Carbon-doped cobaltosic oxide and cerium dioxide ultra-long hollow nanotube composite catalyst, preparation method thereof and application of carbon-doped cobaltosic oxide and cerium dioxide ultra-long hollow nanotube composite catalyst in photocatalytic degradation of micro-plastics

Abstract

The invention relates to a carbon-doped cobaltosic oxide and cerium dioxide ultra-long hollow nanotube composite catalyst, a preparation method thereof and application of the carbon-doped cobaltosic oxide and cerium dioxide ultra-long hollow nanotube composite catalyst to photocatalytic degradation of micro-plastics, and belongs to the technical field of nano composite materials and photocatalysis. The composite catalyst is synthesized by taking polyvinylpyrrolidone (PVP) as a precursor, adding cobalt nitrate hexahydrate (Co (NO3) 3.6 H2O) and cerium nitrate hexahydrate (Ce (NO3) 3.6 H2O) through a high-voltage electrostatic spinning technology by a one-step method; according to the composite catalyst, hollow nanotubes are interwoven to form a net structure, and a cobaltosic oxide and cerium dioxide heterogeneous interface is formed. The catalyst provided by the invention promotes the separation and transmission of photo-induced electrons and holes by utilizing the mutual cooperation of heterogeneous interfaces of cobaltosic oxide and cerium dioxide, has excellent catalytic performance in the reaction of photocatalytic degradation of polyethylene glycol terephthalate micro-plastic wastes, and realizes efficient degradation.

Description

Technical Field

[0001] The present invention belongs to the technical fields of nanocomposites and photocatalysis, and particularly relates to a preparation method of a composite catalyst of carbon-doped cobalt ferrite and cerium dioxide ultra-long hollow nanotubes and its application in photocatalytic degradation of microplastics. Background Art Polyethylene terephthalate (PET) plastics are widely used in the manufacture of food plastic films, beverage bottles, household appliances, and precision instruments, with an annual output of 70 million tons. More importantly, due to the chemical stability of PET plastics, they cannot be effectively degraded in the natural environment and can only be treated through deposition in centralized landfills and incineration. These methods lead to a large amount of waste of plastic resources, and the generated microplastics flow into water bodies, ultimately endangering biological health. Developing efficient recycling and processing technologies for PET plastics can reduce white pollution and carbon emissions. However, at present, the PET plastic recycling technology is not mature, and the recycling methods may not be able to effectively balance the goals of environmental protection and providing economic benefits.

[0002] Photocatalysis is a green technology with good application prospects. However, simple degradation technologies cannot achieve effective plastic degradation in a short time. Currently, advanced oxidation processes based on persulfate (PMS) can provide good solutions for the treatment of PET plastics in the environment because they have high redox properties. This technology destroys the bonds between aromatic rings in PET through electrophilic substitution, promoting the degradation of PET plastics in the environment. For example, 3D layered H2-reduced Mn-doped CeO2 nanoflowers are used as highly efficient Fenton-like photocatalysts activated by persulfate (PMS). However, due to its wide bandgap, the CeO2 photocatalyst is difficult to be excited by visible light, which severely limits its wide application. Therefore, CeO2 needs to be modified by other methods to improve the pollutant removal activity of PMS under visible light irradiation.

[0003] Recent studies have shown that constructing heterojunction composite catalysts can promote the separation of photogenerated electrons and holes. Cerium dioxide is a low-cost n-type semiconductor with excellent redox properties and stable properties. The valence states of Ce 3+ and Ce 4+ in CeO2 can be flexibly transformed, endowing it with good electron / ion conductivity and reversible surface oxygen ion exchange. There is currently no research report on constructing a composite catalyst of carbon-doped cobalt ferrite and cerium dioxide ultra-long hollow nanotubes for the efficient degradation of polyethylene terephthalate microplastic waste. Summary of the Invention

[0004] The object of the present invention is to overcome the above-mentioned deficiencies of the prior art, and to provide a preparation method and application of a carbon-doped cobalt ferrite and cerium dioxide ultra-long hollow nanotube composite catalyst, which will be used in the reaction of photocatalytic degradation of polyethylene terephthalate microplastic waste.

[0005] The technical solution adopted by the present invention is as follows: The present invention provides a carbon-doped cobalt ferrite and cerium dioxide ultra-long hollow nanotube composite catalyst, which is synthesized by a one-step method through a high-voltage electrospinning technique with polyvinylpyrrolidone PVP as a precursor and adding cobalt nitrate hexahydrate Co(NO3)3·6H2O and cerium nitrate hexahydrate Ce(NO3)3·6H2O; the composite catalyst is formed by hollow nanotubes intertwined into a network structure to form a heterogeneous interface of cobalt ferrite and cerium dioxide.

[0006] In the above technical solution, further, the diameter of the hollow nanotube is 300-400 nm and the length is 50-60 µm.

[0007] In the above technical solution, further, the molar mass ratio of cobalt ferrite and cerium dioxide in the composite catalyst is 1:1-8, and the calculated theoretical mass of cobalt ferrite and cerium dioxide is the actual mass after the calcined nanotubes are ground.

[0008] In the above technical solution, further, the preparation method of the composite catalyst includes the following steps: (1) Add PVP, Ce(NO3)3·6H2O and Co(NO3)2·6H2O to distilled water and absolute ethanol, and stir at room temperature to obtain a homogeneous and transparent composite sol; the dosage ratio of PVP, Ce(NO3)3·6H2O, Co(NO3)3·6H2O, distilled water, and absolute ethanol is 1 g: 0.1-0.3 g: 0.7-0.9 g: 4-7 ml: 4-7 ml; (2) Electrospin the prepared composite sol at room temperature to obtain composite microfibers; The parameters of the electrospinning are: the diameter of the needle head is 1 mm, the angle with the horizontal plane is about 15-30°, the DC voltage is 17-18 kV, the curing distance is 20-25 cm, the injection speed is 0.7-1 mm·min -1 , and the roller speed is 300-350 r·min -1 ; (3) Dry, calcine, and cool the prepared composite microfibers.

[0009] In the above technical solution, further, the stirring time in step (1) is 24-26 h.

[0010] In the above technical solution, further, the drying temperature in step (3) is 40-60 °C, and the drying time is 10-14 h; the calcination temperature is 500-550 °C, the calcination time is 2-4 h, and the heating rate is 5-10 °C / min.

[0011] The present invention also provides the application of the aforementioned carbon-doped cobalt tetroxide and cerium dioxide ultra-long hollow nanotube composite catalyst in the photocatalytic degradation of polyethylene terephthalate microplastic waste. The composite catalyst of the present invention has fine fibers, a large specific surface area, a relatively wide band gap, a large contact area with microplastics, which is conducive to the migration of carriers to the surface of the catalyst and the occurrence of redox reactions with adsorbed substances, thereby improving the photocatalytic activity.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention uses a simple method to add cobalt nitrate hexahydrate and cerium nitrate hexahydrate to a polyvinylpyrrolidone precursor solution, and prepares a carbon-doped cobalt tetroxide and cerium dioxide ultra-long hollow nanotube composite catalyst by one-step electrospinning technology. During the electrospinning process, the hollow nanotubes of cobalt tetroxide and cerium dioxide are arranged into uniform, thin and long hollow tubes, which are intertwined into a network structure and form a heterojunction interface. This catalyst shows excellent catalytic performance in the photocatalytic degradation of polyethylene terephthalate microplastic waste. In the presence of 20 °C, a light irradiation time of 6 h and 3 mM PMS, the weight loss of polyethylene terephthalate microplastics is 93.725 ± 4.32%. This result indicates that the mutual synergy of the cobalt tetroxide and cerium dioxide heterojunction interface promotes the separation and transfer of photogenerated electrons and holes, realizing the efficient degradation of polyethylene terephthalate microplastic waste by photocatalysis. Description of the Drawings

[0013] Figure 1 are the electron microscopy characterizations of the cobalt tetroxide and cerium dioxide composite catalyst at different ratios.

[0014] Figure 2 are the XRD characterizations of the carbon-doped cobalt tetroxide, carbon-doped cerium dioxide, and carbon-doped cobalt tetroxide and cerium dioxide composite catalysts.

[0015] Figure 3 are the electron microscopy characterizations of the carbon-doped cobalt tetroxide and cerium dioxide composite catalyst.

[0016] Figure 4 are the specific surface area characterizations of the carbon-doped cobalt tetroxide, carbon-doped cerium dioxide, and carbon-doped cobalt tetroxide and cerium dioxide composite catalysts.

[0017] Figure 5Uv-vis DRS characterization and Tauc plots of carbon-doped cobalt ferrite, carbon-doped cerium dioxide, and composite catalysts of carbon-doped cobalt ferrite and cerium dioxide; a. Uv-vis DRS characterization, b. Tauc plot of carbon-doped cerium dioxide, c. Tauc plot of carbon-doped cobalt ferrite.

[0018] Figure 6 Photovoltaic properties of carbon-doped cobalt ferrite, carbon-doped cerium dioxide, and composite catalysts of carbon-doped cobalt ferrite and cerium dioxide; a. Mott-Schottky curve of carbon-doped cerium dioxide, b. Mott-Schottky curve of carbon-doped cobalt ferrite, c. Transient photocurrent response curve of composite catalysts of carbon-doped cobalt ferrite and cerium dioxide, d. EIS spectrum.

[0019] Figure 7 Photocatalytic degradation performance of carbon-doped cobalt ferrite, carbon-doped cerium dioxide, and composite catalysts of carbon-doped cobalt ferrite and cerium dioxide for polyethylene terephthalate microplastic waste; a. Performance of different catalysts, b. Performance at different time periods, c. Kinetic fitting curve. Detailed implementation mode

[0020] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited in any way.

[0021] To enable those skilled in the art to better understand the technical solutions of the present invention, the preparation method and application of a composite catalyst of carbon-doped cobalt ferrite and cerium dioxide ultra-long hollow nanotubes provided by the present invention will be described in detail below in conjunction with embodiments. The following embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0022] Example 1 Preparation of a composite catalyst of carbon-doped cobalt ferrite and cerium dioxide ultra-long hollow nanotubes 1 g of PVP, 0.1628 g of Ce(NO3)3·6H2O, and 0.8731 g of Co(NO3)2·6H2O were added to 6 ml of distilled water and 7 ml of absolute ethanol, and stirred at room temperature for 24 h to obtain a homogeneous and transparent composite sol. The prepared composite sol was injected into a syringe with a needle, and the needle diameter was 1 mm. The positive copper wire of the high-voltage DC power supply was inserted into the solution of the syringe, the inclination angle of the needle to the horizontal plane was adjusted to about 15°, the applied DC voltage was appropriately adjusted to 17 kV, the curing distance (the distance between the tip of the syringe needle and the collected aluminum foil) was 20 cm, and the injection speed was 0.7 cm·min -1 , and the roller speed was 300 r·min -1, electrospinning was carried out at room temperature, and the composite microfibers could be collected on the aluminum foil connected to the negative pole of the high-voltage power supply. The prepared composite fibers were placed in an oven at 60 °C and dried for 12 h, then put into a crucible and placed in a programmed heating furnace and calcined at 500 °C for 4 h, with a heating rate of 5 °C / min. After heating, the sample was naturally cooled to room temperature with the furnace, and the molar ratio of Co3O4 and CeO2 in the composite catalyst of carbon-doped cobalt tetroxide and cerium dioxide ultra-long hollow nanotubes was 1:8. Meanwhile, according to the above preparation method, the difference was only that cerium nitrate hexahydrate or cobalt nitrate hexahydrate was not added, and a carbon-doped cobalt tetroxide catalyst or a carbon-doped cerium dioxide catalyst was prepared.

[0023] According to the above preparation method, the addition amounts of distilled water and absolute ethanol were changed. 1 g of PVP, 0.1628 g of Ce(NO3)3·6H2O and 0.8731 g of Co(NO3)2·6H2O were added to 8 ml of distilled water and 9 ml of absolute ethanol, and electrospinning was carried out at room temperature. It was found that the solution was too viscous to form a shape, as Figure 1 a; 1 g of PVP, 0.1628 g of Ce(NO3)3·6H2O and 0.8731 g of Co(NO3)2·6H2O were added to 3 ml of distilled water and 8 ml of absolute ethanol; it was found that the solution was too dilute to form a shape, as Figure 1 b; 1 g of PVP, 0.1628 g of Ce(NO3)3·6H2O and 0.8731 g of Co(NO3)2·6H2O were added to 9 ml of distilled water and 10 ml of absolute ethanol. During the electrospinning process, a large number of droplets would fall, resulting in an unformed structure, as Figure 1 c.

[0024] The cobalt nitrate hexahydrate used in the present invention was of analytical purity with a purity ≥ 99.0%, the cerium nitrate hexahydrate was of analytical purity with a purity ≥ 99.0%, and the absolute ethanol was of analytical purity with a purity ≥ 99.7%. The composite catalyst of carbon-doped cobalt tetroxide and cerium dioxide ultra-long hollow nanotubes, the carbon-doped cerium dioxide catalyst, and the carbon-doped cobalt tetroxide catalyst prepared in the present invention were respectively labeled as C / Co3O4 / CeO2, C / CeO2, and C / Co3O4.

[0025] Figure 2XRD patterns of the synthesized catalysts are shown. The carbon-doped cobalt tetroxide sample gave diffraction peaks at 31.27°, 36.85°, 59.35°, and 65.23°, corresponding to the (220), (311), (511), and (440) crystal planes of cobalt tetroxide, respectively, indicating that the synthesized sample is pure-phase cobalt tetroxide. For the carbon-doped cerium dioxide sample, the diffraction peaks at 28.55°, 33.07°, 47.48°, and 56.34° corresponded to the (111), (200), (220), and (311) crystal planes of cerium dioxide, respectively, indicating that the synthesized sample is pure-phase cerium dioxide. In the XRD pattern of the composite catalyst of carbon-doped cobalt tetroxide and cerium dioxide, only the diffraction peaks corresponding to the single-phase cobalt tetroxide and cerium dioxide samples appeared, and no other diffraction peaks were observed, indicating the formation of a composite catalyst of cobalt tetroxide and cerium dioxide.

[0026] Figure 3 Morphological characterization of the composite catalyst of carbon-doped cobalt tetroxide and cerium dioxide is presented. From the figure, it can be clearly seen that the composite catalyst of cobalt tetroxide and cerium dioxide consists of uniform, thin, and long hollow tubes with a diameter of 300 - 400 nm and a length of 50 - 60 µm, which are intertwined into a network structure.

[0027] Figure 4 Specific surface area characterization of carbon-doped cobalt tetroxide, carbon-doped cerium dioxide, and the composite catalyst of carbon-doped cobalt tetroxide and cerium dioxide is shown. From the figure, it can be seen that for cerium dioxide, as the relative pressure increases, the adsorption amount continuously increases, and when the relative pressure is relatively high, the adsorption amount increases significantly faster, indicating that cerium dioxide has a strong adsorption capacity at high relative pressures and may have more mesopores or macropores, which is beneficial for gas adsorption under high pressure. The adsorption amount of the composite catalyst of cobalt tetroxide and cerium dioxide increases with the increase of relative pressure, and the overall change trend of the adsorption amount is between that of cobalt tetroxide and cerium dioxide. Its adsorption characteristics are similar to those of cerium dioxide, but the adsorption capacity is slightly weaker, probably due to differences in the number or properties of the pore structures. For cobalt tetroxide, the adsorption amount is low throughout the relative pressure range and changes little with the increase of relative pressure, perhaps because its pore structure is less or the pore size distribution is not conducive to this adsorption process, mostly micropores with a small pore volume.

[0028] Energy band structure of the synthesized catalyst in Example 2 The energy band structure of the synthesized catalyst was determined by ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) and Mott-Schottky curve (MS curve), using Lambda 355 and CHI760D, respectively.

[0029] Figure 5a is the UV-Vis DRS of the synthesized catalyst. The absorption edge of cerium dioxide is located at 450 nm, indicating that cerium dioxide can only absorb ultraviolet light, has a relatively wide band gap, and has a band structure. In CC-8, its absorption edge extends to 800 nm, which is exactly the effect produced by the heterojunction. Then, the band gaps of cerium dioxide and cobalt tetroxide were determined by the Tauc plot method ( Figure 5 b), where the band gap values of cerium dioxide and cobalt tetroxide were determined to be 3.01 eV and 2.08 eV, respectively.

[0030] Figure 6 a and Figure 6 b are the MS curves of cerium dioxide and cobalt tetroxide, respectively. The slope of the MS curve represents the type of semiconductor, indicating that cerium dioxide is an n-type semiconductor and cobalt tetroxide is a p-type semiconductor, with electronic conduction. The intersection value of the tangent of the straight-line segment of the MS curve on the X-axis represents the flat-band potential (Ef) of the material. Therefore, Ef(CeO2)=-0.72 V vs. SSC and Ef(Co3O4)=0.82 V vs. SSC. Converting the potential of the saturated silver chloride electrode (SSC) to the potential of the standard hydrogen electrode (NHE), that is, Ef(CeO2)=-0.52 V vs. NHE and Ef(Co3O4)=1.02 V vs. NHE. Since the conduction band potential of an n-type semiconductor is generally 0.2 V smaller than the flat-band potential, and the conduction band potential of a p-type semiconductor is generally 0.2 V larger than the flat-band potential, therefore, ECB(CeO2)=-0.72V vs. SSC and ECB(Co3O4)=1.22V vs. SSC; finally, the valence band potential of CeO2 was calculated based on the band gap value of CeO2, that is, EVB(CeO2)=2.29 V vs. NHE, and the valence band potential of Co3O4 was calculated based on the band gap value of Co3O4, that is, EVB(Co3O4)=-0.86 V vs. NHE.

[0031] Photovoltaic properties of the synthesized catalyst in Example 3 The photovoltaic properties of the synthesized catalyst were tested on an electrochemical workstation (CHI760D). This test involved the assembly of a three-electrode system. The counter electrode was a Pt electrode, and the reference electrode included a silver chloride electrode. The working electrode was prepared as follows: 50 mg of the catalyst was evenly dispersed in 2 mL of ethanol and 30 μL of perfluorinated resin aqueous solution, and ground in a mortar until the solution became thick. Then, the viscous liquid was evenly coated on the conductive side of the FTO conductive glass with a pipette gun, and the conductive glass coated with the catalyst was further dried in an infrared oven for 20 min to prevent the catalyst coating from falling off during the test. The electrolyte solution was 0.5 M Na2SO4 solution. In the measurement of photocurrent, a 300 W xenon lamp was still used as the light source.

[0032] The catalysts used were carbon-doped cobalt ferrite, carbon-doped cerium dioxide, and a composite catalyst of carbon-doped cobalt ferrite and cerium dioxide prepared in Example 1, respectively. Figure 6 c shows the transient photocurrent response curves of the carbon-doped cobalt ferrite, carbon-doped cerium dioxide, and the composite catalyst of carbon-doped cobalt ferrite and cerium dioxide. The transient photocurrent intensity of the composite catalyst of cobalt ferrite and cerium dioxide is higher than that of cobalt ferrite and cerium dioxide, indicating that after the separation of photogenerated carriers of the composite catalyst of cobalt ferrite and cerium dioxide is enhanced, more photoelectrons are transferred to the photocatalytic surface to participate in the activation of PMS. Figure 6 d shows the EIS spectra of the synthesized catalysts. Among them, the Nyquist arc radius of the composite catalyst of cobalt ferrite and cerium dioxide is the smallest, indicating the best conductivity; the arc radius of cobalt ferrite and cerium dioxide is the largest, indicating that the photogenerated carriers of cobalt ferrite and cerium dioxide are most likely to recombine. The Nyquist arc radius of the composite material decreases significantly, which can improve the separation effect of photogenerated carriers.

[0033] Photocatalytic degradation reaction of polyethylene terephthalate microplastic waste in Example 4 For the photocatalytic degradation reaction of polyethylene terephthalate microplastic waste, in a 200 ml reactor, 30 mg of the C / Co3O4 / CeO2 catalyst prepared in Example 1, single-phase carbon-doped cobalt ferrite, and single-phase carbon-doped cerium dioxide, 20 mg of microplastics, 3 mM PMS, and 100 mL of water were added respectively. After mixing evenly, the reactor was sealed. A 300 W xenon lamp was used to simulate sunlight. The xenon lamp was turned on for illumination, and condensed water was introduced into the reactor to maintain room temperature to avoid excessive temperature. The photocatalytic degradation experiment time was 6 h. A 0.1 μm organic system filter head that had been dried and weighed was used to filter the solid product. The filter tip was kept dry in the oven for 72 hours until the mass did not change. The liquid-phase product was filtered through the filter head, collected, and detected by GC-MS. All tests were repeated more than 3 times and the average value was taken. The calculation formula for the degradation efficiency is formula (1): weight loss (%) = (w0 - w t ) / w0 × 100%.

[0034] As can be seen from Figure 7 a, the composite catalyst C / Co3O4 / CeO2 of carbon-doped cobalt ferrite and cerium dioxide ultra-long hollow nanotubes shows enhanced reaction activity compared with single-phase carbon-doped cobalt ferrite and carbon-doped cerium dioxide. In the presence of a reaction time of 6 h and 3 mM PMS, the weight loss of polyethylene terephthalate microplastics is 95.987 ± 4.32%. As can be seen from Figure 7 b, with the increase of the reaction time, the degradation efficiency of C / Co3O4 / CeO2 gradually increases. As can be seen from Figure 7It can be seen that the degradation rate of C / Co3O4 / CeO2 is (0.40308 h -1 ) under the conditions of a reaction time of 6 h and 3 mM PMS.

[0035] By constructing a heterojunction between semiconductors, not only can the defects of individual semiconductors be compensated for, which is beneficial for preparing advanced catalysts for target reactions, but also the structure-activity relationship between the catalyst structure and reaction performance can be deeply understood. In the present invention, a composite catalyst of carbon-doped cobalt tetroxide and cerium dioxide ultra-long hollow nanotubes is prepared by a one-step electrospinning method. Because its fibers are relatively thin, it has a large specific surface area, a relatively wide band gap, a large contact area with microplastics, which is conducive to the migration of carriers to the catalyst surface, and the adsorbed substances undergo redox reactions, thereby improving the photocatalytic activity.

[0036] The above examples of the present invention have been described in detail in combination with the embodiments. However, the present invention is not limited to the above examples. Various changes can be made within the scope of knowledge possessed by those of ordinary skill in the art without departing from the gist of the present invention, and these should also be regarded as the protection scope of the present invention.

Claims

1. A carbon-doped cobalt ferrite and cerium dioxide composite catalyst, characterized in that, The composite catalyst uses polyvinylpyrrolidone PVP as a precursor, and cobalt nitrate hexahydrate Co(NO3)3·6H2O and cerium nitrate hexahydrate Ce(NO3)3·6H2O are added, and it is synthesized by a one-step method through high-voltage electrospinning technology; the composite catalyst is composed of hollow nanotubes intertwined into a network structure to form a cobalt ferrite and cerium dioxide heterojunction interface.

2. The carbon-doped cobalt ferrite and cerium dioxide composite catalyst according to claim 1, wherein The diameter of the hollow nanotubes is 300-400 nm and the length is 50-60 µm.

3. The carbon-doped cobalt ferrite and cerium dioxide composite catalyst according to claim 1, characterized in that, The molar mass ratio of cobalt ferrite and cerium dioxide in the composite catalyst is 1:1-8.

4. The carbon-doped cobalt ferrite and cerium dioxide composite catalyst according to claim 1, wherein The preparation method of the composite catalyst includes the following steps: (1) PVP, Ce(NO3)3·6H2O and Co(NO3)2·6H2O are added to distilled water and absolute ethanol, and stirred at room temperature to obtain a homogeneous and transparent composite sol; the dosage ratio of PVP, Ce(NO3)3·6H2O, Co(NO3)3·6H2O, distilled water, and absolute ethanol is 1g: 0.1-0.3g: 0.7-0.9g: 4-7ml: 4-7ml; (2) The prepared composite sol is electrospun at room temperature to obtain composite microfibers; The parameters of the electrospinning are as follows: the diameter of the needle tip is 1 mm, the angle with the horizontal plane is about 15 - 30°, the DC voltage is 17 - 18 kV, the curing distance is 20 - 25 cm, the injection speed is 0.7 - 1 mm·min -1 , the rotating speed of the roller is 300 - 350 r·min -1 ; (3) The prepared composite microfibers are dried, calcined, and cooled.

5. The carbon-doped cobalt ferrite and cerium dioxide composite catalyst according to claim 4, wherein The stirring time in step (1) is 24-26h.

6. The carbon-doped cobalt ferrite and cerium dioxide composite catalyst according to claim 4, wherein The drying temperature in step (3) is 40-60 °C, and the drying time is 10-14h; the calcination temperature is 500-550 °C, the calcination time is 2-4 h, and the heating rate is 5-10 °C / min.

7. Application of the carbon-doped cobalt ferrite and cerium dioxide composite catalyst according to any one of claims 1 to 6 in photocatalytic degradation of polyethylene terephthalate microplastic waste.

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