Method for realizing selective extraction of lithium in lepidolite ore by using urea thermal reduction
Through the urea thermal reduction method, combined with pretreatment, roasting and leaching steps, the problem of selective extraction of lithium in lithium mica ores in the prior art was successfully solved, and efficient and economical lithium ion recovery was achieved, reducing environmental pollution.
Patent Information
- Application Number
- CN202411167187.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-23
- Publication Date
- 2025-02-14
AI Technical Summary
The existing methods of selective lithium extraction from lithium mica ore have problems such as easy corrosion of production equipment, high energy consumption, and high pollution in the production process, and are relatively expensive, making it difficult to achieve efficient selective recycling.
By using the urea thermal reduction method, the three steps of pretreatment, calcination and leaching, urea is used as a reducing agent, and cosolvents such as NaCl or Na2SO4, the calcination temperature and time are optimized, and the lattice structure of lithium mica is destroyed and the efficiency of lithium ions is achieved. Selective recycling.
It improves the recovery rate of lithium ions, realizes efficient and selective recovery of lithium ions, reduces production costs, reduces environmental pollution, and uses low price and good stability.
Abstract
Description
Technical Field
[0001] The invention belongs to the field of lithium extraction from lithium ore, and specifically relates to a method for selectively extracting lithium from lepidolite ore by utilizing urea thermal reduction. Background Art
[0002] Lepidolite is a special resource in Jiangxi. Yichun Tantalum-Niobium Mine is not only the largest tantalum mine in my country, but also the largest lithium mine in the world. The proven exploitable lithium oxide reserves are 1.1 million tons, ranking first in the world. The Li2O content in Yichun lepidolite concentrate is generally about 4.5%, and it also contains useful minerals such as Rb2O, Cs2O, and K2O. How to develop this resource is of great significance to my country's lithium industry. At present, there are many methods for extracting lithium from lepidolite and preparing lithium salts, including potassium sulfate method, chloride method, limestone method, mixed alkali pressure boiling method, sulfuric acid method, sulfuric acid roasting method, etc. Most of these methods can achieve the purpose of lithium extraction, but there are also problems such as extremely easy corrosion of production equipment, high energy consumption, and high pollution in the production process. In particular, according to the current price of raw materials and products, the cost of producing lithium salts with lepidolite is much greater than the cost of producing lithium salts with brine and spodumene. Therefore, it is necessary to develop other methods and consider comprehensive utilization to make the process of producing lithium salts with lepidolite as raw material better applied. Summary of the invention
[0003] In view of the problems faced in the existing selective extraction of lithium from lepidolite ore, the purpose of the present invention is to provide a method for selectively extracting lithium from lepidolite ore using urea thermal reduction, aiming to improve the recovery rate of lithium ions and achieve efficient and selective recovery of lithium ions.
[0004] The method provided by the present invention for selectively extracting lithium from lepidolite ore by urea thermal reduction comprises the following steps:
[0005] Step 1), preprocessing:
[0006] The lepidolite ore material is crushed, screened, washed, filtered, and dried to obtain the lepidolite ore pre-treated material;
[0007] Step 2), roasting:
[0008] The lithium mica ore pretreatment material obtained in step 1) and the reducing agent urea are added into a tubular furnace according to a set ratio, and a co-solvent is added, and roasted in an inert atmosphere. After the roasting is completed, roasted slag is obtained;
[0009] Step 3), leaching:
[0010] Water is added to the roasted slag obtained in step 2) for leaching, and a leaching solution rich in lithium ions is obtained after the leaching is completed.
[0011] The present invention innovatively combines the lithium mica ore material with the effects of a reducing agent and a solvent, and further combines the roasting temperature, time, and the ratio of the reducing agent / solvent, so as to achieve synergy, help to effectively destroy the lattice structure of the lithium mica, and realize efficient and selective recovery of lithium ions.
[0012] In the method of the present invention, there is no special requirement for the lithium content in the lepidolite ore. Considering the economic efficiency of the process, the lithium content in the lepidolite ore is preferably above 10wt.%, more preferably above 12wt.%, and further preferably 12-15wt.%.
[0013] In step 1), the lithium mica ore material is pretreated. The specific operation steps are crushing and screening to obtain fine particles with a particle size of 10 to 15 microns, thereby increasing its specific surface area and thus increasing its reaction activity, making the roasting process more complete.
[0014] Preferably, in step 2), the mass ratio of the lepidolite ore pretreatment material to the reducing agent urea is 1:3-8.
[0015] Preferably, in step 2), the co-solvent is at least one of NaCl and Na2SO4.
[0016] Preferably, in step 2), the amount of the co-solvent added is 5 to 15 wt % of the mass of the pretreated lepidolite ore.
[0017] Preferably, in step 2), the inert atmosphere is argon.
[0018] Preferably, in step 2), the calcination temperature is 300-600° C. and the calcination time is 1-4 hours.
[0019] Preferably, in step 3), the leaching process conditions are: liquid-solid ratio is 10-30 ml:1 g, leaching time is 0.5-1 h, and leaching temperature is room temperature.
[0020] Principle and beneficial effects of the present invention
[0021] The present invention innovatively combines the lithium mica ore material with the effects of a reducing agent and a co-solvent, and further combines the roasting temperature, time, and the ratio of the reducing agent / co-solvent, so as to achieve synergy, help effectively destroy the lattice structure of the lithium mica, and achieve efficient and selective recovery of lithium ions. The main reaction equations involved are as follows:
[0022] CO(NH2)2+H2O→2NH3↑+CO2↑ (1)
[0023] 6Li2O·Al2O3·3SiO2+20O2+28NH3+2SiO2→12LiOH+3H4SiO4+6Al2O3+2Si
[0024] O+
[0025] 14N2(2)
[0026] Urea first undergoes a high-temperature decomposition reaction to produce NH3 and CO2. NH3 is reducing at high temperatures and can react with lithium mica to destroy its structure. In addition, the CO2 gas produced by the decomposition of urea can increase the rate of the gas-solid reaction, making the reduction reaction more thorough. Finally, the soluble LiOH can be separated by simple water immersion. The reducing agent urea used is cheap and has great economic advantages over existing reducing agents. Compared with the use of sulfuric acid roasting, which will produce a large amount of sulfide fumes, and sulfuric acid is an explosive reagent, the urea used in the method of the present invention is stable in nature, the product is pollution-free, and it is environmentally friendly. Compared with carbon thermal reduction, the greenhouse gas produced by urea is greatly reduced. DETAILED DESCRIPTION
[0027] The present invention will be further described in detail below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments.
[0028] In the following examples and comparative examples, the lepidolite ore is selected from a lepidolite mine in Jiangxi, and the components of the lepidolite ore mainly include Li2O·Al2O3·3SiO2, MgO, etc.; wherein the lithium content is 13wt.%Li2O.
[0029] Example 1
[0030] ① Pretreatment: The lithium mica ore material is crushed, screened, washed, filtered, and dried to obtain a lithium mica ore pretreatment material with a particle size of 12 microns;
[0031] ② Calcination: The pretreated lepidolite ore material and urea are uniformly mixed in a mass ratio of 1:5, the mixture is placed in a tubular furnace, 7wt.% of NaCl relative to the pretreated lepidolite ore material is added, argon is introduced, and the mixture is calcined at 400°C for 2h to obtain calcined slag;
[0032] ③ Leaching: Place the roasted slag in water and stir to leach it. The liquid-to-solid ratio is 20ml:1g. The leaching time is 1h and the temperature is room temperature. After the leaching is completed, a leaching solution rich in lithium ions is obtained.
[0033] According to the test and calculation, the leaching rate of Li in the leachate is 98.5%, and the leaching rates of other metal ions are all less than 3%. This is because the NH3 produced by urea can only reduce SiO2 wrapped on the surface of the particles to SiO, thereby destroying the basic structure of lithium mica, and lithium can escape from its structure, but stable oxides such as Al2O3 and MgO will not be reduced, so only lithium can be leached, and other metals basically do not exist in the leachate.
[0034] Example 2
[0035] Compared with Example 1, the only difference is that the addition amount of the co-solvent NaCl solid is 10% of the mass of the pretreated lepidolite ore, and the other operations and parameters are the same as Example 1.
[0036] According to the test and calculation, the leaching rate of Li in the leaching solution is 99.3%, and the leaching rates of other metal ions are all lower than 3%.
[0037] Example 3
[0038] Compared with Example 2, the only difference is that the co-solvent NaCl is replaced by Na2SO4, and the other operations and parameters are the same as Example 2.
[0039] According to the test and calculation, the leaching rate of Li in the leaching solution is 99.5%, and the leaching rates of other metal ions are all lower than 3%.
[0040] Example 4
[0041] Compared with Example 2, the only difference is that NaCl is replaced by a mixture of NaCl and Na2SO4, wherein the mass ratio of the two is 1:1, and the other operations and parameters are the same as those in Example 2.
[0042] According to the test and calculation, the leaching rate of Li in the leaching solution is 99.7%, and the leaching rates of other metal ions are all less than 2%.
[0043] Example 5
[0044] Compared with Example 1, the only difference is that the mass ratios of the lepidolite ore pretreatment material and urea are adjusted to 1:3 and 1:8 respectively.
[0045] After testing and calculation, the leaching rates of Li in the leaching solution were 97.8% and 99.2%, respectively, and the leaching rates of other metal ions were all lower than 2%.
[0046] Example 6
[0047] Compared with Example 1, the only difference is that the calcination temperatures are adjusted to 300° C. and 600° C. respectively.
[0048] After testing and calculation, the leaching rates of Li in the leaching solution were 98.1% and 99.6%, respectively, and the leaching rates of other metal ions were all lower than 2%.
[0049] Example 7
[0050] Compared with Example 1, the only difference is that the solid ratio of the leaching liquid is adjusted to 10 ml: 1 g and 30 ml: 1 g respectively.
[0051] After testing and calculation, the leaching rates of Li in the leaching solution were 98.3% and 99.5%, respectively, and the leaching rates of other metal ions were all lower than 2%.
[0052] Example 8
[0053] Compared with Example 1, the only difference is that the leaching time is adjusted to 0.5h and 0.75h respectively.
[0054] After testing and calculation, the leaching rates of Li in the leaching solution were 97.9% and 98.3% respectively, and the leaching rates of other metal ions were all lower than 2%.
[0055] Comparative Example 1
[0056] Compared with Example 1, the only difference is that the mass ratio of the pretreated lepidolite ore material to urea is adjusted to 1:1. Other operations and parameters are the same as in Example 1.
[0057] After detection and calculation, the leaching rate of Li in the leaching solution was 71.4%. Compared with Example 1, the leaching rate of Li was reduced because the concentration of the reducing agent was reduced, which hindered the forward reaction.
[0058] Comparative Example 2
[0059] Compared with Example 1, the only difference is that the mass ratio of the lepidolite ore pretreatment material to urea is adjusted to 1:15. Other operations and parameters are the same as in Example 1.
[0060] After testing and calculation, the leaching rate of Li in the leaching solution was 99.5%, while the leaching rate of other metals reached 40%. Compared with Example 1, the leaching rate of other metals increased because the concentration of the reducing agent increased, resulting in the reduction of other metals.
[0061] Comparative Example 3
[0062] Compared with Example 3, the only difference is that Na2SO4 is replaced by CaSO4, and the other operations and parameters are the same as Example 1.
[0063] After testing and calculation, the leaching rate of Li in the leaching solution is 83.7%. Compared with Example 3, the leaching rate of Li is reduced because CaSO4 will adhere to the surface of the particles and affect the reaction.
[0064] Comparative Example 4
[0065] Compared with Example 1, the only difference is that the roasting temperature is changed to 200° C., and the other operations and parameters are the same as Example 1.
[0066] After testing and calculation, the leaching rate of Li in the leaching solution was 64.8%. Compared with Example 1, the leaching rate of Li was greatly reduced, because low temperature would reduce the thermodynamics and kinetics of the reduction reaction during the roasting process, affecting the reaction activity.
[0067] Comparative Example 5
[0068] Compared with Example 1, the only difference is that the roasting temperature is changed to 700° C., and the other operations and parameters are the same as Example 1.
[0069] After testing and calculation, the leaching rate of Li in the leaching solution is 63.4%. Compared with Example 1, the leaching rate of Li is greatly reduced because high temperature will cause lithium metal solid solution, which limits the escape of lithium.
[0070] Comparative Example 6
[0071] Compared with Example 1, the only difference is that urea is not added, and other operations and parameters are the same as Example 1.
[0072] After testing and calculation, the leaching rate of Li in the leaching solution is 18.6%. Compared with Example 1, the leaching rate of Li is greatly reduced because the addition of no reducing agent will cause the lithium mica structure to be unable to be destroyed, and only a small amount of lithium on the surface will escape.
[0073] Comparative Example 7
[0074] Compared with Example 1, the only difference is that no co-solvent is added, and other operations and parameters are the same as Example 1.
[0075] After testing and calculation, the leaching rate of Li in the leaching solution is 46.7%. Compared with Example 1, the leaching rate of Li is greatly reduced, because the solvent can reduce the roasting temperature, and if the solvent is not added, the roasting temperature will be insufficient and the structure of the lithium mica cannot be destroyed.
Claims
1. A method for selectively extracting lithium from lepidolite ore using urea thermal reduction, comprising the following steps: Step 1), preprocessing: The lepidolite ore material is crushed, screened, washed, filtered, and dried to obtain the lepidolite ore pre-treated material; Step 2), roasting: The lithium mica ore pretreatment material obtained in step 1) and the reducing agent urea are added into a tubular furnace according to a set ratio, and a co-solvent is added, and roasted in an inert atmosphere. After the roasting is completed, roasted slag is obtained; Step 3), leaching: Water is added to the roasted slag obtained in step 2) for leaching, and a leaching solution rich in lithium ions is obtained after the leaching is completed.
2. The method according to claim 1, characterized in that In step 2), the mass ratio of the lepidolite ore pretreatment material to the reducing agent urea is 1:3-8.
3. The method according to claim 1, characterized in that In step 2), the co-solvent is at least one of NaCl and Na2SO4.
4. The method according to claim 1, characterized in that: In step 2), the amount of the co-solvent added is 5 to 15 wt % of the mass of the pretreated lepidolite ore.
5. The method according to claim 1, characterized in that In step 2), the inert atmosphere is argon.
6. The method according to claim 1, characterized in that In step 2), the calcination temperature is 300-600° C. and the calcination time is 1-4 hours.
7. The method according to claim 1, characterized in that In step 3), the leaching process conditions are: liquid-solid ratio is 10-30 ml: 1 g, leaching time is 0.5-1 h, and leaching temperature is room temperature.