A synergistic effect of photocatalysis and ozonation on decomposition of formic acid in an aqueous solution

Shinpon Wang, Fumihide Shiraishi, Katsuyuki Nakano

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92 Citations (Scopus)

Abstract

A synergistic effect of photocatalysis and ozonation on the decomposition of formic acid dissolving in an aqueous solution has been studied. In the photocatalysis over a thin film of titanium oxide immobilized on the inner surface of a glass tube, a 6W blacklight blue fluorescent lamp (wavelength: 300-400nm) was used as a light source. The initial decomposition rates followed a Langmuir-Hinshelwood type and the hydrogen peroxide generated during the photocatalytic reaction played an important role in the decomposition of formic acid. In the ozonation, a 6W low-pressure mercury lamp (wavelength: 185nm) was used to produce ozone by irradiation of the air with UV. When this air was circulated in a closed system with a water-holding glass container, the ozone concentrations in the air and water reached 0.350gm-3 air and 0.037gm-3 liquid, respectively, at maximum. The decomposition rate of formic acid by ozone was higher for a lower liquid temperature and a higher pH value. For comparison, the Langmuir-Hinshelwood type was also used to analyze both the experimental values obtained in the ozonation alone and in the combination of photocatalysis and ozonation. A relationship between the reaction rate and reactant concentration was calculated using the kinetic parameters determined from the experimental values in each reaction system. As a result, the decomposition rate of formic acid by the combination of photocatalysis and ozonation was found to be 31% higher at maximum than the sum of the decomposition rates when formic acid was individually decomposed by the two methods, which indicates the presence of a synergistic effect of the photocatalysis and ozonation. This effect may be explained by the promoted production of hydroxyl radicals by ozone over titanium oxide.

Original languageEnglish
Pages (from-to)261-271
Number of pages11
JournalChemical Engineering Journal
Volume87
Issue number2
DOIs
Publication statusPublished - Jun 28 2002
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Environmental Chemistry
  • Chemical Engineering(all)
  • Industrial and Manufacturing Engineering

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