In-situ preparation method of ZnFe2O4 / foamed zinc-nickel for efficiently purifying gaseous benzene

Abstract

The invention belongs to material preparation and efficient removal of volatile organic pollutants (VOCs), and particularly relates to an in-situ preparation method of ZnFe2O4 / foamed zinc nickel for efficiently purifying gaseous benzene. Foamed zinc-nickel is adopted as a zinc source, ZnO grows on the foamed zinc-nickel in situ through a hydrothermal method, and then the ZnFe2O4 / foamed zinc-nickel photocatalyst is prepared through calcination and is used for degrading gaseous benzene; results show that the ZnFe2O4 / foamed zinc-nickel has a degradation rate of 99.8% and a mineralization rate of 99.7% for 600 ppm of benzene within 20 min under simulated sunlight irradiation, meanwhile, the material has good cycle stability and can be used as a long-acting treatment material for gaseous benzene, and the foamed zinc-nickel used in the invention can improve the defects of difficult recovery and poor reusability of a traditional powder catalyst on one hand, and can also be used as a catalyst for treating gaseous benzene on the other hand; on the other hand, the foamed zinc nickel is used as a zinc source for in-situ growth of the ZnFe2O4 / foamed zinc nickel photocatalyst, the preparation process is simple, environment-friendly and long-term stable, and gaseous benzene in a wide concentration range can be efficiently and rapidly removed, so that the ZnFe2O4 / foamed zinc nickel photocatalyst has a good application prospect in removal of benzene and related VOCs gas pollutants in indoor and industrial emission environments and the like.

Description

Technical Field

[0001] The invention relates to a synthesis method for preparing ZnFe2O4 / foamed zinc nickel by in-situ growth of ZnFe2O4 in zinc nickel foam and its application in efficient degradation of gaseous benzene. The invention relates to the field of gas pollution treatment in engineering and the field of material synthesis and photocatalysis in technology. Background Art

[0002] Volatile organic compounds (VOCs) refer to organic compounds with a boiling point of 50~260℃ at room temperature and a saturated vapor pressure of 133.33 Pa. Most VOCs are easily combined with other gaseous pollutants in the atmosphere (such as SO x 、NO x ) forms secondary pollution, causes photochemical smog, destroys the atmospheric ozone layer, and affects the global environment. At the same time, some VOCs are carcinogenic, irritating to the human eyes, cardiovascular system, lungs, and liver, and toxic to the nervous system.

[0003] The United States Environmental Protection Agency (USEPA) has listed benzene (a typical aromatic volatile organic compound) as a hazardous pollutant and human carcinogen (Group A). ​​The increasing emission of benzene has caused serious threats to the environment and human health. In view of the harm of benzene to the environment and health, it is necessary to develop sustainable and efficient technologies to treat it, such as incineration, adsorption and photocatalysis. Photocatalytic oxidation is considered to be a promising option for removing benzene, which converts benzene into environmentally friendly end products through a cheap and green catalytic pathway.

[0004] Traditional semiconductor photocatalysts only respond to ultraviolet light (such as TiO2), and traditional powder catalysts are very easy to agglomerate, resulting in the recombination of photogenerated carriers, which inhibits the photocatalytic activity. The low sunlight utilization rate and high electron recombination rate directly lead to incomplete mineralization of gaseous benzene, thereby producing highly toxic by-products.

[0005] The ZnFe2O4 / foamed zinc-nickel photocatalyst uses foamed zinc-nickel as a zinc source and replaces Zn with dilute hydrochloric acid. 2+ , further adding sucrose to functionalize the composite material to carry more hydroxyl groups, helps to disperse the electrons of benzene, makes the stable benzene ring easier to open, and in the process of photocatalytic degradation of benzene, can quickly and efficiently degrade benzene and decompose it into water and carbon dioxide; the present invention solves the problems of difficulty in opening benzene rings and difficulty in recycling powder catalysts, and provides a new solution for the purification of benzene pollutants in the air.

[0006] The specific technical solutions of the present invention are as follows: Step 1: Pretreatment of zinc nickel foam: The foamed zinc-nickel was cut into pieces, the surface was rinsed with water twice, then immersed in 30 mL of ethanol and ultrasonically treated for 20 min to remove surface impurities, and then dried for later use; Step 2: Preparation of precursor ZnO / foamed zinc nickel: The cleaned zinc-nickel foam was placed in 0.167 M dilute hydrochloric acid to displace the Zn 2+ , then 5 mmol sucrose and 1.25 mmol urea were added, and the mixture was hydrothermally heated at 180 °C for 20 h, cooled, cleaned, and dried to obtain ZnO / foamed zinc-nickel. By adding different concentrations of dilute hydrochloric acid (0.03, 0.067, 0.1, 0.13, 0.167, 0.2 M), the concentration of zinc ions was controlled to be 1 mmol, 2 mmol, 3 mmol, 4 mmol, 5 mmol, and 6 mmol, respectively, to prepare ZnO / foamed zinc-nickel with different ZnO contents, named xZnO / foamed zinc-nickel, where x represents the amount of zinc ions, which are 1 mmol, 2 mmol, 3 mmol, 4 mmol, 5 mmol, and 6 mmol, respectively. Step 3, preparation of ZnFe2O4 / foamed zinc-nickel photocatalyst: The precursor 5ZnO / foam zinc nickel solution after hydrothermal treatment in step 2 was transferred to a beaker, and 10 mmol ferric nitrate and 20 mL 13.2 M ammonia water were added thereto. After standing, washing and drying, the solution was placed in a tube furnace and calcined at 450 °C for 4 h under a nitrogen atmosphere to obtain 5ZnFe2O4 / foam zinc nickel, named 5ZFO / ZNF. According to the same steps, different proportions of precursors 1ZnO / foam zinc nickel, 2ZnO / foam zinc nickel, 3ZnO / foam zinc nickel, 4ZnO / foam zinc nickel, and 6ZnO / foam zinc nickel were used, and 2 mmol, 4 mmol, 6 mmol, 8 mmol, and 12 mmol ferric nitrate were added respectively to prepare ZnFe2O4 / foam zinc nickel in different proportions, named 1ZFO / ZNF, 2ZFO / ZNF, 3ZFO / ZNF, 4ZFO / ZNF, and 6ZFO / ZNF.

[0007] Figure 1 Figure 1 is the XRD spectra of ZnFe2O4 / foam zinc-nickel with different proportions, indicating that the method successfully prepared ZnFe2O4 / foam zinc-nickel; in the figure, 1ZnO / ZNF, 2ZnO / ZNF, 3ZnO / ZNF, 4ZnO / ZNF, 5ZnO / ZNF, and 6ZnO / ZNF represent ZnO / foam zinc-nickel with different molar ratios, respectively, and their corresponding calcined products are represented as 1ZFO / ZNF, 2ZFO / ZNF, 3ZFO / ZNF, 4ZFO / ZNF, 5ZFO / ZNF, and 6ZFO / ZNF, respectively.

[0008] Figure 2 Scanning electron microscope images of the prepared samples, a and b are pure phase zinc nickel foam with a three-dimensional porous structure, c and d are pure phase ZnFe2O4, showing a stacked block structure, e and f are 5ZnO / zinc nickel foam, nanoflower-like ZnO composed of thin sheets is in situ grown on the zinc nickel foam; g and h are the morphology of 5ZnFe2O4 / zinc nickel foam, and blocky ZnFe2O4 grows on the three-dimensional skeleton of zinc nickel foam.

[0009] Figure 3 a is the photocatalytic degradation effect of different ratios of ZnFe2O4 / foamed zinc nickel on 600 ppm benzene. As the content of ZnFe2O4 increases, the degradation effect of benzene is significantly improved; Figure 3 b is the mineralization rate of 5ZnFe2O4 / foam zinc-nickel and the production rates of CO2 and CO. The degradation rate of 5ZnFe2O4 / foam zinc-nickel for 600 ppm of benzene within 20 min is 99.8%, and the mineralization rate is 99.7%.

[0010] Figure 4 This is a cyclic test of the degradation of benzene by 5ZnFe2O4 / foam zinc nickel. After 32 cycles of testing, the degradation of benzene by 5ZnFe2O4 / foam zinc nickel did not decrease significantly, indicating that the catalyst has excellent performance in degrading benzene and good cyclic stability.

[0011] Figure 5 This is the degradation effect diagram of 5ZnFe2O4 / foamed zinc-nickel on benzene of different concentrations. It has excellent degradation performance for benzene in the concentration range of 200-2000ppm.

[0012] Figure 6 In-situ diffuse reflectance Fourier transform infrared spectrum of 5ZnFe2O4 / foamed zinc nickel to 600 ppm benzene; Figure 6 a is the in-situ infrared image of the adsorption of benzene on 5ZnFe2O4 / foam zinc nickel under dark reaction conditions. As time goes by, the characteristic peak of benzene continues to increase. Figure 6 bd is the in situ DRIFTs spectrum of photocatalytic degradation of benzene, located at 2093 and 3046 cm -1 The characteristic peaks at 1494 and 1482 cm-1 belong to the CH stretching vibration of the phenyl aromatic ring. -1 The characteristic peaks at 1068-1024 cm are related to the skeleton stretching vibration and C=C stretching vibration of the aromatic ring. -1 The above characteristic peaks gradually decrease with the increase of photocatalytic reaction time; then, the intermediate products of benzene degradation, such as phenols (1614-1575 cm -1 ), benzoquinone (1698,1660 cm -1), maleic acid species (1546, 1530, 1511, 1315 cm -1 ) and acetate (1338 cm -1 ) gradually increased, and the final product was CO2 (2339, 2357 cm -1 ).

[0013] The present invention will be further described below with reference to embodiments: Embodiment 1

[0014] In this example, a 3×3 cm zinc-nickel foam was used for the experiment. The Zn 2+ The precursor ZnO / foamed zinc nickel was prepared by hydrothermal method, and then calcined to prepare ZnFe2O4 / foamed zinc nickel photocatalyst for the degradation of gaseous benzene. The prepared photocatalyst was placed in a closed reactor and purged with nitrogen to remove carbon dioxide in the air. The gaseous benzene was transferred to the reaction device by air bubbling method, and a 300 W xenon lamp was used as the light source of simulated sunlight. The concentration of gaseous benzene was adjusted by gas flow rate and injection volume. The concentration change of gaseous benzene in the reaction gas and the concentration change of the product (the main product is CO2, followed by a small amount of CO) were detected by a gas infrared detector. The concentration of gaseous benzene was changed to evaluate the degradation of benzene in a wide range of concentrations by the photocatalyst. Under simulated sunlight, the degradation rate of 5ZnFe2O4 / foamed zinc nickel photocatalyst for benzene with an initial concentration of 600 ppm was 99.8% in 20 min, and the mineralization rate was 99.7%.

Claims

1. An in-situ preparation method of ZnFe2O4 / foamed zinc-nickel for efficient purification of gaseous benzene, characterized in that: It includes the following steps: Preparation of ZnFe2O4 / foam zinc nickel: Step 1: Pretreatment of zinc nickel foam: Cut the zinc nickel foam into small pieces of 3×3 cm², rinse the surface with water twice, and then wash the zinc nickel foam in ethanol for 30 min under ultrasonic conditions to remove surface impurities, and dry it in an oven at 60 ℃ for later use; Step 2: Preparation of precursor ZnO / foamed zinc nickel: The cleaned zinc-nickel foam is placed in dilute hydrochloric acid to displace Zn 2+ Then, a certain amount of sucrose and urea were added, and the mixture was fully stirred and hydrothermally reacted at 180 °C for 20 h. The foamed zinc-nickel after hydrothermal reaction was alternately washed with water and ethanol for several times, and dried to obtain ZnO / foamed zinc-nickel. Step 3, preparation of ZnFe2O4 / foamed zinc-nickel catalyst: The precursor solution after hydrothermal treatment in step 2 was transferred to a beaker, to which a certain amount of ferric nitrate and 20 mL 13.2 M ammonia solution were added. After standing with magnetic stirring, washing and drying, the solution was heated to 450 °C in a N2 atmosphere and calcined for 4 h to obtain ZnFe2O4 / foamed zinc nickel.

2. Application of ZnFe2O4 / foamed zinc-nickel catalyst prepared according to claim 1 in efficient degradation of gaseous benzene The prepared ZnFe2O4 / foam zinc-nickel catalyst was placed in a closed reactor connected to an air circulation device. Before the reaction, the reactor was purged with nitrogen to remove carbon dioxide in the air. Gaseous benzene was brought into the reaction device by air bubbling, and the benzene concentration was adjusted by the gas flow rate. A 300 W xenon lamp was used as a light source to simulate sunlight, and an infrared photoacoustic spectrometer was used to detect the concentration changes of gaseous benzene and generated carbon dioxide in the reaction gas, and the catalytic activity of the catalyst for different benzene concentrations was evaluated.

3. The method for preparing ZnFe2O4 / foamed zinc-nickel according to claim 1, characterized in that: Foamed zinc nickel was used as a catalyst carrier and zinc source, and ferric nitrate and ammonia were added to grow ZnFe2O4 by an in-situ method, thereby preparing a ZnFe2O4 / foamed zinc nickel photocatalyst.

4. The method for preparing ZnFe2O4 / foamed zinc-nickel according to claim 1, characterized in that: During the preparation process, the addition of sucrose and ammonia water allows the catalyst to carry a large number of hydroxyl and amino groups, which is beneficial to the transfer of electrons from benzene and makes it easier for benzene to open its ring.

5. Application of ZnFe2O4 / foamed zinc-nickel prepared by the preparation method according to claim 1 in purifying gaseous benzene, characterized in that: The prepared ZnFe2O4 / foamed zinc-nickel can efficiently degrade benzene in a concentration range of 200-2000ppm under simulated sunlight, achieving complete mineralization, and the products are carbon dioxide and water.

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