Catalytic material for degrading perfluoro-polyfluorinated compound as well as preparation method and application of catalytic material

Abstract

The invention is applicable to the technical field of treatment of organic pollutants in water, and provides a catalytic material for degrading perfluoro-polyfluorinated compounds as well as a preparation method and application of the catalytic material. Through defect engineering and crystal face regulation and control, the CoFe2O4 / BiOCl (010)-Ovs heterojunction material rich in oxygen vacancies is constructed. According to the material, the conductivity is remarkably enhanced, the light response range is widened, reaction active sites are enriched, separation and migration of photon-generated carriers are promoted, the electron-hole utilization efficiency is improved, and then the photoelectrocatalysis performance is improved. The material accelerates the redox cycle of Co < 2 + > / Co < 3 + > and Fe < 2 + > / Fe < 3 + >, significantly improves the activation efficiency of PMS and the generation of active oxygen species, and has the multifunctional characteristics of photoelectrocatalysis and PMS activation. The PMS / PMS composite material is prepared into a photo-anode, the photo-anode is applied to a photoelectrocatalysis-PMS coupling system, under low voltage, PMS is activated through photon-generated carriers to generate ROS, a multi-ROS synergistic oxidation path is formed, and efficient degradation and defluorination mineralization of PFASs are achieved. The system has excellent stability and environmental adaptability, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of treatment of organic pollutants in water, and particularly relates to a catalytic material for degrading perfluoro and polyfluoro compounds and a preparation method and application thereof. BACKGROUND

[0002] Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are known as “forever chemicals” due to their chemical inertness, low molecular polarity, high carbon-fluorine bond energy (536 kJ mol -1 ), short C-F bond length, amphiphilic, surfactant properties and thermal stability. They are widely used in food packaging, waterproof coatings, semiconductor products, fire-fighting foam and other product manufacturing, but at the same time, they have become new pollutants that persist in the natural environment and are difficult to remove. Among them, perfluorooctanoic acid (PFOA), as one of the most representative PFASs, has strong accumulation and potential carcinogenic risk, and has certain toxicity to reproductive system, nervous system and liver and other organs. PFOA widely exists in water environment and can enter the human body through drinking water, forming a potential exposure pathway. Its extremely high chemical stability and anti-degradation ability make it difficult for conventional water treatment processes such as flocculation, anaerobic digestion and activated sludge process to effectively remove it, and membrane separation technology has problems such as concentrated liquid treatment and membrane pollution. Although advanced oxidation processes such as photocatalysis and electrocatalysis can achieve degradation of PFASs, they usually rely on ultraviolet light, high voltage, high energy consumption, and lack of oxygen, which limits their large-scale application in actual water remediation. Therefore, developing an efficient, green and sustainable PFOA removal technology has become an urgent need for current environmental governance.

[0003] Among the existing advanced oxidation technologies, photoelectrocatalysis combines the advantages of photocatalysis and electrocatalysis, and promotes the effective separation of photo-generated electron-hole pairs by applying an external voltage, thereby enhancing the catalytic activity, improving the catalytic efficiency and reducing the injection of external energy. It is considered as a potential means of pollutant degradation. The preparation of catalysts is the key technology in photoelectrocatalysis technology, and the common photoelectrocatalytic materials still have problems such as narrow light response range, high recombination rate of photo-generated electron-hole pairs and poor conductivity. When treating structurally stable organic pollutants (such as PFASs), this technology still faces the bottlenecks of slow degradation rate, low defluorination efficiency and high voltage required for reaction, making it difficult to achieve green, economic and sustainable degradation of PFASs in water. Among them, BiOCl is an excellent photoelectrocatalytic material, which mainly has advantages in the separation efficiency of photo-generated carriers: the [Bi2O2] 2+The polarization valence band generated by the hybridization of O 2p and Bi 6s orbitals in the layer generates an induced internal electric field, which can promote the separation of photo-generated charges. However, BiOCl still has deficiencies in practical applications: the large band gap width causes it to only effectively absorb photons in the ultraviolet band, and the spectral response capability in the visible light region is significantly limited; at the same time, the separation efficiency of photo-generated carriers is low. CoFe2O4 is widely used in the activation of peroxymonosulfate (PMS) and the degradation of pollutants in spinel ferrite; CoFe2O4 has unique physicochemical properties, such as high surface active sites, large specific surface area, high chemical stability, and controllable size and shape, which make it widely used in many fields.

[0004] Currently, some studies attempt to overcome these difficulties by constructing new catalytic systems. For example, the invention patent with publication number CN109759116A discloses a method for promoting the decomposition and purification of perfluorinated compounds by photoelectric coupling, prepares carbon nanosheet / g-C3N4 / BiWO6 photo-cathode, and successfully constructs a photoelectric catalytic purification system to effectively treat PFOA. However, this system requires the addition of sodium bisulfite, a hazardous chemical, and relies on continuous aeration, and the removal rate of PFOA is less than 50% within 120 minutes without aeration. In addition, this technology mainly uses reduction degradation as the main path, and the defluorination rate of PFOA cannot be detected, which may generate more toxic fluorine-containing intermediates during the reaction process, easily causing secondary pollution, limiting the safety of its practical application. Another invention patent with publication number CN115231649A discloses a method for removing perfluorinated compounds in groundwater by photoelectric catalysis and PRB, prepares TiO2 nanotube array (TNTA) photo-anode, and constructs a photoelectric catalytic system PEC to cooperatively treat PFOA and PFOS with PRB. Under the reaction voltage of 5 V and the photoelectric catalysis and PRB system, the removal rate of PFOA is 98.1% within 60 days. However, the removal of PFASs in water mainly relies on the oxidation of PFASs by the photo-anode, and the working voltage is too high during the treatment process, the reaction conditions are harsh, and it needs to cooperate with fillers such as PRB to remove PFASs, which takes too long. This technology is mainly designed for groundwater scenes and is difficult to promote to surface water or industrial wastewater treatment, and the defluorination rate and mineralization efficiency of perfluorinated compounds are not detected, which cannot comprehensively evaluate the degradation depth and environmental risk.

[0005] Based on the deficiencies of the prior art, the present application provides a catalytic material for degrading perfluorinated and polyfluorinated compounds, a preparation method and application thereof. SUMMARY

[0006] The present application aims to provide a catalytic material for degrading perfluorinated and polyfluorinated compounds, a preparation method and application thereof, which aims to solve the problems raised in the background art.

[0007] The object of the present application is achieved by the following technical solutions: A catalytic material for degrading perfluorinated polyfluorinated compounds, CoFe2O4 is used as a PMS activated substrate material, a heterojunction is constructed with BiOCl(010) material, and oxygen vacancies are introduced through defect engineering to form a CoFe2O4 / BiOCl(010)-Ovs catalytic material, wherein BiOCl(010)-Ovs represents a BiOCl(010) material with oxygen vacancies.

[0008] Further, the proportion of oxygen vacancies in the catalytic material is 21.3%.

[0009] A preparation method of the catalytic material according to the above, comprising the following steps: Step 1: CoFe2O4 and BiOCl(010) are synthesized by a hydrothermal method, oxygen vacancies are introduced by irradiating BiOCl(010) with ultraviolet light to obtain BiOCl(010)-Ovs material; Step 2: BiOCl(010)-Ovs material is added to the synthesis system of CoFe2O4 by a hydrothermal method to obtain CoFe2O4 / BiOCl(010)-Ovs catalytic material.

[0010] Further, in the step 1: The preparation process of CoFe2O4 is: cobalt nitrate hexahydrate and iron nitrate nonahydrate are dissolved in deionized water and stirred, NaOH solution is added to adjust the pH to 10.0, 70 °C oil bath heating and stirring for 1 h, then transferred to a reaction kettle and heated at 160 °C for 12 h, the target product is washed, dried at 60 °C for 24 h, and then ground to obtain; The preparation process of BiOCl(010) is: bismuth nitrate pentahydrate and potassium chloride are dispersed in deionized water and stirred, NaOH solution is added to adjust the pH to 6.0, stirred for 30 min, then transferred to a reaction kettle and reacted at 160 °C for 24 h, the target product is washed, dried at 60 °C overnight, and then ground to obtain; The preparation process of BiOCl(010)-Ovs is: BiOCl(010) powder is uniformly dispersed in deionized water, irradiated with a UV high-pressure mercury lamp for 30 min, and then centrifuged and dried to obtain.

[0011] Further, the specific process of step 2 is as follows: BiOCl(010)-Ovs material is added into deionized water and stirred for 30 min, then cobalt nitrate hexahydrate and ferric nitrate nonahydrate are added, NaOH solution is added to adjust the pH to 10.0, after stirring in an oil bath at 70 DEG C for 1 h, it is transferred into a reaction kettle and reacted at 160 DEG C for 12 h, and after washing, drying at 60 DEG C overnight, the target product is obtained by grinding.

[0012] A photoanode prepared from the catalytic material described above, the preparation steps are: the catalytic material is mixed with isopropanol and Nafion solution and ultrasonicated to obtain a catalyst solution, the catalyst solution is uniformly drop-coated on a carbon cloth material, and the photoanode is obtained by heating and drying at 80 DEG C for 12 h.

[0013] An application of the photoanode described above in degrading perfluorinated and polyfluorinated compounds, the photoanode is applied to a photoelectrocatalysis-PMS coupling system.

[0014] Further, the construction conditions of the photoelectrocatalysis-PMS coupling system include: taking the photoanode as the anode, platinum as the cathode, Na2SO4 solution as the electrolyte, applying a working voltage of 0-2 V, taking a 300 W xenon lamp as the visible light source, and adding 0.5-2.5 mM PMS to the system.

[0015] Further, the perfluorinated and polyfluorinated compound is PFOA.

[0016] Further, the pH of the photoelectrocatalysis-PMS coupling system is 3-11, and the degradation time is 1-2 h.

[0017] Compared with the prior art, the beneficial effects of the present application are: The present application uses a double strategy of defect engineering and crystal face regulation, takes CoFe2O4 as a PMS activation substrate material, and constructs a heterojunction with BiOCl(010) material; high-concentration oxygen vacancies are introduced on the BiOCl(010) crystal face to regulate the electronic structure of the material, effectively increase the active sites, broaden the light response range, and inhibit the recombination of photo-generated carriers; then a CoFe2O4 / BiOCl(010)-Ovs heterojunction is constructed by a hydrothermal method, a built-in electric field is formed at the interface to promote the directional migration of photo-generated charges, significantly improve the separation efficiency of photo-generated carriers and the interface charge transfer rate, enhance the conductivity of the material, and simultaneously improve the utilization efficiency of photo-generated electrons and holes, thereby significantly enhancing the photoelectrocatalytic performance of the material, achieving the removal of PFASs in water under mild conditions; meanwhile, the photo-generated electrons also accelerate the Co 2+ / Co 3+ and Fe 2+ / Fe 3+The cyclic dynamics of the redox pair significantly improves the activation efficiency of PMS, and enhances the generation rate and amount of various reactive oxygen species (ROS). The CoFe2O4 / BiOCl(010)-Ovs heterojunction material exhibits excellent multifunctional properties in photocatalysis, electrocatalysis, and PMS catalysis. When the catalytic material is prepared into a photoanode and applied to a photoelectrocatalysis-PMS coupling system, under low operating voltage conditions, the photo-generated carriers can quickly activate PMS to generate various ROS, forming a photo-generated hole and sulfate radical-mediated multi-ROS synergistic oxidation pathway, which significantly reduces the degradation energy barrier of PFASs, greatly reduces the energy required for the reaction, and accelerates the reaction rate, achieving efficient degradation and deep defluorination mineralization of PFASs in water. The system is simple to operate, does not require additional aeration, and can operate stably under low pressure and low energy consumption conditions. Compared with the method of removing PFASs by photoelectron reduction, it also has the advantages of fast degradation rate and high defluorination mineralization degree. At the same time, the system has excellent stability and environmental resistance, and shows broad application prospects when treating actual water bodies. It is suitable for both surface water in-situ remediation and groundwater remediation, providing a new green, low-consumption, and efficient technical route for PFASs pollution control in water, and a feasible solution for efficient remediation of actual PFASs contaminated water, ultimately achieving the goal of water purification. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A schematic diagram of a photoelectrocatalysis system device.

[0019] Figure 2 XRD patterns of CoFe2O4, BiOCl(010)-Ovs, and CoFe2O4 / BiOCl(010)-Ovs materials.

[0020] Figure 3 XPS O1s patterns of the materials; wherein: (a) is the XPS O1s pattern of the CoFe2O4 / BiOCl(010)-Ovs material, and (b) is the XPS O1s pattern of the CoFe2O4 / BiOCl(010) material.

[0021] Figure 4 Transient photocurrent test results of the CoFe2O4 / BiOCl(010)-Ovs photoanode.

[0022] Figure 5 Electrochemical impedance spectroscopy test results of the CoFe2O4 / BiOCl(010)-Ovs photoanode.

[0023] Figure 6 UV-vis DRS test results of the CoFe2O4 / BiOCl(010)-Ovs photoanode.

[0024] Figure 7 PFOA degradation performance results; wherein: Figure 7 (a) in the table is the PFOA degradation performance of different materials based on photoelectrocatalytic activation of PMS system, Figure 7 (b) in the table is the PFOA degradation performance of CoFe2O4 / BiOCl(010)-Ovs under different systems.

[0025] Figure 8 CoFe2O4 / BiOCl(010)-Ovs is the defluorination rate of PFOA based on photoelectrocatalytic activation of PMS system.

[0026] Figure 9 CoFe2O4 / BiOCl(010)-Ovs is the regeneration performance and recycling performance of the photoanode; wherein: Figure 9 (a) in the table is the PFOA removal performance in the degradation cycle for five times, Figure 9 (b) in the table is the PFOA removal rate in the degradation cycle for five times.

[0027] Figure 10 CoFe2O4 / BiOCl(010)-Ovs is the mechanism diagram of photoelectrocatalytic activation of PMS system by the photoanode.

[0028] In the figure: 1-photoanode, 2-counter electrode, 3-PFOA solution, 4-electrolytic cell, 5-electrode clamp, 6-magnetic stirrer, 7-movable power supply, 8-xenon lamp, 9-peroxymonosulfate. DETAILED DESCRIPTION

[0029] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present application, the technical solutions of the present application will be described in detail below, but it cannot be understood as limiting the scope of the present application. Unless otherwise specified, the methods used in the present application are conventional methods in the technical field. In the present application, the materials, reagents or instruments used are not specified by the manufacturer, and are conventional products that can be obtained by market purchase.

[0030] The present application provides a catalytic material for degrading perfluorinated compounds, which uses BiOCl as the photoanode base material and CoFe2O4 as the PMS activation base material. The BiOCl photoelectrocatalytic material is regulated by a double strategy of defect engineering (introducing oxygen vacancies) and crystal face regulation to increase its reaction sites and broaden its light response range. By constructing a CoFe2O4 / BiOCl(010)-Ovs heterojunction, the separation efficiency of photo-generated carriers and the interface charge transfer rate are significantly improved, the conductivity and visible light response ability are enhanced, and the electrochemical activity and photocatalytic ability are improved, thereby accelerating the Co 2+ / Co3+ with Fe 2+ / Fe 3+ Redox pair cycling rate promotes PMS activation. Among them, in addition to BiOCl, other Bi-based oxide materials can also be used as the base material of the photoanode, such as BiOBr, BiOI, BiOF, Bi2MoO6, BiVO4, etc.; in addition to CoFe2O4, other composite metal oxides can also be used as the base material of PMS activation, such as CuCo2O4, MnFe2O4, ZnCu2O4, CoNi2O4, CuMn2O4, ZnCo2O4, etc.

[0031] After the CoFe2O4 / BiOCl(010)-Ovs catalytic material is prepared into a photoanode, it is applied to a photoelectrocatalysis-PMS coupling system, and the core mechanism of the system for degrading PFASs is as shown in Figure 10 The system couples PMS activation technology with photoelectrocatalysis technology, and under low working voltage conditions, the photo-generated carriers transiently activate PMS to generate various ROS such as sulfate radicals (SO4• - ), hydroxyl radicals (•OH), singlet oxygen (1O2), superoxide radicals (O2• 1 ), and the like, forming photo-generated holes and SO4• - . -The mediation-multiple ROS synergistic oxidation pathway, combined with the photo-generated carrier redox, drives the rupture of C-C and C-F bonds in the PFOA molecule, realizes the efficient degradation and deep defluorination mineralization of PFOA, and achieves the goal of water purification. In addition, the system exhibits anti-interference ability and long-term stability in actual water bodies, providing a new engineering idea for the continuous and deep treatment of PFASs contaminated water bodies. In addition to PMS, peroxymonosulfate (PDS) and other reagents can also be applied to the photoelectrocatalytic coupling system. In addition to PFOA, the system can also be applied to remove other types of PFASs, such as trifluoroacetic acid (TFA), perfluoropropionic acid (PFPrA), perfluorobutyric acid (PFBA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorononanoic acid (PFNA), perfluorooctanesulfonic acid (PFOS), perfluorohexanesulfonic acid (PFHxS), trifluoromethanesulfonic acid (TFMS), perfluorobutanesulfonic acid (PFBS), perfluoropropanesulfonic acid (PFPrS), perfluoroethanesulfonic acid (PFEtS), fluorotelomer alcohol (FTOH), fluorotelomer sulfonic acid (FTSAs), 6:2 fluorotelomer unsaturated carboxylic acid (6:2 FTUCA), 8:2 fluorotelomer unsaturated carboxylic acid (8:2 FTUCA), 10:2 fluorotelomer unsaturated carboxylic acid (10:2 FTUCA), 6:2 fluorotelomer carboxylic acid (6:2 FTCA), 8:2 fluorotelomer carboxylic acid (8:2 FTCA), 6:2 chlorinated polyfluoroether sulfonic acid (6:2 Cl-PFESA), 8:2 chlorinated polyfluoroether sulfonic acid (8:2 Cl-PFESA), hexafluoropropylene oxide dimer acid (HFPO-DA), 4,8-dioxa-3H-perfluorononanoic acid ammonium (ADODA), perfluorooctane phosphonic acid (PFOPA), perfluorodecyl phosphonic acid (PFDPA), 1H,1H,2H,2H-perfluorodecyl phosphate (8:2 PAP), 1H,1H,2H,2H-perfluorooctyl phosphate (6:2 PAP), (1H,1H,2H,2H-perfluorooctyl) phosphate (6:2 diPAP), (1H,1H,2H,2H-perfluorodecyl) phosphate (8:2 diPAP), sodium perfluoroalkyleneoxybenzene sulfonate (OBS), perfluoroalkyl sulfonamide derivatives (PFASDs), and the like. Without departing from the principles of the present application, equivalent substitutions and scaling applications of the photoanode substrate material, activated substrate material, persulfate reagent type, and PFAS molecular structure treated by the present application should be considered within the scope of protection of the present application.

[0032] The specific implementation of the present application is described in detail below in conjunction with specific examples.

[0033] Example 1: Preparation and application of catalytic material 1. The preparation method of the catalytic material comprises the following steps: Step 1: CoFe2O4, BiOCl(010) were synthesized by hydrothermal method, respectively, and then oxygen vacancies were introduced by UV irradiation to obtain BiOCl(010)-Ovs materials; The preparation process of CoFe2O4 is as follows: first, add cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 5 mmol, 1.455 g) and iron nitrate hydrate (Fe(NO3)3·9H2O, 10 mmol, 4.04 g) into a beaker containing 60 mL of deionized water, ultrasonically mix for 10 min, magnetically stir for 30 min, and record as solution A. Weigh 2.00 g of NaOH and dissolve it in 10 mL of deionized water, and record as solution B. Then, use a rubber dropper to slowly add an appropriate amount of solution B to solution A while stirring to adjust the pH of the system to 10.0. At this time, a reddish-brown precipitate gradually forms in the solution. Place the mixture in a 70 °C oil bath and continue to heat and stir for 1 h, then transfer it to an 80 mL high-pressure reaction kettle with a polytetrafluoroethylene liner, and react at 160 °C for 12 h. After the reaction is completed, the obtained solid product is sequentially washed with deionized water and absolute ethanol by alternating centrifugation, and the process is repeated three times to remove impurities. The washed sample is dried in a 60 °C oven for 24 h, and then ground to obtain the sample, which is CoFe2O4.

[0034] The preparation process of BiOCl(010) is as follows: disperse bismuth nitrate pentahydrate (Bi(NO3)3·5H2O, 4 mmol, 1.94 g) and an equal amount of potassium chloride (KCl, 4 mmol, 0.298 g) into 60 mL of deionized water, and magnetically stir until completely dissolved. Under continuous stirring, add 1 mol / L sodium hydroxide solution dropwise to adjust the pH of the reaction system to 6.0. At this time, the solution gradually turns into a milky white color. After continuous stirring for 30 min, the solution is transferred to an 80 mL high-pressure reaction kettle with a polytetrafluoroethylene liner, sealed, and placed in an oven at 160 °C for constant temperature reaction for 24 h. After the reaction kettle is naturally cooled, the obtained product is purified by multiple centrifugal washing with deionized water and absolute ethanol, and then dried in a 60 °C drying oven overnight. After being ground thoroughly, the sample is recorded as BiOCl(010).

[0035] The preparation process of BiOCl(010)-Ovs is as follows: accurately weigh 0.5 g of BiOCl(010) powder and disperse it uniformly in 50 mL of deionized water to form a suspension. Then, place it under a UV high-pressure mercury lamp for continuous irradiation for 30 min. After centrifugal drying, it is BiOCl(010)-Ovs.

[0036] Step 2: BiOCl(010)-Ovs is added into the synthesis system of CoFe2O4 by hydrothermal method to obtain CoFe2O4 / BiOCl(010)-Ovs catalytic material, and the photoelectrocatalytic performance is enhanced.

[0037] The preparation process of CoFe2O4 / BiOCl(010)-Ovs composite material is as follows: BiOCl(010)-Ovs material (5 mmol, 1.302 g) is ultrasonically dispersed into 60 mL deionized water and stirred for 30 min to form a uniform suspension, and then cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 5 mmol, 1.455 g) and iron nitrate nonahydrate (Fe(NO3)3·9H2O, 10 mmol, 4.04 g) are added in sequence, and magnetic stirring is performed until complete dissolution. Under stirring conditions, 1 mol / L sodium hydroxide solution is added dropwise until the pH of the system is 10.0, at which time red-brown precipitate is observed to be generated. The above-mentioned mixed system is placed in a 70 °C oil bath, and after stirring for 1 h, it is transferred to a high-pressure reaction kettle lined with polytetrafluoroethylene, and hydrothermal reaction is carried out at 160 °C for 12 h. After the reaction is completed, the obtained solid is washed by centrifugation with deionized water and anhydrous ethanol alternately, and then placed in a 60 °C oven for drying overnight. After being fully ground, the obtained sample is CoFe2O4 / BiOCl(010)-Ovs catalytic material rich in oxygen vacancies.

[0038] 2. The prepared catalytic material is applied to the photoelectrocatalytic system for degrading perfluorinated and polyfluorinated compounds in water, and the specific operation is as follows: (1) Construction of photoelectrocatalytic system: The schematic diagram of the photoelectrocatalytic reaction system constructed in this study is shown in Figure 1 . The specific device includes a light anode 1, a counter electrode 2, a PFOA solution 3, an electrolytic cell 4 (quartz electrolytic cell), an electrode clamp 5, a magnetic stirrer 6, a mobile power supply 7 (direct current stabilized power supply), a xenon lamp 8 (300 W xenon lamp light source), and a peroxymonosulfate 9, etc. In the experiment, the prepared CoFe2O4 / BiOCl(010)-Ovs composite material is used as the light anode, a platinum sheet electrode is used as the cathode, and a Na2SO4 solution is used as the electrolyte. A direct current stabilized power supply is used to apply a working voltage of 0 to 2 V to the system, a xenon lamp 8 is used to provide visible light irradiation, and a magnetic stirrer 6 is used to keep the solution in the system uniformly mixed.

[0039] The preparation steps of the CoFe2O4 / BiOCl(010)-Ovs photoanode are as follows: 10 mg of CoFe2O4 / BiOCl(010)-Ovs catalytic material is weighed, mixed with 2 mL of isopropyl alcohol and 9 μL of Nafion solution, and after ultrasonic treatment, a uniformly dispersed catalyst suspension is formed. 0.2 mL of the suspension is uniformly taken on a carbon cloth substrate with a size of 2×1 cm 2 at 60 °C and dried overnight to obtain the CoFe2O4 / BiOCl(010)-Ovs photoanode.

[0040] (2) Preparation of target pollutants: PFOA is selected as a representative substance of perfluoroalkyl carboxylic acids. 10 mg of PFOA is accurately weighed and placed in a brown bottle containing 100 mL of deionized water, and magnetically stirred for 24 h to fully dissolve, obtaining a PFOA solution with a concentration of 100 mg / L as a mother liquor. 1 mL of the mother liquor is diluted to 100 mL to obtain a PFOA solution with a concentration of 5 mg / L -1 as a reaction solution.

[0041] (3) Operation process of photoelectrocatalytic degradation: PFOA reaction solution and PMS are added to the electrolytic tank containing Na2SO4 electrolyte solution, and the dosage of PMS is 0.5-2.5 mM. Subsequently, the anode and cathode are inserted into the electrolytic tank. Before starting the light and the applied electric field (0-2 V), HCl and NaOH are added to adjust the pH value of the mixed system to 3-11. After the reaction starts, photoelectrocatalysis-PMS coupling is realized to degrade perfluorinated compounds. Samples are taken at different time nodes, filtered through a filter head, and collected for subsequent determination of pollutant concentration and defluorination rate. The entire photoelectrocatalysis-PMS coupling degradation process lasts for 1-2 h.

[0042] (4) Analysis of pollutant concentration and defluorination rate; The concentration of PFOA is analyzed and determined by high performance liquid chromatography mass spectrometry (U3000 / TSQ quantum), and detected by electrospray ionization source (ESI) negative ion mode. The chromatographic separation conditions are as follows: isocratic elution, mobile phase is a mixture of 5 mM ammonium acetate aqueous solution and acetonitrile (volume ratio is 70:30), flow rate is set to 0.1 mL min -1 , injection volume is 5 μL, and column temperature is 50 °C. The mass spectrometry key parameters include: ion source spray voltage 3000 V, ion transmission tube temperature 350 °C, sheath gas 40 arb; auxiliary gas 10 arb.

[0043] To quantitatively analyze, PFOA standard solutions are prepared in the range of 0-100 μg L -1 (the concentrations are 10, 20, 50, 80, 100 μg L-1 ), and the peak area was determined by high performance liquid chromatography-mass spectrometry (HPLC-MS), and a relationship diagram of PFOA concentration and peak area was established.

[0044] The defluorination rate was calculated by determining the concentration change of fluoride ions (F - ) in the sample before and after the reaction by ion chromatography.

[0045] Example 2: Characterization of CoFe2O4 / BiOCl(010)-Ovs catalytic material by X-ray diffraction (XRD); The crystal structure of the material was analyzed by powder X-ray diffraction (PXRD). The characterization parameters were set as follows: Cu target, Kα ray, λ = 1.54 Å, angle range 5-80 °, scanning speed 5 ° min -1 .

[0046] The test results are shown in Figure 2 , and it can be seen that the characteristic diffraction peaks of BiOCl(010) and CoFe2O4 of CoFe2O4 / BiOCl(010)-Ovs are retained, which proves that the CoFe2O4 / BiOCl(010)-Ovs catalytic material is successfully synthesized.

[0047] Example 3: Characterization of CoFe2O4 / BiOCl(010)-Ovs catalytic material by X-ray photoelectron spectroscopy (XPS); XPS was used to analyze the types and proportions of oxygen elements in the material to verify whether the oxygen vacancy structure was successfully synthesized and to calculate the proportion of oxygen vacancies in the material. Avantage was used to fit the element structure peaks to analyze the proportion of vacancies in the material. XPS testing used monochromatic Al-Kα ray as the excitation source (photon energy 1486.6 eV) to calibrate C 1s (284.6 eV) to ensure the accuracy and comparability of the measurement results.

[0048] The test results are shown in Figure 3 (a) and (b), and it can be seen that the proportion of oxygen vacancies in the CoFe2O4 / BiOCl(010)-Ovs catalytic material is 21.3%, which is significantly higher than that of the untreated CoFe2O4 / BiOCl(010) material (11.5%), indicating that the CoFe2O4 / BiOCl(010)-Ovs catalytic material has been successfully prepared.

[0049] Example 4: Evaluation of the photoelectrochemical performance of CoFe2O4 / BiOCl(010)-Ovs photoanode; The photocurrent curve of the sample was tested by an electrochemical workstation standard three-electrode test system. In the standard three-electrode system, 0.1 M sodium sulfate solution was used as the electrolyte, Ag / AgCl (0.195 V vs SHE, KCl saturated solution) was used as the reference electrode, platinum plate was used as the counter electrode, and CoFe2O4 / BiOCl(010)-Ovs coated on indium tin oxide (ITO) glass was used as the working electrode. The light source used for electrochemical test was a 300 W xenon lamp, and the photoelectrochemical performance of CoFe2O4 / BiOCl(010)-Ovs photoanode was evaluated by transient photocurrent test and electrochemical impedance spectroscopy. The light absorption performance of the semiconductor material was determined by ultraviolet-visible diffuse reflectance spectroscopy test, and BaSO4 was used as the background in the test, and the scanning range was 250-825 nm.

[0050] Figure 4 For the transient photocurrent test results of CoFe2O4, BiOCl, BiOCl(010) and CoFe2O4 / BiOCl(010)-Ovs, it can be seen that pure CoFe2O4 and BiOCl exhibit relatively low photocurrent density, while the photocurrent density of CoFe2O4 / BiOCl(010)-Ovs material is the largest. The light absorption capacity and carrier separation efficiency of BiOCl material are improved by the synergistic strategy of crystal face engineering and defect engineering, and the directional migration of electrons is accelerated after being compounded with CoFe2O4.

[0051] Figure 5 For the electrochemical impedance spectroscopy test results, it can be seen that the interface charge transfer resistance of CoFe2O4 / BiOCl(010)-Ovs is the lowest, which proves that the construction of the composite material accelerates the carrier migration.

[0052] Figure 6 For the ultraviolet-visible diffuse reflectance spectroscopy test results, the results show that the oxygen vacancy regulation makes the light absorption edge of BiOCl(010)-Ovs red shift from 373 nm to 448 nm, and the visible light absorption is significantly enhanced. The light absorption edge of CoFe2O4 is 558 nm, and after being compounded, the light absorption edge of CoFe2O4 / BiOCl(010)-Ovs further shifts to 514 nm compared with that of BiOCl(010)-Ovs. This indicates that the improvement of the visible light response of the material is due to the introduction of oxygen vacancies and the synergistic effect of the compounding with CoFe2O4.

[0053] Example 5: Setting of performance test reaction conditions The performance test of PFOA degradation by photoelectrocatalytic activation of PMS system was carried out in a 100 mL electrolytic cell containing 50 mL 0.05 mol L -1Sodium sulfate electrolyte was prepared, and PFOA and PMS were added to achieve initial concentrations of 5 mg / L. -1 and 2.5 mmol L -1 The reaction was carried out using CoFe₂O₄ / BiOCl(010)-Ovs as the working electrode and a platinum sheet as the counter electrode, under an applied voltage of 2 V and visible light irradiation by a xenon lamp. Sampling times were set to 0, 10, 30, 60, 90, and 120 min. After filtration through a filter membrane, the PFOA concentration was determined using high-performance liquid chromatography-mass spectrometry (HPLC-MS / MS).

[0054] CoFe2O4 / BiOCl(010)-Ovs was used as the working electrode, and a platinum sheet was used as the counter electrode. To evaluate the degradation effect of PFOA under different systems, the following control groups were set up: light irradiation only, 2 V voltage applied only, photoanode only, and PMS only.

[0055] Figure 7 (a) shows the PFOA degradation performance of different materials based on the photoelectrocatalytic activation of PMS system. Figure 7 (b) shows the PFOA degradation performance of CoFe2O4 / BiOCl(010)-Ovs in different systems. It is evident that the CoFe2O4 / BiOCl(010)-Ovs composite photoanode exhibits the best PFOA degradation efficiency compared to single materials. Furthermore, the photoelectrocatalysis + PMS system achieves a PFOA degradation efficiency of 79.7% within 120 min, significantly higher than other single or control systems, confirming the significant advantages and application potential of this synergistic system in PFOA degradation.

[0056] Example 6: PFOA defluorination performance test; The PFOA degradation experiment was conducted according to the experimental conditions in Example 5, and the F in the sample was tested using ion chromatography. - Concentration. PFOA defluorination performance results are as follows: Figure 8 As shown, the CoFe2O4 / BiOCl(010)-Ovs photoanode has a strong defluorination effect on PFOA in the photoelectrocatalytic activation PMS system, with a defluorination rate of 67.03% within 120 min, indicating that the system can effectively achieve deep mineralization and efficient removal of PFOA.

[0057] Example 7: Stability and recyclability of CoFe2O4 / BiOCl(010)-O vs photoanode; The PFOA degradation experiment was carried out according to the experimental conditions in Example 5. After each experiment, the electrode was washed with ultrapure water and ethanol and then dried. This process was repeated 4 times.

[0058] Figure 9 In the figure, (a) represents the PFOA removal performance in five consecutive degradation cycles.Figure 9 The degradation efficiency of PFOA removal in (b) is the degradation efficiency of PFOA removal for five consecutive times. After 5 times of reuse, the degradation efficiency of PFOA by CoFe2O4 / BiOCl(010)-Ovs photoanode only shows a small decrease, showing good cycle stability and potential for practical application.

[0059] Example 8: Machine analysis; In the photoelectrocatalytic system, visible light irradiation excites the CoFe2O4 / BiOCl(010)-Ovs photoanode to produce a large number of photo-generated electron-hole pairs. The built-in electric field of the heterojunction promotes the enrichment of photo-generated holes in the valence band of BiOCl(010)-Ovs, while the photo-generated electrons migrate to the conduction band of CoFe2O4, realizing the spatial separation of the carriers; at the same time, under the action of an external electric field, the separation and migration rate of photo-generated electrons and holes are significantly improved, thereby enhancing the catalytic activity and reaction rate of the system. In the system, under the driving of the electric field, PMS is adsorbed on the surface of the photoanode, and the electrons and holes produced in the photoelectrocatalytic process can activate PMS to produce various ROS, including SO4• - , •OH, O2• - and 1 O2; in addition, the cycle of Co 2+ / Co 3+ and Fe 2+ / Fe 3+ redox pairs in the CoFe2O4 / BiOCl(010)-Ovs photoanode composite also promotes the activation process of PMS, and the synergistic effect enhances the generation rate and amount of ROS, so that the system can realize efficient degradation of pollutants at low voltage, with the technical advantages of low consumption and high efficiency. Among them, the photo-generated holes and the strong oxidizing SO4• - synergistically act on the PFOA molecule, converting it into a C7F 13 COO• intermediate, which further triggers the defluorination reaction to generate unstable C7F 15 OH. C7F 15 OH is further converted to C7F - OF under the attack of various ROS (such as •OH, O2• 1 and 13 O2), and releases F - ; then, C7F 13 OF is converted to C6F - COOH (PFHpA) by hydrolysis reaction and removal of another molecule of F 13 ; PFHpA continues to degrade along a similar path to generate a series of short-chain perfluorinated compounds. Short-chain products and F -Eventually, the PFOA desorbed from the electrode surface and diffused to the solution bulk, making the electrode active sites regenerated. The above reaction cycle proceeds until the PFOA is completely defluorinated and mineralized.

[0060] The above merely describes the preferred embodiments of the present application, and it should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, and these should also be considered as the protection scope of the present application, which will not affect the effect and practicability of the present application.

Claims

1. A catalytic material for degrading a perfluorinated polyfluorinated compound, characterized by, CoFe2O4 is used as a PMS-activated substrate material to construct a heterojunction with BiOCl(010) material, and oxygen vacancies are introduced by defect engineering to form a multifunctional catalytic material CoFe2O4 / BiOCl(010)-Ovs, wherein BiOCl(010)-Ovs represents a BiOCl(010) material with oxygen vacancies.

2. The catalytic material of claim 1, wherein, The proportion of oxygen vacancies in the catalytic material is 21.3%.

3. A method for the preparation of a catalytic material according to claim 1 or 2, characterized in that, The method comprises the following steps: Step 1: CoFe2O4 and BiOCl(010) are synthesized by a hydrothermal method, oxygen vacancies are introduced into BiOCl(010) by ultraviolet irradiation, and BiOCl(010)-Ovs material is obtained; Step 2: BiOCl(010)-Ovs material is added to the synthesis system of CoFe2O4 by a hydrothermal method to obtain CoFe2O4 / BiOCl(010)-Ovs catalytic material.

4. The production method according to claim 3, characterized by, In the step 1: The preparation process of CoFe2O4 is as follows: cobalt nitrate hexahydrate and ferric nitrate nonahydrate are dissolved in deionized water and stirred, NaOH solution is added to adjust the pH to 10.0, 70 °C oil bath heating and stirring for 1 h, then transferred into a reaction kettle and reacted at 160 °C for 12 h, and the target product is obtained by washing, drying at 60 °C for 24 h and grinding; The preparation process of BiOCl(010) is as follows: bismuth nitrate pentahydrate and potassium chloride are dissolved in deionized water and stirred, NaOH solution is added to adjust the pH to 6, stirred for 30 min, then transferred into a reaction kettle and reacted at 160 °C for 24 h, and the target product is obtained by washing, drying at 60 °C for 12 h and grinding; The preparation process of BiOCl(010)-Ovs is as follows: BiOCl(010) powder is dispersed in deionized water, and irradiated with a UV high-pressure mercury lamp for 30 min.

5. The preparation method according to claim 3, characterized in that, The specific process of the step 2 is as follows: BiOCl(010)-Ovs material is added to deionized water and ultrasonically stirred for 30 min, then cobalt nitrate hexahydrate and ferric nitrate nonahydrate are added, NaOH solution is added to adjust the pH to 10.0, 70 °C oil bath heating and stirring for 1 h, then transferred into a reaction kettle and reacted at 160 °C for 12 h, and the target product is obtained by washing, drying at 80 °C for 12 h and grinding.

6. A photoanode, characterized by, The catalytic material prepared by the method of any one of claims 1 or 2, the preparation steps are as follows: the catalytic material is mixed with isopropanol and Nafion solution under ultrasonic, to obtain a catalyst solution, the catalyst solution is uniformly dropped and coated on a carbon cloth material, and heated and dried at 80 °C for 12 h to obtain a photoanode.

7. Use of a photoanode according to claim 6 for the degradation of perfluorinated polyfluorinated compounds, characterized in that, The photoanode is applied to a photoelectrocatalysis-PMS coupling system.

8. Use according to claim 7, characterized in that, The construction conditions of the photoelectrocatalysis-PMS coupling system include: using the photoanode as the anode, platinum sheet as the cathode, Na2SO4 solution as the electrolyte, applying a working voltage of 0-2 V, using a 300 W xenon lamp as the visible light source, and adding 0.5-2.5 mM PMS to the system.

9. Use according to claim 7, characterized in that, The perfluoro and polyfluorinated compounds are perfluorooctanoic acid and perfluorooctane sulfonic acid.

10. Use according to claim 7, characterized in that, The photoelectrocatalysis-PMS coupling system has a pH of 3-11 and a degradation time of 1-2 h.

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