Method for selectively extracting lithium from waste lithium iron phosphate battery through cooperation of micro-nano bubbles and alkali

Abstract

The invention belongs to the technical field of recovery of waste lithium batteries, and particularly relates to a method for selectively extracting lithium from waste lithium iron phosphate batteries by micro-nano bubbles cooperating with alkali, which comprises the following steps: adding strong alkali and a positive electrode material of the waste lithium iron phosphate batteries into water, and introducing oxidizing gas into the water through a micro-nano bubble generator, and after stirring and leaching for a period of time, carrying out solid-liquid separation to obtain a lithium-rich solution. According to the method, under the acid-free condition, lithium is selectively leached through cooperation of micro-nano bubbles and alkali, iron, phosphorus and the like are enriched in leached residues, high-selectivity and efficient leaching of lithium is achieved, use of a large amount of acid and consumption of other reagents are avoided, the waste water amount and the leaching cost are reduced, meanwhile, the pH value of the leachate is high, direct recovery of lithium is facilitated, and the method is suitable for industrial production. In particular, the selective lithium leaching method disclosed by the invention also has an excellent selective lithium leaching effect at low temperature, and solves the problems of high reagent consumption, high energy consumption, high lithium loss rate, large wastewater amount and relatively high cost in the traditional wet process.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste lithium battery recycling, and in particular relates to a method for selectively extracting lithium from waste lithium iron phosphate batteries by using micro-nano bubbles in conjunction with alkali. Background Art

[0002] Lithium is a key component of lithium-ion batteries. However, global lithium resources are unevenly distributed and reserves are limited. With the rapid development of industries such as electric vehicles, the demand for lithium continues to grow, and the scarcity of lithium resources has become increasingly prominent. With the rapid development of the new energy vehicle industry and the issue of battery life, power batteries are gradually entering a peak period of retirement, and the continued growth in the scale of retirement has placed higher demands on efficient recycling technologies for lithium resources. Lithium iron phosphate positive electrode materials are being chosen by more and more automakers due to their wide range of sources, excellent thermal stability, outstanding safety performance and low cost. As a key "urban mineral", retired lithium iron phosphate battery positive electrode materials have a high lithium content and a relatively simple impurity composition, which has significant recycling advantages compared to primary ore resources.

[0003] The current mainstream process for recycling spent lithium iron phosphate battery cathode materials uses sulfuric acid and hydrogen peroxide to dissolve the lithium iron phosphate, achieving a high leaching rate of lithium from the lithium iron phosphate cathode material. However, this process requires first dissolving the lithium iron phosphate, oxidizing the ferrous ions with hydrogen peroxide, and then reacting with phosphate to form a precipitation to remove impurities. This process is complex, consumes a lot of reagents, is costly, and generates wastewater pollution. Furthermore, during the precipitation and removal process, lithium can be adsorbed or entrained, resulting in a high loss rate.

[0004] The lithium in the cathode material of spent lithium iron phosphate batteries is highly valuable, while the iron and phosphorus are less valuable. If lithium can be selectively leached during the leaching process and the iron and phosphorus can be concentrated in the leached residue, the technical difficulty of the process can be significantly reduced, the process can be shortened, and costs can be significantly reduced. To this end, we have developed a new process for selectively recovering lithium from spent lithium iron phosphate battery cathode material and concentrating the iron and phosphorus in the residue. Summary of the Invention

[0005] The present invention aims to provide a method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali, so as to solve the problems of high reagent consumption, high energy consumption, high loss rate of lithium in the leaching solution after impurity removal, large amount of wastewater, complicated process and high cost in the traditional wet process.

[0006] In order to achieve the above object, the present invention provides a method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali, comprising the following steps:

[0007] S1. The waste lithium iron phosphate battery is processed to obtain the waste lithium iron phosphate battery positive electrode material;

[0008] S2. Add a strong base and the waste lithium iron phosphate battery positive electrode material obtained in step S1 into water, and introduce an oxidizing gas into the water through a micro-nano bubble generator. After stirring and leaching for a period of time, solid-liquid separation is performed to obtain a lithium-rich solution.

[0009] The working principle and beneficial effects of this solution are as follows: the present invention utilizes micro-nano bubbles to cooperate with alkali to selectively leach lithium, enriching iron, phosphorus, etc. in the leached residue. Specifically, under acid-free conditions, through a micro-nano bubble generator, under the synergistic effect of a small amount of strong alkali and oxidizing gas, most of the lithium can be leached, and the leaching of iron and phosphorus is suppressed, achieving high selectivity and efficient leaching of lithium, and avoiding the large-scale use of acid and other reagent consumption, reducing the production of wastewater, and also reducing the leaching cost. Secondly, this solution selectively leach lithium without leaching iron and phosphorus, and the pH of the leachate is high, which is suitable for direct recovery of lithium, shortening the lithium recovery process, improving the recovery efficiency of lithium, and reducing the recovery cost. In addition, compared with the method of leaching at 80°C with sulfuric acid and hydrogen peroxide, this solution can operate at a lower temperature, has a wide temperature range, and low energy consumption. The alkaline environment and oxidizing environment provided by this solution can effectively remove COD in the leachate, laying the foundation for subsequent wastewater treatment and the preparation of high-quality lithium salt products.

[0010] Optionally, in step S2, the strong base is one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, cesium hydroxide and sodium amide.

[0011] Optionally, in step S2, the temperature of the stirring leaching is 1-40°C.

[0012] Optionally, in step S2, the stirring and leaching time is 120 to 360 minutes.

[0013] Optionally, in step S2, the rotation speed of the stirring leaching is 300 to 800 rpm.

[0014] Optionally, in step S2, the inlet flow rate of the micro-nano bubble generator is 500-1500 mL / min.

[0015] Optionally, in step S2, the ratio of the waste lithium iron phosphate battery positive electrode material to water is 20 to 300 g:1 L.

[0016] Optionally, in step S2, the amount of the strong base used is 30-200% of the mass of the waste lithium iron phosphate battery positive electrode material.

[0017] Optionally, in step S1, the waste lithium iron phosphate battery positive electrode material is a powder with an average particle size of 30 to 250 μm obtained by discharging, disassembling, crushing, screening, washing and drying the waste lithium iron phosphate batteries.

[0018] Optionally, the device used in the method includes the following components:

[0019] The leaching container is used to hold the positive electrode material of the waste lithium iron phosphate battery, the strong alkali and the water. The leaching container is provided with a cylinder, and the bottom end of the cylinder is fixedly connected to a solid receiving basket made of a filter screen, and the mesh number of the filter screen is 2000-3000 mesh;

[0020] A micro-nano bubble generator is used to generate oxidizing micro-nano bubbles, and has a liquid inlet port, a liquid outlet port, and an air inlet port. The liquid inlet port is connected to the bottom of the leaching container through a pipe, and the liquid outlet port is connected to a delivery pipe. The end of the delivery pipe away from the micro-nano bubble generator is located in the solid holding basket.

[0021] A vacuum pump having a vacuum pumping port connected to the top of the leaching container through a pipeline;

[0022] At least one gas production or storage module is used to store or produce oxidizing gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a flow chart of a method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali according to an embodiment of the present invention;

[0024] Figure 2 This is a schematic structural diagram of the equipment used in a method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0026] The present invention provides a method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali, comprising the following steps:

[0027] S1. After the waste lithium iron phosphate batteries are discharged, disassembled, crushed, sieved, washed and dried, a waste lithium iron phosphate battery positive electrode material with an average particle size of 30 to 250 μm is obtained.

[0028] S2. Add a strong base and the waste lithium iron phosphate battery positive electrode material obtained in step S1 to water, maintain the water temperature at 1-40°C, stir and leach at a stirring speed of 300-800 rpm, and simultaneously introduce an oxidizing gas into the water through a micro-nano bubble generator. After stirring and leaching for 120-360 minutes, solid-liquid separation is performed to obtain a lithium-rich solution. The inlet gas rate of the micro-nano bubble generator is 500-1500 mL / min; the strong base is one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, cesium hydroxide, and sodium amide; the amount of the strong base is 30-200% of the mass of the waste lithium iron phosphate battery positive electrode material; and the ratio of the waste lithium iron phosphate battery positive electrode material to water is 20-300 g:1 L.

[0029] The present invention also provides a device used in a method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali, the device comprising the following components:

[0030] The leaching container is used to hold the positive electrode material of the waste lithium iron phosphate battery, the strong alkali and the water. The leaching container is provided with a cylinder, and the bottom end of the cylinder is fixedly connected to a solid receiving basket made of a filter screen, and the mesh number of the filter screen is 2000-3000 mesh;

[0031] A micro-nano bubble generator is used to generate oxidizing micro-nano bubbles, and has a liquid inlet port, a liquid outlet port, and an air inlet port. The liquid inlet port is connected to the bottom of the leaching container through a pipe, and the liquid outlet port is connected to a delivery pipe. The end of the delivery pipe away from the micro-nano bubble generator is located in the solid holding basket.

[0032] A vacuum pump having a vacuum pumping port connected to the top of the leaching container through a pipeline;

[0033] At least one gas production or storage module is used to store or produce oxidizing gas, and the oxidizing gas is one or more of air, oxygen and ozone.

[0034] The following specific examples are given to illustrate the present invention in detail. It should also be understood that the following examples are only used to specifically illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are only an example within a suitable range, that is, those skilled in the art can make a selection within a suitable range based on the description herein, and are not limited to the specific values ​​​​exemplified below. In addition, the waste lithium iron phosphate positive electrode material used in the following examples and comparative examples contains Li 4.23%, Fe 19.27%, and P 33.6%.

[0035] Example 1

[0036] This embodiment provides a method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali. The equipment used in this method is basically as follows: Figure 2 As shown, it includes the following components:

[0037] The leaching vessel is used to hold the cathode material of used lithium iron phosphate batteries, a strong base, and water. It contains a cylindrical body, the bottom of which is fixedly connected to a solids holding basket made of a 3000-mesh filter. The solids holding basket is equipped with a stirring blade to achieve stirring. A pressure control valve is installed at the top of the leaching vessel to adjust the internal air pressure.

[0038] The micro-nano bubble generator is used to generate oxidizing micro-nano bubbles. It has a liquid inlet, a liquid outlet, and a gas inlet. The liquid inlet is connected to the bottom of the leaching container via a pipe. The liquid outlet is connected to a delivery tube. The end of the delivery tube, remote from the micro-nano bubble generator, is located within the solids holding basket. In this embodiment, the micro-nano bubble generator uses a Venturi gas dispersion device.

[0039] The vacuum pump has a vacuum pumping port, which is connected to the top of the leaching container through a pipeline and is used to create negative pressure in the leaching container.

[0040] The ozone generator is used to generate ozone and has an air inlet port and an air outlet port. The air outlet port of the ozone generator is connected to the air inlet port of the micro-nano bubble generator through a pipeline.

[0041] The gas cylinder is used to store an oxidizing gas. In this embodiment, the gas cylinder is used to store oxygen. The gas cylinder has a gas outlet port, and the gas outlet port of the gas cylinder is connected to the gas inlet port of the ozone generator through a pipeline.

[0042] This embodiment provides a method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in combination with alkali. The method is basically as follows: Figure 1 As shown, the following steps are included:

[0043] 1) After the waste lithium iron phosphate battery is discharged, disassembled, crushed, sieved, washed and dried, a powder with an average particle size of 30 to 250 μm is obtained, namely the waste lithium iron phosphate battery positive electrode material.

[0044] 2) Measure 1000mL of water and pour it into the leaching container, and preheat it to 40°C in a water bath. Turn on the stirring and vacuum pump, set the stirring speed in the solid holding basket to 500rpm, and balance the liquid level in the solid holding basket and the liquid level in the leaching container to the appropriate position by adjusting the pressure control valve. Open the gas cylinder valve and the ozone generator, turn on the micro-nano bubble generator (Venturi gas dispersion device), and set the inlet flow rate of the micro-nano bubble generator (Venturi gas dispersion device) to 1500mL / min, so that ozone is sent into the water in the form of micro-nano bubbles. Weigh 300g of sodium hydroxide solid and 300g of the waste lithium iron phosphate battery positive electrode material in step 1), add them to the solid holding basket, and react for 360min under stirring conditions (500rpm). After the reaction is completed, close the gas cylinder valve, ozone generator and micro-nano bubble generator (Venturi gas dispersion device), and continue to filter to achieve solid-liquid separation in the solid holding basket to obtain a lithium-rich solution. The lithium-rich solution is the liquid at the bottom of the leaching container. The lithium-rich solution was sent for ICP testing and analysis. Calculations showed that the lithium leaching rate was 95.23%, the iron leaching rate was 0.21%, and the phosphorus leaching rate was 0.35%.

[0045] Example 2

[0046] This embodiment provides a method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali. The equipment used in this method is the same as that used in Example 1. The method in this embodiment includes the following steps:

[0047] 1) After the waste lithium iron phosphate battery is discharged, disassembled, crushed, sieved, washed and dried, a powder with an average particle size of 30 to 250 μm is obtained, namely the waste lithium iron phosphate battery positive electrode material.

[0048] 2) Measure 1000mL of water and pour it into the leaching container, and use a water bath to control the temperature to 20°C. Turn on the stirring and vacuum pump, set the stirring speed in the solid holding basket to 500rpm, and balance the liquid level in the solid holding basket and the liquid level in the leaching container to the appropriate position by adjusting the pressure control valve. Open the gas cylinder valve and the ozone generator, turn on the micro-nano bubble generator (Venturi gas dispersion device), and set the inlet flow rate of the micro-nano bubble generator (Venturi gas dispersion device) to 1500mL / min, so that ozone is sent into the water in the form of micro-nano bubbles. Weigh 300g of sodium hydroxide solid and 300g of the waste lithium iron phosphate battery positive electrode material in step 1), add them to the solid holding basket, and react for 360min under stirring conditions (500rpm). After the reaction is completed, close the gas cylinder valve, ozone generator and micro-nano bubble generator (Venturi gas dispersion device), and continue to filter to achieve solid-liquid separation in the solid holding basket to obtain a lithium-rich solution. The lithium-rich solution is the liquid at the bottom of the leaching container. The lithium-rich solution was sent for ICP testing and analysis. Calculations showed that the lithium leaching rate was 88.64%, the iron leaching rate was 0.11%, and the phosphorus leaching rate was 0.18%.

[0049] Example 3

[0050] This embodiment provides a method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali. The equipment used in this method is the same as that used in Example 1. The method in this embodiment includes the following steps:

[0051] 1) After the waste lithium iron phosphate battery is discharged, disassembled, crushed, sieved, washed and dried, a powder with an average particle size of 30 to 250 μm is obtained, namely the waste lithium iron phosphate battery positive electrode material.

[0052] 2) Measure 1000mL of water and pour it into the leaching container. Use a water bath to control the temperature to 25°C. Turn on the stirring and vacuum pump, set the stirring speed in the solid holding basket to 500rpm, and balance the liquid level in the solid holding basket and the liquid level in the leaching container to the appropriate position by adjusting the pressure control valve. Open the gas cylinder valve and the ozone generator, turn on the micro-nano bubble generator (Venturi gas dispersion device), and set the inlet flow rate of the micro-nano bubble generator (Venturi gas dispersion device) to 1500mL / min, so that ozone is sent into the water in the form of micro-nano bubbles. Weigh 300g of sodium hydroxide solid and 300g of the waste lithium iron phosphate battery positive electrode material in step 1), add them to the solid holding basket, and react for 360min under stirring conditions (500rpm). After the reaction is completed, close the gas cylinder valve, ozone generator and micro-nano bubble generator (Venturi gas dispersion device), and continue to filter to achieve solid-liquid separation in the solid holding basket to obtain a lithium-rich solution. The lithium-rich solution is the liquid at the bottom of the leaching container. The lithium-rich solution was sent for ICP testing and analysis. Calculations showed that the lithium leaching rate was 92.87%, the iron leaching rate was 0.14%, and the phosphorus leaching rate was 0.23%.

[0053] Example 4

[0054] This embodiment provides a method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali. The equipment used in this method is the same as that used in Example 1. The method in this embodiment includes the following steps:

[0055] 1) After the waste lithium iron phosphate battery is discharged, disassembled, crushed, sieved, washed and dried, a powder with an average particle size of 30 to 250 μm is obtained, namely the waste lithium iron phosphate battery positive electrode material.

[0056] 2) Measure 1000mL of water and pour it into the leaching container. Use a water bath to control the temperature to 25°C. Turn on the stirring and vacuum exhaust machine, set the stirring speed in the solid holding basket to 500rpm, and balance the liquid level in the solid holding basket and the liquid level in the leaching container to the appropriate position by adjusting the pressure control valve. Open the gas cylinder valve and the ozone generator, turn on the micro-nano bubble generator (Venturi gas dispersion device), and set the inlet flow rate of the micro-nano bubble generator (Venturi gas dispersion device) to 1000mL / min, so that ozone is sent into the water in the form of micro-nano bubbles. Weigh 40g of sodium hydroxide solid and 20g of the waste lithium iron phosphate battery positive electrode material in step 1), add them to the solid holding basket, and react for 120min under stirring conditions (500rpm). After the reaction is completed, close the gas cylinder valve, ozone generator and micro-nano bubble generator (Venturi gas dispersion device), and continue to filter to achieve solid-liquid separation in the solid holding basket to obtain a lithium-rich solution. The lithium-rich solution is the liquid at the bottom of the leaching container. The lithium-rich solution was sent for ICP testing and analysis. Calculations showed that the lithium leaching rate was 99.96%, the iron leaching rate was 0.61%, and the phosphorus leaching rate was 0.82%.

[0057] Example 5

[0058] This embodiment provides a method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali. The equipment used in this method is the same as that used in Example 1. The method in this embodiment includes the following steps:

[0059] 1) After the waste lithium iron phosphate battery is discharged, disassembled, crushed, sieved, washed and dried, a powder with an average particle size of 30 to 250 μm is obtained, namely the waste lithium iron phosphate battery positive electrode material.

[0060] 2) Measure 1000mL of water and pour it into the leaching container, and use a water bath to control the temperature to 25°C. Turn on the stirring and vacuum pump, set the stirring speed in the solid holding basket to 500rpm, and balance the liquid level in the solid holding basket and the liquid level in the leaching container to the appropriate position by adjusting the pressure control valve. Open the gas cylinder valve and the ozone generator, turn on the micro-nano bubble generator (Venturi gas dispersion device), and set the inlet flow rate of the micro-nano bubble generator (Venturi gas dispersion device) to 500mL / min, so that ozone is sent into the water in the form of micro-nano bubbles. Weigh 40g of sodium hydroxide solid and 20g of the waste lithium iron phosphate battery positive electrode material in step 1), add them to the solid holding basket, and react under stirring conditions (500rpm) for 120min. After the reaction is completed, close the gas cylinder valve, ozone generator and micro-nano bubble generator (Venturi gas dispersion device), and continue to filter to achieve solid-liquid separation in the solid holding basket to obtain a lithium-rich solution. The lithium-rich solution is the liquid at the bottom of the leaching container. The lithium-rich solution was sent for ICP testing and analysis. Calculations showed that the lithium leaching rate was 96.04%, the iron leaching rate was 0.63%, and the phosphorus leaching rate was 0.79%.

[0061] Example 6

[0062] This embodiment provides a method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali. The equipment used in this method is the same as that used in Example 1. The method in this embodiment includes the following steps:

[0063] 1) After the waste lithium iron phosphate battery is discharged, disassembled, crushed, sieved, washed and dried, a powder with an average particle size of 30 to 250 μm is obtained, namely the waste lithium iron phosphate battery positive electrode material.

[0064] 2) Measure 1000mL of water and pour it into the leaching container, and use a water bath to control the temperature to 20°C. Turn on the stirring and vacuum exhaust machine, set the stirring speed in the solid holding basket to 500rpm, and balance the liquid level in the solid holding basket and the liquid level in the leaching container to the appropriate position by adjusting the pressure control valve. Open the gas cylinder valve and the ozone generator, turn on the micro-nano bubble generator (Venturi gas dispersion device), and set the inlet flow rate of the micro-nano bubble generator (Venturi gas dispersion device) to 500mL / min, so that ozone is sent into the water in the form of micro-nano bubbles. Weigh 45g of sodium hydroxide solid and 150g of the waste lithium iron phosphate battery positive electrode material in step 1), add them to the solid holding basket, and react for 360min under stirring (500rpm). After the reaction is completed, close the gas cylinder valve, ozone generator and micro-nano bubble generator (Venturi gas dispersion device), continue to filter to achieve solid-liquid separation in the solid holding basket, and obtain a lithium-rich solution. The lithium-rich solution is the liquid at the bottom of the leaching container. The lithium-rich solution was sent for ICP testing and analysis. Calculations showed that the lithium leaching rate was 81.12%, the iron leaching rate was 0.17%, and the phosphorus leaching rate was 0.24%.

[0065] Example 7

[0066] This embodiment provides a method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali. The equipment used in this method is the same as that used in Example 1. The method in this embodiment includes the following steps:

[0067] 1) After the waste lithium iron phosphate battery is discharged, disassembled, crushed, sieved, washed and dried, a powder with an average particle size of 30 to 250 μm is obtained, namely the waste lithium iron phosphate battery positive electrode material.

[0068] 2) Measure 1000mL of water and pour it into the leaching container. Use a low-temperature circulating cooling pump to control the temperature to 2°C. Turn on the stirring and vacuum exhaust machine, set the stirring speed in the solid holding basket to 800rpm, and balance the liquid level in the solid holding basket and the liquid level in the leaching container to the appropriate position by adjusting the pressure control valve. Open the gas cylinder valve and the ozone generator, turn on the micro-nano bubble generator (Venturi gas dispersion device), and set the inlet flow rate of the micro-nano bubble generator (Venturi gas dispersion device) to 1000mL / min, so that ozone is sent into the water in the form of micro-nano bubbles. Weigh 40g of sodium hydroxide solid and 80g of the waste lithium iron phosphate battery positive electrode material in step 1), add them to the solid holding basket, and react under stirring conditions (800rpm) for 240min. After the reaction is completed, close the gas cylinder valve, ozone generator and micro-nano bubble generator (Venturi gas dispersion device), and continue to filter to achieve solid-liquid separation in the solid holding basket to obtain a lithium-rich solution. The lithium-rich solution is the liquid at the bottom of the leaching container. The lithium-rich solution was sent for ICP testing and analysis. Calculations showed that the lithium leaching rate was 90.50%, the iron leaching rate was 0.12%, and the phosphorus leaching rate was 0.29%.

[0069] Comparative Example 1

[0070] This comparative example provides a method for selectively extracting lithium from waste lithium iron phosphate batteries. The equipment used in this method is the same as that in Example 1. The method in this comparative example includes the following steps:

[0071] 1) After the waste lithium iron phosphate battery is discharged, disassembled, crushed, sieved, washed and dried, a powder with an average particle size of 30 to 250 μm is obtained, namely the waste lithium iron phosphate battery positive electrode material.

[0072] 2) Measure 1000mL of water and pour it into the leaching container, and preheat it to 40°C in a water bath. Turn on the stirring and vacuum pump, set the stirring speed in the solid holding basket to 500rpm, and balance the liquid level in the solid holding basket and the liquid level in the leaching container to the appropriate position by adjusting the pressure control valve. Open the gas cylinder valve and the ozone generator, turn on the micro-nano bubble generator (Venturi gas dispersion device), and set the inlet flow rate of the micro-nano bubble generator (Venturi gas dispersion device) to 1500mL / min, so that ozone is sent into the water in the form of micro-nano bubbles. Weigh 300g of the waste lithium iron phosphate battery positive electrode material in step 1), add it to the solid holding basket, and react for 360min under stirring (500rpm). After the reaction is completed, close the gas cylinder valve, the ozone generator, and the micro-nano bubble generator (Venturi gas dispersion device), and continue to filter to achieve solid-liquid separation in the solid holding basket to obtain a lithium-rich solution. The lithium-rich solution is the liquid at the bottom of the leaching container. The lithium-rich solution was sent for ICP testing and analysis. Calculations showed that the lithium leaching rate was 73.65%, the iron leaching rate was 0.27%, and the phosphorus leaching rate was 0.43%.

[0073] Comparative Example 2

[0074] This comparative example provides a method for selectively extracting lithium from waste lithium iron phosphate batteries. The equipment used in this method is the same as that in Example 1. The method in this comparative example includes the following steps:

[0075] 1) After the waste lithium iron phosphate battery is discharged, disassembled, crushed, sieved, washed and dried, a powder with an average particle size of 30 to 250 μm is obtained, namely the waste lithium iron phosphate battery positive electrode material.

[0076] 2) Measure 1000mL of water and pour it into the leaching container, and use a water bath to control the temperature to 20°C. Turn on the stirring and vacuum pump, set the stirring speed in the solid holding basket to 500rpm, and balance the liquid level in the solid holding basket and the liquid level in the leaching container to the appropriate position by adjusting the pressure control valve. Open the gas cylinder valve and the ozone generator, turn on the micro-nano bubble generator (Venturi gas dispersion device), and set the inlet flow rate of the micro-nano bubble generator (Venturi gas dispersion device) to 1500mL / min, so that ozone is sent into the water in the form of micro-nano bubbles. Weigh 300g of the waste lithium iron phosphate battery positive electrode material in step 1), add it to the solid holding basket, and react for 360min under stirring (500rpm). After the reaction is completed, close the gas cylinder valve, ozone generator and micro-nano bubble generator (Venturi gas dispersion device), continue to filter to achieve solid-liquid separation in the solid holding basket, and obtain a lithium-rich solution. The lithium-rich solution is the liquid at the bottom of the leaching container. The lithium-rich solution was sent for ICP testing and analysis. Calculations showed that the lithium leaching rate was 64.89%, the iron leaching rate was 0.22%, and the phosphorus leaching rate was 0.38%.

[0077] Comparative Example 3

[0078] This embodiment provides a method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali. The equipment used in this method is the same as that used in Example 1. The method in this embodiment includes the following steps:

[0079] 1) After the waste lithium iron phosphate battery is discharged, disassembled, crushed, sieved, washed and dried, a powder with an average particle size of 30 to 250 μm is obtained, namely the waste lithium iron phosphate battery positive electrode material.

[0080] 2) Measure 1000mL of water and pour it into the leaching container. Use a low-temperature circulating cooling pump to control the temperature to 2°C. Turn on the stirring and vacuum exhaust machine, set the stirring speed in the solid holding basket to 800rpm, and balance the liquid level in the solid holding basket and the liquid level in the leaching container to the appropriate position by adjusting the pressure control valve. Open the gas cylinder valve and the ozone generator, turn on the micro-nano bubble generator (Venturi gas dispersion device), and set the inlet flow rate of the micro-nano bubble generator (Venturi gas dispersion device) to 1000mL / min, so that ozone is sent into the water in the form of micro-nano bubbles. Weigh 80g of the waste lithium iron phosphate battery positive electrode material in step 1), add it to the solid holding basket, and react for 240min under stirring conditions (800rpm). After the reaction is completed, close the gas cylinder valve, ozone generator and micro-nano bubble generator (Venturi gas dispersion device), and continue to filter to achieve solid-liquid separation in the solid holding basket to obtain a lithium-rich solution. The lithium-rich solution is the liquid at the bottom of the leaching container. The lithium-rich solution was sent for ICP testing and analysis. Calculations showed that the lithium leaching rate was 54.98%, the iron leaching rate was 0.26%, and the phosphorus leaching rate was 0.44%.

[0081] As can be seen from Examples 1-7, the present invention utilizes micro-nano bubbles of oxidizing gas in conjunction with alkali to selectively leach lithium under acid-free conditions, enriching iron, phosphorus, etc. in the leached residue, and the lithium leaching rate can reach up to 99.96%. Through Comparative Examples 1, 2, and 3, it is not difficult to find that in the absence of a strong base, it is difficult to achieve a high lithium leaching rate using only micro-nano bubbles of oxidizing gas. In particular, in Comparative Example 3, at 2°C, the addition of a strong base can increase the lithium leaching rate from 54.98% to 90.50%. That is, in the present invention, a strong base can significantly increase the lithium leaching rate while having little effect on the leaching rates of iron and phosphorus.

[0082] In summary, the present invention utilizes micro-nano bubbles of oxidizing gas in conjunction with alkali to selectively leach lithium, enriching iron, phosphorus, etc. in the leaching residue, thereby achieving a high leaching rate and efficient leaching of lithium, and avoiding the large-scale use of acid and other reagent consumption, shortening the process flow, reducing wastewater production and leaching costs, and avoiding lithium loss caused by subsequent impurity removal steps. In addition, the present invention can operate at 1 to 40°C, has low energy consumption, and has good industrial application prospects.

[0083] The above are only embodiments of the present invention. The invention is not limited to the fields involved in this implementation case. Common knowledge such as the known specific structures and characteristics in the scheme is not described in detail here. Ordinary technicians in the relevant field are aware of all the common technical knowledge in the technical field to which the invention belongs before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply conventional experimental means before that date. Ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the inspiration given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the present invention. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali, characterized by: The following steps are involved: S1. The waste lithium iron phosphate battery is processed to obtain the waste lithium iron phosphate battery positive electrode material; S2. Add a strong base and the waste lithium iron phosphate battery positive electrode material obtained in step S1 into water, and introduce an oxidizing gas into the water through a micro-nano bubble generator. After stirring and leaching for a period of time, solid-liquid separation is performed to obtain a lithium-rich solution.

2. The method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali according to claim 1, characterized in that: In step S2, the strong base is one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, cesium hydroxide and sodium amide.

3. The method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali according to claim 1, characterized in that: In step S2, the temperature of stirring and leaching is 1-40°C.

4. The method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali according to claim 1, characterized in that: In step S2, the stirring and leaching time is 120 to 360 minutes.

5. The method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali according to claim 1, characterized in that: In step S2, the rotation speed of the stirring leaching is 300 to 800 rpm.

6. The method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali according to claim 1, characterized in that: In step S2, the inlet flow rate of the micro-nano bubble generator is 500-1500 mL / min.

7. The method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali according to claim 1, characterized in that: In step S2, the ratio of the waste lithium iron phosphate battery positive electrode material to water is 20 to 300 g:1 L.

8. The method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali according to claim 1, characterized in that: In step S2, the amount of the strong base used is 30-200% of the mass of the waste lithium iron phosphate battery positive electrode material.

9. The method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali according to claim 1, characterized in that: In step S1, the waste lithium iron phosphate battery positive electrode material is a powder with an average particle size of 30 to 250 μm obtained by discharging, disassembling, crushing, screening, washing and drying the waste lithium iron phosphate battery.

10. The method for selectively extracting lithium from waste lithium iron phosphate batteries using micro-nano bubbles in conjunction with alkali according to claim 1, characterized in that: The device used in the method includes the following components: The leaching container is used to hold the positive electrode material of the waste lithium iron phosphate battery, the strong alkali and the water. The leaching container is provided with a cylinder, and the bottom end of the cylinder is fixedly connected to a solid receiving basket made of a filter screen, and the mesh number of the filter screen is 2000-3000 mesh; A micro-nano bubble generator is used to generate oxidizing micro-nano bubbles, and has a liquid inlet port, a liquid outlet port, and an air inlet port. The liquid inlet port is connected to the bottom of the leaching container through a pipe, and the liquid outlet port is connected to a delivery pipe. The end of the delivery pipe away from the micro-nano bubble generator is located in the solid holding basket. A vacuum pump having a vacuum pumping port connected to the top of the leaching container through a pipeline; At least one gas production or storage module is used to store or produce oxidizing gas.

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