A method for recycling lithium-containing waste aluminum electrolyte

Abstract

The application relates to a resource utilization method of lithium-containing waste aluminum electrolyte, which comprises the following steps: mixing lithium-containing waste aluminum electrolyte powder to be treated with a dissolving solution, stirring and dissolving, then performing solid-liquid separation to obtain filter residue A and filter liquor B; mixing the filter residue A with water and an additive, then performing reaction and solid-liquid separation to obtain filter residue E and filter liquor F; using the filter liquor B for lithium precipitation to obtain a lithium salt; mixing the filter residue E with an acid pickling agent, stirring and reacting, then performing solid-liquid separation when the pH value of the reaction system is 4.0-6.5 to obtain a fluorite product and acid pickling liquor H; or adding crystal seeds into the filter liquor F, stirring and reacting, then standing, performing solid-liquid separation to obtain an aluminum hydroxide product and solution G; and then returning the acid pickling liquor H and the solution G to construct the dissolving solution. The process flow is short, the lithium-containing waste aluminum electrolyte can be fully utilized, the method is green and efficient, closed-loop treatment is achieved, the treatment cost is low, and the method has extremely high economic value.

Description

Technical Field

[0001] This invention relates to a method for the resource utilization of lithium-containing waste aluminum electrolyte, belonging to the field of resource utilization of metallurgical solid waste. Background Technology

[0002] Low-grade bauxite (rock) often contains abundant lithium resources (equivalent to Li₂O > 0.58 wt%). This lithium is not effectively removed during mining, beneficiation, and smelting, resulting in lithium entering the alumina product. During aluminum electrolysis, alumina is continuously added to the electrolytic cell, and the lithium it contains accumulates within the cell, leading to a gradual increase in the lithium content of the electrolyte. For example, in some aluminum electrolysis plants, the lithium content in the electrolyte is as high as 1-3 wt%, equivalent to 2.1-6.4 wt% Li₂O, close to the lithium content in spodumene ore (1.5-7 wt% Li₂O), and even higher than the lithium content in Yichun lepidolite ore (0.5-3.27 wt% Li₂O), indicating extremely high lithium extraction value. Therefore, this type of lithium-containing waste aluminum electrolyte holds promise as an important lithium extraction resource with broad prospects for resource utilization.

[0003] Phase analysis showed that lithium in lithium-containing waste aluminum electrolytes mainly exists in the form of Na2LiAlF6 and NaLi2AlF6. These lithium sodium cryolites have similar properties to cryolite (Na3AlF6) and are poorly soluble in water, which increases the difficulty of lithium extraction from waste aluminum electrolytes.

[0004] Chinese invention patent CN 109930174B discloses a method for the purification and recovery of lithium from aluminum electrolyte. The method involves leaching lithium-containing aluminum electrolyte with 2-6 mol / L HNO3 at 40-120℃ for 0.5-10 hours. The lithium-containing leachate is filtered and evaporated. When the concentration reaches 3-8 g / L, the mother liquor is naturally cooled and crystallized to obtain NaNO3. The pH is then adjusted to 6-7, and natural cooling continues to obtain secondary NaNO3. The filtrate is purified by adding calcium salt and oxalic acid sequentially. Then, an alkaline substance is added as needed to precipitate lithium. The main products are Li2CO3 or LiOH.

[0005] Chinese invention patent application CN 108569711 A proposes to use 5-8% sulfuric acid to heat and leach at 90-95℃ for 0.5-1.5h to obtain a lithium sulfate solution. The resulting leachate is then purified and concentrated by evaporation to precipitate lithium.

[0006] Chinese invention patent application CN 105543504 A proposes to uniformly mix sodium fluoride with lithium-containing aluminum electrolyte and keep it at 400-1000℃ for 2-3 hours to achieve the mineral phase transformation of lithium-containing phase. The subsequent processing uses strong acid leaching with 7-14 mol / L.

[0007] Chinese invention patent application CN 112919507 A proposes using a sodium hydroxide solution with a concentration of 2.5-5.0 mol / L to leach the electrolyte at 80-100℃, converting Na₂LiAlF₆ to LiF. After solid-liquid separation, a filter residue containing LiF is obtained. The filter residue is then leached with 1-4 mol / L acid at 50-90℃ to dissolve the LiF into the solution. This process reduces the acid concentration and decreases the volatilization of HF.

[0008] It is evident that most current lithium extraction processes from waste electrolytes involve acid leaching, which inevitably generates HF, easily causing equipment corrosion and environmental degradation.

[0009] Furthermore, the applicant's previous invention patent application CN 115216630 A discloses a method for the resource recovery of waste lithium-containing aluminum electrolyte. The method involves pulverizing the waste lithium-containing aluminum electrolyte to obtain powder; mixing the powder with a first reactant and performing a phase inversion treatment via wet leaching to obtain a mixture; mixing the mixture with a second reactant and water, stirring and reacting, then filtering to obtain filter residue and filtrate; using the filtrate for lithium precipitation to obtain lithium salts; reacting the filter residue with dilute acid, filtering to obtain fluorite powder and filtrate a; subsequently evaporating and crystallizing filtrate a to obtain a mixture of calcium and aluminum salt crystal water. While this resource recovery method can achieve lithium extraction, it requires continuous consumption of reactants, and the main byproduct is a mixture of calcium and aluminum salt crystal water, thus its value needs further improvement.

[0010] Therefore, it is particularly important to develop green and efficient processes for the comprehensive utilization and closed-loop disposal of lithium-containing waste aluminum electrolytes. Summary of the Invention

[0011] To address the shortcomings of existing technologies, this invention provides a method for the resource utilization of lithium-containing waste aluminum electrolyte, thereby reducing processing costs.

[0012] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0013] A method for the resource utilization of lithium-containing waste aluminum electrolyte includes the following steps:

[0014] S1. Crush the lithium-containing waste aluminum electrolyte to be processed to obtain aluminum electrolyte powder;

[0015] S2. Mix the aluminum electrolyte powder with the dissolution solution, stir to dissolve, and then separate the solid and liquid to obtain filter residue A and filtrate B.

[0016] The dissolution solution contains Ca. 2+ OH - Al(OH)4 -An aqueous solution of alkali metal ions and acid radical ions, wherein the acid radical ions include Cl- - SO4 2- NO3 - One or more of the following; the alkali metal ion is Na. + and / or K + Ca in the dissolution solution 2+ The concentration is 70-140 g / L;

[0017] S3. Mix the filter residue A with water and additives, react at 75-120℃ for 60-90 min, and then separate the solid and liquid to obtain filter residue E and filtrate F.

[0018] The filtrate B was used to precipitate lithium to obtain lithium salt;

[0019] The additive is a water-soluble carbonate and / or a water-soluble bicarbonate.

[0020] S4. Mix the filter residue E with the pickling agent and stir to react. When the pH value of the reaction system is 4.0-6.5, separate the solid and liquid to obtain fluorite product and pickling solution H.

[0021] The pickling agent contains Cl. - SO4 2- NO3 - A dilute solution of one or more inorganic acids;

[0022] S5. When the Al2O content in filtrate F is <100g / L (usually, this situation applies in the first few cycles), the pickling solution H and filtrate F are combined and returned to step S2 to construct the dissolution solution.

[0023] When the Al2O content in filtrate F is ≥100g / L (usually after several cycles, this condition is met), seed crystals are first added to filtrate F, and the mixture is stirred and reacted at a temperature of ≤25℃. After standing and aging, solid and liquid are separated to obtain aluminum hydroxide product and solution G. Then, the pickling solution H and solution G are combined and returned to step S2 to construct the dissolution solution.

[0024] The seed crystals include one or more of α-Al2O3, γ-Al2O3, and Al(OH)3.

[0025] Furthermore, in S1, the particle size of the aluminum electrolyte powder is ≤0.8mm, even more so, less than 0.5mm, preferably less than 0.2mm, and most preferably ≤0.1mm.

[0026] Furthermore, in S2, the liquid-to-solid ratio of the leaching solution to the aluminum electrolyte powder is 5-25 mL:1 g; even further, it is 7-20 mL:1 g; even further, it is 8-15 mL:1 g; and preferably, it is 10-12 mL:1 g.

[0027] The leaching solution contains 30-100 g / L of alkali (based on Na2O) and 5-95 g / L of aluminum (based on Al2O3).

[0028] Furthermore, in S2, during the stirring dissolution process, the temperature is controlled at 65-120℃, the stirring dissolution time is 30-180 min, and the stirring rate is 200-600 r / min.

[0029] Further, in S2, the aluminum electrolyte powder is mixed with the dissolution solution, and after one or more stages of stirring and dissolution, solid-liquid separation is performed to obtain filter residue A and filtrate B.

[0030] Furthermore, between S2 and S3, there is also a step of washing the filter residue A with water, that is, after washing the filter residue A with water, solid-liquid separation is performed to obtain washed residue C and washing liquid D;

[0031] In S3, the washed residue C is mixed with water and additives. After reaction, solid and liquid separation is performed to obtain filter residue E and filtrate F.

[0032] Preferably, the washing solution D is returned to step S2 for constructing the dissolution solution.

[0033] Further, the filtrate B is evaporated and concentrated, cooled and crystallized, and then the solid and liquid are separated to obtain a lithium-rich mother liquor and salt; then water-soluble carbonate or its solution is added to the lithium-rich mother liquor, precipitated, filtered, and lithium carbonate product and residual liquid are obtained.

[0034] Preferably, the water washing is a three-stage countercurrent washing process.

[0035] Further, in S3, the additive includes one or more of Na2CO3, NaHCO3, K2CO3, KHCO3, (NH4)2CO3, and NH4HCO3. Preferably, the additive is one or more of Na2CO3 and NaHCO3. Preferably, the mass ratio of filter residue A to carbonate and / or bicarbonate in the additive is 3-6:1.

[0036] Furthermore, in S3, the reaction temperature is controlled at 80-110℃ and the reaction time is 45-80 min.

[0037] Further, in S4, the inorganic acid includes one or more of HCl, HNO3, and H2SO4. Preferably, the concentration of the inorganic acid in the dilute inorganic acid solution is 3-21 wt%. Preferably, the filter residue E is mixed with the pickling agent and stirred at 50-100°C. When the pH of the reaction system is 4.0-6.5, the solid and liquid are separated to obtain the fluorite product and the pickling solution H.

[0038] Optionally, the pickling agent is prepared from one or more of the following: 3-5 wt% HCl solution, 5-8 wt% HNO3 solution, and 5-8 wt% H2SO4 solution.

[0039] Furthermore, in S5, the amount of seed crystals added is 5-15 wt% of the filtrate F.

[0040] Further, in step S5, seed crystals are added to the filtrate F, and the mixture is stirred and reacted at 5-25°C for 12-24 hours. After standing and aging for 60-150 minutes, solid-liquid separation is performed to obtain aluminum hydroxide product and solution G.

[0041] Optionally, the lithium-containing waste aluminum electrolyte is derived from one or more of the following: furnace electrolyte generated during aluminum electrolysis production, electrolyte adhering to the covering material, and flotation material obtained by flotation separation of carbon slag.

[0042] Optionally, in the lithium-containing waste aluminum electrolyte, lithium exists in one or more of the following forms: Na2LiAlF6, NaLi2AlF6, and LiF.

[0043] Furthermore, the lithium-containing waste aluminum electrolyte comprises 25-80wt% Na3AlF6, 8-70wt% Na2LiAlF6, 5-25wt% Na2KAlF6, 1-4wt% Al2O3, 1-5wt% CaF2, 0.5-1.5wt% MgF2, and 1-10wt% LiF.

[0044] Alternatively, during the construction of the dissolution solution, calcium-containing substances can be added to increase the calcium content of the resulting dissolution solution. 2+ The concentration reaches 70-140 g / L; wherein, the calcium-containing substance includes one or more of calcium chloride, calcium nitrate, calcium sulfate, and calcium hydroxide.

[0045] In this invention, lithium-containing waste aluminum electrolyte powder is mixed with a leaching solution and stirred to dissolve it. This process converts lithium in the waste aluminum electrolyte into easily soluble lithium salts (such as LiOH, Li₂SO₄, LiNO₃, LiCl, etc.), while fluorine in the waste aluminum electrolyte enters the slag phase as insoluble CaF₂. Aluminum in the waste aluminum electrolyte enters the slag phase as aluminum-calcium insoluble substances (such as 2CaO·Al₂O₃·4H₂O, 3CaO·Al₂O₃·6H₂O, CaO·2Al₂O₃·5H₂O, etc.), and sodium in the waste aluminum electrolyte combines with acid radicals and enters the liquid phase as soluble sodium salts. This achieves the separation of lithium from aluminum, calcium, fluorine, sodium, and other elements in the electrolyte. Subsequently, through solid-liquid separation, a lithium-rich product can be obtained. + Na + The filtrate B and filter residue A, rich in aluminum-calcium insolubles and CaF2, are used for lithium precipitation to prepare lithium salt products. After further reaction and dissolution with additives, the calcium in the aluminum-calcium insolubles is converted into calcium carbonate and enters filter residue E, while the aluminum in the aluminum-calcium insolubles is converted into Al(OH)4. - The CaF2 in filter residue A is retained in filter residue E, while filtrate F enters filtrate F. Afterward, filtrate F can be directly returned to S2 to construct the leachate, or, after the aluminum content has accumulated to a certain level, seed crystals can be added to decompose and dealuminize, obtaining aluminum hydroxide and products containing Al(OH)4. - OH - The filtrate G is then returned to S2 to construct the dissolution solution, thus realizing Al(OH)4. - OH - The plasma is recycled; after the filter residue E is acid-washed with a dilute inorganic acid solution, calcium carbonate is converted into soluble calcium salts and enters the acid washing solution H. Since the pH endpoint of the acid washing is controlled at 4-6.5, CaF2 is still retained in the residue phase. Therefore, solid-liquid separation after acid washing yields fluorite products, which are rich in Ca. 2+ After the pickling solution H is combined with the filtrate F or solution G (H in pickling solution H) + The amount is very limited, so there is no need to worry about the H in the pickling solution H. + Excessive consumption of Al(OH)4 in filtrate F or solution G - and / or OH - S2 is returned to construct the dissolution solution for recycling.

[0046] The present invention has a short process flow, can realize the full utilization of lithium-containing waste aluminum electrolyte, is green and efficient, has a closed-loop treatment, does not generate secondary pollution, has low treatment cost, and has extremely high economic value.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0048] (1) The resource-based treatment method of the present invention achieves solid fluoride removal and aluminum removal simultaneously during the leaching process. The resulting lithium-containing leachate does not need to be purified again and can be concentrated and then lithium precipitated. The process is short, the equipment is simple, and the industrialization feasibility is high.

[0049] (2) In the entire process of this invention, the OH in the leachate - Al(OH)4 - It can be completely recycled without the need for external addition, has low consumption of leachate, low processing cost, excellent economic benefits, and is feasible for large-scale promotion and application.

[0050] (3) Compared with the alkaline treatment technology such as CN 112919507 A, the present invention can effectively reduce the amount of acid and alkali used and reduce the treatment cost.

[0051] (4) The entire process of the present invention realizes the comprehensive recycling of lithium-containing waste aluminum electrolyte. It not only extracts high-value lithium, but also recovers valuable components Al and F in the electrolyte with high added value, effectively improving the comprehensive treatment efficiency of waste aluminum electrolyte, without generating secondary pollution, and the purity of calcium fluoride and aluminum hydroxide products meets the current national standards. Attached Figure Description

[0052] Figure 1 This is a flowchart of a method for the comprehensive utilization of lithium-containing aluminum electrolytes according to the present invention.

[0053] Figure 2 This is the XRD pattern of the lithium-containing waste aluminum electrolyte used in Example 1.

[0054] Figure 3 This is the XRD pattern of filter residue A obtained in Example 1.

[0055] Figure 4 This is the XRD pattern of the lithium carbonate product obtained in Example 1.

[0056] Figure 5 This is the XRD pattern of the fluorite product obtained in Example 6. Detailed Implementation

[0057] The present invention will be described in detail below with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other. Unless otherwise specified, the relevant percentages refer to mass percentages.

[0058] Example 1

[0059] In this embodiment, the method for resource utilization of lithium-containing waste aluminum electrolyte includes the following steps:

[0060] S1. Take 100g of lithium-containing waste aluminum electrolyte from an aluminum plant (Na3AlF6 40.3%, Na2LiAlF6 34.5%, Na2KAlF6 16.3%, Al2O3 5.1%, CaF2 2.9%, MgF2 0.5%). See the phase analysis spectrum for details. Figure 2 The aluminum electrolyte powder was crushed to obtain 100g of aluminum electrolyte powder with a particle size ≤0.1mm.

[0061] S2. Mix 100g of aluminum electrolyte powder with 1000mL of dissolution solution (liquid-solid ratio of 10ml / g), place in a reaction vessel, stir at 90℃ and 300rpm for 0.5h to dissolve, then separate the solid and liquid to obtain filter residue A and filtrate B.

[0062] The dissolution solution contains Ca. 2+ OH - Na + Al(OH)4 - An aqueous solution of an acid radical ion, wherein the acid radical ion is Cl. - Alkali content in the leachate (as Na2O) 苛 The content of calcium (calculated as Al2O3) is 30 g / L, the content of aluminum (calculated as Al2O3) is 10 g / L, and the content of calcium (calculated as free calcium) is 90 g / L.

[0063] Figure 3 The XRD pattern of filter residue A after dissolution of electrolyte powder in S2 shows that the diffraction peaks corresponding to cryolite phases in lithium-containing waste aluminum electrolyte, including Na3AlF6, Na2KAlF6, and Na2LiAlF6, have completely disappeared. The main products generated by the reaction are aluminum-calcium substances including 3CaO·Al2O3·6H2O and 2CaO·Al2O3·4H2O, as well as CaF2, Ca(OH)2, and soluble salts such as Li2SO4, Na2SO4, K2SO4, LiCl, NaCl, and KCl, which are present in filtrate B.

[0064] The obtained lithium carbonate product was analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES). Three parallel sets of samples were weighed, with 1.0 g of each sample. The samples were digested and diluted to volume with 1.40 mol / L hydrochloric acid before analysis. The average purity of the product reached 99.20%. The XRD pattern of the lithium carbonate product is shown below. Figure 4 The calculated lithium recovery rate was 83.7%.

[0065] Example 2

[0066] Example 1 was repeated, except that in S2, a first-stage dissolution was performed at 95°C for 1 hour with stirring at 400 rpm, followed by a second-stage dissolution at 80°C for 1.5 hours with stirring at 200 rpm. The alkali content of the dissolution solution (as Na₂O) was... 苛 The content of calcium (calculated as Al2O3) is 60 g / L, the content of aluminum (calculated as Al2O3) is 15 g / L, and the content of calcium (calculated as free calcium) is 105 g / L.

[0067] The purity of the obtained lithium carbonate product was 98.7%. The lithium recovery rate was 89.1%.

[0068] Example 3

[0069] Example 1 was repeated, except that in S2, a first-stage dissolution was performed at 120°C for 0.5 hours with stirring at 400 rpm, followed by a second-stage dissolution at 90°C for 2.0 hours with stirring at 200 rpm. The alkali content of the dissolution solution (as Na₂O) was... 苛 The content of calcium (calculated as Al2O3) is 95 g / L, the content of aluminum (calculated as Al2O3) is 5 g / L, and the content of calcium (calculated as free calcium) is 135 g / L.

[0070] The purity of the obtained lithium carbonate product was 99.1%. The lithium recovery rate was 93.6%.

[0071] Example 4

[0072] Repeat Example 3, except that it also includes the following steps:

[0073] The filter residue A obtained in step S2, 295.3g, was subjected to a three-stage countercurrent washing process with a washing water volume of 885.9mL, a washing water temperature of 60℃, and a single-stage countercurrent washing time of 30 minutes. After washing, the residue C and washing liquid D were obtained.

[0074] The obtained washing residue C, 265.77 g, was mixed with the additive, and 280 mL of deionized water was added. The mixture was stirred at 300 rpm and reacted at 100 °C for 1.0 h. After filtration, filter residue E and filtrate F were obtained. The additive consisted of sodium carbonate and sodium bicarbonate, with a mass ratio of sodium carbonate to sodium bicarbonate of 3:1. The mass ratio of washing residue C to the total mass of carbonate and bicarbonate ions in the additive was 6:1.

[0075] 351.8g of filter residue E was mixed with 1055.4g of 3wt% HCl solution and stirred at 100rpm at 75°C. When the pH of the solution reached 5.4, the mixture was filtered to obtain pickling solution H and 175.9g of fluorite product.

[0076] The filtrate F and washing solution D are combined and returned to S2 to construct the dissolution solution. When the calcium concentration in the dissolution solution obtained by combining filtrate F and washing solution D is less than 135 g / L, calcium chloride is added to the resulting dissolution solution to make the calcium concentration (calculated as free calcium) in the dissolution solution reach 135 g / L.

[0077] Fluorite products were analyzed using fluorescence spectroscopy. Three sets of samples were weighed in parallel, with 3.0 g of each sample. The average purity of the fluorite products was 65.70%.

[0078] The purity of the obtained lithium carbonate product was 85.3%. The overall lithium recovery rate was 79.1%.

[0079] Example 5

[0080] Example 4 was repeated, except that the ratio of the mass of the washed residue C to the total mass of carbonate and bicarbonate in the additive was 4.1:1.

[0081] Fluorite products were analyzed using fluorescence spectroscopy. Three sets of samples were weighed in parallel, with 3.0 g of each sample. The average purity of the fluorite products was 79.70%.

[0082] The purity of the obtained lithium carbonate product was 90.6%. The overall lithium recovery rate was 86.1%.

[0083] Example 6

[0084] Example 4 was repeated, except that the ratio of the mass of the washed residue C to the total mass of carbonate and bicarbonate in the additive was 3.0:1.

[0085] Fluorite products were analyzed using fluorescence spectroscopy. Three parallel sets of samples were weighed, with 3.0 g from each set. The average purity of the fluorite products reached 93.30%, meeting the requirements of fluorite concentrate FC-93 in YB / T 5217-2005. The XRD pattern of fluorite is shown below. Figure 5 .

[0086] The purity of the obtained lithium carbonate product was 98.9%. The overall lithium recovery rate was 93.1%.

[0087] Comparative Example 1

[0088] Example 4 was repeated, except that the ratio of the mass of the washed residue C to the total mass of carbonate and bicarbonate in the additive was 7:1.

[0089] Fluorite products were analyzed using fluorescence spectroscopy. Three sets of samples were weighed in parallel, with 3.0 g of each sample. The average purity of the fluorite products was 45.80%.

[0090] The purity of the obtained lithium carbonate product was 65.3%. The overall lithium recovery rate was 54.1%.

[0091] Comparative Example 2

[0092] Example 4 was repeated, except that the ratio of the mass of the washed residue C to the total mass of carbonate and bicarbonate in the additive was 2.5:1.

[0093] Fluorite products were analyzed using fluorescence spectroscopy. Three sets of samples were weighed in parallel, with 3.0 g of each sample. The average purity of the fluorite products was 63.10%.

[0094] The purity of the obtained lithium carbonate product was 97.5%. The overall lithium recovery rate was 90.3%.

[0095] The comparison shows that the ratio of the mass of the washed residue C to the total mass of carbonate and bicarbonate in the additive needs to be controlled within a certain range. If the ratio is too high, the calcium ion content in the leaching solution may be too low, which will lead to a decrease in the purity of the lithium carbonate product and a decrease in the lithium recovery rate. If the ratio is too low, there may be too much residual sodium carbonate or sodium bicarbonate in the filter residue E, which will affect the subsequent acid washing process and reduce the purity of the fluorite product.

[0096] Example 7

[0097] Example 6 was repeated, except that after filtrate F was recycled 5 times, the Al2O content in filtrate F reached 130 g / L.

[0098] It also includes the following steps:

[0099] 200g of filtrate F was placed in a cold water bath, and 10g of aluminum hydroxide seed crystals were added. The mixture was stirred at 500rpm and kept at 5℃ for 12h. After the reaction was completed, the mixture was allowed to stand for 100min and then filtered to obtain filter cake and solution G.

[0100] After drying, the filter cake yielded 40.3g of aluminum hydroxide product.

[0101] The filtrate G, pickling solution H, and washing solution D are combined and returned to S2 to construct the dissolution solution for recycling. When the calcium concentration in the dissolution solution obtained by combining filtrate G, pickling solution H, and washing solution D is less than 135 g / L, calcium chloride is added to the dissolution solution to make the calcium content concentration (calculated as free calcium) in the dissolution solution reach 135 g / L.

[0102] The purity of the obtained lithium carbonate product was 98.50%. The lithium recovery rate was 94.1%.

[0103] The Al2O3 content before and after dealuminization was detected by inductively coupled plasma atomic emission spectrometry. The aluminum content (calculated as Al2O3) in the filtrate F before dealuminization was 144 g / L, and the aluminum content (calculated as Al2O3) in the solution G after dealuminization decreased to 15 g / L.

[0104] The aluminum hydroxide product was analyzed by fluorescence spectroscopy. Three sets of samples were weighed in parallel, with 3.0 g of each sample. The average purity of the aluminum hydroxide product was 98.30%, which meets the requirements for the main component content of grade AH-2 in GB / T 4294-2010.

[0105] As can be seen from the results of the above embodiments, the method provided by the present invention can recover valuable lithium, aluminum, and fluorine from lithium-containing waste aluminum electrolytes in the forms of lithium carbonate, aluminum hydroxide, and calcium fluoride, respectively, achieving high-value-added full-scale utilization of aluminum electrolytes. The content illustrated in the above embodiments should be understood as merely for illustrating the present invention more clearly, and not for limiting the scope of the present invention. After reading this invention, any modifications of the present invention in various equivalent forms by those skilled in the art fall within the scope defined by the appended claims.

Claims

1. A method of resource utilisation of lithium-containing spent aluminium electrolyte, characterised by, The method comprises the following steps: S1, crushing the lithium-containing waste aluminum electrolyte to be treated to obtain aluminum electrolyte powder; S2, mixing the aluminum electrolyte powder with a leaching solution, stirring and leaching, then solid-liquid separation to obtain filter residue A and filter liquor B; The leaching solution is an aqueous solution containing Ca 2+ , OH - , Al(OH)4 - , alkali metal ions, and acid radical ions, wherein the acid radical ions are one or more of Cl - , SO4 2- , and NO3 - ; the alkali metal ions are Na + and / or K + ; the concentration of Ca 2+ in the leaching solution is 70-140g / L; the temperature is controlled at 65-120℃ during stirring and leaching, and the stirring and leaching time is 30-180min. S3, mixing the filter residue A with water and additives, reacting at 75-120℃ for 60-90min, then solid-liquid separation to obtain filter residue E and filter liquor F; The filter liquor B is used for lithium precipitation to obtain lithium salt; The additive is water-soluble carbonate and / or water-soluble bicarbonate; the mass ratio of filter residue A to the total mass of carbonate and bicarbonate in the additive is 3-4.1:1; S4, mixing the filter residue E with pickling agent, stirring and reacting, then solid-liquid separation when the pH value of the reaction system is 4.0-6.5 to obtain fluorite product and pickling liquor H; The pickling agent is a dilute solution of inorganic acid containing one or more of Cl - , SO4 2- , NO3 - - S5, when the Al2O3 content in the filter liquor F is <100g / L, the pickling liquor H and the filter liquor F are combined and returned to step S2 to construct the leaching solution; When the Al2O3 content in the filter liquor F is ≥100g / L, first, seed crystals are added to the filter liquor F, then stirring and reacting at a temperature ≤25℃, followed by standing and aging, then solid-liquid separation to obtain aluminum hydroxide product and solution G; then the pickling liquor H and the solution G are combined and returned to step S2 to construct the leaching solution; The seed crystals comprise one or more of α-Al2O3, γ-Al2O3 and Al(OH)3.

2. The method of claim 1, wherein, In S1, the particle size of the aluminum electrolyte powder is ≤0.8mm.

3. The method of claim 2, wherein, In S1, the particle size of the aluminum electrolyte powder is ≤0.1mm.

4. The method of claim 1, wherein, In S2, the liquid-solid ratio of the leaching solution to the aluminum electrolyte powder is 5-25mL:1g; The content of alkali in the leaching solution is 30-100g / L in terms of Na2O; the content of aluminum is 5-95g / L in terms of Al2O3.

5. The method of claim 1, wherein, In S2, the stirring rate is 200-600r / min.

6. The method of resource utilization of claim 1, wherein, Between S2 and S3, there is a step of washing the filter residue A with water, i.e. washing the filter residue A with water, then solid-liquid separation to obtain washed residue C and washing liquor D; In S3, the washed residue C is mixed with water and additives, then solid-liquid separation after reaction to obtain filter residue E and filter liquor F.

7. The method of resource utilization of claim 6, wherein, The washing liquor D is returned to step S2 to construct the leaching solution.

8. The method of resource utilization of claim 1, wherein, In S3, the additive is one or more of Na2CO3, NaHCO3, K2CO3, KHCO3, (NH4)2CO3 and NH4HCO3.

9. The method of resource utilization of claim 1, wherein, In S3, the reaction temperature is controlled at 80-110℃, and the reaction time is 65-80min.

10. The method of resource utilization of claim 1, wherein, In S4, the inorganic acid comprises one or more of HCl, HNO3 and H2SO4.

11. The method of resource utilization of claim 10, wherein, In S4, the concentration of the inorganic acid in the dilute inorganic acid solution is 3-21wt%.

12. The method of claim 10, wherein, In S4, the filter residue E is mixed with pickling agent, then stirring and reacting at 50-100℃, then solid-liquid separation when the pH value of the reaction system is 4.0-6.5 to obtain fluorite product and pickling liquor H.

13. The method of resourceful utilization of claim 1, wherein, In S5, the addition amount of the seed crystals is 5-15wt% of the filter liquor F.

14. The method of claim 13, wherein, In S5, seed crystal is added to the filtrate F, and after stirring at 5-25°C for 12-24h, the mixture is aged for 60-150min, and then solid-liquid separation is performed to obtain the aluminum hydroxide product and solution G.

15. The method of resourceful utilization of claim 1, wherein, In the construction of the dissolution liquid, the concentration of the obtained dissolution liquid Ca 2+ reaches 70-140g / L by supplementing calcium-containing substances; wherein the calcium-containing substances include one or more of calcium chloride, calcium nitrate, calcium sulfate, calcium hydroxide.

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