WO2024159599A1

WO2024159599A1 - Method for resource utilization of iron-aluminum slag

Info

Publication number: WO2024159599A1
Application number: PCT/CN2023/083923
Authority: WO
Inventors: 程青云; 郑宇�; 刘勇奇; 巩勤学; 李长东
Original assignee: 广东邦普循环科技有限公司; 湖南邦普循环科技有限公司
Priority date: 2023-01-31
Filing date: 2023-03-26
Publication date: 2024-08-08
Also published as: CN116103502B; CN116103502A

Abstract

The present application discloses a method for resource utilization of iron-aluminum slag, comprising adding an acid liquid to iron-aluminum slag for leaching and dissolving, extracting the leachate using a co-extraction extractant to obtain an iron-containing organic phase and an aluminum-containing raffinate, adding a sodium hydroxide solution to the aluminum-containing raffinate to react to obtain a sodium metaaluminate solution, then adding a first ammonium fluoride solution to react to prepare cryolite, adding a second ammonium fluoride solution to the iron-containing organic phase for reverse extraction, separating to obtain an organic phase and ammonium hexafluoroferrate, and adding aqueous ammonia to the ammonium hexafluoroferrate to react to obtain a solution of ferric hydroxide and ammonium fluoride. The ferric hydroxide can be further prepared to obtain a battery-grade iron phosphate product.

Description

A method for resource utilization of iron and aluminum slag

Technical Field

The present application belongs to the field of hydrometallurgy in waste battery recycling, and specifically relates to a method for resource utilization of iron and aluminum slag.

Background Art

In recent years, with the rapid development of consumer electronics, electric vehicles and various energy storage markets, the demand for lithium batteries has also skyrocketed. Among them, ternary lithium batteries are widely used due to their high energy density and good power. Ternary lithium batteries contain rich resources such as nickel, cobalt, and manganese. However, a large number of ternary lithium batteries have become waste ternary lithium batteries after batches of discharge. If the waste ternary lithium batteries are not properly disposed of, there is a risk of polluting the environment. Therefore, recycling and reusing waste ternary lithium batteries to prepare new ternary lithium batteries not only realizes resource regeneration, greatly reduces the pollution caused by waste batteries to the environment, but also reduces the preparation cost of ternary lithium batteries.

In the process of preparing ternary positive electrode precursors for recycling waste ternary lithium batteries, the commonly used process flow in the factory is: pretreatment-leaching-extraction-synthesis of ternary precursors. Among them, iron and aluminum removal is a very important step in leaching and impurity removal, and iron-aluminum slag, as the only outlet for iron and aluminum, often has the problems of large output and high processing cost. Patent CN105506290A introduces a method for comprehensive utilization of iron-aluminum slag: selectively leaching iron-aluminum slag to dissolve nickel, cobalt, aluminum, and iron in the slag; then adding sodium sulfide to the nickel, cobalt, and aluminum leaching solution, precipitating and recovering nickel and cobalt in the solution, and obtaining a crude aluminum sulfate solution; adding an oxidant and sodium hydroxide to the crude aluminum sulfate solution to remove the iron therein, and then adding sodium sulfate salt to prepare the solution into a stock solution for producing sodium aluminum sulfate; the stock solution is evaporated and crystallized to obtain a sodium aluminum sulfate product. Although this method of preparing sodium aluminum sulfate from ferroaluminum slag is simple, easy and low-cost, the selective leaching with sulfuric acid will result in incomplete separation of iron and aluminum, and cause loss and waste of the main metal - Fe in the ferroaluminum slag.

Summary of the invention

The present application aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present application proposes a method for resource utilization of iron-aluminum slag, using the iron-aluminum slag produced in the process of removing iron and aluminum from waste ternary batteries as raw materials, using new The carboxylic acid extractant BC196 and the phosphoric acid extractant P204 cooperate to separate iron and aluminum to obtain relatively pure iron and aluminum sources. After removing impurities and adding auxiliary materials to control the reaction conditions, iron phosphate and cryolite products are prepared, turning waste into treasure, conforming to the concept of environmental protection, and at the same time obtaining economic benefits through iron phosphate and cryolite products.

According to one aspect of the present application, a method for resource utilization of iron and aluminum slag is proposed, comprising the following steps:

S1: adding acid solution to the iron and aluminum slag for leaching and dissolution, and separating the solid and liquid to obtain the leachate;

S2: extracting the leachate with a synergistic extractant to obtain an iron-containing organic phase and an aluminum-containing raffinate, wherein the synergistic extractant is composed of an extractant BC196, an extractant P204 and solvent oil;

S3: adding sodium hydroxide solution to the aluminum-containing raffinate to react, filtering and removing impurities to obtain a sodium aluminate solution, and then adding the first ammonium fluoride solution to react to obtain cryolite; adding the second ammonium fluoride solution to the iron-containing organic phase to perform stripping, and separating to obtain an organic phase and ammonium hexafluoroferrate; cryolite preparation formula: 3Na ⁺ +6F ^- +4NH ₄ ⁺ +AlO ₂ ^- →Na ₃ AlF ₆ ↓+4NH ₃ ↑+2H ₂ O;

S4: adding ammonia water to the ammonium hexafluoroferrate to adjust the pH to 8.5-9.0 for reaction to obtain ferric hydroxide and ammonium fluoride solution.

In some embodiments of the present application, in step S1, the main metal components of the ferroaluminum slag include yellow sodium ferroaluminum slag and aluminum hydroxide.

In some embodiments of the present application, in step S1, the temperature of the leaching and dissolving is 85-95° C. Further, the reaction time of the leaching and dissolving is 3-4 hours.

In some embodiments of the present application, in step S1, the iron-aluminum slag is further ground before leaching, and the particle size of the iron-aluminum slag powder obtained by grinding is 200-500 meshes.

In some preferred embodiments of the present application, in step S1, the acid solution is a sulfuric acid solution with a mass concentration of 50%-80%. Further, the solid-liquid ratio of the iron-aluminum slag to the acid solution is 100-200 g/L.

In some embodiments of the present invention, in step S2, the extractant BC196 is a carboxylic acid compound, and its structure is: Wherein, m and n are each independently selected from integers of 1-21, and 10≤m+n≤22. Further, the extractant BC196 is provided by Suzhou Bocui Circulation Technology Co., Ltd.

In some embodiments of the present application, in step S2, in the synergistic extractant, the volume fraction of the extractant BC196 is 1%-10%, and the volume fraction of the extractant P204 is 25%-40%.

In some embodiments of the present application, in step S2, the solvent oil is at least one of kerosene, glycerol or octanol.

In some embodiments of the present application, in step S2, the volume ratio of the leaching solution to the co-extraction agent is 1:(2-4), and the extraction temperature is 10-45° C. Further, the extraction time is 5-10 min; further, the number of extraction stages is 3-5; further, the pH at the extraction equilibrium is 1.0-1.8.

In some embodiments of the present application, in step S3, the molar ratio of sodium hydroxide in the sodium hydroxide solution to aluminum ions in the aluminum-containing raffinate is (6-8):1.

In some embodiments of the present application, in step S3, the mass concentration of the sodium hydroxide solution is 40%-60%.

In some embodiments of the present application, in step S3, the temperature for adding the sodium hydroxide solution for reaction is 60-80° C., and the reaction time is 4-6 hours.

In some embodiments of the present application, in step S3, the molar ratio of ammonium fluoride in the first ammonium fluoride solution to sodium aluminate in the sodium aluminate solution is (6.5-8): 1. Furthermore, the mass concentration of the first ammonium fluoride solution is 20%-30%.

In some embodiments of the present application, in step S3, the temperature for adding the first ammonium fluoride solution to react is 85-95° C., and the reaction time is 1.5-3 h.

In some embodiments of the present application, in step S3, the mass concentration of the second ammonium fluoride solution is 20%-30%, and the volume ratio of the iron-containing organic phase to the second ammonium fluoride solution is (2-3):1.

In some embodiments of the present application, in step S3, the stripping temperature is 25-50° C. and the time is 3-8 min. Further, the stripping stage is single stage.

In some embodiments of the present application, in step S3, the separated organic phase is washed with water and then returned to step S2 for recycling as an extractant.

In some embodiments of the present application, during the process of preparing the cryolite in step S3, the reaction product also includes ammonia gas, and the ammonia gas is used to prepare the ammonia water in step S4.

In some embodiments of the present application, in step S4, the temperature for adding the ammonia water to react is 80-90° C. Furthermore, the time for adding the ammonia water to react is 0.5-1 h.

In some embodiments of the present application, in step S4, the ammonium fluoride solution is reused in step S3 as a raw material for preparing the cryolite or a stripping agent for the iron-containing organic phase.

In some embodiments of the present application, step S4 further includes: mixing the ferric hydroxide with phosphoric acid to react to obtain ferric phosphate. Specifically, the ferric hydroxide and phosphoric acid are mixed, the temperature is adjusted to 90-95°C, the pH is 1.8-2.0, the reaction is continued with stirring and then allowed to stand, and finally the ferric phosphate is obtained after cooling, filtering, washing, and drying. Furthermore, the method for adjusting the pH is to add ammonia water with a mass concentration of 20%-50%, and the stirring reaction time is continued for 2-3 hours; further, the standing time is 3-8 hours.

In some embodiments of the present application, in step S4, the mass concentration of the phosphoric acid is 40%-60%, and the molar ratio of the iron element in the ferric hydroxide to the phosphorus element in the phosphoric acid is 1:(1.1-1.3).

According to a preferred embodiment of the present application, at least the following beneficial effects are achieved:

1. The present application uses a novel carboxylic acid extractant BC196 and a phosphoric acid extractant P204 for synergistic extraction, which is not only low-cost and easy to industrialize, but also the synergistic extraction of the two improves the purity and extraction rate of the iron source in the organic phase (>95%), so that most of the aluminum, calcium, nickel, cobalt, and manganese enter the raffinate (extraction rate <1%), while achieving the dual effects of iron-aluminum separation and iron source impurity removal.

2. The present application adds excess sodium hydroxide for impurity removal, which can not only convert impurities such as iron, nickel, cobalt, and manganese in the raffinate into hydroxide precipitation and then filter to achieve impurity removal, but also convert aluminum ions in the raffinate into sodium aluminate, which becomes a precursor for preparing cryolite.

3. In the present application, ammonium fluoride is added to the aluminum resource recovery process to prepare cryolite, and the generated ammonia gas is collected and used to prepare an ammonia solution, which is used to adjust the pH of ammonium hexafluoroferrate obtained by stripping ammonium fluoride in the iron resource recovery process. While generating iron hydroxide, an ammonium fluoride solution is also obtained, thereby realizing the regeneration and circulation of ammonium fluoride and saving resources.

4. As a preferred embodiment, the organic phase is washed after stripping in the present application, so as to achieve the regeneration and circulation of the extractant and save resources.

5. This application utilizes the iron-aluminum slag as a resource to prepare cryolite and ferric hydroxide, which can be used to The battery-grade iron phosphate product can be prepared in one step, which not only reduces the amount of solid waste and lowers the outsourcing cost, but also has a simple process, low cost, and is easy to industrialize, thus achieving certain economic benefits.

BRIEF DESCRIPTION OF THE DRAWINGS

The present application is further described below with reference to the accompanying drawings and embodiments, wherein:

FIG1 is a process flow chart of Example 1 of the present application;

FIG2 is an XRD diagram of the iron-aluminum slag of Example 1 of the present application;

FIG3 is a 5000-fold SEM image of the iron-aluminum slag in Example 1 of the present application;

FIG4 is a SEM image of the iron-aluminum slag at 10,000 times magnification in Example 1 of the present application;

FIG5 is a SEM image of the iron-aluminum slag at 50,000 times magnification in Example 1 of the present application;

FIG6 is a SEM image of cryolite of Example 1 of the present application;

FIG7 is an XRD diagram of cryolite of Example 1 of the present application;

FIG8 is a SEM image of iron phosphate in Example 1 of the present application;

FIG. 9 is an XRD diagram of iron phosphate in Example 1 of the present application.

DETAILED DESCRIPTION

The following will clearly and completely describe the concept of the present application and the technical effects produced in combination with the embodiments, so as to fully understand the purpose, features and effects of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of them. Based on the embodiments of the present application, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present application.

Example 1

A method for resource utilization of iron and aluminum slag, referring to FIG1, the specific process is as follows:

(1) Obtain 100 g of ferroaluminum slag, the morphology of which is shown in Figures 3-5. The composition thereof is measured by XRD (Figure 2) as follows: sodium ferroaluminum-aluminum hydroxide. The metal content thereof is measured by ICP as follows: Fe: 10.10 wt%, Al: 6.30 wt%, Ni: 0.63 wt%, Co: 0.21 wt%, Mn: 0.41 wt%, Li: 0.13 wt%, Ca: 0.18 wt%, Mg: 0.01 wt%;

(2) Dry and grind the wet iron and aluminum slag to a particle size of 200 mesh, add 100 ml of pure water and 500 ml of concentrated Add 60% sulfuric acid, adjust the temperature to 85°C, stir at 300r/min for 4h, and filter and take 500ml of the leaching liquid;

(3) With a volume fraction of BC196-5% (provided by Suzhou Bocui Circulation Technology Co., Ltd., the structural formula is as follows: ), P204-30%, kerosene-65% synergistic extraction agent was used for 3-stage extraction at 25°C, the synergistic extraction agent and the leaching solution ratio O:A=2:1, the time was 8min, the stable pH was 1.55, and after extraction, 500ml of aqueous aluminum sulfate solution and iron-containing organic phase were separated;

(4) ICP detected that the Al content in the aqueous phase was 5.80 g/L, and a 40% sodium hydroxide solution was added, the molar amount of the added sodium hydroxide was 7 times the molar amount of aluminum ions in the solution, the temperature was adjusted to 80°C, and the reaction was stirred at a speed of 300 r/min for 4 hours; after cooling and filtration, a sodium aluminate solution was obtained, and then 140 ml of a 20% ammonium fluoride solution was added, the temperature was adjusted to 90°C, and the reaction was continued at a speed of 300 r/min for 3 hours. After standing for 1 hour, it was cooled, filtered, and dried to obtain 20.59 g of cryolite;

(5) adding a 30% ammonium fluoride solution to the iron-containing organic phase obtained in step (3) for stripping, wherein the ratio of the iron-containing organic phase to the ammonium fluoride solution during stripping is 2:1, the reaction time is 5 min, and the reaction temperature is 45° C. After stripping, the white precipitate and the organic phase are separated by standing, and the organic phase is washed with pure water and returned to step (3) for reuse as an extractant;

(6) collecting ammonia gas generated by the cryolite preparation reaction in step (4) and introducing it into pure water to prepare an ammonia solution, adjusting the temperature of the water bath where the white precipitate is located to 85° C., starting an automatic stirrer at a speed of 300 r/min, adding ammonia water thereto to adjust the pH to 8.74, continuing stirring for 0.5 hour, and filtering and separating to obtain a red iron hydroxide precipitate and an ammonium fluoride solution; the ammonium fluoride solution can be used for the cryolite preparation reaction in step (4) or as a stripping agent for stripping and reuse in step (5);

(7) According to the molar ratio of iron to phosphorus being 1:1.1, 24 ml of 40% phosphoric acid was added to the red precipitate, the temperature was adjusted to 95°C, stirring was started at a speed of 300 r/min, the pH was adjusted to 1.86 with 40% ammonia solution, and stirring was continued for 3 h. After standing for 8 h, 13.38 g of battery-grade iron phosphate product was prepared by filtering, washing and drying.

Example 2

A method for resource utilization of iron and aluminum slag, the specific process is:

(1) Obtain 100 g of ferroaluminum slag, and determine the composition thereof by XRD: sodium ferroaluminum-aluminum hydroxide, and determine the metal content thereof by ICP: Fe: 10.10 wt%, Al: 6.30 wt%, Ni: 0.63 wt%, Co: 0.21 wt%, Mn: 0.41 wt%, Li: 0.13 wt%, Ca: 0.18 wt%, Mg: 0.01 wt%;

(2) Dry and grind the wet iron-aluminum slag to a particle size of 200 mesh, add 100 ml of pure water and 500 ml of 80% sulfuric acid, adjust the temperature to 90° C., stir at 300 r/min for 3 h, and filter and collect 500 ml of the leaching solution;

(3) A three-stage extraction was carried out at 25° C. with a volume fraction of BC196-8% (provided by Suzhou Bocui Circulation Technology Co., Ltd.), P204-35%, and kerosene-57%. The ratio of the synergistic extractant to the leaching solution was O:A=2:1, the time was 5 min, and the stable pH was 1.34. After extraction, 500 ml of aqueous aluminum sulfate solution and an iron-containing organic phase were separated;

(4) ICP detected that the Al content in the aqueous phase was 6.08 g/L, and a 40% sodium hydroxide solution was added, the molar amount of the added sodium hydroxide was 7 times the molar amount of the aluminum ion, the temperature was adjusted to 80°C, and the reaction was stirred at a speed of 300 r/min for 5 hours; after cooling and filtration, a sodium aluminate solution was obtained, and then 146 ml of a 20% ammonium fluoride solution was added, the temperature was adjusted to 95°C, and the reaction was continued at a speed of 300 r/min for 3 hours. After standing for 1 hour, the mixture was cooled, filtered, and dried to obtain 22.12 g of cryolite;

(5) adding a 30% ammonium fluoride solution to the iron-containing organic phase obtained in step (3) for stripping, wherein the ratio of the iron-containing organic phase to the ammonium fluoride solution during stripping is 2:1, the reaction time is 6 min, the reaction temperature is 50° C., and after stripping, standing and separating to obtain a white precipitate and an organic phase, washing the organic phase with pure water and returning to step (3) for reuse as an extractant;

(6) collecting ammonia gas generated by the cryolite preparation reaction in step (4) and introducing it into pure water to prepare an ammonia solution, adjusting the temperature of the water bath where the white precipitate is located to 90° C., starting the automatic agitator at a speed of 300 r/min, adding ammonia water thereto to adjust the pH to 8.67, continuing stirring for 0.5 hour, filtering and separating to obtain a red iron hydroxide precipitate and an ammonium fluoride solution; the ammonium fluoride solution can be used for the cryolite preparation reaction in step (4) or as a stripping agent for stripping and reuse in step (5);

(7) According to the molar ratio of iron to phosphorus of 1:1.1, add 18 ml of 60% phosphoric acid to the red precipitate, adjust the temperature to 90°C, start stirring at 300 r/min, and adjust the pH with 40% ammonia solution. After the pH reaches 1.98, stirring is continued for 3 hours. After standing for 8 hours, filtration, washing and drying are performed to prepare 14.51 g of battery-grade iron phosphate product.

Example 3

(1) Obtain 100 g of ferroaluminum slag, and determine the composition thereof by XRD: yellow sodium iron alum-aluminum hydroxide, and determine the metal content thereof by ICP: Fe: 12.73 wt%, Al: 6.23 wt%, Ni: 0.98 wt%, Co: 0.52 wt%, Mn: 0.50 wt%, Li: 0.31 wt%, Ca: 0.23 wt%, Mg: 0.02 wt%;

(3) A three-stage extraction was carried out at 25° C. with a volume fraction of BC196-8% (provided by Suzhou Bocui Circulation Technology Co., Ltd.), P204-35%, and kerosene-57%. The ratio of the synergistic extractant to the leaching solution was O:A=2:1, the time was 5 min, and the stable pH was 1.18. After extraction, 500 ml of aqueous aluminum sulfate solution and an iron-containing organic phase were separated;

(4) ICP detected that the Al content in the aqueous phase was 5.98 g/L, and a 60% sodium hydroxide solution was added, the molar amount of the added sodium hydroxide was 8 times the molar amount of the aluminum ion, the temperature was adjusted to 80°C, and the reaction was stirred at a speed of 300 r/min for 5 hours; after cooling and filtration, a sodium aluminate solution was obtained, and then 144 ml of a 20% ammonium fluoride solution was added, the temperature was adjusted to 95°C, and the reaction was continued at a speed of 300 r/min for 3 hours. After standing for 1 hour, the mixture was cooled, filtered, and dried to obtain 21.03 g of cryolite;

(5) adding a 30% ammonium fluoride solution to the iron-containing organic phase obtained in step (3) for stripping, wherein the ratio of the iron-containing organic phase to the ammonium fluoride solution during stripping is 2:1, the reaction time is 5 min, the reaction temperature is 50° C., and after stripping, standing and separating to obtain a white precipitate and an organic phase, washing the organic phase with pure water and returning to step (3) for reuse as an extractant;

(6) collecting ammonia gas generated by the cryolite preparation reaction in step (4) and introducing it into pure water to prepare an ammonia solution, adjusting the temperature of the water bath where the white precipitate is located to 90° C., starting the automatic agitator at a speed of 300 r/min, adding ammonia water thereto to adjust the pH to 8.56, continuing stirring for 0.5 hour, and filtering and separating to obtain a red iron hydroxide precipitate and an ammonium fluoride solution; the ammonium fluoride solution can be used for the cryolite preparation reaction in step (4) or as a stripping agent for stripping and reuse in step (5);

(7) According to the molar ratio of iron to phosphorus being 1:1.1, 17 ml of 60% phosphoric acid was added to the red precipitate, the temperature was adjusted to 95°C, stirring was started at a speed of 300 r/min, the pH was adjusted to 1.83 with a 40% ammonia solution, and stirring was continued for 3 h. After standing for 8 h, 13.78 g of battery-grade iron phosphate product was prepared by filtering, washing and drying.

Comparative Example 1

A method for resource utilization of iron and aluminum slag, which differs from Example 1 in that no extractant BC196 is added, and the specific process is as follows:

(2) Dry and grind the wet iron-aluminum slag to a particle size of 200 mesh, add 100 ml of pure water and 500 ml of 60% sulfuric acid, adjust the temperature to 85° C., stir at 300 r/min for 4 h, and filter and collect 500 ml of leaching solution;

(3) performing a three-stage extraction at 25° C. with an extractant having a volume fraction of P204-30% and kerosene-70%, the ratio of the extractant to the leaching solution being O:A=2:1, the extraction time being 8 min, the stable pH being 1.55, and separating after extraction to obtain 500 ml of an aqueous phase and an iron-containing organic phase;

(4) ICP detected that the Al content in the aqueous phase was 4.87 g/L, and a 40% sodium hydroxide solution was added, the molar amount of the added sodium hydroxide was 7 times the molar amount of aluminum ions in the solution, the temperature was adjusted to 80°C, and the reaction was stirred at a speed of 300 r/min for 4 hours; after cooling and filtration, a sodium aluminate solution was obtained, and then 118 ml of a 20% ammonium fluoride solution was added, the temperature was adjusted to 90°C, and the reaction was continued at a speed of 300 r/min for 3 hours. After standing for 1 hour, the mixture was cooled, filtered, and dried to obtain 18.91 g of cryolite;

(6) The ammonia gas generated by the reaction of preparing cryolite in step (4) was collected and introduced into pure water to prepare an ammonia solution, the temperature of the water bath where the white precipitate was located was adjusted to 85° C., the automatic stirrer was started at a speed of 300 r/min, and the ammonia solution was added. After adjusting the pH to 8.73, stirring was continued for 0.5 hours, and red iron hydroxide precipitate and ammonium fluoride solution were obtained by filtration and separation; the ammonium fluoride solution can be used for the cryolite preparation reaction in step (4) or as a stripping agent for stripping and reuse in step (5);

(7) According to the molar ratio of iron to phosphorus being 1:1.1, 20 ml of 40% phosphoric acid was added to the red precipitate, the temperature was adjusted to 95°C, stirring was started at a speed of 300 r/min, the pH was adjusted to 1.84 with 40% ammonia solution, and stirring was continued for 3 h. After standing for 8 h, 11.11 g of battery-grade iron phosphate product was prepared by filtering, washing and drying.

Comparative Example 2

A method for resource utilization of iron and aluminum slag, which is different from Example 1 in that the composition of the synergistic extraction agent is different, and the specific process is:

(3) A three-stage extraction was carried out at 25° C. with a volume fraction of BC196-15%, P204-15%, and kerosene-70%, the ratio of the synergistic extractant to the leaching solution was O:A=2:1, the extraction time was 8 min, the stable pH was 1.55, and after extraction, 500 ml of aqueous phase and iron-containing organic phase were separated;

(4) ICP detected that the Al content in the aqueous phase was 5.07 g/L, and a 40% sodium hydroxide solution was added, the molar amount of the added sodium hydroxide was 7 times the molar amount of aluminum ions in the solution, the temperature was adjusted to 80°C, and the reaction was stirred at a speed of 300 r/min for 4 hours; after cooling and filtration, a sodium aluminate solution was obtained, and then 130 ml of a 20% ammonium fluoride solution was added, the temperature was adjusted to 90°C, and the reaction was continued at a speed of 300 r/min for 3 hours. After standing for 1 hour, it was cooled, filtered, and dried to obtain 18.67 g of cryolite;

(5) adding a 30% ammonium fluoride solution to the iron-containing organic phase obtained in step (3) for stripping, wherein the ratio of the iron-containing organic phase to the ammonium fluoride solution is 2:1, the reaction time is 5 min, the reaction temperature is 45° C., and after stripping, the white precipitate and the organic phase are separated by standing. The organic phase is washed with pure water and then returned to step (3) as the extraction Recycling of the agent;

(6) collecting ammonia gas generated by the cryolite preparation reaction in step (4) and introducing it into pure water to prepare an ammonia solution, adjusting the temperature of the water bath where the white precipitate is located to 85° C., starting an automatic stirrer at a speed of 300 r/min, adding ammonia water thereto to adjust the pH to 8.77, continuing stirring for 0.5 hour, and filtering and separating to obtain a red iron hydroxide precipitate and an ammonium fluoride solution; the ammonium fluoride solution can be used for the cryolite preparation reaction in step (4) or as a stripping agent for stripping and reuse in step (5);

(7) According to the molar ratio of iron to phosphorus being 1:1.1, 22 ml of 40% phosphoric acid was added to the red precipitate, the temperature was adjusted to 95°C, stirring was started at a speed of 300 r/min, the pH was adjusted to 1.89 with 40% ammonia solution and stirring was continued for 3 h. After standing for 8 h, 12.27 g of battery-grade iron phosphate product was prepared by filtering, washing and drying.

Performance Testing

Table 1 Synergistic extraction and separation effect

As can be seen from Table 1, the BC196+P204 synergistic extraction system used in this application can separate relatively pure Fe, with an extraction rate of >95%, while the extraction rate of other impurity ions is <1%. The synergistic extraction mainly utilizes the different selective complexing abilities of the two extractants for metal ions. The synergistic extraction can achieve a better complexing curve, thereby increasing the extraction rate of iron and reducing the extraction rates of aluminum and other impurities. Compared with the comparative example 1, which only uses P204 for extraction and separation, it effectively realizes deep extraction of iron, and the organic phase separated has fewer impurities, which improves the purity; the extractant components of the synergistic extraction system used in comparative example 2 exceed the BC196: 1%-10%, P204: 25-40% specified in this application, and its effect of separating iron and aluminum is obviously not as good as that of Example 1, and there are more impurity components in the organic phase.

Table 2 Cryolite performance test

As shown in Table 2, the quality of the cryolite product prepared in this application is better than that of the comparative example, and meets the national standard for cryolite products.

Standard: Al ≥ 12%, F ≥ 52%, Na ≤ 33%.

Table 3 Battery grade iron phosphate performance test

It can be seen from Table 3 that the quality of the battery-grade iron phosphate product produced in the present application is better than that of the control example, and meets the corporate standard Q/CSBP J061.001-2022 "Iron phosphate products from lithium battery waste recycling" of the Brunp Group: Fe is 35.8%-36.8%, P is 20.0%-21.0%, and the iron-phosphorus ratio is 0.96-1.02.

The embodiments of the present application are described in detail above in conjunction with the accompanying drawings, but the present application is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

A method for resource utilization of iron-aluminum slag, characterized in that it comprises the following steps:

S1: adding acid solution to the iron and aluminum slag for leaching and dissolution, and separating the solid and liquid to obtain the leachate;

S2: extracting the leachate with a synergistic extractant to obtain an iron-containing organic phase and an aluminum-containing raffinate, wherein the synergistic extractant is composed of an extractant BC196, an extractant P204 and solvent oil;

S3: adding a sodium hydroxide solution to the aluminum-containing raffinate to react, filtering and removing impurities to obtain a sodium aluminate solution, and then adding a first ammonium fluoride solution to react to obtain cryolite; adding a second ammonium fluoride solution to the iron-containing organic phase to perform stripping, and separating to obtain an organic phase and ammonium hexafluoroferrate;

S4: adding ammonia water to the ammonium hexafluoroferrate to adjust the pH to 8.5-9.0 for reaction to obtain ferric hydroxide and ammonium fluoride solution.
The method according to claim 1, characterized in that in step S2, the extractant BC196 is a carboxylic acid compound, and its structure is: wherein m and n are each independently selected from integers of 1-21, and 10≤m+n≤22.
The method according to claim 1 is characterized in that, in step S2, in the synergistic extractant, the volume fraction of the extractant BC196 is 1%-10%, and the volume fraction of the extractant P204 is 25%-40%.
The method according to claim 1, characterized in that in step S2, the solvent oil is at least one of kerosene, glycerol or octanol.
The method according to claim 1 is characterized in that, in step S2, the volume ratio of the leaching solution to the co-extraction agent is 1:(2-4), and the extraction temperature is 10-45°C.
The method according to claim 1 is characterized in that in step S3, the molar ratio of sodium hydroxide in the sodium hydroxide solution to aluminum ions in the aluminum-containing raffinate is (6-8):1.
The method according to claim 1, characterized in that in step S3, the molar ratio of ammonium fluoride in the first ammonium fluoride solution to sodium aluminate in the sodium aluminate solution is (6.5-8):1.
The method according to claim 1 is characterized in that, in the process of preparing the cryolite in step S3, the reaction product also includes ammonia gas, and the ammonia gas is used to prepare the ammonia water in step S4.
The method according to claim 1, characterized in that in step S4, the ammonium fluoride solution is recycled In step S3, it is used as a raw material for preparing the cryolite or as a stripping reagent for the iron-containing organic phase.
The method according to claim 1 is characterized in that step S4 further comprises: mixing the iron hydroxide and phosphoric acid to react to obtain iron phosphate.