Liquid-phase Photocatalytic Degradation of Formaldehyde via near-UV/TiO2

• Main Authors: Cheng-Yuan Cheng, 鄭正垣
• Other Authors: Chung-Hsuang Hung
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/46733020441689604369

碩士 === 國立高雄第一科技大學 === 環境與安全衛生工程所 === 94 === Abstract This study investigated liquid-phase photocatalytic oxidation of formaldehyde by using TiO2 as the photocatalyst. The experiments were conducted in a batch photocatalytic slurry reactor. Four fluorescent black light lamps (365nm) were applied as the light source. Formaldehyde concentration was determined by HPLC/DAD after its derivatization reaction with DNPH (2, 4-Dinitrophenylhydrazine) to form the HCHO-DNPH hydrazones. Several experimental parameters including solution pH, the dosage of catalyst and the light intensity were investigated to discuss their effects on degradation rates and mineralization ratios of formaldehyde. The experimental results indicated that solution pH level had a significant effect on the degradation of formaldehyde. The degradation rate of formaldehyde increased with increasing solution pH level and illumination light intensity, typically. It was observed that the fastest degradation rate occurred as slution pH equal to 11 due to more formation of hydroxyl radicals. More than 84% conversion ratio for formaldehyde was achieved after a 120-min reaction period. Different TiO2 dosage tests showed that the formaldehyde degradation rates increas with photocatalyst concentrations as TiO2 concentration below 1000 mg/L. The highest degradation V rate of formaldehyde was observed as TiO2 concentration equal to 1000 mg/L while 73% formaldehyde decomposes. The mineralization ratio of formaldehyde was in the order of pH= 7 > pH= 3 > pH= 11. Some degradation intermediates might be formed at pH= 11, which caused low mineralization ratio in this condition. This study also developed an empirical formula relationship for predicting the pseudo-first order degradation rate of formaldehyde as a function of formaldehyde concentration, TiO2 concentration and irradiated light intensity.