A method for extracting lithium from waste lithium molecular sieve

Abstract

The present application belongs to the technical field of lithium molecular sieve recovery, and particularly relates to a method for extracting lithium from waste lithium molecular sieve. The present application adopts a low-temperature salt leaching process to extract lithium, consumes less auxiliary raw materials, and has low energy consumption. After grinding and sieving the waste lithium molecular sieve, sodium salt solution is added for leaching. The filtered lithium leaching solution is adjusted to pH=5-6 with acid solution, and then silicon and aluminum are removed at 60-90 DEG C for 0.5-1h, and the resulting first clean solution is precisely filtered. Sodium carbonate and sodium hydroxide are added to the first clean solution, which is heated to 80-90 DEG C and then kept for 0.5-1h to deposit calcium and magnesium, and the resulting lithium-containing clean solution is precisely filtered. Then, lithium carbonate is deposited. The lithium extraction method is a high-efficiency and selective lithium extraction process, and the single lithium leaching rate is more than 98%, and a small amount of silicon and aluminum is leached, which greatly facilitates the next step of impurity removal and purification, and has significant technical and economic advantages.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of recovery of lithium molecular sieve, and particularly relates to a method for extracting lithium from waste lithium molecular sieve. BACKGROUND

[0002] Lithium molecular sieve is mainly used in pressure swing adsorption oxygen generating device. After repeated use for several times, the adsorption performance of lithium molecular sieve decreases, and it needs to be eliminated from the economic benefits. In recent years, with the growth of household and medical oxygen demand, a large amount of lithium molecular sieve is used to prepare oxygen, thereby resulting in a large amount of waste lithium molecular sieve generated every year.

[0003] Lithium molecular sieve is a lithium X-type silico-aluminate crystal, in which the content of lithium is about 4%, which is much higher than the content of lithium in spodumene and lepidolite, two kinds of lithium ores, and has high recycling value. Since lithium molecular sieve is a silico-aluminate, such a substance is easily destroyed by acid or alkali, so that lithium, silicon and aluminum in it exist in a free state in the solution. In the process of precipitating lithium carbonate, a large amount of silicon and aluminum impurities are wrapped in the product, resulting in low product purity. How to selectively extract lithium from waste lithium molecular sieve economically and simply has become a technical problem. SUMMARY

[0004] In order to solve the problems existing in the prior art, the present application provides a method for efficiently recovering lithium from waste lithium molecular sieve, which can efficiently leach lithium while basically not leaching silicon and aluminum.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0006] A method for extracting lithium from waste lithium molecular sieve, comprising the following steps:

[0007] (1) Raw material pretreatment: grinding and sieving the waste lithium molecular sieve (preferably sieving through a 100-mesh sieve);

[0008] (2) Lithium leaching: adding 20wt%-35wt% of a sodium salt solution to the sieved lithium molecular sieve powder, uniformly stirring and mixing, and then heating to 30-80℃ for leaching. The molar ratio of sodium to lithium in the sodium salt solution to the lithium in the lithium molecular sieve is (2-5):1 (preferably 4:1), and the leaching time is 1-3h;

[0009] (3) Separation of leaching solution: after leaching is completed, solid-liquid separation is performed by using a filtering device to obtain filter residue and lithium leaching solution. The lithium leaching solution enters the first impurity removal process of step (4), the filter residue is washed with water, the washing liquid is returned to be used for preparing the sodium salt solution, and the filter residue after washing is treated as solid waste;

[0010] (4) primary impurity removal: after adjusting the pH of the lithium leaching solution to 5-6 with an acid solution, stirring to raise the temperature to 65-80°C, then keeping the temperature at 65-80°C for 0.5-1h to remove silicon and aluminum, and precision filtering to obtain a primary purified solution;

[0011] (5) secondary impurity removal: according to the content of calcium and magnesium in the primary purified solution, adding sodium carbonate and sodium hydroxide thereto, heating to 80-90°C, then keeping the temperature for 0.5-1h to deposit calcium and magnesium, and precision filtering to obtain a lithium-containing purified solution;

[0012] (6) lithium carbonate deposition: after raising the lithium (in terms of Li ions) concentration of the lithium-containing purified solution to 30-35g / L by evaporation and concentration, adding a sodium carbonate solution with a concentration of 250-300g / L thereto to deposit lithium carbonate, and drying the obtained lithium carbonate after washing with hot water to obtain a lithium carbonate product.

[0013] Further, the sodium salt solution in step (2) is a sodium chloride solution, a sodium sulfate solution or a sodium nitrate solution.

[0014] Further, the acid solution in step (4) is 2-4mol / L hydrochloric acid, sulfuric acid or nitric acid.

[0015] Further, the drying conditions in step (6) are drying at 150°C for 2h.

[0016] Further, the leaching conditions in step (2) are leaching at 60-70°C for 1.5-2h.

[0017] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0018] 1. Compared with the conventional ore lithium extraction process, the present application uses a low-temperature salt leaching process, consumes less auxiliary raw materials and has low energy consumption, while the acid leaching, salt leaching and alkali leaching processes of the conventional ore lithium extraction process consume more auxiliary raw materials and require high-temperature reactions, resulting in serious equipment corrosion and high energy consumption.

[0019] 2. Compared with the ordinary water solution exchange method, the present application is a high-efficiency lithium extraction process, and the single lithium leaching rate can reach more than 98%, while the single exchange rate of the ordinary water solution exchange method is only 20-30%, and high-concentration salt solution is required for continuous multiple exchanges, resulting in low salt solution utilization rate and large consumption (Li Zhiliang, Zhi Jianping, Zhang Yulin, Initial Material for Li + , Ca 2+ Mixed-type low-silicon X-type molecular sieve (LSX) preparation and influence of adsorption performance [j], Journal of Inorganic Materials, Vol. 23, No. 5, Sep., 2008);

[0020] 3、The lithium extraction method is a high-efficiency selective lithium extraction process, and the single lithium leaching rate is 98% or more, a small amount of silicon and aluminum is leached, which provides great convenience for the next step of impurity removal and purification, and the technical and economic efficiency is remarkable. DETAILED DESCRIPTION

[0021] The technical solutions of the present application will be described in detail below in combination with specific embodiments.

[0022] The waste lithium molecular sieve used in the following examples is an adsorbent eliminated from a pressure swing adsorption oxygen generator of Yingde Gas Group, and the lithium content thereof is 4.15wt%.

[0023] The specific operation process of precision filtration in the following examples is as follows: three layers of 12.5cm medium-speed filter paper are laid in a round funnel, and then part of the 12.5cm medium-speed filter paper is cut into shreds, soaked in pure water to form paper pulp, the obtained paper pulp is laid on the filter paper in the funnel, the edge is compacted with a glass rod, and after vacuum filtration, a filter cake is formed and then filtration is performed.

[0024] Example 1 A method for extracting lithium from waste lithium molecular sieve, the specific steps are as follows:

[0025] 200g of waste lithium molecular sieve is ground through a 100 mesh sieve, mixed with a 25wt% sodium chloride solution at a sodium-lithium ion molar ratio of 4:1, fully stirred into a slurry, heated to 60℃, and kept at this temperature for 2h of leaching, filtered to obtain 780ml of lithium chloride leaching solution, and the filter residue is washed with 800ml of cold pure water to obtain 800ml of lithium chloride washing solution, ICP detection shows that the lithium ion content in the lithium chloride leaching solution and the lithium chloride washing solution is 9.54g / L and 0.53g / L respectively, and the calculation shows that the leaching rate of lithium is 98.2% (in the present application, the leaching rate of lithium = the percentage of lithium content in the lithium chloride leaching solution and the waste lithium molecular sieve), the lithium chloride washing solution is returned to the previous step to prepare the sodium chloride solution, and the filter residue after pure water washing is treated as solid waste;

[0026] The obtained lithium chloride leaching solution was adjusted to pH = 6.0 with hydrochloric acid of 2 mol / L concentration, and then heated to 80°C. After 0.5 h stirring at this temperature to remove silicon and aluminum, the primary filtrate was obtained by precision filtration. The calcium ion and magnesium ion contents in the primary filtrate were 0.2219 g / L and 0.2353 g / L respectively, as measured by ICP. 1 g of sodium carbonate and 2 g of sodium hydroxide were added to the primary filtrate, which was then heated to 80°C. After 0.5 h stirring at this temperature to remove calcium and magnesium, the lithium chloride net solution was obtained by precision filtration. The lithium ion concentration in the lithium chloride net solution was 9.43 g / L, as measured by ICP. The obtained lithium chloride net solution was concentrated by evaporation to a lithium ion concentration of 30 g / L, and then 230 ml of sodium carbonate solution of 300 g / L concentration was added to precipitate lithium carbonate. The obtained lithium carbonate was washed twice with hot water (hot water washing temperature was 70-80°C, the same below) and then baked at 150°C for 2 h. The lithium carbonate content in the baked sample was 99.4%, the silicon content was 15.8 ppm, and the aluminum content was 4.6 ppm.

[0027] Example 2 A method for extracting lithium from waste lithium molecular sieve, the specific steps are as follows:

[0028] 200 g of waste lithium molecular sieve was ground through a 100 mesh sieve and mixed with 25 wt% sodium sulfate solution at a sodium-lithium ion molar ratio of 4:1. After sufficient stirring to form a slurry, the temperature was raised to 70°C, and the slurry was stirred for 1.5 h at this temperature. After filtration, 1360 ml of lithium sulfate leaching solution was obtained. The filter residue was washed with 1400 ml of cold pure water to obtain 1390 ml of lithium sulfate washing solution. The lithium ion concentrations in the lithium sulfate leaching solution and the lithium sulfate washing solution were 5.41 g / L and 0.351 g / L respectively, as measured by ICP. The lithium leaching rate was calculated to be 98.1%. The obtained lithium sulfate leaching solution was adjusted to pH 5.0 with 2 mol / L sulfuric acid, and then heated to 70°C. After 0.5 h stirring at this temperature to remove silicon and aluminum, the filtrate was obtained by precision filtration. The calcium ion and magnesium ion contents in the filtrate were 0.1665 g / L and 0.1765 g / L respectively, as measured by ICP. 1.2 g of sodium carbonate and 2.4 g of sodium hydroxide were added to the filtrate, which was then heated to 80°C. After 0.5 h stirring at this temperature to remove calcium and magnesium, the lithium sulfate net solution was obtained by precision filtration. The lithium ion concentration in the net solution was 5.62 g / L, as measured by ICP. The lithium sulfate net solution was concentrated by evaporation to a lithium ion concentration of 32 g / L, and then 270 ml of sodium carbonate solution of 250 g / L concentration was added to precipitate lithium carbonate. The obtained product was washed twice with hot water and then baked at 150°C for 2 h. The lithium carbonate content in the baked sample was 99.2%, the silicon content was 21.5 ppm, and the aluminum content was 5.3 ppm.

[0029] Example 3 A method for extracting lithium from waste lithium molecular sieve, the specific steps are as follows:

[0030] Take 200 g of waste lithium molecular sieve, grind through 100 mesh sieve, 25 wt% sodium nitrate solution is fully stirred according to the sodium lithium ion molar ratio of 4:1, heated to 65℃, stirred at this temperature for 2h, after filtration, the lithium nitrate leaching solution is 1650 ml, the filter residue is washed with 1700 ml of cold pure water to obtain 1700 ml of lithium nitrate washing solution, ICP detection shows that the lithium ion concentration in the lithium nitrate leaching solution and the lithium nitrate washing solution is 4.6 g / L and 0.165 g / L respectively, and the lithium leaching rate is calculated to be 98.5%. After adjusting the pH of the obtained lithium nitrate leaching solution to 5.5 with 2 mol / L nitric acid, heating to 65℃, and stirring at 65℃ for 0.5h to remove silicon and aluminum, the contents of calcium and magnesium ions in the filtrate are 0.1601 g / L and 0.1059 g / L respectively after precise filtration and ICP detection. Add 1.4 g of sodium carbonate and 1.8 g of sodium hydroxide to the filtrate, heat to 70℃, and keep at 70℃ for 0.5h to remove calcium and magnesium, then precise filtration to obtain lithium nitrate net solution, ICP detection shows that the lithium ion concentration in the lithium nitrate net solution is 4.75 g / L. Concentrate the net solution to a lithium ion concentration of 35 g / L, add 200 ml of 350 g / L sodium carbonate solution to precipitate lithium carbonate, and wash the obtained product with hot water twice, then bake at 150℃ for 2h. The lithium carbonate content in the baked sample is 99.5%, the silicon content is 12.4 ppm, and the aluminum content is 2.8 ppm.

[0031] Example 4 A method for extracting lithium from waste lithium molecular sieve, the specific steps are as follows:

[0032] Take 200 g of waste lithium molecular sieve, grind through 100 mesh sieve, and mix with 25 wt% sodium chloride solution at a molar ratio of sodium to lithium ions of 3:1 to form a slurry. Heat to 60°C and keep soaking for 2 hours at 60°C. Filter to obtain 650 ml of lithium chloride leaching solution. Rinse the filter residue with 660 ml of cold pure water to obtain 650 ml of lithium chloride washing solution. ICP detection shows that the lithium ion concentrations in the lithium chloride leaching solution and the lithium chloride washing solution are 10.7 g / L and 0.5662 g / L, respectively. The lithium leaching rate of this step is 91.6%, which basically meets the leaching requirements. Impurity removal stage: adjust the pH of the obtained lithium chloride leaching solution to 6.0 with 2 mol / L hydrochloric acid, then heat to 80°C, and stir for 0.5 hours at 80°C to remove silicon and aluminum. After precision filtration, ICP detection shows that the calcium and magnesium ion contents in the filtrate are 0.2322 g / L and 0.2615 g / L, respectively. Add 0.8 g of sodium carbonate and 1.7 g of sodium hydroxide to the filtrate, heat to 80°C, and stir for 0.5 hours at 80°C to remove calcium and magnesium. After precision filtration, obtain lithium chloride pure solution. ICP detection shows that the lithium ion concentration in the lithium chloride pure solution is 11.2 g / L. Concentrate the pure solution to a lithium ion concentration of 30 g / L, and add 190 ml of 300 g / L sodium carbonate solution to precipitate lithium carbonate. The obtained product is washed with hot water twice and baked at 150°C for 2 hours. The lithium carbonate content in the dried sample is 99.5%, the silicon content is 11.6 ppm, and the aluminum content is 2.5 ppm.

[0033] Comparative Example 1

[0034] Take 200 g of waste lithium molecular sieve, grind through 100 mesh sieve, and mix with 25 wt% sodium chloride solution at a molar ratio of sodium to lithium ions of 3:1 to form a slurry. Heat to 60°C and keep soaking for 2 hours at 60°C. Filter to obtain 650 ml of lithium chloride leaching solution. Rinse the filter residue with 660 ml of cold pure water to obtain 650 ml of lithium chloride washing solution. ICP detection shows that the lithium ion concentrations in the lithium chloride leaching solution and the lithium chloride washing solution are 10.7 g / L and 0.5662 g / L, respectively. The lithium leaching rate of this step is 91.6%, which basically meets the leaching requirements. Impurity removal stage: adjust the pH of the obtained lithium chloride leaching solution to 6.0 with 2 mol / L hydrochloric acid, then heat to 80°C, and stir for 0.5 hours at 80°C to remove silicon and aluminum. After precision filtration, ICP detection shows that the calcium and magnesium ion contents in the filtrate are 0.2322 g / L and 0.2615 g / L, respectively. Add 0.8 g of sodium carbonate and 1.7 g of sodium hydroxide to the filtrate, heat to 80°C, and stir for 0.5 hours at 80°C to remove calcium and magnesium. After precision filtration, obtain lithium chloride pure solution. ICP detection shows that the lithium ion concentration in the lithium chloride pure solution is 11.2 g / L. Concentrate the pure solution to a lithium ion concentration of 30 g / L, and add 190 ml of 300 g / L sodium carbonate solution to precipitate lithium carbonate. The obtained product is washed with hot water twice and baked at 150°C for 2 hours. The lithium carbonate content in the dried sample is 99.5%, the silicon content is 11.6 ppm, and the aluminum content is 2.5 ppm.

[0035] Comparative Example 2:

[0036] The same waste lithium molecular sieve as in Example 1 was selected, except that the leaching temperature was changed to room temperature (25°C) for 2 h, and other conditions were the same as in Example 1. The lithium chloride leach liquor was filtered, and the filter residue was rinsed to obtain the lithium chloride rinse liquor. The lithium leaching rate of this step was 88.69%, and the leaching rate was low, which was not economical.

[0037] Comparative Example 3:

[0038] The same waste lithium molecular sieve as in Example 1 was selected, except that the leaching time was changed to 1 h, and other conditions were the same as in Example 1. The lithium chloride leach liquor was filtered, and the filter residue was rinsed to obtain the lithium chloride rinse liquor. The lithium leaching rate of this step was 83.6%, and the leaching rate was low, which was not economical.

[0039] Comparative Example 4:

[0040] The same waste lithium molecular sieve as in Example 1 was selected, except that the leaching agent was changed to sulfuric acid instead of sodium chloride, and other conditions were the same as in Example 1. 200 g of the waste lithium molecular sieve was ground to pass through a 100 mesh sieve, and then mixed with 183 ml of sulfuric acid with a mass concentration of 25% at a hydrogen ion to lithium ion molar ratio of 4:1 by fully stirring. After the temperature was increased to 60°C and leached for 2 h, the lithium molecular sieve gradually broke down as the reaction proceeded. In the later stage of leaching, the system was in a colloidal state, which was difficult to filter.

Claims

1. A method for extracting lithium from waste lithium molecular sieve, comprising the following steps: (1) raw material pretreatment: grinding and sieving the waste lithium molecular sieve; (2) lithium leaching: adding 20wt%-35wt% sodium salt solution to the sieved lithium molecular sieve, stirring and mixing uniformly, then heating to 60-80℃ for leaching, the molar ratio of sodium to lithium in the sodium salt solution to lithium in the lithium molecular sieve is (3-5):1, the leaching time is 1.5-3h; the sodium salt solution is sodium chloride solution, sodium sulfate solution or sodium nitrate solution; the leaching process conditions are: leaching at 60-70℃ for 1.5-2h; (3) leaching solution separation: after leaching, solid-liquid separation is carried out to obtain filter residue and lithium leaching solution, the lithium leaching solution enters the first impurity removal process of step (4), the filter residue is washed with water, the washing liquid is returned to prepare the sodium salt solution, and the filter residue after washing is treated as solid waste; (4) first impurity removal: adjusting the pH of the lithium leaching solution to 5-6 with acid solution, stirring and heating to 65-80℃, then incubating at 65-80℃ for 0.5-1h to remove silicon and aluminum, and precision filtering to obtain first clean liquid; the acid solution is 2-4mol / L hydrochloric acid, sulfuric acid or nitric acid; (5) second impurity removal: according to the content of calcium and magnesium in the first clean liquid, sodium carbonate and sodium hydroxide are added, heated to 80-90℃ and incubated for 0.5-1h to deposit calcium and magnesium, and precision filtered to obtain lithium-containing clean liquid; (6) lithium carbonate deposition: the lithium concentration of the lithium-containing clean liquid is increased to 30-35g / L by evaporation and concentration, then 250-300g / L sodium carbonate solution is added to deposit lithium carbonate, and the obtained lithium carbonate is washed with hot water and dried to obtain lithium carbonate product.

2. The method of claim 1, wherein, The drying conditions in step (6) are: drying at 150℃ for 2h.