스테인레스 mesh에 도포된 TiO2 광촉매를 이용한 Phenol 및 Chlorophenol류 수용액의 광산화분해 반응

Abstract

TiO2 nanoparticles were synthesized using spray process. Particles with and without silver ion dopant were obtained. X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy measurements confirmed the stoicheometry of the TiO2 nanoparticles. X-ray diffraction patterns showed a polycrystalline anatase structure of TiO2 nanoparticles. Transmission electron microscopy revealed that these particles are of nanoscale dimensions. Exact particle size and size distribution analyses were done by dynamic light scattering. The average particle size was determined to be 31~38nm. The nanosize particles provide large surface area of photocatalysis and a large number of free surface charge carriers which are crucial for the enhancement of photocatalytic activity. In order to improve the photocatalytic activity, silver metal ion(Ag+) was added to pure TiO2 nanoparticles. In this study, TiO2 nanoparticles was added with 1.0% Ag+ion was coated as thin films on the surface of stainless steel mesh(SS) and quartz glass tube(QGT). The coating depth was about 500nm. and the structure of TiO2 nanoparticles were polycrystalline particles with almost anatase type. The effects of Ag(Ⅰ) dopant on the photocatalytic activity were revealed by the degradation of phenol and chlorophenols with an UV light source. The phtocatalytic efficiency was enhanced by the introduction of Ag+-doped TiO2 nanoparticles coated on the surface stainless steel mesh [TiO2(Ag+)-SS] showed the largest enhancement. These effects were related to the position of the Ag+- dopant in the nanparticles and the difference in the Ag+ionic radii respect to that Ti4+. Especially, the phtocatalytic efficiency of the TiO2(Ag+)-SS was remarkably enhanced by introduction of only auxiliary oxidant as a H2O2. However, effect of auxiliary oxidant without photocatalysis was almost limited in the photodegradation process of the contaminate organic solution. This study investigated the photocatalytic-photooxidation kinetics of 2-chlorophenol aqueous solution without pH control. Intermediates and by-products generated during the process were rigorously identified and quantified. The major products are four carboxylic acids: tartaric, oxalic, maleic, and hydroxymalonic acid. The generation of these organic acids is in agreement with theoretical product ions. But hydroxylated compounds are more favorable to produce than thir corresponding non-hydroxylated ones. Based on the information concerning the generation of organic acids and other intermediates, the complete reaction pathways toward mineralization can be proposed and mathematically modelled. The fitted second-order rate constants are in the same order magnitude with the results from other studies. Using these oxidation pathways and the corresponding kinetic model, by-products generated in photodegradation process can be predicted. This can help in optimizing the design and operation of any photo-oxidation process on the organic contaminates.