High-valued utilization method of fluorine, lithium, aluminum and sodium elements in lithium-containing electrolyte

Abstract

The invention relates to a high-valued utilization method of fluorine, lithium, aluminum and sodium elements in a lithium-containing electrolyte, which is characterized in that valuable elements Li < + >, F <->, Al < 3 + > and Na < + > in the lithium-containing electrolyte are recovered under the condition of leaching the lithium-containing electrolyte in a mild aluminum sulfate solution environment, and the valuable elements are selectively separated by adding an auxiliary agent. The whole technological process is simple, high-valued utilization of the lithium-containing electrolyte is achieved, the valuable element recovery rate is high, the production cost is low, the comprehensive benefits of the lithium-containing electrolyte are effectively improved, secondary pollution is avoided, and the purity of aluminum fluoride and sodium carbonate products meets the current national standard requirement.

Description

Technical Field

[0001] The present invention relates to the technical field of resource recovery and treatment of hazardous wastes in the electrolytic aluminum industry, and in particular to a method for high-value utilization of fluorine, lithium, aluminum and sodium elements in a lithium-containing electrolyte. Background Art

[0002] In the process of electrolytic aluminum production, the molten salt connecting the anode and cathode is the electrolyte, which is mainly composed of cryolite and alumina, and there are some additives such as aluminum fluoride and lithium fluoride. With the overhaul and maintenance of the electrolytic cell, a large amount of electrolyte is taken out in various ways. The waste electrolyte is mainly composed of cryolite, alumina and fluoride. Because it contains a large amount of valuable elements such as fluoride and lithium fluoride aluminum, if it is not handled properly, it will not only cause serious harm to the environment and human health, but also lead to the waste of valuable element resources in the waste electrolyte. In addition, most of the substances in the waste electrolyte are difficult to dissolve in water and difficult to completely dissolve in acidic and alkaline environments, which increases the difficulty of recycling the waste electrolyte.

[0003] At present, there are relatively many studies on the extraction of lithium from waste electrolytes, in which lithium mostly exists in the form of sodium lithium cryolite. Acid leaching or roasting is mainly used to extract lithium. For example: CN109930174A discloses a method for separating and purifying aluminum electrolytes and recovering lithium. It proposes to use 2-6 mol / L nitric acid to leach lithium-aluminum electrolytes under 60-120°C. The lithium-containing leachate is filtered and evaporated, and naturally cooled and crystallized to separate sodium nitrate. After the filtrate is purified and impurities are removed, alkaline substances are added to precipitate lithium. CN113684369A discloses a method for treating waste industrial lithium-aluminum electrolytes. The method is to roast the lithium-aluminum electrolytes together with additives at high temperature. The additives are sodium hydroxide or potassium hydroxide powder to convert sodium lithium cryolite into more soluble LiAl2(OH)7 and LiF. CN113981232A discloses a method for directly leaching and recovering lithium from aluminum electrolyte waste residue by aluminum sulfate, which comprises the following steps: (1) grinding and screening the lithium-containing aluminum electrolyte waste residue, mixing with aluminum sulfate and water for reaction, and filtering to obtain filtrate A and filter residue B; (2) adding sodium carbonate to filtrate A for reaction, and filtering to obtain filtrate C and filter residue D; (3) adding water to filter residue D, and then introducing CO2, and filtering to obtain filtrate E and filter residue F; (4) filtrate E is subjected to thermal decomposition, filtration and drying to obtain lithium carbonate; (5) filtrate C is evaporated and concentrated to obtain sodium sulfate as a byproduct, and the evaporated and concentrated mother liquor is recycled to step (2). (6) filter residue F is reacted with sulfuric acid to obtain aluminum sulfate, which is recycled to step (1).

[0004] The above process involves concentrated acid and high temperature / strong alkali, which is harsh and energy-intensive. The lithium-containing leaching solution is difficult to handle, and hydrogen fluoride gas is inevitably produced during the process, causing corrosion and secondary pollution of equipment. At the same time, because only lithium is recovered, valuable elements such as sodium fluoride and aluminum are often ignored, resulting in a waste of resources. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for high-value utilization of fluorine, lithium, aluminum and sodium elements in lithium-containing electrolytes. The valuable element Li in the lithium-containing electrolyte is leached in a mild aluminum sulfate solution environment. + 、F - 、Al 3+ 、Na + The valuable elements are recovered and selectively separated by adding additives. The whole process is simple, the recovery rate of valuable elements is high, the production cost is low, and it has significant economic value.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium, the method comprising the following steps:

[0008] S1, mixing the lithium-containing electrolyte with the aluminum sulfate solution, fully stirring and leaching, and obtaining filtrate A and leaching residue after solid-liquid separation;

[0009] S2, adding alkali solution to the filtrate A, reacting sufficiently, and obtaining filtrate B and intermediate product hydroxyaluminum fluoride after solid-liquid separation;

[0010] S3, supplementing fluorine with the intermediate product hydroxyaluminum fluoride, reacting with a fluorine source, separating the solid from the liquid and drying the solid to obtain an aluminum fluoride product;

[0011] S4, freezing and crystallizing the filtrate B, and obtaining the filtrate C and the sodium salt product after solid-liquid separation;

[0012] S5, measuring the lithium concentration in the filtrate C and determining the qualified concentration. When the lithium concentration is ≥ the qualified concentration, the filtrate C enters the S6 lithium precipitation step; when the lithium concentration is < the qualified concentration, the filtrate C is supplemented with aluminum sulfate and then returns to S1 to participate in leaching;

[0013] S6. After removing impurities from the filtrate C with a qualified lithium concentration, carbon dioxide is introduced to precipitate lithium, and after solid-liquid separation, a lithium carbonate product is obtained.

[0014] According to the present invention, preferably, the aluminum sulfate solution described in S1 is an acidic aluminum sulfate solution, and more preferably, it is prepared by mixing aluminum sulfate and dilute sulfuric acid solution, and the aluminum ion concentration is 0.5-1.5 mol / L, and more preferably 0.5-1.0 mol / L;

[0015] Preferably, the pH of the dilute sulfuric acid solution is 2-3.

[0016] According to the present invention, preferably, in S1, the liquid-to-solid ratio of the aluminum sulfate solution to the lithium-containing electrolyte is 5-20 mL / g, preferably 7-10 mL / g.

[0017] According to the present invention, preferably, in S1, the leaching temperature is controlled to be 50-100°C, the leaching time is controlled to be 0.5-2h, and the stirring rate is 200-400rpm.

[0018] According to the present invention, preferably, in S1, the solid-liquid separation method can be one of filtration / filter pressing / centrifugation.

[0019] According to the present invention, preferably, in S1, during solid-liquid separation, the leached residue is washed 1-2 times with clean water, and the washing water is mixed with the filtrate A.

[0020] According to the present invention, preferably, between S1 and S2, a step of heating the filtrate A is further included, and the temperature of the filtrate A is 70-100°C.

[0021] According to the present invention, preferably, the alkali solution in S2 is a sodium hydroxide solution.

[0022] According to the present invention, preferably, the concentration of hydroxide ions in the alkali solution in S2 is 0.5-5 mol / L.

[0023] According to the present invention, preferably, the addition rate of the alkali solution in S2 is 5-20 mL / min.

[0024] According to the present invention, preferably, in S2, the pH of the filtrate A is adjusted to 4-6 by adding alkali solution.

[0025] According to the present invention, preferably, in S2, the solid-liquid separation method can be one of filtration / filter pressing / centrifugation.

[0026] According to the present invention, preferably, in S2, during solid-liquid separation, the intermediate product hydroxyaluminum fluoride is washed 1-2 times with clean water, and the washing water is mixed with the filtrate B.

[0027] According to the present invention, preferably, the fluorine source supplemented in S3 can be hydrofluoric acid liquid or hydrogen fluoride gas, wherein the molar ratio of HF to hydroxyaluminum fluoride is 1-2:1.

[0028] According to the present invention, preferably, the solid-liquid separation method in S3 can be one of filtration / filter pressing / centrifugation.

[0029] According to the present invention, preferably, the drying temperature in S3 is 90-120°C.

[0030] According to the present invention, preferably, the temperature of the freezing crystallization in S4 is 0-10°C.

[0031] According to the present invention, preferably, the qualified concentration of lithium in the filtrate C in S5 is ≥10 g / L.

[0032] According to the present invention, preferably, the filtrate C in S5 is returned to S1 to participate in leaching by preparing a dilute sulfuric acid mixed solution.

[0033] According to the present invention, preferably, the impurity removal method in S6 is to add alkali solution to adjust the pH of the filtrate C.

[0034] According to the present invention, preferably, the alkali solution required for removing impurities in S6 is a sodium hydroxide solution.

[0035] According to the present invention, preferably, the pH of the filtrate C in S6 after impurities removal is 10-14.

[0036] According to the present invention, preferably, the method of introducing carbon dioxide in S6 can be air flow stirring or micro-nano bubbles.

[0037] According to the present invention, preferably, the solid-liquid separation method in S6 can be one of filtration / centrifugation.

[0038] Compared with the prior art, the advantages of the present invention are as follows:

[0039] 1. The treatment method of the present invention allows high-value elements such as lithium, fluorine, aluminum, sodium, etc. in the waste electrolyte to be dissolved into the leachate simultaneously during the leaching process, and produces aluminum fluoride, sodium salt and lithium salt products through the subsequent three-step selective separation. The process flow is short, the equipment is simple, and the industrial feasibility is high.

[0040] 2. The present invention increases the yield of aluminum fluoride by reacting the generated intermediate hydroxyaluminum fluoride with a fluorine-containing acid.

[0041] 3. According to the solubility characteristics of sodium sulfate, the present invention adopts the method of freezing crystallization to remove sodium and water circulation to efficiently leach and enrich lithium, thereby reducing the evaporation and concentration of lithium-containing solutions, thereby saving energy and reducing consumption.

[0042] 4. The present invention adopts cyclic repeated leaching to increase the lithium concentration in the leaching solution while reducing the amount of water used and reducing the processing cost.

[0043] 5. The entire process of the present invention realizes the high-value utilization of lithium-containing electrolytes, effectively improves the comprehensive benefits of lithium-containing electrolytes, does not produce secondary pollution, and the purity of aluminum fluoride and sodium carbonate products meets the current national standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The present invention is a process flow chart of the method for high-value utilization of fluorine, lithium, aluminum and sodium elements in lithium-containing electrolytes.

[0045] Figure 2This is the XRD diagram of the lithium-containing electrolyte raw material in Example 1 of the present invention.

[0046] Figure 3 This is the XRD diagram of the sodium sulfate product obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0047] The invention uses a mild aluminum sulfate solution environment to leaching lithium-containing electrolytes, and the valuable element Li in the lithium-containing electrolytes is + 、F - 、Al 3+ 、Na + The valuable elements are recovered and selectively separated by adding additives. The whole process is simple, the recovery rate of valuable elements is high, the production cost is low, and it has significant economic value.

[0048] The present invention provides a method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium, the method comprising the following steps:

[0049] S1, mixing the lithium-containing electrolyte with the aluminum sulfate solution, fully stirring and leaching, and obtaining filtrate A and leaching residue after solid-liquid separation;

[0050] S2, adding alkali solution to the filtrate A, reacting sufficiently, and obtaining filtrate B and intermediate product hydroxyaluminum fluoride after solid-liquid separation;

[0051] S3, supplementing fluorine with the intermediate product hydroxyaluminum fluoride, reacting with a fluorine source, separating the solid from the liquid and drying the solid to obtain an aluminum fluoride product;

[0052] S4, freezing and crystallizing the filtrate B, and obtaining the filtrate C and the sodium salt product after solid-liquid separation;

[0053] S5, measuring the lithium concentration in the filtrate C and determining the qualified concentration. When the lithium concentration is ≥ the qualified concentration, the filtrate C enters the S6 lithium precipitation step; when the lithium concentration is < the qualified concentration, the filtrate C returns to S1 to participate in leaching;

[0054] S6. After removing impurities from the filtrate C with a qualified lithium concentration, carbon dioxide is introduced to precipitate lithium, and after solid-liquid separation, a lithium carbonate product is obtained.

[0055] According to the present invention, the main components of the lithium-containing electrolyte in S1 are cryolite (Na3AlF6), alumina (Al2O3), β-alumina (NaAl 11 O 17 ), calcium fluoride (CaF2), sodium lithium cryolite (Na2LiAl3F6), and carbon (C).

[0056] The lithium-containing electrolyte is mixed with aluminum sulfate solution, and the main chemical reactions are:

[0057] Na3AlF6+5Al 3+ =3Na + +6AlF 2+

[0058] Na3AlF6+2Al 3+ =3Na + +3AlF2 +

[0059] CaF2+2Al 3+ +SO4 2- =CaSO4+2AlF 2+

[0060] CaF2+Al 3+ +SO4 2- =CaSO4+AlF2 +

[0061] The main substances in filtrate A are AlF 2+ 、AlF2 + 、Na + , Li + 、SO4 2- wait.

[0062] The main components of leaching residue are Al2O3, NaAl 11 O 17 , C, CaSO4, etc.

[0063] In one or more preferred embodiments, the aluminum sulfate solution described in S1 is an acidic aluminum sulfate solution, more preferably a mixture of aluminum sulfate and dilute sulfuric acid solution, and the aluminum ion concentration is 0.5-1.5 mol / L, more preferably 0.5-1.0 mol / L;

[0064] Preferably, the pH of the dilute sulfuric acid solution is 2-3.

[0065] On the one hand, the invention adds sulfuric acid in the process of preparing the aluminum sulfate solution to inhibit the hydrolysis of aluminum ions. On the other hand, during the leaching process, a part of the fluoroaluminum complex ions will precipitate in the form of hydroxyaluminum fluoride. Under acidic conditions, this loss can be solved.

[0066] In one or more preferred embodiments, in S1, the liquid-to-solid ratio of the aluminum sulfate solution to the lithium-containing electrolyte is 5-20 mL / g, preferably 7-10 mL / g.

[0067] In the present invention, the reactions of cryolite and calcium fluoride with aluminum ions are all endothermic reactions. The higher the temperature, the faster the reaction rate and the more complete the reaction. However, if the temperature is too high, fluorine may overflow in the form of hydrogen fluoride gas, so the inlet and outlet temperatures must be controlled within a reasonable range.

[0068] In one or more preferred embodiments, in S1, the leaching temperature is controlled to be 50-100°C, the leaching time is controlled to be 0.5-2h, and the stirring rate is 200-400rpm.

[0069] In one or more preferred embodiments, in S1, the solid-liquid separation method can be one of filtration / filter pressing / centrifugation; preferably, in S1, during solid-liquid separation, the leached residue is washed 1-2 times with clean water, and the washing water is mixed with the filtrate A.

[0070] According to the present invention, preferably, between S1 and S2, there is also a step of heating the filtrate A, and the temperature of the filtrate A after heating is 70-100°C.

[0071] According to the present invention, the main chemical reactions occurring in S2 are:

[0072] AlF 2+ +2OH - =AlF(OH)2

[0073] AlF2 + +OH - =AlF2OH

[0074] The main substances in filtrate B in S2 are Na + , Li + 、SO4 2- wait

[0075] The intermediate product is aluminum hydroxyfluoride, the chemical formula of which can be expressed as AlF x (OH) 3-x ·yH2O, x is 1-2, y is 0.375-1.5.

[0076] In one or more preferred embodiments, the alkali solution in S2 is a sodium hydroxide solution.

[0077] In one or more preferred embodiments, the concentration of hydroxide ions in the alkali solution in S2 is 0.5-5 mol / L.

[0078] In one or more preferred embodiments, the addition rate of the alkali solution in S2 is 5-20 mL / min.

[0079] In one or more preferred embodiments, in S2, the pH of the filtrate A is adjusted to 4-6 by adding alkaline solution.

[0080] In one or more preferred embodiments, in S2, the solid-liquid separation method can be one of filtration / filter pressing / centrifugation. In S2, during solid-liquid separation, the intermediate product hydroxyaluminum fluoride is washed 1-2 times with clean water, and the washing water is mixed with the filtrate B.

[0081] According to the present invention, the main chemical reactions occurring in S3 are:

[0082] AlF(OH)2+2HF=AlF3+2H2O

[0083] AlF2OH+HF=AlF3+H2O

[0084] In one or more preferred embodiments, the fluorine source supplemented in S3 may be hydrofluoric acid liquid or hydrogen fluoride gas, wherein the molar ratio of HF to hydroxyaluminum fluoride is 1-2:1.

[0085] In one or more preferred embodiments, the solid-liquid separation method in S3 may be one of filtration / filter pressing / centrifugation.

[0086] In one or more preferred embodiments, the drying temperature in S3 is 90-120°C.

[0087] According to the present invention, in S4, freezing crystallization is used to remove sodium according to the solubility characteristics of sodium sulfate.

[0088] The main substances in the filtrate C of S4 are Na + , Li + 、SO4 2- wait.

[0089] In one or more preferred embodiments, the temperature of the freeze crystallization in S4 is 0-10°C.

[0090] According to the present invention, in order to be more conducive to the subsequent lithium precipitation step, so that the lithium concentration is higher and more conducive to the lithium precipitation process, the lithium concentration in the filtrate C is measured, and the qualified concentration is determined. When the lithium concentration is ≥ the qualified concentration, the filtrate C enters the S6 lithium precipitation step; when the lithium concentration is < the qualified concentration, the filtrate C returns to S1 to participate in leaching;

[0091] In one or more preferred embodiments, the qualified concentration of lithium in the filtrate C in S5 is ≥10 g / L.

[0092] In one or more preferred embodiments, the filtrate C in S5 is returned to S1 to participate in leaching by preparing a dilute sulfuric acid mixed solution.

[0093] According to the present invention, the main chemical reactions occurring in S6 are:

[0094] 2Li + +CO3 2- =Li2CO3

[0095] In one or more preferred embodiments, the impurity removal method in S6 is to add alkali solution to adjust the pH of the filtrate C.

[0096] In one or more preferred embodiments, the alkali solution required for impurity removal in S6 is a sodium hydroxide solution.

[0097] In one or more preferred embodiments, the pH of the filtrate C after impurities removal in S6 is 10-14.

[0098] In one or more preferred embodiments, the carbon dioxide can be introduced in S6 by air flow stirring or micro-nano bubbles. The solid-liquid separation method in S6 can be one of filtration / centrifugation.

[0099] In the present invention, by mixing the lithium-containing electrolyte with the aluminum sulfate solution and stirring for leaching, the high-value elements such as Li, F, Al, etc. in the lithium-containing electrolyte are converted into ions in the solution, and the impurities such as Ca, C, etc. in the lithium-containing electrolyte enter the slag phase because they are insoluble or do not react with the aluminum sulfate solution. After solid-liquid separation, a filtrate A rich in Li, F, Al and Na and a leached slag mainly composed of carbon can be obtained. The F and Al elements in the aluminum liquid are mainly in the form of AlF 2+ 、AlF2 + In the form of, by adding alkali solution to the filtrate, supplement OH - , the intermediate hydroxyaluminum fluoride precipitate for preparing high-value product aluminum fluoride can be obtained. At this time, filtrate B contains a large amount of sodium salt, which is removed by freezing and crystallization to obtain filtrate C with lower salt concentration. At the same time, Li still exists in filtrate C in the form of ions. Since the amount of lithium obtained from one leaching is limited, filtrate C can be directly returned to leaching for the preparation of aluminum sulfate solution. This cycle process can efficiently leach and enrich lithium and reduce the amount of water, avoiding the waste of a large amount of water during the evaporation, concentration and enrichment of dilute lithium solution, and effectively reducing energy consumption. The intermediate hydroxyaluminum fluoride cannot be used directly at present. By supplementing fluorine, aluminum fluoride products can be produced, effectively recovering fluorine in lithium-containing electrolytes.

[0100] The process flow of the invention is simple, and can realize the high-value recovery and utilization of fluorine, lithium, sodium and aluminum in lithium-containing electrolytes. It is green, efficient, environmentally friendly, does not generate secondary pollution, and has extremely high environmental and economic value.

[0101] The present invention is further described below by means of specific examples, but is not limited thereto.

[0102] The main chemical composition of the lithium-containing electrolyte in the embodiment is as follows:

[0103] Na3AlF6, Al2O3, NaAl 11 O 17 , CaF2, Na2LiAl3F6, C, etc. Due to the different pre-treatment effects, there are certain differences in the composition and content of the raw materials.

[0104] Example 1

[0105] A method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium, the method comprising the following steps:

[0106] S1. Mix 50g of lithium-containing electrolyte from a certain factory with 350mL of aluminum sulfate solution with an aluminum ion concentration of 1.3mol / L, stir and leach for 2h at 90℃ and 300rpm, and after solid-liquid separation, obtain filtrate A and 11g of leaching residue.

[0107] S2. Add 1 mol / L sodium hydroxide solution to the filtrate A at 5 mL / min until the pH is 5, react sufficiently, and after solid-liquid separation, obtain filtrate B and 75 g of intermediate product hydroxyaluminum fluoride.

[0108] S3. The intermediate product hydroxyaluminum fluoride is supplemented with fluorine by reacting with 55 mL of 40 wt % hydrofluoric acid solution, and after solid-liquid separation and solid drying, 66 g of aluminum fluoride product is obtained.

[0109] S4. The filtrate B was subjected to freeze crystallization at 0°C, and after solid-liquid separation, filtrate C and 102 g of aqueous sodium sulfate product were obtained.

[0110] S5. The lithium concentration in the filtrate C is judged. The lithium ion concentration is 0.075 g / L, which is unqualified. Return to S1 to participate in leaching until the lithium ion concentration is ≥10 g / L.

[0111] S6. After multiple cycles, add sodium hydroxide solution to 350 mL of filtrate C with qualified lithium concentration to adjust the pH of filtrate C to 11, then filter and remove impurities, pass carbon dioxide micro-nano bubbles into the filtrate after impurities removal to carry out lithium precipitation reaction, filter after the reaction is completed, and obtain 17 g of lithium carbonate product.

[0112] Example 2

[0113] A method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium, the method comprising the following steps:

[0114] S1. Mix 200g of lithium-containing electrolyte from a certain factory with 2000mL of aluminum sulfate solution with an aluminum ion concentration of 0.9mol / L, stir and leach for 1.5h at 90°C and 300rpm, and after solid-liquid separation, obtain filtrate A and 48g of leaching residue.

[0115] S2. Add 1 mol / L sodium hydroxide solution to the filtrate A at 8 mL / min until the pH is 5, react sufficiently, and after solid-liquid separation, obtain filtrate B and 295 g of intermediate product hydroxyaluminum fluoride.

[0116] S3. The intermediate product hydroxyaluminum fluoride is supplemented with fluorine by reacting with 218 mL of a 40 wt % hydrofluoric acid solution, and after solid-liquid separation and solid drying, 261 g of an aluminum fluoride product is obtained.

[0117] S4. The filtrate B was subjected to freeze crystallization at 1°C, and after solid-liquid separation, filtrate C and 482 g of aqueous sodium sulfate product were obtained.

[0118] S5. The lithium concentration in the filtrate C is judged. The lithium ion concentration is 0.074 g / L, which is unqualified. Return to S1 to participate in leaching until the lithium ion concentration is ≥10 g / L.

[0119] S6. After multiple cycles, sodium hydroxide solution is added to 2000 mL of filtrate C with qualified lithium concentration to adjust the pH of filtrate C to 13, and then the filtrate is filtered to remove impurities. The filtrate after impurity removal is stirred by a carbon dioxide gas flow to perform lithium precipitation reaction. After the reaction is completed, it is filtered to obtain 96 g of lithium carbonate product.

[0120] Example 3

[0121] A method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium, the method comprising the following steps:

[0122] S1. Mix 160g of lithium-containing electrolyte from a certain factory with 2000mL of aluminum sulfate solution with an aluminum ion concentration of 0.72mol / L, fully stir and leach at 90°C and 300rpm for 2h. After solid-liquid separation, obtain filtrate A and 44g of leached residue.

[0123] S2. Add 0.5 mol / L sodium hydroxide solution to the filtrate A at 10 mL / min until the pH is 4.5, react sufficiently, and obtain filtrate B and 223 g of intermediate product hydroxyaluminum fluoride after solid-liquid separation.

[0124] S3. The intermediate product hydroxyaluminum fluoride is supplemented with fluorine by reacting with 165 mL of 40 wt % hydrofluoric acid solution, and after solid-liquid separation and solid drying, 197 g of aluminum fluoride product is obtained.

[0125] S4. The filtrate B was subjected to freeze crystallization at 3°C, and after solid-liquid separation, filtrate C and 407 g of aqueous sodium sulfate product were obtained.

[0126] S5. The lithium concentration in the filtrate C is judged. The lithium ion concentration is 0.081 g / L, which is unqualified. Return to S1 to participate in leaching until the lithium ion concentration is ≥10 g / L.

[0127] S6. After multiple cycles, sodium hydroxide solution is added to 2000 mL of filtrate C with qualified lithium concentration to adjust the pH of filtrate C to 11, and then the filtrate is filtered to remove impurities. Micro-nano carbon dioxide bubbles are passed into the filtrate after impurity removal to carry out lithium precipitation reaction. After the reaction is completed, it is filtered to obtain 92 g of lithium carbonate product.

[0128] Example 4

[0129] A method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium, the method comprising the following steps:

[0130] S1. Mix 200g of lithium-containing electrolyte from a certain factory with 2000mL of aluminum sulfate solution with an aluminum ion concentration of 1.05mol / L, stir and leach for 2h at 80°C and 300rpm, and after solid-liquid separation, obtain filtrate A and 42g of leached residue.

[0131] S2. Add 1 mol / L sodium hydroxide solution to the filtrate A at 6 mL / min until the pH is 4.8, react sufficiently, and after solid-liquid separation, obtain filtrate B and 336 g of intermediate product hydroxyaluminum fluoride.

[0132] S3. The intermediate product hydroxyaluminum fluoride is supplemented with fluorine by reacting with 248 mL of 40 wt % hydrofluoric acid solution, and after solid-liquid separation and solid drying, 297 g of aluminum fluoride product is obtained.

[0133] S4. The filtrate B was subjected to freeze crystallization at 1°C, and after solid-liquid separation, filtrate C and 472 g of aqueous sodium sulfate product were obtained.

[0134] S5. The lithium concentration in the filtrate C is judged. The lithium ion concentration is 0.077 g / L, which is unqualified. Return to S1 to participate in leaching until the lithium ion concentration is ≥10 g / L.

[0135] S6. After multiple cycles, add sodium hydroxide solution to 2000 mL of filtrate C with qualified lithium concentration to adjust the pH of filtrate C to 12, then filter and remove impurities, pass carbon dioxide micro-nano bubbles into the filtrate after impurities removal to carry out lithium precipitation reaction, filter after the reaction is completed, and obtain 95 g of lithium carbonate product.

[0136] Example 5

[0137] A method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium, the method comprising the following steps:

[0138] S1. Mix 120g of lithium-containing electrolyte from a certain factory with 2000mL of aluminum sulfate solution with an aluminum ion concentration of 0.5mol / L, stir and leach for 2h at 90°C and 300rpm, and after solid-liquid separation, obtain filtrate A and 39g of leaching residue.

[0139] S2. Add 1 mol / L sodium hydroxide solution to the filtrate A at 5 mL / min until the pH is 5, react sufficiently, and obtain filtrate B and 140 g of intermediate product hydroxyaluminum fluoride after solid-liquid separation.

[0140] S3. The intermediate product hydroxyaluminum fluoride is supplemented with fluorine by reacting with 103 mL of 40 wt % hydrofluoric acid solution, and after solid-liquid separation and solid drying, 124 g of aluminum fluoride product is obtained.

[0141] S4. The filtrate B was subjected to freeze crystallization at 5°C, and after solid-liquid separation, filtrate C and 347 g of aqueous sodium sulfate product were obtained.

[0142] S5. The lithium concentration in the filtrate C is judged. The lithium ion concentration is 0.073 g / L, which is unqualified. Return to S1 to participate in leaching until the lithium ion concentration is ≥10 g / L.

[0143] S6. After multiple cycles, sodium hydroxide solution is added to 2000 mL of filtrate C with qualified lithium concentration to adjust the pH of filtrate C to 11, and then the filtrate is filtered to remove impurities. Micro-nano carbon dioxide bubbles are passed into the filtrate after impurity removal to carry out lithium precipitation reaction. After the reaction is completed, it is filtered to obtain 95 g of lithium carbonate product.

[0144] Example 6

[0145] A method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium, the method comprising the following steps:

[0146] S1. Mix 200g of lithium-containing electrolyte from a certain factory with 2000mL of aluminum sulfate solution with an aluminum ion concentration of 0.9mol / L, stir and leach for 2h at 90°C and 300rpm, and after solid-liquid separation, obtain filtrate A and 60g of leaching residue.

[0147] S2. Add 1 mol / L sodium hydroxide solution to the filtrate A at 5 mL / min until the pH is 5, react sufficiently, and after solid-liquid separation, obtain filtrate B and 348 g of intermediate product hydroxyaluminum fluoride.

[0148] S3. The intermediate product hydroxyaluminum fluoride was supplemented with fluorine by reacting with 257 mL of 40% hydrofluoric acid solution, and after solid-liquid separation and solid drying, 308 g of aluminum fluoride product was obtained.

[0149] S4. The filtrate B was subjected to freeze crystallization at 2°C, and after solid-liquid separation, filtrate C and 487 g of aqueous sodium sulfate product were obtained.

[0150] S5. The lithium concentration in the filtrate C is judged. The lithium ion concentration is 0.079 g / L, which is unqualified. Return to S1 to participate in leaching until the lithium ion concentration is ≥10 g / L.

[0151] S6. After multiple cycles, sodium hydroxide solution is added to 2000 mL of filtrate C with qualified lithium concentration to adjust the pH of filtrate C to 13, and then the filtrate is filtered to remove impurities. Micro-nano carbon dioxide bubbles are passed into the filtrate after impurity removal to carry out lithium precipitation reaction. After the reaction is completed, it is filtered to obtain 96 g of lithium carbonate product.

[0152] Test Example 1

[0153] The XRD pattern of the raw material containing lithium electrolyte in Test Example 1 is as follows: Figure 2 shown.

[0154] It can be seen that the main chemical compositions of lithium-containing electrolytes are: Na3AlF6, Al2O3, NaAl 11 O 17 , CaF2, Na2LiAl3F6, C, etc.

[0155] Test Example 2

[0156] The yield and purity of the products of Examples 1-6 were tested, and the results are shown in Table 1.

[0157] Table 1

[0158] Project / No. Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Aluminum fluoride purity 96.6％ 97.1％ 96.9％ 96.9％ 96.5％ 96.5％ Aluminum fluoride yield 94.3％ 94.8％ 94.7％ 94.7％ 94.9％ 94.8％ Sodium sulfate purity 98.8％ 99.4％ 99.5％ 98.6％ 98.8％ 98.9％ Sodium sulfate yield 98.0％ 97.5％ 95.6％ 95.4％ 97.3％ 98.5％ Lithium carbonate purity 99.3％ 99.8％ 99.9％ 99.7％ 99.5％ 99.4％ Lithium carbonate yield 96.2％ 97.0％ 96.8％ 95.6％ 96.4％ 96.6％

[0159] Test Example 3

[0160] The element content of the aluminum fluoride product obtained in Example 1 was tested, and the test results are shown in Table 2.

[0161] Table 2

[0162] Test items unit result F ％ 66.67 Al ％ 29.92 Na ％ 0.028 <![CDATA[SiO2]]> ％ 0.008 <![CDATA[Fe2O3]]> ％ 0.176 <![CDATA[SO4 2- ]]> ％ 0.122 <![CDATA[P2O5]]> ％ 0.009 Burn reduction ％ 0.14

[0163] It can be seen from Table 2 that the aluminum fluoride product obtained by the present invention has high purity and good quality.

[0164] Test Example 4

[0165] The XRD pattern of the sodium sulfate product obtained in Test Example 1 is as follows Figure 3 shown.

[0166] It can be seen that the XRD spectrum of the sodium sulfate product of the present invention has no impurity peaks and has a high matching degree with the standard PDF, indicating that the product has high purity.

Claims

1. A method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium, the method comprising the following steps: S1, mixing the lithium-containing electrolyte with the aluminum sulfate solution, fully stirring and leaching, and obtaining filtrate A and leaching residue after solid-liquid separation; S2, adding alkali solution to the filtrate A, reacting sufficiently, and obtaining filtrate B and intermediate product hydroxyaluminum fluoride after solid-liquid separation; S3, supplementing fluorine with the intermediate product hydroxyaluminum fluoride, reacting with a fluorine source, separating the solid from the liquid and drying the solid to obtain an aluminum fluoride product; S4, freezing and crystallizing the filtrate B, and obtaining the filtrate C and the sodium salt product after solid-liquid separation; S5, measuring the lithium concentration in the filtrate C and determining the qualified concentration. When the lithium concentration is ≥ the qualified concentration, the filtrate C enters the S6 lithium precipitation step; when the lithium concentration is < the qualified concentration, the filtrate C returns to S1 to participate in leaching; S6. After removing impurities from the filtrate C with a qualified lithium concentration, carbon dioxide is introduced to precipitate lithium, and after solid-liquid separation, a lithium carbonate product is obtained.

2. The method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium according to claim 1, characterized in that: The aluminum sulfate solution described in S1 is an acidic aluminum sulfate solution, preferably a mixture of aluminum sulfate and dilute sulfuric acid solution; Preferably, the aluminum ion concentration is 0.5-1.5 mol / L.

3. The method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium according to claim 1, characterized in that: In S1, the liquid-to-solid ratio of the aluminum sulfate solution to the lithium-containing electrolyte is 5-20 mL / g, preferably 7-10 mL / g.

4. The method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium according to claim 1, characterized in that: In S1, the leaching temperature is controlled at 50-100°C.

5. The method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium according to claim 1, characterized in that: The alkali solution in S2 is sodium hydroxide solution; Preferably, the concentration of hydroxide ions in the alkali solution in S2 is 0.5-5 mol / L; Preferably, in S2, the pH of the filtrate A is adjusted to 4-6 by adding alkali solution.

6. The method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium according to claim 1, characterized in that: The fluorine source supplemented in S3 is hydrofluoric acid liquid or hydrogen fluoride gas, wherein the molar ratio of HF to hydroxyaluminum fluoride is 1-2:

1.

7. The method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium according to claim 1, characterized in that: The temperature of the freeze crystallization in S4 is 0-10°C.

8. The method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium according to claim 1, characterized in that: The qualified concentration of lithium in the filtrate C in S5 is ≥10g / L.

9. The method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium according to claim 1, characterized in that: The impurity removal method in S6 is to add alkali solution to adjust the pH of the filtrate C; Preferably, the pH of the filtrate C in S6 after impurities removal is 10-14.

10. The method for high-value utilization of lithium-containing electrolyte fluorine-lithium-aluminum-sodium according to claim 1, characterized in that: The method of introducing carbon dioxide in S6 is air flow stirring or micro-nano bubbles.

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