Method for recycling aluminum electrolysis waste and application thereof

Abstract

The application provides a recycling method and application of aluminum electrolysis waste. The method comprises the following steps: step 1, crushing the aluminum electrolysis waste to be treated; step 2, heating and leaching the electrolysis waste particles with an alkali solution or roasting the electrolysis waste particles with alkali under low-temperature conditions; step 3, crushing the modified aluminum electrolyte and mixing it with low-concentration acid liquor to obtain cryolite and filtrate A; step 4, repeating step 3 to obtain filtrate B with higher concentration and cryolite; step 5, neutralizing and adjusting the filtrate B to obtain filter residue and filtrate C; step 6, performing a lithium precipitation reaction to obtain lithium carbonate or lithium phosphate products and a lithium precipitation mother liquor; step 7, mixing the lithium precipitation mother liquor with the cryolite; step 8, performing acid pickling to obtain high-purity cryolite, and performing water washing and drying for use in the aluminum electrolysis process; and step 9, concentrating and evaporating the filtrate obtained in step 7. The application reduces the overall process cost, avoids causing a large amount of resource waste and environmental problems.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metallurgical solid waste resource processing, and relates to a regeneration method and application of aluminum electrolysis waste. BACKGROUND

[0002] Aluminum is the largest metal element in reserves and an important non-ferrous metal. The primary aluminum production ranks first in the production of various non-ferrous metals. While the world's aluminum industry is developing rapidly, China's aluminum industry has also made remarkable achievements and played an important role in promoting the development of the world's aluminum industry.

[0003] While the aluminum industry has achieved outstanding results, the problems existing in the aluminum electrolysis industry as a traditional high-energy-consumption industry are still prominent. As is known to all, the transformation of the physical and chemical properties of the electrolyte has an extremely important influence on the stable operation of the electrolytic cell. In the current aluminum electrolysis industry, the main raw material is alumina, and the electrolyte is cryolite, aluminum fluoride and calcium fluoride. However, a large amount of lithium and potassium is contained in the raw material in China, and lithium salt and potassium salt also enter the electrolytic cell during long-term operation of the electrolytic cell, causing continuous change of the composition of the electrolyte and great influence on the dissolution process of alumina.

[0004] It is proposed in some documents that the addition of lithium fluoride and potassium fluoride can reduce the initial crystallization temperature of the electrolyte and improve the solubility of alumina, which has a positive driving effect on the aluminum electrolysis industry. In the complex aluminum electrolyte system, the concentration of lithium fluoride is controlled at 1.5%-2.5%, which can maintain the optimal state of the aluminum electrolysis process. However, when the content of lithium and potassium exceeds 3% during long-term operation, it will cause continuous hazards such as current efficiency reduction, energy consumption increase and production process difficulty to control, which seriously affects the stable operation of the aluminum electrolytic cell and reduces the service life of the cell. Moreover, potassium has a high damage effect on the carbon cathode of the aluminum electrolytic cell. Therefore, a large amount of aluminum electrolysis waste needs to be scooped out after a period of operation and new electrolyte needs to be supplemented to stabilize the electrolytic cell. The accumulation and abandonment of a large amount of aluminum electrolysis waste cause a large amount of resource waste and environmental problems.

[0005] Therefore, it is particularly important to carry out research on the formation mechanism of each component in the complex aluminum electrolysis waste system, analyze the content of each component, solve the problems caused by the complex aluminum electrolysis waste and recover various resources in the waste. SUMMARY

[0006] The problems existing in the prior art are solved. The purpose of the present application is to provide a regeneration method and application of aluminum electrolysis waste. The present application reduces the overall process cost and avoids a large amount of resource waste and environmental problems.

[0007] The technical scheme of the present application is: a regeneration method of aluminum electrolysis waste, comprising the following steps:

[0008] Step 1: crushing the aluminum electrolysis waste to be treated to obtain electrolysis waste particles;

[0009] Step 2: heating leaching modification of the electrolysis waste particles in step 1 with an alkali solution or roasting modification of the electrolysis waste particles with an alkali under low temperature conditions to obtain modified aluminum electrolyte; when the heating leaching modification is performed, the solid-liquid ratio of the electrolysis waste particles to the alkali solution is 1g:2-10ml, and the molar concentration of the alkali solution is 1-2mol / L; when the roasting modification is performed, the mass ratio of the alkali to the electrolysis waste particles is 10%;

[0010] Step 3: crushing the modified aluminum electrolyte in step 2 and mixing with a low-concentration acid solution, stirring and reacting at 0-30℃, and then filtering to obtain cryolite and filtrate A;

[0011] Step 4: the filtrate A in step 3 is a lithium-containing leaching solution, the lithium ion concentration in the filtrate A is detected by an instrument, if the lithium ion concentration in the filtrate A does not reach the ideal concentration, the filtrate is introduced into the reaction kettle again, and step 3 is repeated to obtain filtrate B with higher concentration and cryolite;

[0012] Step 5: neutralizing and adjusting the filtrate B after detection in step 4 to remove residual hydrogen ions, fluorine ions and aluminum ions in the solution, and then separating and filtering to obtain filter residue and filtrate C;

[0013] Step 6: passing the filtrate C in step 5 into a water-soluble carbonate or phosphate for heating and stirring to perform lithium precipitation reaction, and then separating and filtering to obtain lithium carbonate or lithium phosphate product and lithium precipitation mother liquor;

[0014] Step 7: mixing the lithium precipitation mother liquor in step 6 with the cryolite obtained in steps 3 and 4 in a certain proportion, fully stirring, and then separating the solid and liquid to obtain cryolite containing calcium phosphate or calcium carbonate;

[0015] Step 8: acid washing the cryolite containing calcium phosphate or calcium carbonate obtained in step 7 to obtain high-purity cryolite, and then washing with water and drying, and then applying the cryolite to the electrolytic aluminum process again; the acid solution is recycled and reused until it becomes neutral, and then it is replaced;

[0016] Step 9: concentrating and evaporating the filtrate obtained in step 7 to obtain sodium or potassium salt containing chloride, carbonate, sulfate, nitrate and phosphate; and evaporating and concentrating the neutral solution in step 8 to obtain calcium chloride or calcium nitrate.

[0017] Further, the aluminum electrolysis waste in step 1 includes aluminum electrolysis overhaul slag and aluminum electrolyte.

[0018] Further, the alkali solution in step 2 is one or more of sodium hydroxide, potassium hydroxide and calcium hydroxide.

[0019] Further, in the step 2, the filtrate after the modified aluminum electrolyte is obtained is used for adjusting the pH value of the subsequent leaching solution.

[0020] Further, in the step 3, the solid-liquid ratio of the modified aluminum electrolyte after crushing and the low-concentration acid solution is 1g:1-5ml; the low-concentration acid solution is one or more of hydrochloric acid, sulfuric acid and nitric acid, and the acid solution concentration is 0.5-2mol / L; and the molar ratio of sodium fluoride to aluminum fluoride in the cryolite is 2.0-2.5.

[0021] Further, in the step 5, the neutralization adjustment is adjusted by using an alkali solution, wherein the alkali solution is an alkali solution or the alkali solution separated in the step 2.

[0022] Further, in the step 6, the water-soluble carbonate is one or both of sodium carbonate and potassium carbonate and a hydrate thereof, the phosphate is one or both of potassium phosphate and sodium phosphate, and the reaction time is 30-120min.

[0023] Further, in the step 7, the solid-liquid ratio of the cryolite to the lithium precipitation mother liquor is 1g:1-5ml; the concentration of carbonate or phosphate in the lithium precipitation mother liquor is 0.5-2mol / L;

[0024] Further, in the step 8, the acid concentration in the pickling process is 0.1-0.5mol / L, the solid-liquid ratio of the acid solution to the cryolite containing calcium phosphate or calcium carbonate is 1-3:1, the acid is one or more of hydrochloric acid and nitric acid, the water washing amount to the high-purity cryolite in the water washing process is 1-2:1, and the molar ratio of sodium fluoride to aluminum fluoride in the high-purity cryolite is 2.5-3.

[0025] Further, according to the application of any one of the aluminum electrolysis waste regeneration methods, the regenerated high-purity cryolite is reused in the aluminum electrolysis process, the obtained lithium carbonate or lithium phosphate product is used in the battery and semiconductor industries, the obtained sodium salt or potassium salt is used in the ceramic and fertilizer industries, and the obtained calcium chloride and calcium nitrate are used in the fertilizer and drying agent industries.

[0026] The beneficial effects of the present application are as follows:

[0027] The method of the present application obtains a modified aluminum electrolyte with high purity through alkali leaching or roasting modification, then uses a low-concentration acid solution for leaching, and obtains high-purity cryolite by reacting a lithium precipitation mother liquor with the cryolite, which is reused in the aluminum electrolysis process. The by-products (leaching solution) contain lithium, potassium, sodium and calcium metal ions, which have high economic value. The leaching solution is neutralized, impurities are removed, lithium is precipitated, and evaporation crystallization is performed to recover lithium, potassium, sodium and calcium salts, so that the aluminum electrolysis waste resources are fully recycled and utilized.

[0028] Compared with the prior art, the electrolyte is modified, the lithium and potassium ions in the electrolyte are replaced, the cryolite is purified, and the byproduct with high economic value is obtained.

[0029] The acid liquid used in the application has low concentration and is continuously consumed in the reaction process, and the leaching liquid produced will not damage the equipment and environment. The structure of the cryolite is not damaged in the reaction process, and the generated hydrofluoric acid is reacted with calcium and magnesium ions in the solution, and no hydrofluoric acid is generated.

[0030] The application can carry out the reaction under relatively low temperature conditions, thereby reducing the overall process cost.

[0031] The above description is only a summary of the technical solutions of the application, in order to more clearly understand the technical means of the application, and can be implemented according to the content of the specification, the following will be described in detail with the preferred embodiments of the application and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments or the prior art, the drawings needed in the embodiments will be briefly introduced below, and obviously, the drawings in the following description can be obtained by those skilled in the art without creative labor.

[0033] Figure 1 is a flowchart of the application; DETAILED DESCRIPTION

[0034] The application will be described in detail below in combination with the embodiments shown in the drawings, but it should be noted that these embodiments are not a limitation on the application, and equivalent transformations or replacements of functions and methods made by those skilled in the art based on these embodiments are within the protection scope of the application.

[0035] In order to objectively evaluate the technical effects of the embodiments of the application, the application will be described in detail by the following examples.

[0036] In the following examples, in order to ensure that the examples are compared under the same test conditions, the raw materials used in each example have the same properties, or are all obtained by the same method.

[0037] As shown in the following formula: Figure 1 The regeneration method of the aluminum electrolysis waste of the application comprises the following steps:

[0038] Step 1: crushing the aluminum electrolysis waste to be treated to obtain electrolysis waste particles;

[0039] Further, the aluminum electrolysis waste in step 1 includes aluminum electrolysis overhaul slag and aluminum electrolyte.

[0040] Further, the particle size of the electrolytic aluminum waste is 80-200 mesh. It is found through experimental research that the reaction can be sufficient when the particle size is between 80-200 mesh, less than 80 mesh cannot be fully reacted, and more than 200 mesh increases the cost and cycle.

[0041] Step 2: The electrolytic waste particles in step 1 are heated and leached with an alkali solution to modify or are calcined with alkali under low temperature conditions to obtain modified aluminum electrolyte; when the heating and leaching modification is performed, the solid-liquid ratio of the electrolytic waste particles to the alkali solution is 1g:2-10ml, and the molar concentration of the alkali solution is 1-2mol / L; when the calcination modification is performed, the mass ratio of alkali to electrolytic waste particles is 10%.

[0042] Further, the heating and leaching modification of the electrolytic waste particles with the alkali solution is specifically: the electrolytic waste particles and the alkali solution are mixed uniformly according to the ratio, heated at 70-90℃, and modified for 1-3h; the upper layer of carbon powder is obtained by screening and is recycled to the electrolytic aluminum process; the lower layer of solution containing modified aluminum electrolyte particles is separated by solid-liquid separation to obtain modified aluminum electrolyte.

[0043] Preferably, the screening-solid-liquid separation is specifically: the hot slurry is pumped into a filtering device, and a bubble scraper is directly used to collect the carbon powder on the upper layer of the solution and recycle it to the electrolytic aluminum process. The lower layer of solution containing modified aluminum electrolyte particles is separated by a centrifuge to obtain modified aluminum electrolyte, and the separation temperature is cooled to ≤50℃. The screening aperture is 80-200 mesh.

[0044] Further, the calcination modification is specifically: the electrolytic waste particles are uniformly mixed with 10% of the mass ratio of alkali, granulated, and calcined at a low temperature of 400-600℃ in a rotary kiln for 1-2h, and then screened through an 80-200 mesh sieve to obtain modified aluminum electrolyte. The particles larger than the 80-200 mesh sieve are recycled to the electrolytic aluminum process.

[0045] Further, the alkali solution in step 2 is one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0046] After the heating and leaching modification of the alkali solution in step 2, the filtrate remaining after obtaining the modified aluminum electrolyte is used for subsequent adjustment of the pH value of the leaching solution.

[0047] Step 3: The modified aluminum electrolyte in step 2 is crushed and mixed with a low-concentration acid solution, stirred and reacted at 0-30℃, filtered, and ice crystals and filtrate A are obtained.

[0048] Further, the solid-liquid ratio of the modified aluminum electrolyte after crushing in step 3 and the low-concentration acid liquid is 1g:1-5ml; the low-concentration acid liquid is one or several of hydrochloric acid, sulfuric acid, and nitric acid, and the acid liquid concentration is 0.5-2mol / L.

[0049] In the stirring reaction process, the low-concentration acid liquid dissolves lithium, potassium, calcium and other ions in the modified aluminum electrolyte, reduces the content of each ion in the cryolite, and improves the purity of the cryolite.

[0050] Step 4: The filtrate A in step 3 is a lithium-containing leaching solution. The lithium ion concentration in the filtrate A is detected by an instrument. If the lithium ion concentration in the filtrate A does not reach the ideal concentration, the filtrate is re-introduced into the reaction kettle to repeat step 3 to obtain a filtrate B with higher concentration and cryolite.

[0051] In step 3, the ratio of sodium fluoride to aluminum fluoride in the cryolite is 2.0-2.5, and it contains about 2% calcium fluoride. It does not reach the required purity of the cryolite for the aluminum electrolysis process. Subsequent purification operation is required. The composition of the cryolite in step 4 is basically the same as that obtained in step 3.

[0052] Further, the instrument for detecting the concentration of the leaching solution is an inductively coupled plasma emission spectrometer, an atomic absorption spectrometer, a flame photometer, etc.

[0053] Further, the filtrate is re-introduced into the reaction kettle to repeat step 3, which is specifically: the filtrate is introduced into the reaction kettle, and the modified aluminum electrolyte is crushed and re-introduced into the low-concentration acid liquid for re-leaching, so as to increase the concentration of the leaching solution and reduce the concentration of hydrogen ions in the leaching solution. After obtaining the ideal concentration, the filtrate B and the cryolite are separated and filtered. This step can be repeated multiple times.

[0054] Further, the lithium ion concentration in the filtrate A is 3-5g / L, and the hydrogen ion concentration is 0.1-0.4mol / L; the lithium ion concentration in the filtrate B is 12-16g / L, and the solution pH is 2-5. The filtrate A is the initial leaching solution, and the filtrate B is the leaching solution with a concentration of repeated leaching (leaching times≥2 times). Because the electrolyte needs to be leached with dilute acid, re-leaching can reduce the hydrogen ion concentration in the leaching solution and increase the solution concentration.

[0055] Step 5: The filtrate B after detection in step 4 is neutralized and adjusted to remove the remaining hydrogen ions, fluorine ions and aluminum ions in the solution. After separation and filtration, the filter residue and the filtrate C are obtained. The filtrate C is the final leaching solution. The filtrate A, the filtrate B and the filtrate C are all lithium-containing leaching solutions.

[0056] Further, in the step 5, the neutralization adjustment is adjusted by an alkali solution, wherein the alkali solution is an alkali liquor or the alkali solution separated in the step 2. Preferably, the alkali liquor can be one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, etc.

[0057] Further, in the step 5, the main components of the filter residue are calcium fluoride and aluminum hydroxide, and the calcium fluoride can be used as an electrolyte or as a raw material for producing hydrofluoric acid; the aluminum hydroxide is used as a flame retardant or in the plastic building material industry.

[0058] After adding the alkali liquor, the precipitate is aluminum hydroxide, calcium fluoride, etc. The solid-liquid separation is performed by a centrifuge or a plate and frame filter press.

[0059] When the modification is performed by roasting, the subsequent pH adjustment is performed by using the prepared alkali liquor.

[0060] Step 6: The filtrate C in step 5 is passed into a water-soluble carbonate or phosphate and heated and stirred to perform a lithium precipitation reaction; after separation and filtration, lithium carbonate or lithium phosphate products and a lithium precipitation mother liquor are obtained.

[0061] Further, according to the ratio of the amount of substance of carbonate in the water-soluble carbonate solution to the amount of substance of lithium ions in the filtrate C is 1-1.5:2, and the lithium precipitation reaction is performed at 70-90°C. According to the ratio of the amount of substance of phosphate in the phosphate to the amount of substance of lithium ions in the filtrate C is 1-1.5:2, and the lithium precipitation reaction is performed at 20-40°C.

[0062] Further, in the step 6, the water-soluble carbonate is one or both of sodium carbonate, potassium carbonate and hydrates thereof, and the phosphate is one or both of potassium phosphate and sodium phosphate; the reaction time is 30-120 min.

[0063] Step 7: The lithium precipitation mother liquor in step 6 is mixed with cryolite obtained in steps 3 and 4 in a proportion, and after sufficient stirring, solid-liquid separation is performed to obtain cryolite containing calcium phosphate or calcium carbonate.

[0064] Further, in the step 7, the mixing ratio of the lithium precipitation mother liquor to the cryolite in steps 3 and 4 is 1g:1-5ml; the concentration of phosphate or carbonate in the lithium precipitation mother liquor is 0.5-2mol / L.

[0065] Step 8: The cryolite containing calcium phosphate or calcium carbonate obtained in step 7 is subjected to acid washing to obtain high-purity cryolite; and after water washing and drying, it is used again in the electrolytic aluminum process; the acid liquor is recycled and reused.

[0066] Further, the acid concentration in the pickling process in step 8 is 0.1-0.5 mol / L, the solid-liquid ratio of the acid solution to the ice crystal containing calcium phosphate or calcium carbonate is 1-3:1; the acid is one or several of hydrochloric acid and nitric acid; the water washing amount and the solid-liquid ratio of the high-purity ice crystal in the water washing process are 1-2:1; the molar ratio of sodium fluoride to aluminum fluoride in the high-purity ice crystal is 2.5-3, and the content of calcium fluoride in the high-purity ice crystal is reduced to 0.1%-0.3% at this time; and the purity of the ice crystal can meet the requirements of the electrolytic aluminum process.

[0067] Step 9: The filtrate obtained in step 7 is concentrated and evaporated to obtain sodium or potassium salts containing chloride, carbonate, sulfate, nitrate and phosphate; and the neutral solution in step 8 is evaporated and concentrated to obtain calcium chloride or calcium nitrate.

[0068] The regenerated high-purity ice crystal can be reused in the electrolytic aluminum process.

[0069] The by-products produced in the application are used to prepare lithium carbonate or lithium phosphate products, which are applied to the battery and semiconductor industries. The potassium salt generated in the application can be used to produce potassium fertilizer, and the sodium salt can be used for ore smelting and glass-ceramic preparation. The calcium chloride obtained in the application is used in the industries of drying agent, chelating agent and salt making; and the calcium nitrate is used in the industries of salt making and fertilizer.

[0070] On the basis of the above, in order to better illustrate, the following is a specific example of application. Example 1

[0071] A regeneration method of aluminum electrolysis waste, the steps are as follows:

[0072] 1. Take 1 kg of electrolysis waste, use a jaw crusher and a vibration mill to crush the electrolysis waste into fine powder with a size of 80 mesh.

[0073] 2. Mix the aluminum electrolysis waste with 1 mol / L sodium hydroxide solution according to the solid-liquid ratio of 1:2, modify at 70°C for 1h, use a bubble scraper to recover the carbon powder, and use a filter or centrifuge to separate the remaining solution and the lower electrolyte at 50°C to obtain modified aluminum electrolyte.

[0074] According to instrument test, the ratio of sodium fluoride / aluminum fluoride in the modified aluminum electrolyte is 1.5, and the lithium oxide content is 2%.

[0075] 3. Add the separated modified aluminum electrolyte in the lower layer to 0.5 mol / L dilute hydrochloric acid solution according to the solid-liquid ratio of 1:3, stir at room temperature for 1h, and separate the ice crystal and the initial leaching solution. Among them, the ratio of sodium fluoride to aluminum fluoride in the ice crystal is 2.2, the lithium concentration in the lithium solution in the leaching solution is 2.5 g / L, and the remaining hydrogen ion concentration is 0.1 mol / L.

[0076] 4, the beginning of the leaching solution is re-introduced into the reactor, and new aluminum electrolyte is added, step 3 is repeated, after repeating 4 times, cryolite solid and repeated leaching solution are obtained, wherein the repeated leaching solution is: lithium ion concentration is 12g / L lithium-containing leaching solution.

[0077] 5, the repeated leaching solution of step 4 is adjusted to neutral by using the lye of step 2, and solid-liquid separation is carried out; through detection, the lithium ion concentration in the obtained final leaching solution is 10g / L, the precipitate is aluminum fluoride and aluminum hydroxide, the precipitate is recycled, the aluminum fluoride is reused in the electrolytic aluminum process, and the aluminum hydroxide is used as a flame retardant;

[0078] 6, according to the molar ratio of sodium carbonate to lithium ion 1:2, sodium carbonate solution is introduced into the final leaching solution, after the addition is completed, stirring reaction is carried out at 70℃ for 30min; solid-liquid separation is carried out, and lithium carbonate product with a purity of 98.5% and lithium precipitation mother liquor are obtained;

[0079] 7, the lithium precipitation mother liquor is mixed with the cryolite obtained in steps 3 and 4 according to a solid-liquid ratio of 1:2, fully stirred for 2h, and then solid-liquid separation is carried out to obtain cryolite containing calcium carbonate;

[0080] 8, the cryolite containing calcium carbonate in step 7 is acid washed according to a solid-liquid ratio of 1:2, the acid solution is a dilute hydrochloric acid solution with a concentration of 0.2mol / L, after acid washing, the cryolite is washed with solid water with a volume of 2 times, and high-purity cryolite is obtained;

[0081] Through detection, the molar ratio of sodium fluoride to aluminum fluoride in the cryolite is 2.7.

[0082] 9, the filtrate in step 7 is evaporated and concentrated to obtain calcium chloride, which is used in the salt industry to prepare other acid calcium salts. Example 2

[0083] A method for regenerating aluminum electrolysis waste, the steps of which are as follows:

[0084] 1, 1kg of electrolysis waste is weighed, and the electrolysis waste is crushed into fine powder with a size of 80 meshes using an e-type crusher and a vibration mill;

[0085] 2, the aluminum electrolysis waste is fully mixed with alkali according to a mass ratio of 10:1, low-temperature roasting modification is carried out at 400℃ for 1h, and after the modification is completed, the modified aluminum electrolyte is again crushed into fine powder with a size of 80 meshes.

[0086] Through instrument testing, the ratio of sodium fluoride to aluminum fluoride in the modified aluminum electrolyte is 1.5, and the lithium oxide content is 2%.

[0087] 3、The modified aluminum electrolyte is added to the 0.5 mol / L dilute hydrochloric acid solution according to the solid-liquid ratio of 1:3, and stirred at room temperature for 1 h. The carbon powder in the upper layer is recovered by using a bubble scraper, and the remaining solution and electrolyte are separated by solid-liquid separation to obtain cryolite and initial leaching solution. Among them, the sodium fluoride / aluminum fluoride ratio in the cryolite is 2.3, the lithium concentration in the leaching solution is 2.8 g / L, and the remaining hydrogen ion concentration is 0.15 mol / L;

[0088] 4、The initial leaching solution is introduced into the reaction kettle again, and new aluminum electrolyte is added, and step 3 is repeated. After repeating 5 times, cryolite solid and repeated leaching solution are obtained, and the repeated leaching solution is a lithium-containing leaching solution with a lithium ion concentration of 14 g / L.

[0089] 5、The repeated leaching solution of step 4 is adjusted to neutral by using the prepared calcium hydroxide solution, and solid-liquid separation is performed. The final leaching solution has a lithium ion concentration of 12 g / L, and the precipitate is calcium fluoride and aluminum hydroxide. The precipitate is recycled, the calcium fluoride is used as a raw material for producing hydrofluoric acid, and the aluminum hydroxide is used as a flame retardant.

[0090] 6、According to the molar ratio of sodium carbonate to lithium ions of 1:2, sodium carbonate solution is introduced into the final leaching solution. After the addition is completed, the solution is stirred at 70°C for 30 min. Solid-liquid separation is performed to obtain lithium carbonate products with a purity of 99.0% and a lithium precipitation mother liquor.

[0091] 7、The lithium precipitation mother liquor is mixed with the cryolite obtained in steps 3 and 4 according to a solid-liquid ratio of 1:2, and is stirred thoroughly for 2 h. After solid-liquid separation, a cryolite containing calcium carbonate is obtained.

[0092] 8、The cryolite containing calcium carbonate in step 7 is subjected to acid washing according to a solid-liquid ratio of 1:2, and the acid solution is a 0.2 mol / L dilute hydrochloric acid solution. After acid washing, the cryolite is washed with an amount of water that is twice the solid, and high-purity cryolite is obtained.

[0093] After detection, the molar ratio of sodium fluoride to aluminum fluoride in the high-purity cryolite is 2.8.

[0094] 9、The filtrate in step 7 is evaporated and concentrated to obtain calcium chloride, which is used in the salt industry to prepare other acid calcium salts. Example 3

[0095] The regeneration method of aluminum electrolytic waste in Example 3 is basically the same as that in Example 1, except for the following differences:

[0096] 1) In step 2, the solid-liquid ratio is changed from 1:2 to 1:10, and the concentration of sodium hydroxide solution is changed to 2 mol / L. After detection, the sodium fluoride / aluminum fluoride ratio in the cryolite is 1.8, and the lithium oxide content is 2.5%.

[0097] 2) Step 3, the concentration of dilute hydrochloric acid solution is changed to 2 mol / L, and after 2h reaction at room temperature, solid-liquid separation is carried out, and through detection, the obtained cryolite sodium fluoride / aluminum fluoride ratio is 2.2, and the lithium ion concentration in the initial leaching solution is 3.5g / L; after repeating 4 times, the lithium ion concentration in the repeated leaching solution is increased to 15g / L;

[0098] 3) According to the molar ratio of sodium carbonate to lithium ions 1.5:2, sodium carbonate solution is added, and stirring reaction is carried out at 90℃ for 90min, and the purity of the obtained lithium carbonate product is 99.5%;

[0099] 4) The molar ratio of sodium fluoride to aluminum fluoride in the obtained high-purity cryolite is 2.6. Example 4

[0100] The regeneration method of aluminum electrolysis waste in Example 4 is basically the same as that in Example 2, and the only difference is:

[0101] 1) In step 2, the electrolysis waste is mixed with 10% alkali by mass ratio, and then modified by calcination at 600℃ for 2h; through detection, the sodium fluoride / aluminum fluoride ratio in the electrolyte is 1.6, and the lithium oxide content is 2.3%;

[0102] 2) In step 3, the concentration of dilute hydrochloric acid solution is changed to 2 mol / L, and after 2h reaction at room temperature, solid-liquid separation is carried out, and through detection, the obtained cryolite sodium fluoride / aluminum fluoride ratio is 2.3, and the lithium ion concentration in the initial leaching solution is 3.4g / L; after repeating 4 times, the lithium ion concentration in the repeated leaching solution is increased to 16g / L;

[0103] 3) According to the molar ratio of sodium carbonate to lithium ions 1.5:2, sodium carbonate solution is added, and stirring reaction is carried out at 90℃ for 90min, and the purity of the obtained lithium carbonate product is 99.2%;

[0104] 4) The molar ratio of sodium fluoride to aluminum fluoride in the obtained high-purity cryolite is 2.6. Example 5

[0105] The regeneration method of aluminum electrolysis waste in Example 5 is basically the same as that in Example 1, and the only difference is:

[0106] 1) In step 3, the dilute hydrochloric acid solution is replaced with dilute sulfuric acid solution, and the acid concentration is 0.5mol / L. After reaction, detection is carried out to obtain the sodium fluoride / aluminum fluoride ratio in the cryolite is 2.0, and the lithium ion concentration in the initial leaching solution is 3g / L;

[0107] 2) According to the molar ratio of sodium carbonate to lithium ions 1.2:2, sodium carbonate solution is added, and stirring reaction is carried out at 90℃ for 90min, and the purity of the obtained lithium carbonate product is 99.2%;

[0108] 3) The generated lithium precipitation mother liquor is concentrated by evaporation to obtain sodium sulfate crystals, which are used to prepare water glass, glass, ceramic and other products.

[0109] 4) The molar ratio of sodium fluoride to aluminum fluoride in the obtained high-purity cryolite is 2.6. Example 6

[0110] The regeneration method of the aluminum electrolysis waste in Example 6 is basically the same as that in Example 3, except that:

[0111] 1) Sodium phosphate solid is added according to a sodium phosphate: lithium ion molar ratio of 1:3, and the reaction is stirred at 30°C for 60 min to obtain a lithium phosphate product with a purity of 90%;

[0112] 2) The generated lithium precipitation mother liquor is concentrated by evaporation to obtain sodium chloride crystals containing a small amount of sodium phosphate, and the sodium chloride is applied to the chlor-alkali industry; Example 7

[0113] The regeneration method of the aluminum electrolysis waste in Example 7 is basically the same as that in Example 1, except that:

[0114] 1) The dilute hydrochloric acid solution is replaced with a nitric acid solution with a concentration of 1.5 mol / L, and after the reaction, the leaching solution has a cryolite sodium fluoride / aluminum fluoride ratio of 2.4 and a lithium ion concentration of 3.1 g / L. Repeat step 3 operation, and after repeating 3 times, the leaching solution has a lithium ion concentration of 10 g / L;

[0115] 2) Sodium phosphate solid is added according to a sodium phosphate: lithium ion molar ratio of 1.5:3, and the reaction is stirred at 30°C for 60 min to obtain a lithium phosphate product with a purity of 91%;

[0116] 3) The generated lithium precipitation mother liquor is concentrated by evaporation to obtain sodium nitrate crystals containing a small amount of sodium phosphate, and the sodium nitrate is used as a raw material for the glass, ceramic, and fertilizer industries. Example 8

[0117] The regeneration method of the aluminum electrolysis waste in Example 8 is basically the same as that in Example 2, except that:

[0118] 1) In step 2, the electrolysis waste is mixed with 10% of the alkali by mass and then modified by calcination at 500°C for 2h;

[0119] After detection, the modified aluminum electrolyte has a sodium fluoride / aluminum fluoride ratio of 1.6 and a lithium oxide content of 2.1%;

[0120] 2) the concentration of the dilute hydrochloric acid solution in step 3 is changed to 2 mol / L of dilute sulfuric acid solution, and after reaction at room temperature for 2 h, solid-liquid separation is performed, and it is detected that the obtained cryolite sodium fluoride / aluminum fluoride ratio is 2.4, and the lithium ion concentration in the initial leaching solution is 3.4 g / L; after repeating 4 times, the lithium ion concentration is increased to 16 g / L;

[0121] 3) sodium carbonate solution is added according to a sodium carbonate: lithium ion molar ratio of 1.2:2, and stirring reaction is performed at 90℃ for 90 min, and a lithium carbonate product with a purity of 99.3% is obtained;

[0122] 4) the obtained high-purity cryolite has a sodium fluoride / aluminum fluoride molar ratio of 2.7. Example 9

[0123] The regeneration method of the aluminum electrolysis waste in Example 9 is basically the same as that in Example 2, and the only difference is that:

[0124] 1) in step 2, the electrolysis waste is uniformly mixed with 10% of alkali by mass, and then modified by calcination at 600℃ for 2 h;

[0125] It is detected that the modified aluminum electrolyte has a sodium fluoride / aluminum fluoride ratio of 1.6 and a lithium oxide content of 2.1%;

[0126] 2) in step 3, the concentration of the dilute hydrochloric acid solution is changed to 1 mol / L of dilute nitric acid solution, and after reaction at room temperature for 2 h, solid-liquid separation is performed, and it is detected that the obtained cryolite sodium fluoride / aluminum fluoride ratio is 2.4, and the lithium ion concentration in the initial leaching solution is 3.4 g / L; after repeating 4 times, the lithium ion concentration is increased to 16 g / L;

[0127] 3) sodium phosphate is added according to a sodium phosphate: lithium ion molar ratio of 1.2:2, and stirring reaction is performed at 30℃ for 90 min, and a lithium phosphate product with a purity of 92% is obtained;

[0128] 4) the obtained high-purity cryolite has a sodium fluoride / aluminum fluoride molar ratio of 2.8.

[0129] In order to better illustrate the effect of the present application, the following is a comparative example:

[0130] Comparative Example 1

[0131] The aluminum electrolyte is crushed and sieved to 80 mesh, and the cryolite sodium fluoride / aluminum fluoride ratio is 2.1 and the lithium oxide content is 2%;

[0132] The fine material is uniformly mixed with sodium hydroxide at a mass ratio of 1:1, and is calcined at 450℃ for 1 h to obtain a calcined material;

[0133] According to the solid-liquid ratio 1:10, pure water leaching is added to obtain filtrate A and residue A, and the filtrate A is adjusted to pH 9 using 10% hydrochloric acid solution to obtain cryolite product and filtrate B. The cryolite sodium fluoride / aluminum fluoride ratio is 2.4;

[0134] The residue A is dissolved using 10% dilute hydrochloric acid, and the pH is controlled at about 1.5 to obtain filtrate C;

[0135] Sodium hydroxide solution is added to the filtrate C to obtain a neutral leaching solution;

[0136] The neutral leaching solution is evaporated and concentrated, and sodium carbonate solution is added to the concentrated solution to prepare sodium carbonate, and finally a lithium carbonate product with a purity of 97.5% is obtained.

[0137] Comparative Example 2

[0138] The aluminum electrolyte is crushed and sieved to 80 mesh, and the cryolite sodium fluoride / aluminum fluoride ratio is 2.0, and the lithium oxide content is 2%;

[0139] The fine material is uniformly mixed with sodium hydroxide at a mass ratio of 1:1.5, and is calcined at 550°C for 2h to obtain calcined material;

[0140] According to the solid-liquid ratio 1:10, pure water leaching is added to obtain filtrate A and residue A, and the filtrate A is adjusted to pH 9 using 10% hydrochloric acid solution to obtain cryolite product and filtrate B. The cryolite sodium fluoride / aluminum fluoride ratio is 2.4;

[0141] The residue A is dissolved using 10% dilute hydrochloric acid, and the pH is controlled at about 1.5 to obtain filtrate C;

[0142] Sodium hydroxide solution is added to the filtrate C to obtain a neutral leaching solution;

[0143] The neutral leaching solution is evaporated and concentrated, and sodium carbonate solution is added to the concentrated solution to prepare sodium carbonate, and finally a lithium carbonate product with a purity of 97.5% is obtained.

[0144] Comparative Example 3

[0145] The aluminum electrolyte is crushed and sieved to 200 mesh, and the cryolite sodium fluoride / aluminum fluoride ratio is 2.1, and the lithium oxide content is 2%;

[0146] The fine material is uniformly mixed with sodium hydroxide at a mass ratio of 1.5:1, and is calcined at 450°C for 1h to obtain calcined material;

[0147] According to the solid-liquid ratio 1:10, pure water leaching is added to obtain filtrate A and residue A, and the filtrate A is adjusted to pH 9 using 10% hydrochloric acid solution to obtain cryolite product and filtrate B. The cryolite sodium fluoride / aluminum fluoride ratio is 2.4;

[0148] The filter residue A is dissolved with 10% dilute hydrochloric acid by mass fraction, and the pH is controlled at about 1.5 to obtain filtrate C;

[0149] Sodium hydroxide solution is added to the filtrate C to obtain a neutral leaching solution;

[0150] The neutral leaching solution is evaporated and concentrated, and sodium carbonate solution is added to the concentrated solution to prepare sodium carbonate, and finally a lithium carbonate product with a purity of 98.8% is obtained.

[0151] Comparative Example 4

[0152] A method for regenerating aluminum electrolysis waste, comprising the following steps:

[0153] 1. Take 1 kg of electrolysis waste, and use an e-type crusher and a vibration mill to crush the electrolysis waste into fine powder with a size of 60 mesh;

[0154] 2. Mix the aluminum electrolysis waste with 1 mol / L sodium hydroxide solution according to a solid-liquid ratio of 1:1, modify at 70°C for 1h, recover the carbon powder using a foam scraper, and separate the remaining solution and the lower electrolyte at 50°C using a filter or a centrifuge;

[0155] After instrument testing, the ratio of sodium fluoride / aluminum fluoride in the electrolyte is 1.5, and the lithium oxide content is 2%;

[0156] 3. Add the separated aluminum electrolyte in the lower layer to 0.5 mol / L dilute hydrochloric acid solution according to a solid-liquid ratio of 1:6, stir at room temperature for 1h, and separate the solid and the liquid to obtain high-purity cryolite and lithium-containing acidic leaching solution. Among them, the ratio of sodium fluoride / aluminum fluoride in the cryolite is 1.9, the lithium concentration in the leaching solution is 1.7g / L, and the remaining hydrogen ion concentration is 0.3mol / L;

[0157] 4. Reintroduce the leaching solution into the reaction kettle and add new aluminum electrolyte, repeat step 3 to obtain cryolite solid and lithium-containing leaching solution, and repeat 6 times to obtain lithium-containing leaching solution with a lithium ion concentration of 10g / L;

[0158] 5. Adjust the pH of the leaching solution in step 4 to neutral using the alkali solution in step 2, and separate the solid and the liquid. After testing, the lithium ion concentration in the leaching solution is 8g / L, the precipitate is aluminum fluoride and aluminum hydroxide, the precipitate is recycled, the aluminum fluoride is reused in the aluminum electrolysis process, and the aluminum hydroxide is used as a flame retardant;

[0159] 6. Pass sodium carbonate solution into the neutral leaching solution according to a sodium carbonate:lithium ion molar ratio of 1:2, stir at 70°C for 30min after the addition is completed; separate the solid and the liquid to obtain a lithium carbonate product with a purity of 97.6% and a lithium-containing mother liquor;

[0160] 7. The lithium-sink mother liquor is mixed with the cryolite obtained in step 3 and step 4 according to a solid-liquid ratio of 1:3, and stirred for 2 hours, and then solid-liquid separation is performed to obtain the cryolite containing calcium carbonate;

[0161] 8. The cryolite containing calcium carbonate in step 7 is subjected to acid washing according to a solid-liquid ratio of 1:2, and the acid solution is a dilute hydrochloric acid solution with a concentration of 0.2 mol / L, and then the cryolite is washed with solid water with a volume of 2 times, to obtain high-purity cryolite;

[0162] It is detected that the molar ratio of sodium fluoride to aluminum fluoride in the cryolite is 2.4.

[0163] Through comparison of the above examples and comparative examples, in the examples, the electrolyte is regenerated by using the method of the application, so that the purity of the cryolite in the electrolytic waste material can reach a degree that meets the requirements of the aluminum electrolysis process; and the purity of the lithium carbonate prepared by using the by-product can reach an industrial grade or even higher, and the purity of the lithium phosphate prepared is also above 90%; the cryolite prepared by using other processes or not according to the method of the application cannot meet the purity requirements of the aluminum electrolysis process; the leaching solution is used to prepare lithium salt, and the purity of the lithium carbonate prepared is low, which cannot reach an industrial grade, and needs to be purified again.

[0164] Through comparison, the method provided by the application can achieve one-step regeneration and purification of the cryolite in the electrolytic waste material, and can prepare industrial-grade lithium carbonate or even higher purity by one-step method. Compared with the prior art, the method has lower cost and higher efficiency.

[0165] Those skilled in the art can understand that the above-mentioned embodiments are specific examples for implementing the application, and in actual application, various changes can be made in form and details without departing from the spirit and scope of the application. The process parts and structures not described in detail in the embodiments are common knowledge in the industry, and are not described here.

Claims

1. A method for regenerating aluminum electrolysis waste, characterized in that, Includes the following steps: Step 1: Crush the aluminum electrolysis waste to be processed to obtain electrolysis waste particles; Step 2: Modify the electrolytic waste particles from Step 1 by heating and leaching with an alkaline solution, or by calcining the electrolytic waste particles with an alkali under low-temperature conditions to obtain modified aluminum electrolyte; during the heating and leaching modification, the solid-liquid ratio of the electrolytic waste particles to the alkaline solution is 1g:2-10ml, and the molar concentration of the alkaline solution is 1-2mol / L; during the calcination modification, the alkali accounts for 10% of the mass of the electrolytic waste particles. Step 3: The modified aluminum electrolyte pulverized in Step 2 is mixed with a low-concentration acid solution and stirred at 0-30℃. After stirring, the mixture is filtered to obtain cryolite and filtrate A. Step 4: The filtrate A in step 3 is a lithium-containing leachate. The lithium ion concentration in filtrate A is detected by an instrument. If the lithium ion concentration in filtrate A does not reach the ideal concentration, the filtrate is reintroduced into the reaction vessel, and step 3 is repeated to obtain filtrate B with a higher concentration and cryolite. The filtrate B is the concentration of the leaching solution for repeated leaching, and the leaching is performed ≥ 2 times; Step 5: Neutralize and adjust the filtrate B after the test in Step 4 to remove the remaining hydrogen ions, fluoride ions and aluminum ions in the solution. After separation and filtration, filter residue and filtrate C are obtained. Step 6: Pass the filtrate C from Step 5 into a water-soluble carbonate or phosphate solution, heat and stir to carry out the lithium precipitation reaction; after separation and filtration, the lithium carbonate or lithium phosphate product and the lithium precipitation mother liquor are obtained. Step 7: Mix the lithium precipitation mother liquor from Step 6 with the cryolite obtained from Steps 3 and 4 in a certain proportion, stir thoroughly, and then separate the solid and liquid to obtain cryolite containing calcium phosphate or calcium carbonate. Step 8: Acid wash the cryolite containing calcium phosphate or calcium carbonate obtained in Step 7 to obtain high-purity cryolite; then wash and dry it with water, and reuse it in the electrolytic aluminum process; the acid solution is recycled and reused until it becomes neutral before being replaced. Step 9: Concentrate and evaporate the filtrate obtained in Step 7 to obtain sodium or potassium salts containing chloride, carbonate, sulfate, nitrate, and phosphate; evaporate and concentrate the neutral solution in Step 8 to obtain calcium chloride or calcium nitrate.

2. The method for regenerating aluminum electrolysis waste according to claim 1, characterized in that, The aluminum electrolysis waste in step 1 includes aluminum electrolysis overhaul slag and aluminum electrolyte.

3. The method for regenerating aluminum electrolysis waste according to claim 1, characterized in that, In step 2, the alkali in the alkaline solution and the alkali used for calcination are either sodium hydroxide or potassium hydroxide, or calcium hydroxide.

4. The method for regenerating aluminum electrolysis waste according to claim 1, characterized in that, In step 2, during the alkaline solution heating and leaching modification, the remaining filtrate after obtaining the modified aluminum electrolyte is used for subsequent pH adjustment of the leaching solution.

5. The method for regenerating aluminum electrolysis waste according to claim 1, characterized in that, In step 3, the solid-liquid ratio of the pulverized modified aluminum electrolyte and the low-concentration acid solution is 1g:1-5ml; the low-concentration acid solution is one or more of hydrochloric acid, sulfuric acid, and nitric acid, and the acid solution concentration is 0.5-2mol / L; the molar ratio of sodium fluoride to aluminum fluoride in the cryolite is 2.0-2.

5.

6. The method for regenerating aluminum electrolysis waste according to claim 1, characterized in that, In step 5, neutralization adjustment is performed using an alkaline solution, which is either an alkaline solution or the alkaline solution separated in step 2.

7. The method for regenerating aluminum electrolysis waste according to claim 1, characterized in that, The water-soluble carbonate in step 6 is one or two of sodium carbonate, potassium carbonate and their hydrates, and the phosphate is one or two of potassium phosphate and sodium phosphate; the reaction time is 30-120 min.

8. The method for regenerating aluminum electrolysis waste according to claim 1, characterized in that, In step 7, the solid-liquid ratio of cryolite to lithium precipitation mother liquor is 1g:1-5ml; the concentration of carbonate or phosphate in the lithium precipitation mother liquor is 0.5-2mol / L.

9. A method for regenerating aluminum electrolysis waste according to claim 1, characterized in that, In step 8, the acid concentration during pickling is 0.1-0.5 mol / L, and the solid-liquid ratio of the acid to cryolite containing calcium phosphate or calcium carbonate is 1-3:1; the acid is one or more of hydrochloric acid and nitric acid; during water washing, the water washing volume to high-purity cryolite solid-liquid ratio is 1-2:1; the molar ratio of sodium fluoride to aluminum fluoride in the high-purity cryolite is 2.5-3.

10. The application of a method for regenerating aluminum electrolytic waste according to any one of claims 1-9, characterized in that, The recycled high-purity cryolite is reused in the electrolytic aluminum process, and the resulting lithium carbonate or lithium phosphate products are used in the battery and semiconductor industries; the resulting sodium or potassium salts are used in the ceramics and fertilizer industries. The obtained calcium chloride and calcium nitrate are used in the fertilizer and desiccant industries.

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