Lanthanum-deficient lanthanum ferrite catalysts, methods of making and use in photocatalytic degradation of plastics

Abstract

The application discloses a lanthanum-deficient lanthanum ferrite catalyst and a preparation method and application thereof in photocatalytic degradation of plastics, wherein the lanthanum-deficient lanthanum ferrite catalyst is LaFeO3 containing La vacancies. The preparation method of the lanthanum-deficient lanthanum ferrite catalyst comprises the following steps: mixing lanthanum salt, iron salt, urea and water, stirring until uniform, to obtain a lanthanum ferrite catalyst precursor solution; mixing citric acid and the lanthanum ferrite catalyst precursor solution, stirring until uniform, and then stirring at 70-80 DEG C until gelatinous, to obtain a lanthanum-deficient lanthanum ferrite catalyst precursor; drying the lanthanum-deficient lanthanum ferrite catalyst precursor, grinding, calcining at 750-900 DEG C for 3-5 h, and then reducing to room temperature, to obtain the lanthanum-deficient lanthanum ferrite catalyst. The lanthanum-deficient lanthanum ferrite catalyst prepared by the application has strong pollutant degradation and conversion capacity for microplastics, especially polyethylene. The degradation rate of PE can reach 92%, and the conversion into finished oil mainly composed of C7-C16 fatty chain carboxylic acid and dicarboxylic acid with low molecular weight can reach about 70%.

Description

Technical Field

[0001] This invention belongs to the field of microplastic degradation technology, specifically relating to a lanthanum-deficient lanthanum ferrite catalyst, its preparation method, and its application in photocatalytic degradation of plastics. Background Technology

[0002] Plastics are widely used in various aspects of life due to their low cost, strong water resistance, and stable physical and chemical properties. However, their stability also prevents them from undergoing rapid natural degradation, leading to the suffocation and death of many animals in their natural habitats due to ingestion. Plastic products can be broken down into small-diameter plastic particles under physical, chemical, and biological conditions. Microplastics (MPs) refer to plastic particles with a diameter of less than 5 mm, accounting for 92.4% of plastic waste. They mainly include polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyacrylonitrile (PAN), and polyethylene terephthalate (PET). Compared to plastic pollution, microplastic pollution can lead to more serious environmental, ecological, and health problems. Microplastics (MPs) are widely present on the surface of aquatic ecosystems, providing unique ecological niches for the enrichment of microorganisms in the aquatic environment and posing potential threats to ecosystems and human health.

[0003] Polyethylene (PE) is highly stable and constitutes the largest proportion of microplastics. Catalytic hydrogenolysis can effectively convert it into low-molecular-weight alkane products for reintroduction into the energy cycle. However, catalytic hydrogenolysis typically involves reactions at temperatures above 200°C and is highly dependent on hydrogen (H2). Currently, H2 mainly comes from fossil fuels, increasing fossil fuel consumption, driving carbon dioxide emissions, and further exacerbating the greenhouse effect. Therefore, developing new processes to convert microplastics into valuable carbon-containing products under milder conditions remains challenging.

[0004] In domestic research, Liu Xianrui et al. (Biological depolymerization and high-value conversion of polyethylene waste plastics, bioprocessing engineering) reviewed various biological treatment technologies for waste plastics. They used the supernatant after primary sedimentation to add sufficient reducing agent to reduce microplastics. They also analyzed the differences between chemical and biological high-value products of polyethylene waste plastics and proposed a solution to construct an artificial system by mixing two or more degrading colonies. However, there are still problems such as the actual treatment effect not being obvious and being subject to many limiting factors.

[0005] Traditional wastewater treatment technologies are ineffective at converting and removing microplastics. Advanced oxidation processes (AOPs) have proven to be effective technologies for drug degradation and mineralization. In recent years, photocatalysis-related AOPs have received increasing attention in water treatment fields such as the removal of persistent organic pollutants and the decontamination of organometallic complexes.

[0006] Meng Yachu et al. (CN117843072A) designed a photocatalytic degradation system that can effectively treat microplastics in boiling water. Yuan Haoran et al. (CN117920307A) prepared a nitrogen-deficient oxygen-doped g-C3N4 photocatalyst, which removed 73% of polystyrene, 68% of polypropylene, and 64% of polyethylene after 200 hours. However, in the above two patents, the actual removal efficiency of the photocatalysts is still low, requiring long-term treatment and incomplete degradation of pollutants, resulting in high actual treatment costs and making them unsuitable for the degradation and transformation of microplastics in actual water bodies. In conclusion, neither domestically nor internationally, there are suitable materials that can effectively remove and transform microplastics, represented by polyethylene, in actual aquatic environments. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a lanthanum ferrite catalyst with lanthanum defects.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned lanthanum-deficient lanthanum ferrite catalyst, wherein the preparation method employs the sol-gel method.

[0009] Another objective of this invention is to provide the use of the aforementioned lanthanum-deficient lanthanum ferrite catalyst in the photocatalytic degradation of plastics. This lanthanum-deficient lanthanum ferrite catalyst generates electrons and holes through light irradiation in a photocatalytic system, achieving rapid degradation of various types of microplastics. By manufacturing a perovskite catalyst containing La vacancies in lanthanum ferrite (LaFeO3), after strong alkali pretreatment, the degradation rate (weight loss) of PE can reach 92%, while the recovery rate of organic matter mainly composed of low molecular weight C7-C16 aliphatic chain carboxylic acids and dicarboxylic acids can reach approximately 70%.

[0010] The objective of this invention is achieved through the following technical solution.

[0011] A lanthanum-deficient lanthanum ferrite catalyst, which is LaFeO3 containing La vacancies.

[0012] A method for preparing a lanthanum-deficient lanthanum ferrite catalyst includes the following steps:

[0013] S1, mix lanthanum salt, iron salt, urea and water, stir until uniform to obtain lanthanum ferrite catalyst precursor solution, wherein, by molar amount, the ratio of lanthanum in lanthanum salt to iron in iron salt and urea is 1:1:(1~6);

[0014] In S1, the ratio of lanthanum in the lanthanum salt, iron in the iron salt, and urea, by molar amounts, is preferably 1:1:(2-5), and more preferably 1:1:3.

[0015] In S1, the ratio of the molar amount of lanthanum to the volume amount of water in the lanthanum salt is (0.05~0.2):1, where the molar amount is in mol and the volume amount is in mL.

[0016] In S1, the lanthanum salt is lanthanum nitrate hexahydrate, the iron salt is ferric nitrate nonahydrate, and the water is deionized water.

[0017] In S1, the stirring time is at least 20 minutes, preferably 20 to 40 minutes.

[0018] S2, mix citric acid and lanthanum ferrite catalyst precursor solution, stir until uniform, and then stir at 70-80℃ until gel-like to obtain lanthanum-deficient lanthanum ferrite catalyst precursor, wherein, by molar amount, the ratio of lanthanum in citric acid to lanthanum in lanthanum salt is (1-1.2):1;

[0019] In S2, the time for stirring until homogeneous is 1 to 2 hours.

[0020] In S2, the stirring time until a gel-like state is reached is 3 to 6 hours.

[0021] In S2, the stirring rate to the gel state is 300–700 r / min.

[0022] S3. The lanthanum-deficient lanthanum ferrite catalyst precursor is dried, ground, calcined at 750–900℃ for 3–5 h, and then cooled to room temperature to obtain the lanthanum-deficient lanthanum ferrite catalyst.

[0023] In step S3, the drying temperature is 120–150°C, and the drying time is 10–15 hours.

[0024] In S3, the heating rate of the calcination is 5-10 °C / min.

[0025] In S3, the rate of cooling to room temperature is 5–10 °C / min.

[0026] In S3, the gas atmosphere for calcination is air.

[0027] In S3, the room temperature is 20-25°C.

[0028] The above-mentioned lanthanum-deficient lanthanum ferrite catalysts are used in the photocatalytic degradation of plastics.

[0029] In the above technical solution, the lanthanum-deficient lanthanum ferrite catalyst catalyzes the degradation of plastics under visible light.

[0030] In the above technical solution, the photocatalytic degradation of plastics is carried out at normal temperature and pressure (25°C, 1 standard atmosphere).

[0031] In the above technical solution, the plastic is soaked in a 0.1 mol / L NaOH solution for 24 hours before photocatalytic degradation.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. The preparation method of the present invention is simple and easy to operate.

[0034] 2. The lanthanum-deficient lanthanum ferrite catalyst prepared in this invention exhibits strong pollutant degradation and conversion capabilities for microplastics, particularly polyethylene. Compared to existing lanthanum ferrite (LaFeO3) nanomaterials, the lanthanum-deficient lanthanum ferrite catalyst demonstrates nearly four times the degradation capability for polyethylene, enabling the degradation and resource conversion of recalcitrant microplastics, such as polyethylene.

[0035] 3. The lanthanum-deficient lanthanum ferrite catalyst prepared by this invention can form a mechanism for the synergistic removal of pollutants by electrons and holes, which can achieve efficient and rapid removal of recalcitrant pollutants in real complex and variable aquatic environments, and is suitable for application in real water bodies.

[0036] 4. Compared with lanthanum ferrite catalyst (LFO), the lanthanum-deficient lanthanum ferrite catalyst prepared by this invention has better visible light absorption performance and higher utilization rate. Attached Figure Description

[0037] Figure 1 The images show TEM images and elemental mappings of the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1, where (a) is a TEM image, (b) is a lattice fringe pattern, (c) is an EDS image of La, (d) is an EDS image of Fe, and (e) is an EDS image of O.

[0038] Figure 2 The XRD patterns of the lanthanum ferrite catalyst (LFO) prepared in Example 5 and the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1 are shown in the inset (partial magnified view).

[0039] Figure 3The specific surface area and pore size distribution of the lanthanum ferrite catalyst (LFO) prepared in Example 5 and the lanthanum-defective lanthanum ferrite catalyst (3U-LFO) prepared in Example 1 are shown in Figure 1.

[0040] Figure 4 The UV-Vis diffuse reflectance spectra of the lanthanum ferrite catalyst (LFO) prepared in Example 5 and the lanthanum-defective lanthanum ferrite catalyst (3U-LFO) prepared in Example 1.

[0041] Figure 5 The degradation effects of the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1, the lanthanum-deficient lanthanum ferrite catalyst (U-LFO) prepared in Example 2, the lanthanum-deficient lanthanum ferrite catalyst (2U-LFO) prepared in Example 3, the lanthanum-deficient lanthanum ferrite catalyst (6U-LFO) prepared in Example 4, and the lanthanum ferrite catalyst (LFO) prepared in Example 5 on polyethylene are shown in the figure.

[0042] Figure 6 The graphs show the degradation effects of the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1 and the lanthanum ferrite catalyst (LFO) prepared in Example 5 on different microplastics.

[0043] Figure 7 The graph shows the degradation effect of the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1 on polyethylene under different water conditions.

[0044] Figure 8 The graph shows the degradation effect of the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1 on polyethylene under different influencing factors. Among them, (a) shows the effect of different pH on polyethylene degradation, (b) shows the effect of different lanthanum-deficient lanthanum ferrite catalyst contents on polyethylene degradation, (c) shows the effect of different polyethylene concentrations on degradation effect, and (d) shows the effect of different light intensity on polyethylene degradation.

[0045] Figure 9 (a) is a free radical quenching experiment diagram of the lanthanum ferrite catalyst (LFO) prepared in Example 5. Figure 9 (b) is a free radical quenching experiment of the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1;

[0046] Figure 10 The electrochemical spectra of the lanthanum ferrite catalyst (LFO) prepared in Example 5 and the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1 are shown, where (a) is a cyclic voltammogram, (b) is a linear voltammogram, (c) is an electrochemical impedance spectroscopy (EIS) spectrum, and (d) is an MS spectrum.

[0047] Figure 11 (a) shows the instantaneous photocurrent response of the lanthanum ferrite catalyst (LFO) prepared in Example 5 and the lanthanum-defective lanthanum ferrite catalyst (3U-LFO) prepared in Example 1. Figure 11 (b) is Figure 11 Enlarged view of part (a);

[0048] Figure 12 The image shows the GC-MS diagram of the degradation of PE microplastics by the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) in Example 1. Detailed Implementation

[0049] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0050] The raw materials and their manufacturers involved in the following examples are as follows:

[0051] In the following examples, deionized water is used.

[0052] In the examples below, the lanthanum salt is lanthanum nitrate hexahydrate, and the iron salt is ferric nitrate nonahydrate.

[0053] Lanthanum nitrate hexahydrate (La(NO3)3·6H2O), ferric nitrate nonahydrate (Fe(NO3)3·9H2O), urea (CO(NH)2), and citric acid were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0054] Citric acid, urea, and metal nitrates (La(NO3)3·6H2O and Fe(NO3)3·9H2O) were all of analytical grade.

[0055] The instruments and their model information involved in the following embodiments are as follows:

[0056] A xenon lamp (CEL-HX F300, Beijing, China, 420nm cutoff filter) was used as the light source (maximum power 350W).

[0057] The crystallinity of the product was characterized using a Rigaku D / Max 2200PC X-ray diffractometer (λ = 0.15418 nm).

[0058] Its morphology and microstructure were observed using a Talos f200x transmission electron microscope (TEM) equipped with an energy dispersive spectrometer (EDS).

[0059] The UV-Vis diffuse reflectance (DRS) spectra were recorded on the UV-3600i Plus UV-Vis spectrophotometer (Shimadzu).

[0060] The N2 adsorption-desorption isotherm was recorded using an automated gas adsorption analyzer (Quantachrome).

[0061] The content of microplastics was determined by gravimetric method. GC-MS was used for quantitative analysis of microplastics and their conversion products.

[0062] The photoelectrochemical experiments were conducted on an electrochemical workstation (Shanghai Chenhua CHI660B).

[0063] Examples 1-4

[0064] A method for preparing a lanthanum-deficient lanthanum ferrite catalyst includes the following steps:

[0065] S1, Lanthanum salt (La(NO3)3·6H2O), iron salt (Fe(NO3)3·9H2O), urea (CO(NH)2) and water are mixed and magnetically stirred at 500 r / min for 20 min until homogeneous to obtain a lanthanum ferrite catalyst precursor solution. In this solution, the ratio of lanthanum in the lanthanum salt, iron in the iron salt and urea is W, and the ratio of the molar amount of lanthanum to the volume amount of water in the lanthanum salt is 0.1:1. The unit of molar amount is mol and the unit of volume amount is mL.

[0066] S2, citric acid and lanthanum ferrite catalyst precursor solution are mixed and stirred for 1 hour until homogeneous, and then magnetically stirred at 500 r / min for 3 hours in a water bath at 70°C until water evaporates and a gel is formed, to obtain lanthanum-deficient lanthanum ferrite catalyst precursor, wherein, by molar amount, the ratio of citric acid to lanthanum in the lanthanum salt in S1 is 1.05:1.

[0067] S3. The lanthanum-deficient lanthanum ferrite catalyst precursor was dried at 120℃ for 12h, taken out, ground in a mortar, placed in a crucible in a muffle furnace, heated to 800℃ at a rate of 5℃ / min in air atmosphere, and calcined at 800℃ for 3h. After calcination, it was cooled to room temperature (20-25℃) at a rate of 5℃ / min to obtain the lanthanum-deficient lanthanum ferrite catalyst.

[0068] The W and numbering of the lanthanum-deficient lanthanum ferrite catalysts prepared in Examples 1-4 are shown in Table 1.

[0069] Table 1

[0070] Example W Numbering of Lanthanum-Defective Lanthanum Ferrite Catalysts Example 1 1:1:3 3U-LFO Example 2 1:1:1 U-LFO Example 3 1:1:2 2U-LFO Example 4 1:1:6 6U-LFO

[0071] Example 5

[0072] A lanthanum ferrite catalyst (LFO) is prepared in a manner that is basically the same as that in Example 1 above, except that urea (CO(NH)2) is not added in this example.

[0073] Figure 1 The images show TEM images of the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1 and elemental mapping diagrams of the lanthanum-deficient lanthanum ferrite catalyst. Figure 1 As shown in (a), the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1 was successfully synthesized, and the crystals are plate-like. Figure 1 As shown in (b), the lattice fringe spacing of the lanthanum-defective lanthanum ferrite catalyst (3U-LFO) prepared in Example 1 is 0.283 nm, which is slightly smaller than that of lanthanum ferrite (the lattice fringe spacing of the lanthanum ferrite catalyst (LFO) prepared in Example 5 is 0.285 nm). This indicates that the lanthanum-defective lanthanum ferrite catalyst constructed in Example 1 achieves the deletion of La atoms. Figure 1 (c) is the EDS diagram of La element in the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1, further verifying the generation of La defects. Figure 1 As can be seen from (c), (d), and (e), the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1 exhibits a uniform distribution of different elements within it.

[0074] Figure 2 The XRD patterns are shown for the lanthanum ferrite catalyst (LFO) prepared in Example 5 and the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1. Figure 2 It can be seen that after constructing La defects, the diffraction peak of the lanthanum ferrite catalyst (3U-LFO) with lanthanum defects prepared in Example 1 shifts to a higher angle. This is because the appearance of La defects causes A-site vacancies in the perovskite, thereby exposing more Fe sites, which in turn causes the diffraction peak to shift to a higher angle, thus verifying the appearance of La defects.

[0075] Figure 3 The figures (a) show the specific surface area and (b) show the pore size distribution of the lanthanum ferrite catalyst (LFO) prepared in Example 5 and the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1. Figure 3 As shown in (a), the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1 has a specific surface area of ​​10.69 m². -2 g -1 The specific surface area of ​​the catalyst is greater than that of the lanthanum ferrite catalyst (LFO) prepared in Example 5 (8.09 m²). -2 g -1 ),Depend on Figure 3 As shown in (b), the pore size of 3U-LFO is smaller than that of LFO, and the preparation is more uniform, which verifies its better specific surface area.

[0076] Figure 4The images show the UV-Vis diffuse reflectance spectra of the lanthanum ferrite catalyst (LFO) prepared in Example 5 and the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1. Figure 4 It can be seen that the lanthanum-deficient lanthanum ferrite catalyst prepared in Example 1 not only has a higher response in the visible light region, but also a higher response in the near-infrared light region, indicating that the lanthanum-deficient lanthanum ferrite catalyst can achieve effective utilization of visible and near-infrared light.

[0077] A method for degrading microplastic pollutants under visible light using a catalyst: Microplastics are soaked in a 1 mol / L sodium hydroxide aqueous solution for 24 hours, filtered, rinsed repeatedly with water and ethanol, and then dried in an oven at 80℃ for 12 hours to obtain strongly alkali-treated microplastics. The microplastics are one of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and polyacrylonitrile (PAN). A mass of strongly alkali-treated microplastics (m0 = 100 mg) is uniformly dispersed in water to prepare a microplastic aqueous solution with a concentration of 1 g / L. The pH of the microplastic aqueous solution is approximately 7 (slightly higher than 7). The water is one of deionized water, tap water, lake water, and secondary wastewater.

[0078] 25 mg of catalyst was added to 100 mL of microplastic aqueous solution (i.e., 100 mg of microplastics were uniformly dispersed in 100 mL of water). The microplastics were degraded under irradiation with a 25 W xenon lamp (with a filter to ensure a wavelength greater than 420 nm) at a rotation speed of 500 r / min for 12 h. The obtained sample was filtered to remove the catalyst and water, dried, and weighed. The mass was recorded as m. The xenon lamp was turned off after the experiment to terminate the reaction. The catalyst was one of the following: the lanthanum-deficient lanthanum ferrite catalyst (3 U-LFO) prepared in Example 1; the lanthanum-deficient lanthanum ferrite catalyst (U-LFO) prepared in Example 2; the lanthanum-deficient lanthanum ferrite catalyst (2 U-LFO) prepared in Example 3; the lanthanum-deficient lanthanum ferrite catalyst (6 U-LFO) prepared in Example 4; and the lanthanum ferrite catalyst (LFO) prepared in Example 5.

[0079] The calculation method for Weight Loss (%) is: WL = m0 - m / m0.

[0080] Following the "Method for Degrading Microplastic Pollutants with Catalysts under Visible Light," one of the following catalysts was used as a catalyst to degrade PE (microplastics are polyethylene (PE)) using deionized water: the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1, the lanthanum-deficient lanthanum ferrite catalyst (U-LFO) prepared in Example 2, the lanthanum-deficient lanthanum ferrite catalyst (2U-LFO) prepared in Example 3, the lanthanum-deficient lanthanum ferrite catalyst (6U-LFO) prepared in Example 4, and the lanthanum ferrite catalyst (LFO) prepared in Example 5. The weight loss (%) at a degradation time of 12 hours was as follows: Figure 5 As shown, the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1 has the highest degradation effect on polyethylene, and can degrade 92% of polyethylene in 12 hours.

[0081] Following the method for "Degradation of Microplastic Pollutants by Catalysts under Visible Light," one of the lanthanum-deficient lanthanum ferrite (3U-LFO) prepared in Example 1 and the lanthanum ferrite catalyst (LFO) prepared in Example 5 was used as a catalyst to degrade one of PE, PP, PVC, and PAN (using deionized water). The degradation effect of the catalyst on various other microplastic pollutants was tested, and the weight loss (%) at a degradation time of 12 hours was as follows: Figure 6 As shown, compared with the lanthanum ferrite catalyst (LFO) prepared in Example 5, the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1 can achieve efficient degradation of microplastic pollutants within 12 hours.

[0082] Following the "Method for Degrading Microplastic Pollutants under Visible Light with Catalysts," lanthanum-deficient lanthanum ferrite (3U-LFO) prepared in Example 1 was used as a catalyst for degradation (microplastics were polyethylene (PE), and water was one of deionized water, tap water, lake water, and secondary wastewater). The weight loss (%) at a degradation time of 12 hours was as follows: Figure 7 As shown, the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1 can still maintain the degradation of at least 80% of polyethylene within 12 hours under different water quality conditions.

[0083] Degradation of polyethylene under different influencing factors: Polyethylene was soaked in 1 mol / L sodium hydroxide aqueous solution for 24 h, filtered, rinsed repeatedly with water and ethanol, and then dried in an oven at 80 °C for 12 h to obtain strongly alkali-treated polyethylene. A polyethylene aqueous solution of mass m1 (treated with strongly alkali) was uniformly dispersed in 100 mL of deionized water. The pH of the polyethylene aqueous solution was adjusted to p by adding hydrochloric acid (0.1 mol / L) or sodium hydroxide aqueous solution (0.1 mol / L). Lanthanum-deficient lanthanum ferrite catalyst prepared in Example 1 (mass m3) was added to 100 mL of the polyethylene aqueous solution. The polyethylene was degraded for 12 h under xenon lamp irradiation (with a filter to ensure a wavelength greater than 420 nm) at a rotation speed of 500 r / min. The resulting sample (with lanthanum-deficient lanthanum ferrite catalyst removed) and water were filtered, dried, and weighed. The mass was recorded as m2. The reaction was terminated by turning off the xenon lamp after the experiment.

[0084] In the "Experiment on the Degradation of Polyethylene under Different Influencing Factors", when m3 = 25 mg, xenon lamp irradiation intensity is 25 W, and m1 is 100 mg, adjusting p to 3, 5, 7, 9, or 11 results in the following weight loss of polyethylene: Figure 8 As shown in (a). From Figure 8 As can be seen from (a), the lanthanum-deficient lanthanum ferrite catalyst prepared in Example 1 exhibits the best degradation effect on polyethylene (PE) under neutral conditions.

[0085] In the "Degradation Experiment of Polyethylene under Different Influencing Factors", when p=7, xenon lamp irradiation intensity is 25W, and m1 is 100mg, adjusting m3 to 5mg, 10mg, 15mg, 20mg, or 25m affects the weight loss of polyethylene as follows: Figure 8 As shown in (b). From Figure 8 As can be seen from (b), as the content of the lanthanum-deficient lanthanum ferrite catalyst prepared in Example 1 increases, its degradation effect on PE continuously improves.

[0086] In the "Degradation Experiment of Polyethylene under Different Influencing Factors", when m3 = 25 mg, xenon lamp irradiation intensity is 25 W, and p = 7, adjusting m1 to 50 mg, 100 mg, 150 mg, 200 mg, or 250 mg resulted in the following weight loss of polyethylene: Figure 8 As shown in (c).

[0087] In the "Degradation Experiment of Polyethylene under Different Influencing Factors", when m3 = 25 mg, m1 = 100 mg, and p = 7, the weight loss of polyethylene was as follows when the xenon lamp illumination intensity was adjusted to 5 W, 10 W, 15 W, 20 W, or 25 W. Figure 8 As shown in (d), from Figure 8As shown in (d), the best degradation effect can be achieved under a light intensity of 25W.

[0088] Figure 8 The calculation method for Weight Loss (%) is: WL = m1 - m2 / m1.

[0089] Figure 9 (a) is a free radical quenching experiment diagram of the lanthanum ferrite catalyst (LFO) prepared in Example 5 after 12 h of degradation. Figure 9 (b) Free radical quenching experiment diagram of lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) in Example 1 after 12 h of degradation. According to the "Method for Catalyst Degradation of Microplastic Pollutants under Visible Light", one of the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) prepared in Example 1 and the lanthanum ferrite catalyst (LFO) prepared in Example 5 was used as a catalyst to degrade PE (water was deionized water). The experimental results are respectively marked as "Blank" in Figures (a) and (b), referring to the "Blank" experimental method. Five quenching experiments were set up for each catalyst. Before deuterium lamp irradiation, 10 mmol of quencher was added to each catalyst. The quencher was one of the following: tert-butanol (TBA), carotene, potassium dichromate (K2Cr2O7), disodium ethylenediaminetetraacetate (EDTA-2Na), and superoxide dismutase (SOD). The quenchers quenched hydroxyl radicals (·OH) in the tert-butanol system, singlet oxygen in the carotene system, electrons in the potassium dichromate system, and holes in the EDTA-2Na system. + SOD quenches superoxide radicals (O2) - To identify the species that play a major role in the degradation of microplastics. For example... Figure 9 As shown, the degradation system of polyethylene by the lanthanum-deficient lanthanum ferrite catalyst is a photocatalytic system, and the hole h plays a major role in the degradation process. + This method achieves efficient separation and utilization of electrons and holes, with electrons also being converted into superoxide radicals (O2) through reaction, thus enabling efficient degradation of microplastics. It also allows for efficient degradation of microplastics in complex aquatic environments.

[0090] Figure 10 The images show the electrochemical properties of the lanthanum ferrite catalyst (LFO) prepared in Example 5 and the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) in Example 1. In the images, (a) is a cyclic voltammogram, (b) is a linear voltammogram, (c) is an electrochemical impedance spectroscopy (EIS) spectrum, and (d) is a Mott-Schottky curve (MS spectrum). Figure 10 (a) and (b) show that the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) in Example 1 exhibits greater electron mobility, resulting in the generation of more electrons. Figure 10(c) and (d) show that the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) in Example 1 has lower impedance, higher conductivity and carrier concentration than the lanthanum ferrite catalyst (LFO) prepared in Example 5, confirming that lanthanum defects do indeed accelerate photoexcited carrier transfer kinetics.

[0091] Figure 11 (a) shows the instantaneous photocurrent response of the lanthanum ferrite catalyst (LFO) prepared in Example 5 and the lanthanum-defective lanthanum ferrite catalyst (3U-LFO) prepared in Example 1. Figure 11 (b) is Figure 11 A partial enlarged view of (a). The results show that the instantaneous photoelectron concentration of the lanthanum-defect lanthanum ferrite catalyst (3U-LFO) prepared in Example 1 is higher than that of the lanthanum ferrite catalyst (LFO) prepared in Example 5, and its photoelectron self-annihilation rate is lower than that of the lanthanum ferrite catalyst (LFO) prepared in Example 5. The above photophysical studies clearly demonstrate that the construction of La defects achieves effective separation of electrons and holes, slows down their self-annihilation rate, and thus improves photocatalytic activity.

[0092] Figure 12 The image shows the GC-MS diagram of the degradation of PE microplastics by the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) in Example 1. The appearance of each peak indicates the presence of different carbon chain substances. According to the determination methods of different substances, the peaks that appear with the extension of the peak time on the vertical axis correspond to hydrocarbon chain substances with different numbers of carbon atoms, while the relative height and area of ​​the peaks correspond to the relative content of hydrocarbon chain substances. GC-MS results show that the peak with a peak time of 1.33 min corresponds to methane, the peak with a peak time of 18.92 min corresponds to a C8 aliphatic hydrocarbon chain, the peak with a peak time of 21.96 min corresponds to a C10 aliphatic hydrocarbon chain, and the peak with a peak time of 25.74 min corresponds to a C12 aliphatic hydrocarbon chain. The sharp small peaks that appear in between indicate the presence of different derivatives with the same number of C atoms. According to the standard GC-MS spectrum, the main products generated by the lanthanum-deficient lanthanum ferrite catalyst (3U-LFO) in Example 1 after the degradation of PE microplastics are C7-C16 aliphatic carboxylic acids and dicarboxylic acids, indicating that the system successfully selectively oxidizes PE into long-chain organic matter and achieves the goal of resource utilization of microplastics. Based on the integral calculation of peak area, approximately 70 wt% of PE degrades to generate C7-C16 long-chain aliphatic carboxylic acids and dicarboxylic acids. These long-chain aliphatic carboxylic acids and dicarboxylic acids are raw materials for synthesizing high-grade fragrances and high-performance nylon, possessing significant utilization value. This represents a resource-based upgrade of PE microplastics, and the recycling experiments demonstrate the catalyst's stability and application prospects.

[0093] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. Use of a lanthanum-deficient lanthanum ferrite catalyst for the photocatalytic degradation of plastics, characterized in that, The lanthanum-deficient lanthanum ferrite catalyst is a photocatalytic system, and a hole h plays a main role in the degradation process + The main products generated after the lanthanum-deficient lanthanum ferrite catalyst degrades PE microplastics are C7-C16 fatty chain carboxylic acid and dicarboxylic acid; The lanthanum-deficient lanthanum ferrite catalyst is LaFeO3 containing La vacancies; the preparation method of the lanthanum-deficient lanthanum ferrite catalyst comprises the following steps: S1, mixing a lanthanum salt, an iron salt, urea and water, stirring until uniform, to obtain a lanthanum ferrite catalyst precursor solution, wherein the ratio of lanthanum in the lanthanum salt, iron in the iron salt and urea is 1:1:(1-6) in terms of the amount of substance; S2, mixing citric acid and the lanthanum ferrite catalyst precursor solution, stirring until uniform, and then stirring at 70-80 DEG C until gelatinous, to obtain a lanthanum-deficient lanthanum ferrite catalyst precursor, wherein the ratio of citric acid and lanthanum in the lanthanum salt is (1-1.2):1 in terms of the amount of substance; S3, drying the lanthanum-deficient lanthanum ferrite catalyst precursor, grinding, calcining at 750-900 DEG C for 3-5 h, and then cooling to room temperature, to obtain the lanthanum-deficient lanthanum ferrite catalyst.

2. Use according to claim 1, characterized in that, In S1, the ratio of lanthanum in the lanthanum salt, iron in the iron salt and urea is preferably 1:1:(2-5) in terms of the amount of substance.

3. Use according to claim 1, characterized in that, In S1, the ratio of the amount of substance of lanthanum in the lanthanum salt to the volume fraction of water is (0.05-0.2):1, wherein the unit of the amount of substance is mol and the unit of the volume fraction is mL.

4. Use according to claim 1, characterized in that, In S1, the stirring time is at least 20 min.

5. Use according to claim 1, characterized in that, In S2, the stirring time until gelatinous is 3-6 h.

6. Use according to claim 1, characterized in that, In S3, the gas atmosphere of the calcination is air.

7. Use according to claim 1, characterized in that, In S3, the heating rate of the calcination is 5-10 DEG C / min.

8. Use according to claim 2, characterized in that, In S1, the ratio of lanthanum in the lanthanum salt, iron in the iron salt and urea is 1:1:3 in terms of the amount of substance.

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