阅读说明：本技术 太阳光催化高效降解丙烯腈废水用FSBi掺杂TiO2/SiO2催化剂的制备及使用 (FSBi-doped TiO for efficiently degrading acrylonitrile wastewater by sunlight catalysis2/SiO2Preparation and use of the catalyst ) 是由 欧阳峰 王韫 戴方为 于 2019-01-10 设计创作，主要内容包括：太阳光催化高效降解丙烯腈废水用FSBi掺杂TiO<Sub>2</Sub>/SiO<Sub>2</Sub>催化剂的制备及使用,本发明涉及模拟及自然日光条件照射下光催化降解丙烯腈实际废水COD满足国家排放标准的F、S、Bi共掺杂改性二氧化钛复合氧化物催化剂及其制备方法。本发明首先提供了优化溶胶凝胶法F掺杂的TiO<Sub>2</Sub>催化剂制备方法基础上,即利用硝酸铋和硫脲作为前驱体进行S、Bi共掺杂。F、S、Bi共掺杂改性后的TiO<Sub>2</Sub>催化剂协同作用优势明显,催化剂的光响应范围拓宽,样品表面的酸性位点强度大,特别是硅胶的加入所形成凸凹不平超细纳米粒子的表观形貌和孔结构造成的光散射,有利于光吸收,这对光催化活性的提高起了重要的作用。最适宜的Ti、F、S、Bi的比例为1∶1∶0.5-5％∶0.1-3％,适宜的煅烧温度和煅烧时间分别为400-550℃和3h,该催化剂重复3次,COD仍可从约102降至40mg/L以下。(FSBi-doped TiO for efficiently degrading acrylonitrile wastewater by sunlight catalysis 2 /SiO 2 The invention relates to a F, S, Bi codope modified titanium dioxide composite oxide catalyst for photocatalytic degradation of acrylonitrile actual wastewater COD under simulation and natural sunlight irradiation to meet national emission standard and a preparation method thereof. The invention firstly provides an optimized sol-gel method F-doped TiO 2 Based on the catalyst preparation method, the S, Bi co-doping is carried out by using bismuth nitrate and thiourea as precursors. F. S, Bi Co-doping modified TiO 2 The synergistic effect of the catalyst has obvious advantages, the photoresponse range of the catalyst is widened, the acid site strength on the surface of a sample is high, and particularly, the convex-concave uneven superfine nano-particles formed by adding silica gelThe optimum ratio of Ti, F, S and Bi is 1: 0.5-5% to 0.1-3%, the appropriate calcination temperature and calcination time are 400-550 ℃ and 3h respectively, the catalyst is repeated for 3 times, and the COD can still be reduced from about 102 to below 40 mg/L.)

1. An F, S, Bi composite oxide catalyst for degrading acrylonitrile actual wastewater is TiO modified by using 100-200 mesh silicon dioxide as a carrier to carry fluorine, sulfur and bismuth and simultaneously existing codoping₂Catalyst, hydrogen fluoride, bismuth nitrate and thiourea as dopant precursors.

2. The method for preparing a composite oxide catalyst according to claim 1, comprising the steps of:

step 1, dropwise adding 1-7m L of butyl titanate into 11-15m L of absolute ethyl alcohol, mixing with the butyl titanate to obtain a clear solution A,

and 2, sequentially adding 11-31m L of absolute ethyl alcohol, 0.5-2m L of deionized water, 2.2-5.2m L of glacial acetic acid, 14-34mg of thiourea, 39-59mg of bismuth nitrate pentahydrate and 0.4L-1.4 m L of hydrofluoric acid into a 100m L beaker, and carrying out ultrasonic treatment for 2min to obtain a solution B.

And 3, dropwise adding the solution B into the solution A, sealing and stirring for 1-3h to form uniform oily sol, continuously stirring for a period of time to form oily sol, and then adding 100-300-mesh silicon dioxide until gel is formed.

And 4, aging the gel for about 8-12h in a room temperature environment, drying in a drying oven at 80-130 ℃, uniformly grinding the obtained dry powdery catalyst precursor, and finally calcining for 2h at 400-550 ℃ in a tubular furnace to obtain the modified SiO doped with the three nonmetals₂Supported TiO₂A catalyst.

3. The method according to claim 2, wherein the fluorine precursor is a commercially available 40% aqueous hydrogen fluoride solution, the sulfur precursor is prepared from analytically pure thiourea, and the bismuth precursor is analytically pure bismuth nitrate.

4. F modification with optimum activity by using F element as doping hostTiO₂On the basis of the catalyst, precursors of S and Bi elements with different contents are doped (F: S: Bi is 1: 0.5-5%: 0.1-3%).

5. The preparation method according to claim 2, wherein the method for efficiently photocatalytic degradation of acrylonitrile actual wastewater by the catalyst is characterized in that the co-doping of F, S and Bi improves the acidity strength and light absorption capability of the surface of the catalyst, and particularly, the light scattering caused by the apparent morphology and pore structure of the irregular ultrafine nanoparticles formed by adding silica gel is beneficial to light absorption, which plays an important role in improving the photocatalytic activity.

Technical Field

The invention relates to a composite oxide catalyst for photocatalytic degradation of actual acrylonitrile wastewater, in particular to a preparation method of a photocatalyst for photocatalytic degradation of actual acrylonitrile wastewater in a water phase by using silicon dioxide as titanium dioxide carrying fluorine, sulfur and bismuth codoped and modified, and belongs to the technical field of environmental protection.

Background

Acrylonitrile (CH 2 ═ CH-CN, for short, AN) is a monomer for synthesizing ABS industrial plastics, acrylic fibers, nitrile rubbers and resins, and is AN important chemical raw material with wide application. In the production and use processes, various environmental pollution problems caused by acrylonitrile are increasingly highlighted, and the fourth row in the name list of the preferentially controlled toxic chemicals released in China has strong toxicity, difficult degradation and long residual time. The acrylonitrile wastewater not only destroys the water ecosystem, but also has great hidden danger to the health of human beings. However, in view of the market demand for acrylonitrile, the application of acrylonitrile cannot be avoided in a short time, and a scheme for efficiently treating acrylonitrile wastewater needs to be proposed. At present, the methods for treating acrylonitrile mainly include an adsorption method, an incineration method, a circulating activated sludge method and the like. The method has the advantages of high cost, insufficient removal, strict requirements on working conditions and difficulty in realizing effective control on acrylonitrile wastewater pollution. The most difficult contaminant to treat in acrylonitrile waste water is polymer. It is mainly derived from low molecular polymers or copolymers of nitriles. The polymers generally exist in a colloidal state or a dissolved state in water, are difficult to hydrolyze and are utilized by microorganisms, and cannot be effectively removed, so that the acrylonitrile production wastewater belongs to the well-known refractory high-concentration organic wastewater.

The photocatalyst oxidation is that the catalyst absorbs light energy to generate electron transition and generate electron hole pair to the pollutant adsorbed on the surfaceDirectly carrying out oxidation reduction to generate hydroxyl radical with strong oxidizing property, and oxidizing the pollutants. The heterogeneous photocatalysis applied to water treatment has the following unique advantages: the organic matters and the degraded intermediate products can be completely mineralized, and no secondary pollution is generated; reduced operating costs. The generation of highly active oxidizing species favors TiO₂The separation of surface photogenerated electrons and holes and the efficient mineralization of organic pollutants. To date, TiO has been added₂The application of photocatalysts to the field of water treatment still faces many problems and challenges, and how to treat TiO in treated wastewater₂The separation is a great obstacle, the activity of the catalyst can be greatly reduced due to the agglomeration phenomenon of the catalyst in sewage with complex actual conditions, the photoresponse range of the photocatalyst and the problem of the recombination of photo-generated electrons and holes are solved, and the research of the photocatalytic reactor is still in the starting stage.

TiO₂The photocatalytic activity of (A) can be improved by adding silica gel to increase its specific surface area. In recent years, various reports have been made on the manner of supporting titanium dioxide, for example, TiO supported on activated carbon₂Molecular sieve supported TiO₂Glass bead-supported TiO₂TiO supported on silica₂. The mineralization capability of the catalyst to the degradation pollutants can be improved by utilizing the adsorption characteristic of the carrier. The activity of the supported catalyst is greatly improved compared with that of the unsupported titanium dioxide, because a synergistic effect can be formed between the titanium dioxide and the carrier. Wherein, the silicon dioxide has good adsorption performance and larger specific surface area. TiO supported on silica₂The catalyst has the advantages of thermal stability and mechanical stability of silicon dioxide, is transparent, and can reduce light scattering, thereby effectively improving the degradation performance of the catalyst. Adding SiO₂Can effectively control TiO₂The crystal particles grow, the agglomeration phenomenon of the catalyst is effectively inhibited, and the catalyst obtains smaller particle size and higher specific surface area. TiO supported on silica gel₂It also undergoes interfacial diffusion with silicon dioxide to form Si-O-Ti bonds. The formation of Si-O-Ti bond can inhibit anatase type TiO₂Rutile type TiO₂And (4) converting. Jinliang et al found that nano titanium dioxide can effectively degrade acrylonitrile in water in an open reactor under sufficient and stable illumination conditions. Pang D.D et al found that F-doped SiO using HF as the F source₂Supported TiO₂The composite photocatalyst shows the highest activity of degrading acrylonitrile. The results of in situ IR and NH3-TPD show that F doping improves SiO₂Supported TiO₂The surface acid position number and the acid strength of the composite photocatalyst. When the molar ratio of HF to Ti is 1: 1 and the loading amount of TiO2 is 36%, the removal rate of acrylonitrile can reach 66% in 6min under the irradiation of simulated sunlight.

Improvement of TiO by doping modification of non-metal elements₂One advantage of activity is the ability to extend TiO₂The visible light catalytic activity does not affect the catalytic activity of the catalyst ultraviolet light. At present, F, C, S, P, B, N and other non-metal doped TiO have been researched and synthesized by a plurality of catalyst preparation methods₂. Furthermore, it is well known that the particle size, shape, composition and crystal phase of the catalyst strongly influence TiO₂The photocatalytic performance of (a). In various forms, the spherical TiO₂The granule has good stability and single layer property. Pan et al report a single-layer dispersed mesoporous F-doped TiO₂Has excellent light collection performance in dye degradation and better photocatalytic activity. HF can be used as a doping precursor of a fluorine source, and has a shape control function due to the etching property. It has also been reported that F doping can reduce the recombination of photo-induced electrons and holes and thus improve the photocatalytic performance.

Another way to effectively increase the catalytic and activity is to increase the number of surface acid sites. It has been demonstrated that photocatalytic activity increases with an increase in the number of acid sites on the surface of the catalyst. Cui et al 1995 reported that TiO could be doped by metal oxides₂To increase its surface acidity and photocatalytic activity. Wang et al 2006 reported that there was an amorphous TiO₂And sulfur compound at high temperature to synthesize sulfur-doped TiO₂And the photocatalyst can be prepared by using the photocatalyst with acid sites. However, few reports have been made on the photocatalytic degradation of acrylonitrile using an acidic catalyst.

Ciya et al reported that Bi element is present in TiO₂In the nanoparticles with Bi₂O₃Is present in the form that the Co-doping of Bi and S fails to change the TiO₂Of anatase type. After doping Bi, Bi-O-Ti bonds are formed on TiO₂Impurity energy level is generated in the forbidden band, and the forbidden band width of the nano material is reduced, so that the light absorption efficiency is improved.

Disclosure of Invention

The invention aims to provide a high-efficiency reusable photocatalyst for photocatalytic degradation of acrylonitrile actual wastewater, silicon dioxide with 100-200 meshes is used as a dispersing agent, hydrogen fluoride, bismuth nitrate and thiourea are used as doping precursors to prepare the catalyst with a mesoporous structure and a large specific surface area, and the composite doping of F, S and Bi in the catalyst improves the acid strength and the light absorption capacity of the surface of the catalyst, so that the photocatalytic activity and the anti-interference capacity are improved.

The invention also aims to provide a preparation method of the catalyst for photocatalytic degradation of actual acrylonitrile wastewater, and the titanium dioxide composite oxide catalyst doped with silicon dioxide dispersed fluorine, sulfur and bismuth is prepared by a sol-gel method.

The inventor of the invention discovers that F is doped with TiO through research₂The catalyst shows excellent effect on the actual wastewater degradation of acrylonitrile, and the dark adsorption quantity of the catalyst compared with organic matters is also greatly improved in P25, and analysis shows that an adsorption effect exists between an acid center on the surface of the catalyst and lone pair electrons in the organic matters of the acrylonitrile wastewater.

In order to further improve the photocatalytic activity of the catalyst, the composite oxide catalyst provided by the invention adopts fluorine, sulfur and bismuth co-doping in the sol-gel preparation process, hydrogen fluoride, bismuth nitrate and thiourea solution are added into the catalyst as doping precursors, and then the catalyst is calcined at high temperature to form the fluorine-doped catalyst, which has more surface acid sites. Especially, the light scattering caused by the apparent appearance and the pore structure of the uneven superfine nano particles formed by adding the silica gel is beneficial to light absorption, which plays an important role in improving the photocatalytic activity. Can greatly improve the photocatalytic activity.

The invention also provides a preparation method of the composite oxide photocatalyst, which comprises the following steps:

1-7ml of butyl titanate is dropwise added into 11-15m L of absolute ethyl alcohol and mixed with the absolute ethyl alcohol to obtain a clear solution A.

11-31m L of absolute ethyl alcohol, 0.5-2m L of deionized water, 2.2-5.2m L of glacial acetic acid, 14-34mg of thiourea, 39-59mg of bismuth nitrate pentahydrate and 0.4-1.4m L of hydrofluoric acid are sequentially added into a 100m L beaker, and the solution B is obtained after 2min of ultrasonic treatment.

Dropwise adding the solution B into the solution A, sealing and stirring for 1-3h to form uniform oily sol, continuously stirring for a period of time until oily sol is formed, and adding 100-mesh 200-mesh silicon dioxide until gel is formed.

Aging the gel for about 8-12h at room temperature, drying in a drying box at 80-130 ℃, uniformly grinding the obtained dry powdery catalyst precursor, and finally calcining for 2h at 550 ℃ in a tubular furnace at 400-. Thus obtaining the modified SiO doped with the three nonmetals₂Supported TiO₂/SiO₂A catalyst. The composition ratio of Ti to F to S to Bi is 1 to 0.5-5 to 0.1-3 percent,

the TEM results (left panel) show the catalyst as particles of about 20nm in diameter, and the enlarged right panel more clearly shows that these particles are made up of seemingly smaller particle agglomerates.

F. S, Bi Co-doping modified TiO₂/SiO₂And organic matters in the acrylonitrile actual wastewater are selected as target degradation products for activity evaluation of the photocatalyst.

From the angles of research comparison and practical application, two light sources, namely a 350w AHD350 type spherical xenon lamp and a sunlight, are respectively selected to treat the actual acrylonitrile wastewater.

Drawings

FIG. 1 shows F-S-Bi-TiO₂/SiO₂TEM images of the samples.

FIG. 2 shows the use of F-S-Bi-TiO₂/SiO₂The COD of the actual wastewater of the acrylonitrile treated by the catalyst for the first time changes along with the change curve of the simulated solar illumination time.

FIG. 3 shows the use of F-S-Bi-TiO₂/SiO₂The COD of the actual wastewater of the acrylonitrile treated by the catalyst for the first time changes along with the time of natural illumination.

Detailed Description

The following examples are provided to illustrate the present invention and to demonstrate the advantageous effects thereof, but should not be construed as limiting the scope of the invention in any way.

Method for evaluating catalyst activity:

the method specifically comprises the steps of selecting low-concentration acrylonitrile actual wastewater as a target degradation product for activity evaluation of a photocatalyst, pouring 180m L actual wastewater into a quartz reactor, adding 1g of the photocatalyst, sealing the reactor, stirring in the dark for 30min to achieve adsorption and desorption balance, turning on a xenon lamp to start illumination, selecting a 350w AHD350 spherical xenon lamp light source as the light source, and taking out two groups of 4m L wastewater suspensions at intervals of 0.5h in the illumination process.

The detection method comprises the steps of measuring COD by using a Unihua L H-5B-3B (V8) type COD rapid determinator, measuring COD error at +/-10%, measuring the COD of a sample by taking a suspended water sample as the total amount of the COD, immediately filtering the sample by using a filter membrane with the aperture of 0.45 mu m, measuring the sample to obtain the COD content in a supernatant, and determining the difference between the COD content and the COD content in the supernatant to obtain the COD adsorption amount on the catalyst.

As the illumination time is prolonged, the COD in the catalyst and the solution is reduced to a curve as shown in figure 3, and after 8.5h of illumination, the total COD in the solution is reduced from 102 to nearly zero, thereby demonstrating the complete degradation of organic matters. The catalyst has stronger adsorption capacity and 90% of pollutants in the initial stage. As the reaction proceeds, these adsorbates react and desorb, which results in an increase in the concentration of intermediate products in the solution. The intermediate products in the later stage are further degraded and finally approach zero. .

In the same way, the actual wastewater of acrylonitrile is degraded to COD (chemical oxygen demand) of 30 mg/L after 13.5h of reaction under the irradiation of sunlight, and the sunlight intensity is found to be lower than that of a xenon lamp because the irradiation condition of the light is cloudy, so the reaction is carried outA convex lens with the diameter of 50cm is added at the position of 20cm at the upper end of the device for condensing light, so that the sunlight intensity is 100mW/cm in sunny days²When cloudy, about 10mW/cm²。