Recycling method of aluminum electrolyte

Abstract

The invention provides an aluminum electrolyte recycling method which comprises the following steps: (1) mixing an aluminum electrolyte and a leaching agent solution, and carrying out slurrying leaching to obtain slurry and hydrogen fluoride gas; the molar concentration of hydrogen ions in the leaching agent solution is 2.5-25 mol / L; (2) carrying out liquid-solid separation on the slurry obtained in the step (1) to obtain leaching liquid and leaching residues, and carrying out post-treatment on the leaching residues to obtain basic aluminum fluoride; the immersion liquid is reused in the step (1). According to the method, the aluminum electrolyte can be completely dissolved in the strong acid solution under the conditions of high temperature and high pressure, so that the high-purity alkaline aluminum fluoride product is obtained, the recovery rate of aluminum and fluorine resources is high, the immersion liquid can be recycled, the technological process is simple, and the method has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical metallurgy and relates to a method for recycling aluminum electrolyte. Background Art

[0002] The main component of aluminum electrolyte is cryolite (Na3AlF6), which is a mixture of sodium fluoride, aluminum fluoride, potassium fluoride, lithium fluoride, magnesium fluoride, and calcium fluoride, with a fluorine content of about 40% to 50%. According to the fluorine content of cryolite, the fluorine ion concentration of its saturated aqueous solution exceeds 100 mg / L, which is higher than the leaching toxicity standard for hazardous waste identification (fluoride ion content 100 mg / L). Although aluminum electrolyte solid waste has not yet been included in the national hazardous waste list, it is likely that the fluorine ion concentration in its leaching toxicity index exceeds the standard.

[0003] Some electrolytic aluminum production enterprises use open-air storage or direct landfill to treat aluminum electrolyte solid waste, which not only occupies a large amount of space, but also the soluble fluoride contained in the solid waste will flow into rivers, surface water or seep into the ground with rainwater to pollute the soil and groundwater, causing great harm to the surrounding ecological environment, human health and plant and animal growth. According to the aluminum production capacity of 40 million tons / year, the annual waste aluminum electrolyte is 720,000-1.2 million tons. At present, there is no better treatment method to deal with these waste aluminum electrolytes. Many enterprises store them in large quantities in the factory area, which not only pollutes the environment, but also causes waste of fluorine.

[0004] At present, aluminum electrolyte is usually used to prepare aluminum fluoride salts and other methods for recovery. CN114314625A discloses a method for recovering fluoride salts from aluminum electrolytes, wherein the aluminum electrolyte is successively prepared by aluminum sulfate roasting, pickling, lithium removal and other processes to obtain aluminum fluoride, sodium fluoride or cryolite, and the alkaline leaching solution is reacted with acid to obtain aluminum hydroxide. CN108754543A discloses a method for separating carbon slag from aluminum electrolytes, wherein the method uses an acidic solution to leach the aluminum electrolyte in the carbon block, and separates the solid and liquid from the carbon block, reacts the leachate with an aluminum salt solution, and separates the fluoride ions in the solution by sedimentation. The remaining acidic solution after separation is returned to the acidic solution leaching process for recycling, thereby obtaining a carbon slag product containing less than 3% fluoride salts, and at the same time obtaining products such as basic metal aluminum fluoride. However, the current method of using aluminum electrolytes to recover aluminum fluoride salts has problems such as high dosage of reagents, long process flow, and high cost.

[0005] In summary, it is urgent to develop a short-process, low-cost, recyclable and clean aluminum electrolyte recycling method to achieve efficient extraction and recovery of fluorine and aluminum. Summary of the invention

[0006] The object of the present invention is to provide a method for recycling aluminum electrolyte, which can completely dissolve the aluminum electrolyte in a strong acid solution under high temperature and high pressure conditions to obtain a high-purity basic aluminum fluoride product. The aluminum and fluorine resource recovery rate is high, the leaching liquid can be recycled, the process flow is simple, and the method has broad application prospects.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for recycling aluminum electrolyte, which comprises the following steps:

[0009] (1) mixing an aluminum electrolyte and a leaching agent solution, performing slurry leaching, and obtaining a slurry and hydrogen fluoride gas;

[0010] The molar concentration of hydrogen ions in the leaching agent solution is 2.5-25 mol / L, for example, it can be 2.5 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, 12 mol / L, 13 mol / L, 14 mol / L, 15 mol / L, 16 mol / L, 17 mol / L, 18 mol / L, 19 mol / L, 20 mol / L, 21 mol / L, 22 mol / L, 23 mol / L, 24 mol / L or 25 mol / L, etc., but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable;

[0011] (2) subjecting the slurry of step (1) to liquid-solid separation to obtain an leaching solution and a leaching residue, and subjecting the leaching residue to post-treatment to obtain basic aluminum fluoride;

[0012] The immersion liquid is reused in step (1).

[0013] The aluminum electrolyte recycling method provided by the present invention comprises the following steps: slurrying and leaching the aluminum electrolyte with a leaching agent solution, decomposing components such as cryolite, aluminum oxide, and calcium fluoride in the aluminum electrolyte under the action of a strong acid, and converting them into easily soluble sodium sulfate and calcium hydrogen sulfate leaching solutions and insoluble basic aluminum fluoride leaching residues; the basic aluminum fluoride leaching residues are post-treated to obtain a high-purity basic aluminum fluoride product, and the residual sulfuric acid concentration in the leaching solution is very high, so the leaching solution can be returned to step (1) for recycling; and hydrogen fluoride gas is generated due to the high acid concentration in the slurrying and leaching process, and the hydrogen fluoride gas can be used to prepare the calcium fluoride product.

[0014] It is worth noting that the impurity ions in the aluminum electrolyte can be completely dissolved in a strong acid solution under specific conditions, and impurity ions such as calcium can be taken away by the sodium sulfate by-product, so that a basic aluminum fluoride product with almost no impurities can be obtained, thereby realizing the recovery of aluminum and fluorine resources in the aluminum electrolyte. The extraction rate of aluminum and fluorine in the aluminum electrolyte is high, the purity of aluminum and fluorine products is high, and the leaching liquid can be recycled.

[0015] As a preferred technical solution of the present invention, the components of the aluminum electrolyte in step (1) include cryolite, aluminum oxide and calcium fluoride.

[0016] In the present invention, the mass content of F element in the aluminum electrolyte is ≥30%.

[0017] Preferably, before the aluminum electrolyte is slurried and leached in step (1), the process further includes: crushing and grinding the aluminum electrolyte in sequence to obtain aluminum electrolyte powder.

[0018] Preferably, the particle size of the aluminum electrolyte powder is ≤100 μm, for example, it can be 100 μm, 90 μm, 80 μm, 70 μm, 60 μm, 50 μm, 40 μm, 30 μm, 20 μm or 10 μm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] As a preferred technical solution of the present invention, the solid-liquid ratio of the aluminum electrolyte and the leaching agent solution in step (1) is 1: (1-8) t / m 3 , for example, it can be 1:1t / m 3 1:1.5t / m 3 1:1.75t / m 3 , 1:2t / m 3 , 1:2.5t / m 3 1:2.75t / m 3 , 1:3t / m 3 1:3.25t / m 3 、1:3.5t / m 3 1:3.85t / m 3 , 1:4t / m 3 1:4.12t / m 3 1:4.25t / m 3 、1:4.5t / m 3 、1:4.75t / m 3 , 1:5t / m 3 1:5.25t / m 3 1:5.75t / m 3 、1:5.86t / m 3 , 1:6t / m 3 1:6.35t / m3 1:6.85t / m 3 , 1:7t / m 3 1:7.25t / m 3 、1:7.55t / m 3 1:7.75t / m 3 1:7.95t / m 3 or 1:8t / m 3 etc., but are not limited to the listed values. Other values ​​not listed in the numerical range are also applicable. Preferably, it is 1: (4-6) t / m 3 .

[0020] Preferably, the molar concentration of hydrogen ions in the leaching agent solution in step (1) is 3 to 15 mol / L, for example, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, 12 mol / L, 13 mol / L, 14 mol / L or 15 mol / L, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0021] Preferably, the leaching agent solution in step (1) is sulfuric acid and aluminum sulfate.

[0022] Preferably, after the mixing in step (1), the molar ratio of aluminum element to fluorine element in the slurry is 1:(0.5-3), for example, it can be 1:0.5, 1:0.75, 1:1, 1:1.5, 1:1.75, 1:2, 1:2.25, 1:2.75 or 1:3, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 1:(1-2).

[0023] It is worth noting that by controlling the solid-liquid ratio of the aluminum electrolyte and the leaching agent solution, the molar ratio of the aluminum element to the fluorine element in the solution, the temperature and time of the slurry leaching and other parameter ranges, the aluminum electrolyte can be completely decomposed to generate basic aluminum fluoride and hydrogen fluoride gas, thereby promoting the recovery of fluorine and aluminum.

[0024] As a preferred technical solution of the present invention, the slurry leaching in step (1) is carried out in a closed pressure device.

[0025] In the present invention, the initial pressure of the sealed pressure device is normal pressure.

[0026] It is worth noting that the slurry leaching process of the present invention needs to be carried out in a closed pressure device. The hydrogen fluoride gas generated by the reaction gathers in the container, which increases the reaction pressure. The high pressure further promotes the decomposition of the aluminum electrolyte. At the same time, the closed pressure device avoids the leakage of hydrogen fluoride gas. After the reaction is completed, the hydrogen fluoride gas can be released and recovered in a controllable manner, which also improves the efficiency, effect and environmental protection performance of the reaction process.

[0027] Preferably, the temperature of the slurry leaching in step (1) is 100-200°C, for example, it can be 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 195°C or 200°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 130-190°C, more preferably 150-180°C.

[0028] It is worth noting that when the aluminum electrolyte and the leaching agent solution are slurried for leaching under high temperature conditions, combined with the increase in reaction pressure and the control of the molar concentration of hydrogen ions in the system to be 2.5-25 mol / L, under high temperature, high pressure and strong acid conditions, the activity of hydrogen ions, sulfate ions and bisulfate ions in the solution becomes higher, and the decomposition effect of cryolite, alumina, calcium fluoride and other components in the aluminum electrolyte is good, so that the aluminum electrolyte is completely decomposed, and thus the fluorine and aluminum leaching rates are high.

[0029] It is worth mentioning that the inventors have found that in a strong acid, high temperature and high pressure leaching system, a part of the fluoride ions are complexed with aluminum ions. Unexpectedly, the complex can combine with hydroxide ions under strong acid, high temperature and high pressure conditions to form basic aluminum fluoride precipitation, and another part of the fluoride ions are combined with hydrogen ions to form hydrogen fluoride gas, forming a dynamic equilibrium between the liquid phase and the gas phase in a closed pressure device. Subsequently, due to the complete decomposition of the aluminum electrolyte, the sodium sulfate and a small amount of impurity calcium in the leaching solution are regularly recovered, resulting in less residual solids in the leaching residue and a simple solution composition, so the basic aluminum fluoride product has high purity.

[0030] Preferably, the slurry leaching time in step (1) is 0.5 to 5 h, for example, it can be 0.5 h, 0.75 h, 1 h, 1.5 h, 1.75 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h or 5 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] As a preferred technical solution of the present invention, the hydrogen fluoride gas in step (1) is cooled by a closed pressure device and then discharged.

[0032] Preferably, the temperature of the discharged hydrogen fluoride gas is 80-120°C, for example, it can be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] In the present invention, by controlling the release temperature of hydrogen fluoride gas, the introduction of water vapor and impurities such as sulfuric acid carried by it is reduced, and the absorption rate of hydrogen fluoride gas in subsequent calcium hydroxide is accelerated, thereby significantly improving the purity of calcium fluoride products and the absorption efficiency of hydrogen fluoride gas.

[0034] As a preferred technical solution of the present invention, the method for treating the hydrogen fluoride gas in step (1) comprises:

[0035] The calcium hydroxide slurry is first used to absorb hydrogen fluoride gas to obtain a mixed slurry, and then the mixed slurry is secondly used to absorb hydrogen fluoride gas, followed by sequentially performing liquid-solid separation, second washing and second drying to obtain calcium fluoride.

[0036] As a preferred technical solution of the present invention, the solid content of the calcium hydroxide slurry is 0.5-20%, for example, can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20% etc., but is not limited to the enumerated numerical value, other unenumerated numerical values ​​within this numerical range are equally applicable.

[0037] Preferably, the first absorption level is 2 to 5, for example, it can be 2, 3, 4 or 5, etc., but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] Preferably, the index for performing the liquid-solid separation is: the mass concentration of calcium hydroxide in the mixed slurry is 0.01 to 0.05 g / L, for example, it can be 0.01 g / L, 0.02 g / L, 0.03 g / L, 0.04 g / L or 0.05 g / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] It is worth noting that, under the condition of controlling the release temperature of hydrogen fluoride gas, the calcium hydroxide slurry is used to absorb hydrogen fluoride gas in multiple stages, thereby improving the absorption efficiency of fluorine. When the concentration of calcium hydroxide in the mixed slurry is reduced to 0.01g / L-0.05g / L, the purity of the obtained calcium fluoride product is relatively high. After washing and drying, the purity of the obtained calcium fluoride product can reach 99.5%-99.9%.

[0040] Preferably, in the second washing, the solid-to-liquid ratio of solid to washing liquid is 1:(5-25) t / m 3 , for example, it can be 1:5t / m 3 , 1:5.5t / m 3 , 1:6t / m 3 、1:6.5t / m 3 , 1:7t / m 3 1:7.5t / m 3 、1:8t / m 3 、1:8.5t / m 3 , 1:9t / m 3 、1:9.5t / m 3 , 1:10t / m 3 , 1:10.5t / m 3 1:11t / m 3 、1:11.5t / m 3 1:12t / m 3 、1:12.75t / m 3 1:13t / m 3 、1:13.5t / m 3 1:14t / m 3 , 1:14.5t / m 3 1:15t / m 3 , 1:15.5t / m 3 1:16t / m 3 , 1:16.5t / m 3 1:17t / m 3 , 1:17.5t / m 3 , 1:18t / m 3 , 1:18.5t / m 3 1:19t / m 3 、1:19.5t / m 3 , 1:20t / m 3 1:21t / m 3 , 1:22t / m 3 , 1:23t / m 3 , 1:24t / m 3 or 1:25t / m 3 The above range is not limited to the listed values, and other values ​​not listed within the above range are also applicable.

[0041] Preferably, the solution after the second washing is reused in step (1).

[0042] Preferably, the second drying temperature is 50-100°C, for example, it can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] As a preferred technical solution of the present invention, the immersion liquid in step (2) is evaporated and crystallized to recover sodium sulfate.

[0044] In the present invention, since the residual sulfuric acid concentration in the initial leaching solution is very high, it can be reused in step (1). When the sodium sulfate concentration in the leaching solution is close to saturation during recycling, the leaching solution is evaporated and crystallized to obtain sodium sulfate byproduct. The filtrate after evaporation and crystallization can still be reused in step (1).

[0045] As a preferred technical solution of the present invention, the post-treatment in step (2) includes sequentially performing a first washing and a first drying.

[0046] Preferably, in the first washing, the solid-liquid ratio of the leaching residue to the washing liquid is 1:(5-25) t / m 3 , for example, it can be 1:5t / m 3 , 1:5.5t / m 3 , 1:6t / m 3 、1:6.5t / m 3 , 1:7t / m 3 1:7.5t / m 3 、1:8t / m 3 、1:8.5t / m 3 , 1:9t / m 3 、1:9.5t / m 3 , 1:10t / m 3 , 1:10.5t / m 3 1:11t / m 3 、1:11.5t / m 3 1:12t / m 3 、1:12.75t / m 3 1:13t / m 3 、1:13.5t / m 3 1:14t / m 3 , 1:14.5t / m 3 1:15t / m 3 , 1:15.5t / m 3 1:16t / m 3 , 1:16.5t / m 3 1:17t / m 3 , 1:17.5t / m 3 , 1:18t / m3 , 1:18.5t / m 3 1:19t / m 3 、1:19.5t / m 3 , 1:20t / m 3 1:21t / m 3 , 1:22t / m 3 , 1:23t / m 3 , 1:24t / m 3 or 1:25t / m 3 The above range is not limited to the listed values, and other values ​​not listed within the above range are also applicable.

[0047] Preferably, the solution after the first washing is reused in step (1).

[0048] Preferably, the first drying temperature is 50-100°C, for example, it can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] Preferably, the purity of the basic aluminum fluoride in step (2) is ≥99.5%, for example, it can be 99.5%, 99.6%, 99.7%, 99.8% or 99.9%, etc., but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] As a preferred technical solution of the present invention, the recycling method comprises the following steps:

[0051] (1) The aluminum electrolyte is crushed and ground in sequence to obtain an aluminum electrolyte powder with a particle size of ≤100 μm, and the solid-liquid ratio is 1:(1-8) t / m 3 Aluminum electrolyte powder and leaching agent solution are mixed and slurry leached in a closed pressure device at a temperature of 100 to 200° C. for 0.5 to 5 hours to obtain slurry and hydrogen fluoride gas;

[0052] The molar concentration of hydrogen ions in the leaching agent solution is 2.5-25 mol / L; the leaching agent solution is sulfuric acid and aluminum sulfate; after the mixing, the molar ratio of aluminum element to fluorine element in the slurry is 1:(0.5-3);

[0053] The hydrogen fluoride gas is cooled to 80-120°C by a closed pressure device and then discharged;

[0054] (2) subjecting the slurry of step (1) to liquid-solid separation to obtain an leaching solution and a leaching residue, and subjecting the leaching residue to a first washing and a first drying in sequence to obtain basic aluminum fluoride with a purity of ≥99.5%;

[0055] In the first washing, the solid-liquid ratio of the leaching residue to the washing liquid is 1:(5-25) t / m 3 ; The solution after the first washing is reused in step (1);

[0056] The immersion liquid is reused in step (1);

[0057] (3) using calcium hydroxide slurry having a solid content of 0.5 to 20% to first absorb the hydrogen fluoride gas in step (1) to obtain a mixed slurry, and then using the mixed slurry to secondly absorb the hydrogen fluoride gas, and when the mass concentration of calcium hydroxide in the mixed slurry is 0.01 to 0.05 g / L, liquid-solid separation is performed, and then a second washing and a second drying are performed in sequence to obtain calcium fluoride;

[0058] The first absorption level is 2 to 5;

[0059] In the second washing, the solid-liquid ratio of solid to washing liquid is 1:(5-25) t / m 3 ; The solution after the second washing is reused in step (1).

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] (1) The aluminum electrolyte recycling method provided by the present invention is to slurry the aluminum electrolyte and the leaching agent solution, and control the slurry leaching to be carried out under high temperature, high pressure and strong acid conditions to promote the complete dissolution of the aluminum electrolyte and convert it into a leachate and a high-purity basic aluminum fluoride leach residue. The residual sulfuric acid concentration in the leachate is very high and can be returned to step (1) for recycling; the hydrogen fluoride gas generated at the same time can be used to prepare a calcium fluoride product;

[0062] (2) The aluminum electrolyte recycling method provided by the present invention has a high aluminum and fluorine resource recovery rate, and the leaching liquid can be recycled. It has low production cost, simple process flow, clean process and no pollution, and has broad application prospects. DETAILED DESCRIPTION

[0063] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0064] In the following embodiments and comparative examples, the elements in the aluminum electrolyte include, by weight percentage: Al 12.34wt%, F 46.98wt%, Na 29.26wt%, K 1.72wt%, Ca 2.73wt%, and the remainder is O and impurities.

[0065] Example 1

[0066] This embodiment provides a method for recycling aluminum electrolyte, which includes the following steps:

[0067] (1) The aluminum electrolyte is crushed and ground in turn to obtain an aluminum electrolyte powder with a particle size of 10 μm, and the solid-liquid ratio is 1:1 t / m 3 Aluminum electrolyte powder and leaching agent solution are mixed, and slurry leaching is performed in a closed pressure device at a temperature of 100° C. for 1 hour to obtain slurry and hydrogen fluoride gas;

[0068] The molar concentration of hydrogen ions in the leaching agent solution is 3 mol / L; the leaching agent solution is sulfuric acid and aluminum sulfate; after the mixing, the molar ratio of aluminum element to fluorine element in the slurry is 1:1;

[0069] The hydrogen fluoride gas is cooled to 80°C through a closed pressure device and then discharged;

[0070] (2) subjecting the slurry of step (1) to liquid-solid separation to obtain an leaching solution and a leaching residue, and subjecting the leaching residue to a first washing and a first drying in sequence to obtain basic aluminum fluoride;

[0071] In the first washing, the solid-liquid ratio of the leaching residue to the washing liquid is 1:5 t / m 3 ; The solution after the first washing is reused in step (1); The temperature of the first drying is 60°C;

[0072] The leaching solution is reused in step (1), and the leaching solution is periodically evaporated and crystallized to recover sodium sulfate.

[0073] Example 2

[0074] This embodiment provides a method for recycling aluminum electrolyte, which further includes the following steps based on Embodiment 1:

[0075] (3) using calcium hydroxide slurry with a solid content of 2% to first absorb the hydrogen fluoride gas in step (1) to obtain a mixed slurry, and then using the mixed slurry to secondly absorb the hydrogen fluoride gas, and when the mass concentration of calcium hydroxide in the mixed slurry is 0.02 g / L, liquid-solid separation is performed, and then a second washing and a second drying are performed in sequence to obtain calcium fluoride;

[0076] The first absorption order is 2;

[0077] In the second washing, the solid-liquid ratio of solid to washing liquid is 1:25t / m 3 ; The solution after the second washing is reused in step (1); The temperature of the second drying is 50°C.

[0078] Example 3

[0079] This embodiment provides a method for recycling aluminum electrolyte, which includes the following steps:

[0080] (1) The aluminum electrolyte is crushed and ground in turn to obtain an aluminum electrolyte powder with a particle size of 100 μm, and the solid-liquid ratio is 1:8 t / m 3 Aluminum electrolyte powder and leaching agent solution are mixed, and slurry leaching is performed in a closed pressure device at a temperature of 150° C. for 0.5 h to obtain slurry and hydrogen fluoride gas;

[0081] The molar concentration of hydrogen ions in the leaching agent solution is 5 mol / L; the leaching agent solution is sulfuric acid and aluminum sulfate; after the mixing, the molar ratio of aluminum element to fluorine element in the slurry is 1:3;

[0082] The hydrogen fluoride gas is cooled to 90°C through a closed pressure device and then discharged;

[0083] (2) subjecting the slurry of step (1) to liquid-solid separation to obtain an leaching solution and a leaching residue, and subjecting the leaching residue to a first washing and a first drying in sequence to obtain basic aluminum fluoride;

[0084] In the first washing, the solid-liquid ratio of the leaching residue to the washing liquid is 1:25 t / m 3 ; The solution after the first washing is reused in step (1); The temperature of the first drying is 50°C;

[0085] The leaching liquid is reused in step (1), and the leaching liquid is periodically evaporated and crystallized to recover sodium sulfate;

[0086] (3) using calcium hydroxide slurry with a solid content of 0.5% to first absorb the hydrogen fluoride gas in step (1) to obtain a mixed slurry, and then using the mixed slurry to secondly absorb the hydrogen fluoride gas, and when the mass concentration of calcium hydroxide in the mixed slurry is 0.05 g / L, liquid-solid separation is performed, and then a second washing and a second drying are performed in sequence to obtain calcium fluoride;

[0087] The first absorption level is 3;

[0088] In the second washing, the solid-liquid ratio of solid to washing liquid is 1:5t / m 3 ; The solution after the second washing is reused in step (1); The temperature of the second drying is 100°C.

[0089] Example 4

[0090] This embodiment provides a method for recycling aluminum electrolyte, which includes the following steps:

[0091] (1) The aluminum electrolyte is crushed and ground in turn to obtain an aluminum electrolyte powder with a particle size of 20 μm, and the solid-liquid ratio is 1:2 t / m3 Aluminum electrolyte powder and leaching agent solution are mixed, and slurry leaching is performed in a closed pressure device at a temperature of 110° C. for 5 hours to obtain slurry and hydrogen fluoride gas;

[0092] The molar concentration of hydrogen ions in the leaching agent solution is 25 mol / L; the leaching agent solution is sulfuric acid and aluminum sulfate; after the mixing, the molar ratio of aluminum element to fluorine element in the slurry is 1:0.5;

[0093] The hydrogen fluoride gas is cooled to 95°C through a closed pressure device and then discharged;

[0094] (2) subjecting the slurry of step (1) to liquid-solid separation to obtain an leaching solution and a leaching residue, and subjecting the leaching residue to a first washing and a first drying in sequence to obtain basic aluminum fluoride;

[0095] In the first washing, the solid-liquid ratio of the leaching residue to the washing liquid is 1:10 t / m 3 ; The solution after the first washing is reused in step (1); The temperature of the first drying is 100°C;

[0096] The leaching liquid is reused in step (1), and the leaching liquid is periodically evaporated and crystallized to recover sodium sulfate;

[0097] (3) using calcium hydroxide slurry with a solid content of 20% to first absorb the hydrogen fluoride gas in step (1) to obtain a mixed slurry, and then using the mixed slurry to secondly absorb the hydrogen fluoride gas, and when the mass concentration of calcium hydroxide in the mixed slurry is 0.01 g / L, liquid-solid separation is performed, and then a second washing and a second drying are performed in sequence to obtain calcium fluoride;

[0098] The first absorption order is 2;

[0099] In the second washing, the solid-liquid ratio of solid to washing liquid is 1:10 t / m 3 ; The solution after the second washing is reused in step (1); The temperature of the second drying is 60°C.

[0100] Example 5

[0101] This embodiment provides a method for recycling aluminum electrolyte, which includes the following steps:

[0102] (1) The aluminum electrolyte is crushed and ground in turn to obtain an aluminum electrolyte powder with a particle size of 30 μm, and the solid-liquid ratio is 1:3 t / m 3 Aluminum electrolyte powder and leaching agent solution are mixed, and slurry leaching is performed in a closed pressure device at a temperature of 200° C. for 2 hours to obtain slurry and hydrogen fluoride gas;

[0103] The molar concentration of hydrogen ions in the leaching agent solution is 2.5 mol / L; the leaching agent solution is sulfuric acid and aluminum sulfate; after the mixing, the molar ratio of aluminum element to fluorine element in the slurry is 1:1.5;

[0104] The hydrogen fluoride gas is cooled to 100°C through a closed pressure device and then discharged;

[0105] (2) subjecting the slurry of step (1) to liquid-solid separation to obtain an leaching solution and a leaching residue, and subjecting the leaching residue to a first washing and a first drying in sequence to obtain basic aluminum fluoride;

[0106] In the first washing, the solid-liquid ratio of the leaching residue to the washing liquid is 1:15 t / m 3 ; The solution after the first washing is reused in step (1); The temperature of the first drying is 70°C;

[0107] The leaching liquid is reused in step (1), and the leaching liquid is periodically evaporated and crystallized to recover sodium sulfate;

[0108] (3) using calcium hydroxide slurry with a solid content of 5% to first absorb the hydrogen fluoride gas in step (1) to obtain a mixed slurry, and then using the mixed slurry to secondly absorb the hydrogen fluoride gas, and when the mass concentration of calcium hydroxide in the mixed slurry is 0.03 g / L, liquid-solid separation is performed, and then a second washing and a second drying are performed in sequence to obtain calcium fluoride;

[0109] The first absorption level is 3;

[0110] In the second washing, the solid-liquid ratio of solid to washing liquid is 1:15t / m 3 ; The solution after the second washing is reused in step (1); The temperature of the second drying is 70°C.

[0111] Example 6

[0112] This embodiment provides a method for recycling aluminum electrolyte, which includes the following steps:

[0113] (1) The aluminum electrolyte is crushed and ground in turn to obtain an aluminum electrolyte powder with a particle size of 40 μm, and the solid-liquid ratio is 1:4 t / m 3 Aluminum electrolyte powder and leaching agent solution are mixed, and slurry leaching is performed in a closed pressure device at a temperature of 160° C. for 3 hours to obtain slurry and hydrogen fluoride gas;

[0114] The molar concentration of hydrogen ions in the leaching agent solution is 7.5 mol / L; the leaching agent solution is sulfuric acid and aluminum sulfate; after the mixing, the molar ratio of aluminum element to fluorine element in the slurry is 1:2;

[0115] The hydrogen fluoride gas is cooled to 105°C through a closed pressure device and then discharged;

[0116] (2) subjecting the slurry of step (1) to liquid-solid separation to obtain an leaching solution and a leaching residue, and subjecting the leaching residue to a first washing and a first drying in sequence to obtain basic aluminum fluoride;

[0117] In the first washing, the solid-liquid ratio of the leaching residue to the washing liquid is 1:20 t / m 3 ; The solution after the first washing is reused in step (1); The temperature of the first drying is 80°C;

[0118] The leaching liquid is reused in step (1), and the leaching liquid is periodically evaporated and crystallized to recover sodium sulfate;

[0119] (3) using calcium hydroxide slurry with a solid content of 10% to first absorb the hydrogen fluoride gas in step (1) to obtain a mixed slurry, and then using the mixed slurry to secondly absorb the hydrogen fluoride gas, and when the mass concentration of calcium hydroxide in the mixed slurry is 0.01 g / L, liquid-solid separation is performed, and then a second washing and a second drying are performed in sequence to obtain calcium fluoride;

[0120] The first absorption level is 4;

[0121] In the second washing, the solid-liquid ratio of solid to washing liquid is 1:20 t / m 3 ; The solution after the second washing is reused in step (1); The temperature of the second drying is 80°C.

[0122] Example 7

[0123] This embodiment provides a method for recycling aluminum electrolyte, which includes the following steps:

[0124] (1) The aluminum electrolyte is crushed and ground in turn to obtain an aluminum electrolyte powder with a particle size of 50 μm, and the solid-liquid ratio is 1:5 t / m 3 Aluminum electrolyte powder and leaching agent solution are mixed, and slurry leaching is performed in a closed pressure device at a temperature of 160° C. for 4 hours to obtain slurry and hydrogen fluoride gas;

[0125] The molar concentration of hydrogen ions in the leaching agent solution is 15 mol / L; the leaching agent solution is sulfuric acid and aluminum sulfate; after the mixing, the molar ratio of aluminum element to fluorine element in the slurry is 1:2.5;

[0126] The hydrogen fluoride gas is cooled to 110°C through a closed pressure device and then discharged;

[0127] (2) subjecting the slurry of step (1) to liquid-solid separation to obtain an leaching solution and a leaching residue, and subjecting the leaching residue to a first washing and a first drying in sequence to obtain basic aluminum fluoride;

[0128] In the first washing, the solid-liquid ratio of the leaching residue to the washing liquid is 1:15 t / m 3 ; The solution after the first washing is reused in step (1); The temperature of the first drying is 90°C;

[0129] The leaching liquid is reused in step (1), and the leaching liquid is periodically evaporated and crystallized to recover sodium sulfate;

[0130] (3) using calcium hydroxide slurry with a solid content of 15% to first absorb the hydrogen fluoride gas in step (1) to obtain a mixed slurry, and then using the mixed slurry to secondly absorb the hydrogen fluoride gas, and when the mass concentration of calcium hydroxide in the mixed slurry is 0.02 g / L, liquid-solid separation is performed, and then a second washing and a second drying are performed in sequence to obtain calcium fluoride;

[0131] The first absorption level is 3;

[0132] In the second washing, the solid-liquid ratio of solid to washing liquid is 1:15t / m 3 ; The solution after the second washing is reused in step (1); The temperature of the second drying is 90°C.

[0133] Example 8

[0134] This embodiment provides a method for recycling aluminum electrolyte, which includes the following steps:

[0135] (1) The aluminum electrolyte is crushed and ground in turn to obtain an aluminum electrolyte powder with a particle size of 60 μm, and the solid-liquid ratio is 1:6 t / m 3 Aluminum electrolyte powder and leaching agent solution are mixed, and slurry leaching is performed in a closed pressure device at a temperature of 170° C. for 4 hours to obtain slurry and hydrogen fluoride gas;

[0136] The molar concentration of hydrogen ions in the leaching agent solution is 20 mol / L; the leaching agent solution is sulfuric acid and aluminum sulfate; after the mixing, the molar ratio of aluminum element to fluorine element in the slurry is 1:2.75;

[0137] The hydrogen fluoride gas is cooled to 120°C through a closed pressure device and then discharged;

[0138] (2) subjecting the slurry of step (1) to liquid-solid separation to obtain an leaching solution and a leaching residue, and subjecting the leaching residue to a first washing and a first drying in sequence to obtain basic aluminum fluoride;

[0139] In the first washing, the solid-liquid ratio of the leaching residue to the washing liquid is 1:10 t / m 3 ; The solution after the first washing is reused in step (1); The temperature of the first drying is 95°C;

[0140] The leaching liquid is reused in step (1), and the leaching liquid is periodically evaporated and crystallized to recover sodium sulfate;

[0141] (3) using calcium hydroxide slurry having a solid content of 16% to first absorb the hydrogen fluoride gas in step (1) to obtain a mixed slurry, and then using the mixed slurry to secondly absorb the hydrogen fluoride gas, and when the mass concentration of calcium hydroxide in the mixed slurry is 0.02 g / L, liquid-solid separation is performed, and then a second washing and a second drying are performed in sequence to obtain calcium fluoride;

[0142] The first absorption level is 3;

[0143] In the second washing, the solid-liquid ratio of solid to washing liquid is 1:20 t / m 3 ; The solution after the second washing is reused in step (1); The temperature of the second drying is 95°C.

[0144] Example 9

[0145] This embodiment provides a method for recycling aluminum electrolyte, which includes the following steps:

[0146] (1) The aluminum electrolyte is crushed and ground in turn to obtain an aluminum electrolyte powder with a particle size of 70 μm, and the solid-liquid ratio is 1:7 t / m 3 Mixing aluminum electrolyte powder and leaching agent solution, and slurry leaching for 3 hours at a temperature of 180° C. in a closed pressure device to obtain slurry and hydrogen fluoride gas;

[0147] The molar concentration of hydrogen ions in the leaching agent solution is 12.5 mol / L; the leaching agent solution is sulfuric acid and aluminum sulfate; after the mixing, the molar ratio of aluminum element to fluorine element in the slurry is 1:2;

[0148] The hydrogen fluoride gas is cooled to 115°C through a closed pressure device and then discharged;

[0149] (2) subjecting the slurry of step (1) to liquid-solid separation to obtain an leaching solution and a leaching residue, and subjecting the leaching residue to a first washing and a first drying in sequence to obtain basic aluminum fluoride;

[0150] In the first washing, the solid-liquid ratio of the leaching residue to the washing liquid is 1:25 t / m 3 ; The solution after the first washing is reused in step (1); The temperature of the first drying is 100°C;

[0151] The leaching liquid is reused in step (1), and the leaching liquid is periodically evaporated and crystallized to recover sodium sulfate;

[0152] (3) using calcium hydroxide slurry with a solid content of 17% to first absorb the hydrogen fluoride gas in step (1) to obtain a mixed slurry, and then using the mixed slurry to secondly absorb the hydrogen fluoride gas, and when the mass concentration of calcium hydroxide in the mixed slurry is 0.05 g / L, liquid-solid separation is performed, and then a second washing and a second drying are performed in sequence to obtain calcium fluoride;

[0153] The first absorption level is 5;

[0154] In the second washing, the solid-liquid ratio of solid to washing liquid is 1:25t / m 3 ; The solution after the second washing is reused in step (1); The temperature of the second drying is 100°C.

[0155] Example 10

[0156] This embodiment provides a method for recycling aluminum electrolyte, which includes the following steps:

[0157] (1) The aluminum electrolyte is crushed and ground in turn to obtain an aluminum electrolyte powder with a particle size of 80 μm, and the solid-liquid ratio is 1:8 t / m 3 Mixing aluminum electrolyte powder and leaching agent solution, and slurry leaching for 4 hours at a temperature of 190° C. in a closed pressure device to obtain slurry and hydrogen fluoride gas;

[0158] The molar concentration of hydrogen ions in the leaching agent solution is 10 mol / L; the leaching agent solution is sulfuric acid and aluminum sulfate; after the mixing, the molar ratio of aluminum element to fluorine element in the slurry is 1:3;

[0159] The hydrogen fluoride gas is cooled to 100°C through a closed pressure device and then discharged;

[0160] (2) subjecting the slurry of step (1) to liquid-solid separation to obtain an leaching solution and a leaching residue, and subjecting the leaching residue to a first washing and a first drying in sequence to obtain basic aluminum fluoride;

[0161] In the first washing, the solid-liquid ratio of the leaching residue to the washing liquid is 1:10 t / m 3 ; The solution after the first washing is reused in step (1); The temperature of the first drying is 80°C;

[0162] The leaching liquid is reused in step (1), and the leaching liquid is periodically evaporated and crystallized to recover sodium sulfate;

[0163] (3) using calcium hydroxide slurry with a solid content of 18% to first absorb the hydrogen fluoride gas in step (1) to obtain a mixed slurry, and then using the mixed slurry to secondly absorb the hydrogen fluoride gas, and when the mass concentration of calcium hydroxide in the mixed slurry is 0.03 g / L, liquid-solid separation is performed, and then a second washing and a second drying are performed in sequence to obtain calcium fluoride;

[0164] The first absorption level is 4;

[0165] In the second washing, the solid-liquid ratio of solid to washing liquid is 1:10 t / m 3 ; The solution after the second washing is reused in step (1); The temperature of the second drying is 80°C.

[0166] Embodiment 11

[0167] This embodiment provides a method for recycling aluminum electrolyte, which includes the following steps:

[0168] (1) The aluminum electrolyte was crushed and ground in turn to obtain an aluminum electrolyte powder with a particle size of 90 μm, and the solid-liquid ratio was 1:6.5 t / m 3 Mixing aluminum electrolyte powder and leaching agent solution, and slurry leaching for 3 hours at a temperature of 185° C. in a closed pressure device to obtain slurry and hydrogen fluoride gas;

[0169] The molar concentration of hydrogen ions in the leaching agent solution is 24 mol / L; the leaching agent solution is sulfuric acid and aluminum sulfate; after the mixing, the molar ratio of aluminum element to fluorine element in the slurry is 1:2;

[0170] The hydrogen fluoride gas is cooled to 100°C through a closed pressure device and then discharged;

[0171] (2) subjecting the slurry of step (1) to liquid-solid separation to obtain an leaching solution and a leaching residue, and subjecting the leaching residue to a first washing and a first drying in sequence to obtain basic aluminum fluoride;

[0172] In the first washing, the solid-liquid ratio of the leaching residue to the washing liquid is 1:15 t / m 3 ; The solution after the first washing is reused in step (1); The temperature of the first drying is 90°C;

[0173] The leaching liquid is reused in step (1), and the leaching liquid is periodically evaporated and crystallized to recover sodium sulfate;

[0174] (3) using calcium hydroxide slurry with a solid content of 19% to first absorb the hydrogen fluoride gas in step (1) to obtain a mixed slurry, and then using the mixed slurry to secondly absorb the hydrogen fluoride gas, and when the mass concentration of calcium hydroxide in the mixed slurry is 0.01 g / L, liquid-solid separation is performed, and then a second washing and a second drying are performed in sequence to obtain calcium fluoride;

[0175] The first absorption level is 3;

[0176] In the second washing, the solid-liquid ratio of solid to washing liquid is 1:15t / m 3 ; The solution after the second washing is reused in step (1); The temperature of the second drying is 90°C.

[0177] Example 12

[0178] This embodiment provides a method for recycling aluminum electrolyte. Except that the temperature of the slurry leaching in step (1) is 90° C., other conditions are the same as those in Example 2.

[0179] Example 13

[0180] This embodiment provides a method for recycling aluminum electrolyte. Except that the temperature of the slurry leaching in step (1) is 220° C., other conditions are the same as those in Example 2.

[0181] Embodiment 14

[0182] This embodiment provides a method for recycling aluminum electrolyte. Except that after mixing in step (1), the molar ratio of aluminum element to fluorine element in the slurry is 1:0.2, other conditions are the same as those in Example 2.

[0183] Embodiment 15

[0184] This embodiment provides a method for recycling aluminum electrolyte. Except that after mixing in step (1), the molar ratio of aluminum element to fluorine element in the slurry is 1:5, other conditions are the same as those in Example 2.

[0185] Example 16

[0186] This embodiment provides a method for recycling aluminum electrolyte. Except that hydrogen fluoride gas is discharged in real time through a pipeline during the slurry leaching process in step (1), other conditions are the same as those in Example 2.

[0187] Embodiment 17

[0188] This embodiment provides a method for recycling aluminum electrolyte. Except that the hydrogen fluoride gas in step (1) is cooled to 150° C. through a closed pressure device and then discharged, other conditions are the same as those in Example 5.

[0189] Embodiment 18

[0190] This embodiment provides a method for recycling aluminum electrolyte. Except for performing liquid-solid separation when the mass concentration of calcium hydroxide in the mixed slurry is 0.1 g / L in step (3), other conditions are the same as those in Example 2.

[0191] Comparative Example 1

[0192] This comparative example provides a method for recycling aluminum electrolyte. Except that the molar concentration of hydrogen ions in the leaching agent solution in step (1) is 0.1 mol / L, other conditions are the same as those in Example 2.

[0193] Comparative Example 2

[0194] This comparative example provides a method for recycling aluminum electrolyte. Except that the molar concentration of hydrogen ions in the leaching agent solution in step (1) is 30 mol / L, other conditions are the same as those in Example 2.

[0195] The aluminum and fluorine contents in the basic aluminum fluoride and calcium fluoride obtained in the above examples and comparative examples were tested by ICP-OES, fluoride ion meter or lanthanum nitrate potentiometric titration, and the recovery rates of fluorine and aluminum and the purity of the products were calculated. The results are shown in Table 1.

[0196] Table 1

[0197]

[0198]

[0199] From Table 1, we can see that:

[0200] (1) The recycling method provided in Examples 1-11 of the present invention controls the slurry leaching to be carried out under high temperature, high pressure and strong acid conditions, promotes the complete dissolution of the aluminum electrolyte, and converts it into a leachate and high-purity basic aluminum fluoride leaching residue. The residual sulfuric acid concentration in the leachate is very high and can be returned to step (1) for recycling; the hydrogen fluoride gas generated at the same time is controlled to release and absorb the hydrogen fluoride gas to prepare a calcium fluoride product; wherein the recovery rates of aluminum and fluorine can reach more than 95%, and the purity of basic aluminum fluoride and calcium fluoride products can reach more than 99.5%;

[0201] (2) By comparing Example 2 with Examples 12-13, it can be seen that when the temperature of slurry leaching is low, the aluminum electrolyte dissolution effect is poor and the impurity content is high, resulting in a low fluorine / aluminum recovery rate and a low purity of basic aluminum fluoride; when the temperature of slurry leaching is high, a large amount of hydrogen fluoride overflows, resulting in a small amount of basic aluminum fluoride, that is, most of the fluorine is converted into calcium fluoride by hydrogen fluoride, and the amount of fluorine converted into basic aluminum fluoride is small, the fluorine recovery rate is not affected, the product purity is basically not affected, the aluminum recovery rate is reduced, and some aluminum ions are dissolved in the solution;

[0202] (3) By comparing Example 2 with Examples 14-15, it can be seen that when the ratio of aluminum to fluorine in the slurry is too low or too high, the fluorine / aluminum recovery rate is low and the purity of basic aluminum fluoride is low due to poor dissolution of the aluminum electrolyte and high impurity content;

[0203] (4) By comparing Example 2 with Example 16, it can be seen that during the slurry leaching process, the hydrogen fluoride gas is discharged in real time through the pipeline, which cannot increase the reaction pressure, and thus cannot promote the decomposition of the aluminum electrolyte, resulting in a low fluorine / aluminum recovery rate and low purity of basic aluminum fluoride. In addition, when the high-temperature hydrogen fluoride gas is released and carries impurities such as sulfuric acid, it is difficult to accurately control the release and absorption process of the hydrogen fluoride gas, resulting in low purity of the calcium fluoride product;

[0204] (5) It can be seen from the comparison between Example 5 and Example 17 or Example 2 and Example 18 that when the hydrogen fluoride gas is released at high temperature or the mass concentration of calcium hydroxide in the mixed slurry is too high, liquid-solid separation is performed. Since the high-temperature hydrogen fluoride gas is released with impurities such as sulfuric acid and the hydrogen fluoride gas is not completely absorbed in the calcium hydroxide slurry, it is difficult to accurately control the release and absorption process of the hydrogen fluoride gas, resulting in low purity of the calcium fluoride product;

[0205] (6) By comparing Example 2 with Comparative Examples 1-2, it can be seen that when the molar concentration of hydrogen ions in the leaching agent solution is too low, the aluminum electrolyte dissolution effect is poor and the impurity content is high, resulting in a low fluorine / aluminum recovery rate and low purity of basic aluminum fluoride; when the molar concentration of hydrogen ions in the leaching agent solution is high, excessive hydrogen fluoride will be generated in a short time, causing the pressure in the reactor to rise sharply, which is difficult for the equipment to withstand. At the same time, most of the fluorine is converted into calcium fluoride through hydrogen fluoride, and the amount of fluorine converted into basic aluminum fluoride is small. The fluorine recovery rate is not affected, the product purity is basically not affected, the aluminum recovery rate is reduced, and some aluminum ions are dissolved in the solution.

[0206] The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for recycling aluminum electrolyte, characterized in that: The recycling method comprises the following steps: (1) mixing an aluminum electrolyte and a leaching agent solution, performing slurry leaching, and obtaining a slurry and hydrogen fluoride gas; The molar concentration of hydrogen ions in the leaching agent solution is 2.5 to 25 mol / L; (2) subjecting the slurry of step (1) to liquid-solid separation to obtain an leaching solution and a leaching residue, and subjecting the leaching residue to post-treatment to obtain basic aluminum fluoride; The immersion liquid is reused in step (1).

2. The recycling method according to claim 1, characterized in that: The aluminum electrolyte in step (1) comprises cryolite, aluminum oxide and calcium fluoride; Preferably, before the aluminum electrolyte is slurried and leached in step (1), the process further comprises: crushing and grinding the aluminum electrolyte in sequence to obtain aluminum electrolyte powder; Preferably, the particle size of the aluminum electrolyte powder is ≤100 μm.

3. The recycling method according to claim 1 or 2, characterized in that: The solid-liquid ratio of the aluminum electrolyte and the leaching agent solution in step (1) is 1:(1-8) t / m 3 , preferably 1: (4-6) t / m 3 ; Preferably, the molar concentration of hydrogen ions in the leaching agent solution in step (1) is 3 to 15 mol / L; Preferably, the leaching agent solution in step (1) is sulfuric acid and aluminum sulfate; Preferably, after the mixing in step (1), the molar ratio of aluminum element to fluorine element in the slurry is 1:(0.5-3), preferably 1:(1-2).

4. The recycling method according to any one of claims 1 to 3, characterized in that: The slurry leaching in step (1) is carried out in a closed pressure device; Preferably, the temperature of the slurry leaching in step (1) is 100-200°C, preferably 130-190°C, more preferably 150-180°C; Preferably, the slurry leaching time in step (1) is 0.5 to 5 hours.

5. The recycling method according to any one of claims 1 to 4, characterized in that: The hydrogen fluoride gas in step (1) is cooled by a closed pressure device and then discharged; Preferably, the temperature of the discharged hydrogen fluoride gas is 80-120°C.

6. The recycling method according to any one of claims 1 to 5, characterized in that: The method for treating the hydrogen fluoride gas in step (1) comprises: The calcium hydroxide slurry is first used to absorb hydrogen fluoride gas to obtain a mixed slurry, and then the mixed slurry is secondly used to absorb hydrogen fluoride gas, followed by sequentially performing liquid-solid separation, second washing and second drying to obtain calcium fluoride.

7. The recycling method according to claim 6, characterized in that: The solid content of the calcium hydroxide slurry is 0.5-20%; Preferably, the first absorption level is 2 to 5; Preferably, the index for performing the liquid-solid separation is: the mass concentration of calcium hydroxide in the mixed slurry is 0.01 to 0.05 g / L; Preferably, in the second washing, the solid-to-liquid ratio of solid to washing liquid is 1:(5-25) t / m 3 ; Preferably, the solution after the second washing is reused in step (1); Preferably, the second drying temperature is 50-100°C.

8. The recycling method according to any one of claims 1 to 7, characterized in that: The leaching solution in step (2) is evaporated and crystallized to recover sodium sulfate.

9. The recycling method according to any one of claims 1 to 8, characterized in that: The post-treatment in step (2) comprises sequentially performing a first washing and a first drying; Preferably, in the first washing, the solid-liquid ratio of the leaching residue to the washing liquid is 1:(5-25) t / m 3 ; Preferably, the solution after the first washing is reused in step (1); Preferably, the first drying temperature is 50-100°C; Preferably, the purity of the basic aluminum fluoride in step (2) is ≥99.5%.

10. The recycling method according to any one of claims 1 to 9, characterized in that: The recycling method comprises the following steps: (1) The aluminum electrolyte is crushed and ground in sequence to obtain an aluminum electrolyte powder with a particle size of ≤100 μm, and the solid-liquid ratio is 1:(1-8) t / m 3 Aluminum electrolyte powder and leaching agent solution are mixed and slurry leached in a closed pressure device at a temperature of 100 to 200° C. for 0.5 to 5 hours to obtain slurry and hydrogen fluoride gas; The molar concentration of hydrogen ions in the leaching agent solution is 2.5-25 mol / L; the leaching agent solution is sulfuric acid and aluminum sulfate; after the mixing, the molar ratio of aluminum element to fluorine element in the slurry is 1:(0.5-3); The hydrogen fluoride gas is cooled to 80-120°C by a closed pressure device and then discharged; (2) subjecting the slurry of step (1) to liquid-solid separation to obtain an leaching solution and a leaching residue, and subjecting the leaching residue to a first washing and a first drying in sequence to obtain basic aluminum fluoride with a purity of ≥99.5%; In the first washing, the solid-liquid ratio of the leaching residue to the washing liquid is 1:(5-25) t / m 3 ; The solution after the first washing is reused in step (1); The immersion liquid is reused in step (1); (3) using calcium hydroxide slurry having a solid content of 0.5 to 20% to first absorb the hydrogen fluoride gas in step (1) to obtain a mixed slurry, and then using the mixed slurry to secondly absorb the hydrogen fluoride gas, and when the mass concentration of calcium hydroxide in the mixed slurry is 0.01 to 0.05 g / L, liquid-solid separation is performed, and then a second washing and a second drying are performed in sequence to obtain calcium fluoride; The first absorption level is 2 to 5; In the second washing, the solid-liquid ratio of solid to washing liquid is 1:(5-25) t / m 3 ; The solution after the second washing is reused in step (1).

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