A Study of photocatalyzation of Acid Orange 7 by TiO2 with oxidants

• Main Authors: Shao-Jhan Syu, 徐紹展
• Other Authors: Jao-Jia Horng
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/31275617103888212608

碩士 === 雲林科技大學 === 環境與安全工程系碩士班 === 98 === Many researchers studied the decolorization and mineralization of dyes by photodegradation. With different degradation intermediates and paths, the dyes may produce toxic substances in the degradation process. However, few literatures discussed the effects of different light wavelengths and different oxidants would lead to different intermediates and degradation mechanisms. This study investigated photocatalytic degradation of Azo dyes (AO7) by titanium dioxide systems with UV and visible lights and the addition of different oxidants. The intermediates and decomposition pathways were identified. In experiments, HPLC was used to measure six possible intermediates. The degradation of AO7’s three main structures by UV light, Azo-linkage (485 nm), Naphthalene (310 nm), and Benzene (229 nm), was studied. Irradiating by UV light and adding oxidant KMnO4, UV light could effectively decompose Azo-linkage and Naphthalene, but not Benzene structure. The main AO7’s intermediates of UV decomposition were Phthalide and Coumarine while products of 2-hydroxy-1,4-Naphthalenedione, Phthalide, and Coumarine were produced under yellow light. The addition of oxidants could open different degradation pathways as different intermediates, Sulfanilic acid and 2-Naphthol, were found. Adding oxidants on the photodegradation of AO7 could break Azo bond (－N＝N－) and produce Sulfanilic acid through attacking OH radicals rapidly. The secondary pathway was breaking the carbon-nitrogen bond (－C－N－) as 2-Naphthol rapidly degraded into Coumarine, 2-hydroxy-1,4- Naphthalenedione and 1,2-Naphthalenediol. Then, the complete mineralization of those products followed. Our experiments of identifying intermediate products also suggested that AO7’s degradation pathways were different as light sources and oxidants changed. However, there are many intermediates while degrading AO7 and could not measure all in low concentrations. The combination of enrichment technique and LC/MS/MS analysis should be used in the future for identifying more intermediate species.