Cobalt-doped zinc oxide nanocatalysts, their preparation methods and applications

Abstract

This invention discloses a cobalt-doped zinc oxide nanocatalyst, its preparation method, and its application. The preparation method of the cobalt-doped zinc oxide nanocatalyst includes the following steps: dissolving zinc salt and citric acid in deionized water, adding cobalt salt and mixing thoroughly, stirring at room temperature (15–25°C) to obtain a sol liquid, reacting the sol liquid at 70–80°C to obtain a wet gel, drying the wet gel at 160–180°C, grinding to obtain a precursor powder, calcining the precursor powder at 480–520°C for 5–5.5 h in air, washing, and drying to obtain the cobalt-doped zinc oxide nanocatalyst. This cobalt-doped zinc oxide nanocatalyst can efficiently activate PMS, achieving 100% aniline removal within 5 min, and exhibits strong anti-interference ability and stability, demonstrating stable degradation performance across different coexisting ions and a wide pH range.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a cobalt-doped zinc oxide nanocatalyst, its preparation method, and its application. Background Technology

[0002] With population growth, industrial development, and climate change, freshwater scarcity has become a global challenge, affecting approximately 4 billion people worldwide, and this problem is likely to worsen in the near future. Chemicals containing electron-donating groups (EDGs) such as -OH and -NH2 are widely used in modern industry due to their excellent chemical reactivity, biocompatibility, and functionalization capabilities, especially in industrial parks with intensive industrial activity. Consequently, industrial parks also generate large quantities of wastewater with high concentrations of electron-rich pollutants (e-RNPs) rich in electron-donating groups. Although this wastewater can be diluted to some extent by municipal pipe networks, the electron-rich pollutants are still difficult to remove by municipal wastewater treatment systems and cause significant damage to subsequent biological treatment structures.

[0003] Traditional pre-oxidation processes, primarily based on hydrolysis and acidification, can effectively reduce electron-donating reactive oxygen species (e-RNPs) in wastewater, improve its biodegradability, and decrease biotoxicity. However, due to their long hydraulic retention time and sensitivity to environmental conditions (such as temperature and pH), they are prone to producing foul odors and large amounts of sludge, making it difficult to meet increasingly stringent water quality discharge standards. Therefore, there is an urgent need to adopt advanced treatment processes to treat electron-rich pollutants containing electron-donating groups, in order to increase the supply of freshwater outside the hydrological cycle and alleviate the water crisis.

[0004] In recent years, potassium persulfate (PMS) advanced oxidation technology has gained attention due to its ability to generate strong oxidizing free radicals (such as sulfate and hydroxyl radicals) and selective non-free radicals (such as singlet oxygen). 1O2 is highly favored because it can rapidly oxidize recalcitrant organic pollutants, and the system exhibits high stability without generating secondary pollution. However, coexisting ions in complex water bodies can hinder the generation of non-selective free radicals or cause false attacks. Furthermore, single non-free radicals have insufficient oxidizing power and an extremely short lifetime (approximately 2 to 4 microseconds) in water, thus limiting the degradation of target pollutants. (Xu,Jiang,X.;Zhou,B.;Yang,W.;Chen,J.;Miao,C.;Guo,Z.;Li,H.;Hou,Y.;Xu,X.;Zhu,L.;et al. Precise coordination of high-loading Fe single atoms with sulfur boosts selective generation of...) (nonradicals.Proc.Natl.Acad.Sci.USA2024,121(4),e2309102121.) et al. significantly increased the yield of high-valence iron-oxygen species and singlet oxygen by precisely controlling the short-distance S coordination of Fe single atoms. However, it relies on single-atom catalysts to achieve two or more pathways, which is limited by the electron cycle of a single active metal center and the substrate electron transfer efficiency. The synergistic effect of multiple catalytic pathways is difficult to control, thus affecting the further improvement of catalytic activity. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a cobalt-doped zinc oxide nanocatalyst. This cobalt-doped zinc oxide nanocatalyst breaks the original charge symmetry of ZnO through Co doping, thereby constructing local dipoles in adjacent Zn and Co atom site regions, promoting PMS activation and improving the removal of pollutants.

[0006] Another objective of this invention is to provide a method for preparing cobalt-doped zinc oxide nanocatalysts.

[0007] Another object of the present invention is to provide an application of cobalt-doped zinc oxide nanocatalyst in the removal of pollutants.

[0008] The objective of this invention is achieved through the following technical solutions.

[0009] A method for preparing a cobalt-doped zinc oxide nanocatalyst includes the following steps:

[0010] Step 1: Dissolve zinc salt and citric acid in deionized water, add cobalt salt and mix well. Stir at room temperature (15-25°C) for 1-1.5 hours to obtain a sol liquid. React the sol liquid at 70-80°C for 3-4 hours to obtain a wet gel. Dry the wet gel at 160-180°C for 3-3.5 hours and grind it to obtain a precursor powder. The ratio of zinc in zinc salt to cobalt and citric acid in cobalt salt is 15:(0.75-1.05):45 by molar amount.

[0011] In step 1, the molar ratio of zinc in the zinc salt to the volume ratio of deionized water is 1:

[0012] (25-35), where the molar fractions of the substance are in mmol and the volume fractions are in mL.

[0013] In step 1, the zinc salt is zinc nitrate hexahydrate, and the cobalt salt is cobalt nitrate hexahydrate.

[0014] In step 1, the grinding time is 4 to 6 minutes.

[0015] Step 2: Calcine the precursor powder at 480–520°C for 5–5.5 h in an air atmosphere, wash and dry to obtain cobalt-doped zinc oxide nanocatalyst.

[0016] In step 2, the temperature is heated to 480-520°C at a rate of 4-6°C / min.

[0017] In step 2, the washing operation includes: centrifuging with water and ethanol at least three times each at a speed of 8000-10000 r / min, with each centrifugation lasting 3-5 min.

[0018] In step 2, the drying temperature is 60–80°C, and the drying time is 10–12 hours.

[0019] The cobalt-doped zinc oxide nanocatalyst obtained by the above preparation method.

[0020] The above-mentioned cobalt-doped zinc oxide nanocatalysts are used in the removal of pollutants.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The cobalt-doped zinc oxide nanocatalyst of the present invention can efficiently activate PMS by constructing local dipoles, achieving 100% aniline removal within 5 min, with a maximum reaction rate constant of 1.6351 min. -1 .

[0023] 2. The cobalt-doped zinc oxide nanocatalyst of the present invention has strong anti-interference ability and stable degradation performance in different coexisting ions and a wide pH range.

[0024] 3. The cobalt-doped zinc oxide nanocatalyst of the present invention exhibits excellent selectivity for electron-rich pollutants containing electron-donating groups, which can greatly improve the biodegradability of wastewater while reducing its biotoxicity.

[0025] 4. The cobalt-doped zinc oxide nanocatalyst of the present invention has high stability, good structural integrity and low metal ion leakage during the efficient activation of PMS.

[0026] 5. The cobalt-doped zinc oxide nanocatalyst of the present invention can achieve the following in the process of activating PMS to remove electron-rich pollutants: 1 O2 and Co IV =O Selective production of two species. Attached Figure Description

[0027] Figure 1 (a) TEM image, (b) high-resolution transmission electron microscopy (HRTEM) and (c) elemental mapping of the cobalt-doped zinc oxide nanocatalyst prepared in Example 3;

[0028] Figure 2 The images show X-ray diffraction patterns. (a) shows the zinc oxide catalyst prepared in Comparative Example 1 and the cobalt-doped zinc oxide nanocatalyst prepared in Example 3. (b) shows the Co-doped ZnO catalyst prepared in Comparative Example 2.

[0029] Figure 3 The removal efficiency diagrams are as follows: (a) shows PMS, the zinc oxide catalyst prepared in Comparative Example 1, and the cobalt-doped zinc oxide nanocatalyst prepared in Example 3; (b) shows the cobalt-doped zinc oxide nanocatalyst prepared in Examples 1-4.

[0030] Figure 4 The removal rate of aniline by the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 under different coexisting ions;

[0031] Figure 5 The removal rate and reaction rate constant of aniline by the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 at different pH conditions;

[0032] Figure 6 The removal rates of different pollutants by the cobalt-doped zinc oxide nanocatalyst prepared in Example 3;

[0033] Figure 7 The fluorescence spectra are obtained from three-dimensional excitation-emission matrix (3D-EEM). (a) shows the actual wastewater before the pollutant removal experiment, and (b) shows the actual wastewater after the pollutant removal experiment.

[0034] Figure 8 The Co-doped zinc oxide nanocatalyst prepared in Example 3 and the Co-doped ZnO catalyst prepared in Comparative Example 2 are examples of Co-doped zinc oxide nanocatalysts. 2+ Leakage

[0035] Figure 9 The removal efficiency of aniline by the cobalt-doped zinc oxide nanocatalyst prepared in Example 3, the Co-doped ZnO catalyst prepared in Comparative Example 2, and cobalt nitrate hexahydrate was compared.

[0036] Figure 10 (a) represents the activation of PMS by the catalyst group and the PMS group to produce 1 EPR spectrum of O2 Figure 10 (b) shows the PMSO consumption of the catalyst group and the PMS group at different times;

[0037] Figure 11 (a) is the ELF calculation plot of the zinc oxide catalyst prepared in Comparative Example 1. Figure 11 (b) is the ELF calculation diagram of the cobalt-doped zinc oxide nanocatalyst prepared in Example 3. Figure 11 (c) is a diagram illustrating the dipole effect. Detailed Implementation

[0038] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0039] The pharmaceutical products, molecular formulas, purities, and manufacturers of purchase involved in the following embodiments are shown in Table 1.

[0040] Table 1

[0041]

[0042] The instruments, models, and manufacturers involved in the following embodiments are shown in Table 2.

[0043] Table 2

[0044]

[0045]

[0046] Examples 1-4

[0047] A method for preparing a cobalt-doped zinc oxide nanocatalyst includes the following steps:

[0048] Step 1: Dissolve zinc salt and citric acid in deionized water, add cobalt salt and mix well. Stir with a magnetic stirrer at room temperature (15-25℃) for 1 hour to obtain a sol liquid. React the sol liquid in a 70℃ water bath for 4 hours (partial water evaporation) to obtain a wet gel. Place the wet gel in an electric thermostatic drying oven at 170℃ for 3 hours (evaporation of water). Grind for 5 minutes to obtain a precursor powder. The zinc salt is zinc nitrate hexahydrate, and the cobalt salt is cobalt nitrate hexahydrate. The ratio of zinc in the zinc salt to cobalt and citric acid in the cobalt salt is W, and the ratio of the amount of zinc in the zinc salt to the volume of deionized water is 1:25. The unit of amount of amount is mmol, and the unit of volume is mL.

[0049] Step 2: In an air atmosphere, the precursor powder is placed in a muffle furnace, heated to 500°C at a rate of 5°C / min, and calcined at 500°C for 5 hours. It is then washed three times each with water and ethanol at a speed of 8000 r / min, with each centrifugation lasting 3 minutes. After centrifugation, it is dried at 60°C for 10 hours to obtain cobalt-doped zinc oxide nanocatalyst.

[0050] The W values ​​of the cobalt-doped zinc oxide nanocatalysts prepared in Examples 1-4 are shown in Table 3.

[0051] Table 3

[0052]

[0053]

[0054] Comparative Example 1

[0055] A method for preparing a zinc oxide catalyst (No.: ZnO) is basically the same as that in Example 1, except that the sol liquid is different. In step 1 of this comparative example, zinc salt (zinc nitrate hexahydrate) and citric acid are dissolved in deionized water and stirred with a magnetic stirrer at room temperature of 15-25°C for 1 hour to obtain a sol liquid. The ratio of zinc to citric acid in the zinc salt is 15:45 by molar amount.

[0056] Comparative Example 2

[0057] A method for preparing Co-doped ZnO catalyst, see Example 1 of Chinese Invention Patent Publication No. CN 113976125 A.

[0058] The morphology, crystal structure, and elemental distribution of the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 were characterized using transmission electron microscopy (TEM) and aberration-corrected condenser electron microscopy (AC-TEM). The results are as follows: Figure 1 As shown, Figure 1(a) TEM image, (b) high-resolution transmission electron microscopy (HRTEM) image, and (c) elemental mapping image of the cobalt-doped zinc oxide nanocatalyst prepared in Example 3. Figure 1 As shown in (a) and (b), Co is distributed as single Co atoms in the cobalt-doped zinc oxide nanocatalyst prepared in Example 3. Figure 1 As can be seen from (c), Zn, Co and O are uniformly distributed in the cobalt-doped zinc oxide nanocatalyst prepared in Example 3.

[0059] Figure 2 The images show X-ray diffraction patterns: (a) the zinc oxide catalyst prepared in Comparative Example 1 and the cobalt-doped zinc oxide nanocatalyst prepared in Example 3; and (b) the Co-doped ZnO catalyst prepared in Comparative Example 2. Figure 2 As shown in (a), the diffraction peaks of the zinc oxide catalyst prepared in Comparative Example 1 and the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 can be well correlated with the standard card (JCPD) of zinc oxide. S 36-1451) correspond one-to-one. In the X-ray diffraction pattern of the cobalt-doped zinc oxide nanocatalyst prepared in Example 3, no characteristic peaks related to Co were found. This is mainly because Co exists in single-atom form and at a low content in the cobalt-doped zinc oxide nanocatalyst prepared in Example 3. Figure 2 As shown in (b), the Co-doped ZnO catalyst prepared in Comparative Example 2 simultaneously possesses the crystal structure of zinc oxide and cobalt oxide (JCPD with Co3O4). S The crystal structure (corresponding to the standard card 42-1467) shows that, at the same angle, the peak intensity of the characteristic peak of the Co-doped ZnO catalyst prepared in Comparative Example 2 is lower than that of the cobalt-doped zinc oxide nanocatalyst prepared in Example 3, indicating that its crystallinity is greatly reduced. This may be the reason why the Co-doped ZnO catalyst prepared in Comparative Example 2 has an unstable structure and extremely high metal ion leakage.

[0060] Example 5

[0061] Contaminant removal experiment: 10 mg of catalyst, 15 mg of PMS, and 50 mL of contaminant solution were placed in a 100 mL beaker to obtain the test solution. The test solution was stirred for 5 min at 25 °C. At minute T, 3 mL of the test solution was taken to measure its absorbance, determining the concentration (C) of the contaminant at minute T. T was 0 min, 0.5 min, 1 min, 2 min, 3 min, 4 min, and 5 min. The catalyst was one of the cobalt-doped zinc oxide nanocatalysts prepared in Examples 1-4 and the zinc oxide catalyst prepared in Comparative Example 1. The contaminant solution was a mixture of contaminant and water. The contaminant was aniline, with an initial concentration (C0) of 10 mg / L. The pH of the contaminant solution was 7.0. The test results are as follows: Figure 3 As shown;

[0062] Control Experiment: The control experiment is basically the same as the "Contaminant Removal Experiment," except for the test solution. In the control experiment, the test solution does not contain a catalyst. Specifically, the preparation method for the test solution in the control experiment is as follows: 15 mg of PMS and 50 mL of contaminant solution are placed in a 100 mL beaker to obtain the test solution. The test results are as follows: Figure 3 As shown in "PMS".

[0063] Depend on Figure 3 As shown in (a), in the control experiment, the ability of PMS (without catalyst) to remove aniline is very weak, and the ability of the zinc oxide catalyst prepared in Comparative Example 1 to remove aniline is also very weak. Figure 3 In (b), as the Co doping amount increases, the removal efficiency of aniline by the cobalt-doped zinc oxide nanocatalysts prepared in Examples 1-4 gradually increases. The cobalt-doped zinc oxide nanocatalysts prepared in Examples 3-4 have the best removal efficiency for aniline, with a removal rate of 100% within 5 minutes.

[0064] Example 6

[0065] To further investigate the stability and anti-interference ability of the cobalt-doped zinc oxide nanocatalyst prepared in Example 3, the following experimental groups were set up:

[0066] Control group: The cobalt-doped zinc oxide nanocatalyst prepared in Example 3 was used as a "catalyst" to perform the "pollutant removal experiment" in Example 5 above on the pollutant solution (aniline, pH 7). The removal rate was as follows: Figure 4 As shown in "control";

[0067] Coexisting ion group: Essentially the same as the control group, except for the test solution. 10 mg of catalyst, 15 mg of PMS, salt, and 50 mL of contaminant solution were placed in a 100 mL beaker to obtain the test solution. The salt was KCl (which releases K+ into the test solution). + As a coexisting ion), CaCl2 (Ca is released into the test solution). 2+ As a coexisting ion), NaCl (free Na in the test solution) + and Cl - (as coexisting ions), MgCl2 (which releases Mg in the test solution) 2+ As a coexisting ion, NH4Cl (NH4 is released into the test solution). + As a coexisting ion), NaF (free F in the test solution) - As a coexisting ion), NaNO3 (NO3 is released into the test solution). - As a coexisting ion), Na2SO4 (SO4 is released in the test solution).2- As a coexisting ion), NaH2PO4 (HPO4 is released into the test solution). - As a coexisting ion), Na2CO3 (CO3 is released into the test solution). 2- As a coexisting ion), NaHCO3 (HCO3 is released into the test solution). - As coexisting ions), humic acid (HA) and NaAC (which release AC in the test solution). - As one of the coexisting ions, the salt concentration in the test solution was 10 mmol / L, and the test results were as follows. Figure 4 As shown, by Figure 4 It can be seen that none of the coexisting ions have a significant effect on the removal rate of aniline.

[0068] The cobalt-doped zinc oxide nanocatalyst prepared in Example 3 was used as a "catalyst" to perform the "contaminant removal experiment" in Example 5 on contaminant solutions (the contaminant was aniline, with pH values ​​of 3, 5, 7, and 9). The pH was adjusted by using 0.1 mol / L hydrochloric acid or 0.1 mol / L sodium hydroxide aqueous solution. The removal rate and reaction rate constant of the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 are as follows: Figure 5 As shown, by Figure 5 It can be seen that, within the pH range of 3–11, the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 exhibits excellent removal rate of aniline and also has a high reaction rate constant, both within 0.8 min. -1 The highest value is 1.6351 min. -1 At pH 7, the reaction rate constant is 1.4785 min. -1 The zinc oxide catalyst prepared in Comparative Example 1 (with a reaction rate constant of 0.04346 min at pH 7) is shown. -1 34 times that of ) combined Figure 4 and Figure 5 It can be seen that the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 is minimally affected by common environmental matrices in real water bodies.

[0069] Example 7

[0070] This study investigated the selectivity of the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 for the degradation of common pollutants. Referring to the pollutant removal experiment using the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 of Example 5 as the "catalyst," the aniline in the pollutant solution was replaced with any one of the following pollutants: Rhodamine B (RhB), methylene blue (MB), aniline (AN), tetracycline (TC), doxycycline hydrochloride (DOXH), o-aminophenol (O-PA), carbamazepine (CBZ), acetaminophen (APAP), sulfachlorpyridazine (SCP), sulfamethoxazole (SMX), o-nitrophenol (O-NP), p-nitrophenol (P-NP), nitrobenzene (NB), and benzoic acid (BA). The initial concentration (CO) of the pollutant in the pollutant solution was 10 mg / L, and the pH of the pollutant solution was 7. The removal rates of each pollutant by the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 are as follows: Figure 6 As shown.

[0071] Depend on Figure 6 It was found that pollutants containing electron-donating groups (EDGs) such as hydroxyl, amino, methyl, halogen, or organosulfur groups could be removed more effectively by the cobalt-doped zinc oxide nanocatalyst prepared in Example 3, with removal rates exceeding 80.0% for RhB, MB, AN, TC, DOXH, O-PA, CBZ, and APAP. In contrast, the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 showed decreased removal rates for O-NP and P-NP, which simultaneously possess EDGs and electron-withdrawing groups (EWGs), and poor removal rates for pollutants containing carboxyl groups and -NO2, with NB and BA being difficult to remove, achieving removal rates of only 16.7% and 12.2%, respectively. These results indicate that the cobalt-doped zinc oxide nanocatalyst exhibits higher selectivity and reactivity for pollutants containing electron-donating groups.

[0072] Example 8

[0073] Referring to the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 of Example 5 as the "catalyst" for pollutant removal experiments, the pollutant solution was replaced with actual sewage (from the Jinan Sewage Treatment Plant of Nankai University) for qualitative analysis.

[0074] Three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy was performed on the actual wastewater before and after the above degradation. The results are as follows: Figure 7 As shown, by Figure 7 As shown in (a), a fluorescence peak was observed near the excitation wavelength / emission wavelength (Ex / Em) = 285 / 335 nm (e.g. Figure 7 (I) in (a) corresponds to tryptophan, and a fluorescence peak was observed near Ex / Em = 235 / 335 nm. Figure 7(II) in (a) corresponds to an aromatic protein, and a fluorescence peak was observed near Ex / Em = 340 / 425 nm. Figure 7 (III) in (a) corresponds to humic acid, and a fluorescence peak was observed near Ex / Em = 240 / 425 nm. Figure 7 (IV) in (a) corresponds to fulleric acid substances. Therefore, actual wastewater contains tryptophan, aromatic proteins, humic acid, and fulleric acid substances. Figure 7 As shown in (b), after degradation by the cobalt-doped zinc oxide nanocatalyst prepared in Example 3, the intensity of the fluorescence peaks in these EEMs was significantly reduced, especially the peaks related to aromatic proteins. This indicates that the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 can effectively reduce recalcitrant substances in actual wastewater.

[0075] Example 9

[0076] 10 mg of catalyst (the catalyst was either the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 or the Co-doped ZnO catalyst prepared in Comparative Example 2) and 50 mL of contaminant solution were placed in a 100 mL beaker and stirred for 30 min. After stirring, 15 mg of PMS was added to obtain the detection solution. The detection solution was stirred for 10 min at 25 °C to carry out degradation. The concentration of Co metal ions in the detection solution was measured at T1 min, which were 0 min, 5 min, and 10 min. The test results are as follows: Figure 8 As shown, by Figure 8 It can be seen that after 10 minutes of degradation with PMS, the concentration of Co metal ions in the detection solution containing the Co-doped ZnO catalyst prepared in Comparative Example 2 reached as high as 31.05 mg / L. This indicates that the Co-doped ZnO catalyst prepared in Comparative Example 2 has poor structural stability and generates a large amount of Co metal ion leakage during use, causing secondary pollution and making it difficult to directly apply to environmental water purification processes. In contrast, the Co-doped zinc oxide nanocatalyst prepared in Example 3 showed a low leakage of Co metal ion concentration of 0.5169 mg / L without the addition of PMS. The leakage is likely due to the high concentration of Co metal ions (Co...) after 10 minutes of degradation with PMS. 2+ This facilitates the transfer of 2 electrons to react with PMS to produce Co. IV =O, so that the concentration of Co metal ions in the detection solution is only 0.1273mg / L, which is far lower than the 1mg / L specified in the "Emission Standard of Pollutants for Copper, Nickel and Cobalt Industries" (GB25467-2010). This shows that the cobalt-doped zinc oxide nanocatalyst of the present invention has high structural stability and environmental friendliness.

[0077] Example 10

[0078] The cobalt-doped zinc oxide nanocatalyst prepared in Example 3 (dosage = 10 mg), the Co-doped ZnO catalyst prepared in Comparative Example 2 (dosage = 10 mg), and cobalt nitrate hexahydrate were used as "catalysts" in the pollutant removal experiment in Example 5. When cobalt nitrate hexahydrate was used as the "catalyst," its concentration in the test solution was set to 0.1273 mg / L and 31.05 mg / L, respectively (designed based on the Co metal ion leakage rate after 10 min of degradation). The test results are as follows: Figure 9 As shown, the test results of the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 are as follows: Figure 9 As shown in "Example 3 (10 mg)", the test results of the Co-doped ZnO catalyst prepared in Comparative Example 2 are as follows: Figure 9 As shown in "Comparative Example 2 (10 mg)", the test results for cobalt nitrate hexahydrate at a concentration of 0.1273 mg / L are as follows. Figure 9 The results for cobalt nitrate hexahydrate (0.1273 mg / L) at a concentration of 31.05 mg / L are shown in the figure. Figure 9 The figure shows "cobalt nitrate hexahydrate (31.05 mg / L)".

[0079] Depend on Figure 9 It can be seen that at 5 min, the removal rate of the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 was 100%, and the removal rate of the Co-doped ZnO catalyst prepared in Comparative Example 2 was 98%, both of which had very high removal rates. The removal rate of using 31.05 mg / L cobalt nitrate hexahydrate was almost the same as that of the Co-doped ZnO catalyst prepared in Comparative Example 2. This indicates that the Co-doped ZnO catalyst prepared in Comparative Example 2, as a Fenton-like catalyst, mainly relies on the leaked Co metal ions to activate PMS and degrade aniline. When the concentration of cobalt nitrate hexahydrate was 0.1273 mg / L, the removal rate of aniline within 5 minutes was only 4.7%. This indicates that the leakage of Co metal ions in the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 had little impact on the removal rate. The cobalt-doped zinc oxide nanocatalyst prepared in Example 3 itself had a high removal rate of aniline. Under the same catalyst mass, the Co ion doping amount in the Co-doped ZnO catalyst prepared in Comparative Example 2 was much higher than that in the cobalt-doped zinc oxide nanocatalyst prepared in Example 3. Therefore, this invention achieved a significant improvement in catalyst performance by constructing local dipoles with extremely low Co ion doping amount.

[0080] The cobalt content in the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 and the Co-doped ZnO catalyst prepared in Comparative Example 2 was determined using inductively coupled plasma mass spectrometry (ICP-MS). The cobalt content in the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 was 3.06 wt%, and the cobalt content in the Co-doped ZnO catalyst prepared in Comparative Example 2 was 25.08 wt%. Therefore, under the same cobalt mass conditions as 10 mg of the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 (containing approximately 0.3 mg of Co), 1.2 mg of the Co-doped ZnO catalyst prepared in Comparative Example 2 (containing 0.3 mg of Co) was used as the "catalyst" for the contaminant removal experiment in Example 5. The results are as follows. Figure 9 As shown in “Comparative Example 2 (1.2 mg)”, the Co-doped ZnO catalyst prepared in Comparative Example 2 had a removal rate of only 25% for the same mass of Co element.

[0081] Example 11

[0082] capture 1 The O2 experiment was set up with the following experimental groups:

[0083] Catalyst assembly: 10 mg catalyst, 15 mg PMS, trapping agent, and 50 mL contaminant solution were placed in a 100 mL beaker to obtain a mixed solution. The mixed solution was stirred at 25 °C for 5 min, and the results were analyzed using a Bruker A200 electron paramagnetic resonance (EPR) spectrometer. 1 O2, wherein the catalyst is one of the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 and the zinc oxide catalyst prepared in Comparative Example 1, and the scavenging agent is 2,2,6,6-tetramethylpiperidine, the concentration of 2,2,6,6-tetramethylpiperidine in the mixed solution is 30 μmol / L, and the test results are as follows. Figure 10 As shown in (a);

[0084] PMS group: Related to the above "capture" 1 The catalyst group used in the "O2 experiment" was basically the same, the difference being the mixed solution. PMS, the trapping agent, and 50 mL of pollutant solution were placed in a 100 mL beaker to obtain the mixed solution. The concentration of PMS in the mixed solution was 0.3 mg / mL. The test results are as follows: Figure 10 As shown in (a).

[0085] High-priced cobalt oxide (Co) IV =O) The following experimental groups were set up:

[0086] Catalyst group: "Co" IV =O experiment" catalyst group and "capture" 1The catalyst group for the "O2 experiment" was basically the same, the difference being the trapping agent and stirring time. The trapping agent was methyl phenyl sulfoxide (PMSO), and the initial concentration (C0) of PMSO in the mixed solution was 100 μmol / L. After stirring for 10 min, the concentration of PMSO (C0) was measured at T2 min using a Thermo Fisher Dionex UltiMate U3000 high-performance liquid chromatograph. t T2min were 0 min, 1 min, 2 min, 3 min, 5 min, 7 min, and 10 min, respectively, to obtain the PMSO consumption (ΔPMSO = C). t -C0), due to PMSO and Co IV =O reacts, therefore the amount of PMSO consumed can be used to determine Co. IV The generation of =O, and the test results are as follows: Figure 10 As shown in (b);

[0087] PMS group: Similar to the above "Co" IV The catalyst group for the "=O experiment" was basically the same, except that the mixed solution did not contain a catalyst. Specifically, PMS, the trapping agent, and 50 mL of pollutant solution were placed in a 100 mL beaker to obtain the mixed solution. The concentration of PMS in the mixed solution was 0.3 mg / mL, and the initial concentration (CO) of PMSO in the mixed solution was 100 μmol / L. The test results are as follows: Figure 10 As shown in (b).

[0088] Depend on Figure 10 From (a), we can see that in "capture" 1 In the "O2 experiment," no information was detected in the PMS group. 1 Characteristic signals of O2 were detected in the mixed solution of zinc oxide catalyst prepared in Comparative Example 1 within the catalyst group. 1 The characteristic signal of O2 was detected in the mixed solution of cobalt-doped zinc oxide nanocatalyst prepared in Example 3, which showed a stronger signal. 1 The characteristic signal of O2 indicates that the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 can more efficiently activate PMS generation. 1 O2. (From) Figure 10 As shown in (b), the mixed solution of cobalt-doped zinc oxide nanocatalyst prepared in Example 3 showed a higher PMSO consumption, which indicates that the cobalt-doped zinc oxide nanocatalyst can more efficiently activate PMS production. 1 O2 and Co IV =O.

[0089] Example 12

[0090] Figure 11 (a) is the calculated electronic localization function (ELF) plot of the zinc oxide catalyst prepared in Comparative Example 1. Figure 11 (b) is the ELF calculation plot of the cobalt-doped zinc oxide nanocatalyst prepared in Example 3. Figure 11 As shown in (a) and (b), atomic charge analysis confirmed that the Baader charge at the Co atom sites in the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 was +0.805e, and the Baader charge at the adjacent Zn atom sites was +1.056e. In contrast, the Baader charge at the Zn atom sites in the zinc oxide catalyst prepared in Comparative Example 1 was +0.906e. This indicates that compared to the zinc oxide catalyst prepared in Comparative Example 1, the charge density distribution of the cobalt-doped zinc oxide nanocatalyst prepared in Example 3 is asymmetrical, with the charge density distribution at the Co atom sites being higher than that at the adjacent Zn atom sites. This is because the electronegativity between metal atoms Zn and Co and O atoms differs, resulting in bond dipole moments forming on the Zn-O and Co-O bonds. The vector superposition of these bond dipole moments will form a local dipole in the adjacent annular region of the central metal site, producing a dipole effect (e.g., ...). Figure 11 As shown in (c), this leads to a difference in charge density between Co and Zn atomic sites. The dipole effect effectively modulates the electron density of Co and the surrounding Zn atoms, disrupting the original charge balance and forming positive (Zn atomic sites) and negative (Co atomic sites) polarized charge centers. The Zn atomic site polarized charge centers promote the self-decomposition of the two PMS molecules, resulting in highly selective polarization. 1 O2. The polarized charge centers at the Co atomic sites promote 2-electron transfer to produce Co. IV =O, therefore, the regulation of PMS activation by cobalt-doped zinc oxide nanocatalysts depends on 1 O2 and Co IV =O synergistic effect, exhibiting high catalytic activity for electron-rich pollutants.

[0091] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. Use of a cobalt-doped zinc oxide nanocatalyst in the removal of pollutants, characterized in that, Cobalt-doped zinc oxide nanocatalyst activates pms to generate 1 O2 and high-valent oxygenated cobalt to degrade a pollutant, the pollutant being one of rhodamine B, methylene blue, aniline, tetracycline, doxycycline hydrochloride, o-aminophenol, carbamazepine, and acetaminophen, the method of making the cobalt-doped zinc oxide nanocatalyst comprising the steps of: Step 1, dissolving the zinc salt and citric acid in deionized water, adding the cobalt salt and mixing uniformly, stirring at room temperature for 1-1.5 h at 15-25℃, obtaining a sol liquid, reacting the sol liquid at 70-80℃ for 3-4 h, obtaining a wet gel, drying the wet gel at 160-180℃ for 3-3.5 h, grinding, obtaining a precursor powder, wherein the ratio of zinc in the zinc salt, cobalt in the cobalt salt and citric acid is 15: (0.75-1.05): 45 in terms of the amount of substance; Step 2, calcining the precursor powder at 480-520℃ for 5-5.5 h under an air atmosphere, washing, drying, obtaining a cobalt-doped zinc oxide nanocatalyst.

2. Use according to claim 1, characterized in that, The ratio of the amount of substance of zinc in the zinc salt to the volume fraction of deionized water is 1: (25-35), the unit of the amount of substance is mmol, and the unit of the volume fraction is mL.

3. Use according to claim 1, characterized in that, The zinc salt is zinc nitrate hexahydrate, and the cobalt salt is cobalt nitrate hexahydrate.

4. The use according to claim 1, characterized in that, The grinding time is 4-6 min.

5. The use according to claim 1, characterized in that, Heating at a rate of 4-6℃ / min to 480-520℃.

6. The use according to claim 1, characterized in that, The washing operation comprises: sequentially centrifuging with water and ethanol at a rotation speed of 8000-10000 r / min for at least three times, and the centrifuging time of each time is 3-5 min.

7. The use according to claim 1, characterized in that, The drying temperature is 60-80℃.

8. The use according to claim 1, characterized in that, The drying time is 10-12 h.

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