Method for recovering lithium in waste lithium iron phosphate positive electrode material leachate through homogeneous membrane electrodialysis

Abstract

The invention discloses a method for recovering lithium in a waste lithium iron phosphate positive electrode material leachate through homogeneous membrane electrodialysis, which belongs to the technical field of lithium resource recovery, and comprises the following steps: feeding the waste lithium iron phosphate positive electrode material leachate containing lithium ions and iron ions into a light chamber of a homogeneous membrane electrodialysis device to circularly flow, the method comprises the following steps: placing water in a concentrated chamber of a homogeneous membrane electrodialysis device to circularly flow, applying a potential difference to a homogeneous membrane under the action of a direct-current electric field, only allowing lithium ions to penetrate through the homogeneous membrane so as to realize selective separation of the lithium ions and iron ions, and obtaining a separated high-purity lithium-containing solution in the concentrated chamber of the homogeneous membrane electrodialysis device, the method provided by the invention can realize selective separation of lithium ions and iron ions in the leaching solution of the lithium iron phosphate positive electrode material, directly obtains the high-purity lithium-containing solution, is simple and convenient to operate, and is green and environment-friendly.

Description

Technical Field

[0001] The invention relates to a method for recovering lithium in a waste lithium iron phosphate positive electrode material leachate, and in particular to a method for recovering lithium in a waste lithium iron phosphate positive electrode material leachate by homogeneous membrane electrodialysis, belonging to the technical field of lithium resource recovery. Background Art

[0002] With the adjustment of global energy structure and the increasing awareness of environmental protection, the market demand for lithium-ion batteries has shown a trend of sustained growth. Among them, lithium iron phosphate batteries have been widely used in electric vehicles, energy storage systems and other fields due to their significant advantages such as long life, low cost and non-toxicity. However, with the extensive use of lithium iron phosphate batteries, the number of waste batteries has increased exponentially, and improper handling of waste lithium iron phosphate batteries will bring serious problems such as environmental pollution and waste of resources.

[0003] Since the recycling value of graphite negative electrode and electrolyte of lithium-ion battery is low, the current recycling research of waste lithium-ion battery is mainly focused on positive electrode materials. Waste positive electrode materials contain abundant valuable metals such as lithium and iron, and their recycling processes are mainly divided into pyrometallurgy and hydrometallurgy. Pyrometallurgy is to catalytically reduce the high-valent valuable metals in the positive electrode material by high-temperature roasting, and then extract the target metal material through subsequent separation. Its process flow is simple and the processing capacity is large, but there are problems such as large loss of lithium in smelting slag, large energy consumption, complex equipment and high cost, so it is generally not used for the recovery of lithium iron phosphate positive electrode materials. Traditional hydrometallurgy uses acid or alkaline solution to leach metal ions and then recover them. Among them, the separation and extraction methods for valuable metals in the leachate of lithium iron phosphate positive electrode materials mainly include chemical precipitation method and solvent extraction method. Chemical precipitation method uses the principle of co-precipitation to add precipitant to recover valuable metals. Solvent extraction method is based on the selective adsorption of different ions by the extractant, so as to achieve the separation and extraction of different mixed ions in the solution. Although the above method has a high lithium recovery rate and low energy consumption, the operation process is complicated, and the equipment investment and operating costs are high. At the same time, the circulation of the added chemical solvent is poor, which will produce a large amount of salt-containing wastewater, increasing the treatment cost.

[0004] Electrodialysis is another relevant technology widely used in desalination processes, which can advantageously reduce the environmental impact, capital expenditure and operating expenditure of hydrometallurgical processes. However, few studies have addressed the use of electrodialysis in lithium-ion battery recycling processes. Summary of the invention

[0005] In view of this, the present invention provides a method for recovering lithium from waste lithium iron phosphate positive electrode material leachate by homogeneous membrane electrodialysis, which can achieve selective separation of lithium ions and iron ions in the lithium iron phosphate positive electrode material leachate, directly obtain a high-purity lithium-containing solution, and is simple to operate and environmentally friendly.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] The method for recovering lithium from waste lithium iron phosphate positive electrode material leachate by homogeneous membrane electrodialysis comprises the following steps:

[0008] The waste lithium iron phosphate positive electrode material leachate containing lithium ions and iron ions is fed into the dilute chamber of the homogeneous membrane electrodialysis device for circulation, and water is placed in the concentrated chamber of the homogeneous membrane electrodialysis device for circulation. Under the action of a DC electric field, an electric potential difference is applied to the homogeneous membrane, allowing only lithium ions to pass through the homogeneous membrane to achieve selective separation of lithium ions and iron ions, and a separated high-purity lithium-containing solution is obtained in the concentrated chamber of the homogeneous membrane electrodialysis device.

[0009] On the basis of the above technical solution, the present invention further defines the solution as follows:

[0010] Further, the operating current of the homogeneous membrane electrodialysis device is 0 to 4.4A, preferably 0 to 2.2A;

[0011] The working voltage is a DC voltage of 0 to 25V, preferably 0 to 15V;

[0012] The working temperature is 5℃~40℃, preferably 15℃~40℃;

[0013] The running time is 10 to 200 minutes, preferably 10 to 120 minutes;

[0014] The working parameters are adjusted according to the ion concentration in the waste lithium iron phosphate positive electrode material leachate.

[0015] Furthermore, the homogeneous membrane of the homogeneous membrane electrodialysis device is a monovalent cation selective membrane or a free lithium selective membrane, preferably a monovalent cation selective membrane. The monovalent cation selective membrane is characterized in that, under the action of a direct current electric field, monovalent cations are allowed to pass through the membrane pores, while multivalent cations are blocked on one side of the membrane and cannot pass through, thereby achieving selective separation of monovalent cations and multivalent cations;

[0016] The electrode liquid is a 2-4 wt% sodium chloride solution or a 2-4 wt% sodium sulfate solution, preferably a 2-4 wt% sodium chloride solution;

[0017] The water is distilled water, deionized water or ultrapure water, preferably ultrapure water.

[0018] Further, the mass concentration ratio of lithium ions to iron ions in the waste lithium iron phosphate positive electrode material leachate containing lithium ions and iron ions is not higher than 3:1, preferably 1-3:1, which can be 1:1, 2:1, 3:1 and any value therebetween;

[0019] The concentration of lithium ions in the waste lithium iron phosphate positive electrode material leachate containing lithium ions and iron ions is not less than 100 mg / L, preferably not less than 1000 mg / L.

[0020] Furthermore, the method also includes adjusting the pH value of the waste lithium iron phosphate positive electrode material leaching solution containing lithium ions and iron ions to 2-3 before feeding into the dilute chamber of the homogeneous membrane electrodialysis device.

[0021] The beneficial effects of the present invention are:

[0022] 1. Compared with traditional methods such as chemical precipitation and solvent extraction, it completely avoids the addition of chemical agents, greatly reduces secondary pollution, and conforms to the concept of green environmental protection;

[0023] 2. It can directly and effectively separate lithium iron from the leachate of lithium iron phosphate cathode material without complicated intermediate steps, and is easy to operate, which is conducive to practical industrial application;

[0024] 3. Directly obtain high-purity lithium-containing solution, which reduces the difficulty and cost of subsequent processing, provides high-quality raw materials for the subsequent utilization of lithium resources, and promotes the formation of a complete lithium resource recovery closed loop. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the electrodialysis principle of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The homogeneous membrane electrodialysis device involved in the present invention refers to a device capable of performing homogeneous membrane electrodialysis, which can also be referred to as a homogeneous membrane system or a homogeneous membrane device, and is generally composed of three major parts: a main unit, a membrane stack, and a liquid tank. Among them, the membrane stack is a homogeneous membrane stack, which is the core component of the device, and is composed of multiple groups of pairs of membranes (cation exchange membranes and anion exchange membranes) stacked together, and is installed between the anode frame and the cathode frame of the electrodialysis device to form an electrodialysis chamber; the liquid tank is divided into an electrode water tank, a material tank (dilute chamber) and a separation tank (concentrated chamber), which are respectively connected to the electrode liquid inlet and outlet pipes, the material liquid inlet and outlet pipes and the separation liquid inlet and outlet pipes to form a circulation route for the electrode liquid, the material liquid and the separation liquid;

[0028] The type of homogeneous membrane electrodialysis device is not limited. Any homogeneous membrane electrodialysis device with a dilute chamber and a concentrated chamber known or publicly known in the art can be applied to the present application. Those skilled in the art can choose according to actual needs. In the following embodiments, the homogeneous membrane electrodialysis device used is a desktop electrodialysis device produced by Hangzhou Lanran Technology Co., Ltd., model EX-3BT.

[0029] The leaching solution of waste lithium iron phosphate positive electrode materials is simulated by using a synthetic salt water solution with appropriate amount of LiCl and FeCl3·6H2O (balance is water) and pH value adjusted to 2-3;

[0030] The principle diagram of the present invention is as follows Figure 1 As shown, Figure 1 In the membrane, membrane A is an anion exchange membrane, and membrane C is a cation exchange membrane.

[0031] Example 1

[0032] The method for recovering lithium from waste lithium iron phosphate positive electrode material leachate by homogeneous membrane electrodialysis comprises the following steps:

[0033] (1) Using 2-4 wt% sodium chloride solution as the electrode liquid and a monovalent cation selective membrane as the cation exchange membrane (C membrane), 500 mL of waste lithium iron phosphate positive electrode material leachate with a lithium ion concentration of 2000 mg / L and a lithium iron mass concentration ratio of 1:1 is fed into the dilute chamber of a homogeneous membrane electrodialysis device for circulation, and 500 mL of ultrapure water is placed in the concentrated chamber of the homogeneous membrane electrodialysis device for circulation;

[0034] (2) applying direct current to the homogeneous membrane of the homogeneous membrane electrodialysis device at 15° C., with a current of 2.2 A and a direct current voltage of 15 V;

[0035] (3) After running for 120 minutes, the mass concentrations of lithium ions and iron ions in the concentration chamber of the detection device are detected, and the separation of lithium and iron in the leaching solution of waste lithium iron phosphate positive electrode materials is completed.

[0036] Example 2

[0037] The method for recovering lithium from waste lithium iron phosphate positive electrode material leachate by homogeneous membrane electrodialysis comprises the following steps:

[0038] (1) Using 2-4 wt% sodium chloride solution as the electrode liquid and a monovalent cation selective membrane as the cation exchange membrane (C membrane), 500 mL of waste lithium iron phosphate positive electrode material leachate with a lithium ion concentration of 6000 mg / L and a lithium iron mass concentration ratio of 3:1 was fed into the dilute chamber of a homogeneous membrane electrodialysis device for circulation, and 500 mL of ultrapure water was placed in the concentrated chamber of the homogeneous membrane electrodialysis device for circulation;

[0039] (2) applying direct current to the homogeneous membrane of the homogeneous membrane electrodialysis device at 15° C., with a current of 2.2 A and a direct current voltage of 15 V;

[0040] (3) After the device has been running for 120 minutes, the mass concentrations of lithium ions and iron ions in the concentration chamber of the device are detected to complete the separation of lithium and iron in the leaching solution of waste lithium iron phosphate positive electrode materials.

[0041] Example 3

[0042] The method for recovering lithium from waste lithium iron phosphate positive electrode material leachate by homogeneous membrane electrodialysis comprises the following steps:

[0043] (1) Using 2-4 wt% sodium chloride solution as the electrode liquid and a monovalent cation selective membrane as the cation exchange membrane (C membrane), 500 mL of waste lithium iron phosphate positive electrode material leachate with a lithium ion concentration of 4000 mg / L and a lithium iron mass concentration ratio of 2:1 is fed into the dilute chamber of a homogeneous membrane electrodialysis device for circulation, and 500 mL of ultrapure water is placed in the concentrated chamber of the homogeneous membrane electrodialysis device for circulation;

[0044] (2) applying direct current to the homogeneous membrane of the homogeneous membrane electrodialysis device at 15° C., with a current of 2.2 A and a direct current voltage of 15 V;

[0045] (3) After running for 120 minutes, the mass concentrations of lithium ions and iron ions in the concentration chamber of the detection device are detected, and the separation of lithium and iron in the leaching solution of waste lithium iron phosphate positive electrode materials is completed.

[0046] Example 4

[0047] The method for recovering lithium from waste lithium iron phosphate positive electrode material leachate by homogeneous membrane electrodialysis comprises the following steps:

[0048] (1) Using 2-4 wt% sodium chloride solution as the electrode liquid and a monovalent cation selective membrane as the cation exchange membrane (C membrane), 500 mL of waste lithium iron phosphate positive electrode material leachate with a lithium ion concentration of 4500 mg / L and a lithium iron mass concentration ratio of 3:1 was fed into the dilute chamber of a homogeneous membrane electrodialysis device for circulation, and 500 mL of ultrapure water was placed in the concentrated chamber of the homogeneous membrane electrodialysis device for circulation;

[0049] (2) applying direct current to the homogeneous membrane of the homogeneous membrane electrodialysis device at 15° C., with a current of 2.2 A and a direct current voltage of 15 V;

[0050] (3) After running for 120 minutes, the mass concentrations of lithium ions and iron ions in the concentration chamber of the detection device are detected, and the separation of lithium and iron in the leaching solution of waste lithium iron phosphate positive electrode materials is completed.

[0051] Example 5

[0052] The method for recovering lithium from waste lithium iron phosphate positive electrode material leachate by homogeneous membrane electrodialysis comprises the following steps:

[0053] (1) Using a 2-4% sodium sulfate solution and a free lithium selective membrane as a cation exchange membrane (C membrane), 500 mL of a waste lithium iron phosphate positive electrode material leachate having a lithium ion concentration of 5000 mg / L and a lithium iron mass concentration ratio of 2:1 is fed into a dilute chamber of a homogeneous membrane electrodialysis device for circulation, and 500 mL of distilled water is placed in a concentrated chamber of the homogeneous membrane electrodialysis device for circulation;

[0054] (2) applying direct current to the homogeneous membrane of the homogeneous membrane electrodialysis device at 5°C, with a current of 1.2 A and a direct current voltage of 12 V;

[0055] (3) After the device has been running for 10 minutes, the mass concentrations of lithium ions and iron ions in the concentration chamber of the device are detected to complete the separation of lithium and iron in the leaching solution of waste lithium iron phosphate positive electrode materials.

[0056] Example 6

[0057] The method for recovering lithium from waste lithium iron phosphate positive electrode material leachate by homogeneous membrane electrodialysis comprises the following steps:

[0058] (1) Using 2-4% sodium sulfate solution as the electrode liquid and a free lithium selective membrane as the cation exchange membrane (C membrane), 500 mL of waste lithium iron phosphate positive electrode material leachate with a lithium ion concentration of 5000 mg / L and a lithium iron mass concentration ratio of 1:1 is fed into the dilute chamber of a homogeneous membrane electrodialysis device for circulation, and 500 mL of deionized water is placed in the concentrated chamber of the homogeneous membrane electrodialysis device for circulation;

[0059] (2) applying direct current to the homogeneous membrane of the homogeneous membrane electrodialysis device at 40° C., with a current of 4.4 A and a direct current voltage of 25 V;

[0060] (3) After the device has been running for 200 minutes, the mass concentrations of lithium ions and iron ions in the concentration chamber of the device are detected to complete the separation of lithium and iron in the leaching solution of waste lithium iron phosphate positive electrode materials.

[0061] Example 7

[0062] In the iron-lithium separation process of Example 1-4, the initial ion concentration (the measured ion concentration in the waste lithium iron phosphate positive electrode material leachate) and the separation liquid ion concentration (the measured ion concentration of the separation liquid in the concentration chamber of the homogeneous membrane electrodialysis device) were collected, and the recovery rate and the retention rate were calculated based on this;

[0063] The recovery rate is calculated as follows: recovery rate = separation liquid ion concentration * separation liquid volume / (initial ion concentration * waste lithium iron phosphate positive electrode material leachate volume) * 100%;

[0064] The interception rate is calculated as interception rate = [1-separation liquid ion concentration*separation liquid volume / (initial ion concentration*waste lithium iron phosphate cathode material leachate volume)]*100%;

[0065] The results are shown in Table 1.

[0066] Table 1

[0067]

[0068]

[0069] As can be seen from Table 1, the method of the present invention can achieve effective separation of lithium and iron ions in the waste lithium iron phosphate positive electrode material leachate, wherein the iron ion retention rate reaches more than 99.5%, indicating that the obtained separated liquid is a lithium-containing solution with a relatively high purity.

Claims

1. A method for recovering lithium from waste lithium iron phosphate positive electrode material leachate by homogeneous membrane electrodialysis, characterized in that: The following steps are involved: The waste lithium iron phosphate positive electrode material leachate containing lithium ions and iron ions is fed into the dilute chamber of the homogeneous membrane electrodialysis device for circulation, and water is placed in the concentrated chamber of the homogeneous membrane electrodialysis device for circulation, and the lithium ions and iron ions are separated under the action of a DC electric field, and a separated high-purity lithium-containing solution is obtained in the concentrated chamber of the homogeneous membrane electrodialysis device.

2. The method according to claim 1, characterized in that: The working current of the homogeneous membrane electrodialysis device is 0-4.4A; the working voltage is a direct current voltage of 0-25V; the working temperature is 5°C-40°C; and the operating time is 10-200min.

3. The method according to claim 2, characterized in that The homogeneous membrane electrodialysis device has an operating current of 0 to 2.2A, an operating voltage of 0 to 15V DC, an operating temperature of 15°C to 40°C, and an operating time of 10 to 120 minutes.

4. The method according to claim 1, characterized in that The homogeneous membrane of the homogeneous membrane electrodialysis device is a monovalent cation selective membrane or a free lithium selective membrane; The electrode liquid is 2-4wt% sodium chloride solution or 2-4wt% sodium sulfate solution; Water is distilled water, deionized water or ultrapure water.

5. The method according to claim 4, characterized in that The homogeneous membrane of the homogeneous membrane electrodialysis device is a monovalent cation selective membrane; The electrode liquid is 2-4wt% sodium chloride solution; The water was ultrapure water.

6. The method according to claim 1, characterized in that The ratio of the mass concentration of lithium ions to iron ions in the leaching solution of waste lithium iron phosphate positive electrode materials containing lithium ions and iron ions is not higher than 3:

1.

7. The method according to claim 6, characterized in that The mass concentration ratio of lithium ions to iron ions in the waste lithium iron phosphate positive electrode material leachate containing lithium ions and iron ions is 1-3:

1.

8. The method according to any one of claims 1 to 7, characterized in that: The method also includes adjusting the pH value of the waste lithium iron phosphate positive electrode material leaching solution containing lithium ions and iron ions to 2-3 before feeding into the dilute chamber of the homogeneous membrane electrodialysis device.

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