WO2019015013A1 - Process for extracting lithium hydroxide from amblygonite using acidification method - Google Patents

Abstract

Provided is a process for extracting lithium hydroxide from amblygonite using an acidification method, comprising the following steps: the amblygonite is ground and prepared with concentrated sulphuric acid; roasting; clinker slurry leaching; purifying and removal of impurities; evaporation and concentration; causticising; freezing and sodium precipitation; evaporation and crystallisation; re-crystallisation; drying and packaging. The method can extract lithium from amblygonite into a lithium hydroxide monohydrate product conforming to standards, the yield of lithium reaching over 86%.

Description

Process for extracting lithium hydroxide from lithium phosphite by acidification method Technical field:

The invention relates to the technical field of lithium extraction research and development of lithium phosphite, in particular to a process for extracting lithium hydroxide from lithium phosphite by an acidification method.

BACKGROUND OF THE INVENTION The industrial minerals of lithium on the earth mainly include the following:

Table 1 Industrial minerals of lithium

Among them, spodumene is the most famous, because the spodumene is large in scale and simple in composition. The lithium process is mature and is currently the most used lithium mineral. Although lithium mica is also a relatively large scale of mineralization, due to its complex composition and complex lithium extraction process, it is used for less lithium, mainly used in the glass ceramic industry. Iron-lithium mica, lithium-phosphorite and lithium feldspar are sparsely distributed, and the metallogenic scale is small. So far, there have been no reports on industrial applications, and there is no public report on the lithium extraction process for these three minerals.

The lithium-aluminite that we want to study is a lithium mineral with the highest lithium content. Its pure mineral contains 10.1% of lithium oxide, but it is not common in nature. It is occasionally found to be small scale and not used as industrial mining. the value of. But the lithium phosphite mine discovered in Africa now has a certain scale and has the value of industrial mining.

Lithium phosphite is often irregular and nearly equiaxed, and its color is gray, yellow, white, green and white. Due to a certain amount of other symbiotic minerals, it actually contains Li ₂ O8-9.5%, which is the highest industrial mineral containing lithium. It is produced in granitic pegmatites and is sometimes found in Yunyingyan and high-temperature quartz veins. Lithium phosphite is a lithium- and aluminum-containing fluorophosphate produced in granitic pegmatite and symbiotic with spodumene, tourmaline, lithium mica and apatite, and is mainly used as a resource for extracting lithium.

The composition of lithium phosphite is as follows: %

Table 2

Summary of the invention:

One of the objects of the present invention is to provide a process for extracting lithium hydroxide from lithium phosphite by an acidification method, and more particularly to a process for extracting lithium hydroxide from lithium phosphite by a pioneering acidification method.

In order to achieve the above object, the present invention adopts the following technical scheme: a process for extracting lithium hydroxide from lithium phosphite by an acidification method, which comprises the following steps:

(1) Raw material grinding: grinding the lithium phosphite raw material;

(2) Ingredients: the lithium phosphite and the concentrated sulfuric acid after the step (1) are mixed at a weight ratio of 1:0.25 to 0.37;

(3) roasting: the material after mixing in step (2) is calcined to obtain clinker;

(4) slurry leaching: the step (3) clinker is placed in the reaction vessel, water is added and heated and stirred to obtain a lithium-containing leachate;

(5) Purifying and removing impurities: removing impurities such as aluminum or calcium from the solution leached in the step (4);

(6) Evaporation and concentration: the solution after completion of the reaction in the step (5) is concentrated by evaporation to obtain a lithium sulfate solution;

(7) causticization: the lithium sulfate and the crude mother liquor concentrated in step (6) are added together with a sodium hydroxide solution in which the calculated amount of lithium is converted into lithium hydroxide by 20-40%, and then Filtration to obtain a mixed solution of lithium and sodium containing sulfate and hydroxide;

(8) frozen sodium precipitation: a lithium-sodium-containing sulfate and hydroxide mixed solution obtained after completion is frozen;

(9) Evaporation crystallization: the low-sodium mixed solution obtained after the completion of the step (8) is subjected to evaporation crystallization together with the fine mother liquid;

(10) Recrystallization: The solid lithium hydroxide monohydrate obtained after the completion of the step (9) is dissolved in water, heated and stirred to dissolve all of the solution, and then filtered, and the filtrate is again subjected to evaporation crystallization;

(11) Drying: The fine lithium hydroxide monohydrate obtained after the completion of the step 9 is dried.

Preferably, the raw material in the lithium phosphite is ground to 100 to 200 mesh in the step (1).

Preferably, in step (3), the temperature is controlled to be calcined at 500 ° C to 800 ° C, and the calcination time is 20 to 60 minutes.

Preferably, after the material is calcined in the middle of the step (4), the clinker is ground to 100 to 200 mesh.

Preferably, in step (4)), the liquid-solid ratio is 3 to 5:1, the leaching temperature is 20 to 150 ° C, and the constant temperature leaching time is 0.5 to 2 hours.

Preferably, in the step (8), the mixed solution is placed in a refrigerator for freezing, and when the temperature is lowered to about -10 ° C, a large amount of sodium sulfate is precipitated as crystals of sodium sulfate decahydrate.

After separation, a low sodium solution and sodium sulfate decahydrate crystals were obtained.

Preferably, in the step (10), the mixture is heated to 60-90 ° C, stirred to dissolve all of the solution, and then filtered, and the filtrate is again subjected to evaporation crystallization. After a certain amount of crystallization occurs in the solution, the heating is stopped, the stirring is continued, and naturally After cooling to below 50 ° C, it is separated by suction filtration to obtain a fine lithium hydroxide product and a fine mother liquor.

Preferably, the lithium hydroxide monohydrate in step (10) is dissolved in water to a liquid to solid ratio of 3:1.

Preferably, in the step (5), the leachate obtained in the step (4) is adjusted to a pH of 7 to 8 with solid sodium hydroxide, and the solution is heated to 80 to 90 ° C and reacted at a constant temperature for 10 to 15 minutes; To neutralize the acid in the solution and remove impurities such as aluminum in the solution, and then filter the aluminum after completion of the reaction; then add sodium hydroxide to adjust the pH to 14; then add a calculated excess of 10% sodium carbonate saturated solution or in production Lithium mother liquor, the solution is heated to 80-90 ° C during the reaction and reacted at a constant temperature for 10-15 minutes. After the reaction is completed, it is filtered. The filtered supernatant is then adjusted to pH 6.5-7.5 with sulfuric acid to remove the calcium impurities in depth. .

The advantages of the invention are:

1, providing a pioneering process for extracting lithium hydroxide from lithium phosphite; it is ground by lithium phosphite and mixed with concentrated sulfuric acid → roasting → clinker grinding and leaching → purification and removal → evaporation Extracting lithium hydroxide monohydrate product by concentration → causticization → freezing sodium precipitation → evaporation crystallization → recrystallization → drying;

2. The ratio of the materials provided by the present invention, the reaction time, etc. can be economically extracted and utilized to meet the commercial value of the development of the raw materials, so as to further improve the market competitiveness of the products;

3, the experimental scheme is reliable, the impurities are few, the process route is simple, and the mother liquor in the processing process can be further utilized;

4, lithium can be extracted from lithium phosphite to become a standard lithium hydroxide monohydrate product, the yield of lithium can reach more than 86%, lithium phosphite is used to extract lithium, broadening the lithium extraction The range of raw materials.

BRIEF DESCRIPTION OF THE DRAWINGS:

1 is a flow chart of a process for extracting lithium hydroxide monohydrate from lithium phosphite by an acidification method of an embodiment;

Figure 2 is a graph showing the solubility of sodium sulfate as a function of temperature for the examples.

Detailed ways:

Example 1: A process for extracting lithium hydroxide from lithium phosphite by an acidification method, comprising: the following steps:

(1) Raw material grinding: grinding the lithium phosphite raw material;

(2) Ingredients: the lithium phosphite and the concentrated sulfuric acid after the step (1) are mixed at a weight ratio of 1:0.25 to 0.37;

(3) roasting: the material after mixing in step (2) is calcined to obtain clinker;

(4) slurry leaching: the step (3) clinker is placed in the reaction vessel, water is added and heated and stirred to obtain a lithium-containing leachate;

(5) Purifying and removing impurities: removing impurities such as aluminum or calcium from the solution leached in the step (4);

(6) Evaporation and concentration: the solution after completion of the reaction in the step (5) is concentrated by evaporation to obtain a lithium sulfate solution;

(7) causticization: the lithium sulfate and the crude mother liquor concentrated in step (6) are added together with a sodium hydroxide solution in which the calculated amount of lithium is converted into lithium hydroxide by 20-40%, and then Filtration was carried out to obtain a mixed solution of a sulfate and a hydroxide containing lithium and sodium.

(8) frozen sodium precipitation: a lithium-sodium-containing sulfate and hydroxide mixed solution obtained after completion is frozen;

(9) Evaporation crystallization: the low-sodium mixed solution obtained after the completion of the step (8) is subjected to evaporation crystallization together with the fine mother liquid;

(10) Recrystallization: The solid lithium hydroxide monohydrate obtained after the completion of the step (9) is dissolved in water, heated and stirred to dissolve all of the solution, and then filtered, and the filtrate is again subjected to evaporation crystallization;

(11) Drying: The fine lithium hydroxide monohydrate obtained after the completion of the step 9 is dried.

Preferably, the lithium phosphite raw material is ground to 100 to 200 mesh in the step (1).

Preferably, in step (3), the temperature is controlled to be calcined at 500 ° C to 800 ° C, and the calcination time is 20 to 60 minutes.

Preferably, after the material is calcined in the middle of the step (4), the clinker is ground to 100 to 200 mesh.

Preferably, in step (4)), the liquid-solid ratio is 3 to 5:1, the leaching temperature is room temperature (about 20 ° C) to 150 ° C, and the constant temperature leaching time is 0.5 to 2 hours.

Preferably, in the step (8), the mixed solution is placed in a refrigerator for freezing, and when the temperature is lowered to about -10 ° C, a large amount of sodium sulfate is precipitated as crystals of sodium sulfate decahydrate, and after separation, low sodium is obtained. Solution and sodium sulfate decahydrate crystals.

Preferably, in the step (10), the mixture is heated to 60-90 ° C, stirred to dissolve all of the solution, and then filtered, and the filtrate is again subjected to evaporation crystallization. After a certain amount of crystallization occurs in the solution, the heating is stopped, the stirring is continued, and naturally After cooling to below 50 ° C, it is separated by suction filtration to obtain a fine lithium hydroxide product and a fine mother liquor.

Preferably, the lithium hydroxide monohydrate in step (10) is dissolved in water to a liquid to solid ratio of 3:1.

Preferably, in the step (5), the leach solution obtained in the step (4) is adjusted to a pH of 7 to 8 with solid sodium hydroxide, and the solution is heated to 80 to 90 ° C and reacted at a constant temperature for 10 to 15 minutes; The acid is removed and the impurities such as aluminum in the solution are removed, and the aluminum is filtered after completion of the reaction; then, the pH is adjusted to 14 by adding sodium hydroxide; and the saturated sodium carbonate solution of 10% of the calculated amount or the lithium mother liquor in the production is added. During the reaction, the solution is heated to 80-90 ° C and reacted at a constant temperature for 10-15 minutes. After the reaction is completed, it is filtered, and the filtered supernatant is then adjusted with sulfuric acid. To 6.5 to 7.5, the calcium impurities are removed in depth.

The main process routes and technical features of the present invention are detailed as follows:

1, raw materials grinding and ingredients

Grinding the raw materials and mixing them in the batching process is beneficial to the smooth progress of the solid phase reaction. The ingredients are added to react with the lithium mayenite ore and convert the lithium to the water-soluble lithium compound to the maximum extent, thereby facilitating the subsequent The process extracts lithium.

1.1. The lithium aluminite is ground to 180 mesh, then weighed and placed in a porcelain crucible. The concentrated sulfuric acid is then added in proportions and then mixed by hand until the mixture is homogeneous.

The ratio of lithium phosphite to sulfuric acid is: lithium phosphite: sulfuric acid = 1:0.25 ~ ~ 0.37 After the pre-selection of the formula, several groups of main formulas are listed.

The specific test formula is shown in Table 3 below:

Numbering	1	2	3	4
formula	1:0.25	1:0.30	1:0.35	1:0.37

2, roasting

By calcination, the water-insoluble lithium in the material is converted into a water-soluble lithium compound.

The prepared material is placed in a muffle furnace for heating and calcination, the baking temperature is controlled at 500 to 700 ° C (each sample is set to a different baking temperature), and the constant temperature baking time is controlled to 30 minutes.

The calcination temperature is determined by experiments, and the constant temperature roasting time is based on the passage time of the high temperature section of the general roasting kiln in industrial production for about half an hour. Taking the four formulations in the table as an example, the lithium conversion rates at different calcination temperatures are as follows:

Table 4

Calcination temperature

500 ° C

600 ° C

650 ° C

700 ° C

800 ° C

1:0.25	51.26%	55.31%	58.45%	59.68%	59.98%
1:0.30	71.84%	77.19%	82.56%	83.95%	84.12%
1:0.35	76.34%	86.13%	94.36%	95.20	95.52
1:0.37	79.65%	86.96%	95.11%	97.48%	97.58%

The calcination temperature is determined by experiments, and the constant temperature roasting time is based on the passage time of the high temperature section of the general roasting kiln in industrial production for about half an hour. Taking the four formulations in the table as an example, the lithium conversion rates at different calcination temperatures are as follows:

Table 4-1 (Example of roasting with lithium aluminite: sulfuric acid = 1:0.37 ratio)

Table 4-2 (for example, lithium aluminite: sulfuric acid = 1:0.37 ratio and 30 minutes constant temperature roasting)

Fine fineness (mesh)	500 ° C	600 ° C	650 ° C	700 ° C	800 ° C
100	32.49%	35.26%	45.25%	56.28%	63.63%
180	79.65%	86.96%	95.11%	97.48%	97.69%
200	81.52%	87.32%	95.45%	97.62%	97.96%

3, slurry leaching

The calcined clinker is ground to 180 mesh, and then a certain amount (generally 2.5 to 10 g) is weighed into the reaction vessel, and then 100 ml of distilled water is added to the reaction vessel, the reaction vessel is installed, and heating and stirring are started. , set the reaction temperature to 95 ~ 150 ° C, the reaction time is 1 ~ 2 hours, After the reaction is finished, the heating is turned off, the stirring is continued, and the cooling is cooled, then filtered, and the filtrate is sampled and analyzed. The leaching residue is added with 50 ml of water, heated and stirred, washed, filtered, and slag is further washed with 50 ml of water twice, filtered, placed in an oven for drying, and cooled. After weighing and sampling, the amount of lithium oxide contained in the slag was analyzed. The slag water is returned for leaching (no leaching due to measurement and analysis reasons during the test).

In order to obtain a higher concentration and a larger volume of lithium solution, 200 to 400 grams of calcined clinker is weighed each time in a ratio of 3 to 5:1 in a stainless steel reaction pot, and an electric furnace is used for heating, and electric heating is used. Stir. The reaction temperature is also 95 to 150 ° C, and the reaction time is 1 to 2 hours. After the reaction is completed, it is naturally cooled, then filtered, vacuum filtered with a Buchner funnel and a filter bottle, and a vacuum pump. After filtering, the leaching residue is taken out, and the liquid-solid ratio is 3:1, and the mixture is heated and stirred for heating for 10 to 20 minutes. The heating temperature is 10 ° C. 80 ° C or so, and then suction filtration, to be drained, rinsed twice with water, each rinse solution solid ratio of 0.5:1, filtered and dried, taken out and dried in an oven, cooled, weighed and sampled The slag contains lithium oxide, and the slag water can be returned for leaching (no leaching due to measurement and analysis reasons during the test).

Leachate analysis results (1#, 2# corresponding formulations are 1:0.35 and 1:0.37, respectively)

Table 5 (mg/l)

Note: 1#2# is the result of using the reactor at high liquid to solid ratio, and 3# is the result of using the reaction pot at low liquid to solid ratio.

The effects of different leaching temperatures and different leaching times on the leaching rate are as follows

Table 6

The results of the leaching slag analysis are as follows:

Table 7 (%)

4, purification and impurity removal

The leachate obtained in the third step is adjusted to pH 7-8 with solid sodium hydroxide, and the solution is heated to 80 to 90 ° C and reacted at a constant temperature for 10 to 15 minutes to neutralize the acid in the solution and remove impurities such as aluminum in the solution. After the reaction was completed, it was filtered. Then, solid sodium hydroxide was added to adjust the pH to 14 to remove impurities such as magnesium and part of calcium in the solution. In order to remove the calcium in depth, a saturated sodium carbonate solution with a calculated excess of 10% is added (in the production, the lithium hydroxide mother liquor can be used instead of the carbonate). During the reaction, the solution should be heated to 80-90 ° C and reacted at a constant temperature for 10-15 minutes. After the reaction is completed, it is filtered. The filtered supernatant was adjusted to pH 6.5-7.5 with sulfuric acid.

The main chemical reactions for purifying impurities are as follows:

Al ³⁺ +OH ^- →Al(OH) ₃ ↓

Mg ²⁺ +OH ^- →Mg(OH) ₂ ↓

Ca ²⁺ +OH ^- →Ca(OH) ₂ ↓

Ca ²⁺ +CO ₃ ² →CaCO ₃ ↓

5, evaporation and concentration

The solution obtained after the completion of the fourth step is added into a beaker or a stainless steel reaction pot, and placed on an electric furnace to be heated and concentrated by evaporation. When the concentration of lithium oxide in the solution is about 45 g/l, the heating is stopped, and the evaporation is removed by suction filtration. Some impurities precipitated (mainly It is an impurity such as calcium and magnesium which is supersaturated and precipitated, and a clear lithium sulfate concentrate is obtained. The composition of the solution is as follows: (g/l)

Table 8

6, caustic

The concentrated lithium sulphate solution (sample No. 2#) obtained after the completion of the fifth step is added to the sodium hydroxide solution (concentration of sodium hydroxide solution 30%) in a calculated excess amount of 40% together with the crude mother liquor to make all the lithium therein It is converted into lithium hydroxide and then filtered to obtain a mixed solution of a sulfate and a hydroxide containing lithium and sodium. The concentration of Li ₂ O in the solution after causticization is 45 to 50 g/l, and the concentration of OH ^- is 75 to 80 g/l.

7, frozen sodium

The lithium-sodium-containing sulfate and hydroxide mixed solution obtained after the completion of the sixth step is frozen. In the causticized solution, a large amount of sodium sulfate is contained. If the solution is directly evaporated, sodium sulfate is precipitated at the same time as lithium hydroxide monohydrate is precipitated, so that most of the sodium sulfate must be removed first. By utilizing the property that the solubility of sodium sulfate decreases sharply with the decrease of temperature, the above mixed solution is placed in a refrigerator for freezing, and when the temperature is lowered to about -10 ° C, a large amount of sodium sulfate is precipitated as crystals of sodium sulfate decahydrate, and after separation, A low sodium solution and sodium sulfate decahydrate crystals were obtained. In the separated solution The sulfate content is reduced to about 30 g/l. In industrial production, the separated sodium sulfate decahydrate can be directly sold as a by-product, or it can be made into anhydrous sodium sulfate for sale. The curve of sodium sulfate solubility with temperature is shown in Figure 2.

8, evaporation crystallization

The low-sodium mixed solution obtained after the completion of the seventh step is evaporated together with the fine mother liquid. As the concentration of lithium is continuously increased, the lithium hydroxide is gradually supersaturated and precipitates crystals of lithium hydroxide monohydrate, and the amount of the crystal to be crystallized reaches a certain amount. After that, the heating and evaporation were stopped, and the mixture was gradually cooled under slow stirring to precipitate more lithium hydroxide monohydrate crystals. After cooling to near room temperature, separation was carried out to obtain a lithium hydroxide monohydrate solid and a crystallization mother liquor. The obtained solid lithium hydroxide monohydrate is referred to as a crude product, and the impurity content is high, and recrystallization purification is also required. The separated crude mother liquor is returned to the causticizing process and is again causticized with the lithium sulfate concentrated solution.

9, recrystallization

The solid lithium hydroxide monohydrate obtained after the completion of the eighth step is dissolved in distilled water or purified water, the liquid-solid ratio is 3:1, heated to about 80 ° C, stirred to dissolve all, and then filtered. The filtrate is again evaporated and crystallized. After a certain amount of crystals appear in the solution, the heating is stopped, the stirring is continued, and the mixture is naturally cooled to below 50 ° C, and then separated by suction filtration to obtain a fine lithium hydroxide product and a fine mother liquor. Lithium hydroxide is transferred to the next step, and the fine mother liquor is returned to the eighth step of the crude product.

10, drying

Put the fine lithium hydroxide monohydrate obtained after the completion of step 9 into a small porcelain plate, cover the lid, leave a little gap of water vapor, heat it, set the heating temperature to 95 ° C, It was dried at 95 ° C for one hour, taken out and placed in a desiccator. After cooling to room temperature, it was weighed and sampled for analysis.

Table 9

Example 2:

(1) Raw material grinding and ingredients:

The lithium phosphite is first ground to 180 mesh. Take a porcelain crucible, wash and dry, weigh, then weigh the ground lithium-phosphorite powder into the porcelain crucible, weigh it to 400 grams, and then weigh 140 grams of concentrated sulfuric acid with a plastic beaker. The good concentrated sulfuric acid is added to the porcelain crucible and mixed with the lithium aluminophosphate, and mixed by hand. The formula and ratio at this time are: lithium phosphite: sulfuric acid = 1:0.35.

(2) Roasting:

Put the material prepared in the first step with two porcelain crucibles, put them into the muffle furnace, turn on the heating, and set the maximum temperature to 700 °C. After the temperature in the muffle furnace rises to 700 ° C, the temperature is baked for 30 minutes. After the time, the switch is turned off to stop heating. Then, after the temperature of the furnace was lowered, it was taken out in a desiccator, cooled to room temperature, and weighed. It is then ground to a sieve of 180 mesh.

(3-1) Leaching:

Weigh 400 g of the clinker after grinding to 180 mesh in the second step, add 400 g into the stainless steel reaction pot, add 2000 ml of distilled water to the stainless steel reaction pot according to the ratio of liquid to solid ratio of 5:1, and place the reaction pot. On the electric furnace, install electric stirring, cover the lid, turn on heating and stirring, and react at a constant temperature of about 95 °C for 1 hour. During the reaction, the water is replenished several times to ensure that the liquid-solid ratio is basically unchanged.

After the reaction is completed, the hot solution is filtered. Here, a suction filter was used for suction filtration to obtain 1827 ml of the filtrate, which was sampled and analyzed. The analysis results were as follows: (g/l)

The leach residue is heated and stirred and washed at a liquid-solid ratio of about 3:1, and then rinsed. The wet slag weighs 427 grams, and the measuring cylinder is used to measure 1000 ml of distilled water into a stainless steel reaction pot. The reaction pot is placed on an electric furnace, charged with electric stirring, then heated and stirred, and stirred at 70-80 ° C for 15 minutes, and then used. The filter bottle is vacuum filtered, and rinsed twice with water. Each time 100 ml of water is added and filtered. The washed wet slag is placed in an oven with an enamel pan, dried at 105 ° C, and then weighed after cooling. And sample analysis, the analysis results are as follows: (%)

(3-2) Leaching:

The second step of the milled clinker is ground to 100 mesh, 400 g is weighed into a stainless steel reaction pot, and 1600 ml of distilled water is weighed into a stainless steel reaction pot according to a ratio of liquid to solid ratio of 4:1. Place the pot on the electric stove, install the electric stirring, cover the lid, turn on the heating and stirring, and react at a constant temperature of about 95 °C for 1 hour. After the reaction is completed, the hot solution is filtered. Here, a suction filter was used for suction filtration to obtain 1455 ml of the filtrate, which was sampled and analyzed. The analysis results were as follows: (g/l)

The leach residue is heated and stirred and washed at a liquid-solid ratio of about 3:1, and then rinsed. The wet slag weighs 410 grams, and the measuring cylinder is used to measure 1000 ml of distilled water into a stainless steel reaction pot. The reaction pot is placed on an electric furnace, charged with electric stirring, then heated and stirred, and stirred at 70-80 ° C for 15 minutes, and then used. The filter bottle is vacuum filtered, and rinsed twice with water. Each time 100 ml of water is added and filtered. The washed wet slag is placed in an oven with an enamel pan, dried at 105 ° C, and then weighed after cooling. And sample analysis, the analysis results are as follows: (%)

(3-3) Leaching:

The second step of the milled clinker is ground to 200 mesh, 400 g is weighed into a stainless steel reaction pot, and 1200 ml of distilled water is weighed into a stainless steel reaction pot according to a ratio of liquid to solid ratio of 3:1, and the reaction is carried out. Place the pot on the electric stove, install the electric stirring, cover the lid, turn on the heating and stirring, and react at a constant temperature of about 95 °C for 1 hour.

After the reaction is completed, the hot solution is filtered. Here, a suction filter was used for suction filtration to obtain 1056 ml of filtrate, which was sampled and analyzed. The analysis results were as follows: (g/l)

The leach residue is heated and stirred and washed at a liquid-solid ratio of about 3:1, and then rinsed. The wet slag weighs 413 grams, and the measuring cylinder is used to measure 1000 ml of distilled water into a stainless steel reaction pot. The reaction pot is placed on an electric furnace, equipped with electric stirring, then heated and stirred, and stirred at 70-80 ° C for 15 minutes, and then used. The filter bottle is vacuum filtered, and rinsed twice with water. Each time 100 ml of water is added and filtered. The washed wet slag is placed in an oven with an enamel pan, dried at 105 ° C, and then weighed after cooling. And sample analysis, the analysis results are as follows: (%)

(4) purification and impurity removal

The leaching solution obtained in the step 3-1 is adjusted to pH 7-8 with solid sodium hydroxide, and the solution is heated to 80 to 90 ° C and reacted at a constant temperature for 10 to 15 minutes to neutralize the acid in the solution and remove the aluminum in the solution. Impurities, filtered after completion of the reaction. Then, solid sodium hydroxide was added to adjust the pH to 14 to remove impurities such as magnesium and part of calcium in the solution. In order to remove the calcium in depth, a saturated sodium carbonate solution with a calculated excess of 10% is added (in the production, the lithium hydroxide mother liquor can be used instead of the carbonate). During the reaction, the solution should be heated to 80-90 ° C and reacted at a constant temperature for 10-15 minutes. After the reaction is completed, it is filtered. The filtered supernatant was adjusted to pH 6.5-7.5 with sulfuric acid.

(5) Evaporation and concentration:

1794ml of the solution obtained after the completion of the fourth step is added to the beaker, placed on an electric furnace and heated to evaporate and concentrate. When it is concentrated to about 550 ml of the solution, the heating is stopped, the cooling is allowed to stand, and then some filtration is carried out to remove some impurities precipitated during the evaporation process ( Mainly super-saturated precipitated calcium and magnesium impurities, etc., to obtain a clear lithium sulphate concentrate 541ml, the composition of the solution is as follows: (g / l)

Solution composition	Li 2 O	Na	K	Ca	Mg	Fe	SO 4
Test results	46.74	9.63	0.54	0.055	0.003	0.003	169.26

(6-1) causticizing

The concentrated lithium sulfate solution obtained after the completion of the fifth step is added together with the crude mother liquor, and a sodium hydroxide solution (30% sodium hydroxide solution concentration) in which the total amount of lithium is converted into lithium hydroxide is calculated. Then, it was filtered to obtain a mixed solution of a sulfate and a hydroxide containing lithium and sodium. The concentration of Li ₂ O in the solution after causticization is 45 to 50 g/l, and the concentration of OH ^- is 65 to 70 g/l.

(6-2) causticizing

The concentrated lithium sulfate solution obtained after the completion of the fifth step is added together with the crude mother liquor, and a sodium hydroxide solution (30% sodium hydroxide solution concentration) in which the excess amount of lithium is converted into lithium hydroxide is calculated. Then, it was filtered to obtain a mixed solution of a sulfate and a hydroxide containing lithium and sodium. After causticizing the solution concentration of Li ₂ O 48 ~ 52g / l, OH ^- concentration of 60 ~ 65g / l.

(7) frozen sodium

The lithium-sodium-containing sulfate and hydroxide mixed solution obtained after the completion of the step 6-1 is frozen. In the causticized solution, a large amount of sodium sulfate is contained. If the solution is directly evaporated, sodium sulfate will be precipitated at the same time as lithium hydroxide monohydrate is precipitated. Therefore, most of the sodium sulfate must be removed first, and sodium sulfate is used first. The solubility is drastically lowered as the temperature is lowered. The mixed solution is placed in a refrigerator for freezing, and a large amount of sodium sulfate is precipitated as sodium sesquihydrate crystals, and after separation, a low sodium solution and sodium sulfate decahydrate crystals are obtained.

(8) Evaporation crystallization

The low-sodium mixed solution obtained after the completion of the seventh step is evaporated together with the fine mother liquid. As the concentration of lithium is continuously increased, the lithium hydroxide is gradually supersaturated and precipitates crystals of lithium hydroxide monohydrate, and the amount of the crystal to be crystallized reaches a certain amount. After that, the heating and evaporation were stopped, and the mixture was gradually cooled under slow stirring to precipitate more lithium hydroxide monohydrate crystals. After cooling to near room temperature, separation was carried out to obtain a lithium hydroxide monohydrate solid and a crystallization mother liquor. The obtained solid lithium hydroxide monohydrate is referred to as a crude product, and the impurity content is high, and recrystallization purification is also required. The separated mother liquor is returned to the causticization process and is again causticized with the lithium sulfate concentrated solution.

(9) Recrystallization

The solid lithium hydroxide monohydrate obtained after the completion of the eighth step is dissolved in distilled water or purified water, the liquid-solid ratio is 3:1, heated to about 80 ° C, stirred to dissolve all, and then filtered. The filtrate is again evaporated and crystallized. After a certain amount of crystals appear in the solution, the heating is stopped, the stirring is continued, and the mixture is naturally cooled to below 50 ° C, and then separated by suction filtration to obtain a fine lithium hydroxide product and a fine mother liquor. Lithium hydroxide is transferred to the next step, and the fine mother liquor is returned to the eighth step of the crude product.

(10) drying

Put the fine lithium hydroxide monohydrate obtained after the completion of step 9 into a small porcelain plate, cover the lid, leave a gap of water vapor, heat it, set the heating temperature to 95 ° C, and dry at 95 ° C. After one hour, it was taken out and placed in a desiccator. After cooling to room temperature, it was weighed and sampled for analysis.

The lithium hydroxide monohydrate product obtained through the above process meets the industry standard, and the recovery rate of lithium is greater than 86%.

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto. Therefore, all equivalent changes in the principles of the present invention should be included in the scope of the present invention.

Claims (10)

1. A process for extracting lithium hydroxide from lithium phosphite by an acidification method, comprising: the following steps:

   (1) Raw material grinding: grinding the lithium phosphite raw material;

   (2) Ingredients: the lithium phosphite and the concentrated sulfuric acid after the step (1) are mixed at a weight ratio of 1:0.25 to 0.37;

   (3) roasting: the material after mixing in step (2) is calcined to obtain clinker;

   (4) slurry leaching: the step (3) clinker is placed in the reaction vessel, water is added and heated and stirred to obtain a lithium-containing leachate;

   (5) Purifying and removing impurities: removing impurities such as aluminum or calcium from the solution leached in the step (4);

   (6) Evaporation and concentration: the solution after completion of the reaction in the step (5) is concentrated by evaporation to obtain a lithium sulfate solution;

   (7) causticization: the lithium sulfate and the crude mother liquor concentrated in step (6) are added together with a sodium hydroxide solution in which the calculated amount of lithium is converted into lithium hydroxide by 20-40%, and then Filtration to obtain a mixed solution of lithium and sodium containing sulfate and hydroxide;

   (8) frozen sodium precipitation: a lithium, sodium-containing sulfate and hydroxide mixed solution obtained after completion is frozen, and then the sodium sulfate decahydrate crystal is separated;

   (9) Evaporation crystallization: the low-sodium mixed solution obtained after the completion of the step (8) is subjected to evaporation crystallization together with the fine mother liquid;

   (10) Recrystallization: The solid lithium hydroxide monohydrate obtained after the completion of the step (9) is dissolved in water, heated and stirred to dissolve all of the solution, and then filtered, and the filtrate is again subjected to evaporation crystallization;

   (11) Drying: The fine lithium hydroxide monohydrate obtained after the completion of the step 9 is dried.
2. The process for extracting lithium hydroxide from lithium phosphite according to an acidification method according to claim 1, wherein the lithium phosphite raw material is ground to 100 to 200 mesh in the step (1).
3. The process for extracting lithium hydroxide from lithium phosphite according to an acidification method according to claim 1, wherein in the step (3), the temperature is controlled at 500 ° C to 800 ° C for baking, and the baking time is 20 ～. 60 minutes.
4. The process for extracting lithium hydroxide from lithium phosphite according to an acidification method according to claim 1, characterized in that after the material is calcined in the step (4), the clinker is ground to 100 to 200 mesh after cooling.
5. The process for extracting lithium hydroxide from lithium phosphite according to an acidification method according to claim 1, wherein the liquid-solid ratio is leached from 3 to 5:1 in the step (4)).
6. The process for extracting lithium hydroxide from lithium phosphite according to an acidification method according to claim 1, wherein the leaching temperature is 20 to 150 ° C in the step (4), and the constant temperature leaching time is 0.5 to 2 hours. .
7. The process for extracting lithium hydroxide from lithium phosgene according to an acidification method according to any one of claims 1 to 6, wherein in the step (8), the mixed solution is placed in a refrigerator for freezing. When it is lowered to about -10 ° C, a large amount of sodium sulfate is precipitated as crystals of sodium sulfate decahydrate, and after separation, a low sodium solution and sodium sulfate decahydrate crystals are obtained.
8. The process for extracting lithium hydroxide from lithium phosphite according to an acidification method according to any one of claims 1 to 6, wherein in the step (10), the mixture is heated to 60-90 ° C and stirred. After all the solution is dissolved, the filtrate is again evaporated and crystallized. After a certain amount of crystals appear in the solution, the heating is stopped, the stirring is continued, and the mixture is naturally cooled to below 50 ° C and then filtered. Leaving, get the fine lithium hydroxide product and fine mother liquor.
9. The process for extracting lithium hydroxide from lithium phosphite according to an acidification method according to any one of claims 1 to 6, characterized in that: the solid lithium hydroxide monohydrate in step (10) is dissolved in water, and the liquid is solid. The ratio is 3:1.
10. The process for extracting lithium hydroxide from lithium phosgene according to an acidification method according to any one of claims 1 to 6, wherein in the step (5), the leaching solution obtained in the step (4) is solid. Adjust the pH to 7-8 with sodium hydroxide, heat the solution to 80-90 ° C and react at a constant temperature for 10-15 minutes; neutralize the acid in the solution and remove impurities such as aluminum from the solution, and then filter the aluminum after the reaction is completed; then Add sodium hydroxide to adjust the pH to 14; then add a saturated sodium carbonate solution with a calculated excess of 10% or a sinking lithium mother liquor in the process. During the reaction, the solution is heated to 80-90 ° C and the reaction is kept at a constant temperature for 10-15 minutes. After filtration, the filtered supernatant was adjusted to pH 6.5-7.5 with sulfuric acid to remove the calcium impurities in depth.

Images