阅读说明：本技术 光催化还原Cr6+的MIL-125/Ag/BiOBr复合催化剂、制备方法及应用 (Photocatalytic reduction of Cr6+MIL-125/Ag/BiOBr composite catalyst, preparation method and application ) 是由 桑东雪 邹学军 董玉瑛 于 2020-06-30 设计创作，主要内容包括：本发明提供了BiOBr复合催化剂,将表面修饰有Ag<Sup>0</Sup>的MIL-125复合于BiOBr载体,得到BiOBr复合催化剂；所述BiOBr复合催化剂的微观形貌为曲面纳米片；纳米片的直径为600～1200nm；纳米片具有3～5层,每层具有若干缺陷孔,每层由若干纳米颗粒构成,纳米颗粒的粒径为10～30nm。本发明与现有技术相比具有如下优点：MIL-125/Ag/BiOBr复合纳米材料的比表面积大,吸附能力强；MIL-125/Ag/BiOBr复合纳米材料与其他修饰方法修饰的BiOBr相比,具有更好的可见光吸收性能,对光催化还原Cr<Sup>6+</Sup>有很大的稳定性；MIL-125/Ag/BiOBr复合纳米材料的制备方法比较简单,易于操作,适于工业生产。(The invention provides a BiOBr composite catalyst, the surface of which is modified with Ag 0 MIL-125 of (2) is complexed with BAn iOBr carrier to obtain a BiOBr composite catalyst; the microscopic morphology of the BiOBr composite catalyst is a curved nanosheet; the diameter of the nanosheet is 600-1200 nm; the nano sheet has 3-5 layers, each layer has a plurality of defect holes, each layer is composed of a plurality of nano particles, and the particle size of the nano particles is 10-30 nm. Compared with the prior art, the invention has the following advantages: the MIL-125/Ag/BiOBr composite nano material has large specific surface area and strong adsorption capacity; compared with BiOBr modified by other modification methods, the MIL-125/Ag/BiOBr composite nano material has better visible light absorption performance and reduces Cr by photocatalysis 6+ The stability is very high; the preparation method of the MIL-125/Ag/BiOBr composite nano material is simple, easy to operate and suitable for industrial production.)

1. A BiOBr composite catalyst characterized by: the surface is modified with Ag⁰The MIL-125 is compounded on a BiOBr carrier to obtain a BiOBr composite catalyst; the microscopic morphology of the BiOBr composite catalyst is a curved nanosheet; the diameter of the nanosheet is 600-1200 nm; the nano sheet has 3-5 layers, each layer has a plurality of defect holes, each layer is composed of a plurality of nano particles, and the particle size of the nano particles is 10-30 nm.

2. A method for preparing the BiOBr composite catalyst according to claim 1, wherein: firstly, respectively preparing BiOBr and MIL-125 by a hydrothermal method; then adopting photo-reduction method to make Ag⁰Modifying on the surface of MIL-125 to obtain an MIL-125/Ag compound; and finally loading the MIL-125/Ag compound on the BiOBr to obtain the BiOBr compound catalyst.

3. The method of claim 2, wherein: the method comprises the following steps:

(1) dropping CTAB to Bi (NO)₃)₃·5H₂Mixing and stirring the mixture in the O-EG solution for 30 min; then adding a 25 wt% sodium carbonate solution to a pH value of 3-6, and stirring at room temperature for 30min to obtain a solution I; transferring the obtained solution I into a hydrothermal reaction kettle, and reacting for 4-10 h at 130-180 ℃; after the reaction, respectively cleaning, filtering and drying the precipitate to obtain white BiOBr powder;

Bi(NO₃)₃·5H₂in O-EG solution, Bi (NO)₃)₃·5H₂The mass ratio of O to EG is 1: 20;

CTAB and Bi (NO)₃)₃·5H₂The molar ratio of O is 1: 1;

(2) mixing the components in a mass ratio of 1: 2: 4: 35 Ti (O-iPr)₄、H₂BDC、CH₃OH and DMF are mixed and stirred for 1 hour to obtain a solution II; transferring the solution II into a hydrothermal reaction kettle, and reacting for 30-60 h at 130-180 ℃; after the reaction, respectively cleaning, filtering and drying the precipitate to obtain MIL-125 powder;

(3) MIL-125 and AgNO prepared in the step (2)₃Dispersed to 5% PEG-H₂Transferring the O solution into a water-cooled reactor, and irradiating for 0.5-2 h under a 500Xe lamp to obtain a solution III;

5% PEG and H₂The volume ratio of O is 1:100, and the mass ratio of MIL-125 to water is 2: 1;

AgNO₃the mass ratio of the mixed solution to MIL-125 is 1: 25;

(4) dispersing the BiOBr prepared in the step (1) into the solution III, and stirring for 2-8 h at the temperature of 40-80 ℃; cooling to room temperature, washing with deionized water and absolute ethyl alcohol for three times respectively, and drying in a vacuum oven at 50-100 ℃ for 12-24 h to obtain the BiOBr composite catalyst;

the mass of BiOBr and MIL-125 is 1: 20-1: 5.

4, carrying out photocatalytic reduction on Cr by using BiOBr composite catalyst⁶⁺The application of (1): BiOBr composite catalyst and Cr⁶⁺The mass ratio of the substrate is 5:1, Cr⁶⁺The concentration of the substrate solution was 50mg/L, and the light source was a xenon lamp.

Technical Field

The invention relates to photocatalytic reduction of Cr⁶⁺The MIL-125/Ag/BiOBr composite catalyst belongs to the technical field of environmental chemical photocatalytic water treatment, and particularly relates to visible light treatment of Cr⁶⁺And (4) waste water.

Background

Diseases and death events caused by heavy metal pollution are frequent in countries of the world. Such as Japanese pain and water bearing disease events, China cadmium rice events, Shaanxi 174 children lead poisoning events and the like. According to the research result of mutation rate toxicity evaluation of Linliqin, the toxicity and lethal effect of heavy metals are second to those of pesticides and other substances. Therefore, in the face of toxic and harmful pollutants such as heavy metals, research on corresponding removal methods is becoming a hot spot. The photocatalysis technology is an advanced oxidation technology which is environment-friendly, efficient and free of secondary pollution, shows wide application prospects in the fields of energy development and environmental pollution treatment, and attracts wide attention and research of scholars at home and abroad.

The more used photocatalyst at present is TiO₂However, TiO₂The semiconductor is a wide-bandgap semiconductor, can only absorb ultraviolet light, and electrons and holes are easy to combine, so that the large-scale industrial application of the semiconductor is restricted. In recent years, in order to improve photocatalytic performance, researchers have been dedicated to develop novel efficient visible light-responsive photocatalyst materials, including metal hydroxides, multi-element metal oxides, layered compounds, and structured oxides, wherein the layered compound bismuth oxyhalide (BiOX, X ═ F, Cl, Br, and I) has a unique layered structure, and can significantly reduce the electron-hole recombination rate.

Bismuth oxybromide (BiOBr) is an important photocatalyst in the bismuth oxyhalide family because it is visible light-sensitiveThe area has good absorption, relatively stable property under illumination, proper forbidden bandwidth, excellent photocatalytic performance and relatively strong pollutant decomposing capacity under visible light conditions, thus becoming a research hotspot in the field of photocatalysis gradually. But the catalytic effect and stability are not ideal when the catalyst is used alone. In order to further improve the photocatalytic activity and stability of the BiOBr, the BiOBr can be modified by adopting methods such as metal doping, non-metal doping, semiconductor doping and the like. For example, Shuai Fu, Wei Yuan, Xianming Liu, et al₂[ journal of color and Interface science 569(2020) 150-163 ] of WS with rich oxidative genes for enhancing dbread-specific photonic performance₂The catalyst is weak in stability, and the photocatalyst is easy to deactivate after being used for a plurality of times.

Disclosure of Invention

The invention aims to provide a Cr-containing alloy with visible light response⁶⁺The preparation process of the MIL-125/Ag/BiOBr composite nano catalyst has the advantages of high-efficiency reduction capability, simple preparation, good stability and difficult corrosion.

To achieve this object, the present invention provides:

a BiOBr composite catalyst with Ag modified on its surface⁰The MIL-125 is compounded on a BiOBr carrier to obtain a BiOBr composite catalyst; the microscopic morphology of the BiOBr composite catalyst is a curved nanosheet; the diameter of the nanosheet is 600-1200 nm; the nano sheet has 3-5 layers, each layer has a plurality of defect holes, each layer is composed of a plurality of nano particles, and the particle size of the nano particles is 10-30 nm.

Preferably, the BiOBr and the MIL-125 are prepared by a hydrothermal method respectively; then adopting photo-reduction method to make Ag⁰Modifying on the surface of MIL-125 to obtain an MIL-125/Ag compound; and finally loading the MIL-125/Ag compound on the BiOBr to obtain the BiOBr compound catalyst.

Preferably, the method comprises the steps of:

(1) dropping CTAB to Bi (NO)₃)₃·5H₂Mixing and stirring the mixture in the O-EG solution for 30 min; then 25 wt% sodium carbonate solution was addedStirring for 30min at room temperature until the pH value is 3-6 to obtain a solution I; transferring the obtained solution I into a hydrothermal reaction kettle, and reacting for 4-10 h at 130-180 ℃; after the reaction, respectively cleaning, filtering and drying the precipitate to obtain white BiOBr powder;

Bi(NO₃)₃·5H₂in O-EG solution, Bi (NO)₃)₃·5H₂The mass ratio of O to EG is 1: 20;

CTAB and Bi (NO)₃)₃·5H₂The molar ratio of O is 1: 1;

(2) mixing the components in a mass ratio of 1: 2: 4: 35 Ti (O-iPr)₄、H₂BDC、CH₃OH and DMF are mixed and stirred for 1 hour to obtain a solution II; transferring the solution II into a hydrothermal reaction kettle, and reacting for 30-60 h at 130-180 ℃; after the reaction, respectively cleaning, filtering and drying the precipitate to obtain MIL-125 powder;

(3) MIL-125 and AgNO prepared in the step (2)₃Dispersed to 5% PEG-H₂Transferring the O solution into a water-cooled reactor, and irradiating for 0.5-2 h under a 500Xe lamp to obtain a solution III;

5% PEG and H₂The volume ratio of O is 1:100, and the mass ratio of MIL-125 to water is 2: 1;

AgNO₃the mass ratio of the mixed solution to MIL-125 is 1: 25;

(4) dispersing the BiOBr prepared in the step (1) into the solution III, and stirring for 2-8 h at the temperature of 40-80 ℃; cooling to room temperature, washing with deionized water and absolute ethyl alcohol for three times respectively, and drying in a vacuum oven at 50-100 ℃ for 12-24 h to obtain the BiOBr composite catalyst;

the mass of BiOBr and MIL-125 is 1: 20-1: 5.

the invention also provides a BiOBr composite catalyst for photocatalytic reduction of Cr⁶⁺The application of (1): BiOBr composite catalyst and Cr⁶⁺The mass ratio of the substrate is 5:1, Cr⁶⁺The concentration of the substrate solution was 50mg/L, and the light source was a xenon lamp.

Compared with the prior art, the invention has the following advantages:

(1) the MIL-125/Ag/BiOBr composite nano material has large specific surface area and strong adsorption capacity;

(2) compared with BiOBr modified by other modification methods, the MIL-125/Ag/BiOBr composite nano material has better visible light absorption performance and reduces Cr by photocatalysis⁶⁺The stability is very high;

(3) the preparation method of the MIL-125/Ag/BiOBr composite nano material is simple, easy to operate and suitable for industrial production.

Drawings

FIG. 1 is a scanning electron micrograph of the MIL-125/Ag/BiOBr composite catalyst of example 1.

FIG. 2 is a graph of the physical adsorption and specific surface area of MIL-125/Ag/BiOBr composite catalyst in example 1 versus pure BiOBr, MIL-125.

FIG. 3 is a graph comparing the effect of MIL-125/Ag/BiOBr composite catalyst in example 1 on the photocatalytic degradation of potassium dichromate with pure BiOBr.

FIG. 4 is a graph showing the effect of degrading potassium dichromate by photocatalysis of MIL-125/Ag/BiOBr composite catalyst in example 1 in a recycling manner.

Detailed Description

The following non-limiting examples are presented to enable those of ordinary skill in the art to more fully understand the present invention and are not intended to limit the invention in any way.

Photocatalytic reduction of Cr⁶⁺The MIL-125/Ag/BiOBr composite catalyst consists of porous multilayer nanosheet units consisting of particles having an average particle size of 15nm, the nanosheet units having a diameter of 900 nm.

The preparation method of the MIL-125/Ag/BiOBr composite catalyst comprises the following steps:

(1) will react with Bi (NO)₃)₃·5H₂The molar ratio of O is 1:1 CTAB to Bi (NO)₃)₃·5H₂In O-EG solution, Bi (NO)₃)₃·5H₂The mass ratio of O to EG is 1: 20 mixing and stirring for 30 min; then, adding a 25 wt% sodium carbonate solution to a pH value of 3-6, and stirring at room temperature for 30 min; finally, transferring the solution into a hydrothermal reaction kettle, and reacting for 4-10 h at 130-180 ℃; after the reaction, the precipitates were washed, filtered, and dried, respectively, to obtain white bibbr powder.

(2) Mixing the components in a mass ratio of 1: 2: 4: 35 Ti (O-iPr)₄、H₂BDC、CH₃OH and DMF are mixed and stirred for 1 hour; transferring the solution into a hydrothermal reaction kettle, and reacting at 130-180 ℃ for 30-60 hours; after the reaction, the precipitate was washed, filtered and dried, respectively, to obtain MIL-125 powder.

(3) Mixing the MIL-125 prepared in the step (2) with the MIL-125 in a mass ratio of 1: 25 AgNO₃Dispersed to 5% PEG-H₂In O solution, 5% PEG and H₂The volume ratio of O is 1:100, and the mass ratio of MIL-125 to water is 2: 1; and then transferring the floating liquid into a water-cooled reactor, and irradiating for 0.5-2 h under a 500Xe lamp.

(4) Mixing the mixture with MIL-125 by mass as 1: 20-1: 5, dispersing the BiOBr prepared in the (1) into the solution prepared in the (3), and stirring for 2-8 h at the temperature of 40-80 ℃; and cooling to room temperature, washing with deionized water and absolute ethyl alcohol for three times respectively, and drying in a vacuum oven at 50-100 ℃ for 12-24 h.

Application of MIL-125/Ag/BiOBr composite catalyst

MIL-125/Ag/BiOBr catalyst and Cr⁶⁺The mass ratio of the substrate is 5:1, Cr⁶⁺The concentration of the substrate solution was 50mg/L, and the light source was a xenon lamp.

The invention provides a method for photocatalytic reduction of Cr⁶⁺The MIL-125/Ag/BiOBr composite catalyst, and a preparation method and application thereof. The MIL-125/Ag/BiOBr composite catalyst is composed of porous multilayer nanosheet units consisting of particles with an average particle size of 15nm, and the diameter of the nanosheet units is 900 nm. The preparation method of the MIL-125/Ag/BiOBr composite catalyst comprises the following steps: firstly, respectively preparing BiOBr and MIL-125 by a hydrothermal method; then adopting photo-reduction method to make Ag⁰Modifying on the surface of MIL-125; and finally modifying MIL-125/Ag by using BiOBr. The MIL-125/Ag/BiOBr composite catalyst realizes the purpose of pollutant Cr under the irradiation of visible light⁶⁺And (4) efficient reduction. The MIL-125/Ag/BiOBr composite nano material has large specific surface area and strong adsorption capacity; the visible light absorption performance is better, and the photocatalytic oxidation degradation of organic pollutants is greatly improved; and the preparation method of MIL-125/Ag/BiOBr is simple and easy to operate.