Method for combined treatment of aluminum dross and spent aluminum electrolyte

Abstract

The application discloses a combined treatment method of aluminum ash and waste aluminum electrolyte, and belongs to the field of metallurgical solid waste resource treatment. 2+ The combined treatment method comprises the following steps: mixing aluminum ash with an inorganic acid solution, performing solid-liquid separation after reaction, and obtaining filtrate a; mixing waste aluminum electrolyte with a solution containing Fe After the combined treatment method, the aluminum ash and the waste aluminum electrolyte generated in the aluminum industry process can be jointly recovered and treated, the cost of raw materials and reaction reagents is low, the obtained aluminum fluoride product meets the national standard requirements, and the process has remarkable industrialization value, and has important practical significance for promoting the green and sustainable development of the aluminum electrolysis industry.

Description

Technical Field

[0001] This invention relates to a method for the combined treatment of aluminum ash and waste aluminum electrolyte, belonging to the field of metallurgical solid waste resource utilization. Background Technology

[0002] The aluminum electrolysis production process continuously generates fluorine-containing solid hazardous waste such as aluminum ash and waste aluminum electrolyte. Producing one ton of aluminum yields 20-30 kg of aluminum ash and 10-30 kg of waste aluminum electrolyte. Based on a primary aluminum production capacity of 45 million tons, this translates to 900,000-1.35 million tons of aluminum ash and 450,000-1.35 million tons of waste aluminum electrolyte. Aluminum ash, containing aluminum nitride and soluble fluorine, is already classified as hazardous waste. Waste aluminum electrolyte also contains a large amount of soluble fluorides, which can easily seep into the ground with rainwater during storage, polluting soil and groundwater resources. Aluminum ash and waste aluminum electrolyte contain significant amounts of aluminum, fluorine, lithium, and sodium resources. Their resource utilization can not only alleviate the environmental pressure on aluminum companies but also bring significant benefits.

[0003] Chinese patent applications CN111485252A, CN113149052A, CN115465876A, CN114804171A, and CN114314625A disclose methods for the resource-based recycling of waste aluminum electrolytes to prepare aluminum fluoride. The core reaction in all of these methods involves roasting waste aluminum electrolytes and aluminum salts to convert them into aluminum fluoride. These methods are all continuations of the process for preparing aluminum fluoride by roasting fluorine-containing materials with aluminum sulfate, as proposed in Russian patent RU2462418C1. The roasting additives (aluminum sulfate, aluminum nitrate, aluminum chloride, and their hydrates) used in the above patents are all chemical raw materials, which are costly and limit the industrial application value of this process. Because waste aluminum electrolytes contain multiple phases such as Na3AlF6, CaF2, Na2LiAlF6, and K2NaAlF6, resulting in complex composition, and because the solid-solid roasting reaction has high requirements for material particle size and mixing uniformity, the roasting reaction efficiency is low. The sodium content in the aluminum fluoride product obtained after water leaching of the roasted clinker is relatively high, usually 0.8-3%, which is far higher than the sodium content standard for industrial AF-1 grade aluminum fluoride (Na≤0.4%) specified in the national standard GB / T 4292-2017. At the same time, since CaF2 and the aluminum sulfate roasting product CaSO4 are slightly soluble in water, they are difficult to remove during the water leaching process, resulting in a high sulfate content in the aluminum fluoride product (usually 2-6%), which is far higher than the ≤0.6% required by the national standard GB / T 4292-2017. The presence of calcium sulfate also reduces the purity of the aluminum fluoride product. Although using aluminum chloride and aluminum nitrate as calcination additives can avoid the formation of calcium sulfate, aluminum nitrate completely decomposes into aluminum oxide and toxic nitrogen oxides at 190℃. Aluminum oxide will enter the product and affect the purity of aluminum fluoride. Aluminum chloride sublimates in bimolecular form at 181℃ and easily absorbs moisture from the air and hydrolyzes into hydrogen chloride. Solid-solid reactions require high temperatures to promote diffusion and mass transfer. If a large amount of aluminum salt additives are required to ensure a relatively complete reaction during high-temperature calcination, it is necessary to consume a large amount of aluminum salt additives.

[0004] Chinese invention patent applications CN114890447A and CN114853042A propose a waste electrolyte to aluminum fluoride conversion process based on the above-mentioned technology, using low-temperature roasting (50-135℃) or even no roasting. However, the slow solid-solid reaction rate and low conversion efficiency at low temperatures result in low purity of the aluminum fluoride product. Therefore, from the perspectives of environmental protection, cost, and product purity, the application value of aluminum chloride and aluminum nitrate as roasting additives is limited. Furthermore, when aluminum sulfate is used as a roasting agent, the impact of calcium sulfate on product purity must be addressed.

[0005] Chinese invention patent application CN119736671A discloses a method for treating calcium-containing waste aluminum electrolyte and a method for preparing aluminum fluoride. The method mainly includes first reacting the waste aluminum electrolyte with potassium nitrate and soluble aluminum salts to form soluble calcium salts, filtering to remove most of the calcium in one step; then reacting with a calcium complexing agent to remove calcium a second time, thus removing calcium from the calcium-containing waste aluminum electrolyte in a two-step process to obtain a low-calcium electrolyte; finally, calcining the low-calcium aluminum electrolyte with aluminum sulfate to obtain a low-calcium sulfate aluminum fluoride product. This process provides an effective approach to calcium removal, but when the waste aluminum electrolyte reacts with potassium nitrate and soluble aluminum salts, it reacts with the main components of the aluminum electrolyte, such as Na3AlF6, while removing CaF2, resulting in a large amount of electrolyte dissolving into the solution and wasting raw materials. Furthermore, CaF2 is extremely difficult to dissolve in water, and using complexing agents such as disodium ethylenediaminetetraacetate to remove CaF2 by complexing Ca ions has limited effectiveness, requiring a large amount of complexing agent, leading to high costs for complexing agent usage and subsequent treatment.

[0006] In summary, the existing process for preparing aluminum fluoride by roasting waste aluminum electrolyte has problems such as high production cost, low product quality, and difficulty in industrialization. Therefore, it is of great importance to develop a new process for converting waste aluminum electrolyte into aluminum fluoride with low production cost and high product quality. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this invention is to provide a combined treatment method for aluminum ash and waste aluminum electrolyte that has low processing cost and high product quality.

[0008] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0009] A method for the combined treatment of aluminum ash and waste aluminum electrolyte includes the following steps:

[0010] S1. Mix aluminum ash with an inorganic acid solution. After the reaction, separate the solid and liquid to obtain filtrate a and filter cake b.

[0011] Waste aluminum electrolyte and Fe 2+After the solutions were mixed, hydrogen peroxide was added dropwise under stirring. After the reaction, the solid and liquid were separated, washed, and filter cake c was obtained.

[0012] S2. After the filtrate a and filter cake c are mixed evenly, they are calcined to obtain calcined cooked material.

[0013] S3. The roasted clinker is mixed with a chloride salt solution, leached, and then the solid and liquid are separated to obtain filtrate d and filter cake e.

[0014] The chloride salt solution contains Cl - During leaching, the pH value of the reaction system should be controlled to be <3.

[0015] S4. After drying the filter cake e, aluminum fluoride product is obtained.

[0016] Furthermore, in S1, aluminum ash is mixed with inorganic acid and then subjected to a calcination reaction or a leaching reaction, followed by solid-liquid separation.

[0017] The calcination temperature for the calcination reaction is 100-400℃, or more specifically 120-380℃, and the calcination time is 1-5h, or more specifically 2-4h. The leaching temperature for the leaching reaction is 20-100℃, or more specifically 40-80℃, and the leaching time is 0.5-5h, or more specifically 1-4h. During leaching, the initial liquid-to-solid ratio of the reaction system is controlled to be 2-20mL / g, or more specifically 4-18mL / g.

[0018] Further, in S1, the mass ratio of the solute (i.e., inorganic acid) to the aluminum ash in the inorganic acid solution is 0.5-4:1, preferably 0.8-1.5:1;

[0019] And / or, the inorganic acid solution is one or more of hydrochloric acid, sulfuric acid, and nitric acid. Preferably, the concentration of the inorganic acid solution is 20-100 wt%, more preferably 25-98 wt%, and even more preferably 30-90 wt%.

[0020] Optionally, in S1, the washing method is water washing.

[0021] Further, in S1, the aluminum ash includes at least one of electrolytic aluminum ash, cast aluminum ash, and alloy aluminum ash; the waste aluminum electrolyte includes at least one of aluminum electrolyte retrieved from aluminum electrolytic cells, aluminum electrolyte obtained from carbon slag flotation, and wet regeneration of cryolite from overhaul slag.

[0022] Preferably, the particle size of the aluminum ash and / or waste aluminum electrolyte is <0.5 mm, more preferably <0.15 mm. Optionally, before S1, the aluminum ash and waste aluminum electrolyte are crushed and ground separately to obtain the corresponding target particle size.

[0023] Optionally, the waste aluminum electrolyte contains 8-18% Al, 40-60% F, 15-35% Na, 0.2-2% Li, 1-3% K, and 1.5-4.5% Ca.

[0024] Optionally, the aluminum ash contains 20-40% Al, 20-40% F, 10-30% O, 5-20% Na, 1-2.5% K, and 0.1-1.5% Li.

[0025] Furthermore, in S1, the waste aluminum electrolyte is mixed with Fe... 2+ After mixing the solutions, the pH of the reaction system is adjusted to 0.5-4 (preferably 1-3, more preferably 1-1.5). Hydrogen peroxide is added dropwise under stirring. After the reaction, the solid and liquid are separated, washed, and filter cake c is obtained.

[0026] And / or, containing Fe 2+ Fe in solution 2+ The concentration is 0.01-0.5 mol / L, preferably 0.05-0.4 mol / L, and the waste aluminum electrolyte contains Fe. 2+ The mass-to-volume ratio of the solution is 1g:2.5-5mL, preferably 1g:3-4mL;

[0027] Preferably, sulfuric acid is used to adjust the pH of the reaction system to 1-4.

[0028] Furthermore, in S1, the waste aluminum electrolyte is mixed with Fe... 2+ After mixing the solutions, hydrogen peroxide is added dropwise under stirring. Once the reaction system has completely turned reddish-brown and stabilized (i.e., the color remains stable), the solid and liquid are separated, washed, and filter cake c is obtained. Optionally, hydrogen peroxide is added slowly dropwise under stirring.

[0029] Optionally, the concentration of hydrogen peroxide is 5-25 wt%, or even 10-20 wt%.

[0030] Filter cake b is an oxide with alumina as its main component, which can be used to produce ceramics and can be sold externally.

[0031] Optionally, in S2, the roasting method is gradient roasting. Therefore, by dehydrating the material step by step through gradient roasting, problems such as material caking or incomplete reaction caused by excessively rapid heating can be effectively avoided, thus helping to improve the roasting effect.

[0032] Furthermore, in S2, during calcination, it is first calcined at 100-300℃ for 2-10 hours; then the temperature is raised to 500-700℃ and calcined for 1-5 hours.

[0033] Furthermore, in S2, during calcination, it is first calcined at 120-280℃ for 4-6 hours; then the temperature is raised to 550-650℃ and calcined for 2-4 hours.

[0034] And / or, during calcination, first raise the temperature to 100-300℃ at a rate of 0.1-1℃ / min and calcine for 2-10 hours; then raise the temperature to 500-700℃ at a rate of 0.5-5℃ / min and calcine for 1-5 hours.

[0035] Therefore, low-temperature roasting dehydration and high-temperature roasting activation reactions are carried out sequentially. Through complex roasting reactions, aluminum and fluorine elements in the system are reconstructed to obtain aluminum fluoride. Subsequently, the obtained roasted clinker is leached by dissolving it in a weakly acidic chloride solution to dissolve sulfates such as sodium sulfate and calcium sulfate, as well as impurities such as cone ice crystals produced in the reaction. The product is obtained by filtration. After the filtrate is adjusted for pH and impurities by adding alkali solution, it is evaporated and concentrated, and sodium carbonate is precipitated to obtain lithium carbonate product.

[0036] Furthermore, in S2, the initial molar ratio of F to Al in the mixed slurry obtained after mixing filtrate a and filter cake c is 1-3.5:1, preferably 2-3:1.

[0037] Furthermore, in S3, during leaching, a chloride salt solution is added to the reaction system to make the initial liquid-to-solid ratio of the reaction system 2-10 ml / g, preferably 4-8 ml / g; hydrochloric acid is added to maintain the pH value of the reaction system at 0.5-2.

[0038] And / or, the chloride salt in the chloride salt solution is a water-soluble chloride salt, preferably at least one of sodium chloride and potassium chloride;

[0039] And / or, the concentration of chloride salt in the chloride salt solution is 0.5-5 mol / L, more preferably 1-4.5 mol / L, and most preferably 1.5-4 mol / L.

[0040] Furthermore, in S3, the mixture is stirred and leached at 20-90°C for 10-60 minutes; even further, it is stirred and leached at 30-80°C for 20-50 minutes.

[0041] Further, after S3, the pH of filtrate d is adjusted to 6-10, followed by solid-liquid separation, evaporation and concentration, and lithium precipitation to obtain the lithium salt product. Optionally, an alkaline solution is used to adjust the pH of filtrate d. Optionally, sodium carbonate is added to precipitate lithium.

[0042] Optionally, the lithium salt product is lithium carbonate.

[0043] Optionally, the solute in the alkaline solution is at least one of sodium carbonate, sodium bicarbonate, and sodium hydroxide.

[0044] At least in some embodiments of the present invention, the present invention can recover F and Al elements from aluminum ash and waste aluminum electrolyte through joint treatment to prepare aluminum fluoride, while recovering valuable elements such as Li and Na, thereby realizing the resource utilization of fluorine-containing waste.

[0045] In step S1 of this invention, an inorganic acid is used to leach components such as aluminum oxide, metallic aluminum, aluminum nitride, and cryolite from aluminum ash into a solution. The possible chemical reaction equations are as follows:

[0046] Al2O3 + 6H + = 2Al 3+ + 3H2O;

[0047] AlN + 3H2O = Al(OH)3 + NH3;

[0048] Al(OH)3 + 3H + = Al 3+ + 3H2O;

[0049] 2Al + 6H2O = 2Al(OH)3 + 3H2;

[0050] Na3AlF6 + 6H + = Al 3+ + 6HF + 3Na + .

[0051] Additionally, in step S1, hydrogen peroxide and Fe are used. 2+ The strong oxidizing properties of the hydroxyl groups produced in the reaction first oxidize the amorphous carbon and other carbon materials in the waste aluminum electrolyte into carbon dioxide for removal, preparing for subsequent roasting. The possible chemical reaction equations are as follows:

[0052] Fe 2+ + H2O2 = Fe 3+ + ·OH + OH - ;

[0053] C + 2·OH = CO2 + H2O.

[0054] In step S2, the filtrate a obtained from leaching aluminum ash with inorganic acid is mixed evenly with filter cake c and then calcined. Gradient calcination is preferred, first calcining to dehydrate the aluminum, and then calcining to react and obtain aluminum fluoride. The possible chemical reaction equations during this process are as follows:

[0055] 2Na3AlF6 + Al2(SO4)3·18H2O = 4AlF3 + 3Na2SO4 + 18H2O↑;

[0056] 2Na3AlF6 + 3Al(SO4)F·5H2O = 5AlF3 + 3Na2SO4 + 5H2O↑;

[0057] Na3AlF6 + NaAl(SO4)2·12H2O = 2AlF3 + 2Na2SO4 + 12H2O↑;

[0058] 2Na3AlF6 + 2KAl(SO4)2·12H2O = 4AlF3 + K2SO4 + 3Na2SO4 + 24H2O↑;

[0059] 6Na3AlF6 + 6NH4Al(SO4)2·12H2O = 12AlF3 + 3SO2↑ + N2↑ + 4NH3↑ + 9Na2SO4 +78H2O↑.

[0060] In step S3, hydrochloric acid is used to maintain the pH of the solution, removing impurities such as cone-shaped cryolite and single cryolite produced in the reaction, thereby improving the purity of the aluminum fluoride product. The possible chemical reaction equations are as follows:

[0061] Na5Al3F 14 + 14H + = 3Al 3+ + 14HF + 5Na + ;

[0062] NaAlF4 + 4H + = Al 3+ + 4HF + Na + .

[0063] This invention uses inorganic acid to leach aluminum oxide, metallic aluminum, aluminum nitride, cryolite, and other components from aluminum ash into a solution, forming a solution containing F and Al elements. This solution is then mixed with pretreated waste aluminum electrolyte and subjected to high-temperature roasting to generate aluminum fluoride and sulfate. The roasted clinker is then leached through an acidic chloride solution to dissolve impurities such as sulfate, cryolite, and aluminum oxide produced in the reaction. Simultaneously, calcium sulfate is removed by utilizing the high solubility of calcium sulfate in chloride solutions, ultimately yielding a high-quality aluminum fluoride product. Subsequently, an alkaline substance can be added to the filtrate (d) to adjust the pH and remove impurities such as F and Al. The resulting solution is then concentrated by evaporation and lithium precipitation to obtain a lithium carbonate product.

[0064] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0065] (1) The combined treatment method of the present invention utilizes the F and Al elements in aluminum ash and waste aluminum electrolyte to recover aluminum fluoride, avoiding the disadvantages of using chemical raw materials such as aluminum sulfate in traditional processes, realizing the combined treatment of two major solid and hazardous wastes in the aluminum industry, significantly reducing production costs and increasing industrial value.

[0066] (2) The combined treatment method of the present invention uses an inorganic acid leaching aluminum ash to obtain an F and Al solution and pretreated waste aluminum electrolyte wet mixing to form a pulp. The components such as aluminum sulfate, aluminum fluorosulfate, sodium aluminum sulfate, and aluminum ammonium sulfate in the F and Al solution are mixed evenly with the waste aluminum electrolyte. Compared with the traditional aluminum salt and waste aluminum electrolyte solid-phase powder mixing system, the uniformity is significantly improved, the reaction efficiency is high, the reaction is more complete, and the aluminum fluoride conversion rate is higher.

[0067] (3) The combined treatment method of the present invention introduces hydrogen peroxide into the ferrous aluminum electrolyte slurry system to induce a Fenton reaction, generating a large number of highly oxidizing hydroxyl radicals. This oxidizes the amorphous carbon (or highly active carbon) and other carbon impurities mixed in the waste aluminum electrolyte, avoiding the oxidation-reduction reaction between carbon impurities and components such as aluminum sulfate, aluminum fluorosulfate, sodium aluminum sulfate, aluminum ammonium sulfate, and sodium sulfate during high-temperature roasting to generate sulfur dioxide and aluminum oxide. This improves the environmental friendliness and product purity of the process and ensures the yield of aluminum fluoride products, effectively solving the problems of environmental protection and low product purity faced when combining aluminum ash and waste aluminum electrolyte. In addition, the above-mentioned oxidation method for removing carbon impurities in the present invention does not introduce other impurities. Residual iron elements, hydrogen peroxide, etc., can be effectively removed by simple washing, without worrying about adverse effects on subsequent processes.

[0068] (4) The combined processing method of the present invention utilizes the high solubility of calcium sulfate in chloride salt solution to dissolve and remove calcium sulfate impurities in aluminum fluoride products. At the same time, the solution pH is controlled to be less than 3, which can more effectively dissolve and remove impurities such as cone ice crystals generated in the reaction, and can significantly improve the purity of aluminum fluoride products and increase the added value of products.

[0069] (5) The combined treatment method of the present invention realizes the combined recycling and treatment of two major solid and hazardous wastes, aluminum ash and waste aluminum electrolyte, generated in the aluminum industry. The raw materials and reaction reagents are inexpensive, and the obtained aluminum fluoride products meet the national standards. The process has significant industrialization value and is of great practical significance for promoting the green and sustainable development of the aluminum electrolysis industry. Attached Figure Description

[0070] Figure 1 This is the phase analysis diagram (XRD pattern) of the aluminum fluoride product obtained in Example 1.

[0071] Figure 2 This is the phase analysis diagram (XRD pattern) of the aluminum fluoride product obtained in Example 2. Detailed Implementation

[0072] 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.

[0073] Example 1

[0074] The combined treatment method for aluminum ash and waste aluminum electrolyte in this embodiment includes the following steps:

[0075] (1) Take 100.0g each of waste aluminum electrolyte (Al: 13.5%; F: 51.7%; Na: 25.3%; Li: 1.1%; K: 2.3%; Ca: 3.2%) and aluminum ash (Al: 28.5%; F: 30.3%; O: 22.6%; Na: 13.1%; K: 1.68%; Li: 0.7%) from an aluminum plant in Henan Province, and crush and grind them respectively to obtain waste electrolyte powder of -100 mesh and aluminum ash powder of -100 mesh;

[0076] (2) Aluminum ash leaching: 100.0g of aluminum ash powder obtained above is mixed with 120.0g of 98% concentrated sulfuric acid. Water is added to control the initial liquid-solid ratio to 5mL / g. The mixture is stirred and leached at 90℃ for 2h to obtain a reaction slurry. The slurry is filtered to obtain filtrate a and filter cake b.

[0077] Waste aluminum electrolyte pretreatment: 86.1g of the above-obtained waste aluminum electrolyte powder was placed in 300mL of 0.1mol / L ferrous sulfate solution, sulfuric acid was added to adjust the pH of the reaction system to 3, and then hydrogen peroxide (concentration 27.5%) was slowly added dropwise under stirring. After the reaction system completely turned reddish-brown and stabilized, it was filtered, washed with deionized water, and dried to obtain filter cake d.

[0078] (3) Mix all the filtrate a obtained in step (2) with all the filter cake d obtained, place them in a furnace, first raise the temperature to 250°C at a rate of 0.5°C / min, keep the temperature for 5 hours, then raise the temperature to 600°C at a rate of 3°C / min, keep the temperature for 2 hours, and obtain the roasted clinker.

[0079] (4) Grind the above-obtained calcined material into powder, place it in a stirring tank, add 2 mol / L sodium chloride solution to control the initial liquid-solid ratio of the reaction system to 4 ml / g, stir and leach at 20-90℃ for 40 minutes, add hydrochloric acid during the leaching process to control the pH value of the reaction system to 1-1.2, filter after the reaction is completed to obtain filtrate c and filter cake e, wash and dry filter cake e to obtain 105.4g of aluminum fluoride product;

[0080] (5) Add sodium carbonate solution to the above-obtained filtrate c to adjust the pH to 6, filter, evaporate and concentrate, add sodium carbonate to precipitate lithium, and obtain 6.5g of lithium carbonate product.

[0081] XRF analysis of the composition of aluminum fluoride products was performed according to standard YST 581.4-2024 (the same applies below). The results are shown in Table 1. The obtained aluminum fluoride products contain Na and SO4. 2- The contents were 0.23% and 0.08% respectively, which are very low, and all components meet the national standard AF-0 grade aluminum fluoride requirements; phase analysis of this aluminum fluoride product yielded the following results: Figure 1 As shown, aluminum fluoride diffraction peaks are significant, and there are no obvious impurity diffraction peaks.

[0082] Comparative Example 1

[0083] Repeat Example 1, except that in step (4), the sodium chloride solution used is replaced with deionized water and hydrochloric acid is not used to adjust the pH of the solution.

[0084] The compositional analysis of the obtained aluminum fluoride product is shown in Table 1. The content of Na and sulfate impurities is very high, which leads to low levels of F and Al elements. Therefore, the product composition does not meet the national standard AF-0 grade aluminum fluoride requirements. Phase analysis results are as follows: Figure 2 As shown, its phases contain obvious cone cryolite and calcium sulfate impurity phases.

[0085] Comparative Example 2

[0086] Repeat Example 1, except that in step (4), the sodium chloride solution used is replaced with deionized water.

[0087] Comparative Example 3

[0088] Repeat Example 1, except that hydrochloric acid is not used to adjust the pH of the solution in step (4).

[0089] Comparative Example 4

[0090] Repeat Example 1, except that the waste aluminum electrolyte pretreatment step in step (2) is omitted, and an equal amount of untreated waste aluminum electrolyte powder is used to replace filter cake d in step (3).

[0091] Comparative Example 5

[0092] Repeat Example 1, except that in step (3), the filtrate a obtained in step (2) is stirred and mixed evenly with the obtained filter cake d, placed in a furnace, heated to 600°C at 3°C / min, and kept warm for 2 hours to obtain roasted clinker.

[0093] The analysis results of the relevant element content in the aluminum fluoride products of each embodiment and comparative example are shown in Table 1.

[0094] Table 1. Results of elemental content analysis (wt.%) in aluminum fluoride products

[0095] Example 1 64.20 32.49 0.23 0.08 0.09 0.04 0.02 Comparative Example 1 60.47 30.76 1.80 4.56 0.12 0.11 0.03 Comparative Example 2 61.04 31.98 0.25 3.98 0.08 0.05 0.02 Comparative Example 3 63.53 32.25 1.98 0.09 0.11 0.10 0.03 Comparative Example 4 63.02 32.97 0.20 0.08 0.08 0.03 0.01 Comparative Example 5 59.73 31.48 5.85 0.08 0.09 0.04 0.02 GB / T 4292-2017 (AF-0) ≥61.0 ≥31.5 ≤0.30 ≤0.10 ≤0.10 ≤0.06 ≤0.03

[0096] The above embodiments should be understood as being used only to illustrate the present invention more clearly, and not to limit the scope of the present invention. After reading the present 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 for the combined treatment of aluminum ash and waste aluminum electrolyte, characterized in that, Includes the following steps: S1. Mix aluminum ash with an inorganic acid solution. After the reaction, separate the solid and liquid to obtain filtrate a and filter cake b. Waste aluminum electrolyte and Fe 2+ After the solutions were mixed, hydrogen peroxide was added dropwise under stirring. After the reaction, the solid and liquid were separated, washed, and filter cake c was obtained. S2. After the filtrate a and filter cake c are mixed evenly, they are calcined to obtain calcined cooked material. S3. The roasted clinker is mixed with a chloride salt solution, leached, and then the solid and liquid are separated to obtain filtrate d and filter cake e. The chloride salt solution contains Cl - During leaching, the pH value of the reaction system should be controlled to be <3. S4. After drying the filter cake e, aluminum fluoride product is obtained.

2. The combined processing method according to claim 1, characterized in that, In S1, aluminum ash is mixed with inorganic acid and then subjected to a calcination reaction or a leaching reaction, followed by solid-liquid separation. The roasting temperature for the roasting reaction is 100-400℃ and the roasting time is 1-5h; the leaching temperature for the leaching reaction is 20-100℃ and the leaching time is 0.5-5h. During leaching, the initial liquid-to-solid ratio of the reaction system is controlled to be 2-20mL / g.

3. The combined processing method according to claim 1, characterized in that, In S1, the mass ratio of the solute to the aluminum ash in the inorganic acid solution is 0.5-4:1; And / or, the inorganic acid solution is one or more of hydrochloric acid, sulfuric acid, and nitric acid.

4. The combined processing method according to claim 3, characterized in that, The mass ratio of the solute to the aluminum ash in the inorganic acid solution is 0.8-1.5:

1.

5. The combined processing method according to claim 3, characterized in that, The concentration of the inorganic acid solution is 20-100 wt%.

6. The combined processing method according to claim 5, characterized in that, The concentration of the inorganic acid solution is 25-98 wt%.

7. The combined processing method according to claim 1, characterized in that, In S1, the aluminum ash includes at least one of electrolytic aluminum ash, cast aluminum ash, and alloy aluminum ash; the waste aluminum electrolyte includes at least one of aluminum electrolyte retrieved from aluminum electrolytic cells, aluminum electrolyte obtained from carbon slag flotation, and wet regeneration of cryolite from overhaul slag.

8. The combined processing method according to claim 7, characterized in that, The particle size of the aluminum ash and / or waste aluminum electrolyte is <0.5 mm.

9. The combined processing method according to claim 8, characterized in that, The particle size of the aluminum ash and / or waste aluminum electrolyte is <0.15 mm.

10. The combined processing method according to claim 1, characterized in that, In S1, waste aluminum electrolyte is mixed with Fe... 2+ After mixing the solutions, the pH of the reaction system was adjusted to 0.5-4, and hydrogen peroxide was added dropwise under stirring. After the reaction, the solid and liquid were separated, washed, and filter cake c was obtained. And / or, containing Fe 2+ Fe in solution 2+ The concentration is 0.01-0.5 mol / L, and the waste aluminum electrolyte contains Fe. 2+ The mass-to-volume ratio of the solution is 1g:2.5-5mL.

11. The combined processing method according to claim 1, characterized in that, In S1, waste aluminum electrolyte is mixed with Fe... 2+ After the solutions are mixed, hydrogen peroxide is added dropwise under stirring. Once the reaction system has completely turned reddish-brown and stabilized, the solid and liquid are separated, washed, and filter cake c is obtained.

12. The combined processing method according to any one of claims 1-11, characterized in that, In S2, during calcination, it is first calcined at 100-300℃ for 2-10 hours; then the temperature is raised to 500-700℃ and calcined for 1-5 hours. And / or, during calcination, first raise the temperature to 100-300℃ at a rate of 0.1-1℃ / min and calcine for 2-10 hours; then raise the temperature to 500-700℃ at a rate of 0.5-5℃ / min and calcine for 1-5 hours.

13. The combined processing method according to any one of claims 1-11, characterized in that, In S2, the initial molar ratio of F to Al in the mixed slurry obtained after mixing filtrate a and filter cake c is 1-3.5:

1.

14. The combined processing method according to claim 13, characterized in that, The initial molar ratio of F to Al in the mixed slurry obtained after mixing filtrate a and filter cake c is 2-3:

1.

15. The combined processing method according to any one of claims 1-11, characterized in that, In S3, during leaching, a chloride salt solution is added to the reaction system to make the initial liquid-to-solid ratio of the reaction system 2-10 ml / g; hydrochloric acid is added to maintain the pH value of the reaction system at 0.5-2. And / or, the chloride salt in the chloride salt solution is a water-soluble chloride salt; And / or, the concentration of chloride salt in the chloride salt solution is 0.5-5 mol / L.

16. The combined processing method according to claim 15, characterized in that, The chloride salt is at least one of sodium chloride and potassium chloride.

17. The combined processing method according to any one of claims 1-11, characterized in that, After S3, the pH of the filtrate d is adjusted to 6-10, followed by solid-liquid separation, evaporation and concentration, and lithium precipitation to obtain the lithium salt product.

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