Method for comprehensively utilizing aluminum electrolysis waste

Abstract

The invention belongs to the technical field of aluminum electrolysis waste recovery treatment, and particularly relates to a comprehensive utilization method for aluminum electrolysis waste. The method comprises the following steps: after crushing the aluminum electrolysis waste, reacting the crushed aluminum electrolysis waste with an alkaline solution to generate a mixed solution containing a sodium metaaluminate component and filter residues A; washing the filter residue A for multiple times, and extracting a sodium fluoride saturated solution and a filter residue B; heating and evaporating the mixed solution to separate out sodium fluoride; the pH value of the solution is adjusted through carbon dioxide, and a high-purity aluminum hydroxide and sodium carbonate solution is prepared; separating the washed mixed solution by adopting an electrochemical method to obtain a hydrogen fluoride / ammonium fluoride solution and a sodium hydroxide / sodium carbonate / sodium bicarbonate solution; reacting the filter residue B with dilute acid to prepare a lithium-containing solution, purifying and concentrating, adding sodium carbonate to precipitate lithium to prepare a lithium carbonate product, and reacting aluminum hydroxide with hydrogen fluoride to prepare high-purity aluminum fluoride. According to the method, comprehensive recovery of the aluminum electrolysis waste is achieved, environmental pollution is effectively reduced, and the utilization rate of resources is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of recycling and processing of aluminum electrolysis waste, and specifically relates to a method for comprehensive utilization of aluminum electrolysis waste. Background Art

[0002] In the field of aluminum electrolysis industry, the electrolysis process inevitably produces a certain amount of waste. These wastes not only contain a large amount of aluminum, but also contain other valuable metal components. However, at present, the common methods for treating these aluminum electrolysis wastes include direct landfill, incineration, and simple physical recycling. These traditional methods have many disadvantages, such as waste of resources, increased environmental pollution, high treatment costs, and low recycling efficiency. Specifically, the direct landfill method not only occupies a large amount of land resources, but also may cause potential pollution to the soil and groundwater; and the simple physical recycling method often cannot effectively separate aluminum from other impurities, resulting in the recycled aluminum metal of low quality, which is difficult to meet the needs of industrial applications. In addition, although the incineration method can reduce the volume of waste to a certain extent, toxic gases will be generated during the incineration process, causing serious pollution to the atmospheric environment. Therefore, in order to achieve efficient and environmentally friendly treatment of aluminum electrolysis waste, it is urgent to develop new technical means to improve resource utilization, reduce environmental pollution, reduce treatment costs, and improve recycling efficiency. Summary of the invention

[0003] The purpose of the present invention is to provide a method for comprehensive utilization of aluminum electrolysis waste, aiming to solve the problems of low resource recovery rate, serious environmental pollution and incomplete treatment in the prior art, thereby improving resource recovery efficiency, reducing environmental impact, and promoting high value-added utilization of aluminum electrolysis waste.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A comprehensive recycling method for aluminum electrolysis waste, comprising the following steps:

[0006] Step 1: crushing the aluminum electrolysis waste to be treated, mixing it evenly with an alkaline solution and reacting it to obtain a mixed solution containing sodium metaaluminate, sodium fluoride, and sodium hydroxide and a filter residue A;

[0007] Step 2: washing the filter residue A obtained in step 1 with water for multiple times to obtain a saturated sodium fluoride solution and a filter residue B;

[0008] Step 3: heating the mixed solution obtained in step 1 to evaporate and precipitate sodium fluoride, introducing carbon dioxide into the filtrate after solid-liquid separation, adjusting the pH of the solution, and obtaining high-purity aluminum hydroxide and sodium carbonate solution; the aluminum hydroxide is used to prepare high-purity aluminum fluoride, and the sodium carbonate solution is used to subsequently prepare lithium carbonate;

[0009] Step 4: Separate the mixed solution of step 2 using an electrochemical method to generate a hydrogen fluoride / ammonium fluoride solution and a sodium hydroxide / sodium carbonate / sodium bicarbonate solution; the hydrogen fluoride / ammonium fluoride is used to prepare high-purity aluminum fluoride, and the sodium hydroxide / sodium carbonate / sodium bicarbonate solution is reused;

[0010] Step 5: reacting the filter residue B obtained in step 2 with a dilute acid solution to obtain a lithium-containing solution, and after removing impurities and concentrating, adding a sodium carbonate solution to carry out lithium precipitation reaction to obtain a lithium carbonate product;

[0011] Step 6: reacting the aluminum hydroxide prepared in steps 4 and 5 with hydrogen fluoride to prepare high-purity aluminum fluoride.

[0012] Preferably, the aluminum electrolysis waste includes one or more of aluminum electrolysis carbon slag, covering material, overhaul slag and aluminum electrolyte.

[0013] Preferably, the alkali is one or more of sodium hydroxide, sodium oxide, potassium oxide and potassium hydroxide.

[0014] Preferably, the mass ratio of the electrolytic waste: alkali is 1:0.3-0.9, and the solid-liquid ratio is 1:3-10.

[0015] Preferably, the mass ratio of the electrolytic waste: alkali is 1:0.5-0.8, and the solid-liquid ratio is 1:5-8.

[0016] Preferably, the reaction temperature range is 20-80°C, and the reaction time is 30-150 min.

[0017] Preferably, the reaction temperature range is 40-60° C., and the reaction time is 60-90 min.

[0018] Preferably, the solution is evaporated and concentrated until the fluoride ion concentration is ≤100 ppm, and the pH value of the solution is adjusted to 10-12.

[0019] Preferably, the fluoride ion concentration of the evaporated solution is ≤50 ppm, and the pH of the solution is adjusted to 10.5-11.

[0020] Preferably, the electrochemical method includes a bipolar membrane method, wherein the solution passing through the bipolar membrane is a sodium fluoride solution with an ion concentration of 4 g / L saturated solution; the bipolar membrane prepares a hydrogen fluoride solution with a concentration of 0.1-4 mol / L; and the prepared sodium hydroxide solution has a concentration of 0.1-4 mol / L.

[0021] Preferably, the electrochemical method includes an ion recombination method, using the FCDI method to obtain an ammonium fluoride solution and a sodium hydroxide solution or a sodium salt; the ammonium fluoride solution is used to prepare high-purity aluminum fluoride, and is reused in the sodium hydroxide solution or the sodium salt.

[0022] Preferably, the hydrogen fluoride solution is a hydrogen fluoride solution with a mass fraction of 0.4%-30%.

[0023] The method for comprehensive utilization of aluminum electrolysis waste of the present invention effectively solves the problems of low recycling efficiency, serious environmental pollution and incomplete treatment in the prior art, and has the following advantages:

[0024] 1. Through the combination of chemical reaction and electrochemical separation, efficient recovery of multiple valuable components in aluminum electrolysis waste is achieved;

[0025] 2. Using carbon dioxide to adjust the pH value of the solution is both environmentally friendly and economical, and high-purity aluminum hydroxide and sodium carbonate solutions are prepared at the same time;

[0026] 3. Through electrochemical separation technology, hydrogen fluoride / ammonium fluoride solution and sodium hydroxide / sodium carbonate / sodium bicarbonate solution are effectively separated, thus improving the utilization rate of resources;

[0027] 4. The filter residue B is treated with dilute acid to prepare a high-purity lithium carbonate product, thus realizing the high-value utilization of lithium resources;

[0028] 5. High-purity aluminum fluoride is prepared by the reaction of hydrogen fluoride and aluminum hydroxide, providing a new source of raw materials for the production of aluminum fluoride. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] A comprehensive recycling method for aluminum electrolysis waste, comprising the following steps:

[0032] Step 1: crushing the aluminum electrolysis waste to be treated, mixing it evenly with an alkaline solution and reacting it to obtain a mixed solution containing sodium metaaluminate, sodium fluoride, and sodium hydroxide and a filter residue A;

[0033] Step 2: washing the filter residue A obtained in step 1 with water for multiple times to obtain a saturated sodium fluoride solution and a filter residue B;

[0034] Step 3: heating the mixed solution obtained in step 1 to evaporate and precipitate sodium fluoride, introducing carbon dioxide into the filtrate after solid-liquid separation, adjusting the pH of the solution, and obtaining high-purity aluminum hydroxide and sodium carbonate solution; the aluminum hydroxide is used to prepare high-purity aluminum fluoride, and the sodium carbonate solution is used to subsequently prepare lithium carbonate;

[0035] Step 4: Separate the mixed solution of step 2 using an electrochemical method to generate a hydrogen fluoride / ammonium fluoride solution and a sodium hydroxide / sodium carbonate / sodium bicarbonate solution; the hydrogen fluoride / ammonium fluoride is used to prepare high-purity aluminum fluoride, and the sodium hydroxide / sodium carbonate / sodium bicarbonate solution is reused;

[0036] Step 5: reacting the filter residue B obtained in step 2 with a dilute acid solution to obtain a lithium-containing solution, and after removing impurities and concentrating, adding a sodium carbonate solution to carry out lithium precipitation reaction to obtain a lithium carbonate product;

[0037] Step 6: reacting the aluminum hydroxide prepared in steps 4 and 5 with hydrogen fluoride to prepare high-purity aluminum fluoride.

[0038] Preferably, the aluminum electrolysis waste includes one or more of aluminum electrolysis carbon slag, covering material, overhaul slag and aluminum electrolyte.

[0039] Preferably, the alkali is one or more of sodium hydroxide, sodium oxide, potassium oxide and potassium hydroxide. The reaction equation is:

[0040] Na 3 AlF 6 + 4NaOH=6NaF+NaAlO 2 +2H 2 O

[0041] Preferably, the mass ratio of the electrolytic waste: alkali is 1:0.3-0.9, and the solid-liquid ratio is 1:3-10.

[0042] Preferably, the mass ratio of the electrolytic waste: alkali is 1:0.5-0.8, and the solid-liquid ratio is 1:5-8.

[0043] Preferably, the reaction temperature range is 20-80°C, and the reaction time is 30-150 min.

[0044] Preferably, the reaction temperature range is 40-60° C., and the reaction time is 60-90 min.

[0045] Preferably, the solution is evaporated and concentrated until the fluoride ion concentration is ≤100 ppm, and the pH value of the solution is adjusted to 10-12.

[0046] Preferably, the fluoride ion concentration of the evaporated solution is ≤50 ppm, and the pH of the solution is adjusted to 10.5-11.

[0047] Preferably, the electrochemical method includes a bipolar membrane method, wherein the solution passing through the bipolar membrane is a sodium fluoride solution with an ion concentration of 4 g / L saturated solution; the bipolar membrane prepares a hydrogen fluoride solution with a concentration of 0.1-4 mol / L; and the prepared sodium hydroxide solution has a concentration of 0.1-4 mol / L.

[0048] Preferably, the electrochemical method includes an ion recombination method, using the FCDI method to obtain an ammonium fluoride solution and a sodium hydroxide solution or a sodium salt; the ammonium fluoride solution is used to prepare high-purity aluminum fluoride, and is reused in the sodium hydroxide solution or the sodium salt.

[0049] Preferably, the hydrogen fluoride solution is a hydrogen fluoride solution with a mass fraction of 0.4%-30%. The reaction equation is:

[0050] 3HF+Al(OH) 3 =AlF 3 +3H 2 O

[0051] 6NH 4 F+Al(OH) 3 =(NH 4 ) 3 AlF 6 +3NH 3

[0052]

[0053] Example 2

[0054] The method for comprehensive utilization of aluminum electrolysis waste in Example 1 is used to recycle aluminum electrolysis waste, and the steps are as follows:

[0055] Step 1: Weigh 500g of aluminum electrolyte, crush it into 100 mesh particles, and carry out mixed leaching according to the electrolytic waste: alkali mass ratio of 1:0.8 and the solid-liquid ratio of 1:3, and react at a temperature of 40°C for 90min to obtain a mixed solution of sodium aluminate, sodium hydroxide, sodium fluoride, etc.;

[0056] Step 2: Wash the filter residue in step 1 with water for 6 times at a solid-liquid ratio of 1:5, and collect a saturated sodium fluoride solution;

[0057] Step 3: heating and evaporating the mixed solution obtained in step 1 to precipitate sodium fluoride; after solid-liquid separation, introducing carbon dioxide into the filtrate to adjust the solution pH to 12 to obtain a high-purity aluminum hydroxide and sodium carbonate solution;

[0058] After testing, the fluoride ion concentration in the solution was 20 mg / L; the aluminum content in aluminum hydroxide was 33.24%, and the concentration of sodium carbonate solution was 120 g / L;

[0059] Step 4: using a bipolar membrane to separate the sodium fluoride solutions obtained in step 2 and step 3 to obtain a hydrogen fluoride solution and a sodium hydroxide solution; the hydrogen fluoride solution is used to prepare aluminum fluoride, and the sodium hydroxide is reused;

[0060] After testing, the concentration of hydrogen fluoride solution was 2.4 mol / L; the concentration of sodium hydroxide solution was 2.4 mol / L;

[0061] Step 5: washing and leaching the filter residue in step 1 with a 1.5 mol / L sulfuric acid solution to obtain a lithium-containing solution, removing impurities with sodium hydroxide, adding sodium carbonate at a lithium:carbonate molar ratio of 2:1 at 90° C. for 60 min, separating and washing to obtain a lithium carbonate product;

[0062] After testing, the purity of lithium carbonate is 99.51%, which meets the national standard requirements for battery-grade lithium carbonate;

[0063] Step 6: reacting the hydrogen fluoride solution prepared in step 4 with the aluminum hydroxide prepared in step 3 to prepare aluminum fluoride;

[0064] After testing, the prepared aluminum fluoride has a fluorine content of 60.28% and an aluminum content of 29.87%, which meets the national standard requirements for aluminum fluoride.

[0065] Example 3

[0066] The method for comprehensive utilization of aluminum electrolysis waste in Example 1 is used to recycle aluminum electrolysis waste, and the steps are as follows:

[0067] Step 1: Weigh 500g of aluminum electrolysis system, crush it into 100 mesh particles, and carry out mixed leaching according to the electrolytic waste: alkali mass ratio of 1:0.8 and the solid-liquid ratio of 1:3, and react at a temperature of 40°C for 90min to obtain a mixed solution of sodium aluminate, sodium hydroxide, sodium fluoride, etc.;

[0068] Step 2: Wash the filter residue in step 1 with water for 6 times at a solid-liquid ratio of 1:5, and collect a saturated sodium fluoride solution;

[0069] Step 3: heating and evaporating the mixed solution obtained in step 1 to precipitate sodium fluoride; after solid-liquid separation, introducing carbon dioxide into the filtrate to adjust the solution pH to 12 to obtain a high-purity aluminum hydroxide and sodium carbonate solution;

[0070] After testing, the fluoride ion concentration in the solution was 27.4 mg / L; the aluminum content in aluminum hydroxide was 32.59%; the concentration of sodium carbonate solution was 112 g / L;

[0071] Step 4: using an FCDI ion recombination device to separate the sodium fluoride solutions obtained in steps 2 and 3 to obtain an ammonium fluoride solution and a sodium carbonate solution; the hydrogen fluoride solution is used to prepare aluminum fluoride, and the sodium carbonate is reused;

[0072] After testing, the fluoride ion concentration in the ammonium fluoride solution was 20g / L; the concentration of the sodium carbonate solution was 103g / L;

[0073] Step 5: washing and leaching the filter residue in step 1 with a 1.5 mol / L sulfuric acid solution to obtain a lithium-containing solution, removing impurities with sodium hydroxide, adding sodium carbonate at a lithium:carbonate molar ratio of 2:1 at 90° C. for 60 min, separating and washing to obtain a lithium carbonate product;

[0074] After testing, the purity of lithium carbonate is 99.56%, which meets the national standard requirements for battery-grade lithium carbonate;

[0075] Step 6: reacting the hydrogen fluoride solution prepared in step 4 with the aluminum hydroxide prepared in step 3 to prepare aluminum fluoride;

[0076] After testing, the prepared aluminum fluoride has a fluorine content of 60.42% and an aluminum content of 29.36%, which meets the national standard requirements for aluminum fluoride.

[0077] Example 4

[0078] The method for comprehensive utilization of aluminum electrolysis waste in Example 4 is basically the same as that in Example 2, except that:

[0079] 1. Replace the electrolyte with aluminum electrolysis covering material;

[0080] 2. Carbon dioxide was introduced to adjust the pH to 10.5. After testing, the fluoride ion concentration in the solution was 17.8 mg / L; the aluminum content in aluminum hydroxide was 32.18%, and the concentration of sodium carbonate solution was 126 g / L;

[0081] 3. Preparation of bipolar membrane: Hydrogen fluoride solution concentration 2.2 mol / L; Sodium hydroxide solution concentration 2.2 mol / L;

[0082] 4. The purity of lithium carbonate products is 99.53%, which meets the national standard requirements for battery-grade lithium carbonate;

[0083] 5. The fluorine content of the prepared aluminum fluoride is 59.21%, and the aluminum content is 28.96%, which meets the national standard requirements for aluminum fluoride.

[0084] Example 5

[0085] The method for comprehensive utilization of aluminum electrolysis waste in Example 5 is basically the same as that in Example 3, except that:

[0086] 1. Replace the electrolyte with aluminum electrolysis overhaul slag;

[0087] 2. Carbon dioxide was introduced to adjust the pH to 11. After testing, the fluoride ion concentration in the solution was 35.4 mg / L; the aluminum content in aluminum hydroxide was 32.84%, and the concentration of sodium carbonate solution was 116 g / L;

[0088] 3. The ion recombination device contains sodium fluoride solution and ammonium bicarbonate solution respectively; the FCDI ion recombination prepares the ammonium fluoride solution with a fluoride ion concentration of 19g / L; the sodium bicarbonate solution has a concentration of 86g / L;

[0089] 4. Use the sodium bicarbonate solution prepared in step 3 to prepare lithium bicarbonate, and then heat to prepare a lithium carbonate product, the purity of the lithium carbonate product is 99.53%, which meets the national standard requirements for battery-grade lithium carbonate;

[0090] 5. The fluorine content of the prepared aluminum fluoride is 59.35%, and the aluminum content is 29.11%, which meets the national standard requirements for aluminum fluoride.

[0091] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A method for comprehensive utilization of aluminum electrolysis waste, characterized in that: The following steps are involved: Step 1: crushing the aluminum electrolysis waste to be treated, mixing it evenly with an alkaline solution and reacting it to obtain a mixed solution containing sodium metaaluminate, sodium fluoride, and sodium hydroxide and a filter residue A; Step 2: washing the filter residue A obtained in step 1 with water for multiple times to obtain a saturated sodium fluoride solution and a filter residue B; Step 3: heating the mixed solution obtained in step 1 to evaporate and precipitate sodium fluoride, introducing carbon dioxide into the filtrate after solid-liquid separation, adjusting the pH of the solution, and obtaining high-purity aluminum hydroxide and sodium carbonate solution; the aluminum hydroxide is used to prepare high-purity aluminum fluoride, and the sodium carbonate solution is used to subsequently prepare lithium carbonate; Step 4: Separate the mixed solution of step 2 using an electrochemical method to generate a hydrogen fluoride / ammonium fluoride solution and a sodium hydroxide / sodium carbonate / sodium bicarbonate solution; the hydrogen fluoride / ammonium fluoride is used to prepare high-purity aluminum fluoride, and the sodium hydroxide / sodium carbonate / sodium bicarbonate solution is reused; Step 5: reacting the filter residue B obtained in step 2 with a dilute acid solution to obtain a lithium-containing solution, and after removing impurities and concentrating, adding a sodium carbonate solution to carry out lithium precipitation reaction to obtain a lithium carbonate product; Step 6: reacting the aluminum hydroxide prepared in steps 4 and 5 with hydrogen fluoride to prepare high-purity aluminum fluoride.

2. The method for comprehensive utilization of aluminum electrolysis waste according to claim 1, characterized in that: The aluminum electrolysis waste in step 1 includes one or more of aluminum electrolysis carbon slag, covering material, overhaul slag and aluminum electrolyte. The alkali in the alkaline solution in step 1 is one or more of sodium hydroxide, sodium oxide, potassium oxide and potassium hydroxide. The mass ratio of electrolytic waste to alkali in step 1 is 1:0.3-0.9, and the solid-liquid ratio is 1:3-10.

3. The method for comprehensive utilization of aluminum electrolysis waste according to claim 1, characterized in that: In the step 1, the mass ratio of electrolytic waste to alkali is 1:0.5-0.8, and the solid-liquid ratio is 1:5-8.

4. The method for comprehensive utilization of aluminum electrolysis waste according to claim 1, characterized in that: The reaction temperature range in step 1 is 20-80° C., and the reaction time is 30-150 min.

5. The method for comprehensive utilization of aluminum electrolysis waste according to claim 1, characterized in that: The reaction temperature range in step 1 is 40-60° C., and the reaction time is 60-90 min.

6. The method for comprehensive utilization of aluminum electrolysis waste according to claim 1, characterized in that: In the step 3, the solution is evaporated and concentrated until the fluoride ion concentration is ≤100 ppm, and the pH value of the solution is adjusted to 10-12.

7. The method for comprehensive utilization of aluminum electrolysis waste according to claim 1, characterized in that: In step 3, the solution is evaporated and concentrated until the fluoride ion concentration is ≤50 ppm, and the pH value of the solution is adjusted to 10.5-11.

8. The method for comprehensive utilization of aluminum electrolysis waste according to claim 1, characterized in that: The electrochemical method in step 4 is a bipolar membrane method or an ion recombination method, wherein the solution in the bipolar membrane is a sodium fluoride solution, and the ion concentration is a 4g / L saturated solution; the bipolar membrane prepares a hydrogen fluoride solution with a concentration of 0.1-4mol / L; the prepared sodium hydroxide solution has a concentration of 0.1-4mol / L; the ion recombination method uses the FCDI method to obtain an ammonium fluoride solution and a sodium hydroxide solution or a sodium salt; the ammonium fluoride solution is used to prepare high-purity aluminum fluoride and is reused in a sodium hydroxide solution or a sodium salt.

9. The method for comprehensive utilization of aluminum electrolysis waste according to claim 1, characterized in that: The hydrogen fluoride solution in step 6 is a hydrogen fluoride solution with a mass fraction of 0.4%-30%.

10. A method for comprehensive utilization of aluminum electrolysis waste according to claims 1-9, characterized in that: The prepared high-purity aluminum fluoride is reused in the aluminum electrolysis process or used as a catalyst in the synthesis of organic compounds and organic fluorine compounds, and the obtained lithium carbonate or lithium phosphate products are used in the battery and semiconductor industries.

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