Method for comprehensive recycling of waste cathode from aluminum electrolysis by water immersion-pressure purification

Abstract

The present application provides a method for comprehensive recycling of aluminum electrolysis waste cathode water leaching and pressurized purification, which relates to the field of solid waste recycling. The method comprises: mixing raw materials including aluminum electrolysis waste cathode, water and hydrogen peroxide, heating for water leaching, and then performing solid-liquid separation to obtain filtrate and water-leached material; mixing the water-leached material with concentrated sulfuric acid for a first high-pressure closed acid leaching, and performing solid-liquid separation on the reaction system to obtain filtrate residue; mixing the filtrate residue, concentrated sulfuric acid, concentrated hydrochloric acid, hydrogen peroxide solution and water, and performing a second high-pressure closed acid leaching, and performing solid-liquid separation on the reaction system to obtain artificial graphite. The method is simple to operate, has little corrosion to the equipment, and can not only obtain a graphite particle product with a fixed carbon content of more than 97%, but also recover the fluorine in the waste cathode in the form of hydrofluoric acid. On the basis of effectively solving the problem of fluoride pollution in the waste cathode, it also realizes the high-quality utilization of fluoride and graphite in the waste cathode.

Description

Technical Field

[0001] The present application relates to the field of solid waste treatment, and in particular to a method for comprehensive recycling of aluminum electrolysis waste cathodes by water immersion-pressurized purification. Background Art

[0002] The spent cathode of aluminum electrolysis is an important component of overhaul slag. During the long-term (usually 3-10 years) aluminum electrolysis process, due to the molten salt reaction and chemical reaction caused by thermal, chemical, mechanical erosion, electrical, sodium and electrolyte penetration, etc., the cathode of aluminum electrolysis will be infiltrated with NaF, AlF 3 、Al 2 O 3 , metallic sodium, Na 2 CO 3 , NaCN, etc.; when the cathode has large cracks, its conductivity changes significantly and may cause damage to the electrolytic cell, it needs to be removed and becomes a waste cathode. At present, there is no practical technology for harmless disposal of waste cathodes in China. Most companies use landfill or storage to dispose of them, but due to the solubility and high corrosiveness of fluorides, the disposal cost is very high and it is difficult to prevent long-term secondary pollution; some companies also use combustion methods, but the secondary pollution caused by fluorides is difficult to meet the requirements of environmental protection. Under the current environmental protection situation, electrolytic aluminum companies are in urgent need of applicable waste cathode harmless disposal and resource utilization technologies.

[0003] Researchers have conducted a lot of research on the harmless and resource-based disposal technology of waste cathodes. Shi Zhongning, Li Wei, et al. (Study on the Acid-Base Method for the Treatment of Waste Aluminum Electrolysis Cathodes, Master's Degree Thesis of Northeastern University) extracted graphite from waste cathode carbon blocks by alkali leaching followed by acid leaching at 60-100°C. This method has strict requirements on temperature and equipment, high cost, and is prone to cause serious corrosion to equipment and factory buildings, making it difficult to achieve industrial production; Patent CN107902649A (A method for treating waste cathode carbon blocks of electrolytic aluminum by combined ultrasonic alkali leaching and microwave digestion) uses ultrasonic alkali leaching to obtain carbon powder, and then microwave digestion under acidic conditions of 150-210°C and pressure of 0.1-2MPa to obtain graphite powder. This method has relatively harsh conditions, is prone to corrosion of equipment, is costly, and the purity of the obtained graphite is low; Patent CN 111170299 A (a method for recovering waste cathode carbon blocks from aluminum electrolysis) adopts the method of mixed pulping-pressure leaching-evaporation concentration-two-stage roasting-calcination to obtain purified carbon and uses alumina dry method to recover the fluorine-containing flue gas generated during the roasting process. Although this method can achieve clean treatment and comprehensive recovery of fluorine, aluminum and carbonaceous materials in waste cathodes, it uses wet process and pyroprocess to coordinate treatment, and the process is lengthy. Summary of the invention

[0004] The purpose of this application is to provide a method for comprehensive recycling of aluminum electrolysis waste cathode by water immersion-pressure purification to solve the above-mentioned problems.

[0005] To achieve the above objectives, this application adopts the following technical solutions:

[0006] A method for comprehensive recycling of aluminum electrolysis waste cathode by water leaching-pressurization purification, comprising:

[0007] Mixing raw materials including aluminum electrolysis waste cathode, water and hydrogen peroxide, heating and soaking, and then performing a first solid-liquid separation to obtain a filtrate and a material after soaking; evaporating and crystallizing the filtrate to obtain sodium fluoride;

[0008] The water-soaked material is mixed with concentrated sulfuric acid to perform a first high-pressure closed acid leaching, the gas obtained by the reaction is sent into water to obtain hydrofluoric acid, and the reaction system is subjected to a second solid-liquid separation to obtain filter residue;

[0009] The filtrate residue, concentrated sulfuric acid, concentrated hydrochloric acid, hydrogen peroxide solution and water are mixed and subjected to a second high-pressure closed acid leaching. The gas obtained by the reaction is sent into water to obtain a mixed solution of hydrofluoric acid and hydrochloric acid. The reaction system is subjected to a third solid-liquid separation to obtain artificial graphite.

[0010] Preferably, the aluminum electrolysis waste cathode is crushed to a particle size of less than or equal to 70 mm before use.

[0011] Preferably, during the water immersion, the mass of water is 2-4 times the mass of the aluminum electrolysis waste cathode, and the mass of hydrogen peroxide is 0.05%-0.1% of the mass of the aluminum electrolysis waste cathode.

[0012] Preferably, the water immersion temperature is 70-95°C and the time is 2-4h.

[0013] Preferably, the filtrate is reused 2-5 times before the evaporation crystallization.

[0014] Preferably, the pressure of the first high-pressure closed acid leaching is 0.5-5MPa, the temperature is 150-300°C, and the time is 1-3h;

[0015] Preferably, during the first high-pressure closed acid leaching, the mass ratio of concentrated sulfuric acid to the material after water leaching is 2-5:1.

[0016] Preferably, the filter residue is washed until the pH of the filtrate is 2-4 before use.

[0017] Preferably, during the second high-pressure closed acid leaching, the amount of concentrated sulfuric acid used is 10%-30% of the mass of the slag in the filter, the amount of concentrated hydrochloric acid used is 5%-10% of the mass of the slag in the filter, the amount of hydrogen peroxide solution used is 0.5%-2% of the mass of the slag in the filter, and the amount of water used is 20%-50% of the mass of the slag in the filter.

[0018] Preferably, the second high-pressure closed acid leaching has a pressure of 0.5-5 MPa, a temperature of 150-400° C., and a time of 0.5-2 h.

[0019] Preferably, the third solid-liquid separation further includes washing and drying;

[0020] Preferably, the material of the reaction equipment used in the first high-pressure closed acid leaching and the second high-pressure closed acid leaching is polytetrafluoroethylene or zirconium-hafnium alloy.

[0021] Compared with the prior art, the beneficial effects of this application include:

[0022] The method for comprehensive recycling of aluminum electrolysis waste cathodes by water leaching and pressure purification provided in the present application can not only obtain a graphite particle product with a fixed carbon content of more than 97% through water leaching, a first high-pressure closed acid leaching, and a second high-pressure closed acid leaching, but also recover the fluorine in the waste cathode in the form of sodium fluoride and hydrofluoric acid. On the basis of effectively solving the fluoride pollution problem of the waste cathode, it also realizes the high-quality utilization of fluoride and graphite in the waste cathode. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0024] Figure 1 A schematic flow chart of a method for comprehensive recycling of waste cathode from aluminum electrolysis by water leaching and pressure purification provided in an embodiment. DETAILED DESCRIPTION

[0025] As used herein:

[0026] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0027] The conjunction "consisting of excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed-ended so that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0028] When an amount, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described in this article, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0029] In these examples, parts and percentages are by mass unless otherwise indicated.

[0030] "Parts by mass" refers to the basic unit of measurement for expressing the mass ratio of multiple components. 1 part can represent any unit mass, such as 1g or 2.689g. If we say that the mass of component A is a parts and the mass of component B is b parts, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it means that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number, indicating a multiple factor). It should not be misunderstood that, unlike the mass parts, the sum of the mass of all components is not limited to 100 parts.

[0031] "And / or" is used to indicate that one or both of the stated situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0032] A method for comprehensive recycling of aluminum electrolysis waste cathode by water leaching-pressurization purification, comprising:

[0033] Mixing raw materials including aluminum electrolysis waste cathode, water and hydrogen peroxide, heating and soaking, and then performing a first solid-liquid separation to obtain a filtrate and a material after soaking; evaporating and crystallizing the filtrate to obtain sodium fluoride;

[0034] The water-soaked material is mixed with concentrated sulfuric acid to perform a first high-pressure closed acid leaching, the gas obtained by the reaction is sent into water to obtain hydrofluoric acid, and the reaction system is subjected to a second solid-liquid separation to obtain filter residue;

[0035] The filtrate residue, concentrated sulfuric acid, concentrated hydrochloric acid, hydrogen peroxide solution and water are mixed and subjected to a second high-pressure closed acid leaching. The gas obtained by the reaction is sent into water to obtain a mixed solution of hydrofluoric acid and hydrochloric acid. The reaction system is subjected to a third solid-liquid separation to obtain artificial graphite.

[0036] During the first high pressure closed acid leaching and the second high pressure closed acid leaching, the following reactions occur:

[0037] NaF+CaF 2 +AlF 3 +Na 3 AlF 6 +H 2 SO 4 +H 2 O→HF(l)+CaSO 4 +nNa 2 SO 4 ·Al 2 (SO

[0038] 4 ) 3 ·mH 2 O.

[0039] In an optional embodiment, the aluminum electrolysis waste cathode is crushed to a particle size of less than or equal to 70 mm before use.

[0040] In an optional embodiment, during the water immersion, the mass of water is 2-4 times the mass of the aluminum electrolysis waste cathode, and the mass of hydrogen peroxide is 0.05%-0.1% of the mass of the aluminum electrolysis waste cathode.

[0041] Optionally, during the water immersion, the mass of water can be 2 times, 3 times, 4 times or any value between 2-4 times the mass of the aluminum electrolysis waste cathode, and the mass of hydrogen peroxide can be 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1% or any value between 0.05%-0.1% of the mass of the aluminum electrolysis waste cathode.

[0042] In an optional embodiment, the water immersion temperature is 70-95° C. and the time is 2-4 hours.

[0043] Optionally, the water immersion temperature may be 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or any value between 70-95°C, and the immersion time may be 2h, 3h, 4h or any value between 2-4h.

[0044] In an optional embodiment, the filtrate is reused 2-5 times before performing the evaporative crystallization.

[0045] Optionally, the filtrate can be reused 2 times, 3 times, 4 times, or 5 times.

[0046] In an optional embodiment, the first high-pressure closed acid leaching has a pressure of 0.5-5 MPa, a temperature of 150-300° C., and a time of 1-3 h;

[0047] In an optional embodiment, during the first high-pressure closed acid leaching, the mass ratio of concentrated sulfuric acid to the material after water leaching is 2-5:1.

[0048] Optionally, the pressure of the first high-pressure closed acid leaching can be 0.5MPa, 1MPa, 1.5MPa, 2MPa, 2.5MPa, 3MPa, 3.5MPa, 4MPa, 4.5MPa, 5MPa or any value between 0.5-5MPa, the temperature can be 150℃, 200℃, 250℃, 300℃ or any value between 150-300℃, and the time can be 1h, 2h, 3h or any value between 1-3h; during the first high-pressure closed acid leaching, the mass ratio of concentrated sulfuric acid to the material after water leaching can be 2:1, 3:1, 4:1, 5: or any value between 2-5:1.

[0049] In an optional embodiment, the filter residue is washed until the pH of the filtrate is 2-4 before use.

[0050] Optionally, the filter residue is washed to a pH value of 2, 2.5, 3, 3.5, 4 or any value between 2 and 4 before use.

[0051] In an optional embodiment, during the second high-pressure closed acid leaching, the amount of concentrated sulfuric acid used is 10%-30% of the mass of the slag in the filter, the amount of concentrated hydrochloric acid used is 5%-10% of the mass of the slag in the filter, the amount of hydrogen peroxide solution used is 0.5%-2% of the mass of the slag in the filter, and the amount of water used is 20%-50% of the mass of the slag in the filter.

[0052] Optionally, during the second high-pressure closed acid leaching, the amount of the concentrated sulfuric acid may be 10%, 15%, 20%, 25%, 30% or any value between 10% and 30% of the mass of the slag in the filter; the amount of the concentrated hydrochloric acid may be 5%, 6%, 7%, 8%, 9%, 10% or any value between 5% and 10% of the mass of the slag in the filter; the amount of the hydrogen peroxide solution may be 0.5%, 1.0%, 1.5%, 2% or any value between 0.5% and 2% of the mass of the slag in the filter; and the amount of water may be 20%, 30%, 40%, 50% or any value between 20% and 50% of the mass of the slag in the filter.

[0053] In an optional embodiment, the second high-pressure closed acid leaching has a pressure of 0.5-5 MPa, a temperature of 150-400° C., and a time of 0.5-2 h.

[0054] Optionally, the pressure of the second high-pressure closed acid leaching can be 0.5MPa, 1MPa, 1.5MPa, 2MPa, 2.5MPa, 3MPa, 3.5MPa, 4MPa, 4.5MPa, 5MPa or any value between 0.5-5MPa, the temperature can be 150℃, 200℃, 250℃, 300℃, 350℃, 400℃ or any value between 150-400℃, and the time can be 0.5h, 1h, 1.5h, 2h or any value between 0.5-2h.

[0055] In an optional embodiment, the third solid-liquid separation further includes washing and drying;

[0056] In an optional embodiment, the material of the reaction equipment used in the first high-pressure closed acid leaching and the second high-pressure closed acid leaching is polytetrafluoroethylene or zirconium-hafnium alloy.

[0057] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If specific conditions are not specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0058] It should be noted that in this application, concentrated sulfuric acid is H 2 SO 4 Mass percentage 70% H 2 SO 4 The mass percentage of hydrochloric acid is 36-38% of HCl in aqueous solution, and the mass percentage of hydrogen peroxide is H 2 O 2 The mass percentage of H is 30% 2 O 2 of aqueous solution.

[0059] The raw materials are waste cathode carbon blocks after overhaul of an electrolytic aluminum plant, with the approximate composition (mass percentage): C: 63.34%, O: 2.52%, F: 12.31%, Na: 14.21%, Al: 3.25%, Si: 2.12%, S: 0.12%, Ca: 1.20%, Fe: 0.54%.

[0060] Example 1

[0061] like Figure 1As shown, this embodiment provides a method for comprehensive recycling of aluminum electrolysis waste cathode water leaching-pressurization purification, which specifically includes the following steps:

[0062] (1) crushing the waste cathode of aluminum electrolysis to -70 mm, then adding water twice the mass of the waste cathode and 0.05% hydrogen peroxide, heating to 75°C and soaking in water for 2 hours;

[0063] (2) filtering the slurry, reusing the filtrate three times, evaporating and crystallizing the filtrate to obtain a secondary sodium fluoride product with a yield (compared to the spent cathode) of 6.2%, and a cyanide content of 6 ppm in distilled water;

[0064] (3) adding the pellets after water leaching into an autoclave, and then adding concentrated sulfuric acid twice (by mass ratio) of the amount of waste cathode fed into the autoclave, pressurizing the autoclave to 0.5 MPa and then acid leaching for 1 hour;

[0065] (4) After pressurized acid leaching, the vent of the autoclave is opened, and the gas in the autoclave is passed into deionized water to obtain a hydrofluoric acid solution;

[0066] (5) Filter and wash the material in the autoclave, then add the resulting filter residue together with new concentrated sulfuric acid (10% of the waste residue mass), concentrated hydrochloric acid (10% of the waste residue mass), hydrogen peroxide solution (0.5% of the waste residue mass) and high-purity water into the autoclave, pressurize to 0.5 MPa, and acid leaching for 1 hour;

[0067] (6) After pressurized acid leaching, the vent of the autoclave is opened, and the gas in the autoclave is passed into water to obtain a mixed solution containing hydrofluoric acid and hydrochloric acid; then the cathode particles are poured out of the autoclave, filtered, washed, and dried to obtain artificial graphite particles with a carbon content of 97% and a cyanide content of 0 ppm in the filtrate.

[0068] Example 2

[0069] This embodiment provides a method for comprehensive recycling of aluminum electrolysis waste cathode by water immersion-pressurization purification, which specifically includes the following steps:

[0070] (1) crushing the waste cathode of aluminum electrolysis to -70 mm, then adding water twice the mass of the waste cathode and 0.05% hydrogen peroxide, heating to 75°C and soaking in water for 2 hours;

[0071] (2) filtering the slurry, reusing the filtrate three times, evaporating and crystallizing the filtrate to obtain a secondary sodium fluoride product with a yield (compared to the spent cathode) of 6.2%, and a cyanide content of 6 ppm in distilled water;

[0072] (3) Add the pellets after water leaching into an autoclave, then add concentrated sulfuric acid twice (by mass ratio) of the amount of waste cathode fed, pressurize the autoclave to 1.5 MPa, and then acid-leach for 1 hour;

[0073] (4) After pressurized acid leaching, the vent of the autoclave is opened, and the gas in the autoclave is passed into deionized water to obtain a hydrofluoric acid solution;

[0074] (5) Filter and wash the material in the autoclave, then add the resulting filter residue together with new concentrated sulfuric acid (10% of the waste residue mass), concentrated hydrochloric acid (10% of the waste residue mass), hydrogen peroxide solution (0.5% of the waste residue mass) and high-purity water into the autoclave, pressurize to 1.5 MPa, and acid leaching for 1 hour;

[0075] (6) After pressurized acid leaching, the vent of the autoclave is opened, and the gas in the autoclave is passed into water to obtain a mixed solution containing hydrofluoric acid and hydrochloric acid; then the cathode particles are poured out of the autoclave, filtered, washed, and dried to obtain artificial graphite particles with a carbon content of 97.8% and a cyanide content of 0 ppm in the filtrate.

[0076] Example 3

[0077] This embodiment provides a method for comprehensive recycling of aluminum electrolysis waste cathode by water immersion-pressurization purification, which specifically includes the following steps:

[0078] (1) crushing the waste cathode of aluminum electrolysis to -30 mm, then adding water twice the mass of the waste cathode and 0.1% hydrogen peroxide, heating to 85°C and soaking in water for 2 hours;

[0079] (2) filtering the slurry, reusing the filtrate three times, evaporating and crystallizing the filtrate to obtain a secondary sodium fluoride product with a yield (compared to the waste cathode) of 7.2%;

[0080] (3) adding the pellets after water leaching into an autoclave, and then adding concentrated sulfuric acid twice (by mass ratio) of the amount of waste cathode fed into the autoclave, pressurizing the autoclave to 3 MPa and then acid leaching for 2 h;

[0081] (4) After pressurized acid leaching, the vent of the autoclave is opened, and the gas in the autoclave is passed into deionized water to obtain a hydrofluoric acid solution;

[0082] (5) Filter and wash the material in the autoclave, then add the resulting filter residue together with new concentrated sulfuric acid (15% of the waste residue mass), concentrated hydrochloric acid (20% of the waste residue mass), hydrogen peroxide solution (0.1% of the waste residue mass) and high-purity water into the autoclave, pressurize to 3 MPa, and acid leaching for 2 hours;

[0083] (6) After pressurized acid leaching, the vent of the autoclave is opened, and the gas in the autoclave is passed into water to obtain a mixed solution containing hydrofluoric acid and hydrochloric acid; then the cathode particles are poured out of the autoclave, filtered, washed, and dried to obtain artificial graphite particles with a carbon content of 98.5% and a cyanide content of 0 ppm in the filtrate.

[0084] Comparative Example 1

[0085] Compared with Example 1, the leaching pressure of step (3) and step (5) of Example 2 is increased, and other conditions remain unchanged. The carbon content of the graphite finally obtained is 97.8%, indicating that lower pressure is not conducive to the removal of impurities such as fluorine, thereby affecting the purity of graphite.

[0086] Comparative Example 2

[0087] Compared with Example 1 and Example 2, in step (1) of Example 3, the particle size of the waste cathode is reduced, the water immersion temperature is increased, and the amount of hydrogen peroxide is increased. Other conditions remain unchanged. The yield of sodium fluoride is increased by 1 percentage point, and the cyanide content in distilled water is 4 ppm, indicating that reducing the particle size of the waste cathode and increasing the water immersion temperature are beneficial to the leaching of sodium fluoride, and increasing the amount of hydrogen peroxide is beneficial to increasing the decomposition rate of cyanide; the leaching pressure of step (3) and step (5) is increased and the leaching time is prolonged. Other conditions remain unchanged. The graphite carbon content of the finally obtained graphite fragments is 98.5%, indicating that higher leaching pressure and prolonged leaching time are beneficial to the removal of impurities such as fluorine.

[0088] The advantages of the method provided in the embodiment of the present application are:

[0089] 1. The present application utilizes concentrated sulfuric acid to react with non-carbon components in waste cathode carbon blocks in a high-temperature and high-pressure reactor to generate HF, and recovers gaseous HF through high-purity water. Compared with the roasting method, it effectively avoids the agglomeration problem caused by products such as calcium sulfate.

[0090] 2. This application uses a high-pressure autoclave liner and supporting pipes made of polytetrafluoroethylene or zirconium-hafnium alloy, which can work under strong acid and high temperature conditions.

[0091] 3. The leached liquid obtained by filtration in this application can be reused for high temperature and high pressure acid leaching and mixed acid oxidation leaching, effectively reducing the discharge of wastewater.

[0092] 4. The carbon content of the graphite product obtained by the two-stage leaching in this application is above 97%, and the recovery rate is basically 100%; the F element is also effectively recovered, and the recovery rate can reach above 90%, obtaining high-purity hydrofluoric acid and sodium fluoride of secondary grade or above.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0094] In addition, those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present application and form different embodiments. For example, in the above claims, any one of the claimed embodiments may be used in any combination. The information disclosed in this background technology section is intended only to deepen the understanding of the overall background technology of the present application and should not be regarded as an admission or in any form of implication that the information constitutes prior art known to those skilled in the art.

Claims

1. A method for comprehensive recycling of aluminum electrolysis waste cathode by water leaching-pressurization purification, characterized in that: include: Mixing raw materials including aluminum electrolysis waste cathode, water and hydrogen peroxide, heating and soaking, and then performing a first solid-liquid separation to obtain a filtrate and a material after soaking; evaporating and crystallizing the filtrate to obtain sodium fluoride; The water-soaked material and concentrated sulfuric acid are mixed for a first high-pressure closed acid leaching, the gas obtained by the reaction is fed into water to obtain hydrofluoric acid, and the reaction system is subjected to a second solid-liquid separation to obtain a filter residue; the pressure of the first high-pressure closed acid leaching is 0.5-5MPa, the temperature is 150-300°C, and the time is 1-3h; during the first high-pressure closed acid leaching, the mass ratio of concentrated sulfuric acid to the water-soaked material is 2-5:1; The slag in the filter, concentrated sulfuric acid, concentrated hydrochloric acid, hydrogen peroxide solution and water are mixed, and a second high-pressure closed acid leaching is performed, the gas obtained by the reaction is sent into water to obtain a mixed solution of hydrofluoric acid and hydrochloric acid, and the reaction system is subjected to a third solid-liquid separation to obtain artificial graphite; during the second high-pressure closed acid leaching, the amount of the concentrated sulfuric acid is 10%-30% of the mass of the slag in the filter, the amount of the concentrated hydrochloric acid is 5%-10% of the mass of the slag in the filter, the amount of the hydrogen peroxide solution is 0.5%-2% of the mass of the slag in the filter, and the amount of water is 20%-50% of the mass of the slag in the filter; the pressure of the second high-pressure closed acid leaching is 0.5-5MPa, the temperature is 150-400°C, and the time is 0.5-2h.

2. The method according to claim 1, characterized in that The aluminum electrolysis waste cathode is crushed to a particle size of less than or equal to 70 mm before use.

3. The method according to claim 1, characterized in that During the water immersion, the mass of water is 2-4 times the mass of the aluminum electrolysis waste cathode, and the mass of hydrogen peroxide is 0.05%-0.1% of the mass of the aluminum electrolysis waste cathode.

4. The method according to claim 1, characterized in that: The water immersion is carried out at a temperature of 70-95°C and for a time of 2-4 hours.

5. The method according to claim 1, characterized in that The filtrate is reused 2-5 times before the evaporation crystallization is performed.

6. The method according to claim 1, characterized in that The filter residue is washed before use until the pH of the filtrate is 2-4.

7. The method according to any one of claims 1 to 6, characterized in that: The third solid-liquid separation further includes washing and drying.

8. The method according to claim 1, characterized in that The material of the reaction equipment used in the first high-pressure closed acid leaching and the second high-pressure closed acid leaching is polytetrafluoroethylene or zirconium-hafnium alloy.

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