Preparation method and application of heterogeneous activated persulfate catalyst

Abstract

The invention discloses a preparation method and application of a heterogeneous activated persulfate catalyst, and the preparation method comprises the following steps: step 1, immersing a decommissioned LiFePO4 soft package battery in a 5% NaCl solution for 24 hours, and reducing the voltage of the battery to 0.5 V or below; then the discharged battery is disassembled in a glove box filled with nitrogen, and an aluminum plastic film, a negative pole piece and a diaphragm are separated out; separating an aluminum foil from a positive electrode material by using a scraper for the detached positive electrode plate, placing the material in 1: 1 hydrochloric acid, performing acid leaching for 2 hours, then performing ultrasonic water washing until the material is neutral, placing the material in an air dry oven, and drying at the temperature of 80 DEG C; and finally, the heterogeneous activated persulfate catalyst based on the retired LiFePO4 material is obtained. The preparation method provides dual solutions for high-value utilization of the retired battery material and organic wastewater treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of heterogeneous catalytic sewage treatment materials, and particularly relates to a preparation method and application of a heterogeneous activated persulfate catalyst. Background Art

[0002] Since the discovery of lithium iron phosphate (LiFePO4, LFP) material in 1997, the related research and application have been rapidly developed and widely used in electric vehicles, large energy storage equipment, power tools, medical equipment and other fields. Lithium iron phosphate material has a unique olivine structure, high theoretical specific capacity (about 170mAh / g), stable voltage platform (3.5VvLi / Li + ), excellent safety performance and good cycle stability, making it the first choice for lithium-ion battery positive electrode materials.

[0003] However, as a large number of lithium iron phosphate batteries reach the end of their service life, the number of retired batteries has increased dramatically. If these retired batteries are not effectively treated and reused, it will not only cause a waste of resources, but may also cause potential pollution to the environment. Therefore, exploring the reuse of retired lithium iron phosphate materials has important practical significance. At the same time, advanced oxidation technology based on persulfate is highly favored because it can efficiently degrade organic pollutants in wastewater. Persulfate can produce highly oxidizing sulfate radicals (·SO4 - ) and hydroxyl radicals (·OH). These free radicals possess extremely high oxidative power and can effectively degrade various organic and heavy metal pollutants. However, traditional activation methods such as direct thermal decomposition of persulfate or ultraviolet light excitation are limited by low activation efficiency and harsh reaction conditions. Therefore, the development of efficient and stable catalysts to activate persulfate and improve its efficiency in generating active free radicals has become a key research topic. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the existing defects and provide a preparation method and application of a heterogeneous activated persulfate catalyst to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing a heterogeneous activated persulfate catalyst, comprising the following steps:

[0006] Step 1: Immerse the retired LiFePO4 soft-pack battery in a NaCl solution; disassemble the discharged battery to separate the aluminum-plastic film, the negative electrode plate and the separator; separate the aluminum foil from the LiFePO4 positive electrode material, and then soak it in N-methylpyrrolidone (NMP) solution to remove the residual electrolyte and other impurities on the surface of the positive electrode plate, and then dry and powder the obtained LiFePO4 positive electrode material;

[0007] Step 2: After the powder is pulverized, ultrasonic washing is performed. The ultrasonic water contains 1% citric acid. The ultrasonic time is set to 10 minutes each time. After the ultrasonication, the deionized water is replaced. The operation is repeated three times to completely remove the excess electrolyte and binder on the positive electrode material.

[0008] Step 3: Place the ultrasonically washed material in a blast drying oven and dry it at 80°C. Place the dried positive electrode material and anhydrous glucose (1:1 wt%) in a ball mill and set the speed to 500 r / min for 2 hours without oxygen.

[0009] Step 4: Place the ground material in a tube furnace, add hydrogen at 0.5 L / min, heat at 2°C / min to 400°C, keep warm for 3 hours, heat at 5°C / min to 700°C, keep warm for 10 hours, and cool naturally;

[0010] Step 5: After cooling, the material is placed in a ball mill, the speed is set to 500 r / min, and oxygen-free ball milling is performed for 2 hours; the material is placed in 1:1 hydrochloric acid for acid leaching for 2 hours, then ultrasonically washed with water until neutral, placed in a blast drying oven, and dried at 80°C; finally, a heterogeneous activated persulfate catalyst based on retired LiFePO4 material is obtained.

[0011] Preferably, the preparation process of retired lithium iron phosphate material includes the following steps:

[0012] Step 1: Immerse the retired LiFePO4 soft-pack battery in a NaCl solution; disassemble the discharged battery to separate the aluminum-plastic film, the negative electrode plate and the separator; separate the aluminum foil from the LiFePO4 positive electrode material, and then soak it in N-methylpyrrolidone (NMP) solution to remove the residual electrolyte and other impurities on the surface of the positive electrode plate, and then dry and powder the obtained LiFePO4 positive electrode material;

[0013] Step 2: After the powder is pulverized, ultrasonic washing is performed. The ultrasonic water contains 1% citric acid. The ultrasonic time is set to 10 minutes each time. After the ultrasonication, the deionized water is replaced. The operation is repeated three times to completely remove the excess electrolyte and binder on the positive electrode material.

[0014] Step 3: Place the ultrasonically washed material in a blast drying oven and dry it at 80°C. Place the dried positive electrode material and anhydrous glucose (1:1 wt%) in a ball mill and set the speed to 500 r / min for 2 hours without oxygen.

[0015] Step 4: Place the ground material in a tube furnace, add hydrogen at 0.5 L / min, heat at 2°C / min to 400°C, keep warm for 3 hours, heat at 5°C / min to 700°C, keep warm for 10 hours, and cool naturally;

[0016] Step 5: After cooling, the material is placed in a ball mill, the speed is set to 500 r / min, and oxygen-free ball milling is performed for 2 hours; the material is placed in 1:1 hydrochloric acid for acid leaching for 2 hours, then ultrasonically washed with water until neutral, placed in a blast drying oven, and dried at 80°C; finally, a heterogeneous activated persulfate catalyst based on retired LiFePO4 material is obtained.

[0017] Preferably, in the step 2, ultrasonic water washing is performed after the powdering, the ultrasonic water contains 1% citric acid, and the ultrasonic time is set to 10 minutes each time. After the ultrasonic treatment, deionized water is replaced, and the operation is repeated three times to completely remove excess electrolyte and binder on the positive electrode material.

[0018] Preferably, in step three, the ultrasonically washed material is placed in a blast drying oven and dried at 80° C. The dried positive electrode material and anhydrous glucose (1:1 wt%) are placed in a ball mill, the speed is set to 500 r / min, and oxygen-free ball milling is performed for 2 hours.

[0019] Preferably, in step 4, the ground material is placed in a tubular furnace, hydrogen is supplied at 0.5 L / min, the temperature is raised to 400° C. at 2° C. / min, kept warm for 3 hours, the temperature is raised to 700° C. at 5° C. / min, kept warm for 10 hours, and cooled naturally.

[0020] Preferably, in the step five, after cooling, the material is placed in a ball mill, the speed is set to 500 r / min, and oxygen-free ball milling is performed for 2 hours; the material is placed in 1:1 hydrochloric acid for acid leaching for 2 hours, then ultrasonically washed with water until neutral, placed in a blast drying oven, and dried at 80°C; finally, a heterogeneous activated persulfate catalyst based on retired LiFePO4 material is obtained.

[0021] A method for applying a heterogeneous activated persulfate catalyst uses a catalyst prepared by the method for preparing a heterogeneous activated persulfate catalyst to activate a persulfate oxidation reaction.

[0022] Compared with the prior art, the present invention provides a preparation method and application of a heterogeneous activated persulfate catalyst, which has the following beneficial effects:

[0023] 1. In the process of preparing retired lithium iron phosphate materials in the present invention, an ultrasonic water washing operation is performed on the powder after the powder is pulverized. The ultrasonic water contains 1% citric acid. The ultrasonic time is set to 10 minutes each time. After the ultrasonic treatment, deionized water is replaced. The operation is repeated three times to completely remove the excess electrolyte and binder on the positive electrode material; Step 3, the ultrasonically washed material is placed in a blast drying oven and dried at 80°C. The dried positive electrode material and anhydrous glucose (1:1wt%) are placed in a ball mill, the speed is set to 500r / min, and oxygen-free ball milling is performed for 2 hours; Step 4, The ground material was placed in a tube furnace, hydrogen was 0.5 L / min, the temperature was raised to 400°C at 2°C / min, the temperature was kept for 3 hours, the temperature was raised to 700°C at 5°C / min, the temperature was kept for 10 hours, and the material was naturally cooled; step 5: after cooling, the material was placed in a ball mill, the speed was set to 500 r / min, and oxygen-free ball milling was performed for 2 hours; the material was acid-leached in 1:1 hydrochloric acid for 2 hours, then ultrasonically washed with water until neutral, placed in a blast drying oven, and dried at 80°C; the above steps make the obtained catalyst have great application potential in the field of activated persulfate treatment of wastewater;

[0024] 2. The present invention does not show significant performance degradation in the LFP / PDS system during cyclic use; taking methyl orange as a typical pollutant, when used for the first time, C / C o The performance degradation was rapidly reduced from 1.0 to 0.019, and COD was reduced from 209 mg / L to 22.5 mg / L. After the third cycle, C / C0 was only reduced to 0.113, and COD remained at 33 mg / L. The LFP characterization results and the analysis of the influencing factors of the LFP / PDS system showed that the main reason for the performance degradation was Fe 2+ / Fe 3+ The circulation is blocked, resulting in a weakening of the PDS activation ability; in addition, as the reaction proceeds, the adsorption of intermediates and the aggregation of particles increase, resulting in blurred boundaries and coverage of active sites;

[0025] 3. The cyclic stability of the SLFP / PDS system of the present invention is reduced compared to the cyclic stability of the LFP / PDS system; in the first cycle, the C / C0 dropped to 0.119 and the COD dropped to 31 mg / L; after the third cycle, the C / C0 could still be reduced to 0.223, and the COD dropped to 48 mg / L. The characterization results of LFP and SLFP and the analysis of the influencing factors show that the main reason for the reduced cyclic stability of the SLFP / PDS system is that the deintercalation / intercalation of lithium ions in LFP during the charge and discharge process leads to the accumulation of local lattice stress, the appearance of grain boundary defects or microstrain in some areas, and the formation of FePO4 phases, resulting in insufficient active sites.

[0026] 4. In the field of material applications, this invention converts retired lithium iron phosphate cathode materials into highly efficient water treatment catalysts, addressing the environmental pollution issues associated with retired batteries. Through a simple treatment process, it successfully transforms battery waste into catalytically active nanomaterials, creating a closed-loop chain of "retired batteries → catalyst → wastewater treatment," creating a high-value-added utilization path for lithium battery recycling.

[0027] 5. The present invention reveals the Fe in the LiFePO4 olivine structure 2+ / Fe 3+ The catalytic mechanism of redox pairs; the complete crystal structure provides stable active sites. It was found that although the lattice defects generated by the cycle of SLFP reduced the catalytic activity, it still had an efficiency of 80%, providing a theoretical basis for the reuse of defective materials; by combining new energy materials (LFP) with advanced oxidation technology, a new process for treating organic pollutants with high-efficiency catalysts was developed, which has lower costs than commercial catalysts and meets the requirements of industrial catalytic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 These are scanning electron microscope images of retired lithium iron phosphate obtained in the present invention; wherein a is a scanning electron microscope image of the LFP described in the present invention; wherein b is a scanning electron microscope image of the SLFP described in the present invention; wherein c is a scanning electron microscope image of the LFP after the reaction described in the present invention; wherein d is a scanning electron microscope image of the SLFP after the reaction described in the present invention;

[0030] Figure 2 : The scanning electron microscope photograph of the retired lithium iron phosphate obtained in the present invention; wherein e is the EDS element mapping image of the Fe element in the SLFP of the present invention; wherein f is the EDS element mapping image of the P element in the SLFP of the present invention; wherein g is the EDS element mapping image of the O element in the SLFP of the present invention;

[0031] Figure 3 is the XRD pattern of SLFP obtained in the present invention;

[0032] Figure 4 is the Raman spectrum of SLFP obtained by the present invention;

[0033] Figure 5 This is a graph showing the degradation of methyl orange by the SLFP / PDS system under different initial pH values ​​of the SLFP of the present invention;

[0034] Figure 6This is a graph showing the degradation of methyl orange by the SLFP / PDS system under conditions of different sodium persulfate concentrations according to the present invention;

[0035] Figure 7 This is a graph showing the degradation of methyl orange by the SLFP / PDS system under different SLFP dosage conditions;

[0036] Figure 8 This is a diagram of the degradation of methyl orange by the SLFP / PDS system under conditions of different initial methyl orange concentrations. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0038] See also Figure 1-8 The present invention provides a technical solution: a method for preparing a heterogeneous activated persulfate catalyst, comprising:

[0039] Step 1: Immerse the retired LiFePO4 soft-pack battery in a NaCl solution; disassemble the discharged battery to separate the aluminum-plastic film, the negative electrode plate and the separator; separate the aluminum foil from the LiFePO4 positive electrode material, and then soak it in N-methylpyrrolidone (NMP) solution to remove the residual electrolyte and other impurities on the surface of the positive electrode plate, and then dry and powder the obtained LiFePO4 positive electrode material;

[0040] Step 2: After the powder is pulverized, ultrasonic washing is performed. The ultrasonic water contains 1% citric acid. The ultrasonic time is set to 10 minutes each time. After the ultrasonication, the deionized water is replaced. The operation is repeated three times to completely remove the excess electrolyte and binder on the positive electrode material.

[0041] Step 3: Place the ultrasonically washed material in a blast drying oven and dry it at 80°C. Place the dried positive electrode material and anhydrous glucose (1:1 wt%) in a ball mill and set the speed to 500 r / min for 2 hours without oxygen.

[0042] Step 4: Place the ground material in a tube furnace, add hydrogen at 0.5 L / min, heat at 2°C / min to 400°C, keep warm for 3 hours, heat at 5°C / min to 700°C, keep warm for 10 hours, and cool naturally;

[0043] Step 5: After cooling, the material is placed in a ball mill, the speed is set to 500 r / min, and oxygen-free ball milling is performed for 2 hours; the material is placed in a 1:1 hydrochloric acid acid leaching for 2 hours, and then ultrasonically washed with water until neutral, placed in a blast drying oven, and dried at 80°C; finally, a heterogeneous activated persulfate catalyst based on retired LiFePO4 material is obtained;

[0044] The catalyst prepared by the invention is used for activating persulfate oxidation reaction.

[0045] Example

[0046] The morphology and particle distribution of LFP and SLFP material samples are as follows Figure 1 a. Figure 1 As shown in b; Figure 1 As shown in a, the LFP particles have smooth surfaces, clear boundaries, irregular polygonal shapes, and uniform sizes of about 1-2 μm, which is consistent with the sizes reported in the literature. This result confirms that the original LFP maintains a complete olivine-type crystal structure, providing a stable Fe 2+ / Fe 3+ Redox active sites; According to SEM observation results, the SLFP material shows similar but slightly different features to LFP in morphology; the SLFP particles as a whole still maintain an irregular polygonal shape, confirming the retention of the olivine-type crystal skeleton, but the increase in surface roughness indicates that lithium ion deintercalation / intercalation during charge and discharge leads to local lattice stress accumulation, and grain boundary defects or microstrain appear in some areas; From the SEM images of LFP and SLFP materials after reaction, as shown Figure 1 c. Figure 1 d It can be clearly seen that as the reaction proceeds, the particle aggregation increases, resulting in blurred boundaries;

[0047] Figure 3 The X-ray diffraction (XRD) spectra of LFP and SLFP materials were presented and compared with those of the post-reaction spectra. The XRD patterns of LFP and SLFP showed that the positions of the main diffraction peaks remained essentially unchanged and corresponded one-to-one with the characteristic peaks in the standard PDF card, indicating that the SLFP material is mainly composed of LFP. However, the peak width of SLFP was somewhat wider than that of LFP. In addition, a weak peak appeared near 30° (2θ) in SLFP and the post-reaction LFP and SLFP, which was not observed in the XRD pattern of LFP. This may be attributed to the formation of FePO4 or local structural deformation within the material.

[0048] like Figure 4 As shown in the figure, the Raman spectra of LFP and SLFP materials are displayed and compared with the spectra after reaction; LFP is at about 950cm -1There is a sharp PO43-symmetric stretching vibration peak at about 300 cm -1 The vibration peak of Fe-O bond is shown at 900 cm-1, while the PO43-symmetric stretching vibration peak of SLFP is shifted to 900 cm-1. -1 The peak width increases, indicating that lithium ion deintercalation / intercalation weakens the PO bond and introduces lattice stress during charge and discharge. In addition, SLFP and the reacted LFP and SLFP have a peak width of 200 cm *1 New peaks appeared below, which indicated the formation of FePO4 phase;

[0049] like Figure 5 As shown in the figure, the MO removal efficiency is the highest at low pH value (2.7-3.0), and C / C0 drops sharply from 1.0 to nearly 0.6 within 0-2 minutes; acidic conditions accelerate the removal of Fe on the surface of SLFP. 2+ / Fe 3+ The redox cycle promotes the activation of PDS to generate SO4 - free radicals, while inhibiting Fe 3+ Hydrolyzes to Fe(OH)3 colloid to maintain the activity of the catalyst; when the pH rises to 3.5-5.0, the reaction efficiency decreases significantly (at pH = 5, C / C0 is still higher than 0.9 after 10 minutes). 3+ Forming colloids to cover active sites, hindering PDS activation and free radical generation;

[0050] Figure 6 The results show that when the PDS dosage increased from 1mM to 10mM, C / C0 decreased from 0.68 to 0.3, indicating that the PDS concentration is positively correlated with the amount of free radicals generated. In the initial stage (0-2 minutes), all curves decreased rapidly, which was attributed to the rapid activation of PDS by SLFP and the explosive generation of free radicals. In the later stage (2-10 minutes), the reaction rate slowed down, which may be related to the decrease in MO concentration, free radical consumption, or competition of intermediates for active sites. However, high PDS dosage (such as 10mM) can still improve the final degradation efficiency by continuously supplying free radicals.

[0051] like Figure 7 As shown in the figure, when the SLFP dosage increased from 0.1 g / L to 0.6 g / L, the degradation rate of MO increased significantly; the increase in SLFP dosage (such as 0.4-0.6 g / L) provided more surface active sites, enhanced PDS activation and free radical generation, and made the C / C0 lower than 0.3 after 10 minutes; the C / C0 dropped sharply (0.1-0.6) in the early stage of the reaction (0-2 minutes), and the rate slowed down in the later stage (6-10 minutes), due to the decrease in MO concentration and the accumulation of intermediate products, which led to a decrease in free radical utilization;

[0052] Figure 8The results showed that at low MO concentration (0.05 mM), C / C0 dropped to 0 within 6 minutes, indicating sufficient free radical oxidation capacity; after the concentration rose to 0.11 mM, C / C0 dropped to 0.4 in 10 minutes; at high concentration (0.14 mM), a plateau period (C / C0≈0.5) appeared after 4 minutes, because the free radical generation rate could not match the pollutant oxidation demand, and the intermediates consumed free radicals and occupied active sites, resulting in limited degradation efficiency.

[0053] The preparation method of the retired lithium iron phosphate material provided by the present invention is simple, safe, and low in energy consumption. No toxic solvents are used in the preparation process, which is green and environmentally friendly. It exhibits efficient catalytic persulfate oxidation efficiency, and the cost and catalytic persulfate oxidation efficiency have important industrial application value.

[0054] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a heterogeneous activated persulfate catalyst, characterized in that: The following steps are involved: Step 1: Immerse the retired LiFePO4 soft-pack battery in a NaCl solution; disassemble the discharged battery to separate the aluminum-plastic film, the negative electrode plate and the separator; separate the aluminum foil from the LiFePO4 positive electrode material, and then soak it in N-methylpyrrolidone (NMP) solution to remove the residual electrolyte and other impurities on the surface of the positive electrode plate, and then dry and powder the obtained LiFePO4 positive electrode material; Step 2: After the powder is pulverized, ultrasonic washing is performed. The ultrasonic water contains 1% citric acid. The ultrasonic time is set to 10 minutes each time. After the ultrasonication, the deionized water is replaced. The operation is repeated three times to completely remove the excess electrolyte and binder on the positive electrode material. Step 3: Place the ultrasonically washed material in a blast drying oven and dry it at 80°C. Place the dried positive electrode material and anhydrous glucose (1:1 wt%) in a ball mill and set the speed to 500 r / min for 2 hours without oxygen. Step 4: Place the ground material in a tube furnace, add hydrogen at 0.5 L / min, heat at 2°C / min to 400°C, keep warm for 3 hours, heat at 5°C / min to 700°C, keep warm for 10 hours, and cool naturally; Step 5: After cooling, the material is placed in a ball mill, the speed is set to 500 r / min, and oxygen-free ball milling is performed for 2 hours; the material is placed in 1:1 hydrochloric acid for acid leaching for 2 hours, then ultrasonically washed with water until neutral, placed in a blast drying oven, and dried at 80°C; finally, a heterogeneous activated persulfate catalyst based on retired LiFePO4 material is obtained.

2. The preparation method of the heterogeneous activated persulfate catalyst according to claim 1, wherein The preparation process of retired lithium iron phosphate material includes the following steps: Step 1: Immerse the retired LiFePO4 soft-pack battery in a NaCl solution; disassemble the discharged battery to separate the aluminum-plastic film, the negative electrode plate and the separator; separate the aluminum foil from the LiFePO4 positive electrode material, and then soak it in N-methylpyrrolidone (NMP) solution to remove the residual electrolyte and other impurities on the surface of the positive electrode plate, and then dry and powder the obtained LiFePO4 positive electrode material; Step 2: After the powder is pulverized, ultrasonic washing is performed. The ultrasonic water contains 1% citric acid. The ultrasonic time is set to 10 minutes each time. After the ultrasonication, the deionized water is replaced. The operation is repeated three times to completely remove the excess electrolyte and binder on the positive electrode material. Step 3: Place the ultrasonically washed material in a blast drying oven and dry it at 80°C. Place the dried positive electrode material and anhydrous glucose (1:1 wt%) in a ball mill and set the speed to 500 r / min for 2 hours without oxygen. Step 4: Place the ground material in a tube furnace, add hydrogen at 0.5 L / min, heat at 2°C / min to 400°C, keep warm for 3 hours, heat at 5°C / min to 700°C, keep warm for 10 hours, and cool naturally; Step 5: After cooling, the material is placed in a ball mill, the speed is set to 500 r / min, and oxygen-free ball milling is performed for 2 hours; the material is placed in 1:1 hydrochloric acid for acid leaching for 2 hours, then ultrasonically washed with water until neutral, placed in a blast drying oven, and dried at 80°C; finally, a heterogeneous activated persulfate catalyst based on retired LiFePO4 material is obtained.

3. The preparation method of the heterogeneous activated persulfate catalyst according to claim 2, wherein In the step 2, after the powdering, an ultrasonic water washing operation is performed, the ultrasonic water contains 1% citric acid, and the ultrasonic time is set to 10 minutes each time. After the ultrasonication is completed, deionized water is replaced, and the operation is repeated three times to completely remove excess electrolyte and binder on the positive electrode material.

4. The preparation method of the heterogeneous activated persulfate catalyst according to claim 2, wherein In the step 3, the ultrasonically washed material is placed in a blast drying oven and dried at 80° C. The dried positive electrode material and anhydrous glucose (1:1 wt%) are placed in a ball mill, the speed is set to 500 r / min, and oxygen-free ball milling is performed for 2 hours.

5. The preparation method of the heterogeneous activated persulfate catalyst according to claim 2, wherein In the step 4, the ground material is placed in a tubular furnace, hydrogen is introduced at a rate of 0.5 L / min, the temperature is raised to 400° C. at 2° C. / min, the temperature is kept at that temperature for 3 hours, the temperature is raised to 700° C. at 5° C. / min, the temperature is kept at that temperature for 10 hours, and the material is cooled naturally.

6. The method for preparing a heterogeneous activated persulfate catalyst according to claim 2, wherein: In the step 5, after cooling, the material is placed in a ball mill, the speed is set to 500 r / min, and oxygen-free ball milling is performed for 2 hours; the material is placed in 1:1 hydrochloric acid for acid leaching for 2 hours, then ultrasonically washed with water until neutral, placed in a blast drying oven, and dried at 80° C.; finally, a heterogeneous activated persulfate catalyst based on retired LiFePO4 material is obtained.

7. An application of a heterogeneous activated persulfate catalyst, characterized in that: The heterogeneous activated persulfate catalyst according to any one of claims 1 to 5 is used, characterized in that the catalyst prepared based on retired lithium iron phosphate material is used to activate the persulfate system to degrade organic pollutants.

Images