Measurement of the hydroxyl radical formation from H2O2, NO3 -, and Fe(III) using a continuous flow injection analysis

Bum Gun Kwon, Jung-Hwan Kwon

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12 Citations (Scopus)

Abstract

Production of hydroxyl radical ({radical dot}OH) is of significant concern in engineered and natural environment. A simple in situ method was developed to measure {radical dot}OH formation in UV/H2O2, UV/Fe(III), and UV/NO3 - systems using trapping of {radical dot}OH by benzoic acid (BA) and measuring fluorescence signals from hydroxylated products of BA. Method development included characterization of {radical dot}OH trapping mechanism and measurement of quantum yields (Φ{radical dot}OH) for {radical dot}OH. The distribution of OHBA isomers was in the order of o-OHBA > p-OHBA > m-OHBA, although it changed with the H2O2 concentration and light intensity. This supports that {radical dot}OH attacks dominantly on the benzene rings. The quantum yields for {radical dot}OH formation in the UV/H2O2 process were 1.02 and 0.59 at 254 and 313 nm, which were in good agreement with the literature values, confirming that the method is suitable for the measurement of {radical dot}OH production from UV/H2O2 processes. Using the continuous flow method developed, quantum yields for {radical dot}OH in UV/H2O2, UV/Fe(III), and UV/NO3 - systems were measured varying the initial concentration of {radical dot}OH precursors. The Φ{radical dot}OH values increased with increasing concentrations of H2O2, Fe(III), and NO3 - and approached constant values as the concentration increased. The Φ{radical dot}OH values were 0.009 for H2O2 at 365 nm, showing that {radical dot}OH production is not negligible at such high wavelength. The Φ{radical dot}OH values during the photolysis of Fe(OH)2+ (pH 3.0) and Fe(OH)2 + (pH 6.0) at 254 nm were 0.34 and 0.037, respectively. The Φ{radical dot}OH values for NO3 - approached a constant value of 0.045 at 254 nm at the initial concentration of 10 mM.

Original languageEnglish
Pages (from-to)193-199
Number of pages7
JournalJournal of Industrial and Engineering Chemistry
Volume16
Issue number2
DOIs
Publication statusPublished - 2010 Mar 25
Externally publishedYes

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Keywords

  • Advanced oxidation process
  • Hydroxybenzoic acid
  • Photo-degradation
  • Quantum yield

ASJC Scopus subject areas

  • Chemical Engineering(all)

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