A method for purifying the lithium leaching solution from aluminum electrolysis waste

Abstract

The present application relates to a method for purifying a lithium leaching solution from aluminum electrolysis waste, belonging to the field of purification and refinement of lithium-containing leaching solutions in the process of extracting lithium from aluminum electrolysis waste. The technical problem to be solved by the present application is that in the prior art, the lithium loss rate is high and the lithium carbonate recovery rate is low during the purification process of the lithium leaching solution from aluminum electrolysis waste. The technical solution provided by the present application is as follows: After adding a stabilizer calcium nitrate / calcium chloride to the leaching solution, an alkaline substance is added to adjust the pH value of the solution to 8.0 - 9.0, and then the reaction is continued. After solid-liquid separation, solution A and filter residue A are obtained. Subsequently, sodium carbonate is added to solution A for reaction. After the purification process, the concentrations of calcium ions and fluoride ions in the leaching solution are lower than 10 mg / L, and the concentrations of magnesium ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, copper ions, etc. are close to or equal to zero. The lithium ions are basically not lost. The overall disposal process is short, there is no requirement for the original leaching solution, the lithium loss rate is low, and the impurity removal effect is good and the efficiency is high.

Description

Technical Field

[0001] This application relates to the field of purification of lithium-containing leaching solution in the process of extracting lithium from aluminum electrolysis waste, and particularly relates to a method for purifying the leaching solution of lithium extracted from aluminum electrolysis waste. Background Art

[0002] At present, there are mainly three technologies for extracting lithium from aluminum electrolysis waste in industry. The first is direct acid leaching, the second is acid leaching or salt leaching after roasting, and the third is salt leaching. No matter which lithium extraction method is used, it is inevitable that the leaching solution contains impurity elements other than lithium, mainly including fluoride ions, aluminum ions, calcium ions, iron ions, and there are also a small amount of manganese ions, magnesium ions, copper ions, nickel ions, etc. In order to ensure the purity of the final lithium carbonate product, these impurity ions need to be removed.

[0003] The existing technologies for preparing lithium carbonate products by extracting lithium from aluminum electrolysis waste mainly focus on the leaching process of lithium salts, but the records of the key leaching solution purification process are not detailed enough. Most of them are too simple, and the types of removed impurities are less, the types of removed impurities are not complete enough, and the lithium loss rate is too high, resulting in too low yield of lithium carbonate products and being difficult to be actually applied. Therefore, how to comprehensively remove impurities in the lithium extraction leaching solution on the premise of low lithium loss rate is a technical problem that needs to be solved urgently at present. Summary of the Invention

[0004] This application provides a method for purifying the leaching solution of lithium extracted from aluminum electrolysis waste to solve the technical problems of high lithium loss rate and low lithium carbonate yield in the purification process of the leaching solution of lithium extracted from aluminum electrolysis waste in the prior art.

[0005] This application provides a method for purifying the leaching solution of lithium extracted from aluminum electrolysis waste, and the method includes:

[0006] Adding a first set substance to stabilize lithium ions in the leaching solution;

[0007] Adding a second set substance to adjust the leaching solution to a first set pH value, performing a first chemical reaction, and separating solid and liquid to obtain a first solution;

[0008] Adding a third set substance to the first solution, performing a second chemical reaction, and separating solid and liquid to obtain a second solution.

[0009] Optionally, the first set substance is a stabilizer, including at least one of the following: calcium nitrate, calcium chloride.

[0010] Optionally, the addition amount of the first set substance and the mass-volume ratio of the leaching solution is 1.0 kg / m 3 ~2.5 kg / m 3 .

[0011] Optionally, the second set substance includes at least one of the following: sodium hydroxide and potassium hydroxide.

[0012] Optionally, the first set pH value ranges from 8.0 to 9.0.

[0013] Optionally, the duration of the first chemical reaction ranges from 60 min to 90 min.

[0014] Optionally, the third set substance includes sodium carbonate.

[0015] Optionally, the ratio of the actual addition amount to the theoretical addition amount of the third set substance is 1.5 - 3.0.

[0016] Optionally, the duration of the second chemical reaction ranges from 10 min to 30 min.

[0017] Optionally, when the fluoride ion concentration in the first solution is lower than 10 mg / L, the third set substance is added again; otherwise, the addition operations of the first set substance and the second set substance are repeated until the fluoride ion concentration in the first solution is lower than 10 mg / L.

[0018] The above technical solution provided by the embodiments of the present application has the following advantages compared with the prior art:

[0019] For the method provided by the embodiments of the present application, by first adding a stabilizer to the leaching solution to stabilize the lithium ions in the leaching solution, on the premise of ensuring that there is basically no loss of lithium in the leaching solution, impurity ions in the leaching solution are removed through two chemical reactions, so that the fluoride ion and calcium ion concentrations in the purified solution are lower than 10 mg / L, and the concentrations of magnesium ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, and copper ions are all close to or equal to zero, with a low lithium loss rate, good impurity removal effect, and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings here are incorporated into the specification and constitute a part of this specification, showing the embodiments consistent with the present application and used together with the specification to explain the principles of the present application.

[0021] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0022] Figure 1 It is a schematic flow chart of a method for purifying a lithium leaching solution from aluminum electrolysis waste provided by the embodiments of the present application;

[0023] Figure 2A purification flowchart of the lithium extraction leaching solution from aluminum electrolysis waste provided by the embodiment of the present application;

[0024] Figure 3 A device flowchart for purifying the lithium extraction leaching solution from aluminum electrolysis waste provided by the embodiment of the present application. Specific embodiments

[0025] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some but not all of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the scope of protection of the present application.

[0026] Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments and equipment used in the present application can be obtained through market purchase or can be prepared by existing methods.

[0027] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and single values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0028] In the present application, unless otherwise stated, the orientation terms such as "upper" and "lower" specifically refer to the drawing directions in the drawings. Additionally, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to".

[0029] In this text, relative terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this text, "and / or" describes the associated relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Where A and B can be singular or plural. In this text, "at least one" means one or more, and "a plurality" means two or more. "At least one kind", "at least one of the following items", or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or, "at least one of a, b, and c" can both represent: a, b, c, a - b (that is, a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0030] The technical solution provided by the embodiments of the present application to solve the above technical problems has the following overall idea:

[0031] Add a first set substance to stabilize lithium ions in the dissolution solution;

[0032] Add a second set substance to adjust the dissolution solution to a first set pH value, perform a first chemical reaction, and perform solid-liquid separation to obtain a first solution;

[0033] Add a third set substance to the first solution, perform a second chemical reaction, and perform solid-liquid separation to obtain a second solution.

[0034] In this embodiment, the aluminum electrolysis waste mainly includes electrolyte, carbon slag, and overhaul slag. The main components of the electrolyte are Na3AlF6, calcium fluoride, alumina, K2NaAlF6, LiNa2AlF6, and LiF; the composition of the overhaul slag is complex and mainly includes carbonaceous, aluminum-silicon, sodium fluoride, calcium fluoride, lithium fluoride, cryolite, etc.; the main components of the carbon slag are carbonaceous and electrolyte.

[0035] In this embodiment, in addition to obtaining the first solution and the second solution through solid-liquid separation, there are also filter residue A and filter residue B. After the filter residue A and filter residue B are washed, the washing liquid is returned to the dissolution solution for recycling. The liquid-solid ratio of the washing is 3 - 4:1, and the number of washing times is not less than 1 time to ensure that all lithium in the filter residue is recovered without loss.

[0036] In some embodiments, the first set substance includes at least one of the following: calcium nitrate, calcium chloride.

[0037] In some embodiments, the addition amount of the first set substance to the mass-volume ratio of the dissolution solution is 1.0 kg / m3 ~2.5 kg / m 3 。

[0038] In this embodiment, the first set substance is a stabilizer. By controlling the addition of the stabilizer and its addition amount, on the one hand, lithium in the leaching solution can exist in the form of stable lithium ions. When adding the second set substance to adjust the pH value, lithium ions will not combine with the second set substance and the precipitate generated during the pH value adjustment process, resulting in the loss of lithium in the leaching solution. On the other hand, even if a small amount of lithium combines with the second set substance and the generated precipitate, the addition of an appropriate amount of calcium nitrate and calcium chloride will separate lithium from the combination, replace lithium ions with calcium ions, and generate a calcium salt that is more insoluble in water. Lithium is displaced and exists in the form of water-soluble lithium nitrate and lithium chloride, which is actually still lithium ions, to ensure no loss of lithium. In addition, the addition of stabilizers calcium nitrate and calcium chloride can remove some fluoride ions in the leaching solution, causing them to form calcium fluoride precipitate to reduce the fluoride ion content in the leaching solution.

[0039] In some embodiments, the second set substance includes at least one of the following: sodium hydroxide, potassium hydroxide.

[0040] In some embodiments, the value of the first set pH is 8.0 - 9.0.

[0041] In this embodiment, the main function of the second set substance is to adjust the pH value of the leaching solution to the first pH value of 8.0 - 9.0. Specifically, it can be 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, and any value between 8.0 - 9.0. The addition of the second set substances sodium hydroxide and potassium hydroxide to control the pH value of the leaching solution between 8.0 - 9.0 can ensure that impurity ions in the solution are removed completely. Among them, iron ions, aluminum ions, magnesium ions, nickel ions, boron ions, silicon ions, etc. are all close to or equal to zero, and the fluoride ion content is less than 10 mg / L. When the pH value is lower than 8.0, the removal effects of magnesium ions and silicon ions are poor. When the pH value is higher than 9.0, too much sodium hydroxide and potassium hydroxide are added, resulting in high sodium ions and potassium ions in the solution, affecting the subsequent concentration multiple of the solution, and further affecting the lithium precipitation rate and the quality of lithium carbonate products. In addition, when the pH value is too high, aluminum ions will form aluminate instead of aluminum hydroxide, and aluminate is soluble in water and exists in the solution, resulting in poor removal effect of aluminum ions.

[0042] In some embodiments, the duration of the first chemical reaction is 60 min - 90 min.

[0043] In this embodiment, the first set duration ranges from 60 min to 90 min, specifically it can be 60 min, 61 min, 62 min, 63 min, 64 min, 65 min, 66 min, 67 min, 68 min, 69 min, 70 min, 71 min, 72 min, 73 min, 74 min, 75 min, 76 min, 77 min, 78 min, 79 min, 80 min, 81 min, 82 min, 83 min, 84 min, 85 min, 86 min, 87 min, 88 min, 89 min, 90 min and any value between 60 min and 90 min. The reaction time is mainly used for the reaction after the addition of sodium hydroxide and potassium hydroxide. As the pH value increases, different impurity ions continuously react with hydroxide ions to form precipitates to remove the impurity ions in the leaching solution. If the reaction time is less than 60 min, the reaction between the impurity ions and hydroxide ions is insufficient, affecting the impurity removal effect. If the reaction time is more than 90 min, the time is too long, affecting the purification efficiency, and after more than 90 min, the content of impurity ions in the leaching solution basically no longer changes.

[0044] In some embodiments, the third set substance includes: sodium carbonate.

[0045] In some embodiments, the ratio of the actual addition amount to the theoretical addition amount of the third set substance is 1.5 - 3.0.

[0046] In this embodiment, the theoretical addition amount is the mass required for the complete reaction of the third set substance with calcium ions in the leaching solution. Specifically, the ratio of the actual addition amount to the theoretical addition amount can be 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0 and any value between 1.5 and 3.0. While increasing the pH value of the leaching solution, sodium carbonate is mainly used to remove calcium ions in the purified solution. If the addition amount of sodium carbonate is less than 1.5 times, the calcium removal effect is poor, and if it is more than 3.0 times, it causes waste of sodium carbonate. At the same time, the carbonate radical in sodium carbonate will combine with lithium to form lithium carbonate precipitate and enter the filter residue, resulting in the loss of lithium in the leaching solution.

[0047] In some embodiments, the duration of the second chemical reaction ranges from 10 min to 30 min.

[0048] In this embodiment, the value of the second set duration is 10 min - 30 min. Specifically, it can be 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, and any value between 10 min and 30 min. Sodium carbonate is itself easily soluble in water and combines with calcium ions relatively quickly. When the reaction time is less than 10 min, the reaction is unstable and the calcium removal effect is unstable. When the reaction time is more than 30 min, the time is too long, which affects the purification efficiency. And after more than 30 min, the calcium content basically no longer changes.

[0049] In some embodiments, when the fluoride ion concentration in the first solution is less than 10 mg / L, the third set substance is added. Otherwise, the addition operations of the first set substance and the second set substance are repeated until the fluoride ion concentration in the first solution is less than 10 mg / L.

[0050] In this embodiment, the first set substance is added to stabilize lithium ions in the leaching solution; the second set substance is added to adjust the leaching solution to the first set pH value for the first chemical reaction, and solid-liquid separation is performed to obtain the first solution; the fluoride ion concentration in the first filtrate is measured. When the fluoride ion concentration in the first solution is less than 10 mg / L, the third set substance is added. Otherwise, the addition operations of the first set substance and the second set substance are repeated, that is, the stabilizer calcium nitrate / calcium chloride is continuously added to the leaching solution to stabilize lithium ions in the leaching solution, and then sodium hydroxide / potassium hydroxide is added to adjust the pH value to 8 - 9. After the reaction, the fluoride ion concentration in the first solution is measured until the fluoride ion concentration in the first solution is less than 10 mg / L, and then the third set substance sodium carbonate is added. Aluminum ions, iron ions, manganese ions, copper ions, nickel ions, magnesium ions, etc. in the leaching solution are mainly removed by adding sodium hydroxide / potassium hydroxide to adjust the pH value, and the solution pH will be further increased after adding the third set substance sodium carbonate, consolidating and enhancing the removal effect; while the fluoride ions in the solution are mainly removed by controlling the addition of the stabilizer and sodium hydroxide / potassium hydroxide, and the two need to cooperate. And the third set substance sodium carbonate has no effect on fluoride ion removal. Therefore, after determining that the fluoride ion concentration in the first solution is less than 10 mg / L, the second chemical reaction is carried out to ensure that the fluoride and calcium ion concentrations in the purified solution are less than 10 mg / L, and the concentrations of magnesium ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, and copper ions are all close to or equal to zero.

[0051] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. For the experimental methods without specific conditions in the following embodiments, they are usually determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0052] Flow schematic diagrams of the purification methods for the lithium-extracted leaching solution from aluminum electrolysis waste in Examples 1-3 and Comparative Examples 1-2 are as Figure 1 shown;

[0053] The flowchart of the leaching solution purification is as Figure 2 shown; the device flowchart of the leaching solution purification is as Figure 3 shown.

[0054] Example 1:

[0055] Add the lithium-extracted leaching solution from aluminum electrolysis waste into reaction tank 101, and add 1.0 kg / m 3 of calcium nitrate to stabilize the lithium ions in the solution. Then add sodium hydroxide to adjust the leaching solution to the first set value of 8.0, and react for 60 min to remove fluoride ions, magnesium ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, copper ions, etc. After the reaction, solid-liquid separation is carried out by solid-liquid separator 102. The solid-liquid separator 102 can be a vertical filter press, a diaphragm plate and frame filter press, etc. The filter residue enters the washing tank 105 to be washed, and the filtrate enters reaction tank 103 to measure the fluoride ion content in reaction tank 103.

[0056] If the fluoride ion concentration in the solution of reaction tank 103 is lower than 10 mg / L, add sodium carbonate 1.5 times the theoretical value to reaction tank 103 and react at room temperature for 10 min to remove calcium ions. After the reaction, solid-liquid separation is carried out by solid-liquid separator 104. The solid-liquid separator 104 can be a vertical filter press, a diaphragm plate and frame filter press, etc. The filter residue enters the washing tank 105 to be washed, and the filtrate is the purified solution. After the filter residue in reaction tank 105 is washed, solid-liquid separation is carried out by solid-liquid separator 106, and the filtrate is returned to the leaching solution for recycling.

[0057] If the fluoride ion concentration in the solution of reaction tank 103 is higher than 10 mg / L, introduce the solution of reaction tank 103 into reaction tank 101, and continue to add 1.0 kg / m 3Calcium nitrate is added to stabilize lithium ions in the solution. Then sodium hydroxide is added to adjust the leaching solution to the first set value of 8.0. The first chemical reaction is carried out for 60 minutes. Solid-liquid separation is carried out by a 102 solid-liquid separator. The filter residue enters the 105 washing tank for washing, and the filtrate enters the 103 reaction tank. The fluoride ion content in the 103 reaction tank is measured. If the fluoride ion concentration in the solution of the 103 reaction tank is lower than 10 mg / L, sodium carbonate 1.5 times the theoretical value is added to the 103 reaction tank for the second chemical reaction. If the fluoride ion concentration in the solution of the 103 reaction tank is higher than 10 mg / L, the solution in the 103 reaction tank is introduced into the 101 reaction tank, and the operation is repeated until the fluoride ion content in the solution in the 103 reaction tank is lower than 10 mg / L.

[0058] After purification, the loss of lithium ions is basically zero, the concentrations of fluoride ions and calcium ions are lower than 10 mg / L, and the concentrations of magnesium ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, copper ions, etc. are all close to or equal to zero. The ion contents in the leaching solution before and after purification are shown in the following table.

[0059]

[0060] Example 2:

[0061] The lithium leaching solution from aluminum electrolysis waste is added to the reaction tank 101, and 2.5 kg / m 3 of calcium nitrate is added to the reaction tank 101 to stabilize lithium ions in the solution. Then sodium hydroxide is added to adjust the leaching solution to the first set value of 9.0, and the reaction is carried out for 90 minutes to remove fluoride ions, magnesium ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, copper ions, etc. After the reaction, solid-liquid separation is carried out by a 102 solid-liquid separator. The filter residue enters the 105 washing tank for washing, and the filtrate enters the 103 reaction tank.

[0062] Sodium carbonate 3.0 times the theoretical value is added to the 103 reaction tank, and the reaction is carried out at room temperature for 30 minutes to remove calcium ions. After the reaction, solid-liquid separation is carried out by a 104 solid-liquid separator. The filter residue enters the 105 washing tank for washing, and the filtrate is the purified solution. After the filter residue in the 105 reaction tank is washed, solid-liquid separation is carried out by a 106 solid-liquid separator, and the filtrate is returned to the leaching solution for recycling.

[0063] After purification, the loss of lithium ions is basically zero, the concentrations of fluoride ions and calcium ions are lower than 10 mg / L, and the concentrations of magnesium ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, copper ions, etc. are all close to or equal to zero. The ion contents in the leaching solution before and after purification are shown in the following table.

[0064]

[0065] Example 3:

[0066] Add the lithium-extracted leaching solution from aluminum electrolysis waste to reaction tank 101, and add 2.0 kg / m 3 of calcium chloride to stabilize the lithium ions in the solution. Then add potassium hydroxide to adjust the leaching solution to the first set value of 8.5, and react for 80 min to remove fluoride ions, magnesium ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, copper ions, etc. After the reaction, carry out solid-liquid separation through solid-liquid separator 102. The filter residue enters washing tank 105 for washing, and the filtrate enters reaction tank 103.

[0067] Add sodium carbonate at 2.2 times the theoretical value to reaction tank 103, react at room temperature for 20 min to remove calcium ions. After the reaction, carry out solid-liquid separation through solid-liquid separator 104. The filter residue enters washing tank 105 for washing, and the filtrate is the purified solution. After the filter residue in washing tank 105 is washed, carry out solid-liquid separation through solid-liquid separator 106, and the filtrate returns to the leaching solution for recycling.

[0068] After purification, the lithium ions are basically lossless, the concentrations of fluoride ions and calcium ions are lower than 10 mg / L, and the concentrations of magnesium ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, copper ions, etc. are all close to or equal to zero. The ion contents in the leaching solution before and after purification are shown in the following table.

[0069]

[0070] Comparative Example 1:

[0071] Add the lithium-extracted leaching solution from aluminum electrolysis waste to reaction tank 101, and add 0.5 kg / m 3 of calcium chloride to stabilize the lithium ions in the solution. Then add sodium hydroxide to adjust the leaching solution to 7.5, and react for 120 min to remove fluoride ions, magnesium ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, copper ions, etc. After the reaction, carry out solid-liquid separation through solid-liquid separator 102. The filter residue enters washing tank 105 for washing, and the filtrate enters reaction tank 103.

[0072] Add sodium carbonate at 1.0 times the theoretical value to reaction tank 103, and react at room temperature for 45 min. After the reaction, carry out solid-liquid separation through solid-liquid separator 104. The filter residue enters washing tank 105 for washing, and the filtrate is the purified solution. After the filter residue in washing tank 105 is washed, carry out solid-liquid separation through solid-liquid separator 106, and the filtrate returns to the leaching solution for recycling. The ion contents in the leaching solution before and after purification are shown in the following table.

[0073]

[0074] In Comparative Example 1, the addition amount of calcium chloride is reduced to 0.5 kg / m 3, in the first step, the pH value was adjusted to 7.5, resulting in a relatively high fluoride ion content of 56.9 mg / L in the purified solution. The lithium ion content decreased from 2529 mg / L to 2099.5 mg / L, with a large loss. In addition, the contents of iron ions, silicon ions, etc. all increased. In Comparative Example 1, the amount of sodium carbonate added was reduced to 1.0 times the theoretical value. Although the reaction time was increased to 45 minutes, the calcium removal effect was still poor, and the calcium ion content in the purified solution reached 165.3 mg / L, indicating a poor calcium removal effect.

[0075] Comparative Example 2:

[0076] The lithium-extracted leaching solution from aluminum electrolysis waste was added to reaction tank 101, and 3.5 kg / m 3 of calcium nitrate was added to reaction tank 101 to stabilize the lithium ions in the solution. Then potassium hydroxide was added to adjust the leaching solution to 10.2, and the reaction was carried out for 120 minutes to remove fluoride ions, magnesium ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions, copper ions, etc. After the reaction, solid-liquid separation was carried out by a 102 solid-liquid separator. The filter residue entered the 105 washing tank for washing, and the filtrate entered the 103 reaction tank.

[0077] Sodium carbonate 3.5 times the theoretical value was added to reaction tank 103, and the reaction was carried out at room temperature for 8 minutes. After the reaction, solid-liquid separation was carried out by a 104 solid-liquid separator. The filter residue entered the 105 washing tank for washing, and the filtrate was the purified solution. After the filter residue in the 105 reaction tank was washed, solid-liquid separation was carried out by a 106 solid-liquid separator, and the filtrate was returned to the leaching solution for recycling. The ion contents in the leaching solution before and after purification are shown in the following table.

[0078]

[0079] In Comparative Example 2, the amount of calcium nitrate added was increased to 3.5 kg / m 3 , and the pH value adjusted in the first step was 10.2. The fluoride ion content in the purified solution reached 6.8 mg / L, and the decrease was very limited. Moreover, the potassium ion content in the purified solution increased from 1578.2 to 7985.6, which restricted the subsequent concentration multiple and was likely to cause the premature precipitation of potassium salts, affecting the quality of lithium carbonate products. In Comparative Example 1, when the amount of sodium carbonate added was increased to 3.5 times the theoretical value, the calcium removal effect was good, but the loss of lithium was large. The lithium content in the solution decreased from 2847.7 mg / L to 2492.3 mg / L. Moreover, the addition of a large amount of sodium carbonate led to the final pH value of the solution reaching 13.0, and the aluminum ion content in the purified solution was relatively high, reaching 33.4 mg / L.

[0080] In summary, the method provided by this patent first adds a stabilizer to the leaching solution to stabilize the lithium ions in the leaching solution. On the premise of ensuring that there is basically no loss of lithium in the leaching solution, impurity ions in the leaching solution are removed through two chemical reactions. At the same time, the fluoride ion concentration in the solution after the first chemical reaction is strictly controlled to ensure that the fluoride ion and calcium ion concentrations in the purified solution are lower than 10 mg / L, and the concentrations of magnesium ions, iron ions, aluminum ions, boron ions, silicon ions, manganese ions, nickel ions and copper ions are all close to or equal to zero, meeting the requirements of subsequent concentration and lithium precipitation. The overall disposal process is short, there is no requirement for the original leaching solution, the lithium loss rate is low, and the impurity removal effect is good and the efficiency is high.

[0081] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the description of the range has specifically disclosed all possible sub-ranges and single values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, and this applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0082] In the present application, unless otherwise stated, the orientation terms such as "upper" and "lower" specifically refer to the drawing direction in the drawings. Additionally, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to".

[0083] In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects and indicates that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Where A and B can be singular or plural. In this article, "at least one" means one or more, and "a plurality" means two or more. "At least one kind", "at least one of the following (items)", or similar expressions refer to any combination of these items, including any combination of single item (s) or plural item (s). For example, "at least one of (an) a, b, or c", or, "at least one of (an) a, b, and c" can all represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0084] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for purifying the lithium leaching solution from aluminum electrolysis waste, characterized in that, The method includes: Adding a first specified substance to stabilize lithium ions in the dissolution solution; Adding a second specified substance to adjust the dissolution solution to a first specified pH value, conducting a first chemical reaction with a duration ranging from 60 min to 90 min, and performing solid-liquid separation to obtain a first solution; Adding a third specified substance to the first solution, conducting a second chemical reaction with a duration ranging from 10 min to 30 min, and performing solid-liquid separation to obtain a second solution; The addition amount of the first specified substance and the mass-volume ratio of the dissolution solution are 1.0 kg / m³ to 2.5 kg / m³, and the first specified pH value ranges from 8.0 to 8.5; the third specified substance is sodium carbonate, and the ratio of the actual addition amount to the theoretical addition amount of the third specified substance is 1.5 to 3.0; When the fluoride ion concentration in the first solution is lower than 10 mg / L, add the third specified substance again; otherwise, repeat the addition operations of the first specified substance and the second specified substance until the fluoride ion concentration in the first solution is lower than 10 mg / L; The first specified substance is a stabilizer, including at least one of the following: calcium nitrate, calcium chloride; The second specified substance includes at least one of the following: sodium hydroxide, potassium hydroxide.

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