CN116947113A - A method for processing lithium cobalt oxide and lithium manganate mixed waste - Google Patents

Abstract

The invention discloses a method for processing mixed waste of lithium cobalt oxide and lithium manganate, which belongs to the field of waste lithium battery recycling and solves the problems of complex processes, environmental pollution and lithium loss existing in the existing processing methods. The method of the present invention: mixed waste materials are calcined; sulfuric acid and hydrogen peroxide are added to react and solid-liquid separation is carried out; calcined materials are added to the liquid, and sulfuric acid and hydrogen peroxide are reacted to solid-liquid separation; the liquid and liquid are heated; solid-liquid separation is performed while hot to obtain manganese sulfate crystals, and the liquid The temperature is lowered to obtain cobalt sulfate crystals, and the liquid is returned to the previous leaching step. The lithium in the liquid is continuously enriched. The pH is adjusted to prepare a mixture of cobalt hydroxide and manganese hydroxide, as well as a lithium sulfate solution, and the lithium is further recovered. The invention takes advantage of the different solubility characteristics of cobalt sulfate and manganese sulfate as the temperature changes. After the temperature changes, the supersaturation is used to crystallize and separate out the manganese sulfate and cobalt sulfate respectively. Multiple cycles of feeding can continuously precipitate manganese sulfate and cobalt sulfate.

Description

A method for processing lithium cobalt oxide and lithium manganate mixed waste

Technical field

The invention belongs to the field of waste lithium battery recycling, and specifically relates to a method for processing lithium cobalt oxide and lithium manganate mixed waste materials.

Background technique

With the rapid development of the lithium battery industry, more and more used lithium batteries are produced, causing waste of resources and environmental pollution. Therefore, it is of great significance to recycle valuable metals in used lithium batteries. Currently, the main processing methods for cathode materials of lithium cobalt oxide and lithium manganate include fire method and wet method. During wet recovery, solvent extraction is used to prepare cobalt sulfate and manganese sulfate from valuable metals. When recovering cobalt and manganese, the solvent extraction method requires saponification of the solvent first, and finally back-extraction to produce cobalt sulfate and sulfuric acid. manganese. This method requires the use of a large amount of organic solvents, has a complicated production process, easily causes environmental pollution, and produces a large amount of sodium sulfate decahydrate to take away valuable metal lithium.

Contents of the invention

The object of the present invention is to provide a method for processing lithium cobalt oxide and lithium manganate mixed waste to solve the problems of complex processes, environmental pollution, and lithium loss existing in existing treatment methods.

The technical solution of the present invention is: a method for processing lithium cobalt oxide and lithium manganate mixed waste, which includes the following steps:

A. Calculate the mixed waste of lithium cobalt oxide and lithium manganate under the condition of air flow;

B. Add a mixed solution of sulfuric acid and hydrogen peroxide to the calcined lithium cobalt oxide and lithium manganate mixed waste, the reaction temperature is 80-90°C, the reaction time is 1-3 hours, and then solid-liquid separation is performed to obtain leachate I and leach residue I;

C. Continue to add the calcined lithium cobalt oxide and lithium manganate mixed waste and the sulfuric acid and hydrogen peroxide mixed solution to the leachate I obtained in step B. The reaction temperature is 65-70°C, the reaction time is 1-3h, and solid-liquid separation is obtained For leach liquid II and leach residue II, the liquid temperature after filtration is maintained at 60-65°C;

D. Raise the temperature of the leachate II to no less than 95°C, separate the solid and liquid while it is hot, and keep the liquid temperature at 90-95°C after filtration to obtain manganese sulfate crystals and leachate III;

E. Continue to lower the temperature of leach solution III to 25-30°C, and finally obtain cobalt sulfate crystals and leach solution IV;

F. Return the leach solution IV to step C, repeat C-E to continuously precipitate out cobalt sulfate and manganese sulfate. When the lithium content in the leach solution reaches 20-25g/L, stop adding the calcined lithium cobalt oxide and lithium manganate mixed waste as well as sulfuric acid and The hydrogen peroxide mixed solution is heated to 90°C-95°C, the pH is adjusted to 11-12, and settled and filtered to obtain a mixture of cobalt hydroxide and manganese hydroxide, and a lithium sulfate solution, and then further recover lithium.

As a further improvement of the present invention, in step A, the calcination temperature is 500-700°C and the calcination time is 1-3h;

As a further improvement of the present invention, in step B, the amount of lithium cobalt oxide and lithium manganate mixed waste is added according to the concentration of manganese in the solution after leaching (leaching liquid I), which is 85-90g/L, and the concentration of cobalt is 100-110g. /L calculation.

As a further improvement of the present invention, in step C, the amount of mixed waste materials of lithium cobalt oxide and lithium manganate is added according to the concentration of manganese in the solution after leaching (leaching solution II), which is 170-180g/L, and the concentration of cobalt is 200-220g. /L calculation.

As a further improvement of the present invention, the leaching residue I and the leaching residue II are returned to step B to continue leaching and dissolving.

As a further improvement of the present invention, the steps for further recovering lithium are as follows:

S1. Add sodium carbonate to the lithium sulfate solution obtained in step F for reaction. The reaction time is 60-80 min, the reaction temperature is 90°C-100°C, and solid-liquid separation is performed to obtain lithium carbonate and carbonized liquid;

S2. Add acid to the carbonized liquid obtained in step S1 to adjust the pH to 5-6, and then freeze it. The freezing temperature is -10-0°C, the freezing time is 30-60 minutes, and solid-liquid separation is performed to obtain sodium sulfate decahydrate and sodium sulfate decahydrate. Lithium sulfate solution containing sodium sulfate;

S3. Evaporate and concentrate the hot-melt sodium sulfate decahydrate obtained in step S2 until the volume is 1/2-1/3 of the original volume, and separate the solid and liquid while hot to obtain a lithium-containing solution and Yuanming powder;

S4. Add phosphoric acid to the lithium-containing solution obtained in step S3, add alkali to adjust the pH to 10-11, and perform solid-liquid separation to obtain lithium phosphate.

As a further improvement of the present invention, in step S1, the amount of sodium carbonate used is 9-9.5 times the total lithium mass in the lithium sulfate solution.

As a further improvement of the present invention, the sodium sulfate-free lithium sulfate solution obtained in step S2 is returned to step B to continue leaching.

The beneficial effects of the present invention are:

1. The method of the present invention cleverly utilizes the different solubility characteristics of cobalt sulfate and manganese sulfate as the temperature changes. The solubility of cobalt sulfate gradually increases with the increase of temperature, and the solubility of manganese sulfate increases first with the increase of temperature. After increasing, it decreases. Manganese sulfate and cobalt sulfate have different degrees of saturation at the same temperature, causing manganese sulfate and cobalt sulfate to reach their respective supersaturation points. After the temperature changes, the supersaturation is used to crystallize and separate out manganese sulfate and cobalt sulfate respectively. Multiple cycles of feeding can continuously precipitate manganese sulfate and cobalt sulfate. The method of the invention avoids the use of organic solvents, does not pollute the environment, has simple process flow, is easy to control, and is low in cost.

2. The present invention uses a cyclic feeding method to continuously enrich lithium in the solution and facilitate recovery. A method of combining hot melting and freezing is used to recover valuable metal lithium in the by-product sodium sulfate decahydrate crystal water to reduce lithium loss. Usually, during the production process, due to long pipelines and large external temperature differences, the sodium sulfate generated is often sodium sulfate decahydrate crystallized water, which will dissolve part of the valuable metal lithium, causing the loss of lithium. In order to reduce the loss of lithium, the present invention uses a hot melt method to utilize the crystal water in sodium sulfate decahydrate to dissolve it into a solution, which changes the traditional method of adding a large amount of water to dissolve sodium sulfate decahydrate and greatly reduces the impact on the production system. volume requirements. After the solution evaporates, a large amount of anhydrous sodium sulfate will precipitate. Solid-liquid separation is performed while it is hot to obtain Yuanming powder. The lithium content in Yuanming powder is extremely low, which can effectively avoid the loss of metallic lithium. After the hot-melted solution is frozen, the sodium sulfate decahydrate can be completely separated from the solution to obtain a lithium sulfate solution without sodium sulfate decahydrate, which can be returned to the leaching process for recycling.

Detailed ways

The present invention will be described in detail below with reference to specific embodiments.

Example 1,

A method for processing lithium cobalt oxide and lithium manganate mixed waste, including the following steps:

A. Take 3000g of lithium cobalt oxide and lithium manganate mixed waste and calcine it under air flow conditions. The calcining temperature is 600°C and the calcining time is 2 hours;

B. Add 250ml sulfuric acid (98% concentrated sulfuric acid), 350ml hydrogen peroxide (35% hydrogen peroxide) and 400ml pure water to the calcined lithium cobalt oxide and lithium manganate mixed waste. The reaction temperature is 95°C and the reaction time is 80 minutes. After leaching, the concentration of cobalt in the solution is 110g/L and the concentration of manganese is 90g/L. Then the solid-liquid separation is performed to obtain leachate I and leach residue I; the temperature of leachate I is 66°C. Return leach residue I to step B to continue leaching. dissolve; dissolve

C. Continue to add the calcined lithium cobalt oxide and lithium manganate mixed waste and the sulfuric acid and hydrogen peroxide mixed solution to the leaching solution I obtained in step B. The amount of the lithium cobalt oxide and lithium manganate mixed waste is added according to the amount of manganese in the solution after leaching. The concentration is 180g/L, the cobalt concentration is 220g/L, the reaction temperature is 87°C, and the reaction time is 2h. Solid-liquid separation is performed to obtain leachate II and leaching residue II. After filtration, the liquid temperature is maintained at 63°C; return leaching residue II Step B continues leaching and dissolution; return the leaching residue I to Step B to continue leaching and dissolution;

D. Raise the temperature of the leachate II to 98°C, separate the solid and liquid while it is hot, and keep the liquid temperature at 95°C after filtration to obtain manganese sulfate crystals and leachate III;

E. Continue to lower the temperature of leach solution III to 26°C, and finally obtain cobalt sulfate crystals and leach solution IV;

F. Return the leachate IV to step C, repeat C-E to continuously precipitate out cobalt sulfate and manganese sulfate. When the lithium content in the leachate is enriched to 20g/L, stop adding the calcined lithium cobalt oxide and lithium manganate mixed waste as well as sulfuric acid and Mix the hydrogen peroxide solution, heat the leach solution to 93°C, add sodium hydroxide to adjust the pH to 12, settle and filter to obtain a mixture of cobalt hydroxide and manganese hydroxide, and a lithium sulfate solution;

G. Add sodium carbonate to the lithium sulfate solution obtained in step F for reaction. The amount of sodium carbonate is 9 times the total lithium mass in the lithium sulfate solution. The reaction time is 60 minutes. The reaction temperature is 90°C. Solid-liquid separation is performed to obtain lithium carbonate. and carbonized liquid;

H. Add sulfuric acid to the carbonized liquid obtained in step G to adjust the pH to 5, and then freeze it. The freezing temperature is -10°C, the freezing time is 60 minutes, and solid-liquid separation is performed to obtain sodium sulfate decahydrate and lithium sulfate without sodium sulfate. Solution; return the sodium sulfate-free lithium sulfate solution to step B to continue leaching;

1. The hot-melt sodium sulfate decahydrate obtained in step H is evaporated and concentrated until the volume is 1/3 of the original volume, and solid-liquid separation is performed while hot to obtain a lithium-containing solution and Yuanming powder;

J. Add 1.05 times the theoretical amount of phosphoric acid to the lithium-containing solution obtained in step I, add alkali to adjust the pH to 12, and perform solid-liquid separation to obtain lithium phosphate.

Example 2-Example 4,

The difference between Example 2-Example 4 and Example 1 is that in step A, the calcination temperature is different. The effect of calcination temperature on the slag yield in the acid leaching step is shown in Table 1.

It can be seen from Table 1 that when the calcination temperature is 650-700°C, the slag extraction rate during acid leaching is only 1%, and the slag extraction rate is low. Therefore, the calcination temperature is preferably 650°C.

Example 5-Example 8,

The difference between Example 5 to Example 8 and Example 1 is that in step A, the calcination time is different. The effect of calcination time on the slag yield rate in the acid leaching step is shown in Table 2.

It can be seen from Table 2 that when the calcination time is 2 hours, the slag yield rate during acid leaching is only 1%. If the reaction time is continued to be extended, there will be no improvement in the reduction of the slag yield rate in the acid leaching step. Therefore, the preferred reaction time is 2 h.

Example 9-Example 13,

The difference between Example 9-Example 13 and Example 1 is that in step B, the concentrations of cobalt and manganese in leachate I are different. The effects of different concentrations of cobalt and manganese in leach solution I on whether the crystals will saturate and crystallize are as shown in Table 3.

It can be seen from Table 3 that when the concentration of manganese in the leachate is 70-110g/L and the concentration of cobalt is 70-110g/L, the leachate I will not saturate and crystallize at 60-70°C after solid-liquid separation. Therefore, the preferred concentration of manganese is 85-90g/L and the concentration of cobalt is 100-110g/L.

Example 14-Example 19,

The difference between Example 14-Example 19 and Example 1 is that in step C, the concentration of manganese in the leachate II is different. The effects of different concentrations of manganese in leach solution II on whether the crystals will be saturated and precipitated are shown in Table 4.

It can be seen from Table 4 that when the concentration of manganese in leach solution II is less than 185g/L, manganese sulfate crystals will not precipitate at a temperature of 60-65°C after filtration. Therefore, the preferred concentration of manganese is 170-180g/L.

Embodiment 20-Embodiment 29,

The difference between Examples 20 to 29 and Example 1 is that in step C, the concentration of cobalt in the leach solution II is different. The effects of different concentrations of cobalt in leach solution II on whether the crystals will be saturated and precipitated are shown in Table 5.

It can be seen from Table 5 that when the concentration of cobalt in the leach solution is less than 230g/L, cobalt sulfate crystals will not precipitate at a temperature of 60-65°C after filtration. Therefore, the preferred concentration of cobalt is 200-220g/L.

Embodiment 30-Embodiment 36,

The difference between Examples 30 to 36 and Example 1 is that in step D, the temperature of the filtered liquid is different. The influence of the temperature of the filtered liquid on whether the manganese sulfate crystals will be saturated and crystallized is as shown in Table 6.

As can be seen from Table 6, solid-liquid separation is performed while hot, and the liquid temperature after filtration is maintained at 80-95°C to obtain manganese sulfate crystals. Therefore, it is preferable to keep the temperature of the filtered liquid at 90-95°C.

Embodiment 37-Embodiment 47,

The difference between Examples 37 to 47 and Example 1 is that the temperature of the leachate III in step E is different. The effects of different lowering temperatures of leach solution III on whether cobalt sulfate crystals will be saturated and crystallized are as shown in Table 7.

As can be seen from Table 7, cobalt sulfate crystals can be obtained when the temperature of leach solution III in step E is reduced to 25-50°C. Therefore, it is preferable to lower the temperature to 25-30°C.

Embodiment 48-Embodiment 51,

The difference between Example 48-Example 51 and Example 1 is that in step G, the reaction time after adding sodium carbonate is different. The effect of reaction time on the conversion rate of lithium carbonate is shown in Table 8.

It can be seen from Table 8 that when the reaction time in step G is 60 minutes, the conversion rate of lithium carbonate can reach about 99%. Continuing to extend the reaction time has little effect on the conversion rate of lithium carbonate. Therefore, the optimal reaction time is 60 minutes.

Embodiment 52-Embodiment 55,

The difference between Example 52-Example 55 and Example 1 is that the reaction temperature after adding sodium carbonate in step G is different. The effect of reaction temperature on the conversion rate of lithium carbonate is shown in Table 9.

It can be seen from Table 9 that when the reaction time in step G is 90 minutes, the conversion rate of lithium carbonate can reach about 99%. Continuing to increase the reaction temperature has little effect on the conversion rate of lithium carbonate. Therefore, the preferred reaction temperature is 90°C.

Embodiment 56-Embodiment 65,

The difference between Examples 56 to 65 and Example 1 is that in step H, the freezing temperature is different. The effect of freezing temperature on the sodium sulfate content in the filtered liquid is shown in Table 10.

It can be seen from Table 10 that when the freezing temperature in step H is -10°C, the sodium sulfate content in the liquid after freezing and filtration is low. Therefore, the preferred freezing temperature is -10°C.

Embodiment 66-Embodiment 70,

The difference between Examples 66 to 70 and Example 1 is that in step G, the amount of sodium carbonate used is different. The effect of sodium carbonate dosage on lithium carbonate conversion rate is shown in Table 11.

It can be seen from Table 11 that when the amount of sodium carbonate in step G is 9 times the total mass of lithium in the solution, the conversion rate of lithium carbonate can reach about 99%. The impact of continuing to increase the amount of sodium carbonate on the conversion rate of lithium carbonate Not big. Therefore, the dosage of preferred sodium carbonate is 9 times the total mass of lithium.

Claims (8)

1. A method for processing lithium cobalt oxide and lithium manganate mixed waste, which is characterized by comprising the following steps: A. Calculate the mixed waste of lithium cobalt oxide and lithium manganate under the condition of air flow; B. Add a mixed solution of sulfuric acid and hydrogen peroxide to the calcined lithium cobalt oxide and lithium manganate mixed waste. The reaction temperature is 80-90°C and the reaction time is 1-3 h. Then the solid-liquid separation is performed to obtain leachate I and leach residue I. Separate The temperature of the post-liquid leaching liquid I is maintained at 60-70°C; C. Continue to add the calcined lithium cobalt oxide and lithium manganate mixed waste and the sulfuric acid and hydrogen peroxide mixed solution to the leachate I obtained in step B. The reaction temperature is 65-70°C, the reaction time is 1-3h, and solid-liquid separation is obtained For leach liquid II and leach residue II, the liquid temperature after filtration is maintained at 60-65°C; D. Raise the temperature of the leachate II to no less than 95°C, separate the solid and liquid while it is hot, and keep the liquid temperature at 90-95°C after filtration to obtain manganese sulfate crystals and leachate III; E. Continue to lower the temperature of leach solution III to 25-30°C, and finally obtain cobalt sulfate crystals and leach solution IV; F. Return the leach solution IV to step C, repeat C-E to continuously precipitate out cobalt sulfate and manganese sulfate. When the lithium content in the leach solution reaches 20-25g/L, stop adding the calcined lithium cobalt oxide and lithium manganate mixed waste as well as sulfuric acid and The hydrogen peroxide mixed solution is heated to 90°C-95°C, the pH is adjusted to 11-12, and settled and filtered to obtain a mixture of cobalt hydroxide and manganese hydroxide, and a lithium sulfate solution, and then further recover lithium. 2. A method for processing lithium cobalt oxide and lithium manganate mixed waste according to claim 1, characterized in that in step A, the calcination temperature is 650-700°C and the calcination time is 1-3h. 3. A method for processing lithium cobalt oxide and lithium manganate mixed waste materials according to claim 2, characterized in that: in step B, the addition amount of lithium cobalt oxide and lithium manganate mixed waste materials is according to the amount in the solution after leaching. The concentration of manganese is 85-90g/L and the concentration of cobalt is 100-110g/L. 4. The processing method of a kind of lithium cobalt oxide and lithium manganate mixed waste material according to claim 3, characterized in that: in step C, the addition amount of lithium cobalt oxide and lithium manganate mixed waste material is according to the amount in the solution after leaching. The concentration of manganese is 170-180g/L and the concentration of cobalt is 200-220g/L. 5. A method for processing lithium cobalt oxide and lithium manganate mixed waste according to claim 4, characterized in that: returning leaching residue I and leaching residue II to step B to continue leaching and dissolving. 6. A method for processing lithium cobalt oxide and lithium manganate mixed waste according to any one of claims 1 to 5, characterized in that: the steps for further recovering lithium are as follows: S1. Add sodium carbonate to the lithium sulfate solution obtained in step F for reaction. The reaction time is 60-80 min, the reaction temperature is 90°C-100°C, and solid-liquid separation is performed to obtain lithium carbonate and carbonized liquid; S2. Add acid to the carbonized liquid obtained in step S1 to adjust the pH to 5-6, and then freeze it. The freezing temperature is -10-0°C, the freezing time is 30-60 minutes, and solid-liquid separation is performed to obtain sodium sulfate decahydrate and sodium sulfate decahydrate. Lithium sulfate solution containing sodium sulfate; S3. Evaporate and concentrate the hot-melt sodium sulfate decahydrate obtained in step S2 until the volume is 1/2-1/3 of the original volume, and separate the solid and liquid while hot to obtain a lithium-containing solution and Yuanming powder; S4. Add phosphoric acid to the lithium-containing solution obtained in step S3, add alkali to adjust the pH to 10-11, and perform solid-liquid separation to obtain lithium phosphate. 7. The processing method of a kind of lithium cobalt oxide and lithium manganate mixed waste according to claim 6, characterized in that: in step S1, the consumption of sodium carbonate is 9-9.5 times of the total lithium mass in the lithium sulfate solution. . 8. A method for processing lithium cobalt oxide and lithium manganate mixed waste according to claim 7, characterized in that: the sodium sulfate-free lithium sulfate solution obtained in step S2 is returned to step B to continue leaching.