| Summary: | 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.
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