CN102295303A - Extraction method of lithium carbonate - Google Patents

Abstract

The invention discloses a method for extracting lithium carbonate, which uses lepidolite as a raw material, adopts 1) calcination to remove fluorine, and first puts lepidolite powder in a rotary furnace to calcine and pulverize; 2) acid leaching, and the pulverized lithium Mica is impregnated with sulfuric acid solution, 3) filter to remove residue, and remove the filter residue from the solid-liquid mixed solution in the previous step to obtain mother liquor 1; 4) Freeze and separate, add aluminum hydroxide solution to mother liquor 1, freeze and separate potassium , aluminum, rubidium, and cesium alum to obtain mother liquor 2; 5) Lithium sinking to separate the product, add liquid ammonia to mother liquor 2, then filter and separate to remove residue, add calcium hydroxide emulsion to the filtrate, neutralize, concentrate, and Add sodium carbonate solution to the concentrated solution for reaction, filter and separate, dry the solid to obtain lithium carbonate product, and recover the separated filtrate for recycling. The invention adopts calcination and acid leaching to remove fluorine, the low-temperature extraction process conditions are mild, and the production cost is low.

Description

Method for extracting lithium carbonate

Technical field : the present invention relates to a method for extracting lithium carbonate, particularly a method for extracting lithium carbonate from lepidolite raw materials.

Background technology: Lithium carbonate is an important chemical raw material. With the national new energy development plan, lithium battery new energy is one of the key energy industries supported by the state; and lithium carbonate is an important basic raw material for the development of lithium battery new energy. Its production and demand The quantity is getting bigger and bigger, and the price is getting higher and higher.

Jiangxi Yichun tantalum-niobium-lithium mine is currently the largest tantalum-niobium-lithium mine in Asia. It is rich in tantalum-niobium-lithium resources. The content of lithium dioxide in lepidolite is 4.5%, which has the advantage of extracting lithium carbonate resources. Lepidolite contains potassium, rubidium, A variety of valuable metal elements such as cesium and aluminum, and comprehensive utilization of these resources can greatly increase the utilization value of lithium carbonate extracted from lepidolite, thereby greatly reducing the production cost of lithium carbonate. Therefore extracting lithium carbonate with lepidolite as raw material has a wider market prospect and better economic benefits.

At present, the preparation methods of lithium carbonate mainly include solid ore and liquid ore in terms of raw materials. The liquid ore is mainly extracted from salt lake brine. This method is easy to extract due to low raw material cost, and the process is very mature. The content of magnesium ions is higher, and it is easier to produce industrial-grade lithium carbonate, but the production cost of battery-grade lithium carbonate is also higher. The second is to use ore as raw material, mainly lepidolite and spodumene as raw materials for extraction. The current extraction method is sulfuric acid method or potassium sulfate and limestone sintering method, because the limestone calcination method only uses impurities such as fluorine in the calcined raw materials to be difficult to extract. Remove completely, lithium recovery rate is also low, and product cost is high, as Chinese Patent No. is ZL85101989 " potassium sulfate method handles lepidolite to produce lithium carbonate technology method " promptly carries out high-temperature roasting after potassium sulfate and lepidolite are mixed by proportioning, in Roasting at a temperature of 930° C. for 2 hours, and then carrying out a second-stage four-stage leaching process on the roasted material to extract lithium carbonate products. This method is complicated and causes certain pollution to the environment; The method for extracting lithium in the Chinese medicine industry is based on lepidolite as the raw material, and still only adopts the calcination method to remove fluorine extraction process, the fluorine removal is not clean, the follow-up treatment is difficult, and the lithium yield is not high, so the production cost is high, and the equipment investment is large. Product yield is low.

Summary of the invention : The object of the present invention is to provide a method for extracting lithium carbonate, which uses lepidolite as raw material, adopts calcination, acid leaching to remove fluorine, low-temperature extraction process, mild process conditions, stable operation process, short production cycle, and equipment A method with high utilization rate and low production cost.

The present invention uses lepidolite as a raw material, and adopts a combined method of calcination and acid leaching, including calcination, acid leaching, filtration, freezing, separation, concentration, and lithium precipitation. It is characterized in that the steps are as follows:

1) To remove fluorine by calcination, first place the lepidolite powder in a rotary furnace and calcinate it at a temperature of 840°C-860°C for 2-4 hours, and crush the calcined lepidolite to 250-400 mesh;

2) Acid leaching, mixing the pulverized lepidolite and a sulfuric acid solution with a concentration of 10-30Wt% according to a solid-to-liquid ratio of 1:3-4 for 3-6 hours to obtain a solid-liquid mixed solution;

3) Filter to remove residue, filter the solid-liquid mixed solution in step 2) with a filter press, remove the filter residue, and obtain the filtrate as mother liquor 1;

4) Freezing and separation, adding aluminum hydroxide to the mother liquor 1 to make the solution a saturated solution of K ⁺ and Al ³⁺ , freezing the saturated solution to separate potassium, aluminum, rubidium and cesium alum, and obtaining the filtrate through filtration. mother liquor 2;

5) Lithium sinking separation products, adding liquid ammonia to the mother liquor 2, controlling the pH of the solution to 3-4, then filtering to separate and remove the residue, washing and filtering the filter residue, recovering the filtrate, adding calcium hydroxide emulsion to the filtrate, After neutralization and concentration, a concentrated solution is obtained, and sodium carbonate solution is added to the concentrated solution for reaction, filtration and separation, and the solid is dried to obtain a lithium carbonate product, and the separated filtrate is recovered and recycled. the

The freezing described in the present invention is secondary freezing, that is, primary freezing. The mother liquor 1 is cooled to -5 to 40°C under stirring, and after the solid rubidium, cesium, potassium, and aluminum alum are separated, they are separated by filtration to obtain the separated filtrate; Secondary freezing of the separated filtrate is to cool the separated filtrate to -8～-30°C under stirring, control the concentration in the solution to ≤0.2-0.5g/L, filter and separate, wash the filter residue fully with cold water, and separate the solid potassium alum , and the filtrate is recovered as mother liquor 2.

The method for extracting lithium carbonate described above is preferably step 5) separation, which is to control the mass concentration of Fe ³⁺ , Mg ²⁺ , F ^- , Si ⁴⁺ , and Ca ²⁺ ions in the solution after detecting the solid-liquid mixed solution When ≤0.05%, filter and separate.

The process steps of the present invention are as follows: filler→calcination, defluorination, crushing→acid leaching→separation→slagging→freezing→separation→neutralization→separation→concentration→filtering→lithium sinking.

The present invention adopts the new technology of extracting lithium carbonate from lepidolite ore by calcination and low-temperature acid leaching to remove fluorine. Compared with the existing pure high-temperature roasting method, it has mild process conditions, stable operation process, short production cycle, high equipment utilization rate, lithium carbonate The production method has high yield, low production cost and little impact on the environment.

Utilize lithium carbonate produced by the inventive method to reach more than 99.5% through detection purity, and technical index is as table 1

Li ₂ CO ₃ 99.5% Na ⁺ 0.025% K ⁺ 0.001% Fe ³⁺ 0.002% Ca ²⁺ 0.005% Mg ²⁺ 0.002% SO ₄ ^2- 0.05% ^Cl- 0.005% Cu ²⁺ 0.001% Si 0.005% H ₂ O 0.4% Pb+Zn+Al 0.0008%

In the production process of the present invention, the main chemical reaction equation involved:

Li ₂ O+H ₂ SO ₄ →Li ₂ SO ₄ +H ₂ O K ₂ O+H ₂ SO ₄ →K ₂ SO ₄ +H ₂ O Na ₂ O+H ₂ SO ₄ →Na ₂ SO ₄ +H ₂ O

Al ₂ O ₃ +3H ₂ SO ₄ →AL ₂ (SO ₄ ) ₃ +3H ₂ O Rb ₂ O ₃ +3H ₂ SO ₄ →Rb ₂ (SO ₄ ) ₃ +3H ₂ O

Cs ₂ O+H ₂ SO ₄ →Cs ₂ SO ₄ +H ₂ O Li ₂ SO ₄ + Na ₂ CO ₃ →LiCO ₃ +Na ₂ SO ₄

NH ₃ +Al ₂ (SO ₄ ) ₃ →NH ₄ Al(SO ₄ ) ₂ .

Specific embodiments: the present invention will be further described in detail below in conjunction with the examples.

Embodiment 1 The concentration involved in the embodiment is mass concentration;

The main chemical components in the raw material lepidolite powder are as follows (wt%)

Li ₂ O K ₂ O + Na ₂ O Al ₂ O ₃ SiO _{2 Fe2O3 _} Rb ₂ O Cs ₂ O f 4.0% 8.5% 23.0% 53.57% 0.19% 1.30% 0.20% 4.1%

(1) Calcination and acid leaching to remove fluorine: as a filler, put lepidolite in a rotary kiln, calcinate at 840-860°C for 3 hours to remove most of the fluorine, and then crush it to 250-400 mesh; after testing The content of F in lepidolite powder is about 1.01 wt%;

(2) Re-acid leaching to remove fluoride, take the pulverized lepidolite powder, add dilute sulfuric acid into the reaction kettle according to a certain solid-liquid mass ratio, and boil it. During the boiling process, keep stirring to fully react. At the same time, the water vapor containing hydrofluoric acid in the reaction kettle is extracted, and after being condensed, it becomes a liquid solution for recovery;

The process condition that this embodiment adopts in this step is:

The mass ratio of lepidolite to 25% dilute sulfuric acid solid and liquid is 1:3;

The reaction temperature is 120°C;

The reaction time is 4h;

(3) filter to remove residue, filter the solid-liquid mixed solution in step 2) with a filter press, remove the filter residue, and obtain the filtrate as mother liquor 1;

(4) freezing and separating, adding aluminum hydroxide to the mother liquor 1 to make the solution form a saturated solution of K ⁺ and Al ³⁺ , freezing the saturated solution, separating the mixture of potassium, rubidium, cesium and aluminum alum, and filtering to obtain Filtrate, mother liquor 2; when freezing, this example adopts secondary freezing, and primary freezing is to inject mother liquor 1 in the freezing tank, and under constant stirring conditions, when the temperature drops to -5～40°C, rubidium, cesium, and potassium are obtained. , a mixture of aluminum alum. After the mixed solution is separated, the slag is washed with cold water at a temperature of 25°C to separate the solid rubidium, cesium and potassium alum, and the washing solution is returned to the mother liquor tank as the washing solution; secondary freezing: inject the washing solution described last time In the freezing tank, under constant stirring, continue to lower the temperature to -8～-30°C to obtain the mother liquor 2;

(5) Lithium-precipitation separation products, liquid ammonia is passed into the mother liquor 2, the pH value of the solution is controlled to 3-4, and then the residue is filtered and separated to remove the ammonium aluminum sulfate, and the filter residue is washed and filtered to recover the filtrate;

Add calcium hydroxide emulsion to the filtrate, neutralize and concentrate to obtain a concentrated solution, add sodium carbonate solution to the concentrated solution, react, filter, separate, wash and dry the solid to obtain a lithium carbonate product, and recover the separated filtrate for recycling ;

Adding calcium hydroxide emulsion to separate and control the mass concentration of Fe ³⁺ , Al ³⁺ , Mg ²⁺ , F, ^ε Si ⁴⁺ , and Ca ²⁺ ions in the solution in this step is ≤0.05%. Separated by filtration. The slag is dried and recovered after being washed;

Concentration is to concentrate the solution to a Li ⁺ concentration of 20-45g/L, and then filter; the filtered solution is treated and recycled again.

Claims (3)

1. A method for extracting lithium carbonate, using lepidolite as raw material, adopting a combination method of calcination and acid leaching, comprising calcination, acid leaching, filtration, freezing, separation, concentration, lithium precipitation, characterized in that, it is carried out as follows : 1) Calcination to remove fluorine, first place the lepidolite powder in a rotary furnace and calcinate at 840°C-860°C for 2-4 hours, and crush the calcined lepidolite to 250-400 mesh; 2) Acid leaching, mixing the pulverized lepidolite and a sulfuric acid solution with a concentration of 10-30Wt% according to a solid-to-liquid ratio of 1:3-4 for 3-6 hours to obtain a solid-liquid mixed solution; 3) Filter to remove residue, filter the solid-liquid mixed solution in step 2) with a filter press, remove the filter residue, and obtain the filtrate as mother liquor 1; 4) Freezing and separation, adding aluminum hydroxide to the mother liquor 1 to form a saturated solution of K ⁺ and Al ³⁺ , freezing the saturated solution to separate potassium, rubidium, and cesium alum, and filtering to obtain the filtrate, mother liquor 2 ; 5) Lithium sinking separation products, adding liquid ammonia to the mother liquor 2, controlling the pH of the solution to 3-4, then filtering to separate and remove the residue, washing and filtering the filter residue, recovering the filtrate, adding calcium hydroxide emulsion to the filtrate, After neutralization and concentration, a concentrated solution is obtained, and sodium carbonate solution is added to the concentrated solution for reaction, filtration and separation, and the solid is dried to obtain a lithium carbonate product, and the separated filtrate is recovered and recycled. 2. according to the method for extracting Lithium Retard described in claim 1, it is characterized in that described freezing is secondary freezing namely primary freezing, is that mother liquor 1 is under agitation, is cooled to-5～40 ℃, separates solid rubidium, After cesium and potassium alum, filter and separate to obtain the separated filtrate; then carry out secondary freezing on the separated filtrate, which is to cool the separated filtrate to -8～-30°C under stirring, and control the concentration in the solution to be ≤0.2-0.5g/L. Separation by filtration, washing the filter residue, separating solid potassium, rubidium and cesium alum, and recovering the filtrate as mother liquor 2. 3. The method for extracting lithium carbonate from lepidolite according to claim 1, characterized in that 5) step separation, after detecting the solid-liquid mixed solution, controlling Fe ³⁺ , Mg ²⁺ , F ^- in the solution , Si ⁴⁺ , and Ca ²⁺ ions are separated by filtration when the mass concentration of ions is ≤0.05%.