49.60 g; according to the above formulas (3)-(6), the theoretical precipitation rate ε of each metal impurity element at different pH values under the current reaction temperature is calculated. [M] , and the curve relationship diagram of the theoretical precipitation rate and pH value as shown in Figure 2 is plotted. According to Figure 2 , it can be known that the minimum pH value that can make the precipitation rate of all metal impurity elements greater than 99.9% under the current reaction temperature is 9.53; according to the above formula (7) and the lithium element content in Table 1, the lithium element extraction rate is calculated, and the results are shown in Table 3;

[0127] 5) Add 52.08 g of sodium phosphate to the lithium-containing filtrate according to 1.05 times the theoretical dosage of sodium phosphate, adjust the pH value to 9.53 with sulfuric acid, and then filter with a filter membrane with a pore size of 0.22 μm to obtain the purified lithium solution; measure the content of each metal element in the purified lithium solution, and calculate the removal rate of each metal element according to formula (8), and the results are shown in Table 2.

[0128] Example 3

[0129] 1) First, weigh 600 g of lithium-containing material #3 with a lithium content of 0.56%, mix it with 78.3 g of composite salt, and then, under the conditions of a grinding bead to solid mass ratio of 3:1, a rotation speed of 600 rpm, and a time of 2 h, perform multiple ball milling and screening to obtain a powder with a particle size less than 30 μm; the molar ratio of Na element in the composite salt to Li element in the lithium-containing material is 2:1, the composite salt consists of sodium sulfate and sodium persulfate, and the mass fraction of sodium persulfate is 30%.

[0130] 2) Press the powder prepared in step 1) into blocks, then calcine at 850 °C for 1 h to obtain calcined block materials, and then, under the conditions of a grinding bead to solid mass ratio of 3:1, a rotation speed of 600 rpm, and a time of 2 h, ball mill and screen the calcined block materials to obtain a powder with a particle size less than 30 μm.

[0131] 3) Take the ball-milled powder prepared in step 2), add a dilute sulfuric acid solution with a concentration of 0.1 mol / L, and the mass ratio of the dilute sulfuric acid solution to the powder solid is 4:1. Then, under the conditions of a grinding bead to solid mass ratio of 3:1, a rotation speed of 600 rpm, and a time of 8 h, perform wet milling. After wet milling is completed, filter the slurry with a filter membrane with a pore size of 0.22 μm to obtain a lithium-containing filtrate.

[0132] 4) Measure the volume of the lithium-containing filtrate obtained in step 3) and the concentration of each metal element in the lithium-containing filtrate. The measurement results are shown in Table 1. Then, according to the above formulas (1)-(2) and the data in Table 1, calculate the precipitating agent sodium phosphate (molecular formula Na 3 PO 4 ·12H 2(O) The required amount is 49.47 g; according to the above formulas (3)-(6), the theoretical precipitation rate ε of each metal impurity element at different pH values under the current reaction temperature is calculated. [M] , and a curve relationship diagram of the theoretical precipitation rate and pH value as shown in Figure 3 is plotted. According to Figure 3 , it can be known that the minimum pH value that can make the precipitation rate of all metal impurity elements greater than 99.9% under the current reaction temperature is 9.89; according to the above formula (7) and the lithium element content in Table 1, the lithium element extraction rate is calculated, and the results are shown in Table 3;

[0133] 5) After adding 54.41 g of sodium phosphate to the lithium-containing filtrate at 1.1 times the theoretical amount of sodium phosphate, the pH value is adjusted to 9.89 with sulfuric acid, and then the purified lithium solution is obtained by filtering with a filter membrane with a pore size of 0.22 μm; the contents of each metal element in the purified lithium solution are measured, and the removal rate of each metal element is calculated according to formula (8), and the results are shown in Table 2.

[0134] Comparative Example 1

[0135] 1) First, weigh 600 g of lithium-containing material #1 with a lithium content of 1.43%, mix it with 131.7 g of sodium sulfate, and then, under the conditions of a grinding bead to solid mass ratio of 3:1, a rotation speed of 600 rpm, and a time of 2 h, perform multiple ball milling and screening to obtain a powder with a particle size less than 30 μm; the molar ratio of Na element in sodium sulfate to Li element in the lithium-containing material is 1.5:1.

[0136] 2) Press the powder prepared in step 1) into a block, then roast it at 1000 °C for 1 h to obtain a roasted block material, and then, under the conditions of a grinding bead to solid mass ratio of 3:1, a rotation speed of 600 rpm, and a time of 2 h, ball mill and screen the roasted block material to obtain a powder with a particle size less than 30 μm.

[0137] 3) Take the ball-milled powder prepared in step 2), add a dilute sulfuric acid solution with a concentration of 0.1 mol / L, and the mass ratio of the dilute sulfuric acid solution to the powder solid is 4:1. Then, under the conditions of a grinding bead to solid mass ratio of 3:1, a rotation speed of 600 rpm, and a time of 8 h, perform wet milling. After wet milling is completed, filter the slurry with a filter membrane with a pore size of 0.22 μm to obtain a lithium-containing filtrate.

[0138] 4) Measure the volume and lithium element content of the lithium-containing filtrate obtained in step 3), and calculate the lithium element extraction rate. The results are shown in Table 3.

[0139] Comparative Example 2

[0140] 1) First, weigh 600 g of lithium-containing material #2 with a lithium content of 1.63%, mix it with 150.1 g of sodium sulfate, and then perform multiple ball milling and screening under the conditions of a grinding bead to solid mass ratio of 3:1, a rotation speed of 600 rpm, and a time of 2 h to obtain a powder with a particle size less than 30 μm; the molar ratio of Na element in sodium sulfate to Li element in the lithium-containing material is 1.5:1;

[0141] 2) Press the powder obtained in step 1) into a block, then place it in a furnace at 1000 °C for roasting for 1 h to obtain a roasted block material, and then perform ball milling and screening on the roasted block material under the conditions of a grinding bead to solid mass ratio of 3:1, a rotation speed of 600 rpm, and a time of 2 h to obtain a powder with a particle size less than 30 μm;

[0142] 3) Take the ball-milled powder obtained in step 2), add a dilute sulfuric acid solution with a concentration of 0.1 mol / L, and the mass ratio of the dilute sulfuric acid solution to the powder solid is 4:1. Then perform wet milling under the conditions of a grinding bead to solid mass ratio of 3:1, a rotation speed of 600 rpm, and a time of 8 h. After wet milling is completed, filter the slurry with a filter membrane with a pore size of 0.22 μm to obtain a lithium-containing filtrate;

[0143] 4) Measure the volume of the lithium-containing filtrate obtained in step 3) and the lithium element content, and calculate the lithium element extraction rate. The results are shown in Table 3.

[0144] Comparative Example 3

[0145] 1) First, weigh 600 g of lithium-containing material #3 with a lithium content of 0.56%, mix it with 68.8 g of sodium sulfate, and then perform multiple ball milling and screening under the conditions of a grinding bead to solid mass ratio of 2:1, a rotation speed of 600 rpm, and a time of 2 h to obtain a powder with a particle size less than 30 μm; the molar ratio of Na element in sodium sulfate to Li element in the lithium-containing material is 1.5:1;

[0146] 2) Press the powder obtained in step 1) into a block, then place it in a furnace at 1000 °C for roasting for 1 h to obtain a roasted block material, and then perform ball milling and screening on the roasted block material under the conditions of a grinding bead to solid mass ratio of 3:1, a rotation speed of 600 rpm, and a time of 2 h to obtain a powder with a particle size less than 30 μm;

[0147] 3) Take the ball-milled powder obtained in step 2), add a dilute sulfuric acid solution with a concentration of 0.1 mol / L, and the mass ratio of the dilute sulfuric acid solution to the powder solid is 4:1. Then perform wet milling under the conditions of a grinding bead to solid mass ratio of 3:1, a rotation speed of 600 rpm, and a time of 8 h. After wet milling is completed, filter the slurry with a filter membrane with a pore size of 0.22 μm to obtain a lithium-containing filtrate;

[0148] 4) The volume of the lithium-containing filtrate obtained in step 3) and the lithium content were measured to calculate the lithium extraction rate. The results are shown in Table 3.

[0149] Table 1 Volume of lithium-containing filtrate and concentration of each metal element in Examples 1-3

[0150]

[0151] Table 2 Content and removal rate of each metal element in the purified lithium solution in Examples 1-3

[0152]

[0153] nd in the table means it is lower than the minimum detection value of the equipment

[0154] It can be seen from Table 2 above that when the amount of precipitant required for impurity removal and the optimal pH value for impurity precipitation calculated by the method of the present invention are applied to the impurity removal of lithium-containing filtrate, the removal rate of metal impurity elements exceeds 98%, and the lithium loss rate is controlled below 10%, indicating that the method of the present invention can not only greatly improve the accuracy and efficiency of impurity removal, but also can maximize the retention of lithium elements while ensuring the maximum removal of impurities, effectively improving the comprehensive yield and purity of the final lithium salt.

[0155] Table 3 Lithium extraction rate in Examples 1-3 and Comparative Examples 1-3

[0156]

[0157] As can be seen from Table 3, the extraction rates of lithium obtained by the extraction method of the present invention and the extraction method of Comparative Examples 1-3 are similar and both exceed 90%. This comparison result strongly proves that the addition of persulfate can reduce the roasting temperature while maintaining the extraction efficiency of lithium.

[0158] In summary, it should be noted that the above is only a preferred embodiment of the present invention and does not overly limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, for those skilled in the art, they can still make some simple deductions, replacements, or equivalent replacements for some of the technical features of the technical solutions recorded in the aforementioned embodiments without departing from the concept of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for extracting lithium from lithium-containing resources, characterized in that: The following steps are involved: 1) mixing the lithium-containing material with a composite salt, ball-milling and sieving for multiple times to obtain a powder, wherein the composite salt is obtained by mixing a sulfate and a persulfate; 2) pressing the powder obtained in step 1) into blocks, calcining to obtain blocks, and then ball-milling and sieving the blocks to obtain powder; 3) adding dilute sulfuric acid to the powder obtained in step 2) for wet grinding, and filtering to obtain a lithium-containing filtrate; 4) measuring the volume of the lithium-containing filtrate obtained in step 3) and the concentration of each metal element in the lithium-containing filtrate, calculating the amount of precipitant required for impurity removal and the optimal pH value for precipitation of metal impurities, then adding the precipitant to the lithium-containing filtrate and adjusting the pH value, filtering to obtain purified lithium liquid; Wherein, the calculation method of the amount of precipitant required for impurity removal in step 4) is: a. According to the following formula (1), and the concentration of each metal impurity element measured Calculate the required precipitant anion concentration and The units are all mol / L; In the formula, n represents the number of metal impurity elements. represents the concentration of the i-th metal impurity element, x i is the charge number of the i-th metal impurity element ion, and y is the charge number of the precipitant anion; b. The general formula of the precipitant is R c N d According to the following formula (2), the volume of the lithium-containing filtrate V is determined L , and the precipitant anion concentration calculated in step a above Calculate the amount of precipitant m; In the formula, is the molecular weight of the selected precipitant, in g / mol; Wherein, the calculation method of the optimal pH value of the metal impurity precipitation in step 4) is: c. According to the following formulas (3) and (4), and the hydrolysis constant of each metal ion at the current reaction temperature and the hydrolysis constant of the precipitant anion (n is an integer starting from 1), calculate the metal ions (W x+ ) distribution coefficient and precipitant anions (N y- ) distribution coefficient d. According to the following formula (5), the solubility product of the sparingly soluble salt formed by each metal ion and the precipitant anion at the current reaction temperature is The precipitant anion concentration calculated in step a above is And the distribution coefficients of the precipitant anions and each metal ion calculated in step c above, calculate the critical concentration [W] of each metal element in the solution L ; e. According to the following formula (6), the concentration of each metal element is measured and the critical concentration of each metal element calculated in step d above [W] L , the theoretical precipitation rate ε of each metal element at different pH values ​​was calculated [W] ; f. The theoretical precipitation rate ε of each metal element at different pH values ​​calculated in step e [W] , draw a curve relationship between theoretical precipitation rate and pH value, and calculate the minimum pH value that can make the precipitation rate of all metal impurity elements greater than 99.9%. This pH value is the optimal pH value of the impurity removal process.

2. A method for extracting lithium from lithium-containing resources according to claim 1, characterized in that: In the step 1), the mass ratio of sulfate to persulfate in the composite salt is 1-4:1, and the molar ratio of the total metal elements in the composite salt to the lithium element in the lithium-containing material is 0.5-4:

1.

3. A method for extracting lithium from lithium-containing resources according to claim 1, characterized in that: The particle size of the powder obtained in step 1) and step 2) is less than 30 μm.

4. A method for extracting lithium from lithium-containing resources according to claim 1, characterized in that: During the ball milling process of step 1) and step 2), the mass ratio of grinding beads to solid is 1-10:1, the rotation speed is 300-1000 rpm, and the time is 2-12 hours.

5. A method for extracting lithium from lithium-containing resources according to claim 1, characterized in that: In the step 2), the calcination reaction temperature is 700-850° C. and the time is 0.5-3 h.

6. A method for extracting lithium from lithium-containing resources according to claim 1, characterized in that: The concentration of the dilute sulfuric acid in step 3) is 0.05-0.25 mol / L, and the mass ratio of the dilute sulfuric acid solution to the powder solid is 2-4:

1.

7. A method for extracting lithium from lithium-containing resources according to claim 1, characterized in that: In the step 3), the mass ratio of grinding beads to slurry during wet grinding is 1-10:1, the rotation speed is 300-1000 rpm, the time is 4-12 hours, and the pore size of the filter membrane used in the filtration process is 0.22 μm.

8. A method for extracting lithium from lithium-containing resources according to claim 1, characterized in that: In the step 4), the precipitant is one or more of sodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium carbonate, sodium bicarbonate, sodium oxalate, sodium hydroxide, potassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium carbonate, potassium bicarbonate, potassium oxalate, potassium hydroxide, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium carbonate, ammonium bicarbonate, and ammonium oxalate, and the actual amount of the precipitant is 1.02-1.2 times the amount of the precipitant required for impurity removal calculated.

9. A method for extracting lithium from lithium-containing resources according to claim 1, characterized in that: The reagent used to adjust the pH value in step 4) is one or more of saturated sodium hydroxide solution, potassium hydroxide, ammonia water, and concentrated sulfuric acid, and the pore size of the filter membrane used in the filtration process is 0.22 μm.

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