CN106517341A - Method for preparing manganese dioxide nano-catalyst and application thereof - Google Patents

Abstract

The invention discloses a method for preparing α- _MnO2 nanometer catalyst and its application. The invention synthesizes and obtains _MnO2 nanometer material through a two-step method. Firstly, the precursor δ-MnO ₂ is obtained through the self-decomposition of potassium permanganate under alkaline conditions. Then GO was added to the sonicated δ-MnO ₂ for sonication, and transferred to a muffle furnace for 24 hours to obtain the final α-MnO ₂ nanomaterial. The advantages of the present invention are: 1. The present invention is the first synthesis of nanofibrous _MnO2 catalyst. 2. The catalyst of the present invention has a better ability to degrade organic pollutants, can catalyze the self-decomposition of PMS, and generate a large amount of •OH and SO ₄ ^• ¯ free radicals, thereby improving the degradation efficiency of p-nitrophenol. 3. The preparation method of the catalyst mentioned in the present invention is simple and easy, the production cost is low, and the yield and purity are high. The _MnO2 nanofibers synthesized by hydrothermal method are a kind of homogeneous morphology, high specific surface area and high thermal stability. good catalyst.

Description

A kind of method and application thereof for preparing manganese dioxide nano-catalyst

technical field

The invention relates to a method for preparing manganese dioxide nanometer catalyst and its application.

Background technique

In recent years, the rapid development of industry has not only driven the growth of the national economy, but also led to the frequent occurrence of water pollution disasters. The pollution of water resources is one of the most prominent environmental problems, and it is also one of the problems that countries all over the world are currently facing and need to be solved urgently. After entering the water body, different kinds of multi-organic pollutants are not easy to decompose and can exist in the water body stably for a long time. Most of them are toxic in themselves. The effect of "three effects" poses a huge threat to human health. For these refractory organic pollutants, especially persistent organic pollutants (POPs), it is difficult to remove them by traditional physical, chemical and biological treatment processes. Therefore, how to efficiently synthesize catalysts with excellent performance and efficiently remove a large number of POPs existing in the environment is the focus of current research. The problem of water pollution in the environment is not only a problem in our country, it is an important problem that is difficult to solve in other countries and even in the world.

Manganese dioxide is a class of manganese oxides with many excellent chemical properties. It has a rich crystal structure and variable valence states. α-MnO ₂ is a black fluffy substance composed of MnO ₆ as a structural unit, which has a one-dimensional octahedral tunnel structure. The morphology of α-MnO ₂ nanofibers is of great help to the improvement of the degradation rate of organic matter.

The hydrothermal synthesis method is under subcritical and supercritical hydrothermal conditions. Because the reaction is at the molecular level, the reactivity is improved, so the hydrothermal reaction can replace some high-temperature solid-state reactions. And because the homogeneous nucleation and heterogeneous nucleation mechanism of hydrothermal reaction is different from the diffusion mechanism of solid phase reaction, new compounds and new materials that cannot be prepared by other methods can be created. The advantage of the hydrothermal synthesis method is that the obtained product has high purity, good dispersibility, and easy control of particle size. However, the present invention makes good use of the advantages of the hydrothermal synthesis method, and successfully synthesizes a catalyst α-MnO ₂ with strong uniformity and good stability.

Contents of the invention

The purpose of the present invention is to provide a method for preparing manganese dioxide nano-catalyst and its application, which provides a more efficient material for degrading persistent organic pollutants (POPs), and effectively improves the degradation efficiency of POPs and the efficiency of POPs. degree of mineralization.

The present invention is realized in this way, a kind of method for preparing manganese dioxide nano-catalyst, preparation α-MnO ₂ nano-catalyst, this catalyst is obtained by the synthesis of simple and easy two-step method, first obtains δ- MnO ₂ , and then convert δ-MnO ₂ into α-MnO ₂ through hydrothermal reaction, and α-MnO ₂ has better crystallinity, larger specific surface area, and better degradation of persistent organic pollutants Ability; It is characterized in that the method steps are as follows:

(1) Preparation of δ-MnO ₂ : Weigh 15-18 grams of KOH and dissolve in 50-100 ml of ethanol and water mixed solution, the volume ratio of ethanol and water is 1:1, stir well to obtain solution A. Weigh 4-8 grams of potassium permanganate and dissolve it in 20-40 ml of deionized water, and stir well to obtain solution B. Slowly add solution A dropwise to solution B, and mix well to react. Vacuum suction filtration, drying in an 80-degree blast drying oven for 6-12 hours to obtain δ-MnO ₂ .

(2) Preparation of α-MnO ₂ : Weigh 250 mg of the dried sample in (1) and dissolve it in 65-85 ml of deionized water, sonicate for 10-40 minutes; add 10-20 ml of 2.3 g/L graphite oxide Alkene, ultrasonic for 10-40 minutes; put the obtained solution into a polytetrafluoroethylene reactor, put it in a muffle furnace at 150-200°C for hydrothermal reaction for 24-40 hours. The hydrothermally synthesized substance is subjected to vacuum filtration, washed with deionized water several times, and put into a vacuum drying oven for drying to obtain α-MnO ₂ .

The advantages of the present invention are: 1. The catalyst of the present invention is nanofiber-like MnO ₂ . 2. The catalyst of the present invention has a better effect of degrading organic pollutants. In the field of advanced oxidation, MnO ₂ can catalyze the self-decomposition of PMS, producing a large amount ^of OH and SO ₄ ¯ free radicals, thereby effectively improving the efficiency of nitro Phenol degradation efficiency. 3. The preparation method of the present invention is simple and easy, the production cost is low, and the yield and purity are high. The synthesized _MnO2 nanofiber is a catalyst with strong uniformity in shape, high specific surface area and good thermal stability.

Description of drawings

Fig. 1 is a comparison diagram of X-ray powder diffraction of the α-MnO ₂ catalyst of the present invention and the precursor δ-MnO ₂ .

Fig. 2 is a scanning electron micrograph of the α-MnO ₂ catalyst of the present invention.

Fig. 3 is a comparison diagram of the degrading effect of the α-MnO ₂ catalyst of the present invention and the precursor δ-MnO ₂ catalyst under various conditions in degrading p-nitrophenol.

Fig. 4 is a full-band scanning diagram of the filtrate at different sampling times when the α- _MnO2 catalyst of the present invention degrades p-nitrophenol.

detailed description

The embodiments of the present invention will be described in further detail below in conjunction with the accompanying drawings, but the present embodiments are not intended to limit the present invention, and any similar structures and similar changes of the present invention should be included in the protection scope of the present invention.

Synthesis of catalyst material of the present invention:

(1) Preparation of δ-MnO ₂ : Weigh 15-18 grams of KOH and dissolve in 50-100 ml of ethanol and water mixed solution, the volume ratio of ethanol and water is 1:1, stir well to obtain solution A. Weigh 4-8 grams of potassium permanganate and dissolve it in 20-40 ml of deionized water, and stir well to obtain solution B. Slowly add solution A dropwise to solution B, and mix well to react. Vacuum suction filtration, drying in an 80-degree blast drying oven for 6-12 hours to obtain δ-MnO ₂ .

(2) Preparation of α-MnO ₂ : Weigh 250 mg of the dried sample in (1) and dissolve it in 65-85 ml of deionized water, sonicate for 10-40 minutes; add 10-20 ml of 2.3 g/L graphite oxide Alkene, ultrasonic for 10-40 minutes; put the obtained solution into a polytetrafluoroethylene reactor, put it in a muffle furnace at 150-200°C for hydrothermal reaction for 24-40 hours. The hydrothermally synthesized substance is subjected to vacuum filtration, washed with deionized water several times, and put into a vacuum drying oven for drying to obtain α-MnO ₂ .

As shown in Figure 1, the X-ray powder diffraction test results show that the catalyst diffraction pattern synthesized by the hydrothermal method of the present invention basically corresponds to the α- _MnO2 standard card (JCPDS NO. 00-029-1020), which shows that this The pure α- _MnO2 catalyst was successfully synthesized by the hydrothermal method used in the invention.

As shown in FIG. 2 , it can be seen from the electron microscope test results that the α-MnO ₂ synthesized by the present invention is a nanofiber with a diameter of about 50-60 nanometers.

As shown in Figure 3, the present invention compared the self-degradation of p-nitrophenol (4-NP), the degradation of 4-NP by PMS, and the adsorption of two different crystal catalysts on 4-NP and the adsorption of 4-NP. degradation effect. When pH=3.48, 100 ml of 25 mg/L p-nitrophenol was basically completely degraded within 80 min. Compared with the precursor δ-MnO ₂ , the degradation efficiency is inferior.

As shown in Figure 4, the present invention samples the degradation experiments at different times, and gets the filtrate to carry out full-band scanning to obtain a full-band scanning figure. As can be seen from the figure, as the reaction proceeds, the nitrophenol 317nm The strongest absorption peak decreases continuously, transforms into absorption peaks of other substances, and finally disappears.

The catalyst of the present invention is nanofibrous MnO ₂ ; the synthesized catalyst of the present invention can strongly promote the self-decomposition of PMS, thereby generating more • OH and SO ₄ ^• ¯ free radicals, which provide a basis for the degradation of POPs . The preparation method of the catalyst provided by the invention is simple and easy, the production cost is low, and the yield and purity are high. It will have potential application prospects in the fields of environmental functional materials, sewage treatment, and heavy metal adsorption.

Claims (1)

1. A method for preparing manganese dioxide nano-catalysts, preparing α-MnO ₂ nano-catalysts, this catalyst is synthesized by two-step method, at first obtains δ- _MnO by precipitation synthesis, then by hydrothermal reaction, the δ-MnO ₂ is transformed into α-MnO ₂ ; it is characterized in that the method steps are as follows: (1) Preparation of δ-MnO ₂ : Weigh 15-18 grams of KOH and dissolve in 50-100 ml of ethanol and water mixed solution, the volume ratio of ethanol and water is 1:1, stir well to obtain solution A; Weigh 4-8 grams of potassium permanganate and dissolve in 20-40 milliliters of deionized water, stir well to obtain solution B; Slowly add solution A dropwise to solution B, mix well and react; Vacuum filtration, drying in an 80-degree blast drying oven for 6-12 hours to obtain δ-MnO ₂ ; (2) Preparation of α-MnO ₂ : Weigh 250 mg of the dried sample in (1) and dissolve in 65-85 ml of deionized water, and ultrasonicate for 10-40 minutes; Add 10-20 ml of 2.3 g/L graphene oxide, and sonicate for 10-40 minutes; Put the obtained solution into a polytetrafluoroethylene reaction kettle, put it into a muffle furnace at 150~200°C for hydrothermal reaction for 24-40 hours; The hydrothermally synthesized substance is subjected to vacuum filtration, washed with deionized water several times, and put into a vacuum drying oven for drying to obtain α-MnO ₂ .