Method for removing pollutants in peroxymonosulfate system reinforced by CuO / ZnO photocatalyst rich in double-charge oxygen vacancies

Abstract

The invention belongs to the technical field of industrial water treatment, and relates to a double-charge oxygen vacancy-rich CuO / ZnO photocatalyst reinforced peroxymonosulfate system pollutant removal method, which comprises the following steps: preparing a ZIF-8 precursor, preparing a double-charge oxygen vacancy-rich copper oxide / zinc oxide composite catalyst, dispersing the composite catalyst in a pollutant solution, and carrying out ultrasonic treatment to obtain the double-charge oxygen vacancy-rich CuO / ZnO photocatalyst reinforced peroxymonosulfate system pollutant removal method. Stirring in a dark state until adsorption and desorption are balanced, adding peroxymonosulfate into the solution, performing illumination to realize accurate generation of singlet oxygen and high-valence copper oxygen active species, taking a pollutant solution every 5 minutes, detecting the concentration of the pollutant solution and the content change of total organic carbon until the concentration of the pollutant is not obviously reduced any more, and preparing a metal organic framework precursor by accurately designing the metal organic framework precursor. The synthesis of the metal oxide catalyst derived from the metal organic framework rich in double-charge oxygen vacancies is realized, the activation of PMS is promoted, singlet oxygen and high-valence metal oxygen species are generated, and the singlet oxygen and the high-valence metal oxygen species synergistically remove refractory pollutants in water through hydroxylation and oxidation reactions of the pollutants respectively.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial water treatment and relates to a method for removing pollutants from a peroxymonosulfate system by strengthening a CuO / ZnO photocatalyst rich in doubly charged oxygen vacancies. Background Art

[0002] Phenol-containing industrial wastewater tailwater is rich in various difficult-to-degrade pollutants, and direct discharge will seriously threaten the safety of aquatic ecosystems. Due to its advantages such as wide pH adaptability, strong oxidizing active species, and long-lasting reaction capacity, photo-Fenton technology has become a research hotspot in the field of difficult-to-degrade pollutant treatment in recent years. This system activates peroxymonosulfate (PMS) through photocatalysis, and can simultaneously produce multiple types of active species such as sulfate radicals, hydroxyl radicals, superoxide radicals, singlet oxygen, and high-valent metal oxygen species, achieving efficient degradation and deep mineralization of pollutants. How to precisely control the catalyst structure to generate target active species and optimize pollutant removal efficiency has become a key scientific issue in this field.

[0003] Singlet oxygen ( 1 As an important reactive oxygen species, reactive oxygen species (ROS) have applications in water treatment due to their selective degradation of electron-rich substrates and promotion of pollutant hydroxylation reactions. However, their limited redox potential (0.81 V relative to the normal hydrogen electrode (NHE)) hinders the further removal of hydroxylation intermediates. High-valent metal oxide (HVMO) species, due to their strong redox potential (>1.95 V relative to NHE), offer a potential for further removal of hydroxylation intermediates, but their simultaneous generation in a photocatalyst-activated PMS system remains challenging.

[0004] PMS can transfer electrons to oxygen vacancies (V o ), increase V o The electron-deficient ability of oxygen vacancies can enhance the electron transfer process of PMS. o 0 ), single charge (V o + ) and doubly charged oxygen vacancies (V o 2+ Among them, neutral oxygen vacancies are the easiest to obtain due to their lowest formation energy and the most thermodynamic stability; doubly charged oxygen vacancies have lower electron cloud density and higher reaction activity, which can also enhance electron transport through hopping conduction; however, obtaining doubly charged oxygen vacancies requires overcoming a large energy barrier and is not easy to obtain, and it is difficult to obtain by regulating the local electron density and V o 2+ There is no precedent for the activation of PMS to further efficiently degrade new pollutants. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the existing technology and to provide a method for removing pollutants from a peroxymonosulfate system enhanced by a CuO / ZnO photocatalyst rich in doubly charged oxygen vacancies. By precisely designing a metal-organic framework precursor, the synthesis of a metal oxide catalyst derived from a metal-organic framework rich in doubly charged oxygen vacancies is achieved, promoting the activation of PMS and generating singlet oxygen and high-valent metal oxygen species. The two, through the hydroxylation and oxidation reactions of the pollutants, respectively, achieve synergistic removal of difficult-to-degrade pollutants in water.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions: A method for removing pollutants from a peroxymonosulfate system enhanced by a CuO / ZnO photocatalyst rich in doubly charged oxygen vacancies comprises the following steps: S1. Preparation of ZIF-8 precursor: dissolving dimethylimidazole in methanol to prepare solution A, dissolving zinc salt in methanol to prepare solution B, quickly mixing solution A and solution B and stirring thoroughly, washing and drying in a vacuum drying oven to obtain a ZIF-8 precursor, and then calcining the ZIF-8 precursor to obtain zinc oxide solid; S2. Preparation of composite catalyst: ultrasonically dispersing ZIF-8 precursor in an ethanol solution containing a copper salt, stirring thoroughly to obtain a dispersion, drying the dispersion, and calcining it in a furnace to obtain a copper oxide / zinc oxide (CZO) composite catalyst rich in doubly charged oxygen vacancies; S3. Pollutant removal: The composite catalyst obtained in step S2 is dispersed in the pollutant solution, stirred in the dark until adsorption and desorption equilibrium is reached, peroxymonosulfate (PMS) is added thereto, and light is applied to achieve the precise generation of singlet oxygen and high-valent copper oxide active species. Every 5 minutes, an appropriate amount of the pollutant solution is taken out and its concentration and total organic carbon content are detected to evaluate the pollutant removal efficiency until the pollutant concentration no longer decreases significantly.

[0007] As a further technical solution of the present invention, in step S1, the concentration of solution A is 32-32.5 g / L, preferably 32.45 g / L; the concentration of solution B is 9-9.5 g / L, preferably 9.34 g / L; and the volume ratio of solution A to solution B is 1:1.

[0008] As a further technical solution of the present invention, the drying temperature of the vacuum drying oven in step S1 is 50-70 o C, preferably 60 o C.

[0009] As a further technical solution of the present invention, the concentration of the ZIF-8 precursor in the dispersion in step S2 is 2.3-2.7 g / L, preferably 2.5 g / L; the concentration of the copper salt is 0.4-0.6 g / L, preferably 0.5 g / L.

[0010] As a further technical solution of the present application, the calcination temperature in step S2 is 500-700 o C, preferably 600 o C, and the calcination time is 2 h.

[0011] As a further technical solution of the present application, the amount of the composite catalyst in step S3 is 0.03-0.05 g / L, preferably 0.04 g / L.

[0012] As a further technical solution of the present application, the pollutant solution in step S3 is a solution of bisphenol A, sulfamethoxazole, phenol, acetaminophen, atrazine, carbamazepine, 3-bromophenol, and 4-chlorophenol, or coking wastewater tail water.

[0013] Compared with the prior art, the present application has the following beneficial effects: (1) It is first proposed to realize the precise generation of a metal oxide heterostructure with double-charge oxygen vacancies by designing a metal organic framework precursor; (2) It is first realized to realize the directional generation of high-valence metal oxygen and singlet oxygen active species under a persulfate system through the structure of a double-charge oxygen vacancy photocatalyst; (3) The proposed double-charge oxygen vacancy-rich photocatalyst strengthens the pollutant removal method in the persulfate system, provides experimental methods and theoretical basis for the advanced treatment and mechanism analysis of industrial wastewater tail water, and provides theoretical guidance for the targeted design of catalysts in industrial wastewater treatment. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 Catalyst characterization figures of A-ZnO (product of flow air calcination of ZIF-8), ZnO, A-CZO-3 (product of flow air calcination of copper-doped ZIF-8), and CZO-3 described in Example 1 of the present application, wherein a-f are, in turn, X-ray diffraction patterns of the prepared catalysts, electron paramagnetic resonance spectra, Cu 2p and O 1s X-ray photoelectron spectra of A-CZO-3 and CZO-3, Gaussian-fitted fluorescence spectra, and oxygen vacancy content figures.

[0015] Figure 2 Bisphenol A removal efficiency evaluation and active species identification figures provided by the present application, wherein a-e are, in turn, (a) bisphenol A removal efficiency, (b) free radical capture experiment, (c) 5,5-dimethyl-1-pyrroline-N-oxide (DMPO)-•OH / SO4 •− and 2,2,6,6-tetramethylpiperidine (TEMP) 1O2 map, (d) in situ Raman map under peroxymonosulfate / visible light (PMS / vis) system, (e) consumption map of methyl phenyl sulfoxide (PMSO) in the presence or absence of nitrobenzene (NB) in CZO-3 / PMS / vis and A-CZO-3 / PMS / vis systems.

[0016] Figure 3 This is the degradation curve of CZO-3 described in the present invention for different pollutants.

[0017] Figure 4 This is the performance evaluation of CZO-3 on coking wastewater tail water and the inhibitory effect on zebrafish embryos in Example 6 of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be further described below through examples with reference to the accompanying drawings.

[0019] Example 1: This embodiment provides a method for removing pollutants from a peroxymonosulfate system using a CuO / ZnO photocatalyst rich in doubly charged oxygen vacancies, which specifically includes the following steps: S1. Prepare 5.192 g of dimethylimidazole and dissolve it in 160 mL of methanol to obtain solution A. Prepare 2.348 g of zinc nitrate and dissolve it in 160 mL of methanol to obtain solution B. Quickly add solution A to solution B and stir vigorously for 2 h. After the precipitate is centrifuged with anhydrous ethanol, the product is heated at 60 o C in a vacuum drying oven for 12 h to obtain the product ZIF-8, which was collected and o C / min and heat up to 600 o C was calcined for 2 h to obtain ZnO; S2, 0.1 g ZIF-8 solid was dispersed in 40 mL ethanol, and 0.020 g copper nitrate was added to dissolve it, ultrasonically dispersed for 30 min and stirred for 2 h, and the obtained product was heated at 60 o C in a vacuum drying oven for 12 h to obtain the copper-doped ZIF-8 precursor, and the copper-doped ZIF-8 precursor was collected and o C / min and heat up to 600 o C was calcined for 2 h to obtain a copper oxide / zinc oxide (CZO) composite catalyst rich in doubly charged oxygen vacancies, which was designated as CZO-3; S3. Disperse 2.0 mg of the catalyst in 50.0 mL of 5 mg / L bisphenol A solution, stir in the dark for 1 h, add 1.0 mM potassium permonosulfate, and irradiate under a 150 W xenon lamp (filter out ultraviolet light) with an irradiation intensity of 122.5 mW / cm −2 , the irradiated area is 3.34 cm2 , and the concentration change of bisphenol A was tested after 30 min.

[0020] In this example, the catalysts of A-ZnO (product of ZIF-8 calcined by flowing air), ZnO, A-CZO-3 (product of copper-doped ZIF-8 calcined by flowing air) and CZO-3 were characterized. Figure 1 As shown in Figure 2, X-ray diffraction (XRD) patterns indicate that copper has been successfully incorporated into the ZnO structure. Compared with A-ZnO and A-CZO-3, the electron paramagnetic resonance (EPR) signals of ZnO and CZO-3 at g = 2.003 are enhanced, indicating that the oxygen-deficient conditions during annealing can lead to oxygen vacancies in the catalyst (V o ) number increases. X-ray photoelectron spectroscopy (XPS) reveals the specific existence state of copper. The proportion of Cu(I) in oxygen vacancy-rich CZO-3 is higher than that in A-CZO-3, increasing from 48.5% to 59.6%; the O 1s XPS spectrum can be decomposed into two peaks, corresponding to lattice oxygen (530.1eV) and oxygen vacancies (531.7 eV); the surface oxygen vacancy level of CZO-3 is the highest, which may be attributed to heteroatom modification and oxygen-deficient conditions. The photoluminescence (PL) spectrum of the catalyst mainly consists of two parts, one is concentrated in the ultraviolet region (385 nm), and the other is a strong defect-related band in the visible light region (460-800 nm). The former is attributed to the near-band edge emission generated by the recombination of free excitons in zinc oxide, and the latter corresponds to copper oxide (490 nm), neutral oxygen vacancies (V o 0 , 520-570 nm), singly charged oxygen vacancies (V o + , 570-620 nm), doubly charged oxygen vacancies (V o 2+ , 620-670 nm) and interstitial oxygen (O i , 670-720 nm and 720-780 nm). The relative content of doubly charged oxygen vacancies in the catalysts is in the following order: CZO-3 (58.6%) > A-CZO-3 (47.2%) > ZnO (43.2%) > A-ZnO (40.8%). Due to the increase in the concentration of doubly charged oxygen vacancies, the PL peak of CZO-3 undergoes a significant red shift compared with A-CZO-3. The intensity of doubly charged oxygen vacancies in CZO-3 is 2.42 times that of A-CZO-3, indicating that oxygen-deficient conditions and the rational construction of heterojunctions can lead to an increase in the number of doubly charged oxygen vacancies.

[0021] Example 2: The difference between this embodiment and embodiment 1 is that the mass of copper nitrate is 0.005 g, and the other steps and parameters are the same as those in embodiment 1.

[0022] Example 3: The difference between this embodiment and embodiment 1 is that no xenon lamp irradiation or peroxymonosulfate (PMS) is added. The other steps and parameters are the same as those in embodiment 1. The results are as follows: Figure 2 As shown in the figure. Visible light alone and the combination of the two are ineffective in degrading bisphenol A (BPA). The PMS / visible light system can enhance the removal of BPA. The synergy factor "S" is 2.2, indicating a positive interaction between photogenerated carriers and PMS decomposition and activation. The apparent rate constant (k obs ) is 0.0993 min −1 , is A-CZO-3 (0.0626 min −1 ) is 1.6 times.

[0023] Example 4: The difference between this embodiment and embodiment 1 is that the copper-doped ZIF-8 was calcined in a tube furnace with flowing air. The other steps and parameters were the same as those in embodiment 1. The results of active species identification are shown in FIG. Figure 2 As shown in the figure, compared with ZnO, A-ZnO and A-CZO-3, CZO-3 has the best degradation effect. obs 0.0993 min −1 , showed the highest PMS consumption rate (36.9%), which indicates that it has a strong PMS activation ability, which is beneficial to the Cu(III)-O and 1 In the CZO-3 / PMS / vis system, the presence of methylphenyl sulfoxide (PMSO) and furfuryl alcohol (FFA) almost completely inhibited the degradation of BPA (inhibition rates were 91.4% and 87.0%, respectively), indicating that Cu(III)-O and 1 O2 is the main active species, while sulfate radical, hydroxyl radical and superoxide radical are the secondary active species in the decomposition of BPA. In the A-CZO-3 / PMS / vis system, the inhibition rates of PMSO and FFA decreased, while the inhibition rates of tert-butyl alcohol (TBA), methanol (MeOH) and nitrogen (N2) increased significantly, by 24.6%, 13.1% and 3.5%, respectively. These results indicate that Cu(III)-O and 1 The contribution of O2 decreased, while the role of sulfate radicals, hydroxyl radicals and superoxide radicals in driving BPA degradation increased. In situ Fourier transform infrared spectroscopy was used to investigate the interaction between CZO-3, PMS and BPA ( Figure 2 c); 3456 cm −1 and 1636 cm −1The peaks at 1058 cm-1 and 1067 cm-2 are attributed to OH stretching vibration and H2O bending vibration, respectively. Compared with PMS alone, when CZO-3 is added into PMS solution, the SO bond stretching vibration peak increases from 1058 cm-1 to 1067 cm-1. −1 Blue shift to 1110 cm −1 , further shifted to 1113 cm after the introduction of BPA −1 , proving the strong interaction between CZO-3, PMS and BPA. In situ Raman spectroscopy revealed the presence of Cu(III)-O and its dynamic evolution during the reaction ( Figure 2 d). PMS does not show any obvious peaks in the 200-800 nm range. However, pure CZO-3 shows obvious peaks corresponding to Cu(II)-O bonds at 282 nm, 326 nm, and 623 nm. After the addition of PMS, these peaks are red-shifted, indicating a strong interaction between the Cu sites on the catalyst surface and the PMS molecules. As the reaction time increases, a clear peak gradually appears at 615 nm, indicating the formation of Cu(III)-O. At 4 min and 6 min, the Cu(III)-O peak intensity of CZO-3 significantly exceeds that of A-CZO-3. The contribution of Cu(III)-O can be more accurately determined by quantifying the consumption of PMSO ( Figure 2 e) In order to eliminate the effect of hydroxyl radicals on PMSO consumption, nitrobenzene was added because it reacts faster with hydroxyl radicals, while nitrobenzene can hardly be degraded by Cu(III)-O. The CZO-3 / PMS / vis system consumed 49.0% of PMSO, of which hydroxyl radicals and Cu(III)-O contributed 4.5% and 95.5%, respectively. In contrast, in the A-CZO-3 / PMS / vis system, the consumption of PMSO decreased by 4.5%, of which the contribution of Cu(III)-O decreased by 4.8%. Based on the above results, it can be concluded that oxygen vacancies in the catalyst promote the degradation of Cu(III)-O and 1 The generation of O2 simultaneously inhibits the generation of hydroxyl radicals and sulfate radicals, achieving a directional shift from a free radical pathway to a non-free radical pathway.

[0024] Example 5: The difference between this embodiment and embodiment 1 is that the pollutant solution is replaced by a 10 mg / L solution of sulfamethoxazole, phenol, acetaminophen, atrazine, carbamazepine, 3-bromophenol and 4-chlorophenol. The other steps and parameters are the same as those in embodiment 1.

[0025] Example 6: The difference between this embodiment and Example 1 is that the pollutant solution is coking wastewater tail water, and its corresponding chromaticity, total organic carbon, total nitrogen and total phosphorus are 624.1 hazen, 121.3 mg / L, 19.5 mg / L and 15.0 mg / L, respectively. The treatment time is 4 h, and zebrafish embryos are cultured using coking wastewater tail water. The other steps and parameters are the same as those in Example 1.

Claims

1. A method for removing pollutants from a peroxymonosulfate system using a CuO / ZnO photocatalyst rich in doubly charged oxygen vacancies, characterized in that: The specific steps include: S1. Preparation of ZIF-8 precursor: dissolving dimethylimidazole in methanol to prepare solution A, dissolving zinc salt in methanol to prepare solution B, quickly mixing solution A and solution B and stirring thoroughly, washing and drying in a vacuum drying oven to obtain a ZIF-8 precursor, and then calcining the ZIF-8 precursor to obtain zinc oxide solid; S2. Preparation of composite catalyst: ultrasonically dispersing ZIF-8 precursor in an ethanol solution containing a copper salt, stirring thoroughly to obtain a dispersion, drying the dispersion and calcining it in a furnace to obtain a copper oxide / zinc oxide composite catalyst rich in doubly charged oxygen vacancies; S3. Pollutant removal: The composite catalyst obtained in step S2 is dispersed in the pollutant solution, stirred in the dark until adsorption and desorption equilibrium is reached, peroxymonosulfate is added thereto, and light is applied to achieve the precise generation of singlet oxygen and high-valent copper oxide active species. The pollutant solution is taken out every 5 minutes and its concentration and total organic carbon content are detected to evaluate the pollutant removal efficiency until the pollutant concentration no longer decreases significantly.

2. The method for removing pollutants from a peroxymonosulfate system using a CuO / ZnO photocatalyst rich in doubly charged oxygen vacancies according to claim 1, characterized in that: In step S1, the concentration of solution A is 32-32.5 g / L, the concentration of solution B is 9-9.5 g / L, and the volume ratio of solution A to solution B is 1:

1.

3. The method for removing pollutants from a peroxymonosulfate system using a CuO / ZnO photocatalyst rich in doubly charged oxygen vacancies according to claim 2, wherein: The drying temperature of the vacuum drying oven in step S1 is 50-70 o C.

4. The method for removing pollutants from a peroxymonosulfate system using a CuO / ZnO photocatalyst rich in doubly charged oxygen vacancies according to claim 3, wherein: The concentration of the ZIF-8 precursor in the dispersion in step S2 is 2.3-2.7 g / L; the concentration of the copper salt is 0.4-0.6 g / L.

5. The method for removing pollutants from a peroxymonosulfate system using a CuO / ZnO photocatalyst rich in doubly charged oxygen vacancies according to claim 4, wherein: The calcination temperature in step S2 is 500-700 o C, calcination time is 2 h.

6. The method for removing pollutants from a peroxymonosulfate system using a CuO / ZnO photocatalyst rich in doubly charged oxygen vacancies according to claim 5, characterized in that: The dosage of the composite catalyst in step S3 is 0.03-0.05 g / L.

7. The method for removing pollutants from a peroxymonosulfate system using a CuO / ZnO photocatalyst rich in doubly charged oxygen vacancies according to claim 6, wherein: The pollutant solution in step S3 is bisphenol A, sulfamethoxazole, phenol, acetaminophen, atrazine, carbamazepine, 3-bromophenol, 4-chlorophenol solution or coking wastewater tail water.

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