A-site defect-precipitated perovskite catalyst, preparation method and application

Abstract

The present invention discloses a perovskite catalyst with A-site defect precipitation, a preparation method and an application. The chemical formula of the catalyst is Pr x Ba x Sc y Co 1‑y O 3‑δ , where 0.3 < x < 0.5, 0.1 < y < 1, δ is the oxygen vacancy content, and 0 ≤ δ ≤ 1. The preparation method includes: dissolving praseodymium nitrate hexahydrate, barium nitrate, scandium nitrate hexahydrate and cobalt nitrate hexahydrate in deionized water, adding citric acid monohydrate and ethylenediaminetetraacetic acid for reaction, adjusting the pH to 3.00 - 9.00 with an ammonia aqueous solution, heating and stirring to form a gel, drying, grinding and calcining the obtained gel to obtain an A-site defect perovskite material; grinding the A-site defect perovskite material and then performing secondary calcination under the condition of introducing H2 to obtain the perovskite catalyst with A-site defect precipitation. The perovskite catalyst of the present invention has extremely high reaction activity and can be used to activate persulfate to degrade organic pollutants in wastewater.

Description

Technical Field

[0001] The present invention relates to a perovskite catalyst with A-site defect precipitation, a preparation method and an application, belonging to the fields of water treatment and environmental catalysis. Background Art

[0002] Since the 20th century, with the rapid progress of global technology, the pollutants discharged by human society into the environment have become complex and difficult to treat. In most cases, the damage caused by these pollutants to the environment exceeds the self-regulating ability of the ecosystem. Wastewater containing organic compounds discharged from households and industries may have harmful effects on human health and the environment. In recent years, this concern, combined with limited clean water resources, has promoted the development of treatment technologies for removing organic pollutants from wastewater.

[0003] Advanced oxidation processes (SR-AOPs) based on sulfate (SO4 ·- ) have attracted much attention. As a further exploration and development of the Fenton process, SO4 ·- exhibits a higher redox potential and a longer lifespan than the hydroxyl radical ·OH. In addition, in SR-AOPs systems, other reactive oxygen species (ROS) can also be generated, such as singlet oxygen ( 1 O2). These ROS have strong oxidation capabilities and can convert organic wastewater pollutants into environmentally safe chemicals in a relatively short time, and even mineralize them into CO2 and H2O, etc. Peroxymonosulfate (PMS) and peroxydisulfate (PDS) can both act as effective SR-AOP oxidants. PDS has high stability and a symmetric structure, with an O-O bond distance of while PMS has an asymmetric structure, with an O-O bond distance of When the pH is less than 6 or the pH is 12, PMS is stable. When the pH is 9, PMS has the worst stability, and half of the HSO5 - decomposes into SO5 2- , and its asymmetric structure also makes its O-O bond easier to break, making it easier to activate than PDS.

[0004] Perovskite oxides, as compounds with a general ABO 3-δTypical mixed metal oxides of the structure exhibit good catalytic activity due to their unique adjustable structure and properties. In perovskite oxides, the A-site cations are alkali metals or rare earth metals, and the B-site cations are usually 3d transition metals. Since the 6-fold coordinated B-site cations are surrounded by 12-fold coordinated oxygen, the substitution or defect generation of cations at the A or B site can change the structure of perovskite and regulate its physical and chemical properties. ABO3-type perovskite oxides with multiple active metal sites and stable texture structures have attracted much attention in the field of heterogeneous catalysis, including the catalysis of peroxymonosulfate (PMS) for wastewater treatment. In advanced oxidation technologies, ABO3-type perovskite oxides exhibit excellent catalytic ability due to the generation of oxygen vacancies. However, metal ions are dangerous to human health and the environment, and the related metal ion leaching problem limits the application of traditional metal catalysts. It has been reported that the perovskite Co / PMS process is very effective for the degradation of organic compounds, but the use of Co ions has the problem of metal ion leakage causing environmental pollution. Introducing the perovskite system can well solve this problem. However, to our knowledge, there are few reports on activating PMS by regulating the cation defects of perovskite. At the same time, the active sites of metal cations and surface oxygen species for PMS activation are still unclear. Summary of the Invention

[0005] The purpose of the present invention is to provide a perovskite catalyst with A-site defect precipitation, which has excellent catalytic activity, stable structure, and can effectively catalyze the degradation of organic pollutants, aiming at the deficiencies of the prior art. Another purpose of the present invention is to provide a preparation method of the perovskite catalyst with A-site defect precipitation. The final purpose of the present invention is to provide the application of the perovskite catalyst with A-site defect precipitation in treating organic wastewater.

[0006] To achieve the above purposes, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a perovskite catalyst with A-site defect precipitation, and the chemical formula of the catalyst is Pr x Ba x Sc y Co 1-y O 3-δ , where 0.3 < x < 0.5, 0.1 < y < 1, δ is the oxygen vacancy content, and 0 ≤ δ ≤ 1.

[0008] Further, x is 0.45, y is 0.8; or x is 0.42, y is 0.8; or x is 0.4, y is 0.8.

[0009] In the second aspect, the present invention provides a preparation method of the perovskite catalyst with A-site defect precipitation, including:

[0010] According to the chemical formula Pr x Bax Sc y Co 1-y O 3-δ Weigh praseodymium nitrate hexahydrate, barium nitrate, scandium nitrate hexahydrate and cobalt nitrate hexahydrate, dissolve them in deionized water, add citric acid monohydrate and ethylenediaminetetraacetic acid for complexation reaction, then adjust the pH to 3.00 - 9.00 with ammonia water solution, heat and stir until the water is evaporated to form a gel, and obtain the A-site defective perovskite material by drying, grinding and calcining the obtained gel; grind the obtained A-site defective perovskite material and perform secondary calcination under the condition of introducing H₂ to obtain the A-site defective precipitated perovskite catalyst.

[0011] Furthermore, in the preparation method of the A-site defective precipitated perovskite catalyst, the molar ratio of citric acid monohydrate to the total molar amount of the four raw materials of praseodymium nitrate hexahydrate, barium nitrate, scandium nitrate hexahydrate and cobalt nitrate hexahydrate is 1.2 - 2:1.

[0012] Furthermore, in the preparation method of the A-site defective precipitated perovskite catalyst, the molar ratio of ethylenediaminetetraacetic acid to the total molar amount of the four raw materials of praseodymium nitrate hexahydrate, barium nitrate, scandium nitrate hexahydrate and cobalt nitrate hexahydrate is 0.8 - 1.5:1.

[0013] Furthermore, in the preparation method of the A-site defective precipitated perovskite catalyst, the temperature of heating and stirring is 70 - 110 °C.

[0014] Furthermore, in the step of drying, grinding and calcining the obtained gel in the preparation method of the A-site defective precipitated perovskite catalyst, dry in an air atmosphere at 160 - 400 °C for 4 - 12 hours, and during calcination, increase the temperature to 500 - 1000 °C at a heating rate of 1 - 5 °C / min and roast for 4 - 10 hours.

[0015] Furthermore, in the step of performing secondary calcination under the condition of introducing H₂ in the preparation method of the A-site defective precipitated perovskite catalyst, increase the temperature to 500 - 1000 °C at a heating rate of 1 - 5 °C / min and calcine for 1 - 4 hours, and the flow rate of H₂ introduced during the calcination process is 10 - 50 ppm.

[0016] In the third aspect, the present invention provides the application of the A-site defective precipitated perovskite catalyst described in the first aspect in treating organic wastewater, including: using the A-site defective precipitated perovskite catalyst to activate persulfate and degrade organic pollutants in the wastewater.

[0017] Furthermore, in the application of the A-site defect-precipitated perovskite catalyst in treating organic wastewater, the concentration of pollutants in the organic wastewater is 20 - 50 mg / L, the catalyst dosage is 0.1 - 0.6 g / L, the concentration of persulfate in the wastewater is 0.2 - 10 g / L, the pH of the reaction system is 3.00 - 9.00, the reaction time is 15 - 60 min, and the reaction temperature is 5 - 50 °C.

[0018] Compared with the prior art, the beneficial technical effects achieved by the present invention are as follows:

[0019] (1) The perovskite catalyst of the present invention is obtained by A-site defect precipitation, which can not only provide new active sites but also greatly increase the oxygen vacancies, endowing it with extremely high reaction activity.

[0020] (2) The perovskite catalyst of the present invention has good stability and can be reused multiple times with less reduction in the degradation effect.

[0021] (3) For the perovskite catalyst of the present invention, the generation of reactive oxygen is not affected by pH under different environmental parameters and water compositions, and it has strong anti-interference ability.

[0022] (4) The perovskite catalyst of the present invention shows strong catalytic degradation ability for different antibiotics.

[0023] (5) The perovskite catalyst of the present invention has certain magnetism and can be recycled. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the XRD pattern of the Co@D-PBSC catalyst prepared in Example 1 of the present invention.

[0025] Figure 2 It is the SEM image of the Co@D-PBSC catalyst prepared in Example 1 of the present invention.

[0026] Figure 3 It is the oxygen vacancy distribution map of the Co@D-PBSC catalyst prepared in Example 1 of the present invention.

[0027] Figure 4 It is the XPS spectra of the Co@D-PBSC catalyst prepared in Example 1 of the present invention before and after the reaction.

[0028] Figure 5 It is the comparison and influence diagram of the degradation rate of levofloxacin by the Co@D-PBSC catalyst prepared in Example 1 of the present invention and the Pr 0.5 Ba 0.5 Sc 0.8 Co 0.2 catalyst in Comparative Example 1.

[0029] Figure 6 Figure showing the influence of the Co@D-PBSC catalyst prepared in Example 1 of the present invention on the degradation rates of different antibiotics;

[0030] Figure 7 Figure showing the influence of the Co@D-PBSC catalyst prepared in Example 1 of the present invention on the degradation rate of levofloxacin under the condition of changing the pH value of the reaction system;

[0031] Figure 8 Figure showing the influence of the change in the dosage of the Co@D-PBSC catalyst prepared in Example 1 of the present invention on the degradation rate of levofloxacin;

[0032] Figure 9 Figure showing the influence of the Co@D-PBSC catalyst prepared in Example 1 of the present invention on the degradation rate of levofloxacin under the condition of different initial concentrations of levofloxacin in water.

[0033] Figure 10 Figure showing the degradation of levofloxacin in water by the Co@D-PBSC catalyst prepared in Example 1 of the present invention after being recycled and used five times. Detailed implementation manners

[0034] The present invention will be further described below in conjunction with specific embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention.

[0035] Example 1

[0036] A perovskite catalyst with A-site defect precipitation, its chemical formula is: Pr 0.45 Ba 0.45 Sc 0.8 Co 0.2 O 3-δ (Co@D-PBSC), the preparation method includes the following steps:

[0037] (1) Dissolve 0.0045 mol of praseodymium nitrate hexahydrate, 0.0045 mol of barium nitrate, 0.008 mol of scandium nitrate hexahydrate and 0.002 mol of cobalt nitrate hexahydrate in 180 mL of deionized water. Add 0.019 mol of ethylenediaminetetraacetic acid (EDTA) and 0.038 mol of citric acid monohydrate as complexing agents to the solution to form a transparent nitrate solution, and then add NH3·H2O dropwise to the obtained solution to adjust the pH to 7. The solution is then heated under vigorous stirring at 80 °C until the water is evaporated to form a gel;

[0038] (2) Dry the concentrated gel in an oven at 160 °C in air for 5 hours to obtain perovskite precursor powder; after grinding the obtained perovskite precursor powder, put it into a muffle furnace and heat it to 850 °C at a heating rate of 2 °C / min for calcination for 10 hours. After cooling to room temperature, obtain an A-site defective perovskite material in the form of black powder; after grinding the obtained black powder A-site defective perovskite material, put it into a tube furnace and heat it to 800 °C at a heating rate of 2 °C / min for calcination for 2 hours, and introduce H2 at a flow rate of 20 ppm during the calcination process to obtain an A-site defective precipitated perovskite catalyst.

[0039] Example 2

[0040] An A-site defective precipitated perovskite catalyst, whose chemical formula is: Pr 0.42 Ba 0.42 Sc 0.8 Co 0.2 O 3-δ (Co@D-PBSC), and the preparation method includes the following steps:

[0041] (1) Dissolve 0.0042 mol of praseodymium nitrate hexahydrate, 0.0042 mol of barium nitrate, 0.008 mol of scandium nitrate hexahydrate and 0.002 mol of cobalt nitrate hexahydrate in 180 mL of deionized water. Add 0.0184 mol of ethylenediaminetetraacetic acid (EDTA) and 0.0368 mol of citric acid monohydrate as complexing agents to the solution to form a transparent nitrate solution, and then add NH3·H2O dropwise to the obtained solution to adjust the pH to 7. The solution is then heated with vigorous stirring at 80 °C until the water is evaporated to form a gel;

[0042] (2) Dry the concentrated gel in an oven at 160 °C in air for 5 hours to obtain perovskite precursor powder; after grinding the obtained perovskite precursor powder, put it into a muffle furnace and heat it to 850 °C at a heating rate of 2 °C / min for calcination for 10 hours. After cooling to room temperature, obtain an A-site defective perovskite material in the form of black powder; after grinding the obtained black powder A-site defective perovskite material, put it into a tube furnace and heat it to 800 °C at a heating rate of 2 °C / min for calcination for 2 hours, and introduce H2 at a flow rate of 20 ppm during the calcination process to obtain an A-site defective precipitated perovskite catalyst.

[0043] Example 3

[0044] An A-site defective precipitated perovskite catalyst, whose chemical formula is: Pr 0.4 Ba 0.4 Sc 0.8 Co 0.2 O 3-δ (Co@D-PBSC), and the preparation method includes the following steps:

[0045] (1) Dissolve 0.004 mol of praseodymium nitrate hexahydrate, 0.004 mol of barium nitrate, 0.008 mol of scandium nitrate hexahydrate and 0.002 mol of cobalt nitrate hexahydrate in 180 mL of deionized water. Add 0.018 mol of ethylenediaminetetraacetic acid (EDTA) and 0.036 mol of citric acid monohydrate as complexing agents to the solution to form a transparent nitrate solution. Then, add NH₃·H₂O dropwise to the obtained solution to adjust the pH to 7. The solution is then heated under vigorous stirring at 80 °C until the water is completely evaporated to form a gel;

[0046] (2) Dry the concentrated gel in an oven at 160 °C in air for 5 hours to obtain perovskite precursor powder; after grinding the obtained perovskite precursor powder, put it into a muffle furnace and heat it to 850 °C at a heating rate of 2 °C / min for calcination for 10 hours. After cooling to room temperature, a black powder of A-site defective perovskite material is obtained; after grinding the obtained black powder of A-site defective perovskite material, put it into a tube furnace and heat it to 800 °C at a heating rate of 2 °C / min for calcination for 2 hours. During the calcination process, H₂ is introduced at a flow rate of 20 ppm to obtain an A-site defective precipitated perovskite catalyst.

[0047] Comparative Example 1

[0048] A perovskite catalyst with the chemical formula: Pr 0.5 Ba 0.5 Sc 0.8 Co 0.2 O 3-δ , and the preparation method includes the following steps:

[0049] (1) Dissolve 0.005 mol of praseodymium nitrate hexahydrate, 0.005 mol of barium nitrate, 0.008 mol of scandium nitrate hexahydrate and 0.002 mol of cobalt nitrate hexahydrate in 180 mL of deionized water. Add 0.02 mol of ethylenediaminetetraacetic acid (EDTA) and 0.04 mol of citric acid monohydrate as complexing agents to the solution to form a transparent nitrate solution. Then, add NH₃·H₂O dropwise to the obtained solution to adjust the pH to 7. The solution is then heated under vigorous stirring at 80 °C until the water is completely evaporated to form a gel;

[0050] (2) Dry the concentrated gel in an oven at 160 °C in air for 5 hours to obtain perovskite precursor powder; after grinding the obtained perovskite precursor powder, put it into a muffle furnace and heat it to 850 °C at a heating rate of 2 °C / min for calcination for 10 hours. After cooling to room temperature, a black powder of perovskite catalyst is obtained.

[0051] Figure 1XRD pattern of the Co@D-PBSC catalyst prepared in Example 1 of the present invention. It can be seen that the Co@D-PBSC catalyst prepared in Example 1 shows a perovskite structure without a second phase. The PBSC sample conforms to the perovskite standard, indicating good crystallinity therein. Doping of Sc and Co within a certain range does not destroy the PBSC structure, thus contributing to the synthesis of a stable PBSC perovskite catalyst. Annealing of PBSC in a hydrogen atmosphere results in the appearance of a cobalt metal peak at around 42° of the diffraction angle, which indicates that metal ions Co shift in the perovskite lattice and precipitate onto the surface. Therefore, metal ions transfer from the bulk lattice to the surface without destroying the layered perovskite structure. This spontaneous dissolution of perovskite occurs in a reducing atmosphere. In-situ growth of Co nanoparticles on the surface leads to uniform dispersion on the perovskite surface without any obvious agglomeration.

[0052] Figure 2 SEM image of the Co@D-PBSC catalyst prepared in Example 1 of the present invention. From the figure, it can be observed that the morphology of the material is spherical nanoparticles, uniformly covering the surface of the parent perovskite. Smaller particle sizes will expose more active sites, and these nanoparticles show an aggregated state, consistent with the SEM observation results. The above characterization results indicate that the prepared Co@D-PBSC material has a high degree of crystallinity, and all metal elements are successfully doped into the perovskite structure, which is consistent with the XRD results.

[0053] Figure 3 Oxygen vacancy distribution map of the Co@D-PBSC catalyst prepared in Example 1 of the present invention. The peak signal of the OVs content of the catalyst detected by electron paramagnetic resonance (EPR), Co@D-PBSC has a strong OVs signal peak intensity, indicating that an appropriate number of defects at the A site enhance the ratio of oxygen vacancies on the catalyst surface. Oxygen vacancies promote the attachment of adsorbed oxygen molecules, which are then converted to O2 2- / O - by electron charge transfer. A large number of oxygen vacancies confirm the existence of abundant OVs on the surface of the Co@DPBSC catalyst, confirming that the catalytic performance of the Co@D-PBSC catalyst for PMS activation has been widely enhanced.

[0054] Figure 4 XPS spectra of the Co@D-PBSC catalyst before and after the reaction in Example 1 of the present invention. The average valence of elements before and after the reaction is further verified by X-ray photoelectron spectroscopy (XPS), corresponding to Co 3+ and Co 2+ peaks are deconvoluted to determine their peak areas, thereby determining their ratios and average valence numbers. Surface Co 0 has higher catalytic activity and oxidizability than bulk Co cations, which confirms that Co is the main active site, surface Redox couples may be involved in the activation of PMS. The present invention also studied the valence states of surface O. Four deconvoluted peaks at approximately 528.2, 529.5, 531.05, and 532.35 eV were attributed to lattice oxygen (O 2- ), surface dissociative oxygen (O2 2- / O - ), less electron-rich ·OH, and adsorbed H2O. Molecular oxygen tends to adsorb on Co sites adjacent to oxygen vacancies. Then electrons are withdrawn from the bonded Co sites to the adsorbed oxygen sites, resulting in the elongation and dissociation of the O-O bond. This leads to the formation of O2 2- / O - species, which are widely considered to be closely related to oxygen vacancies.

[0055] Example 4

[0056] Degradation experiments were carried out in a beaker. The catalysts prepared in Example 1 and Comparative Example 1 were used to catalytically activate potassium monopersulfate (PMS), and the results were evaluated by degrading the pollutant levofloxacin (OFX):

[0057] (1) 0.1 g / L of the catalyst of Example 1 was added to 150 mL of a buffer solution containing 20 mg / L of the pollutant at an initial concentration. The initial pH value was adjusted to 7 using NaOH. After stirring for 1 hour, 0.3 g / L of potassium monopersulfate was added. 2.2 mL of water samples were taken every 5 minutes, filtered through a 0.45 μm membrane, and 1 mL of methanol quencher was added. The reaction conditions were: the stirring speed was 350 revolutions per second, and the test temperature was 25 °C. And the pollutant concentration was measured in a UV-visible spectrophotometer (λ = 274 nm). All experiments were repeated at least three times. At the same time, in order to investigate the recyclability of Co@D-PBSC, the reaction catalyst was filtered and washed with deionized water and ethanol, and the washed catalyst was dried and the degradation experiment was carried out again;

[0058] (2) The catalyst of Comparative Example 1 was added for the degradation experiment, and the other steps and conditions were the same as those in (1).

[0059] Figure 5 For the Co@D-PBSC catalyst prepared in Example 1 of the present invention and the Pr 0.5 Ba 0.5 Sc 0.8 Co 0.2 O 3-δ catalyst prepared in Comparative Example 1, the comparative influence diagram of the degradation rate of levofloxacin (OFX) can be seen from the figure. It can be seen that Co@D-PBSC of Example 1 has extremely high catalytic degradation effect on levofloxacin compared with the catalyst of Comparative Example 1, which proves that the catalyst of the present invention has extremely excellent degradation effect.

[0060] Example 5

[0061] The degradation experiment was carried out in a beaker. The catalyst prepared in Example 1 was used to catalytically activate potassium monopersulfate (PMS), and the result was evaluated by degrading the pollutant tetracycline hydrochloride (TC). The steps were as follows: 0.1 g / L of the catalyst in Example 1 was added to 150 mL of buffer solution containing the pollutant with an initial concentration of 20 mg / L. The initial pH value was adjusted to 7 using NaOH. After stirring for 1 hour, 0.3 / L of potassium monopersulfate was added. 2.2 mL of water sample was taken every 5 minutes, filtered through a 0.45 μm membrane, and then 1 mL of methanol quencher was added. The reaction conditions were: the stirring speed was 350 revolutions per second, and the test temperature was 25 °C. And the pollutant concentration was measured in a UV-visible spectrophotometer (λ = 274 nm). The initial pH value was adjusted to 7 using NaOH. All experiments were repeated at least three times. At the same time, to investigate the recyclability of Co@D-PBSC, the reaction catalyst was filtered and washed with deionized water and ethanol, and the washed catalyst was dried and the degradation experiment was carried out again.

[0062] Example 6

[0063] The degradation experiment was carried out in a beaker. The catalyst prepared in Example 1 was used to catalytically activate potassium monopersulfate (PMS), and the result was evaluated by degrading the pollutant rhodamine B (RhB). The steps were the same as those in Example 5.

[0064] Figure 6 The influence diagram of the degradation rate of levofloxacin, tetracycline hydrochloride, and rhodamine B by the Co@D-PBSC catalyst prepared in Example 1 of the present invention. It can be seen from the figure that Co@D-PBSC has extremely high catalytic degradation effects on levofloxacin, tetracycline hydrochloride, and rhodamine B, proving the universality and excellent degradation effect of the catalyst of the present invention.

[0065] Example 7

[0066] On the basis of Example 4, the pH value of the reaction system was changed to 3.2, 5.1, 7.0, and 8.7 respectively, and other conditions remained unchanged. The degradation effect of levofloxacin was tested, and the test results are as Figure 7 shown. It can be seen from the figure that the Co@D-PBSC catalyst prepared in the present invention has good degradation effects on levofloxacin under different pH conditions, and the degradation rate is the highest at pH = 7.0. Its degradation rate of levofloxacin can reach 84% within 1 minute.

[0067] Example 8

[0068] On the basis of Example 4, the input amount of the Co@D-PBSC catalyst was changed, which were: without catalyst, catalyst addition amounts of 0.05 g / L, 0.1 g / L, and 0.6 g / L. With other conditions unchanged, the degradation effect of levofloxacin was tested, and the test results are as Figure 8 shown. It can be seen from the figure that when no catalyst is added, the reaction hardly degrades pollutants, and a catalyst needs to be added to generate active substances for degrading pollutants. As the catalyst content increases, the catalytic degradation rate of levofloxacin shows an increasing trend, and the best reaction effect is achieved when the catalyst addition amount is 0.6 g / L.

[0069] Example 9

[0070] On the basis of Example 4, the initial concentration of levofloxacin in the sewage was changed, which were 20 mg / L, 30 mg / L, 40 mg / L, and 50 mg / L. With other conditions unchanged, the degradation effect of levofloxacin was tested, and the test results are as Figure 9 shown. From Figure 9 it can be seen that the best pollutant degradation effect is achieved when the levofloxacin concentration in the sewage is 20 mg / L.

[0071] Figure 10 This is the degradation diagram of the Co@D-PBSC catalyst prepared in Example 1 of the present invention for catalytic degradation of levofloxacin in water after being recycled five times. It can be seen from the figure that when the Co@D-PBSC prepared in Example 1 is used for the fifth time to catalytically degrade levofloxacin in water, the degradation effect is still very good and the reduction is less, proving that the Co@D-PBS catalyst of the present invention has good stability and good recyclability and can be reused many times.

[0072] The present invention has been disclosed in the above preferred embodiments, but it is not intended to limit the present invention. Any technical solutions obtained by adopting equivalent substitution or equivalent transformation shall fall within the protection scope of the present invention.

Claims

1. Application of an A-site defective perovskite catalyst in treating organic wastewater, characterized in that, The chemical formula of the catalyst is Pr x Ba x Sc y Co 1-y O 3-δ , where 0.3 < x < 0.5, 0.1 < y < 1, δ is the oxygen vacancy content, 0 ≤ δ ≤ 1; the A-site defective perovskite catalyst is used to activate persulfate to degrade organic pollutants in wastewater; the organic pollutants are levofloxacin, tetracycline hydrochloride or rhodamine B.

2. The application according to claim 1, characterized in that, x is 0.45, y is 0.8; or x is 0.42, y is 0.8; or x is 0.4, y is 0.

8.

3. The application according to claim 1, wherein The preparation method of the A-site defect-precipitated perovskite catalyst includes: According to the chemical formula Pr x Ba x Sc y Co 1-y O 3-δ Weigh praseodymium nitrate hexahydrate, barium nitrate, scandium nitrate hexahydrate and cobalt nitrate hexahydrate, dissolve them in deionized water, add citric acid monohydrate and ethylenediaminetetraacetic acid for complexation reaction, then adjust the pH to 3.00 - 9.00 with ammonia water solution, heat and stir until the water is evaporated to form a gel. The obtained gel is dried, ground and calcined to obtain an A-site defective perovskite material; the obtained A-site defective perovskite material is ground and then calcined twice under the condition of introducing H2 to obtain an A-site defective precipitated perovskite catalyst.

4. The application according to claim 3, wherein The molar ratio of citric acid monohydrate to the total molar amount of four raw materials of praseodymium nitrate hexahydrate, barium nitrate, scandium nitrate hexahydrate, and cobalt nitrate hexahydrate is 1.2 - 2:

1.

5. The application according to claim 3, characterized in that, The molar ratio of ethylenediaminetetraacetic acid to the total molar amount of four raw materials of praseodymium nitrate hexahydrate, barium nitrate, scandium nitrate hexahydrate, and cobalt nitrate hexahydrate is 0.8 - 1.5:

1.

6. The application according to claim 3, characterized in that The temperature of heating and stirring is 70 - 110 °C.

7. The application according to claim 3, characterized in that, In the steps of drying, grinding, and calcining the obtained gel, it is dried in an air atmosphere at 160 - 400 °C for 4 - 12 hours, and when calcining, it is heated to 500 - 1000 °C at a heating rate of 1 - 5 °C / min and calcined for 4 - 10 hours.

8. The application according to claim 3, wherein In the step of secondary calcination carried out under the condition of introducing H2, it is heated to 500 - 1000 °C at a heating rate of 1 - 5 °C / min and calcined for 1 - 4 hours, and the flow rate of H2 introduced during the calcination process is 10 - 50 ppm.

9. The application according to claim 1, characterized in that The concentration of pollutants in the organic wastewater is 20 - 50 mg / L, the catalyst dosage is 0.1 - 0.6 g / L, the concentration of persulfate in the wastewater is 0.2 - 10 g / L, the pH of the reaction system is 3.00 - 9.00, the reaction time is 15 - 60 min, and the reaction temperature is 5 - 50 °C.

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