Method for upcycling decommissioned lithium iron phosphate battery into fe single-atom catalyst, and use of fe single-atom catalyst
By employing electrochemical leaching and the preparation of Fe-NC catalysts, the problems of recycling retired lithium iron phosphate batteries and degrading organic pollutants have been solved, achieving resource utilization and efficient degradation.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SUZHOU UNIV OF SCI & TECH
- Filing Date
- 2025-01-14
- Publication Date
- 2026-07-16
AI Technical Summary
Existing technologies struggle to effectively recover graphite and iron phosphate when processing retired lithium iron phosphate batteries, and traditional single-atom catalyst processes are complex and costly, failing to efficiently degrade organic pollutants.
Fe-NC catalysts were prepared by electrochemically leaching retired lithium iron phosphate batteries and combining them with surfactant and nitrogen source treatment. These catalysts were then used to activate peroxymonosulfate for advanced oxidation to degrade organic pollutants.
It achieves the cascade recovery of iron phosphate and lithium carbonate, reduces processing costs, improves the stability and activity of the catalyst, and can efficiently degrade organic pollutants such as bisphenol A, thus having good economic and environmental benefits.
Smart Images
Figure CN2025072171_16072026_PF_FP_ABST
Abstract
Description
A method for upgrading retired lithium iron phosphate batteries to prepare iron single-atom catalysts and its application Technical Field
[0001] This invention relates to the field of water pollution treatment technology, and in particular to a method for upgrading retired lithium iron phosphate batteries to prepare iron single-atom catalysts and their applications. Background Technology
[0002] With the rapid development of the new energy vehicle industry, the demand for power batteries, mainly lithium iron phosphate batteries, has increased rapidly. However, this has also brought the challenge of disposing of an increasing number of retired lithium iron phosphate batteries. In 2023, my country generated 168,000 tons of retired power batteries. It is estimated that by 2030, my country will generate more than 1 million tons of retired power batteries, of which more than 60% will be lithium iron phosphate batteries. Therefore, the rational and efficient treatment and recycling of retired lithium iron phosphate batteries can not only recover a large amount of non-ferrous metal resources such as lithium, iron, nickel, and cobalt, but also avoid irreversible damage to the ecological environment caused by heavy metals and fluorinated electrolytes.
[0003] Currently, hydrometallurgy has become the mainstream process for disposing of retired lithium iron phosphate (LFP) batteries. Valuable metals in retired LFP batteries are ionized using acidic solvents (organic or inorganic acids), followed by cascaded recovery through chemical precipitation, extraction, membrane separation, and adsorption. To address the stable olivine structure (FeLiPO4) and coating layers (conductive agents, binders, and graphite), strong acid leaching agents (HCl and H2SO4) and oxidants (H2O2, Cl2, and active oxygen) are used to enhance the decomposition of retired LFP batteries. However, after the valuable metals are leached, the remaining graphite and iron phosphate are often overlooked and not recycled due to their difficulty in separation and low value.
[0004] Advanced oxidation processes (AOPs) based on peroxymonosulfate (PMS) are widely considered an effective method for removing organic pollutants from wastewater. The reactive oxygen species (ROS) generated by activating PMS are strong oxidants with highly efficient pollutant degradation capabilities. Since traditional physical methods (such as ultraviolet light, gamma rays, ultrasound, microwaves, and heat) involve significant energy consumption, single-atom catalysts are superior in activation methods. Among these, metal nitrogen-carbon catalysts, made by co-doping carbon materials with transition metals (such as iron, copper, nickel, cobalt, and manganese) and nitrogen, have significant advantages in aquatic environment remediation due to their high atom utilization, uniform active sites, and high stability.
[0005] For example, CN 119076036 A describes the preparation of an N-coordinated metal-organic framework by precipitation of Cu salt and N-containing organic ligands, followed by pyrolysis at 300–800 °C to obtain a metal single-atom catalyst (i.e., CuO@CN catalyst) supported on a metal oxide and carbon-nitrogen composite support, which effectively improves its efficiency in catalytically activating the degradation of phenol by persulfate.
[0006] For example, CN 118949990 A utilizes the strong metal-support interaction between synthesized titanium dioxide nanosheets and Co single atoms, and obtains Co-supported titanium dioxide nanosheets (i.e., Co / TiO2NS catalyst) after air calcination. The Co single atom acts as a catalytic site, efficiently activating peroxymonosulfate to generate highly oxidizing hydroxyl radicals, achieving efficient oxidative degradation of novel antibiotic pollutants. However, the aforementioned single-atom catalysts all suffer from significant drawbacks such as complex processes and high costs.
[0007] In view of this, the present invention is hereby proposed. Summary of the Invention
[0008] To address the above technical problems, this invention provides a method for upgrading retired lithium iron phosphate batteries to prepare iron single-atom catalysts and its application. The method provided by this invention not only offers a sustainable and economical approach to the resource recovery of waste materials from retired lithium iron phosphate batteries, but also has significant implications for reducing the treatment costs of organic pollutants such as bisphenol A (BPA).
[0009] The first objective of this invention is to provide a method for upgrading retired lithium iron phosphate batteries to prepare iron single-atom catalysts, comprising the following steps:
[0010] (1) Add retired lithium iron phosphate powder to the electrolyte solution, insert the graphene aerogel GA electrode and the Ag / AgCl reference electrode, and connect it to the electrochemical workstation;
[0011] (2) Add a surfactant to the electrolyte solution in step (1) and continuously pass oxygen to carry out electrolysis, electrochemically leach retired lithium iron phosphate, and perform solid-liquid separation on the electrolyte after electrolysis to obtain leachate and filter residue. The filter residue is washed and dried to obtain recycled waste containing iron phosphate and graphite. The leachate is recycled to obtain iron phosphate and lithium carbonate products.
[0012] (3) Add a nitrogen source to the recovered waste obtained in step (2), ball mill and high temperature roasting to obtain an iron single-atom catalyst.
[0013] In some embodiments of the present invention, in step (1), the amount of decommissioned lithium iron phosphate powder added is 0.5 to 2 g / L. The preferred amounts of decommissioned lithium iron phosphate powder added are 0.5 g / L, 1 g / L, 1.5 g / L, and 2 g / L, or any range between any two values.
[0014] In some embodiments of the present invention, in step (1), the electrolyte solution is one or more of sulfuric acid, phosphoric acid, oxalic acid, and acetic acid solutions; preferably, it is a sulfuric acid solution.
[0015] In some embodiments of the present invention, the concentration of the electrolyte solution is 0.01 to 0.4 M, for example, it can be 0.05 M, 0.1 M, 0.15 M, 0.2 M, 0.25 M, 0.3 M and 0.35 M, or any range between any two values.
[0016] In some embodiments of the present invention, in step (2), the surfactant is sodium dodecyl sulfate. The present invention reduces the surface tension of the sulfuric acid medium by adding a surfactant, allowing the waste lithium iron phosphate powder to fully dissolve in the low-concentration sulfuric acid electrolyte.
[0017] In some embodiments of the present invention, in step (2), the amount of surfactant added is 0.05 to 0.3 g / L. The preferred amount of surfactant added is 0.1 g / L, 0.15 g / L, 0.18 g / L, and 0.2 g / L, or any range between any two values.
[0018] In some embodiments of the present invention, in step (2), the electrochemical leaching is an enhanced leaching process that electrogenerates H2O2. Specific parameters include an applied voltage of -1 to -1.5V, an electrolysis time of 2 to 5 hours, and a stirring speed of 300 to 600 rpm. The electrolysis time is preferably 2 to 4 hours, for example, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, or any range between any two values.
[0019] In some embodiments of the present invention, in step (3), the nitrogen source is selected from one or more of dicyandiamine, urea, ethylenediamine, and hydrazine hydrate. More preferably, dicyandiamine is used.
[0020] In some embodiments of the present invention, the amount of nitrogen source used in the recycled waste is 22.5 to 50 g / g, preferably 25 to 30 g / g, for example, it can be 25 g / g, 26 g / g, 27 g / g, 28 g / g, 29 g / g and 30 g / g, or any range between any two values.
[0021] In some embodiments of the present invention, in step (3), the ball milling speed is 200 to 600 rpm;
[0022] In some embodiments of the present invention, the high-temperature calcination temperature is 600–900°C, and the calcination time is 2–5 hours. Preferably, the high-temperature calcination temperature is 600°C, 650°C, 700°C, 750°C, or 800°C, or any range between any two values. Preferably, the calcination time is 2 hours, 2.5 hours, 3 hours, 3.5 hours, or 4 hours, or any range between any two values.
[0023] In some embodiments of the present invention, in step (3), the recovery process of the leachate is a chemical precipitation process including: adjusting the pH of the leachate to about 2.5, adding 5-10 g / L of ammonia water and reacting for 2-4 hours, then separating the solid and liquid to obtain ferric phosphate; then adding 0.5-2 g / L of sodium carbonate and reacting for 2-4 hours, and then filtering, rinsing and drying to obtain lithium carbonate.
[0024] The second objective of this invention is to provide an iron single-atom catalyst prepared by the method described above, wherein the iron single-atom catalyst is a carbon-based nanomaterial co-doped with Fe and N (Fe-NC catalyst).
[0025] A third objective of this invention is to provide the application of the aforementioned iron single-atom catalyst in the degradation of organic pollutants by activated peroxymonosulfate.
[0026] In some embodiments of the present invention, the organic pollutant includes one or more of bisphenol A (BPA), phenol (PN), rhodamine B (RhB), ofloxacin (OFC), and tetracycline (TC). The present invention utilizes sulfate free radicals (SO42-). - ·), hydroxyl radicals (·OH), and singlet oxygen (·) 1 Advanced oxidation technology (AOP) using O2 enables the deep degradation of pollutants such as BPA.
[0027] In some embodiments of the present invention, the amount of the iron single-atom catalyst used is 0.05 to 0.2 g / L.
[0028] In this invention, the advanced oxidation technology (AOP) based on Fe-NC catalyst-activated peroxymonosulfate (PMS) for degrading bisphenol A (BPA) contaminants includes the following chemical reactions:
[0029] This invention provides a method for upgrading retired lithium iron phosphate (LFP) batteries to prepare a single-atom catalyst and its application. The method involves upgrading the "recycled waste" from the electro-oxidative leaching of retired LFP batteries to prepare an Fe-NC catalyst, which activates peroxymonosulfate (PMS) to efficiently degrade bisphenol A (BPA) pollutants. Based on traditional leaching methods, electrochemical leaching technology enhances the leaching of retired LFP batteries through the generated H2O2. The leachate undergoes a series of recycling processes to obtain iron phosphate and lithium carbonate products, while the iron- and graphite-containing recycled waste undergoes nitrogen doping, ball milling, and calcination to prepare the Fe-NC catalyst. The activation effect of the Fe-NC catalyst on PMS is manifested in the adsorption of oxygen atoms from the peroxide bonds at the Fe active sites, leading to the breaking of the O2O bonds and the generation of sulfate radicals (SO4). - ·) and hydroxyl radicals (·OH), while the N active site adsorbs terminal oxygen bound to the S element single bond on PMS, promoting singlet oxygen (·) 1 The formation of O2 in the Fe-NC catalyst not only prevents Fe leaching and improves catalyst stability, but also promotes the generation of singlet oxygen (O2). 1 The generation of O2 is used to degrade BPA pollutants. Based on the aforementioned advanced oxidation technology (AOP) using both free radicals and non-free radicals, BPA pollutants can be directly degraded into CO2 and H2O. Furthermore, the Fe-NC catalyst can recover the activity of deactivated Fe-NC catalysts through a "self-etching" effect under pyrolysis conditions.
[0030] The technical solution of the present invention has the following advantages compared with the prior art:
[0031] (1) This invention provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application. By utilizing an "advanced oxidation process" for electro-generating H2O2 and a "recovery process" for chemical precipitation, it avoids secondary pollutants (Cl2 or ClO) caused by traditional electrochemical oxidation technologies. - This technology enables the tiered recycling of iron phosphate products, lithium carbonate products, and recycled waste, resulting in significant economic and social benefits and promising application prospects.
[0032] (2) Electrochemical leaching in a low-concentration sulfuric acid medium is mild and reduces equipment requirements; the low-concentration sulfuric acid medium is conducive to 2e - Electrocatalytic oxidation-reduction reaction (ORR) produces more H2O2, which can enhance the oxidation and decomposition of retired lithium iron phosphate batteries; the low concentration sulfuric acid medium used greatly reduces acid consumption and facilitates the subsequent treatment of waste liquid.
[0033] (3) This invention provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application. The "upgrading treatment" realizes the resource reuse of iron-containing waste from retired lithium iron phosphate batteries, which is of great significance for improving the sustainability of waste management of retired lithium iron phosphate batteries.
[0034] (4) This invention provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application. The obtained Fe single-atom catalyst (i.e. Fe-NC catalyst) exhibits high catalytic activity, strong stability, low Fe ion leaching and excellent recycling performance, and can be used for long-term recycling.
[0035] (5) This invention provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application. Compared with single-atom catalysts of Cu, Ag, Co and Mn, Fe-NC catalysts have the advantages of being easy to obtain, non-toxic, environmentally friendly and low cost.
[0036] (6) This invention provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application. Based on the advanced oxidation technology (AOP) of Fe-NC catalyst-activated peroxymonosulfate (PMS), the generated active oxygen (ROS) can achieve deep degradation of bisphenol A pollutants (BPA), and is expected to be applicable to the treatment of other organic pollutants such as phenol (PN), rhodamine B (RhB), ofloxacin (OFC), and tetracycline (TC). The biodegradability of the treated organic wastewater is greatly improved, and it has good environmental applicability. Attached Figure Description
[0037] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...
[0038] Figure 1 is a process flow diagram of a method for preparing iron single-atom catalysts for upgrading retired lithium iron phosphate batteries provided by the present invention and its application.
[0039] Figure 2 shows the effect of sulfuric acid medium concentration of the present invention on the leaching rate of Li and Fe in decommissioned lithium iron phosphate batteries (a) and the electrochemical H2O2 production (b) (Examples 1, 2 and Comparative Examples 1-2).
[0040] Figure 3 shows the differences in Li and Fe leaching rates in decommissioned lithium iron phosphate batteries under different experimental conditions (without H2O2, with H2O2, and electrochemical) in 0.1M sulfuric acid medium and their quenching experiments (Example 1 and Comparative Examples 3-4).
[0041] Figure 4 shows the effect of the amount of dicyandiamine added in this invention on the catalytic performance of Fe single-atom catalyst in degrading bisphenol A (BPA) pollutants (Examples 1, 5 and Comparative Examples 8-9).
[0042] Figure 5 is a spherical aberration projection electron microscope image of the Fe single-atom catalyst of the present invention. Detailed Implementation
[0043] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.
[0044] In some embodiments of the present invention, the process for degrading bisphenol A (BPA) organic pollutants includes the following steps:
[0045] Organic pollutants such as BPA were weighed, ultrasonically heated for 1 hour, and dissolved in 1 L of aqueous solution to obtain 50 μM BPA pollutant.
[0046] Prepare 10 centrifuge tubes and add 0.05 mL of 1.0 M sodium thiosulfate solution (quencher). Transfer 5 mL of 50 μM BPA contaminant to the centrifuge tubes and label them as S1.
[0047] Measure 100 mL of BPA contaminant into a beaker, and disperse 0.1 g / L Fe-NC catalyst into the BPA contaminant. First, ultrasonically disperse for 10 min, then magnetically stir. After 15 min and 30 min, respectively, take 5 mL of BPA solvent into centrifuge tubes and label them as S2 and S3.
[0048] Then add 0.5 mL of 0.2 M PMS solution to start the reaction. At 10 s, 20 s, 40 s, 60 s, 2 min, 4 min, and 8 min, take 5 mL of BPA solvent into centrifuge tubes and label them as S4 to S10.
[0049] The solutions from 10 centrifuge tubes were filtered through a filter and then added to a liquid chromatography vial (0.5-1 mL). The concentration change of BPA in the solvent was tested by high performance liquid chromatography to evaluate the catalytic performance of the Fe-NC catalyst.
[0050] Example 1:
[0051] This embodiment provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, including the following steps:
[0052] (1) Add 0.1g of retired lithium iron phosphate powder to 100mL of 0.1M sulfuric acid electrolysis medium, insert the graphene aerogel GA electrode (i.e., working electrode and counter electrode) and Ag / AgCl reference electrode, and connect it to the electrochemical workstation;
[0053] (2) Add 0.1 g / L sodium dodecyl sulfate to the electrolyte solution in step (1) and continuously introduce oxygen. Under the conditions of -1.2 V voltage, 2 h electrolysis time and 400 rpm stirring speed, decommissioned lithium iron phosphate is electrochemically leached. The filter residue is washed and dried to obtain recycled waste. The leachate is recycled to obtain iron phosphate and lithium carbonate products.
[0054] (3) Weigh 0.2g of the recycled waste obtained in step (2), add 25g / g of dicyandiamide (recycled waste), ball mill at 400rpm for 4h, and then prepare Fe single-atom catalyst (i.e. Fe-NC catalyst) in N2 atmosphere at a calcination temperature of 700℃ and a calcination time of 4h.
[0055] Performance testing:
[0056] The Fe-NC catalyst obtained in step (3) was used to activate peroxymonosulfate (PMS) and effectively degraded 50 μM bisphenol A (BPA) pollutant under the conditions of reaction temperature of 25 °C and reaction time of 8 min.
[0057] Testing showed that 6.8 mM H2O2 was produced after 2 hours of electrolysis, and the leaching rate of lithium in the retired lithium iron phosphate battery reached 99.8%, the leaching rate of iron reached 98.5%, and the removal efficiency of BPA pollutants by the Fe-NC / PMS system reached 98.5%.
[0058] Example 2:
[0059] This embodiment provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, which is basically the same as that in Example 1, except that the concentration of sulfuric acid electrolysis medium in step (1) is 0.05M.
[0060] Performance testing:
[0061] Testing showed that 6.5 mM H2O2 was produced after 2 hours of electrolysis, and the leaching rate of lithium in the retired lithium iron phosphate battery reached 99.5%, and the leaching rate of iron reached 98.2%. At the same time, the Fe-NC / PMS system had a BPA pollutant removal efficiency of over 98%.
[0062] Example 3:
[0063] This embodiment provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, which is basically the same as that in Example 1, except that in step (2), the amount of sodium dodecyl sulfate added is 0.2 g / L.
[0064] Performance testing:
[0065] Tests showed that the lithium leaching rate in the retired lithium iron phosphate batteries reached 99.9%, and the iron leaching rate reached 98.8%.
[0066] Example 4:
[0067] This embodiment provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, which is basically the same as that in embodiment 1, except that the electrolysis time in step (2) is 4 hours.
[0068] Performance testing:
[0069] Testing revealed that 4 hours of electrolysis produced 11.5 mM H2O2, achieving a lithium leaching rate of 99.9% and an iron leaching rate of 98.8% in the retired lithium iron phosphate batteries. Clearly, 2 hours of electrolysis producing H2O2 achieves sufficient oxidation decomposition and resource recovery of retired lithium iron phosphate batteries; extending the electrolysis time would increase energy consumption.
[0070] Example 5:
[0071] This embodiment provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, which is basically the same as that in embodiment 1. The difference is that in step (3), the amount of dicyandiamine added is 30g / g (recycled waste).
[0072] Performance testing:
[0073] Testing showed that the Fe-NC / PMS system achieved a BPA removal efficiency of 99.5%. Furthermore, the Fe content in the treated solution was less than 0.1 mg / L. The N active sites in the Fe-NC catalyst not only prevent Fe leaching and improve catalyst stability, but also promote the release of singlet oxygen (…). 1 The generation of O2 helps degrade BPA pollutants.
[0074] Example 6:
[0075] This embodiment provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, which is basically the same as that in embodiment 1, except that the calcination temperature in step (3) is 800℃.
[0076] Performance testing:
[0077] Testing showed that the Fe-NC / PMS system achieved a BPA removal efficiency of 98.2%. Furthermore, the Fe content in the treated solution was less than 0.1 mg / L.
[0078] Example 7:
[0079] This embodiment provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, which is basically the same as that in embodiment 1, except that the calcination time in step (3) is 3 hours.
[0080] Performance testing:
[0081] Testing showed that the Fe-NC / PMS system achieved a BPA removal efficiency of 98.6%. Furthermore, the Fe content in the treated solution was less than 0.1 mg / L.
[0082] Comparative Example 1:
[0083] This comparative example provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, which is basically the same as Example 1, except that: in step (1), the concentration of sulfuric acid electrolysis medium is 0.5M.
[0084] Performance testing:
[0085] Tests showed that only 2.6 mM H2O2 was produced after 2 hours of electrolysis, and the leaching rate of lithium in the retired lithium iron phosphate battery was 80.5% and the leaching rate of iron was 83%.
[0086] Comparative Example 2:
[0087] This comparative example provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, which is basically the same as Example 1, except that: in step (1), the concentration of sulfuric acid electrolysis medium is 1M.
[0088] Performance testing:
[0089] Tests showed that only 4.2 mM H2O2 was produced after 2 hours of electrolysis, and the leaching rate of lithium and iron in the retired lithium iron phosphate battery was 71.5%.
[0090] Comparative Example 3:
[0091] This embodiment provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, which is basically the same as that in Example 1. The difference is that in step (1), the mixed solution of retired lithium iron phosphate powder and sulfuric acid medium is not subjected to electrochemical leaching.
[0092] Performance testing:
[0093] Tests showed that the leaching rate of lithium in retired lithium iron phosphate batteries was 38%, and the leaching rate of iron was 39%.
[0094] Comparative Example 4:
[0095] This comparative example provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, which is basically the same as Example 1. The difference is that in step (1), the mixed solution of retired lithium iron phosphate powder and sulfuric acid medium is not subjected to electrochemical leaching, but 6.8 mM H2O2 is added.
[0096] Performance testing:
[0097] Testing revealed that the leaching rate of lithium in retired lithium iron phosphate batteries was 60%, and the leaching rate of iron was 42%. Furthermore, in the comparative example, with the presence of a quencher (H₂O₂ quenching), the leaching rate of lithium was 38%, and the leaching rate of iron reached 28%. However, in Example 1, with the presence of a quencher (H₂O₂ quenching), the leaching rate of lithium reached 87%, and the leaching rate of iron reached 85%. Based on the results of the quenching experiment, the in-situ generation of H₂O₂ during electrochemical leaching differs from the method of adding additional H₂O₂. Only under the action of "electro-oxidation enhanced leaching" can lithium and iron in retired lithium iron phosphate batteries achieve efficient leaching.
[0098] Comparative Example 5:
[0099] This comparative example provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, which is basically the same as Example 1, except that in step (2), the amount of sodium dodecyl sulfate added is 0 g / L.
[0100] Performance testing:
[0101] Tests showed that the leaching rate of lithium in retired lithium iron phosphate batteries was 88.5%, and the leaching rate of iron was 86%.
[0102] Comparative Example 6:
[0103] This comparative example provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, which is basically the same as Example 1, except that in step (2), the electrolysis time is 1 hour.
[0104] Performance testing:
[0105] Tests showed that the leaching rate of lithium in retired lithium iron phosphate batteries was 62%, and the leaching rate of iron was 80.5%.
[0106] Comparative Example 7:
[0107] This comparative example provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, which is basically the same as Example 1, except that the electrolysis time in step (2) is 1.5h.
[0108] Performance testing:
[0109] Tests showed that the leaching rate of lithium in retired lithium iron phosphate batteries was 65%, and the leaching rate of iron was 82%.
[0110] Comparative Example 8:
[0111] This comparative example provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, which is basically the same as Example 1, except that: in step (3), the amount of dicyandiamine added is 15g / g (recycled waste).
[0112] Performance testing:
[0113] Testing showed that the Fe-NC / PMS system achieved a 92% removal efficiency for BPA contaminants. However, the Fe concentration in the treated solution was only 0.3 mg / L. The low N doping level resulted in instability of the Fe single-atom catalyst, leading to easy leaching of Fe.
[0114] Comparative Example 9:
[0115] This comparative example provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, which is basically the same as Example 1, except that: in step (3), the amount of dicyandiamine added is 20g / g (recycled waste).
[0116] Performance testing:
[0117] Testing showed that the Fe-NC / PMS system achieved a 96% removal efficiency for BPA contaminants. However, the Fe concentration in the treated solution was 0.15 mg / L.
[0118] Comparative Example 10:
[0119] This comparative example provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, which is basically the same as Example 1, except that the calcination temperature in step (3) is 500℃.
[0120] Performance testing:
[0121] Tests showed that the Fe-NC / PMS system achieved a BPA removal efficiency of 76%.
[0122] Comparative Example 11:
[0123] This comparative example provides a method for upgrading retired lithium iron phosphate batteries to prepare single-atom catalysts and its application, which is basically the same as Example 1, except that: in step (3), the calcination time is 1h.
[0124] Performance testing:
[0125] Tests showed that the Fe-NC / PMS system achieved a 65% removal efficiency for BPA contaminants.
[0126] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A method for upgrading retired lithium iron phosphate batteries to prepare iron single-atom catalysts, characterized in that, Includes the following steps: (1) Add retired lithium iron phosphate powder to the electrolyte solution, insert the graphene aerogel GA electrode and the Ag / AgCl reference electrode, and connect it to the electrochemical workstation; (2) Add a surfactant to the electrolyte solution in step (1) and continuously pass oxygen to carry out electrolysis, electrochemically leach retired lithium iron phosphate, and perform solid-liquid separation on the electrolyte after electrolysis to obtain leachate and filter residue. The filter residue is washed and dried to obtain recycled waste containing iron phosphate and graphite. The leachate is recycled to obtain iron phosphate and lithium carbonate products. (3) Add a nitrogen source to the recycled waste obtained in step (2), and ball mill and high temperature calcination to obtain an iron single-atom catalyst.
2. The method according to claim 1, characterized in that, In step (1), the amount of retired lithium iron phosphate powder added is 0.1-5 g / L; The electrolyte solution is one or more of sulfuric acid, phosphoric acid, oxalic acid, and acetic acid solutions; The concentration of the electrolyte solution is 0.01–0.4 M.
3. The method according to claim 1, characterized in that, In step (2), the surfactant is sodium dodecyl sulfate; The amount of surfactant added is 0.05 to 0.3 g / L.
4. The method according to claim 1, characterized in that, In step (2), the electrochemical leaching is an electro-oxidation enhanced leaching process that produces H2O2. The specific parameters include an applied voltage of -1 to -1.5V, an electrolysis time of 2 to 5h, and a stirring speed of 300 to 600rpm.
5. The method according to claim 1, characterized in that, In step (3), the nitrogen source is selected from one or more of dicyandiamine, urea, ethylenediamine, and hydrazine hydrate; The amount of nitrogen source used in the recycled waste is 22.5–50 g / g.
6. The method according to claim 1, characterized in that, In step (3), the ball milling speed is 200-600 rpm; The high-temperature roasting temperature is 550–900℃, and the roasting time is 2–5 hours.
7. The method according to claim 1, characterized in that, In step (3), the leachate recovery process is a chemical precipitation process.
8. A single-atom iron catalyst, characterized in that, The iron single-atom catalyst is prepared by the method described in any one of claims 1 to 7, wherein the iron single-atom catalyst is a carbon-based nanomaterial co-doped with Fe and N.
9. The application of the iron single-atom catalyst according to claim 8 in the degradation of organic pollutants by activated peroxymonosulfate.
10. The application according to claim 9, characterized in that, The organic pollutants include one or more of bisphenol A, phenol, rhodamine B, ofloxacin, or tetracycline.