Preparation Titanium Dioxide Nanotube Arrays Based Ag And Reduced Graphene Oxide Nanocomposites And Study On Photocatalytic Degradation Of Ethylene By Ultraviolet

Fruits and vegetables are rich in resources in China. Due to the backwardness of the storage and transport technology, a large amount of them are deteriorated, resulting in a huge economic losses. Ethylene gas is one of the key factors which causes the deterioration of horticultural products. When stored in the airtight preservation environment, it can speed up the respiration intensity of fruits and vegetables, enhance metabolic activity of enzyme, accelerate the cell membrane's permeability, and make fruits soft and vegetables degreening, which lowers the quality of storage and shortens the shelf life of horticultural products. Some of the traditional method of ethylene removing technologies?such as physical absorption, oxidized by potassium permanganate, high temperature catalyzed and decompression? has some defects or negative effects in the practical application, which causes slow development of garden stuff fresh-keeping in China.TiO₂ nanotubes arrays?TNAs? possesses characteristics of larger surface area and strong combination with titanium-based sheets. Besides, it is chemically stable, cheap and has excellent charge transport properties and the carrier life characteristics, widely used in degradation of organic pollutants and other fields. However, without the mutual composite of the electrons and the holes under the UV irradiation, nanometer TiO₂ shows a stronger redox activity. In practical applications, the mutual composite reacts easily, which limits the application of TiO₂. The only solution to this problem is modifying the TNAs from external, decreasing the recombination rate of photo electrons and the holes. It can effectively improve the photocatalytic degradation performance and has great research value in the field of agricultural products storage, environmental protection and so on.Degradating ethylene is the purpose of this study gas in cold storage room, 60Co-? ray irradiation reduction technique was used to modify ^*TNAs which was made by the anodic oxidation method. Then used ultrasound stripping and irradiation reduction method to prepare graphene oxide. After that, we prepared nanometer sliver and reduced graphene oxide composite material by one-step irradiation reduction technology. Finally, modified ^*TNAs doped with graphene oxide, nano-Ag and graphene oxide composite materials were made into semiconductor photocatalysts. The modified ^*TNAs was used for degradating ethylene under ultraviolet. Through different methods such as AFM, SEM, FTIR, Raman, XRD and XPS, we compare ethylene degradating rate between different ^*TNAs, research their structure-function relationship and reaction mechanism, which provides a method to repair technique for fruits and vegetables storage environment. The results of the study are as follows:?1? We adopted ultrasonic to strip graphite oxide and ?ray irradiation to reduce graphite oxide. And compared r GO-^*TNAs' abilities of degradation of ethylene by Langmuir-Hinshelwood Model. The effects of degradation were measured by degradation rate constant K'. The single factor experiment showed that with the increase of independent variable, the degradation effect of ethylene is increased and then decreased, the values of K' increased firstly and then decreased. It has the best degradation effect of ethylene when the dose is 570 W, 150 min, 30 KGy and 3.828 mg/m2.?2? By means of the Box-Behnken design and regression fitting, quadratic multinomial model of r GO-^*TNAs reaction constant of doping dose of graphite oxide, ultrasonic power, ultrasonic time and the irradiation dose on the degradation of ethylene was established. The validity of the model was verified, and parameters of reaction system were optimized at the same time. The optimal conditions was that dose of graphite oxide was 3.60 mg/m2, ultrasonic power was 657.62 W, ultrasonic time was 179.25 min, and the irradiation dose was 39.57 KGy.?3? We prepared Ag NP/r GO-^*TNAs under the above optimal solution. It had optimal degradation of ethylene when the Ag nano particles doping was 0.00140 mol on the ^*TNAs per square meter and irradiation dose was 20 KGy.?4? By means of quadratic rotary combination experiment and regression fitting, quadratic multinomial model of Ag/r GO-^*TNAs reaction constant of dose of reduced graphite oxide, Ag nano particles and the irradiation dose on the degradation of ethylene was established. The validity of the model was verified, and parameters of reaction system were optimized at the same time. The optimal conditions was that amount of r GO was 3.93 mg/m2, Ag nano particles was 0.00142 mol/m2, and irradiation dose was 20.92 KGy.?5? The results AFM and FSEM showed that the ^*TNAs pipe diameter was about 60 to 80 nm, and the thickness of pipe wall was about 5 to 10 nm. The reduced graphite oxide had a huge lamelliform structure, its sizes range from 100 nm to 500 nm with slight folds, and the thickness of the slice layer was about 1 2 nm. Ag particles were evenly distributed on the graphene layers, loaded in ^*TNAs nozzle and not close TiO₂ nozzles.?6? The analysis results of FTIR showed that absorption peaks of oxygen functional groups in graphite oxide had weaken but didn't disappear. The results of Raman showed that reduced graphene oxide and graphene oxide had difference in G peak. It indicated that deoxidized reaction had happened between reduced graphene oxide and graphene oxide. And the the orderly degree of sp2 carbon network structure ordering degree was so high, and the sample's C-H vibration D* peak also manifested existence of hydrogenated nanometer graphene structure.?7? The analysis results of XRD showed that the size of nano TiO₂ has decreased with the irradiation dose increased during the crystallization process,and the characteristic diffraction peaks of rutile failed to observe. It mean that the 60Co-? ray irradiation can only transform the amorphous ^*TNAs into anatase ^*TNAs. After doped with Ag, which indicated that with the introduction of Ag, and the size of anatase nano TiO₂ has decreased, the specific surface area of ^*TNAs increased because of the decrease of the anatase nano TiO₂ size, which improves the adsorption ability of ethylene.?8? The analysis results of XPS showed that the content of Ti3+,hydroxyl oxygen and nano-Ag on the substance of ^*TNAs increased with the irradiation dose increase during the crystallization process,and therefore improve the photocatalytic activity of TiO₂. After ?-ray irradiation, the surface reactive oxygen-containing groups decreased, indicating that the irradiation of graphene oxide reduction is effective.?9? The research can provide a reference for the technology of preparation titanium dioxide nanotube arrays based Ag and reduced graphene oxide nanocomposites and photocatalytic degradation of ethylene by ultraviolet in the application of storage and transportation equipment of horticultural products.