A ZnO-ZnMnO3 catalyst and its preparation method and application

Abstract

The present invention discloses a ZnO-ZnMnO3 catalyst and its preparation method and application. The preparation method is as follows: first, zinc salt and manganese salt are dissolved in deionized water, then sodium hydroxide solution is added, and then an appropriate amount of hydrogen peroxide is added to form a suspension. The suspension obtains a precursor through a hydrothermal reaction. The dried precursor is calcined at high temperature and ground to obtain a ZnO-ZnMnO3 catalyst. The obtained ZnO-ZnMnO3 can activate persulfate to treat antibiotic pollutants in sewage. The present invention prepares a ZnO-ZnMnO3 catalytic material through a hydrothermal and calcination method. It can activate persulfate (PMS) to effectively degrade a variety of common antibiotics. It has low operating costs, simple experimental operation, a green degradation process, and low secondary pollution.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment, and in particular relates to a ZnO-ZnMnO3 catalyst and a preparation method and application thereof. Background Art

[0002] In recent years, the high use of antibiotics in daily life and clinical medical research has led to antibiotic pollution. Therefore, solving this problem is imperative. Numerous methods for treating antibiotics have been studied. Among the numerous antibiotic removal methods, advanced oxidation processes (AOPs) have broad prospects for development due to their rapid reaction and high removal efficiency. Compared to traditional hydroxyl radical (·OH)-based advanced oxidation processes (HR-AOPs), persulfate (PMS) is activated to break the OO bond to form SO4· − Sulfate-based advanced oxidation processes (SR-AOPs) are considered to be antibiotic treatment methods with better removal efficiency, higher stability and milder operating conditions.

[0003] However, relying solely on PMS to degrade pollutants is far from sufficient. It requires the collaboration of other materials, such as catalytic materials, to achieve significant degradation effects. However, many single catalytic materials are ineffective in synergizing with PMS to degrade antibiotics, while some composite catalytic materials have shown better results. However, the preparation of composite catalytic materials is complex, tedious, and costly, and the catalytic degradation performance of the materials is significantly affected by the preparation conditions.

[0004] Among transition metal oxides, ZnO offers advantages such as simple preparation and low cost, and holds significant potential for development in applications such as ultraviolet light-emitting diodes, lasers, solar cells, and piezoelectric materials. Manganese, a transition metal element, is environmentally friendly, non-toxic, readily available, and exhibits excellent performance. This invention, inspired by the excellent CIP degradation efficiency demonstrated by the previously developed Mn3O4-ZnMn2O4 / SnO2 catalyst, provides an alternative catalyst capable of activating PMS to effectively degrade antibiotic contaminants. Summary of the Invention

[0005] The present invention provides a ZnO-ZnMnO3 catalyst and a preparation method and application thereof, aiming to solve the problems existing in the above-mentioned background technology.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for preparing a ZnO-ZnMnO3 catalyst comprises the following steps:

[0008] (1) Dissolving zinc salt and manganese salt with a molar ratio of Zn to Mn of 2:1 in deionized water to form solution A; dissolving sodium hydroxide in deionized water to form solution B; rapidly pouring solution B into solution A under stirring conditions, and then adding excess hydrogen peroxide to the mixture to form a suspension in order to oxidize low-valent manganese to high-valent manganese, and then placing the suspension in an autoclave for hydrothermal reaction. After the reaction is completed, the obtained product is washed several times by centrifugation with deionized water and ethanol and then dried to obtain a precursor;

[0009] (2) The precursor is heated and calcined in a tube furnace, cooled, and ground to obtain a ZnO-ZnMnO3 catalyst.

[0010] The above preparation method adopts a hydrothermal method and a calcination method, and the obtained ZnO-ZnMnO3 catalyst activated persulfate can effectively degrade multiple common antibiotics.

[0011] Preferably, the zinc salt is zinc nitrate hexahydrate, and the manganese salt is manganese chloride tetrahydrate.

[0012] Preferably, the hydrothermal reaction conditions are a hydrothermal temperature of 120-180°C and a holding time of 8-20 hours. The effects of hydrothermal reaction conditions on the properties of the product, ZnO-ZnMnO3, were experimentally analyzed to determine the optimal hydrothermal conditions for preparing the ZnO-ZnMnO3 catalyst. Experimental analysis determined that a hydrothermal temperature of 160°C and a holding time of 16 hours were optimal.

[0013] Preferably, the calcination conditions are a calcination temperature of 400-700°C, a heating rate of 5°C / min, and a calcination time of 1-4 hours. Experimental tests in the present invention have shown that the following calcination conditions are optimal: a calcination temperature of 600°C, a heating rate of 5°C / min, and a calcination time of 2 hours.

[0014] The prepared ZnO-ZnMnO3 catalyst demonstrated excellent performance in sewage treatment. The ZnO-ZnMnO3 catalyst can activate persulfate to degrade medical wastewater containing antibiotics (such as ciprofloxacin, tetracycline, bisphenol A, etc.) with high degradation efficiency and low secondary pollution.

[0015] Compared with the shortcomings and deficiencies of the prior art, the present invention has the following beneficial effects:

[0016] The present invention prepares a ZnO-ZnMnO3 catalyst through a simple hydrothermal and calcination method. Degradation tests show that the ZnO-ZnMnO3 catalyst, activated with persulfate, can effectively degrade a variety of common antibiotics, such as ciprofloxacin, tetracycline, and bisphenol A, and has a wide range of applications. Furthermore, the ZnO-ZnMnO3 catalyst has low toxicity and is unlikely to cause secondary environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the XRD diffraction pattern of ZnO, ZnMnO3, and ZnO-ZnMnO3 provided in the embodiments of the present invention.

[0018] Figure 2 This is a graph showing the degradation of ciprofloxacin by different degradation systems of the ZnO-ZnMnO3 catalyst provided in an embodiment of the present invention.

[0019] Figure 3 This is a diagram of the PMS degradation efficiency of ZnO-ZnMnO3 catalyzed at different catalyst dosages provided in an embodiment of the present invention.

[0020] Figure 4 This is a diagram showing the efficiency of ciprofloxacin degradation by ZnO-ZnMnO3 at different PMS addition amounts provided by the present invention.

[0021] Figure 5 This is a graph showing the degradation efficiency of different antibiotics by the ZnO-ZnMnO3 catalyst provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0023] 1. Preparation of ZnO-ZnMnO3 catalyst

[0024] Raw materials: zinc nitrate hexahydrate, manganese chloride tetrahydrate, sodium hydroxide, hydrogen peroxide, anhydrous ethanol, water.

[0025] 0.773 g of zinc nitrate hexahydrate and 0.257 g of manganese chloride tetrahydrate were dissolved in deionized water to form solution A. 0.312 g of sodium hydroxide was dissolved in deionized water to form solution B. Solution B was quickly poured into solution A under stirring, and 1 mL of hydrogen peroxide was added to form a suspension. The suspension was then transferred to a 100 mL polytetrafluoroethylene-lined stainless steel reactor for hydrothermal reaction and then removed. The product was washed several times with deionized water and ethanol by centrifugation and then dried. The dried product was then heated and sintered in a tube furnace and ground to obtain a ZnO-ZnMnO3 catalyst. The XRD patterns of ZnO, ZnMnO3, and the prepared ZnO-ZnMnO3 are shown in Figure 2. Figure 1 shown.

[0026] 2. Optimization of preparation conditions

[0027] (1) Optimization of hydrothermal reaction conditions:

[0028] a. Prepare ZnO-ZnMnO3 materials at different hydrothermal reaction temperatures (100°C, 120°C, 140°C, 160°C, 180°C, and 200°C) with a reaction time of 16 h. Sinter the materials at 600°C in air at a rate of 5°C / min for 2 h.

[0029] The ZnO-ZnMnO3 materials obtained at different hydrothermal temperatures were used to degrade ciprofloxacin solution. According to the degradation efficiency and stability, it was found that the degradation performance of the ZnO-ZnMnO3 materials prepared at hydrothermal reaction temperatures of 120℃, 140℃, 160℃ and 180℃ was better, while the degradation performance of the ZnO-ZnMnO3 materials prepared at hydrothermal reaction temperatures of 100℃ and 200℃ was poor. Therefore, the hydrothermal temperature should be selected from 120℃-180℃, with 160℃ being the best.

[0030] b. The hydrothermal reaction temperature was selected as 160°C, and the reaction times were selected as 8 h, 12 h, 16 h, 18 h, 20 h, and 24 h, respectively. The calcination conditions were set to heating and sintering at a rate of 5°C / min in air at 600°C for 2 h.

[0031] The ZnO-ZnMnO3 materials obtained at different reaction times were used to degrade ciprofloxacin solution. According to the degradation efficiency and stability, the suitable reaction times when the hydrothermal reaction temperature was 160℃ were 12 h, 16 h, and 18 h, and the optimal reaction time was 16 h.

[0032] (2) Optimization of calcination reaction conditions:

[0033] The hydrothermal reaction temperature was set to 160 °C, the reaction time was 16 h, and the calcination conditions were as follows:

[0034] Calcination at 300℃ for 2 h, calcination at 400℃ for 2 h, calcination at 500℃ for 1 h, calcination at 500℃ for 2 h, calcination at 600℃ for 2 h, calcination at 600℃ for 4 h, calcination at 700℃ for 2 h, and calcination at 800℃ for 2 h.

[0035] The obtained ZnO-ZnMnO3 materials were used to degrade ciprofloxacin solution respectively. According to the degradation efficiency and stability, the suitable calcination conditions were screened out as follows: calcination at 400℃ for 2 h, calcination at 500℃ for 1 h, calcination at 500℃ for 2 h, calcination at 600℃ for 2 h, calcination at 600℃ for 4 h, and calcination at 700℃ for 2 h, with calcination at 600℃ for 2 h being preferred.

[0036] 3. Degradation experiment of antibiotics in water

[0037] (1) Preparation of test materials: The raw materials are zinc nitrate hexahydrate, manganese chloride tetrahydrate, sodium hydroxide, hydrogen peroxide, anhydrous ethanol, and water. The hydrothermal reaction temperature is 160°C and the reaction time is 16 h; the calcination temperature is 600°C and the calcination time is 2 h to prepare ZnO-ZnMnO3 material.

[0038] Degradation experiment: Use a graduated cylinder to measure 100 mL of 10 mg·L -1 The ciprofloxacin solution was placed in a conical flask and the following 6 experiments were performed simultaneously, with the following degradation materials added:

[0039] ① No addition, blank group;

[0040] ② 30mg persulfate (PMS);

[0041] ③ 30mg ZnO + PMS;

[0042] ④ 30mg ZnMnO3+ PMS;

[0043] ⑤ 30mg ZnO-ZnMnO3+ PMS;

[0044] ⑥30mg ZnO-ZnMnO3.

[0045] Each experimental group was placed on a magnetic stirrer, the speed was adjusted to a certain level, and samples were taken at specific intervals. After sampling, the absorbance was measured using a UV spectrophotometer. The results were as follows: Figure 2 As shown, the degradation rate of ciprofloxacin was calculated by absorbance, degradation rate = (1-C / C0) × 100%.

[0046] Depend on Figure 2 As can be seen, the blank group had almost no degradation effect on ciprofloxacin. The experimental groups adding only PMS and ZnO or ZnMnO3 materials showed some degradation of ciprofloxacin, but the degradation efficiency was very low. However, the experimental groups adding ZnO-ZnMnO3 and PMS significantly improved the degradation efficiency of ciprofloxacin, reaching approximately 70% after 90 minutes of degradation, achieving good results. This shows that after adding PMS, the ZnO-ZnMnO3 material activates persulfate (PMS), promotes the generation of active free radicals, and improves the degradation efficiency of pollutants in water.

[0047] (2) Experimental analysis of the effects of the amount of ZnO-ZnMnO3 material and PMS on the degradation effect during the degradation process:

[0048] First, the effect of the dosage of ZnO-ZnMnO3 material on the degradation efficiency was experimentally studied. 30 mg, 50 mg, 60 mg, 70 mg, and 80 mg of ZnO-ZnMnO3 were used as degradation materials, ciprofloxacin solution was used as the solution to be degraded, and 30 mg of PMS was added to carry out degradation experiments. After sampling, the sample absorbance was measured by ultraviolet spectrophotometer. The results are as follows: Figure 3 As shown in the figure, the amount of ZnO-ZnMnO3 material has a certain influence on the degradation efficiency. The degradation efficiency is the best when the amount of ZnO-ZnMnO3 material is 70 mg. ZnO-ZnMnO3 can catalyze PMS to produce SO4 with strong oxidizing properties. − and •OH react with pollutants and then degrade them into small molecules of CO2 and H2O.

[0049] Secondly, the effect of the amount of PMS on the degradation efficiency was experimentally studied. 70 mg ZnO-ZnMnO3 was used as the catalytic degradation material, ciprofloxacin solution was used as the solution to be degraded, and 5 mg, 10 mg, 20 mg, 30 mg, and 40 mg PMS were added to perform degradation experiments. After sampling, the sample absorbance was measured by ultraviolet spectrophotometer. The results are shown in Figure 2. Figure 4 As shown in the results, the PMS dosage has an impact on the degradation effect, and when the PMS dosage exceeds 10 mg / L, the degradation effect decreases with the increase of the dosage. This may be because the excessive PMS causes autolysis.

[0050] (3) Degradation tests were conducted on different antibiotics. Other test conditions remained unchanged. 70 mg ZnO-ZnMnO3 and 10 mg PMS were added to the solution. Tetracycline and bisphenol A were selected as pollutants. The results are shown in Figure 2. Figure 5 As shown, the degradation effects of tetracycline and bisphenol A were good, at 93.52% and 98.55%, respectively. ZnO-ZnMnO3 has low toxicity, minimal secondary pollution, and simple operation during the wastewater degradation process. Therefore, the ZnO-ZnMnO3 catalyst prepared by the present invention has broad application prospects.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Application of a ZnO-ZnMnO3 catalyst in the treatment of sewage containing antibiotic pollutants by activating persulfate, characterized in that: The preparation method of the ZnO-ZnMnO3 catalyst comprises the following steps: (1) Dissolving zinc salt and manganese salt with a molar ratio of Zn to Mn of 2:1 in deionized water to form solution A, and dissolving sodium hydroxide in deionized water to form solution B; rapidly pouring the solution B into the solution A under stirring conditions, then adding excess hydrogen peroxide to the mixture to form a suspension, and then placing the suspension in an autoclave for hydrothermal reaction, wherein the conditions of the hydrothermal reaction are: hydrothermal temperature of 120-180°C, and heat preservation for 8-20 hours; after the reaction, the obtained product is washed several times with deionized water and ethanol by centrifugation and then dried to obtain a precursor; (2) The precursor is dried and then calcined at a high temperature. The calcination conditions are as follows: calcination temperature of 400-700°C, heating rate of 5°C / min, and calcination time of 1-4 h to obtain a ZnO-ZnMnO3 catalyst.

2. The use according to claim 1, characterized in that The zinc salt is zinc nitrate hexahydrate, and the manganese salt is manganese chloride tetrahydrate.

3. The use according to claim 1, characterized in that The conditions of the hydrothermal reaction are: hydrothermal temperature 160° C., and heat preservation for 16 h.

4. The use according to claim 1, wherein The calcination conditions are as follows: calcination temperature is 600° C., heating rate is 5° C. / min, and calcination time is 2 h.

5. The use according to claim 1, characterized in that The antibiotic pollutants include ciprofloxacin, tetracycline or bisphenol A.

Images