Manufacture of Nano-TiO2 catalytic materials and application of electrocatalytic technique to treat dye wastewater

• Main Authors: Shan-yi shen, 沈善鎰
• Other Authors: Jih-Hsing Chang
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/32722355501302039843

碩士 === 朝陽科技大學 === 環境工程與管理系碩士班 === 96 === Hydroxyl radicals produced by water molecule interacting with the catalytic materials in the aquatic system, which are effectively able to oxidize the organic pollutants into harmless water and carbon dioxide, have been extensively applied to wastewater and air pollution treatment. This study focuses on the manufacture and characterization of nano-titanium dioxide powders and the plate. In addition, the above materials were employed as the electrocatalytic electrode to test the color removal efficiency of methyl orange dye wastewater. The nano scale TiO2 powder was fabricated by Sol-Gel process. The additional of sodium hexametaphosphate (NaPO3)6 (surface dispersant) with different concentration was used to prevent nano-powders from aggregation. Moreover, different reflux time and temperature of calcinations were also tested to find out the relatively appropriate operation parameters. It can be shown that more nano-scale TiO2 particles accrue with few powder aggregates under the dispersant concentration of 1.63×10-2 mM according to the images of field emission scanning electrical microscopy (FE-SEM). The aggregation was also reduced when the reflux time was increased to 6 hr. By EDS, the powder was demonstrated to be composed mostly of Ti and O element. By XRD, the anatase lattice of TiO2 powder can be formed at calcination temperature of 500oC. The best specific surface area of the nano TiO2 powders is 129 m2 g-1. The manufacture of nano-scale titanium dioxide film by chemical vapor deposition (CVD) was supplied from the physiochemical treatment laboratory of professor Yung-Hsu Hsieh at department of Environmental engineering in Chung Hsing University. Discussion the surface characteristics of coating and conformation of titanium dioxide plate is based on different coating times and oxidation time. It can be seen that nano-scale size of TiO2 particles effectively pile on the substrate according to the FE-SEM images. Increase of coating times and the oxidation time will facilitate the homogenization of titanium dioxide pile on the substrate. The interstice of the TiO2 film can be improved and the particle sizes can be reduced from 42 nm to 20 nm approximately. It can be demonstrated that surface film was composed of element Ti and O and was anatase crystallization mostly based on the analysis of EDS and XRD. For treating methyl orange dye wastewater by electrocatalytic technique, the nano-scale titanium dioxide (twice coating and 10 hr of oxidation) plate, commercially available TiO2 plate, and graphite plate were used. To understand the degradation phenomenon of these electrodes, the variation of color, total organic carbon (TOC), pH of wastewater were measured during the decomposing process. According to experimental results, the color and TOC removal efficiency of wastewater can achieve about 97% and 56%, respectively under the operation conditions of the nano-scale titanium dioxide plate (twice coating), current density of 20 mA cm-2, and 160-minute treatment.