A method for one-step in-situ preparation of tightly interfaced Z-type NiMn2O4 / NiO composite photocatalysts and its application

Abstract

This invention relates to a one-step in-situ preparation method for a tightly interfaced Z-type NiMn2O4 / NiO composite photocatalyst and its application. First, MnCl2·4H2O and Ni(NO3)2·6H2O are dispersed separately in distilled water at a certain molar ratio. An appropriate amount of NaOH solution is added, and the mixture is stirred thoroughly to allow precipitation, which is then collected. The collected precipitate is mixed evenly, filtered, washed, dried, ground, and calcined to form the NiMn2O4 / NiO composite photocatalyst. This invention provides a simple one-step in-situ preparation of the Z-type NiMn2O4 / NiO composite photocatalyst. The in-situ construction creates a tight interface between NiMn2O4 and NiO, which is beneficial for electron transfer in the system. The composite photocatalyst prepared by this invention is simple, has a high effective Z-type yield, and exhibits a good catalyst crystal structure, enabling efficient photocatalytic degradation of organic pollutants in water under sunlight.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysts and their applications, specifically involving a one-step in-situ preparation method for a tightly interfaced Z-type NiMn2O4 / NiO composite photocatalyst using chemical precipitation and in-situ synthesis methods, and its application. Background Technology

[0002] Cetirizine hydrochloride (CTC), a medical antibiotic, is widely used for disease prevention due to its broad-spectrum activity, strong antibacterial and antiprotozoal activity, and low cost. However, because CTC is difficult to digest after ingestion, a significant portion is released into water as an active drug during metabolism, causing a series of organic pollution problems in water. In recent years, semiconductor-based photocatalytic oxidation technology has received widespread attention for the treatment of organic pollutants in water due to its advantages such as strong redox capacity, high energy efficiency, low cost, and no secondary pollution.

[0003] As a typical transition metal oxide, NiO possesses a relatively stable and wide bandgap, making it a promising p-type semiconductor material. It is widely used in photocatalysis for photocatalytic degradation of organic dyes and photoelectrochemical water splitting. However, among semiconductor photocatalysts, single broadband semiconductor photocatalysts suffer from narrow photoresponse ranges and limited photogenerated electron-hole (e-hole) ratios. - -h + This approach addresses drawbacks such as high recombination rate and poor quantum efficiency. Inspired by plant photosynthesis, constructing a Z-type composite photocatalyst using two semiconductor materials is a promising option. NiMn₂O₄, a spinel, possesses a band gap of approximately 2.1 eV, attracting attention due to its narrow band gap and excellent photocatalytic performance. Therefore, constructing a Z-type photocatalytic system by combining NiO and NiMn₂O₄ can not only enhance the system's photogenerated energy... - -h +The composite photocatalyst exhibits improved separation efficiency and, due to the combination of different bandgap structures, a wider photoresponse range, thus significantly enhancing its activity. However, when preparing binary Z-type photocatalysts using certain conventional methods, a significant contact interface always exists between the two semiconductor nanoparticles, limiting electron transport and resulting in insufficient usability of the Z-type photocatalyst. Furthermore, obtaining a high proportion of effective Z-type nanocomposite photocatalysts is crucial for improving photocatalytic activity. Therefore, this invention, based on NiO photocatalysts, constructs a binary Z-type composite photocatalyst with a tight interface in situ to further improve its photocatalytic activity and explore its catalytic degradation effect on CTCs in water. The preparation process of this invention is ingenious, simple, and low-cost, and the composite catalyst has a high yield and good crystal structure, exhibiting strong degradation capabilities for both antibiotic and dye wastewater. This technology is expected to play a role in constructing highly efficient photocatalysts and utilizing sunlight to catalytically degrade organic pollutants in water. Summary of the Invention

[0004] The purpose of this invention is to achieve a one-step in-situ synthesis of a Z-shaped interface-tight NiMn2O4 / NiO composite photocatalyst by controlling the proportion of raw materials and the calcination temperature and time during the preparation process. This invention features a simple and low-cost preparation process, and the resulting NiMn2O4 / NiO nanoparticles exhibit a tight interface and a well-defined crystal structure, leading to a high yield of effective Z-shaped structures. This not only improves the redox capability of the system but also effectively reduces photogenerated electrons. - -h + The high recombination rate fully utilizes sunlight, enhancing its photocatalytic degradation ability.

[0005] Another objective of this invention is to utilize a Z-type NiMn2O4 / NiO composite photocatalyst for the catalytic degradation of antibiotics in medical wastewater. The technical solution adopted in this invention is a one-step in-situ method for preparing a tightly interfaced Z-type NiMn2O4 / NiO composite photocatalyst, comprising the following steps:

[0006] (1) A certain proportion of MnCl2·4H2O and Ni(NO3)2·6H2O were dispersed in distilled water, stirred thoroughly, and then a certain amount of NaOH solution was added to each of them. After stirring for 1.0 h, a precipitate was obtained.

[0007] (2) After the precipitate is evenly mixed, it is washed, the pH is adjusted to alkaline, centrifuged, filtered and collected, and dried at 80℃ for 12h.

[0008] (3) After the dried mixed precipitate powder is uniformly ground, it is calcined to obtain the target product NiMn2O4 / NiO.

[0009] In the above-described one-step in-situ preparation method of tightly interfaced Z-type NiMn2O4 / NiO composite photocatalyst, in step (1), the optimal molar ratio is Ni 2+ :Mn 2+ =1.0~2.0:1.0.

[0010] In the above-described one-step in-situ preparation method of tightly interfaced Z-type NiMn2O4 / NiO composite photocatalyst, in step (1), the optimal molar ratio is Ni 2+ :Mn 2+ =1.5:1.0.

[0011] In the above-described one-step in-situ preparation method of interfacially tight Z-type NiMn2O4 / NiO composite photocatalyst, the adjustment to alkalinity refers to adjusting the pH to 9-10.

[0012] The above-described method for one-step in-situ preparation of interfacially compact Z-type NiMn2O4 / NiO composite photocatalyst involves a calcination temperature of 800℃ and a calcination time of 1.0–3.0 h.

[0013] Application of the interfacially compact Z-type NiMn2O4 / NiO composite photocatalyst prepared according to the above preparation method in the degradation of medical antibiotics under sunlight.

[0014] The above application is carried out as follows: Z-type NiMn2O4 / NiO composite photocatalyst is added to a solution containing antibiotics and irradiated under sunlight for 2.0 to 3.0 hours.

[0015] In any of the above applications, the medical antibiotic is a tetracycline antibiotic.

[0016] In the above application, the tetracycline antibiotic is chlortetracycline hydrochloride.

[0017] In the above application, the concentration of chlortetracycline hydrochloride is 15 mg / L.

[0018] The beneficial effects of this invention are as follows: This invention prepares Z-type NiMn2O4 / NiO photocatalysts via chemical precipitation and in-situ synthesis. The preparation method is simple, ingenious, low-cost, and yields a high composite catalyst. It enables the formation of a tight interface between NiMn2O4 and NiO nanoparticles, resulting in a well-formed crystal structure, which is beneficial for achieving a high yield of effective Z-type structures and improving the transmission efficiency of photogenerated electrons in the system. The construction of the tightly interfaced Z-type NiMn2O4 / NiO composite photocatalyst not only effectively utilizes sunlight but also increases the electron transport efficiency in the system. - -h + The improved separation efficiency enhances the system's redox capacity, thereby increasing its ability to photocatalytically degrade organic pollutants in water. Attached Figure Description

[0019] Figure 1 This is an X-ray diffraction pattern of NiMn2O4 nanoparticles.

[0020] Figure 2 This is an X-ray diffraction pattern of NiO nanoparticles.

[0021] Figure 3 This is the X-ray diffraction pattern of the NiMn2O4 / NiO composite photocatalyst. Detailed Implementation

[0022] Example 1

[0023] (I) A tightly interfacial Z-type NiMn2O4 / NiO composite photocatalyst, prepared by the following method:

[0024] First, mix MnCl2·4H2O and Ni(NO3)2·6H2O in a certain molar ratio (Ni 2+ :Mn 2+ =1.0:1.0, 1.5:1.0, 2.0:1.0) were dispersed in deionized water and magnetically stirred for 30 min until completely dissolved. Next, an appropriate amount of 1.0 mol / L NaOH solution was added dropwise to each of the above solutions until the precipitate was completely formed. After magnetic stirring for 1.0 h, the mixture was allowed to stand, and the precipitate was collected and mixed. The precipitate mixture was thoroughly stirred to homogenize, the pH was adjusted to 9-10, and then filtered. The filtered mixed precipitate was dried at 80℃ for 12 h. After drying, the powder was uniformly ground and calcined in a muffle furnace. Calcination was performed at 800℃ for 1.0 h, 2.0 h, and 3.0 h, respectively, to obtain the product (Ni). 2+ :Mn 2+ =1.5:1.0) are respectively labeled as NiMn2O4 / NiO(800-1), NiMn2O4 / NiO(800-2), and NiMn2O4 / NiO(800-3).

[0025] (II) Comparative Example

[0026] Preparation of NiO nanoparticles: First, weigh 2.908 g of Ni(NO3)2·6H2O and dissolve it in 50 mL of distilled water. Stir continuously for 30 min until completely dissolved. Add an appropriate amount of 1.0 mol / L NaOH solution dropwise until the precipitate is completely formed. Stir magnetically for 1.0 h and let stand. After complete precipitation, remove the supernatant. Wash the precipitate with distilled water until the pH of the washing solution is 9-10. Centrifuge and collect the precipitate. Dry the collected precipitate at 80 °C for 12 h. Grind the dried powder evenly in a mortar. Place the uniform powder into a crucible and calcine it in a muffle furnace at 800 °C for 1.0 h to obtain NiO nanoparticles.

[0027] Preparation of NiMn2O4 nanoparticles: MnCl2·4H2O and Ni(NO3)2·6H2O were mixed in a molar ratio (Ni 2+ :Mn 2+ The solutions (ratio 1.0:2.0) were dispersed separately in deionized water and magnetically stirred for 30 min until completely dissolved. Further, a suitable amount of 1.0 mol / L NaOH solution was added dropwise to each solution until complete precipitation. The mixture was magnetically stirred for 1.0 h and allowed to stand, allowing the precipitate to form. This precipitate was collected and mixed. The precipitate mixture was thoroughly stirred to ensure homogeneity, and the pH was adjusted to 9-10 before filtration. The filtered precipitate mixture was dried at 80℃ for 12 h. After drying, the powder was uniformly ground and calcined in a muffle furnace at 800℃ for 1.0 h to obtain NiMn2O4 nanoparticles.

[0028] (III) Characterization of Catalysts

[0029] Figure 1 The images show the XRD patterns of NiMn2O4 nanoparticles prepared in a comparative manner. Figure 1 As shown, the characteristic peaks of NiMn2O4 are obvious and sharp, and consistent with the standard card (JCPDS 01-1110). This result indicates that the present invention successfully prepared NiMn2O4 nanoparticles with good crystal structure.

[0030] Figure 2 These are the XRD patterns of NiO nanoparticles prepared in a comparative manner. Figure 2 As shown, the characteristic peaks of NiO are obvious and sharp, and correspond one-to-one with the standard card (JCPDS 47-1049), indicating that NiO nanoparticles were successfully prepared and have good crystal structure.

[0031] Figure 3 This is the XRD pattern of a tightly interfaced Z-type NiMn2O4 / NiO composite photocatalyst. (Example:) Figure 3 As shown, characteristic peaks belonging to NiMn2O4 and NiO nanoparticles can be observed, indicating that the present invention successfully prepared a NiMn2O4 / NiO composite photocatalyst with a good crystal structure.

[0032] Example 2: Application of tightly interfacial Z-type NiMn2O4 / NiO composite photocatalyst in the degradation of medical antibiotics under sunlight (I) Effect of different molar ratios of catalyst on the degradation of chlortetracycline hydrochloride

[0033] Experimental Methods: A 300W xenon lamp was used as a simulated solar light source. 1.0 g / L NiMn2O4 / NiO composite photocatalyst was added to 100 mL of a CTC solution with an initial concentration of 15 mg / L. The solution was irradiated under simulated sunlight for 3.0 h. After centrifugation, the supernatant was collected, filtered, and its absorbance was measured. The degradation rate of CTC was calculated based on the absorbance. The results are shown in Table 1.

[0034] Degradation rate (%) = (1-C) t / C0)×100% (where C0: the concentration of CTC in the stock solution; C t (The concentration of CTC in the sample).

[0035] Table 1 Effect of different catalyst molar ratios on the degradation rate of chlortetracycline hydrochloride

[0036]

[0037] Table 1 shows the molar ratio (Ni) 2+ :Mn 2+ When the ratio of NiMn2O4 to NiO is 1.5:1.0, the prepared composite photocatalyst has the best effect on CTC degradation, and can degrade 78.82% of CTC in 3.0 h under simulated sunlight.

[0038] (II) Effect of different calcination times of catalyst on the degradation of chlortetracycline hydrochloride

[0039] Experimental Methods: A 300W xenon lamp was used as a simulated solar light source. NiMn₂O₄ / NiO composite photocatalysts calcined for 1.0 h, 2.0 h, and 3.0 h were added to 100 mL of CTC solution with an initial concentration of 15 mg / L. The dosage of the composite photocatalyst was 1.0 g / L. After irradiation under simulated sunlight for 3.0 h, the supernatant was collected by centrifugation, filtered, and its absorbance was measured. The degradation rate of CTC was calculated based on the absorbance. The results are shown in Table 2.

[0040] Table 2 Effect of catalyst calcination time on degradation rate of chlortetracycline hydrochloride

[0041]

[0042] As shown in Table 2, the NiMn2O4 / NiO(800-1) composite photocatalyst prepared with a calcination time of 1.0 h showed the best degradation effect on CTC, with a degradation rate of 78.82%.

[0043] (III) Effects of different catalysts on the degradation of chlortetracycline hydrochloride

[0044] Experimental Method: Equal masses of NiMn₂O₄, NiO, and NiMn₂O₄ / NiO(800-1) photocatalysts were added to 100 mL of a CTC solution with an initial concentration of 15 mg / L, with each catalyst added at a concentration of 1.0 g / L. The solution was irradiated under simulated sunlight for 3.0 h, centrifuged, and the supernatant was collected. The supernatant was then filtered, and its absorbance was measured. The degradation rate of CTC was calculated based on the absorbance. The results are shown in Table 3.

[0045] Table 3. Effects of different catalysts on the degradation rate of chlortetracycline hydrochloride

[0046]

[0047] As shown in Table 3, compared with NiMn2O4 and NiO monomer photocatalysts, the Z-type NiMn2O4 / NiO(800-1) composite photocatalyst with a tight interface prepared in this invention exhibits the best degradation effect on CTC pollutants, achieving a degradation rate of 78.82% after 3.0 hours of simulated sunlight irradiation. These results indicate that the in-situ constructed Z-type NiMn2O4 / NiO possesses high photocatalytic activity. The tight interface facilitates electron transfer between systems, thereby enabling the NiMn2O4 / NiO composite photocatalyst to exhibit high redox capacity.

[0048] (iv) Effect of illumination time on the degradation rate of chlortetracycline hydrochloride

[0049] Experimental Methods: A 300W xenon lamp was used as a simulated solar light source. 1.0 g / L NiMn₂O₄ / NiO(800⁻¹) composite photocatalyst was added to 100 mL of a CTC solution with an initial concentration of 15 mg / L. Under simulated sunlight, 3.0 mL of CTC solution was extracted every 30 min, centrifuged, filtered, and its absorbance was measured. The degradation rate of CTC was calculated based on the absorbance. The results are shown in Table 4.

[0050] Table 4. Effect of illumination time on the degradation rate of chlortetracycline hydrochloride

[0051]

[0052] As shown in Table 4, the degradation degree of CTC by the NiMn2O4 / NiO(800-1) composite photocatalyst increases with the increase of irradiation time. When irradiated for 180 min, the degradation degree of CTC is the largest, and the degradation rate can reach 78.82%.

[0053] (V) The effect of catalyst recycling on the degradation of chlortetracycline hydrochloride

[0054] Experimental Methods: A 300W xenon lamp was used as a simulated solar light source. 1.0 g / L NiMn2O4 / NiO(800-1) composite photocatalyst was added to 100 mL of a CTC solution with an initial concentration of 15 mg / L. The solution was irradiated under simulated sunlight for 3.0 h. The supernatant was collected by centrifugation and then filtered to measure its absorbance. The catalyst was then collected, rinsed, and boiled to remove residual CTC molecules from its surface. Finally, the catalyst was dried for the next experiment. This experiment was repeated 5 times to obtain the degradation of CTC by the NiMn2O4 / NiO(800-1) composite photocatalyst after different usage cycles. The results are shown in Table 5.

[0055] Table 5. Effect of catalyst usage frequency on the degradation of chlortetracycline hydrochloride

[0056]

[0057] As shown in Table 5, the degradation rate of CTC by the composite photocatalyst NiMn2O4 / NiO(800-1) was still as high as 70.15% after being reused 5 times, indicating that the tightly packed Z-type NiMn2O4 / NiO(800-1) composite photocatalyst constructed in situ in this study has high reusability.

[0058] In the above embodiments, the medical antibiotic used is chlortetracycline hydrochloride, but this does not limit the antibiotic degraded by the present invention to chlortetracycline hydrochloride. The method of the present invention is applicable to the degradation of medical antibiotics and dye wastewater, etc.

Claims

1. A method for one-step in-situ preparation of interfacially compact Z-type NiMn2O4 / NiO composite photocatalysts, characterized in that, Includes the following steps: (1) A certain proportion of MnCl2·4H2O and Ni(NO3)2·6H2O were dispersed in distilled water, stirred thoroughly, and then a certain amount of NaOH solution was added to each. After stirring for 1.0 h, precipitates were obtained. The optimal molar ratio was Ni 2+ :Mn 2+ =1.0~2.0:1.0; (2) After the precipitate is evenly mixed, it is washed, the pH is adjusted to 9-10, centrifuged, filtered and collected, and dried at 80℃ for 12 h; (3) After the dried mixed precipitate powder is uniformly ground, it is calcined at 800 °C for 1.0 ~ 3.0 h to obtain the target product NiMn2O4 / NiO.

2. The method for one-step in-situ preparation of interfacially compact Z-type NiMn2O4 / NiO composite photocatalyst according to claim 1, characterized in that, In step (1), the optimal molar ratio, Ni 2+ :Mn 2+ =1.5:1.

0.

3. The application of the interfacially compact Z-type NiMn2O4 / NiO composite photocatalyst prepared according to any one of claims 1-2 in the degradation of medical antibiotics by sunlight.

4. The application according to claim 3, characterized in that, The method is as follows: Add Z-type NiMn2O4 / NiO composite photocatalyst to a solution containing antibiotics and irradiate it under sunlight for 2.0 ~ 3.0 h.

5. The application according to claim 4, characterized in that, The medical antibiotics mentioned are tetracycline antibiotics.

6. The application according to claim 5, characterized in that, The tetracycline antibiotic in question is chlortetracycline hydrochloride.

7. The application according to claim 6, characterized in that, The concentration of chlortetracycline hydrochloride is 15 mg / L.

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