P-Co3O4 catalyst capable of improving conversion efficiency of persulfate to free radicals as well as preparation method and application of P-Co3O4 catalyst

Abstract

According to the P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate to free radicals, the appearance of the P-Co3O4 catalyst is of a particle stacked spongy structure, crystal lattice fringes belonging to the 311 surface of cobaltosic oxide only exist in the microstructure of the P-Co3O4 catalyst, unique reaction raw materials and auxiliaries are adopted, the fine process is accurately controlled, and the yield of the catalyst is greatly improved. A common transition metal oxide Co3O4 is used as a template, a reducing P element is introduced into the structure of the template, the P-Co3O4 catalyst with a special morphology structure and more active sites is prepared, the P-Co3O4 catalyst has a unique action mechanism on persulfate, the conversion efficiency of the persulfate to free radicals in a reaction system can be remarkably improved, and the conversion efficiency of the persulfate to free radicals is remarkably improved. Further, effective degradation of organic matters in the wastewater is realized.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of cobalt trioxide catalysts for organic wastewater treatment, in particular to a P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate to free radicals, and a preparation method and application thereof. Background Art

[0002] With the continuous improvement of the level of industrialization in modern society, the effective treatment of various organic wastewaters, especially those containing refractory organic pollutants, is facing increasing pressure. The advanced oxidation technology based on persulfate has good application prospects because it can achieve rapid treatment of organic pollutants, has little secondary pollution, and has good economic efficiency.

[0003] Among the various common methods for activating persulfate, heterogeneous transition metal activation has received extensive attention. In order to further improve the catalytic performance of heterogeneous transition metal catalysts, researchers have used methods such as multi-metal synergy, size regulation, and active ingredient loading to prepare heterogeneous catalysts of various forms, revealing the activation mechanism of these catalysts for persulfate, which has promoted the improvement of the catalytic performance of heterogeneous transition metal catalysts to a certain extent.

[0004] However, there are still some technical difficulties and research defects in the current research. The most representative one is that when the catalysts in the existing technology catalyze the degradation of organic wastewater, the conversion efficiency of the oxidant persulfate into free radicals is low, which significantly limits the improvement of the oxidation efficiency in the heterogeneous transition metal catalytic activation persulfate system.

[0005] Therefore, how to structurally transform the existing heterogeneous transition metal catalysts so that they can improve the conversion efficiency of persulfate to free radicals and achieve full utilization of materials is of great significance for reducing the treatment cost of organic wastewater and enhancing the sewage treatment effect. Summary of the invention

[0006] The technical purpose of the present invention is to adopt unique reaction raw materials and auxiliary agents, as well as fine process precision control, take the common transition metal oxide Co3O4 as a template, introduce the reducing P element into its structure, and prepare a P-Co3O4 catalyst with a special morphological structure and more active sites. The P-Co3O4 catalyst has a unique mechanism of action on persulfate, can significantly improve the conversion efficiency of persulfate to free radicals in the reaction system, and thus realize the effective degradation of organic matter in wastewater.

[0007] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate into free radicals, wherein the P-Co3O4 catalyst has an appearance of a sponge-like structure of accumulated particles, and only lattice fringes belonging to the 311 face of cobalt tetroxide exist in its microscopic crystal structure.

[0008] A method for preparing a P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate to free radicals comprises the following steps: Step 1: Follow Co 2+ 、CO3 2- The molar ratio of the cobalt and P elements is 17:5:(0.1-5), soluble cobalt salt, soluble carbonate and alkali metal acid phosphate are respectively added to deionized water, and ultrasonic vibration treatment is performed to fully mix them to obtain a mixed raw material solution with a pH value of 11-13, which is set aside; Step 2: add an alkali source and ethylene glycol to the mixed raw material solution prepared in step 1, stir the mixture thoroughly with magnetic stirring to obtain a reaction raw material solution with a pH value of 9.5 to 10.5, and set aside; Step 3: Transfer the reaction raw material liquid obtained in step 2 to a reaction kettle and heat at 100-160 o C for 9-15 h to obtain the reaction product for later use; Step 4: centrifuge the reaction product obtained in step 3, wash the obtained solid with ethanol and deionized water for multiple times, and then transfer it to a vacuum freeze dryer for drying for 10 to 20 hours to obtain a product precursor for standby use; Step 5: Place the product precursor obtained in step 4 in a calcining furnace and calcine at 300-450° C. for 1-2 h to obtain a finished P-Co3O4 catalyst.

[0009] Furthermore, in step 1, the soluble cobalt salt is at least one of CoCl2 and Co(NO3)2·6H2O, and the soluble carbonate is Na2CO3 or K2CO3.

[0010] Furthermore, in step 1, the alkali metal acid phosphate is at least one of NaH2PO4·2H2O, K2HPO4·3H2O and KH2PO4.

[0011] Furthermore, in step 1, the ultrasonic oscillation treatment time is 5 to 15 minutes.

[0012] Further, in step 2, the alkali source is any one of urea, NaOH or ammonia water, and the amount of ethylene glycol added is 2+The molar amount is 1 / 50, the magnetic stirring time is 20-40 min, and the temperature is 20-40°C.

[0013] Furthermore, in step five, the heating rate of the calcining furnace is 2-4 °C / min.

[0014] The invention discloses an application of a P-Co3O4 catalyst which can improve the conversion efficiency of persulfate to free radicals in catalyzing persulfate to treat wastewater with organic pollutants.

[0015] The invention discloses an application method of a P-Co3O4 catalyst which can improve the conversion efficiency of persulfate into free radicals. The P-Co3O4 catalyst and the oxidant persulfate are added to organic pollutant wastewater with a pH value of 7 to 9 according to the addition amount of 0.03 to 0.06 g / L of P-Co3O4 catalyst and 0.2 to 0.5 g / L of persulfate, and a degradation reaction is carried out at 25 to 30°C.

[0016] Furthermore, the persulfate is peroxymonosulfate.

[0017] Beneficial effects of the present invention: 1. A method for preparing a P-Co3O4 catalyst that can improve the conversion efficiency of persulfate to free radicals of the present invention, by introducing a reducing P element into a typical transition metal oxide Co3O4, a P-Co3O4 catalyst with a special morphological structure and a large number of active sites is prepared. The P-Co3O4 catalyst has unique physical and chemical properties and a large number of new reactive active sites, which can effectively reduce the energy barrier for the conversion of persulfate to free radicals, thereby significantly improving the conversion efficiency of persulfate to free radicals, providing a material basis for exploring the efficient generation mechanism of free radicals in the persulfate catalytic activation system, and also achieving effective degradation of organic matter in wastewater.

[0018] 2. The P-Co3O4 catalyst prepared by the preparation process of the present invention can be used to catalyze persulfate to treat refractory organic wastewater, and especially exhibits a good catalytic effect when used to catalyze peroxymonosulfate. The amount of catalyst and oxidant used during use is small; the catalytic degradation reaction conditions are mild, the equipment is simple, and the investment is small; the participation of the P element promotes the efficient generation of free radicals and improves the utilization rate of persulfate; the reaction has strong adaptability to the solution pH and a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a SEM and TEM comparison diagram of the P-Co3O4 catalyst prepared in Example 1 and the Co3O4 catalyst prepared in Comparative Example 1; Among them, a is the SEM image of the Co3O4 catalyst, b is the SEM image of the P-Co3O4 catalyst, c is the TEM image of the Co3O4 catalyst, and d is the TEM image of the P-Co3O4 catalyst; Figure 2 is an XRD comparison diagram of the P-Co3O4 catalysts prepared in Example 1, Example 2 and Example 3 and the Co3O4 catalyst prepared in Comparative Example 1; Figure 3 FTIR comparison chart of the P-Co3O4 catalysts prepared in Example 1, Example 2 and Example 3 and the Co3O4 catalyst prepared in Comparative Example 1; Figure 4 It is a H2-TPR comparison chart of the P-Co3O4 catalysts prepared in Example 1, Example 2 and Example 3 and the Co3O4 catalyst prepared in Comparative Example 1; Figure 5 It is a comparison chart of the XPS full spectra of the P-Co3O4 catalysts prepared in Examples 1, 2 and 3 and the Co3O4 catalyst prepared in Comparative Example 1; Figure 6 It is the activation PMS mechanism diagram of the P-Co3O4 catalyst prepared by the present invention; Figure 7 It is a comparison diagram of the effects of activating PMS to degrade pollutants by the P-Co3O4 catalysts prepared in Examples 1, 2 and 3 and the Co3O4 catalyst prepared in Comparative Example 1; Figure 8 It is an EPR comparison spectrum of the free radical capture experiment of the PMS system catalytically activated by the P-Co3O4 catalyst prepared in Example 1, Example 2 and Example 3 and the Co3O4 catalyst prepared in Comparative Example 1; Fig. 9 The P-Co3O4 catalysts prepared in Examples 1, 2 and 3 and the Co3O4 catalyst prepared in Comparative Example 1 were activated by SO4 in the PMS system. •- (a) and comparison of the production dynamic analysis of •OH (b); Fig.10 Decomposition kinetics of P-Co3O4 catalysts prepared in Example 1, Example 2 and Example 3 and Co3O4 catalyst prepared in Comparative Example 1 during activation of PMS (a), PMS to SO4 •- (b) and computational analysis comparison of the conversion efficiency of •OH (c). DETAILED DESCRIPTION

[0020] In order to better understand the present invention, the contents of the present invention are further illustrated in combination with some examples below. However, the present invention is not limited to the following examples. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0021] The present invention provides a P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate into free radicals, a preparation method and an application thereof. The invention aims to prepare the P-Co3O4 catalyst by using the common transition metal oxide Co3O4 as a template and introducing a reducing P element, and to regulate the conversion efficiency of persulfate into free radicals in the reaction system by utilizing the unique action mechanism of the new P species on persulfate.

[0022] Embodiment 1: The preparation method of a P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate to free radicals in this embodiment specifically comprises the following steps: (1) Dissolve 1 g Co(NO3)2·6H2O, 0.1 g Na2CO3, and 0.01 g NaH2PO4·2H2O in 10 mL deionized water and treat with ultrasonic vibration for 10 min to mix thoroughly. Then, add 15 mL NaOH (0.1 M) and 20 mL ethylene glycol and stir magnetically for 30 min.

[0023] (2) The obtained mixed solution was transferred to a 50 mL reactor and heated to 140 °C for hydrothermal reaction for 12 h. The collected product was washed repeatedly with ethanol and deionized water for 3 times and then dried in a vacuum freeze dryer overnight. Finally, the product was heated to 350 °C at a heating rate of 3 °C / min and calcined in air for 1.2 h to obtain the finished P1-Co3O4 catalyst.

[0024] Embodiment 2: The preparation method of a P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate to free radicals in this embodiment specifically comprises the following steps: (1) Dissolve 0.45 g CoCl2, 0.1 g Na2CO3, and 0.05 g K2HPO4·3H2O in 10 mL deionized water and treat with ultrasonic vibration for 15 min to mix thoroughly. Then, add 15 mL ammonia (0.1 M) and 20 mL ethylene glycol and stir magnetically for 30 min.

[0025] (2) The obtained mixed solution was transferred to a 50 mL reactor and heated to 100 °C for hydrothermal reaction for 15 h. The collected product was washed repeatedly with ethanol and deionized water for 3 times and then dried in a vacuum freeze dryer for 20 h. Finally, the product was heated to 450 °C at a heating rate of 4 °C / min and calcined in air for 1 h to obtain the finished P2-Co3O4 catalyst.

[0026] Embodiment 3: The preparation method of a P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate to free radicals in this embodiment specifically comprises the following steps: (1) Dissolve 1 g Co(NO3)2·6H2O, 0.1 g Na2CO3, and 0.1 g KH2PO4 in 10 mL deionized water and treat with ultrasonic vibration for 15 min to mix thoroughly. Then, add 0.3 g urea and 20 mL ethylene glycol and stir magnetically for 30 min.

[0027] (2) The obtained mixed solution was transferred to a 50 mL reactor and heated to 160 °C for hydrothermal reaction for 9 h. The collected product was washed repeatedly with ethanol and deionized water for 3 times and then dried in a vacuum freeze dryer for 10 h. Finally, the product was heated to 300 °C at a heating rate of 2 °C / min and calcined in air for 2 h to obtain the finished P3-Co3O4 catalyst.

[0028] Embodiment 4: The preparation method of a P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate to free radicals in this embodiment specifically comprises the following steps: (1) Dissolve 0.45 g CoCl2, 0.1 g Na2CO3, and 0.15 g KH2PO4 in 10 mL deionized water. Then, add 15 mL NaOH and 20 mL ethylene glycol and stir magnetically for 30 min.

[0029] (2) The obtained mixed solution was transferred to a 50 mL reactor and heated to 160 °C for hydrothermal reaction for 9 h. The collected product was washed repeatedly with ethanol and deionized water for 3 times and then dried in a vacuum freeze dryer for 10 h. Finally, the product was heated to 300 °C at a heating rate of 2 °C / min and calcined in air for 2 h to obtain the finished P4-Co3O4 catalyst.

[0030] Comparative Example 1: The preparation method of a Co3O4 catalyst in this comparative example specifically comprises the following steps: (1) Dissolve 1 g of Co(NO3)2·6H2O in 10 mL of deionized water. Then, add 0.3 g of urea and 20 mL of ethylene glycol and stir magnetically for 30 min.

[0031] (2) The obtained mixed solution was transferred to a 50 mL reactor and heated to 140 °C for hydrothermal reaction for 12 h. The collected product was washed repeatedly with ethanol and deionized water for three times and then dried in a vacuum freeze dryer overnight. Finally, the product was calcined in air at 350 °C for 1.2 h at a heating rate of 2 °C / min to obtain the finished Co3O4 catalyst.

[0032] Test determination 1. Product morphology and structural performance The finished product P1-Co3O4 catalyst prepared in Example 1 of the present invention and the Co3O4 catalyst prepared in Comparative Example 1 were subjected to SEM analysis and TEM analysis, respectively. The results are shown in the attached figure. Figure 1 As shown, Figure 1 a is the SEM image of the Co3O4 catalyst, b is the SEM image of the P1-Co3O4 catalyst, c is the TEM image of the Co3O4 catalyst, and d is the TEM image of the P1-Co3O4 catalyst.

[0033] Depend on Figure 1 The SEM analysis in the experiment showed that the prepared Co3O4 was in the form of nanoparticles, while a sponge-like structure of particle accumulation was observed in the P1-Co3O4 catalyst. Figure 1 TEM analysis in the results showed that the microstructure of the Co3O4 catalyst contained lattice fringes belonging to the Co3O4 (111), (220) and (311) planes, while the P1-Co3O4 catalyst only contained lattice fringes belonging to the Co3O4 (311) plane. This indicates that the doping of P significantly changed the surface and microscopic morphology of the catalyst.

[0034] The finished product P1-Co3O4 catalyst prepared in Example 1 of the present invention, the finished product P2-Co3O4 catalyst prepared in Example 2, the finished product P3-Co3O4 catalyst prepared in Example 3, and the Co3O4 catalyst prepared in Comparative Example 1 were subjected to XRD analysis, FTIR analysis, H2-TPR and XPS analysis, and the results are shown in the attached figures. Figure 2 To Attachment Figure 5 shown.

[0035] Depend on Figure 2 The XRD analysis in shows that the introduction of P element does not cause significant changes in the basic crystal structure of Co3O4.

[0036] Depend on Figure 3FTIR analysis shows that with the increase of P doping amount, the number of PO bonds in the finished catalyst gradually increases.

[0037] Depend on Figure 4 The H2-TPR analysis shows that the addition of P has a significant effect on the reducing ability of Co species in the finished catalyst.

[0038] Depend on Figure 5 From the XPS full spectrum analysis, it can be seen that the finished catalysts prepared in Examples 1 to 3 contain elements such as Co, P, and O, which further confirms the successful introduction of P.

[0039] In the drawings of the specification Figure 6 The activation mechanism of P-Co3O4 on PMS is demonstrated, indicating the influence mechanism of P doping on the formation of free radicals.

[0040] 2. Catalytic degradation performance test The finished P1-Co3O4 catalyst prepared in Example 1 of the present invention, the finished P2-Co3O4 catalyst prepared in Example 2, the finished P3-Co3O4 catalyst prepared in Example 3 and the Co3O4 catalyst prepared in Comparative Example 1 were used to carry out corresponding comparative tests on the degradation of organic pollutants by activated persulfate.

[0041] The oxidant used in the test is persulfate, the catalyst is Co3O4 prepared in Comparative Example 1 and P-Co3O4 catalysts with different P doping amounts prepared in Examples 1, 2 and 3, and the target pollutant is 4-NBA solution.

[0042] The specific test steps are as follows: 0.005 g of catalyst and 0.04 g of PMS were added to a solution containing 100 mL of 4-NBA (10 ppm), and the mixture was placed in a magnetic constant temperature water bath at 30°C for reaction. The initial pH of the reaction was 7. The degradation effects of different catalysts are shown in the attached figure. Figure 7 shown.

[0043] Depend on Figure 7 It can be seen that under the reaction conditions, the degradation efficiency of PMS activated by P-Co3O4 catalyst with an ideal P doping amount for 4-NBA reached 100% within 20 min, while the degradation efficiency of PMS activated by Co3O4 for 4-NBA was 52.2%. This shows that P doping can improve the activation efficiency of Co3O4 for PMS.

[0044] 3. Free radical generation test Use EPR to explore the main oxygen species in each reaction system, such as Figure 8As shown, free radicals were found in the Co3O4 catalytic activation PMS system prepared in Comparative Example 1 and the P-Co3O4 catalytic activation PMS systems with different P doping amounts prepared in Examples 1, 2, and 3, and as the P doping amount increased, the total amount of free radicals generated in the same time increased, indicating that the addition of P promoted the generation of free radicals.

[0045] 4. Quantitative analysis test of free radical production The finished product P1-Co3O4 catalyst prepared in Example 1 of the present invention, the finished product P2-Co3O4 catalyst prepared in Example 2, the finished product P3-Co3O4 catalyst prepared in Example 3 and the Co3O4 catalyst prepared in Comparative Example 1 were respectively used to perform catalytic activation of PMS, and the SO4 •- The test results are shown in the attached Fig. 9 shown.

[0046] Depend on Fig. 9 It can be seen that SO4 •- The concentrations of 11.26 μM, 120.01 μM, 176.45 μM and 217.71 μM respectively; the production of •OH was 2.45 μM, 46.94 μM, 70.78 μM and 79.69 μM respectively. The results show that with the increase of P doping amount, the activity of the catalyst is greatly improved, and the system produces more free radicals.

[0047] 5. Measure the consumption of PMS in each reaction system and the conversion efficiency of PMS to free radicals like Fig.10 As shown in the figure, in the Co3O4 / PMS, P1-Co3O4 / PMS, P2-Co3O4 / PMS and P3-Co3O4 / PMS systems, the PMS consumption rates are 39.2%, 69.8%, 91.4% and 100%, respectively. In addition, after calculation, the stoichiometric efficiency (PMS) of •OH in the Co3O4 / PMS, P1-Co3O4 / PMS, P2-Co3O4 / PMS and P3-Co3O4 / PMS systems is •OH ) are 0.005, 0.052, 0.059, 0.061, respectively, and the corresponding SO4 •- The stoichiometric efficiencies are 0.022, 0.132, 0.148, and 0.167, respectively, indicating that P doping significantly increases the effective consumption of PMS by the catalyst, allowing more PMS to react with Co 2+ The reaction produces OH and SO4 •- .

[0048] 6. Study the effect of persulfate activated by the P3-Co3O4 catalyst prepared in Example 3 on the treatment of 4-NBA at different dosages The specific steps are exactly the same as the above catalytic degradation performance test, except that the catalyst dosage is changed to 0.002 g, 0.005 g, and 0.01 g. After the reaction, samples are taken for analysis, and the results are shown in Table 1 below.

[0049] Table 1 Catalyst dosage (g) 0.002 0.005 0.01 4-NBA (%) 90.1 100 100 It can be seen from Table 1 that when the dosage of P3-Co3O4 catalyst is 0.002g, 0.005g and 0.01g respectively, the degradation efficiency of 4-NBA in the reaction system reaches 90.1%, 100% and 100% respectively, which indicates that P3-Co3O4 has a high activation efficiency for PMS.

[0050] 7. Study the effect of persulfate on the treatment of 4-NBA by the P3-Co3O4 catalyst prepared in Example 3 at different PMS dosages Except for the different PMS dosage, the process flow and reaction conditions used are exactly the same as the above catalytic degradation performance test. The PMS dosage was changed to 0.01 g, 0.02 g, 0.04 g, and 0.06 g. After the reaction, samples were taken for analysis, and the results are shown in Table 2 below.

[0051] Table 2 PMS dosage (mM) 0.01 0.02 0.04 0.06 4-NBA (%) 41.2 63.2 100 100 It can be seen from Table 2 that when the PMS dosage is 0.01 mM, 0.02 mM, 0.04 mM, and 0.06 mM, the degradation efficiency of 4-NBA in the reaction system reaches 41.2%, 63.2%, 100%, and 100%, respectively. This shows that the P3-Co3O4 / PMS system has a high utilization rate of PMS.

[0052] 8. Study the effect of persulfate on the treatment of 4-NBA by the P3-Co3O4 catalyst prepared in Example 3 at different temperatures Except for the reaction temperature, the process flow and reaction conditions used are exactly the same as those of the above catalytic degradation performance test. The reaction temperature was changed to 20 ℃, 30 ℃, and 40 ℃ respectively. After the reaction, samples were taken for analysis, and the results are shown in Table 3 below.

[0053] Table 3 Reaction temperature (℃) 20 30 40 4-NBA (%) 83 100 100 It can be seen from Table 3 that when the reaction temperature is set to 20°C, 30°C, and 40°C, respectively, the degradation efficiency of 4-NBA in the P3-Co3O4 / PMS reaction system reaches 83%, 100%, and 100%, respectively.

[0054] 9. Study the effect of persulfate on the treatment of 4-NBA by the P3-Co3O4 catalyst prepared in Example 3 at different pH values Except for the different pH, the process flow and reaction conditions used are exactly the same as those in the above catalytic degradation performance test. The pH of the reaction system was changed to 4, 6, 7, 8, and 10. After the reaction, samples were taken for analysis, and the results are shown in Table 4 below.

[0055] Table 4 pH 4 6 7 8 10 4-NBA (%) 65.6 83.9 100 100 88.8 It can be seen from Table 4 that when the pH is set to 4, 6, 7, 8, and 10, the degradation efficiency of 4-NBA in the reaction system reaches 65.6%, 83.9%, 100%, 100%, and 100%, respectively. This shows that the P3-Co3O4 / PMS system has strong adaptability to pH.

[0056] The above shows and describes the main features, methods of use, basic principles and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements according to actual conditions, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate to free radicals, characterized in that: The P-Co3O4 catalyst has an appearance of a sponge-like structure of accumulated particles, and its microscopic crystal structure contains only lattice fringes belonging to the 311 face of cobalt tetroxide.

2. The method for preparing a P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate to free radicals according to claim 1, characterized in that: The following steps are involved: Step 1: Follow Co 2+ 、CO3 2- The molar ratio of the cobalt and P elements is 17:5:(0.1-5), soluble cobalt salt, soluble carbonate and alkali metal acid phosphate are respectively added to deionized water, and ultrasonic vibration treatment is performed to fully mix them to obtain a mixed raw material solution with a pH value of 11-13, which is set aside; Step 2: add an alkali source and ethylene glycol to the mixed raw material solution prepared in step 1, stir the mixture thoroughly with magnetic stirring to obtain a reaction raw material solution with a pH value of 9.5 to 10.5, and set aside; Step 3: Transfer the reaction raw material liquid obtained in step 2 to a reaction kettle and heat at 100-160 o C for 9-15 h to obtain the reaction product for later use; Step 4: centrifuge the reaction product obtained in step 3, wash the obtained solid with ethanol and deionized water for multiple times, and then transfer it to a vacuum freeze dryer for drying for 10 to 20 hours to obtain a product precursor for standby use; Step 5: Place the product precursor obtained in step 4 in a calcining furnace and calcine at 300-450° C. for 1-2 h to obtain a finished P-Co3O4 catalyst.

3. The method for preparing a P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate to free radicals according to claim 2, characterized in that: In step 1, the soluble cobalt salt is at least one of CoCl2 and Co(NO3)2·6H2O, and the soluble carbonate is Na2CO3 or K2CO3.

4. The method for preparing a P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate to free radicals according to claim 2, characterized in that: In step 1, the alkali metal acid phosphate is at least one of NaH2PO4·2H2O, K2HPO4·3H2O and KH2PO4.

5. The method for preparing a P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate to free radicals according to claim 2, characterized in that: In step 1, the ultrasonic oscillation treatment time is 5 to 15 minutes.

6. The method for preparing a P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate to free radicals according to claim 2, characterized in that: In step 2, the alkali source is any one of urea, NaOH or ammonia water, and the amount of ethylene glycol added is 2+ The molar amount is 1 / 50, the magnetic stirring time is 20-40 min, and the temperature is 20-40°C.

7. The method for preparing a P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate to free radicals according to claim 2, characterized in that: In step five, the heating rate of the calcining furnace is 2-4°C / min.

8. Use of the P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate to free radicals as claimed in claim 1 in catalyzing persulfate to treat organic pollutant wastewater.

9. The method for applying the P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate to free radicals according to claim 8, characterized in that: According to the addition amount of P-Co3O4 catalyst 0.03~0.06 g / L and persulfate 0.2~0.5 g / L, P-Co3O4 catalyst and oxidant persulfate were added to the organic pollutant wastewater with a pH value of 7~9, and the degradation reaction was carried out at 25~30℃.

10. The method for applying the P-Co3O4 catalyst capable of improving the conversion efficiency of persulfate to free radicals according to claim 9, characterized in that: The persulfate is peroxymonosulfate.

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