CN116692917B

CN116692917B - A method for resource utilization of lithium-containing waste aluminum electrolyte

Info

Publication number: CN116692917B
Application number: CN202310062017.9A
Authority: CN
Inventors: 吕晓军; 吴勇聪; 谭璇; 韩泽勋
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2023-01-19
Filing date: 2023-01-19
Publication date: 2025-11-25
Anticipated expiration: 2043-01-19
Also published as: CN116692917A

Abstract

This invention relates to a method for the resource utilization of lithium-containing waste aluminum electrolyte. The method involves mixing the lithium-containing waste aluminum electrolyte powder to be treated with a leaching solution, stirring to dissolve it, and then separating the solid and liquid phases to obtain filter residue A and filtrate B. Filter residue A is mixed with water and additives, reacted, and then separated again to obtain filter residue E and filtrate F. Filtrate B is used for lithium precipitation to obtain lithium salt. Filter residue E is mixed with an acid washing agent, stirred, and reacted. When the pH of the reaction system reaches 4.0-6.5, solid-liquid separation is performed to obtain fluorite product and acid washing solution H. The acid washing solution H and filtrate F are combined and returned to construct the leaching solution. Alternatively, seed crystals are first added to filtrate F, stirred, reacted, and then allowed to stand for solid-liquid separation to obtain aluminum hydroxide product and solution G. The acid washing solution H and solution G are then returned to construct the leaching solution. This invention features a short process flow, enables the full utilization of lithium-containing waste aluminum electrolyte, is green and efficient, involves closed-loop treatment, has low processing costs, and possesses extremely high economic value.

Description

Resource utilization method of lithium-containing waste aluminum electrolyte

Technical Field

The invention relates to a resource utilization method of lithium-containing waste aluminum electrolyte, belonging to the field of resource treatment of metallurgical solid wastes.

Background

A large amount of lithium resources (equivalent to Li ₂ O >0.58 wt%) are often associated with low-grade bauxite (rock), and the lithium cannot be effectively removed in the process of dressing and smelting, so that the lithium enters an alumina product. In the process of aluminum electrolysis, aluminum oxide is continuously added into an electrolytic tank as a raw material, and lithium contained in the aluminum oxide is continuously enriched in the electrolytic tank, so that the lithium content in the electrolyte is gradually increased. For example, in the electrolyte of the electrolytic aluminum plant in some areas, the Li content is as high as 1-3wt%, which is equivalent to the Li ₂ O content of 2.1-6.4wt%, and is close to the Li content in the diabase ore (1.5-7 wt% calculated by Li ₂ O), even higher than the Li content in the Yu Yichun lepidobase ore (0.5-3.27 wt% calculated by Li ₂ O), and the lithium extraction value is extremely high. Therefore, the lithium-containing waste aluminum electrolyte is expected to become an important lithium extraction resource, and has wide resource utilization prospect.

Phase analysis shows that lithium exists in the lithium-containing waste aluminum electrolyte mainly in the form of Na ₂LiAlF₆、NaLi₂AlF₆, and the lithium sodium cryolite and cryolite (Na ₃AlF₆) have similar properties and are difficult to dissolve in water, so that the difficulty in extracting lithium from the waste aluminum electrolyte is increased.

Chinese patent No. 109930174B discloses a method for separating, purifying and recovering lithium from aluminum electrolyte, and proposes leaching lithium-containing aluminum electrolyte by using 2-6mol/L HNO ₃ at 40-120 ℃ for 0.5-10h. Filtering and evaporating the lithium-containing leaching solution, naturally cooling and crystallizing the evaporating mother solution when the evaporating mother solution is evaporated to 3-8g/L, separating to obtain NaNO ₃, then regulating the pH value to 6-7, continuously naturally cooling, and separating to obtain secondary NaNO ₃. Adding calcium salt and oxalic acid into the filtrate in turn to purify and remove impurities, adding alkaline substances to precipitate lithium according to the requirement, and mainly obtaining Li ₂CO₃ or LiOH.

The Chinese patent application CN 108569711A proposes that 5-8% sulfuric acid is used for heating and leaching for 0.5-1.5 hours at 90-95 ℃ to obtain lithium sulfate solution, and the obtained leaching solution is evaporated, concentrated and precipitated with lithium after purification and impurity removal.

Chinese patent application CN 105543504A proposes that after uniformly mixing sodium fluoride and lithium-containing aluminum electrolyte, preserving heat for 2-3 hours at 400-1000 ℃ to realize the ore phase transformation of the lithium-containing phase, and leaching by 7-14mol/L strong acid in the subsequent treatment process.

Chinese patent application CN 112919507A proposes leaching electrolyte with sodium hydroxide solution of concentration 2.5-5.0mol/L at 80-100deg.C to convert Na ₂LiAlF₆ into LiF, and solid-liquid separating to obtain filter residue containing LiF. Leaching the filter residue with 1-4mol/L acid at 50-90deg.C, and dissolving LiF into solution. The process reduces acid concentration and HF volatilization.

It can be seen that most of the current waste electrolyte lithium extraction processes involve acid leaching, HF is inevitably generated, equipment corrosion is easily caused, and site environment is easily deteriorated.

In addition, the applicant has previously filed an invention patent application CN 115216630A discloses a recycling treatment method of waste lithium-containing aluminum electrolyte, which comprises the steps of crushing the waste lithium-containing aluminum electrolyte to be treated to obtain powder, uniformly mixing the powder with a first reactant, carrying out phase inversion treatment in a wet leaching mode to obtain a mixture, mixing the mixture with a second reactant and water, stirring for reaction, filtering to obtain filter residues and filtrate, using the filtrate for precipitating lithium to obtain lithium salt, reacting the filter residues with dilute acid, filtering to obtain fluorite powder and filtrate a, and subsequently evaporating and crystallizing the filtrate a to obtain a crystal water mixture of calcium salt and aluminum salt. Although the recycling treatment method can realize lithium extraction, the reactant is required to be continuously consumed, and the produced byproducts are mainly a crystallized water mixture of calcium salt and aluminum salt, so that the value is required to be further improved.

Therefore, it is particularly important to develop a full-scale comprehensive utilization and closed-loop disposal process of the green and efficient lithium-containing waste aluminum electrolyte.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a resource utilization method of lithium-containing waste aluminum electrolyte so as to reduce the treatment cost.

In order to solve the technical problems, the technical scheme of the invention is as follows:

A resource utilization method of lithium-containing waste aluminum electrolyte comprises the following steps:

s1, crushing lithium-containing waste aluminum electrolyte to be treated to obtain aluminum electrolyte powder;

s2, mixing the aluminum electrolyte powder with the dissolution liquid, stirring and dissolving out, and then carrying out solid-liquid separation to obtain filter residue A and filtrate B;

Wherein the dissolved solution is an aqueous solution containing Ca ²⁺、OH^-、Al(OH)₄ ^-, alkali metal ions and acid radical ions, the acid radical ions comprise one or more of Cl ^-、SO₄ ^2-、NO₃ ^-, the alkali metal ions are Na ⁺ and/or K ⁺, and the concentration of Ca ²⁺ in the dissolved solution is 70-140g/L;

S3, mixing the filter residue A with water and additives, and performing solid-liquid separation after reacting for 60-90min at 75-120 ℃ to obtain filter residue E and filtrate F;

the filtrate B is used for precipitating lithium to obtain lithium salt;

Wherein the additive is water-soluble carbonate and/or water-soluble bicarbonate;

s4, mixing the filter residue E with a pickling agent, stirring for reaction, and carrying out solid-liquid separation when the pH value of a reaction system is 4.0-6.5 to obtain a fluorite product and a pickling agent H;

wherein the pickling agent is an inorganic acid dilute solution containing one or more of Cl ^-、SO₄ ^2-、NO₃ ^-;

S5, when the Al ₂ O content in the filtrate F is less than 100g/L (usually, the situation is corresponding to the previous cycle process), merging the pickling solution H and the filtrate F, and returning to the step S2 for constructing a leaching solution;

When the Al ₂ O content in the filtrate F is more than or equal to 100G/L (usually, after a few times of circulation process, corresponding to the situation), seed crystals are added into the filtrate F, stirring is carried out at the temperature of less than or equal to 25 ℃ for reaction, standing and aging are carried out, and solid-liquid separation is carried out, thus obtaining an aluminum hydroxide product and a solution G;

wherein the seed crystal comprises one or more of alpha-Al ₂O₃、γ-Al₂O₃、Al(OH)₃.

Further, in S1, the particle size of the aluminum electrolyte powder is 0.8mm or less, further still, less than 0.5mm, preferably, less than 0.2mm, and preferably, 0.1mm or less.

Further, in S2, the liquid-solid ratio of the dissolved solution to the aluminum electrolyte powder is 5-25 mL/1 g, further 7-20 mL/1 g, still further 8-15 mL/1 g, and preferably 10-12 mL/1 g.

Wherein, the content of alkali in the dissolved solution is 30-100g/L calculated by Na ₂ O, and the content of aluminum is 5-95g/L calculated by Al ₂O₃.

Further, in S2, during stirring and dissolving, the temperature is controlled to be 65-120 ℃, the stirring and dissolving time is 30-180min, and the stirring speed is 200-600r/min.

In step S2, the aluminum electrolyte powder is mixed with the dissolution liquid, and after one or more sections of stirring dissolution, solid-liquid separation is carried out to obtain filter residue A and filtrate B.

Further, between S2 and S3, the method further comprises the step of washing the filter residue A, namely, after washing the filter residue A, carrying out solid-liquid separation to obtain washed residue C and washing liquid D;

s3, mixing the washed slag C with water and additives, and carrying out solid-liquid separation after reaction to obtain filter residue E and filtrate F;

Preferably, the washing liquid D is returned to step S2 for constructing a dissolution liquid.

Further, evaporating and concentrating the filtrate B, cooling and crystallizing, separating solid from liquid to obtain lithium-rich mother liquor and salt, adding water-soluble carbonate or its solution into the lithium-rich mother liquor, precipitating, filtering to obtain lithium carbonate product and residual liquor.

Preferably, the water wash is a three stage counter current wash.

Further, in S3, the additive comprises one or more of Na₂CO₃、NaHCO₃、K₂CO₃、KHCO₃、(NH₄)₂CO₃、NH₄HCO₃, preferably one or more of Na ₂CO₃、NaHCO₃, and preferably the mass ratio of filter residue A to carbonate and/or bicarbonate in the additive is 3-6:1.

Further, in S3, the reaction temperature is controlled to be 80-110 ℃ and the reaction time is controlled to be 45-80min.

Further, in S4, the inorganic acid comprises one or more of HCl and HNO ₃、H₂SO₄, preferably, the concentration of the inorganic acid in the inorganic acid dilute solution is 3-21wt%, preferably, the filter residue E and the pickling agent are mixed and stirred for reaction at 50-100 ℃, and when the pH value of a reaction system is 4.0-6.5, the fluorite product and the pickling agent H are obtained through solid-liquid separation.

Optionally, the pickling agent is prepared from one or more of 3-5wt% of HCl solution, 5-8wt% of HNO ₃ solution and 5-8wt% of H ₂SO₄ solution.

Further, in S5, the seed crystal is added in an amount of 5 to 15wt% of the filtrate F.

Further, in S5, adding seed crystal into the filtrate F, stirring and reacting for 12-24 hours at 5-25 ℃, standing and aging for 60-150min, and carrying out solid-liquid separation to obtain an aluminum hydroxide product and a solution G.

Optionally, the lithium-containing waste aluminum electrolyte is one or more selected from a planer electrolyte generated in the aluminum electrolysis production process, electrolyte adhered in the covering material and a flotation material obtained by performing flotation separation on carbon residues.

Optionally, in the lithium-containing aluminum scrap electrolyte, lithium exists in one or more of Na ₂LiAlF₆、NaLi₂AlF₆ and LiF.

Further, the lithium-containing waste aluminum electrolyte comprises Na ₃AlF₆25-80wt%、Na₂LiAlF₆ NaLi₂AlF₆8-70wt%、Na₂KAlF₆5-25wt%、Al₂O₃1-4wt%、CaF₂1-5wt%、MgF₂0.5-1.5wt%、LiF1-10wt%.

Optionally, when the dissolution liquid is constructed, the concentration of the obtained dissolution liquid Ca ²⁺ reaches 70-140g/L by supplementing calcium-containing substances, wherein the calcium-containing substances comprise one or more of calcium chloride, calcium nitrate, calcium sulfate and calcium hydroxide.

In the invention, lithium in the lithium-containing waste aluminum electrolyte is converted into soluble lithium salt (such as LiOH, li ₂SO₄、LiNO₃, liCl and the like) by mixing the lithium-containing waste aluminum electrolyte powder and the dissolution solution and stirring and dissolution, fluorine in the lithium-containing waste aluminum electrolyte enters a slag phase in the form of insoluble CaF ₂, aluminum in the lithium-containing waste aluminum electrolyte enters the slag phase in the form of aluminum-calcium insoluble substances (such as 2CaO·Al₂O₃·4H₂O、3CaO·Al₂O₃·6H₂O、CaO·2Al₂O₃·5H₂O and the like), sodium in the lithium-containing waste aluminum electrolyte is combined with acid radical ions and enters a liquid phase in the form of soluble sodium salt, thereby realizing that lithium and aluminum in the electrolyte, and separating elements such as calcium, fluorine, sodium and the like. then, the filtrate B rich in Li ⁺、Na⁺ and the insoluble substances rich in aluminum and calcium are obtained through solid-liquid separation, And after the filter residue A is further reacted with the additive and then dissolved out, converting calcium in the aluminum-calcium insoluble substances into calcium carbonate to enter the filter residue E, converting aluminum in the aluminum-calcium insoluble substances into Al (OH) ₄ ^- to enter the filter liquor F, and retaining CaF ₂ in the filter residue A in the filter residue E. after the filter residue E is washed by inorganic acid dilute solution, calcium carbonate is converted into soluble calcium salt to enter a pickling solution H, and the pH end point of the pickling solution is controlled to be 4-6.5, caF ₂ is still remained in a slag phase, so that a fluorite product can be obtained after the pickling solution H rich in Ca ²⁺ is combined with the filtrate F or the solution G (the amount of H ⁺ in the pickling solution H is very limited, and the H ⁺ in the pickling solution H does not need to excessively consume the filtrate F or Al (OH) ₄ ^- and/or OH ^- in the solution G, and the recycling is realized after the filter residue E is returned to S2 for constructing the pickling solution.

The method has the advantages of short process flow, capability of realizing full-scale utilization of the lithium-containing waste aluminum electrolyte, environment-friendly and efficient closed-loop treatment, no secondary pollution, low treatment cost and extremely high economic value.

Compared with the prior art, the invention has the following beneficial effects:

(1) The recycling treatment method synchronously realizes fluorine fixation and dealumination in the leaching process, the obtained lithium-containing leaching solution does not need to be purified again, lithium can be precipitated after concentration, the process flow is short, the equipment is simple, and the industrialization feasibility is high.

(2) In the whole process flow, OH ^-、Al(OH)₄ ^- and the like in the dissolved liquid can be completely recycled, exogenous addition is not needed, the consumption of the dissolved liquid is small, the treatment cost is low, the economic benefit is excellent, and the feasibility of large-scale popularization and application is realized.

(3) Compared with the alkali treatment technology such as CN 112919507A, the invention can effectively reduce the use amount of acid and alkali and reduce the treatment cost.

(4) The whole process flow realizes the comprehensive recycling of the lithium-containing aluminum scrap electrolyte, not only extracts high-value lithium, but also carries out high-added-value recycling on valuable components Al and F in the electrolyte, effectively improves the comprehensive treatment benefit of the aluminum scrap electrolyte, does not generate secondary pollution, and ensures that the purities of calcium fluoride and aluminum hydroxide products meet the current national standard requirements.

Drawings

FIG. 1 is a flow chart of a method for comprehensive utilization of lithium-containing aluminum electrolyte resources according to the present invention.

Fig. 2 is an XRD pattern of the lithium-containing aluminum scrap electrolyte used in example 1.

FIG. 3 is an XRD pattern of residue A obtained in example 1.

Fig. 4 is an XRD pattern of the lithium carbonate product obtained in example 1.

Figure 5 is an XRD pattern of the fluorite product obtained in example 6.

Detailed Description

The present invention will be described in detail with reference to examples. It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other. The relevant percentages refer to mass percentages unless otherwise indicated.

Example 1

In this embodiment, the method for recycling lithium-containing waste aluminum electrolyte includes the following steps:

S1, taking a phase analysis map of a lithium-containing waste aluminum electrolyte 100g(Na₃AlF₆40.3%、Na₂LiAlF₆34.5%、Na₂KAlF₆16.3%、Al₂O₃5.1%、CaF₂2.9%、MgF₂0.5%, of an aluminum factory, referring to figure 2, and crushing to obtain 100g of aluminum electrolyte powder with the particle size less than or equal to 0.1 mm;

s2, mixing 100g of aluminum electrolyte powder with 1000mL of dissolution liquid (the liquid-solid ratio is 10 mL/g), placing the mixture in a reaction kettle, stirring and dissolving the mixture at 90 ℃ for 0.5h at the stirring speed of 300rpm, and carrying out solid-liquid separation to obtain filter residue A and filtrate B;

wherein the dissolved solution is an aqueous solution containing Ca ²⁺、OH^-、Na⁺、Al(OH)₄ ^- and acid radical ions, the acid radical ions are Cl ^-, the alkali content (calculated by Na ₂O_{Causticizing process}) in the dissolved solution is 30g/L, the aluminum content (calculated by Al ₂O₃) is 10g/L, and the calcium content (calculated by free calcium) is 90g/L;

fig. 3 shows the XRD pattern of the residue a after the electrolyte powder is dissolved out in S2, and it is seen that the diffraction peak corresponding to the cryolite class included in Na ₃AlF₆、Na₂KAlF₆、Na₂LiAlF₆ in the lithium-containing waste aluminum electrolyte has completely disappeared, and the main products generated by the reaction are the calcium-aluminum class substances including 3cao·al ₂O₃·6H₂O、2CaO·Al₂O₃·4H₂ O and CaF ₂、Ca(OH)₂, and the soluble salts such as Li ₂SO₄、Na₂SO₄、K₂SO₄, liCl, naCl, KCl, etc. exist in the filtrate B.

And (3) carrying out full-element detection analysis on the obtained lithium carbonate product by adopting an inductive coupling plasma emission spectrometer, weighing three groups of samples in parallel, taking 1.0g of each group of samples, and determining after digestion and volume fixation by using 1.40mol/L hydrochloric acid, wherein the average purity of the product can reach 99.20 percent. The XRD pattern of the lithium carbonate product is shown in figure 4. The recovery of lithium was calculated to be 83.7%.

Example 2

Example 1 was repeated except that in S2, the reaction was carried out for 1 hour at 95℃with stirring at 400rpm for one-stage elution, and the reaction was carried out for 1.5 hours at 80℃with stirring at 200rpm for two-stage elution with stirring. The alkali content (calculated as Na ₂O_{Causticizing process}) of the dissolution solution was 60g/L, the aluminum content (calculated as Al ₂O₃) was 15g/L, and the calcium content (calculated as free calcium) was 105g/L.

The purity of the lithium carbonate product obtained was 98.7%. The recovery rate of lithium was 89.1%.

Example 3

Example 1 was repeated except that in S2, the reaction was carried out for 0.5h at 120℃with stirring at 400rpm to carry out the first-stage elution, and the reaction was carried out for 2.0h at 90℃with stirring at 200rpm to carry out the second-stage elution. The alkali content (calculated as Na ₂O_{Causticizing process}) of the dissolution solution was 95g/L, the aluminum content (calculated as Al ₂O₃) was 5g/L, and the calcium content (calculated as free calcium) was 135g/L.

The purity of the obtained lithium carbonate product is 99.1%. The recovery rate of lithium was 93.6%.

Example 4

Example 3 was repeated with the difference that the method further comprises the steps of:

And (3) carrying out three-stage countercurrent washing on 295.3g of filter residue A obtained in the step (S2), wherein the water consumption for washing is 885.9mL, the water temperature for washing is 60 ℃, the single-stage countercurrent washing time is 30 minutes, and filtering after washing is completed to obtain washed residue C and washing liquid D.

Mixing 265.77g of the obtained washed slag C with additives, adding 280mL of deionized water, stirring at 300rpm, maintaining the temperature at 100 ℃ for reaction for 1.0h, and filtering to obtain filter residue E and filtrate F. Wherein the additive is sodium carbonate and sodium bicarbonate, the mass ratio of the sodium carbonate to the sodium bicarbonate is 3:1, and the ratio of the mass of the washed slag C to the total mass of carbonate and bicarbonate in the additive is 6:1.

Filter residue E351.8 g was mixed with 1055.4g of 3wt% HCl solution, maintained at 75deg.C with stirring at 100rpm, and filtered to give pickle liquor H and fluorite product 175.9g when the pH of the solution was 5.4.

And combining the filtrate F and the washing liquid D, and returning to S2 for constructing the dissolution liquid, wherein when the calcium concentration in the dissolution liquid obtained by combining the filtrate F and the washing liquid D is less than 135g/L, calcium chloride is supplemented into the obtained dissolution liquid, so that the calcium concentration (calculated as free calcium) in the dissolution liquid reaches 135g/L.

And (3) detecting and analyzing the fluorite product by adopting a fluorescence spectrum method, weighing three groups of samples in parallel, taking 3.0g of each group of samples, and preparing and measuring, wherein the average purity of the fluorite product is 65.70%.

The purity of the obtained lithium carbonate product was 85.3%. The overall recovery of lithium was 79.1%.

Example 5

Example 4 was repeated except that the ratio of the mass of the washed slag C to the total mass of carbonate and bicarbonate in the additive was 4.1:1.

And (3) detecting and analyzing the fluorite product by adopting a fluorescence spectrum method, weighing three groups of samples in parallel, taking 3.0g of each group of samples, and preparing and measuring, wherein the average purity of the fluorite product is 79.70%.

The purity of the obtained lithium carbonate product was 90.6%. The overall recovery of lithium was 86.1%.

Example 6

Example 4 was repeated except that the ratio of the mass of the washed slag C to the total mass of carbonate and bicarbonate in the additive was 3.0:1.

And (3) detecting and analyzing the fluorite product by adopting a fluorescence spectrum method, weighing three groups of samples in parallel, taking 3.0g of each group of samples, and preparing and measuring, wherein the average purity of the fluorite product can reach 93.30%, and meets the requirements of fluorite concentrate FC-93 in YB/T5217-2005. The XRD pattern of fluorite is shown in FIG. 5.

The purity of the obtained lithium carbonate product was 98.9%. The overall recovery of lithium was 93.1%.

Comparative example 1

Example 4 was repeated except that the ratio of the mass of the washed slag C to the total mass of carbonate and bicarbonate in the additive was 7:1.

And (3) detecting and analyzing the fluorite product by adopting a fluorescence spectrum method, weighing three groups of samples in parallel, taking 3.0g of each group of samples, and preparing and measuring, wherein the average purity of the fluorite product is 45.80%.

The purity of the obtained lithium carbonate product was 65.3%. The overall recovery of lithium was 54.1%.

Comparative example 2

Example 4 was repeated except that the ratio of the mass of the washed slag C to the total mass of carbonate and bicarbonate in the additive was 2.5:1.

And (3) detecting and analyzing the fluorite product by adopting a fluorescence spectrum method, weighing three groups of samples in parallel, taking 3.0g of each group of samples, and preparing samples for measurement, wherein the average purity of the fluorite product is 63.10%.

The purity of the obtained lithium carbonate product was 97.5%. The overall recovery of lithium was 90.3%.

As can be seen from comparison, the ratio of the mass of the washed slag C to the total mass of carbonate and bicarbonate in the additive needs to be controlled within a certain range, and the ratio is too high, so that calcium ions in the dissolved solution are possibly low, the purity of a lithium carbonate product is reduced, the recovery rate of lithium is reduced, and the ratio is too low, so that residual sodium carbonate or sodium bicarbonate in filter residues E is possibly excessive, the subsequent acid washing process is influenced, and the purity of fluorite products is reduced.

Example 7

Example 6 was repeated except that after the filtrate F was recycled 5 times, the Al ₂ O content in the filtrate F reached 130g/L;

The method also comprises the following steps:

200G of filtrate F is placed in a cold water bath, 10G of aluminum hydroxide seed crystal is added, the temperature is maintained at 5 ℃ under the stirring of 500rpm, the reaction is carried out for 12 hours, and after the reaction is finished, the mixture is kept stand for ageing 100 min and filtered, thus obtaining a filter cake and a solution G.

After the filter cake was dried, 40.3g of an aluminum hydroxide product was obtained.

And combining the filtrate G with the pickling solution H and the washing solution D, returning to S2 for constructing a dissolution solution, and recycling, wherein when the concentration of calcium in the dissolution solution obtained by combining the filtrate G with the pickling solution H and the washing solution D is less than 135G/L, calcium chloride is supplemented into the obtained dissolution solution, so that the concentration of calcium content (calculated as free calcium) in the dissolution solution reaches 135G/L.

The purity of the lithium carbonate product obtained was 98.50%. The recovery rate of lithium was 94.1%.

And detecting the content of Al ₂O₃ before and after decomposition and dealumination by adopting an inductive coupling plasma emission spectrometer, wherein the content of aluminum (calculated by Al ₂O₃) in the filtrate F before decomposition and dealumination is 144G/L, and the content of aluminum (calculated by Al ₂O₃) in the solution G after decomposition and dealumination is reduced to 15G/L.

And (3) detecting and analyzing the aluminum hydroxide product by adopting a fluorescence spectrum method, weighing three groups of samples in parallel, taking 3.0g of each group of samples, preparing the samples, and measuring, wherein the average purity of the aluminum hydroxide product is 98.30%, and meets the requirement of the GB/T4294-2010 on the content of the main component in the AH-2 brand.

From the results of the above examples, it can be seen that the method provided by the application can recover valuable lithium, aluminum and fluorine in the lithium-containing waste aluminum electrolyte in the forms of lithium carbonate, aluminum hydroxide and calcium fluoride, respectively, so as to realize the full-scale utilization of the aluminum electrolyte with high added value. The foregoing examples are set forth in order to provide a more thorough description of the present application and are not intended to limit the scope of the application, and various modifications of the application, which are equivalent to those skilled in the art upon reading the present application, will fall within the scope of the application as defined in the appended claims.

Claims

1. The method for recycling the lithium-containing waste aluminum electrolyte is characterized by comprising the following steps of:

wherein the dissolved solution is an aqueous solution containing Ca ²⁺、OH^-、Al(OH)₄ ^-, alkali metal ions and acid radical ions, the acid radical ions are one or more of Cl ^-、SO₄ ^2-、NO₃ ^-, the alkali metal ions are Na ⁺ and/or K ⁺, the concentration of Ca ²⁺ in the dissolved solution is 70-140g/L, the temperature is controlled to be 65-120 ℃ during stirring and dissolving, and the stirring and dissolving time is 30-180min;

the filtrate B is used for precipitating lithium to obtain lithium salt;

Wherein the additive is water-soluble carbonate and/or water-soluble bicarbonate, and the ratio of the total mass of carbonate and bicarbonate in the filter residue A and the additive is 3-4.1:1;

S5, when the Al ₂O₃ content in the filtrate F is less than 100g/L, merging the pickling solution H and the filtrate F, and returning to the step S2 for constructing a leaching solution;

When the content of Al ₂O₃ in the filtrate F is more than or equal to 100G/L, adding seed crystals into the filtrate F, stirring and reacting at the temperature of less than or equal to 25 ℃, standing and ageing, and carrying out solid-liquid separation to obtain an aluminum hydroxide product and a solution G;

2. The recycling method according to claim 1, wherein in S1, the particle size of the aluminum electrolyte powder is not more than 0.8mm.

3. The recycling method according to claim 2, wherein in S1, the particle size of the aluminum electrolyte powder is not more than 0.1mm.

4. The recycling method according to claim 1, wherein in S2, the liquid-solid ratio of the dissolved solution to the aluminum electrolyte powder is 5-25 ml/1 g;

5. The method for recycling according to claim 1, wherein in S2, the stirring rate is 200-600r/min when stirring and dissolving.

6. The recycling method according to claim 1, further comprising a step of washing the filter residue a between S2 and S3, i.e., after washing the filter residue a with water, performing solid-liquid separation to obtain a washed residue C and a washing liquid D;

And S3, mixing the washed slag C with water and additives, and carrying out solid-liquid separation after reaction to obtain filter residue E and filtrate F.

7. The recycling method according to claim 6, wherein the washing liquid D is returned to step S2 for constructing a dissolution liquid.

8. The recycling method according to claim 1, wherein in S3, the additive is one or more of Na₂CO₃、NaHCO₃、K₂CO₃、KHCO₃、(NH₄)₂CO₃、NH₄HCO₃.

9. The recycling method according to claim 1, wherein in S3, the reaction temperature is controlled to be 80-110 ℃ and the reaction time is controlled to be 65-80min.

10. The recycling method according to claim 1, wherein in S4, the inorganic acid comprises one or more of HCl and HNO ₃、H₂SO₄.

11. The recycling method according to claim 10, wherein in S4, the concentration of the inorganic acid in the dilute inorganic acid solution is 3 to 21wt%.

12. The recycling method according to claim 10, wherein in S4, the filter residue E is mixed with the pickling agent, stirred and reacted at 50-100 ℃, and subjected to solid-liquid separation when the pH value of the reaction system is 4.0-6.5, thereby obtaining fluorite product and pickling agent H.

13. The recycling method according to claim 1, wherein in S5, the seed crystal is added in an amount of 5 to 15wt% of the filtrate F.

14. The recycling method according to claim 13, wherein in S5, seed crystals are added to the filtrate F, and after stirring reaction is performed for 12-24 hours at 5-25 ℃, the mixture is left to stand and age for 60-150 minutes, and solid-liquid separation is performed, thereby obtaining an aluminum hydroxide product and a solution G.

15. The recycling method according to claim 1, wherein the concentration of the obtained dissolved solution Ca ²⁺ is up to 70-140g/L by supplementing calcium-containing substances when the dissolved solution is constructed, wherein the calcium-containing substances comprise one or more of calcium chloride, calcium nitrate, calcium sulfate and calcium hydroxide.