Application of MnO2 ion-sieve graphite felt as an electrodialysis membrane for selective recovery of lithium ions

Abstract

The application provides an application of MnO2 ion sieve graphite felt as an electrodialysis membrane for selectively recovering lithium ions, and relates to the technical field of electrochemistry. The graphite felt is modified by loading MnO2 ion sieve. The MnO2 ion sieve graphite felt prepared in the application can effectively separate lithium ions and cobalt ions, and can help the preliminary treatment of waste liquid when applied in lithium battery waste liquid recovery. Since the market price of the graphite felt is lower than that of traditional ion exchange resins, the recovery cost can be reduced, and the synchronous development of economic benefits and ecological benefits can be realized. The MnO2 ion sieve graphite felt prepared in the application can be used for lithium battery waste liquid recovery, and provides a new idea for waste liquid recovery.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, and in particular to the application of a MnO2 ion sieve graphite felt as an electrodialysis membrane for the selective recovery of lithium ions. Background Technology

[0002] Graphite felt is widely used in electrode fabrication due to its reasonable electrical conductivity, mechanical flexibility, compressibility, and cost. However, the poor surface activity of graphite felt, including poor hydrophilicity and insufficient active sites, limits the electrochemical kinetics of redox reactions. To increase the contact area and wettability between the electrode and redox-active materials, and to improve the electrocatalytic activity of the electrode, low-cost, electrocatalytically active, and readily available manganese oxides (such as Mn3O4 and MnO2) have been widely used in many fields, including supercapacitors and flow batteries.

[0003] Currently, there is no research on combining MnO2 ion-sieve modified graphite felt with cation exchange membranes for selective recovery treatment via electrodialysis. Therefore, this invention utilizes MnO2 ion-sieve graphite felt to construct a three-cell electrodialysis experimental device to recover lithium ions from waste liquid, thereby improving the lithium ion recovery rate. Summary of the Invention

[0004] In view of this, the present invention provides an application of MnO2 ion-screen graphite felt as an electrodialysis membrane for the selective recovery of lithium ions. In the present invention, the pore size of the graphite felt modified by the MnO2 ion screen is reduced, which increases the resistance when ions pass through. However, since the ionic radius of lithium ions is smaller than that of other ions to be filtered in wastewater, the resistance is reduced, thus enabling the separation of lithium ions from other ions and achieving selective recovery of lithium ions.

[0005] This invention is achieved using the following technical solution:

[0006] An application of MnO2 ion-sieve graphite felt as an electrodialysis membrane for the selective recovery of lithium ions, wherein the preparation method of MnO2 ion-sieve graphite felt includes the following steps:

[0007] (1) Pretreatment of graphite felt in acid solution;

[0008] (2) Dissolve potassium permanganate in deionized water, heat to 60℃-70℃, and then adjust the pH to acidic to obtain an acidic solution;

[0009] (3) Place the pretreated graphite felt in the acidic solution and stir in a water bath at 60℃-70℃ for 3-4 hours. After the reaction is complete, wash and dry at 100℃-105℃ to obtain MnO2 ion sieve graphite felt.

[0010] Preferably, the acid solution is a nitric acid solution.

[0011] Furthermore, the concentration of the nitric acid solution is 67 wt%.

[0012] Preferably, the pretreatment temperature is 65℃-75℃ and the time is 2h-3h.

[0013] Preferably, the solid-liquid ratio of potassium permanganate and deionized water is 0.01g-0.03g:15mL.

[0014] Furthermore, in (3), hydrochloric acid is used to adjust the pH value to acidity, and the pH value is 2-3.

[0015] Preferably, the molar concentration of the hydrochloric acid is 2 mol / L.

[0016] Furthermore, the cleaning process uses deionized water.

[0017] Another object of the present invention is to provide a MnO2 ion sieve graphite felt, which is prepared by the preparation method of the above-mentioned MnO2 ion sieve graphite felt as an application of electrodialysis membrane for selective recovery of lithium ions.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The MnO2 ion-sieving graphite felt prepared by this invention can be used for lithium battery waste liquid recycling, providing a new approach to waste liquid recycling. The MnO2 ion-sieving graphite felt prepared by this invention can effectively separate lithium ions and cobalt ions. Its application in lithium battery waste liquid recycling can help with the preliminary treatment of waste liquid. Furthermore, since the market price of graphite felt is lower than that of traditional ion exchange resins, it can reduce recycling costs and achieve simultaneous development of economic and ecological benefits.

[0020] 2. Compared with unmodified graphite felt, the MnO2 ion sieve graphite felt prepared in this invention can selectively recover lithium ions better. Traditional graphite felt has a porous structure and high specific surface area, which can provide more adsorption sites and reaction interfaces, enabling it to more effectively adsorb pollutants in wastewater and achieve efficient filtration. However, the MnO2 ion sieve graphite felt prepared in this invention has a smaller pore size, which increases the resistance when ions pass through. Furthermore, since the ionic radius of lithium ions is smaller than that of other ions to be filtered in wastewater, the resistance is reduced, thus enabling the separation of lithium ions from other ions and achieving selective recovery of lithium ions.

[0021] 3. The MnO2 ion sieve graphite felt prepared by this invention already contains MnO2 ions, so there is no need to add manganese dioxide as a catalyst or treatment agent. Therefore, the process of recycling graphite felt and treating waste graphite felt is reduced, thereby reducing the process cost. Attached Figure Description

[0022] Figure 1 Schematic diagram of a selective lithium-ion recovery device using a MnO2 ion sieve graphite felt coupled with electrodialysis;

[0023] Figure 2 The removal rate of lithium and cobalt ions in the wastewater chamber during the separation of wastewater containing 250 mg / L LiCl and 250 mg / L CoCl2·6H2O in Example 1;

[0024] Figure 3 The lithium and cobalt ion removal rate in the recovery chamber during the separation of wastewater containing 250 mg / L LiCl and 250 mg / L CoCl2·6H2O in Example 1;

[0025] Figure 4 The components separated in Example 1 included 150 mg / L LiCl and 150 mg / L CoC. 12 The removal rates of lithium, cobalt, magnesium, and nickel ions in the wastewater chamber when the wastewater contains 6H2O, 150 mg / L MgCl2, and 150 mg / L Ni(NO3)2;

[0026] Figure 5 The components separated in Example 1 included 150 mg / L LiCl and 150 mg / L CoC. 12 The removal rates of lithium, cobalt, magnesium, and nickel ions in the recovery chamber of wastewater containing 6H2O, 150 mg / L MgCl2, and 150 mg / L Ni(NO3)2;

[0027] Figure 6 The components separated in Example 1 included 200 mg / L LiCl and 200 mg / L CoC. 12 The removal rates of lithium, cobalt, magnesium, and nickel ions in the wastewater chamber when the wastewater contains 6H2O, 200 mg / L MgCl2, and 200 mg / L Ni(NO3)2;

[0028] Figure 7 The components separated in Example 1 included 200 mg / L LiCl and 200 mg / L CoC. 12 The removal rates of lithium, cobalt, magnesium, and nickel ions in the recovery chamber of wastewater containing 6H2O, 200 mg / L MgCl2, and 200 mg / L Ni(NO3)2;

[0029] Figure 8 The components separated for Comparative Example 1 included 150 mg / L LiCl and 150 mg / L CoC. 12 The removal rates of lithium, cobalt, and nickel ions in the wastewater chamber when the wastewater contains 6H2O, 150 mg / L MgCl2, and 150 mg / L Ni(NO3)2;

[0030] Figure 9 The components separated for Comparative Example 1 included 150 mg / L LiCl and 150 mg / L CoC. 12 The removal rates of lithium, cobalt, and nickel ions in the recovery chamber of wastewater containing ·6H2O, 150 mg / L MgCl2, and 150 mg / L Ni(NO3)2. Detailed Implementation

[0031] The present invention will be further described below with reference to the embodiments.

[0032] Example 1

[0033] A method for preparing MnO2 ion-sieve graphite felt includes the following steps:

[0034] (1) Place the graphite felt in a 67wt% nitric acid solution and soak it at 70°C for 2 hours;

[0035] (2) Dissolve 80 mg of potassium permanganate in 60 mL of deionized water, heat to 65 °C, and then adjust the pH value to 2 with hydrochloric acid with a molar concentration of 2 mol / L to obtain an acidic solution.

[0036] (3) Place the pretreated graphite felt in the obtained acidic solution and stir in a water bath at 65°C for 3 hours. After the reaction is complete, wash with deionized water and dry at 100°C overnight to obtain MnO2 ion sieve graphite felt.

[0037] Comparative Example 1

[0038] Ordinary traditional graphite felt is used as an electrodialysis membrane to recover lithium ions.

[0039] The MnO2 ion-sieve graphite felt prepared in Example 1 is used as an electrodialysis membrane for selective recovery of lithium ions. The present invention utilizes an electrodialysis selective lithium ion recovery device coupled with MnO2 ion-sieve graphite felt, as shown in the diagram. Figure 1 As shown, this device is a three-cell electrodialysis unit, consisting of an anode chamber, a wastewater chamber, and a recovery chamber (cathode chamber) from left to right. The electrode plates are made of titanium. The anode chamber contains a 0.5M Na₂SO₄ solution, the recovery chamber (cathode chamber) contains a 0.5M HCl solution, and the wastewater chamber contains lithium-ion wastewater containing various interfering ions. Under the electric field generated by the voltage across the electrodes, the metal ions in the wastewater chamber move directionally. After passing through the modified graphite felt and cation exchange membrane, the interfering ions are blocked on the ion sieve graphite felt, while the lithium ions enter the recovery chamber, thus achieving the selective recovery of lithium ions.

[0040] 1. When the wastewater composition includes 250 mg / L LiCl and 250 mg / L CoCl2·6H2O

[0041] according to Figure 2 and Figure 3 It can be seen that the separation of lithium ions and cobalt ions is different. After 1 hour of separation, the removal rate of cobalt ions in the wastewater chamber is significantly higher than that of lithium ions. This is because the MnO2 ion sieve graphite felt has the ability to adsorb cobalt ions, causing cobalt ions to be adsorbed on the MnO2 ion sieve graphite felt. Lithium ions, on the other hand, have a smaller radius and can pass through the fiber pores of the MnO2 ion sieve graphite felt and the MnO2 ion sieve itself. In the recovery chamber, the recovery rate of lithium ions is comparable to that in the wastewater chamber, indicating that most lithium ions can be recovered, while the recovery rate of cobalt ions is almost zero, showing significant separation of lithium and cobalt ions.

[0042] Meanwhile, after the separation was completed, the MnO2 ion sieve graphite felt was washed with 80 mL of 0.5 mol / L HCl for 24 h, and then inductively coupled plasma (ICP) was performed. The results showed that Li: 1.3 mg / L and Co: 9.35 mg / L, indicating that a large amount of cobalt ions were enriched on the MnO2 ion sieve graphite felt, which promoted the separation of lithium and cobalt.

[0043] 2. When the wastewater composition includes 150 mg / L LiCl, 150 mg / L CoC l2 • 6H2O, 150 mg / L MgCl2 and 150 mg / L Ni(NO3)2

[0044] The removal rate and recovery rate of each ion in the wastewater chamber and the recovery chamber after 10 hours of separation and recovery are shown in Table 1.

[0045] Table 1

[0046]

[0047] To better understand the fate of ions in the wastewater, the graphite felt was washed with 80 mL of 0.5 M HCl for 24 h, and the data were measured as shown in Table 2.

[0048] Table 2

[0049]

[0050] according to Figure 4 and Figure 5It can be seen that, from the perspective of removal rate, the removal rate of lithium ions increases rapidly during the separation process, especially in the first four hours, when the removal rate is approximately twice that of other ions. However, as the experimental time progresses, the removal rates of the various ions become similar, which is related to the directional migration of metal ions under the influence of the electric field. From the perspective of recovery rate, the recovery rate of lithium ions is significantly higher than that of the other ions, and the recovery rate of lithium ions is comparable to the removal rate, indicating that most lithium ions can be recovered. The recovery rates of the other ions, except for magnesium ions, are generally below 10%, indicating significant separation between lithium ions and other ions. Therefore, this MnO2 ion sieve graphite felt can selectively recover lithium ions. Furthermore, from the perspective of ion fate, it was found that the MnO2 ion sieve graphite felt has a certain adsorption effect on ions in wastewater, and the adsorption capacity for ions of different particle sizes varies.

[0051] 3. When the wastewater composition includes 200 mg / L LiCl, 200 mg / L CoCl2·6H2O, 200 mg / L MgCl2, and 200 mg / L Ni(NO3)2

[0052] The removal rate and recovery rate of each ion in the wastewater chamber and the recovery chamber after 10 hours of separation and recovery are shown in Table 3.

[0053] Table 3

[0054]

[0055] according to Figure 6 and Figure 7 and through with Figure 4 and Figure 5 The comparison shows that the recovery rates of various ions decrease with increasing wastewater concentration, indicating that a certain limit needs to be placed on the concentration of the wastewater to achieve a higher recovery rate. However, besides lithium ions, the recovery rates of other ions are almost zero, providing an effective approach for selective lithium ion recovery. Therefore, using MnO2 ion sieves to repair graphite felt for selective lithium ion recovery requires comprehensive consideration of both the recovery rate and the difficulty of separating other ions.

[0056] 4. Using conventional graphite felt from Comparative Example 1 as an electrodialysis membrane to recover lithium ions, when the wastewater composition includes 150 mg / L LiCl and 150 mg / L CoC... l2 • 6H2O, 150 mg / L MgCl2 and 150 mg / L Ni(NO3)2

[0057] according to Figure 8 and Figure 9It can be seen that traditional unmodified graphite felt has a high removal rate for lithium ions, cobalt ions, and nickel ions, indicating that the larger pores of the unmodified graphite felt allow it to absorb a large number of ions. However, the recovery rate is significantly lower compared to the unmodified graphite felt, because most of the ions are adsorbed on the graphite felt. Furthermore, the recovery rates of lithium ions are not significantly different from those of cobalt ions and nickel ions, indicating that ordinary traditional graphite felt does not have the ability to selectively recover lithium ions.

[0058] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An application of MnO2 ion-sieve graphite felt as an electrodialysis membrane for the selective recovery of lithium ions, characterized in that, The preparation method of the MnO2 ion sieve graphite felt includes the following steps: (1) Pretreatment of graphite felt in acid solution; (2) Dissolve potassium permanganate in deionized water, heat to 60℃-70℃, and then adjust the pH to acidic to obtain an acidic solution; (3) Place the pretreated graphite felt in the acidic solution and stir in a water bath at 60℃-70℃ for 3-4 hours. After the reaction is complete, wash and dry at 100℃-105℃ to obtain MnO2 ion sieve graphite felt. The acid solution is a nitric acid solution; The concentration of the nitric acid solution is 67 wt%. The pretreatment temperature is 65℃-75℃, and the time is 2h-3h; The solid-liquid ratio of potassium permanganate and deionized water is 0.01g-0.03g:15mL; In step (2), hydrochloric acid is used to adjust the pH value to acidity, and the pH value is 2-3.

2. The application of the MnO2 ion sieve graphite felt according to claim 1 as an electrodialysis membrane for the selective recovery of lithium ions, characterized in that, The concentration of the hydrochloric acid is 2 mol / L.

3. The application of the MnO2 ion sieve graphite felt according to claim 1 as an electrodialysis membrane for the selective recovery of lithium ions, characterized in that, The cleaning process uses deionized water.

4. A type of MnO2 ion sieve graphite felt, characterized in that, It is prepared using the preparation method described in any one of claims 1-3 for the selective recovery of lithium ions by electrodialysis membrane.

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