Method for treating fluorine and lithium in acid leaching cathode alkali leaching residue and jointly treating alkali leaching waste liquid

Abstract

The present application relates to a kind of methods for treating fluorine and lithium in acid leaching cathode alkali leaching residue and combined processing alkali leaching waste liquid, belong to aluminum electrolysis waste cathode recovery technical field, the alkali leaching residue of aluminum electrolysis waste cathode is added in AlCl3 solution ultrasonic leaching, and using hydrochloric acid adjusts leaching pH value, after leaching, solid-liquid separation obtains primary carbon powder and first filtrate;First filtrate returns system and is recycled, obtains electrolyte content relatively saturated final leaching solution;Primary carbon powder is washed with deionized water and is treated to obtain high-purity carbon powder;Final leaching solution is mixed with waste cathode alkali waste leaching liquid and is precipitated to obtain lithium-containing cryolite and precipitate liquid, and precipitate liquid can return alkali leaching system and be used for preparing alkali liquor.The present application effectively realizes the recovery of valuable material in alkali leaching residue and alkali leaching waste liquid in aluminum electrolysis waste cathode, simultaneously realizes the harmless treatment of waste cathode, greatly simplifies the recovery process of valuable material in alkali leaching residue and alkali leaching waste liquid of aluminum electrolysis waste cathode.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aluminum electrolysis waste cathode recovery, in particular to a method for acid leaching of fluorine and lithium in cathode alkali leaching residue and combined treatment of alkali leaching waste liquid. BACKGROUND

[0002] Waste cathode is one of solid wastes generated by the electrolytic aluminum industry. According to statistics, 50 Kg of electrolyte is consumed to produce 1 t of metal aluminum, and 30-50 Kg of waste cathode material is generated. Waste cathode is a mixture of multiple elements and multiple substances, which is listed as hazardous waste. At the same time, it contains carbon, sodium fluoride, cryolite, lithium fluoride and other substances with high recycling value, which can be regarded as a kind of concentrate, and has high recycling value.

[0003] At present, the treatment of waste cathode mainly includes physical method, high-temperature fire method and wet treatment method, etc. Through these treatment methods, the harmless and partial resource recovery of waste cathode are realized. The goals of waste cathode treatment are as follows: (1) harmless treatment: mainly aiming at the toxic substances in waste cathode, so that the waste cathode becomes a harmless solid after treatment; (2) recovery of valuable substances: mainly recovering various valuable components in waste cathode, such as carbon, fluorine, sodium, lithium, etc. The wet treatment method can well meet the two goals.

[0004] Wet treatment mainly separates and purifies various substances in waste cathode through the difference in solubility and chemical properties of the substances in the solution. Wet treatment mainly includes oxidation method, water immersion method and alkali leaching method, among which the alkali leaching method is a commonly used method. After alkali leaching of waste cathode, part of fluoride, lithium ions and alkali are still left in the leaching residue. The alkali concentration of the leaching liquid is too high to be treated, so the leaching residue and the leaching liquid need to be treated again. SUMMARY

[0005] In view of the problems in the background art, the application provides a method for acid leaching of fluorine and lithium in cathode alkali leaching residue and combined treatment of alkali leaching waste liquid. The method is characterized in that the alkali leaching residue of aluminum electrolytic waste cathode is treated by ultrasonic acid leaching with aluminum chloride solution, and hydrochloric acid is added to adjust the pH value during acid leaching, so that the fluorine and lithium in the waste cathode are effectively leached out. The acid leaching liquid and the alkali leaching residue of aluminum electrolytic waste cathode are combined for treatment, which can directly generate cryolite, effectively realizing the recovery of valuable substances in the alkali leaching residue and the alkali leaching waste liquid of aluminum electrolytic waste cathode, and realizing the harmless treatment of waste cathode.

[0006] To achieve the above purpose, the application is implemented by the following technical scheme:

[0007] The method for acid leaching of fluorine and lithium in cathode alkali leaching residue and combined treatment of alkali leaching waste liquid comprises the following steps:

[0008] (1) crushing the alkali leaching residue of the waste and old cathode;

[0009] (2) leaching the crushed alkali leaching residue of the waste and old cathode with AlCl3 solution under ultrasonic condition, and adding hydrochloric acid to adjust the pH value of the AlCl3 solution;

[0010] (3) liquid-solid separation, obtaining primary carbon powder and leaching solution;

[0011] (4) adding the leaching solution into the alkali leaching waste liquid of the waste and old cathode to produce cryolite.

[0012] Further, in step (2), the concentration of the AlCl3 solution is 0.2-1.2 mol / L, and the pH value is 0-1.7.

[0013] Further, the reaction end point pH value of step (4) is 13.6-9.

[0014] Further, the solid-liquid ratio of step (2) leaching is 1:3~8 g / mL, the leaching temperature is 50-70℃, and the leaching time is 20~120 min.

[0015] Further, the leaching solution of step (3) is recycled to step (2), and after the electrolyte in the leaching solution is relatively saturated, the leaching solution is added into the alkali leaching waste liquid of the waste and old cathode in step (4) as the final leaching solution.

[0016] Further, the alkali leaching residue of step (1) is crushed to a particle size of 200-800 mesh, and the material of 90~100wt.% is obtained.

[0017] Further, the primary carbon powder obtained in step (3) is washed with deionized water, solid-liquid separation, and drying, and then recovered; and the washing liquid is used to prepare the AlCl3 solution.

[0018] Further, the solid-liquid ratio g:mL of the primary carbon powder and deionized water is 1:1~3, and the water immersion washing time is 5~10 min.

[0019] The beneficial effects of the present application are:

[0020] 1. The present application realizes high leaching rate of fluorine and lithium in the alkali leaching residue of the waste and old cathode by leaching the alkali leaching residue of the waste and old cathode with aluminum chloride solution under ultrasonic condition, and adding hydrochloric acid to adjust the leaching pH value.

[0021] 2、The application adds aluminum chloride into the leaching solution when leaching the alkali leaching residue of the aluminum electrolysis waste cathode, and the aluminum chloride reacts with the fluoride and lithium ions in the alkali leaching residue when the final leaching solution is added into the alkali leaching residue, to generate lithium fluoride-containing cryolite. The leaching of the fluoride and lithium in the alkali leaching residue is realized, and the recovery of the fluoride and lithium ions in the alkali leaching residue is realized, so that the recovery process of the valuable substances in the alkali leaching residue of the aluminum electrolysis waste cathode and the alkali leaching residue is greatly simplified.

[0022] 3、The application can improve the leaching effect of the fluoride and lithium ions and save the amount of AlCl3 solution by recycling the leaching solution, and the fluoride in the alkali leaching residue can be fully reacted when the final acid leaching solution is reacted with the alkali leaching residue.

[0023] 4、The alkali leaching residue of the aluminum electrolysis waste cathode is leached under ultrasonic conditions, and the cavitation effect, mechanical effect and thermal effect of the ultrasonic waves are used to synergistically strengthen the leaching, so that the reaction can be accelerated, the leaching time can be shortened, and the leaching effect of the electrolyte can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The process flowchart of the application is shown in the figure;

[0025] Figure 2 The XRD comparison chart of the alkali leaching residue of the waste cathode before and after reaction in Example 1 is shown in the figure.

[0026] Figure 3 The SEM comparison chart of the alkali leaching residue of the waste cathode before and after reaction in Example 1 is shown in the figure. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and beneficial effects of the application clearer, the technical scheme of the application will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the application, not all the embodiments. Based on the embodiments of the application, other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0028] The following examples take the aluminum electrolysis waste cathode residue (hereinafter referred to as cathode alkali leaching residue) and alkali leaching residue (hereinafter referred to as alkali leaching residue) after alkali leaching from a certain factory. The main element content (wt.%) in the cathode alkali leaching residue is C 73.89%, Na 2.04%, F 2.66%, Al 3.84%, O 4.36%, and Li 0.25%. The main element concentration in the alkali leaching residue is F 19.35g / L and Li 265.8mg / L. Example 1

[0029] The method for leaching fluoride and lithium in the acid leaching cathode alkali leaching residue and jointly treating the alkali leaching residue is as follows:

[0030] (1) The cathode alkaline leaching residue is dried and crushed to a particle size of 200-800 mesh, and the material accounting for 95wt.% is obtained;

[0031] (2) An AlCl3 solution of 0.4mol / L is prepared, and the pH value of the AlCl3 solution is adjusted to 1.7 with hydrochloric acid (concentration of 3mol / L). After the preparation of the solution is completed, the cathode alkaline leaching residue particles are added to the leaching solution to start the ultrasonic intensification leaching process. The solid-liquid ratio g:mL of the cathode alkaline leaching residue and the leaching solution is 5:1, the ultrasonic power is 250W, the leaching temperature is 70℃, and the time is 40min. The primary carbon powder and the first filtrate are obtained by solid-liquid separation;

[0032] (3) The first filtrate returns to step (2) to leach new cathode alkaline leaching residue, and the leaching is repeated for 5 times to obtain the final filtrate;

[0033] (4) The primary carbon powder is washed by water immersion with deionized water, and the solid-liquid separation and vacuum drying are carried out to obtain high-purity carbon powder. The washing liquid is used to prepare the AlCl3 solution. The solid-liquid ratio g:mL of the primary carbon powder and the deionized water is 1:2, and the water immersion washing time is 3-5min.

[0034] (5) The final filtrate is slowly dropped into the alkaline leaching waste liquid for reaction, the reaction end point pH value is 10, and after the reaction, the solid-liquid separation is carried out, and the solid phase is vacuum dried to obtain lithium fluoride-containing cryolite. The lithium-containing cryolite returns to the aluminum electrolysis system for use, and the filtrate returns to the alkaline leaching system of the waste cathode for preparation of the alkaline solution.

[0035] The X-ray diffraction patterns of the cathode alkaline leaching residue and the high-purity carbon powder of the embodiment are shown in Figure 2 (the left graph is the cathode alkaline leaching residue, and the right graph is the high-purity carbon powder), and the comparison of the two graphs shows that Figure 2 After leaching, the characteristic peaks of calcium fluoride, conical cryolite (NaF 11 O 17 ) and other substances have disappeared;

[0036] The scanning electron microscope graphs of the cathode alkaline leaching residue before and after reaction, i.e. the comparison of the cathode alkaline leaching residue and the high-purity carbon powder, are shown in Figure 3 (the left graph is the cathode alkaline leaching residue, and the right graph is the high-purity carbon powder), and the comparison of the two graphs shows that Figure 3 From the graph before reaction, it can be seen that the carbon material structure is compact before leaching, and part of the bright substance is embedded in the carbon material, mainly fluoride, and is agglomerated into spherical shape. It is detected that the spherical fluoride is mainly calcium fluoride which is insoluble in alkali. From the graph after leaching, it can be seen that after ultrasonic assisted leaching, the carbon material structure is more compact, and the carbon material mainly presents a layered structure, and the morphology changes greatly compared with that before leaching. Because before leaching, most of the electrolyte in the cathode alkaline leaching residue is wrapped by the carbon layer, and the cavitation effect and high-speed vibration during ultrasonic leaching will open the carbon layer to make the electrolyte contact with the AlCl3 solution.

[0037] The fluoride content in the high-purity carbon powder of the embodiment is 1.05%, the lithium ion content is 0.06%, and the purity of the carbon powder is 97.56 wt.%; the fluoride concentration in the filtrate is 0.79 g / L, and the lithium ion concentration is 24.3 mg / L.

[0038] Comparative Example 1

[0039] The difference between the present comparative example and Example 1 is that no ultrasonic is introduced in steps (2) and (3);

[0040] The fluoride content in the high-purity carbon powder of the present comparative example is 1.36%, the lithium ion content is 0.13%, and the purity of the carbon powder is 88.35 wt.%; the fluoride concentration in the filtrate is 1.33 g / L, and the lithium ion concentration is 56.1 mg / L. Example 2

[0041] The method for treating fluoride and lithium in the acid leaching cathode alkali leaching residue and the alkali leaching waste liquid together, and the specific steps are as follows:

[0042] (1) The cathode alkali leaching residue is dried and crushed to 200-800 mesh in particle size, accounting for 95 wt.% of the alkali leaching residue particles, to obtain cathode alkali leaching residue particles;

[0043] (2) An AlCl3 solution with a concentration of 0.6 mol / L is prepared, and hydrochloric acid (concentration of 3 mol / L) is used to adjust the pH value of the AlCl3 solution to 1. After the preparation of the solution is completed, the cathode alkali leaching residue particles are added to the AlCl3 solution to start the ultrasonic enhanced leaching process. The solid-liquid ratio g:mL of the cathode alkali leaching residue to the leaching liquid is 6:1, the ultrasonic power is 250 W, the leaching temperature is 60°C, and the time is 40 min. The solid-liquid separation obtains primary carbon powder and a first filtrate;

[0044] (3) The first filtrate returns to step (2) to continue leaching new cathode alkali leaching residue into the leaching liquid for 5 times to obtain a final filtrate;

[0045] (4) The primary carbon powder is treated by deionized water leaching and washing, solid-liquid separation, and vacuum drying to obtain high-purity carbon powder. The washing liquid returns to the system for preparing the AlCl3 solution. The solid-liquid ratio g:mL of the primary carbon powder to deionized water is 1:2, and the water leaching and washing time is 3-5 min;

[0046] (5) The final filtrate is slowly dropped into the alkali leaching waste liquid to adjust the pH value to 10, the mixture is separated after precipitation, and the solid phase is vacuum dried to obtain lithium fluoride-containing cryolite which returns to the aluminum electrolysis system for use, and the filtrate returns to the alkali leaching system of the waste cathode for preparing alkali liquor.

[0047] The fluoride content in the high-purity carbon powder of the embodiment is 0.76%, the lithium ion content is 0.05%, and the purity of the carbon powder is 98.33 wt.%; the fluoride concentration in the filtrate is 0.11 g / L, and the lithium ion concentration is 25 mg / L. Example 3

[0048] The method for treating fluoride and lithium in the acid leaching cathode alkaline leaching residue and jointly treating alkaline leaching waste liquid is specifically as follows:

[0049] (1) The cathode alkaline leaching residue is dried and crushed to 95 wt.% of the cathode alkaline leaching residue particles with a particle size of 200-800 mesh, to obtain cathode alkaline leaching residue particles;

[0050] (2) An AlCl3 solution with a concentration of 0.8 mol / L is prepared, and the pH value of the AlCl3 solution is adjusted to 1 by using hydrochloric acid (concentration of 3 mol / L); after the preparation of the solution is completed, the cathode alkaline leaching residue particles are added to the AlCl3 solution to start the ultrasonic intensification leaching process. The solid-liquid ratio g:mL of the cathode alkaline leaching residue and the leaching liquid is 5:1, the ultrasonic power is 250 W, the leaching temperature is 60°C, and the time is 60 min. The primary carbon powder and the first filtrate are obtained through solid-liquid separation;

[0051] (3) The first filtrate returns to step (2) to continue leaching new cathode alkaline leaching residue into the electrolyte in the leaching liquid for 5 times to obtain the final filtrate;

[0052] (4) The primary carbon powder is treated by deionized water leaching and washing, solid-liquid separation, and vacuum drying to obtain high-purity carbon powder. The washing liquid returns to the system and is used for preparing the AlCl3 solution. The solid-liquid ratio g:mL of the primary carbon powder and deionized water is 1:2, and the water leaching and washing time is 3-5 min;

[0053] (5) The final filtrate is slowly dripped into the alkaline leaching waste liquid to adjust the pH value to 10, and after mixing and precipitation, solid-liquid separation is performed, and the solid phase is vacuum dried to obtain lithium fluoride-containing cryolite which returns to the aluminum electrolysis system for use, and the filtrate returns to the alkaline leaching system for preparing alkali liquor.

[0054] The fluoride content in the high-purity carbon powder of the embodiment is 0.45%, the lithium ion content is 0.03%, and the purity of the carbon powder is 99.17 wt.%; the fluoride concentration in the filtrate is 0.28 g / L, and the lithium ion concentration is 0.82 mg / L. Example 4

[0055] The method for treating fluoride and lithium in the acid leaching cathode alkaline leaching residue and jointly treating alkaline leaching waste liquid is specifically as follows:

[0056] (1) The cathode alkaline leaching residue is dried and crushed to 95 wt.% of the cathode alkaline leaching residue particles with a particle size of 200-800 mesh, to obtain cathode alkaline leaching residue particles;

[0057] (2) AlCl3 solution with concentration of 1 mol / L is prepared, and the pH value of the AlCl3 solution is adjusted to 0.8 by using hydrochloric acid (concentration of 3 mol / L), then the cathode alkaline leaching residue particles are added into the AlCl3 solution to start the ultrasonic enhanced leaching process. The solid-liquid ratio g:mL of the cathode alkaline leaching residue and the leaching solution is 7:1, the ultrasonic power is 250 W, the leaching temperature is 60°C, and the time is 90 min. The primary carbon powder and the first filtrate are obtained through solid-liquid separation;

[0058] (3) The first filtrate returns to step (2) to continue leaching new cathode alkaline leaching residue into electrolyte in the leaching solution for 5 times to obtain the final filtrate;

[0059] (4) The primary carbon powder is washed by water immersion with deionized water, solid-liquid separation, and vacuum drying to obtain high-purity carbon powder. The washing liquid returns to the system to be used for preparing the AlCl3 solution. The solid-liquid ratio g:mL of the primary carbon powder and the deionized water is 1:2, and the water immersion washing time is 3-5 min;

[0060] (5) The final filtrate is slowly dripped into the alkaline leaching waste liquid to adjust the pH value to 10, and then solid-liquid separation is performed after mixing and precipitation. The solid phase is vacuum dried to obtain cryolite containing lithium fluoride, which returns to the aluminum electrolysis system for use, and the filtrate returns to the alkaline leaching system for preparing the alkaline solution.

[0061] The fluoride content in the high-purity carbon powder of the embodiment is 0.38%, the lithium ion content is 0.03%, and the purity of the carbon powder is 99.42 wt.%. The fluoride concentration in the filtrate is 0.024 g / L, and the lithium ion concentration is 0.14 mg / L.

[0062] Comparative Example 2 without adding aluminum chloride solution during leaching

[0063] The method for acid leaching of the cathode alkaline leaching residue includes the following specific steps:

[0064] (1) The cathode alkaline leaching residue is dried and crushed to obtain cathode alkaline leaching residue particles, in which the particle size of 200-800 mesh accounts for 95 wt.%;

[0065] (2) Hydrochloric acid (concentration of 3 mol / L) is used to prepare a solution, and the pH value of the solution is adjusted to 0.8. The cathode alkaline leaching residue particles are added into the hydrochloric acid to start the ultrasonic enhanced leaching process. The solid-liquid ratio g:mL of the cathode alkaline leaching residue and the leaching solution is 7:1, the ultrasonic power is 250 W, the leaching temperature is 60°C, and the time is 90 min. The primary carbon powder and the first filtrate are obtained through solid-liquid separation;

[0066] (3) The first filtrate returns to step (2) to continue leaching new cathode alkaline leaching residue into electrolyte in the leaching solution for 5 times to obtain the final filtrate;

[0067] (4) The primary carbon powder is washed by water immersion with deionized water, solid-liquid separation, and vacuum drying to obtain carbon powder.

[0068] (5) slowly drop the final filtrate into the alkali leaching waste liquid to adjust the pH value to 10, and after mixing and precipitating, separate the solid and liquid.

[0069] The content of fluoride in the carbon powder of the present comparative example is 1.13%, the content of lithium ion is 0.06%, and the purity of the carbon powder is 98.14wt.%; the concentration of fluoride in the filtrate is 3g / L, the concentration of lithium ion is 147.5mg / L, and a large amount of fluoride and lithium ion cannot be precipitated.

[0070] Finally, it should be pointed out that the above preferred embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present application.

Claims

1. A method for treating fluorine and lithium in acid-leaching cathode residue and alkaline leaching wastewater in combination, characterized in that, The method comprises the following steps: (1) crushing the alkali leaching residue of the waste cathode; (2) leaching the crushed alkali leaching residue of the waste cathode with an AlCl3 solution under ultrasonic condition, and adding hydrochloric acid to adjust the pH value of the AlCl3 solution to 0-1.7; (3) liquid-solid separation to obtain primary carbon powder and leaching solution; (4) adding the leaching solution dropwise into the alkali leaching waste liquid of the waste cathode to produce cryolite; The leaching solution of step (3) is recycled to step (2), and after the electrolyte in the leaching solution is relatively saturated, the leaching solution is added dropwise into the alkali leaching waste liquid of the waste cathode in step (4) as the final leaching solution.

2. The method for treating fluorine and lithium in acid leaching cathode alkaline leaching residue and alkaline leaching waste liquid jointly according to claim 1, characterized in that, In step (2), the concentration of the AlCl3 solution is 0.2-1.2 mol / L.

3. The method for treating fluorine and lithium in acid leaching cathode alkaline leaching residue and alkaline leaching waste liquid jointly according to claim 1, characterized in that, In step (4), the pH value at the reaction endpoint is 13.6-9.

4. The method for treating fluorine and lithium in acid leaching cathode alkaline leaching residue and alkaline leaching waste liquid jointly according to any one of claims 1 to 3, characterized in that, In step (2), the solid-liquid ratio of the leaching is 1:3-8 g / mL, the leaching temperature is 50-70 ℃, and the leaching time is 20-120 min.

5. The method for treating fluorine and lithium in acid leaching cathode alkali leaching residue and alkali leaching waste liquid jointly according to claim 1, characterized in that, In step (1), the alkali leaching residue is crushed to a particle size of 200-800 mesh, and the material of 90-100 wt.% is obtained.

6. The method for treating the fluoride and lithium in the acid leaching cathode alkali leaching residue and the alkali leaching waste liquid jointly according to claim 1, characterized in that, The primary carbon powder obtained in step (3) is washed with deionized water, solid-liquid separated, and dried to be recovered; and the washing liquid is used to prepare the AlCl3 solution.

7. The method for treating fluorine and lithium in acid leaching cathode alkaline leaching residue and alkaline leaching waste liquid jointly according to claim 6, characterized in that, The solid-liquid ratio g:mL of the primary carbon powder and deionized water is 1:1-3, and the water immersion washing time is 5-10 min.

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