Preparation method of multi-vacancy type core-shell zn o@zn s heterojunction, product and application

Abstract

The application discloses a preparation method of a multi-vacancy core-shell ZnO@ZnS heterojunction, and a product and application thereof. The method uses a metal-coordination polymer ZnTMT as a template, and through a hydrothermal and high-temperature calcination process, a ZnO@ZnS heterojunction with excellent photocatalytic performance is prepared. The ZnO@ZnS heterojunction contains rich zinc vacancies, oxygen vacancies and sulfur vacancies, can significantly improve the separation efficiency of photo-generated carriers, enhance the photocatalytic activity, and can be applied to degrading organic pollutants in seawater under visible light irradiation. The preparation method is simple, efficient, easy to operate, low in cost and beneficial to large-scale production. The ZnO@ZnS heterojunction can realize efficient degradation of organic pollutants in seawater without increasing additional energy consumption, and has important environmental value and economic value.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of photocatalysis, in particular to a preparation method of a multi-vacancy core-shell ZnO@ZnS heterojunction, a product and application thereof. BACKGROUND

[0002] In modern society, marine pollution problems are becoming increasingly serious and have become a global focus. Marine pollution not only destroys the balance of the marine ecosystem, but also has a serious impact on human health and economic development. The sources of marine pollution are diverse, including heavy metal pollution (such as mercury, arsenic, cadmium, etc.), plastic pollution, oil spills, and organic matter pollution discharged by agricultural and industrial activities. In particular, with the continuous expansion of marine and aquaculture activities, antibiotic pollution problems have become increasingly serious. These pollutants cause long-term harm to marine organisms and affect human health through the food chain. Therefore, developing efficient and environmentally sustainable methods for treating seawater pollution has become an important field of research in contemporary society.

[0003] ZnS and ZnO are typical II-VI group wide-bandgap semiconductor materials that can effectively generate photo-carriers under ultraviolet light and exhibit photocatalytic activity. These two materials have shown great application potential in the field of photocatalysis due to their unique electronic structure and optical properties. However, the wide bandgap of ZnO (band gap Eg = 3.2 eV) and ZnS (band gap Eg = 3.6 eV) limits their efficiency in utilizing solar energy, as they mainly absorb ultraviolet light, while their ability to absorb visible light is weak. In addition, photo-generated carriers are prone to recombination in these materials, which greatly hinders their application in photocatalytic processes.

[0004] To overcome these limitations, researchers have explored the formation of heterojunction structures by combining ZnO and ZnS. Heterojunction structures can lower the photo-excitation threshold and reduce the recombination rate of electron-hole pairs, thereby improving photocatalytic efficiency. Both materials have similar metal elements and compatible band structures, which promotes effective lattice matching, making it possible to construct S-type heterojunctions in situ between ZnS and ZnO. When preparing catalysts containing ZnO or ZnS, a large number of vacancies are usually formed on the surface of the catalyst. These vacancies can effectively capture charge carriers that reach the surface, thereby improving charge separation efficiency. This process helps to form impurity energy bands, broadens the spectral response range, and ultimately improves the activity of photo-oxidation or reduction processes.

[0005] As prior art CN118002152A, the invention name is a ZnO / ZnS composite material with zinc and oxygen double vacancies and its preparation method and application. The ZnO / ZnS composite material disclosed therein belongs to a hollow spherical structure, which has zinc and oxygen double vacancies and has the performance of photocatalytic decomposition of water to produce hydrogen. Prior art CN106622291A, the invention name is a method for preparing a zinc oxide / zinc sulfide nano-heterojunction photocatalyst. The ZnO / ZnS nano-heterojunction photocatalyst disclosed therein also has the performance of photocatalytic decomposition of water to produce hydrogen, and has high photocatalytic hydrogen production efficiency, but its preparation method is relatively complex, which has limitations for large-scale production. Prior art CN114558592B, the invention name is a ZnO / ZnS nanorod core-shell structure photocatalyst and its preparation method, wherein a rod-shaped core-shell photocatalyst is prepared by combining electrodeposition and spin coating method, the preparation method is complex, the cost is high, and it is not conducive to large-scale production. And the above prior art has not studied the performance under complex environmental conditions, such as high salinity seawater.

[0006] Therefore, the existing heterojunction ZnO@ZnS and its preparation method and application still have disadvantages and need to be further improved. How to create a new preparation method of multi-vacancy core-shell ZnO@ZnS heterojunction and its product and application, so that it can simply and conveniently prepare a core-shell S-type heterojunction ZnO@ZnS with zinc vacancies, oxygen vacancies and sulfur vacancies, significantly improve the separation efficiency of photo-generated carriers, enhance the photocatalytic performance, effectively degrade pollutants in high salinity seawater, and provide practical application value for seawater pollution treatment. SUMMARY

[0007] The technical problem to be solved by the present application is to provide a preparation method of multi-vacancy core-shell ZnO@ZnS heterojunction, so that it can simply and conveniently prepare a core-shell S-type heterojunction ZnO@ZnS with zinc vacancies, oxygen vacancies and sulfur vacancies, significantly improve the separation efficiency of photo-generated carriers, enhance the photocatalytic performance, effectively degrade pollutants in high salinity seawater, and provide practical application value for seawater pollution treatment, thereby overcoming the shortcomings of the existing ZnO@ZnS heterojunction and its preparation method.

[0008] To solve the above technical problems, the present application provides a preparation method of multi-vacancy core-shell ZnO@ZnS heterojunction, characterized in that it comprises the following steps:

[0009] (1) Preparation of ZnTMT:

[0010] Put the sodium hydroxide aqueous solution into a water bath at 60-80℃, add TMT powder, and continuously stir to form solution A;

[0011] Weigh the zinc nitrate hexahydrate and dissolve it in water, continuously stir to form solution B;

[0012] Slowly add solution A to solution B, form a white solution, then stir at room temperature for 24-48h to form metal-ligand polymer ZnTMT precipitate, centrifuge the precipitate at low speed, wash, dry at 60-80℃ overnight to obtain metal-ligand polymer ZnTMT powder;

[0013] (2) Preparation of ZnS:

[0014] Weigh ZnTMT powder, add ultrapure water, stir at room temperature for 30-60min, transfer to the reaction kettle, keep at 140-200℃ for 12-18h, take the precipitate and wash, dry at 60-80℃ overnight to obtain light yellow ZnS powder;

[0015] (3) Preparation of ZnO@ZnS heterojunction:

[0016] Weigh ZnS powder, evenly place it in an alumina crucible, and perform high-temperature calcination at 300-600℃ in a tube furnace, then naturally cool to room temperature to obtain multi-vacancy core-shell ZnO@ZnS heterojunction.

[0017] Further improvement, step (1) is specifically:

[0018] Weigh 0.03-0.05mol of NaOH and dissolve it in 200-400mL of ultrapure water, place it in a 60-80℃ water bath, and add 0.01-0.03mol of TMT powder, continue to stir to form solution A;

[0019] Weigh 0.03-0.05mol of Zn(NO3)2·6H2O and add it to 200-400mL of ultrapure water, continue to stir at room temperature for 30-60min to form solution B;

[0020] Slowly add solution A to solution B, form a white solution, then stir at room temperature for 24-48h to form metal-ligand polymer ZnTMT precipitate, centrifuge the precipitate at low speed, wash with ultrapure water, dry at 60-80℃ overnight to obtain metal-ligand polymer ZnTMT powder.

[0021] Further improvement, step (2) is specifically:

[0022] Weigh 1-3g of ZnTMT powder, add 50-100mL of ultrapure water, stir at room temperature for 30-60min, transfer to the reaction kettle, keep at 140-200℃ for 12-18h, take the precipitate and wash, dry at 60-80℃ overnight to obtain light yellow ZnS powder.

[0023] Further improvement, the calcination time in step (3) is 1-3h.

[0024] Further improvement, step (3) also includes the step of delivering air into the reaction furnace by an external air pump in the initial stage of calcination to enhance the contact of the reactants with oxygen and optimize the conversion conditions of ZnS to ZnO.

[0025] Further improvement, the flow rate of air delivered into the reaction furnace is 100 mL / min.

[0026] As a further improvement of the present application, the present application also provides a multi-vacancy-like core-shell ZnO@ZnS heterojunction prepared by the preparation method of the multi-vacancy-like core-shell ZnO@ZnS heterojunction. The multi-vacancy-like core-shell ZnO@ZnS heterojunction is in a spherical structure, with a ZnS core inside and a ZnO shell outside, and the ZnO@ZnS heterojunction has a multi-vacancy structure, which includes zinc vacancies, oxygen vacancies and sulfur vacancies.

[0027] As a further improvement of the present application, the present application also provides a multi-vacancy-like core-shell ZnO@ZnS heterojunction prepared by the preparation method of the multi-vacancy-like core-shell ZnO@ZnS heterojunction. The multi-vacancy-like core-shell ZnO@ZnS heterojunction is in a spherical structure, with a ZnS core inside and a ZnO shell outside, and the ZnO@ZnS heterojunction has a multi-vacancy structure, which includes zinc vacancies, oxygen vacancies and sulfur vacancies.

[0028] The degradation rate of the multi-vacancy-like core-shell ZnO@ZnS heterojunction in the degradation of OTC in seawater under visible light irradiation is greater than 50%.

[0029] After adopting such design, the present application has at least the following advantages:

[0030] 1. The method for preparing the ZnO@ZnS heterojunction is efficient, simple, easy to operate and low in cost, and is conducive to large-scale production. The ZnO@ZnS heterojunction prepared has a plurality of vacancy defects, including zinc vacancies, oxygen vacancies and sulfur vacancies. In the process of photocatalysis, these vacancies can effectively capture the charge carriers reaching the surface, improve the charge separation efficiency, help to form an impurity energy band, broaden the spectral response range, and ultimately improve the activity of the photooxidation or reduction process, thereby enhancing the photocatalytic activity.

[0031] 2. By adjusting the types and concentrations of different salts, the performance of the ZnO@ZnS heterojunction in degrading high-concentration OTC under visible light is explored, and photocatalytic degradation is carried out in actual seawater, which confirms that the ZnO@ZnS heterojunction has excellent photocatalytic degradation performance under visible light irradiation in simulated or real seawater, indicating that the ZnO@ZnS heterojunction can realize efficient degradation of organic pollutants in seawater without increasing additional energy consumption, which has important environmental and economic values. BRIEF DESCRIPTION OF DRAWINGS

[0032] The above is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, the present application is further described in detail below in combination with the drawings and specific embodiments.

[0033] Figure 1 is a flow chart of the preparation method of the ZnO@ZnS heterojunction of the present application.

[0034] Figure 2 is a scanning electron microscope (SEM) image of the ZnO@ZnS heterojunction prepared by the present application.

[0035] Figure 3 is a transmission electron microscope (TEM) image of the ZnO@ZnS heterojunction prepared by the present application.

[0036] Figure 4 is an electron paramagnetic resonance (EPR) spectrum of the ZnO@ZnS heterojunction prepared by the present application.

[0037] Figure 5 is an ultraviolet-visible absorption spectrum of OTC in a simulated seawater solution containing 3.5wt% NaCl in Example 4.

[0038] Figure 6 is a standard curve of absorbance of OTC in a high-salt solution and an aqueous solution at a wavelength of 355 nm in Example 4.

[0039] Figure 7 is a dynamic change curve of the degradation efficiency of OTC in a simulated seawater solution by different catalysts in Example 4 of the present application.

[0040] Figure 8 is a degradation efficiency graph of OTC by the ZnO@ZnS heterojunction in different salt concentrations and Bohai seawater in Examples 5 and 6 of the present application. DETAILED DESCRIPTION

[0041] Exemplary embodiments of the present application will be described in greater detail below with reference to the accompanying drawings. Although exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present application can be more thoroughly understood and the scope of the present application can be accurately conveyed to those skilled in the art.

[0042] Example 1: Preparation of multi-site core-shell ZnO@ZnS heterojunction

[0043] Figure 1 The preparation process of the ZnO@ZnS heterojunction is shown, including the preparation of the ZnTMT template, the synthesis of ZnS, and the formation of the final ZnO@ZnS heterojunction. The specific preparation is as follows:

[0044] 1. Chemical reagents

[0045] Sodium hydroxide: NaOH, National Pharmaceutical Group Chemical Reagent Co., Ltd.; Zinc nitrate: Zn(NO3)2·6H2O, National Pharmaceutical Group Chemical Reagent Co., Ltd.; Trithiocyanic acid: C3H3N3S3, TMT, Shanghai Aladdin Biochemical Technology Co., Ltd. It is explained that the reagents used in this application are all commercially available chemical reagents.

[0046] 2. Preparation method

[0047] (1) Preparation of ZnTMT template

[0048] 0.03 mol of NaOH was weighed and dissolved in 200 mL of ultrapure water, placed in a 60°C water bath for heating, then 0.01 mol of TMT powder was added, and stirring was continued for 30 min to form a uniformly mixed solution A.

[0049] 0.03 mol of Zn(NO3)2·6H2O was weighed and added to 200 mL of ultrapure water, and stirring was continued at room temperature for 45 min to form solution B.

[0050] Solution A was slowly added to solution B to form a white precipitate, which was then stirred at room temperature for 24 h to form a ZnTMT metal-ligand polymer precipitate.

[0051] The precipitate was centrifuged at low speed, the precipitate was collected, washed with ultrapure water three times, and then dried at 60°C overnight to obtain a metal-ligand polymer ZnTMT white powder.

[0052] (2) Preparation of ZnS

[0053] 1 g of ZnTMT powder was weighed and added to 100 mL of ultrapure water, and stirred at room temperature for 30 min. The above solution was transferred to a 100 mL polytetrafluoroethylene reaction kettle, and kept at 140°C for 12 h. After the reaction was completed, the precipitate was washed with ultrapure water three times, and dried at 60°C overnight to obtain ZnS powder.

[0054] (3) Preparation of ZnO@ZnS heterojunction

[0055] 0.5 g of ZnS powder was weighed and uniformly dispersed in an alumina crucible, and high-temperature calcination at 550°C was carried out in a tube furnace, and the calcination time was 2 h. After calcination was completed, it was naturally cooled to room temperature to obtain a multi-vacancy core-shell ZnO@ZnS heterojunction powder.

[0056] Example 2: Preparation of multi-vacancy core-shell ZnO@ZnS heterojunction

[0057] 1. Chemical reagents

[0058] Sodium hydroxide: NaOH, National Pharmaceutical Group Chemical Reagent Co., Ltd.; Zinc nitrate: Zn(NO3)2·6H2O, National Pharmaceutical Group Chemical Reagent Co., Ltd.; Trithiocyanic acid: C3H3N3S3, TMT, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0059] 2. Preparation method

[0060] (1) Preparation of ZnTMT template

[0061] Weigh 0.05 mol of NaOH and dissolve it in 400 mL of ultrapure water, place it in a 80°C water bath for heating, then add 0.03 mol of TMT powder, continue stirring for 30 min, form a uniform solution A.

[0062] Weigh 0.05 mol of Zn(NO3)2·6H2O and add it to 400 mL of ultrapure water, continue stirring at room temperature for 60 min, form solution B.

[0063] Slowly add solution A to solution B, form a white precipitate, then stir at room temperature for 48 h, form a ZnTMT metal-ligand polymer precipitate.

[0064] Centrifuge the precipitate at low speed, collect the precipitate, wash it with ultrapure water three times, then dry it at 80°C overnight, get the metal-ligand polymer ZnTMT white powder.

[0065] (2) Preparation of ZnS

[0066] Weigh 3g of ZnTMT powder, add it to 100 mL of ultrapure water, stir at room temperature for 50 min. Transfer the above solution to a 100 mL polytetrafluoroethylene reaction kettle, keep it at 200°C for 18 h. After the reaction is completed, wash the precipitate with ultrapure water three times, dry it at 80°C overnight, get ZnS powder.

[0067] (3) Preparation of ZnO@ZnS heterojunction

[0068] Weigh 1.0g of ZnS powder, evenly disperse it in an alumina crucible, perform high-temperature calcination at 600°C in a tube furnace, calcination time is 3h.

[0069] And in the initial stage of calcination within 30 min, air is delivered into the furnace through an external air pump, flow rate is 100 mL / min, to enhance the contact of reactants with oxygen.

[0070] After calcination is completed, naturally cool it to room temperature, get multi-vacancy-like core-shell ZnO@ZnS heterojunction powder.

[0071] Example 3 Structure detection of multi-vacancy-like core-shell ZnO@ZnS heterojunction

[0072] The ZnO@ZnS heterojunction powder obtained in Example 1 was subjected to scanning electron microscope (SEM), transmission electron microscope (TEM), and electron paramagnetic resonance (EPR) detection, and the results are shown in Figures 1-3. Figure 2 、 3 、4.

[0073] Figure 2 Figure 1 shows a scanning electron microscope (SEM) image of the ZnO@ZnS heterojunction, showing the spherical structure and size of the ZnO@ZnS heterojunction, and an EDS spectrum, revealing the distribution of elements such as Zn, S, and O in the heterojunction.

[0074] Figure 3 Figure 2 shows a transmission electron microscope (TEM) image of the ZnO@ZnS heterojunction. As can be seen from the figure, the inner layer is a ZnS core, and the outer layer is a ZnO shell. The ZnS core and ZnO shell in the ZnO@ZnS heterojunction are chemically bonded.

[0075] Figure 4 Figure 3 shows an electron paramagnetic resonance (EPR) spectrum of the ZnO@ZnS heterojunction. As can be seen from the figure, there are various vacancy defects on the surface of the ZnO@ZnS heterojunction, including zinc vacancies, oxygen vacancies, and sulfur vacancies.

[0076] Example 4 Verification of photocatalytic degradation activity of ZnO@ZnS heterojunction

[0077] In actual seawater pollutant detection, terramycin is one of the representative antibiotics in the detected antibiotic pollution, the main reason for which is that terramycin is common and widespread in veterinary antibiotics, which often leads to the abuse of terramycin. Similarly, the same problem exists in marine aquaculture, and these abused terramycins are released into the ocean in large quantities along with the discharge of marine aquaculture wastewater, thereby exacerbating antibiotic pollution in the ocean. Therefore, terramycin (OTC) was selected as a representative pollutant of marine organic pollutants in this example, and the degradation rate of OTC in simulated seawater under high salt concentration was verified to illustrate that the ZnO@ZnS heterojunction prepared by the present application has strong photocatalytic degradation effect, which can provide reliable basis for the degradation of seawater organic pollutants under visible light conditions.

[0078] First, the optimal test wavelength of OTC was determined

[0079] OTC solutions with different concentrations were prepared, and 3.5wt% NaCl solution was used as the solvent to obtain OTC solutions with concentrations of 5, 10, 20, 30, 40, and 50 ppm. Spectral measurement was performed using a UV spectrophotometer, and the test spectral range was 200-450 nm. The obtained UV spectrophotometer spectrum is shown in Figure 4. Figure 5 ​

[0080] From Figure 5 It can be seen that OTC has two maximum absorption wavelengths at 275nm and 355nm. Considering that the intermediate products of OTC in the degradation process may affect the absorbance in the ultraviolet region, 355nm is selected as the optimal test wavelength.

[0081] Secondly, the difference in absorbance of OTC in high-salt water and pure water is investigated

[0082] In order to exclude the influence of high-salt environment on the degradation of the catalyst, the difference in absorbance of OTC in pure water and high-salt water is also compared in this embodiment. The specific method is as follows:

[0083] Pure water or 3.5wt% NaCl solution is used as the solvent to prepare OTC solutions with concentrations of 5, 10, 20, 30, 40, and 50ppm, respectively. The prepared solutions are tested for absorbance at a test wavelength of 355nm, and the standard curve of OTC solution in different solvents is drawn. The results are shown in FIG. 2. Figure 6

[0084] From Figure 6 It can be seen that the standard curve of OTC aqueous solution and OTC high-salt solution is basically the same at a wavelength of 355nm, with no significant difference. The results show that OTC in high-salt solution is uniformly dispersed and has no effect on the degradation of the catalyst.

[0085] Next, on the basis of the above, the catalytic effect of ZnO@ZnS heterojunction prepared by the application as a photocatalyst is compared. The specific method is as follows:

[0086] A 3.5wt% NaCl solution is used as the solvent to prepare an OTC solution with a concentration of 50ppm, which is divided into four equal parts. 0.03g of ZnO, ZnS, ZnTMT, and ZnO@ZnS is added as different catalysts. Dark adsorption is carried out for 30min in the dark to allow the catalysts and OTC to reach adsorption equilibrium, excluding possible adsorption effects in the subsequent photocatalytic degradation process. After the adsorption equilibrium time is reached, the xenon lamp source is turned on for photocatalytic degradation experiments.

[0087] During the experiment, 1mL of a syringe is used to take 1mL of sample from each OTC solution every 30min. The obtained solution is filtered through a 0.22μm water filter to obtain a clear OTC solution, which is subjected to absorbance measurement by ultraviolet spectrophotometry at a wavelength of 355nm. The degradation rate of OTC by different catalysts is calculated, and the results are shown in Table 1 and FIG. 3. Figure 7

[0088] Table 1 Degradation rate of OTC by different catalysts

[0089] ​​ Different catalysts OTC degradation rate (%) ZnO 50.9 ZnS 8.5 ZnTMT 21.9 ZnO@ZnS 73.6

[0090] From Table 1 and Figure 7 It can be seen that, under the same NaCl high salt environment, the ZnO@ZnS heterojunction has always shown the best photocatalytic degradation effect of OTC in the solution. And, when the light is irradiated for 240 min, the degradation rate of OTC by the ZnO@ZnS heterojunction reaches 73.6%, which is much higher than the degradation rate of ZnTMT, ZnS and ZnO alone, showing the excellent photocatalytic degradation performance of the ZnO@ZnS heterojunction under high salt conditions.

[0091] Example 5: Photocatalytic degradation experiment of ZnO@ZnS heterojunction under different salt concentrations

[0092] Since seawater contains various salts, in order to verify the photocatalytic degradation effect of the ZnO@ZnS heterojunction under different salt concentrations, the following experiments are designed in this embodiment.

[0093] Simulated seawater solutions containing 3.5wt% NaCl, 4.46wt% KCl, 2.84wt% MgCl2, 3.32wt% CaCl2, 4.25wt% Na2SO4 and 7.34wt% KBr were prepared respectively, each taking 50mL, and OTC was added to make the concentration of OTC 50ppm.

[0094] Then, 0.03g of ZnO@ZnS heterojunction was added to each high salt solution, and dark adsorption was carried out for 30min in the dark. After the adsorption equilibrium time arrived, the xenon lamp light source was turned on, and the photocatalytic degradation experiment was carried out.

[0095] During the experiment, 1mL of syringe was used to take 1mL of sample from each high salt solution every 30min. The obtained solution was filtered through a 0.22μm water filter head, and the obtained clear solution was subjected to absorbance measurement by ultraviolet spectrophotometer under the condition of wavelength 355nm. The degradation rate of OTC by the photocatalyst ZnO@ZnS heterojunction in different high salt solutions was calculated, and the results are shown in Table 2 and the accompanying Figure 8

[0096] Table 2 Degradation rate of OTC by photocatalyst ZnO@ZnS heterojunction in different high salt solutions

[0097] Different high salt solutions OTC degradation rate (%) 3.5 wt% NaCl 73.6 4.46 wt% KCl 73.0 2.84 wt% MgCl2 50.7 3.32 wt% CaCl2 59.4 4.25 wt% Na2SO4 68.7 7.34 wt% KBr 70.7

[0098] From Table 2 and Figure 8 It can be seen that, under the same NaCl high salt environment, the ZnO@ZnS heterojunction has always shown the best photocatalytic degradation effect of OTC in the solution. And, when the light is irradiated for 240 min, the degradation rate of OTC by the ZnO@ZnS heterojunction reaches 73.6%, which is much higher than the degradation rate of ZnTMT, ZnS and ZnO alone, showing the excellent photocatalytic degradation performance of the ZnO@ZnS heterojunction under high salt conditions.

[0091] Example 5: Photocatalytic degradation experiment of ZnO@ZnS heterojunction under different salt concentrations

[0092] Since seawater contains various salts, in order to verify the photocatalytic degradation effect of the ZnO@ZnS heterojunction under different salt concentrations, the following experiments are designed in this embodiment.

[0093] Simulated seawater solutions containing 3.5wt% NaCl, 4.46wt% KCl, 2.84wt% MgCl2, 3.32wt% CaCl2, 4.25wt% Na2SO4 and 7.34wt% KBr were prepared respectively, each taking 50mL, and OTC was added to make the concentration of OTC 50ppm.

[0094] Then, 0.03g of ZnO@ZnS heterojunction was added to each high salt solution, and dark adsorption was carried out for 30min in the dark. After the adsorption equilibrium time arrived, the xenon lamp light source was turned on, and the photocatalytic degradation experiment was carried out.

[0095] During the experiment, 1mL of syringe was used to take 1mL of sample from each high salt solution every 30min. The obtained solution was filtered through a 0.22μm water filter head, and the obtained clear solution was subjected to absorbance measurement by ultraviolet spectrophotometer under the condition of wavelength 355nm. The degradation rate of OTC by the photocatalyst ZnO@ZnS heterojunction in different high salt solutions was calculated, and the results are shown in Table 2 and the accompanying

[0099] Example 6: Photocatalytic degradation experiment of ZnO@ZnS heterojunction in actual seawater

[0100] In order to evaluate the photocatalytic performance of ZnO@ZnS heterojunction in the actual seawater environment, the present embodiment is as follows:

[0101] Take seawater from Bohai as the solvent, and add OTC to make the concentration of OTC 50 ppm.

[0102] Then 0.03 g of ZnO@ZnS heterojunction is added to the seawater solution. Similarly, the dark adsorption is carried out for 30 min in the dark condition, and after the adsorption equilibrium time arrives, the xenon lamp light source is turned on to carry out the photocatalytic degradation experiment.

[0103] During the experiment, 1 mL of the seawater solution is sampled every 30 min using a 1 mL syringe. The obtained solution is filtered through a 0.22 μm water filter head to obtain a clear solution, and the absorbance of the clear solution is measured by ultraviolet spectrophotometry at a wavelength of 355 nm. The degradation rate of OTC in the seawater solution by the photocatalyst ZnO@ZnS heterojunction is calculated, and the results are shown in Table 3 and FIG. 2. Figure 8

[0104] Table 3 Degradation rate of OTC in seawater solution by photocatalyst ZnO@ZnS heterojunction

[0105] Seawater solutions OTC degradation rate (%) Bohai seawater 68.9

[0106] From Table 3 and Figure 8 It can be seen that the degradation efficiency of OTC by the ZnO@ZnS heterojunction in the actual seawater condition can reach 68.9%, which further proves the effectiveness and application potential of the ZnO@ZnS heterojunction in the actual seawater pollution treatment. That is, the ZnO@ZnS heterojunction can degrade organic pollutants in seawater under visible light irradiation, which provides practical application value for the treatment of organic pollutants in seawater.

[0107] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Those skilled in the art can make some simple modifications, equivalent changes or modifications by using the disclosed technical content, which are all within the protection scope of the present application.​

Claims

1. Application of a multi-vacancy core-shell ZnO@ZnS heterojunction in degradation of seawater organic pollutants under visible light irradiation, wherein the multi-vacancy core-shell ZnO@ZnS heterojunction is in a spherical structure, with a ZnS core and a ZnO shell, and the ZnO@ZnS heterojunction has a multi-vacancy structure, including zinc vacancies, oxygen vacancies and sulfur vacancies; a preparation method of the multi-vacancy core-shell ZnO@ZnS heterojunction, comprising the following steps: (1) Preparation of ZnTMT: placing a sodium hydroxide aqueous solution in a water bath at 60-80°C, adding TMT powder, continuously stirring to form solution A; weighing zinc nitrate hexahydrate and dissolving it in water, continuously stirring to form solution B; slowly adding solution A to solution B, stirring at room temperature for 24-48 hours after forming a white solution, forming a metal-ligand polymer ZnTMT precipitate, centrifuging the precipitate at low speed, washing, drying at 60-80°C overnight to obtain metal-ligand polymer ZnTMT powder; (2) Preparation of ZnS: weighing ZnTMT powder, adding ultrapure water, stirring at room temperature for 30-60 minutes, transferring to a reaction kettle, keeping at 140-200°C for 12-18 hours, washing the precipitate, drying at 60-80°C overnight to obtain light yellow ZnS powder; (3) Preparation of ZnO@ZnS heterojunction: weighing ZnS powder, uniformly placing it in an alumina crucible, high-temperature calcining at 300-600°C in a tube furnace, naturally cooling to room temperature after calcining to obtain a multi-vacancy core-shell ZnO@ZnS heterojunction.

2. Use of the multi-lattice core-shell ZnO@ZnS heterojunction according to claim 1 for degrading seawater organic pollutants under visible light irradiation, characterized in that, The degradation rate of the multi-vacancy core-shell ZnO@ZnS heterojunction in degradation of OTC in seawater under visible light irradiation is greater than 50%.

3. Use of the multi-lacuna core-shell ZnO@ZnS heterojunction according to claim 1 for degrading seawater organic pollutants under visible light irradiation, characterized in that, Step (1) is specifically: weighing 0.03-0.05 mol of NaOH and dissolving it in 200-400 mL of ultrapure water, placing it in a water bath at 60-80°C, and adding 0.01-0.03 mol of TMT powder, continuously stirring to form solution A; weighing 0.03-0.05 mol of Zn(NO3)2·6H2O and adding it to 200-400 mL of ultrapure water, continuously stirring at room temperature for 30-60 minutes to form solution B; slowly adding solution A to solution B, stirring at room temperature for 24-48 hours after forming a white solution, forming a metal-ligand polymer ZnTMT precipitate, centrifuging the precipitate, washing with ultrapure water, drying at 60-80°C overnight to obtain metal-ligand polymer ZnTMT powder.

4. Use of the multi-lacuna core-shell ZnO@ZnS heterojunction according to claim 1 for degrading seawater organic pollutants under visible light irradiation, characterized in that, Step (2) is specifically: weighing 1-3 g of ZnTMT powder, adding 50-100 mL of ultrapure water, stirring at room temperature for 30-60 minutes, transferring to a reaction kettle, keeping at 140-200°C for 12-18 hours, washing the precipitate, drying at 60-80°C overnight to obtain light yellow ZnS powder.

5. Use of the multi-lacuna core-shell ZnO@ZnS heterojunction according to claim 1 for degrading seawater organic pollutants under visible light irradiation, characterized in that, The calcining time in step (3) is 1-3 hours.

6. Use of the multi-lacuna core-shell ZnO@ZnS heterojunction according to claim 5 for degrading seawater organic pollutants under visible light irradiation, characterized in that, Step (3) further includes a step of delivering air into the reaction furnace through an external air pump at the initial stage of calcining.

7. Use of the multi-lacuna core-shell ZnO@ZnS heterojunction according to claim 6 for degrading seawater organic pollutants under visible light irradiation, characterized in that, The flow rate of air delivered into the reaction furnace is 100 mL / min.

Images